一种基于传输线阻抗变换理论的土壤水分测量仪

土壤含水量的快速、准确测量问题由于其特有的复杂性至今尚未得到圆满的解决。将微波传输线阻抗变换理论应用于土壤水分测量,据此理论提出的测量方案从数学上证明其可行,所设计出的便携式土壤水分测量仪不仅成本低,而且测量精度满足使用要求。     

基于超声多重反射法测量高衰减流体媒质声阻抗及浓度

利用超声波在固(钢)液界面处声阻抗差异导致的多重反射回波,该文建立了测量被测流体媒质声阻抗及浓度的测量系统.用该系统测量了甲醇、乙醇、蒸馏水和丙三醇4种媒质的声阻抗,与标准值相比,发现测量的误差随被测媒质阻抗增加而迅速减小;同时用系统测量了CaCl2溶液的声阻抗,结果表明溶液阻抗与浓度呈显著线性关系,最大拟合误差小于2.7 g/L.检测中,由于无需声波穿透被测媒质,此法尤其适合于工业中测定管道、容器内高衰减媒质的阻抗及浓度.     

Image reconstruction of electrical impedance tomography based on particle swarm optimization algorithm

Electrical impedance tomography (EIT) has many advantages in practical application,but image reconstruction of EIT is a highly ill-posed, non-linear inverse problem. Newton-Raphson algorithms are widely used in EIT, which have to calculate the Jacobian matrix and use regularization techniques. So this kind of algorithms is complex and less stable. To address the problem, a new static image reconstruction method for EIT is proposed based on particle swarm optimization (PSO) algorithm. PSO is a population-based, adaptive search optimization technique. It is simple in concept, few in parameters, quick in convergence and easy in implementation. The model of EIT forward problem is given and some appropriate improvements in PSO are made to accommodate the solution of EIT. Compared with Newton-Raphson(MNR) algorithms, PSO only uses an iterative processing to get the best solution instead of using a complicated Jacobian matrix. The experimental results indicate that using PSO-based algorithm to solve image reconstruction of EIT, the position of mutation region is more accurate and graphics space resolution is much higher.     

基于交流阻抗法的小麦秸秆含水率检测仪设计

为了给秸秆含水率的检测提供廉价、便捷的检测仪,该文基于交流阻抗法设计了以单片机为控制器,能够检测阻抗、温度和压力的小麦秸秆含水率检测仪。建立了阻抗与小麦秸秆的湿基含水率（10.4%～19.7%）、温度（5～40℃）和容积密度（75.3～101.3 kg/m3）的三元三次关系模型,分析了各因素对模型影响的显著性,指出容积密度对模型影响不显著。进而建立了阻抗与湿基含水率和温度的二元三次模型;验证了模型的可靠性以及基于阻抗和温度预测秸秆含水率的精度。与烘干法相比,该文所设计的小麦秸秆含水率检测仪对于含水率10%～20%,温度在5～40℃的小麦秸秆含水率的绝对测量误差为-2.0%～0.9%,当单片机的晶振频率为11.0592 MHz时,检测响应时间小于1.5 s。该研究为小麦秸秆含水率的快速、现场检测提供了一种装置。     

B染色体组短臂对丰、缺氮下小麦幼苗干物质积累和氮效率的影响

以中国春(CS)及其B染色体组双端体(1BL~7BL)为材料,研究了丰、缺氮条件下小麦B染色体组短臂对小麦植株干重和氮效率的影响。结果表明:与CS相比,3BL和7BL端体,3BL、4BL和5BL端体分别在丰、缺氮条件下表现出幼苗长势变差、单株干重降低等特征,这些特征可能与端体相应短臂的缺失有关;同时,丰氮下4BL、5BL和7BL及缺氮下2BL和7BL的含氮量分别较CS显著降低,丰氮下3BL、4BL和7BL及缺氮下2BL的单株氮累积量较CS显著降低,丰、缺氮下供试双端体的氮效率与CS相比无显著差异。表明丰氮下,小麦幼苗氮累积量、株高、单株叶面积、单株地上部干重和单株根干重与单株干重呈显著正相关,缺氮下,单株氮累积量、单株叶面积、单株地上部干重和单株根干重与单株干重呈显著正相关;丰、缺氮下的含氮量与氮效率均呈显著负相关。     

