Application of Decellularized Scaffold Combined with Loaded Nanoparticles for Heart Valve Tissue Engineering in vitro

The purpose of this study was to fabricate decelluarized valve scaffold modified with polyethylene glycol nanoparticles loaded with transforming growth factor-β1（TGF-β1）,by which to improve the extracellular matrix microenvironment for heart valve tissue engineering in vitro.Polyethylene glycol nanoparticles were obtained by an emulsion-crosslinking method,and their morphology was observed under a scanning electron microscope.Decelluarized valve scaffolds,prepared by using trypsinase and TritonX-100,were modified with nanoparticles by carbodiimide,and then TGF-β1 was loaded into them by adsorption.The TGF-β1 delivery of the fabricated scaffold was measured by asing enzyme-linked immunosorbent assay.Whether unseeded or reseeded with myofibroblast from rats,the morphologic,biochemical and biomechanical characteristics of hybrid scaffolds were tested and compared with decelluarized scaffolds under the same conditions.The enzyme-linked immunosorbent assay revealed a typical delivery of nanoparticles.The morphologic observations and biological data analysis indicated that fabricated scaffolds possessed advantageous biocompatibility and biomechanical property beyond decelluarized scaffolds.Altogether this study proved that it was feasible to fabricate the hybrid scaffold and effective to improve extracellular matrix microenvironment,which is beneficial for an application in heart valve tissue engineering.

Fault Diagnosis of Valve Clearance in Diesel Engine Based on BP Neural Network and Support Vector Machine

Based on wavelet packet transformation(WPT), genetic algorithm(GA), back propagation neural network(BPNN)and support vector machine(SVM), a fault diagnosis method of diesel engine valve clearance is presented. With power spectral density analysis, the characteristic frequency related to the engine running conditions can be extracted from vibration signals. The biggest singular values(BSV)of wavelet coefficients and root mean square(RMS)values of vibration in characteristic frequency sub-bands are extracted at the end of third level decomposition of vibration signals, and they are used as input vectors of BPNN or SVM. To avoid being trapped in local minima, GA is adopted. The normal and fault vibration signals measured in different valve clearance conditions are analyzed. BPNN, GA back propagation neural network(GA-BPNN), SVM and GA-SVM are applied to the training and testing for the extraction of different features, and the classification accuracies and training time are compared to determine the optimum fault classifier and feature selection. Experimental results demonstrate that the proposed features and classification algorithms give classification accuracy of 100%.

A Multi-Gap Multi-Channel Gas Switch for the Linear Transformer Driver

A multi-gap and multi-channel gas switch with convexo-convex discal planet electrodes was designed and investigated. Eight gaps are formed in series by a trigger electrode, six intermediate electrodes and two high voltage electrodes with a uniform gap length of 5 ram. The self breakdown and triggered breakdown performance of the switch are reported. Both the delay time and jitter decrease with the increase in the trigger voltage, switching coefficient and the decrease in the trigger isolating resistor. The delay time of the switch is about 40 ns, and the jitter is less than 2 ns when charged with 4-85 kV and triggered by a voltage pule of -75 kV. The inductance of the switch is about 30 nH.

Bone morphogenetic protein-4 and transforming growth factor-beta1 mechanisms in acute valvular response to supra-physiologic hemodynamic stresses

