• 한국기계가공학회지
• /
• 제19권3호
• /
• pp.36-41
• /
• 2020

Mechanical systems installed in transport devices, such as vehicles, airplanes, and ships, are mostly subject to translational accelerations at the joints during operations. This base acceleration excitation has a large influence on the performance of the system, therefore, its response must be well analyzed. However, the existing methods for dynamic analysis of structures have some limitations in use. This study presents a new numerical method using relative acceleration to solve these limitations. If the governing equation of motion is linear and the mass matrix, the damping matrix, and the stiffness matrix are constant over time in the finite element analysis, the proposed method can be applied to the transient behavior analysis and the harmonic response analysis of the structure. Because it is not necessary to introduce a virtual mass and the rigid body motions are removed from the analysis, it is possible to use not only the direct integration method in the time domain but also the mode superposition method to obtain the dynamic responses. This paper demonstrates with three examples how the present method is suitable for the dynamic analysis of a structure with multi-degree of freedom.

• 한국조경학회지
• /
• 제28권6호
• /
• pp.96-105
• /
• 2001

The purpose of this study is to establish landscape planning, and to find out to administrative system and improvement way on landscape plan in Korea. We have sought for research trend and the concept of landscape planning related to the landscape planning through the investigation of books and documents, and have analyzed the characteristics on the law for landscape plan in United State of America, United Kingdom,, France, Germany, Japan and Korea. As the results of this study are as follows; 1) A state developing local self-governing body as United State of America, United Kingdom and Germany carried out individually landscape plan. Especially, it raises clarity of administration to fix residents participation(Nonprofit Organization : NPO) and secures responsibility. 2) A state of centralized authoritarian rule as France and Japan applies common law to the nationwide but commission's concrete management or conference. 3) And so in Korea and applicable landscape plan was made on the basis of town-planning law and managed with ordinances for landscape. In here the important thing is division of role of central and local government and residents. This study proposes the system of planning and analyzed the related laws for the landscape formation and management. The future research on the character of the local areas, providing many chances with people in the community through publicity activities, and rearing the expert group on this matter should be made in the future.

• Wind and Structures
• /
• 제20권3호
• /
• pp.423-448
• /
• 2015

In this paper the unsteady fluid-structure interaction (FSI) problems with large structural displacement are solved by partitioned solution approaches in the arbitrary Lagrangian-Eulerian finite element framework. The incompressible Navier-Stokes equations are solved by the characteristic-based split (CBS) scheme. Both a rigid body and a geometrically nonlinear solid are considered as the structural models. The latter is solved by Newton-Raphson procedure. The equation governing the structural motion is advanced by Newmark-${\beta}$ method in time. The dynamic mesh is updated by using moving submesh approach that cooperates with the ortho-semi-torsional spring analogy method. A mass source term (MST) is introduced into the CBS scheme to satisfy geometric conservation law. Three partitioned coupling strategies are developed to take FSI into account, involving the explicit, implicit and semi-implicit schemes. The semi-implicit scheme is a mixture of the explicit and implicit coupling schemes due to the fluid projection splitting. In this scheme MST is renewed for interfacial elements. Fixed-point algorithm with Aitken's ${\Delta}^2$ method is carried out to couple different solvers within the implicit and semi-implicit schemes. Flow-induced vibrations of a bridge deck and a flexible cantilever behind an obstacle are analyzed to test the performance of the proposed methods. The overall numerical results agree well with the existing data, demonstrating the validity and applicability of the present approaches.

• 대한기계학회논문집B
• /
• 제26권12호
• /
• pp.1699-1706
• /
• 2002

In this paper, the investigation about the elevation control and the formation of the free surface of magnetic fluids is carried out theoretically and experimentally on the basis of magnetic fluids is carried out theoretically and experimentally on the basis of Rosensweig' Ferrohydrodynamic Bernoulli Equation. Governing equations of magnetic fields are solved using the concept of vector potential. While applied magnetic fields are induced by 4$\times$4 electromagnet located under the magnetic fluid, the fee surface of the magnetic fluid is formed the balance of surface force, gravity, pressure difference, magnetic normal pressure and magnetic body force. The results of numerical simulation and experiment show the formation of the free surface of the magnetic fluid. Using PID control, an experiment for the elevation control of the free surface of magnetic fluids is performed.

• 안보군사학연구
• /
• 통권2호
• /
• pp.23-89
• /
• 2004

The protective area of military installations can be a essential investment goods for producting public goods like military installations and national security. For the purpose of this, The protective area of military installations are set up and applicated at important strategic areas. It causes colplications and frictions among the people, government and army inevitably to set up the protective area of military installations, as the relation between the army which produces security or public goods and the people that make and use valuable goods is opposed and contradictory to each other. Heretofore, the civil petition of the protective affair to military installations has been presented individually. As local self- government is fixed, a local selg-governing body presents many civil petitions now. Therefore the protective affair to military installations came to be examined carefully in the aspecs of improving the relationship between the civil and army, raising natinal competitiveness, and increasing efficiency of military operations. Though the relationship between the civil and army is opposed and contradictory, it is required to be in keeping with each other with a situation around society, that is, changes and trend of national security, politics, economy, society. Accordingly, if you drive plans of rational management to the protective area of military installations, you can not only achieve successful military installations, but also be a great help to growth of a local community. Then 「The Army with the people」worthy of the name can be real.

