• Structural Engineering and Mechanics
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• 제58권5호
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• pp.931-947
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• 2016

The effects of nanotechnology and smartness on the buckling reduction of pipes are the main contributions of present work. For this ends, the pipe is simulated with classical piezoelectric polymeric cylindrical shell reinforced by armchair double walled boron nitride nanotubes (DWBNNTs), The structure is subjected to combined electro-thermo-mechanical loads. The surrounding elastic foundation is modeled with a novel model namely as orthotropic nonhomogeneous Pasternak medium. Using representative volume element (RVE) based on micromechanical modeling, mechanical, electrical and thermal characteristics of the equivalent composite are determined. Employing nonlinear strains-displacements and stress-strain relations as well as the charge equation for coupling of electrical and mechanical fields, the governing equations are derived based on Hamilton's principal. Based on differential quadrature method (DQM), the buckling load of pipe is calculated. The influences of electrical and thermal loads, geometrical parameters of shell, elastic foundation, orientation angle and volume percent of DWBNNTs in polymer are investigated on the buckling of pipe. Results showed that the generated ${\Phi}$ improved sensor and actuator applications in several process industries, because it increases the stability of structure. Furthermore, using nanotechnology in reinforcing the pipe, the buckling load of structure increases.

• 한국안전학회지
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• 제29권3호
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• pp.1-7
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• 2014

In this study, for the evaluation of the static and fatigue joining strength of the joint, the geometry of the cross-tension specimen was adopted. The specimens were produced with optimal joining force and fatigue life of the clinch joint specimens was evaluated. The material selected for use in this study was cold rolled mild steel (SPCC) with a thickness of 0.8 mm. The maximum tensile load was 708 N for the specimen with single point. The fatigue endurance limit (=42.6 N) per point approached to 6% of the maximum tensile strength at a load ratio of 0.1, suggesting that the joints are vulnerable to cross-tension loading during fatigue. Compared to equivalent stress and maximum principal stress, the SWT fatigue parameter and equivalent strain can properly predict the current experimental fatigue life. The SWT parameter can be expressed as $SWT=2497.5N^{-0.552)_f$.

• 한국터널지하공간학회 논문집
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• 제19권6호
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• pp.1013-1028
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• 2017

본 논문은 원형 자유면을 이용한 암반 파쇄에 대한 수치해석적 연구이다. 암반 파쇄시 균열 발생에 대한 메커니즘을 알아보기 위하여 수치해석을 통해 응력 및 변형율 경로를 분석하였다. 수치해석 결과로부터 균열선의 주응력 분석으로 최대 주응력을 산출하여 취성 재료의 파괴와 균열 진전에 대하여 분석 규명하였다. 또한 본 연구결과를 통하여 암반파쇄시 균열 진전 방향이 전환되는 거동 메커니즘을 제시하였다.

• 한국산학기술학회논문지
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• 제16권11호
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• pp.7377-7384
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• 2015

농업용 트랙터는 전도 사고 발생 시 운전자를 보호하기 위해 전도보호구조(ROPS: Roll Over Protective Structures)의 역할을 할 수 있어야 한다. 본 연구에서는 ROPS 강도시험 규격을 만족하는 트랙터 캐빈 프레임의 제작 기간과 비용을 줄이기 위해서 유한요소해석과 최적설계를 수행하였다. 해석 결과로부터 얻은 변위와 주 변형률의 크기를 통해 캐빈 프레임의 초기설계안은 ROPS 강도시험에 합격하는 것으로 나타났다. 또한 캐빈 프레임의 경량화 설계안을 도출하기 위하여 다구찌 실험계획을 이용해 최적설계를 수행하였다. 이를 통하여 캐빈 프레임 무게가 초기설계안보다 7% 저감된 최적설계안을 도출하였다.

