Monolithic silicon opto-electro-mechanical light modulator

A Fabry-Perot light beam modulator of the reflection-type has been designed with process and performance parameters optimized. This design takes advantage of the economies of surface micromaching using silicon substrates and selected thin films. High performance with a low drive voltage are achieved using electrostatic actuation of a thin polysilicon diaphragm. The diaphragm is a novel corrugated structure which has maximum compliance and maintains planarity during actuation. In addition, the corrugationsuspension used provides an improved linearity of amplitude modulation response as a function of the actuation voltage. A preliminary version of this device has been fabricated through a contract foundry using some industry- standard film thicknesses. The preliminary version of the device confirms the physical mask design without optimal film processing. The optimized Fabry-Perot structure is designed for operation at a wavelength of 1.3 nm. Using a thin, corrugated diaphragm of 190 nm thickness a 48.90% modulation index is obtained with an actuation voltage of 5 volts based on detailed simulation results. The final optimized device will be fabricated at NJIT at a future date. The proposed optimized device contains a titanium-tungsten metal film deposited into a cavity of half wavelength depth and insulated from the monolithic silicon substrate. An additional quarter wavelength film of silicon nitride is deposited over the metal to increase the modulation index. In the fabrication process a 325 nm sacrificial film of spinon glass is deposited to fill the cavity and form the spacer between the Fabry-Perot etalon entrance and reflecting surfaces. The optical entrance surface is obtained next in the fabrication process by depositing an infrared-transmissive film of polysilicon. The selected polysilicon thickness is 190 nm or any odd integer multiple of a half wavelength. This device can be used as an economical light modulator in near-infrared communications and control systems. This device suitable for relatively low bandwidth applications is expected to provide cost and reliability advantages over competing torsion mirror and macro-sized modulators

Evaluating the quality of undergraduate hospitality, tourism and leisure programmes

In this study, an instrument for measuring the quality of undergraduate programmes in hospitality, tourism and leisure (HTLP) was developed and empirically cross-validated. The study considered how total quality management (TQM) and context-input-process-product (CIPP) perspectives could be integrated to develop the framework, using documentary analysis, focus groups and content validity. Survey responses from 430 full-time teachers were used to verify the instrument for HTLP (IHTLP) via exploratory and confirmatory factor analysis, and six standards, 12 dimensions and 63 indicators were identified. The six standards, in terms of relative importance, are curriculum and instruction; faculty; strategic planning; administrative management; student achievements; and resources. The implications for HTLP are also discussed

Comparative Analysis of Supply Chain Management Practices by Boeing and Airbus: Long-Term Strategic Implications

Research Goals and Approach: Goals - • Develop an improved understanding of emerging supply chain management strategies and practices in the commercial aerospace industry • Explore the longer-term implications of the findings for supply chain management practices in the aerospace industry in the future/ Approach - • Conduct a comparative analysis of supply chain management practices by Boeing and Airbus • Focus on two large development programs -- the Boeing 787 Dreamliner and the Airbus A380 Navigator • Concentrate on the common set of suppliers supporting both programs to develop a sharp “compare-and contrast” perspective, looking at Boeing & Airbus from the vantage point of these common suppliers • Capture bottom-up “supplier’s voice” to complement “top-down” perspective, while controlling for any “embellished” top-down view from the two companie

A comparative analysis of supply chain management practices by Boeing and Airbus : long-term strategic implications

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2007.Includes bibliographical references (p. 127-131).The goal of this research is to develop an improved understanding of supply chain management strategies and practices being pursued by Boeing and Airbus in the 787 Dreamliner and the A380 Navigator programs, respectively, and to identify their long-term strategic implications for supply chain management in the future. The research takes as its point of departure a review and synthesis of supply chain management principles and practices, with particular emphasis on lean supply chain management concepts. Guided by this review, the research focuses on the common set of suppliers supporting both programs and employs a questionnaire survey, followed by telephone interviews with representatives of selected suppliers. The research also makes extensive use of the open source information on both companies, on both programs and on the common suppliers.(cont.) A major finding is that Boeing's new supply chain model in the 787 program represents a significant break with past practices in the aerospace industry, allowing major partnering suppliers an unprecedented role in terms of design, development, production and after-market support, where they are integrated early in the concept development stage and are incentivized to collaborate with Boeing, as well as among themselves, as risk-sharing partners with deep responsibility for system integration, involving detailed interface control at the system and subsystem levels. Airbus, as well, is found to rely heavily on its major suppliers in connection with the A380 program, but acting as the primary system integrator in the more traditional mode and exercising much greater control of all design interfaces. Also, both Boeing and Airbus have been outsourcing more and more activities to suppliers located in non-traditional regions, such as Eastern Europe and the Asia-Pacific region. Finally, aerospace manufacturers, in general, are aggressively adopting information technologies (e.g., EDI, PLM, 3-D Digital Model, RFID) to facilitate greater data sharing and communications with their partners and lower-tier suppliers dispersed in many geographical regions, as part of a broader trend involving more collaborative supplier relationships reaching down to the subtier level.by Tzu-Ching Horng.S.M

