• International Journal of Naval Architecture and Ocean Engineering
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• 제7권2호
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• pp.315-323
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• 2015

The weld scallop has been used for joining T-bars. There are a lot of weld scallops in shipbuilding. It is difficult to perform scallop welding due to the inconvenient welding position. This results in many problems such as porosity, slag inclusion, etc. In this study, a new method is devised to remove weld scallops by incorporating a Ceramic Backing Material (CBM). The weld scallop is removed by an elongation of the v groove. In order to insert a CBM into the groove without a weld scallop, a wedge-shaped CBM is developed. The top side of the developed CBM is similar to the shape of a general back bead. The bottom surface has a saw-toothed shape for cutting at a suitable length. This can be attached to the root side of a face plate using adhesive tape, just like a general CBM. Welding experiments in normal and abnormal conditions are carried out and the possibility of burn-through is examined. This CBM's applicability to shipbuilding is verified.

• 열처리공학회지
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• 제3권2호
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• pp.32-36
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• 1990

For the accurate measurements of hardness in a material, it is necessary to have a thorough understanding of the effects of test variables on the accuracy of hardness value. For the rebound hardness test, major test variables are the radius of hammer ball tip, type of backing materials, size and roughness of the specimen. In this study, effects of these variables on Equo-Tip hardness value were investigated. Hardness measurements were carried out using WC balls with various sizes of worn-ot zone. The sample materials chosen for the experiments were commercial standard hardness blocks and SM45C steel bars subjected to either normalization or quench and temper treatments. As backing materials, aluminum, steel and rubber plates were used in all the experiments. Experimental results show that for the accurate measurements of Equo-tip hardness, it is necessary to use the hammer ball with a worn-out zone parameter of less than 0.23, and the recommended minimum thickness and width of the specimen are 25mm and 70mm, respectively. Further for the surface preparation, the specimens need to be polished with an emery paper of No. 400 or finer, and for the backing matrials, it is recommended to use steels or rubbers.

• 비파괴검사학회지
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• 제35권2호
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• pp.112-119
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• 2015

고해상도 분자 영상이 가능한 광음향 현미경의 공간해상도는 초음파 변환기에 의해 결정되기 때문에 높은 동작 주파수, 광대역, 높은 신호 수신 효율을 갖는 광음향 수신 변환기는 고성능 광음향 현미경에 필수적이다. Polyvinylidene fluoride (PVDF)는 이러한 광음향 수신 변환기 성능 확보가 가능한 압전소재이다. 그러나 PVDF는 낮은 음향 임피던스로 인해 사용되는 흡음층에 의해서 중심주파수 및 대역폭이 영향을 받게된다. 본 논문에서는 광음향 현미경에 적합한 PVDF 기반 고주파수 초음파 수신 변환기의 최적 흡음층 소재의 음향 임피던스가 최종 변환기 성능에 어떠한 영향을 주는지에 관한 연구를 수행하였다. 이를 위해 EPO-TEK 301, E-Solder 3022, RTV를 각각 흡음층 물질로 사용하여 고주파수 초음파 수신 변환기를 제작하고 그 음향 특성을 평가하였다. 제작된 변환기의 공간해상도를 평가하기 위해 $25{\mu}m$ 직경을 갖는 철심을 표적으로 사용하여 영상을 획득하였으며, 실험을 통해 얻은 펄스-에코 신호 크기 및 중심주파수, -6 dB 대역폭, 공간해상도 평가를 통해 PVDF의 음향 임피던스보다 약간 높은 음향 임피던스를 갖는 EPO-TEK 301이 가장 적합한 흡음층 물질임을 알 수 있었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1999년도 춘계학술발표강연 및 눈문개요집
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• pp.19-19
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• 1999

• 한국세라믹학회지
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• 제32권3호
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• pp.366-370
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• 1995

The ballistic efficiency of alumina tiles with various sizes, shapes, and target configurations was measured by the thick backing plate technique. The ballistic efficiency of square tiles roughly 8 mm thick struck by 12.7mm diameter bullets rapidly increased with tile size up to about 100mm, then tended to saturate. Circular shape tiles had lower ballistic efficiencies than those of square shape tiles for the same width and thickness. Small tiles (50mm) that were recessed in aluminum wells had a significantly higher ballistic efficiency than tiles placed on a flat surface. However, the difference in the ballistic efficiency between the two target configurtions became small at larger tile sizes. All the results could be explained by the effect of reflected waves at edges and the propagation of resulting cracks on the penetration process.

