The American Civil War Essay Example for Free

The American Civil War Essay The American Civil War has also been called the War Between the States or the War of Rebellion or the War for Southern Independence. It was a clash between the United States of America or the Union and the Confederate States of America or the Confederacy. The Civil War was fought from 1861 to 1865. There were many reasons for the outbreak of this Civil War such as States’ rights and slavery. The principle cause for this War was purely economic. The Southern states had always tried to become independent because of the fact that the people and the state were becoming wealthier due to extensive use of slave labor. These states feared a drastic reduction in their wealth if slavery were to be abolished (Guisepi, 2002). Subsequent to the election of Abraham Lincoln as president of the United States, the South became apprehensive as they felt that slavery would be abolished, accordingly they started the civil war. On the 12th of April, 1861 the Confederate army in Charleston, S. C. , started firing on Fort Sumter, which was held by the Union forces. This marked the commencement of hostilities between the North and the South. The prima facie objective of the South was to gain independence and that of the North was to preserve the integrity of the Union. In the year 1862, Abraham Lincoln announced the Emancipation Proclamation and this constituted a major cause for the war. If the North emerged victorious then slavery would be abolished and if the South had won the war then slavery would have been protected in all the Confederate states (Guisepi, 2002). Economic disparities had been on the increase during the early nineteenth century. More than fifty seven per cent of cotton exports from the US had originated in the South and this was mainly due to the employment of slave labor. However, the North had acquired its wealth by establishing industries and as such the inhabitants of the North were opposed to slave labor. In order to cope with the demand for labor, the North encouraged immigration. Therefore, there were a large number of European immigrants who worked as laborers in industries and in the construction of railways in the North. The South was a laggard as far as industrialization was concerned and this forced them to import manufactured goods from the North. The southern states opposed the overwhelming taxes and tariffs on imported goods, which was the main source of revenue for the Federal government. The Federal government was unwilling to reduce the taxes since it had to support various welfare measures and provide infrastructure like roads. This led to a further disagreement between the North and the South (Gallagher, 2005 ). Initially, in the republic there were sectional differences between the regions, which were overlooked, owing to the fact that the vast distances rendered communication difficult if not impossible. The Northerners favored a central government in order to enable them to construct railroads, roads, and infrastructure, protect complex trade interests and thereby control the national currency. The Southerners, on the other hand, were not in favor of forming a central government since their dependence on the Federal government was much lesser. They also believed that a central government would prevent them from practicing slavery. The US Constitution prohibits the federal government from interfering with slavery within the states. Opponents of slavery in the Northern states were limited to restricting the use of slaves and the spreading of slavery to other regions. This is borne out by the fact that in 1820, Missouri was admitted to the Union as a slave state whereas Maine was admitted as a free state to maintain the balance in the Senate (Gallagher, 2005 ). In 1857, the Supreme Court of the United States added fuel to fire of mounting tensions by its judgment in the case of Dred Scott. In that case Scott a Missouri slave sought freedom on the basis that his master had taken him to live in a free state. The Court opined that Negroes were not citizens of the United States and that accordingly Scott could not approach the Court as he had no rights to do so. Moreover, the Supreme Court ruled that the US laws prohibiting slavery were unconstitutional. Subsequently, on the 16th of October 1859, John Brown a convict of the Pottawatomie massacre raided the Harpers Ferry, VA, in order to free the slaves and to encourage them to start a guerrilla war against the whites in the South. This incident shook the Southerners as they felt that it was the beginning of organized Northern efforts to abolish slavery (Guisepi, 2002). With the election of Abraham Lincoln as the President of the Union, the Southerners seriously contemplated secession from the Union and South Carolina was the first state to secede from the Union. Other Southern states quickly withdrew from the Union and these secessionists occupied many southern forts. The Artillery of the Confederates opened fire on Fort Sumter and this marked the beginning of the war (Guisepi, 2002). The Civil War had the dubious distinction of resolving the issue of secession permanently as has been borne out by the fact that since 1861, there have been no attempts by the states of the Union to secede. Another major change wrought by the Civil War was the abolition of slavery, subsequent to the Emancipation Proclamation announced by Lincoln. However, the Civil War was unable to make the blacks the equals of the whites and it was also unsuccessful in emotionally reuniting the North and the South, as had been hoped by Abraham Lincoln. References Gallagher, G. (2005 ). American Civil War. Microsoft ® Encarta ® 2006 [DVD] . Redmond, WA: Microsoft Corporation. Guisepi, R. (2002). American Civil War. Retrieved June 23, 2007, from http://history-world. org/american_civil_war. htm

Building Economics And Life Cycle Costs Construction Essay

Building Economics And Life Cycle Costs Construction Essay Economic understanding regarding building designs usually aim for steering building decisions to achieve for two situations: economic efficiency and/or cost effectiveness. For instance, a building design that, besides assuring to be profitable is promising to be more profitable than other available solutions, can be considered to be the economically efficient choice for an investor. Yet, a building decision that is considered cost-effective, guarantees, for instance, that a design solution with benefits equal or better to those of competing alternatives has lower costs. Cost-effectiveness is thus understood as a subset of economic efficiency; yet, both conditions can appear in one solution, but dont have to. The use of optimization thus reflects the strategy of achieving specific economic goals. Consequently, by minimizing life-cycle costs or maximizing net benefits, an economic analysis is applied to determine the most cost-effective or the economic efficient choice respectively . Overview The reflection and analysis of life-cycle costs (LCC) is an economic evaluation technique that determines the total amount of cost of a product or project over time. Having in common that the role is to provide insight in future matters regarding all occurring costs, LCC assessment in business organizations today, serves mainly three purposes : To be an effective engineering tool for use in design, planning and project execution To be a design and engineering tool for environmental purposes To be applied proactively in cost management. A similar understanding applies to the building sector. With the increasing need to deliver economic solutions, developers, designers, planners, engineers and managers try to foresee, steer and control costs at all stages of a buildings life-cycle. By overseeing a building projects inherent costs and directing attention toward its root causes, building projects can get useful decision support before, during and after its realization, performed on large and small buildings, on partial building elements, or on isolated building systems . Throughout the design, development and operation of building projects, LCC can thus be successfully used to compare alternatives to find the most cost effective solution . With the growing pressure of governments to hold companies responsible for the costs that their products generate to society and its environment, consumers are likely to benefit from the use of LCC assessment. Sustainable building strategies require foreseeing a reduction and control of significant LCC, such as energy costs for projected building designs. Consequently, organizations such as the National Institute for Building Science or the Whole System Integrative Process (WSIP, 2006) demand for early integration of cost related planning issues into the building design process. Eventually, future building designs that are less costly may also be considered better in terms of quality when all costs of a buildings life-cycle are adequately included. A strong commitment of building design is thus to enhance the practical value of buildings. While the value of products is defined as proportionate to the satisfaction of needs divided by the use of resources, its value is proportionate to quality divided by costs . Value-driven building designs therefore require being both: quality driven and cost conscious. In addition, probably the most important condition for resource optimization is appreciation of the built structure by its users: only buildings that are valued will achieve a long lifespan (Eberle, 2007). Proactive cost management is understood as an effort to eliminate product costs before they occur, as opposed to reducing costs after they are incurred, which is considered reactive cost management . Expecting the design and planning of building projects to be proactive view is inevitable, since changes in the later planning and execution phases or even during building operation become more and more difficult to deal with. Especially during initial design stage, the consideration of LCC can help designers to make their decision-making process become more cost efficient . In reality, a proactive involvement of cost might not be the case. Essentially, comparisons or studies on the building design and its influence on the cost of building operations over the life of a building are barely explored during the early design phase. If of any concern, financial aspects during early stages of design are mainly focusing on preventing uncontrolled cost expansion of initial, predominantly constru ction costs. The possibility of actively integrating all LCC