• 한국가시화정보학회지
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• 제8권4호
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• pp.19-25
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• 2010

The flow field measurements were conducted on the planes between impeller blades, and the gap between the impeller and turbine blades under speed ratio of 0.4. The study showed that high velocity regions move from locations near the suction surface of the impeller to the pressure blade, shroud corner as flow progresses from the mid-chord of impeller passage to exit and out into the gap region. Planes 3 through 5 also showed flow reversal occurring in the area near the shell surface and progress far into the impeller passage from the impeller passage exit, near shell surface. This affected the converter efficiency negatively. This study would aid in the construction of higher accuracy CFD models of this complex turbomachinery device.

• 대한기계학회논문집B
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• 제30권9호
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• pp.913-920
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• 2006

Three-dimensional flow and aerodynamic loss in the tip-leakage flow region of a high-turning first-stage turbine rotor blade with a squealer tip have been measured with a straight miniature five-hole probe for the tip gap-to-chord ratio, h/c, of 2.0%. This squealer tip has a indent-to-chord ratio, $h/{st}/c$, of 5.5%. The results are compared with those for a plane tip $(h_{st}/c=0.0%)$. The squealer tip tends to reduce the mass flow through the tip gap and to suppress the development of the tip-leakage vortex. Therefore, it delivers lower aerodynamic loss in the near-tip region than the plane tip does. At the mid-span, however, the aerodynamic loss has nearly the same value for the two different tips.

• 한국표면공학회지
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• 제30권2호
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• pp.136-143
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• 1997

The photvoltaic power system has received considerable attention as the petroleumalterative energies to the environmental problems in the wored scale. $CuLnSe_2$is one ofthe most promising materials for the fabrication of large-area modules and low cost photovoltaic devices. Sulfur solute CuInSe2 thin films were prepared by RF sputtering using powder targer which were previously compacted by powder of $Cu_2Se, \;In_2Se_3, \;Cu_2S, \;and\;In_2S_3$ in various ratios. The results induicated that the sulfur ratio, the(112) texture, and the energy band gap were increased by the increase of the S/(S+Se) that was controlled by stoichiometric compound. The energy band gap can be shifted from 1.04eV to 1.50eV by abjusting the S/(S+Se) ratio, which maich it possible to obtain perfect match to the solar spectrum.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.161-164
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• 2006

Three-dimensional flow and aerodynamic loss in the tip-leakage flow region of a high-turning first-stage turbine rotor blade with a squealer tip have been measured with a straight miniature five-hole probe for the tip gap-to-chord ratio, h/e, of 2,0%. This squealer tip has a indent-to-chord ratio, $h_{st}/c$, of 5.5%. The results are compared with those for a plane tip ($h_{st}/c\;=\;0.0%$). The squealer tip tends to reduce the mass flow through the tip gap and to suppress the development of the tip-leakage vortex. Therefore, it delivers lower aerodynamic loss in the near-tip region than the plane tip does. At the mid-span, however, the aerodynamic loss has nearly the same value for the two different tips.

• 한국전산유체공학회지
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• 제20권4호
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• pp.51-57
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• 2015

In the present study, two-dimensional numerical investigation of flow past a square cylinder beneath the free surface has been performed to identify the effects of presence of the free surface. An immersed boundary method was adopted for implementation of the cylinder cross-section in a Cartesian grid system. Also, a level-set method was used to capture the interface of two fluids. To prevent transition to three-dimensional flow, Reynolds number chosen for this simulation was 150. The cases for Froude number 0.2 and gap ratio(h/D) between 0.25 and 5.00 were examined. At the specific Reynolds number, we study the effects of gap ratio on flow characteristics around a square cylinder by computing flow fields, force coefficients and Strouhal number.

• Geomechanics and Engineering
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• 제29권5호
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• pp.509-522
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• 2022

Tail-grouting is an effective measure in shield engineering for filling the gap at the shield tail to reduce ground deformation. However, the gap-filling ratio affects the value of the gap parameters, leading to different surface settlements. It is impossible to adjust the fill ratio indiscriminately to study its effect, because the allowable adjustment range of the grouting quantity is limited to ensure construction site safety. In this study, taking the shield tunnel section between Chaoyanggang Station and Shilihe Station of Beijing Metro Line 17 as an example, the correlation between the tail-grouting parameter and the surface settlement is investigated and the optimal grouting quantity is evaluated. This site is suitable for conducting field tests to reduce the tail-grouting quantity of shield tunneling over a large range. In addition, the shield tunneling under different grouting parameters was simulated. Furthermore, we analyzed the evolution law of the surface settlement under different grouting parameters and obtained the difference in the settlement parameters for each construction stage. The results obtained indicate that the characteristics of the grout affect the development of the surface settlement. Therefore, reducing the setting time or increasing the initial strength of the grout could effectively suppress the development of surface subsidence. As the fill ratio decreases, the loose zone of the soil above the tunnel expands, and the soil deformation is easily transmitted to the surface. Meanwhile, owing to insufficient grout support, the lateral pressure on the tunnel segments is significantly reduced, and the segment moves considerably after being removed from the shield tail.

