Sample records for ac impedance analysis
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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.
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DEFF Research Database (Denmark)
Li, Chendan; Chaudhary, Sanjay Kumar; Savaghebi, Mehdi
2017-01-01
In the low-voltage (LV) ac microgrids (MGs), with a relatively high R/X ratio, virtual impedance is usually adopted to improve the performance of droop control applied to distributed generators (DGs). At the same time, LV dc MG using virtual impedance as droop control is emerging without adequate...... power flow studies. In this paper, power flow analyses for both ac and dc MGs are formulated and implemented. The mathematical models for both types of MGs considering the concept of virtual impedance are used to be in conformity with the practical control of the DGs. As a result, calculation accuracy...... is improved for both ac and dc MG 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 of the impact to the system of internal control parameters...
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Directory of Open Access Journals (Sweden)
Gonzalo Abad
2018-05-01
Full Text Available This paper presents an analytical model, oriented to study harmonic mitigation aspects in AC grids. As it is well known, the presence of non-desired harmonics in AC grids can be palliated in several manners. However, in this paper, a power electronic-based active impedance at selective frequencies (ACISEF is used, due to its already proven flexibility and adaptability to the changing characteristics of AC grids. Hence, the proposed analytical model approach is specially conceived to globally consider both the model of the AC grid itself with its electric equivalent impedances, together with the power electronic-based ACISEF, including its control loops. In addition, the proposed analytical model presents practical and useful properties, as it is simple to understand and simple to use, it has low computational cost and simple adaptability to different scenarios of AC grids, and it provides an accurate enough representation of the reality. The benefits of using the proposed analytical model are shown in this paper through some examples of its usefulness, including an analysis of stability and the identification of sources of instability for a robust design, an analysis of effectiveness in harmonic mitigation, an analysis to assist in the choice of the most suitable active impedance under a given state of the AC grid, an analysis of the interaction between different compensators, and so on. To conclude, experimental validation of a 2.15 kA ACISEF in a real 33 kV AC grid is provided, in which real users (household and industry loads and crucial elements such as wind parks and HVDC systems are near inter-connected.
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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.
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Application of ac impedance in fuel cell research and development
Energy Technology Data Exchange (ETDEWEB)
Selman, J R; Lin, Y P [Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Chemical Engineering
1993-10-01
In applying ac impedance to fuel cells and their porous (gas diffusion) electrodes the emphasis lies on different fuel cell components, and their properties, according to the fuel cell type. The focus has been directed at the electrode/electrolyte interface in MCFC and PAFC, whereas in SOFC and PEMFC the ionic/electronic conductivity of the electrolyte or the characteristics of its composite with the electrocatalyst is of primary interest. The limitations of ac impedance in fuel cell application are in part due to difficulties of interpretation and in part due to experimental difficulties because of the generally fast electrode reaction kinetics. Further research directions are indicated. (author)
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Development of AC impedance methods for evaluating corroding metal surfaces and coatings
Knockemus, Ward
1986-01-01
In an effort to investigate metal surface corrosion and the breakdown of metal protective coatings the AC Impedance Method was applied to zinc chromate primer coated 2219-T87 aluminum. The model 368-1 AC Impedance Measurement System recently acquired by the MSFC Corrosion Research Branch was used to monitor changing properties of coated aluminum disks immersed in 3.5% NaCl buffered at ph 5.5 over three to four weeks. The DC polarization resistance runs were performed on the same samples. The corrosion system can be represented by an electronic analog called an equivalent circuit that consists of transistors and capacitors in specific arrangements. This equivalent circuit parallels the impedance behavior of the corrosion system during a frequency scan. Values for resistances and capacities 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 coating. A suitable equivalent circuit was determined that predicts the correct Bode phase and magnitude for the experimental sample. The DC corrosion current density data are related to equivalent circuit element parameters.
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El-Shabaan, M. M.
2018-02-01
Impedance spectroscopy and alternating-current (AC) conductivity (σ AC) studies of bulk 3-amino-7-(dimethylamino)-2-methyl-hydrochloride (neutral red, NR) have been carried out over the temperature (T) range from 303 K to 383 K and frequency (f) range from 0.5 kHz to 5 MHz. Dielectric data were analyzed using the complex impedance (Z *) and complex electric modulus (M *) for bulk NR at various temperatures. The impedance loss peaks were found to shift towards high frequencies, indicating an increase in the relaxation time (τ 0) and loss in the material, with increasing temperature. For each temperature, a single depressed semicircle was observed at high frequencies, originating from the bulk transport, and a spike in the low-frequency region, resulting from the electrode effect. Fitting of these curves yielded an equivalent circuit containing a parallel combination of a resistance R and constant-phase element (CPE) Q. The carrier transport in bulk NR is governed by the correlated barrier hopping (CBH) mechanism, some parameters of which, such as the maximum barrier height (W M), charge density (N), and hopping distance (r), were determined as functions of both temperature and frequency. The frequency dependence of σ AC at different temperatures indicated that the conduction in bulk NR is a thermally activated process. The σ AC value at different frequencies increased linearly with temperature.
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Impedance and ac conductivity studies of Ba (Pr1/2Nb1/2) O3 ceramic
Indian Academy of Sciences (India)
Home; Journals; Bulletin of Materials Science; Volume 36; Issue 4. Impedance and a.c. conductivity studies of ... Abstract. 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 ...
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AC impedance behavior of a practical-size single-cell SOFC under DC current
Energy Technology Data Exchange (ETDEWEB)
Momma, Akihiko; Kaga, Yasuo; Takano, Kiyonami; Nozaki, Ken; Negishi, Akira; Kato, Ken; Kato, Tohru [Fuel Cell Group, Energy Electronics Institute, National Institute of Advanced Industrial Science and Technology, Umezono Tsukuba-shi, Ibaraki 305-8568 (Japan); Inagaki, Toru; Yoshida, Hiroyuki [Energy Use R and D Center, The Kansai Electric Power Company, Inc., 11-20 Nakoji, 3-Chome, Amagasaki, Hyogo 661-0974 (Japan); Hosoi, Kei; Hoshino, Koji; Akbay, Taner; Akikusa, Jun; Yamada, Masaharu; Chitose, Norihisa [Central Research Institute, Naka Research Center, Mitsubishi Materials Corp. 1002-14 Mukohyama, Naka-machi, Naka-gun, Ibaraki 311-0102 (Japan)
2004-10-29
AC impedance measurements were carried out using practical-size planar disc-type SOFC which employs lanthanum gallate as a solid electrolyte. The data were obtained under practical conditions of gas flow rate and DC current. Under these conditions, the gas conversion impedance (GCI), which originates from the change of the electromotive force (EMF) caused by the change in anodic gaseous concentrations along the flow direction, was observed in the low-frequency range of the data obtained. The overlapping impedance together with GCI on the low-frequency arc was also estimated. Experimentally obtained GCI was in good agreement with that calculated. It was concluded that GCI was predominant in the impedance data obtained under practical conditions. The shift of the high-frequency intercept in the complex impedance diagrams was shown to appear as a result of the change in the distribution of gaseous composition in the anode. The dependency of the low-frequency arc on temperature was also shown, and it was assumed that the overlapped impedance varies as the temperature changes. The validity of the impedance measurement, as a diagnostic means to evaluate the gas flow in SOFC stack, was suggested.
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Mitigating voltage lead errors of an AC Josephson voltage standard by impedance matching
Zhao, Dongsheng; van den Brom, Helko E.; Houtzager, Ernest
2017-09-01
A pulse-driven AC Josephson voltage standard (ACJVS) generates calculable AC voltage signals at low temperatures, whereas measurements are performed with a device under test (DUT) at room temperature. The voltage leads cause the output voltage to show deviations that scale with the frequency squared. Error correction mechanisms investigated so far allow the ACJVS to be operational for frequencies up to 100 kHz. In this paper, calculations are presented to deal with these errors in terms of reflected waves. Impedance matching at the source side of the system, which is loaded with a high-impedance DUT, is proposed as an accurate method to mitigate these errors for frequencies up to 1 MHz. Simulations show that the influence of non-ideal component characteristics, such as the tolerance of the matching resistor, the capacitance of the load input impedance, losses in the voltage leads, non-homogeneity in the voltage leads, a non-ideal on-chip connection and inductors between the Josephson junction array and the voltage leads, can be corrected for using the proposed procedures. The results show that an expanded uncertainty of 12 parts in 106 (k = 2) at 1 MHz and 0.5 part in 106 (k = 2) at 100 kHz is within reach.
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AC impedance spectroscopy of NASICON type Na3Fe2(PO4)3 ceramic
Mandal, Biswajit; Thakur, A. K.
2018-05-01
Super ionic conductors (e.g.; A3M2(XO4)3, A=Li, Na) have received attention in applied research due to their interesting electrochemical property and inherently high ionic conductivity [1]. However, structural and compatibility requirements for fast ion transport is stringent and it plays a crucial role. In A3M2(XO4)3, a suitable cage formation in the crystal framework due to corner sharing arrangement of XO4 tetrahedra and MO6 octahedra creates voids that acts as host/guest site for cation transport. In this work, we report Nasicon structure Na3Fe2(PO4)3 (NFP) prepared via sol-gel route mediated by citric acid. Structural analysis confirmed that NFP sample belongs to monoclinic crystal structure having Cc space group (S. G. No 9) with lattice parameters, a=15.106 Å, b=8.722 Å, c=8.775 Å and β=124.96°. Electrical properties of the prepared sample have been studied by AC impedance spectroscopy technique. The AC conductivity results indicated typical signature of ionically conducting system.
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Energy Technology Data Exchange (ETDEWEB)
Musiani, M.M.; Mengoli, G.; Pagura, C.
1985-04-01
Electrochemically synthesized polyoxphenylene coatings on mild steel exposed to NaCl or H2SO4 solutions were investigated by ac impedance measurements. The influence of coating cohesion, adhesion to substrate, and surface pretreatment on the corrosion behaviour of the samples is clarified.
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High temperature impedance spectroscopy of barium stannate
Indian Academy of Sciences (India)
... differential thermal analysis, thermogravimetric analysis and Fourier transform infrared techniques. Electrical properties were studied using a.c. impedance spectroscopy technique in the temperature range of 50–650 °C and frequency range of 10 Hz–13 MHz. The complex impedance plots at temperature ≥ 300 °C show ...
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Yadav, Abhinav; Mantry, Snigdha Paramita; Fahad, Mohd.; Sarun, P. M.
2018-05-01
Sodium niobate (NaNbO3) ceramics is prepared by conventional solid state reaction method at sintering temperature 1150 °C for 4 h. The structural information of the material has been investigated by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FE-SEM). The XRD analysis of NaNbO3 ceramics shows an orthorhombic structure. The FE-SEM micrograph of NaNbO3 ceramics exhibit grains with grain sizes ranging between 1 μm to 5 μm. The surface coverage and average grain size of NaNbO3 ceramics are found to be 97.6 % and 2.5 μm, respectively. Frequency dependent electrical properties of NaNbO3 is investigated from room temperature to 500 °C in wide frequency range (100 Hz-5 MHz). Dielectric constant, ac-conductivity, impedance, modulus and Nyquist analysis are performed. The observed dielectric constant (1 kHz) at transition temperature (400 °C) are 975. From conductivity analysis, the estimated activation energy of NaNbO3 ceramics is 0.58 eV at 10 kHz. The result of Nyquist plot shows that the electrical behavior of NaNbO3 ceramics is contributed by grain and grain boundary responses. The impedance and modulus spectrum asserts that the negative temperature coefficient of resistance (NTCR) behavior and non-Debye type relaxation in NaNbO3.
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AC impedance electrochemical modeling of lithium-ion positive electrodes
International Nuclear Information System (INIS)
Dees, D.; Gunen, E.; Abraham, D.; Jansen, A.; Prakash, J.
2004-01-01
Under Department of Energy's Advanced Technology Development Program,various analytical diagnostic studies are being carried out to examine the lithium-ion battery technology for hybrid electric vehicle applications, and a series of electrochemical studies are being conducted to examine the performance of these batteries. An electrochemical model was developed to associate changes that were observed in the post-test analytical diagnostic studies with the electrochemical performance loss during testing of lithium ion batteries. While both electrodes in the lithium-ion cell have been studied using a similar electrochemical model, the discussion here is limited to modeling of the positive electrode. The positive electrode under study has a composite structure made of a layered nickel oxide (LiNi 0.8 Co 0.15 Al 0.05 O 2 ) active material, a carbon black and graphite additive for distributing current, and a PVDF binder all on an aluminum current collector. The electrolyte is 1.2M LiPF 6 dissolved in a mixture of EC and EMC and a Celgard micro-porous membrane is used as the separator. Planar test cells (positive/separator/negative) were constructed with a special fixture and two separator membranes that allowed the placement of a micro-reference electrode between the separator membranes (1). Electrochemical studies including AC impedance spectroscopy were then conducted on the individual electrodes to examine the performance and ageing effects in the cell. The model was developed by following the work of Professor Newman at Berkeley (2). The solid electrolyte interface (SEI) region, based on post-test analytical results, was assumed to be a film on the oxide and an oxide layer at the surface of the oxide. A double layer capacity was added in parallel with the Butler-Volmer kinetic expression. The pertinent reaction, thermodynamic, and transport equations were linearized for a small sinusoidal perturbation (3). The resulting system of differential equations was solved
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International Nuclear Information System (INIS)
Habib, K.; Abdullah, A.
1995-01-01
An electrochemical study on Fe-Co-B-Si amorphous electrodes has been conducted. The study was focused on determining the electrochemical impedance spectroscopy (EIS) of four different alloys of Fe-Co-B-Si in various HCl acid solutions. The A.C. impedance and the capacitance of Fe-Co-B-Si, Co-Fe-Ni-B-Si, Co-Fe-Mn-B-Si, and Co-Fe-Ni-Mo-B-Si alloys were obtained in 25, 50, 75 and 100% of HCl acid at room temperature. Electrochemical parameters, i.e., impedance, were found to vary depending on additions of the Ni, Mn, Ni-Mo to Fe-Co-B-Si alloy, the acid concentration, and the nanoscopic surface roughness of the electrodes. Consequently, a correlation between the obtained data is established
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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.
