• Korean Journal of Environment and Ecology
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• v.15 no.4
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• pp.361-368
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• 2002

The valley forests located at the east-facing slope and the west facing slope in Hambaeksan area were studied to investigate forest structure in relation to aspect and altitude of the slope. There was little difference in density. mean DBH and basal area of the tree layer between east-facing slope and west-facing slope. The importance percentages of Tilia amurensis and Betula costata in west-facing slope were higher than those in east-facing slope. However, the importance percentages of Quercus mongilica and Fraxinus rhynchophylla in the west facing slope were lower than those in east-facing slope. Species diversity of the west-facing slope was 1.415 and that of the east-facing slope was 1.328. Elevation trends were also found for forest structure. As elevation Increased basal area and mean height of the tree layer decreased in both of east-facing slope and west-facing slope. There was a tendency that number of species, species diversity and evenness decreased with increasing elevation. The importance percentage of Quercus mongolica increased with increasing elevation while those of Betula costata and Maackia amurensis decreased. The result of cluster analysis for the tree and subtree layer indicated that the studied forests were classified into the mixed forest community of broad-leaved tree species at west-facing slope and the low and middle elevation belts of east-facing slope and Quercus mongolica community at the high elevation belt of east-facing slope. Quercus mongolica was significantly and positively correlated with Symplocos chinensis for. pilosa, Acer tschonoskii var. rubripes and deutzia glabrata. Betula costata was significantly and negatively correlated with Quercus mongolica and Acer pseudo-sieboldianum.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2589-2592
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• 2003

In this paper, a robust mixed H$_2$/H$\_$$\infty$/ output feedback control method is applied to the design of loop filter for PLL carrier phase tracking. The proposed method successfully copes with large S-curve slope uncertainty and a significant decision delay in the closed-loop that may exist In modern receivers due to a convolutional decoder or an equalizer. The objective is to design an output feedback controller which minimizes the H$_2$performance while satisfying the H$\_$$\infty$/ performance to guarantee the gain margin and phase margin for linear time invariant(LTI) polytopic uncertain systems. LMIs based approach is given to solve this problem. We can verify the H$\_$$\infty$/ performance satisfaction and minimize the phase detector error through the simulation result.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.10a
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• pp.8-15
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• 1993

The transition membrane elements with drilling freedom have been developed. The functionals for the linear problem, in which the drilling rotations are introduced as independent variables, have been presented by Hughes & Bressi. And 4-node membrane elements with drilling degrees of freedom were developed by Ibrahimbegovic. The transition elements can be efficiently used in modelling the in-plane structures, in particular, where the stress concentration exists. A modified Gaussian quadrature adopted to evaluate the stiffness matrices of these transition elements which have slope discontinuity of displacement within the elements. Detailed numerical studies show the excellent performance of the transition elements.

• Tunnel and Underground Space
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• v.9 no.4
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• pp.315-327
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• 1999

Rock fracture mechanics has been widely applied to blasting, hydraulic fracturing, rock slope and many other practical problems in rock engineering. But a measuring method for the fracture toughness of rock, one of the mort important parameters in fracture mechanics as an intrinsic property of rock, has not been yet well established. To obtain mode I rock fracture toughness, the more favorable disc-typed specimens such as CCNBD, SCB, chevron-notched SCB and BDT were used in this study. Rock fracture toughness under mixed-mode and mode II conditions was measured by using the STCA applied to the CCNBD specimen. Size effects such as specimen thickness, diameter and notch length on fracture toughness were investigated. From the mixed-mode results, fracture envelops were obtained by applying various regression curves. The mixed-mode results were also compared with three mixed-mode failure criteria. In each fracture toughness test, acoustic emission was measured to get the data for determining the load levels of different crack propagation patterns.

• YAKHAK HOEJI
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• v.30 no.2
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• pp.100-103
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• 1986

The second derivative absorption spectra of acetaminophen in commercial tablet forms were measured without prior separation from other pharmaceutical adjuvants. The second derivative spectra of acetaminophen were found to have no influence on the characteristic absorbance band of it. A plot of 25 sets of the ordinate (Z) values with various acetaminophen concentrations mixed in other additives gave a straight line (correlation coefficient, 0.9999) and the slope was 2.901${\times}10^{-2}Z$ value/($\mu\textrm{g}$/ml). The procedures were sufficiently sensitive, precise and economical for the assay of tablets of acetaminophen.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.117-126
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• 2021

An experimental study was carried out to investigate the applicability of cement-based materials for green soil which is a soil for promoting plant growth. The results show that the shear strength of the green soil mixed with gypsum cement (No.3) was low, but the hardness (23.6mm) and pH value (7.4) was most suitable for the vegetation environment. In addition, the initial vegetation germination of green soil, which improved performance by adding a moisturizer, was slower than that of general green soil, and the conductivity value tended to be slightly higher. On the other hand, the slope adhesion of advanced green soil was high, and it was found that the plant growth rate and the regeneration capacity were superior after time passed.

