• 대한기계학회논문집B
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• 제31권9호
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• pp.780-789
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• 2007

Lock-on phenomenon in the wake of a circular cylinder is investigated at the Reynolds number of 360 using direct numerical simulation (DNS). To induce lock-on, a streamwise velocity perturbation with a frequency of twice the natural shedding frequency is superimposed on the free stream velocity. The Reynolds stress distributions are investigated to analyze the streamwise force balance acting on the recirculation region and the results are compared with the previous experimental result. When the lock-on occurs, the pressure force on the recirculation region is shown to increase mainly due to the reversal of the Reynolds shear stress distribution, which is consistent with our previous results using PIV measurement. It is also shown that, with the lock-on, the strength of the primary vortices increases whereas that of the secondary vortices decreases significantly. Further, under the lock-on condition the wavelength of the secondary vortices increases by as much as 2.5 times.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 추계학술대회 논문집
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• pp.18-21
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• 2004

Lock-on characteristics of the flow around a circular cylinder performing a rotationally oscillation with a relatively high forcing frequency have been investigated experimentally using flow visualization and hot-wire measurements. Dominant parameters are Reynolds number (Re), amplitude of oscillation $(\theta_A)$, and frequency ratio $F_R=f_f\;/\;f_n$, where $f_f$ is the forcing frequency and if is the natural frequency of vortex shedding. Experiments were carried out under the conditions of $Re=4.14\times10^3,\;\pi/15\leq\theta_A\leq\pi/3$, and $F_R=1.0$. The effects of this active control technique on the lock-on flow regime of the cylinder wake were evaluated through wake velocity measurements and spectral analysis of hot-wire signals. The rotary oscillation modified the flow structure of near wake significantly. The lock-on phenomenon was found to occur in the range of frequency encompassing the natural vortex shedding frequency. In addition, when the amplitude of oscillation is less than a certain value, the lock-on phenomenon was occurred only at $F_R=1.0$. The lock-on range expanded and vortex formation length decreased as the amplitude of oscillation increases. The rotary oscillation generated small-scale vortex structure just near the cylinder surface.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
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• pp.601-604
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• 2003

The magnetic field generated in the iron core, which is required for the magnetic field to link each coil of the flux-lock type reactor, affects the fault current limiting characteristics of the flux-lock type high-Tc superconducting fault current limiter(SFCL). By applying numerical analysis for equivalent circuit of flux-lock type SFCL, the magnetic field induced in the iron core including currents of each coil was investigated. Through the analysis of magnetic field, we have analyzed that the magnetic field linked the 3rd coil, which is wound in the iron core, prevents the saturation of the iron core, but decreases the impedance of the flux-lock type SFCL.

• 한국구조물진단유지관리공학회 논문집
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• 제4권3호
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• pp.197-204
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• 2000

Tensile strength (stress) of bar splice is important in the research of mechanical behavior of reinforced concrete structures-beam, column etc.- with bar splice. The purpose of this research is to evaluate the flexural behavior - deflection of beam specimens, strain of main bars - of reinforced concrete beam with Lock Joint Coupler. To make a comparative research, reinforced concrete beam specimens with normal deformed bar and lap splice are tested and analyzed. Test results, Comparing a deflection of three types flexural specimens, a flexural specimen with Lock Joint Coupler is 40% greater than the other flexural specimens. At the center of flexural specimen, the strain of main bar(D29) with lock joint coupler is 50% less, and vice versa, at the point of 14cm far from the center of flexural specimen, the strain of main bar(D29) with lock joint coupler is 9% larger than the strain of main bar(D29) which calculated using the classical flexure theory. A discords, between a deflection behavior of the flexural specimens and a strain of the main bar, are caused by the difference of strain between the lock joint coupler and main bar, near the lock joint coupler. So, additional research is need to verify as stated above discords.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.289-289
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• 2008

We investigated the operational characteristics of the separated three-phase flux-lock type superconducting fault current limiter (SFCL). The single-phase lock type SFCL consist of two coils, which are wound in parallel through an iron core. The high-$T_c$ superconducting(HSTC) thin film connected in series with secondary coil. The separated three-phase flux-lock type SFCL consist of three single-phase flux-lock type SFCL. In a normal condition, the SFCL is not operate. When a fault occurs, the current of a HSTC thin film exceeds its critical current by fault current, the resistance of the HSTC thin film generated. Therefore fault current was limited by SFCL. The separated three-phase flux-lock type SFCL are operated in fault condition such as the the single line-to-ground fault, the double line-to-ground fault and the triple line-to-ground fault. The experimental results, the SFCL operational characteristics was dependent on fault condition.

