• The Journal of Engineering Geology
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• v.3 no.1
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• pp.21-37
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• 1993

In order to investigate the correlation of sedimentary rock properties. specific gravity, porosity, water content, sonic wave velodty, and point4oad strength index of core samples of limestones, sandstones and shales were measured. The relationships between density and velocity show $V_p=16300d-38719.3,{\;}V_s1896.4d-29225.1$ of regression equation for sandstones and $Vp=4085d-10264.8,{\;}V_s=3519d-7841.3$ for shales and <$Vp=4085d^2-20747d+303,{\;}V_s=3899d^2-21442d+318$ for limestones. Seismic wave velocity of shales which have high density is lower than that of sandstones, and this seems to be an effect of bedding in shale. P-wave velocity and S-wave velocity of limestones, sandstones and shales show the linear relationships as a whole. The regression equations are respectively calculated V_s=0.26V_p+1041.6m/sec,{\;}V_s=0.43V_p+424.2m/sec,{\;}and{\;}Vs=0.51V_p+261.9m/sec$ and the correlation coefficients of the velocity show r= 0.86 in sandstones, r= 0.75 in limestones and r=0.86 in shales. According to the point4oad strength test for limestones, point4ord strength anisotropy was not so dear even though the specimens show generally the banded structure. Variations of dip angle of bedding whihin the range $30^{\circ}-60^{\circ}$ does not have much influence upon the diametral strength index and axial strength index. From the result of point load test, P-wave velocity increases with point4ord strength index but the regression equations are $V_p=98.5lI{s_d}+4082.1m/sec,{\;}V_p=106.41{s_a}+3954m/sec$ and their correlation coefficient is low.

• Journal of Korea Water Resources Association
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• v.43 no.2
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• pp.153-165
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• 2010

Large-Scale Particle Image Velocimetry (LSPIV) is an extension of particle image velocimetry (PIV) for measurement of flows spanning large areas in laboratory or field conditions. LSPIV is composed of six elements - seeding, illumination, recording, image transformation, image processing, postprocessing - based on PIV. Possible error elements at each step of Mobile LSPIV (MLSPIV), which is a mobile version of LSPIV, in field applications are identified and summarized the effect of the errors which were quantified in the previous studies. The total number of elemental errors is 27, and five error sources were evaluated previously, seven elemental errors are not effective to the current MLSPIV system. Among 15 elemental errors, four errors - sampling time, image resolution, tracer, and wind - are investigated through an experiment at a laboratory to figure out how those errors affect to velocity calculation. The analysis to figure out the effect of the number of images used for image processing on the velocity calculation error shows that if over 50 images or more are used, the error due to it goes below 1 %. The effect of the image resolution on velocity calculation was investigated through various image resolution using digital camera. Low resolution image set made 3 % of velocity calculation error comparing with high resolution image set as a reference. For the effect of tracers and wind, the wind effect on tracer is decreasing remarkably with increasing the flume bulk velocity. To minimize the velocity evaluation error due to wind, tracers with high specific gravity is favorable.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.155-162
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• 2012

The Thomsen-Haskell method was used to determine sensitivities of the Rayleigh-wave phase velocities and spectral amplitude of vertical ground motion to insertion of a single velocity-anomaly layer into overburden underlain by a basement. The reference model comprised a 9-m thick overburden with shear-wave velocity (${\nu}_s$ of 300 m/s above a half-space with ${\nu}_s$ = 1000 m/s. The inserted layer, with a velocity of 150, 225, 375, or 450 m/s and a thickness of 1, 2, or 3 m, was placed at depths increasing from the surface in increments of 1 m. Phase velocities were computed for frequencies of 4 to 30 Hz. For inserted layer models, we placed an anomalous layer with thickness of 1 ~ 3 m, shear-wave velocity of 150 ~ 450 m/s, and at depths of 0 ~ 8 m in the overburden. The frequency range of 8 ~ 20 Hz were the most sensitive to the difference of $C_R$ between the inserted and reference models (${\Delta}C_R$) for h = 1 m and the frequency range got wide as h increased. For all of the models, the spectral amplitudes of the fundamental mode exceeded those of the $1^{st}$-higher mode except at frequencies just above the low-frequency cutoff of the $1^{st}$-higher mode.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.4
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• pp.422-429
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• 2018