• 한국정밀공학회지
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• 제17권6호
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• pp.96-102
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• 2000

The finishing process for dies and molds is an important process because it has influence on final quality of products. And it is difficult to automatize finishing process so that the process has depended on expert's skill until now. However, recently a study on development of die automatic finishing machine has been progressed, and actually this machine is applied to fabrication of die. But the research about tooling system is not enough and finishing tool must have high machining efficiency and adaptability of curved surface. So, this study investigated the application of conductive elastic tool which is composed of metal-resin bonded pellet and elastic backing material. The metal-resin bonded pellet is used to finish the surface by conventional mechanical grinding or electro-chemial grinding method. And elastic backing material is used to follow the curved surface. So conductive elastic tool has long lifetime, uniform removal rate and adaptability of curved surface.

• 대한음성학회지:말소리
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• 제65호
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• pp.13-36
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• 2008

This paper attempts to analyze the characteristics of Korean vowel production by 12 Korean native speakers and 36 adult learners. The analyses have been performed with investigations of F1and F2 values. Results showed that there's no significant difference between /ㅔ/ and /H/ and between /ㅗ/ and /ㅜ/ in Korean native speakers' pronunciations. The distinguishing tendencies found in the analyses of foreign learners' pronunciations are fronting and lowering of /ㅗ/ by English speakers, backing and heightening of /ㅓ/ by Japanese speakers and backing and lowering of /ㅏ/ by Chinese speakers. For the limitations of this paper, it has a meaning of a preliminary study and could be developed into further research to show the order of acquisition and L1 transference.

• 제어로봇시스템학회논문지
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• 제19권9호
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• pp.755-759
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• 2013

A broad-band underwater acoustic transducer that uses thickness vibration mode, derived from a disk type piezoelectric ceramic, has been proposed and designed for DVL (Doppler Velocity Log). Three different types of acoustic transducer were evaluated with respect to the transmitting voltage response, receiving voltage sensitivity and bandwidth of the transducer. The effect of the acoustic impedance matching layer and backing layer is discussed. The results demonstrated that three matching layer with lossy backing layer is the best configuration for underwater transducer. The trial underwater acoustic transducer with three matching layer has a frequency bandwidth of 55%, maximum transmitting voltage response of 200 dB and a maximum receiving voltage sensitivity of -187.3 dB.

• ETRI Journal
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• 제34권5호
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• pp.696-705
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• 2012

Accurate synthesis models based on artificial neural networks (ANNs) are proposed to directly obtain the physical dimensions of an asymmetric coplanar waveguide with conductor backing and substrate overlaying (ACPWCBSO). First, the ACPWCBSO is analyzed with the conformal mapping technique (CMT) to obtain the training data. Then, a modified genetic-algorithm-Levenberg-Marquardt (GA-LM) algorithm is adopted to train ANNs. In the algorithm, the maximal relative error (MRE) is used as the fitness function of the chromosomes to guarantee that the MRE is small, while the mean square error is used as the error function in LM training to ensure that the average relative error is small. The MRE of ANNs trained with the modified GA-LM algorithm is less than 8.1%, which is smaller than those trained with the existing GA-LM algorithm and the LM algorithm (greater than 15%). Lastly, the ANN synthesis models are validated by the CMT analysis, electromagnetic simulation, and measurements.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.255-257
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• 2004

This report presents S-N testing results of the butt and T-joint weldment which are produced by single sided welding with cenramic backing material. The specimen is designed in accordance with JISZ 3103 aid the test is peformed by the JSME S002. The nominal and hot spot stress based design S-N curves derived from fatigue tests are compared with the BS design curve. For butt and T-joint, it can be known that the double-sided butt welding process could be replaced by the single sided butt welding.