Distance-Enhancing Constrained Codes with Parity-Check Constraints for Data Storage Channels

This paper proposes efficient distance-enhancing constrained codes with parity-check (PC) constraints for data storage channels. We first propose simple and efficient finitestate encoding methods to design various distance-enhancing constrained codes, including a repeated minimum transition runlength (RMTR) code for optical recording channels, as well as a maximum transition run (MTR) code for magnetic recording channels. We further propose a general and systematic code design methodology, which can efficiently combine constrained codes with PC codes. The constrained codes can be any distanceenhancing constrained codes. The PC codes can be any linear binary PC codes. The rates of the designed codes are only a few tenths of a percent below the theoretical maximum. The proposed method enables soft information to be available to the PC decoder and soft decoding of PC codes. Examples of several newly designed distance-enhancing constrained PC codes are illustrated. Simulation results with blu-ray disc (BD) systems show that the proposed new RMTR code and RMTR constrained 4-bit PC code perform 0.2 dB and 0.85 dB better than the standard 17PP code, respectively, at error correction code (ECC) failure rate (EFR) of 10^-12 and high recording density.     

Analysis of mode quality factors and mode reflectivities for nanowire cavity by FDTD technique

The mode frequency and the quality factor of nanowire cavities are calculated from the intensity spectrum obtained by the finite-difference time-domain (FDTD) technique and the Pade/spl acute/ approximation. In a free-standing nanowire cavity with dielectric constant /spl epsiv/=6.0 and a length of 5 /spl mu/m, quality factors of 130, 159, and 151 are obtained for the HE/sub 11/ modes with a wavelength around 375 nm, at cavity radius of 60, 75, and 90 nm, respectively. The corresponding quality factors reduce to 78, 94, and 86 for a nanowire cavity standing on a sapphire substrate with a refractive index of 1.8. The mode quality factors are also calculated for the TE/sub 01/ and TM/sub 01/ modes, and the mode reflectivities are calculated from the mode quality factors.     

Sn-Bi焊点发黑问题分析

针对锡铋焊膏形成焊点表面发黑问题以及回流过程中出现的黑色物质,通过扫描电子显微镜、能谱分析、X射线晶体衍射等方法,采用焊点表面黑色残留物直接测试以及高温下提取黑色物质测试两种方法进行分析。结果证明,焊点表面发黑的原因与元素Bi有关,并根据焊点形成条件的不同生成单质铋或铋的氧化物。     

Theoretical Study on the Gain and Tuning Characteristics of Miniature Optically Pumped NH3 Submillimeter Laser

The gain and the tuning characteristics of miniature optically pumped super-radiant NH₃ submillimeter-wave gas laser have been studied theoretically based on the quantum density matrix equations. The density matrix equations of three-level quantum system have been solved, and the gain and the output density versus different frequency detuning of submillimeter laser and infrared pumping laser have been calculated respectively by means of iteration method. The characteristic curves corresponding to ideal monochromatic IR pumping model and broadened IR pumping model have been obtained. Meanwhile, the tuning and the nonlinear properties of the system have been revealed.     

量子点在生命科学中的应用及其进展

量子点因其独特的光学和电子学性质而具有很高的实用价值。本文概述了量子点的特性和制备方法,着重阐述了其在生命科学,尤其是免疫生物学和临床检验学中的应用进展,并对其发展进行了展望。     

魔芋、草莓复合颗粒果汁饮料加工工艺的研究

以魔芋精粉和草莓为主要原料,采用正交试验和感官评定确定了产品的合理配方和加工工艺。最佳工艺参数为：草莓果汁７０％;魔芋凝胶颗粒８％;蔗糖２５％;琼脂０．５％;杀菌温度９０℃;时间１５ｍｉ     

Multiple-wavelength up-conversion laser in Tm/sup 3+/-doped ZBLAN glass fiber

In this letter, we report on a multiple-wavelength up-conversion laser in Tm/sup 3+/-doped ZrF/sub 4/--BaF/sub 2/--LaF/sub 3/--AlF/sub 3/--NaF glass fiber pumped by an 1120-nm fiber laser. Single-wavelength, two-wavelength, and three-wavelength up-conversion lasers can be obtained by adjusting the distance between the coupler mirror and the fiber end, which is attributed to the frequency-filter effect in the etalon composed of the coupler mirror and the fiber end. The effects of the pump power on the performance of dual-wavelength laser were also discussed.     

太平溪小流域水土保持蓄水减沙效益初步研究

太平溪小流域地处三峡库乎宜昌县西部，距三峡坝５ｋｍ的长江西陵峡北岸，治理前水土流失严重，大量坡面商沙以沟道推移直接进入三峡库区。     

中国电信业战略实施浅探

随着电信业的重组以及3G牌照的发放,势必也将引来中国电信运营商的新一轮洗牌,电信业格局将在激烈的竞争中逐渐演变形成,为了在新的格局中占据有利位置,三大电信运营商在提高自已网络实力的前提下,一场关系到市场营销的企业变革也将随之跟进,变革的深度及广度将决定了向前推进的后继力量。     

Design and Evaluation of DNS as Location Manager for HIP

Host Identity Protocol (HIP) is designed to provide secure and continuous communication by separating the identifier and locator roles of the Internet Protocol (IP) address. HIP also has efficient solutions to support host mobility. In this paper, we propose a location management scheme based on Domain Name System (DNS) for HIP. In the proposed scheme, a new DNS HIP resource record is used to translate a domain name into a host identity tag and an IP address. We also develop an analytical model to study the performance of DNS as location manager in terms of success rate, which takes into account the velocity of mobile nodes, the radius of a subnet, the regional network size, the packet transmission delay between the mobile node and the rendezvous server, and the packet processing delay at the DNS and the rendezvous server. The performance results show that for a reasonable range, the DNS is a feasible solution for location management with high success rate for HIP.