• Transactions of Materials Processing
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• v.7 no.2
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• pp.177-185
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• 1998

The kinematically admissible veolcity field is developed for the shapes of dead metal zone and the curving velocity distribution in the eccentric plane dies extrusion. The shape of dead metal zone is defined as the boundary surface with the maximum friction constant between the deformable zone and the rigid zone. The curving phenomenon in the eccentric lane dies is caused by the eccentricity of plane dies. The axial velocity distribution in the plane dies is divided in to the uniform velocity and the deviated velocity. The deviated velocity is linearly changed with the distance from the center of cross-section of the workpiece. The results show that the curvature of products and the shapes of the dead metal one are determined by the minimization of the plastic work and that the curvature of the extruded products increase with the eccentricity.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.41-45
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• 2002

The zone-conditioned CMC equations are derived by taking an unconditional average of the generic conservation equations multiplied by delta and Heaviside functions in terms of mixture fraction and reaction progress variable. The resulting equations are essentially in the same form as the single zone CMC equations except for separate flow fields for burned and unburned gas. The zone-conditioned two-fluid equations are applied to a stagnating turbulent premixed flame brush of Cheng and Shepherd[5l. It is shown that the flame stretch factor is of crucial importance to accurately reproduce the measured mean reaction progress variable and conditional velocities. Further work is in progress for the relationship between surface and volume averages and extension to partially premixed combustion on the basis of a triple flame structure, e. g. in a lifted turbulent diffusion flame.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.250-253
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• 1998

The kinematically admissible velocity field is developed for the shapes of dead metal zone and the curving velocity distribution in the eccentric plane dies extrusion. The shape of dead metal zone is defined as the boundary surface with the maximum friction constant between the deformable zone and the rigid zone. The curving phenomenon in the eccentric plane dies is caused by the eccentricity of plane dies. The axial velocity distribution in the plane dies is divided in to the uniform velocity and the deviated velocity. The deviated velocity is linearly changed with the distance from the center of cross-section of the workpiece. The results show that the curvature of products and the shapes of the dead metal zone are determined by the minimization of the plastic work and that the curvature of the extruded products increases with the eccentricity.

• Korean Journal of Organic Agriculture
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• v.22 no.4
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• pp.581-591
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• 2014

This study analyze the policy efficiency of the environment-friendly farming zone program using data envelopment analysis. On analyzed results, the average policy efficiency is 0.185 and 98.3% of zones are inefficient. 97.8% of zones are in increasing returns to scales. The empirical results indicate that more work need to be done to increase the efficiency of the program.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2405-2408
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• 2011

In recent time, the cause analysis and the reduction of the track irregularity have become the most important issue in the ballasted track on the high-speed railway bridge. This is because that the frequency of the maintenance work at the bridge expansion joint zone is on the rise. The track irregularity on the railway bridge starts at the end of the bridge-deck and spreads along the bridge. Due to the dynamic vibration and the thermal expansion of the bridge, the compaction of the ballast gravel on the bridge expansion joint zone become loose and then the progress of the track irregularity result from the train-induced dynamic impact is accelerating further. Among the several options for reducing the track irregularity on the bridge expansion joint zone, the application and efficiency of the zero longitudinal restraint(ZLR) and tied sleeper are investigated in this paper. Field test construction has been conducted, then the progress of the track irregularity and the frequency of the maintenance work are analyzed before and after the filed test construction. Of the two methods, it is shown that the installation of the ZLR seems to be better than the tied sleeper.

• Journal of Welding and Joining
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• v.26 no.4
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• pp.73-78
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• 2008

In this paper, research was the variation of microstructure and mechanical properties of clad(A4045/A3003) Al alloy sheet by gas tungsten arc welding. Tensile properties of the gas tungsten arc welding joint decreased because of the softened heat affected zone(HAZ). The hardness of HAZ was lower than that of base metal, because relieved the work hardening effect of the welding heat. Hardness distribution of the weld zone with the base metal appears similarly, but the hardness of HAZ decreased remarkably. The microstructure in the weld zone of A4045 clad layer was formed a coarse columner grains of Si-rich. In the case of large weld heat input, the Si of the A4045 were diffused and until A3003 weld zone they decreased the strength.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.197-201
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• 2009

