Charge transfer on porous silicon membranes studied by current-sensing atomic force microscopy

A visible rectification effect on the current-voltage curves of metal/porous silicon/p-silicon has been observed by current-sensing atomic force microscopy. The current-voltage curves of porous silicon membranes with different porosities, prepared through variation of etching current density for a constant time, indicate that a higher porosity results in a higher resistance and thus a lower rectification, until the current reaches a threshold at a porosity 〉55%. We propose that the conductance mode in the porous silicon membrane with porosities 〉55% is mainly a hopping mechanism between nano-crystallites and an inverse static electric field between the porous silicon and p-Si interface blocks the electron injection from porous silicon to p-Si, but with porosities ≤55%, electron flows through a direct continuous channel between nano-crystallites.

Design and Verification of a High Performance LED Driver with an Efficient Current Sensing Architecture

A high power buck-boost switch-mode LED driver delivering a constant 350 mA with a power efficient current sensing scheme is presented in this paper. The LED current is extracted by differentiating the output capacitor voltage and maintained by a feedback. The circuit has been fabricated in a standard 0.35 μm AMS CMOS process. Measurement results demonstrated a power-conversion efficiency over 90% with a line regulation of 8%/V for input voltage of 3.3 V and current output between 200 mA and 350 mA.

Nanometer Thick Diffused Hafnium and Titanium Oxide Light Sensing Film Structures

We examine 10 nm thick film structures containing either Hf or Ti sandwiched between two respective oxide layers. The layers are deposited onto heated substrates to create a diffusion region. We observe a high degree of light sensitivity of the electric current through the film thickness for one polarity of an applied voltage. For the other polarity, the current is not affected by the light. We explain the observed phenomenology using the single-particle model based on the existence of interface states on the metal-oxide interfaces.

Buck Converter Current Measurement Using Differential Amplifier

The accuracy of the measured current is a preeminent parameter for Current Control based Power Converter applications to ensure genuine operation of the designed converter.The current measurement accuracy can be affected by several parameters which includes the type of technology used,components used for the selected technology,aging,usage,operating and environmental conditions.The effect of gain resistors and their manufacturing tolerances on differential amplifier-based buck converter current measurement is investigated in this work.The analysis mainly focused on the output voltage variation and its accuracy with respect to the change in gain resistance tolerances.The gain resistors with 5%,1%,0.5%and 0.1%manufacturing tolerances taken for the worst-case analysis and the calculated performance results are compared and verified with the simula-tion results.The Operational amplifiers(Op-Amp)for high frequency power con-verter applications must operate in a high frequency noise environment and the intended current measuring system must manage common mode noise distur-bances paired with the signal to be measured.Based on the Common Mode Rejec-tion Ratio(CMRR)the common mode voltages and noise signals will effectively getfiltered out.Lesser CMRR results in lower common mode signal rejection,resulting in poor precision and noise rejection.In differential amplifiers,the CMRR predominantly depends on gain resistors.So,the variations in Common Mode Rejection Ratio due to gain resistor tolerances also analyzed and compared with the output voltage variations.Besides the effects of resistor tolerances,this paper also examines the effect of Op-Amp offset voltage on output accuracy spe-cifically for low magnitude input currents.The obtained results from this analysis clearly shows that the gain resistors with 0.1%tolerance gives maximum accuracy with improved CMRR and accuracy at low magnitude input currents will get well improved by using Op-Amps with Low Offset voltage specifications.

