SungSuk Kim

Characterizing and Classifying Desktop Grid

Desktop Grid has recently received the strong attraction for executing high throughput applications as CPU, storage and network capacities improve and become cheaper. Desktop Grid is different from Grid in many respects, but there is no general survey or taxonomy for desktop Grid. Therefore, we propose a new comprehensive taxonomy and survey of desktop Grid in order to characterize and categorize desktop Grid.

Thermomigration of tellurium precipitates in CdZnTe crystals grown by vertical Bridgman method

Te precipitates in CdZnTe have been characterized by x-ray diffraction at room and higher temperatures. From the x-ray results at room temperature, it has been confirmed that Te precipitates in CdZnTe have the same structural phase as observed in elemental Te under high pressure. The x-ray results at higher temperature indicate that Te precipitates melt around 440°C. CdZnTe samples containing Te precipitates have been annealed at temperatures below and above 440°C with thermal gradient of ∼70°C/cm. Results of the observation with infrared microscope before and after the annealings indicate distinct occurrence of thermomigration of Te precipitates in samples annealed at temperature above 440°C compared with ones annealed at temperature below 440°C. Thermomigration velocity obtained from these results is ∼50 μm/h. The average value for the effective diffusion coefficient of the metallic atoms in Te precipitates calculated by using the thermomigration velocity is ∼3 x 10−5 cm2/s.

The comparison on the performance of a gamma-ray spectrometer with the variation of Pt(Au)/CdZnTe/Pt(Au) interface

Abstract Cd1−xZnxTe grown by high-pressure Bridgman method (HPB) has been known to be a good candidate for gamma-ray detection material. The metal contacting conditions are very important for the performance of gamma-ray detector. Therefore, it is essential to find proper contact technology. For these purposes, various contact methods (electroless deposition, thermal vacuum evaporation) and materials (Au, Pt) are attempted. From the measurement of current–voltage characteristics, gamma-ray spectroscopy and auger electron spectroscopy (AES), the physical properties of metal contact on the CdZnTe are analyzed and contact methods compared with one another. Electroless Pt deposition is found to have better properties than others in many respects.

Using reordering technique for mobile transaction management in broadcast environments

As computer hardware and wireless network technologies are developed to a high degree, there are many research efforts which intend to utilize data broadcasting to a large population of mobile clients through wireless channels. In recent years, different models of data delivery have been explored, particularly the periodic push model where the server repetitively disseminates information without any explicit request. In this paper, we devise new transaction processing algorithms, O-Post for update transactions and O-Pre for read-only transactions, in broadcast environments. Basically, each client executes its transactions in an optimistic manner and does some consistency checks based on periodic invalidation reports. When any kind of conflicts is found, the conflict order is determined according to the notion of reordering and the remaining operations are executed to hold the decision. We also develop a cache algorithm to cope with frequent restarts due to the optimistic execution. Experimental results are given to show the benefits of the proposed algorithms.

Growth of Polycrystalline Cd0.8Zn0.2Te Thick Films for X‐Ray Detectors

Cd 1-x Zn x Te is known as promising medical X-ray detector material but CdZnTe as a single crystal is not available in large sizes. As an alternative to single crystal, CdZnTe thick film was grown by vacuum thermal evaporator to 100 μm thickness. The characteristics of thick films were analyzed by XRD, EDS, SEM and current-voltage measurements. Zn composition is x = 0.2 and resistivity is higher than 10 9 Ω cm.

Vertical Bridgman techniques to homogenize zinc composition of CdZn Te substrates

In order to improve the Zn homogeneity along the axial direction of CdZnTe boule, we have employed a modified Bridgman technique using a (Cd, Zn) alloy source in communication with the melt, whose temperature has been gradually changed from 800 to 840°C during growth. Electron probe microanalysis (EPMA) measurements of Zn composition in the boule shows an excellent homogeneity of Zn along the axis of the CdZnTe boule compared with results in a boule grown by using a fixed source temperature. We have performed a numerical simulation to obtain the approximate temperatures of additional heating and cooling needed to improve the radial Zn homogeneity. CdZnTe boule has been grown by seeded vertical Bridgman furnace with two zones of heater and cooler. Ultraviolet/visible spectroscopic measurements of Zn composition over the length of the boule indicate that the radial distribution of Zn composition is very homogeneous in the body region of the boule, where the radial variation of Zn composition is ±0.0005.

Task scheduling scheme based on resource clustering in desktop grids

Desktop grids are platforms for grid computing that incorporate desktop resources into a grid infrastructure. The purpose of this computing paradigm is to process a massive computational tasks by exploiting the donated resources connected over the Internet. In desktop grids, it is important to guarantee fast turnaround time in the presence of dynamic properties, such as volatility and heterogeneity. To achieve this objective, we propose a task scheduling scheme based on resource clustering that can selectively allocate tasks to those resources that are most suitable for the current situation of a desktop grid environment. As a classifier of resources, the k-means clustering algorithm is introduced to classify resources according to their own task execution availability and result-return probability. The experimental results show that our scheduling scheme is more efficient than existing scheduling schemes with respect to reducing both the turnaround time and the quantity of resources consumed. Copyright

Performance evaluation of a predeclaration-based transaction processing in a hybrid data delivery

Push-based broadcasting in wireless information services is a very effective technique to disseminate information to a massive number of clients when the number of data items is small. When the database is large, however, it may be beneficial to integrate a pull-based (client-to-server) backchannel with the push-based broadcast approach, resulting in a hybrid data delivery. In this paper, we analyze the performance behavior of a predeclaration-based transaction processing, which was originally devised for a push-based data broadcast, in the hybrid data delivery through an extensive simulation. Simulation results show that the use of predeclaration-based transaction processing can provide significant performance improvement not only in a pure push data delivery, but also in a hybrid data delivery.

The effect of Cl-doping concentration on the resistivity of polycrystalline CdZnTe:Cl thick film

Polycrystalline CdZnTe thick films were grown by thermal evaporation method using CdZnTe and CdZnTe:Cl source. We obtained polycrystalline CdZnTe thick films having high resistivity (5times10 9 Omegamiddotcm) similar that of single crystals. Cl-doped polycrystalline CdZnTe thick films(Cl: 100, 200, 300, 400 ppm) were prepared on polished graphite substrate keeping substrate temperature between 350~500 degC. The average grain size and resistivity are similar each other. This paper present the effect of Cl-doping on the resistivity of polycrystalline CdZnTe thick films.

O-PreH : optimistic transaction processing algorithm based on pre-reordering in hybrid broadcast environments

In recent years, there has been a lot of research effort in the periodic push model where the server repetitively disseminates information without explicit request. We call the broadcast model supporting backchannel as hybrid broadcast. In this paper, we devise a new transaction processing algorithm called O-PreH, which is based on the notion of pre-reordering. If one or more conflicts for mobile transactions are found from servers periodic invalidation report, conflict orders are determined not to violate the consistency( pre-reordering) and then the remaining operations have to be executed pessimistically.