• Explosives and Blasting
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• v.23 no.1
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• pp.47-54
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• 2005

An explosion modeling technique was developed by using the spherical discrete element code, $PFC^{3D}$, which can be used to model the dynamic stress wave propagation phenomenon. The modeling technique is simply based on an idea that the explosion pressure should be applied to a $PFC^{3D}$ particle assembly not in the form of an external force (body force), but in the form of a contact force (surface force). A test blast was conducted for a RC column, whose dimension was $600\times300\times1800$ in millimeters. The initial velocities of the surface movements were measured to be in the range of $14\~18\;m/s$ with the initiation times of $1.5\~2.0m$. Then the blasting procedure was simulated by using the modeling technique. The particle assembly representing the concrete was made of cement mortar and coarse aggregates, whose mirco-properties were obtained from the calibration processes. As a result, the modeling technique developed in this study made it possible for the burden to move with the velocity of $17\~24\;m/s$, which are slightly higher values compared to those of the test blast.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.163-163
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• 1999

MOSFET, MESFET 그리고 MODFET는 Logic ULSIs, high speed ICs, RF MMICs 등에서 중요한 역할을 하고 있으며, 그것의 gate electrode, contact, interconnect 등의 물질로는 refractory metal을 이용한 CoSi2, MoSi2, TaSi2, PtSi2, TiSi2 등의 효과를 얻어내고 있다. 그중 TiSi2는 비저항이 가장 낮고, 열적 안정도가 좋으며 SAG process가 가능하므로 simpler alignment process, higher transconductance, lower source resistance 등의 장점을 동시에 만족시키고 있다. 최근 소자차원이 scale down 됨에 따라 TiSi2의 silicidation 과정에서 C49 TiSi2 phase(high resistivity, thermally unstable phase, larger grain size, base centered orthorhombic structure)의 출현과 그것을 제거하기 위한 노력이 큰 issue로 떠오르고 있다. 여러 연구 결과에 따르면 PAI(Pre-amorphization zimplantation), HTS(High Temperature Sputtering) process, Mo(Molybedenum) implasntation 등이 C49를 bypass시키고 C54 TiSi2 phase(lowest resistivity, thermally stable phase, smaller grain size, face centered orthorhombic structure)로의 transformation temperature를 줄일 수 있는 가장 효과적인 방법으로 제안되고 있지만, 아직 그 문제가 완전히 해결되지 않은 상태이며 C54 nucleation에 대한 physical mechanism을 밝히진 못하고 있다. 본 연구에서는 증착 시 기판온도의 변화(400~75$0^{\circ}C$)에 따라 silicon 위에 DC/RF magnetron sputtering 방식으로 Ti/Si film을 각각 제작하였다. 제작된 시료는 N2 분위기에서 30~120초 동안 500~85$0^{\circ}C$의 온도변화에 따라 RTA법으로 각각 one step annealing 하였다. 또한 Al을 cosputtering함으로써 Al impurity의 존재에 따른 영향을 동시에 고려해 보았다. 제작된 시료의 분석을 위해 phase transformation을 XRD로, microstructure를 TEM으로, surface topography는 SEM으로, surface microroughness는 AFM으로 측정하였으며 sheet resistance는 4-point probe로 측정하였다. 분석된 결과를 보면, 고온에서 제작된 박막에서의 C54 phase transformation temperature가 감소하는 것이 관측되었으며, Al impuritydmlwhswork 낮은온도에서의 C54 TiSi2 형성을 돕는다는 것을 알 수 있었다. 본 연구에서는 결론적으로, 고온에서 증착된 박막으로부터 열적으로 안정된 phase의 낮은 resistivity를 갖는 C54 TiSi2 형성을 보다 낮은 온도에서 one-step RTA를 통해 얻을 수 있다는 결과와 Al impurity가 존재함으로써 얻어지는 thermal budget의 효과, 그리고 그로부터 기대할 수 있는 여러 장점들을 보고하고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.378-385
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• 2016

