Design mechanical engineering
 
Category: Design mechanical engineering
• Strong heating at the equator caused air to rise, diverge towards the pole, sink back to the surface and returned to the equator. • Due to the Earth’s rotation the winds would move east to west.• Strong solar heating leads to rising air which diverges towards the poles. – Creates Intertropical Convergence Zone (ITCZ) • Aloft, air moves poleward but acquires a west to east motion. • Air descends at 20°-30° latitude to form subtropical highs. – Creates desert conditions • Air moves towards the equator at the surface and a weak Coriolis force creates the NE trade winds.
1303 days ago
 
Every single observation made by the instruments that measures different properties of the Earth atmosphere tells us the same thing – everything is local and nothing is global. In total contrast, the whole concept of man-made global warming and man-made climate change is based on the assumption that everything is in equilibrium, that the whole atmosphere can be treated as a homogeneous system and the Earth’s annual temperature can represented by a single number. The main conflict that has been raging on for last 20 years or so and is highlighted in my paper is that the instrumental data, i.e. thermometer, is telling us that no alarming trends could be detected in temperature patterns observed in last 161 years, while the trends observed in purely theoretical (based on calculations) space of annual averages,
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The introductionof the course is broken into two sections The rst section describes the importance of friction and wear to todays engineer and introduces some of the basic concepts that will be pursued later in more detail The second section briey outlines the history of tribology so that we understand where we are coming from to better understand where we are goingThe mechanics of friction and wear covers a portion of a larger eld known as tribology Tribology is the SCIENCE and TECHNOLOGY of interacting surfaces in relative motion and the practices related thereto.
1303 days ago
 
Hydrodynamic lubrication suggests that the load-carrying surfaces of the bearing are separated by a relatively thick film of lubricant, so as to prevent metal to metal contact, and the stability thus obtained can be explained by the laws of fluid mechanics. Hydrodynamic lubrication depends on the existence of an adequate supply of lubrication at all times rather than having lubrication under pressure. The film pressure is created by moving surface itself pulling the lubricant into a wedge-shaped zone at a velocity sufficiently high to create the pressure necessary to separate the surfaces against the load on the bearing.
1303 days ago
 
Lubricants play a critical role in nearly every type of machinery, and their performance is often critical to the speed, reliability, and life of the machines. As part of the product development process, lubricant manufacturers are continually faced with the need to evaluate the performance of candidate lubricants under many different conditions. Likewise, manufacturers of machinery frequently need to test the performance of alternative lubrications in order to determine the formulation that will enable their products to deliver the best performance and life. In the past, lubricant evaluation was typically based on intuition and experience. Today’s requirements for products to run faster, longer, and more efficiently make it essential to use a scientific approach in lubricant development and application.
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Fluid film lubrication is a hydrodynamic phenomenon characterized by a lubricant flowing in the narrow gap between two closely spaced surfaces. Notes 1 develops, from the fundamental equations of fluid mechanics – mass and momentum transport of a Newtonian fluid, the classical equations for motion of a lubricant in a thin film. An order of magnitude analysis reveals that the pressure does not vary across the film, and hence, one momentum transport equation is not needed. In addition, the analysis reveals that fluid inertia effects are seldom important in most thin film lubricant configurations, i.e. those in which the film thickness is orders of magnitude smaller than the wetted surfaces dimensions. Reynolds numbers for shear type flow and squeeze film type flow are defined. Applications where thin film fluid inertia effects are important are noted.
1303 days ago
 
Nowadays, the trends in the machine component industry are looking for higher performance, improving reliability and tolerances, more environment friendly products, less lubrication, and reduced frictional losses (Johnston et al, 2005). Owing to their attractive tribological properties, diamond-like carbon (DLC) coatings represent one of the means to achieve these goals (Rosado et al, 1997). The extremely hardness, high elastic modulus, excellent wear and corrosion resistance, high thermal and chemical stability, and low friction nature of DLC coatings make them good prospects for a wide range of space (Santos et al, 2006) and industrial components (Capote et al, 2008). Their expected life-time is very long and the film costs are normally very low compared to the component costs.
1303 days ago
 
Note: Bearing definitions marked are for informational purposes only and are not covered in these specifications. Bearing œ a structural device that transmits loads while facilitating translation and/or rotation. *Bronze Bearing œ A bearing which displacements or rotations take place by the slip of a bronze surface against a mating surface. Cotton Duck Reinforcement Pad (CDP) œ A pad made from closely spaced layers of elastomer and cotton duck, bonded together during vulcanization. *Disc Bearing œ A bearing which accommodates rotation by deformation of a single elastomeric disc, molded from a urethane compound. It may contain a device for partially confining the disc against lateral expansion.
1303 days ago
 
