电子文件中心、电子文件备份中心和电子政务灾备中心辨析

随着2007年4月"全国电子文件中心建设经验交流会"的召开,国家档案局研究和部署了进一步推进电子文件中心的建设。本文将对此次交流会上提到的"电子文件中心"、"电子文件备份中心"和"电子政务灾备中心"进行分析和比较,找出它们的区别和联系,以免在电子政务建设中出现概念混淆、重复建设等问题。     

Usability Research in the Writing Lab: Sustaining Discourse and Pedagogy

Redesigning Purdue's Online Writing Lab (OWL) presented the opportunity for collaboration among Writing Center and Professional Writing Program members. While the article briefly describes the OWL redesign process, the argument focuses on collaboration and presents a model for sustainable intraprogram collaboration. Following Hawhee, usability research is defined as “invention-in-the-middle,” which offers a model for understanding research process as part of the infrastructure of new media instruction as described by DeVoss, Cushman, and Grabill. This article offers four stakeholder perspectives on the process of participatory technology design: of writing center administrators, graduate students, technical writing practitioners, and writing program graduate faculty members. The model asserted by this article presents a dynamic understanding of expertise and of fluidity in the roles of participants. Collaborative usability research, seen as invention-in-the-middle, contributes both to long-term sustainability of technological artifacts as well as the discursive interactions among stakeholders whose work supports these artifacts.     

基于K0honen网络和OLS算法的RBFNN中心选择方法

提出了一种优化选择径向基神经网络数据中心的算法,该算法结合了Kohonen网络的模式分类能力,将初步分类结果用作RBFNN的初始数据中心,然后采用OLS算法进行优化,对比仿真实验表明该算法效果比单独使用OLS算法生成的RBFNN性能更好。     

考虑多种储能的数据中心综合能源系统配置优化

数据中心是中国数字化发展的关键基础设施,如何通过配置多种储能设施以降低数据中心综合用能成本亟须研究。对数据中心采用的储能技术路径进行了效益分析,考虑了数据中心综合能源系统配置优化及能源系统运行策略。以北京某数据中心为例,进行算例分析,结果表明数据中心优化配置应急与调峰储能及系统运行策略对数据中心提高能源供应可靠性、降低运行成本具有积极作用。     

无人机载PolInSAR城区散射机制初步分析

极化干涉合成孔径雷达（PolInSAR）在城市遥感领域中扮演着重要角色。它能够提高图像的相干性并提高反演结果的精度,所以对于其散射机制的解释往往受到许多研究人员的关注。相关的研究多从极化分解的角度考虑,却少有人从散射中心高度方面进行分析。本文使用Ku波段无人机载极化干涉SAR系统,实现了使用无人机SAR系统对地面进行成像,比较了极化干涉最优分解与Pauli分解作用在不同人造目标时散射中心的关系。我们初步分析了极化干涉SAR的物理意义,并使用C波段的机载极化干涉SAR系统对结论进行验证。     

Secure Key Management Based Mobile Authentication in Cloud

Authentication is important to the security of user data in a mobile cloud environment. Because of the server’s user credentials, it is subject to attacks. To maintain data authentication, a novel authentication mechanism is proposed. It consists of three independent phases: Registration, login, and authentication and key agreement. The user registers with the Registration Center (RC) by producing a secret number that isn’t stored in the phone, which protects against privileged insider attacks. The user and server generate a nonce for dynamic user identity and agree on a session secret key for safe communication. The passwords are not stored on the computer or provided in plain text, they are resistant to replay, guessing, and stolen verification attacks. The suggested protocol uses a one-way hash function and XOR operations, with the client having remote access to a large number of servers over a secure communication channel. Concentrates on HMAC and SHA3 for Collision Free Hashing and to overcome length extension attacks. HMACs are substantially less affected by collisions than their underlying hashing algorithms alone. So adding an HMAC to an MD5 or SHA hash would make it substantially more difficult to break via a rainbow table.     

