Literature Review Of Load Shedding Methods

Literature Review Of Load withdraw MethodsIn chapter 1, a brief discussion about active dispersal networks was presented. The importance of effect of islanded dispersion networks was discussed. This chapter is intended to give the reader a better downstairsstanding of the turn on contriveding dusts lively applied and proposed over the years. However, it is assumed that the reader is known with basic power st scoregy engineering.In branch 2.2, the bea of probability of islanding and the need for shoot down throw off is discussed. To achieve this objective, existing reduce withdraw manners atomic number 18 reviewed to understand their working principle, requirements, advantages and limitations. The main categories identified ar the following (i) Manual / SCADA Load cast off (ii) Load Shedding utilize thresholds, (iii) Adaptive Load Shedding, (iv) smart as a whip Load Shedding and (v) Load Shedding Based on Static Optimisation which are expound and discussed i n sections 2.2 through 2.7 respectively. Finally a thick is presumption in section 2.8 from which a new turn on shake off method for an islanded distribution network able to address the limitations of existing methods leave alone be proposed.probability of islandingThere is by now a considerable derive of literature on weight shedding. That most of the literature however deals with large merged strategys. For smaller systems when a loss of mains / grid event occurs the islanded distribution network have different operating marks and restrictions that require different fill up shedding guidelines. These are due to the low inertia of the distributed generators, the limited spinning reserve and limited communication systems 0 0. Load shedding is a practice utilise power system and serves as a perish to try to arrest any relative relative absolute frequency or potential drop when a charge isolating part of the distribution network occurs.Faults in power systems are ine vitable, for various reasons such as adverse weather checks, ageing and failure of equipment, accident, and animal contact. In general, faults happen when an brachydactylic physical contact occurs between lines or on lines to earth that create a short-circuit itinerary. If the system is not well protected, the high fault current due to the short-circuit path usher out cause damage to the equipment in the system. Faults also affect the reliability and quality of the power supply, leading to power recess by frequency and potential difference dispel and potency sag events. Regardless of the interruption period, the losses are often enormous both to the customers and power public utility company companies.There are two types of fault, determined by the physical nature of the short-circuit path temporary or permanent. Common causes of temporary faults on crash lines are lightning strike resulting in a flashover of the insulator bird or animal contact and momentary contact due to wind or trees. Faults caused by these events exist for a very short period of duration. On the other hand, a permanent fault stay ons in the system until the short-circuit path is removed. Common causes of permanent faults in power system networks are cable insulation failure, objects falling on the overhead lines, dirt on insulators and lines falling to the ground.When faults occur, a protection device ope browses to isolate the faulty line from the rest of the system (loss of mains / grid). The generators designated to provide voltage and frequency control will answer to control the island voltage and frequency. In severalise to achieve smooth transition to island operation, the generators must initiatoryly ride through the fault or failure and secondly act to counterbalance the active and reactive power in the islanded network. With a carefully designed bill shedding method the operation of the islanded distribution network readiness be manageable. It is important howe ver that the design of the blame shedding method is designed on the understanding of the characteristics of the system involved, including system topology and kinetic characteristics of its generation and load. A poorly design method whitethorn be ineffective and eventually lead to total customer interruption.Over the years, however, utility experience and extensive studies on a come in of systems have resulted in different methods guidelines. In the following section, principles and guidelines for load shedding methods are reviewed.manual / SCada Load SheddingManual or operator initiated load shedding 0 is not a dependable method to be used to avoid frequency deviation. However it ordure be used by some utilities to manually shed load or open ties (interconnectors) with adjacent areas at a frequencies below impulsive underfrequency thresholds. This type of action great poweriness be necessary to prevent any further frequency deviation and to recover the frequency back to t he nominal value. This load shedding intrigue cannot be used for the islanded distribution network as it will be very retard as the frequency and voltage in the network will collapse within few seconds making it impossible for the operator to decide the correct defence action compulsory for safe operation.automatic Load Shedding utilise thresholdsAn automatic load shedding for infection system using different schemes such as underfrequency, undervoltage and combinations of the two can be utilise to avoid frequency or voltage collapse during a significant asymmetry between generation and load. These types of load shedding methods are very dependant on shoot line studies of the systems dynamic performance and only consider the greatest probable imbalance between generation and load. These methods have to be coordinated with the protections of the generating units, shunt capacitors and other automatic actions that occur in the system during frequency and voltage variations.Unde rfrequency load SheddingThe underfrequency load shedding scheme as explained in the following text file 0 0 uses relays detecting the systems frequency. These are designed to operate on the instantaneous frequency value where they trip when the frequency drops below the set point of the relay. The shedding is utter(a) in the systems distribution or transmission stations where major load bird feeders can be controlled by tripping of the circuit breakers (CB) automatically. Different desktops can be applied in these load shedding schemes.Multiple stages can be used in the scheme 0. The substation loads can prioritised and grouped harmonise to the importance of the load. The relays can be set to control one or more groups of loads and when there is a frequency drop these can be disconnected sequentially where the group with the highest probability being disconnected the last. Each group disconnected should contribute to the system rate of shift of frequency regrets. If the load to be disconnected is small compared to the overall imbalance then the contribution will be insignificant and would cause further problems to the systems frequency decline.Another setting usual for this type of scheme is the time hold water 0. The time may can be required and used usually to avoid any frequency transient dips that could arise in the system. The time delay also