Wednesday, November 27, 2019

INTERNAL-COMBUSTION ENGINE Essays - Piston Engines, Free Essays

INTERNAL-COMBUSTION ENGINE Essays - Piston Engines, Free Essays INTERNAL-COMBUSTION ENGINE INTRODUCTION Internal Combustion Engine, a heat engine in which the fuel is burned ( that is, united with oxygen ) within the confining space of the engine itself. This burning process releases large amounts of energy, which are transformed into work through the mechanism of the engine. This type of engine different from the steam engine, which process with an external combustion engine that fuel burned apart from the engine. The principal types of internal combustion engine are : reciprocating engine such as Otto-engine, and Diesel engines ; and rotary engines, such as the Wankel engine and the Gas-turbine engine. In general, the internal combustion engine has become the means of propulsion in the transportation field, with the exception of large ships requiring over 4,000 shaft horsepower ( hp). In stationary applications, size of unit and local factor often determine the choice between the use of steam and diesel engine. Diesel power plants have a distinct economic advantage over steam engine when size of the plant is under about 1,000 hp. However there are many diesel engine plants much large than this. Internal combustion engines are particularly appropriate for seasonal industries, because of the small standby losses with these engines during the shutdown period. History The first experimental internal combustion engine was made by a Dutch astronomer, Christian Huygens, who, in 1680, applied a principle advanced by Jean de Hautefeuille in 1678 for drawing water. This principle was based on the fact that the explosion of a small amount of gunpowder in a closed chamber provided with escape valves would create a vacuum when the gases of combustion cooled. Huygens, using a cylinder containing a piston, was able to move it in this manner by the external atmospheric pressure. The first commercially practical internal combustion engine was built by a French engineer, ( Jean Joseph ) Etienne Lenoir, about 1859-1860. It used illuminating gas as fuel. Two years later, Alphonse Beau de Rochas enunciated the principles of the four-stroke cycle, but Nickolaus August Otto built the first successful engine ( 1876 ) operating on this principle. Reciprocating Engine Components of Engines The essential parts of Otto-cycle and diesel engines are the same. The combustion chamber consists of a cylinder, usually fixed, which is closed at one end and in which a close-fitting piston slides. The in-and-out motion of the piston varies the volume of the chamber between the inner face of the piston and the closed end of the cylinder. The outer face of the piston is attached to a crankshaft by a connecting rod. The crankshaft transforms the reciprocating motion of the piston into rotary motion. In multi-cylindered engines the crankshaft has one offset portion, called a crankpin, for each connecting rod, so that the power from each cylinder is applied to the crankshaft at the appropriate point in its rotation. Crankshafts have heavy flywheels and counterweights, which by their inertia minimize irregularity in the motion of the shaft. An engine may have from 1 to as many as 28 cylinders. Fig. 1, Component of Piston Engines. The fuel supply system of an internal-combustion engine consists of a tank, a fuel pump, and a device for vaporizing or atomizing the liquid fuel. In Otto-cycle engines this device is a carburetor. The vaporized fuel in most multi-cylindered engines is conveyed to the cylinders through a branched pipe called the intake manifold and, in many engines, a similar exhaust manifold is provided to carry off the gases produced by combustion. The fuel is admitted to each cylinder and the waste gases exhausted through mechanically operated poppet valves or sleeve valves. The valves are normally held closed by the pressure of springs and are opened at the proper time during the operating cycle by cams on a rotating camshaft that is geared to the crankshaft . By the 1980s more sophisticated fuel-injection systems, also used in diesel engines, had largely replaced this traditional method of supplying the proper mix of air and fuel; computer-controlled monitoring systems improved fu! el economy and reduced pollution. Ignition In all engines some means of igniting the fuel in the cylinder must be provided. For example, the ignition system of Otto-cycle engines , the mixture of air and gasoline vapor delivered to the cylinder from the carburetor