• Structural Engineering and Mechanics
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• 제59권1호
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• pp.153-186
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• 2016

This paper addresses temperature-dependent nonlinear vibration and instability of embedded functionally graded (FG) pipes conveying viscous fluid-nanoparticle mixture. The surrounding elastic medium is modeled by temperature-dependent orthotropic Pasternak medium. Reddy third-order shear deformation theory (RSDT) of cylindrical shells are developed using the strain-displacement relations of Donnell theory. The well known Navier-Stokes equation is used for obtaining the applied force of fluid to pipe. Based on energy method and Hamilton's principal, the governing equations are derived. Generalized differential quadrature method (GDQM) is applied for obtaining the frequency and critical fluid velocity of system. The effects of different parameters such as mode numbers, nonlinearity, fluid velocity, volume percent of nanoparticle in fluid, gradient index, elastic medium, boundary condition and temperature gradient are discussed. Numerical results indicate that with increasing the stiffness of elastic medium and decreasing volume percent of nanoparticle in fluid, the frequency and critical fluid velocity increase. The presented results indicate that the material in-homogeneity has a significant influence on the vibration and instability behaviors of the FG pipes and should therefore be considered in its optimum design. In addition, fluid velocity leads to divergence and flutter instabilities.

• Nuclear Engineering and Technology
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• 제52권5호
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• pp.1079-1092
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• 2020

A parametric study of several parameters relevant to design safety on the spent nuclear fuel (SNF) rod response under a drop accident is presented. In the view of the complexity of interactions between the independent safety-related parameters, a factorial design of experiment is employed as an efficient method to investigate the main effects and the interactions between them. A detailed single full-length fuel rod is used with consideration of post-irradiated fuel conditions under horizontal and vertical free-drops onto an unyielding surface using finite-element analysis. Critical drop heights and critical g-loads that yield the threshold plastic strain in the cladding are numerically estimated to evaluate the fuel rod structural resistance to impact load. The combinatory effects of four uncertain parameters (pellet-cladding interfacial bonding, material properties, spacer grid stiffness, rod internal pressure) and the interactions between them on the fuel rod response are investigated. The principal finding of this research showed that the effects of above-mentioned parameters on the load-carrying capacity of fuel rod are significantly different. This study could help to prioritize the importance of data in managing and studying the structural integrity of the SNF.

• Journal of Microbiology and Biotechnology
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• 제32권3호
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• pp.333-340
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• 2022

Leuconostoc has been used as a principal starter in natural kimchi fermentation, but limited research has been conducted on its phages. In this study, prophage distribution and characterization in kimchi-derived Leuconostoc strains were investigated, and phage induction was performed. Except for one strain, 16 Leuconostoc strains had at least one prophage region with questionable and incomplete regions, which comprised 0.5-6.0% of the bacterial genome. Based on major capsid protein analysis, ten intact prophages and an induced incomplete prophage of Leu. lactis CBA3626 belonged to the Siphoviridae family and were similar to Lc-Nu-like, sha1-like, phiMH1-like, and TPA_asm groups. Bacterial immunology genes, such as superinfection exclusion proteins and methylase, were found on several prophages. One prophage of Leu. lactis CBA3626 was induced using mitomycin C and was confirmed as belonging to the Siphoviridae family. Homology of the induced prophage with 21 reported prophages was not high (< 4%), and 47% identity was confirmed only with TPA_asm from Siphoviridae sp. isolate ct3pk4. Therefore, it is suggested that Leuconostoc from kimchi had diverse prophages with less than 6% genome proportion and some immunological genes. Interestingly, the induced prophage was very different from the reported prophages of other Leuconostoc species.

