External Bypass Research Articles

A Patient with the LEAD-Complicated Mid-Aortic Syndrome with Bilateral External Iliac Artery Hypoplasia Underwent Bilateral Common Iliac-Common Femoral Artery Bypass Surgery

A Patient with the LEAD-Complicated Mid-Aortic Syndrome with Bilateral External Iliac Artery Hypoplasia Underwent Bilateral Common Iliac-Common Femoral Artery Bypass Surgery

Mid-aortic syndrome in a 5-year-old girl: multimodal imaging approaches and treatment and successful external anatomic bypass surgery

Mid-aortic syndrome in a 5-year-old girl: multimodal imaging approaches and treatment and successful external anatomic bypass surgery

Influence of internal bypass conditions on the double bypass matching characteristics of variable cycle high-pressure compression system

The variable cycle high-pressure compression system (VCHCS) consists of a core driven fan stage (CDFS) and a high-pressure compressor (HPC), which are crucial components for controlling the variable cycle engine's bypass ratio. However, the double bypass (DB) matching mechanism of the VCHCS remains insufficiently understood. This study focuses on investigating the DB matching characteristics of the VCHCS under different representative internal bypass conditions. The findings demonstrate that as the internal bypass conditions transition from near choke to near stall, the external bypass stability margin of the VCHCS decreases progressively, and the external bypass characteristic curve of the HPC exhibits an approximate “counter-clockwise rotation” pattern. Furthermore, the operating state of the CDFS and the redistribution of internal and external bypass flow rate, collectively determine the matching state of the compressor system. Building upon the aforementioned summarization regarding the impact of internal bypass conditions on the matching characteristics of the VCHCS, this research integrates flow field analysis to explicate the mechanism of stall under typical operating conditions. The investigation reveals that, when the internal bypass condition under design point and the external bypass condition approaches the stall boundary, an excessive accumulation of low-energy fluid occurs at the external bypass outlet guide vane, subsequently triggers the occurrence of stall. Specifically, when the internal bypass conditions under the near stall point, the predominant limitation on further elevation or reduction of external bypass back pressure lies in the extensive blockage of a massive low-energy fluid on the suction surface of the HPC second stage stator.

Effect of double bypass conditions on the thermodynamic characteristics and internal flow mechanisms in a variable core cycle compression system

The performance of variable cycle core compression system (VCCCS) is crucial for achieving mode transition in variable cycle engine (VCE). The double bypass matching characteristics and internal flow mechanisms of the VCCCS under various conditions are investigated in this study. The results indicate that, in the low bypass ratio (LBR) mode, Under the near choke or design point conditions of external bypass, internal bypass throttling causes the excessive blockage of low-energy fluid near the suction surface of high-pressure compressor (HPC) second stator, which leading the flow instability in VCCCS. Under the near stall condition of external bypass, internal bypass throttling causes the CDFS to reach the stall boundary firstly. The flow instability is triggered by the interaction between tip leakage flow and shock waves in CDFS rotor tip. Following mode transition, the CDFS exhibits lower flow and load, resulting in changes in the matching state of HPC due to the strong coupling effects of upstream components, thereby altering the matching characteristics and flow instability mechanisms of the VCCCS. The impact of different bypass conditions on VCCCS performance is elucidated, further establishing the association between bypass exit meridian velocity and VCCCS performance, which is helpful to select key design parameters.

Research on the pitching hydrodynamic performance of pump-jet propelled submersible

Abstract Most of the current research in the world on the dynamical characteristics of pump-jet propelled submersibles has focused on the dynamic response of non-vector propulsion. However, the dynamics characteristics of water jet vector propulsion by external bypass excitation have been neglected. Therefore, this paper explores the variable vector deflection angle-controlled pitching motion in the vertical plane of the submersible and the isokinetic constant linear pitching motion water motion. ANSYS software is used to perform numerical calculations to investigate the changes of drag and Lifting force with velocity under different navigation states. Conclusion: In the process of surfacing, the change trend of Lifting force and drag is the same: when adjusting the navigation deflection angle, it increases rapidly, and then when floating in a constant straight line, it gradually decreases, and finally, the decrease rate tends to level off; when the elevation angle increases, the change amplitude of drag and Lifting force increases. During the dive, the drag force decreases and the Lifting force increases, gradually, the rate of decrease of drag force and the rate of increase of Lifting force become smaller; when the pitch angle increases, the Lifting force decreases rapidly and the decrease of drag force becomes larger.