Single particle tracking of fluorescent nanodiamonds in cells and organisms

Ever since the discovery of fullerenes in 1985, nanocarbon has demonstrated a wide range of applications in various areas of science and engineering. Compared with metal, oxide, and semiconductor nanoparticles, the carbon-based nanomaterials have distinct advantages in both biotechnological and biomedical applications due to their inherent biocompatibility. Fluorescent nanodiamond (FND) joined the nanocarbon family in 2005. It was initially developed as a contrast agent for bioimaging because it can emit bright red photoluminescence from negatively charged nitrogen-vacancy centers built in the diamond matrix. A notable application of this technology is to study the cytoplasmic dynamics of living cells by tracking single bioconjugated FNDs in intracellular medium. This article provides a critical review on recent advances and developments of such single particle tracking (SPT) research. It summarizes SPT and related studies of FNDs in cells (such as cancer cell lines) and organisms (including zebrafish embryos, fruit fly embryos, whole nematodes, and mice) using assorted imaging techniques.     

Engineering Bimetallic Ag–Cu Nanoalloys for Highly Efficient Oxygen Reduction Catalysts: A Guideline for Designing Ag‐Based Electrocatalysts with Activity Comparable to Pt/C‐20%

Development of highly active and stable Pt‐free oxygen reduction reaction catalysts from earth‐abundant elements remains a grand challenge for highly demanded metal–air batteries. Ag‐based alloys have many advantages over platinum group catalysts due to their low cost, high stability, and acceptable oxygen reduction reaction (ORR) performance in alkaline solutions. Nevertheless, compared to commercial Pt/C‐20%, their catalytic activity still cannot meet the demand of commercialization. In this study, a kind of catalysts screening strategy on Ag_x Cu_100?x nanoalloys is reported, containing the surface modification method, studies of activity enhancement mechanism, and applied research on zinc–air batteries. The results exhibit that the role of selective dealloying (DE) or galvanic displacement (GD) is limited by the “parting limitation”, and this “parting limitation” determines the surface topography, position of d‐band center, and ORR performance of Ag_x Cu_100?x alloys. The GD‐Ag₅₅Cu₄₅ and DE‐Ag₂₅Cu₇₅ catalysts alloys present excellent ORR performance that is comparable to Pt/C‐20%. The relationship between electronic perturbation and specific activity demonstrates that positive shift of the d‐band center (≈0.12 eV, relative to Ag) for GD‐Ag₅₅Cu₄₅ is beneficial for ORR, which is contrary to Pt‐based alloys (negative shift, ≈0.1 eV). Meanwhile, extensive electrochemical and electronic structure characterization indicates that the high work function of GD‐Ag₅₅Cu₄₅ (4.8 eV) is the reason behind their excellent durability for zinc–air batteries.     

基于自然冷却技术应用的数据中心空调节能分析

本文基于数据中心空调系统的选型和节能设计,以风冷直膨式机组、风冷双冷源冷水机组和热管复合式制冷机组为研究对象,建立了三种类型空调系统的能效计算模型;基于DEST提供的广州、上海、北京和哈尔滨四个城市的气象数据,以相同的空调负荷和回风参数为条件,对三类空调的年均能效(AEER)进行计算和对比分析。结果表明:三类机组的年均能效自南向北随着平均气温的降低而逐渐提高,分别为4.07~4.45、4.00~6.84、4.27~8.20;相比前二类机组,热管复合式制冷机组的节能幅度分别为4.8%~46%和6.4%~16.6%;双冷源制冷机组由于能够应用自然冷却替代或部分替代高能耗的压缩制冷,相比风冷直膨式机组节能优势明显;与风冷双冷源冷水机组相比,热管复合式制冷机组的制冷剂输送功小、换热端工作效率高、没有防冻问题等优点,是年均气温较低地区数据中心空调的首选。     

爆破成井装药结构与中心孔药量的模拟与实践

为研究小断面急倾斜天井采用VCR法一次爆破成井的中心孔药量问题,采用ANSYS/LS-DYNA对成井过程进行了数值模拟。根据C·W利文斯顿球状药包理论,采用5孔布置、单孔中心掏槽、同分层中心孔与边孔不等高装药模拟成井过程。通过观察爆炸作用下岩石塑性应变场的变化,确定该方法能够很好地解决岩石夹制性问题。进而,改变中心孔药量进行多组模拟,发现不同中心孔药量与井壁上不同位置的单元应力对岩石抗拉强度的二阶矩的值呈非线性关系,并由此总结出中心孔药量的确定方法。工程实例验证了采用不等高装药与使用合理的药量能够达到理想的成井效果。