• Structural Engineering and Mechanics
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• 제81권4호
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• pp.523-527
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• 2022

The objective of this study is to simulate the flow in pipes with various boundary conditions. Free-pressure fluid model, is used in the pipe based on Navier-Stokes equation. The models are solved by using the numerical method. A problem called "stability of pipes" is used in order to compare frequency and critical fluid velocity. When the initial conditions of problem satisfied the instability conditions, the free-pressure model could accurately predict discontinuities in the solution field. Employing nonlinear strains-displacements, stress-strain energy method the governing equations were derived using Hamilton's principal. Differential quadrature method (DQM) is used for obtaining the frequency and critical fluid velocity. The results of this paper are analyzed by hyperbolic numerical method. Results show that the level of numerical diffusion in the solution field and the range of well-posedness are two important criteria for selecting the two-fluid models. The solutions for predicting the flow variables is approximately equal to the two-pressure model 2. Therefore, the predicted pressure changes profile in the two-pressure model is more consistent with actual physics. Therefore, in numerical modeling of gas-liquid two-phase flows in the vertical pipe, the present model can be applied.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3677-3691
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• 2023

Since containment building is the major shielding structure to ensure safety of nuclear power plant, the structural behavior and ultimate pressure capacity of containments must be studied in depth. This paper addresses ambiguous issue of determining free-field position for liner failure by suggesting an expanded free-field region and comparing internal pressure capacities obtained by test data, conservative assumption and suggested free-field region. For this purpose, a practical approach to determine the free-field position for the evaluation of liner tearing is carried out. The maximum principal strain histories versus internal pressure capacities among different free-field positions at various azimuths and elevations are compared with those at the equipment hatch as a conservative assumption. The comparison shows that there are considerable differences in the internal pressure capacity at liner failure within the expanded free-field region compared to the vicinity of the equipment hatch. Additionally, this study proposes an approximate correlation with conservative factors by considering the expanded free-field ranges and material characteristics to determine realistic failure criteria for liner. The applicability of the proposed correlation is demonstrated by comparing the internal pressure capacities of full-scale containment buildings following liner failure criteria according to RG 1.216 and an approximate correlation.

• 대한간호학회지
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• 제26권4호
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• pp.917-929
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• 1996

The purpose of this study is to explore types of postpartum depression and to understand the nature and structure of the postpartum depression by using Q-methodological approach. As a way of research, 55 statements concerning postpartum depression were selected through individual interviews with postpartum mothers and literature review. 30 women were chosen as a subject group for the study, with opinions shown in 55 statements divided into 9 scales by forced distribution. PC QUANL Program was used for analysis and Q-factors were analyzed by using principal component analysis. As a result, postpartum depression experience was classified into 5 types. There are "Role-Strain Type", "Unattributional Depression Type", "Psychosomatic Symptoms Type", "Self-Compassion Type", and "Role-Crisis Type". Type I was named "Role-Strain Type", referring to the strain generally experienced by mothers with regard to the new role as a mother and as a social member. Type II was named "Unattributional Depression Type", referring to the symptom experienced by people who were in a state of vanity and a sense of loss. They often break into tears for no specific reasons. In case of Type III, people in a state of "Psychosomatic Symptoms Type" develop physical symptoms after suffering from inherent emotional conflict. Type IV was named "Self-Compassion Type" refers to the symptom shown by those who feel pity for their children and for themselves. And they show inability to cope with the reality properly. Type V was named "Role -Crisis Type", which is experienced by people who have a burden and a severe fear of their own job and their children in their mind, also showing serious conflict with maternal role. Futhermore, it was carried out to examine structure of postpartum depression in terms of degree of depression and adjustment ability. Type I showed mild degree of depression and relatively good adjustment ability. Type II showed broad range of degree in depression and moderate adjustment ability. Type III showed moderate depression and relatively low adjustment ability. Type IV revealed relatively serious degree of depression and the lowest adjustment ability. Type V revealed very serious degree of depression and the lowest adjustment ability. As a result, considering the structure of postpartum depression. Type I is considered to be a normal depression sympton which most mothers generally experience, followed by Type II, Type III, Type IV and Type V, each of which show increasingly worse degree of depression and lower adjustment ability. In conclusion, it seems to be it is necessary to understand distinct symptoms of postpartum depression and to examine the characteristics and structure of those types, so that it could lead to more individual nursing approach.cteristics and structure of those types, so that it could lead to more individual nursing approach.