• 대기
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• 제24권3호
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• pp.317-329
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• 2014

Eddy covariance data have been analyzed to investigate the influence of surface heterogeneity on turbulent transfer over farmland and industrial sites near Nakdong river, Korea, where both large and small scale heterogeneities co-exist. For this purpose, basic turbulent statistics, quadrant analysis and multi-resolution decomposition have been analyzed during the daytime. Basic turbulent statistics were compared with typical turbulent statistics in the surface layer. Such comparisons were in close agreement for momentum and heat at both sites but not for water vapor at industrial site. The correlation coefficient between water vapor and vertical velocity ($r_{wq}$) is relatively low and skewness of water vapor ($sk_q$) is very low at industrial site, possibly due to limited water source. For heat at both sites and water vapor at farmland, the quadrant analysis show similar behavior to that over homogeneous site but for water vapor at industrial site, the presence of river and limited water source at industrial site seems to influence on water vapor transfer by coherent eddy motion by increasing sweep contribution and decreasing ejection contribution. Multi-resolution decomposition analysis shows that large scale heterogeneity leads to low $r_{Tq}$ at large averaging time regardless of season at both sites and there are seasonal changes of $r_{Tq}$ in mid-averaging times at industrial site, possibly due to seasonal change of trees and grasses near the site.

• Advances in nano research
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• 제8권2호
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• pp.115-134
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• 2020

In this paper, the free vibrations analysis of the nanoplates made of three-directional functionally graded material (TDFGM) with small scale effects is presented. To study the small-scale effects on natural frequency, modified strain gradient theory (MSGT) has been used. Material properties of the nanoplate follow an arbitrary function that changes in three directions along the length, width and thickness of the plate. The equilibrium equations and boundary conditions of nanoplate are obtained using the Hamilton's principle. The generalized differential quadrature method (GDQM) is used to solve the governing equations and different boundary conditions for obtaining the natural frequency of nanoplate made of three-directional functionally graded material. The present model can be transformed into a couple stress plate model or a classic plate model if two or all parameters of the length scales set to zero. Finally, numerical results are presented to study the small-scale effect and heterogeneity constants and the aspect ratio with different boundary conditions on the free vibrations of nanoplates. To the best of the researchers' knowledge, in the literature, there is no study carried out into MSGT for free vibration analysis of FGM nanoplate with arbitrary functions.

• 한국광물학회:학술대회논문집
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• 한국광물학회.한국암석학회 2001년도 공동학술발표회 논문집
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• pp.75-75
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• 2001

We report Sr, Nd and Pb isotope data of clinopyroxene separates from ultramafic xenoliths and their host basaltic rocks in Jeju Island, Baekryeong Island, Boeun and Ganseong, Korea. The isotopic data of the xenoliths and host basalts are distinctly different from those of Korean basement rocks. Except for two xenoliths from Ganseong, all samples in this study have isotopic ratios within the combined range of MORB-OIB data. All basaltic rocks have Nd-Sr-Pb isotope compositions different from those of xenoliths, indicating that the host basaltic magma did not derive from the lithospheric mantle where the xenoliths originated. The range of isotopic composition of xenoliths is much greater than that observed in host basalts, which reflects small-scale heterogeneity of the lithospheric mantle. The greater isotopic heterogeneity of the lithospheric mantle probably reflects its long-term stability. The spinel peridotite xenolith data of Jeju Island, Baekryeong Island and Boeun display mixing hyperbolas between DMM and EM II end members. Since Jeju basalts have EM II-like isotopic signature, the mixing relationship shown by the isotopic data of the Jeju xenoliths can be interpreted as the result of infiltration of metasomatic fluid or melt derived from basaltic magma into DMM-like lithospheric mantle. In contrast to other xenolith sites, the Ganseong xenoliths are dominantly clinopyroxene megacryst and pyroxenite. Clinopyroxene megacrysts have different isotopic ratios from their host basalt, reflecting its exotic origin. Two Ganseong xenoliths (wherlite and clinopyroxenite) have much enriched Sr and Nd isotopic ratios and Nd model ages of 2.5-2.9 Ga, and plot in an array away from the MORB-OIB field. The mantle xenoliths from Korean Peninsula have similar $\^$87/Sr/$\^$86/Sr,$\^$143/Nd/$\^$144/Nd and $\^$207/Pb/$\^$204/Pb ratios to, but higher $\^$208/Pb/$\^$204/Pb ratios than, those from eastern China, indicating that Korean xenoliths are derived from the lithospheric mantle with higher Th/U ratio compared with Chinese ones. The isotopic data of xenolith-bearing basalts of Baekryeong Island and Ganseong, along with Ulreung and Dok Islands, show a mixing trend betlveen DMM and EM I in Sr-Nd-Pb isotopic correlation diagrams, which is also observed in tile northeastern Chinese basalts. However, the Jeju volcanic rocks show an EM II signature that is observed in southeastern Chinese basalts. The isotopic variations in volcanic rocks from the northern and southern portions of the East Asia reflect a large-scale isotopic heterogeneity in their source mantle.

