• Title/Summary/Keyword: depth calibration

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An Efficient Pedestrian Recognition Method based on PCA Reconstruction and HOG Feature Descriptor (PCA 복원과 HOG 특징 기술자 기반의 효율적인 보행자 인식 방법)

  • Kim, Cheol-Mun;Baek, Yeul-Min;Kim, Whoi-Yul
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.10
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    • pp.162-170
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    • 2013
  • In recent years, the interests and needs of the Pedestrian Protection System (PPS), which is mounted on the vehicle for the purpose of traffic safety improvement is increasing. In this paper, we propose a pedestrian candidate window extraction and unit cell histogram based HOG descriptor calculation methods. At pedestrian detection candidate windows extraction stage, the bright ratio of pedestrian and its circumference region, vertical edge projection, edge factor, and PCA reconstruction image are used. Dalal's HOG requires pixel based histogram calculation by Gaussian weights and trilinear interpolation on overlapping blocks, But our method performs Gaussian down-weight and computes histogram on a per-cell basis, and then the histogram is combined with the adjacent cell, so our method can be calculated faster than Dalal's method. Our PCA reconstruction error based pedestrian detection candidate window extraction method efficiently classifies background based on the difference between pedestrian's head and shoulder area. The proposed method improves detection speed compared to the conventional HOG just using image without any prior information from camera calibration or depth map obtained from stereo cameras.

Relationship of the Thermal Stratification and Critical Flow Velocity Near the Baekje Weir in Geum River (금강 백제보 구간 수온성층 형성과 임계유속 관계)

  • Kim, Dong-min;Park, Hyung-Seok;Chung, Se-Woong
    • Journal of Korean Society on Water Environment
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    • v.33 no.4
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    • pp.449-459
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    • 2017
  • In Geum River of Korea, three multi-purpose weirs were built at the downstream of Daecheong Reservoir during the Four Major River Restoration Project (FMRRP). The weirs have altered the hydraulic characteristics of the river, and consequently transformed the large areas of flowing ecosystem to deep and wide stagnant environment. In every summer, a thermal stratification occurred near the Baekje Weir having mean depth of 4.0 m, and the surface algal blooms dominated by buoyant cyanobacteria have been frequently formed after the FMRRP. The objective of this study was to investigate the relationship between flow velocity and thermal stability of the waterbody using a three-dimensional (3D) hydrodynamic model (EFDC+) after calibration against the thermistor chain data obtained in 2014. A new Sigma-Zed vertical grid system of EFDC+ that minimize the pressure gradient errors was used to better simulate the thermodynamics of the waterbody. The model reasonably simulated the vertical profiles of the observed water temperatures. The vertical mean flow velocity and the Richardson Number (Ri) that represents the stability of waterbody were estimated for various management water levels and flow rates scenarios. The results indicated that the thermal stability of the waterbody is mostly high ($Ri{\gg}0.25$) enough to establish stratification, and largely depend on the flow velocity. The critical flow velocity that can avoid a persistent thermal stratification was found to be approximately 0.1 m/s.

Development of the Phased Array Ultrasonic Test Technique for the Weld Inspection of Reactor Coolant System 3" Branch Connection Lines in Nuclear Power Plants (원자로냉각재계통 3" 분기관 용접부 위상배열초음파탐상검사(PAUT)기법 개발)

  • Lee, Seung-Pyo;Moon, Yong-Sig;Jung, Nam-Du;Cho, Yong-Bae;Kim, Chang-Soo
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.4 no.2
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    • pp.40-45
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    • 2008
  • There exist many types of pipe and component fatigue through vibrations, thermal fatigues or shifting. In some cases of thermal stratification/thermal fatigue, pipes & components are receiving thermal stress by means of material expansion and shrinkage by continuous thermal repetitive variation. Small cracks initially occur on the inside surface by thermal stress. These cracks grow in depth the pipe wall and finally come to a rupture. Pipe parts of susceptibility to thermal stratification and thermal fatigue are now being examined by conventional UT(ultrasonic test) as volumetric examination. It is difficult to fully satisfy the code & standards requirements because 3" weldolet weldments of RCS 16" pipe to 3" branch connection lines have complex structural shape. To solve the problems of conventional UT examination, we made a realistic mock-up and UT calibration block. We performed a simulation of phased array UT utilizing CIVA as NDE(Non-Destructive Examination) simulation software. Also we designed phased array UT transducer and wedge, optimal frequency by using simulation data. We performed phased array UT experiment through mock-up including artificial flaws(notch). The phased array UT technique is finally developed to improve the reliability of ultrasonic test at RCS 16" pipe to 3" branch connection weld.

