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排序方式: 共有1686条查询结果,搜索用时 31 毫秒
11.
Efficient driving-capability programmable frequency divider with a wide division ratio range 总被引:1,自引:0,他引:1
A programmable frequency divider with close-to-50% output duty-cycle, with a wide division ratio range, is presented. The proposed divider has also provisions for binary division ratio controls, and has demonstrated operation at frequencies as high as 3.5 GHz. With the above features, the proposed divider can be used in phase-locked loops, and is capable of driving various clocked circuits, which need different clock frequencies. The proposed divider has division ratios from 8 to 510, but it can easily be extended to higher ranges by simply adding more divider stages. The divider circuit has been realised in a 0.18-mum RF CMOS process. Test results show that the output duty-cycle is 50% when the division ratio is an even number. For odd division ratios the worst-case duty-cycle is 44.4% when the division ratio is 9. The output duty-cycle becomes closer to 50% when the division ratio is an increasing odd number. For each division ratio, the output duty-cycle remains constant for different chips, with different input frequencies from gigahertz down to kilohertz ranges, and with different power supply voltages. 相似文献
12.
M. R. Islam R. V. Chelakaea J. G. Neff K. G. Fertitta P. A. Grudowski A. L. Holmes F. J. Ciuba R. D. Dupuis J. E. Fouquet 《Journal of Electronic Materials》1995,24(6):787-792
AlGaAs double heterostructures are grown by low-pressure metalorganic chemical vapor deposition to evaluate the level of oxygen
contamination in different trimethylaluminum sources. Effects of arsine purifiers, misoriented substrates, atmospheric exposure
of the growth chamber, and possible phosphorus contamination are also studied. Extensive characterization is performed on
these films by a variety of methods, including high-resolution x-ray diffraction, photoluminescence (PL), time-resolved photoluminescence,
and secondary-ion mass spectrometry. The PL intensities for structures grown with the low-alkoxide grade are reproducibly
much greater than those grown with the regular-grade TMA1. The use of AsH3 purification improves the PL intensity. 相似文献
13.
M. A. Islam 《应用聚合物科学杂志》1992,46(7):1215-1219
A mechanical model consisting of three elements (elastic, viscoelastic, and plastic) is proposed to describe the deformational behavior of a polymeric membrane operating in a pressure-driven process. The changes in the membrane thickness are proposed to be calculated from the experimentally obtained flux data. The advantages of a mechanical model over the conventional method of hysteresis area measurement as the mechanical stability of the polymeric membranes are discussed. © 1992 John Wiley & Sons, Inc. 相似文献
14.
In the framework of the European research project PV2GO, a new AC-module inverter was developed, taking into account all relevant aspects from a European market's point of view (standards, market, application, and research and development goals). The project goal was to achieve the overall system costs of 3 Euro per Wp for a modular plug-and-play photovoltaic system. For the photovoltaic-module, a standard 130-Wp Eurosolare module was chosen. The research and development (R&D) goal was to develop an advanced DC-control system consisting of a state-of-the-art programmable digital device and an Application Specific Integrated Circuit (ASIC) for the AC-control of the inverter. According to the topology concept, thermal and magnetic designs were optimized with regard to production technology and packaging for large-scale production. The new AC-modules were tested in a number of field-test sites in various parts of Europe and their reliability was assessed through Highly Accelerated Stress Tests. Efficiency and power quality have been tested in the laboratory. Further in the PV2GO project an optimization study of the manufacturing process of the new generation of AC-modules for high volume output was done. Another task was the pre-certification procedure to assure compliance with the European guidelines and standards. 相似文献
15.
16.
