• 대한환경공학회지
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• 제29권4호
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• pp.444-451
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• 2007

본 연구에서는 $\gamma-Al_2O_3$에 전이금속들을 함침시킨 촉매를 고정층 반응기에 충전시킨후 휘발성유기물질(VOCs)인 밴젠을 일정농도로 공급하면서 촉매산화 특성을 살펴보았다. 전이금속으로는 구리, 니켈, 망간, 철등을 포함해 8가지 금속을 선정하였고, 실험조건은 반응온도 $200\sim500^{\circ}C$, 벤젠의 농도 $1,000\sim3,000$ ppm, 공간속도 $5,000\sim60,000\;hr^{-1}$의 범위로 적용하였다. BET분석, 전자주사현미경(SEM), XRD분석을 통해 제조된 촉매의 물성을 조사하였으며, VOC 촉매산화반응의 전환율에 대하여 고찰하였다. 실험결과, VOC농도와 공간속도가 낮을수록 VOC산화반응의 전환율은 증가함을 알 수 있었다. 여러 전이금속촉매들 중에 Cu촉매가 벤젠에 대해 가장 높은 활성을 나타내었고, 소성온도 $500^{\circ}C$조건에서 전이금속의 함침율이 15 wt%일 경우 가장 높은 전환율을 나타내었다.

• 한국재난정보학회 논문집
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• 제11권1호
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• pp.35-43
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• 2015

본 연구에서는 상수도시설물에 대해 손상단계를 기능수행과 붕괴방지로 나누고, 해외실측지진과 한반도형 인공지진에 대해 각각의 최대지반가속도에 따른 취약도 함수를 도출하였다. 손상단계 및 지반가속도를 이용하여 상수도시설물의 지진파에 따른 취약도 곡선을 도출하여 비교분석하였다. 해석결과, 도복장강관과 덕타일 주철관에 한반도형인공지진을 재하하는 경우, 해외실측지진을 재하하는 경우에 비하여 중앙값이 최소 0.1에서 최대 0.4까지 작아지는 것으로 나타났다. 본 연구에서 제안된 한반도형 인공지진을 이용한 지진취약도 곡선은 국내실정에 맞는 합리적인 내진 설계에 활용될 수 있을 것이다.

• 한국구조물진단유지관리공학회 논문집
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• 제16권5호
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• pp.40-48
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• 2012

이 연구에서는 철강 공정에서 발생되는 전기로 산화슬래그 골재를 사용한 철근콘크리트 보의 전단 성능을 평가하였다. 이를 위하여 총 6개의 단순지지형 실험체를 제작하여 전단실험을 수행하였다. 주요 실험변수는 골재의 종류와 전단철근의 유무로 하였다. 실험체는 전단경간비가 2.5, 폭 200mm, 유효깊이가 300mm인 직사각형 단면으로 4점가력을 받도록 계획하였다. 기존 강도식을 사용하여 실험체의 전단강도를 예측하였으며, 전단해석모델을 사용한 유한요소해석을 수행하여 전기로 산화슬래그 골재를 사용한 실험체의 전단거동을 예측하였다. 실험결과로부터, 전기로 산화슬래그 골재를 사용한 실험체의 전단 성능은 천연골재를 사용한 실험체와 서로 유사한 것을 확인할 수 있었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제32권1호
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• pp.52-59
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• 2006

Purpose: The purpose of this study was to evaluate the influence of apical-coronal implant position on the stress distribution after occlusal and oblique loading. Materials and Methods: The cortical and cancellous bone was assumed to be isotropic, homogeneous, and linearly elastic. The implant was apposed to cortical bone in the crestal region and to cancellous bone for the remainder of the implant-bone interface. The cancellous core was surrounded by 2-mm-thick cortical bone. An axial load of 200 N was assumed and a 200-N oblique load was applied at a buccal inclination of 30 degrees to the center of the pontic and buccal cusps. The 3-D geometry modeled in Iron CAD was interfaced with ANSYS. Results: When only the stress in the bone was compared, the minimal principal stress at load Points A and B, with a axial load applied at 90 degrees or an oblique load applied at 30 degrees, for model 5. The von Mises stress in the screw of model 5 was minimal at Points A and B, for 90- and 30-degree loads. When the von Mises stress of the abutment screw was compared at Points A and B, and a 30-degree oblique load, the maximum principal stress was seen with model 2, while the minimum principal stress was with model 5. In the case of implant, the model that received maximum von Mises stress was model 1 with the load Point A and Point B, axial load applied in 90-degree, and oblique load applied in 30-degree. Discussion and Conclusions: These results suggests that implantation should be done at the supracrestal level only when necessary, since it results in higher stress than when implantation is done at or below the alveolar bone level. Within the limited this study, we recommend the use of supracrestal apical-coronal positioning in the case of clinical indications.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권11호
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• pp.601-611
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• 2002

