• Structural Engineering and Mechanics
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• v.77 no.2
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• pp.293-304
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• 2021

Structural failure due to seismic pounding between two adjacent buildings is one of the major concerns in the context of structural damage. Pounding between adjacent structures is a commonly observed phenomenon during major earthquakes. When modelling the structural response, stiffness of impact spring elements is considered to be one of the most important parameters when the impact force during collision of adjacent buildings is calculated. Determining valid and realistic stiffness values is essential in numerical simulations of pounding forces between adjacent buildings in order to achieve reasonable results. Several impact model stiffness values have been presented by various researchers to simulate pounding forces between adjacent structures. These values were mathematically calculated or estimated. In this study, a linear spring impact element model is used to simulate the pounding forces between two adjacent structures. An experimental model reported in literature was adopted to investigate the effect of different impact element stiffness k on the force intensity and number of impacts simulated by Finite Element (FE) analysis. Several numerical analyses have been conducted using SAP2000 and the collected results were used for further mathematical evaluations. The results of this study concluded the major factors that may actualise the stiffness value for impact element models. The number of impacts and the maximum impact force were found to be the core concept for finding the optimal range of stiffness values. For the experimental model investigated, the range of optimal stiffness values has also been presented and discussed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.2
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• pp.58-64
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• 2019

This paper describes the analysis of dynamic characteristics and prediction of the stiffness for the joint between structural members. In the process of deriving the governing equations, the stiffness values responsible for the moment and shear force were modelled by using linear and torsional springs in the middle of a clamped-clamped beam. The sensitivities of the natural frequency and modal assurance criterion were investigated as a function of the dimensionless linear and torsional spring stiffness. The reliability of the predictions for the linear and torsional stiffness values was verified by the inverse computations of the stiffness matrix. The predictive and exact theoretical stiffness values were compared for the stiffness element in the finite element formulation, and their results show an excellent correlation. It is strongly anticipated that although the proposed methodology is currently limited to the analytical utilization, it will provide a useful tool to estimate unknown joint stiffness values based on the experimental natural frequency and mode shape.

• International Journal of Railway
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• v.8 no.2
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• pp.50-54
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• 2015

The primary function of the trackbed in a conventional railway track system is to decrease the stresses in the subgrade to be in an acceptable level. A properly designed trackbed layer performs this task adequately. Many design procedures have used assumed and/or are based on critical stiffness values of the layers obtained mostly in the field to calculate an appropriate thickness of the sublayers of the trackbed foundation. However, those stiffness values do not consider strain levels clearly and precisely in the layers. This study proposes a method of computation of stiffness that can handle with strain level in the layers of the trackbed foundation in order to provide properly selected design values of the stiffness of the layers. The shear modulus values are dependent on shear strain level so that the strain levels generated in the subgrade in the trackbed under wheel loading and below plate of Repeated Plate Bearing Test (RPBT) are investigated by finite element analysis program ABAQUS and PLAXIS programs. The strain levels generated in the subgrade from RPBT are compared to those values from RC (Resonant Column) test after some consideration of strain levels and stress consideration. For comparison of shear modulus G obtained from RC test and stiffness moduli $E_{v2}$ obtained from RPBT in the field, many numbers of mid-size RC tests in laboratory and RPBT in field were performed extensively. It was found in this study that there is a big difference in stiffness modulus when the converted $E_{v2}$ values were compared to those values of RC test. It is verified in this study that it is necessary to use precise and increased loading steps to construct nonlinear curves from RPBT in order to get correct $E_{v2}$ values in proper strain levels.

• Composites Research
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• v.17 no.5
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• pp.25-38
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• 2004

In this study, the stiffness of spatially reinforced composites (SRC) are predicted by using superposition of a rod and matrix stiffnesses in an arbitrary direction. To confirm the predicted values, the material properties of SRC are measured. The predicted values from the volume average of stiffness matrix are consistent with the tested values in a rod direction, but are inconsistent in an off-rod direction while reverse is true fur the volume average of compliance matrix. Therefore, the harmony function from superposition of stiffness and compliance matrix is introduced. The predicted values from the harmony function are consistent with the tested values in both the rod and the off-rod directions.

• Korean Journal of Digital Imaging in Medicine
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• v.14 no.1
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• pp.21-29
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• 2012

The purpose of this study is to evaluate the mutual relations by measuring SNR from T2 weighted image and ADC values on the basis of the stiffness values from liver tissues. This study was conducted that total 37 people(23 of males and 11 of females) were taken the liver MRI examination and average age was $54.5{\pm}12.7$ years old. The equipment was MAGNETOM Skyra 3.0T (SIEMENS, Erlangen, Germany) and 32 channel body-array coil. The examination were conducted with HASTE T2 weighted image by axial plane, Spin-echo EPI (echo planner image) DWI (b-value = 800) and Magnetic resonance elastography. The ROIs (region of interest: 200-300 $mm^2$) were established on the basis of the first axial stiffness image corresponded 95% confidence interval from axial stiffness image and then were measured values. After drawing the grid lines, signals were measured SNR from T2 weighted image and ADC values on the same locations that were analysed other 3 planes respectively. The results were showed correlation (0.057) that were increased to SNR from T2 weighted image by increasing stiffness value that no significant difference statistically p = 0.003. Other results were showed correlations (-0.301) that were decreased to ADC values by increasing stiffness values that no significant difference statistically p = 0.088. In the 3.0T equipment, the results may be error in much the same fashion as the 1.5T from ADC values by evaluation of fibrosis stage. However, Magnetic resonance elastography would be useful method that is used to diagnose exactly liver fibrosis stages in the 3.0T.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.525-532
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• 1998

