OLAP核心技术—数据立方体的研究现状与展望

该文从OLAP的基本功能出发，综述了其核心技术－数据立方体（Data Cube)的研究现状，主要讨论了3个方面：数据立方体建模，数据立方体计算和数据立方体操作，最后展望了该领域的研究方向。     

Discrete Simulation of a Class of Distributed Systems Using Functional Analytic Methods

This paper investigates the discrete simulation of the solution of initial-boundary-value problems that typically arise in technical areas. Since many of them lead to unbounded and non-self-adjoint differential operators, we have to use a rather general theory as a mathematical basis. For the class of sectorial operators with a compact resolvent operator, the solution of initial-boundary-value problem can be represented by means of a certain holomorphic semigroup. It is shown that the solution can be expanded with respect to the canonical system of the considered operator. Such an expansion corresponds to a multi-dimensional functional transformation in the frequency domain. This fact leads to simple structures for the realization of the resulting system. Computationally efficient numerical algorithms can be derived by proper methods well-known from the theory of digital signal processing. Published online: April 2006     

气相色谱在煤气热值成分分析中的应用

各大钢铁企业均需分析煤气的热值成分并计算煤气的热值以满足不同生产部门的需要，气相色谱同时使用毛细管柱和填充柱混合色谱柱，兼备毛细管柱和填充柱的优点；采用自动切换载气的办法，实现对钢铁企业煤气中轻烃和永久性气体的分析。文章分析了气相色谱检测煤气热值组分的准确度和精密度，并对气体组分多点校正标准曲线进行了研究。结果表明，气相色谱分析煤气组分时具有很高的准确度和精密度，多点校正曲线也具有很好的回归线性，完全可以应用于煤气的热值成分分析。     

Design patent map visualization display

Design patent map is an important strategic tool for establishing design strategies. Of types of patents, design patents occupy a unique patent field, since design patents are not as definitive as other patent fields. Therefore, the construction of design patent map is extremely difficult. Until now, in world-renowned patent periodicals, studies on design patent map have not been found; thus, this study is very innovative. In this study, design patents from between 2005 and 2007 in the United States were selected, 74 patent samples in the car industry were selected as research subjects. Ten design patent examiners who have an average of 10 years of patent evaluation experience in the Taiwan Intellectual Property Office (TIPO) and 29 industrial designers who have had an average of over 3 years of design experience are enlisted to assist in construction of design patent map. Corporations can use the concrete steps provided by this study, with the multi-dimensional scale, to establish a design patent map and use this to form patent strategies. This strategic tool will become a new tool for competition for firms facing the knowledge economy era!     

Steady-state heat conduction in multi-layer bodies

The mathematical formulation of the steady-state temperature field in multi-dimensional and multi-layer bodies is presented. The numerical examples are for two-layer bodies and they include boundary conditions of the first, second, and third kind. This study includes tables to assist the selection of eigenfunctions and computation of the eigenvalues. The computations include the contribution of contact resistance to the temperature solution. An efficient computational scheme for calculating the eigenvalues is used. For multi-dimensional, multi-layer bodies, the eigenfunctions are real if each layer is homogeneous; they may become imaginary if layers are orthotropic.     

Exploiting sequential access when declustering data over disks and MEMS-based storage

Due to the large difference between seek time and transfer time in current disk technology, it is advantageous to perform large I/O using a single sequential access rather than multiple small random I/O accesses. However, prior optimal cost and data placement approaches for processing range queries over two-dimensional datasets do not consider this property. In particular, these techniques do not consider the issue of sequential data placement when multiple I/O blocks need to be retrieved from a single device. In this paper, we reevaluate the optimal cost of range queries by declustering two-dimensional datasets over multiple devices, and prove that, in general, it is impossible to achieve the new optimal cost. This is because disks cannot facilitate two-dimensional sequential access which is required by the new optimal cost. Then we revisit the existing data allocation schemes under the new optimal cost, and show that none of them can achieve the new optimal cost. Fortunately, MEMS-based storage is being developed to reduce I/O cost. We first show that the two-dimensional sequential access requirement can not be satisfied by simply modeling MEMS-based storage as conventional disks. Then we propose a new placement scheme that exploits the physical properties of MEMS-based storage to solve this problem. Our theoretical analysis and experimental results show that the new scheme achieves almost optimal I/O costs. Recommended by: Sunil Prabhakar This research is supported by the NSF grants under IIS-0220152 and CNF-0423336.     

