• Journal of Korean Association for Spatial Structures
• /
• v.11 no.1
• /
• pp.121-130
• /
• 2011

Space frame structures have the advantage of constructing a large space structures without column and it may be considered as a shell structure. Nevertheless, with the characteristics of thin and long term of spacing, the unstable problem of space structure could not be set up clearly, and there is a huge difference between theory and experiment. Therefore, in this work, the tangential stiffness matrix of space frame structures is studied to solve the instability problem, and the nonlinear incremental analysis of the structures considering rise-span ratio(${\mu}$) and the ratio of load($R_L$) is performed for searching unstable points. Basing on the results of the example, global buckling can be happened by low rise-span ratio(${\mu}$), nodal buckling can be occurred by high rise-span ratio(${\mu}$). And in case of multi node space structure applying the ratio of load($R_L$), the nodal buckling phenomenon occur at low the ratio of load($R_L$), the global buckling occur a1 high the ratio of load($R_L$). In case of the global buckling, the load of bifurcation is about from 50% to 70% of perfect one's snap-through load.

• Journal of applied mathematics & informatics
• /
• v.31 no.1_2
• /
• pp.1-25
• /
• 2013

In this paper we have developed a mathematical model of alcohol abuse. It consists of four compartments corresponding to four population classes, namely, moderate and occasional drinkers, heavy drinkers, drinkers in treatment and temporarily recovered class. Basic reproduction number $R_0$ has been determined. Sensitivity analysis of $R_0$ identifies ${\beta}_1$, the transmission coefficient from moderate and occasional drinker to heavy drinker, as the most useful parameter to target for the reduction of $R_0$. The model is locally asymptotically stable at disease free or problem free equilibrium (DFE) $E_0$ when $R_0$ < 1. It is found that, when $R_0$ = 1, a backward bifurcation can occur and when $R_0$ > 1, the endemic equilibrium $E^*$ becomes stable. Further analysis gives the global asymptotic stability of DFE. Our aim of this analysis is to identify the parameters of interest for further study with a view for informing and assisting policy-makers in targeting prevention and treatment resources for maximum effectiveness.

• Journal of applied mathematics & informatics
• /
• v.31 no.5_6
• /
• pp.747-767
• /
• 2013

In this paper we have constructed a mathematical model of alcohol abuse which consists of four compartments corresponding to four population classes, namely, moderate and occasional drinkers, heavy drinkers, drinkers in treatment and temporarily recovered class. Basic reproduction number $R_0$ has been determined and sensitivity analysis of $R_0$ indicates that ${\beta}1$ (the transmission coefficient from moderate and occasional drinker to heavy drinker) is the most useful parameter for preventing drinking habit. Stability analysis of the model is made using the basic reproduction number. The model is locally asymptotically stable at disease free or problem free equilibrium (DFE) $E_0$ when $R_0&lt;1$. It is found that, when $R_0=1$, a backward bifurcation can occur and when $R_0&gt;1$, the endemic equilibrium $E^*$ becomes stable. Further analysis gives the global asymptotic stability of DFE under some conditions. Our important analytical findings are illustrated through computer simulation. Epidemiological implications of our analytical findings are addressed critically.

• Journal of Korean Society of Steel Construction
• /
• v.17 no.6 s.79
• /
• pp.707-715
• /
• 2005

Corrugated webs have been used for composite prestressed concrete box girder bridges. Innovative steel plate girders using corrugated webs have been proposed. It has been found that analytical and experimental researches conducted to determine the strength of trapezoidally corrugated webs can fail with respect to three different buckling modes: local, global, and interactive shear buckling. Shear buckling capacity equations based on classical and orthotropic plate buckling theories have been proposed,but these equations show some differences. In this paper, geometric parameters that influence interactive shear buckling behavior with interaction effects are identified via extensive bifurcation buckling analysis using the finite element meth.

• Journal of applied mathematics & informatics
• /
• v.28 no.1_2
• /
• pp.193-207
• /
• 2010

In this paper, a predator-prey model with stage structure and distributed delay is investigated. Mathematical analyses of the model equation with regard to boundedness of solutions, nature of equilibria, permanence, extinction and stability are performed. By the comparison theorem, a set of easily verifiable sufficient conditions are obtained for the global asymptotic stability of nonnegative equilibria of the model. Taking the product of the per-capita rate of predation and the rate of conversing prey into predator as the bifurcating parameter, we prove that there exists a threshold value beyond which the positive equilibrium bifurcates towards a periodic solution.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11a
• /
• pp.65-72
• /
• 2001