• 한국전산유체공학회지
• /
• 제3권1호
• /
• pp.11-21
• /
• 1998

A vorticity-based method for the numerical solution of the two-dimensional incompressible Navier-Stokes equations is presented. The governing equations for vorticity, velocity and pressure variables are expressed in an integro-differential form. The global coupling between the vorticity and the pressure boundary conditions is fully considered in an iterative procedure when numerical schemes are employed. The finite volume method of the second order TVD scheme is implemented to integrate the vorticity transport equation with the dynamic vorticity boundary condition. The velocity field is obtained by using the Biot-Savart integral. The Green's scalar identity is used to solve the total pressure in an integral approach similar to the surface panel methods which have been well established for potential flow analysis. The present formulation is validated by comparison with data from the literature for the two-dimensional cavity flow driven by shear in a square cavity. We take two types of the cavity now: (ⅰ) driven by non-uniform shear on top lid and body forces for which the exact solution exists, and (ⅱ) driven only by uniform shear (of the classical type).

• 대한조선학회 특별논문집
• /
• 대한조선학회 2011년도 특별논문집
• /
• pp.5-11
• /
• 2011

In this paper, the dynamic response analysis of a floating crane with elastic booms and a cargo is performed. The objective is to consider the effects of the elastic boom in the lifting design stage. Governing equations of the motion for the system which consists of interconnected rigid and flexible bodies are derived based on the formulation of flexible multibody system dynamics. To model the boom as a flexible body, floating reference frame and nodal coordinates are used. Coupled surge, pitch, and heave motion of the floating crane with the cargo which has 3 degree of freedom is simulated by solving the equation numerically. Finally, the effects of the elastic boom for the lifting design that the floating crane is required to lift a heavy cargo are discussed by comparing the simulation result between with the elastic boom and with the rigid one.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2009년 추계학술대회논문집
• /
• pp.164-169
• /
• 2009

Study on swimming of microorganisms like, sperm motility, cilia beating, bacterial flagellar propulsion has found immense significance in the field of biological fluiddynamics. Because of the complexity involved, it is challenging for the researchers to model such problems. Immersed boundary method has proved its efficacy in the field of biological fluiddynamics, The present work aims at performing a numerical study on the microorganism locomotion using the immersed boundary method proposed by Peskin[1]. A two-dimensional model of the microorganism is modeled as thin elastic filament described as a sine wave. The neutrally buoyant organism undergoing deformations is immersed in a viscous and incompressible fluid. The fluid quantities are described using Eulerian coordinates and the immersed body is represented by Lagrangian coordinates. The Eulerian and Lagrangian variables are connected by the Dirac delta function. The Navier-Stokes equations governing the fluid flow are solved using the fractional step method on a staggered Cartesian grid system. The developed numerical code in FORTRAN will be validated by comparing the numerical results with the available results.

• Advances in aircraft and spacecraft science
• /
• 제5권3호
• /
• pp.335-348
• /
• 2018

The structural dynamics (SD) behavior of Elastic Flapping Wings (EFWs) is investigated analytically as a novel approach in EFWs analysis. In this regard an analytical SD solution of EFW undergoing a prescribed rigid body motion is initially derived, where the governing equations are expressed in modal space. The inertial forces are also analytically computed utilizing the actuator induced acceleration effects on the wing structure, while due to importance of analytical solution the linearity assumption is also considered. The formulated initial-value problem is solved analytically to study the EFW structural responses, where the effect of structure-actuator frequency ratio, structure-flapping frequency ratio as well as the structure damping ratio on the EFW pick amplitude is analyzed. A case study is also simulated in which the wing is modeled as an elastic beam with shell elements undergoing a prescribed sinusoidal motion. The corresponding EFW transient and steady response in on-off servo behavior is investigated. This study provides a conceptual understanding for the overall EFW SD behavior in the presence of inertial forces plus the servo dynamics effects. In addition to the substantial analytical results, the study paves a new mathematical way to better understanding the complex role of SD in dynamic EFWs behavior. Specifically, similar mathematical formulations can be carried out to investigate the effect of aerodynamics and/or gravity.

• Advances in nano research
• /
• 제13권3호
• /
• pp.297-312
• /
• 2022

Coughing and breath shortness are common symptoms of nano (small) cell lung cancer. Smoking is main factor in causing such cancers. The cancer cells form on the soft tissues of lung. Deformation behavior and wave vibration of lung affected when cancer cells exist. Therefore, in the current work, phase velocity behavior of the small cell lung cancer as a main part of the body via an exact size-dependent theory is presented. Regarding this problem, displacement fields of small cell lung cancer are obtained using first-order shear deformation theory with five parameters. Besides, the size-dependent small cell lung cancer is modeled via nonlocal stress/strain gradient theory (NSGT). An analytical method is applied for solving the governing equations of the small cell lung cancer structure. The novelty of the current study is the consideration of the five-parameter of displacement for curved panel, and porosity as well as NSGT are employed and solved using the analytical method. For more verification, the outcomes of this reports are compared with the predictions of deep neural network (DNN) with adaptive optimization method. A thorough parametric investigation is conducted on the effect of NSGT parameters, porosity and geometry on the phase velocity behavior of the small cell lung cancer structure.