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Gupta, Surbhi; Deshpande, S. K.; Sathe, V. G.; Siruguri, V.
2018-04-01
We present dielectric, complex impedance, modulus spectroscopy and AC conductivity studies of the compound BaFe10Sc2O19 as a function of temperature and frequency to understand the conduction mechanism. The variation in complex dielectric constant with frequency and temperature were analyzed on the basis of Maxwell-Wagner-Koop's theory and charge hopping between ferrous and ferric ions. The complex impedance spectroscopy study shows only grain contribution whereas complex modulus plot shows two semicircular arcs which indicate both grain and grain boundary contributions in conduction mechanism. AC conductivity has also been evaluated which follows the Jonscher's law. The activation energy calculated from temperature dependence of DC conductivity comes out to be Ea˜ 0.31eV.
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Impedance Analysis of Silicon Nanowire Lithium Ion Battery Anodes
Ruffo, Riccardo; Hong, Seung Sae; Chan, Candace K.; Huggins, Robert A.; Cui, Yi
2009-01-01
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
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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...
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Liu, Hai-Tao; Wen, Zhi-Yu; Xu, Yi; Shang, Zheng-Guo; Peng, Jin-Lan; Tian, Peng
2017-09-01
In this paper, an integrated microfluidic analysis microsystems with bacterial capture enrichment and in-situ impedance detection was purposed based on microfluidic chips dielectrophoresis technique and electrochemical impedance detection principle. The microsystems include microfluidic chip, main control module, and drive and control module, and signal detection and processing modulet and result display unit. The main control module produce the work sequence of impedance detection system parts and achieve data communication functions, the drive and control circuit generate AC signal which amplitude and frequency adjustable, and it was applied on the foodborne pathogens impedance analysis microsystems to realize the capture enrichment and impedance detection. The signal detection and processing circuit translate the current signal into impendence of bacteria, and transfer to computer, the last detection result is displayed on the computer. The experiment sample was prepared by adding Escherichia coli standard sample into chicken sample solution, and the samples were tested on the dielectrophoresis chip capture enrichment and in-situ impedance detection microsystems with micro-array electrode microfluidic chips. The experiments show that the Escherichia coli detection limit of microsystems is 5 × 104 CFU/mL and the detection time is within 6 min in the optimization of voltage detection 10 V and detection frequency 500 KHz operating conditions. The integrated microfluidic analysis microsystems laid the solid foundation for rapid real-time in-situ detection of bacteria.
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International Nuclear Information System (INIS)
Maqbool, Syed Asad; Mehmood, Malik Sajjad; Mukhtar, Saqlain Saqib; Baluch, Mansoor A.; Khan, Shamim; Yasin, Tariq; Khan, Yaqoob
2017-01-01
The dielectric behavior of γ-irradiated ultra-high molecular weight polyethylene (UHMWPE) and its nano composites (NCs) with γ-ray modified multi wall carbon nano tubes (γ-MWCNTs) and MWCNTs had been studied using impedance spectroscopy. The study had been carried out in the frequency range of 20–2 MHz at room temperature. All samples (pure and NCs) were prepared in the form of sheets and irradiated with γ-dose of 50 kGy and 100 kGy, respectively. The comprehensive analysis of results revealed that resistivity of UHMWPE for conduction decreased on irradiation and incorporation of MWCNTs (whether γ ray modified or un-modified) due to the radiation induced damage and conductive networks induced by MWCNTs. At low frequency range a significant increase in the dielectric constant had been observed because of irradiation and addition of MWNCTs. The trend of loss tangent and ac conductivity for each investigated sample depended on resistivity offered and had a decreasing trend as a function of frequency. Moreover, dissipation factor increased with the incorporation of MWNCTs and irradiation from 0.12 to 0.22. In addition to this, non-frequency dependent static dielectric constant was also found to increase with irradiation and incorporation of MWCNTs. The relaxation time was found to increase from 1.2 to 4.3 ms due to hindrance offered by radiation induced mutual cross linking of PE chains and polymer-MWNCTs bindings. - Highlights: • The resistivity for conduction in pristine UHMWPE is decreased with γ-irradiation. • Conduction in PE/MWCNTs nanocomposites increased due to MWCNTs addition. • Static dielectric constant of UHMWPE increased with γ-irradiation. • Static dielectric constant of UHMWPE increased due to MWCNTs incorporation.
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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.
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Directory of Open Access Journals (Sweden)
M. Saidi
2015-03-01
Full Text Available Polycrystalline of [(Na0.535K0.4800.966Li0.058](Nb0.90Ta0.10O3 samples were prepared using the high-temperature solid-state reaction technique. X-ray diffraction (XRD analysis indicates the formation of a single-phase with orthorhombic structure. AC impedance plots were used as tool to analyze the electrical behavior of the sample as a function of frequency at different temperatures. The AC impedance studies revealed the presence of grain effect, from 425°C onwards. Complex impedance analysis indicated non-Debye type dielectric relaxation. The Nyquist plot showed the negative temperature coefficient of resistance (NTCR characteristic of NKLNT. The AC conductivity results were used to correlate with the barrier hopping (CBH model to evaluate the binding energy (Wm, the minimum hopping distance (Rmin, the density of states at Fermi level (N(Ef, and the activation energy of the compound.
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Energy Technology Data Exchange (ETDEWEB)
Deslouis, C.; Tribollet, B. (Physique des Liquides et Electrochimie Lab., Univ. Pierre et Marie Curie, 75 - Paris (France)); Musiani, M.M. (Ist. di Polarografia ed Elettrochimica Preparativa del CNR, Padua (Italy))
1990-09-01
The oxidation of hydroquinone on Pt electrodes modified by electrosynthesized p-ethylcarbazole is studied in 5 M HClO{sub 4}. Electrohydrodynamical and a.c. impedance measurements yield the redox capacitance of the film and electron diffusivity D{sub E} with reasonable dependence on the thickness. D{sub E} values near to 10{sup -7} cm{sup 2} s{sup -1} confirm the average conductivity of this polymer. Change-transfer resistances in agreement with {alpha}=0.5 are measured. These results {alpha} posteriori justify the hypotheses put forward when developing the theoretical impedance model used for the analysis of the data. (orig.).
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Schulz, Tobias; Weinmüller, Christian; Nabavi, Majid; Poulikakos, Dimos
A single cell micro-direct methanol fuel cell (micro-DMFC) was investigated using electrochemical impedance spectroscopy. The electrodes consisted of thin, flexible polymer (SU8) film microchannel structures fabricated in-house using microfabrication techniques. AC impedance spectroscopy was used to separate contributions to the overall cell polarization from the anode, cathode and membrane. A clear distinction between the different electrochemical phenomena occurring in the micro-DMFC, especially the distinction between double layer charging and Faradaic reactions was shown. The effect of fuel flow rate, temperature, and anode flow channel structure on the impedance of the electrode reactions and membrane/electrode double layer charging were investigated. Analysis of impedance data revealed that the performance of the test cell was largely limited by the presence of intermediate carbon monoxide in the anode reaction. Higher temperatures increase cell performance by enabling intermediate CO to be oxidized at much higher rates. The results also revealed that serpentine anode flow microchannels show a lower tendency to intermediate CO coverage and a more stable cell behavior than parallel microchannels.
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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.
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Impedance-based Analysis of DC Link Control in Voltage Source Rectifiers
DEFF Research Database (Denmark)
Lu, Dapeng; Wang, Xiongfei; Blaabjerg, Frede
2018-01-01
This paper analyzes the dynamics influences of the outer dc link control in the voltage source rectifiers based on the impedance model. The ac-dc interactions are firstly presented by means of full order small signal model in dq frame, which shows the input voltage and load condition are the two...
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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...
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Directory of Open Access Journals (Sweden)
Suzana Sopčić
2018-05-01
Full Text Available Electrochemical impedance spectroscopy (EIS technique is used for characterization of single cell symmetric capacitors having different mass loadings of activated carbon (AC. Relevant values of charge storage capacitance (CT and internal resistance (ESR were evaluated by the single frequency and multi-frequency analyses of measured impedance spectra. Curve fittings were based on the non-ideal R-C model that takes into account the parasitic inductance, contributions from electrode materials/contacts and the effects of AC porosity. Higher CT and lower ESR values were obtained not only for the cell with higher mass of AC, but also using the single vs. multi-frequency approach. Lower CT and higher values of ESR that are generally obtained using the multi-frequency method and curve fittings should be related to the not ideal capacitive response of porous AC material and too high frequency chosen in applying the single frequency analysis.
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Effect of temperature on the AC impedance of protein
Indian Academy of Sciences (India)
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 ...
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Characterization and evaluation of EB-PVD thermal barrier coatings by impedance spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Zhang Chunxia; Liu Fushun; Gong Shengkai; Xu Huibin [School of Materials Science and Engineering, Beihang Univ., Beijing, BJ (China)
2005-07-01
Two layer thermal barrier coatings (TBCs) were prepared by EB-PVD (electron beam-physical vapor deposition) at different substrate temperatures in the range of 823 to 1123 K, and their microstructure was investigated with SEM and AC impedance as a function of substrate temperature and thermal cycling time. YSZ layer of all TBCs samples is in column structure, but the grain size and growth orientation are different with substrate. In this research, impedance spectra (IS) was measured as a function of thermal cycling between 1323 K and 298 K for these thermal barrier coatings. Grain boundary and bulk can be distinguished from analysis of AC impedance spectroa to provide information about the relation between microstructure and electric properties. The change in IS until failure was found to be related with the thickness, microcracks and macrocracks of TGO and the change in the interfacial of TGO/YSZ. (orig.)
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Energy Technology Data Exchange (ETDEWEB)
Kimura, Tomoharu; Yamada, Hirofumi, E-mail: h-yamada@kuee.kyoto-u.ac.jp [Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan); Kobayashi, Kei [Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510 (Japan); The Hakubi Center for Advanced Research, Kyoto University, Kyoto 615-8520 (Japan)
2015-08-07
The device performances of organic thin film transistors are often limited by the metal–organic interface because of the disordered molecular layers at the interface and the energy barriers against the carrier injection. It is important to study the local impedance at the interface without being affected by the interface morphology. We combined frequency modulation atomic force microscopy with scanning impedance microscopy (SIM) to sensitively measure the ac responses of the interface to an ac voltage applied across the interface and the dc potential drop at the interface. By using the frequency-modulation SIM (FM-SIM) technique, we characterized the interface impedance of a Pt electrode and a single pentacene grain as a parallel circuit of a contact resistance and a capacitance. We found that the reduction of the contact resistance was caused by the reduction of the energy level mismatch at the interface by the FM-SIM measurements, demonstrating the usefulness of the FM-SIM technique for investigation of the local interface impedance without being affected by its morphology.
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Energy Technology Data Exchange (ETDEWEB)
Ciovati, G [Jefferson Lab (United States)
2014-07-01
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.
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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.
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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.
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Impedance-spectroscopy analysis and piezoelectric properties of Pb2KNb5O15 ceramics
International Nuclear Information System (INIS)
Rao, K. Sambasiva; Murali Krishna, P.; Swarna Latha, T.; Madhava Prasad, D.
2006-01-01
Preparation, dielectric, piezoelectric, hysteresis, impedance spectroscopy and AC conductivity studies in the Pb 0.8 K 0.4 Nb 2 O 6 ferroelectric ceramic have been presented. The Pb 1-x K 2x Nb 2 O 6 (PKN) characterized for ferroelectric and impedance spectroscopy studies from room temperature to 600 deg. C. The sample shows a single phase with orthorhombic structure from X-ray diffraction studies. The Cole-Cole plots and electric modulus plots at different temperatures are drawn. The results obtained from the impedance spectroscopy are analyzed, to understand the conductivity behavior of PKN. The piezoelectric constant, d 33 , has been found to be 75 x 10 -12 C/N
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Impedance analysis on organic ultrathin layers
Energy Technology Data Exchange (ETDEWEB)
Bom, Sidhant; Wagner, Veit [Jacobs University Bremen, School of Engineering and Science, Campus Ring 8, 28759 Bremen (Germany)
2008-07-01
Impedance spectroscopy is a standard technique for thin film analysis to obtain important information as thicknesses, diffusion properties of mobile ions and leakage currents. The measured electrical impedance of a sample is modeled by a physical equivalent circuit of resistors and capacitors. In the present work this information is obtained as a function of frequency also for ultrathin organic layers in the monolayer regime. A series of semiconducting and insulating polymers (regioregular poly-3-hexylthiophene (rr-P3HT), polymethylmethacrylate (PMMA)) and self assembled monolayers (octadecyltrichlorosilane (OTS), hexamethyldisilazane (HMDS), thiolated phospholipids) were deposited either on highly n-doped silicon wafers or on gold surfaces. E.g. ultrathin layers were obtained by dip coating a silicon wafer in rr-P3HT solution in chloroform. The thickness of 2 nm determined for this system by impedance measurement agrees well with the atomic force microscopy analysis and corresponds to a single layer of polymer chains. The leakage current is seen as an ohmic contribution at low frequencies and allows a systematic optimization of process parameters. In summary, impedance spectroscopy allows very fast and convenient analysis of thin organic layers even down to the monolayer regime.
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Dey, Arka; Dhar, Joydeep; Sil, Sayantan; Jana, Rajkumar; Ray, Partha Pratim
2018-04-01
In this report, bias voltage-dependent dielectric and electron transport properties of ZnS nanoparticles were discussed. ZnS nanoparticles were synthesized by introducing a modified hydrothermal process. The powder XRD pattern indicates the phase purity, and field emission scanning electron microscope image demonstrates the morphology of the synthesized sample. The optical band gap energy (E g = 4.2 eV) from UV measurement explores semiconductor behavior of the synthesized material. The electrical properties were performed at room temperature using complex impedance spectroscopy (CIS) technique as a function of frequency (40 Hz-10 MHz) under different forward dc bias voltages (0-1 V). The CIS analysis demonstrates the contribution of bulk resistance in conduction mechanism and its dependency on forward dc bias voltages. The imaginary part of the impedance versus frequency curve exhibits the existence of relaxation peak which shifts with increasing dc forward bias voltages. The dc bias voltage-dependent ac and dc conductivity of the synthesized ZnS was studied on thin film structure. A possible hopping mechanism for electrical transport processes in the system was investigated. Finally, it is worth to mention that this analysis of bias voltage-dependent dielectric and transport properties of as-synthesized ZnS showed excellent properties for emerging energy applications.
