• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.7-12
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• 2003

When the wind turbine is used in cold regions, the mechanical properties and dimension stability of the blade will be changed. The proposal of this paper is to test the durability of the blade for wind turbine. It is necessary to select the most comfortable materials and fabrication processes for more stable wind turbine blade in cold regions. To select the most comfortable materials and processes, the static strength has to know through the tensile static tests at the severe condition as cold regions. First, the tensile static specimens made by RIM (Resin injection molding) process & vacuum bagging process with reinforcement materials and resin. Tensile static tests were carried out on three laminate lay-ups (carbon prepreg, carbon fiber dry fabric and glass fiber dry fabric) at different test temperature($24^{\circ}$, $-30^{\circ}$), determining properties such as the mechanical strength, stiffness and strain to failure. At different test temperature, in order to test the tensile strengths of these specimens used the low temperature chamber. Next, the results of this test were compared with each other. Finally, the most comfortable materials and fabrication processes can select based on these results. The results show the changes in the static behavior of three laminate lay-ups at different test temperatures. At low temperatures, the static strengths are higher than the ones at room temperature.

• 한국정밀공학회지
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• 제24권1호
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• pp.57-63
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• 2007

Wire drawing process of the high carbon steel with a high speed is usually conducted at room temperature using a number of passes or reductions through consequently located dies. In the multi-pass drawing process, temperature rise in each pass affects the mechanical properties of the final product such as bending, torsion, and tensile property, etc. This temperature rise during the deformation promotes the occurrence of delamination, and deteriorates the torsion property and durability of wire. This study investigates the occurrence of delamination in the wire through the torsion test and the evaluation of wire temperature. The excessive wire temperature leads to the occurrence of the delamination. Based on the calculation of the wire temperature, a new pass schedule, which can prevent the delamination due to the excessive wire temperature rise, is designed through the isothermal pass schedule.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1977-1979
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• 1996

Single-crystaIline silicon diaphgrams and features are fabricated without using an etch stop process. The process involves vertical dry etching, double-sided alignment, followed by wet-chemical etching from the back side. The abvantages of this process are that $5{\sim}50{\mu}m$ diaphgrams and features can be fabricated accurately and inexpensively. In addition, since no impurity-based process is introduced, highly uniform and homogenous properties can be achieved

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1652-1663
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• 2002

It is desirable to perform nondestructive evaluation to assess material properties and part homogeneity because manufacturing of carbon/carbon (C/C) composites requires complicated and costly processes. In this work several ultrasonic techniques were applied to carbon/carbon composites for the evaluation of spatial variations in material properties that are attributable to the manufacturing process. In a large carbon/carbon composite manufactured by chemical vapor infiltration (CVI) method, the spatial variation of ultrasonic velocity was measured and found to be consistent with the densification behavior in CVI process in order to increase the density of C/C composites. Ultrasonic velocity and attenuation depend on a density variation of materials. Low frequency through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity These results were compared with that obtained by dry-coupling ultrasonics. Pulse-echo C-scans was used to image near-surface material property anomalies such as the placement of spacers between disks during CVI. Also, optical micrograph had been examined on the surface of C/C composites using a destructive way.

• 한국물환경학회지
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• 제33권3호
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• pp.273-281
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• 2017

The objective of this study is to evaluate the performance of stream purification equipment system combined MBP (Micro Bubble Process) and AGBP (Aerobic Granular Biofilm Process). Based on results, the optimal HRT (Hydraulic Retention Time) of MBP and AGBP set as 0.72 and 2.4 h, respectively. In the results of continuous operation on combined MBP and AGBP, it is possible to achieve a BOD, TSS and T-P removal efficiency of 85, 90 and 94%, respectively. It also confirmed that the water quality of the stream can be purified with increasing circulation flow through water simulation evaluation applied the QUAL-NIER model. Consequently this purification system can resolve the stream purification and dry stream problem.