Evolution of distal limb perfusion management in adult peripheral venoarterial extracorporeal membrane oxygenation with femoral artery cannulation.

Limb ischaemia is a clinically relevant complication of venoarterial extracorporeal membrane oxygenation (VA ECMO) with femoral artery cannulation. No selective distal perfusion or other advanced techniques were used in the past to maintain adequate distal limb perfusion. A more recent trend is the shift from the reactive or emergency management to the pro-active or prophylactic placement of a distal perfusion cannula to avoid or reduce limb ischaemia-related complications. Multiple alternative cannulation techniques to the distal perfusion cannula have been developed to maintain distal limb perfusion, including end-to-side grafting, external or endovascular femoro-femoral bypass, retrograde limb perfusion (e.g., via the posterior tibial, dorsalis pedis or anterior tibial artery), and, more recently, use of a bidirectional cannula. Venous congestion has also been recognized as a potential contributing factor to limb ischaemia development and specific techniques have been described with facilitated venous drainage or bilateral cannulation being the most recent, to reduce or avoid venous stasis as a contributor to impaired limb perfusion. Advances in monitoring techniques, such as near-infrared spectroscopy and duplex ultrasound analysis, have been applied to improve decision-making regarding both the monitoring and management of limb ischaemia. This narrative review describes the evolution of techniques used for distal limb perfusion during peripheral VA ECMO.

Sacrificing Internal Carotid Artery-External Carotid Artery-Radial Artery-Middle Cerebral Artery Bypass for the Treatment of Complex Intracranial Artery Cavernous Sinus Aneurysms.

The treatment of complex intracranial aneurysms has always been a great challenge in neurosurgery. Craniotomy has a high risk of clipping, there is a risk of rupture at any time, endovascular embolization is relatively low risk, but expensive and easy to relapse, the best treatment needs to be further discussed. Cavernous sinus aneurysms with pituitary adenomas are rare. This case reports a case of complex intracranial aneurysms. Chief complaints are: (1) blepharoptosis with blurred vision for 1 year, (2) headache for 3 days, and (3) digital subtraction angiography showed right internal carotid artery cavernous sinus aneurysm. Combined with the patient's condition and family condition, the external carotid artery-radial artery-middle cerebral artery bypass was selected. After surgical treatment, the symptoms of the patients were improved, the postoperative recovery was good, and the condition was stable. After follow-up, the patient's brain computed tomography showed intra-aneurysm thrombosis.

Moya –Moya disease revealed by a subarachnoid hemorrhage: A case report

Background: Hemorrhage is a major category of the clinical symptoms of moyamoya disease (MMD). Intracerebral and intraventricular hemorrhages are the most common hemorrhages in MMD, and subarachnoid hemorrhages (SAHs) are notably rare. Case report: A 43 year old female patient, with no previous pathological history, admitted with a frank meningeal syndrome followed by a disorder of consciousness.She was admitted with a GCS at 15, which was subsequently reduced to 10. She was hemodynamically and respiratory stable with a BP of 12/8 cm/Hg, a respiratory rate of 16 cycles/min and a heart rate of 92 beats/min. Initial imaging showed subarachnoid hemorrhage Fisher IV. A cerebral angiography-CT showed vascular thrombosis of the internal carotid artery whitout aneurysm and arteriovenous malformation and dural fistulas. An EVD (external ventricular drain) was placed. After three days of hospitalization in the intensive care unit, a cerebral arteriogram was performed showing vascular arrest in the right internal carotid artery in its pre-cavernous portion with absence of visualization of the right sylvian artery and the presence of several perforating cerebral artery and external carotid artery bypass systems suggestive of Moya Moya. Conclusion: Moya Moya disease is a rare entity of unknown origin. Subarachnoid hemorrhage is a rare manifestation. It’s mainly occurs in a young adult. Cerebral angiography remains the gold standard for diagnosis.

External carotid artery-radial artery graft-posterior cerebral artery bypass for complex vertebrobasilar aneurysms: efficacy and analysis of outcome in a single center.