members during the early design stages remains difficult to achieve as current methods of sequential design and cost estimation make it hard to foresee the impact of investment and to reduce building operation costs to an extent that would change the perception of these capital costs. In addition, the implementation of such proactive cost management quite often incurs more costs up front, for instance for the extended amount of research and development that projects then require for. Such consequences, and with them the traditional view on cost management can easily challenge the implementation of proactive consideration of LCC assessment, where necessary time and funding for the early stages of design and planning appears insufficient . A consideration of proactive design understanding and its use of LCC assessment thus also involve necessary changes in terms of thinking, such as from a partial focus to holistic thinking (Eberle, 2010), from structure orientation to process orientation or from cost allocation to cost tracing . Life Cycle Cost (LCC) With emphasis on cost-effectiveness the consideration of life-cycle costs (LCC) is used to evaluate competing alternatives primarily on the basis of costs, allowing for choices for a given building, facility or system. The method is to compute the LCC for a particular course of action by summing all significant, time adjusted costs associated with it over the relevant period of time. The method of using LCC is thus applicable to building decisions that require for cost related decision-support, such as system modification, replacements or combinations of interdependent budgets, budget allocations, or lease or buy decisions. Yet, it is also applicable for the evaluation of competing building designs; suitable, when focusing on cost rather than benefits for two or more mutually exclusive project alternatives. Typically, the analysis or assessment of LCC includes all initial and future costs that are affected by the decision and excludes others that are not. The exclusion of costs is no t necessarily required when their contribution can help to better understand the impact between cost consideration and the amount of improvement (Ruegg Marshall, 1990). LCC of building projects are often distinguished according to the building projects phase and are likely to be separated into initial (capital) cost, operational and post-operational costs Pushkar et al. (Pushkar, et al., 2005). Figure 2.x: Life-cycle Costs of a building life cycle The diagram in Figure 2.x illustrates the occurrence of different LCC members of the BVO model over growing operation time. It also demonstrates the increasing significance of continuous, operation costs over a projects running time, as its percentage of the total expenditure steadily increases compared to the initial investments at the project commencement. Net Present value (NPV) Besides LCC considerations of evaluating building designs, economic understanding of monetary systems requires to foresee their change of value over time, due to inflation, its investment to generate future profit, or both. In the building sector, the most commonly used methods of LCC assessment are accounting systems, initially developed to determine the financial worth of an investment; they are as follows : Simple payback: defined as the time taken for the return on an investment to repay the investment. Net present value: defined as the sum of money that needs to be invested today to meet all future financial requirements as they arise throughout the life of the investment. Internal rate of return: defined as the percentage earned on the amount of capital invested in each year of the life of the project after allowing for the repayment of the sum originally invested. LCC analysis is commonly performed using present value currency representation. In the following, the use of net present value is explained more closely as it has been implemented in the BVO model as it complies with the decision to use LCC for the assessment of design and its use allows for appropriate representation of costs elements in reference to their timely occurrence. The use and implementation of Net Present Value (NPV) models enables the adjustment of currency amounts in relation to their time of occurrence. It is thus a considerable measure when include costs elements of different time occurrences. The NPV is thus typically suggested to analyze the profitability of long term investments or projects, or the evaluation of available options (Dale, 1993). Essentially, it compares the value of money today to the value of that same amount in the future, taking inflation and returns into account. Among others, Ruegg (1990) defines the net present value as: (x) , where is the estimated cost in year t, d is the discount rate, and T is the period of analysis in years. The NPV of a building project takes into account all the apparent variables acting upon a cash stream; it is thus sensitive to the  reliability of future cash inflows that an investment or project will yield.  If the NPV is positive, it should be accepted. However, if NPV is negative, the project should possibly be rejected because cash flows will also be negative. Discount rate The discount rate is a method of determining the time value of money. To prevent the value of investment eroding by the effects of inflation, the factor of inflation can be integrated into the discount rate, known as the net of inflation discount rate and calculated as : (x) For instance, if inflation is 5% per annum and interest is received at 10%, then: (x) Thus, to make the influence of the discount rate become realistic it requires for reliable input to foresee the appropriate adjustment of financial aspect of interest and inflation. Similar to the typically practiced modification of construction costs that are based of earlier cases, such modification is necessary for future costs to remain representative. The accuracy of predicting and adjusting the monetary value may appear, however, problematic with growing life-time estimations of a building, as long term predictions become increasingly vague. Setting the study period The consideration of a LCC study period is expected to relate to the following factors such as the investors and stakeholders projected time horizon, the anticipated life time of the building, project, etc., the decision whether to accept or reject the choice, or whether the perspective is individually private or public perspective oriented. For instance, an investor or project developer might only be interested in short term cost as it is intended in creating revenue from the sale of the finished building project, while a building owner or operator might rather focus on evaluation the operative cost of a building design and their involvement over the complete life-cycle. When considering the overall sustainability of a building project, the complete life-cycle must be considered and anticipated. LCC assembly Buildings LCC are categorized by the three phases that they go through during their life-cycle. They are the initial or capital cost (1) at the beginning of a building project that involve its planning, design and realization, the operational cost (2) occurring during the buildings active phase of use, and the post-operational cost (3) that assemble the costs at a building lifes end. Though the three life cycle phases for buildings are clearly defined, their transition at a specific point of time can be vague, for example a building might already be partly operating while other areas of the building are still under construction. Figure 2.x describes the three phases and their overlapping character of transition between them. Figure 2.x: A buildings life-cycle phases In addition, operational phases can be interrupted, or at least obstructed by renovation or refurbishment phases to ensure or reinstall a buildings quality and use. For instance, building developments of industrialized countries with a high demand on energy costs, suggest that a buildings life-cycle performance can be improved when taking a renovation period of 25-30 years with a constant improvement of the buildings insulation properties into account . Figure 2.x describes how the buildings life cycles can be extend through periodic renovations and/or refurbishments. Figure 2.x: Extend a buildings operational phase through periodical renovations and refurbishments Initial (Capital) Cost The initial (capital) cost comprises all the costs necessary that ensure the building realization up to the moment of its active building use. Occurring costs are thus not only the construction of a building but also all related processes of project planning and development that are involved such as: Land costs, such as costs for acquisitions and necessary preparation of land. Professional fees, which apply for involvement of building planning professionals such as architect, engineer, lawyer, etc. Construction Cost, encompass all cost for the erection of the building and installment of projected building systems Commissioning Cost, comprising all cost applicable to certify necessary fulfillment of standards and requirements or the approval for building operations of building systems involved. Promotional and sale cost, for informing the  prospects  about special discounts,  sale, or  schemes. Funding costs, In general,  price  of obtaining  equity capital Management costs, comprising all cost necessary for the organizing  and  coordinating  the  activities  of an enterprise in accordance with certain  policies  and in achievement of project realization. Operational Cost The operational phase encompasses all the cost necessary to utilize and use the building according to its original purpose. Operational cost are becoming more and more noticeable over the life cycle of a project; due to the long period of building use they can grow significantly bigger than initial costs (). For instance, when à ¢Ã¢â€š ¬Ã‚ ¦ According to Ruegg and Marshall (1990), operational costs can be identified as: Energy Costs, includes necessary fuel and all applicable energy costs Operation and Maintenance Cost, includes non-fuel operation costs, such as management, cleaning, servicing, rates and taxes, sewerage, salvage, funding costs, routine maintenance, furnishings, supply à ¢Ã¢â€š ¬Ã‚ ¦ (check Ruegg) Repair and Refurbishment Costs, includes appraisal of all foreseen and estimated cost for repair or replacements of building systems or elements during a buildings use. Post-Operational Cost Post-operational cost includes the collection of all cost necessary cost that may