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1.
Residential fire sprinklers have long proven themselves as life-safety technologies to the fire service community. Yet, about 1% of all one- and two-family dwelling fires occur in homes protected by sprinklers. It has been argued that measured sprinkler performance has ignored factors confounding the relationship between sprinkler use and performance. In this analysis, sprinkler performance is measured by comparing ‘like’ structure fires, while conditioning on smoke detection technology and neighborhood housing and socioeconomic conditions, using propensity score matching. Results show that residential fire sprinklers protect occupant and firefighter health and safety, and are comparable to other life-safety technologies. 相似文献
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Abstract In order to assure safety and serviceability, structural responses are kept within certain limits by active control methods. Control forces as well as responses (displacement and velocity) are considered constraints in an optimal control system. The exact solution of the optimal control system under the aforementioned constraints is derived in the first part of the paper. An approximate solution is also suggested in the paper. An example dealing with a six‐story building is presented in the last part of the paper to demonstrate the application of the approximate approach. 相似文献
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Recent experimental techniques in multicolor waveform synthesis allow the temporal shaping of strong femtosecond laser pulses with applications in the control of quantum mechanical processes in atoms, molecules, and nanostructures. Prediction of the shapes of the optimal waveforms can be done computationally using quantum optimal control theory. In this work we demonstrate the control of above-threshold photoemission of one-dimensional hydrogen model with pulses feasible for experimental waveform synthesis. By mixing different spectral channels and thus lowering the intensity requirements for individual channels, the resulting optimal pulses can extend the cutoff energies by at least up to 50% and bring up the electron yield by several orders of magnitude. Insights into the electron dynamics for optimized photoelectron emission are obtained with a semiclassical two-step model. 相似文献
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就一类离散非线性系统的迭代学习控制 ,提出了最优迭代因果学习律的存在性条件 .如果迭代初态严格重复 ,则迭代输出收敛于期望输出 .该结论直接推广了线性离散系统最优迭代学习相关结果 相似文献
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Distributed arrival time control (DATC) is a heuristic feedback control algorithm for scheduling which has been developed for a real-time distributed scheduling of heterarchical systems. It has been renowned not only for its fast solution searching algorithm but also for its flexibility to changing environment. However, the optimality of this heuristic method has not been analytically explained until recently because it has been designed to discover a near optimal solution instead of the true optimum. In this paper, we provide a novel optimal search method for the DATC scheduling problem by introducing a scalar cost function over the vector space of time and show the existence and location of true optima for the DATC scheduling problem through geometric approach. This geometrical interpretation enables us to find the true optimal by direct projection without iterations like previous DATC approaches. Based on the true optimum found, we evaluate the optimality of DATC algorithms by examining their dependency on initial conditions and explain their intrinsic causality mechanism for the discrepancy with true optimum. The implication of this study is on the new viewpoint over the vector space of DATC, which not only solves the optimality issue of DATC but also provides a new direction of direct search approach like projection method for the true optimum. 相似文献
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A. Masserey J.‐R. Poirier 《International journal for numerical methods in engineering》2005,62(12):1721-1736
We consider an optimal control problem arising in an induction heating process. The main difficulty is to obtain accurate and efficient derivatives of the discrete form of the cost function. In this work we use automatic differentiation. Unlike numerical differentiation based on finite differences, derivatives generated by automatic differentiation are free of truncation error. Numerical results show the performance of the method in terms of accuracy and computational efficiency. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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在分析了压水型反应堆功率控制系统的前提下,针对其特殊的控制要求,运用基于输出反馈的次最优控制的设计方法和Matlab中的NCD模块,最终实现了系统的优化设计,并对系统进行了某一功率水平下的仿真试验和其它工况下的鲁棒性试验.结果表明。改进后的系统性能有了较大改善。 相似文献
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The control chart based on cumulative count of conforming (CCC) items between the occurrence of two non‐conforming ones, or the CCC chart, has been shown to be very useful for monitoring high‐quality processes. However, as in the implementation of other Shewhart‐type control charts, it is usually assumed that the inspection is free of error. This assumption may not be valid and this may have a significant impact on the interpretation of the control chart and the setting of control limits. This paper first investigates the effect of inspection errors and discusses the setting of control limits in such cases. Even if inspection errors are considered, the average time to alarm increases in the beginning when the process deteriorates. Since this is undesirable, the control limits in the presence of inspection errors should be set so as to maximize the average run length when the process is at the normal level. A procedure is presented for solving this problem. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
9.
