Area-Efficient Min-Sum Decoder Design for High-Rate Quasi-Cyclic Low-Density Parity-Check Codes in Magnetic Recording

We report a silicon area efficient method for designing a quasi-cyclic (QC) low-density parity-check (LDPC) code decoder. Our design method is geared to magnetic recording that demands high code rate and very high decoding throughput under stringent silicon cost constraints. The key to designing the decoder is to transform the conventional formulation of the min-sum decoding algorithm in such a way that we can readily develop a hardware architecture with several desirable features: 1) silicon area saving potential inherent in the min-sum algorithm for high-rate codes can be fully exploited; 2) the decoder circuit critical path may be greatly reduced; and 3) check node processing and variable node processing can operate concurrently. For the purpose of demonstration, we designed application-specific integrated circuit decoders for four rate-8/9 regular-(4, 36) QC-LDPC codes that contain 512-byte, 1024-byte, 2048-byte, and 4096-byte user data per codeword, respectively. Synthesis results show that our design method can meet the beyond-2 Gb/s throughput requirement in future magnetic recording at minimal silicon area cost.     

Quasi-Reduced-State Soft-Output Viterbi Detector for Magnetic Recording Read Channel

Reduced-state trellis detection with decision feedback is widely used to reduce the energy consumption of trellis detectors, particularly for soft-output trellis detectors that are energy-hungry by nature. However, the decision feedback tends to increase the circuit critical path and, more important, makes it difficult to apply some well-proven high-speed trellis detector design techniques such as bit-level pipelining. This paper presents a method, referred to as quasi-reduced-state trellis detection, to tackle such speed bottlenecks. The basic idea is to simply obviate the use of decision feedback by mapping only the data storage block of the trellis detector onto a reduced-state trellis and keeping the trellis state metric computation on the original full-state trellis. This makes sense because the data storage block tends to dominate the overall energy consumption while the decision feedback is due to the reduced-state trellis metric computation. Therefore, it is intuitive that such quasi-reduced-state detectors may largely maintain the energy saving potentials of reduced-state trellis detection without being subject to decision-feedback-induced speed bottlenecks. We demonstrated the effectiveness of this proposed design method by using soft-output Viterbi algorithm (SOVA) detection for a magnetic recording read channel as a test vehicle.     

可逆变长编码的解码器设计及VLSI实现

变长编码(VLCs,Variable Length Codes)因其高效的数据压缩能力被广泛地应用在多媒体压缩领域,但VLCs的自身性质使它对信道错误的恢复能力很弱。随着在不可靠信道,如无线信道和网络上进行视频传送需求的增加,视频通讯的错误控制和错误恢复技术变得越来越重要。可逆变长编码(RVLCs,Reversible Variable Length Codes),当遇到传输错误时,充分利用了可用的数据,错误恢复能力强于VLCs。许多视频标准,如ITU H．263 ,ISO MPEG-4已经采用了RVLCs。本文详细描述了RVLCs解码器的解码算法和解码器的体系结构设计,给出了一个基于MPEG-4 ASP@L5的解码器VLSI实现。结果表明,该实现完全适用于MPEG-4实时编解码系统。     

一种新的二维光正交码的设计与性能分析

针对二维光码分多址(OCDMA)系统地址码,本文在单重合序列(OCS)的基础上,构造了一种新的二维光正交码EQC/OCS.该地址码是以扩展二次同余码(EQC)为时间扩频伪随机序列,以OCS或截短OCS为波长跳频伪随机序列进行构造的.与EQC/PC相比,EQC/OCS的波长数可以是任意整数,不局限于素数.EQC/OCS不仅构造灵活,而且充分利用了系统的有效波长资源.当二维OCDMA系统的有效波长数不是素数时,在相同码长和码重的情况下,EQC/OCS增加了二维OCDMA系统的码字容量,从而增加了接入用户数.另一方面,与EQC/PC相比,EQC/OCS的码字的自相关和互相关限保持不变.     

隐含式防伪磁码及鉴别技术研究

一种定量鉴别标识物微磁编码的机械物理特征以达成译码的新型防伪技术。由于其隐含性、微量化、多特征编码及加密技术、低成本、操作快速简便的特点而成为极具应用前景的新型防伪技术。包括为提高隐含式防伪磁码与防伪力度的基础性研究及鉴别仪、微机系统分析仪及微磁性特征编码标识物的研制内容。该成果的推广应用将成为国家技术监督、防伪打假的有力工具。     

隐含式防伪磁码及鉴别技术研究

一种定量鉴别标识物微磁编码的机械物理特征以达成译码的新型防伪技术。由于其隐含性、微量化、多特征编码及加密技术、低成本、操作快速简便的特点而成为极具应用前景的新型防伪技术。包括为提高隐含式防伪磁码与防伪力度的基础性研究及鉴别仪、微机系统分析仪及微磁性特征编码标识物的研制内容。该成果的推广应用将成为国家技术监督、防伪打假的有力工具。     

Integral Code Systems for Recording Ionizing Radiation: Iterative Image Reconstruction Algorithms for Focal Plane Processing

Two iterative algorithms are considered for reconstructing three-dimensional radiation source distributions in an integral code measurement system. Those algorithms are found to be viable in the focal-plane method and also that there is substantial advantage in the directional discrepancy method by comparison with the steepest-descent method for coding collimators with low radiation transmission.     