The internal circuit of the bus-bar for an electrical switch board is a prime cause of electric shock and short circuit accidents due to the exposure of live parts. Electrical fires can also be caused by animals and foreign substances in the switchboard that connect the components with a difficult structure resulting in overheating due to an increase in contact resistance. Preventing these types of accidents is a prime concern in the manufacturing process, such as cutting and bending. In this study, the cutting bus bar of a switch board contained improved modules as a flame retardant that isolates a separate blocks to prevent such problems. This was implemented as a scalable and flexible means of reducing electrical switchboard hazards to offer a safe switch board bus-bar structure of a new connecter type

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.67.2-67.2
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• 2017

본 연구에서는 $SiO_2$ 미세구조 상에 Pd 나노입자(NPs)를 증착하여, 불소화된 마이크로-나노 계층구조를 갖는 Pd-decorated $SiO_2$($Pd/SiO_2$)를 제작하였다. 마이크로 크기의 거칠기를 갖는 $SiO_2$ 층은 졸-겔 공정을 사용해서 제조된 용액을 전기분사함으로써 제조되었다. 이어서, 자외선(UV)을 이용한 광 환원법을 이용해 Pd 나노입자를 $SiO_2$ 층에 형성했다. 생성된 표면은 마이크로-나노의 계층구조 형태를 보여주었다. 해당 시편의 불소화 처리 후, 마이크로-나노의 계층구조 표면은 $170^{\circ}$ 이상의 물 접촉각(water contact angle; WCA) 및 $5^{\circ}$ 이하의 슬라이딩 각(sliding angle)을 보여줌으로써 물에 대해 탁월한 소수성을 나타내었다. 또한, 커피($CA=161^{\circ}$), 우유($CA=162^{\circ}$), 쥬스($CA=163^{\circ}$), 그리고 글리세롤($CA=165^{\circ}$)에 대해서도 우수한 소수 특성을 보여주었다. 또한, 이들 $Pd/SiO_2$ 층은 우수한 장기내구성 및 자외선 저항성을 보여주었다. 그리고 이어진 기름에 대한 접촉각 측정을 통해 해당 시편이 소유 특성이 아닌 친유 특성을 보여준다는 것을 확인할 수 있었고, 기름에 대한 CA는 약 ${\sim}10^{\circ}$로 매우 우수한 친유 특성을 나타내었다. 이와 같은 결과는 자체세정이 가능한 표면 및 지능형 물/기름 분리 시스템과 같은 스마트 장치에서 초소수성-친유성 특성을 갖는 계층구조의 $Pd/SiO_2$ 층을 사용할 가능성을 명확하게 보여준다고 판단된다.

• Explosives and Blasting
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• v.37 no.4
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• pp.26-35
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• 2019

In designing a gravity-type anchorage of earth-anchored suspension bridge, the contact friction between a blasted rock mass and the concrete anchorage plays a key role in the stability of the entire anchorage. Therefore, it is vital to understand the shear behavior of the interface between the blasted rock mass and concrete. In this study, a portable 3D LiDAR scanner was utilized to scan the blasted bottom surfaces, and rock surface roughness was quantitatively analyzed from the scanned profiles to apply to 3D FEM modelling. In addition, based on the 3D FEM model, a three-dimensional dynamic fracture process analysis (DFPA-3D) technique was applied to study on the shear behavior of the interface between blasted rock and concrete through direct shear tests, which was analyzed under constant normal load (CNL). The effects of normal stress and the joint roughness on shear failure behavior are also analyzed.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.5
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• pp.112-119
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• 2015

The pulp mold attract the increasing concern as recyclable, biodegradable, and eco-friendly packaging materials. In order to broaden the applicability of the pulp mold as substitutes of the expanded styrofoam, the properties of various raw materials for the pulp mold were evaluated and the way for improving water resistance properties of the pulp mold were also tested by applying some additives. The higher value in the fines contents and in the water retention value were shown for the TMP (thermomechanical pulp), which resulted in the bulkier pulp mold with the higher moisture absorption property. In case of water resistance properties, the pulp mold made of white ledger stock showed the higher value in water contact angle and very slow water absorption rate. The addition of oil palm EFB fiber showed the improvement in the water resistance of the pulp mold made of UBKP. The effects of various additives on the improvement in the water resistance properties of the pulp mold were tested by using AKD, PVAm, epoxy resin. The application of AKD leaded to the higher increase in the water resistance. The results in this study showed the effects of AKD for the pulp mold could be improved and optimized by the application with fixing agent and by the ageing treatment after production.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.3
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• pp.285-291
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• 2016

