Stochastic models for performance analysis of multistate flexible manufacturing cells

Performance analysis of flexible manufacturing cells (FMCs) can help companies find the pros and cons of production processes. However, the emphasis has been on issues like cell formation, layout design and scheduling optimization. Little seems to have been done to assess the reliability of an FMC. In this paper, we develop the stochastic models for the performance analysis mainly on the reliability of two different FMCs configured from a set of teaching intelligent flexible manufacturing system (TIFMS). The closed form solutions of probabilities of system states are obtained. Then, utilization rate of equipment in the cell and productivities of the two FMCs as the performance indexes are calculated and optimized. Compared to simulation methods, the closed form solutions make calculations of the performance indexes faster and more accurate. When random variables in the stochastic models are assumed to follow non-exponential distributions, the effects of them on the performance indexes are discussed. The objective of this paper is to fill up the gap that the closed form solutions are difficult to obtain as the number of machine tool increases. Another objective is to optimize the performance indexes to help engineers better evaluate the performance of FMC. Numerical analysis cases are used to illustrate the proposed stochastic models.     

直觉模糊推理的三I约束算法

研究了直觉模糊推理三I约束算法,给出了IFMP、IFMT问题的直觉模糊推理三I约束算法解的表达形式和分解形式,在此基础上,指出了直觉模糊推理三I约束算法是模糊推理三I约束算法的推广,并给出了相应的证明。     

Solitary waves,homoclinic breather waves and rogue waves of the (3+1)-dimensional Hirota bilinear equation

In this paper, the $(3+1)$-dimensional Hirota bilinear equation is investigated, which can be used to describe the nonlinear dynamic behavior in physics. By using the Bell polynomials, the bilinear form of the equation is derived in a very natural way. Based on the resulting bilinear form, its $N$-solitary waves are further obtained by using the Hirota’s bilinear theory. Finally, by using the Homoclinic test method, we obtain its rational breather wave and rogue wave solutions, respectively. In order to better understand the dynamical behaviors of the equation, some graphical analyses are discussed for these exact solutions.     

一种自由曲线廓形误差的高效可靠评价方法

为实现对自由曲线廓形误差的高效可靠评价,提出了一种结合多项式方程求根与 实数编码遗传算法(RCGA)的评价方法。首先,根据最小二乘准则建立了廓形误差评价的优化模 型;进而,通过构造多项式方程,并采用 Halley 迭代对方程求根,实现了点到自由曲线距离的 高效计算;然后,采用 RCGA 完成了优化模型的求解,并与分割逼近法得到的结果进行了对比。 结果表明,该方法高效可靠,相同条件下计算时间约为分割逼近法的 5%,能够满足自由曲线 廓形误差的评价。     

Incipient fault detection with smoothing techniques in statistical process monitoring

In modern industry, detecting incipient faults timely is of vital importance to prevent serious system performance deterioration and ensure optimal process operation. Recently, multivariate statistical process monitoring (MSPM) techniques have been extensively studied and widely applied to modern industrial systems. However, conventional fault detection indices utilized in statistical process monitoring are not sensitive to incipient faults with small magnitude. In this paper, by introducing two representative smoothing techniques, novel incipient fault detection strategies based on a generic fault detection index in MSPM are proposed. Fault detectability for each proposed strategy is analyzed. In addition, the effects of the smoothing parameters on fault detection, including advantages and disadvantages, are also investigated. Finally, case studies on a numerical example and two practical industrial processes are carried out to demonstrate the effectiveness of the proposed incipient fault detection strategies.     

CVI改性泡沫炭的研究

化学气相渗透技术是制备高性能C/C复合材料的一种重要方法。采用均热式CVI炉，对400℃不同压力下制备的泡沫炭进行化学气相渗透。分析了泡沫炭在CVI处理中的沉积过程，通过SEM观察了泡沫炭沉积形貌和热解炭的微观结构，测试了材料的力学性能。结果表明：利用CVI工艺能在较短的时间内对泡沫炭进行有效的致密，降低显气孔率。其中400℃，5MPa条件下制备的泡沫炭，CVI前后显气孔率下降最明显，由77.7%降到55.6%，降幅达到近30%；体积密度在CVI前后也显著增大，在400℃，5MPa条件下，由最初的0.434g/cm^3增大到0.825g/cm^3，增大0.9倍以上。泡沫炭基体中沉积一定量的热解炭，可以显著提高泡沫炭的抗压缩强度。400℃，4MPa制备条件下，CVI前后压缩强度增大将近6倍。     

利用IT重塑景德镇陶瓷企业的成功组织形态

本文着重分析了现在景德镇陶瓷企业的组织特点、IT对组织结构变革的影响以及IT对商业技术的新发展,指出利用飞速发展的信息技术,景德镇地区的陶瓷业可以避免资金缺乏,组织规模过小的竞争弱势,建立一个新型成功企业组织形态和商业生态环境,以设计和技术优势重塑品牌,改进销售渠道,重新取得景德镇地区陶瓷业在全球陶瓷市场中的竞争优势。     

手性药物的活性分析与生物转化

手性药物有着不同的药理活性,对人体产生各种生理效应,对其进行合理的分离纯化可以减小药物的毒副作用,增强药效,同时能够带来巨大的经济效益.手性药物的分离已成为当今新药开发的一个重要领域,积极寻找有效的分离方法是药物纯化分离的关键.利用生物手段对药物进行分离起源较晚,但由于其独特的优点,现今已经成为药物分离的热点.     

陶瓷污泥中微量镉催化光度法测定

利用还原型若丹明B(RRhB)与KClO3的显色反应,对含镉(Ⅱ)陶瓷污泥中痕量镉(Ⅱ)进行测定。结果表明,在pH5.3HAc-NaAc缓冲溶液中具有高灵敏的显色反应,产物的最大吸收波长为560nm,方法的检出限为3.0×10-8gCd2 /L,催化程度与镉(Ⅱ)量在0～0.045mg/L范围内符合比耳定律,加标回收率为97.4%～103.8%(n=6)。结合KI—MIBK萃取分离,满意地测定了陶瓷污泥中的微量镉。     

一种新型气固分离器内气相流场的数值模拟

针对催化裂化原料日益重质化的趋势,提出了一种后置烧焦管式组合再生工艺. 后置烧焦管出口的气固分离装置是实现这种工艺的关键设备之一. 为此,设计了一种基于离心与惯性分离原理相结合的新型气固分离器.为了详细研究该分离器,结合流场实验结果,采用数值模拟方法对该分离器内的气相流场进行了数值模拟,数学模型为标准湍流模型.模拟结果给出了分离器内的流场总体特征为:气流以切向速度为主,竖直向上进入分离器的气体绕排气管做旋转运动,先后由排气管上的窄缝排出,部分气体由排气管下方空间返回入口区;拱形分离空间内切向气速随径向位置的增加而减小.排气管上的开缝形式是分离器压降增加的主要因素.将排气管上的两条窄缝改成总面积与排气管内截面积相等的均匀切向窄缝,避免了管内旋流涡核的偏心,分离器压降明显降低.