• Structural Engineering and Mechanics
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• 제31권2호
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• pp.181-210
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• 2009

This paper presents the theoretical developments of an exact finite strip for the buckling and initial post-buckling analyses of isotropic flat plates. The so-called exact finite strip is assumed to be simply supported out-of-plane at the loaded ends. The strip is developed based on the concept that it is effectively a plate. The present method, which is designated by the name Full-analytical Finite Strip Method in this paper, provides an efficient and extremely accurate buckling solution. In the development process, the Von-Karman's equilibrium equation is solved exactly to obtain the buckling loads and the corresponding form of out-of-plane buckling deflection modes. The investigation of thin flat plate buckling behavior is then extended to an initial post-buckling study with the assumption that the deflected form immediately after the buckling is the same as that obtained for the buckling. It is noted that in the present method, only one of the calculated out-of-plane buckling deflection modes, corresponding to the lowest buckling load, i.e., the first mode is used for the initial post-buckling study. Thus, the postbuckling study is effectively a single-term analysis, which is attempted by utilizing the so-called semi-energy method. In this method, the Von-Karman's compatibility equation governing the behavior of isotropic flat plates is used together with a consideration of the total strain energy of the plate. Through the solution of the compatibility equation, the in-plane displacement functions which are themselves related to the Airy stress function are developed in terms of the unknown coefficient in the assumed out-of-plane deflection function. These in-plane and out-of-plane deflected functions are then substituted in the total strain energy expressions and the theorem of minimum total potential energy is applied to solve for the unknown coefficient. The developed method is subsequently applied to analyze the initial postbuckling behavior of some representative thin flat plates for which the results are also obtained through the application of a semi-analytical finite strip method. Through the comparison of the results and the appropriate discussion, the knowledge of the level of capability of the developed method is significantly promoted.

• 한국전산구조공학회논문집
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• 제15권3호
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• pp.511-521
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• 2002

내부튜브를 가진 튜브 구조물의 보에 있는 전단응력을 평가하기 위하여 수치적인 해석기법이 제안되었다 이 기법은 휨과 전단변형을 고려한 튜브 보 개념 위에서 각각의 튜브를 연속 보로서 모델링 한다. 전단응력에 대한 수치해석은 패널에 작용하는 응력에 대한 탄성이론과 수학적인 유도를 기초로 하고 있다. 내부와 외부 튜브에 있는 변형곡선에 대한 표현식을 가정함으로써, 그 튜브에 있는 전단응력은 작용하중과 단면 2차 모멘트 그리고 구조물의 기하학적인 표현으로 구성된 선형 함수로서 표현된다 전단지체와 축 응력을 다룬 이전의 연구가 튜브내에 존재하는 전단응력을 수치적으로 해석하기 위하여 보완 발전되었다. 제안된 방법의 정확성과 유용성이 3개의 튜브 구조물의 해석을 통하여 증명 되었다

• Journal of Microbiology and Biotechnology
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• 제31권8호
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• pp.1060-1068
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• 2021

Community-associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA) is notorious as a leading cause of soft tissue infections. Despite several studies on the Agr regulator, the mechanisms of action of Agr on the virulence factors in different strains are still unknown. To reveal the role of Agr in different CA-MRSA, we investigated the LACΔagr mutant and the MW2Δagr mutant by comparing LAC (USA300), MW2 (USA400), and Δagr mutants. The changes of Δagr mutants in sensitivity to oxacillin and several virulence factors such as biofilm formation, pigmentation, motility, and membrane properties were monitored. LACΔagr and MW2Δagr mutants showed different oxacillin sensitivity and biofilm formation compared to the LAC and MW2 strains. Regardless of the strain, the motility was reduced in Δagr mutants. And there was an increase in the long chain fatty acid in phospholipid fatty acid composition of Δagr mutants. Other properties such as biofilm formation, pigmentation, motility, and membrane properties were different in both Δagr mutants. The Agr regulator may have a common role like the control of motility and straindependent roles such as antibiotic resistance, biofilm formation, change of membrane, and pigment production. It does not seem easy to control all MRSA by targeting the Agr regulator only as it showed strain-dependent behaviors.