The purpose of this research was to demonstrate the effectiveness and clinical outcome of an external carotid artery-radial artery graft-posterior cerebral artery (ECA-RAG-PCA) bypass in the treatment of complex vertebrobasilar artery aneurysms (VBANs) in a single-center retrospective study. An ECA-RAG-PCA bypass may be a last and very important option in the treatment of complex VBANs when conventional surgical clipping or endovascular interventions fail to achieve the desired outcome. This study retrospectively analyzed the clinical presentation, case characteristics, aneurysm location, size and morphology, choice of surgical strategy, complications, clinical follow-up, and prognosis of the patients enrolled. The data involved were analyzed by the appropriate statistical methods. A total of 24 patients with complex VBANs who met the criteria were included in this study. Eighteen (75.0%) were male and the mean age was 54.1 ± 8.83years. The aneurysms were located in the vertebral artery, the basilar artery, and in the vertebrobasilar artery with simultaneous involvement. All patients underwent ECA-RAG-PCA bypass surgery via an extended middle cranial fossa approach, with 8 (33.3%) undergoing ECA-RAG-PCA bypass only, 3 (12.5%) undergoing ECA-RAG-PCA bypass combined with aneurysm partial trapping, and 12 (50.0%) undergoing ECA-RAG-PCA bypass combined with proximal occlusion of the parent artery. The average clinical follow-up was 22.0 ± 13.35months. The patency rate of the high-flow bypass was 100%. At the final follow-up, 15 (62.5%) patients had complete occlusion of the aneurysm, 7 (29.2%) patients had subtotal occlusion of the aneurysm, and 2 (8.3%) patients had stable aneurysms. The rate of complete and subtotal occlusion of the aneurysm at the final follow-up was 91.7%. The clinical prognosis was good in 21 (87.5%) patients and no procedure-related deaths occurred. Analysis of the good and poor prognosis groups revealed a statistically significant difference in aneurysm size (P = 0.034, t-test). Combining the results of this study and the clinical experience of our center, we propose a surgical algorithm and strategy for the treatment of complex VBANs.The technical approach of ECA-RAG-PCA bypass for complex VBANs remains important, even in an era of rapid advances in endovascular intervention. When conventional surgical clipping or endovascular intervention has failed, an ECA-RAG-PCA bypass plays a role that cannot be abandoned and is a very important treatment option of last resort.

Quantitative analysis of external carotid artery bypass donor vessels by recipient and approach

IntroductionUtilization an in-situ pedicle of the external carotid artery (ECA) as an arterial donor can allow for the successful augmentation or replacement of flow to a large vascular territory. We propose a mathematical model for quantitatively analyzing and grading the suitability of donor and recipient bypass vessels based on a set of anatomical and surgical variables in order to predict which pair has the greatest possibility for success. Using this method, we analyze all of the potential donor-recipient pairs for each ECA donor vessel—including the superficial temporal (STA), middle meningeal (MMA), and occipital (OA) arteries. MethodsThe ECA pedicles were dissected in frontotemporal, middle fossa, subtemporal, retrosigmoid, far lateral, suboccipital, supracerebellar, and occipital transtentorial approaches. For each approach, every potential donor-recipient pair was identified, and donor length and diameter were measured as well as depth of field, angle of exposure, ease of proximal control, maneuverability, and length and diameter of the recipient segment. Anastomotic pair scores were determined by adding the weighted donor and recipient. ResultsThe best overall anastomotic pairs were OA-vertebral artery (V3, 17.1) and STA-insular (M2, 16.3) and STA-sylvian (M3, 15.9) segments of the middle cerebral artery. Other strong anastomotic combinations were OA- telovelotonsillar (15) and OA- tonsilomedullary (14.9) segments of the posterior inferior cerebellar artery, and MMA-lateral pontomesencephalic segment of the superior cerebellar artery (14.2). ConclusionsThis novel model for anastamotic pair scoring can serve as a useful clinical tool for selecting the optimal donor, recipient, and approach combination that can help facilitate a successful bypass.

Right axillopopliteal artery bypass using a combined transiliac and lateral popliteal approach for groin infection and lymph fistula.