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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.
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Effect of temperature on the AC impedance of protein and ...
Indian Academy of Sciences (India)
2016-08-26
Aug 26, 2016 ... 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 ...
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Aziz, Nor Diyana Abdul; Kamarulzaman, Norlida; Subban, Ri Hanum Yahaya; Hamzah, Ahmad Sazali; Ahmed, Azni Zain; Osman, Zurina; Rusdi, Roshidah; Kamarudin, Norashikin; Mohalid, Norhanim; Romli, Ahmad Zafir; Shaameri, Zurina
2017-09-01
Polymer electrolytes have been an essential area of research for many decades. One of the reasons was the need to find new electrolyte materials suitable for device applications like solid-state batteries, supercapacitors, fuel cells, etc. with enhanced characteristics. For more than 40 years, polyimide has been known as a super-engineering plastic due to its excellent thermal stability (Tg > 250 °C) and mechanical properties. Therefore, in an effort to develop new polymer electrolytes, polyimide as a polymer matrix was chosen. Composite films of the polymer doped with lithium salt, LiCF3SO3 was prepared. These PI based polymer electrolyte films were investigated by the alternating current (a.c.) impedance spectroscopy method in the temperature range from 300 K to 373 K. It was observed that conductivity increased with the increase of temperature and amount of doping salt. Alternatively, the activation energy (Ea) of the composite films decreased with the increase of the doping salt, LiCF3SO3.
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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 (transmission line (MITL) center conductors, of 40 and 80 ohms flow impedance. We have operated in-situ heating and discharge-cleaning hardware in the load region, in order to address the tendency of some shots to undergo premature impedance (Z) collapse, defined as a fall in impedance beyond that due to normal movement of electrode plasmas that reduces the effective A-K gap. The goal of heating/cleaning was to reduce the volume of evolving gases near the A-K gap. Despite clear evidence that the cleaning techniques removed the proton portion of beam current, we observed no consistent increase in diode impedance (ZDIODE). This forced an examination of the role that the 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.
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Directory of Open Access Journals (Sweden)
Sancarlos-González Abel
2017-12-01
Full Text Available AC lines of industrial busbar systems are usually built using conductors with rectangular cross sections, where each phase can have several parallel conductors to carry high currents. The current density in a rectangular conductor, under sinusoidal conditions, is not uniform. It depends on the frequency, on the conductor shape, and on the distance between conductors, due to the skin effect and to proximity effects. Contrary to circular conductors, there are not closed analytical formulas for obtaining the frequency-dependent impedance of conductors with rectangular cross-section. It is necessary to resort to numerical simulations to obtain the resistance and the inductance of the phases, one for each desired frequency and also for each distance between the phases’ conductors. On the contrary, the use of the parametric proper generalized decomposition (PGD allows to obtain the frequency-dependent impedance of an AC line for a wide range of frequencies and distances between the phases’ conductors by solving a single simulation in a 4D domain (spatial coordinates x and y, the frequency and the separation between conductors. In this way, a general “virtual chart” solution is obtained, which contains the solution for any frequency and for any separation of the conductors, and stores it in a compact separated representations form, which can be easily embedded on a more general software for the design of electrical installations. The approach presented in this work for rectangular conductors can be easily extended to conductors with an arbitrary shape.
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Sancarlos-González, Abel; Pineda-Sanchez, Manuel; Puche-Panadero, Ruben; Sapena-Bano, Angel; Riera-Guasp, Martin; Martinez-Roman, Javier; Perez-Cruz, Juan; Roger-Folch, Jose
2017-12-01
AC lines of industrial busbar systems are usually built using conductors with rectangular cross sections, where each phase can have several parallel conductors to carry high currents. The current density in a rectangular conductor, under sinusoidal conditions, is not uniform. It depends on the frequency, on the conductor shape, and on the distance between conductors, due to the skin effect and to proximity effects. Contrary to circular conductors, there are not closed analytical formulas for obtaining the frequency-dependent impedance of conductors with rectangular cross-section. It is necessary to resort to numerical simulations to obtain the resistance and the inductance of the phases, one for each desired frequency and also for each distance between the phases' conductors. On the contrary, the use of the parametric proper generalized decomposition (PGD) allows to obtain the frequency-dependent impedance of an AC line for a wide range of frequencies and distances between the phases' conductors by solving a single simulation in a 4D domain (spatial coordinates x and y, the frequency and the separation between conductors). In this way, a general "virtual chart" solution is obtained, which contains the solution for any frequency and for any separation of the conductors, and stores it in a compact separated representations form, which can be easily embedded on a more general software for the design of electrical installations. The approach presented in this work for rectangular conductors can be easily extended to conductors with an arbitrary shape.
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Bioelectrical impedance analysis for bovine milk: Preliminary results
Bertemes-Filho, P.; Valicheski, R.; Pereira, R. M.; Paterno, A. S.
2010-04-01
This work reports the investigation and analysis of bovine milk quality by using biological impedance measurements using electrical impedance spectroscopy (EIS). The samples were distinguished by a first chemical analysis using Fourier transform midinfrared spectroscopy (FTIR) and flow citometry. A set of milk samples (100ml each) obtained from 17 different cows in lactation with and without mastitis were analyzed with the proposed technique using EIS. The samples were adulterated by adding distilled water and hydrogen peroxide in a controlled manner. FTIR spectroscopy and flow cytometry were performed, and impedance measurements were made in a frequency range from 500Hz up to 1MHz with an implemented EIS system. The system's phase shift was compensated by measuring saline solutions. It was possible to show that the results obtained with the Bioelectrical Impedance Analysis (BIA) technique may detect changes in the milk caused by mastitis and the presence of water and hydrogen peroxide in the bovine milk.
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DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede
2014-01-01
This paper investigates the effect of grid impedance variation on harmonic resonant current controllers for gridconnected voltage source converters by means of impedance-based analysis. It reveals that the negative harmonic resistances tend to be derived from harmonic resonant controllers...... in the closed-loop output admittance of converter. Such negative resistances may interact with the grid impedance resulting in steady state error or unstable harmonic compensation. To deal with this problem, a design guideline for harmonic resonant controllers under a wide range of grid impedance is proposed...
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Modeling and reliability analysis of three phase z-source AC-AC converter
Directory of Open Access Journals (Sweden)
Prasad Hanuman
2017-12-01
Full Text Available This paper presents the small signal modeling using the state space averaging technique and reliability analysis of a three-phase z-source ac-ac converter. By controlling the shoot-through duty ratio, it can operate in buck-boost mode and maintain desired output voltage during voltage sag and surge condition. It has faster dynamic response and higher efficiency as compared to the traditional voltage regulator. Small signal analysis derives different control transfer functions and this leads to design a suitable controller for a closed loop system during supply voltage variation. The closed loop system of the converter with a PID controller eliminates the transients in output voltage and provides steady state regulated output. The proposed model designed in the RT-LAB and executed in a field programming gate array (FPGA-based real-time digital simulator at a fixedtime step of 10 μs and a constant switching frequency of 10 kHz. The simulator was developed using very high speed integrated circuit hardware description language (VHDL, making it versatile and moveable. Hardware-in-the-loop (HIL simulation results are presented to justify the MATLAB simulation results during supply voltage variation of the three phase z-source ac-ac converter. The reliability analysis has been applied to the converter to find out the failure rate of its different components.
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Timmer, B.; Sluyters-Rehbach, M.; Sluyters, J.H.
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
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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)
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International Nuclear Information System (INIS)
Pons, E.; Lemaitre, C.; Crusset, D.; David, D.
2004-01-01
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)
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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
2009-01-01
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 produce the correct volt...
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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.
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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.
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Impedance Analysis of SOGI-FLL-Based Grid Synchronization
DEFF Research Database (Denmark)
Yi, Hao; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
The latest research has pointed out that the Phase-Locked Loop (PLL) plays an important role in shaping the impedance of grid-connected converters, yet most of the works so far merely focus on the synchronous reference-frame PLL. Alternatively, this letter presents the impedance analysis...
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Large-Signal Lyapunov-Based Stability Analysis of DC/AC Inverters and Inverter-Based Microgrids
Kabalan, Mahmoud
study. This will enable future studies to save computational effort and produce the most accurate results according to the needs of the study being performed. Moreover, the effect of grid (line) impedance on the accuracy of droop control is explored using the 5th order model. Simulation results show that traditional droop control is valid up to R/X line impedance value of 2. Furthermore, the 3rd order nonlinear model improves the currently available inverter-infinite bus models by accounting for grid impedance, active power-frequency droop and reactive power-voltage droop. Results show the 3rd order model's ability to account for voltage and reactive power changes during a transient event. Finally, the large-signal Lyapunov-based stability analysis is completed for a 3 bus microgrid system (made up of 2 inverters and 1 linear load). The thesis provides a systematic state space large-signal nonlinear mathematical modeling method of inverter-based microgrids. The inverters include the dc-side dynamics associated with dc sources. The mathematical model is then used to estimate the domain of asymptotic stability of the 3 bus microgrid. The three bus microgrid system was used as a case study to highlight the design and optimization capability of a large-signal-based approach. The study explores the effect of system component sizing, load transient and generation variations on the asymptotic stability of the microgrid. Essentially, this advancement gives microgrid designers and engineers the ability to manipulate the domain of asymptotic stability depending on performance requirements. Especially important, this research was able to couple the domain of asymptotic stability of the ac microgrid with that of the dc side voltage source. Time domain simulations were used to demonstrate the mathematical nonlinear analysis results.
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International Nuclear Information System (INIS)
Spencer, G.L.
1976-01-01
The surface impedances and ac critical fields of superconducting thin tin films were studied. These experiments were performed using a superconducting frequency stabilized microwave cavity of high Q. Measurements of the power losses in the cavity and the center frequency of the cavity were used to determine the surface impedance and the critical field of a thin film sample placed in the cavity. In this case a theoretical treatment based on a model proposed by I.O. Kulik was used to fit the data. The general agreement between the modified Kulik treatment and the data, obtained in this experiment, was substantial. The second method was to modify the thin film data to correspond to a bulk situation. This modification was accomplished by taking into account the measuring techniques used and the geometric consideration inherent in the experiment. The comparison between the modified experimental data and calculations obtained from the Mattis-Bardeen bulk model was generally very good. One aspect of the results which was not explained was the presence of a slight increase in the surface resistance in the vicinity of the transition temperature. The critical field measurements were compared to the (1 - (T/T/sub c/)/sup 1/2) dependence predicted by Bardeen. If it is assumed that substantial microwave heating took place in the sample near T/sub c/, then remarkable agreement with the Bardeen model can be reached
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Dielectric and impedance spectral characteristics of bulk ZnIn2Se4
El-Nahass, M. M.; Attia, A. A.; Salem, G. F.; Ali, H. A. M.; Ismail, M. I.
2014-02-01
The frequency and temperature dependence of ac conductivity, dielectric constant and dielectric loss of ZnIn2Se4 in a pellet form were investigated in the frequency range of 102-106 Hz and temperature range of 293-356 K. The behavior of ac conductivity was interpreted by the correlated barrier hopping (CBH) model. Temperature dependence of ac conductivity indicates that ac conduction is a thermally activated process. The density of localized states N(EF) and ac activation energy were estimated for various frequencies. Dielectric constant and dielectric loss showed a decrease with increasing frequency and an increase with increasing in temperature. The frequency dependence of real and imaginary parts of the complex impedance was investigated. The relaxation time decreases with the increase in temperature. The impedance spectrum exhibits the appearance of the single semicircular arc. The radius of semicircular arcs decreases with increasing temperature which suggests a mechanism of temperature-dependent on relaxation.
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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...
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ac impedance, DSC and FT-IR investigations on (x)PVAc-(1 - x)PVdF blends with LiClO4
International Nuclear Information System (INIS)
Baskaran, R.; Selvasekarapandian, S.; Kuwata, N.; Kawamura, J.; Hattori, T.
2006-01-01
The blended polymer electrolytes comprising poly(vinyl acetate) (PVAc)-poly(vinylidene fluoride) (PVdF) have been prepared for different blend composition with constant lithium perchlorate (LiClO 4 ) ratio by solution casting technique. The formation of the blend polymer electrolyte complex has been confirmed by FT-IR spectroscopy analysis. DSC analysis has been performed in order to observe the change in transition temperature that is caused by the blending of polymers and addition of LiClO 4 . The ac impedance and dielectric spectroscopy studies are carried out on the blended matrix to identify the optimized blend composition, which is having high ionic conductivity. The temperature dependence of conductivity of the polymer electrolytes is found to follow VTF type equation. The high ionic conductivity of 6.4 x 10 -4 S cm -1 at 343 K has been observed for blended polymer electrolyte having blend ratio 75:25 (PVAc:PVdF). The ionic transference number of mobile ions has been estimated by Wagner's polarization method and the value is reported to be t ion is 0.95-0.98 for all the blended samples. The modulus spectra reveal the non-Debye nature and distribution of relaxation times of the samples. The dielectric spectra show the low frequency dispersion, which implies the space charge effects arising from the electrodes
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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.
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ELECTRONIC SYSTEM FOR EXPERIMENTATION IN AC ELECTROGRAVIMETRY I: TECHNIQUE FUNDAMENTALS
Directory of Open Access Journals (Sweden)
Róbinson Torres
Full Text Available Basic fundamentals of AC electrogravimetry are introduced. Their main requirements and characteristics are detailed to establish the design of an electronic system that allows the appropriate extraction of data needed to determine the electrogravimetric transfer function (EGTF and electrochemical impedance (EI, in an experimental set-up for the AC electrogravimetry technique.
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AC-Conductivity measurements on γ-aluminium oxynitride
Willems, H.X.; Hal, van P.F.; Metselaar, R.; With, de G.
1995-01-01
AC-conductivity measurements were performed on aluminium oxynitrides (Alons) because of their interesting defect structure. Although it became apparent that these Alons are not stable in the temperature range used, the electrical properties of the materials could be measured with impedance
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Impedance analysis of subwoofer systems
Berkhoff, Arthur P.
