• 한국유체기계학회 논문집
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• 제5권1호
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• pp.20-26
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• 2002

This study reports the analysis of the pressure drop characteristics for the air-particle flow in powder transport piping system. The pressure drop characteristics of air-particle flow in piping system is not well understood due to the complexity of particles motion mechanism. Particles or powders suspended in air flow cause the increase of the pressure drop and affect directly the transportation efficiency. In this study, the pressure drop in powder transport piping system with straight and curved pipes is analyzed for the interactions of air flow and particle motion. The total pressure drop increases with increasing of the pipe length, the mixture ratio, and the friction factor of particles due to the increasing friction loss by air and particles in a coal piping system. For the coal powders of $74{\mu}m$ size and powder-to-air mass mixture ratio of 0.667, the total pressure drop by the consideration of powders and air flow is $30\%$ higher than that of air flow only.

• 한국생산제조학회지
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• 제20권5호
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• pp.553-558
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• 2011

This study have goal with conceptual design for offshore structures of high pressure drop control valve for localization valve for development accomplished with flow analysis based on provision of ANSI B16.34, ANSI B16.10, ANSI B16.25. In order to localize the Offshore structures high pressure drop control valve. This study is numerical analysis for zambil offshore project of high pressure drop control valve. The solver which ANSYS workbench used for offshore structures analysis. The working fluids assumed the glycerin(C3H8O3). The structural analysis used ANSYS which is a commercial code. Stress analysis result of internal pressure in valve showed lower than yield strength. This is expect to need more detail design and verification for stem and disk structure. In this study a multi-disk of high pressure drop control valve is designed and manufactured. Then, the flow rate and high pressure dorp of fluids flowing in the high pressure drop control valve is CAE. So, this system can be easily substituted for the existing zambil offshore project system. Finally, safety estimation for trim design of high pressure drop control valve for offshore structures.

• The Journal of Korean Physical Therapy
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• 제22권6호
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• pp.29-33
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• 2010

Purpose: This study was designed to investigate inter-rater and intra-rater reliability of navicular drop measurements by clinicians in sitting and standing positions. Methods: Fourteen subjects with pronated foot were recruited. Two physical therapists randomly assessed the same patients on different occasions but on the same day. Almost all patients were assessed on more than one day. The intra-rater and inter-rater reliability of navicular dropwas estimated by calculation of the intraclass correlation coefficient (ICC). Results: The intra-rater reliability of navicular drop measurements ranged from 0.93 to 0.87, the inter-rater reliability from 0.98 to 0.70 with the patient in standing and sitting positions. These results showed good reliability for calculated variables. Intra-rater and inter-rater reliability of navicular drop in standing position was higher than those of sitting position. Conclusion: Although inter-rater and intra-rater reliability of navicular drop in the sitting position was lower than in the standing position, measurement of navicular drop in the sitting position showed good reliability and was acceptable for patients who could not stand alone without assistance. We recommend that having the patient in the standing position is appropriate in navicular drop measurement.

• 한국항해학회지
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• 제22권3호
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• pp.73-92
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• 1998

Today the number of high school drop-outs is increasing , and also it is serious social problems. But almost factor analyses on the drop-outs are projected by questionnaire. This paper find out by the real data form the concerned documents what factors of drop-outs are. In order to accomplish this study purpose, the methodology are used such as Fequency Analysis, Correlation Analysis, Crosstabulation Analysis. Through the this study this paper could siome suggestions as followings. The first , all education authority should analysis what factors of drop-outs and what drop-out situation is . The second, every teacher should counsel with all problem students sincerely regarding to their characters, future occupations, life course and etc. The third, the most and worst important factors of drop-out is runaway. Because it is very difficult for teacher to teach, lead and guide a runaway student, therefore thepreventino of runaway is efficient for reducing of drop-outs. The fouth, the students violating rules are retrained propoerly in view of guide for good path. The fifth, besides of the above factors. there are drop-out factors such as the health, disease, dafety accidents . All parents. teachers, and students should try their best to solve. To the end, education authority try to encourage teachers to do their role with maximum sense of duty.

• 동력기계공학회지
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• 제11권1호
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• pp.63-69
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• 2007

The evaporation pressure drop of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and an evaporator (test section). The test section consists of a smooth, horizontal stainless steel tube of 4.57 mm inner diameter. The experiments were conducted at saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$, and heat flux of 10 to $40kW/m^2$. The test results showed that the evaporation pressure drop of $CO_2$ are highly dependent on the vapor quality, heat flux and saturation temperature. The measured pressure drop during the evaporation process of $CO_2$ increases with increased mass flux, and decreased saturation temperature. The evaporation pressure drop of $CO_2$ is much lower than that of R 22. In comparison with test results and existing correlations, the best fit of the present experimental data is obtained with the previous correlation. But existing correlations failed to predict the evaporation pressure drop of $CO_2$. Therefore, it is necessary to develop reliable and accurate predictions determining the evaporation pressure drop of $CO_2$ in a horizontal tube.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2491-2498
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• 2020

