• Computers and Concrete
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• 제7권4호
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• pp.317-329
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• 2010

The paper describes localization of deformation in a bar under tensile loading. The material of the bar is considered as non-linear viscous elastic and the bar consists of two symmetric halves. It is assumed that the model represents behavior of the quasi-brittle viscous material under uniaxial tension with different loading rates. Besides that, the bar could represent uniaxial stress-strain law on a single plane of a microplane material model. Non-linear material property is taken from the microplane material model and it is coupled with the viscous damper producing non-linear Maxwell material model. Mathematically, the problem is described with a system of two partial differential equations with a non-linear algebraic constraint. In order to obtain solution, the system of differential algebraic equations is transformed into a system of three partial differential equations. System is subjected to loadings of different rate and it is shown that localization occurs only for high loading rates. Mathematically, in such a case two solutions are possible: one without the localization (unstable) and one with the localization (stable one). Furthermore, mass is added to the bar and in that case the problem is described with a system of four differential equations. It is demonstrated that for high enough loading rates, it is the added mass that dominates the response, in contrast to the viscous and elastic material parameters that dominated in the case without mass. This is demonstrated by several numerical examples.

• Smart Structures and Systems
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• 제23권6호
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• pp.579-587
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• 2019

In this paper, pounding tuned mass dampers (PTMDs) were designed to mitigate the multi-mode vortex-induced vibration (VIV) of stay cable utilizing the viscous-elastic material's energy-dissipated ability. The PTMD device consists of a cantilever metal rod beam, a metal mass block and a specially designed damping element covered with viscous-elastic material layer. Wind-tunnel experiment on VIV of stay cable model was set up to validate the effectiveness of the PTMD on multi-mode VIV mitigation of stay cable. By analyzing and comparing testing results of all testing cases, it could be verified that the PTMD with viscous-elastic pounding boundary can obviously mitigate the VIV amplitude of the stay cable. Moreover, the installed location and the design parameters of the PTMD device based on the controlled modes of the primary stay cable, would have a certain extent suppression on the other modal vibration of the stay cable, which means that the designed PTMDs are effective among a large band of frequency for the multi-mode VIV control of the stay cable.

• Coupled systems mechanics
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• 제8권3호
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• pp.199-218
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• 2019

This paper studies the forced vibration of the hydro-elastic system consisting of the anisotropic (orthotropic) plate, compressible viscous fluid and rigid wall within the scope of the exact equations and relations of elastodynamics for anisotropic bodies for describing of the plate motion, and with utilizing the linearized exact Navier-Stokes equations for describing of the fluid flow. For solution of the corresponding boundary value problem it is employed time-harmonic presentation of the sought values with respect to time and the Fourier transform with respect to the space coordinate on the coordinate axis directed along the plate length. Numerical results on the pressure acting on the interface plane between the plate and fluid are presented and discussed. The main aim in this discussion is focused on the study of the influence of the plate material anisotropy on the frequency response of the mentioned pressure. In particular, it is established that under fixed values of the shear modulus of the plate material a decrease in the values of the modulus of elasticity of the plate material in the direction of plate length causes to increase of the absolute values of the interface pressure. The numerical results are presented not only for the viscous fluid case but also for the inviscid fluid case.

• 한국식품영양과학회지
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• 제26권2호
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• pp.198-202
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• 1997

김치 담글 때 조미료로 sucrose를 첨가한 경우, 발효 시간의 경과와 더불어 김치국물의 정도가 증가한다. 이 현상은 장김치에서 두드러지는 것으로 관찰되었으므로 본 연구에서는 소금으로 담근 김치를 대조구로 하여 간장으로 담근 장김치에서의 정도 증가를 비교하였으며 이 점성물질의 본성을 밝힘과 동시에 그 생성조건을 검토하였다. 장김치국물에 에탄올을 가하여 생성된 침전물을 산으로 가수분해하여 HPLC로 분석한 결과 glucose를 단위체로 한 polysaccharide인 dextran으로 밝혀졌다. 이 dextran의 생성에는 glucose 보다는 sucrose가 효과적이며, sucrose의 농도가 10%까지 증가함에 따라 점도는 비례하여 증가하였다. 또 소금보다는 간장으로 담근 김치에서 정도가 높았으며, 협기적인 조건보다는 호기적인 조건에서 점도가 높았다. 장김치는 소금김치 보다 산생성이 많았으며 당을 첨가한 경우 산 생성량은 증가하였다. 또 환원당량은 sucrose를 첨가한 경우 김치숙성 초기에 크게 증가하였다. 김치발효과정 중 총 균수와 Leuconostoc 세균수의 변화를 살펴 본 결과 발효 1일째에 Leuconostoc 균수, 총 균수가 최대에 달했으며 Leuconostoc 균수는 그 후 점차 감소하였다. 장김치와 소금김치 간에는 발효 중 균수의 차이가 없었으며 sucrose를 첨가한 경우에도 큰 차이는 없는 것으로 나타나 김치에서 점성물질이 생성되는 것은 균수에 의한 차이가 아니라 점성물질 생성 조건의 차이에 의한 것으로 생각되었다.

• 한국산학기술학회논문지
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• 제10권2호
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• pp.407-411
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• 2009

본 논문에서는 전편에 개발된 간단한 전단속도 의존적 구성모델의 각 모델변수에 대한, 정의, 값 결정법 및 결과에 미치는 영향 등에 대하여 분석하였다. 분석결과, 특히 전단속도 및 점성 핵 관련 모델변수의 영향이 보편적 범위 내에 있는 것으로 나타났다 이러한 관점에서 점성 및 소성 항복면을 동일시하는 개념의 모델 간략화 수정을 하였으며, 결과는 비교적 성공적으로 나타났다.