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Estimating Human Size in 2D Image for Improvement of Detection Speed in Indoor Environments (실내 환경에서 검출 속도 개선을 위한 2D 영상에서의 사람 크기 예측)

  • Gil, Jong In;Kim, Manbae
    • Journal of Broadcast Engineering
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    • v.21 no.2
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    • pp.252-260
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    • 2016
  • The performance of human detection system is affected by camera location and view angle. In 2D image acquired from such camera settings, humans are displayed in different sizes. Detecting all the humans with diverse sizes poses a difficulty in realizing a real-time system. However, if the size of a human in an image can be predicted, the processing time of human detection would be greatly reduced. In this paper, we propose a method that estimates human size by constructing an indoor scene in 3D space. Since the human has constant size everywhere in 3D space, it is possible to estimate accurate human size in 2D image by projecting 3D human into the image space. Experimental results validate that a human size can be predicted from the proposed method and that machine-learning based detection methods can yield the reduction of the processing time.

Numerical Simulation of Dynamic Soil-pile-structure Interaction in Liquefiable Sand (액상화 가능한 지반에 근입된 지반-말뚝-구조물 동적 상호작용의 수치 모델링)

  • Kwon, Sun-Yong;Yoo, Min-Taek;Kim, Seok-Jung
    • Journal of the Korean Geotechnical Society
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    • v.34 no.7
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    • pp.29-38
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    • 2018
  • Three-dimensional continuum modeling of dynamic soil-pile-structure interaction embedded in a liquefiable sand was carried out. Finn model which can model liquefaction behavior using effective stress method was adopted to simulate development of pore water pressure according to shear deformation of soil directly in real time. Finn model was incorporated into Non-linear elastic, Mohr-Coulomb plastic model. Calibration of proposed modeling method was performed by comparing the results with those of the centrifuge tests performed by Wilson (1998). Excess pore pressure ratio, pile bending moment, pile head displacement-time history according to depth calculated by numerical analysis agreed reasonably well with the test results. Validation of the proposed modeling method was later performed using another test case, and good agreement between the computed and measured values was observed.

Study on Arching Characteristics of a Grand-Section Tunnel with Pre-Steel-Rib Nail Reinforcement (대단면 터널의 선지보네일 보강에 따른 아칭특성 연구)

  • Seo, Donghyun;Cheun, Seungyul;Lee, Seungho
    • Journal of the Korean GEO-environmental Society
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    • v.10 no.6
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    • pp.79-88
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    • 2009
  • In this study, it was studied on arching characteristics of a grand section tunnel with pre-steel-rib nail reinforcement. In this study, we examine the adaptation of tunnel plan and the case which is based on the strengthening method for preexistence tunnel and other pre-steel-rib nail while the upper part of cover depth is low or soil condition is bad. When the pre-steel-rib nail as new technology and method reinforces the foundation placed of grand section tunnel, it is much better in strengthening effect, safety and effectiveness than the conventional one. After investigation about the plan pre-steel-rib nail method, construction case and calibration data, it was confirmed and examined about the upper part of tunnel for strengthening the pre-steel-rib nail thereby arching characteristics of grand section tunnel using MIDAS/GTS finite element program. Moreover we present the method that could upgrade the accurate installation interval and adaptation method for strengthening effect to adapt the pre-steel-rib nail method in a foundation placed over a tunnel.

