生物拆分制备(S)-α-乙基-2-氧-1-吡咯烷乙酸工艺研究

耐酪氨酸冢村氏菌(Tsukamurella tyrosinosolvens)E105可选择性催化(R,S)-α-乙基-2-氧-1-吡咯烷乙酸乙酯生物拆分制备左乙拉西坦关键手性中间体(S)-α-乙基-2-氧-1-吡咯烷乙酸.通过单因素实验和响应面法对菌株产酶培养条件进行优化,并考察含酶静息细胞催化制备(S)-α-乙基-2-氧-1-吡咯烷乙酸的反应过程.结果表明:最优产酶培养条件为装液量30%,接种量4%,发酵36h;培养基组成为葡萄糖17.70g/L,酵母膏16.53g/L,NH4Cl 9.5g/L,K2HPO42g/L,KH2PO41g/L,NaCl 0.6g/L,MgSO4·7H2O 0.5g/L,初始pH值7.32.在优化条件下,酶活力为19.33U/g,细胞干重达4.13g/L,分别较优化前提高了32.6%和60.1%.当细胞加量为30g/L,底物浓度60mmol/L,反应体系为300mL,拆分24h后,产率和ee值分别为48%和99%,(S)-α-乙基-2-氧-1-吡咯烷乙酸浓度达28.8mmol/L,较优化前提高了32.1%.     

Virt-RSBAC:一种防御云计算内部威胁的框架

针对来自云计算平台的内部威胁,为了保护云用户的隐私,缓减平台提供者的安全监控需求与用户隐私之间的策略冲突,本文提出一种虚拟化环境下的特权控制框架Virt-RSBAC。通过在虚拟机监视器（VMM）中添加特权控制和基于角色的资源隔离规则,实现对特权域管理权限的分离,简化对云用户的管理,借助于创建相互信任的安全虚拟机（SVM）为云平台提供者和云用户提供安全服务。最后,在Xen上实现了该框架的原型,实验与分析表明该框架能够防止恶意管理员获取用户隐私并提供检测功能,对原有系统的性能损耗在可接受范围内。     

电涡流缓速器结构参数的节能优化设计

分析了电涡流缓速器的节能特性,提出了两个适用于电涡流缓速器的节能评价指标:制动增益系数和单位质量能量密度。以此评价指标为目标函数,建立了电涡流缓速器结构参数的节能优化设计数学模型。运用遗传算法寻求设计变量的全局最优解。获得的最优解表明:基于节能设计的优化结果优于以最大制动力矩为目标函数的优化结果,对电涡流缓速器的结构设计有一定的指导意义。     

基于路面使用性能评价的车辙指标研究

文章基于现有沥青路面使用性能评价规范和标准,运用简化的车辙积水模型,围绕高速公路沥青路面车辙深度主观评价标准,针对现有车辙评价模型的不足,通过采用Sigmoid函数,主要探索了车辙深度指数RDI评价模型。结果表明:结合求解的车辙内不致积水的临界车辙深度,将路面车辙深度等级划分为更精细的"轻、中、重"三个等级更加合理;优化的沥青路面车辙深度指数RDI评价模型弥补了现有车辙评价指标的不合理性;在保留现有车辙深度指数评价模型的同时,通过分析路面车辙槽的几何特征增加了车辙的其他指标,初步构建了车辙综合评价模型,对全面评价车辙的危害性及进行路面车辙的养护管理更具有实际意义。     

神龙城投资的分析与预测模型及推广

为了反映不同因素对湖南省株洲市神龙城商业圈发展的影响,将人口数量、居民人均可支配收入和商业区的住房成本作为商业圈发展的主要影响因素,并运用层次分析法判断该城市房价的合理性。进一步利用回归分析法,将3个影响因素作为变量,通过商业圈房价的未来走势来预测神龙城商业圈未来的发展。最后借助Matlab软件和有关数据对模型进行了检验,发现预测结果与实际结果比较吻合,有一定的通用性。     

枝向量矩阵反馈环算法的MATLAB实现*

找到系统中的全部反馈环是系统动力学模型分析的基础。针对这一问题,比较了几种常见的反馈环计算方法,得出在时间复杂度上矩阵算法优于行列式算法。在计算机上用MATLAB实现了基于流率基本入树和强简化流率基本入树枝向量矩阵计算所有反馈环的矩阵算法,分析了算法的复杂性,并给出了相应的算例。     

