• Journal of the Korean Society for Precision Engineering
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• v.12 no.7
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• pp.178-188
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• 1995

A study on the temperature distribution of tungsten carbide alloy steel(WC-Co) in surface grinding was conducted to improve the surface finish and to find optimum grinding conditions which would lead to efficient grinding operation by theoretical finite element method analysis and experimental test of workpiece under various conditions. Based on the comparixion of test results and FEM analysis data, it is concluded that the FEM computer simulation of heat transfer is useful in predicting the temperature distribution of test material that the increase of temperature is more infuleneced by the grinding depth than the grinding speed. And that the grinding energy flux of dey grinding is 4 to 6 time greater than wet grinding regardless of grinding speed and finally that the heat transfer does not take place in depth deeper than 3mm from the grinding surface.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.677-686
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• 2004

This study deals with literature review, developing a predicting equation for the ultimate stress of internal and external prestressing steel, and an experimental test with the parameters affecting the ultimate stress of prestressing steel in prestressed concrete beams strengthened by external prestressing tendons. The proposed predicting equation takes rationally the effect of internal and external prestressing steels into consideration as a function of prestressing steel depth to neutral depth ratio. In the experimental study, prestressed concrete beams strengthened using external steel tendons are tested with the test parameters having a large effect on the ultimate stress of internal and external prestressing steel. The test parameters include internal and external prestressing steel reinforcement ratio and span to depth ratio. The test results are analyzed to confirm the rationality and applicability of the proposed equation for predicting the ultimate stress of internal and external prestressing steel. This research shows that the results obtained by the proposed equation for predicting the ultimate stress agreed very well with the test results.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.173-180
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• 2001

This research is aimed at investigating the dynamic response of cut-and-cover tunnel to seismic waves. We carried out shaking table test which is used a 1/40-scale(the width of prototype tunnel is about 14.2m, the height is about 8.5m) model for this research, and we analyzed the effect of depth of tunnel and slope of the ground in relation to the dynamic responses of tunnel. As a result of the test, the stress and acceleration along the tunnel decreased accordingly to the depth of increment, and this phenomenon is caused by the increase of the confining effect of ground. Also, the dynamic responses of tunnel showed a tendency to rise according as ground declined gently. In comparison the result of shaking table test with that of structural analysis on ordinary condition, we conclude that seismic waves do not affect cut-and-cover tunnel when the depth of tunnel is over the diameter of tunnel.

• Journal of Ocean Engineering and Technology
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• v.19 no.2 s.63
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• pp.67-73
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• 2005

This paper describes depth, heading and speed control of an underwater vehicle that has four stern thrusters of which forces are coupled in the diving and, steering motion, as well as the speed of the vehicle. The optimal linear quadratic controller is designed based on a linearized- state space model, developed by combining the dynamic equations of speed, steering and diving motion. The designed controller gives provides an optimal thrust distribution, minimizing the given performance index to control speed, depth and heading simultaneously. To validate the performance of the controller, a simulation and tank-test are carried out with DUSAUV (Dual Use Semi-Autonomous Underwater Vehicle), developed by KORDI as a test-bed for testing new underwater technologies. Optimal gains of the controller are tuned, using a computer simulation environment with a nonlinear 6-DOF numerical DUSAUV model, developed by PMM (Planner Motion Mechanism) test. To verify the performance of the presented controller in experiment, a tank-test with DUSAUV is carried out in the ocean engineering basin in KORDI. The experimental results are also compared with the simulation results to investigate the accordance of the numerical and the real mode.

• Journal of Periodontal and Implant Science
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• v.28 no.1
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• pp.57-70
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• 1998

The purpose of this study was to evaluate the clinical and microbiological effects of metronidazole 25% dental gel that was applied to periodontal pockets who have moderate to advanced chronic adult periodontitis were selected for this study. The quadrants that had 2 or 3teeth with 5-8mm probing pocket depth were selected and divided into test side and control side according to the split-mouth design. The metronidazole 25% dental gel applied on test side and 0.12% chlorhexidine solution applicated on positive control side, normal saline irrigation into periodontal pocket was applicated to negative control side respectively. Above procedures followed scaling and root planing at baseline(0week). The subgingival sterile saline irrigation and chlorhexidine irrigation were done for about 30 seconds respectively. The metronidazole 25% dental gel was applied to periodontal pocket at 0,1 week in the test side. The clinical and microbiological analysis carried out at baseline(0week) and 4,8 weeks. The results of this study were as follows; 1. The sulcular bleeding index, probing pocket depth were significantly reduced in the test group. The relative proportions of spirochetes and motile rods were significantly reduced to negative control group and the proportion of cocci was correspondingly increased in the test group. 2. The sulcular bleeding index, probing pocket depth were significantly reduced in metronidazole group. and, there was a significant differences between 2 groups. Also, the relative proportions of spirochetes and motile rods were reduced in both group. And, there was a significant differences between 2 groups. In conclusion, application of metronidazole 25% dental gel as an adjunct to mechanical debridement of root surfaces may improved the clinical and microbiological status of periodontal disease sites.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.4
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• pp.184-192
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• 2016

A profiling monitoring system has been developed to monitor the water quality variations according to each water depth and applied for a test-bed. The key parameters were derived to disclose the aquatic ecology and environment of river systems, and the real-time monitoring techniques to profile the variations of each parameter were verified. Monitoring parameters were configured to include water quality, hydrodynamic, and weather conditions. Considering the water depth of the 4 major rivers in Korea, a profiling monitoring system with 1.0 m water depth interval for each monitoring has been established. To understand the real-time variation properties in the Han river, the monitoring system has been installed and operated at the YangHwa-Dock as a test-bed. Based on the results of the detailed analyses on the spring season, as the characteristic diurnal and water-depth-related variations for water temperature, pH, dissolved oxygen (DO), and chlorophyll-a were observed, it could be concluded that the real-time water-depth profiling monitoring system is a very effective tool for the proper management of river environment.

