• Interaction and multiscale mechanics
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• v.1 no.1
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• pp.143-156
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• 2008

Elliptical tubes may buckle in an elastic local buckling failure mode under uniform compression. Previous analyses of the local buckling of these members have assumed that the cross-section is hollow, but it is well-known that the local buckling capacity of thin-walled closed sections may be increased by filling them with a rigid medium such as concrete. In many applications, the medium many not necessarily be rigid, and the infill can be considered to be an elastic material which interacts with the buckling of the elliptical tube that surrounds it. This paper uses an energy-based technique to model the buckling of a thin-walled elliptical tube containing an elastic infill, which elucidates the physics of the buckling phenomenon from an engineering mechanics basis, in deference to a less generic finite element approach to the buckling problem. It makes use of the observation that the local buckling in an elliptical tube is localised with respect to the contour of the ellipse in its cross-section, with the localisation being at the region of lowest curvature. The formulation in the paper is algebraic and it leads to solutions that can be determined by implementing simple numerical solution techniques. A further extension of this formulation to a stiffness approach with multiple degrees of buckling freedom is described, and it is shown that using the simple one degree of freedom representation is sufficiently accurate for determining the elastic local buckling coefficient.

• International Journal of Automotive Technology
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• v.8 no.2
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• pp.219-224
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• 2007

Recently, atmospheric contaminations has become worse due to the increased number of automobile. The PCV (Positive Crankcase Ventilation) valve acts as a flow control to allow re-combustion of blow-by gas by having it flow from a crankcase to an inlet manifold suction tube. Also, during the fabrication of the PCV valve, micro cracks may occur in the valve body and be extended under operation. The excessive stress distribution and crack initiation on the PCV valve body would bring an unstable blow-by gas flow rate control and would cause valve failure. The purpose of this study is to examine the crack affects on the stress and strain variations on the PCV valve according to the inlet and outlet manifold under differential pressures. From the results, we can explain the behavior of the crack extension for a safe condition of PCV valve.

• Asian Journal of Innovation and Policy
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• v.6 no.1
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• pp.58-84
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• 2017

This article aims at demonstrating location specific approach for agricultural technology promotion and adoption in improving the livelihood of the small farmers in the haor basin and coastal belt of Bangladesh. Innovative technologies that have potentials are initially screened by ex-ante investigation and instrumented by the business model canvas, which is used as a bottom-up approach for sustainability of the adoption of proposed technology innovations. Village-level extension farmers, sub-district extension officers and farmers' cooperative are the unique and central features to the business models and forward linkages. Extension service, power tiller, low-lift pump, sunflower, shallow tube well, quality seed, forward linkage for farmed duck eggs, live ducks and open catch fish etc. are the suggested potential technology innovations for the small farmers. The technology adoption business model can be reinvented for different locations within or beyond the country considering the local agricultural problems and prospects for greater sustainability.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.1
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• pp.33-45
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• 1997

Axisymmetric shear layers around a free jet is forced by co-flowing and counter-flowing secondary jets from/to an annular tube around the jet nozzle. The jet potential core extends far downstream with co-flowing secondary jets due to inhibited vortex developing and pairing. For counter-flowing cases, the axisymmetric shear layer around the jet transits from convective instability to absolute instability for velocity ratios R＝1.3～l.65 for the uniform velocity jets. Consequently, the jet potential core length increases and the turbulence level in the jet core is reduced significantly. The jets are controlled better with extension collars attached to the outer nozzle exit because the annular secondary flow is guided well by the extension collars. For the vectoring of jet, the annular tube around the jet is divided in two parts and the only one part is used for suction. The half suction makes the different shear layer around the jet and vectoring the jet by Coanda effect. The vectoring and turbulent components are varied significantly by the suction ratio. The experiments are carried out to investigate the characteristics of forced free jets using flow visualization, velocity and turbulence measurements.

• Journal of the Korea Institute of Building Construction
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• v.13 no.5
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• pp.434-440
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• 2013

Generally, the envelope of a freeform building is composed of a structure made with rectangular or C-shaped steel pipe, and steel or aluminum panel finishes on the structure. However, these construction methods increase material loss and cost and time. There are also numerous cases of misunderstanding of design and difficulties in construction, which frequently cause construction errors. Such construction errors decrease construction productivity, resulting in poor construction quality and the need for rework, as well as cost and time overruns. To solve the problem, this study proposes a 3D coordinate control technology for freeform structure implemented through a CNC(Computerized Numerical Control) Twisted tube method, and by extension, develops a BIM-based envelope construction method for freeform building.

