• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.129-133
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• 2005

Vibration transmitted through rolling tire is a major source of road noise in vehicle interior noise on the range of low frequency.($0{\sim}500Hz$) Among various road noises, tire cavity noise has very peak on $200{\sim}250Hz$. And generally it is generated by cavity resonance of tire. In this paper, tire cut-sample is used to calculate the tire cavity frequency. Cavity resonance frequency of tire is measured through vertical/tangential forces at load cell of axle using drum cleat impact. This method is useful to find cavity peak because measured forces do not have complex peaks. And changing the test conditions (air inflation, loads), tire cavity resonance characteristics are identified. Finally, vehicle interior noise is measured as tire/vehicle are changing. As difference of tire vertical force is bigger, interior noise level is higher at cavity frequency. Also we can assume that vehicle sensitivity is important factor at tire cavity noise.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.452-455
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• 2008

A new passive control technique of cavity-induced pressure oscillations has been investigated numerically for a supersonic two-dimensional flow over open rectangular cavities at Mach number 1.83 just upstream of a cavity, in which a sub-cavity system is installed on the backward-facing step of the main cavity. A third-order TVD (Total Variation Diminishing) finite difference scheme with MUSCL is used to discretize the spatial derivatives in the unsteady compressible Navier-Stokes equations. The results obtained show that the present sub-cavity system is very effective in reducing cavity-induced pressure oscillations. The results also showed that the resultant amount of attenuation of cavity-induced pressure oscillations was dependent on the length and thickness of the flat plate, and also on the depth of the sub-cavity used as an oscillation suppressor.

• Korean Journal of Animal Reproduction
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• v.18 no.4
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• pp.245-250
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• 1995

The appearance and function of corpora lutea(CL) with a central cavity in the ovaries of Korean Native Cattle (KNC) were investigated endocrinologically and histochemically. The CL were enucleated from KNC ovaries within 2~3 hrs local slaughter house and classified with central cavity CL or not. Enzymatically dispersed luteal cell (1$\times$106 live cell/ml of Dulbecco's Modified Eagle Media) with or without cavity of CL cultured at 37$^{\circ}C$ in a humidified incubation (5% CO2 : 95% air) for 72hr. A central cavity in the CL of KNC was found in 58.8% of CL-1, 34.9% of CL 2, 39.1% of CL-3, and 11.1% of CL-4, respectively. There were no significant difference between protein content of CL with and without a central cavity. Mean progesterone secretion after 36h of in vitro luteal cell culture were significantly (p<0.05) higher in CL with central cavity than without cavity. However, the luteal cavitic wall was composed of the connective tissue band of the reticular and collagen fibers and then these connective tissue band extended into the CL with cavity. These results suggest that the central cavity of CL may be caused infertility in KNC.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.397-400
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• 2006

In this study, we experimentally investigate the possibility of skin-friction drag reduction by series of transverse cavities in a turbulent boundary layer flow. The effects of cavity depth (d), cavity length (l) and cavity spacing (s) on the skin friction drag are examined in the range of $Re_{\theta}\;=\;4030\;{\sim}\;7360$, $d/{\theta}_0\;=\;0.13\;{\sim}1.03$, l/d = 1 ~ 4 and s/d = 5 ~ 20. We perform experiments for twenty different cavity geometries and directly measure total drag force using in-house force measurement system. In most cases, the skin friction drag is increased. At several cases, however, small drag reduction is obtained. The variation of the skin ftiction drag is more sensitive to the cavity length than to the cavity depth or cavity spacing, and drag is reduced at $s/l\;{\geq}\;10$ and $l/{\theta}_0\;{\leq}\;0.26$ irrespective of the cavity depth. At $l/\bar{\theta}_0\;=\;0.13$ and s/l = 10, maximum 2% drag reduction is achieved. When the skin friction drag is reduced, there is little interaction between the flows inside and outside cavity, and the flow changed by the cavity is rapidly recovered at the following crest. A stable vortex is formed inside a cavity in the case of drag reduction. This vortex generates negative skin friction drag at the cavity bottom wall. Although there is form drag due to the cavity itself, total drag is reduced due to the negative skin friction drag.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.82-89
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• 2005