appear at a building end of use. Mostly due to economic needs or owner related circumstances the buildings operational use becomes infeasible and a variety of options require to be considered. Unlike industrial products, the end of a buildings life cycle does not necessarily determine the end of a buildings life but instead refers to the end of a buildings original determined use. A building can thus have more than one operational cycle, when through post-operational interventions a new cycle of building use can be created. Post-operational cost can thus be categorized as Renovations Cost, represent minor repairs and makeovers necessary to maintain or reinstall building quality and use. Refurbishment Cost, include the cost necessary for major overhauls of buildings or building elements that otherwise result in obsolete building conditions. Refurbishment may also include the change of a buildings original use. Demolition, Disassembly and Recycling Cost likely occur at the end of a building life cycle. While in typical product life cycle the terms represent individual strategies involving separate specifications and costs, contemporary building removals mostly include the three them associating to separate treatment of individual buildings elements. Moreover, a number of regained materials and building elements may even create cost reduction due to their existing value possible reuse or recycling purposes. Sale, though the sale of a building does not essentially represent a cost per se, such case can occur when the new owner faces major difficulties for further use of the facility (i.e. due to contamination). Still, even if not a cost, the sale of a building can be used for LCC considerations, for instance if the sale of a building can be seen as a considerable reduction of buildings LCC due to the buildings inherited value. LCC declaration During a programming phase of building projects, cost estimations require to determine individual element of cost or benefits. To do such Tempelmans Plat (2001) points out that each demand and supply requires being determined in terms of quality, quantity, time and money. While quite often there is no or little basis of estimating future cost, estimations of future costs start by reflecting the current cost or benefit values as point of departure. Since cost estimations are subject to time related changes, costs or benefits require thought, whether to expect fundamental changes in the demand and supply of goods and services in question over time, or if considerable change of service or quality of goods are to be expected. If there is no sound basis to believe otherwise, it deems appropriate to assume that changes of prices will be approximately the same as prices in general (Ruegg Marshall, 1990). Still, the estimation of all cost elements usually poses a major difficulty due to their probabilistic nature and the distinctive character between individual costs elements. Common uncertainties for the prediction of long-life projects are: its life-cycles prediction, the interpretation of operation and maintenance costs, revenues and unforeseen or unpredictable factors that affect project economics. Since dealing with so many unknowns, it appears difficult to anticipate cost and benefit related developments. Existing methods of dealing with high risk exposure are best guess, relating to individual risk attitudes and risk adjustment through the introduction of methods using probability and statistics (Ruegg Marshall, 1990). The consideration of a LCC study period is expected to relate to the following factors such as the investors and stakeholders projected time horizon, the anticipated life time of the building, project, etc., the decision whether to accept or reject the choice, or whether the perspective is individually private or public perspective oriented. For instance, an investor or project developer might only be interested in short term cost as it is intended in creating revenue from the sale of the finished building project, while a building owner or operator might rather focus on evaluation the operative cost of a building design and their involvement over the complete life-cycle. When considering the overall sustainability of a building project, the complete life-cycle must be considered and anticipated. Cost estimation during early design stages During a schematic design phase of a building design, traditionally only construction costs are estimated. Such procedure comes with the disadvantage that long term costs that, if considered, may significantly influence design outcomes are usually not reflected. The practice of introducing operational and/or post operational costs thus require for designers specific estimation and understanding to prevent a decision-making and in a premature design situation. Since experiences of cost estimation for construction costs originate from knowledge gained during earlier comparable projects, a case-based oriented approach, such as suggested by Sowa and Hovestadt (2008), can also be used and practiced for other LCC members. Because such estimation and declaration of costs generally requires for extensive experience, the use and creation of databases that allow for differentiation and declaration may not easily compensate for. Cost estimators usually have considerable experience gained through working in the building construction industry, estimating and monitoring building costs through all the stages realization stages of a project (NIBS, 2010). The estimation of cost thus not only require for skills such as a clear judgment and straightforward attitude, but for qualities such as awareness, uniformity, consistency, verification, documentation, evaluation, and analysis . Yet, with the growing complexity of building projects, it seems vital to have the cost estimations involved right from the very beginning to ensure that the project estimations reflect the decisions made. Especially during the early design stage, changes will require estimates to be prepared at different levels during the design process with increasing degrees of information provided. At any point of a design, not all portions of the design would be at the same level of completeness. Yet typical, such contingencies for the aforementioned will be reduced as more design documentation is produced (NIBS, 2010). For instance, the estimation of construction costs typically corresponds to the phases of the building design and development process in a top-down manner, meaning that cost estimates improve their precision and detailing with the progressing stages of design realization. In addition, cost estimates usually try to comply with considered standards within the building industry. In the United States, for instance, a widely accepted system provided for cost estimates is the UniFormatà ¢Ã¢â‚¬Å¾Ã‚ ¢ or, for later planning stages the MasterFormatà ¢Ã¢â‚¬Å¾Ã‚ ¢ (CSI, 2011) system, which allows design teams to evaluate  alternative building designs and systems. In Europe, cost estimates are usually practiced according to DIN regulations such as the DIN 276/277 for cost estimation and declaration of building designs (Frà ¶hlich, 2007). A building projects first cost estimates can already appear during the architectural programming phase with the purpose to facilitate budgetary and feasibility determinations. Usually based on past information with adjustments made for specific project conditions such estimates are prepared to develop a project budget. At such level, design schemes normally do not yet exit, required data for cost appraisals are thus drawn from general functional description, schematic layout, and geographic location, building size expressed as floor-area, numbers of people, seats, cars, etc., and intended use. Respective estimates are thus based on costs per square units, and/or alternatively number of cars/rooms/seats, etc. During the schematic design phase, the purpose of estimate is to create a more complete assessment that is typically based on a better definition of the scope of work. While also compared to earlier budgetary and feasibility determinations, an estimate at this level may be used to price various design schemes in order to see which scheme best fits the budget, or it may be used to price various design alternatives, or construction materials and methods for comparison. The more developed schematic design criteria such as a detailed building program, schematic drawings, sketches, renderings, diagrams, conceptual plans, elevations, sections and preliminary specifications are reflected. Available information is typically supplemented with descriptions of soil and geotechnical conditions, utility requirements, foundation requirements, construction type/size determinations, and any other information that may have an impact on the estimated construction cost. The goal at the end of schematic design is to have a design scheme, program, and estimate that can be contained within budget . Net Benefits (NB) LCC considerations are typically used to make cost-effective choices, as its technique is to compare alternatives competing primarily on the basis of costs (Ruegg Marshall, 1990). Yet, if a building design is planned to generate revenue, a comparison of invested costs to its predicted returns can help to determine advantages between designs options. In such case, the method of calculating the net benefits (NB) of a building option is considered an applicable way of finding the most economically efficient choice among alternatives. In such case, the calculation of NB is achieved by subtracting the time-adjusted costs of an investment from its time-adjusted benefits (Ruegg and Marshall, 1990). In relation to building-volume optimization, because the optimization of cost is generally expected to steer a building-volume design towards minimized volume/surface ratio, window/opening ratio and/or net surface areas, the integration of revenue considerations can help to justify the amount of indispensable volume reduction when practicing BVO. Similar to cost considerations, the estimation of buildings projected revenue can be established by floor-area declarations. In addition, while a buildings annual income is expected to change depended on its market value over the span of a buildings life-cycle; the diagram in figure 2.x shows how a buildings generated income can be perceived as originating from a products marketing perspective, which consists of at least four stages of introduction, growth, maturity and decline . Figure 2.x: A products marketing perspective over a life cycle. Source: Kà ¶nig (2009) The prediction