• Journal of the Korean Institute of Gas
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• v.8 no.2 s.23
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• pp.1-7
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• 2004

The physical properties of rigid polyurethane foam(PUF) synthesized using various types of blowing agents such as water, HFC-365mfc, HFC-245fa, HCFC-l4lb, CFC-11 and n-pentane were studied. The blending effect of blowing agents were also studied. The thermal conductivity, reaction rate, and cell morphology of the PUF with various blending ratio of blowing agents were investigated. The PUF blown by water shows the highest compressive strength among other single blowing agents. The thermal conductivity of PUFs blown by HFC-245fa and HFC-365mfc are close to that of PUFs blown by CFC-11. When HFC-365mfc was mixed with HFC-245fa(30mo1e$\%$) as coblowing agent, the mechanical property shows the highest value among other coblowing agents. It is that the thermal conductivity of PUFs depends on cell size of PUFs as well as thermal conductivity of blowing agent in gaseous form.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.17-26
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• 2002

The pressure distributions on a semi-span wing 1/12 scale mode and sic component aerodynamic forces and moments on a complete 1/16 scale advanced trainer model were measured. To reduce wing-tip vortex strength, 3 wing-tip jet slot shaped(forward $35{^{\circ}C}$ direction, straigt direction, backward $35{^{\circ}C}$ direction) and 3 blowing coefficents (0.004, 0.009, 0.017) were considered. From experiment results, the case of straight direction and blowing coefficent of 0.017 was the best effective in the reduction of drag and in increase of lift-drag ratio and A rate of drag decrease and a rate of lift-drag ratio increase were of most effective on angle of attack 8 degree.

• Journal of Animal Environmental Science
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• v.5 no.3
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• pp.181-188
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• 1999

This study was carried out to investigate the effect of blowing fan for reducing heat stress in lactating dairy cows in summer. Treatment conditions were divided into 3 types ; No blow(T1), blow to oblique angle(T2) and blow to right angle(T3). Feed intake milk yield, respiration rate, rectal temperature and plasma cortisol concenration were measured to investigate the effect of hot environment on the physiological, productive responses in lactating dairy cows. The results obtained are summarized as follows: The daily milk yields were 20.47, 22.82 and 24.31kg per head in T1, T2 and T3 during experimental period, respectively. The respiration rate was significantly (p<0.05) higher in T1 than those of T2 and T3. The rectal temperature in T1(39.4$^{\circ}C$) was higher than those of T2(39.1$^{\circ}C$), (P<0.05). The plasma cortisol concentration was higher in T1 than those of T2 and T3(P<0.05). It was suggested that blowing fan installed in the pen was effective means to reduce heat stress.

• The KSFM Journal of Fluid Machinery
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• v.11 no.3
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• pp.14-21
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• 2008

A numerical simulation on the flow field of a valveless bidirectional piezoelectric micropump has been performed. In this type of micropump, the oscillation of the piezoelectric diaphragm generates the blowing and suction flow through the oblique channel from the pumping chamber. The angle between the oblique and main channel causes the variation of flow distribution through upstream and downstream channels in suction and blowing modes. In the suction flow mode, the working fluid flows from both the upstream and downstream of the main channel to the pumping chamber through the oblique channel. However, in the blowing flow mode, the fluid pushed out of the pumping chamber flows more toward the downstream of the main channel due to the inertia of the fluid. In the present study, the effects of geometries such as the angle of oblique channel and the shape of main channel on the flow rate of the up/downstream were investigated. The flow rate obtained from the pump and the energy required to the pump were also analyzed for various displacements and frequencies of the oscillation of the diaphragm.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.897-902
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• 2001

SBOS(Soot blower Optimum System) analyzes the accumulated fouling rate of a coal-fired boiler plant at short intervals, compares it with a reference data, and determines the optimal time of soot blowing. In this paper, ANFIS algorithm which is an optimal algorithm to detect variation of boiler performance with time, updating the reference data and to eliminate the effects of noise in field signal is used to clean heating surface and to reduce steam needed to blow the soot.