• 재활치료과학
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• 제9권4호
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• pp.107-120
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• 2020

목적 : 척수손상환자를 대상으로 한 무작위 대조군 연구의 체계적 고찰과 메타분석을 통해 척수손상환자의 재활 중재의 효과성과 근거를 알아보고자 한다. 연구방법 : 국외 논문데이터베이스에서 검색어를 사용하여 학술지에 게재된 연구를 2명의 연구자가 독립적으로 검색하여 선정하였다. 선정기준에 부합한 연구는 총 21편이었고, PEDro Scale을 사용하여 연구의 질적 평가를 실시하였다. 메타분석은 Comprehensive Meta-Analysis 3.0 프로그램을 사용하였다. 결과 : 분석된 연구에 참여한 연구대상자는 총 713명이었고, 메타분석을 실시한 결과 신체활동을 이용한 중재는 0.406(95.0% 신뢰구간: 0.221~0.591), 전기 자극 치료중재는 0.505(95.0% 신뢰구간: 0.449~1.528)로 중간크기(Medium)의 효과를 보이는 것으로 나타났고 교육적 방법 중재는 0.248(95.0% 신뢰구간: 0.033~0.464), 복합 중재는 0.280(95.0% 신뢰구간: 0.122~0.438)로 작은 크기(Small)의 효과를 보이는 것으로 나타났다. 통계적 이질성 검정에서 유의미한 이질성이 있어 연구결과 통합 시 랜덤효과 모형을 선택하여 분석하였고, 출판편견은 유의미하지 않아 신뢰할만한 연구결과였다. 결론 : 분석된 결과 척수손상환자를 대상으로한 재활 중재는 효과적임을 알 수 있었다. 척수손상환자를 대상으로한 재활분야에서 임상가들이 대상자의 라이프 스타일을 개선하기 위한 프로그램을 구성할 때 기여할 것으로 사료된다.

• 벤처창업연구
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• 제12권6호
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• pp.41-47
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• 2017

본 연구는 중소벤처기업무역이익에 관한 실증적 분석을 위하여 수행되었다. 그간 무역후생에 대한 연구들이 우리나라 전체 기업규모를 대상으로 수행되었거나, 대표적 기업(평균)을 중심으로 이루어졌으나, 본 연구에서는 중소벤처기업과 대기업을 분리하여 파레토 및 대수 정규기업규모분포에 대한 결정모수를 추정하고, 이 자료를 바탕으로 무역이익을 분석하였다. 분석결과는 다음과 같이 요약된다. 첫째, 기업규모의 이질성이 클수록 무역후생이 크게 나타났다. 이 결과는 중소벤처기업 및 대기업의 경우에도 동일하게 나타났다. 무역이익은 파레토규모분포를 가정할 경우 대수정규분포를 가정한 경우보다 압도적으로 크게 나타났다. 둘째, 대기업의 경우가 중소벤처기업의 경우보다 무역후생이 크게 나타났다. 이 분석결과는 대기업규모분포가 중소벤처기업규모분포보다 이질성이 더 크기 때문에 나타난 결과이다. 셋째, 기업규모분포가 동질적이라고 가정할 경우에 무역후생의 차이가 존재하지 않았다. 마지막으로 본 연구의 정책적 시사점으로 무역후생증대의 관점에서 기업규모이질성은 매우 중요한 역할을 차지한다. 중장기적으로 중소벤처기업의 다양성을 증대시키는 중소벤처기업정책이 필요한 이유이다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.197-202
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• 2007

