Mendrek, M. J.; Higgins, R. H.; Danford, M. D.
1988-01-01
To investigate metal surface corrosion and the breakdown of metal protective coatings, the ac impedance method is applied to six systems of primer coated and primer topcoated 4130 steel. Two primers were used: a zinc-rich epoxy primer and a red lead oxide epoxy primer. The epoxy-polyamine topcoat was used in four of the systems. The EG and G-PARC Model 368 ac impedance measurement system, along with dc measurements with the same system using the polarization resistance method, were used to monitor changing properties of coated 4230 steel disks immersed in 3.5 percent NaCl solutions buffered at pH 5.4 over periods of 40 to 60 days. The corrosion system can be represented by an electronic analog called an equivalent circuit consisting of resistors and capacitors in specific arrangements. This equivalent circuit parallels the impedance behavior of the corrosion system during a frequency scan. Values for the resistors and capacitors, that can be assigned in the equivalent circuit following a least-squares analysis of the data, describe changes that occur on the corroding metal surface and in the protective coatings. Two equivalent circuits have been determined that predict the correct Bode phase and magnitude of the experimental sample at different immersion times. The dc corrosion current density data are related to equivalent circuit element parameters. Methods for determining corrosion rate with ac impedance parameters are verified by the dc method.
Grid impedance estimation based hybrid islanding detection method for AC microgrids
DEFF Research Database (Denmark)
Ghzaiel, Walid; Jebali-Ben Ghorbal, Manel; Slama-Belkhodja, Ilhem;
2017-01-01
This paper focuses on a hybrid islanding detection algorithm for parallel-inverters-based microgrids. The proposed algorithm is implemented on the unit ensuring the control of the intelligent bypass switch connecting or disconnecting the microgrid from the utility. This method employs a grid impe...... that the resonance excitation is canceled and the resistive and inductive grid impedance parts are estimated. Simulation results are carried out to illustrate the effectiveness of the proposed method....
Alternating current(AC) corrosion analyzed by electrochemical impedance spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Ha, Tae Hyun; Kim, Dae Kyeong; Bae, Jeong Hyo; Lee, Hyun Goo; Lee, Sung Jin [Korea Electrotechnology Research Institute, Changwon (Korea, Republic of)
2002-12-15
So far, many research results on AC corrosion have been reported but each one is not consistent with another. In order to understand the characteristics and factors affecting on AC corrosion, Electrochemical impedance spectroscopy (E.I.S) was used and changes in kinetics and surface properties was analyzed. Generally, E.I.S. test has been used mainly for the diagnosis of the concrete corrosion and coating material. However, considering the outstanding functions of E.I.S. test, it can be adopted as a good method to study AC corrosion. Electrolyte resistance (R{sub sol}), double layer capacitance (C{sub dl}) and polarization resistance (R{sub p}) are the basic circuit elements. Using the model which is consist of these basic elements, various results of E.I.S. test can be interpreted. And through this method the mechanism and characteristics of AC corrosion can be explained
AC Impedance Behaviour of Black Diamond Films
Institute of Scientific and Technical Information of China (English)
Haitao YE; Olivier GAUDIN; Richard B.JACKMAN
2005-01-01
The first measurement of impedance on free-standing diamond films from 0.1 Hz to 10 MHz up to 300℃ were reported. A wide range of chemical vapour deposition (CVD) materials were investigated, but here we concentrate are well fitted to a RC parallel circuit model and the equivalent resistance and capacitance for the diamond films have been estimated using the Zview curve fitting. The results show only one single semicircle response at each temperature measured. It was found that the resistance decreases from 62 MΩ at room temperature to 4 kΩ at300℃, with an activation energy around 0.51 eV. The equivalent capacitance is maintained at the level of 100 pF up to 300℃ suggesting that the diamond grain boundaries are dominating the conduction. At 400℃, the impedance at low frequencies shows a linear tail, which can be explained that the AC polarization of diamond/Au interface occurs.
Equivalent circuit models for ac impedance data analysis
Danford, M. D.
1990-01-01
A least-squares fitting routine has been developed for the analysis of ac impedance data. It has been determined that the checking of the derived equations for a particular circuit with a commercially available electronics circuit program is essential. As a result of the investigation described, three equivalent circuit models were selected for use in the analysis of ac impedance data.
Directory of Open Access Journals (Sweden)
Jan Gimsa
2014-11-01
Full Text Available Lab-on-chip systems (LOCs can be used as in vitro systems for cell culture or manipulation in order to analyze or monitor physiological cell parameters. LOCs may combine microfluidic structures with integrated elements such as piezo-transducers, optical tweezers or electrodes for AC-electrokinetic cell and media manipulations. The wide frequency band (<1 kHz to >1 GHz usable for AC-electrokinetic manipulation and characterization permits avoiding electrochemical electrode processes, undesired cell damage, and provides a choice between different polarization effects that permit a high electric contrast between the cells and the external medium as well as the differentiation between cellular subpopulations according to a variety of parameters. It has been shown that structural polarization effects do not only determine the impedance of cell suspensions and the force effects in AC-electrokinetics but can also be used for the manipulation of media with inhomogeneous temperature distributions. This manuscript considers the interrelations of the impedance of suspensions of cells and AC-electrokinetic single cell effects, such as electroorientation, electrodeformation, dielectrophoresis, electrorotation, and travelling wave (TW dielectrophoresis. Unified models have allowed us to derive new characteristic equations for the impedance of a suspension of spherical cells, TW dielectrophoresis, and TW pumping. A critical review of the working principles of electro-osmotic, TW and electrothermal micropumps shows the superiority of the electrothermal pumps. Finally, examples are shown for LOC elements that can be produced as metallic structures on glass chips, which may form the bottom plate for self-sealing microfluidic systems. The structures can be used for cell characterization and manipulation but also to realize micropumps or sensors for pH, metabolites, cell-adhesion, etc.
Energy Technology Data Exchange (ETDEWEB)
Breuer, G D; Chow, J H; Lindh, C B; Miller, N W; Numrich, F H; Price, W W; Turner, A E; Whitney, R R
1982-09-01
Improved methods are needed to characterize ac system harmonic behavior for ac filter design for HVDC systems. The purpose of this General Electric Company RP1138 research is to evaluate the present filter design practice and to investigate methods for calculating system harmonic impedances. An overview of ac filter design for HVDC systems and a survey of literature related to filter design have been performed. Two methods for calculating system harmonic impedances have been investigated. In the measurement method, an instrumentation system for measuring system voltage and current has been assembled. Different schemes of using the measurements to calculate system harmonic impedances have been studied. In the analytical method, a procedure to include various operating conditions has been proposed. Computer programs for both methods have been prepared, and the results of the measurement and analytical methods analyzed. A conclusion of the project is that the measurement and analytical methods both provided reasonable results. There are correlations between the measured and analytical results for most harmonics, although there are discrepancies between the assumptions used in the two methods. A sensitivity approach has been proposed to further correlate the results. From the results of the analysis, it is recommended that both methods should be tested further. For the measurement method, more testing should be done to cover different system operating conditions. In the analytical method, more detailed models for representing system components should be studied. In addition, alternative statistical and sensitivity approaches should be attempted.
Equivalent Circuits For AC-Impedance Analysis Of Corrosion
Danford, M. D.
1992-01-01
Report presents investigation of equivalent circuits for ac-impedance analysis of corrosion. Impedance between specimen and electrolyte measured as function of frequency. Data used to characterize corrosion electrochemical system in terms of equivalent circuit. Eleven resistor/capacitor equivalent-circuit models were analyzed.
Impedance Localization Measurements using AC Dipoles in the LHC
Biancacci, Nicolo; Papotti, Giulia; Persson, Tobias; Salvant, Benoit; Tomás, Rogelio
2016-01-01
The knowledge of the LHC impedance is of primary importance to predict the machine performance and allow for the HL-LHC upgrade. The developed impedance model can be benchmarked with beam measurements in order to assess its validity and limit. This is routinely done, for example, moving the LHC collimator jaws and measuring the induced tune shift. In order to localize possible unknown impedance sources, the variation of phase advance with intensity between beam position monitors can be measured. In this work we will present the impedance localization measurements performed at injection in the LHC using AC dipoles as exciter as well as the underlying theory.
DEFF Research Database (Denmark)
Nielsen, Jimmi; Jacobsen, Torben
2010-01-01
The Finite-Element-Method (FEM) was used for the simulations of the effect of a changing current distribution during AC impedance spectrum recording on electroceramic point contact and thin film model electrodes. For pure electronic conducting point contact electrodes the transition from...... regarding its significance is provided. The associated characteristic impedance spectrum shape change is simulated and its origin discussed. Furthermore, the characteristic shape of impedance spectra of thin electroceramic film electrodes with lateral ohmic resistance is studied as a function...
MD 349: Impedance Localization with AC-dipole
Biancacci, Nicolo; Metral, Elias; Salvant, Benoit; Papotti, Giulia; Persson, Tobias Hakan Bjorn; Tomas Garcia, Rogelio; CERN. Geneva. ATS Department
2016-01-01
The purpose of this MD is to measure the distribution of the transverse impedance of the LHC by observing the phase advance variation with intensity between the machine BPMs. Four injected bunches with different intensities are excited with an AC dipole and the turn by turn data is acquired from the BPM system. Through post-processing analysis the phase variation along the machine is depicted and, from this information, first conclusions of the impedance distribution can be drawn.
AC impedance study of degradation of porous nickel battery electrodes
Lenhart, Stephen J.; Macdonald, D. D.; Pound, B. G.
1987-01-01
AC impedance spectra of porous nickel battery electrodes were recorded periodically during charge/discharge cycling in concentrated KOH solution at various temperatures. A transmission line model (TLM) was adopted to represent the impedance of the porous electrodes, and various model parameters were adjusted in a curve fitting routine to reproduce the experimental impedances. Degradation processes were deduced from changes in model parameters with electrode cycling time. In developing the TLM, impedance spectra of planar (nonporous) electrodes were used to represent the pore wall and backing plate interfacial impedances. These data were measured over a range of potentials and temperatures, and an equivalent circuit model was adopted to represent the planar electrode data. Cyclic voltammetry was used to study the characteristics of the oxygen evolution reaction on planar nickel electrodes during charging, since oxygen evolution can affect battery electrode charging efficiency and ultimately electrode cycle life if the overpotential for oxygen evolution is sufficiently low.
Impedance, AC conductivity and dielectric behavior Adeninium Trichloromercurate (II)
Fersi, M. Amine; Chaabane, I.; Gargouri, M.
2016-09-01
In this work, we report the measurements impedance spectroscopy technique for the organic-inorganic hybrid compound (C5H6N5) HgCl3, 11/2H2O measured in the 209 Hz-5 MHz frequency range from 378 to 428 K. Besides, the Cole-Cole (Z″ versus Z‧) plots were well fitted to an equivalent circuit built up by a parallel combination of resistance (R), fractal capacitance (CPE) and capacitance (C). Furthermore, the AC conductivity was investigated as a function of temperature and frequency in the same range. The experiment results indicated that AC conductivity (σac) was proportional to σdc + A ωS . The obtained results are discussed in terms of the correlated barrier hopping (CBH) model. An agreement between the experimental and theoretical results suggests that the AC conductivity behavior of Adeninium Trichloromercurate (II) can be successfully explained by CBH model. The contribution of single polaron hopping to AC conductivity in a present alloy was also studied.
Detection of electrical properties of soybean milk based on AC impedance method%基于交流阻抗法的豆浆电特性检测
Institute of Scientific and Technical Information of China (English)
宋华鲁; 闫银发; 宋占华; 陈晨; 李法德
2015-01-01
in the impedance of the soybean milk with the frequency, combining with the equivalent circuit model, it was concluded that the frequency of the power for ohmic heating should be in the range from 300 Hz to 300 kHz. The experimental results also showed that the equivalent resistance (R) of soybean milk decreased with the increase in the temperature and the solids content, respectively. By the regression analysis on the data, it was found that the relationship between the equivalent resistance (R) and the temperature could be described by a negative exponential function (the coefficient of determination R2 was 0.996 at the solid content of 9.58%, P<0.01), the relationship between the equivalent resistance (R) and the solid content could be also described by a negative exponential function (the coefficient of determination R2 was 0.992 at 40 °C, P<0.01). The value of Q (one of the parameters for describing the CPE) decreased with the increase in temperature;however, if the solid content of soybean milk was more than 3.5%, the value of Q increased sharply. The value of n (the other parameter for describing the CPE) increased with the increase in temperature, but it did not changed significantly with the solid content (ranged from 1.01%to 9.58%). The results in this research should be taken as a reference for selecting the frequency of the power for designing an ohmic heating system. In addition, the results also founded a method for detecting rapidly soybean milk quality on the analysis of electric parameters of soybean milk.%为实现豆浆品质快速检测和通电加热电源频率的优化，该文利用精密阻抗分析仪和DJS-10电导电极通过50 mV的激励电压在20 Hz～12 MHz频率范围内测量了不同温度（30～85℃）和不同固形物含量（1.01%～9.58%）的豆浆的交流阻抗。试验结果表明，豆浆阻抗模值与阻抗相位角随测量频率变化具有明显规律。豆浆的阻抗特性与温度以及固形物
Nasri, S.; Megdiche, M.; Gargouri, M.
2016-10-01
In this paper, Ag0.6Na0.4FeP2O7 has been synthesized by solid state reaction method. The ceramic compound was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrational spectroscopy and impedance measurements. In fact, the investigated sample has shown single phase type monoclinic structure with P21/C space group. The frequency-dependent electrical data are analyzed in the frame-work of conductivity and electric modulus formalisms. The real and imaginary parts of complex impedance are well fitted to equivalent circuit model based on the Z-View-software. Besides, the observed frequency dependence of conductivity is found to obey Jonscher's universal law. The temperature dependence of both ac conductivity and the parameter s is reasonably well interpreted by the correlated barrier hopping (CBH). The theoretical fitting between the proposed model and the experimental data showed good agreement. The contribution of single polaron and bipolaron hopping to a.c. conductivity in present compound is also studied. The ionic conductivity is discussed on the basis of the structural characteristics of the sample.
AC impedance spectroscopy on copper phthalocyanine thin films
Robinson, Kyle P.
Impedance spectroscopy is used to study copper phthalocyanine thin films in order to disentangle the contributions of the crystal and the unavoidable grain boundaries. The spectroscopy data is fit with an equivalent circuit model to determine resistance, capacitance, and activation energy for different grain morphologies. The copper phthalocyanine thin films are deposited via thermal evaporation on platinum interdigitated electrodes on glass substrates at different temperatures from 300 to 530 K with constant thickness of 22 nm. AC measurements, implementing a precision LCR meter are taken from 20Hz - 2 MHz, and at measurement temperatures from 25 - 90 °C. Stabilizing current by subjecting samples to 5 days in the dark, the impedance spectrum can be represented by Cole-Cole plots, which show either one or two peaks. The two maxima may be attributed to the crystalline bulk and grain boundaries of the film. We observe that the grain boundary resistance component changes by three orders of magnitude when varying the grain morphology, and the capacitance changes by one order of magnitude. The resistance of the grain boundary shows a minimum near the phase transition temperature of 450 K, followed by an increase in resistance for samples deposited at higher temperatures. The capacitance on the other hand, shows a maximum near the phase transition temperature. Similarly, the activation energy for the grain boundary peaks at 1.29 +/- 0.12 eV at the same phase-transition tempemture, whereas the crystalline bulk component has a constant activation energy of 0.36 +/- 0.08 eV for all sample of different grain sizes. Additional data taken using a perpendicular configuration for a 30 nm thick cobalt phthalocyanine thin film shows a double peak. The low temperature measurements for these samples are interpreted to have two contributions from micro-shorts and crystalline bulk.
Richardson, John G.
2009-11-17
An impedance estimation method includes measuring three or more impedances of an object having a periphery using three or more probes coupled to the periphery. The three or more impedance measurements are made at a first frequency. Three or more additional impedance measurements of the object are made using the three or more probes. The three or more additional impedance measurements are made at a second frequency different from the first frequency. An impedance of the object at a point within the periphery is estimated based on the impedance measurements and the additional impedance measurements.
DEFF Research Database (Denmark)
Li, Chendan; Chaudhary, Sanjay Kumar; Savaghebi, Mehdi
2017-01-01
adequate power flow studies. In this paper, power flow analyses for both AC and DC microgrids are formulated and implemented. The mathematical models for both types of microgrids considering the concept of virtual impedance are used to be in conformity with the practical control of the distributed...... generators. As a result, calculation accuracy is improved for both AC and DC microgrid power flow analyses, comparing with previous methods without considering virtual impedance. Case studies are conducted to verify the proposed power flow analyses in terms of convergence and accuracy. Investigation...
Power flow analysis for droop controlled LV hybrid AC-DC microgrids with virtual impedance
DEFF Research Database (Denmark)
Li, Chendan; Chaudhary, Sanjay; Vasquez, Juan Carlos
2014-01-01
The AC-DC hybrid microgrid is an effective form of utilizing different energy resources and the analysis of this system requires a proper power flow algorithm. This paper proposes a suitable power flow algorithm for LV hybrid AC-DC microgrid based on droop control and virtual impedance. Droop...... and virtual impedance concepts for AC network, DC network and interlinking converter are reviewed so as to model it in the power flow analysis. The validation of the algorithm is verified by comparing it with steady state results from detailed time domain simulation. The effectiveness of the proposed...
New Regularization Method in Electrical Impedance Tomography
Institute of Scientific and Technical Information of China (English)
侯卫东; 莫玉龙
2002-01-01
Image reconstruction in elecrical impedance tomography(EIT)is a highly ill-posed inverse problem,Regularization techniques must be used in order to solve the problem,In this paper,a new regularization method based on the spatial filtering theory is proposed.The new regularized reconstruction for EIT is independent of the estimation of impedance distribution,so it can be implemented more easily than the maxiumum a posteriori(MAP) method.The regularization level in our proposed method varies spatially so as to be suited to the correlation character of the object's impedance distribution.We implemented our regularization method with two dimensional computer simulations.The experimental results indicate that the quality of the reconstructed impedance images with the descibed regularization method based on spatial filtering theory is better than that with Tikhonov method.
基于交流阻抗法的离子交换膜电阻研究%Study on conductivity of ion exchange membranes with AC impedance method
Institute of Scientific and Technical Information of China (English)
范永生; 陈晓; 王保国
2011-01-01
Using AC impedance measurement, this study proposed a method to investigate ion exchange membrane area resistances; a two-polar cell holds membrane immersed in electrolyte solution, area resistance was determined by the difference of electricity resistance measured with or without a membrane The error can be minimized by using a parallel electricity resistance.This method was proofed reliable and effective by measuring area resistances of a cation or an anion exchange membranes in electrolyte solution,including aqueous sulfuric acid, sodium chloride, and the real electrolyte used in vanadium redox flow battery(VRB).The measured results revealed the various adsorption behaviors of cation and anion exchange membranes, and showed membrane area resistance dependence upon electrolyte solution concentration.This study will facilitate the development of ion exchange membranes and its application in renewable energy technology.%利用交流阻抗谱测定技术,建立一种离子交换膜导电性能评价方法;使用两极室槽电解池,分别测得电解质溶液,以及膜和电解质溶液之和的电阻值,相减后得到离子交换膜在该电解液中的电阻值.通过并联电阻形成完整的半圆弧形交流阻抗谱,能够有效减小测量误差.利用硫酸水溶液体系、氯化钠水溶液体系,以及全钒液流电池的钒电解液体系验证基于交流阻抗谱的膜电阻测定技术准确性、实用性.在此基础上揭示阳离子交换膜、阴离子交换膜对离子的不同吸附特性,以及膜面电阻对电解质溶液浓度依存特性.研究结果对于发展离子交换膜快速表征技术,以及开发新能源领域的离子交换膜具有重要价值.
Asymmetrical magneto-impedance in a sandwich film with a transverse anisotropy using an AC bias
Makhnovskiy, D P; Mapps, D J
2000-01-01
A new method of obtaining asymmetrical magneto-impedance in a film system consisting of two outer magnetic layers and an inner conductive lead is proposed, which utilizes a high-frequency longitudinal bias field. For a certain magnetic structure, as in the case of antisymmetrical transverse magnetization in the outer layers, in the presence of a longitudinal DC magnetic field H sub e sub x the AC bias field induces a high-frequency circulatory magnetization which contributes to the voltage measured across the film. Depending on the sign of H sub e sub x , this voltage is in phase or counter-phase with that induced by the current flowing along the film layers. As a result, the total voltage does not respond in the same way to positive and negative H sub e sub x. This process is described in terms of the surface impedance tensor. The contribution to the voltage due to the current and the bias field is given by the diagonal and off-diagonal components of this tensor, respectively, which have a different symmetry...
AC impedance studies on LiFe{sub 5-x}Mn{sub x}O{sub 8} ferrites
Energy Technology Data Exchange (ETDEWEB)
Ramesh, B., E-mail: bramesh9@rediffmail.com [Department of Physics, Osmania University, Hyderabad, A.P. (India); Ramesh, S.; Kumar, R. Vijaya; Lakshmipathi Rao, M. [Department of Physics, Osmania University, Hyderabad, A.P. (India)
2012-02-05
Highlights: Black-Right-Pointing-Pointer The materials were prepared by sol-gel method and single phase formation was conformed. Black-Right-Pointing-Pointer Z Prime and Z Double-Prime magnitude decrease with increasing temperature. Black-Right-Pointing-Pointer Relaxation time of the prepared samples varies linearly with temperature Black-Right-Pointing-Pointer The cole-cole impedance plots of the present investigation clearly shows an interesting phenomenon involved in the conduction mechanism of the samples. - Abstract: A systematic investigation of AC impedance studies of Mn doped Lithium ferrites with composition formula, LiFe{sub 5-x}Mn{sub x}O{sub 8} (x = 0.0, 0.2, 0.4, and 0.6) has been undertaken. The materials were prepared by sol-gel method. Complex impedance data measured in the frequency range 200 Hz to 1 MHz at different temperatures was analyzed systematically. It has been observed that the magnitudes of real (Z Prime ) and imaginary (Z Double-Prime ) components of the impedance are found to decrease with increasing temperature. It is interesting to note that the relaxation time varies linearly with temperature. The Nyquist impedance plots of the present investigation clearly depicts the inherent phenomenon involved in conduction mechanism of Mn doped Lithium ferrites.
AC Impedance Studies on Metal/Nanoporous Silicon/p-Silicon Structures
Mabrook, M. F.; Ray, A. K.
2016-11-01
Alternating current (AC) impedance measurements have been performed on 10- to 15-μm thick porous silicon layers on a (100) p-type silicon (p(+)Si) substrate with the aluminium (Al) top electrode in a sandwich configuration in the range of 20 Hz-1 MHz and in the temperature ranging between 152 K and 292 K. The ac conductivity σ ac was found to increase with frequency f according to the universal power law: σ_{ac} = Afs where the exponent s is a frequency and temperature-dependent quantity. A hopping process is found to be dominant at low temperatures and high frequencies, while a thermally activated free band process is responsible for conduction at higher temperatures. Capacitance is found to decrease with frequency but increase with temperature. Frequency dependence of the loss tangent is observed with a temperature-dependent minimum value.
Virtual Impedance Based Fault Current Limiters for Inverter Dominated AC Microgrids
DEFF Research Database (Denmark)
Lu, Xiaonan; Wang, Jianhui; Guerrero, Josep M.
2017-01-01
virtual impedance control loops. The proposed VI-FCL features flexible and low-cost implementation and can effectively suppress the fault current and the oscillation in the following fault restoration process in AC microgrids. The systematic model of the inverter dominated AC microgrid is derived......In this paper, a virtual impedance based fault current limiter (VI-FCL) is proposed for islanded microgrids comprised of multiple inverter interfaced distributed generators (DGs). Considering the increased fault current capability induced by high penetration of renewable energy sources (RESs), FCLs...... are employed to suppress the fault current and the subsequent oscillation and even instability in the modern distribution network with microgrids. In this study, rather than involving extra hardware equipment, the functionality of FCL is achieved in the control diagram of DG inverters by employing additional...
Laser Raman and ac impedance spectroscopic studies of PVA: NH4NO3 polymer electrolyte.
Hema, M; Selvasekarapandian, S; Hirankumar, G; Sakunthala, A; Arunkumar, D; Nithya, H
2010-01-01
Ion conducting polymer electrolyte PVA:NH(4)NO(3) has been prepared by solution casting technique and characterized using XRD, Raman and ac impedance spectroscopic analyses. The amorphous nature of the polymer films has been confirmed by XRD and Raman spectroscopy. An insight into the deconvoluted Raman peaks of upsilon(1) vibration of NO(3)(-) anion for the polymer electrolyte reveals the dominancy of ion aggregates at higher NH(4)NO(3) concentration. From the ac impedance studies, the highest ion conductivity at 303 K has been found to be 7.5x10(-3)Scm(-1) for 80PVA:20NH(4)NO(3). The conductivity of the polymer electrolytes has been found to depend on the degree of dissociation of the salt in the host polymer matrix. The combination of the above-mentioned analyses has proven worth while and in fact necessary in order to achieve better understanding of these complex systems.
Institute of Scientific and Technical Information of China (English)
KONG Lijuan; HOU Lirong; WANG Yuhua; SUN Guowen
2016-01-01
Three different types and sizes of coarse aggregate were chosen, and the alternating current (AC) impedance of cement paste samples with and without aggregate was measured at different curing ages. Based on Song’s equivalent circuit model, the electrical properties from the AC impedance results were obtained, and the resistance of connected pores RCCP was used to characterize the microstructure of the interfacial transition zone (ITZ). The results show that the RCCP of concrete sample with aggregate is lower than that of cement paste sample, which indicates that the introduction of aggregate in cement paste makes the ITZ porous. Furthermore, for the same type of aggregate, an increase in particle size leads to a more porous ITZ, which accounts for the “water effect” and a larger aggregate would accumulate a thicker water iflm around it. In addition, for the same size of aggregate, the physical interaction between aggregate and cement paste is dominant in early age, and the microstructure of the ITZ around limestone aggregate is denser, which mainly depends on its rough surface and high water absorption. However, the microstructures of the ITZ around granite and basalt aggregates are denser in later age, which may be due to their higher chemical activity, and the chemical interaction between them and cement paste resulting in the generation of more hydrates. AC impedance spectroscopy thus proves to be powerful for evaluation of the microstructure of the ITZ.
An Impedance-Based Stability Analysis Method for Paralleled Voltage Source Converters
DEFF Research Database (Denmark)
Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang
2014-01-01
This paper analyses the stability of paralleled voltage source converters in AC distributed power systems. An impedance-based stability analysis method is presented based on the Nyquist criterion for multiloop system. Instead of deriving the impedance ratio as usual, the system stability...... is assessed based on a series of Nyquist diagrams drawn for the terminal impedance of each converter. Thus, the effect of the right half-plane zeros of terminal impedances in the derivation of impedance ratio for paralleled source-source converters is avoided. The interaction between the terminal impedance...... of converter and the passive network can also be predicted by the Nyquist diagrams. This method is applied to evaluate the current and voltage controller interactions of converters in both grid-connected and islanded operations. Simulations and experimental results verify the effectiveness of theoretical...
Effect of temperature on the AC impedance of protein and carbohydrate biopolymers
Indian Academy of Sciences (India)
S Muthulakshmi; S Iyyapushpam; D Pathinettam Padiyan
2014-12-01
The influence of temperature on the electrical behaviour of protein biopolymer papain and carbohydrate biopolymers like gum acacia, gum tragacanth and guar gum has been investigated using AC impedance technique. The observed semi-circles represent the material’s bulk electrical property that indicate the single relaxation process in the biopolymers. An increase in bulk electrical conductivity in the biopolymers with temperature is due to the hopping of charge carriers between the trapped sites. The depression parameter reveals the electrical equivalent circuit for the biopolymers. The AC electrical conductivity in the biopolymers follows the universal power law. From this, it is observed that the AC conductivity is frequency dependent and the biopolymer papain obeys large polaron tunnelling model, gum acacia and gum guar obey ion or electron tunnelling model, and gum tragacanth obeys the correlated barrier hopping model of conduction mechanisms.
Method for conducting nonlinear electrochemical impedance spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Adler, Stuart B.; Wilson, Jamie R.; Huff, Shawn L.; Schwartz, Daniel T.
2015-06-02
A method for conducting nonlinear electrochemical impedance spectroscopy. The method includes quantifying the nonlinear response of an electrochemical system by measuring higher-order current or voltage harmonics generated by moderate-amplitude sinusoidal current or voltage perturbations. The method involves acquisition of the response signal followed by time apodization and fast Fourier transformation of the data into the frequency domain, where the magnitude and phase of each harmonic signal can be readily quantified. The method can be implemented on a computer as a software program.
Poly Meta-Aminophenol: Chemical Synthesis, Characterization and Ac Impedance Study
Directory of Open Access Journals (Sweden)
Thenmozhi Gopalasamy
2014-01-01
Full Text Available The present work is an investigation of AC impedance behaviour of poly(meta-aminophenol. The polymer was prepared by oxidative chemical polymerization of meta-aminophenol in aqueous HCl using ammonium persulfate as an oxidant at 0–3°C. The synthesized polymer was characterized by GPC, Elemental analysis, UV-VIS-NIR, FT-IR, 1H NMR, XRD, SEM, and TGA-DTA. The AC conductivity and dielectric response were measured at a temperature range from 303 to 383 K in the frequency range of 20 Hz to 106 Hz. The AC conductivity data could be described by the relation σacω=AωS, where the parameter “S” and Rb values decrease in the entire range of study and hence follow Correlated Barrier Hopping conduction mechanism. Both dielectric constant and dielectric loss increase with the decrease of frequency exhibiting strong interfacial polarization at low frequency and the dissipation factor also decreases with frequency. Complex electric modulus and dissipation factor exhibit two relaxation peaks, indicating two-phase structure as indicated by a bimodal distribution of relaxation process. The activation energies corresponding to these two relaxation processes were found to be 0.07 and 0.1 eV.
Study of metal corrosion using ac impedance techniques in the STS launch environment
Calle, Luz M.
1989-01-01
AC impedance measurements were performed to investigate the corrosion resistance of 19 alloys under conditions similar to the STS launch environment. The alloys were: Zirconium 702, Hastelloy C-22, Inconel 625, Hastelloy C-276, Hastelloy C-4, Inconel 600, 7Mo + N, Ferralium 255, Inco Alloy G-3, 20Cb-3, SS 904L, Inconel 825, SS 304LN, SS 316L, SS 317L, ES 2205, SS 304L, Hastelloy B-2, and Monel 400. AC impedance data were gathered for each alloy after one hour immersion time in each of the following three electrolyte solutions: 3.55 percent NaCl, 3.55 percent NaCl-0.1N HCl, and 3.55 percent NaCl-1.0N HCl. The data were analyzed qualitatively using the Nyquist plot and quantitatively using the Bode plot. Polarization resistance, Rp, values were obtained using the Bode plot. Zirconium 702 was the most corrosion resistant alloy in the three electrolytes. The ordering of the other alloys according the their resistance to corrosion varied as the concentration of hydrochloric acid in the electrolyte increased. The corrosion resistance of Zirconium 702 and Ferralium 255 increased as the concentration of hydrochloric acid in the electrolyte increased. The corrosion resistance of the other 17 alloys decreased as the concentration of the hyrdochloric acid in the electrolyte increased.
Low frequency and low temperature behavior of ZnO-based varistor by ac impedance measurements
Al Abdullah, K.; Bui, A.; Loubiere, A.
1991-04-01
This paper reports on an original work on the study of the behavior of ZnO-based varistor by ac impedance measurements. The measurements of complex impedance response to small ac signals applied to samples have been achieved in the frequency range 10-3-7×106 Hz and a temperature range -196-145 °C. In the temperature range below -120±10 °C, a complete semicircular relaxation phenomenon has been observed, which is in good agreement with the Debye model. In the temperature range above -120±10 °C, the appearance of the depression angle θ may arise from the heterogeneity of the barriers of the ceramic varistor. A Cole-Cole distribution function of the relaxation time constants was used to characterize the response of the ceramic device as a function of temperature. No observable influence in the response was introduced by either the space charge or the electrode. Using the leakage resistance measurements from the complex plane, two values of the activation energies were observed; 0.36±0.02 eV and 0.01±0.001 eV. Similarly, the boundary layer equivalent capacitance measurements detect two other energy levels: 0.06±0.005 eV and about 0 eV.
Gholipur, Reza; Khorshidi, Zahra; Bahari, Ali
2017-03-27
Metamaterials have surprisingly broadened the range of available practical applications in new devices such as shielding, microwave absorbing, and novel antenna. More researches are related to the tuning DNG frequency bands of ordered or disordered metamaterials, and far less research has focused on the importance of impedance matching behavior, and is not effort and attention in adjusting the magnitude of negative permittivity values. This is particularly important if devices deal with low amplitude signals such as radio or TV antenna. The carbon/hafnium nickel oxide (C/Hf0.9Ni0.1Oy) nanocomposites with simultaneously negative permittivity and negative permeability, excellent metamaterial performance and good impedance matching could become an efficient alternative for the ordered metamaterials in wave-transparent, microwave absorbing, and solar energy harvesting fields. In this study, we prepared C/Hf0.9Ni0.1Oy nanocomposites by solvothermal method, and we clarified how the impedance matching and double negative (DNG) behaviors of C/Hf0.9Ni0.1Oy can be tuned by an external AC electric field created by electric quadrupole system. External electric field allows for the alignment of the well-dispersed nanoparticles of carbon with long-range orientations order. We believe that this finding broadens our understanding of moderate conductive material-based random metamaterials (MCMRMs), and provides a novel strategy for replacing high loss ordered or disordered metamaterials with MCMRMs.
Impedance adaptation methods of the piezoelectric energy harvesting
Kim, Hyeoungwoo
In this study, the important issues of energy recovery were addressed and a comprehensive investigation was performed on harvesting electrical power from an ambient mechanical vibration source. Also discussed are the impedance matching methods used to increase the efficiency of energy transfer from the environment to the application. Initially, the mechanical impedance matching method was investigated to increase mechanical energy transferred to the transducer from the environment. This was done by reducing the mechanical impedance such as damping factor and energy reflection ratio. The vibration source and the transducer were modeled by a two-degree-of-freedom dynamic system with mass, spring constant, and damper. The transmissibility employed to show how much mechanical energy that was transferred in this system was affected by the damping ratio and the stiffness of elastic materials. The mechanical impedance of the system was described by electrical system using analogy between the two systems in order to simply the total mechanical impedance. Secondly, the transduction rate of mechanical energy to electrical energy was improved by using a PZT material which has a high figure of merit and a high electromechanical coupling factor for electrical power generation, and a piezoelectric transducer which has a high transduction rate was designed and fabricated. The high g material (g33 = 40 [10-3Vm/N]) was developed to improve the figure of merit of the PZT ceramics. The cymbal composite transducer has been found as a promising structure for piezoelectric energy harvesting under high force at cyclic conditions (10--200 Hz), because it has almost 40 times higher effective strain coefficient than PZT ceramics. The endcap of cymbal also enhances the endurance of the ceramic to sustain ac load along with stress amplification. In addition, a macro fiber composite (MFC) was employed as a strain component because of its flexibility and the high electromechanical coupling
DC current and AC impedance measurements on boron-doped single crystalline diamond films
Energy Technology Data Exchange (ETDEWEB)
Ye, Haitao; Gaudin, O.; Jackman, R.B. [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Muret, P.; Gheeraert, E. [Laboratoire d' Etudes des Proprietes Electroniques des Solides, BP166, 38042 Grenoble Cedex 9 (France)
2003-09-01
In this paper, we report the first measurement of impedance on boron-doped single crystalline diamond films from 0.1 Hz to 10 MHz with the temperature ranging from -100 C up to 300 C. The Cole-Cole (Z' via Z{sup ''}) plots are well fitted to a RC parallel circuit model and the equivalent Resistance and Capacitance for the diamond films have been estimated using the Zview curve fitting. The results show only one single semicircle response at each temperature measured. It was found that the resistance decreases from 70 G{omega} at -100 C to 5 k{omega} at 300 C. The linear curve fitting from -100 C to 150 C shows the sample has an activation energy of 0.37 eV, which is consistent with the theoretical value published of this kind of material. The equivalent capacitance is maintained at the level of pF up to 300 C suggesting that no grain boundaries are being involved, as expected from a single crystal diamond. The activation energy from the dc current-temperature curves is 0.36 eV, which is consistent with the value from ac impedance. The potential of this under-used technique for diamond film analysis will be discussed. (copyright 2003 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Novel method for planar microstrip antenna matching impedance
Ali, Mahdi; Samet, Mounir
2010-01-01
Because all microstrip antennas have to be matched to the standard generator impedance or load, the input impedance matching method for antenna is particularly important. In this paper a new methodology in achieving matching impedance of a planar microstrip antenna for wireless application is described. The method is based on embedding an Interdigital capacitor. The fine results obtained by using a microstrip Interdigital capacitor for matching antenna impedance led to an efficient method to improve array antenna performance. In fact, a substantial saving on the whole surfaces as well as enhancement of the gain, the directivity and the power radiated was achieved.
AC impedance spectroscopy and conductivity studies of Dy doped Bi4V2O11 ceramics
Bag, Sasmitarani; Das, Parthasarathi; Behera, Banarji
2017-03-01
The ac impedance and conductivity properties of Dy doped Bi4V2 - x Dy x O11 (x = 0.05, 0.10, 0.15 and 0.20) ceramics prepared by solid-state reaction technique, in a wide frequency range at different temperatures have been studied. All the samples exhibited β-type phase orthorhombic structure at room temperature. The Nyquist plot confirmed the presence of both grain and grain boundary effects for all Dy doped samples. Double relaxation behavior was also observed. The grain and grain boundary resistance decreases with rise in temperature for all the concentration and exhibits a typical negative temperature co-efficient of resistance (NTCR) behavior. An analysis of the electric modulus suggests the possible hopping mechanism for electrical transport processes of all the materials. The ac conductivity spectrum obeys Jonscher's universal power law. DC conductivity of the materials were also studied and values of the activation energy found to be 0.40, 0.49, 0.73 and 0.78 eV for the compositions x = 0.05, 0.10, 0.15 and 0.20, respectively, at different temperatures (150-375 °C).
A new monitoring method for electrochemical aggregates by impedance spectroscopy
Kurzweil, P.; Fischle, H.-J.
A variant of ac impedance spectroscopy is applied to monitor and control electrochemical cells and appliances without need for reference values and knowledge of control points in advance. Electrolyzers, fuels cells, energy stores, sensors and electrochemical reactors are steered to an optimum operating state by continuous evaluation of capacitance and the derivatives thereof. Dry and humid electrode-electrolyte interfaces are distinguished with the aid of the low-frequency impedance. The problem is solved in order to determine electrolyte concentrations unambiguously from electrolyte resistance, although the conductivity of the solution has a maximum and changes nonlinearly with the concentration.
Energy Technology Data Exchange (ETDEWEB)
Pons, E.; Lemaitre, C.; Crusset, D.; David, D. [Laboratoire Roberval de Mecanique, UMR 6066 du CNRS, Universite de Technologie de Compiegne, BP 20529, F - 60205 Compiegne cedex (France)
2004-07-01
The corrosion of historical objects from World War I fields were studied by using two methods: characterization of the corrosion products by Raman Laser Spectroscopy, and behaviour of the corrosion layers by using electrochemical studies. The first technique, previously used, had shown that two layers are present on these objects, containing both different oxides and oxy-hydroxides of iron. In the present part of the work, the A.C. Impedance Spectroscopy was used to show the differences between the two layers concerning the corrosion of these objects. In order to observe the different behaviours, the specimens were studied in three surface states: with the two layers, with the internal layer only, and without oxide. The results have shown that the internal layer limits the corrosion kinetics. Then this layer was especially studied, particularly its porosity, by a comparison of the impedance results in two media with very different conductivity, and the evolution of these results with different immersion times. The buried objects had the behaviour of a porous electrode, due to the presence of the internal layer. Thus, this behaviour can be modelled with the simplified De Levie's theory, considering that each porosity is a semi-infinite hole. It appeared that the corrosion process at the oxidized interface corresponds to the transport in the electrolyte in the pores completed by a part of transport in the solid phase. These properties can be used to predict the long term corrosion behaviour of carbon steels in soils for long periods. (authors)
Graph-Analytical Method of Determining Impedance in Electrical Transformers
Directory of Open Access Journals (Sweden)
Zorica Bogicevic
2015-01-01
Full Text Available This paper presents a graph-analytical method for determining the electrical impedance of alternate energy sources, especially small power transformers and current transformers in electric networks. Unlike conventional short-circuit and idle tests, according to proposed method, in this paper, transformer parameters are determined in a new way, which is based on measurement of voltages and currents on the active and reactive load (inductive or capacitive. The effectiveness of the proposed model was verified using an adapted simulation in the software package MATLAB Simulink. The simulation was performed for three types of ABB transformers with a 100% load. Simulation results were obtained for power transformers: Sn1=1 [MVA], Sn2=2 [MVA], Sn3=3.15 [MVA]. If we compare measurement result values of RT, XT, which are contained in a brochure for ABB transformers and those obtained through simulation, different tolerances are obtained. For reactance results, deviations are up to 20% for all three tested transformers. For results of active resistance tolerances are up to 5% for all three tested transformers. This method can be used not only to determine the active and inductive AC power source parameters but also to determine and analyze the impendence of electrical sources with high frequencies.
A self-consistent impedance method for electromagnetic surface impedance modeling
Thiel, David V.; Mittra, Raj
2001-01-01
A two-dimensional, self-consistent impedance method has been derived and used to calculate the electromagnetic surface impedance above buried objects at very low frequencies. The earth half space is discretized using an array of impedance elements. Inhomogeneities in the complex permittivity of the earth are reflected in variations in these impedance elements. The magnetic field is calculated for each cell in the solution space using a difference equation derived from Faraday's and Ampere's laws. It is necessary to include an air layer above the earth's surface to allow the scattered magnetic field to be calculated at the surface. The source field is applied above the earth's surface as a Dirichlet boundary condition, whereas the Neumann condition is employed at all other boundaries in the solution space. This, in turn, enables users to use both finite and infinite magnetic field sources as excitations. The technique is shown to be computationally efficient and yields reasonably accurate results when applied to a number of one- and two-dimensional earth structures with a known surface impedance distribution.
The AC Impedance Characteristic of High Power Li4Ti5O12-based Battery Cells
DEFF Research Database (Denmark)
Stroe, Ana-Irina; Stroe, Daniel Loan; Swierczynski, Maciej Jozef;
2015-01-01
This paper studies the impedance characteristics of a fresh 13 Ah high-power lithium titanate oxide (LTO) battery cell and analyses its dependence on the temperature and state-of-charge. The impedance of the battery cell was measured by means of the electrochemical impedance spectroscopy (EIS...
Directory of Open Access Journals (Sweden)
Uttam Mohan
2016-05-01
Full Text Available Solid charge transfer complex of n-donor 3, 5-dimethylpyridine (3, 5-Lutidine with σ acceptor iodine was prepared and characterised by using elemental analysis, UV-Vis, FTIR, 1H NMR spectroscopy and powder XRD techniques. The electrical parameters of the prepared complex in the pellet form were studied at various temperatures and at wide frequency range by employing AC complex impedance spectroscopic technique. The Nyquist (cole-cole plots have been successfully explained by employing (RC(RC(RC equivalent circuit corresponding to grain , grain boundary and electrode contributions. The radii of the semicircular arc decrease with increase in temperature which suggests that the material exhibits negative temperature coefficient of resistance (NTCR behaviour like semiconductors. Dielectric constant, ɛ′ and dielectric loss, ɛ″ seems to decrease sharply with increase in frequency. The ac conductivity obeys the power law of frequency.
Impedance plethysmography: a new method for continuous muscle perfusion monitoring.
Concannon, M J; Stewart, D H; Welsh, C F; Puckett, C L
1991-08-01
Vigilant postoperative monitoring of the buried muscle flap is critical after free transfer because early diagnosis of vascular insufficiency is essential to allow prompt correction. We have identified a monitoring method utilizing needle electrodes and impedance plethysmography that gives a beat-to-beat representation of muscular perfusion. In 25 New Zealand White rabbits the gastrocnemius muscle was isolated on its vascular pedicle, and two intramuscular needle electrodes were placed. The instantaneous impedance changes of the muscle (corresponding to the pulsatile volume changes of perfusion) were measured and recorded. Using this representation of perfusion, an independent judge was able to correctly diagnose muscular ischemia 100 percent of the time (n = 25). Further, the judge was able to correctly distinguish the ischemia as arterial (n = 10) or venous (n = 10) in origin 100 percent of the time. Additionally, we monitored muscle perfusion transcutaneously in five free muscle flaps and demonstrated a reliable impedance signal that correlated with perfusion.
NEW BIOTESTING METHOD WITH THE APPLICATION OF MODERN IMPEDANCE TECHNOLOGIES
Directory of Open Access Journals (Sweden)
Sibirtsev V.S.
2015-03-01
Full Text Available The paper deals with new concepts of biotesting method updating. Modern conductometric technologies and the analysis of microbial «growth curves» are used. The registration occurs in a real time mode for the set of parallel samples. Results are shown for comparison of the proposed impedance biotesting technique with standard cultural determination method for total amount of microorganismes in the tested samples. Results are presented for practical application of the proposed impedance biotesting technique to the analysis as inhibitory action of clorhexidine disinfectant on the vital activity of Escherichia coli, as milk ripening process at the presence of various microorganisms species and protein preparations. The impedance biotesting method, proposed in the present work, provides high level of its own data convergence with the data, being received as a result of application of standard cultural biotesting techniques. Thus, the proposed method has such advantages, as: an opportunity of the detailed information reception about dynamics change of magnitude of population and intensity of test microorganisms metabolism, significant reduction of the culture media amount used, as well as researcher's temporary and labor efforts while the analyses realization, and the growth of analysis objectivity.
Simon, Peter; Frankowski, Marcin; Bock, Nicole; Neukammer, Jörg
2016-06-21
We developed a microfluidic sensor for label-free flow cytometric cell differentiation by combined multiple AC electrical impedance and light scattering analysis. The measured signals are correlated to cell volume, membrane capacity and optical properties of single cells. For an improved signal to noise ratio, the microfluidic sensor incorporates two electrode pairs for differential impedance detection. One-dimensional sheath flow focusing was implemented, which allows single particle analysis at kHz count rates. Various monodisperse particles and differentiation of leukocytes in haemolysed samples served to benchmark the microdevice applying combined AC impedance and side scatter analyses. In what follows, we demonstrate that AC impedance measurements at selected frequencies allow label-free discrimination of platelets, erythrocytes, monocytes, granulocytes and lymphocytes in whole blood samples involving dilution only. Immunofluorescence staining was applied to validate the results of the label-free cell analysis. Reliable differentiation and enumeration of cells in whole blood by AC impedance detection have the potential to support medical diagnosis for patients with haemolysis resistant erythrocytes or abnormally sensitive leucocytes, i.e. for patients suffering from anaemia or leukaemia.
Diffusion and Gas Conversion Analysis of Solid Oxide Fuel Cells at Loads via AC Impedance
Directory of Open Access Journals (Sweden)
Robert U. Payne
2011-01-01
Full Text Available Impedance measurements were conducted under practical load conditions in solid oxide fuel cells of differing sizes. For a 2 cm2 button cell, impedance spectra data were separately measured for the anode, cathode, and total cell. Improved equivalent circuit models are proposed and applied to simulate each of measured impedance data. Circuit elements related to the chemical and physical processes have been added to the total-cell model to account for an extra relaxation process in the spectra not measured at either electrode. The processes to which elements are attributed have been deduced by varying cell temperature, load current, and hydrogen concentration. Spectra data were also obtained for a planar stack of five 61 cm2 cells and the individual cells therein, which were fitted to a simplified equivalent circuit model of the total button cell. Similar to the button cell, the planar cells and stack exhibit a pronounced low-frequency relaxation process, which has been attributed to concentration losses, that is, the combined effects of diffusion and gas conversion. The simplified total-cell model approximates well the dynamic behavior of the SOFC cells and the whole stack.
Energy Technology Data Exchange (ETDEWEB)
Kim, Chang-Soo; Song, Rak-Hyun; Choi, Byung-Woo [Korea Institute of Energy Research, Taejon (Korea, Republic of)] [and others
1996-12-31
In PAFC, the degradation on cathode electrode caused by carbon corrosion, platinum dissolution and growth is especially severe. An acceleration test is a good technique for evaluating the degradation of electrode performance, because it does not need long time. Coleman et al used thermal cycling and on-off cycling as an acceleration test. Song et al showed that hydrogen shortage decreased the electrode performance more rapidly than that of air shortage in gas shortage test. Honji et al reported that the rate of coarsening of Pt particle is rapid in open circuit potential and this is one of major causes on the performance degradation of electrode. The cathode performance has been studied by using acid absorption, acceleration and ac-impedance measurements as functions of the polytetrafluoroethylene (PTFE) contents and sintering temperatures of the electrode.
A dielectrophoresis-impedance method for protein detection and analysis
Mohamad, Ahmad Sabry; Hamzah, Roszymah; Hoettges, Kai F.; Hughes, Michael Pycraft
2017-01-01
Dielectrophoresis (DEP) has increasingly been used for the assessment of the electrical properties of molecular scale objects including proteins, DNA, nanotubes and nanowires. However, whilst techniques have been developed for the electrical characterisation of frequency-dependent DEP response, biomolecular study is usually limited to observation using fluorescent markers, limiting its applicability as a characterisation tool. In this paper we present a label-free, impedance-based method of characterisation applied to the determination of the electrical properties of colloidal protein molecules, specifically Bovine Serum Albumin (BSA). By monitoring the impedance between electrodes as proteins collect, it is shown to be possible to observe multi-dispersion behaviour. A DEP dispersion exhibited at 400 kHz is attributable to the orientational dispersion of the molecule, whilst a second, higher-frequency dispersion is attributed to a Maxwell-Wagner type dispersion; changes in behaviour with medium conductivity suggest that this is strongly influenced by the electrical double layer surrounding the molecule.
Gerteisen, Dietmar; Hakenjos, Alex; Schumacher, Jürgen O.
A one-dimensional model of the PEM fuel cell cathode is developed to analyse ac impedance spectra and polarisation curves. The porous gas diffusion electrode is assumed to consist of a network of dispersed catalyst (Pt/C) forming spherically shaped agglomerated zones that are filled with electrolyte. The coupled differential equation system describes: ternary gas diffusion in the backing (O2 , N2 , water vapour), Fickian diffusion and Tafel kinetics for the oxygen reduction reaction (ORR) inside the agglomerates, proton migration with ohmic losses and double-layer charging in the electrode. Measurements are made of a temperature-controlled fuel cell with a geometric area of 1.4 cm × 1.4 cm. Lateral homogeneity is ensured by using a high stoichiometry of λmin . The model predicts the behaviour of measured polarisation curves and impedance spectra. It is found that a better humidification of the electrode leads to a higher volumetric double-layer capacity. The catalyst layer resistance shows the same behaviour depending on the humidification as the membrane resistance. Model parameters, e.g. Tafel slope, ionic resistance and agglomerate radius are varied. A sensitivity analysis of the model parameters is conducted.
Directory of Open Access Journals (Sweden)
Farouk Rashwan
2005-01-01
Full Text Available The Electrochemical Impedance Spectroscopic techniques (EIS were used to investigate the behavior of some dye compounds (quinoid systems characterized with 2e-transfer processes. For this purpose, Alizarin Red S (ARS, Alizarin Cyanine (AC, Alizarin Viridin (AV and carminic acid were chosen for the measurements. The EIS experiments were performed using a small AC amplitude (10 mV p-p in addition to a relatively wide frequency range (0.01 Hz â¤ f â¤ 105 Hz. The investigations were carried out at room temperature in aqueous media (HClO4, NaClO4 and KNO3 on the Hanging Mercury Drop Electrode (HMDE and for comparison one experiment only was measured in aprotic solvent (DMF on the Pt-disc electrode. The EIS diagrams of these systems were characterized in the complex plane by two fundamental observations, the first of which is a straight line crossing the real axis at an angle of 45Â° (or at least nearly so and the second one is two semicircles beside each other corresponding to high-frequency and low-frequency regions, which are implying the presence of well-separated time constants. The EIS characteristic parameters for these dye systems were calculated and discussed.
Energy Technology Data Exchange (ETDEWEB)
Lee, Ju-hyung; Lee, Jong-Hak; Choi, Woojin [Department of Electrical Engineering, Soongsil University, 1-1 Sangdo-dong, Dongjak-gu, Seoul 156-743 (Korea); Park, Kyung-Won [Department of Chemical/Environmental Engineering, Soongsil University, 1-1 Sangdo-dong, Dongjak-gu, Seoul 156-743 (Korea); Sun, Hee-Young [Samsung Advanced Institute of Technology, Mt. 14-1, Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-712 (Korea); Oh, Jae-Hyuk [Samsung Electronics, 416 Maetan-dong, Youngtong-gu, Suwon-si, Gyeonggi-do 443-370 (Korea)
2010-09-15
This paper proposes a new method for estimating the state and lifespan of fuel cells in operation by fuel cell equivalent impedance modeling by electrochemical impedance spectroscopy (EIS) and observing degradation. The performance change of fuel cells takes place in the form of changes in each parameter value comprising an equivalent AC impedance circuit; monitoring such changes allows for the prediction of the state and lifespan of a fuel cell. In the experiments, the AC impedance of high-temperature proton exchange membrane (PEM) fuel cells was measured at constant time intervals during their continuous operation for over 2200 h. The expression for the lifespan of a fuel cell was deduced by curve fitting the changes in each parameter to a polynomial. Electric double layer capacitance and charge transfer resistance, which show the reduction reaction of the cathode, were used as major parameters for judging the degradation; a method of using time constants is proposed to more accurately estimate the degree of degradation. In addition, an algorithm that can evaluate the soundness and lifespan of a fuel cell is proposed; it compares the measured time constant of the fuel cell being tested with that of average lifespan fuel cell. (author)
Energy Technology Data Exchange (ETDEWEB)
Lebrini, M.; Fontaine, G. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, LSPES UMR CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Gengembre, L. [Unite de Catalyse et Chimie du solide UMR 8181 Bat C3, USTL, F-59655 Villeneuve d' Ascq Cedex (France); Traisnel, M. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, LSPES UMR CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France)], E-mail: Michel.Traisnel@ensc-lille.fr; Lerasle, O.; Genet, N. [TOTAL France, Centre de Recherche de Solaize, Chemin du canal, BP 22, F-69360 Solaize (France)
2008-08-30
The efficiency of a new triazole derivative, namely, 2-{l_brace}(2-hydroxyethyl)[(4-methyl-1H-1,2,3-benzotriazol-1-yl)methyl]amino{r_brace} ethanol (TTA) has been studied for corrosion inhibition of galvanized steel and electroplating steel in aqueous solution. Corrosion inhibition was studied using electrochemical impedance spectroscopy (EIS). These studies have shown that TTA was a very good inhibitor. Data obtained from EIS show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. The corrosion behaviour of galvanized steel and electroplating steel in aqueous solution was also investigated in the presence of 4-methyl-1H-benzotriazole (TTA unsubstituted) by EIS. These studies have shown that the ability of the molecule to adsorb on the steel surface was dependent on the group in triazole ring substituent. X-ray photoelectron spectroscopy surface analysis with TTA shows that it chemisorbed on surface of galvanized steel and electroplating steel.
Directory of Open Access Journals (Sweden)
S. N. Bandarenka
2015-01-01
Full Text Available One of the most prospective directions in preservation and increase of service live of road pavements is a construction of automobile roads with cement concrete surface. Modern tendencies for provision of road construction quality presuppose a necessity to control processes of solidification and subsequent destruction of the material while forming and using cement concrete conglomerate being considered as a basic element of the road surface. Multiyear practical experience of automobile road operation using cement concrete pavements reveals an importance for monitoring such processes as formation and destruction of cement concrete materials. An impedance spectroscopy method has been tried out and proposed as a tool for solution of the given problem.Experimental samples of cement concrete have been prepared for execution of tests, graded silica sand and granite chippings with particle size from 0.63 to 2.5 mm have been used as a fine aggregate in the samples. Dependencies of resistance (impedance on AC-current frequency have been studied for samples of various nature and granulometric composition. The Gamry G300 potentiostat has been used for measurement of complex impedance value. A spectrum analysis and calculation of equivalent circuit parameters calculation have been carried out while using EIS Spectrum Analyzer program.Comparison of impedance spectra for the prepared cement concrete samples have made it possible to reveal tendencies in changing spectrum parameters during solidification and subsequent contact with moisture in respect of every type of the sample. An equivalent electrical circuit has been developed that characterizes physical and chemical processes which are accompanied by charge transfer in cement concrete conglomerate. The paper demonstrates a possibility to use an impedance spectroscopy for solution of a number of actual problems in the field of cement concrete technology problems. Particularly, the problems
Studies of an Adaptive Kaczmarz Method for Electrical Impedance Imaging
Li, Taoran; Isaacson, David; Newell, Jonathan C.; Saulnier, Gary J.
2013-04-01
We present an adaptive Kaczmarz method for solving the inverse problem in electrical impedance tomography and determining the conductivity distribution inside an object from electrical measurements made on the surface. To best characterize an unknown conductivity distribution and avoid inverting the Jacobian-related term JTJ which could be expensive in terms of memory storage in large scale problems, we propose to solve the inverse problem by adaptively updating both the optimal current pattern with improved distinguishability and the conductivity estimate at each iteration. With a novel subset scheme, the memory-efficient reconstruction algorithm which appropriately combines the optimal current pattern generation and the Kaczmarz method can produce accurate and stable solutions adaptively compared to traditional Kaczmarz and Gauss-Newton type methods. Several reconstruction image metrics are used to quantitatively evaluate the performance of the simulation results.