This study was performed to investigate the behavior and spatial distribution of fuel mixtures with different wall angle and diameter of piston cavity in a DI gasoline engine. The spatial distribution of fuel mixtures after impingement of the spray against a piston cavity is one of the most important. factors for the stratification of fuel mixture. Thus, it is informative to understand in detail the behavior and spatial distribution of fuel mixtures after impingement in the cavity. Two dimensional spray fluorescence images of liquid and vapor phase were acquired to analyze the behavior and distribution of fuel mixtures inside cylinder by exciplex fluorescence method. The exciplex system of fluorobenzene/DEMA in non-fluorescing base fuel of hexane was employed. Cavity wall angle was defined as an exterior angle of piston cavity. Wall angles of the piston cavity were set to 30, 60 and 90 degrees, respectively. The spray impinges on the cavity and diffuses along the cavity wall by its momentum. In the case of 30 degrees, the rolling-up moved from the impinging location to the round and fuel-rich mixture distributed at periphery of cylinder. In the case of 60 and 90 degrees, the rolling-up recircurated in the cavity and fuel mixtures concentrated at center region. High concentrated fuel vapor phase was observed in the cavity with 90 degrees. From. present study, it was found that the desirable cavity wall angle with cavity diameter for stratification in a Dl gasoline engine was demonstrated.

• Journal of the Korean Geosynthetics Society
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• v.18 no.3
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• pp.79-88
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• 2019

This study described a results of groundwater injection test in cavity, in order to evaluate characteristics of cavity expansion under pavement. That is, groundwater amount proportional to the cavity volume was injected into the generated cavity step by step, and then the cavity with the changed size was monitored as the injected groundwater was drained. The test result showed that the cavity volume by groundwater injection increased, and then it converged or decreased. This means that some of the relaxation soil around the cavity collapsed, and the fine-grained soils in some soils filled the void in the surrounding soils when the cavity is expanded by groundwater injection. The volume change and expansion characteristics of the cavity according to the groundwater injection step were analyzed. The result showed that the cavity extended laterally. Therefore, it was found that the cavity expansion is caused by the repetition of the relaxation soil collapse due to the groundwater flow and the loss of the collapsed soil below the cavity.

• Geomechanics and Engineering
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• v.37 no.1
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• pp.9-19
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• 2024

This study presents an energy analysis for large-strain cavity expansion problem based on the general strength criterion and energy theory. This study focuses on the energy dissipation problem during the cavity expansion process, dividing the soil mass around the cavity into an elastic region and a plastic region. Assuming compliance with the small deformation theory in the elastic region and the large deformation theory in the plastic region, combined with the general strength criterion of soil mass and energy theory, the energy dissipation solution for cavity expansion problem is derived. Firstly, from an energy perspective, the process of cavity expansion in soil mass is described as an energy conversion process. The energy dissipation mechanism is introduced into the traditional analysis of cavity expansion, and a general analytical solution for cavity expansion related to energy is derived. Subsequently, based on this general analytical solution of cavity expansion, the influence of different strength criterion, large-strain, expansion radius, cavity shape and characteristics of soil mass on the stress distribution, displacement field and energy evolution around the cavity is studied. Finally, the effectiveness and reliability of theoretical solution is verified by comparing the results of typical pressure-expansion curves with existing literature algorithms. The results indicate that different strength criterion have a relatively small impact on the displacement and strain field around the cavity, but a significant impact on the stress distribution and energy evolution around the cavity.