Wound infection in the groin is a serious complication after vascular bypass surgery. The combined treatment of critical limb ischemia and recurrent infection presents challenges for vascular surgery(1Lounes Y. Ozdemir B. Alric P. Canaud L. Trans-iliac Bypass for Critical Limb Ischaemia with Groin Necrosis: A Case Report.EJVES Short Reports. 2019; 42: 31-33https://doi.org/10.1016/j.ejvssr.2019.01.002Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar, 2Multon S. Jayet J. Javerliat I. Coscas R. Coggia M. Aortic–tibial transiliac wing extra-anatomic bypass with distal fistula for treatment of an infected deep femoral pseudoaneurysm.J Vasc Surg Cases, Innov Tech. 2022; 8: 201https://doi.org/10.1016/j.jvscit.2022.02.008Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar, 3Engin C, Posacioglu H, Ayik F, Apaydin A . Management of vascular infection in the groin. Texas Hear Inst J (2005) 32:529–534.Google Scholar). In this case, we successfully managed the wound infection in the groin after axillofemoral artery bypass grafting, using a combination of trans-iliac bypass and lateral popliteal approach(4Enzmann F.K. Nierlich P. Eder S. Aspalter M. Dabernig W. Aschacher T. et al.Trans-Iliac Bypass Grafting for Vascular Groin Complications.Eur J Vasc Endovasc Surg. 2019; 58: 930-935https://doi.org/10.1016/j.ejvs.2018.11.003Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar, 5Benzing C. Fellmer P. Lateral Approach to the Distal Femoral Artery in Femoro-Anterior-Tibial Bypass Surgery.Eur J Vasc Endovasc Surg. 2016; 52: 267https://doi.org/10.1016/j.ejvs.2016.04.024Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar). A 74-year-old man, having Buerger's disease and arteriosclerosis obliterans, presented with extensive lymphatic fistula and necrosis of the groin (Fig.1) after right axillary artery to the right deep femoral artery bypass, which had been patented for last five years after the several revascularizations of iliac arteries and femoral arteries. Due to the several open surgeries, such as aorto-right external iliac artery bypass, aorto-left popliteal artery bypass, cholecystectomy and resection of gastric cancer, we chose right axillopopliteal artery bypass grafting, through the iliac wing. The skin incision was made along the iliac crest and the external oblique muscle fascia was separated to reach the pelvis, and a longitudinal incision was made anterosuperior to the greater trochanter to create a gluteal pathway to bypass the infected groin. 10-mm hole was made by shaving the bone about 4 cm from the iliac crest, and the graft was passed through the hole. (Fig 2). A lateral popliteal approach was selected for revascularization owing to extensive groin and medial thigh infective wounds. After that the extensive lymphatic fistula and necrosis were controlled with using negative pressure wound therapy.Figure 2View Large Image Figure ViewerDownload Hi-res image Download (PPT) The postoperative course was uneventful, and contrast-enhanced computed tomography confirmed proper arrangement of the graft, without bending (Fig 3 and Fig 4). He was discharged from the hospital on the 14th postoperative day. The computed tomography which was taken one year later showed the patency of this graft. The combination of trans - iliac bypass and lateral popliteal approach was shown to be effective in this case of extensive groin and medial compartment infection, and can potentially be applied in similar future cases.Figure 4View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Development of integrated semi-active adaptive vibration control system for bridges subjected to traffic loads

Nowadays, the fluid viscous damper is the most conventional energy dissipation system implemented in bridge structures to control the vibrations due to traffic loads. However, to effectively protect the bridge against frequent and severer vibrations, it is required to adapt the function of the damper according to the variable traffic loads. In this research, an Integrated Semi-Active Adaptive Vibration Control System is developed for the bridge structures. This control system consists of a Semi-Active Bypass Fluid Damper (SABFD), a programmable logic controller (PLC), pressure transducers, and displacement sensors. Semi-Active Bypass Fluid Damper is a hydraulic cylinder with a pair of external bypass pipes with motorized electric flow control valves which are installed in the middle of pipes to control the flow rate of the fluid. A programmable logic controller (PLC) is implemented to manage the operation of motorized valves according to the movement of the bridge.Therefore, the integrated control system is able to function as a real-time controller during its operation. To develop the control system, the performance of the SABFD device has been assessed through analytical model of the various control valve positions. Then, according to the structure response, a fuzzy control algorithm has been adapted in the PLC controller.Afterward, the prototypes of the SABFD and the PLC controller have been fabricated and a series of cyclic load tests have been conducted by using a dynamic actuator. The outcomes of the numerical analysis and results of the experimental tests revealed that the developed device is capable of generating a wide range of forces during device operation. The developed fuzzy control algorithm is then implemented to the finite element model of the bridge equipped with SABFD, and the results proved that the real-time control system effectively limits the bridge displacements according to the pre-defined fuzzy control rules.

