• The Korean Journal of Ecology
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• 제23권2호
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• pp.83-88
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• 2000

When interpreting change over time in forest ecosystems, distinguishing the effects of forest succession from the effects of environmental stress can be difficult. The result may be a simplistic interpretation. citing a specific successional or environmental cause of forest change when both types may be occurring. We present two case studies of changes in the forest floor in northern hardwoods. First, the belief that 50% of soil organic matter is lost in the first 20 years after logging was based on a study comparing northern hardwood stands of different ages. We resampled a series of 13 such stands after an interval of 15 years, and found that the young stands were not, in fact. losing organic matter as rapidly as predicted from the original chronosequence study. The pattern of higher organic matter content in the forest floors of older stands compared to young stands could be equally well explained by changes in logging practices over the last century as by the aging of the stand. The observed pattern of forest floor organic matter as a function of stand age was previously interpreted as a successional pattern, ignoring changes in treatment history. In the second case study, observed losses of base cations from the forest floor were attributed to cation depletion caused by acid rain and declining calcium deposition. We found that young stands were gaining base cations in the forest floor; losses of base cations were restricted to older stands. Differences in litter chemistry in stands of different ages may explain some of the pattern in cation gains and losses. In this case, the contribution of successional processes to cation loss had been overlooked in favor of environmental stress as the dominant mechanism behind the observed changes. Studies of environmental stress use repeated measures over time. but often don't consider stand age as a factor. Studies of successional change often assume that environmental factors remain constant. We were able to consider both forest succession and external factors because we repeatedly sampled stands of different ages.

• Journal of Forest and Environmental Science
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• 제29권3호
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• pp.219-225
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• 2013

The correlation between disturbance intensity and stand development was evaluated on the basis of natural forest community type classification in areas of Baekhaksan (more disturbed area) and Hwangaksan (less disturbed area). The vegetation data were collected by point-centered quarter sampling method, and they were subjected to cluster analysis for classifying community types and to analysis of species composition and species diversity for reviewing ecological characteristics. By the method of cluster analysis, natural forests of Baekhaksan were classified into Quercus forest community, Pinus densiflora community, Q. variabilis community, and Q. mongolica community. Those of Hwangaksan were divided into P. densiflora community, Q. mongolica community, Q. forest community, and Mixed mesophytic community. It is presumed that more developed and less disturbed forest area shows multiple species community pattern and more diversified structure than less developed and more disturbed forest area. In Korean peninsula, the abundance of red pine may play an important indicator to estimate the developmental pattern of the forest after artificial disturbance. The overall evaluation indicated that less disturbed Hwangaksan area had more developed stand pattern with mixed mesophytic community, more complicated species composition, and higher species diversity than Baekhaksan area.

• 정보화연구
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• 제10권1호
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• pp.33-45
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• 2013

본 연구는 중소기업 기술경쟁력 강화를 위해서 대기업과의 하도급 관계가 어떤 영향을 미치는지 실증 분석하였다. 대 중소기업간 거래 특성과 구조 특성에 따라 중소기업 유형을 종속형, 주변형, 협력형, 독립형 4가지로 구분하여 유형에 따라 중소기업 기술경쟁력에 어떤 영향력을 미치는지 측정하였다. 추가적으로 기술지원정책을 활용하였을 때 기술경쟁력의 영향도도 측정하였다. 분석결과 중소기업 기술경쟁력과 연관성이 높은 기업 유형은 협력형과 독립형이며, 독립형은 기술지원정책 활용을 통해 기술경쟁력이 더 높아지는 것으로 확인되었다. 대기업 종속형 기업은 기술경쟁력이 낮았고 정책 활용이 기술경쟁력에 유의미한 영향을 주지 못하였다. 주변형 기업은 하도급 관계가 기술경쟁력 수준에 부정적 영향을 주지만 정책 활용시 개선되었다. 하도급 관계 중 구조 특성이 중소기업 기술경쟁력에 상당한 영향을 주는 것으로 확인되었으므로 하도급 기업 특성에 따라 특성화된 정책 활용, 특히 대 중소기업 동반성장 정책의 성공 가능성을 기대할 수 있다. 중소기업 기술경쟁력 강화를 위해 기술지원 정책과 함께 불공정한 하도급 관계가 개선되어야 함을 시사점으로 제안한다.

