• Steel and Composite Structures
• /
• 제49권5호
• /
• pp.547-570
• /
• 2023

In the present work, a comparative study has been carried out between power, exponential, and sigmoidal sandwich FGM plates for free vibration conditions under hygro-thermal conditions. Rules of mixture is used to determine effective material properties across the thickness for power-law and sigmoid sandwich FGM plates. Exponential law is used to plot effective material properties for exponentially graded sandwich FGM plates. Temperature and moisture dependent material properties were used during the analysis. Free vibration analysis is carried out using recently proposed finite element based HOZT. Present formulation satisfies interlayer transverse stress continuity conditions at interfaces and transverse shear stress-free conditions at the plate's top and bottom surfaces. The present model is free from any penalty or post-processing requirements. Several new results are reported in the present work, especially for unsymmetric sandwich FGM plates and exponential and sigmoidal sandwich FGM plates.

• 한국산림과학회지
• /
• 제85권3호
• /
• pp.360-371
• /
• 1996

산림휴양자원의 효과적인 관리를 위해서는 휴양지의 현재 관리상태를 평가하고 이를 토대로 지속적으로 관리할 수 있는 객관적이고 수량화된 평가기준의 설정이 필요하다. 규범적 접근방법은 이러한 평가기준을 설정할 수 있는 하나의 대안으로써, 학자들 사이에 이에 대한 관심이 증대되고 있으며 그 유용성 또한 강조되어 왔다. 본 연구는 1993년도에 지리산 국립공원내의 두 야영장(뱀사골 야영장과 제2야영장)을 이용하는 야영객들을 대상으로 실시한 현지설문조사를 토대로 수행되었다. 규범적 접근방법을 이용하여 8개 지표항목에 대한 평가기준을 설정하고 이를 토대로 현재 야영장 관리상태를 평가하였다. 뱀사골 야영장과 제2야영장에서 모두 소음시간과 쓰레기 버리는 행위에 대한 현재 상태가 본 연구에서 설정된 평가기준보다 좋지 않은 것으로 나타났으며, 무례한 행위, 텐트수, 야영객수, 급수시설을 이용하기 위해 기다리는 시간은 뱀사골 야영장에서만 평가기준보다 불량한 것으로 나타났다. 텐트사이의 거리와 화장실을 이용하기 위해 기다라는 시간에 대한 현재 상태는 두 야영장에서 모두 평가기준보다 양호했다. 본 연구는 규범적 접근방법이 평가기준설정을 위해 실질적으로 어떻게 이용될 수 있는가를 소개하고, 분석결과를 토대로 휴양자원 관리개선방안을 제시하였다.

• 한국환경과학회지
• /
• 제8권5호
• /
• pp.575-586
• /
• 1999

From the environmental aspects, primary productivity of phytoplankton plays the most improtant role in enhancement of marine culture oyster production. This study may be divided into two branches; one is estimation of maximum oyster meat production per unit facility(Carrying Capacity) under the present enviromental conditions in Kamak Bay, the other is improvement of carrying from increase of primary productivity by changing the environmental conditions that cause not ot form an unfavorable environment such as the formation of oxygen deficient water mass using the eco-hydrodynamic model. By simulation of three-dimensional hydrdynamic model and ecosystem model, the comparison between observed and computed data showed good agreement. The results of sensitivity analysis showed that phytoplankton maximum growth rate was the most important parameter for phytoplankton and dissolved oxygen. The estimation of mean primary productivity of Wonpo, Kamak, Pyongsa, and Kunnae culture grounds in Kamak Bay during culturing period were 3.73gC/$m^2$/d, 2.12gC/$m^2$/d, 1.98gC/$m^2$/d, and 1.26gC/$m^2$/d, respectively. Under condition not ot form the oxygen deficient water mass, four times increasing of pollutants loading as much as the present loading from river increased mean primary productivity of whole culture grounds to 4.02gC/$m^2$/d. Sediment N, P fluxes that allowed for 35% increasing from the present conditions increased mean primary productivity of whole culture grounds to 3.65gC/$m^2$/d. Finally, ten times increasing of boundary loadings from the present conditions increased mean primary productivity of whole culture grounds to 3.95gC/$m^2$/d. The maximum oyster meat production per year and that of unit facility in actual oyster culture grounds under the present conditions were 6,929ton and 0.93ton, respectively. This 0.93ton/unit facility is considered to be the carrying capacity in study area, and if the primary productivity is increased by changing the environmental conditions, oyster production can be increased.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
• /
• 제6권10호
• /
• pp.23-30
• /
• 2000

The purpose of this study is to provide the basic data that helps the supplying medical resources through understanding the present conditions of medical resources and the territory of diagnosis in Uijongbu city. To achieve this goal, the statistical data related to the medical resources of Uijongbu city were analyzed; the number of population, medical facility, beds for inpatients, medical personnels and so on. Through the analysis of statistical data, it was revealed that the present conditions of medical resources are so insufficient in Uijongbu city. The results of the study were as follows; Firstly, it should be added to the beds for inpatients. Secondly, it should be characterized by specialization of hospitals. Thirdly, it should be added to the herb medicine hospital.

