• Geotechnical Engineering
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• v.10 no.2
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• pp.25-40
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• 1994

In order to investigate behavior of lateral flow by plasticity of soils and construction control due to it, in the case of unsymmetrical surcharge load on the soft soils, we examine the existing theoretical background, and compared and analysed the experimental results by model test. After model test fabricated by model test apparatus, which made full remolding samples of soft soils, we observed the state of behavior for deformation with increasing load step to constant time interval. The critical surcharge and ultimate capacity showed tendency to approach to the proposed value of Jaky and Meyerhof, and the lateral flow pressure of which the maximum value was acted on the depth calculated by z/H=0.26+1.71cu and one third value of the maximum lateral flow pressure acted on the ground surface, approach the trapezoid distribution And maximum lateral flow pressure will be calculated by proposed equation of Hong or simple equation which($\alpha=0.4$) the flow pressure coefficient . of proposed equation by Tschebotarioff exchanged to($\alpha=K_0$) . Basides, the failure surcharge by [(q/$y_m$)-q] and [$S_y-(y_m/S_y)$] showed the smaller than ultimate bearing capacity, especially failure criteria line of control diagram of [$S_y(y_m/S_y)$] will be calculated by following equation. $S_y.=3.15exp[-0.58(y_m/S_y)$

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.885-888
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• 1999

This study was carried out to determine the reaction kinetic constant of the dehydration - thermal decomposition of $Na_2B_4O_7{\cdot}10H_2O/Na_2B_4O_7{\cdot}5H_2O$ and to investigate the durability during the repeated use of a chemical heat-storage material and the reproducibility of reaction system. The order of the dehydration reaction was 1st-order. The reaction rate was directly proportional to a partial pressure difference of water steam. The kinetic constant was 0.27 and the reproducibility of dehydration reaction for a kinetic constant and a reaction order was excellent. The activity variation in the durability test of a chemical heat-storage material was within range of ${\pm}5%$ during the repeatedly use in several times.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.5
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• pp.403-409
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• 2008

Polymer electrolyte membrane fuel cell (PEMFC) is very interesting power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, improvement of performance, effect of temperature and initial start at low temperature. These problems can be approached to be solved by using experiment and mathematical method which are general principles for analysis and optimization of control system for heat and hydrogen detecting management. In this paper, insulation vessel and control system for stable operation of fuel cell at low temperature were developed for experiment. The constant temperature capability and the heating time at sub-zero temperatures with insulation control system were studied by using a heating bar of 60W class. PEMFC stack which was made by 4 cells with $50\;mc^2$ active area in each cell is a thermal source. Times which take to reach constant temperature by the state of insulation vacuum were measured at variable environment temperatures. The test was performed at two conditions: heating mode and cooling mode. Constant temperature capability was better at lower environment temperature and vacuum pressure. The results of this experiment could be used as basis data about stable operation of fuel cell stack in low temperature zone.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.3
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• pp.323-333
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• 2014

In this paper, the wakes behind a square cylinder were simulated using two kinds of different turbulence models for the eddy viscosity concept such as the zero- and the one-equation model in which the former is the mixing length model and the latter is the k-equation model. For comparison between numerical and analytical solutions, we employed three skill assessments: the correlation coefficient(r) for the similarity of the wake shape, the error of maximum velocity difference(EMVD) for the accuracy of wake velocity and the ratio of drag coefficient(RDC) for the pressure distribution around the structure. On the basis of the numerical results, the feasibility of each model for wake simulation was discussed and a suitable value for the empirical constant was suggested in these turbulence models. The zero-equation model, known as the simplest turbulence model, overestimated the EMVD and its absolute mean error(AME) for r, EMVD and RDC was ranging from 20.3 % to 56.3 % for all test. But the AME by the one-equation model was ranging from 3.4 % to 19.9 %. The predicted values of the one-equation model substantially agreed with the analytical solutions at the empirical mixing length scale $L=0.6b_{1/2}$ with the AME of 3.4 %. Therefore it was concluded that the one-equation model was suitable for the wake simulation behind a square cylinder when the empirical constant for eddy viscosity would be properly chosen.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1864-1866
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• 1999

