• Clinics in Shoulder and Elbow
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• v.22 no.4
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• pp.235-240
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• 2019

Ulnar collateral ligament injuries of the elbow are frequent among overhead athletes. The incidence of ulnar collateral ligament reconstructions (UCLRs) in high-level players has increased dramatically over the past decade, but the optimal technique of UCLR is controversial. Surgeons need to manage the patients' expectations appropriately when considering the mode of treatment. This article reviews current studies on the management of ulnar collateral ligament injuries, particularly in overhead athletes.

• Structural Engineering and Mechanics
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• v.8 no.2
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• pp.193-205
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• 1999

A formulation for the dynamic stability analysis of cylindrical shells resting on elastic foundations is presented. In this previously not studied problem, a normal-mode expansion of the partial differential equations of motion, which includes the effects of the foundation as well as a harmonic axial loading, yields a system of Mathieu-Hill equations the stability of which is analyzed using Bolotin's method. The present study examines the effects of the elastic foundation on the instability regions of the cylindrical shell for the transverse, longitudinal and circumferential modes.

• Journal of applied mathematics & informatics
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• v.41 no.2
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• pp.363-372
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• 2023

We consider Kuo problem of hydrodynamic stability which deals with incompressible, inviscid, parallel shear flows in the 𝛽-plane. For this problem, we derived instability region without any approximations and which intersects with Howard semi-circle region under certain condition. Also, we derived upper bound for growth rate and amplification factor of an unstable mode and proved Howard's conjecture.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2971-2976
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• 2007

The mode change from Taylor cone-jet to dripping in electrospraying has been analytically investigated. The change has been predicted by the dynamic behavior of a liquid drop at the tip of the cone-jet. Conservation laws are applied to determine the upward motion of the drop, and an instability model of electrified jets is used to determine the jet breakup. Finally, for the first time, the analysis enables prediction of the transition in terms of the Weber number and electric Bond number. The predictions are in good agreement with experimental data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.8 s.227
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• pp.945-952
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• 2004

Acoustic characteristics of combustion chamber having various baffle configurations are numerically investigated by linear acoustic analysis to suggest reliable baffle specifications in first stage of KSLV-I. To determine the configuration of baffles, an acoustic modal analysis as well as the macroscopic analysis has been done. Hub has another effect of suppressing transverse acoustic mode by confining flow in baffled compartment over general effect of increase in acoustic damping of radial acoustic modes. So, a sufficient number of hub needs to be installed to obtain acoustic damping capacity. 3-blade configuration designed to suppress the first tangential mode has relatively low damping capacity, compared to 5 or 6-blade one. Optimum value of axial baffle length has been determined by comparing acoustic characteristics of combustion chamber having various baffle lengths.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1141-1142
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• 2011

An electrical vehicle (EV) is a huge issue in the automotive industry. The EV have many electrical units: electric motors, batteries, converters, ets. The DC power distribution system (PDS) is essential for the EV. The DC PDS offers many advantages. However, multiple loads in the DC PDS may affect the severe instability on the DC bus voltage. Therefore, a voltage bus conditioner (VBC) may use the DC PDS. The VBC is used to mitigate the voltage transient on the bus. In this paper, sliding mode controller (SMC) is designed for the VBC of DC PDS in the EV. The simulation results by PISM simulation package are presented for validating the proposed control technique.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.86-91
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• 2007

A study was performed to understand self-excited pressure fluctuations in the lean premixed flames and to evaluate the effect of Helmholtz resonator on the pressure fluctuations. As low-frequency pressure fluctuations have been reported to cause fatal damage to the combustor and the entire system, Helmholtz-type resonators, which reduce the damage by low-frequency pressure fluctuation in the combustor, are attached to the channel of unburned mixture flow. It is found that the range of low-frequency pressure fluctuations of flame mode 2 is narrowed by the attachment of Helmholtz resonators. From this result, if Helmholtz-type resonators are applied to actual gas turbine combustor, it is confirmed that Helmholtz resonators attached on the fuel discharge hole are also effective for narrowing the range of flame mode 2

• Transactions on Electrical and Electronic Materials
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• v.4 no.4
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• pp.7-9
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• 2003

Viewing angle characteristics of a nematic liquid crystal (NLC) using a in-plane driven (IPD) vertical alignment (VA) cell without a negative compensation film on a homeotropic alignment layer were studied. Good voltage-transmittance (V - T) curves were obtained using the rubbing aligned IPD- VA cell. However, instability and low transmittances of V - T characteristics in photo aligned IPD- VA cell was measured. The EO performance of a rubbingaligned IPD- VA cell without a negative compensation film was wider than that of photoaligned IPD- VA cell and conventional VA cell. Also, the fabrication processes using the rubbing aligned IPD- VA cell mode be carried out with only one-sided rubbing.

• Journal of Ocean Engineering and Technology
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• v.3 no.2
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• pp.87-100
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• 1989

해양구조물의 원통형 조인트에 대한 파괴역학적 피로수명 산출방법이 개발되었다. 개발된 방법을 이용해서 2평면 K형 조인트에 대한 피로수명을 구체적인 파괴역학적 방법으로 산출 하였다. 이 분석을 위해 용접부위 표면균열의 응력확대 계수를 3차원 유한요소법에 의해 계산하였다. 계산된 결과에 의하면 용접부위 표면균열 첨단은 단순한 Mode I형태를 보이지 않고 Mode I, II, III이 복합된 형태임이 입증되었다. 계산된 응력확대 계수를 사용해서 16개의 용접부위균열 성장형태를 일반적인 피로균열 성장법칙을 적용해서 계산하였고, 균열성장의 안정분석을 통해 각 균열의 최종 파괴상태를 파괴해석도면(failure assessment diagram)법을 이용해서 계산하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.12 s.243
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• pp.1344-1351
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• 2005

Three-dimensional, time-dependent solutions of fluid flow past a circular cylinder with a periodic array of circular fins are obtained using an accurate and efficient spectral multidomain methodology. A Fourier expansion with a corresponding uniform grid is used along the circumferential direction. A spectral multidomain method with Chebyshev collocation is used along the r-z plane to handle the periodic array of circular fins attached to the surface of the cylinder. Unlike the flow past a circular cylinder, Second instabilities like mode A and mode B are not found in the Reynolds number range $100\~500$. It is found that three-dimensional instability of vortical structures is suppressed due to the presence of fin. The present numerical solutions report the detailed information of flow quantities near wake of finned cylinder.