• Proceedings of the Korean Magnestics Society Conference
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• 2009.12a
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• pp.95-96
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• 2009

• Structural Engineering and Mechanics
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• v.50 no.6
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• pp.723-740
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• 2014

A fracture criterion based on the strain energy density (SED) over a control volume, which embraces the notch edge, is employed in the present paper to assess the fracture loads of some U-notched Brazilian disk (UNBD) specimens. The specimens are made of commercial graphite and have been tested under pure mode I, pure mode II and mixed mode I/II loading. The results show that the SED criterion allows to successfully assess the fracture loads of graphite specimens for different notch tip radii and various mode mixity conditions with discrepancies that fall inside the scatter band of ${\pm}20%$.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.6
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• pp.62-71
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• 1996

In this paper, we design tripel-mode channel filter using iris optimization technique and investigate its response. The cavity diameter is determined to resonate three orthogonal modes coincidently and inter-cavity iris is optimized in which one slot control one TE-TE mode and other TM-TM mode couplings simultaneously. Since the electric/magnectic field is variable due to slot position, the center position of the slot which handle coupling coefficients of two modes should be designe dwith optimizatin technique presented here. The implemented triple-mode filter in this paper saves its mass and volume upto 33% relating to the dual-mode filter, caused by the reduced number of cavities.

• Journal of Yeungnam Medical Science
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• v.35 no.2
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• pp.165-170
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• 2018

Background: The purpose of this study was to investigate whether tidal volume (TV) of 8 mL/kg without positive end-expiratory pressure (PEEP) and TV of 6 mL/kg with or without PEEP in pressure-controlled ventilation-volume guaranteed (PCV-VG) mode can maintain arterial oxygenation and decrease inspiratory airway pressure effectively during one-lung ventilation (OLV). Methods: The study enrolled 27 patients undergoing thoracic surgery. All patients were ventilated with PCV-VG mode. During OLV, patients were initially ventilated with TV 8 mL/kg (group TV8) without PEEP. Ventilation was subsequently changed to TV 6 mL/kg with PEEP ($5cmH_2O$; group TV6+PEEP) or without (group TV6) in random sequence. Peak inspiratory pressure ($P_{peak}$), mean airway pressure ($P_{mean}$), and arterial blood gas analysis were measured 30 min after changing ventilator settings. Ventilation was then changed once more to add or eliminate PEEP ($5cmH_2O$), while maintaining TV 6 mL/kg. Thirty min after changing ventilator settings, the same parameters were measured once more. Results: The $P_{peak}$ was significantly lower in group TV6 ($19.3{\pm}3.3cmH_2O$) than in group TV8 ($21.8{\pm}3.1cmH_2O$) and group TV6+PEEP ($20.1{\pm}3.4cmH_2O$). $PaO_2$ was significantly higher in group TV8 ($242.5{\pm}111.4mmHg$) than in group TV6 ($202.1{\pm}101.3mmHg$) (p=0.044). There was no significant difference in $PaO_2$ between group TV8 and group TV6+PEEP ($226.8{\pm}121.1mmHg$). However, three patients in group TV6 were dropped from the study because $PaO_2$ was lower than 80 mmHg after ventilation. Conclusion: It is postulated that TV 8 mL/kg without PEEP or TV 6 mL/kg with $5cmH_2O$ PEEP in PCV-VG mode during OLV can safely maintain adequate oxygenation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.434-440
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• 2013

With polymer properties and ceramic volume fraction as design variables, the optimal structure of 1-3 piezocomposites has been determined to maximize the thickness mode electromechanical coupling factor. When the piezocomposite vibrates in a thickness mode, inter-pillar resonant modes are likely to occur between lattice-structured piezoceramic pillars and polymer matrix, which significantly deteriorates the performance of the piezocomposite. In this work, a new method to design the structure of the 1-3 type piezocomposite is proposed to maximize the thickness mode electromechanical coupling factor while preventing the occurrence of the inter-pillar modes. Genetic algorithm was used for the optimal design, and the finite element analysis method was used for the analysis of the inter-pillar mode.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.7
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• pp.81-90
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• 2009