As resent trends in structural construction have been to build taller and larger structures than any time in the past, they have had high flexibility and low damping that can cause large vibration response under severe environmental loading such as earthquakes, winds, and mechanical excitations. The damper with mass and sqring is one aproach to safeguarding the structure against excessive vibrations. In this paper, a large capacity hybrid-type linear motor damper(LMD) was designed and fabricated for the application to the vibration control of a large building structure model. It has been designed to be able to move the damper mass, 1,500 kg up to ${\pm}250mm$ strokes at the first mode natural frequency of the building structure model, ${\pm}0.51Hz$. Linear motor is consisted of the fixed coil and the movable NdFeB permanent magnets field part. The PM field part composed magnet modules and iron yoke, is the damper mass itself, 1500kg. LMD therefore has a simplified structure and requires a few elements in the driving system, being compared with a rotary motor damper and a hydraulic damper. However, the manufacture of large PM linear actuator is difficult because of the limit of PM size and the attraction and repulsion at the assembly of PM. Therefore, large damper system is manufactured and tested for dynamic characteristics and frequency response.

• Elastomers and Composites
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• 제51권2호
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• pp.113-121
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• 2016

Magneto-rheological elastomer (MRE) is a material which shows reversible and various modulus under magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb broader frequency range of vibration. These characteristic phenomena result from the orientation of magnetic particle (i.e., chain-like formation) in rubber matrix. In this study, silicone rubber was used as a matrix of MREs. Carbonyl iron particle (CIP) was used to give magnetic field reactive modulus of MRE. The surface of the CIP was modified with chemical reactants such as silane coupling agent and poly(glycidyl methacrylate), to improve interfacial adhesion between matrix and CIP. The mechanical properties of MREs were measured without the application of magnetic field. The results showed that the tensile strength was decreased while the hardness was increased with the addition of CIP. Also, surface modification of CIP resulted in the improvement of physical properties of MRE, but the degree of orientation of CIP became decreased. The analysis of MR effect was carried out using electromagnetic equipment with various magnetic flux. As the addition of CIP and magnetic flux increased, increment of MR effect was observed. Even though the surface modification of CIP gave positive effect on the mechanical properties of MRE, MR effect was decreased with the surface modification of CIP due to decrease of CIP orientation. Throughout this study, it was found that the loading amounts of CIP affected the mechanical properties of MRE, and surface property of CIP was an important factor on MR effect of MRE.

• 한국수소및신에너지학회논문집
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• 제27권3호
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• pp.290-297
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• 2016

The absorbent loss due to degradation in $CO_2$ capture process using aqueous alkanol amine solution has adverse effect on the economics of overall process. The degradation causes absorbent loss, equipment corrosion, foaming, adhesive material producing and viscosity increase in operation. In this study, the degradation characteristics of $CO_2$ capture process using MEA (monoehtanolamine) under various conditions such as $O_2$ partial pressure, $CO_2$ loading and absorbent temperature. The effects of iron, which generated from the equipment corrosion, on absorbent degradation were studied using $Fe_2SO_4$ containing MEA solution. The produced gases were analyzed by FT-IR(Fourier Transform Infrared Spectrophotometer) and the specifically measured $NH_3$ concentration was used as a degradation degree of aqueous MEA solution. The experiments showed that the higher $CO_2$ loadings (${\alpha}$), $O_2$ fraction ($y_{O2}$) and reaction temperature enhanced the more degradation of aqueous MEA solution. Comparing other operation parameters, the reaction temperature most affected on the degradation. Therefore, it could be concluded that the above parameters affects on degradation should be considered for the selections of $CO_2$ absorbent and operating conditions.

