• 지질공학
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• 제29권4호
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• pp.439-449
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• 2019

하천 건천화 예방 및 하천수와 지하수의 효율적 연계 이용을 위해서는 지하수 이용이 하천의 수량에 미치는 영향 평가가 수반되어야 한다. 이를 위해서는 대수층과 하천의 다양한 수리특성 조건에 대해 지하수 양수에 따른 하천수량의 변화 분석이 필요하다. 본 연구에서는 하천수위 변동을 반영할 수 있고 지하수 양수에 따른 하천수 감소량을 산정할 수 있는 Baalousha 해석해를 이용하여 하천수위가 지수함수적으로 감소하는 경우와, 감소 후 다시 회복되는 경우에 대해 지하수 양수로 인한 하천수 감소량의 변화 특성을 분석하였다. 대수층의 수리특성으로 투수량계수 10~100 ㎡/d 및 저류계수 0.05~0.3, 하천의 수리특성으로 하상수리전도성 0.01~20 m/d, 하천수위 감수상수 0.1~1.0 1/d, 그리고 하천과 관정의 이격거리 100~500 m 조건에 대해 지하수 양수량 대비 하천수 감소량인 하천수 기여도를 산정하고 그 거동 특성을 하천수위 변동 유무에 따라 종합적으로 분석, 제시하였다. 하천수위 감소 영향을 고려하였을 경우 하천수 기여도가 크게 감소하고 하천-관정 이격거리와 수리확산도의 함수인 하천고갈인자 값에 영향을 작게 받는 것으로 나타났으며, 반면에 하천수위 감소 후 회복되는 조건에서의 하천수 기여도는 하천수위 변동이 없는 경우와 큰 차이가 없는 것으로 나타났다. 이러한 결과는 하천수위 조절을 통해 지하수 양수시 하천수 및 대수층 저류량에 미치는 상대적 영향의 통제가 가능함을 의미한다.

• 수산해양기술연구
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• 제37권3호
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• pp.174-180
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• 2001

부레를 가시고 있는 어류는 그 부레가 반사강도에 많은 영향을 미치고 있다. 해중에서 어류의 부레가 등방향 반사강도에 미치는 영향을 알아보기 위하여 제주도 주변 정치망에서 어획된 독가시치 8마리에 대하여 200 kHz 송수파기를 이용하여 등방향 반사강도를 측정하였다. 등방향 반사강도에 대한 부레의 역할 정도에 관한 조사를 위해서는 X-ray 사진을 이용하여 주사기로서 부레의 가스를 제거하기 전후의 등방향 반사강도를 비교.분석하였다. 독가시치의 유영자세별 등방향 반사강도의 최대치는 수평상태에서 6$^{\circ}$만금 머리를 아래로 향하여 보다 깊은 수심으로 유영하여 가는 자세에서 -30.69 dB 이었다. 부레속에 가스가 있을 때의 실험어의 전장과 체중에 따른 평균 등방향 반사강도를 나타내는식은 각각, TS : -65.16 + 20 log L TS : -50.50 + 20/3 log W 이었다. 또한 부레속의 가스를 제거한 후 실험어의 전장과 체중에 따른 평균 등방향 반사강도를 나타내는 식은 각각, TS : -65.29 + 20 log L TS : -52.62 + 20/3 log W으로서 전장과 체중에 대하여 모두 2.12~2.13 dB의 차이가 있었다. 독가시치는 부레속의 가스를 제거하기 전의 등방향 반사강도가 제거한 후보다 최고5.87 dB, 평균 2.01 dB 높았는데 이는 회귀직선식으로 구한 차이와 거의 같은 값이었다. 그러나. $\pm{30}^\circ$ 전후의 유영자세에서 부분적으로 반사강도의 역전현상이 나타났으며. 유영자세 $27^\circ$에서 2.12 dB 이나 낮게 나타났다.

