Application of adjoint assimilation technique in simulating tides and tidal currents of the Bohai Sea, the Yellow Sea and the East China Sea

Considering the interaction of different tidal waves, an adjoint numerical model is developed to simulate M2, S2, K1 and O1 tidal waves in the Bohai Sea, the Yellow Sea and the East China Sea （B-Y-E） simultaneously. Compared with previous researches, by using the adjoint assimilation technique to inverse open boundary conditions and bottom friction coefficients based on altimetric data from TOPEX/Poseidon （T/P） and tidal gauges data, the precision of the numerical simulation is significantly improved. Selecting 14 days of simulated results after the initial wanning run to conduct harmonic analysis, the results can show the characteristics of M2, S2, K1 and O1 tidal wave systems perfectly in B-Y-E. Compared with 9 current stations, the calculated harmonic constants of tidal currents for M2 and K1 are in good agreement with the observed ones.

Temperature Effects on the Electrical Performance of Large Area Multicrystalline Silicon Solar Cells Using the Current Shunt Measuring Technique

The temperature effects on the electrical performance of a large area multicrystalline silicon solar cell with back-contact technology have been studied in a desert area under ambient conditions using the current shunt measuring technique. Therefore, most of the problems encountered with traditional measuring techniques are avoided. The temperature dependency of the current shunt from 5oC up to 50oC has been investigated. Its temperature coefficient proves to be negligible which means that the temperature dependency of the solar cell is completely independent of the current shunt. The solar module installed in a tilted position at the optimum angle of the location, has been tested in two different seasons (winter and summer). The obtained solar cell short circuit current, open circuit voltage and output power are correlated with the measured incident radiation in both seasons and all results are discussed.

Investigations of Tracking Phenomena in Silicone Rubber Using Moving Average Current Technique

In the present work, tracking phenomenon in Silicone rubber material has beenstudied under AC and DC voltage, with ammonium chloride as a contaminant. It is observed that thetracking is more severe under the DC voltages. The tracking time is less under negative DC comparedto the positive DC voltage. The tracking mechanism is explained in detail. The leakage currentduring the tracking studies was as measured and the moving average technique was adopted tounderstand the trend in current flow. The leakage current magnitude is high with thermally agedspecimens compared to the virgin specimen, irrespective of the type of applied voltage. It isrealized that the tracking time and the leakage current magnitude shows an inverse relationship.

Applied the Large Scale Particle Image Velocimetry Technique for Measurement the Velocity of Gravity Currents in the Laboratory

This study includes a series of laboratory experiments for investigated the gravity current of fresh water with density ρ-?ρ, and initial speed u0 upon the free surface of an ambient liquid (salty water) with density ρ at rest in a basin. It’s have been presented to illuminate the dominant flow and transport phenomena in the presence of river, stream and wetland ecology, stream corridor restoration, in the case of accidental pollution spills. The characterized of the local kinematic field, i.e. the local velocity and vorticity fields, the measurement methods include particle image velocimetry (PIV) at the water surface using a technique similar to large scale of particle image velocimetry (LSPIV).

Application of Line Boundary Technique to 2D Tidal Current Simulation

To deal with the problems concerning the shore boundary, moving boundary and engineering boundary which are encountered frequently in 2D tidal current simulation by the finite difference method, the concept of line boundary is introduced and studied here, and then the line boundary technique in common use is proposed in this paper. Analysis of some calculation cases shows that this technique is practical, effective, and simple in 2D tidal current simulation involving different boundaries.

Investigation of Current Control Techniques of AC-DC Interleaved Boost PFC Converter

This paper presents the comparison of various current control strategies employed for an interleaved power factor correction (PFC) boost converter for improving the power quality. The major control strategies discussed in this paper are: peak current control, average current control, hysteresis control, borderline current control and non-linear control. These strategies are implemented in MATLAB/SIMULINK and the performance of the proposed converter is compared under open loop and closed loop operation. From the results, the input current waveform was close to input voltage waveform implying improved power factor and reduced total harmonic distortion for nonlinear current control technique. Experimental results validate the proposed method.

