通用关系数据库与模糊数据库的比较研究

比较了处理精确数据的通用关系数据库与基于关系数据模型的模糊数据库在关系模式、关系操作、数据库语言、概念设计方法、体系结构等方面的异同点。

逆流色谱溶质出峰顺序的预测

根据逆流色谱保留方程可知,溶质的出峰顺序主要取决于其在互不混溶的两液相间分配系数的大小顺序。以饱和及不饱和脂肪酸乙酯、2,4 二硝基苯胺基脂肪醇和对硝基苯基葡萄糖甙等结构较为简单、极性差别较大的溶质系列为研究对象,应用修正的通用基团活度系数(UNIFAC)(Dortmund)模型,通过相平衡计算,预测了它们在含水或不含水的溶剂体系中分配系数的变化趋势,并与前人的工作进行了对比。结果表明,由该方法预测出的相似结构溶质分配系数的顺序基本上与实验值相同,其中对饱和脂肪酸乙酯在己烷 乙腈(体积比为1∶1)体系中分配系数的预测最好。这种预测方法的建立将对逆流色谱非电解质溶剂体系的选择具有较大的指导意义。

低温保护剂载入关节软骨过程的传质建模

掌握加载过程中软骨组织内部低温保护剂浓度的时空分布特性,这对合理设计加载程序进而成功保存关节软骨至关重要,为此构建描述低温保护剂载入关节软骨过程的扩散传质模型。根据二元扩散热力学模型,将有效扩散系数与无限稀释扩散系数进行关联,活度系数采用UNIFAC模型估算,扩散系数的浓度依赖性采用Vignes公式表示,无限稀释扩散系数采用Siddiqi-Lucas公式计算。对于二甲亚砜(Me2SO)、甘油(GLY)、乙二醇(EG)和丙二醇(PG)这4种典型的低温保护剂(CPA),由模型计算得到的软骨组织内CPA的平均浓度与文献报道的实验值之间的平均相对偏差(MRE)和决定系数(R2)分别为1.90%~36.29%和0.959~0.998(Me2SO),13.56%~19.19%和0.990~0.995(GLY),8.89%~22.09%和0.969~0.988(EG),5.35%~23.76%和0.971~0.992(PG)。结果表明,该模型能较好地适用于这4种CPA,可用于直接预测加载过程中软骨组织内部CPA浓度的时空分布,从而指导加载程序的设计与优化。

DISTRIBUTED SIMULATION SYSTEM BASED ON UNIVERSAL COMPONENTS

Based on MATRIXx, a universal real-time visual distributed simulation system is developed. The system can receive different input data from network or local terminal. Application models in the simulation modules can automatically get such data to be analyzed and calculated, and then produce real-time simulation control information. Meanwhile, this paper designs relevant simulation components to implement the input and output data, which can guarantee the real-time and universal of the data transmission. Result of the experimental system shows that the real-time performance of the simulation is perfect.

Dynamic model of saturator based on a global heat and mass transfer coefficient

Saturator is one of the core components of humid air turbine （HAT） and is the main feature of HAT making it different from other gas turbine cycles. Due to the lack of sufficient experience in commercial plant operation, HAT cycle has a great demand for modeling and simulation of the system and its components, especially the saturator, to provide reference for system design and optimization. The conventional saturator models are usually based on the theory of heat and mass transfer, which need two accurate coefficients to ensure convincing results. This work proposes a global heat and mass transfer coefficient based on cooling tower technology to model the saturator in small-scale HAT cycle. Compared with the experimental data, the simulation results show that the proposed model well predicts the dynamic humidity and temperature distribution characteristics of saturator at low air pressure and temperature.

超临界水反应堆传热分析

超临界水堆(SCWR)是是被国际上选定为第四代核电系统长远开发的六种堆型之一,是在现有的轻水堆和超临界火电基础上开发出革新型设计。在超临界水堆的堆芯设计过程中,棒束间子通道内冷却剂流动的换热情况和子通道间的湍流交混系数的关系式是重要的参考数据。本文采用最目前世界上流行模拟软件fluent,利用gambit对子通道进行几何建模,主要分析目标为子通道间湍流交混系数β和对流换热系数h,得到换热系数在子通道中沿轴向的变化情况和子通道间湍流交混系数β在不同入口工况下的变化情况,最后拟出湍流交混系数通用经验关系式。

An XML-based approach to represent generic bill of materials

To solve the difficulty in describing the generic bill of material (GBOM) with the conventional tabular structure in a relational database system,a novel XML-based approach is presented to represent GBOM. It can represent and maintain one generic structure that encompasses all variants of a product. With the combination of product-oriented notation,this approach further gives a high degree of flexibility to support the user in the product variant specification task. The generic BOM system is then introduced for the particular product variant,and a prototype system has been developed. It is indicated that the presented approach is feasible.