GJT25-09型煤层气专用固井半挂车研制

煤层气勘探开发井的钻井深度浅、固井作业压力低、水泥浆用量少,使用常规固井设备时操作复杂、经济性不高。采用一体化结构设计,实现固井车的混浆单元、泵送单元、供灰单元、供气单元的集成设计。利用“双泵合流-双马达串/并联切换”技术,实现设备全液压驱动,开发了煤层气专用固井半挂车,并介绍了该车的技术参数、技术与结构特点、测试应用情况。可对煤层气固井作业起到较好的降本增效作用,对煤层气的大力开发提供支持。     

Bioelectrochemical sulfate reduction enhanced nitrogen removal from industrial wastewater containing ammonia and sulfate

Low organic carbon-to-nitrogen ratio and existing sulfate (SO₄²⁻) in industrial wastewater limited nitrogen removal. Coupling SO₄²⁻ reduction with sulfide autotrophic denitrification provides a novel strategy. Herein, bioelectrochemical sulfate reduction was coupled with heterotrophic sulfate reduction to drive sulfide autotrophic denitrification. In this coupled system, total nitrogen (TN) removal efficiency was increased from ~25% to ~85% by inputting −45 mA electricity. With the help of supplying electrons to denitrification through SO₄²⁻ reduction, coulomb efficiency was improved to 61.5%. Also, bioelectrochemical sulfate reduction could improve sulfur recovery and thus increase TN removal efficiency. Furthermore, through tuning turnover numbers of SO₄²⁻, high TN removal efficiency can be obtained at various concentrations of SO₄²⁻. Moreover, main functional bacteria in this system were identified. Finally, ~75% TN removal efficiency was achieved with real wastewater in this system. Overall, this work offered a new approach for efficient nitrogen removal from industrial wastewater containing SO₄²⁻.     

Roles of interaction between components in CZZA/HZSM-5 catalyst for dimethyl ether synthesis via CO2 hydrogenation

The roles of interaction between two catalyst components in CuO–ZnO–ZrO₂–Al₂O₃ (CZZA)/HZSM-5 bifunctional catalyst for dimethyl ether (DME) synthesis via carbon dioxide hydrogenation were investigated. It was found that CZZA catalyst showed excellent stability during methanol (MeOH) synthesis for 100 h, while there was a severe loss of catalytic activity in the bifunctional catalyst for DME synthesis. Hence, the effects of different degrees of intimacy of two catalyst components were studied for DME synthesis, including mixed and separated modes. For the mixed mode, the particle size of catalysts and the amount of reaction intermediates were proven to influence the catalyst deactivation. For the separated mode, the catalysts showed rapid deactivation within a short time. Various characterizations indicated that the remarkable deactivation of separated mode was mainly caused by the decrease of copper active centers (e.g., sintering and oxidation) and blockage of acid sites via increased coke deposition on HZSM-5.     

Theoretical study on composition-dependent properties of ZnO·nAl2O3 spinels. Part II: Mechanical and thermophysical

Knowledge on the mechanical and thermophysical properties of ZnO·nAl₂O₃ is essential for practical applications. Based on the first-principles calculations and the bond valence method, the disordered spinel-type structure of ZnO·nAl₂O₃ (n = 1–4) was constructed to investigate the composition-dependent mechanical and thermophysical properties. The effects of cation substitution on the hardness, elastic modulus, thermal expansion, and thermal conductivity were revealed from the insights into the chemical bonds. At a higher n, the tetrahedral bond is stronger, manifested as its higher hardness and bulk modulus as well as smaller thermal expansion coefficient. Meanwhile, the octahedral bond is weaker, leading to the lower hardness and bulk modulus, along with the larger expansion coefficient. In consequence, the hardness and elastic moduli of ZnO·nAl₂O₃ are improved moderately while the expansion coefficient is decreased with the rise of n. Due to the different vibration characteristics of Zn^IV and Al^IV, the cation disorder in the 8a site provides the primary source of phonon scattering, resulting in the dramatic reduction of thermal conductivity as n increases. The understanding offers guidance on the application-oriented design of new oxide spinels.