• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.1-4
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• 2008

Fuel cells have the potential of providing several times higher energy storage densities than those possible using current state-of-the-art lithium-ion batteries, but current energy density of fuel cell system is not better than that of lithium-ion batteries. To achieve the high energy density, volume and weight of fuel cell system need to be reduced by miniaturizing system components such as stack, fuel tank, and balance-of-plant. In this paper, the thin flexible PCB (Printed circuit board) is used as a current collector to reduce the stack volume. Two end plates are made from light weight aluminum alloy plate. The plate surface is wholly oxidized through the anodizing treatment for electrical insulation. The opening rate of cathode plate hole is optimized through unit cell performance measurement of various opening rates. The performances are measured at room temperature and ambient pressure condition without any repulsive air supply. The active area of MEA is 10.08 $cm^2$ and active area per a unit cell is 1.68 $cm^2$. The peak power density is about 210 mW/$cm^2$ and the air-breathing planar stack of 2 Wis achieved as a small volume of 18 cc.

• Korean Journal of Veterinary Research
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• v.58 no.3
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• pp.131-136
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• 2018

Blood pressure (BP) measurement plays a pivotal role in veterinary medicine for diagnosing cardiovascular disorders and monitoring anesthesia of animals. Although indirect BP measurement has been widely applied to monitor BP because of its convenience and non-invasiveness, it is still unclear whether indirect BP measurement is compatible with direct BP measurement in minipigs. In addition, the effect of animal posture during BP measurement is not well understood in minipigs despite its importance to cardiovascular performance. Therefore, both systolic and diastolic arterial BPs in minipigs were measured via femoral artery catheterization for direct BP measurement and using a compressive cuff as an indirect BP measurement under the dorsal or right lateral recumbent postures. Numerical values were processed by the Bland-Altman method to calculate the bias ${\pm}$ SD and the limits of agreement (LOA). In accordance with the American College of Veterinary Internal Medicine guidelines, the results between direct and indirect BP measurements were determined as apparent disagreements in both systolic and diastolic arterial BPs under all postures because of large bias ${\pm}$ SD and wide LOA. The results of the present will help prevent misinterpretation of the anesthetized patient's condition during monitoring of BP by indirect measurement.

• Journal of Biomedical Engineering Research
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• v.19 no.6
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• pp.563-570
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• 1998

The purpose of this study was to investigate the effects of scintillator and collimator parameters that tradeoff between system sensitivity and spatial resolution. The parameters simulated using Monte Carlo program were scintillator thickness, colimator hole shape, septal thickness, and hole length. The results show that the sensitivity increases exponentially upto about 1 cm of scintillator thickness as the thickness increases. However the sensitivity is almost constant when the scintiallator is thicker than about 1 cm. The simulation of collimator hole shape shows that the hexagonal hole gives the best spatial resolution for the same system sensitivity. The system statical resolution is improved, as both collimator septal thickness and hole length increase, however that system sensitivity is rapidly decreased. In conclusion, The optimization of scintillator and collimator parameters using monte carlo simulation may be useful to develop a high-resolution miniature gamma probe.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.1
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• pp.69-77
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• 2011

A peristaltic micropump with lightweight piezo-composite actuator (LIPCA) membrane valves is presented. The micropump contained three cylinder chambers that were connected by microchannels and two active membrane valves. A circular miniature LIPCA was developed and manufactured to be used as actuating diaphragms. The LIPCA diaphragm acted as an active membrane valve that alternate between open and closed positions at the inlet and outlet in order to produce high pumping pressure. In this LIPCA, a lead zirconium titanate ceramic with a thickness of 0.1 mm was used as an active layer. The results confirmed that the actuator produced a large out-of-plane deflection. During the design process, a coupled field analysis was conducted in order to predict the actuating behavior of the LIPCA diaphragm; the behavior of the actuator was investigated from both a theoretical and experimental perspective. The active membrane valve concept was introduced as a means for increasing pumping pressure, and microelectromechanical system techniques were used to fabricate the peristaltic micropump. The pumping performance was analyzed experimentally in terms of the flow rate, pumping pressure and power consumption.

• The Korean Journal of Physiology and Pharmacology
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• v.6 no.2
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• pp.63-70
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• 2002

Cholinergic modulation of GABAergic spontaneous miniature inhibitory postsynaptic currents (mIPSCs) by the activation of muscarine receptors was investigated in mechanically dissociated rat nucleus basalis of the Meynert neurons using the conventional whole-cell patch recording configuration. Muscarine $(10{\mu}M)$ reversibly and concentration-dependently decreased mIPSC frequency without affecting the current amplitude distribution. Muscarine action on GABAergic mIPSCs was completely blocked by $1{\mu}M$ methoctramine, a selective $M_2$ receptor antagonist, but not by $1{\mu}M$ pirenzepine, a selective $M_1$ receptor antagonist. NEM $(10{\mu}M),$ a G-protein uncoupler, attenuated the inhibitory action of muscarine on GABAergic mIPSC frequency. Muscarine still could decrease GABAergic mIPSC frequency even in the $Ca^{2+}-free$ external solution. However, the inhibitory action of muscarine on GABAergic mIPSCs was completely occluded in the presence of forskolin. The results suggest that muscarine acts presynaptically and reduces the probability of spontaneous GABA release, and that such muscarine-induced inhibitory action seems to be mediated by G-protein-coupled $M_2$ receptors, via the reduction of cAMP production. Accordingly, $M_2$ receptor-mediated disinhibition of nBM neurons might play one of important roles in the regulation of cholinergic outputs from nBM neurons as well as the excitability of nBM neurons themselves.