基于MCS-SBL算法的配电网故障定位方法

配电网拓扑结构复杂,传统方法往往需要大量测点信息且难以实现快速有效的故障定位,本文提出基于少量测点信息的故障定位方法。首先,利用等效原理建立一个欠定的故障节点电压方程;其次,利用多重测量向量模型的贝叶斯压缩感知算法求解方程,根据重构稀疏电流矩阵的非零元素位置求解故障区域,实现故障定位;最后,在IEEE33节点配电系统上进行仿真实验,结果表明,所提方法仅需要少量测点的故障前后正序电压分量便可有效定位故障,计算速度较快,并且基本不受故障类型、过渡电阻的影响,同时适用于单故障和多重故障的场景,具有较强的抗噪能力。

结合全局特征与局部互通的河流断流接续优化

高分辨率遥感影像的水体提取常因地物类型复杂、部分河流狭窄等因素导致水体提取结果不完整、不连续。因此,结合水体自身光谱和纹理特征,提出了一种结合全局特征与局部互通的遥感影像水体提取优化方法。首先,在水体提取初始结果的基础上,通过多尺度Frangi滤波和大津法(OTSU)分割算法提取线性支流,对河流进行补充得到初步优化结果。然后,结合局部互通的断流接续算法,对初步优化结果中的断流部分进行连接。最后,通过K-means聚类提取水体部分,并与精确优化结果进行拓扑检查及光谱检查,实现块状水体的验证筛选。实验结果表明,本文方法能够提取到细小支流,提高优化的准确度;断流接续算法的加入,有助于提高河流提取的完整性。与其他方法相比,本文方法的总体精度分别提高1.04%、1.50%,F1分别提高5.84%、8.28%,可以作为有效提升水体优化后处理的手段,提高了水体提取的完整度和精度。

抗寄生参数变动的无电流采样图腾柱PFC控制

针对无电流采样图腾柱功率因数校正(PFC)采用占空比直接计算受寄生参数变动影响导致输入电流畸变的问题,此处提出一种抗寄生参数变动的无电流采样控制策略。首先分析图腾柱PFC的工作原理,建立开关平均等效模型,由此推导包含寄生参数的占空比表达式;然后分析输入电流与输出低频纹波电压之间的关系,通过控制低频纹波角频率与移相角来改善输入电流波形;最后搭建样机完成稳态和瞬态测试。在额定功率为1 000 W时,实现400V的恒压输出和0.998的功率因数,变换器效率可达98.35%。

应用于忆阻器阵列存内计算的低延时低能耗新型感知放大器

存内计算(Computing In Memory,CIM)在人工智能神经网络的卷积运算方面具有巨大的应用潜力。基于忆阻器阵列的多位存内计算由于具备写入速度快、与互补金属氧化物半导体(Complementary Metal Oxide Semiconductor,CMOS)工艺兼容等特点,有望成为解决“内存墙”的有效手段。然而,当前多位存内计算电路架构面临输出延时高和能耗大的问题,主要原因为传统感知放大器的性能制约,为此本文提出了一种低延时低能耗多位电流型感知放大器(Low-delay Low-power Multi-bit Current-mode Sense Amplifier,LLM-CSA),通过减少传统CSA电路工作状态数量、简化工作时序来优化功能;采用新型低位检测模块的电路设计思路,来多层次系统性地降低输出延时并优化能耗。使用中芯国际40 nm低漏电逻辑工艺(SMIC40 nm LL),利用Cadence电路设计平台,仿真验证所提LLM-CSA的功能和延时-能耗性能。通过对比分析发现:LLM-CSA比传统CSA输出延时降低1.42倍,能量消耗降低1.56倍。进一步地,以一种4 bit输入、4 bit权重、11 bit输出的忆阻器阵列多位存内计算架构为应用,对比验证所提LLM-CSA的性能:与基于传统CSA的存内计算系统相比,新架构延时降低1.18倍,能耗降低1.03倍。LLM-CSA的提出对促进感知放大器设计思路和忆阻器阵列存内计算架构的发展,具有一定的理论和现实意义。

功率MOS开关的高精度电流检测电路设计

随着军工设备、工业控制、智能汽车等领域的发展,功率MOS开关驱动器的需求量不断提升,其可靠性、安全性等性能要求也在逐步提高。为保证功率MOS管在安全电流下工作,设计了一款高精度高边电流检测电路。利用复合式斩波放大器,大幅降低失调电压对电流采样精度的影响,并保证电路系统有足够的响应速度。该电路采用CSMC 0.18μm高压BCD工艺进行设计,在添加10mV的输入失调电压后,测量精度依然可以达到99%,带宽达到3MHz。

