Report on Multi User Operating Systems Essay Example for Free

Report on Multi User Operating Systems Essay Resources Sharing Concepts of Resource Sharing A multi user operating system can support more that one user at a time, this means that multiple users can share the same system resources simultaneously. The users of a multi user operating system can share both hardware and software resources, the operating system carries out complicated routines to manage all the processes that the users are running. List of shared resources: * Hardware CPU Power, RAM, Hard drive, Peripherals (printer, Scanner, CD ROM) Other peripherals may be made available in a MUOS for users who require them (Floppy disk drive, Speakers, Head Phones, Video Cameras etc. ) * Software Scheduler Software (needed to manage and prioritise tasks). Batch Job Some processes take a long time to complete and can often disturb other computer tasks that are important. A Batch Job is a file that does not require any user interaction, so it is set up to run a number of processes at a later time, often late at night. One example is overnight maintenance at a bank when they update all the accounts so it will not disrupt the other processes during the day. Multi-Tasking Concepts of multi-tasking Multi tasking is when the operating system switches between tasks at a very high speed, it can sometimes seem as though it is performing more than one task at a time. For example, a user could be printing and typing at the same time, and listening to a CD. Many users can access the same resources at (what appears to be) the same time. One disadvantage of this is that it requires a great deal of memory and the processes may run slower. The two types of multi-tasking are co-operative and pre-emptive: * Pre-emptive This is when the applications are forced to give up the CPU after a certain length of time so that the other processes get an equal share of CPU time. (time-sliced). * Co-operative multi-tasking is when it is the current running tasks responsibility to share the CPU to the other processes. One task must finish before the other starts. It is called Co-operative because all the tasks must co-operate for this type of processing to work and there is no time limit on each task. (Round Robin). Advantages / Disadvantages An advantage of Pre-emptive multi-tasking is that some important tasks may be allocated a more time slices so it will not be stalled by other smaller tasks. A disadvantage of both types of multi-tasking is that it requires a large amount of memory to work properly. Background Processing Concepts of background / foreground processing When a task will require a long time to process and requires no user input e.g. downloading a large file from the internet, it can be processed later when the computer is not processing other tasks. Background processing is often used in banks and businesses to process the customers accounts at the end of each day, the operating system can be left to run the process overnight or when the CPU is not currently being used by a task that requires a great deal of processing. Unix command to run background processing Control-Z = Leave process running in background bg = Continue process at background Control-C = move foreground process to background Fg = move the process to foreground Example of a background process If you need to run a large print job, e.g. printing out one hundred copies of a Workbook for a group of students, it can be set as a background process and will only use CPU power when other tasks are not running. Types of Multi-User Operating System Multi-Processor More than one CPU Multi user operating systems can sometimes have more that one processor. In some expensive operating systems it is possible to connect more CPUs to the system and have them work together to execute tasks. Multiprocessing can significantly reduce the time taken to execute each process. An operating system with multiple processors can perform different tasks separately or a task can be split up and processed by different CPUs. Advantages / Disadvantages An advantage is that multi processing systems can be very speedy at completing tasks. A disadvantage is that this type of system is very expensive. Time-Sliced As multi user operating systems share resources, different processes can require different amounts of time. It is possible and to interrupt a large process so that a smaller process to be completed. If you were using a time slicing system then the processor will switch between processes at timed intervals (Pre-emptive). The amount of time allocated to each process is called a time slice. The length of time given for each time-slice is allocated by a program called a scheduler. An advantage is that larger or more important processes may be given more time slices than a smaller task so it can be completed, however this could also be a disadvantage if there are many users executing smaller tasks as they will take longer to be finished. Distributed The distributed system is where a number of systems are connected through a Local Area Network. This can be more powerful than a single processor system and it is capable of online sharing. Hardware Components Processor The CPU is the brain of the operating system. It responds to and processes and instructions that control the computer. The control unit in a CPU controls everything which happens within, the ALU does calculations and is responsible for decision making and the accumulator stores the last data that was decoded for future processes. There are various registers within the CPU, they are the instruction register, which holds the instruction that is being decoded, the program counter stores what part of the program we have reached, the memory address register points to the location where data is being fetched or written and the memory data register is a storage area for data that is currently being transferred between the memory and the CPU. The Fetch-Decode-Execute Cycle has three important stages. * FETCH The CPU collects an instruction from the RAM * DECODE The control unit figures out what to do with it. * EXECUTE The instruction is carried out The speed of an FDE cycle depends on how fast the processor is (the length of time it takes for the signals to be sent to the control bus, and how many T-cycles each assembly instruction takes to execute. Memory Random Access Memory is sometimes known as main memory. RAM is volatile, which means it loses all the stored information when the power is cut off. Some computers also use virtual memory, which is stored in the hard drive but acts like RAM, this is much slower than physical memory. Another type of memory is Read Only Memory (ROM) which can be written to but cannot be erased. Data Storage Devices Floppy disk can be written to and erased, 1.44Mb CD ROM Can be written to but not erased, 700Mb Hard Drive stores many Gigabytes, can be written to and erased Zip Drive can be written to and erased, 100 250Mb Terminals Dumb Terminal A dumb terminal has no processing capabilities as they have no memory or processor of their own, it has only a monitor, keyboard and mouse. They are connected to a central