• Water for future
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• v.27 no.4
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• pp.155-160
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• 1994

External foces acting on a pipe bend change when a transient pressure wave propagates through the bend. Analytical expressions are derived to compute the changes of these forces when the instantaneous pressure wave passes through the bends. This analysis reveals that these forces depend mainly on static pressure rather than fluid momentum. The analysis also reveals that the change of the vertical component of the force acting on a pipe bend with an angle larger than 90$^{\circ}$ may reverse in direction during the passage of a pressure wave through the bend.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.341-345
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• 2017

In this study, the Inlet/Isolator model experiments performed at Texas University were performed by 2-dimensional RANS computerized analysis. First, supersonic flow conditions were analyzed and compared with experimental surface pressure results, and the flow structure was analyzed by confirming Mach number distribution and numerical shadowgraph. Then, the inlet unstart condition was given by changing the back pressure, and the URANS analysis was performed to confirm the progress of inlet unstart.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.17-22
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• 1997

ASME SA508 Class 3 원자로압력용기강을 대상으로, 용접열영향부(heat affected zone, HAZ)의 최고온도(peak temperature) 등온분포도(isothermal diagram)를 작성 및 해석하였고, 재현(simulated) 열영향부 시험편을 제작하여 미세조직검사 및 기계적특성 시험을 실시하였다. 그 결과, 최고온도 등온분포도를 이용하여, 미소열영향부(subzone of HAZ)의 미세조직(microstructure)에 미치는 예열(preheat)온도와 용접입열량(weld heat input)의 크기 효과를 예측할 수 있었다. 또한, 재현 HAZ 의 기계적특성 시험결과, 용접용융선(fusion line) + 1 mm 이내의 위치로 대표되는 열 cycle 조건에서는 모재보다 양호한 강도와 인성을 보였고, 용접용융선 + 2~3mm부근에서 가장 미세한 조직(fine tempered lower bainite)과 우수한 충격인성을 나타냈다. 한편, 용접용융선 + 약 5mm 위치에서의 열 cycle 을 재현한 시험편에서는 미세조직의 변화(spheroidization of carbides)와 함께 인성 및 기계적 특성이 저하하여 모재보다 낮은 값을 보이는 것을 발견할 수 있었다.

• 열병합발전
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• s.55
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• pp.5-12
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• 2007

• 열병합발전
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• s.33
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• pp.27-32
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• 2003

• Journal of the Korean Society for Railway
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• v.15 no.5
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• pp.436-441
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• 2012

Pressure waves are generated and propagate in tunnel when train enters a tunnel with high speed. Compression wave due to the entry of train head propagates along the tunnel and is reflected at tunnel exit as expansion wave. While expansion wave due to the entry of train tail propagates along the tunnel and is reflected at tunnel exit as compression wave. These pressure waves are repeatedly propagated and reflected at tunnel entrance and exit. Severe pressure change per second causes ear-discomfort for passengers in cabin and micro pressure wave around tunnel exit. It is necessary to analyze the transient pressure phenomena in tunnel qualitatively and quantitatively, because pressure change rate is considered as one of major design parameters for an optimal tunnel cross sectional area and the repeated fatigue force on car body. In this study, we developed the characteristics method analysis based on fixed mesh system and compared with the results of real train test. The results of simulation agreed with that of experiment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.8
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• pp.669-675
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• 2015

In this study, we investigate the performance variations of an automotive turbocharger compressor with respect to the height variation of the recirculating casing treatment (RCT). We use three RCT heights, namely 1.2 mm, 1.5 mm, and 1.8 mm. We vary the compressor speed from 90,000 to 150,000 rpm, and the flow rate from 0.015 kg/s to 0.08 kg/s. The calculation results of the total pressure ratio and isentropic efficiency showed good agreement with the performance data provided by the manufacturer within a 0.7 percent error. The results showed that the RCT heights of 1.2 mm, 1.8 mm, and 1.5 mm, in that order, exhibited a more uniform pressure distribution, higher pressure ratio, and wider operational range. As the number of revolutions per minute increased, we obtained typical characteristics of a compressor map having a narrower operational range in the region of higher pressure ratio.