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The Effects of Time Scale Variation on The Runoff Calculation of TOPMODEL (TOPMODEL 유출계산에서 시간 스케일에 대한 영향 분석)

  • Kim, Kyung-Hyun;Lee, Hak-Su;Kim, Won;Jung, Sung-Won;Kim, Sang-Hyun
    • Journal of Korea Water Resources Association
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    • v.35 no.2
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    • pp.125-136
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    • 2002
  • The effects of the temporal scale of input hydrological data on runoff simulation have been studied using hydrological data with various time scales. TOPMODEL has been employed to explores these effects. The Genetic a1gorithm was used to calibrate model Parameters. The results of sensitivity analysis in various time scales provide the insight of parameter space for TOPMODEL operation of different time scale. The variation of temporal scale of input hydrological data appeared to have significant impacts on the model efficiency, average water table depth, the ratio of the surface runoff to the total runoff and the calibrated parameters. Generally, the longer the time scale, the more surface runoff and the less average water table death were calculated. It is found that the impact of lime scale to runoff simulation results from the structure of TOPMODEL and the hydrographic morphology.

Computation of Plug Capacity for Open -Ended Piles Driven into Sands (모래지반에 타입된 개단말뚝의 관내토지지력 산정)

  • 백규호;이승래
    • Geotechnical Engineering
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    • v.9 no.4
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    • pp.7-16
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    • 1993
  • Calibration chamber tests were conducted on open -ended model piles driven into dried siliceous sands with different soil conditions in order to clarify the effect of soil conditions on plug capacity, The model pile used in the test series was devised so that the bearing capacity of an open -ended pile could be measured out into three components , outside shaft resistance. plug resistance and tip resistance. Under several assumption, the value of earth pressure coefficient in the soil plug is calculated. It is gradually reduced with increase in the longitudinal distance from the pile tip. At the bottom of soil plug, it tends to decrease with increase in the penetration depth and relative density, and to increase with the increase of ambient pressure. In comparison of measured and calculated plug capacities using the one -dimensional analysis, we note that API code and one -dimensional analysis combined with P suggested by Randolph et al. and O'Neill et al. result in great underestimation of the plug capacity. Therefore, based on the test results, an empirical equation was suggested to compute the earth pressured coefficient to be used in the calculation of plug capacity using the one -dimensional analysis. and it produces proper plug capacities for all soil conditions.

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Application of Generalized Transmissivity Decreasing Function in TOPMODEL Operation (TOPMODEL 투수량계수 감소함수 일반화과정의 적용에 관한 연구)

  • Jeong, Seon-Hui;Kim, Sang-Hyeon
    • Journal of Korea Water Resources Association
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    • v.32 no.6
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    • pp.637-647
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    • 1999
  • This study investigated the applicability of generalized TOPMODEL approach which introduces the power law of decreasing transimissivity with depth instead of the traditional exponential decreasing function. The 50m digital elevation model(DEM) of Dongkog subwatershed at Wichon Test Watershed was used to perform runoff simulation. Random number generation algorithm was integrated into the calibration process for the reliable of model performance. General power law version of TOPMODEL with exponent 2 and 3 showed higher simulation efficiency than other the approaches. This results from the fact that the power law models with exponent 2 and 3 can represent the soil characteristics of study area better than other models.

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Drawing of Impedance Plane Diagrams of Absolute Coil ECT Signals by finite Element Analysis (유한요소해석에 의한 절대코일 와전류 신호의 임피던스 평면도 작성)

  • Shin, Young-Kil;Lee, Yun-Tai;Lee, Jeong-Ho;Song, Myung-Ho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.24 no.4
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    • pp.315-324
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    • 2004
  • In eddy current testing(ECT), differential probes have been frequently used since they .an reduce the number of parameters that influence ECT signals. However, differential signal is actually the difference of the two coils' impedance so that signal prediction and interpretation are not easy, On the other hand, absolute coil signal is rather straightforward to predict and analyze. Therefore, combined use of the two types of signals would increase the test reliability. In this paper, absolute coil signals from Inconel plate and tubes are predicted by the finite element analysis and efforts of lift-off, fill-factor, conductivity, operating frequency, test specimen thickness, inner diameter defects, and outer diameter defects are investigated. As a result, various impedance plane diagrams are drawn and analyzed. Significant practical knowldege about absolute signals is accumulated and similar characteristics of the two types of signal could be understood. Finally, slope angle versus defect depth calibration corves are prepared for three different frequencies.