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春节前后,吉安市遭遇到罕见的冰冻雨雪灾害天气,连续出现了低温、阴雨和雨夹雪,成为全省灾情最严重地区之一.特别是1月25日以后,出现了持续大范围的雨雪冰冻天气.冰冻损坏了市区的电网,压垮了树枝,封锁了道路和桥梁. 相似文献
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收集了2010年7月~2011年6月世界塑料工业的相关资料,介绍了2010~2011年世界塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况。按通用热塑性树脂(聚乙烯、聚丙烯、聚氯乙烯、聚苯乙烯、ABS树脂),工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚),特种工程塑料(聚苯硫醚、液晶聚合物、聚醚醚酮),通用热固性树脂(酚醛、不饱和聚酯树脂、环氧树脂、聚氨酯)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍。 相似文献
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萜类化合物具有可观的经济价值,但是目前的生产过程复杂、产量低。酿酒酵母甲羟戊酸途径为萜类化合物的合成提供直接前体,因此酿酒酵母细胞具有合成异源萜类化合物的天然优势。对酿酒酵母甲羟戊酸途径的清晰认识是对其进行有效利用的基础,本文从代谢途径、关键酶的特点和全局调控机制3个方面对该途径进行了介绍。从代谢途径的构建和优化、模块与底盘细胞的适配、模块构建及组装方式的角度概述了酿酒酵母细胞异源合成单萜、倍半烯萜、二萜、三萜类化合物的研究进展。指出实现酿酒酵母高效合成萜类化合物所需要解决的基础问题是对酿酒酵母甲羟戊酸途径进行更为全面了解和对萜类化合物的天然代谢途径进行明确解析;另外,合成生物学的进一步发展也将为此提供应用基础。 相似文献
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我公司回转窑规格为Φ4.0m×60m.窑内使用的耐火砖为镁铬砖、隔热尖晶石、蓝晶石和黏土砖以及硅莫砖.镁铬砖规格为(81×90×150×200)mm,其它耐火砖规格皆为(81×90×200×200)mm.尽管每个品种的砖品质相同,但由于在镶砌和使用过程中方法不同,寿命有长有短.通过多年实践,现总结如下. 相似文献
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《日用化学品科学》编辑部 《日用化学品科学》2008,31(6)
2006年12月7日~2006年12月8日化妆品化学家年会在美国纽约举行,该年会为化学品供应商提供了参与REACH法规的机会.REACH法规的实施引起了业界的广泛关注,来自世界各地的著名化学品及化妆品公司对REACH法规的实施所带来的一些问题,以及新原料、新技术进行了交流.会议主要对就REACH法规、制造及规模化和神经美容品等方面展开了研讨. 相似文献
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Rosendo Monroy-Loperena Jose Alvarez-Ramirez 《Chemical Engineering Communications》2002,189(7):923-941
This paper addresses the problem of designing an indirect feedforward controller, also called cascade control, to regulate the product composition of distillation columns to overcome load disturbances. The overall controller is composed of two cascaded controllers. The primary controller is basically a low-gain controller, which uses slow (delayed) composition measurements to provide servo responses (composition control). The secondary controller has the structure of a high-gain proportional-integral (PI) controller with an antireset windup scheme, which uses fast temperature measurements at a given distillation tray to track the output of the primary controller. In this way, the secondary controller also provides protection against load disturbances. A simulated example is used to illustrate the functioning of the proposed controller. 相似文献
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Rosendo Monroy-Loperena Jose Alvarez-Ramirez 《Chemical Engineering Communications》2013,200(7):923-941
This paper addresses the problem of designing an indirect feedforward controller, also called cascade control, to regulate the product composition of distillation columns to overcome load disturbances. The overall controller is composed of two cascaded controllers. The primary controller is basically a low-gain controller, which uses slow (delayed) composition measurements to provide servo responses (composition control). The secondary controller has the structure of a high-gain proportional-integral (PI) controller with an antireset windup scheme, which uses fast temperature measurements at a given distillation tray to track the output of the primary controller. In this way, the secondary controller also provides protection against load disturbances. A simulated example is used to illustrate the functioning of the proposed controller. 相似文献
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无模型控制器与PI控制器的性能对比分析 总被引:2,自引:0,他引:2
通过仿真,比较CyboCon无模型单输入单输出控制器、基于鲁棒性能指标设计的PI控制器和基于经验整定方法设计的PI控制器在对象模型精确和模型变化情况下的控制性能,得出CyboCon无模型单输入单输出控制器与基于经验整定方法设计的Pl控制器在性能上是相同的,基于鲁棒性能指标设计的PI控制器设计时应该考虑约束条件。 相似文献