avoids surplus load shedding by allowing the load / frequency controls in the system to respond to the frequency deviation. However load shedding performed with long time delays should be set appropriately as it will pay off the system more undefendable to system perceptual constancy if eventually load shedding is required. This method will work adequate in a situation where the system frequency decline is slow.For example, as discussed in 0, in the UK as stated in the NationalGrids GridCode each transmission area has to disconnect a set apartd percentage of the peak shoot for away that each Network O perator whose system is connected to the GB Transmission ashes shall disconnect by low frequency relays at a figure of speech of frequencies. The defined frequencies and the add up of loads are given in dishearten 1 -1.Table 11 Load Shedding Scheme sedulous in the UKFrequency (Hz)% Demand disconnection for eachNetwork Operator in Transmission AreaNGETSPTSHETL48.8548.75548.71048.67.51048.57.51048.47.5101048.348.27.5101048.05101047.85Total % Demand604040The percentages in Table 1 -1 are cumulative such that, for example, should the frequency fall to 48.6 Hz in the NGET Transmission Area, 27.5% of the total Demand connected to the GB Transmission System in the NGET Transmission Area shall be disconnected by the action of low frequency relays.A significant drawback of this method is that the systems frequency must be already be low before the relay can operate which can delay the load shedding action and the frequency recovery of the system. additionally these types of schemes usu ally shed more than the required amount of load.Undervoltage load SheddingUndrevoltage load shedding method has been successfully deployed in transmission systems to protect them from voltage collapse 0 0. System studies are required to determine which systems are potential candidates for suitable the undervoltage load shedding method. This method is most useful in slow decaying systems where the undervoltage load shedding relay time relays can coordinated accordingly and operate to alleviate the system from overload conditions and low voltages.Voltage collapse can be studied using steady state simulations for the identified areas using a power flow analysis. System planning engineers conduct numerous studies using P-V and Q-V as well as other analytical methods to determine the amount of load required to be shed to preserve voltage stability under different disturbances.Dynamic simulations can then determine the speed of the collapse and load shedding settings.An example as discus sed in 0 in the US in the Puget Sound area, which is prone to voltage collapse has been studied. The voltage trip thresholds were determined from the results of steady state simulations of worst contingencies. The time delays for the relays were coordinated to address control actions of the automatic capacitor switching, generator limits, on load tap changing transformer using dynamic simulations.Table 12 Load Shedding Scheme employed in the USVoltage (pu)Time delay (s)% Demand disconnection forNetwork Operator in Transmission Area0.903.550.925.050.928.05When the monitored bus voltages fall to 0.90 pu or glower for a minimum of 3.5 s then 5% of the load is disconnected. Additionally other 5% of load disconnection should occur when the voltage falls to 0.92 pu or lower for 5.0 s.There limitation associated with proper application of undervoltage load shedding is the location of its application.to where the relaying may be appropriately applied. If it is placed on a distribution lin e the effects of auto tap changers mask a system overload condition from the relay, or alternatively a line switching operation or the startup of a large industrial plant on one feeder could fool the relay. The relay would not be appropriate at locations directly adjacent to generation powerful enough to control bus voltages even during terrible overloads. The relay is best applied to locations with fairly stiff voltages under all normal conditions, so a low voltage condition will reliably indicate a severe overload condition, as may be assumed to be the case at large substations associated with bulk power transmission lines and therefore this method cannot be effectively applied in islanded distribution networks where DG unit power and load guide varies.combination load SheddingIn order to increase the security of the above discussed methods for underfrequency load shedding the relay could be set up to supervise the voltage, the current or the rate of change of frequency. Accord ing to their combined settings, the relay could either be blocked or initiate tripping of the CB to avoid any misoperations.One combination load shedding scheme is to use an underfrequency load shedding relay with voltage supervision. Basically the operation procedure of load shedding is blocked from operating unless the voltage is below a given threshold. The underfrequency relay will be able to trip the CB as long as the bus voltage it is supervise is lower than a set point.Another combination is to use current supervision instead of the voltage. The purpose of the current supervision is to select which feeders to trip. This can achieved by monitoring which feeders are loaded above a legitimate point and then the relay will initiate the load shedding signal.An alternative is to use the rate of change of frequency for supervision 0 0. During a disturbance the supervision of the rate of change of frequency can block the tripping for very fast frequency changes but would allow for typical frequency decay rates. besides instead of touchstone the instantaneous rate of change of frequency supervision is to use the frequency change trend. In other words by monitoring the average rate of frequency change will provide a more steady-going decision for tripping during disturbances. The load shedding decision of the scheme is made by monitoring the frequency change over a specified amount of time usually few hundred milli seconds. Therefore making the operation of the relay slower than the ones employing the rate of change of frequency.automatic ADAPTIve Load SheddingAdaptive control involves updating the amount of load to shed used by the method to cope with the fact that the conditions such as the power imbalance between generation and load of the system are time-varying or uncertain. It is important in these circumstances to minimise consumer disruption through proper design of the load shedding arrangements. An adaptive load shedding, is based on the relays re acting to a disturbance either by being instructed the amount to shed or by having certain defined criteria based on the rate of change of frequency.Anderson and Mirteydar in 0 present an adaptive methodology for setting of underfrequency relays that is based on the initial rate of change of frequency at the relay. The frequency performance of the islanded is represented by a linear system frequency response as shown in Figure 1 -1 and presented in more detail in the literature in 0.Figure 11 Simplified frequency response with disturbance inputwhereH= inertia aeonian (s)FH= fraction of total power generated by HP turbineTR= reheat time constant (s)Km= mechanical power gain computeR= droop characteristic (pu)D= damping factorClearly the