共查询到20条相似文献,搜索用时 11 毫秒
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Caffeine consumption and target scanning performance 总被引:1,自引:0,他引:1
J M Childs 《Human factors》1978,20(1):91-96
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Design of a PID-like compound fuzzy logic controller 总被引:3,自引:0,他引:3
The paper describes a novel method for the design of a fuzzy logic controller (FLC) with near-optimal performance for a variety of operating conditions. The approach is based on the analysis of the system behaviour in the error state-space. The final control structure, in a form of a compound FLC, is arrived at in two stages. The first stage encompasses design and tuning of a PID-like fuzzy controller. The second stage consists of placing an additional fuzzy controller, of a structure similar to that of the first one, in parallel with the PID-like fuzzy controller designed in the first stage. The resulting compound controller is characterised with high performance in the wide range of operating conditions, and with small number of parameters that can be adjusted using simple optimisation methods. The controller is developed and tested for a plant comprising a vector controlled induction motor drive. 相似文献
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Manufacture of a micro-sized piezoelectric ceramic structure using a sacrificial polymer mold insert
Jong Hyun Kim Si-Young Choi Jae-Ho Jeon Geunbae Lim Suk Sang Chang 《Microsystem Technologies》2013,19(3):343-349
There have been technical limitations to manufacture microstructures due to difficulty of demolding during replication process of high aspect ratio microstructure in mass production technologies. In the present study, the fabrication of a novel sacrificial micro mold insert and powder injection molding process using such a micro mold insert is proposed and developed. It utilizes a synchrotron radiation to fabricate the shape of polymer based sacrificial mold inserts and then these mold inserts were exposed at X-ray once more to adjust its solubility. This second X-ray exposure facilitates dissolving of mold inserts instead of demolding process which have difficulties like pattern collapses or defects in case of precise replication process. In this manner, severe problems of demolding process in conventional mass production technologies can be efficiently overcome. To verify the usefulness of the proposed technique, polymer based micro mold inserts with several tens of micrometer sized structure for piezoelectric sensor applications were fabricated using X-ray micromachining process radiated synchrotron. The solubility of mold inserts were optimized by the second X-ray exposure without an X-ray mask and then subsequent powder injection molding process was utilized with a piezoelectric based material. Finally, piezoelectric ceramics with micrometer-scale and high aspect ratio of 5 were successfully fabricated, verifying that the present sacrificial mold system is useful for the precise replication process such as the fabrication of microstructure with high aspect ratio or complicated structure. 相似文献
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针对传统幂次趋近律存在的抖振以及全局收敛缓慢的问题,提出一种新型复合滑模趋近律,该趋近律通过引入正切函数以及对传统幂次趋近律的改进,实现趋近律的快速收敛和无抖振特性.首先,引入正切函数,在初始状态已知的情况下使系统更快地收敛;其次,通过设计的趋近律改进传统幂次趋近律中含符号函数乘积项容易引起的抖振;然后,理论证明新型复合趋近律能够快速收敛且无抖振,并推导出趋近速率及稳态误差界;最后,以直线磁悬浮同步电动机磁悬浮系统为例,与双幂次趋近律和多幂次趋近律仿真对比,进一步验证新型复合趋近律能够明显缩短系统的动态过程并消除抖振,且存在模型不确定性及外加干扰作用下,系统仍能迅速地收敛到平衡点附近的领域内. 相似文献
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《Sensors and actuators. B, Chemical》2003,88(2):120-131
This paper describes the design of, and the effects of basic environmental parameters on, a microelectromechanical (MEMS) hydrogen sensor. The sensor contains an array of 10 micromachined cantilever beams. Each cantilever is 500 μm wide×267 μm long×2 μm thick and has a capacitance readout capable of measuring cantilever deflection to within 1 nm. A 20-nm-thick coating of 90% palladium–10% nickel bends some of the cantilevers in the presence of hydrogen. The palladium–nickel coatings are deposited in ultra-high-vacuum (UHV) to ensure freedom from a “relaxation” artifact apparently caused by oxidation of the coatings. The sensor consumes 84 mW of power in continuous operation, and can detect hydrogen concentrations between 0.1 and 100% with a roughly linear response between 10 and 90% hydrogen. The response magnitude decreases with increasing temperature, humidity, and oxygen concentration, and the response time decreases with increasing temperature and hydrogen concentration. The 0–90% response time of an unheated cantilever to 1% hydrogen in air is about 90 s at 25 °C and 0% humidity. 相似文献
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针对网络扫描工具在进行扫描时面临的溯源问题,提出了一种匿名网络扫描系统。首先将匿名系统与网络扫描工具结合以实现匿名扫描;然后在现有匿名系统的基础上实现了该系统的本地私有化;接着通过流量分析发现,Nmap的多进程扫描因为代理链的原因会变成单进程扫描而导致其扫描扫描性能较低;最后提出了一种基于多Namp进程并发的性能优化方案,将总体扫描任务分割为多个扫描任务,并分配给多个单独的Nmap进程并行运行。实验结果表明,该性能优化方案的扫描时延接近正常扫描情况下的时延,达到了提高匿名扫描系统性能的目的。因此,该优化后的网络匿名扫描系统在阻碍溯源的同时提升了扫描效率。 相似文献
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Sudhakar G.N.M. Karmouch A. Georganas N.D. 《Knowledge and Data Engineering, IEEE Transactions on》1993,5(5):888-894
Multimedia information management and communications systems for medical applications have been undergoing design and development. The aim of these activities has been the development of distributed computer systems providing storage, processing, and communication services required by the medical community. One of the main critical issues of such systems is the handling of multimedia information (i.e., text, images, graphics, and voice) in a uniform way and the fast access to images through the network. We present the design architecture and concepts used in our multimedia database system, along with its performance evaluation. The evaluation focuses on the response times of a multimedia medical database server, as seen by remote workstations for various retrieval and image transfer requests. For this purpose, a queueing network model was developed and simulated. Communications between the workstations and the database server are governed by the client-server model using TCP/IP and appropriate application protocols on a 10 Mb/s Ethernet LAN 相似文献
