• 사회복지연구
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• 제45권3호
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• pp.127-150
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• 2014

급격히 증가하고 있는 맞벌이 부부의 가장 심각한 문제로 지목되고 있는 것은 자녀 양육 문제이다. 이로 인해 맞벌이 부부는 심각한 양육스트레스를 경험하게 되는 것으로 보고되고 있으며 특히 어린 자녀를 두고 있는 맞벌이 부부의 양육스트레스는 다른 연령에 비해 매우 높아 이 시기 부부 관계에까지 부정적 영향을 미칠 가능성이 있음이 지적되고 있다. 이러한 부부간의 갈등은 결혼 안정성을 해칠 뿐만 아니라 어린 자녀들의 문제행동을 야기하는 등 매우 심각한 부정적 영향들을 야기하게 된다. 이에 본 연구는 맞벌이 부부의 결혼안정성을 높일 수 있는 사회적 지원 및 서비스의 기초자료를 제공하기 위해 양육스트레스가 이들의 부부관계에 어떠한 영향을 미치는지를 실증적으로 검증하였다. 특히 선행연구가 부부간의 상호 영향을 주고받는 상호역동적인 관계 양상을 자료 수집 및 분석 과정에서 포함하지 못해왔다는 한계를 극복하고자 상호의존적 연구모형을 구성하여 이를 실증적으로 검증하였다. 본 연구는 한국아동패널의 4차년도 데이터를 활용하여 629쌍의 커플 자료(dyadic data)를 Actor-Partner interdependence model(APIM)로 분석하여 맞벌이 부부의 부부갈등과 양육스트레스에 대한 이해를 확장하고자 하였다. 연구결과 맞벌이 부부의 양육스트레스가 남편과 아내 각각의 부부갈등에 정적으로 유의한 영향을 미치고 있었으며, 남편의 양육스트레스가 아내의 부부갈등에 정적 영향을 미치고 있었으며 아내의 양육스트레스 또한 남편의 부부갈등에 정적 영향을 미치고 있었다. 즉, 양육스트레스의 부부갈등에 대한 자기효과와 상대방효과가 모두 유의한 정적 관계를 보인 것이다. 이러한 결과는 맞벌이 부부의 양육스트레스와 부부갈등에 대한 문제 파악 및 개입 시 부부의 상호의존적인 영향 관계를 반드시 고려해야할 필요성과 그에 따라 부부를 한 단위(unit)로 접근해야 함을 실증적으로 입증한 결과라 하겠다.

• 대한가정학회지
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• 제44권6호
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• pp.47-58
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• 2006

This research focused on the family stress and family strengths in double-income couples. The subjects of this study were 171 double-income couples, in the Kyeongnam Area, Korea. The major findings from the study are as follows. 1) The degree of family stress of the husband and wife in double-income couples was 2.90 and 2.97, respectively, on a scale of 0-5.0. The significant variables were economic level, self-esteem and marital satisfaction in double-income couples' husband, and having a housework-helper, job satisfaction, self-esteem and marital satisfaction in double-income couples' wife. 2) The degree of family strengths of the husband and wife in double-income couples was 3.84 and 3.82, respectively, on a scale of 0-5.0. The significant variables were job satisfaction, self-esteem and marital satisfaction in double-income couples' husband, and the educational level, job type, self-esteem and marital satisfaction in double-income couples' wife. 3) There was a close inverse correlation between the lamely stress and family strengths in the husband and wife of double-income couples.

• Computers and Concrete
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• 제32권5호
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• pp.439-454
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• 2023

In this article, the surface stress effects on the buckling analysis of the annular sandwich plate is developed. The proposed plate is composed of two face layers made of carbon nanotubes (CNT) reinforced composite with assuming of fully bonded to functionally graded porous core. The generalized rule of the mixture is employed to predict the mechanical properties of the microcomposite sandwich plate. The derived potentials energy based on higher order shear deformation theory (HSDT) and modified couple stress theory (MCST) is solved by employing the Ritz method. An exact analytical solution is presented to calculate the critical buckling loads of the annular sandwich plate. The predicted results are validated by carrying out the comparison studies for the buckling analysis of annular plates with those obtained by other analytical and finite element methods. The effects of various parameters such as material length scale parameter, core thickness to total thickness ratio (hc/h), surface elastic constants based on surface stress effect, various boundary condition and porosity distributions, size of the internal pores (e0), Skempton coefficient and elastic foundation on the critical buckling load have been studied. The results can be served as benchmark data for future works and also in the design of materials science, injunction high-pressure micropipe connections, nanotechnology, and smart systems.