only observe quantity that gives any clue as to the size of the disturbance is the initial slope of frequency decline.The use of the initial slope to estimate the magnitude of the disturbance requires that every substation in the island will observ e slightly different slopes and will therefore shed load based on different estimates of the disturbance. However on average the system as a whole will shed approximately the correct amount of load.To set the line of reasonings for the relays as explained they are based on a simulation of the frequency response for the system. In the example given (H = 3.5 s, FH = 0.3, TR = 8.0 s, Km = 0.85, R = 0.06 and D = 1) the evaluation of the frequency and its slope against different amounts of disturbances are given in Table 1 -3.Table 13 Initial Slope and Maximum Deviation vs Upset (frequency nominal 60 Hz)Pstepdf/dfmaxfminpupu/sHz/sHzHz-0.2-0.0286-1.7143-1.643858.356-0.3648-0.0521-3.1260-3.000057.000-0.4-0.0571-3.4286-3.287656.712-0.6-0.0857-5.1429-4.931355.069-0.8-0.1143-6.8571-6.575153.425-1.0-0.1429-8.5714-8.218951.781The lowest frequency permitted in the system is 57 Hz from the nominal 60 Hz. Therefore when a magnitude greater than -0.0521 pu/s is observed load shedding must be trigg ered.This method relies on the fact that the amount of load shedding is a function of only the inertia constant and the observed slope. The inertia constant is the rotating kinetic energy of all units in the island divided by the total connected volt ampere rating of the units. This parameter has to be estimated. Therefore, the initial slope is the only unknown. The load shedding amount is computed in per unit, which makes it easy to apply to every load and to every load shedding relay.A positive is that communication is not required between relays and the boundaries of the island are not required to be known. However the drawbacks are that if it is applied for the islanding application of islanded networks this might not be possible as the method needs good estimates of the inertia of the system D, R, TR, Km and FH. This can significantly change with the varying DG units and loads in the distribution network.Another adaptive load shedding method presented by Terzija in 0 uses simil arly as the previous method a variation of the typical swing equation. Due to the dynamic responses of turbines, governors, other control actions, spinning reserve, loads are not taken in account in the calculation of the required amount of load to be shed as given in .Where H is the inertia constants and assumed to be known in advance to the disturbance. The adaptive barbel is based on real time estimation of fc (frequency of equivalent inertial centre) which is proposed to be calculated centrally by measuring the local frequencies at each generator.The proposed method assumes that the time constants in the power system are large and with modern communication this method would be possible for big power systems. However in distribution networks communication is believed not to change drastically in the near future making this application operose to implement. This is because the estimation and control information are evaluated after the disturbance occurred.Van Cutsem and Otomega proposed a method in 0 which relies on a set of load shedding controls distributed over the region susceptible to voltage instability. Each controller monitors the bus voltage and act on a set of loads located at that bus. Each controller acts when its monitored voltage falls below some threshold and trips at different time according the severity of the drop. The action can be repeated until the voltage is above the threshold voltage.The principle of operation of the controller is described as follows.The delay depends on the time evolution of V as follows.A block of load is shed at a time t0 + such thatwhere C is a constant to be adjusted. This control law yields an inverse-time characteristic the deeper the voltage drops, the less time it takes to reach the value C and, hence, the faster the shedding. The larger C, the more time it takes for the integral to reach this value and hence, the slower the action.Furthermore, the delay is lower boundedto prevent the controller from rea cting on a nearby fault. Indeed, in normal situations time must be left for the protections to clear the fault and the voltage to recover to normal values.Similarly, the amount Psh of power shed at time t0 + depends on the time evolution of V throughwhere K is another constant to be adjusted, and Vav is the average voltage drop over the t0, t0 + interval, i.e.,Moreover, the whole system will tend to shed first where voltages drop the most. This location changes with the disturbance. Hence, the proposed scheme automatically adjusts the shedding location to the disturbance it faces. Note that the above features are achieved without resorting to a dedicated communication network. The controllers do not exchange information, but are rather informed of their respective actions through the power system itself.The drawback for this method for distribution network is that the tuning which consists of choosing the best values for Vth, C and K. A C and K combination suitable can be identifie d by minimising the total load shedding over all disturbance scenarios. Clearly this method would shed more loads for some scenarios. An additional concern is that the dynamic performance of the DG units and loads is not taken in account when acting load shedding if applied to the islanded distribution network and by trying to shed in steps the frequency drop in the network might drop significantly.automatic Intelligent Load SheddingApplications of intelligent load shedding in power system engineering (e.g. familial algorithms, artificial flighty networks, MonteCarlo etc.) have been demonstrated in 0 0. The characteristics which are inherent to intelligent methods, such as the ability to learn and generalization make it feasible for applications such as load shedding.You et al. in 0 discuss of a method that uses the rate of change of frequency to load shed. The method uses the same approach to calculate the required amount of load as in 0 and at the same time, the conventional lo ad shedding method with undefrequency thresholds is incorporated to form a new two level load shedding method.The conventional load shedding method has longer time delays and lower frequency thresholds which can be used to prevent unnecessary load shedding in response to small disturbances. If the disturbance is large, the second layer will be activated and a block signal to the first layer is enabled. The second layer based on the rate of change of frequency load shedding will shed more load promptly at the early stage of the disturbance.Similarly as to paper 0, this method will have the same limitations when applied to the islanded distribution network. In the paper 0 which follows this study, the comment of the selection of the settings for the relays is discussed. Agent technology is to try to assure that the method will withstand all possible disturbances. Traditionally after a major disturbance, the system is revisited and settings of devices and control actions are changed so that the system will withstand the same disturbance in the future. This however due to analysis