• Restorative Dentistry and Endodontics
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• 제31권4호
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• pp.290-299
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• 2006

본 연구에서는 상아질의 항복인장강도 (UTS)나 탄성계수 (E)와 같은 물리적 특성이 적용된 용매틀의 각각에 대한 Hoy의 수소결합 용해도 매개변수에 반비례한다는 가설을 설정하고 실험한 결과 가설이 입증되었으며 이를 토대로 다음과 같은 결론을 유도하여 보았다. 첫째는 탈회된 상아질의 인장 특성 및 물성이 가해진 극성 용매의 수소결합능에 밀접히 연관되어 있다는 것이며, 둘째는 낮은 수소결합능을 가진 용매는 교원섬유 층 내에서 새로운 펩타이드간 수소결합을 유도함으로써 탈회된 상아질의 인장력 및 탄성계수를 증가시킨다는 결과이다. 셋째로는 이러한 결과들을 토대로 높은 수소결합능을 가진 용매들은 새로운 펩타이드간 수소결합의 형성을 차단하여 탈회된 상아질의 구조적 특성을 유지시킬 수 있다는 결론을 도출하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.116-119
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• 1999

The effects of secondary phase morphology and carbon content on the plastic deformation of 0.2C-1.5Si-1.5mn TRIP(TRansformed Induced Plasticity) steel have been investigated at various annealing and bainitic transformation temperatures. The morphology of ferrite and secondary phases was controlled by the annealing temperature and the distribution of secondary phase was controlled by the bainitic transformation temperature. The secondary phase contributed to elongation and/or UTS depending on the ferrite morphology which determined deformation mode simple elongation or rotation of secondary phase along the tensile direction In case of the sample containing the granular type retained austenite the elongation was improved as carbon stabilized the austenite phase. If the film-shape retained austenite in acicular ferrite was dominant however UTS was enhanced as the transformed martensite was hardened by carbon.

• 한국주조공학회지
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• 제24권2호
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• pp.79-84
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• 2004

In this study, the electromagnetic vibration is adopted for modifying eutectic Si phase and reducing its size. The higher the current density and frequency of electromagnetic vibration(EMV), the finer the size of eutectic Si phase. The tensile strength and elongation of EMVed alloy were highly improved. Measured twin probability of EMVed alloy at a frequency of 1000 Hz was approximately six times as high as that of the normal alloy. The mechanism for the increase in twin density due to EMV during solidification could be supposed from the fact that the preferential growth along <112> in silicon was suppressed by preventing Si atom from attaching to the growing interface of Si phase and by changing the solid/liquid interfacial energy of silicon. According to the result of UTS test, because of modification of eutectic Si, UTS and elongation are highly increased.

• 한국분말재료학회지
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• 제1권1호
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• pp.66-71
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• 1994

Optical microstructures and mechanical properties of Na gas atomized Al-20Si-5Fe alloying powder and its hot extrudates were studied on 3 different types of powder size distribution. This powder showed the size distribution of 10~210 $\mu\textrm{m}$. Also the microstructures of $\alpha$-Al, primary and eutectic Si and needle shaped intermetallic compounds were observed by optical microscope. These needle shaped intermetallic compounds were identified as ${\delta}Al_4FeSi_2$- by XRD and EDX analysis. The ultimate tensile strength(UTS) of these alloy extrudates was increased from 324 to 390 MPa with decreasing powder size range from 120~210 $\mu\textrm{m}$ to 10~64 $\mu\textrm{m}$. A value of Micro-vic-kers hardness was simillar to the result of UTS. These extrudates showed better wear resistance than those of Al-20Si-2X(X : Ni, Cr, Zr), although they are insensitive to the size distribution. These results indicate that the presentation of ${\delta}Al_4FeSi_2$ intermetallic compounds contributed to the wear resistance improvement.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.141-143
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• 2007

Increasing demand of using low weight materials in recent automotive trends has been the challenge to develop a sound welding of aluminum alloys. A heat treatable AA6082-T6 and a non-heat treatable AA5083-0 aluminum alloys were joined in this study. Investigations revealed that about 60 UTS will be reduced due to welding process. Fracture happened in the interface between fusion zone and base metal of top specimen where penetration is shallow. Therefore, lower welding torch angle produced the better strength which allows deeper penetration to the top specimen. PWHT at $560^{\circ}C$ for 2 hours can be used to return the original UTS of the specimens.

• 한국표면공학회지
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• 제33권5호
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• pp.329-338
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• 2000

In this study, as an effort to improve the brittlement of coating layer, aluminum bronze coatings formed on steel substrates by arc jet spray process were subjected to post heat treatment. After each treatment, mechanical properties such as hardness, and UTS, and microstructural characterization of the specimens were investigated. The results showed that the hardness in the coatings slightly decreased with increasing heat treatment tine and temperature. The UTS of as-sprayed coatings was 4.31kgf/$\textrm{mm}^2$ and slightly increased to 5.51kgf/$\textrm{mm}^2$ after heat treatment at $900^{\circ}C$ for 120min. On the other hand, the interdiffusion of copper and aluminum particles after heat treatment lead to decrease of the porosity density and increase the bond strength.