• 한국해양공학회지
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• 제7권2호
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• pp.162-172
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• 1993

In the present paper, the overall state of the arts of ice mechanics which is the most typical research topic of the artic engineering field was studied. And also, ice loads genrated by ice-structure interaction were estimated using numerical approach. The effects of viscous property of ice sheets to the ice load were investigated. The time dependent deformation behaviors of ice was modeled by visco-plastic problem using the finite element formalism. Constitutive model representing the material properties of ice was idealized by comblned rheological model with Maxwell and Voigt models. Numerical calculations for the bending and crushing behavior of ice sheet which are the most typical interaction modes between ice sheets and structures were carried out. The time dependent viscous behaviors of ice sheets interaction forces acting on structures were analyzed and the results were studied in detail.

• 한국어병학회지
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• 제18권2호
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• pp.167-178
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• 2005

본 연구에서는 S. iniae의 병원성 요인으로 작용할 수 있는 capsule의 존재 여부를 확인하고 그에 따른 capsule과 병원성과의 상관 관계를 조사하였다. 즉, 집락의 형태학적 특성에 따라 viscous form (V+)과 non-viscous form (V-)의 균주로 구분하여 그 특성을 비교 분석하였다. 분리균의 생리학적 및 생화학적 특성으로는 숙주의 방어 기작에 대한 저항성이나 병원성 차이를 구분할 수 없었으나 형태학적으로 큰 차이를 있음을 알 수 있었다. 즉, V+인 경우 cell wall 표면에 capsule이 존재하지만 V-에서는 capsule이 존재하지 않는 것으로 확인되었다. V+는 넙치 혈청에서 증식할 수 있지만 V-는 넙치 혈청에 의해 살균되는 것으로 나타나 capsule의 유무에 따라 넙치의 체액성 면역 요소에 대한 저항력에서 차이가 나는 것을 알 수 있었다. 또한, V+는 넙치 신선 혈청으로 감작한 경우에도 V-에 비해 macrophage의 식균율이 낮았으며 식균된 이후에는 균 수가 지속적으로 감소하는 것을 확인할 수 있었고 일반 어류 주화 세포 내로 침입하여 생존 및 증식할 수 있는 것으로 나타났다. 이들 결과는 앞으로의 백신 개발에 유용한 기초 자료로 사용될 수 있을 것으로 사료되었다.

• Earthquakes and Structures
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• 제5권4호
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• pp.461-475
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• 2013

A new experimental system of base-isolated structures is proposed. There are two kinds of dampers usually used in the base-isolated buildings, one is a viscous-type damper and the other is an elastic-plastic hysteretic-type damper. The base-isolated structure with a viscous damper and that with an elastic-plastic hysteretic damper are compared in this paper. The viscous damper is modeled by a mini piston and the elastic-plastic hysteretic damper is modeled by a low yield-point steel. The capacity of both dampers is determined so that the dissipated energies are equivalent at a specified deformation. When the capacity of both dampers is determined according to this criterion, it is shown that the response of the base-isolated structure with the elastic-plastic hysteretic damper is larger than that with the viscous damper. This characteristic is demonstrated through the comparison of the bound of the aspect ratio. It is shown that the bound of aspect ratio for the base-isolated structure with the elastic-plastic hysteretic damper is generally smaller than that with the viscous damper. When the base-isolated structure is subjected to long-duration input, the mechanical property of the elastic-plastic hysteretic damper deteriorates and the response of the base-isolated structure including that damper becomes larger than that with the viscous damper. The effect of this change of material properties on the response of the base-isolated structure is also investigated.

• Structural Engineering and Mechanics
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• 제64권4호
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• pp.515-526
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• 2017

Dynamic response of functionally graded Carbon nanotubes (FG-CNT) reinforced pipes conveying viscous fluid under accelerated moving load is presented. The mixture rule is used for obtaining the material properties of nano-composite pipe. The radial force induced by viscous fluid is calculated by Navier-Stokes equation. The material properties of pipe are considered temperature-dependent. The structure is simulated by Reddy higher-order shear deformation shell theory and the corresponding motion equations are derived by Hamilton's principal. Differential quadrature (DQ) method and the Integral Quadrature (IQ) are applied for analogizing the motion equations and then the Newmark time integration scheme is used for obtaining the dynamic response of structure. The effects of different parameters such as boundary conditions, geometrical parameters, velocity and acceleration of moving load, CNT volume percent and distribution type are shown on the dynamic response of pipe. Results indicate that increasing CNTs leads to decrease in transient deflection of structure. In accelerated motion of the moving load, the maximum displacement is occurred later with respect to decelerated motion of moving load.

• Coupled systems mechanics
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• 제9권3호
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• pp.289-309
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• 2020

The paper studies the fluid flow profile contained between the orthotropic plate and rigid wall under the action of the moving load on the plate and main attention is focused on the fluid velocity profile in the load moving direction. It is assumed that the plate material is orthotropic one and the fluid is viscous and barotropic compressible. The plane-strain state in the plate and the plane flow of the fluid is considered. The motion of the plate is described by utilizing the exact equations of elastodynamics for anisotropic bodies, however, the flow of the fluid by utilizing the linearized Navier-Stokes equations. For the solution of the corresponding boundary value problem, the moving coordinate system associated with the moving load is introduced, after which the exponential Fourier transformation is employed with respect to the coordinate which indicates the distance of the material points from the moving load. The exact analytical expressions for the Fourier transforms of the sought values are obtained, the originals of which are determined numerically. Presented numerical results and their analyses are focused on the question of how the moving load acting on the face plane of the plate which is not in the contact with the fluid can cause the fluid flow and what type profile has this flow along the thickness direction of the strip filled by the fluid and, finally, how this profile changes ahead and behind with the distance of the moving load.