Femtosecond electron pulse compression by using the time focusing technique in ultrafast electron diffraction

We present a new model of an electron gun for generating subrelativistic femtosecond （fs） electron pulses. The basic idea is to utilize a dc acceleration stage combined with a time focusing region, the time focusing electrode generates an electron energy chirp for bunching at the target. Without considering the space charge effects, simulations of the electron gun were carried out under the conditions of different dc voltages and various slopes of the voltage added on the time focusing electrode. Tracing and simulating large numbers of photoelectrons through Monte-Carlo and finite difference methods, the electron pulses with 1 ps can be compressed to 55 fs, which will allow significant advances in the field of ultrafast diagnosis.

Effect of low-frequency pulse percutaneous electric stimulation on peripheral nerve injuries at different sites

BACKGROUND： The postoperative recovery of nerve function in patients with peripheral nerve injury is always an important problem to solve after treatment. The electric stimulation induced electromagnetic field can nourish nerve, postpone muscular atrophy, and help the postoperative neuromuscular function. OBJECTIVE： To observe the effects of low-frequency pulse percutaneous electric stimulation on the functional recovery of postoperative patients with peripheral nerve injury, and quantitatively evaluate the results of electromyogram （EMG） examination before and after treatment. DESIGN ： A retrospective case analysis SETTING： The Sixth People＇s Hospital affiliated to Shanghai Jiaotong University PARTICIPANTS： Nineteen postoperative inpatients with peripheral nerve injury were selected from the De- partment of Orthopaedics, the Sixth People＇s Hospital affiliated to Shanghai Jiaotong University from June 2005 to January 2006, including 13 males and 6 females aged 24-62 years with an average of 36 years old. There were 3 cases of brachial plexus nerve injury, 3 of median nerve injury, 7 of radial nerve injury, 3 of ul- nar nerve injury and 3 of common peroneal nerve injury, and all the patients received probing nerve fiber restoration. Their main preoperative manifestations were dennervation, pain in limbs, motor and sensory disturbances. All the 19 patients were informed with the therapeutic program and items for evaluation. METHODS： ① Low-frequency pulse percutaneous electric stimulation apparatus： The patients were given electric stimulation with the TERESA cantata instrument （TERESA-0, Shanghai Teresa Health Technology, Co., Ltd.）. The patients were stimulated with symmetric square waves of 1-111 Hz, and the intensity was 1.2-5.0 mA, and it was gradually adjusted according to the recovered conditions of neural regeneration following the principle that the intensity was strong enough and the patients felt no obvious upset. They were treated for 4- 24 weeks, 10-30 minutes for each time, 1-3 times a day, and 6 weeks as a course. ② EMG examination was applied to evaluate the recoveries of recruitment, motor conduction velocity （MCV） and sensory conduction velocity （SCV） before and after treatment. The patients were examined with the EMG apparatus （DIS- A2000C, Danmark） before and after the treatment of percutaneous electric stimulation. ③Standards for evaluating the effects included cured （complete recovery of motor functions, muscle strength of grade 5, no abnormality in EMG examination）, obviously effective [general recovery of motor function, muscle strength of grade 4, no or a few denervation potentials, motor conduction velocity （MCV） and sensory conduction velocity （SCV）], improved （partial recovery of motor function, muscle strength of grade 3, denervation potentials and reinneration potentials, slowed MCV and SCV, invalid （no obvious changes of motor function）. MAIN OUTCOME MEASURES： ① Ameliorated degree of the nerve function of the postoperative patients with peripheral nerve injury treated with percutaneous electric stimulation; ② Changes of EMG examination before and after treatment. RESULTS： All the 19 postoperative patients with peripheral nerve injury were involved in the analysis of results. ① Comparison of nerve function before and after treatment in 19 patients with peripheral nerve injury of different sites： For the patients with radial nerve injury （n=7）, the nerve functions all completely recovered after 8-week treatment, and the cured and obvious rate was 100% （7/7）; For the patients with brachial plexus nerve injury （n=3）, 1 case had no obvious improvement, and the cured and obvious rate was 67% （2/3）; For the patients with common peroneal nerve injury （n=3）, the extension of foot dorsum generally recovered in 1 case of nerve contusion after 4-week treatment, and the cured and obvious rate was 67% （2/3）; For the patients with median nerve injury （n=3）, muscle strength was obviously recovered, and the cured and obvious rate was 100% （3/3）; For the patients with ulnar nerve injury （n=3）, 1 case only had recovery of partial senses, and the cured and obvious rate was 67% （2/3）. Totally 9 cases were cured, 7 were obviously effective, 1 was improved, and only 2 were invalid. After 4 courses, the cured rate of damaged nerve function after four courses was 47% （9/19）, and effective rate was 89% （17/19）.② Comparison of EMG examination before and after treatment： Before and after percutaneous electric stimulation, he effective rates of recruitment, MCV and SCV were 89% （17/19）, 58% （11/19）, 47% （9/19） respectively, and there were extremely obvious differences （P〈 0.01）. CONCLUSION： ①Low-frequency pulse percutaneous electric stimulation can improve the nerve function of postoperative patients with peripheral nerve injury of different sites, especially that the injuries of radial nerve and median nerve recover more obviously. ②Percutaneous electric stimulation can ameliorate the indexes of EMG examination, especially the recruitment, in postoperative patients with peripheral nerve injury.

