配电系统零线断线保护原理及现场应用

当三相低压供电系统零线断线时,用户侧将出现中性点位移电压,可能引起设备及人身安全等事故。论文分析了三相配电系统零线断线时中性点位移电压和负载不平衡度的特征关系。基于零线断线时中性点出现位移电压但没有零线电流的特征,提出了带零线电流闭锁判据的识别零线断线的保护原理,并研究了零线断线保护的布点方案。

Gender differences in cardiovascular disease

Cardiovascular disease(CVD)is one of the leading causes of death worldwide.Although the incidence of CVD in women is usually lower than in men,women have a higher mortality and worse prognosis after acute cardiovascular events.These gender differences exist in various CVDs,including coronary heart disease,stroke,heart failure and aortic diseases.These gender differences have caused widespread concerns and the consideration of gender differences is of great importance for the prevention,diagnosis,treatment and management of CVD.This review aims to provide an overview of gender-related differences in several typical CVDs and to list and to analyze the possible causes associated with the differences,in order to highlight the necessity of taking into account gender differences in determination of the cardiovascular risk profile.Future research can focus on how to define and add gender-related indicators to current risk assessment and management strategies.

A new way to evaluate thrombotic risk in failure heart and ventricular assist devices

Thrombosis is one of the main complications in patients implanted with ventricular assist device(VAD).The complicated structure and disturbed flow field within failure heart and blood pump play an important role in thrombosis formation.In this study,the influence of Left ventricular(LV)volumes on flow field contributing to thrombosis formation within failure heart and VAD was investigated.Computational Fluid Dynamics(CFD)methods were employed to investigate the effect of different LV volumes on the thrombogenic potential of failure heart and VAD.Lagrangian methods were utilized to obtain information on platelet voyage trajectories.The concepts of mean and threshold of stress accumulation and residence time were introduced to accurately assess the likelihood of thrombus.Eulerian methods were used to identify thrombus-prone locations.CFD results showed that residence time(RT)was the main cause of thrombus formation in the failure heart,and the percentage of platelet trajectories above the RT threshold increased significantly with increasing LV volume.The RT in the left atrial appendage and LV increased significantly with LV volume increasing,which indicated that thrombus is prone to form there.Compared with the failure heart,non-physiological shear stress(NPSS)-caused platelet activation is the main reason for thrombus formation within VAD.The narrow zones(top clearance and secondary flow passage)within VAD have a high incidence of thrombus generation.In VAD patients,the LV volume has an important impact on thrombosis probability within failure heart,in which the larger size of the LV volume is,the higher risk of thrombosis will be.The size of LV volume has little effect on the thrombosis formation probability of VAD,where the NPSS plays the leading role in thrombosis formation.The finding of this study can be utilized to guild the clinical treatment and VAD structure optimization design for reducing the thrombosis risk.

Non-physiological shear stress-induced blood damage in ventricular assist device

Ventricular assist devices(VADs)have been used for treating the end-stage heart failure(HF)patients in the past few decades,which had improved survival rates.In parallel,clinical applications of VADs are accompanied with endangered complications,such as thrombosis,bleeding and infection,which hamper the patient recovery.Nonphysiological shear stress(NPSS)is inevitably created during VAD application.When HF patients implanted with VADs,this high level NPSS can induce damage on blood components including blood cells(red blood cells,platelets,leukocytes et al.)and protein(von Willebrand Factor(VWF)).The damage of these blood cells and proteins may lead to the dysfunction of coagulation and immune systems,contributing to complications in VAD patients.To understand how VADs-created NPSS induces blood damage,and find the link between NPSS-induced blood damage and VAD related complications would potentially help to guide the VAD optimization and to find the effect way for treating VAD associated complications.Here we provide a review to investigate what is currently known about NPSS-induced blood damage within VADs and how the NPSS-induced blood damage links to complications(thrombosis,bleeding and infection)in VAD patients.

A systematic review of DVT and stent restenosis after stent implantation for iliac vein compression syndrome

Iliac vein compression syndrome(IVCS)is a common venous disease caused by joint compression of the right common iliac artery and the lumbosacral vertebrae.The compression of iliac vein not only causes venous hypertension in the lower extremities,but also induces venous valve dysfunction and superficial varicose veins in lower extremities.Moreover,the compression of iliac vein is an important potential factor for iliofemoral vein thrombosis.Currently,open surgery and stent implantation are the main treatment for IVCS.Due to the advantages of minimally invasive and postoperative patency,stent implantation for IVCS has gradually become the standard treatment.However,when the stent is implanted into the iliac vein to treat IVCS,the complications,such as restenosis,deep vein thrombosis(DVT)appear,which affect the patency of stent and hamper the patient recovery.Up to now,the mechanism how the stent implantation induces the restenosis and DVT is still unclear.In this review,we summarized the clinical symptoms,treatment methods of IVCS and the complications after stent implantation,and analyzed the mechanism of stent restenosis and DVT,and finally discuss the iliac vein stent design specifically for treating IVCS.

The impact of ECMO lower limb cannulation on the aortic flow features under differential blood perfusion conditions

The purpose of this study is to investigate the impact of veno-arterial(VA)ECMO cannulation on hemodynamic distribution and organ perfusion within aorta under differential blood perfusion conditions.The total blood flow volume supplied by failure heart and ECMO keep constant,flow volume ratio of heart output(FVR-HO)increases from 0%to 100%and correspondingly flow volume ratio of ECMO(FVR-ECMO)decreases from 100%to 0%.The flow patterns within aorta,wall shear stress(WSS),oscillatory shear index(OSI),relative retention time(RRT)were analyzed.The locations of oxygenated and de-oxygenated blood mixing region(BMR)was influenced by FVR-HO.With FVR-HO increasing,BMR moves from proximal to distal side of heart.When FVR-HO was 0%,oxygenated blood supplied by ECMO completely perfuses the aortic vessels.High WSS appears in the iliac artery and abdominal aorta vessel walls closed to cannula position.When FVR-HO was in the range of 10%–30%,the BMR was in aortic arch.The higher OSI and RRT were exhibited in ascending aorta and aorta arch.When FVR-HO was 40%and 50%,the BMR was in ventral trunk for systolic period and in aortic arch for diastolic period.The higher OSI and RRT regions enlarge and metastasize to the descending aorta.When FVR-HO was larger than 50%,the BMR was in the downstream region of the renal artery.Of note,when FVR-HO increases from 0%to 100%,the flow ratios in the two renal arteries change from significant different to be closed at systolic period.Peripheral VA-ECMO with various perfusion levels from cardiac output and ECMO has significant effect on aortic flow surrounding.Partial recovery of heart function can impel BMR moves from proximal to distal side of the heart,which may lead to inadequate supply of oxygenated blood to the upper limb and cephalic vessels.