processor. Intelligent Terminal An intelligent terminal contains memory and a CPU and is a standalone device. It only has to connect to the central processor when needed. Command to find terminal type terminfo Input / Output Devices Dumb Terminal Input keyboard and mouse. Output monitor Intelligent Terminal Input keyboard, mouse, scanner, touch screen. Output monitor, printer, speakers Software Components Kernel The Kernel is the heart of the operating system, the lowest level or the central part. Communication with the hardware is through the kernel. In multi user operating systems it is the kernels job to keep each process and user separate and to organize access to the system hardware, including CPU, memory, disk and other I/O devices. Device Handlers A device is any piece if hardware that is used in an operating system. A device handler is a piece of software within the operating system that communicates with the devices and tells them what to do. This is part of the operating system that is responsible for servicing requests of the device request queue. Spoolers (Simultaneous peripheral operations on-line) Spooling is used when data is waiting to go to an output device after it has been processed. The data is placed into a queue so that the CPU can process something else instead of having to slow down to the speed of the output device. Spoolers are used on mainly old devices e.g. old printers that can only handle one job at a time User Interface This is how the user can view the data within the operating system. The main types of user interfaces are; the graphical user interface e.g. Windows and Command driven interface e.g. MS DOS and standard UNIX. The CDI was more complicated to use than a GUI as you would have to know certain commands to do very basic tasks. Bibliography Index http://physinfo.ulb.ac.be/cit_courseware/opsys/ostart.htm http://electronics.howstuffworks.com/operating-system1.htm http://physinfo.ulb.ac.be/cit_courseware/opsys/ostart.htm http://www.canberra.edu.au/~sam/whp/unix-cmd.html http://cm.bell-labs.com/

Introduction Of Engine Block

Introduction Of Engine Block Until recently, cast iron and aluminum alloys have been successfully used to manufacture most diesel and conventional gasoline-powered engine blocks. However, with a greater emphasis on increasing the efficiency of the engine via weight reduction, there is a search for alternative alloys that are lighter than cast iron and aluminum alloys, while retaining the necessary strength to withstand the forces of an engine. In the late 1990s engine blocks made from plastic and other experimental materials were being used in prototype cars with the hope of developing more lightweight, efficient vehicles . Also lately new manufacturing processes have been developed that have brought to light two new alloys suitable for use in an engine block, magnesium alloy AMC-SC1 and compacted graphite cast iron (CGI). Thus this project will cover, the functional requirements of the engine block, the processes used to manufacture the part, and the mechanical properties of the alloys. INTRODUCTION: Todays engines are an integral component of an automobile that are built in a number of configurations and are considerably more complex than early automotive engines. The use of lighter and stronger engineering materials to manufacture various components of the engine has also had an impact allowing engineers to increase the power-to-weight of the engine, and thus the automobile. Since the engine block is also a relatively large component, it constitutes 20-25% of the total weight of an engine. Thus there is much interest in reducing the blocks weight.[Keay, Sue: Diet of Australian metal lightens cars and pollution, Media release, 14 October 2002.] Many early engine blocks were manufactured from cast iron alloys primarily due to its high strength and low cost. But, as engine designs became more complicated, the weight of the engine (and thus the vehicle) had increased. Thus the need to come up with lighter alloys that were as strong as cast irons arose. One such material that was being used as a substitute was aluminum alloys. Together, these two metals were used exclusively to fabricate engine blocks. Lately , however, a new material process has made a magnesium alloy suitable for use in engines. The alloy, called AMC-SC1, weighs less than both cast iron and aluminum alloys and represents new possibilities in engine manufacturing. A new manufacturing process have made compacted graphite cast iron (CGI) a viable alternative to gray cast iron for the manufacture of diesel engine blocks. Like magnesium alloys, this material offers a higher strength and lower weight than gray cast iron. Thus this section will cover materials used to manufacture engine blocks , component discussion, its functional requirements, and the materials used to manufacture the part. The mechanical properties of the individual alloys will be incorporated, along with the manufacturing processes used to fabricate the component. DESCRIPTION OF THE PRODUCT: WHAT IS AN ENGINE BLOCK? : The engine block is vital structure of vehicles which run on internal combustion, providing the powerhouse for the vehicle. The engine block is termed a block because it is usually a solid cast, housing the cylinders and their components inside a cooled and lubricated crankcase .Common components found in an engine include pistons, camshafts, timing chains,rocker arms, and other various parts. When fully stripped of all components, the core of the engine can be seen: the cylinder block. The cylinder block (popularly known as the engine block) is the strongest component of an engine that provides much of the housing for the hundreds of parts found in a modern engine. The block is typically arranged in a V, inline, or horizontally-opposed (also referred to as flat) configuration and the number of cylinders range from either 3 to as much as 16. Figure 1 shows engine blocks with V configuation. opposed configurations. Functional Requirements of a Cylinder Block: Because engine blocks are a critical component of an engine, it must satisfy a number of functional requirements. These requirements include withstanding high cycle fatigue stresses, thermal strains, and aggressive wear conditions over the full life of the engine, housing internal moving parts and fluids, ease of service and maintenance. REQUIRED MATERIAL PROPERTIES: The one-dimensional era of engine design is finished. The current approach considers the loads acting at each point of the engine block. (Vollrath, 2003) In order for an engine block to meet the above functional requirements, the engineering material(s) used to manufacture the the cylinder block material should have adequate strength and rigidity in compression, bending, and torsion. This is necessary to resist the gas pressure loads and also for the components, which convert the reciprocating motion of individual piston into a single rotary motion. The cylinder-block material should (a) be relatively cheap, (b) readily produce castings with good impressions, (c) be easily machined, (d) be rigid and strong enough in both bending and torsion, (e) have good abrasion resistance, (f) have good corrosion resistance, (h) have a high thermal conductivity,(to prevent failure under high temperatures). (i) retain its strength at high operating temperatures, and (J) have a relatively high thermal expansion, low density.