• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2004년도 춘계학술발표회
• /
• pp.807-814
• /
• 2004

Land seismic reflection survey has been increasingly demanded in various civil engineering works because of its own ability to delineate layers, water table, to detect cavities or fracture zones, to estimate seismic velocities of each layer. However, our shallow subsurface structures are very complex. The relatively thin layer(mostly soil) to the wavelength directly followed by a basic rock with high impedance used to generate complicated surface waves, kind of channel waves with high amplitude that is dominate in entire seismograms and hence the useful reflection events will be almost hopelessly immersed in the undesired surface waves. Thus, it would seem that the use of traditional seismic survey could not be likely to provide in itself a satisfactory information about our exploration targets. This paper hence introduces an efficient measuring strategy illustrating a properly controlled arrangement of the vertical single force sources commonly used, yielding a very sharply elongated form of P-energy with a minimum of S radiation energy, what we call, P-beam source. Abundant experiments of physical modeling showed that in that way the surface waves could be enormously reduced and the reflection events would be additive and thus reinforced. Examples of field data are also illustrated. The contribution of P-beam source will be great in civil engineering area as well as in general geological exploration area.

• Journal of Mechanical Science and Technology
• /
• 제16권2호
• /
• pp.203-210
• /
• 2002

For effective response surface modeling during sequential approximate optimization (SAO), the normalized and the augmented D-optimality criteria are presented. The normalized D-optimality criterion uses the normalized Fisher information matrix by its diagonal terms in order to obtain a balance among the linear-order and higher-order terms. Then, it is augmented to directly include other experimental designs or the pre-sampled designs. This augmentation enables the trust region managed sequential approximate optimization to directly use the pre-sampled designs in the overlapped trust regions in constructing the new response surface models. In order to show the effectiveness of the normalized and the augmented D-optimality criteria, following two comparisons are performed. First, the information surface of the normalized D-optimal design is compared with those of the original D-optimal design. Second, a trust-region managed sequential approximate optimizer having three D-optimal designs is developed and three design problems are solved. These comparisons show that the normalized D-optimal design gives more rotatable designs than the original D-optimal design, and the augmented D-optimal design can reduce the number of analyses by 30% - 40% than the original D-optimal design.

• 대한조선학회논문집
• /
• 제29권2호
• /
• pp.30-37
• /
• 1992

선체는 매우 복잡한 구조물이므로 설계 및 생산의 효율적인 수행을 위하여 선체구조의 모델링에 의한 작업이 필수적이다. 선체모델 구축에 있어서 구조면의 모델링은 초기선형정의에서부터, 선각정보처리, 구획배치, 의장설계, 배관설계, 구조해석 등 선체관련분야와 직접 연관된다. 본 연구에서는 구조면의 효과적인 모델링을 위하여 구조면들간의 위상학적인 자료구조를 구성하므로써 선체구조의 기하학적 정보를 설계의 단계에 따라 발전시켜 나가고 효율적으로 변경시킬 수 있도록 하였다. 본 연구에서 수행된 구조면의 모델링은 선체설계에서부터 생산에 이르기까지 일관된 정보처리를 위한 통합선체모델(Unified Hull Model)구축의 기초가 될 것이다. 구축된 모델의 가시화를 위하여 컴퓨터그래픽스를 이용하여 선체모델을 실물감 있게 표현하였다.

• 한국광물학회지
• /
• 제11권2호
• /
• pp.106-116
• /
• 1998

The adsorption of Cs-137 and Sr-90 onto kaolinite in prescence of major groundwater cations (Ca2+, K+, Na+) with different concentrations was simulated by using triple-layer surface complexation model (TL-SCM). The site density (8.73 sites/nm2) of kaolinite used for TL-SCM was calculated from it's CEC and specific surface area. TL-SCM modeling results indicate that concentrations dependence on 137Cs and 90Sr adsorption onto kaolinite as a function of pH is best modeled as an outer-sphere surface reaction. This suggests that Cs+ and Sr2+ are adsorbed at the $\beta$-layer in kaolinite-water interface where the electrolytes, Nacl, KCl and CaCl2, bind. However, TL-SCM results on Sr adsorption show a discrepancy between batch data and fitting data in alkaline condition. This may be due to precipitation of SrCO3 and complexation such as SrOH+. Intrinsic reaction constants of ions obtained from model fit are as follows: Kintcs=10-2.10, KintSr=10-2.30, KintK=10-2.80, KintCa=10-3.10 and KintNa=10-3.32. The results are in the agreement with competition order among groundwater ions (K+>Ca2+>Na+) and sorption reference of nuclides (Cs-137>Sr-90) at kaolinite-water interface showed in batch test.

• 지구물리와물리탐사
• /
• 제3권2호
• /
• pp.61-69
• /
• 2000

지표 경계 조건은 유한 차분법을 이용한 탄성파 파동 방정식 모델링에서 수치해의 정확성을 떨어뜨리는 한편 포아송 비에 따른 해의 안정성을 제한하는 주 요인이 된다. 본 연구에서는 지표 경계 조건과 같은 Neumann 경계 조건의 처리에 효과적인 적분법(integration method)에 기반 하여 차분식을 유도하고, 이로부터 중간점 차분 기법을 제안하였다. 또한, 개발된 알고리즘을 Lamb의 문제에 적용하여 이론해와 비교함으로써 타당성을 검증하였다.

