• International Journal of Automotive Technology
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• v.3 no.4
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• pp.157-163
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• 2002

It is well recognized that the ultrasonic method is one of the most common and reliable nondestructive testing (NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interfacial crack length in the adhesively bonded joints of double-cantilever beam (DCB). An optimal condition of transmission coefficients and experimental accuracy by the ultrasonic method in the adhesively bonded joints have been investigated and discussed. The experimental values are in good agreement with the computed results by boundary element method (BEM) and Ripling's equation.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.4
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• pp.171-178
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• 1996

DCB(pure mode I) and CLS(mixed mode) tests were performed to investigate the effect of fracture mode on the interlaminar fracture of composite laminate. Mode I critical strain energy release rate was found to be $133J/m^2$ from the DCB test and total strain energy release rate decreased from $1, 270J/m^2$ as thickness ratio(tl/t) varied from 0.333 to 0.667 from the crease from the CLS test. Crack length had no effect on the total strain energy release rate and load was almost constant during the crack growth of the specimen which had the specific thickness ratio. Crack initiated when the stress of the strap ply reached constant stress $42kgf/mm^2$ which was found to be independent of the thickness ratio.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.1
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• pp.43-48
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• 2021

Most existing studies on the wide-area differential global positioning system (WADGPS) used standard positioning service (SPS) receivers in their observation reference stations which provide the central control station global positioning system (GPS) measurements to generate augmentation data. In the present study, it is considered to apply a precise positioning service (PPS) receiver to an observation reference station which is located in the threatened jamming area. Therefore, the reference station network consists of a PPS receiver based observation reference station and SPS receiver based observation reference stations. In this case, to maintain correction performance P1C1 differential code bias (DCB) should be compensated. In this paper, P1C1 DCB estimation algorithm was applied to the PPS/WADGPS system and performance test results using measurements in the Korean Peninsula were presented.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.101-105
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• 2019

The adhesion reliability of the epoxy molding compound (EMC) and the printed circuit board (PCB) interface is critical to the quality and lifetime of the chip package since the EMC protects PCB from the external environment during the manufacturing, storage, and shipping processes. It is necessary to measure adhesion energy accurately to ensure product reliability by optimizing the manufacturing process during the development phase. This research deals with the measurement of EMC/PCB interfacial adhesion energy of chip package that has warpage induced by the coefficient of thermal expansion (CTE) mismatch. The double cantilever beam (DCB) test was conducted to measure adhesion energy, and the spring back force of specimens with warpage was compensated to calculate adhesion energy since the DCB test requires flat substrates. The result was verified by comparing the adhesion energy of flat chip packages come from the same manufacturing process.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.357-364
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• 2002

The resistance curves (R-curves) for 381 m crack extension of CLWL-DCB specimens had been determined. The average velocities of the crack extension measured with strain gages were 0.70 and 55 ㎜/sec. The measured rotation angle of the notch faces showed the existence of the singularity at least before 171 and 93 mm crack extensions for the 0.70 and 55 ㎜/sec crack velocities, respectively. The maximum slopes of the R-curves occurred between 25 and 89 ㎜ crack extensions for 0.70 ㎜/sec crack velocity and between 51 and 127 ㎜ crack extensions for 55 ㎜/sec crack velocity During the maximum slopes of the R-curves, the micro-crack localization can be expected, and faster crack velocity may form longer micro-cracking and micro-crack localizing zones. The fracture resistance of 0.70 ㎜/sec crack velocity reached a roughly constant maximum value of 143 N/m at 152 ㎜ crack extension, while that of 55 ㎜/sec crack velocity increased continuously to 245 N/m at 254 ㎜ crack extension and then decreased to the value of 0.70 ㎜/sec crack velocity. The R-curve of 55 ㎜/sec crack velocity was similar to that of the small size three-point bend test, and it showed that small size specimen or fast crack velocity could cause more brittle behavior.