Güren, Onan; Çayören, Mehmet; Ergene, Lale Tükenmez; Akduman, Ibrahim
2014-10-01
A new microwave imaging method that uses microwave contrast agents is presented for the detection and localization of breast tumours. The method is based on the reconstruction of breast surface impedance through a measured scattered field. The surface impedance modelling allows for representing the electrical properties of the breasts in terms of impedance boundary conditions, which enable us to map the inner structure of the breasts into surface impedance functions. Later a simple quantitative method is proposed to screen breasts against malignant tumours where the detection procedure is based on weighted cross correlations among impedance functions. Numerical results demonstrate that the method is capable of detecting small malignancies and provides reasonable localization.
Na＋导电陶瓷的交流阻抗谱%AC Impedance Characteristics of Na＋ Conductive Ceramic Electrodes
Institute of Scientific and Technical Information of China (English)
倪蕾蕾; 杨座国; 曾乐才; 刘宇; 祝铭
2012-01-01
以β″-Al2O3导电陶瓷为电解质，研究制备银／碳毡／低熔点钠盐电极（Ag／C／（NaNO3＋NaNO2）），并选择银电极作为对比电极。测试条件为：温度275～400℃、频率12～105Hz。采用交流阻抗谱法（Ac）进行β″-Al2O3导电陶瓷与金属Na＋界面兼容性和界面离子传导机理研究。结果表明：β″-Al2O3导电陶瓷的电导与温度关系服从于阿仑尼乌斯公式。比较两种电极可以发现，电极／电解质的界面接触对电极／电解质界面迁移阻抗和阻抗谱测试结果会有较大程度的影响。%Alumina conductive ceramic was used as solid electrolyte. Using the silver electrode as comparison one, a new electrode, silver / carbon felt / low melting sodium electrode （Ag/C/（NaNO3 ＋ NaNO2）） as the test electrode was designed and prepared. The testing temperature ranged from 275 ℃ to 400℃ and frequency ranged from 12 Hz to 10^5Hz. The AC impedance spectroscopy was employed to study the compatibility and ion conduction mechanism between β″-Al2O3 ceramic and Na＋. The results show that the conductivity of β″-Al2O3 ceramic and temperature obey the Arrhenius equation. In comparison of two electrodes, the contact between electrode and solid electrolyte plays an important role in electrode/ electrolyte interface transfer impedance and electrochemical impedance spectroscopy.
A method to separate process contributions in impedance spectra by variation of test conditions
DEFF Research Database (Denmark)
Jensen, Søren Højgaard; Hauch, Anne; Hendriksen, Peter Vang;
2007-01-01
Many processes contribute to the overall impedance of an electrochemical cell, and these may be difficult to separate in the impedance spectrum. Here, we present an investigation of a solid oxide fuel cell based on differences in impedance spectra due to a change of operating parameters and present...... the result as the derivative of the impedance with respect to ln(f). The method is used to separate the anode and cathode contributions and to identify various types of processes....
Measurement of AC loss of superconductors by vaporizing method
Energy Technology Data Exchange (ETDEWEB)
Wakabayashi, Hiroshi; Isono, Takaaki; Matsui, Kunihiro; Fujisaki, Reishi; Nunoya, Yoshihiko; Koizumi, Norikiyo; Takahashi, Yoshikazu; Tsuji, Hiroshi [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment
1995-07-01
In Japan Atomic Energy Research Institute, the development of superconducting pulse conductors for next period nuclear fusion reactors has been carried out. For these conductors, the rated current of 46 kA and the rated magnetic field of 13T are demanded. When the pulse excitation of superconductors is carried out, AC loss arises, and the temperature of the superconductors rises, and when it exceeds a certain value, the superconducting state cannot be maintained. Therefore, the AC loss of pulse conductors must be limited to a low value. It is difficult to evaluate the AC loss of superconductors by calculation, therefore, it is evaluated by actual measurement. There are magnetizing method and vaporizing method for measuring the AC loss. This time, the equipment for measuring the AC loss of 40 kA class superconductors by vaporizing method which measures the helium gas quantity vaporizing at the time of AC loss occurrence was designed and manufactured for the first time. The method of measuring the AC loss, the structure of the measuring equipment, the helium gas recovering part and the measuring part, the countermeasures for preventing helium gas leakage, the resistance heater for calibration, and the results of measurement are reported. (K.I.)
Iterative Reconstruction Methods for Hybrid Inverse Problems in Impedance Tomography
DEFF Research Database (Denmark)
Hoffmann, Kristoffer; Knudsen, Kim
2014-01-01
For a general formulation of hybrid inverse problems in impedance tomography the Picard and Newton iterative schemes are adapted and four iterative reconstruction algorithms are developed. The general problem formulation includes several existing hybrid imaging modalities such as current density...... impedance imaging, magnetic resonance electrical impedance tomography, and ultrasound modulated electrical impedance tomography, and the unified approach to the reconstruction problem encompasses several algorithms suggested in the literature. The four proposed algorithms are implemented numerically in two...... be based on a theoretical analysis of the underlying inverse problem....
Method of estimating pulse response using an impedance spectrum
Energy Technology Data Exchange (ETDEWEB)
Morrison, John L; Morrison, William H; Christophersen, Jon P; Motloch, Chester G
2014-10-21
Electrochemical Impedance Spectrum data are used to predict pulse performance of an energy storage device. The impedance spectrum may be obtained in-situ. A simulation waveform includes a pulse wave with a period greater than or equal to the lowest frequency used in the impedance measurement. Fourier series coefficients of the pulse train can be obtained. The number of harmonic constituents in the Fourier series are selected so as to appropriately resolve the response, but the maximum frequency should be less than or equal to the highest frequency used in the impedance measurement. Using a current pulse as an example, the Fourier coefficients of the pulse are multiplied by the impedance spectrum at corresponding frequencies to obtain Fourier coefficients of the voltage response to the desired pulse. The Fourier coefficients of the response are then summed and reassembled to obtain the overall time domain estimate of the voltage using the Fourier series analysis.
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
1 Results Investigations on the sensing mechanism is important for understanding the electrical responses of humidity sensors to humidity change,and could provide guidelines for the design and synthesis of humidity sensitive materials with desirable properties.In this work,the sensing mechanism of humidity sensors based on quaternized poly(4-vinylpyridine) (PVP)/carbon black (CB) composite[1] was studied by measuring their AC impedance spectra at various humidities at room temperature.Under low humidity...
An effective measured data preprocessing method in electrical impedance tomography.
Yu, Chenglong; Yue, Shihong; Wang, Jianpei; Wang, Huaxiang
2014-01-01
As an advanced process detection technology, electrical impedance tomography (EIT) has widely been paid attention to and studied in the industrial fields. But the EIT techniques are greatly limited to the low spatial resolutions. This problem may result from the incorrect preprocessing of measuring data and lack of general criterion to evaluate different preprocessing processes. In this paper, an EIT data preprocessing method is proposed by all rooting measured data and evaluated by two constructed indexes based on all rooted EIT measured data. By finding the optimums of the two indexes, the proposed method can be applied to improve the EIT imaging spatial resolutions. In terms of a theoretical model, the optimal rooting times of the two indexes range in [0.23, 0.33] and in [0.22, 0.35], respectively. Moreover, these factors that affect the correctness of the proposed method are generally analyzed. The measuring data preprocessing is necessary and helpful for any imaging process. Thus, the proposed method can be generally and widely used in any imaging process. Experimental results validate the two proposed indexes.
DEFF Research Database (Denmark)
Kim, Jaehong; Guerrero, Josep M.; Rodriguez, Pedro;
2011-01-01
in islanded and grid-connected mode. The proposed control scheme does not need any mode switching action. Thus, it is relatively simple in control for full mode of operation. Smooth transitions between the operation modes and the effectiveness of the proposed control scheme are evaluated through simulation...... control combined with a derivative controller is used in islanded mode. In grid-connected mode, to strictly control the power factor in the point of common coupling (PCC), a droop method combined with an integral controller is adopted. Small-signal analysis of the proposed control is shown both...
Castaneda-Lopez, Homero
A methodology for detecting and locating defects or discontinuities on the outside covering of coated metal underground pipelines subjected to cathodic protection has been addressed. On the basis of wide range AC impedance signals for various frequencies applied to a steel-coated pipeline system and by measuring its corresponding transfer function under several laboratory simulation scenarios, a physical laboratory setup of an underground cathodic-protected, coated pipeline was built. This model included different variables and elements that exist under real conditions, such as soil resistivity, soil chemical composition, defect (holiday) location in the pipeline covering, defect area and geometry, and level of cathodic protection. The AC impedance data obtained under different working conditions were used to fit an electrical transmission line model. This model was then used as a tool to fit the impedance signal for different experimental conditions and to establish trends in the impedance behavior without the necessity of further experimental work. However, due to the chaotic nature of the transfer function response of this system under several conditions, it is believed that non-deterministic models based on pattern recognition algorithms are suitable for field condition analysis. A non-deterministic approach was used for experimental analysis by applying an artificial neural network (ANN) algorithm based on classification analysis capable of studying the pipeline system and differentiating the variables that can change impedance conditions. These variables include level of cathodic protection, location of discontinuities (holidays), and severity of corrosion. This work demonstrated a proof-of-concept for a well-known technique and a novel algorithm capable of classifying impedance data for experimental results to predict the exact location of the active holidays and defects on the buried pipelines. Laboratory findings from this procedure are promising, and
Directory of Open Access Journals (Sweden)
Hoi Shun Lui
2010-01-01
Full Text Available A short review of the receiving-mutual-impedance method (RMIM for mutual coupling compensation in direction finding applications using linear array is conducted. The differences between the conventional-mutual-impedance method (CMIM and RMIM, as well as the three different determination methods for receiving mutual impedance (RMI, will be discussed in details. As an example, direction finding with better accuracies is used for demonstrating the superiority of mutual coupling compensation using RMIM.
Application of impedance spectroscopy method for analysis of benzanol fuels
Directory of Open Access Journals (Sweden)
Mamykin A. V.
2015-06-01
Full Text Available The authors have developed a method for express control of three component «gasoline-alcohol-water» fuel mixtures based on the spectral impedance investigation of benzanol mixture in the frequency range of 500 Hz — 10 kHz. A correlation dependence between the dielectric constant and the specific resistance of the fuel mixture on content of ethanol and water in the mixture has been found. On the basis of this dependence a calibration nomogram to quantify the gasoline and water-alcohol components content in the test benzanol fuel in the actual range of concentrations has been formed. The nomogram allows determining the water-alcohol and gasoline parts in the analyzed fuel with an error of no more than 1% vol., while the strength of water-alcohol solution is determined with an error of no more than 0.8% vol. The obtained nomogram can also give information about critical water content in the benzanol fuel to prevent its eventual phase separation. It is shown that the initial component composition of different gasoline brands has no significant effect on the electrical characteristics of the studied benzanol fuels, which makes the evaluation of alcohol and water content in the fuel sufficiently accurate. for practical applications.
Energy Technology Data Exchange (ETDEWEB)
Kinoshita, Katsuyuki
2015-02-01
We have developed a method for detecting fatigue in aluminum alloys that is based on a applying a ferromagnetic electroless Ni–Co–P plating and then using an electromagnetic impedance (EMI) method to determine its permeability properties by measuring the high-frequency AC impedance of a coil sensor in the presence of a static magnetic field. The results obtained confirmed that this method can estimate the fatigue evolution of a specimen until the point at which the cumulative strain becomes saturated by using measurements obtained by the EMI method under tensile deformation and FEM analysis results. - Highlights: • Plating aluminum alloy with Ni–Co–P film increases its fatigue strength by 13−16%. • The tensile direction is the stress induced “hard axis” of the Ni–Co–P plating. • In-plane permeability determines the coil impedance for out-of-plane excitation. • This method can measure fatigue up to saturation of the substrate's residual strain.
Zhou, Liming; Yang, Yuxing; Yuan, Shiying
2006-02-01
A new algorithm, the coordinates transform iterative optimizing method based on the least square curve fitting model, is presented. This arithmetic is used for extracting the bio-impedance model parameters. It is superior to other methods, for example, its speed of the convergence is quicker, and its calculating precision is higher. The objective to extract the model parameters, such as Ri, Re, Cm and alpha, has been realized rapidly and accurately. With the aim at lowering the power consumption, decreasing the price and improving the price-to-performance ratio, a practical bio-impedance measure system with double CPUs has been built. It can be drawn from the preliminary results that the intracellular resistance Ri increased largely with an increase in working load during sitting, which reflects the ischemic change of lower limbs.
DEFF Research Database (Denmark)
Sørensen, Stefan; Nielsen, Hans Ove
2002-01-01
In this paper we present comparison of different line and cable series impedance calculation methods, where the correction of a discovered PSCAD/EMIDC v.3.0.8 calculation error of the cable series impedance results n deviation under 0.1% instead of the previous method which gave approximately 10%...
DEFF Research Database (Denmark)
Swierczynski, Maciej Jozef; Stroe, Daniel Loan; Stanciu, Tiberiu
by Barsoukov et al. proposed electrothermal impedance spectroscopy (ETIS) as a novel and non-destructive method of characterizing the thermal properties of batteries by defining frequency dependent thermal impedance. This paper aims to systematize the state of knowledge about ETIS, presents measurement methods...
A New Method of On-line Grid Impedance Estimation for PV Inverter
DEFF Research Database (Denmark)
Teodorescu, Remus; Asiminoaei, Lucian; Blaabjerg, Frede
2004-01-01
for on-line measuring the grid impedance is presented. The presented method requires no extra hardware being accommodated by typical PV inverters, sensors and CPU, to provide a fast and low cost approach of on-line impedance measurement. By injecting a non-characteristic harmonic current and measuring...
IMPEDANCE METHOD OF MEASURING OF THE TITRATABLE ACIDITY OF YOGURT
Directory of Open Access Journals (Sweden)
Miroslav Vasilev
2016-10-01
Full Text Available In the present work are analyzed studies related to changes in the active impedance component of the dairy environment caused by the flow of lactic fermentation and coagulation of casein in milk. The aim of this work was to determine the relationship between the relative change of titratable acidity and the relative change of active impedance component of the dairy environment with lactic fermentation, causing coagulation of the casein in milk. . The data were interpolated with cubic spline, visualizing how when the fat content increases, the electrical resistance increases too. All data, collected during the tests would complement and be used for solving the optimization problem to determine the time of completion of the coagulation in future work.
Measuring System of Magnetostriction Under AC Excitation Using Optical Methods
Nakase, Tomoya; Nakano, Masanori; Fujiwara, F.; TAKAHASHI, N
1998-01-01
A measuring system for magnetostriction of silicon steel sheet using optical methods and a single sheet tester has been developed to establish a standard test method for IEC and JIS. Various factors affecting measurement accuracy and reproducibility of the developed system are examined. Two optical instruments, such as a laser Doppler vibrometer and a heterodyne displacement meter, are compared. 3-D characteristics of magnetostriction under ac excitation in the rolling direction are measured ...
Comparative Study of Impedance Eduction Methods, Part 2: NASA Tests and Methodology
Jones, Michael G.; Watson, Willie R.; Howerton, Brian M.; Busse-Gerstengarbe, Stefan
2013-01-01
A number of methods have been developed at NASA Langley Research Center for eduction of the acoustic impedance of sound-absorbing liners mounted in the wall of a flow duct. This investigation uses methods based on the Pridmore-Brown and convected Helmholtz equations to study the acoustic behavior of a single-layer, conventional liner fabricated by the German Aerospace Center and tested in the NASA Langley Grazing Flow Impedance Tube. Two key assumptions are explored in this portion of the investigation. First, a comparison of results achieved with uniform-flow and shear-flow impedance eduction methods is considered. Also, an approach based on the Prony method is used to extend these methods from single-mode to multi-mode implementations. Finally, a detailed investigation into the effects of harmonic distortion on the educed impedance is performed, and the results are used to develop guidelines regarding acceptable levels of harmonic distortion
Giurgiutiu, Victor; Rogers, Craig A.
1998-07-01
The emerging electro-mechanical impedance technology has high potential for in-situ health monitoring and NDE of structural systems and complex machinery. At first, the fundamental principles of the electro-mechanical impedance method are briefly reviewed and ways for practical implementation are highlighted. The equations of piezo- electric material response are given, and the coupled electro-mechanical impedance of a piezo-electric wafer transducer as affixed to the monitored structure is discussed. Due to the high frequency operation of this NDE method, wave propagation phenomena are identified as the primary coupling method between the structural substrate and the piezo-electric wafer transducer. Attention is then focused on several recent advancements that have extended the electro-mechanical impedance method into new areas of applications and/or have developed its underlying principles. US Army Construction Engineering Research Laboratory used the electro-mechanical impedance method to monitor damage development in composite overlaid civil infrastructure specimens under full-scale static testing. A simplified E/M impedance measuring technique was employed at the Polytechnic University of Madrid, Spain, to detect damage in GFRP composite specimens. The development of miniaturized `bare-bones' impedance analyzer equipment that could be easily packaged into transponder-size dimensions is being studied at the University of South Carolina. US Army Research Laboratory developed novel piezo-composite film transducers for embedment into composite structures. Disbond gauges for monitoring the structural joints of adhesively bonded rotor blades have been studies in the Mechanical Engineering Department at the University of South Carolina. These recent developments accentuate the importance and benefits of using the electro-mechanical impedance method for on-line health monitoring and damage detection in a variety of applications. Further investigation of the electro
Impedance and a.c. conductivity studies of Ba(Pr1/2Nb1/2)O3 ceramic
Indian Academy of Sciences (India)
K Amar Nath; K Prasad; K P Chandra; A R Kulkarni
2013-08-01
Impedance and electrical conduction studies of Ba(Pr1/2Nb1/2)O3 ceramic prepared through conventional ceramic fabrication technique are presented. The crystal symmetry, space group and unit cell dimensions were estimated using Rietveld analysis. X-ray diffraction analysis indicated the formation of a single-phase cubic structure with space group, $\\bar{3}$. EDAX and SEM studies were carried out to study the quality and purity of compound. To find a correlation between the response of the real system and idealized model circuit composed of discrete electrical components, the model fittings were presented using impedance data. Complex impedance as well as electric modulus analyses suggested dielectric relaxation to be of non-Debye type and negative temperature coefficient of resistance character. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in Ba(Pr1/2Nb1/2)O3. The a.c. conductivity data were used to evaluate density of states at Fermi level, minimum hopping length and apparent activation energy.
Directory of Open Access Journals (Sweden)
Ansu K. Roy
2013-06-01
Full Text Available Lead-free piezoelectric perovskite ceramic (Bi0.5Na0.50.95Ba0.05TiO3 (BNT-BT0.05, prepared by conventional high temperature solid state reaction technique at 1160 °C/3h in air atmosphere, is investigated by impedance and modulus spectroscopy in a temperature range 35–400 °C, over a frequency range 100 Hz–1 MHz. The crystal structure, microstructure, and piezoelectric properties as well as the AC conductivity of the sample were studied. Powder X-ray diffraction pattern derived from the resulting data at the room temperature subjected to Rietveld refinements and Williamson-Hall plot analysis confirmed the formation of phase pure compound with monoclinic unit cells having a crystallite-size ~33.8 nm. Observed SEM micrograph showed a uniform distribution of grains inside the sample having an average grain size ~3 mm. Longitudinal piezoelectric charge coefficient of the sample poled under a DC electric field of ~ 2.5 kV/mm at 80 °C in a silicone oil bath was found to be equal to 95 pC/N. The frequency and temperature dependent electrical data analysed in the framework of AC conductivity, complex impedance as well as electric modulus formalisms showed negative temperature coefficient of resistance (NTCR character of the material and the dielectric relaxation in the material to be of non-Debye type. Double power law for the frequency-dependence of AC conductivity and Jump Relaxation Model (JRM were found to explain successfully the mechanism of charge transport in BNT-BT0.05.
Circuits and methods for impedance determination using active measurement cancelation
Energy Technology Data Exchange (ETDEWEB)
Jamison, David K.
2016-12-13
A delta signal and opposite delta signal are generated such that a sum of the two signals is substantially zero. The delta signal is applied across a first set of electrochemical cells. The opposite delta signal is applied across a second set of electrochemical cells series connected to the first set. A first held voltage is established as the voltage across the first set. A second held voltage is established as the voltage across the second set. A first delta signal is added to the first held voltage and applied to the first set. A second delta signal is added to the second held voltage and applied to the second set. The current responses due to the added delta voltages travel only into the set associated with its delta voltage. The delta voltages and the current responses are used to calculate the impedances of their associated cells.
Time-harmonic impedance tomography using the T-matrix method.
Otto, G P; Chew, W C
1994-01-01
A time-harmonic formulation for the electrical impedance tomography (EIT) inverse problem accounting for electrodynamic effects is derived. This work abandons the standard electrostatic impedance model for a full-wave T-matrix model. The advantage of this method is an accurate physical model that includes finite frequency effects, such as diffusion phenomena, and electrode contact impedance effects. This model offers the potential for increased resolution and larger invertible contrast objects than other methods when used on experimental data, because it may represent a more realistic physical model. Also, an accurate gradient matrix is used in the Newton iterative method so the image reconstruction converges in a few iterations. These advantages are realized with no increase in the computational complexity of this algorithm, compared to the static finite element model. A calibration technique is suggested for measurement systems, to test the validity of a theoretical model that includes electrode contact impedance effects.
AC Conductivity and Impedance Properties of 0.65Pb(Mg1/3Nb2/3O3-0.35PbTiO3 Ceramics
Directory of Open Access Journals (Sweden)
Banarji Behera
2009-01-01
impedance spectroscopy technique. The impedance and electric permittivity were strongly temperature and frequency dependent. The activation energy, calculated from the temperature dependence of AC conductivity of the ceramics was found to be ∼0.5 eV. The relaxation process in the ceramics was found to be of non-Debye type. The nature of Cole-Cole diagram reveals the contribution of grain (bulk and grain boundary permittivity in the ceramics.
Harth, Yoram; Lischinsky, Daniel
2011-03-01
The thermal effects of monopolar and bipolar radiofrequency (RF) have been proven to be beneficial in skin tightening. Nevertheless, these effects were frequently partial or unpredictable because of the uncontrolled nature of monopolar or unipolar RF and the superficial nature of energy flow for bipolar or tripolar configurations. One of the hypotheses for lack or predictability of efficacy of the first-generation RF therapy skin tightening systems is lack of adaptation of delivered power to differences in individual skin impedance. A novel multisource phase-controlled system was used (1 MHz, power range 0-65 W) for treatment and real-time skin impedance measurements in 24 patients (EndyMed PRO™; EndyMed, Cesarea, Israel). This system allows continuous real-time measurement of skin impedance delivering constant energy to the patient skin independent of changes in its impedance. More than 6000 unique skin impedance measurements on 22 patients showed an average session impedance range was 215-584 Ohm with an average of 369 Ohm (standard deviation of 49 Ohm). Analyzing individual pulses (total of 600 readings) showed a significant decrease in impedance during the pulse. These findings validate the expected differences in skin impedance between individual patients and in the same patients during the treatment pulse. Clinical study on 30 patients with facial skin aging using the device has shown high predictability of efficacy (86.7% of patients had good results or better at 3 months' follow-up [decrease of 2 or more grades in Fitzpatrick's wrinkle scale]). The real-time customization of energy according to skin impedance allows a significantly more accurate and safe method of nonablative skin tightening with more consistent and predictable results.
Indian Academy of Sciences (India)
Anji Reddy Polu; Ranveer Kumar
2011-08-01
Polyvinyl alcohol (PVA)–polyethylene glycol (PEG) based solid polymer blend electrolytes with magnesium nitrate have been prepared by the solution cast technique. Impedance spectroscopic technique has been used, to characterize these polymer electrolytes. Complex impedance analysis was used to calculate bulk resistance of the polymer electrolytes. The a.c.-impedance data reveal that the ionic conductivity of PVA–PEG–Mg(NO3)2 system is changed with the concentration of magnesium nitrate, maximum conductivity of 9.63 × 10-5 S/cm at room temperature was observed for the system of PVA–PEG–Mg(NO3)2 (35–35–30). However, ionic conductivity of the above system increased with the increase of temperature, and the highest conductivity of 1.71 × 10-3 S/cm was observed at 100°C. The effect of ionic conductivity of polymer blend electrolytes was measured by varying the temperature ranging from 303 to 373 K. The variation of imaginary and real parts of dielectric constant with frequency was studied.
A straightforward method for wall impedance eduction in a flow duct.
Jing, Xiaodong; Peng, Sen; Sun, Xiaofeng
2008-07-01
The development of the advanced liner technology for aeroengine noise control necessitates the impedance measurement method under realistic flow conditions. Currently, the methods for this need are mainly based on the inverse impedance eduction principle, confronting with the problems of initial guess, high computation cost, and low convergence. In view of this, a new strategy is developed that straightforwardly educes the impedance from the sound pressure information measured on the duct wall opposing to the test acoustic liner embedded in a flow duct. Here, the key insight is that the modal nature of the duct acoustic field renders a summed-exponential representation of the measured sound pressure; thus, the characterizing axial wave number can be readily extracted by means of Prony's method, and further the unknown impedance is calculated from the eigenvalue and dispersion relations based on the classical mode-decomposition analysis. This straightforward method is simple in its basic principle but remarkably has the advantages of ultimately overcoming the drawbacks inherent to the inverse methods, incorporating the realistic multimode nonprogressive wave effects, high computational efficiency, possibly reducing the measurement points, and even avoiding the necessity of the duct exit impedance that bothers perhaps all the existing waveguide methods.
Directory of Open Access Journals (Sweden)
Jianfei An
2014-01-01
Full Text Available A new method that is based on genetic algorithm (GA is developed to design electrical impedance matching network for broadband piezoelectric ultrasound transducer. The new method can both optimize the topology of the matching network and perform optimization on the components at the same time. Results of classical algorithms are referenced to reduce the number of candidate topologies and greatly simplify the calculation process. Some calculation strategies, such as elitist strategy and clearing niche method, are adopted during optimization to make sure that the algorithm can convergence to global optimal result. Simulation results show that the new method has advantages over designing complex impedance matching network.
Institute of Scientific and Technical Information of China (English)
姜洪喆; 赵昕; 褚璇; 王伟; 刘声泉
2016-01-01
牛奶的质量和安全是食品安全的重要组成部分，关系到老百姓的身体健康和生命安全。保障牛奶质量能确保消费者从牛奶中获得足够的期望营养物质，而保障牛奶安全能避免对消费者造成危害。交流阻抗技术是一种具有潜力的检测方法，最早应用在电化学检测，在食品检测方面应用时间较短。国内外学者针对交流阻抗技术在牛奶质量安全方面的检测做了一些研究，发现其是一种快速、有效的检测方法。本文对交流阻抗技术应用在牛奶乳脂含量、含水量、酸败和货架期等质量方面的检测以及体细胞数、抗生素残留、细菌总数和掺假等安全方面的检测进行了综述，以供我国相关方面的研究学者、产品开发者和奶牛养殖者借鉴和参考。%Milk quality and safety is an important part of food safety, which relates to people's health and life safety. Guaranteeing milk quality could ensure consumers get enough nutrients expected from milk whereas milk safety for avoiding damages. AC impedance technology is a kind of potential detection measurement which was earliest applied in electrochemical detection however, it has been short time using in food detection if eld. Based on AC impedance technology, domestic and foreign scholars do some research which shows it is a fast and eff ective detection method. This paper reviews the application of AC impedance technology in the detection of milk quality (milk fat content, moisture content, rancidity and shelf life) and milk safety (somatic cell count, the total number of bacteria, antibiotic residues and adulteration) to provide certain references for our related research scholars, product developers and dairy farmers.
System and method for determining stator winding resistance in an AC motor using motor drives
Lu, Bin; Habetler, Thomas G; Zhang, Pinjia
2013-02-26
A system and method for determining the stator winding resistance of AC motors is provided. The system includes an AC motor drive having an input connectable to an AC source and an output connectable to an input terminal of an AC motor, a pulse width modulation (PWM) converter having switches therein to control current flow and terminal voltages in the AC motor, and a control system connected to the PWM converter. The control system generates a command signal to cause the PWM converter to control an output of the AC motor drive corresponding to an input to the AC motor, selectively generates a modified command signal to cause the PWM converter to inject a DC signal into the output of the AC motor drive, and determines a stator winding resistance of the AC motor based on the DC signal of at least one of the voltage and current.
Methods for Addressing Missing Data with Applications from ACS Exams
Brandriet, Alexandra; Holme, Thomas
2015-01-01
As part of the ACS Examinations Institute (ACS-EI) national norming process, student performance data sets are collected from professors at colleges and universities from around the United States. Because the data sets are collected on a volunteer basis, the ACS-EI often receives data sets with only students' total scores and without the students'…
Comparative Study of Impedance Eduction Methods. Part 1; DLR Tests and Methodology
Busse-Gerstengarbe, Stefan; Bake, Friedrich; Enghardt, Lars; Jones, Michael G.
2013-01-01
The absorption efficiency of acoustic liners used in aircraft engines is characterized by the acoustic impedance. World wide, many grazing ow test rigs and eduction methods are available that provide values for that impedance. However, a direct comparison and assessment of the data of the di erent rigs and methods is often not possible because test objects and test conditions are quite di erent. Only a few papers provide a direct comparison. Therefore, this paper together with a companion paper, present data measured with a reference test object under similar conditions in the DLR and NASA grazing ow test rigs. Additionally, by applying the in-house methods Liner Impedance Non-Uniform ow Solving algorithm (LINUS, DLR) and Convected Helmhholtz Equation approach (CHE, NASA) on the data sets, similarities and differences due to underlying theory are identi ed and discussed.
An approach to the diagnosis of metabolic syndrome by the multi-electrode impedance method
Furuya, N.; Sakamoto, K.; Kanai, H.
2010-04-01
It is well known that metabolic syndrome can induce myocardial infarction and cerebral infarction. So, it is very important to measure the visceral fat volume. In the electric impedance method, information in the vicinity of the electrodes is strongly reflected. Therefore, we propose a new multi-electrode arrangement method based on the impedance sensitivity theorem to measure the visceral fat volume. This electrode arrangement is designed to enable high impedance sensitivity in the visceral and subcutaneous fat regions. Currents are simultaneously applied to several current electrodes on the body surface, and one voltage electrode pair is arranged on the body surface near the organ of interest to obtain the visceral fat information and another voltage electrode pair is arranged on the body surface near the current electrodes to obtain the subcutaneous fat information. A simulation study indicates that by weighting the impedance sensitivity distribution, as in our method, a high-sensitivity region in the visceral and the subcutaneous fat regions can be formed. In addition, it was confirmed that the visceral fat volume can be estimated by the measured impedance data.
Ho, Kung-Chu; Su, Vin-Cent; Huang, Da-Yo; Lee, Ming-Lun; Chou, Nai-Kuan; Kuan, Chieh-Hsiung
2017-01-01
This paper reports the investigation of strong electrolytic solutions operated in low frequency regime through an accurate electrical impedance method realized with a specific microfluidic device and high resolution instruments. Experimental results show the better repeatability and accuracy of the proposed impedance method. Moreover, all electrolytic solutions appear the so-called relaxation frequency at each peak value of dielectric loss due to relaxing total polarization inside the device. The relaxation frequency of concentrated electrolytes becomes higher owing to the stronger total polarization behavior coming from the higher conductivity as well as the lower resistance in the electrolytic solutions.
Dolgin, M; Einziger, P D
2006-01-01
A novel electrical impedance tomography method is introduced for reconstruction of layered biological tissues with continuous plane-stratification. The algorithm implements the recently proposed reconstruction scheme for piecewise constant conductivity profiles, based on an improved Prony method in conjunction with Legendre polynomial expansion (LPE). It is shown that the proposed algorithm is capable of successfully reconstructing continuous conductivity profiles with moderate (WKB) slop. Features of the presented reconstruction scheme include, an inherent linearity, achieved by the linear LPE transform, a locality feature, assigning analytically to each spectral component a local electrical impedance associated with a unique location, and effective performance even in the presence of noisy measurements.
Impedance-Source Networks for Electric Power Conversion Part II
DEFF Research Database (Denmark)
Siwakoti, Yam P.; Peng, Fang Zheng; Blaabjerg, Frede
2015-01-01
Impedance-source networks cover the entire spectrum of electric power conversion applications (dc-dc, dc-ac, ac-dc, ac-ac) controlled and modulated by different modulation strategies to generate the desired dc or ac voltage and current at the output. A comprehensive review of various impedance......-source-network-based power converters has been covered in a previous paper and main topologies were discussed from an application point of view. Now Part II provides a comprehensive review of the most popular control and modulation strategies for impedance-source network-based power converters/inverters. These methods...... topology at a certain power level, switching frequency and demanded dynamic response....
New equivalent-electrical circuit model and a practical measurement method for human body impedance.
Chinen, Koyu; Kinjo, Ichiko; Zamami, Aki; Irei, Kotoyo; Nagayama, Kanako
2015-01-01
Human body impedance analysis is an effective tool to extract electrical information from tissues in the human body. This paper presents a new measurement method of impedance using armpit electrode and a new equivalent circuit model for the human body. The lowest impedance was measured by using an LCR meter and six electrodes including armpit electrodes. The electrical equivalent circuit model for the cell consists of resistance R and capacitance C. The R represents electrical resistance of the liquid of the inside and outside of the cell, and the C represents high frequency conductance of the cell membrane. We propose an equivalent circuit model which consists of five parallel high frequency-passing CR circuits. The proposed equivalent circuit represents alpha distribution in the impedance measured at a lower frequency range due to ion current of the outside of the cell, and beta distribution at a high frequency range due to the cell membrane and the liquid inside cell. The calculated values by using the proposed equivalent circuit model were consistent with the measured values for the human body impedance.
Experimental facility and void fraction calibration methods for impedance probes
Energy Technology Data Exchange (ETDEWEB)
Oliveira, Fernando L. de; Rocha, Marcelo S., E-mail: floliveira@ipen.br, E-mail: msrocha@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)
2013-07-01
An experimental facility was designed and constructed with aims of to calibrate a capacitance probe for gas-liquid flow void fraction measurements. The facility is composed of a metallic hack with a vertical 2,300 mm high glass tube with 38 mm ID with stagnant water and compressed air bubbling system simulating the gas phase (vapor). At the lower part, a mixing section with a porous media element releases the air bubbles into the water, and the compressed air flow is measured by two calibrated rotameters. At the upper part a stagnant water tank separates the liquid and gas. Two pressure taps are located near the lower and upper sides of the glass tube for pressure difference measurement. The pressure difference is used for low void fraction values (0-15%) calibration methods, as described in the work. Two electrically controlled quick closing valves are installed between the porous media element and the upward separation tank for high void fraction values measurement (15-50%) used to calibrate the capacitance probe. The experimental facility design, construction, capacitance probe calibration methods and results, as well as flow pattern visualization, are presented. Finally, the capacitance probe will be installed on a natural circulation circuit mounted at the Nuclear Engineering Center (CEN/IPEN/CNEN-SP) for measurement of the instantaneous bulk void. Instantaneous signals generated by the capacitance probe will allow the determination of natural circulation loop global energy balance. (author)
Impedance ratio method for urine conductivity-invariant estimation of bladder volume
Directory of Open Access Journals (Sweden)
Thomas Schlebusch
2014-09-01
Full Text Available Non-invasive estimation of bladder volume could help patients with impaired bladder volume sensation to determine the right moment for catheterisation. Continuous, non-invasive impedance measurement is a promising technology in this scenario, although influences of body posture and unknown urine conductivity limit wide clinical use today. We studied impedance changes related to bladder volume by simulation, in-vitro and in-vivo measurements with pigs. In this work, we present a method to reduce the influence of urine conductivity to cystovolumetry and bring bioimpedance cystovolumetry closer to a clinical application.
Method, system and computer-readable media for measuring impedance of an energy storage device
Energy Technology Data Exchange (ETDEWEB)
Morrison, John L.; Morrison, William H.; Christophersen, Jon P.; Motloch, Chester G.
2016-01-26
Real-time battery impedance spectrum is acquired using a one-time record. Fast Summation Transformation (FST) is a parallel method of acquiring a real-time battery impedance spectrum using a one-time record that enables battery diagnostics. An excitation current to a battery is a sum of equal amplitude sine waves of frequencies that are octave harmonics spread over a range of interest. A sample frequency is also octave and harmonically related to all frequencies in the sum. A time profile of this sampled signal has a duration that is a few periods of the lowest frequency. A voltage response of the battery, average deleted, is an impedance of the battery in a time domain. Since the excitation frequencies are known and octave and harmonically related, a simple algorithm, FST, processes the time profile by rectifying relative to sine and cosine of each frequency. Another algorithm yields real and imaginary components for each frequency.
Absorption and impedance boundary conditions for phased geometrical-acoustics methods
DEFF Research Database (Denmark)
Jeong, Cheol-Ho
2012-01-01
Defining accurate acoustical boundary conditions is of crucial importance for room acoustic simulations. In predicting sound fields using phased geometrical acoustics methods, both absorption coefficients and surface impedances of the boundary surfaces can be used, but no guideline has been...... developed on which boundary condition produces accurate results. In this study, various boundary conditions in terms of normal, random, and field incidence absorption coefficients and normal incidence surface impedance are used in a phased beam tracing model, and the simulated results are validated...... with boundary element solutions. Two rectangular rooms with uniform and non-uniform absorption distributions are tested. Effects of the neglect of reflection phase shift are also investigated. It is concluded that the impedance, random incidence, and field incidence absorption boundary conditions produce...
Absorption and impedance boundary conditions for phased geometrical-acoustics methods.
Jeong, Cheol-Ho
2012-10-01
Defining accurate acoustical boundary conditions is of crucial importance for room acoustic simulations. In predicting sound fields using phased geometrical acoustics methods, both absorption coefficients and surface impedances of the boundary surfaces can be used, but no guideline has been developed on which boundary condition produces accurate results. In this study, various boundary conditions in terms of normal, random, and field incidence absorption coefficients and normal incidence surface impedance are used in a phased beam tracing model, and the simulated results are validated with boundary element solutions. Two rectangular rooms with uniform and non-uniform absorption distributions are tested. Effects of the neglect of reflection phase shift are also investigated. It is concluded that the impedance, random incidence, and field incidence absorption boundary conditions produce reasonable results with some exceptions at low frequencies for acoustically soft materials.
Rangom, Yverick; Tang, Xiaowu Shirley; Nazar, Linda F
2015-07-28
We report the fabrication of high-performance, self-standing composite sp(2)-carbon supercapacitor electrodes using single-walled carbon nanotubes (CNTs) as conductive binder. The 3-D mesoporous mesh architecture of CNT-based composite electrodes grants unimpaired ionic transport throughout relatively thick films and allows superior performance compared to graphene-based devices at an ac line frequency of 120 Hz. Metrics of 601 μF/cm(2) with a -81° phase angle and a rate capability (RC) time constant of 199 μs are obtained for thin carbon films. The free-standing carbon films were obtained from a chlorosulfonic acid dispersion and interfaced to stainless steel current collectors with various surface treatments. CNT electrodes were able to cycle at 200 V/s and beyond, still showing a characteristic parallelepipedic cyclic votammetry shape at 1 kV/s. Current densities are measured in excess of 6400 A/g, and the electrodes retain more than 98% capacity after 1 million cycles. These promising results are attributed to a reduction of series resistance in the film through the CNT conductive network and especially to the surface treatment of the stainless steel current collector.
In vivo assessment of the impedance ratio method used in electronic foramen locators
Directory of Open Access Journals (Sweden)
Rambo Marcos VH
2010-09-01
Full Text Available Abstract Background The results of an in vivo study on the "ratio method" used in electronic foramen locators (EFL are presented. EFLs are becoming widely used in the determination of the working length (WL during the root canal treatment. The WL is the distance from a coronal reference point to the point at which canal preparation and filling should terminate. The "ratio method" was assessed by many clinicians with the aim of determining its ability to locate the apical foramen (AF. Nevertheless, in vivo studies to assess the method itself and to explain why the "ratio method" is able to locate the apical foramen and is unable to determine intermediate distances were not published so far. Methods A developed apparatus applies an electrical current signal with constant amplitude of 10 μARMS through the endodontic file within the root canal. The applied current signal is composed by summing six sine waves, from 250 Hz to 8 kHz. Data were acquired with the endodontic file tip at 7 different positions within root canals. In the frequency domain the quotients between the amplitude of a reference frequency and the amplitudes of the other frequencies components were calculated. Twenty one root canals were analyzed in vivo, during the endodontic treatment of twelve teeth of different patients, with age between 20 to 55 years. Results For the range of frequencies used in the commercial EFLs and for distances ranging from -3 mm to -1 mm of the AF, the impedance of the root canal is mainly resistive. However, when the file tip gets closer to AF, the root canal electrical impedance starts to change from a mainly resistive to a complex impedance. This change in the measured root canal impedance starts when the file tip is near -1.0 mm from the AF, getting stronger as the file tip gets closer to the AF. This change in the impedance behavior affects the ratio (quotient of the impedance measured at different frequencies. Through graphic analysis it is
Miles, Robin R.; Belgrader, Phillip; Fuller, Christopher D.
2007-01-02
Impedance measurements are used to detect the end-point for PCR DNA amplification. A pair of spaced electrodes are located on a surface of a microfluidic channel and an AC or DC voltage is applied across the electrodes to produce an electric field. An ionically labeled probe will attach to a complementary DNA segment, and a polymerase enzyme will release the ionic label. This causes the conductivity of the solution in the area of the electrode to change. This change in conductivity is measured as a change in the impedance been the two electrodes.
Pulse wave detection method based on the bio-impedance of the wrist
He, Jianman; Wang, Mengjun; Li, Xiaoxia; Li, Gang; Lin, Ling
2016-05-01
The real-time monitoring of pulse rate can evaluate the heart health to some extent, and the measurement of bio-impedance has the potential in wearable health monitoring system. In this paper, an effective method, which contains self-balancing bridge, flexible electrode, and high-speed digital lock-in algorithm (DLIA) with over-sampling, was designed to detect the impedance pulse wave at the wrist. By applying the self-balancing bridge, the basic impedance can be compensated as much as possible, and the low amplitude of impedance variation related to heart pulse can be obtained more easily. And the flexible conductive rubber electrode used in our experiment is human-friendly. Besides, the over-sampling method and high-speed DLIA are used to enhance the effective resolution of the existing data sampled by analog to digital converter. With the high-speed data process and simple circuit above, this proposed method has the potential in wrist-band wearable systems and it can satisfy quests of small volume and low power consumption.
Directory of Open Access Journals (Sweden)
Jayant Kolte
2015-09-01
Full Text Available In this paper, major reduction in sintering time,temperautre and significant improvement over final density of sitnered sample is reported for the microwave sintered nanocrystalline BiFeO3 (BFO ceramic. Also, different sintering time and temperatures have been used to tailor the grain size and the final density of the resulting BFO ceramics synthesized from phase pure BFO nanoparticles ( d ̄ ≈ 10 n m . Microwave sintering resulted in reducing the sintering time substantially (by 1h, and has resulted in submicron sized grains and high resistivity ∼1.8 GΩ-cm. The AC conductivity is seen to follow the Jonscher’s power law behavior, suggesting correlated barrier hopping (CBH mechanism in the sample. The role of oxygen vacancies at high temperature, due to volatility of bismuth, in dielectric and conductivity behavior is also discussed. Further, the sample displayed dielectric anomaly near magnetic transition temperature (∼180 °C indicating bearing of magnetic moments on the dielectric properties. Using Impedance Spectroscopy (IS we have established, the electrical heterogeneity of the ceramic BFO reavealing semiconducting nature of grains and insulating nature of grain boundary. This, formation of network of insulating grain boundaries and semiconducting grains could lead to formation of internal barrier layer capacitance (IBLC leading to high dielectric constant in microwave sintered BFO.
Indian Academy of Sciences (India)
S Rodrigues; N Munichandraiah; A K Shukla
2001-10-01
Metal-hydride electrodes made of an AB2 alloy of the composition Zr0.5Ti0.5V0.6Cr0.2Ni1.2 are studied for AC impedance behaviour at several of their state-of-charge values. Impedance data at any state-of-charge comprise two RC-time constants and accordingly are analysed by using a nonlinear-least-square-fitting procedure. Resistance of the electrode and frequency maximum (*) of the lowfrequency semicircle are found useful for predicting state-of-charge of the metalhydride electrodes.
Derek Johnson; Matthew Smith; Kevin R. Cooper
2008-01-01
The development of impedance-based array devices is hindered by a lack of robust platforms and methods upon which to evaluate and interrogate sensors. One aspect to be addressed is the development of measurement-time efficient techniques for broadband impedance spectroscopy of large electrode arrays. The objective of this work was to substantially increase the low frequency impedance measurement throughput capability of a large channel count array analyzer by developing true parallel measurem...
A study on calculation method for mechanical impedance of air spring
Changgeng, SHUAI; Penghui, LI; Rustighi, Emiliano
2016-09-01
This paper proposes an approximate analytic method of obtaining the mechanical impedance of air spring. The sound pressure distribution in cylindrical air spring is calculated based on the linear air wave theory. The influences of different boundary conditions on the acoustic pressure field distribution in cylindrical air spring are analysed. A 1-order ordinary differential matrix equation for the state vector of revolutionary shells under internal pressure is derived based on the non-moment theory of elastic thin shell. Referring to the transfer matrix method, a kind of expanded homogeneous capacity high precision integration method is introduced to solve the non-homogeneous matrix differential equation. Combined the solved stress field of shell with the calculated sound pressure field in air spring under the displacement harmonic excitation, the approximate analytical expression of the input and transfer mechanical impedance for the air spring can be achieved. The numerical simulation with the Comsol Multiphysics software verifies the correctness of theoretical analysis result.
A method for modelling and optimizing an electrical impedance tomography system.
Hartinger, Alzbeta Elizabeth; Gagnon, Hervé; Guardo, Robert
2006-05-01
Electrical impedance tomography (EIT) image reconstruction is an ill-posed problem requiring maximum measurement precision. Recent EIT systems claim 60 to 80 dB precision. Achieving higher values is hard in practice since measurements must be performed at relatively high frequency, on a living subject, while using components whose tolerance is usually higher than 0.1%. To circumvent this difficulty, a method for modelling the electronic circuits of an EIT system was developed in order to optimize the circuits and incorporate the model in the reconstruction algorithms. The proposed approach is based on a matrix method for solving electrical circuits and has been applied to the scan-head which contains the front-end electronic circuits of our system. The method is used to simulate the system characteristic curves which are then optimized with the Levenberg-Marquardt method to find optimal component values. A scan-head was built with the new component values and its simulated performance curves were compared with network analyser measurements. As a result of the optimization, the impedance at the operating frequency was increased to minimize the effects of variations in skin/electrode contact impedance. The transconductance and gain frequency responses were also reshaped to reduce noise sensitivity and unintended signal modulation. Integrating the model in the reconstruction algorithms should further improve overall performance of an EIT system.
Brandão, Eric; Flesch, Rodolfo C C; Lenzi, Arcanjo; Flesch, Carlos A
2011-07-01
The pressure-particle velocity (PU) impedance measurement technique is an experimental method used to measure the surface impedance and the absorption coefficient of acoustic samples in situ or under free-field conditions. In this paper, the measurement uncertainty of the the absorption coefficient determined using the PU technique is explored applying the Monte Carlo method. It is shown that because of the uncertainty, it is particularly difficult to measure samples with low absorption and that difficulties associated with the localization of the acoustic centers of the sound source and the PU sensor affect the quality of the measurement roughly to the same extent as the errors in the transfer function between pressure and particle velocity do.
Voltage Based Detection Method for High Impedance Fault in a Distribution System
Thomas, Mini Shaji; Bhaskar, Namrata; Prakash, Anupama
2016-09-01
High-impedance faults (HIFs) on distribution feeders cannot be detected by conventional protection schemes, as HIFs are characterized by their low fault current level and waveform distortion due to the nonlinearity of the ground return path. This paper proposes a method to identify the HIFs in distribution system and isolate the faulty section, to reduce downtime. This method is based on voltage measurements along the distribution feeder and utilizes the sequence components of the voltages. Three models of high impedance faults have been considered and source side and load side breaking of the conductor have been studied in this work to capture a wide range of scenarios. The effect of neutral grounding of the source side transformer is also accounted in this study. The results show that the algorithm detects the HIFs accurately and rapidly. Thus, the faulty section can be isolated and service can be restored to the rest of the consumers.
Development of a new salmon salting smoking method and process monitoring by impedance spectroscopy
Rizo Parraga, Arancha Maria; Fuentes López, Ana; Fernández Segovia, Isabel; Masot Peris, Rafael; Alcañiz Fillol, Miguel; Barat Baviera, José Manuel
2013-01-01
[EN] In this work two objectives were proposed: (i) to optimize a new salmon salting smoking method using vacuum packaging and (ii) to evaluate the application of impedance spectroscopy (IS) to the on-line monitoring of the process. Different processing conditions were evaluated (4 smoke flavoring (SF) salt concentrations, 3 salting times, salting in vacuum or in air). Physico-chemical analyses and IS measurements were performed with three different sensors during the process. Salting with 16...
A Convergent Method of Auxiliary Sources for Two-Dimensional Impedance Scatterers With Edges
DEFF Research Database (Denmark)
Karamehmedovic, Mirza; Breinbjerg, Olav
2001-01-01
A modification to the Method of Auxiliary Sources (MAS) is introduced which renders the method operational for two-dimensional impedance scatterers with edges. The modification consists in letting the auxiliary surface converge to the scatterer physical surface for increasing number of auxiliary...... sources, whereby MAS approaches a surface integral equation (IE) method. Hereby, a systematic procedure for selecting the number and locations of the auxiliary sources is provided, and convergence of numerical results is obtained. The new method resulting from this modification thus combines the desirable...
A method to detect heart rate based on electrical bio-impedance
Directory of Open Access Journals (Sweden)
Li Kun-Yang
2016-01-01
Full Text Available As a basic health indicator, heart rate has been widely used in clinical measurement and daily health care. Electrical bio-impedance (EBI measurement provides non-invasive method for heart rate detection. Therefore, this paper proposed a method to detect heart rate based on EBI. With the BIOPAC EBI module, the signal can be de-noised in real-time. Finally, the de-noised EBI signal is used to compute heart rate. Four electrodes are located at radial artery of left upper limb in this method. The result proves that this method has high accuracy on heart rate measurement.
Ac Impedance Spectroscopic Studies on Li2xPb2xBaP2O7
Vijayakumar, M.; Selvasekarapandian, S.
2002-12-01
The complex diphosphate (P2O7)4- ions have been used as a building blocks in wide variety of crystal phases for a wide spectrum of physical and chemical properties. Lithium barium diphsophate doped with lead {Li2-xPb2xBaP2O7 (x = 0, 0.2 & 0.4)} has been prepared by solid state reaction method The conductivity is found to be decreasing with the doping of lead. The lithium ion dynamics parameters such as hopping frequency and relaxation frequency were calculated from the frequency dependent conductivity and modulus analysis.
Zhu, J. G.; Sun, Z. C.; Wei, X. Z.; Dai, H. F.
2015-01-01
The power battery thermal management problem in EV (electric vehicle) and HEV (hybrid electric vehicle) has been widely discussed, and EIS (electrochemical impedance spectroscopy) is an effective experimental method to test and estimate the status of the battery. Firstly, an electrochemical-based impedance matrix analysis for lithium-ion battery is developed to describe the impedance response of electrochemical impedance spectroscopy. Then a method, based on electrochemical impedance spectroscopy measurement, has been proposed to estimate the internal temperature of power lithium-ion battery by analyzing the phase shift and magnitude of impedance at different ambient temperatures. Respectively, the SoC (state of charge) and temperature have different effects on the impedance characteristics of battery at various frequency ranges in the electrochemical impedance spectroscopy experimental study. Also the impedance spectrum affected by SoH (state of health) is discussed in the paper preliminary. Therefore, the excitation frequency selected to estimate the inner temperature is in the frequency range which is significantly influenced by temperature without the SoC and SoH. The intrinsic relationship between the phase shift and temperature is established under the chosen excitation frequency. And the magnitude of impedance related to temperature is studied in the paper. In practical applications, through obtaining the phase shift and magnitude of impedance, the inner temperature estimation could be achieved. Then the verification experiments are conduced to validate the estimate method. Finally, an estimate strategy and an on-line estimation system implementation scheme utilizing battery management system are presented to describe the engineering value.
System and method for determining stator winding resistance in an AC motor
Lu, Bin; Habetler, Thomas G.; Zhang, Pinjia; Theisen, Peter J.
2011-05-31
A system and method for determining stator winding resistance in an AC motor is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of an AC motor. The circuit includes at least one contactor and at least one switch to control current flow and terminal voltages in the AC motor. The system also includes a controller connected to the circuit and configured to modify a switching time of the at least one switch to create a DC component in an output of the system corresponding to an input to the AC motor and determine a stator winding resistance of the AC motor based on the injected DC component of the voltage and current.
Energy Technology Data Exchange (ETDEWEB)
Kim, In-Tae; Egashira, Minato; Yoshimoto, Nobuko [Department of Applied Chemistry, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1, Tokiwadai, Ube 755-8611 (Japan); Morita, Masayuki, E-mail: morita@yamaguchi-u.ac.jp [Department of Applied Chemistry, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1, Tokiwadai, Ube 755-8611 (Japan)
2011-08-30
Highlights: {center_dot} We monitored resonance frequency change of smooth surface carbon electrode to determine mass changes during electrochemical polarization.{center_dot} This was done from viewpoints of ensuring the electric double-layer structure in organic electrolytes.{center_dot} Clear difference was observed in the mass changes among the electrolyte composition.{center_dot} It were related with differences in the double-layer capacitance at carbon. - Abstract: ac impedance and electrochemical quartz crystal microbalance (EQCM) techniques have been applied to analyze the structure of electric double-layer formed at carbon/organic electrolyte solution interface using a sputtered carbon electrode. The mass changes caused by electrochemical adsorption (accumulation) of ions have been estimated in the solutions of propylene carbonate (PC) dissolving tetrafluoroborate (BF{sub 4}{sup -}) salts of lithium (Li{sup +}), tetraethylammonium (TEA{sup +}) and tetra-n-butylammonium (TBA{sup +}) cations. The observed mass changes during the cathodic polarization in the solutions containing TEA{sup +} and TBA{sup +} were well consistent with those expected by the calculation based on mono-layer adsorption of the cations with giving the consideration to the surface roughness. On the other hand, the mass change observed in the solution containing Li{sup +} salt showed that the solvation of Li{sup +} with three or four molecules of PC would be the charge compensation species at the interface. Comparison of the quantity of the electricity passed during the EQCM measurements with that from theoretical calculation with simple Helmholtz-layer model revealed that the major part of the double-layer capacitance would be based on the electrostatic polarization of the solvent molecule directly adsorbed at the carbon surface.
Institute of Scientific and Technical Information of China (English)
吴方劼; 史梦梦; 胡志坚; 王小飞; 陈彬; 汤鹏; 邱骁奇
2016-01-01
换流站母线处谐波阻抗值可为直流输电系统中滤波器的设计提供参数依据,对抑制系统谐波至关重要.在完善发电机、变压器、线路、母线负荷等电气元件谐波阻抗模型的基础上,研究基于中国版BPA数据的系统谐波阻抗等值计算方法.提出基于半动态-遗传算法的节点编号优化方法,利用连线矩阵改进节点导纳矩阵的形成,采用稀疏矩阵技术中的排零存储和排零运算提高程序的运行效率.用PSCAD对标准的IEEE 9节点系统进行仿真,验证了所提方法的正确性和有效性.根据电网BPA数据,对某特高压直流输电工程的谐波阻抗进行阻抗扫描,在N-O、N-1及N-2开断方式下分别对丰大、丰小、枯大、枯小运行方式进行谐波阻抗计算,得到了阻抗随频率变化的阻抗图及扇形包络图,为该地区特高压直流输电系统的交流滤波器参数设计提供了依据.%The harmonic impedance at the bus of converter station is a critical parameter in the filter design of HVDC transmission system for suppressing harmonics.The electric element harmonic impedance models are improved for generator,transformer,line and bus load,based on which,the method for calculating the system harmonic impedance equivalent is researched based on the BPA data of China version.A node numbering optimization method based on the semi-dynamic genetic algorithm is proposed,the connection matrix is adopted to improve the formation of node admittance matrix,and the zero-exclusive storage & operation of sparse matrix technology are used to improve the operational efficiency of program.PSCAD simulation is carried out for the standard IEEE 9-bus system to verify the correctness and effectiveness of the proposed method.Based on the BPA data,the harmonic impedance equivalent of a HVDC transmission system is calculated respectively for three switching patterns,i.e.N-0,N-1 and N-2,in four operating modes,i.e.,flood season large power flow
Timmer, B.; Sluyters-Rehbach, M.; Sluyters, J.H.
