• Journal of Korean Ophthalmic Optics Society
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• v.18 no.2
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• pp.193-196
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• 2013

Purpose: This study was investigated to find out a useful instrument instead of direct ophthalmoscope for ocular photostress recovery time (PSRT) test. Methods: The PSRT test was performed using direct ophthalmoscope, trans illuminator, pen light, and camera flash for 48 subjects (average age 22.88 years, 96 eyes) who were corrected to 0.8~1.2 of visual acuity. Results: Each mean of PSRT measured by direct ophthalmoscope, trans illuminator, pen light, and camera flash was $27.90{\pm}18.40$ sec, $23.73{\pm}12.99$ sec, $21.31{\pm}15.57$ sec, and $18.98{\pm}11.64$ sec, respectively. The difference of PSRT between the eyes corrected more than 1.0 and the other eyes corrected under 1.0 of visual acuity was not found significantly. And there was no difference between dominant eyes and nondominant eyes of PSRT. Conclusions: Though the nearest instrument to direct ophthalmoscope was trans illuminator, pen light and camera flash could be the useful instruments for PSRT test.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.203-208
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• 2008

The purpose of this study is to compare the different shapes of condenser of the direct contact heat transfer from the heat pipe condenser to the receiving water using CFD. The heat transfer from the working fluid of the heat pipe to receiving fluid flows through the manifolder is one of the important part in evacuated solar collector system. The retrenchment of the thermal resistance between the heat pipe and the manifolder could increase the thermal performances of the whole system. Recently, direct heat transfer from the heat pipe condenser wall to the receiving water was suggested and accompanied experiments were achieved. This experiment shows the better performances of the direct contact heat transfer analogically. Preceding calculations are carried out for the performance comparison: mesh dependence test, discretization method test and equation model test. with these preceding tests, 4 different shapes of condenser are compared and each case were set up for the same heat flux at the condenser wall. The calculation result shows that the efficiency of the extended surface condenser shape is 10% higher then the that of the others.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.323-326
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• 2005

Uniaxial tension test of Glass Fiber Reinforced Polymer (GFRP) bar reinforced concrete prisms was performed. The objective was to investigate the adequate cover thickness of the GFRP rebars. The tension stiffening effect of GFRP bar reinforced concrete was also studied. The test variables included rebar types (conventional steel rebar and two different GFRP rebars) and cover thicknesses (five different cover thicknesses ranging between 1-3db). Normal strength concrete was used. Cracking patterns on concrete surface and cracking loads were careful1y observed during the direct tensile test. The test results indicated that the adequate cover thickness of the GFRP rebars may even be larger than that of the steel rebars and that the cover thickness of 2db commonly specified for the GFRP rebars may not be large enough. The tension stiffening effect of the GFRP rebars was also quantified and documented from the test results.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.2
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• pp.181-188
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• 2012

The most recent, Digital photogrammetric camera, Airborne LiDAR and GPS/INS same sensors are used to acquire spatial information of various kinds in the field of aerial survey. In addition, Direct Georeferencing technology has been widely utilized with digital photogrammetric camera and GPS/INS. However, the sensor Calibration to be performed according to the combination of various sensors is followed by problems. Most of all, boresight calibration of integrated sensors is a critical element in the mapping process when using direct georeferencing or using the GPS/INS aerotriangulation. The establishment of a national test-bed in Sejong-si for aerial sensor calibration is absolutely necessary to solve this problem. And accurate calibration with used to integration of GPS/INS by aerotriangulation of aerial imagery was necessary for determination of system parameters, evaluation of systematic errors. Also, an investigation of efficient method for Direct georeferencing to determine the exterior orientation parameters and assessment of geometric accuracy of integrated sensors are performed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.138-147
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• 2011

The objective of this study which it sees direct shear stress and comparative analysis of flexural shear stress leads and it is a shear stress analysis which it follows in load direction of the structure which uses Perfobond Rib shear connectors. To analyze direct shear stress, five Perfobond Rib shear connect experiments were fabricated with five variables and conducted Push-out Tests. After experiments, mechanism of Perfobond Rib shear connector was examined and direct shear formula was proposed based on primary factors which influence direct shear stress. Also, for the analysis of flexural shear steel-concrete composite slab specimens were fabricated and static flexural test. Based on the static flexural test it analyzed the flexural behavior and the flexural shear stress it calculated. Direct shear stress and EN 1994-1-1 to lead and be calculated, it compared the flexural shear stress and it analyzed in about the shear resistance stress which it follows in load direction.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.565-578
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• 2019