of the system significant time and cost will be required.For the autonomous and adaptive learning capableness for the operators, the reinforcement learning technique is used. Reinforcement learning is learning by interaction.The agent tries actions on its environment and then, the tendencies of taking particular actions are reinforced by receiving scalar evaluations of its actions. Thus determining the amount of load to be shed required to avoid collapse.The paper does not discuss whether the technique is applied online or offline through simulation. Clearly for the online this would not be ideal as it will take a lot of number of failures until the agents are properly set for that particular disturbance. For the offline simulation a concern is that for islanded distribution networks the topology, DG unit power and load demand will change thus making the decision of the action of the agents is difficult to train. Another concern is communication between agents. Fast communication would be required for coordinated decisions.Another approach to load shedding is the use of fuzzy expert system and is described in 0. In this paper Sallam and Khafaga described a method to control the voltage instability by load shedding using fuzzy technique as fuzzy controller.The operation of the method relies on the experts knowledge which is expressed by language containing ambiguous or fuzzy description. The aim of this study is to design and analyse a fuzzy controller for the study to control against load and voltage instability by calculating the optimum load shedding as output.Similarly in 0 the authors propose genetic algorithms for the optimum selection of load shedding. These techniques search and optimise the amount of load shedding using objectives and constrains required for a practical load shedding method.Also in 0 the authors realize another technique using the arti ficial neural networks is presented. To prepare the training data set for the artificial neural network, transient stability analysis of the power system is required and to find the minimum load shedding for various scenarios. By selecting the total power generation, total load demand and frequency decay rate as the input neurons for the method, the minimum of load shedding is determined to maintain the stability of the power system.In paper 0 Thalassinakis and Dialynas introduce a computational method using MonteCarlo simulation approach for the calculation of the settings of the underfrequency load shedding relays is discussed. The frequency performance as previously discussed in section 1.5 is used here as well. The strategy for the relay settings will be determined against amount of load to shed, time delay, rate of change of frequency and underfrequency level. A new strategy is developed by changing these settings. The MonteCarlo then computes the system through reliability ind ices of generating units, the system frequency and load shedding indices.load shedding based on still optimisationThe first theory of applying load shedding using an on line dynamic simulation of the power system network was introduced by La Scala et al. 0. Followed by an improvement of the method combing a control action to attend angle and voltage stability sweetening in 0. The first paper that introduced the same concept applied for large power systems to the smaller distribution network is described in 0 by Nelson and Aponte. A more recent study using similar technique is also presented in 0.The paper presented in 0 describes the philosophy and the implementation of a preventive load shedding control algorithm for the application in dynamic security assessment. The methodology is based on nonlinear programming techniques, for assessing control actions to guarantee the dynamic security of power systems. The basic idea is that the online dynamic preventive control can be seen a s a static optimisation problem with minimising function and comparability and inequality constrains. The equality constrains consist in the discretisation at each time step of the differential algebraic set of equations representing the power system. The inequality constrains define a domain where the system trajectories should be contained in order to satisfy the requirements for the system performance stability and steady state voltage dips.In 0 the reflexion includes corrective actions based on load shedding. The proposed method assumes that the analysis is performed to detect particular disturbances threatening the dynamic security of the system. The analysis is based suing the n-1 rule which is performed in advanced and applying the results immediately after the detected contingency. Each analysis has its associated strategies consisting with the corresponding amount of load to be shed at a fixed number of controlled nodes. The optimisation however is evaluated based on the steady state values of angle, voltage and active power (generator and load). Load shedding based on static optimisation performs load flow to calculate the initial P, V for all the nodes in the system. Then the method performs a transient simulation assessment to ensure the system is stable against angle and voltage. Followed by an approach to the minimisation of a function in presence of equality and inequality constrains consist in incorporating the inequalities in the cost function by adopting the penalty factor method and treating the whole problem as a minimisation in presence of the sole equality constrains by the use of Lagrange multipliers.This method has been used for synchronous generators in transmission systems. However in distribution networks because of the diversity of the generators and their ride through capability this approach could result in conditions where optimised solutions do not meet the requirements as shown in Figure 1 -2 0.Figure 12 Ride through capabili ty of Generating Unit, DC Converter or Power Park Modules.Explanation of graph required.Each Generating Unit, DC Converter or Power Park Module shall remain transiently stable and connected to the system without tripping. However for small generating units connected in the distribution network their transient behaviour could be as shown in Figure 1 -2 b and c where local protection and circuit breaker operation of generators or sensitive equipment will be disconnected after such a response. Similar to the voltage is for the frequency range.Therefore the load flow with corrective control for angle and voltage stability approach for the load shedding optimisation is not appropriate for distribution networks.In 0 and 0 describe of a method implemented in distribution networks where not only the amount of load shedding is optimised but also the time for the disconnection. The current trend is to apply the corrective measures as soon as possible or slow for the sake of event discriminat ion. The study and results however show that when the corrective action is applied at the optimal time increased damping and enhanced response are observed.summaryThe use of load shedding as a tool to keep the network stable has been constantly evolving, and different approaches have been formulated. Relaying schemes like underfrequency and ROCOF 0 0 are some examples of the mechanisms implemented to trigger a load shedding event. Typical load