• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 503
  • 76
  • 69
  • 58
  • 56
  • 32
  • 20
  • 17
  • 16
  • 12
  • 10
  • 4
  • 4
  • 4
  • 3
  • Tagged with
  • 1042
  • 120
  • 86
  • 81
  • 74
  • 57
  • 57
  • 56
  • 48
  • 48
  • 46
  • 45
  • 43
  • 43
  • 43
  • 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.
411

Ion Current Dependence on Operating Condition and Ethanol Ratio

Gustafsson, Karin January 2006 (has links)
This masters thesis investigates the possibility to estimate the ethanol content in the fuel using ion currents. Flexible fuel cars can be run on gasoline-ethanol blends with an ethanol content from0 to 85 percentage. It is important for the engine control system to have information about the fuel. In todays cars the measurements of the fuel blend are done by a sensor. If it is possible to do this with ion currents this can be used to detect if the sensor is broken, and then estimate the ethanol content until the sensor gets fixed. The benefit of using ion currents is that the signal is measured directly from the spark plug and therefore no extra hardware is needed. To be able to see how the ethanol ratio affects the ion currents, the dependencies of the operating point have been investigated. This has been done by a literature review and by measurements in a Saab 9-3. Engine speed, load, ignition timing, lambda and spark plugs effects on the ion currents are especially studied. A black box model for the ion currents dependence on operating point is developed. This model describes the engine speed, load and ignition timing dependencies well, but it can not be used to estimate the ethanol ratio.
412

Investigation of typical 0.13 µm CMOS technology timing effects in a complex digital system on-chip

Johansson, Anders January 2004 (has links)
This master's thesis deals with timing effects in complex on chip systems. It is written in cooperation with the research and development centre of Infineon Technologies. One primary goal of all integrated circuit designers is to make the chips as small as possible. In deep sub micron designs timing effects like crosstalk have severe impact on the functionality of the chip. Therefore, accurate timing analyses must be made before the chip is ready for manufacturing. Otherwise the production yield can be reduced drastically. A case study on timing analysis with the 0.13 µm technology is made on the bus system of the device S-GOLD. The computer-based program PrimeTime is used to carry out the timing analysis. During the evolution of 0.13 µm technology three design packages have been developed to characterize the timing. Two releases of SGOLD have been designed based on the first and the second design package. The different design packages were compared, with and without pin capacitance variations, on chip variations and crosstalk. Furthermore the two releases are compared. The result from the analysis tool may not correlate well with what you see on the manufactured chips. In order to investigate the correlation, some tests were finally performed on an evaluation board. The results from the timing analysis are as expected. The second netlist version is better optimized than the first one. Design package three is most pessimistic among the three design packages. Design package one is most optimistic and does not match the real performance. Both design package two and three fit to the real performance well. Among the three design packages, design package three fits the real performance best.
413

Clock Edge Timing Adjustment Techniques for Correction of Timing Mismatches in Interleaved Analog-to-Digital Converters

Shirtliff, Jason Neil January 2010 (has links)
Time-interleaved analog-to-digital converters make use of parallelization to increase the rate at which an analog signal can be digitized. Using M channels at their maximum sampling frequency allows for an overall sampling frequency of M times the individual converters' sampling rate. However, the performance of interleaved systems suffers from mismatches between the sub-converters. Offset mismatches, gain mismatches, and timing mismatches all contribute to the degradation of the resolution of the ADC system. Offset and gain mismatches can be corrected for in the digital domain with minimal extra processing. However, the effects of timing mismatches (specifically, the magnitude of the spurious tones that are introduced) are dependent on the frequency of the input, so digital correction is not a trivial task. This makes a circuit-based correction mechanism a much more desirable solution to the problem. This work explores the effect of timing mismatches on interleaved analog-to-digital converter performance. A set of requirements is derived to specify the performance of a variable-delay circuit for the tuning of sample clocks. Since the mismatches can be composed of both fixed and random components, several candidate architectures are modeled for their delay and jitter performance. One candidate is selected for design, based on its jitter performance and on practical considerations. A practical implementation of the clock-adjustment circuit is designed, featuring low-noise differential clock paths with high precision delay adjustment. A means of testing the circuit and verifying the precision of adjustment is presented. The design is implemented for fabrication, and post-layout simulations are shown to demonstrate the feasibility and functionality of the design.
414