• 한국구조물진단유지관리공학회 논문집
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• 제17권2호
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• pp.10-20
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• 2013

보 구조물의 안전성을 평가하기 위해서, 해당 부재의 구조적 상태를 보여주는 보여줄 수 있는 변형률을 기반으로 한 모니터링 시스템이 이용되고 있다. 하지만 최대 변형률과 같은 부재의 상태를 대표할 수 있는 변형률이 발생하는 정확한 위치에 센서를 설치하지 않은 한, 계측된 변형률을 토대로 합리적인 평가를 할 수 있게 하는 추가적인 프로세스가 필요하다. 이에 따라 본 연구는 변형률계에 의해 계측된 이산데이터를 이용하여 강재 보 구조물의 변형률 분포를 추정하는 기법을 제안한다. 본 기법에서는 보 구조물에 작용하는 하중을 미지의 하중으로 가정하였기 때문에, 실제 적용성을 향상 시켰다. 최종적인 변형률 분포는 회귀 분석을 통해서 함수 형태로 주어진다. 본 기법을 이용한 추정 성능을 검증하기 위해서 분포하중, 집중하중, 모멘트가 동시에 작용하는 강재 보 구조물의 휨 실험을 수행하였다. 실험을 통해 추정 변형률의 값을 직접 계측한 값과 비교해 본 결과, 임의의 위치에서도 절대 오차 $2.32{\mu}{\varepsilon}$ 이내로 변형률을 추정할 수 있었으며, 전체 변형률 분포는 3.32% 이내의 상대오차로 얻을 수 있었다. 따라서 강재 보 모니터링 시스템에 효과적으로 적용할 수 있을 것으로 기대된다.

• Geomechanics and Engineering
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• 제10권3호
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• pp.357-386
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• 2016

In this research work, an exact analytical solution for thermal stability of solar functionally graded rectangular plates subjected to uniform, linear and non-linear temperature rises across the thickness direction is developed. It is assumed that the plate rests on two-parameter elastic foundation and its material properties vary through the thickness of the plate as a power function. The neutral surface position for such plate is determined, and the efficient hyperbolic plate theory based on exact neutral surface position is employed to derive the governing stability equations. The displacement field is chosen based on assumptions that the in-plane and transverse displacements consist of bending and shear components, and the shear components of in-plane displacements give rise to the quadratic distribution of transverse shear stress through the thickness in such a way that shear stresses vanish on the plate surfaces. Therefore, there is no need to use shear correction factor. Just four unknown displacement functions are used in the present theory against five unknown displacement functions used in the corresponding ones. The non-linear strain-displacement relations are also taken into consideration. The influences of many plate parameters on buckling temperature difference will be investigated. Numerical results are presented for the present theory, demonstrating its importance and accuracy in comparison to other theories.

• Journal of Microbiology and Biotechnology
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• 제16권5호
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• pp.795-798
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• 2006

The phosphoenolpyruvate-dependent carbohydrate phosphotransferase system (PTS) is responsible for the simultaneous transfer and phosphorylation of various carbon sources in Escherichia coli. The ptsG gene encoding the enzyme $IICB^{Glc}$, the membrane component of the glucose-specific PTS, is repressed by Mlc and activated by the CRP cAMP complex; various other factors, such as Fis, FruR, and ArcA, are also known to be involved in ptsG regulation. Thus, in an attempt to discover a novel gene affecting the regulation of ptsG, a mutant with a decreased ptsG transcription in the presence of glucose compared with the wild-type strain was screened using transposon random mutagenesis. The mutant was found to have a transposon insertion in yhjV, a putative gene encoding a transporter protein whose function is yet unknown.

• The Plant Pathology Journal
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• 제15권3호
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• pp.131-136
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• 1999

In fungi known as ascomycetes, ability to mate is controlled by a single mating type (MAT) locus with two dissimilar sequences called idiomorphs carrying genes encoding transcription factors that are unrelated to each other. Fungi requiring strains with different MAT genes to complete the sexual process are heterothallic (self-sterile); species in which as single strain is able to undergo sexual reproduction are homothallic (self-fertile). Previous analysis of sequences from several heterothallic and homothallic species of the ascomycete genus Cochliobolus showed that homothallics evolve from heterothallics and that each known Cochliobolus homothallic species arose independently, from a different heterothallic ancestral species. Here we report detailed comparative analyses of MAT sequences ad their flanking regions, and show that: (1) The level of MAT gene similarity is not correlated with reproductive life style; (2) MAT proteins from all Cochliobolus species are conserved within the transcription factor signature sequences; they are not conserved in the carboxy terminal half of MAT-1, or third of MAT-2, except in those from very closely related species; (3) A gene (ORF1) of unknown function, consistently found on the MAT flank, is more conserved than are the MAT genes themselves; (4) The intergenic sequences diverge sharply among species.

