• Journal of Chest Surgery
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• v.57 no.3
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• pp.231-239
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• 2024

Background: Although the modified Blalock-Taussig shunt remains the mainstay method of palliation for augmenting pulmonary blood flow in various congenital heart diseases, the shunt must be carefully designed to achieve the best outcomes. This study investigated the effect of shunt configuration on pulmonary artery growth and growth discrepancy. Methods: Twenty patients with successful modified Blalock-Taussig shunt takedown were analyzed. Pulmonary artery and shunt characteristics were obtained using computed tomography scans. Differences in the baseline and follow-up diameter ratios and growth in the ipsilateral and contralateral arteries were calculated. The angle between the shunt and pulmonary artery, as well as the distance from the main pulmonary artery bifurcation, were measured. Correlations between pulmonary arteries and shunt configurations were analyzed. Results: The median interval time between shunt placement and takedown was 154.5 days (interquartile range, 113.25-276.25 days). Follow-up values of the ipsilateral-to-contralateral pulmonary artery diameter ratio showed no significant correlation with the shunt angle (ρ=0.429, p=0.126) or distance (ρ=0.110, p=0.645). The shunt angle and distance from the main pulmonary bifurcation showed no significant correlation (ρ=-0.373, p=0.189). Pulmonary artery growth was negatively correlated with shunt angle (ipsilateral, ρ=-0.565 and p=0.035; contralateral, ρ=-0.578 and p=0.030), but not with distance (ipsilateral, ρ=-0.065 and p=0.786; contralateral, ρ=-0.130 and p=0.586). Conclusion: Shunt configuration had no significant effect on growth imbalance. The angle and distance of the shunt showed no significant correlation with each other. A more vertical shunt was associated with significant pulmonary artery growth. We suggest a more vertical graft design for improved pulmonary artery growth.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.123-130
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• 2007

Hypoplastic left heart syndrome is currently the most lethal cardiac malformation of the newborn infant. Survival following a Norwood operation depends on the balance between systemic and pulmonary blood flow, which is highly dependent on the fluid dynamics through the interposition shunt between the two circulations. The purpose of this study is an optimization of the systemic-to-pulmonary artery shunt. In this study, We used computational fluid dynamic(CFD) models to determine the velocity profile in a systemic-to-pulmonary artery shunt and suggested a simplified method of calculating the blood flow in the shunt based on Ultrasound systems. We analyzed the flow characteristic variations and oscillatory shear index(OSI) due to the anastomosis angle and shunt diameter changing. Four different CFD models were constructed with the shunt sizes ranging from 3 to 3.5mm. The angle between the brachiocephalic trunk(BCT) and the shunt were $30^{\circ}$ and $45^{\circ}$, respectively. When the diameter is 3.0 mm, the oscillatory shear index decreased by 1.2% at $30^{\circ}$ as opposed to at $45^{\circ}$. When the diameter is 3.5 mm, it increased by 18% more at $30^{\circ}$ as opposed to at $45^{\circ}$. When the joint angle is $30^{\circ}$ and the diameter is 3.0 mm, the oscillatory shear index decreased by 4.1% in comparison with the 3.5 mm diameter. When the angle is $45^{\circ}$ and the diameter is 3.0 mm, the index increased by 14.6% in comparison with the 3.5 mm diameter.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.5
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• pp.250-256
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• 2006

Both ratio error and phase angle error in current transformer(CT) depend critically on values of CT burden. Thus, precise measurement of CT burden is very important for the evaluation of CT. A method for the measurement of CT burden has been developed by employing the portable shunt precise resistor with negligible AC-DC resistance difference less than $10^{-5}$. The burden value(value and power factor) can be calculated from resistance and reactance obtained by measuring the change of ratio error and phase angle error caused by the change of shunt resistor. The uncertainty for the method is evaluated and found to be abut 2 %.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.680-683
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• 1999

A thyristor controlled shunt compensator, which is installed in the middle of the transmission line is adopted for controlling real power flow in a simple power transmission system. By means on the Fourier series representation of the thyristor switching action and the system parameters, the thyristor current equations are derived, which transmit the required real power of the simple power transmission system and inform the thyristor firing angle, the thyristor conduction angle, the power flows and the harmonic characteristics EMTP simulations at the various operating points show the dynamic characteristics of the thyristor controlled shunt compensator and correspond to the results calculated with the Fourier series representation.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.285-287
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• 1997

An AC shunt with low phase angle has been designed for an AC current measurement, such as currents with harmonics. This $0.2\;{\Omega}$ shunt of 5 A rated current is composed of fifty $10\;{\Omega}$ metal film resistors and applicable to the frequency band of DC to 1 kHz.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.977-978
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• 2007

The phase angle which is mainly depend on time constant $\tau$ of the calculable 10 A and 0.1 ${\Omega}ac/dc$ resistor has been analysed. The low values of resistors are usually inductive and time constant $\tau$ very large compare to high values of resistors. The numerical analysis has been shown that the time constant $\tau$ becomes zero when introduce the compensation capacitance geometrically to the resistive coil with proper dimension. As a result a very low phase angle can be achieved within the realizable dimensions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.926-932
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• 2007

A recently developed methods for on-site calibration of the current transformer (CT) comparator system have been reviewed in the paper. The method utilizes several traveling standards, which consist of the CT, non-reactive standard resistors, wide ratio error CT, and shunt resistors. The traveling CT is used for absolute evaluation of a standard CT belonging to industry. The non-reactive standard resistors and a wide ratio error CT are used for the linearity check of errors in the current comparator. The shunt resistors are used for evaluation of CT burden of industry.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.468-470
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• 1995

In this paper, a series compensator with a resonant LC circuit and a shunt compensator with the resonant circuit are compared based on the respective rating of its circuit elements. The rating are calculated over a range of compensation and over a range of bus angle. The components ratings are expressed in a per unit values. The results of this study can be easily converted to actual MVA by a simple change in scale. The methodology presented to rate the various components within the system will help to determine the feasibility of various FACTS devices in costs.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.5
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• pp.249-257
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• 2002

In this paper, a novel control scheme compensating source voltage unbalance and harmonic currents for the combined system of series active and shunt passive power filter is proposed, where no low/high-pass filters are used in deriving the reference voltage for compensation. The phase angle and the reference voltages compensating for harmonic current and unbalanced voltage are derived from the positive sequence component of the unbalanced voltage set, which is simply obtained by using digital all-pass filters. In order to remove the phase delay in generating the reference voltage for compensation, the reference of 5th and 7th harmonic components is predicted one-sampling ahead. The validity of the proposed scheme has been verified for 3[kVA] proto-type active power filter system.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.586-590
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• 2001

In this paper, a novel control scheme compensating source voltage unbalance and harmonic currents for hybrid active power filters is proposed, where no low/high-pass filters are used in compensation voltage composition. The phase angle and compensation voltages for source harmonic current and unbalanced voltage components are derived from the positive sequence component of the unbalanced voltage set, which is simply obtained by using digital all-pass filters. Since a balanced set of the source voltage obtained by scaling the positive sequence components is used as reference values for source current and load voltage, it is possible to eliminate the necessity of low/high-pass filters in the reference generation. Therefore the control algorithm is much simpler and gives more stable performance than the conventional method. In addition, the source harmonic current is eliminated by compensating for the harmonic voltage of the load side added to feedback control of the fundamental component.