1967-01-01
A theoretical treatment for the potential dependence of the faradaic impedance, in the case that the electrode reaction behaves irreversibly with respect to the direct current, using the steady-state concept, is presented. An analysis of the expressions obtained in the complex impedance plane is giv
三相交流异步电动机阻抗参数计算%Impedance Parameter Calculation of Three-phase AC Asynchronous Motor
Institute of Scientific and Technical Information of China (English)
姚家祎
2016-01-01
结合电动机产品样本数据，分别采用计算法、 GB/T 21066-2007《船舶和移动式及固定式近海设施的电气装置三相交流短路电流计算方法》给出的推荐值和试验法3种方法进行计算，分析比较其计算结果的准确性，建议尽量按电动机容量相应的技术数据，用计算方法求电动机阻抗参数；并建议电动机厂商在样本中给出阻抗值，方便工程设计人员计算电动机短路电流。%Based on the sample data of motor, three methods, i. e. calculation method, recommended value and test method, of which the recommended value is recorded in the Electrical Installations of Ships and Mobile and Fixed Offshore Units—Procedures for Calculating Short-circuit Currents in Three-phase A. C. (GB/T 21066-2007), are adopted respectively, so as to analyze and compare the accuracy of computations. It is suggested that the motor impedance parameter is determined by the calculation method according to the technical data of motor capacity, and that the impedance is available for the sample of motor manufacturer so that the engineering designer can calculate the short-circuit current of motor more easily.
Energy Technology Data Exchange (ETDEWEB)
Bentiss, F. [Laboratoire de Chimie de Coordination et d' Analytique, Faculte des Sciences, Universite Chouaib Doukkali, B.P. 20, M-24000 El Jadida (Morocco)]. E-mail: f.bentiss@pop.ensc-lille.fr; Lebrini, M. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, PERF-LSPES UMR-CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Lagrenee, M. [Unite de Catalyse et de Chimie du Solide, UMR-CNRS 8181, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Traisnel, M. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, PERF-LSPES UMR-CNRS 8008, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Elfarouk, A. [Laboratoire de Mathematiques Pures et Appliquees, Universite du Littoral-Cote d' Opale, C.U. de la Mi-Voix, 50 Rue F. Buisson, BP 699, F-62228 Calais Cedex (France); Vezin, H. [Laboratoire de Chimie Organique et Macromoleculaire, UMR-CNRS 8009, USTL Bat C4, F-59655 Villeneuve d' Ascq Cedex (France)
2007-08-01
The new 2,5-disubstituted 1,3,4-thiadiazoles were investigated as corrosion inhibitors of mild steel in 1 M HCl using AC impedance technique. Four of these compounds exhibit good inhibition properties, while two of them, 2,5-bis(4-nitrophenyl)-1,3,4-thiadiazole and 2,5-bis(4-chlorophenyl)-1,3,4-thiadiazole, stimulate the corrosion process especially at low concentrations. The experimental data obtained from this method show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. Possible correlations between experimental inhibition efficiencies and quantum chemical parameters such as dipole moment ({mu}), highest occupied (E {sub HOMO}) and lowest unoccupied (E {sub LUMO}) molecular orbitals were investigated. The models of the inhibitors were optimised with the Density Functional Theory formalism (DFT) using hybrid B3LYP/6-31G (2d,2p) as a higher level of theory. The Quantitative Structure Activity Relationship (QSAR) approach has been used and composite index of some quantum chemical parameters were constructed in order to characterize the inhibition performance of the tested molecules.
D-bar method for electrical impedance tomography with discontinuous conductivities
DEFF Research Database (Denmark)
Knudsen, Kim; Lassas, Matti; Mueller, Jennifer L.;
The effects of truncating the (approximate) scattering transform in the D-bar reconstruction method for 2-D electrical impedance tomography are studied. The method is based on Nachman s uniqueness proof [Ann. of Math. 143 (1996)] that applies to twice differentiable conductivities. However......, the reconstruction algorithm has been successfully applied to experimental data, which can be characterized as piecewise smooth conductivities. The truncation is shown to stabilize the method against measurement noise and to have a smoothing effect on the reconstructed conductivity. Thus the truncation can...... be interpreted as regularization of the D-bar method. Numerical reconstructions are presented demonstrating that features of discontinuous high contrast conductivities can be recovered using the D-bar method. Further, a new connection between Calder´on s linearization method and the D-bar method is established...
Yang, Qingxia; Xu, Jun; Cao, Binggang; Li, Xiuqing
2017-01-01
Identification of internal parameters of lithium-ion batteries is a useful tool to evaluate battery performance, and requires an effective model and algorithm. Based on the least square genetic algorithm, a simplified fractional order impedance model for lithium-ion batteries and the corresponding parameter identification method were developed. The simplified model was derived from the analysis of the electrochemical impedance spectroscopy data and the transient response of lithium-ion batteries with different states of charge. In order to identify the parameters of the model, an equivalent tracking system was established, and the method of least square genetic algorithm was applied using the time-domain test data. Experiments and computer simulations were carried out to verify the effectiveness and accuracy of the proposed model and parameter identification method. Compared with a second-order resistance-capacitance (2-RC) model and recursive least squares method, small tracing voltage fluctuations were observed. The maximum battery voltage tracing error for the proposed model and parameter identification method is within 0.5%; this demonstrates the good performance of the model and the efficiency of the least square genetic algorithm to estimate the internal parameters of lithium-ion batteries. PMID:28212405
Yang, Qingxia; Xu, Jun; Cao, Binggang; Li, Xiuqing
2017-01-01
Identification of internal parameters of lithium-ion batteries is a useful tool to evaluate battery performance, and requires an effective model and algorithm. Based on the least square genetic algorithm, a simplified fractional order impedance model for lithium-ion batteries and the corresponding parameter identification method were developed. The simplified model was derived from the analysis of the electrochemical impedance spectroscopy data and the transient response of lithium-ion batteries with different states of charge. In order to identify the parameters of the model, an equivalent tracking system was established, and the method of least square genetic algorithm was applied using the time-domain test data. Experiments and computer simulations were carried out to verify the effectiveness and accuracy of the proposed model and parameter identification method. Compared with a second-order resistance-capacitance (2-RC) model and recursive least squares method, small tracing voltage fluctuations were observed. The maximum battery voltage tracing error for the proposed model and parameter identification method is within 0.5%; this demonstrates the good performance of the model and the efficiency of the least square genetic algorithm to estimate the internal parameters of lithium-ion batteries.
Directory of Open Access Journals (Sweden)
NEJLA OUESLATI,
2011-03-01
Full Text Available This paper presents an integral equation analysis of planar microstrip circuits. In the developed approach, the Moment Method (MoM with wavelet expansion is combined to the generalized equivalent circuit (GEC to characterize microstrip structures. The interest of the (GEC method is to simplify the implementation of the moment method by the translation of an electromagnetic problem to an electric one with the use of the impedance operator. In the multiresolution moment method (MRMoM-GEC, an excitation on the plane of the circuit is used in conjunction with compactly supported wavelets trial functions. This approach generates a sparse linear system. The application of the Discrete Wavelet Transform (DWT,especially for large structures, allows a significant reduction of the unit time of central processing.
DEFF Research Database (Denmark)
Swierczynski, Maciej Jozef; Stroe, Daniel Loan; Stanciu, Tiberiu;
2016-01-01
for parametrization. Recent research initiated by Barsoukov et al. proposed electrothermal impedance spectroscopy as a novel and non-destructive method of characterizing the thermal properties of batteries by defining frequency dependent thermal impedance. Despite its usefulness, the electrothermal impedance...... spectroscopy method can be still improved in terms of e.g. accuracy and measurement time and it has a potential to be extended to new applications. Performed review indicates that the electrothermal impedance spectroscopy is a very promising, non-destructive, simple and especially cost-efficient method...... for thermal characterization of batteries. The scientific intention of this paper is to collect and systematize the state of knowledge about electrothermal impedance spectroscopy and present different measurement methods on the example of a high-power lithium battery cell and finally to discuss the prospect....
Directory of Open Access Journals (Sweden)
İhsan Çetin
2015-12-01
Full Text Available Objective: In this study, it was aimed to evaluate segmental body composition of children diagnosed with obesity using bioelectrical impedance analysis method in terms of different gender. Methods: 48 children, aged between 6-15 years, 21 of whom were boys while 27 were girls, diagnosed with obesity in Erciyes University Medical Faculty Department of Pediatric Endocrinology Outpatient Clinic were included in our study from April to June in 2011. Those over 95 percentile were defined as obese group. Tanita BC-418 device was used to analyze the body composition. Results: As a result of bioelectrical impedance analysis, lean body mass and body muscle mass were found to be statistically significantly higher in obese girls compared with obese boys. However, lean mass of the left arm, left leg muscle mass and basal metabolic rate were found to be statistically significantly lower in obese girls compared with obese boys. Conclusion: Consequently, it may be suggest that segmental analysis, where gender differences are taken into account, can provide proper exercise pattern and healthy way of weight loss in children for prevention of obesity and associated diseases including obesity and type 2 diabetics and cardiovascular diseases.
Daniel Medale; Sebastien Rolet; Jean Yves Fourniols; Sabeha Zedek; Christophe Escriba; Hamza Boukabache
2012-01-01
The work reported on this paper describes a new methodology implementation for active structural health monitoring of recent aircraft parts made from carbon-fiber-reinforced polymer. This diagnosis is based on a new embedded method that is capable of measuring the local high frequency impedance spectrum of the structure through the calculation of the electro-mechanical impedance of a piezoelectric patch pasted non-permanently onto its surface. This paper involves both the laboratory based E/M...
Amako, Eri; Enjoji, Takaharu; Uchida, Satoshi; Tochikubo, Fumiyoshi
Constant monitoring and immediate control of fermentation processes have been required for advanced quality preservation in food industry. In the present work, simple estimation of metabolic states for heat-injured Escherichia coli (E. coli) in a micro-cell was investigated using dielectrophoretic impedance measurement (DEPIM) method. Temporal change in the conductance between micro-gap (ΔG) was measured for various heat treatment temperatures. In addition, the dependence of enzyme activity, growth capacity and membrane situation for E. coli on heat treatment temperature was also analyzed with conventional biological methods. Consequently, a correlation between ΔG and those biological properties was obtained quantitatively. This result suggests that DEPIM method will be available for an effective monitoring technique for complex change in various biological states of microorganisms.
DEFF Research Database (Denmark)
Ghzaiel, Walid; Jebali-Ben Ghorbal, Manel; Slama-Belkhodja, Ilhem
2014-01-01
This paper presents a hybrid islanding detection algorithm integrated on the distributed generation unit more close to the point of common coupling of a Microgrid based on parallel inverters where one of them is responsible to control the system. The method is based on resonance excitation under...... parameters, both resistive and inductive parts, from the injected resonance frequency determination. Finally, the inverter will disconnect the microgrid from the faulty grid and reconnect the parallel inverter system to the controllable distributed system in order to ensure high power quality. This paper...... shows that grid impedance variation detection estimation can be an efficient method for islanding detection in microgrid systems. Theoretical analysis and simulation results are presented to validate the proposed method....
Segmented superconducting tape having reduced AC losses and method of making
Foltyn, Stephen R.; Jia, Quanxi; Arendt, Paul N.; Holesinger, Terry G.; Wang, Haiyan
2009-09-22
A superconducting tape having reduced AC losses. The tape has a high temperature superconductor layer that is segmented. Disruptive strips, formed in one of the tape substrate, a buffer layer, and the superconducting layer create parallel discontinuities in the superconducting layer that separate the current-carrying elements of the superconducting layer into strips or filament-like structures. Segmentation of the current-carrying elements has the effect of reducing AC current losses. Methods of making such a superconducting tape and reducing AC losses in such tapes are also disclosed.
Barak, C; Leviatan, Y; Inbar, G F; Hoekstein, K N
1992-09-01
Using the electrical impedance measurement technique to investigate stroke volume estimation, three models of the ventricle were simulated. A four-electrode impedance catheter was used; two electrodes to set up an electric field in the model and the other two to measure the potential difference. A new approach, itself an application of the quasi-static case of a method used to solve electromagnetic field problems, was used to solve the electric field in the model. The behaviour of the estimation is examined with respect to the electrode configuration on the catheter and to catheter location with respect to the ventricle walls. Cardiac stroke volume estimation was found to be robust to catheter location generating a 10 per cent error for an offset of 40 per cent of the catheter from the chamber axis and rotation of 20 degrees with respect to the axis. The electrode configuration has a dominant effect on the sensitivity and accuracy of the estimation. Certain configurations gave high accuracy, whereas in others high sensitivity was found with lower accuracy. This led to the conclusion that the electrode configuration should be carefully chosen according to the desired criteria.
Wang, Qi; Wang, Huaxiang; Zhang, Ronghua; Wang, Jinhai; Zheng, Yu; Cui, Ziqiang; Yang, Chengyi
2012-10-01
Electrical impedance tomography (EIT) is a technique for reconstructing the conductivity distribution by injecting currents at the boundary of a subject and measuring the resulting changes in voltage. Image reconstruction in EIT is a nonlinear and ill-posed inverse problem. The Tikhonov method with L(2) regularization is always used to solve the EIT problem. However, the L(2) method always smoothes the sharp changes or discontinue areas of the reconstruction. Image reconstruction using the L(1) regularization allows addressing this difficulty. In this paper, a sum of absolute values is substituted for the sum of squares used in the L(2) regularization to form the L(1) regularization, the solution is obtained by the barrier method. However, the L(1) method often involves repeatedly solving large-dimensional matrix equations, which are computationally expensive. In this paper, the projection method is combined with the L(1) regularization method to reduce the computational cost. The L(1) problem is mainly solved in the coarse subspace. This paper also discusses the strategies of choosing parameters. Both simulation and experimental results of the L(1) regularization method were compared with the L(2) regularization method, indicating that the L(1) regularization method can improve the quality of image reconstruction and tolerate a relatively high level of noise in the measured voltages. Furthermore, the projected L(1) method can also effectively reduce the computational time without affecting the quality of reconstructed images.
Improved Design Methods for Robust Single- and Three-Phase ac-dc-ac Power Converters
DEFF Research Database (Denmark)
Qin, Zian
becomes a emerging challenge. Accordingly, installation of sustainable power generators like wind turbines and solar panels has experienced a large increase during the last decades. Meanwhile, power electronics converters, as interfaces in electrical system, are delivering approximately 80 % electricity...... aspects as: control methods, auxiliary circuits, and application criteria. The details are as follows: 1. new modulation schemes of single-phase B6 and H6 converters for improved performance, 2. an optimal active power decoupling approach for kW-scale single-phase converters to achieve high power density......After a century of fast developing, the society is facing energy issues again, e.g. the exhaustion of fossil fuel, emission caused air pollution, radiation leakage of nuclear generation, and so on. How to produce and use electricity in a more sustainable, efficient, and cost-effective way thus...
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Sanju Gupta
2016-07-01
Full Text Available Graphene nanosheets and graphene nanoribbons, G combined with vanadium pentoxide (VO nanobelts (VNBs and VNBs forming GVNB composites with varying compositions were synthesized via a one-step low temperature facile hydrothermal decomposition method as high-performance electrochemical pseudocapacitive electrodes. VNBs from vanadium pentoxides (VO are formed in the presence of graphene oxide (GO, a mild oxidant, which transforms into reduced GO (rGOHT, assisting in enhancing the electronic conductivity coupled with the mechanical robustness of VNBs. From electron microscopy, surface sensitive spectroscopy and other complementary structural characterization, hydrothermally-produced rGO nanosheets/nanoribbons are decorated with and inserted within the VNBs’ layered crystal structure, which further confirmed the enhanced electronic conductivity of VNBs. Following the electrochemical properties of GVNBs being investigated, the specific capacitance Csp is determined from cyclic voltammetry (CV with a varying scan rate and galvanostatic charging-discharging (V–t profiles with varying current density. The rGO-rich composite V1G3 (i.e., VO/GO = 1:3 showed superior specific capacitance followed by VO-rich composite V3G1 (VO/GO = 3:1, as compared to V1G1 (VO/GO = 1:1 composite, besides the constituents, i.e., rGO, rGOHT and VNBs. Composites V1G3 and V3G1 also showed excellent cyclic stability and a capacitance retention of >80% after 500 cycles at the highest specific current density. Furthermore, by performing extensive simulations and modeling of electrochemical impedance spectroscopy data, we determined various circuit parameters, including charge transfer and solution resistance, double layer and low frequency capacitance, Warburg impedance and the constant phase element. The detailed analyses provided greater insights into physical-chemical processes occurring at the electrode-electrolyte interface and highlighted the comparative performance of
Calorimetric method of ac loss measurement in a rotating magnetic field.
Ghoshal, P K; Coombs, T A; Campbell, A M
2010-07-01
A method is described for calorimetric ac-loss measurements of high-T(c) superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.
Hoche, S; Hussein, M A; Becker, T
2015-03-01
The accuracy of density, reflection coefficient, and acoustic impedance determination via multiple reflection method was validated experimentally. The ternary system water-maltose-ethanol was used to execute a systematic, temperature dependent study over a wide range of densities and viscosities aiming an application as inline sensor in beverage industries. The validation results of the presented method and setup show root mean square errors of: 1.201E-3 g cm(-3) (±0.12%) density, 0.515E-3 (0.15%) reflection coefficient and 1.851E+3 kg s(-1) m(-2) (0.12%) specific acoustic impedance. The results of the diffraction corrected absorption showed an average standard deviation of only 0.12%. It was found that the absorption change shows a good correlation to concentration variations and may be useful for laboratory analysis of sufficiently pure liquids. The main part of the observed errors can be explained by the observed noise, temperature variation and the low signal resolution of 50 MHz. In particular, the poor signal-to-noise ratio of the second reflector echo was found to be a main accuracy limitation. Concerning the investigation of liquids the unstable properties of the reference material PMMA, due to hygroscopicity, were identified to be an additional, unpredictable source of uncertainty. While dimensional changes can be considered by adequate methodology, the impact of the time and temperature dependent water absorption on relevant reference properties like the buffer's sound velocity and density could not be considered and may explain part of the observed deviations.
Heifetz, Alexander; Bakhtiari, Sasan; Lu, Juan; Aranson, Igor S.; Vinokur, Valerii M.; Bentivegna, Anthony F.
2017-02-01
Aging concrete degradation due to alkali silica reaction (ASR) is a challenge to sustainability of critical infrastructure, such as nuclear power plants. Currently, there is no standard, nondestructive method for detecting ASR in concrete. We report on the progress in developing electromagnetic (EM) methods, consisting of microwave and impedance spectroscopy techniques, for nondestructive detection of ASR. The microwave and impedance spectroscopy methods are complementary since they provide information about material electrical properties in GHz and Hz to KHz EM spectral bands, respectively. Preliminary studies were conducted using accelerated testing concrete prism specimens developed according to ASTM C1293 standard. Microwave and impedance spectroscopy measurements were performed on ASR specimens at the first and the second month maturity level, as well as on age-matched controls. Microwave tests consisted of reflection and transmission measurements using dielectric-loaded antennas, with the focus on X-band spectrum. Impedance measurements were performed using flexible electrode patches. Measurement results by both microwave and impedance spectroscopy methods indicate observable differences in electrical properties between reactive and non-reactive specimens. In addition, trends in measurement data obtained with the two complementary EM techniques are consistent and correlate with ASR progression in specimens.
A new method for calculation of low-frequency coupling impedance
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S.S.; Stupakov, G.V.
1993-05-01
In high-energy proton accelerators and storage rings the bunch length is typically at least a few times larger than the radius of the vacuum chamber. For example, the SSC will have an rms bunch length above 6 cm and a beam-pipe radius below 2 cm. The main concern for beam stability in such a machine is the low-frequency impedance, i.e., the coupling impedance at frequencies wen below the cut-off frequency of the vacuum chamber. In the present paper we develop a new analytical approach for calculation of the low-frequency impedance of axisymmetric structures that allows us to give quick and reliable estimates of contributions to the impedance from various chamber discontinuities. Simple formulae for the longitudinal impedance of some typical discontinuities are obtained.
Evaluation of Wall Boundary Conditions for Impedance Eduction Using a Dual-Source Method
Watson, W. R.; Jones, M. G.
2012-01-01
The accuracy of the Ingard-Myers boundary condition and a recently proposed modified Ingard-Myers boundary condition is evaluated for use in impedance eduction under the assumption of uniform mean flow. The evaluation is performed at three centerline Mach numbers, using data acquired in a grazing flow impedance tube, using both upstream and downstream propagating sound sources, and on a database of test liners for which the expected behavior of the impedance spectra is known. The test liners are a hard-wall insert consisting of 12.6 mm thick aluminum, a linear liner without a facesheet consisting of a number of small diameter but long cylindrical channels embedded in a ceramic material, and two conventional nonlinear liners consisting of a perforated facesheet bonded to a honeycomb core. The study is restricted to a frequency range for which only plane waves are cut on in the hard-wall sections of the flow impedance tube. The metrics used to evaluate each boundary condition are 1) how well it educes the same impedance for upstream and downstream propagating sources, and 2) how well it predicts the expected behavior of the impedance spectra over the Mach number range. The primary conclusions of the study are that the same impedance is educed for upstream and downstream propagating sources except at the highest Mach number, that an effective impedance based on both the upstream and downstream measurements is more accurate than an impedance based on the upstream or downstream data alone, and that the Ingard-Myers boundary condition with an effective impedance produces results similar to that achieved with the modified Ingard-Myers boundary condition.
Murata, T; Akagi, K; Ostapenko, V V; Isoda, H; Nagata, K; Nasu, R; Shiga, T; Tanaka, Y; Yamamoto, I
1998-01-01
Capacitive heating is widely used in hyperthermic treatment of human malignancies. However, the pain on the body surface or thermoesthesia in the subcutaneous fatty layer may prevent an elevation of temperature in the tumors. Impedance matching is improved by a subtrap method entailing the application of two copper plates (10 x 850 x 0.06 mm) as a subtrap circuit to each of two capacitive electrodes. In a clinical trial the Tmax, Tave, Tmin for the subtrap method were all higher in comparison with those for the conventional technique (42.5 +/- 0.7 degrees C, 41.9 +/- 1.0 degrees C, 41.3 +/- 1.1 degrees C vs. 41.1 +/- 1.5 degrees C, 40.6 +/- 1.3 degrees C, 40.0 +/- 1.3 degrees C). Although the maximal radiofrequency (RF) power applied to patients was higher with the subtrap method (875 +/- 189 W vs. 763 +/- 200 W), the incidence of surface pain was reduced dramatically. It is concluded that the subtrap method substantially improves the RF capacitive heating of deep-seated tumors.
T., M P Ramirez; Hernandez-Becerril, R A
2012-01-01
Based upon elements of the modern Pseudoanalytic Function Theory, we analyse a new method for numerically approaching the solution of the Dirichlet boundary value problem, corresponding to the two-dimensional Electrical Impedance Equation. The analysis is performed by interpolating piecewise separable-variables conductivity functions, that are eventually used in the numerical calculations in order to obtain finite sets of orthonormal functions, whose linear combinations succeed to approach the imposed boundary conditions. To warrant the effectiveness of the numerical method, we study six different examples of conductivity. The boundary condition for every case is selected considering one exact solution of the Electrical Impedance Equation. The work intends to discuss the contributions of these results into the field of the Electrical Impedance Tomography.
Kraft, R. E.; Yu, J.; Kwan, H. W.
1999-01-01
The primary purpose of this study is to develop improved models for the acoustic impedance of treatment panels at high frequencies, for application to subscale treatment designs. Effects that cause significant deviation of the impedance from simple geometric scaling are examined in detail, an improved high-frequency impedance model is developed, and the improved model is correlated with high-frequency impedance measurements. Only single-degree-of-freedom honeycomb sandwich resonator panels with either perforated sheet or "linear" wiremesh faceplates are considered. The objective is to understand those effects that cause the simple single-degree-of- freedom resonator panels to deviate at the higher-scaled frequency from the impedance that would be obtained at the corresponding full-scale frequency. This will allow the subscale panel to be designed to achieve a specified impedance spectrum over at least a limited range of frequencies. An advanced impedance prediction model has been developed that accounts for some of the known effects at high frequency that have previously been ignored as a small source of error for full-scale frequency ranges.
Directory of Open Access Journals (Sweden)
Ye. S. Sherina
2014-01-01
Full Text Available This research has been aimed to carry out a study of peculiarities that arise in a numerical simulation of the electrical impedance tomography (EIT problem. Static EIT image reconstruction is sensitive to a measurement noise and approximation error. A special consideration has been given to reducing of the approximation error, which originates from numerical implementation drawbacks. This paper presents in detail two numerical approaches for solving EIT forward problem. The finite volume method (FVM on unstructured triangular mesh is introduced. In order to compare this approach, the finite element (FEM based forward solver was implemented, which has gained the most popularity among researchers. The calculated potential distribution with the assumed initial conductivity distribution has been compared to the analytical solution of a test Neumann boundary problem and to the results of problem simulation by means of ANSYS FLUENT commercial software. Two approaches to linearized EIT image reconstruction are discussed. Reconstruction of the conductivity distribution is an ill-posed problem, typically requiring a large amount of computation and resolved by minimization techniques. The objective function to be minimized is constructed of measured voltage and calculated boundary voltage on the electrodes. A classical modified Newton type iterative method and the stochastic differential evolution method are employed. A software package has been developed for the problem under investigation. Numerical tests were conducted on simulated data. The obtained results could be helpful to researches tackling the hardware and software issues for medical applications of EIT.
Fundamental impedance identification method for grid-connected voltage source inverters
DEFF Research Database (Denmark)
Sun, Xiaofeng; Chen, J.; Guerrero, Josep M.
2014-01-01
Considering the importance of line fundamental impedance from the inverter to the point of common coupling (PCC) in microgrids, this study analyses the influence of fundamental impedance on system stability. Line fundamental impedance values not only apply to decoupled droop control, which can...... realise accurate control between active and reactive power, but also regulate the droop coefficient to eliminate system circulation, realise power sharing and improve system stability when a multi-distributed generation system operates in parallel. Moreover, the PCC can sense grid fault on the basis...
Directory of Open Access Journals (Sweden)
M Bayat KASHKOLİ
2011-12-01
Full Text Available The goal of present research is estimating and validity of body density with methods of Body Mass Index, Skin Fold, Bio-Electrical Impedance and Criterion Method of Hydrostatic in men athletes of swimming. The present research has been conducted with semi-experimental and functional method. For doing so 25 men swimming athletes were randomly selected (N= 120. Statistical analysis was conducted with Pearson coefficient, correlated T-test, TE & SEE. The results of statistical analysis show that the method of Skin Fold Stat with hydrostatic criterion method has meaningful difference in society of swimmers. Also there is meaningful difference between body mass index and criterion method. There was not any meaningful difference between bio-electrical impedance and criterion method in swimmers. (TE=3.01, SEE=2.91, R=0.924, P=0.064. The findings show that that bio-electrical impedance in swimmer athletes is more suitable method.
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M.S. Ould Brahim
2011-04-01
Full Text Available Our objective in this study is to determine the effective thermal insulating layer of a composite towplaster. The characterization of thermal insulating material is proposed from the study of the thermal impedance in dynamic two-dimensional frequency. Thermo physical properties of the material tow-plaster are determined from the study of the thermal impedance. Nyquist representations have introduced an interpretation of certain phenomena of heat transfer from the series and shunt resistors. The overall coefficient of heat exchange is determined from the Bode plots. A method for determining the thermal conductivity is proposed.
Dekker, B.G.; Sluyters-Rehbach, M.; Sluyters, J.H.
1969-01-01
The applicability of the complex plane method for the evaluation of the impedance parameters in the case of two simultaneously proceeding electrode reactions is discussed. It is shown that the possibility of the evaluation depends strongly on the values of the irreversibility quotients of both react
Stepanishen, P. R.; Ramakrishna, S.
1994-09-01
A new internal source distribution method is combined with the singular value decomposition method to determine the acoustic impedance and associated impulse response for an infinite cylinder with a plane of symmetry and a normal velocity with a specified circumferential variation. An internal linear distribution of unknown monopole and/or dipole line sources along the plane of symmetry is determined to match the specified harmonic normal velocity on the surface in a least mean square error sense. After the discretization of the source distributions, the subsequent solution of a set or sets of linear algebraic equations for the internal source distributions is obtained using the singular value decomposition method. Line integrals for the associated surface pressure, the acoustic impedance and the corresponding impulse response are then simply evaluated by quadrature methods. Numerical results for the acoustic impedances and associated impulse responses are presented for circular cylinders vibrating with various natural in vacuo modal shapes. Numerical results for acoustic impedances and associated impulse responses for elliptical cylinders vibrating with various natural in vacuo modal shapes are then presented, and their characteristics are discussed and compared to the corresponding results for circular cylinders.
DEFF Research Database (Denmark)
Karamehmedovic, Mirza; Breinbjerg, Olav
2002-01-01
The Method of Auxiliary Sources (MAS) is applied to 3D scattering problems involving spherical impedance scatterers. The MAS results are compared with the reference spherical wave expansion (SWE) solution. It is demonstrated that good agreement is achieved between the MAS and SWE results....
Marsili, P M; Mounié, G; Granié, M; Morucci, J P
1992-01-01
Optimal control techniques have been combined with Alessandrini's singular perturbation method and Wexler's algorithm to reconstruct images in impedance imaging. We have also considered an integral formulation of the potential problem, which has led us to introduce an array of dipoles whose position, orientation and length can be optimised to model the conductivity discontinuities.
Directory of Open Access Journals (Sweden)
Neda Alijanian
2012-01-01
Full Text Available Background: Dry weight (DW is an important concept related to patients undergoing hemodialysis. Conventional method seems to be time consuming and operator dependent. Bio impedance analysis (BIA is a new and simple method reported to be an accurate way for estimating DW. In this study, we aimed to compare the conventional estimation of DW with measuring DW by BIA. Materials and Methods: This study involved 130 uremic patients, performed in Isfahan, Iran. DW was calculated by both conventional (CDW and BIA (BIADW method and results were compared based on different grouping factors including sex, underlying cause of renal failure (RF (diabetic RF and non-diabetic RF, body mass index (BMI status, and sessions of hemodialysis. We also calculated the difference between DWs of 2 methods (DW diff = CDW-BIADW. Results: The mean of BIADW was significantly lower than CDW (57.20 ± 1.82 vs 59.36 ± 1.77, P value < 0.001. After grouping cases according to the underlying cause, BMI, sex, and dialysis sessions BIADW was significantly lower than CDW. Conclusion: Based on the combination of problems with CDW measurement which are corrected by BIA, and more clinical reliability of CDW, we concluded that although conventional method is a time-consuming and operator-dependent way to assess DW, DW could be estimated by combining both of these methods by finding the mathematic correlation between these methods.
AC/DC Power Flow Computation Based on Improved Levenberg-Marquardt Method
Cao, Jia; Yan, Zheng; Fan, Xiang; Xu, Xiaoyuan; Li, Jianhua; Cao, Lu
2015-02-01
Under the case of ill-conditioning system, this paper is concerned with the AC/DC power flow calculation. The improved Levenberg-Marquardt (ILM) method with adaptive damping factor selection is applied to solve the AC/DC power flow problem. The main purpose of this paper is as follows: one is to provide comparison reference between Newton method, classical LM method (CLM) and ILM method under the well-conditioning system; the other is to research what is the maximal load withstood by power system, under the case of ill-conditioning. Finally, those methods are tested on the 22-bus, the IEEE 118-bus AC/DC system, respectively. Numerical results indicate that the ILM method has the advantage of fast convergent speed. When expanding loads in a certain extent, ILM method can at least find least square solutions, whereas Newton method and CLM method would divergent, and the convergent property of Newton method can be improved by taking some measurements using the information of a least square solution obtained by ILM method.
Comparison and optimization of the method for Cry1Ac protoxin preparation in HD73 strain
Institute of Scientific and Technical Information of China (English)
ZHOU Zi-shan; YANG Su-juan; SHU Chang-long; SONG Fu-ping; ZHOU Xue-ping; ZHANG Jie
2015-01-01
Bacil us thuringiensis is one of the most widely used bioinsecticides, and cry gene is the major insecticidal gene. Because Cry1Ac protein shows strong toxicity against many lepidopteran species, it has been applied widely in spraying products and transgenic Bt-crops. The preparation of Cry protoxin is the ifrst step in the very important processes of understanding the insecticidal mechanism, resistance screening, and biosafety assessments. The media for crystal production and the method for Cry protoxin preparation were varied, however, it was not clear which was better for preparing a larger amount of Cry protoxin. In this paper, three media for crystal production and the method for Cry1Ac protoxin preparation from HD73 strain were compared to ifnd an efifcacious way to prepare a large number of Cry1Ac protoxin. The results showed that the 1/2 LB (Luria-Bertani) medium was the ideal medium for crystal production, because the total yield of Cry1Ac protoxin in 300 mL 1/2 LB medium was (112.38±5.64) mg, the highest one among three media;the repeated crystal solubilization method was better for the preparation of the Cry protoxin comparing with the continuous crystal solubilization method. It wil be a reference for other Cry protoxin preparation, especial y for larger number.
Boukabache, Hamza; Escriba, Christophe; Zedek, Sabeha; Medale, Daniel; Rolet, Sebastien; Fourniols, Jean Yves
2012-10-11
The work reported on this paper describes a new methodology implementation for active structural health monitoring of recent aircraft parts made from carbon-fiber-reinforced polymer. This diagnosis is based on a new embedded method that is capable of measuring the local high frequency impedance spectrum of the structure through the calculation of the electro-mechanical impedance of a piezoelectric patch pasted non-permanently onto its surface. This paper involves both the laboratory based E/M impedance method development, its implementation into a CPU with limited resources as well as a comparison with experimental testing data needed to demonstrate the feasibility of flaw detection on composite materials and answer the question of the method reliability. The different development steps are presented and the integration issues are discussed. Furthermore, we present the unique advantages that the reconfigurable electronics through System-on-Chip (SoC) technology brings to the system scaling and flexibility. At the end of this article, we demonstrate the capability of a basic network of sensors mounted onto a real composite aircraft part specimen to capture its local impedance spectrum signature and to diagnosis different delamination sizes using a comparison with a baseline.
Boukabache, Hamza; Escriba, Christophe; Zedek, Sabeha; Medale, Daniel; Rolet, Sebastien; Fourniols, Jean Yves
2012-01-01
The work reported on this paper describes a new methodology implementation for active structural health monitoring of recent aircraft parts made from carbon-fiber-reinforced polymer. This diagnosis is based on a new embedded method that is capable of measuring the local high frequency impedance spectrum of the structure through the calculation of the electro-mechanical impedance of a piezoelectric patch pasted non-permanently onto its surface. This paper involves both the laboratory based E/M impedance method development, its implementation into a CPU with limited resources as well as a comparison with experimental testing data needed to demonstrate the feasibility of flaw detection on composite materials and answer the question of the method reliability. The different development steps are presented and the integration issues are discussed. Furthermore, we present the unique advantages that the reconfigurable electronics through System-on-Chip (SoC) technology brings to the system scaling and flexibility. At the end of this article, we demonstrate the capability of a basic network of sensors mounted onto a real composite aircraft part specimen to capture its local impedance spectrum signature and to diagnosis different delamination sizes using a comparison with a baseline. PMID:23202013
Directory of Open Access Journals (Sweden)
Daniel Medale
2012-10-01
Full Text Available The work reported on this paper describes a new methodology implementation for active structural health monitoring of recent aircraft parts made from carbon-fiber-reinforced polymer. This diagnosis is based on a new embedded method that is capable of measuring the local high frequency impedance spectrum of the structure through the calculation of the electro-mechanical impedance of a piezoelectric patch pasted non-permanently onto its surface. This paper involves both the laboratory based E/M impedance method development, its implementation into a CPU with limited resources as well as a comparison with experimental testing data needed to demonstrate the feasibility of flaw detection on composite materials and answer the question of the method reliability. The different development steps are presented and the integration issues are discussed. Furthermore, we present the unique advantages that the reconfigurable electronics through System-on-Chip (SoC technology brings to the system scaling and flexibility. At the end of this article, we demonstrate the capability of a basic network of sensors mounted onto a real composite aircraft part specimen to capture its local impedance spectrum signature and to diagnosis different delamination sizes using a comparison with a baseline.
Micro pumping methods based on AC electrokinetics and Electrorheologically actuated PDMS valves
Soni, Gaurav; Squires, Todd; Meinhart, Carl
2006-11-01
We have developed 2 different micropumping methods for transporting ionic fluids through microchannels. The first method is based on Induced Charge Electroosmosis (ICEO) and AC flow field-effect. We used an AC electric field to produce a symmetric ICEO flow on a planar electrode, called `gate'. In order to break the symmetry of ICEO, we applied an additional AC voltage to the gate electrode. Such modulation of the gate potential is called field effect and produces a unidirectional pumping over the gate surface. We used micro PIV to measure pumping velocities for a range of ionic concentration, AC frequency and gate voltage. We have also conducted numerical simulations to understand the deteriorating effect of lateral conduction of surface charge on the pumping velocities. The second method is based on vibration of a flexible PDMS diaphragm actuated by an electrorheological (ER) fluid. ER fluid is a colloidal suspension exhibiting a reversible liquid-to-solid transition under an electric field. This liquid-to-solid transition can yield very high shear stress and can be used to open and close a PDMS valve. Three such valves were fabricated and actuated in a peristaltic fashion in order to achieve positive displacement pumping of fluids.
Indian Academy of Sciences (India)
Syed Mahboob; G Prasad; G S Kumar
2006-08-01
Electrical conduction studies on Ba(Nd0.2Ti0.6Nb0.2)O3 ceramic samples prepared through conventional and microwave sintering route are presented in this paper. D.C. and a.c. conductivities of these samples as a function of temperature from 300–900 K have been studied. Two types of conduction processes are evident from the frequency dependant conductivity plots, i.e. low-frequency conduction due to short-range hopping and high-frequency conduction due to the localized relaxation (reorientational) hopping mechanism. Grain and grain boundary contributions to the conductivity in these samples are obtained from impedance/admittance measurements via equivalent circuit modelling.
Applicability of impedance measuring method to the detection of irradiation treatment of potatoes
Energy Technology Data Exchange (ETDEWEB)
Hayashi, Toru; Todoriki, Setsuko; Otobe, Kazunori; Sugiyama, Junnichi (National Food Research Inst., Tsukuba, Ibaraki (Japan))
1993-05-01
The incubation condition of potato tubers prior to impedance measurement greatly influenced the reliability of detection of irradiated potatoes; the impedance ratio at 5 kHz to 50 kHz (Z[sub 5k]/Z[sub 50k]) determined at 22degC at an apical region of tuber which was pre-incubated at 22degC for 3 days or longer resulted in the best detection of radiation treatment of potatoes. The impedance ratio was dependent upon dose applied to potato tubers. Potatoes irradiated at 100 Gy could be distinguished from unirradiated potatoes for 10 cultivars of potatoes. The impedance ratio of potatoes irradiated at the same dose was little influenced by the planting locality if the cultivar was the same, although the ratio varied with potato cultivars. These results indicate that irradiated potatoes can be detected if the potato cultivar is known. Potatoes 'Danshaku' commercially irradiated at the Shihiro Potato Irradiation Center could be differentiated from unirradiated 'Danshaku' at different planting localities; the impedance ratio was lower than 2.75 for the unirradiated potatoes and higher than 2.75 for the irradiated ones. (author).
McLean, James; Sutton, Robert; Post, John
2003-10-01
One useful method of acoustic impedance measurement involves the measurement of the electrical impedance ``looking into'' the electrical port of a reciprocal electroacoustic transducer. This reaction on the source method greatly facilitates the measurement of acoustic impedance by borrowing highly refined techniques to measure electrical impedance. It is also well suited for in situ acoustic impedance measurements. In order to accurately determine acoustic impedance from the measured electrical impedance, the characteristics of the transducer must be accurately known, i.e., the characteristics of the transducer must be ``removed'' completely from the data. The measurement of acoustic impedance via the measurement of the reaction on the source is analogous to modern microwave measurements made with an automatic vector network analyzer. The action of the analyzer is described as de-embedding the desired data (such as acoustic impedance) from the raw data. Such measurements are fundamentally substitution measurements in that the transducer's characteristics are determined by measuring a set of reference standards. The reaction on the source method is extended to take advantage of improvements in microwave measurement techniques which allow calibration via imperfect standard loads. This removes one of the principal weaknesses of the method in that the requirement of high-quality reference standards is relaxed.
Dewberry, B.
2000-01-01
Electrical impedance spectrometry involves measurement of the complex resistance of a load at multiple frequencies. With this information in the form of impedance magnitude and phase, or resistance and reactance, basic structure or function of the load can be estimated. The "load" targeted for measurement and estimation in this study consisted of the water-bearing tissues of the human calf. It was proposed and verified that by measuring the electrical impedance of the human calf and fitting this data to a model of fluid compartments, the lumped-model volume of intracellular and extracellular spaces could be estimated, By performing this estimation over time, the volume dynamics during application of stimuli which affect the direction of gravity can be viewed. The resulting data can form a basis for further modeling and verification of cardiovascular and compartmental modeling of fluid reactions to microgravity as well as countermeasures to the headward shift of fluid during head-down tilt or spaceflight.
Jaffrin, Michel Y; Morel, Hélène
2008-12-01
This paper reviews various bioimpedance methods permitting to measure non-invasively, extracellular, intracellular and total body water (TBW) and compares BIA methods based on empirical equations of the wrist-ankle resistance or impedance at 50 kHz, height and weight with BIS methods which rely on an electrical model of tissues and resistances measured at zero and infinite frequencies. In order to compare these methods, impedance measurements were made with a multifrequency Xitron 4200 impedance meter on 57 healthy subjects which had undergone simultaneously a Dual X-ray absorptiometry examination (DXA), in order to estimate their TBW from their fat-free-mass. Extracellular (ECW) and TBW volumes were calculated for these subjects using the original BIS method and modifications of Matthie[Matthie JR. Second generation mixture theory equation for estimating intracellular water using bioimpedance spectroscopy. J Appl Physiol 2005;99:780-1], Jaffrin et al. [Jaffrin MY, Fenech M, Moreno MV, Kieffer R. Total body water measurement by a modification of the bioimpédance spectroscopy method. Med Bio Eng Comput 2006;44:873-82], Moissl et al. [Moissl UM, Wabel P, Chamney PW, Bosaeus I, Levin NW, et al. Body fluid volume determination via body composition spectroscopy in health and disease. Physiol Meas 2006;27:921-33] and their TBW resistivities were compared and discussed. ECW volumes were calculated by BIA methods of Sergi et al. [Sergi G, Bussolotto M, Perini P, Calliari I, et al. Accuracy of bioelectrical bioimpedance analysis for the assessment of extracellular space in healthy subjects and in fluid retention states. Ann Nutr Metab 1994;38(3):158-65] and Hannan et al. [Hannan WJ, Cowen SJ, Fearon KC, Plester CE, Falconer JS, Richardson RA. Evaluation of multi-frequency bio-impedance analysis for the assessment of extracellular and total body water in surgical patients. Clin Sci 1994;86:479-85] and TBW volumes by BIA methods of Kushner and Schoeller [Kushner RF
Zhou, Guoding; Cai, Shengmin; Song, Liqun; Yang, Huaquan; Fujishima, A.; Ibrahim, A.; Lee, Y. G.; Loo, B. H.
1991-11-01
The inhibition effects of benzotriazole (BTA) and 6-aniline-1,3,5-triazine-2,4-dithiol (ATD) monosodium salt on copper corrosion have been studied by the potentiodynamic polarization, AC impedance and surface-enhanced Raman spectroscopic techniques. The polarization resistance Rp increases with the concentration of either BTA or ATD. From the plots of the phase shift θ versus logarithm of the frequency, it is found that θ is close to 90° after the copper electrode is immersed for a long period of time in BTA-containing solution which indicates the behavior of an ideal capacitor. In ATD-containing solutions, θ is close to 45 ° which shows the appearance of a Warburg impedance for a diffusion process. Surface-enhanced Raman spectroscopic studies of the competitive adsorption of BTA and ATD on copper surfaces indicate that BTA adsorbs better than ATD. Based on these results, it is concluded that the inhibition action of BTA is better than that of ATD.
Marco Pedro Ramirez-Tachiquin; Cesar Marco Antonio Robles Gonzalez; Rogelio Adrian Hernandez-Becerril; Ariana Guadalupe Bucio Ramirez
2013-01-01
Based upon the elements of the modern pseudoanalytic function theory, we analyze a new method for numerically solving the forward Dirichlet boundary value problem corresponding to the two-dimensional electrical impedance equation. The analysis is performed by introducing interpolating piecewise separable-variables conductivity functions in the unit circle. To warrant the effectiveness of the posed method, we consider several examples of conductivity functions, whose boundary condi...
Evaluation of different methods for measuring the impedance of Lithium-ion batteries during ageing
DEFF Research Database (Denmark)
Stroe, Daniel Loan; Swierczynski, Maciej Jozef; Stroe, Ana-Irina;
2015-01-01
The impedance represents one of the most important performance parameters of the Lithium-ion batteries since it used for power capability calculations, battery pack and system design, cooling system design and also for state-of-health estimation. In the literature, different approaches are presen......The impedance represents one of the most important performance parameters of the Lithium-ion batteries since it used for power capability calculations, battery pack and system design, cooling system design and also for state-of-health estimation. In the literature, different approaches...
Measurement of Phase Dependent Impedance for 3-phase Diode Rectifier
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth
2016-01-01
This paper presents a new method to measure the phase dependent impedance from an experimental set up. Though most of power electronics based system is gradually migrating to IGBT based voltage source converter due to their controllability, the rectifier composed of diode or thyristor components...... are still widely used in AC-DC applications because of their cost effectiveness and reliability. However, these topologies generate harmonic problems in their network due to their switching instant variation caused by the frequency and phase of grid voltage. Hence, a lot of solutions have been proposed...... application. It is found that the phase dependent impedance shows different properties with the impedance profiles, which have been proposed in the research. This paper explains a method to measure the phase dependent impedance profile from an experimental set up. Furthermore, the results are compared...
DEFF Research Database (Denmark)
Swierczynski, Maciej Jozef; Stroe, Daniel Loan; Stanciu, Tiberiu
2017-01-01
spectroscopy method can be still improved in terms of e.g. accuracy and measurement time and it has a potential to be extended to new applications. Performed review indicates that the electrothermal impedance spectroscopy is a very promising, non-destructive, simple and especially cost-efficient method...... for thermal characterization of batteries. The scientific intention of this paper is to collect and systematize the state of knowledge about electrothermal impedance spectroscopy and present different measurement methods on the example of a high-power lithium battery cell and finally to discuss the prospect....
Kory, Carol L.
1999-01-01
The phenomenal growth of commercial communications has created a great demand for traveling-wave tube (TWT) amplifiers. Although the helix slow-wave circuit remains the mainstay of the TWT industry because of its exceptionally wide bandwidth, until recently it has been impossible to accurately analyze a helical TWT using its exact dimensions because of the complexity of its geometrical structure. For the first time, an accurate three-dimensional helical model was developed that allows accurate prediction of TWT cold-test characteristics including operating frequency, interaction impedance, and attenuation. This computational model, which was developed at the NASA Lewis Research Center, allows TWT designers to obtain a more accurate value of interaction impedance than is possible using experimental methods. Obtaining helical slow-wave circuit interaction impedance is an important part of the design process for a TWT because it is related to the gain and efficiency of the tube. This impedance cannot be measured directly; thus, conventional methods involve perturbing a helical circuit with a cylindrical dielectric rod placed on the central axis of the circuit and obtaining the difference in resonant frequency between the perturbed and unperturbed circuits. A mathematical relationship has been derived between this frequency difference and the interaction impedance (ref. 1). However, because of the complex configuration of the helical circuit, deriving this relationship involves several approximations. In addition, this experimental procedure is time-consuming and expensive, but until recently it was widely accepted as the most accurate means of determining interaction impedance. The advent of an accurate three-dimensional helical circuit model (ref. 2) made it possible for Lewis researchers to fully investigate standard approximations made in deriving the relationship between measured perturbation data and interaction impedance. The most prominent approximations made
A Digital Method for AC/AC Converter Controller by Natural-commutation%自然换流AC/AC变频控制器数字化实现方法
Institute of Scientific and Technical Information of China (English)
李光叶; 苏玉民; 文小青
2011-01-01
For the dead band in AC/AC converter controller,a design method of both software and hardware is presented. All the trigger pulses are created by DSP.The full digitalization of the system is completed.The self-commutation of the controller is achieved by intelligent utilization of two timers of DSP.The dead band of commutation is greatly reduced.The quality of output waveform is improved observably .The experimental result verify the outstanding effectiveness and precision of the controller.%针对AC/AC变频电路存在的换流死区问题,提出了一种AC/AC变频控制器软、硬件设计方法.该方法中6路触发脉冲均由DSP生成,完成对系统的全数字化控制.通过DSP中两个定时器的合理使用,实现了AC/AC变频器的自然换流,减小了换流死区对输出波形的影响.实验结果表明,所设计的AC/AC变频数字控制系统具有较高的控制精度和较好的控制效果.
Meijer, J.H.; Boesveldt, S.; Elbertse, E.; Berendse, H.W.
2008-01-01
The time difference between the electrocardiogram and impedance cardiogram can be considered as a measure for the time delay between the electrical and mechanical activities of the heart. This time interval, characterized by the pre-ejection period (PEP), is related to the sympathetic autonomous ner
Method for Flow Measurement in Microfluidic Channels Based on Electrical Impedance Spectroscopy
Arjmandi, Nima; Van Roy, Willem; Lagae, Liesbet; Borghs, Gustaaf; 10.1007/s10404-011-0843-0
2012-01-01
We have developed and characterized two novel micro flow sensors based on measuring the electrical impedance of the interface between the flowing liquid and metallic electrodes embedded on the channel walls. These flow sensors are very simple to fabricate and use, are extremely compact and can easily be integrated into most microfluidic systems. One of these devices is a micropore with two tantalum/platinum electrodes on its edges; the other is a micro channel with two tantalum /platinum electrodes placed perpendicular to the channel on its walls. In both sensors the flow rate is measured via the electrical impedance between the two metallic electrodes, which is the impedance of two metal-liquid junctions in series. The dependency of the metal-liquid junction impedance on the flow rate of the liquid has been studied. The effects of different parameters on the sensor's outputs and its noise behavior are investigated. Design guidelines are extracted and applied to achieve highly sensitive micro flow sensors wit...
Lu, Bin; Luebke, Charles John; Habetler, Thomas G.; Zhang, Pinjia; Becker, Scott K.
2011-12-27
A system and method for measuring and controlling stator winding temperature in an AC motor while idling is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of a multi-phase AC motor. The circuit further includes a plurality of switching devices to control current flow and terminal voltages in the multi-phase AC motor and a controller connected to the circuit. The controller is configured to activate the plurality of switching devices to create a DC signal in an output of the motor control device corresponding to an input to the multi-phase AC motor, determine or estimate a stator winding resistance of the multi-phase AC motor based on the DC signal, and estimate a stator temperature from the stator winding resistance. Temperature can then be controlled and regulated by DC injection into the stator windings.
Wakefields and coupling impedances
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S. (Superconducting Super Collider Laboratory, 2550 Beckleymeade Ave., Dallas, Texas 75237 (United States))
1995-02-01
After a short introduction of the wake potentials and coupling impedances, a few new results in impedance calculations are discussed. The first example is a new analytical method for calculating impedances of axisymmetric structures in the low frequency range, below the cutoff frequency of the vacuum chamber. The second example demonstrates that even very small discontinuities on a smooth waveguide can result in appearance of trapped modes, with frequencies slightly below the waveguide cutoff frequency. The high-frequency (above the cutoff) behavior of the coupling impedance of many small discontinuities is discussed in the third example. [copyright] 1995 [ital American] [ital Institute] [ital of] [ital Physics
Wakefields and coupling impedances
Kurennoy, Sergey
1995-02-01
After a short introduction of the wake potentials and coupling impedances, a few new results in impedance calculations are discussed. The first example is a new analytical method for calculating impedances of axisymmetric structures in the low frequency range, below the cutoff frequency of the vacuum chamber. The second example demonstrates that even very small discontinuities on a smooth waveguide can result in appearance of trapped modes, with frequencies slightly below the waveguide cutoff frequency. The high-frequency (above the cutoff) behavior of the coupling impedance of many small discontinuities is discussed in the third example.
Institute of Scientific and Technical Information of China (English)
MA Zhi; CAO Chen-Tao; LIU Qing-Fang; WANG Jian-Bo
2012-01-01
A delta-function method is proposed to quantitatively evaluate the electromagnetic impedance matching degree.Measured electromagnetic parameters of α-Fe/Fe3B/V2O3 nanocomposites are applied to calculate the matching degree by the method.Compared with reflection loss and quarter-wave principle theory,the method accurately reveals the intrinsic mechanism of microwave transmission and reflection properties.A possible honeycomb structure with promising high-performance microwave absorption,devised according to the method,is also proposed.
Shitanda, Isao; Inoue, Kazuya; Hoshi, Yoshinao; Itagaki, Masayuki
2014-02-01
The internal resistances of dye-sensitized solar cells (DSCs) with and without current collecting electrodes (CCEs) were analyzed using electrochemical impedance spectroscopy (EIS) with a finite element method (FEM). Three different DSC models with or without current collecting electrodes were designed. Theoretical values of the internal resistance were estimated by FEM on changing the position and size of the current collecting electrodes. Large DSCs with current collecting electrodes were fabricated using a screen-printing technique, and experimental values of the internal resistance were analyzed by EIS and compared with the theoretical values. The internal resistances obtained from the impedance measurements were in good agreement with those obtained by simulation. The internal resistance was found to decrease with increasing width and thickness of the CCEs, below a threshold value. EIS was found to be extremely useful for evaluating CCE design for improved DSCs.
Impedance Scaling and Impedance Control
Energy Technology Data Exchange (ETDEWEB)
Chou, W.; Griffin, J.
1997-06-01
When a machine becomes really large, such as the Very Large Hadron Collider (VLHC), of which the circumference could reach the order of megameters, beam instability could be an essential bottleneck. This paper studies the scaling of the instability threshold vs. machine size when the coupling impedance scales in a ``normal`` way. It is shown that the beam would be intrinsically unstable for the VLHC. As a possible solution to this problem, it is proposed to introduce local impedance inserts for controlling the machine impedance. In the longitudinal plane, this could be done by using a heavily detuned rf cavity (e.g., a biconical structure), which could provide large imaginary impedance with the right sign (i.e., inductive or capacitive) while keeping the real part small. In the transverse direction, a carefully designed variation of the cross section of a beam pipe could generate negative impedance that would partially compensate the transverse impedance in one plane.
Study on Transformer Magnetic Biasing Control Method for AC Power Supplies
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
This paper presents a novel transformer magnetic biasing control method for high-power high-performance AC power supplies. Serious consequences due to magnetic biasing and several methods to overcome magnetic biasing are first discussed. The causes of the transformer magnetic biasing are then analyzed in detail. The proposed method is based on a high-pass filter inserted in the forward path and the feedforward control. Without testing magnetic biasing of transformer, this method can eliminate magnetic biasing of transformer completely in real-time waveform feedback control systems though the aero error of the Hall effect sensors varies with time and temperature. The method has already been employed in a 90KVA AC power supply. It is shown that it offers improved performance over existing ones. In this method, no sensors are used such that the zero error of the Hall effect sensors has not any influence on the system. It is simple to design and implement. Furthermore, the method is suitable for various power applications.
电阻抗图象重建的新正则化方法%New Regularization Method in Electrical Impedance Tomography
Institute of Scientific and Technical Information of China (English)
侯卫东; 莫玉龙
2002-01-01
Image reconstruction in electrical impedance tomography(EIT) is a highly ill-posed inverse problem. Regularization techniques must be used in order to solve the problem. In this paper, a new regularization method based on the spatial filtering theory is proposed. The new regularized reconstruction for EIT is independent of the estimation of impedance distribution, so it can be implemented more easily than the maximum a posteriori(MAP) method. The regularization level in our proposed method varies spatially so as to be suited to the correlation character of the object's impedance distribution. We implemented our regularization method with two dimensional computer simulations. The experimental results indicate that the quality of the reconstructed impedance images with the descibed regularization method based on spatial filtering theory is better than that with Tikhonov method.
Grönlund, J U; Jalonen, J; Korhonen, I; Rolfe, P; Välimäki, I A
1995-05-01
We studied the pulsatile component of cerebral circulation with transcephalic electrical impedance (delta Z) in six preterm newborns, three of whom had severe cerebral bleeding, peri-intraventricular haemorrhage (PIVH). The transcephalic electrical impedance delta Z signal, ECG, arterial blood pressure, (aBP) and respirogram were recorded on analogue magnetic tape for 30 min. Artefact-free stationary segments (lasting for 2 min) of the four signals were digitised. A digital multivariate autoregressive (MAR) model was used to study frequency-specific variability in the signals and to quantify interrelations between the variabilities of delta Z, HR, aBP and respiratory signals. MAR modelling describes a system where all the signals simultaneously explain each other. The inherent variability of delta Z was lower and the influences of respiration and aBP on delta Z significantly greater in infants with severe PIVH than in controls. These changes were observed at high frequencies corresponding to respiration and heart rate. This may be interpreted as a marker of pressure passivism in the cerebral circulation following PIVH. We conclude that in preterm babies the application of MAR modelling, together with transcephalic impedance, may be a new, helpful and quantitative method for the study of simultaneous interrelations between variables of cerebral and systemic circulations and respiration.
Pham Quang, Phuong; Guérin, Christophe; Meunier, Gérard; Lembeye, Yves
2009-01-01
International audience; This paper presents a model for calculating a posteriori electric field in non conducting regions in steady state AC magnetic application. The computation method used is the finite elements method in 3 dimensions. The approach is validated by calculating the equivalent impedance of a coil on which the resolution of the full Maxwell's equations can be performed.
