Optimization of polymer light emitting devices using TiOx electron transport layers and prism sheets

The internal and external efficiency of polymer light emitting devices were found can be simultaneously improved by insertion a high refractive index material, titanium oxide (TiO_x), to the emission layer and a prism sheet attached to the substrate. The TiO_x layer increased the internal efficiency due to a better electron injection and hole confinement. However, it led a wider angular emission profile with more photons trapped in the substrate. By using the prism sheet, those trapped light was efficiently coupled to the air. The extraction efficiency enhancement was increased from 33.1% to 54.4% and the overall current efficiency was improved up to 86%.     

Integrating PSONN and Boltzmann function for feature selection and classification of lymph nodes in ultrasound images

Lymph nodes (LNs), part of the lymphatic system, are important in the proper functioning of the immune system. LN metastasis is an important index for staging malignant tumors. The present study proposes a system that classifies lymph nodes according to pathological change from ultrasound (US) images. Features are selected and extracted from the US images. A feature selection method that integrates the particle swarm optimization neural network (PSONN) with the Boltzmann function is proposed to select significant features. A multi-class support vector machine (SVM) is adopted to classify diseases of the LN in the region of interests (ROIs) of US images into six categories. The experimental results show that the proposed approach decreases the number of selected features and that its classification is highly accurate.     

带约束的复FIR数字滤波器Chebyshev设计算法

本文主要讨论了复FIR数字滤波器的频域不等式约束Chebyshev设计问题.作者首先把文献[1]中的复交错点组定理扩展到有不等式约束的情况,之后根据扩展定理中对最优解特性的描述,并结合复Remez算法[1]及赖晓平的迭代Remez算法[2][3],提出了一种有效的算法来解决频域带不等式约束的复FIR数字滤波器的Chebyshev设计问题.如果问题的解存在,则算法能保证收敛到最优解.作者用MATLAB语言对上述算法进行了实现并做了仿真分析.     

High-powered thermal gel degradation evaluation on board-level HFCBGA subjected to reliability tests

HFCBGA is a thermally enhanced FCBGA with its heat spreader extending the heat conduction area by connecting itself to the rear side of the silicon die. A thermal interface material plays an important role as a heat conduction path. The thermal performance should not only be checked at time zero, and several reliability tests have to be undertaken to uncover the field conditions faced by end users. A temperature cycling test, highly-accelerated temperature and humidity stress test and multiple reflows are utilized to investigate the thermal resistance of junction to case of a selected thermal gel.     

A fractional-N frequency synthesizer for single-chip UHF RFID reader

A novel fractional-N frequency synthesizer which is based on delta sigma modulator (DSM) and specialized for single-chip UHF 860-to-960 MHz band radio frequency identification (RFID) reader is proposed in this paper. The fractional-N synthesizer is implemented in 0.18 μm CMOS process. The phase noise of the fractional-N synthesizer is approximately ?109 and ?129 dBc/Hz at 200 kHz and 1 MHz offset from 900 MHz operating frequency while drawing 9.6 mA from 1.8 V power supply. The synthesizer is evaluated by implementing it in a direct conversion RF front-end. The front-end features a noise figure of 3.5 dB and an input-referred third-order intercept point of 5 dBm.     

A review of three-dimensional viscoelastic models with an application to viscoelasticity characterization using nanoindentation

This work reviewed different three-dimensional viscoelastic models, including Hooke, Newton, Maxwell, Voigt, Boltzmann, Zener, Tsay, Burgers, Weichert, and Kelvin models. The relaxation moduli and creep compliances are derived and related via the viscoelastic parameters. Physical meanings of viscoelastic parameters are also explained for each model. The formulae of relaxation test, creep test, and dynamic loading test for each viscoelastic models are formulated. Relaxation moduli and creep compliances are drawn for visualizing and comparing. The less discussed time-dependent Poisson’s ratios are also emphasized and compared in this work. All viscoelastic functions can be represented as the relaxation-creep duality representation. The instantaneous and permanent moduli and compliances as well as the fractions of exponential and complementary exponential pairs with different characteristic times can be immediately understood via the relaxation-creep duality representation. The three-dimensional Burgers model is selected to describe the viscoelastic behavior of PMMA with nanoindentation test. The two-step curve fitting method is introduced to fit the P–t curve and h–t curve separately. The fitting results are better than the direct fitting of P–h curve in the literature. The relaxation moduli and creep compliances can then be used to understand the viscoelastic behavior of PMMA.     

Image super-resolution by textural context constrained visual vocabulary

Example-based super-resolution (SR) approach hallucinates the missing high-resolution (HR) details by learning the example image patches. This approach implicitly assumes that the similarity of the low-resolution (LR) patches can infer the similarity of the corresponding HR patches. However, this similarity preserving assumption may not be held in practice. Thus the example-based super-resolved image inevitably contains artifacts not close to the ground truth. In this paper, we propose a novel single-image SR method by integrating an enforced similarity preserving process by using visual vocabulary into example-based SR approach. By jointly learning the HR and LR visual vocabularies, we can obtain a geometric co-occurrence prior to make the geometric similarity preserved within each visual word. We further propose a two-step framework for SR. The first step estimates the optimum visual word using textural context cue while the second step enforces the visual word subspace constraint and reconstruction constraint for estimating the final result. Experiments demonstrate the effectiveness of our method for recovering the missing HR details, especially texture.     

Investigation of Laser-Assisted Microcrystalline SiGe Films Deposited at Low Temperature

SiGe films deposited by conventional plasma-enhanced chemical vapor deposition (PECVD) were compared with microcrystalline SiGe (μc-SiGe) films deposited at a low temperature using a laser-assisted plasma-enhanced chemical vapor deposition (LAPECVD). In the LAPECVD system, a CO₂ laser was used to assist the pyrolytic decomposition of SiH₄ and GeH₄ reactant gases. The μc-SiGe structure was identified using electron diffraction patterns from high-resolution transmission electron microscopy images. Microcrystalline SiGe films were analyzed using various measurements.     

A study of the backup reprovisioning problem for FIPP p-cycles on WDM networks

As networks grow in size and complexity, both the probability and the impact of failures increase. The pre-allocated backup bandwidth cannot provide 100% protection guarantee when multiple failures occur in a network. In this article, we focus on how to recover the protecting capabilities of FIPP (Failure-independent path-protecting) p-cycles against the subsequent links failure on WDM networks, after recovering the working paths affected by the failure of link. Two recovering policies are designed to recover the protecting capabilities of the FIPP p-cycles if possible, unless there is no sufficient network resource. They are Cycle Recovery Policy and Path Recovery Policy. In addition, a Cycle Adjust algorithm is proposed and used to recover the affected cycles. The simulation results of the proposed methods are also given.     

基于BACnet/6Lo WPAN协议的无线传感器网络设计与实现

提出一种基于BACnet/6LowPAN协议的无线传感器网络设计方案,并对网络中的硬件与软件平台以及网络拓扑进行了详细的论述,设计并实现了与用户交互及监控整个网络工作状态的平台。系统测试表明,该无线网络工作正常,达到预期目的。