(to resist expanding under high operating temperatures) High strength is a particular concern in diesel engines, since compression ratios are normally 17.0:1 or higher compared to about 10.0:1 for conventional engines. , and thermal conductivity . Good machinability and castability of the metal alloy are also important factors in selecting the proper material, as the harder it is to machine the product, the higher the costs of manufacturing. In addition to the previously mentioned properties, the alloys must possess good vibration damping to absorb the vibrations of the moving parts. METALS USED IN THE MANUFACTURE OF THE CYLINDER BLOCKS: Based on the functional requirements of the cylinder block and the material properties required to meet the functional requirements, industries have used cast iron and aluminum alloys to manufacture the blocks. EXISTING MATERIALS: 1)Cast iron alloys are used because of the combination of good mechanical properties, low cost, and availability. 2)Certain aluminum alloys combine the characteristics of iron alloys with low weight, thereby making the material more attractive to manufacturers who are seeking a competitive edge. NEW MATERIALS: 3)Compacted graphite cast iron is lighter and stronger than gray cast iron, making the alloy a more attractive alternative to the latter in the production of cylinder blocks, particularly in diesel engines. 4)Magnesium alloys, which were previously unsuited for use as an engine block material, have the advantage of being the lightest of all the mentioned metals, yet still retains the required strength demanded by a block. 1)GRAY CAST IRON ALLOYS: Gray cast iron alloy have been the dominant metal that was used to manufacture conventional gas-powered engine blocks. Though extensive use of aluminum alloys has minimized the popularity of this material, it still finds wide use in diesel-fueled blocks, where the internal stresses are much higher. The use of cast iron blocks has been wide spread due to its low cost and good formability. Generally types of gray cast iron of pearlite microstructure is used in the manufacturing of engine block. Gray cast iron alloys typically composition: A typical cast iron is a gray cast iron, which contains 2.5-4 wt.% carbon, 1-3 wt.% silicon, 0.2-1.0 wt.% manganese, 0.02-0.25 wt.% sulfur, and 0.02-1.0 wt.% phosphorus [Anyalebechi, P.N.: Essentials of Materials Science Engineering, January 2005, p. 94.]. and the balance (93.6%) iron. The carbon improves lubrication property of graphite, the silicon controls the formation of a laminated structure, called pearlite, which has good wear resistance, and the manganese strengthens and toughens the iron structure. A common aluminium alloy composition is 11.5% silicon, 0.5% manganese, and 0.4% magnesium, with the balance (87.6%) aluminium. The high silicon content in this alloy reduces expansion but improves cast-ability, strength, and abrasion resistance, while the other two elements strengthen the aluminium structure. While this alloy provides a good corrosion resistance, it can absorb only moderate shock loads. Types of cast iron used in engine block: SAE grade G2500- used for small engine blocks. SAE grade G3500-used for heavy and larger diesel engine blocks. Also some ductile iron are also used in manufacturing engine blocks. SAE AMS 5313C: mechanical properties: [alloying: understanding the basics , by joseph R devis.] Grade or class Hardness HB(a) Tensile strength min(b) MPa Yield strength min(b) MPa Elongtion in 50 mm(2in),%(b) Class A 190 max 414 310 15 Gray cast iron has excellent damping capacity, good wear and temperature resistance, is easily machinable, and is inexpensive to produce. However, gray cast irons are relatively weak and are prone to fracture and deformation. Although cast iron meets most of these requirements, it has a low thermal conductivity and is comparatively heavier. Due to these limitations, light aluminium alloys have been used as alternative cylinder-block materials for petrol engines. Cylinder liners are optional with cast-iron blocks; but are more essential with the relatively soft light aluminum alloy blocks, as they cannot directly withstand wear resistance. Because of the lower strength of the aluminum alloys, the blocks are cast with thicker sections and additional support ribs, so that their weight becomes about half of the equivalent cast-iron blocks. Due to these problems, compacted graphite iron has recently begun to compete with gray cast iron as the choice material to produce diesel engine blocks. COMPACTED GRAPHITE CAST IRON: Compacted graphite cast iron (CGI), which was accidentally discovered while trying to produce ductile cast iron, possesses higher tensile strength and elastic modulus than gray cast iron due to the compacted graphite found on the microstructure of CGI. Figure 8 CGI typical microstructure: 5% nodularity, 9% graphite, 265 particles/mm2. 3. CGI a new combination of properties: As shown in Fig. 8, the compacted graphite iron graphite particles appear as individual worm-shaped or vermicular particles. The particles are elongated and randomly oriented as in gray iron; however they are shorter and thicker, and have rounded edges. The compacted graphite morphology inhibits crack initiation and growth and is the source of the improved mechanical properties, as compared to gray iron. Compacted graphite iron invariably includes some nodular (spheroidal) graphite particles. As the nodularity increases, the strength and stiffness also increase, but only at the expense of castability and thermal conductivity (Guesser et all, 2001). It is usual to set a limit of 20% nodularity for CGI specifications. Table 1 shows mechanical properties of CGI, with grades from 300 to 500 MPa. In the case of cylinder blocks and heads, where castability, machinability and heat transfer are all of paramount importance, it is necessary to impose a more narrow specification. A typical specification for a CGI cylinder block or head can be summarised as follows: 1) 0-20% nodularity, for optimal castability, machinability and heat transfer 2) No free flake graphite, flake type graphite (as in grey iron) causes local weakness 3) >90% pearlite, to provide high strength and consistent properties 4) This general specification will result in a minimum-measured tensile strength of 450 MPa in a 25 mm diameter test bar, and will satisfy the ISO 16112 Compacted Graphite Iron standard for Grade GJV 450. The typical mechanical properties for this CGI Grade, in comparison to conventional grey cast iron and aluminium are summarised in Table 1: Mechanical and Physical Propertiesof CGI in comparison to conventional grey cast iron and aluminium at 20 °C Property Units GJV 450 GJL 250 GJL 300 A 390.0 Ultimate Tensile Strength MPa 450 250 300 275 Elastic Modulus GPa 145 105 115 80 Elongation % 1 to 2 0 0 1 Rotating-Bending Fatigue 20 °C) MPa 210 110 125 100 Rotating-Bending Fatigue (225 °C) MPa 205 100 120 35 Thermal Conductivity W/m-K 36 46 39 130 Thermal Expansion ÃŽÂ ¼m-m-K 12 12 12 18 Density g/cc 7.1 7.1 7.1 2.7 Brinnell Hardness BHN 10-3000 215-255 190-225 215-225 110-150 The results allow the comparison between CGI and gray iron. It can be seen the increase on tensile strength, moving from gray iron to CGI. CGI also shows a higher elastic modulus, when compared to gray iron. [- Mechanical properties of gray iron and CGI grades 400-450. 