Due to environmental issues, the development of low energy consumption products has become one of the main topics in the home appliance industry. The energy consumption of a refrigerator depends on the efficiency of its compressor as well as on the refrigerator cycle design, such as the capacity modulation. In this study, a dual capacity, i.e., two-step capacity modulation (TCM), reciprocating compressor is developed. In a TCM compressor, capacity modulation is achieved by changing the dead volume in the cylinder. Instead of a concentric sleeve, an eccentric sleeve, a key, and a spring are used to change the dead volume for the clockwise and counterclockwise rotation of a motor. When the compressor changes its operating mode from full capacity to partial capacity or in opposite direction, the key may collide with the eccentric sleeve. The structural reliability and mode change reliability were confirmed by analysis and experiment.

• Korean Journal of Veterinary Research
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• v.44 no.2
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• pp.317-322
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• 2004

This study was performed to evaluate echocardiographic parameters in dogs with experimental mitral regurgitation subjected to dobutamine stress testing. In 8 beagle dogs, a 4-prong grasping forceps was inserted into the left ventricle through the carotid artery with fluoroscopic guidance. The disruption of chordae or mitral valve leaflet was performed. Echocardiographic protocols included quantitative Doppler echocardiography and M-mode measurement for evaluating left ventricle function. After all measurement was obtained at rest, dobutamine was infused incrementally. In stress testing, all measurement also was performed at rest as the same method. In stress Doppler echocardiography, regurgitant fraction and aortic stroke volume was increased significantly (P<0.001). Effective regurgitant orifice and regurgitant volume was not changed. In M-mode examination, fractional shortening was increased significantly at stress test (P<0.001). From the results obtained in this study, it could be suggested that dobutamine stress echocardiography increase left ventricle performance in non-functional mitral regurgitation and quantitative Doppler echocardiography is non-invasive, accurate method in valvular regurgitation.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.802-805
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• 1988

The objective of the present study was to manufacture the piezoelectric composites of Lead Zirconate Titanate (PZT) - polymer for applications such as ultrasonic medical diagnosis and hydrophone. The PZT rod-polymer composites have been prepared with 4.5 to 57 volume percent PZT using 1.5 mm rod, so the connectivity pattern of the two phase is 1-3 type. The electromechanical coupling factors of radial mode ($k_{p}$) and thickness mode ($k_{t}$) were nearly independent of the volume percent PZT, which were 0.3 and 0.65, respectively. The acoustic impedance of the piezoelectric composites was measured by the resonance technique in the frequency range 50 KHz-1.5 MHz, which was in the range of 3.8 - 60 Mrayl.

• Journal of Welding and Joining
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• v.16 no.2
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• pp.73-83
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• 1998

This study investigated the relationships between the microstructure and the wear resistance of hardfaced iron/chromium alloys to examine the low stress abrasive wear mechanism. The effects of volume fraction of reinforcing phases(chromium carbide and eutectic phase) were studied. The alloys were deposited once or twice on a mild steel plate using a self-shielding flux cored arc welding process. The low stress abrasion resistance of he alloys against dry sands was measured by the Dry Sand/Ruber Wheel Abrasion Tester (RWAT). The wear resistance of hypoeutectic alloys, below 0.36 volume fraction of chromium-carbide phase (VFC), behaved as Equal Pressure Mode (EPM) for the inverse rule of mixture whereas the wear resistance of hypereutectic alloys, above 0.36 VFC, represented Equal Wear Mode (EWM) for the linear rule of mixture.

• Korean Journal of Optics and Photonics
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• v.16 no.5
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• pp.456-461
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• 2005

We numerically investigate the characteristic of single Nd:YAG rod laser with the convex-plane resonator configuration in order to get the best condition for high efficient intra-cavity second harmonic generation(SHG). The beam quality is analyzed with ABCD matrixes including the thermal lensing characteristic of Nd:YAG rod. The analysis is focused on stability, M2, beam waist and mode-volume of laser beam inside the resonator. The best conditions for SHG is obtained when a laser rod is set near the curved laser mirror.