迷失在塑料袋时代

让人看着舒服的塑料袋是有的:极富装饰感的设计、洁净的外表、内里装了精致的礼品或是衣物,看似不经意地拎在手里,心里却是在享受着袋子里面那一份钟爱的物品带来的喜悦,这时候的塑料袋是实用而知趣的,毫不张扬,却恰如其分地代表了主人的品位。当印有高尚品牌标志的塑料袋     

气相色谱分析中丢峰原因浅析

对N－甲基苯胺色谱分析中出现丢峰现象的种种作了细致的分析，并对避免出现丢峰现象的预防措施作了阐述。     

10kV配网进线电缆的失压检测

分析10kv配网进线电缆在失压又得电的情况下,计算机后台监控系统发出错误信号报警的原因。采取了有效的PLC失压检测技术,可靠地保障了10kv配网供电系统的正常供电。     

怎样避免蒸汽疏水阀失效

提出疏水阀选择和应用设计中应注意的问题 ,以便能够长期稳定地运行。     

循环冷却水系统蒸发损失的计算与分析

利用国内某些水处理专业书中介绍循环水系统蒸发损失的计算公式,对三个实际工况进行计算,发现利用这些计算公式计算出的结果和通过进出口空气容量、通风量等进行精确计算出的结果相差较大,分析了蒸发损失相差大的原因,提出企业应根据不同的用途来计算循环水蒸发损失量。     

劳动合同法下用人单位败诉节点提示

从用人单位法律适用实务操作角度出发,结合作者在司法实践中的多年经验,探寻劳动合同法框架下用人单位最容易败诉的节点并给予提示,尽量以简练的几句话进行剖析并提供解决方案,给用人单位在适用劳动合同法时提供一些有益的参考.     

某食品厂洗水罐意外失稳分析

食品轻工行业中经常使用一些大型的不锈钢储罐和容器,由于节约原因,这类设备通常常造得很薄,在进行蒸汽消毒或热水清洗过程中,常会出现内部真空而导致罐体失稳(凹陷)。究其原因,多数是由于设计不良(通气口设置过小、未设置真空漏放装置或操作不当所致。     

进口刀盘圆环失效原因及改进

首先从材料力学角度分析了抚顺石化公司干法腈纶装置原进口切断刀盘圆环失效的原因 ,认为此种切断刀盘圆环系二维增强结构层压板 ,层间没有纤维增强 ,需要解决由二维增强向三维增强的过渡。给出了改进办法 ,寻求到三维增强的替代材料。同时介绍了机械加工测试及在线实验     

圆模成型三角带底胶失效的机理分析

从橡胶三角带的生产工艺出发,分析了圆模成型橡胶三角带传动失效机理,为橡胶三角带的设计和制造提供了科学依据。     

Complex Mutation Pattern of Omicron BA.2: Evading Antibodies without Losing Receptor Interactions

BA.2, a sublineage of Omicron BA.1, is now prominent in many parts of the world. Early reports have indicated that BA.2 is more infectious than BA.1. To gain insight into BA.2 mutation profile and the resulting impact of mutations on interactions with receptor and/or monoclonal antibodies, we analyzed available sequences, structures of Spike/receptor and Spike/antibody complexes, and conducted molecular dynamics simulations. The results showed that BA.2 had 50 high-prevalent mutations, compared to 48 in BA.1. Additionally, 17 BA.1 mutations were not present in BA.2. Instead, BA.2 had 19 unique mutations and a signature Delta variant mutation (G142D). The BA.2 had 28 signature mutations in Spike, compared to 30 in BA.1. This was due to two revertant mutations, S446G and S496G, in the receptor-binding domain (RBD), making BA.2 somewhat similar to Wuhan-Hu-1 (WT), which had G446 and G496. The molecular dynamics simulations showed that the RBD consisting of G446/G496 was more stable than S446/S496 containing RBD. Thus, our analyses suggested that BA.2 evolved with novel mutations (i) to maintain receptor binding similar to WT, (ii) evade the antibody binding greater than BA.1, and (iii) acquire mutation of the Delta variant that may be associated with the high infectivity.     

