• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.17-25
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• 2016

Revetments help protect levee slopes from erosion. If the design of the revetment is not appropriate, the levee may collapse as a result of scouring due to the strong flow velocity and tractive force. Therefore, when designing a revetment, it is very important to calculate the representative velocity. However, the average velocity and depth calculated by 1-D varied flow analysis are generally applied to the design, which do not reflect the increase in velocity caused by the free and force vortex. Therefore, it is necessary to correct the representative velocity in order to ensure the stability of the revetment in a meandering channel. In this study, the applicability of the method of calculating the representative velocity considering the curve and scour was studied (by comparing it with) the average and maximum velocities determined by numerical simulation. The representative velocity corrected for the effect of the curve and scour and the maximum velocity calculated by the numerical simulation were found to match quite well. In addition, the riprap size of the gabion in the meandering and straight channels were compared by applying them to the conventional design formulas. In the future, it is necessary to perform additional numerical simulations for various rivers with different characteristics, in order to propose a method of designing a suitable revetment for Korean characteristics. At this time, the results of this study are expected to be able to be used as basic data.

• YAKHAK HOEJI
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• v.41 no.3
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• pp.389-398
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• 1997

Non-adenergic non-cholinergic (NANC) innervation on the circular muscle of the rabbit gastric body was investigated by observing the magnitudy of relaxations induced by the elec trical field stimulation (EFS). Strips were cut from the greater curvature of the gastric body and stimulated with 5s trains of 0.5 ms pulses at 1-20 Hz, 40 V. The EFS induced transient frequency-dependent contractons, followed by a slowly recovering relaxation ewpecially at higher frequency of the EFS. In the presence of atropine and guanethidine, the contractions were virtually abolished, while the frequency-dependent relaxations by the EFS remained unaffected. The magnitude of relaxations progressively decreased as the location of the strips gets closer to the bottom of the gastric body. The relaxations were ablished by tetrodotoxin, indicating that their orgin is the NANC nerve stimulation. NG-nitro-L-arginine (L-NNA, 10-$100{\mu}M$), the inhibitor of nitric oxide (NO)-synthase, caused a concentration-dependent inhibition of the NANC relaxations. The inhibitory effects of L-NNA were not affected gy the location of the strips and were reversed by L-arginine, the precursor of NO-biosynthesis. Hemoglobin (20-$60{\mu}M$), a NO scavenger, inhibited the NANC relaxation s in a concentration-dependent manner. This inhibition was more prominent in the NANC relaxations observed in the lower portion of the gastric body and the relaxations induced ly lower frequencies of the EFS. Methyelne blue (10-$100{\mu}M$), an inhibitor of cytosolic guanylate cyclase, markedly inhibited the NANC relaxations, almost abolishing the response at a higher dose ($100{\mu}M$). These results suggest that NANX innervation of the rabbit gastric body progeressively decrease as he location of the strips gets closer to the bottom of the gastric body, and that the NANC relaxation is primarily mediated by NO-guanosine 3',5'-cyclic monophophate (cyclic GMP).

• Tunnel and Underground Space
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• v.22 no.1
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• pp.69-76
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• 2012

Theoretical backgrounds on the experimental methods of explosive welding, explosive forming and shock consolidation of powders are introduced. Explosive welding experiments of titanium (Ti) and stainless steel (SUS 304) plate were carried out. It was revealed that a series of waves of metal jet are generated in the contact surface between both materials; and that the optimal collision velocity and collision angle is about 2,100~2,800 m/s and $15{\sim}20^{\circ}$, respectively. Also, explosive forming experiments of Al plate were performed and compared to a conventional press forming method. The results confirmed that the shock-loaded Al plate has a larger curvature deformation than those made using conventional press forming. For shock consolidation of powders, the propagation behaviors of a detonation wave and underwater shock wave generated by explosion of an explosive are investigated by means of numerical calculation. The results revealed that the generation and convergence of reflected waves occur at the wall and center position of water column, and also the peak pressure of the converged reflected waves was 20 GPa which exceeds the detonation pressure. As results from the consolidation experiments of metal/ceramic powders ($Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$), shock-consolidated $Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$ bulk without cracks was successfully obtained by adapting the suggested water container and strong bonding between powder particles was confirmed through microscopic observations.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.1-19
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• 2008

