• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.61-64
• /
• 2008

A combination of CFT column and RC flat plate without formworks is very effectively rapid constructions. This paper verified the lateral resisting capacity of CFT column-RC flat plate exterior connection in comparison with general RC column-flat plate connection and detected moment capacity and ductility capacity of connection according to moment-displacement ratio. We made and tested specimens which have different variables respectively and as a result derive a following conclusion. In CFT-E2 specimen a critical section was extended and maximum moment increased 20% respectively in comparison to general RC column specimen. In BME and CFT-E1 specimens generally shear governed behaviors and CFT-E2 specimen complemented with seismic band, flexure behavior region of slab was extended and also ductility ratio and energy absorptance increased.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.2
• /
• pp.211-216
• /
• 2012

The availability of thermal energy has been widely recognized recently, and the cascade usage of thermal energy from combustion has been encouraged. Within this framework, a 1-kW-class Stirling-engine.based cogeneration system has been proposed as a unit of a distributed energy system. The capacity has been designed to be adequate for domestic usage, which requires high compactness as well as low emissions and noise. To develop a highly efficient system satisfying these requirements, a premixed slot-type short-flame burner has been proposed, and a series of experiments has been performed to understand its combustion characteristics. Flame images have been captured to observe the dependence of the flame mode on the combustion load and air/fuel ratio. The exhaust gas has been sampled and analyzed to study the emission characteristics for each flame mode.

• Explosives and Blasting
• /
• v.35 no.4
• /
• pp.36-47
• /
• 2017

Due to civil complaints on vibrations and noises arising from blasting, mechanical excavation has been widely used for tunneling rather than the method of blasting, especially in the case of being in a close-proximity of 10M-20M range to a safety-thing. However, mechanical excavation, though less, it does increase the cost of whole construction project as the period of excavation is much prolonged from lack of constructability. This study aims to research and develop an effective blasting method that can ensure the constructability of shortened excavation period whilst not compromising the safety of the safety-things in a proximity to the blasting site by using a combination of an electronic detonator that can accurately control its delay period and a Low Vibration Explosives(LoVEX) that is effective on vibration control.

• Journal of Animal Environmental Science
• /
• v.15 no.1
• /
• pp.59-68
• /
• 2009

This study investigated the evaluation of maturity, stability, nutrient and heavy metal from rotating drum composter of food waste amended with poultry manure composting inoculated with effective microorganisms(EM). Composting were performed for the first, drying reactor($15m^3$) 3 hours and the second, composting reactor($30m^3$) 24 hours, and parameters monitored this period included moisture content, NaCl, pH, electrical conductivity(EC), C/N ratio, organic matter(OM), nutrient content and heavy metal. Changes in compost temperature during composting were maintained constantly in the range of $60{\sim}80^{\circ}C$ using firewood boiler(450 MJ/h). We examined physicochemical parameters and heavy metals in order to assess their effectiveness as stability and maturity, nutrient and harmful indicators such as seed germination rate<60%, potassium 1>%, dm and NaCl>1%, dm at the end of the final compost. The finished compost obtained after decomposition phase at the end of the 2nd composter could not be utilized for land improvement or reclamation.

• The Journal of the Acoustical Society of Korea
• /
• v.36 no.1
• /
• pp.57-63
• /
• 2017

This paper presents an active acoustic-reflection control algorithm based on a single sensor. The proposed algorithm operates in a system comprising a single sensor located nearby the reflective surface and a control transducer mounted on the reflective surface. First, the incident and reflected acoustic signals are separated from the sensor signal, and a control signal is generated using the separated signals. For the signal separation, the proposed algorithm requires the response of the reflection path which is estimated from the acoustic response between an external sound source and the sensor. Finally, the control filter is adjusted using the FxLMS (Filtered-x Least Mean Square) algorithm. To verify the effectiveness of the proposed algorithm, it was implemented in real time using a DSP (Digital Signal Processing) board, and the experimental results obtained in one-dimensional air-acoustic environment show that the reflections of the 1 kHz burst can be reduced by 11.6 dB.

• Clean Technology
• /
• v.10 no.3
• /
• pp.121-130
• /
• 2004

Pelletizer of dry ice snow produced by adiabatic expansion of liquid carbon dioxide and their blaster were designed and manufactured. The blaster had a high cleaning power against various contaminants on the surface such as stain, oily dirt, lacquer film and paints with low blasting pressure and low consumption of blasting air. The capacity of hopper for dry ice pellet supply was 12 kg and the mass rate of pellet blasting was controlled in 0 to 1.2 kg/min. The impact of the pellets was independent of standoff distance within a certain limiting distance, and dependent on the impact stress, angle and mass rate of dry ice pellet blasting. On the other hand the cleaning power was influenced by thermal properties and surface roughness of the substrates and decreased in the order of glass, copper, brass, steel and acryl. The power was also affected by hardness and adhesion of the contaminant on the substrate, and decreased in the order of grease, epoxy and paint. The noise was detected during blasting in the range of 85 to 100dBA.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.1
• /
• pp.17-23
• /
• 2013

In a subway vehicle, a lateral damper is used for compensating the lateral stiffness deterioration due to the air-spring as a secondary suspension. This lateral damper can reduce the lateral vibration of the carbody. When the damping force of the lateral damper is lowered, the running stability and ride quality of the subway vehicles worsens and the lateral motion of the carbody is increased. In this study, the lateral displacement variation of the carbody according to the damping force of the lateral damper was analyzed by multi-body dynamics to solve the abnormal impact problem during vehicle operation. Furthermore, the noise and vibration due to abnormal impact were considered. An adequate damping coefficient of the lateral damper for the subway vehicle treated in this paper was suggested for preventing abnormal impact.