• Herbal Formula Science
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• v.13 no.2
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• pp.41-57
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• 2005

This study has been carried out to understand the effect of Danchisoyosangagambang (DC) on the hyperglycemic mice induced with streptozotocin(STZ). Experimental groups were made diabetic mice by intraperitoneal injection of STZ(60 mg/kg of body weight) tw ice by 24 h interval and then 120 mg/kg STZ was injected again 3 days after the earlier treatment. Control group was administered mice with 0.9 % saline(2 mL/kg), and experim ental groups were administered DC extract(DCA group, 10 mg/kg/day; DCB group, 30 mg/kg/day) after hyperglycemic induction for 6 weeks. The body weight of experimental groups was lower than control. The blood glucose concentration increased continuously, rea ching to 298.9 mg/dL after 6 weeks, however, experimental groups of the DCA and DCB groups significantly(p<0.0l) decreased in the 4, 5, and 6 weeks groups. Blood glucose tolerance test was not significant between control and experimental groups. We examined the blood transaminase activities to know the effect of herbal medicine on liver function. The GOT activities were lower in group DCB than in control. The GPT activities were lower in group DCA and DCB than in control. The content of triglyceride was significantly increased in group DCA compared to control. The SOD and catalase activities were higher in the group DCA compared to control. The results of immunohistochemical study, a few of insulin positive cells observed in the control and experimental group. These results suggest that administration of DC extract to the hyperglycemic mice decreased the blood glucose level.

• Composites Research
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• v.32 no.2
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• pp.102-107
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• 2019

Several studies related to reinforce composites structures in the through thickness direction have been developed along the years. As follows, in this study a new reinforced process is proposed based on previous experimental results using a novel stitching process in T-joints and one-stitched specimens. It was established the need to perform more analysis under standard test methods to obtain a better understanding. FEM analysis were compared after performed mode I interlaminar fracture toughness test, using different stitching patterns to analyze the through thickness strength with reference laminates without stitching. The stitching patterns were defined in $2{\times}2$ and $3{\times}3$, where the upper and lower head of the non-continuous stitching process (I-Fiber) has proven to influence in a higher through thickness strength of the laminate. In order to design the numerical model, cohesive parameters were required to define the surface to surface bonding elements using the cohesive zone method (CZM) and simulate the crack opening behavior from the double cantilever beam (DCB) test.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.719-724
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• 2009

In this study, DCB(double cantilever beam) specimens of woven fabric carbon/epoxy and glass/epoxy were manufactured and mode I fracture toughness of specimen was measured according to ASTM 5528-01. And FE analysis was conducted in the same condition and evaluated the behavior of delamination analytically. Mode I fracture toughness measured by test was $845.7\;J/m^2$ in the case carbon/epoxy and that of glass/epoxy was $1,042\;J/m^2$. FE analysis was conducted using cohesive elements for adhesive layer and applied measured fracture toughness. To verify the result of analysis, the reaction force measured at the end of specimen and that calculated by Timoshenko beam theory were compared. The numerical results show good agreements with the measured one.

• Composites Research
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• v.26 no.2
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• pp.129-134
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• 2013

The strength of adhesive joints employed in composite structures under cryogenic environments, such as LNG tanks, is affected by thermal residual stress generated from the large temperature difference between the bonding process and the operating temperature. Aramid fibers are noted for their low coefficient of thermal expansion (CTE) and have been used to control the CTE of thermosetting resins. However, aramid composites exhibit poor adhesion between the fibers and the resin because the aramid fibers are chemically inert and contain insufficient functional groups. In this work, electrospun meta-aramid nanofiber-reinforced epoxy adhesive was fabricated to improve the interfacial bonding between the adhesive and the fibers under cryogenic temperatures. The CTE of the nanofiber-reinforced adhesives were measured, and the effect on the adhesion strength was investigated at single-lap joints under cryogenic temperatures. The fracture toughness of the adhesive joints was measured using a Double Cantilever Beam (DCB) test.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.99-100
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• 2006

지금까지 국내 디지털 보호계전기의 성능 검증은 동작치 특성 시험 등 정특성시험(steady-state performance) 검증 위주로 수행되어 왔으며, 신규개발 디지털 보호계전기 및 신규 도입 디지털 보호계전기에 대해서는 정특성 시험과 함께 시뮬레이터를 이용한 동특성 시험을 병행하여 왔다. 동특성 시험은 보호계전기에 내장된 계전요소들의 유기적인 성능을 검증할 수 있는 시험으로서 복수 개의 보호계전요소를 탑재하고 있는 디지털 보호계전기를 검증하기 위해서는 필수적인 성능검증 수단이다. 그러나 이러한 장점들과 편리함에도 불구하고 디지털 보호계전기의 성능검증에 사용되는 계통 모델이 실 계통을 정확하게 반영하지 못할 경우 검증 결과의 신뢰성을 보장하기가 어렵다. 본 논문에서는 154kV 송전선로 보호용 디지털 보호계전기의 성능 검증을 위한 기반 구축 과정 및 결과에 대해서 기술한다.