• Journal of the Korean Geotechnical Society
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• v.37 no.3
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• pp.5-17
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• 2021

This study aims to investigate the causes and countermeasures for the occurrence of tension cracks in the slope of the rock mass of heavy equipment for road construction. Electric resistivity survey was performed to investigate the expandable tensile crack range. As a result of examining the distribution of soft zones in the rock mass, a low specific resistance zone was found at the bottom of the access road where tensile cracks occurred. It was confirmed that a low resistivity zone was distributed near the top of the excavation slope. Therefore, reinforcements was performed by determining the location of the possible tensile crack as the top of the excavation slope. Two rows of reinforced piles and anchors were proposed as a reinforcement method, and the slope stability analysis showed that the allowable safety factor was satisfied after reinforcements.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.5
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• pp.477-484
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• 1997

Intracellular recordings of oscillatory firing (bursting activity) were obtained from Purkinje cells (PCs) in rat cerebellar slices. Apamin inhibited post-burst hyperpolarizations (PBHs) progressively and finally terminated oscillatory firing activity of PCs. Apamin did not affect the amplitude or duration of the after-hyperpolarization (AHP) between spikes within the burst. In the voltage clamp mode, apamin shifted the whole-cell, quasi-steady state I/V relationship in an inward direction and abolished the zero slope resistance (ZSR) region by blocking outward current. Nickel ($Ni^{2+}$) terminated oscillatory activity and also abolished the ZSR region. However, $Ni^{2+}$ did not have progressive blocking action on the post-burst hyperpolarization before it blocked oscillatory activity. $Ni^{2+}$ blocked an inward current at potentials positive to approximately -65 mV, which was responsible for the ZSR region and outward current at more negative potentials. These data indicated that oscillatory activity of PCs is sustained by a balance between a slow $Ni^{2+}$-sensitive inward current and an apamin-sensitive outward current in the region of ZSR of the whole-cell I/V curve.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.904-909
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• 2004

The study area adjoins with Yangsan fault in Sangbuk-myeon, Samsam-ri, Kyongsang-namdo and consist of the natural steep slope. After drawing data layer which have altitude by using digital topography data, it is converted to lattice DEM of $10m{\times}10m$ size. From this, gradient map of unit lattice, slant direction map and shadow relif map are made. Using flow apportioning algorithm, upper slope contributing area and wetness index by established lattice can be calculated. Area that have high wetness index shows lineament structure of northwest-southeast direction, and this agrees with shear fracture system. The result of electricity specific resistance survey in the study area shows that area of high wetness index has low electricity specific resistance anomaly. That is, wetness index conforms with distribution of fractured zone that accompanied chemical weathering of rock. Therefore, wetness index can be used as the method of detecting fractured zones and judging the stability of the area.

• Korean Journal of Materials Research
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• v.21 no.9
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• pp.477-481
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• 2011

Composites of insulating polyethylene and carbon black are widely used in switching elements, conductive paint, and other applications due to the large gap of resistance value. This research addresses the critical exponent of dielectric breakdown strength of polymer matrix composites (PMC) made with carbon black and polyethylene below the percolation threshold (Pt) for the first time. Here, Pt means the volume fraction of carbon black of which the resistance of the PMC is transferred from its sharp decrease to gradual decrease in accordance with the increase of carbon-black-filled content. First, the Pt is determined based on the critical exponents of resistivity and relative permittivity. Although huge cohesive bodies of carbon black are formed in case of being less than the Pt, a percolation path connecting the conducting phases is not formed. The dielectric breakdown strength (Dbs) of the PMC below Pt is measured by using an impulse voltage in the range from 10 kV to 40 kV to avoid the effect of joule heating. Although the observed Dbs data seems to be well fitted to a straight line with a slope of 0.9 on a double logarithm of (Pt-$V_{CB}$) and Dbs, the least squares method gives a slope of 0.97 for the PMC. It has been found that finite carbon-black clusters play an important role in dielectric breakdown.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.455-465
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• 2008

In this study, the load distribution and deformation of rock-socketed drilled shafts subjected to axial load are investigated based on small scale model tests. In order to analyze the effects of major influencing factors of end bearing capacity, Hoek-cell triaxial tests were performed. From the test results, it was found that the initial slope of end bearing load transfer (q-w) curve was highly dependent on rock mass modulus and pile diameter, while the ultimate unit toe resistance ($q_{max}$) was influenced by rock mass modulus and the spacing of discontinuities. End bearing load transfer function of drilled shafts socketed in rock was proposed based on the Hoek-cell triaxial test results and the field loading tests which were performed on granite and gneiss in South Korea. Through the comparison with pile load tests, it is found that the load-transfer curve by the present study is in good agreement with the general trend observed by field loading tests, and thus represents a significant improvement in the prediction of load transfer of drilled shaft.