• Smart Media Journal
• /
• v.7 no.3
• /
• pp.29-34
• /
• 2018

This paper presents a study on adapting optical communication technology using infrared ray for the enhancement of hearing aids in noisy environment. The transmitter module containing microphone and infrared ray-emitting diode converts audio signal to infrared optical signal and sends it out in the air. The receiver module located in a distance receives the infrared signal, converts it to electrical signal, and transfers it to an input of a digital hearing aid. Especially, the receiver module needs to be small, low voltage, and consume low power since it will be attached to hearing aids. Experiments with applying infrared communication technology of digital modulation method and analog non-modulation method show that the analog non-modulation method is adequate for infrared communication of approximately 5m distance indoor. Prototypes of transmitter module and receiver module were manufactured, and internal parameters of the digital hearing aid were adjusted to confirm normal transmit-receive operation of audio signals.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2016.05a
• /
• pp.103-103
• /
• 2016

최근 기후변화에 따른 집중호우로 도시홍수의 피해가 급격히 증가하고 있다. 특히 인구가 밀집하고 교통량이 많은 대도시의 경우 동일한 호우에 대하여 녹지나 농경지 등에 비해 그 피해가 더 심각하다. 일반적으로 홍수 피해의 직접원인은 외수로 인한 피해와 내수로 인한 피해로 크게 구분할 수 있다. 외수피해는 주로 소하천 및 지천의 범람, 제방의 붕괴 등으로 발생한 것이며 내수피해는 배수로, 하수도 및 펌프장의 내수배제능력 부족이 주된 원인이다. 따라서 도시홍수를 효과적으로 방어하기 위해서는 우선적으로 내배수시설의 성능개선이 선행되어야 할 필요가 있다. 이러한 내배수 시설의 성능 개선을 위해서는 현재 기 설치되어 있는 빗물펌프장의 설계 및 내배수 효율에 대한 성능평가가 필요하다. 하지만 현재 국내 펌프설계기준에는 빗물펌프장의 설계 및 운영에 대한 구체적인 성능 평가 방법이 제시되어 있지 않은 실정이다. 만약, 펌프 흡입수조 및 흡입파이프의 형상이 적절하게 설계되지 못한다면 물이 파이프 입구로 부드럽게 흡입되지 못하고 볼텍스 및 스월이 발생하게 된다. 이러한 볼텍스 및 스월은 펌프 입구 쪽으로 물 뿐 아니라 공기를 함께 흡입시킴으로써 펌프의 효율저하, 소음, 진동을 발생시키며 펌프 파손의 원인이 될 수 있다. 따라서 펌프를 설치하기 전 펌프 설치 후에 발생되는 펌프 흡입부 주변의 흐름특성 변화 및 흐름특성이 구조물에 미치는 영향 등을 고려하기 위하여 수리모형실험이 필요한데, 수리모형실험은 많은 시간과 비용이 들어가기 때문에 이를 대체할 수 있는 방안이 요구된다. 그런 이유로 최근에는 수리모형실험 대신 수치모의를 이용하는 경우가 많다. 수치모의의 결과는 수리실험의 결과와 비교, 검증을 거쳐 신뢰성을 얻는다. 본 연구에서는, 3차원 수치모형의 다양한 난류모델을 이용하여 흡입파이프로 물이 유입될 때 흡입부 내, 외의 수심 별 유속 변화를 분석하고, 그 결과를 이용하여 FLOW 3D 모형의 검증을 수행하였다.

• Tunnel and Underground Space
• /
• v.31 no.6
• /
• pp.578-592
• /
• 2021

This study performed to investigate the propagation characteristics of overpressure, impulse, vibration in underwater blasting. The difference between air blasting and underwater blasting is that noise and vibration propagate through water as a medium. In some cases, the noise and vibration propagates through various media (rock, water, air, etc.). In this study, the underwater blasting was simulated using AUTODYN, and the propagation characteristics of overpressure, impulse and vibration induced by blasting were analyzed. We mainly focused on the effect of mesh size on the overpressure, impulse and peak particle velocity from the underwater blasting simulation. The numerical results indicated that the overpressure and peak particle velocity tended to decrease as the mesh size increased, while the impulse increased with the mesh size. The results also indicated that the mesh dependence varied depending on the explosive charge and scaled distance.