Determination of reasonable finished state of self-anchored suspension bridges

A systematic and generic procedure for the determination of the reasonable finished state of self-anchored suspension bridges is proposed, the realization of which is mainly through adjustment of the hanger tensions. The initial hanger tensions are first obtained through an iterative analysis by combining the girder-tower-only finite element(FE) model with the analytical program for shape finding of the spatial cable system. These initial hanger tensions, together with the corresponding cable coordinates and internal forces, are then included into the FE model of the total bridge system, the nonlinear analysis of which involves the optimization technique. Calculations are repeated until the optimization algorithm converges to the most optimal hanger tensions(i.e. the desired reasonable finished bridge state). The "temperature rigid arm" is introduced to offset the unavoidable initial deformations of the girder and tower, which are due to the huge axial forces originated from the main cable. Moreover, by changing the stiffness coefficient K in the girder-tower-only FE model, the stiffness proportion of the main girder, the tower or the cable subsystem in the whole structural system could be adjusted according to the design intentions. The effectiveness of the proposed method is examined and demonstrated by one simple tutorial example and one self-anchored suspension bridge.

Tests and numerical simulation of aerodynamic characteristics of airfoils for general aviation applications

This paper was to validate the effects of airfoil thickness ratio on the characteristics of a family of airfoils. Research was carried out in different ways. First,tests were conducted in the wind tunnel. And numerical simulation was performed on the basis of tests. Results from calculation were consistent with tests,indicating that numerical method could help evaluate characteristics of airfoils. Then the results were confirmed by compared with empirical data. The study also showed that the determining factor of lift is not only the thickness ratio,but the angle of attack,the relative camber and the camber line. The thickness ratio appears to have little effect on lift coefficient at zero angle of attack,since the angle of zero lift is largely determined by the airfoil camber. According to the research,numerical simulation can be used to determine the aerodynamic characteristics of airfoils in different environment such as in the dusty or humid air.

Innovation and practice of TD-LTE for intelligent transportation systems (ITS)

Intelligent transportation system (ITS) has become a popular research topic to meet the increased demands of transportation safety,traffic efficiency,comfort in the journey and environment protection,etc. ITS applications impose higher requirements on wireless communication systems. For example,safety-related ITS services must always be low latency and entertainment-related ITS services need high data rate. The ITS dedicated short range communications (DSRC) technology to support the safetyrelated application is still under development, while long term evolution (LTE),as the next generation mobile communication systems,offers an efficient communication platform for ITS information exchange , which can meet most ITS services requirements of latency,data rate as well as communication range. In this paper,based on the time-division duplex (TDD) mode of LTE,i.e. TD-LTE,an enhanced TD-LTE network architecture is introduced to better support safety-related ITS application with low latency requirement,and some enhanced access schemes of TD-LTE are proposed to improve the performance of supporting the high-speed IP-based ITS applications in hotspots. At last,two practical application scenarios of enhanced TD-LTE systems are given.

Design of universal data structure and interface based on dynamic self-incremental record

In the software of data management system, there are some different lengths of records needed storing in an array, and the number of records often increases in use of the software. A universal data structure is presented in the design, and it provide an unified interface for dynamic storage records in different length, so that the developers can call the unified interface directly for the data storage to simplify the design of data management system.

Aerodynamic/mechanism optimization of a variable camber Fowler flap for general aviation aircraft

A conventional Fowler flap is designed to improve the take-off and landing performances of an aircraft. Because the flight states of general aviation aircraft vary significantly. A Fowler flap with a double-sliding track has been designed, which is ca- pable of changing airfoil camber while cruising and climbing as well as meeting low-speed performance requirements. The aerodynamic characteristics of the variable camber Fowler flap were studied by computational simulation, and cambering was found to be beneficial for improving the lift-to-drag ratio when the lift coefficient was larger than the critical value, below which decambering was more effective; this critical value differed somewhat under different conditions. Taking the mecha- nism into account, the take-off and landing configurations were optimized on the basis of the GA （W）-1 airfoil with a 30% chord Fowler flap. Compared with reference configuration, the maximum lift coefficient of optimized take-off configuration was increased by 6.6% as well as the stalling angle and the lift-to-drag ratio were increased by 1.3° and 7.58%, respectively. Moreover, the maximum lift coefficient of the optimized landing configuration was increased by 6.3%, and the stalling angle was increased by 1.1°; however, the nose-down pitching moment of both configurations increased. Similar results were at- rained on a general aviation aircraft wing/body combination nism was established in a computer-aided design system, achieved by the double-sliding track. A 3D model of the variable-camber Fowler flap driving mecha- and the results showed that all design configurations could be

超宽皮带输送机驱动功率计算方法初探

在计算超宽皮带输送机的总驱动功率时,按设计手册给定的方式无法确定其带宽系数,通过对设计手册所确定的带宽和带宽系数进行研究和分析,利用MATLAB数据拟合工具,得出带宽和带宽系数的通用函数公式,解决了超宽皮带输送机驱动功率计算问题。