遥感技术在作物氮素营养诊断中的应用现状分析

根据遥感技术在作物氮素营养诊断应用中的发展脉络,阐述可见光遥感、卫星遥感和光谱遥感在作物氮素营养诊断方面的理论进展、发展现状和应用前景。就目前研究可以看出,利用遥感技术获取的作物冠层特征参数与作物氮素营养指标之间具有较好的相关性,但作物图像获取、分析处理及特征参数优化等技术方法须要更深入地研究,探寻更简便、精准的方法。

基于磁场反演的三芯电缆电流非接触测量仿真研究

三芯电缆因其敷设工作量小,大量应用于中低压电网线路,三芯电缆的电流检测对于研究电网电能质量具有重要意义。基于磁场的钳形电流传感器具有非接触式传感,操作方便的特点,然而正常稳态运行时三芯电缆三相电流矢量和为零,常规的基于磁场的电流传感器无法对三芯电缆的电流进行测量。因此,提出一种基于磁传感器阵列的三芯电缆电流测量方法,采用COMSOL软件得到三芯电缆周围磁场分布:磁场在周围圆周上呈周期性分布,最大值出现在距离导体最近的位置,磁场幅值受导体距离和电流频率的影响,距离导体越远,电流频率越高,磁场越小。基于该分布,通过磁传感器阵列测量结果反演计算得到三芯电缆的电流,该方法可以准确测量三芯电缆电流的大小,算例误差小于3%,为三芯电缆电流的非接触测量提供了新方法。

基于光纤光栅的配网故障定位仿真模型研究

针对配电网环境复杂,监测的数据容易受到干扰或丢失,从而影响最终的故障定位准确性的问题,文中提出了一种基于光纤光栅技术的配电网故障仿真模型。该模型利用光纤光栅电流传感器来收集电流数据,发挥抗干扰性强、数据不易丢失等优点,通过电流波动来判断故障位置。利用该方法,从源头上提高监测的数据质量,依靠安装在配电网线路上的光纤电流传感器采集电缆中电流,当输电线路上某点发生故障时,计算出故障点相邻的前后两个光纤电流传感器检测到电流波动差值,通过阈值比较来实现故障位置的快速定位。该模型成功应用于某两个供电局,故障判断的准确率达到了98.89%,还考虑了无法确认故障是否真实发生的情况,具备良好的实用性及准确性。

广东省三级甲等医院药师科研获得感现状调查及影响因素分析

目的 了解广东省三级甲等医院药师科研获得感现状,分析其主要影响因素。方法 采用横断面研究法,于2023年3月至5月通过“问卷星”微信小程序向广东省内10家三级甲等医院的药师发放调查问卷,调查并分析药师科研获得感现状,采用单因素分析及多元线性回归分析探讨其影响因素,并建立结构方程模型进行路径分析及中介效应分析。结果 共回收问卷521份,有效500份,有效回收率为95.97%。科研获得感量表、组织支持感量表、工作压力量表、工作激情量表(维度)平均得分率均约为60%,且仅组织支持感量表得分率高于60%。相关性分析结果显示,科研获得感与组织支持感、工作激情均呈显著正相关(P <0.01);工作压力与组织支持感、工作激情、科研获得感均呈显著负相关(P <0.01)。单因素分析结果显示,职称和学历对科研获得感有显著影响(P <0.05)。多元线性回归分析结果显示,职称(β=0.11,P <0.01),学历(β=0.10,P <0.05),组织支持感(β=0.22,P <0.01),工作激情(β=0.20,P <0.01),工作压力(β=-0.18,P <0.01)均对药师的科研获得感有显著影响。路径分析结果显示,组织支持感和工作激情对科研获得感有显著正向影响(β=0.19,Z=3.30,P <0.001;β=0.21,Z=3.94,P <0.001);工作压力对科研获得感有显著负向影响(β=-0.19,Z=-3.86,P <0.001)。中介效应检验结果显示,组织支持感不单可直接影响科研获得感,也可通过影响工作激情和工作压力来间接影响科研获得感。结论 影响广东省三级甲等医院药师科研获得感的主要因素分别为组织支持感、工作激情、工作压力、职称和学历。提高组织支持感和工作激情,以及减少工作压力,可促进药师科研获得感的提升。

