General Consideration of Measuring System for Operational Test of Thyristor Valves of Ultra High Voltage DC Power Transmission

Thyristor valve is one of the key equipments for ultra high voltage direct current(UHVDC) power transmission projects.Before being installed on site,they need to be tested in a laboratory in order to verify their operational performance to satisfy the technical specification of project related.Test facilities for operational tests of thyristor valves are supposed to enable to undertake more severe electrical stresses than those being applied in the thyristor valves under test(test objects).On the other hand,the stresses applied into the test objects are neither higher nor lower than specified by the specification,because inappropriate stresses applied would result in incorrect evaluation of performance on the test objects,more seriously,would cuase the damage of test objects with expensive cost losing.Generally,the process of operational tests is complicated and performed in a complex synthetic test circuit(hereafter as STC),where there are a lot of sensors used for measuring,monitoring and protection on line to ensure that the test circuit functions in good condition.Therefore,the measuring systems embedded play a core role in STC,acting like "eyes".Based on the first project of building up a STC in China,experience of planning measuring systems is summarized so as to be referenced by related engineers.

Effect of L-carnitine on Cardiomyocyte Apoptosis and Cardiac Function in Patients Undergoing Heart Valve Replacement Operation

Summary： The effects of L-carnitine, as an ingredient of cardioplegia solution, on cardiac function and cardiomyocyte apoptosis in patients undergoing heart valve replacement operation were investigated. Twenty-three cases undergoing heart valve replacement with cardiopulmonary bypass （CPB） were randomly allocated into two groups： L-carnitine group （n=12, 12 g/L L-carnitine was put in the ST. Thomas cardioplegia） and control group （n=11, identical to the L-carnitine group except that normal saline was administered instead of L-carnitine）. Serum cardial troponin I （cTnI） levels, the left ventricular ejection fraction （LVEF）, and cardiac index （CI） were measured perioperatively. A bit of myocardial tissue obtained from right atria was taken before CPB and by the end of intracardiac procedure to undergo electron microscopy examination and estimate apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling （TUNEL）. From the end of CPB to 3 days after operation, the serum levels of cTnI in the L-carnitine group was significantly lower than that in the control group （P〈0.05）. Heart color ultrasonogram showed that the CI index and LVEF at 7th day postoperatively in the L-carnitine group were significantly higher than in the control group （P〈0.05）. Compared to the control group, L-carnitine significantly alleviated the morphologic changes of cardiac muscle cells （electron microscopy examination） and decreased the amounts of apoptotic cardiac muscle cells （TUNEL）. Furthermore, the dosage of vasoactive drugs used after operation was significantly less in the L-carnitine group （P〈0.01）. It was concluded that L-carnitine cardioplegia solution could improve cardiac function in patients undergoing heart valve replacement operation and alleviate CPB-mediated apoptosis of cardiac muscle cells.

An Operational Test Method for VSC-HVDC Valves Based on Modular Multi-level Converters

为给基于模块化多电平换流器（modular multi-levelconverter,MMC）的电压源换流器高压直流输电（voltagesourced converter HVDC,VSC-HVDC）换流阀提供有效的检验手段,以验证其设计的正确性及其运行可靠性,对换流阀的运行特性和关键应力进行分析,提出基于原理等效的MMC阀运行试验方法,设计试验电路并阐明其运行机理。搭建的PSCAD电磁暂态仿真模型和实际的试验验证证明了试验方法的正确性和有效性。

Investigation into Equivalency of Synthetic Test Circuit Used for Operational Tests of Thyristor Valves for UHVDC

With the growth of capacity of high voltage direct current(HVDC) transmission lines,the ratings of thyristor valves,which are one of the most critical equipments,are getting higher and higher.Verification of performance of thyristor valves particularly designed for HVDC project plays an important role in the handover of products between the manufacturer and the client.Conventional test facilities based on philosophy of direct test cannot meet the requirements for modern thyristor valves.New test facilities with high ratings are necessarily built based on philosophy of synthetic test.Over the conventional direct test circuit,the later is an economical and feasible solution with less financial investment and higher test capability.However,the equivalency between the synthetic test and the direct test should be analyzed technically in order to make sure that the condition of verification test in a synthetic test circuit should satisfy the actual operation condition of thyristor valves existing in a real HVDC project,just as in a direct test circuit.Equivalency analysis is focused in this paper,covering the scope of thyristor valves' steady state,and transient state.On the basis of the results achieved,a synthetic test circuit of 6 500 A/50 kV for operational tests of thyristor valves used for up to UHVDC project has newly been set up and already put into service in Xi'an High Voltage Apparatus Research Institute Co.,Ltd.(XIHARI),China.Some of the results have been adopted also by a new national standard of China.