• 대한조선학회논문집
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• 제58권6호
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• pp.400-406
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• 2021

The primary effect of the far-field underwater explosion (UNDEX) is the whipping of the ship hull girder. This paper aims to verify why inelastic effects should be considered in the whipping response estimations from the UNDEX simulations. A navy ship was modeled using Timoshenko beam elements over the ship length uniformly keeping the constant midship section modulus. The transient UNDEX pressure was produced using two types of the Geers-Hunter doubly-asymptotic models: compressible and incompressible fluids. Because the UNDEX model based on incompressible fluid assumption provided more increased fluid volume acceleration in the bubble phase, the incompressible fluid-based UNDEX model was adopted for the inelastic whipping response analyses. The non-linear hull girder bending moment-curvature curve was used to embed inelastic effects in the UNDEX analyses where the Smith method was applied to derive the non-linear stiffness. We assumed two stand-off distances to see more apparent inelastic effects: 40.5 m and 35.5 m. In the case of the 35.5 m stand-off distance, there was a statistically significant inelastic effect in terms of the average of peak moments and the average exceeding proportional limit moments. For the conservative design of a naval ship under UNDEX, it is recommended to use incompressible fluid. In the viewpoint of cost-effective naval ship design, the inelastic effects should be taken into account.

• 한국언어정보학회지:언어와정보
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• 제19권1호
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• pp.37-57
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• 2015

This paper is primarily intended to provide a new insight on which the structural properties of As-Parenthetical constructions shown by Potts (2002) might be regarded as cross-linguistically common one. As a first attempt, it introduces the characteristics of Korean As-Parenthetical by carefully investigating them through the data, focusing on the similarities or differences between two languages with a constructional theoretical perspective. The paper here provides three properties of Korean as-clauses in the morphological and syntactic aspects. First, the morpheme 'as' in English as-clause would be realized as three different morphemes as a bound one. Korean as-clauses can be introduced by three different morphemes, '-tusi, -chelem, -taylo' and unlike that in English as-clauses, they behave as bound morphemes which do not stand alone. Even though they are attached into different morpho-syntactic stems, they do not make any meaning change only under this clause. Secondly, two syntactic types of as-clauses can also be found in Korean, similarly to those of English: CP-As type and Predicate-As type, depending on which types of gap they involve in. English has one more subtype of Predicate-As type (called inverted Predicate-As clause), while Korean does not show this subtype. Thirdly, the various mismatches attributed by the gap and the antecedent come from the constructional restrictions of as-clauses in Korean. In addition, the paper attempts to display various ambiguities from the as-clauses through disjoint references or negative sentences in As-Parenthetical constructions.

• 한국산림과학회지
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• 제94권1호통권158호
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• pp.26-33
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• 2005

본 연구는 강원도 평창 지역의 천연 활엽수림을 대상으로 입지유형별 임분의 생장 특성과 생태적 특성을 구명함으로써 각 임분 특성에 맞는 산림관리 방안을 제시하고자 하였다. 이를 위해 연구 대상지를 방위, 해발고도, 지형 조건에 따라 36개의 입지유형으로 구분하고 각 입지유형별로 직경 생장량과 직경 생장률 그리고 Shannon-Wither의 다양성지수, 균재도, 풍부도를 파악하여 임분의 생장 특성과 생태적 특성을 비교 분석하였으며, 이를 근거로 산림관리 방안을 제시하였다. 임분의 생장 특성은 방위에 따라서는 동쪽 사면과 서쪽 사면이, 해발고도에 따라서는 서쪽 사면을 제외하고는 해발고도가 낮아짐에 따라, 그리고 지형 조건에 따라서는 사면과 계곡이 양호한 생장 상태를 유지하고 있었다. 생태적 특성은 적정한 습도 조건을 유지할 수 있는 지역으로 방위별로는 북쪽 사면과 서쪽 사면, 지형 조건별로는 계곡의 종 다양성이 높게 나타난 반면 해발고도에 따른 일정한 경향은 찾아볼 수 없었다. 입지유형별 산림관리 방안은 남쪽 사면과 동쪽 사면의 경우 임목 생장과 생태적 특성을 함께 고려한 무육작업이 필요한 반면 서쪽 사면과 북쪽 사면은 생장 촉진을 위주로 한 밀도조절이 필요한 것으로 파악되었다. 해발고도에 따라서는 저지대는 생태적 특성을 고려한 무육관리가 필요하며, 고지대와 중지대는 직경 생장률이 2% 미만인 지역에 대해서는 생장 촉진을 위한 무육작업이 시급한 것으로 나타났다. 한편 지형 조건에 따라서는 남쪽 사면의 중지대와 고지대를 제외하고는 계곡의 생태적 안정성이 기장 양호한 것으로 나타나 친환경적 경영에 가장 적합한 지역으로 평가되었다.

