• Earthquakes and Structures
• /
• 제21권6호
• /
• pp.563-576
• /
• 2021

The rocking foundation is effective for reducing structural seismic demand and avoiding overdesign of the foundation. It is crucial to evaluate the performance of rocking foundations because they cause plastic hinging in the soil. In this study, to derive optimized ground motion intensity measures (IMs) for rocking foundations, the efficiency of IMs correlated with engineering demand parameters (EDPs) was estimated through the coefficient determination using a physical modeling database for rocking shallow foundations. Foundation deformations, the structural horizontal drift ratio, and contribution in drift from foundation rotation and sliding were selected as crucial EDPs for the evaluation of rocking foundation systems. Among 15 different IMs, the peak ground velocity exhibited the most efficient parameters correlated with the EDPs, and it was discovered to be an efficient ground motion IM for predicting the seismic performance of rocking foundations. For vector regression, which uses two IMs to present the EDPs, the IMs indicating time features improved the efficiency of the regression curves, but the correlation was poor when these are used independently. Moreover, the ratio of the column-hinging base shear coefficient to the rocking base shear coefficient showed obvious trends for the accurate assessment of the seismic performance of rocking foundation-structure systems.

• 한국수자원학회논문집
• /
• 제54권spc1호
• /
• pp.1061-1069
• /
• 2021

최근 이상 기후로 인해 극한 호우 및 국지성 호우의 규모 및 빈도가 증가하여 하천 주변의 홍수 피해가 증가하고 있다. 이에 따라 하천 또는 유역 내 수문학적 시스템의 비선형성이 증가하고 있으며, 기존의 물리적 기반의 수문 모형을 활용하여 홍수위를 예측하기에는 선행시간이 부족한 한계점이 존재한다. 본 연구에서는 Deep Neural Network (DNN) 및 Long Short-Term Memory (LSTM)기반의 딥러닝 기법을 적용하여 울산시(태화교) 지점의 수위를 0, 1, 2, 3, 6, 12시간에 대해 선행 예측을 수행하였고 예측 정확도를 비교 분석하였다. 그 결과 sliding window 개념을 적용한 DNN 모형이 선행시간 12시간까지 상관계수 0.97, RMSE 0.82 m로 가장 높은 정확도를 보이고 있음을 확인하였다. 향후 DNN 모형을 활용하여 딥러닝 기반의 수위 예측을 수행한다면 기존의 물리적 모형을 통한 홍수위 예측보다 향상된 예측 정확도와 충분한 선행시간을 확보할 수 있을 것으로 판단된다.

• Safety and Health at Work
• /
• 제3권1호
• /
• pp.22-30
• /
• 2012

Objectives: To challenge the problem of slipperiness, various slipmeters have been developed to assess slip hazard. The performance of in-situ slipmeter is, however, still unclear under the various floor conditions. The main objectives of this study were to evaluate the performance of three kinds of slipmeters under real conditions, and to find their dynamic and kinematic characteristics, which were compared with gait test results. Methods: Four common restaurant floor materials were tested under five contaminants. Slipmeters and human gaits were measured by high speed camera and force plate to find and compare their dynamic and kinematic characteristics. Results: The contact pressures and built-up ratio were below those of subjects. The sliding velocity of British Pendulum Tester was above those of subjects, while those of BOT-3000 and English XL were below those of subjects. From the three meters, the English XL showed the highest overall correlation coefficient (r = 0.964) between slip index and $R_a$, while the rest did not show statistical significance with surface roughness parameters ($R_a$, $R_z$). The English XL only showed statistical significance (p < 0.01) between slip index and contaminants. The static coefficient of friction obtained with the BOT-3000 showed good consistency and repeatability (CV < 0.1) as compared to the results for the BPT (CV > 0.2) and English XL (CV < 0.2). Conclusion: It is unclear whether surface roughness can be a reliable and objective indicator of the friction coefficient under real floor conditions, and the viscosity of contaminants can affect the friction coefficient of the same floors. Therefore, to evaluate slipperiness, the performance of the slipmeters needed to improve.

• 대한전자공학회논문지TC
• /
• 제43권5호
• /
• pp.162-168
• /
• 2006

전파 특성의 이해는 무선 통신 시스템의 설계와 서비스의 구축을 위해 매우 중요하다. 본 논문에서는 곡선형 지하철 터널환경에서 2.45GHz 주파수 대역의 전파 특성을 측정하고 분석하였다. 슬라이딩 코릴레이션 기반의 채널 측정 시스템을 구성하고 안테나의 빔 형태에 따른 특성을 비교하기 위해 5 종류의 안테나를 사용하였다. 터널내 경로손실은 자유공간에 비하여 안테나에 따라 평균 $4.38^{\sim}14.41dB$가 적고 원편파 안테나의 경로손실이 가장 적다. 또한 곡선구간에서 수신 안테나의 위치가 바깥쪽에 위치할 때 경로손실이 가장 적다. 모든 안테나의 지연성분의 90%가 20ns 이내에 존재하며, 지향성 안테나가 무지향성 안테나보다 더 넓은 코히어런스 대역폭을 갖는다. 측정결과 경로손실과 지연 특성을 고려할 때 지하철 터널에서는 원편파 안테나를 사용하는 것이 적합한 것으로 판단된다.

