6 Ways Nurses Can Stay Healthy During Flu Season

6 Ways Nurses Can Stay Healthy During Flu Season Chances are, the hospital or facility you work at requires you to get your flu shot. But sometimes even that is not enough. Here are 6 more preventative measures you can take to protect yourself from getting sick this season. 1. Treat Your Body Like a TempleJunk food is not your friend. Red Bull and french fries and Snickers bars might get you through a shift, but they won’t get you through flu season. Try and eat healthier (and make sure to include fruits and vegetables!) so your body gets the vitamins and minerals it needs to fight things off. And stay hydrated!2. Get Some SleepYou’re working overtime and the time off you do have is full of holiday activity. Make sure to rest as much and as well as you can so you don’t have to lose work time or play time.3. Be Travel SmartStay hydrated and boost your vitamin intake. Carry Airborne or Zicam or Emergen-C and a packet of sanitizing wipes on planes and trains and buses so you don’t pick up any germs.4. Be Vi gilantStart to get a sniffle or a sneeze? Feel a little achy? Stop what you’re doing and take care of yourself. Take your vitamins, get some rest, drink lots of fluids. Use hand sanitizer often. Get a humidifier. If you’re proactive enough, you can head the flu off at the start.5. Get CleanClean your kitchen and bathroom regularly. But don’t forget to also sanatize the things you carry with you, like your cell phone or your keys. A few disinfectant wipes will do a lot of good in fending off the army of germs. And if you do get sick, remember to change your toothbrush.6. Be an EnforcerYou’re a nurse, so you’re a hand washing and sanitizing pro. But the rest of your family probably isn’t. Get on your soapbox and make sure everyone you love is following the same guidelines. No sick people preparing food! Use tissues to sneeze! Wash hands after coughing! Protect your loved ones and protect yourself.

Holiday Truth essays

Holiday Truth essays Halloween should this holiday be celebrated or reconsidered? Halloween is a time to go out and have fun, collect and eat candy, and dress up to deliver or receive a great scare right? Wrong, this idea is what most Americans believe Halloween is all about. In reality the truth behind the reasons of why Halloween is celebrated are hardly ever discussed. According to William Schnoebeian, author of Lucifer Dethroned he states that when people take part in celebrating Halloween they are opening the door to Satanism. On the day of Halloween many satanic rituals and sacrifices are made to Satan. Many of these sacrifices include children and animals of all sizes. Americans are blinded by the great costume parties and the sugary mouths and they are not aware of what they are really participating in when they celebrate this horrific holiday. Although not popular until the 1800s, Halloween dates back to 200 B.C. A tribe called the Celts was the first to commence the original Halloween customs. The Celts were described as terrifying people who hung human heads. Halloween was called Samhain and was the holiday celebrated above all. Samhain was the Celtic lord of death, Halloween was the festival used to celebrate him. The celebration represented the beginning of the cold season when days grew darker sooner. The Celtics believed that this season represented death. They also believed that the souls of the dead returned to their homes on earth on October 31. The Druids, priests, and teachers ordered all the people to create bonfires on the evening of this celebration. Druids are the priests of the Celtic religion. The word bonfire also dates back to these days when the word originally was bone-fire. This word referred to the large bonfires that contained burned animals, crops, and human beings. The reason they crea ted these bonfires was to help the sun survive the winter, to frighten off evil spirits, a...

Memsitors, the new kid on the block Essay Example | Topics and Well Written Essays - 1000 words