To make students recognize the danger of fire smoke that may occur in ships and to improve the response capability, spaces for safety educ ation were built inside the training ship, and scenarios were developed. This study is an analysis of the movement characteristics of the students acquire d under each scenario. Followings are the summary of the analysis results. In the non-smoke environments, there was no difference in the velocity of escape movement between the case of without block on the familiar route and the case of with unexpected block. However, when the indoor was filled with smoke, the visibility became very low because of the smoke density and the average velocity was 62.5 % slower than the case where it was not. Regardless of the scenarios, the average equivalent velocity on the complex path was faster than the simple straight path, and the standard deviation was smaller. Under the smoke-fullfilled environment, although the relative velocity probability distributions of the complex passage and the entire passag e are very similar, the inter-individual fluctuation of the relative velocity ratio of the complex passage to that of the entire passage was very large. On the other hand, equivalent velocity could be expressed by the logarithmic function of the visibility. Also, as the tension of the students increased, the equivalent velocities were accelerated on all scenarios.

• Journal of Veterinary Clinics
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• v.36 no.1
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• pp.62-67
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• 2019

This study was performed to apply the measurement of heart rate and velocity in training horses for assessing race performance. Additionally, we aimed to identify parameters that can be used to evaluate the training level and exercise capacity. Eleven healthy 2- to 6-year-old Thoroughbreds were trained by the standard training program and heart rate and velocity were measured by using heart monitoring system and GPS. Regression analysis in heart rate and velocity data was performed to calculate velocity parameters. The mean maximal heart rate in gallop was $214{\pm}11bpm$. The mean $V_{140}$, $V_{180}$, $V_{200}$ and $VHR_{max}$ were $13.8{\pm}4.3km/h$, $37.5{\pm}3.8km/h$, $49.3{\pm}4.3km/h$ and $57.4{\pm}7.1km/h$ respectively. The mean $V_{140}$ of high performance racehorses was significantly higher than that of low performance racehorses (P < 0.05). Moreover, analyzing the correlation between velocity parameters and racing ability-related categories showed that $V_{140}$ was positively correlated with rating (P < 0.05), $V_{180}$ and $VHR_{max}$ were positively correlated with prize money per race (P < 0.05). Also, $V_{140}$ was significantly correlated with G1F (P < 0.05). The results of this study have shown that the measurement of heart rate and velocity during training could be useful methods to assess fitness for races or performance potential. Especially, $V_{140}$ is a good parameter to evaluate a performance of racehorses in Korea.

• Journal of Aerospace System Engineering
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• v.13 no.2
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• pp.34-42
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• 2019

The existence of different thermodynamic properties results in various undesirable effects, such as thermal deformation and residual stress, in heat-welding processes. The solid-state junction, by using explosive or electromagnetic forces, i.e., high-velocity impact welding without employing heat is advantageous in joining materials with different thermodynamic properties. In the solid-state junction, the joining is performed within a short time, a high velocity and large deformations are accompanied by interfacial surfaces. The numerical analysis models play an important role in the understanding of the mechanism of high-velocity impact welding. However, in the analysis of high velocity and large deformations, the conventional Lagrangian method has low reliability due to the occurrence of entanglements. In this study, high-velocity impact welding between Cu and CP-Ti with different thermodynamic properties was performed using a un-gridded numerical method, SPH (Smoothed Particle Hydrodynamics), and interfacial morphology occurred. As a result of the analysis, the interfacial morphology was confirmed and the compared degree of shape (straight, vortex), period, length, and so on appeared differently depending on the relationship between the parameters (impact angle and speed).

• Journal of the Korean Geotechnical Society
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• v.24 no.10
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• pp.33-43
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• 2008

In this study, for the purpose of evaluating the shear wave velocity in core zone, cross-hole test, down-hole test, MASW (Multi-channel Analysis of Surface Wave), and seismic reflection survey were carried out on the crest of the existing 'Y' dam. The results of field tests were compared one another. Furthermore, the field test results were compared with the result by the Sawada's empirical recommendation method. The purpose of this study is to compare the results of four kinds of field tests for evaluation of shear wave velocity in core zone of existing dam, to verify applicability of the empirical method which was recommended by Sawada and Takahashi, and to recommend a reasonable method for evaluation of shear wave velocity which is needed to evaluate tile maximum shear modulus of core zone. From the results of four kinds of field tests such as cross-hole test, down-hole test, MASW, and seismic reflection survey, it was found that the shear wave velocity distributions were similar within 18 m in depth and the results obtained by MASW and seismic reflection survey were almost the same by 30 m in depth. For evaluation of shear wave velocity in core zone of the existing dam, in consideration that it is not easy to bore the hole ill the core zone of existing dam, surface surveys such as MASW and seismic reflection method are recommended as realistic methods. On condition that it is impossible to conduct the field test and it is preliminary investigation, it is recommended that Sawada's low bound empirical equation be used.

