• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.6
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• pp.290-302
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• 2022

In this study, it was examined for the reduction of wave overtopping and water level fluctuation in front of the revetment when applying a reinforcement method to revetment where wave overtopping occurs. As a result of the study, in the case of the cross-sectional experiment. more than 70% of the wave overtopping reduction effect depending on the reinforcement conditions was occurred, and it was analyzed that the result increases by about four times or more in the comparison with the 3d test. The average water level in front of the revetment was lowered when a low crest structure was not installed. and there was a tendency to rise under the condition of low crest structures installed. In the comparison with the wave basin test, there was a difference of about 0.5 to 0.6 times when a low crest structure was not installed, and it was increased by 5.5 times after low crest structures were installed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4B
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• pp.365-376
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• 2009

The importance of resonable treatment of tide characteristics has been shown by Kweon, et al. (2005, 2006) for the crest elevation estimation because of a big difference of tidal elevation along Korean coast. For the procedure of crest elevation design, the expected overtopping probability (EOP) was estimated by Kweon, et al. (2006). The comparisons on each sea showed that EOP was lower east, south and west sea in order. The results involved the assumption that the tide and design level wave height meet any time in a year. However, big waves mainly occur in summer or winter in Korean coast, the study focuses on the encounter probability of big waves and seasonal tide level. A theory of the encounter probability is not derived by the present study but it shows reasonable acceptability of the proposed scenario in which the expected overtopping probability could be an index for the crest elevation estimation in Korean coast. The calculation based on the scenario gives the possibility range for the crest elevation estimation which has no tendency of each sea along Korean peninsular. The range is within the expected overtopping probability of 1% in the whole coast of Korea.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.517.2-517.2
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• 2006

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.36 no.5
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• pp.380-385
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• 2010

Introduction: The iliac crest has been the accepted place to obtain bone for reconstruction in oral and maxillofacial surgery. The iliac crest has many advantages because of its accessibility, large amount of cancellous bone, relative ease of bone harvest, possibility of two team approach and ability to close the wound primarily. This study evaluated retrospectively the morbidity of bone harvesting from the anterior iliac crest to provide a logical guide for recognizing the complications and morbidities of an iliac crest bone graft. Materials and Methods: Fifty healthy patients (mean age of 35.5 years; range 7 to 59) underwent iliac crest bone harvesting for a maxillofacial reconstruction from January 2007 to September 2009 at the Department of Oral and Maxillofacial Surgery in Kyungpook National University Hospital. Age, sex, size and kind of grafted bone, duration of pain on donor site, duration of gait disturbance, sensory deficit, scar, contour defect were measured in each patients by retrospective research. Results: The mean duration of pain is 6.7 days, and mean duration of gait disturbance is 7.2 days. Most patients were free from gait disturbances and pain within 2 weeks and there was no correlation between the size of the harvesting block bone and the duration of gait disturbance or pain. However, this study showed that the duration of pain is associated with gait disturbance. In addition, most patients had no complaints regarding their surgical scar and contour defect, and only one patient had permanent impairment of the sensory function. Moreover, an iliac bone graft did not extend the length of hospitalization. Conclusion: This study suggests that split thickness bone harvesting from the inner table of the anterior iliac crest is a well accepted procedure with relatively low morbidity.

• Journal of Korea Water Resources Association
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• v.42 no.9
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• pp.715-724
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• 2009

In case of inclined crest groyne, flow constriction with water is different. Therefore, it is proper to apply to narrow channel or there is a risk of overflow with water level rising caused by installation of groynes. This study were conducted experiments on inclined crest groyne. Main factors of inclined crest groyne are angles of crests slope and changes of water level. Velocity profile around groyne was measured by LSPIV (Large Scale Particle Image Velocimetry). Flow fields around groyne were analyzed focused on main channel and recirculation area. From the results, Thalweg change has little an effect on rate length and height of recirculation rises on increasing rate length. Length of recirculation area was about 12$\sim$16 times of rate length of groyne. Maximum velocity in main channel area was measured about 1.45$\sim$2.1 times of approach velocity and has little an effect on crest angle of groyne. Back water velocity recirculation area was decreased on approach velocity. This result presents to make stable flow to bank protection.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.139-148
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• 2000