Memsitors, the new kid on the block - Essay Example For example, when Bell telephone laboratories announced to the world the invention of the transistor in 1948, the press of the day announced that more than hundred could be held in the palm of the hand (Hayes, 2011). Today with the current technologies more than a 100 billion of these can be held at the palm of the hand. What is more interesting was that the transistors even cost less than dollar per a billion today. They are therefore the most abundant and cheapest electronic gadgets in the human history. Currently the trinity fundamental components in electronics that consist of the resistor, the transistor and the capacitor are well known in the electronic field. In 1971 an Engineer in the university of California Berkeley, predicted that there should be a fourth element; a memory resistor, or memristor though no one seemed aware of it or how to build one (Williams, 2008). 37 years later in 2008 the field of electronics got small enough to reveal the identity and the nature of the fourth element to complete the above set as was predicted by the engineer. Hewlett Packard researchers revealed in the journal nature of the fourth component; the memristor, which is the new kid on the block in the electronics field. The story behind memristor dates back to about 40 years ago from the insight by IEEE Fellow and nonlinear circuit theory pioneer Leon Chua (Adee, 2008). Chua when examining the relationship between the flux resistors and charge in resistors, capacitors and inductors in a 1971 paper, he postulated the existence of a fourth element called the memory resistor. According to Chua such a device once discovered would provide similar relationship and proportions between the magnetic flux and charge the same that a resistor gives between voltage and current. Therefore, Chua argued that the memory resistor would act like a resistor whose value could be able to vary according to the current passing through it and that could remember the value long after the curre nt disappears (Adee, 2008). This was to be realized more than 30 years later, when Stanley Williams a HP senior fellow and his group were critically analyzing and working on molecular electronics when they noticed strange behavior in their devices. It was after critically examining the theoretical works and especially the work of Chua that Williams noticed that the strange phenomena that they observed were actually as a result of memristors. One important aspect of memristors is that it proves right the suspicion that many researchers had for a long time that detailed that artificial intelligence was not possible with the traditional hardware due to its rigid use of the Boolean logic and the vast separation that exist between the memory and processing (Versace & Chandler, 2010). It was in 2008 when the HP researchers built the new class of electronic device; the memristor. Before this invention, it would have been impossible to create a new circuit with the memory structure of a bra in, the instantaneous internal communications and the low power requirements. Form the invention of the memristor, it was evident that the three components could be coaxed and trained to behave just a like a normal brain with more emphasis with form that was termed to be a major fusion in this set up. Generally, memristors are small, cheap and most efficient to fill this gap in the electronics industry. They might be explained to have characteristics that resemble those of synapses in normal humans,

The History of Socially Desirable Female Body Types Essay

The History of Socially Desirable Female Body Types - Essay Example Personally, my fixation is for those round ones. They not only resemble the full luminescent moon but overdrive the imagination with pictures of the full frame all its glory. Poets swooned. Cleopatra is reputed to have had the most attractive face - one that launched a thousand ships of war! The desire to be thin is widespread among women. Many starve themselves almost to death in the quest for the thin, graceful frame. However, I am of the view that majority of my fellow males will agree that there is something divine about the layers of flesh and soft skin and their contour that make the female extraordinarily fabulous. (Ximena A Ramirez). To me, the peach and cream skin or the golden color is the most arresting. Not to say that the colored or black fare any worse. Given the right proportion and features, they could be equally magnetizing. Thanks to the herbals, the cosmetics, the Fair and Lovely creams and lotions, they all look scintillating in the light. The female figure has been the object of famous artists, sculptors and architects. The female bust may consist of flesh, blood, muscles and glands. But the rounded shape, the graceful ebb and flow of her movements, create their own impact and envy. Since ancient times, the form of women have been embellished and preserved through art and dances. (Kapila Vatsyayan). Year after year, prized beauties vie for beauty crowns that are there for the best combination of beauty and brains. The present day wonder, Jennifer Lopez's anatomical assets are insured in cool millions! (Stephen Wilson). Conclusion Movie makers and advertisers rake in millions by depicting female silhouettes in countless poses, outfits, angles, coverings, hiding something here and there, and arousing emotions and imaginations. The males may be stronger and more muscular. But in aesthetics and grace, the female body wins the prize, hands down! Sources: Kapila Vatsyayan, A Holistic Eye On Cultural Interface and Synergy, Across the Himalayan Gap, http://ignca.nic.in/ks_41014.htm. Natural Complexion & Body Bars, Alpine Naturals, http://www.alpinenaturals.com/complexionbars.html. Stephen Wilson, Excerpts from Information Arts: Intersections of Art, Science, and Technology, San Francisco State University, http://userwww.sfsu.edu/swilson/papers/wilson.body.infoarts.html. Ximena A Ramirez, Thin is In, An Analysis of Media Endorsed Ideals of Physical Attractiveness and Their Affects on College-Aged Women, A Senior Honor's Thesis, Department of Communication, Boston College, May 2007, http://www.bc.edu/schools/cas/communication/meta-elements/pdf/thesis07.ramirez.pdf. Pictures: Complexion, Warm & Fuzzy, http://www.istockphoto.com/imageindex/432/0/432062. Figures, Rock Painting of Female Figures, http://www.srilanka.fr/imagebank/sigiriya/pages/Rock%20Painting%20of%20Female%20Figures.htm. The first crush, Demi Moore, IMDB, The Internet Movie Database, http://www.imdb.com/media/rm4085684224/nm0000193.

