• 터널과지하공간
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• 제5권1호
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• pp.1-10
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• 1995

The behavior of a jointed rock mass depends mainly on the geometrical and mechanical properties of joints. The failure mode of a rock mass and kinematics of rock blocks are governed by the orientation, spacing, and persistence of joints. The mechanical properties such as dilation angle, shear strength, maximum closure, strength of asperities and friction coeffiient play important roles on the stability and deformation of the rock mass. The normal and shear behaviour of a joint are coupled due to dilation, and the joint deformation depends also on the boundary conditions such as stiffness conditons. In this paper, the joint constitutive law including the dilatant behaviour of a joint is numerically modelled using the edge-to-edge contact logic in distinct element method. Also, presented is the method to quantify the input parameters used in the joint law. The results from uniaxial compression and direct shear tests using the numeical model of the single joint were compared to the analytic results from them. The boundary effect on the behaviour of a joint is verified by comparing the results of direct shear test under constant stress boundary condition with those under constant stiffness boundary condition. The numerical model developed is applied to a complex jointed rock mass to examine its performance and to evaluate the effect of joint dilation on tunnel stability.

• 전산구조공학
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• 제10권4호
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• pp.143-154
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• 1997

본 연구에서는 지하암반구조물의 구조해석시 불연속암반체의 물성변이를 고려할 수 있는 확률론적 해석기법을 개발하였다. 수치해석적 접근은 몬테칼로모사기법의 단점을 보완한 LHS기법을 사용하였고, 불연속면의 영향은 단층, 벽개 등과 같이 불연속성이 뚜렷한 지역에서 적용성이 높은 절리유한요소모델을 사용하였다. 재료특성에 대한 확률변수는 불연속면의 수직강성과 전단강성을 다확률변수로 사용하였으며, 이들은 확률공간에서 정규분포를 갖는 경우에 대하여 고려하였다. 본 연구에서 개발된 수치해석프로그램은 검증예제를 통하여 타당성을 확인하였으며, 가상의 불연속면군이 존재하는 지하원형공동에 대한 해석을 통하여 프로그램의 적용성을 확인하였다.

• 지질공학
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• 제1권1호
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• pp.38-53
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• 1991

지하공동의 설계는 지반이 본래 가지고 있는 물리적 특성을 최대한 이용하는 것을 기본 개념으로 하므로 지반자체의 복잡다양한 역학적 특성들을 평가하여 설계에 반영하는 것은 지극히 어려운 일이며, 이러한 특성들을 일률적으로 평가하는 것도 거의 불가능하다. 컴퓨터의 발달과 수치해석 기술의 적용이 본격화 되기까지는 지반의 거동을 지배하는 몇가지 주요요소의 정성적 혹은 정량적 특성에 의하여 지반을 몇가지 등급으로 분류하여 통계자료의 분석 및 경험적 판단에 의해 설계를 수행하여 왔다. 지하공동구조물 설계시으 지반거동해석은 이완영역의 가정에 의한 방법, 경험적 접근법에 의한 방법 및 최근에 와서 수치해석 기술의 발달에 따라 주로 사용되는 공학적 해석 방법에 의한 지반거동해석 등으로 구분하여 정리하였다.

• 펄프종이기술
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• 제33권1호
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• pp.38-44
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• 2001

The effects of refining load on the paper properties were investigated. HwBKP, SwBKP and SwUKP were refined with PFI mill at the load of 3.33 N/mm and 6.00 N/mm. Higher Scott bond was obtained at the higher refining load for three pulp used in this study. However any changes in the light scattering coefficient with the change of refining load were not observed. Although the effect of refining load on the formation index for SwUKP was not observed, higher refining load gave the better formation for HwBKP and SwBKP. The fiber mass and fiber crowding factor were not affected by the refining load. Higher apparent density and tensile index were obtained with the higher refining load. However, the higher refining load did not improve the tensile index at the same apparent density. The tear index was decreased with the increase of refining load.

• 대한기계학회논문집B
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• 제32권7호
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• pp.487-496
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• 2008

Quartz crystal oscillator is frequently used in measuring a very small amount of mass attached to or adsorbed on the surface of an electrode on the quartz plate. The physical principle is that the resonance frequency of the shear vibration of the quartz caused by an applied electric field is a function of the mass. Recently, effort has been tried to measure physical properties of viscoelastic fluids, such as viscosity and shear modulus. This paper presents useful formula that can be used in estimating the properties of viscoelastic fluids. Important finding in this analysis is that the formula can produce multiple values for the physical properties of the viscoelastic materials.

