• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.241-246
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• 1996

An analytical model to calculate rate of vapor generation due to heterogeneous wall nucleation in flashing flow is developed. In the present model, an important parameter of the vapor generation term, i.e. nucleation site density is calculated by integrating its probability distribution function with respect to active cavity radius. The limits of integration are minimum and maximum active cavity radii, and these are formulated using an active cavity model for nucleate boiling. This formulation, therefore. can statistically account for the effect of surface specific thermo-physical and geometric conditions on the vapor generation rate and flashing inception. For verifying the adequacy of the present model, steady state two-fluid and the bubble transport equations are solved with applicable constitutive equations. The applicable region of the bubble transport equation is also extended to churn-turbulent flow regime to predict interfacial area concentration at high void fraction. Predicted results in terms of axial pressure and void fraction profiles along the channels are compared with experimental data of Super Moby Dick and BNL Reasonable agreements have been achieved and this shows the applicability of the present model to flashing flow analysis.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.87-94
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• 2012

For soils with high void ratios, the inverse method of utilizing results obtained from centrifuge model test was used to find the constitutive relation of effective stress - void ratio - permeability whereas conventional oedometer test and constant rate of strain consolidation(CRS) test about settlement of interface and pore pressure and distribution with time were compared with numerically estimated values to confirm such a constitutive relation as obtained from the inverse method. As results of numerical method, the volumetric ratio and reclamation velocity were obtained for the reclamation condition.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.6
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• pp.852-859
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• 2009

For the analysis of solids containing a number of microinclusions or microvoids, in which the mechanical effect of each inclusion or void, a numerical approach is need to be developed to understand the mechanical behavior of damaged solids containing these defects. In this study, the simulation method using the natural element method is proposed for the analysis of effective elastic moduli. The mechanical effect of each inclusion or void is considered by controlling the material constants for Gaussian points. The relationship between area fraction of microinclusions or microvoids and effective elastic moduli is studied to verify the validity of the proposed method. The obtained results are in good agreement with the theoretical results such as differential method, self-consistent method, Mori-Tanaka method, as well as the numerical results by rigid body spring model.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.813-816
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• 2006

Recently, improvements in the standard of living in industrial area require the establishment of a convenient residential environment in order to enhance the quality of living. To achieve such an environment, it is necessary to effectively reduce or prevent various environmental problems occurring in and around residential areas. Although conventional concrete has been regarded as a destroyer of nature, water and air can pass freely through concrete when it is made porous concrete by forming continuous void. In view of the harmony between nature and concrete, various research paths are being taken focusing on coarse aggregates to make porous concrete having continuous voids so as to improve water and air permeability, acoustic absorption, water purification, and applicability to vegetation. In this study, the Physical and Mechanical Properties of porous concrete according to compaction method analyzed by void ratio, coefficient of permeability and compressive strength.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.7
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• pp.802-808
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• 1992

To investigate degradation procedure and life time of the oxidized PE and the unoxidized PE, alternative voltage is applied to the CIGRE Method-II (CM-II) electrode system, which is loaded artificial void, and measures the distribution of partial discharging generation. From the results, the samples etched by oxidation had wide degradation area of dielectric strength. Furthermore, discharge starting voltage was shifted to low voltage, the discharge generation frequency was high and consequently, the quantity of mean charge becomes small. Also, life time of the oxdized sample is shortened according as the oxidation time is longer.

• Proceedings of the KSR Conference
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• 2002.05a
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• pp.250-255
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• 2002

The transition between bridge and earthwork often causes the problems of maintenance. The damages of the track on the transition area influence running safety of train and serviceability, increase the maintenance cost. Therefore it is very important to evaluate the dynamic responses of transition and take a efficient measure. In order to evaluate the dynamic behavior of track, the field estimations are performed at the transition area of a conventional line between bridge and earthwork. And the track system on the transition area numerically analyzed to evaluate the dynamic behavior of damaged track with void sleeper. The measured values and Analysis results such as wheel contact force, rail stress, displacement acceleration and track irregularity in the transition area show the dynamic forces are severe. So it is recommended that the transition area should be improved the rigidity by reinforcing the rail.