Research and Verification on the Solution of Pressure Fluctuation of the Fan Air Inlet of Civil Aircraft Pneumatic System

The cold side bleeds air of the precooler in the pneumatic system of civil aircraft is usually drawn out from the external bypass of the engine fan and enters the precooler for heat exchange through the fan air inlet, bellows, and fan air valve. When the fan air valve is closed, a closed dead cavity is formed in the fan air inlet. When the airflow passes through the mouth at high speed, the pressure of the fan air inlet into the mouth will oscillate at high frequency, resulting in pressure fluctuation, which will lead to the damage of the bellows and the loss of bleed air function. CFD is proposed in this paper. The method of dynamic simulation combined with limited test parameters successfully located the root causes of the fan air inlet pressure fluctuations, solved the fan air inlet pressure fluctuation phenomenon, and creatively put forward the fan air inlet with hat, fan air inlet with ventilation branch 2 broad categories, and 8 kinds of potential solution design train of thought. CFD simulation method is used to analyze and compare each potential solution in detail. Finally, the solution was selected according to the test results and applied to the aircraft.

PS-R06-5: CASE REPORT OF INCREASED ARTERIAL STIFFNESS IN MOYAMOYA DISEASE IN A YOUNG CHINESE PATIENT PRESENTING AS RECURRENT STROKE IN SINGAPORE

Introduction: Moyamoya disease (MMD) is characterised by progressive stenosis of distal ICA and the resulting hazy network of basal collateral vessels. Increase arterial stiffness in MMD is not well described. Case report: We describe a young patient ML, a 42-year-old Chinese female, presented to hospital in June 2015 with headaches, on a background of known hypertension diagnosed at the age of 28 years. Her systemic examination was normal. Investigations were unremarkable. She was followed in General Medicine (GM) clinic from 2015, which ruled out secondary causes of hypertension, including renovascular disease, renal artery stenosis, phaeochromocytoma and hyperthyroidism. ML was treated for presumptive essential hypertension. Over time, her BP remained stable on candesartan 16 mg and bisoprolol 2.5 mg once daily. She continued to have intermittent headaches. Recurrent ischaemic strokes and diagnosis of Moyamoya disease ML presented with intermittent right-sided facial numbness in February 2017. A magnetic resonance imaging (MRI) brain done showed no acute infarct or hemorrhage, but moderately severe narrowing of the left terminal internal carotid artery (ICA), associated with poor flow signals in both the A1 segment of the left anterior cerebral artery (ACA) and the M1 segment of the left middle cerebral artery (MCA). She was started on clopidogrel 75 mg and atorvastatin 40 mg daily. The second stroke occurred in March 2019, when ML presented with acute right upper and lower limb weakness, and right facial, upper and lower limb numbness. Magnetic resonance angiography (MRA) demonstrated severe stenosis at the left terminal ICA, also involving the left M1 and A1 segments; collateral flow was observed. The third stroke happened in April 2019, presenting with acute right-sided facial and upper limb weakness, with BP of 201/86mmHg. MRI and MRA of the brain revealed new acute infarcts scattered in the territories of the left MCA and ACA. A CT angiogram re-demonstrated severe steno-occlusive disease involving the left ICA T-junction and left M1 and A1 segments, with extensive basal collaterals. In light of these findings, Moyamoya disease (MMD) was diagnosed. ML underwent a left external carotid-internal carotid bypass in June 2019. An arterial stiffness study by syphgmoCor in June 2020 using markedly increased arterial stiffness. Conclusion: We present first and very rare case of hypertension in a young patient with MMD associated with increased arterial stiffness. Systemic vascular affection in MMD may be the cause of increased arterial stiffness.

Spotlight on clinical strategies of Chronic Internal Carotid Artery Occlusion: Endovascular interventions and external-intracarotid bypasses compared to conservative treatment.

