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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Digitally Assisted Multi-Channel Receivers

Pentakota, Krishna Anand Santosh Spikanth 2010 August 1900 (has links)
This work presents a data estimation scheme for wide band multi-channel charge sampling receivers with sinc filter banks together with a complete system calibration and synchronization algorithm for the receiver. A unified model has been defined for the receiver containing all first order mismatches, offsets and imperfections and a technique based on least mean squares algorithm is employed to track these errors. The performance of this technique under noisy channel conditions has been verified. The sinc filter bank is compared with the conventional analog filter banks and it is shown that the sinc filter banks have very low computational complexity in data estimation Nextly, analytical tools for the design of clock-jitter tolerant multi-channel filterbank receivers have been developed. Clock-jitter is one of the most fundamental obstacles for the future generation of wideband receivers. Additionally all the trade-offs and specifications of a design example for a multi-channel receiver that can process a 5 GHz baseband signal with 40 dB of signal-to-noise-ratio (SNR) using sampling clocks that can tolerate up to 5 ps of clock-jitter standard deviation are presented. A novel bandwidth optimization technique has been presented. As a part of it the bandwidth of the filters present in each path is optimized thereby improving the performance of the receiver further in the presence of sampling clock jitter. The amount of bandwidth reduction possible depends on the order of the filter and the noise amplification provided by the reconstruction matrix. It has been shown that 3rd order filters of bandwidth 1 GHz can be replaced with 1st order filters of bandwidth 100 MHz without any depreciation in the output resolution, implying huge power savings.
182

Wireless data acquisition system for multi-phase electric power equipment

Goodsell, Douglas Andreas 2008 May 1900 (has links)
Industrial facilities that plan the shutdown of equipment for service have large financial savings compared to those managing unplanned shutdowns. To this end, a variety of algorithms have been developed and published in the literature that can monitor a machine's health and indicate when the machine starts to develop a fault. In order for such algorithms to be effective, they require raw data collected from machines. Often this involves the placement of accelerometers and other sensory devices for measurements of mechanical behavior. It is possible to extract much of the required information from the electrical signals of the equipment. This is normally a less expensive installation since one only needs access to the lines supplying electric power to the equipment. If these data acqusistion modules are accessible wirelessly, then one can monitor all the interfaced equipment from a central location. To successfully monitor such electrical equipment, a data acquisition unit is required that can sample on five or six channels simultaneously, depending on the switch gear configuration. This thesis details the development of an "endpoint" device that samples the required number of channels to monitor the electrical signals of industrial equipment, and interfaces to a wireless network. The hardware and software design of the "endpoint" is discussed in detail. Also, the software design of the server that receives the data from the "endpoint" is presented. The designed "endpoint" samples up to six channels simultaneously, at a rate of at least 8 kHz per channel, and a data resolution of 16 bits. The data are then transmitted wirelessly to a central server for processing. The system has been tested both in a laboratory environment and at an industrial environment. The desired specifications of the "endpoint" have been verified in both environments. Several "endpoints" have been assembled to form a network and have been tested in a laboratory setting. This work has resulted in the demonstration that an "endpoint" can be constructed using of the shelf components that is suitable for the continuous health monitoring of multi-phase electric machines through a wireless network.
183

FMRPU: Design of Fine-grain Multi-context Reconfigurable Processing Unit

Lin, Ren-Bang 13 July 2004 (has links)
At present the scale of multimedia and communication systems has become more and more complicated due to the fast development of them. In order to improve the capability of real-time processing and shorten system development time, the ability to reconfigure system architecture becomes an important and flexible design consideration. In this thesis, we propose a reconfigurable processing unit, FMRPU, which is a fine-grain multi-context reconfigurable processing unit targeting at high-throughput and data-parallel applications. It contains 64 reconfigurable logic arrays, 16 switch boxes, and connects with each other via three hierarchical-level connectivities. To avoid the excessive routing path to be the bottleneck of mapped circuits, we design the data stream switch to rearrange data streams. According to the simulation results, the longest routing path of FMRPU only takes 6.5 ns at 0.35 processes, which is able to construct the required logic circuit efficiently. Compare with same kind devices in dealing with Motion Estimation operations, the performance is raise to 17% and is excellent to other same kind architectures in executing other DSP algorithms.
184

Applying loop mirror and ring resonator in the fabrication and design of semiconductor laser