• Steel and Composite Structures
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• 제27권4호
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• pp.525-536
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• 2018

This paper focuses on the application of the first-order shear deformation theory (FSDT) to thermo-elastic static problems of functionally graded carbon nanotubes reinforced composite (FG-CNTRC) cylindrical pressure vessels. A symmetric displacement field is considered as unknown function along the longitudinal direction, whereas a linear distribution is assumed along the thickness direction. The cylindrical pressure vessels are subjected to an inner and outer pressure under a temperature increase. Different patterns of reinforcement are applied as distribution of CNTs. The effective material properties of FG-CNTRC cylindrical pressure vessels are measured based on the rule of mixture, whereas the governing equations of the problem are here derived through the principle of virtual works. A large parametric investigation studies the effect of some significant parameters, such as the pattern and volume fraction of CNTs, on the longitudinal distribution of deformation, strain and stress components, as useful tool for practical engineering applications.

• The Plant Pathology Journal
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• 제27권3호
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• pp.285-290
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• 2011

Fusarium graminearum virus 2 (FgV2) infects Fusarium graminearum strain 98-8-60 and has at least five segments of double-stranded RNAs (dsRNAs), denoted as dsRNA-1 to dsRNA-5. In this study, the genome of FgV2 was sequenced and its phylogenetic relationship with other mycoviruses was analyzed. The lengths of FgV2 dsRNAs 1-5 ranged from 2414 to 3580 base pairs (bp). The 5' and 3' untranslated regions (UTRs) are highly conserved, and each dsRNA segment had 78-105 and 84-306 bp of 5' and 3' UTRs, respectively. Each dsRNA segment contained a single open reading frame (ORF). Computer analysis of dsRNA-1 revealed a putative open reading frame (ORF) that shows high sequence identity with an RNA-dependent RNA polymerase (RdRp) containing eight conserved motifs. dsRNAs 2-5 also each contain one putative ORF coding for products of unknown function. The sequences of FgV2 dsRNA-2 and dsRNA-3 have significant sequence identity with Magnaporthe oryzae chrysovirus 1 (MoCV1) dsRNA-3 and -4, respectively. When compared to other dsRNA mycoviruses in a phylogenetic analysis of the putative RdRp protein, FgV2 was found to form a distinct virus clade with Aspergillus mycovirus 1816 and MoCV1 in the family Chrysoviridae.

• Structural Engineering and Mechanics
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• 제12권5호
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• pp.507-526
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• 2001

In standard finite element algorithms, the local stability conditions are not accounted for in the formulation of the tangent stiffness matrix. As a result, the loss of the local stability is not adequately related to the onset of the global instability. The phenomenon typically arises with material-type localizations, such as shear bands and plastic hinges. This paper addresses the problem in the context of the planar, finite-strain, rate-independent, materially non-linear beam theory, although the proposed technology is in principle not limited to beam structures. A weak formulation of Reissner's finite-strain beam theory is first presented, where the pseudocurvature of the deformed axis is the only unknown function. We further derive the local stability conditions for the large deformation case, and suggest various possible combinations of the interpolation and numerical integration schemes that trigger the simultaneous loss of the local and global instabilities of a statically determined beam. For practical applications, we advice on a procedure that uses a special numerical integration rule, where interpolation nodes and integration points are equal in number, but not in locations, except for the point of the local instability, where the interpolation node and the integration point coalesce. Provided that the point of instability is an end-point of the beam-a condition often met in engineering practice-the procedure simplifies substantially; one of such algorithms uses the combination of the Lagrangian interpolation and Lobatto's integration. The present paper uses the Galerkin finite element discretization, but a conceptually similar technology could be extended to other discretization methods.