Role of the Entrepreneur Essay Example | Topics and Well Written Essays - 500 words

Role of the Entrepreneur - Essay Example Managing the business is the next step the business must take and the entrepreneur must ascertain that the incomes the business makes are higher than the expenses incurred while conducting the business. Understanding the drivers in the industry is important in as it makes the entrepreneur innovative which is a chief success attribute of an entrepreneur (Kingsland, 2007). Making the right decisions is paramount for the entrepreneur and he must ensure that resources are directed towards the right channels to ascertain there is no squander of resources, which would lead to losses. The actions of a firm earning profits add the value of resources as the firm is able to procure more resources into the business and operate at economies of scale. When a firm earns profits, the entrepreneur will be able to expand operations because they will have more money to spend to purchase more resources from the profits the organization makes. The organization will also be able to venture more into technology and move with the trends in the market so as to compete favorably with other business because they have enough revenues and this helps the organization to venture into new markets or improve their business operations. When losses are present, the value of resources diminishes, and this is because the business does not have adequate revenue to continue with its operations. Losses will eat into the capital of the business and some resources will be lost because the organization cannot put up with the high operational costs. When losses are present, operational costs will be high and this means that resources of the business will not be put into full potential hence the value of the resources will diminish. Some businesses are even forced to let go of some of the resources so as to maintain operational costs and this means that the value of the resources is diminished. It is not bad if a company making losses goes out of business, and this is because the central

