• International Journal of Highway Engineering
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• v.2 no.4 s.6
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• pp.123-131
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• 2000

The compaction equipment and the Marshall stability head are the two important testing equipment for the Marshall test. The compaction equipment is closely related to the air void, VMA and compactability of the mixtures, and the stability head is related to the Marshall stability and the flow, therefore the size and the shape of the equipment is essential for finding the accurate optimum asphalt content for the asphalt mix design. However, the size and the shape of the equipment currently used and the condition of the installation of compaction pedestal in this country are different from each agency and manufacturer. The national inspection of the Marshall equipment is necessary because the difference can affect the test results and also the performance of the asphalt pavement.

• 전기의세계
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• v.24 no.2
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• pp.25-32
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• 1975

경제개발의 추진과 국민생활수준의 향상으로 에너지 소비는 매년 신장되고 있는 중에서도 수송 및 변환이 용이하고 사용에 편리한 전력의 수요는 계속적으로 증가하고 있다. 이에 반하여 한정된 에너지 자원의 편재 특히 산유국의 자의적인 가격인상에 따라 소위 에너지파동에 심각하게 되는 한편, 다른 산업분야와 마찬가지로 전력사업에 의한 공해내지 환경오염의 문제가 심각하게 부각되어 일부 선진국에서는 전원개발에 큰 타격을 주고 있는 실정에 있다. 우리나라에서는 아직까지는 그렇게 심각하지는 않으나 전원개발의 계속적인 추진에 따라서 전력계통의 공해문제가 곧 심각하게 부각될 것이 예상되므로 전력계통의 공해의 요인과 그 방지책을 요약해 보고저 한다.

• Journal of the Korean GEO-environmental Society
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• v.18 no.2
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• pp.39-45
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• 2017

This paper is to grasp the applicability of a cumulative rebound angle measured from the rebound action generated after impacting an object for the assessment of compressive strength of construction materials nondestructively and to propose the test results. For this study, an impact device was devised and used for impacting an object by an initial rotating free falling impact and following repetitive impacts from the rebound action which eventually disappears. Five types of construction materials, which are soil cement, cement paste, wood (pine tree), and two types of rock (shale and granite), were tested and both peak rebound angle and cumulative rebound angle were measured for each material by using a high-speed camera. The measured angles were compared with the directly measured compressive strength for each material. The comparison showed that for materials such as cement and rock the cumulative rebound angle, which reflects energy dissipation, rather than the peak rebound angle is more appropriate indicator for assessing the compressive strength of a material, but for a construction material such as wood which has a high toughness the magnitude of rebound is not an indicator to assess the compressive strength of a material.

• Land and Housing Review
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• v.6 no.3
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• pp.139-145
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• 2015

To improve the pile design efficiency(design bearing capacity/the strength of materials) from 70 percent(160tonf) to 80 percent(190tonf), this paper analysed the existing pile loading test data and performed the precise dynamic loading test and Bi-directional loading test for the first time in Korea. Analysis result of the existing dynamic loading test data by Davisson method showed that bearing capacity of piles penetrated at weathered rock stratum(N=50/15) exceeded 190tonf. But the analysis result by CAPWAP method showed that piles less than the target bearing capacity were 40% due to the lack of impact energy. To get the target bearing capacity from the dynamic loading test, using the hammer over 6tonf to trigger the enough impact energy is necessary. Allowable bearing capacty of Bi-directional static loading test by Davisson method was 260.0~335tonf(ave. 285.3tonf) and exceeded overwhelmingly the target capacity. And this exceeded the bearing capacity of precise dynamic loading test(ave. 202.3tonf) performed on the same piles over 40%. The difference between the capacity of Bi-directional loading test and dynamic loading test was caused by the insufficient impact energy during dynamic loading test and increase by interlocking effect by near piles during Bi-directional static loading test.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.1
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• pp.47-56
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• 2009

Rock bolts and shotcrete play a crucial role as a main support system in the underground space. Thus, the safety of the underground space may be affected by the defect of rock bolts. In order to evaluate the rock bolt integrity by using non-destructive technique, the transmission method of the guided ultrasonic waves, which are generated by using the piezo disk elements has been successfully performed. The energy generated by the piezo disk elements, however, is not enough for the rock bolts in the field. In addition, the piezo disk elements should be installed at the end of the steel bar during construction of the rock bolts. The purpose of this study is the devolvement of the reflection method, which may generate enough energy, and the application in the field rock bolts. Both laboratory and field tests are carried out. The guided ultrasonic waves with high energy are generated by the hammer impact with the center punch, and the AE sensor is used to measure the reflected guided waves. The received guided waves are analyzed by the wavelet transform. The peak value of the wavelet transform produces the energy velocity, which is used for the evaluation of the rock bolt integrity. The energy velocity increases with an increase in the defect ratio in both laboratory and field rock bolts. This study demonstrates that the hammer-impact reflection method may be a suitable method for the evaluation of the rock bolt in the field.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.180.2-180.2
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• 2005

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.197-199
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• 2013

• 해운
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• s.81
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• pp.11-16
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• 2011

2011년 1분기에는 예기치 못한 일본 대지진과 중동사태 등으로 세계경제는 큰 타격을 입었으며 그로 인해 신재생 에너지 개발과 에너지 효율적인 경제구조 확립, 부품 소재 산업의 경쟁력 강화와 공급처 다변화의 중요성이 대두되었다. 이에 따라 한국 경제는 그 전략을 점진적으로 세워야 한다는 지적이 나왔다. 그러므로 우리는 이 시점에서 세계경제를 분석하고 한국 경제의 중장기적인 계획을 세워 보아야 할 필요가 있다. 다음은 삼성경제연구소에서 발표한 "2011년 세계경제 및 한국경제 전망"의 주요 내용을 정리 요약한 것이다.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.154-160
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• 2004

Hydraulic breaker of excavator has been used for the destruction and disassembling of buildings, crashing road pavement, breaking rocks at quaky and etc. The performance of breakers is evaluated their own destructive force and the number of impact by input hydraulic flow rate and pressure on the operating conditions. Because hydraulic breakers generate high impact energy, the accurate measurement of the impact force has been facing a technical challenge. In this study, the hydraulic pressure transducer system was developed based on the characteristics of pressure variation in closed vessel fur testing the impact energy. The hydraulic pressure transducer system is consisted with a hydraulic cylinder, main base, pressure & temperature sensors, LVDT, data acquisition system and etc. The developed hydraulic pressure transducer system was applied to measure the impact energy for hydraulic breaker. The measured impact force was 438.8 kgf.m within the designed impact force bounds. The developed hydraulic pressure transducer system as a simple tester could be applied to measure the impact force and the number of impact.

• 연구논문집
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• s.32
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• pp.45-53
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• 2002

Hydraulic breaker attached excavator generally used for the destroying and disassembling of buildings, crashing road pavement, breaking rocks at quarry and etc. The developed breaker are determined their own destructive force and number of impact by the input hydraulic flow rate and pressure than the operating conditions, In this study, the characteristics of pressure variation in closed vessel is invested for testing the impact energy of hydraulic breaker. To test the impact energy, the test system is designed as a mechanism consisted with a hydraulic cylinder, main base, pressure sensor, LVDT, data acquisition system and etc.. The developed test system is applied to measure the impact energy for hydraulic breaker. The proposed testing method could be applied for conventional impact test and the control system evaluation for hydraulic breakers.