合金元素Ni对NbCr2/Nb合金热稳定性的影响

采用机械合金化+热压工艺制备了(NbCr_2/Nb)-Ni合金,通过探讨1 200℃下100h高温热暴露后合金室温组织和性能的变化,研究了Ni元素对NbCr_2/Nb合金热稳定性的影响。结果表明:Ni主要分布于Laves相NbCr_2中,整个热暴露过程中,合金无明显物相变化;添加Ni后,Ni部分取代Cr的位置,在一定程度上松弛了Laves相的结构,使得合金的维氏硬度、屈服强度略有下降,而塑性应变增加;热暴露过程中,添加Ni后NbCr_2/Nb合金的维氏硬度、抗压强度以及塑性应变的变化幅度明显减小,合金元素Ni提高了NbCr_2/Nb合金的热稳定性。     

Optimizing Operation Rules of Sluices in River Networks Based on Knowledge-driven and Data-driven Mechanism

Many river networks are controlled by sluices, especially in plain area. To prevent potential floods, maintain water level, and improve water environment in the inner river, the water transfer of river networks is needed and executed often in terms of optimized operation rules of sluices planned in advancing. To guarantee maintaining the optimized operation status, the provision of appropriate operating framework of sluices in river networks is necessary and presented in this study based on the knowledge-driven and data-driven mechanism. The general framework is formed by River Networks Mathematical Model (RNMM), Artificial Neural Networks (ANN) and Genetic Algorithms (GA), in which, ANN is used to build a rapid simulation of the flow variables in river networks, RNMM is used to train the ANN model, and GA method, whose fitness function is constructed by the ANN model, is used to optimize the operation rules of sluices. As a demonstration, the framework was applied to water transfer project of the tidal river networks locating in Pudong New Area of Shanghai in mainland China. Firstly, RNMM of Pudong was built and validated according to observed data during water transfer tests. Then, the Backward Propagation Neural Networks (BPNN) model was established as the fast simulation tool of flow variables of river networks through the numerical experiments with RNMM. The Generalized Genetic Algorithms (GGA) was recommended as optimization algorithm of sluices operation rules. Through comparing the optimization results with the RNMM simulation outputs under eight cases, it is verified that the framework can offer sub-optimal operation rules of sluices in river networks and present excellent speediness, robustness and flexibility. It is encouraged to be applied to more complicated, practical problems.     

Efficient processing of top-k twig queries over probabilistic XML data

The flexibility of XML data model allows a more natural representation of uncertain data compared with the relational model. Matching twig pattern against XML data is a fundamental problem in querying information from XML documents. For a probabilistic XML document, each twig answer has a probabilistic value because of the uncertainty of data. The twig answers that have small probabilistic value are useless to the users, and usually users only want to get the answers with the k largest probabilistic values. To this end, existing algorithms for ordinary XML documents cannot be directly applicable due to the need for handling probability distributional nodes and efficient calculation of top-k probabilities of answers in probabilistic XML. In this paper, we address the problem of finding twig answers with top-k probabilistic values against probabilistic XML documents directly. We propose a new encoding scheme called PEDewey for probabilistic XML in this paper. Based on this encoding scheme, we then design two algorithms for finding answers of top-k probabilities for twig queries. One is called ProTJFast, to process probabilistic XML data based on element streams in document order, and the other is called PTopKTwig, based on the element streams ordered by the path probability values. Experiments have been conducted to study the performance of these algorithms.     

忆阻细胞神经网络在车牌定位中的应用

将新型的电路元件忆阻器与传统细胞神经网络相结合,构建出体积小、功耗低、计算速度快的忆阻细胞神经网络。用该网络实现对车牌图像定位的预处理,对应的计算机仿真结果验证了方案的有效性。提出的忆阻细胞神经网络将提高硬件电路实现的集成度,同时也有利于车牌识别速度和效率的提高。     

基于状态空间实现的EDS频率与时延联合估计

针对指数衰减正弦信号(EDS)模型提出了状态空间实现的频率、衰减因子及时延联合估计方法.在此方法中,得到了一个状态过渡矩阵和观测矩阵,频率和衰减因子估计由状态过渡矩阵的特征值获得,时延由观测矩阵和估计的频率和衰减因子得到,结果具有闭式解,不需要搜索计算.由于状态空间方法具有对模型误差不敏感的优点,因而具有更好的数值稳定性.仿真实验表明在一定信噪比的情况下,该方法性能接近相应的CRLB下界.     