Literature Review Of Load Shedding Methods

Literature Review Of Load Shedding Methods In chapter 1, a brief discussion about active distribution networks was presented. The importance of operation of islanded distribution networks was discussed. This chapter is intended to give the reader a better understanding of the load shedding methods currently applied and proposed over the years. However, it is assumed that the reader is familiar with basic power system engineering. In section 2.2, the area of probability of islanding and the need for load shedding is discussed. To achieve this objective, existing load shedding methods are reviewed to understand their working principle, requirements, advantages and limitations. The main categories identified are the following (i) Manual / SCADA Load Shedding (ii) Load Shedding using thresholds, (iii) Adaptive Load Shedding, (iv) Intelligent Load Shedding and (v) Load Shedding Based on Static Optimisation which are described and discussed in sections 2.2 through 2.7 respectively. Finally a summary is given in section 2.8 from which a new load shedding method for an islanded distribution network able to address the limitations of existing methods will be proposed. probability of islanding There is by now a considerable amount of literature on load shedding. That most of the literature however deals with large interconnected systems. For smaller systems when a loss of mains / grid event occurs the islanded distribution network have different operating characteristics and restrictions that require different load 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 used power system and serves as a function to try to arrest any frequency or voltage drop when a fault isolating part of the distribution network occurs. Faults in power systems are inevitable, for various reasons such as adverse weather conditions, ageing and failure of equipment, accident, and animal contact. In general, faults happen when an abnormal physical contact occurs between lines or on lines to earth that create a short-circuit path. If the system is not well protected, the high fault current due to the short-circuit path can cause damage to the equipment in the system. Faults also affect the reliability and quality of the power supply, leading to power interruption by frequency and voltage collapse and voltage sag events. Regardless of the interruption period, the losses are often enormous both to the customers and power utility 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 overhead 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 time. On the other hand, a permanent fault remains 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 operates 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 respond to control the island voltage and frequency. In order to achieve smooth transition to island operation, the generators must firstly ride through the fault or failure and secondly act to balance the active and reactive power in the islanded network. With a carefully designed load shedding method the operation of the islanded distribution network might be possible. It is important however that the design of the load shedding method is designed on the understanding of the characteristics of the system involved, including system topology and dynamic characteristics of its generation and load. A poorly design method may be ineffective and eventually lead to total customer interruption. Over the years, however, utility experience and extensive studies on a number of systems have resulted in different methods guidelines. In the following section, principles and guidelines for load shedding methods are reviewed. manual / SCada Load Shedding Manual or operator initiated load shedding [0] is not a reliable method to be used to avoid frequency deviation. However it can be used by some utilities to manually shed load or open ties (interconnectors) with adjacent areas at a frequencies below automatic underfrequency thresholds. This type of action might be necessary to prevent any further frequency deviation and to recover the frequency back to the nominal value. This load shedding scheme cannot be used for the islanded distribution network as it will be very slow 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 required for safe operation. automatic Load Shedding using thresholds An automatic load shedding for transmission system using different schemes such as underfrequency, undervoltage and combinations of the two can be employed to avoid frequency or voltage collapse during a significant imbalance between generation and load. These types of load shedding methods are very dependant on off 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. Underfrequency load Shedding The underfrequency load shedding scheme as explained in the following papers [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 accomplished in the systems distribution or transmission stations where major load feeders can be controlled by tripping of the circuit breakers (CB) automatically. Different settings can be applied in these load shedding schemes. Multiple stages can be used in the scheme [0]. The substation loads can prioritised and grouped according 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 change of frequency decline. 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 delay [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 unnecessary 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 make the system more vulnerable to system stability 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 defined percentage of the peak Demand that each Network Operator whose system is connected to the GB Transmission System shall disconnect by low frequency relays at a range of frequencies. The defined frequencies and the amount of loads are given in Table 1 -1. Table 1à ¢Ã¢â€š ¬Ã¢â‚¬Ëœ1: Load Shedding Scheme employed in the UK Frequency (Hz) % Demand disconnection for each Network Operator in Transmission Area NGET SPT SHETL 48.8 5 48.75 5 48.7 10 48.6 7.5 10 48.5 7.5 10 48.4 7.5 10 10 48.3 48.2 7.5 10 10 48.0 5 10 10 47.8 5 Total % Demand 60 40 40 The 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 usually shed more than the required amount of load. Undervoltage load Shedding Undrevoltage 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 discussed 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 1à ¢Ã¢â€š ¬Ã¢â‚¬Ëœ2: Load Shedding Scheme employed in the US Voltage (pu) Time delay (s) % Demand disconnection for Network Operator in Transmission Area 0.90 3.5 5 0.92 5.0 5 0.92 8.0 5 When the monitored bus voltages fall to 0.90 pu or lower for a minimum of 3.5 s then 5% of the load is disconnected. Additionally another 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 line 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 severe 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 demand varies. combination load Shedding In 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. According 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 monitoring 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 certain 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. Also instead of measuring 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 secure 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 Shedding Adaptive 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 reacting 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 1à ¢Ã¢â€š ¬Ã¢â‚¬Ëœ1: Simplified frequency response with disturbance input where: H = inertia constant (s) FH = fraction of total power generated by HP turbine TR = reheat time constant (s) Km = mechanical power gain factor R = droop characteristic (pu) D = damping factor Clearly the only observed 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 observe 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 parameters 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 1à ¢Ã¢â€š ¬Ã¢â‚¬Ëœ3: Initial Slope and Maximum Deviation vs Upset (frequency nominal 60 Hz) Pstep df/df ΆÃƒ Ã¢â‚¬ °max fmin pu pu/s Hz/s Hz Hz -0.2 -0.0286 -1.7143 -1.6438 58.356 -0.3648 -0.0521 -3.1260 -3.0000 57.000 -0.4 -0.0571 -3.4286 -3.2876 56.712 -0.6 -0.0857 -5.1429 -4.9313 55.069 -0.8 -0.1143 -6.8571 -6.5751 53.425 -1.0 -0.1429 -8.5714 -8.2189 51.781 The 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 triggered. 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 similarly 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 approach 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 difficult 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 controllers 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 à Ã¢â‚¬Å¾ depends on the time evolution of V as follows. A block of load is shed at a time t0 + à Ã¢â‚¬Å¾ such that: where 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 bounded: to prevent the controller from reacting 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 ΆPsh of power shed at time t0 + à Ã¢â‚¬Å¾ depends on the time evolution of V through where K is another constant to be adjusted, and ΆVav is the average voltage drop over the [t0, t0 + à Ã¢â‚¬Å¾]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 identified 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 performing 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 Shedding Applications of intelligent load shedding in power system engineering (e.g. genetic algorithms, artificial neural 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 load 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 quickly 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 explanation 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 capability for the agents, 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 introduce another technique using the artificial 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 indices of generating units, the system frequency and load shedding indices. load shedding based on static optimisation The 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 ensure angle and voltage stability enhancement 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 as a static optimisation problem with minimising function and equality 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 formulation 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 incorpora ting 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 1à ¢Ã¢â€š ¬Ã¢â‚¬Ëœ2: Ride through capability 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 delayed for the sake of event discrimination. The study and results however show that when the corrective action is applied at the optimal time increased damping and enhanced response are observed. summary The 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. Too few frequency levels could lead to overshedding, but on the other 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