Most of seismic reflection prospecting assumes subsurface formation to be homogeneous media. These models are not capable of estimating small scale heterogeneity which is verified by well log data or drilling core. And those synthetic seismograms by homogeneous media are limited to explain various changes at field data. So we developed a inhomogeneous velocity model which can estimate inhomogeneity of background medium to implement numerical modeling from homogeneous medium and inhomogeneous medium on the model. Background medium using three autocorrelation functions in order to generate inhomogeneous velocity media was according to dominant wavelength of background medium and correlation length of random medium. And then we compared shot gathers. The results show that numerical modeling implemented at inhomogeneous medium depicts complex wave propagation of field data.

• 대한지리학회지
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• 제29권3호
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• pp.340-359
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• 1994

This study intends to describe the characteristics of the transformation of the rural society by tracing the changing social and economic processes of traditional clan villiage (Yeolmi-ri, Silchon-myeon, Kwangju-gun, Kyunggi-province) in the suburbs of Seoul Metropolitan Area. Rural society has experienced serious change of the social structure by the ever expanding urbanization and industrialization since 1960's. The suburbs of Seoul Metropolitan Area is the representative case area of such transformation. This study analyzed various chracteristics of population structure of a villiage, the processes of residential movement and the occupational shift of each household of the villiage in terms of household's life-history collected by interviewing with each household. And the whole households of a villiage is divided by two groups of the native clan group and the non-dan in-migrant group. The results of this study are summarized as follows. 1) This villiage is located within a lineal distance of 40km and a time distance of about 30 to 40 minutes, adjoined dy the Joongbu(중부) national highway, the Kyungchoong (경충) industrial road, the local road between Yangpyuna(양평) and Gonjiam(곤지암) and having a advantageous iocational linkage to Seoul capital city. 2) It is a typical traditional dan villiae constituted of dan family Gu(구) one of whose ancestors had appointed to the prime minister of Chosun Dynasty, and until 1979, 56 out of 60 families of the villiage households were clan families. 3) Since 1979, as the villiage invaded by the out-movement of the small scale manufacturing industries from Seoul capital city, labours moved in this vallige from outside and increased villiage size up to 203 households in 1993, consequently the constitutional proportion between the native clan group and the non-clan in-migrant group was reversed up to 28% vs 72% deepening the sociological heterogeneity. 4) Because of the small scale of industries in this villiage and the vicinity with the city of Seoul, the population turnover of this villiage is very high. The turnover frequency is firstly high within same administrative district of gun(군) level and secondly high between this villiage and the city of Seoul. Thus short-distance movement is identified. 5) There is a close correlation between the residential movement and the occupational shift. The most numbers of non-farm native group have the experiences of migration while the members of native farming group don't shift both the job and the place of residence. The inmigrant group had several migration experiences but few occupational shifts. Thus occupatioanl shift is high for the native group while residential shift is high for the in-migrant group. It is concluded that the change proceeded in Metropolitan suburbs was not directed to form the traditional rural village as 'gesund Gebiet' with respect to the ballance among the economic, cultural and environmental adequency.

