基于PT-PFM激励阻抗谱数字重构的电缆故障诊断定位

由于传统频谱测试仪器增益带宽积有限,高频区间内输出电压过低,在针对长距离电缆测试时信号衰减较为严重,导致阻抗谱在高频区间内存在一定失真问题。该文提出一种基于伪梯形波激励阻抗谱数字重构算法的电缆故障诊断定位算法。分析不同故障类型下电力电缆的局部故障阻抗对电缆输入阻抗谱的影响规律、首端激励电压信号的衰减特性和不同电压幅值的功率传输特性。设计一种基于Si C高速逆变器的大容量伪梯形励磁系统,用于测量最高频率7 MHz的阻抗谱信息,利用阻抗谱数字重构方法实现0.1 Hz~60 MHz宽频区间的全覆盖。与传统的低压正弦激励相比,采用该时空转换函数的定位结果具有更小的区间振荡和更快的收敛速度。缺陷定位精度提高了80%,验证了该方法的有效性和准确性。

Magnetic resonance imaging of extraocular rectus muscles abnormalities in acute acquired concomitant esotropia

AIM:To investigate the difference of medial rectus(MR)and lateral rectus(LR)between acute acquired concomitant esotropia(AACE)and the healthy controls(HCs)detected by magnetic resonance imaging(MRI).METHODS:A case-control study.Eighteen subjects with AACE and eighteen HCs were enrolled.MRI scanning data were conducted in target-controlled central gaze with a 3-Tesla magnetic resonance scanner.Extraocular muscles(EOMs)were scanned in contiguous image planes 2-mm thick spanning the EOM origins to the globe equator.To form posterior partial volumes(PPVs),the LR and MR cross-sections in the image planes 8,10,12,and 14 mm posterior to the globe were summed and multiplied by the 2-mm slice thickness.The data were classified according to the right eye,left eye,dominant eye,and non-dominant eye,and the differences in mean cross-sectional area,maximum cross-sectional area,and PPVs of the MR and LR muscle in the AACE group and HCs group were compared under the above classifications respectively.RESULTS:There were no significant differences between the two groups of demographic characteristics.The mean cross-sectional area of the LR muscle was significantly greater in the AACE group than that in the HCs group in the non-dominant eyes(P=0.028).The maximum cross-sectional area of the LR muscle both in the dominant and non-dominant eye of the AACE group was significantly greater than the HCs group(P=0.009,P=0.016).For the dominant eye,the PPVs of the LR muscle were significantly greater in the AACE than that in the HCs group(P=0.013),but not in the MR muscle(P=0.698).CONCLUSION:The size and volume of muscles dominant eyes of AACE subjects change significantly to overcome binocular diplopia.The LR muscle become larger to compensate for the enhanced convergence in the AACE.

一种基于DCM下的漏极反馈反激变换器在PFM峰值电流模式控制下的稳定性分析

针对原边反馈反激变换器具有辅助绕组而成本偏高的问题,基于原边反馈与峰值电流控制方案,提出了一种基于开关管漏极反馈的反激变换器模型。与原边反馈反激变换器相比,漏极反馈反激变换器能够减少变压器辅助绕组,降低了成本,且具有较高的稳定性。首先,对此漏极反馈反激变换器模型进行了理论分析,并提出了一种高精度漏极采样方法。其次,基于开关网络模型法对工作在断续导通模式(Discontinuous conduction mode,DCM)下脉冲频率调制(Pulse frequency modulation,PFM)的漏极反馈反激变换器进行了小信号建模并进行补偿设计。通过Matlab/Simulink搭建模型验证其正确性;最后搭建试验平台来进行验证。结果表明,所提出的漏极反馈反激变换器模型是可行的。

用于LLC谐振拓扑的PFM发生器IP核设计

阐述LLC谐振拓扑的结构和频率特性,针对LLC谐振变换器对占空比固定为50%、频率可调节的需求,基于国产Seal 5000系列SA5Z-30-D1平台,提出一种带死区和互补输出的PFM发生器IP核。提出的IP核内部具有上下计数模式计数器和死区与互补生成模块,通过寄存器设置计数器最大值与自增量,以计数器方向信号作为PFM输出送入死区与互补生成模块,在死区与互补生成模块中产生反相信号并插入死区。通过示波器观测实际输出信号表明该IP核输出效果良好,可以灵活地输出可配置的带有死区、互补输出的PFM波形。