195-230 HB. Samples taken from the castings (Guesser, 2003)]. Figure 10 [Elastic modulus of gray iron and CGI grade 400. 12.0L I6 cylinder block (Guesser, 2003).] The results in Figure 10 were obtained from two sources: test bars and main bearings of a 12.0L cylinder block. The increase in elastic modulus, from 100 GPa for gray iron to 150 GPa for CGI, results in slighter cylinder bore distortion as reported by Tholl et all (1996), therefore reducing oil consumption and emissions. Results of fatigue strength tests can be seen on figure 11, comparing gray iron grade 250 and CGI grade 450, samples from an I6 5.9L diesel cylinder block. The fatigue limit for the gray iron is 62-79 MPa, depending on the carbon content, while for the CGI the fatigue limit is 175 MPa. The raise of fatigue strength allows the designer to reduce the cylinder block weight. As a result of mechanical properties improvements, a design study conducted by AVL Austria (Sorger Holland, 1999) has evaluated downsizing opportunities for a 1.8 L diesel engine cylinder block, converting from gray iron to CGI. The benefits of this conversion included: 1)9% reduction in overall weight of the finished engine 2) 22% reduction in weight of machined cylinder block 3) 15% reduction in overall length of the finished engine 4) 5% reduction in both; height and width of the finished engine Like gray cast iron, compacted graphite cast iron has good damping capacity and thermal conductivity, but its difficulty to machine has limited the wide-scale use of CGI. A new manufacturing process, however, has opened the way for larger applications of CGI. The development of rotary insert tools has increased the life of the tools used to machine the metal, thus allowing manufacturers to use CGI without worrying about purchasing new tools [Georgiou, George: Iron engines may be in your future, Tooling Production, September 2003, Vol. 69, issue 9, p. 26.]. MAGNESIUM ALLOYS: Magnesium alloys have been used in engines before, but not for cylinder blocks. Rather. The main advantage of this alloy is that the material is much lighter than cast iron and aluminum alloys and has the same strength as cast iron and aluminum alloys[Lampman, Steven: Tuning Up the Metals in Auto Engines, Advanced Materials Processes, May 1991, p. 17.][Anonymous, Magnesium alloy resists high temperature in engine blocks, Advanced Materials and Processes, August 2003, vol. 161, issue 8, p. 13.]. Material scientists and engineers were determined to exploit these characteristics of magnesium alloy and use it to fabricate engine blocks. There were a number of magnesium alloys available that met or exceeded the requirements demanded by manufacturers for an engine block, but insufficient material stability at high temperatures hindered their actual use. Following are the two alloys which have been found suitable for mass production of engine blocks. AMC-SC1: In 2003 material scientists and engineers from the Cooperative Research Center for Cast Metals Manufacturing and the Australian Magnesium Corporation presented their discovery of sand-cast AMC-SC1 magnesium alloy [Anonymous, Magnesium alloy resists high temperature in engine blocks, Advanced Materials and Processes, August 2003, vol. 161, issue 8, p. 13.]. This grade of magnesium alloy contains two rare earth elements, lanthanum and cerium, and was heat-treated with T6. This stabilizes the strength of the alloy at high engine operating temperatures, which is a necessary requirement for a cylinder block material [16]. Bettles et al. had performed experiments to determine the yield and creep strengths of AMC-SC1 and their results are shown in Table 3 [Bettles, C. et al., AMC-SC1: A New Magnesium Alloy Suitable for Powertrain Applications, Society of Automotive Engineers, 2003, p. 2.]. From Table 3, the most significant point is that the yield strength of AMC-SC1 essentially stays the same at 177 °C as it does at room temperature. Table 3: Yield and creep strengths of magnesium AMC-SC1 at room temperature, 150 °C, and 177 °C [17]. Room temperature 24 °C 150 °C 177 °C Yield strength, MPa 120 116 117 Creep strength, MPa 120 98 This means that the material is able to tolerate a wide range of operating temperatures without a loss in strength. Other properties of the magnesium alloy 10 include good thermal conductivity, excellent machining and casting qualities, and excellent damping characteristics. To demonstrate the significant weight savings of magnesium alloy over cast iron and aluminum alloy, consider BMWs inline-6 R6 (shown in Figure 4), which replaced the companys M54 aluminum engine. Its cylinder block is made of AMC-SC1 and is said to have decreased the weight of a comparably-built gray cast iron and aluminum alloy block by 57% and 24% [Jost, Kevin: BMW builds better inline six, Automotive Engineering International, January 2005, pp. 20-32.]. So far, BMW is the only company to have used magnesium alloy cylinder blocks in production vehicles. But, with a significant weight advantage over the current alloys used today and negligible increase in cost, other manufacturers will begin to consider the use of AMC-SC1 and possibly other grades of magnesium alloys for engine blocks. Figure 4: BMWs 6-cylinder R6 powerplant uses a magnesium alloy AMC-SC1-fabricated cylinder block [Jost, Kevin: BMW builds better inline six, Automotive Engineering International, January 2005, pp. 20-32.]. PRODUCTION PROCESS: STANDARD CASTING WITH SOME MODIFICATIONS: This alloy can be cast using a standard production process, with some modifications. For a magnesium alloy engine to be economically viable, it is not merely the cost of the alloy that is important. The casting process must also be commercially viable. There are several modifications required if an existing casting line of cast iron or aluminum is to be converted to one producing magnesium parts. These can be summarised as follows: à ¢Ã¢â€š ¬Ã‚ ¢ A new inhibitor in the sand cores to prevent reaction between the melt and the sand. à ¢Ã¢â€š ¬Ã‚ ¢ A redesign of the runner and gating system to ensure adequate filling (magnesium alloys have a low heat content). à ¢Ã¢â€š ¬Ã‚ ¢ Preheating of the core package to 150 °C. à ¢Ã¢â€š ¬Ã‚ ¢ Modifications to the core package design to allow low pressure rather than gravity filling and feeding. AM-HP2: AM-HP2 A High Pressure Diecasting Magnesium Alloy: The AM-HP2 magnesium alloy has similar high-temperature strength to AM-SC1 and has been specially tailored for use in the high pressure diecasting process. Like AM-SC1, the light-weight alloy significantly increases fuel-efficiency, environmental sustainability and vehicle agility and is suitable for the powertrain components of vehicles, such