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排序方式: 共有4148条查询结果,搜索用时 11 毫秒
91.
Elena Laukhina Victor Lebedev Vladimir Laukhin Angel Pérez del Pino Elsa B. Lopes Ana I.S. Neves Dulce Belo Manuel Almeida Jaume Veciana Concepció Rovira 《Organic Electronics》2012,13(5):894-898
The paper reports all-organic strain and stress sensitive films that use electrical monitoring approach. The films were prepared by self-metallizing polycarbonate films with the single component molecular conductor [Au(α-tpdt)2]0 (tpdt = 2,3-thiophenedithiolate). It was shown that [Au(α-tpdt)2]0 by its nature is able to form metallic solid material with low crystallinity. Electromechanical tests demonstrated that the developed films are strain-resistive materials with advanced elastic properties: their electrical resistance varies linearly with uniaxial elongation up to relative strain being of 1.0% that is about five times larger than that for conventional metals. The gauge factor of the films is 4.4 and stress sensitivity is 30 Ω/bar. The processing characteristics of polycarbonate films, self-metalized with a metallic [Au(α-tpdt)2]0-based layer, make them potentially useful for engineering flexible, lightweight, strain and pressure sensors. Due to electromechanical characteristics these films are suited to strain sensing applications requiring miniature strain control in a wide deformation range. 相似文献
92.
2004 年,飞思卡尔半导体在标准产品及汽车芯片应用上已推出了超过200 多个新产品。在无线领域,推出的U W B 芯片组成为全球第一家获得F C C ( 美国联邦通信委员会) 批准的UWB 通信方案。在刚刚结束的 CES 展上,飞思卡尔演示了多个采用UWB 技术的无线消费电子产品和原型设计,包括支持UWB 功能的手机。这种手机可以通过UWB 实现与笔记本电脑的无线连接,使手机能够通过笔记本电脑从互联网下载MP3 文件,或是向笔记本电脑传送用手机拍得的图像。 预测2005年中国半导体市场持续 走强,预示消费类电子市场将保持活 跃,DVD、数码相机等终端产品的销售 量也将继续稳定。消费者对移动性的 需要是刺激无线联网及其它新兴应用 市场成长的主要动力。新应用还将提 升消费者的无线体验。MP3正向MP4发 展,后者实际上是便携式多媒体播放 机,它不仅能播放音乐,还能储存和播 放电影等视频文件。同时,我们正进入 无线通信的新时代,不仅人与人之间 能够无线通信,机器与机器之间也... 相似文献
93.
This paper deals with a multiuser detector based on a new decorrelating approach for asynchronous uplink DS/CDMA communications in which the QPSK modulation scheme is used in transmission. It is shown here that the receiver proposed is near–far resistant and exhibits a low complexity which allows realtime operation. Performance is expressed in terms of bit error rate (BER) which has been derived by simulations under the assumption of a slowly frequencyselective Rayleigh fading channel. 相似文献
94.
Aitor Del Coso Umberto Spagnolini Christian Ibars 《Selected Areas in Communications, IEEE Journal on》2007,25(2):402-414
The large number of network nodes and the energy constraints make Wireless Sensor Networks (WSN) one of the most important application fields for Cooperative Diversity. Node cooperation increases the spatial diversity of wireless channels and, thus, reduces the transmitted power. In this paper, we propose a multi-hop WSN with nodes grouped in cooperative clusters that exploits transmit and receive cooperation among cluster nodes. Multi-hop transmission is carried out by concatenating single cluster-to-cluster hops, where every cluster-to-cluster link is defined as a cooperative distributed multiple-input-multiple-output (MIMO) channel. Transmit diversity is exploited through a time-division, decoder-and-forward, relaying scheme based upon two time slots: the Intracluster Slot, used for data sharing within the cluster, and the Intercluster Slot, used for transmission between clusters. At the receiver side, a distributed reception protocol is devised based upon a Selection Diversity algorithm. The proposed multi-hop cooperative WSN is optimally designed for minimum end-to-end outage probability by deriving the optimum time and power allocated on the intracluster and intercluster slots of every single hop, given a per-link energy constraint. A simplified suboptimum resource allocation is also proposed, which performs close to the optimal policy. Results show that the proposed scheme achieves diversity equal to the equivalent MIMO system and significantly reduces energy consumption with respect to. the non-cooperative channel 相似文献
95.
