Linux下高性能网络服务器的设计

本文讨论了Linux下一种高性能网络服务器的设计,采用线程池和内存池技术,AIO技术和缓存技术以及消恩队列可以大幅度提升系统性能,减少服务端开销,可胜任高负荷高吞吐量环境需求,测试表明该系统性能优势在高负荷情况尤其明显.     

恒压排液桶式气泵供液制冷工艺的应用研究

笔者在1989年设计、安装了800吨低温库恒压排液桶气泵式连续供液制冷工艺的基础上,经过多年的运行考察和研究工作,于1993年又将改进型的该系统成功地应用于高负荷、强波动的大型制冷系统,从而证实了该系统完全适用于各类氨制冷系统。 该系统不仅简化了设计,而且简化了控制,使得实际应用更加切实可行。 本文就该系统应用的目的及用途,主要技术参数、设计及技术关键,所采取的技术方案与措施,以及与国内外各类气泵系统的性能及效益的对比分析等作一可行性论证。     

浅谈油液污染对道路除雪机械液压系统的影响

液压传动技术在道路除雪机械领域得到广泛的应用,但是液压系统在恶劣环境下长时间高负荷工作很容易被污染,从而引起除雪上装设备多种故障。本文就液压系统的污染对设备的影响及如何预防和保护进行了阐述。     

蒸发式空气冷却器解决直接空冷系统夏季高负荷研究

本文分析现有电站直接空冷系统夏季高负荷的原因,并提出了几种解决方案,其中针对蒸发式空冷器做出了详细介绍。概述了蒸发冷却技术的工作原理,并详细介绍了直冷系统中并联蒸发式空冷器的工艺流程,及蒸发式空冷器在直冷系统中起到的关键作用,同时也提出了采用这种复合式空冷系统还需要进一步解决的问题。     

PS／OMMT纳米复合材料作为润滑油添加剂的摩擦学性能

用乳液聚合法制备了聚苯乙烯/有机蒙脱土(PS/OMMT)纳米复合材料,并利用 XRD对其结构进行表征.利用四球机考察了纳米复合材料在AN 10油中的摩擦学性能,表明所合成的PS/OMMT纳米杂化材料能提高基础油的抗磨性能及承载能力,降低其摩擦系数;复合材料中OMMT含量对摩擦学性能影响很大.EDX能谱研究结果表明,在低负荷下PS/OMMT纳米复合材料在钢球表面铺展成膜,在高负荷下,聚合物分解,裸露出纳米结构的高度分散蒙脱土片层具有高活性,能在钢球的磨斑表面成膜,改善润滑油高负荷下的摩擦学性能.     

关f丙烯腈装置回收塔憋压问题的探讨

回收塔是阳烯腈装置的重要组成部分,是精制回收系统的核心,随着装置高负荷的运行,回收塔表现出了憋压的问题。     

锅炉高负荷时磷酸盐“隐藏”的算法研究

结合舰船锅炉高负荷时的运行特点，建立了舰船锅炉炉水磷酸盐“隐藏”的数学模型和相应的计算方法，并对某型锅炉高负荷时炉水磷酸盐的递减速度进行了计算，为下一步时舰艇锅炉水处理技术进行全面改进提供了可靠的依据．     

开发人员如何优化ORACLE执行语句

各个领域中,对数据库的使用力度不断增加:更多的企业级数据库被使用,使用情况多样化、数据库容量增大化的趋势明显。与此同时,基于实际业务需要的应用也想数据库提出了更高效率的要求:数据库调优势在必行。报告的作者具有多年大型系统开发和企业级数据库维护的经验,基于SQL语句在Oracle数据库中的执行逻辑,在以下报告中提出多种数据库优化的方法,从而达到提高Oracle数据库性能、改善应用系统运行环境的目的。     

多线程技术在虚拟仪器软件开发中的应用

多线程技术是Win32操作系统的一项重要软件技术,能够更好地开发并行性任务和提高系统性能,在避免阻塞、减少运行时间和最大程度利用多处理器的性能方面具有明显的优点.在简要介绍虚拟仪器的基础上,对LabWindows软件开发平台下利用多线程技术实现数据采集进行了研究.将多线程应用到虚拟仪器软件设计中,大大提高了系统的性能和CPU的利用率.     