传感器网络中基于多维标度定位算法的改进

针对基于经典多维标度的MDS-MAP算法在定位精度方面的不足,为提高传感器定位精度,提出一种基于Euclidean算法的改进型多维标度定位算法(Euclidean-based MDS-MAP(P,C))。算法与经典多维标度算法的区别在于,Euclidean算法能够算出每个节点与其两跳邻居节点间的欧氏距离,然后用这个欧氏距离来进行多维标度,显然能提高精度。仿真实验表明基于Euclidean算法的改进型多维标度算法与经典多维标度算法相比具有很低的定位误差以及很高的定位精度。     

柴油机缸内辐射换热的多维数值模拟研究

对柴油机来说,辐射换热极为重要,在缸内总传热量中占有非常大的比重,直接关系到发动机热效率及因传热引起的各种热负荷、热强度问题,同时,辐射换热对燃烧系统的研究也十分重要,辐射热流量会深刻影响内燃机的燃烧性能,对发动机的各种燃烧产物的形成产生至关重要的影响。为此,利用离散传递法实现柴油机缸内辐射换热的多维数值模拟,通过多维模拟计算同时考察燃烧室部件表面发射率及喷雾提前角对柴油机缸内辐射换热的影响。结果表明：活塞的辐射热流量峰值高于缸盖的辐射热流;缸盖的辐射热流量的最大值并不在中心位置处,而是随时间变化;随着壁面辐射率的增加,缸内向燃烧室部件辐射换热量逐渐增大;喷雾提前角直接影响所有燃烧室部件表面的辐射热流密度。     

Charge stratification to control HCCI: Experiments and CFD modeling with n-heptane as fuel

An optimized reduced mechanism of n-heptane including 42 species and 58 elementary reactions adapted to charge stratification combustion is developed first in this study. Some engine experiments and a fully coupled CFD and reduced chemical kinetics model with n-heptane as fuel are adopted to investigate the combustion processes of HCCI-like charge stratification combustion aimed at diesel HCCI application. For premixed/direct-injected stratification combustion, the low temperature reaction occurs in the regions with homogeneous fuel first and high temperature reaction begins from high fuel concentration regions involved in the spray process. With the increase of the injection ratio, the high temperature reaction occurs in advance, the pressure rise rate reduces, UHC emissions decrease and CO emissions increase. At larger injection ratio, the onset of the high temperature reaction advances and the maximum pressure rise rate decreases with the retarding of injection timing. UHC and CO emissions have relation to the fuel spray penetration at different injection timings. NO_x emissions increase rapidly with the increase of the stratification degree.     

Condensation heat transfer with noncondensable gas for passive containment cooling of nuclear reactors

Noncondensable gases that come from the containment and the interaction of cladding and steam during a severe accident deteriorate a passive containment cooling system's performance by degrading the heat transfer capabilities of the condensers in passive containment cooling systems. This work contributes to the area of modeling condensation heat transfer with noncondensable gases in integral facilities. Previously existing correlations and models are for the through-flow of the mixture of steam and the noncondensable gases and this may not be applicable to passive containment cooling systems where there is no clear passage for the steam to escape. This work presents a condensation heat transfer model for the downward cocurrent flow of a steam/air mixture through a condenser tube, taking into account the atypical characteristics of the passive containment cooling system. An empirical model is developed that depends on the inlet conditions, including the mixture Reynolds number and noncondensable gas concentration.