There has been an accelerating increase in water reuse due to growing world population, rapid urbanization, and increasing scarcity of water resources. However, it is well recognized that water reuse practice is associated with many human health and ecological risks due to numerous chemicals and pathogenic microorganisms. Especially, the potential transmission of infectious disease by hundreds of pathogenic viruses in wastewater is one of the most serious human health risks associated with water reuse. In this study, we determined the response of different bacteriophages representing various bacteriophage groups to chlorination in real wastewater in order to identify a more reliable bacteriophage indicator system for chlorination in wastewater. Different bacteriophages were spiked into secondary effluents from wastewater plants from three different geographic areas, and then subjected to various doses of free chlorine and contact time at $5^{\circ}C$ in a bench-scale batch disinfection system. The inactivation of ${\phi}X174$ was relatively rapid and reached ~4 log10 with a CT value of 5 mg/L*min. On the other hand, the inactivation of bacteriophage PRD1 and MS2 were much slower than the one for ${\phi}X174$ and only ~1 log10 inactivation was achieved by a CT value of 10 mg/L*min. Overall, the results of this study suggest that bacteriophage both MS2 and PRD1 could be a reliable indicator for human pathogenic viruses for chlorination in wastewater treatment processes and water reuse practice.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.6
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• pp.1673-1675
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• 2005

The pulse diagnosis is an important and universal method in Oriental medicine. Nevertheless, because of characteristic that depends on subjective sense of Oriental medicine doctor (OMD), it is not recognized by objective basis. The Korean Institute of Oriental Medicine(KIOM) and Daeyo Medi. Co. Ltd. developed the 3-D Mac using arrey piezoresistive sensors and multi-axial robot. 133 healthy subjects participated in this study, 75 males and 58 females, between 20 and 70 years of age. All subjects were relaxed in a supine position on a comfortable chair for twenty minutes before the measurement was taken. The measured position is the radial artery of subject's left wrist and the position is called Chon, Kwan and Chuck in Oriental medicine. To detect floating and sinking pulse, we established coefficient of floating and sinking(CFS). CFS means relative position of maximum pulse pressure in PH curve. The lower CFS value means that the pulse has floating tendency. There was significant diffence between CFS and diagnosis of floating-sinking pulse by OMD(p=0.020). CFS value of over 40's group was significantly larger than those of 20's and 30's(p=0.000). There was no significant difference between male and female(p=0.061).

• Journal of Korean Society of Water and Wastewater
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• v.25 no.4
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• pp.591-596
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• 2011

Surface floating air cathode microbial fuel cell (MFC) having horizontal flow was developed for the application of MFC technology. RVC (Reticulated vitreous carbon) coated with anyline was used as anode electrode and carbon cloth coated with Pt (5.0 g Pt/$m^2$, GDE LT250EW, E-TEK) was used as cathode electrode. As results of continuous operation with changing the flow rate from 4.3 mL/min to 9.5 mL/min, maximum power density of 4.5 W/$m^3$ was acquired at 5.4 mL/min, which was at 0.35 m/hr of flow velocity under anode electrode. When the ratio of cathode surface area to anode surface area($A_c/A_a$) was changed to 1.0, 0.5, and 0.25, the maximum power density of 2.7 W/$m^3$ was shown at the ratio of 1.0. As the ratio decreased from 1.0 to 0.25, the power density also decreased, which is caused by increasing the internal resistance resulted from reducing the surface area to contact with oxygen. Actually, internal resistances of the ratio of 1.0, 0.5, and 0.25 were 63.75${\Omega}$, 142.18${\Omega}$, and 206.12${\Omega}$, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.11
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• pp.1009-1014
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• 2013

In the present study, using a variation of rib height, the transient response and the performance are investigated. The cell voltage is acquired according to the current density change($0.8A/cm^2$ to $1.0A/cm^2$) under same stoichiometry and relative humidity. The different level of undershoots appeared at the different clamping pressure(1.5MPa and 2.0MPa) and different rib height. At 1.5MPa clamping pressure, rib manufactured cut at $100{\mu}m$ height goes to steady state faster than reference plate and has lower maximum undershoot voltage. But performance is lower than reference plate due to increasing contact resistance.