单级无桥Sepic谐振LED驱动电路及其APWM-PFM混合控制

针对传统两级式LED驱动电源中存在着半导体功率器件数目多,控制电路复杂,效率低,成本高,可靠性差等问题,提出一种单级无桥Sepic谐振LED驱动电路,通过将单开关无桥Sepic电路主开关管与半桥LLC电路下开关管复用集成单级LED驱动电路,减少了半导体功率器件数目,简化控制电路,提高了电路效率和工作可靠性。详细分析了所提出电路的工作原理和工作过程,深入开展了电路输入输出电压变比、网侧特性、软开关特性等稳态特性推导和电路关键参数设计,并针对所提出单级电路由于输入电压变化引起直流母线电压变动范围大等问题,分析设计了一种APWM-PFM混合控制策略。最后进行计算机仿真分析,并设计一台交流输入185~265 V_(rms)、额定输出2 A/96 W的实验样机,样机效率最高可达91.5%,PF最大值为0.995,THD最小为5.5%,不同交流电压下直流母线电压总体变化范围在60 V以内,实现直流母线电压限压。计算机仿真结果和实验结果验证所提出电路和混合控制策略的理论预期和有效性。

STEAM教育理念下PFM混合教学模式在妇产科见习教学中的应用

目的:研究STEAM教育理念下PFM混合教学模式在妇产科见习教学中的应用效果。方法:将100名2020级临床医学专业的见习学生随机分为2组,分别通过STEAM教育理念下PFM混合教学模式(观察组)和传统的教学模式(对照组)接受临床见习教学。见习结束后,对2组学员的临床综合能力进行测评,另外用问卷调查的方法调查教学效果。结果:观察组学生在临床思维能力、学习兴趣以及与病人的沟通交流能力方面均显著优于对照组(P<0.01)。结论:STEAM教育理念下PFM混合教学模式在妇产科见习教学中切实可行,具有良好的教学效果。

A"messenger zone hypothesis"based on the visual three-dimensional spatial distribution of motoneurons innervating deep limb muscles

Coordinated contraction of skeletal muscles relies on selective connections between the muscles and multiple classes of the spinal motoneuro ns.Howeve r,current research on the spatial location of the spinal motoneurons innervating differe nt muscles is limited.In this study,we investigated the spatial distribution and relative position of different motoneurons that control the deep muscles of the mouse hindlimbs,which were innervated by the obturator nerve,femoral nerve,inferior gluteal nerve,deep pe roneal nerve,and tibial nerve.Locations were visualized by combining a multiplex retrograde tracking technique compatible with three-dimensional imaging of solvent-cleared o rgans(3DISCO)and 3-D imaging technology based on lightsheet fluorescence microscopy(LSFM).Additionally,we propose the hypothesis that"messenger zones"exist as interlaced areas between the motoneuron pools that dominate the synergistic or antagonist muscle groups.We hypothesize that these interlaced neurons may participate in muscle coordination as messenger neurons.Analysis revealed the precise mutual positional relationships among the many motoneurons that innervate different deep muscles of the mouse.Not only do these findings update and supplement our knowledge regarding the overall spatial layout of spinal motoneurons that control mouse limb muscles,but they also provide insights into the mechanisms through which muscle activity is coordinated and the architecture of motor circuits.