• Polymer(Korea)
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• v.24 no.4
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• pp.538-544
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• 2000

The characteristics of cell growth and foamed cell structures of PP were investigated by a continuous foaming process. The operating parameters were the contents of blowing agent and nucleating agent, nucleating agent contents, die temperatures and die dimensions. The foaming cells grew without collapse at less than 14.5 wt% of blowing agent, isopentane. But the cells were collapsed when the blowing agent content was more than 14.5 wt%. The foam density dramatically decreased when a very small amount of the nucleating agent, 1 wt%, was added. After the nucleating agent was added, the cell's weight plummeted to one-seventh of its previous weight. Stable foam cell structures were formed at the die temperature of 17$0^{\circ}C$. However, the effects of the pressure drop rate on the cell morphology were not serious.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.4
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• pp.283-289
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• 2008

An experimental investigation was conducted to investigate the heat/mass transfer for impingement/effusion cooling system with inclined jet. Jets with inclined angle of 60 are applied to impingement/effusion cooling. At the jet Reynolds number of 10,000, the experiments were carried out for blowing ratios ranging from 0.0 to 1.5. The local heat/mass transfer coefficients on the effusion plate are measured using a naphthalene sublimation method. The result indicates that the inclined jet causes the non-uniform and low heat/mass transfer compared to the vertical jet. At stagnation region, the peak position is shifted from the geometrical center of injection hole due to Coanda effect and its level is higher than that of vertical jet due to increase in turbulence intensity by steep velocity gradient near the stagnation region. Further, the secondary peak region disappears because the interaction between adjacent wall jets weakens. When the initial crossflow occurs, the distorted heat/mass transfer pattern appears. As the blowing ratio (crossflow rate) increases, the heat/mass transfer distributions become similar to those of the vertical jet. This is because the effect of crossflow is dominant compared to that of inclined jet under high blowing ratio $(M{\geq}1.0)$. At low blowing ratio $(M{\leq}0.5)$, averaged Sh value is 10% lower than that of vertical jet, whereas its value at high blowing ratio $(M{\geq}1.0)$ is similar to that of vertical jet.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.1
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• pp.34-41
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• 2001

A study has been conducted to observe the slot film cooling effect on a convergent nozzle wall. The slot film cooling is used to protect the nozzle wall from the hot combusted gas by the coolant injected from the slot around the inner wall of the nozzle. The film cooling effectiveness and the heat transfer to the nozzle wall are influenced significantly by the blowing ratio of the coolant to the main flow and those are also influenced by the shape of the slot and the flow acceleration in the nozzle. In the present study, the heat transfer for the various blowing ratios has been performed by the experimental method and the results are compared with the results computed by the empirical formula. The numerical method has been conducted to compare the film cooling effectiveness of the convergent nozzle with that of the cylinder. For the relatively low blowing ratio, the cooling effectiveness increases sharply as the blowing ratio increases, and the increasing rate slows down for the high blowing ratio.

• The Journal of the Convergence on Culture Technology
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• v.7 no.4
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• pp.203-210
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• 2021

This study examined the effect of the respiratory training centered at forced breathing exercise of blowing out a candle on the improvement of adults' respiratory ability, which means the increased muscle strength of body trunk. After the four-week candle-blowing breathing training, the forced vital capacity (FVC) increased statistically significantly (p<.05). The forced expiratory volume in one second (FEV1) did not show a statistically significant difference before and after the four-week intervention(p>.05). The peak expiratory flow rate (PEF) statistically significantly increased after the four-week blowing-out-the-candle training (p<.05). This study examined the relationship between forced breathing training and pulmonary function of healthy adults including FVC, FEV1, and PEF, which means the increased muscle strength of body trunk, by implementing blowing-out-the-candle breathing exercise centered at forced respiratory exercise and obtained significant results. Further studies that use a sample of patients with advanced respiratory system disease for whom physical therapy is absolutely necessary will be required in the future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.652-655
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• 2001

In this paper, I have studied minimization of the kerf-width and surface burning which are occurred after the singulation process of multi layer $\mu$-BGA( thickness 1.1 mm, 0.9 mm) with a pulsed Nd:YAG( = 532 nm, repetition rate = 10 Hz) laser. The thermal energy of a pulsed Nd:YAG laser is used to cut the copper layer. I have studied are minimization of the surface burning and kerf-width using a photo resist, $N_2$blowing and polyester double sided tape as a cutting parameter. The $N_2$blowing reduces a laser energy loss by debris and suppresses a surface carbonization. Also, I have studied characters of cutting with a choice of side of laser beam incidence. The SEM(Scanning Electron Microscope), non-contact 3D inspector and high-resolution microscope are used to measure kerf width and surface state. The optimum value of 1.1 mm $\mu$-BGA singulation is 524 $\mu$m that is reduced kerf width of 60 % with $N_2$blowing. And I obtained reduction of carbonization of 68 % with a polyester double side tape in 0.9 mm $\mu$-BGA. I used laser intensity of 1.91$\times$10$^{6}$ / $\textrm{cm}^2$ in this study.