AIM:To explore ex vivo the role of bone morphogenetic protein-4(BMP-4) and transforming growth factorbeta1(TGF-β1) in acute valvular response to fluid shear stress(FSS) abnormalities.METHODS:Porcine valve leaflets were subjected ex vivo to physiologic FSS,supra-physiologic FSS magnitude at normal frequency and supra-physiologic FSS frequency at normal magnitude for 48 h in a double-sided cone-and-plate bioreactor filled with standard culture medium. The role of BMP-4 and TGF-β1 in the valvular response was investigated by promoting or inhibiting the downstream action of those cytokines via culture medium supplementation with BMP-4 or the BMP antagonist noggin,and TGF-β1 or the TGF-β1 inhibitor SB-431542,respectively. Fresh porcine leaflets were used as controls. Each experimental group consisted of six leaflet samples. Immunostaining and immunoblotting were performed to assess endothelial activation in terms of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expressions,paracrine signaling in terms of BMP-4 and TGF-β1 expressions and extracellular matrix(ECM) remodeling in terms of cathepsin L,cathepsin S,metalloproteinases(MMP)-2 and MMP-9 expressions. Immunostained images were quantified by normalizing the intensities of positively stained regions by the number of cells in each image while immunoblots were quantified by densitometry. R E S U LT S :Regardless of the culture medium,physiologic FSS maintained valvular homeostasis. Tissue exposure to supra-physiologic FSS magnitude in standard medium stimulated paracrine signaling(TGF-β1:467% ± 22% vs 100% ± 6% in freshcontrols,BMP-4:258% ± 22% vs 100% ± 4% in fresh controls; P < 0.05) and ECM degradation(MMP-2:941% ± 90% vs 100% ± 19% in fresh controls,MMP-9:1219% ± 190% vs 100% ± 16% in fresh controls,cathepsin L:1187% ± 175% vs 100% ± 12% in fresh controls,cathepsin S:603% ± 88% vs 100% ± 13% in fresh controls; P < 0.05),while BMP-4 supplementation also promoted fibrosa activation and TGF-β1 inhibition reduced MMP-9 expression to the native tissue level(MMP-9:308% ± 153% with TGF-β1 inhibition vs 100% ± 16% in fresh control; P > 0.05). Supra-physiologic FSS frequency had no effect on endothelial activation and paracrine signaling regardless of the culture medium but TGF-β1 silencing attenuated FSS-induced ECM degradation via MMP-9 downregulation(MMP-9:302% ± 182% vs 100% ± 42% in fresh controls; P > 0.05).CONCLUSION:Valvular tissue is sensitive to FSS abnormalities. The TGF-β1 inhibitor SB-431542 is a potential candidate molecule for attenuating the effects of FSS abnormalities on valvular remodeling.

FPGA based multi-channel variable-length FFT implementation

High-speed real-time digital frequency analysis is one major field of Fast Fourier Transform(FFT)application,such as Synthetic Aperture Radar(SAR)processing and medical imaging.In SAR processing,the image size could be 4 k×4 k in normal and it has become larger over the years.In the view of real-time,extensibility and reusable characteristics,an Field Programmable Gate Array(FPGA)based multi-channel variable-length FFT architecture which adopts radix-2 butterfly algorithm is proposed in this paper.The hardware implementation of FFT is partially reconfigurable architecture.Firstly,the proposed architecture in the paper has flexibility in terms of chip area,speed,resource utilization and power consumption.Secondly,the proposed architecture combines serial and parallel methods in its butterfly computations.Furthermore,on system-level issue,the proposed architecture takes advantage of state processing in serial mode and data processing in parallel mode.In case of sufficient FPGA resources,state processing of serial mode mentioned above is converted to pipeline mode.State processing of pipeline mode achieves high throughput.

Simulation and Experimental Study on Influence of Multi⁃port Integrated Hydraulic Transformer Port Number on Transformer Ratio Characteristics

The integrated hydraulic transformer has a compact structure and no throttling loss in the process of pressure regulation.It is widely used in the common pressure rail hydrostatic transmission system.The integrated hydraulic transformer is realized by designing more than three ports on the distribution plate,and the voltage transformation characteristics of the integrated hydraulic transformer with different port numbers are different.In this paper,the influence of port number on the pressure ratio of integrated hydraulic transformer was studied,and the pressure ratio characteristics of 3⁃ports,4⁃ports,and 5⁃ports integrated hydraulic transformer were obtained,and an experimental platform was built for experimental verification,which shows that the simulation results are consistent with the experimental results and provides a theoretical basis for the design of integrated hydraulic transformer.