Temporal and spatial regulation of biomimetic vascularization in 3D-printed skeletal muscles

In the intricate skeletal muscle tissue,the symbiotic relationship between myotubes and their supporting vasculature is pivotal in delivering essential oxygen and nutrients.This study explored the complex interplay between skeletal muscle and endothelial cells in the vascularization ofmuscle tissue.By harnessing the capabilities of three-dimensional(3D)bioprinting and modeling,we developed a novel approach involving the co-construction of endothelial and muscle cells,followed by their subsequent differentiation.Our findings highlight the importance of the interaction dynamics between these two cell types.Notably,introducing endothelial cells during the advanced phases of muscle differentiation enhanced myotube assembly.Moreover,it stimulated the development of the vascular network,paving the way for the early stages of vascularized skeletal muscle development.The methodology proposed in this study indicates the potential for constructing large-scale,physiologically aligned skeletal muscle.Additionally,it highlights the need for exploring the delicate equilibrium and mutual interactions between muscle and endothelial cells.Based on the multicell-type interaction model,we can predict promising pathways for constructing even more intricate tissues or organs.

Catalpa bignonioides extract improves exercise performance through regulation of growth and metabolism in skeletal muscles

Objective:To evaluate the effects of Catalpa bignonioides fruit extract on the promotion of muscle growth and muscular capacity in vitro and in vivo.Methods:Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.Cell proliferation was assessed using a 5-bromo-2’-deoxyuridine(BrdU)assay kit.Western blot analysis was performed to determine the protein expressions of related factors.The effects of Catalpa bignonioides extract were investigated in mice using the treadmill exhaustion test and whole-limb grip strength assay.Chemical composition analysis was performed using high-performance liquid chromatography(HPLC).Results:Catalpa bignonioides extract increased the proliferation of C2C12 mouse myoblasts by activating the Akt/mTOR signaling pathway.It also induced metabolic changes,increasing the number of mitochondria and glucose metabolism by phosphorylating adenosine monophosphate-activated protein kinase.In an in vivo study,the extract-treated mice showed improved motor abilities,such as muscular endurance and grip strength.Additionally,HPLC analysis showed that vanillic acid may be the main component of the Catalpa bignonioides extract that enhanced muscle strength.Conclusions:Catalpa bignonioides improves exercise performance through regulation of growth and metabolism in skeletal muscles,suggesting its potential as an effective natural agent for improving muscular strength.

In vivo imaging and computational modeling of nonlinear shear waves in living skeletal muscles

How the state of living muscles modulates the features of nonlinear elastic waves generated by external dynamic loads remains unclear because of the challenge of directly observing and modeling nonlinear elastic waves in skeletal muscles in vivo,considering their active deformation behavior.Here,this important issue is addressed by combining experiments performed with an ultrafast ultrasound imaging system to track nonlinear shear waves(shear shock waves)in muscles in vivo and finite element analysis relying on a physically motivated constitutive model to study the effect of muscle activation level.Skeletal muscle was loaded with a deep muscle stimulator to generate shear shock waves(SSWs).The particle velocities,second and third harmonics,and group velocities of the SSWs in living muscles under both passive and active states were measured in vivo.Our experimental results reveal,for the first time,that muscle states have a pronounced effect on wave features;a low level of activation may facilitate the occurrence of both the second and third harmonics,whereas a high level of activation may inhibit the third harmonic.Finite element analysis was further carried out to quantitatively explore the effect of active muscle deformation behavior on the generation and propagation of SSWs.The simulation results at different muscle activation levels confirmed the experimental findings.The ability to reveal the effects of muscle state on the features of SSWs may be helpful in elucidating the unique dynamic deformation mechanism of living skeletal muscles,quantitatively characterizing diverse shock wave-based therapy instruments,and guiding the design of muscle-mimicking soft materials.

Study on Electromyographic Characteristics of Neck Muscles in College Students with Chronic Neck Pain

Objective:To provide new insights for the evaluation and diagnosis of chronic neck pain(CNP).Methods:22 patients with CNP and 22 healthy individuals were recruited from South China Normal University,who were all college students.The subjects'neck extensor muscle strength in the head neutral position,the natural anteversion position,and the maximum forward flexion position were measured by an isometric muscle strength tester respectively.The neck extensor strength of CNP patients and healthy subjects were compared.Results:In the neutral position,the maximum isometric muscle strength of neck extensor muscles was 12.31 kg for CNP patients and 15.16 kg for healthy individuals,resulting in a ratio of 81%strength in patients compared to healthy subjects.This difference was highly significant(P<0.000).In the natural anteversion position,the respective values were 12.6 kg for CNP patients and 15.05 kg for healthy individuals,with a ratio of 83%,and a significant difference between groups(P<0.001).In the maximum forward flexion position of the head,the values were 13.36 kg for CNP patients and 16.15 kg for healthy individuals,with a ratio of 82%,and a highly significant difference(P<0.000).Conclusion:The neck extensor muscle strength levels in college students with CNP were significantly lower compared to healthy college students across all measured positions.

