• Journal of the Korea Concrete Institute
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• v.17 no.2 s.86
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• pp.263-271
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• 2005

HPFRCC(High Performance Fiber Reinforced Cementitious Composite) is a class of FRCCs(Fiber Reinforced Cementitious Composites) that exhibit multiple cracking. Multiple cracking leads to improvement in properties such as ductility, toughness, fracture energy, strain hardening, strain capacity, and deformation capacity under tension, compression, and bending. These improved properties of HPFRCCs have triggered unique and versatile structural applications, including damage reduction, damage tolerance, energy absorption, crack distribution, deformation compatibility, and delamination resistance. These mechanical properties of HPFRCCs become different from the kinds and shapes of used fiber, and it is known that the effective size of fiber in macro crack is different from that in micro crack. This paper reports an experimental findings on the mechanical properties of HPFRCCs reinforced with the micro fiber(PP50, PVA100 and PVA200) and macro fiber(PVA660, SF500). Uniaxial compressive tests and three point bending tests are carried out in order to compare with the mechanical properties of HPFRCCs reinforced with micro fibers or hybrid fibers such as compressive strength, ultimate bending stress, toughness, deformation capacity and crack pattern under bending, etc.,

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.84-84
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• 2000

수소화된 비정질 실리콘(a-Si:H)과 미세결정질 실리콘 ($\mu$c-Si:H)은 저온.건식 공정인 PECVD로 값싼 유리 기판을 사용하여 넓은 면적에 증착이 가능하다는 큰 장점으로 인해 광전소자(photovoltaic device)와 박막 트랜지스터(TFTs)등에 폭넓게 응용되어 왔으며 최근에는 nm 크기의 실리콘 결정(nc-Si)에서 가시광선 영역의 발광 현상이 발견됨에 따라 광소자로서의 특성을 제어하기 위해서는 성장 조건과 공정 변수에 따른 구조 변화에 대한 연구가 선행되어야 한다. 본 연구에서는 UHV-ECR-PECVD 법을 이용하여 H2로 희석된 SiH4로부터 a-Si:H과 $\mu$c-Si:H를 증착하였다. 그림 1은 SiH4 20sccm/H2 50sccm/25$0^{\circ}C$에서 기판의 DC bias를 변화시키면서 박막을 증착시킬 때 나타나는 박막의 구조 변화를 raman spectrum의 To phonon peak의 위치와 반가폭의 변화로 나타낸 것이다. 비정질 실리콘 박막은 DC bias를 증가시킴에 따라 무질서도가 증가하다가 어떤 critical DC bias에서 최대치를 이룬후 다시 질서도가 증가한다. 이온의 충격력에 의해 박막내에 응력이 축적되면 박막의 에너지 상태가 높아지고 이 축적된 응력이 ordering에 대한 에너지 장벽을 넘을 수 있을 만큼 커지게 되면 응력이 풀리면서 ordering이 가능해지는 것으로 생각된다. 그림 2는 수소 결합 형태의 변화이다. 박막의 무질서도가 증가할 경우 알려진 바와 같이 2000cm-1근처의 peak은 감소하고 2100cm-1 부근이 peak이 증가하는 현상을 보였다. 본 논문에서는 여러 공정 변수, 특히 DC bias에 따르는 박막의 구조 변화와 다른 성장 조건(온도, 유량비)이 critical DC bias나 결정화, 결정성 등에 미치는 영향에 대한 분석결과를 보고하고자 한다.등을 이용하여 광학적 밴드갭, 광흡수 계수, Tauc Plot, 그리고 파장대별 빛의 투과도의 변화를 분석하였으며 각 변수가 변화함에 따라 광학적 밴드갭의 변화를 정량적으로 조사함으로써 분자결합상태와 밴드갭과 광 흡수 계수간의상관관계를 규명하였고, 각 변수에 따른 표면의 조도를 확인하였다. 비정질 Si1-xCx 박막을 증착하여 특성을 분석한 결과 성장된 박막의 성장률은 Carbonfid의 증가에 따라 다른 성장특성을 보였고, Silcne(SiH4) 가스량의 감소와 함께 박막의 성장률이 둔화됨을 볼 수 있다. 또한 Silane 가스량이 적어지는 영역에서는 가스량의 감소에 의해 성장속도가 둔화됨을 볼 수 있다. 또한 Silane 가스량이 적어지는 영역에서는 가스량의 감소에 의해 성장속도가 줄어들어 성장률이 Silane가스량에 의해 지배됨을 볼 수 있다. UV-VIS spectrophotometer에 의한 비정질 SiC 박막의 투과도와 파장과의 관계에 있어 유리를 기판으로 사용했으므로 유리의투과도를 감안했으며, 유리에 대한 상대적인 비율 관계로 투과도를 나타냈었다. 또한 비저질 SiC 박막의 흡수계수는 Ellipsometry에 의해 측정된 Δ과 Ψ값을 이용하여 시뮬레이션한 결과로 비정질 SiC 박막의 두께를 이용하여 구하였다. 또한 Tauc Plot을 통해 박막의 optical band gap을 2.6~3.7eV로 조절할 수 있었다. 20$0^{\circ}C$이상으로 증가시켜도 광투과율은 큰 변화를 나타내지 않았다.부터 전분-지질복합제의 형성 촉진이 시사되었다.이것으로 인하여 호화억제에 의한 노화 방지효과가 기대되었지만 실제로 빵의 노화는 현저히 진행되었다. 이것은 quinua 대체량 증가에 따른 반죽의 안정성이 저하되어 버린 것으로 생각되어진다. 더욱이 lipase를 첨가하면 반죽이 분화하는 경향이 보여졌지만 첨가량 75ppm에 있어서 상당히 비용적의 증대가 보였다. 이것은 lipase의 가수분해에 의해

