化学机械抛光工艺中的硅片背压力控制与优化

化学机械抛光（Chemical Mechanical Polishing,CMP）技术是最有效的晶圆全局平坦化技术,抛光头是CMP设备中最核心的部件之一,新一代抛光头的设计主要采用区域压力控制技术。硅片抛光质量不仅取决于抛光液,还取决于对硅片抛光压力的精确控制。在CMP抛光工艺过程中各腔室的压力设定值通常并非一致,而且由于柔性弹性隔膜的存在各腔室之间相互耦合。由于耦合现象的存在使得多区腔室压力控制变得复杂化,针对这一耦合现象本文提出了一种用于多区解耦的控制方法,并基于该方法对多腔室进行了系统辨识以及控制参数整定,最后进行了多腔室同时加压实验,实验结果表明该解耦控制方法的可行性以及正确性。     

Performance analysis of cooperative spatial multiplexing networks with AF/DF relaying and linear receiver over Rayleigh fading channels

Cooperative spatial multiplexing (CSM) system has played an important role in wireless networks by offering a substantial improvement in multiplexing gain compared with its cooperative diversity counterpart. However, there is a limited number of research works that consider the performance of CSM systems. As such, in this paper, we have derived exact performance of CSM with amplify‐and‐forward and decode‐and‐forward relays in terms of outage capacity and ergodic capacity. We have shown that CSM systems yield a unity diversity order regardless of the number of antennas at the destination and the number of relays in the networks, which is the direct result of diversity and multiplexing gain trade‐off. Our analytical expressions are corroborated by Monte‐Carlo simulations. Copyright © 2013 John Wiley & Sons, Ltd.     

Synergistic activation of CTP:phosphocholine cytidylyltransferase by phosphatidylethanolamine and oleic acid

CTP:phosphocholine cytidylyltransferase present in rat liver cytosol was activated almost 30-fold when assayed in the presence of liposomes containing 60 mole % dioleoyl phosphatidylethanolamine (DOPE). During the assay, some of the DOPE was degraded to lysoPE and oleic acid. Whereas cytidylyltransferase activity was not affected when assayed in the presence of liposomes containing lysoPE, liposomes containing oleic acid activated the enzyme. Activation by oleic acid could be eliminated by the addition of fatty acid-free bovine serum albumin (BSA) to the assay. When cytidylyltransferase activity was measured in the presence of both BSA and liposomes containing DOPE, enzyme activity was increased almost 20-fold, as compared with assays performed in the absence of added lipid. The 1.5-fold difference in cytidylyltransferase activity observed when cytosol was assayed with DOPE containing liposomes in the absence or presence of BSA (30-fold stimulation vs 20-fold stimulation) cannot be explained by the loss of activation attributable to oleic acid alone. Activation of the enzyme in the presence of liposomes containing DOPE and oleic acid is several-fold greater than the sum of the activations caused by the individual compounds. These data suggest that PE and oleic acid act synergistically in activating the cytidylyltranferase.     

Cognitive amplify‐and‐forward relay networks with beamforming under primary user power constraint over Nakagami‐m fading channels

In this paper, we analyze the performance of cognitive amplify‐and‐forward (AF) relay networks with beamforming under the peak interference power constraint of the primary user (PU). We focus on the scenario that beamforming is applied at the multi‐antenna secondary transmitter and receiver. Also, the secondary relay network operates in channel state information‐assisted AF mode, and the signals undergo independent Nakagami‐m fading. In particular, closed‐form expressions for the outage probability and symbol error rate (SER) of the considered network over Nakagami‐m fading are presented. More importantly, asymptotic closed‐form expressions for the outage probability and SER are derived. These tractable closed‐form expressions for the network performance readily enable us to evaluate and examine the impact of network parameters on the system performance. Specifically, the impact of the number of antennas, the fading severity parameters, the channel mean powers, and the peak interference power is addressed. The asymptotic analysis manifests that the peak interference power constraint imposed on the secondary relay network has no effect on the diversity gain. However, the coding gain is affected by the fading parameters of the links from the primary receiver to the secondary relay network. Copyright © 2012 John Wiley & Sons, Ltd.     

Compression artifacts reduction with multiscale tensor regularization

Multidimensional Systems and Signal Processing - We study a multiscale tensor regularization based JPEG decompression artifact removal in digital images. Structure tensor eigenvalues based robust...     

Optimization of an RFID location identification scheme based on the neural network

An indoor localization technology is increasingly critical as location‐aware applications evolve. Researchers have proposed several indoor localization technologies. Because most of the proposed indoor localization technologies simply involve using the received signal strength indicator value of radio‐frequency identification (RFID) for indoor localization, radio‐frequency interference, and environmental factors often limit the accuracy of localization results. Therefore, this study proposes an accurate RFID localization based on the neural network (ARL‐N²), a passive RFID indoor localization scheme for identifying tag positions in a room, combining a location identification based on dynamic active RFID calibration algorithm with a backpropagation neural network (BPN). The proposed scheme composed of two phases: in the training phase, an appropriate BPN architecture is constructed using the training data derived from the coordinates of reference tags and the coordinates obtained using the localization algorithm. By contrast, the online phase involves calculating the tracking tag coordinates and using these values as BPN inputs, thereby enhancing the estimated location. A performance evaluation of the ARL‐N² schemes confirms its high localization accuracy. The proposed method can be used to locate critical objects in difficult‐to‐find areas by creating minimal errors and applying and economical technique. Copyright © 2013 John Wiley & Sons, Ltd.     

Symmetric Orthogonal Complex-Valued Filter Bank Design by Semidefinite Programming

A new design method for complex-valued two-channel finite impulse response (FIR) filter banks with both orthogonality and symmetry properties is developed. Based on a novel linear matrix inequality (LMI) characterization of trigonometric curves, the optimal design of perfect-reconstruction filter banks is cast into a semidefinite programming (SDP) problem. The dimension of the resulting SDP problem is further reduced by exploiting convex duality. Consequently, the globally optimal solution can be found for any practical filter length and desired regularity order.     

Numerical Study of Self-Complementary Antenna Characteristics on Substrate Lenses at Terahertz Frequency

This paper presents a numerical study of self-complementary antennas on substrate lenses made of high-permittivity dielectric material. Bowtie, logarithmically periodic, and logarithmic spiral antennas with the same outer and inner dimensions were selected for study, and their overall performances were compared in the terahertz band at frequencies up to 5.0?THz. The resonance and radiation characteristics of the three antennas were investigated in terms of input impedance, directivity, and radiation efficiency, using a full electromagnetic simulator. This study provides useful guidelines and partially solves the difficult problems of choosing the proper feed and optimizing the lens structure for a THz broadband integrated lens antenna.