of generating buildings revenue thus requires for understanding and forecasting these changes over a given period; its moments of rise and decline that strongly depend on a buildings perceived value and its decay due to intensity of use (elaborate further, see Koenig). Shown in Figure 2.x, when plotting a typical development of cost and revenue predictions the financial profitability of building occurs at point a, and becomes obsolete when the cost of become larger than the income generated. Such situation appears at operation time b with operation cost appearing higher than the income; at least at this point the buildings economic purpose becomes unsuccessful. Figure 2.x Cost vs. Revenue. Source: Kà ¶nig (2009) When adapting a buildings foreseen lifecycle to this understanding, a buildings lifetime and the creation of revenue can be exceeded by interference of the maturity process through possible renovation or refurbishment measures. In Figure 2.x a buildings generated income during a foreseen life-cycle may thus be illustrated by separating the building operation period by new construction constructions phases that are required for the renovation and/or refurbishment of the building. Figure 2.x: A buildings generated income extended through renovation and refurbishment top. Source: Kà ¶nig (2009) In reality, the periods between theses interventions very much vary from the owners intention to keep high-level building quality or the necessity to prevent a building from becoming obsolete or having higher operation costs that income. From an economic standpoint, interventions to improve the buildings ideally take place when profitability can be increased or maintained. For instance, Kà ¶nig et al. (2009) suggest that, in an industrialized country, a replacement and improvement of buildings insulation performance should take place after a period of 20-30 years. Especially with the amount of operation costs strongly increasing due to continuously rising energy costs, the need for innovations and improvement for reducing buildings energy consumptions became highly prominent. Finally, because a clear definition of a buildings income require for experiences of earlier comparable cases, the use of existing data are necessary to help predicting the revenue curve and the point of interventions for necessary building improvements. An optimization, particularly of passive resource oriented building improvement thus depends on well implemented predictions and assumptions of a buildings foreseen life-cycle and performances. Yet, when of a designer existing experience or the amount available data is not sufficient and/or its quality is questionable, the building-volume optimization process may clearly suffer from it. Conclusion The use of assessing life-cycle costs (LCC) is seen as tool that helps associating estimated costs over a projects foreseen life span. LCC of a building or a building system are defined as the total discounted amount of cost of owning, operating, maintaining and disposing over a defined period of time . The consideration to use life-cycle cost as an objective for the BVO model is based on its ability to include different building costs over a specified period, allowing for comparison and impact analysis between, for instance, initial and operational costs. The establishment of LCC as an objective for building performance optimization thus defines the primary BVO model goal. To be effective, the attempt of reducing overall building costs requires for a cost distribution that allows for effective declaration and activation of significant building elements during early architectural design stages. According to volume geometry, this can be building-volume surfaces as well as building flo or-areas. With the possibility to link costs to selected areas, the model requires a wider variation of costs to be successful. Because early design stages mostly refer to estimated costs; cost distribution and specification is more likely to be based on users experience or existing available data originating from earlier comparable building design cases . For the BVO model currently only initial and operational have been integrated because convincing and direct associations between post-operational costs and building elements at a buildings lifes end are hard to foresee and the available options appear diverse. Still, eventual costs for the renovation or refurbishment of buildings or building parts can be integrated as they are usually more common and estimations based on area declaration exist. While the main aim of the BVO model lies in the improvement of the buildings geometry (volume of the building) and not in the building system that eventually operates it, the induced process is understood as to eliminate or reduce the amount of incurring cost of a projected design before they occur. Once a building-volume design is established, system considerations may then further reduce costs by means of using appropriate technology as practiced by engineers. As mentioned earlier, Eberle (2007) suggested that active and passive design features are responsive towards each other, thus the priority in the design process should aim for optimizing passive design features first as they do not require the use of additional resources. Because constant definitions already include premade assumptions and partial definitions on an incorporated system they should be chosen wisely as not to affect unrealistic results. BVO design is thus understood proactive, as its primary intention is the improving passive design elements of the building-volume. Yet, the integration of LCC helps to understand significance of individual cost members and effectively use the diff

Citric Acid to Remove Stains | Experiment

Citric Acid to Remove Stains | Experiment BACKGROUND AND PURPOSE: Knowledge about natural bleaches to remove stain may be useful in our daily life. Natural bleaches can be found in various types of fruits juice and many more. This green bleaches are more friendly to environment and cheaper than commercial product. Citric acid is one of bleaching agent that can be found in the citrus fruits such as lemon. This paper will discuss on the process of removing stains by citric acid in different type of fruit juices. The investigation was focused on How does the type of citrus fruits used affect the rate of reaction of stain removable? Since stains have different types, the effectiveness of citric acid on two types of stains (synthetic and vegetable based stain) had been discussed more in this investigation. MATERIALS AND METHODS: The experiment was conducted with different type of fruits; lemon, lime, navel orange and pineapple. The time taken for the different type of stain to be removed by different type of fruits had been recorded and be analyzed to identify the most best used as natural bleaches. RESULTS: Even though the lemon juice is more popularly known as natural bleach but based on the experiment, the best used citrus fruit as bleaching agent is lime and the citric acid is most effective used to remove vegetable based stain. Table of Contents (Jump to) Introduction 1.0: Bleaches 1.1: Chemistry in Bleach 1.2: Mechanism of Bleaching 1.3: Rationale of Study 1.4: Significance of Study 1.5: Limitation of Study 1.6: Research Question Hypothesis Variables 3.0: Apparatus and Materials 4.0 Procedure and Analysis 4.1: Extraction of juices from citrus fruits 4.2: Citric acid determination 4.3: Procedure for stain removable Conclusion Evaluation INTRODUCTION Bleaches Bleaches used worldwide in household to remove or decolorize stains which whiten or lighten the color of clothes. Chemically, bleaches will breaks the stain molecules into smaller molecule that easily be removed. D.Noemia Souza (2008) stated that bleaches are chemical that capable to whitening the fabrics and removing stains by destroying colouring matter. There are two types of reaction that involve in bleaching. Commonly bleaching process involves in oxidation processes such as hydrogen peroxide and some involve the reduction processes such as sodium chlorite. However in bleaching processes, the oxidation and reduction also can occur simultaneously. Bleaching process for stains most effective when both an oxidative and a reductive bleaching steps worked together and this referred as full bleaching (J.M. Cardamone W.N. Marker, 1995) There are various types of bleaches, and each type of bleach is specifically used for certain type of fabrics. The fabrics are very specific and if use d with wrong bleach, the fabric will wear out. Concentration, pH, time and temperature are the various conditions which are affect the action of bleach on fabrics. Chemistry of Bleach Hydrogen peroxide is the most prominent bleach and usually used in commercial bleaches. However, according to D.Noemia Souza (2008), the strongest bleach is sodium hypochlorite while the weakest is sodium chlorate and the hydrogen peroxide is milder. Sodium hypochlorite(Chlorine-containing oxidants) Usually, the sodium hypochlorite will contain 15-18% of chlorine (D.Noemia Souza, 2008). Under certain condition, the solution will decompose into sodium chlorite (eq1) which then reacts with hypochlorite and produce the sodium chlorate (eq2). The sodium hypochlorite will undergoes further reaction to release oxygen (eq3). Thus it is classified as chlorine bleach 2NaOCl NaCl + NaClO2 (1) NaOCl +NaClO2 NaCl+NaClO3. (2) Overall equation: 3 NaOCl 2NaCl+NaClO3 (3) 2NaOCl 2NaCl+O2 (4) Hydrogen peroxide(preoxygen bleach) Hydrogen peroxide bleaching will dissociates into H+ and per hydroxyl ions HOO-(eq1).The per hydroxyl ions is the active bleaching agent. Under alkaline conditions it will release oxygen (eq2).Cotton would damage under this conditions as the bleaching effect is slow and the bleaching rate is fast. The activator and stabilizers are added to control this condition (J.M. Cardamone W.N. Marker, 1995). H2O2 HO2- + H+.. (1) 2H2O2 2H2O +O2 (2) Hydrogen peroxide is a universal bleaching and D.Noemia Souza (2008) said it is the only oxidizing bleach that can be safely used on protein. Mechanism of Bleaching Based on ProcterGamble (2005) the process of bleaching is divided into two, which are; Breaking up the stain The stain consist of molecule chains covering the fabrics The bleach molecule will break the stains into smaller pieces After that process, bleach molecule will disappear The stain is now broken into smaller pieces which can be easily removed by the surfactant Decolorizing the stains The stains color has its origin in the double-bond connections Then, the bleach will break up the