Treatment time influences the effects of a low-frequency pulsed electric field on synthesis of tyrosine hydroxylase and dopamine in PC12 cells

BACKGROUND： Electromagnetic radiation can influence dopamine （DA） synthesis in brain tissues or ceils, but electromagnetic frequencies, intensities, and radiation time can produce different effects. In addition, the signal pathway by which electromagnetic radiation influences DA synthesis remains controversial. OBJECTIVE： To determine tyrosine hydroxylase （TH） expression in PC12 cells and DA levels in cell culture media after different periods of low-frequency pulsed electric field （LF-PEF） stimulation, and to determine how LF-PEF signaling stimulates TH synthesis using inhibitors. DESIGN, TIME AND SETTING： A parallel, controlled, cell experiment was performed at the Laboratory of Cell Biology, School of Life Science, East China Normal University, between January and October 2006. MATERIALS： PC12 cells were purchased from the Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, China. Nerve growth factor was purchased from PeproTech, USA. The protein kinase A inhibitor, H-89, and mitogen-activated protein kinase kinase inhibitor, U0126, were purchased from Sigma, USA. METHODS： （1） Following routine culture in Dulbecco＇s modified eagle medium, primary PC12 cells were stimulated under LF-PEF （pulse frequency 50.Hz, pulse width 20 μs, peak field strength 1 V/m） for 5, 10, 15, 20, and 30 minutes. （2） Inhibitors （H-89 or U0126, 1 μmol/L） were added 30 minutes before LF-PEF stimulation for 10 minutes. MAIN OUTCOME MEASURES： （1） TH expression was determined by Western blot in PC12 cells at 0.5, 1,2, 3, and 4 days after LF-PEF stimulation. Similarly, DA was measured by high-performance liquid chromatography in media at 2, 3, 4, or 5 days after LF-PEE （2） TH expression was detected 1 day after H-89 or U0126 treatment and LF-PEE RESULTS： （1） Short-term LF-PEF stimulation （5 and 10 minutes） increased TH expression and media DA levels after short-term culture （2 days） （P 〈 0.01）, but both parameters decreased with longer culture （3 4 days） （P 〈 0.01）. Long-term LF-PEF stimulation （15, 20, or 30 minutes） decreased TH and DA synthesis, followed by a rapid increase （P 〈 0.01）. （2） H89 could completely inhibit TH expression in PC12 cells stimulated by LF-PEF for 10 minutes, while the inhibition rate of U0126 was 53.2%. CONCLUSION： Short-term LF-PEF first promotes then inhibits, while long-term LF-PEF first inhibits then promotes, TH and DA synthesis. LF-PEF stimulation regulates TH expression primarily by activating protein kinase A to regulate DA synthesis.