Basic friction angles of Hwangdeung granite, Berea sandstone, Jeongsun marble, Hongcheon gneiss, Pungam shale and Eumseong sandy shale were measured by direct shear test, tilt test and pull test. Characteristics of basic friction angle and the accuracy of test methods were compared and the optimal method in measuring basic friction angle was suggested. Although basic friction angles might be measured accurately by direct shear test, the test apparatus is expensive and procedures are complicated. Tilt tests which is the suggested method for measuring basic friction angle by International Association for Rock Mechanics also provided similar basic friction angles measured by direct shear test. However, the error measured for the same rock type is higher than 7° and values by repeated measurements in one sample show different trends, such as increasing or decreasing or almost constant as measurements continued. The difference measured in one gneiss sample is higher 12°, indicating that tilt test may be not a reliable method for measuring basic friction angle. Not only pull test provided accurate and consistent results under low normal stresses, but also test apparatus is simple and inexpensive and procedure is not complicated, indicating that pull test may be the optimal method for measuring basic friction angle.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.433-436
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• 2008

In order to estimate the mechanical properties of ultra high performance concrete, the most important is to evaluate its tensile behavior. The tensile behavior of concrete is generally characterized by the elastic behaviour before cracking and tensile stress-crack width relationship after cracking. We carried out the direct tensile and flexural tensile test and compared the tensile behaviors obtained by the direct tensile test and by inverse analysis of the flexural tensile test results. We compared the obtained tensile behavior with that of JSCE recommendations for ultra high performance concrete as well. we could see that the tensile stress-crack width relationship obtained from the flexural tensile test results using inverse analysis had good agreement with directly obtained tensile behaviour with direct tensile test and showed similar tensile softening behaviour introduced in JSCE recommendations for ultra high performance concrete.

• Journal of the Korean GEO-environmental Society
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• v.8 no.1
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• pp.41-47
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• 2007

Recent investigations into earthquake-induced damage have reported that liquefaction may take place on not only sands but also fine-contained soils or non-plastic silts. Although not a few study has been performed to understand the liquefaction of sands, relatively little effort has been devoted to improving our understanding of the liquefaction characteristics for non-plastic soils. Given that liquefaction strength is largely associated to shear wave velocity, bender element test as well as direct simple shear test is employed to examine the stiffness of non-plastic silt more precisely. Through the soil tests, the stiffness of non-plastic silts from the bender element tests is identified as slightly greater than that from the direct simple shear test. Further, the stiffness of non-plastic silts appears to be smaller than that of clay.

• The Journal of Asian Finance, Economics and Business
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• v.6 no.3
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• pp.123-130
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• 2019

The paper aims to investigate whether foreign direct investment (FDI) has positive effect on the labour productivity in Vietnam. Labour productivity is the elemental determinant of a country's development level in long-term. In recent years, although increasing consistently, labour productivity of Vietnam remains low in comparison to other South East Asian countries. To identify the direction of effect and the level of effect of FDI and human capital on the labour productivity of Vietnam, Autoregressive Distributed Lag (ARDL) model was used to examine the effect of FDI and human capital on labour productivity in Vietnam from 1986 to 2014. The results of bounds test confirm the existence of cointegration among the variables. Further, the Toda and Yamamoto Granger causality test affirms that there is unidirectional causality running from foreign direct investment and human capital index to labour productivity. The empirical results provide strong statistical evidence that foreign direct investment and human capital has a positive impact on labour productivity in Vietnam in long-term. These findings imply that workers are expected to further improve their knowledge, skills and that policy-maker should establish concrete plans to increase human capital. Results from this study provide suggestion necessary for Vietnam to achieve sustainable development.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.176-179
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• 2009

The performance of direct methanol fuel cells is affected by operating conditions such as, methanol feeding temperatures, methanol concentrations, and methanol flow rates during the operation in different environmental conditions. In this study, effects of the environmental temperature on performance of direct methanol fuel cells have been investigated in order to test a applicability of direct methanol fuel cell to the vehicle. The environmental temperature (ET) was varied from $-20^{\circ}C$ to $+30^{\circ}C$. The inside fuel cell temperature (CT) during test at various operating conditions was monitored and the performance of fuel cell was measured in the I-V polarization curve. With increasing the ET, the performance of the fuel cell was significantly improved and the CT also almost linearly increased. However, at below $0^{\circ}C$ ET, the DMFC showed very poor performance and needed to control CT or methanol feeding temperature (MFT), methanol flow rate(MFR) to obtain enough power of the vehicle.