• Journal of Ecology and Environment
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• v.47 no.4
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• pp.200-210
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• 2023

Background: Cambaroides similis is an endangered candidate species living in the stream of South Korea. Freshwater crayfish is known to decline rapidly not only domestically, but also internationally. Its decline is projected to be further exacerbated due to climate change. Understanding physical characteristics of the habitat is crucial for the conservation of an organism. However, comprehensive data regarding the distribution and physical habitat characteristics of C. similis are currently unavailable in South Korea. Thus, the objective of this study was to ascertain preferred ranges for water depth, current velocity, and streambed substrate of C. similis using Weibull model. Results: In this study, C. similis was found at 59 sites across 12 regions in South Korea. Its optimal water depth preferences ranged from 11.9 cm to 30.1 cm. Its current velocity preferences ranged from 9.8 cm s^-1 to 29.1 cm s^-1. Its substrate preferences ranged from -5.1 𝜱_m to -2.5 𝜱_m. Median values of central tendency were determined as follows: water depth of 21.4 cm, current velocity of 21.2 cm s^-1, and substrate of -4.1 𝜱_m. Mean values of central tendency were determined as follows: water depth of 21.8 cm, current velocity of 22.0 cm s^-1, and substrate of -4.4 𝜱_m. Mode values of central tendency were determined as follows: water depth of 21.7 cm, current velocity of 20.1 cm s^-1, and substrate of -3.7 𝜱_m. Conclusions: Based on habitat suitability analysis, physical microhabitat characteristics of C. similis within a stream were identified as Run section with coarse particle substrate, low water depth, and slow current velocity. Due to high sensitivity of these habitats to environmental changes, prioritized selection and assessment of threats should be carried out as a primary step.

• Journal of Navigation and Port Research
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• v.31 no.3 s.119
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• pp.223-228
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• 2007

In recent trends of the enlargement and specialization, container ship, LNCG, PCC and passenger ship which have relatively large hull and superstructure above the water line, are already being operated in the world It is very important information for the safety operation of these vessels to estimate the ship's performance under the specific wind condition while berthing, unberthing or low-speed sailing. In this paper, the effect of wind force and moment acting on the training ship HANNARA is investigated by using the numerical calculations. The results of drift angle and counter rudder angle with the relative wind direction and force, the critical wind velocity with the ratio of wind velocity and ship's speed and maximum heeling angle with the wind velocity are shown The presented results can be applied directly to T/S HANNARA in berthing maneuver and avoiding typhoons, and utilized as an educational materials.

• Journal of Environmental Science International
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• v.22 no.2
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• pp.215-223
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• 2013

The objective of this study was to evaluate fish passage efficiency, based on fish-trap monitoring methodology, in the fishway of Seungchon Weir, which was constructed on the lower region of Yeongsan River in 2011. Seasonal patterns and diel variations of fish movements, fish fauna, and compositions in the fishway were analyzed in relation to the current velocity and location of the trap-setting in the fishway. For the analysis, we conducted seven times surveys in 2012 on the fishway and also conducted intensive monitoring of the fishway as 3 hrs interval for the diel variations of fish fauna and compositions in the fishway. According to the fish-trap monitoring methodology, the total number of fish species was 13 species, which was a 43.3% of the total. Most dominant fish used the fishway was Squalidus chankaensis tsuchigae and the relative abundance of the species used the fishway was 33.5% of the total. The season and time zone (in diel variation) observed most frequently in the fishway were July and 18:00-21:00 PM, respectively. The fish movements and use-rates of fishway varied depending on the locations of trap-setting; Fish biomass and the number of species were statistically (p < 0.05) greater in the most right or left-sided traps than in the mid-traps. Also, fish movements and use-rates of fishway were influenced by current velocity on the fishway; fish in the fishway preferred the low current velocity (mean 0.71 m/sec) than the high current velocity (mean 1.13 m/sec). Further long-term studies should be monitored for the efficiency evaluations of the fishway.