Control of transient effects in distributed and lumped Ramanamplifiers

A robust control scheme for suppressing transients in both lumped and distributed Raman amplifiers is demonstrated. The control method uses only output power monitoring and holds gain fluctuations on surviving channels to <±0.06 dB in an experiment     

Crosstalk reduction through wavelength assignment in WDM photonicswitching networks

As the deployment of wavelength-division multiplexing (WDM) transmission facilities speeds up, the next step is to add cross-connects to route WDM signals. Electro-optical directional couplers (DCs) are well suited for the task since they can pass WDM signals. However, DCs suffer an intrinsic crosstalk problem. Removing crosstalk has been an important design issue. In this paper, we show how to take advantage of the multiple-wavelength characteristic of a WDM signal to reduce crosstalk in a DC-based photonic switching system     

MPPA光动力作用诱导人鼻咽癌细胞凋亡的实验研究

为观察MPPa光动力作用对鼻咽癌细胞凋亡的影响,应用AnnexinV—PI双染结合流式细胞仪分析MPPa光动力作用后人鼻咽癌细胞株CNE2细胞发生凋亡和继发性坏死的比率。结果显示MPPa光动力作用实验组人鼻咽癌细胞株CNE2细胞发生凋亡和继发性坏死的比率分别增加到16.43 %和4.64 % ,且均显著高于单纯光照射组、单纯MMPa光敏剂处理组和假照射组(P <0 .0 1) ,而三对照组间无明显差异(P >0 .0 5 )。表明MPPa光动力作用能有效诱导低分化人鼻咽癌细胞株CNE2细胞凋亡的发生。这也可能是MPPa光动力作用杀伤鼻咽癌的重要机制之一。     

Secure group communications using key graphs

Many emerging network applications are based upon a group communications model. As a result, securing group communications, i.e., providing confidentiality, authenticity, and integrity of messages delivered between group members, will become a critical networking issue. We present, in this paper, a novel solution to the scalability problem of group/multicast key management. We formalize the notion of a secure group as a triple (U,K,R) where U denotes a set of users, K a set of keys held by the users, and R a user-key relation. We then introduce key graphs to specify secure groups. For a special class of key graphs, we present three strategies for securely distributing rekey messages after a join/leave and specify protocols for joining and leaving a secure group. The rekeying strategies and join/leave protocols are implemented in a prototype key server we have built. We present measurement results from experiments and discuss performance comparisons. We show that our group key management service, using any of the three rekeying strategies, is scalable to large groups with frequent joins and leaves. In particular, the average measured processing time per join/leave increases linearly with the logarithm of group size     

Soft quasi-maximum-likelihood detection for multiple-antenna wireless channels

The paper addresses soft maximum-likelihood (ML) detection for multiple-antenna wireless communication channels. We propose a soft quasi-ML detector that maximizes the log-likelihood function by deploying a semi-definite relaxation (SDR). Given perfect channel state information at the receiver, the quasi-ML SDR detector closely approximates the performance of the optimal ML detector in both coded and uncoded multiple-input, multiple-output (MIMO) channels with quadrature phase-shift keying (QPSK) modulation and frequency-flat Rayleigh fading. The complexity of the quasi-ML SDR detector is much less than that of the optimal ML detector, thus offering more favorable performance/complexity characteristics. In contrast to the existing sphere decoder, the new quasi-ML detector enjoys guaranteed polynomial worst-case complexity. The two detectors exhibit quite comparable performance in a variety of ergodic QPSK MIMO channels, but the complexity of the quasi-ML detector scales better with increasing number of transmit and receive antennas, especially in the region of low signal-to-noise ratio (SNR).     

An inverted U-shaped patch antenna for compact operation

By using a novel inverted U-shaped radiating patch in place of the conventional planar patch, compact operation of air-substrate patch antennas is presented. The inverted U-shaped patch is formed by adding two downward rims at the two radiating edges of a planar rectangular or square patch. And owing to the added rims, the excited patch's surface current paths are lengthened, which effectively lowers the antenna's resonant frequency and results in large antenna size reduction (>50%). The proposed compact design has been successfully applied to air-substrate patch antennas fed by an aperture-coupled feed. In addition to large size reduction obtained, the proposed antenna with an air-substrate thickness about 5% the wavelength of the center operating frequency can have an impedance bandwidth (10-dB return loss) greater than 9%, a peak antenna gain of about 6.4 dBi, and good broadside radiation patterns with cross-polarization levels better than 20 dB in principal planes.     

