Physics AT1-Resistance of a wire Essay Example

Physics AT1-Resistance of a wire Essay The electric current in a solid is a movement of tiny negative charged electrons. As these electrons move they collide with the particles of the solid which makes the electrons movement difficult. Resistance is a measure of how difficult it is for the electrons to move. A high resistance means that the electrons will make lots of collisions and lose lots of energy. The circuit itself can resist the flow of particles if the wires are either very thin or very long. e.g.The filament across an electric bulb is quite thin as needs to resist the flow of particles for the bulb to glow. Resistance is measured in ohms. The higher the resistance, the lower the current. If there is high resistance, to get the same current a higher voltage will be needed to provide an extra push for the electricity. Some metals have less resistance than others. Wires are always made out of copper because copper has a low resistance and therefore it is a good conductor. The length and width of a wire also has an effect.Ohms Law: The current is proportional to the voltage, provided the temperature remains constant.FactorsThe resistance of a wire depends on certain factors. Some of these variables are listed below:à ¯Ã‚ ¿Ã‚ ½ Length of wireà ¯Ã‚ ¿Ã‚ ½ Diameter or thickness of wireà ¯Ã‚ ¿Ã‚ ½ Temperature at which wire is keptà ¯Ã‚ ¿Ã‚ ½ The material of which the wire is made out ofà ¯Ã‚ ¿Ã‚ ½ The potential difference or voltageà ¯Ã‚ ¿Ã‚ ½ Humidityà ¯Ã‚ ¿Ã‚ ½ Cross sectional areaà ¯Ã‚ ¿Ã‚ ½ Voltage across circuitI will be investigating the diameter of a wire and how it effects the resistance. All the other factors will have to be kept constant whilst doing the experiment to ensure that the investigation is a fair test. I have decided to investigate how the diameter of a wire affects its resistance because other factors such as temperature are harder to control and get a good set of results. The way in which the diameter of a wire affects the resistance is an efficient experiment to do b ecause:* A graph can be plotted easily* There is a large range of results* The results can be recorded easilyIn order for the investigation to be a fair test, all other factors should be kept constant. The investigation has to be done in a fair way otherwise the results will be inaccurate and the conclusion will be incorrect. The variables that must be kept constant are:1) Temperature When the temperature of a wire increases the resistance of that wire increases. This is because when the temperature increases the atoms inside the wire vibrate more vigorously because of the increase in energy. This means that the electrons have more difficulty getting through the wire as they collide with the other in their pathway. This increases the amount of collisions therefore there is more resistance. To make sure the temperature does not effect my result too much it is essential I use a low voltage because it means a low current, which wont heat up the wires. If a high voltage is used the ener gy would be in form of heat which would make the experiment unfair. The investigation will be done at room temperature. The temperature cannot be investigated because it is hard to control the range of temperature needed without the correct apparatus.2) Length of wire The longer a wire, the larger the resistance. This is because there are more atoms in the wire so there is more chance that the electrons would collide with one of the atoms therefore there is more resistance. In a long wire electrons have a longer distance to travel so there are more collisions so this will change the resistance up and in a short wire electrons have a short distance to travel so they collide less and therefore there is a lower resistance. This is because when you have a long wire, the electrons have to squeeze together for longer to be able to pass through the wire than they do in order to be able to pass through a short wire. It is important to keep the length of the wire the same each time otherwise it could not be certain which variable is changing the resistance. If I had a 30 cm wire and a 60 cm wire, the 60 cm wire would have a resistance twice that of the 30 cm wire.3) Type of material Different materials have different resistances because the materials atomic structures are different so some wires have low resistances and some have high resistances. Therefore it is important to keep the material the same throughout the experiment. If different materials are used throughout the investigation, it will affect the results. For example if sometimes copper is used and sometimes nichrome is used, the results where copper is used will be of a low resistance because of the material and not because of the diameter of the wire. Throughout the experiment nichrome wires will be used. The type of material will affect the amount of free electrons that are able to flow through the wire. If the particles in the material are tightly packed together, the electrons will have more collisions and therefore more resistance.All these factors must be kept constant to make the investigation fair. All the other factors must also be kept constant as well. The same apparatus must be used throughout the investigation. It is also important to take two repeats and find the mean so if one result is very inaccurate, the other will average it out.QuestionWhat effect does the diameter of a wire have on the resistance through it?PredictionMy hypothesis is that the thinner the wire, the higher the resistance. The thicker the wire, the lower the resistance. This is because the thinner the wire is, the less paths there are for electrons in the wire therefore the harder it is for current to flow. This results in the energy not being able to spread out as much, so the resistance will be higher. This theory is similar to that of a door, where people represent the electrons and the door represents the diameter of the wire. If the door is wider, more people can get through, more easily. If th e door is small, people have more difficulty and not as many people can walk in or out of the door. It is the same principal for electrons. If the diameter of a wire is thicker more electrons can go through the wire, therefore less resistance. The atoms from the