• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.505-511
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• 2018

Recently, a new foundation model called "Dynamic foundation model" was proposed for the dynamic analysis of structures on the foundation. This model includes a linear elastic spring, shear layer, viscous damping and the special effects of mass density parameter of foundation during vibration. However, the relationship of foundation property parameters with the experimental parameter of the influence of foundation mass also has not been established in previous research. Hence, the purpose of the paper presents a simple experimental model in order to establish relationships between foundation properties such as stiffness, depth of foundation and experimental parameter of the influence of foundation mass. The simple experimental model is described by a steel plate connected with solid rubber layer as a single degree of freedom system including an elastic spring connected with lumped mass. Based on natural circular frequencies of the experimental models determined from FFT analysis plots of the time history of acceleration data, the experimental parameter of the influence of foundation mass is obtained and the above relationships are also discussed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.22-30
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• 2011

This study analyzes harmonic vibration with natural frequency according to the configuration of damper clutch. In the case of double spring, equivalent stress at same direction of the revolution at inner and outer coil spring is over 30% as compared with at its opposite direction. Natural frequency or harmonic response with maximum deformation in case of the less coil pitch is below 3Hz as compared with in case of the more coil pitch. As the coil pitch of damper spring as the case 2 or 4 becomes smaller, its mass and deformation can be large. In these cases, spring constant and natural frequency become smaller. In the case 5 or 6 of double spring at natural vibration or harmonic response, the frequency becomes over 300Hz. As the result of this study is applied by the design of damper spring, the damage at its connected part is prevented and the durability can be predicted.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2236-2241
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• 2008

To predict the dynamic behaviour of railway vehicle, the complex vehicle structure has been described by mathmatical model such as mass, spring and damper. Air-spring has played a major role to improve dynamic characteristics, vibration isolation and ride comfort. The mechanical behaviour of air spring is very complicated. The behaviour is based on fluid and thermodynamic mechanisms. The main parameters of air spring are stiffness due to compression of the air in the spring and surge reservoir, change of area stiffness and orifice damping. In this paper, we have studied an air-spring modeling method and compared the difference between calculation and test.

• Journal of Drive and Control
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• v.10 no.2
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• pp.1-6
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• 2013

This study describes a method which can attenuate reaction force effectively for an air spring system composed of an air spring and auxiliary chamber. For the analysis, the nonlinear governing equation of the air spring system is derived. For a performance improvement of the system, change of the heat transfer effect and the mass flow rates is included in the analysis of the air spring system. The simulation study is presented to show the reaction force is changed by variations in heat transfer characteristics and the air spring system of isothermal process has the best performance. As a result, to improve attenuation characteristics of reaction force, a process in the air spring system should be maintained near isothermal process.

• Structural Engineering and Mechanics
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• v.34 no.4
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• pp.399-416
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• 2010

The purpose of this paper is to utilize the numerical assembly method (NAM) to determine the exact natural frequencies and mode shapes of a multi-step beam carrying multiple rigid bars, with each of the rigid bars possessing its own mass and rotary inertia, fixed to the beam at one point and supported by a translational spring and/or a rotational spring at another point. Where the fixed point of each rigid bar with the beam does not coincide with the center of gravity the rigid bar or the supporting point of the springs. The effects of the distance between the "fixed point" of each rigid bar and its center of gravity (i.e., eccentricity), and the distance between the "fixed point" and each linear spring (i.e., offset) are studied. For a beam carrying multiple various concentrated elements, the magnitude of each lumped mass and stiffness of each linear spring are the well-known key parameters affecting the free vibration characteristics of the (loaded) beam in the existing literature, however, the numerical results of this paper reveal that the eccentricity of each rigid bar and the offset of each linear spring are also the predominant parameters.

• Journal of the Korean Society of Safety
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• v.13 no.1
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• pp.3-12
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• 1998

On the stability of the cantilever beam subjected to a follower force at the free end, the influences of the translational spring and the moment of inertia of a tip mass at the free end have been studied by numerical methods. The centroid of a tip mass is offset from the free end of a Beam and is located along its extended axis to vary the value of moment of inertia of a tip mass. It is proved that as the constants of a spring supporting the free end are augmented, the critical flutter loads of the above system decrease, whereas they increase without a tip mass.

