光学记录、存储与器件

TP333.42007010465用于多阶存储系统的3元(2,10)游程受限编码=Ternary(2,10)run-length li mited code for multilevel recordingchannels[刊,中]/胡恒(清华大学精密仪器与机械学系.北京(100084)),潘龙法…//光学技术.—2006,32(5).—710-712,716提出了一种用于多阶光存储的3元     

多阶游程长度受限编码的光盘读出信号

多阶游程长度受限(ML-RLL)编码可以在保持原有记录符尺寸和记录单元数量的情况下将CD光盘存储容量提高2.4倍。借助标量衍射理论建立了多阶游程长度受限记录符的计算模型,对采用多阶游程长度受限编码的CD光盘的读出信号进行了仿真分析。结果表明,记录坑长度的变化对读出信号幅值影响较小,有利于将记录坑长度和记录坑的宽度两个参数进行分离检测,但在3T长度、不同宽度的记录坑相连的情况下,从读出信号中很难分辨出记录符的分界位置。     

信息光学 光学记录、存储与器件

TP333.42006054289光存储系统中的游程长度受限编码=Run-length-li mitedcodes for optical storage system[刊,中]/胡华(清华大学精密仪器与机械学系,光盘国家工程研究中心.北京(100084)),徐端颐…//光学技术.—2006,32(3).—323-326,329游程长度受限编码广泛应用于光(磁)存储系统中,通过将用户数据转换为符合特定信道约束的码元序列,从而提高数据传输的效率与可靠性。介绍了游程长度受限编码的基本理论,从原理上分析了有限状态编码器与滑块分组译码器模型,并对主要的编码构造方法进行了概述,展望了游程长度受限编码的发展方向。图4参16(…     

多阶光存储的调制原理分析与编码设计研究

根据编码理论的状态切分算法，提出一种新型的8阶(1,3)游程长度受限码，在最小记录符上能够存储3.0比特的用户数据，并且编码与译码逻辑简明，可用于未来高密度多阶游程长度调制光盘系统.     

光存储系统中的游程长度受限编码

游程长度受限编码广泛应用于光(磁)存储系统中,通过将用户数据转换为符合特定信道约束的码元序列,从而提高数据传输的效率与可靠性。较为系统的介绍了游程长度受限编码的基本理论,从原理上分析了有限状态编码器与滑块分组译码器模型,并对主要的编码构造方法进行了概述,展望了游程长度受限编码的发展方向。     

游程长度受限码RLL(4,18)的研究

介绍了一种新的用于高密度光盘存储的游程长度受限码。给出RLL(4,18)码的构造方法和编解码步骤。对RLL(4,18)码的编码器和解码器进行了CPLD实现。对不同游程长度受限码的主要性能参数进行了比较。     

一种4阶RLL(2,12)调制码的CPLD的实现

现有的光存储系统采用二值的记录模式,普遍使用的是游程长度受限(Run-length limited,RLL)的调制编码,并将信息编码记录在信息符的长度中。新型多阶RLL光存储采用多阶RLL编码方案,将信息同时记录在信息符的长度和信号幅值中,从而大幅度地提高了光盘的容量。为了研究多阶RLL编码的逻辑正确性和电路复杂度,设计了基于可编程逻辑器件的硬件平台。多阶RLL编码可以用有限数量逻辑门实现编码,有望用于未来高密度多阶光存储系统。     

基于联合编码调制的调光控制方案实现

针对可见光通信系统中闪烁抑制与调光控制功能的实现,提出了一种采用联合编码调制进行调光控制的方法。该方法利用脉冲宽度调制(PWM)匹配数据帧内与帧间的占空比,同时结合游程长度受限编码(RLL)实现闪烁抑制;通过分别采用多脉冲位置调制(MPPM)和重叠脉冲位置调制(OPPM)实现光强调节,以满足功率效率或频谱效率需求。理论分析表明,与典型的可变脉冲位置调制(VPPM)相比,占空比为0.9的MPPM的归一化功率可节省2.24dB,而占空比为0.5的OPPM的频谱利用率高出0.8bps/Hz,即OPPM具有较高的频谱效率。此外,基于FPGA平台开发实现提出2种调制方案,实验结果验证了联合调制调光方案可以在保证数据有效传输的条件下抑制光源闪烁并可进行高精度的调光控制。     

光谱编码成像系统的数据压缩技术

利用时间拉伸显微成像系统观察并记录非重复动态随机现象,在其超高成像速度和高空间分辨率下必定会产生大量的数据。一种基于差分检测和游程编码的数据压缩方法,可以有效地解决时间拉伸成像系统的数据存储问题。差分检测可以消除连续相同的信号,只检测出相邻信号的差异,从而提高游程编码算法的有效性。实验中,采用扫描频率为77.76 MHz的时间拉伸显微成像对分辨率板、人红细胞和人乳腺癌细胞线性扫描成像。实验结果表明,数据压缩比可以达到8.47,对比分析发现经过差分检测方法可以获得更高的压缩比。另外,通过计算重建后的图像与原图的结构相似性(SSIM)值发现,经过数据压缩后高质量的图像可以被重建。     

