• Journal of Biosystems Engineering
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• v.36 no.6
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• pp.444-452
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• 2011

In this study the characteristics of natural ventilation of Venlo-type greenhouse with continuous roof vents were analyzed using commercial computational fluid dynamics (CFD) code. Developed CFD simulation model was verified by comparison with experimental data. Simulation errors were 1.9-46.0% for air velocity and 1.7-11.2% for air temperature at each measurement point. CFD simulations were conducted to estimate the effect of roof vents opening direction, opening angle, outside wind velocity and wind directions on ventilation rate and climate condition in greenhouse. The results of this study showed that ventilation rate of the present greenhouse was increased linearly in proportion to the increase of roof vent opening angle and outside wind velocity over 2.0 m/s. According to the analysis on the effects of different roof vent opening direction, simultaneous opening of wind and leeward vents showed the highest ventilation rate and lowest mean temperature in greenhouse.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.179-188
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• 2011

Steel structures have been allowed to have fatigue damage tolerance in fact. If it would be assessed whether fatigue crack is growing or not and How fast fatigue crack is propagating, we should make a rational decision on methods and a period of reinforcement in the maintenance. In this study, fatigue crack growth tests on two kinds of through-thickness cracked steel plates and a out-of-plane gusset welded joint were conducted to evaluate fatigue crack growth rate using the COD(Crack Opening Displacement), and COD measurement using strain gauges was examined to offer a practical method. As a result, we proposed a reasonable assessing method for fatigue crack growth rate using the COD and it was experimentally proved practical to estimate the COD through measuring strains.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.4
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• pp.370-377
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• 2018

Ball valve has been widely used in the field of high-pressure gas pipeline as an important component because of its low flow resistance and good leakage performance. The present paper focuses on the flow nature at the downstream of the ball valve used for gas pipelines according to valve opening rates. Steady 3-D RANS equations, SC/Tetra, have been introduced to analyze the flow characteristics inside the ball valve. Numerical boundary conditions at the inlet and outlet of the valve system are imposed by mass flow-rate and pressure, respectively. Velocity distributions obtained by numerical simulation are compared with respect to the valve opening rates of 30, 50, and 70%. Cavity distributions, asymmetry flow velocity and the flow stabilization point at each opening rate are also compared. When the valve opening rates are 30 and 50%, the flow stabilization requires the sufficient length of 10D or more due to the influence of the recirculation flow at the downstream of the valve.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.908-917
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• 1995

The constant .DELTA.K fatigue tests are performed in SS41 and its weldments to investigate crack opening behavior and fatigue crack propagation behavior at each parts of weldment and its boundary layer. The weldments were annealed after welding for the purpose of relieving residual stress. Every weldments has notch at weld metal zone, and fatigue crack propagates from weld metal zone to vase metal zone perpendicular to weld line. The Laser ISDG method is used in order to determine the crack opening ratio, this method is more precise than indirect measurement method, and faster and easier than other direct measurement method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.121-127
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• 2008

This paper investigates the effects of outdoor pressure fluctuations on natural ventilation through an opening on a building envelope. The ventilation airflow rate depends on the magnitude and the period of the pressure fluctuations, the size of the opening relative to the space volume, and the resistance characteristics of the opening. Non-dimensional parameters have been derived, which determine indoor pressure responses due to outdoor pressure fluctuations. The flow regions are categorized into (1) synchronized region, (2) opening resistance region, and (3) transition region depending on the non-dimensional parameter derived. Pressure fluctuations and flow characteristics are investigated numerically using the 4th order Runge-Kutta method.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.216-217
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• 2020

As the fire inside the building grows rapidly, ejected flame from an opening occurs due to flashover. As a result, the number of cases where the flame spreads to the exterior of the building and rapidly expands to the upper floor is increasing. In particular, in the case of the fire in the Daebong Green Apartment, Uijeongbu in 2015, it was a case where the flame spread to adjacent buildings due to the opening eruption flame from the first ignited building, causing great damage to three apartments. Therefore, this study is to introduce an international standard under development that estimates the shape and properties of the ejected flame from an opening and quantitatively evaluates the radiant heat flux received by the exterior wall of the building by assuming the occurrence of the ejected flame from an opening.