Walters, William J.; Haghighat, Alireza
2014-06-01
A new collision source method has been developed to solve the Linear Boltzmann Equation (LBE) more efficiently by adaptation of the angular quadrature order. The angular adaptation method is unique in that the flux from each scattering source iteration is obtained separately, with potentially a different quadrature order. This allows for an optimal use of processing power, by using a high order quadrature for the first few iterations that need it, before shifting to lower order quadratures for the remaining iterations. This is essentially an extension of the first collision source method, and we call it the adaptive collision source method (ACS). The ACS methodolog y has been implemented in the TITAN discrete ordinates code, and has shown a speedup of 2-3 on a test problem, with very little loss of accuracy (within a provided adaptive tolerance). Further, the code has been extended to work in parallel environments by angular decomposition. Although the method requires increased parallel communication, tests have shown excellent scalability, with parallel fractions of up to 99%.
Directory of Open Access Journals (Sweden)
K. Kamala Bharathi
2012-03-01
Full Text Available The structure and electrical characteristics of Gd doped Ni ferrite materials, namely NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4, are reported to demonstrate their improved electrical properties compared to that of pure NiFe2O4. NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds crystallize in the cubic inverse spinel phase with a very small amount of GdFeO3 additional phase while pure NiFe2O4 crystallize in inverse spinel phase without any impurity phase. The back scattered electron imaging analysis indicate the primary and secondary formation in NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds. Atomic force microscopy measurements indicate that the bulk grains are ∼2-5 micron size while the grain boundaries are thin compared to bulk grains. Impedance spectroscopic analysis at different temperature indicates the different relaxation mechanisms and their variation with temperature, bulk grain and grain-boundary contributions to the electrical conductivity (Rg and capacitance (Cg of these materials. The conductivity in pure NiFeO4 is found to be predominantly due to intrinsic bulk contribution (Rg=213 kΩ and Cg=4.5 x 10-8 F. In the case of NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds, grain and grain-boundary contributions to the conductivity are clearly observed. The DC conductivity values (at 300 K of NiFe2O4, NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds are found to be 1.06 x 10-7 Ω-1 cm-1, 5.73 x 10-8 Ω-1 cm-1 and 1.28 x 10-8 Ω-1 cm-1 respectively.
A New Impedance Matching Method for an Ultra-Wide Band and Dual Circularly Polarised Feed
Li, Sha; Yan, Yi Hua; Wang, Wei; Chen, Zhi Jun; Liu, Dong Hao; Zhang, Fu Shun; Jeffrey, Natasha
2016-12-01
In traditional antenna design, metal components are not placed in the central part of the antenna as they change the characteristics of near field radiation. However, we show that placing a metal ring in the centre of the strip lines, which connect the ends of folded high-frequency dipoles, does not damage the performance of the feed. Instead it significantly improves the voltage standing wave ratio of the feed whilst other performance indicators are not compromised. Thus, our findings show an excellent way of improving the wide band feed. Based on this foundation, a new circularly polarised feed for operation between 0.4 to 2 GHz is introduced for the Chinese Spectral Radioheliograph in this paper. The issue of a feed impedance matching network is investigated. By optimising the impedance matching, the performance of the feed is enhanced with respect to the previous realisations of the Eleven feed. The simulation and experimental results show that the gain of the feed is about 10 dBi, and the VSWR is less than 2:1. In addition, the feed has a low axial ratio, fixed phase centre location, and constant beam width in the range of 0.4 to 2 GHz.
Approach for Wide Use of Diagnostic Method for XLPE Cables Using Harmonics in AC Loss Current
Tsujimoto, Tomiyuki; Nakade, Masahiko; Yagi, Yukihiro; Ishii, Noboru
Water tree is one of the degradation aspects of XLPE cables used for under-ground distribution or transmission lines. We have developed the loss current method using 3rd harmonic in AC loss current for cable diagnosis. Harmonic components in loss current arise as a result of the non-linear voltage-current characteristics of water trees. We confirmed that the 3rd harmonic in AC loss current had good correlation with water tree growth and break down strength. After that, we have applied this method to the actual 66kV XLPE cable lines. Up to now, the number of the application results is more than 130 lines. In case of cable lines terminated at gas-insulated switchgear (GIS), we have to remove the lightning arrestor (LA) and the potential transformer (PT) out of the test circuit. The reason is that we are afraid that each of LA and PT disturbs the degradation signal from cable lines. It takes extra time (1 or 2 days) and costs more to remove LA and PT in GIS out of a circuit. In order to achieve easy and reasonable diagnosis, we have developed a new method for cable lines terminated at GIS, by utilizing a technique, which enables to reduce signal of LA and PT from disturbed signal of cable lines. We confirmed the effect of the new method by experiments with actual cables.
Institute of Scientific and Technical Information of China (English)
贺鸿珠; 陈志源; 史美伦
2000-01-01
Reinforced concrete under the long-term intrusion of seawater has been studied by the K-Ktransform of AC impedance spectroscopy. The stability and durability of the reinforced concrete can bemeasured by the relative deviation of the values measured from that calculated by K-K transform. Withthe increase of the time of the intrusion, the concrete and the rebar is less and less stable and durable.Under the same condition, concrete with fly ash is more stable than ordinary concrete.%应用交流阻抗谱中的Kramers-Kronig变换对受海水长期侵蚀的混凝土和钢筋分别进行了研究．混凝土和钢筋的稳定性可用K-K变换值与实测值之间相对偏差的大小来进行衡量．随着海水侵蚀时间的增加，混凝土和钢筋的稳定性越来越差．在同样条件下，掺粉煤灰混凝土的稳定性优于普通混凝土．
Point of collapse and continuation methods for large ac/dc systems
Energy Technology Data Exchange (ETDEWEB)
Canizares, C.A. (Escuela Politecnica Nacional, Quito (Ecuador)); Alvarado, F.L. (Univ. of Wisconsin, Madison, WI (United States))
1993-02-01
This paper describes the implementation of both Point of Collapse (PoC) methods and continuation methods for the computation of voltage collapse points (saddle-node bifurcations) in large ac/dc systems. A comparison of the performance of these methods is presented for real systems of up to 2,158 buses. The paper discusses computational details of the implementation of the PoC and continuation methods, and the unique challenges encountered due to the presence of high voltage direct current (HVDC) transmission, area interchange power control regulating transformers, and voltage and reactive power limits. The characteristics of a robust PoC power flow program are presented, and its application to detection and solution of voltage stability problems is demonstrated.
Homentcovschi, Dorel; Miles, Ronald N.
2010-01-01
The paper gives a new method for analyzing planar discontinuities in rectangular waveguides. The method consists of a re-expansion of the normal modes in the two ducts at the junction plane into a system of functions accounting for the velocity singularities at the corner points. As the new expansion has an exponential convergence, only a few terms have to be considered for obtaining the solution of most practical problems. To see how the method works some closed form solutions, obtained by the conformal mapping method, are used to discuss the convergence of the re-expanded series when the number of retained terms increases. The equivalent impedance accounting for nonplanar waves into a plane-wave analysis is determined. Finally, the paper yields the scattering matrix which describes the coupling of arbitrary modes at each side of the discontinuity valid in the case of many propagating modes in both parts of the duct. PMID:20707432
An Improved DC Recovery Method from AC Coefficients of DCT-Transformed Images
Li, Shujun; Saupe, Dietmar; Kuo, C -C Jay
2010-01-01
Motivated by the work of Uehara et al. [1], an improved method to recover DC coefficients from AC coefficients of DCT-transformed images is investigated in this work, which finds applications in cryptanalysis of selective multimedia encryption. The proposed under/over-flow rate minimization (FRM) method employs an optimization process to get a statistically more accurate estimation of unknown DC coefficients, thus achieving a better recovery performance. It was shown by experimental results based on 200 test images that the proposed DC recovery method significantly improves the quality of most recovered images in terms of the PSNR values and several state-of-the-art objective image quality assessment (IQA) metrics such as SSIM and MS-SSIM.
Energy Technology Data Exchange (ETDEWEB)
Shekharam, T., E-mail: tshekharam@gmail.com; Laxminarasimha Rao, V.; Yellaiah, G.; Mohan Kumar, T.; Nagabhushanam, M., E-mail: mamidala_nb@yahoo.com
2014-12-25
Graphical abstract: A plot of 1−s versus T (K) for Cd{sub 0.8−x}Pb{sub x}Zn{sub 0.2}S (x = 0, 0.1–0.8), inset: plot of s versus T (K) for x = 0. - Highlights: • Activation energy of relaxation process of Cd{sub 0.8−x}Pb{sub x}Zn{sub 0.2}S (x = 0, 0.1–0.8) compounds has been determined. • Grain resistances and grain capacitances of the compounds were estimated at different temperatures. • Relaxation time for all the compounds has been determined at different temperatures. - Abstract: The samples of Cd{sub 0.8−x}Pb{sub x}Zn{sub 0.2}S (x = 0, 0.1–0.8) are prepared by Controlled Co-Precipitation Method. X-ray diffraction studies have confirmed the polycrystalline nature of the samples with Hexagonal and Cubic phases of Wurtzite structure. AC conductivity (σ{sub ac}) measurements of Cd{sub 0.8−x}Pb{sub x}Zn{sub 0.2}S samples at different temperatures (between 40 and 300 °C), in the frequency range 5 kHz–20 MHz were made. The results showed that σ{sub ac} obeys the relation σ{sub ac}(ω) = Aω{sup s}. The exponent “s” was found to decrease with increase in temperature. Further analysis revealed that, the AC conductivity of the samples follow correlated barrier hopping (CBH) model. The dielectric constant (∊′) and dielectric loss (Tan δ) were observed to (i) increase with the increase in temperature and the increase is higher at lower frequencies and (ii) decrease rapidly at low frequencies and remains almost constant at higher frequencies. The cole–cole plot showed a single semicircle, indicating an equivalent circuit with a single parallel resistor R{sub g} and capacitance C{sub g} network with a series resistance R{sub s}. The plots also show the grain contribution toward AC conductivity. The relaxation frequencies, determined from these plots are used to calculate the activation energies E{sub a} of relaxation process using Log τ versus 10{sup 3}/T plots. The values of E{sub a} for all the studied compounds range from 0.05 to 0
一种DDR信号阻抗匹配的新方法%New method of DDR signal impedance matching
Institute of Scientific and Technical Information of China (English)
王征
2012-01-01
There are two ways of DDR signal impedance marching:add the series-resistance in the source or add the shunt-resistance in the terminal.The two methods have their advantages and disadvantages.Source matching will increase the PCB plate area.Terminal matching will increase the power.This paper uses the shunt-capacitor to replace the shunt-resistance,which can solve the problem of PCB layout area,and the problem of single board power increased.It is a new method of DDR signal impedance matching.%DDR信号的阻抗匹配一般有两种方法：源端增加串联电阻和终端增加并联电阻。这两种方法各有利弊。其中源端串阻匹配会增加单板PCB的布板面积,终端并联匹配则会增加单板的功耗。本文则采用并联电容来替代并联电阻,这样即可以解决PCB布板面积的问题,也可以解决单板机功耗增加的问题,是DDR信号匹配的一种新方法。
Giovinazzo, G.; Ribas, N.; Cinca, J.; Rosell-Ferrer, J.
2010-04-01
Previous studies have shown that it is possible to evaluate heart graft rejection level using a bioimpedance technique by means of an intracavitary catheter. However, this technique does not present relevant advantages compared to the gold standard for the detection of a heart rejection, which is the biopsy of the endomyocardial tissue. We propose to use a less invasive technique that consists in the use of a transoesophageal catheter and two standard ECG electrodes on the thorax. The aim of this work is to evaluate different parameters affecting the impedance measurement, including: sensitivity to electrical conductivity and permittivity of different organs in the thorax, lung edema and pleural water. From these results, we deduce the best estimator for cardiac rejection detection, and we obtain the tools to identify possible cases of false positive of heart rejection due to other factors. To achieve these objectives we have created a thoracic model and we have simulated, with a FEM program, different situations at the frequencies of 13, 30, 100, 300 and 1000 kHz. Our simulation demonstrates that the phase, at 100 and 300 kHz, has the higher sensitivity to changes in the electrical parameters of the heart muscle.
Mousa, Ghassan; Golnaraghi, Farid; DeVaal, Jake; Young, Alan
2014-01-01
When a proton exchange membrane (PEM) fuel cell runs short of hydrogen, it suffers from a reverse potential fault that, when driven by neighboring cells, can lead to anode catalyst degradation and holes in the membrane due to local heat generation. As a result, hydrogen leaks through the electrically-shorted membrane-electrode assembly (MEA) without being reacted, and a reduction in fuel cell voltage is noticed. Such voltage reduction can be detected by using electrochemical impedance spectroscopy (EIS). To fully understand the reverse potential fault, the effect of hydrogen crossover leakage in a commercial MEA is measured by EIS at different differential pressures between the anode and cathode. Then the signatures of these leaky cells were compared with the signatures of a no-leaky cells at different oxygen concentrations with the same current densities. The eventual intent of this early stage work is to develop an on-board diagnostics system that can be used to detect and possibly prevent cell reversal failures, and to permit understanding the status of crossover or transfer leaks versus time in operation.
Energy Technology Data Exchange (ETDEWEB)
Ciovati, Gianluigi [JLAB
2015-02-01
This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.
DEFF Research Database (Denmark)
Larsen, Niels Vesterdal; Breinbjerg, Olav
2004-01-01
To facilitate the validation of the numerical Method of Auxiliary Sources an analytical Method of Auxiliary Sources solution is derived in this paper. The Analytical solution is valid for transverse magnetic, and electric, plane wave scattering by circular impedance Cylinders, and it is derived...... of the numerical Method of Auxiliary Sources for a range of scattering configurations....... with their singularities at different positions away from the origin. The transformation necessitates a truncation of the wave transformation but the inaccuracy introduced hereby is shown to be negligible. The analytical Method of Auxiliary Sources solution is employed as a reference to investigate the accuracy...
A new non-iterative reconstruction method for the electrical impedance tomography problem
Ferreira, A. D.; Novotny, A. A.
2017-03-01
The electrical impedance tomography (EIT) problem consists in determining the distribution of the electrical conductivity of a medium subject to a set of current fluxes, from measurements of the corresponding electrical potentials on its boundary. EIT is probably the most studied inverse problem since the fundamental works by Calderón from the 1980s. It has many relevant applications in medicine (detection of tumors), geophysics (localization of mineral deposits) and engineering (detection of corrosion in structures). In this work, we are interested in reconstructing a number of anomalies with different electrical conductivity from the background. Since the EIT problem is written in the form of an overdetermined boundary value problem, the idea is to rewrite it as a topology optimization problem. In particular, a shape functional measuring the misfit between the boundary measurements and the electrical potentials obtained from the model is minimized with respect to a set of ball-shaped anomalies by using the concept of topological derivatives. It means that the objective functional is expanded and then truncated up to the second order term, leading to a quadratic and strictly convex form with respect to the parameters under consideration. Thus, a trivial optimization step leads to a non-iterative second order reconstruction algorithm. As a result, the reconstruction process becomes very robust with respect to noisy data and independent of any initial guess. Finally, in order to show the effectiveness of the devised reconstruction algorithm, some numerical experiments into two spatial dimensions are presented, taking into account total and partial boundary measurements.
Dielectric Properties of Bi4Ti3O12 Ceramics by Impedance Spectroscopic Method
Institute of Scientific and Technical Information of China (English)
CHEN Yong; SU Huyin; XUE Simin; LI Zhaozhi; ZHANG Cancan; CHEN Qi; XU Lingfang; CAO Wanqiang; HUANG Zhaoxiang
2016-01-01
Various lead-free ceramics have been investigated in search for new high-temperature dielectrics. In particular, Bi4Ti3O12 is a type of ferroelectric ceramics, which is supposed to replace lead-containing ceramics for its outstanding dielectric properties in the near future. Ferroelectric ceramics of Bi4Ti3O12 made by conventional mixed oxide route have been studied by impedance spectroscopy in a wide range of temperature. X-ray diffraction patterns show that Bi4Ti3O12 ceramics are a single-phase of ferroelectric Bi-layered perovskite structure whether it is calcined at 800℃ or after sintering production. This study focused on the effect of the grain size on the electric properties of BIT ceramics. The BIT ceramics with different grain sizes were prepared at different sintering temperatures. Grain becomes coarser with the sintering temperature increasing by 50℃, relative permittivity and dielectric loss also change a lot. When sintered at 1 100℃, r values peak can reach 205.40 at a frequency of 100 kHz, the minimum dielectric losses of four different frequencies make no difference, all close to 0.027. The values ofEa range from 0.52 to 0.68 eV. The dielectric properties of the sample sintered at 1 100℃ are relatively better than those of the other samples by analyzing the relationship of the grain, the internal stresses, the homogeneity and the dielectric properties. SEM can better explain the results of the dielectric spectrum at different sintering temperatures. The results show that Bi4Ti3O12 ceramics are a kind of dielectrics. Thus, Bi4Ti3O12 can be used in high-temperature capacitors and microwave ceramics.
Directory of Open Access Journals (Sweden)
M.A. Radhika
2013-02-01
Full Text Available In general aerospace, civil and mechanical (ACM structures are often subjected to some or the other forms of loading during their service life. It has been reported that about 75% of aerospace structures fail due to fatigue cyclic loading. The civil-structural components are subjected to some form of axial and transverse loading which continuously deteriorates the health of the structure. Mechanical components are also subjected to stresses due to contact pressures between several components. Thus for ACM structures, effective monitoring through-out the entire life is required as these often involve public life and huge investments. Owing to such necessity, researchers around the world are continuously working on the development of smart sensor based effective monitoring techniques. Piezo electric (PZT transducer based electromechanical impedance (EMI is one such technique which was developed for structural health monitoring (SHM. In this technique, PZT transducers are usually attached to the structure to be monitored and are then subjected to unit sinusoidal electric voltage to generate the electromechanical (EM admittance signatures when interrogated to the desired frequency range of excitations. These signatures consist of real (conductance and imaginary (susceptance parts which serve as indicator to predict the structural health. Any deviations in these signatures during the monitoring period indicate disturbance in the structure. However, the EMI technique was not widely explored for structural load monitoring (such as fatigue cyclic load, monotonous load, axial and transverse load compared to damage detection. In this paper, systematic experiments were presented on the specimens for axial load variations, transverse load variations, monotonous and fatigue load variation with discussions on boundary effect and buckling effects. For axial, fatigue, monotonic load, the conductance was found to be effective where as for transverse load
Acoustic impedances of ear canals measured by impedance tube
DEFF Research Database (Denmark)
Ciric, Dejan; Hammershøi, Dorte
2007-01-01
During hearing sensitivity tests, the sound field is commonly generated by an earphone placed on a subject ear. One of the factors that can affect the sound transmission in the ear is the acoustic impedance of the ear canal. Its importance is related to the contribution of other elements involved...... in the transmission such as the earphone impedance. In order to determine the acoustic impedances of human ear canals, the standardized method for measurement of complex impedances used for the measurement of the audiometric earphone impedances is applied. It is based on the transfer function between two microphone...... locations in an impedance tube. The end of the tube representing the measurement plane is placed at the ear canal entrance. Thus, the impedance seen from the entrance inward is measured on 25 subjects. Most subjects participated in the previous measurement of the ratio between the pressures at the open...
Annamdas, Venu Gopal Madhav; Radhika, Madhav Annamdas; Yang, Yaowen
2009-03-01
Impedance-based structural health monitoring (SHM) technique has been developed using piezo-ceramic (PZT) transducers either by surface bonding or embedding inside the structure to detect damage at the earliest possible stage using signatures. However, this technique requires PZT to be permanently attached to the structures. Furthermore permanent attachment will influence the appearance of the host structure and during replacement of faulty transducer, the use of de bonding tools may spoils the surface and beneath. Hence the present study is aimed to fabricate a portable structure, where PZTs are bonded on it and later the portable structure is attached to the host structure. This portable structure is easy to install during monitoring period and uninstall after recording the monitoring signatures of the host structure. This method protects the surface of the host structure to be monitored and will have same efficiency as that of permanently attached PZTs.
A.c. conductivity and dielectric study of LiNiPO4 synthesized by solid-state method
Indian Academy of Sciences (India)
M Ben Bechir; A Ben Rhaiem; K Guidara
2014-05-01
LiNiPO4 compound was prepared by the conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, infrared, Raman analysis spectroscopy and electrical impedance spectroscopy. The compound crystallizes in the orthorhombic system, space group with = 10.0252(7) Å, = 5.8569(5) Å and = 4.6758(4) Å. Vibrational analysis was used to identify the presence of PO$^{3-}_{4}$ group in this compound. The complex impedance has been measured in the temperature and frequency ranges 654–716 K and 242 Hz–5 MHz, respectively. The ' and '' vs frequency plots are well-fitted to an equivalent circuit consisting of series of combination of grains and grain boundary elements. Dielectric data were analysed using complex electrical modulus * for the sample at various temperatures. The modulus plots are characterized by the presence of two peaks thermally activated. The frequency dependence of the conductivity is interpreted in terms of equation: _a.c.() = [g/(1 + 22) + (∞22/1 + 22) + An]. The near values of activation energies obtained from the analysis of ", conductivity data and equivalent circuit confirms that the transport is through ion hopping mechanism dominated by the motion of Li+ in the structure of the investigated material.
Effect of HIPing on conductivity and impedance measurements of DyBi5Fe2Ti3O18 ceramics
Indian Academy of Sciences (India)
N V Prasad; G Prasad; Mahendra Kumar; S V Suryanarayana; T Bhimasankaram; G S Kumar
2000-12-01
X-ray diffraction, a.c. impedance and conductivity (a.c. and d.c.) have been used to characterize DyBi5Fe2Ti3O18. Samples were prepared by solid state double sintering method. A few samples were also subjected to hot isostatic pressing (HIP) at 800°C for 2 h at 100 MPa pressure. The data on XRD, impedance and conductivity of two sets of samples are compared to understand study of effect of HIPing on the properties of DyBi5Fe2Ti3O18.
Measuring ac-loss in high temperature superconducting cable-conductors using four probe methods
DEFF Research Database (Denmark)
Kühle (fratrådt), Anders Van Der Aa; Træholt, Chresten; Olsen, Søren Krüger;
1999-01-01
Measuring the ac-loss of superconducting cable conductors have many aspects in common with measuring the ac-loss of single superconducting tapes. In a cable conductor all tapes are connected to each other and to the test circuit through normal metal joints in each end. This makes such measurement...
Microwave Impedance Measurement for Nanoelectronics
Directory of Open Access Journals (Sweden)
M. Randus
2011-04-01
Full Text Available The rapid progress in nanoelectronics showed an urgent need for microwave measurement of impedances extremely different from the 50Ω reference impedance of measurement instruments. In commonly used methods input impedance or admittance of a device under test (DUT is derived from measured value of its reflection coefficient causing serious accuracy problems for very high and very low impedances due to insufficient sensitivity of the reflection coefficient to impedance of the DUT. This paper brings theoretical description and experimental verification of a method developed especially for measurement of extreme impedances. The method can significantly improve measurement sensitivity and reduce errors caused by the VNA. It is based on subtraction (or addition of a reference reflection coefficient and the reflection coefficient of the DUT by a passive network, amplifying the resulting signal by an amplifier and measuring the amplified signal as a transmission coefficient by a common vector network analyzer (VNA. A suitable calibration technique is also presented.
基于ACS-GA算法的车辆路径问题研究%An ACS-GA Hybrid Optimization Method to Solve Vehicle Routing Problem
Institute of Scientific and Technical Information of China (English)
赵婉忻; 曲仕茹
2011-01-01
Vehicle routing problem is an important research area in intelligent transportation and business logistics. Planning the vehicle routes reasonably, reducing the delivery mileage and minimizing the cost of logistic distribution are great significance to increase economic efficiency. The paper focuses on vehicle routing problem with time windows in logistic distribution and establishes an improved mathematical model in which the delivery time and delivery distance is shortest. A novel hybrid optimization method integrating ant colony system with genetic algorithm ( ACS - GA) is presented. The initial solution is obtained by ant colony system. A genetic algorithm is used to improve the performance of ACS by reproduction, crossover and mutation operations. The ACS - GA hybrid optimization method can overcome the premature phenomenon and enhance the global search ability. Based on the benchmark datasets of vehicle routing problem with time windows, the experimental results demonstrate that the proposed method has a better ability to search the global optimal solution than other optimization methods.%物流配送车辆路径问题是智能交通和商业物流领域中一个重要研究方面.合理规划车辆的行驶路线,减少配送里程,降低物流成本,对提高经济效益具有重要意义.重点分析了带时间窗的物流配送车辆路径问题,建立了兼顾配送时间与配送距离最短的改进数学模型.提出了基于蚁群系统算法和遗传算法相融合的混合算法.该算法利用蚁群系统算法得到初始解,运用遗传算法中复制、交叉、变异操作对解的种群多样性进行扩充,克服了蚁群系统算法的早熟现象,增强了算法的全局搜索能力.基于标准数据集的实验结果表明,该算法与其他优化方法相比较,具有较好的搜索车辆路径最优解的能力.
Na, Wongi S.
2016-05-01
Damage accumulation in structures may result in a structural failure which is a serious problem when ensuring public safety. Although various non-destructive techniques are available to seek for the existence of damage at an early stage, most of these techniques rely on the experience of the experts. To date, automated structural health monitoring systems have been extensively researched and one of the methods, known as the electromechanical impedance (EMI) method, has shown promising results. However, the EMI method is a local method requiring a large number of sensors for covering large areas such as in bridges and buildings. In addition, attaching these sensors onto a surface can be time consuming since adhesives are used for attaching the sensors where its curing time increases the setting up time even further. In this study, the performance of the reusable piezoelectric (PZT) device for metal structures is examined against two different types of progressive damage scenarios. Overall, the reusable PZT device shown in this study has successfully identified damage with a possibility of weight loss detection.
Energy Technology Data Exchange (ETDEWEB)
Kim, Moo Whan; Kang, Hie Chan; Kwon, Jung Tae; Huh, Deok; Yang, Hoon Cheul [Pohang University of Science and Technology, Pohang (Korea)
2000-04-01
Impedance method was carried out to design the electrode that can measure the void fraction of the bubbly flow in pool reservoir. To find out the optimum electrode shape, Styrofoam-Simulator tests were performed in a specially designed acrylic reservoir. Three kinds of electrodes were designed to compare the measuring characteristics of water-air flow. The resistance increased with the increase of the void fraction and the capacitance decreased with the increase of the void fraction. The resistance is a main parameter to express the nature of the water-air flow in impedance method. Almost of impedance values come out from the resistance. The degree of deviation from the mean-resistance values showed reasonable results. Electrode type-I expressed excellent results among the three electrode shapes. The sensor developed can simultaneously measure the void fraction and the water level. 7 refs., 51 figs., 4 tabs. (Author)
Complex Impedance of Manganese Ferrite Powders Obtained by Two Different Methods
Directory of Open Access Journals (Sweden)
Mălăescu I.
2015-12-01
Full Text Available Two samples of manganese ferrite powder were obtained by the calcination method (sample A and hydrothermal method (sample B. The crystal structure of the samples has been determined using X-ray diffraction analysis (XRD. The results shown that the sample A has three phases (FeMnO3, Mn2O3 and Fe2O3 and the prevailing phase is FeMnO3 with perovskite structure and the sample B has only a single phase (MnFe2O4.
DEFF Research Database (Denmark)
Jensen, Kåre Jean; Munk, Steen M.; Sørensen, John Aasted
1998-01-01
processes and communication systems lead to demands for improved monitoring of power distribution networks so that the quality of power delivery can be kept at a controlled level. The ground fault localization method for each feeder in a network is based on the centralized frequency broadband measurement...... of three phase voltages and currents. The method consists of a feature extractor, based on a grid description of the feeder by impulse responses, and a neural network for ground fault localization. The emphasis of this paper is the feature extractor, and the detection of the time instance of a ground fault...
Frequency Synchronization Analysis in Digital lock-in Methods for Bio-impedance Determination
Directory of Open Access Journals (Sweden)
Brajkovič Robert
2014-12-01
Full Text Available The lock-in method is one of the most frequently used methods for reconstruction of measured signals and as such frequently applied in the (bioimpedance method to determine the modulus and phase of the (bioimpedance. In implementation of the method in a (bioimpedance measurement device one has to consider possible non synchronized frequencies of the reference and the analyzed signals as well as potential sources of noise. In this work we analyzed these errors theoretically and experimentally. We show that both amplitude and phase errors depend on the relative difference of the frequencies of the reference and investigated signal as well as the number of integration periods. Theoretically, these errors vanish during the determination of the (bioimpedance modulus and phase. In practical implementation the inaccuracies appear at points of very low determined signal amplitudes due to the limited accuracy of analog to digital converters and are distributed around these points due to other sources of noise inherent in implementation of the measurement device.
Directory of Open Access Journals (Sweden)
Rafaela Siqueira Ferraz
2015-03-01
Full Text Available The aim of this study was to develop and validate a UV spectrophotometric method for determination of LPSF/AC04 from inclusion complex and encapsulated into liposomes. The validation parameters were determined according to the International Conference on Harmonisation (ICH and National Health Surveillance Agency (ANVISA guidelines. LPSF/AC04 was determined at 250 nm in methanol by a UV spectrophotometric method, exhibiting linearity in the range from 0.3 to 2 µg.mL−1 (Absorbance=0.18068 x [LPSF/AC04 µg.mL-1] + 0.00348, (r2=0.9995. The limits of detection and quantification were 0.047µg.mL−1 and 0.143µg.mL−1, respectively. The method was accurate, precise, reproducible and robust since all the samples analyzed had coefficient of variation of less than 5% and no statistically significant difference between theoretical and practical concentrations was detected. Thus, a rapid, simple, low cost and sensitive spectrophotometric method was developed and validated for determining the content of inclusion complex and liposomes containing LPSF/AC04.
Directory of Open Access Journals (Sweden)
Chalas Renata
2014-06-01
Full Text Available The diagnostic management is a very important and integral part of the entire treatment process and has a direct influence on the decision-taking on the choice of the most appropriate form of therapy consistent with current knowledge. Knowledge of the morphology of hard dental tissues lesions has led to the development of quantitative methods for diagnosis and monitoring of dental caries, which enabled the implementation of appropriate treatments aimed at repairing than replacing damaged tissue. The aim of the study was to compare selected diagnostic methods: visual (ICDAS, impedance spectroscopy (CarieScan PRO and laser fluorescence (Diagnodent Pen in detecting caries in grooves on the chewing surfaces of molars and premolars. The obtained results indicated a high concordance of measurements performed with the Diagnodent Pen with the results of visual examination and a lower compliance of visual examination with the results obtained using the CarieScan PRO. A combination of visual and tactile method with tests using advanced technology provides greater opportunity to confirm the diagnosis of carious lesions requiring medical intervention.
A non-iterative method for the electrical impedance tomography based on joint sparse recovery
Lee, Ok Kyun; Kang, Hyeonbae; Ye, Jong Chul; Lim, Mikyoung
2015-07-01
The purpose of this paper is to propose a non-iterative method for the inverse conductivity problem of recovering multiple small anomalies from the boundary measurements. When small anomalies are buried in a conducting object, the electric potential values inside the object can be expressed by integrals of densities with a common sparse support on the location of anomalies. Based on this integral expression, we formulate the reconstruction problem of small anomalies as a joint sparse recovery and present an efficient non-iterative recovery algorithm of small anomalies. Furthermore, we also provide a slightly modified algorithm to reconstruct an extended anomaly. We validate the effectiveness of the proposed algorithm over the linearized method and the multiple signal classification algorithm by numerical simulations. This work is supported by the Korean Ministry of Education, Sciences and Technology through NRF grant No. NRF-2010-0017532 (to H K), the Korean Ministry of Science, ICT & Future Planning; through NRF grant No. NRF-2013R1A1A3012931 (to M L), the R&D Convergence Program of NST (National Research Council of Science & Technology) of Republic of Korea (Grant CAP-13-3-KERI) (to O K L and J C Y).
O'Rourke, Michelle; Duffy, Noel; Marco, Roland De; Potter, Ian
2011-06-23
Electrochemical impedance spectroscopy (EIS) has been used to estimate the non-frequency dependent (static) dielectric constants of base polymers such as poly(vinyl chloride) (PVC), cellulose triacetate (CTA) and polystyrene (PS). Polymer inclusion membranes (PIMs) containing different amounts of PVC or CTA, along with the room temperature ionic liquid Aliquat 336 and plasticizers such as trisbutoxyethyl phosphate (TBEP), dioctyl sebecate (DOS) and 2-nitrophenyloctyl ether (NPOE) have been investigated. In this study, the complex and abstract method of EIS has been applied in a simple and easy to use way, so as to make the method accessible to membrane scientists and engineers who may not possess the detailed knowledge of electrochemistry and interfacial science needed for a rigorous interpretation of EIS results. The EIS data reported herein are internally consistent with a percolation threshold in the dielectric constant at high concentrations of Aliquat 336, which illustrates the suitability of the EIS technique since membrane percolation with ion exchangers is a well-known phenomenon.
Directory of Open Access Journals (Sweden)
Michelle O’Rourke
2011-06-01
Full Text Available Electrochemical impedance spectroscopy (EIS has been used to estimate the non-frequency dependent (static dielectric constants of base polymers such as poly(vinyl chloride (PVC, cellulose triacetate (CTA and polystyrene (PS. Polymer inclusion membranes (PIMs containing different amounts of PVC or CTA, along with the room temperature ionic liquid Aliquat 336 and plasticizers such as trisbutoxyethyl phosphate (TBEP, dioctyl sebecate (DOS and 2-nitrophenyloctyl ether (NPOE have been investigated. In this study, the complex and abstract method of EIS has been applied in a simple and easy to use way, so as to make the method accessible to membrane scientists and engineers who may not possess the detailed knowledge of electrochemistry and interfacial science needed for a rigorous interpretation of EIS results. The EIS data reported herein are internally consistent with a percolation threshold in the dielectric constant at high concentrations of Aliquat 336, which illustrates the suitability of the EIS technique since membrane percolation with ion exchangers is a well-known phenomenon.
Na, Wongi S.; Lee, Hyeonseok
2016-11-01
In general, the pipelines within a nuclear power plant facility may experience high temperatures up to several hundred degrees. Thus it is absolutely vital to monitor these pipes to prevent leakage of radioactive substances which may lead to a catastrophic outcome of the surrounding environment. Over the years, one of the structural health monitoring technique known as the electromechanical impedance (EMI) technique has been of great interests in various fields including civil infrastructures, mechanical and aerospace structures. Although it has one of the best advantages to be able for a single piezoelectric transducer to act as a sensor and an actuator, simultaneously, its low curie temperature makes it difficult for the EMI technique to be conducted at high temperature environment. To overcome this problem, this study shows a method to avoid attaching the piezoelectric transducer directly onto the target structure using a metal wire for damage detection at high temperature. By shifting the frequency to compensate the signature changes subjected to the variations in temperature, the experimental results indicate that damage identification is more successful above 200 oC, making the metal wire method suitable for the EMI technique at high temperature environment.
O'Rourke, Michelle; Duffy, Noel; De Marco, Roland; Potter, Ian
2011-01-01
Electrochemical impedance spectroscopy (EIS) has been used to estimate the non-frequency dependent (static) dielectric constants of base polymers such as poly(vinyl chloride) (PVC), cellulose triacetate (CTA) and polystyrene (PS). Polymer inclusion membranes (PIMs) containing different amounts of PVC or CTA, along with the room temperature ionic liquid Aliquat 336 and plasticizers such as trisbutoxyethyl phosphate (TBEP), dioctyl sebecate (DOS) and 2-nitrophenyloctyl ether (NPOE) have been investigated. In this study, the complex and abstract method of EIS has been applied in a simple and easy to use way, so as to make the method accessible to membrane scientists and engineers who may not possess the detailed knowledge of electrochemistry and interfacial science needed for a rigorous interpretation of EIS results. The EIS data reported herein are internally consistent with a percolation threshold in the dielectric constant at high concentrations of Aliquat 336, which illustrates the suitability of the EIS technique since membrane percolation with ion exchangers is a well-known phenomenon. PMID:24957616
SYNTHESIS METHODOLOGY FOR ACTIVE ELEMENT USING IMPEDANCES –BASED BOND GRAPH METHODS
Directory of Open Access Journals (Sweden)
Nasta TANASESCU
2004-12-01
Full Text Available This paper introduces a synthesis methodology for active elements within systems that uses frequency response function as a basis for describing required behavior. The method is applicable in the design of a new system or in the retrofit of an existing system in which an active element is required or desired. The two basis principles of bond graph modeling are the “reticulation principle” which decomposes a physical into elemental physical laws represented as network elements interacting through ports and the “power postulate” which assembles the complete model through a network of power flows representing the exchange of energy between the elements. Moreover the bond graph model leads to a rigorous definitions of the structure of the associated dynamical equations.
Optically stimulated differential impedance spectroscopy
Maxey, Lonnie C; Parks, II, James E; Lewis, Sr., Samuel A; Partridge, Jr., William P
2014-02-18
Methods and apparatuses for evaluating a material are described. Embodiments typically involve use of an impedance measurement sensor to measure the impedance of a sample of the material under at least two different states of illumination. The states of illumination may include (a) substantially no optical stimulation, (b) substantial optical stimulation, (c) optical stimulation at a first wavelength of light, (d) optical stimulation at a second wavelength of light, (e) a first level of light intensity, and (f) a second level of light intensity. Typically a difference in impedance between the impedance of the sample at the two states of illumination is measured to determine a characteristic of the material.
DEFF Research Database (Denmark)
Anastassiu, H.T.; D.I.Kaklamani, H.T.; Economou, D.P.;
2002-01-01
A novel combination of the method of auxiliary sources (MAS) and the standard impedance boundary condition (SIBC) is employed in the analysis of transverse magnetic (TM) plane wave scattering from infinite, coated, perfectly conducting cylinders with square cross sections. The scatterer is initia...
Directory of Open Access Journals (Sweden)
Jikai Chen
2016-12-01
Full Text Available At present, the research is still in the primary stage in the process of fault disturbance energy transfer in the multilevel modular converter based high voltage direct current (HVDC-MMC. An urgent problem is how to extract and analyze the fault features hidden in MMC electrical information in further studies on the HVDC system. Aiming at the above, this article analyzes the influence of AC transient disturbance on electrical signals of MMC. At the same time, it is found that the energy distribution of electrical signals in MMC is different for different arms in the same frequency bands after the discrete wavelet packet transformation (DWPT. Renyi wavelet packet energy entropy (RWPEE and Renyi wavelet packet time entropy (RWPTE are proposed and applied to AC transient fault feature extraction from electrical signals in MMC. Using the feature extraction results of Renyi wavelet packet entropy (RWPE, a novel recognition method is put forward to recognize AC transient faults using the information fusion technology. Theoretical analysis and experimental results show that the proposed method is available to recognize transient AC faults.
Creasy, M. Austin
2016-03-01
Impedance models of pipes can be used to estimate resonant frequencies of standing waves and model acoustic pressure of closed and open ended pipes. Modelling a pipe with impedance methods allows additional variations to the pipe to be included in the overall model as a system. Therefore an actuator can be attached and used to drive the system and the impedance model is able to include the dynamics of the actuator. Exciting the pipe system with a chirp signal allows resonant frequencies to be measured in both the time and frequency domain. The measurements in the time domain are beneficial for introducing undergraduates to resonances without needing an understanding of fast Fourier transforms. This paper also discusses resonant frequencies in open ended pipes and how numerous texts incorrectly approximate the resonant frequencies for this specific pipe system.
Ma, Chun-hui; Zu, Yuan-gang; Yang, Lei; Li, Jian
2015-01-22
In this study, two solid-phase recycling method for basic ionic liquid (IL) 1-butyl-3-methylimidazolium acetate ([C4mim]Ac) were studied through a digestion extraction system of extracting biphenyl cyclooctene lignans from Schisandra chinensis. The RP-HPLC detection method for [C4mim]Ac was established in order to investigate the recovery efficiency of IL. The recycling method of [C4mim]Ac is divided into two steps, the first step was the separation of lignans from the IL solution containing HPD 5000 macroporous resin, the recovery efficiency and purity of [C4mim]Ac achieved were 97.8% and 67.7%, respectively. This method cannot only separate the lignans from [C4mim]Ac solution, also improve the purity of lignans, the absorption rate of lignans in [C4mim]Ac solution was found to be higher (69.2%) than that in ethanol solution (57.7%). The second step was the purification of [C4mim]Ac by the SK1B strong acid ion exchange resin, an [C4mim]Ac recovery efficiency of 55.9% and the purity higher than 90% were achieved. Additionally, [C4mim]Ac as solvent extraction of lignans from S. chinensis was optimized, the hydrolysis temperature was 90°C and the hydrolysis time was 2h.
Methods, systems and apparatus for controlling operation of two alternating current (AC) machines
Gallegos-Lopez, Gabriel; Nagashima, James M.; Perisic, Milun; Hiti, Silva
2012-02-14
A system is provided for controlling two AC machines. The system comprises a DC input voltage source that provides a DC input voltage, a voltage boost command control module (VBCCM), a five-phase PWM inverter module coupled to the two AC machines, and a boost converter coupled to the inverter module and the DC input voltage source. The boost converter is designed to supply a new DC input voltage to the inverter module having a value that is greater than or equal to a value of the DC input voltage. The VBCCM generates a boost command signal (BCS) based on modulation indexes from the two AC machines. The BCS controls the boost converter such that the boost converter generates the new DC input voltage in response to the BCS. When the two AC machines require additional voltage that exceeds the DC input voltage required to meet a combined target mechanical power required by the two AC machines, the BCS controls the boost converter to drive the new DC input voltage generated by the boost converter to a value greater than the DC input voltage.
Directory of Open Access Journals (Sweden)
Martin Winter
2013-07-01
Full Text Available A new approach to study the chemical stability of electrodeposited lithium on a copper metal substrate via measurements with a fast impedance scanning electrochemical quartz crystal microbalance is presented. The corrosion of electrochemically deposited lithium was compared in two different electrolytes, based on lithium difluoro(oxalato borate (LiDFOB and lithium hexafluorophosphate, both salts being dissolved in solvent blends of ethylene carbonate and diethyl carbonate. For a better understanding of the corrosion mechanisms, scanning electron microscopy images of electrodeposited lithium were also consulted. The results of the EQCM experiments were supported by AC impedance measurements and clearly showed two different corrosion mechanisms caused by the different salts and the formed SEIs. The observed mass decrease of the quartz sensor of the LiDFOB-based electrolyte is not smooth, but rather composed of a series of abrupt mass fluctuations in contrast to that of the lithium hexafluorophosphate-based electrolyte. After each slow decrease of mass a rather fast increase of mass is observed several times. The slow mass decrease can be attributed to a consolidation process of the SEI or to the partial dissolution of the SEI leaving finally lithium metal unprotected so that a fast film formation sets in entailing the observed fast mass increases.
Implantable Impedance Plethysmography
2014-01-01
We demonstrate by theory, as well as by ex vivo and in vivo measurements that impedance plethysmography, applied extravascularly directly on large arteries, is a viable method for monitoring various cardiovascular parameters, such as blood pressure, with high accuracy. The sensor is designed as an implant to monitor cardiac events and arteriosclerotic progression over the long term.
IMPEDANCE SPECTROSCOPY OF POLYCRYSTALLINE TIN DIOXIDE FILMS
Directory of Open Access Journals (Sweden)
D. V. Adamchuck
2016-01-01
Full Text Available The aim of this work is the analysis of the influence of annealing in an inert atmosphere on the electrical properties and structure of non-stoichiometric tin dioxide films by means of impedance spectroscopy method. Non-stoichiometric tin dioxide films were fabricated by two-step oxidation of metallic tin deposited on the polycrystalline Al2O3 substrates by DC magnetron sputtering. In order to modify the structure and stoichiometric composition, the films were subjected to the high temperature annealing in argon atmosphere in temperature range 300–800 °С. AC-conductivity measurements of the films in the frequency range 20 Hz – 2 MHz were carried out. Variation in the frequency dependencies of the real and imaginary parts of the impedance of tin dioxide films was found to occur as a result of high-temperature annealing. Equivalent circuits for describing the properties of films with various structure and stoichiometric composition were proposed. Possibility of conductivity variation of the polycrystalline tin dioxide films as a result of аnnealing in an inert atmosphere was demonstrated by utilizing impedance spectroscopy. Annealing induces the recrystallization of the films, changing in their stoichiometry as well as increase of the sizes of SnO2 crystallites. Variation of electrical conductivity and structure of tin dioxide films as a result of annealing in inert atmosphere was confirmed by X-ray diffraction analysis. Analysis of the impedance diagrams of tin dioxide films was found to be a powerful tool to study their electrical properties.
Short-circuit impedance measurement
DEFF Research Database (Denmark)
Pedersen, Knud Ole Helgesen; Nielsen, Arne Hejde; Poulsen, Niels Kjølstad
2003-01-01
Methods for estimating the short-circuit impedance in the power grid are investigated for various voltage levels and situations. The short-circuit impedance is measured, preferably from naturally occurring load changes in the grid, and it is shown that such a measurement system faces different...
Li, Shiyang; Zheng, Limei; Jiang, Wenhua; Sahul, Raffi; Gopalan, Venkatraman; Cao, Wenwu
2013-09-14
The most difficult task in the characterization of complete set material properties for piezoelectric materials is self-consistency. Because there are many independent elastic, dielectric, and piezoelectric constants, several samples are needed to obtain the full set constants. Property variation from sample to sample often makes the obtained data set lack of self-consistency. Here, we present a method, based on pulse-echo ultrasound and inverse impedance spectroscopy, to precisely determine the full set physical properties of piezoelectric materials using only one small sample, which eliminated the sample to sample variation problem to guarantee self-consistency. The method has been applied to characterize the [001]C poled Mn modified 0.27Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 single crystal and the validity of the measured data is confirmed by a previously established method. For the inverse calculations using impedance spectrum, the stability of reconstructed results is analyzed by fluctuation analysis of input data. In contrast to conventional regression methods, our method here takes the full advantage of both ultrasonic and inverse impedance spectroscopy methods to extract all constants from only one small sample. The method provides a powerful tool for assisting novel piezoelectric materials of small size and for generating needed input data sets for device designs using finite element simulations.
Compensation methods applied in current control schemes for large AC drive systems
DEFF Research Database (Denmark)
Rus, D. C.; Preda, N. S.; Teodorescu, Remus;
2012-01-01
The paper deals with modified PI current control structures for large AC drive systems which use surface mounted permanent magnet synchronous machines or squirrel-cage induction motors supplied with voltage source inverters. In order to reduce the power losses caused by high frequency switching...
Gerbracht, Eberhard H. -A.
2007-01-01
Being inspired by phasor analysis in linear circuit theory, and its algebraic counterpart - the AC-(operational)-calculus for sinusoids developed by W. Marten and W. Mathis - we define a complex structure on several spaces of real-valued elementary functions. This is used to algebraize inhomogeneous linear ordinary differential equations with inhomogenities stemming from these spaces. Thus we deduce an effective method to calculate particular solutions of these ODEs in a purely algebraic way.
An improvement to the data processing course of electrochemical impedance technique
Institute of Scientific and Technical Information of China (English)
Yinglv Jiang; Yinshun Wu; Hong Chu
2003-01-01
For some electrochemical systems the traditional data processing methods can not be met, so it is necessary to develop a new method to deal with these problems. When processing the electrochemical AC impedance data of titanium alloy TA12 in 3% NaC1 solution (at free corrosion potential, room temperature) a new method is developed which can detach the information of the interface resistance demonstrably from the interface capacitance. The results show that the interface resistance and capacitance are all functions of frequency. And the AC impedance of the resistance and capacitance obey the following relations: C(f) = 104.01982 f-0.9292,R(f) =104.80011 (f+0.008)-0.90897, which is completely different from the traditional conception that the interface resistance and capacitance are constants. And this phenomenon is ubiquitous in titanium alloys according to the study. So perhaps it is an innate characteristic of interface.
Electrochemical impedance studies of methanol oxidation on GC/Ni and GC/NiCu electrode
Energy Technology Data Exchange (ETDEWEB)
Danaee, I.; Jafarian, M.; Forouzandeh, F.; Mahjani, M.G. [Department of Chemistry, K.N. Toosi University of Technology, PO Box 15875-4416, Tehran (Iran); Gobal, F. [Department of Chemistry, Sharif University of Technology, PO Box 11365-9516, Tehran (Iran)
2009-01-15
The electro-oxidation of methanol on nickel and nickel-copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) in a 1 M NaOH solution at different concentrations of methanol was studied by the method of ac-impedance spectroscopy. Two semicircles in the first quadrant of a Nyquist diagram were observed for electro-oxidation of methanol on GC/Ni corresponding to charge transfer resistance and adsorption of intermediates. Electro-oxidation of methanol on GC/NiCu shows negative resistance in impedance plots as signified by semi-circles terminating in the second quadrant. The impedance behavior shows different patterns at different applied anodic potential. The influence of the electrode potential on impedance pattern is studied and a mathematical model was put forward to quantitatively account for the impedance behavior of methanol oxidation. At potentials higher than 0.49 V vs. Ag/AgCl, a pseudoinductive behavior is observed but at higher than 0.58 V, impedance patterns terminate in the second quadrant. The conditions required for this behavior are delineated with the use of the impedance model. (author)
DEFF Research Database (Denmark)
Canali, Chiara; Mazzoni, Chiara; Larsen, Layla Bashir
2015-01-01
) cells were encapsulated in gelatin to form artificial 3D cell constructs and detected when placed in different positions inside large gelatin scaffolds. Taken together, these results open new perspectives for impedance-based sensing technologies for non-invasive monitoring in tissue engineering...
Institute of Scientific and Technical Information of China (English)
史国生; 赵阳; 颜伟; 董颖华; 朱志毅
2012-01-01
针对传导电磁干扰滤波器设计中人工电源网络阻抗、噪声源内阻抗、负载阻抗与EMI滤波器的阻抗匹配问题,建立了插入损耗法的误差理论模型及其等效电路.分别分析了串联和并联插入损耗法的测量精度及其系统误差,据此提出了相应的测试条件和测试方法,即当被测阻抗远大于负载阻抗时,采用串联插入损耗法；当被测阻抗远小于负载阻抗时,采用并联插入损耗法；当被测阻抗与负载阻抗相当时,可改变负载阻抗.理论与试验研究表明,该方法在适用范围内能够快速有效地提取EMI噪声源内阻抗,从而实现噪声源与EMI滤波器之间的最大阻抗适配,为EMI滤波器的设计及传导电磁干扰噪声抑制提供理论依据.%In order to solve the impedance matching problem for conducted EMI filter designing of artificial mains network (AMN) impedance, noise source impedance, load impedance and EMI filter impedance, the error theoretical model and equivalent circuits of insertion loss (IL) method were established. The measurement accuracy and system error of series and parallel IL methods were analyzed to provide improved test condition and methods. Series IL method was used when the measured impedance was much larger than load impedance. Parallel IL method was utilized when the measured impedance was much smaller than load impedance. The load impedance was altered when the measured impedance approximately equaled to load impedance. Theoretical analysis and experimental results show that the proposed method can extract EMI noise impedance effectively in certain range, where it can also realize the maximum impedance adapter between noise impedance and EMI filter. The proposed method has good validity for EMI filter design and conducted EMI noise suppression.
Impedance source power electronic converters
Liu, Yushan; Ge, Baoming; Blaabjerg, Frede; Ellabban, Omar; Loh, Poh Chiang
2016-01-01
Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key features: Comprehensive analysis of the impedance source converter/inverter topologies, including typical topologies and derived topologies. Fully explains the design and control techniques of impedance source converters/inverters, including hardware design and control parameter design for corresponding control methods. Presents the latest power conversion solutions that aim to advance the role of pow...
Ionic conductivity measurements of zirconia under pressure using impedance spectroscopy
Takebe, H; Ohtaka, O; Fukui, H; Yoshiasa, A; Yamanaka, T; Ota, K; Kikegawa, T
2002-01-01
We have set up an electrical conductivity measurement system under high-pressure and high-temperature conditions with a multi-anvil high-pressure apparatus using an AC complex impedance method. With this system, we have successfully measured the electrical conductivity of stabilized ZrO sub 2 (Y sub 2 O sub 3 -ZrO sub 2 solid solution) under pressures up to 5 GPa in the temperature range from 300 to 1200 K. The electrical conductivities obtained under pressure are compatible with those of previous results measured at ambient pressure.
Isolation of sequences flanking Ac insertion sites by Ac casting.
Wang, Dafang; Peterson, Thomas
2013-01-01
Localizing Ac insertions is a fundamental task in studying Ac-induced mutation and chromosomal rearrangements involving Ac elements. Researchers may sometimes be faced with the situation in which the sequence flanking one side of an Ac/Ds element is known, but the other flank is unknown. Or, a researcher may have a small sequence surrounding the Ac/Ds insertion site and needs to obtain additional flanking genomic sequences. One way to rapidly clone unknown Ac/Ds flanking sequences is via a PCR-based method termed Ac casting. This approach utilizes the somatic transposition activity of Ac during plant development, and provides an efficient means for short-range genome walking. Here we describe the principle of Ac casting, and show how it can be applied to isolate Ac macrotransposon insertion sites.
Energy Technology Data Exchange (ETDEWEB)
Bentiss, F., E-mail: fbentiss@enscl.f [Laboratoire de Chimie de Coordination et d' Analytique (LCCA), Faculte des Sciences, Universite Chouaib Doukkali, B.P. 20, M-24000 El Jadida (Morocco); Mernari, B. [Laboratoire de Chimie de Coordination et d' Analytique (LCCA), Faculte des Sciences, Universite Chouaib Doukkali, B.P. 20, M-24000 El Jadida (Morocco); Traisnel, M. [Unite Materiaux et Transformations (UMET), Ingenierie des Systemes Polymeres, CNRS UMR 8207, ENSCL, B.P. 90108, F-59652 Villeneuve d' Ascq Cedex (France); Vezin, H. [Laboratoire de Spectrochimie Infrarouge et Raman (LASIR), UMR-CNRS 8516, Universite des Sciences et Technologies de Lille, Batiment C5, F-59655 Villeneuve d' Ascq Cedex (France); Lagrenee, M., E-mail: michel.lagrenee@ensc-lille.f [Unite de Catalyse et de Chimie du Solide (UCCS), UMR-CNRS 8181, ENSCL, B.P. 90108, F-59652 Villeneuve d' Ascq Cedex (France)
2011-01-15
Research highlights: {yields}2,5-Bis(n-pyridyl)-1,3,4-thiadiazoles (n-PTH) act as good inhibitors for the mild steel in acidic media. {yields}The inhibiting protection depends on the position of the nitrogen on the pyridinium substituent according to order 3-PTH > 2-PTH > 4-PTH. {yields}The adsorption of n-PTH is found to follow the Langmuir's adsorption isotherm. {yields}Data obtained from quantum chemical calculations using DFT method were correlated to the experimentally obtained inhibition efficiencies. - Abstract: The inhibition properties of 2,5-bis(n-pyridyl)-1,3,4-thiadiazoles (n-PTH) on corrosion of mild steel in different acidic media (1 M HCl, 0.5 M H{sub 2}SO{sub 4} and 1 M HClO{sub 4}) were analyzed by electrochemical impedance spectroscopy (EIS). The n-PTH derivatives exhibit good inhibition properties in different acidic solutions and the calculated values of {Delta}G{sub ads}{sup 0} revealed that the adsorption mechanism of n-PTH on steel surface is mainly due to chemisorption. While in 1 M HClO{sub 4}, both 2-PTH and 4-PTH isomers stimulate the corrosion process especially at low concentrations. Quantum chemical calculations using the density functional theory (DFT) were performed on n-PTH derivatives to determine the relationship between molecular structure and their inhibition efficiencies. The results of the quantum chemical calculations and experimental inhibition efficiency were subjected to correlation analysis and indicate that the inhibition effects of n-PTH may be explained in terms of electronic properties.
Electrochemical Impedance of Ethanol Oxidation in Alkaline Media
Institute of Scientific and Technical Information of China (English)
DANAEE Iman; JAFARIAN Majid; GOBAL Fereydoon; SHARAFI Mahboobeh; MAHJANI Mohammad-ghasem
2012-01-01
Nickel modified NiOOH electrodes were used for the electrocatalytic oxidation of ethanol in alkaline solutions.The electro-oxidation of ethanol in a 1 mol/L NaOH solution at different concentrations of ethanol was studied by ac impedance spectroscopy.Electrooxidation of ethanol on Ni shows negative resistance on impedance plots.The impedance shows different patterns at different applied anodic potential.The influence of the electrode potential on impedance was studied and a quantitative explanation for the impedance of ethanol oxidation was given by means of a proposed mathematical model.At potentials higher than 0.52 V(vs.Ag/AgCl),a pseudoinductive behavior was observed,but at those higher than 0.57 V,impedance patterns were reversed to the second and third quadrants.The conditions required for the reversing of impedance pattern were delineated with the impedance model.
S. Baker(Department of Physics and Astronomy, University College London, London, United Kingdom); Bedard, R.; Patton, M.; Wilson, O.
1990-01-01
A method is described by which the free-field, open-circuit voltage sensitivity of a reversible underwater acoustic transducer may be obtained from measurements of its input electrical impedance in water and in air. This method, which we have termed the Delta-Z reciprocity calibration method, is being developed for the in-service calibration of sonar transducers installed in domes which can be flooded and purged. The application of the Delta-Z method to the calibration of a single tonpilz-typ...