• The Korean Journal of Physiology and Pharmacology
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• v.6 no.2
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• pp.81-85
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• 2002

Conventional views of synaptic transmission generally overlook the possibility of 'postfusional-control' the regulation of the speed or completeness of transmitter release upon vesicular fusion. However, such regulation often occurs in non-neuronal cells where the dynamics of fusion-pore opening is critical for the speed of transmitter release. In case of synapses, the slower the transmitter release, the smaller the size and rate-of-rise of postsynaptic responses would be expected if postsynaptic neurotransmitter receptors were not saturated. This prediction was tested at hippocampal synapses where postsynaptic AMPA-type glutamate receptors (AMPAR) were not generally saturated. Here, we found that the small miniature excitatory postsynaptic currents (mEPSCs) showed significantly slower rise times than the large mEPSCs when the sucrose-induced mEPSCs recorded in cyclothiazide (CTZ), a blocker for AMPAR desensitization, were sorted by size. The slow rise time of the small mEPSCs might result from slow release through a non-expanding fusion pore, consistent with postfusional control of neurotransmitter release at central synapses.

• Journal of Veterinary Clinics
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• v.21 no.3
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• pp.264-269
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• 2004

A retrospective analysis was performed with 270 cases of canine urolithiasis examined at Laboratory of Clinical Pathology, College of Veterinary Medicine, Seoul Nat'l University in the period between January 2001 and December 2003. The Shih-Tzu (64 cases), Yorkshire terrier (60 cases), miniature schnauzer (41 cases) and maltese terrier (36 cases) had higher incidences than other breeds. Canine urolithiasis occurred from 4 months to 15 years of age, but the most prevalent age was 3 years. Mean age was $5.68\pm3.14$ years. The major mineral component. of calculi was struvite (54.1%) and calcium oxalate (30.4%). There was no sex prevalences: male 131 cases, female 132 cases. The most prevalent anatomic locations of calculi were urinary bladder (53 of 131 cases), urethra (24 of 131 cases) and bladder/urethra (45 of 131 cases) in males and urinary bladder (103 of 132 Cases) in females. The major mineral component of calculi in urinary bladder was struvite (102 of 160 cases), and that in urethra (13 of 25 cases) and multiple locations (29 of 62 cases) was calcium oxalate: The major components of calculi were not always consistent with the components which could be expected from urine pH and crystals. So it is suggested that the components of the calculi must be analyzed after surgical removal to prevent the recurrence when the calculi could not be dissolved by diets or urine pH modifiers.

• Tribology and Lubricants
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• v.19 no.4
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• pp.230-236
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• 2003

In applications such as MEMS and NEMS devices, the adhesion force and contact load may be of the same order of magnitude and the static friction coefficient can be very large. Such large coefficient may result in unacceptable and possibly catastrophic adhesion, stiction, friction and wear. To obtain the static friction coefficient of contacting real surfaces without the assumption of an empirical coefficient value, numerical simulations of the contact load, tangential force, and adhesion force are preformed. The surfaces in dry contact are statistically modeled by a collection of spherical asperities with Gaussian height distribution. The asperity micro-contact model utilized in calculation (the ZMC model), considers the transition from elastic deformation to fully plastic flow of the contacting asperity. The force approach of the modified DMT model using the Lennard-Jones attractive potential is applied to characterize the intermolecular forces. The effect of the surface topography on the static friction coefficient is investigated for cases rough, intermediate, smooth, and very smooth, respectively. Results of the static friction coefficient versus the external force are presented for a wide range of plasticity index and surface energy, respectively. Compared with those obtained by the GW and CEB models, the ZMC model is more complete in calculating the static friction coefficient of rough surfaces.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.903-912
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• 2007

Faults of rotating parts of a train normally generate unexpected frequency band or impulsive sound[1] which has a period when it moves with a constant speed. The former can be detected by the moving frame acoustic holography method, which visualizes sound field that is generated by a moving and emitting pure tone or band limited noise source. We have attempted to apply the method to the latter case: the periodic impulsive sound which generate different signal compared with what can be measured by the band limited noise. The signal to noise ratio which determines the success of early fault detection must also be studied with the impulsive and moving signal. This research shows how the problems related with these issues can be resolved. The main idea is that periodic impulsive signal can be expressed by infinite set of discrete pure tones. This enables us to obtain lots of holograms that visualize periodic impulsive sound field including noise by using the moving frame acoustic holography method. Therefore holograms can be averaged to improve the signal to noise ratio until having reliable information that exhibits where the impulsive sources are. Theory and experiment by using the miniature vehicle are described [Work supported by BK21 & KRRI].

• Korean Journal of Veterinary Research
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• v.48 no.2
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• pp.227-233
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• 2008

Portosystemic shunt (PSS) was diagnosed in 43 dogs by mesenteric portogram from January, 2002 to June 2007 in Haemaru referral animal hospital. PSS was found in various breeds including Maltese, Miniature Schnauzer and Yorkshire Terrier and there was no predisposition in gender. In laboratory parameters, mean cell volume was lower than normal value in single shunt and alanine aminotransferase was higher than normal range in multiple shunts with clinical significance. Cystic calculi were found in over 50% dogs with PSS and even in 70.8% dogs with single shunt. In 81% dogs with PSS, extrahepatic single shunt such as portocarval type and portoazygous type was identified. Extrahepatic multiple shunt and intrahepatic single shunt were observed in 4 dogs, respectively. Gradual attenuation using ameroid constrictor was applied to 35 dogs with extrahepatic single shunt and the prognosis of these dogs were good except two dogs, which showed poor prognosis because of acquired multiple PSS and renal disease unrelated with PSS, respectively.