• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.449-457
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• 2013

In this study, we performed a numerical analysis to investigate the effect of rotation on the blood flow and arterial wall behavior by using the FSI (fluid-structure interaction) technique. The geometry of the artery included 50% stenosis at the center. To simulate the rotational effect, 2-6 rps of axial velocity was applied to the arterial model. A spiral wave and asymmetric flow occurred due to the stenosis and axial rotation both in the rigid body model and in the FSI model. However, the arterial wall motion caused periodic and transient blood flow changes in the FSI model. The FRZ (fluid recirculation zone) decreased in the FSI model, which is a known predictor for the formation and vulnerability of plaque. Therefore, it is observed that arterial wall motion also influences the generation of the FRZ.

• Proceedings of the Korean Society for Quality Management Conference
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• 1998.11a
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• pp.580-593
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• 1998

The small composite design for second order response surface might be appropriate when experimentation is expensive, difficult, or time-consuming, especially when an independent estimate of experimental error is available. It is important that the small composite designs for response surface analysis would be rotatable and slope-rotatable. Therefore the small composite designs are studied from the viewpoint of rotatability and slope-rotatability, and the optimal values of a(the distance of axial points from the center) are investigated as k(the number of independent variables) and $n_0$(the number of center points) are changed.

• Journal of Energy Engineering
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• v.20 no.1
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• pp.21-25
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• 2011

In order to monitor a rotating cylindrical separator for radioactive waste, an electrical resistance method is proposed and its mathematical model is investigated. In a rotating radioactive waste separator, the electrical resistance between a pair of electrodes mounted on the inner wall of the vessel is related to the thickness of annular region of insoluble particle formed around the periphery and the concentration of the insoluble particle in that region. This work presents an analytical relationship among the aforementioned parameters based on a two-dimensional solution to the electrical potential equation and an empirical conductivity-concentration relation. Also, the feasibility of electrical resistance method for monitoring rotating cylindrical separators is discussed.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.3
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• pp.189-198
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• 2003

Videooculography (VOG) is one of the eye-movement measurement methods used for objective evaluation of vestibule -ocular reflex. A key feature of VOG is to estimate accurately the center of pupil and ocular torsion with being less influenced by the upper eyelid droop, eyelashes, corneal reflection, and eye blinks. Especially, it Is important to find the accurate center of the pupil in 3-D VOG because the inaccurate pupil center causes significant errors on measuring torsional eye movement. A new algorithm was proposed to find the center of pupil which is a little influenced by factors mentioned above. In this study, real time three-dimensional VOG which can measure horizontal, vortical, torsional eye movements, and the diameter of pupil was implemented using the proposed method.

• KSBB Journal
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• v.17 no.1
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• pp.14-19
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• 2002

The objective of this study is to investigate optimum condition for lignin peroxidase production by white rot fungi Phanerochaete chysosporium IFO 31249 immobilized in a rotating bioreactor. The maximum lignin peroxidase activity of batch culture in rotating bioreactor was 300 U/L. The optimum rotating speed and packing ratio of support for lignin peroxidase production in a rotating bioreactor were 1 rpm and 20%, respectively. The optimum concentration of $MnSO_4$$\cdot$$H_2O$ for manganese-dependent peroxidase production in a rotating bioreactor was 50 ppm. The sufficient supply of oxygen was the most important factor to achieve maximum lignin peroxidase production. It was possible to produce lignin peroxidase (LiP) and manganese-dependent peroxidase (MnP) for at least 3 times successive repeated-batch cultures, respectively.

• Journal of the Korean Chemical Society
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• v.32 no.3
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• pp.163-170
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• 1988

The MNDO calculations were performed on the various rotamers of N-methyl formamide, N,N-dimethyl formamide, N-methyl acetamide, and N,N-dimethylacetamide in order to investigate the contribution of the one-electron and the steric effect on their rotational barriers about the C-N bond. Results show that while the conformational stabilities of formamides depend mainly on the one-electron factor, those of acetamides depend mainly on the steric factor. According to results obtained by calculations on the rotational barriers about C-N bond, for N-monosubstituted amides the steric effect is larger in the rotational ground state than in the transition state and for N,N-disubstituted amides the steric effect is larger in the rotational transition state.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.49-57
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• 2003

The flight trajectory of a boomerang is predicted with the momentum theory (actuating disk theory) and the blade element method generally used as tools to analyze in the rotary-wing aerodynamics. Boomerangs made by students are actually compared with the computational results, utilized to get the physical intuition. The transition from helicopter mode to autogyro mode with the gyroscopic precession is observed in numerical analysis and experiment like a 'flying rotor' after the boomerang taking off. The whole system is shown to be highly nonlinear and very sensitive to the initial conditions. Various flight loci may be obtained if we change the parameters.