• Journal of The Korean Association For Science Education
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• v.26 no.7
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• pp.790-797
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• 2006

The purpose of this study was to examine the effects of the level-differentiated laboratory activities suggested by the 7th national curricula compared to the in-depth level activities only and supplementary level activities only. Two hundred 7th grade students attending a coed middle school were selected for this study and divided into three groups; level-differentiated, in-depth, and supplementary group. In each group, the students were subdivided into the in-depth level and the supplementary level by the formative test after completing the basic learning course. The in-depth and the supplementary laboratory activities were developed and engaged to the respective students in the level-differentiated group for one semester, while only the in-depth activities were engaged to the in-depth group and only the supplementary activities were engaged to the supplementary group. To examine the effects of treatments, the science knowledge test and the inquiry process skill test were administered before and after treatments and the students' opinions about the level-differentiated instruction were surveyed. The results showed that there were significant differences in the science knowledge achievements between the groups while no significant difference was found in the inquiry process skills. Post hoc analysis showed these differences were found between the level-differentiated group and the supplementary group. After the activities, most students in the level-differentiated group responded positively on doing level-differentiated activities except a few students in the supplementary level, These results justify the effectiveness of the level-differentiated laboratory activities compared to the supplementary only laboratory activities in middle school science classes.

• Journal of Broadcast Engineering
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• v.17 no.2
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• pp.363-373
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• 2012

This paper proposes a method to generate a depth image at an arbitrary intermediate view-point, which is targeting a video service for free-view, auto-stereoscopy, holography, etc. It assumes that the leftmost and the rightmost depth images are given and they both have been camera-calibrated and image-rectified. This method calculates and uses a disparity increment per depth value. In this paper, it is obtained by stereo matching for the given two depth image by considering more general cases. The disparity increment is used to find the location in the intermediate view-point depth image (IVPD) for each depth in the given images. Thus, this paper finds two IVPDs, from left image and from right image. Noises are removed and holes are filled in each IVPDs and the two results are combined to get the final IVPD. The proposed method was implemented and applied to several test sequences. The results revealed that the quality of the generated IVPD corresponds to 33.84dB of PSNR in average and it takes about 1 second to generate a HD IVPD. We evaluate that this image quality is quite good by considering the low correspondency among the left images, intermediate images, and the right images in the test sequences. If the execution speed is improved, the proposed method can be a very useful method to generate an IVPD at an arbitrary view-point, we believe.

• The Journal of Engineering Geology
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• v.22 no.2
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• pp.233-241
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• 2012

The objectives of this study were to test geothermal conductivity (k), water velocity, water quantity, and pipe pressure from a ground heat exchanger in the field, and then to analyze these data in relation to the effectiveness and economical efficiency for application of geothermal energy. After installation of the apparatus required for field tests, geothermal conductivity values were obtained from three different cases (second, third, and fourth). The k values of the second case (506 m depth) and third case (151 m depth) are approximately 2.9 and 2.8, respectively. The k value of the fourth case (506 m depth, double pipe) is 2.5, which is similar to the second and third cases. This result indicates that hole depth is a critical factor for geothermal applications. Analysis of the field data (k, water velocity, water quantity, and pipe pressure) reveals that a single geothermal system at 506 m depth is more economically efficient than three geothermal systems at depths intervals of 151 m. Although it is more expensive to install a geothermal system at 506 m depth than at 151 m depth, test results showed that the geothermal system of the fourth case (506 m, double pipe) is more economically efficient than the system at 151 m depth. Considering the optional cost of maintenance, which is a non-operational expense, the geothermal system of the fourth case is economically efficient. Large cities and areas with high land prices should make greater use of geothermal energy.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.4
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• pp.476-492
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• 2003

Purpose : The purpose of this study was to compare HEMA and TEGDMA as diluents for the composite resin. Material and methods : Eight kinds of experimental light curable composite resins were prepared and used. Concentrations of monomer and filler were same for all experimental composites, except, the diluent's ratios to the monomer. The ratio of diluents to Bis-GMA were 15%, 20%, 25%, and 30%, and two kinds of diluents were used, so total experimental groups were eight including one control group of 25% TEGDMA. Results : Depth of cure, flexural strength, shear bond strength to bovine enamel, shear bond strength to bovine dentin, water absorption and solubility of composites in water were measured. Sample size for each groups were 10. Arithmetic means were used as each groups representative values, and regression test for two diluents and low concentrations, Duncan's multiple range test, and Two-way ANOVA test were done for kinds of diluents and its concentrations at level of 0.05. Conclusion : Following results were obtained ; 1. There were not significant differences in effects of HEMA and TEGDMA to depth of cure, flexural strength of composites and shear bond strength to bovine enamel (p>0.05). 2. Increase of the concentrations of the diluents made the depth of cure (p<0.001) and flexural strength (p<0.05) a little higher. 3. Shear bond strength to dentin was higher on HEMA containing composites than TEGDMA containing composites (p<0.001). 4. Water absorption was higher on HEMA containing composites than TEGDMA containing composites (p<0.01).