• Journal of ILASS-Korea
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• v.21 no.1
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• pp.20-28
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• 2016

This paper presents an experimental study on the GDI injector with Bosch method. The injection characteristics, such as the injection quantity, the injection rate, the maximum velocity of the nozzle exit and the injection delay were studied through the change of the injection pressure, the tube pressure and energizing duration in injection rate measurement device using nheptane. The injection quantity is increased by increasing injection pressure, decreasing tube pressure or increasing energizing duration. As the difference of the injection quantity changed, the shape of injection rate was moved with a constant form. The maximum velocity of the nozzle exit showed a tendency to increase as the injection pressure is increased. However, tube pressure did not affect. Overall, it was confirmed that the closing delay is longer than the opening delay in all conditions. As the injection pressure increased, the result has a tendency to decrease the closing delay, it did not affect the opening delay. Reduction of the closing delay showed the reduction of the injection duration. the tube pressure and energizing duration did not affect the injection delay (opening delay, closing delay).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.263-268
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• 2001

The constant .DELTA. K fatigue tests are performed in SS41 and its weldment. The LASER ISDG method is used in determination of crack opening ratio. This method is more precise than indirect measurement method, faster and easier than other direct measurement method. And obtained results are followed 1) Crack opening ratio U is proportional to fatigue crack growth rate da/dN at constant .DELTA. K 2) Fatigue crack growth rate da/dN in weldment increases in weld metal and heat affected zone, decreases in base metal as crack grows.

• Korean journal of applied entomology
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• v.56 no.3
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• pp.253-259
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• 2017

Fumigation using chlorine dioxide ($ClO_2$) has been regarded as a potential control technique against stored grain insect pests. The control efficacy can be enhanced with increase of opening rates of spiracles by facilitating the toxic gas delivery to internal body. To test this hypothesis, this study used the Indianmeal moth, Plodia interpunctella, which was known to be susceptible to $ClO_2$, and analyzed the opening rate of spiracles. A total of 9 pairs of spiracles were observed in P. interpunctella larvae, in which one pair was located on the prothorax and eight pairs were on the abdomen. Within the body, the spiracles were connected to longitudinal and transverse tracheal trunks. The open spiracles were determined by the dye-infiltration method. Based on this method, the opening rate of spiracles increased up to about 60% with increase of ambient temperatures. Furthermore, exposure to carbon dioxide stimulated the opening rate of spiracles up to about 95%. In contrast, exposure to $ClO_2$ prevented the spiracle opening and resulted in only 25% of spiracles in an opening state. The addition of carbon dioxide to $ClO_2$ treatment rescued the opening rate of spiracles as much as the carbon dioxide single treatment. Based on this modulatory activity of carbon dioxide against spiracles, the combined treatment of $ClO_2$ with carbon dioxide resulted in significant increase of its toxicity against P. interpunctella compared to a single $ClO_2$ treatment.

• Korean Journal of Environmental Biology
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• v.20 no.4
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• pp.386-390
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• 2002

The opening phenomenon of mature female cone in Pinus densiflora aye observed from the anatomical characteristics. The differentiation of tissue in young cone aye not complete and are going on. In the green cone as large as the adult cone, shrink-age rate of vascular strands and sclerenchyma aye 1.0∼1.5％ and 14.0∼16.0% respectively. The end parts of cone scales are composed of the parenchymatous cell and sclerenchyma. The middle parts in cone scales are composed of the sclerenchyma and vascular strands with the same thickness and more thin than the thickness of the end part and basal one. But thickness of sclerenchyma which compose of scale prop in the basal part of cone scale aye twice than that of vascular strand. In mature cone, the opening phenomenon of the pine cone results from the difference of shrinkage rate between vascular bundle and sclerenchyma. Especially, opening of cone scales are due to larger shrinkage rate of sclerenchyma than vascular strands in the basal part of cone scale.