The electrical impedance of four low-frequency loudspeaker systems is analyzed. The expression for this impedance is obtained directly from the acoustical analogous circuit. Formulas are derived for calculating the small-signal parameters from the frequencies of impedance minima and maxima of two
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Analysis and design of complex impedance transforming marchand baluns
DEFF Research Database (Denmark)
Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke; Tamborg, Kjeld M.
2014-01-01
A new type of Marchand balun is presented in this paper, which has the property of complex impedance transformation. To allow the Marchand balun to transform between arbitrary complex impedances, three reactances should be added to the circuit. A detailed analysis of the circuit gives the governing...
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Study of Body Composition by Impedance Analysis
González-Solís, J. L.; Vargas-Luna, M.; Sosa-Aquino, M.; Bernal-Alvarado, J.; Gutiérrez-Juárez, G.; Huerta-Franco, R.; Sanchis-Sabater, A.
2002-08-01
This work presents a set of impedance measurements and preliminary results on the analysis of body composition using impedance spectroscopy. This study is made using a pork meat sample and spectra from fat and flesh region were independently obtained using the same electrodes array. From these measurements, and theoretical considerations, it is possible to explain the behavior of the composite sample flesh-fat-flesh and, fitting the electrical parameters of the model, it shows the plausibility of a physical and quantitative application to human corporal composition.
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Šály, V.; Perný, M.; Janíček, F.; Huran, J.; Mikolášek, M.; Packa, J.
2017-04-01
Progressive smart photovoltaic technologies including heterostructures a-SiC/c-Si with ITO antireflection film are one of the prospective replacements of conventional photovoltaic silicon technology. Our paper is focused on the investigation of heterostructures a-SiC/c-Si provided with a layer of ITO (indium oxide/tin oxide 90/10 wt.%) which acts as a passivating and antireflection coating. Prepared photovoltaic cell structure was investigated at various temperatures and the influence of temperature on its operation was searched. The investigation of the dynamic properties of heterojunction PV cells was carried out using impedance spectroscopy. The equivalent AC circuit which approximates the measured impedance data was proposed. Assessment of the influence of the temperature on the operation of prepared heterostructure was carried out by analysis of the temperature dependence of AC equivalent circuit elements.
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Wavelet analysis of the impedance cardiogram waveforms
Podtaev, S.; Stepanov, R.; Dumler, A.; Chugainov, S.; Tziberkin, K.
2012-12-01
Impedance cardiography has been used for diagnosing atrial and ventricular dysfunctions, valve disorders, aortic stenosis, and vascular diseases. Almost all the applications of impedance cardiography require determination of some of the characteristic points of the ICG waveform. The ICG waveform has a set of characteristic points known as A, B, E ((dZ/dt)max) X, Y, O and Z. These points are related to distinct physiological events in the cardiac cycle. Objective of this work is an approbation of a new method of processing and interpretation of the impedance cardiogram waveforms using wavelet analysis. A method of computer thoracic tetrapolar polyrheocardiography is used for hemodynamic registrations. Use of original wavelet differentiation algorithm allows combining filtration and calculation of the derivatives of rheocardiogram. The proposed approach can be used in clinical practice for early diagnostics of cardiovascular system remodelling in the course of different pathologies.
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Wavelet analysis of the impedance cardiogram waveforms
International Nuclear Information System (INIS)
Podtaev, S; Stepanov, R; Dumler, A; Chugainov, S; Tziberkin, K
2012-01-01
Impedance cardiography has been used for diagnosing atrial and ventricular dysfunctions, valve disorders, aortic stenosis, and vascular diseases. Almost all the applications of impedance cardiography require determination of some of the characteristic points of the ICG waveform. The ICG waveform has a set of characteristic points known as A, B, E ((dZ/dt) max ) X, Y, O and Z. These points are related to distinct physiological events in the cardiac cycle. Objective of this work is an approbation of a new method of processing and interpretation of the impedance cardiogram waveforms using wavelet analysis. A method of computer thoracic tetrapolar polyrheocardiography is used for hemodynamic registrations. Use of original wavelet differentiation algorithm allows combining filtration and calculation of the derivatives of rheocardiogram. The proposed approach can be used in clinical practice for early diagnostics of cardiovascular system remodelling in the course of different pathologies.
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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......) technique for the entire state-of-charge (SOC) interval and considering five temperatures between 5oC and 45oC. By analyzing the measured impedance spectra of the LTO-based battery cell, it was found out that the cell’s impedance is extremely dependent on the operating conditions. By further processing...
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Energy Technology Data Exchange (ETDEWEB)
Taer, E.; Awitdrus,; Farma, R. [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Department of Physics, Faculty of Mathematics and Natural Sciences, University of Riau, 28293 Pekanbaru, Riau (Indonesia); Deraman, M., E-mail: madra@ukm.my; Talib, I. A.; Ishak, M. M.; Omar, R.; Dolah, B. N. M.; Basri, N. H.; Othman, M. A. R. [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Kanwal, S. [ICCBS, H.E.J. Research Institute of Chemistry, University of Karachi, 75270 Karachi (Pakistan)
2015-04-16
Activated carbon powders (ACP) were produced from the KOH treated pre-carbonized rubber wood sawdust. Different conductive materials (graphite, carbon black and carbon nanotubes (CNTs)) were added with a binder (polivinylidene fluoride (PVDF)) into ACP to improve the supercapacitive performance of the activated carbon (AC) electrodes. Symmetric supercapacitor cells, fabricated using these AC electrodes and 1 molar H{sub 2}SO{sub 4} electrolyte, were analyzed using a standard electrochemical impedance spectroscopy technique. The addition of graphite, carbon black and CNTs was found effective in reducing the cell resistance from 165 to 68, 23 and 49 Ohm respectively, and increasing the specific capacitance of the AC electrodes from 3 to 7, 17, 32 F g{sup −1} respectively. Since the addition of CNTs can produce the highest specific capacitance, CNTs were chosen as a conductive material to produce AC composite electrodes that were added with 2.5 %, 5 % and 10 % (by weight) electro-active material namely ruthenium oxide; PVDF binder and CNTs contents were kept at 5 % by weight in each AC composite produced. The highest specific capacitance of the cells obtained in this study was 86 F g{sup −1}, i.e. for the cell with the resistance of 15 Ohm and composite electrode consists of 5 % ruthenium oxide.
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Soybean oil in water-borne coatings and latex film formation study by AC impedance
Jiratumnukul, Nantana
Conventional coalescing agents such as butyl cellosolve, butyl carbitol, and TexanolRTM are widely use in the latex coatings industry to facilitate film formation at ambient temperature. Coalescent aids are composed of solvents with low evaporation rates. After water evaporates, coalescent aids would help soften polymer molecules and form continuous films, then gradually evaporates from the film. Coalescent aids, therefore, are considered as volatile organic compounds (VOC), which are of environmental concern. The main purpose of this research project was to prepare a fatty acid glycol ester from soybean oil and glycol (polyols). The soybean oil glycol ester can be used as a coalescent aid in latex paint formulation. The soybean oil glycol ester not only lowered the minimum film formation temperature of latex polymers and continuous film formed at ambient temperature, but also after it has facilitated film formation, does not substantially evaporate, but becomes part of the film. Soybean oil glycol esters, therefore, can reduce the VOC levels and facilitate film formation of latex paints. In the second part of this research AC-Impedance was used to investigate the efficiency of soybean oil coalescent aid in latex film formation relative to the conventional ones. The coating resistance showed that the efficiency of film formation was increased as a function of dry time. The coating resistance also exhibited the effect of soybean oil ester in latex film formation in the same fashion as a conventional coalescent aid, TexanolRTM.
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Investigation of body's impedance under different conditions for electro-acupuncture
International Nuclear Information System (INIS)
Ahmed, M.M.; Abrarov, S.; Khan, R.R.; Maqsood, R.S.; Qaiser, M.A.; Karimov, Kh. S.
2001-01-01
A computer controlled automated setup has been designed to investigate the body acupuncture points (bio-active points) by using a probes matrix which exerts a uniform pressure on the body. 16 probes matrix was placed in a 15 : 15 mm/sup 2/ dielectric substrate with 5 mm inter probe distance, compatible with the average diameter of the points. These probes have been designed to facilitate a semiconductor injection laser for probing of the points along with optical and/or electric signal. The bioactive points were identified by evaluating the impedance between each probe and a hand held electrode through a micro-controlled scan. This also allowed the selection of an appropriate signal - DC, AC or tidal waveform, for the electric treatment of bioactive points. It has been found that body impedance decreases with the increase of measuring voltage. Moreover, for current-voltage characteristics a nonlinearity coefficient in the range 2-3 was also observed. The study revealed that at low applied voltages 0.l V, the impedance depends on the polarity of the applied signal. Furthermore, body impedance decreases nonlinearly by increasing the probe's pressure on the skin, which may be attributed to piezo resistive effect. By using the AC and Dc measurements an appropriate body equivalent circuit is proposed in this investigation. (author)
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International Nuclear Information System (INIS)
Šály, V; Pern, M; Janíček, F; Mikolášek, M; Packa, J; Huran, J
2017-01-01
Progressive smart photovoltaic technologies including heterostructures a-SiC/c-Si with ITO antireflection film are one of the prospective replacements of conventional photovoltaic silicon technology. Our paper is focused on the investigation of heterostructures a-SiC/c-Si provided with a layer of ITO (indium oxide/tin oxide 90/10 wt.%) which acts as a passivating and antireflection coating. Prepared photovoltaic cell structure was investigated at various temperatures and the influence of temperature on its operation was searched. The investigation of the dynamic properties of heterojunction PV cells was carried out using impedance spectroscopy. The equivalent AC circuit which approximates the measured impedance data was proposed. Assessment of the influence of the temperature on the operation of prepared heterostructure was carried out by analysis of the temperature dependence of AC equivalent circuit elements. (paper)
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Song, Sen; McCune, Robert C.; Shen, Weidian; Wang, Yar-Ming
One task under the U.S. Automotive Materials Partnership (USAMP) "Magnesium Front End Research and Development" (MFERD) Project has been the evaluation of methodologies for the assessment of protective capability for a variety of proposed protection schemes for this hypothesized multi-material, articulated structure. Techniques which consider the entire protection system, including both pretreatments and topcoats are of interest. In recent years, an adaptation of the classical electrochemical impedance spectroscopy (EIS) approach using an intermediate cathodic DC polarization step (viz. AC/DC/AC) has been employed to accelerate breakdown of coating protection, specifically at the polymer-pretreatment interface. This work reports outcomes of studies to employ the AC/DC/AC approach for comparison of protective coatings to various magnesium alloys considered for front end structures. In at least one instance, the protective coating system breakdown could be attributed to the poorer intrinsic corrosion resistance of the sheet material (AZ31) relative to die-cast AM60B.
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Analysis of Input and Output Ripples of PWM AC Choppers
Directory of Open Access Journals (Sweden)
Pekik Argo Dahono
2008-11-01
Full Text Available This paper presents an analysis of input and output ripples of PWM AC choppers. Expressions of input and output current and voltage ripples of single-phase PWM AC choppers are first derived. The derived expressions are then extended to three-phase PWM AC choppers. As input current and output voltage ripples specification alone cannot be used to determine the unique values of inductance and capacitance of the LC filters, an additional criterion based on the minimum reactive power is proposed. Experimental results are included in this paper to show the validity of the proposed analysis method.
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Y-source impedance-network-based isolated boost DC/DC converter
DEFF Research Database (Denmark)
Siwakoti, Yam P.; Town, Graham; Loh, Poh Chiang
2014-01-01
A dc-dc converter with very high voltage gain is proposed in this paper for any medium-power application requiring a high voltage boost with galvanic isolation. The proposed converter topology can be realized using only two switches. With this topology a very high voltage boost can be achieved even...... with a relatively low duty cycle of the switches, and the gain obtainable is presently not matched by any existing impedance network based converter operated at the same duty ratio. The proposed converter has a Y-source impedance network to boost the voltage at the intermediate dc-link side and a push......-pull transformer for square-wave AC inversion and isolation. The voltage-doubler rectifier provides a constant dc voltage at the output stage. A theoretical analysis of the converter is presented, supported by simulation and experimental results. A 250 W down-scaled prototype was implemented in the laboratory...
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Alizadeh Sahraei, Abolfazl; Ayati, Moosa; Baniassadi, Majid; Rodrigue, Denis; Baghani, Mostafa; Abdi, Yaser
2018-03-01
This study attempts to comprehensively investigate the effects of multi-walled carbon nanotubes (MWCNTs) on the AC and DC electrical conductivity of epoxy nanocomposites. The samples (0.2, 0.3, and 0.5 wt. % MWCNT) were produced using a combination of ultrason and shear mixing methods. DC measurements were performed by continuous measurement of the current-voltage response and the results were analyzed via a numerical percolation approach, while for the AC behavior, the frequency response was studied by analyzing phase difference and impedance in the 10 Hz to 0.2 MHz frequency range. The results showed that the dielectric parameters, including relative permittivity, impedance phase, and magnitude, present completely different behaviors for the frequency range and MWCNT weight fractions studied. To better understand the nanocomposites electrical behavior, equivalent electric circuits were also built for both DC and AC modes. The DC equivalent networks were developed based on the current-voltage curves, while the AC equivalent circuits were proposed by using an optimization problem according to the impedance magnitude and phase at different frequencies. The obtained equivalent electrical circuits were found to be highly useful tools to understand the physical mechanisms involved in MWCNT filled polymer nanocomposites.
