An efficient local search for partial vertex cover problem

In this paper, an efficient local search framework, namely GRASP-PVC, is proposed to solve the minimum partial vertex cover problem. In order to speed up the convergence, a novel least-cost vertex selecting strategy is applied into GRASP-PVC. As far as we know, no heuristic algorithms have ever been reported to solve this momentous problem and we compare GRASP-PVC with a commercial integer programming solver CPLEX as well as a 2-approximation algorithm on two standard benchmark libraries called DIMACS and BHOSLIB. Experimental results evince that GRASP-PVC finds much better partial vertex covers than CPLEX and the approximation algorithm on most instances. Additional experimental results also confirm the validity of the least-cost vertex selecting strategy.

     

电容式密度传感器低密度液氢校准实验研究

设计、搭建了一套可调节密度式多点电容式密度传感器校准装置,并进行了电容式密度传感器低密度液氢的校准试验。实现了对液氢在一定低密度范围内(50—70kg/m3)的调节,突破了传统的常压单一密度点校准技术,实现了液氢多密度点的校准,提高了校准结果的可靠性。对电容式密度传感器校准装置各因素引入的不确定度分量进行了评定,分析得到了该装置的不确定度,试验结果表明采用给液氢增压的方式可以对液氢低密度进行准确控制,该调节装置的不确定度满足电容式密度传感器校准设计要求,并且能够对电容式密度传感器在多种低温流体介质中进行较宽密度范围校准。     

Actively Perceiving and Responsive Soft Robots Enabled by Self‐Powered,Highly Extensible,and Highly Sensitive Triboelectric Proximity‐ and Pressure‐Sensing Skins

Robots that can move, feel, and respond like organisms will bring revolutionary impact to today's technologies. Soft robots with organism‐like adaptive bodies have shown great potential in vast robot–human and robot–environment applications. Developing skin‐like sensory devices allows them to naturally sense and interact with environment. Also, it would be better if the capabilities to feel can be active, like real skin. However, challenges in the complicated structures, incompatible moduli, poor stretchability and sensitivity, large driving voltage, and power dissipation hinder applicability of conventional technologies. Here, various actively perceivable and responsive soft robots are enabled by self‐powered active triboelectric robotic skins (tribo‐skins) that simultaneously possess excellent stretchability and excellent sensitivity in the low‐pressure regime. The tribo‐skins can actively sense proximity, contact, and pressure to external stimuli via self‐generating electricity. The driving energy comes from a natural triboelectrification effect involving the cooperation of contact electrification and electrostatic induction. The perfect integration of the tribo‐skins and soft actuators enables soft robots to perform various actively sensing and interactive tasks including actively perceiving their muscle motions, working states, textile's dampness, and even subtle human physiological signals. Moreover, the self‐generating signals can drive optoelectronic devices for visual communication and be processed for diverse sophisticated uses.     

MoS2/HfO2/Silicon‐On‐Insulator Dual‐Photogating Transistor with Ambipolar Photoresponsivity for High‐Resolution Light Wavelength Detection

Photogating detectors based on 2D materials attract significant research interests. However, most of these photodetectors are only sensitive to the incident intensities and lack the ability to distinguish different wavelengths. Color imaging based on these detectors usually requires additional optical filter arrays to collect red, green, and blue (RGB) colors in different photodetectors to restore the true color of one pixel. In this study, an MoS₂/HfO₂/silicon‐on‐insulator field effect phototransistor with wavelength distinguishing ability is presented, where the photogating effect can be simultaneously formed in the top MoS₂ gate and bottom Si substrate gate. These two individual photogating effects can reduce and increase the read current in the middle 12 nm Si channel, respectively. Thus, by tuning the applied voltages on these two gates, the device can be used to obtain tunable ambipolar photoresponsivity from +7000 A W^?1 (Si bottom gate dominated) to 0 A W^?1 (balanced), and finally to ?8000 A W^?1 (MoS₂ gate dominated). In addition, the experimental results show that the corresponding top gate voltage to the zero responsivity (0 A W^?1) point can be positively shifted by the increasing of incident wavelength with high resolution up to 2 nm and is insensitive to the incident intensity.     

面向云平台非可信Hypervisor的保护机制综述

大数据时代背景下,多租户云平台的作用越显重要。然而,虚拟化作为云平台的关键构建技术之一,其安全性的保证尚不充分。Hypervisor是虚拟化技术中关键的软件层次,它管理着客户虚拟机和裸机物理资源之间的资源分配、共享和隔离等重要事务。但是Hypervisor本身存在着漏洞和攻击面,使得任意针对Hypervisor的攻击对多租户云平台和上层应用造成不可估计的威胁。因此,面向云平台非可信Hypervisor的保护机制应运而生。对现有保护机制进行综述,包括:分析其构建的可行性与挑战,并对保护机制进行分类;梳理和剖析保护机制中的完整性检测机制、防御机制以及隔离机制方面的相关工作;展望未来研究趋势,为未来虚拟化技术安全性的研究以及构建可靠的多租户云平台的研究提供有价值的参考。     

基于城市内涝点的防洪排涝模式研究

通过分析洪涝灾害成灾特点,针对我国的《防洪标准》(GB 50201—94)和最新修订的《室外排水设计规范》(2014年修订版)等规范性文件存在的问题,提出对内涝点重点防洪排涝的理念。在此理念的基础上,建立了暴雨强度与内涝点淹没水深关系的模型。以太原理工大学迎西校区为试验区域,以太原市两次典型降雨过程为例,计算试验区域的产汇流量,并根据该区域出水口容积特性曲线,发现模型计算内涝点积水深度与当日实测积水深度相吻合,由此验证了模型的合理性,使由降雨量来推断城市淹没损失大小成为可能。     

等高齿弧锥齿轮铣刀盘焊接变形数值模拟

根据等高齿弧锥齿轮铣刀盘的结构,利用ANSYS Workbench有限元分析软件对刀盘焊接进行数值模拟,得到刀槽焊接过程中的变形情况,绘制温度变形图得出相应的数学模型,为刀盘的焊接技术提供理论依据。在实际环境下进行焊接试验并对焊接结果进行检测,与模拟结果对比得出数值模拟的合理性。     

激电中间梯度法在云南东川某铅锌矿勘查中的应用

在基本掌握测区及周边地质情况和外围电法勘探成果（物性、方法、装置）信息的基础上,进行野外电法不同方法技术的有效性试验,选择采用单一的双频激电中间梯度法及短剖面装置,有效观测视极化率、视电阻率参数,在地质成矿条件及成矿环境有利的前提下,可发现深部的隐伏矿体,且已得到钻探工作证实。不过电法勘探找矿,必须结合多种方法和多种技术来完成。     

基于直接和推荐可信度的P2P综合信任模型

提出了一种新的P2P网络环境下的综合信任模型。明确区分了服务质量和反馈质量,不是简单地将节点的信任度作为推荐权重,而是通过节点推荐可信度来计算节点的推荐信任度,并且通过动态权重因子平衡自身交互历史经验和其他节点的推荐信任来计算节点的综合信任度,同时为每个节点引入信誉积分属性以鼓励节点提供服务和推荐信息,提高节点参与网络活动的主动性,给出了信任模型的实现算法和仿真实验。实验结果表明,信任模型能准确计算节点信任度,并且能抵抗恶意节点的夸大、诋毁、协同作弊等恶意行为,具有良好的性能。