bond and convert it into single bond, eliminating its ability to absorb visible light. After that, the bleach molecules will disappear. Once the double-bond connections are broken up, the stains isnt visible anymore. Citric Acid as Natural Bleach Citric acid is weak organic acid and one of the acids found in citrus fruits such as lime and lemon. It popularly used in food industrial as perservative. It also can act as natural bleaching agent and an antioxidant. So it is useful in our daily life to remove stain or dirt from fabric and bleach the spot. Citric acid exist in many type of vegetables and fruits but more concentrated in lime and juice where the dry weight of citric acid in fruit comprimise as much as 8 percent (sciencedaily.com).The concentration of cotric acid in fruits range from 0.005 mol/L for oranges to 0.30 mol/L in lemons and limes (Wiki.Org) Rationale of the Study Nowadays, most of people prefer to use biodegradable product or green product. Especially in current downturn economy, many people change to less expensive products. Using citrus fruits as an alternative ways to remove stain is the good choice. The question that arises here is what the significance of knowing which of the citrus fruits is best used in removing stains? Significance of the Study Sodium hypochlorite (chlorine bleach) and hydrogen peroxide (oxygen bleach) are extremely popular in the market to whiten the fabrics and in stain removable. However, there are some disadvantages using oxygen and chlorine bleaches. Most of them are hazardous if ingested or inhaled and should be used with care. Lindsay Evans (2009) also explained the chlorine can cause negative health effects. Besides, they are costly and give a bad impact to our environment especially rivers and lakes ecosystem. Chlorine that flowing into rivers or lakes will combine with other chemical to form a stable compound where it will remain unchanged in groundwater for many years (Wisconsin, 2010). On the other hand, citric acid best uses as natural bleaches because it does less harm to ecology of rivers and lake. Limitation of the study All of the experiment will conduct in the Mara College Serembans laboratory. Most of the material such as citrus fruits; lemon, lime, navel oranges and pineapple and table salt are obtained from Carrefour Cheras in Cheras, Selangor, Malaysia. So, all of the fruits are not in the same level of freshness due to different condition during storage that may affect the freshness of the fruits. Besides that, the fruits might not come from same tree and this will affect the concentration of acid in the fruits. Research Question The focus of study is to investigate the ability of citrus fruits as natural bleach to remove stain from fabric. The main objective of this study is to identify which of the citrus fruits; lime, lemon, pineapple, and navel oranges is best used as bleaching agent. So the research question of the study is How does the different type of citrus fruit used; lime, lemon, pineapple, and navel oranges affect the rate of reaction of stain removable? The study uses 4 different types of citrus fruits which are lime, lemon, pineapple, and navel oranges that will extract into juice and add with table salt (sodium chloride). Hypothesis The research question of the study is How does the type of citrus fruits used affect the rate of reaction of stain removable? The rate of reaction of stain removable is the highest at the most acidic solution. So the hypothesis is the most acidic fruit in this case is lime or lemon as both contains high concentration of citric acid. Variables Independent Variable There are two independent variables in this experiment as the experiment is divided into several parts. The first independent variable is the different types of citrus fruit juices; lemon, navel orange, lime and pineapple. While the second independent variable is the different type of stains where synthetic stain (syrup) and vegetable stain(tomatoes) are used throughout the experiment. Dependent Variable Rate of reaction to remove the stain from fabric will be the dependent variable. The time taken will be record by stopwatch for the stain to decolorize. Then by using the graph the gradient is determine which represent the rate of reaction. Fixed Variable The fixed variables are type of cloth (cotton), volume of juice (5oml), temperature (100ËÅ ¡c) and volume (100ml) of water bath and quantity of sodium hydroxide (3 teaspoon). All of this material will be use in same quantity throughout of the experiment. Apparatus and Materials Material Quantity Fruit juices (lemon, lime, navel oranges, and pineapples) 50 cm3 100 ËÅ ¡c of water bath 100 cm3 Phenolphthalein Distilled water 40 ml Table salt 1.0M of NaOH solution Dried KHP 3 teaspoon 10 cm3 1.0 g 4.0 Procedure and Analysis Preparation of an approximately 0.1 M Sodium Hydroxide Solution followed by the Standardization of the Sodium Hydroxide Before testing the concentration of citric acid, the standard sodium hydroxide solution needs to be prepared. In order to prepare 0.1 M of NaOH, 9.0 cm3 of 1.0M sodium hydroxide solution was diluted with 100.00cm3 of distilled water. Then the sodium hydroxide solution was standardizing to determine its concentration by titrated it with KHP. This acid base reaction is shown in Equation 1(M.L.Gillette, 1999); KHP(aq) + NaOH (aq) NaKP(aq) + H2O(l)(eq1) Two portion of 0.5g of dried potassium hydrogen phthalate (KHP) was weighed and dissolved with 50ml distilled water in conical flask. The Phenolphthalein solution was added for 2-3 drops into KHP solution to indicate the end point of titration. Phenolphthalein was used because the pH range of product is 8-10 .The sodium hydroxide was titrated with KHP solution until pale pink color was produced. The volume of NaOH solution added was recorded. Data Collection for Standardization of NaOH Number of trials 1sttrial 2ndtrial Initial Burette reading/cm3 ( ±0.05cm3) 0.00 0.00 Final Burette reading/cm3 ( ±0.05cm3) 23.50 25.40 Volume NaOH solution added/cm3 ( ±0.05cm3) 23.50 25.40 Observation After few minutes, the clear solution turned into pale pink before disappeared. After few minutes, the clear solution turned into pale pink before disappeared. Table 4.0 Data Analysis The purpose to standardize sodium hydroxide solution against potassium hydrogen phthalate is to determine the exact value of sodium hydroxide concentration. By titrate the 0.1M of sodium hydroxide solution against KHP solution the results collected are more accurate. The concentration of sodium hydroxide was found to be 0.1002M Calculation for determining the concentration of the sodium hydroxide; KHP (aq) + NaOH (aq) NaKP(aq) + H2O To calculate the number of mole of KHP Number of mole= mass/molar mass = 0.5g KHP/ 204.2 = 2.449ÃÆ'-10-3mol KHP To calculate the number of mole of NaOH required to neutralized KHP solution No. of moles of NaOH = No. of moles of KHP = 2.449ÃÆ'-10-3mol NaOH To calculate molarity of NaOH solution Concentration of NaOH = (number of moles/ volume of NaOH)ÃÆ'-1000 = (2.449ÃÆ'-10-3/ 24.45) ÃÆ'-1000 = 0.1002M Percentage uncertainty of the concentration of the 0.1M of sodium hydroxide % Uncertainty of Concentration of 0.1M NaOH = Volume(H2O) + Volume(NaOH)+ Concentration of NaOH(1.0M) % Uncertainty of VH2o = 0.04/100.00 ÃÆ'- 100 = 0.040% % Uncertainty of VNaOH = 0.05/9 ÃÆ'- 100 = 0.600% % Uncertainty of CNaOH = 0.040+ 0.600 =0.64% Extraction of juices from citrus fruits. The lemon was cut into small pieces and blend with blender. The juice released was putted into the beaker and labeled with A. First step was repeated again until half of the beaker filled. Then, the extracted juice was filtered through muslin cloth. The whole procedure were used again with another type of fruits, lime, navel orange and pineapple and labeled with; Beaker Type of juice A Lemon B Lime C Navel orange D Pineapple Citric Acid Determination The reason of citric acid determination is because to know the exact value of citric acid in juices for data analysis. This process is carried out by adding NaOH into the fruit juices. The approximately 10 mL of lime juice was prepared by using pipette and transferred into a conical flask. Then, the lime juice was diluted with 20ml of distilled water and three drops of phenolphthalein was added into solution. The solution with 0.1M sodium hydroxide (NaOH) was added from burette to the juice sample while swirling the mixture until the reaction mixture turned into faint pink color. The end point was reached when the pink color persists for thirty seconds. The volume of NaOH added was recorded. The processes were repeated again to increase the accuracy. Then, the procedure was repeated with different type of juice; lemon, orange and pineapple. By using the formula, the molarity of citric acid in the fruit juice was calculated. Data Collection for citric acid Determination Type of juice Lemon Number of trials 1sttrial 2ndtrial 3rdtrial Volume of juice pipette/( ±0.5)ml 10 10 10 Final burette 27.6 49.6 76.1 Initial burette 0 27.6 49.6 Volume of NaOH ( ±0.1)mL 27.6 22.0 26.5 Average Volume of NaOH 23.98 Qualitative Data The colour of solution in conical flask change from white colour to faint pink colour. Data Analysis- calculation for determining the citric acid concentration through sodium hydroxide added. The citric fruits consist of citric acid. Citric acid contains carboxyl acid group and reacts with hydroxide ion as indicate in equation 2 (Dr. Ewa Thomas, 2007). The sodium hydroxide will ionize to form sodium ions and hydroxide ions (eq 1). NaOH (s) Na+ (aq) + OH (aq) (eq 1) C3H5O (COOH)3 (aq) + 3 OH- (aq) C3H5O(COO)33- (aq) + 3 H2O (l) (eq 2) The purpose of this experiment is to determine the concentration of citric acid on the citrus fruit by titrating the citrus juice with standard sodium hydroxide solution. The concentration of citric acid can be calculated by measuring the volume of sodium hydroxide used (eq 3). Molarity,M= (eq 3) M1V1 = M2V2 (eq 4) Based on the equation, the molarity of the OH- ions equal with sodium hydroxide as the molecular ratio is 1:1. So, the molarity of hydroxide ions can be known. By using equation 4, the concentration of citric acid can be determined. Calculating the concentration of citric acid By using the data given above, I had calculated the concentration of citric acid in citrus juices. The citric acid C6H8O7 is a triple basic acid that consists of three carboxylic acids and react with one hydroxide ion ,eq 1(Ewa Peter Thomas M Moffet, 2007). In this experiment, I assumed that the citric acid is sole acid found in the citrus fruits. C3H5O(COOH)3 (aq) + 3 OH- (aq) C3H5O(COO)3 (aq) + 3 H2O (l).