Michelle O’Rourke; Noel Duffy; Roland De Marco; Ian Potter
2011-01-01
Electrochemical impedance spectroscopy (EIS) has been used to estimate the non-frequency dependent (static) dielectric constants of base polymers such as poly(vinyl chloride) (PVC), cellulose triacetate (CTA) and polystyrene (PS). Polymer inclusion membranes (PIMs) containing different amounts of PVC or CTA, along with the room temperature ionic liquid Aliquat 336 and plasticizers such as trisbutoxyethyl phosphate (TBEP), dioctyl sebecate (DOS) and 2-nitrophenyloctyl ether (NPOE) have been in...
Structural and impedance studies of LiNi0.5Mn1.5O4 synthesized by sol-gel method
Lobo, Laurel Simon; Rubankumar, A.; Kalainathan, S.
2016-05-01
LiNi0.5Mn1.5O4 is synthesized by sol-gel method by using succinic acid as chelating agent. X-ray diffraction pattern confirms the material is spinel cubic structure with Fd3m space group. Impedance spectroscopy analysis of spinel LiNi0.5Mn1.5O4 was performed under a wide frequency and temperature range of 50 Hz to 5 MHz and 303 K to 783 K respectively. The hopping of the electrons, ionic conductivity and activation energy were analyzed from the relaxation frequency of the imaginary impedance (Z"). The activation energy Ea is calculated from the Arrhenius plots and it is found to be 0.3713 eV, which indicates the existence of oxygen vacancy in the material. Nyquist plot indicates the presence of grain effect in the material and suppression in the grain effect is observed with increasing temperature.
Energy Technology Data Exchange (ETDEWEB)
Varilci, A [Faculty of Arts and Sciences, Department of Physics, Abant Izzet Baysal University, 14280 Bolu (Turkey)
2007-04-15
We report the results of an investigation of the influence of magnetic fields on hysteretic ac losses in bulk MgB{sub 2} superconductor by using Hall probe ac susceptibility. The external magnetic field in this study had an ac part with frequency 10 Hz and magnitude in the range 240-1200 A m{sup -1} and no dc part. We have measured the imaginary part of the magnetic susceptibility and analysed data by using Bean's critical state model of cylindrical geometry for four different temperature values 39.55, 39.51, 39.47 and 39.41 K. The result of this analysis indicates that Bean's model is adequate to explain the experimental findings. Calculated hysteretic ac loss versus applied magnetic field curve is given by using the critical state model. We have also measured the magnetization versus applied magnetic field and determined the first critical magnetic field of a MgB{sub 2} sample as 500 A m{sup -1} at 35 K.
Acoustic ground impedance meter
Zuckerwar, A. J. (Inventor)
1984-01-01
A method and apparatus are presented for measuring the acoustic impedance of a surface in which the surface is used to enclose one end of the chamber of a Helmholz resonator. Acoustic waves are generated in the neck of the resonator by a piston driven by a variable speed motor through a cam assembly. The acoustic waves are measured in the chamber and the frequency of the generated acoustic waves is measured by an optical device. These measurements are used to compute the compliance and conductance of the chamber and surface combined. The same procedure is followed with a calibration plate having infinite acoustic impedance enclosing the chamber of the resonator to compute the compliance and conductance of the chamber alone. Then by subtracting, the compliance and conductance for the surface is obtained.
Tsujimoto, Tomiyuki; Nakade, Masahiko; Yagi, Yukihiro; Ishii, Noboru
Water tree is one of the degradation aspects of XLPE cables used for under-ground distribution or transmission lines. We have developed the loss current method using 3rd harmonic in AC loss current for cable diagnosis. Harmonic components in loss current arise as a result of the non-linear voltage-current characteristics of water trees. We confirmed that the 3rd harmonic in AC loss current had good correlation with water tree growth and break down strength. After that, we have applied this method to the actual 66kV XLPE cable lines. Up to now, the number of the application results is more than 120 lines. In this method, it is sometimes said that the degradation signal (3rd harmonic in loss current) is affected by the 3rd harmonic in the test voltage. To indicate and solve this problem, we investigated the extent of influence by 3rd harmonic in the test voltage, and found the rule of the influence. As a result, we developed a new technique of harmonic-noise reduction in loss current method that enabled a more highly accurate diagnosis and confirmed the effectiveness of this new technique by simulations and experiments with actual cables.
Terasaka, K; Yoshimura, S; Kato, Y; Furuta, K; Aramaki, M; Morisaki, T; Tanaka, M Y
2014-11-01
High-impedance Wire Grid (HIWG) detector has been developed to study spatiotemporal behavior of a hot electron clump generated in an electron cyclotron resonance (ECR) plasma. By measuring the floating potentials of the wire electrodes, and generating structure matrix made of geometrical means of the floating potentials, the HIWG detector reconstructs the spatial distribution of high-temperature electron clump at an arbitrary instant of time. Time slices of the spike event in floating potential revealed the growth and decay process of a hot spot occurs in an ECR plasma.
Electrical impedance along connective tissue planes associated with acupuncture meridians
Directory of Open Access Journals (Sweden)
Hammerschlag Richard
2005-05-01
Full Text Available Abstract Background Acupuncture points and meridians are commonly believed to possess unique electrical properties. The experimental support for this claim is limited given the technical and methodological shortcomings of prior studies. Recent studies indicate a correspondence between acupuncture meridians and connective tissue planes. We hypothesized that segments of acupuncture meridians that are associated with loose connective tissue planes (between muscles or between muscle and bone visible by ultrasound have greater electrical conductance (less electrical impedance than non-meridian, parallel control segments. Methods We used a four-electrode method to measure the electrical impedance along segments of the Pericardium and Spleen meridians and corresponding parallel control segments in 23 human subjects. Meridian segments were determined by palpation and proportional measurements. Connective tissue planes underlying those segments were imaged with an ultrasound scanner. Along each meridian segment, four gold-plated needles were inserted along a straight line and used as electrodes. A parallel series of four control needles were placed 0.8 cm medial to the meridian needles. For each set of four needles, a 3.3 kHz alternating (AC constant amplitude current was introduced at three different amplitudes (20, 40, and 80 μAmps to the outer two needles, while the voltage was measured between the inner two needles. Tissue impedance between the two inner needles was calculated based on Ohm's law (ratio of voltage to current intensity. Results At the Pericardium location, mean tissue impedance was significantly lower at meridian segments (70.4 ± 5.7 Ω compared with control segments (75.0 ± 5.9 Ω (p = 0.0003. At the Spleen location, mean impedance for meridian (67.8 ± 6.8 Ω and control segments (68.5 ± 7.5 Ω were not significantly different (p = 0.70. Conclusion Tissue impedance was on average lower along the Pericardium meridian, but not
Energy Technology Data Exchange (ETDEWEB)
Durrett, Timothy; Ohlrogge, John; Pollard, Michael
2016-05-03
The present invention relates to novel diacylglycerol acyltransferase genes and proteins, and methods of their use. In particular, the invention describes genes encoding proteins having diacylglycerol acetyltransferase activity, specifically for transferring an acetyl group to a diacylglycerol substrate to form acetyl-Triacylglycerols (ac-TAGS), for example, a 3-acetyl-1,2-diacyl-sn-glycerol. The present invention encompasses both native and recombinant wild-type forms of the transferase, as well as mutants and variant forms. The present invention also relates to methods of using novel diacylglycerol acyltransferase genes and proteins, including their expression in transgenic organisms at commercially viable levels, for increasing production of 3-acetyl-1,2-diacyl-sn-glycerols in plant oils and altering the composition of oils produced by microorganisms, such as yeast, by increasing ac-TAG production. Additionally, oils produced by methods of the present inventions comprising genes and proteins are contemplated for use as biodiesel fuel, in polymer production and as naturally produced food oils with reduced calories.
Impedance Source Power Electronic Converters
DEFF Research Database (Denmark)
Liu, Yushan; Abu-Rub, Haitham; Ge, Baoming
Impedance Source Power Electronic Converters brings together state of the art knowledge and cutting edge techniques in various stages of research related to the ever more popular impedance source converters/inverters. Significant research efforts are underway to develop commercially viable...... control methods. Presents the latest power conversion solutions that aim to advance the role of power electronics into industries and sustainable energy conversion systems. Compares impedance source converter/inverter applications in renewable energy power generation and electric vehicles as well...... and technically feasible, efficient and reliable power converters for renewable energy, electric transportation and for various industrial applications. This book provides a detailed understanding of the concepts, designs, controls, and application demonstrations of the impedance source converters/inverters. Key...
HDR reservoir flow impedance and potentials for impedance reduction
Energy Technology Data Exchange (ETDEWEB)
DuTeau, R.; Brown, D.
1993-06-01
The data from flow tests which employed two different production zones in a well at Fenton Hill indicates the flow impedance of a wellbore zone damaged by rapid depressurization was altered, possibly by pressure spallation, which appears to have mechanically propped the joint apertures of outlet flow paths intersecting the altered wellbore. The rapid depressurization and subsequent flow test data derived from the damaged well has led to the hypothesis that pressure spallation and the resultant mechanical propping of outlet flow paths reduced the outlet flow impedance of the damaged wellbore. Furthermore, transient pressure data shows the largest pressure drop between the injection and production wellheads occurs near the production wellbore, so lowering the outlet impedance by increasing the apertures of outlet flow paths will have the greatest effect on reducing the overall reservoir impedance. Fenton Hill data also reveals that increasing the overall reservoir pressure dilates the apertures of flow paths, which likewise serves to reduce the reservoir impedance. Data suggests that either pressure dilating the wellbore connected joints with high production wellhead pressure, or mechanically propping open the outlet flow paths will increase the near-wellbore permeability. Finally, a new method for calculating and comparing near-wellbore outlet impedances has been developed. Further modeling, experimentation, and engineered reservoir modifications, such as pressure dilation and mechanical propping, hold considerable potential for significantly improving the productivity of HDR reservoirs.
Plasmonic-Based Electrochemical Impedance Spectroscopy: Application to Molecular Binding
Lu, Jin; Wang, Wei; Wang, Shaopeng; Shan, Xiaonan; Li, Jinghong; Tao, Nongjian
2012-01-01
Plasmonic-based electrochemical impedance spectroscopy (P-EIS) is developed to investigate molecular binding on surfaces. Its basic principle relies on the sensitive dependence of surface plasmon resonance (SPR) signal on surface charge density, which is modulated by applying an AC potential to a SPR chip surface. The AC component of the SPR response gives the electrochemical impedance, and the DC component provides the conventional SPR detection. The plasmonic-based impedance measured over a range of frequency is in quantitative agreement with the conventional electrochemical impedance. Compared to the conventional SPR detection, P-EIS is sensitive to molecular binding taking place on the chip surface, and less sensitive to bulk refractive index changes or non-specific binding. Moreover, this new approach allows for simultaneous SPR and surface impedance analysis of molecular binding processes. PMID:22122514
Energy Technology Data Exchange (ETDEWEB)
Jlassi, I., E-mail: ifa.jlassi@fst.rnu.tn [Laboratoire Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Département de Physique, Faculté des Sciences de Tunis, Université de Tunis ElManar, Campus Universitaire Farhat Hachad, ElManar 2092 (Tunisia); Sdiri, N. [Laboratoire Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Elhouichet, H. [Laboratoire Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Département de Physique, Faculté des Sciences de Tunis, Université de Tunis ElManar, Campus Universitaire Farhat Hachad, ElManar 2092 (Tunisia); Ferid, M. [Laboratoire Physico-chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95, Hammam-Lif 2050 (Tunisia)
2015-10-05
Highlights: • We have prepared a new lithium diphosphate glasses doped MgO. • Investigate structural and electrical properties at room temperature. • Investigate relation between structure and electrical conductivity of the glass. - Abstract: Lithium diphosphate glasses doped MgO was prepared via a melt quenching technique. The samples were characterized by X-ray diffraction (XRD), Raman and impedance spectroscopy. XRD spectra reflected the amorphous nature of the glasses Raman spectra show structural network modifications with the composition variations of the studied glasses. Raman spectra of the studied glasses contain also typical phosphate glasses bands. Thus the band at ∼698 cm{sup −1} assigned to symmetric stretching vibrations of P−O−P groups and that from ∼1168 cm{sup −1} is attributed to symmetric stretching motions of the non-bridging oxygen (NBO) atoms bonded to phosphorous atoms (PO{sub 2}) in phosphate tetrahedron. Electric properties were investigated using complex impedance spectroscopy in a frequency range from 40 Hz to 6 MHz at room temperature. The impedance spectra were analyzed in terms of equivalent circuits involving resistors, capacitors and constant phase elements (CPE). Constant-phase elements (CPE) are used in equivalent electrical circuits for the fitting of experimental impedance data. The AC conductivity exhibited a Jonscher’s universal power law according with the relation σ(ω) = σ(0) + Aω{sup s} and it is observed that as the MgO content increases, frequency exponent (s) decreases.
Wheat straw moisture meter based on alterative current impedance method%基于交流阻抗法的小麦秸秆含水率检测仪设计
Institute of Scientific and Technical Information of China (English)
郭文川; 杨军; 刘驰; 朱新华
2013-01-01
Wheat straw is a main kind of straws in China. Since it contains a large amount of fiber, wheat straw is used to make paper and produce particleboards in different densities. Moreover, high energy content in wheat straw provides an opportunity to convert straw’s heat energy to electric power. Since the unit price of wheat straw is based on weight and straw decays when kept in a high moisture state, moisture content is listed as a main criterion in wheat straw consuming market. It is also an important factor in straw’s application. Therefore, moisture content detection is very important during wheat straw marketing, storing and processing. Since the traditional oven drying method has the major disadvantages for long time measurement and unsuitable for on-site detection in collection fields, developing the new kinds of wheat straw moisture meters with advantages of convenience, rapid measurement and high precision is needed in wheat straw industry. In this study, based on alterative current (AC) impedance method, a straw moisture meter, which can detect impedance, temperature and pressure, was designed with an 8-bit single-chip microcomputer as controller. Experiment was conducted at five moisture content levels from 10.4%to 19.7%at wet basis, temperature range from 5 to 40ºC at 5ºC interval, and three bulk density levels (75.3~101.3 kg/m3) at each moisture content to study the effect of moisture content, temperature and bulk density on impedance. A cubic equation on impedance as functions of moisture content, temperature and bulk density was established. The significance effect of each variable on the regressed equation was analyzed. The results indicate that bulk density has no significant effect on the equation at the significance level of 0.05. Therefore, a cubic equation of impedance with two variables of moisture content and temperature was regressed. The test results showed that the regressed cubic model with two variables can describe the relationship
Veena, M.; Somashekarappa, A.; Shankaramurthy, G. J.; Jayanna, H. S.; Somashekarappa, H. M.
2016-12-01
Nanocrystalline Ni1-xZnxFe2-yDyyO4 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0; y=0.0 and 0.1) ferrites were synthesized by combustion method. Ni-Zn-Dy nanoferrites were investigated by X-ray diffraction, scanning electron microscopy, dielectric and impedance properties, before and after γ-irradiation process by 60Co γ-radiation with a dose rate of 310 kGy. The lattice parameter of irradiated samples increased attributed to the conversion of smaller size Fe3+ ions to larger size Fe2+ ions on ionizing effect of gamma radiation. Experimental results reveal that reduction in dielectric constant (ε‧), loss tangent (tan δ), real (Z‧) and imaginary (Z‧‧) impedance and increase in ac conductivity (σac) have been increased with increasing in frequency. It was found that ε‧, tan δ, σac increase, Z‧‧ and Z‧‧ reach a maximum value and thereafter decrease with further Zn ion substitution. The values of ε‧, tan δ and σac decrease with Dy3+ substitution and enhanced after irradiation. The complex impedance analysis suggesting predominant contribution to conduction was through the grain boundary.
Yan Hong; Yong Wang; Wang Ling Goh; Yuan Gao; Lei Yao
2015-08-01
This paper presents a mathematic method and a cost-efficient circuit to measure the value of each component of the bio-impedance model at electrode-electrolyte interface. The proposed current excited triple-time-voltage oversampling (TTVO) method deduces the component values by solving triple simultaneous electric equation (TSEE) at different time nodes during a current excitation, which are the voltage functions of time. The proposed triple simultaneous electric equations (TSEEs) allows random selections of the time nodes, hence numerous solutions can be obtained during a single current excitation. Following that, the oversampling approach is engaged by averaging all solutions of multiple TSEEs acquired after a single current excitation, which increases the practical measurement accuracy through the improvement of the signal-to-noise ratio (SNR). In addition, a print circuit board (PCB) that consists a switched current exciter and an analog-to-digital converter (ADC) is designed for signal acquisition. This presents a great cost reduction when compared against other instrument-based measurement data reported [1]. Through testing, the measured values of this work is proven to be in superb agreements on the true component values of the electrode-electrolyte interface model. This work is most suited and also useful for biological and biomedical applications, to perform tasks such as stimulations, recordings, impedance characterizations, etc.
Energy Technology Data Exchange (ETDEWEB)
Outirite, Moha; Lagrenee, Michel; Lebrini, Mounim [Unite de Catalyse et de Chimie du Solide, UMR-CNRS 8181, ENSCL, B.P. 90108, F-59652 Villeneuve d' Ascq Cedex (France); Traisnel, Michel; Jama, Charafeddine [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, PERF UMR-CNRS 8008, ENSCL, B.P. 90108, F-59652 Villeneuve d' Ascq Cedex (France); Vezin, Herve [Laboratoire de Chimie Organique et Macromoleculaire, UMR-CNRS 8009, USTL Bat C4, F-59655 Villeneuve d' Ascq Cedex (France); Bentiss, Fouad, E-mail: fbentiss@enscl.f [Laboratoire de Chimie de Coordination et d' Analytique, Faculte des Sciences, Universite Chouaib Doukkali, B.P. 20, M-24000 El Jadida (Morocco)
2010-02-01
The corrosion inhibition properties of a new class of oxadiazole derivatives, namely 3,5-bis(n-pyridyl)-1,2,4-oxadiazoles (n-DPOX) for C38 carbon steel corrosion in 1 M HCl medium were analysed by electrochemical impedance spectroscopy (EIS). An adequate structural model of the interface was used and the values of the corresponding parameters were calculated and discussed. The experimental results showed that these compounds are excellent inhibitors for the C38 steel corrosion in acid solution and that the protection efficiency increased with increasing the inhibitors concentration. Electrochemical impedance data demonstrate that the addition of the n-DPOX derivatives in the corrosive solution decreases the charge capacitance and simultaneously increases the function of the charge/discharge of the interface, facilitating the formation of an adsorbed layer over the steel surface. Adsorption of these inhibitors on the steel surface obeys to the Langmuir adsorption isotherm. X-ray photoelectron spectroscopy (XPS) and the thermodynamic data of adsorption showed that inhibition of steel corrosion in normal hydrochloric solution by n-DPOX is due to the formation of a chemisorbed film on the steel surface. Quantum chemical calculations using the Density Functional Theory (DFT) and the Quantitative Structure Activity Relationship (QSAR) approach were performed on n-DPOX derivatives to determine the relationship between molecular structure and their inhibition efficiencies. The results of the quantum chemical calculations and experimental inhibition efficiency were subjected to correlation analysis and indicate that their inhibition effect is closely related to E{sub HOMO}, E{sub LUMO}, and dipole moment (mu).
Dielectric and impedance spectroscopic studies of neodymium gallate
Energy Technology Data Exchange (ETDEWEB)
Sakhya, Anup Pradhan, E-mail: npshakya31@gmail.com [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India); Dutta, Alo [Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Sinha, T.P. [Department of Physics, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009 (India)
2016-05-01
The AC electrical properties of a polycrystalline neodymium gallate, NdGaO{sub 3} (NGO), synthesized by the sol–gel method have been investigated by employing impedance spectroscopy in the frequency range from 42 Hz to 5 MHz and in the temperature range from 323 K to 593 K. The X-ray diffraction analysis shows that the compound crystallizes in the orthorhombic phase with Pbnm space group at room temperature. Two relaxation processes with different relaxation times are observed from the impedance as well as modulus spectroscopic measurements, which have been attributed to the grain and the grain boundary effects at different temperatures in NGO. The complex impedance data are analyzed by an electrical equivalent circuit consisting of a resistance and a constant phase element in parallel. It has been observed that the value of the capacitance and the resistance associated with the grain boundary is higher than those associated with the grain. The temperature dependent electrical conductivity shows the negative temperature coefficient of resistance. The frequency dependent conductivity spectra are found to follow the power law.
Dielectric and impedance spectroscopic studies of neodymium gallate
Sakhya, Anup Pradhan; Dutta, Alo; Sinha, T. P.
2016-05-01
The AC electrical properties of a polycrystalline neodymium gallate, NdGaO3 (NGO), synthesized by the sol-gel method have been investigated by employing impedance spectroscopy in the frequency range from 42 Hz to 5 MHz and in the temperature range from 323 K to 593 K. The X-ray diffraction analysis shows that the compound crystallizes in the orthorhombic phase with Pbnm space group at room temperature. Two relaxation processes with different relaxation times are observed from the impedance as well as modulus spectroscopic measurements, which have been attributed to the grain and the grain boundary effects at different temperatures in NGO. The complex impedance data are analyzed by an electrical equivalent circuit consisting of a resistance and a constant phase element in parallel. It has been observed that the value of the capacitance and the resistance associated with the grain boundary is higher than those associated with the grain. The temperature dependent electrical conductivity shows the negative temperature coefficient of resistance. The frequency dependent conductivity spectra are found to follow the power law.
Institute of Scientific and Technical Information of China (English)
赵凯岐; 张殿华; 兰海; 岳文杰; 张强
2011-01-01
In design process of high-capacity AC-DC converter in ship electric propulsion system, the RC snubber circuit should be connected to the thyristor in parallel in order to absorb the energy generated at the moment of thyristor switching and suppress overvoltage impulses and high voltage change rate du/dt.However, parameter selection, which is generally depended on empirical formula, sometimes leads to a rather great error. Once the selection of protection parameters is unreasonable, a high spike voltage is likely to occur and render power electronic components will be easily damaged, which threatens the operation safety of equipments. In this paper, a new optimal design method of RC snubber circuit is proposed for thyristor in high-capacity AC-DC converter, R and C parameters and resistor power is deduced more accurately, and the reliability of the AC-DC converter is improved as a result. Numerical simulations and physical experiments are conducted to verify the feasibility and viability of the method.%船舶电力推进系统大功率AC-DC变换器设计时,必须在晶闸管的两端并联阻容缓冲器,以吸收器件关断过程反向恢复电流的能量,抑制高的过电压冲击及高的电压应力du/dt.但是,阻容参数的设计大多依靠经验公式,参数选取有时产生很大偏差,一旦选取不合理,便会产生很高的尖峰过电压,造成电力电子器件的损坏,影响系统安全运行.针对大功率AC-DC变换器晶闸管阻容缓冲器进行研究,提出了阻容缓冲器优化设计方法,推导出较精确的阻容参数值和电阻的功率,提高大功率AC-DC变换器的可靠性,仿真及实验验证了本方法的可行性.
Energy Technology Data Exchange (ETDEWEB)
Chang, Ho, E-mail: f10381@ntut.edu.tw [Graduate Institute of Manufacturing Technology, National Taipei University of Technology, Taipei 10608, Taiwan (China); Chen, Chih-Hao [Department of Thoracic Surgery, Mackay Memorial Hospital, Taipei 10419, Taiwan (China); Graduate Institute of Mechanical and Electrical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan (China); Kao, Mu-Jung [Department of Vehicle Engineering, National Taipei University of Technology, Taipei 10608, Taiwan (China); Chien, Shu-Hua [Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan (China); Chou, Cheng-Yi [Graduate Institute of Manufacturing Technology, National Taipei University of Technology, Taipei 10608, Taiwan (China)
2013-06-15
The paper studies the photoelectrode thin film of dye-sensitized solar cell (DSSC) fabricated by anodizing method, explores the structure and properties of the fabricated photoelectrode thin film, measures the photoelectric conversion efficiency of DSSC, and finds the electrochemical impedance properties of DSSCs assembled by photoelectrode thin films in different thicknesses. Besides, in order to increase the specific surface area of nanotubes, this paper deposits TiO{sub 2} nanoparticles (TNP) on the surface of titanium oxide nanotube (TNT). As shown in experimental results, the photoelectric conversion efficiency of the DSSC fabricated by the study rises to 6.5% from the original 5.43% without TnB treatment, with an increase of photoelectric conversion efficiency by 19.7%. In addition, when the photoelectrode thin film is fabricated with mixture of TNTs and TNP in an optimal proportion of 2:8 and the photoelectrode thin film thickness is 15.5 μm, the photoelectric conversion efficiency can reach 7.4%, with an increase of 36.7% from the original photoelectric conversion efficiency at 5.43%. Besides, as found in the results of electrochemical impedance analysis, the DSSC with photoelectrode thin film thickness at 15.5 μm has the lowest charge-conduction resistance (R{sub k}) value 9.276 Ω of recombined electron and conduction resistance (R{sub w}) value 3.25 Ω of electrons in TiO{sub 2}.
Institute of Scientific and Technical Information of China (English)
Guang Han LU; Chuan Yin LIU; Hong Yan ZHAO; Wei LIU; Li Ping JIANG; Ling Yan JIANG
2004-01-01
Interfacial proton transfer reactions of pure mercaptoacetic acid (MA) and 2-mercaptobenzothiazole (Mbz) mixed self-assembled monolayers (SAMs) have been studied using a.c. impedance titration method. The charge-transfer resistance (Rct) is measured with the monolayer composition and the ionic strength of pH solution. The surface pKa can be obtained by the plots of Rct and pH, the reasons of shifts of surface pKa are also explained.
Mushtaq, Abid; Frei, Stephan
2016-09-01
In the power drive system of the Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs), High Voltage (HV) cables play a major role in evaluating the EMI of the whole system. Transfer impedance (ZT) is the most commonly used performance parameter for the HV cable. To analyse and design HV cables and connectors with better shielding effectiveness (SE), appropriate measurement and simulation methods are required. In this paper, Ground Plate Method (GPM) with improvements has been proposed to measure ZT. Use of low-frequency ferrites to avoid ground-loop effects has also been investigated. Additionally, a combination of analytical model with a circuit model has been implemented to simulate limitations (frequency response) of the test setup. Also parametrical studies using the analytical model have been performed to analyse the shielding behaviour of HV cables.
de Oliveira, Helinando P; de Melo, Celso P
2011-06-01
Molecular aggregation plays a key role in the physicochemical properties of dyes and surfactants. In this work, we show that electrical impedance spectroscopy (EIS) provides a practical method for the investigation of processes such as micellization in surfactants and dye dimerization. The electrical characterization of the structural phase transitions associated with aggregation events in these systems allows an accurate and direct determination of relevant parameters such as the corresponding critical concentrations for micelle formation and dimerization of these types of molecules, without the need of recurring to the use of auxiliary probe or reporter molecules. Because of its competitive advantages with respect to currently used methods (such as conductimetry and spectroscopic techniques), we argue that when implemented along the procedures described in this work, EIS becomes a simple and convenient technique for the characterization of aggregation processes in soft matter.
Gilad, Ori; Ghosh, Anthony; Oh, Dongin; Holder, David S
2009-05-30
Electrical impedance tomography (EIT) is a recently developed medical imaging method which has the potential to produce images of fast neuronal depolarization in the brain. The principle is that current remains in the extracellular space at rest but passes into the intracellular space during depolarization through open ion channels. As current passes into the intracellular space across the capacitance of cell membranes at higher frequencies, applied current needs to be below 100 Hz. A method is presented for its measurement with subtraction of the contemporaneous evoked potentials which occur in the same frequency band. Neuronal activity is evoked by stimulation and resistance is recorded from the potentials resulting from injection of a constant current square wave at 1 Hz with amplitude less than 25% of the threshold for stimulating neuronal activity. Potentials due to the evoked activity and the injected square wave are removed by subtraction. The method was validated with compound action potentials in crab walking leg nerve. Resistance changes of -0.85+/-0.4% (mean+/-SD) occurred which decreased from -0.97+/-0.43% to -0.46+/-0.16% with spacing of impedance current application electrodes from 2 to 8 mm but did not vary significantly with applied currents of 1-10 microA. These tallied with biophysical modelling, and so were consistent with a genuine physiological origin. This method appears to provide a reproducible and artefact free means for recording resistance changes during neuronal activity which could lead to the long-term goal of imaging of fast neural activity in the brain.
Institute of Scientific and Technical Information of China (English)
张爱萍; 唐佳妮; 刘东红
2011-01-01
As a rapid detection method of microorganisms,the impedance method can be used to rapidly detect the total number of colonies, coliform, mold, yeast, and so on.There is great prospect for the rapid detection of pathogens in food as the research of the impedance method developed.The development of the traditional impedance method and the latest research of the impedance method were reviewed ,aimed at the future research of the impedance method for rapid detection of microorganisms in food.%阻抗法作为微生物快速检测方法,可用于食品中菌落总数、大肠菌群、霉菌、酵母等常规微生物的快速检测;随着研究的深入,其在食品病原菌快速检测中也大有前景.综述了传统阻抗微生物检测的发展历程及阻抗法最新研究方向,旨在为今后阻抗法快速检测食品中微生物的研究奠定基础.
Method Development and Monitoring of Cyanotoxins in Water (ACS Central Presentation)
Increasing occurrence of cyanobacterial harmful algal blooms (HABs) in ambient waters has become a worldwide concern. Numerous cyanotoxins can be produced during HAB events which are toxic to animals and humans. Validated standardized methods that are rugged, selective and sensit...
Energy Technology Data Exchange (ETDEWEB)
Bentiss, F. [Laboratoire de Chimie de Coordination et d' Analytique, Faculte des Sciences, Universite Chouaib Doukkali, B.P. 20, M-24000 El Jadida (Morocco)], E-mail: fbentiss@enscl.fr; Lebrini, M. [Unite de Catalyse et de Chimie du Solide, UMR-CNRS 8181, ENSCL, BP. 90108, F-59652 Villeneuve d' Ascq Cedex (France); Vezin, H. [Laboratoire de Chimie Organique et Macromoleculaire, UMR-CNRS 8009, USTL Bat C4, F-59655 Villeneuve d' Ascq Cedex (France); Chai, F. [Groupe de Recherche sur les biomateriaux, Laboratoire de Biophysique, UPRES EA 1049, Faculte de Medecine, F-59045 Lille Cedex (France); Traisnel, M.; Lagrene, M. [Laboratoire des Procedes d' Elaboration des Revetements Fonctionnels, PERF UMR-CNRS 8008, ENSCL, B.P. 90108, F-59652 Villeneuve d' Ascq Cedex (France)
2009-09-15
We report here the use of macrocyclic polyether compounds containing a 1,3,4-thiadiazole moiety (n-MCTH) in the corrosion inhibition of C38 carbon steel in 0.5 M H{sub 2}SO{sub 4} acid medium. The aim of this work is devoted to study the inhibition characteristics of these compounds for acid corrosion of C38 steel using electrochemical impedance spectroscopy (EIS). Data obtained from EIS show a frequency distribution and therefore a modeling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. The experimental results obtained revealed that these compounds inhibited the steel corrosion in acid solution and the protection efficiency increased with increasing inhibitors concentration. The difference in their inhibitive action can be explained on the basis of the number of oxygen atoms present in the polyether ring which contribute to the chemisorption strength through the donor acceptor bond between the non bonding electron pair and the vacant orbital of metal surface. Adsorption of n-MCTH was found to follow the Langmuir's adsorption isotherm. The thermodynamic functions of adsorption process were calculated and the interpretation of the results is given. These results are complemented with quantum chemical study in order to provide an explanation of the differences between the probed inhibitors. Correlation between the inhibition efficiency and the structure of these compounds are presented.
Tliha, M.; Khaldi, C.; Lamloumi, J.
2016-04-01
The decrease of Cobalt content in alloy is very beneficial to reduce the production cost of the alloy, whereas the effect of Co on cycle life of the AB5-type hydrogen-storage alloys is extremely important. Therefore, it is interesting to investigate low-Co and/or Co-free AB5-type alloys in which Co was substituted by other elements. Iron is a key element in the development of low-Co AB5-type alloys. The aim of this work is to systematically investigate the effect of the real surface area on the all kinetic properties of a low-Co LaNi3.55Mn0.4Al0.3Co0.6Fe0.15 alloy under cycling using electrochemical impedance spectroscopy (EIS) technique. All kinetic properties of the electrode, such as exchange density, limiting current density, high-rate charge/discharge ability, cycle life time, electrocatalytic activity, and diffusion rate are related to the real surface area. During the EIS analysis, interestingly, we found that with increasing number of charge/discharge cycles, the metal hydride alloy powders undergo micro-cracking into smaller particles, and thus the real surface area of the alloy increases, which then influences the kinetic properties of the electrode reactions.
Abascal, Juan-Felipe P J; Arridge, Simon R; Atkinson, David; Horesh, Raya; Fabrizi, Lorenzo; De Lucia, Marzia; Horesh, Lior; Bayford, Richard H; Holder, David S
2008-11-01
Electrical Impedance Tomography (EIT) is an imaging method which enables a volume conductivity map of a subject to be produced from multiple impedance measurements. It has the potential to become a portable non-invasive imaging technique of particular use in imaging brain function. Accurate numerical forward models may be used to improve image reconstruction but, until now, have employed an assumption of isotropic tissue conductivity. This may be expected to introduce inaccuracy, as body tissues, especially those such as white matter and the skull in head imaging, are highly anisotropic. The purpose of this study was, for the first time, to develop a method for incorporating anisotropy in a forward numerical model for EIT of the head and assess the resulting improvement in image quality in the case of linear reconstruction of one example of the human head. A realistic Finite Element Model (FEM) of an adult human head with segments for the scalp, skull, CSF, and brain was produced from a structural MRI. Anisotropy of the brain was estimated from a diffusion tensor-MRI of the same subject and anisotropy of the skull was approximated from the structural information. A method for incorporation of anisotropy in the forward model and its use in image reconstruction was produced. The improvement in reconstructed image quality was assessed in computer simulation by producing forward data, and then linear reconstruction using a sensitivity matrix approach. The mean boundary data difference between anisotropic and isotropic forward models for a reference conductivity was 50%. Use of the correct anisotropic FEM in image reconstruction, as opposed to an isotropic one, corrected an error of 24 mm in imaging a 10% conductivity decrease located in the hippocampus, improved localisation for conductivity changes deep in the brain and due to epilepsy by 4-17 mm, and, overall, led to a substantial improvement on image quality. This suggests that incorporation of anisotropy in
Impedance-Source Networks for Electric Power Conversion Part I
DEFF Research Database (Denmark)
Siwakoti, Yam P.; Peng, Fang Zheng; Blaabjerg, Frede;
2015-01-01
Impedance networks cover the entire of electric power conversion from dc (converter, rectifier), ac (inverter), to phase and frequency conversion (ac-ac) in a wide range of applications. Various converter topologies have been reported in the literature to overcome the limitations and problems...... of the traditional voltage source, current source as well as various classical buck-boost, unidirectional, and bidirectional converter topologies. Proper implementation of the impedance-source network with appropriate switching configurations and topologies reduces the number of power conversion stages in the system...... power chain, which may improve the reliability and performance of the power system. The first part of this paper provides a comprehensive review of the various impedance-source-networks-based power converters and discusses the main topologies from an application point of view. This review paper...
Definition of the characteristic impedance
Institute of Scientific and Technical Information of China (English)
徐云生; Abbas Sayed OMAR
1996-01-01
Currently available definitions of the characteristic impedance are ambiguous andior inaccurate.A general definition,based on the description of discontinuities between adjacent waveguides,is given.This definition is accurate and independent of the structure concerned.So it can be applied to the design of passive components in any type of transmission lines.Using this definition,a given structure can be uniquely characterized,but the absolute value of the characteristic impedance has no sense any more.As an example,the design of a microstrip impedance transformer using this new definition is presented.Numerical results using the mode-matching method prove the accuracy of the theory.
Chen, Z.; Hering, P.; Brown, S. B.; Curry, C.; Tsui, Y. Y.; Glenzer, S. H.
2016-11-01
To study the rapid evolution of AC conductivity from ultrafast laser excited warm dense matter (WDM), a spatial chirp single-shot method is developed utilizing a crossing angle pump-probe configuration. The pump beam is shaped individually in two spatial dimensions so that it can provide both sufficient laser intensity to excite the material to warm dense matter state and a uniform time window of up to 1 ps with sub-100 fs FWHM temporal resolution. Temporal evolution of AC conductivity in laser excited warm dense gold was also measured.
Impedance model for nanostructures
Directory of Open Access Journals (Sweden)
R. S. Akhmedov
2007-06-01
Full Text Available The application of the impedance model for nanoelectronic quantum-mechanical structures modelling is described. Characteristics illustrating the efficiency of the model are presented.
Experimental Verification of Acoustic Impedance Inversion
Institute of Scientific and Technical Information of China (English)
郭永刚; 王宁; 林俊轩
2003-01-01
Well controlled model experiments were carried out to verify acoustic impedance inversion scheme, and different methods of extracting impulse responses were investigated by practical data. The acoustic impedance profiles reconstructed from impulse responses are in good agreement with the measured value and theoretical value.
Optimization of the AC-gradient method for velocity profile measurement and application to slow flow
Kartäusch, Ralf; Helluy, Xavier; Jakob, Peter Michael; Fidler, Florian
2014-11-01
This work presents a spectroscopic method to measure slow flow. Within a single shot the velocity distribution is acquired. This allows distinguishing rapidly between single velocities within the sampled volume with a high sensitivity. The technique is based on signal acquisition in the presence of a periodic gradient and a train of refocussing RF pulses. The theoretical model for trapezoidal bipolar pulse shaped gradients under consideration of diffusion and the outflow effect is introduced. A phase correction technique is presented that improves the spectral accuracy. Therefore, flow phantom measurements are used to validate the new sequence and the simulation based on the theoretical model. It was demonstrated that accurate parabolic flow profiles can be acquired and flow variations below 200 μm/s can be detected. Three post-processing methods that eliminate static background signal are also presented for applications in which static background signal dominates. Finally, this technique is applied to flow measurement of a small alder tree demonstrating a typical application of in vivo plant measurements.
Impedance plethysmography of thoracic region: impedance cardiography.
Directory of Open Access Journals (Sweden)
Deshpande A
1990-10-01
Full Text Available Impedance plethysmograms were recorded from thoracic region in 254 normal subjects, 183 patients with coronary artery disease, 391 patients with valvular heart disease and 107 patients with congenital septal disorder. The data in 18 normal subjects and 55 patients showed that basal impedance decreases markedly during exercise in patients with ischaemic heart disease. Estimation of cardiac index by this technique in a group of 99 normal subjects has been observed to be more consistent than that of the stroke volume. Estimation of systolic time index from impedance plethysmograms in 34 normal subjects has been shown to be as reliable as that from electrocardiogram, phonocardiogram and carotid pulse tracing. Changes in the shape of plethysmographic waveform produced by valvular and congenital heart diseases are briefly described and the role of this technique in screening cardiac patients has been highlighted.
Zhao, Sipei; Qiu, Xiaojun; Cheng, Jianchun
2015-09-01
This paper proposes a different method for calculating a sound field diffracted by a rigid barrier based on the integral equation method, where a virtual boundary is assumed above the rigid barrier to divide the whole space into two subspaces. Based on the Kirchhoff-Helmholtz equation, the sound field in each subspace is determined with the source inside and the boundary conditions on the surface, and then the diffracted sound field is obtained by using the continuation conditions on the virtual boundary. Simulations are carried out to verify the feasibility of the proposed method. Compared to the MacDonald method and other existing methods, the proposed method is a rigorous solution for whole space and is also much easier to understand.
Tracking of electrochemical impedance of batteries
Piret, H.; Granjon, P.; Guillet, N.; Cattin, V.
2016-04-01
This paper presents an evolutionary battery impedance estimation method, which can be easily embedded in vehicles or nomad devices. The proposed method not only allows an accurate frequency impedance estimation, but also a tracking of its temporal evolution contrary to classical electrochemical impedance spectroscopy methods. Taking into account constraints of cost and complexity, we propose to use the existing electronics of current control to perform a frequency evolutionary estimation of the electrochemical impedance. The developed method uses a simple wideband input signal, and relies on a recursive local average of Fourier transforms. The averaging is controlled by a single parameter, managing a trade-off between tracking and estimation performance. This normalized parameter allows to correctly adapt the behavior of the proposed estimator to the variations of the impedance. The advantage of the proposed method is twofold: the method is easy to embed into a simple electronic circuit, and the battery impedance estimator is evolutionary. The ability of the method to monitor the impedance over time is demonstrated on a simulator, and on a real Lithium ion battery, on which a repeatability study is carried out. The experiments reveal good tracking results, and estimation performance as accurate as the usual laboratory approaches.
Glowacki, B A; Majoros, M
2009-06-24
Magnetic materials can help to improve the performance of practical superconductors on the macroscale/microscale as magnetic diverters and also on the nanoscale as effective pinning centres. It has been established by numerical modelling that magnetic shielding of the filaments reduces AC losses in self-field conditions due to decoupling of the filaments and, at the same time, it increases the critical current of the composite. This effect is especially beneficial for coated conductors, in which the anisotropic properties of the superconductor are amplified by the conductor architecture. However, ferromagnetic coatings are often chemically incompatible with YBa(2)Cu(3)O(7) and (Pb,Bi)(2)Sr(2)Ca(2)Cu(3)O(9) conductors, and buffer layers have to be used. In contrast, in MgB(2) conductors an iron matrix may remain in direct contact with the superconducting core. The application of superconducting-magnetic heterostructures requires consideration of the thermal and electromagnetic stability of the superconducting materials used. On one hand, magnetic materials reduce the critical current gradient across the individual filaments but, on the other hand, they often reduce the thermal conductivity between the superconducting core and the cryogen, which may cause destruction of the conductor in the event of thermal instability. A possible nanoscale method of improving the critical current density of superconducting conductors is the introduction of sub-micron magnetic pinning centres. However, the volumetric density and chemical compatibility of magnetic inclusions has to be controlled to avoid suppression of the superconducting properties.
Fractional Order Element Based Impedance Matching
Radwan, Ahmed Gomaa
2014-06-24
Disclosed are various embodiments of methods and systems related to fractional order element based impedance matching. In one embodiment, a method includes aligning a traditional Smith chart (|.alpha.|=1) with a fractional order Smith chart (|.alpha.|.noteq.1). A load impedance is located on the traditional Smith chart and projected onto the fractional order Smith chart. A fractional order matching element is determined by transitioning along a matching circle of the fractional order Smith chart based at least in part upon characteristic line impedance. In another embodiment, a system includes a fractional order impedance matching application executed in a computing device. The fractional order impedance matching application includes logic that obtains a first set of Smith chart coordinates at a first order, determines a second set of Smith chart coordinates at a second order, and determines a fractional order matching element from the second set of Smith chart coordinates.
Estimating the short-circuit impedance
DEFF Research Database (Denmark)
Nielsen, Arne Hejde; Pedersen, Knud Ole Helgesen; Poulsen, Niels Kjølstad
1997-01-01
A method for establishing a complex value of the short-circuit impedance from naturally occurring variations in voltage and current is discussed. It is the symmetrical three phase impedance at the fundamental grid frequency there is looked for. The positive sequence components in voltage and curr......A method for establishing a complex value of the short-circuit impedance from naturally occurring variations in voltage and current is discussed. It is the symmetrical three phase impedance at the fundamental grid frequency there is looked for. The positive sequence components in voltage...... and current are derived each period, and the short-circuit impedance is estimated from variations in these components created by load changes in the grid. Due to the noisy and dynamic grid with high harmonic distortion it is necessary to threat the calculated values statistical. This is done recursively...
An impedance grasping strategy
Muñoz Arias, Mauricio; Scherpen, Jacqueline M.A.; Macchelli, Alessandro
2014-01-01
This work is devoted to an impedance grasping strategy for a class of standard mechanical systems in the port- Hamiltonian framework. The presented control strategy re- quires a set of coordinate transformations, since the impedance control in the port-Hamiltonian framework with structure preservati
Directory of Open Access Journals (Sweden)
Wongi S Na
2016-12-01
Full Text Available Unmanned aerial vehicles (UAVs, commonly known as drones, are a rising topic in remote sensing technologies for structural health monitoring. With technology advancement in cameras, the visual inspection method using drones is gaining much attention in the field of civil engineering. However, although visual inspection methods are feasible for finding cracks in structures, the limitations of image processing for finding internal damage or small defects cannot be ignored. To overcome this problem, a possible application concept of UAV, combined with a vibration-based non-destructive health monitoring method, is proposed. The idea is for the drone to temporarily attach the piezoelectric transducer onto a specific region where excitation and data acquisition occurs simultaneously. This eliminates the need for a structure to be covered with hundreds of sensors for monitoring, as this concept uses a single piezoelectric transducer for monitoring a structure. The proposed work offers new areas of research by converging UAV with a vibration-based method, as associated problems are required to be solved.
Thermal conductivity of Gd{sub 2}Zr{sub 2}O{sub 7} thin films using thermal-impedance method
Energy Technology Data Exchange (ETDEWEB)
Kim, J.W. [Department of Mechanical Engineering, Pusan National University, Busan 609-735 (Korea, Republic of); Jeong, G.E. [Department of Physics, Pusan National University, Busan 609-735 (Korea, Republic of); Yang, Ho-Soon [Department of Mechanical Engineering, Pusan National University, Busan 609-735 (Korea, Republic of); Department of Physics, Pusan National University, Busan 609-735 (Korea, Republic of)
2011-05-15
Pyrochlore-structured rare-earth materials have been of interest recently as thermal-barrier coating materials because they show low thermal conductivity due to the oxygen vacancy. This study reports the preparation and thermal characterization of Gd{sub 2}Zr{sub 2}O{sub 7} films deposited on YSZ and Al{sub 2}O{sub 3} substrates. Since the thermal properties of Gd{sub 2}Zr{sub 2}O{sub 7} and YSZ are not obviously different, the thermal-impedance method (the extended 3{omega} method) is used to study the films in this work. Gd{sub 2}Zr{sub 2}O{sub 7} thin films of various thicknesses are deposited using a pulsed laser deposition method. The thermal conductivity of Gd{sub 2}Zr{sub 2}O{sub 7} thin films exhibits a dependence on film thickness. The thickness-dependent thermal conductivity is ascribed to the interfacial thermal resistance between the Gd{sub 2}Zr{sub 2}O{sub 7} film and substrates. The interfacial resistance is obtained by fitting the thickness-dependent thermal conductivity with the effective thermal-conductivity equation. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Directory of Open Access Journals (Sweden)
Jendrysek Marek
2015-11-01
Full Text Available Purpose: Body composition evaluation of youth aged 17-18 of a different physical activity with the help of bioelectric impedance method. Material and Methods: 18 boys practicing swimming and 19 boys not practicing it took part in the study, making up a control group. Height, weight, BMI, lean body mass, the content of fat and water, Rohr factor were evaluated. Non-parametric Mann-Whitney test has been used to evaluate the differences in the range of the tissue components between the two groups. Results: Statistically significant differences were found on the p<0,05 level in % fat content. Mean body weight in experimental group was 71.5 kg, while in control group it was 69.4 kg. Minimum and maximum weight in group of swimming-practicing persons was: 56.6-92.2 kg. Increased body weight in the group of swimmers can result from greater amount of active tissue in this group compared with persons of low physical activity. Proportionally, it amounted to 64.3 kg and 61.3 kg. In the tested groups, minimal and maximal values of amount of active tissue proportionately amounted to: 54.1-78 and 49.5-72,3 kg. Conclusions: Physical activity modifies body composition. Active lifestyle is one of the methods for prevention of overweight and obesity.
A Maximum Likelihood Method for Harmonic Impedance Estimation%系统谐波阻抗估计的极大似然估计方法
Institute of Scientific and Technical Information of China (English)
华回春; 贾秀芳; 曹东升; 赵成勇
2014-01-01
In order to estimate the harmonic impedance more accurately, the complex maximum likelihood estimation method was proposed in the paper. Firstly, the complex multivariate Gaussian random variable was defined by imitating the real multivariate Gaussian random variable definition. According to the meaning of covariance, the calculation formula of the complex covariance was given. Secondly, the probability density function of the complex Gaussian distribution was deduced by the algebra isomorphism theory. Data selection was performed by the statistical theory, and then the complex maximum likelihood estimation function was established for the selected data. Finally, harmonic impedance was estimated by maximizing the complex maximum likelihood estimation function. A case study based on the IEEE 14-bus test system was operated, which shows that the proposed method can give more accurate result compared with the traditional methods.%为更加准确地估计系统谐波阻抗，提出复数域极大似然估计方法。首先，仿照实数域多元正态分布的定义给出复数域多元正态随机变量的定义，根据协方差的含义，定义复协方差的计算公式。然后利用代数同构理论，推导复数域正态分布的概率密度函数，利用统计学理论进行数据筛选，采用筛选后的数据代入复数域极大似然估计函数。最后利用极值理论进行求解，实现系统谐波阻抗的估计。对IEEE 14节点系统进行仿真，结果表明，与传统方法相比，所提方法估计结果更为准确。
Park, Chang-In; Jeon, Su-Jin; Hong, Nam-Pyo; Choi, Young-Wan
2016-03-01
Lock-in amplifier (LIA) has been proposed as a detection technique for optical sensors because it can measure low signal in high noise level. LIA uses synchronous method, so the input signal frequency is locked to a reference frequency that is used to carry out the measurements. Generally, input signal frequency of LIA used in optical sensors is determined by modulation frequency of optical signal. It is important to understand the noise characteristics of the trans-impedance amplifier (TIA) to determine the modulation frequency. The TIA has a frequency range in which noise is minimized by the capacitance of photo diode (PD) and the passive component of TIA feedback network. When the modulation frequency is determined in this range, it is possible to design a robust system to noise. In this paper, we propose a method for the determination of optical signal modulation frequency selection by using the noise characteristics of TIA. Frequency response of noise in TIA is measured by spectrum analyzer and minimum noise region is confirmed. The LIA and TIA circuit have been designed as a hybrid circuit. The optical sensor is modeled by the laser diode (LD) and photo diode (PD) and the modulation frequency was used as the input to the signal generator. The experiments were performed to compare the signal to noise ratio (SNR) of the minimum noise region and the others. The results clearly show that the SNR is enhanced in the minimum noise region of TIA.
Institute of Scientific and Technical Information of China (English)
ZHANG Wenliang; JIANG Jun; GUO Jian; LU Jiayu
2012-01-01
There will be more and more AC transmission lines near oil/gas pipelines in the future.So in order to determine the safe distance between them,simple and effective methods are required for engineers to efficiently evaluate the electromagnetic effect on oil/gas pipelines due to faults of AC transmission lines.In this paper,an easily handled fitting formula is obtained based on multiple calculation results,which is the maximum voltage on the pipeline anticorrosive coating produced by 1 000 kV AC transmission line under single phase ground fault.Although the calculation results obtained from the fitting formula differ from those gained by precise calculation with softwares,the verification of the formula shows that it is applicable for engineering calculation.This research could be applied to evaluate the electromagnetic effect of 1 000 kV AC transmission line under single-phase ground fault on nearby pipelines,as well as to determine the safe distance or the maximum parallel length.
Todd, Craig
1995-12-01
AC-3 is a system for coding up to 5.1 channels of audio into a low bit-rate data stream. High quality may be obtained with compression ratios approaching 12-1 for multichannel audio programs. The high compression ratio is achieved by methods which do not increase decoder memory, and thus cost. The methods employed include: the transmission of a high frequency resolution spectral envelope; and a novel forward/backward adaptive bit allocation algorithm. In order to satisfy practical requirements of an emissions coder, the AC-3 syntax includes a number of features useful to broadcasters and consumers. These features include: loudness uniformity between programs; dynamic range control; and broadcaster control of downmix coefficients. The AC-3 coder has been formally selected for inclusion of the U.S. HDTV broadcast standard, and has been informally selected for several additional applications.
Impedance and Collective Effects
Metral, E; Rumolo, R; Herr, W
2013-01-01
This document is part of Subvolume C 'Accelerators and Colliders' of Volume 21 'Elementary Particles' of Landolt-Börnstein - Group I 'Elementary Particles, Nuclei and Atoms'. It contains the Chapter '4 Impedance and Collective Effects' with the content: 4 Impedance and Collective Effects Introduction 4.1 Space Charge 4.2 Wake Fields and Impedances 4.3 Coherent Instabilities 4.4 Landau Damping 4.5 Two-Stream Effects (Electron Cloud and Ions) 4.6 Beam-Beam Effects 4.7 Numerical Modelling
Directory of Open Access Journals (Sweden)
Gučević Jelena
2012-01-01
Full Text Available The existing topographic and cadastral maps of the former Yugoslav republics are in Gauss-Krüger projection on Bessel ellipsoid. For the collected GPS data to comply with the existing cartographic material, it is necessary to provide the transformation parameters from WGS84 to Bessel ellipsoid and according to the principles of cartographic mapping, to make mappings in the plane of the State Coordinate System (SCS. The aim of this research is to present the surveying activities necessary for the establishment and maintenance of digital cartographic basis, which is shown in the test area of “VRŠAC MOUNTAINS”, a Serbian region with outstanding characteristics. In order to establish a connection between the collected data, it is necessary to primarily calculate the parameters of transformation from WGS84 into the SCS. After the vectorisation of projected boundaries from bases made in the SCS, the transformation of vectorised boundary lines from SCS into the WGS84 is carried out, followed by staking the boundaries. To understand the fundamental differences in the methodology of using GPS receivers, it is important to emphasise that the concept of GPS determination of the coordinates is generally divided into absolute and relative positioning. If the correct procedure of GPS positioning, applied to certain environmental conditions, is not followed, the error up to 200 m could be expected. Conclusions are drawn about the selection of staking methods, related to the applied instruments and specific field conditions. The stakeout procedures are given in accordance with the principles of geodetic positioning. [Projekat Ministarstva nauke Republike Srbije, br. 043007: Istraživanje klimatskih promena i njihovog uticaja na životnu sredinu: praćenje uticaja, adaptacija i ublažavanje
Indian Academy of Sciences (India)
Priyanka; A K Jha
2013-02-01
This paper reports complex impedance analysis of polycrystalline complex perovskite structured BaZr0.025Ti0.975O3 prepared by solid state reaction method. XRD analysis reveals the formation of single phase perovskite structure. SEM has been used to investigate grain morphology of the material. Impedance plots have been used as a tool to analyse electrical properties of the sample as a function of frequency and temperature. Bulk resistance is observed to decrease with an increase in temperature showing a typical negative temperature coefficient of resistance (NTCR) type behaviour. Nyquist (Cole–Cole) plots show both inter and intra grain boundary effects. Relaxation time is found to decrease with increasing temperature and it obeys the Arrhenius relationship. The variation of d.c. and a.c. conductivity as a function of temperature is also reported.
Impedance and component heating
Métral, E; Mounet, N; Pieloni, T; Salvant, B
2015-01-01
The impedance is a complex function of frequency, which represents, for the plane under consideration (longitudinal, horizontal or vertical), the force integrated over the length of an element, from a “source” to a “test” wave, normalized by their charges. In general, the impedance in a given plane is a nonlinear function of the test and source transverse coordinates, but it is most of the time sufficient to consider only the first few linear terms. Impedances can influence the motion of trailing particles, in the longitudinal and in one or both transverse directions, leading to energy loss, beam instabilities, or producing undesirable secondary effects such as excessive heating of sensitive components at or near the chamber wall, called beam-induced RF heating. The LHC performance limitations linked to impedances encountered during the 2010-2012 run are reviewed and the currently expected situation during the HL-LHC era is discussed.
Impedance of goat eye lens at different DC voltages.
Kohli, K S; Rai, D V; Jindal, V K; Goyal, N
1998-09-01
A computer assisted AC impedance system is used to measure the DC voltage-current (V-I) characteristics and AC impedance of a goat eye lens using a two-probe Ag-AgCl electrode system. The measurement of the V-I characteristics shows that when a DC voltage from 0 mV to 30 mV is applied, the resultant current decreases from an initial value of 0.58 microA to 0.006 microA. However, when the voltage is increases beyond 30 mV, the current increases and reaches a value of 0.9 microA at 100 mV. The data on the frequency response (0.01-10 Hz) of the impedance of lens tissue show an inverse relationship with frequency. The effect of various DC voltages, namely 0, 30, 50, 100 and 200 mV, on the impedance of the eye lens is also investigated over a frequency range of 0.01-10 Hz. The measurement results for both V-I characteristics and AC impedance further suggest the presence of a 30 mV voltage compartment in the goat eye lens.
Impedance Analysis Method for Sound Insulation of Double Panels%双层板结构隔声性能阻抗法分析
Institute of Scientific and Technical Information of China (English)
王佐民; 姜在秀
2011-01-01
应用阻抗分析法与少量实样测试相结合的研究途径,探讨具有确定平面尺寸和边界条件的双层板结构的隔声量,进而得到相应的半理论半经验拟合公式.对3种不同夹层形式的双层板结构的倍频程隔声量进行实例分析,得到各自的拟合公式.3种夹层形式分别为吸声材料夹层、空气夹层(空腔)和空气-吸声材料夹层.利用这些拟合公式,可以便捷、高效地开展隔声结构参量的工程筛选.%The sound insulation of double panels with a certain plane dimensions and boundary condition can be analyzed by a combinative way of impedance analysis method and a few measurements, and an expert formula can be obtained. Three kinds of sandwich material constructions were analyzed respectively. Its sound insulations and expert formulae were obtained in octave band. These three kinds of sandwich materials are absorbing sandwich, air sandwich, and air-absorbing sandwich. It will be convenient and high efficient to screen insulation construction parameters by these expert formulae in engineering design.
