• Journal of the Korean Geotechnical Society
• /
• v.21 no.5
• /
• pp.153-161
• /
• 2005

A series of installation damage tests and creep tests are performed to assess the combined effect of installation damage and creep deformation far the long-term design strength of geogrid reinforcement. Three types of geogrids are used to investigate the influence of the geogrid types. From the experimental results, it is shown that installation damage and creep deformation of geogrids significantly depends on the polymer types of the geogrids and the larger the installation damage, the more the combined effect of installation damage and creep deformation. In addition, The results of this study show that the tensile strength reduction factor, RF, considering the combined effect between installation damage and creep deformation is less than that calculated by the current design practice which calculates the long-term design strength of geogrids damaged during installation by multiplying two partial safety factors, $RF_{ID}$ and $RF_{CR}$.

• Journal of Welding and Joining
• /
• v.11 no.4
• /
• pp.70-78
• /
• 1993

An attempt was made to investigate the effect of brazing time on microstructure, microhardness, and corrosion of Zircaloy -4as well as the beryllium diffusion into its sheet. The sheets were coated with beryllium and brazed at $1020^{\circ}C$ for 20-40 minutes in $2{\times}10^{-5}$ torr vacuum atmosphere. 1. Microstructurally the brazed zone was largely divided into three regions: a region of continuous or partially formed of eutectic liquid films along grain boundaries; a region of precipitation in both grains and grain boundaries; a region of elongated wide structure of .alpha.-laths, which was not affected by beryllium. 2. Due to the precipitates, the beryllium-migrated region was hardened and the width of the hardened region increased with increasing brazing time. 3. Beryllium brazed Zircaloy -4 sheets showed a higher corrosion rate than those of as-received and heat-treated at a brazing temperature. 4. Diffusion coefficient of beryllium into Zircaloy -4 at $1020^{\circ}C$ for 30 minutes was $7.67{\times}10^{-7}cm^2/sec.$ It seemed that Be penetrated Zircaloy -4 by forming eutectic liquid films along grain boundaries in the proximity of Be/Zr interface and it, thereafter, diffused into Zircaloy mainly by interstitial solid solution.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.34 no.2 s.115
• /
• pp.26-35
• /
• 2006

The purpose of this research is to suggest the planting methods and the reasonable target levels of IGS for promoting green streetscape in Seoul. Using the three dimensional computer simulations, various greening methods were applied to evaluate effectiveness of promoting green streetscape. The results of this study suggest that promoting tree planting on car lane is more effective than on pedestrian side walks. In wide streets, the height of tree has positive effects on promoting green streetscape. In both car lane and pedestrian side walks, the greening effects of tree planting both in zig-zag pattern and in parallel pattern were similarly most high. The width of strip in side strip planting has positive effect on promoting green streetscape. Promoting stratified planting is very effective. Promoting greening wall on pedestrian side walks is more effective than on car lane. Combined the results of IGS survey with the public officials and complex simulations, suggest that the optimal levels of IGS is ranging from 12.0% in alleys to 54.0% in car lanes among arterial roads.

• Nuclear Engineering and Technology
• /
• v.33 no.3
• /
• pp.315-326
• /
• 2001

Direct ECC bypass phenomena that occur in a reactor vessel downcomer with a Direct Vessel Injection (DVI) system during the reflood phase of a Large Break Loss-of-Coolant Accident (LBLOCA) are experimentally investigated using a transparent l/7.5 scaled down test facility of the Upper Plenum Test Facility (UPTF). A series of separate effect tests are peformed in order to investigate the mechanisms of direct ECC bypass and to find out its scaling parameters. Various flow regimes and phasic distribution in downcomer are identified and mapped, and the fraction of direct ECC bypass is measured under a wide range of air and water injection conditions. From the counterpart test of the UPTF Test 21-D, the dimensionless gas velocity ( $j^{*}$$_{g,eff}$) is derived experimentally, which is believed to be a major scaling parameter for the fraction of direct ECC bypass. And it is found out that the direct ECC bypass is greatly affected by the spreading width of ECC water film and the geometric configuration of the downcomer.r.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1998.03a
• /
• pp.144-147
• /
• 1998

VCR is a back-up roll with a special contour which leads to the length of the contact line between back-up roll and work becones self adjustable in accordance with the width of the strip. The simulation of a finite element model and the on-line test at production mill demonstrate that the VCR roll may keep the crown of the roll gap relatively stable, and at same time, permit the rolling pressure to be adjusted over a wider range, and increase the effect of work roll bending on the roll gap. The VCR rolls have been successfully used at the first stands of two largest cold rolling mills in China, and on-line test has been done at a wide hot strip finishing train. The use of VCR roll has created favorable conditions for subsequent rolling passes and the achievement of better flatness quality.