Huang, Tzu-chien 21 July 2005 (has links)
We present design and fabrication of ring cavity semiconductor lasers and single ring filter with simple fabrication processes. A 1.55-£gm symmetric quantum well InGaAlAs epi-layer wafer is used to fabricate the lasers. In device design, we apply loop mirror to obtain reflection instead of cleaved facet and take 1x2, and 2x2 Multi-Mode Interference (MMI) with different splitting ratio(50%:50%¡F15%:85%) as a coupler. Then we combine MMI couplers with ring cavities to control the output of specific wavelength. Therefore we can obtain filter and lasers with the property of wavelength selection. We also design two kinds of special waveguides to achieve low reflectivity. One is a tapered spiral waveguide tail. The other waveguide is expanded in a curve and then cut off at the Brewster¡¦s angle. In loop mirror, two curvature radius(260,160£gm) were introduced to study bending loss and material loss. In single ring filter, we design two kinds of resonator lengths(1479,1385£gm) and the corresponding Free Spectrum Range (FSR) are 63.4, 67.75GHz, respectively. In fabrication, owing to the unstable dry etch condition for InGaAlAs, we adopted multi-step etch technology. In the part of curved waveguide, we also use this method to make deep-etching to increase the difference of refractive index between waveguide and the outside part. Finally, we use the etch solution (HBr:HCl:H2O2:H2O=5:4:1:70) to smooth the sidewall of the waveguide, and to reduce scattering loss of the device.
185

Applying loop-mirror reflector in the fabrication and design of Fabry-Perot laser

Lai, Chun-ming 10 July 2006 (has links)
The purpose of this research is to present design and fabrication of resonant loop-mirror Fabry-Perot lasers. Single filter has simple fabrication processes and good potential for intergration. A 1.55-£gm symmetric quantum well InGaAlAs epi-layer wafer is used to fabricate the laser. In device design, we apply loop mirror to obtain reflection instead of cleaved facet and take 1x2, 2x2 Multi-Mode Interference (MMI) with different splitting ratio (50%:50%¡F15%:85%) as a coupler. Then we combine MMI couplers with ring cavities to reflect specific wavelength at particular position. Therefore we can obtain semiconductor laser with property of wavelength-selection filter. In this design of the mask, we add a mask of deep-etch around MMI in order to decrease the loss of higher mode inside MMI. In the part of devices design, we apply multi-step technology for wet etch to obtain necessary depth. Finally, we use the etch solution (HBr¡GHCl¡GH2O2¡GH2O¡×5¡G4¡G1¡G70) to smooth the sidewall of the waveguide, and to reduce scattering loss of the device. In the part of planarization, we can adhere dummy wafers to surround the main sample and extend the total area. If we can fill the gap flat, the problem of high edge by spinning will be solved. However, we were not able to fill the gap.
186

Characterization and Fabrication of Recessed Multi-Gate SOI MOSFET

Chang, Shih-Chang 20 July 2001 (has links)
Abstract In this thesis, we propose and fabricate a triple recessed multi-gate SOI device that has high transconductance and low series resistance. The SOI device structure has three unique features. First, it uses mesa isolation instead of using conventional LOCOS and trench isolation to avoid the bird¡¦s beak effect in LOCOS isolation and the complexity of digging trench in trench isolation. Second, it combines the rounded and gate recessed structure to reduce the edge effect and lower the source/drain parasitic resistance. Third, it has three surfaces of gate structure that can increase the effective channel width of the device to enhance the current drivability of the device without reducing the packing density of the integrated circuit. From our experiment results the trends of device characteristics exhibits good agreement with the 3 ¡V D simulation results. According to the simulation results of 3 ¡V D DAVINCI and the measurement results, triple recessed multi-gate SOI MOSFET¡¦s presents four unique characteristics, which are superior to conventional SOI with the same device parameter in deep sub-micrometer regime. First, multi-gate SOI has better short channel effect and drain induce barrier lowing immunity conventional SOI device than conventional SOI device. Second, it has higher transconductance and higher current drive capability. Third, the breakdown voltage is higher than that of conventional SOI device. Fourth, self-heating effect would not increase with current gain increase, triple recessed multi-gate SOI device has better self-heating effect immunity. These four advantages show the triple recessed multi-gate SOI MOSFET¡¦s is suitable for high speed and low power applications along shrink of device dimensions.
187

Multi-area network analysis

Zhao, Liang 17 February 2005 (has links)
After the deregulation of the power systems, the large-scale power systems may contain several areas. Each area has its own control center and each control center may have its own state estimator which processes the measurements received from its local substations. When scheduling power transactions, which involve several control areas a system-wide state estimation solution is needed. In this dissertation, an estimation approach which coordinates locally obtained decentralized estimates while improving bad data processing capability at the area boundaries is presented. It is assumed that synchronized phasor measurements from different area buses are available in addition to the conventional measurements provided by the substation remote terminal units. The estimator with hierarchical structure is implemented and tested using different measurement configurations for two systems having 118 and 4520 buses. Furthermore, we apply this multi-area solution scheme to the problem of Total Transfer Capability (TTC) calculation. In a restructured power system, the sellers and buyers of power transactions may be located in different areas. Computation of TTC will then require system-wide studies. We investigate a multi-area solution scheme, which takes advantage of the system-wide calculated Power Transfer Distribution Factors (PTDF) in order for each area to calculate its own TTC while a central entity coordinates these results to determine the final value. The proposed problem formulation and its solution algorithm are presented. 30 and 4520 bus test systems are used to demonstrate the approach and numerically verify the proposed TTC calculation method.
188