MDA transformation: A case study of embedded systems

Liu, Jo-Chan 13 July 2010 (has links)
Object-oriented analysis and design approach has become the mainstream of today¡¦s systems development technique. The Timing Diagram and State Machine Diagram from the Unified Modeling Language (UML) are becoming the major tools for modeling the platform independent model (PIM) of an embedded system. Once these two diagrams are constructed, the results can then be transformed into its platform specific model and template code based on the model driven architecture (MDA) approach. However, the detailed guideline for the transformation from Timing Diagram and State Machine Diagram to the template code is lacking. Therefore, this study presents a methodology which provides guidelines for the transformation from State Machine Diagram and Timing Diagram to template code for the embedded system. The research methodology is articulated using the design science research methodology. A usability evaluation with a real-world embedded system case is performed to demonstrate its applicability. The results indicated that with this proposed method, the system developer can effectively transform the PIM of an embedded system into its template code.
415

Factors Related to the Timing of Intestinal Stoma Closure and Outcomes after the Surgery

Wu, Chin-Yu 05 February 2011 (has links)
Patients of stoma caused by the colorectal disease or trauma are increasing and most of the patients are keen to have their stoma closed as early as possible to lower the burdens in their life. However, stoma often associated with complications such as wound. The interval between constructing and closing of stoma is still controversial. This study will figure out a way to predict an appropriate timing of stoma closure to get better outcome by using NHI database, from January 1, 2007 to December 31, 2008, in Taiwan. In 463 stoma closure patients, mean age: 65.94 years, ratio of male to female: 1.66, 70.19% Colostomy, 29.81% Ileostomy, mean timing: 156.73 days, mean length of stay: 10.81 days, mean fees: 57,698.06 TWD, only one death in hospital, 35 readmission within 30 days after discharged; with £\ = 0.05 level, the timing is significant in comorbidity, primary diagnosis; the outcomes are associated with the timing of stoma closure, comorbidity, patients¡¦ age and gender, hospital ownership and physician annual volume. Through this study, a perfect timing of stoma closure should be determined by the characteristics of patient and physician. Physicians could predict the timing through the stratified analysis and well organize the resource of hospital to improve the quality of medical care.
416

Reproductive ecology of Cardisoma carnifex (Brachyura) in Hengchun Peninsula, Taiwan

Chen, Tzu-chieh 04 July 2012 (has links)
The aim of this study was to investigate the reproductive ecology including fecundity, reproductive season, timing of larval release, evaporative water loss during reproductive migration, and the salinity tolerance of first zoeal stage of Cardisoma carnifex in Houwan, Hengchun Peninsula. The average carapace width of ovigerous females was 70.5 ¡Ó 6.57 mm, with a size range of 56.0-93.7 mm. Fecundity intimates increased with size and the number of hatched larvae from individual female varied from 90,000 to 490,000. The reproductive season of C. carnifex began at the onset of the rainy season and ends approximately at the end of that season. The reproductive season was from June to Oct. in 2009 and May to Sept. in 2010. The peaks of larval release occurred in July in 2009, 2010. Some females had the capacity in spawning twice during a reproductive season. Ovigerous females releasing larvae synchronously. The relationship between larval release timing and environmental cycle is listed in decreasing order of importance: diel rhythm, semilunar rhythm, tidal amplitude rhythm, and a low correlation was found with the tidal rhythm. Ovigerous females of C. carnifex started to release larvae after the new and full moon, lasting for 6-8 days with peaks occurring 4-6 days after the new and full moon. The peaks of larval release occurred within 2-3 hours after the sunset time (i.e., between 1930H and 2130H). This species exhibits different larval release timing and behavior compare to other species of Gecarcinidae; ovigerous females of gecarcinid crabs follow a lunar rhythm but C. carnifex follow a semilunar rhythm. More than half of the ovigerous females stayed in the water for up to 10 min (average 5.5 ¡Ó 2.87 min) and could move to deep water (i.e., 120 cm) to release their larvae. A few females even released their larvae in the freshwater environment. For C. carnifex, a mean of 15¢H of its original weight was lost by the time they died and the osmolality of the hemolymph is 856 mOsm kg-1. Compare with the hemolymph osmolality of ovigerous females (694 ¡Ó 6.3 mOsm kg-1), the results indicated that the ovigerous females at Houwan may not experience severe water loss during larval release migration. The first zoeal stage of C. carnifex could not survive in the freshwater, all larvae died within 2 hours. However, at salinities large than 5‰, most larvae could survive for more than 3 days. The results show first zoeal stage of C. carnifex had adapted to the low salinity in the estuary.
417

Effect of an upper temperature threshold on heat unit calculations, defoliation timing, lint yield, and fiber quality in cotton

