• Journal of the Chungcheong Mathematical Society
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• v.25 no.1
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• pp.105-113
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• 2012

Generalizing modular lattices, a concept of modular ordered sets was introduced by Chajda and Rachunek. In this paper, we characterize modular ordered sets as those partially ordered set P satisfying that for $a,\;b,\;c\;{\in}\;P\;with\;b\;{\leq}\;c,\;l(a,\;b)\;=\;l(a,\;c)\;and\;u(a,\;b)\;=\;u(a,\;c)$ imply $b\;=\;c$. Using this, we obtain a sufficient condition for them. We also discuss the modularity of the Dedekind-MacNeille completions of ordered sets.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.1-7
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• 2018

This study examined the effect of binder-to-soil ratio(B/S) and water-to-binder ratio(W/B) on the flow and compressive strength development of soil concrete using high-volume supplementary cementitious materials. As a partial replacement of ordinary portland cement, 10% by-pass dust, 40% ground granulated blast-furnace slag, and 25% circulating fluidized bed combustion fly ash were determined in the preliminary tests. Using the low-cement binder incorporated with clay soil or sandy soil, a total of 18 soil concrete mixtures was prepared. The flow of the soil concrete tended to increase with the increase in W/B and B/S, regardless of the type of soils. The compressive strength was commonly higher in sandy soil concrete than in clay soil concrete with the same mixture condition. Considering the high-workability and compressive strength development, it could be recommended for low-cement soil concrete to be mixed under the following condition: B/S of 0.35 and W/B of 175%.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.255-262
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• 2010

This study was conducted at 5 sites of Bocheong Stream basin in May and September 2009 for the evaluate of fish assemblage and chemical water quality. For the study, the models of Index of Biological Integrity (IBI) and Qualitative Habitat Evaluation Index (QHEI) were modified as 8 and 11 metric attributes, respectively. We also analyzed patterns of chemical water quality at the sampling site over the period of 2005~2009, using the water chemistry dataset, obtained from the Ministry of Environment, Korea. The survey showed that total sampled fishes were 34 species and the most dominant species was Zacco platypus (24.3%). In Bocheong Stream basin, values of IBI averaged 28 (n=5), which is judged as a "Good". IBI score at B1, B4 and B5 indicating a "Good" condition whereas, B2 and B3 were as 21 and 22, indicating "Fair" condition, respectively. QHEI was 152 (n=5), judged as "Fair" habitat condition. Values of BOD and COD averaged 1.0 $mgL^{-1}$ (scope: 0.3~4.0 $mgL^{-1}$) and 2.3 $mgL^{-1}$ (scope: 0.3~18.7 $mgL^{-1}$), respectively. Total nitrogen (TN), total phosphorus (TP) and suspended solid (SS) were distinct spatial variation. Based on the IBI, QHEI and chemical water quality dataset, ecological health of Bocheong Stream basin was evaluated that generally good.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.3275-3284
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• 2012

This study analyzed a 3D hydrodynamic advection diffusion using the EFDC model (Environmental Fluid Dynamics Code) in the agriculture lake to prevent stratification when we install a water circulator. EFDC model was predicted the range of the water circulator and various operational parameters ware derived for minimize the impact of the internal lake. Through EFDC simulation, water circulation is started overall circulation after 30days and a lake overall circulation showed that it was possible operated the water circulator after about 100days. Also, advection diffusion concentration was low in a lake when water circulator operate intermittent condition than continuous condition. And the entire circulation was stable in this condition. The S/B (Surface/Bottom) ratio can reduce the impact of lake as the surface water mixing a lot of. When the same condition (S/B ratio(3:1)), Case 8 (50days operation: 50days stop) of condition were able to minimize the impact of lake.