Ocean surface currents estimated from satellite remote sensing data based on a global hexagonal grid

Global ocean surface currents estimated from satellite derived data based on a regular global grid are affected by the grid’s shape and placement.Due to different neighbourhood relationships,the rectangular lat/lon grids lose accuracy when interpolating andfitting elevation data.Hexagonal grids have shown to be advantageous due to their isotropic,uniform neighbourhood.Considering these merits,this paper aims to estimate global ocean surface current using a global isotropic hexagonal grid from satellite remote sensing data.First,gridded satellite altimeter data and wind data with different resolutions are interpolated into the centre of the global isotropic hexagonal grid.Then,geostrophic and Ekman currents components are estimated according to the Lagerlof Ocean currents theory.Finally,the inversion results are verified.By analyzing the results,we conclude that the ocean surface currents estimated based on the global isotropic hexagonal grid have considerable accuracy,with improvement over rectangular lat/lon grids.

适用于新能源多特征参量的宽动态高准确度电能计量方案研究

随着传统能源逐渐由新能源替代、国网智能电网的发展,新能源发电并网成为可能。在新型电力系统中,高比例新能源接入下不确定性强、波动性大,电流波形严重畸变,会冲击传统电能计量设备,导致原有电能计量设备在使用时存在较大测量误差。为了适应新型电力系统计量需求,本文基于零磁通电流传感技术、无极平滑放大技术、高精度角差补偿方法等,实现电能表在宽动态多特征参量下的精确计量。实验结果表明,新的电能计量方案可适用于新能源接入下的宽动态、低功率因数与双向潮流等工况,有效提高了电力系统的整体效率。文章的研究成果对各种电能计量技术、算法的优化设计与适用于新能源的电能计量领域应用具有重要指导意义。

土地利用变化遥感制图与时空变化分析——以韶关市武江区龙归镇为例

城镇土地利用变化是人类活动塑造地表形态的重要表现形式。基于韶关市武江区2012-2022年2期土地利用变更调查遥感监测数据和DEM数据,借助GIS多元空间分析方法,对武江区龙归镇近10年间土地利用变化进行了系统分析。研究结果表明:10年间,龙归镇各土地利用类型时空变化显著,其中林地、建设用地、其他农用地和园地地类面积发生增加,林地增加面积最大为997.23 hm^(2),耕地、草地、未利用地的面积呈现减少状态,其中耕地减少面积最大为673.7 hm^(2)。在地形坡度方面,耕地与建设用地和其他地类间的转化主要体现在低坡度区域,坡度较高的地方,受限于自然环境,人类活动较弱,土地利用变化不明显。研究可为粤北山区城镇级别的土地综合开发管理和利用、地理空间规划等提供数据依据和理论参考。

高压直流电场非接触测量传感器的设计与研究

电力运营商应定期维护和检修直流设备,确保直流输电系统的安全生产和应用。在设备维护时,必须检测直流设备是否带电,是否超过电场强度安全阈值,以保证操作人员的寿命和设备的安全。本文采用非接触法测量高压直流电场。基于电容式传感器原理,研制了一种自反馈低功耗直流电场传感器。通过反馈调整传感器的范围和灵敏度。通过优化直流电场传感单元结构参数的设计,得出当感应电流信号幅值最大时,感应电极扇形叶片开度叶数为n=6。屏蔽电极与传感电极之间的距离d=3 mm。传感电极采用差分信号输出,抑制共模信号的干扰。传感器标定实验表明,该范围为±65 kV/m,灵敏度系数65.6,精度0.5 kV/m,测量误差小于2%。传感器在内部具有良好的一致性和可靠性±40 kV/m。该传感器不仅可以用于测量高压直流电场的强度,而且在航空航天和气象雷电研究中,具有广阔的应用前景。