• Horticultural Science & Technology
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• v.29 no.6
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• pp.568-574
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• 2011

Measuring tray as a component in irrigation control system using drainage electrodes was designed and applied for tomato perlite bed culture, and the effectiveness of the irrigation control system was investigated in terms of cultural development and cultivation costs. Five different types of measuring trays equipped with drainage electrodes were tested and the traditional tray was used as the control equipped with time clock. After the first experiment, "Tube-2" was removed because of instability of water content in the substrate. After second experiment, "Tube-1" was removed because of instability of water content in the substrate and low plant yields. In third experiment, "Up-Board" exhibited the best stability in water contents and yields as well as efficiencies in water and fertilizer utilization. The "Up-Board" was the most economical and the easiest system among the tested trays. Therefore, the "Up-Board" system was concluded as the excellent design to apply for the control method using drainage electrodes for tomato perlite bed culture.

• Steel and Composite Structures
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• v.20 no.5
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• pp.1067-1085
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• 2016

Recent research on steel moment-resisting connection between steel beams and concrete filled steel tubes has shown that there are considerable advantages to be obtained by anchoring the connection to the concrete infill within the tube using anchors in blind bolts. In the research reported here, extensive experimental tests and numerical analyses have been performed to study the anchorage behaviour of cogged deformed reinforcing bars within concrete filled circular steel tubes. This data in essential knowledge for the design of the steel connections that use anchored blind bolts, both for strength and stiffness. A series of pull-out tests were conducted using steel tubes with different diameter to thickness ratios under monotonic and cyclic loading. Both hoop strains and longitudinal strains in the tubes were measured together with applied load and slip. Various lead-in lengths before the bend and length of tailed extension after the bend were examined. These dimensions were limited by the dimensions of the steel tube and did not meet the requirements for "standard" cogs as specified in concrete standards such as AS 3600 and ACI 318. Nevertheless, all of the tested specimens failed by bar fracture outside the steel tubes. A comprehensive 3D Finite Element model was developed to simulate the pull-out tests. The FE model took into account material nonlinearities, deformations in reinforcing bars and interactions between different surfaces. The FE results were found to be in good agreement with experimental results. This model was then used to conduct parametric studies to investigate the influence of the confinement provided by the steel tube on the infilled concrete.

• Journal of Mushroom
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• v.12 no.4
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• pp.275-279
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• 2014

Pleurotus pulmonarius usually grows on the dead wood of deciduous trees from mid summer to early fall. Cultivation of this mushroom is recently increasing due to its good flavour and fragrance. This study was conducted to find out the favorable substrate formulation in the bottle and bag cultivation of P. pulmonarius. The V formulation (10 : 50 : 20 : 20 mixing ratio of poplar sawdust, cottonseed hull, cottonseed meal and beet pulp) showed the fastest mycelial growth in the test tube column medium and highest yields in both bottle cultivation and bag cultivation. Those chemical conditions were pH 5.52, 29.07% organic matter contents, 1.12% total nitrogen, 25.95 OM/N ratio, 0.16% CaO, 0.51% $K_2O$, 0.17 MgO and 0.26 $P_2O_5$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.749-755
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• 2002

In order to develop a multi-type heat pump system with two indoor units of non-uniform capacities, the optimum refrigerant circuit was developed using capillary tubes. The refrigerant circuit was composed of four main parts, a heating circuit, a cooling circuit, a by-pass circuit and a balance circuit. The system characteristics of multi-type heat pump was investigated through the rating test and the reliability test, using the multi-type psy-chrometric calorimeter. The results of the rating test showed that the capacity of the multi-type heat pump was about 93% of the design value. In particular, the capacity of cooling single mode was about 13% higher than the design value, and the capacity of heating multi mode was about 5% higher than the design value. The reliability of the multi-type heat pump was verified by various reliability tests (overload, extension tube, freeze up, under/over charging, sweat, flood back). The optimal amount of refrigerant charge and compressor capacity were determined from the present work.

• Applied Microscopy
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• v.45 no.3
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• pp.177-182
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• 2015

The boiler tubes of X20CrMoV12.1 used in fossil-fired power plants were obtained and analyzed for the effect of water treatment on the steam corrosion-induced oxide scale in an effort to better understand the oxide formation mechanism, as well as pertinent method of maintenance and lifetime extension. The specimens were analyzed using various microscopy and microanalysis techniques, with focuses on the effect of water treatment on the characters of scale. X-ray diffraction analysis showed that the scales of specimens were composed of hematite ($Fe_2O_3$), magnetite ($Fe_3O_4$), and chromite ($FeCr_2O_4$). Electron backscatter diffraction analysis showed that the oxides were present in the following order on the matrix: outer $Fe_2O_3$, intermediate $Fe_3O_4$, and inner $FeCr_2O_4$. After all volatile treatment or oxygenated treatment, a dense protective $Fe_2O_3$ layer was formed on the $Fe_3O_4$ layer of the specimen, retarding further progression of corrosion.