• Korean Journal of Agricultural Science
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• v.39 no.2
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• pp.271-277
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• 2012

Dimensions, operation conditions and improvement items for round roof windows were investigated in arch shape single-span plastic greenhouse with roof vents, and natural ventilation performance was analyzed based on the ventilation theory. Diameter of round roof windows was mostly 60 cm, and chimney height projected on roof was average 30 cm. Installation space was mostly 5 to 6 m but farmhouse of 10 m and over was 16.7% also. A round roof window which has 60 cm diameter was installed to 6 m space generally and 80 cm diameter was installed to 10 m space, but correct standards did not exist. There were a lot of opinions that ventilation effect of round roof windows is fairly good and user satisfaction is generally excellent. It is problem that there is few effects in summer and that vinyl around each vent tears well and rainwater leaks, and improvement hope item required development of automatic control system. In the wind speed of 0.3 m/s, it was estimated that natural ventilation rates were 0.69, 0.55, 0.50 and 0.48 volumes per minute in case of 2, 4, 6 and 8 m installation space for round roof windows, respectively. It was analyzed that the ratio of ventilation due to buoyancy out of total ventilation were 65.2, 41.9, 29.9 and 22.8% in case of 2, 4, 6 and 8m installation space, respectively. By the round roof windows installed at space of 6 m, ventilation rate was estimated to 0.5 volumes per minute, and we can expect the increase in ventilation rate of 30%. In order to meet the recommended ventilation rate for summer season, we have to install the round roof windows at space of 1 to 2 m. However, it is difficult to apply those installation space because of falling productivity due to lower light transmittance as well as rising costs. It is estimated that the installation space of 6m is appropriate for spring or fall season. Therefore it is necessary to encourage installing the roof windows in single-span plastic greenhouses.

• Food Science and Preservation
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• v.15 no.1
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• pp.43-48
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• 2008

This experiment investigated the characteristics of salted and fresh Chinese cabbages of different cultivars and using various cultivation methods. We measured the numbers of leaves, sizes, thicknesses, moisture contents, and firmness qualities of fresh Chinese cabbage grown in a plastic house, and outdoors. 'The bulb sizes, leaf thicknesses, and moisture contents of leaves were higher after plastic house cultivation than after growth in the field. Plastic house culture increased the growth rate of Chinese cabbage. Firmness and osmolarity showed better values after outdoor cultivation, however. The growth rates and the levels of chemical components were affected by interactions between cultivation methods and cultivars of Chinese cabbage. The salt levels of salted Chinese cabbage were 1.21.7% (w/w) after cabbages cultivated outdoors were preserved, and 0.91.2 % (w/w) after vegetables grown in a plastic house were treated. The quality properties of postharvest Chinese cabbages after salting varied with cultivation method even when the same cultivars of Chinese cabbage were used. The salt contents of salted Chinese cabbage thus varied with different cultivation methods. The results indicate that the properties of Chinese cabbage vary with the culture systems adapted.

• Steel and Composite Structures
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• v.3 no.6
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• pp.421-438
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• 2003

Aging and deterioration of existing steel structures necessitate the development of simple and efficient rehabilitation techniques. The current study investigates a methodology to enhance the flexural capacity of steel beams by bonding Glass Fibre Reinforced Plastic (GFRP) sheets to their flanges. A heavy duty adhesive, tested in a previous study is used to bond the steel and the GFRP sheet. In addition to its ease of application, the GFRP sheet provides a protective layer that prevents future corrosion of the steel section. The study reports the results of bending tests conducted on a W-shaped steel beam before and after rehabilitation using GFRP sheets. Enhancement in the moment capacity of the beam due to bonding GFRP sheet is determined from the test results. A closed form analytical model that can predict the yield moment as well as the stresses induced in the adhesive and the GFRP sheets of rehabilitated steel beam is developed. A detailed finite element analysis for the tested specimens is also conducted in this paper. The steel web and flanges as well as the GFRP sheets are simulated using three-dimensional brick elements. The shear and peel stiffness of the adhesive are modeled as equivalent linear spring systems. The analytical and experimental results indicate that a significant enhancement in the ultimate capacity of the steel beam is achieved using the proposed technique. The finite element analysis is employed to describe in detail the profile of stresses and strains that develop in the rehabilitated steel beam.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.177-184
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• 2011

This paper describes an analytical study on the design approach of PC system with continuous connections at member ends. In multi-ribbed moment resisting slab (MRS) system, double tee members are connected continuously over inverted tee beams with the continuous reinforcements placed within topping concrete. Thus, negative moments are concentrated within the narrow connection area. In order to propose a design method, experimental results of the companion study were examined using detailed nonlinear analysis. Then nonlinear static analysis was used to evaluate the partial continuity effect and the moment redistribution mechanism. Material and cross sectional properties were obtained from experimental results of the companion study. Plastic hinge properties for nonlinear static analysis were modeled with cracking moment, nominal moment, corresponding member deformations, etc. The analysis results showed that a large amount of negative moment of MRS slab can be reduced by applying partial continuity and moment redistribution in MRS joint.