Saturday, November 23, 2019

Nikes Dispute With The University Of Oregon Example

Nikes Dispute With The University Of Oregon Example Nike's Dispute With The University Of Oregon – Article Example Nike’s dispute with the of Oregon At the center of Nike’s dispute with the of Oregon were ethical business practices with emphasis on organizational accountability on wage rates, working environment and social corporate responsibility. Nike had support for the Fair Labor Association (FLA) which had legal and ethical loopholes that could still help multinationals gain through exploitative labor conditions and wage rates outside the United States. On the other hand University of Oregon joined in the spirit of solidarity with other universities to champion for Worker Rights Consortium (WRC) which fought to ensure strict adherence to human work condition for all the multinationals that sought their market in Apparel and sports kit. It is evident that WRC sought to eliminate the stakeholders’ interest among firms in the Apparel industry and this was seen by Nike as betrayal by its perennial benefactor in philanthropic financial donations.According to Friedman’s and Freeman’s theories, shareholder wealth maximization is the primary goal of a firm. In this regard managers ensure that firms operate under the protections of limited liability. The essence in this case is seen in how such a goal allows companies to privatize their gains while externalizing losses. Some of the tactics used by the company to achieve the goal include limited expenditure on safety workplace environment and low wages which sums up to be the bone of contention between Nike and University of Oregon. Nike therefore withdrew its support to University of Oregon as it saw the opportunity of manipulating minimum wage and other local, international and industrial labor laws was not achievable in the presence of Worker Rights Consortium.

Thursday, November 21, 2019

Mobility Management for LTE-Advanced Relay Systems Research Paper

Mobility Management for LTE-Advanced Relay Systems - Research Paper Example These different technologies can cooperate together In order to improve the user’s quality of service and granting mobile users the ability of roaming across different wireless networks in a seamless manner. However, the different characteristics of each wireless technology with regards to QoS brought many challenges for provisioning the continuous services (e.g. audio/video streaming) in a seamless way. In such a heterogeneous environment, to support mobile user’s requirements, a mobility management mechanism is a key issue. Index Terms— Heterogeneous network, LTE-Advanced, Relay System, Vertical Handoff I. INTRODUCTION With the increase in demand and rapid development of wireless communication quality over the past 3 decades, the initial 1G has run into 4G with a high data rate and better mobility support. The 4G technique-International Mobile Telecommunications-Advanced (IMT-Advanced) systems include new capabilities that go significantly beyond those of the I MT-2000. Key requirements of the IMT Advanced systems, for instance, include improved mobility support and cell edge performance, increased spectral bandwidth and efficiency, reduced handover interruption time and reduced User plane latency and Control [1]. Considered as the main trend in future wireless communications, 3GPP LTE-Advanced has advanced features, for instance coordinated multipoint processing, carrier aggregation. It also considered as one of the top candidates towards achieving the IMT Advanced requirements. In 3GPP, high speed train scenario is agreed as the main scenario in Rel11 study item, mobile relay for E-UTRA. Here, when train rushes at a high speed the channel characteristics change and result in Doppler spread. Also the vehicles are vehicles are more crowded than other areas and therefore passengers are more likely to use high data rate services, for instance, browsing, playing games and watching videos so as to pass time [2]. The high data rate transmission requires strong signal strengths and high throughput, plus better mobility management, so mobile relay station for large vehicles are proposed for Broadband Wireless Access (BWA) system. A relay system may be mobile, which means it is a dedicated network node equipped on the vehicles to provide a fixed access link to those travelling on the vehicles. It is very suitable to solve the capacity gain of the high speed vehicles if it is well deployed. In a conventional cellular network, user equipment (UE) is connected directly to a Base Station (BS), and when a user moves away from the cell center, he/she will get less bandwidth which means lower data rates. However relaying technique has been introduced in 3GPP release 10 & 11 to allow establishing an indirect two-hop link between UE and BS through a Relay Node (RN). Relay nodes can also be used to spread out the cell coverage and increase the coverage outside main area (e.g. at cell edge). The two major challenges addressed in this c ontext are maintaining the throughput and ensure a seamless mobility and service continuity to all UEs. Hence, the objective of this paper is to develop, implement, and evaluate intelligent algorithms for next generation wireless communications systems with focus on throughput and service continuity. Specifically, the paper mainly addresses to the following aspects: Relaying in heterogeneous network, resources and mobility management. The rest of the paper is arranged as follows. Firstly, the overview of fixed and mobile relay system is given is Section II. In Section III, the paper presents a Handoff Analysis. Section IV presents a system level simulation and results. The paper concludes with section V. II. FIXED AND MOBILE RELAY SYSTEMS OVERVIEW A. Background