He, Jie; Bahr, James; Chisholm, Bret J; Li, Jun; Chen, Zhigang; Balbyshev, Séva N; Bonitz, Verena; Bierwagen, Gordon P
2008-01-01
The objective of the study was to develop a high-throughput electrochemical impedance spectroscopy (HT-EIS) method for rapid and quantitative evaluation of corrosion protective coatings. A 12-element, spatially addressable electrochemical platform was designed, fabricated, and validated. This platform was interfaced to a commercial EIS instrument through an automated electronic switching unit. The HT-EIS system enables four parallel EIS measurements to be run simultaneously, which significantly reduces characterization time compared to that of serial EIS measurements using a multiplexer. The performance of the HT-EIS system was validated using a series of model systems, including a Randles equivalent circuit, an electrochemical reaction (Ti/K4FeCN6, K3FeCN6), a highly uniform polymer film, and several polymer coatings. The results of the validation studies showed that the HT-EIS system enables a major reduction in characterization time and provides high quality data comparable to data obtained with conventional, single-cell EIS measurement systems.
Energy Technology Data Exchange (ETDEWEB)
Zotter, B. [European Organization for Nuclear Research, Geneva (Switzerland)
1996-08-01
This report describes a number of measurements and computations of the impedance of the Large Electron Positron collider LEP at CERN. The work has been performed over several years, together with D. Brandt, K. Cornelis, A. Hofmann, G. Sabbi and many others. The agreement between measurements of single bunch instabilities on the machine and computer simulations is in general excellent and gives confidence in the impedance model used. (author)
Dielectric, Impedance and Conduction Behavior of Double Perovskite Pr2CuTiO6 Ceramics
Mahato, Dev K.; Sinha, T. P.
2016-08-01
Polycrystalline Pr2CuTiO6 (PCT) ceramics exhibits dielectric, impedance and modulus characteristics as a possible material for microelectronic devices. PCT was synthesized through the standard solid-state reaction method. The dielectric permittivity, impedance and electric modulus of PCT have been studied in a wide frequency (100 Hz-1 MHz) and temperature (303-593 K) range. Structural analysis of the compound revealed a monoclinic phase at room temperature. Complex impedance Cole-Cole plots are used to interpret the relaxation mechanism, and grain boundary contributions towards conductivity have been estimated. From electrical modulus formalism polarization and conductivity relaxation behavior in PCT have been discussed. Normalization of the imaginary part of impedance (Z″) and the normalized imaginary part of modulus (M″) indicates contributions from both long-range and localized relaxation effects. The grain boundary resistance along with their relaxation frequencies are plotted in the form of an Arrhenius plot with activation energy 0.45 eV and 0.46 eV, respectively. The ac conductivity mechanism has been discussed.
Dielectric, Impedance and Conduction Behavior of Double Perovskite Pr2CuTiO6 Ceramics
Mahato, Dev K.; Sinha, T. P.
2017-01-01
Polycrystalline Pr2CuTiO6 (PCT) ceramics exhibits dielectric, impedance and modulus characteristics as a possible material for microelectronic devices. PCT was synthesized through the standard solid-state reaction method. The dielectric permittivity, impedance and electric modulus of PCT have been studied in a wide frequency (100 Hz-1 MHz) and temperature (303-593 K) range. Structural analysis of the compound revealed a monoclinic phase at room temperature. Complex impedance Cole-Cole plots are used to interpret the relaxation mechanism, and grain boundary contributions towards conductivity have been estimated. From electrical modulus formalism polarization and conductivity relaxation behavior in PCT have been discussed. Normalization of the imaginary part of impedance ( Z″) and the normalized imaginary part of modulus ( M″) indicates contributions from both long-range and localized relaxation effects. The grain boundary resistance along with their relaxation frequencies are plotted in the form of an Arrhenius plot with activation energy 0.45 eV and 0.46 eV, respectively. The ac conductivity mechanism has been discussed.
Impedance Biosensing to detect food allergens, endocrine disrupting chemicals, and food pathogens
Radhakrishnan, Rajeswaran
Electrochemical impedance biosensors can be viewed as an AC electroanalytical method for the analyte detection in the fields of biomedicine, environmental monitoring, and food and agriculture, amongst others. The most common format for AC impedance biosensing involves surface immobilization of an antibody, receptor protein, DNA strand, or other species capable of bio-recognition, and AC impedance detection of the binding event. Technological application of AC impedance biosensors has been hindered by several obstacles, including the more complex circuitry required for AC relative to DC electrochemistry, chemical and physical interference arising from non-specific adsorption, and the stability and reproducibility of protein immobilization. One focus of these PhD studies is on methods to reduce or compensate for non-specific adsorption, including sample dilution, site blocking with BSA, and the use of control electrodes onto which reference antibodies are immobilized. Examples that will be presented include impedance detection of food pathogens, such as Listeria monocytogenes, using a mouse monoclonal antibody immobilized onto an Au electrode. This yields detection limits of 5 CFU/ml and 4 CFU/ml for ideal solutions and filtered tomato extract, respectively. Control experiments with an Au electrode onto which a mouse monoclonal antibody to GAPDH is immobilized demonstrate that non-specific adsorption is insignificant for the system and methodology studied here. Control experiments with Salmonella enterica demonstrate no cross-reactivity to this food pathogen. In addition, Detection of two endocrine-disrupting chemicals (EDC), norfluoxetine and BDE-47, is reported here by impedance biosensing, with a detection limit of 8.5 and 1.3 ng/ml for norfluoxetine and BDE-47, respectively. Additional research has focused on alternative substrates and linker chemistries for protein immobilization, including the use of degenerate (highly doped) Si and bidendate thiol monolayer
Institute of Scientific and Technical Information of China (English)
吴良超; 汪茂光
1995-01-01
Under the exact impedance boundary condition (EIBC), by using wave equations and the longitudinal field method, the electromagnetic scattenng by an impedance wedge has been analysed in detail, following the Maliuzhinets approach, and the uniform diffraction coefficient of the diffracted field has been presented.
The electrochemical impedance of metal hydride electrodes
DEFF Research Database (Denmark)
Valøen, Lars Ole; Lasia, Andrzej; Jensen, Jens Oluf
2002-01-01
The electrochemical impedance responses for different laboratory type metal hydride electrodes were successfully modeled and fitted to experimental data for AB5 type hydrogen storage alloys as well as one MgNi type electrode. The models fitted the experimental data remarkably well. Several AC......, explaining the experimental impedances in a wide frequency range for electrodes of hydride forming materials mixed with copper powder, were obtained. Both charge transfer and spherical diffusion of hydrogen in the particles are important sub processes that govern the total rate of the electrochemical...... hydrogen absorption/desorption reaction. To approximate the experimental data, equations describing the current distribution in porous electrodes were needed. Indications of one or more parallel reduction/oxidation processes competing with the electrochemical hydrogen absorption/desorption reaction were...
Microwave impedance imaging on semiconductor memory devices
Kundhikanjana, Worasom; Lai, Keji; Yang, Yongliang; Kelly, Michael; Shen, Zhi-Xun
2011-03-01
Microwave impedance microscopy (MIM) maps out the real and imaginary components of the tip-sample impedance, from which the local conductivity and dielectric constant distribution can be derived. The stray field contribution is minimized in our shielded cantilever design, enabling quantitative analysis of nano-materials and device structures. We demonstrate here that the MIM can spatially resolve the conductivity variation in a dynamic random access memory (DRAM) sample. With DC or low-frequency AC bias applied to the tip, contrast between n-doped and p-doped regions in the dC/dV images is observed, and p-n junctions are highlighted in the dR/dV images. The results can be directly compared with data taken by scanning capacitance microscope (SCM), which uses unshielded cantilevers and resonant electronics, and the MIM reveals more information of the local dopant concentration than SCM.
Institute of Scientific and Technical Information of China (English)
蔡志远; 庞佳; 陈廷辉
2011-01-01
Shortage of residual current protection method which can not distinguish the signals caused by switching on the leakage current impedance from those by switching it off is analyzed according to residual current protection theory.A new method based on residual current and leakage current impedance is proposed, which distinguishes the two signals through metering that the real part of impedance is positive or negative, and it can theoretically eliminate the fault performance caused by residual current change due to cutting off leakage current impedance based on original residual current protection.Based on the trigonometric functions, a new method using two points in wave signal to figure out the vector is also proposed.The method is easy for programming and with which the vector parameter needed for computing the leakage impedance can be quickly gotten.%根据剩余电流的保护原理,分析了剩余电流保护中不能够区分由于投入漏电负载和切除漏电负载产生的漏电信号的缺陷,提出了一种基于剩余电流和漏电阻抗的保护方法.该方法通过观察漏电负载阻抗的实部正负特征来加以区分这两种信号,在原有的剩余电流保护方法的基础上,在理论上消除了切除漏电负载引起的剩余电流变化导致的误动作.提出了一种基于三角函数的两点法测定向量参数,易于编程化,能够快速地提取出计算漏电阻抗所需要的向量参数.
Electrical Impedance Measurements of PZT Nanofiber Sensors
Directory of Open Access Journals (Sweden)
Richard Galos
2017-01-01
Full Text Available Electrical impedance measurements of PZT nanofiber sensors were performed using a variety of methods over a frequency spectrum ranging from DC to 1.8 GHz. The nanofibers formed by electrospinning with diameters ranging from 10 to 150 nm were collected and integrated into sensors using microfabrication techniques. Special matching circuits with ultrahigh input impedance were fabricated to produce low noise, measurable sensor outputs. Material properties including resistivity and dielectric constant are derived from the impedance measurements. The resulting material properties are also compared with those of individual nanofibers being tested using conductive AFM and Scanning Conductive Microscopy.
Institute of Scientific and Technical Information of China (English)
李正义; 曹汇敏
2014-01-01
针对机器人阻抗控制在实际应用中其性能受环境的阻尼、刚度参数未知或变化影响的问题，提出了一种机器人自适应阻抗控制方法。在定义机器人阻抗控制性能指标的基础上结合阻抗模型刚度变化的几何表示，给出了阻抗模型刚度参数初值计算方法，提出了基于人工神经网络的环境等效刚度在线估计方法，并结合二阶系统临界阻尼条件计算阻抗模型阻尼参数初值。机器人力控制实验结果验证了该方法较已有的机器人阻抗控制方法在参考轨迹平滑性、力控制稳定性和易于工程实践方面有一定的优势。%The robot impedance control performance decreases with the efffects of changing or un-known environment stiffness and damping parameters in practical applications ,this paper presented a self-adaptive robot impedance control method to resolve this problem .Based on the definition of the robot impedance control performance index and the geometric representation for the impedance model stiffness variation ,the calculation method was illustrated for intitial values of the the impedance mod-el stiffness .Designing an artificial neural network to estimate the environmental equivalent stiffness online and combining with critical damping condition of the second-order system ,a calculation method was provided for the impedance model damping initial values .The results of robot force control experi-ments demonstrate smoother reference trajectory ,improved robot force control stability and feasibility in practices compared to the existing robot impedance control methods.
Directory of Open Access Journals (Sweden)
Hideki Taniguchi, Toshio Sasaki, Hisae Fujita
2012-01-01
Full Text Available Aim: Preoperative fasting is an established procedure to be practiced for patients before surgery, but optimal preoperative fasting time still remains controversial. The aim of this study was to investigate the effect of “shortened preoperative fasting time” on the change in the amount of total body water (TBW in elective surgical patients. TBW was measured by multi-frequency impedance method.Methods: The patients, who were scheduled to undergo surgery for stomach cancer, were divided into two groups of 15 patients each. Before surgery, patients in the control group were managed with conventional preoperative fasting time, while patients in the “enhanced recovery after surgery (ERAS” group were managed with “shortened preoperative fasting time” and “reduced laxative medication.” TBW was measured on the day before surgery and the day of surgery before entering the operating room. Defecation times and anesthesia-related vomiting and aspiration were monitored.Results: TBW values on the day of surgery showed changes in both groups as compared with those on the day before surgery, but the rate of change was smaller in the ERAS group than in the control group (2.4±6.8% [12 patients] vs. −10.6±4.6% [14 patients], p<0.001. Defecation times were less in the ERAS group. Vomiting and aspiration were not observed in either group.Conclusion: The results suggest that preoperative management with “shorted preoperative fasting time” and “reduced administration of laxatives” is effective in the maintenance of TBW in elective surgical patients.
交流接触器的常见故障及处理方法%Common failures and processing method of AC contactor
Institute of Scientific and Technical Information of China (English)
吕俊霞
2012-01-01
AC contactor is the most common application of a kind of electrical appliances in power system. The AC contactor common faults, the fault cause and the specific methods removing the faults are analyzed, including contactor inadequate suction, coil overheat or burn out, interphase short circuit and abnormal arcing etc..% 交流接触器是电力系统应用最普遍的一种电器。分析了交流接触器的常见故障、产生故障的原因及排除故障的具体方法，主要涉及接触器吸力不足、线圈过热或烧坏、相间短路、灭弧装置不正常灭弧等。
Boguslawsky, Iliya; Hayakawa, Masashi
2017-01-01
In this monograph the authors solve the modern scientific problems connected with A.C. motors and generators, based first on the detailed consideration of their physical phenomena. The authors describe the theory and investigative methods they developed and applied in practice, which are considered to be of essential interest for specialists in the field of the electrical engineering industry in European countries, the USA, Argentina, and Brazil, as well as in such countries as India, China, and Iran. This book will be of interest to engineers specialized in the field of the manufacture, operation, and repair of A.C. machines (motors and generators) as well as electric drives; to professors, lecturers, and post-graduate students of technical universities, who are specializing in the field of electric machine engineering and electric drives; and to students who are engaged in the field of high current techniques, electric drives, and electric machine engineering.
Finemet cavity impedance studies
Persichelli, S; Migliorati, M; Salvant, B
2013-01-01
The aim of the study is to evaluate the impedance of the Finemet kicker cavity to be installed in the PS straight section 02 during LS1, under realistic assumptions of bunch length. Time domain simulations with CST Particle Studio have been performed in order to get the impedance of the cavity and make a comparison with the longitudinal impedance measured for a single cell prototype. The study has been performed on simplified 3D geometries imported from a mechanical CATIA drawing, assuming that the simplications have small impact on the nal results. Simulations confirmed that the longitudinal impedance observed with measurements can be excited by bunches circulating in the PS. In the six-cells Finemet cavity, PS bunches circulating in the center can excite a longitudinal impedance, the real part of which has a maximum of 2 kOhm at 4 MHz. This mode does not seem to have any transverse component. All the eigenmodes of the cavity are strongly damped by the Finemet rings: we predict to have no issues regarding tr...
Nagamuthu, S; Vijayakumar, S; Muralidharan, G
2014-12-14
Silver incorporated Mn3O4/amorphous carbon (AC) nanocomposites are synthesized by a green chemistry method. X-ray diffraction studies revealed the structural changes in Mn3O4/AC nanocomposites attributable to the addition of silver. Cyclic voltammetry, charge-discharge and ac-impedance studies indicated that the Ag-Mn3O4/AC-5 electrode was the most suitable candidate for supercapacitor applications. From the galvanostatic charge-discharge studies, a higher specific capacitance of 981 F g(-1) at a specific current of 1 A g(-1) was obtained. An Ag-Mn3O4/AC-symmetric supercapacitor consisting of an Ag-incorporated Mn3O4/AC composite as an anode as well as a cathode, and an asymmetric supercapacitor consisting of an Ag-incorporated Mn3O4/AC composite as a cathode and an activated carbon as an anode have been fabricated. The symmetric device exhibits a specific cell capacitance of 72 F g(-1) at a specific current of 1 A g(-1) whereas the asymmetric device delivers a specific cell capacitance of 180 F g(-1) at a high current rate of 10 A g(-1). The asymmetric supercapacitor device yields a high energy density of 81 W h kg(-1). This is higher than that of lead acid batteries and comparable with that of nickel hydride batteries.
Broadband electrical impedance matching for piezoelectric ultrasound transducers.
Huang, Haiying; Paramo, Daniel
2011-12-01
This paper presents a systematic method for designing broadband electrical impedance matching networks for piezoelectric ultrasound transducers. The design process involves three steps: 1) determine the equivalent circuit of the unmatched piezoelectric transducer based on its measured admittance; 2) design a set of impedance matching networks using a computerized Smith chart; and 3) establish the simulation model of the matched transducer to evaluate the gain and bandwidth of the impedance matching networks. The effectiveness of the presented approach is demonstrated through the design, implementation, and characterization of impedance matching networks for a broadband acoustic emission sensor. The impedance matching network improved the power of the acquired signal by 9 times.
Impedance adaptation for optimal robot-environment interaction
Ge, Shuzhi Sam; Li, Yanan; Wang, Chen
2014-02-01
In this paper, impedance adaptation is investigated for robots interacting with unknown environments. Impedance control is employed for the physical interaction between robots and environments, subject to unknown and uncertain environments dynamics. The unknown environments are described as linear systems with unknown dynamics, based on which the desired impedance model is obtained. A cost function that measures the tracking error and interaction force is defined, and the critical impedance parameters are found to minimise it. Without requiring the information of the environments dynamics, the proposed impedance adaptation is feasible in a large number of applications where robots physically interact with unknown environments. The validity of the proposed method is verified through simulation studies.
Kopp, Joachim; Slatyer, Tracy R; Wang, Xiao-Ping; Xue, Wei
2016-01-01
We consider a new class of thermal dark matter models, dubbed "Impeded Dark Matter", in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. We demonstrate that either case can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. For positive mass splitting, we show that the annihilation cross-section is suppress...
Ngo, Son Tung; Mai, Binh Khanh; Hiep, Dinh Minh; Li, Mai Suan
2015-10-01
The binding mechanism of AC1NX476 to HIV-1 protease wild type and mutations was studied by the docking and molecular dynamics simulations. The binding free energy was calculated using the double-annihilation binding free energy method. It is shown that the binding affinity of AC1NX476 to wild type is higher than not only ritonavir but also darunavir, making AC1NX476 become attractive candidate for HIV treatment. Our theoretical results are in excellent agreement with the experimental data as the correlation coefficient between calculated and experimentally measured binding free energies R = 0.993. Residues Asp25-A, Asp29-A, Asp30-A, Ile47-A, Gly48-A, and Val50-A from chain A, and Asp25-B from chain B play a crucial role in the ligand binding. The mutations were found to reduce the receptor-ligand interaction by widening the binding cavity, and the binding propensity is mainly driven by the van der Waals interaction. Our finding may be useful for designing potential drugs to combat with HIV.
Institute of Scientific and Technical Information of China (English)
林永水; 吴卫国; 甘进
2016-01-01
This paper proposes a wave dynamic response matrix method to investigate the problem of im-peding structure-borne sound transmission from wave impedance facilities based on the wave approach, impedance method and finite element idea. The structure is discretized into many wave elements and a gen-eral wave dynamic response equilibrium equation is developed according to the displacement compatibility, force and moment equilibrium at the junction node. And, the wave dynamic response matrices of wave ele-ments and the added wave dynamic response matrices of wave impedance facilities are deduced. The vibra-tion amplitudes of wave elements are obtained by resolving the equilibrium equation and the transmission efficiencies and transmission loss are then obtained. The method is illustrated by a series of wave attenua-tion models such as blocking mass, elastic interlayer and dynamic vibration absorber. Finally, numerical analysis focuses on the attenuation of structure-borne sound through the composite wave impedance facilities.The numerical simulation results show that the wave transmission loss of the whole frequency domain will be greatly improved by using composite wave impedance technique with reasonable selection of design pa-rameters and the optimal layout. This study provides a new analysis method for the structural acoustic design of composite wave impedance facilities and a new kind of control policy, which has great theoretical signif-icance and important value for engineering application in the field of noise and vibration reduction.%基于有限元思想，综合运用波分析法和阻抗法，提出了波阻元件阻抑结构声传递的波动力响应矩阵分析法。将结构离散为多个波导单元和波阻单元，根据连接节点的位移连续，力与力矩平衡，建立附加波阻元件的结构连接广义波动力响应平衡方程，推导出波单元波动力响应特征矩阵及波阻元件附加波动响应特征矩阵，并代入波
Degtiarenko, Pavel V.; Popov, Vladimir E.
2011-03-22
A first stage electronic system for receiving charge or current from voltage-controlled sensors or detectors that includes a low input impedance current receiver/converter device (for example, a transimpedance amplifier), which is directly coupled to the sensor output, a source of bias voltage, and the device's power supply (or supplies), which use the biased voltage point as a baseline.
Impedance spectroscopy of food mycotoxins
Bilyy, Oleksandr I.; Yaremyk, Roman Ya.; Kotsyumbas, Ihor Ya.; Kotsyumbas, Halyna I.
2012-01-01
A new analytical method of high-selective detection of mycotoxins in food and feed are considered. A method is based on optical registration the changes of conduct of the electric polarized bacterial agents in solution at the action of the external gradient electric fields. Measuring are conducted in integrated electrode-optical cuvette of the special construction, which provides the photometric analysis of forward motion of the objects registration in liquid solution under act of the enclosed electric field and simultaneous registration of kinetics of change of electrical impedance parameters solution and electrode system.
Directory of Open Access Journals (Sweden)
XUE BU HU
2010-09-01
Full Text Available Two composite cathode materials containing LiFePO4 and activated carbon (AC were synthesized by an in-situ method and a direct mixing technique, which are abbreviated as LAC and DMLAC, respectively. Hybrid battery–capacitors LAC/Li4Ti5O12 and DMLAC/Li4Ti5O12 were then assembled. The effects of the content of LiFePO4 and the preparation method on the cyclic voltammograms, the rate of charge–discharge and the cycle performance of the hybrid battery–capacitors were investigated. The results showed the overall electrochemical performance of the hybrid battery–capacitors was the best when the content of LiFePO4 in the composite cathode materials was in the range from 11.8 to 28.5 wt. %, while the preparation method had almost no impact on the electrochemical performance of the composite cathodes and hybrid battery–capacitors. Moreover, the hybrid battery–capacitor devices had a good cycle life performance at high rates. After 1000 cycles, the capacity loss of the DMLAC/Li4Ti5O12 hybrid battery–capacitor device at 4C was no more than 4.8 %. Moreover, the capacity loss would be no more than 9.6 % after 2000 cycles at 8C.
Wave impedance retrieving via Bloch modes analysis
DEFF Research Database (Denmark)
Andryieuski, Andrei; Ha, S.; Sukhorukov, A.;
2011-01-01
of the Bloch mode, respectively. Case studies prove that our ap-proach can determine material and wave effective parameters of lossy and lossless metamaterials. In some examples when the passivity is violated we made further analysis and showed that this is due to the failure of concept of impedance retrieving......-ciples violation, like antiresonance behaviour with Im(ε) mode analysis of periodic metamaterials to extract the dominating (fundamental) Bloch mode. Then it is possible to determine the Bloch and wave impedances by the surface and volume aver-aging of the electromagnetic field......The main bottleneck in the restoration of electromagnetic effective parameters is connected to the impedance retrieving. The S-parameters method gives the input (Bloch) impedance, which, being then used for permittivity and permeability determination, causes some fundamental physics prin...
A Rotative Electrical Impedance Tomography Reconstruction System
Energy Technology Data Exchange (ETDEWEB)
Yu, F-M [St. John' s and St. Mary' s Institute of Technology, Department of computer science and information Engineering, 499, Sec. 4, Tam King Road Tamsui, Taipei, Taiwan (China); Huang, C-N [National Central University, Department of Electrical Engineering, No.300, Jungda Rd, Jhongli City, 320 Taoyuan, Taiwan (China); Chang, F-W [National Central University, Department of Electrical Engineering, No.300, Jungda Rd, Jhongli City, 320 Taoyuan, Taiwan (China); Chung, H-Y [National Central University, Department of Electrical Engineering, No.300, Jungda Rd, Jhongli City, 320 Taoyuan, Taiwan (China)
2006-10-15
Electrical impedance tomography (EIT) is a powerful tool for mapping the conductivity distribution of estimated objects. The EIT system is entirely implemented by electrical technique, so it is a relatively cheap system and data can be collected very rapidly. But it has few commercially medical EIT systems available. This is because impedance image unable to achieve the essential spatial resolution and this technique has an intrinsically poor signal to noise ratio. In this paper, we have developed a high performance rotative EIT system (REIT) for expanding the independent measurements. By rotate the electrodes successive, REIT could change the position of electrodes and acquire more measurement data. This rotative measurement method not only can increase the resolution of impedance images, but also reduce the complexity of measurement system. We hope the improvement of REIT will bring some help in electrical impedance tomography.
VISUALIZATION OF BIOLOGICAL TISSUE IMPEDANCE PARAMETERS
Directory of Open Access Journals (Sweden)
V. I. Bankov
2016-01-01
Full Text Available Objective. Investigation the opportunity for measurement of biological tissue impedance to visualize its parameters.Materials and methods. Studies were undertook on the experimental facility, consists of registrating measuring cell, constructed from flat inductors system, formed in oscillatory circuit, herewith investigated biological tissue is the part of this oscillatory circuit. An excitation of oscillatory circuit fulfilled by means of exciter inductor which forms impulse complex modulated electromagnetic field (ICM EMF. The measurement process and visualizations provided by set of certificated instruments: a digital oscillograph AKTAKOM ADS-2221MV, a digital generator АКТАКОМ AWG-4150 (both with software and a gauge RLC E7-22. Comparative dynamic studies of fixed volume and weight pig’s blood, adipose tissue, muscular tissue impedance were conducted by contact versus contactless methods. Contactless method in contrast to contact method gives opportunity to obtain the real morphological visualization of biological tissue irrespective of their nature.Results. Comparison of contact and contactless methods of impedance measurement shows that the inductance to capacitance ratio X(L / X(C was equal: 17 – for muscular tissue, 4 – for blood, 1 – for adipose tissue. It demonstrates the technical correspondence of both impedance registration methods. If propose the base relevance of X (L and X (C parameters for biological tissue impedance so contactless measurement method for sure shows insulating properties of adipose tissue and high conductivity for blood and muscular tissue in fixed volume-weight parameters. Registration of biological tissue impedance complex parameters by contactless method with the help of induced ICM EMF in fixed volume of biological tissue uncovers the most important informative volumes to characterize morphofunctional condition of biological tissue namely X (L / X (C.Conclusion. Contactless method of biological
Energy Technology Data Exchange (ETDEWEB)
Senthil, P. [Coimbatore Institute of Engineering and Technology, Coimbatore (India); Amirthagadeswaran, K. S. [Government College of Technology, Coimbatore (India)
2012-04-15
This paper reports a research in which an attempt was made to prepare AC2A aluminium alloy castings of a non symmetrical component through squeeze casting process. The primary objective was to investigate the influence of process parameters on mechanical properties of the castings. Experiments were conducted based on orthogonal array suggested in Taguchi's offline quality control concept. The experimental results showed that squeeze pressure, die preheating temperature and compression holding time were the parameters making significant improvement in mechanical properties. The optimal squeeze casting condition was found and mathematical models were also developed for the process.
Antenna impedance matching with neural networks.
Hemminger, Thomas L
2005-10-01
Impedance matching between transmission lines and antennas is an important and fundamental concept in electromagnetic theory. One definition of antenna impedance is the resistance and reactance seen at the antenna terminals or the ratio of electric to magnetic fields at the input. The primary intent of this paper is real-time compensation for changes in the driving point impedance of an antenna due to frequency deviations. In general, the driving point impedance of an antenna or antenna array is computed by numerical methods such as the method of moments or similar techniques. Some configurations do lend themselves to analytical solutions, which will be the primary focus of this work. This paper employs a neural control system to match antenna feed lines to two common antennas during frequency sweeps. In practice, impedance matching is performed off-line with Smith charts or relatively complex formulas but they rarely perform optimally over a large bandwidth. There have been very few attempts to compensate for matching errors while the transmission system is in operation and most techniques have been targeted to a relatively small range of frequencies. The approach proposed here employs three small neural networks to perform real-time impedance matching over a broad range of frequencies during transmitter operation. Double stub tuners are being explored in this paper but the approach can certainly be applied to other methodologies. The ultimate purpose of this work is the development of an inexpensive microcontroller-based system.
2008-01-01
Transition metal oxides have been suggested as innovative, high-energy electrode materials for lithium-ion batteries because their electrochemical conversion reactions can transfer two to six electrons. However, nano-sized transition metal oxides, especially Co3O4, exhibit drastic capacity decay during discharge/charge cycling, which hinders their practical use in lithium-ion batteries. Herein, we prepared nano-sized Co3O4with high crystallinity using a simple citrate-gel method and used electrochemical impedance spectroscopy method to examine the origin for the drastic capacity fading observed in the nano-sized Co3O4anode system. During cycling, AC impedance responses were collected at the first discharged state and at every subsequent tenth discharged state until the 100th cycle. By examining the separable relaxation time of each electrochemical reaction and the goodness-of-fit results, a direct relation between the charge transfer process and cycling performance was clearly observed.
Impedance spectroscopy for the detection and identification of unknown toxins
Riggs, B. C.; Plopper, G. E.; Paluh, J. L.; Phamduy, T. B.; Corr, D. T.; Chrisey, D. B.
2012-06-01
Advancements in biological and chemical warfare has allowed for the creation of novel toxins necessitating a universal, real-time sensor. We have used a function-based biosensor employing impedance spectroscopy using a low current density AC signal over a range of frequencies (62.5 Hz-64 kHz) to measure the electrical impedance of a confluent epithelial cell monolayer at 120 sec intervals. Madin Darby canine kidney (MDCK) epithelial cells were grown to confluence on thin film interdigitated gold electrodes. A stable impedance measurement of 2200 Ω was found after 24 hrs of growth. After exposure to cytotoxins anthrax lethal toxin and etoposide, the impedance decreased in a linear fashion resulting in a 50% drop in impedance over 50hrs showing significant difference from the control sample (~20% decrease). Immunofluorescent imaging showed that apoptosis was induced through the addition of toxins. Similarities of the impedance signal shows that the mechanism of cellular death was the same between ALT and etoposide. A revised equivalent circuit model was employed in order to quantify morphological changes in the cell monolayer such as tight junction integrity and cell surface area coverage. This model showed a faster response to cytotoxin (2 hrs) compared to raw measurements (20 hrs). We demonstrate that herein that impedance spectroscopy of epithelial monolayers serves as a real-time non-destructive sensor for unknown pathogens.
Longitudinal impedance of RHIC
Energy Technology Data Exchange (ETDEWEB)
Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Brennan, J. M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Mernick, K. [Brookhaven National Lab. (BNL), Upton, NY (United States)
2015-05-03
The longitudinal impedance of the two RHIC rings has been measured using the effect of potential well distortion on longitudinal Schottky measurements. For the blue RHIC ring Im(Z/n) = 1.5±0.2Ω. For the yellow ring Im(Z/n) = 5.4±1Ω.
三相不对称条件下的电网阻抗检测方法%A Grid Impedance Detection Method Under Unbalanced Three-phase Conditions
Institute of Scientific and Technical Information of China (English)
蔡文; 刘邦银; 段善旭; 邹常跃
2012-01-01
Grid impedance detection is an anti-islanding method which is widely used in grid-connected inverters.Grid-impedance detection based on the single harmonic current injection is feasible in single-phase and balanced three-phase grids.However,under unbalanced three-phase conditions,the harmonic voltage caused by the injected symmetric harmonic current is asymmetric,which affects the computation of the impedances and leads to a failed detection.Firstly,this paper analyzed the failure mechanism of the conventional grid-impedance detection under unbalanced three-phase conditions.And then,a new method wais proposed to detect the impedances of the grid with two different non-characteristic harmonic current injections and the Discrete Fourier Transformation（DFT） algorithm.Finally,experiments were carried out in impedance-unbalanced grids.Theoretical analysis and experiment results prove that the proposed method is feasible.%电网阻抗检测法是一种在并网逆变器中广泛使用的孤岛检测方法。基于单次谐波电流注入的常规电网阻抗检测法在单相和三相对称电网中可准确检测出孤岛,但当三相电网不对称时,注入的对称谐波电流将引起谐波电压不对称,从而影响电网阻抗的计算,可能导致孤岛检测失败。该文首先分析了基于谐波电流注入的常规阻抗检测方法在三相不对称条件下的失效机理,然后提出一种采用2种不同频率非特征谐波电流注入的方式,结合离散傅里叶变换（discrete Fourier transformation,DFT）算法检测三相电网阻抗的方法,并分析了该方法的基本原理和性能,最后在三相电网阻抗不对称的条件下进行了实验验证。理论分析和实验结果表明该文所提出的阻抗检测方法是有效可行的。
Locating Impedance Change in Electrical Impedance Tomography Based on Multilevel BP Neural Network
Institute of Scientific and Technical Information of China (English)
彭源; 莫玉龙
2003-01-01
Electrical impedance tomography (EIT) is a new computer tomography technology, which reconstructs an impedance (resistivity, conductivity) distribution, or change of impedance, by making voltage and current measurements on the object's periphery.Image reconstruction in EIT is an ill-posed, non-linear inverse problem. A method for finding the place of impedance change in EIT is proposed in this paper, in which a multilevel BP neural network (MBPNN) is used to express the non-linear relation between theimpedance change inside the object and the voltage change measured on the surface of the object. Thus, the location of the impedance change can be decided by the measured voltage variation on the surface. The impedance change is then reconstructed using a linear approximate method. MBPNN can decide the impedance change location exactly without long training time. It alleviates some noise effects and can be expanded, ensuring high precision and space resolution of the reconstructed image that are not possible by using the back projection method.
Machine Tool Used AC Contactor Reliability Evaluation Method%机床用交流接触器可靠性评估方法
Institute of Scientific and Technical Information of China (English)
陆宾; 陆俭国
2014-01-01
Introduction was made to AC contactor reliability study development situations both at home and abroad. This paper described the reliability test method of machine tool used AC contactor mechanical operation and the evaluation method, pointing out that the product failure distribution type is Weibull distribution when AC contactor turning on/off the rating electrical load, failure rate is not constant, it is not suitable to adopt failure rate value as reliability index, but to adopt reliability measurement test, and the corresponding methods were given.%介绍了国内外开展交流接触器可靠性研究概况，阐述了机床用交流接触器机械操作可靠性试验方法与评估方法。指出交流接触器通断实际电气负载时产品失效分布类型为威布尔分布，失效率不是常数，不宜采用失效率大小作为交流接触器通断实际电气负载时的可靠性指标，而应采用可靠性测定试验，并给出了交流接触器通断实际电气负载时可靠性试验方法与提供可靠性数据的评估方法。
Jahnke, Heinz-Georg; Heimann, Axel; Azendorf, Ronny; Mpoukouvalas, Konstantinos; Kempski, Oliver; Robitzki, Andrea A; Charalampaki, Patra
2013-08-15
Until today, brain tumors especially glioblastoma are difficult to treat and therefore, results in a poor survival rate of 0-14% over five years. To overcome this problem, the development of novel therapeutics as well as optimization of neurosurgical procedures to remove the tumor tissue are subject of intensive research. The main problem of the tumor excision, as the primary clinical intervention is the diffuse infiltration of the tumor cells in unaltered brain tissue that complicates the complete removal of residual tumor cells. In this context, we are developing novel approaches for the label-free discrimination between tumor tissue and unaltered brain tissue in real-time during the surgical process. Using our impedance spectroscopy-based measurement system in combination with flexible microelectrode arrays we could successfully demonstrate the discrimination between a C6-glioma and unaltered brain tissue in an in vivo rat model. The analysis of the impedance spectra revealed specific impedance spectrum shape characteristics of physiologic neuronal tissue in the frequency range of 10-500 kHz that were significantly different from the tumor tissue. Moreover, we used an adapted equivalent circuit model to get a deeper understanding for the nature of the observed effects. The impedimetric label-free and real-time discrimination of tumor from unaltered brain tissue offers the possibility for the implementation in surgical instruments to support surgeons to decide, which tissue areas should be removed and which should be remained.
Impedance calculation for ferrite inserts
Energy Technology Data Exchange (ETDEWEB)
Breitzmann, S.C.; Lee, S.Y.; /Indiana U.; Ng, K.Y.; /Fermilab
2005-01-01
Passive ferrite inserts were used to compensate the space charge impedance in high intensity space charge dominated accelerators. They study the narrowband longitudinal impedance of these ferrite inserts. they find that the shunt impedance and the quality factor for ferrite inserts are inversely proportional to the imaginary part of the permeability of ferrite materials. They also provide a recipe for attaining a truly passive space charge impedance compensation and avoiding narrowband microwave instabilities.
Real-time measurement of glucose using chrono-impedance technique on a second generation biosensor.
Mayorga Martinez, Carmen C; Treo, Ernesto F; Madrid, Rossana E; Felice, Carmelo C
2011-11-15
Chrono-impedance technique (CIT) was implemented as a new transduction method for real time measurement of glucose in a biosensor system based in carbon paste (CP)/Ferrocene (FC)/glucose oxidase (GOx). The system presents high selectivity because the optimal stimulation signal composed by a 165mV DC potential and 50mV(RMS) AC signal at 0.4Hz was used. The low DC potential used decreased the interfering species effect and the biosensor showed a linear impedance response toward glucose detection at concentrations from 0mM to 20mM,with 0.9853 and 0.9945 correlation coefficient for impedance module (|Z|) and phase (Φ), respectively. The results of quadruplicate sets reveal the high repeatability and reproducibility of the measurements with a relative standard deviation (RSD) less than 10%. CIT presented good accuracy (within 10% of the actual value) and precision did not exceed 15% of RSD for high concentration values and 20% for the low concentration ones. In addition, a high correlation coefficient (R(2)=0.9954) between chrono-impedance and colorimetric methods was obtained. On the other hand, when two samples prepared at the same conditions were measured in parallel with both methods (the measurement was repeated four times), it should be noticed that student's t-test produced no difference between the two mentioned methods (p=1). The biosensor system hereby presented is highly specific to glucose detection and shows a better linear range than the one reported on the previous article.
Tamura, Yuji; Takasaki, Shinji; Irokawa, Shoichi; Takeda, Hideo; Takagi, Kikuo; Noro, Yasuhiro; Ametani, Akihiro
AC filter design method for SVC and HVDC is commonly known in the relevant CIGRE technical brochure and IEC technical report. However the conventional method requires many iterative calculations of the harmonic voltages and currents until the calculation results become within the regulation levels by changing filter parameters based on the experience. In this respect, a new improved design method is proposed, which enables efficient evaluation on the complex impedance plane to confirm as to whether the proposed filter impedance is in the permissible range. In an actual project of Okuura SVC of Kyusyu Electric Power Co., Inc., the new method was applied to the AC filter design. This paper describes on the actual procedure of the AC filter design with the new method, the actual references of the harmonic performance calculation, and the field test measurement results on Okuura SVC. The calculation results and the filed measurement results are consistent with each other, thus the validity of the new design method is verified on its accuracy and effectiveness.
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba; Christopher J. Ziolkowski
2004-06-30
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2003-10-01
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2003-04-01
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba; Christopher J. Ziolkowski
2005-01-17
This project aimed at developing a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GTI. GTI proposed to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or non-metallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2003-01-30
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba; Christopher J. Ziolkowski
2004-10-29
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or non-metallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2002-08-30
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2004-02-01
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2002-11-27
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD
DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION
Energy Technology Data Exchange (ETDEWEB)
Maximillian J. Kieba
2004-05-03
This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging
Kopp, Joachim; Liu, Jia; Slatyer, Tracy R.; Wang, Xiao-Ping; Xue, Wei
2016-01-01
We consider a new class of thermal dark matter models, dubbed "Impeded Dark Matter", in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. We demonstrate that either case can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonst...
2010-11-30
ELECTROMAGNEETIC SURFACE IMPEDANCE PROPERTIES FA9550-09-C-0198 DR. ADOUR KABAKIAN HUGHES RESEARCH LABS AFOSR / RSE 875 North Randolph Street, Suit...325 Room 3112 Arlington, Virginia 22203-1768 AFOSR / RSE AFRL-OSR-VA-TR-2012-0770 Distribution A We have investigated and determined how the tensor...the case of a TM wave, which favors propagation along the shorter principal axis. Standard terms apply U U U UU Arje Nachman RSE (Program Manager
Resonance reduction for AC drives with small capacitance in the DC link
DEFF Research Database (Denmark)
Máthé, Lászlo; Török, Lajos; Wang, Dong;
2016-01-01
Pulse Width Modulated AC drives equipped with small DC-link capacitor are becoming an attractive solution for electric drive applications with moderate requirements for shaft dynamic performance. However, when these drives are fed from a weak grid a resonance between the line side impedance and t...... from the motor current. The method has been experimentally validated and the results show excellent performance. Moreover, the proposed compensation method can be applied for any kind of load connected to a three-phase passive rectifier equipped with small capacitor....... and the DC-link capacitor appears. Due to this resonance, the THD and the partially weighted harmonic distortion of the line currents are increased, which may rise compatibility problems with the AC line harmonic standards. By using vector control the motor drive is transformed into a constant power load...
Institute of Scientific and Technical Information of China (English)
黄建明; 吴春华; 徐坤; 付立
2012-01-01
The operation principle of photovoltaic optimizer system and the essence of maximum power point tracking (MPPT) are introduced. Each PV module adopts MPPT control algorithm in photovoltaic optimizer system, which leads to wrong judgment of the traditional MPPT method due to the load impedance perturbation. Based on the equivalent load impedance perturbation, the distributed maximum power point tracking (DMPPT) is proposed to solve the problem. Considering the disturbance of control variables and load impedance to track MPP, the interaction between individual modules in the photovoltaic optimizer system is avoided. Finally, comparative experiments prove that the DMPPT method based on the equivalent load impedance perturbation proposed in this paper has the advantage of quick response and perturbation resistance to load impedance. Furthermore, the stability of this method is better than conventional MPPT method.%介绍了光伏优化器系统的工作原理及最大功率点跟踪的本质.针对光伏优化器系统中每块光伏组件进行MPPT控制,造成传统MPPT方法由于负载阻抗扰动而引起误判断的问题,提出了一种基于等效负载阻抗扰动的分布式最大功率点跟踪方法.该方法综合考虑控制量扰动和负载阻抗扰动进行MPPT判断,避免光伏优化器系统中各个独立模块之间的相互影响.通过对比实验证明提出的基于等效负载阻抗扰动的最大功率点跟踪方法具有快速的响应能力及抗负载阻抗扰动能力,其稳定性优于传统的MPPT方法.
AC 410 AC410 AC410 Unit 7 Homework Assignment
Laynebaril1
2017-01-01
AC 410 AC410 AC410 Unit 7 Homework Assignment Click Link Below To Buy: http://hwcampus.com/shop/ac410-unit-7-homework-assignment/ Questions Requiring Analysis 14-30 Early in your first audit of Star Corporation, you notice that sales and year-end inventory are almost unchanged from the prior year. However, cost of goods sold is less than in the preceding year, and accounts payable also are down substantially. Gross profit has increased, but this increase has not c...
Directory of Open Access Journals (Sweden)
Shanming Wang
2015-01-01
Full Text Available Now electric machines integrate with power electronics to form inseparable systems in lots of applications for high performance. For such systems, two kinds of nonlinearities, the magnetic nonlinearity of iron core and the circuit nonlinearity caused by power electronics devices, coexist at the same time, which makes simulation time-consuming. In this paper, the multiloop model combined with FE model of AC-DC synchronous generators, as one example of electric machine with power electronics system, is set up. FE method is applied for magnetic nonlinearity and variable-step variable-topology simulation method is applied for circuit nonlinearity. In order to improve the simulation speed, the incomplete Cholesky conjugate gradient (ICCG method is used to solve the state equation. However, when power electronics device switches off, the convergence difficulty occurs. So a straightforward approach to achieve convergence of simulation is proposed. At last, the simulation results are compared with the experiments.
Line impedance estimation using model based identification technique
DEFF Research Database (Denmark)
Ciobotaru, Mihai; Agelidis, Vassilios; Teodorescu, Remus
2011-01-01
into the operation of the grid-connected power converters. This paper describes a quasi passive method for estimating the line impedance of the distribution electricity network. The method uses the model based identification technique to obtain the resistive and inductive parts of the line impedance. The quasi......The estimation of the line impedance can be used by the control of numerous grid-connected systems, such as active filters, islanding detection techniques, non-linear current controllers, detection of the on/off grid operation mode. Therefore, estimating the line impedance can add extra functions...
A compact wideband precision impedance measurement system based on digital auto-balancing bridge
Hu, Binxin; Wang, Jinyu; Song, Guangdong; Zhang, Faxiang
2016-05-01
The ac impedance spectroscopy measurements are predominantly taken by using impedance analyzers based on analog auto-balancing bridge. However, those bench-top analyzers are generally complicated, bulky and expensive, thus limiting their usage in industrial field applications. This paper presents the development of a compact wideband precision measurement system based on digital auto-balancing bridge. The methods of digital auto-balancing bridge and digital lock-in amplifier are analyzed theoretically. The overall design and several key sections including null detector, direct digital synthesizer-based sampling clock, and digital control unit are introduced in detail. The results show that the system achieves a basic measurement accuracy of 0.05% with a frequency range of 20 Hz-2 MHz. The advantages of versatile measurement capacity, fast measurement speed, small size and low cost make it quite suitable for industrial field applications. It is demonstrated that this system is practical and effective by applying in determining the impedance-temperature characteristic of a motor starter PTC thermistor.
Observations involving broadband impedance modelling
Energy Technology Data Exchange (ETDEWEB)
Berg, J.S. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)
1996-08-01
Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impedance. This paper discusses three aspects of broadband impedance modelling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f. cavity. The last is a discussion of requirements for the mathematical form of an impedance which follow from the general properties of impedances. (author)
Characterization of electro-acoustics impedance and its application to active noise control
Institute of Scientific and Technical Information of China (English)
HOU Hong; YANG Jianhua
2004-01-01
Characteristics of radiation impedance and its inducing variation of electrical impedance for a controllable source have been investigated. An impedance-based error criterion has been proposed and its application to Active Noise Control is demonstrated through a coil driven loudspeaker. A general formula of radiation impedance is derived for two control strategies, according to the criterion of total acoustic power output. The radiation impedances of some commonly used sound sources are calculated. We discuss in detail the relation between variation of the input electrical impedance and radiation impedance for the two control strategies. The measured data of the input electrical impedance from a loudspeaker agree fairly well with theoretical analysis. An AC- bridge circuit is designed in order to measure the weak variation of electrical impedance resulted from radiation impedance. The bridge relative output is unique for a certain control strategy, from which an impedance-based error criterion is then proposed and the implementation of its application to an active control system is analyzed.Numerical results of such criterion are presented. An analogue control system is set up and experiments are carried out in a semi-anechoic chamber to verify the new control approach.
Reciprocity and mutual impedance formulas within lossy cavities
Directory of Open Access Journals (Sweden)
F. Gronwald
2005-01-01
Full Text Available We discuss the validity of reciprocity and mutual impedance formulas within lossy cavities. Mutual impedance formulas are well-known from antenna theory and useful to describe the electromagnetic coupling between electromagnetic interference sources and victims. As an example the mutual impedance between two dipole antennas within a lossy rectangular cavity is calculated from a system of coupled Hallén's equations that efficiently is solved by the method of moments.
Line Impedance Estimation Using Active and Reactive Power Variations
DEFF Research Database (Denmark)
Timbus, Adrian Vasile; Rodriguez, Pedro; Teodorescu, Remus;
2007-01-01
This paper proposes an estimation method of power system impedance based on power variations caused by a distributed power generation system (DPGS) at the point of common coupling (PCC). The proposed algorithm is computationally simple and uses the voltage variations at the point of common coupling...... (PCC) caused by the variations of the power delivered to utility network to derive the value of grid impedance. Accurate estimation of both resistive and inductive part of the impedance is obtained, as the results presented show....
DEFF Research Database (Denmark)
Kwon, JunBum; Wang, Xiongfei; Bak, Claus Leth;
2014-01-01
This paper addresses the harmonic compensation error problem existing with parallel connected inverter in the same grid interface conditions by means of impedance-based analysis and modeling. Unlike the single grid connected inverter, it is found that multiple parallel connected inverters and grid...... impedance can make influence to each other if they each have a harmonic compensation function. The analysis method proposed in this paper is based on the relationship between the overall output impedance and input impedance of parallel connected inverter, where controller gain design method, which can...
Blaskiewicz, M.; Dooling, J.; Dyachkov, M.; Fedotov, A.; Gluckstern, R.; Hahn, H.; Huang, H.; Kurennoy, S.; Linnecar, T.; Shaposhnikova, E.; Stupakov, G.; Toyama, T.; Wang, J. G.; Weng, W. T.; Zhang, S. Y.; Zotter, B.
1999-12-01
The impedance working group was charged to reply to the following 8 questions relevant to the design of high-intensity proton machines such as the SNS or the FNAL driver. These questions were first discussed one by one in the whole group, then each ne of them assigned to one member to summarize. On the lst morning these contributions were publicly read, re-discussed and re-written where required—hence they are not the opinion of a particular person, but rather the averaged opinion of all members of the working group. (AIP)
Beam measurements of the LHC impedance and validation of the impedance model
Esteban Müller, J F; Bohl, T; Mounet, N; Shaposhnikova, E; Timko, H
2014-01-01
Different measurements of the longitudinal impedance of the LHC done with single bunches with various intensities and longitudinal emittances during measurement sessions in 2011-2012 are compared with particle simulations based on the existing LHC impedance model. The very low reactive impedance of the LHC, with Im Z=n = 0.08, is not easy to measure. The most sensitive observation is the loss of Landau damping, which shows at which energy bunches become unstable depending on their parameters. In addition, the synchrotron frequency shift due to the reactive impedance was estimated following two methods. Firstly, it was obtained from the peak-detected Schottky spectrum. Secondly, a sine modulation in the RF phase was applied to the bunches of different intensities and the modulation frequency was scanned. In both cases, the synchrotron frequency shift was of the order of the measurement precision.
Huang, Jun; Li, Zhe; Zhang, Jianbo
2015-01-01
In this study, a novel implementation of dynamic electrochemical impedance spectroscopy (DEIS) is proposed. The method first measures the impedance continuously at a single frequency during one charging/discharging cycle, then repeats the measurement at a number of other selected frequencies. The impedance spectrum at a specific SOC is obtained by interpolating and collecting the impedance at all of the selected frequencies. The charge transfer resistance, Rct, from the DEIS is smaller than that from the steady EIS in a wide state-of-charge (SOC) range from 0.4 to 1.0, the Rct during charging is generally smaller than that during discharging for the battery chemistry used in this study.
Energy Technology Data Exchange (ETDEWEB)
Hayat, N. [Graduate School, Toyohashi Univ. of Technology, Toyohashi-city, Aichi (Japan); Toda, H.; Kobayashi, T. [Faculty of Engineering, Toyohashi Univ. of Technology, Toyohashi-city, Aichi (Japan); Wade, N. [Topy Industries Ltd., Toyohashi-city, Aichi (Japan)
2002-07-01
This study investigates the fatigue characteristics of AC4CH cast aluminum alloys fabricated through the semi-solid metal (rheocasting) process by employing the inclined cooling plate technique with a wide range of spherical {alpha} size (38-160 {mu}m) and compares with those of the conventional squeeze casting. Rheocasting process employing an inclined cooling plate is based on the crystal separation theory. The results of measured microstructural parameters indicate that aspect ratio and size of eutectic Si and size of intermetallic compound decrease with the decrease in primary {alpha} size. The fatigue strength increases with decreases in primary {alpha} size and the material with the minimum primary {alpha} size (i.e. 38 {mu}m) shows 11.3% higher fatigue strength at 10{sup 7} cycles than that of the squeeze cast material. Although difference in damage accumulation behaviors during tensile loading is quantified by the in-situ studies, however, it does not seem to have discernable effect on the fatigue properties. The Si and intermetallic compound particles remain almost intact below 250 MPa and 200 MPa respectively in all of the materials and damage evolution occurs at the lowest stress level in the squeeze cast material. Moreover, the maximum fraction of the damaged particles depends upon the primary {alpha} size and reaches the maximum with the minimum primary {alpha} size. The crack growth rates through each phase indicate that the main difference between the rheocast and the squeeze cast material is in the crack propagation across the grain boundaries with the other regions having almost comparable crack propagation rates in the same as well as between different materials. The fact that even decrease in grain size does not lead to the impressive improvement in fatigue strength can not be attributed to the difference in grain structure according to quantitative investigation of misorientation angles between neighboring grains utilizing a scanning electron
Institute of Scientific and Technical Information of China (English)
郑子迎; 车汉生; 吴源伟
2014-01-01
The sealing method of samples is an important factor affecting the measurement results in the measurement of sound transmission loss in the impedance tube. This paper introduces the test method and focuses on the specimen installation and sealing method in the impedance tube. By comparing 4 kinds of sealing methods, the performances of these methods are sorted. It provides reference for measurement of the sound transmission loss.%阻抗管法法向入射隔声量测试过程中，试样与阻抗管间的密封方式是测量结果的一个重要的影响因素。介绍了阻抗管测量法向入射隔声量的方法，重点介绍在阻抗管中的试样安装和密封方法，通过实施4种不同的密封方法，得出密封效果的排序，对阻抗法测量隔声量的试验实施具有参考价值。
Electrical transport properties of CoMn0.2−xGaxFe1.8O4 ferrites using complex impedance spectroscopy
Directory of Open Access Journals (Sweden)
Chien-Yie Tsay
2016-05-01
Full Text Available In this study, we report the influence of Ga content on the microstructural, magnetic, and AC impedance properties of Co-based ferrites with compositions of CoMn0.2−xGaxFe1.8O4 (x=0, 0.1, and 0.2 prepared by the solid-state reaction method. Experimental results showed that the as-prepared Co-based ferrites had a single-phase spinel structure; the Curie temperature of Co-based ferrites decreased with increasing Ga content. All ferrite samples exhibited a typical hysteresis behavior with good values of saturation magnetization at room temperature. The electrical properties of Co-based ferrites were investigated using complex impedance spectroscopy analysis in the frequency range of 100 kHz-50 MHz at temperatures of 150 to 250 oC. The impedance analysis revealed that the magnitudes of the real part (Z’ and the imaginary part (Z” of complex impedance decreased with increasing temperature. Only one semicircle was observed in each complex impedance plane plot, which revealed that the contribution to conductivity was from the grain boundaries. It was found that the relaxation time for the grain boundary (τgb also decreased with increasing temperature. The values of resistance for the grain boundary (Rgb significantly increased with increasing Ga content, which indicated that the incorporation of Ga into Co-based ferrites enhanced the electrical resistivity.
Electrical transport properties of CoMn0.2-xGaxFe1.8O4 ferrites using complex impedance spectroscopy
Tsay, Chien-Yie; Lin, Yi-Hsiang; Wang, Yao-Ming; Chang, Horng-Yi; Lei, Chien-Ming; Jen, Shien-Uang
2016-05-01
In this study, we report the influence of Ga content on the microstructural, magnetic, and AC impedance properties of Co-based ferrites with compositions of CoMn0.2-xGaxFe1.8O4 (x=0, 0.1, and 0.2) prepared by the solid-state reaction method. Experimental results showed that the as-prepared Co-based ferrites had a single-phase spinel structure; the Curie temperature of Co-based ferrites decreased with increasing Ga content. All ferrite samples exhibited a typical hysteresis behavior with good values of saturation magnetization at room temperature. The electrical properties of Co-based ferrites were investigated using complex impedance spectroscopy analysis in the frequency range of 100 kHz-50 MHz at temperatures of 150 to 250 oC. The impedance analysis revealed that the magnitudes of the real part (Z') and the imaginary part (Z") of complex impedance decreased with increasing temperature. Only one semicircle was observed in each complex impedance plane plot, which revealed that the contribution to conductivity was from the grain boundaries. It was found that the relaxation time for the grain boundary (τgb) also decreased with increasing temperature. The values of resistance for the grain boundary (Rgb) significantly increased with increasing Ga content, which indicated that the incorporation of Ga into Co-based ferrites enhanced the electrical resistivity.
Lorentz Force Electrical Impedance Tomography
Grasland-Mongrain, Pol; Chapelon, Jean-Yves; Lafon, Cyril
2014-01-01
This article describes a method called Lorentz Force Electrical Impedance Tomography. The electrical conductivity of biological tissues can be measured through their sonication in a magnetic field: the vibration of the tissues inside the field induces an electrical current by Lorentz force. This current, detected by electrodes placed around the sample, is proportional to the ultrasonic pressure, to the strength of the magnetic field and to the electrical conductivity gradient along the acoustic axis. By focusing at different places inside the sample, a map of the electrical conductivity gradient can be established. In this study experiments were conducted on a gelatin phantom and on a beef sample, successively placed in a 300 mT magnetic field and sonicated with an ultrasonic transducer focused at 21 cm emitting 500 kHz bursts. Although all interfaces are not visible, in this exploratory study a good correlation is observed between the electrical conductivity image and the ultrasonic image. This method offers...