不同运动模式影响心肌梗死致心力衰竭大鼠骨骼肌重塑的机制

背景:急性心肌梗死可引起心脏重塑和心力衰竭,同时导致骨骼肌病变,影响患者生活质量。运动疗法是心力衰竭患者的重要康复手段,然而最佳运动处方尚未明确。目的:对比不同运动模式(有氧运动、抗阻运动)对急性心肌梗死诱导心力衰竭模型大鼠骨骼肌重塑的影响,探讨其可能的作用机制,为优化运动康复方案提供依据。方法:48只SD大鼠随机分为假手术组、心肌梗死组、有氧运动组和抗阻运动组。利用冠状动脉结扎术进行心力衰竭模型制作,3个月后有氧运动组和抗阻运动组进行12周相应运动模式干预,假手术组和心肌梗死组于鼠笼内安静饲养。实验后,利用递增负荷跑台运动实验和爬梯实验分别测定大鼠最高跑速和最大负重,超声心动图评估心脏结构与功能;分离出心脏,分别行苏木精-伊红染色和天狼星红染色观察心脏重塑情况;分离出腓肠肌,行ATP酶染色观察肌纤维类型和细胞横截面积改变,二氢乙锭法评估活性氧水平,酶联免疫吸附法测定丙二醛含量以及抗氧化酶活性,免疫印迹法测定泛素-蛋白酶体系统蛋白表达量,双重免疫荧光染色检测活化的卫星细胞数(Pax7^(+)/MyoD^(+))。结果与结论:①运动能力:与假手术组比较,心肌梗死组最高跑速和最大负重下降(P<0.05);与心肌梗死组比较,有氧运动组最高跑速以及抗阻运动组最大负重增加(P<0.05)。②心脏重塑:与假手术组比较,心肌梗死组梗死面积、心肌细胞横截面积、心肌胶原含量升高(P<0.05),左心室射血分数和左心室缩短分数下降(P<0.05);与心肌梗死组比较,有氧运动组和抗阻运动组上述各参数均无统计学差异(P>0.05)。③骨骼肌重塑:与假手术组比较,心肌梗死组腓肠肌质量、腓肠肌质量指数、细胞横截面积、超氧化物歧化酶活性、谷胱甘肽过氧化物酶活性、活化的卫星细胞数量下降(P<0.05),活性氧、丙二醛含量以及泛素、MuRF1、MAFbx蛋白表达量上调(P<0.05);与心肌梗死组比较,有氧运动组和抗阻运动组腓肠肌质量指数、超氧化物歧化酶活性、活化的卫星细胞数量增加(P<0.05),活性氧水平以及泛素、MuRF1、MAFbx蛋白表达量降低(P<0.05);与有氧运动组比较,抗阻运动组腓肠肌质量、腓肠肌质量指数、细胞横截面积、活性氧水平、丙二醛含量、活化的卫星细胞数量升高(P<0.05),超氧化物歧化酶活性、谷胱甘肽过氧化物酶活性下调(P<0.05)。结果表明:有氧运动和抗阻运动均可提升心力衰竭大鼠的运动能力,其机制与减轻氧化应激、抑制泛素-蛋白酶体系统活性以及激活卫星细胞进而改善骨骼肌重塑有关。有氧运动对于改善骨骼肌氧化应激作用更佳,而抗阻运动促进骨骼肌再生方面效果更为显著。

