Using situation calculus for e-business agents

As the Internet grows, it is becoming less feasible for customers and merchants to manually visit each web site, analyze the information there, and make sound business decisions regarding the trading of goods or services. To cope with this evolution, software agents can be designed that are capable of automating the more routine, tedious, and time-consuming tasks involved in current trading processes. At a higher level agents may also be able to negotiate and make autonomous decisions and commitments on behalf of their owners.

This paper describes an agent implementation using the situation calculus, which offers a possibly unifying paradigm for dynamic agents. Interesting applications are currently being developed. Our contribution is a situation calculus agent system developed for e-business. Ongoing work is focused on implementing this system in an open marketplace environment.     

A model for volume lighting and modeling

Direct volume rendering is a commonly used technique in visualization applications. Many of these applications require sophisticated shading models to capture subtle lighting effects and characteristics of volumetric data and materials. For many volumes, homogeneous regions pose problems for typical gradient-based surface shading. Many common objects and natural phenomena exhibit visual quality that cannot be captured using simple lighting models or cannot be solved at interactive rates using more sophisticated methods. We present a simple yet effective interactive shading model which captures volumetric light attenuation effects that incorporates volumetric shadows, an approximation to phase functions, an approximation to forward scattering, and chromatic attenuation that provides the subtle appearance of translucency. We also present a technique for volume displacement or perturbation that allows realistic interactive modeling of high frequency detail for both real and synthetic volumetric data.     

From safety analysis to software requirements

Software for safety critical systems must deal with the hazards identified by safety analysis. This paper investigates, how the results of one safety analysis technique, fault trees, are interpreted as software safety requirements to be used in the program design process. We propose that fault tree analysis and program development use the same system model. This model is formalized in a real-time, interval logic, based on a conventional dynamic systems model with state evolving over time. Fault trees are interpreted as temporal formulas, and it is shown how such formulas can be used for deriving safety requirements for software components     

Eigenvalue sensitivity analysis of stiffened plates with respect to the location of stiffeners

This paper formulates the eigenvalue sensitivity of a stiffened plate with respect to stiffener location; the analysis is based on the generalized Rayleigh quotient of the combined platebeam system. The results show that the eigenvalue sensitivity is proportional to the force between the plate and the stiffener as well as to the slope of the eigenfunction at the interface between the plate and the stiffener.     

Dynamic adaptation of network connections in mobile environments

Most network applications assume continuous connectivity-an assumption that does not “migrate” to wireless environments. The authors present the design of a communication layer for mobile computing that dynamically adapts to changes in network connections. Our work was part of AMIGOS (Advanced Mobile Integration in General Operating Systems), a collaboration between researchers at the University of Copenhagen in Denmark and the University of Minho in Portugal. The AMIGOS project provides transparent support for semi connected operations on mobile computers running a standard operating system; the project home page is at http://www.econ.cbs.dk/people/birger/AMIGOS/. Briefly, our design lets a mobile user connect a mobile host to a LAN, then disconnect the host from it. The user then can reconnect, for example, via a Global System for Mobile Communications (GSM) cellular modem without losing TCP/IP connections. We want to allow existing TCP/IP based applications to be used in a mobile environment, without application modifications     

Extrudate expansion model in a twin-screw extrusion cooking process considering melt rheological property

A new extrudate bulk density model framework was developed, which is taking into account the melt rheological effects based on mixing principle and non-Newtonian power law theory for a twin-screw extrusion cooking process. The main ingredients in the extrusion process investigation were wheat, fish meal and soybean protein. The average absolute deviation (AAD) of the model prediction for extrudate bulk density is 5.3 % for the investigated process. The prediction results demonstrate that the proposed equation can be used to model the extrudate bulk density in the twin-screw extruder extrusion cooking process.     

Electric Properties of Semiconductor Nanopillars

We studied the electrical transport through epitaxial, 8 nm long and about 100 nm diameter, GaAs pillars. They are fabricated with molecular beam epitaxy using a self-assembling method called local droplet etching. The nanopillars are embedded in an AlGaAs tunneling barrier between two epitaxial GaAs layers. Because of the epitaxial growth, the pillars are connected to these GaAs layers without additional interfaces. They thus can be considered as electronic point contacts between three-dimensional electron reservoirs. Voltage-current characteristics of the structures feature a characteristic asymmetry that is not observed in reference samples. Furthermore, the behavior of the resistance in magnetic fields applied parallel and perpendicular to the current direction is compared for samples with and without pillars. Clear differences are found that are associated with current-carrying states in the pillars.     

明式家具的丹麦知音

<正>即使在北欧人力费用极高的情况下,卡尔·汉森·桑仍以近乎苛刻的标准进行手工制作,并将这份永恒的经典和淡然的精致传递给全世界的使用者。丹麦设计界流传着这样一则故事:1807年,英国轰炸丹麦首都哥本哈根。时任丹麦国王下令从斯德哥尔摩南部到汉堡北部,用一切办法遍植橡树以躲避战争的创伤,并规定:"每棵树都不可被砍掉,除非新种一棵。"结果,战争的炮火并未殃及丹麦,这些橡树幸运存活了下来,年复一年,长成茂密森林。闻着木香,我们来到哥本哈根繁华都市的心脏处——自1780年起就开始引领丹麦设计与工艺时尚的Bredgade大街,百年品牌卡尔·汉森·桑(Carl Hansen&Son)全球旗舰店就坐落于此。