• Korean Journal of Optics and Photonics
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• v.28 no.6
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• pp.351-355
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• 2017

In this paper, we conduct a simulation of manipulating various pulsed laser operations through tuning the modulation depth of the saturable absorber in a laser cavity. The research, showing that various pulsed operations could be manipulated from Q-switching through Q-switched mode locking to mode locking by tuning the modulation depth of the saturable absorber in a cavity, has been studied by experimental means. We conduct a simulation with the Haus master equation to verify that these experimental results are consistent with expectations from theory. The time dependence of the gain was considered to express Q-switching fluctuation through applying a rate equation with the Haus master equation. Laser operation was manipulated from mode locking through Q-switched mode locking to Q-switching as modulation depth was increased, and this result agreed well with the theoretical expectation.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.149-153
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• 2008

The cavity of mold is exposed to high pressure during injection molding operation. Injection molded articles with deep depth are often demanded as design variety increases. Mold becomes weak and deformation increases as the mold depth increases. Thus the injection molds for deep depth articles should be designed to hold out high pressure or stress and large deformation. Through this study, equation for mold design was examined and suggested novel method to determine equation for mold design with deep depth. Novel equation developed in this study was consisted with cantilever and two points bending while previous equation was modified from just cantilever bending. The validity of novel equation was verified through computer simulation.

• Restorative Dentistry and Endodontics
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• v.19 no.2
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• pp.641-654
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• 1994

This study was executed to evaluate adaptability of dentin bonding agents to dentinal wall with measuring contraction gap on interface between cavity wall and composite resin by SEM study. 6 kinds of dentin bonding agents were investigated for this study : Gluma, Super Bond C & B, All bond 2, Scotchbond multipurpose, Scotchbond 2 and Clearfil photo bond. 30 of fresh extracted teeth were randomly selected and divided into 6 groups with each 5. The round shaped cavities with 3mm dia. and 1.5mm depth were prepared on cementoenamel junction of buccal surface of teeth. Dentin bonding agents were applied to cavity wall and then the composite resin was filled in the cavity. Specimens were sectioned longitudinally on buccal surface. Sectioned aspects of specimens were impressioned with rubber base materials and finally precise replica were made of epoxy resin poured in negative impression. Contraction gaps were examined on interface between cavity wall and composite resin under condition of 200 and 2000 magnification of SEM. The results were as follows. 1. There were no gap on interface between enamel and composite resin in all specimens, but gaps were mainly exhibited on apical side of lateral wall of dentin of cavity. 2. In Gluma, 2 cases of 5 specimens exhibited excellent adaptation to the cavity wall, indicating no gaps on interface between cavity wall and composite resin. The other specimens showed gaps with range of $0{\sim}15{\mu}m$ width. 3. In Super Bond C & B, gaps with range of $0{\sim}10{\mu}m$ width were mainly exhibited on apical side of lateral wall of dentin of cavity. 4. In All bond 2, all specimens showed the most exellent adaptation to cavity wall when compared to the other materials, indicating no gap interface between cavity wall and composite resin. 5. In Scotchbond multipurpose, gaps with range of $0{\sim}10{\mu}m$ width were locally located on cavity wall. 6. In Scotchbond 2, all specimens showed great amount of gap with range of $5{\sim}25{\mu}m$, indicating the worst adaptation to cavity wall compared to the other materials. 7. In Clearfil photo bond, 2 case of 5 specimens exhibited exellent adaptation to cavity wall, indicating no gap. the other specimens showed gap with range of $0{\sim}15{\mu}m$ width on inferface between cavity wall and composite resin.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.493-507
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• 2016

Scaled model tests were performed to investigate the stability of a foundation located above limestone cavities. Cavity shape was assumed to be an ellipse having 1/3 for the ratio of minor to major axis lengths. 12 different test models which have various depths, locations, inclinations, sizes and numbers of cavity were experimented and they were classified into 5 different groups. Crack initiation pressure, maximum pressure, deformation behaviors, failure modes and subsidence profiles of test models were obtained, and then the influences of those parameters on the foundation stability were investigated. No cavity model showed a general shear failure, whereas the models including various cavities showed the complicated three different failure modes which were only punching failure, both punching and shear failures, and double shear failure. The stability of foundation was found to be decreased as the cavity was located at shallower depth, the size and number of cavity were increased. Differential settlements appeared when the cavity was located under the biased part of foundation. Furthermore, subsidence profiles were found to depend on the distribution of underground cavities.

• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.311-320
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• 1996

If root and resection is done during surgical endodontic treatment, newly exposed dentinal tubules form pathways between the canal and the peripheral tissue. Nd : YAG laser was used to block this phenomenon, and its effect was studied with dye penetration and SEM techniques. 40 intact single rooted teeth were divided into 4 groups(10 each) : control group and test groups, in which retrograde cavity surface, cutting surface, retrograde cavity surface & cutting surface were treated with laser(1 watt 15pps) and finally retrograde filling with IRM was conducted. After that, they were stained with 2 % methylene blue, sectioned and evaluated by the maximum infiltration depth. And to observe surface change, they were prepared for SEM. The results were as follows ; 1. All experimental groups showed microleakage with variation in amount. 2. The 2nd group which treated both the retrograde cavity and cutting surface showed significantly less microleakage than the other groups(p<0.05). There was no significant difference between groups treated on one side only. 3. As a result of SEM observation of dentin surface, obstruction of dentinal tubules with marble shaped granules, which were different from normal dentin could be seen. Cracks could be seen also. 4. In summary of this experiment, it is thought that effort to obstruct the exposed dentinal tubules as well as retrograde cavity after root end resection is needed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.64-71
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• 2005

To achieve efficient supersonic combustion within a manageable length, a successful fuel injection scheme must provide rapid mixing between fuel and airstream. In former days, various injection concepts have been investigated. Cavity flow is the open type, that is, length-to-depth ratio L/D=4.8, aft ramp angle is $22.5^{\circ}$. An experimental study on a transverse cross jet injection into a Mach 1.92 supersonic main stream which flows over a cavity was carried out to investigate the effect of the momentum flux ratio(J), the jet interaction characteristics, and the pressure distribution in the combustor and using the primary diagnostics : schlieren visualization and wall static pressure measurements. Fuel penetration height and jet interaction characteristics depend strongly on the momentum flux ratio.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1508-1515
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• 2022

In the present study, the cavity module of the MELCOR code is used for the simulation of molten corium concrete interaction (MCCI) during the late phase of postulated large break loss of coolant (LB-LOCA) accident in the APR1400 reactor design. Using the molten corium composition data from previous MELCOR Simulation of APR1400 under LB-LOCA accident, the ex-vessel phases of the accident sequences with long-term MCCI are recalculated with stand-alone cavity package of the MELCOR code to investigate the impact of water ingression and melt eruption models which were hitherto absent in MELCOR code. Significant changes in the MCCI behaviors in terms of the heat transfer rates, amount of gases released, and maximum cavity ablation depths are observed and reported in this study. Most especially, the incorporation of these models in the new release of MELCOR code has led to the reduction of the maximum ablation depth in radial and axial directions by ~38% and ~32%, respectively. These impacts are substantial enough to change the conclusions earlier reached by researchers who had used the older versions of the MELCOR code for their studies. and it could also impact the estimated cost of the severe accident mitigation system in the APR1400 reactor.

