• 대한기계학회논문집A
• /
• 제20권7호
• /
• pp.2108-2117
• /
• 1996

The purpose of this paper is to investigate the influence of the exciter attached for the measurement of natural frequencies when extracting the frequency response functions of the test structure in experimental modal analysis. The procedure is first to model the attached exciter as an additional degree of freedom system and next to verify the suggested model by experimentally extracting the natural frequencies of the test structure with various values of exciter mass, stinger stiffness and attachment position of the exciter on the test structure. It is concluded that as additional degree of freedom system which includes the natural frequency of the exciter itself and axial stiffness of stinger should be considered to quantatively define the coupling effects of structure-exciter interaction on the measured natural frequencies. It is not the mass of the exciter itself but the coupling effect of the additional degree of freedom mass-spring system consisting of exciter body and armature coil that characterizes the natural frequency deviation. Therefore, when the natural frequency of this additional mass-spring system is outside of the test frequency range, the coupling effect of structure-exciter interaction can be minimized.

• 한국정밀공학회지
• /
• 제31권10호
• /
• pp.929-934
• /
• 2014

Reaction force compensation (RFC) mechanism can relieve the vibration of base system caused by acceleration and deceleration of mover. In this paper, we propose a new passive RFC mechanism with a movable additional mass to reduce vibration of the system base as well as displacement of the magnet track. First, equation of motion for the new passive RFC mechanism is derived and simulated to tune design parameters such as masses and spring coefficients. Simulation results show that the vibration of the system base of the stage with the new RFC mechanism.

• Structural Engineering and Mechanics
• /
• 제3권1호
• /
• pp.61-74
• /
• 1995

A linearly tapered, doubly symmetric thin-walled closed member, such as power-transmission towers and tourist towers, are often characterized by local variation in mass and/or rigidity, due to additional mass and rigidity. On the preliminary stage of design the closed-form solution is more effective than the finite element method. In order to propose approximate solutions, the discontinuous and local variation in mass and/or rigidity is treated continuously by means of a usable function proposed by Takabatake(1988, 1991, 1993). Thus, a simplified analytical method and approximate solutions for the free and forced transverse vibrations in linear elasticity are demonstrated in general by means of the Galerkin method. The solutions proposed here are examined from the results obtained using the Galerkin method and Wilson-${\theta}$ method and from the results obtained using NASTRAN.

• International Journal of Contents
• /
• 제10권3호
• /
• pp.84-89
• /
• 2014

The mass-spring model has been typically employed in physical-based simulators for clothes or patches. The mass-spring model frequently utilizes equal mass and the gravity factor. The model structure of masses supports a shape applicable to fishing nets. Therefore, to create a simulation model of a fishing net, we consider the mass-spring model and adopt the tidal-current and buoyancy effects in underwater environments. These additional factors lead to a more realistic visualization of fishing-net simulations. In this paper, we propose a new mass-spring model for a fishing-net and a method to simplify the calculation equations for a real-time simulation of a fishing-net model. Our 3D mass-spring model presents a mesh-structure similar to a typical mass-spring model except that each intersection point can have different masses. The motion of each mass is calculated periodically considering additional dynamics. To reduce the calculation time, we attempt to simplify the mathematical equations that include the effect of the tidal-current and buoyancy. Through this research, we expect to achieve a real-time and realistic simulation for the fishing net.

• 한국소음진동공학회논문집
• /
• 제15권2호
• /
• pp.161-168
• /
• 2005

The absorbing material is mostly used to changing the acoustic energy to the heat energy in the passive control, and that consists of the porous media. That controls an air borne noise while the stiffened plates, damping material and additional mass control a structure borne noise. The additional mass can decrease the sound by mass effect and shift of natural frequency, and damping material can decrease the sound by damping effect. The passive acoustic control using these kinds of control materials has an advantage that is possible to control the acoustic in the wide frequency band and the whole space at a price as compared with the active control using the various electronic circuit and actuator. But the space efficiency decreased and the control ability isn't up to the active control. So it is necessary to maximize the control ability in the specific frequency to raise the capacity of passive control minimizing the diminution of space efficiency such an active control. Therefore, the characteristics of control materials and the optimum layout of control materials that attached to the boundary of structure-acoustic coupled cavity were studied using sequential optimization on this study.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1993년도 봄 학술발표회논문집
• /
• pp.95-99
• /
• 1993

Conventional tuned mass dampers are located on the top floor of tall buildings, which reduce the fundamental mode response of buildings. Higher modes may have a greater contribution toward the acceleration response of tall buildings. To reduce this, additional tuned mass dampers are required and could be substituted as building equipments. This paper shows, with a numerical ezample, how the lecate tuned mass damper in order to reduce the higher mode response effectively

• Structural Engineering and Mechanics
• /
• 제4권4호
• /
• pp.462-465
• /
• 1996

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2003년도 춘계 학술발표회논문집
• /
• pp.259-266
• /
• 2003

This paper begins with the seismic performance evaluation of an existing building, which exhibits the need of additional damping to reduce its response. Required damping ratio is found by capacity spectrum method to satisfy a target response. It is expressed with the design parameter of active mass damper by adopting Linear Quadratic Regulator, Optimal gains are obtained and then weighting matrices are found. Finally the seismic performance by added active mass damper is demonstrated, which satisfies the target response.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 추계학술대회논문집
• /
• pp.1218-1223
• /
• 2007

In this study, we experimentally investigate the equivalent ring theory for a slightly asymmetric ring. The slightly asymmetric ring has mode pair and frequency pair due to the small asymmetry and this mode pair generates beat in vibration and sound. In this paper, a slightly asymmetric ring is modeled as the equivalent ring, i.e., the assemblage of a symmetric ring and imperfect point masses. The equivalent ring has the same mode pair condition as that of the original asymmetric ring. Effect of the additional mass attachment is investigated by the equivalent ring theory and the result is compared with those of the measurement and the finite element analysis. It is confirmed that the original ring and the equivalent ring show the same change in frequency and mode under the various additional imperfection mass conditions. The equivalent ring theory explains how the asymmetric elements influence the mode characteristics and provides useful information to tune the beat property.

• 한국임상수의학회지
• /
• 제19권2호
• /
• pp.256-259
• /
• 2002

A 39 kg, 7-year-old male Labrador Retriever dog with a 3-month history of epistaxis, sneezing, and nasal discharge was referred to the Veterinary Medical Center of the Tokyo University. On the plain X-ray and computed tomography (CT) of the head showed increased density of the soft tissue in the left nasal cavity and the tumor infiltrated to nasal septum. The tumor mass removed by rhinotomy. Histopathological examination of the mass revealed adenocarcinoma. Four weeks after the surgery, the radiation therapy was performed twice a week for f weeks. 4 months after surgery, the dog had a recurrence in nasal cavity and administered carboplatin 300 mg/$m^2$ twice. However, the tumor had no response to chemotherapy, additional surgery and additional radiation therapy, and the dog was euthanized at the owner's request. At necropsy, metastatic proliferation was confirmed in the lung, lymph nodes and nasal cavity.