• 한국의류학회지
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• 제20권6호
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• pp.1166-1177
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• 1996

The purpose of this study was to analyze the change in modes of expression represented in fashion illustrations between the 1910s and the 1990s. 639 fashion illustrations were analyzed by content analysis and by qualitative analysis in five aspects. Typical traits in the modes of expression infashion illustrations in each period were described. The outstanding transformation in modes of expression from "before'70s" to " after'70s" were confirmed. The findings support two hypothesis: that modes of expression in fashion illustrations evolve and that changing modes of expression in fashion illustrations is a reflection of "spirit of the times".uot;spirit of the times".uot;.

• Journal of the Optical Society of Korea
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• 제18권4호
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• pp.377-381
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• 2014

Coupled guided modes, proposed in various modified hollow hexagonal cavities each attached internally to a hexagon, were demonstrated by investigating the laser oscillations in semiconductor cavities. The mode spacing between two adjacent lasing peaks decreased as the size of the internal hexagon increased, due to the increased round-trip length of the coupled guided modes. The linear dependency of the inverse mode spacing to the calculated round-trip length strongly confirmed the lasing of the coupled guided modes. The proposed modes in common-sized external cavities showed resonance structure that could be adjusted widely by controlling the size of the internal hexagon.

• 대한기계학회논문집B
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• 제20권2호
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• pp.616-623
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• 1996

This paper investigates the linear stability of reacting mixing layers with special emphasis on the existence of multiple unstable modes. The governing equations for laminar flows are from two-dimensional compressible boundary-layer equations. The chemistry is a finite rate single step irreversible reaction with Arrhenius kinetics. For the incompressible reacintg mixing layer with variable density. A necessary condition for instability has been derived. The condition requires that the angular momentum, not the vorticity, to have a maximum in the flow domain. New inflectional modes of instability are found to exist in the outer part of the mixing layer. For the compressible reacting mixing layer, supersonic unstable modes may exist in the abscence of a generalized inflection point. The outer modes at high Mach numbers in the reacting mixing layer are continuations of the inflectional modes of low Mach number flows. However, the generalized inflection point is less important at supersonic flows.

• 대한전기학회논문지:전력기술부문A
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• 제50권5호
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• pp.218-224
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• 2001

This paper describes the identification of torsional modes and power oscillation modes including the inter-area modes and local modes of KEPCO using the proposed DFT analysis algorithm which is applied to the digitally recorded RMS values of power system variables such as steady-state measured active power, load angle and so on. As a result, the inter-area mode of 0.65Hz and the local modes of the three different generators were identified. In addition the torsional modes of two steam-turbo generators were analyzed by applying the DFT algorithm. Thus, this paper clearly shows the availability of the proposed DFT algorithm that can analyze the digitally recorded effective values measured from the equipment such as PMU of DSM.

• 대한기계학회논문집B
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• 제22권12호
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• pp.1763-1773
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• 1998

In the present experimental study, the flow behavior in a semi-closed two-phase natural circulation loop was examined. Water was used as the working fluid. Heat flux, heater-inlet subcooling, and flow restrictions at the heater-inlet and at the expansion-tank-line were taken as the controlling parameters Six circulation modes were identified by changing heat flux and inlet subcooling conditions ; single-phase continuous circulation, periodic circulation (A), two-phase continuous circulation, and periodic circulations (B), (C), and (D). Among these, the single-phase and two-phase continuous-circulation modes exhibit no significant oscillations and are considered to be stable. Periodic circulation (A) is characterized by the large amplitude two-phase f10w oscillations with the temporal single-phase circulation between them, while periodic circulation (B) featured by the flow oscillations with continuous boiling inside the heater section. Periodic circulation (C) appears to be the manometric oscillation with continuous boiling. Periodic circulation (D) has the longer period than periodic circulation (B) and a substantial amount of liquid flow back and forth through the expansion-tank-line periodically ; this mode is considered the pressure drop oscillation. Parametric study shows that the increases of the inlet- and expansion-tank-line- restrictions and the decrease of inlet subcooling broaden the range of the stable two-phase(continuous circulation) mode.

