• 한국토양비료학회지
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• 제11권2호
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• pp.61-66
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• 1979

토양(土壤)의 물리성(物理性)이 심근성작물(深根性作物) 재배(栽培)에 극(極)히 불량(不良)한 토양(土壤)의 물리성(物理性)을 개량(改良)하여 우량과원(優良果園)으로 조성(造成)할 수 있는 손쉽고도 경제적(經濟的)인 방법(方法)을 찾기 위하여 저구릉지(低丘陵地)에 많이 분포(分布)되어 있는 전남식양토(全南埴壤土)에 대하여 1m 깊이에서 폭파처리하여 토양물리(土壤物理) 성화(性化)를 조사(調査)한 결과(結果)를 요약(要約)하면 아래와 같다. 1. 무처리구의 물리성(物理性)은 가비중(假比重), 경도(硬度)가 과도(過度)하게 크고 공극률(孔隙率) 및 기상이 근신장(根伸張)에 상당한 저해를 줄 정도로 낮았다. 이런 현상(現象)은 표토(表土)보다 심토(深土)에서 더욱 심(甚)하였다. 2. 화약폭파는 토양(土壤)을 파쇄시키고 균열을 만들어 줌으로서 가비중(假比重)과 경도(硬度)를 낮추고 공극량(孔隙量) 특히 대공극(大孔隙)을 늘려주는 효과가 크다고 인정(認定)되었다. 3. 물리성(物理性)을 적정수준(適正水準)으로 개량(改良)하는 효과범위는 폭약 두개를 사용(使用)한 경우 60cm 깊이에서 1m 반경이고 80cm 깊이에서는 30cm 반경이었다. 그러나 폭약 3개를 사용(使用)할 경우는 80cm 깊이에서도 1m 반경까지도 적정수준(適正水準)으로 물리성(物理性)이 개량(改良)되었다. 4. 파쇄 및 균열된 정도는 두개 사용시(使用時)는 불균일(不均一) 하였으나 3개 사용시(使用時)는 효과범위내에서 균일(均一)한 물리성(物理性) 분포(分布)를 나타내어 더욱 효과적이라고 볼 수 있다. 5. 폭약 2개를 사용(使用)하였을 경우 폭속(爆速)이 4,000m/sec, 폭발위력(爆發威力)이 50%인 초안폭약의 효과가 폭속(爆速)과 위력(威力)이 각각 5,000m/sec, 60%인 Gelatin 폭약보다 좋은 효과를 나타내었다.

• 천문학회보
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• 제44권1호
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• pp.33.1-33.1
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• 2019

Protostars grow their mass by the accretion of disk material, which is infalling from the envelope. This accretion process is important to the physical and chemical conditions of the disk and envelope, and thus, the planets yet to be formed from the disk material. Therefore, if we map the physical and chemical properties of disks and envelopes, we can study indirectly the accretion process in star formation. In particular, the chemical distribution in the disk and the inner envelope of a young stellar object is greatly affected by the thermal history, which is mainly determined by the accretion process in the system. In my talk, I will review the episodic accretion model for the low mass star formation and observational efforts to find the evidence of episodic accretion. Finally, I will present our recent ALMA detection of several complex organic molecules associated directly with the planet formation in V883 Ori, which is in the burst accretion phase.

• 한국지형학회지
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• 제23권1호
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• pp.1-16
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• 2016

This study estimates relationships between physical and chemical weathering indices of various rock types and topographical relief. Physical weathering properties such as rock strength and joint and chemical weathering indices such as the $SiO_2/Al2O_3$, CIA and WPI were analyzed from 18 rock outcrops in mountain and valley areas consisting of 9 rock types. The results indicate that the elevation and relief of topography increase physical strength of rock increases. It can be suggested that the total r(rock-mass strength rating) and R(rock rebound strength by Schmidt Hammer) are most useful indices as a quantitative weathering property factor to explain formative causes of topographical relief. The results also suggest that rock types such as sandstone, granite, gneiss and schist are most suitable to explain meaningful difference in topographical relief with the physical and chemical weathering indices.

