• Journal of computational fluids engineering
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• v.7 no.4
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• pp.35-41
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• 2002

The projectile afterbodies for zero-lift drag reduction has been analyzed using the Navier-Stokes equations with the κ-εturbidence model. The numerical method of a second order upwind scheme has been used on an unstructured adaptive grid system. Base drag reduction methods that have been found effective on axisymmetric bodies are boattailing, base bleed, base combustion, locked vortex afterbodies and multistep afterbodies. In this paper, turbulence flow and pressure charateristics have been studied for geometries of multistep afterbodies. The important geometrical and flow parameters relevant to the design of such afterbodies have been identified by step number, length and height. The flow over multistep aftoerbodies or base have many kinds of compressible flow characteristics including expansion waves at the trailing edge, recompression waves, separation and recirculating flow in the base region, shear flow and wake flow. The numerical results have been compared and analyzed with the experimental data. The flow characteristics have been clearly shown.

• Journal of The Korean Astronomical Society
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• v.43 no.5
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• pp.169-181
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• 2010

We develop a proto-model of an off-axis reflective telescope for infrared wide-field observations based on the design of Schwarzschild-Chang type telescope. With only two mirrors, this design achieves an entrance pupil diameter of 50 mm and an effective focal length of 100 mm. We can apply this design to a mid-infrared telescope with a field of view of $8^{\circ}{\times}8^{\circ}$. In spite of the substantial advantages of off-axis telescopes in the infrared compared to refractive or on-axis reflective telescopes, it is known to be difficult to align the mirrors in off-axis systems because of their asymmetric structures. Off-axis mirrors of our telescope are manufactured at the Korea Basic Science Institute (KBSI). We analyze the fabricated mirror surfaces by fitting polynomial functions to the measured data. We accomplish alignment of this two-mirror off-axis system using a ray tracing method. A simple imaging test is performed to compare a pinhole image with a simulated prediction.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.11-20
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• 1994

The error rate equation of DS-CDMA/DQPSK skgnal adopting ARQ scheme has been derived in indoor radio channel which is characterized by AWGN, multi-user interference (MUI) and Rician fading, Using the derived equation the error performance has been evaluated and shown in figures as a function of direct to diffuse signal power ratio(KS1rT), the number of active users (K), PN code sequence length (N), the number of parity bit of linear code (b), forward channel BER, and ES1bT/NS1OT. From the results it is known that in severe fading environments (KS1rT=6) the performance of DS-CDMA/DQPSK system is not reliable so it is needed to adopt techniques for improvement. When an ARQ scheme is adopted, as a method for improving error performance, the performance improves compared with that of non-ARQ scheme and the degree of improvement is proportional to the number of parity bits of linear code. As increasing the number of parity bits, system performance is improved vut system throughput efficiency must be considered. In severe fading channel Hybrid ARQ scheme is more effective than ARQ scheme. As a result, ARQ scheme is appropriate for the high-reliability data communication systems over the radio channel in which the real time processing is not required.

• Korea Journal of Hospital Management
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• v.19 no.2
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• pp.44-54
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• 2014

In spite of effective curative therapy, morbidity and mortality remain high for hospitalized patients with tuberculosis(TB) in Korea. The purpose of this study was to identify patient and hospital characteristics associated with hospital care outcome. Using annual patient survey data produced by Korea Institute for Health and Social Affair, we identified 8,562 hospital discharge with primary diagnosis of TB. Logistic regression analyses were performed on a model that included age, gender, residence area, insurance status, hospital admission source, length of stay, hospital ownership and class of hospital as the explanatory variables and outcome of treatments as the dependent variable. The results show that negative outcome was associated with the patients older than 65 years, medical aid beneficiary, admission through emergency department, and the patients admitted to public owned hospitals. On the other hand, the patients who were admitted to teaching hospitals were associated with positive outcome. To improve hospital treatment outcome of TB patients, more vigorous strategies should be implemented targeting the older and poor population in regard to social support as well as the clinical management and prevention.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.12
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• pp.1140-1145
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• 2008

In conventional cutting system of Heat-Shrink-Tube, workers operate cutting system after considering about length and quantity of heat-shrink-tube. So, not only work time and production cost is increased but also material is wasted because the data that workers have to consider is so much. In this paper, an effective cutting system of heat-shrink-tube was developed to reduce production cost, work time and waste of material. The cutting system consists of a supervisory computer installed inside a control room, a on-site computer installed on the work area, and a PLC system. In the developed system, a supervisory computer send work order to the on-site computer using LAN and the on-site computer operates the cutting system of the heatshrink-tube after it makes an array production order. Also, the on-site computer reports information to the supervisory computer when an accident happened.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.996-1000
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• 2002