as engines blocks etc. Need for New alloy:AM-HP2 AM-HP2 has been specifically developed as a diecasting alloy for high temperature automotive powertrain applications, such as engine blocks, structural sumps and automatic transmission housings. The alloy is based upon the successful sand casting alloy, AM-SC1, with a modified composition to make it suitable for the high pressure die casting process. Commercial Opportunities AM-HP2 Magnesium Alloy in the Auto industry: High pressure diecasting is a highly productive process for mass production of light alloy components. While the casting integrity of sand casting and low pressure/gravity permanent mould castings is higher than high pressure diecasting, the latter technology is cheaper. Thus, this process is gaining popularity among auto manufacturers for casting of aluminium engine blocks. It is also the common process for powertrain components such as transmission housings. There is a strong demand in the automotive industry for a suitable high pressure diecasting magnesium alloy for high volume powertrain applications. AM-HP2 exhibits good diecastability and the required high temperature mechanical properties for engine components (including engine blocks) and automatic transmission housings. It has similar creep properties to alloy, AM-SC1. Advantages of AM-HP2 Magnesium over Other Alloys: A key advantage of AM-HP2 is that the alloy is more diecastable than competitor high temperature creep resistant magnesium alloys.Thus, the alloy can be more readily cast into complex shapes with fewer rejects and a wider operating window. The alloy also has better high temperature creep strength than its competitors and thus offers considerable advantage to engine designers seeking to obtain maximum performance for lowest weight and cost. current status of AM-HP2 magnesium development: Pilot scale diecasting trials and laboratory testing of mechanical properties have demonstrated the suitability of AM-HP2 for mass produced powertrain components. PRODUCTION PROCESSES: 3.2 Casting Processes There are two methods used to cast engine blocks for all materials: green sand molding or lost foam casting. The latter, pioneered by General Motors for their Saturn vehicles, have[11] become more popular due to its capability to produce near net shape components, provide tight tolerances for critical components, and reduce machine maintenance and cost [19]. Green sand molding, however, is still widely used in industry as material costs are low and most metals can be cast by this method [Luther, Norris: Metalcasting and Molding Processes, [Online], 22 March 2005-last visited, Available: http://www.castingsoruce.com/tech_art_metalcasting.asp.]. 3.2.1 Green Sand Molding: Green sand molding the common method to cast engine blocks. The term green denotes the presence of moisture in the molding sand . Figure demonstrates the pattern used in sand casting. The pattern mounted into the moulding box along with the runner and ingate system ready to produce a mould. [http://www.dmdaustralia.com.au/block1.html] From Figure 2, a combination of silica sand, clay, and water poured in one-half of the block pattern with a wood or metal frame. The mold is then compacted by squeezing or jolting, and the process is repeated for the other half of the mold. A core consisting of hardened sand is used for support. Then, molten cast iron, aluminum, or magnesium alloy is poured into the combined molds and solidifies. Once the latter part has been completed, the molds are removed, and the cylinder block is cleaned and inspected. Heat treatment of the block is then undertaken to improve the mechanical properties of the alloy for suitable use. [7]. 12 LOST FOAM CASTING: THE PROCESS: Figure 6: Graphical description of the last 6 of 7 methods of the lost foam casting method [Anonymous, Aluminum Cylinder Block for General Motors Truck/SUV engines, A Design Study in Aluminum Casings, pp. 1-31.] The lost foam casting process uses a expanded polystyrene replica of the part being cast. 1)The coated replica/pattern is placed in a flask and loose sand is placed around the pattern and shaken into its voids. 2)Molten metal is then poured through a foam sprue, or funnel, into the sand where the hot metal melts and displaces the foam of the pattern. 3)the metal cools in the shape of the part. The basic steps of the lost foam casting process are: 1) Pattern Molding Bead Pre expansion and Conditioning, Tool Preheat, Pattern Molding, Pattern Aging 2)Pattern/Cluster Assembly 3)Pattern Coating and Drying 4)Sand Fill and Compaction Metal Casting and Cooling 5)Shakeout, Clean-up, and Finishing Lost foam casting is a more reliable and efficient casting technique of the manufacture of engine blocks than green sand molding. The technique begins with the use of polystyrene beads placed in preexpanders for wet expansion to control bead size and density to produce four separate block moldings to be glued together to form the final mold [7, 19]. Next, the metal tool is preheated to remove any moisture and then filled with the beads. The tool is then heated via steam and placed in an autoclave, where it is subjected to high pressures in order to create the molds [7]. The tool is removed from the autoclave and immersed in water to finish the moldings. Precise control over the heating and cooling aspect ensures dimensionally accurate, smooth and strong molds [Anonymous, Aluminum Cylinder Block for General Motors Truck/SUV engines, A Design Study in Aluminum Casings, pp. 1-31.]. If the tool was not heated before the beads were injected, the results would be rough finishes in the molds with low-strength sections. If the tool and beads stay heated for an extended period of time, or is not cooled enough, the beads become overfused, which produces surface variations in the moldings. If the tool has been inadequately cooled, the molds will contain variations in dimensions [Anonymous, Aluminum Cylinder Block for General Motors Truck/SUV engines, A Design Study in Aluminum Casings, pp. 1-31.]. Figure 3 shows the final half stages of the lost foam casting method. . From Figure 3, once the individual molds are glued together, the assembly is placed in a vat with water-based ceramic liquid to prevent molten metal from destroying the mold, stiffen the assembly, and provide a smooth finish [Anonymous, Aluminum Cylinder Block for General Motors Truck/SUV engines, A Design Study in Aluminum Casings, pp. 1-31.]. The assembly can also be sprayed with the ceramic liquid, but is a time-consuming process. Next, the coated foam engine block is filled with sand,[13] compacted, and immersed in the molten metal alloy. Once cooled, sand is removed from the metal casting, cleaned, and undergoes heat treatment to increase the mechanical properties of the block. Finally, coolant and oil passages are machined into the block. Advantages over conventional sand casting: Unlike conventional sand casting, the lost foam process allows more complex and detailed passages and other features to be cast directly into the part. The lost foam process: 1) Forms complex internal passages and features without cores. 2) Reduces part mass with near net shape capability. 