Yasumichi Tatsumi Mitsuhiro Kimura Shigeru Yamada 《Quality and Reliability Engineering International》1999,15(3):229-233
The initial production phase of new products or the initial installation phase of new manufacturing facilities is often unstable because of inexperienced workers and many defective products. An initial production process control, in which the defects in design, production technologies and products are fully fixed and removed, is switched to a normal process control whenever it is ready for actual mass production. This paper discusses a method of deciding the optimal initial production control period, based on a quality growth model. It is determined by the number of products with the minimum expected total quality control cost. Finally a penalty cost due to unattainable loss to the quality goal is introduced in the quality control cost: the realized stabilization level of the initial production process control is lower than the original quality objective. Numerical illustrations of the optimal policy are also presented. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
10.
Guanyu Wang 《Journal of the Royal Society Interface》2012,9(75):2723-2734
Bistability is a fundamental phenomenon in nature. In biology, a number of fine properties of bistability have been identified. However, these properties are only consequences of bistability at the physiological level, which do not explain why it had to emerge during evolution. Using optimal homeostasis as the first principle, I find that bistability emerges as an indispensable control mechanism. It is the only solution to a dilemma in glucose homeostasis: high insulin efficiency is required to confer rapidness in plasma glucose clearance, whereas an insulin sparing state is required to guarantee the brain''s safety during fasting. The optimality consideration renders a clear correspondence between the molecular and physiological levels. This new perspective can illuminate studies on the twin epidemics of obesity and diabetes and the corresponding intervening strategies. For example, overnutrition and sedentary lifestyle may represent sudden environmental changes that cause the lose of optimality, which may contribute to the marked rise of obesity and diabetes in our generation. Because this bistability result is independent of the parameters of the mathematical model (for which the result is quite general), some other biological systems may also use bistability to control homeostasis. 相似文献
11.
Ferrero F Muñoz M Kozanoglu B Casal J Arnaldos J 《Journal of hazardous materials》2006,137(3):1293-1302
By performing a series of pool fire experiments, the authors attempt to apply knowledge of thin-layer boilover to the large scale (pool diameter from 1.5 to 6 m). Two commercial hydrocarbons were used: gasoline and diesel. As expected, only in the case of diesel did the phenomenon of thin-layer boilover occur. Data were used to analyze various features of thin-layer boilover in fires, particularly its intensity and onset time. A comparison with results published in the literature shows the importance of this study. 相似文献
12.
针对动态供应链系统中市场需求扰动引起的牛鞭效应问题,提出一种基于前馈补偿的最优跟踪控制设计方法.首先,针对需求扰动可模型化为线性外系统的情形,引入了一个渐近稳定的期望系统;然后,基于线性二次型性能指标,给出了受需求扰动的供应链系统的前馈反馈最优跟踪控制器设计方法.控制器的反馈增益和前馈增益可分别通过求解Riccati方程和Stein方程得到.仿真结果表明,提出的前馈反馈最优跟踪控制方法能有效抑制需求扰动对供应链系统的影响,改善供应链系统的动态性能,且该方法明显优于经典的最优跟踪控制. 相似文献
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摘要 在线消除转子系统的振动对保证旋转机械的可靠和高效运行是至关重要的。在转子振动控制初期,需要一个试探性的控制力,该力可能会使系统振动加剧或减小,这取决于控制力与原激振力相位之间的关系。为此本研究在转子系统动力学及电磁力可控特性分析的基础上对控制力相位进行区域划分,建立系统寻优控制模型并提出具体寻优策略;采用有限元分析的方法获取工作转速下转子系统理论滞后角,初步确定控制力相位;以此相位值作为寻优参数起始值,按照既定寻优策略实现转子自动平衡控制,并确保控制全过程转子振幅不大于初始不平衡故障振幅;最后建立实验台并对算法进行实验验证,结果表明该方法是有效的。 相似文献
14.