Isotropic conductive adhesives filled with low-melting-point alloyfillers

Conventional isotropic conductive adhesives (ICAs) are composed of a polymeric matrix and silver (Ag) flakes. As an alternative to lead-bearing solder, ICAs offer a number of benefits, but limitations do exist for ICA technology. ICAs filled with silver flakes generally show higher initial contact resistance, unstable contact resistance, and inferior impact strength. In this study, a new class of isotropic conductive adhesives was developed by using two different fillers, silver flakes and a low-melting-point-alloy filler, into the ICA formulations. After curing, the metallurgical connections between silver particles, and between silver particles and nickel (Ni) substrate were observed using scanning electron microscopy (SEM). Electrical properties including bulk resistance, initial contact resistance, and contact resistance shifts of the ICA were investigated and compared to those of a commercial ICA, an in-house ICA filled with only the silver flake, and a eutectic Sn/Pb solder. It was found that: (1) the low-melting-point alloy filler could wet the silver flakes and nickel substrate to form metallurgical connections, (2) this ICA had much lower bulk resistance than the commercial ICA and the in-house ICA filled with only the silver flake, and (3) this ICA showed especially low initial contact resistance and more stable contact resistance during aging on nickel metal compared to the ICA filled only with silver flakes     

Three-dimensional virtual-reality surgical planning and soft-tissueprediction for orthognathic surgery

Complex maxillofacial malformations continue to present challenges in analysis and correction beyond modern technology. The purpose of this paper is to present a virtual reality workbench for surgeons to perform virtual orthognathic surgical planning and soft-tissue prediction in three dimensions. A resulting surgical planning system, i.e., three-dimensional virtual reality surgical planning and soft-tissue prediction for orthognathic surgery, consists of four major stages: computed tomography (CT) data post-processing and reconstruction, three-dimensional (3-D) color facial soft-tissue model generation, virtual surgical planning and simulation, soft-tissue-change preoperative prediction. The surgical planning and simulation are based on a 3D CT reconstructed bone model, whereas the soft-tissue prediction is based on color texture-mapped and individualized facial soft-tissue model. Our approach is able to provide a quantitative osteotomy-simulated bone model and prediction of postoperative appearance with photorealistic quality. The prediction appearance can be visualized from any arbitrary viewing point using a low-cost personal computer-based system. This cost-effective solution can be easily adopted in any hospital for daily use     

Multi-Fidelity High-Throughput Optimization of Electrical Conductivity in P3HT-CNT Composites

Combining high-throughput experiments with machine learning accelerates materials and process optimization toward user-specified target properties. In this study, a rapid machine learning-driven automated flow mixing setup with a high-throughput drop-casting system is introduced for thin film preparation, followed by fast characterization of proxy optical and target electrical properties that completes one cycle of learning with 160 unique samples in a single day, a > 10 ×  improvement relative to quantified, manual-controlled baseline. Regio-regular poly-3-hexylthiophene is combined with various types of carbon nanotubes, to identify the optimum composition and synthesis conditions to realize electrical conductivities as high as state-of-the-art 1000 S cm⁻¹. The results are subsequently verified and explained using offline high-fidelity experiments. Graph-based model selection strategies with classical regression that optimize among multi-fidelity noisy input-output measurements are introduced. These strategies present a robust machine-learning driven high-throughput experimental scheme that can be effectively applied to understand, optimize, and design new materials and composites.     

A new framework for part failure-rate prediction models

This paper presents a framework for developing part failure-rate models. It is a partial result of an effort sponsored by the US Air Force for the development of reliability prediction models for military avionics. Published data show that the existing reliability prediction methods fall far short of providing the required accuracy. One of the problems in the existing methods is the exclusion of critical factors. The new framework is based on the premise that essentially all failures are caused by the interactions of built-in flaws, failure mechanisms, and stresses. These three ingredients contribute to form the failure distribution which are functions of stress application duration (eg, aging time), number of thermal cycles, and vibration duration. The Weibull distribution has been selected as the general distribution. The distribution is then modified by the critical factors such as flaw quantities, effects of environmental stress screening, calendar-time reliability improvements, and vendor quality differences, to provide the part failure-rate functions. To provide credibility for the framework, only well published data and information have been used