• Mass Spectrometry Letters
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• v.11 no.4
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• pp.90-94
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• 2020

Interest in aspects of industrialization relating to human health has increased. Accordingly, the use of labels such as 'natural foods' and 'organic ingredients' has become more widespread, and greater emphasis is being placed on improving quality of life. Water is an essential element for human life, and water quality has a significant impact on human health. However, technology that can precisely determine the substances present in water is still lacking. This study was conducted to establish a complete mass spectrometry process, from pretreatment to analysis, to measure and characterize natural organic matter (NOM) in Korean spring water samples. Salts and other matrices were removed from the samples using solid-phase extraction (SPE) with two different columns (PPL and C18). After establishing an accurate analysis method, the experimental results were evaluated based on Van Krevelen diagrams and analysis of molar O/C and H/C ratios. The method for characterizing NOM introduced herein should facilitate evaluation of water quality.

• Ocean and Polar Research
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• v.30 no.4
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• pp.379-399
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• 2008

Spatial-temporal variations in physiochemical water qualities (temperature, salinity, DO, SPM, POC and nutrients) of surface and bottom waters were investigated along the mid-western coastal area (Taean Peninsula to Gomso Bay) of Korea. Spatial distribution patterns of temperature and salinity were mostly controlled by the physical mixing process of freshwater from Geum River and/or Gyunggi Bay with nearby coastal water. A strong tidal front is formed off Taean Peninsula during spring and summer. Seasonal variations in nutrient concentrations, lower in spring and summer and higher in fall and winter, are primarily regulated by magnitude of phytoplankton occurrence rather than freshwater loadings into the bay. Based on seasonal and spatial variability of physicochemical parameters, water quality of the study area can be divided into four water masses; Gyunggi Bay-influenced Water Mass (GBWM), Geum River-influenced Water Mass (GRWM), Yellow Sea Bottom Cold Water Mass (YSBCWM) and Cheonsu Bay Water Mass (CBWM). Water quality of the GBWM (Taean Peninsula coastal area), which has relatively low salinity and high concentrations of nutrients, is strongly controlled by the Gyunggi Bay coastal water, which is under influence of the Han River freshwater. In this water mass, the mixed layer is always developed by strong tidal mixing. As a result, a tidal front is formed along the offshore boundary of the mixed layer. Such tidal fronts probably play an important role in the distribution of phytoplankton communities, SPM and nutrients. The GRWM, with low salinity and high nutrients, especially during the flood summer season, is closely related to physiochemical properties of the Geum River. During the flood season, nutrient-enriched Geum River water mass extends up to 60 km away from the river mouth, potentially causing serious environmental problems such as eutrophication and unusual and/or noxious algal blooms. Offshore (<$30{\sim}40m$ in water depth) of the study area, YSBCWM coupled with a strong thermocline can be identified in spring-summer periods, exhibiting abundant nutrients in association with low temperature and limited biological activity. During spring and summer, a tidal front is formed in a transition zone between the coastal water mass and bottom cold water mass in the Yellow Sea, resulting in intensified upwelling and thereby supplying abundant nutrients to the GBWM and GRWM. Such cold bottom water mass and tidal front formation seems to play an important role in controlling water quality and further regulating physical ecosystem processes along mid-western Korean coastal area.

• Journal of Korea Multimedia Society
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• v.14 no.10
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• pp.1262-1274
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• 2011

A fast and stable deformation model is essential for realistic simulation of image morphing. In order to stabilize deformation, we used two internal thin plate mass-spring systems that compute the displacements of the x- and y-components of all nodes on the mesh. The deformation results are globally smoother and more stable due to the direction limitation of thin plate mass-spring systems. One-to-one deformation is one of the important issues in image morphing. We focus on fast removing overlaps in the process of deformation. To rapidly remove overlaps, the external forces are set automatically on four or eight neighboring nodes. The speed of removing overlaps is faster when external forces are set on four or eight neighbouring nodes than when on two neighbouring nodes.

• Journal of the Korea Computer Graphics Society
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• v.25 no.3
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• pp.55-63
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• 2019

Recently, the GPU computing method has been utilized to improve the performance of the physics simulation field. In particular, in the case of a deformed object simulation requiring a large amount of computation, a GPU-based parallel processing algorithm is required to guarantee real-time performance. We have studied the parallel structure design method to improve the performance of the mass spring simulation method which is one of the methods of implementing the deformation object simulation. We used OpenGL's GLSL, a graphics library that allows direct access to the GPU, and implemented the GPGPU environment using an independent pipeline, the compute shader. In order to verify the effectiveness of the parallel structure design method, the mass - spring system was implemented based on CPU and GPU. Experimental results show that the proposed method improves computation speed by about 6,000% compared to the CPU Environment. It is expected that the lightweight simulation technology can be effectively applied to the augmented reality and the virtual reality field by using the design method proposed later in this research.