• Smart Structures and Systems
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• 제32권3호
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• pp.153-166
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• 2023

Health monitoring of civil infrastructures, in particular, old bridges that are still in service, has become more than necessary, given the risk that a possible degradation or failure of these infrastructures can induce on the safety of users in addition to the resulting commercial and economic impact. Bridge integrity assessment has attracted significant research efforts over the past forty years with the aim of developing new damage identification methods applicable to real structures. The bridge of Ouled Mimoun (Tlemcen, Algeria) is one of the oldest railway structure in the country. It was built in 1889. This bridge, which is too low with respect to the level of the road, has suffered multiple shocks from various machines that caused considerable damage to its central part. The present work aims to analyze the stability of this bridge by identifying damages and evaluating the damage rate in different parts of the structure on the basis of a finite element model. The applied method is based on an inverse analysis of the normal stress responses that were calculated from the corresponding recorded strains, during the passage of a real train, by means of a set of strain gauges placed on certain elements of the bridge. The results obtained from the inverse analysis made it possible to successfully locate areas that were really damaged and to estimate the damage rate. These results were also used to detect an excessive rigidity in certain elements due to the presence of plates, which were neglected in the numerical reference model. In the case of the continuous bridge monitoring, this developed method will be a very powerful tool as a smart health monitoring system, allowing engineers to take in time decisions in the event of bridge damage.

• 한국수소및신에너지학회논문집
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• 제34권5호
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• pp.421-430
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• 2023

Fe-Ni-Pt nanocatalysts were loaded on carbon black powders which were synthesized by a spontaneous reduction reaction of iron (II) acetylacetonate, nickel (II) acetylacetonate and platinum (II) acetylacetonate. The morphology and the loading weight of Fe-Ni-Pt nanoparticles were characterized by transmission electron microscopy and thermogravimetric analyzer. The amount of Fe-Ni-Pt catalyst supported on the carbon black surface was about 6.42-9.28 wt%, and the higher the Fe content and the lower the Pt content, the higher the total amount of the metal catalyst supported. The Brunauer-Emmett-Teller Analysis (BET) specific surface area of carbon black itself without metal nanoparticles supported was 233.9 m²/g, and when metal nanoparticles were introduced, the specific surface area value was greatly reduced. This is because the metal nanocatalyst particles block the pore entrance of the carbon black, and thereby the catalytic activity of the metal catalysts generated inside the pores is reduced. From the I-V curves, as the content of the Pt nanocatalyst increased, the electrolytic properties of water increased, and the activity of the metal nanocatalyst was in the order of Pt > Ni > Fe.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제31권3호
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• pp.248-254
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• 2005

The purpose of this study was to investigate the distribution of stress within the regenerated bone surrounding the implant using three dimensional finite element stress analysis method. Using ANSYS software revision 6.0 (IronCAD LLC, USA), a program was written to generate a model simulating a cylindrical block section of the mandible 20 mm in height and 10 mm in diameter. The $5.0{\times}11.5-mm$ screw implant (3i, USA) was used for this study, and was assumed to be 100% osseointegrated. And it was restored with gold crown with resin filling at the central fossa area. The implant was surrounded by the regenerated type IV bone, with 4 mm in width and 7 mm apical to the platform of implant in length. And the regenerated bone was surrounded by type I, type II, and type III bone, respectively. The present study used a fine grid model incorporating elements between 250,820 and 352,494 and nodal points between 47,978 and 67,471. A load of 200N was applied at the 3 points on occlusal surfaces of the restoration, the central fossa, outside point of the central fossa with resin filling into screw hole, and the functional cusp, at a 0 degree angle to the vertical axis of the implant, respectively. The results were as follows: 1. The stress distribution in the regenerated bone-implant interface was highly dependent on both the density of the native bone surrounding the regenerated bone and the loading point. 2. A load of 200N at the buccal cusp produced 5-fold increase in the stress concentration at the neck of the implant and apex of regenerated bone irrespective of surrounding bone density compared to a load of 200N at the central fossa. 3. It was found that stress was more homogeneously distributed along the side of implant when the implant was surrounded by both regenerated bone and native type III bone. In summary, these data indicate that concentration of stress on the implant-regenerated bone interface depends on both the native bone quality surrounding the regenerated bone adjacent to implant and the load direction applied on the prosthesis.