3) Eliminates parting lines. 4) Reduces machining operations and costs. 5)Provides for tight tolerances in critical areas and features. Lost Foam Casting for Fine Features: The lost foam casting process allows more complex and detailed passages and other features to be cast directly into the cylinder block. 1) In the cylinder block, oil galleries, crank case ventilation channels, oil drain back passages, and coolant passages are cast into the block. 2) These features would otherwise require drilling or external plumbing (with a potential for leaks). 3)Lost Foam castings have tighter dimensional tolerances compared to sand castings, because variations caused by core shift and core variability are eliminated and there is much less tool wear over the production life. The direct result is a significant reduction in machining costs and infrastructure investment and fewer opportunities for errors in machining and assembly. A comparison of green sand casting to lost foam casting shows a number of distinct advantages for lost foam: Property Green Sand Casting Lost Foam Casting Complex Internal Features and Part Consolidation Complexity determined by sand core limitations geometry, strength, and cost. Extensive and complex internal features (as small as 0.20) available in lost foam, based on detail duplication and pattern assembly in foam. Dimensional Tolerances +/- 0.030 is typical depending on part size, complexity, and geometry +/- 0.005-0.010 is typical depending on part size, complexity, and geometry. Surface Finish Capabilities 250-600 microinches typical. Depends on grain fineness of sand. 60-250 microinches typical. Depends on bead size and ceramic coating grain fineness. Feature Accuracy Core movement and shift between mold halves across the parting line limit feature accuracy. No cores or mold halves to shift and degrade feature accuracy Parting Line and Draft Angles Parting lines and draft angles are necessary for molding. No parting lines in the mold and minimal draft on tools. Environmental Costs Sand recovery requires binder removal and time consuming sand clean-up Sand is binder free, so it can be easily and rapidly recovered a

Things Fall Apart By Chinua Ac :: essays research papers

Chinua Achebe wrote the novel, Things Fall Apart, which is a great piece of African literature that deals with the Ibo culture, society, and history. One place where the Ibo religion is practiced is in the village of Umuofia in Africa, where the story takes place. On the other hand, Christianity is a very common religion that is practiced all over the world. Although Christianity and Ibo are both types of religions, they have many differences. One way the religions are different is the Ibo practice polytheism and Christians practice monotheism. A second difference is the Ibo believe in animate Gods unlike Christians who believe in an inanimate God. Another contrast is the Ibo practice polygamy unlike the Christians who practice monogamy. A final contrast is the afterlives of the two religions. First of all, the Ibo practice polytheism and Christians practice monotheism. Polytheism is the belief in more than one God, and monotheism is the belief in one God. Christians believe in one supreme creator of the heavens and the earth, who is called God. In contrast, the Ibo have various gods who they worship. The conversation between Mr. Brown, a Christian missionary in the village of Umuofia, and Akunna, a member of Umuofia, explains the Ibo religion very well. Akunna said that the Ibo believe in one supreme God also, but they call him Chukwu because â€Å"he made all the world and the other gods.† Mr. Brown made the comment that the Ibo worship carved wood and Akunna replied by saying,†The tree from which it came was made by Chukwu, as indeed all the minor gods were.† Akunna also said that the Ibo â€Å"make sacrifices to the little gods, but when they fail and there is no one else to turn to they go to Chukwu.† (179-180). Another god, besides carved wood, that the Ibo worship is the Oracle of the Hills and the Caves. The Ibo believe they must do whatever the Oracle of the Hills and Caves says or they will be punished. An example of this is when the Oracle of the Hills and Caves pronounces that Ikemefuna, the boy living with Okonkwo, be killed. Since the Oracle of the Hills and Caves had said it must be done, the men of Umuofia took the boy outside the village and killed him. (57). Another god the Ibo worship is the snake, which is called the sacred python.

Samuel Huntingtons The Clash of Civilizations and the Remaking of Worl

Abstract Samuel Huntington's The Clash of Civilizations and the Remaking of World Order defines eight major civilizations on the basis of religion. This division of global powers can be used to prove that the Western civilization will never completely dominate the global media. While Western thought tends to lead to a more representative form of government, and consequently a more libertarian or social responsibility-based media, the other belief systems of the global powers tend to lead to more authoritarian government and media formats. This difference creates constant conflict between the global powers, thus disabling any one civilization from subjugating the others. Issue Paper In The Clash of Civilizations and the Remaking of World Order, Samuel Huntington asserts the idea that the end of the Cold War marked the beginning of a realignment of global powers. Huntington believes these powers, or civilizations, can be distinguished by religion, and he divides the post-Cold War world into eight major civilizations: Sinic/Confucian; Japanese; Hindu; Islamic; Orthodox; Western; Latin American; and possibly African (45-47). This division of power among religion is the basis for the argument against complete Anglo-dominance of a "global media." The vast differences among the various civilizations' treatment of the media will prove too great for even the transnational corporations to overcome. To take Huntington's theory one step further, the religious differences among these civilizations will be at the heart of the inability of the Western (Anglo-dominated) world to exert total power over the rest of the world. Huntington is careful to separate each religion, excepting Japanese, Latin American and African, from any particul... ...ations of the Moscow Patriarchate, "The Russian Orthodox Church Today." 1996. Grice, Corey. "Russia, Latin America installing fiber-optic networks." CNET News.com. February 3, 2000. Hickerson, Delvin and Trevor Kirkland, The Geography of Confucianism. May 17, 1999. Huntington, Samuel, The Clash of Civilizations and the Remaking of World Order. New York: Simon & Schuster, 1996. Infobeat / AP. "Japan publishers pressured to tone down descriptions." November 11, 1999. Newsday / AP. "Japan Crown Prince attacks press." February 23, 2000. Sprunger, Meredith. The Urantia Book -- On-line Reference Edition. 2000. The New York Times / AP. "Algeria detains photographer." April 03, 2000. The Washington Post. "War reports limited on Russian TV." October 11, 1999. Yahoo / Reuters. "Afghanistan art gallery reopens, but portraits banned." February 22, 2000.

