An Investigation of the Dynamic Response of Spur Gear Teeth with Moving Loads

Two concepts relating to gear dynamics were studied. The first phase of the analysis involved the study of the effect of the speed of a moving load on the dynamic deflections of a gear tooth. A single spur gear tooth modelled using finite elements was subjected to moving loads with variable velocities. The tooth tip deflection time histories were plotted, from which it was seen that the tooth tip deflection consisted of a quasistatic response with an oscillatory response superimposed on it whose amplitude was dependent on the type of load engagement. Including the rim in the analysis added flexibility to the model but did not change the general behavior of the system. The second part of the analysis involved an investigation to determine the effect on the dynamic response of the inertia of the gear tooth. A simplified analysis using meshing cantilever beams was used. In one case, the beams were assumed massless. In the other, the mass (inertia) of the beams was included. From this analysis it was found that the inertia of the tooth did not affect the dynamic response of meshing cantilever beams

Improving relationships between public transit authorities and medical centers : case studies and applications to the Illinois Medical District (Chicago, Illinois) and Centro Medico (Sun Juan, Puerto Rico)

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2003.Includes bibliographical references (leaves 65-66).This thesis addresses transportation and mobility at urban medical centers, concluding that prioritizing transit access at medical centers has the potential to fundamentally transform the hospital experience by reducing congestion, increasing efficiency, improving the built environment, avoiding the deadening effect of parking garages, and improving quality of care. The thesis considers the implications of improved public transportation on medical centers, as well as the impact of hospital ridership on transit authorities via a softened peak service period, increased off-peak ridership, and the availability of origin-destination data. The institutional structure and physical design of four major medical research centers are examined for successes and flaws, as are the policies and service of the associated transit authority. Observations from these case studies are then applied to Chicago's Illinois Medical District and San Juan's Centro Medico, areas currently undergoing major capital investments in transportation infrastructure.by Lillian C. Shuey.M.C.P

Life Support System Considerations for Space Station

With the growing desire to initiate a Space Station program, the interest in advanced, regenerative life support systems is also increasing. This paper briefly reviews this future spacecraft and concentrates on the advanced technology in some of the key functions of life support for this application. This paper reviews the basics of life support and its importance within a space station program. It concentrates«on the impact of major requirements and discusses some of the key influences that impact the design of the system. It also projects some of the key functional areas of the life support system which are most likely to be implemented from today\u27s current technology. The imminent availability of the Space Shuttle has rekindled interest in the longer duration space missions and permanent orbiting space platforms. Studies are underway to define missions and concept the orbiting facilities based on the capabilities available with and limitations imposed by the Space Transportation System. A work base in space is required to economically perform the long duration, complex missions of the future and to utilize the Space Shuttle in its intended role as a space truck. The term Space Station is again coming into vogue, although other titles for this program are currently in use

Optimal pricing strategies for capacity leasing based on time and volume usage in telecommunication networks

In this study, we use a monopoly pricing model to examine the optimal pricing strategies for “pay-per-time”, “pay-per-volume” and “pay-per both time and volume” based leasing of data networks. Traditionally, network capacity distribution includes short/long term bandwidth and/or usage time leasing. Each consumer has a choice to select volume based, connection-time based or both volume and connection-time based pricing. When customers choose connection-time based pricing, their optimal behavior would be utilizing the bandwidth capacity fully, which can cause network to burst. Also, offering the pay-per-volume scheme to the consumer provides the advantage of leasing the excess capacity to other potential customers serving as network providers. However, volume-based strategies are decreasing the consumers’ interest and usage, because the optimal behaviors of the customers who choose the pay-per-volume pricing scheme generally encourages them to send only enough bytes for time-fixed tasks (for real time applications), causing quality of the task to decrease, which in turn creating an opportunity cost. Choosing pay-per time and volume hybridized pricing scheme allows customers to take advantages of both pricing strategies while decreasing (minimizing) the disadvantages of each, because consumers generally have both time-fixed and size-fixed task such as batch data transactions. However, such a complex pricing policy may confuse and frighten consumers. Therefore, in this study we examined the following two issues: (i) what (if any) are the benefits to the network provider of providing the time and volume hybridized pricing scheme? and (ii) would this offering schema make an impact on the market size? The main contribution of this study is to show that pay-per both time and volume pricing is a viable and often preferable alternative to the only time and/or only volume-based offerings for a large number of customers, and that judicious use of such pricing policy is profitable to the network provider

Searching for solutions: health concerns expressed in letters to an East African newspaper column

This study examined health care questions from an unusual data set: 1252 unsolicited letters written over a three–year period to an advice column in an East African newspaper. Analysis of the letters was a non-intrusive method of ascertaining prevalent health questions and opinions. People wrote seeking information, advice, solutions, and reassurance about health problems. Emotions expressed in the letters ranged from hope to fear and frustration. The written format allowed questions which are generally too embarrassing or stigmatized to present in other public or interpersonal settings. More than half the total letters raised questions about sexual behaviour, sexually transmitted diseases, and HIV/AIDS. The letters present not only personal health concerns, but also expectations of health-care quality and reflections on the medical options presently available in Uganda. As a whole, the letters express dissatisfaction not only with the outcomes of health encounters, but with the process. Of the letter writers with specific physical complaints, more than one-third had already sought medical care and were dissatisfied with the results. The letters were seeking solutions, especially for alleviation of symptoms and discomfort. Almost equally prevalent was a plea for accurate and relevant health information; people not only want to feel better, but they also want to understand their own health