• Ocean and Polar Research
• /
• 제34권4호
• /
• pp.431-444
• /
• 2012

We simulated and compared present and future ocean circulation in the East China Sea using an East Asia Regional Ocean model. Mean climate states for 1990~1999 and 2030~2039 were used as surface conditions for simulations of present and future ocean circulation, which were derived from the simulations of three different global climate models, ECHAM5-MPI, GFDL-CM2.0 and MIROC3.2_hires, for the 20th century and those of 21st century as projected by the IPCC SRES A1B. East Asia Regional Ocean model simulated the detailed patterns of temperature, salinity and current fields under present and future climate conditions and their changes instead of the simple structures of global climate models. To some extent, there are consistent ocean circulation changes derived from the three pairs corresponding to the global climate model in so much as the temperature increases not only in winter but summer at both the surface and bottom and that temperature and salinity changes are prominent near the Chinese coast and in the Changjiang bank. However, the simulated circulations are different among each other depending on the prescribed atmospheric conditions not only under present climate but also with regard to future climate conditions. There is not a coincident tendency in ocean circulation changes between present and future simulations derived from the three pairs. This suggests that more simulations with different pairs are needed.

• Earthquakes and Structures
• /
• 제11권1호
• /
• pp.63-82
• /
• 2016

In this study, the bending and dynamic behaviors of laminated composite plates is examined by using a refined shear deformation theory and developed for a bending analysis of orthotropic laminated composite plates under various boundary conditions. The displacement field of the present theory is chosen based on nonlinear variations in the in-plane displacements through the thickness of the plate. By dividing the transverse displacement into the bending and shear parts and making further assumptions, the number of unknowns and equations of motion of the present theory is reduced and hence makes them simple to use. In the analysis, the equation of motion for simply supported thick laminated rectangular plates is obtained through the use of Hamilton's principle. Numerical results for the bending and dynamic behaviors of antisymmetric cross-ply laminated plate under various boundary conditions are presented. The validity of the present solution is demonstrated by comparison with solutions available in the literature. Numerical results show that the present theory can archive accuracy comparable to the existing higher order shear deformation theories that contain more number of unknowns.

• Steel and Composite Structures
• /
• 제33권2호
• /
• pp.163-180
• /
• 2019

A semi analytical method is employed to analyze free vibration characteristics of uniform and stepped functionally graded circular cylindrical shells under complex boundary conditions. The analytical model is established based on multi-segment partitioning strategy and first-order shear deformation theory. The displacement functions are handled by unified Jacobi polynomials and Fourier series. In order to obtain continuous conditions and satisfy complex boundary conditions, the penalty method about spring technique is adopted. The solutions about free vibration behavior of functionally graded circular cylindrical shells were obtained by approach of Rayleigh-Ritz. To confirm the dependability and validity of present approach, numerical verifications and convergence studies are conducted on functionally graded cylindrical shells under various influencing factors such as boundaries, spring parameters et al. The present method apparently has rapid convergence ability and excellent stability, and the results of the paper are closely agreed with those obtained by FEM and published literatures.

• Advances in nano research
• /
• 제15권5호
• /
• pp.411-422
• /
• 2023

In the present study, the axial vibration of the nanorods is investigated in the framework of the doublet mechanics theory. The equations of motion and boundary conditions of nanorods are derived by applying the Hamilton principle. A finite element method is developed to obtain the vibration frequencies of nanorods for different boundary conditions. A two-noded higher order rod finite element is used to solve the vibration problem. The natural frequencies of nanorods obtained with the present finite element analysis are validated by comparing the results of classical doublet mechanics and nonlocal strain gradient theories. The effects of rod length, mode number and boundary conditions on the axial vibration frequencies of nanorods are examined in detail. Mode shapes of the nanorods are presented for the different boundary conditions. It is shown that the doublet mechanics model can be used for the dynamic analysis of nanotubes, and the presented finite element formulation can be used for mechanical problems of rods with unavailable analytical solutions. These new results can also be used as references for the future studies.

• Advances in aircraft and spacecraft science
• /
• 제7권1호
• /
• pp.19-40
• /
• 2020

In the present study, a fifth-order shear and normal deformation theory using a polynomial function in the displacement field is developed and employed for the static analysis of laminated composite and sandwich simply supported spherical shells subjected to sinusoidal load. The significant feature of the present theory is that it considers the effect of transverse normal strain in the displacement field which is eliminated in classical, first-order and many higher-order shell theories, while predicting the bending behavior of the shell. The present theory satisfies the zero transverse shear stress conditions at the top and bottom surfaces of the shell. The governing equations and boundary conditions are derived using the principle of virtual work. To solve the governing equations, the Navier solution procedure is employed. The obtained results are compared with Reddy's and Mindlin's theory for the validation of the present theory.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
• /
• 제4권7호
• /
• pp.31-38
• /
• 1998

Korea is facing the problems of old aging society recently. In the future the ploblems will become more serious. Specially health care services for the aged are very poor in the aspect of both systems of services and supplies of facilities. This paper aims to identify the types as well as present statistical conditions of health care facilities for the aged in Korea.