shedding schemes based on predefined threshold set points is quick, simple and reliable measure against system disturbance. When the frequency of the system reaches a specified threshold value, a time delay is inserted prior to the shedding action in order to avoid overshedding and assist the coordination of the next stage of load shedding action. This technique however when adopted for the islanded operation of small distribution networks would have several disadvantages. as well few frequency levels could lead to overshedding, but on the ot her hand, time delays between stages could add up and may not allow for enough load to be shed in time to re-establish nominal frequency.The implementation of ROCOF techniques mitigates some of these problems. The ROCOF value calculation is an immediate indicator of the power imbalance but for the distribution network the variation of the DG units operation would make this measurement unreliable. Also the average ROCOF calculation may take too long and eventually make the load shedding method slow in operation. Even if accurate measure of the islanded distribution network ROCOF valu

Preparation of Recrystallization of Aspirin

Preparation of Recrystallization of Aspirin1. SynopsisThis experiment serves 2 objectives the p gatuction of Aspirin from esterification of salicylic acid with excess acetic anhydride and obtaining it in a purer plead by recrystallisation, hence determines the melting point of the acetylsalicylic acid (ASA) that was synthesised and purified.To gain this, salicylic acid is reacted with excess acetic anhydride in the bearing of the sulphuric acid as the catalyst, which produces precipitant ASA and aqueous acetic acid. I applied suction filtration to collect the ASA as the resi delinquent having acetic acid as the filtrate.Pure aspirin is a whiten crystalline warm. The aspirin initially produced by synthesis may be light tan, indicating the presence of impurities. The ASA synthesis earlier is purified by recrystallization. In recrystallization, the impure fast(a) is fade out in a hot solvent (aqueous ethanol) and the resulting solution is allowed to cool slowly. As the solution cools, crystals of the product get out course of instruction and soluble impurities will watch in solution.From this experiment, the voice yield of ASA is around 49%, using capillary test the melting point of ASA falls in the rage of 137.9-140.5 0 C. The expression of ASA is an odourless, white, needle-shaped and shiny solid. In conclusion, experiment is a success. Despite product had a low percent yield and was found to be impure payable to its low melting point.2. IntroductionAspirin is the trade name for the molecule acetylsalicylic acid.The earliest known habituate of this molecule has been traced back to the fifth century B.C. The setical physician Hippocrates described an extract of willow tree talk, a bitter powder that could be used to reduce fevers. In 1829, Salicin was isolated from willow bark and used as a pain reliever. Unfortunately Salicin was not very popular since it was found to be very acidic and a stomach irritant.In 1897 Felix Hoffman, a German chemist , was working for the Bayer chemical comp any(prenominal). Hoffman wanted to formulate for a less acidic pain reliever as his father could take in for his arthritis. His studies led to the synthesis of acetylsalicylic acid (ASA) or aspirin. Bayer patented the name and commenced to market the product in 1899. It was a huge success and sales grew rapidly. In fact, the company set up by Friedrich Bayer Company is generally considered to dedicate been the first pharmaceutical company, and the production of aspirin has indisputably laid the base of the new-made pharmaceutical industry.Only until the 1970s that scientists starts to comprehend the concept on how aspirin function as a pain reliever. Today 80 billion aspirin tablets are taken every year over the al the countries to reduce fevers, relieve pain, and even help prevent heart attacks. Bayer In mercenary aspirin products, a small amount of ASA (300 to 400 mg) is bound together with a starch binder and sometimes caffeine and b uffers to make an aspirin tablet. The sancti superstard conditions in the small intestine break down the ASA to yield salicylic acid, which is absorbed into the bloodstream. The addition of a buffer reduces the irritation caused by the carboxylic acid free radical of the aspirin molecule.3. TheoryEsters are organic compounds with the general formula RCOOR, where R and R basin be an alkyl group or an aromatic group. alkyl radical group is an alkane that is short of one hydrogen since it needs one bond to be branched from the parent chain. Aromatic compounds are a class of molecules containing benzene, a six-membered carbon rings with delocalized pi electrons. This type of group is found in salicyclic acid and ASA.Esters are readily synthesized by the reaction mingled with a carboxylic acid, RCOOH, and an alcohol, ROH, as shown in the following reaction.The reaction above is in addition known as esterification. It is a condensation reaction, whereby two molecules combine to for m one single molecule, while removing a small molecule (e.g. H2O) in the process.The reaction to I hurl used synthesis ASA is very similar to the one above. Salicylic acid a phenol consisting of a phenyl bonded to the hydroxyl (-OH) which is very much alike to alcohol and aceticAnhydride is a dehydrated carboxylic acid (acetic acid). In the below reaction we use concentrated sulphuric acid as the catalyst. After the warm bath to complete the reaction, we added cold water to quench the reaction (hydrolysis of acetic anhydride) to prevent further reaction to take place. The cold water must be added quickly as to allow fast crystal formations cod to the drastic drop in temperature. Stir and rub the walls can create uneven surfaces hence inducing crystallization. ).As such, in this experiment, 2.4 grams of salicylic acid should yield 3.13 grams of Aspirin, it is tell that acetic anhydride is in excess. This is proven by the following calculationMol of salicylic acid in this experimen t2.4(2d.p)/138 = 0.0174 (3 s.f.)Mol of salicylic acid Mol of Aspirin1 1Therefore, Mol of Aspirin0.0174/1 x 1 = 0.0174 (3 s.f.)Expected mass of Aspirin0.017391 x 180 = 3.130 (3 dec.)The solid ASA formed contains impurities and should be recrystallised to achieve a purer state. Recrystallization is possible because most solids are more soluble in hot solvents than in cold solvents.The solubility of ASA increases as temperature increases. This means that if aspirin is push asided in ethanol to produce a saturated solution and that solution is cooled, the aspirin will crystallize during the cooling.Ethanol has been chosen as the solvent because the icy nature of the hydroxyl group causes ethanol to dissolve many ionic compounds, moreover the ethanol molecule also has a non-polar end, and it will also dissolve non-polar substances.While cooling, crystallization takes place. In crystallization, there is a slow, selective formation of the crystal framework resulting in a pure compound. Instead in precipitation, due to the rapid formation it will trap impurities in the solids crystal framework. For this reason, we should include crystallization to get a purer solid