• Geomechanics and Engineering
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• 제10권4호
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• pp.423-436
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• 2016

Currently, there is a great interest in the coupling between multiphase fluid flow and geomechanical effects in hydrocarbon reservoirs and surrounding rocks. The ideal solution for this coupled problem is to introduce the geomechanical effects through the stress analysis solution and implement an algorithm, which assures that the equations governing the flow and stress analyses are obeyed in each time step. This paper deals with the implementation of a program (FORTRAN90 interface code), which was developed to couple conventional reservoir (ECLIPSE) and geomechanical (ABAQUS) simulators, using a partial coupling algorithm. The explicit coupled hydro-mechanical behavior of Iranian field during depletion and $CO_2$ injection is studied using the soils consolidation procedure available in ABAQUS. Time dependent reservoir pressure fields obtained from three dimensional compositional reservoir models were transferred into finite element reservoir geomechanical models in ABAQUS as multi-phase flow in deforming reservoirs cannot be performed within ABAQUS. The FEM analysis of the reservoir showed no sign of plastic strain under production and $CO_2$ injection scenarios in any part of the reservoir and the stress paths do not show a critical behavior.

• Steel and Composite Structures
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• 제41권6호
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• pp.805-820
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• 2021

In this research, the buckling and free vibration of three-phase carbon nanotubes/ fiber/ polymer piezoelectric nanocomposite face sheet sandwich microbeam with microsensor and micro-actuator surrounded in elastic foundation based on modified couple stress theory (MCST) is investigated. Three types of porous materials are considered for sandwich core. Higher order (Reddy) and sinusoidal shear deformation beam theories are employed for the displacement fields. Sinusoidal surface stress effects are extracted for sinusoidal shear deformation beam theory. The equations of motion are derived by Hamilton's principle and then the natural frequency and critical buckling load are obtained by Navier's type solution. The determined results are in good agreement with other literatures. The detailed numerical investigation for various parameters is performed for this microsensor-microactuator. The results reveal that the microsensor-microactuator enhanced by increasing of Skempton coefficient, carbon nanotubes diameter length to thickness ratio, small scale factor, elastic foundation, surface stress constants and reduction in porous coefficient, micro-actuator voltage and CNT weight fraction. The valuable results can be expedient for micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) systems.

• Steel and Composite Structures
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• 제31권3호
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• pp.261-276
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• 2019

The study investigates the free vibration of a nano-scale sandwich beam by an extended high order approach, which has not been reported in the existing literature. First-order shear deformation theory for steel skins and so-called high-order sandwich panel theory for the core are applied. Next, the modified couple stress theory is used for both skins and cores. The Hamilton principle is utilized for deriving equations and corresponding boundary conditions. First, in the study the three-mode shapes natural frequencies for various material parameters are investigated. Also, obtained results are evaluated for two types of stiff and soft cores and isotropic, homogenous steel skins. In the research since the governing equations and also the boundary conditions are nonhomogeneous, therefore some closed-form solutions are not applicable. So, to obtain natural frequencies, the boundary conditions are converted to initial conditions called the shooting method as the numerical one. This method is one of the most robust approaches to solve complex equations and boundary conditions. Moreover, three types of simply supported on both sides of the beam (S-S), simply on one side and clamp supported on the other one (S-C) and clamped supported on both sides (C-C) are scrutinized. The parametric study is followed to evaluate the effect of nano-size scale, geometrical configurations for skins, core and material property change for cores as well. Results show that natural frequencies increase by an increase in skins thickness and core Young modulus and a decrease in beam length, core thickness as well. Furthermore, differences between obtained frequencies for soft and stiff cores increase in higher mode shapes; while, the more differences are evaluated for the stiff one.

• Advances in nano research
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• 제10권5호
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• pp.449-460
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• 2021

Flexoelectricity is an interesting materials' property that is more touchable in small scales. This property beside the sandwich structures placed in the center of scientists' attention due to their extraordinary effects on the mechanical properties. Furthermore, in the passage of decades, more elaborated sandwich structures took into consideration results from using honeycomb core. This kind of structure, inspiring from honeycomb core, provides more stiffness to weight ratio, which plays a crucial role in different industries. In this paper, based on the Love-Kirchhoff's hypothesis, Hamilton's principle, modified couple stress theory and Fourier series analytical method, equations of motion for a sandwich plate containing a honeycomb core integrated by two face-sheets have derived and solved analytically. The equations of both face sheets have derived by flexoelectricity consideration. Moreover, it should be noticed that the whole structure rests on the visco-Pasternak foundation. Conducting current research provided an acceptable and throughout study based on flexoelectricity to address the effect of materials' characteristics, length-scale parameter, aspect, and thickness ratios and boundary conditions on the natural frequency of honeycomb sandwich plates. Also, based on the presented figures and tables, there is a close agreement between previous studies and recent work. Due to the high ratio of strength to weight, current model analyzing is capable of taking into account for different vehicles' manufacturing in a high range of industries.

