• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1A
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• pp.39-48
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• 2012

This study deals with numerical determination of stress intensity factors of adhesively patch-repaired plates with cracks at V-shaped or semicircular notches. The p-convergent anisoparametric model are considered and then three-dimensional virtual crack closure technique is presented using formulations of anisoparametric elements. In assumed displacement fields of an element, strain-displacement relations and three-dimensional constitutive equations are derived with three-dimensional hierarchical shape functions expanded from one-dimensional Lobatto functions. Transfinite mapping technique is used to represent a circular boundary. The present model provides accuracy and simplicity in terms of stress concentration factor, stress distribution, the number of degrees of freedom, and non-dimensional stress intensity factor as compared with previous works in literatures. Stress intensity factors obtained by the three-dimensional virtual crack closure technique are estimated with respect to the variation of width of finite plate, radius of notch root, angular inclination of V-shaped notch, and crack length.

• Journal of Science Education
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• v.33 no.1
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• pp.56-68
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• 2009

The purpose of this study was to investigate students' ontological categories about rocks and the earth's crust and plate tectonics. A total of 169 high school students in the first grade were involved in the study, and in order to extend the boundary and tendency of the research, structuralized questions and coding frame were generated. Additionally, the results from all students were codified in four levels according to coding frame (matter, transformation, proto-process, and process). Followings are the results. First, the ontological categories of students about the concepts of this research were classified dominantly into a matter and transformation within the boundary of 67% of rocks, and 75% of the crust. The propensity of plate tectonics in terms of ontological category were analyzed by being codified into 68% of process category which proved to have relatively process-oriented perspective. Secondly, the inclination to allocate ontological categories of each students in terms of field concepts were confirmed in 16% and 31% per each student that were codified into process categories and matter categories. Most students that were codified into matter category responded to high tendency to view the world as a combination of simple substances. Moreover, the students had ontological faith that speculates only through a state or an incident in terms of concepts that form a structure of knowledge.

• Journal of the Ergonomics Society of Korea
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• v.30 no.2
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• pp.357-363
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• 2011

Objective: The aim of this study is to set the design direction of the lift chair's tilting seat for development. Background: Great attention has been shown to the development of senior friendly product, because of increasing elderly population rapidly in Korea. Therefore, we need to study on sit-to-stand(STS) motion of elderly systematically for developing lift chair that is one of senior friendly products. Method: In this study, we analyzed joint moment(knee, hip) and muscle activity (Erector spinae, Rectus femoris, Vastus lateralis) on STS motion of elderly(female, 60~70: 7) and young people(female, 20~30: 7) using 3 dimension motion capture camera, force plate, wireless EMG. Results: The results of muscle activity showed a similar trend but the results of joint moment were a lot of differences between the young and the elderly. Conclusion: The results of knee joint moment suggest the angle(10~30deg)-adjustable seat that can be better than to find the optimal seat's angle. Application: The method and results of this study are expected to develop senior friendly product and verification as well as be available to various application.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.1
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• pp.61-67
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• 2005

The objective of this study was to investigate community structure of attached algae and microbes in sedimentation basin of water and wastewater treatment plants by using respiratory quinone profile. There was an evident difference, in microbial community structure and attached algae species, between inclination plate settler and drainage canal in the sedimentation basin. The algae was composed of species in following order; Chlorophyceae>Bascillariophyceae>Cyanophyceae. The dominant quinone types of attached microorganisms in the wastewater treatment plant were plastoquinone (PQ)-9, vitamin(V)K-1 followed by UQ-8, but those for water treatment plant were VK-1, PQ-9 followed by UQ-8. These results suggests that nutrients, seasons and material of sedimentation basin have notable influence on composition of attached algae and microbial community structure in water and wastewater treatment plants.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.34-40
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• 1999

An experimental study has been conducted to determine the effects of inclined impinging jet on the local heat transfer coefficients. A single jet with nozzle diameter of 24.6 mm was tested for Reynolds numbers from 10,000 to 70,000 and nozzle-to-plate spacings of 2~6 jet diameters. The angle of inclination of the impingement surface relative to the horizontal surface was varied from $0^{\cire}$ (normal impingement) to $60^{\cire}$. The results indicate that the point of maximum heat transfer is moved up from the geometrical stagnation point of inclined surface by Coanda effect. The local heat transfer coefficients on the minor jet region decrease more rapidly than on the major jet region, thus creating an imbalance in the cooling capabilities on the two sides.

