飞机三级式发电系统建模与仿真

在飞机电源系统的优化设计中,飞机发电系统为机载用电设备正常工作提供条件,而在负载发生突变情况下能否快速做出反应以保证供电质量和可靠性能,直接影响到飞机的性能.为保证可靠性,分析了飞机三级发电系统组成结构和工作原理,建立飞机发电系统仿真模型的基础上,设计了用于调节电能质量的控制器——调压器,在MATLAB/Simulink环境下建立整个系统的模型,并对飞机发电系统部分进行动态仿真.仿真结果表明,能较真实的反应飞机电源系统的动、静态性能,证明所建立的模型是正确的,采用的方法是可行的,为飞机电源系统的设计提供有效的研究手段与参考依据.     

企业组织模型结构和建模方法研究

组织建模对于企业实施先进制造战略具有重要意义。文章在研究分析了多种组织结构形式的基础上,应用工作流和过程建模等概念和方法,定义了一种新型的企业组织模型结构,通过引入新型建模元素,可以更为全面地描述企业组织静、动态层次结构,并可以表现业务过程到组织的映射。基于该结构,采用面向对象和构件化方法,提出了一种柔性的、数据表达一致并且可以有力地支持过程模型的动态执行的组织建模方法,并开发了相应的软件工具。     

Ada中实时结构的Petri网建模与分析

本文从一般时间网出发，派生出一种简单时间网，并建模了延迟，分支选择，异步选择，优先权等Ada实时结构，特别是把优先权处理为一种时间特性，这样不仅扩充了Petri网在Ada中的建模能力，同时可以更加准确刻画Ada程序行为。     

三级监控系统的设计和实现

论文介绍了一套三级监控系统的设计与实现。该监控系统采用了三级分层树形结构,能够同时对多个监控点进行监控,适用于LAN、PSTN、ISDN等多种网络,传输全数字化的视频与音频信息。文章中对该系统的整体组成、硬件结构以及软件设计等方面都进行了较为详细的讨论。     

Bacillus fordii MH602海因酶序列及同源建模分析

海因酶是5-取代海因生物转化制备手性氨基酸的关键酶.通过同源建模法建立MH602海因酶的三维结构,经分析,91.3%的氨基酸残基在可信区间,无氨基酸残基在不可信区间,而且能量处于较低水平,此模型可进一步研究.将MH602海因酶序列和PDB数据库中现有的6个海因酶序列比较(PDB编号为:1KID,1YNY,1NFG,1GKP,1GKQ,1GKR),结果显示了保守的活性位点残基(4个HIS,1个ASP),3个立体化学环(SGLs)和底物环外侧链结合的残基(MET63,PHE65,LEU94,PHE152,TYR155,VAL158,LEU159).通过比较发现MH602海因酶在159位是LEU,比其他海因酶的PHE159提供更大的底物结合空间,可能降低了对映体选择性但增加了对羟基苯海因的活力.为利用定点突变改造酶分子,提高MH602菌株生产L氨基酸的能力提供理论指导.     

基于UML技术高职院校矩阵式组织结构建模

目前我国许多高职院校正处在二级管理变革中,需要直面的问题就是组织结构调整。文章讨论了高职院校如何利用新型组织结构,借助UML技术,以最快和最合理的方式建立具有柔性和实用性的组织模型,依据该模型进行组织结构调整,以期在今后的竞争中取得先机。     

基于UML的C4KISR体系结构建模技术研究

C4KISR系统存在系统规模庞大、开发研制周期长、耗资巨大、技术复杂、对抗性和实时性强、涉及部门和人员多、观念相异等问题,仿真技术为这类问题地解决提供了一条捷径,而建模技术对仿真的有效实施提供了保障.本文在深入分析C<'4>KISR体系结构和功能模型基础上,提出采用UML技术对C<'4>KISR体系结构进行建模,该方法将静态模型和动态模型相结合,采用图形化设计,大大提高系统设计开发效率.     

牛血清白蛋白的同源模建与结构解析

鉴于蛋白质数据库(PDB)中尚无牛血清白蛋白(BSA)这一重要模式蛋白物的结构信息,本文采用同源模建的方法,基于BSA和人血清白蛋白(HSA)的高序列同源性(76．52%),以HSA与血红素(heme)复合物(1n5u)为模版,应用Modeller8．0模拟软件,完成了BSA的结构解析：其高级结构呈心形,由3个相似的结构域组成,每一结构域由10个螺旋片段构成,顺次包含2个亚域A、B;分子中共有35个Cys残基,17对二硫键,形成8对双二硫桥,并构成9个环;二级结构主要为α-螺旋,占67%,无β-折叠,其余为舒展而柔顺的转角。上述结构信息可为涉及BSA的各项理论研究提供重要的基础数据。     

人尿酸氧化酶结构的同源模建和生物信息学分析

以微生物来源的尿酸氧化酶晶体结构为模板,根据推测的人尿酸氧化酶序列,利用同源模建技术预测人尿酸氧化酶的三维结构。人尿酸氧化酶结构具有两个相同的T-fold结构域。叠合不同来源的尿酸氧化酶结构证实,人尿酸氧化酶与其他来源尿酸氧化酶的活性中心的结构高度保守。另外找到一些不利于人尿酸氧化酶聚合的因素,这些因素可能是使人尿酸氧化酶基因在进化中失活的部分原因。     

Development of a structural equation modeling-based decision tree methodology for the analysis of lung transplantations

