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71.
Don Kelleher 《Information Systems Journal》1995,5(2):137-157
Abstract. An Information Systems Methodology is usually presented as a sequential set of tasks — planning, analysis, design and construction — resulting in a new business application. This classical 'forward-engineering' approach must be adapted to changing business needs — business process redesign, quality management, process and systems templates, advanced technologies, application packages, the reuse of existing information systems resources, and rapid delivery cycles. Using the most general concept of a Business Programme, this paper describes a methodological approach incorporating these modern themes that is qualitatively and quantitatively different from the classical model. It provides a framework for the integration of otherwise independent methodologies, and shows how an entire programme can be formulated, planned and executed. An example is provided, and the approach is justified. 相似文献
72.
合成了十六烷基辛基二甲基溴化铵和十六烷基癸基二甲基溴化铵两个新型杀生剂。用元素定量分析和红外光谱核磁共振谱等方法进行分析和结构鉴定。评定了两个化合物对硫酸盐还原菌的杀生作用。结果表明,两个化合物有很好的杀生效果。 相似文献
73.
A. Kussmaul S. Vernon P. C. Colter R. Sudharsanan A. Mastrovito K. J. Linden N. H. Karam N. H. Karam S. C. Warnick M. A. Dahleh 《Journal of Electronic Materials》1997,26(10):1145-1153
We have used spectroscopic ellipsometry to perform real-time monitoring during metalorganic chemical vapor deposition growth
of AlGaAs (on GaAs) and InGaAs (on GaAs and InP). Optical constants for these materials were obtained up to growth temperatures
of 600 to 700°C. This information permits real-time extraction of composition and layer thickness from the raw ellipsometric
data at sample rates on the order of 0.5 Hz. We describe closed-loop control of composition and total layer thickness on AlGaAs-based
structures, including Bragg reflectors. In-situ data obtained on double-heterostructure quantum-well laser structures demonstrate that spectroscopic ellipsometry is an extremely
powerful monitoring and quality-control tool, giving important real-time information on complex structures that would be difficult
and time-consuming to obtain after growth. 相似文献
74.
一种新型声波降粘防蜡装置 总被引:1,自引:1,他引:0
新型声波降粘防措装置由上、下接头、振动簧片和收缩喷嘴构成。装置安装在抽油泵泵简之下,尾管之上,在压差作用下井下流体以较大速度从装置的喷嘴射出,冲击振动簧片,产生机械振动声波,油水混合液在声波中产生相应的声波力学效应和分散乳化作用等,使混合液在油管内的粘度降低,蜡晶不易聚集长大,从而达到降粘防蜡延长油井热洗周期的目的。室内试验及现场近20口井的应用情况表明,这种装置具有结构简单、成本低廉、应用方便等特点,具有明显的降粘防蜡效果。 相似文献
75.
This paper presents a highly stable steady-state torque control system with a feedback of a secondary current signal. The torque control system is constructed with a feedback of the secondary current (I2) signal using a quick response magnetic-field sensor constructed with an amorphous core multivibrator bridge, which can solve the secondary resistance change problem for temperature variation in the IM. Moreover, we added a state feedback to the system to improve the response speed for the unit step function of a torque order. The I2 sensor method has advantages especially at a low-speed range, in which conventional method using an integrator shows control errors. 相似文献
76.
离散事件动态系统的代数模型及其控制器的分析计算 总被引:4,自引:2,他引:2
本文在离散事件动态系统的Petri网图形描述的基础上建立了相应的代数模型,该模型可以用来计算无竞争无回路Petri网的“最大状态”;该“最大状态”的计算在本文给出的动态反馈控制器中得到了应用。 相似文献
77.
78.
128kb/s电视电话系统中数码率缓存器的控制策略研究 总被引:2,自引:0,他引:2
本文探讨了电视电话/会议电视的H,261建议中低码率时(p=2)数码率缓存器的控制问题,提出一种既有宏观预分配又有微观分割的控制策略(简称GALS),并用测试图像序列进行了计算机模拟。将本文方法与RM8中有关策略作了比较,实验结果表明图像的主观质量有所改善。 相似文献
79.
The paper addresses the design of two-level power system stabilizers using an optimal reduced order model whose state variables are torque angles and speeds. The reduced order model retains their physical meaning and is used to design a two-level linear feedback controller that takes into account the realities and constraints of electrical power systems. The two-level control strategy is used, and a global control signal is generated from the output variables to minimize the effect of interactions. The effectiveness of this controller is evaluated and a multimachine system is given as an example to illustrate the advantages of the proposed method. Responses of the system with a two-level scheme and an optimal reduced order scheme are included for comparative analysis. 相似文献
80.
Tucker Don M.; Luu Phan; Frishkoff Gwen; Quiring Jason; Poulsen Catherine 《Canadian Metallurgical Quarterly》2003,112(4):667
Functional neuroimaging suggests that limbic regions of the medial frontal cortex may be abnormally active in individuals with depression. These regions, including the anterior cingulate cortex, are engaged in both action regulation, such as monitoring errors and conflict, and affect regulation, such as responding to pain. The authors examined whether clinically depressed subjects would show abnormal sensitivity of frontolimbic networks as they evaluated negative feedback. Depressed subjects and matched control subjects performed a video game in the laboratory as a 256-channel EEG was recorded. Speed of performance on each trial was graded with a feedback signal of A, C, or F. By 350 ms after the feedback signal, depressed subjects showed a larger medial frontal negativity for all feedback compared with control subjects with a particularly striking response to the F grade. This response was strongest for moderately depressed subjects and was attenuated for subjects who were more severely depressed. Localization analyses suggested that negative feedback engaged sources in the anterior cingulate and insular cortices. These results suggest that moderate depression may sensitize limbic networks to respond strongly to aversive events. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献