• Nuclear Engineering and Technology
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• v.47 no.7
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• pp.907-914
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• 2015

The energetic steam explosion caused by contact between the high temperature molten core and water is one of the phenomena that may threaten the integrity of the containment vessel during severe accidents of light water reactors (LWRs). We examined the dependence of steam explosion loads in a typical reactor cavity geometry on selected model parameters and initial/boundary conditions by using a steam explosion simulation code, JASMINE, developed at Japan Atomic Energy Agency (JAEA). Among the parameters, we put an emphasis on the water pool depth that has significance in terms of accident mitigation strategies including cavity flooding. The results showed a strong correlation between the load and the premixed mass, defined as the mass of the molten material in low void zones (void fraction < 0.75). The jet diameter and velocity that comprise the flow rate were the primary factors to determine the premixed mass and the load. The water pool depth also showed a significant impact. The energy conversion ratio based on the enthalpy in the premixed mass was in a narrow range ~4%. Based on this observation, we proposed a simplified method for evaluation of the steam explosion load. The results showed fair agreement with JASMINE.

• The Korean Journal of Nuclear Medicine
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• v.32 no.1
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• pp.99-108
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• 1998

Intraperitoneal administration of radioisotopes is suggested to treat the metastatic ovarian cancer in the peritoneal cavity. Administering beta-emitting radioisotopes into the peritoneal cavity allows the maximum energy delivery to the cancerous cells of the peritoneal wall surface while sparing the normal cells located in deep site of the peritoneal wall. In this study, dose estimates of the peritoneal wall are provided to be used for prescribing the amount of $^{166}Ho$-chitosan complex administered. The $^{166}Ho$-chitosan complex diffused in the peritoneal fluid may attach to the peritoneal wall surface. The attachment fraction of $^{166}Ho$-chitosan complex to the peritoneal wall surface is obtained by simulating the ascites with Fischer rats. Both volume source in the peritoneal fluid and the surface source over the peritoneal wall surface are counted for the contribution to the peritoneal wall dose. The Monte Carlo code EGS4 is used to simulate the energy transfer of the beta particles emitted from $^{166}Ho$. A plane geometrical model of semi-infinite volume describes the peritoneal cavity and the peritoneal wall. A semi-infinite plane of $10{\mu}m$ in thickness at every 1 mm of depth in the peritoneal wall is taken as the target in dose estimation. Greater than 98 percents of attachment fraction has been observed from the experiments with Fischer rats. Given $1.3{\mu}Ci/cm^2$ and $2.4{\mu}Ci/ml$ of uniform activity density, absorbed dose is 123 Gy, 8.59 Gy, 3.00 Gy, 1.03 Gy, and .327 Gy at 0 mm, 1 mm, 2 mm, 3 mm, and 4 mm in depth to the peritoneal wall, respectively.

• Journal of the Korean Society of Industry Convergence
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• v.7 no.2
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• pp.153-159
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• 2004

The purpose of this research is to investigate the performance of swirl combustion chamber diesel engine by changing the jet passage area, the depth and shape of the piston top cavity (main chamber). The performance of diesel engine with newly changed swirl combustion chamber was tested through the experimental conditions as engine speed, load and injection timing etc. The test results were compared and analyzed. And another purpose of this research is to make a new diesel engine that is satisfied fuel consumption and regulation value of exhaust gas. 1. The rate of fuel consumption was affected significantly by the jet passage area at the high speed and load than low speed and low load. The influence of jet passage large area was proven to decrease the rate of fuel consumption. 2. Smoke was affected significantly by the depth of the piston top cavity, but exhaust temperature and the rate of fuel consumption wasn't affected. The rate of fuel consumption was affected by changing injection timing. 3. The rate of fuel consumption, exhaust temperature and Smoke were affected significantly by the shape of the piston top cavity from rectangular to trapezoid. That is we have all high value. The exhaust smoke density and exhaust gas temperature depended sensitively on variation of the injection timing rather than the shape of the combustion chamber within the experimental conditions. 4. We made a new diesel engine that is satisfied design target values(sfc=190 g/hr, NOx + THC=6.0 g/KWh, PM=0.3 KWh), the rate of fuel consumption and emission standard etc., through changing injection timing at the maximum torque point and rated power point. Although we have a little high NOx value.