Chronic internal carotid artery occlusion (CICAO) has high prevalence and incidence rates, and patients with CICAO can be completely asymptomatic, experience a devastating stroke or die. It is important to note that CICAO causes cerebrovascular accidents. Currently, the external carotid-internal carotid (EC-IC) bypass technique is used to treat CICAO. However, many clinical studies showed that EC-IC bypass was not beneficial for many patients with CICAO. Meanwhile, endovascular intervention treatment options for CICAO are evolving, and an increasing number of patients are undergoing endovascular intervention therapy. Accordingly, a review comparing both techniques is warranted. For this review, we searched PubMed and collected relevant case study reports comparing endovascular interventional therapy and internal and external cervical bypass surgeries to provide strategies for clinical treatment.

Internal carotid artery embolization in endoscopic salvage surgery for recurrent nasopharyngeal carcinoma: a single-center retrospective study

Objective: To evaluate the efficiency of internal carotid artery (ICA) embolization technology in endoscopic salvage surgery for recurrent nasopharyngeal carcinoma (rNPC) invading the ICA. Methods: From January 2016 to March 2021, 83 patients with rNPC who invaded the ICA and underwent endoscopic extended nasopharyngectomy were retrospectively collected from the Eye & ENT Hospital in Fudan University, including 60 males and 23 females. The age of the patients ranged from 27 to 77 years. The standard of ICA invasion was that the distance from the lesion to the ICA on enhanced MRI was ≤ 1.8 mm. The clinical characteristics, ICA management strategy and survival prognosis of patients were analyzed, and the effectiveness of ICA embolization was evaluated. Kaplan-Meier method was used to calculate the survival rate and Log-rank test was used to compare the difference. Results: In 83 patients with rNPC, there were 13 patients with rT2, 38 patients with rT3, 32 patients with rT4, and 16 patients had lymph node metastasis. A total of 37 patients (44.6%) underwent ICA coil embolization before surgery, of which 2 cases underwent external carotid-middle cerebral artery artery bypass grafting and ICA embolization due to positive balloon occlusion test (BOT). Patients with positive surgical margin accounted for 24.1% (20/83). Among them, patients with rT4 and patients without ICA embolization had a higher positive rate of surgical margin (P value was 0.001, 0.043, respectively). The 3-year overall survival (OS) and progression free survival (PFS) rate of all patients was 46.5% and 26.7%, respectively. In addition, the 3-year OS and PFS of patients with ICA embolization was significantly higher than those without ICA embolization, respectively (69.1% vs 27.8%, P=0.003; 33.9% vs 18.9%, P=0.018). Only 2 patients (2/37, 5.4%) had cerebral infarction complications after coil embolization of the affected ICA due to negative BOT. Conclusion: Preoperative ICA embolization can be used to treat patients with rNPC invading the ICA, improve the total removal rate and survival rate of patients, which is an effective salvage treatment.

Experimental investigation on piston offset and performance of helium valved linear compressor with an external gas bypass

The valved linear compressor(VLC) is a significant part of the Joule-Thomson (JT) cryocooler at the liquid helium temperature zone. The use of clearance seals in the VLC inevitably causes the piston offset which affects the VLC performance and the JT cryocooler performance. Based on the VLC developed in our lab, an experimental bench for studying piston offset inhibition using the external gas bypass is built. The external gas bypass connects the compressor shell to the suction line by a bypass regulating valve which controls the mass flow, a solenoid valve that controls the number of connections and a bypass mass flowmeter which measurs the mass flow rate. The experiments focus on the effects of bypass regulating valve opening and solenoid valve action frequency on the piston offset and performance of the VLC. The experimental results show that there is an optimal opening to minimize the offset and the VLC obtains the best performance at the same time. When the solenoid valve is activated at a high frequency(greater than 1 Hz), the VLC obtains the best performance. This research provides a scheme to inhibit the piston offset by using an external gas bypass to improve the VLC performance.

Transient DC Over-Voltage Protection for ITER PF AC/DC Converter

The International Thermonuclear Experimental Reactor (ITER) poloidal field (PF) AC/DC converters are composed by thyristor-based phase controlled converter modules. As the core component of ITER PF AC/DC converter, the thyristor is very sensitive to over-voltage and damaged in microseconds, therefore, the transient over-voltage protection strategy is desperately essential to ensure the converter safety operation. In this paper, a nanosecond respond and high reliability protection strategy which combined by Metal Oxide Varistor (MOV) and external bypass is proposed to protect the ITER PF AC/DC converter from transient DC over-voltage. The MOV is designed to certify the fast respond in nanosecond. Moreover, a bidirectional BreakOver Diode (BOD) circuit board is designed to activate external bypass to ensure the reliability of the transient DC over-voltage protection strategy. The performance-testing platform is built to study its performance. The experiments on ITER PF AC/DC converter test facility are carried out. According to the experiment results, the external bypass is triggered by BOD board effectively and the load current is transferred to the external bypass in 2 us when BOD suffers from an over-voltage. The effectiveness of the proposed transient DC over-voltage protection strategy is verified.