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Large polaron tunneling, magnetic and impedance analysis of magnesium ferrite nanocrystallite
Energy Technology Data Exchange (ETDEWEB)
Mahato, Dev K., E-mail: drdevkumar@yahoo.com [Department of Physics, National Institute of Technology Patna, Patna 800 005 (India); Majumder, Sumit [Department of Physics, Jadavpur University, Kolkata 700032 (India); Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India); Banerjee, S. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)
2017-08-15
Graphical abstract: The diffraction peaks corresponding to the planes (111), (220), (311), (222), (400), (422), (511), (440), (620), (533) and (444) provide a clear evidence for the formation of spinel structure of the ferrites. The lattice parameter ‘a’ determined as 8.392 Å matches well with JCPDS (73-2410) file for MgFe{sub 2}O{sub 4.} The volume of the unit cell is 591.012 Å{sup 3}. The crystallite size of the synthesized powder estimated from X-ray peak broadening of (311) highest intensity diffraction peak using Scherer formula was 56.4 nm. - Highlights: • Both the grain and grain boundaries contribution to conductivity of the Mg-ferrite has been observed. • Polydispersive nature of the material is checked using Cole – Cole relation. • The ac conductivity of magnesium ferrite followed σ{sub ac} ∝ ω{sup n} dependence. • The variation of the exponent ‘n’ with temperature suggests that overlapping large polaron tunnelling is the dominant conduction mechanism. • The superparamagnetic behavior of this Mg-ferrite has been observed for sample S1 annealed at 500 °C. - Abstract: Single phase MgFe{sub 2}O{sub 4} (MFO) ferrite was prepared through sol-gel auto-combustion route. The Rietveld analysis of X-ray patterns reveals that our samples are single phase. The increase in average particle size with annealing temperature and formation of nanoparticle agglomerates is observed in MgFe{sub 2}O{sub 4}. The structural morphology of the nanoparticles is studied using Scanning Electron Microscopy (SEM). Formation of spinel structure is confirmed using Fourier transform infrared spectroscopy (FTIR). The Zero-Field-Cooled (ZFC) and Field-Cooled (FC) magnetization measurements show the maximum irreversibility at 700 °C annealing temperature. The formation of a maximum at blocking temperature, T{sub B}∼ 180 K for sample annealed at 500 °C in the ZFC curve shows the superparamagnetic behavior of the sample. The increase of saturation magnetism (M
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AC impedance behaviour and state-of-charge dependence of Zr0 ...
Indian Academy of Sciences (India)
Unknown
measurement encompasses a wide range of AC signal frequencies, various characteristic parameters of the electrochemical cell and kinetics of the associated reactions can be evaluated. Metal-hydride (MH) electrodes form the anode or the negative plate of a nickel-metal- hydride battery. However, the development of MH ...
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Smartphone-Based Bioelectrical Impedance Analysis Devices for Daily Obesity Management
Directory of Open Access Journals (Sweden)
Ahyoung Choi
2015-09-01
Full Text Available Current bioelectric impedance analysis (BIA systems are often large, cumbersome devices which require strict electrode placement on the user, thus inhibiting mobile capabilities. In this work, we developed a handheld BIA device that measures impedance from multiple frequencies (5 kHz~200 kHz with four contact electrodes and evaluated the BIA device against standard body composition analysis systems: a dual-energy X-ray absorptiometry (DXA system (GE Lunar Prodigy, GE Healthcare, Buckinghamshire, UK and a whole-body BIA system (InBody S10, InBody, Co. Ltd, Seoul, Korea. In the study, 568 healthy participants, varying widely in body mass index, age, and gender, were recruited at two research centers: the Samsung Medical Center (SMC in South Korea and the Pennington Biomedical Research Center (PBRC in the United States. From the measured impedance data, we analyzed individual body fat and skeletal muscle mass by applying linear regression analysis against target reference data. Results indicated strong correlations of impedance measurements between the prototype pathways and corresponding InBody S10 electrical pathways (R = 0.93, p < 0.0001. Additionally, body fat estimates from DXA did not yield significant differences (p > 0.728 (paired t-test, DXA mean body fat 29.45 ± 10.77 kg, estimated body fat 29.52 ± 12.53 kg. Thus, this portable BIA system shows a promising ability to estimate an individual’s body composition that is comparable to large stationary BIA systems.
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Impedance analysis of acupuncture points and pathways
International Nuclear Information System (INIS)
Teplan, Michal; Kukucka, Marek; Ondrejkovicová, Alena
2011-01-01
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.
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Impedance-Based High Frequency Resonance Analysis of DFIG System in Weak Grids
DEFF Research Database (Denmark)
Song, Yipeng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
Resonance (SSR). However, the High Frequency Resonance (HFR) of DFIG systems due to the impedance interaction between DFIG system and parallel compensated weak network is often overlooked. This paper thus investigates the impedance characteristics of DFIG systems for the analysis of HFR. The influences...
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Application of Vertical Electrodes in Microfluidic Channels for Impedance Analysis
Directory of Open Access Journals (Sweden)
Qiang Li
2016-05-01
Full Text Available This paper presents a microfluidic device with electroplated vertical electrodes in the side walls for impedance measurement. Based on the proposed device, the impedance of NaCl solutions with different concentrations and polystyrene microspheres with different sizes was measured and analyzed. The electroplating and SU-8-PDMS (SU-8-poly(dimethylsiloxane bonding technologies were firstly integrated for the fabrication of the proposed microfluidic device, resulting in a tightly three-dimensional structure for practical application. The magnitude of impedance of the tested solutions in the frequency range of 1 Hz to 100 kHz was analyzed by the Zennium electrochemical workstation. The results show that the newly designed microfluidic device has potential for impedance analysis with the advantages of ease of fabrication and the integration of 3D electrodes in the side walls. The newly designed impedance sensor can distinguish different concentrations of polystyrene microspheres and may have potential for cell counting in biological areas. By integrating with other techniques such as dielectrophoresis (DEP and biological recognition technology, the proposed device may have potential for the assay to identify foodborne pathogen bacteria.
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AC characterization of bulk organic solar cell in the dark and under illumination
International Nuclear Information System (INIS)
Váry, Michal; Perný, Milan; Šály, Vladimír; Packa, Juraj
2014-01-01
Highlights: • A study of organic bulk photovoltaic (PV) solar cell. • Current–voltage characteristics in the dark and under illumination. • AC measurements, both under illumination and in the dark conditions. • Equivalent AC circuit. • Effective lifetime assigned with electron–hole recombination and diffusion time of the electron was estimated. - Abstract: Impedance spectroscopy has been used widely to evaluate the transport processes in photovoltaic, mainly based on inorganic semiconductors, structures – solar cells. The aim of this research was to characterize improved organic bulk photovoltaic (PV) solar cells exploiting this method. Progress in technology of investigated organic solar cell involves the use of an active layer based on low band gap type of polymer. The organic PV cell with front transparent electrode and rear metal electrode and active layer produced by Konarka Technologies was analyzed by electrical DC and AC measurements. Current–voltage (I–V) characteristics in the dark and under illumination were measured and basic PV parameters were calculated. AC measurements, both under illumination and in the dark conditions, were processed in order to identify electronic behavior using equivalent AC circuit which was suggested by fitting of measured impedance data. Circuit with the best correlation to measured data is analyzed in details. Voltage and frequency dependences of fitted equivalent circuit components and calculated parameters are explained and presented in the paper
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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...
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Automated AC Electrical Impedance Measurement of Ceramic Oxides by means of a Lock-in Amplifier
International Nuclear Information System (INIS)
Al-Khawaja, S.; Al-Sous, M. B.; Nasrallah, F.
2009-06-01
In this study, the electrical impedance of some ceramic oxides has been investigated employing the Perkin Elmer DSP 7280 Lock-in amplifier, while recording the electric response versus frequency and temperature at constant amplitude. Via integral automation of this lock-in with other delicate electrical measuring devices, a control program has been developed to accurately and swiftly acquire the frequency response of the sample, in order to lately infer the resulting samples' impedance in volt and ampere. Two maxima peaks characterising the impedance, in the curve of the doped molybdenum oxide have been observed discerning two phases in the sample (doped with 40% of niobium oxide), which shows a remarkable relaxation related to improvement in its ionic conductivity within the solid phase, with respect to increasing frequency. (author)
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Impedance analysis of the PEP-II vacuum chamber
International Nuclear Information System (INIS)
Ng, C.K.; Weiland, T.
1995-05-01
The PEP-II high energy ring (HER) vacuum chamber consists of a copper tube with periodically spaced pumping slots. The impedance of the vacuum chamber due to the slots is analyzed. Both narrow-band and broadband impedances are considered as well as longitudinal and transverse components thereof. It is found that although the broad-band impedance is tolerable, the narrow-band impedance may exceed the instability limit given by the natural damping with no feedback system on. Traveling wave modes in the chamber are the major source of this high value narrow-band impedance. We also study the dependences of the impedance on the slot length and the geometrical cross section
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An impact analysis of the fault impedance on voltage sags
Energy Technology Data Exchange (ETDEWEB)
Ramos, Alessandro Candido Lopes [CELG - Companhia Energetica de Goias, Goiania, GO (Brazil). Generation and Transmission. System' s Operation Center], E-mail: alessandro.clr@celg.com.br; Batista, Adalberto Jose [Federal University of Goias (UFG), Goiania, GO (Brazil)], E-mail: batista@eee.ufg.br; Leborgne, Roberto Chouhy [Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil)], E-mail: rcl@ece.ufrgs.br; Emiliano, Pedro Henrique Mota, E-mail: ph@phph.com.br
2009-07-01
This paper presents an impact analysis of the fault impedance, in terms of its module and angle, on voltage sags caused by faults. Symmetrical and asymmetrical faults are simulated, at transmission and distribution lines, by using a frequency-domain fault simulation software called ANAFAS. Voltage sags are monitored at buses where sensitive end-users are connected. In order to overcome some intrinsic limitations of this software concerning its automatic execution for several cases, a computational tool was developed in Java programming language. This solution allows the automatic simulation of cases including the effect of the fault position, the fault type, and the proper fault impedance. The main conclusion is that the module and angle of the fault impedance can have a significant influence on voltage sag depending on the fault characteristics. (author)
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Cui, Chanjuan; Qiao, Rui; Zhang, Jie
2016-01-01
A reliable laboratory test to monitor onclopidogrel platelet reactivity (PR) is very necessary. In addition, genetic factors also play an important part in onclopidogrel PR. This study aimed to modify the original impedance whole blood platelet aggregation assay associated with the release assay to monitor onclopidogrel PR and assess their relationship with genotype. We adjusted the concentration of calcium in the in vitro reaction system of platelet aggregation to modify the original impedance whole blood platelet aggregation assay. Meanwhile, chronolume, which quantified the adenosine triphosphate (ATP) released from platelet dense granules, is added to this reaction system to reflect the platelet release function. In the modified assay, platelet magnified activation time (MAT) and the maximal platelet ATP release value (RV) were used to reflect platelet function parameters. In the original assay, the electrical resistance (omega) and RV were used to reflect platelet function parameters. Onclopidogrel PR was detected by the original impedance whole blood platelet aggregation assay, modified assay, and flow cytometric vasodilator stimulated phosphoprotein (VASP) assay in 168 patients with acute coronary syndromes (ACS). CYP2C19*2 and CYP2C19*3 polymorphisms were also detected in all of these patients. This modified method showed that when 12.5 microL CaCl2 (0.2 mmol/L) was added to the reaction system, MAT was appropriate (93 +/- 23 seconds). The CVs for the modified impedance assay and release assay were 9.31% and 6.13%, respectively. The mean VASP-PRI in the patient group treated with clopidogrel was significantly lower than that in the control group without antiplatelet therapy (54.88 +/- 16.81% vs. 79.86 +/- 10.24%, p 50% group were shorter than that in the PRI 50% group were higher than that in the PRI omega) and RV of the original method showed no differences between the two groups [0 (0-2) vs. 0 (0-1.25), 0.05 (0-0.25) vs. 0.08 (0-0.24); p > 0.05, p > 0
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MVAC Submarine cable, impedance measurements and analysis
DEFF Research Database (Denmark)
Arentsen, Martin Trolle; Expethit, Adrian; Pedersen, Morten Virklund
2017-01-01
influence the losses. Secondly, cable parameters such as component impedances, positive-, zero-sequence impedances and losses are measured for varying currents and frequencies. Zero sequence is measured for two setups, one with armour grounded, and with armour open to match CIGREs formula assumption......-sequence impedance is found between the measurements and the CIGRÉ formulas. It is concluded that the formulas are not accurate for the specific cable under test....
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DEFF Research Database (Denmark)
Blaabjerg, Frede; Aquila, A. Dell; Liserre, Marco
2004-01-01
of dc/dc converters via a 50 Hz frequency-shift. The input admittance is calculated and measured for two study examples (a three-phase active rectifier and a single-phase photovoltaic inverter). These examples show that the purpose of a well designed controller for grid-connected converters......A systematic approach to study dc/ac and ac/dc converters without the use of synchronous transformation is proposed. The use of a frequency-shift technique allows a straightforward analysis of single-phase and three-phase systems. The study of dc/ac and of ac/dc converters is reported to the study...... is to minimize the input admittance in order to make the grid converter more robust to grid disturbance....
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D'Andrea, M.; Argan, A.; Lotti, S.; Macculi, C.; Piro, L.; Biasotti, M.; Corsini, D.; Gatti, F.; Torrioli, G.
2016-07-01
The ATHENA observatory is the second large-class mission in ESA Cosmic Vision 2015-2025, with a launch foreseen in 2028 towards the L2 orbit. The mission addresses the science theme "The Hot and Energetic Universe", by coupling a high-performance X-ray Telescope with two complementary focal-plane instruments. One of these is the X-ray Integral Field Unit (X-IFU): it is a TES based kilo-pixel order array able to provide spatially resolved high-resolution spectroscopy (2.5 eV at 6 keV) over a 5 arcmin FoV. The X-IFU sensitivity is degraded by the particles background expected at L2 orbit, which is induced by primary protons of both galactic and solar origin, and mostly by secondary electrons. To reduce the background level and enable the mission science goals, a Cryogenic Anticoincidence (CryoAC) detector is placed address the final design of the CryoAC. It will verify some representative requirements at single-pixel level, especially the detector operation at 50 mK thermal bath and the threshold energy at 20 keV. To reach the final DM design we have developed and tested the AC-S7 prototype, with 1 cm2 absorber area sensed by 65 Ir TESes. Here we will discuss the pulse analysis of this detector, which has been illuminated by the 60 keV line from a 241Am source. First, we will present the analysis performed to investigate pulses timings and spectrum, and to disentangle the athermal component of the pulses from the thermal one. Furthermore, we will show the application to our dataset of an alternative method of pulse processing, based upon Principal Component Analysis (PCA). This kind of analysis allow us to recover better energy spectra than achievable with traditional methods, improving the evaluation of the detector threshold energy, a fundamental parameter characterizing the CryoAC particle rejection efficiency.