(eq 1) However, according to experiment conducted by Law.C Solak.E(2009) the citric acid does not always have the 3 carboxylic acid. So, in this experiment I will assume that the citric acids only have 1 carboxylic acids but its less accurate. The following reaction takes place in the titration; C6H8O7 + OH- à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ H2O + C6H7O7- (eq 2) Based on the equation(eq 2), the molarity of the OH- ions equal with C6H8O7 as the molecular ratio is 1:1. By using equation below, the concentration of citric acid can be determined. M1V1 = M2V2 where : m1 = molarity of Sodium hydroxide, NaOH v1 = volume of Sodium hydroxide Solution, NaOH m2 = molarity of dilute citric acids, C6H8O7 v2 = volume of dilute citric acids Solution, C6H8O7 Example of calculation: By Using the volume of NaOH use to titrate lemon juice 0.1M NaOH ÃÆ'- 23.98 ml = M2 ÃÆ'- 10 ml 0f C6H8O7 2.298 mmol OH- = M2 ÃÆ'- 10 ml C6H8O7 M2 = = 0.2398 mole/L C6H8O7 (The calculations showed above are applied to all other experiment, table 5.5) Calculating Uncertainties Percentage uncertainty of Concentration = [(Άn / n) + (ΆVolume / Volume)] x 100% Example; Percentage uncertainty of concentration for Lemon = = 6% Absolute uncertainty of concentration = Percentage uncertainty x Concentration / 100% Example for Lemon = 6% ÃÆ'-0.24/100% = 0.014 moldm-3 0.01 moldm- Data Presentation Type of juice Average NaOH used( ±0.1)mL Concentration of citric acid (mol/L) Lemon 23.98 0.2398 Lime 10.78 0.1078 Navel Oranges 5.35 0.0535 Pineapples 2.95 0.0295 Table 4.6 Procedure for process of stain removable The white cloth cotton was cut into3cmÃÆ'-3cm size for 20 pieces and each pieces of cloth were stained with syrup solution. Then the stained clothes were dried for about 1 hour. 20 cm3 of lime juice was prepared and the initial pH of juice was recorded by using pH meter. For the first trial, a stained cloth was held under the running water and was soaked in the lime solution for more than 30 minutes. After that, the stained cloth was put into100ËÅ ¡c hot water bath and the time taken for the stained decolorize was recorded. However, the stained took longer time to decolorize where the average of time taken cannot be recorded. So I used another method by adding 3 teaspoon of table salt (sodium chloride) into lime juice. The pH value of juice was recorded. The stained cloth was rubbed with salt before soaked into the solution for an hour. Then, the stained cloth was putted into 100 °C hot water bath and the time taken for the stained decolorized was recorded. In order to identi fy the best fruit best use to remove the stain, the whole step was repeated again with another type of fruits; lemon, navel orange, and pineapple. The results from different type of fruits were compared. Besides that, I also used the different type of stain to test which one is more effective been bleached by citric acid. In this experiment I used vegetable based stain which is tomato stain. The first method is used; without adding the table salt (sodium chloride) and the result was recorded and be compared with synthetic stain (syrup). Data Collection for Removable of stain Qualitative data For synthetic stain: The pinks colour of stain turns into colourless. Fabrics become white Fabric cloths smell fruity. The juices become more slippery when added with sodium chloride. For organic stain The red colour of tomatoes decolorize The fabric colour turn into redish The fabric turns white after held under running water. Data Analysis According to the data collected, the different type of fruits and different type of stain will affect the time taken for the stain to decolorize. For the syrup stain, there must be influenced by sodium chloride (cooking salt) as it is hard to remove by citric acid alone. Adding the cooking salt involved the osmosis concept where the solution will become more saturated, the water will moving from the cloth to the salt and taking the stain together (T. Lister J. Renshaw, 2000). When the cooking salt is added into the juice, the pH of juices drop and become more acidic. However, chemically the cooking salt does not affect the acidity of citric acid. The drop in pH value may be due the presence of water in the juices which react with the salt and release the hydrogen ions which might cause this to be happened. The reason putting stained cloth into the hot water is to increase the reaction by increase the movement of particle and reduce the time taken to remove the stain (Kenneth M.S, 194 2). The highest rate of reaction (Table 4.9) calculated is lime juice and the lowest rate of reaction is pineapple juice. The reaction for both juices can be related with its pH and concentration. In term of concentration of citric acid, the higher the concentration of citric acid will increase the acidity of juice and the time taken for stain removable will become faster. However, this might not be true for lemon juices. Even though, it has highest citric acid concentration but the time taken for stain removable is not the fastest. This probably because of error and limitation occurred and will be discussed more in other section. Meanwhile, graph 4.4 shows the rate of reaction of stain removable for both type of stain by using Microsoft Excel. It is show that the rate of reaction for removable stain in tomatoes stain is 0.154, higher than syrup stain. This is might be because the syrup stain is more thick and viscous. While the vegetable based stained (tomatoes) is easier to remove because it is organic in nature and more soluble in lemon juice. 8.0: Conclusion and Evaluation Conclusion The experiments showed that the type of citrus fruits used does affect the average time taken to remove the stain. The hypothesis that rate of reaction would be highest in the most acidic fruit (lime) which consist high concentration of citric acid, is also supported based on the data collected. The pH of lime is 2.2; most acidic among the others citrus fruits. The main objective of this essay is to identify which of the type of citrus fruits; lime, lemon, pineapple, and navel oranges are best used as bleaching agent. As mention above, the type of citrus fruit does affect the rate of reaction to remove the stain. However, it also depends on the type of stain. Test on fabric with synthetic stain without adding sodium chloride (salt) required a long time where the average time taken cannot be collected. Meanwhile, citrus fruits are best used on fabric with vegetable based stain as there in no influence with sodium chloride. It can be said that the sodium chloride act as catalyst and ma king the removable of stain easier. In addition, the time taken to remove the stain for vegetable based stain is fastest compare than synthetic stain. The hot temperature was used in the experiment to speed up the reaction. Thus it can be concluded that, the lime is the best used as bleaching agent but with certain condition; type of stain and temperature. Evaluation Some error and limitation occurring during the experiment which causes the result collected imprecise. The limitation and errors in these experiments can be divided into several parts. For the first part is problem in procedure A. Initially, the sodium hydroxide prepared had been assumed exactly 1.00M. However, to test the accuracy of the concentration, the sodium hydroxide had been standardized using KHP solution. After calculating the concentration of the sodium hydroxide, the concentration of sodium hydroxide is approximately 0.1M with 0.2% of percentage error. There is a limitation occur when calculating the concentration of citric acid by titrate it with sodium hydroxide solution. One problem is the citrus fruits contain several type of acid. So, in the experiment the citric acid had been assumed as sole acid in citrus fruits and be supported by Dr. Ewa Thomas. As a result, the amounts of citric acid concentrations calculated are inaccurate and larger than theoretical value. The citric acid should been standardized to know the exact concentration, where it reduce the uncertainties. Besides that, some common mistake occurred in the experiment such as improper position of burette and parallax error in taking the measurement. To overcome this, there is no other solution except reduce the parallax error by positioning the eyes straight to the scale reading needed and position the apparatus used at the smooth surface. Moreover, it was hard to determine that the colour of the solution turned to faint pink colour because if the titration of NaOH was titrated without care the solution will become too red. So the result of the first faint pink colour come out should be observed and detected properly so it needs a particular partner in doing that job. Based on data collected, there is error between the concentration of citric acid and pH value for lemon juices where supposedly the pH of lemon juice should be most acidic as it has highest citric acid concentration. The problem may arise in determining the citric acid concentration where the value of citric acid calculated in lemon juice was incorrect. Because of the lemon used are in different freshness (as mention earlier in limitation of study), it might affect the result. So, the same lemon must be use throughout the experiment. In the last part (procedure D), one of the error occurs is during taking the average time taken to remove the stain from fabric. When the stained fabric is place into hot water, it is difficult to identify whether the cloth decolorize or not because it is possible for fabric to turn into white without be rub. To improve this, the experiment must be repeated for several times to increase the accuracy. There is also a limitation where the removable of stain cannot be seen clearly when test conducted with coffee at first. So, to overcome this problem, the stain was changed into syrup which the red colour can be seen clearly. However the problem had comes when there is change in pH value of fruit juice after adding with NaCl due to presence f water. This might be because limitation that occurred during extraction of juice. So, it is necessary to ensure all the equipment to rinse and dry first before conducting any experiment. Recommendation for further research More work could be done on the use of sodium chloride (cooking salt) in removing stain; is it effective used and how it will increase the effectiveness of citric acid in removing stain? The other use of citric acid beside remove stain should be investigated as if citric has potential in other cleaning process. Besides that, while