• 전자공학회논문지SC
• /
• 제47권4호
• /
• pp.55-60
• /
• 2010

설치류는 수염을 통해서 물체를 인식하는 능력을 갖추고 있다. 단연 설치류뿐만 아니라 많은 수의 포유류가 사물을 인식하는데 수염을 이용하지만 특히 설치류는 수염을 통해서 마이크로미터 단위의 표면의 거칠기 차이도 구별 할 수 있다. 설치류는 수염을 앞, 뒤로 능동적으로 움직이며 물체의 모양이나 표면의 거칠기, 패턴 따위를 판별한다. 실제 쥐 수염에는 수염뿌리 가까운 모낭 안에 수많은 신경이 모여 있어서 수염이 떨리거나 구부러질 때의 신호를 받아들인다. 쥐의 이러한 능력을 모방하여, 본 논문에서는 마이크로폰을 이용하여 쥐 수염 센서를 제작하고 제작한 수염 센서를 통해 물체 표면의 거칠기에 대한 정보를 얻고자 한다.

• 한국분무공학회지
• /
• 제27권1호
• /
• pp.11-17
• /
• 2022

In upcoming Post Stage-V and Tier 5 regulations of construction machineries, nitrogen oxide (NOx) emissions are strictly limited in cold start conditions. In response to this, a method of improving NOx conversion efficiency has been applied by installing an electric heating catalyst (EHC) in front of conventional urea-SCR systems so that the evaporation and thermal decomposition of urea-water solution can be promoted in cold start conditions. In this strategy, the evaporation and thermal decomposition of urea-water solution and corresponding NOx conversion efficiency are governed by temperature conditions inside the EHC. Therefore, characterizing the temperature distribution in the EHC under various operating conditions is crucial for the optimized operation and control of the EHC in Urea-SCR systems. In this study, a 1-D modeling analysis was performed to predict the heater surface temperature distribution in EHC under various operating conditions. The reliability of prediction results was verified by comparing them with measurement results obtained using an infrared (IR) camera. Based on 1-D analysis results, the effects of various EHC operation parameters on the heater surface temperature distribution were analyzed and discussed.

• Journal of Positioning, Navigation, and Timing
• /
• 제4권1호
• /
• pp.33-41
• /
• 2015

Compact Network Real-Time Kinematic (RTK) is a method that combines compact RTK and network RTK, and it can effectively reduce the time and spatial de-correlation errors. A network RTK user receives multiple correction information generated from reference stations that constitute a network, calculates correction information that is appropriate for one's own position through a proper combination method, and uses the information for the estimation of the position. This combination method is classified depending on the method for modeling the GPS error elements included in correction information, and the user position accuracy is affected by the accuracy of this modeling. Among the GPS error elements included in correction information, tropospheric delay is generally eliminated using a tropospheric model, and a combination method is then applied. In the case of a tropospheric model, the estimation accuracy varies depending on the meteorological condition, and thus eliminating the tropospheric delay of correction information using a tropospheric model is limited to a certain extent. In this study, correction information modeling accuracy performances were compared focusing on the Low-Order Surface Model (LSM), which models the GPS error elements included in correction information using a low-order surface, and a modified LSM method that considers tropospheric delay characteristics depending on altitude. Both of the two methods model GPS error elements in relation to altitude, but the second method reflects the characteristics of actual tropospheric delay depending on altitude. In this study, the final residual errors of user measurements were compared and analyzed using the correction information generated by the various methods mentioned above. For the performance comparison and analysis, various GPS actual measurement data were collected. The results indicated that the modified LSM method that considers actual tropospheric characteristics showed improved performance in terms of user measurement residual error and position domain residual error.

• 지구물리와물리탐사
• /
• 제6권2호
• /
• pp.77-86
• /
• 2003

자유면 경계조건을 정착하게 묘사할 수 있는 변위근사 유한차분법을 이용하는 시간영역 탄성파 모델링법을 고안하였다. 기존의 변위근사 유한차분법의 경우 변위와 매질의 물성을 격자점에 정의하는 격자군(격자점 기반의 격자군)을 이용하였으나, 이 연구에서 제시하는 새로운 유한차분법에서는 변위는 격자점에 정의하지만 매질의 물성을 격자점으로 둘러싸인 면에 정의하는 격자군(셀 기반의 격자군)을 이용한다. 매질의 물성을 셀에 정의할 경우 자유면에서 응력이 사라진다는 자유면 경계조건을 추가로 적용할 필요가 없으며 매질의 물성 변화만으로 자유면 경계조건을 표현할 수 있다. 수치예를 통한 정확도 분석 결과 셀 기반의 격자군을 이용할 경우 계산된 수치석인 해가 해석적인 해에 매우 근사함을 알 수 있었다.

• Tribology and Lubricants
• /
• 제35권6호
• /
• pp.337-342
• /
• 2019

This paper presents an experimental investigation of friction and wear characteristic with respect to patterns occurring on the surface of 3D printed polymer products by fused deposition modeling method. The purpose of this study was to investigate the effect of the patterns and sliding directions on the tribological properties of 3D printed polymer surface. A cubic specimen was printed using polylactic acid filament as the printing material. Friction tests were conducted for different directions with respect to the patterns that were generated on the top and the side surfaces of the specimen, by using a ball-on-reciprocating type tribotester. SUJ2 bearing ball of which the diameter was 11 times greater than the width of the largest pattern was used as the counter surface to assess the frictional behavior. Friction tests were conducted on the top and the side surfaces with respect to the patterns in 3 (0°, 45°, 90°) different directions respectively. Coefficient of friction increased as cycles increased in all cases. The results of the tests showed that the lowest coefficient of friction was measured with the 45° sliding direction on the side surface. The wear rate was the lowest at 45° sliding direction on the side surface, while it was the highest at 0° sliding direction on the top surface. Coefficient of friction of about 0.45 was determined to be the converging value on the top compared to the side surface.