The paper concentrates on an experimental study of the pressure drop in double-layered packed beds formed by glass spheres, having the configuration of horizontal and vertical stratification. Both single-phase and two-phase flow tests are performed. The pressure drop during the test is recorded and the measured data are compared with those of homogeneous beds consisting of mono-size particles. The results show that for the horizontally stratified bed with fine particles atop coarse particles, the pressure drop in top layer is found higher than those of homogenous bed consisting of the same smaller size particles, while the measured pressure drop of bottom part is similar with those of similar homogenous bed. But for the homologous bed with upside-down structure, the stratification has little or no effect on the pressure drop of the horizontally stratified bed, and the pressure drop of each layer is almost same as that of homogeneous bed packed with corresponding spheres. Additionally, in vertically stratified bed, the pressure drops on the left and right side is almost equal and between those in homogeneous beds. It is speculated that vertically stratified structure may lead to lateral flow which redistributes the flow rate in different parts of packed bed.

• 한국통신학회논문지
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• 제29권4A호
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• pp.363-369
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• 2004

본 논문에서는 파장분할다증(WDM) 첨가(add)/절취(drop)망에서 채널의 add/drop에 따라 망 내에 있는 EDFA의 이득을 제어함에 있어 세계 최초로 외란 간측기법을 적용하는 새로운 이득-클램핑(gain-clamping) 방법을 제안한다. 이득-클램핑을 위한 제어신호는 공칭 제어신호와 채널의 add/drop에 따른 이득변동을 보정하기 위한 부가제어신호로 구성된다. 외란 관측기법에 근거하여, 부가 제어신호는 채별의 add/op에 의해 발생하는 추정 외란을 보정할 수 있도록 설계하였다. 이러한 부가 제어신호를 생성하는 회로는 간단한 전자소자를 이용하여 쉽게 구현할 수 있다. 모의실험을 통해 본 논문에서 제안하는 방법을 사용할 때 채널의 add/drop 과정에서 EDFA의 출력 파형에 나타나는 이득변화에 따른 요철이 최소로 됨을 보여줌으로써 본 방법이 기존의 여타 방법들에 비해 월등함을 입증하였다.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.187-194
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• 1999

In the design of catalytic converter, velocity distribution is more important than pressure drop because monolith pressure drop is about 80% of overall pressure drop. For the catalytic converter with single diffuser, pressure drop is decreased as the angle of diffuser decrease, but when the angle is below 18$^{\circ}$, the effect is almost negligible . For the catalytic converter with double diffuser, variation of the angle of the first diffuser shows the same trend as the pressure drop while the shape of diffuser gives little influence on that The outlet shape gives negligible effect on the pressure drop and velocity . distribution . Results show that recirculation region of commercial model is aoubt 30% of the total area in the front of monolith. For the catalytic converter with Model 11 that was presented in the study, recirculation region was not detected more uniform velocity distribution was obtained, and pressure drop was also decreased.

• 한국운동역학회지
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• 제24권4호
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• pp.385-390
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• 2014

The purpose of this study was to investigate the effects of landing tasks on the anterior cruciate ligament (ACL) injury risk factors in female basketball players. Fifteen female basketball players performed a drop landing and a drop landing with a vertical jump on the 40 cm height box. Three-dimensional motion analysis system and ground reaction force system was used for calculate the ACL injury risk factors. Paired samples t-test with Bonfferoni correction were performed. The drop landing with a vertical jump had the higher knee flexion angle, peak knee varus moment, trunk flexion angle than a drop landing. However, the drop landing had the higher trunk rotation angle than a drop landing with a vertical jump. These results indicate that seemingly minor variations between drop landing and drop landing with a vertical jump may influence the ACL injury risk factors. Caution should be used when comparing studies using different landing tasks.

• 국제물리치료학회지
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• 제10권4호
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• pp.1903-1906
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• 2019

Background: Foot drop is a common symptom after stroke and causes walking disorders. Therefore, its proper treatment is important for improving the walking ability of patients with foot drop. Objective: This study aimed to investigate the effects of electrostimulation during walking on the walking ability of patients with foot drop after stroke. Design: Quasi-experial study. Methods: The study enrolled 18 patients with foot drop after stroke. All subjects were assigned to the experimental or control group. The experimental group underwent electric stimulation during walking, while the control group used ankle foot orthoses. Both groups received treatment 20 minutes a day 5 times a week for 4 weeks. Outcome measures were assessed for walking and balance ability using the 10-m walking test (10MWT), 6-min walking test (6MWT), and Timed Up and Go test (TUG) Results: After the intervention, both groups showed significant improvements in 6MWT and TUG results. However, the experimental group showed significantly better improvement on all tests than the control group. Conclusion: The foot drop stimulator effectively improved the walking and balance ability of patients with foot drop after stroke.