• Structural Engineering and Mechanics
• /
• 제61권4호
• /
• pp.527-538
• /
• 2017

The evaluation of the loss-of-support conditions of frictional beam-to-column connections using simplified numerical models describing the transverse response of a portal-like structure is presented in this paper considering the effects of the seismic-hazard disaggregation. Real earthquake time histories selected from European Strong-motion Database (ESD) are used to show the effects of the seismic-hazard disaggregation on the beam loss-of-support conditions. Seismic events are classified according to different values of magnitudes, epicentral distances and soil conditions (stiff or soft soil) highlighting the importance of considering the characteristics of the seismic input in the assessment of the loss-of-support conditions of frictional beam-to-column connections. A rigid and an elastic model of a frame of a precast industrial building (2-DoF portal-like model) are presented and adopted to find the minimum required friction coefficient to avoid sliding. Then, the mean value of the minimum required friction coefficient with an epicentral distance bin of 10 km is calculated and fitted with a linear function depending on the logarithm of the epicentral distance. A complete parametric analysis varying the horizontal and vertical period of vibration of the structure is performed. Results show that the loss-of-support condition is strongly influenced by magnitude, epicentral distance and soil conditions determining the frequency content of the earthquake time histories and the correlation between the maxima of the horizontal and vertical components. Moreover, as expected, dynamic characteristics of the structure have also a strong influence. Finally, the effect of the column nonlinear behavior (i.e. formation of plastic hinges at the base) is analyzed showing that the connection and the column are a series system where the maximum force is limited by the element having the minimum strength. Two different longitudinal reinforcement ratios are analyzed demonstrating that the column strength variation changes the system response.

• 융합신호처리학회논문지
• /
• 제6권4호
• /
• pp.206-211
• /
• 2005

본 논문에서는 블루투스 기저대역에 적용하기 위한 상관기와 액세스 코드 생성모듈의 설계에 대해 다룬다. 상관기와 액세스 코드 생성 모듈은 블루투스 유닛 사이의 연결설정과 패킷판별, 클록 동기화를 수행한다. 상관기 모듈은 1Mb/s 전송속도를 가지는 입력신호에 대해 슬라이딩 윈도우 상관을 취하여 유용한 패킷판별과 클록 동기화를 행하며, 그 구성은 Wallace tree 구조의 CSA(Carry Save Adder)와 임계 값 판별기로 구성된다. 액세스 코드 생성모듈은 블루투스 표준안에서 제시한 4단계의 생성과정에 따라 설계하였으며 BCH(Bose-Chadhuri-Hocquenghem)순회 부호기(cyclic code)와 제어장치로 구성된다. 의사 랜덤 시퀀스는 동기화 문제를 해결하기 위해 임의의 저장장치에 저장된 형태로 사용하였다. 본 논문에서 제시한 상관기와 액세스 코드 생성모듈은 하드웨어 묘사언어인 VHDL로 설계되었으며 시뮬레이션 및 테스트를 위해 Xilinx FPGA를 사용하여 검증하였다. 설계된 회로의 합성결과는 치대 4.689ns의 임계지연과 최대 7-bit까지의 상관허용 오차를 보여준다.

• Transactions on Electrical and Electronic Materials
• /
• 제8권2호
• /
• pp.67-72
• /
• 2007

High Pressure Micro Jet (HPMJ) pad conditioning system was investigated as an alternative to diamond disc conditioning in copper CMP. A series of comparative 50-wafer marathon runs were conducted at constant wafer pressure and sliding velocity using Rohm & Haas IC1000 and Asahi-Kasei EMD Corporation (UNIPAD) concentrically grooved pads under ex-situ diamond conditioning or HPMJ conditioning. SEM images indicated that fibrous surface was restored using UNIPAD pads under both diamond and HPMJ conditioning. With IC1000 pads, asperities on the surface were significantly collapsed. This was believed to be due to differences in pad wear rates for the two conditioning methods. COF and removal rate were stable from wafer to wafer using both diamond and HPMJ conditioning when UNIPAD pads were used. Also, HPMJ conditioning showed higher COF and removal rate when compared to diamond conditioning for UNIPAD. On the other hand, COF and removal rates for IC1000 pads decreased significantly under HPMJ conditioning. Regardless of pad conditioning method adopted and the type of pad used, linear correlation was observed between temperature and COF, and removal rate and COF.

