含Cl^-溶液中SO4^2-对316不锈钢临界点蚀温度的影响

采用外加恒电位下腐蚀电流-温度扫描方法研究了在0．5％Cl^-溶液中，SO4^2-浓度对316不锈钢点腐蚀行为的影响．结果表明，随着SO4^2-浓度的增加，钝化电流增加，开路电位降低．当SO4^2-浓度低于0．42％时，316不锈钢的临界点蚀温度比不存在SO4^2-时的临界点蚀温度低；当SO4^2-浓度大于0．42％时，临界点蚀温度比不存在SO4^2-时的临界点蚀温度高．从离子竞争吸附的角度进行分析，对SO4^2-加速与抑制点蚀两种作用规律的形成原因进行了解释．     

(Short communication) Degradation of corrosion resistance of Zircaloy-4 in LiOH aqueous solution

To investigate the degradation of corrosion resistance of Zircaloy-4 in LiOH aqueous solution, SIMS (secondary ion mass spectrometry) analysis was performed to examine the profiles of Li~ , K~ , and OH~- in oxide layers formed in the same concentration (0.1 mol/L) LiOH and KOH solutions. Even though the oxide layers have an equal thickness, the penetration depth of K~ is shallower than that of Li~ , and the penetration depth of OH~- corroded in KOH solution is also shallower than that corroded in LiOH solution. It shows that the diffusion of OH~- into oxide layer is accompanied by the corresponding cation. The difference of degradation effect of LiOH and KOH solutions on the corrosion resistance of Zircaloy-4 was discussed.     

Global robust output tracking control for a class of cascade nonlinear systems with unknown control directions

We investigate the global robust tracking problem via output feedback for a class of cascade nonlinear systems with dynamic uncertainties and non-vanishing disturbances. It does not require a priori knowledge of the sign of the high-frequency gain. A recursive design scheme is presented using the ideas of pseudosign function, Nussbaum-type gain technique and the deadzone method. It is shown that under some conditions, the tracking error can be guaranteed asymptotic to the interval [?ε, ε]?? with arbitrary prescribed ε>0 after a finite time, while keeping all signals of the resulting closed-loop systems bounded. The simulation results demonstrate the effectiveness of the proposed algorithm.     

连续型Δ∑调制器设计综述

Δ∑调制器作为数字转换器中重要的类型,以其较高精度及对CMOS工艺演进的更强适应性得到广泛应用.阐述了Δ∑调制器中连续型的Δ∑调制器的主要设计要点,介绍了国内外在连续型Δ∑调制器上的研究现状,并对相应设计方法进行分类总结.分析了连续Δ∑调制器的工作原理、系统结构、电路误差及模型,对其发展趋势以及面临的挑战进行了总结.结果说明合理地利用新工艺及新型积分器可以有效提高连续型Δ∑调制器的带宽及能效.     

Incorporating Intra‐Query Term Dependencies in an Aspect Query Language Model

Query language modeling based on relevance feedback has been widely applied to improve the effectiveness of information retrieval. However, intra‐query term dependencies (i.e., the dependencies between different query terms and term combinations) have not yet been sufficiently addressed in the existing approaches. This article aims to investigate this issue within a comprehensive framework, namely the Aspect Query Language Model (AM). We propose to extend the AM with a hidden Markov model (HMM) structure to incorporate the intra‐query term dependencies and learn the structure of a novel aspect HMM (AHMM) for query language modeling. In the proposed AHMM, the combinations of query terms are viewed as latent variables representing query aspects. They further form an ergodic HMM, where the dependencies between latent variables (nodes) are modeled as the transitional probabilities. The segmented chunks from the feedback documents are considered as observables of the HMM. Then the AHMM structure is optimized by the HMM, which can estimate the prior of the latent variables and the probability distribution of the observed chunks. Our extensive experiments on three large‐scale text retrieval conference (TREC) collections have shown that our method not only significantly outperforms a number of strong baselines in terms of both effectiveness and robustness but also achieves better results than the AM and another state‐of‐the‐art approach, namely the latent concept expansion model. © 2014 Wiley Periodicals, Inc.     

一种便携式室内空气质量快速检测仪设计

设计一种涉及室内甲醛（ HCHO）、氨（ NH3）和苯（ C6 H6）三种有害气体浓度的便携式快速检测仪。该仪器采用新型电化学传感器与基于FPGA的新型高精度信号处理电路得到对应气体的初始浓度值,并结合室内环境气压和温湿度实时监测情况,修正初始浓度值,对浓度超标气体进行声光报警。该仪器具有检测速度快、精度高和携带方便等优点,为大众家庭实时快速检测室内空气质量提供一种简单可靠的方法与手段。     

p53抑癌基因电化学阻抗传感器研究

基于电化学阻抗技术构建了一种检测p53抑癌基因的电化学传感器.首先利用自组装作用将末端带巯基的探针p53抑癌基因(p53-DNA)固定于金电极表面,根据传感器结合前后电子转移阻抗值的变化,对目标p53-DNA进行了测定.以pH =7.4的5mmol/L K3[Fe(CN)6]-5mmol/L K4[Fe(CN)6]平衡电对溶液作为检测液,检测目标p53-DNA的线性浓度范围为1.0×10-8～ 1.0×10-6 mol/L,其检出限为3.0×10-9 mol/L(S/N =3).对5.0×10-8 mol/L的目标p53-DNA进行11次平行测定,其RSD为3.4％.该传感器制作简单、灵敏高、选择性好,且无需标记,易于操作.     

基于超声衍射时差法的缺陷检测技术仿真分析

采用有限元方法对超声衍射时差(TOFD)检测技术进行分析.首先使用COMSOL有限元分析软件对超声TOFD检测技术建模;而后基于该模型分析超声波的产生、传播和接收过程;最后通过改变模型参数,研究缺陷几何尺寸对超声TOFD检测信号的影响.研究结果表明:超声TOFD信号中直通波、上端衍射波、下端衍射波、底面反射波信号的相位依次变化180°;当缺陷位于工件上表面或下表面时,探头只能接收到四种基本超声信号中的一部分.     

基于不等长序列相似度挖掘的数据关联算法

针对不等长序列数据的关联问题,提出基于滑动窗口的最优匹配增权法不等长序列相似度度量算法。以较短序列作为滑动窗口遍历较长序列得到一组滑动相似度,利用这组相似度形成最优权重,加权得到不等长序列的相似度,并根据相似度大小对序列数据进行关联判决,以解决截断法相似度度量仅能反映截断序列局部相似度的问题。仿真实验验证了所提出算法对不等长序列数据关联的有效性,并对序列长度和量测误差等因素对相似度度量和关联效果的影响进行了讨论。     

一种基于群组判断离差的偏好集结方法

针对群决策偏好集结中违反Pareto 最优性的情况, 设计一种基于群组判断几何离差的同质性集结方法. 该方法在集结前进行几何离差测试, 以确定个体决策信息的离差水平. 离差较小时, 可基于几何平均集结; 对于离差较大且修正复杂度较高的决策信息, 采用主成分分析(PCA) 从高维决策信息中提取大多数相关信息, 在不依赖主观分析的情况下进行加权集结. 仿真实验表明, 所提出的方法能够在不违背Pareto 最优性的基础上集结离差较大的群决策信息.