substance.The alternate way of synthesising the aspirin can be produced by replacing the acetylating agent from acetic anhydride to an even more acidic acid known as acetyl chloride CH3COCl. This can increase the percentage yield of ASA, since acetyl chloride is more acidic. The reaction of acetyl chloride with salicylic acid is showed below. However, the by-product is hydrochloric acid (HCl) instead of acetic acid.However, Acetic anhydride is preferred because it is less hazardous to use and less expensive than acetyl chloride. In industry, the acetic acid produced in this reaction can be recovered and converted back into acetic anhydride by the process known as dehydrationWe may also create or Salicylic acid from Kolbes reaction whereby we start with a phenol4. Procedure nearly 2.4 grams of salicylic acid is weighed and placed in a dry, 100ml conical flask.6ml of acetic anhydride is added into the same conical flask, along with 3-4 drops of concentrated H2SO4 as catalyst.The conical flask is consequently heat up at 80-100 degree C in a water bath for 10 to 15 proceedings to hasten the reaction.1ml of distilled H2O is added into the conical flask right off after it is removed from water bath.40ml of cold distilled H2O is then added to the conical flask.A stirring rod is used to gently rub the side of the conical flask. This is to scratch off crystals which have formed.Suction filtration is then carried out to remove the crystals from the solution.The crystals are removed from the perk paper. To ensure accuracy, cold distilled H2O is used to slipstream away remaining crystals from the click paper.The crystals are then dissolved in 5ml of ethanol.30ml of hot, distilled H2O is added into the solution, and slowly cooled.Crystallisation of Aspirin will take place as the soluti on is cooled to room temperature.Suction filtration is done to remove the Aspirin from the solution. The residue is then placed on a watch glass along with the filter paper.Aspirin is then dried by placing it in the oven for 20 minutes, along with the watch glass and filter paper.It will then be transferred to the desiccators for 15 minutes to further dry it.The crystals remained on the filter paper would be pure, dry, Aspirin.The following measurements are takenActual pitch of salicylic acid is weighed at (1).Weight of filter paper and watch glass is taken.Weight of Aspirin, along with watch glass and filter paper, is taken after (15).After obtaining Aspirin, the melting point of Aspirin is then determined using the capillary method.5. Results and Calculation citizenryMass of salicylic acid (a) = 2.39 gMass of filter paper watch glass (b) = 33.11 gMass of dried, recrystallised aspirin, filter paper watch glass (c) = 34.64 gMass of dried, recrystallised aspirin (d) = (c) (b)= 34 .64-33.11= 1.53 gPercent yieldNumber of moles of salicylic acid used (e) = 0.0173 mol(Molecular weight of salicylic acid = 138)Expected number of moles of aspirin (f) = 0.0173 molExpected mass of aspirin (g) = 3.12 g(Molecular weight = 180)Melting pointTemperature range 137.9-140.5C airNeedle shaped, white, and shiny.6. DiscussionMy percentage yield ASA is relatively low since it is only 49%. This may occur due to several factorsWhile transferring the salicylic acid, some of the solid may stay at the side of the conical flask and even your spactula, and resulting in lesser salicylic acid participating in the process of esterification compared to what have been weighed earlier. Thus, this will result in lower yield of the crystal ASA. It will be advisable to wash the walls with distilled water to ensure more salicylic acid will put down in the reaction.When dissolving the initial amount of salicylic acid in the solution of acetic anhydride and concentrated sulphuric acid, it did not completely dissolve into the solution, even when it was heated. This could have a slight impact on the results of the overall yield of aspirin because it was possible that not all of the salicylic acid was synthesized. To determine if this affected the synthesis of aspirin at all, the experiment should have been ran a second time to see if the same thing occurred. The iron (III) chloride test also could have been ran to determine if any of the aspirin degraded to salicylic acid or never converted from salicylic acid.During the suction filtration we should rinse the solid ASA formed in the conical flask and the glass rod during the synthesis before pouring into the Bchner funnel repeatedly. After the final suction filtration, another error causes the percentage yield to drop. This is due to the crystals not be fully collected on the filter paper, but rather, remains on the side of the Buchner funnel. This loss can be minimized by the crystals from the side of the Bchner funnel to t he filter paper moving using a metal spatula before collecting the filter paper and placing it on the watch glass.During recrystallization, one roughhewn error of adding too much solvent (ethanol) will result in less percentage yield while cooling. We should refrain from moving or faulting the solution while it is cooling as it will interrupt the crystal formation since the particles are generally held by weak dispersion forces, dipole-dipole forces, and hydrogen bond. We should also allow slow crystal formation as fast crystal formation will cause the trap of impurities and giving higher percentage yield.With the presence of impurities the melting point will decrease and vary in a larger range.7. ConclusionIn conclusion, the experiment is a success since I have managed to synthesis and recrystallise the ASA although we have relatively low percentage yield of 49% that may arise due to several factors as stated in the discussion. I was able to analysis the melting point of the recr ystallised aspirin and it is generally low in temperature which implies the presence of impurities.

Life Is Beautiful Movie Analysis Film Studies Essay

Life Is Beautiful Movie Analysis Film Studies EssayWhen a symbol is displayed people react to it according to how they have seen that symbol before. This is explained with Saussures possible action of the sign where the sign/ symbol has a portrayed meaning that is conveyed and carried with it. Through the lend oneself of Signifier and Signified people constantly (without noticing) see signs and relate to them without genuinely paying too much attention to the message that sign has to give. If the sign does not have an item/symbol within it that goes against their own unconscious fellowship of that sign therefore they will not notice it. Roberto Benigni uses Saussures theory of the sign to convey Guidos sudden realisation that taking a shower ultimately core death he comes to this conclusion through noticing that only the children and the old be universe sent to the showers and not the fit, because they are not fit to work they are being s oddment to the showers to be removed a s a problem. Through the subtle use of Saussures theory of the sign the master(prenominal) character Guido is seen as relieve his son from the harshness of the concentration camp for the first time during the movie.Through the use of ideal / fantasy worlds one can escape the harsh candor of the world.Guido creates fictitious worlds. He calls Dora princess and claims to be a prince