The characteristics of welding currents in a rotating arc leadtandem GMAW process and the weld-seam tracking

Tandem gas metal arc welding （ T-GMAW） process shows a high deposition rate that up to three times o f the single electrode GMAW, so the welding speed could be significantly increased in this process. However, the majority o f this process applications are based on the pre-programmed robotic welding, which does not allow them to track the seam real-time during welding. Rotating arc sensor, sensing the seam position by detecting the changing of welding currents, has been widely adopted in the automatic robot welding process. It is proposed in this paper to integrate the rotating arc sensor with a trailing torch to develop a new approach of rotating arc lead tandem gas metal arc welding （RLT-GMAW） process. The characteristics of the welding currents in the proposed new welding process were firstly studied, and then a self-turning fuzzy control seam tracking strategy was developed for the mobile robot automatic welding. The experimental results showed that the proposed RLT-GMAW process had an excellent seam tracking performance and high welding deposition rate. Even if there were some electromagnetic interactions between the two arcs, the deviation of the welding seam could also be reflected by the fluctuation of the welding currents on the leading arc once the correct welding parameters were selected. Based on the detected deviation, the welding tracking experiments showed that the proposed self-turning fuzzy controller had a good performance for the RLT-GMAW process seam tracking.

Effects of Intrathecally Administerd NaV1.8 Antisense Oligonucleotide on the Expression of Sodium Channel mRNA in Dorsal Root Ganglion

Neuropathic pain has been hypothesized to be the result of aberrant expression and function of sodium channels at the site of injury. To investigate the effects of NaV1.8 antisense oligonucleotide on the expression of sodium channel mRNA in dorsal root ganglion （DRG） neurons in chronic neuropathic pain. 24 Sprague-Dawley rats weighing 200--260 g were anesthetized with the intraperitoneal injection of 300 mg· kg^-1 choral hydrate. The CCI model was made by loose ligation of sciatic nerve trunk by 4--0 chromic gut. The mechanical and thermal pain threshold were measured before operation and 1, 3, 5, 7, 9, 11, 13 days after operation. A PE-10 catheter was implanted in subarachnoid space at lumbar region. On the 7th postoperative day the animals were randomly divided into 4 groups. The drugs were injected intrathecally twice a day for 5 consecutive days in group 2--4. The animals were decapitated 14 days after the surgery. The L4--L6 DRG of the operated side was removed and crushed, and total RNA was extracted with Trizol reagent. The contralateral side was used as control. The change of NaV1.8 sodium channel transcripts was determined by RT-PCR. Pain threshold was significantly lowered after CCI as compared with that in control group and was elevated 3 days after antisense oligonucleotide injection. Sensory neuron specific TTX-R sodium channel NaV1.8 transcript was down-regulated after antisense oligonucleotide injection at the dosage of 45 μg as compared with that in CCI group （P〈0.01）, and it was even greater at the dosage of 90 μg. The intrathecally injected NaV1.8 antisense oligonucleotide can reduce the mechanical allodynia and thermal hyperalgesia partially by downregulating the SNS transcript expression.

具有电流检测功能的IGBTsense研究

本文研究了将电流检测功能集成到ＩＧＢＴ中去的模块ＩＧＢＴｓｅｎｓｅ，对ＩＧＢＴｓｅｎｓｅ的基本结构和等效电路进行了分析，提出了一种适于ＰＳＰＩＣＥ分析的ＩＧＢＴｓｅｎｓｅ模型，并详细给出了确定模型参数的方法。根据该模型对ＩＧＢＴｓｅｎｓｅ的主要特性进行了ＰＳＰＩＣＥ分析。结果表明，电流检测率Ｒ在整个工作范围内有良好的线性，但随集电极电流、温度、栅电压的变化而有较小的变化；检测单元的实际输出电容大于估算值，但对ＩＧＢＴｓｅｎｓｅ的瞬态特性影响不大。本文还研究了几种可行的过流检测电路，分析了电路的基本工作原理。