The magnetic nondestructive test can be applied to evaluate the magnetic material characteristics and the fracture properties through the internal defects of SA-508 used in the pressure vessels of the nuclear power plants as the direct and accurate in-situ testing methods. The fracture toughness, yield strength and the stress distribution around the defects in the surface and sub-surface of magnetic materials can be directly estimated by Bark-hausen noise(BN) methods as NDT. The testing process of SA-508 by Barkhausen noise method was advanced by controlling the austenizing peak temperature and the time of maintenance at a constant austenizing peak temperature, therefore causing the variation of fracture toughness. Through above process. we can evaluate the variations of effective grain size and the correlation of effective grain size and FATT at each situation. And the stress distribution around the defects can be quantified nondestructively through Barkhausen method.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.14-19
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• 1999

In order to evaluate the effect of Nb on wear properties of high speed steel by powder metallurgy(PM-HSS), niobium-alloyed PM-HSS have been prepared by adding 0%, 1%, 3% and 5%Nb to PM-HSS of 6%W-5%Mo-4%Cr-5%V-5%Co presented in the previous paper. Sliding wear test have been conducted in various sliding speed conditions under the constant pressure using a pin-on-disc type machine. The results of this study shows that the wear resistance of PM-HSS has been increased by the addition of Nb in the range of experimental sliding speed. However, the amount of Nb shows to be unimportant parameter for the improvement of the wear resistance. It may be due to the thermal stability of carbide and high temperature properties of matrix by adding Nb comparing to the case of no addition.

• Transactions of The Korea Fluid Power Systems Society
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• v.3 no.3
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• pp.20-24
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• 2006

Air balancer is a conveyance cargo-handling machine, used in assembly and process lines of car and machining industries. This can lift up an object, the weight of which is from 5 to 200 kg, and moves it to a position. As industrial technologies evolve, it is required to move an object and fit it into a specified position with greater accuracy, rather than performing simple tasks such as lifting objects up and down as conventional ones do. There is also a demand to handle an object with one hand, rather than with two hands,. Through designs of manifold unit for an air balancer function, pilot regulator unit to keep pressure constant, hand unit for an accurate load perception function, and air balancer circuit, this study enables everybody to work it with ease and convenience. Experiments and comparisons were conducted for the performance evaluation of the circuit.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.269-278
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• 2000

The pressure-time profile of the explosion gases can controlled for the use of cartridge explosive with two techniques known as Decoupling and spacing of the charges. Decoupling consists of a space between the explosive column and wall of the blast hole. Four different decoupling index 1.4, 1.8, 2.34, 3.0 are selected in this field study. The level of ground vibrations with each decoupling index was measured and the empirical particle velocity equation from these data was obtained. The condition of new cracks at blast hole are also examined. As the decoupling index is increased, the level of the blast vibration is decreased. But the cracks in rock masses are efficiently formed to remove the broken rock. The vibration constant associated with test sites is given as $K=1564.5(D.L)^{-1.3233}$ in terms of D.I.(decoupling index).

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.296-301
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• 2002

In this study, we investigated the machinability of machinable ceramics which were developed by a research lab. of Inha Univ., Korea. The effect of the nozzle scanning times, the size of patterns and compositions of BN in ceramics on the erosion depth of samples with no mask and samples with three different mask pattern in powder blasting of machinable ceramics. The blasting conditions were the impact angles 90$^{\circ}$, scanning times of noble up to 30 and the stand-off distances 100mm. The widths of mask pattern were 0.1mm, 0.5mm and 1 mm. The powder was alumina sharp particles, WA#600. The mass flow rate of powder during the erosion test was fixed constant at 150g/min and the blasting pressure of powder at 0.25Mpa

• Journal of Korean Society of Water and Wastewater
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• v.24 no.2
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• pp.231-236
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• 2010

A compressible media filtration process with synthetic fiber media was studied for combined sewer overflows (CSOs) treatment. Since the operation performance of fiber media filtration was dependent on the pattern of CSOs, the flow rate of CSOs was investigated and it was characterized by a big fluctuation. Thus, in this study, the fiber media filtration process was tested with wide range of filtration velocity. The removal efficiency was proportion to the increase in compressibility. As the filtration velocity was increased, the treatment efficiency was decreased and consequently leveled off when the velocity exceeded 750 $m^3/m^2$/d. An exponential equation was introduced to express the relationship between the removal efficiency and up-flow velocity. At columm test, six repetition of filtration and backwash cycle did not after the filtering velocity under the constant pressure condition.