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.686-686
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• 2013

Automotive turbochargers have become common in gasoline engines as well as diesel engines. They are excellent devices to effectively increase fuel efficiency and power of the engines, but they unfortunately cause several noise problems. The noises are classified into mechanical noises induced from movement of a rotating shaft and aerodynamic noises by air flow in turbochargers. In addition to, there is a mechanical noise caused from movement of an actuator, electronically controlling a wastegate valve. It is called as valve rattle noise. The actuator is connected to a valve through a linkage. The noise occurs only if the valve is open, where the linkage is freely contact to neighbor structures without being constrained by any external forces. This condition allows impacts by the pulsation of exhaust gas, and the vibration from the impacts spreads out through turbine housing, causing the rattle noise. The noise is not in mechanical operating wastegate turbochargers because the linkage of an actuator is strongly connected by actuating force. For the electronic wastegate turbocharger, this paper proposed a test device to show the noise generating mechanism with a small vibration motor having an unbalanced shaft. It also shows how to reduce the noise - reduction of linkage clearances, inserting wave washers into a connection, and applying loose fitting in bushing embracing a valve lever to turbine housing.

• Journal of the Korean Geotechnical Society
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• v.26 no.12
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• pp.5-17
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• 2010

Coarse granular material is used as important fill material in most of large embankments such as railway, road, dam and so on. Therefore, the accurate design parameters of the coarse granular material are necessarily required in design and construction. The behavior of the coarse granular material was not well understood because of the lack of large testing equipment capable of coarse granular material. A large triaxial testing system was developed in this research, capable of large specimens of 500 mm, 300 mm and 150 mm in diameter. In the new large triaxial testing system, the load cell is installed inside the triaxial cell and axial displacement is measured locally on a specimen in order to improve control and measurement in small strain level. Urethane specimens of 300 mm and 50 mm in diameter were prepared. The large triaxial tests were performed on the 300 mm diameter urethane specimens while RC/TS and impact echo tests on the 50 mm diameter urethane specimens to verify this testing system. In this verification test results, we could ascertain the reasonable test results of the KRRI large triaxial testing system.

• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.2
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• pp.57-65
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• 2008

Wastewater containing strong organic matter is very difficult to treat by utilizing general sewage treatment plant. but the wastewater is adequate to generate biomass energy (bio-gas; methane gas) by utilizing anaerobic digestion. EcoDays Plug Flow Reactor (E-PFR), which was already proved as an excellent aerobic wastewater treatment reactor, was adapted for anaerobic food wastewater digestion. This research was performed to improve the efficiency of bio-gas production and to optimize anaerobic wastewater treatment system. Food wastewater from N food waste treatment plant was applied for the pilot scale experiments. The results indicated that the efficiency of anaerobic wastewater treatment and the volume of bio-gas were increased by applying E-PFR to anaerobic digestion. The structural characteristics of E-PFR can cause the high efficiency of anaerobic treatment processes. The unique structure of E-PFR is a diaphragm dividing vertical hydraulic multi-stages and the inversely protruded fluid transfer tubes on each diaphragm. The unique structure of E-PFR can make gas hold-up space at the top part of each stage in the reactor. Also, E-PFR can contain relatively high MLSS concentration in lower stage by vertical up-flow of wastewater. This hydraulic flow can cause high buffering capacity against shock load from the wastewater in the reactor, resulting in stable pH (7.0~8.0), relatively higher wastewater treatment efficiency, and larger volume of bio-gas generation. In addition, relatively longer solid retention time (SRT) in the reactor can increase organic matter degradation and bio-gas production efficiency. These characteristics in the reactor can be regarded as "ideal" anaerobic wastewater treatment conditions. Anaerobic wastewater treatment plant design factor can be assessed for having 70 % of methane gas content, and better bio-gas yielding and stable treatment efficiency based on the results of this research. For example, inner circulation with generated bio-gas in the reactor and better mixing conditions by improving fluid transfer tube structure can be used for achieving better bio-gas yielding efficiency. This research results can be used for acquiring better improved regenerated energy system.

• Journal of Animal Environmental Science
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• v.6 no.3
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• pp.175-184
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• 2000

A lab-scale MF membrane reactor was installed to investigate the membrane permeability, characteristics of membrane fouling at each conditions, and quality of permeate (liquid livestock manure) in the separation of solid-matters using membrane. Experiment was divided three filtration type such as follows; continuous filtration, gravity filtration, and intermittent filtration. As a result of experiment, flux 1 LMH was maintained for 7days, and trans-membrane pressure(TMP) was increased gradually under 10cmHg, but it was increased immediately after 10cmHg, respectively. However, the flux was increased, the Tmax was decreased exponential more and more. During the pure-flux test, most of the fouling of membrane was reversible. At the gravity filtration, permeate could be obtained as 1.75 LMH for 3.5days without any other electronic pressure. As an investigation of membrane surface, this study could be decided that the reason of fouling at the lower flux (Run 1 and 2) was attached matters in membrane surface, but at the higher flux (Run 4-6) was concentration polarization.