• 천문학회보
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• 제44권1호
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• pp.84.3-84.3
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• 2019

We investigate 3D radiation-hydrodynamics (RHD) for surface convection of the solar-type low-mass stars (M = 0.8, 0.9, and 1.0 Msun). The outer convection zone (CZ) of low-mass stars is an extremely turbulent region composed of partly ionized compressible gases at high temperature. Particularly, the super-adiabatic layer (SAL), the top of the CZ is the transition region where the transport of energy changes drastically from convection to radiation. In order to accurately describe physical processes, a realistic treatment of radiation should be considered as well as convection. As a starting model, the initial stratification in the outer envelope calculated using the solar calibrations in the context of the standard stellar theory. When the numerical fluid becomes thermally relaxed, the thermodynamic structure of the steady-state turbulent flow was explicitly collected. In this presentation, we compared thermodynamic properties of turbulent convection of the solar-type low-mass stars.

• 자원환경지질
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• 제39권6호
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• pp.739-752
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• 2006

북동태평양 클라리온-클리퍼톤 균열대(Clarion-Clipperton Fracture Zone) 사이에 위치한 연구지역 퇴적물의 입도, 함수율, 입자 밀도, 전밀도, 공극비, 그리고 공극률 등 물리적 특성과 퇴적학적 변화요인을 파악하기 위하여 1999년부터 2002년까지 7회의 조사작업을 통해 연구지역 각 지점에서 다중주상시료채취기로 채취된 69개 표층퇴적물을 분석하였다. 연구지역 퇴적물은 원양성 적점토가 분포하는 북부지역(북위 16-17도), 생물기원의 규질 퇴적물이 분포하는 중부지역(북위 10-11도), 탄산질 퇴적물이 분포하는 남부지역(북위 5-6도)으로 구분되며, 퇴적물의 물리적 특성은 이들 퇴적물의 유형에 따라 뚜렷이 다른 특성을 보인다. 북부지역은 수층의 기초생산성이 낮고 육성기원 입자의 유입이 많으므로 입도는 세립질이며, 함수율이 낮은 특성을 보인다. 반면에 중부지역은 수층의 생산성이 높고 수심이 탄산염보 상심도보다 깊으므로 다공질이며 입자크기가 큰 생물기원 규질 입자의 유입이 높아 평균입도는 가장 조립질이며, 함수율이 매우 높다. 한편, 남부지역은 수심이 탄산염보상심도보다 얕으므로 수층으로부터 유입되는 탄산질 퇴적물이 용해되지 않고 지속적으로 퇴적되어 가장 낮은 함수율과 높은 밀도를 보인다. C-C지역 퇴적물의 물리적 특성과 연관된 주요 요인들은 적도부근 해역의 높은 생산성에 따른 생물기원 입자의 유입, 탄산염보상심도를 고려한 수심 수층 생산성에 비례하는 퇴적률, 대륙으로부터 바람에 의해 유입되는 육성기원 입자의 공급, 그리고 생물기원 퇴적입자의 용해 및 자생광물의 형성과 연관된 저층해수의 화학적 특성 등으로 판단할 수 있다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.95-102
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• 1996

In this study, a stochastic finite element model is proposed with a view to consider the uncertainty of physical properties of discontinuous rock mass in the analysis of structural behavior on underground caverns. In so doing, the LHS(Latin Hypercube sampling) technique has been applied to make up weak points of the Crude Monte Carlo technique. Concerning the effect of discontinuities, a joint finite element model is used that is known to be superior in explaining faults, cleavage, things of that nature. To reflect the uncertainty of material properties, the variables such as the the elastic modulus, the poisson's ratio, the joint shear stiffness, and the joint normal stiffness have been used, all of which can be applicable through normal distribution, log-normal distribution, and rectangulary uniform distribution. The validity of the newly developed computer program has been confirmed in terms of verification examples. And, the applicability of the program has been tested in terms of the analysis of the circular cavern in discontinuous rock mass.