• Journal of Korean society of Dental Hygiene
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• v.6 no.4
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• pp.387-402
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• 2006

This research carried out a survey for 569 students in a junior college of jeollanamdo to provide a needful basic data in developing suitable health promotion program and creating a direction of the oral hygiene education process to intial adult population after holding the oral cavity health action and a affecting factors to it. A collected data obtained the following conclusion. According to school grade, a difference of action factor is Chi-square and Pearson's correlation coeficient in actionfactor and acknowledgement-perception factor and a step-by-step recurrence analysis processed a related factor of the oral health action. 1. A related action factor of the oral health appeared meaningful difference of the oral cavity medical examination, the oral cavity clean device use or not, dental surgery prevention cure or not among the third grade who had the most experience of the oral hygiene education within one year recently. 2. A significant of the oral cavity health acknowledged and perceived and a concern of the oral cavity health, acknowledged the oral cavity health state distribution are the highest in the third grade. 3. According to monthly income, a large income is higher than a small income about self-effects in a relation between the oral cavity health action and acknowledgement-perception factor. the average of a large income is 30.59(${\pm}5.79$). The obstacle of the oral cavity health action is 12.51(${\pm}3.19$). a large income is highest. according to school career, under middle school layer obtained the highest average 16.33(${\pm}3.53$). according to a school year, acknowledge-perception factor of the oral cavity health control of the third grade is the highest(38.81(${\pm}6.25$). 4. In mutual relation between acknowledge-perception factor and the oral cavity health action, a variable constants of meaningful mutual relation are the oral cavity health perception, self-effects, the oral cavity health action obstacle, the oral cavity health action benefit, the oral health action control, aggressive. and they are self-effects, the oral cavity health action in the oral cavity health perception. A significant of the oral cavity health and the oral cavity health action obstacle are the oral cavity health action benefit and the oral cavity health action control. 5. The affecting factors to the oral health action are self-effects, action factor, acknowledged the oral health control.

• Journal of the Society of Disaster Information
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• v.18 no.1
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• pp.218-227
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• 2022

Purpose: In the case of cavity discovered by ground penetrating radar exploration, it is necessary to accurately predict the filling amount in the cavity in advance, fill the cavity sufficiently and exert strength to ensure stability and prevent ground subsidence. Method: The cavity waveform analysis method by GPR exploration and the method using the cavity shape imaging equipment were performed to measure the cavity shape with irregular size and shape of the actual cavity, and the amount of cavity filling of the injection material was calculated during rapid restoration. Result: The expected filling amount was presented by analyzing the correlation between the cavity size and the filling amount of injection material according to the cavity scale and soil depth through the method by GPR exploration and the cavity scale calculation using the cavity shaping equipment. Conclusion: The cavity scale measured by the cavity imaging equipment was found to be in the range of 20% to 40% of the cavity scale by GPR exploration. In addition, the filling amount of injection material compared to the cavity scale predicted by GPR exploration was in the range of about 60% to 140%, and the filling amount of the injection material compared to the cavity size by the cavity shaping equipment was confirmed to be about 260% to 320 Purpose: The purpose of this study is to examine the types of crimes taking place in the metaverse, and to establish a crime prevention strategy and find a legal deterrent against it. Method: In order to classify crime types in the metaverse, crime types were analyzed based on the results of previous studies and current incidents. Result: Most of the crimes taking place in the metaverse are done in games such as Roblox or Zeppetto. Most of the game users were teenagers. Looking at the types, there are many teens for sexual crimes, violent crimes, and defamation, but professional criminals are often included in copyright infringement, money laundering using virtual currency, and fraud. Conclusion: Since the types of crimes in the metaverse are diverse, various institutional supplementary mechanisms such as establishment of police crime prevention strategies, legal regulations, and law revisions will have to be prepared.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.55-64
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• 2018

The purpose of this study is to evaluate the suitability of emergency underground cavity restoration method filling cavity with expansive material based on numerical analysis. For the numerical analysis, experiments were conducted to evaluate properties of expansive material. Based on the measured expansion pressure of the expansive material from the experiment, behavior of underground cavity restoration with various cavity dimensions (variation of height and width of rectangular-shape cavity) was numerically assessed. As a result of analysis, the vertical displacements of the top and bottom of cavity were significantly influenced by the cavity width and lateral displacements of cavity sides were highly dependent on cavity height. These vertical and lateral displacements were increased with increasing expansion pressure of expansive material. Also, when the expansion pressure was applied, the vertical displacement of the upper surface layer of the road was less dependent on cavity height, and was greatly influenced by cavity width.