左江山秀水电站工程施工导流设计

山秀水电站坝址的特点是河床比较狭窄、枯水期水面宽小(约130m)、水较深(平均为10.25m),给施工导流,尤其是一期临时围堰的布置带来较大困难。本文分析了工程施工导流的主要影响因素,简述了施工导流方式、导流标准、围堰型式及布置、运行效果。     

不同条件对蜂蜜发酵过程中高级醇生成的影响

为探究不同条件对酵母发酵蜂蜜过程中高级醇生成的影响,以蜂蜜、麦曲、酵母为原料,以高级醇含量为指标,通过单因素试验分别考察了发酵温度、酵母添加量、发酵时间、磷酸氢二铵添加量和发酵液糖度对酵母发酵蜂蜜过程中高级醇生成的影响。响应面优化结果表明,当麦曲添加量为4%,干酵母的加入量为0.2%,磷酸氢二铵添加量600 mg/L,起始发酵液的糖度为30.0%,pH为4.5,培养温度为34℃,培养时间为4 d,在此条件下得到高级醇的最低值43.72 mg/L。     

A framework for improved video text detection and recognition

Text displayed in a video is an essential part for the high-level semantic information of the video content. Therefore, video text can be used as a valuable source for automated video indexing in digital video libraries. In this paper, we propose a workflow for video text detection and recognition. In the text detection stage, we have developed a fast localization-verification scheme, in which an edge-based multi-scale text detector first identifies potential text candidates with high recall rate. Then, detected candidate text lines are refined by using an image entropy-based filter. Finally, Stroke Width Transform (SWT)- and Support Vector Machine (SVM)-based verification procedures are applied to eliminate the false alarms. For text recognition, we have developed a novel skeleton-based binarization method in order to separate text from complex backgrounds to make it processible for standard OCR (Optical Character Recognition) software. Operability and accuracy of proposed text detection and binarization methods have been evaluated by using publicly available test data sets.     

Provably secure robust threshold partial blind signature

Threshold digital signature and blind signature are playing important roles in cryptography as well as in practical applications such as e-cash and e-voting systems. Over the past few years, many cryptographic researchers have made considerable headway in this field. However, to our knowledge, most of existing threshold blind signature schemes are based on the discrete logarithm problem. In this paper, we propose a new robust threshold partial blind signature scheme based on improved RSA cryptosystem. This scheme is the first threshold partial blind signature scheme based on factoring, and the robustness of threshold partial blind signature is also introduced. Moreover, in practical application, the proposed scheme will be especially suitable for blind signature-based voting systems with multiple administrators and secure electronic cash systems to prevent their abuse.     

连续式低压铸造技术的研究与开发

传统的低压铸造方法存在效率低、无法连续生产、金属液品质及气压加压压力波动大的缺陷,为此开发出一种基于PLC和触摸屏技术的新型连续式低压铸造技术.该技术将现有传统的低压浇注兼保温坩埚分成3个独立的坩埚即保温坩埚、加压坩埚、浇注坩埚,3个坩埚底部由过道连通,分别完成加、补料、液面加压及升液浇注3个主要动作.加压坩埚具有定量功能,每次浇注前液面均保持在恒定高度,加压时升液曲线稳定、精确,重复性高.保温坩埚实现了外部补料与加压浇注互不干涉,保证了生产的连续性,生产效率显著提高.     

UAV-assisted data gathering in wireless sensor networks

An unmanned aerial vehicle (UAV) is a promising carriage for data gathering in wireless sensor networks since it has sufficient as well as efficient resources both in terms of time and energy due to its direct communication between the UAV and sensor nodes. On the other hand, to realize the data gathering system with UAV in wireless sensor networks, there are still some challenging issues remain such that the highly affected problem by the speed of UAVs and network density, also the heavy conflicts if a lot of sensor nodes concurrently send its own data to the UAV. To solve those problems, we propose a new data gathering algorithm, leveraging both the UAV and mobile agents (MAs) to autonomously collect and process data in wireless sensor networks. Specifically, the UAV dispatches MAs to the network and every MA is responsible for collecting and processing the data from sensor nodes in an area of the network by traveling around that area. The UAV gets desired information via MAs with aggregated sensory data. In this paper, we design a itinerary of MA migration with considering the network density. Simulation results demonstrate that our proposed method is time- and energy-efficient for any density of the network.     

An attack-and-defence game for security assessment in vehicular ad hoc networks

Recently, there is an increasing interest in Security and Privacy issues in Vehicular ad hoc networks (or VANETs). However, the existing security solutions mainly focus on the preventive solutions while lack a comprehensive security analysis. The existing risk analysis solutions may not work well to evaluate the security threats in vehicular networks since they fail to consider the attack and defense costs and gains, and thus cannot appropriately model the mutual interaction between the attacker and defender. In this study, we consider both of the rational attacker and defender who decide whether to launch an attack or adopt a countermeasure based on its adversary’s strategy to maximize its own attack and defense benefits. To achieve this goal, we firstly adopt the attack-defense tree to model the attacker’s potential attack strategies and the defender’s corresponding countermeasures. To take the attack and defense costs into consideration, we introduce Return On Attack and Return on Investment to represent the potential gain from launching an attack or adopting a countermeasure in vehicular networks. We further investigate the potential strategies of the defender and the attacker by modeling it as an attack-defense game. We then give a detailed analysis on its Nash Equilibrium. The rationality of the proposed game-theoretical model is well illustrated and demonstrated by extensive analysis in a detailed case study.     

U75V重轨钢280mm×380mm连铸坯加热工艺的试验研究

在钢厂利用Thermophil STOR测试系统(黑匣子)进行步进式加热炉内U75V重轨钢280 mm×380mm铸坯加热过程温度跟踪,并用Origin软件进行数据处理,得出铸坯加热温度、升温速度、表面与中心温差等曲线.结果表明,铸坯平均加热温度为1 220℃,当在炉时间超过180 min,应降低均热段控制温度约20℃...     

基于混合同步控制的构网型逆变器并网系统小扰动稳定性分析

由于构网型逆变器并网系统的混合同步控制(HSC)中直流电压控制、锁相环(PLL)、功率同步环(PSL)与电网阻抗间存在复杂交互,同步控制参数在不同电网强度下对并网系统小扰动稳定性的影响规律尚不清楚。针对该问题,首先建立了基于HSC的构网型逆变器并网系统状态空间模型,并基于根轨迹法分析了不同电网强度混合同步环中同步参数对并网系统小扰动稳定性与失稳模式的影响规律;在此基础上,给出了混合同步环中附加PLL支路参数和PSL参数的协同选取方法,以实现HSC构网型逆变器在宽电网强度下范围稳定运行。基于MATLAB/Simulink的仿真分析验证了理论分析的正确性。     

方圆管固定短芯棒拉拔工艺分析

运用非线性有限元软件ABAQUS对ITER计划导体套管成形工艺进行模拟仿真,得到稳定拉拔阶段的等效塑性应变、轴向和径向应力以及接触压力的分布规律,并分析了拉拔力和拉拔成形过程中能量的分布变化。结果表明,采用优化后的工艺参数拉拔成形时可得到套管内外表面质量较好的产品,从而解决了拉拔工艺中材料内径缩孔和裂纹缺陷的问题。