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다짐지반의 모관흡수력 변화에 따른 탄성계수 평가를 위한 VPPE-BE 시험 시스템 개발
이세현,서원석,추연욱,김동수 한국지반공학회 2008 한국지반공학회논문집 Vol.24 No.5
The volumetric pressure plate extractor (VPPE) was modified for the measurement of shear wave velocity (Vs) at various levels of matric suction as well as soil water characteristic curve (SWCC). A non-destructive technique with a pair of bender element (BE) was employed in order to measure the Vs and the corresponding maximum shear modulus (Gmax) of unsaturated soil specimens. Three types of soil were collected from different road construction sites in Korea. For all test soils, the variations in Gmax with the various levels of water content and matric suction were investigated using the developed apparatus. Compared with the preceding results from the suction-controlled torsional shear (TS) testing system and in-situ seismic tests, the feasibility for evaluating modulus characteristics of unsaturated compacted soils with the developed VPPE-BE system was assessed. It was confirmed that the newly developed system would be potentially helpful in modeling seasonal variation of modulus.
대역폭 제한 조건과 Gram 행렬의 단위행렬로의 사영을 이용한 압축센싱 능동소나 송신파형 설계
이세현,이근화,임준석,정명준,Lee, Sehyun,Lee, Keunhwa,Lim, Jun-Seok,Cheong, Myoung-Jun 한국음향학회 2019 韓國音響學會誌 Vol.38 No.5
거리-도플러 추정을 위한 압축센싱(Compressive Sensing,CS) 모델은 과소결정계인 y = Ax 선형시스템으로 표현할 수 있다. 압축센싱 기법으로 위 선형시스템의 해를 찾으려면 행렬 A가 충분히 비간섭적이고 x가 희소해야 한다. 본 연구는 행렬 A가 비간섭적이도록 행렬 A의 상호간섭성을 낮추는 동시에 소나시스템에서 요구하는 대역폭을 유지하는 송신파형 설계 방법을 제안하였다. 제안한 방법은 행렬사영으로 센싱행렬을 최적화하는 방법과 DFT(Discrete Fourier Transform) 행렬을 이용하여 원하지 않은 주파수밴드를 억압하는 두 가지 방법을 결합한 것이다. 정합필터와 압축센싱 기법을 이용하여 기존파형 LFM(Linear Frequency Modulated)과 설계한 파형의 거리-도플러 추정 성능을 비교하였다. 시뮬레이션을 통해 설계한 송신파형이 기존파형(LFM)보다 탐지성능이 우수함을 보인다. The compressive sensing model for range-Doppler estimation can be expressed as an under-determined linear system y = Ax. To find the solution of the linear system with the compressive sensing method, matrix A should be sufficiently incoherent and x to be sparse. In this paper, we propose a transmission waveform design method that maintains the bandwidth required by the sonar system while lowering the mutual coherence of the matrix A so that the matrix A is incoherent. The proposed method combines two methods of optimizing the sensing matrix with the alternating projection and suppressing unwanted frequency bands using the DFT (Discrete Fourier Transform) matrix. We compare range-Doppler estimation performance of existing waveform LFM(Linear Frequency Modulated) and designed waveform using the matched filter and the compressive sensing method. Simulation shows that the designed transmission waveform has better detection performance than the existing waveform LFM.
비배수 조건에서 반복하중을 받는 사질토의 B값(간극수압계수)에 따른 P파, S파 속도 및 간극수압 측정
이세현,김동수,추연욱,윤준웅 한국지반공학회 2007 한국지반공학회논문집 Vol.23 No.2
Liquefaction resistance depends strongly upon the degree of saturation, which is expressed in terms of the pore pressure coefficient, B. The B-value has been widely used to quantify the state of saturation of laboratory samples. However, it is practically impossible to determine in situ state of saturation by using the B-value. So, P-wave velocity can be alternatively used as a convenient index for evaluating the in situ state of saturation. In this paper, the Stokoe type torsional shear (TS) testing system was modified to saturate the specimen, with which it is also possible to measure P (), S-wave velocity () and the excess pore water pressure buildup in order to examine the effect of B-value for nearly saturated sands. A series of the tests were carried out at 3 relative densities (40%, 50% and 75%) and various B-values using Toyoura sand. Based on the test results, the variations of and with B-value were analyzed and compared with a existing theoretically derived formula. The normalized pore water pressure, and cyclic threshold shear strain, with B-value were also analyzed. Additionally the test results related to pore water pressure were analyzed by to apply to the field seismic analysis.
이세현,박병기 한국아동교육학회 2018 아동교육 Vol.27 No.1
The purpose of this study was to synthesize the effect of the early childhood education programs on the children aged from 3 to 5. The results were meta-analyzed by using CMA(Comprehensive Meta Analysis ver.2.0) program. This study searched researches from 1960 to 2016 including 119 dissertations, 260 theses, 38journal articles, 417 researches in total. Out of the subjects 517 effect size (variable-based) were extracted and the random effects model was selected rather than fixed model as an analysis model. The results showed that The effect size of policy based was .937. The effect sizes of the policy based in the sub-domains(physical exercise and nature search) were .954 and 1.132 respectively. However the effect sizes of the emergent curriculums in the sub-domains(artic experience, communication, and creativity) were 1.737, 1.228 and .862 respectively. The effect sizes of education programs based on the moderating variables were as in the following. The highest score was .919 (2012-2016), .992 (the small group), 1.190 (age 3), 1.017(farming and fishing area). The best treatment period were 30 and over weeks, 5-6 in per week, total number was 60 and over, and 41-60 per time. Based on the previous research, this study identifies early childhood education programs related to the variables through meta-analysis, realizes the evidence-based actuality through a comprehensive analysis of the mean effect sizes, and finally suggests the direction of future configuration of early childhood education programs. 본 연구의 목적은 만 3세에서 5세까지의 유아를 대상으로 유아교육 프로그램 관련 변인들을 확인해서 분류하고 각 변인과 프로그램 간 효과의 크기를 밝히고자 하였다. 분석대상 논문은 1960년부터 2016년까지의 박사학위논문 119편, 석사학위논문 260편, 학술지논문 38편 등 총 417편의 실험연구논문을 선정하였다. 자료의 분석은 CMA(Comprehensive Meta Analysis, V3)를 활용하여 메타분석을 실시하였다. 총 417편의 논문으로부터 총 517개의 표본수준 효과크기와 3,710개의 변수수준 효과크기를 산출하여 분석하였다. 효과크기의 분석모형으로서 고정모형과 무선모형 중 전체 연구의 효과크기를 확인하기 위해서 연구들이 표본, 척도 등이 서로 다르다는 가정을 가진 무선효과모형(random-effect model)을 적용하였다. 연구결과, 유아교육 프로그램의 전체효과크기는 .862로서 높은 효과 크기를 나타냈다. 프로그램 범주에 따른 결과는 정책적 기반 프로그램의 평균효과크기는 .937로 철학/심리학기반 프로그램의 .641 효과크기와 발현적 기반 프로그램의 .765 효과크기에 비해 높은 효과크기를 나타났다. 성별의 경우 남아의 평균효과크기가 1.084 로 집단유형은, 2-10명 사이인 소집단이 높은 효과크기를 보였다. 처치변인별 결과로는 주당 횟수는 7-20회, 총 횟수 11-20회주 회당시간은 21-40분이 가장 높은 효과크기를 보였으며 적용기간과 효과크기가 계속 비례하는 것은 아니라는 결과가 나타났다. 연구결과의 함의를 논의한 후 유아교육프로그램에 대한 시사점을 제안하였다.