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This paper introduces DISK, a distributed Java Virtual Machine for networks of heterogenous workstations. Several research issues are addressed. A novelty of the system is its object-based, multiple-writer memory consistency protocol (OMW). The correctness of the protocol and its Java compliance is demonstrated by comparing the nonoperational definitions of release consistency, the consistency model implemented by OMW, with the Java Virtual Machine memory consistency model (JVMC), as defined in the Java Virtual Machine Specification. An analytical performance model was developed to study and compare the design trade-offs between OMW and the lazy invalidate release consistency (LI) protocols as a function of the number of processors, network characteristics, and application types. The DISK system has been implemented and running on a network of 16 Pentium III computers interconnected by a 100 Mbps Ethernet network. Experiments performed with two applications: parallel matrix multiplication and traveling salesman problem confirm the analytical model 相似文献
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Suk-Sang Chang Jin-Pyoung Lee Guk-Bae Kim Sang-Joon Lee Jong-Hyun Kim 《Microsystem Technologies》2008,14(9-11):1657-1661
Due to the weak refraction of X-rays in matter, a focusing or deflection of X-ray using conventional refractive optics was not feasible. However, since compound X-ray refractive lens (CXRL) with consecutive holes array was proposed, it becomes currently a noticeable issue in X-ray optics. In this paper, we report on fabrication and performance test of two types of PMMA (polymethyl methacrylate) CXRLs. Firstly, one dimensional refractive X-ray lenses of parabolic and circular shape is fabricated by LIGA process. Based on the results, we conduct a fabrication of 2-D CXRLs. Here we suggest a LIGA-self align method which doesn’t need a special align equipment and is simpler method than conventional one. Through performance tests, we show experimentally that CXRLs are novel optical components for the hard X-ray range of about 8 keV and that they have possibilities to apply the X-ray optics for micro-focusing, imaging, and lithography. 相似文献
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A numerical investigation on the impingement and spreading of a micro-sized droplet with nonzero impact velocities on a surface with heterogeneous wettability is presented in this paper. The numerical model was implemented through phase-field simulation with finite element formulation. A simple scheme based on interfacial phase-field function gradient was proposed to track the velocity of contact line which was required to specify the dynamic contact angle based on hydrodynamic theory and molecular kinetic approach. For a circular pattern with a higher wettability than the surrounding surface, the impinging droplet final spread diameter decreases with an increasing wettability contrast. The droplet conforms to the circular patterns with smaller diameters up to a threshold, which is dictated by the wettability of the surface surrounding the pattern. Impact velocity of the droplet affects the maximum spread diameter but not the final conformability to a wettability pattern. Impingement and anisotropic spreading of a droplet on a stripe pattern was also demonstrated in a three-dimensional simulation. The high wettability contrast between the inner and outer regions of the stripe pattern confines droplet spreading and elongates the droplet in the direction of the stripe. These simulations demonstrated the conditions for a jetted micro-sized droplet to be confined to a specific area through wettability patterning, which can potentially improve the precision of current inkjet printing technology. 相似文献
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分析计算机性能监控平台存在的不足,采用WMI和消息中间件技术,构建一种跨操作系统、跨设备的综合性能监控管理模型,通过在金融行业的具体实现证明该模型能高效管理各种IT资源,及时报告故障前兆,具备自动修复能力,可扩展性强,适用于信息高度集中的大中型企业。 相似文献
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针对典型电子支付协议存在的安全目标单一,不能满足日益提高的安全需求等问题,提出了一种能够满足认证性、密钥新鲜性、密钥秘密性、非否认性、公平性、可追究性和原子性等多种安全属性的复合型安全支付协议,该协议的认证子协议基于令牌概念设计,能够实现高效认证及会话密钥协商。通过引入公钥证书证明协议主体的身份、借助可信方传递付款收据以及采用FTP方式传送电子货币和付款收据等方式提出了支付子协议。使用逻辑分析方法对该协议进行严格逻辑推理验证,结果表明该协议能够满足多种安全属性。 相似文献
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In this paper, we propose a new method for determining the optimal base-stock level in a single echelon inventory system where the demand is a compound Erlang process and the lead-time is constant. The demand inter-arrival follows an Erlang distribution and the demand size follows a Gamma distribution. The stock is controlled according to a continuous review base-stock policy where unfilled demands are backordered. The optimal base-stock level is derived based on a minimization of the total expected inventory cost. A numerical investigation is conducted to analyze the performance of the inventory system with respect to the different system parameters and also to show the outperformance of the approach that is based on the compound Erlang demand assumption as compared to the classical Newsboy approach. This work allows insights to be gained on stock control related issues for both slow and fast moving stock keeping units. 相似文献
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使用MEMS技术研制出一种高灵敏度热温差式流量传感器。器件采用热隔离性能良好的衬底挖空结构,且热敏电阻器与热源距离可调,保证了系统的灵敏度和响应速度。同时热敏电阻器、加热电阻器与电桥电阻器集成在传感器片内,提高了系统的稳定性。实验表明:合适的电阻器间距可以获得较高的灵敏度,而在0~20 mL/min的量程范围内系统线性度较好,因此,在生化检测、医疗等领域具有良好的推广前景。 相似文献