• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.4
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• pp.318-328
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• 1993

A series of long wave measurements was made in the region of Shikotan Island (the South Kuril Islands) during 1990-1992: 7 bottom pressure stations were installed in 5 bays and inlets of Shikotan and 3 precise microbarographs were situated at the shore. The observations were taken in order to monitor tsunami waves, estimate resonance features of coastal topography, and investigate seiche generation mechanism. It was found that forced long waves dominate in the motions with periods exceeding 2 hours, freely propagating long waves prevail at periods of 30-120 min and eigen-oscillations of bays (seiches) are the predominant type of long waves at periods less than 30 min. The Helmholtz mode with period 30 min in Krabovaya Bay and 18.5 min in Malokurilskaya Bay is the most important type of wave motion in the inner Shikotan basins. There is a good correlation between passages of atmospheric disturbances and generation of seiches near the coast of Shikotan Island. In particular, jumps in atmospheric pressure excite seiches in different bays simultaneously, in each one with the corresponding dominant period. The atmospheric spectra were remarkably smooth and stable, and could be described by a $\omega$$^{-2}$26/ power law.

• The Journal of Engineering Geology
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• v.13 no.3
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• pp.335-344
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• 2003

This study is focused to the physical and shear strength properties of the weathered limestone soils distributed in Changsung and Hwasun area, Chonnam province. Disturbed soil was used as soil samples. To grasp the physical and shear strength properties of weathered limestone soil, specific gravity test, atterberg limit, grain size distribution and direct shear test were conducted in the laboratory. The physical and shear strength properties of the weathered limestone soil in the study areas are as follows. The range of specific gravity (Gs) is 2.78 to 2.80, liquid limits (LL) 37 to 38 (%), plasticity index (PI) 13.7 to 15.4, and soil classification CL. The range of strength parameters by direct shear test (vd, $1.5t/\textrm{m}^3$) is 3.07 to 4.4 ($t/\textrm{m}^2$) of cohesion and 34.8 to $42.4^{\circ}$ of internal friction angle in unsaturated soils. As a result of comparing with the weathered granite soils (Yang, 1997: Mun, 1998: Park, 1998), it is considered that physical properties of the weathered limestone soils in this study are different from the weathered granite soils. On the other hand, internal friction angle of shear parameters is found to be similar.

• Korean Journal of Plant Resources
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• v.29 no.2
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• pp.171-188
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• 2016

This study was carried out to investigate the flora of Mt. Baegam (1,099 m) from March, 2014 to July, 2015. The vascular plants were summarized as 506 taxa, including 90 families, 293 genera, 435 species, 5 subspecies, 58 varieties and 8 forms. Among the investigated 506 taxa, 14 Korean endemic, 16 rare plants and 80 specially designated plants (V degree: 3 taxa, IV degree: 7 taxa, III degree: 22 taxa, II degree: 21 taxa, I degree: 27 taxa) by the Ministry of Environment were also included. The naturalized plants were 36 taxa including 3 ecosystem disturbance wild plant. The urbanization index and percent of naturalized plants species were estimated as 11.2% and 7.1%, respectively. Useful plants of 506 taxa listed consists of 207 taxa (40.9%) of edible plants, 200 taxa (39.5%) of pasture plants, 146 taxa (28.9%) of medicinal plants, 58 taxa (11.5%) of ornamental plants and 15 taxa (3.0%) of timber plants, respectively.

• Geotechnical Engineering
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• v.11 no.1
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• pp.113-126
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• 1995

Both resonant column (RC) and torsional shear(TS) tests were performed at small to intermediate strain levels to investigate deformational characteristics of cohesive soils. The effects of variables such as strain amplitude, loading frequency, and number of loading cycles were studied. Plasticity index was found to be an important variables in evaluating these effects. Soils tested include undisturbed silts and clays and compacted subgrade soils. At small strains below the elastic threshold, shear modulus is independent of number of loading cycles and strain amplitude. Small strain material damping exists wi th ranges be tween 1.1% and 1.7% for 75 tests. The elastic threshold strain increases as confining pressure and plasticity index increases. Above the cyclic threshold strain, the modulus of cohesive soil decreases with increasing number of cycles while damping ratio is almost independent of number of load cycles. Moduli and damping ratios of cohesive soils obtanined by RC test are higher than those from 75 test because of the frequency effect. Shear modulus of cohesive soil increases linearly as a function of the logarithm of loading frequency.

• Journal of Korea Water Resources Association
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• v.37 no.1
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• pp.1-11
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• 2004

The purpose of this study consists in introducing and examining the previous river classification systems applicable to the river improvement technique including geomorphological considerations, and developing a new system using the geomorphological criteria which represent the morphology of rivers. A newly developed system uses the channel reach as a classifying unit which is delineated by upstream and downstream tributaries. It adopts three basic geomorphological criteria for classification: 1) valley-floor width index(VI) reflecting the confinement of the channel in the valley, 2) sinuosity(P) which expresses the channel planform, and 3) bed material($d_{50}$). The system is composed of 24 stream types. Concerning every stream type, valley forms, principal bed forms and fluvial processes with disturbance elements are briefly presented. Finally, the applicability of this system to the Chungmi Stream and the Imjin River data in comparison with that of Rosgen system is examined.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.4
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• pp.395-404
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• 2000