• 재활복지공학회논문지
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• 제6권2호
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• pp.15-22
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• 2012

외골격 보행보조로봇은 로봇 시스템을 인체에 직접 착용하는 형태이므로 기구적인 측면에서는 인체 근골격 구조에 최적화된 메커니즘으로 구성되어야 하며, 제어적인 측면에서는 근골격계의 손상을 일으킬 수 있는 로봇의 부적합한 거동을 예방할 수 있는 안전장치를 갖추어야 한다. 외골격 보행보조로봇을 개발하기 위해서는 보행이나 근골격계의 거동특성에 대한 이해 및 분석이 필요하다. 본 연구에서는 최적화된 로봇시스템 설계를 위하여 구동장치의 관절력과 동력 용량을 예측하였으며 몇 가지 보행동작에 대한.관절거동특성을 파악할 수 있는 자료를 획득하였다. 평지보행을 제외한 나타나는 주요한 동작으로는 계단오르고 내리기, 안기, 서기, 경사면 걷기 등이 있다. 본 연구에서는 경사면 걷기를 제외한 모든 동작에 대한 동작 실험을 수행하고 분석하였다.

• 화약ㆍ발파
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• 제36권3호
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• pp.19-28
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• 2018

지진 및 예기치 못한 외부하중에 의하여 손상된 구조물의 경우, 2차적인 국부손상 및 이로 인한 붕괴가 발생할 수 있어 발파해체공법에 의한 철거가 우선시 고려되고 있다. 특히 철재로 이루어진 교량 및 구조물의 경우 성형폭약을 이용한 발파해체기법이 적용되어 오고 있다. 최근에는 구리판을 드로잉 가공한 성형폭약용기에 상용폭약을 장전하여 두꺼운 철판을 절단하는 발파공법이 제안되었다. 본 연구에서는 LS-DYNA 동해석소프트웨어를 이용하여 드로잉 가공 성형폭약용기와 상용폭약을 적용한 25mm 두께의 철판 절단실험발파를 모사하고 절단형상 및 깊이를 비교분석하여 적용구성모델의 입력변수를 결정하였다. 해석모델을 이용하여 폭약의 종류, 구리 라이너의 두께, 이격거리의 변화에 따른 철판 내 관통깊이 및 관통 폭을 분석하였다.

• 한국의류학회지
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• 제14권1호
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• pp.20-30
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• 1990

In order to investigate the mechanism of the formation of clothing microclimate with different blouse designs and materials, physiological and subjective sensational changes were measured. Experimental clothing were four types of blouse made of $100\%$ cotton, $100\%$ regular polyes­ter, and $100\%$ hygroscopic polyester. Four types of box style blouse were with stand collar and long sleeve, with stand collar and sleeveless, with long sleeve and collarless, and sleeveless and collarless. Five healthy female were chosen as subjects. Experiments were carried out in the environ­mental chamber controlled at $28{\pm}1^{\circ}C$ , $70{\pm}5\%$ RH. and still-air condition for SO min. The skin temperature (9 spots), oral temperature, humidity inside chest, and subjective sensations were measured. Obtained results are: I) Material which is capable of absorbing sweat effectively and transfering moisture rapidly made a comfortable feeling, because cloth­ing humidity is increasing slowly at this material. 2) During exercise period, covered arms have more influenced on thermal comfort than a covered neck.

• Journal of Plant Biology
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• 제25권2호
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• pp.83-99
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• 1982

In this study, thirty-two stands in Kwangnung forest located in the central part of Korea were preferentially selected. In each stand, all stems for trees and shrubs were recorded by species and their girths were measured down to 5cm. In addition, several enviromental factors such as field soil pH, field soil moisture, soil compressibility, depth of soil, thickness of litter layer, elevation and basal area were measured. Three soil cores were sampled and various physical and chemcial properties was determined. The vegetational data were subjected to three kinds of multivariate ordination(PO, PCA, RA). The results suggested that Kwangnung forest was consisted of three forest types: coniferous, mixed and broad leaved forest communities. The relation between the stand scores of ordination and several environmental factors were investigated in terms of correlation analysis in order to examine the relationships between the vegetation and certain environmental factors. As a result of this analysis, the amount of sand content in A1 horizon decreased frm the coniferous to broad leaved forest, while maximum field capacity, pore space, exchangeable cations, loss on ignition, soil pH nad the amount of total nitrogen had a tendancy to increase significantly. However, easily soluble phosphorus appeared to have little to do with the forest types. The result of species ordination of centered-standardized PCA suggested that the major successional pathway in Kwangnung forest was; Pinus densifloralongrightarrowQuercus mongolica, Q. serrata, Q. alienalongrightarrowCarpinus laxifloralongrightarrowC. erosa in sequence. This trend is in good agreement with the past studies. In three kinds of ordination (centered PCA, centered-standardized PCA and RA) based on nineteen species and twenty-five stands, the total variances accounted for the first three axes were 77%, 46% and 63% respectively. The estimated beta diversity in Kwangnung forest assumed as a coenocline, was 1.5~1.8 HC. Increasing the effect of the sampling errors on ordination perfermance, this low heterogeneity seems to cause the poor concentration of the total variance. The results from the four kinds of ordination were in good agreement with each other, especially between PO, centered-standardized PCA and RA appeared robust. It seems to be worthy of applying multivariate method for analyzing other forest communities in Korea.