This research is to analyze the force on landing 3 Type of Halfpipe Curves(Ellipse, Circle, Brachistochrone) based on the mechanical calculation of normal force on a sloping surface. Jumping off a platform on a bard horizontal surface, the flexing of the legs, the softness of the snow, the angle of the landing surface, initial velocity and the forward motion of the snowboarder can contribute to reducing the force on landing. But halfpipe is significantly determined by the curvature of surface. It is definitely verified that the Brachistochrone curve is more safety than others. However currently using the Ellipse curve is mostly safe too. If we consider the efficiency of construction, we can easily think there is no use of another curves except normal ellipse curved halfpipe. It would better that geometrically verity curved halfpipe should be designed for improving fluent skills to snowboarders. This methode of research can be a model of scientifical research on sports safety how can sportsman reduce critical injury by designing optimal halfpipe facilities and manual.

• Journal of Korea Soil Environment Society
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• v.2 no.1
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• pp.51-61
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• 1997

The objective of this study is to evaluate the feasibility of Pumping-and-Treatment system (PTS) for remediation of the saturated zones contaminated with NAPLs. A simulation is carried out for the removal of DNAPLs (denser-than-water non-aqueous phase liquids) and LNAPLS (lighter-than-water non-aqueous phase liquids) distributing at and below the water table. In the study, LNAPL and DNAPL are assumed to be n-hexane and 1,1-dichloroacetone, respectively. The model system studied consists of four heterogeneous soil layers with different permeabilities. Groundwater flows through the bottom layer and a pumping well is located under the initial water table. The time-driven deformation of the water table and removal efficiency of contaminants are estimated after vacuum application to the inlet of the well. In the calculation, FVM (Finite Volumetric Method) with SIMPLEC algorithm is applied. Results show that removal efficiencies of both DNAPL and LNAPL are negligible for the first 5 days after the PTS operation. However, when the cone-shape water table is formed around the inlet of the pumping well, the rapid removal rate is obtained since NAPLs migrate rapidly through the curvature of the water table. The removal efficiency of DNAPL is estimated to be higher than that of LNAPL due to the gravity. The results also show that the fluctuation or cone-shaped depression of the water table enhances the removal efficiency of NAPLs in saturated zones. The simulation results could provide a basis of the PTS design for the removal of NAPLs in saturated zones.

• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.1-12
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• 2017

This paper proposes nominal flexural strength considering strain-hardening effect of HSB600 high performance steel for compact composite I-girders in positive bending. Unlike conventional steels, HSB600 undergoes strain-hardening just after yielding without going through yield plateau. However, because the nominal flexural strength specified in domestic and foreign bridge design specifications has been developed for the conventional steel composite girders, the nominal flexural strength does not appropriately consider the strain-hardening of HSB600. Therefore, plastic moment considering a strain-hardening is proposed so as to consider effect of the strain-hardening of HSB600 on flexural strength and then moment-curvature analysis is performed to a wide range of cross-sections. From results of the analysis, a parameter representing the effect of the strain-hardening on the flexural strength of HSB600 composite girders is proposed. Furthermore, by using this parameter, the nominal flexural strength considering the strain-hardening effect for HSB600 composite I-girders in positive bending is proposed and then evaluated by comparing with the current AASHTO LRFD bridge design specifications.

• Journal of Korean Society of Transportation
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• v.29 no.3
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• pp.103-114
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• 2011

In this study, we discuss a fatal accident severity model obtained from the analysis of 112 crash sites collected since 2000, and the resulting relationship between fatal accidents and roadway geometry design. From the 720 times computer simulations for improving driving safety, we then reached the following conclusions:. First, the result of cross and frequency-analyses on the car accident sites showed that 43.7% of the accidents occurred on the curved roads, 60.7% on the vertical curve section, 57.2% on the roadways with radius of curvature of 0 to 24m, 83.9% on the roads with superelevation of 0.1 to 2.0% and 49.1% on the one-way 2-lane roads; vehicle types involved are passenger vehicles (33.0%), trucks (20.5%) and buses (14.3%) in order of frequency. The results also show that the superelevation is the most influencing factor for the fatal accidents. Second, employing the Ordered Probit Model (OPM), we developed a severity model for fatal accidents being a function of on various road conditions so as to the damages can be predicted. The proposed model possibly assists the practitioners to predict dangerous roadway segments, and to take appropriate measures in advance. Third, computer simulation runs show that providing adequate superelevation on the segment where a fatal accident occurred could reduce similar fatal accidents by at least 85%. This result indicates that the regulations specified in the Rule for Road Structure and Facility Standard (description and guidelines) should be enhanced to include more specific requirement for providing the superelevation.