metals cannot stop or collide with as many electrons because the diameter of the wire is larger.This diagram shows the negatively charged electrons travelling through a wire colliding with the wire particles. The more these electrons collide the more resistance there is. In a thick wire there is more space in between the wire particles and the electrons will collide less. In a thin wire there is less space between the particles and so the electrons will collide more. This is why I believe that the thinner the wire, the higher the resistance and the thicker the wire, the lower the resistance.PlanTo prove the prediction above I plan to do as follows. I am going to test the resistance through different diameters of wires. To do this I will need a voltmeter, ammeter, power pack and some different wire diameters. I plan to test five wires all with different diameters. I plan to set up my circuit as shown below:Where the wire is position I will have a pair of crocodile clips to hold it in place. I plan to use 70cm of each nichrome wire and I plan to coil each wire. To help keep my results accurate I plan to only use a low current when testing; this will keep the temperature of the wire down. For each wire I plan to take one reading from the voltmeter at a constant current of 0.5 A. I then plan to repeat the reading of each wire three times and take the average result . I shall then be able to calculate the resistance of the wire using the equation resistance = volts/amps and represent this data in the form of a graph.Fair TestI have already mentioned which factor I am investigating and which factors I will keep constant (see pages 1 and 2). I will do the following things to make the experiment a fair test:* Use the same material for each wire* Use the same length of each wire* Take readings using a low current (keeps temp. down)* Use same equipment for each testSafety PrecautionsI will take the following precautions and make sure others are safe as well:* I will wear safety glasses* I will make sure there are no bag or obstacles on the floor causing a hazard* I will be careful with the electricity present* I will not run around* I will not touch live wiresMethodApparatus* Voltmeter* Ammeter* 2 Crocodile clips* 5 nichrome wires (0.28mm, 0.31mm, 0.40mm, 0.45mm, 0.50mm)* Power Supply Pack* Circuit wiresI first set up the apparatus as shown below:Then for each diameter of wire I followed the following steps:1. I measured 70cm of the wire and coiled it around a pen2. I placed the coiled wire in the circuit attaching it with the crocodile clips3. I took a reading of the voltage through the wire at one certain point, which was 0.14. I presented the readings for the wire in a table of voltage against current (V against A) and calculated the resistance which is voltage divided by the current (constant at 0.5 A)5. I repeated the readings (using the same equipment) for the same diameter of wire three times to make sure they were accurate6. From the results I took an average for resistance7. I then repeated the process for the other four wiresResultsFrom the following results I will produce graphs to show what was found out more clearly.Set 1Wire Diameter (mm)Current (A)Voltage (V)Resistance (Ohms)0.280.55.711.40.310.54.28.40.400.53.16.20.450.52.040.500.51.42.8Set 2Wire Diameter (mm)Current (A)Voltage (V)Resistance (Ohms)0.280.55.811.60.310.54.38.60.400.53.46.80.450.52.550.500.51.32.6Set 3Wire Diameter (mm)Current (A)Voltage (V)Resistance (Ohms)0.280.55.611.20.310.54.28.40.400.53.36.60.450.52.34.60.500.51.32.6Average SetWire Diameter (mm)Average Resistance (Ohms)0.2811.40.318.40.406.50.454.50.502.6ConclusionThe results shown on my tables and my graph clearly show that the th inner a wire the greater the resistance of that wire .From my tables you can see that I got three sets of results. My repeated results all (to a reasonable degree of accuracy) agree with my first set.From my graph we can clearly see the average results and also see that there is one anomaly, which does not fit in with my line of best fit. Looking at the table I can see that it is not just one reading that made the average an anomaly. There could be several reasons for the anomalous result. Firstly maybe the wire I used had been damaged from previous experiments or perhaps it was not exactly the diameter 0.31mm. Secondly maybe I didnt read off the voltmeter accurately. Thirdly, I used crocodile clips to fix the wire and perhaps I didnt fix the wire sufficiently well in the clip.I observed that the thinner a wire the higher the resistance. This is because of collisions inside a wire. Imagine a metal wire it contains lots of particles which make up the wire. The electrons have to trav el through this wire. As the electrons travel through the wire they will collide with the particles of the wire. The more collisions the electrons have, the higher the resistance. However, in a thick wire the particles are more spread out and the electrons have more room to travel through. There are fewer collisions and hence the resistance is less.Even though there is a result which doesnt fit the pattern, the majority of results still follow my prediction.Improvements and EvaluationAlthough I took precautions to ensure this was a fair test, there were some areas where accuracy could have been improved. The anomalous result suggests that I would need to repeat at least that part of the experiment for that width of wire. It could be that I didnt accurately measure out 70 cm of wire or I didnt read the voltmeter correctly. However, I think this last explanation is unlikely because I read the voltmeter three times and each time the reading was almost the same (4.2,4.3,4.2). This sugge sts to me that the reason for this discrepancy is more likely to be an inaccurate measurement of either the width or length. There is also the question of whether the current was measured accurately.Repeating my results more than 3 times would further improve my results and maybe correct the anomaly. To improve my experiment I should have taken more time making sure wires are correct lengths and thickness.Further work that could be done is to look at each wire in more detail. Trying more currents and investigating more factors for example or maybe trying more diameters of wires would be further ideas.