A porous tube, comprised of a resin-coated woven fabric has recently been used as an effective component for use in intake systems of internal combustion engines to reduce the intake roaring. For the prediction of the acoustic performance of an engine intake system with a porous woven hose, the acoustic wall impedance of the hose must be known. Because of its peculiar acoustical and structural characteristics, the accurate measurement of the wall impedance ofa porous woven hose is not easy. A new measurement technique is proposed herein, that is valid over the low to mid frequency ranges. The acoustics impedance is inversely estimated from an overdetermined set of measured pressure transmission coefficients for specimens of different lengths and the reflection coefficient of end termination. The method involves only one measurement, and, as a result, it is very simple. The measured TL for samples with arbitrary conditions, arbitrary porous frequency, arbitrary length, and arbitrary mean flow condition, are in reasonably good agreement with values predicted from curve-fitted impedance data.

• Journal of the Korean Society of Safety
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• v.21 no.1 s.73
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• pp.105-113
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• 2006

The footing of a bridge is a very essential part that support the whole load induced by the bridge itself and the traffic as well. However, once a bridge is built, the footing is buried under soil so the footing is invisible from outside. Therefore, the safety or condition of the footing is very difficult to estimate. Not only the length of the imbedded part of the footings but also the type of footings are unknown once the design record is gone. Some nondestructive techniques can be used to evaluate invisible part of the footings but the results have not been successful yet. Using GPR (Ground Penetrating Radar), which has been used for the nondestructive evaluation in military purposes, the condition assessment of the footings have been successfully conducted in this research. The field evaluation and laboratory tests have been conducted to find effective factors in the condition assessment of the footings. The equipment and basic theory of the GPR has been presented. The field test results show that the GPR can be successfully used for the safety evaluation of the footings. More test results and field data are needed for more precise evaluation of the footings.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.952-962
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• 2015

Various types of altitude compensation nozzles have been investigated to develop an effective propulsion system. In order to obtain baseline data for future study of dual bell nozzles, main characteristics and key parameters of dual bell nozzles are summarized and described by analysing DLR dual bell nozzles. DLR's experimental researches show that inflection angle is proportional to transition NPR, and extension length is proportional to side load, but inversely proportional to transition NPR and transition duration. Therefore, the nozzle geometry can be determined through the performance prediction process and thus the optimization process is required to meet performance requirements between parameters.

• Journal of Korean Academy of Rural Health Nursing
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• v.1 no.1
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• pp.49-58
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• 2006

Purpose: This study was done to investigate the effects of **the Thera-band exercise program on the lower extremities muscle strength and balance in rural female farmers. Method: The participants were 19 rural women age of 40 or over who were living in the area within the jurisdiction of a public health center in North Chung Province and who agreed to participate in the study. The Thera-band exercise program was implemented for 10 weeks from Jan 17. to Mar 31. 2005. Total time was 60 minutes, 5 times a week. Paired t-test was used to analyze the data using the SPSS program. Result: The results of study showed that thigh muscle strength(t= 6.718, p <.001) and the dynamic balance(t=4.934, p <.001) decreased significantly. Ankle muscle strength(t=-6.739, pp <.001) and static balance (t=-2.395, p=.025) increased significantly. Conclusion: The results suggest that the Thera-band exercise program could be effective in improving thigh muscle strength, ankle muscle strength, the static balance, and the dynamic balance of rural female farmers. Further study is needed to compare strength and balance before and after the exercise program and to use a control group for comparison. Also it is needed to do more study on the appropriate length of time that the intervention should be given in order to achieve maximum results.

• Journal of Magnetics
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• v.19 no.2
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• pp.181-184
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• 2014

The aim of the present study was to examine whether motor imagery (MI) practice in conjunction with repetitive transcranial magnetic stimulation (rTMS) applied to stroke patients could improve theirgait ability. This study was conducted with 29 subjects diagnosed with hemiparesis due to stroke.The experimental group consisted of 15 members who were performed MI practice in conjunction with repetitive transcranial magnetic stimulation, while the control group consisted of 14 members who were performed MI practice and sham therapy. Both groups received traditional physical therapy for 30 minutes a day, 5 days a week, for 6 weeks; additionally, they received mental practice for 15 minutes. The experimental group was instructed to perform rTMS and the control group was instructed to apply sham stimulation for 15 minutes. Gait analysis was performed using a three-dimensional motion capture system, which is a real-time tracking device that delivers data via infrared reflective markers using six cameras. Results showed that the velocity, step length, and cadence of both groups were significantly improved after the practice (p<0.05). Significant differences were found between the groups in velocity and cadence (p<0.05) as well as with respect to the change rate (p<0.05) after practice. The results showed that MI practice in conjunction with rTMS is more effective in improving gait ability than MI practice alone.