• Journal of Korea Foundry Society
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• v.20 no.3
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• pp.167-172
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• 2000

Squeeze casting was performed to fabricate the SiC whisker reinforced magnesium matrix composites, and the suitability of the squeeze casting for the production of the sound composites was determined by micro/macro-structures observations and tensile test. The two-directional infiltration of the melt and the removal of air during infiltration using the devised mold were necessary to produce the composites. The pressure of 100 MPa was effective for the production of composites with the SiC whisker volume fraction of 30%, but the pressure should be lower than 50 MPa in case of below 20% in the volume fraction. The SiC whiskers in the squeeze cast composites were randomly and densely aligned, and the SiC whiskers/magnesium interfaces were continuously well-bonded. The elastic modulus, 0.2% proof stress and tensile strength in the composite were about 2.5times, l0times and 4times as large as those of magnesium, respectively, indicating that the squeeze casting sufficiently provides the high strength magnesium composites reinforced with SiC whiskers.

• Speech Sciences
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• v.11 no.2
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• pp.105-117
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• 2004

Recently, many scholars have emphasized the importance of English listening ability for smoother communication. Most audio materials, however, were recorded in a quiet sound-proof booth. Therefore, students who have spent so much time listening to the ideal audio materials are expected to have difficulty communicating with native speakers in the real life. In this study, we examined how well thirty three Korean university students and five native speakers will repeat the recorded English sentences under noise and speed conditions. The subjects' production was scored by listening to each recorded sentence and counting the number of words correctly produced and determined the percent ratios of correctly produced words to the total words in each sentence. Results showed that the student group correctly repeated around 65% of all the words in each sentence while the native speakers demonstrated almost perfect match. It seemed that the students had difficulty perceiving and repeating function words in various conditions. Also, high-proficiency student group outperformed the low-proficiency student group particularly in their repetition of function words. In addition, the student subjects' accuracy of repetition remarkably dropped when the normal sentences were both sped up and mixed with noise. Finally, it was observed that the Korean students' percent correct ratio fell down as the stimulus sentence became longer.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.379-381
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• 2008

본 논문에서는 도시의 소음문제와 기존 방음벽의 문제를 근본적으로 해결하기 위해서는 도시 생태계를 고려한 생태식생방음벽의 개발이 필요하며 이를 위해 시스템 및 소재개발, 설계 및 시공기술들을 개발이 필요하다. 방음벽의 소음의 저감을 위한 단순한 구조물차원을 벗어나 소음 저감 기능을 가지는 환경친화적인 녹화구조물로 개발될 필요가 있다. 이는 절대 녹지의 부족과 단절로 인해 파생되는 도시 생태적 문제를 적극적으로 해결할 수 있는 현실적인 대안이 될 수 있을 뿐만 아니라, 도시경관 및 운전자와 주민 정서의 순화에 크게 기여할 것으로 예상된다. 결론적으로, 도시생태환경에 악영향을 가져왔던 기존의 방음벽에 반해서, 도시 전체적으로 녹지의 확대와 더불어 경관의 향상, 생태계 복원 등 시너지 효과를 가져올 식생방음벽의 개발은 도시환경의 질적 개선을 위한 현실적인 대안으로 연구 개발이 필요하다고 판단된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.4796-4801
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• 2014

To increase the riding comfort and running stability of articulated type high speed railway vehicles(HSRV), it is important that the gangway connections for the passenger car satisfied fire safety, sound proof and durability under triaxial angular displacement (rolling/yawing/pitching) modes. On the other hand, a domestic test standard on the durability of the rubber components has not been determined. In this study, the fatigue life was predicted using the results of the nonlinear finite element analysis and the fatigue properties. Moreover, a fatigue rig test of the component was constructed to examine the durability.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.10
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• pp.104-110
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• 2008

Desire about agreeable habitat by enhancement of standard of living has been increased, and common complaints by transformer noise have been happening constantly. It has been installed resonator and sound-proof shutter in order to solve substation's noise problems. But those methods are not effective. Therefore, It is necessary to study transformer noise level that can satisfy noise regulation standard. In this paper described that predicted transformer noise level of substation boundary by operating situation at the indoor substation. Also, Presented most suitable noise level of transformer that satisfy noise regulation standard at the indoor substations through predicted results.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.9
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• pp.705-709
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• 2016