Globalization of the Local

Globalization of the Local Globalization of the local is a concept developed by Thomas Friedman in his book â€Å"The World is Flat†. The author claims that globalization does not entail one entirely new civilization that is coming to neutralize all existing cultures. He argues that with globalization, all local cultures are getting the opportunity to become global; that is to extend their influences.Advertising We will write a custom critical writing sample on Globalization of the Local specifically for you for only $16.05 $11/page Learn More Of course, not all of the existing cultures are getting the same opportunity. Those which are more developed, and perceived by the majority of the world’s population as superior, are more likely to have greater influence in this new global culture. In addition, new forms of media are providing a chance for people to cherish their cultural origins in distant parts of the world. This is very important because globalization is causing many people to migrate to other countries in order to pursue their careers. This way, these new technologies are contributing to the quicker flow of ideas and customs. Undoubtedly, in the near future, this will result in a complete integration of different cultures into one global culture which will be quite different from all the existing ones. Many people oppose this idea of a transformed global culture for fear of losing their national heritage and other components of their identity. However, this view is problematic in various aspects. Frist off, cultural transformation is not anything new. It is known that under the influence of social and economic forces, cultures have been changing tremendously throughout history. Secondly, experience has taught us that external intervention cannot stop the changes in the society that are occurring organically. A good example of this is the emancipation of Afro-Americans and women. These two processes faced serious opposition, but they were, nonetheless, completed. Finally, globalization offers an opportunity to build up a culture which is superior to all others that we have witnessed in our past. In this effort, education is definitely going to play the crucial role, and thanks to the advent of new technologies, we now have the opportunity to make education available to everyone. In conclusion, globalization is an unstoppable process, which if carried out in the right way, can be a great step in the development of human race.Advertising Looking for critical writing on american literature? Let's see if we can help you! Get your first paper with 15% OFF Learn More Dell Theory In his book â€Å"The World is Flat†, Thomas Friedman suggests an interesting theory about international relations and conflicts, which he calls â€Å"Dell Theory†. The name comes from the famous company that produces electronic equipment – Dell. Dell is widely known for its supply-demand chain, which en compasses several companies around the globe. These companies supply Dell’s assembly lines with all the necessary parts so that the assembly line is never interrupted. Friedman argues that once countries are connected through supply chains such as this one, they develop codependency relationship in which every side has some benefits. For that reason, Friedman argues that those countries would never declare war on each other because doing so would disrupt the supply chain from which both of them benefit (Friedman, 2005, pp. 420-422). This is a very interesting theory which has been proven right on several occasions in recent history. However, I would argue that Friedman was not the first person to notice that connecting two nations through economic bonds reduces the possibility of a major conflict. It takes only one look at the history of Europe in past centuries to see that politics of economic isolationism always culminated in wars with devastating consequences, WWI and WWII are the most obvious examples. The politics of open borders and cooperation, which was introduced after WWII, finally brought peace to Europe. In conclusion, the cases of Dell’s supply chain and European Union are only two of many examples where it is evident that Friedman’s theory has firm empirical grounding. Since globalization faces many challenges mirrored in ideological, religious and cultural differences, this principle of establishing economic ties is perhaps the best tool for overcoming those difficulties. Friedman, Thomas L.. The world is flat: a brief history of the twenty-first century. New York: Farrar, Straus and Giroux, 2005. Print.