Oxidization resistance of Ni76Cr19AlTi valve alloy at temperatures under operating mode of heavy-duty engines

The oxidization resistance of the Ni76Cr19A1Ti alloy was studied by a static oxidization experiment at 600-800℃. The results show that the oxidation behavior of the alloy can be explained by a kinetic equation： （△m/S）2 = Kpt ＋ C, where Kp is a kinetic constant of the nickel-base alloy. The higher the experimental temperature, the higher the value of Kp. It is discovered that the microstructure of the oxide scales is compact and the thickness of it is less than 10 μm The oxidization of the alloy is in the first grade. It is also found that the oxide scales are mainly composed of Cr2O3 and TiO2. Chrome and titanium react more easily with oxygen at temperatures under the operating mode.

New Type Regulating Valve Applied in Cooling System of Blast Furnace

A new type regulating valve with the cooling mode of constant temperature difference water supply, temperature difference self operated regulating valve, was introduced into blast furnace cooling system to overcome shortcomings of the cooling mode of constant flow rate water supply. The results show that the temperature difference between inlet and outlet water of cooling wall can be decreased greatly and steadily, and the water supply for blast furnace cooling can be reduced considerably.

41 CASES REPORT OF CLINICAL APPLICATION OF MITRAL VALVE RECONSTRUCTION

Mitral valve reconstruction was performed on 41 patients from 1980 to 1991. Two died early and one died later.38 survivals were followed up in 3 to 108 months,35 cases'heart function improved to grades 1～2,3 cases to grade 3,they need small dose medication support.The operative indicationcontra-indication and the surgical technique are discussed.It is concluded that mitral valve reconstruction is suitable for membranaceous or simple thickness, but mitral valve replacement should be chosen when severe valve calcificatlon or sub-valve diseases are present.

Long-Term Outcome and Risk Factor Analysis of Surgical Pulmonary Valve Replacement in Congenital Heart Disease

Objectives:To establish long-term outcome of surgical pulmonary valve replacement(PVR)in congenital heart disease(CHD)and to identify risk factors for overall mortality,operative mortality,and repetitive PVR.Methods:This is a retrospective study of 375 surgical PVR in 293 patients who underwent surgical PVR for CHD between January 2000 and May 2020.We only included patients with index PVR with previous open-heart surgery regardless of the number of PVRs.The previous surgical history of patients who underwent PVR during the study period was also included.Patients who underwent the Rastelli operation,and those who underwent single PVR without previous open-heart surgery were excluded.Results:The median age of the patients at the time of surgical PVR was 14.9 years(Interquartile range,IQR,11.0–22.0).The median follow-up duration was 10.5 years(IQR,5.5–14.8 years).There were 3 patients with operative mortality(1.0%)and 15 patients with overall mortality(5.1%).The survival rate was 95.1%over 20 years follow-up period.Multivariate analysis demonstrated that more than 3 times of previous open-heart surgeries before surgical PVR,older age at the first operation,longer cardiopulmonary bypass(CPB)time and longer intensive care unit(ICU)stay were predictors for overall mortality.Patients who underwent surgical PVR after more than 3 times of previous open-heart surgeries had significantly higher mortality than those who underwent open-heart surgeries less than 3 times(P<0.001).Age younger than 10 years,male,multiple valve problems and longer ICU stay were significant predictors for repetitive PVR by multivariate analysis.Conclusions:Though surgical PVR has excellent long-term outcome,it should be performed with caution for those who previously underwent multiple open-heart surgeries,especially if patient received more than 3 times of open-heart surgeries.

