• Journal of Power Electronics
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• 제11권4호
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• pp.576-582
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• 2011

This paper presents a novel control strategy for selective compensation of power quality (PQ) problems, depending upon the limited rating of voltage source inverters (VSIs), through a unified power quality conditioner (UPQC) in a three-phase four-wire distribution system. The UPQC is realized by the integration of series and shunt active power filters (APFs) sharing a common dc bus capacitor. The shunt APF is realized using a three-phase, four-leg voltage source inverter (VSI), while a three-leg VSI is employed for the series APF of the three-phase four-wire UPQC. The proposed control scheme for the shunt APF, decomposes the load current into harmonic components generated by consumer and distorted utility. In addition to this, the positive and negative sequence fundamental frequency active components, the reactive components and harmonic components of load currents are decomposed in synchronous reference frame (SRF). The control scheme of the shunt APF performs with priority based schemes, which respects the limited rating of the VSI. For voltage harmonic mitigation, a control scheme based on SRF theory is employed for the series APF of the UPQC. The performance of the proposed control scheme of the UPQC is validated through simulations using MATLAB software with its Simulink and Power System Block set toolboxes.

• Journal of Chest Surgery
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• 제50권6호
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• pp.448-452
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• 2017

Background: Proper monitoring of cerebral perfusion during carotid artery surgery is crucial for determining if a shunt is needed. We compared the safety and reliability of near-infrared spectroscopy (NIRS) w ith transcranial Doppler (TCD) for cerebral monitoring. Methods: This single-center, retrospective review was conducted on patients who underwent carotid endarterectomy (CEA) using selective shunt-based TCD or NIRS at Daegu Catholic University Medical Center from November 2009 to June 2016. Postoperative complications were the primary outcome, and the distribution of risk factors between the 2 groups was compared. Results: The medical records of 74 patients (45 TCD, 29 NIRS) were reviewed. The demographic characteristics were similar between the 2 groups. One TCD patient died within the 30-day postoperative period. Postoperative stroke (n=4, p=0.15) and neurologic complications (n=10, p=0.005) were only reported in the TCD group. Shunt usage was 44.4% and 10.3% in the TCD and NIRS groups, respectively (p=0.002). Conclusion: NIRS-based selective shunting during CEA seems to be safe and reliable for monitoring cerebral perfusion in terms of postoperative stroke and neurologic symptoms. It also reduces unnecessary shunt usage.

• Journal of Power Electronics
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• 제10권4호
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• pp.419-427
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• 2010

A parallel control strategy in capacity proportion frequency allocation mode for shunt active power filters (APFs) is proposed to overcome some of the difficulties in high power applications. To improve the compensation accuracy and overall system stability, an improved selective harmonic current control based on multiple synchronous rotating reference coordinates is presented in a single APF unit, which approximately implements zero steady-state error compensation. The combined decoupling strategy is proposed and theoretically analyzed to simplify selective harmonic current control. Improved selective harmonic current control forms the basis for multi-APF parallel operation. Therefore, a parallel control strategy is proposed to realize a proper optimization so that the APFs with a larger capacity compensate more harmonic current and the ones with a smaller capacity compensate less harmonic current, which is very practical for accurate harmonic current compensation and stable grid operation in high power applications. This is verified by experimental results. The total harmonic distortion (THD) is reduced from 29% to 2.7% for a typical uncontrolled rectifier load with a resistor and an inductor in a laboratory platform.

• Journal of Chest Surgery
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• 제16권3호
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• pp.316-321
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• 1983

Left ventricular-right atrial [LV-RA] shunt is a relatively uncommon defect but is being encountered with increasing frequency. The diagnosis is often not suspected on the basis of clinical findings and so the specific anatomic diagnosis depends upon the use of selective left ventriculography. Recently we experienced LV-RA shunt associated with PDA, which was underwent successful surgical correction under the cardiopulmonary bypass. On the preoperative diagnosis coexistence of PDA was overlooked and identified at the time of operation. The type of LV-RA shunt was supravalvular, which was closed by direct suture with pledget.

• 전력전자학회논문지
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• 제19권5호
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• pp.450-456
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• 2014

In HVDC converters that employ a line-commutated control, reactive power is absorbed by the rectifier and inverter terminals during AC/DC conversion. An AC filter usually consists of filters and large shunt capacitors to supply reactive power to the HVDC station. When STATCOM is used to supply reactive power to the HVDC system with AC filter, the low-order harmonics generated from STATCOM can result in a resonance between the shunt capacitor and AC network. Therefore, a control strategy based on selective harmonic elimination is adopted to minimize the low-order harmonics from STATCOM. The cancellation of harmonic instabilities is verified through simulations in PSCAD/EMTDC.

• Journal of Power Electronics
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• 제15권3호
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• pp.819-829
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• 2015

This paper presents a shunt active power filter (SAPF) for compensating inter-harmonics and harmonics when inter-harmonics content is evident in the grid. The principle of inter-harmonics generation in the grid was analyzed, and the inter-harmonics effect on repetitive controllers was discussed in terms of control performance. Traditional repetitive controllers are not applicable in inter-harmonic compensation. Moreover, the effect of an ideal controller on harmonics signals was analyzed on the basis of the internal model principle. The repetitive controller was improved in the form of a basis function according to theoretical analysis. The finite-dimensional repetitive controller, which is also called the multiple-period repetitive controller, was designed for the control of multiple periodic signals. A selective harmonic compensation system was developed with SAPF. This system can be used to compensate harmonics and inter-harmonics in the grid. Finally, system control performance was verified by simulation and experimental results.