光致变色多阶游程光存储研究

多阶游程存储是一种不改变光学系统而显著提高光存储容量和数据传输率的新方法.介绍了光致变色多阶游程存储原理和实验系统.提出了基于光致变色原理的多阶游程存储数学模型，该模型反映了记录符反射率与曝光功率、曝光时间之间的非线性关系，并在此基础上确定了光致变色多阶游程存储的写策略.基于650nm光致变色材料进行了4阶游程存储的动态实验.结果表明，实验中采用的650nm光致变色材料可用于多阶游程存储，采用的写策略能够有效地使记录信道线性化，利于采用适合线性系统的信号处理方法. 关键词： 多阶游程 光致变色 光存储 写策略     

刚体与SPH耦合的三维数值方法研究

 研究了刚性体与SPH（Smoothed Particle Hydrodynamics）方法相耦合的计算方法和技术,以此技术为核心,在原有三维综合拉氏程序CL3D的基础上,研制了适用于斜侵彻问题数值研究的刚性弹体与SPH靶体耦合计算的拉氏三维数值模拟程序CRSPH3D。针对金属材料编入了Johnson-Cook本构模型计算模块,针对混凝土材料编入了Johnson-Holmquist本构模型及与之配套的损伤模型和状态方程等的计算模块。用研制的计算程序对弹体分别正碰和斜碰穿透中厚铝靶和侵彻厚混凝土靶的过程进行了数值模拟计算和分析。结果表明,对于铝靶穿透问题,模拟计算得到的弹体剩余速度、弹体动能损失和贯穿图像与实验结果符合得较好。对于混凝土靶的侵彻问题也得到了与实验现象一致的、定性合理的图像。     

Performance of GPRML-AR system in perpendicular magnetic recording channel with thermal decay

The bit-error rate (BER) performance of the generalized partial response maximum likelihood with autoregressive (GPRML-AR) channel model system in perpendicular magnetic recording (PMR) channel with thermal decay is obtained. The 128/130(0,16/8) run-length-limited (RLL) code is used as a recording code. The GPR channel consists of the PR1 channel followed by the reduction circuit of predicted noise. The BER performance is evaluated by computer simulation using a thermal decay model. The model has been obtained by using an approximate equation that represents amplitude degradation of the reproducing waveform with elapsed time based on the experimental data for CoPtCr-SiO₂ PMR media. The Viterbi detector with an AR channel model is employed. Furthermore, long-term degradation of the required SNR to achieve a BER of 10⁻⁴ with elapsed time is obtained and the performance is compared with that of PR1ML system. The results show that the poorer the thermal stability of the medium becomes, the larger the SNR gain of the GPR1ML-AR system over the PR1ML system becomes. The SNR gain also increases with elapsed time.     

基于RS编码及网格编码调制的光PPM通信纠错技术

分析了RS(Reed-Solomon)纠错码和网格编码调制（Trellis Coded Modulation,TCM）技术在光脉冲位置调制通信中的应用.在此基础上,提出了以RS码作为外码,以网格编码调制技术作为内码,用于光脉冲位置调制通信的新编码方案,能以几乎不减少通信速率的优势,提高传统RS码系统在时变带限光信道中的通信性能.模拟研究了在不同空间光信道条件下,传统RS码的符号正确传输率和误码率,并对网格编码调制的编码增益、RS码与网格编码调制级联时的编码增益进行了仿真研究,证实了本方案的有效性.     

Dissolve: next generation software for the interrogation of total scattering data by empirical potential generation

A new code for the simulation of total scattering data based on the refinement of structure via generation of empirical potentials is presented. The code implements methodology similar to that in the Empirical Potential Structure Refinement code by A. K. Soper, but has been built from the ground up with complex and large target systems in mind. Results from a preliminary version of the code are shown to be consistent with those expected from its predecessor, and the new method is shown to be capable (presently) of handling systems of up to 3×10⁶ atoms.     

Magnetic evaluation of advanced metal-evaporated tape in an advanced linear tape drive

Demand for increased data storage has resulted in the development of various types of magnetic tapes. To achieve higher recording density, tape manufacturers are developing thin-film tapes, such as advanced metal-evaporated (AME) tape, for use in linear tape drives. In recent studies, these new AME tapes have demonstrated sustainable mechanical durability at low tensions suitable for use in linear tape drives. An evaluation of the magnetic performance of these AME tapes including the impact of tape cupping and initial edge quality was the goal of this study. Head output, dropouts, head–tape interface friction, and lateral tape motion (LTM) were monitored throughout testing. As track widths continue to narrow, LTM has become one of the critical limitations of magnetic performance. To more accurately measure LTM during drive development, a new method involving the output voltage of a head-read element that has been adjusted to be halfway off the recorded track on tape was implemented (LTM_M). It is shown that positively cupped AME tapes will result in similar head output and fewer dropouts than the current MP tapes. The negatively cupped AME sample produced the lowest head output data and the highest amount of dropouts of all the tapes evaluated in this investigation. All the tapes evaluated demonstrated similar values of LTM when monitored at the center of the tape. When LTM was monitored at the lower edge of the tape, the positively cupped AME tape with the worst relative edge contour length resulted in the highest LTM_M. As found in previous studies, AME tapes produced slightly lower values of coefficient of friction than the MP tapes. From this investigation, positively cupped AME tapes with good initial relative edge contour length are recommended for use in linear tape drives, similar to those used in this study.