Use of Project Management Software in Business Essay -- Business Manag

Use of Project Management Software in Business Project Management is using the concepts of information technology in businesses to meet the requirements of a particular project. It depends on the process it needs to take to implement a project. The application of knowledge, skills, and tools and techniques is needed (http://www.asp.org/infoglossary/p). There are 3 main phases of project management, they are planning, scheduling and controlling. How the process is implemented is through different types of software applications used to efficiently and effectively run a business to save time, money and resources. A goal (project) is set, the project should be defined, and schedule out each task needed for completion, and identify teams and resources. By controlling, managers need to revise or change plans by monitoring resources, cost, and quality. Lastly, scheduling involves sequencing and allotting time to all project activities. This is where time and resources come in to see how much time is needed to complete, the people to work, and materials needed for the project. There are different project scheduling approaches depending on the project. Project Management in business is very important now that technology is all around us. It has made a difference in customer relationship management by meeting the needs of the customer. It gives the customer a broad range of information to choose from and with the types of information that are readily available. As well as with the customer service and support that is there for customers. It is also important to the businesses when it comes to supply chain management. They are better equipped to develop a fast, efficient, and low cost network of business with their partners to get products from concept to market. I have observed in our readings that the ERP software have failures, but I have seen in my previous employments, that businesses do implement certain software before they do a test run. Some companies who have the software are usually good about doing orientation and training to employees before they begin using the applications. It takes time away from the organizations to do training and also correcting mistakes that happen along the way, but in the end it pays off. I recommend that businesses could implement an overview of the new software before it is implemented. Th... ...ter over the internet, as we call it e-commerce. The difference between the past and future is enormous in the world of project management. It is so important to businesses, consumers, and all stakeholders. Although, not all software work for certain businesses, but with more training and knowledge in project management will improve the process of implementing technology in businesses. Summary: In researching project management, it is an innovation that has a continuing change. People change through knowledge and every innovation does not stay the same. Implementations of projects are also different and the software process has to meet the demands of businesses. For a company to stay abrupt of the changing cycle of technology is an advantage to stay ahead of their competitors. The complexity of documentations has opened the interenterprise of technology in customer relationship management, supply chain management, and enterprise resource planning. Bibliography http://www.asp.org/infoglossary/p http://www.aceproject.com/features.htm http://www.cob.sjsu.edu http://www.cidainc.com Last, first. Operations Management p.58, 60. Date. Page #

English Language Anxiety Essay

English as all know is the international communication language which plays a great role in many important aspects of a society. In Malaysia, English as a second language after Malay language, is not only used in terms of education system, but is extensively used in inter-cultural communication and professions such as law, medicine, engineering and of course business. In this era of increasing globalization, Malaysia will have to face with tighter and rigid competition from other foreign countries. In accordance to that, Malaysian students will have to get themselves ready for the upcoming circumstances especially those involving the usage of English. Malaysian students have been learning English continuously for at least 11 years starting from primary school till secondary school before enrolling themselves into a third-level education. English has been a compulsory subject for students in Malaysia in which they need to pass in all the major examinations in Malaysia such as UPSR, PMR and SPM. In higher education, English is used more expressively as entire main and core subjects such as medical, law, algebra and business use English as the principal language. Whether it is a local university or a private one, English has become the main source of commandment other than becoming a subject in the curriculum. To exemplify, universities which use English as the medium of language such as International Islamic Universities Malaysia (IIUM), which has been an English-medium university since it was first established in 1983, require its students to pass a standard level of English before enrolling into the university. The students will be tested again during their orientation week on English language by undergoing an English Placement Test ( EPT). Students who gain level 6 and below will be placed in English classes till they have reached the standard of exemption. These English classes are necessary as all the subjects taught are in English. These efforts show the importance of English in education. After graduation, students who are proficient in English will have a better future as they will be easily employed by multinational companies. One of the job’s specifications in Malaysia is to have soft skills especially the ability to communicate in good English. Furthermore, job interviews nowadays are also conducted in English. Here it is clear that, in order to have better chances in future, one must have full confidence in using English language. Nonetheless, English is not the first language for most Malaysian students. Most Malaysian students use their own mother language, for example Malay language, Mandarin and Tamil when communicating with family and friends. This will cause their English language skills to rot if it is continuously being practiced which will later on lead to anxiety in the process of learning English. After a minimum of 11 years of studying English in both the primary and secondary schools, students in the Centre for Foundation Studies ( CFS), IIUM still have difficulties in using the language effectively. For example, a study by Mohd Hilmi Bin Hamzah ( 2007) in CFS, â€Å"in Semester 1, 2006/2007, more than 40% of the students taking first level English obtained grade â€Å"D† in their papers, while only 5% of them obtained an â€Å"A†Ã¢â‚¬ . This shows that the students have not yet mastered the language before entering the university. The writer added that despite of having English Intensive Class Programme and extra classes by individual English lecturers, the level of English proficiency remains dissatisfactory. With the increasing usage of English globally, it is really necessary to find out the factors which may hinder English language learning. One of the factors which has not been paid attention to is language learning anxiety. â€Å"Anxiety is a major factor that affects second/foreign language learning† ( Mohammad Javad Riasati, 2011). He also states that levels of anxiety differ from one individual to another but is always present. Most of today’s education and economy uses English as the language of commandment. For that reason, it is really important to find out the factors which affect anxiety and ways to reduce it to increase the performance of an English language learner. Different students have different proficiency levels in English language skills namely reading, writing, listening and speaking. With that reason, different students will also encounter different levels of anxiety for all those skills. One student may feel more anxious in speaking while the other in writing. As all of these four skills are needed to be mastered in order to be proficient in English, even by losing confidence in only one of it might cause difficulties in carrying out tasks in both education and job. This study will help both the educators and learners of English language in CFS, IIUM. The teachers will get information about the factors causing anxiety among students. They will also be given information on the rank of students’ anxiety in possessing the 4 language skills namely writing, listening, reading and speaking so that the teachers will consider about which one of these 4 language skills should be given more attention to. Last but not least, the findings of this study will help both the students and teachers to design a suitable strategy on ways to reduce anxiety in order to increase the performance of mastering English language. This study specifically addresses the following 3 research questions: 1) Which language skill namely writing, listening, speaking and reading creates the highest anxiety level among students in CFS, IIUM? 2) What are the factors that are probable to cause anxiety? 3) What are the ways used by the students to reduce anxiety? The objectives of this study are as follows: 1) To identify specific language skill in which students in CFS, IIUM feel most anxious. 2) To identify the factors which are more probable to cause anxiety. 