Volha Varlamava Giovanni De Amicis Andrea Del Monte Stefano Perticaroli Rosario Rao Fabrizio Palma 《Journal of Infrared, Millimeter and Terahertz Waves》2016,37(8):737-752
In this paper, we present a new rectifying device, compatible with the technology of CMOS image sensors, suitable for implementing a direct-conversion detector operating at room temperature for operation at up to terahertz frequencies. The rectifying device can be obtained by introducing some simple modifications of the charge-storage well in conventional CMOS integrated circuits, making the proposed solution easy to integrate with the existing imaging systems. The rectifying device is combined with the different elements of the detector, composed of a 3D high-performance antenna and a charge-storage well. In particular, its position just below the edge of the 3D antenna takes maximum advantage of the high electric field concentrated by the antenna itself. In addition, the proposed structure ensures the integrity of the charge-storage well of the detector. In the structure, it is not necessary to use very scaled and costly technological nodes, since the CMOS transistor only provides the necessary integrated readout electronics. On-wafer measurements of RF characteristics of the designed junction are reported and discussed. The overall performances of the entire detector in terms of noise equivalent power (NEP) are evaluated by combining low-frequency measurements of the rectifier with numerical simulations of the 3D antenna and the semiconductor structure at 1 THz, allowing prediction of the achievable NEP. 相似文献
96.
This paper presents a simple distance estimation for implicit polynomial fitting. It is computed as the height of a simplex built between the point and the surface (i.e., a triangle in 2-D or a tetrahedron in 3-D), which is used as a coarse but reliable estimation of the orthogonal distance. The proposed distance can be described as a function of the coefficients of the implicit polynomial. Moreover, it is differentiable and has a smooth behavior . Hence, it can be used in any gradient-based optimization. In this paper, its use in a Levenberg-Marquardt framework is shown, which is particularly devoted for nonlinear least squares problems. The proposed estimation is a generalization of the gradient-based distance estimation, which is widely used in the literature. Experimental results, both in 2-D and 3-D data sets, are provided. Comparisons with state-of-the-art techniques are presented, showing the advantages of the proposed approach. 相似文献
97.
Juan?A.?Morales-Cordovilla Victoria?SánchezEmail author Angel?M.?Gómez Antonio?M.?Peinado 《Circuits, Systems, and Signal Processing》2012,31(2):727-736
This paper deals with the problem of searching for a suitable window for robust speech recognition in noisy conditions. A
set of asymmetric windows, so-called DDR
c,w
, are proposed which are controlled by two parameters, center c and width w. These windows are derived from the DDR window used in the higher-lag autocorrelation spectrum estimation (HASE) method and
act over the OSA (One-Sided Autocorrelation) in order to perform spectral estimation. The two parameters, c and w, allow us to control the level of weight given to the first noisy autocorrelation coefficients and to emphasize the important
ones. Finally, it is shown that the best window of the proposed set is the DDR
62,200. This window is centered around the average pitch of human speech and it provides a higher speech recognition performance
over the Aurora-2 and Aurora-3 databases than those obtained by previously proposed windows. 相似文献
98.
Angel Cobos María I. Cambero Juan A Ordez Lorenzo De La Hoz 《Journal of the science of food and agriculture》1993,62(1):83-88
The effects of beef tallow-, soya and sunflower olein- and soya bean oil-enriched (3%) diets on the chemical and fatty acid composition of total, a polar and polar lipids of rabbit meat have been studied. No significant differences (P > 0.05) in the meat chemical composition were observed between groups. However, a large effect of the diet on the total and apolar lipid fatty acids was found, with C18:1 and C18:2 the most affected fatty acids. The influence of the diets on the fatty acids of the polar fraction was less marked. It is concluded that the enrichment of the rabbit diet with either soya and sunflower oleins or soya bean oil allows the production of rabbit meat with a higher unsaturation degree than is obtained by using conventional diets, which constitutes an important nutritional benefit to the human being. 相似文献
99.
The eigenfilter approach is an appealing way of designing digital filters, mainly because of the simplicity of its implementation. In this correspondence, a new method of applying the eigenfilter approach to the design of infinite impulse response (IIR) filters is described. The procedure works in the frequency domain and yields the coefficients of a causal rational transfer function having an arbitrary number of poles and zeros. Some examples of filter design are given to show the effectiveness of the method presented 相似文献
100.
Off-state breakdown in power pHEMTs: the impact of the source 总被引:1,自引:0,他引:1
Somerville M.H. Del Alamo J.A. Saunier P. 《Electron Devices, IEEE Transactions on》1998,45(9):1883-1889
Conventional wisdom suggests that in pseudomorphic high electron mobility transistors (pHEMTs), the field between the drain and the gate determines off-state breakdown, and that the drain to gate voltage therefore sets the breakdown voltage of the device. Thus, the two terminal breakdown voltage is a widely used figure of merit, and most models for breakdown focus on the depletion region in the gate-drain gap, while altogether ignoring the source. We present extensive new measurements and simulations that demonstrate that for power pHEMTs, the electrostatic interaction of the source seriously degrades the device's gate-drain breakdown. We identify the key aspect ratio that controls the effect, LG:xD where LG is the gate length and xD is the depletion region length on the drain. This work establishes that the design of the source must be taken into consideration in the engineering of high-power pHEMT's 相似文献