• Journal of Korean Neurosurgical Society
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• 제40권6호
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• pp.434-440
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• 2006

Objective : The purpose of this study is to examine the influence of cranioplasty on dynamics of cerebral blood flow[CBF] and cerebrovascular reserve capacity[CVRC], and to investigate the usefulness of single photon emission computed tomography [SPECT] as a prognostic factor for neurological improvement after cranioplasty. Methods : Between March 2003 and December 2005, a prospective study was performed on 24 patients who had undergone total 25 cranioplasty operations. Cerebral blood flow velocities in the middle cerebral artery[MCA] and internal carotid artery[ICA] were obtained by transcranial Doppler ultrasonography[TCD]. The CVRC was assessed by SPECT in the natural state and after stimulation with 1g of acetazolamide. Neurological improvement after cranioplasty was compared between patients who showed hyperactivity to acetazolamide-activated SPECT [Group 1, n=7] and hypoactivity to acetazolamide-activated SPECT [Group 2, n=17]. These measurements were obtained two weeks prior to and two weeks after cranioplasty. Results : The blood flow velocities at the opposite site to the cranioplasty as well as at the cranioplasty site were significantly increased [P<0.05]. Compared with Group 2, there was significant increase in CBF and neurological improvement after cranioplasty in Group 1. Conclusion : Among patients with surgical bony defects, the patients who had normal reactivity of the CVRC showed a significant increase in CBF and neurological improvement after cranioplasty. The authors suggest that CVRC measurement prior to surgery may be an important prognostic factor for neurological improvement after cranioplasty.

• 대한가정학회지
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• 제38권1호
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• pp.99-122
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• 2000

The purpose of this study was to develop a program for the enhancement of Korean married women's quality of life(LQ) based on the results of the first year study(1996) and the second year research(1998). In order to construct a program, a psycological type test was conducted to 505 women and four preliminary programs were carried out focusing on self-esteem, understanding of one's own personality dynamics, efficient communication, positive emotion, social belongingness and expressions of feelings of unfinished business. For the final program, Jung's theory of psychological type(MBTI, Satir's family therapy approach and psychodrama were applied. An experimental and a control group were designed consisting 16 women for each group. The program was carried out for 6 weeks for the experimental group. The result of treatment were as follows: 1) There was a difference statistically in LQ related to family harmony, serif-achievement and improvement of relationship with in-laws. 2) There was a statistical change in psychological factors of expression of feelings, self-esttem, communication, and positive emotions. 3) The program participants self reports indicate that the program was effective for the reconstruction of family relationship, self-understanding, group coherence, and instigation of hope. The reports also shows that the program was effective for the perceptual changes in parent-child, wife-husband and siblings' relationships. In conclusion, the program developed for the enhancement of Korean married women's life quality(LQ) based on the Jung's psychological type theory, Satir's family therapy approach and psychodrama was erective for the improvement of LQ.

• International Journal of Fluid Machinery and Systems
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• 제9권4호
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• pp.370-381
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• 2016

As a single-channel pump is used for wastewater treatment, this particular pump type can prevent performance reduction or damage caused by foreign substances. However, the design methods for single-channel pumps are different and more difficult than those for general pumps. In this study, a design optimization method to improve the hydrodynamic performance of a single-channel pump impeller is implemented. Numerical analysis was carried out by solving three-dimensional steady-state incompressible Reynolds-averaged Navier-Stokes equations using the shear stress transport turbulence model. As a state-of-the-art impeller design method, two design variables related to controlling the internal cross-sectional flow area of a single-channel pump impeller were selected for optimization. Efficiency was used as the objective function and was numerically assessed at twelve design points selected by Latin hypercube sampling in the design space. An optimization process based on a radial basis neural network model was conducted systematically, and the performance of the optimum model was finally evaluated through an experimental test. Consequently, the optimum model showed improved performance compared with the base model, and the unstable flow components previously observed in the base model were suppressed remarkably well.

• Nuclear Engineering and Technology
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• 제42권4호
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• pp.339-364
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• 2010

Following a joint OECD/NEA-IAEA-sponsored meeting to define the current role and future perspectives of the application of Computational Fluid Dynamics (CFD) to nuclear reactor safety problems, three Writing Groups were created, under the auspices of the NEA working group WGAMA, to produce state-of-the-art reports on different aspects of the subject. The work of the second group, WG2, was to document the existing assessment databases for CFD simulation in the context of Nuclear Reactor Safety (NRS) analysis, to gain a measure of the degree of quality and trust in CFD as a numerical analysis tool, and to take initiatives to extend the existing databases. The group worked over the period of 2003-2007 and produced a final state-of-the-art report. The present paper summarises the material gathered during the study, illustrating the points with a few highlights. A total of 22 safety issues were identified for which the application of CFD was considered to potentially bring real benefits in terms of better understanding and increased safety. A list of the existing databases was drawn up and synthesised, both from the nuclear area and from other parallel, non-nuclear, industrial activities. The gaps in the technology base were also identified and discussed. In order to initiate new ways of bringing experimentalists and numerical analysts together, an international workshop -- CFD4NRS (the first in a series) -- was organised, a new blind benchmark activity was set up based on turbulent mixing in T-junctions, and a Wiki-type web portal was created to offer online access to the material put together by the group giving the reader the opportunity to update and extend the contents to keep the information source topical and dynamic.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2077-2083
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• 2022