A damage detection and assessment algorithm is developed by measuring accelerations at limited locations of a structure under forced vibrations. The developed algorithm applies a time-domain system identification (SI) method that identifies a structure by solving a linearly constrained nonlinear optimization problem for optimal structural parameters. An equation error of the dynamic equilibrium of motion is minimized to estimate optimal parameters. An adaptive parameter grouping scheme is applied to localize damaged members with sparse measured accelerations. Damage is assessed in a statistical manner by applying a time-windowing technique to the measured time history of acceleration. Displacements and velocities at the measured degrees of freedom (DOF) are computed by integrating the measured accelerations. The displacements at the unmeasured DOF are estimated as additional unknowns to the unknown structural parameters, and the corresponding velocities and accelerations we computed by a numerical differentiation. A numerical simulation study with a truss structure is carried out to examine the efficiency of the algorithm. A data perturbation scheme is applied to determine the thresholds lot damage indices and to compute the damage possibility of each member.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.04a
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• pp.76-76
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• 2018

화학적 살충제는 빠르고 정확하게 해충을 방제하는 효과를 나타내지만, 인간과 다른 유기체에 대한 살충제 잔류의 위험성, 화학적 살충에 대한 저항성을 가진 해충의 출현, 생태계의 교란 등 다양한 부작용이 있다. 이 때문에 생물적 방제를 통한 해충 방제는 효과적인 수단이 될 수 있다. 특히 채소 작물 등에 주로 발생하는 응애는 생산량 저하 및 품질 저하 등과 같은 다양한 문제를 일으킬 수 있다. 특히 진딧물이나 점박이응애는 화학적 살충제에 대해 높은 저항성이 발달되어 문제가 되고 있다. 본 연구에서는 아이비(Hedera helix), 란타나(Lantana camara), 예루살렘체리(Solanum pseudocapsicum)를 통한 천연 식물 추출물의 응애에 대한 생물적 방제 효과를 확인하였다. 각 추출물은 0.5%, 0.05% 주정 및 메탄올로 추출하였으며, 응애 방제 효과(%)는 아이비>란타나>예루살렘체리로 나타났다. 각 추출물은 GC/MS 분석을 통해 생리활성 후보 물질을 확인하였다. 이를 통해 농업 이익 증대, 생산량 유지와 더불어 환경 및 인간과 다른 유기체에 피해를 주지 않으며 효과적으로 응애를 방제 할 수 있는 천연 생물적 방제제로의 가치를 확인하였다.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.181-194
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• 1999

Both the chemical components and the physical and mechanical properties of the compacted and undisturbed weathered granite soils were estimated to investigate the influences of the degree of weathering and saturation on the shear strength. The weathered granite soils used in this study were taken from six different sites in Korea. The results showed that the shear strength of weathered granite soil decreased with increasing the degree of weathering and saturation. Under the normal stresses less that 40kPa, the shape of Mohr-Coulomb failure envelope followed curved or hyperbolic relationship and a half of cohesion value obtained by the common shear test was observed. Using the Sueoka's method, the values of CWI were ranged from 21.5 to 31.26 which can be characterized as a completely weathered granite soil. Large decrease in shear strength and remarkable variation in dilatancy were observed in saturated granite soil compared to unsaturated soil. It was also found that the shear strength of undisturbed weathered granite soil of Pungam site can be expressed approximately by the equation of ${(\tau)_{sat}= 1.0(\tau)_{unsat}-12.48}$ and this equation can be extended to the other sites considered in this study.

• Korean Journal of Environment and Ecology
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• v.22 no.2
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• pp.128-137
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• 2008

The purpose of this study is to analyze the effect of hiking trails on forest landscape's fragmentation, based on which also to assess the landscape-ecology-based integrity by small drainage area by selecting Bukhansan National Park as a survey target. The results of effect analysis are as follow; size of forest patch decreased; the density of patch and edge increased; patch shape became complicated; the dimensions of core area noticeably decreased and proximity degree between patch increased after trail-building. In addotion, the assessment results of overall landscape ecology-based integrity by small drainage basin showed that the Bukhansan catchment area was highest making 3.7 point, while Gugi catchment area was rated the lowest making 1.6 point. Putting the above results together, it is necessary to prohibit the opening up of unnecessary trails and to make room for ecological restoration of damaged and disturbance area to their original state as nature goes for landscape-ecology-based conservation and management of forests.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.10
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• pp.893-899
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• 2010

A previous study showed that hemodynamics is correlated with stenosis in the coronary artery. The flow characteristics and the distributions of the hemodynamic wall parameters in the coronary artery are investigated under physiological flow condition. The present study also aims to establish the mechanism of the generation of atherosclerosis by analyzing the hemodynamic variables in the coronary artery where atherosclerosis frequently occurs. The stenosis phenomena due to atherosclerosis are related to not only the biochemical reaction between blood and blood vessels but also the hemodynamic factors sush as flow separation and oscillatory wall shear stress. As the bifurcated angle increases, the size of the recirculation area that appears in the cross section increases and disturbed flow is observed in this area. We speculate that this area is the starting point of atherosclerosis in the coronary artery.