• Korean Journal of Materials Research
• /
• v.22 no.12
• /
• pp.711-716
• /
• 2012

Tungsten bronze structure $Sr_{1-x}Ba_xNb_2O_6$ (SBN) single crystals were grown primarily using the Czochralski method, in which several difficulties were encountered: striation formation and diameter control. Striation formation occurred mainly because of crystal rotation in an asymmetric thermal field and unsteady melt convection driven by thermal buoyancy forces. To optimize the growth conditions, bulk SBN crystals were grown in a furnace with resistance heating elements. The zone of $O_2$ atmosphere for crystal growth is 9.0 cm and the difference of temperature between the melt and the top is $70^{\circ}C$. According to the growth conditions of the rotation rate, grown SBN became either polycrystalline or composed of single crystals. In the case of as-grown $Sr_{1-x}Ba_xNb_2O_6$ (x = 0.4; 60SBN) single crystals, the color of the crystals was transparent yellowish and the growth axis was the c-axis. The facets of the crystals were of various shapes. The length and diameter of the single crystals was 50~70 mm and 5~10 mm, respectively. Tungsten bronze SBN growth is affected by the temperature profile and the atmosphere of the growing zone. The thermal expansion coefficients on heating and on cooling of the grown SBN single crystals were not matched. These coefficients were thought to influence the phase transition phenomena of SBN.

• The Journal of Society for e-Business Studies
• /
• v.8 no.3
• /
• pp.131-141
• /
• 2003

For workflow systems using XML documents for saving workflow process definition and especially for XML-based worflow systems, a repository needed to provide control for XML documents. The repository allows uniform access to shared data and facilitates integration among tools in workfolw systems. An XML repository gives the best solution to maintain, exchane, and modify the workflow process definition meta data, which is in the form of XML documents . The XML repository, where users can lookup the worflow definition objects, serves as the metadata foundation of the workflow system. In this paper, we developed for XML Repository(called REPOWO : REPOsitory for Workflow) that can store, delete, search and transform XML documents. REPOWO is implemented by combining EJB components based on RDBMS. By REPOWO, workfolw process definitions, data type definitions and transition informations can be easily manage.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.318.2-318.2
• /
• 2016

FeM2X4 spinel structures, where M is a transition metal and X is oxygen or sulfur, are candidate materials for spin filters, one of the key devices in spintronics. Both the Fe and M ions can occupy tetrahedral and octahedral sites; therefore, these types of compounds can display various physical and chemical properties [1]. On the other hand, the electronic and magnetic properties of these spinel structures could be modified via the control of cation distribution [2, 3]. Among the spinel oxides, iron manganese oxide is one of promising materials for applications. FeMn2O4 shows inverse spinel structure above 390 K and ferrimagnetic properties below the temperature [4]. In this work, we report on the structural and magnetic properties of epitaxial FeMn2O4 thin film on MgO(100) substrate. The reflection high energy electron diffraction (RHEED) and X-ray diffraction (XRD) results indicated that films were epitaxially grown on MgO(100) without the impurity phases. The valance states of Fe and Mn in the FeMn2O4 film were carried out using x-ray photoelectron spectrometer (XPS). The magnetic properties were measured by vibrating sample magnetometer (VSM), indicating that the samples are ferromagnetic at room temperature. The structural detail and origin of magnetic ordering in FeMn2O4 will be discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.8
• /
• pp.721-728
• /
• 2009

Equal/unequal 4-way power divider suitable for satellite communication using SIW technology is presented in this paper. The control of positions of guiding posts provides equal or unequal power division ratios by maintaining the width of the SIW unchanged. In addition, the detailed descriptions for the proposed power divider include the general characteristics of radial waveguide, feeding part using coaxial cable, simple SIW structure, power-guiding posts, and transition for measurement. The comparison between the simulated and measured data shows a good agreement at a center frequency of 10 GHz. The measured input impedance bandwidths for equal and unequal power divisions are about 2.1 GHz and 3 GHz under the condition of less than VSWR 2:1, respectively.

• Journal of computational fluids engineering
• /
• v.21 no.2
• /
• pp.112-119
• /
• 2016

NEXTSat-1 is the next-generation small-size artificial satellite system planed by the Satellite Technology Research Center(SatTReC) in Korea Advanced Institute of Science and Technology(KAIST). For the control of attitude and transition of the orbit, the system has adopted a RHM(Resisto-jet Head Module), which has a very simple geometry with a reasonable efficiency. An axisymmetric model is devised with two coil-resistance heaters using xenon(Xe) gas, and the minimum required specific impulse is 60 seconds under the thrust more than 30 milli-Newton. To design the module, seven basic parameters should be decided: the nozzle shape, the power distribution of heater, the pressure drop of filter, the diameter of nozzle throat, the slant length and the angle of nozzle, and the size of reservoir, etc. After quasi one-dimensional analysis, a theoretical value of specific impulse is calculated, and the optima of parameters are found out from the baseline with a series of multi-physical numerical simulations based on the compressible Navier-Stokes equations for gas and the heat conduction energy equation for solid. A commercial code, COMSOL Multiphysics is used for the computation with a FEM (finite element method) based numerical scheme. The final values of design parameters indicate 5.8% better performance than those of baseline design after the verification with all the tuned parameters. The present method should be effective to reduce the time cost of trial and error in the development of RHM, the thruster of NEXTSat-1.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.5
• /
• pp.1829-1840
• /
• 2013