Clinton Administration Policy Toward The Caribbean Country Of Haiti :: William Jefferson Clinton Essays

Clinton Administration Policy Toward the Caribbean Country of Haiti The topic for this paper is the United States policy towards the Caribbean country of Haiti during the Clinton administration. The subjects which will be discussed are the issues of: Refugees, Foreign Aide as well as human rights the United States involvement in Haiti issues of national interests. What will also be examined is what the Clinton administration trying to achieve concerning Haiti. What the United Nations and the U.S. roles were, and what the public thought was concerning these issues. Also why the United States was involved with the internal dispute of a third world country where the national interest was not clearly defined. The issue of why was it or was not so important for the United States to send troops to Haiti will also be discussed. The problem in Haiti was the pro democratic elected president Aristide was exile from Haiti during a military coup. Several issues arose out of Haiti after the exile of Aristide. Issues of: human rights there were reports that the new regime brought back "death squads" killing people who opposed the new leaders. One of the main targets of the Clinton policy is a group called the Front for the Advancement and Progress of Haiti of FRAPH. The administration has targeted this group for their continued backing and support of General Cedras, for their human rights violations. Issues of , refugee's illegally trying to enter the United States creating an economic burden on much of south Florida. All of these issues arose during president Bush's term in office. The Bush administration was to turn back the refugee's. The Bush administration saw no vital national interest in concerning it self with the internal problems of Haiti ,because there were so many problems at home in the United States, other than to turn the refugee's away from south Florida. When president Clinton took over the office of the presidency he would become very indecisive and weak on the issue of Haiti. President Clinton began badly on Haiti. With his continual indecision and lack of any real back bone to the policies which were decided upon. "First, he gave charge of his policy to Bush administration holdovers who over the previous year had made clear their intent to construct in Haiti a version of democracy that left the president in exile but with an Aristide - appointed prime minister and cabinet. This tortured scenario was doomed to failure because over two thirds of the Haitian people equated democratic government with the return of Aristide and no arrangement that excluded his presence could