Inductor Losses Estimation in DC-DC Converters by Means of Averaging Technique

A suitable inductor modeling for power electronic DC-DC converters is presented in this paper. It is developed with the aim of improving inductor losses estimation achievable by averaged models, which inherently neglect inductor current ripple. In order to account for its contribution to the overall inductor losses, an appropriate parallel resistance is thus enclosed into the inductor model, whose value should be chosen in accordance with the DC-DC converter operating conditions. This allows the development of improved averaged models of DC-DC converters, especially in terms of power losses estimation. The effectiveness of the proposed modeling approach has been validated through a simulation study, which refers to the case of a boost DC-DC converter and is performed by means of a suitable circuit simulator designed for rapid modelling of switching power systems （SIMetrix/SIMPLIS）.

高精度电压电流转换电路中电流镜校准技术

电流镜输出误差主要由3个不同失配源造成:漏源电压(V_(DS)),阈值电压(V_(th)),跨导系数(β)。其中,第一项V_(DS)失配通常是由有限输出阻抗引起的确定性误差,该误差可以通过使用级联结构以及增益提升技术避免,后两项V_(th)和β失配是由工艺引起的随机性误差。为解决电流镜因工艺失配现象导致的电压电流(Voltage to Current)转换电路精度、线性度较差的问题,提出了一种动态元件匹配(Dynamic Element Match,DEM)以及修调技术(TRIM)相结合的电流镜校准方法,该方法使用TRIM技术将待校准输出电流镜支路和基准电流镜支路之间的误差电流,通过电容与MOS管转换成校准电流后反馈流入待校准输出电流镜支路完成校准,并通过DEM技术切换多条待校准输出电流镜支路完成校准的同时使输出误差平均化。本文采用SMIC 0.18μm BCD工艺对所提出的V-I转换电路进行了电路设计,仿真结果表明,V-I转换电路的输出电流的失配误差从0.12%下降到了0.03%,有效位数ENOB达到了11.2 bit,总谐波失真THD为−72.6 dB。

铜合金海水管路腐蚀防护及检测技术研究现状

介绍了铜及铜合金海水管路腐蚀的研究进展,并指出铜合金海水管路的腐蚀特征,进而分析适用于海水管路的腐蚀防护技术,并介绍海水管路腐蚀检测与评估的方法,为海水管路的腐蚀防护提供参考。

1 A/mm高电流密度金刚石微波功率器件

基于自对准栅电极制备技术,研制了具有低导通电阻和高电流密度的氢终端金刚石微波功率器件。采用高功函数金属Au与氢终端金刚石实现了良好的欧姆接触,接触电阻为0.73Ω·mm。得益于较低的源漏串联电阻和低损伤Al2O3栅介质原子层沉积工艺,金刚石微波器件的导通电阻低至4Ω·mm,饱和电流密度达1.01 A/mm,最大跨导为213 mS/mm,最大振荡频率达58 GHz。研究了该器件在2 GHz和10 GHz频率下连续波功率输出特性,发现在15 V低工作电压下即可分别实现1.56 W/mm和1.12 W/mm的输出功率密度,展现出自对准技术在研制高电流和高输出功率金刚石微波器件上的潜力。

