• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1650-1658
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• 2003

This paper deals with a novel shunt circuit, which is capable of suppressing multimode vibration amplitudes by using a pair of piezoceramic patches. In order to describe the characteristic behaviors of a piezoelectric damper connected with a series and a parallel resistor-negative capacitor branch circuit, the stiffness ratio and loss factor with respect to the non-dimensional frequency are considered. The mechanism of the shunt damper is also described by considering a shunt voltage constrained by shunt impedance. To obtain a guideline model of the piezo/beam system with a negative capacitive shunting, the governing equations of motion are derived through the Hamilton's principle and a piezo sensor equation as well as a shunt-damping matrix is developed. The theoretical analysis shows that the piezo/beam system combined with a series and a parallel resistor-negative capacitor branch circuit developed in this study can significantly reduce the multiple-mode vibration amplitudes over the whole structural frequency range.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.216-221
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• 2002

In this paper, the transmitted noise reduction of smart panels of which passive piezoelectric shunt damping is used, is experimentally studied. Shunt damping experiments are based on the measured electrical impedance model. A passive shunt circuit composed of inductors, and a load resistor is devised to dissipate the maximum energy into the joule heat energy. For multi-mode shunt damping, the shunt circuit is redesigned by adding a blocking circuit. Also the optimal location of the piezoelectric patch is studied by FEM in order to cause the maximum admittance from the patch for each mode of aluminum plate. In results, the transmitted sound pressure level of panels is efficiently reduced for multi-modes

• Journal of Korean Neurosurgical Society
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• 제43권6호
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• pp.300-303
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• 2008

Shunt infections are a common complication of ventriculoperitoneal (VP) shunts, but the formation of a brain abscess related to a shunt system is very rare. A 44-year-old woman had a VP shunt inserted for hydrocephalus secondary to a subarachnoid hemorrhage. She suffered an episode of meningitis and sepsis 8 months after the shunt operation. After recovering from the meningitis, she complained of a loss of cognitive function. An enhancing mass was found in the frontal lobe, around the frontal horn of the lateral ventricle, and the ventricular catheter was embedded inside the mass. The ventricular catheter and cerebral abscess were removed using neuroendoscopy. We present an interesting case of a shunt-related brain abscess which illustrates the usefulness of neuroendoscopy.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.699-702
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• 2002

Shunt valves implanted in the subcutaneous tissue of brain to treat patient with hydrocephalus were numerically simulated to investigate influence of pressure pulsation on their flow control characteristics. Shunt valves are subjected to pressure variation since ventricles enclosing the brain are under pressure pulsation rather than uniform pressure due to blood pressure variation. We modeled flow orifice through shunt valve and imposed pulsating pressure and valve diaphragm movement to compute flow through the valve. The results of our study indicated that flow rate increased by $40{\%}$ by introducing pressure pulsation and diaphragm movement on the shunt valve. Our results demonstrate the pressure-flow control characteristics of shunt valves unplanted above human brain may be quite different from the characteristics obtained by syringe pump test with uniform pressure and no diaphragm movement.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.51-54
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• 2003

We investigated the quench characteristics of thin film type SFCLs with shunt layers of various thickness. The SFCLs ware based on 2 inch diameter YBa$_2$Cu$_3$O$_{7}$ thin films coated in-situ with a gold shunt layer. The shunt layer thickness was varied by Ar ion milling. The limiters were tested with simulated fault currents at various source voltages. The thinner the shunt layer was, the slower was the rise of SFCL temperatures. This means SFCLs of thinner shunt layers had higher voltage ratings. The voltage rating was approximately inversely proportional to the square root of the shunt layer thickness. This result could be understood through the concept of heat balance.e.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 학술대회 논문집
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• pp.242-245
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• 2003

We investigated the quench characteristics of thin film type SFCLs with shunt layers of various thickness. The SFCLs ware based on 2 inch diameter YBa$_2$Cu$_3$3O$_{7}$ thin films coated in-situ with a gold shunt layer. The shunt layer thickness was varied by Ar ion milling. The limiters were tested with simulated fault currents at various source voltages. The thinner the shunt layer was, the slower was the rise of SFCL temperatures. This means SFCLs of thinner shunt layers had higher voltage ratings. The voltage rating was approximately inversely proportional to the square root of the shunt layer thickness. This result could be understood through the concept of heat balance.e.

• 한국정밀공학회지
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• 제3권2호
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• pp.39-54
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• 1986

One of the important factors in practical welding situations is shunt effect which deteriorates weld quality due to a shunt current which flows in the exis- ting spot. Previously, this effect has not been analytically investigated, since the mechanism of shunt effect shows very complicated phenomena in the thermal and electrical behavior. In this paper this effect is extensively studied through theoretical and experimental analysis. The theoretical results obtained from a numerical analysis of the modelling of shunt effect are compared with experimental ones. Both results show good agreement and represent well the mechanism of shunt effect.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.541-544
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• 2005

In this paper, admittance is introduced to represent electro-mechanical characteristics of piezoelectric structures and to predict the performance of piezoelectric shunt system. Finite element method is used to obtain numerical admittance. In order to illuminate the effect of noise reduction in the shunt system, two experimental setups were constructed. One is for matching the resonant shunt damping. The other is a standard test setup according to SAE J1400 used to measure the transmission loss for the smart panel with shunt circuit. Shunt performance and noise reduction of smart panel are realized by these two experiments.

• Journal of Chest Surgery
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• 제15권2호
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• pp.194-203
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• 1982

In this investigation we undertook to evaluate the utility of radionuclide cardiac angiography in the detection of cardiac shunts before and after surgical correction. Time-activity curves of ventricles and lungs were evaluated after bolus intravenous injection of 99mTc-human serum albumin in 512 preoperative patients and 551 post-operative patients. Omitting 31 cases of technical failure due to poor bolus, we detected shunts in 459 cases of 481 preoperative evaluations, so the detectability was 95.4%. The cases which couldn`t be detected by this method had small amount of shunt. Also the degree of shunt detected by radioisotope methods were well correlated with oxymetry method. [r=0.89, p<0.01 ] In postoperative evaluations, 18 out of 411 patients with left to right shunt and 10 out of 140 right to left shunt were found to have remnant shunts with radionuclide cardiac angiography. Of the 28 cases with failed operation, 2 were confirmed in reoperation, 2 by cardiac catheterization, 2 by two -dimensional echocardiography. All except one .f these patients had membranous ventricular septal defects and those with left to right shunts had moderate to severe pulmonary hypertension and shunt amount. Also those had larger septal defects than control group. We consider that radionuclide cardiac angiography is a simple and noninvasive method which can show the preoperative diagnosis and postoperative follow up of cardiac shunts.

• 대한수의학회지
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• 제48권2호
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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.