黄腐酸及黄腐酸钠对糖尿病小鼠的降糖作用研究

研究黄腐酸及黄腐酸钠的降血糖作用,并对其降糖机制进行初步探讨．采用腹腔注射四氧嘧啶诱导糖尿病小鼠造模,考察黄腐酸及黄腐酸钠对正常小鼠血糖,对糖尿病小鼠血糖、总胆固醇（TC）、血清甘油三酯（TG）以及口服糖耐量的影响．研究表明,中、高剂量黄腐酸及黄腐酸钠能明显降低正常小鼠的血糖含量（P〈0．01）;中、高剂量黄腐酸及黄腐酸钠明显降低糖尿病小鼠体内血糖、TC、TG的含量（P〈0．05或P〈0．01）,低剂量黄腐酸钠、“旱地龙”、“双龙”黄腐酸则有不同程度的影响;对于口服糖耐量试验,中、高剂量黄腐酸及黄腐酸钠能明显快速降低糖尿病小鼠血糖（P〈0．05）．结论：黄腐酸及黄腐酸钠明显降低小鼠体内血糖、TC、TG的含量,增加小鼠的口服糖耐量,提示黄腐酸及黄腐酸钠具有降血糖及改善脂质代谢作用．     

基于BP神经网络的复合材料超声波检测缺陷类型识别

以碳纤维复合材料的分层、孔隙和疏松缺陷的超声波检测信号为研究对象，对包含缺陷信息的复合材料超声波检测信号进行小波包变换，从近似系数及细节系数提取样本的特征值。建立并训练了一种用于实现缺陷识别的BP神经网络，该网络使用Levenberg-Marquardt算法可以快速地完成对数据的处理。使用该网络可进行缺陷类型的识别。     

旋转锉加工的半成形法

研究了加工特种回转面刀具的精确理论,导出了工艺系统运动函数非线性方程组;采用这种方法,一条刀刃是用成形法加工,另一条刀刃是按接触条件得到,概念简单,计算方便.     

A static/opportunistic hybrid-scheduling scheme for MIMO wireless networks

Multiple Input Multiple Output (MIMO) based Spatial Time Division Multiple Access (STDMA) Wireless Mesh Networks (WMNs) have attracted extensive research attention. However, there are two problems in existing studies: (1) the employed MIMO link rate models are not suitable for a MIMO link of a practical STDMA WMN, and (2) the designed scheduling algorithms usually cannot take advantage of the multi-user diversity in a WMN. In this paper, we develop an analytical model for determining the MIMO link rate of an STDMA WMN. Based on a node-based slot assignment and scheduling algorithm (Chen and Lea in IEEE Trans Veh Technol 62(1):272–283, 2013), we propose a static/opportunistic hybrid scheduling framework that can exploit multi-user diversity and channel fading. The performance evaluation shows that the proposed framework has 33–46 % throughput gain over the prior joint routing and time slot assignment schemes for MIMO WMNs.     

降胆固醇功能性食品的研究进展

心血管疾病是世界范围内威胁人类健康的主要疾病之一，并已成为造成我国成人死亡的首要原因。导致心血管疾病的重要危险因素之一是高胆固醇血症。治疗高胆固醇血症的药物主要有他汀类、消胆胺和依泽替米贝，但长期服用会导致严重的副作用。降胆固醇功能性食品因能够发挥与药物类似的功效，且没有任何副作用的特点，开始逐渐被当作药物的替代品。本文将从胆固醇的代谢入手，探讨胆固醇在机体内的合成、代谢、排泄过程，以及机体自身对胆固醇平衡的调节机制。同时，概括总结具有降胆固醇效果的功能性食品及有效成分，并归纳其降胆固醇机制。