• Journal of Sensor Science and Technology
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• v.31 no.1
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• pp.6-11
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• 2022

To date, various techniques have been utilized to assess the contractility of cardiomyocytes and their response to drug-induced toxicity. However, these techniques are either invasive or involve complex fabrication methods and expertise. Here, we introduce the use of video-based analysis software to track the motion of cardiomyocytes and assess their contractility. The software, called "Tracker", is freely available and this is the first attempt at using it for cardiac contractility measurement. We used the software to measure the contractile properties of cells cultured on a rigid substrate and two flexible polydimethylsiloxane (PDMS) substrates having different elastic moduli day-wise up to eight days. Contractility was found to be highest in the most flexible substrate. Subsequently, the cardiotoxicity response of the cells on three different substrates was analyzed with verapamil. It was observed that the cells on rigid substrate were primarily affected by drug-induced toxicity, while the drug had a lesser impact on cells on the more flexible PDMS substrate. Evidently, the flexible substrate aided the maturation of cells and had lower drug toxicity, while the cells on PS could not fully mature. The assessment of cardiomyocytes using "Tracker" proved to be simple and reliable.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.5
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• pp.247-251
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• 2004

We report highly improved yield strength of nickel thin film, prepared using electroplating. The micro-scaled nickel cantilever is found to have significantly higher yield strength than bulk nickel. For the yield strength test, the heights of the micro-scaled cantilever were varied up to 60 ${\mu}{\textrm}{m}$ and electrostatic force was used for actuation. Stress of the bent cantilever was estimated using the FEM large deflection model. The yield strength of the thin nickel film is found to be over five times higher than that of the bulk nickel previously published. Results from this study indicate that metal microstructures can be used for MEMS applications requiring large deflection.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.295-300
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• 2001

Significant improvements in bond strength between new and existing concrete can be achieved through the modification of the new concrete by latex modification. But, no test method has been adopted as a standard to measure the bond strength between the concrete used to repair and the substrate being repaired. The performance of old and the new concrete construction defends upon band strength between old and the new concrete. Current adhesion strength measurement method is inaccurate method that ignore effect of stress concentration by shape of specimens. Therefore, this research calculates stress concentration coefficient using finite element analysis and direction tensile strength test (pull-off test). The result shows that the required core depth is 2.5 cm. Elastic modulus and overlay thickness do not influence in stress concentration.

• Tunnel and Underground Space
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• v.8 no.1
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• pp.67-73
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• 1998

This paper presents the results of deformation measurement and numerical analysis carried out to study the behaviour of the rock mass around large underground oil storage caverns. Displacements during excavation have been monitored using borehole extensometers which had been installed before the excavation of caverns proceeded. Numerical analysis has been carried out to examine the three-dimensional behaviour of rock and the face advance effect. The input parameters for this analysis were determined from the results of laboratory and field tests. The deformation modulus of the rock mass was determined from plate loading test at the site and in-situ stresses were measured from the overcoring method with USBM deformation gauge. The results from this study gave a clear picture for three-dimensional behaviour of the rock mass, hence would be used for the optimum design.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.619-622
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• 2005

Purpose of this study is to investigate the size-dependent mechanical properties in micron scale medium. Theories such as the couple stress theory and strain gradient theory explain that the deformation in the micron scale is dependent upon the size of the medium. Specimens of the cantilever type, bridge type and paddle type beam that have thickness of 900, 1000 and 1200 nm and width of 10, 20, 30 and $50{\mu}m$ were fabricated by the MEMS technique. We carried out the bending and torsion test to measure the mechanical properties such as the young's modulus, yield strength and torsional rigidity using the AFM(Atomic Force Microscopy).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.729-732
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• 2004

An experimental and numerical approach has been carried out for to see the noise characteristics of a circular diamond saw. The noise level measurement result for the several kinds of shanks shows us that the noise level reduction in high frequency range could be an effective way to control the noise problem. Sandwich type shank whose center part is laminated with a low Young‘s modulus material greatly reduces the noise level. The noise level for the shank where several curve shaped slits are provided in the circumferential direction is reduced considerably too. The response spectrum analysis by the FEM shows us to be an alternative for predicting the noise characteristics of the shank.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.349-354
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• 2002

Significant improvements in bond strength between new and existing concrete can be achieved through the modification of the new concrete by latex modification. But, no test method has been adopted as a standard to measure the bond strength between the concrete used to repair and the substrate being repaired. The performance of old and the new concrete construction depends upon bond strength between old and the new concrete. Current adhesion strength measurement method ignores the effect of stress concentration by shape of specimens. Therefore, this research calculates stress concentration coefficient using finite element analysis and direction tensile strength test (pull-off test). The result shows that the required core depth is 2.5cm. Elastic modulus and overlay thickness do not influence in stress concentration.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.601-606
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• 2002

This study explored physical properties of a hardened cement and a concrete specimen using a high performance cement type solidification consisting of a weathered granite soil and a yellow soil mainly. Also the development of high performance cement type solidification was purposed for an intensity improvement and a long-term durability. As the experimental results, a mortar used by the weathered granite soil shows positive result, however using the yellow soil as a mortar Shows less positive result at the compressive strength. Also the dynamic modulus of elasticity measurement result, the concrete specimens used by the weathered granite and the yellow soil reached above 90%, so it seems to have the durability of freezing and thawing.

• Journal of the Korean Ceramic Society
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• v.30 no.4
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• pp.265-272
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• 1993

Effect of mixing homogeneity in powder mixtures of Si3N4 and sintering additive (10mol% YAG) prepared by coprecipitation on the mechanical properties of pressureless-sintered body was investigated. Sintering was performed in a graphtie furnace at 1850℃ for 0.5h under 0.15MPa N2 atmosphere using Si3N4 powder bed. Results from the measurement of Young's modulus, Vickers hardness, 4-point-bending strength, and KIC for the coprecipitation-treated (CP) and the mechanically-mixed specimens(MM) showed that a remarkable improvement in flexural strength and Weibull parameter can be achieved for the CPspecimens: (677±68MPa, 12.0) for CP samples and (539±108MPa, 5.5) for MM. Other properties were almost same irrespective of preparation methods.

• Journal of Biosystems Engineering
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• v.24 no.3
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• pp.243-252
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• 1999

The damage caused in the processes and distributions after harvesting the fruits and vegetables is attributed to the mechanical factors such as compressive and impact forces. Compression tests of biological materials provide an objective method for determining the apparent modulus of elasticity and mechanical properties which are significant in quality evaluation and control, and them maximum allowable compressive forces for minimizing mechanical damage. This study was performed to determine the mechanical properties of apple and pear, and to investigate effect of specimen shapes on the mechanical properties of them. A computer program was developed for measuring the mechanical properties and analyzing the data obtained from the measurement. Compression tests on the sample were performed with then replications at each treatment and at 25 mm/min loading rate. Mechanical properties of the apple was generally shown the higher value than those of the pear, and it was though that data obtained form the cylindrical specimen removed from the sample was more reliable than from the specimen cut in half.