A lot of work is carried out concerning to acicular ferrite formation in the weld metal of high strength and low-alloy steel. Those results are suggesting that oxides that contain titanium elements provides nucleation site of intragranular ferrite, referred as acicular ferrite. Thus, when intragranular ferrite is expected to form in heat-affected zone, oxide containing titanium element should be formed in the steel. However, normal steel is deoxidized by using aluminum element (Al-killed steel) with little oxygen content. It means almost oxygen is deoxidized with aluminum elements. In the present work, in order to form the acicular ferrite in the heat affected zone, with the same concept in the case of weld metal, the steel deoxidized with titanium element (titanium killed-steel) is prepared and the acicular ferrite formation is observed in detail by using laser-conforcal microscopy technique. The confocal technique makes it possible that the morphological change along the phase transformation from austenite to ferrite is in-situ tracked. Thus, the inclusion that stimulated the ferrite nucleation could be directly selected from the observed images, in the HAZ of the Ti-killed steel. The chemical composition of the selected inclusion is analyzed and the nucleation potential is discussed by changing the nucleation site with boron element. The potency for the ferrite nucleation is summarized and the existence of effective and ineffective manganese sulfide for nucleation is made clear.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.6
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• pp.124-140
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• 2017

There exists a limitation to provide proper advance information for safe maneuvering through guidance and caution signs in freeway mobile work zones, unlike fixed work zones. Although a work-protection vehicle is currently deployed at the rear of the work vehicle, more active countermeasures to prevent crashes are required. The purpose of this study was to propose a method to evaluate the safety in mobile work zones and to present effective countermeasures. Driving simulation experiments were conducted to analyze characteristics of driver's behavior in mobile and fixed work zones. Safety distance index (SDI) based on the comparison of stopping distances of a work-protection vehicle and a following subject vehicle was used to evaluate traffic safety. More dangerous driving behavior was observed in the mobile work zone. Especially, it was identified that the lane-change of vehicles following the work- protection vehicle was late. Therefore, it is necessary to actively introduce methods to provide warning information so that the driver can recognize the work-protection vehicle in advance and carry out appropriate evasive maneuvers.

• Economic and Environmental Geology
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• v.7 no.4
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• pp.157-173
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• 1974

The Red Hill deposit of the Dongjom Copper Mine is the most promising deposit of the mine and under intensive exploration at present although there are eight more deposits of vein type. With total 2160m drilling of 9 holes completed and 400m drilling on two holes underway, the nature of the Red Hill deposit has come more clear. The copper content in the whole ore body is meager so far as the exploration done up to present indicates, but there are evidences that mineralization covers all over the granodiorite cupola at the Red Hill area. The petrological work and assay on the samples taken by the writers indicate that granodiorite rocks can be divided into fresh zone and alteration zone. Alteration zone consists of potassic and argillic zones accompanyied by silicification zone on basis of Lowell and Guilbert model Argillic zone has closely related with a mineralization in the Red Hill deposit. It has been cleared that the alteration acompanyied with the mineralization took place not only &long vertical fissures but also in the irregular lateral zone, the nature of which is unknown. Judging from the results of exploration and petrochemical study on the Red Hill deposit which is imbedded in a southern part of the granodiorite cupola, it can be concluded by the writer's opinion that the Red Hill deposit is possibly a porphyry copper deposit, because the shape of the ore body, mineral zoning and paragenesis and wall rock alteration resemble to those of typical porphyry copper deposits. It is the writers' opinion that more exploration work is required so as to evaluate the deposit.

• Korean Journal of Materials Research
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• v.3 no.1
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• pp.58-64
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• 1993

The degree of work hardening in the subsurface zones varied with the experimental conditions under the rolling contact fatigue wear test of high carbon Cr-Ti alloy steel was evaluated by the distribution of residual stresses. Surface residual stresses before the test did not affect the wear property. Surface residual stresses after the test decreased by the increase of contact stress and running. velocity. but the maximum compressive residual stress and its depth of saturation in the subsurface zone increased. The relationship between these experimental results and the distribution of the theoritical shear stress was also discussed.