Continuous multi-phase feeding of broiler chickens

Nasril 17 February 2005 (has links)
Continuous multi-phase feeding of broiler chickens was evaluated to optimize broiler nutrition and minimize environmental impact related to excess nitrogen in poultry manure. Four experiments were conducted. Experiments 1 and 2 studied effects of continuous multi-phase feeding during a 3-week starting period using battery brooders while experiments 3 and 4 evaluated multi-phase feeding during a traditional 7-week growing period using both battery brooders and floor pens. In the first and second experiments, the nutrient content of the multi-phase diets was changed every 24 hours in comparison to single-phase feeding. Results indicated that during the starter period, continuous multi-phase feeding had no significant influence on feed consumption, daily gain, feed to gain ratio or fecal nitrogen. In the third and fourth experiments, a four phase industry type broiler feeding program was compared to intensive multi-phase feeding programs created by linearly blending three different diets based on typical industry nutrient values and a commercial nutrient modeling computer program (EFG Natal®). In both intensive multi-phase feeding programs, the diets were changed every three days over a 7-week growth period. Broilers in experiment 3 were raised in Petersime battery brooders to primarily access nitrogen balance while birds in experiment 4 were raised in a floor pen on pine shaving litter to resemble commercial broiler production. The results indicated that intensive multi-phase feeding improved body weight gain and feed to gain ratio only in weeks 5 and 6 but not during the overall 7-week period. Nitrogen excretion and nitrogen retention were unaffected by the intensive multi-phase feeding systems. Economic analysis indicated that intensive multi-phase feeding programs could potentially lower feed costs per kilogram of gain. However, the high cost of implementing a continuous multi-phase feeding system may not justify the relatively small gain in lower feed cost per kilogram of gain. In conclusion, continuous multi-phase feeding of broiler chickens using corn-soy diets does not appear to be justified by either increased performance or reduced nitrogen excretion.
189

A network design model for multi-zone truckload shipments

Maheshwari, Nimish 12 April 2006 (has links)
Truckload shipments constitute a significant portion of the freight transportation industry. In recent years, truckload industry is facing a serious problem of high driver turn over rate. In this research, we present a mathematical model for multi-zone dispatching method to solve this issue. Multi-zone dispatching is a method in which a service area is divided into many zones. Truckload within a zone is carried by local drivers and the truckload between zones is carried by lane drivers. Apart from reducing the driver tour length to a desirable level, the model for multi-zone also contains some unique constraints to address some issues from the perspectives of the company and the customer. The binary integer program is solved by exact methods. As the problem size increases, exact methods fail quickly. Hence, a construction heuristic within tabu search framework is developed to solve the model. Analysis of various parameters concerned is provided to gain better insights of varied aspects of the problem. Computational results for analysis of parameters and comparison of exact and heuristic methods are provided.
190

Proactive communication in multi-agent teamwork

Zhang, Yu 25 April 2007 (has links)
Sharing common goals and acting cooperatively are critical issues in multiagent teamwork. Traditionally, agents cooperate with each other by inferring others' actions implicitly or explicitly, based on established norms for behavior or on knowledge about the preferences or interests of others. This kind of cooperation either requires that agents share a large amount of knowledge about the teamwork, which is unrealistic in a distributed team, or requires high-frequency message exchange, which weakens teamwork efficiency, especially for a team that may involve human members. In this research, we designed and developed a new approach called Proactive Communication, which helps to produce realistic behavior and interactions for multiagent teamwork. We emphasize that multi-agent teamwork is governed by the same principles that underlie human cooperation. Psychological studies of human teamwork have shown that members of an effective team often anticipate the needs of other members and choose to assist them proactively. Human team members are also naturally capable of observing the environment and others so they can establish certain parameters for performing actions without communicating with others. Proactive Communication endows agents with observabilities and enables agents use them to track others’ mental states. Additionally, Proactive Communication uses statistical analysis of the information production and need of team members and uses these data to capture the complex, interdependent decision processes between information needer and provider. Since not all these data are known, we use their expected values with respect to a dynamic estimation of distributions. The approach was evaluated by running several sets of experiments on a Multi- Agent Wumpus World application. The results showed that endowing agents with observability decreased communication load as well as enhanced team performance. The results also showed that with the support of dynamic distributions, estimation, and decision-theoretic modeling, teamwork efficiency were improved.

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