图像边缘提取的定位误差产生机理分析

本文分析了使用Dmarr的LOG方法检测图像边缘时,零交叉点定位误差的产生机理,指明边缘中心邻域关于边缘中心不对称是造成零交叉点定位误差的主要原因,各类边缘的零交叉点是否定位准确与噪声存在与否并无直接的联系,关键在于噪声是否破坏了边缘相对其中心的奇函数特性。     

Real-time teleconsultation with high-resolution and large-volumemedical images for collaborative healthcare

Real-time consultation between referring physicians or radiologists with an expert is critical for timely and adequate management of problem cases. During consultation, both sides need to: 1) synchronously manipulate high-resolution digital radiographic images or large volume MR/CT images; 2) perform interpretation interactively; and 3) converse with audio. We present a specifically designed teleconsultation system in a digital imaging and communication in medicine picture archiving and communication systems (PACS) clinical environment. The system uses bidirectional remote control technology to meet critical teleconsultation application requirements with high-resolution and large-volume medical images operated in a limited bandwidth network setting. We give the system design and implementation methods, and also describe the teleconsultation procedure and protocol used in this system. Finally, laboratory and clinical evaluation results are discussed     

Low-temperature sensitive, compressively strained InGaAsP active(λ=0.78-0.85 μm) region diode lasers

This letter reports comparative studies between (Al)GaAs versus InGaAsP active region edge-emitting semiconductor lasers for emission wavelength in the IR regime (λ=0.78-0.85 μm). High characteristic temperature T₀(200 K) and T₁ (450 K) edge-emitting diode lasers have been demonstrated by using the compressively strained (Δa/a=0,6%) Al-free (InGaAsP) active region with an emission wavelength of 0.85 μm. The high T₀ and T ₁ a result of low active-layer carrier leakage, will be beneficial for high-temperature and high-power operation. Implementation for InGaAsP-active VCSEL's with compressively strained InGaAsP-active layers and conventional DBR's is also discussed     

Improved light-load efficiency for synchronous rectifier voltageregulator module

DC/DC converter with high efficiency over a wide load range is necessary for many low voltage applications, such as battery supplied systems and micro-processor power supplies-voltage regulator module (VRM). In order to improve the efficiency of low voltage converters, synchronous rectifier technology is widely used. The disadvantage of this technology is low efficiency at light load. This paper proposes a new technology, which utilizes the duty cycle signal, to improve light load efficiency with simple implementation. Since current sensors are not required, high density and high efficiency can be achieved that makes the whole circuit suitable for integration. In the paper, two application examples are given. Experimental results verified that the proposed control schemes significantly improve the efficiency of synchronous rectifier buck converters at light load     

A performance analysis of all-optical clock extraction circuit based on stimulated Brillouin scattering

In this paper, we develop an analytical method to deal with the timing performance in an optical clock extraction circuit based on stimulated Brillouin scattering (SBS). Three kinds of SBS active filters are considered and their frequency-transfer functions are obtained under the assumption that pump depletion caused by SBS is negligible. When pump depletion is taken into account, an SBS active filter acts as a nonlinear filter. To investigate the timing performance at this situation, we introduce the concept of "dynamic frequency-transfer function" to describe its frequency-response property for a fixed-signal light and pump light. Using the obtained "frequency-transfer function," we give analytical expressions for both root-mean-square (rms) phase jitter and rms amplitude jitter of the extracted optical clock, in which we have taken the impacts of SBS gain, pump light linewidth, optical pulse chirp, and pump detuning into account. Finally, a detailed numerical investigation on the timing performance for the three active filters is presented.     

展望21世纪Si基光子学的发展

本文从２１世纪信息高科技的发展需求出发,对高速、大容量光纤传输网络和高速电子计 算机以及智能化神经网络系统的发展现状与未来给予评述,尤其着重指出Ｓｉ基光子器件和光 子学在未来信息高科技发展领域中的重要作用。     

红外光谱辐射计的研制

介绍了红外光谱辐射计的组成及工作原理,分析了其信号处理方法。红外光谱辐射计的核心是分光元件、光学系统及信号处理部分。该设备采用容易调整的高像质反射光学系统和波长在２５～１４μｍ连续可变的分光系统,并采用高集成度、高精度的数据采集、数字锁相和数据处理、存储系统。观察瞄准、探测接收的光学系统以及数据采集、处理系统都被放到一个体积很小的测量头中,具有体积小、质量轻牢固可靠、抗干扰性能强和使用方便等优点。入瞳的最小可探测率为１０－１２Ｗ／ｃｍ２,光谱分辨率为２％,测量速度为１０条谱线／ｓ。经实际检测和使用,该设备的性能达到国内外先进水平,并具有野外工作的特点。     

ATM网络异种复用业务信元丢失率快速估计的新算法

ＡＴＭ网络信元丢失率（ＣＬＲ）的估计是呼叫接入和流量控制的关键技术,基于信元丢失机制的分析,本文了一种改进的简单业务模型,并进而得到一种新的算法,能够对异种混合业务复用的ＡＴＭ网络进行快速的ＣＬＲ估计,该算法处理速度快,能够做到呼叫的实时响应,模型采用国际规范的标准参数构造,可以直接应用于实际操作,仿真结果表明,算法的精度,运算复杂度和算法鲁棒性都比较理想,具有较高的实用价值。     

激光熔覆Ni-Cr-B-Si-C合金涂层显微组织的透射电镜研究

激光熔覆Ni-Cr-B-Si-C合金涂层组织由块状CrB型硼碳化物,树枝状Cr7C3型碳化物,胞枝状γ-Ni固溶体以及共晶产物组成。依局部成份条件,形成γ-Ni M23C6共晶和γ-Ni 镍硼化物共晶。熔覆过程的非平衡性质导致γ-Ni/Ni3B稳定凝固和γ-Ni/Ni2B亚稳定凝固并存。受快速凝固引起的热应力所致在Cr7C3和M23C6中发生高密度孪生。此外,涂层中存在非晶相,由非晶相包围的γ-Ni固溶体形成调制结构。     

SSPD器件及其应用

以ＣＬ１２８Ｅ型ＳＳＰＤ线列阵为例,介绍了ＳＳＰＤ器件的工作原理、主要特性及其应用。