Micro-electro-mechanical systems (MEMS) gyroscopes are widely used in various robot applications. However, these conventional gyroscopes need to vibrate the proof mass using a built-in actuator at a fixed resonance frequency to sense the Coriolis force. When a robot is not moving, the meaningless vibration of the gyroscope wastes power. In addition, this continuous vibration makes the sensor vulnerable to external sound waves with a frequency close to the proof-mass resonance frequency. In this paper, a feasibility study of a new type of gyroscope inspired by insect halteres is presented. In dipterous insects, halteres are a biological gyroscope that measures the Coriolis force. Wing muscles and halteres are mechanically linked, and the halteres oscillate simultaneously with wing beats. The vibrating haltere experiences the Coriolis force if the insect is going through a rotational motion. Inspired by this haltere structure, a gyroscope using a thin mast integrated with a robot actuation mechanism is proposed. The mast vibrates only when the robot is moving without requiring a separate actuator. The Coriolis force of the mast can be measured with an accelerometer installed at the tip of the mast. However, the signal from the accelerometer has multiple frequency components and also can be highly corrupted with noise, such that raw data are not meaningful. This paper also presents a suitable signal processing technique using the amplitude modulation method. The feasibility of the proposed haltere-inspired gyroscope is also experimentally evaluated.

• Journal of the Korea Organic Resources Recycling Association
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• v.9 no.4
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• pp.89-98
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• 2001

Present vermicomposting technology needs the broad land. Because of the high land cost, the land saving technology such as multistage must be needed. And present operation practices are mostly based on human power, mechanization and automation is needed. Also, present control practices based on individual experience need the scientific base control system. Even though the rough estimation of organic waste treatment showed that vermicompostiong could obtain more benefits than costs. But, the estimation is based on an ideal case without considering the technical and market. Generally, vermicomposting is considered as the more expensive technology than composting. Therefore, the practical proof the economic factor would be the most important to the market increase. Vermicomposting as the recycling technology has better condition than incineration and landfill. Propagation and advocating focused on its environmentally sound aspects would be needed continuously. Especially, demonstration and distribution of household vermicomposting would be a good approach. Vermicomposting facilities area was becoming larger, and earthworm feeding materials were also expanding to various organic sludges. These trends showed that vermicomposting is being enlightened to treat and recycle the organic wastes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.468-474
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• 2020

Metal ducts for transporting air conditioning and heating inside ships have recently been replaced by cloth ducts that have the advantage of delivering air evenly to the compartments, with excellent noise reduction in major compartments, such as combat command rooms, steering rooms, and sound detector cabins. Since the performance requirements of fabric ducts for vessels are strict, and the entire length of the ducts was imported from Korea, the government wants to create economic effects through localization of fabric ducts. Air permeability and fire prevention performance tests verified the applicability to naval vessels of fabric ducts developed by Hyundai Heavy Industries and HiDact, and performance requirements presented in the POS were verified. As a result of the tests, the fabric ducts met the requirements for air permeability and fireproof performance.

• Composites Research
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• v.29 no.4
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• pp.203-208
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• 2016

Metal and polymer sandwich composites, which are made of sheet metal sheath and polymer or fiber reinforced plastic core, have been reconsidered as an alternative to sheet metal due to their lightness and multifunctional properties such as damping and sound-proof properties. For the successful applications of these composites, the delamination prediction based on the adhesion strength is important element. In this study, the numerical simulation of the delamination behavior of polymeric adhesive tapes with metallic surfaces was performed using cohesive zone elements and finite element software. The traction-separation law of the cohesive zone element was defined using the fracture energy derived from peel mechanics and experimental results from peel test and implemented in finite element software. The peel test of the polymeric adhesive film against steel surface was simulated and compared with experiments, demonstrating reasonable agreement between simulation and experiment.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.5
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• pp.2015-2020
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• 2012

Oleanolic acid (OA) is a naturally occurring triterpenoid in food materials and is a component of the leaves and roots of Olea europaea, Viscum album L., Aralia chinensis L. and more than 120 other plant species. There are several reports validating its antitumor activity against different cancer cells apart from its hepatoprotective activity. However, antitumor activity against skin cancer has not beed studied well thus far. Hence the present study of effects of OA against HaCaT (immortalized keratinocyte) cells - a cell-based epithelial model system for toxicity/ethnopharmacology-based studies - was conducted. Radical scavenging activity ($DPPH{\cdot}$) and FRAP were determined spectrophotometrically. Proliferation was assessed by XTT assay at 24, 48 and 72 hrs with exposure to various concentrations (12.5-200 ${\mu}M$) of OA. Apoptotic induction potential of OA was demonstrated using a cellular DNA fragmentation ELISA method. Morphological studies were also carried out to elucidate its antitumor potential. The results revealed that OA induces apoptosis by altering cellular morphology as well as DNA integrity in HaCaT cells in a dose-dependent manner, with comparatively low cytotoxicity. The moderate toxicity observed in HaCaT cells, with induction of apoptosis, possibly suggests greater involvement of programmed-cell death-mediated mechanisms. We conclude that OA has relatively low toxicity and has the potential to induce apoptosis in HaCaT cells and hence provides a substantial and sound scientific basis for further validation studies.