High Speed On/Off Valve Control Hydraulic Propeller

The work-class remotely-operated-underwater-vehicles（ROVs） are mainly driven by hydraulic propulsion system,and the effeciency of hydraulic propulsion system is an important performance index of ROVs.However,the efficiency of traditional hydraulic propulsion system controlled by throttle valves is too low.Therefore,in this paper,for small and medium ROVs,a novel propulsion system with higher efficiency based on high speed on/off valve control hydraulic propeller is proposed.To solve the conflict between large flow rate and high frequency response performance,a two-stage high speed on/off valve-motor unit with large flow rate and high response speed simultaneously is developed.Through theoretical analysis,an effective fluctuation control method and a novel pulse-width-pulse-frequency-modulation（PWPFM） are introduced to solve the conflict among inherently fluctuation,valve dynamic performance and system efficiency.A simulation model is established to evaluate the system performance.To prove the advantage of system in energy saving,and test the dynamic control performance of high speed on/off valve control propeller,a test setup is developed and a series of comparative experiments is completed.The smimulation and experiment results show that the two-stage high speed on/off valve has an excellent dynamic response performance,and can be used to realize high accuracy speed control.The experiment results prove that the new propulsion system has much more advantages than the traditional throttle speed regulation system in energy saving.The lowest efficiency is more than 40%.The application results on a ROV indicate that the high speed on/off valve control propeller system has good dynamic and steady-state control performances.Its transient time is only about 1 s-1.5 s,and steady-state error is less than 5%.Meanwhile,the speed fluctuation is small,and the smooth propeller speed control effect is obtained.On the premise of good propeller speed control performance,the proposed high speed on/off valve control propeller can improve the effeciency of ROV propulsion system significantly,and provides another attractive ROV propulsion system choice for engineers.

Konno Procedure for Managing Small Aortic Root during Aortic Valve Replacement Surgery: An Experience of 12 Cases

Background: Small aortic annulus during aortic valve replacement can lead to implanting a smaller sized valve compared to the body surface area thereby causing patient prosthesis mismatch. Various aortic root enlargement techniques have been described depending on anterior or posterior approach. Konno procedure uses anterior approach for aortic root enlargement. In this study, we reviewed results of Konno procedure done from 2011 to 2019 by a single surgeon. Methods: 12 adult patients who underwent aortic valve replacement along with Konno procedure for small aortic root by a single surgeon at a single center between 2011 and 2019 were reviewed. Echocardiographic and demographic data and post-operative data were obtained from medical records. Symptomatic profile was assessed as per New York Heart Association Classification. Intraoperative findings and post-operative period findings were noted. Follow up symptom profile was assessed for these patients. Results: 12 patients underwent Konno procedure between 2011 and 2019 for small aortic root along with valve replacement. The main indication for surgery was aortic stenosis with small aortic annulus, with or without involvement of the mitral valve. Preoperatively, 3 patients had NYHA class II and 9 patients had NYHA class III symptoms. Mean age at operation was 26.42 years, minimum age 10 years, and maximum age 39 years. 3 were females and 9 were males. Mean bypass time was 106.4 minutes and aortic cross clamp time was 80.67 minutes. Mechanical aortic valves were implanted in all patients. Mean post-operative blood loss was 134.2 ml and duration of ventilation before extubation was 14.5 hours. Mean duration of intensive care unit (ICU) stay was 2.83 days and hospital stay was 9.1 days. Mean gradient in the post-operative period was 10.75 mm Hg. There was no mortality in these 12 patients and no reoperation was needed in the follow up period. Follow up in the outpatient department suggested all patients had NYHA class I symptoms and anticoagulation with warfarin adjusted to prothrombin time— International normalised ratio. Conclusion: Konno procedure is effective for managing small aortic root as bigger outflow orifice area through the larger valve prosthesis improves ventricular outflow and hence, improves the outcomes.

Anatomic Correlates of Mitral Systolic Anterior Motion in Transposition of the Great Arteries Following Atrial Switch Operation