EU Rights to citizenship Essay Example | Topics and Well Written Essays - 1000 words

EU Rights to citizenship - Essay Example Karl and Gabrielle are the two visitors from Kazakhstan while Sylvia belongs to Hungary. Charles, Bill and Muriel play an intricate role in the lives of all three foreign individuals. The first character Gabrielle has a work permit which qualifies up to three months. Article 6(1) provides that EU citizens shall have the right of residence in another Member State for a period of up to three months without any restrictions or formalities other than the obligation to hold a valid identity card or passport. Also, according to Article 4 and 5 all EU citizens have the right to leave or enter another Member State by having a valid identity card or valid passport. According to Art 7(1) Gabrielle can exceed the three months period if (a) she is engaged in an economic activity in the host Member State such as UK on an employment or self-employed basis, (b) if she has health insurance and (c) if she is following a course of study in the host Member State. Article (8 a) does not provide every citizen of the Union with an open-ended right to reside freely within every Member State. Gabrielle may have obtained the right of permanent residence in UK after a five years period of continuous legal residence according to Art 16 (1). This is as long as the eviction decision has not been enforced against her by virtue of Art 21. Therefore, she is allowed the right to permanent residence without needing to oblige any conditions.

Influence of European Enlightenment on modern schooling Essay

Influence of European Enlightenment on modern schooling - Essay Example It also aimed to reform the society by using reasoning and understanding of the phenomena’s by using scientific knowledge. It aligned majority of the thinkers on the lines of reason and understanding during the 17th and 18th century. It was also referred to as an ‘Age of Reason’ by Thomas Paine (Hackett 1992). It is still believed by many that the basis of modern concepts and thoughts lie in the age of Enlightenment. Science, skepticism and intellectual understanding was promoted during this era as opposed to the superstitious thinking and intolerance by church and state (Wilson 2004). Origin of Age of Enlightenment The Era of Enlightenment was sparked by the great philosophers and thinkers of that time. Baruch Spinoza (1632-1677),Pierre Bayle (1647-1706),physicist Issac Newton (1643-1727) and Philosophers Voltaire were the major proponents in originating the Enlightenment movement (Casey 2008). The revolutionary leaders of the Enlightenment movement hailed themse lves as the courageous elites. They claimed to take the world out of the dark period of doubtful traditions and ecclesiastical tyranny due to which the historical wars took place. Education in the Age of Enlightenment The basic purpose of the movement of Enlightenment was to spread scientific knowledge and reasoning among masses and to take people out of the ignorance in which they were plunged in during the Middle Ages.The role of the educational system was very important in spreading the ideas and concepts of Enlightenment among the people. Continuous development took place in the educational system in Europe throughout the Enlightenment period and the French Revolution. The educational development increased and flourished rapidly during the Enlightenment period. Educational history prior to Enlightenment Period Before the period of Enlightenment, religious dogmatic believes and superstitious thinking was given value. The education was considered the sole right of males who belong ed to the upper stratus of the society such as nobles, mercantile and professional class. With the spread of the scientific revolution traditional religious and superficial beliefs gave way to scientific thinking and reasoning. Novel and revolutionary scientific ideas were proposed by the philosophers such as John Locke proposed that sensation and reflection plays a part in obtaining knowledge. Locke later developed a theory which was based on the same idea that every human being are equal in the capacity of sensation detection and that education should be made public and reachable by all classes of the society. The roots of Pedagogy as science, also has its roots in the in the Age of Enlightenment. The education was considered a basic tool by the philosophers and thinkers of that time to fight against ignorance and superstition. It was considered a way to achieve an open-minded and egalitarian society (Farzaneh 2009). They fought against censorship and worked towards the practice o f free speech. They wanted Declarations of Human rights and an easy and free access to education for all people. Spread and growth of Education system The education before the Age of Enlightenment was considered the divine right of only rich and noble upper class of the society. During the 18th and 17th century there was a significant

Human Resource Management Research Paper Example | Topics and Well Written Essays - 1750 words - 1