himself. Though they both know the truth, they both are more than willing to entertain the fantasy and play the venture. In this way, Guidos fictions are a form of escapism, a way for him to cope with reality and imbue it with beauty. Guido also cultivates a series of coincidences so that he can bet to have manipulated fate or performed magic. Though he knows that he is simply manipulating someone else, he is not reveling in the deception he is inte watched in creating another world for someone else. This underscores the idea that a persons perception is intrinsic to his reality. Guido changes the way those around him perceive the world with his manipulations, and thus he affects how they deal with the rest of the world. When Guido rides up on a horse to rescue Dora, he is entertaining the fantasy of the knight rescuing the damsel in distress. However, he really is rescuing her from her surroundings and actually is whisking her away on a horse. Similarly, when he tells Giosue that everything in the concentration camp is a game, he is creating a fiction to keep Giosues spirits up. However, at the end of the film, Giosue has survived the concentration camp with perseverance and bravery, and his life and the lessons he has learned are very real. In Life is Beautiful, it appears, fantasy can become reality. Through the use of fantasy the harsh world is forgotten and replaced with a ideal reality. Roberto uses fantasy to overcome reality and thus through this semiotic way Guido can keep up his son from the truth.Changing of the truth can make the direst moments into fun games. Duri ng the momentsThe movie life is beautiful is directed by Roberto Benigni and is based in two main parts, before the holocaust and during it. Guido realises taking a shower is a term for Gassing people he decides to keep his son with him. Guido tells Joshua that the entire point of being dressed they way they are, and to hide from the guards is so that they could win a cooler if he is the last one found. Guido makes out the entire experience to be a game by doing funny actions to make his son feel like this is a game instead of a concentration camp , he does this up into his own bitter end.Roberto Benigni uses the film Life Is Beautiful to show how the use of semiotics can make Guidos humorous actions during the holocaust unique in economic system his son from the harshness of the holocaust. Through the use of semiotics the title of the film can be seen through the sons eyes.By the time life is beautiful was film many young people were too far from World War II to completely appreci ate the horrors of the war and the beauty of survivalSignifier 1 this is where Guido makes up the tank game. The signifier is claiming to understand German. This is signified by Guido raising his hand. By Guido doing this he protects his son from the harshness of the holocaust by making up a set of rules for the competition to win a tank. Roberto uses the simple hand raising to signify that even though he does not understand nor treat German he will pretend to in order cover the truth from his son. Again Stuart halls encoding and decoding theory is shown here as the earshot knows that this is what Guido is doing even without Guido having to say it.This is Guidos death scene. In this scene Roberto displays that Guido will do anything to save his son from the harshness of the holocaust, Guido is caught looking for his wife Dora and is being marched to his death , antecedently he hid Joshua in a metal mail box so he would be safe. Through Stuart halls encoding and decoding theory the viewer sees this as saving his son from the harshness of the holocaust instead of just being funny for Joshua. Roberto uses winking between Joshua and Guido as a link to the imaginary game they are playing this creates a sense that he is safe and is only knocked out of the game.While marching past his son he acting as a marching illumination soldier. The signifier is Guido marching like a toy soldier. Through the use of filming Guido marching as a toy soldier it shows the viewer that this is what Joshua is seeing, and nothing else before or after is seen by Joshua there for he believes fully that he will win the tank and his overprotect is out of the game. To the audience that knows what the German concentration camps where he will be killed.The main signifiers include life is beautiful, winking marching and making up the tank game. This signifies that life is beautiful in Joshuas eyes, and that he is saved from the real truth of the holocaust.Thank you for your time and attentio nREFRENCE(http//changingminds.org/explanations/critical_theory/concepts/signifier_signified.htm)

Love and Time in Rossettis Poems Essay -- Dante Gabriel Rossetti Poet

Love and Time in Rossettis PoemsIt is evident that themes of love and m are frequently referred toin several of Rossettis poems and I believe that she treats thesethemes in a variety of ways. Regarding love, Rossetti explores thedisappointment and betrayal caused by love, her love of God as thoughpart of an intimate relationship and the temptation that love causes tender women to abandon the traditional rules. Using seasonal imagery,Rossetti relates to time contradicting herself as she often impliesthat we should take time to enjoy and observe life sentence whilst she alsostates that she is unable to be satisfied with earthly life and it isdeath that leave al iodine provide the ultimate fulfilment.Aware of the inevitable that seasons will always change and can neverbe controlled, Rossetti uses the motif of life cycles in order todemonstrate that we should be satisfied with all that God provided uswith on earth. Life nursed in its expunge by death, In SpringRossetti implies a sign ificant image that death is the protector oflife and nurtures new growing life. Supporting this in harsh forsweet, Rossetti stimulates us not to rush through life but observemore and slow down, Its sun and perfumes and sweet flowers.Demonstrating that rapid changes in life take place and as humans wenever notice these Rossetti chose to present this poem in only 8lines, however in this she progresses through 4 months. This conveysthat cycles are to be anticipated and using a passage of time throughseasons she is able to symbolise the journey through life, And evenautumn closes. aspect back at her life in regret in Another Spring she confessesIf I might see another Spring/ Id listen to the daylight birds... ...ing to lookforward to as she believes that death will enable her a trulysatisfying life. To conclude, I believe that Rossetti treats the themeof time by creating a parallel to the inevitability of seasonsemphasizing that with all good comes bad and that however hard you tryto control life, it never stands still and you will never be able toturn back in time. Presenting her warnings about love and her doubtsthat she will ever find happiness, Rossetti treats the theme of loveas a challenge as she states that if you are able to find love onearth, you are lucky and therefore able to enjoy your time on earth. thus far if like Rossetti you are unable to find your perfect partner,you may resolve into finding your faith in God as inevitably no onewill ever match up to him and he is responsible for our happinesswhether we find it on earth or by death.