• Journal of Korean Society of Water and Wastewater
• /
• v.27 no.2
• /
• pp.185-196
• /
• 2013

In Yongwon channel, its natural flow of seawater is blocked by the construction of Busan Newport including the container berth. The channel was transformed into a narrow and long one, where it is possible that ships are only allowed to pass through the north-side channel of Gyeonmado located at the point of river mouth to Songjeongcheon. In addition, Yongwon channel is approximately 100 m wide on average and 3,600 m long, which has the highest slenderness ratio (length/width=36). So it is considered that the changes in the terrain characteristics of Yongwon channel is likely to alter the circulation of sea water, thereby changing its water quality. In this study, the seasonal change and the spatial variation of the water quality in Yongwon channel was analyzed for the effect of land pollution using the measurement data. The mass balance calculation method is used to analyze the water pollution resulting from sediment pollutants. This result shows that the improvement of the water quality in Yongwon channel can be obtained from the sewer pipe modification and the environmental dredging.

• Transactions of Materials Processing
• /
• v.20 no.4
• /
• pp.296-302
• /
• 2011

The objective of this paper is to determine the effect of process parameters on the behavior of a 18Cr-10Mn-$0.44N_2$ nitrogen steel sample deformed by hot rolling. Compression tests were carried out at high temperatures to determine the flow stresses needed for a finite element(FE) analysis. The strain rate, ranging from 0.1 to $1.0s^{-1}$, significantly affected the flow stress at temperatures higher than $1,000^{\circ}C$. Non-isothermal rolling simulations and laboratory rolling tests were performed with plate specimens 14.5mm thick, 135mm wide and 226mm long. A rolling reduction of 15% per pass leading to a cumulative rolling reduction of 60% was determined as optimal. The extension ratio of 176.5% in the length direction was about 30.4 times greater than the extension ratio of 5.8% in the width direction. Isotropic properties for tensile strength, microstructure and grain size were measured after mock-up hot rolling tests. The results from the mockup tests were found to be in good agreement with those of the simulations.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.2
• /
• pp.386-391
• /
• 2006

In this paper, a design of V-type Linearly Tapered Slot Antenna(V-LTSA) with uniplanar microstrip-to-coplanar stripline(CPS) transitions is presented. The effect of reducing and increasing with taper width G, teper length L and opening angle are also considered at 5.8 GHz. In the result of a simulation by using CST-MWS, the return loss characteristic came very wide band about 4.3GHz, or 1.8 Octave. Proposed V-LTSA design schemes are expected to be a good antenna for microwave and millimeter-wave communcations.

• International Journal of Automotive Technology
• /
• v.8 no.2
• /
• pp.249-258
• /
• 2007

This paper proposes a method that can be used for the resistance estimation of a PWM (Pulse Width Modulation)-driven solenoid. By using estimated solenoid resistance, the PWM duty ratio was compensated to be proportional to the solenoid current. The proposed method was developed for use with EHB (Electro-Hydraulic Braking) systems, which are essential features of the regenerative braking system of many electric vehicles. Because the HU (Hydraulic Unit) of most EHB systems performs not only ABS/TCS/ESP (Electronic Stability Program) functions but also service braking function, the possible duration of continuous solenoid driving is so long that the generated heat can drastically change the level of solenoid resistance. The current model of the PWM-driven solenoid is further developed in this paper; from this a new resistance equation is derived. This resistance equation is solved by using an iterative method known as the FPT (fixed point theorem). Furthermore, by taking the average of the resistance estimates, it was possible to successfully eliminate the effect of measurement noise factors. Simulation results showed that the proposed method contained a sufficient pass-band in the frequency response. Experimental results also showed that adaptive solenoid driving which incorporates resistance estimations is able to maintain a linear relationship between the PWM duty ratio and the solenoid current in spite of a wide variety of ambient temperatures and continuous driving.

• Structural Engineering and Mechanics
• /
• v.17 no.6
• /
• pp.751-766
• /
• 2004

This paper extends the use of the hierarchic degenerated shell element to geometric non-linear analysis of composite laminated skew plates by the p-version of the finite element method. For the geometric non-linear analysis, the total Lagrangian formulation is adopted with moderately large displacement and small strain being accounted for in the sense of von Karman hypothesis. The present model is based on equivalent-single layer laminate theory with the first order shear deformation including a shear correction factor of 5/6. The integrals of Legendre polynomials are used for shape functions with p-level varying from 1 to 10. A wide variety of linear and non-linear results obtained by the p-version finite element model are presented for the laminated skew plates as well as laminated square plates. A numerical analysis is made to illustrate the influence of the geometric non-linear effect on the transverse deflections and the stresses with respect to width/depth ratio (a/h), skew angle (${\beta}$), and stacking sequence of layers. The present results are in good agreement with the results in literatures.