Human Resource Management - Research Paper Example Human Resource Management Unionization can be defined as the act of forming groups among the workers and staff members. Originally the concept of unionization within the organization initiated during the early 18th century. But with the course of time the system became prominent in different parts of the world. Historically the concept of unionization was welcomed by several eminent scholars around the globe, but scholars such as Paul Smith an economist of the 18th century stated that labor union has been an illegal practice. A union is an agency of personnel’s that have collaborated together to improve the condition of its members in context with pay packages and other benefits (Libcom, n.d.). The organization can be made up of individual professional, past working staffs, trainees, students and unemployed persons. The common aims are generally demands for higher pay packages, increase in the number of employees for a particular job, to improve the condition of working, demand for various facilities, rules and regulations pertaining to hiring and firing, promotion of workers, procedures of lodging complaints, safety within the workplace and about the different policies of the organization. A union also relies on the fact that joint efforts are superior to individual effort and also aid in achieving the goals more flexibly. This has also led to the concept of collective bargaining. Collective bargaining can be defined as the process by which a group of employee’s demands for something from the employers regarding different issues related to the job.

Large Scale Tunnel And Bridge Construction Project Construction Essay

Large Scale Tunnel And Bridge Construction Project Construction Essay Temporary Works are considered any temporary construction used to construct highway, bridge and tunnel related structures but are not incorporated into the final structure. Temporary works required for construction of permanent structures include: temporary detour bridge, Work Bridge, falsework, formwork, shoring, cofferdams and temporary retaining structures. Temporary Works shall be designed according to the guide design specifications for Temporary Works unless specified otherwise herein. Where failure of a temporary structure would have an impact on environmental protection, traffic, or public safety shall be designed and constructed using the criteria. This report is to discuss the role of temporary works and equipment in large scale Tunnel and bridge construction project with an example of a large scale tunnel and bridge project, explain the impact of temporary works and equipment on the total cost of the project. The aim for this project is to Improve the knowledge and understanding on principles of designing and measurement of bridge and tunnel works in civil Engineering construction. Introduction Temporary work Holmes, R (1995) stated that On many civil engineering projects the cost and design of temporary works forms a very high proportion of the total contract. Therefore care in design and planning is essential. Each temporary structure must be considered on its merits in relation to the importance of the contract and especially the consequences of failure. If under-design could lead to failure in operating conditions, then the cost of delay, together with loss the saving in design. It is therefore important to design all structure to take the full in the erection of such structues in bad weather. Supervision in the erection, removal and maintenance of all these structures is paramount. Where materials are used more than once, for example as in the case of falsework, they should be checked to ensure that they have not been weakened by their initial uses. Second-hand materials should be subject to careful scrutiny before being used in situations where the design was based on new materials. Typical examples of temporary works are: Ground support,eg cofferdams, timbering, underpinning and shoring. Access bridges. Gantries and scaffolding Trackwork for cranes and trains Dewatering systems Specialised topics are dealt with in detail in subsequent chapters of the book. Builders Plant or equipment According to the Chudley and Greeno (2006) page 144 the builders plant ranging from small hand held power tools to larger pieces of plant such as mechanical excavators and tower cranes can be considered for use for one or more of the following reasons:- Increase production Reduction in overall construction costs. Carry out activities which cannot be carried out by the traditional manual methods in the context of economics. Eliminate heavy manual work thus reducing fatigue and as a consequence increasing productivity. Replacing labour where there is a shortage of personnel with the necessary skills. Maintain the high standards required particularly in the context of structural engineering works. Bridge and Temporary Work The bridge I choose for this topic is Juscelino Kubitschek Bridge, Brazil. Juscelino Kubitschek was built in 2000-2002, Juscelino Kubitschek is a Arch bridge suspended deck. According to Holmes, R(2006),stated that Arch Bridge can supprt better loads-carrying member, the arch is in a state of compression throughout. This will make the design suited to materials which are weak in tension. The Juscelino bridge Foundation blocks, of dimensions 24 x 40 x 4m, were cast 1.5m below the water surface for architectural effect. Steel shuttering was installed and the water extracted before the concrete was poured in shallow layers, thus avoiding excessive thermal effects and cracking. 1.2m diameter piles were driven to depths in excess of 50m. Looking back to Figure 7, you will notice that the foundations are much deeper on the right hand side than on the left. The largely poor and extremely variable ground conditions meant that piles were driven until the desired capacity was reached, often exceeding the expected depths. Horizontal thrusts are transmitted into the foundations due to the rotation of the arches out of their normal plane. To accommodate these residual forces, the pile configuration has both vertical and inclined piles. The inclined piers and arch starters were then constructed on the completed foundation blocks ready to accept the deck and prefabricated arch sections. The arch starters are comprised of a curved and tapered concrete hollow section, as shown in Figure 13. Two types of deck construction have been used for the JK Bridge: the approach spans comprises of a profiled steel under tray and concrete slab; whereas the central 720m supported by the three arches is comprised of a steel under tray and orthotropic plate.Temporary piers were erected to support the central portions of the bridge whilst the deck was constructed (Figure 14). Once the deck substructure had been completed, gigantic steel truss falsework was erected from this platform, with the temporary piers remaining in place below. A total of 1,350 tons (approx. 