A numerical model is represented to calculate the wave fields such as the reflected waves, the transmitted waves, and depth averaged velocities over submerged breakwaters for the normally incident wave trains of nonlinear monochromatic wave. The numerical model is correctly formulated by using both the finite amplitude shallow water equations with the effects of bottom friction and the explicit dissipative Lax-Wendroff finite difference scheme, also satisfactorily verified by comparison with the other results. The behaviors of reflected and transmitted waves with respect to geometric parameters of submerged breakwater such as the slope, crest depth, and crest width are numerically analyzed in this study. In particular, the reflection and transmission coefficients are quantitatively calculated as the function of geometric parameter of submerged breakwater. It is found that the crest depth among parameters related to practical design may be the most important parameter in designing the submerged breakwater. Therefore, the effective and economic performances of submerged breakwater should be depended on the determination of optimal crest depth.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.1
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• pp.71-79
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• 2014

In this study, an experiment with large-scale model was performed according to raising the embankment in order to investigate the behavior of failure for embankment and spillway transitional zone due to overtopping. The pore water pressure, earth pressure, settlement and failure pattern by a rapid drawdown and overtopping were compared and analyzed. The pore water pressure and earth pressure at spillway transitional zone by overtopping increased a rapidly with the expansion of seepage erosion, but the crest showed a smally change due to effect of the inclined core type. And it is considered an useful data that can accurately estimate the possibility of failure of the reservoirs. A settlement at overtopping decreased a rapidly due to failure of crest. The relative settlement difference due to change of the water level at the upstream and downstream slope cause increase largely crack of crest. The behavior of failure by overtopping was gradually enlarged towards reservoirs crest from the bottom of the spillway transition zone, the inclined core after the raising the embankment was influenced significantly to prevent the seepage erosion.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1438-1445
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• 2008

The purpose of this study is to evaluate the fundamental frequency of the dam by the various methods using real microearthquake records which were measured on 'H' dam site and to compare each results. In this study, the fundamental frequency was evaluated by the frequency analysis of the microearthquake records which were measured on the dam crest, by the evaluation of acceleration amplification ratio between the foundation and the crest of dam, and by the evaluation of acceleration response spectrum ratio between the foundation and the crest of dam, respectively. Among these methods, it was found that the method by the evaluation of acceleration response spectrum ratio between the foundation and the crest of dam was the most effective method. But, if the simple engineering judgement can be considered, it was thought that the all three methods could reasonably evaluate the fundamental frequency of the dam.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.312-315
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• 2002

This paper summarizes the results of a numerical study conducted to analyze the effect of selected process parameters on material flow and thread profile in thread rolling of large diameter blanks. Based on the previous work where a plane strain mode was found to provide a reasonable approximation of the thread rolling process, the effect of varying thread form, friction factor, flow stress, and blank diameter on effective strain and thread height was analyzed using the finite element code DEFORM. This study show that effective strain for flank angle, that blank diameter had important effect on the as-rolled thread while flow stress, friction factor, and crest round of dies had significant impact on effective strain at the thread root and crest and load of thread rolling. While the rate of strain harding was found to have an effect on the crest profile, the results indicate that it is the primary factor responsible for seam formation in rolled threads.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.29 no.1
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• pp.191-201
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• 1999

Purpose: To know whether there would be a difference among spiral tomograms of different slice thicknesses in the measurement of distances which are used for dental implant planning. Materials and Methods: 10 dry mandibules and 40 metal balls were used to take total 120 Scanorailll tomograms with the slice thickness of 2 mm, 4 mm and 8 mm. 3 oral radiologists interpreted each tomogram to measure the distances from the mandibular canal to the alveoalr crest and buccal. lingual and inferior borders of mandible. 3 observers recorded grades of 0, 1 or 2 to evaluate the perceptibility of alveolar crest and the superior border of mandibular canal. ANOVA with repeated measure. Chi-square tests and intrac!ass correlation coefficient(R₂, α) were used For statistical analysis. Results: There was not a statistically significant difference among spiral tomograms with different slice thicknesses in the measurement of the distances and in the perceptibility of alveolar crest and mandibular canal(p>0.05). All of them showed a good relationship in the reliability analysis. The perceptibility of alveolar crest and mandibular canal was almost similar and an excellent relationship was seen on all of them. Conclusions: There would be no significant difference. no matter which spiral tomogram of any slice thickness may be used in dental implant planning. considering the thickness of dental implant fixture.