• Bulletin of the Society of Naval Architects of Korea
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• v.6 no.1
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• pp.25-34
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• 1969

From viewpoints of over-all ship economy the straight framed V-bottom hull forms with chines are considered to be attractive even for usual commercial vessels, because increments of resistance over that of round hull forms, if any, can be well compensated with reduction in construction cost.[1] To investigate the influences of both prismatic coefficient and chine elevation on resistance performance, three models of straight-framed V-bottom hull forms which are similar to Prof. C. Ridgely-Nevitt's W-18, W-8, and W-20[2],[3] in size and hull form coefficients were tested at the SNU Ship Model Towing Tank for resistance measurements. They are of Cp=0.60, 0.65 and 0.70 and of ${\Delta}/(0.01L)^3=300$. Influence of variation of chine elevation on resistance performance were observed with the test results obtained at normal condition, and at the trimed by the stern by 2% and 4% of $L_{bp}$ at normal condition under same displacement. The hull form characteristics are shown in Table 1, and in Fig. 1, 2, 3, 4 and 5. The test results are shown in Fig 8, 9 and 10 in the form of Cr vs. $V/\sqrt{L}$ curves taking Cp as a parameter for normal condition, trim by the stern in 2% and 4% $L_{bp}$ at normal condition , respectively. Cr vs. $V/\sqrt{L}$ curves taking trim condition as a parameter are also shown in Fig 11, 12 and 13 for Cp=0.60 and 0.70, respectively. The best and the worst trim condition at given $V/\sqrt{L}$ in viewpoint of Cr are plotted for each Cp-value as shown in Fig 14, 15 and 16. From the above results the following conclusions are derived: (1) In general, the resistance performance of the straight-framed V-bottom hull forms are not inferior to those of round hull forms. At a certain range of $V/\sqrt{L}$ the former gives less resistance than the latter. (2) Regarding influences of Cp on Cr, it is observed that, at $V/\sqrt{L}$ less than about 0.925, the greater Cp-value gives the more increment of Cr, and that, at $V/\sqrt{L}$ greater than about 0.925 the smaller Cp-value gives the more increment of Cr. It is also noteworthy that the model of Cp=0.70 has remarkable hump on Cr vs. $V/\sqrt{L}$ curve between $V/\sqrt{L}=0.80$ and 0.90. (3) For higher speed within the test range, the chine elevation having the steeper slope around bow and the easier slope around amidship and stern, refered to watering, give the better results in resistance performance. (4) Assuming the chine elevations adopted for the tested models were not of the best, we would expect further improvement of resistance performance for such form. Hence, a systematic study on chine elevation is very disirable to prepare design data of general purpose for the such hull forms.

• International Journal of Highway Engineering
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• v.6 no.3 s.21
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• pp.37-46
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• 2004

This study was performed to establish valid methodology for determining dynamic stability(DS) of deformation-cycle curve which is obtained through wheel tracking(WT) test, the most widely used method for forecast of rutting tendency of asphalt mixture. Existing Korean and Japanese methods for DS are unrealistic and do not really reflect characteristics of rut resistance of asphalt concretes especially when the slope of deformation-cycle curve is stabilized at the end. It was proved that the new DS developed in this study reflected rut resistance characteristics better than existing methods. It is especially effective to distinguish the mixtures with high DR(depth of rut) but stable slope at the end of curve from the mixture with lower DR and continuous slope. The field evaluation must be followed to prove whether the mixture which shows a high DS value this method perform well in the filed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.41-51
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• 2008

The load distribution and deformation of single piles which is embedded in Jumunjin sand and Kimhae clay are investigated, based on small scale model tests. Special attention is given to the consideration of flexural rigidity in laterally loaded piles. To consider the flexural rigidity of the pile, tests are performed with the aluminium piles of three different length under different relative densities and undrained shear strength. The test results indicate that the initial slope from the results of tests is proportional to the depth and pile-soil rigidity in both soils. But the increasing rate of the initial slope in the clay is less than in the sand. In addition, the soil resistance is more related to the depth and soil condition than the pile rigidity. Base on the test results, an empirical formula is proposed, which is good agreement with previously published small scale model test and field lateral load test.

• Journal of the Korean Geosynthetics Society
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• v.13 no.3
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• pp.21-30
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• 2014

In this study, the applicability of the lightweight dynamic cone penetrometer in the domestic slope site was investigated using the weathered granite soil sampled form the Namwon slope site. And then, the lightweight dynamic cone penetration tests according to the change in the degree of compaction and water content were performed and it was analyzed with the correlations between the degree of compaction, the void ratio, the degree of saturation and the value of cone resistance. From the laboratory test results, the cone penetration resistance was rapidly increased in the dry side of the optimum moisture content, and it was largely decreased in the wet side of the optimum moisture content. Moreover, when the degree of compaction and the degree of saturation are large, the cone resistance is increased linearly. And a high correlativity was shown between water content, void ratio, the degree of saturation and the cone resistance. From these results, it is judged that the lightweight dynamic cone penetrometer can be applied to the investigation on the site slope.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.141-146
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• 2003

This paper calculates the elapsed time to go down a straight as a function of the corner exit speed and considers air resistance, rolling resistance, and slope resistance to figure out the force for forward acceleration. In a car racing, the most critical comer in a course is the one before the longest straight. A driver can lose a quite amount of time by taking a bad line in a corner. Taking a bad line also causes poor comer exit speed which in turn costs more elapsed time to go down a straight. The results are not so dramatic as in the case of cornering but are showing why one should take the correct corner racing line to get the maximum exit speed. Also, for the case of drag race, the elapsed time to go 1/4 mile is calculated.