3) To identify the ways students use to reduce anxiety. According to Hansen (1977), anxiety is â€Å"an experience of general uneasiness, a sense of foreboding, a feeling of tension† (p. 91). Anxiety is a type of psychological phenomena and ranges from mixture of open views of behavioral attribution. Due to anxiety’s impact on the students’ performance in learning English as a second language, it has been continuously studied by many researchers. Learning a second language will cause awareness among the learners that they are using a language which they have not yet mastered to communicate (Toth, 2011). This phenomenon will lead to many upcoming problems the learners have to face in using English as they have not completely accepted a second language as a part of their lives. This is according to Cohen and Norst ( 1989) â€Å" language and self/identity are so closely bound, if indeed they are not one and the same thing, that a perceived attack on one is an attack on the other† (p. 76). This will somehow lead students of English learners to feel less enjoyable during their class. Few studies conducted about the factors that affect anxiety are communication apprehension ( McCroskey, 1970), fear of negative evaluation ( Watson & Friend, 1969) and test anxiety ( Sarason, 1978). Communication apprehension for example is the difficulty in understanding teacher’s instructions, negative evaluation for example is the fear of correction and last but not least, example of test anxiety is the fear of failing in the class. According to Young ( n.d.), language anxiety is caused by â€Å" (a) personal and interpersonal Anxiety, (b) learner beliefs about language learning, (c) instructor beliefs about language teaching, (d) instructor-learner interactions, (e) classroom procedures and (f) language testing† ( Mohammad Javad Riasati, 2011, p.908). The 4 language skills namely writing, speaking, reading and writing plays vital role in helping students to attain proficiency in English Language. A study of anxiety in learning English as a foreign language by Wilson (2006) and Mohd Hilmi Bin Hamzah (2007) have included the findings on language skills. Wilson (2006) states that â€Å"†¦anxiety might exert a deleterious influence on language achievement and equally intuitively, that poor language achievement might arouse even more anxiety† (p. 25). In Wilson’s (2006) research, although a four-skills approach is used (taking in listening, speaking, writing and reading) the oral skill was emphasized. This shows that most students are afraid of speaking English as a second language during class. In his study, Young (1991) interviewed Krashen who stated that teachers often expect new students to perform beyond their expectations which increases the level of anxiety among students. This will further discourage the students to use English in their lives. â€Å" A students who believes that one must never say anything in English until it can be said correctly will probably avoid speaking most of the time† ( Khairi Izwan Abdullah and Nurul Lina Bt. Abdul Rahman, n.d.). An arouse of language anxiety from different language skills such as writing, listening, reading, speaking and grammar have further been studied by Brantmeier (2005), Hussein Elkafaifi (2005), Greyersen and Horwitz (2002) and Casado (2001). This will lead the learners to perform poorly especially in speaking. The feeling of anxiety needs to be treated to avoid students that have been affected by this problem to be carried away into some other serious problems. In some studies, it was found that anxiety levels were highest during the early stages of language learning and lessened at an advanced level. This has been concluded by MacIntyre and Gardner (1991, p.111), â€Å"an experience and proficiency increase, anxiety declines in a fairly consistent manner†. This means that if students keep on practicing all the language skills of English by reading books, listening to English songs, writing blogs and communicating in English continuously, they will be able to overcome the feelings of anxiety and will perform better. Methodology The main purpose of this study is to investigate the level of English learning Anxiety among the students of Centre for Foundation Studies (CFS), International Islamic University Malaysia (IIUM). A population from CFS, IIUM was chosen to identify the specific language skills in which students in CFS, IIUM feel most anxious, the factors which are more probable to cause anxiety and the ways the students use to reduce anxiety. Data for this research was collected through a set of questionnaire. This research employed the use of questionnaire research methodology. The instrument used to collect the data was a questionnaire containing nine questions. The questionnaire was passed to thirty students of the CFS, IIUM randomly where its scope of distribution was not limited on a certain course, level of study, age or gender. To ensure that the questions were fully understood by the students, a brief introduction about the topic was provided at the top of each questionnaire.

An AP prompt essay discussing how writers must prepare to be unsatisfied Essay

Everyday more and more people try to make a profession in being a successful writer. In this passage, aspiring writer Melusina Fay Peirce writes to novelist Marian Evans Lewes asking if beginning writing at thirty is too old. Evans is moved by this letter and responds mentioning thirty is not too old. In the letter, she comments that even an accomplished writer such as herself is rarely satisfied with hours of work. It is impossible to be an accomplished writer without having years of wisdom behind you. Throughout the passage, she utilizes various persuasive techniques such as refutation and analogies in order to depict novice work as tasteless. In Lewes response to Peirce, she incorporates many rhetorical strategies in order to convey that writers must prepare to be unsatisfied and must not be concerned about flattery because success in writing comes only with maturity. In the beginning of the letter, Evans uses a plethora of rhetorical strategies which suggest that in order to be a writer one must be ready to be unsatisfied. Evans declares her â€Å"consciousness is not of the triumphant kind†. Beginning her letter with a refutation immediately conveys that being a writer is a difficult life. Although one may put hours of hard work into a novel, satisfaction is not always achieved. She then states that â€Å"Exultation is a dream before achievement and rarely comes after†. Evans suggests that she often fancies admiration before her work is finished only to encounter a deficiency of praise after. While Lewes may be a praised writer, she shocks Peirce when saying she is rarely commended for her work; writers’ dreams are seldom met. When encountering the lack of the praise writers such as Evans tend to feel like a â€Å"poor husk†. Evans uses this word to convey the emptiness in which she feels after writing. One always feels like it is possible to create better work but doesn’t know where to look. She then continues on and inquire to Peirce â€Å"Does these seem melancholy? ‘. This rhetorical question implies that these feelings of â€Å"incompleteness† and emptiness are far less melancholy than self-flattery. This connects to the refutation at the beginning of the paragraph stating that writers seldom feel triumphant. Using the various strategies, Evans conveys that to be a writer one must not be concerned about flattery and must be prepared to be unfulfilled. In the next paragraph, Evans refutes Peirce’s main concern of being too old to start writing by giving support to the idea that success come with maturity. Lewes responds by mentioning â€Å"not to fancy yourself old because you are thirty, or to regret you have not written anything†. This refutation replies to Peirce’s concern that she is too old and tells Peirce not to worry. She then states that it does not even matter if one hasn’t written anything prior to being an established writer. Lewes then mentions that the writing of a young writer is â€Å"no better than trashy, unripe fruit†. The underdeveloped fruit mirrors the underdeveloped minds and writing of the young writers. He then states that there is nothing worse than a writer who has â€Å"exhausted himself†. One cannot burn out writing all of their material while young. A successful writer needs to be patient, as triumph in literature comes with experience in everyday life. Towards the end of the letter, Evans reflects that when she was young â€Å"she began a sort of writing which had no great glory belonging to it, but which she felt certain she could do faithfully and well†. This anecdote also works as an emotional appeal as it sympathizes with Peircr, implying mutual feelings both writers felt while young. Evans suggests that mature and older writers are more patient in their writing, consequently producing better works. Evans is very persuasive in her position which states achievements in writings will come along with maturity. In Lewes’s letter to Peirce, she includes numerous persuasive techniques in order to convey that writers must prepare to be unsatisfied and must not be concerned about flattery because success in writing only comes with maturity. Evans’s main point is that one is never too old to begin writing. An aspiring writer shouldn’t hold back on account that they haven’t produced descent works in the past. Wisdom, compassion and insight all come with years of aging and are needed to produce successful writing.