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AC and DC electrical properties of graphene nanoplatelets reinforced epoxy syntactic foam
Zegeye, Ephraim; Wicker, Scott; Woldesenbet, Eyassu
2018-04-01
Benefits of employing graphene nanopletlates (GNPLs) in composite structures include mechanical as well as multifunctional properties. Understanding the impedance behavior of GNPLs reinforced syntactic foams may open new applications for syntactic foam composites. In this work, GNPLs reinforced syntactic foams were fabricated and tested for DC and AC electrical properties. Four sets of syntactic foam samples containing 0, 0.1, 0.3, and 0.5 vol% of GNPLs were fabricated and tested. Significant increase in conductivity of syntactic foams due to the addition of GNPLs was noted. AC impedance measurements indicated that the GNPLs syntactic foams become frequency dependent as the volume fraction of GNPLs increases. With addition of GNPLs, the characteristic of the syntactic foams are also observed to transition from dominant capacitive to dominant resistive behavior. This work was carried out at Southern University, Mechanical Engineering Department, Baton Rouge, LA 70802, United States of America.
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El-Nahass, M. M.; Attia, A. A.; Ali, H. A. M.; Salem, G. F.; Ismail, M. I.
2018-02-01
The structural characteristics of thermally deposited ZnIn2Se4 thin films were indexed utilizing x-ray diffraction as well as scanning electron microscopy techniques. Dielectric properties, electric modulus and AC electrical conductivity of ZnIn2Se4 thin films were examined in the frequency range from 42 Hz to 106 Hz. The capacitance, conductance and impedance were measured at different temperatures. The dielectric constant and dielectric loss decrease with an increase in frequency. The maximum barrier height was determined from the analysis of the dielectric loss depending on the Giuntini model. The real part of the electric modulus revealed a constant maximum value at higher frequencies and the imaginary part of the electric modulus was characterized by the appearance of dielectric relaxation peaks. The AC electrical conductivity obeyed the Jonscher universal power law. Correlated barrier hopping model was the appropriate mechanism for AC conduction in ZnIn2Se4 thin films. Estimation of the density of states at the Fermi level and activation energy, for AC conduction, was carried out based on the temperature dependence of AC electrical conductivity.
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Transcranial extracellular impedance control (tEIC modulates behavioral performances.
Directory of Open Access Journals (Sweden)
Ayumu Matani
Full Text Available Electric brain stimulations such as transcranial direct current stimulation (tDCS, transcranial random noise stimulation (tRNS, and transcranial alternating current stimulation (tACS electrophysiologically modulate brain activity and as a result sometimes modulate behavioral performances. These stimulations can be viewed from an engineering standpoint as involving an artificial electric source (DC, noise, or AC attached to an impedance branch of a distributed parameter circuit. The distributed parameter circuit is an approximation of the brain and includes electric sources (neurons and impedances (volume conductors. Such a brain model is linear, as is often the case with the electroencephalogram (EEG forward model. Thus, the above-mentioned current stimulations change the current distribution in the brain depending on the locations of the electric sources in the brain. Now, if the attached artificial electric source were to be replaced with a resistor, or even a negative resistor, the resistor would also change the current distribution in the brain. In light of the superposition theorem, which holds for any linear electric circuit, attaching an electric source is different from attaching a resistor; the resistor affects each active electric source in the brain so as to increase (or decrease in some cases of a negative resistor the current flowing out from each source. From an electrophysiological standpoint, the attached resistor can only control the extracellular impedance and never causes forced stimulation; we call this technique transcranial extracellular impedance control (tEIC. We conducted a behavioral experiment to evaluate tEIC and found evidence that it had real-time enhancement and depression effects on EEGs and a real-time facilitation effect on reaction times. Thus, tEIC could be another technique to modulate behavioral performance.
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Impedance spectroscopic and dielectric analysis of Ba0.7Sr0.3TiO3 thin films
International Nuclear Information System (INIS)
Rouahi, A.; Kahouli, A.; Sylvestre, A.; Defaÿ, E.; Yangui, B.
2012-01-01
Highlights: ► The material exhibits the contribution of both grain and grain boundaries in the electric response of Ba 0.7 Sr 0.3 TiO 3 . ► The plot of normalized complex dielectric modulus and impedance as a function of frequency exhibits both short and long-range conduction in the film. ► The frequency dependence of ac conductivity exhibits a polaron hopping mechanism with activation energy of 0.38 eV. ► The complex dielectric modulus analysis confirmed the presence of a non-Debye type of conductivity relaxation deduced from the KWW function. - Abstract: Polycrystalline Ba 0.7 Sr 0.3 TiO 3 thin film with Pt/BST/Pt/TiO 2 /SiO 2 structure was prepared by ion beam sputtering. The film was post annealed at 700 °C. The dielectric and electric modulus properties were studied by impedance spectroscopy over a wide frequency range [0.1–10 5 Hz] at different temperatures [175–350 °C]. The Nyquist plots (Z″ vs . Z′) show the contribution of both grain and grain boundaries at higher temperature on the electric response of BST thin films. Moreover, the resistance of grains decreases with the rise in temperature and the material exhibits a negative temperature coefficient of resistance. The electric modulus plot indicates the non-Debye type of dielectric relaxation. The values of the activation energy computed from both plots of Z″ and M″ are 0.86 eV and 0.81 eV respectively, which reveals that the species responsible for conduction are the same. The scaling behavior of M ″ /M ″ max shows the temperature independent nature of relaxation time. The plot of normalized complex dielectric modulus and impedance as a function of frequency exhibits both short and long-range conduction in the film.
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Study of the dopamine effect into cell solutions by impedance analysis
Paivana, G.; Apostolou, T.; Kaltsas, G.; Kintzios, S.
2017-11-01
Electrochemical Impedance Spectroscopy (EIS) has become a technique that is frequently used for biological assays. Impedance is defined as a complex - valued generalization of resistance and varies depending on its use per application field. In health sciences, bioimpedance is widely used as non-invasive and low cost alternative in many medical areas that provides valuable information about health status. This work focuses on assessing the effects of a bioactive substance applied to immobilized cells. Dopamine was used as a stimulant in order to implement impedance analysis with a specific type of cells. Dopamine constitutes one of the most important catecholamine neurotransmitters in both the mammalian central and peripheral nervous systems. The main purpose is to extract calibration curves at different frequencies with known dopamine concentrations in order to describe the behavior of cells applied to dopamine using an impedance measurement device. For comparison purposes, non-immobilized cells were tested for the same dopamine concentrations.
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Equivalence of Primary Control Strategies for AC and DC Microgrids
Directory of Open Access Journals (Sweden)
Eneko Unamuno
2017-01-01
Full Text Available Microgrid frequency and voltage regulation is a challenging task, as classical generators with rotational inertia are usually replaced by converter-interfaced systems that inherently do not provide any inertial response. The aim of this paper is to analyse and compare autonomous primary control techniques for alternating current (AC and direct current (DC microgrids that improve this transient behaviour. In this context, a virtual synchronous machine (VSM technique is investigated for AC microgrids, and its behaviour for different values of emulated inertia and droop slopes is tested. Regarding DC microgrids, a virtual-impedance-based algorithm inspired by the operation concept of VSMs is proposed. The results demonstrate that the proposed strategy can be configured to have an analogous behaviour to VSM techniques by varying the control parameters of the integrated virtual-impedances. This means that the steady-state and transient behaviour of converters employing these strategies can be configured independently. As shown in the simulations, this is an interesting feature that could be, for instance, employed for the integration of different dynamic generation or storage systems, such as batteries or supercapacitors.
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AC conductivity and dielectric properties of bulk tungsten trioxide (WO3)
El-Nahass, M. M.; Ali, H. A. M.; Saadeldin, M.; Zaghllol, M.
2012-11-01
AC conductivity and dielectric properties of tungsten trioxide (WO3) in a pellet form were studied in the frequency range from 42 Hz to 5 MHz with a variation of temperature in the range from 303 K to 463 K. AC conductivity, σac(ω) was found to be a function of ωs where ω is the angular frequency and s is the frequency exponent. The values of s were found to be less than unity and decrease with increasing temperature, which supports the correlated barrier hopping mechanism (CBH) as the dominant mechanism for the conduction in WO3. The dielectric constant (ε‧) and dielectric loss (ε″) were measured. The Cole-Cole diagram determined complex impedance for different temperatures.
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Shkirskiy, Viacheslav; King, Andrew D; Gharbi, Oumaïma; Volovitch, Polina; Scully, John R; Ogle, Kevin; Birbilis, Nick
2015-02-23
The electrochemical impedance of reactive metals such as magnesium is often complicated by an obvious inductive loop with decreasing frequency of the AC polarising signal. The characterisation and ensuing explanation of this phenomenon has been lacking in the literature to date, being either ignored or speculated. Herein, we couple electrochemical impedance spectroscopy (EIS) with online atomic emission spectroelectrochemistry (AESEC) to simultaneously measure Mg-ion concentration and electrochemical impedance spectra during Mg corrosion, in real time. It is revealed that Mg dissolution occurs via Mg(2+) , and that corrosion is activated, as measured by AC frequencies less than approximately 1 Hz approaching DC conditions. The result of this is a higher rate of Mg(2+) dissolution, as the voltage excitation becomes slow enough to enable all Mg(2+) -enabling processes to adjust in real time. The manifestation of this in EIS data is an inductive loop. The rationalisation of such EIS behaviour, as it relates to Mg, is revealed for the first time by using concurrent AESEC. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Directory of Open Access Journals (Sweden)
Vinod Kumar Singh
2016-09-01
Full Text Available Genome-wide experimental studies in Saccharomyces cerevisiae reveal that autonomous replicating sequence (ARS requires an essential consensus sequence (ACS for replication activity. Computational studies identified thousands of ACS like patterns in the genome. However, only a few hundreds of these sites act as replicating sites and the rest are considered as dormant or evolving sites. In a bid to understand the sequence makeup of replication sites, a content and context-based analysis was performed on a set of replicating ACS sequences that binds to origin-recognition complex (ORC denoted as ORC-ACS and non-replicating ACS sequences (nrACS, that are not bound by ORC. In this study, DNA properties such as base composition, correlation, sequence dependent thermodynamic and DNA structural profiles, and their positions have been considered for characterizing ORC-ACS and nrACS. Analysis reveals that ORC-ACS depict marked differences in nucleotide composition and context features in its vicinity compared to nrACS. Interestingly, an A-rich motif was also discovered in ORC-ACS sequences within its nucleosome-free region. Profound changes in the conformational features, such as DNA helical twist, inclination angle and stacking energy between ORC-ACS and nrACS were observed. Distribution of ACS motifs in the non-coding segments points to the locations of ORC-ACS which are found far away from the adjacent gene start position compared to nrACS thereby enabling an accessible environment for ORC-proteins. Our attempt is novel in considering the contextual view of ACS and its flanking region along with nucleosome positioning in the S. cerevisiae genome and may be useful for any computational prediction scheme.
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Temperature dependence of ac response in diluted half-metallic CrO{sub 2} powder compact
Energy Technology Data Exchange (ETDEWEB)
Chen Yajie; Zhang Xiaoyu; Cai Tianyi; Li Zhenya
2004-10-06
We present a study on temperature dependence of impedance spectra of the cold-pressed chromium dioxide (CrO{sub 2})-titanic dioxide (TiO{sub 2}) composite over the temperature range of 77-300 K, and over the frequency range of 40 Hz-500 kHz. The microstructure of the sample is analyzed using transmission electron microscopy (TEM), SEM and X-ray diffraction (XRD). The impedance spectra exhibit a strong dependence upon temperature. By evaluating the ac electricity behavior of the composite, we find the experimental data are successfully described by a power-law behavior {sigma}{sub ac}=A(T){omega}{sup s}, in which the frequency exponent s shows slightly greater than a universal value (0{<=}s{<=}1), and rises approximately linearly with temperature over a broad range of low temperature.
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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 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...
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A model-based prognostic approach to predict interconnect failure using impedance analysis
Energy Technology Data Exchange (ETDEWEB)
Kwon, Dae Il; Yoon, Jeong Ah [Dept. of System Design and Control Engineering. Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)
2016-10-15
The reliability of electronic assemblies is largely affected by the health of interconnects, such as solder joints, which provide mechanical, electrical and thermal connections between circuit components. During field lifecycle conditions, interconnects are often subjected to a DC open circuit, one of the most common interconnect failure modes, due to cracking. An interconnect damaged by cracking is sometimes extremely hard to detect when it is a part of a daisy-chain structure, neighboring with other healthy interconnects that have not yet cracked. This cracked interconnect may seem to provide a good electrical contact due to the compressive load applied by the neighboring healthy interconnects, but it can cause the occasional loss of electrical continuity under operational and environmental loading conditions in field applications. Thus, cracked interconnects can lead to the intermittent failure of electronic assemblies and eventually to permanent failure of the product or the system. This paper introduces a model-based prognostic approach to quantitatively detect and predict interconnect failure using impedance analysis and particle filtering. Impedance analysis was previously reported as a sensitive means of detecting incipient changes at the surface of interconnects, such as cracking, based on the continuous monitoring of RF impedance. To predict the time to failure, particle filtering was used as a prognostic approach using the Paris model to address the fatigue crack growth. To validate this approach, mechanical fatigue tests were conducted with continuous monitoring of RF impedance while degrading the solder joints under test due to fatigue cracking. The test results showed the RF impedance consistently increased as the solder joints were degraded due to the growth of cracks, and particle filtering predicted the time to failure of the interconnects similarly to their actual timesto- failure based on the early sensitivity of RF impedance.
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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
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Karen Cristina Barcellos Ribeiro; Bruno Rotondo Levenhagem Serabion; Eduardo Lima Nolasco; Chislene Pereira Vanelli; Harleson Lopes de Mesquita; José Otávio do Amaral Corrêa
2013-01-01
INTRODUCTION: The analysis of urine abnormal constituents and sediment (ACS) comprises tests of great diagnostic and prognostic value in clinical practice. When the analysis of ACS cannot be performed within two hours after collection, the sample must be preserved in order to avoid pre-analytical interferences. Refrigeration is the most applied technique due to its cost effectiveness. Moreover, it presents fewer inconveniences when compared to chemical preservation. However, changes in ACS ma...