R. S. Fyath K. N. Darraj M. S. Alam M. N. Islam M. M. Alkhatib 《Optical Memory & Neural Networks》2007,16(3):125-135
A new joint transform correlation (JTC) technique, named two-channel JTC (TJTC), is proposed in this paper for optical pattern
recognition applications. The TJTC technique independently evaluates the autocorrelation and crosscorrelation values of the
reference and the target images and employs a modified decision algorithm. In addition, optical threshold operation and fringe-adjusted
filter are incorporated in the proposed technique to enhance the correlation output and to improve the discrimination performance.
The proposed technique shows better recognition performance compared to existing JTC techniques. Computer simulation are presented
to investigate the salient features of the proposed TJTC technique with noise-free as well as noisy input scenes.
The text was submitted by the authors in English. 相似文献
17.
H K?llstr?m MS Islam PO Berggren AB Jonsson 《Canadian Metallurgical Quarterly》1998,273(34):21777-21782
Neisseria gonorrhoeae and Neisseria meningitidis are Gram-negative bacterial pathogens that infect human mucosal epithelia. Type IV pilus-mediated adherence of these bacteria is a crucial early event for establishment of infection. In this work, we show that the type IV pili transduce a signal into the eucaryotic host cell. Purified adherent pili, but not pili from a low binding mutant, trigger an increase in the cytosolic free calcium ([Ca2+]i) in target epithelial cells, a signal known to control many cellular responses. The [Ca2+]i increase was blocked by antibodies against CD46, a putative pilus receptor, suggesting a role for this protein in signal transduction. Pilus-mediated attachment was inhibited by depletion of host cell intracellular Ca2+ stores but not by removal of extracellular Ca2+. Further, kinase inhibition studies showed that pilus-mediated adherence is dependent on casein kinase II. In summary, these data reveal a novel function of the type IV pili, namely induction of signal transduction pathways in host cells. 相似文献
18.
Microsystem Technologies - Flip-flops are the basic digital components for all types of complex digital electronics systems and sequential logic circuits. In this paper, new nonvolatile, low power,... 相似文献
19.
Islam S. Humail F. Akhtar S.J. Askari M. Tufail Xuanhui Qu 《International Journal of Refractory Metals and Hard Materials》2007,25(5-6):380-385
Tungsten heavy alloys (WHAs) are metal–metal composites consisting of nearly pure spherical tungsten particles embedded in a Ni–Fe–W or Ni–Co–W or Ni–Cu–W ductile matrix. In this dual phase alloy, there are several complicated relations between the ductile matrix and hard tungsten particles. The aim of this research was to examine the effect of varying tungsten content on the microstructure and mechanical properties of tungsten heavy alloys. The microstructural parameters (grain size, connectivity, contiguity and solid volume fraction) were measured and were found to have a significant effect on the mechanical properties of tungsten-based heavy alloys. The result shows that the binding strength between the W and the matrix phase has a major influence on the ductility of tungsten-based alloys. The larger this binding force is, the better the ductility is. 相似文献
20.
Hossein Rajabalipour Cheshmehgaz Md. Nazrul Islam Mohammad Ishak Desa 《Journal of Intelligent Manufacturing》2014,25(4):699-726
In practical multi-objective optimization problems, respective decision-makers might be interested in some optimal solutions that have objective values closer to their specified values. Guided multi-objective evolutionary algorithms (guided MOEAs) have been significantly used to guide their evolutionary search direction toward these optimal solutions using by decision makers. However, most guided MOEAs need to be iteratively and interactively evaluated and then guided by decision-makers through re-formulating or re-weighting objectives, and it might negatively affect the algorithms performance. In this paper, a novel guided MOEA that uses a dynamic polar-based region around a particular point in objective space is proposed. Based on the region, new selection operations are designed such that the algorithm can guide the evolutionary search toward optimal solutions that are close to the particular point in objective space without the iterative and interactive efforts. The proposed guided MOEA is tested on the multi-criteria decision-making problem of flexible logistics network design with different desired points. Experimental results show that the proposed guided MOEA outperforms two most effective guided and non-guided MOEAs, R-NSGA-II and NSGA-II. 相似文献