Ramping Loss Analysis of No-Insulation HTS Coil Under External Field Using an Improved Equivalent Circuit Model

This article is to study the ramping loss of no-insulation (NI) high temperature superconducting (HTS) racetrack coil under different external magnetic fields during the charging process. An improved equivalent circuit electromagnetic coupling model for the HTS racetrack coil is introduced with good computational speed and accuracy. The simulation results show that the turn-to-turn loss and the change of the lowest critical current position are obviously influenced by the external field that have not been mentioned from our knowledge base. During the rising time of the power supply current, there is little difference in current distribution under different external fields. But after that, steady state of charging process is deeply influenced by the external field. A larger external field will lead to a lower charging current and the external bypass phenomenon. Another result is that the relationship between direction of external field and orientation of coils will influence the lowest critical current amount and position. The relationship between turn-to-turn resistivity of co-winding materials and ramping loss is also discussed in the paper. The distributed unevenness and value of the turn-to-turn loss change with the increase of turn-to-turn resistivity.

Delayed Presentation of a Traumatic Radial Artery Pseudoaneurysm

<h3>Introduction & Objective</h3> Radial artery pseudoaneurysms are rare and almost exclusively iatrogenic in origin. Post- traumatic radial artery pseudoaneurysms are even more uncommon, and relevant literature is limited to few case reports which mainly describe an acute presentation and management via external compression, thrombin injection, resection and bypass graft, or radial artery ligation. This case describes a rare diagnosis of traumatic radial artery pseudoaneurysm with a delayed presentation and successful resection with primary end-to-end anastomosis. <h3>Case Report</h3> A 29-year-old right-handed man sustained gunshot wounds to his bilateral forearms. He underwent surgical intervention on his left forearm at an outside institution; his right forearm was managed conservatively. His right forearm was asymptomatic until about one-week post-injury when he lifted groceries and experienced acute forearm pain and subsequent edema. He gradually developed a right forearm mass and increasing pain until 22 days post-injury when he noted decreased right-hand motor function, prompting presentation to our emergency department. A ∼1 cm pulsatile mass on the volar right forearm was noted, and his right proximal and distal interphalangeal joints were in flexion with limited weak extension (Figure 1Figure 1Preoperative Appearance of Right Forearm & HandFigure 1). Volar compartment pressure was normal. CT arteriogram revealed a right forearm hematoma and adjacent short segment of radial artery non-visualization. Ultrasound detailed a 1.4 cm pseudoaneurysm of the right radial artery (Figure 2Figure 2Ultrasound of Pseudoaneurysm with Pathognomonic "Yin-Yang" SignFigure 2) with distal reversal of flow and biphasic doppler signals. Ulnar and palmar arch doppler signals were triphasic with radial artery occlusion. We proceeded to the operating room for right forearm exploration and a large hematoma was evacuated. The radial artery pseudoaneurysm had active extravasation from an anterolateral 7mm segmental disruption of over 50% circumference (Figure 3Figure 3Radial Artery Segmental DisruptionFigure 3). The pseudoaneurysm was resected, and successful tension- free repair performed via primary end-to-end anastomosis (Figure 4Figure 4Radial Artery Following Pseudoaneurysm Resection & Primary AnastomosisFigure 4). At procedure completion triphasic distal radial artery and palmar arch doppler signals were identified. His right-hand motor function significantly improved immediately after surgery, with return to baseline over the following days. At one month follow-up his right radial pulse remained palpable and right hand had no residual deficit. <h3>Discussion</h3> Radial artery pseudoaneurysms are uncommon, but with progressive widespread adoption of trans-radial access for cardiac catheterization and recent literature on growing applications for noncoronary endovascular procedures the incidence is expected to rise. Radial artery pseudoaneurysms can carry significant morbidity including compartment syndrome, critical limb ischemia, and digital necrosis. Providers performing trans-radial procedures should maintain a high index of suspicion for this complication to avoid compromise of functional status and optimize patient outcomes.