Investigation into Impedance Measurements for Rapid Capacity Estimation of Lithium-ion Batteries in Electric Vehicles

With the dramatic increase in electric vehicles(EVs)globally,the demand for lithium-ion batteries has grown dramatically,resulting in many batteries being retired in the future.Developing a rapid and robust capacity estimation method is a challenging work to recognize the battery aging level on service and provide regroup strategy of the retied batteries in secondary use.There are still limitations on the current rapid battery capacity estimation methods,such as direct current internal resistance(DCIR)and electrochemical impedance spectroscopy(EIS),in terms of efficiency and robustness.To address the challenges,this paper proposes an improved version of DCIR,named pulse impedance technique(PIT),for rapid battery capacity estimation with more robustness.First,PIT is carried out based on the transient current excitation and dynamic voltage measurement using the high sampling frequency,in which the coherence analysis is used to guide the selection of a reliable frequency band.The battery impedance can be extracted in a wide range of frequency bands compared to the traditional DCIR method,which obtains more information on the battery capacity evaluation.Second,various statistical variables are used to extract aging features,and Pearson correlation analysis is applied to determine the highly correlated features.Then a linear regression model is developed to map the relationship between extracted features and battery capacity.To validate the performance of the proposed method,the experimental system is designed to conduct comparative studies between PIT and EIS based on the two 18650 batteries connected in series.The results reveal that the proposed PIT can provide comparative indicators to EIS,which contributes higher estimation accuracy of the proposed PIT method than EIS technology with lower time and cost.

Effect of Annealing Temperatures on the Structural and Electrical Properties of Laser Induced Plasma for TiO2x-1Bix Thin Films

In this study, Bismuth doped Titanium dioxide thin films were deposited on glass substrates by a pulse laser deposition using laser. The effect of annealing temperature on the structural and electrical properties was investigated. X-ray diffraction pattern for pure and doped titanium dioxide films with different doping different ratio with Bi show that these films have amorphous structure oanvert to polycrystalline structure with annealing and doping and have a good identically with standard peaks for Anatase and Rutile phases. The orientation was at specific direction for Rutile. The crystalline of films increases by the increase of doping ratio. The crystalline increased with annealing temperature. Annealed films at different annealing temperatures have been studied. The results show that these films have two activation energies and by increasing the doping ratio, the activation energies and the conductivity increase. Both the annealing and composition effects on Hall constant, density of electron carders and Hall mobility are studied. Hall Effect measurements show that all films have n- type charge conductivity and the concentration increases while the mobility decreases with doping and annealing.

高压电脉冲刺激对于热处理花岗岩影响的实验研究

高压电脉冲技术作为一种环保、可控、高效的破碎坚硬岩石的方法,其潜在应用场景值得进一步深入发掘。本文研究了高压电脉冲诱导干热岩产生预损伤和劣化方法的效果。对热处理后花岗岩薄片试样施加了不同峰值电压的高压电脉冲刺激,探讨了高压电脉冲对于热处理花岗岩的影响。此外,还研究了初始温度对高压电脉冲刺激花岗岩的影响。结果表明:当外加峰值电压超过96 kV时,热处理花岗岩试样发生贯穿性的破裂,峰值电压越高,贯穿裂纹网络越复杂。当电压从96 kV增加到144kV时,花岗岩试样的微裂纹密度从8.63 mm/mm^(2)增加到13.26 mm/mm^(2)。随着热处理温度的升高,花岗岩发生电击穿的难度逐渐降低。在120 kV电脉冲放电刺激3次后,所有热处理温度高于400℃的花岗岩试样均能发生贯穿破裂。高压电脉冲刺激造成花岗岩产生的最大损伤发生在300~400℃的温度区间内。通过扫描电子显微镜观察到,随着试样处理温度的升高,内部孔隙和裂缝的发育情况逐渐加剧,孔隙大小、裂缝宽度和深度也随之增加。这项研究有望为建造干热岩人工储层提供新的见解。

直流与交流交联聚乙烯电缆料绝缘特性的差异及其机理分析

为研究交、直流电缆料绝缘特性的差异及其相关机理,对比测试了不同温度下交、直流电缆料的空间电荷和介电性能等主要绝缘特性,并通过红外光谱分析了造成差异的机理。研究结果表明:相比较交流电缆料,直流电缆料的空间电荷性能更优异、直流场下的击穿分散性更小但短时击穿场强稍低、杂质离子电导更少;红外光谱分析发现交、直流电缆料中羰基含量不同,而羰基含量表征了主链的完整程度和极性基团的含量,因此认为交直、流电缆料主链的完整程度和极性基团的含量是影响其绝缘性能差异的主要原因。