• 한국의류학회지
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• 제29권11호
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• pp.1399-1409
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• 2005

The purpose of this study was to analyze the shape of gathered skirts using a three-dimensional measurement system. And in this experiment, I try to accumulate three-dimensional data of wearing model and to figure out analyzing method made by shape of clothes. The experimental design consists of two factorial designs. I set up three different kinds of fabrics, ratio of gathers. Therefore nine samples were made. The instrument and tools for three-dimensional measurement was whole body 3D scanner. Analysis program used in experiment is RapidForm 2004 PP1 and Pattern Design 2000. Data analysis utilizes SPSS WIN 10.0 Package. T-test to effect an inspection of evidence, there was difference about measurement times. One-way ANOVA to analysis effect of gather made by gathering conditions. The following results were obtained; 1. As a result of inspecting an error several times using a three-dimension measurement system, convinced data was obtained. 2. At front, distribution of gap amount was larger than back. And as ratio of gathers increased, distribution of gap amount showed regularly. 3. After analyzing horizontal sectional figure of skirts, as a height of skirt changed from waist to the bottom of skirts, the results showed as follows. While section width, section thickness, node width, node depth increased, node count decreased. 4. With the horizontal section levels of gather skirt, the silhouette on middle hip section was similar with the silhouette of body line. And as ratio of gathers around hip section increased, nodes showed regularly. At the bottom of skirts showed different nodes by different gathering condition.

• Journal of Welding and Joining
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• 제16권2호
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• pp.100-110
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• 1998

In this paper, the laser weldability of thin gage steels for automobile application is discussed. Welding was carried out with a high power carbon dioxide laser system, and the laser energy was concentrated through a plano-convex lens. Test results showed that the joint gap in the butt welding proved to be one of the critical conditions for an acceptable weld. In the case where the ratio of the gap clearance to the material thickness was slightly bigger than optimal value, the weld strength was reduced showing weld metal fracture. It was possible to obtained a weld penetration ratio of 0.91 when the vertical offset ratio was controlled to be 0.4 or smaller. Results also demonstrated that the weld strength of the lap joint was influenced by travel speed. At the travel speeds lower than 37 mm/s, the weld strength indicated higher value than that of class A recommendation strength of a resistance spot weld based on the KS code. It was clear that the complicated effect of specimen alignment should be considered so as to make a sound weld with high integrity when the laser process was applied to the long weld line.

• 대한전자공학회논문지SD
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• 제46권8호
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• pp.6-11
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• 2009

VA Mode LC를 사용하는 Full-HD급 LCOS 마이크로디스플레이에서 셀 상하 간격의 변화에 따른 전기광학적 특성의 변화에 관하여 3차원 LC code를 이용하여 연구하였다. 5가지의 다른 셀 상하 간격 (1.4 ${\mu}m$, 1.8 ${\mu}m$, 2.1 ${\mu}m$, 2.4 ${\mu}m$ 그리고 2.8 ${\mu}m$)의 변화에 따라 Reflectance-Voltage 특성, 반사광 및 반사율 분포, Optical Fill Factor 그리고 명암비를 비교하였다. Surface Anchoring 효과에 의해 상하 간격이 증가하면서 반사율은 증가하였으나 Optical Fill Factor와 명암비를 고려할 경우, 중간 수준의 간격인 2.1 ${\mu}m$ 의 특성이 가장 우수함을 확인할 수 있었다. 동일한 구조를 갖고 있는 0.7 인치 LCOS 패널을 제작하여 광학적 측정을 해 본 결과 시뮬레이션 결과와 통일함을 확인할 수 있었다.

• 한국유체기계학회 논문집
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• 제14권1호
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• pp.48-54
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• 2011

The effect of channel cutback on three-dimensional flow fields and aerodynamic losses downstream of a cavity squealer tip has been investigated in a turbine rotor cascade for the squealer rim height-to-chord ratio and tip gap height-to-chord ratio of $h_{st}/c$ = 5.51% and h/c = 2.0% respectively. The cutback length-to-camber ratio is changed to be $CB/c_c$ = 0.0, 0.1, 0.2 and 0.3. The results show that longer cutback delivers not only stronger secondary flow but also higher aerodynamic loss in the tip leakage vortex region, meanwhile it leads to lower aerodynamic loss in the passage vortex region. The discharge of cavity fluid through the cutback opening provides a beneficial effect in the reduction of aerodynamic loss, whereas there also exists a side effect of aerodynamic loss increase due to local wider tip gap near the trailing edge. With increasing $CB/c_c$ from 0.0 to 0.3, the aerodynamic loss coefficient mass-averaged all over the measurement plane tends to increase slightly.