航空发动机故障诊断方法及测试

航空发动机与一般发动机相比较而言,具有结构复杂、零部件多等特点,在实际的运行中还要求耐高温、高压、高负荷以及高转速,因此,在长时间的反复运行中系统部件的损耗不可避免。由于系统部件的损耗,航空发动机故障就会随即产生,并直接影响了航空器的正常运行,严重威胁飞行安全。对航空发动机故障进行排除和测试能有效避免器路部件故障等导致的飞行安全隐患,提高发动机的稳定性和安全性。本文将就几种典型的航空发动机故障诊断技术进行分析和探讨,并浅议航空器发动机故障测试平台,对其功能参数进行监控和测试,从而使发动机的性能得以提高并更具可靠性。     

Network Based Real Time Condition Monitoring of Rotating Machinery

1　ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｎｅｔｗｏｒｋｔｅｃｈｎｏｌｏｇｙｈａｓｐｒｏｖｉｄｅｄｔｈｅｐｏｓｓｉｂｉｌｉｔｙｔｏｍｏｎｉｔｏｒａｌａｒｇｅｇｒｏｕｐｏｆｒｏｔａｔｉｎｇｍａｃｈｉｎｅｓａｎｄｄｉａｇｎｏｓｅｍａｌｆｕｎｃｔｉｏｎｓｉｎｔｈｅｍｉｎｄｉｓｔａｎｔａｎｄｄｉｆｆｅｒｅｎｔｌｏｃａｔｉｏｎｓ.Ｉｎｔｈｉｓｗａｙ ,ｉｎｖｅｓｔｍｅｎｔａｎｄｒｅｓｏｕｒｃｅｓｃａｎｂｅｓａｖｅｄａｎｄｔｈｅｅｆｆｉｃｉｅｎｃｙｏｆｍａｃｈｉｎｅｍａｎａｇｅｍｅｎｔｗｉｌｌ…     

融入区块链理念的配电网数据池构建方法研究

由于缺少统一的数据管理平台,电网公司发展策划部的数据应用及管理工作存在着工作量大、重复性高、一致性差等问题。为了进一步提升配电网发展业务信息化水平,规范发展业务的数据管理工作,介绍了区块链的定义及特征以及电网公司发展部的常规业务、数据管理、信息化系统应用情况。结合电网规划、电网诊断分析、项目后评价等业务工作成果要求开展数据需求分析,构建支撑供电公司发展业务需求的配网数据平台。同时融入区块链理念,构建数据管理架构、管理流程、管理机制、管理保障,制定配网数据池的记账、存储、共识、激励机制,为促进配网数据池的落实应用提供支撑保证。     

降膜式蒸发器用高效传热管换热性能试验研究

通过试验对降膜式蒸发器用高效传热管的换热性能进行研究,并将其与之相对应的池沸腾换热性能进行比较.由比较数据可知:样管池沸腾换热性能均随热流密度的增大而增强,降膜蒸发性能在一定热流密度下随喷淋流量的增大而增强;在恒定热流密度和恒定喷淋流量下,光管降膜燕发性能低于池沸腾性能,强化管降膜蒸发性能高于池沸腾性能;池沸腾性能高的强化管降膜蒸发性能也强.     

面向网络化制造的机械资源库及其管理系统

建立了开放式可扩展的面向网络化制造的机械资源库,探讨了机械资源库及其管理系统的框架构造,进行了机械资源库管理权限问题和机械资源库运行计费模式的研究,分析了基于机械资源库的协同设计应用实例模型。     

金属激光3D打印过程数值模拟应用及研究现状

数值模拟可以高效、有针对性地对金属激光选区熔化成型过程中的温度场、熔池形状、残余应力和变形、凝固过程微观组织演变等过程建立相应的模型并对成形件的相关性能做出准确预测,为工艺优化提供科学的依据,显著降低工艺开发成本和缩短工艺开发周期,有力推动金属增材制造向工业级应用的转变。本文综述了金属激光增材制造过程中温度场、熔池动力学、成形件内部残余应力和变形、显微组织变化4个方面数值模拟的最新研究进展,概述了金属SLM过程数值模拟所取得的最新进展,分析了金属SLM数值模拟领域的研究热点和所存在的计算时间长、成本高等问题,最后提出金属SLM过程数值模拟应将3D打印过程中快速凝固、微熔池等特征与大数据、人工智能、深度学习等技术相结合,进一步提高数值模拟精度,拓宽金属激光增材制造加工窗口,为个性化产品开发提供指导。     

Multi-VMs Intrusion Detection for Cloud Security Using Dempster-shafer Theory

Cloud computing provides easy and on-demand access to computing resources in a configurable pool. The flexibility of the cloud environment attracts more and more network services to be deployed on the cloud using groups of virtual machines (VMs), instead of being restricted on a single physical server. When more and more network services are deployed on the cloud, the detection of the intrusion likes Distributed Denial-of-Service (DDoS) attack becomes much more challenging than that on the traditional servers because even a single network service now is possibly provided by groups of VMs across the cloud system. In this paper, we propose a cloud-based intrusion detection system (IDS) which inspects the features of data flow between neighboring VMs, analyzes the probability of being attacked on each pair of VMs and then regards it as independent evidence using Dempster-Shafer theory, and eventually combines the evidence among all pairs of VMs using the method of evidence fusion. Unlike the traditional IDS that focus on analyzing the entire network service externally, our proposed algorithm makes full use of the internal interactions between VMs, and the experiment proved that it can provide more accurate results than the traditional algorithm.     