Fromme, Daniel D. 15 May 2009 (has links)
Crop managers need to determine the most profitable time to defoliate cotton (Gossypium hirsutum L.) in a high rainfall environment such as the coastal region of Texas. In cotton production, delaying defoliation exposes open bolls to a higher probability of rainfall, and thus, reduces lint yield and fiber quality. Premature defoliation, however, has detrimental affects on lint yield and fiber quality. A more recent method to determine defoliation is based on heat-unit (HU or DD15) accumulation after physiological cutout or five nodes above white flower (NAWF=5). Results have been inconsistent across a wide range of field environments when utilizing HU accumulation past cutout; therefore, adoption of this method has been limited. Many regions of the Cotton Belt have maximum day time temperatures during the growing season that are above optimum for maximum growth. Field studies were conducted for three consecutive growing seasons in the Brazos River Valley and Upper Gulf Coast regions of Texas. The purpose of this research was to identify an upper temperature threshold (UTT) for calculating degree days for defoliation timing. The experimental design consisted of a split-plot design with four replications. The main plots consisted of three upper temperature thresholds (32°C, 35°C, and no upper limit) and the subplots were five HU timings (361, 417, 472, 528, and 583) accumulated from date of cutout. Utilizing an UTT to calculate daily HU failed to explain differences in the optimum time to defoliate based on accumulated HU from cutout for the upper thresholds investigated. Accumulated HU had a significant impact, however, on defoliation timing. Comparison of the two locations showed that maximum lint yield was obtained at 472 HU and 52% open boll at Wharton County versus a maximum of 528 HU and 62% open boll for the Burleson County location. Employing the NACB=4 method to time defoliation at both locations would have resulted in premature application of harvest aids and reduced lint yields. No differences were observed in adjusted gross income values at Wharton County among the 417, 472, 528, and 583 HU treatments. For Burleson County, adjusted gross income peaked in value at 528 HU.
418

Steiner network construction for signal net routing with double-sided timing constraints

Li, Qiuyang 02 June 2009 (has links)
Compared to conventional Steiner tree signal net routing, non-tree topology is often superior in many aspects including timing performance, tolerance to open faults and variations. In nano-scale VLSI designs, interconnect delay is a performance bottleneck and variation effects are increasingly problematic. Therefore the advantages of non-tree topology are particularly appealing for timing critical net routings in nano-scale VLSI designs. We propose Steiner network construction heuristics which can generate either tree or non-tree of signal net with different slack wirelength tradeoffs, and handle both long path and short path constraints. Extensive experiments in different scenarios show that our heuristics usually improve timing slack by hundreds of pico seconds compared to traditional tree approaches while increasing only slightly in wirelength. These results show that our algorithm is a very promising approach for timing critical net routings.
419

Essays on International Market Entry Strategy

Song, Myunggook 2010 August 1900 (has links)
Two important issues regarding international market entry strategy remain largely unexplored: international launch time window (the elapsed time between product launch in the home country and launch in the focal country) and country sequence. First, I investigate the factors that drive international launch time window and its impact on the performance of new products in foreign markets. The results show that launch time window is positively associated with word of mouth, but negatively related to prelaunch advertising efforts and foreign demand potential. Second, I examine the determinants of the sequence of countries in which firms introduce new products and its impact on performance in foreign countries. The findings include that a country‘s order in the international launch sequence of a new product affects the product‘s performance in that country. Country order is negatively related to country revenues. A country‘s cultural distance (economic openness) is positively (negatively) associated with its order in the sequence. I also find that there is cross-country spillover effect - lagged revenues from other countries and lagged marketing efforts in the home country are positively related to a new product‘s revenues in the focal foreign country. The more culturally sensitive a product, the earlier culturally closer countries are in the launch sequence for that product. Based on the cross-country performance spillover effects, I recommend a launch sequence that can maximize overall performance in foreign markets.
420

Reducing Timing Jitter Error by Using Self-tuning Based MPI- DLL in UWB Systems

Wu, Seng-wen 03 August 2005 (has links)
Ultra-Wideband ¡}UWB¡~Communication Technology is one of the potential technologies in indoor wireless communication applications. Because of the property of fine resolution of transmitted signal by UWB, it is powerful on indoor location applications. In the first place, we need to estimate the time of arrival based on the wireless location applications. Whether synchronization between the template signals and received signals affects directly the SNR of the estimator output and decreases the ranging accuracy. Because of the transmitted signal is the type of impulse radio for UWB system, it is more important on the time accuracy of the internal oscillator. In the thesis, we utilize the Delay-Locked Loop ¡}DLL¡~ structure with Self-tuning function to reduce the timing jitter in the internal oscillator. We can improve the stability in the tracking loop and utilize multipath canceller to cancel the multipath interference in the indoor environment. When reaching synchronization between the template signal and received signal by using the tracking loop, we can improve ranging accuracy and increase location precision according to the received signal.

Page generated in 0.0502 seconds