Lung transplantation has a vital role among all organ transplant procedures since it is the only accepted treatment for the end-stage pulmonary failure. There have been several research attempts to model the performance of lung transplants. Yet, these early studies either lack model predictive capability by relying on strong statistical assumptions or provide adequate predictive capability but suffer from less interpretability to the medical professionals. The proposed method described in this paper is focused on overcoming these limitations by providing a structural equation modeling-based decision tree construction procedure for lung transplant performance evaluation. Specifically, partial least squares-based path modeling algorithm is used for the structural equation modeling part. The proposed method is validated through a US nation-wide dataset obtained from United Network for Organ Sharing (UNOS). The results are promising in terms of both prediction and interpretation capabilities, and are superior to the existing techniques. Hence, we assert that a decision support system, which is based on the proposed method, can bridge the knowledge-gap between the large amount of available data and betterment of the lung transplantation procedures.     

Comparative molecular modeling study of the three-dimensional structures of prostaglandin endoperoxide H2 synthase 1 and 2 (COX-1 and COX-2)

To understand the structural features that dictate the selectivity of diverse nonsteroidal antiinflammatory drugs for the two isoforms of the human prostaglandin H₂ synthase (PGHS), the three-dimensional (3D) structure of human COX-2 was assessed by means of sequence homology modeling. The ovine COX-1 structure, solved by X-ray diffraction methods and sharing a 61% sequence identity with human COX-2, was used as template. Both structures were energy minimized using the AMBER 4.0 force field with a dielectric constant of 4r. (S)-Flurbiprofen, a nonselective COX inhibitor, and SC-558, a COX-2-selective ligand, were docked at the cyclooxygenase binding site in both isozymes, evidencing the role of different residues in the ligand–protein interaction. The 3D structures of the constructed four ligand–enzyme complexes were refined by energy minimization. Molecular dynamics simulations were also carried out, to understand more deeply the structural origins of the selectivity. Distances calculated during the dynamics process between the different ligands and the interacting residues of the two PGHS isozymes provided evidence of the flexible nature of the cyclooxygenase active site, permitting the identification of different conserved and nonconserved residues as responsible for ligand selectivity.     

Modeling the material grading and structures of heterogeneous objects for layered manufacturing

The emphasis of this work is to discuss a scheme for modeling the material grading and structures of heterogeneous objects. To model the material grading of a heterogeneous object, a termed ‘grading source’ is defined. The grading sources are reference features, which specify the type and position of grading, and a material grading function for controlling the material variation within the geometric boundary of the objects. Within the proposed modeling scheme, a concept on representing objects, which are both heterogeneous in material and structure (e.g. composite laminates), will also be elaborated. For downstream layered manufacturing purposes, a contour sub-division algorithm on each layer arising from slicing a heterogeneous object is proposed. Within each slice, the material grading is decomposed into sub-contours according to the different grading variation. A parameter called ‘grading step-width’ is defined to control the number of sub-contours and resolution of the grading. With such discretization, it is, therefore, possible to build a heterogeneous object on layered manufacturing machines of different fabricating precision specification.     

Modeling and characteristic analysis of underwater acoustic signal of the accelerating propeller

The signal feature of propeller cavitation noise during acceleration or deceleration procedure can be used to passively detect and classify moving vessels and underwater vehicles in the port regions.By analyzing the chirp periodicity of the variation of propeller wake velocity under acceleration situation,this paper presents a time domain expression of the modulation envelope signal of the accelerating propeller noise,treating the signal as a Gaussian-shaped chirp periodic pulse train with increasing trend and fluctuating pulse amplitude.The paper investigates the characteristics of simplified fractional Fourier transform(SFRFT)spectrum of the chirp periodic signal,and thus obtains the relation between the chirp periodic signal and its chirp harmonics under the conditions of underwater passive detection.Furthermore,the experimental data of the cavitation tunnel satisfy the results obtained by simulation,which verifies the correctness of the proposed signal model.     

加速螺旋桨水声信号建模及其特性分析

加速或减速旋转螺旋桨的水声信号特征可用于被动探测与分类离靠港船只或水下航行器.文中从阐述螺旋桨匀加速旋转时尾流速度周向变化所具有的chirp周期特性出发,提出匀加速螺旋桨空化噪声的幅度调制包络可通过脉冲间幅度起伏的chirp周期高斯脉冲串信号予以建模,并给出了该模型的时域表达式.文中分析了chirp周期信号的简化分数阶Fourier变换谱特性,得到了在一定条件下chirp周期信号与其谐波系数间的关系式.文中通过水洞试验数据分析与仿真数据分析的比较,验证了匀加速螺旋桨噪声调制包络信号模型的合理性.     

西替利嗪及其盐酸盐电子结构及CD谱的理论解析

采用量子化学密度泛函理论在B3LYP/6-31++G~(**)水平上对西替利嗪及其盐酸盐分子几何构型进行了优化;在优化的基础上进行红外光谱(IR)、振动圆二色谱(VCD)、紫外光谱(UV)和电子圆二色谱(ECD)研究。计算结果表明:盐酸盐中Cl~-与季胺N~+之间的静电吸引作用可能通过Cl…H—N氢键作用进行传递。涉及到或者靠近手性中心的振动在VCD谱上表现出强的Cotton效应;远离手性中心的振动,尽管在IR谱上出现较强的吸收,在VCD谱上也可能不产生Cotton效应。ECD谱分析发现,涉及到手性中心的电子跃迁,在ECD谱上产生Cotton效应。