Comments on "A noncoherent tracking loop with diversity and multipath interference cancellation for direct-sequence spread-spectrum systems"

For original paper see IEEE Trans. Commun., vol.46, p.1516-24 (1998 November). In the original paper, the authors presented a noncoherent tracking loop with diversity and multipath interference cancellation to improve the loop performance on frequency-selective fading channels. However, the effects of imperfections in multipath interference cancellation have been dropped out in the statistical analyses, and only evaluated by using computer simulations. The present authors show that such effects can change the error characteristic, at least in the mean sense, and thus make the analyses of jitter performance improper.     

Turbo encoding and decoding of Reed-Solomon codes through binary decomposition and self-concatenation

This paper presents a two-stage turbo-coding scheme for Reed-Solomon (RS) codes through binary decomposition and self-concatenation. In this scheme, the binary image of an RS code over GF(2/sup m/) is first decomposed into a set of binary component codes with relatively small trellis complexities. Then the RS code is formatted as a self-concatenated code with itself as the outer code and the binary component codes as the inner codes in a turbo-coding arrangement. In decoding, the inner codes are decoded with turbo decoding and the outer code is decoded with either an algebraic decoding algorithm or a reliability-based decoding algorithm. The outer and inner decoders interact during each decoding iteration. For RS codes of lengths up to 255, the proposed two-stage coding scheme is practically implementable and provides a significant coding gain over conventional algebraic and reliability-based decoding algorithms.     

A 21-mW 8-b 125-MSample/s ADC in 0.09-mm/sup 2/ 0.13-/spl mu/m CMOS

This paper presents an 8-b two-step subranging analog-to-digital (ADC) using interpolation, averaging, offset compensation, and pipelining techniques to accomplish an effective number of bits of 7.6 b at 125 MSample/s. The 0.13-/spl mu/m CMOS ADC occupies 0.09 mm/sup 2/ and consumes 21 mW.     

A Photo Certificate-A Framework for Generating Visualized Public Key Certificates

In the proposed photo certificate, the principal component is the image, for example, the user's photo. User-related fields, such as the subject's name, the issuer's name, and the expiration period, which are meaningful to users, are embedded into the surface of the photo by using a visible watermark algorithm, so that the reader can capture this information without the requirement for special software. The remaining fields in the certificate are embedded into a marked photo. Later, the whole photo certificate is cryptographically signed by certification authority (CA) private key to guarantee the integrity of our photo certificate. By such arrangement, the certificate's verification is divided into two layers. The first layer is human visual system oriented and the second layer is the software-oriented. User can determine whether the user's photo and its subject's name are consistent and check whether the expired period is valid first. The second layer's verification is lunched only when the first layer's verification is passed. To sum up, the proposed photo certificate not only inherits the functions of a traditional certificate, but also provides a friendlier operational environment of X.509 certificate.     

去除块效应的图像后处理算法

分析了图像后处理技术的最新发展成果,重点研究了几种重要的后处理算法,比较了它们的性能,最后提出了目前的问题和以后的发展方向。     

Channel interference reduction using random Manchester codes forboth synchronous and asynchronous fiber-optic CDMA systems

We propose the random Manchester codes (RMC) to improve the bit error probability (BEP) performance in both synchronous and asynchronous fiber-optic code-division multiple-access (CDMA) systems. The spreading sequences used in the synchronous and asynchronous systems are modified prime sequence codes and optical orthogonal codes (OOCs), respectively. Thermal noise, shot noise, and avalanche photodiode (APD) bulk and surface leakage currents are taken into consideration in the BEP analyzes. The results show that the proposed systems can support a larger number of simultaneous users than other systems with similar system complexity under the same bit-error probability constraint     

An adaptive 3-D discrete cosine transform coder for medical imagecompression

A new three-dimensional (3-D) discrete cosine transform (DCT) coder for medical images is presented. In the proposed method, a segmentation technique based on the local energy magnitude is used to segment subblocks of the image into different energy levels. Then, those subblocks with the same energy level are gathered to form a 3-D cuboid. Finally, 3-D DCT is employed to compress the 3-D cuboid individually. Simulation results show that the reconstructed images achieve a bit rate lower than 0.25 bit per pixel even when the compression ratios are higher than 35. As compared with the results by JPEG and other strategies, it is found that the proposed method achieves better qualities of decoded images     

Time-dependent dielectric wearout technique with temperature effect for reliability test of ultrathin (<2.0 nm) single layer and dual layer gate oxides

Ultrathin gate oxide is essential for low supply voltage and high drive current for ULSI devices. The continuous scaling of oxide thickness has been a challenge on reliability characterization with conventional time-dependent dielectric breakdown (TDDB) technique. A new technique, the time-dependent dielectric wearout (TDDW), is proposed as a more practical and effective way to measure oxide reliability and breakdown compared to conventional TDDB methodology. The wearout of oxide is defined as the gate current reaches a critical current density with the circuit operating voltage level. It is shown that although a noisy soft breakdown always exists for ultrathin oxide, with constant-voltage stressing, a big runaway can also be observed for oxides down to 1.8 nm by monitoring the I–V characteristics at a reduced voltage. Devices are found still working after soft breakdowns, but no longer functional after the big runaway. However, by applying E-model to project dielectric lifetime, it shows that the dielectric lifetime is almost infinity for the thermal oxide at 1.8 nm range. It is also demonstrated that the dual voltage TDDW technique is also able to monitor the breakdown mechanism for nitride/oxide (N/O) dual layer dielectrics.     

基于DC-SAM液位识别模型的非满管流量计

在工业生产过程中超声流量计凭借非接触测量、适用多种流体介质等优点发挥着重要作用。针对目前超声流量检测抗干扰能力差,检测精度较低等问题,提出了一种结合模式识别的四声道非满管超声流量计;该系统通过带浮点运算的高性能ARM处理器进行FFT运算,求出四声道的综合流速;配合边缘计算芯片来识别出管道的液位,并基于液位修正模型提升识别稳定性。在液位识别模型中利用特征提取模块和空间注意力机制模块来提取有效特征,使用随机森林进行液位分类。实验结果表明,DC-SAM算法相对于其他模型更快收敛,准确率达到96.6%;该系统在流量实验中,对比标定流量计能达到96.5%的准确度,且具有较好的线性度;可以准确识别液位和流量,在保持较高测量精度的同时满足检测的稳定性要求。     

成因与演化信息约束的辫状河储层地质建模——以委内瑞拉奥里诺科重油带M区块为例

委内瑞拉奥里诺科重油带位于全球规模最大的重油富集区,地质储量丰富,开采潜力大。但是,由于该区主要产油层段是以砂质辫状河类型为主的河流相沉积,具有平面相变快、纵向上砂体叠置的特点,储层内部非均质性强,严重制约了后续的产量接替和开发方案实施。为此,以M区块Oficina组下部为例,根据岩心、测井、地震响应等特征,共识别和划分出复合心滩坝、辫状河道沉积、废弃河道沉积、残余洪泛泥岩沉积四种主要成因单元;在沉积模式的指导下,提取地层切片,分析成因单元的演化过程;将这些信息转化为控制地质建模的概率体,以水平井和直井识别结果为硬数据,建立由成因与演化信息约束的地质模型。将该模型用于开发井设计,使水平井油层钻遇率提高至95%以上,表明方法应用效果良好。