The first stage of Rapid Prototyping life cycle as a new technology in the marketplace is gradually ending, and the second stage has already started. Many new vendors have introduced their products in this field, utilized different, new technologies or improvements of the existing ones. The first introduction of the RP concept and Stereolithography created a stunning impression in the marketplace. After a couple of years, as customers and users have gained much experience and understanding or RP technology, the first enthusiasm started making way to more serious and demanding approach. This is very well reflected in the thorough evaluations of the different technologies available today in the marketplace, done by customers looking for a technology that will best fit their needs. This is actually why most of us are here today.
1303 days ago
 
Inspiration hits late one night and you arrive at a world-changing idea: a new network architecture, address scheme, mobility protocol, or a feature to add to a router. With a paper deadline approaching, you have a laptop and three months. What prototyping environment should you use to evaluate your idea? With this question in mind, we set out to create a prototyping workflow with the following attributes: Flexible: new topologies and new functionality should be defined in software, using familiar languages and operating systems. Deployable: deploying a functionally correct prototype on hardware-based networks and testbeds should require no changes to code or configuration.
1303 days ago
 
Selective Laser Sintering is a Layer Manufacturing process that allows generating complex 3D parts by consolidating successive layers of powder material on top of each other [1,2]. Consolidation is obtained by processing the selected areas using the thermal energy supplied by a focused laser beam. Using a beam deflection system (galvano mirrors), each layer is scanned according to its corresponding cross section as calculated from the CAD model. The deposition of successive powder layers with a typical thickness of 20 till 150 µm is realized using a powder deposition system.
1303 days ago
 
Producing tooling directly from CAD models is regarded as an important method for reducing the cost and time to market of new products. Although this is a relatively new trend in manufacturing, it has already had a dramatic impact on the engineering environment. Rapid tooling (RT) typically describes the process in which a rapid prototyping (RP) model is used as a pattern to quickly create a mold or in which the rapid prototyping process itself is used to fabricate a limited volume of tool prototypes. In general, RT is distinguished from conventional tooling in that: a) Tooling time is significantly shorter. b) Tooling cost is less expensive. This applications note describes the advantages of PolyJet Technology to further increase the speed of tooling development. By way of example, it describes in detail how a colorful silicone keypad can be made in a short time after the design of the mold is completed.
1303 days ago
 
Rapid prototyping consists of various manufacturing processes by which a solid physical model of a part is made directly from 3D computer-aided design (CAD) model data. This CAD data may be generated by 3D CAD Modelers, CT and MRI scan data or model data created by 3D digitizing systems (Engineers Handbook, 2006). The Rapid Prototyping techniques have found their place among other manufacturing technologies. They are invaluable when there is a need of quick producing a physical prototype of designed part. In case of necessity of manufacturing a small series of functional products (especially those who would otherwise need dedicated special tooling) it is also hard to find a competitive group of technologies to accomplish the task.
1303 days ago
 
• Usability engineering life cycle is evaluationcentered • Dilemma: Can't evaluate an interface until it is built, but after building, changes are difficult • Solution: Rapid prototyping — producing interactive versions of an evolving interaction design Don't wait until first release or field test * Main technique supporting iterative refinement • Prototype is conversational "prop" to support communication of concepts not easily conveyed verbally [R. Bellamy, Apple Corp.] Concrete baseline for communication between users and developers • Allows user to "take it for a spin" • Encourages early user participation and involvement .
1303 days ago
 
Thedevelopmentofformallanguagesappropriateforthespecification of conceptual models (including ontologies) is an importantissueintheSemanticWebresearchfield. Inwhatfollows we are going to take under consideration two approaches for the definition of ontologies. On one hand, the OWL (Web Ontology Language) class of languages represents the main formalism in order to specify the structure of complex ontologies [6]. Ontheotherhand,therearemoreintuitivemodelingtechnologies, the conceptual (or semantic) models, that are used as tools for, for instance, system design or database schema design. At present,threeofthesearethemostusedlanguagesforconceptual data modeling, i.e. Entity-Relationship (ER) .
1303 days ago
 
Coal-based power generation is still a fundamental part of energy supply throughout the world. Reliability, security of supply, low fuel costs, and competitive cost of electricity make a good case for coal-fired steam power plants. Requests for sustainable use of existing resources and concerns about the effect of CO2 emissions on global warming have strengthened the focus of plant engineers and the power industry on more efficient energy conversion processes and systems.
1303 days ago
 