• JSTS:Journal of Semiconductor Technology and Science
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• 제11권2호
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• pp.73-79
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• 2011

This paper describes a reset-free delay-locked loop (DLL) for a memory controller application, with the aid of a hysteresis coarse lock detector. The coarse lock loop in the proposed DLL adjusts the delay between input and output clock within the pull-in range of the main loop phase detector. In addition, it monitors the main loop's lock status by dividing the input clock and counting its multiphase edges. Moreover, by using hysteresis, it controls the coarse lock range, thus reduces jitter. The proposed DLL neither suffers from harmonic lock and stuck problems nor needs an external reset or start-up signal. In a 0.13-${\mu}m$ CMOS process, post-layout simulation demonstrates that, even with a switching supply noise, the peak-to-peak jitter is less than 30 ps over the operating range of 500-1200 MHz. It occupies 0.04 $mm^2$ and dissipates 16.6 mW at 1.2 GHz.

• 대한전자공학회논문지TC
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• 제41권9호
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• pp.1-7
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• 2004

본 논문은 바코드의 유용성과 편리함을 개인 휴대폰에 결합하기 위한 Lock 시스템 설계 구현에 관한 내용이다. 본 연구에서는 바코드 스캐너 구성, 스캐너 설계, 휴대폰을 이용한 Lock 시스템 설계와 시제품 소개로 구성되어 있다. 본 연구를 보안 시스템에 적용 될 때 물리적 key 개념이 없어지고 휴대폰이 보안의 중심이 될 수 있을 것으로 기대되며 양방향 서비스가 가능해짐으로써 시공간의 제약을 극복한 결제가 가능함으로 활용이 확대될 것으로 예상된다. 향후 연구과제로는 다양한 응용분야에서의 적용 및 고감도 장치 개발을 들 수 있다.

• 대한방사선치료학회지
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• 제16권1호
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• pp.67-72
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• 2004

목 적 : 본원에서는 Whole body용 Vac-Lock을 이용하여 환자의 전신체형을 뜨고 있다. 그러나 몇 가지 애로사항이 발생하여 본 연구에서는 이러한 문제점을 찾아 보고, 애로사항을 해결하고자 자체 제작한 3DCA에 대해 알아보고자 한다. 대상 및 방법 : 본원에서 사용중인 Whole body용 Vac-Lock의 크기는 2종류가 있는데, 그에 따라 제작한 3DCA를 제작하는데 재질은 목재를 이용하였는데, 그것은 비용절감과 직접 제작을 하기 위해서는 쉽게 재질을 다룰 수 있고, 모양을 내기 위해서는 목재가 적정하였다고 사료되었다. 결 과 : Vac-Lock을 사용하면서 애로사항을 4가지로 분석하였고, 이러한 문제점을 해결하기 위해 3DCA를 제작 사용하게 되었다. 첫 번째 문제는 많은 제작 인원으로, 3DCA를 사용하여 전에는 환자의 전신체형을 뜨는데 5명 내지 6명이 동원 되었는데, 이제는 한사람이 할 수 있게 되었다. 두 번째는 제작 시간으로 3DCA를 사용하기 전에는 많은 인원이 동원되어도 1시간 이상이 소요되었으나, 이제는 한사람이 10분 이내로 단축할 수 있었다. 세 번째는 Vac-Lock이 큰 관계로 체형을 뜬 후 치료기기와 충돌하는 경우가 있었으나, 지금은 그러한 현상을 방지할 수 있었다. 네 번째로 3DCA를 사용하기 전에는 Vac-Lock의 외형이 깔끔하지 못했는데, 이제는 매끄럽게 체형을 뜰 수가 있었다. 결 론 : 환자가 치료받은 자세를 치료시 마다 동일하게 유지하기 위해 Vac-Lock을 사용하였는데, Vac-Lock 제품의 특성상 사용시 조금한 불편함이 근무자에게 애로사항으로 다가왔다. 이번 연구도 그러한 불편함을 조금이나마 줄여 보고자 하였고, 실제 문제점을 찾아 보고, 그 문제점을 해결하고자 3DCA를 제작 사용하였는데 많은 효과를 보고 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.515-518
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• 2001

In this study, the electric door lock using the password input system for security improvement was fabricated. The security has been improved by using the multiple micro process. The controller with solenoid valve has been designed indirect driving system for releasing the door lock system. Also, the self checkup system for improving the trustworthy was developed with two kinds of micro process. The results will be applied IC card system and fingerprint identification system for security improvement.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.79-82
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• 2000

This paper describes a delay locked loop with selective starting point for use in a high-frequency systems. SSRDLL (selective starting point RDLL) has been simulated in a 0.25$\mu\textrm{m}$ standard n-well CMOS process parameter to realize a fast lock-on time. This DLL is shown to be insensitive to variations in PVTL. The simulated lock time of the proposed SSRDLL is within 4 clock cycles at 333㎒ clock input.