• Journal of the korean Society of Automotive Engineers
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• v.8 no.1
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• pp.22-28
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• 1986

기관의 성능에 영향을 주는 인자로서는 외적인자(outside factor), 작동인자(operating factor) 및 설계인자(design factor)의 3가지로 나눌 수 있다. 작동인자로서는 기관회전수, 공기연료비, 점화 시기 또는 분사시기 등이면 설계인자로서는 행정체적, 압축비, 흡배기계통의 구조 및 치수, 냉각 방식 등으로 기관에 따라 고유한 값을 가지는 인자이다. 그러나 외적인자인 대기조건 즉 대기 압력, 대기온도 및 대기습도는 계절, 지역 및 기상조건에 따라 달라지므로 이것에 따라 기관이 흡입하는 공기의 압력, 온도 및 습도는 변화하게 된다. 그러므로 대기조건의 변화에 따라서는 기관작동인자인 공기연료비에도 영향을 미치게 할 것이고 또한 연소상태의 변화로 유효압축비 에도 영향을 미치게 할 것이므로 대기상태의 변화는 곧 바로 기관 출력의 변화를 초래하게 될 것이다. 그러므로 같은 운전조건에서의 기관출력도 대기상태의 변화에 따라 변화하게 되므로 임의의 대기 상태에서 측정한 기관출력을 표준대기상태의 기관출력으로 환산해서 평가할 필요가 생긴다. 이것을 일반으로 출력수정(output correction)이라 하고 있으며 각 나라마다 공업규격 또는 기타규격으로 출력정식을 제정하고 있다. 예를 들면 K.S.B 9102, SAE J816B, B.S. 765, DIN 70020, JIS B 8013등이다. 이들 출력수정식들은 많은 문제점을 가지고 있으므로 종래의 출 력수정식으로 출력수정을 하여도 정확하게 맞지 않은 경우가 많다. 출력수정에 관한 문제는 수 10년전부터 많은 연구자에 의하여 연구되고 거론되어 왔으나 과거의 연구자들이 제안하고 거론 되어 왔으나 과거의 연구자들이 제안하고 있는 출력수정식, 또는 규격으로 정하고 있는 출력수 정방법은 어느 것이나 실용상 만족스러운 것이 아직 없다. 그러므로 본 자료는 스파아크 점화 기관의 흡기습도에 관한 출력수정의 문제를 실험적으로 수행한 실험적 출력수정방법에 의한 것과 종래의 출력수정방법에 의한 것과를 비교 검토하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.309-312
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• 2005

High altitude ignition test was performed to understand high altitude ignition characteristics of slinger combustor. To verify ignition limits, test was carried out with variation of altitude and fuel nozzle rotational speed using AETF(Altitude Engine Test Facility) in KARI(Korea Aerospace Research Institute). From the result, the effect of major factors which affect on ignition characteristics was observed. The reduction of ignition limit with increasing altitude and expansion of ignition limit with increasing rotational speed of fuel nozzle was verified. Also minimum rotational speed of fuel nozzle at high altitude must be greater than that of seal level condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.883-890
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• 2011

A numerical study was conducted to determine the optimal design for a vehicle vacuum pump. The degree of vacuum was examined for different design factors such as the angle of vanes, number of vanes, angle and position of the pump inlet-outlet pipe, and angular rotational speed of vanes. The results show that there is a little difference in the degree of vacuum when the angle of vanes are changed, but an angular change in the outlet pipe reduces the pump loss. As the rotational speed is increased, the mass flow rate increases, but a high rotational speed does not result in the maximum degree of vacuum. In addition, when the number of vanes is increased, the scattering range of mass flow rate decreases and pressure drop is abated.