• 한국해양공학회지
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• 제21권5호
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• pp.18-24
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• 2007

The environmental value of coastal vegetation has been widely recognized. Coastal vegetation such as reed forests and seaweed performs several useful functions, including maintaining water quality, supporting fish (and, thus, fisheries), protecting beaches and land from wave attack, stabilizing sea beds and providing scenic value. However, studies on the physical and numerical process of wave propagation, sediment transport and bathymetric change are few and far between compared to those on the hydrodynamic roles of coastal vegetation. In general, vegetation flourishing along the coastal areas attenuates the incident waves through momentum exchange between stagnated water mass in the vegetated area and rapid mass in the un-vegetated area. This study develops a numerical model for describing the wave attenuation and sediment transport in a wave channel in a vegetation area. By comparing these results, the effects of vegetation properties, wave properties and model parameters are clarified.

• Journal of Forest and Environmental Science
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• 제29권2호
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• pp.109-115
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• 2013

Fast-grown wood generally contains a high proportion of juvenile wood that results in inferior dimensional stability and durability against biological deteriorations. In the present research, the Acacia mangium wood from plantation forests in Vietnam was treated with high temperature in air. The effects of heat treatment on physical properties of Acacia mangium wood, including mass loss (ML), water absorption (WA), water-repellent effectiveness (WRE) and anti-swelling efficiency (ASE) were examined. The results showed that the dimensional stability and the water-repellent effectiveness are increased by about 15-46% and 8-18%, respectively. However, the mass and dimension of wood are decreased. The results also indicated that both treatment temperature and treatment duration significantly affect the wood properties of Acacia mangium. It is thus concluded that heat treatment demonstrates an interesting potential to improve the wood quality of Acacia mangium for solid timber products. This technology provides an environmentally safe method of protecting sustainable common woods to give a new generation of value-added biomaterials with increased stability without the use of toxic chemicals.

• Elastomers and Composites
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• 제57권4호
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• pp.188-196
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• 2022

Styrene-butadiene rubber(SBR) is a copolymer of styrene and butadiene. It is composed of 1,2-unit, 1,4-unit, and styrene, and its properties are dependent on its microstructure. In general, rubber composites contain a single rubber or a blended rubber. Similarly, SBR is used by mixing with natural rubber(NR) and butadiene rubber(BR). The composition of a rubber article affects its physical and chemical properties. Herein, an analytical method for determining the microstructure of SBR using via pyrolysis is introduced. Pyrolysis-gas chromatography/mass spectrometry is widely used to analyze the microstructure of polymeric materials. The microstructure of SBR can be determined by analyzing the principal pyrolysis products formed from SBR, such as 4-vinylcyclohexene, styrene, 2-phenylpropene, 3-phenylcyclopentene, and 4-phenylcyclohexene. An analytical method for determining the composition of SBR/NR, SBR/BR, and SBR/NR/BR blends via pyrolysis is introduced. The composition of blended rubber can be determined by analyzing the principal pyrolysis products formed from each rubber component.

• Smart Structures and Systems
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• 제23권6호
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• pp.589-613
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• 2019

Cables are prone to vibration due to their low inherent damping characteristics. Recently, negative stiffness dampers have gained attentions, because of their promising energy dissipation ability. The viscous inertial mass damper (termed as VIMD hereinafter) can be viewed as one realization of the inerter. It is formed by paralleling an inertial mass part with a common energy dissipation element (e.g., viscous element) and able to provide pseudo-negative stiffness properties to flexible systems such as cables. A previous study examined the potential of IMD to enhance the damping of stay cables. Because there are already models for common energy dissipation elements, the key to establish a general model for IMD is to propose an analytical model of the rotary mass component. In this paper, the characteristics of the rotary mass and the proposed analytical model have been evaluated by the numerical and experimental tests. First, a series of harmonic tests are conducted to show the performance and properties of the IMD only having the rotary mass. Then, the mechanism of nonlinearities is analyzed, and an analytical model is introduced and validated by comparing with the experimental data. Finally, a real-time hybrid simulation test is conducted with a physical IMD specimen and cable numerical substructure under distributed sinusoidal excitation. The results show that the chosen model of the rotary mass part can provide better estimation on the damper's performance, and it is better to use it to form a general analytical model of IMD. On the other hand, the simplified damper model is accurate for the preliminary simulation of the cable responses.