• 대한기계학회논문집
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• 제17권11호
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• pp.2704-2710
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• 1993

A simple and straightforward method is introduced for developing continuum beam-rod model of a box-beam typed aircraft wing with composite layered skin based on "energy equivalence." The equivalent continuum structral properties are obtained from the direct comparison of the reduced stiffness and mass matrices for box-beam typed wing with those for continuum beam-rod model. The stiffness and mass matrices are all represented in terms of the continuum degrees-of freedom defined in this paper. The finite-element method. The advantage of the present continuum method is to give every continuum structural properties including all possible coupling terms which represent the couplings between different deformations. To evaluate the continuum method developed in this paper, free vibration analyses for both continuum beam-rod and box-beam are conducted. Numerical tests show that the present continuum method gives very reliable structural and dynamic properties compared to the results by the conventional finite-element analysis. analysis.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.235-237
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• 2012

Geodae-Uksae 1 is a variety of Miscanthus sacchariflorus recently discovered in Korea. It is being mass-cultivated for use as energy crop due to its superior productivity, as high as 30 ton/ha/yr for the dry mass. This study investigates the method of producing biochar and bio-oil from the crop using slow pyrolysis. Especially, the study focused on assessing the biochar properties for its application to soil to improve soil quality and sequestrate carbon. Using an electrically heated packed bed reactor, the products of slow pyrolysis from Geodae-Uksae 1 were produced over a temperature range of $300-700^{\circ}C$ with a heating rate of $10^{\circ}C/min$. The biochar, condensable vapor (bio-oil) and residual gases were characterized for the physical and chemical properties. It was concluded that the ideal temperature for pyrolysis to produce biochar is $500^{\circ}C$.

• Nuclear Engineering and Technology
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• 제33권6호
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• pp.605-618
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• 2001

For the mechanical stability assessment of a deep underground high-level waste repository. computer simulations using FLAC3D were carried out and important parameters including stress ratio, depth, tunnel size, joint spacing, and joint properties were chosen from sensitivity analysis. The main effect as well as the interaction effect between the important parameters could be investigated effectively using fractional factorial design . In order to analyze the stability of the disposal tunnel and deposition hole in a discontinuous rock mass, different modelings were performed under different conditions using 3DEC and the influence of joint distribution and properties, rock properties and stress ratio could be determined. From the three dimensional modelings, it was concluded that the conceptual repository design was mechanically stable even in a discontinuous rock mass.

• 천문학회보
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• 제38권1호
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• pp.32.1-32.1
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• 2013

We use numerical simulations to investigate the evolution of both the star formation rate (SFR) and the observable properties of equal-mass disk merger remnants for 18 different orbital configurations. In our analysis, the photometric properties of the remnants have been constructed by considering dust reddening effect in order to facilitate the comparison with observational data of large surveys such as the Sloan Digital Sky Survey (SDSS). First, we found that the detailed evolutions of merging galaxies are different between the merging characteristics such as merging time scale, SFR history, and burst efficiency. Around $70{\pm}5$ percent of gas turns into stars until the merger-induced starburst ends regardless of merger types. Our study also suggests that merger features involve a small fraction of stars. Merger features last roughly 3 times the final coalescence time of galaxy mergers. For a shallower surface brightness limit, the features seem to survive in a shorter time, which is the reason why detecting merger features by using shallow surveys were difficult in the past.

• 한국세라믹학회지
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• 제44권9호
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• pp.496-501
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• 2007

The properties of the polymer-modified mortars are influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases. Also, this quality of polymer modified cement strongly depend on weather condition. To overcome this problem, polymer-modified cement based on rapid setting cement mortars were prepared by varying polymer/cement mass ratio (P/C) with a constant water/cement mass ratio of 0.5. The effect of polymer on the hydration of this polymer cement is studied on different curing temperature. The results showed that the polymer mortar which is modified with rapid setting cement have superior physical strength properties on independent curing temperature. In addition the PIC ratio, the compressive strength, flexural strength, tensile strength and adhesion strength of mortar is enhances and polymer-modified cement based on rapid setting cement is more beneficial to the improvement of the mortar properties in jobsite.