A dual-boost three-phase DC link active power filter based on coupled impedance

A three-phase DC link active power filter (APF)based on coupled impedance and its control strategy are proposed in order to eliminate the input current harmonics of the three-phase diode rectifier. The presented APF is composed of impedance network and two asymmetric dual Boost converters. Average current control is adopted to control the DC link APF. The switch signals of the two asymmetric Boost converters are obtained respectively by leading and trailing edge modulation methods. Compared with the normal DC link active power filter,this topology reduces an active switch and a capacitance. So it can reduce costs,and there is no voltage imbalance in the DC link. Simulation results verify the correctness of the proposed topology and the corresponding control method.     

Cardiopulmonary effects of a new inspiratory impedance threshold device in anesthetized hypotensive dogs

ObjectiveTo compare the hemodynamic and respiratory effects of an inspiratory impedance threshold device (ITD) in anesthetized normotensive and hypotensive dogs.Study designProspective randomized study.AnimalsTen adult dogs.MethodsDogs were anesthetized with propofol followed by isoflurane. During spontaneous ventilation, tidal volume ( $\dot{\mathrm{V}}$), systolic (SAP), mean (MAP) and diastolic arterial blood pressure, central venous pressure, gastric PCO₂ as an indicator of gastric perfusion, subcutaneous oxygen tension, subcutaneous blood flow, cardiac index (CI), systemic vascular resistance and blood lactate were monitored. To monitor respiratory compliance (RC) and resistance (ResR), animals were briefly placed on mechanical ventilation. Dogs were studied under four different conditions: 1) normotension (MAP > 60 mmHg) with and without the ITD and 2) hypotension (target MAP = 40 mmHg) with and without ITD. These four conditions were performed during one anesthetic period, allowing for stabilization of parameters for each condition. Data were analyzed by anova repeated measure mixed models.ResultsNo cardiovascular changes were detected between no ITD and ITD in the normotensive state. During hypotension, CI was higher with the ITD (5 ± 1.0 L minute^?1 m^?2) compared with no ITD (4 ± 1.3 L minute^?1 m^?2). During hypotension, SAP was increased with ITD (80 ± 14 mmHg) versus without ITD (67 ± 13 mmHg). There was an increase in ResR and decreased RC with the ITD in both normotensive and hypotensive state.Conclusion and clinical relevanceImpedance threshold device in dogs during isoflurane-induced hypotension improved CI and SAP but had negative effects on RC and ResR.     

切花菊耐热性鉴定方法研究

以8个切花菊品种为材料,通过对离体叶片进行50℃高温胁迫后,采用电导法、电阻抗图谱法测定电导率、电阻,并对大田栽培植株进行田间高温胁迫试验,比较品种间的耐热性。结果表明:电导法测得的50℃直接相对电导率、修正相对电导率和电阻抗图谱法测得的胞外电阻在品种间有明显差异,但与田间高温胁迫法测定的热害指数不完全一致。电导法和电阻抗图谱法都可以作为测定切花菊耐热性的方法,但需要结合田间耐热性观察。     

盐碱地区不同观赏树种电阻抗图谱参数和电导率的变化

在盐碱地区对4-6月生长期的两种不同观赏树种垂榆（Ulmus pumila var. pendula）和女贞（Ligustrum lucidum）进行电导率及电阻抗测定,分析春季和初夏生长期间在盐碱地区这两种不同观赏树种电导率和电阻抗图谱参数的变化。结果表明：在自然的盐碱环境条件下生长的垂榆和女贞,随着生长期的延长其电导率和电阻抗图谱参数均出现规律性变化,垂榆和女贞的叶片电导率均表现为先增加、后减小的变化趋势,茎均表现为先减小、后增加的变化趋势;两种观赏树种叶片的胞外电阻率表现为先增加、后减小的变化趋势,茎的胞外电阻率和弛豫时间表现为不断增加或先增加、后减小的变化趋势。相关分析表明应用电阻抗图谱参数可以表征观赏树种受盐胁迫的程度,为垂榆和女贞耐盐碱程度的电阻抗诊断提供初步的参数。