• Biomedical Science Letters
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• v.17 no.2
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• pp.141-149
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• 2011

The purpose of this study was to find out any difference and correlation between the cardiac structure and its function according to the level of obesity as evaluated by waist measurement and BMI (body mass index) in healthy adults. For research subjects, the study selected a final 519 subjects excluding 198 subjects aged 55 or over out of 717 subjects who received echocardiography through a medical checkup at J General Hospital. For the criteria for obesity, men were defined as being obese in case their waist measurement was over 90 cm, whereas women were defined as being obese in case their waist measurement was over 80 cm. Also, regarding the BMI criteria, in case a person's BMI was 30 kg/$m^2$, the subject was classified as belonging to an obese group, and in case a person's BMI was between 25 kg/$m^2$ and 30 kg/$m^2$, the subject was classified as belonging to an overweight group. Concerning the evaluation of cardiac structure and function, they were evaluated using two-dimensional, M-mode, doppler echocardiography. According to the stage of obesity in accordance with waist measurement and BMI, the cardiac structure showed both eccentric and centripetal changes, and the cardiac function was also discovered to show differences according to the stage of obesity. In addition, also in the overweight group, which is a prior stage to obesity, out of the criteria for obesity classification according to BMI, there were differences in the cardiac structure and function. Also, both the waist measurement and BMI were found to have a correlation with cardiac structure and diastolic function. Consequently, cardiac structure and function are correlated with BMI and waist measurement, which are anthropometrical variables, and obesity is assumed to induce not only structural change but also functional change of the heart.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1327-1336
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• 2001

The structural modes driven by the low wave-number components of smooth elastic wall pressure provide a relatively weak coupling between the flow and the wall motion. If the elastic thin plate has any resonant mode whose wave-number of resonance coincides with $\omega$/U$\sub$c/, the power will be transmitted to those modes of vibration by the flows. We examine the problem in which the elastic thin plate is subject to pressure fluctuations under turbulent boundary layer. Measurements are presented of the frequency spectra of the near- and far-field pressures and radiated sound contributed by the various wave modes of the thin elastic plate. Dispersion equation for wave motions of elastic plate is used to investigate the effect of bending waves of relatively low wave number on radiated sound. The low wave-number motion of elastic plate is observed to have much less influence on the low-frequency energy of wall pressure fluctuations than that of the rediated sound. High amplitude events of the wall pressure are observed to weakly couple with high-frequency energy of radiated sound for case of low tension applied to the plate. The sound source localization is applied to the measurement of radiated sound by using acoustic mirror system.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.413-418
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• 2001

Fundamental failure mode in a laminated composite pinned-joint is proposed to assess damage resulting from stress concentration in the plate. The joint area is a region with stress concentrations thus a complicated stress state exists. The modeling of damage in a laminated composite pinned-joint presents many difficulties because of the complexity of the failure process. In order to model progressive from initial to final, finite element methods are used rather than closed form stress analyses. Failure analysis must be a logical combination of suitable failure criteria and appropriate material properties degradation rules. In this study, the material properties which were obtained in previous study, the preparing process of the bearing strength test for a pinned joint CFRP composite plate subjected to in-plane loading at low temperature, and the FEM result of progressive damage model using ANSYS program are summarized to assess the structural safety of CFRP plate used in the magnetic supporting post of KSTAR(Korea Superconducting Tokamak Advanced Research).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1817-1825
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• 2000

The purpose of this study is to examine the fracture toughness of the welded pipe from the viewpoint of FATT for the S38 and S42 steels used widely as the pipe material. Post weld heat treatment(PW HT) was carried out like following conditions: temperature of 67$0^{\circ}C$, I hour of holding time and cooling in furnace. Fracture toughness was obtained by measuring the crack opening displacement(COD) of the notched specimens over the range of temperature from -14$0^{\circ}C$ to -$25^{\circ}C$. Hardness values at fusion line near around were the highest and the microstructures at welded zone were coarsened. Regardless of the pipe materials, COD and temperature curves of the as-welds were moved toward higher temperature compared with those of the parents. However, COD and temperature curves of the PWHT specimens were positioned at lower temperature compared with those of the as-welds. The more heat input causes to decrease the COD values at the constant temperature. It was verified through the recrystallization treatment that PWHT was attributed to move toward lower temperature region considerably due to the improved plastic deformation at the same applied COD value of 0.3mm and softening effect. In case of the weldment of S38 steel, cleavage fracture was observed at -105$^{\circ}C$ unlike the structural steels, in which brittle fracture mode was generally shown at - 196$^{\circ}C$.

• Composites Research
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• v.16 no.3
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• pp.18-24
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• 2003

Sandwich structures have been widely used in the applications of vessel industry, where high structural stiffness is required with small addition of weight. It is so significant to think of the effect of the variables in the design process of the sandwich structure for the concentrated loads. This paper describes the influence of design variables, such as core density, core thickness and face thickness ratio, on the strength of sandwich beam. The theoretical failure loads based on the 2-D elasticity theory agree well with the experimental yield or failure loads, which are measured at the three point bending laboratory test using AS4/3501-6 facing and polyurethane foam core sandwich beam. The comparison of those yield or failure loads was also done with the ratio of the top to bottom face thickness. The theoretical optimum condition is obtained by finding the intersection point of failure modes involved, which gives optimum core density of the sandwich beam for strength and stiffness. In the addition, the effect of unequal face thickness for the optimized and off-optimized sandwich beams for the strength was compared with the ratio of loading length to beam length, and the variations of strength and stiffness were discussed with the relative ratio of core to face mass.