Great Gatsby :: essays research papers

Gatsby EssayReserving Judgements is a Matter of Infinite Hope pg. 6 F. Scott Fitzgeralds The Great GatsbyThis quote is the fundamental axiom that the book revolves around. Nicks father told this to him and he hasnt forgotten the quote or the intrinsic moral significance that goes along with it. So much is spoken and gossiped about Jay Gatsby onwards he is even introduced in the novel that no one knows his true character, except for the fact hes a rich man who throws trigger-happy parties in double-u Egg. In the novel, both accessible image and the perception of wealth play important parts in illustrating the internal class mental synthesis of West and East Egg. The fact the Gatsby is such an enigmatic character makes the audience wonder about the internal make-up of his personality, since most of his life Gatsby has been trying to escapism his true image. In the case with Nick, the narrator, and Gatsby, as long as judgments are not made, Nick can be optimistic about Gatsby and their relationship and intrust for the best, even if the best situation is not always reached. More generally, however, it advocates tolerance and understanding regardless of social status, or preconceived information.Within the first chapter of the novel, at that place is already a contradiction and a questioning of Nicks moral integrity as he regresses from his comment slightly. While he nobly and humbly mentions that he is tolerant and nonjudgmental, he also regards himself as morally privileged, having a greater sense of decencies than other people. It makes sense that New Yorks social dichotomy and the vast oddment between the rich and the poor, the arrogant and the humble has given Nick a complete moral spectrum.This quote not save symbolizes a creed that Nick lives by, but it also represents the ideal morality that unfortunately many of the frantic, materialistic, capitalistic easterners lack. Judgments and stereotypes and the declination of American values play a huge r ole in explaining the relationship with the two distinct sides of the neighborhood. The main distinction is between East Egg and the old rich people, who claimed their wealth through inheritance from ancestors who were among the richest people in the country, and the new rich people, like Gatsby, who obtained their wealth through entrepreneurial business that sometimes lacked integrity and morality. In addition to the difference in the assumption of wealth, the older rich people from East Egg tend to be more humble, graceful, and elegant with their riches, while the new rice West Eggers are ostentatious, and vulgar, as is characterized by Gatsbys tasteless, wild drinking parties.

Adoption of Animals Essay -- Argumentative Persuasive Essays

Adoption of AnimalsAnyone, who visits an animal auspices, as I do, sees an extraordinary number of beautiful, affectionate, and desperate dogs and cats. The majority of animals in any particular shelter are dogs, usually adults, for whom there arent enough adoptive dentures waiting. A few may have come from responsible stock breeders, whose owners do non realize that the breeder will take them back,many are those who are lost, and/or from owners who simply got tired of them. Some are pet shop puppies from a puppy mill that did not meet the owners expectations due to health, temperament, or other reasons. A large number usually turn out to be the result of deliberate and irresponsible home breeding. These people are known as back-yard breeders. And that is not a compliment. The bottom line is that most people who decide to purchase or adopt a companion animal simply do not realize the responsibility they will be taking on for the next one to fifteen (+) years. It is not fair to sa y that most people do not have good intentions in their decision to acquire a pet, especially those who rescue an discarded pet from a neighborhood shelter. What is important is that people become educated about the acquisition of a new pet and the responsibilities that accompany the addition. When rescuing an animal from a shelter or humane society, it is required that the owner spays or neuters the pet within thirty days of date of adoption. Usually, a portion of the fees acquired at the cartridge clip of adoption is used for the spay/neuter surgery. Thomas Shermerhorn,VMD acknowledges that dogs and cats can be spayed quite early (about 8-10 weeks) without the risk of any long-term problems-well before the prototypic heat, which usually happens about six months of a... ...list of courses. 6 Dec. 1999. Information and advocacy Web site. Accurate and current reporting on legislation and humane issues. Extensive tally of associate. Humane Education Network A Voice f or Animals. Home Page. 27 Mar. 1999 6 Dec. 1999. Relevant and accurate information about animal welfare. Relevant links to other on-line educational sites. National Association for Humane and Environmental Education. Community Outreach and Teacher Training. Home Page. 6 Dec. 1999. Extensive and excellent resources for teachers, parents. Information, advocacy, and educational site. delicate links. Zoo to You Online. Non-profit organization formed to help educate Students. 6 Sep. 1999. 5 Dec 1999. Information site dedicated to linking schools with on-line educational and resource communities.

The Tempest the Play by William Shakespeare Essay -- Tempest William S

The Tempest the Play by William ShakespeareRulers in general face many problems, as is the nature of havingpower and authority. However rulers analogous Prospero face even muchdifficulties, as Prospero has the ultimate power of magic and cancontrol and manipulate people and their actions, more so than a congenital ruler.The first difficulty presented is an issue, which is dealt withthroughout the play the idea of how much or how little to intervene?From the beginning of the play we are told of how and why Prospero isusurped from his dukedom, I so neglecting worldly ends, alldedicated/ To closeness, and the bettering of my mind/ With thatwhich, but by being so retired, Oer-prized all popular rate, in myfalse brother. Namely because he did not get involved in running thelanded estate and possibly felt that his job was not to intervene but to bea figure-head for the country and leave the country to run itself, alaissez faire attitude to ruling. This short speech by Prosperoraises the idea that perhaps we should remember that being a rulerinvolves twain rights and responsibilities Prospero wanted the formerbut not the latter.The idea of intervention and responsibility is presented in Act 2,Scene 1, where Prospero intervenes telling Ariel to wake Gonzalobefore Antonio and Sebastian draw their swords and bolt down him. Thisissue, is particularly difficult for a ruler such as Prospero as hehas the power to manipulate the situation to suit him self, raisingmoral as well as personal predicaments?This raises yet another problem faced by rulers, specifically Gonzaloof how much trust you can give your subjects or more appropriatelythose who are next in line to the throne? This idea of trust was... ... construct alcohol. Caliban gives his only power, knowledge ofthe island, as a pledge to his new masters. His take to is that byexchanging masters, he will be able to better his life. This continuesthe idea of trust and the problems faced by those rulers such asProsper o who have slaves who have an inherit need to be incarceratedby a ruler, but unfortunately by any ruler at all and are consequentlynot faithful.In conclusion, Act 2 reveals the difficulties faced by rulers such asProspero, through cleverly interwoven narrative meander which aredeveloped gradually throughout the play. This is especially true ofthe themes of trust and the fixed natures of characters, which bothpose a problem for those in power. Prospero of course has the addeddilemma of possessing supernatural powers which brings with itadditional problems when placed in the role a ruler.