1,225 tonnes) of steel was used in auxiliary structures during the bridges construction. With the falsework in place, the prefabricated steel arch sectors could lifted into place and welded (Figure 15). The final closing weld was welded completed over night to limit internal strain within the arches due to daily temperature fluctuations. The stays are made of galvanised steel strands, protected by a coat of wax and sheaths of high-density polyethane (HDPE). The stay head shown Figure 16 and is fixed, whilst the upper anchor point is turntable allowing for corrections to be made to the stay tensioning. [1] The inclined cable configuration has been adopted to achieve a greater level of lateral restraint within the deck when subject to wind and transverse vehicular loading. The stays were installed in stages (Figures 17- 21) whilst the temporary supports were still in place, to avoid over stressing and damaging the arch. [8] An array of 60 load cells and sensors were installed, along with surveying targets, to monitor the stresses and deformations within the bridge structure during its construction. Many of these devices remain in place today, collecting data to produce a Dynamic Signature which is used to evaluate bridge performance over its service life, and to inform the maintenance programme. A large problem encountered during the construction process was the lack of local skilled labour and knowledge of steel construction. Brazils steel industry is relatively small, and the subsequent lack of use of the material has left the work force unskilled in steel construction techniques. The nations designers also have limited knowledge and experience of working with steel, so the structural design for the arches was outsourced to Danish consultancy COWI. Architect Alexandre Chan hopes that this iconic bridge will act to encourage a wider use of steel within designers, and ultimately stimulate the growth of Brazils steel industry. (http://people.bath.ac.uk/cmb27/proceedings/papers/banthorpe_cm_JUSCELINO_KUBITSCHEK.pdf) Gotthard Base Tunnel and temporary work 3.0 Role of Temporary Works in Tunnel Construction Project. Tunnel Boring Machine (TBM) A tunnel boring machine (TBM), which is shown in Figure 3.1, is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. TBM is a one of temporary works of Tunnel Construction Project. They can bore through hard rock, sand, and almost anything in between. Tunnel diameters can range from a metre (done with micro-TBMs) to almost 16 metres to date. Tunnels of less than a metre or so in diameter are typically done using trenchless construction methods or horizontal directional drilling rather than TBMs. Tunnel boring machines are used as an alternative to drilling and blasting (DB) methods in rock and conventional hand mining in soil. A TBM has the advantages of limiting the disturbance to the surrounding ground and producing a smooth tunnel wall. This significantly reduces the cost of lining the tunnel, and makes them suitable to use in heavily urbanized areas. Another advantage includes relatively high degree of safety against flooding and ground collapse, as the TBM isolates the ground and groundwater from the tunnel proper. Contractors are becoming increasingly familiar with the use of EPB type TBMs in North American but, however, not in this range. The ability to excavate and install water tight precast concrete segments as the final tunnel lining in one pass is another advantage of this method. The major disadvantage of this method is the high initial capital expenditure for the TBM and the long lead time to manufacture, sip, assemble and test the machine, plus the normal inefficiency related to the learning curve on startup. TBMs are expensive to construct, and can be difficult to transport. However, as modern tunnels become longer, the cost of tunnel boring machines versus drill and blast is actually less. This is because tunneling with TBMs is much more efficient and results in a shorter project. Another disadvantage is the very large circular tunnel section required to accommodate the traffic lanes, shoulders and sightline, which for vehicular tunnels is not a very efficient use of space. This is also lead to buoyancy issues and the required mitigation when minimum cover under the channel is employed. Also, there is a potential for the loss of line and grade given the very tight turn radius required and steep decline followed by incline to pass under the channel. Temporary Control Room in Tunnel Project All tunneling activities were monitored and controlled 24 hours a day by the Temporary Control Room, through mimic or video view of all mobile and fixed equipment, thanks to a powerful redundant control system able to centralize all numerical/radio/phone communication, vocal and optical alarms. The safety desk (PCS) connected by direct phone to all emergency services (firemen, ambulances, hospital, etc.). Fixed Equipment Desk (GTC) is including visual permanent control of power, ventilation and pumping, connected to 8000 sensors in tunnel and served by 2 calculators, 1 programmable controller and computer networks. Rail Traffic Desk (PCT) includes vocal communication with all vehicles and optical monitoring of all tunnel activities on a large mimic served by programmable controllers. A dedicated software allowed automatic management of itineraries, location and composition of convoys, tracks and catenaries reservations, and even rolling stock status. Temporary control room is high in itial capital expenditure to manufacture, sip, assemble and test the machine, plus the normal inefficiency related to the learning curve on startup. Temporary Power Supply TBM needs a large power to excavate tunnels with a circular cross section through a variety of soil and rock strata. A large temporary power supply is provided during large scale Tunnel construction project. The high-voltage power supply of the site is in 90 kV through two 90/20 kV transformers of 36 MVA each. Medium-voltage distribution included nine specialized substations, with tunnel power supply of 20 kV and 3.2 kV for lighting. An emergency diesel plant was dedicated to TBMs, ventilation, lighting and pumping systems. Temporary power supply is a high impact of cost toward the total cost of the project. Conclusion Bridge temporary work is totally different with Tunnel temporary work. The bridge temporary work is simple compare with the Tunnel temporary work. Bridge temporary work is such as falsework, formwork and temporary retaining structure. Both of bridge temporary works method is low initial capital expenditure and the short lead time to construct. For Tunnel temporary work, the high technology construction is used during tunnel construction project. TBM is the high initial capital expenditure and the long lead time to manufacture, sip, assemble and test the machine, plus the normal inefficiency related to the learning curve on startup. Large scale tunnel construction projects spend high temporary work cost for control room and power supply. At conclusion, total cost of the bridge project is lower impact compare to the tunnel project.