• Journal of Chest Surgery
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• 제49권1호
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• pp.22-28
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• 2016

Background: Carotid endarterectomy (CEA) with selective shunting is the surgical method currently used to treat patients with carotid artery disease. We evaluated the incidence of major postoperative complications in patients who underwent CEA with selective shunting under transcranial Doppler (TCD) at our institution. Methods: The records of 45 patients who underwent CEA with TCD-based selective shunting under general anesthesia from November 2009 to June 2015 were reviewed. The risk factors for postoperative complications were analyzed using univariate and multivariate analysis. Results: Preoperative atrial fibrillation was observed in three patients. Plaque ulceration was detected in 10 patients (22.2%) by preoperative computed tomography imaging. High-level stenosis was observed in 16 patients (35.5%), and 18 patients had contralateral stenosis. Twenty patients (44.4%) required shunt placement due to reduced TCD flow or a poor temporal window. The 30-day mortality rate was 2.2%. No cases of major stroke were observed in the 30 days after surgery, but four cases of minor stroke were noted. Univariate analysis showed that preoperative atrial fibrillation (odds ratio [OR], 40; p=0.018) and ex-smoker status (OR, 17.5; p=0.021) were statistically significant risk factors for a minor stroke in the 30-day postoperative period. Analogously, multivariate analysis also found that atrial fibrillation (p<0.001) and ex-smoker status (p=0.002) were significant risk factors for a minor stroke in the 30-day postoperative period. No variables were identified as risk factors for 30-day major stroke or death. No wound complications were found, although one (2.2%) of the patients suffered from a hypoglossal nerve injury. Conclusion: TCD-based CEA is a safe and reliable method to treat patients with carotid artery disease. Preoperative atrial fibrillation and ex-smoker status were found to increase the postoperative risk of a small embolism leading to a minor neurologic deficit.

• Journal of Chest Surgery
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• 제21권3호
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• pp.583-587
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• 1988

Bilateral coronary artery-pulmonary artery fistula is very uncommon congenital heart disease which occupy small percentage of all coronary arterio-venous fistulas. We experienced a case who was 52 years old female with bilateral coronary artery-pulmonary artery fistula. She complained exertional dyspnea k angina[coronary steal syndrome]. On physical examination, any cardiac murmur was not audible. There was no 0y step-up in right heart catheterization. But selective coronary angiography revealed tortuous aberrant vessels which originated from the canal branch of the right coronary artery k the left anterior descending coronary artery. Both aberrant vessels traversed the right ventricular outflow tract, and conjoined just proximal the pulmonic annulus and drained into the main pulmonary artery. The operation was performed under the extracorporeal circulation with beating heart. The procedures were suture-ligation of the draining orifice in main pulmonary artery & the feeding vessels on the right ventricular outflow tract. Postoperatively her complaints were completely disappeared and the selective coronary angiography revealed no left-to-right shunt.

• Journal of Chest Surgery
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• 제26권9호
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• pp.710-713
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• 1993

Congenital coronary fistula is a rare condition, and with widespread use of cardiac catheterization, angiography and selective coronary arteriography are being recognized with increasing frequency. Fistula originating from the right coronary artery are more common than those from the left coronary artery. The fistula empties into the right side of the heart in 90% of the cases with the right ventricle being the most common recipient chamber, followed by the right atrium and the pulmonary artery. We report a case of congenital coronary artery fistula of the right coronary artery to the left ventricle with significant shunt in a 20 - year old female. It was detected by transthoracic and transesophageal echocardiography and confirmed by cardiac catheterization and coronary angiography. The fistula opening was closed with 6-0 Prolene continuously under cardiopulmonary bypass and moderate hypothermia [ 28 oC ]. Postoperative course was uneventful and the patient was discharged without specific problem.

• 대한두경부종양학회지
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• 제5권1호
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• pp.5-13
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• 1989

Carotid body paraganglioma is uncommon, with appoximately 900 reports of it in the world literature, and with only 7 documented cases in the Korean literature. The classic carotid body paraganglioma develops in the bifurcation of common carotid artery and involves both the internal and external carotid arteries at it expands. The diagnosis may almost always be established preoperatively by selective angiography which shows a widening of the carotid bifurcation with a well defined vascular mass. Differential consideration of a single, lateral cervical mass in this location include branchial cleft cyst, neurogenic tumor, metastatic thyroid cancer, carotid body aneurysm and salivary gland tumor. Surgical therapy is the preferred method of treatment as these tumors are regarded as radioresistant. Because of their high vascularity and anatomical location, surgical removal of these tumors reguires a considerable degree of caution and a high degree of surgical expertise. With improved diagnostic and surgical technique, the morbidity and mortality has been reduced lately. This report details the management of 3 patients with carotid body paraganglioma who underwent safe resection by subadventitial dissection or using an internal vascular shunt.