• Geomechanics and Engineering
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• 제8권4호
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• pp.559-594
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• 2015

A nonlinear creep function incorporated into the elastic visco-plastic model may describe the long-term soil deformation more accurately. However, by applying the conventional procedure, there are challenges to determine the model parameters due to limitation of suitable data points. This paper presents a numerical solution to obtain several parameters simultaneously for a nonlinear elastic visco-plastic (EVP) model using the available consolidation data. The finite difference scheme using the Crank-Nicolson procedure is applied to solve a set of coupled partial differential equations of the time dependent strain and pore water pressure dissipation. The model parameters are determined by applying the algorithm of trust-region reflective optimisation in conjunction with the finite difference solution. The proposed method utilises all available consolidation data during dissipation of the excess pore water pressure to determine the required model parameters. Moreover, the reference time in the elastic visco-plastic model can readily be adopted as a unit of time; denoting creep is included in the numerical predictions explicitly from the very first time steps. In this paper, the settlement predictions of thick soft clay layers are presented and discussed to evaluate and compare the accuracy and reliability of the proposed method against the graphical procedure to obtain the model parameters. In addition, comparison of the available experimental results to the numerical predictions confirms the accuracy of the numerical procedure.

• Geomechanics and Engineering
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• 제7권5호
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• pp.495-524
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• 2014

To investigate the soil-pile interactive performance under lateral loads, a set of laboratory model tests was conducted on remoulded test bed of soft clay and medium dense sand. Then, a simplified boundary element analysis had been carried out assuming floating pile. In case of soft clay, it has been observed that lateral loads on piles can initiate the formation of a gap, soil heave and the tension crack in the vicinity of the soil surface and the interface, whereas in medium dense sand, a semi-elliptical depression zone can develop. Comparison of test and boundary element results indicates the accuracy of the solution developed. However, in the boundary element analysis, the possible shear stresses likely to be developed at the interface are ignored in order to simplify the existing complex equations. Moreover, it is unable to capture the influence of base restraint in case of a socketed pile. To bridge up this gap and to study the influence of the initial stress state and interface parameters, a field based case-study of laterally-loaded pile in layered soil with socketed tip is explored and modelled using the finite element method. The results of the model have been verified against known field measurements from a case-study. Parametric studies have been conducted to investigate the influence of the coefficient of lateral earth pressure and the interface strength reduction factor on the results of the model.

• Asian-Australasian Journal of Animal Sciences
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• 제8권2호
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• pp.113-118
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• 1995

Eighteen Holstein Friesian ${\times}$ Native heifers with an average live weight of $175.4{\pm}27.8kg$ were allotted to 3 dietary groups. All animals were kept individually in a stanchion barn with free access to water and urea-treated rice straw (UTS). The supplemented feeds were as follows: Group (Gr) 1 - concentrate mixture (15% CP) at 1% body weight (BW), Gr 2 - concentrate mixture at 0.7% BW + free licking of multinutrient block (MNB), Gr 3 - as Gr 2 + 0.3% BW ground com. Multinutrient block composed of 20% mineral mixture, 10% urea, 18% molasses, 20% soybean meal, 22% sesame meal, 10% cement, 0.15 million IU and 50 IU/kg MNB of vitamin A and E. The experimental period lasted 12 weeks. The result revealed that MNB enhanced intake of UTS and total dry matter intake. Animals in Gr 3 consumed a higher amount of feed than the other 2 groups, thus resulting in the highest live weight gain and tended to possess the best feed conversion ratio. Heifers in Gr 2 also performed better than Gr 1 although the difference was not significant. Average MNB intake found to be 0.65 kg/day. Feed cost per kg gain was not significantly different amon groups. However if the cost of MNB could be lower, it would benefit the production cost of animals. The advantage of MNB is the safety of using a high level of urea. Although it was supplemented to UTS which also contained non-protein nitrogen (NPN), no toxic sign was shown. The results indicated that MNB could be partially substituted to concentrate mixture and it was even better when used incombination with soluble carbohydrate feed.

• Geomechanics and Engineering
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• 제6권3호
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• pp.293-320
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• 2014

In this study, in order to evaluate adequacy of considering local site effect, excluding soil-structure interaction (SSI) effects in inelastic dynamic analysis and design of mid-rise moment resisting building frames, three structural models including 5, 10, and 15 storey buildings are simulated in conjunction with two soil types with the shear wave velocities less than 600 m/s, representing soil classes $D_e$ and $E_e$ according to the classification of AS1170.4-2007 (Earthquake actions in Australia) having 30 m bedrock depth. Structural sections of the selected frames were designed according to AS3600:2009 (Australian Standard for Concrete Structures) after undertaking inelastic dynamic analysis under the influence of four different earthquake ground motions. Then the above mentioned frames were analysed under three different boundary conditions: (i) fixed base under direct influence of earthquake records; (ii) fixed base considering local site effect modifying the earthquake record only; and (iii) flexible-base (considering full soil-structure interaction). The results of the analyses in terms of base shears and structural drifts for the above mentioned boundary conditions are compared and discussed. It is concluded that the conventional inelastic design procedure by only including the local site effect excluding SSI cannot adequately guarantee the structural safety for mid-rise moment resisting buildings higher than 5 storeys resting on soft soil deposits.