Ab initio calculations on the mechanism of isobutane and 2-butene alkylation reaction catalyzed by hydrofluoric acid

Ab initio method was employed to determine the mechanism of alkylation reaction of 2-butene with isobutane. The results indicated that 2-butene is rapidly protonated to form sec-butyl carbonium ion, which then reacts with isobutane to form tert-butyl carbonium ion. The resulting carbonium ion is then deprotonated to form isobutene that reacts rapidly with tert-butyl carbonium ion to form trimethylpentane (TMP) carbonium ion. Finally, the TMP⁺ carbonium ion is converted to TMP via the hydride transfer process. The transition states of the interactions were obtained by using the SCAN method (a calculation key word for potential energy surface) first and then the intrinsic reaction coordinates were traced using the Gaussian program. In addition, the energy changes and geometric parameters of the interactions were analyzed. The computed results indicated that the energy barriers are close to or less than zero for the interaction of isobutane with protonated 2-butene or for the interaction of tert-butyl carbonium ion with isobutene, suggesting rapid reaction steps of the carbonium ions. The 2,2,3-TMP is kinetically controlled, while the formation of 2,2,4-TMP is controlled by reaction equilibrium. The calculated results were in good agreement with the experimental results.     

Electron microscopic observations and DNA chain fragmentation studies on apoptosis in bone tumor cells induced by ~(153)Sm-EDTMP

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贝氏体钢内水冷穿孔顶头的粘钢及防止措施

从顶头生产工艺控制的角度,分析了贝氏体钢内水冷穿孔顶头产生粘钢的原因、特点和机制,指出掉鼻、缺肉是顶头粘钢的另一种更为严重的失效形式,强化熔炼工艺控制和保证夹杂物总量在A0.5B1C0.5D1级水平,粘钢问题可以得到有效控制。     

军械调运方案优化算法的设计与仿真

军械调运问题的数学模型和手工算法过去已有研究,但是当问题较为复杂时,手工算法就要花费大量时间而且准确性也难以保证。针对这一缺陷,本文在已有的数学模型和手工算法的基础上,设计了一种可以用计算机实现的基于递归的算法来寻求军械紧急调运问题的最优方案,并使用面向对象的java语言将算法实现。     

万安水利枢纽底孔坝段中隔墙流激振动响应分析

 研究了万安水利枢纽底孔坝段中隔墙在水流脉动壁压作用下的结构随机振动问题，进行了一种泄流工况下的隔墙结构流激振动响应统计量的理论计算，模拟计算了隔墙－水流－基础耦合系统固有频率对流激振动响应的影响，并对水流脉动壁压随机荷载作用下的结构动力可靠度进行了理论分析。     

Study on phase behavior–impact strength relationship of unsaturated polyester/polyurethane hybrid polymer network

The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties.     

Lubricating behavior of iron rhenate and its relation to matching pairs

The iron rhenate was compounded by chemical method, which may be generated during wear process of Fe-Re alloys at elevated temperature. The friction coefficient of iron rhenate has been determined by a pin-on-disc device. The results show that iron rhenate plays role of lubricating at RT-600 °C. The lubricating behavior is related to the matching pairs. The hardness of the materials of matching pairs, compatibility of iron rhenate with materials of matching pairs and surface roughness of disc affect the lubricating behavior of iron rhenate mostly. The principle of matching pairs is proposed. Project supported by the National Natural Science Foundation of China Synopsis of the first author Xiong Dangsheng. associated professor, born in 1960. Current research fields include high-temperature self-lubricating alloys and tribological properties of material.     

Constant boost control of the Z-source inverter to minimize current ripple and voltage stress

This paper proposes two constant boost-control methods for the Z-source inverter, which can obtain maximum voltage gain at any given modulation index without producing any low-frequency ripple that is related to the output frequency and minimize the voltage stress at the same time. Thus, the Z-network requirement will be independent of the output frequency and determined only by the switching frequency. The relationship of voltage gain to modulation index is analyzed in detail and verified by simulation and experiments.