the experiment was done by using citrus fruits as natural bleaching agent other natural bleaching agent should be considered. Investigation on the effectiveness of citric acid by comparing it with the commercial bleaches and color safer bleaches has applications in our daily life. CdS Quantum dots: Synthesis and Optical Properties CdS Quantum dots: Synthesis and Optical Properties CdS Quantum dots: Synthesis and Optical Properties Characterization for Solar Cell Raimy Roy Abstract— In this work CdS quantum dots were synthesized using Successive Ionic Layer Adsorption and Reaction (SILAR) method. Then a study of the morphology and optical property were made for the application of solar cell. The structural characterization were made by XRD while the optical characterization where done by UV-vis-NIR spectroscopy techniques. Index Terms—Quantum dots, SILAR I. INTRODUCTION Quantum dot sensitized solar cell is an emerging field of photovoltaic in which the absorbing material is a quantum dot. The advantage of using such solar cell is size tunability and increased surface to volume ratio. In a quantum dot based solar cell the active layer consist of the quantum dot and the scattering layer is formed by the TiO2 layer. The mesoscopic TiO2 when deposited with CdS quantum dot act as an energy harvester and convert the incident photon to electricity. In this work, a model of the photoanode for the solar cell was made with mesoscopic TiO2 layer as scattering layer and quantum dots as absorbing layer. Here instead of ITO a glass slide was used. [1] To synthesize a quantum dot various techniques are used. Among them Successive Ionic Adsorption and Reaction (SILAR) method is a cost effective and is used to prepare quantum dot. In a SILAR method the time of reaction or the number of cycles can be controlled. Depending on which the size of the quantum dot varies. Another advantage of this technique is that it can be prepared at room temperature. Also this method provides a close contact between the quantum dots and the oxide layer, so it is an attractive method for the preparation of electrodes in a solar cell. [1] Cadmium sulfide (CdS) quantum dot is a direct band gap semiconductor. It is a II-VI compound semiconductor that is used for many optoelectronic devices such as solar cell, laser diodes and photoconductors. It is an inorganic semiconductor which has several advantages over conventional dyes. These advantages are band gap tunability, large extinction coefficient (this means that the dark current can be reduced and the overall efficiency can be improved) and multiple electron generation by utilizing hot electrons. [2] II. EXPERIMENTAL SETUP Chemicals Required Titanium dioxide powder (SD Fine-Chem Limited, purity 60%), 2M nitric acid, 0.05M cadmium nitrate, ethanol, 0.05M sodium sulfide hydrate (Sigma Aldrich, assay=60%), methanol. Preparation of TiO2 layer on glass slide A paste of titania (TiO2) was prepared from TiO2 powder and nitric acid. The chemicals were added in 2:1 proportion. A thin layer of titania paste was coated on the glass slide using a technique called doctor blade method [3]. In this method, either a glass rod or a microscope slide is used. We have used a microscope slide of thickness 1.45mm to coat the paste. A glass slide of dimension 2cm X 1cm was cut and cleaned. With the help of an adhesive tape, the glass slide is positioned firmly on the work bench. Another advantage of using such tape is that we could define an area to coat the paste and to deposit the quantum dot. Now place the paste on one side of the glass slide, positioning the microscope slide in 45à ¯Ã¢â‚¬Å¡Ã‚ ° spread the paste across the glass slide. Repeat the operation till a reasonably homogeneous layer is formed. After coating heat the paste to 80à ¯Ã¢â‚¬Å¡Ã‚ °C followed by annealing at 450à ¯Ã¢â‚¬Å¡Ã‚ °C for 30 min. After sintering the paste is white in color . This provides a better surface for adsorption of the CdS quantum dots since sintering makes the mesoporous films to a continuous network. Deposition of CdS Quantum Dots Successive Ionic-Adsorption and Reaction method is commonly used to deposit metal sulphide onto a nanostructured film. CdS quantum dot was deposited onto titania using this method as described in [4]. The first precursor solution used is 0.05M cadmium nitrate (Cd(NO3)2) and the second precursor solution is 0.05M sodium sulphide (Na2S). The bare TiO2 paste is dipped onto the first precursor solution for one minute. The Cd2+ ions have been deposited onto the TiO2 surface. This is then rinsed in an ethanolic solution for one minute and dried under room temperature. It is then dipped in the anionic precursor for one minute and then rinsed in methanolic solution for one minute and allowed to dry at room temperature. This completes one deposition cycle of SILAR. In this work we have performed four deposition cycles of SILAR. III. RESULT AND DISCUSSION The CdS quantum dot was deposited on to the surface of TiO2. An obvious color change was observed during the deposition cycle which is shown in Fig.1. The color change was pale yellow to golden yellow. The characterization was done using XRD and UV-vis spectroscopy techniques. Fig 1: Photograph of glass slides with CdS coating with increasing SILAR cycles XRD Characterization Fig 2. shows the obtained XRD pattern for TiO2 (Fig.2a), TiO2/ CdS (Fig 2b.) . From the peak obtained, we confirm that CdS quantum dot was deposited onto the film. Since the peaks at 44.1à ¯Ã¢â‚¬Å¡Ã‚ °, 51.9à ¯Ã¢â‚¬Å¡Ã‚ °, 64.3à ¯Ã¢â‚¬Å¡Ã‚ °, 70.4à ¯Ã¢â‚¬Å¡Ã‚ ° and 72.9à ¯Ã¢â‚¬Å¡Ã‚ ° coincides with the intensity pattern as defined by the JCPDS 10-0454 for the CdS QD. The corresponding miller indices are (220), (311), (400), (331) and (420). From this we conclude that CdS QD was deposited. It belongs to the cubic crystal system and the mineral name is hawleyite. For TiO2 the XRD pattern exactly matches with JCPDS 21-1272. It belongs to tetragonal crystal system and its mineral name is anatase. Fig.2 : XRD pattern (a) TiO2 (b) TiO2/CdS Size Characterization The size characterization was done by non-contact mode AFM (Atomic Force Microscopy). The size of the CdS quantum dot was found to be 25.83nm. the thickness of the deposited layer was calculated to be 29.65nm. Fig 3. Fig 3 : AFM non-contact mode characterization of CdS quantum dot UV-vis Characterization The optical property was characterized using Jasco Spectrophotometer V670. The absorption spectrum is shown in Fig 4. The absorption spectrum for the TiO2 and CdS/TiO2 is shown in Fig 4a. and TiO2/CdS alone is shown in Fig.4b. The absorption peak for CdS is as reported by Antonio et.al [4]. From the absorption spectrum we could observe a shift in the peak indicating CdS QD is being deposited. The absorption peak was observed in the range of 386nm-484nm. For TiO2 the absorption peak was observed at 341nm. In Fig 4b. the inset is the absorption spectrum that was reported in [5] Fig 4: Absorption spectrum of (a) TiO2 and TiO2/CdS (b) TiO2/CdS Fig 5: UV-Vis absorption spectra showing increase (~49 %) in absorption due to CdS Figure 5. depicts the percentage increase in the absorption peak of CdS with respect to TiO2. It was calculated to be a 49.08% increase in the absorption peak. Determination of Optical Band gap The DRS (Diffuse Reflectance Spectroscopy) characterization was done to obtain the optical band gap. The optical band gap was calculated by plotting the Tauc plot . It is the plot between energy and absorbance. The optical band gap can be determined by Tauc relation Where à ¯Ã‚ Ã‚ ¡ is the absorption coefficient in cm-1, hà ¯Ã‚ Ã‚ ® is the photon energy in eV and A is a constant. The value of n is given as follows n =  ½ for direct allowed transition n = 2 for indirect allowed transition The Tauc plot for TiO2 and TiO2/CdS is shown in Fig 6. TiO2 is an indirect band gap material whereas CdS is a direct band gap semiconductor. The bandgap value of CdS in bulk is given as 2.42eV [5]. From the experiment we calculated the optical band gap to be 2.38eV. Also the absorbance value of the CdS QD is blue shifted. Using the equation The value of the peak was calculated to be 519.16nm which is within the absorption region. Fig 6. Tauc plot of (a) TiO2 (b)TiO2/CdS IV. CONCLUSION In this work CdS quantum dot have been synthesized using SILAR method. Its structural characterization was done that confirmed the deposition of the CdS quantum dot on to TiO2 paste. The optical property was characterized and analysed using UV-vis-NIR spectroscopy. The optical band gap was calculated to be 2.38 eV. The size of the quantum dot deposited was calculated to be in nanometer. REFERENCES [1] Prashant V Kamat , â€Å"Quantum dot Solar cells.The next Big Thing in Photovoltaics† J.Phys.Chem.Lett. 2013, 4, 908-918. [2] Chang Liu,Yitan Li,Lin Wei,Cuncun Wu,Yanxue Chen,Liangmo MeiandJun Jiao, â€Å"CdS quantum dot-sensitized solar cells based on nano-branched TiO2arrays† Nanoscale Research Letters 2014,9. [3] A. Berni, M. Mennig, H. Schmidt, â€Å"Doctor blade method†, Springer. [4] Antonio Braga,SixtoGimenez, Isabella Concina, Alberto Vomiero and Ivan Mora-Ser, â€Å"Panchromatic Sensitized Solar Cells Based on Metal Sulfide Quantum Dots Grown Directly on Nanostructured TiO2 Electrodes†, J. Phys. Chem. Lett. 2011, 2, 454–460. [5] B. T. Huy, Min-Ho Seo, Jae-Min Lim, Dong-Soo Shin and Yong-Ill Lee, â€Å"A Systematic Study on Preparing CdS Quantum Dots† Journal of the Korean Physical Society, Vol. 59, No. 5, November 2011, 3293-3299

Essay --

​William Faulkner began what would be an extensive exploration of his southern world of what he named Yoknapatawpha County (really the area of New Albany, Mississippi) with the short story â€Å"A Rose for Emily† in 1930.   At this point, Faulkner was 33 years old, having grown up in the smothering and genteel small town atmosphere he uses as the setting for this work.    On one level, this is the tragedy of one person who was stifled and pushed to a monstrous crime, while on a larger scale, the story is a metaphor for the way in which the Old South refused to come to terms with the 20th century and the new demands of American society.    ​The Civil War looms large over Jefferson, from the pride that the community takes in the battle that raged nearby to the graveyard full of honored dead and the very elderly men who still wear Confederate uniforms to funerals.   The town’s mayor uses the title â€Å"Colonel† Sartoris all his life, and it seems as if the war was a breaking point past which families like those of the Griersons just couldn’t get past, as if they were frozen in time.   The experience ...