• Journal of the Korean GEO-environmental Society
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• v.24 no.10
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• pp.15-23
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• 2023

In this study, the infiltration behavior of slopes composed of mixed soils with clay contents of 0%, 5%, and 10% in weathered Gneiss soil, which is a representative weathered soil in Korea, was investigated, and the stability of unsaturated slopes due to rainfall infiltration was examined. For this, in this study, the soil water characteristic curve was obtained through the water retention test, and the strength constant was obtained through the triaxial compression test. Based on the obtained results, the influence of clay content and antecedent rainfall effect (i.e., initial suction) on the formation of saturated zone (i.e., wetting band) and slope stability due to rainfall infiltration was examined through infiltration and stability analyses. As a result, it was found that the hig her the initial suction, the slower the formation of the saturated zone on the slope. In addition, it was found that as the clay content increases, the shear strength of the ground increases and the resistance to rainfall infiltration increases, and eventually the slope stability is greatly improved.

• International Journal of Fluid Machinery and Systems
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• v.2 no.1
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• pp.31-39
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• 2009

The flow instability in a low specific speed mixed-flow pump, having a positive slope of head-flow characteristics was investigated. Based on the static pressure measurements, it was found that a rotating stall in the vaned diffuser occurs at about 65% flow rate of best efficiency point (BEP). A dynamic Particle Image Velocimetry (DPIV) measurement and the numerical simulations were conducted in order to investigate the flow fields. As a result, the diffuser rotating stall was simulated even by Computational Fluid Dynamics (CFD) and the calculated periodic flow patterns agree well with the measured ones by DPIV. It is clarified that a periodical large scaled backflow, generated at the leading edge of the suction surface of the diffuser vane, causes the instability. Furthermore, the growth of the strong vortex at the leading edge of the diffuser vane induces the strong backflow from the diffuser outlet to the inlet. The scale of one stall cell is covered over four-passages in total thirteen vane-passages.

• Atmosphere
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• v.27 no.3
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• pp.317-329
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• 2017

Ocean mixed layer (OML) depth affects diurnal cycle of sea surface temperature (SST) induced by change of solar radiation absorption and heat budget in ocean. The diurnal SST variation can lead to convection over the ocean, which can impact on localized precipitation both over coastal and inland. In this study, we investigate the OML characteristics affecting the diurnal cycle of SST for the Korean Peninsula and surrounding areas. To analyze OML characteristics, HYCOM oceanic mixed layer depth (MLD) and wind field at 10 m from ERA-interim during 2008~2016 are used. In the winter, MLD is deeply formed when the strong wind field is located on perpendicular to continental slope over deep seafloor areas. Besides, cooling SST-induced vertical mixing in OML is reinforced by dry cold air originated from Siberia. The OML in summer is shallowly distributed about 20 m. In order to estimate the impact of OML model in high resolution NWP model, four experimental simulations are performed. At this time, the prognostic scheme of skin SST is applied in NWP to simulate diurnal SST. The simulation results show that CNTL (off-OML) overestimates diurnal cycle of SST, while EXPs (on-OML) indicate similar results to observations. The prediction performance for precipitation of EXPs shows improvement compared with CNTL over coastal as well as inland. This results suggest that the application of the OML model in summer season can contribute to improving the prediction for performance of SST and precipitation over coastal area and inland.

• International Journal of Fluid Machinery and Systems
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• v.6 no.4
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• pp.200-205
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• 2013

In order to investigate the characteristics of unsteady flow in a mixed flow pump guide vane under the small flow conditions, several indicator points in a mixed flow pump guide vane was set, the three-dimensional unsteady turbulence numerical value of the mixed flow pump which is in the whole flow field will be calculated by means of the large eddy simulation (LES), sub-grid scale model and sliding mesh technology. The experimental results suggest that the large eddy simulation can estimate the positive slope characteristic of head & capacity curve. And the calculation results show that the pressure fluctuation coefficients of the middle section in guide vane inlet will decrease firstly and then increase. In guide vane outlet, the pressure fluctuation coefficients of section will be approximately axially symmetrical distribution. The pressure fluctuation minimum of section in guide vane inlet is above the middle location of the guide vane suction surface, and the pressure fluctuation minimum of section in which located the middle and outlet of guide vane. When it is under the small flow operating condition, the eddy scale of guide vane is larger, and the pressure fluctuation of the channel in guide vane being cyclical fluctuations obviously which leads to the area of eddy expanding to the whole channel from the suction side. The middle of the guide vane suction surface of the minimum amplitude pressure fluctuation to which the vortex core of eddy scale whose direction of fluid's rotation is the same to impeller in the guide vane adhere.