• Steel and Composite Structures
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• 제38권3호
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• pp.337-353
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• 2021

Micro-electro-mechanical systems (MEMS) are widely employed in sensors, biomedical devices, optic sectors, and micro-accelerometers. New reinforcement materials such as carbon nanotubes as well as graphene platelets provide stiffer structures with controllable mechanical specifications by changing the graphene platelet features. This paper deals with buckling analyses of functionally graded graphene platelets micro plates with two piezoelectric layers subjected to external applied voltage. Governing equations are based on Kirchhoff plate theory assumptions beside the modified couple stress theory to incorporate the micro scale influences. A uniform temperature change and external electric field are regarded along the micro plate thickness. Moreover, an external in-plane mechanical load is uniformly distributed along the micro plate edges. The Hamilton's principle is employed to extract the governing equations. The material properties of each composite layer reinforced with graphene platelets of the considered micro plate are evaluated by the Halpin-Tsai micromechanical model. The governing equations are solved by the Navier's approach for the case of simply-supported boundary condition. The effects of the external applied voltage, the material length scale parameter, the thickness of the piezoelectric layers, the side, the length and the weight fraction of the graphene platelets as well as the graphene platelets distribution pattern on the critical buckling temperature change and on the critical buckling in-plane load are investigated. The outcomes illustrate the reduction of the thermal buckling strength independent of the graphene platelets distribution pattern while meanwhile the mechanical buckling strength is promoted. Furthermore, a negative voltage, -50 Volt, strengthens the micro plate stability against the thermal buckling occurrence about 9% while a positive voltage, 50 Volt, decreases the critical buckling load about 9% independent of the graphene platelet distribution pattern.

• Advances in nano research
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• 제12권5호
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• pp.467-482
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• 2022

In the current work, static and free torsional vibration of functionally graded (FG) nanorods are investigated using Fourier sine series. The boundary conditions are described by the two elastic torsional springs at the ends. The distribution of functionally graded material is considered using a power-law rule. The systems of equations of the mechanical response of nanorods subjected to deformable boundary conditions are achieved by using the modified couple stress theory (MCST) and taking the effects of torsional springs into account. The idea of the study is to construct an eigen value problem involving the torsional spring parameters with small scale parameter and functionally graded index. This article investigates the size dependent free torsional vibration based on the MCST of functionally graded nano/micro rods with deformable boundary conditions using a Fourier sine series solution for the first time. The eigen value problem is constructed using the Stokes' transform to deformable boundary conditions and also the convergence and accuracy of the present methodology are discussed in various numerical examples. The small size coefficient influence on the free torsional vibration characteristics is studied from the point of different parameters for both deformable and rigid boundary conditions. It shows that the torsional vibrational response of functionally graded nanorods are effected by geometry, small size effects, boundary conditions and material composition. Furthermore, for all deformable boundary conditions in the event of nano-sized FG nanorods, the incrementing of the small size parameters leads to increas the torsional frequencies.

• Structural Engineering and Mechanics
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• 제89권3호
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• pp.225-238
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• 2024

In this paper, a quasi-3D hyperbolic shear deformation theory for the bending responses of a functionally graded (FG) porous micro-beam is based on a modified couple stress theory requiring only one material length scale parameter that can capture the size influence. The model proposed accounts for both shear and normal deformation effects through an illustrative variation of all displacements across the thickness and satisfies the zero traction boundary conditions on the top and bottom surfaces of the micro-beam. The effective material properties of the functionally graded micro-beam are assumed to vary in the thickness direction and are estimated using the homogenization method of power law distribution, which is modified to approximate the porous material properties with even and uneven distributions of porosity phases. The equilibrium equations are obtained using the virtual work principle and solved using Navier's technique. The validity of the derived formulation is established by comparing it with the ones available in the literature. Numerical examples are presented to investigate the influences of the power law index, material length scale parameter, beam thickness, and shear and normal deformation effects on the mechanical characteristics of the FG micro-beam. The results demonstrate that the inclusion of the size effects increases the microbeams stiffness, which consequently leads to a reduction in deflections. In contrast, the shear and normal deformation effects are just the opposite.