• 한국치위생학회지
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• 제12권3호
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• pp.513-520
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• 2012

Objectives : In this study, contact angle and shore D hardness were measured, and a shark fin test was conducted after selecting five addition silicon(Blu-Mousse, BM; EXABITE II, EX; PERFECT, PF; Regisil$^{(R)}$ Rigid, RE; Silagum$^{(R)}$, SI) in order to figure out the properties of elastomeric interocclusal recording materials and reduce errors at interocclusal recording. 8) Methods : A contact angle was measured using a contact angle analyzer. After placing a drop of liquid on the surface of the specimens of interocclusal recording materials, a contact angle was photographed with a CCD camera on the equipment. In terms of a shark fin test, interocclusal recording materials were mixed for the time proposed by the manufacturer and inserted into the split ring of the Shark fin device. Twenty (20) seconds exactly, a metal rod was removed to make the materials slowly absorbed. Once they hardened, fin height was measured with a caliper after separating molds and trimming the specimens. The shore D hardness was measured with a shore D hardness tester(Model HPDSD, Hans Schmidt & Co. Gmbh, Germany) in sixty (60) minutes after fabricating specimens. In each experiment, five specimens, mean and standard deviation were calculated. A one-way ANOVA test was performed at the p>0.05 level of significance. In terms of correlation among the tests, Pearson correlation coefficient was estimated. For multiple comparison, Scheffe's test was carried out. Results : A contact angle was the highest in EX with $99.23^{\circ}$ (p<0.05) while the result of the shark fin test was the longest in RE with 5.45mm. SI was the lowest (0.27mm) with statistical significance. Among the interocclusal recording materials, significant difference was observed in terms of means (p<0.05). The shore D hardness was the highest in SI with 31.0 while RE was significantly low with 16.4 (p<0.05). Among the materials, statistically significant difference was observed in terms of means when compared to the rest materials (RE), BM, RE and SI (PF and EX) and the remaining materials (BM and SI) (p<0.05). In terms of correlations among the tests, a negative correlation occurred between shore D hardness and shark fin test(r=-0.823, p=0.000). Conclusions : According to the study above, it is necessary to understand the properties of interocclusal recording materials and consider contact angle, shark fin test and properties of shore D hardness to select appropriate materials.

• 한국전자파학회논문지
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• 제20권10호
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• pp.1042-1049
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• 2009

본 논문에서는 광대 역 X-Band 추적 레이더의 모노펄스 비교기(comparator)에 적용 가능한 도파관 magic-T 설계 및 최적화 문제에 대해서 고찰하였다. 다층으로 구성된 도체 실린더(cylinder)를 이용하여 기존의 X-Band magic-T에 비해 광대역의 임피던스 정합을 구현하였다. 최적화된 파라미터 도출을 위해 유전 알고리즘과 particle swarm optimization을 결합한 하이브리드 최적화 알고리즘을 설계에 적용하였으며, 최적 설계된 도파관 magic-T는 모든 도파관 포트에 대해, 최소 12% 이상의 대역폭에서 -20 dB 이하의 반사 특성을 나타내었다. 전력 분배 손실은 0.2 dB 이하이며 전력 분배 편차 또한 0.1 dB 이하로 우수한 특성을 보여주었다. 또한 측정된 결과는 시뮬레이션 결과와 잘 일치하는 것을 확인하였다. 마지막으로, 적층 실린더의 차수를 증가시켜 5단 및 7단 적층 된 구조에 대한 대역폭 성능도 분석하였다.

• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.263-267
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• 2006

A new thermal bimorph actuator for large out-of-plane displacement is designed, fabricated and tested. The deflecting beam is composed of polyimide, heater, and polyvinyl difluorides with tetrafluoroethylene (PVDF-TrFE). The large difference of coefficient of thermal expansion (CTE) of two polymer layers (polyimide and PVDF-TrFE) can generate a significant deflection with relatively small temperature rise. Compared to the most conventional micro actuators based on MEMS (micro-electro mechanical system) technology, a large displacement, over 1 mm at 20 mW, could be achieved. Additionally, we can achieve response time of 14.6 ms, resonance frequency of 12 Hz, and reliability ability of $10^5$ cycles. The proposed actuator can find applications where a large vertical displacement is needed while maintaining compact overall device size, such as a micro zooming lens, micro mirror, micro valve and optical application.

• Journal of Welding and Joining
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• 제8권1호
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• pp.43-53
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• 1990

The transient temperature distribution in the continuous friction welding 304 stainless steel bars is investigated by experimental and analytical methods. It is calculated by F.D.M. (finite difference method). The heating pressure, the rotational speed and friction coefficient obtained from experiment are used to determine the heat input at the contacting surface. Thermal properties of the workpiece are the function of temperature. The calculated temperature is well coincided with the measured value. The grain size at weld interface is extremely small due to the severe plastic deformation at high temperature, and result of this refined zone reveals higher hardness value. Because the HAZ is very narror about 2-3 mm, welding defects do not occure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.1157-1161
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• 2007

A construction noise is the main reason for people's petition among the pollution. The purpose of this study is to develop the noise prediction program to see the level of the noise on the construction site more accurately. For this purpose, the database of the power level on the various equipments was made. The noise reduction by distance and the noise reduction by diffraction of barrier were mainly considered and calculated. The simple noise prediction program will provide the information about proper height and length of the potable barrier which satisfies noise criteria of the construction sites from a construction planning stage. To investigate the reliability of this program, the predicted data was compared with the measured data. An average of difference between measured data and predicted data is 1.3 dB(A) and a coefficient of correlation is about 0.95.

• The Journal of the Acoustical Society of Korea
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• 제25권1E호
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• pp.1-7
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• 2006

This study examines the reflection characteristic of a thin transition layer of the ocean bottom showing variability with respect to depth. In order to model the surficial sediment simply, we reduce the Biot model to the depth dependent wave equation for the pseudo fluid using the fluid approximation (weak frame approximation). From the reduced equation, the difference between the inherent frequency dependency of the reflection and the frequency dependency resulting from a thin transition layer is investigated. Using Tang's depth porosity profile model of the surficial sediment [D. Tang et al., IEEE J. Oceanic Eng., vol.27(3), 546-560(2002)], we numerically simulated the reflection loss and investigated the contribution from both frequency dependencies. In addition, the effects of different sediment type and varying depth structure of the sediment are discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.670-677
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• 2009

The purpose of this study is to reveal the quantitative dose-response relationship between the noise emitted in the platform of subway station and the public response. The noise measured in the platform of subway station was used for a jury test. In order to find the factors which influence annoyance response due to the platform noise, jurors were examined for the difference of the annoying response, interrelation of sound quality parameter and annoyance response. The platform noise level was 77.2$\sim$83.9 dBA and the most of passengers at the platform were highly annoyed. And screen door contributes to annoyance reduction of platform noise. The results from analyzing sound quality parameters shows that loudness and annoyance response have a high correlation coefficient.

• 한국소음진동공학회논문집
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• 제20권9호
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• pp.834-840
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• 2010

The Sound reduction indices(SRIs) of interior door with 13 different size apertures are measured in acoustic chamber. Also, as a theoretical approach, the SRIs are estimated using Gomperts' theory. In this study, the aperture of interior door is focused on the lower part of door leaf which is well known as a main cause to deteriorate the sound insulation performance of door. The results show that the SRI of door strongly depends on the aperture width and the dip in the measured sound reduction index curve by the resonance effect within aperture is observed at high-frequency. On the whole, the values calculated by theory are in good agreement with the measured values including the position of resonance dip. The average difference between the measured and the calculated values is 0.9 dB for 13 doors with different size aperture in terms of the weighted SRI.