• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.3
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• pp.84-91
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• 1982

This study was conducted to investigate the consolidation characteristics of repeated increasing and decreasing load m marine clay. Consolidation test was performed by the whole repetition of increasing and decreasing load and the partial repetition of increasing and decreasing load. The results obtained were as follows: 1. The void ratio e was decreased according to the increase of preloading and the repe- tition of increasing and decreasing load. 2. In case of the partial repetition of increasing and decreasing load the compression index Cc was decreased with the increase of preloading and the repetition of increa- sing and decreasing load 3. The expansion rate was greatly increased with the whole repetition of increasing and decreasing load and it was inclined to be increased with the increase of preloading in case of the partial repetition. 4. The coefficient of volume compressibility were decreased according to the repetition of increasing and decreasing load 5. The secondary consolidation coefficient was decreased with the repetition of increasing and decreasing load. Especially in case of the partial repetition, the peaks of secon- dary consolidation curves could be found to move toward the vicinity of preloading.

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.2
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• pp.99-107
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• 2007

We consider (worst-case) robust optimization versions of the Economic Order Quantity (EOQ) model with decreasing cost functions. Two variants of the EOQ model are discussed, in which the purchasing costs are decreasing power functions in either the order quantity or demand rate. We develop the corresponding worst-case robust optimization models of the two variants, where the parameters in the purchasing cost function of each model are uncertain but known to lie in an ellipsoid. For the robust EOQ model with the purchasing cost being a decreasing function of the demand rate, we derive the analytical optimal solution. For the robust EOQ model with the purchasing cost being a decreasing function of the order quantity, we prove that it is a convex optimization problem, and thus lends itself to efficient numerical algorithms.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.4
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• pp.421-428
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• 2007

Many engineering problems on the pipeline flow use continuity, energy, friction loss head equation. To calculate friction loss head in a pipeline, Darcy-Weisbach and many average velocity equations can be used and Hazen-Williams equation is used frequently in the pipe network for the water supply systems. Darcy-Weisbach equation is a general one acquired from applying Bernoulli's equation in the pipeline flow and Hazen-Williams equation is a experimental one in case that pipe velocity is below 3m/sec and pipe diameter is over 50mm. In this study, comparing Darcy-Weisbach with Hazen-Williams equation, relation f and C that are expressed as roughness coefficients of those equations is explained. Next, head losses calculated from using those equations are compared and those are applied in realistic pipelines. Comparing f with C, the f is decreasing linearly according to increase of the Reynolds number Re and increasing in case the C is decreasing. additionally, the C is increasing up to a point and then is decreasing according to increase of the Re. Next, the C is increasing and Re's range for increase of the C lengthens in case of decreasing of the relative roughness ${\varepsilon}/d$. Comparing head losses acquired from the two equations, head loss appears large in case that the C is decreasing and the ${\varepsilon}/d$ is increasing. additionally, Head loss calculated by the Darcy-Weisbach equation varies larger than one by Hazen-Williams equation in regard of the Re. Next, change aspect of head loss acquired by the C is distinguished more clearly than the one by the ${\varepsilon}/d$.

• 전기의세계
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• v.26 no.6
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• pp.59-65
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• 1977

A study on the decreasing method of secondary arc current on single phase reclosing. One of the major problem in case of using the single phase reclosing scheme for long distance UHV transmission line is the time required to deionize secondary arc current. This paper descritbes the way of inducing the formular of secondary arc current originated at the times of opening and closing the ground interrupting switch. The result was investigated by the method of numerical analysis and proved that the secondary arc current was decreasing sufficiently. Application of this method proposed by the authod makes it possible to deduce the dead time and to improve success-rate of reclosing.

• Journal of Power System Engineering
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• v.12 no.1
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• pp.47-52
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• 2008

This study was investigated the effect of subzero treatment in austempered ductile cast iron. Retained austenite transformed to martensite by subzero treatment and strain. With decreasing subzero treatment temperature and increasing strain, retained austenite transformed more to martensite and transformed 30% above by subzero treatment at $-196^{\circ}C$. With decreasing subzero treatment temperature, the value of strength and ratio of increasing of strength, hardness and ratio of increasing of hardness increased but the value of elongation and ratio of decreasing of elongation decreased. With decreasing subzero treatment temperature, impact value and ratio of decreasing of impact value decreased. In case of subzero treatment at $-196^{\circ}C$, hardness value increased about 18% and impact value decreased above 20%. We could find that in subzero treated specimens had a little of effect on the tensile properties but had very much effect on the hardness and value of the impact.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.2
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• pp.211-217
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• 2006