无镁诱导仓鼠原代皮质神经元电生理学特性

目的无镁细胞外液建立癫痫放电模型,利用全细胞膜片钳技术,检测仓鼠原代皮质神经元的电生理学特性。方法采用生后1~2 d新生叙利亚仓鼠,分离大脑皮质培养原代神经元培养至第12天,分别予有镁细胞外液(有镁组)和无镁细胞外液(无镁组)孵育3 h,3 h后均更换为正常孵育液继续培养24 h。利用全细胞膜片钳技术,电压钳模式下记录神经元兴奋性突触后电流(excitatory postsynaptic currents,EPSC),电流钳模式下记录神经元兴奋性突触后电位(excitatory postsynaptic potentials,EPSP)。结果与有镁组相比,无镁组仓鼠原代皮质神经元EPSC[(124.38±75.15)Hz vs.(33.93±22.32)Hz,P<0.001]及EPSP[(37.05±38.37)Hz vs.(5.63±9.52)Hz,P<0.01]的频率升高,且差异有统计学意义;而两组之间EPSC及EPSP的振幅、曲线下面积和半宽度的差异无统计学意义(P>0.05)。结论无镁处理后仓鼠原代皮质神经元兴奋性升高,仓鼠原代皮质神经元可用于构建癫痫细胞模型。

载流滑动摩擦部件表面失效及其修复技术研究进展

滑动电接触部件在电能传递与转换过程中起着举足轻重的作用,其失效和损伤行为带来的安全因素和经济影响重大,因此对其失效机理和修复技术的研究成为当今热点之一.已有众多学者通过试验和计算机模拟仿真等手段研究了电接触部件的表面损伤机制和寿命预测,至今为止,已研究出载流摩擦部件的表面修复技术多达15种以上,修复材料更是有上百种.本文中首先介绍了电接触的基本概念,从有无电流载入2个角度概述了滑动摩擦部件表面失效形式,并从试验研究及仿真模拟研究2个方面对表面损伤机制的研究方法进行了归纳;最后综述了滑动电接触失效部件的表面修复技术和修复材料体系的研究进展,总结了目前滑动电接触部件研究领域存在的问题,提出了利用试验与仿真模拟相结合探究涂层导电耐磨自润滑机理并优化涂层质量的研究思路.

锂离子电池用PET-Cu复合集流体拉伸性能研究

随着锂离子电池技术的不断发展,复合集流体因其具有显著提升电池能量密度和安全性高等优势而引起了产业界的广泛关注。而复合集流体的力学性能可靠性是保证其安全服役的前提,为此,本文针对商业用聚对苯二甲酸乙二醇酯-铜(PET-Cu)复合集流体的拉伸性能开展了系统性的研究。利用扫描电镜、激光共聚焦显微镜、X射线衍射等技术手段对复合集流体材料的表面形貌、微观结构及拉伸断裂行为进行了表征与分析。借助有限元模拟分析了不同几何形状试样在拉伸过程中的应力分布状态;通过数字图像相关技术辅助的拉伸实验研究了取样方向、应变速率及试样几何尺寸对PET-Cu复合集流体拉伸性能的影响规律,并对其应变测量进行了校正。结果表明,采用狗骨状试样并进行应变校正可以更准确地评估复合集流体的拉伸性能;PET-Cu复合集流体的拉伸性能表现出试样取样方向相关性和应变速率敏感性。此外,PET-Cu复合集流体的断裂伸长率表现出明显的试样几何尺寸效应,通过引入几何尺寸系数K可以对不同尺寸的试样拉伸性能进行合理的预测。本研究为聚合物复合集流体实际应用提供了理论依据与可靠性的论证,也为相关试验标准的建立提供了参考,有望推动高性能锂离子电池的开发。