In the unlikely event of core disruptive accident in sodium cooled fast reactors, the reactor containment building would be bottled up with sodium and fission product aerosols. The behavior of these aerosols is crucial to estimate the in-containment source term as a part of nuclear reactor safety analysis. In this work, the evolution of sodium aerosol characteristics (mass concentration and size) is simulated using HAARM-S code. The code is based on the method of moments to solve the integro-differential equation. The code is updated to FORTRAN-77 and run in Microsoft FORTRAN PowerStation 4.0 (on Desktop). The sodium aerosol characteristics simulated by HAARM-S code are compared with the measured values at Aerosol Test Facility. The maximum deviation between measured and simulated mass concentrations is 30% at initial period (up to 60 min) and around 50% in the later period. In addition, the influence of humidity on aerosol size growth for two different aerosol mass concentrations is studied. The measured and simulated growth factors of aerosol size (ratio of saturated size to initial size) are found to be matched at reasonable extent. Since sodium is highly reactive with atmospheric constituents, the aerosol growth factor depends on the hygroscopic growth, chemical transformation and density variations besides coagulation. Further, there is a scope for the improvement of the code to estimate the aerosol dynamics in confined environment.

• 한국추진공학회지
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• 제26권2호
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• pp.72-78
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• 2022

항공기용 엔진제어기는 주어진 환경에서 엔진의 최대 효율로 안전하게 운영될 수 있도록 엔진의 추력을 조절하고, 다른 보기 시스템들의 상태 감시를 수행하여 엔진의 모든 권한을 전자식으로 통합 제어하는 장치이다. 엔진제어기는 매우 높은 온도 환경에서도 정상 작동해야 한다. 따라서 엔진제어기는 내부 발열과 외부 유입 열을 고려한 최적의 방열설계가 필수적이다. 본 논문에서는 엔진제어기의 진공 브레이징 냉각유로를 설계하였다. 냉각유로의 전체 압력손실을 계산하기 위해 기본 형상에 대한 주손실과 입출구의 급격 확대/축소부, 유로 선회를 위한 밴드부 등의 비선형 형상에 대한 부차적손실을 계산하였다. 압력손실 이론식과 전산유체역학(Computational Fluid Dynamics, CFD) 해석을 활용한 합성추정법을 소개하여 각 비선형 형상에 대한 손실계수 계산하였다.

• 대한기계학회논문집 C: 기술과 교육
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• 제3권2호
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• pp.89-96
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• 2015

Based on multi-body dynamic software RecurDyn, this paper proposes a modified form of timing silent chain system combing with the existing problem that vibration and chain tension is too large, which is applied for complicated conditions in a V-type engine, such as high speed, variable loads. The analysis of chain drive meshing characteristics is completed. Using the multi-body dynamic soft-ware RecurDyn, the dynamics characteristics of the improved system is studied, including chain tension, transmission error, chain fluctuations, equivalent spring force in different operating conditions. The study results show that chain tension, transmission error, chain fluctuation and equivalent spring force are within the scope of permission, all of them can meet the design requirement. There-fore, the design of this system is reasonable and practicable. The research results will provide a basis for assessing timing silent chain system in a V-type engine and a theoretical reference for designing and optimizing the timing silent chain system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1491-1495
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• 2004

For the evaluation of the mobile robot performance in complex environments, the experimental approach in an actual physical environment has been commonly taken. In the physical experimental approach, however, it is quite difficult to define the proper environment for the evaluation due to the lack of commonly agreed characteristics of the test environment. Particularly the number of combinations of types and physical parameters of the obstacles that the mobile robot is expected to deal with is practically unlimited. In an effort to simplify and improve the effectiveness of the evaluation process, we propose an evaluation method using decomposed environmental elements, where we evaluated the performance of the robot for a small group of simple and decomposed obstacle components, for examples projection and slope, instead of a large group of complicated random obstacles. The paper describes a set of simple obstacle models and performance parameters that we have chosen for the effective evaluation process. As an alternative to the physical experimental evaluation approach, in this paper, we used a virtual evaluation environment where the robot and the physical test environment has been modeled using a commercial multi-body dynamics analysis packaged called RecurDyn.

• 대한간호학회지
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• 제34권6호
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• pp.1035-1046
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• 2004

Purpose: This one group experimentation was designed to develop a program for relieving 'Hwa-Byung'(HB) symptoms and examine its effects on HB symptoms, pain threshold emotions like anger, anxiety and depression. Method: The program consisted of three components the change of the cognitive thoughts, the formation of a supportive network, and induction of mind-body relaxation. Sixteen middle-aged women with HB were divided into three groups for group dynamics according to the time of the recruitment. Data was collected for nine months at three time points, before, immediately after, and one month later of its application. Result: There were statistically significant differences in the severity level of state anger, state anxiety, depression, and HB symptoms according to the time interval. The means of state anger and state anxiety were reduced after the intervention, but it was slightly increased one month later. The means of depression and HB symptoms were continuously reduced after the intervention and one month later. Conclusion: This was the first management program for HB women in Korea. A future study must be done with the research design formethodological strength revision of the program.

• 한국정밀공학회지
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• 제26권3호
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• pp.40-46
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• 2009

Toroidally-wound brushless direct-current (BLOC) machines are compact, highly efficient, and can work across a large magnetic gap. For these reasons, they have been used in pumps, flywheel energy storage systems and left ventricular assist devices among others. The common feature of these systems is a spinning rotor supported by a set of (either mechanical or magnetic) bearings. From the view point of dynamics, it is desirable to increase the first critical speed of the rotor so that it can run at a higher operating speed. The first critical speed of the rotor is determined by the radial stiffnesses of the bearings and the rotor mass. The motor also affects the first critical speed if the rotor is displaced from the rotating center. In this paper, we analytically derive the flux density distribution in a toroidally-wound BLOC machine and also derive the negative stiffness of the motor, based on the assumption that the rotor displacement perturbs the flux density distribution linearly. The estimated negative stiffness is validated by finite element analyses.