• Journal of Korean Society of Steel Construction
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• v.22 no.3
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• pp.219-228
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• 2010

This paper describes an experimental research on the structural behavior and the ultimate strength of longitudinally stiffened plates subjected to local, distortional, or mixed-mode buckling under compression. The stiffened plate undergoes local, distortional, or interactive local-distortional buckling according to the flexural rigidity of the plate's longitudinal stiffeners and the width-thickness ratios of the sub-panels of the stiffened plate. A significant post-buckling strength in the local and distortional modes affects the ultimate strength of the longitudinally stiffened plate. Compression tests were conducted on stiffened plates that were fabricated from 4mm-thick SM400 steel plates with a nominal yield stress of 235MPa. A simple strength formula for the Direct Strength Method based on the test results was proposed. This paper proves that the Direct Strength Method can properly predict the ultimate strength of stiffened plates when the local buckling and distortional buckling occur simultaneously or nearly simultaneously.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.11
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• pp.1071-1077
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• 2012

Low frequency noises(up to about 200 Hz) such as booming are mainly caused by particular modes, and in general the solutions may be found based on mode controls where conventional methods such as FEM can be used. However, at higher frequencies between 0.3~1 kHz, as the number of modes rapidly increases, radiation characteristics from structures, performances of damping sheets and sound packages may be more crucial rather than particular modes, and consequently the conventional FEM may be less practical in dealing with this kinds of structure-borne problems. In this context, so-called 'mid-frequency simulation model' based on FE-SEA hybrid method is studied and validated to reduce noise in this frequency region. Energy transmission loss(i.e. air borne noise) is also studied. A dash panel component is chosen for this study, which is an important path that transmits both structure-borne and air borne energies into the cavity. Design modifications including structural modifications, attachment of damping sheets and application of different sound packages are taken into account and the corresponding noise characteristics are experimentally identified. It is found that the dash member behaves as a noise path. The damping sheet and sound packages have similar influences on both sound radiation and transmission loss. The comparison between experiments and simulations shows that this model could be used to predict the tendency of noise improvement.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.106-106
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• 2011

Recently, zinc oxide (ZnO) thin films have attracted great attention as a promising candidate for various electronic applications such as transparent electrodes, thin film transistors, and optoelectronic devices. ZnO thin films have a wide band gap energy of 3.37 eV and transparency in visible region. Moreover, ZnO thin films can be deposited in a poly-crystalline form even at room temperature, extending the choice of substrates including even plastics. Therefore, it is possible to realize thin film transistors by using ZnO thin films as the active channel layer. In this work, we investigated influence of oxygen partial pressure on ZnO thin films and fabricated ZnO-based thin film transistors. ZnO thin films were deposited on glass substrates by using a pulsed laser deposition technique in various oxygen partial pressures from 20 to 100 mTorr at room temperature. X-ray diffraction (XRD), transmission line method (TLM), and UV-Vis spectroscopy were employed to study the structural, electrical, and optical properties of the ZnO thin films. As a result, 80 mTorr was optimal condition for active layer of thin film transistors, since the active layer of thin film transistors needs high resistivity to achieve low off-current and high on-off ratio. The fabricated ZnO-based thin film transistors operated in the enhancement mode with high field effect mobility and low threshold voltage.

• Journal of Life Science
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• v.21 no.11
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• pp.1631-1635
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• 2011

The capability of synthesizing polyphenol glycosides was examined using recombinant amylosucrase from the hyperthermophilic bacterium Deinococcus geothermalis. Based on the action mode of amylosucrase, sucrose and twenty-one polyphenols were used as a donor and acceptors respectively. The transglycosylation reaction by amylosucrase produced one or two major polyphenol glycosides depending on the type of polyphenols used. The synthesized polyphenol glycosides were detected by thin-layer chromatography. The structures of the newly synthesized polyphenol glycosides were predicted based on the transglycosylation mechanism of the enzyme. According to the acceptability of the polyphenols, the structural characteristics of polyphenol as an efficient acceptor were evaluated. The results indicate that amylosucrase is an efficient catalyst for the enzymatic synthesis of polyphenol glycosides, which have high potentials in food, cosmetics, and pharmaceutical industries.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.11
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• pp.601-611
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• 2002

As resent trends in structural construction have been to build taller and larger structures than any time in the past, they have had high flexibility and low damping that can cause large vibration response under severe environmental loading such as earthquakes, winds, and mechanical excitations. The damper with mass and sqring is one aproach to safeguarding the structure against excessive vibrations. In this paper, a large capacity hybrid-type linear motor damper(LMD) was designed and fabricated for the application to the vibration control of a large building structure model. It has been designed to be able to move the damper mass, 1,500 kg up to ${\pm}250mm$ strokes at the first mode natural frequency of the building structure model, ${\pm}0.51Hz$. Linear motor is consisted of the fixed coil and the movable NdFeB permanent magnets field part. The PM field part composed magnet modules and iron yoke, is the damper mass itself, 1500kg. LMD therefore has a simplified structure and requires a few elements in the driving system, being compared with a rotary motor damper and a hydraulic damper. However, the manufacture of large PM linear actuator is difficult because of the limit of PM size and the attraction and repulsion at the assembly of PM. Therefore, large damper system is manufactured and tested for dynamic characteristics and frequency response.