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以水合法制丙二醇为例,利用Ziegler-Nichols法及经验法考察了CSTR反应器配备的比例控制器(P)、比例积分控制器(PI)及比例积分微分控制器(PID)的控制参数对CSTR反应器控制效果的影响,进而确定其优化的控制参数值。动态模拟结果表明:当配备P型控制器且控制参数kc=2×107时,控制效果最好,但存在控制余差;当配备PI型控制器时,利用Ziegler-Nichols法对控制参数进行调试;当配备PID型控制器时,采用与PI型控制器相同的控制参数整定方法,能够满足对CSTR反应器的控制要求。 相似文献
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Assessment of control loop performance is one of the important tasks to be carried out in a plant, regardless of the control strategy. The present work utilizes the shape information from single relay feedback test to assess the performance of a feedback system. The process considered is a typical first-order plus dead time process and the controller used is PI type of controller. An ideal relay is introduced in the feedback loop before the controller. The shape of the relay output characterizes the performance of the controller. The mismatch in the integral time can also be observed from the shape. Based on the shape information, analytical expressions for relay feedback responses are derived and straightforward procedures are evolved to assess the performance of the controller. The proposed scheme assesses the controller performance and computes the new tuning parameters, in case retuning of the controller is necessary. The robustness of the method is also tested for second-order plus dead time as well as for higher order systems. More importantly the present approach employs only one relay test for (1) assessment and (2) retuning of the controller. It provides a reliable way that is compatible even to a non-expert operator to assess the controller performance. 相似文献
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针对催化剂生产过程中焙烧窑炉温度控制问题,提出了一种启发式动态规划(heuristic dynamical programming,HDP)控制方法。该方法通过策略评价及策略提升的重复进行逐渐逼近最优的控制策略。采用人工神经网络建立了被控系统和评价指标模型,基于梯度下降原理阐明了控制器各模块的在线学习方法。对某催化剂公司的窑炉温度控制实验表明,与常规PID控制相比,HDP控制方案具有较强的工况适应能力,其控制精度较常规控制提高约70%,加热电流均值减小约5%。 相似文献
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介绍直流调速系统工作原理,在分析模糊PID控制器原理的基础上,充分结合传统PD控制响应速度快和模糊PID控制精度高的特点,设计了一种阈值型模糊PID算法,应用于直流电机调速系统。通过在MATLAB/Simulink中与传统PID控制进行仿真分析对比,证明了这种算法的有效性。 相似文献
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A dynamic model of an alfalfa rotary dryer was developed and used to test the performance of two different feedback controllers. One controller is a conventional PI (Proportional-Integral) controller with fixed tuning parameters whereas the other is a gain-scheduled PI controller with automatically adjusted tuning parameters. The performance of the two controllers was compared with the performance of the dryer under manual control. The gain-scheduled PI controller was found to be superior in the sense that it used less control action and achieved the same control performance as the fixed tuning parameter PI controller. The use of the gain-scheduled controller was shown to reduce energy consumption, increase dryer throughput and had an estimated pay-back time of nine months. 相似文献
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A method of design for an adaptive PID controller in an “actual” form is developed. The controller is expressed as an ideal PID controller with a low-pass filter. The parameters of the controller are determined by using the ITAE criterion based on a first-order plus dead time model which is directly obtained from an identified second-order model. In comparison with the ideal PID controller, the actual one gives better results especially for systems with noises. 相似文献