• Computers and Concrete
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• v.21 no.1
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• pp.75-85
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• 2018

To improve the design equation for the evaluation of the bursting force in the post-tensioned anchorage zone, this paper presents the analyses and design of the post-tensioned (PT) anchorage zone on the basis of three dimensional (3D) finite element (FE) analyses. The structural behavior was investigated through linear elastic finite element analyses upon consideration of the change in design parameters such as the bearing plate size, the eccentricity, and the tendon inclination. Moreover, consideration of the duct hole, which causes an increase of the bursting stress with a change in its distribution along the anchorage zone as well, is emphasized. Since that an exact prediction of the bursting force is the primary interest in design practice, additional parametric analyses are carried out to evaluate the relative contribution of all design parameters in determining the bursting force, and a comparison with the design guidelines mentioned in AASHTO-LRFD has been provided. Finally, an improved design guideline that takes into account the influence by the duct hole is suggested.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.828-833
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• 2003

This work analyzes the effects of the independent variation of different geometric dimensions of compressor valves on the effective flow and force areas using a circular valve plate, such as different geometry of the valve seat, and the valve reed is opened and closed by pressure pulsation, the flow characteristic of the refrigerant passing the valve is very important. In the present study, a circular disk with inclination is assumed to be the valve reed of a reciprocating compressor and numerical analysis of three dimensional velocity fields are performed for theradial flow through the valve model. The effective flow and force area which are required to predict the efficiency of the valve are required to predict the efficiency of the valve are measured and compared with the numerical analysis in this research.

• Journal of Power System Engineering
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• v.4 no.4
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• pp.25-31
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• 2000

This paper represents the vector fields and three dimensional mean velocities in the X-Y plane of cone type swirl gas burner measured by using X-probe from the hot-wire anemometer system. This experiment is carried out at flowrate 350 and $450{\ell}/min$ respectively in the test section of subsonic wind tunnel. The vector plot shows that the maximum axial mean velocity component is focused in the narrow slits distributed radially on the edge of a cone type swirl burner, for that reason, there is some entrainment of ambient air in the outer region of the burner and the rotational flow can be shown in the inner region of the burner because mean velocity W is distributed about twice as large as mean velocity V due to inclined flow velocity ejecting from the swirl vanes of a cone type baffle plate of burner. Moreover, the mean velocities are largely distributed near the outer region of burner within $X/R{\fallingdotseq}1.5$, hence, the turbulent characteristics are anticipated to be distributed largely in the center of this region due to the large inclination of mean velocity and swirl effect.

• Solar Energy
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• v.12 no.2
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• pp.9-17
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• 1992

This is an experimental work concerning about an application of a heat pipe to an evacuated-glass-tube solar collector system. A methanol heat pipe with length of 0.7 m and diameter of 8 mm was manufactured and tested to compare its performance with that of freon thermosyphon which was originally used in a solar collector system fabricated at Thermomax Co.. Then this methanol heat pipe was utilized to be one component, i.e. heat transfer element, of the present experimental model of a solar collector. This model was performed the operation test as its absorber plate was irradiated by infrared lamps. The following results were obtained. (1) The methanol heat pipe was showed a stable operation when the variation of axial heat transport was $0{\sim}40$ watts and that of inclination angle was $30{\sim}90^{\circ}$. (2) The heat transport capability of the heat pipe was proved to be higher than that of the thermosyphon, because the heat transport limitation of the latter was occured at about 30 watt. (3) The heat pipe in a solar collector was also showed good performance as it transmitted absorbed energy.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.163-170
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• 1998

An ion energy spectrometer which has the $45^{\circ}$ parallel electrostatic deflection plate was designed and constructed for measuring ion temperature in high temperature plasma. The energy calibration and the energy resolution were studied in detail for a hydrogen ion at the $0.24{\sim}1.92\;keV$ energy using electrostatic accelerator with a duoplasmatron ion source. The voltage of the deflection plate was linearly increased for the decreased ion detector position at the constant ion energy and decreased for the increased ion energy at the fixed ion detector position. The inclination of the deflection plate voltage to the ion energy was between 0.92 and 1.61, and linearly decreased for the increased the ion detector position. The measured energy resolution, which is $4.2%\;{\sim}\;11.6%$ in this experiment region, was improved for the increased ion dector position and ion energy. The relative efficiency was increased for the decreased the ion detector position. The ion energy spectrum of the DC plasma in the multi-purpose plasma generator was measured using this equipment. The ion temperature was 203-205 eV at the discharge voltage 320 V, discharge current 1.7 A.