Nuclear power is universally controversial. Many would say that it is also universally neededas an alternative or supplement to power generated by fossil fuels. The combustion of fossil fuels produces carbon dioxide, now notorious for the threat of global warming. Nuclear power plants produce neither carbon dioxide nor oxides of sulfur and nitrogen, as does the burning of fossil fuels. Thus nuclear power reduces the global production of carbon dioxide and other pollutants, and helps to alleviate many of the pervasive problems of fossil fuel supply. Petroleum is least available in regions of widest use; natural gas is, for the time being, plentiful and sought after by all; and widely abundant coal has come to be regarded as the great Satan of air pollution.
1303 days ago
 
It=s a form of energy … a renewable resource. Hydropower provides about 96 percent of the renewable energy in the United States. Other renewable resources include geothermal, wave power, tidal power, wind power, and solar power. Hydroelectric powerplants do not use up resources to create electricity nor do they pollute the air, land, or water, as other powerplants may. Hydroelectric power has played an important part in the development of this Nation's electric power industry. Both small and large hydroelectric power developments were instrumental in the early expansion of the electric power industry.
1303 days ago
 
Process of solar thermal power generation: − concentrating solar radiation by means of a collector system; − increasing radiation flux density (i.e. concentrating of the solar radiation onto a receiver), if applicable; − absorption of the solar radiation (i.e. conversion of the radiation energy into thermal energy (i.e. heat) inside the receiver); − transfer of thermal energy to an energy conversion unit; − conversion of thermal energy into mechanical energy using a thermal engine (e.g. steam turbine); − conversion of mechanical energy into electrical energy using a generator.
1303 days ago
 
History records over a century and a half of interest in and work on the gas turbine. However, the history of the gas turbine as a viable energy conversion device began with Frank Whittle’s patent award on the jet engine in 1930 and his static test of a jet engine in 1937. Shortly thereafter, in 1939, Hans von Ohain led a German demonstration of jet-engine-powered flight, and the Brown Boveri company introduced a 4-MW gas-turbine-driven electrical power system in Neuchatel, Switzerland. The success of the gas turbine in replacing the reciprocating engine as a power plant for high-speed aircraft is well known. The development of the gas turbine was less rapid as a stationary power plant in competition with steam for the generation of electricity and with the spark-ignition and diesel engines in transportation and stationary applications.
1303 days ago
 
Earthen materials are widely variable in physical and chemical properties and “in-place” strata conditions. Soil engineering methods have been developed that can be applied to coal ash as shown by decades of academic evaluation and practical experience in the Commonwealth of Pennsylvania. For purposes of engineering, uniformly placed coal ash can be considered as an artificial “soil” type that is usually more uniform than a natural soil layer. Additional testing is needed if different coal types, sources or burning processes may have generated the coal ash being evaluated, and also in the event of visible changes in natural soil types. For example, some coal fired boilers segregate lighter “fly ash” from the heavier “bottom ash” that falls to the bottom of the combustion unit during the combustion process.
1303 days ago
 
The aim of this paper is explore the implications of the new and complex aid landscape for developing country governments. In 2000, development assistance was overwhelmingly provided by traditional bilateral and multilateral donors, which provided aid in specific ways and according to a particular set of norms. Today, this is being complemented by the growth of other forms of development assistance, including from non-Development Assistance Committee (DAC) donors, climate finance funds, social impact investors, philanthropists and global funds, as well as less concessional flows.
1303 days ago
 
Most industrial production processes need cooling waters to operate efficiently and safely. Refineries, steel mills, petrochemical manufacturing plants, electric utilities and paper mills all rely heavily on equipment or processes that require efficient temperature control. Cooling water systems control these temperatures by transferring heat from hot process fluids into cooling water. As this happens, the cooling water itself gets hot. Before it can be used again, it must either be cooled or replaced by a fresh supply of cool water.
1303 days ago
 
The “individual mandate”—the requirement that individuals either have health insurance coverage or pay a fine— is both the best known and the least popular component of the Affordable Care Act (ACA).1 That people know about the mandate—and may even worry about it—is not surprising, given both the heated political controversy and the constitutional challenge surrounding this provision of the law. What may be surprising, however, is that if the ACA were in effect today, 94 percent of the total population (93 percent of the nonelderly population) or 250.3 million people out of 268.8 million nonelderly people—would not face a requirement to newly purchase insurance or pay a fine.
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In our modern world, teams are essential to everything individuals do in daily life. For many, their first exposure to the notion of teams began early on during participation in various youth sports. While playing a position on a team, whether on the soccer pitch or baseball diamond, young athletes are exposed to the timeless adage: “There is no ‘I’ in team.” Taking a quick look at the four letters that comprise this word and one can conclude that, indeed the letter ‘I’ does not make an appearance. Approachthis saying from a figurative perspective, and an entire world of interpretation is made possible. For instance, coaches will often teach their players that everyone on the team has a specific job to perform, and that every job is equal in its importance to overall team success.
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