In this study, dynamic characteristics of catenary that supplies electrical power to high-speed trains is investigated. A particular emphasis is placed on the effect of droppers on the dynamic response of the contact wire, a dropper is an element that connects the contact wire with the messenger wire so as to maintain near uniform compliance, Finite element model compressing 3 spans is constructed. For the linear model, droppers are modeled as linear springs with various stiffness values. Modal analysis is performed to obtain the natural frequencies and modes and the variation in the modal density distribution for changing stiffness values are noted. Impulse response is also obtained through computer simulation. In practice, dropper is a nonlinear element with low stiffness in compression and high stiffness in tension. Hence, dropper can be modeled as a nonlinear spring with hi-directional stiffness values. Impulse and harmonic responses are obtained for the nonlinear model through simulation. The responses aye also compared with the linear cases.

• Journal of the Korean Society of Clothing and Textiles
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• v.8 no.2
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• pp.47-57
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• 1984

Effect on the hand value and mechanical properties of blend ratio and weight had been investigated Oil summer suits for men. Relation between the mechanical properties and the deformation in behavior was also studied. The mechanical properties which influence the hand values and total hand value had been discussed and the relation between mechanical properties, hand values and fabric count had, too. As result, the following conclusions had been obtained. 1) The values of tensile properties increased with the increase of blend ratio of wool. The values of surface properties increased according to the increase of blend ratio of polyester. 2HB(bending properties) of polyester/wool blend showed higher value than that of $100\%$ wool, but there was no change in the shearing properties according to the blend ratio. The values of stiffness, crispness and anti-drape stiffness of blend fabric showed higher values than those of $100\%$ wool fabric. The value of fullness (including softness) of blend fabric showed lower value than that of $100\%$ wool fabric. 2) The correlation between hand values and mechanical properties showed following order. in stiffness : bending properties>surface properties in crispness: surface properties>bending properties in anti-drape stiffness: bending properties>surface properties>shearing properties.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.11
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• pp.1236-1244
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• 2012

A equivalent stiffness modeling has been performed for extracting the equivalent stiffness properties which are orthotropic elastic model from a large scale wind turbine rotor blade so that structure model can be constructed more simply for the three dimensional static aeroelastic analysis. In order to present the procedure of equivalent stiffness modeling, NREL 5MW class wind turbine rotor having the three stiffness information which are flapewise, edgewise and torsional stiffness was chosen. This method is based on applying unit moment at the tip of the blade as well as fixing all degree of freedom at the blade root and calculating the displacement from the load analysis to obtain the elastic modulus corresponding to equivalent stiffness referred to the NREL reports on blade divided into 5 sections respectively. In addition, one section was divided into 3 parts and the trend functions were used to make the equivalent stiffness model more correctly and quickly. Through the comparison of stiffness between the reference values and calculated values from equivalent stiffness model, the investigation of the accuracy on the stiffness values and the efficiency for constructing the model was conducted.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.164-172
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• 2014

This paper presents a method for analyzing the stiffness of full and low DOF (degree of freedom) planar parallel manipulators with serially connected legs. The individual stiffness of each leg is obtained by applying reciprocal screws to the leg twist using passive joints and elastic elements consisting of actuators and links. Because the legs are connected in parallel, the manipulator stiffness is determined by summing the individual leg stiffness values. This method does not require the assumption that springs should be located along reciprocal screws and is applicable to a planar parallel manipulator with a generic or singular configuration. The stiffness values of three planar parallel manipulators with different DOFs are analyzed. The numerical results are confirmed using ADAMS S/W.

• Journal of the Korean Society of Clothing and Textiles
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• v.24 no.7
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• pp.987-994
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• 2000

Cotton fabrics were finished with mixture of BTCA and silicone by pad-dry-cure process to achieve better mechanical properties than those of finished with BTCA alone. The changes of mechanical properties o( finished cotton fabrics were measured with by the KES-FB System and the hand values were calculated from the data of mechanical properties. With the durable press finish with BTCA tensile, bending, shear and compression properties increased. In hand values, Stiffness Crispness and Anti-Drape Stiffness increased, and Fullness & Softness decreased. Whereas silicone treatment reduced bending and shear properties and improved tensile and compressional resilience. Thus, Stiffness Crispness and Anti-Drape Stiffness decreased, and Fullness & Softness increased. These results indicated that BTCA treatment restricts fiber/yarn mobility in the fabric structure due to crosslinking, but silicone treatment reduces inter-fiber and inter-yarn frictional forces. Therefore, finish with mixture of BTCA and silicone provided cotton fabrics with a lower Stiffness, Crispness and Anti-Drape Stiffness and a higher Fullness & Softnesss than finish with BTCA alone.