同时反演地层电阻率与侵入深度的数值方法

作者曾从电法测井的数学模型出发,在假定侵入深度为已知的条件下,给出了反演地层电阻率的一个迭代方法。本文在文献[1]的基础上,将侵入深度也作为反演参数之一,通过适当的变量代换,运用微分方程反问题的数值求解方法,得到了一个可以同时反演地层电阻率与侵入深度的迭代方法。

高压脉冲电场在食品灭菌方面的应用

综述了高压脉冲电场的产生、灭菌原理、灭菌特点、对食品的增鲜作用、对液态食品的灭菌作用、对食品质量的影响,指出了影响高压脉冲电场灭菌的因素,简要分析了高压静电场在食品方面的应用展望。

基于双脉冲电流技术液膜厚度测量系统的研制

以自制的双脉冲电流作为激励,在合理假设的基础上,通过分析环状流形成时传感器管内的电场分布,设计了测量传感器的结构,并推导出了液膜厚度与响应电压之间的关系式,最后,通过虚拟仪器将液膜厚度实时在线显示出来,实现了液膜厚度的动态测量。经测试,该系统操作方便,灵敏度高,重复性好,具有广阔的应用前景。

神经网络用于电热响应曲线的分析

瞬态脉冲试验是一种对桥丝式电火工品进行无损检测的方法。通过瞬态脉冲试验得到火工品的电热响应曲线,正常的电热响应曲线是光滑的,而非正常的电热响应曲线往往有较大的波动,出现非正常电热响应曲线的火工品一般都存在某种疵病。该文将神经网络技术用于对电热响应曲线的分析,以区分正常的电热响应曲线和非正常的电热响应曲线。研究结果表明,该方法可以比较准确地区分这两种电热响应曲线,实现自动判断。

稠油物理场降粘技术研究进展

综述了物理场在稠油降粘过程中的技术进展,包括超声波、电磁场、电场、微波、及低频脉冲波等物理场在稠油降粘中的原理、潜在优势及存在的问题。

电脉冲宽度的数模混合测量法

提出了一种数字技术与模拟技术相结合的电脉冲宽度测量法.该方法以计数器法测取脉冲的主体宽度,用时间-电压转换法测取脉冲的零头时间,并以此作为量化误差的校正值.测量系统以单片机为核心,具有结构简单、测量实时快速及准确度高的特点.

电动汽车电气驱动系统的新技术

电气驱动系统是电动汽车的关键部件。对于高性能的电动汽车 ,电气驱动系统必须效率高、结构紧凑、体积小、重量轻和可靠性高。本文介绍电动汽车电气驱动系统的最新发展 ,重点讨论效率最优控制。

加味生化汤联合低频电脉冲技术对剖宫产术后患者产后恶露及子宫复旧的影响

目的:观察加味生化汤联合低频电脉冲技术对剖宫产术后患者产后恶露及子宫复旧的影响。方法:选取妊娠38周以上并行剖宫产治疗的产妇320例,采用随机数字表法分为治疗组和对照组各160例。所有患者术后予以常规护理和缩宫素治疗,对照组患者加用低频电脉冲技术治疗,治疗组在对照组基础上采用加味生化汤口服治疗,共治疗5天。观察比较2组产妇产后恶露类型、血性恶露量和持续时间、产后42天恶露干净情况、宫底高度情况、子宫三径之和、子宫切口愈合程度、宫腔积液和组织残留情况、产妇术前和术后心理状态评分情况。结果:治疗5天后,治疗组产妇血性恶露量和持续时间显著低于对照组(P<0.05)。治疗5天后,治疗组产妇恶露以浆液恶露为主,显著优于对照组(P<0.05);手术42天后,治疗组恶露干净患者数量多于对照组,差异具有统计学意义(P<0.05)。治疗组总有效率为88.75%,显著高于对照组70.00%,差异具有统计学意义(P<0.05)。治疗前,2组抑郁自评量表(SDS)评分和负性情绪自评量表(SAS)评分比较,差异无统计学意义(P>0.05)。治疗后,治疗组SAS评分和SDS评分较治疗前降低,且显著低于对照组,差异均有统计学意义(P<0.05)。治疗后,治疗组子宫三径之和、宫腔积液、宫底高度显著低于对照组(P<0.05)。结论:加味生化汤联合低频电脉冲技术能有效促进剖宫产术后患者子宫复旧,改善恶露类型,减少恶露量和持续时间,缓解患者产妇负面情绪,提高治疗效果,值得临床推广使用。