It is essential to understand the hydraulic characteristics in accordance with the changes in the river environment and operating hydraulic structures for increasing flood-control capacity. The objective of this study is to analysis the effect of dredging and operation of weirs on hydraulic characteristics in Nakdong River(Seongju~Imhaejin). HEC-RAS model has been used to examine the hydraulic characteristics with considering the flow transition through the unsteady flow analysis and the information about the specifications of multi-functional weirs. The relationship between Manning n and roughness height k, the effect of weir installation and operation on the flow and stage, and the bed change resulted from the river treatment project have been examined by steady and unsteady flow analysis. It is expected that the result from this study can be the basic data for the river treatment and management.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.8 no.2
• /
• pp.269-278
• /
• 2004

In this study, hydraulic and hydrologic safety of an existing dam with morning glory spillway was evaluated and the problems were derived in order to control extreme floods efficiently. For design flood(520cms and EL. 170.3m), the spillway was turned out to have no problem for discharge and negative pressure in vertical transition. However, the critical point for discharge starts with EL. 170.7m which transits weir flow condition to orifice flow condition and there may be negative pressure in weir crest. While maximum water level can not be greater than EL. 170.5m including freeboard according to the dam design criteria, the maximum water level based on reservoir routing was turned out to be EL. 172.46m, and fundamental measures should be requested and planned.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.48 no.1
• /
• pp.27-33
• /
• 2016

This study was carried out in order to investigate the effect of binder properties in pre-coating layer on the characteristics of top-coating layer and print mottle of coated paper. Four different latices were used as a binder in pre-coating layer, and coating color prepared with a same formulation was applied for top-coating. The properties and print mottle of coated paper were evaluated. It was found that glass transition temperature (Tg) was the important factor to control the properties of pre- and top-coating layer. PPS roughness of coated paper was decreased and paper gloss was increased with applying binder which has lower Tg. Properties of top-coating layer were affected by the binder used in pre-coating layer. Print mottle of coated paper was improved with using binder which has lower Tg in pre-coating layer. These results indicate that final printability and properties of top-coating layer can be improved with using suitable binder in pre-coating layer.

• Health Policy and Management
• /
• v.1 no.1
• /
• pp.3-18
• /
• 1991

On the stage of transition from highly centralized government to local self-government in Korea, administrating practice characteristics of the directors of Health Centers is essentially required to be found. This study was conducted in order to find the administration patte군 of the directors of Health Centers in Korea and their opinion on the environment of health administration including personnel management regime for them. The materials were collected from 149 directors of Health Centers with a structured questionaire by mailing. The major findings of this study were as follows. 1. About two-thirds of the directors(69.1%) make plan through the consensus between public service perosonnel in programme department and them in budgt control department. And 75.0% of the directors maintain the planed by the predecessor. 2. More than two-thirds of the directors (71.1%) take subordinates opinion into consideration in case of the programmes facing objections. 3. When the directors face obstacles in pursuing health programmes they usually consult other public service personnel than inhabitants. 4. Only 10.8% of the directors were satisfied with the support of the Ministry of Internal Affairs for health administration while more than half of them were satisfied with the support of health institution in higher level. 5. The directors evaluated the job attitude of the public service personnel in low level as more favorable than that of there higher level public service personnel who work for central government. 6. Only 18.1% of the idrectors were satisfied with their saley. And more than half of them expect the promotion of their position. On the ground of this result the administration attitude of the directors of Health Centers would be evaluated as improved and as more positive than that of other public service personnel in health authorities. However, they are required to consult the inhabitants more frequently for health administration. An the public service personnel in high level who work for central government are required to improve their job attitude.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2004.05a
• /
• pp.603-606
• /
• 2004

Automatic test case generation for testing an embedded software is considered. Existing tools for test case generation such as finite state machine or mutant test usually adopt top down approach and depend upon graphical transition and decision table, which makes it difficult to find out where the bugs exist. Also it is hard to describe the special features of embedded systems such as concurrent execution of individual components. Most of embedded systems interacts with the real world, receiving signals through sensors or switches and sending output signals to actuators that somehow manipulate the environment. Embedded software controls the entire system based on the logics such as interpreting the sensor inputs and making the actuators to start or stop their intended operation. This study proposes an automatic test case generation procedure that tests the system starting from the control logics of sensors, switches and actuators and then their concurrent execution controls, and finally the entire system operation. Such a stepwise approach makes it easy to generate test cases to tell where the bugs of embedded software exist.