• Transactions on Electrical and Electronic Materials
• /
• 제8권2호
• /
• pp.53-57
• /
• 2007

In this study, a novel slurry containing ceria as the abrasive particles was analyzed in terms of its frictional, thermal and kinetic attributes for interlayer dielectric (ILD) CMP application. The novel slurry was used to polish 200-mm blanket ILD wafers on an $IC1000_{TM}$ K-groove pad with in-situ conditioning. Polishing pressures ranged from 1 to 5 PSI and the sliding velocity ranged from 0.5 to 1.5 m/s. Shear force and pad temperature were measured in real time during the polishing process. The frictional analysis indicated that boundary lubrication was the dominant tribological mechanism. The measured average pad leading edge temperature increased from 26.4 to $38.4\;^{\circ}C$ with the increase in polishing power. The ILD removal rate also increased with the polishing power, ranging from 400 to 4000 A/min. The ILD removal rate deviated from Prestonian behavior at the highest $p{\times}V$ polishing condition and exhibited a strong correlation with the measured average pad leading edge temperature. A modified two-step Langmuir-Hinshelwood kinetic model was used to simulate the ILD removal rate. In this model, transient flash heating temperature is assumed to dominate the chemical reaction temperature. The model successfully captured the variable removal rate behavior at the highest $p{\times}V$ polishing condition and indicates that the polishing process was mechanical limited in the low $p{\times}V$ polishing region and became chemically and mechanically balanced with increasing polishing power.

• 한국전자파학회지:전자파기술
• /
• 제5권4호
• /
• pp.47-63
• /
• 1994

지연확산은 이동통신채널을 특정짓는 중요한 파라미터이다. 본 논문에서는 대전 인근의 대표적인 이동통신 서비스 환경에 대하여 측정한 지연파 프로파일의 측정 결과와 이로부터 산출한 지역확산의 분포에 대하여 소개 한다. 측정시스템은 lO23chip의 코드길이와 4Mbps의 PN code를 사용한 슬라이딩 상관법을 이용하여 구성되 었으며, 측정값의 신뢰도를 보장하기 위하여 상용 채널시뮬레이터를 이용하여 시간축과 진폭축에 대한 성능평가를 수행하였다. 지연확산값의 측정 결과는 부도심에서 2.08$\mu\textrm{s}$, 2.12$\mu\textrm{s}$ 그리고 국도상에서는 1.31$\mu\textrm{s}$의 평균값 을 얻었다. 각 측정 지역에서는 50%의 확률로 3.4$\mus$,2.8$\mus$ 그리고 1.5$\mus$, 또한 90%의 확률로 4.5$\mus$,4.2$\mu\textrm{s}$ 그리고 2.9$\mu\textrm{s}$보다 작은 지연확산값을 갖는 것으로 조사되었다. 도심에서 도로를 왕복하면서 측정한 결과의 편차는 7% 이내였으며, 부도심의 경우에는 외국의 발표 자료와 비교하여 지역확산의 분포가 3~4 배정도 큰 값으로 관 측되었다.

• 대한치과교정학회지
• /
• 제15권1호
• /
• pp.67-74
• /
• 1985

The primary objective of this study is to make the prediction percentile tabulation of the sun of mesiodistal width of the unerupted permanent canines and premolars derived from the sum of mesiodistal width of the erupted permanent mandibular incisors in Korean population. The subjects were 316 individuals with normal occlusion aged 11 to 23 years. The sum of mesiodistal width of mandibular incisors, and the sum of mesiodistal width of maxillary canine, first and second premolars, and the sum of mandibular canine, first and second premolars were measured from the dental cast models using the sliding caliper (Mitutoyo Co.). From the study, the results are as follows: 1. The sum of M-D width of mandibular incisors and the sum of M-D width of maxillary canines, first and second premolars, and the sum of M-D width of mandibular canine, first and second premolars were smaller than those of American Caucasians and Negros. 2. The correlation coefficient between the sum of M-D width of mandibular incisors and that of maxillary or mandibular canines, first and second premolars was found to be 0.598 and 0.586, respectively. 3. The regression constants were determined to evaluate the sum of M-D width of the unerupted permanent canines and premolars derived from the sum of M-D width of the erupted permanent incisors. 4. The prediction percentile tabulation were made in an attempt to predict the total M-D width of the unerupted permanent canines and premolars derived from the total M-D width of the erupted permanent mandibular incisors.