亚皮秒电脉冲的产生及其在槽线上的传输特性

采用了飞秒光电导相关技术首次在以低温生长砷化镓(LT-GaAs)为衬底材料的槽线电极结构上产生亚皮秒电脉冲,并对其脉宽与传输特性进行了测量研究,得到电脉冲初始的半高全宽(FWHM)约为0.7ps,传输速度约为真空中光速的1/2.3倍;观察到电脉冲在传输过程中的强度衰减和脉冲的增宽,其衰减系数为20dB/mm,并测得脉冲传输至420后展宽至2.86ps.实验测量值与理论预期值相符.

慢走丝研究现状

根据慢走丝的技术特点,从以下6个方面对其研究现状、技术发展水平及目前存在的主要问题进行了分析:参数优化、仿真分析、加工过程的监测和控制、复合工艺、脉冲电源和轮廓精度控制。最后,结合慢走丝的研究现状和发展趋势对其未来发展进行了展望。

电阻率测井反演方法

本文将油田电阻率测井求地层电阻率分布的物理模型归结为一个带有衔接条件的椭圆型偏微分方程反问题,并用迭代过程求解出地层电阻率,从而给出了一种摆脱图版的测井解释方法。本文最后给出了方法的收敛性证明。

颗粒表面电荷对电阻脉冲法测量粒径的影响

报道了颗粒表面带电量对电阻脉冲(RPS)法测量颗粒粒径的影响规律。利用微流控芯片颗粒差分电阻脉冲检测系统实验测得了磷酸盐缓冲液(PBS)、1.0 mmol/L的十二烷基硫酸钠(SDS)阴离子表面活性剂溶液和十六烷基三甲基溴化铵(CTAB)阳离子表面活性剂溶液中,直径为2μm聚苯乙烯颗粒经过检测区产生的脉冲信号幅值,并计算获得了颗粒有效粒径。研究结果表明:在相同电压下,经表面活性剂处理后的颗粒产生的RPS信号幅值比未处理的大,该现象可以通过带有高表面电荷的聚苯乙烯颗粒的双电层变厚进行解释。研究成果有助于全面认识电阻脉冲法对于测量带有高表面电荷颗粒的粒径的影响程度。

低频电脉冲技术联合新生化颗粒对剖宫产术后患者子宫复旧的影响

目的观察低频电脉冲技术联合新生化颗粒对剖宫产术后患者子宫复旧的影响。方法将70例剖宫产妇随机分为对照组和观察组,每组35例。对照组在剖宫产后常规护理并予缩宫素治疗,观察组在对照组治疗基础上加用新生化颗粒治疗。2组均42 d后统计临床疗效,并观察产妇宫底高度、产后血性恶露量、产后血性恶露持续时间、恶露干净、体重指数(BMI)及恶露类型情况。结果观察组总有效率高于对照组,差异有统计学意义(P<0.05)。2组术后宫底高度均随时间延长而减小,观察组术后第1、3、5天宫底高度与对照组比较差异均有统计学意义(P<0.05)。观察组产后血性恶露量与对照组比较差异有统计学意义(P<0.05);观察组产后血性恶露持续时间与对照组比较差异有统计学意义(P<0.05);2组产后第42天恶露干净情况比较差异有统计学意义(P<0.05)。观察组产后第5天及第42天子宫三径和小于对照组,差异有统计学意义(P<0.05)。产后第42天对照组、观察组宫腔积液发生率比较,差异有统计学意义(P<0.05)。观察组产后第42天BMI低于本组剖宫产前(P<0.05);且与对照组比较差异有统计学意义(P<0.05)。2组剖宫产术后第5天恶露类型比较差异有统计学意义(P<0.05),对照组多为血性恶露,观察组多为浆液恶露。结论低频电脉冲技术联合新生化颗粒能促进剖宫产妇子宫康复,减少产后出血量,缩短恶露干净时间,促进产后尽早恢复,提高产妇生活质量。