游泳运动对大鼠创伤性关节挛缩的影响及机制

背景:早期运动是预防创伤性关节挛缩的主要方式,也是近期研究热点。游泳运动借助水的特殊物理特性,可能是潜在有益的干预方式。目的:观察游泳运动对大鼠关节挛缩发展的影响,探究游泳运动预防关节挛缩的相关机制。方法:24只SD大鼠随机分为空白对照组(n=8)和关节挛缩造模组(n=16),手术制备膝关节挛缩模型后,再随机分为手术对照组(n=8)和游泳干预组(n=8)。游泳干预组在术后第2周开始游泳干预,共干预5周。在术后第6周,测试各组大鼠体质量、术侧膝关节活动度、股四头肌直径,计算直径-体质量指数;苏木精-伊红染色观察膝关节囊和股四头肌病理变化;Masson染色观察关节囊胶原纤维化改变;免疫组化检测膝关节囊中转化生长因子β1和Ⅰ型胶原蛋白表达;Western blot检测股四头肌中MuRF1蛋白的表达。结果与结论:①与空白对照组比较,手术对照组和游泳干预组大鼠膝关节活动度下降,总伸膝受限角度和关节源性伸膝受限角度均明显增加(P<0.01),股四头肌直径下降(P<0.01),关节囊出现明显纤维化表现,股四头肌萎缩,手术对照组直径-体质量指数降低(P<0.01);与手术对照组比较,游泳干预组大鼠膝关节活动度和股四头肌直径明显增加(P<0.01),关节囊纤维化病变和股四头肌萎缩明显改善;②与空白对照组比较,手术对照组和游泳干预组大鼠关节囊中胶原纤维含量、转化生长因子β1和Ⅰ型胶原蛋白表达均增加(P<0.01);与手术对照组比较,游泳干预组大鼠关节囊中胶原纤维含量、转化生长因子β1和Ⅰ型胶原蛋白表达均降低(P<0.01);③与空白对照组比较,手术对照组和游泳干预组大鼠股四头肌中MuRF1蛋白表达增加(P<0.05);与手术对照组比较,游泳干预组大鼠股四头肌中MuRF1蛋白表达降低(P<0.05)。结果表明:早期游泳干预能够降低创伤性挛缩大鼠关节囊中转化生长因子β1和Ⅰ型胶原蛋白表达,降低股四头肌中MuRF1蛋白表达,提高关节活动度和股四头肌直径,抑制关节挛缩的发展。

理筋手法调控兔骨骼肌损伤修复中瘢痕形成的作用机制

背景:理筋手法能够促进骨骼肌修复,治疗骨骼肌损伤。但骨骼肌损伤在修复过程中的纤维化形成、瘢痕组织增生等与损伤修复质量密切相关。开展理筋手法对纤维化形成、瘢痕组织增生的调控作用研究,有利于阐述理筋手法提高骨骼肌损伤修复质量的相关机制。目的:探索理筋手法提高兔骨骼肌损伤后修复质量的作用机制,为临床治疗提供科学依据。方法:45只健康成年日本大耳白兔随机分为空白组、模型组、理筋组,每组15只。其中模型组和理筋组均进行腓肠肌打击造模;造模后理筋组于第3天开始进行理筋手法干预,1次/d,15 min/次。各组在造模后的第7,14,21天分别处死5只兔进行观察。苏木精-伊红染色法观察腓肠肌形态及炎性细胞量,Masson染色法观察腓肠肌胶原纤维量,ELISA法检测腓肠肌白细胞介素6和白细胞介素10的表达量,Western blot和RT-PCR检测配对盒基因7、成肌分化因子、肌细胞生成素、肌动蛋白α、转化生长因子β1、Ⅰ型胶原蛋白的蛋白及mRNA表达,免疫组织化学法检测Ⅰ型胶原蛋白的表达。结果与结论:①苏木精-伊红染色及Masson染色结果显示,与模型组比较,理筋组各观察点炎性细胞浸润减少,胶原纤维量减少(P<0.01),肌纤维逐渐愈合;②ELISA结果显示,与模型组比较,理筋组白细胞介素6表达持续降低(P<0.05),而白细胞介素10在造模后第7天时升高(P<0.05),随后呈下降趋势(P<0.05);③Western blot和RT-PCR结果显示,与模型组比较,理筋组造模后第14天配对盒基因7、成肌分化因子、肌细胞生成素的蛋白及mRNA表达量均显著升高(P<0.05),而第21天时却较之前下降(P<0.05);理筋组各观察点肌动蛋白α、转化生长因子β1、Ⅰ型胶原蛋白的蛋白及mRNA表达量相较于模型组均显著降低(P<0.05);④免疫组化结果显示,理筋组各观察点Ⅰ型胶原蛋白的表达量相较于模型组均显著降低(P<0.05);⑤结果表明,理筋手法能够通过抑制炎症、促进肌卫星细胞的增殖分化、减少纤维化的生成,从而提高兔骨骼肌损伤的修复质量。