• Resources Recycling
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• v.19 no.1
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• pp.33-39
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• 2010

The spheric sintered body with $6{\pm}2mm$ diameter was manufactured in a rotary kiln at $1125^{\circ}C$/15 min using green body formed by pelletizing the batch powder composing of coal bottom ash produced from power plant and dredged soil by 70:30, wt%. And the physical properties of sintered body (BD) were analyzed to confirm the possibility for applying to an absorbent to restore a contaminated soil. The sintered body had a giant pore above 100 ${\mu}m$ and a fine pore below 10 ${\mu}m$, and bulk density was 1.4. Also its specific surface area, porosity and void proportion were $12.0m^2/g$, 30.1% and 38.2% respectively. The crushed body (BD-C), produced by crushing a BD specimen into an irregular shape with a aspect ratio of about 2, was similar to BD specimen at bulk density and pore size distribution. But it had superior values of specific surface area, porosity and void proportion compared with BD specimen owing to a decreased apparent volume due to conversion of closed pore existed at interior of BD to open pore during a crushing process. The IEP of sintered body occurred at about pH=5, so the optimum pH condition of reacting aqueous solution could be known before bonding a microbe to the sintered body. Hence, the optimum void proportion and porosity of an absorbent can be obtained by appropriate mixing a BD with BD-C from the base data calculated in this study.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.1
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• pp.112-120
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• 1996

In this study, the porous glass media was utilized as biomass carrier, and the optimum characteristics of this new media in fixed bed biofilm process were investigated. The characteristics of media considered here are a void volume fraction, a specific surface area, and surface characteristics of media. The effect of surface roughness and material could be clearly demonstrated by the fact that the porous glass media showed a good potential for biofilm development. This might results from the fact that biofilm is initially formed in the surface cavities of the media is protect from the shear effect. Therefore, the microcolonies are not readily detached by the fluid shear. In the steady state, biofilm formation along the packing bed depth was different from media to media. The specific area was also an important factor for the attachment of microorganism on the media surface. The specific area was also an important factor for the attachment of microorganism on the media surface. In the case of porous glass media, about $100m^2/m^3$ was enough to obtain a good organic removal efficiency The organic removal efficiency could be improved by increasing the void volume fraction in the reactor, at least 80% was required to obtain a high removal efficiency and prevent clogging. From the analysis of kinetics study, the yield coefficient, Y, was 0.42 mgMLSS/mgSBOD, endogenous respiration coefficient, ke, was $0.12day^{-1}$ and substrate removel coefficient of Mckinney. km, was $16.8hr^{-1}$ for the porous glass media G-2

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.375-392
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• 2018

The shield TBM method is widely adopted for tunneling works in urban area because it has more beneficial ways to control settlement at ground surface than conventional mined tunneling. In the shield tunneling, backfill grouting at tail void is crucial because it is supposed not only to restraint ground deformation around tail void during excavation but also to compensate precedent ground settlement by pushing up the ground with highly pressurized grout. However, the tail void grouting has been found to be ineffective for settlement compensation particularly in sandy ground, which might be caused by complicate interaction between ground and tail void grouting. In this paper, the effects of tail void grouting on behavior of ground in shield TBM tunneling were investigated based on 3-dimensional finite element analyses. The results of numerical analyses indicated that backfill grouting actually reduces settlement by degrading settlement increasing rate in excavation, which means decrease of volume loss. Meanwhile, the grouting could not contribute to compensate the precedent settlement, because reduction of volume loss by grouting was found to be counterbalanced by volume change of ground.

• The Journal of the Korea Contents Association
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• v.22 no.6
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• pp.619-628
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• 2022

In general, as a method to confirm a urinary tract infection (UTI) in a medical institutions, urine culture including a urinalysis and an antimicrobial susceptibility test is performed. It is important to disinfect the area around the urethra and perineum before collecting urine samples, and it is important to collect it intermediate urine, not the first-void urine. We invented a patent urine cup (Patent No. 10-1732843) that can automatically and easily separate first-void urine and midstream urine and using this, the patent cup and the general cup were compared and evaluated using this. Nitrite (P<0.001), WBC (P=0.005), Bacterial colony count (P=0.001), colony positivity rate (P=0.004) in first-void urine (N=24), midstream urine (N=24) separated by patent cup to obtain a significantly higher value. This can be seen from the fact that the first-void urine and midstream urine separated using the patent cup were well separated. Also, the number of Bacterial colonies was statistically significantly higher in the midstream urine isolated using a patent cup (N=24) than in the midstream urine collected using a general cup (N=24) (average 7.9 vs. 4.0 on average, P= 0.002). Which means that the midstream urine separated using the patent cup is more sensitive to the UTI test than the midstream urine collected using a general cup.