不同扫描体位和定位像方向对单髋关节CT图像及辐射剂量影响

在自动管电流调制(ATCM)技术下,探讨不同扫描体位及定位像方向在单髋关节CT中对图像和辐射剂量的影响。将120例进行单髋关节CT检查患者随机分为4组。A组常规扫描以身体正中线作矢状垂直定位线,定位像前后位+左侧位,扫描视野选择大体型,其余三组以患侧髋关节为中心的等中心扫描,扫描视野均选择小体型,其中B组定位像采用前后位+X线管靠近身体长轴的侧位像;C组采用前后位+X线管远离身体长轴的侧位像;D组仅采用前后位。比较4组患者的容积CT剂量指数(CTDIvol)、剂量长度乘积(DLP),同时测量并计算图像客观噪声、信噪比(SNR)、对比信噪比(CNR),评估图像主观噪声、条纹伪影及诊断信心度。结果显示4组间客观噪声、SNR、CNR、CTDIvol、DLP的差异具有统计学意义(P<0.01),组间比较显示,C与D组各项的差异无统计学意义(均P>0.05),其余组间比较各项的差异具有统计学意义(P<0.01),C、D组辐射剂量整体降低16%~35%;4组图像在主观噪声、条纹伪影及诊断信心度上的差异无统计学意义(P>0.05)。在基于最后一次采集定位像信息的ATCM系统中进行单髋关节CT扫描时,推荐等中心扫描方案同时选择小体型扫描视野,将前后定位像或选择X线管远离身体长轴的侧位定位像作为最后一次执行计划,能保证图像质量同时进一步优化辐射剂量。

关节松动联合干扰电疗法对膝骨关节炎患者功能恢复的影响

以18名膝骨关节炎患者为研究对象,观察关节松动联合干扰电疗法治疗膝骨关节炎的临床疗效.4周治疗结果显示,关节松动联合干扰电疗法明显改善患者的疼痛,增大膝关节活动范围,提高行走和日常生活活动能力,比单纯关节松动治疗的疗效更好.

奶山羊繁殖存在问题与技术应用前瞻

陕西作为我国奶山羊养殖的核心区域,其特色产业不仅承载着农民增收的希望,更是乡村振兴的坚实支柱。近年来奶山羊产业发展受到各级政府的高度重视,但奶山羊产奶量低一直是产业发展的重要制约因素。面对奶山羊产奶量低这一长期困扰产业发展的瓶颈,政府及科研机构正积极行动,聚焦奶山羊繁殖难题,深入探索现代繁殖技术的创新应用。本文围绕奶山羊繁殖问题进行探究,通过现代繁殖技术进一步提升奶山羊生产水平,以期加快奶山羊良种化进程,为陕西乃至全国的奶山羊产业注入强劲动力,助力乡村振兴战略深入实施。

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。

浅析建筑电气智能化弱电工程施工技术

在各类建筑建设过程中,电气工程中的弱电工程是一项重要的建设内容。在电气工程智能化弱电工程施工过程中,涉及诸多复杂的施工技术,具有专业性强、施工难度大等特点。在实际施工过程中,还需要全面分析电气智能化弱电工程的特点和施工需求,把握施工要点,保障施工质量。基于此,本文对建筑电气智能化弱电工程施工的基本内容和特点进行简要介绍,从施工前的准备工作与线路安装施工、各类设备的安装等方面,分析弱电工程施工中涉及的技术问题。

黑龙江省湿地的现状以及湿地监测技术研究

通过湿地监测实验对黑龙江省湿地数据采集和分析,了解黑龙江省湿地的现状,包括湿地的类型、分布和生态功能以及湿地保护的现状,并对分析结果进行讨论;研究远程感应监测技术、GIS技术以及生物监测技术在湿地监测中的应用;探讨生态修复技术、法律政策保护措施和湿地科普教育推广等湿地保护技术措施及策略,展望未来湿地保护的研究方向,对黑龙江省湿地保护工作提供重要的参考。

不同参数电沉积混凝土抗微生物腐蚀性能研究

针对污水管道混凝土结构受微生物腐蚀问题,利用电化学技术将铜复合物沉积到混凝土表面,赋予其抗腐蚀性;通过电沉积试验、微生物抑制试验,使用平板菌落计数法,分析沉积时间和电流密度对复合铜膜沉积效果和混凝土抑菌性能的影响。结果表明,混凝土经过电沉积技术处理具有良好的杀菌能力,样本抑菌率均超过70%。抑菌效果随沉积时间及电流密度的增加而提升,当电流密度为5 A/m^(2)、沉积时间为5 d时试件的抑菌率可达89.5%。