The emissive power (E) of a flame depends on the size of the fire and the type of fuel. In fact, it changes significantly over the flame surface: the zones of luminous flame have high emittance, while those covered by smoke have low E values. The emissive power of each zone (that is, the luminous or clear flame and the non-luminous or smoky flame) and the portion of total flame area they occupy must be assessed when a two-zone model is used. In this study, data obtained from an experimental set-up were used to estimate the emissive power of fires and its behaviour as a function of pool size. The experiments were performed using gasoline and diesel oil as fuel. Five concentric circular pools (1.5, 3, 4, 5 and 6m in diameter) were used. Appropriate instruments were employed to determine the main features of the fires. By superimposing IR and VHS images it was possible to accurately identify the luminous and non-luminous zones of the fire. Mathematical expressions were obtained that give a more accurate prediction of E(lum), E(soot) and the average emissive power of a fire as a function of its luminous and smoky zones. These expressions can be used in a two-zone model to obtain a better prediction of the thermal radiation. The value of the radiative fraction was determined from the thermal flux measured with radiometers. An expression is also proposed for estimating the radiative fraction. 相似文献
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本文提出系统振动最优控制问题的优化方法。首先给出最优线性二次控制的控制力 ,然后根据实际控制目标建立关于权值的约束条件 ,优化控制性能指标 ,以达到最优控制效果。最后 ,通过一个简单例子加以说明。 相似文献
17.
In the present context, optimal portion control refers to the process of preparing can‐filling portions so that the deviation of the portion weight from a specified target weight is minimized. An approach has been developed for achieving this where a batch of objects is placed in a linearly overlapped optimal arrangement and then cut into portions using a series of parallel blades. The parameters of optimization are the arrangement order, orientation and degree of overlap of the objects. The approach has been demonstrated to produce impressive improvements in the application of fish canning. For this application, two approaches of optimal cutting are compared in the present paper. In one approach, the blade spacing is kept fixed and constant at a predetermined value. In the second approach, the blade spacing is varied for each portion after the objects are placed according to the optimal arrangement, where the target weight distribution is allowed to vary within a tolerance interval. The results presented in this paper indicate that the second approach produces a significantly higher percentage of acceptable portions than the first approach. What is presented are results from computer simulations, utilizing true data as measured from actual batches of fish. The paper demonstrates the potential benefit of the optimal portion control approach when applied in an industrial fish‐canning process. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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This paper considers the optimal determination of the length of the production run and the initial setting of a process that exhibits a linear drift that can start at a random point in time. Quadratic off‐target costs and time‐based costs of maintenance and salvage value are included in the formulation. The model includes other models proposed in the literature as particular cases. Numerical examples are provided to illustrate the application of the proposed model. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
20.
Aurelio A. de los Reyes V Eunok Jung Yangjin Kim 《Journal of the Royal Society Interface》2015,12(106)
Glioblastoma, the most aggressive type of brain cancer, has median survival time of 1 year after diagnosis. It is characterized by alternating modes of rapid proliferation and aggressive invasion in response to metabolic stress in the microenvironment. A particular microRNA, miR-451, and its downstream signalling molecules, AMPK complex, are known to be key determinants in switching cell fate. These components form a core control system determining a balance between cell growth and migration which is regulated by fluctuating glucose levels in the microenvironment. An important factor from the treatment point of view is that low levels of glucose affect metabolism and activate cell migration through the miR-451-AMPK control system, creating ‘invisible’ migratory cells and making them inaccessible by conventional surgery. In this work, we apply optimal control theory to deal with the problem of maintaining upregulated miR-451 levels that prevent cell infiltration to surrounding brain tissue and thus induce localization of these cancer cells at the surgical site. The model also considers the effect of a drug that blocks inhibitive pathways of miR-451 from AMPK complex. Glucose infusion control and drug infusion control are chosen to represent dose rates of glucose and drug intravenous administrations, respectively. The characteristics of optimal control lead us to investigate the structure of optimal intravenous infusion regimen under various circumstances and predict best clinical outcomes with minimum expense possible. 相似文献