• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.89-94
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• 2020

The purpose of this study was to investigate the correlation between visual analogue scale(VAS) of the waist and Oswestry Disability Index(ODI) and the muscle strength of the waist for male field hockey athletes. The VAS and ODI were conducted by self-written evaluation, and muscle strength was measured by using DAVID. Pearson correlation was used for data analysis, and the statistical significance level was set to α = .05. The VAS of the waist of male field hockey athletes and the ODI were statistically significant. However, other VAS and the ODI did not correlate to the strength of the lower back. Therefore, there is a need to develop a new exercise program for the rather than strength training during the waist rehabilitation exercise. It is thought that these studies will serve as basic data useful for the development of treatment and exercise programs for athletes in the future.

• Magazine of the Korean Society of Agricultural Engineers
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• v.12 no.3
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• pp.2003-2012
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• 1970

In order to the influence of grain size distribution on compressive strength and coefficient of permeability, unconfined compression test and permeability test were performed for seventy samples that have various grain-size distributions. Its results are as follows: 1. Maximum unconfined compressive strength appears at the dry side of optimum moisture content. 2. Unconfined compressive strength is proportional to the increase of percent passing of No. 200 sieve. 3. Precent of deformation in failure increases in proportion to the increase of percent passing of No. 200 sieve, and modulus of No. 200 sieve, and modulus of deformation also increases in proportion to percent passing of No. 200 sieve. 4. Unconfined compressive strength increases in proportion to uniformity coefficient, liquid limit and plastic index, but it decreases gradually according to the increase of coefficient of grading and classification area. 5. Maximum dry density decreases according to the increase of void ratio. 6. Coefficient of permeability decreases according to the increase of percent passing of No. 200 sieve, and when percent of No. 200 sieve, and when percent passing of No. 200 enlarged more than 40%, it becomes less than $10^{-6}cm/sec$ which is the limit of coefficient of permeability of core material for earth dam proposed by Lee. 7. Coefficient of permeability increases according to the increase of coefficient of grading, classification area and index of Talbot formula r, but it was rather decrease by the increase of uniformity coefficient. 8. Coefficient of permeability seems to depend on the size and the shape of the flow path which is a series of void to be concerned by the size and the proprton of soil grain, even though void ratios are same.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.4
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• pp.63-71
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• 1989

Four series of reinforced concrete beams were tested to determine their shear cracking strengths and ultimate shear capacities. All beams were singly reinforced without shear reinforcement. The concrete strength was the prime variable which was varied from 247 to $708kg/cm^2$(8500 to 10000 psi). Within each series the shear span-to-depth ratio was varied from 2 to 5, while concrete strength was held constant. Test results indicate that the effect of concrete strength on shear capacities is varied as the shear span-to-depth ratio is changed. Furthermore, the current shear design provisions do not provide a consistency with respect to estimating shear capacities of reinforced concrete beams. By introducing the shear failure mode index, a new equation is proposed to predict ultimate shear strengths of reinforced concrete beams without web reinforcement.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.330-338
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• 2012

Though the uniaxial compressive strength (UCS) of rock material is one of the key properties for rockmass characterization purposes, core samples for the test cannot always be obtained from the field. Indirect tests such as the point load test (PLT) can be a useful alternative. In this study, correlation between the UCS and the point load strength index of limestone of Imgye area was analyzed, and the linear regression equation obtained from regression analysis of two variables was suggested. The results of this study were also compared with previous studies on limestone. It was suggested that conversion factors for the same rock type from diverse areas in Korea may have different values, and more data should be obtained to increase the accuracy of regression analysis.

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.602-606
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• 2014

In this study, we observed changes in the physical properties of norbornene dialkyl ester applied to a PVC. The PVC specimens were prepared by blending PVC, norbornene dialkyl ester and stabilizers. Then, the hardness, tensile strength, elongation, tearing strength, transmittancy, haze and yellowness index of these specimens were measured, and were compared with DOP. The hardness of compounds except dicyclohexyl-5-norbornene-2,3-dicarboxylate (DCHN) were an equal to or higher than that of DOP. The tearing strength and tensile characteristic of DCHN could not be analyzed due to its high hardness. Tensile properties such as the tensile strength and elongation were improved for six compounds except diisononyl-5-norbornene-2,3-dicarboxylate (DINN). All compounds measured showed better tearing strength and transmittancy than those of DOP. Also all norbornene derivatives except DDN showed good haze indices. The yellowness index of DON and DPN showed similar values as DOP.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.66.2-66.2
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• 2011

The unexpected rising flux of early-type galaxies at decreasing ultraviolet (UV) wavelengths is a long-standing mystery. One important observational constraint is the correlation between UV-optical colours and Mg2 line strengths found by Burstein et al. (1988). The simplest interpretation of this phenomenon is that the UV strength is related to the Mg line-strength. Under this assumption, we expect galaxies with larger Mg gradients to have larger UV colour gradients. By combining UV imaging from GALEX, optical imaging from MDM and SAURON integral-field spectroscopy, we investigate the spatially-resolved relationships between UV colours and stellar population properties of 34 early-type galaxies from the SAURON survey sample. We find that galaxies with old stellar populations show tight correlations between the FUV colours (FUV-V and FUV-NUV) and the Mg b index, $H{\beta}$ index and metallicity [Z/H]. We have also derived logarithmic internal radial colour, measured line strength and derived stellar population gradients for each galaxy and again found a strong dependence of the FUV-V and FUV-NUV colour gradients on both the Mg b line-strength and the metallicity gradients. In particular, global gradients of Mg b and [Z/H] with respect to the UV colour across galaxies are consistent with their local gradients within galaxies, suggesting that the global correlations also hold locally. From a simple model based on multi-band colour fits of UV upturn and UV-weak galaxies, we have identified a plausible range of parameters that reproduces the observed radial colour profiles. In these models, the centers of elliptical galaxies, where the UV flux is strong, are enhanced in metals by roughly 60% compared to UV-weak regions.