This study is focused on the analysis of the characteristics of marine HVAC duct. These results will be applied to develope a robot which is for maintaining a cabin comfort, convenience and healthy through HVAC duct. The followings are the results of this study. (1) The evaluated items which proposed by at the view point of robot's function can be adapted to other vessels for the same purpose, (2) For the case of round type duct. the maximized conditions which robot has to have are straight length of 40.152mm, inclination of $45^{\circ}$. horizontal bending of $90^{\circ}$. increasing diameter of 1.28 times, and 0.625 times decreasing diameter in branch. (3) For the case of rectangular type duct. the maximized conditions are straight length of 15.987mm. aspect ratio of 4.17:1, inclination of $18.92^{\circ}$. horizontal bending of $90^{\circ}$, and 0.65 times decreasing diameter in branch.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.285-292
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• 2004

Earth Anchor method as a supporting system is widely used in the large scale deep excavation of urban areas or slope excavation project. Considering the application frequency of that method and catastrophe of that method under unproper construction management, we can find out many problems relevant to the domestic design and construction management of earth anchor method. When we encounter the cases of rapid increments and various decrements in earth anchor axial forces, considering the characteristic of earth anchor method, it is an essential point to catch the reasons and to prepare countermeasures. This article introduces two actual monitoring examples based on the close analyses of measured data in a typical large scale deep excavation project and slope excavation project. One is a rapidly increasing case of earth anchor axial forces with the continuous advance of incremental deformation in a geological layer interface. And another is a decreasing case of earth anchor axial forces with the construction conditions. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.2925-2930
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• 2013

We present results of molecular dynamics simulations for hydroxide ion in supercritical water of densities 0.22, 0.31, 0.40, 0.48, 0.61, and 0.74 g/cc using the SPC/E water potential with Ewald summation. The limiting molar conductance of $OH^-$ ion at 673 K monotonically increases with decreasing water density. It is also found that the hydration number of water molecules in the first hydration shells around the $OH^-$ ion decreases and the potential energy per hydrated water molecule also decreases in the whole water density region with decreasing water density. Unlike the case in our previous works on LiCl, NaCl, NaBr, and CsBr [Lee at al., Chem. Phys. Lett. 1998, 293, 289-294 and J. Chem. Phys. 2000, 112, 864-869], the number of hydrated water molecules around ions and the potential energy per hydrated water molecule give the same effect to cause a monotonically increasing of the diffusion coefficient with decreasing water density in the whole water density region. The decreasing residence times are consistent with the decreasing potential energy per hydrated water molecule.

• Journal of Environmental Science International
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• v.20 no.8
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• pp.997-1009
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• 2011

In order to estimate volume transport by upwelling for single artificial seamount, same shape and size of artificial seamount already deployed was applied to numerical experiment. The result showed that strong upwelling appeared at front while took place downwelling at rear. The strongest upwelling existed at the top of the artificial seamount. Volume transport by upwelling was computed as 785 m3/s. Column arrangement was applied to two artificial seamount in three cases; case 1) no clearance, case 2) sixty-five meters of clearance as half of artificial seamount's length, and case 3) hundred-thirty meters of clearance as an artificial seamount's length. All cases of column arrangements showed more upwelling volume transport than that of single seamount. Particularly, the case of no clearance calculated as 106% and appeared the most upwelling effect comparing to two other cases. Row arrangement was also applied to two artificial seamount in three cases; case 4) no clearance, case 5) forty meters of clearance as an artificial seamount's width, and case 6) eighty meters of clearance as twice of artificial seamount's width. Upwelling volume transport in case 4 increased 48% than the case of single seamount. Other two cases of 5 and 6 were estimated as 97% increased and more effective than case 4. According to the case experiments, column arrangements show more upwelling volume transport than that of row arrangements. In cases of column arrangements, with decreasing clearance between two seamount, the effect increases while showing maximum value at clearance zero. In cases of row arrangements, on the contrary, with decreasing clearance between two seamount, the effect decreases while showing minimum value at clearance zero. Since simple barotropic condition was considered for this study, further study is necessary by considering baroclinic condition to get close to reality. In conclusion, in deploying artificial seamount, optimal arrangement should be well designed to enhance primary and secondary productivity and to increase the diversity of species as well as reducing time and space.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6B
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• pp.491-497
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• 2011

In this study, the flow characteristics around the cutter head, which makes the dredging soil suspended, were measured to evaluate the environmental affect of the dredging works. The PIV was used for measuring the flow characteristics around the cutter head for suction and non-suction cases. As the results, the mean velocity was decreased from the cutter head to outward. The mean velocity decreasing rate of the non-suction case was larger than that of the suction case, but the turbulence intensity decreasing rate of the non-suction case was smaller than that of the suction case because of the suction energy which makes the z-direction flow.