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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
881.
Oliveira M. Dart-Mao Cheung C. Al-Zayed A. Chio I.-F.F. Swisher R.R. Lecuyer F. DeLisio M.P. 《Antennas and Propagation, IEEE Transactions on》2002,50(5):698-702
Grid-mixer arrays can achieve high linearity and dynamic range through quasi-optical power combining. We present a 100-element single-ended diode grid mixer operating at 2.45 GHz. Each element incorporates two diodes in series. We measure an input third-order intercept of 11 W (40.5 dBm), and output third-order intercept of 3.4 W (35.4 dBm), and an associated conversion loss of 5.1 dB. The power-handling capability of the array is 100 times larger than that of a microstrip mixer using a single element. The local oscillator (LO) drive requirement for the entire array is 1.4 W (31.6 dBm). The angular dependence of the array's IF power is also presented and is in agreement with theory 相似文献
882.
Sung D. Kwon Sung J. Song Dong H. Bae Young Z. Lee 《Journal of Mechanical Science and Technology》2002,16(9):1084-1092
The frequency dependency of Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward
radiation of the incident ultrasonic wave in two kinds of degraded specimens by scuffing or corrosion. Then, the frequency
dependency is compared with the residual stress distribution or the corrosion-fatigue characteristics for the scuffed or corroded
specimens, respectively. The width of the backward radiation profile increases with the increase of the variation in residual
stress distribution for the scuffed specimens. In the corroded specimens, the profile width decreases with the increase of
the effective aging layer thickness and is inversely proportional to the exponent, m, in the Paris’ law that can predict the
crack size increase due to fatigue. The result observed in this study demonstrates high potential of backward radiated ultrasound
as a tool for nondestructive evaluation of subsurface gradient of material degradation generated by scuffing or corrosion. 相似文献
883.
本文设计了用于千兆以太网基带铜缆接收器均衡的甚高频自适应连续时间Gm-C二阶带通滤波器。基于最陡梯度下降算法,带通滤波器的零点在57-340MHz的频率范围内可以自适应地调节,中心频率为1.278GHz。通过外接电阻伺服环路,滤波器中跨导转换器的跨导值不受工艺偏差和温度变化的影响,采用CSMC-HJ0.6μm CMOS工艺器件模型,用Cadence Spectres仿真器仿真了设计的自适应滤波器电路,仿真结果验证了设计原理和设计的电路。系统的最长学习时间为880个参考时钟周期。 相似文献
884.
Under conditions typical of Harper-Dorn (H-D) creep the statistical slip-length may become comparable to, or even exceed,
the specimen diameter (a size effect). It is demonstrated that a consequence of such a size effect is that the rates of dislocation
storage and dynamic recovery are reduced and the static recovery rate will exceed the dynamic one. Under such conditions,
the analysis shows that the creep rate will scale linearly with the applied stress, a characteristic of H-D creep.
This article is based on a presentation made in the workshop entitled “Mechanisms of Elevated Temperature Plasticity and Fracture,”
which was held June 27–29, 2001, in San Diego, CA, concurrent with the 2001 Joint Applied Mechanics and Materials Summer Conference.
The workshop was sponsored by Basic Energy Sciences of the United States Department of Energy. 相似文献
885.
886.
Chen H.H. Huang T.S. 《IEEE transactions on pattern analysis and machine intelligence》1991,13(9):872-878
The specific problem addressed by the authors is how to detect the true match of a fourth point from among candidate matches in a situation in which three points have already been matched. The two sets of points to be matched are both subject to measurement errors. The depth error is more dominant than errors in the other two coordinates; however, the exact statistical distribution of the measurement errors is not known. The authors present a new method for solving the problem. The method is based on the technique of motion analysis using orthographic views. It discards the noisy z (depth) coordinates and uses only the x and y coordinates of the points to verify the match. The effect of depth errors on the motion estimate is completely prevented. Results show that this method is substantially more effective than previous methods that use all three coordinates 相似文献
887.
Belli F. Jedrzejowicz P. 《IEEE transactions on pattern analysis and machine intelligence》1991,17(3):310-312
An approach to the optimization of software reliability is proposed. The emphasis is put on the software redundancy to achieve fault tolerance, i.e. the results of the optimization process are used to determine the optimal structure of the software to be developed. Two optimization models are formulated covering, respectively, modified recovery block scheme and multiversion programming approaches. Both cases are illustrated by simple examples. The models show that it is possible to formulate and solve some software related reliability optimization problems. They further show that the concept of redundancy to achieve fault tolerance (basic for the traditional theory of reliability) can be used in the field of software reliability optimization 相似文献
888.
889.
890.