Introduction:We sought to investigate whether the development of sub-pulmonic systolic anterior motion(SAM)may be inherent to the anatomy of the the mitral valve(MV)or affected by external factors,such as a dilated right ventricle or chest abnormalities in d-looped transposition of the great arteries post atrial switch operation(d-TGA/AtS).Methods:Analysis was performed of clinical and cardiac imaging studies acquired on 19 adult patients with d-TGA/AtS(age 42±6 years old,56%male)between 2015–2019.Echocardiography data included mitral apparatus anatomy,and CT/MRI data included biventricular dimensions,function,and Haller index(HI)for pectus deformity.Results:Patients with leaflet SAM(n=6)compared to patients without SAM(n=13)had higher MV protrusion height(2.3±0.5 vs.1.5±0.4 cm,p≤0.01)and longer anterior MV leaflet length(3.1±0.4 cm vs.2.6±0.3 cm p≤0.05),when compared to those without.CT/MRI showed higher sub-pulmonic left ventricular ejection fraction(LVEF)in the SAM group(71%±8%vs.54%±7%,respectively).RV size and function,significant chest deformity(HI>3.5),presence of a ventricular lead pacemaker,and septal thickness did not play a role in development of SAM.Conclusions:An elongated mitral apparatus is associated with the development of SAM,and the development of left ventricular outflow tract obstruction(LVOTO),in d-TGA/AtS.LV hyperkinesia is associated with SAM.Systemic RV dimensions,septal thickness,and degree of chest deformity did not differ significantly between subjects with SAM and those without.

地震载荷对核电阀门可运行性影响机理研究

核电阀门在地震期间可否运行主要通过试验进行鉴定,为了降低核电阀门设计成本,以某闸阀为例,总结基于分析法的核电阀门可运行性抗震鉴定流程,并阐明地震对阀门可运行性的影响机理。运用有限元法研究阀门启闭过程中遭受地震载荷时其各部位的应力与接触压力的变化,分别基于可运行性和结构完整性对阀门进行抗震校核。结论如下:地震对阀门可运行性的影响在于放大了阀门滑动摩擦部位的接触压力,导致阀门闭合所需要克服的摩擦力增加,延后阀门闭合动作;与结构完整性分析相比,基于可运行性分析的抗震鉴定过程更加全面、苛刻。

胸肋间筋膜阻滞对心脏瓣膜置换术后早期恢复质量的影响

目的探讨胸肋间筋膜阻滞(PIFB)对心脏瓣膜置换术后早期恢复质量的影响。方法选择择期行正中切口心脏瓣膜置换术患者80例,男45例,女35例,年龄44~75岁,BMI 18~30 kg/m 2,ASAⅡ或Ⅲ级,随机分为两组:全麻联合PIFB组(P组)和全麻组(C组),每组40例。P组麻醉诱导后行双侧胸肋间筋膜平面阻滞,C组不行神经阻滞,术后均使用舒芬太尼静脉自控镇痛。采用15项恢复质量评分量表(QoR-15)评价术前24 h、术后24、72 h恢复情况,记录诱导前、切皮时、锯胸骨时、关胸时、出手术室时的HR和MAP,拔管后4、8、12 h静息和活动(咳嗽)时VAS疼痛评分。记录术中和术后48 h内舒芬太尼用量、拔管时间、重症监护病房(ICU)停留时间、术后首次肛门排气时间、术后住院时间,术后恶心呕吐、低血压、呼吸抑制等不良反应的发生情况和住院期间死亡情况。结果与C组比较,P组术后24、72 h QoR-15评分明显升高(P<0.05),拔管后4、8、12 h静息和活动时VAS疼痛评分明显降低(P<0.05),术中和术后48 h内舒芬太尼用量明显减少(P<0.05),拔管时间、术后首次肛门排气时间、ICU停留时间明显缩短(P<0.05),术后恶心呕吐发生率明显降低(P<0.05)。两组不同时点HR和MAP、术后住院时间、住院期间死亡率差异无统计学意义。P组未发生神经阻滞相关并发症。结论PIFB可以降低正中切口心脏瓣膜置换手术患者术后疼痛,提高术后恢复质量,促进术后康复。

不同频率下缓冲罐体积对有阀线性压缩机管系压力脉动的实验研究

有阀线性压缩机是液氦温区Joule-Thomson(J-T)节流制冷机重要部件,而管系压力脉动会造成制冷机出现温度与制冷量波动,从而影响制冷机温度稳定性。针对有阀线性压缩机管系压力脉动问题,以有线性阻尼的平面波动理论为基础,采用传递矩阵法构造了有阀线性压缩机管路缓冲罐压力脉动传递模型,获得有阀线性压缩机脉动质量流量的量化表达。搭建了有阀线性压缩机管系压力脉动测试平台,讨论了压缩机运行频率与进排气缓冲罐体积对压力脉动的影响。研究结果表明:管系压力脉动与压缩机运行频率有关,随着压缩机运行频率增大,管系压力脉动增大。进排气缓冲罐均可有效抑制压力脉动,但两者的压力脉动抑制能力相互独立,且缓冲罐体积越大,压力脉动抑制效果越好。随着缓冲罐体积的增加,进气缓冲罐进口处压力不均匀度减小到164/423,排气缓冲罐出口处压力不均度减小到8/23。