직사각형 평판이 수직방향으로 조화가진력을 받을 때 그 변위가 큰 경우 두 개의 모드 간의 비선형적 상호작용에 대한 연구이다. 폰 칼만 운동방정식에서 유도된 두 개의 상미분 방정식으로부터 수차에 걸친 좌표변환을 거쳐 자유진동의 경우 정지해와 주기해를 구한다. 말굽형태의 분기 현상이 일어날 수 있는 조건을 호모클리닉 또는 헤테로클리닉 궤적의 유무로부터 결정한다. 혼돈 현상의 발생조건을 구하기 위해 멜니코프 방법이 적용되어질 수 있는 형태로 변환하여 광역섭동법의 수학적 결과를 직접적으로 적용할 수 있는 형태로 변환한다.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.16 no.3
• /
• pp.151-167
• /
• 2012

In this paper, we investigate the dynamic behaviors of a one-prey and two-predator system with Holling-type II functional response and defensive ability by introducing a proportion that is periodic impulsive harvesting for all species and a constant periodic releasing, or immigrating, for predators at different fixed time. We establish conditions for the local stability and global asymptotic stability of prey-free periodic solutions by using Floquet theory for the impulsive equation, small amplitude perturbation skills. Also, we prove that the system is uniformly bounded and is permanent under some conditions via comparison techniques. By displaying bifurcation diagrams, we show that the system has complex dynamical aspects.

• Journal of Biomedical Engineering Research
• /
• v.25 no.6
• /
• pp.497-503
• /
• 2004

Numerical simulation of blood flow has been conducted based on real vessel geometries generated front DICOM medical images of abdominal and iliac bifurcated arteries of a healthy man. A program was developed to read cross sectional images of the three dimensional arteries and smoothly extract boundary coordinates of vessels. Commercial programs were employed for mesh generation and flow simulation. Pressures, velocities, and flow distributions were found to lie within normal physiological ranges. Peak velocity measured in the iliac artery by ultrasound was 20% smaller than that obtained by simulation. The trend of velocity variation in a cardiac cycle was fairly similar between the simulation and the ultrasonic measurements. Simulation based on real vessel geometry of individual patient provides information on pressure, velocity, and its distribution in the diseased arteries or arteries to be surgically treated. The results of simulation may help surgeons to better understand hemodynamic status and surgical need of the patient by revealing variation of the hemodynamic parameters. Futhermore, they may serve as basic data for surgical treatment of arteries. This research is expected to develop to a program in the future that early diagnose atherosclerosis by showing distribution of a hemodynamic index closely related to atherosclerosis in arteries.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.14 no.4
• /
• pp.225-247
• /
• 2010

In this paper, we establish a two-competitive-prey and one-predator Holling type II system by introducing a proportional periodic impulsive harvesting for all species and a constant periodic releasing, or immigrating, for the predator at different fixed time. We show the boundedness of the system and find conditions for the local and global stabilities of two-prey-free periodic solutions by using Floquet theory for the impulsive differential equation, small amplitude perturbation skills and comparison techniques. Also, we prove that the system is permanent under some conditions and give sufficient conditions under which one of the two preys is extinct and the remaining two species are permanent. In addition, we take account of the system with seasonality as a periodic forcing term in the intrinsic growth rate of prey population and then find conditions for the stability of the two-prey-free periodic solutions and for the permanence of this system. We discuss the complex dynamical aspects of these systems via bifurcation diagrams.

• 한국공간정보시스템학회:학술대회논문집
• /
• 2004.05a
• /
• pp.131-138
• /
• 2004

The cable structure is a kind of ductile structural system using the tension cable and compression column as a main element. From mechanical characteristics of the structural material, it is profitable to be subjected to the axial forces than bending moment or shear forces. And we haweto consider the local buckling when it is subjected to compression forces, but tension member can be used until the failure strength. So we can say that the tension member is the most excellent structural member. Cable dome structures are made up of only the tension cable and compression column considering these mechanical efficiency and a kind of structural system. In this system, the compression members are connected by using tension members, not connected directly each other. Also, this system is lightweight and easy to construct. But, the cable dome structural system has a danger of global buckling as external load increases. That is, as the axisymmetric structure is subjected to the axisymmetric load, the unsymmetric deformation mode is happened at some critical point and the capacity of the structure is rapidly lowered by this reason. This phenomenon Is the bifurcation and we have to reflect this in the design process of the large space structures. In this study, We investigated the nonlinear unstable phenomenon of the Geiger, Zetlin and Flower-type cable dome.