心脏瓣膜相关生物力学模型建立的研究进展

心脏瓣膜生物力学是一个迅速发展的、与临床高度相关的研究领域。已知大多数瓣膜疾病都源于生物力学改变,无创成像方式的出现,使评估和研究这些病变原理和治疗方法的技术取得了重大进展。计算机建模、体内外建模技术推动了研究人员更好地理解心脏瓣膜的生物力学、病理学和介入治疗学。其中,体外建模技术更是一种可供临床转化研究的前景巨大的技术,它在计算机建模和体内建模的基础上更加深入的研究瓣膜生物力学。

基于小波包分析和优化KNN的电动开度阀故障检测方法

针对以微控制器MCU为控制核心的电动开度阀控制系统难以集成高效且计算量小的故障检测子系统的问题,基于小波包变换和优化K近邻(K-Nearest Neighbor,KNN)算法提出了一种电动开度阀故障检测方法。对阀门振动信号进行小波包变换,计算小波包节点的能量值与其重构信号的时域特征参数。根据Pearson系数筛选出两种与能量强相关的故障特征参数:峰峰值与均方根,并将两者作为KNN算法的样本评价指标;通过对评价指标进行加权优化了KNN算法的距离计算公式,分别在MATLAB和实验样机中进行故障检测测试,对应最高分类准确率分别为92.5%与86.7%。结果表明:实验测试与仿真分析具有较好的一致性,该故障检测方法的优势在于计算量小、故障识别率较高,并能有效地应用于以MCU为核心的电动开度阀控制系统。

±800kV换流变阀侧套管温度场仿真与大电流温升试验分析

随着我国高压直流输电工程的发展,输送功率不断提升,胶浸纸(resin impregnated paper,RIP)套管的发热问题越发突出。面对±800k V特高压直流输电工程进一步提升输送容量的挑战,为避免RIP套管发热严重、温度过高带来的安全问题,提出了一种RIP换流变阀侧套管的设计方案,并通过仿真模拟与温升试验进行验证。首先,在套管设计方案中,通过引入衬管结构、增加导体直径等手段来降低热点温度;然后,提出了一种针对RIP套管温度场的改进计算方法,对套管热设计进行了仿真校核;最后,对基于该设计方案制造的套管进行了温升试验考核。仿真与温升试验结果表明:该文提出的RIP换流变阀侧套管可以满足工程要求,其载流量(等效工频电流)可达6736 A。

安全阀排放的动响应分析

安全阀排放冲击与响应是振动工程中典型的瞬态响应问题。根据阀后直管段长度L与特征长*度L的关系,讨论了四种可能的冲击形式;利用Laplace变换和逆变换,给出了四种冲击的瞬态响应解析解,表明冲击响应的最大幅值是关于安全阀全开时间与系统自振周期之比的函数;据此对安全阀排放系统的动载系数DFL取值给了分析和建议。

特高压阀侧套管数字孪生系统集成设计方法

提出了一种数字孪生系统的集成设计方法,以满足真实工况下的实际应用。首先,分析了阀侧套管数字孪生系统的功能需求并构建了数字孪生系统框架结构;其次,基于系统框架结构的功能模块设计研发了对应的实现方法;最后,用一起阀侧套管数字孪生系统的应用对该方法进行了展示和验证。所提方法为数字孪生系统的实际应用提供了一种设计思路,可以为电网的数字化转型提供实用而有效的解决方案。