• 한국소음진동공학회논문집
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• 제15권1호
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• pp.112-117
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• 2005

Two modified versions of subspace iteration method using accelerated starting vectors are proposed to efficiently calculate free vibration modes of structures. Proposed methods employ accelerated Lanczos vectors as starting iteration vectors in order to accelerate the convergence of the subspace iteration method. Proposed methods are divided into two forms according to the number of starting vectors. The first method composes 2p starting vectors when the number of required modes is p and the second method uses 1.5p starting vectors. To investigate the efficiency of proposed methods, two numerical examples are presented.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.484-487
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• 2006

In this paper, linear ultrasonic actuators are designed using two dimensional motions of a PMW-PT piezoelectric plate. By equalizing the natural frequencies of longitudinal and transverse vibration modes in the cantilever structure, the ultrasonic motion of the combined vibration modes are generated. We have designed two different PMN-PT actuators: one uses a tip attached on the edge of the actuator and it drives the object in the perpendicular direction of the tip. In other model, the actuator plate moves itself through stationary guides. Prototypes of the two models are manufactured and experiments results are compared to the theoretical and numerical results. The effects of structural characteristics and the friction force existing between the actuator tip and the moving object are considered. Experiments show the possibility of small size ultrasonic linear motors which can be applicable to small form factor information storage and phone camera actuators.

• 한국추진공학회지
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• 제2권2호
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• pp.30-37
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• 1998

연소 반응을 가지는 비압축성 및 압축성 후류유동에 대하여 선형 불안정성 해석을 수행하였따. 기본유동의 속도장 및 온도장은 해석적 함수 및 연소 반응을 포함하는 유동 계산의 결과를 사용하였다. 후류유동은 두 개의 변곡점을 가지며 sinuous mode와 varicose mode의 두 개의 불안정성 모드가 존재한다. 후류유동에서는 sinuous 모드가 varicose 모드보다 더 불안정하여 자유 유동에 가까운 위상 속도를 가지는 sinuous 모드에 의해 지배된다. 해석적 함수의 형태를 가지는 후류 유동의 경우 속도구배가 클수록, 밀도구배가 클수록 운동량의 차이가 커지므로 더욱 불안정하여진다. 계산되어 일관된 유동장과 온도장을 사용한 비압축성과 압축성 후류유동의 경우 모두 완전연소에 가까울수록 유동장의 온도가 증가하고 유체의 점성의 증가로 유동이 안정되어진다. 압축성 후류유동의 경우에는 유속이 증가함에 따라 점성소산에 의한 열발생으로 유동이 안정되는 경향을 보인다.

• 소음진동
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• 제8권4호
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• pp.632-642
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• 1998

A method based on finite element discretization is developed for optimizing the polarization profile of PVDF film to create the modal transducer for specific modes. Using this concept, one can design the modal transducer in two-dimensional structure having arbitrary geometry and boundary conditions. As a practical means for implementing this polarization profile without repoling the PVDF film the polarization profile is approximated by optimizing electrode patterns, lamination angles, and poling directions of the multi-layered PVDF transducer. This corresponds to the approximation of a continuous function using discrete values. The electrode pattern of each PVDF layer is optimized by deciding the electrode of each finite element to be used or not. Genetic algorithm, suitable for discrete problems, is used as an optimization scheme. For the optimization of each layers lamination angle, the continuous lamination angle is encoded into discrete value using binary 5 bit string. For the experimental demonstration, a modal sensor for first and second modes of cantilevered composite plate is designed using two layers of PVDF films. The actuator is designed based on the criterion of minimizing the system energy in the control modes under a given initial condition. Experimental results show that the signals from residual modes are successfully reduced using the optimized multi-layered PVDF sensor. Using discrete LQG control law, the modal peaks of first and second modes are reduced in the amount of 12 dB and 4 dB, resepctively.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.1260-1264
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• 2009

Precipitation time series is a mixture of complicate fluctuation and changes. The monthly precipitation data of 61 stations during 36 years (1973-2008) in Korea are comprehensively analyzed using the EOFs technique and CSEOFs technique respectively. The main motivation for employing this technique in the present study is to investigate the physical processes associated with the evolution of the precipitation from observation data. The twenty-five leading EOF modes account for 98.05% of the total monthly variance, and the first two modes account for 83.68% of total variation. The first mode exhibits traditional spatial pattern with annual cycle of corresponding PC time series and second mode shows strong North South gradient. In CSEOF analysis, the twenty-five leading CSEOF modes account for 98.58% of the total monthly variance, and the first two modes account for 78.69% of total variation, these first two patterns' spatial distribution show monthly spatial variation. The corresponding mode's PC time series reveals the annual cycle on a monthly time scale and long-term fluctuation and first mode's PC time series shows increasing linear trend which represents that spatial and temporal variability of first mode pattern has strengthened. Compared with the EOFs analysis, the CSEOFs analysis preferably exhibits the spatial distribution and temporal evolution characteristics and variability of Korean historical precipitation.