• Journal of the Optical Society of Korea
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• v.14 no.3
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• pp.235-239
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• 2010

In this study, we have fabricated two types of non-invasive fiber-optic respiration sensors that can measure respiratory signals during magnetic resonance (MR) image acquisition. One is a nasal-cavity attached sensor that can measure the temperature variation of air-flow using a thermochromic pigment. The other is an abdomen attached sensor that can measure the abdominal circumference change using a sensing part composed of polymethyl-methacrylate (PMMA) tubes, a mirror and a spring. We have measured modulated light guided to detectors in the MRI control room via optical fibers due to the respiratory movements of the patient in the MR room, and the respiratory signals of the fiber-optic respiration sensors are compared with those of the BIOPAC$^{(R)}$ system. We have verified that respiratory signals can be obtained without deteriorating the MR image. It is anticipated that the proposed fiber-optic respiration sensors would be highly suitable for respiratory monitoring during surgical procedures performed inside an MRI system.

• Korean Journal of Agricultural Science
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• v.41 no.4
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• pp.385-390
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• 2014

To evaluate the impact of nitrogen fertigation on crop growth and $NO_3$-N concentration in the soil solution, field experiment for cucumber cultivation during spring and fall season were carried out in on-farm located in Byeongcheon-myeon, Chunan-si, Chungcheonnam-do. Supplying nitrogen of 120-150 mg/L by fertigation device into soil per week reached to maximum yields of cucumber fruits. However, cucumber growth did not show any significant difference between nitrogen levels. Nitrogen supply of 400 mg/L, highest N levels, did not affect cucumber growth. Difference between green values of cucumber leaves using RGB scores were closely related with cucumber yields, and therefore, this results suggests that green values of cucumber leaves could be used as a way of determining the application rates of nitrogen for cucumber cultivation period under fertigation system.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2011.04a
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• pp.103-108
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• 2011

This study aims to understand the unique housing culture and decoration style in traditional Thai houses. Literature review and site visit were applied for the research method. A steep gable roof, a lifted floor structure on the pillars, a semi-enclosed central flatform(charn) and a outdoor staircase are important plastic elements of exterior decoration in Thai traditional houses. 'Panlom(windbreak on gable)' and 'fa loog fak(wall panel)' are the most unique elements which determine Thai traditional style. In Thai traditional style decoration, the beautifully carved wooden panels and decorations are also the most important factors. The decorations can be analyzed in the aspect of following perspectives. ; The characteristics of Thai traditional house decorations have been developed and evolved as result of influences from regional climate and local material. And also the social-cultural factors such as religion, social and family relationship and life style controlled the forms and culture of traditional housing form and culture. As a result, this study summarises and defines the outstanding and unique meaning and definition of the decoration in Thai traditional houses focused on central region in Thailand.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.2
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• pp.60-68
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• 2009

The objective of this paper is to design stamping die of inner reinforcement panel with DL 950 advanced high strength steel as stamping materials through numerical analyses and experiments. The stamping process was designed as bending dominant process consisting of 1 step of notching and 4 steps of bending processes. In order to obtain a proper design of the stamping die, various three-dimensional elasto-plastic finite element analyses were performed using a commercial code AUTOFORM V4.2. Design parameter of stamping die was chosen as the corner radius of the stamping die for each step. From the results of the FE analysis, feasible corner radii of the stamping die, which can minimize the deviation of corner angle of the stamped part from design data, and forming load for each part were estimated. Stamping experiments were carried out using the manufactured stamping die according to the proposed die design. The results of experiments were shown that the stamping die can successfully manufacture the inner reinforcement panel with DL 950 advanced high strength steel as base stamping material.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.321-325
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• 2005

Bipolar plate is the main part with MEA in automotive PEMFC. It must have a good electrical conductivity and excellent corrosion resistance, be cost effective. Therefore, stainless steels have been studied by many researchers because of its corrosion resistance and cost benefits. But their properties are not sufficient for the application to bipolar plate for automotive PEMFC. In this work, we have performed stamping using various commercial stainless steels to select candidate material for biploar plate and to derive design parameters for stamping simulation. The results showed that a small curvature at the corner of flow field is more favorable due to easier a plastic deformation. Stamping process was simulated by changing surface condition, and the size and angle of channel. The optimum shape and spring back phenomena were evaluated. Surface coating was applied to increase the corrosion resistance and electrical conductivity of stainless steel. The electrical interfacial resistance was 10 to $15m{\Omega}cm^2$ under clamping force of 150psi. But corrosion resistance of coating on the stainless steel was not good due to the unstableness of microstructure.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3185-3194
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• 1994

In this study, an impact model and impact response analysis method was suggested for the impacts between arbitrary shaped bodies. Unlike the impacts between geometrically simple structures, there is no rules to analyze the impacts between general elastic structures First of all, it has been attempted to explain the impoot between arbitrary elastic structures as the elastic deformation of a virtual contact spring in the vicinity of contact points. The contact stiffness and the exponent are determined from the Hertz's contact theory and F. E. analysis. In order to evaluate the validities and limitations of the proposed methods, an impact tester and the miniature of container, missile and isolators have been provided and tested experimentally. All the experiments were performed with various impact conditions. The results obtained by the proposed methods were directly compared with the measured values in terms of maximum contract force, contact duration, the shape of contact force and the structure responses. The computed contact force and responses, using this proposed methods, were very close to the measured results, unless any plastic deformations were presented.