• Fashion & Textile Research Journal
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• v.2 no.3
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• pp.220-226
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• 2000

This study was to determine the characteristics of vapor-permeable waterproof finished fabric by the coating method. 4 different kinds of coating fabrics (A : wet, porous, polyurethane, B : dry, no porous, polyurethane, C : shape memory polyurethane and D : dry, porous polyurethane) were used, which were developed recently With this sample, moisture transport rate ($40^{\circ}C$, 45%RH & $40^{\circ}C$, 95%RH), changes of coating side's shape by washing times, water repellency rate, contracted length, qmax, heat conductivity, heat keeping rate, heat keeping rate with cotton, heat keeping rate on humidity temperature and humidity within clothing etc. were checked. And it was done in a climate chamber under $20{\pm}2^{\circ}C$, $65{\pm}5%RH$. The results of this study were as follow; In the moisture vapor transmission of sample B and C increased on high temperature and high humidity while sample A and D decreased, on this condition. Qmax rate had high relation with ground fabric's surface properties and the order was A>C>D>B. Heat conductivity had high relation with thickness and surface properties. Heat keeping rates on sweat condition showed around half percents of heat keeping rates on normal condition, but had no relation with moisture vapor transport rate. Changes of the fabric's properties by washing times were different in accordance with the construction of fabrics and the coating resin. Sample C had tow heat keeping rate on the high temperature and humidity and high heat keeping rate on the low temperature and humidity Moisture transport rate of vapor-permeable waterproof finished fabrics had high relation with the properties of ground fabrics on low humidity condition, but on the high humidity condition, it was highly related with the properties of coating resin.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.8
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• pp.1097-1104
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• 2003

The current study analyzes Langmuir slip boundary condition theoretically and it is tested in practical numerical analysis for separation-associated flow. Slip phenomenon at the channel wall is properly implemented by various numerical slip boundary conditions including Langmuir slip model. Compressible backward-facing step flow is compared to other analysis results with the purpose of diatomic gas Langmuir slip model validation. The numerical solutions of pressure and velocity distributions where separation occurs are in good agreement with other numerical results. Numerical analysis is conducted for Reynolds number from 10 to 60 for a prediction of separation at T-shaped micro manifold. Reattachment length of flows shows nonlinear distribution at the wall of side branch. The Langmuir slip model predicts fairly the physics in terms of slip effect and separation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.265-273
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• 2003

Numerical analysis of bubble motion during nucleate boiling is performed by imposing a constant heat flux condition at the base of a heater which occurs in most of boiling experiments. The temporal and spatial variation of a solid surface temperature associated with the bubble growth and departure is investigated by solving a conjugate problem involving conduction in the solid. The vapor-liquid interface is tracked by a level set method which is modified to include the effects of phase change at the interface, contact angle at the wall and evaporative heat flux in a thin liquid micro-layer. Based on the numerical results, the bubble growth pattern and its interaction with the heating solid are discussed. Also, the effect of heating condition on the bubble growth under a micro-gravity condition is investigated.

• Bulletin of the Korean Mathematical Society
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• v.55 no.6
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• pp.1713-1726
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• 2018

We study the one-sided regularity of matrices in upper triangular matrix rings in relation with the structure of diagonal entries. We next consider a ring theoretic condition that ab being regular implies ba being also regular for elements a, b in a given ring. Rings with such a condition are said to be commutative at regular product (simply, CRP rings). CRP rings are shown to be contained in the class of directly finite rings, and we prove that if R is a directly finite ring that satisfies the descending chain condition for principal right ideals or principal left ideals, then R is CRP. We obtain in particular that the upper triangular matrix rings over commutative rings are CRP.

• Tribology and Lubricants
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• v.14 no.1
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• pp.45-53
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• 1998

Friction and wear test for two kinds of Cu-based sintered metallic friction material against cast iron disk was carried out by plate-on-disk type friction and wear tester to investigate the friction and wear characteristics of brake system in severe condition. In this experimental study, the counter specimen was cast iron which is being used generally in brakes of heavy duty equipments. Test friction materials were A type which was manufactured by foreign company and B type by domestic company. Friction coefficient and wear volume were measured and compared with each other. The experiment was performed under room temperature. The worn surface of cast iron disk and friction material were observed by scanning electron microscope. The temperature of surface of disk was measured continuously by the non-contacting thermometer. It was found that A type friction material had stable friction coefficient over the wide range of sliding condition, but B type friction material had unstable friction coefficient and lower value of 0.2 under the severe sliding condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.33-42
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• 1999

The effects of wan thermal boundary condition were investigated for a uniform wall temperature, a uniform wall heat flux, and for coupled heat conduction In the channel wall with transverse rectangular ribs. Numerical investigations for steady laminar flow show behavior similar to that observed experimentally in the separated flow region for flow over a cylinder. Conjugate heat transfer with a low solid-fluid thermal conductivity ratio does not lead to the same results as for the uniform heat flux boundary condition, and heat transfer reversal is found on the back sides of the ribs.