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Dielectric and impedance studies of Ba0.50(Na0.25Bi0.25)(Fe0.25Nb0.25)Ti0.50O3 ceramic
Yadav, Anjana; Chandra, K. P.; Kulkarni, A. R.; Prasad, K.
2018-05-01
Lead-free perovskite Ba0.50(Na0.25Bi0.25)(Fe0.25Nb0.25)Ti0.50O3 was prepared using conventional ceramic technique at 1130°C/4h in air atmosphere and characterized by X-ray diffraction, scanning electron microscopy, dielectric and impedance studies. XRD analysis of the compound indicated the formation of a single-phase cubic structure. SEM study was carried out to study the quality and purity of the compound. Compound showed very high dielectric constant (33700). Impedance analysis indicated the negative temperature coefficient of resistance character of the compound. Ac conductivity data followed Jonscher's law and correlated barrier hopping successfully explained the charge carrier transport mechanism in the system.
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BIOELECTRICAL IMPEDANCE VECTOR ANALYSIS IDENTIFIES SARCOPENIA IN NURSING HOME RESIDENTS
Loss of muscle mass and water shifts between body compartments are contributing factors to frailty in the elderly. The body composition changes are especially pronounced in institutionalized elderly. We investigated the ability of single-frequency bioelectrical impedance analysis (BIA) to identify b...
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Estimation of total body water by bioelectrical impedance analysis
International Nuclear Information System (INIS)
Kushner, R.F.; Schoeller, D.A.
1986-01-01
Total body water (TBW) measured by bioelectrical impedance analysis (BIA) was directly compared with deuterium-isotope dilution in a total of 58 subjects. First, sex-specific and group equations were developed by multiple regression analysis in (10 each) obese and nonobese men and women. Height/resistive impedance was the most significant variable used to predict deuterium-dilution space (D2O-TBW) and, combined with weight, yielded R = 0.99 and SE of estimate = 1.75 L. Equations predicted D2O-TBW equally well for obese and nonobese subjects. Second, the equations were prospectively tested in a heterogeneous group of 6 males and 12 females. Sex-specific equations predicted D2O-TBW with good correlation coefficients (0.96 and 0.93), total error (2.34 and 2.89 L), and a small difference between mean predicted and measured D2O-TBW (-1.4 +/- 2.05 and -0.48 +/- 2.83 L). BIA predicts D2O-TBW more accurately than weight, height, and/or age. A larger population is required to validate the applicability of our equations
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Coupling of impedance functions to nuclear reactor building for soil-structure interaction analysis
International Nuclear Information System (INIS)
Danisch, R.; Delinic, K.; Trbojevic, V.M.
1991-01-01
Finite element model of a nuclear reactor building is coupled to complex soil impedance functions and soil-structure-interaction analysis is carried out in frequency domain. In the second type of analysis applied in this paper, soil impedance functions are used to evaluate equivalent soil springs and dashpots of soil. These are coupled to the structure model in order to carry out the time marching analysis. Three types of soil profiles are considered: hard, medium and soft. Results of two analyzes are compared on the same structural model. Equivalent soil springs and dashpots are determined using new method based on the least square approximation. (author)
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DEFF Research Database (Denmark)
Nielsen, Jimmi; Jacobsen, Torben
2010-01-01
the primary current distribution to the DC current distribution restricted to the Three-Phase-Boundary (TPB) zone introduces an error in the determination of the reaction resistance, Rreac = Z(freq. → 0) − Z(freq. → ∞). The error is estimated for different width of the effective TPB zone and a rule of thumb...... 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...
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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.
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Method and device for bio-impedance measurement with hard-tissue applications
International Nuclear Information System (INIS)
Guimerà, A; Calderón, E; Los, P; Christie, A M
2008-01-01
Bio-impedance measurements can be used to detect and monitor several properties of living hard-tissues, some of which include bone mineral density, bone fracture healing or dental caries detection. In this paper a simple method and hardware architecture for hard tissue bio-impedance measurement is proposed. The key design aspects of such architecture are discussed and a commercial handheld ac impedance device is presented that is fully certified to international medical standards. It includes a 4-channel multiplexer and is capable of measuring impedances from 10 kΩ to 10 MΩ across a frequency range of 100 Hz to 100 kHz with a maximum error of 5%. The device incorporates several user interface methods and a Bluetooth link for bi-directional wireless data transfer. Low-power design techniques have been implemented, ensuring the device exceeds 8 h of continuous use. Finally, bench test results using dummy cells consisting of parallel connected resistors and capacitors, from 10 kΩ to 10 MΩ and from 20 pF to 100 pF, are discussed
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Method and device for bio-impedance measurement with hard-tissue applications.
Guimerà, A; Calderón, E; Los, P; Christie, A M
2008-06-01
Bio-impedance measurements can be used to detect and monitor several properties of living hard-tissues, some of which include bone mineral density, bone fracture healing or dental caries detection. In this paper a simple method and hardware architecture for hard tissue bio-impedance measurement is proposed. The key design aspects of such architecture are discussed and a commercial handheld ac impedance device is presented that is fully certified to international medical standards. It includes a 4-channel multiplexer and is capable of measuring impedances from 10 kOmega to 10 MOmega across a frequency range of 100 Hz to 100 kHz with a maximum error of 5%. The device incorporates several user interface methods and a Bluetooth link for bi-directional wireless data transfer. Low-power design techniques have been implemented, ensuring the device exceeds 8 h of continuous use. Finally, bench test results using dummy cells consisting of parallel connected resistors and capacitors, from 10 kOmega to 10 MOmega and from 20 pF to 100 pF, are discussed.
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Structural, dielectric and AC conductivity study of Sb2O3 thin film ...
Indian Academy of Sciences (India)
52
However, to date, no reports have appeared on impedance spectroscopy, modulus behavior, electrical conductivity, dielectric relaxation and dielectric properties of crystalline Sb2O3 thin films. This paper deals for the first time with the frequency and temperature dependence of AC conductivity and complex electric modulus ...
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International Nuclear Information System (INIS)
Li, Guo-Qing; Miao, Xing-Yuan; Hu, Yuan-Tai; Wang, Ji
2013-01-01
A comprehensive study on smart beams with piezoelectric elements using an impedance matrix and the inverse Laplace transform is presented. Based on the authors’ previous work, the dynamics of some elements in beam-like smart structures are represented by impedance matrix equations, including a piezoelectric stack, a piezoelectric bimorph, an elastic straight beam or a circular curved beam. A further transform is applied to the impedance matrix to obtain a set of implicit transfer function matrices. Apart from the analytical solutions to the matrices of smart beams, one computation procedure is proposed to obtained the impedance matrices and transfer function matrices using FEA. By these means the dynamic solution of the elements in the frequency domain is transformed to that in Laplacian s-domain and then inversely transformed to time domain. The connections between the elements and boundary conditions of the smart structures are investigated in detail, and one integrated system equation is finally obtained using the symbolic operation of TF matrices. A procedure is proposed for dynamic analysis and control analysis of the smart beam system using mode superposition and a numerical inverse Laplace transform. The first example is given to demonstrate building transfer function associated impedance matrices using both FEA and analytical solutions. The second example is to verify the ability of control analysis using a suspended beam with PZT patches under close-loop control. The third example is designed for dynamic analysis of beams with a piezoelectric stack and a piezoelectric bimorph under various excitations. The last example of one smart beam with a PPF controller shows the applicability to the control analysis of complex systems using the proposed method. All results show good agreement with the other results in the previous literature. The advantages of the proposed methods are also discussed at the end of this paper. (paper)
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Analysis of Conductor Impedances Accounting for Skin Effect and Nonlinear Permeability
Energy Technology Data Exchange (ETDEWEB)
Perkins, M P; Ong, M M; Brown, C G; Speer, R D
2011-07-20
It is often necessary to protect sensitive electrical equipment from pulsed electric and magnetic fields. To accomplish this electromagnetic shielding structures similar to Faraday Cages are often implemented. If the equipment is inside a facility that has been reinforced with rebar, the rebar can be used as part of a lighting protection system. Unfortunately, such shields are not perfect and allow electromagnetic fields to be created inside due to discontinuities in the structure, penetrations, and finite conductivity of the shield. In order to perform an analysis of such a structure it is important to first determine the effect of the finite impedance of the conductors used in the shield. In this paper we will discuss the impedances of different cylindrical conductors in the time domain. For a time varying pulse the currents created in the conductor will have different spectral components, which will affect the current density due to skin effects. Many construction materials use iron and different types of steels that have a nonlinear permeability. The nonlinear material can have an effect on the impedance of the conductor depending on the B-H curve. Although closed form solutions exist for the impedances of cylindrical conductors made of linear materials, computational techniques are needed for nonlinear materials. Simulations of such impedances are often technically challenging due to the need for a computational mesh to be able to resolve the skin depths for the different spectral components in the pulse. The results of such simulations in the time domain will be shown and used to determine the impedances of cylindrical conductors for lightning current pulses that have low frequency content.
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Energy Technology Data Exchange (ETDEWEB)
Hari Prasad, Kamatam [Department of Physics, Pondicherry University, Puducherry, 605 014 (India); Vinoth, S. [Department of Physics, Pondicherry University, Puducherry, 605 014 (India); Centre for Nanoscience, Pondicherry University, Puducherry, 605014 (India); Jena, Paramananda [Department of Physics, Pondicherry University, Puducherry, 605 014 (India); School of Materials Science and Technology, Indian Institute of Technology(BHU), Varanasi, 221 005 (India); Venkateswarlu, M. [R & D, Amara Raja Batteries Ltd, Karakambadi, 517 520, A.P (India); Satyanarayana, N., E-mail: nallanis2011@gmail.com [Department of Physics, Pondicherry University, Puducherry, 605 014 (India)
2017-06-15
One-dimensional electrospun lead oxide nanofibers synthesized by a simple electrospinning technique. The prepared lead oxide nanofibers investigated by using TG/DTA, FTIR, Raman, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analyzer, scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDX), atomic force microscopy (AFM), Transmission electron microscopy (TEM), and impedance spectroscopy techniques. TG/DTA results confirmed the thermal behavior of the as-spun nanofibers. XRD, FTIR, and Raman spectra results, respectively, confirm the formation of pure orthorhombic crystalline phase and structural coordination of the lead oxide (β-PbO) nanofibers. The BET specific surface area of β-PbO nanofibers sample is found to be 51.23 m{sup 2} g{sup -1}. SEM and AFM micrographs showed the formation of β-PbO nanofibers with a diameter of 85–300 nm. The impedance measurements of lead oxide nanofibers as a function of temperature, 25–150 °C, was evaluated by analyzing the measured impedance data using the winfit software. The electrical conductivity of the lead oxide (β-PbO) nanofibers evaluated by analyzing the measured impedance data using the winfit software is found to be 5.68 × 10{sup -6} S cm{sup -1} at 150 °C. Also, an activation energy (E{sub a}) for the migration of the charge carrier evaluated from the temperature dependence of conductivity plot is found to be 0.27 eV. The temperature dependence AC conductivity of β-PbO nanofibers was evaluated using the measured impedance data and sample dimension. The observed variation of high-frequency AC conductivity attributed to the hopping electrons between the adjacent sites. - Highlights: • First time, β-PbO nanofibers were successfully prepared by electrospinning technique. • Structural, morphological, roughness and electrical properties are studied. • TG/DTA, XRD, FTIR, Raman, SEM/AFM, TEM-EDX, and impedance measurements were made.
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DEFF Research Database (Denmark)
Wei, Baoze; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez
2017-01-01
This paper presents a theoretical study with experimental validation of a circulating-current suppression method for parallel operation of three-phase voltage source inverters (VSI), which may be suitable for modular parallel uninterruptible power supply systems or hybrid AC/DC microgrid applicat......This paper presents a theoretical study with experimental validation of a circulating-current suppression method for parallel operation of three-phase voltage source inverters (VSI), which may be suitable for modular parallel uninterruptible power supply systems or hybrid AC/DC microgrid......, and added into the conventional droop plus virtual impedance control. In the control architecture, the reference voltages of the inverters are generated by the primary control loop which consists of a droop control and a virtual impedance. The secondary control is used to compensate the voltage drop...
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Impedance Scaling and Impedance Control
International Nuclear Information System (INIS)
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
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Ida, Midori; Hirata, Masakazu; Hosoda, Kiminori; Nakao, Kazuwa
2013-02-01
Two novel bioelectrical impedance analysis (BIA) methods have been developed recently for evaluation of intra-abdominal fat accumulation. Both methods use electrodes that are placed on abdominal wall and allow evaluation of intra-abdominal fat area (IAFA) easily without radiation exposure. Of these, "abdominal BIA" method measures impedance distribution along abdominal anterior-posterior axis, and IAFA by BIA method(BIA-IAFA) is calculated from waist circumference and the voltage occurring at the flank. Dual BIA method measures impedance of trunk and body surface at the abdominal level and calculates BIA-IAFA from transverse and antero-posterior diameters of the abdomen and the impedance of trunk and abdominal surface. BIA-IAFA by these two BIA methods correlated well with IAFA measured by abdominal CT (CT-IAFA) with correlatipn coefficient of 0.88 (n = 91, p abdominal adiposity in clinical study and routine clinical practice of metabolic syndrome and obesity.
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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...... 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...
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ON THE ANALYSIS OF IMPEDANCE-DRIVEN REVERSE FLOW DYNAMICS
Directory of Open Access Journals (Sweden)
LEE V. C.-C.
2017-02-01
Full Text Available Impedance pump is a simple valve-less pumping mechanism, where an elastic tube is joined to a more rigid tube, at both ends. By inducing a periodic asymmetrical compression on the elastic tube will produce a unidirectional flow within the system. This pumping concept offers a low energy, low noise alternative, which makes it an effective driving mechanism, especially for micro-fluidic systems. In addition, the wave-based mechanism through which pumping occurs infers many benefits in terms of simplicity of design and manufacturing. Adjustment of simple parameters such as the excitation frequencies or compression locations will reverse the direction of flow, providing a very versatile range of flow outputs. This paper describes the experimental analysis of such impedance-driven flow with emphasis on the dynamical study of the reverse flow in open-loop environment. In this study, tapered section with converging steps is introduced at both ends of the elastic tube to amplify the magnitude of reverse flow. Study conducted shows that the reverse peak flow is rather significant with estimate of 23% lower than the forward peak flow. The flow dynamics on the other hand has shown to exhibit different characteristics as per the forward peak flow. The flow characteristics is then studied and showed that the tapered sections altered the impedance within the system and hence induce a higher flow in the reverse direction.