硬盘磁记录介质的现状与发展

讨论了现有介质、新介质的材料与结构,以及其工艺技术的现状。并展望了高密度硬盘磁记录介质的未来。指出高密度、高信噪比Ｓ／Ｎ的硬盘介质要求有高的矫顽力和小的磁记录畴。     

自动套色系统中误差色标检测光电传感器的设计与实现

针对在凹版印刷中表征套印误差信息的色标信号检测问题.本文依据各颜色画面相对背景色对光能吸收不同的光学原理,利用半透半反光玻片的异面性和光电池光电转换功能,设计和实现了一种色标检测光电传感器.针对光电池光电转换输出信号较弱且非数字性的问题,进行了信号调理.实验结果和现场应用表明,该光电传感器具有结构简单.检测距离远((10±2)mm)、光斑半径小(φ1.5 mm)、灵敏度高、响应速度快(0.2 ms)、性能稳定可靠等优点.     

基于水性油墨的双重防伪二维码的设计与实现

目的 研制温变油墨和立体防伪变色油墨2种绿色环保的水性油墨,开发一种具有双重防伪功能的二维码,加强二维码的防伪功能。方法 研究不同感温变色粉用量对温变油墨色差和色度的影响。采用单因素试验考察发泡温度、发泡剂含量、PU树脂含量对立体防伪变色油墨发泡高度和耐摩擦性的影响。结果 感温变色粉的质量分数为20%时,温变油墨的颜色最接近二维码标准黑色。发泡剂质量分数为20%,发泡温度为120℃时,立体防伪变色油墨的发泡高度达到最佳值。承印物为白卡纸,PU树脂质量分数为3%时,立体防伪变色油墨的耐摩擦性最佳。承印物为金卡纸,PU树脂的质量分数为15%时,立体防伪变色油墨的耐摩擦性最佳。双层防伪二维码的上层图案（黑色二维码）在常温下可见,加热至70℃时消失,同时隐藏在下层的防伪标识显现出来,继续加热防伪标识逐渐呈现立体感,且在120℃时立体感达到最佳,整个过程颜色可逆,但立体感不可逆。结论 双重防伪二维码通过上层和下层图案在不同温度下交替显示和隐藏进行防伪,方便大众进行验证和确认,在不失趣味性的同时强化了防伪功能。     

Magnetic Recording Systems: Magnetic Domain Walls Dynamic Due To Spin Transfer Torque,Spin Orbit Torques and Applied Magnetic Field Simultaneously

Journal of Superconductivity and Novel Magnetism - In this paper, the recording media is considered as nanowire where Domain Wall (DW) can move when a charge pulse current or a current density is...     

基于UCC/EAN-128条码的农产品质量追溯标签的设计与实现

为实现对农产品"从农田到餐桌"的全方位的监控,在对EAN·UCC全球统一标识体系研究的基础上,制定了农产品编码标准,同时结合农产品供应链的实际情况,设计了农产品追溯条码,并基于.net平台实现了农产品追溯标签的自动生成.     

基于漏磁原理的火炮零部件裂纹检测装置的设计与实现

为解决火炮零部件上裂纹等缺陷的检测问题,依据漏磁检测原理及缺陷漏磁场偶极子模型,设计了火炮零部件漏磁检测装置并进行了工程化实现.考虑到火炮零部件结构多样性,采用霍尔器件和磁阻传感器设计了多种结构的检测装置;针对漏磁信号中存在干扰信号和系统噪声的问题,采用自适应滤波和MORET-P小波变换技术,进行了信号的预处理.应用结果表明:该装置原理可行,多种结构的检测装置满足了不同火炮零部件的检测需要,自适应滤波和MORET-P小波变换技术较好地剔除了干扰信号和系统噪声,有效提取出缺陷信号.     

Comparison Between Viterbi Detectors for Magnetic Recording Channels Based on Regressive and Autoregressive Noise Models

A recent work presents a regressive noise model for the data-dependent correlated noise, at the output of a magnetic recording channel detector. We have generalized this channel model, considering digital equalization and a more efficient correlation matrix, in order to make a comparison with the usual detector in a more realistic environment. Simulation results show that the regressive detector performs better when the number of trellis states is lower than needed, while both approaches are comparable when the number of states matches the channel memory.     

