A new approach for cross section evaluations in the high energy region

A new approach for a cross section evaluation above the resonance region is introduced and described. It employs the KALMAN code and the Monte-Carlo tuning program called the TalysTuner to automatically adjust the model parameters. As a nuclear reaction model code, TALYS is used. The cross sections for ²³⁵U are calculated up to 150 MeV using the new method and compared with the available experimental data and other evaluations.     

Correlation analysis of brush temperature in brush-type DC motor for predicting motor life

Some critical components of motors and generators have sliding electrical contacts. Electrical brushes are usually used in these contact points to conduct current between the stationary part and the moving part of the motor. In this paper, studies on brush wear against copper commutators are briefly reviewed. The main influential factors in brush wear are associated with both mechanical wear and electrical wear. Brush wear is affected by various factors, including temperature, material properties, sliding speed, contact force, and interfacial as well as environmental conditions. The mechanical wear of brushes is proportional to brush spring pressure and sliding speed, and the electrical wear of brushes is associated with current and contact voltage drop. For characterization, a brush wear test machine is designed, and influential factors, such as electrical contact resistance, temperature, wear mass loss, and so on, are measured. The wear tests are processed using a small brush-type automotive DC motor. The study primarily aims to investigate the effects of the wear behavior of copper-graphite brushes on small brush-typed DC motors. The variable conditions of electrical current are obtained by changing the brush spring pressure and the sliding speed. The results are electrical contact resistance, voltage drop, brush surface temperature rise, and so on. Brush wear is greatly changed by electrical current, which indicates that high current itself not only produces more Joule heating but also causes an increase in voltage drop that will result in additional Joule heating.     

Mobile cloud computing framework for a pervasive and ubiquitous environment

The increasing use of wireless Internet and smartphone has accelerated the need for pervasive and ubiquitous computing (PUC). Smartphones stimulate growth of location-based service and mobile cloud computing. However, smartphone mobile computing poses challenges because of the limited battery capacity, constraints of wireless networks and the limitations of device. A fundamental challenge arises as a result of power-inefficiency of location awareness. The location awareness is one of smartphone’s killer applications; it runs steadily and consumes a large amount of power. Another fundamental challenge stems from the fact that smartphone mobile devices are generally less powerful than other devices. Therefore, it is necessary to offload the computation-intensive part by careful partitioning of application functions across a cloud. In this paper, we propose an energy-efficient location-based service (LBS) and mobile cloud convergence. This framework reduces the power dissipation of LBSs by substituting power-intensive sensors with the use of less-power-intensive sensors, when the smartphone is in a static state, for example, when lying idle on a table in an office. The substitution is controlled by a finite state machine with a user-movement detection strategy. We also propose a seamless connection handover mechanism between different access networks. For convenient on-site establishment, our approach is based on the end-to-end architecture between server and a smartphone that is independent of the internal architecture of current 3G cellular networks.     

Shielding design calculations for beam dump facility of KOMAC

A project to construct the Korea Multi-purpose Accelerator Complex (KOMAC) is currently underway targeting a high-intensity proton beam with an average current of 4.8 mA. As for the first stage of construction, a 20 MeV linac is planned to be built by 2007 and additional DTL sections will be added to increase the proton energy to 100 MeV by 2012. In this paper, preliminary shielding estimates, such as the evaluation of the gamma ray and neutron dose rate around the beam dump, have been carried out with the three-dimensional (3-D) Monte Carlo transport code MCNPX in order to determine the shielding requirements. The tentative flux calculations using the 3-D deterministic code KATRIN, which can handle a coupled charged-neutral particle transport, were also performed and their results were compared with the MCNPX calculations.     

Synthesis and electrochemical properties of HT-LiCo0.8Ni0.2O2 prepared by molten salt synthesis method using 0.59LiNO3-0.41LiOH system

LiCo_0.8Ni_0.2O₂ powders were prepared by molten salt synthesis method using a 0.59LiNO₃-0.41LiOH melt. The physico-chemical properties of the HT-LiCo_0.8Ni_0.2O₂ powders were investigated by powder X-ray diffraction method, field emission scanning electron microscopy, cyclic voltammetry, and charge-discharge cycling. Uniform size nanocrystalline powder (~40 nm) could be obtained at temperature ranges of 280-480 °C. These nanocrystalline powders showed poor electrochemical properties because of presence of the low temperature phase. Pure single-phase HT-LiCo_0.8Ni_0.2O₂ powder could be obtained at 580 °C. Charge-discharge measurements indicated that this exhibited a good capacity and cyclability without further heat treatment at higher temperatures. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8-10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

A Security Model Based on Relational Model for Semantic Sensor Networks

This paper proposes a novel security model for secure query processing in semantic sensor networks. A semantic sensor network (SSN) is a sensor network including semantics of sensory data and context information, and relationships between the semantics by using Semantic Web technologies. Even though much research has been activated on SSN, there is little activity on how to securely access data in semantic sensor networks. Most of storages have been developed based on relational database model and the relational database model provides a secure and robust security support. Therefore, we need to devise a security model considering such a real environment. This paper proposes a new access control model for secure query processing in semantic sensor networks. The proposed security model is based on relational database security model. This paper shows the overall framework and definitions of the proposal, and the experiment and evaluation is described to show validity of our proposal. With the experiment and evaluation, it is clear that the proposed model provides a secure access control support for SSNs.