Laser weld pool management through diffractive holographic optics

Abstract

Conduction laser welding involves initiating a melt pool by exposure to high power laser induced light and controlled thermal conduction. Existing welding techniques generally provide enough energy to join the component but have no real control over the melt pool. This process can invariably lead to overheating in adjacent areas or even the melt pool itself, often causing unavoidable effects, such as ‘burn through’. The present work presents a procedure in which a desired melt pool shape is conceived, and a bespoke beam irradiance distribution is designed to match. The beam is shaped not by conventional lenses but by a diffractive holographic optical element (DHOE). The DHOE utilises holography to wholly create highly complex three-dimensional energy distributions through constructive and destructive interference. This technique allows novel beam irradiance distributions to be applied to conduction mode laser welding, with the melt pool transverse profile being shaped to a specific design. Holographic conduction laser welding has been shown to be successful and represents a significant step forward in the industry, as demonstrated in this case in both mild and stainless steels. The fusion zone is shown to be particularly influenced by the shape of the illuminating laser beam profile, and many of the welds demonstrate a highly novel weld profile because of this. The use of a bespoke beam irradiance distribution allows control of the heat flow to the workpiece, and this allows greater control over material migration due to surface tension effects. Many of the welds demonstrate unique surface solidification patterns directly linked to the beam profile used. The DHOE also presents a number of additional advantages, such as an increased usable depth of field, allowing for less stringent set-up tolerances. Comprehensive metallography has been performed on samples of these welds through the use of optical microscopy, electron microscopy, electron backscatter diffraction and energy dispersive (X-ray) spectroscopy. These techniques offer in depth analysis of crystal size, shape, orientation and phase. By incorporating DHOEs into a laser welding process, not only does the melt pool shape become controllable, but also the crystal growth is highly influenced. Many of the undesirable attributes of a conventional laser weld are reduced by using a beam distribution created by a DHOE, bringing the microstructure of the weld pool closer to that of the parent material.     

Harsh Environment Silicon Carbide Sensors for Health and Performance Monitoring of Aerospace Systems: A Review

The recent increase in transportation costs and the push for cleaner emissions demands advancements in aerospace technology. The current instrumentation used in aerospace applications is costly, and indirect measurement approaches are often employed due to the inability to locate sensors in harsh environments. Health monitoring technologies for the development of a distributed sensor network can be utilized to improve engine efficiencies and reduce emissions while maintaining safety. This paper reviews the recent advancements in silicon carbide (SiC) process technologies and demonstrations of SiC sensors and electronic circuits in hostile environments, which supports the use of SiC technology for health and performance monitoring of aerospace systems. Further development of this technology can ultimately improve the performance, reliability, and emissions of aerospace systems. However, challenges still remain for the realization of a distributed sensor network for harsh environment applications such as aerospace.     

Blockchain-Based Light-Weighted Provable Data Possession for Low Performance Devices

Provable Data Possession (PDP) schemes have long been proposed to solve problem of how to check the integrity of data stored in cloud service without downloading. However, with the emerging of network consisting of low performance devices such as Internet of Things, we find that there are still two obstacles for applying PDP schemes. The first one is the heavy computation overhead in generating tags for data blocks, which is essential for setting up any PDP scheme. The other one is how to resist collusion attacks from third party auditors with any possible entities participating the auditing. In this paper, we propose a novel blockchain-based light-weighted PDP scheme for low performance devices, with an instance deployed on a cloud server. We design a secure outsourced tag generating method for low performance devices, which enables a kind of “hash-sign-switch” two-phase tag computing. With this method, users with low performance devices can employ third party auditors to compute modular exponential operations that accounts for the largest portion of computation overhead in tag generation, without leaking their data content. Chaincodes in blockchain network ensure the correctness of such outsourcing and prevent collusion attacks. The security analysis and performance evaluation prove that our scheme is both secure and efficient.     

无锡蠡湖项目室内游泳池空调方案对比及分析

介绍了室内游泳池空调两方案对比及经济分析.通过模拟计算,发现采用除湿热泵机组节能并节约运行费用,但其初投资相对较高,静态回收周期长.