• Structural Engineering and Mechanics
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• v.75 no.6
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• pp.643-657
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• 2020

This study presents experimental and numerical investigations on circular steel tube confined ultra high performance concrete (UHPC) columns under axial compression. The plain UHPC without fibers was designed to achieve a compressive strength ranged between 150 MPa and 200 MPa. Test results revealed that loading on only the UHPC core can generate a significant confinement effect for the UHPC core, thus leading to an increase in both strength and ductility of columns, and restricting the inherent brittleness of unconfined UHPC. All tested columns failed by shear plane failure of the UHPC core, this causes a softening stage in the axial load versus axial strain curves. In addition, an increase in the steel tube thickness or the confinement index was found to increase the strength and ductility enhancement and to reduce the magnitude of the loss of load capacity. Besides, steel tube with higher yield strength can improve the post-peak behavior. Based on the test results, the load contribution of the steel tube and the concrete core to the total load was examined. It was found that no significant confinement effect can be developed before the peak load, while the ductility of post-peak stage is mainly affected by the degree of the confinement effect. A finite element model (FEM) was also constructed in ABAQUS software to validate the test results. The effect of bond strength between the steel tube and the UHPC core was also investigated through the change of friction coefficient in FEM. Furthermore, the mechanism of circular steel tube confined UHPC columns was examined using the established FEM. Based on the results of FEM, the confining pressures along the height of each modeled column were shown. Furthermore, the interaction between the steel tube and the UHPC core was displayed through the slip length and shear stresses between two surfaces of two materials.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.6
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• pp.30-35
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• 2013

To conserve wood resources for papermaking, chemical compositions of the hemp (Cannabis sativa L.) bast fiber cultivated in Korea such as holocellulose, ${\alpha}$-cellulose, lignin, alcohol-benzene extractives, hot and cold water extractives, and ash contents were investigated to manufacture the specialty packaging paper effectively. Significantly very low klason lignin content of 3.3% was accomplished by removing of the outer shell of bark. Laboratory soda pulping method which is very useful for the nonwood fiber was adapted, and it was found that there was no significant difference in both kappa number and H-factor between 25% and 30% NaOH charge. Hemp pulp cooked with the laboratory digester in 25% NaOH at $170^{\circ}C$ were mixed together with the wood pulp(NBKP:LBKP=1:1) in order to find the optimum mixture ratio which exhibited acceptable paper strength properties such as tensile index, burst index, and tear strength. When 10% of hemp soda pulps was mixed with 90% of wood pulps comprised of SwBKP and HwBKP (1:1), all physical strength increased significantly. The physical strength decreased as the amount of hemp pulp increased because the cell wall of bast fiber is very thick which causes low conformability and low fiber-fiber bonding. These results showed that paper made of hemp-wood pulp can be used for the specialty packaging paper which requires both the characteristic surface properties and the high physical strength of hemp fiber.

• Tunnel and Underground Space
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• v.33 no.5
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• pp.425-434
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• 2023

To measure the wear amount of the TBM disk cutter in real time, it is important not only to automate the measurement using sensors, but also to stably transmit the measured data to the information processing system. In this study, we investigated the viability of utilizing Bluetooth Low Energy (BLE) technology to wirelessly transmit sensor data from the TBM cutter head to a receiver located at the chamber's rear. Through laboratory experiments, we analyzed the Received Signal Strength Index (RSSI) of the receiver considering various signal strength of the transmitter, separation distances between the transmitter and receiver and chamber fill materials. Our results demonstrate that wireless data transmission is feasible across all tested conditions when the transmitter signal strength is 0 dBm or higher.

• Journal of the Korean Geotechnical Society
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• v.29 no.6
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• pp.53-62
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• 2013

A 5-20 cm thick shocrete has been routinely constructed for NATM tunneling method to stabilize and confine the excavated rock of tunnel construction site. A $40kg/m^3$ of steel fibers are usually mixed into such shotcrete but these steel fibers may not be evenly distributed depending on shotcrete machines, mixing ratios and excavated rock conditions. In this study, square column shotcrete-mimicked concrete specimens of $15cm{\times}15cm{\times}55cm$ were prepared with 5 equal layers and 5 or 20% cement ratio. The specimens were prepared with different reinforced-patterns: non-reinforced, middle layer-reinforced, 1, 3, and 5 layers-reinforced, or all layers reinforced. The specimens were air-cured for 7 days and tested for flexural strength. The influence of steel-fiber distribution on flexural strength and toughness of shotcrete-mimicked concrete specimens was investigated. In the case of a specimen with cement ratio of 20%, a flexural strength increased as a number of fiber-reinforced layer increased. The flexural strength of one-layer reinforced specimen showed 20% less than that of evenly fiber-distributed specimen. On the other hand, a specimen with cement ratio of 5% decreased as the number of fiber-reinforced layers increased. A toughness index increased as the number of fiber-reinforced layers increased, regardless of cement ratios. The toughness index of evenly fiber-distributed specimen showed 2-3 times as large as that of one-layer reinforced specimen.