The Contemporary Conflict of Values :: Morals Ethics Papers

The Contemporary Conflict of Values The conflict between values is the source of many conflicts and problems today. In contrast to the traditional conflict of values, the contemporary conflict is distinguished by these features: (1) extensiveness; (2) complicatedness; (3) profoundness; and (4) continuousness. The plurality and relativity of values is the primary cause of contemporary conflicts. The origin of pluralism lies in an interrelated trio of aspects: commodity economy, democratic politics, and individualism. The contemporary conflict of values is a historical process. Such conflict does not necessarily result in confusion; on the contrary, it can possibly lead to new and higher levels of harmony and vitality. In adjudicating value conflicts, we must (1) permit different values to coexist and respect different choices and the pursuits of values by different individuals; (2) consider the whole and the individual, the entire and the part, the long-term and the short-term, and attempt to have regard for both sides of the conflict; and (3) pursue the best and most suitable. 1. The conflict of values is not the unique phenomenon of our times but the common occurrence in both ancient and modern history. But the traditional conflict of values occurred largely in the moral realm, and its essence and focus lay in the conflict between individual and whole interests. In the premodern times there were also conflicts between various requirements of the same individual self, but this conflict was also moralized because personal life, either inner ideas or outeractions,were put into the scope of moral valuation. Furthermore, traditional morality was double-valued morality of good and evil, and only the requirements benefiting the whole or others was evaluated as moral. Therefore,the traditional conflict of values was in fact moral conflict between good and evil, and significance and function of morality just lay in adjusting and solving all those conflicts. Since the end of the 19th century,however,the conflict of values has become a universal phenomenon. In contrast with the traditional conflict of values, the contemporary conflict of values has four distinguishing charateristics: (1) Extensiveness. Contemporary society is a legalized society, whose greatest difference from moralized traditional society is that such society merely regulates the starting point, not all of people's action, and it does not regulate people's ideology. Thus in traditional society there was almost no possibility of choice in realms other than morality, while in contemporary society,in addition t law, there are many realms possible for people to choose, so that the conflict of values possibly may take place both in the legal realm and other realms.

A Journey into the Heart of American Adolescence

Teenagers will be teenagers.   Perhaps this is the best way to understand the lives of eight teenagers in Hersch’s (1999) book, A Tribe Apart: A Journey into the Heart of American Adolescence.   Although Hersch only writes about American teenagers, adolescents around the world may be able to relate to the eight kids interviewed by the author.They are naughty, to say the least, and their parents seem to have little or no interest in how they are leading or in fact ruining their lives.   The teenagers use illegal drugs, enjoy premarital sex, steal, get into trouble, and essentially do everything that they are most likely to do in the absence of adults from their lives.Adults have abused them through neglect or other means.   Hence, the young people do not have real models to follow.   Instead, they experiment with life so as to learn their own lessons before adulthood strikes.   Many of the lessons that such teenagers may learn will undoubtedly be painful if not plai n sad.It is clear to the reader of A Tribe Apart that these teenagers could have been saved from the difficulties they may inevitably face by following models of propriety.All the same, it is impossible to find such models when their parents are missing from home and out at work.   Teachers may not be able to fill in the gap seeing as it is the parents’ responsibility to teach morality to their kids for the latter to consider it believable.   After all, children are meant to spend more time with their parents than with their teachers.The teenagers of A Tribe Apart do not belong to poor families.   Researchers have often described adolescents from poor families who are neglected or abused by other means before they turn into drug addicts or thieves.Teenagers belonging to poor families are therefore believed by the masses to be morally degraded.   The unique fact about Hersch’s book is that all of the teenagers she has interviewed for her research belong to the h ealthy middle class.   Perhaps this makes it easier for adolescents around the globe to relate to the eight teenagers in her book.Most if not all teenagers may be considered ‘a tribe apart’ as the reader contemplates the fact that both the haves and the have-nots behave in similar ways through adolescence.   Indeed, teenagers belonging to poor families appear to be destroying their lives just like the adolescents interviewed by Hersch for her study.The good news is, however, that Hersch’s book could serve as a warning signal for parents who have neglected or abused their growing kids in other ways.   If parents do not take heed, their growing kids may very well shape themselves as adults that behave like their own parents.   Wealth does not matter in this case.   Rather, teenagers would remain as stereotypical teenagers – experimenting with adulthood in their youth.   They know no boundaries.They are always crossing their limits.   Most impor tantly, there is nobody to guide them out of their troubled existence.   Drugs and sex become the sole source of joy for them.   Thus, Hersch’s book is a wake up call that all parents must give serious thought to.   The fact that eight teenagers confided in Hersch must also be taken seriously.   It is possible for parents to honestly understand their kids.   Hersch has proved this with her research.

Child Labor in India Essay

As a group we choose the topic of Child labor in India, and I am responsible to cover the Sexual exploitation of children’s in this country. My colleagues Olivier Turcotte and Frederic Lamoureux are going to cover others part of the child labor such as the industry labor and why those kids have to work instead of going at school. The objective of our project is to aware people of this reality of the world that medias don’t talk too much about and is kind of taboo. The child labor is something that not much of people are aware or concern about it because they don’t see it , but if we think about it, maybe the t-shirt, the shoes, or even what we eat have been pack by a kid from another country that is only 8 years old and work 30 hours or more per week. In relation with our topic, I will focus on the Sex labor that children are involved and abuse. This illegal activity that has reached a critical level in South Asia, is something that people are not really consciou s about and this is why we need to aware our generation to be less selfish and think about all those that don’t have the same luck to have a happy childhood. Well , about the kiosk, we start having some ideas about the material we will use , like posters and things like that but also we will try to reach association that protect or fight against the companies that abuse of children’s. References Carson, D. K., Foster, J. M., & Tripathi, N. (2013). Child sexual abuse in India: Current issues and research. Psychological Studies, 58(3), 318-325. This article discusses the nature and incidence of the sexual abuse of minors in India and presents an overview of research findings to date. Bandyopadhyay, R. (2012). Child-Sex Tourism, HIV/AIDS, and Social Justice in India. Peace Review, 24(2), 143-146. doi:10.1080/10402659.2012.677320 The article discusses the issues of child-sex tourism, human immunodeficiency virus/acquired immune deficiency syndrome and social justice in India. Jaishankar, K., & Haldar, D. (2006). Prostitution in India: Issues and trends. ERCES Online Quarterly Review, 3(2) Retrieved from http://www.ubishops.ca:2048/docview/61624615?accountid=8636 This paper discusses about prostitution in India that is a serious social problem and its solution has been rendered difficult by the problem of poverty. Prostitution is widely rampant in India and its main markets are i n the big cities and involves children’s prostitution. Joffres, C., Mills, E., Joffres, M., Khanna, T., Walia, H., & Grund, D. (2008). Sexual slavery without borders: trafficking for commercial sexual exploitation in India. International Journal For Equity In Health, 71-11. doi:10.1186/1475-9276-7-22 This paper presents an overview of the trafficking of women and girls for sexual exploitation in India also identifies the health impacts and suggest strategies to respond to trafficking and related issues Ray, N. (2007). Wither Childhood? Child Trafficking in India. Social Development Issues, 29(3), 72-83. This article reviews the current research on domestic trafficking of children in India. Child trafficking in India is a highly visible reality. Children are being sold for sexual and labor exploitation, adoption, and organ harvesting. Sathyanarayana, T. N., & Babu, G. R. (2012).