正交设计法合成共聚物型水泥降失水剂的研究

本文利用2-丙烯酰胺基-2-甲基丙磺酸(AMPS)／丙烯酰胺(AM)／丙烯酸(AA)三种单体,根据自由基聚合原理,合成一种三元共聚物型油井水泥降失水剂。利用正交设计法设计了实验方案,分别考察了单体配比、反应温度、引发剂用量和链转移剂用量等因素对其降失水性能的影响,并对产物进行了’红外光谱、差热分析和N、S元素的测定。分析表明单体配比和反应温度是影响聚合物降失水性能的主要因素,并得到了最佳的合成方案：AMPS：AM：AA=50：42：8,反应温度70℃,引发剂用量2％,链转移剂用量6％。     

Al2O3陶瓷高温釉氢烧失光原因的研究

本文总结并实验对比了国内外的几种高温釉,从而提出釉料化学性质、釉料中氧化铁等变价元素以及原料矿物组成是导致氢烧釉面失光的主要因素,并成功试制出适宜于氧化铝陶瓷以及1450℃金属化工艺的高温釉。     

电除尘器失效分析及整改探讨

阐述了3＃石灰窑电除尘器失效原因分析以及相应的整改措施,提出了一些探讨性的意见。     

苯酐粗制装置部分设备失稳原因分析及对策

对苯酐生产粗制装置中的苯酐冷凝热熔箱体气体进口管道、离心鼓风机空气过滤器和粗苯酐槽在异常工况条件下产生的失稳原因进行了分析,提出了相应的改进和预防对策。实施后取得了较好的效果。     

Condensed-phase control? Or gas-phase control?

Publishing the discussion of two famous researchers in the field of solid propellant combustion, the Editorial Board has to mention that the issues discussed have a long story. The ideas on the leading role of solid-phase reactions in combustion of double-base and composite propellants were formulated by P. F. Pokhil approximately 40 years ago (Combustion, Explosion, and Shock Waves, 1969, Vol. 5, No. 3). Simultaneously, he emphasized that the burning rate in the general case depends on interaction of all stages in the combustion wave. Up to now, it was only an experiment that could offer reliable proof of the existence of some particular mechanism of combustion, and critical discussions of available experimental information are of crucial importance. In this connection, it should be noted that the considerations of the leading role of gas-phase reactions at elevated pressures presented in this discussion can also be revised, because, with appropriate kinetics of solid-phase chemical reactions, their role can become dominating with increasing pressure (and surface temperature). __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 134–136, March–April, 2007.     

Three mode control as an optimal control

Three mode control with Ziegler-Nichols or Cohen-Coon controller settings is shown to be the solution to an optimal control problem for a linear first order system with dead time and a quadratic cost functional. The implication of this result is that in the absence of an economically meaningful cost criterion there is no reason to prefer the results of optimal control theory to traditional design procedures for feedback control systems. The multivariable generalization of the optimal control problem solved here provides the means for extending classical control experience in design of single loop processes to multivariable control systems     

发酵罐温度对象的抗干扰预测控制

啤酒发酵过程由于反应机理复杂,其温度对象目前很难建立精确的数学模型,现阶段针对这类大时滞对象的一些典型的控制算法在模型不精确的情况下,难以取得好的控制效果,尤其当存在不可预测的干扰时,控制效果更难保障。因此本文针对啤酒发酵罐温度控制中的这一问题,基于动态矩阵控制的一步控制的思想,将时间最优控制与动态矩阵控制相结合,形成一种能快速抑制扰动的预测控制策略。通过仿真结果验证该控制策略能对干扰进行快速抑制,对发酵罐温度对象有较好的控制效果。     

串级控制对过程预测控制的影响分析与对策

化工过程控制中普遍设置以流量控制为副回路的串级控制来实现对温度、液位和成分等被控变量的控制。预测控制的操作变量在很多情况下也是流量,其控制作用的实现要靠底层的流量控制回路。本文针对由于现场串级控制结构不允许改变,流量副回路只能接收温度等主控制器的输出作为其给定值,造成上层预测控制的操作变量无法直接下载到流量控制回路的问题,分别提出了一种将上层优化输出通过一阶惯性滤波作用于主回路控制器和一种将串级控制中流量对主被控变量的传递函数嵌入预测控制模型的实施方案,通过Shell标准重油分馏塔的控制问题进行仿真实验证明了两种方案的可行性,并对其控制性能进行了比较分析。两种方法理论上构思简单,实际中易于实现,具有普遍适用性。     

过程控制实验装置的计算机控制

介绍了过程控制实验装置的计算机控制系统的组成及功能特点。控制对象为水槽液位和贮罐压力, 对相应的控制系统作了简介。通过实例给出了测试步骤。