The Afro-American Newspaper Goes to War :: United States History African American Essays

The Afro-American Newspaper Goes to War The Baltimore-based newspaper The Afro-American has been in existence since 1892 under the proprietorship of the Murphy family, and by the 1940’s had forged a place at the forefront of African-American journalism. The newspaper is still in business today and is online at www.afro.com. Founded by John Murphy, a former slave, the Afro-American has grown from a church weekly to one of the nations leading black newspapers. The newspaper has used it’s column inches to campaign for the civil rights of African-Americans throughout the 20th century, from opposing the persistence of racist â€Å"Jim Crow† laws in the South to defending eminent figures such as W.E. DuBois and Paul Robeson during the McCarthy-era anti-communism of the 1950’s.[1] During World War 2, when the U.S. military was still segregated along racial lines The Afro-American sent correspondents to cover the fighting alongside the various black American units that served in both the European and P acific theatres. These men and one woman were relaying to an audience of Maryland and Washington D.C. African Americans the roles fulfilled by black American troops, fighting in a segregated military abroad. The primary impact of black and white Americans serving together was to be felt socially in the post-war years. The Civil Rights movement that gained momentum in the 1950’s owed much to the fact that many people engaged in war work during the 1940’s, who in peacetime would never interact with one another on grounds of race, were challenged by their shared wartime experiences. â€Å"The common danger, the common foe and hardships of battle are bringing American troops closer together†¦Soldier after soldier has told me he can never be narrow-minded again after seeing such widespread human suffering.†[2] Ollie Stewart, correspondent for The Afro American, 1944 Compared with the quality of contemporary reports filed by â€Å"embedded† reporters in the 21st century US military, filtered by both the Pentagon and major media networks, some of the copy from the Afro correspondents is surprising given the circumstances under which it was filed. Despite the circumstances of war the reports filed by Afro correspondents used a number of means to convey the reality of service in a segregated military without alarming the wartime censors, and did so with deep insight, humour and graphic accounts of the full spectrum of roles fulfilled by black service personnel. The Correspondents. Correspondents for the Afro American.