• Korean Journal of Optics and Photonics
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• v.21 no.6
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• pp.247-253
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• 2010

A dual-layer light guide plate (DLGP) was designed and a simulation was done to optimize the structure of the light guide plates used at backlight units while maintaining the luminance, uniformity and viewing angle by reducing the optical sheet. The characteristic of DLGP with prism pattern with curvature on the top surface is simulated and the luminance and uniformity are obtained. In order to improve the uniformity, the V groove prism pattern on the bottom surface was turned by an angle of $90^{\circ}$. In particular, we used the pitch calculation program to select the value of the ratio (Max : Min) between the pitch at the extreme outside and the pitch at the middle, the number of V groove lines and the variance at the bottom pattern of DLGP. After that, the optimum distance between V grooves was determined. For optimizing the DLGP, we examined the uniformity again by changing the number of pattern grooves on the bottom surface of DLGP. As a result of the simulation, we find that the BLU with DLGP has a uniformity of 90.6% and viewing angle $145^{\circ}$.

• Computers and Concrete
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• v.14 no.5
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• pp.599-612
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• 2014

This paper presents the effects of the construction stages using time dependent material properties on the structural behaviour of concrete arch dams. For this purpose, a double curvature Type-5 arch dam suggested in "Arch Dams" symposium in England in 1968 is selected as a numerical example. Finite element models of Type-5 arch dam are modelled using SAP2000 program. Geometric nonlinearity is taken into consideration in the construction stage analysis using P-Delta plus large displacement criterion. In addition, the time dependent material strength variations and geometric variations are included in the analysis. Elasticity modulus, creep and shrinkage are computed for different stages of the construction process. In the construction stage analyses, a total of 64 construction stages are included. Each stage has generally $6000m^3$ concrete volume. Total duration is taken into account as 1280 days. Maximum total step and maximum iteration for each step are selected as 200 and 50, respectively. The structural behaviour of the arch dam at different construction stages has been examined. Two different finite element analyses cases are performed. In the first case, construction stages using time dependent material properties are considered. In the second case, only linear static analysis (not considered construction stages) is taken into account. Variation of the displacements and stresses are obtained from the both analyses. It is highlighted that construction stage analysis using time dependent material strength variations and geometric variations has an important effect on the structural behaviour of arch dams. The maximum longitudinal, transverse and vertical displacements obtained from construction stages and static analyses are 1.35 mm and 0 mm; -8.44 and 6.68 mm; -4.00 and -9.90 mm, respectively. In addition, vertical displacements increase from the base to crest of the dam for both analyses. The maximum S11, S22 and S33 stresses are obtained as 1.60MPa and 2.84MPa; 1.39MPa and 2.43MPa; 0.60MPa and 0.50MPa, respectively. The differences between maximum longitudinal, transverse, and vertical stresses obtained from construction stage and static analyses are 78%, 75%, and %17, respectively. On the other hand, there is averagely 12% difference between minimum stresses for all three directions.

• Spatial Information Research
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• v.8 no.1
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• pp.141-153
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• 2000

The purpose of this study is to develop and apply spatial landslide information system using Geographic information system (GIS) in concerned with spatial data. Landslide locations detected from interpretation of aerial photo and field survey, and topographic , soil , forest , and geological maps of the study area, Yongin were collected and constructed into spatial database using GIS. As landslide occurrence factors, slope, aspect and curvature of topography were calculated from the topographic database. Texture, material, drainage and effective thickness of soil were extracted from the soil database, and type, age, diameter and density of wood were extracted from the forest database. Lithology was extracted from the geological database, and land use was classified from the Landsat TM satellite image. In addition, landslide damageable objects such as building, road, rail and other facility were extracted from the topographic database. Landslide susceptibility was analyzed using the landslide occurrence factors by probability, logistic regression and neural network methods. The spatial landslide information system was developed to retrieve the constructed GIS database and landslide susceptibility . The system was developed using Arc View script language(Avenue), and consisted of pull-down and icon menus for easy use. Also, the constructed database can be retrieved through Internet World Wide Web (WWW) using Internet GIS technology.