• 대한한의학원전학회지
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• 제35권3호
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• pp.91-106
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• 2022

Objectives : To examine the developmental process of the Pi-Yin theory since the Huangdineijing to Miu Xiyong. Methods : Related contents since the Huangdineijing to Miu Xiyong was searched to examine the development of the Pi-Yin theory. Results & Conclusions : In the Huangdineijing and Shanghanzabinglun, the origin of the Pi's body fluids that nurtures everywhere is explained to be the Wei, which limited the development of the Pi-Yin theory. Liu Wansu understood tonification of the Pi by means of moistening medicinals to mean adding Pi-Yin based on the manifestation of dryness in the case of dampness deficiency which is the main Qi of the Pi and Wei. Zhu Danxi understood adding Pi-Yin as accomplished by supplementing Blood. The understanding of the nature of Pi to be 'likes dryness and hates dampness' leading to thinking that drying dampness tonifies the Pi was the reason why the Pi-Yin theory could not develop fully. Miu Xiyong accepted theories of both Li Dongyuan and Zhu Danxi, and constructed the Pi-Yin theory to bring caution to the unwanted effects of using Baizhu wrongly. Through examination of the developmental process of the Pi-Yin theory, it could be understood that rather than focusing on the physiological function of the Pi-Yin and ways of maintaining its proper functioning, the theory was developed to bring caution to using medicinals with dry and hot properties that could dry the Pi-Yin.

• Geomechanics and Engineering
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• 제36권1호
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• pp.9-18
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• 2024

With the rapid development of highways and railways, series of traffic safety issues emerged because of mudstone disintegration. To research on the mechanism and further guarantee the stability and safety of transportation infrastructure built on or near mudstone formations, the mudstone disintegration test of mudstone was carried out based on mudstone and sandy mudstone. The element types, cementation characteristics and pore characteristics of the tested specimens were studied by means of Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Image Pro Plus (IPP). The disintegration index of mudstone was approximately 1%, and even some specimens were difficult to be calculated, while the disintegration index of sandy mudstone is approximately 8.7%. According to the results, the two mudstones belong to grade II and III disintegration respectively, of which the sandy stone presents more extensive disintegration than mudstone. This phenomenon was distinguished that, the clay minerals of mudstone are approximately 25% more abundant than those of sandy mudstone, and the unit pore area is 20 ㎛² larger, which result in different microstructure and water absorption capacities. In the liquid phase, the ions in the mudstone specimens were exchanged and combined with water molecules in the environment during the whole disintegration process. This results in continuous spalling and fragmentation of clay minerals, the emergence of secondary fractures, and the deepening of primary fractures.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.236-239
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• 2003

The spent fuel slitting device is an equipment developed in order to feed UO$_2$pellet to the dry pulverizing/mixing device. In this study, we have compared and analyzed the handling method of the slitting and that of the pellet and hull, processing time, separating time for 20kgHM, the number of blades, on the existing slitting device using in DUPIC, and spent fuel management technology research and test facility. Also, we have compared and analyzed about an advantage and weak point, designing and producing, processing, establishment, operation, maintenance about the vertical and horizontal slitting device. Based on these results, we have developed the vertical slitting device. By using the results, we have enhanced the slitting processing time(over 40%)in comparison with DUPIC device, and it will is effectively applied to available data for designing and producing of the hot test facility.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.51-56
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• 2006

Biases embedded in numerical weather precipitation forecasts by the RDAPS model was determined, quantified and corrected. The ultimate objective is to eventually enhance the reliability of reservoir operation by Korean Water Resources Corporation (KOWACO), which is based on precipitation-driven forecasts of stream flow. Statistical post-processing, so called MOS (Model Output Statistics) was applied to RDAPS to improve their performance. The Artificial Neural Nwetwork (ANN) model was applied for 4 cases of 'Probability of Precipitation (PoP) for wet and dry season' and 'Quantitative Precipitation Forecasts (QPF) for wet and dry season'. The reduction on the large systematic bias was especially remarkable. The performance of both networks may be improved by retraining, probably every month. In addition, it is expected that performance of the networks will improve once atmospheric profile data are incorporated in the analysis. The key to the optimal performance of ANN is to have a large data set relevant to the predictand variable. The more complex the process to be modeled by the ANN, the larger the data set needs to be.

• 항공우주시스템공학회지
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• 제10권1호
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• pp.29-34
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• 2016

Flutter wind-tunnel test is an expensive and complicated process. Also, the test model may has discrepancy in the structural characteristics when compared to those of the real model. "Dry Wind-Tunnel" (DWT) is an innovative testing system which consists of the ground vibration test (GVT) hardware system and software which computationally can be operated and feedback in real-time to yield rapidly the unsteady aerodynamic forces. In this paper, we study on the aerodynamic forces of DWT system to feedback in time domain. The aerodynamic forces in the reduced-frequency domain are approximated by Minimum-state approximation. And we present a state-space equation of the aerodynamic forces. With the two simulation model, we compare the results of the flutter analysis.