Resonant impedance of bellows above cutoff
Energy Technology Data Exchange (ETDEWEB)
Krinsky, S
1980-01-01
The perturbation method of Chatard-Moulin and Papiernik is used to calculate the longitudinal and transverse impedances, Z(..omega..) and Z/sub perpendicular/(..omega..), of a bellows. The bellows shape is defined by its radius a(z) = a (1 + epsilons(z)), where a is the mean radius, epsilon a small parameter, and s(z) describes the convolution of the bellows. A finite wall conductivity is considered and the resonant contribution to the impedance above the cutoff frequency of the unperturbed chamber is determined, obtaining analytic approximations to the resonant frequencies, quality factors, and shunt impedances. The relation Z/sub perpendicular/(..omega..) = (2c/a/sup 2/)Z(..omega..)/..omega.., of course, does not hold as an identity, but it is found to be a useful relation for the shunt impedances, holding exactly for one family of transverse modes and providing an upper bound on the shunt impedances of the second set of transverse modes.
Impedance spectroscopy study of polycrystalline Bi6Fe2Ti3O18
Indian Academy of Sciences (India)
K Srinivas; P Sarah; S V Suryanarayana
2003-02-01
The electrical properties of polycrystalline Bi6Fe2Ti3O18 are investigated by impedance spectroscopy in the temperature range 30–550°C. The imaginary part of impedance as a function of frequency shows Debye like relaxation. Impedance data are presented in the Nyquist plot which is used to identify an equivalent circuit and the fundamental circuit parameters are determined at different temperatures. The grain and grain-boundary contributions are estimated. The results of bulk a.c. conductivity as a function of temperature and frequency are presented. The activation energies for the a.c. conductivity are calculated. The polaron hopping frequencies are estimated from the a.c. conductivity data.
Energy Technology Data Exchange (ETDEWEB)
Radicke, Marcus
2009-12-18
The method presented in this thesis combines ultrasound techniques with the magnetic-resonance tomography (MRT). An ultrasonic wave generates in absorbing media a static force in sound-propagation direction. The force leads at sound intensities of some W/cm{sup 2} and a sound frequency in the lower MHz range to a tissue shift in the micrometer range. This tissue shift depends on the sound power, the sound frequency, the sound absorption, and the elastic properties of the tissue. A MRT sequence of the Siemens Healthcare AG was modified so that it measures (indirectly) the tissue shift, codes as grey values, and presents as 2D picture. By means of the grey values the sound-beam slope in the tissue can be visualized, and so additionally sound obstacles (changes of the sound impedance) can be detected. By the MRT images token up spatial changes of the tissue parameters sound absorption and elasticity can be detected. In this thesis measurements are presented, which show the feasibility and future chances of this method especially for the mammary-cancer diagnostics. [German] Die in dieser Arbeit praesentierte Methode kombiniert Ultraschalltechniken mit der Magnetresonanztomographie (MRT). Eine Ultraschallwelle ruft in absorbierenden Medien eine statische Kraft in Schallausbreitungsrichtung hervor. Die Kraft fuehrt bei Schallintensitaeten von einigen W/cm{sup 2} und einer Schallfrequenz im niederen MHz-Bereich zu einer Gewebeverschiebung im Mikrometerbereich. Diese Gewebeverschiebung haengt ab von der Schallleistung, der Schallfrequenz, der Schallabsorption und den elastischen Eigenschaften des Gewebes. Es wurde eine MRT-Sequenz der Siemens Healthcare AG modifiziert, so dass sie (indirekt) die Gewebeverschiebung misst, als Grauwerte kodiert und als 2D-Bild darstellt. Anhand der Grauwerte kann der Schallstrahlverlauf in dem Gewebe visualisiert werden, und so koennen zusaetzlich Schallhindernisse (Aenderungen der Schallkennimpedanz) aufgespuert werden. Mit den
Outdoor ground impedance models.
Attenborough, Keith; Bashir, Imran; Taherzadeh, Shahram
2011-05-01
Many models for the acoustical properties of rigid-porous media require knowledge of parameter values that are not available for outdoor ground surfaces. The relationship used between tortuosity and porosity for stacked spheres results in five characteristic impedance models that require not more than two adjustable parameters. These models and hard-backed-layer versions are considered further through numerical fitting of 42 short range level difference spectra measured over various ground surfaces. For all but eight sites, slit-pore, phenomenological and variable porosity models yield lower fitting errors than those given by the widely used one-parameter semi-empirical model. Data for 12 of 26 grassland sites and for three beech wood sites are fitted better by hard-backed-layer models. Parameter values obtained by fitting slit-pore and phenomenological models to data for relatively low flow resistivity grounds, such as forest floors, porous asphalt, and gravel, are consistent with values that have been obtained non-acoustically. Three impedance models yield reasonable fits to a narrow band excess attenuation spectrum measured at short range over railway ballast but, if extended reaction is taken into account, the hard-backed-layer version of the slit-pore model gives the most reasonable parameter values.
Harasztosi, Csaba; Gummer, Anthony W.
2011-11-01
The voltage-dependent chloride-channel blocker anthracene-9-carboxylic acid (9AC) has been found to reduce the imaginary but not the real part of the mechanical impedance of the organ of Corti, suggesting that the effective stiffness of outer hair cells (OHCs) is reduced by 9AC. To examine whether 9AC interacts directly with the motor protein prestin to reduce the membrane component of the impedance, the patch-clamp technique in whole-cell configuration was used to measure the nonlinear capacitance (NLC) of isolated OHCs and, as control, prestin-transfected human embryonic kidney 293 (HEK293) cells. Extracellular application of 9AC significantly reduced the NLC of both OHCs and HEK293 cells. Intracellular 9AC did not influence the blocking effect of the extracellular applied drug. These results suggest that 9AC interacts directly with prestin, reducing the effective stiffness of the motor, and that the interaction is extracellular.
Institute of Scientific and Technical Information of China (English)
曹文芳; 孙浩帆; 苏邵
2015-01-01
An AC impedance aptasensor has been developed for label-free adenosine triphosphate (ATP) determination based on gold nanoparticles-decorated MoS2 (AuNPs@ MoS2 ) nanocomposite .AuNPs@ MoS2 nanocomposite has been synthesized by using MoS2 self-reduction ability .The ATP aptamer (ATPA) was immobilized on the surface of AuNPs@ MoS2 modified electrode via Au-S ,which can selectively detect ATP by using K3 Fe(CN)6 and K4 Fe(CN)6 as the electrochemical indicator .The structure of ATPA is switched with the ATP addition ,resulting in the electron transfer is blocked and the resistance value increases .The ex-perimental results show that the linear range of the MoS2-based sensor is 10 nmol/L-1 mmol/L with a detection limit of 1 nmol/L .Moreover ,the sensor can efficiently distinguish ATP ,CTP ,GTP and UTP ,suggesting the sensor has high sensitivity and good selectivity .This proposed biosensor can offer a potential application for other biomolecules detection .%为了实现对三磷酸腺苷（ATP）无标记、高灵敏地检测，构建了基于二硫化钼的交流阻抗适体传感器。利用二硫化钼自身的还原性成功合成了金纳米颗粒功能化二硫化钼（AuNPs＠ MoS2）纳米复合材料，并通过Au-S键将ATP核酸适体组装到AuNPs＠ MoS2修饰电极表面。当核酸适体与ATP结合后，其构型发生变化，将会阻碍电化学信号分子K3Fe（CN）6和K4Fe （CN）6与修饰电极间的电子传递，使该适体传感器的电阻变大。在最优条件下，该传感器检测ATP的线性范围为10 nmol／L～1 mmol／L ，检出限为1 nmol／L ，并能很好地区分ATP与CTP、GTP和UTP ，表明该传感器具有较高的检测灵敏度和良好的特异性。该传感器的成功构建，为其他生物分子的检测提供了新的思路。
Renk, Timothy; Simpson, Sean; Webb, Timothy; Mazarakis, Michael; Kiefer, Mark
2016-10-01
The SMP diode, fielded on the RITS-6 (3.5-8.5 MV) IVA accelerator at Sandia National Laboratories, produces a focused electron beam (IVA flow impedance has on ZDIODE. A preliminary conclusion is that ZDIODE should be at least 1.5 times the flow impedance before ZDIODE is a parameter independent of flow impedance. This has implications for SMP as a load for a IVA, since ZDIODE >100 ohms has not been consistently demonstrated. Data analysis is ongoing, and latest results will be reported. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
On coupling impedances of pumping holes
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S.
1993-04-01
Coupling impedances of a single small hole in vacuum-chamber walls have been calculated at low frequencies. To generalize these results for higher frequencies and/or larger holes one needs to solve coupled integral equations for the effective currents. These equations are solved for two specific hole shapes. The effects of many holes at high frequencies where the impedances are not additive are studied using a perturbation-theory method. The periodic versus random distributions of the pumping holes in the Superconducting Super Collider liner are compared.
Bench Measurements of Low Frequency Transverse Impedance
Caspers, Friedhelm; Mostacci, A
2003-01-01
For frequencies below 10 MHz the classical two wire transmission line method is subject to difficulties in sensitivity and measurement uncertainties. Thus for evaluation of the low frequency transverse impedance properties of the LHC dump kicker a modified version of the two wire transmission line has been used. It consists, in the present case, of a 10 turn loop of approximately 1 meter length and 2 cm width. The change of input impedance of the loop is measured as a function of the surroundings and by using a proper reference (metallic beampipe) these changes are converted into a meaningful transverse beam coupling impedance. Measurements of several calibration objects have shown close agreement with theoretical results.
Impedance properties of circular microstrip antenna
Deshpande, M. D.; Bailey, M. C.
1983-01-01
A moment method solution to the input impedance of a circular microstrip antenna excited by either a microstrip feed or a coaxial probe is presented. Using the exact dyadic Green's function and the Fourier transform the problem is formulated in terms of Richmond's reaction integral equation from which the unknown patch current can be solved for. The patch current is expanded in terms of regular surface patch modes and an attachment mode (for probe excited case) which insures continuity of the current at probe/patch junction, proper polarization and p-dependance of patch current in the vicinity of the probe. The input impedance of a circular microstrip antenna is computed and compared with earlier results. Effect of attachment mode on the input impedance is also discussed.
Impedance plethysmographic observations in thoracic outlet syndrome.
Directory of Open Access Journals (Sweden)
Nerurkar S
1990-07-01
Full Text Available Forty patients with symptoms of neuro-vascular compression in the upper extremities were subjected to impedance plethysmographic study using Parulkar′s method. Two patients recorded decreased blood flow (BFI in supine position and were diagnosed as having partial occlusion at subclavian level. Sixteen of the patients recorded decreased BFI on 90 degrees abduction and hyper-abduction. Twelve of these patients had radiological evidence of anomalous cervicle ribs. In remaining four patients extrinsic impression on the subclavian artery due to fibrous deposits was confirmed by arteriography. Remaining 22 patients recorded normal impedance plethysmograms. Impedance plethysmography thus provided a non-invasive modality for confirmation of vascular compression in thoracic outlet syndrome.
Bio-impedance detector for Staphylococcus aureus exposed to magnetic fields
Younis Yacoob Aldosky, Haval; Barwari, Waleed Jameel Omar; Salih Al-mlaly, Janan M.
2012-12-01
Rapid detection of viability and growth of pathogenic microorganisms is very important in many applications such as food and drug production, health care, and national defense. Measurements on the electrical characteristics of cells have been used successfully in the past to detect many different physiological events. The effect of electromagnetic fields on the growth of bacteria (Staphylococcus aureus) was studied with the bio-impedance technique. The growth situations of bacteria in the absence and presence of different intensities of static and alternative magnetic fields were examined and analyzed. The results show that the impedance of bacteria fell in the presence of DC magnetic fields. In contrast the impedance increased when the bacteria were exposed to AC magnetic fields. Based on these results the bacterial growth indicated by the change in the impedance is inhibited under DC magnetic fields and enhanced under AC fields.
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Blaabjerg, Frede; Galigekere, Veda Prakash;
2016-01-01
A novel A-source impedance network is proposed in this letter. The A-source impedance network uses an autotransformer for realizing converters for any application that demand a very high dc voltage gain. The network utilizes a minimal turns ratio compared to other Magnetically Coupled Impedance S...... with an example single-switch 400 W dc-dc converter. For the closed-loop control design and stability assessment, a small signal model and its analysis of the proposed network are also presented in brief.......A novel A-source impedance network is proposed in this letter. The A-source impedance network uses an autotransformer for realizing converters for any application that demand a very high dc voltage gain. The network utilizes a minimal turns ratio compared to other Magnetically Coupled Impedance...
Yıldız, Alptekin; Canli, Nimet Yilmaz; Karanlık, Gürkan; Ocak, Hale; Okutan, Mustafa; Eran, Belkız Bilgin
2016-12-01
Dielectric spectroscopy (DS) is a very powerful and important for better understanding of the molecular dynamics and relaxation phenomena in liquid crystals. The dielectric and impedance characteristics Ethyl 4-(7,7,8,8,9,9,10,10,10-nonafluorodecyloxy)biphenyl-4‧-carboxylate (ENBC) liquid crystal have been analyzed over the frequency range of 100 Hz to MHz in the temperature region from room temperature to 180 °C. The compound ENBC shows enantiotropic a smectic mesophase in a wide temperature range. The phase transition temperatures T (°C) of the liquid crystal ENBC, which were characterized by Differential Scanning Calorimetry (DSC), have been verified by the dielectric measurements and conductivity mechanisms of the ENBC. The activation energies for some selected angular frequencies have also been calculated.
Bioelectrical impedance analysis--part I
DEFF Research Database (Denmark)
Kyle, Ursula G; Bosaeus, Ingvar; De Lorenzo, Antonio D;
2004-01-01
The use of bioelectrical impedance analysis (BIA) is widespread both in healthy subjects and patients, but suffers from a lack of standardized method and quality control procedures. BIA allows the determination of the fat-free mass (FFM) and total body water (TBW) in subjects without significant ...
Application of dynamic impedance spectroscopy to atomic force microscopy
Directory of Open Access Journals (Sweden)
Kazimierz Darowicki, Artur Zieliński and Krzysztof J Kurzydłowski
2008-01-01
Full Text Available Atomic force microscopy (AFM is a universal imaging technique, while impedance spectroscopy is a fundamental method of determining the electrical properties of materials. It is useful to combine those techniques to obtain the spatial distribution of an impedance vector. This paper proposes a new combining approach utilizing multifrequency scanning and simultaneous AFM scanning of an investigated surface.
Electrochemical impedance spectroscopy in solid state ionics: recent advances
Boukamp, Bernard A.
2004-01-01
Electrochemical Impedance Spectroscopy (EIS) has become an important research tool in Solid State Ionics. Some new developments are highlighted: new methods of automatic parameter extraction from impedance measurements are briefly discussed. The Kramers–Kronig data validation test presents another p
A simple technique for a.c. conductivity measurements
Indian Academy of Sciences (India)
R Padma Suvarna; K Raghavendra Rao; K Subbarangaiah
2002-12-01
An inexpensive, indigenous and a simple electronic instrument based on voltage follower, current–to–voltage converter, zero crossing detector and a phase detector has been developed for measurement of a.c. conductivity. Real and imaginary parts of complex impedance are determined for a given sample as a function of frequency and the given sample is represented by a pure electronic model.
Oh, T; Gilad, O; Ghosh, A; Schuettler, M; Holder, D S
2011-05-01
Electrical impedance tomography (EIT) is a recently developed medical imaging method which has the potential to produce images of fast neuronal depolarization in the brain. Previous modelling suggested that applied current needed to be below 100 Hz but the signal-to-noise ratio (SNR) recorded with scalp electrodes during evoked responses was too low to permit imaging. A novel method in which contemporaneous evoked potentials are subtracted is presented with current applied at 225 Hz to cerebral cortex during evoked activity; although the signal is smaller than at DC by about 10×, the principal noise from the EEG is reduced by about 1000×, resulting in an improved SNR. It was validated with recording of compound action potentials in crab walking leg nerve where peak changes of -0.2% at 125 and 175 Hz tallied with biophysical modelling. In recording from rat cerebral cortex during somatosensory evoked responses, peak impedance decreases of -0.07 ± 0.006% (mean ± SE) with a SNR of >50 could be recorded at 225 Hz. This method provides a reproducible and artefact free means for recording resistance changes during neuronal activity which could form the basis for imaging fast neural activity in the brain.
Harmonic Stability Analysis of Inverter-Fed Power Systems Using Component Connection Method
DEFF Research Database (Denmark)
Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede
2016-01-01
This paper presents a Component Connection Method (CCM)-based harmonic stability analysis for ac power-electronic-fed power systems. In the approach, the system is partitioned as individual components, including the controllers of DG units, LC filters, network impedances, and power loads. They ar...
Cross-Circulating Current Suppression Method for Parallel Three-Phase Two-Level Inverters
DEFF Research Database (Denmark)
Wei, Baoze; Guerrero, Josep M.; Guo, Xiaoqiang
2015-01-01
The parallel architecture is very popular for power inverters to increase the power level. This paper presents a method for the parallel operation of inverters in an ac-distributed system, to suppress the cross-circulating current based on virtual impedance without current-sharing bus...
Analyzing Impedance Spectroscopy Results
Institute of Scientific and Technical Information of China (English)
Yoed Tsur; Sioma Baltianski
2006-01-01
In this contribution we briefly discuss several analysis techniques for impedance spectroscopy experiments. A number of different approaches, which differ even by the definition of the problem, are used in the literature. Some aimed towards finding an equivalent circuit. Others aimed towards finding directly dielectric properties of the material under an assumed model. Others towards finding distribution of relaxation times, either parametric or point-by point. No matter what the approach is, this will always be an ill-posed problem in the sense that there exist a large number of possible solutions that solve the problem (mathematically) equally well. Therefore some a-priori knowledge about the system must be used. In addition, we should remember that the ultimate goal is to get physical insight about the system.
Energy Technology Data Exchange (ETDEWEB)
RoyChaudhuri, C. [Department of Electronics and Telecommunication Engineering, Bengal Engineering and Science University, Shibpur, Botanic Garden, Howrah 711103 (India); Jana, M.; Bandopadhyay, N.R. [School of Materials Science and Engineering, Bengal Engineering and Science University, Shibpur, Botanic Garden, Howrah 711103 (India)
2010-09-15
In this paper, a simple and convenient method based on impedance measurement has been proposed for the first time to evaluate the average porosity, pore radius, and internal surface area of macroporous silicon structure fabricated by electrochemical method. The porosity and the average pore radius have been obtained by developing a geometrical model and applying the generalized effective medium approximation theory to the dc and ac impedance measurement of both unoxidized and thermally oxidized macroporous silicon. The internal surface area per unit volume is then computed from the porosity and the pore radius using the same model. The method has been applied to a wide range of porosity from 30 to 58% fabricated on p-type <100> silicon with a resistivity of 10-20 {omega} cm. Experimental verification of porosity, mean pore radius, and internal surface area have been performed by standard gravimetric technique and by top-view and cross-section SEM imaging, respectively. A typical mean pore radius, porosity, and internal surface area of a macroporous silicon sample has been obtained to be 1.52 {mu}m, 54.2%, and 3565.7 cm{sup 2}/cm{sup 3}, respectively, from the impedance measurement and 1.5 {mu}m, 55%, and 3666.7 cm{sup 2}/cm{sup 3} from SEM and gravimetric analysis which shows that the results are within 2% of the values obtained by conventional methods. The advantages of this method over the other recently reported techniques for similar characterization have been discussed. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Development on electromagnetic impedance function modeling and its estimation
Energy Technology Data Exchange (ETDEWEB)
Sutarno, D., E-mail: Sutarno@fi.itb.ac.id [Earth Physics and Complex System Division Faculty of Mathematics and Natural Sciences Institut Teknologi Bandung (Indonesia)
2015-09-30
Today the Electromagnetic methods such as magnetotellurics (MT) and controlled sources audio MT (CSAMT) is used in a broad variety of applications. Its usefulness in poor seismic areas and its negligible environmental impact are integral parts of effective exploration at minimum cost. As exploration was forced into more difficult areas, the importance of MT and CSAMT, in conjunction with other techniques, has tended to grow continuously. However, there are obviously important and difficult problems remaining to be solved concerning our ability to collect process and interpret MT as well as CSAMT in complex 3D structural environments. This talk aim at reviewing and discussing the recent development on MT as well as CSAMT impedance functions modeling, and also some improvements on estimation procedures for the corresponding impedance functions. In MT impedance modeling, research efforts focus on developing numerical method for computing the impedance functions of three dimensionally (3-D) earth resistivity models. On that reason, 3-D finite elements numerical modeling for the impedances is developed based on edge element method. Whereas, in the CSAMT case, the efforts were focused to accomplish the non-plane wave problem in the corresponding impedance functions. Concerning estimation of MT and CSAMT impedance functions, researches were focused on improving quality of the estimates. On that objective, non-linear regression approach based on the robust M-estimators and the Hilbert transform operating on the causal transfer functions, were used to dealing with outliers (abnormal data) which are frequently superimposed on a normal ambient MT as well as CSAMT noise fields. As validated, the proposed MT impedance modeling method gives acceptable results for standard three dimensional resistivity models. Whilst, the full solution based modeling that accommodate the non-plane wave effect for CSAMT impedances is applied for all measurement zones, including near-, transition
Jung, D. H.; Moon, I. K.; Jeong, Y. H.
2001-01-01
A new ac calorimeter, utilizing the Peltier effect of a thermocouple junction as an ac power source, is described. This Peltier ac calorimeter allows to measure the absolute value of heat capacity of small solid samples with sub-milligrams of mass. The calorimeter can also be used as a dynamic one with a dynamic range of several decades at low frequencies.
Institute of Scientific and Technical Information of China (English)
张胜凯; 黄文娟; 韩高峰
2012-01-01
To improve the utilization of branch roads and reduce the traffic pressure on arterial roads, the optimization approach of one-way traffic organization is proposed from the view of reducing network impedance and improving traffic efficiency. The bievel programming model is developed with the objective of minimizing network impedance and travel time. The minimum objectixie value of the upper model is obtained by optimizing one-way traffic, and the lower one adopts the capacity limitation-incremental loading method to distribute traffic flow. Through establishing virtual road network, the effectiveness of one-way traffic organization is proved by comparing the network impedance and travel time before and after optimization.%为提高支路的利用率，以降低主干道的交通压力，从降低路网阻抗及提高交通效率的角度出发，提出单向交通组织的优化方法。建立以路网阻抗及出行时间最小化为目标的双层优化模型，其中上层模型通过优化支路的单向交通组织方案使得目标值达到最小，下层模型按照容量限制——增量加栽方法进行交通量的重分配。通过建立虚拟路网，类比分析单向交通组织优化前后的路网阻抗及出行时间，验证单向交通组织的优化效果。
Institute of Scientific and Technical Information of China (English)
王泽南
2001-01-01
A simple method of so lving transfer function of mechanical system by mechanical impedance is proposed ,which is similar to the method of complex impedance in electrical system. Three basic elements of mechanical system are fixed into complex domain elements as t he spring, and the calculus of differential equations is reduced. Differing from electrical system, the structural diagrams of mechanical system need the chang e of series combinations of mass elements into parallel combinations, which is v ery simple.%文章提出了一种利用机械阻抗求取机械系统传递 函数的简便方法，它类似于电系统中的复阻抗方法。这种方法将机械系统3种基本元件固化 为类似弹簧的复域元件，使求取系统传递函数免去列写微分方程的环节。与电系统稍有不同 的是，这种方法需将机械系统结构图作适当的改形。改形也很简单，只要将串联形式的质量 元件改为并联即可。
A Multisection Broadband Impedance Transforming Branch-Line Hybrid
Kumar, S; Danshin, T
1995-01-01
Measurements and design equations for a two section impedance transforming hybrid suitable for MMIC applications and a new method of synthesis for multisection branch-line hybrids are reported. The synthesis method allows the response to be specified either of Butterworth or Chebyshev type. Both symmetric (with equal input and output impedances) and non-symmetric (impedance transforming) designs are feasible. Starting from a given number of sections, type of response, and impedance transformation ratio and for a specified midband coupling, power division ratio, isolation or directivity ripple bandwidth, the set of constants needed for the evaluation of the reflection coefficient response is first calculated. The latter is used to define a driving point impedance of the circuit, synthesize it and obtain the branch line immittances with the use of the concept of double length unit elements (DLUE). The experimental results obtained with microstrip hybrids constructed to test the validity of the brute force optim...
Modern Trends in Imaging XI: Impedance Measurements in the Biomedical Sciences
Directory of Open Access Journals (Sweden)
Frederick D. Coffman
2012-01-01
Full Text Available Biological organisms and their component organs, tissues and cells have unique electrical impedance properties. Impedance properties often change with changes in structure, composition, and metabolism, and can be indicative of the onset and progression of disease states. Over the past 100 years, instruments and analytical methods have been developed to measure the impedance properties of biological specimens and to utilize these measurements in both clinical and basic science settings. This chapter will review the applications of impedance measurements in the biomedical sciences, from whole body analysis to impedance measurements of single cells and cell monolayers, and how cellular impedance measuring instruments can now be used in high throughput screening applications.
SoC-Based Dynamic Power Sharing Method with AC-Bus Voltage Restoration for Microgrid Applications
DEFF Research Database (Denmark)
Lu, Xiaonan; Sun, Kai; Guerrero, Josep M.
2012-01-01
In a microgrid system, distributed energy storage units are commonly employed as the energy buffers. In this paper, a dynamic power sharing method based on the state-of-charge (SoC) of each energy storage unit is proposed. Droop control is employed as the basic control strategy for the distributed...... shared in the energy storage system. The relationship between the droop coefficient and SoC are studied deeply and the small signal model is developed to verify the stability of the control system. It is found that the active power sharing speed becomes faster with higher exponent of SoC. At the same...... energy storage units. By using the proposed method, the coefficients in the conventional droop method are adjusted according to the SoC of each energy storage module. The modules with higher SoC delivers more active power, while those with lower SoC delivers less. Meanwhile, the reactive power is equally...
Yoo, Hyun Deog; Jang, Jong Hyun; Ryu, Ji Heon; Park, Yuwon; Oh, Seung M.
2014-12-01
Electrochemical impedance analysis is performed to predict the rate capability of two commercial activated carbon electrodes (RP20 and MSP20) for electric double-layer capacitor. To this end, ac impedance data are fitted with an equivalent circuit that comprises ohmic resistance and impedance of intra-particle pores. To characterize the latter, ionic accessibility into intra-particle pores is profiled by using the fitted impedance parameters, and the profiles are transformed into utilizable capacitance plots as a function of charge-discharge rate. The rate capability that is predicted from the impedance analysis is well-matched with that observed from a charge-discharge rate test. It is found that rate capability is determined by ionic accessibility as well as ohmic voltage drop. A lower value in ionic accessibility for MSP20 is attributed to smaller pore diameter, longer length, and higher degree of complexity in pore structure.
Institute of Scientific and Technical Information of China (English)
王多君; 李和平; 刘丛强; 易丽; 丁东业; 苏根利; 张卫刚
2002-01-01
An electrical conductivity measurement system under high-pressure conditions with a multi-anvil high-pressure apparatus by an ac complex impedance method was set up. With this system, we have successfully measured the electrical conductivity of synthetic quartz under pressure up to approximately 1.0 GPa in the temperature range 661-987K. The values of electrical conductivity decrease with the increasing pressure and increase with the increasing temperature. The activation enthalpies for the α-quartz crystals are 1.10-1.28eV. The electrical conductivity of α-quartz is ionic, with Na ions moving in channels parallel to the c-axis being the predominant current carrier.
Directory of Open Access Journals (Sweden)
Rusalin Lucian R. Păun
2008-05-01
Full Text Available This paper propose a new control technique forsingle – phase AC – AC converters used for a on-line UPSwith a good dynamic response, a reduced-partscomponents, a good output characteristic, a good powerfactorcorrection(PFC. This converter no needs anisolation transformer. A power factor correction rectifierand an inverter with the proposed control scheme has beendesigned and simulated using Caspoc2007, validating theconcept.
Nuclear structure of $^{231}$Ac
Boutami, R; Mach, H; Kurcewicz, W; Fraile, L M; Gulda, K; Aas, A J; García-Raffi, L M; Løvhøiden, G; Martínez, T; Rubio, B; Taín, J L; Tengblad, O
2008-01-01
The low-energy structure of 231Ac has been investigated by means of gamma ray spectroscopy following the beta-decay of 231Ra. Multipolarities of 28 transitions have been established by measuring conversion electrons with a mini-orange electron spectrometer. The decay scheme of 231Ra --> 231Ac has been constructed for the first time. The Advanced Time Delayed beta-gamma-gamma(t) method has been used to measure the half-lives of five levels. The moderately fast B(E1) transition rates derived suggest that the octupole effects, albeit weak, are still present in this exotic nucleus.
Perioperative bioelectrical impedence analysis in neurosurgery.
El-Dawlatly, Abdelazeem A
2005-10-01
The use of bioelectrical impedence (BI) measurement to assess body composition has recently attracted the attention of anesthesiologists. Analysis of BI provides a non-invasive method to quantify fluid distribution in different body compartments. This study was designed to assess whether BI analysis reflects fluid depletion in neurosurgical patients with moderate blood loss. Six adult male patients scheduled for elective craniotomy under general anesthesia were studied. Exclusion criteria included patients with cardio-respiratory disease. BI analysis was performed at three stages, A, day before operation, B, during surgery and C, on the first postoperative day. Total body resistivity was measured by BI analysis with a four-terminal portable impedence analyzer. At each frequency, impedence was calculated as resistance (Rx)2 + reactance (Rc)2. The mean values of total body water (TBW) at stages A, B and C were 39.8 L (range: 33.1-46.7 L), 43.2 L (range: 33.1-66.2 L) and 36.8 L (range: 22.4-36.3 L) respectively with significant differences (P<0.05). The impedence at the three frequencies during stages A, B and C showed significant differences (P<0.05). In conclusion, we have found that in male neurosurgical patients multiple frequency BI measurements has reflected fluid balance perioperatively. Whether this observation remains true for other surgical procedures with massive blood loss, yet to be further investigated.
Electrical impedance spectroscopy and diagnosis of tendinitis.
Yoon, Kisung; Lee, Kyeong Woo; Kim, Sang Beom; Han, Tai Ryoon; Jung, Dong Keun; Roh, Mee Sook; Lee, Jong Hwa
2010-02-01
There have been a number of studies that investigate the usefulness of bioelectric signals in diagnoses and treatment in the medical field. Tendinitis is a musculoskeletal disorder with a very high rate of occurrence. This study attempts to examine whether electrical impedance spectroscopy (EIS) can detect pathological changes in a tendon and find the exact location of the lesion. Experimental tendinitis was induced by injecting collagenase into one side of the patellar tendons in rabbits, while the other side was used as the control. After measuring the impedance in the tendinitis and intact tendon tissue, the dissipation factor was computed. The real component of impedance and the dissipation factor turned out to be lower in tendinitis than in intact tissues. Moreover, the tendinitis dissipation factor spectrum showed a clear difference from that of the intact tendon, indicating its usefulness as a tool for detecting the location of the lesion. Pathologic findings from the tissues that were obtained after measuring the impedance confirmed the presence of characteristics of tendinitis. In conclusion, EIS is a useful method for diagnosing tendinitis and detecting the lesion location in invasive treatment.
Surface impedance and the Casimir force
Bezerra, V B; Romero, C
2002-01-01
The impedance boundary condition is used to calculate the Casimir force in configurations of two parallel plates and a shpere (spherical lens) above a plate at both zero and nonzero temperature. The impedance approach allows one to find the Casimir force between the realistic test bodies regardless of the electromagnetic fluctuations inside the media. Although this approach is an approximate one, it has wider areas of application than the Lifshitz theory of the Casimir force. The general formulas of the impedance approach to the theory of the Casimir force are given and the formal substitution is found for connecting it with the Lifshitz formula. The range of micrometer separations between the test bodies which is interesting from the experimental point of view is investigated in detail. It is shown that at zero temperature the results obtained on the basis of the surface impedance method are in agreement with those obtained in framework of the Lifshitz theory within a fraction of a percent. The temperature c...
Importance of Attenuation Correction (AC) for Small Animal PET Imaging
DEFF Research Database (Denmark)
El Ali, Henrik H.; Bodholdt, Rasmus Poul; Jørgensen, Jesper Tranekjær;
2012-01-01
was performed. Methods: Ten NMRI nude mice with subcutaneous implantation of human breast cancer cells (MCF-7) were scanned consecutively in small animal PET and CT scanners (MicroPETTM Focus 120 and ImTek’s MicroCATTM II). CT-based AC, PET-based AC and uniform AC methods were compared. Results: The activity...
Modeling the Impedance of Nanostructured PV in Simulink/matlab
Houshmand, Mohammad; Zandi, Mohammad. H.; Gorji, Nima E.
2013-08-01
Impedance measurement is a common method to study the electrical properties of thin film photovoltaics. For the first time, we use the MATLAB/Simulink environment to extract the complex impedance of the nanostructured heterojunction solar cells. The impedance magnitude, phase and Nyquist plot of the PV are simulated in LTI Viewer and Impedance versus Frequency analysis tools of SimPower GUI block of Simulink. We examined a variety of the equivalent circuits consisting of capacitance, series and shunt resistances representing the solar cell structure. The model uses the parameters with values reported in the literature at room temperature and zero bias. The effect of the additional capacitance and resistances in the equivalent circuits on the impedance components of the cells is considered by Simulink environment.
Longitudinal Impedance Measurements of the Components for the BEPCII
Zhou, Demin; Kang, Wen; Wang Jiu Qing; Zhou, Lijuan
2005-01-01
A longitudinal impedance measurement system was established for the BEPCII. The measurements, done in the frequency domain, are based on the coaxial wire method using HP/Agilent 8720ES network analyzer. The applications of the TRL calibration technique and absorbers were investigated to find a good approach for impedance measurements. The impedance, larger than 20 Ohm and below 6 GHz, can be measured using the TRL calibration technique in the experiment. And better measurement results were got using the reference pipes with the absorbers. So, this system satisfies the requirements of the BEPCII. This paper gives a review on this impedance measurements system for the BEPCII. The measurements results show that there are no serious impedance problems for BEPCII bellows and injection kickers, agreeing well with the numerical simulations. More improvements on this system are in progress.
Optical approximation in the theory of geometric impedance
Stupakov, G; Zagorodnov, I
2007-01-01
In this paper we introduce an optical approximation into the theory of impedance calculation, one valid in the limit of high frequencies. This approximation neglects diffraction effects in the radiation process, and is conceptually equivalent to the approximation of geometric optics in electromagnetic theory. Using this approximation, we derive equations for the longitudinal impedance for arbitrary offsets, with respect to a reference orbit, of source and test particles. With the help of the Panofsky-Wenzel theorem we also obtain expressions for the transverse impedance (also for arbitrary offsets). We further simplify these expressions for the case of the small offsets that are typical for practical applications. Our final expressions for the impedance, in the general case, involve two dimensional integrals over various cross-sections of the transition. We further demonstrate, for several known axisymmetric examples, how our method is applied to the calculation of impedances. Finally, we discuss the accuracy...
Institute of Scientific and Technical Information of China (English)
郭姗姗; 李春虎; 方光静; 王群; 冯丽娟; 王亮
2013-01-01
采用等体积浸渍法制备了CuO/AC及CuO-CeOJAC双金属催化剂,金属氧化物的前驱体为不同浓度的Cu(NO3)2及Ce(NO3)3溶液.CuO-CeO2/AC双金属氧化物催化剂采用分步浸渍法,对制得的催化剂进行模拟烟气脱硫性能比较.通过SEM和X射线衍射等手段对催化剂表面形貌和表面晶相进行分析.结果表明,添加质量分数1％ CeO2助剂的CuO/AC催化剂脱硫效果最好,因为助剂CeO2能够使CuO在催化剂表面有更高的分散度,负载金属氧化物催化剂的脱硫活性顺序为:CuO-CeO2/AC＞ CuO/AC.%CuO/AC and CuO-CeO2/AC catalysts were prepared by pore volume impregnation of the oxidized AC with aqueous solutions of nitrate salts. The used metal oxide precursors were different concentration Cu(NO3)2 and Ce(NO3)3 solutions. CuO-CeO2/AC catalyst was prepared by stepwise impregnation method. The desulfurization properties of the as-prepared catalysts were investigated by using simulated flue gas. The catalysts were characterized by SEM and XRD. The results showed that CuO/AC catalyst loaded with l wt% CeO2 possessed the best desulfurization effect. CeO2 additive enhanced the dispersion degree of CuO on the surface of the catalyst. The desulfurization activity of AC supported-metal oxides followed the sequence CuO-CeO2/AC > CuO/AC.
Müller, T. M.; Meinhardt, J.; Raether, F.
2013-01-01
Impedance spectroscopy of many ceramics is a challenge due to their high electrical resistance. Small disturbances can significantly alter the measuring results. In the present paper, it is shown how impedance measurements can be performed in an electromagnetically noisy ac furnace, using consequent Faraday shielding of the sample and the electrical connections. As example, the conductivity data of alumina was measured between room temperature and 1000 °C and compared to literature data. In addition, a correction method for the calculation of permittivity was developed to consider the stray fields in the sample-electrode setup. The distribution of the electrical field was simulated by finite element (FE) methods for different sample geometries and electrode arrangements. The deviations from the behavior of an ideal plate capacitor follow a linear trend and are in the order of 5% to 20% for an experimentally reasonable range of sample thicknesses. To check the theoretical results experimentally, alumina samples of varying thickness were measured. The customary calculation of permittivity leads to a clear trend with sample thickness, whereas the correction from the FE-simulation produces almost constant values of the relative permittivity.
2016-01-01
This book aims to cover different aspects of Bias Temperature Instability (BTI). BTI remains as an important reliability concern for CMOS transistors and circuits. Development of BTI resilient technology relies on utilizing artefact-free stress and measurement methods and suitable physics-based models for accurate determination of degradation at end-of-life, and understanding the gate insulator process impact on BTI. This book discusses different ultra-fast characterization techniques for recovery artefact free BTI measurements. It also covers different direct measurements techniques to access pre-existing and newly generated gate insulator traps responsible for BTI. The book provides a consistent physical framework for NBTI and PBTI respectively for p- and n- channel MOSFETs, consisting of trap generation and trapping. A physics-based compact model is presented to estimate measured BTI degradation in planar Si MOSFETs having differently processed SiON and HKMG gate insulators, in planar SiGe MOSFETs and also...
GB-R impedances: new approach to impedance simulation
Serrano, L.; Carlosena, A.
1995-04-01
A new design procedure is presented for obtaining simulated inductors and large capacitors from classical opamp circuits. Such impedances exploit almost all of the available bandwidth of the operational amplifier.
2009-01-01
[EN] In this work, we show the obtained results when characterizing tiles for sound insulation, elaborated by means of Fluff obtained from crushed out of life tires. The acoustic study has been carried out by means of an impedance tube where the coefficient of absorption and the acoustic impedance of different samples are obtained. [ES] En este trabajo se muestran los resultados obtenidos al caracterizar acústicamente losetas para aislamiento acústico, elaboradas mediante Fluff proveniente...
Effect of sow parity on vaginal electrical impedance.
Rezác, P; Kukla, R; Pöschl, M
2002-08-15
The influence of sow parity on the changes of vaginal impedance after weaning was examined. Sows were monitored twice a day for oestrus via exposure to a sexually mature boar. The criterion for confirmation of ovulation was an increase in plasma progesterone levels above 12.5 nmol l(-1) 8 and 12 days after oestrus onset. The impedance measurements were carried out by a four-terminal method. In sows of all parities, the vaginal impedance decreased gradually after weaning (P four-terminal method.
Simplest Analysis Method of AC Circuit%交流电路的一种简便分析方法
Institute of Scientific and Technical Information of China (English)
施尚英; 黄世瑜
2012-01-01
The current and voltage in exchange circuit satisfies Ohm’s law in effective value.,current phase appears ahead of time or lag behind according to different load of current.The simplest method adopted by the author is vector analysis law,which not only applies to series-parallel circuit,also to all circuits of exchange electric.%交流电路中电流与电压的关系在有效值上满足欧姆定律,根据负载的性质不同,相位上存在一个超前与滞后的问题,最简单最精确的分析方法就是矢量分析法,这种方法不仅适用于简单的串并联电路,也适用于交流电的所有电路,所以笔者在这些电路中提取相同的矢量分析法.
Boukamp, Bernard A.
1993-01-01
A method is presented for executing the Kramers-Kronig transforms of electrochemical impedance data on a computer. Attention is paid to the extrapolation techniques for impedance data with a limited frequency range. It is shown that impedance spectra of systems with blocking electrodes, exhibiting a
Yin, Cheng; Cai, Jinjun; Gao, Lingfei; Yin, Jingya; Zhou, Jicheng
2016-03-15
A new microwave catalytic oxidation process based on two kinds of catalysts, the commercially available activated carbon (AC) and Mn2O3 nanoparticle modified AC (Mn2O3/AC), was reported for the degradation of 4-nitrophenol (4-NP) without adding any oxidant. Effects of microwave power, catalyst dosage, irradiation time, and initial concentration for the degradation efficiency were studied. Results indicated that catalyst of Mn2O3/AC showed much higher catalytic activity than pure AC and Mn2O3 particles. Significantly, 4-NP degradation efficiency reached 99.6%, corresponding to 93.5% TOC removal under optimal conditions with microwave power of 400W, Mn2O3/AC dosage of 2g, reaction time of 5min, and initial concentration of 100mg/L. Hydroxyl radicals (OH) generated during catalytic reaction is the main oxidant, and O2 can not effectively improve removal rate. We proposed the microwave 'photoelectric effect' to interpret the generation of OH in view that microwave irradiation can directly excite the catalyst to produce electron-hole pairs and then transform H2O into OH on the surface of catalyst in solution. The obtained kinetic equation for microwave catalytic oxidation degradation of 4-NP was in line with pseudo-first-order kinetic model, that is, apparent rate constant increased as microwave power density increase.
AcsA-AcsB: The core of the cellulose synthase complex from Gluconacetobacter hansenii ATCC23769.
McManus, John B; Deng, Ying; Nagachar, Nivedita; Kao, Teh-hui; Tien, Ming
2016-01-01
The gram-negative bacterium, Gluconacetobacter hansenii, produces cellulose of exceptionally high crystallinity in comparison to the cellulose of higher plants. This bacterial cellulose is synthesized and extruded into the extracellular medium by the cellulose synthase complex (CSC). The catalytic component of this complex is encoded by the gene AcsAB. However, several other genes are known to encode proteins critical to cellulose synthesis and are likely components of the bacterial CSC. We have purified an active heterodimer AcsA-AcsB from G. hansenii ATCC23769 to homogeneity by two different methods. With the purified protein, we have determined how it is post-translationally processed, forming the active heterodimer AcsA-AcsB. Additionally, we have performed steady-state kinetic studies on the AcsA-AcsB complex. Finally through mutagenesis studies, we have explored the roles of the postulated CSC proteins AcsC, AcsD, and CcpAx.
Chiozzi, Gianluca; Šekoranja, Matej
2013-02-01
ALMA Common Software (ACS) provides a software infrastructure common to all ALMA partners and consists of a documented collection of common patterns and components which implement those patterns. The heart of ACS is based on a distributed Component-Container model, with ACS Components implemented as CORBA objects in any of the supported programming languages. ACS provides common CORBA-based services such as logging, error and alarm management, configuration database and lifecycle management. Although designed for ALMA, ACS can and is being used in other control systems and distributed software projects, since it implements proven design patterns using state of the art, reliable technology. It also allows, through the use of well-known standard constructs and components, that other team members whom are not authors of ACS easily understand the architecture of software modules, making maintenance affordable even on a very large project.
Energy Technology Data Exchange (ETDEWEB)
Guillo, J. F.; Lucas, M.; Lucas, R.; Vicente, P. G.
2008-07-01
It has analyzed the impact of distribution losses in the size of solar installations by comparing two methods commonly used in calculating the contribution of solar residential building: f-chart and dynamic simulation. 3 schemes have been analysed in a building 22 houses and 70 occupants located in the IV and climate in the province of Alicante. For comparison between the two methodologies have been used for calculating the same values input from climate data as consumption of ACS. (Author)
IMPEDANCE CHARACTERISTICS OF POLYFURAN FILMS
Institute of Scientific and Technical Information of China (English)
Liang Li; Xiao-bo Wan; Gi Xue
2002-01-01
Electrochemical impedance spectroscopy (EIS) was first used for the characterization of polyfuran (PFu) films that had been formed electrochemically on an Au electrode. The polyfuran was measured in high oxidation state, intermediate oxidation state and reduction state, respectively. As the oxidation level is increased, the ionic conductivity of PFu/BF4-increases. And impedance studies on PFu show that the anion BF4- appears to be mobile with a high diffusion coefficient of approximately 10-8 cm2 @ s-1.
A Simplified Algorithm for Impedance Calculation of Arbitrarily Shaped Radiators
Institute of Scientific and Technical Information of China (English)
YANG Jun; SHA Kan; GAN Woon-Seng; YAN Yong-Hong; TIAN Jing
2005-01-01
@@ It is well known that a computationally efficient model for calculation of radiation impedance of an arbitrarily shaped piston has been developed. We simplify the proposed algorithm by using geometric characteristics and intrinsic relationship between the analytic expressions. As an example, the method accuracy is illustrated and the radiation impedance of a right-angled triangular piston is calculated. The numerical results are in good agreement with that obtained directly by the quadruple integral method.
Institute of Scientific and Technical Information of China (English)
李鑫; 方陈; 张沛超; 包海龙
2013-01-01
For common maximum power point tracking (MPPT) control methods, the complexities of the structures and the controlling effects cannot be balanced very well. Aiming at this problem, an argumentation about the application of maximum power transmission theorytransfer?theorem in the PV system is discussed and a solution onfrom the view of impedance adaption is presented. According to the conclusion, a new MPPT control algorithm, which has the ability of rapid self-optimization, was proposed. The simulation model of three-phase grid-connected PV power system is established through MATLAB/Simulink. And the experiment is implemented under the circumstances such as? fast changes of external environments and load fluctuation. Comparing the improved control method with some classic ones, the results indicate that the tracking effect of proposed improved impedance adaption algorithm is better.%针对光伏发电系统最大功率点跟踪控制中结构复杂度与控制效果难以兼得的问题,文章从阻抗适配角度论证了最大功率传输理论应用于光伏系统控制的正确性,并提出一种具备快速自寻优能力的光伏系统最大功率点跟踪控制方法.通过Matlab仿真并与常见最大功率点跟踪控制方法相比较,文章所提出的算法具有更好的跟踪效果.
Applications of Nonlinear Electrochemical Impedance Spectroscopy (NLEIS)
Adler, S. B.
2013-08-31
This paper reviews the use of nonlinear electrochemical impedance spectroscopy (NLEIS) in the analysis of SOFC electrode reactions. By combining EIS and NLEIS, as well as other independent information about an electrode material, it becomes possible to establish quantitative links between electrochemical kinetics and materials properties, even when systems are unstable with time. After a brief review of the method, this paper summarizes recent results analyzing the effects of Sr segregation in thin-film LSC electrodes. © The Electrochemical Society.
Energy Technology Data Exchange (ETDEWEB)
Onish, Keiichi [Yamaha Motor Co., Shizuoka (Japan); Kim, Young Woo [Daegu Techno Park R and D Center, Seoul (Korea, Republic of); Obinata, Goro [Nagoya University, Nagoya (Japan); Hase, Kazunori [Tokyo Metropolitan University, Tokyo (Japan)
2013-05-15
We investigated impedance perception characteristics of humans in the man-machine interface. Sensibility or operational feel about physical properties of machine dynamics is obtained through perception process. We evaluated the impedance perception characteristics of humans who are operating a mechanical system, based on extended Scheffe's subjective evaluation method in full consideration of the influence of impedance level, impedance difference, experiment order, individual difference and so on. Constant method based quantitative evaluation was adopted to investigate the influence of motion frequency and change of the impedance on human impedance perception characteristics. Experimental results indicate that humans perceive impedance of mechanical systems based on comparison process of the dynamical characteristics of the systems. The proposed method can be applied to quantify the design requirement of man-machine interface. The effectiveness of the proposed method is verified through experimental results.
Institute of Scientific and Technical Information of China (English)
吕自波; 李楚杉; 邓焰; 何湘宁; 谢瑞
2015-01-01
有源电力滤波器(active power filter，APF)是电力系统中实现谐波治理功能的一种新型变流设备。谐波检测作为APF 的关键技术之一，直接决定了其整体性能。针对近来出现的一类基于直接交交变换技术的 APF，提出一种新的谐波检测算法。该算法结合改进的滑窗离散傅里叶变换法以及对称分量法，实现对三相电网各次谐波的各序分量的独立的快速检测。新算法与传统方法相比具有简单快速的优势。尤其是当系统不平衡时，需要在每个谐波频率上对正序与负序分量分别检测的应用场合。此外，该算法同样可用于传统的 APF 中以实现快速的谐波检测。首先对新型直接交交型APF 进行简要的介绍，再详细推导新的谐波检测算法的原理，并将该算法与传统算法进行比较研究。然后基于新的谐波检测算法针，对新型APF提出一整套滤波控制解决方案。最后对新的谐波检测算法进行仿真验证，并在一台3kW新型 APF 样机上对其进行实验验证，仿真与实验结果证明了新算法的正确性与实用性。%Active Power Filter (APF) is a new kind of equipment used in power grids to realize harmonic control function. As a key technology in APF, the harmonic detection algorithm directly determines the overall performance of the system. A new harmonic detection algorithm was proposed for the newly emerging direct AC-AC based APF. It is based on the combination of an improved sliding-window discrete Fourier transform (ISDFT) and symmetrical component method (SCM), which can realize individual fast detection of each sequence components for different orders of harmonics. The algorithm is simpler and faster than the traditional detection ones. It is superior especially when the grid is unbalanced and large numbers of harmonics needs to be detected. Furthermore, the new method can also be used in traditional APF to get rapid harmonic
Experiences with active damping and impedance-matching compensators
Betros, Robert S.; Alvarez, Oscar S.; Bronowicki, Allen J.
1993-09-01
TRW has been implementing active damping compensators on smart structures for the past five years. Since that time there have been numerous publications on the use of impedance matching techniques for structural damping augmentation. The idea of impedance matching compensators came about by considering the flow of power in a structure undergoing vibration. The goal of these compensators is to electronically dissipate as much of this flowing power as possible. This paper shows the performance of impedance matching compensators used in smart structures to be comparable to that of active damping compensators. Theoretical comparisons between active damping and impedance matching methods are made using PZT actuators and sensors. The effects of these collocated and non-collocated PZT sensors and actuators on the types of signals they sense and actuate are investigated. A method for automatically synthesizing impedance matching compensators is presented. Problems with implementing broad band active damping and impedance matching compensators on standard Digital Signal Processing (DSP) chips are discussed. Simulations and measurements that compare the performance of active damping and impedance matching techniques for a lightly damped cantilevered beam are shown.
Impedance spectroscopy and investigation of conduction mechanism in BaMnO{sub 3} nanorods
Energy Technology Data Exchange (ETDEWEB)
Hayat, Khizar [Nanostructured Materials and Devices Group, Department of Chemicals and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences, P.O. Nilore, Islamabad 45650 (Pakistan); Rafiq, M.A., E-mail: fac221@pieas.edu.p [Nanostructured Materials and Devices Group, Department of Chemicals and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences, P.O. Nilore, Islamabad 45650 (Pakistan); Durrani, S.K. [Material Division, Pakistan Institute of Nuclear Science and Technology, P.O. Nilore, Islamabad 45650 (Pakistan); Hasan, M.M. [Nanostructured Materials and Devices Group, Department of Chemicals and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences, P.O. Nilore, Islamabad 45650 (Pakistan)
2011-02-01
BaMnO{sub 3} nanorods were synthesized at 200 {sup o}C and atmospheric pressure using the composite-hydroxide mediated method. X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy were used to investigate the structure, size, morphology, phase purity and elemental composition of BaMnO{sub 3} nanorods. Electrical characterization of BaMnO{sub 3} pellet was performed at 300-400 K and in the frequency range 200 Hz-2 MHz. Temperature dependence of AC conductivity suggests that the BaMnO{sub 3} pellet behaves as a semiconducting material and conduction across the pellet can be explained by the correlated barrier hopping model. Impedance analysis was performed using the equivalent circuit model (R{sub 1}Q{sub 1}C{sub 1})(R{sub 2}C{sub 2}) and it suggests a single relaxation process in the BaMnO{sub 3} pellet at a particular temperature. The analysis reveals that the BaMnO{sub 3} pellet behaves like an n-type semiconductor material due to the presence of oxygen vacancies and some disorder. Modulus spectroscopy also supports the impedance results.
Morris, Graham P.
2013-12-17
Fully automated and computer assisted heuristic data analysis approaches have been applied to a series of AC voltammetric experiments undertaken on the [Fe(CN)6]3-/4- process at a glassy carbon electrode in 3 M KCl aqueous electrolyte. The recovered parameters in all forms of data analysis encompass E0 (reversible potential), k0 (heterogeneous charge transfer rate constant at E0), α (charge transfer coefficient), Ru (uncompensated resistance), and Cdl (double layer capacitance). The automated method of analysis employed time domain optimization and Bayesian statistics. This and all other methods assumed the Butler-Volmer model applies for electron transfer kinetics, planar diffusion for mass transport, Ohm\\'s Law for Ru, and a potential-independent Cdl model. Heuristic approaches utilize combinations of Fourier Transform filtering, sensitivity analysis, and simplex-based forms of optimization applied to resolved AC harmonics and rely on experimenter experience to assist in experiment-theory comparisons. Remarkable consistency of parameter evaluation was achieved, although the fully automated time domain method provided consistently higher α values than those based on frequency domain data analysis. The origin of this difference is that the implemented fully automated method requires a perfect model for the double layer capacitance. In contrast, the importance of imperfections in the double layer model is minimized when analysis is performed in the frequency domain. Substantial variation in k0 values was found by analysis of the 10 data sets for this highly surface-sensitive pathologically variable [Fe(CN) 6]3-/4- process, but remarkably, all fit the quasi-reversible model satisfactorily. © 2013 American Chemical Society.
Tian, Lian; Hunter, Kendall S; Kirby, K Scott; Ivy, D Dunbar; Shandas, Robin
2010-06-01
Pulmonary vascular input impedance better characterizes right ventricular (RV) afterload and disease outcomes in pulmonary hypertension compared to the standard clinical diagnostic, pulmonary vascular resistance (PVR). Early efforts to measure impedance were not routine, involving open-chest measurement. Recently, the use of pulsed-wave (PW) Doppler-measured velocity to non-invasively estimate instantaneous flow has made impedance measurement more practical. One critical concern remains with clinical use: the measurement uncertainty, especially since previous studies only incorporated random error. This study utilized data from a large pediatric patient population to comprehensively examine the systematic and random error contributions to the total impedance uncertainty and determined the least error prone methodology to compute impedance from among four different methods. We found that the systematic error contributes greatly to the total uncertainty and that one of the four methods had significantly smaller propagated uncertainty; however, even when this best method is used, the uncertainty can be large for input impedance at high harmonics and for the characteristic impedance modulus. Finally, we found that uncertainty in impedance between normotensive and hypertensive patient groups displays no significant difference. It is concluded that clinical impedance measurement would be most improved by advancements in instrumentation, and the best computation method is proposed for future clinical use of the input impedance.
Impedances and power losses for an off-axis beam
Kurennoy, S S
1996-01-01
A method for calculating coupling impedances and power losses for off-axis beams is developed. It is applied to calculate impedances of small localized discontinuities like holes and slots, as well as the impedance due to a finite resistivity of chamber walls, in homogeneous chambers with an arbitrary shape of the chamber cross section. The approach requires to solve a two-dimensional electrostatic problem, which can be easily done numerically in the general case, while for some particular cases analytical solutions are obtained.
DC-Modulated PFC Buck-Type AC/AC Converter for Light Dimming
Institute of Scientific and Technical Information of China (English)
罗方林; 叶虹
2007-01-01
Dimmers are very widely applied in theatres, cinemas, dancing-parties, auditoriums and signal systems. They are usually supplied by single-stage AC/AC converters in the past with voltage regulation technique with the disadvantages of high total harmonic distortion, low power factor and poor power transfer efficiency. This paper introduces a novel method-DC-modulation that implements DC/DC conversion technology into AC/AC converters. The DC-modulated single-stage PFC AC/AC converters effectively improved the power factor up to 0.999 and the power transfer efficiency up to 97.8 %. The experimental results verified our design and calculation. This technique will be widely used in light dimming and other industrial applications.
Directory of Open Access Journals (Sweden)
Alka Dohare
2014-02-01
Full Text Available Along with the increase market of the transgenic crops, the demand for testing GMOs and for certifying non-GMO foodstuffs has increased dramatically. Within the arena of expanding techniques for identification and quantification of transgenic crops, two major approaches for detecting GMOs are still applicable on large scale, namely ELISA based protein detection and PCR based gene identification. In present study, ELISA techniques was adopted to identify the specific Cry1Ac and Cry2Ab proteins in some transgenic cotton plants seed samples viz., Gujarat cotton hybrid – 6 (BG II, Gujarat cotton hybrid – 8 (BG II and Gujarat cotton hybrid – 10 (BG II from the Gujarat state of India. The study reveals the presence of both Cry1Ac and Cry2Ab proteins in the transgenic seed samples and also demonstrated that the technique of ELISA for identification of Cry1Ac and Cry2Ab proteins is quite handy and easily adoptable.