• CRM연구
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• v.3 no.2
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• pp.1-20
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• 2010

Due to the nature of teenage students' common tendency of being drawn to consumption conformity engendered by popular trends, and further expanding their unique collectivist culture, this study presumes that middle and high school female students as well have an influential factor that creates their distinctive trait. This study is intended to investigate the students' personal characteristics and effects of social reference groups, and further scrutinize how these influences transcends to deviant make-up behaviors. A total of 297 subjects, middle and high school female students, participated in a survey, using questionnaires focused primarily on the degrees of color makeup and the influences imposed by classmates. The findings of the study are as follows. First, regarding makeup behavior displayed by middle and high school female students, social self-esteem had positive influence on innovation and peer pressure. Second, perceived visibility conversely had negative impacts on innovation and peer pressure. This indicates that if perceived visibility is at a salient level, this already signifies lack of innovation. Third, makeup innovation and peer pressure demonstrated by middle and high school students all showed positive influence on their makeup behaviors. Additionally, peer pressure, in comparison to innovation, had greater influence on makeup behaviors, which indicates that peer pressure play a great role in makeup behavior of middle and high school students. Fourth, makeup behaviors showed strong impacts on makeup satisfaction and rendering deviant behaviors, which indicates that a new direction and perspective regarding middle and high school students' makeup behavior is critical.

• Fire Science and Engineering
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• v.27 no.6
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• pp.1-7
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• 2013

In this study, the effects of various disk shapes of hydrant on the pressure drop are experimentally and numerically analyzed. The test methods for measuring pressure drop of hydrant are comply with standard of Underwriters Laboratory (UL). The hydrant as used in this study has one inlet, diameter 150 mm, and three outlet, 114.3 mm diameter for one outlet and 63.5 mm diameter for the others. The pressure of the hydrant are measured in the range 760 L/min~2,270 L/min for 63.5 mm outlet and 3,030 L/min~6,060 L/min for 114.3 mm outlet. Also, the numerical results of pressure drop are compared with the experiments to verify the accuracy and to analyze the of various valve shape of hydrant on the pressure drop. The engineering parameters, flow coefficients, are reduced from 181.57 to 136.35 ($L/min/kPa^{0.5}$) with inclined angle of disk from $0^{\circ}$ to $45^{\circ}$. These results are able to practical use for design hydrant to minimize pressure drop.

• The Journal of the Korea Contents Association
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• v.10 no.8
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• pp.257-265
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• 2010

The purpose of this study was to investigate the effect of different ramp inclination on the maximum plantar foot pressure and pathway of the center of pressure. Fifteen healthy adults who had no musculoskeletal disorders were participated with this study and descended the ramp with different inclination(level, $-5^{\circ}$, $-10^{\circ}$, $-15^{\circ}$). Plantar foot pressures were recorded by the Matscan system(Tekscan, Boston, USA) during level and descending ramp with barefoot. Plantar foot surface was defined as seven regions for pressure measurement; two toe regions, three forefoot regions, one midfoot region, one heel region. Repeated ANOVA was used to compare each region data of foot according to different ramp inclination. As descending ramp inclination became increased, the pressure of hallux region was significantly increased at $-15^{\circ}$ inclination and the pressure of 2-3 metatasal head region were significantly decreased at $-5^{\circ}$, $-10^{\circ}$, $-15^{\circ}$ inclination. The pathway of COP had a tendency to be shifted inside in forefoot and prolonged to great toe as the descending ramp inclination increased. The results indicated that plantar foot pressure could be changed at hallux and forefoot regions with $-5^{\circ}$ ramp inclination and these findings demonstrated that ramp inclination could affect the structure and function of foot.