• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.35-42
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• 1999

This study is to analyze the buckling and the vibration of the rectangular stiffened plates with elastic springs by Finite Element Method. Boundary conditions are two types, one is all simply supported edges, another all clamped edges. To validate Finite Element Method, the buckling stresses of the stiffened plates without elastic springs are compared with the existing ones. The natural frequency parameters of the stiffened plates with or without elastic springs by Finite Element Method are also compared with the ones of SAP2000. The natural frequency parameters and the buckling stresses of the stiffened plates with elastic springs by Finite Element Method are calculated for the variation of the stiffness of the elastic springs and aspect ratio.

• Steel and Composite Structures
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• v.18 no.3
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• pp.775-791
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• 2015

An analytical and experimental investigation is performed into the mechanical behavior of carbon-fiber/epoxy woven coned annular disk springs. An analytical approach is presented for predicting the deformation behavior of disk springs of specially orthotropic laminates with arbitrary geometric parameters. In addition, an analytical methodology is proposed for obtaining the deformation behavior of a stack of disk springs. The methodology is capable of accounting for parallel and series arrangements for uniform and irregular stacks. Element and assembly experimental results are used to validate the proposed method showing how to achieve flexible spring rates at various deflections ranges. This manuscript also provides guidelines for design and validation of disk spring assemblies.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.129-135
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• 2006

In this study, a two-axis ultra-precision stage driven by piezoelectric elements is presented. The stage has a flexure-type parallel linear guide mechanism consisting of quad-symmetric simple parallel linear springs and quad-symmetric double compound linear springs. While the simple parallel linear springs guide the linear motion of a moving plate in the stage, the double compound linear springs follow the motion of the simple parallel linear spring as well as compensate the parasitic motions caused by the simple parallel linear springs. The linear springs are designed by rectangular beam type flexures that are deformed by bending deflection rather than axial extension, because the axial extension is smaller than the bending deflection at the same force. The designed guide mechanism is analyzed by finite element method(FEM). Then two-axis parallel linear stage is implemented by the linear guide mechanism combined with piezoelectric elements and capacitance type displacement sensors. It is shown that the manufactured ultra-precision stage achieves 3 nm of resolution in x- and y-axis within 30 ${\mu}m$ of operating range.

• ALGAE
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• v.24 no.4
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• pp.185-193
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• 2009

Geothermal springs in India, formed as a result of volcanic or tectonic activities, are characterized by high temperature and relatively abundant reduced compounds. These thermal springs are inhabited by characteristic thermophilic organisms including cyanobacteria. Cyanobacteria are among the few organisms that can occupy high temperature aquatic environments including hot springs. In alkaline and neutral hot springs and streams flowing from them cyanobacteria can form thick colourful mats that exhibit banding patterns. The present investigation involves study of mat forming cyanobacterial flora from hot springs located in Bakreswar, West Bengal, India. The important species found are Synechococcus bigranulatus, S. lividus, Gloeocapsa gelatinosa, G. muralis, Phormidium laminosum, P. frigidum, Oscillatoria princes, O. fragilis, Lyngbya lutea, Pseudanabaena sp., Calothrix thermalis, and Fischerella thermalis. Their distribution pattern in relation to physico-chemical parameters of spring water has also been studied. Three cyanobacterial strains of the above mentioned list were grown in culture and their pigment content and nitrogen fixing capacity were also studied. Nitrogen fixing capacities of Calothrix thermalis, Nostoc sp. (isolated in culture) and Fischerella thermalis are 5.14, 0.29, and 2.60 n mole $C_2H_4/{\mu}g$ of Chl-${\alpha}$/hr respectively. Carotenoid : Chlorophyll-${\alpha}$ ratio of four mat samples collected from Kharkunda, Suryakunda, Dudhkunda and bathing pool are 2.45, 1.60, 1.48, and 1.34, respectively. Higher value of Carotenoid : Chlorophyll-${\alpha}$ ratio coincided with higher temperature.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.6
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• pp.227-235
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• 2022

For a member model in nonlinear structural analysis, a lumped plastic model that idealizes its flexural bending, shear, and axial behaviors by springs with the nonlinear hysteretic model is widely adopted because of its simplicity and transparency compared to the other rigorous finite element methods. On the other hand, a challenging task in its numerical solution is to satisfy the equilibrium condition between nonlinear flexural bending and shear springs connected in series. Since the local forces between flexural and shear springs are not balanced when one or both springs experience stiffness changes (e.g., cracking, yielding, and unloading), the additional unbalanced force due to overshooting or undershooting each spring force is also generated. This paper introduces an iterative scheme for numerical solutions satisfying the equilibrium conditions between flexural bending and shear springs. The effect of equilibrium iteration on analysis results is shown by comparing the results obtained from the proposed method to those from the conventional scheme, where the equilibrium condition is not perfectly satisfied.

• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.223-229
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• 2016

This study proposes a new technology for a smart damper with flag-shaped behavior using the combination of magnetic friction and rubber springs. The magnet provides friction and, thus, energy dissipation, and the rubber springs with precompression contribute to present self-centering capacity of the damper. To verify their performance, this study conducts dynamic tests of magnet frictional dampers and precompressed rubber springs. For the purpose, hexahedron Neodymium (NdFeB) magnets and polyurethane rubber cylinders are used. In the dynamic tests, loading frequency varies from 0.1 to 2.0 Hz. The magnets provide almost perfect rectangular behavior in force-deformation curve. The rubber springs are tested without or with precompression. The rubber springs show larger rigid force with increasing precompression. Lastly, this study discusses combination of rigid-elastic behavior and friction to generate 'flag-shaped' behavior for a smart damper and suggests how to combine the magnets and the rubber springs to obtain the flag-shaped behavior.

• Journal of Korean Electronics
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• v.4 no.9
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• pp.112-116
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• 1984

• Journal of Korean Society of Rural Planning
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• v.13 no.1 s.34
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• pp.85-95
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• 2007

Hot springs development will be more activated with the five-day work week system than before. Nevertheless, investment and development achievement of hot springs has not resulted in a successful performance to foster townships, and this calls upon locals to build a guideline to develop hot springs. This study intends to analyze laws on hot springs, which influence mostly on the hot spring development, to gather up the information on the present state of the development, and to suggest considerations for further development plans. Features of the hot spring development are as follows: One is that metropolitan cities will discover hot spring resources more than small cities. Therefore the development will be twofold : one for resort tour and the other for one-day rest and recreation. In addition, Korean laws on hot springs are more site development-oriented to support tourism and recreation than to protect environment and discover unused resources. This makes hot spring development easier and efficient being supported by hot spring law, law on territory development and use, and tourism promotion law. On the other side, planned landscape trimming can be uniformized and unharmonized in terms of local identity and environment-friendliness. This is why careful considerations such as goods and bads of the local resources, local history and culture are needed in hot spring development. A long-term development project should include remodeling based on local identity and development trends. The third point indicates that Korean hot springs development has recorded relatively low performance due to difficult private capital attraction, and a high fence on land purchase and development approval. It is essential to release restrictions on the hot spring development-especially on those whose development performance has not been successful so that best practice can be supported by the government in remodeling and marketing. New plans on hot spring development should be also examined based on developer's capacity and local authorities' volition on the plan. Last point shows that most hot springs development plans have been designed only based on territory utilizing plan and facilities arrangement, not considering much on fund-raising, operational plan or feasibility analysis. Therefore the tourism promotion law should reinforce guidelines on tourist site approval system by supplementing criteria. At the same time, an education on tourism development planning is necessary to deepen developers' understanding, since most developers are experts more on city development, landscape architecture, designing, constructing and engineering than tourism development.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.11
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• pp.39-45
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• 1998

Gas springs have been widely used in motor vehicles as well as in most areas of industry. Instead of coil springs, these gas springs are easily opreated to open(extension process) or close (compression process) the doors because $N_2$ gas with high pressure and oil are charged in tube. Most of manufacturers are using the trial ＆ error method in order to decide its specification(reaction force, damping force), which tends to waste time and money. Therefore, gas springs have been improved by properly changing the control pressure of $N_2$ Gas with its mounting location and weight to maximize its effect and to minimize its space. Although it has been researched on damping structure to minimize impact which is applied to vehicle when its back door is fully opened, the characteristics of damping structure are not known clearly. There(ore, this paper will not only clearly define the effect of important factors(open ＆ close force)for gas springs through theoretical analysis but also provide optimum design specification through development of program to avoid traditional method of specification determination such as the trail It error method which is widely used in whole industries including automotive industry.

• Composites Research
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• v.35 no.6
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• pp.439-446
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• 2022

In this study, fiber-reinforced composite coil springs for automobiles were manufactured using the braiding method, and mechanical tests and damage evaluation were performed to confirm their safety. Through the analysis of the load-displacement behavior, the stiffness of the springs was evaluated to meet the specifications. In addition, the distribution of voids and the impregnation rate on the spring wire section were analyzed to clearly understand the criteria for the mechanical properties of the composite material. Moreover, the tested springs were visually inspected to confirm the damaged parts, and the failure mode was analyzed by observing crack initiation and propagation behavior of cross-sectional samples taken from the crack and failure adjacent areas of springs using SEM.