• Geomechanics and Engineering
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• 제23권5호
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• pp.419-429
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• 2020

To investigate the effect of spatial variability on hydraulic properties of unsaturated soils, a numerical model is set up which can simulate seepage process in an unsaturated heterogeneous soil. The unsaturated heterogeneous soil is composed of matrix sand embedded with a small proportion of clay for simulating the heterogeneity. Soil-water characteristic curve and unsaturated hydraulic conductivity curve of the unsaturated soil are expressed by Van Genuchten model. Hydraulic parameters of the matrix sand are considered as random fields. Different autocorrelation lengths (ACLs) of hydraulic parameter of the matrix sand and different proportions of clay are assumed to investigate the influence of spatial variability on the equivalent hydraulic properties of the heterogeneous soil. Four model sizes are used in the numerical experiments to investigate the influence of scale effects and to determine the sizes of representative volume element (RVE) in the numerical simulations. Through a number of Monte Carlo simulations of unsaturated seepage analysis, the means and the coefficients of variations (COVs) of the equivalent hydraulic parameters of the heterogeneous soil are calculated. Simulations show that the ACL and model size has little influence on the means of the equivalent hydraulic parameters, but they have a large influence on the COVs of the equivalent hydraulic parameters. The size of an RVE is mainly affected by the ACL and the proportion of heterogeneity. The influence of spatial variability on the hydraulic parameters of the heterogeneous unsaturated soil can be used as a guidance for geotechnical reliability analysis and design related to unsaturated soils.

• Geomechanics and Engineering
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• 제29권4호
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• pp.451-461
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• 2022

The roadways surrounded by rock and coal will lose their stability or even collapse under rock burst. Rock burst mainly involves an evolution of dynamic loading which behaves quite differently from static or quasi-static loading. To compare the dynamic response of coal and rocks with different static strengths, three different rocks and bituminous coal were selected for testing at three different dynamic loadings. It's found that the dynamic compression strength of rocks and bituminous coal is much greater than the static compression strength. The dynamic compression strength and dynamic increase factor of the rocks both increase linearly with the increase of the strain rate, while those of the bituminous coal are irregular due to the characteristics of multi-fracture and heterogeneity. Moreover, the absorbed energy of the rocks and bituminous coal both increase linearly with an increase in the strain rate. And the ratio of absorbed energy to the total energy of bituminous coal is greater than that of rocks. With the increase of dynamic loading, the failure degree of the sample increases, with the increase of the static compressive strength, the damage degree also increases. The static compassion strength of the bituminous coal is lower than that of rocks, so the number of small-scale fragments was the largest after bituminous coal rupture.

• 척추신경추나의학회지
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• 제14권2호
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• pp.15-28
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• 2019

Objectives : This study aimed to systematically and comprehensively review controlled clinical trials on the effectiveness and safety of Chuna Manual Therapy for stroke. Methods : By October 7, 2019, three core databases and three domestic databases were searched. Seven major academic journals on the related field were also hand-searched. Methodological quality of the included studies was evaluated using the Cochrane risk of bias tool. Meta-analysis was conducted and the quality of its evidence was assessed using the GRADE methodology. Results : Five articles met the eligibility criteria. The results of most of included studies were in favor of Chuna Manual Therapy. No study described any adverse events during or after the clinical trials. Meta-analysis of three eligible studies showed that the pre- and post-treatment scores on the Modified Barthel Index (mean difference 8.00, 95% confidence interval 0.26 to 15.74) and Berg Balance Scale (mean difference 3.57, 95% confidence interval 0.64 to 6.51) of the Chuna-treated group were significantly different, but only marginally higher than those of the non-treatment group. Thus, the level of evidence gathered from these studies was assessed to be low. Conclusions : Based on current available evidence, any confirmative conclusions cannot be made on the effectiveness and safety of Chuna Manual Therapy for stroke because of the small sample size, low methodological quality, presence of statistical heterogeneity, and missing safety information. More rigorously designed large-scale multi-center studies are needed to establish more specific and credible evidence to support or oppose the use of Chuna Manual Therapy for stroke.