一种基于优化VMD-CWT-CNN的柱塞泵配流盘磨损状态识别方法

为解决一维振动信号难以充分挖掘表达状态特征信息以及柱塞泵配流盘磨损早期识别问题,基于卷积神经网络(Convolutional neural networks,CNN)优秀的图像处理能力,提出了一个优化VMD-CWT-CNN模型。首先,采用连续小波变换(Continuous wavelet transform,CWT)对信号进行预处理,得到信号的二维时频图,作为CNN模型的一路输入,将状态识别问题转化为CNN图像识别问题。其次,基于相关系数对变分模态分解(Variational mode decomposition,VMD)参数优化后,利用优化VMD对振动信号进行预处理,再以相关系数和峭度值最大为优选原则,甄选出三组蕴含故障特征的本征模态函数(Intrinsic mode function,IMF),将其重组为三通道一维信号,作为CNN模型的另一路输入。最后,在CNN模型中将两路信息汇聚并得到柱塞泵配流盘磨损状态识别分类结果。实验中,此方法分别采用优化VMD和CWT对振动信号预处理,再结合CNN对磨损状态进行分类。实验结果表明,该方法对于配流盘磨损的三种状态的识别效果显著优于单路输入的CNN模型以及典型的深度学习方法和机器学习分类器。因此,优化的VMD-CWT-CNN方法可以更准确地实现柱塞泵配流盘磨损状态识别。

犬心脏二尖瓣退行性疾病研究进展

黏液瘤样二尖瓣疾病(myxomatous mitral valve disease,MMVD)又称为退行性二尖瓣疾病,是瓣膜发生退行性病变的结果。该病是犬最常见心脏病之一,会导致其发生二尖瓣反流(mitral regurgitation,MR)和左侧充血性心力衰竭(congestive heart failure,CHF)等严重后果。MMVD发病率随年龄增长而增加,在某些品种犬中具有高遗传特性。MMVD的病理变化主要是二尖瓣的增厚、脱垂和腱索的伸长甚至断裂。该病的发病机制尚不完全清晰,目前已有的研究分别从组织细胞层面、遗传学和蛋白质组学及信号通路等方面取得了一定的研究结果。从组织细胞层面研究发现,在犬等物种上证实,MMVD与瓣膜间质细胞(valve interstitial cells,VICs)的活化及细胞外基质(extracellular matrix,ECM)中胶原和蛋白聚糖的沉积相关。从遗传学和蛋白质组学层面研究发现,miRNAs可能参与了MMVD的遗传调控,血液循环中的miRNAs有望成为MMVD患犬CHF的生物标志物。从分子信号通路层面研究发现,MMVD与许多信号通路息息相关,其中研究较多的5-羟色胺(5-hydroxytryptamine,5-HT)和转化生长因子β(transforming growth factor-β,TGF-β)通路在VICs的活化中具有重要作用,同时其还受二尖瓣在心脏收缩和舒张时所受的牵拉和血液冲刷的机械应力影响,两条通路相互影响,促使MMVD的发生和发展。笔者就犬MMVD流行病学特征、病理变化、临床症状、诊断分期、治疗手段和疾病相关机制的研究进展做一综述。

光栅光阀型闭环直流电流互感器及温度修正方法研究

为满足直流电力系统电能计量、电量监测、控制与保护需求,提出一种基于微功率光控信号源的闭环光反馈光栅光阀(GLV)型直流电流传感方案,集成一种基于保偏光纤温度双折射效应的全光纤温度传感器,实现GLV探头的实时温度监测,进而实现系统温度误差修正。完成了样机研制及测试(额定电流In=500 A),结果显示,在10%In~110%In范围内,系统比差(RE)波动小于±0.2%;0~1200 Hz范围内,谐波测量误差小于-0.693%;-40℃~85℃范围内,误差修正后的RE波动范围为-0.186%~0.084%;阶跃响应上升时间小于125μs。测试结果表明,系统满足GB/T 26216.1—2019规定的0.2级的误差限值要求。