先导式安全阀整定压力预测方法研究

以自主研制的先导式安全阀为研究对象,针对先导阀的感压控制结构,开展整定压力预测方法研究。根据动作功能和结构原理分析,提出了一种测量整定预紧力的方式,并研制了专用传感器。对样机进行适应性改造和传感器安装后,开展相关冷态实验研究。结果表明,关键力值的监测数据可用于安全阀整定压力的预测,但还需进一步考虑温度等运行参数和阀门结构设计参数的影响,优化预测算法。

法洛四联症合并肺动脉闭锁的先天性心脏病1例并文献复习

法洛四联症(TOF)是最常见的紫绀型先天性心脏病,肺动脉闭锁(PA)也是一种较为复杂的先天性心脏畸形。本文对滨州医学院附属医院收治的1例TOF合并PA的先天性心脏病进行报道,手术方案采用外科生物补片进行肺动脉瓣的重建,缝至右心室切口到原肺动脉瓣处以抗肺动脉瓣反流,最后总结TOF/PA的临床表现、影像诊断、手术方案及未来的治疗前景等。

柔性直流输电用干式直流电容器工况验证试验回路研制

干式直流电容器作为柔性直流输电换流阀的核心组件,尚未开展阀组级工况试验验证。通过对目前实验室条件下换流阀组件运行情况的调研,确定采用被试阀段与陪试阀段对拖运行的拓扑,以满足验证试验回路构建的要求。通过仿真分析和系统试验,证明在满足经济性和实用性要求下,正常工作时回路各阀段至少需要5个子模块串联。考虑到该试验回路需要针对不同型号规格的电容器开展运行试验,叠层母排采用了特殊的设计,方便参数测量和电容器更换。

先导式比例电磁阀电磁力水平特性分析及优化

阻尼可调减振器作为悬架系统的核心部件,对汽车行驶平顺性至关重要,而先导式比例电磁阀作为减振器中的重要元件,对减振器性能起到关键作用。介绍了电磁阀的结构及工作原理,利用Maxwell 2D有限元仿真软件建立电磁铁仿真模型,对静态下的电磁力-位移水平特性进行仿真计算,并根据仿真结果对电磁铁隔磁环倾角、导套厚度、衔铁长度、衔铁宽度等结构参数进行调整分析,通过电磁力水平特性试验,验证仿真模型的准确性。引入正交实验法,对各参数进行协同优化,采用标准差这一指标衡量电磁力水平特性,优化后的产品电磁力标准差为0.635888,优化效果提升7.98%。为阀体的机-电-液-磁耦合仿真分析奠定了基础。

阀冷主泵状态监测与故障诊断技术研究

为了进一步提高电网设备运维管理的支撑能力,建设了阀冷设备智能运维平台,研究了阀冷主泵状态监测与故障诊断技术。介绍了设备状态信号的准确获取技术。给出了能够反映主泵振动特性的测点。阐述了振动传感器的选型。通过对获取的振动信号进行时域和频域分析,得出主泵运行过程中振动超标形成的机理以及造成振动超标的原因。评估振动过程对泵系统中各部件造成的损伤,进而采取针对性措施减轻主泵运行过程中的振动,为阀冷主泵的维护和保养提供建议。研究了阀冷主泵在启停过程中的性能评估方法,提出了在瞬态工况下有效的数据采集处理方法。该研究实现了对阀冷设备状态的智能监测预警与故障诊断,对提高电网精益化管理水平、推动智能电网技术进步具有重要意义。

动脉调转术后新主动脉瓣反流及根部扩张成因、转归及预防

动脉调转术(ASO)是治疗完全性大动脉转位(TGA)及Taussig-Bing畸形(TBA)的首选术式。ASO手术发展至今,大量术后患儿已至成年,因此ASO的晚期并发症逐渐引起关注。新主动脉瓣反流(NAVR)和新主动脉根部扩张(NARD)是ASO术后再次手术的第二大原因。本文拟对现有研究进行回顾,总结ASO术后NAVR及NARD的原因和预后,为临床实践提供参考。