Frequency dependent elastic impedance inversion for interstratified dispersive elastic parameters
Zong, Zhaoyun; Yin, Xingyao; Wu, Guochen
2016-08-01
The elastic impedance equation is extended to frequency dependent elastic impedance equation by taking partial derivative to frequency. With this equation as the forward solver, a practical frequency dependent elastic impedance inversion approach is presented to implement the estimation of the interstratified dispersive elastic parameters which makes full use of the frequency information of elastic impedances. Three main steps are included in this approach. Firstly, the elastic Bayesian inversion is implemented for the estimation of elastic impedances from different incident angle. Secondly, with those estimated elastic impedances, their variations are used to estimate P-wave velocity and S-wave velocity. Finally, with the prior elastic impedance and P-wave and S-wave velocity information, the frequency dependent elastic variation with incident angle inversion is presented for the estimation of the interstratified elastic parameters. With this approach, the interstratified elastic parameters rather than the interface information can be estimated, making easier the interpretation of frequency dependent seismic attributes. The model examples illustrate the feasibility and stability of the proposed method in P-wave velocity dispersion and S-wave velocity dispersion estimation. The field data example validates the possibility and efficiency in hydrocarbon indication of the estimated P-wave velocity dispersion and S-wave velocity dispersion.
Motion discrimination of throwing a baseball using forearm electrical impedance
Nakamura, Takao; Kusuhara, Toshimasa; Yamamoto, Yoshitake
2013-04-01
The extroversion or hyperextension of elbow joint cause disorders of elbow joint in throwing a baseball. A method, which is easy handling and to measure motion objectively, can be useful for evaluation of throwing motion. We investigated a possibility of motion discrimination of throwing a baseball using electrical impedance method. The parameters of frequency characteristics (Cole-Cole arc) of forearm electrical impedance were measured during four types of throwing a baseball. Multiple discriminant analysis was used and the independent variables were change ratios of 11 parameters of forearm electrical impedance. As results of 120 data with four types of throwing motion in three subjects, hitting ratio was very high and 95.8%. We can expect to discriminate throwing a baseball using multiple discriminant analysis of impedance parameters.
Report of the SSC impedance workshop
Energy Technology Data Exchange (ETDEWEB)
NONE
1985-10-28
This workshop focused attention on the transverse, single-bunch instability and the detailed analysis of the broadband impedance which would drive it. Issues discussed included: (1) single bunch stability -- impact of impedance frequency shape, coupled-mode vs. fast blowup regimes, possible stopband structure; (2) numerical estimates of transverse impedance of inner bellows and sliding contact shielded bellows; (3) analytic estimates of pickup and kicker impedance contributions; and (4) feasibility studies of wire and beam measurements of component impedance.
Study of AC/RF properties of SRF ingot niobium
Energy Technology Data Exchange (ETDEWEB)
Dhakal, Pashupati; Tsindlekht, Menachem I; Genkin, Valery M; Ciovati, Gianluigi; Myneni, Ganapati Rao
2013-09-01
In an attempt to correlate the performance of superconducting radiofrequency cavities made of niobium with the superconducting properties, we present the results of the magnetization and ac susceptibility of the niobium used in the superconducting radiofrequency cavity fabrication. The samples were subjected to buffer chemical polishing (BCP) surface and high temperature heat treatments, typically applied to the cavities fabrications. The analysis of the results show the different surface and bulk ac conductivity for the samples subjected to BCP and heat treatment. Furthermore, the RF surface impedance is measured on the sample using a TE011 microwave cavity for a comparison to the low frequency measurements.
AC and Phase Sensing of Nanowires for Biosensing.
Crescentini, Marco; Rossi, Michele; Ashburn, Peter; Lombardini, Marta; Sangiorgi, Enrico; Morgan, Hywel; Tartagni, Marco
2016-04-19
Silicon nanowires are label-free sensors that allow real-time measurements. They are economical and pave the road for point-of-care applications but require complex readout and skilled personnel. We propose a new model and technique for sensing nanowire sensors using alternating currents (AC) to capture both magnitude and phase information from the sensor. This approach combines the advantages of complex impedance spectroscopy with the noise reduction performances of lock-in techniques. Experimental results show how modifications of the sensors with different surface chemistries lead to the same direct-current (DC) response but can be discerned using the AC approach.
A review of time domain impedance boundary conditions
Richter, Christoph
2012-01-01
International audience; Over the last 15 years, time domain impedance boundary conditions have been investigated by various authors. In a review, a general framework of time domain impedance boundary conditions is presented and then filled with a set of outstanding mathematical and numerical methods from literature. All of the authors struggled with an instability with grazing flow. Mainly this is linked to the Ingard or Myers model of the sound propagation through a sheared flow. This is rev...
Input impedance and mutual coupling of rectangular microstrip antennas
Pozar, D. M.
1982-01-01
A moment method solution to the problem of input impedance and mutual coupling of rectangular microstrip antenna elements is presented. The formulation uses the grounded dielectric slab Green's function to account rigorously for the presence of the substrate and surface waves. Both entire basis (EB) and piecewise sinusoidal (PWS) expansion modes are used, and their relative advantages are noted. Calculations of input impedance and mutual coupling are compared with measured data and other calculations.
Artificial Inhomogeneous Tapered Impedance Sheet Characterization and Applications
2010-03-01
properties of the φ-dependent impedance sheet. iv Acknowledgements I would like to express my deepest appreciation to my advisor Dr. Michael Havrilla ...and future. Electromagnetic Compatibility, IEEE Transactions on, 51(1):78–100, Feb. 2009. [2] B. Glover, K. Whites, M. Hyde, and M. Havrilla ...2008. [3] M.W. Hyde, M.J. Havrilla , and P.E. Crittenden. A novel method for deter- mining the r-card sheet impedance using the transmission coefficient
Transverse Impedance of LHC Collimators
Métral, E; Assmann, Ralph Wolfgang; Boccardi, A; Bracco, C; Bohl, T; Caspers, Friedhelm; Gasior, M; Jones, O R; Kasinski, K; Kroyer, T; Redaelli, S; Robert-Demolaize, R; Roncarolo, F; Rumolo, G; Salvant, B; Steinhagen, R; Weiler, T; Zimmermann, F
2007-01-01
The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
Impedances of Laminated Vacuum Chambers
Energy Technology Data Exchange (ETDEWEB)
Burov, A.; Lebedev, V.; /Fermilab
2011-06-22
First publications on impedance of laminated vacuum chambers are related to early 70s: those are of S. C. Snowdon [1] and of A. G. Ruggiero [2]; fifteen years later, a revision paper of R. Gluckstern appeared [3]. All the publications were presented as Fermilab preprints, and there is no surprise in that: the Fermilab Booster has its laminated magnets open to the beam. Being in a reasonable mutual agreement, these publications were all devoted to the longitudinal impedance of round vacuum chambers. The transverse impedance and the flat geometry case were addressed in more recent paper of K. Y. Ng [4]. The latest calculations of A. Macridin et al. [5] revealed some disagreement with Ref. [4]; this fact stimulated us to get our own results on that matter. Longitudinal and transverse impendances are derived for round and flat laminated vacuum chambers. Results of this paper agree with Ref. [5].
Kraft, R. E.
1999-01-01
Single-degree-of-freedom resonators consisting of honeycomb cells covered by perforated facesheets are widely used as acoustic noise suppression liners in aircraft engine ducts. The acoustic resistance and mass reactance of such liners are known to vary with the intensity of the sound incident upon the panel. Since the pressure drop across a perforated liner facesheet increases quadratically with the flow velocity through the facesheet, this is known as the nonlinear resistance effect. In the past, two different empirical frequency domain models have been used to predict the Sound Pressure Level effect of the incident wave on the perforated liner impedance, one that uses the incident particle velocity in isolated narrowbands, and one that models the particle velocity as the overall velocity. In the absence of grazing flow, neither frequency domain model is entirely accurate in predicting the nonlinear effect that is measured for typical perforated sheets. The time domain model is developed in an attempt to understand and improve the model for the effect of spectral shape and amplitude of multi-frequency incident sound pressure on the liner impedance. A computer code for the time-domain finite difference model is developed and predictions using the models are compared to current frequency-domain models.
Hybrid-Source Impedance Networks
DEFF Research Database (Denmark)
Li, Ding; Gao, Feng; Loh, Poh Chiang;
2010-01-01
the cascaded networks would have a higher output voltage gain and other unique advantages that currently have not been investigated yet. It is anticipated that these advantages would help the formed inverters find applications in photovoltaic and other renewable systems, where a high voltage gain is usually......Hybrid-source impedance networks have attracted attention among researchers because of their flexibility in performing buck-boost energy conversion. To date, three distinct types of impedance networks can be summarized for implementing voltage-type inverters with another three types summarized...
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Loh, Poh Chiang; Blaabjerg, Frede;
2014-01-01
This letter introduces a new versatile Y-shaped impedance network for realizing converters that demand a very high-voltage gain, while using a small duty ratio. To achieve that, the proposed network uses a tightly coupled transformer with three windings, whose obtained gain is presently not matched...... by existing networks operated at the same duty ratio. The proposed impedance network also has more degrees of freedom for varying its gain, and hence, more design freedom for meeting requirements demanded from it. This capability has been demonstrated by mathematical derivation, and proven in experiment...
Input impedance characteristics of microstrip structures
Directory of Open Access Journals (Sweden)
A. I. Nazarko
2015-06-01
Full Text Available Introduction. Electromagnetic crystals (EC and EC-inhomogeneities are one of the main directions of microstrip devices development. In the article the input impedance characteristics of EC- and traditional microstrip inhomogeneities and filter based on EC-inhomogeneities are investigated. Transmission coefficient characteristics. Transmission coefficient characteristics of low impedance EC- and traditional inhomogeneities are considered. Characteristics are calculated in the software package Microwave Studio. It is shown that the efficiency of EC-inhomogeneity is much higher. Input impedance characteristics of low impedance inhomogeneities. Dependences of input impedance active and reactive parts of EC- and traditional inhomogeneities are given. Dependences of the active part illustrate significant low impedance transformation of nominal impedance. The conditions of impedance matching of structure and input medium are set. Input impedance characteristics of high impedance inhomogeneities. Input impedance characteristics of high impedance EC- and traditional inhomogeneities are considered. It was shown that the band of transformation by high impedance inhomogeneities is much narrower than one by low impedance inhomogeneities. Characteristics of the reflection coefficient of inhomogeneities are presented. Input impedance characteristics of narrowband filter. The structure of narrowband filter based on the scheme of Fabry-Perot resonator is presented. The structure of the filter is fulfilled by high impedance EC-inhomogeneities as a reflectors. Experimental and theoretical amplitude-frequency characteristics of the filter are presented. Input impedance characteristics of the filter are shown. Conclusions. Input impedance characteristics of the structure allow to analyse its wave properties, especially resonant. EC-inhomogeneity compared with traditional microstrip provide substantially more significant transformation of the the input impedance.
An Improved Method for Purifying Cry1Ac Protein from Bacillus thuringiensis%一种纯化苏云金杆菌Cry1Ac蛋白的方法
Institute of Scientific and Technical Information of China (English)
王发祥; 刘永乐; 丁学知; 夏立秋
2011-01-01
The research of structure and function of Cry proteins was greatly restricted by their purification method. Therefore, a method that purifying Bacillus thuringiensis CrylAc protoxin by using isoelectric precipitation and purifying Bacillus thuringiensis CrylAc activated toxin by using molecular sieve chromatography was proposed. The results showed that the CrylAc protoxin had good effects of precipitation and purification when Ph value was 5.05; activating the purified protoxin to conduct molecular sieve chromatography, high concentration of CrylAc activated toxin could be obtained from the maximum peak of chromatography. This improved method not only has good purification effect, but also contribute a renovation to the purification method of Cry protein, which is significant for promoting researches on structure and function of Cry protein.%Cry蛋白的纯化技术在很大程度上制约了其结构与功能的研究.为此,提出了一种以等电点沉淀方法纯化苏云金杆菌Cry1Ac的原毒素,用分子筛层析纯化其活性毒素的方法.结果表明:Cry1Ac的原毒素在pH值5.05条件下沉淀纯化效果好；以纯化的原毒素激活进行分子筛层析,收集其最大峰便可获得较高浓度的活性毒素；该方法不仅纯化效果好,而且省去层析后的浓缩步骤,是Cry蛋白的纯化方法研究中的一次革新,对推动Cry蛋白的结构和功能研究具有重要的意义.
Method of Measurement of Capacitance and Dielectric Loss Factor Using Artificial Neural Networks
Roj Jerzy; Cichy Adam
2015-01-01
A novel method of dielectric loss factor measuring has been described. It is based on a quasi-balanced method for the capacitance measurement. These AC circuits allow to measure only one component of the impedance. However, after analyzing a quasi-balanced circuit's processing equation, it is possible to derive a novel method of dielectric loss factor measuring. Dielectric loss factor can be calculated after detuning the circuit from its quasi-equilibrium state. There are two possible ways of...
Impedance Analysis of Silicon Nanowire Lithium Ion Battery Anodes
Ruffo, Riccardo
2009-07-02
The impedance behavior of silicon nanowire electrodes has been investigated to understand the electrochemical process kinetics that influences the performance when used as a high-capacity anode in a lithium ion battery. The ac response was measured by using impedance spectroscopy in equilibrium conditions at different lithium compositions and during several cycles of charge and discharge in a half cell vs. metallic lithium. The impedance analysis shows the contribution of both surface resistance and solid state diffusion through the bulk of the nanowires. The surface process is dominated by a solid electrolyte layer (SEI) consisting of an inner, inorganic insoluble part and several organic compounds at the outer interface, as seen by XPS analysis. The surface resistivity, which seems to be correlated with the Coulombic efficiency of the electrode, grows at very high lithium contents due to an increase in the inorganic SEI thickness. We estimate the diffusion coefficient of about 2 × 10 -10 cm 2/s for lithium diffusion in silicon. A large increase in the electrode impedance was observed at very low lithium compositions, probably due to a different mechanism for lithium diffusion inside the wires. Restricting the discharge voltage to 0.7 V prevents this large impedance and improves the electrode lifetime. Cells cycled between 0.07 and 0.70 V vs. metallic lithium at a current density of 0.84 A/g (C/5) showed good Coulombic efficiency (about 99%) and maintained a capacity of about 2000 mAh/g after 80 cycles. © 2009 American Chemical Society.
Smart mug to measure hand's geometrical mechanical impedance.
Hondori, Hossein Mousavi; Tech, Ang Wei
2011-01-01
A novel device, which looks like a mug, has been proposed for measuring the impedance of human hand. The device is designed to have convenient size and light weight similar to an ordinary coffee mug. It contains a 2-axis inertia sensor to monitor vibration and a small motor to carry an eccentric mass (m=100 gr, r=2 cm, rpm=600). The centrifugal force due to the rotating mass applies a dynamic force to the hand that holds the mug. Correlation of the acceleration signals with the perturbing force gives the geometrical mechanical impedance. Experimental results on a healthy subject shows that impedance is posture dependant while it changes with the direction of the applied perturbing force. For nine postures the geometrical impedance is obtained all of which have elliptical shapes. The method can be used for assessment of spasticity and monitoring stability in patients with stroke or similar problems.
Conductive magnetorheological elastomer: fatigue dependent impedance-mechanic coupling properties
Wang, Yu; Xuan, Shouhu; Ge, Lin; Wen, Qianqian; Gong, Xinglong
2017-01-01
This work investigated the relationship between the impedance properties and dynamic mechanical properties of magnetorheological elastomers (MREs) under fatigue loading. The storage modulus and the impedance properties of MREs were highly influenced by the pressure and magnetic field. Under the same experimental condition, the two characteristics exhibited similar fatigue dependent change trends. When pressure was smaller than 10 N, the capacitance of MRE could be divided into four sections with the increase of the cyclic numbers. The relative equivalent circuit model was established to fit the experimental results of the impedance spectra. Each parameter of circuit element reflected the change of fatigue loading, relative microstructure of MRE, MRE-electrode interface layer, respectively. Based on the above analysis, the real-time and nondestructive impedance method was demonstrated to be high potential on detecting the fatigue of the MRE device.
Statistical Properties of Antenna Impedance in an Electrically Large Cavity
Energy Technology Data Exchange (ETDEWEB)
WARNE,LARRY K.; LEE,KELVIN S.H.; HUDSON,H. GERALD; JOHNSON,WILLIAM A.; JORGENSON,ROY E.; STRONACH,STEPHEN L.
2000-12-13
This paper presents models and measurements of antenna input impedance in resonant cavities at high frequencies.The behavior of input impedance is useful in determining the transmission and reception characteristics of an antenna (as well as the transmission characteristics of certain apertures). Results are presented for both the case where the cavity is undermoded (modes with separate and discrete spectra) as well as the over moded case (modes with overlapping spectra). A modal series is constructed and analyzed to determine the impedance statistical distribution. Both electrically small as well as electrically longer resonant and wall mounted antennas are analyzed. Measurements in a large mode stirred chamber cavity are compared with calculations. Finally a method based on power arguments is given, yielding simple formulas for the impedance distribution.
Beam coupling impedances of fast transmission-line kickers.
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S. (Sergey)
2002-01-01
Fast transmission-line kickers contain no ferrite and consist of two long metallic parallel plates supported by insulators inside a beam pipe. A beam is deflected by both the electric and magnetic fields of a TEM wave created by a pulse propagating along the strips in the direction opposite to the beam. Computations of the beam coupling impedances for such structures are difficult because of their length. In the paper, the beam coupling impedances of transmission-line kickers are calculated by combining analytical and numerical methods: the wake potentials computed in short models are extended analytically to obtain the wakes for the long kickers, and then the corresponding beam impedances are derived. At very low frequencies the results are compared with simple analytical expressions for the coupling impedances of striplines in beam position monitors.
一种对机器人阻抗控制中不确定性进行补偿的方法%Method to Compensate Uncertainties in Robot Impedance Control
Institute of Scientific and Technical Information of China (English)
王宇驰; 陈友东; 游玮
2016-01-01
The uncertainties existing in robot models present difficulties to controlling robots precisely. This is especially obvious in robot force control, and limits the usage of robot force control in industry field. Intelligent control, such as fuzzy control and neural network, is an effective method to solve this problem faced by classical control methods. Unsupervised learning network was adopted to compensate the uncertainties existing in robot impedance control online and to improve the performance of force tracking. The effective-ness of the proposed neural algorithm is verified by a simulation.%机器人建模中存在的不确定性,给机器人精确控制带来了困难,在机器人力控制中尤为明显,制约了力控制在实际生产中的应用.采用模糊控制、 神经网络等智能控制方法是解决这些经典控制理论所面临问题的有效手段.文中使用无监督学习的神经网络对不确定性进行在线补偿,提高阻抗控制的力跟踪性能,通过仿真验证了算法的有效性.
Energy Technology Data Exchange (ETDEWEB)
Zhou, Xiao Dong; Pederson, Larry R.; Templeton, Jared W.; Stevenson, Jeffry W.
2009-12-09
The aim of this paper is to address three issues in solid oxide fuel cells: (1) cross-validation of the polarization of a single cell measured using both dc and ac approaches, (2) the precise determination of the total areal specific resistance (ASR), and (3) understanding cathode polarization with LSCF cathodes. The ASR of a solid oxide fuel cell is a dynamic property, meaning that it changes with current density. The ASR measured using ac impedance spectroscopy (low frequency interception with real Z´ axis of ac impedance spectrum) matches with that measured from a dc IV sweep (the tangent of dc i-V curve). Due to the dynamic nature of ASR, we found that an ac impedance spectrum measured under open circuit voltage or on a half cell may not represent cathode performance under real operating conditions, particularly at high current density. In this work, the electrode polarization was governed by the cathode activation polarization; the anode contribution was negligible.
Three-Level AC-DC-AC Z-Source Converter Using Reduced Passive Component Count
DEFF Research Database (Denmark)
Loh, Poh Chiang; Gao, Feng; Tan, Pee-Chin;
2007-01-01
This paper presents a three-level ac-dc-ac Z-source converter with output voltage buck-boost capability. The converter is implemented by connecting a low cost front-end diode rectifier to a neutral-point-clamped inverter through a single X-shaped LC impedance network. The inverter is controlled...... to switch with a three-level output voltage, where the middle neutral potential is uniquely tapped from the star-point of a wye-connected capacitive filter placed before the front-end diode rectifier for input current filtering. Through careful control, the resulting converter can accurately produce...... the correct volt-sec average at its output, while simultaneously achieving inductive voltage boosting. More interestingly, these performance features are achieved with no increase in the number of semiconductor commutations, and hence no increase in switching losses. The proposed converter therefore offers...
Institute of Scientific and Technical Information of China (English)
汤涛; 黄纯; 江亚群; 罗勋华; 刘鹏辉
2016-01-01
谐振接地配电网发生单相接地故障后，健全线路的零序阻抗在最小串联谐振频率以下的各频段呈电容特性；故障线路的零序阻抗在高频段呈电容特性，在低频段呈电感特性。依据这一现象，提出一种基于馈线零序阻抗特性的故障选线方法。通过低通和带通数字滤波器提取母线零序电压和各馈线零序电流的高频分量和低频分量，并分别对母线零序电压的高频分量和低频分量求导。由于容性线路的电压导数与电流的比值为定值，故母线零序电压导数与健全线路零序电流的比值在高频段与低频段相等，其实际差值近似为0；母线零序电压导数与故障线路零序电流的比值在高频段与低频段不等，其差值较大，据此构成故障选线判据。理论分析和仿真结果表明，该方法选线准确、可靠且适应性强。%AbstractAfter the single phase ground fault occurred in the resonant ground distribution network, the zero sequence impedance of the sound line shows capacitance characteristic under the circumstance that the frequency is below the minimum series resonant frequency. However, the zero sequence impedance of the faulty line presents capacitance characteristic in the high frequency and inductance characteristic in the low frequency. In terms of the phenomena above, a faulty line selection method based on zero sequence impedance characteristics of lines is proposed. The high and low frequency components of the bus zero sequence voltage and each feeder zero sequence current are extracted through low-pass and band-pass digital filters. And then the high and low frequency components of the bus zero sequence voltage are derived separately. Since the ratio between the voltage derivative and the current in the capacitive circuit is constant, the ratios between the bus zero sequence voltage derivative and the zero current of the sound line are same both in the high and the low
Acoustic Ground-Impedance Meter
Zuckerwar, A. J.
1983-01-01
Helmoltz resonator used in compact, portable meter measures acoustic impedance of ground or other surfaces. Earth's surface is subject of increasing acoustical investigations because of its importance in aircraft noise prediction and measurment. Meter offers several advantages. Is compact and portable and set up at any test site, irrespective of landscape features, weather or other environmental condition.
Small Signal Loudspeaker Impedance Emulator
DEFF Research Database (Denmark)
Iversen, Niels Elkjær; Knott, Arnold
2014-01-01
Specifying the performance of audio amplifiers is typically done by playing sine waves into a pure ohmic load. However real loudspeaker impedances are not purely ohmic but characterized by the mechanical resonance between the mass of the diaphragm and the compliance of its suspension which vary f...
Lifescience Database Archive (English)
Full Text Available GN=... 37 0.66 tr|B1ACS4|B1ACS4_BALBO DMP1 (Fragment) OS=Balaenoptera borealis ... 37 0.66 tr|B1ACS3|B1ACS3...todon GN=DM... 37 1.1 tr|B1ACT4|B1ACT4_LISBO DMP1 (Fragment) OS=Lissodelphis borealis ... 37 1.1 tr|B1ACS2|B...SSSEEEIQSKNTEMESRRLTVDAY 160 >tr|B1ACS4|B1ACS4_BALBO DMP1 (Fragment) OS=Balaenoptera borealis GN=DMP1 PE=4 S
Huang, Liangsheng; Liu, Yudong; Li, Yong; Liu, Renhong; Xiao, Ouzheng
2015-01-01
The fast extraction kicker system is one of the most important accelerator components, whose inner structure will be the main source of the impedance in the RCS. It is necessary to understand the kicker impedance before its installation into the tunnel. The conventional and improved wire methods are employed for the benchmarking impedance measurement results. The simulation and measurements confirm that the window-frame ferrite geometry and the end plate are the important structures causing the coupling impedance. The total impedance of the eight modules systems is determined by the scaling law from the measurement and the impedance measurement of the kicker system is summarized.
Directory of Open Access Journals (Sweden)
Donald P Bernstein
2010-01-01
Full Text Available Impedance cardiography (ICG is a branch of bioimpedance pimarily concerned with the determination of left ventricular stroke volume (SV. As implemented, using the transthoracic approach, the technique involves applying a current field longitudinally across a segment of thorax by means of a constant magnitude, high frequency, low amplitude alternating current (AC. By Ohm's Law, the voltage difference measured within the current field is proportional to the electrical impedance Z (Ω. Without ventilatory or cardiac activity, Z is known as the transthoracic, static base impedance Z0. Upon ventricular ejection, a characteristic time dependent cardiac-synchronous pulsatile impedance change is obtained, ΔZ(t, which, when placed electrically in parallel with Z0, constitutes the time-variable total transthoracic impedance Z(t. ΔZ(t represents a dual-element composite waveform, which comprises both the radially-oriented volumetric expansion of and axially-directed forward blood flow within both great thoracic arteries. In its majority, however, ΔZ(t is known to primarily emanate from the ascending aorta. Conceptually, commonly implemented methods assume a volumetric origin for the peak systolic upslope of ΔZ(t, (i.e. dZ/dtmax, with the presumed units of Ω·s-1. A recently introduced method assumes the rapid ejection of forward flowing blood in earliest systole causes significant changes in the velocity-induced blood resistivity variation (Δρb(t, Ωcm·s-1, and it is the peak rate of change of the blood resistivity variation dρb(t/dtmax (Ωcm·s-2 that is the origin of dZ/dtmax. As a consequence of dZ/dtmax peaking in the time domain of peak aortic blood acceleration, dv/dtmax (cm·s-2, it is suggested that dZ/dtmax is an ohmic mean acceleration analog (Ω·s-2 and not a mean flow or velocity surrogate as generally assumed. As conceptualized, the normalized value, dZ/dtmax/Z0, is a dimensionless ohmic mean acceleration equivalent (s-2
Directory of Open Access Journals (Sweden)
Xiaochao Hou
2016-11-01
Full Text Available In low-voltage converter-based alternating current (AC microgrids with resistive distribution lines, the P-V droop with Q-f boost (VPD/FQB is the most common method for load sharing. However, it cannot achieve the active power sharing proportionally. To overcome this drawback, the conventional P-ω/Q-V droop control is adopted in the low-voltage AC microgrid. As a result, the active power sharing among the distributed generators (DGs is easily obtained without communication. More importantly, this study clears up the previous misunderstanding that conventional P-ω/Q-V droop control is only applicable to microgrids with highly inductive lines, and lays a foundation for the application of conventional droop control under different line impedances. Moreover, in order to guarantee the accurate reactive power sharing, a guide for designing Q-V droop gains is given, and virtual resistance is adopted to shape the desired output impedance. Finally, the effects of power sharing and transient response are verified through simulations and experiments in converter-based AC Microgrid.
Cooperative Frequency Control for Autonomous AC Microgrids
DEFF Research Database (Denmark)
Shafiee, Qobad; Quintero, Juan Carlos Vasquez; Guerrero, Josep M.;
2015-01-01
Distributed secondary control strategies have been recently studied for frequency regulation in droop-based AC Microgrids. Unlike centralized secondary control, the distributed one might fail to provide frequency synchronization and proportional active power sharing simultaneously, due to having...... not require measuring the system frequency as compared to the other presented methods. An ac Microgrid with four sources is used to verify the performance of the proposed control methodology....
Electrical impedance spectroscopy and the diagnosis of bladder pathology.
Keshtkar, Ahmad; Keshtkar, Asghar; Smallwood, Rod H
2006-07-01
Bladder pathology is usually investigated visually by cystoscopy. At present, definitive diagnosis of the bladder can be made by biopsy only, usually under general anaesthesia. This is a relatively high-cost procedure in terms of both time and money and is associated with discomfort for the patient and morbidity. Thus, we used an electrical impedance spectroscopy technique for differentiating pathological changes in the urothelium and improving cystoscopic detection. For ex vivo study, a whole or part of the patient's urinary bladder was used to take the readings less than half an hour after excision at room temperature, about 27 degrees C, using the Mk3.5 Sheffield System (2-384 kHz in 24 frequencies). In this study, 145 points (from 16 freshly excised bladders from patients) were studied in terms of their biopsy reports matching to the electrical impedance measurements. For in vivo study, a total of 106 points from 38 patients were studied to take electrical impedance and biopsy samples. The impedance data were evaluated in both malignant and benign groups, and revealed a significant difference between these two groups. The impedivity of the malignant bladder tissue was significantly higher than the impedivity of the benign tissue, especially at lower frequencies (p < 0.001). In addition, the receiver operating characteristic (ROC) curve for impedance measurements indicated that this technique could provide diagnostic information (individual classification is possible). Thus, the authors have investigated the application of bio-impedance measurements to the bladder tissue as a novel and minimally invasive technique to characterize human bladder urothelium. Therefore, this technique, especially at lower frequencies, can be a complementary method for cystoscopy, biopsy and histopathological evaluation of the bladder abnormalities.
Damage detection technique by measuring laser-based mechanical impedance
Energy Technology Data Exchange (ETDEWEB)
Lee, Hyeonseok; Sohn, Hoon [Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology (Daehak-ro 291, Yuseong-gu, Daejeon 305-701) (Korea, Republic of)
2014-02-18
This study proposes a method for measurement of mechanical impedance using noncontact laser ultrasound. The measurement of mechanical impedance has been of great interest in nondestructive testing (NDT) or structural health monitoring (SHM) since mechanical impedance is sensitive even to small-sized structural defects. Conventional impedance measurements, however, have been based on electromechanical impedance (EMI) using contact-type piezoelectric transducers, which show deteriorated performances induced by the effects of a) Curie temperature limitations, b) electromagnetic interference (EMI), c) bonding layers and etc. This study aims to tackle the limitations of conventional EMI measurement by utilizing laser-based mechanical impedance (LMI) measurement. The LMI response, which is equivalent to a steady-state ultrasound response, is generated by shooting the pulse laser beam to the target structure, and is acquired by measuring the out-of-plane velocity using a laser vibrometer. The formation of the LMI response is observed through the thermo-mechanical finite element analysis. The feasibility of applying the LMI technique for damage detection is experimentally verified using a pipe specimen under high temperature environment.
Validity of estimating limb muscle volume by bioelectrical impedance.
Miyatani, M; Kanehisa, H; Masuo, Y; Ito, M; Fukunaga, T
2001-07-01
The present study aimed to investigate the validity of estimating muscle volume by bioelectrical impedance analysis. Bioelectrical impedance and series cross-sectional images of the forearm, upper arm, lower leg, and thigh on the right side were determined in 22 healthy young adult men using a specially designed bioelectrical impedance acquisition system and magnetic resonance imaging (MRI) method, respectively. The impedance index (L(2)/Z) for every segment, calculated as the ratio of segment length squared to the impedance, was significantly correlated to the muscle volume measured by MRI, with r = 0.902-0.976 (P estimation was 38.4 cm(3) for the forearm, 40.9 cm(3) for the upper arm, 107.2 cm(3) for the lower leg, and 362.3 cm(3) for the thigh. Moreover, isometric torque developed in elbow flexion or extension and knee flexion or extension was significantly correlated to the L(2)/Z values of the upper arm and thigh, respectively, with correlation coefficients of 0.770-0.937 (P knee flexors or extensors. Thus the present study indicates that bioelectrical impedance analysis may be useful to predict the muscle volume and to investigate possible relations between muscle size and strength capability in a limited segment of the upper and lower limbs.
Optical approximation in the theory of geometric impedance
Stupakov, G.; Bane, K. L. F.; Zagorodnov, I.
2007-05-01
In this paper we introduce an optical approximation into the theory of impedance calculation, one valid in the limit of high frequencies. This approximation neglects diffraction effects in the radiation process, and is conceptually equivalent to the approximation of geometric optics in electromagnetic theory. Using this approximation, we derive equations for the longitudinal impedance for arbitrary offsets, with respect to a reference orbit, of source and test particles. With the help of the Panofsky-Wenzel theorem, we also obtain expressions for the transverse impedance (also for arbitrary offsets). We further simplify these expressions for the case of the small offsets that are typical for practical applications. Our final expressions for the impedance, in the general case, involve two-dimensional integrals over various cross sections of the transition. We further demonstrate, for several known axisymmetric examples, how our method is applied to the calculation of impedances. Finally, we discuss the accuracy of the optical approximation and its relation to the diffraction regime in the theory of impedance.
Copper Phthalocyanine Thin Film Morphology Impact on Impedance Spectrum
Robinson, Kyle; Gredig, Thomas
2012-11-01
Copper phthlacyanine thin films play an important role as the active layer in gas sensors, organic solar cells, and organic field-effect transistors. The surface morphology of such thin films can be controlled via modification of thermal deposition parameters. Thin films were deposited onto platinum interdigitated electrodes for impedance measurements to study the effect of structure on charge transport. The average grain size increases and changes from α- and β-phase for samples deposited in the temperature range of 295-534 K. AC measurements in the temperature range of 295-385 K reveal relaxation peaks in the impedance spectra. From this spectrum, essential properties are retrieved, such as relaxation times and effective capacities, and correlated with the film morphology. Subject to both photo- and 5-day-dark current trials, photodecay rates are extracted via effective impedance circuit analysis using a phenomenological model that includes contributions from the grain boundary and the bulk part of the grain. Results indicate that the resistance contribution of low frequency relaxation peaks decrease while approaching the phase transition temperature, and vice versa for capacitance. We attribute the low-frequency peaks to grain boundaries, which are reduced in high temperature deposited samples. Hyper β-phase deposition temperatures show a sudden rise in resistance and lower capacitance due to increased roughness of samples.
Acoustic impedance inversion of zero-offset VSP data
Institute of Scientific and Technical Information of China (English)
Wang Jing; Liu Yang; Sun Zhe; Tian Hong; Su Hua; Zhao Qianhua; Liu Yingyu
2009-01-01
Highly precise acoustic impedance inversion is a key technology for pre-drilling prediction by VSP data. In this paper, based on the facts that VSP data has high resolution, high signal to noise ratio, and the downgoing and upgoing waves can be accurately separated, we propose a method of predicting the impedance below the borehole in front of the bit using VSP data. First, the method of nonlinear iterative inversion is adopted to invert for impedance using the VSP corridor stack. Then, by modifying the damping factor in the iteration and using the preconditioned conjugate gradient method to solve the equations, the stability and convergence of the inversion results can be enhanced. The results of theoretical models and actual data demonstrate that the method is effective for pre-drilling prediction using VSP data.
Transferring human impedance regulation skills to robots
Ajoudani, Arash
2016-01-01
This book introduces novel thinking and techniques to the control of robotic manipulation. In particular, the concept of teleimpedance control as an alternative method to bilateral force-reflecting teleoperation control for robotic manipulation is introduced. In teleimpedance control, a compound reference command is sent to the slave robot including both the desired motion trajectory and impedance profile, which are then realized by the remote controller. This concept forms a basis for the development of the controllers for a robotic arm, a dual-arm setup, a synergy-driven robotic hand, and a compliant exoskeleton for improved interaction performance.
Beam Coupling Impedances of Small Discontinuities
Kurennoy, S S
2000-01-01
A general derivation of the beam coupling impedances produced by small discontinuities on the wall of the vacuum chamber of an accelerator is reviewed. A collection of analytical formulas for the impedances of small obstacles is presented.
Nonlinear feature identification of impedance-based structural health monitoring
Energy Technology Data Exchange (ETDEWEB)
Rutherford, A. C. (Amanda C.); Park, G. H. (Gyu Hae); Sohn, H. (Hoon); Farrar, C. R. (Charles R.)
2004-01-01
The impedance-based structural health monitoring technique, which utilizes electromechanical coupling properties of piezoelectric materials, has shown feasibility for use in a variety of structural health monitoring applications. Relying on high frequency local excitations (typically > 30 kHz), this technique is very sensitive to minor changes in structural integrity in the near field of piezoelectric sensors. Several damage sensitive features have been identified and used coupled with the impedance methods. Most of these methods are, however, limited to linearity assumptions of a structure. This paper presents the use of experimentally identified nonlinear features, combined with impedance methods, for structural health monitoring. Their applicability to damage detection in various frequency ranges is demonstrated using actual impedance signals measured from a portal frame structure. The performance of the nonlinear feature is compared with those of conventional impedance methods. This paper reinforces the utility of nonlinear features in structural health monitoring and suggests that their varying sensitivity in different frequency ranges may be leveraged for certain applications.
Impedance technique for measuring dielectrophoretic collection of microbiological particles
Allsopp, D W E; Brown, A P; Betts, W B
1999-01-01
Measurement of the impedance change resulting from the collection of microbiological particles at coplanar electrodes is shown to be an effective and potentially quantitative method of detecting dielectrophoresis. Strong correlations between the frequency-dependent dielectrophoretic collection characteristics measured by impedance change and those observed using an established counting method based on image analysis have been obtained for Escherichia coli. In addition it is shown that the new electrical method can be used to sense dielectrophoretic collection of 19 nm diameter latex beads, particles too small to be resolved by conventional optical detection systems. (author)
Different radiation impedance models for finite porous materials
DEFF Research Database (Denmark)
Nolan, Melanie; Jeong, Cheol-Ho; Brunskog, Jonas;
2015-01-01
coupled to the transfer matrix method (TMM). These methods are found to yield comparable results when predicting the Sabine absorption coefficients of finite porous materials. Discrepancies with measurement results can essentially be explained by the unbalance between grazing and non-grazing sound field...... the infinite case. Thus, in order to predict the Sabine absorption coefficients of finite porous samples, one can incorporate models of the radiation impedance. In this study, different radiation impedance models are compared with two experimental examples. Thomasson’s model is compared to Rhazi’s method when...
Superconducting shielded core reactor with reduced AC losses
Energy Technology Data Exchange (ETDEWEB)
Cha, Yung S.; Hull, John R.
2006-04-04
A superconducting shielded core reactor (SSCR) operates as a passive device for limiting excessive AC current in a circuit operating at a high power level under a fault condition such as shorting. The SSCR includes a ferromagnetic core which may be either closed or open (with an air gap) and extends into and through a superconducting tube or superconducting rings arranged in a stacked array. First and second series connected copper coils each disposed about a portion of the iron core are connected to the circuit to be protected and are respectively wound inside and outside of the superconducting tube or rings. A large impedance is inserted into the circuit by the core when the shielding capability of the superconducting arrangement is exceeded by the applied magnetic field generated by the two coils under a fault condition to limit the AC current in the circuit. The proposed SSCR also affords reduced AC loss compared to conventional SSCRs under continuous normal operation.
Directory of Open Access Journals (Sweden)
Kang Jin-Gu
2008-01-01
Full Text Available Abstract Transition metal oxides have been suggested as innovative, high-energy electrode materials for lithium-ion batteries because their electrochemical conversion reactions can transfer two to six electrons. However, nano-sized transition metal oxides, especially Co3O4, exhibit drastic capacity decay during discharge/charge cycling, which hinders their practical use in lithium-ion batteries. Herein, we prepared nano-sized Co3O4with high crystallinity using a simple citrate-gel method and used electrochemical impedance spectroscopy method to examine the origin for the drastic capacity fading observed in the nano-sized Co3O4anode system. During cycling, AC impedance responses were collected at the first discharged state and at every subsequent tenth discharged state until the 100th cycle. By examining the separable relaxation time of each electrochemical reaction and the goodness-of-fit results, a direct relation between the charge transfer process and cycling performance was clearly observed.
A spatial impedance controller for robotic manipulation
Fasse, Ernest D.; Broenink, Jan F.
1997-01-01
Mechanical impedance is the dynamic generalization of stiffness, and determines interactive behavior by definition. Although the argument for explicitly controlling impedance is strong, impedance control has had only a modest impact on robotic manipulator control practice. This is due in part to the
A compact broadband nonsynchronous noncommensurate impedance transformer
DEFF Research Database (Denmark)
Zhurbenko, Vitaliy; Kim, Kseniya; Narenda, Kumar
2012-01-01
Nonsynchronous noncommensurate impedance transformers consist of a combination of high‐ and low‐impedance transmission lines. High‐impedance lines have narrow tracks in strip and microstrip technology, which allows for high flexibility and miniaturization of the layout in comparison to the tradit...
Impedance analysis of acupuncture points and pathways
Teplan, Michal; Kukučka, Marek; Ondrejkovičová, Alena
2011-12-01
Investigation of impedance characteristics of acupuncture points from acoustic to radio frequency range is addressed. Discernment and localization of acupuncture points in initial single subject study was unsuccessfully attempted by impedance map technique. Vector impedance analyses determined possible resonant zones in MHz region.
Tapping mode microwave impedance microscopy
Lai, K.
2009-01-01
We report tapping mode microwave impedance imaging based on atomic force microscope platforms. The shielded cantilever probe is critical to localize the tip-sample interaction near the tip apex. The modulated tip-sample impedance can be accurately simulated by the finite-element analysis and the result agrees quantitatively to the experimental data on a series of thin-film dielectric samples. The tapping mode microwave imaging is also superior to the contact mode in that the thermal drift in a long time scale is totally eliminated and an absolute measurement on the dielectric properties is possible. We demonstrated tapping images on working nanodevices, and the data are consistent with the transport results. © 2009 American Institute of Physics.
Institute of Scientific and Technical Information of China (English)
韦炜
2012-01-01
In comparison with the basic principle, advantages and disadvantages of the traditional analog measuring methods (bridge method and resonance method) and digital intelligent measuring methods for detecting AC parameters of capacitors and inductors, the conclusions that the inductance (capacitancc)-voltage conversion method has more advantages and wider applications were obtained. The development trend of AC parameter measuring methods for capacitors and inductors is pointed out in this paper.%为了测量电容器和电感器的性能,常用的交流参数测量方法有传统模拟式(即电桥法和谐振法)和数字智能化测量方法两大类型.通过对比分析传统模拟式和数字智能化测量方法的基本原理和优缺点得出电感(电容)-电压的转换方法优点多,应用广,并指出电容器和电感器交流参数测量方法的发展趋势.
The topological AC effect on noncommutative phase space
Li, K; Li, Kang; Wang, Jianhua
2006-01-01
The Aharonov-Casher (AC) effect in non-commutative(NC) quantum mechanics is studied. Instead of using the star product method, we use a generalization of Bopp's shift method. After solving the Dirac equations both on noncommutative space and noncommutative phase space by the new method, we obtain the corrections to AC phase on NC space and NC phase space respectively.
Algorithmic Error Correction of Impedance Measuring Sensors
Directory of Open Access Journals (Sweden)
Vira Tyrsa
2009-12-01
Full Text Available This paper describes novel design concepts and some advanced techniques proposed for increasing the accuracy of low cost impedance measuring devices without reduction of operational speed. The proposed structural method for algorithmic error correction and iterating correction method provide linearization of transfer functions of the measuring sensor and signal conditioning converter, which contribute the principal additive and relative measurement errors. Some measuring systems have been implemented in order to estimate in practice the performance of the proposed methods. Particularly, a measuring system for analysis of C-V, G-V characteristics has been designed and constructed. It has been tested during technological process control of charge-coupled device CCD manufacturing. The obtained results are discussed in order to define a reasonable range of applied methods, their utility, and performance.
Algorithmic Error Correction of Impedance Measuring Sensors
Starostenko, Oleg; Alarcon-Aquino, Vicente; Hernandez, Wilmar; Sergiyenko, Oleg; Tyrsa, Vira
2009-01-01
This paper describes novel design concepts and some advanced techniques proposed for increasing the accuracy of low cost impedance measuring devices without reduction of operational speed. The proposed structural method for algorithmic error correction and iterating correction method provide linearization of transfer functions of the measuring sensor and signal conditioning converter, which contribute the principal additive and relative measurement errors. Some measuring systems have been implemented in order to estimate in practice the performance of the proposed methods. Particularly, a measuring system for analysis of C-V, G-V characteristics has been designed and constructed. It has been tested during technological process control of charge-coupled device CCD manufacturing. The obtained results are discussed in order to define a reasonable range of applied methods, their utility, and performance. PMID:22303177
DEFF Research Database (Denmark)
Hou, Xiaochao; Sun, Yao; Yuan, Wenbin
2016-01-01
In low-voltage converter-based alternating current (AC) microgrids with resistive distribution lines, the P-V droop with Q-f boost (VPD/FQB) is the most common method for load sharing. However, it cannot achieve the active power sharing proportionally. To overcome this drawback, the conventional P......-ω/Q-V droop control is adopted in the low-voltage AC microgrid. As a result, the active power sharing among the distributed generators (DGs) is easily obtained without communication. More importantly, this study clears up the previous misunderstanding that conventional P-ω/Q-V droop control is only applicable...... to microgrids with highly inductive lines, and lays a foundation for the application of conventional droop control under different line impedances. Moreover, in order to guarantee the accurate reactive power sharing, a guide for designing Q-V droop gains is given, and virtual resistance is adopted to shape...
A new three-dimensional electromechanical impedance model for an embedded dual-PZT transducer
Wang, Dansheng; Li, Zhi; Zhu, Hongping
2016-07-01
In the past twenty years, the electromechanical (EM) impedance technique has been investigated extensively in the mechanical, aviation and civil engineering fields. Many different EM impedance models have been proposed to characterize the interaction between the surface-bonded PZT transducer and the host structure. This paper formulates a new three-dimensional EM impedance model characterizing the interaction between an embedded circle dual-PZT transducer and the host structure based on the effective impedance concept. The proposed model is validated by experimental results from a group of smart cement cubes, in which three circle dual-PZT transducers are embedded respectively. In addition, a new EM impedance measuring method for the dual-PZT transducer is also introduced. In the measuring method, only a common signal generator and an oscilloscope are needed, by which the exciting and receiving voltage signals are obtained respectively. Combined with fast Fourier transform the EM impedance signatures of the dual-PZT transducers are obtained.
Structural and impedance spectroscopy properties of La0.8Ba0.1Ca0.1Mn1-xRuxO3 perovskites
Chebaane, M.; Talbi, N.; Dhahri, A.; Oumezzine, M.; Khirouni, K.
2017-03-01
Polycrystalline samples La0.8Ba0.1Ca0.1Mn1-xRuxO3 (x=0 and 0.075) were prepared by sol-gel-based Pechini method. The X ray diffraction study has shown that all the samples exhibit a single phase with rhombohedral structure (space group R 3 ̅c, no. 167). The complex impedance has been investigated in the temperature range 160-320 K and in the frequency range 40 Hz-1 MHz. The imaginary part of the complex impedance (Z‧‧) frequency dependence revealed one relaxation peak. The Cole-Cole plots of the impedance values exhibited a semi -circular arc that can be described by an R1+(R2//ZCPE) electrical equivalent circuit. The conductance spectra have been investigated by the Jonscher universal power law: G(ω)=GDC+Aωn, where ω is the frequency of the ac field, and n is the exponent. The activation energy obtained both from the conductance and from time relaxation analyses are very similar, and hence the relaxation process may be attributed to the same type of charge carriers.
Impedance analysis of an enhanced piezoelectric biosensor
Kim, Gi-Ho
This study investigated the usefulness and characteristics of a five-megahertz quartz crystal resonator oscillating in a thickness-shear mode as a sensor of biological pathogens such as Salmonella typhimurium . An impedance analyzer measured the impedance of the oscillating quartz crystal, which determined all mechanical properties of the oscillating quartz and its immediate environment. In this study, the impedance behavior of the bare crystal was characterized in air and in potassium phosphate buffer solution. The potassium phosphate buffer was a Newtonian liquid. The resonance frequency of the oscillating quartz shifted down about 900 Hz by contacting with the buffer. An immobilized-antibody layer on the quartz surface behaved like a rigid mass when immersed in the buffer solution. The quartz crystal with immobilized antibodies was characterized in various solutions containing antibody- coated paramagnetic microspheres and varying concentrations of Salmonella typhimurium (102 - 108 cells/ml). The Salmonella cells were captured by antibody- coated paramagnetic microspheres, and then these complexes were moved magnetically to the oscillating quartz and were captured by antibodies immobilized on the crystal surface. The response of the crystal was expressed in terms of equivalent circuit parameters. The motional inductance and the motional resistance increased as a function of the concentration of Salmonella. The viscous damping was the main contribution to the resistance and the inductance in a liquid environment. The load resistance was the most effective and sensitive circuit parameter. A magnetic force was a useful method to collect the complexes of Salmonella-microspheres on the crystal surface and enhance the response sensor. In this system, the detection limit, based on resistance monitoring, was about 103 cells/ml.
肉果秤锤树花粉活力测定方法%Study on Detection Methods for Pollen Viability of Sinoj ac k ia s ac oc arp a L.Q.Luo
Institute of Scientific and Technical Information of China (English)
伏秦超; 王娟; 张西玉; 刘超; 刘芳
2015-01-01
本研究以离体培养萌发法为参照，从TTC法、I2-KI法、过氧化物酶沉淀法和醋酸洋红法4种方法中筛选出适宜快速测定肉果秤锤树(Sinojackia sarcocarpa L.Q.Luo)花粉活力的方法。结果表明：肉果秤锤树花粉离体培养萌发的最适条件为23℃培养下15%蔗糖、0.01 mg/mL硼酸，萌发率达84.85%；过氧化物酶沉淀法、TTC法、I2-KI法和醋酸洋红法测定的萌发率分别为78.45%、0、100%和37.01%。过氧化物酶沉淀法测定结果与离体培养萌发法的测定结果最接近(p<0.01)，是简单快速测定肉果秤锤树花粉活力的最适方法。本研究筛选出的花粉离体培养萌发条件和花粉活力快速测定方法，可为进一步开展肉果秤锤树育种工作提供理论依据与技术支持。%We firstly investigated the optimum condition of Sinojackia sacocarpa L.Q.Luo's pollen germination under in v itro culture condition, and then recruited four different methods to detect the pollen viability, such as triphenyltetrazolium chloride (TTC), iodine-iodide kalium (I2-KI), peroxide enzyme and acidcarmine method, in comparison with in vitro pollen germination method. Our results showed that a culture medium containing 15%sucrose and 0.01 mg/mL boric acid had the best effect on in vitro pollen germination at 23℃, and the pollen germination rate was up to 84.85%. Furthermore, we found the detection of pollen viability using peroxide enzyme, TTC, I2-KI and acidcarmine method was 78.45%, 0, 100% and 37.01%, respectively; These data suggested that peroxide enzyme method provided a quicker and more convenient means compared to other three methods, because its result was close to true viability ratio and dyeing was fast and clear. This study selected the optional condition for the pollen germination in vitro culture and identified a fast method for detecting the pollen vitality, which should provide the theoretic foundation for breeding work.
大容量发电机出口断路器选择%Circuit Breakers Selection Method for Large-capacity AC High-voltage Generator
Institute of Scientific and Technical Information of China (English)
张爽
2011-01-01
针对大容量发电机出口断路器的选择问题,依据GB/T 14824-2008、IEEE Std C37.013-1997和IEC 60909-0-2001中的计算方法,并结合发电机出口断路器型式试验报告的有关数据,以某百万千瓦级发电机组为例进行了比较计算,分析计算结果,提出了对发电机出口短路器短路电流开断能力不能采用百分比而应采用绝对值进行校验.%For selecting large-capacity AC high-voltage generator circuit breakers in a large generator system, comparative calculations are conducted for a million kilowatts rated generator following the standards of GB/T 14824-2008, IEEE Std C37.013-1997 and IEC 60909-0-2001. The calculation results and the test reports of generator circuit breakers are analyzed, and a suggestion is hence offered that absolute value of short-circuit current should be used for examining the short-circuit current breaking capacity of an AC high-voltage generator circuit breaker instead of percentage value.
An Electronic Measurement Instrumentation of the Impedance of a Loaded Fuel Cell or Battery
2007-01-01
In this paper we present an inexpensive electronic measurement instrumentation developed in our laboratory, to measure and plot the impedance of a loaded fuel cell or battery. Impedance measurements were taken by using the load modulation method. This instrumentation has been developed around a VXI system stand which controls electronic cards. Software under Hpvee® was developed for automatic measurements and the layout of the impedance of the fuel cell on load. The measurement environment, l...
An Islanding Microgrid Power Sharing Approach Using Enhanced Virtual Impedance Control Scheme
DEFF Research Database (Denmark)
He, Jinwei; Li, Yun Wei; Guerrero, Josep M.
2013-01-01
In order to address the load sharing problem in islanding microgrids, this paper proposes an enhanced distributed generation (DG) unit virtual impedance control approach. The proposed method can realize accurate regulation of DG unit equivalent impedance at both fundamental and selected harmonic...... and PCC harmonic voltage compensation are achieved without using any fundamental and harmonic components extractions. Experimental results from a scaled single-phase microgrid prototype are provided to validate the feasibility of the proposed virtual impedance control approach....
Online grid impedance estimation for single-phase grid-connected systems using PQ variations
DEFF Research Database (Denmark)
Ciobotaru, Mihai; Teodorescu, Remus; Rodriguez, Pedro;
2007-01-01
algorithms are used in order to estimate the value of the grid impedance. The online grid impedance estimation method can be used for compliance with the anti-islanding standard requirements (IEEE1574, IEEE929 and VDE0126) and for adaptive control of the grid-connected converters. The proposed method...
Are active elements necessary in the basilar membrane impedance?
Diependaal, R J; Viergever, M A; de Boer, E
1986-07-01
This article is motivated by the current hypothesis [Kim et al., Psychological, Physiological and Behavioural Studies in Hearing (Delft U. P., The Netherlands, 1980); Neely, Doctoral dissertation, Washington University, St. Louis, MO (1981); de Boer, J. Acoust. Soc. Am. 73, 567-573 (1983a) and 73, 574-576 (1983b)] that it is necessary to include active elements in the basilar membrane (BM) impedance in order to explain recent data on the vibration of the BM [Khanna and Leonard, Science 215, 305-306 (1982); Sellick et al., J. Acoust. Soc. Am. 72, 131-141 (1982); Robles et al., Peripheral Auditory Mechanisms (Springer, New York, 1986)]. In order to test this hypothesis, first, a method which is an inversion of the customary description of cochlear mechanics is described. Instead of computing the BM velocity for a given point impedance of the membrane, we show how to compute the impedance function from a given BM velocity pattern in response to a sinusoidal input at the stapes. This method is then used to study the sensitivity of the recovered impedance to perturbations in the velocity pattern. The simulations used show that the real part of the impedance is extremely sensitive to such perturbations. Therefore, measured velocity patterns are unlikely to resolve the issue of whether active elements should be included. Frequency responses measured at a few points on the membrane are even less likely to do so.
Application of plant impedance for diagnosing plant disease
Xu, Huirong; Jiang, Xuesong; Zhu, Shengpan; Ying, Yibin
2006-10-01
Biological cells have components acting as electrical elements that maintain the health of the cell by regulation of the electrical charge content. Plant impedance is decided by the state of plant physiology and pathology. Plant physiology and pathology can be studies by measuring plant impedance. The effect of Cucumber Mosaic Virus red bean isolate (CMV-RB) on electrical resistance of tomato leaves was studied by the method of impedance measurement. It was found that the value of resistance of tomato leaves infected with CMV-RB was smaller than that in sound plant leaves. This decrease of impedances in leaf tissue was occurred with increased severity of disease. The decrease of resistance of tomato leaves infected with CMV-RB could be detected by electrical resistance detecting within 4 days after inoculation even though significant visible differences between the control and the infected plants were not noted, so that the technique for measurement of tomato leaf tissue impedance is a rapid, clever, simple method on diagnosis of plant disease.
In situ impedance measurement of microwave atmospheric pressure plasma
Lee, S. T.; Nam, W. J.; Lee, J. K.; Yun, G. S.
2017-04-01
The impedance of atmospheric pressure argon plasma jets driven by microwave frequency is determined in situ by a novel ‘two frequency method’. In the conventional method of reflection coefficient ({{S}}11) measurement, the frequency of the driving microwave power is scanned, which inevitably affects the plasma characters and leads to uncertainty in the estimated plasma impedance. In our proposed method, the frequency-scanning signal additional to the driving power is used to measure {{S}}11 over a wide frequency range, which enables accurate determination of the plasma impedance based on an equivalent circuit model. The measured resistance and reactance of the plasma increase with the driving power in agreement with the transmission line theory. Based on this in situ measurement of the plasma impedance, the net power coupled to the plasma has been determined. The overall power efficiency remains approximately unchanged around 45% for different input power levels owing to the competing effects between the impedance mismatch and the volume change of the plasma.
Reconstruction of relaxation time distribution from linear electrochemical impedance spectroscopy
Zhang, Yanxiang; Chen, Yu; Yan, Mufu; Chen, Fanglin
2015-06-01
Linear electrochemical impedance spectroscopy (EIS), and in particular its representation of distribution of relaxation time (DRT), enables the identification of the number of processes and their nature involved in electrochemical cells. With the advantage of high frequency resolution, DRT has recently drawn increasing attention for applications in solid oxide fuel cells (SOFCs). However, the method of DRT reconstruction is not yet presented clearly in terms of what mathematical treatments and theoretical assumptions have been made. Here we present unambiguously a method to reconstruct DRT function of impedance based on Tikhonov regularization. By using the synthetic impedances and analytic DRT functions of RQ element, generalized finite length Warburg element, and Gerischer element with physical quantities representative to those of SOFC processes, we show that the quality of DRT reconstruction is sensitive to the sampling points per decade (ppd) of frequency from the impedance measurement. The robustness of the DRT reconstruction to resist noise imbedded in impedance data and numerical calculations can be accomplished by optimizing the weighting factor λ according to well defined criterion.