大功率汽轮机故障工况下高调阀控制方式切换性能研究

无扰切换是当前主流大型汽轮机阀门管理实现的一个重要功能,目前的大部分无扰切换研究工作都集中在设备正常状态的无扰切换实现方法上,尤其是起机并网时的无扰切换实现。为了研究火电机组灵活性,本文以多台600 MW级别机组为研究对象,针对机组存在的阀门管理缺陷进行故障诊断并实施优化改造,使机组安全顺利地投运了顺序阀配汽方式。然后,在此基础上进行了2类非正常运行工况下的无扰切换试验研究,探讨了机组故障状态下的无扰切换快速反应能力和设备故障对无扰切换的影响。试验结果表明:进行阀门管理优化不仅能够提高机组应对故障的反应能力,而且还能够降低机组切换控制系统对辅机等设备故障的敏感性。这对提高机组故障状态下的安全稳定性具有一定的借鉴意义。

特高压换流变压器阀侧套管缩比模型典型缺陷下电场分布特性仿真研究

换流变压器阀侧套管内部混入金属颗粒、电容芯体产生裂纹是目前常见的故障,研究套管在不同电压下的电场分布规律以及缺陷对电场分布的影响对于套管的优化设计及故障分析具有重要意义。文中以±800 kV特高压换流变压器套管为原型,建立了±72.5 kV环氧浸纸电容式套管仿真模型,计算套管在交直流电压下的电位分布和电场分布,并研究了两种缺陷对于套管电场的影响。结果表明套管含金属颗粒或裂纹缺陷时,对于电场的畸变影响较大。研究结果为后续缩比套管模型不同缺陷局部放电试验的分析提供了基础,并为环氧浸纸电容式套管的优化设计提供参考。

基于AR技术的换流变压器阀侧套管局部高温故障多点红外预警方法

为保证换流变压器安全与稳定运行、及时发现套管内部由于放电引起的局部过热问题,研究了基于AR技术的换流变压器阀侧套管局部高温故障多点红外预警方法。考虑换流变压器阀侧套管的材料性能,以设备在实际工作状态下的正常温度变化为条件,根据套管的电流冲击变化形式,描述其温度场分布类型。基于AR技术构建三维虚拟空间,在摄像机三维跟踪过程中,转换现实场景中的被测物体信息,注册套管实时温度网。利用红外测距生成换流变压器阀侧套管温度直方图,以融合特征算法增强温度特征,对局部高温目标点定位,预警故障的具体位置。实验结果表明:本文方法能够在AR技术下对换流变压器阀侧套管进行场景转换,并在局部空间内标记出高温故障点位置,通过红外温度数据完成及时预警,具有应用效果。

S Zorb装置再生器进料罐排气线调节球阀国产化改造研究

S Zorb装置再生器进料罐排气线调节球阀通过调节进料罐压力来控制装置吸附剂的循环速率,直接影响装置的催化剂再生,对装置的正常生产至关重要。由于介质流速快、吸附剂硬度高、阀门正常开度小等原因,冲刷很严重,使用寿命短,给装置安稳生产带来了很大的困扰。通过CFD(Computational Fluid Dynamics,即计算流体动力学分析)分析,对该阀进行国产化改造,提升了调节性能和使用寿命,大幅降低了购置成本,在控制阀国产化方面,具有较高的推广应用价值。

自平衡策略的电流互感器取能调速风冷装置设计

随着我国电力系统输电量逐年上升,输电网络中的换流变压器阀侧套管等关键设备部件热功率也随之增大,因此有必要设计开发散热风机等设备,实现过热故障多发点的主动散热。设计研发一种电流互感器(CT)取能调速风冷装置,利用CT从输电线路上获取能量为散热风机供能,以解决输电线路现场常规电源无法使用的难题。针对CT的取能能力随着输电线路电流不断变化且不受控的问题,设计一种功率主动自平衡新策略,通过利用负载的控制自由度来适应CT二次侧电流的宽变化范围,从而扩展装置的稳定运行区间,提升电源的取能能力。将装置套装在交流输电母排上进行实验验证,母排电流的有效值在上千安培范围内变化,装置始终稳定且保持60%以上的功率容量利用率。