一种PWM/PFM自动切换的DC-DC芯片

提出一种可根据负载变化在脉冲宽度调制(pulse width modulation,PWM)和脉冲频率调制(pulse frequency modulation,PFM)两种工作模式间自动切换的降压DC-DC芯片的设计法,推导出临界切换状态下的负载电流值表达式,在此基础上设计了一种PWM/PFM自动切换的DC-DC芯片.该系统在较大的负载变化范围内均具有较高效率.

基于双频PFM控制模式的升压式DC-DC变换器

为了改善系统在宽负载范围内的整体效率,设计了一种基于双频脉冲频率调制(PFM)控制模式的升压式DC-DC变换器.首先,选定2个固定的频率.通过检测负载的变化,使得变换器在轻载或重载时工作于其中的1个频率下,而中载时则通过选择2个频率的不同组合来稳定输出电压,提高全载效率.继而设计了一个双频振荡器电路模块.整个芯片设计基于0.5μm CMOS工艺,并在Cadence工具中完成模拟仿真和版图设计.流片芯片测试结果表明,系统在整个负载范围内的转换效率高于75%,最大输出电流可达300 mA,芯片的实际性能达到设计要求.因此,采用这种控制方法能有效提高系统的全载效率,所得变换器可望具有良好的电磁干扰特性.

一种低功耗PFM升压型DC-DC开关变换器设计

基于EPISIL 1.5mm 25V 双极工艺,完成了一种低功耗电流控制型PFM DC-DC升压开关变换器芯片的设计,采用Hpsice电路模拟软件对设计进行了验证,达到了相应的设计指标。

基于PFM调制的超低功耗红外光通信装置设计

采用分离元件,以STM32F103ZE微处理器作为控制核心,设计了一种红外光通信装置以及超低功耗三维中继器,实现数字或模拟信号的无线传输以及任意方向转发.该装置主要由红外光发射器、三维中继转发器和红外光接收器等模块组成,使用同步传输协议,以脉冲调频的方式调制解调,实现了数字化无线通信的目的,解决了光通信仅能单一方向传递的问题,具有功耗低,传输距离较远的优点.并以音频传输为原型,在13m左右的三维空间里实时传输0.1~10kHz频带内的音频信号.

一种电流检测PFM型LED驱动IC的设计

基于开关电源系统基本理论,采用电流检测脉频调制(PFM)模式,设计了一种新型大功率LED照明恒流驱动芯片。利用0.5μm CMOS工艺模型仿真,结果表明,该芯片具有高电源抑制比、2.5~400 V宽输入电压范围、10 kHz^2.5 MHz可调工作频率和多种保护功能,LED驱动电流范围为几mA到1 A,可驱动1个到几百个LED灯,特别适合大功率恒流驱动。

PFM系列管端坡口整形机

随着管道自动焊接技术的快速发展,焊接工艺对管端坡口的要求愈来愈高。坡口形式及精度已经成为影响焊缝质量的关键因素。PFM系列管端坡口整形机具有定位取心准确,切削力大,切削速度快,精度高,可加工V型、U型、X型及各种复合型坡口,旋转刀盘上的跟踪仿形机构可确保加工坡口的形状、尺寸均匀一致,液压系统油门自动调节可实现加工速度与怠速互换,操作方便等诸多优点,完全满足工程需求,已成为管道全位置自动焊接不可或缺的关键设备。PFM系列管端坡口整形机的国产化,打破了国外同类产品的技术封锁和价格垄断,满足了自动焊接技术对管端坡口形式及精度的需求,有效提高了我国管道施工的技术水平及经济效益。