商品包装的条形码设计与印刷

论述了商品包装的条形码设计与印刷的必要性,分析了商品包装中的条形码设计的要素和基本层次,提出了商品包装条形码印刷的实施步骤,阐述了保证条形码的设计有效实施所需的内容,从而促进商品包装条形码的设计与印刷的整体塑造。     

离体电生理检测微电极阵列传感器的设计与制备(英文)

针对动物离体组织电生理检测的实际需求,设计并制备了一种以载玻片为基底,以微电极阵列为敏感元件,并将灌流装置集成一体的传感器芯片.采用微电子机械系统(MEMS)技术中的薄膜工艺完成了微电极阵列的制备,其导电层和绝缘层分别是铂和氮化硅.采用聚二甲基硅烷(PDMS)浇铸制成埋有管道的方形灌流槽.该传感器可保持离体组织的生理活性,同时实现电生理信号的64通道同步记录.整个芯片结构紧凑,接口简单,使用方便.对芯片的电学性能进行了研究,结果表明,通过在微电极表面电镀修饰铂黑,可有效降低其交流阻抗,提高信噪比.     

Grain Refining and Decoupling in FePt/SiO2 Nanogranular Films for Magnetic Recording

FePt/SiO₂ nanogranular thin films have been prepared by molecular-beam epitaxy system on MgO (001) substrates with the method of insertion dual SiO₂ layers into Fe/Pt multilayer films. We report the relationships between the inserting thickness of SiO₂ layers and the microstructural and magnetic properties of FePt thin films. It indicated the nanogranular FePt thin films were successfully formed by inserting amorphous SiO₂ layers into the Fe/Pt films. The reduction of grain/domain size and isolation of FePt particles can be achieved by such insertion and maintain (001) texture. The average grain size of FePt films with 5-nm SiO₂ insert layers is estimated to be around 8 nm, while domain rotation is enhanced depicting a decoupling of intergrain interaction. The isolated grains are less magnetically coupled in the rotation mode and the reversal of magnetization is more independent     

A Special Device for Viscous Pressure Forming:Design and Implementation

［1］Junhua Liu, Bert Westhoff, Mustafa A.Ahmetoglu and Taylan Altan: J. Mater. Proc. Technol., 1995, 59, 49. ［2］Bin GUO: J. Plast. Eng., 1997, (3), 92. (in Chinese)     

一种新的二元条码设计与绝对式光电位置编码方法

提出一种新的二元条码设计方法,可用于绝对式光电位置编码.传统的光电编码器主要基于莫尔光栅条纹技术,把位移量变为电脉冲,结构简单,但由于增量式相对测量方式,从而使得光电编码器的应用受到了限制.本文提出的二元条码设计方法,在单码道上设计了包含三种频率信息的光栅,采用二元脉冲编码调制和误差扩散的方法形成二元条码标尺.在光电位置编码器中,标尺上某一段的条码就成像在线阵CCD上.对CCD获取的该段条码信息进行傅里叶变换,滤波和逆傅里叶变换,得到三种频率光栅的相位信息,采用小数重合法得到该段条码的绝对相位分布,从而得到绝对位置信息.新的方法保留了单码道光栅莫尔技术结构简单的优点,同时又能像多码道光栅编码器一样实现绝对位置测量.文中给出了编码方法的详细描述,条码信息处理方法,计算机仿真实验结果,最后给出了绝对式光电位置测量的实验结果.本文提出的方法在绝对式光电位置编码器和数字水准仪等领域具有一定的应用前景.     

Optimal code rates for the Lorentzian channel: Shannon codes and LDPC codes

We take an information-theoretic approach to obtaining optimal code rates for error-control codes on a magnetic storage channel approximated by the Lorentzian channel. Code rate optimality is in the sense of maximizing the information-theoretic user density along a track. To arrive at such results, we compute the achievable information rates for the Lorentzian channel as a function of signal-to-noise ratio and channel density, and then use these information rate calculations to obtain optimal code rates and maximal linear user densities. We call such (hypothetical) optimal codes "Shannon codes." We then examine optimal code rates on a Lorentzian channel assuming low-density parity-check (LDPC) codes instead of Shannon codes. We employ as our tool extrinsic information transfer (EXIT) charts, which provide a simple way of determining the capacity limit (or decoding threshold) for an LDPC code. We demonstrate that the optimal rates for LDPC codes coincide with those of Shannon codes and, more important, that LDPC codes are essentially capacity-achieving codes on the Lorentzian channel. Finally, we use the above results to estimate the optimal bit-aspect ratio, where optimality is in the sense of maximizing areal density.