Inferring Queueing Network Models from High-precision Location Tracking Data

Stochastic performance models are widely used to analyse the performance and reliability of systems that involve the flow and processing of customers. However, traditional methods of constructing a performance model are typically manual, time-consuming, intrusive and labour-intensive. The limited amount and low quality of manually-collected data often lead to an inaccurate picture of customer flows and poor estimates of model parameters. Driven by advances in wireless sensor technologies, recent real-time location systems (RTLSs) enable the automatic, continuous and unintrusive collection of high-precision location tracking data, in both indoor and outdoor environment. This high-quality data provides an ideal basis for the construction of high-fidelity performance models. This thesis presents a four-stage data processing pipeline which takes as input high-precision location tracking data and automatically constructs a queueing network performance model approximating the underlying system. The first two stages transform raw location traces into high-level “event logs” recording when and for how long a customer entity requests service from a server entity. The third stage infers the customer flow structure and extracts samples of time delays involved in the system; including service time, customer interarrival time and customer travelling time. The fourth stage parameterises the service process and customer arrival process of the final output queueing network model. To collect large-enough location traces for the purpose of inference by conducting physical experiments is expensive, labour-intensive and time-consuming. We thus developed LocTrack- JINQS, an open-source simulation library for constructing simulations with location awareness and generating synthetic location tracking data. Finally we examine the effectiveness of the data processing pipeline through four case studies based on both synthetic and real location tracking data. The results show that the methodology performs with moderate success in inferring multi-class queueing networks composed of single-server queues with FIFO, LIFO and priority-based service disciplines; it is also capable of inferring different routing policies, including simple probabilistic routing, class-based routing and shortest-queue routing

Runout Compensation in Peripheral Mllling Using Repetitive Control

Runout due to the eccentricity of the rotating machine tool, the spindle axis, and I or the bearings of a spindle axis reduces the precision of machined parts. When the required precision of machined products is not high, runout effect can be tolerated However, when high precision is required, runout effect needs to be eliminated or reduced to a tolerable level. Conventional controllers such as Proportional-Plus-Integral (PI) and feedback controllers are not adequate for runout compensation, especially when the frequency of runout is high. A new controller, the repetitive controller, had been proposed by other researchers for use in repeated jobs like the tracking of robot manipulators, non-circular machining, and the positioning of computer storage read I write heads. The success of these applications suggests the possibility of applying the repetitive controller on runout compensation for a peripheral milling process. Results are encouraging: They show that, using appropriately selected controller gains and sampling rate, the application is successful. The research results had been written and sent out as a technical paper and been accepted for publication by Symposium on Advances in Manufacturing Systems Engineering, the Winter Annual Meeting of the American Society of Mechanical Engineers, San Francisco, December 1989. This thesis is written based on the framework of that paper which has the same title as this thesis. In addition, more simulation results, more functions and derivations, more detailed discussion and explanation, and more references are presented in this thesis. Such additional information will make this thesis much more easier to read and understand.Mechanical Engineerin

Correlations between subjective treatment responses and plantar pressure parameters of metatarsal pad treatment in metatarsalgia patients: a prospective study

BACKGROUND: Metatarsalgia is related to repetitive high-pressure loading under the metatarsal head (MH) that causes pain. The high pressure under the MH can be reduced by adequately applying metatarsal pads (MPs). Plantar pressure measurements may provide a method to objectively evaluate pressure loading under the MH. However, it is still unclear if the decrease in plantar pressure under the MH after MP treatment is associated with subjective improvement. This study aims to explore the correlations between subjective pain improvement and outcome rating, and the plantar pressure parameters in metatarsalgia patients treated using MPs. METHODS: Thirteen patients (a total of 18 feet) with secondary metatarsalgia were included in this study. Teardrop-shaped MPs made of polyurethane foam were applied just proximal to the second MH by an experienced physiatrist. Insole plantar pressure was measured under the second MH before and after MP application. Visual analog scale (VAS) scores of pain were obtained from all subjects before and after 2 weeks of MP treatment. The subjects rated using four-point subjective outcome scales. The Wilcoxon signed-rank test was used to analyze the difference between the plantar pressure parameters and VAS scores before and after treatment. The Kruskal-Wallis test was applied to compare the plantar pressure parameters in each outcome group. Pearson's correlation was applied to analyze the correlation between the changes in plantar pressure parameters and VAS scores. Statistical significance was set as p < 0.05. RESULTS: MP application decreased the maximal peak pressure (MPP) and pressure-time integral (PTI) under the second MH and also statistically improved subjective pain scores. However, neither the pre-treatment values of the MPP and PTI shift in the position of the MPP after treatment, nor the age, gender and body mass index (BMI) of the subjects were statistically correlated with subjective improvement. Declines in the PTI and MPP values after MP application were statistically correlated with the improvement in VAS scores (r = 0.77, R(2 )= 0.59, p < 0.001; r = 0.60, R(2 )= 0.36, p = 0.009). CONCLUSION: We found that the successful decline in the PTI and MPP under the second MH after MP application was correlated to subjective pain improvement. This study provides a strategy for the further design and application of MPs for metatarsalgia treatment

Design And Fabrication of Condenser Microphone Using Wafer Transfer And Micro-electroplating Technique

A novel fabrication process, which uses wafer transfer and micro-electroplating technique, has been proposed and tested. In this paper, the effects of the diaphragm thickness and stress, the air-gap thickness, and the area ratio of acoustic holes to backplate on the sensitivity of the condenser microphone have been demonstrated since the performance of the microphone depends on these parameters. The microphone diaphragm has been designed with a diameter and thickness of 1.9 mm and 0.6 $\mu$m, respectively, an air-gap thickness of 10 $\mu$m, and a 24% area ratio of acoustic holes to backplate. To obtain a lower initial stress, the material used for the diaphragm is polyimide. The measured sensitivities of the microphone at the bias voltages of 24 V and 12 V are -45.3 and -50.2 dB/Pa (at 1 kHz), respectively. The fabricated microphone shows a flat frequency response extending to 20 kHz.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838