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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.
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Cao, Pei; Qi, Shuai; Tang, J.
2018-03-01
The impedance/admittance measurements of a piezoelectric transducer bonded to or embedded in a host structure can be used as damage indicator. When a credible model of the healthy structure, such as the finite element model, is available, using the impedance/admittance change information as input, it is possible to identify both the location and severity of damage. The inverse analysis, however, may be under-determined as the number of unknowns in high-frequency analysis is usually large while available input information is limited. The fundamental challenge thus is how to find a small set of solutions that cover the true damage scenario. In this research we cast the damage identification problem into a multi-objective optimization framework to tackle this challenge. With damage locations and severities as unknown variables, one of the objective functions is the difference between impedance-based model prediction in the parametric space and the actual measurements. Considering that damage occurrence generally affects only a small number of elements, we choose the sparsity of the unknown variables as another objective function, deliberately, the l 0 norm. Subsequently, a multi-objective Dividing RECTangles (DIRECT) algorithm is developed to facilitate the inverse analysis where the sparsity is further emphasized by sigmoid transformation. As a deterministic technique, this approach yields results that are repeatable and conclusive. In addition, only one algorithmic parameter, the number of function evaluations, is needed. Numerical and experimental case studies demonstrate that the proposed framework is capable of obtaining high-quality damage identification solutions with limited measurement information.
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Impedance measurements on YB/sub 2/Cu/sub 3/O/sub 7-delta) interpretation and trapping parameters
International Nuclear Information System (INIS)
Yasmeen, S.; Mohammad, M.; Khan, A.Y.; Subhani, M.S.
1997-01-01
Two probe impedance spectroscopic studies were carried out on YBa/sub 2/Cu/sub 3/ O/sub 7-delta/ two different sintering conditions i.e. at before final sintering and at after final sintering. In both condition ac impedance studies were done in the frequency range of 1Hz to 100kHz and at different temperatures from room temperature down to 78K. Measurements were done with contacts opposite side (i.e., ceramic behaves as a resister) as well as on opposite sides (i.e., ceramic behaves as a capacitor). Results were obtained in the form of Nyquist plot. Log, Yi/omega Vs log f plot and Yr/omega Vs log f plot. These plots were explained through equivalent circuits. The bulk resistance Rb, the grain boundary resistance R/sub b/ and grain boundary capacitance C/sub gb/ were obtained through these plots. The ac conductivities were also obtained at all temperatures. The log sigma g Vs log omega (frequency) plots were interpreted invoking the theory of ac conductivity in polycrystalline solids. The trapping parameters (binding energy, the hopping distance etc.) were calculated and interpreted. (author)
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Uncertainty and sensitivity analysis of electro-mechanical impedance based SHM system
International Nuclear Information System (INIS)
Rosiek, M; Martowicz, A; Uhl, T
2010-01-01
The paper deals with the application of uncertainty and sensitivity analysis performed for FE simulations for electro-mechanical impedance based SHM system. The measurement of electro-mechanical impedance allows to follow changes of mechanical properties of monitored construction. Therefore it can be effectively applied to conclude about presence of damage. Coupled FE simulations have been carried out for simultaneous consideration of both structural dynamics and piezoelectric properties of a simple beam with bonded transducer. Several indexes have been used to assess the damage growth. In the paper the results obtained with both deterministic and stochastic simulations are shown and discussed. First, the relationship between size of introduced damage and its indexes has been studied. Second, ranges of variation of selected model properties have been assumed to find relationships between them and damage indexes. The most influential parameters have been found. Finally, the overall propagation of considered uncertainty has been assessed and related histograms plotted to discuss effectiveness and robustness of tested damage indexes based on the measurement of electro-mechanical impedance.
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Directory of Open Access Journals (Sweden)
Imene Bekri-Abbes
2015-01-01
Full Text Available The combination of two components with uniform distribution in nanoscale is expected to facilitate wider applications of the material. In this study, polyaniline (PAn and polyaniline/montmorillonite (Mt nanocomposite were prepared by solid reaction using persulfate of ammonium as oxidant. The phase composition and morphology of the nanocomposite were characterized by FTIR, UV-visible spectroscopy, X-ray diffractometer, thermal gravimetric analysis, and scanning electron microscopy. The electrical and dielectric properties were determined using spectroscopy impedance. The analysis of UV-visible and FTIR spectroscopy demonstrated that aniline chloride has been polymerized into PAn in its conducting emeraldine form. Thermogravimetric analysis suggested that PAn chains intercalated in the clay host are more thermally stable than those of free PAn prepared by solid-solid reaction. Electrical measurements were carried out using the complex impedance technique in the frequency range of 10−2 to 104 Hz at different temperatures. The ac conductivity data of different nanocomposites were analyzed as a function of frequency and temperature. It has been found that the incorporation of inorganic clay phase into polyaniline matrix has an effect on the electrical and dielectric properties of the nanomaterial.
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Bioelectrical impedance analysis of bovine milk fat
Veiga, E. A.; Bertemes-Filho, P.
2012-12-01
Three samples of 250ml at home temperature of 20°C were obtained from whole, low fat and fat free bovine UHT milk. They were analysed by measuring both impedance spectra and dc conductivity in order to establish the relationship between samples related to fat content. An impedance measuring system was developed, which is based on digital oscilloscope, a current source and a FPGA. Data was measured by the oscilloscope in the frequency 1 kHz to 100 kHz. It was showed that there is approximately 7.9% difference in the conductivity between whole and low fat milk whereas 15.9% between low fat and free fat one. The change of fatness in the milk can be significantly sensed by both impedance spectra measurements and dc conductivity. This result might be useful for detecting fat content of milk in a very simple way and also may help the development of sensors for measuring milk quality, as for example the detection of mastitis.
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Bioelectrical impedance analysis of bovine milk fat
Energy Technology Data Exchange (ETDEWEB)
Veiga, E A; Bertemes-Filho, P [Department of Electrical Eng., State University of Santa Catarina, Joinville (Brazil)
2012-12-20
Three samples of 250ml at home temperature of 20 Degree-Sign C were obtained from whole, low fat and fat free bovine UHT milk. They were analysed by measuring both impedance spectra and dc conductivity in order to establish the relationship between samples related to fat content. An impedance measuring system was developed, which is based on digital oscilloscope, a current source and a FPGA. Data was measured by the oscilloscope in the frequency 1 kHz to 100 kHz. It was showed that there is approximately 7.9% difference in the conductivity between whole and low fat milk whereas 15.9% between low fat and free fat one. The change of fatness in the milk can be significantly sensed by both impedance spectra measurements and dc conductivity. This result might be useful for detecting fat content of milk in a very simple way and also may help the development of sensors for measuring milk quality, as for example the detection of mastitis.
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Bioelectrical impedance analysis of bovine milk fat
International Nuclear Information System (INIS)
Veiga, E A; Bertemes-Filho, P
2012-01-01
Three samples of 250ml at home temperature of 20°C were obtained from whole, low fat and fat free bovine UHT milk. They were analysed by measuring both impedance spectra and dc conductivity in order to establish the relationship between samples related to fat content. An impedance measuring system was developed, which is based on digital oscilloscope, a current source and a FPGA. Data was measured by the oscilloscope in the frequency 1 kHz to 100 kHz. It was showed that there is approximately 7.9% difference in the conductivity between whole and low fat milk whereas 15.9% between low fat and free fat one. The change of fatness in the milk can be significantly sensed by both impedance spectra measurements and dc conductivity. This result might be useful for detecting fat content of milk in a very simple way and also may help the development of sensors for measuring milk quality, as for example the detection of mastitis.
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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...
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Directory of Open Access Journals (Sweden)
Antoine Dupré
2018-03-01
Full Text Available This paper presents a concept for soft field tomographic scan of all the projections of electromagnetic waves emanating from an array of electrodes. Instead of the sequential excitation of all pairs of electrodes in the list of all projections, the new method present here consists of a single and continuous excitation. This excitation signal is the linear combination of the excitation signals in the projection set at different AC frequencies. The response to a given projection is discriminated by selecting the corresponding AC frequency component in the signal spectra of the digitally demodulated signals. The main advantage of this method is the suppression of transients after each projection, which is particularly problematic in electrical impedance tomography due to contact impedance phenomena and skin effect. The second benefit over the sequential scan method is the increased number of samples for each measurement for reduced noise sensitivity with digital demodulation. The third benefit is the increased temporal resolution in high-speed applications. The main drawback is the increased number of signal sources required (one per electrode. This paper focuses on electrical impedance tomography, based on earlier work by the authors. An experimental proof-of-concept using a simple 4-electrodes electrical impedance tomographic system is presented using simulations and laboratory data. The method presented here may be extended to other modalities (ultrasonic, microwave, optical, etc..
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Energy Technology Data Exchange (ETDEWEB)
Sato, K; Ichinokura, O; Jinzenji, T [Tohoku Univ., Sendai (Japan). Faculty of Engineering; Tajima, K [Akita University, Akita (Japan). Mining College
1991-04-30
This paper reports on a numerical analysis of transient response of an orthogonal-core type dc-ac converter that takes place when the external ac system connected is cut off from it. A model of magnetic circuit of the orthogonal core is presented, which has magnetic inductances to represent effects produced by hysteresis that are connected in series with magnetic reluctances, thereby making it possible to divide each of primary and secondary winding current into magnetization current associated with magnetic reluctances and iron-loss current due to hysteresis. Moreover, a numerical model of the orthogonal core is derived from expressions for non-linear characteristics of these reluctances and inductances to make use of it for analyses employing the circuit simulator SPICE. Transient response of the present converter, namely time variation of both voltage and current in its every part, to the sudden change in condition that is caused by switching off the ac system connected to its secondary side is calculated, while applying square-wave voltage to its primary side. It is noted that calculated wave forms of both secondary winding current and open-circuit voltage are fairly in good agreement with those obtained by an experiment performed on the same condition. 4 refs., 9 figs., 1 tab.
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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
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Directory of Open Access Journals (Sweden)
de Blasio F
2016-09-01
Full Text Available Francesca de Blasio,1 Francesco de Blasio,2,3 Giulia Miracco Berlingieri,2 Andrea Bianco,3,4 Marta La Greca,1 Frits M E Franssen,5 Luca Scalfi1 1Department of Public Health, Medical School, “Federico II” University of Naples, 2Respiratory Medicine and Pulmonary Rehabilitation Section, Clinic Center, Private Hospital, Naples, 3Department of Medicine and Health Sciences “V Tiberio”, University of Molise, Campobasso, 4Department of Cardio-Thoracic and Respiratory Sciences, Second University of Naples, Naples, Italy; 5Department of Research and Education, CIRO, Horn, the NetherlandsBackground: Multifrequency bioelectrical impedance analysis (MF-BIA is a technique that measures body impedance (Z at different frequencies (5, 10, 50, 100, and 250 kHz. Body composition may be estimated using empirical equations, which include BIA variables or, alternatively, raw BIA data may provide direct information on water distribution and muscle quality.Objectives: To compare raw MF-BIA data between COPD patients and controls and to study their relationship with respiratory and functional parameters in COPD patients.Methods: MF-BIA was performed (Human Im-Touch analyzer in 212 COPD patients and 115 age- and BMI-matched controls. Fat-free mass (FFM and fat mass were estimated from BIA data, and low- to high-frequency (5 kHz/250 kHz impedance ratio was calculated. Physical fitness, lung function and respiratory muscle strength were also assessed in COPD patients.Results: After adjusting for age, weight, and body mass index, FFM and the 5/250 impedance ratio were lower in COPD patients (P<0.001 and were negatively affected by disease severity. In both male and female patients, the 5/250 impedance ratio was significantly correlated mainly with age (r=−0.316 and r=−0.346, respectively. Patients with a 5/250 impedance ratio below median value had lower handgrip strength (P<0.001, 6-minute walk distance (P<0.005, respiratory muscle strength (P<0.005, forced
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A physicochemical mechanism of chemical gas sensors using an AC analysis.
Moon, Jaehyun; Park, Jin-Ah; Lee, Su-Jae; Lee, Jeong-Ik; Zyung, Taehyong; Shin, Eui-Chol; Lee, Jong-Sook
2013-06-21
Electrical modeling of the chemical gas sensors was successfully applied to TiO2 nanofiber gas sensors by developing an equivalent circuit model where the junction capacitance as well as the resistance can be separated from the comparable stray capacitance. The Schottky junction impedance exhibited a characteristic skewed arc described by a Cole-Davidson function, and the variation of the fit and derived parameters with temperature, bias, and NO2 gas concentration indicated definitely a physicochemical sensing mechanism based on the Pt|TiO2 Schottky junctions against the conventional supposition of the enhanced sensitivity in nanostructured gas sensors with high grain boundary/surface area. Analysis on a model Pt|TiO2|Pt structure also confirmed the characteristic impedance response of TiO2 nanofiber sensors.
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Silva, S R; Afonso, J; Monteiro, A; Morais, R; Cabo, A; Batista, A C; Guedes, C M; Teixeira, A
2018-06-01
Carcass data were collected from 24 kids (average live weight of 12.5±5.5 kg; range 4.5 to 22.4 kg) of Jarmelista Portuguese native breed, to evaluate bioelectrical impedance analysis (BIA) as a technique for prediction of light kid carcass and muscle chemical composition. Resistance (Rs, Ω) and reactance (Xc, Ω), were measured in the cold carcasses with a single frequency bioelectrical impedance analyzer and, together with impedance (Z, Ω), two electrical volume measurements (VolA and VolB, cm2/Ω), carcass cold weight (CCW), carcass compactness and several carcass linear measurements were fitted as independent variables to predict carcass composition by stepwise regression analysis. The amount of variation explained by VolA and VolB only reached a significant level (Pcarcass fat weight (0.814⩽R 2⩽0.862; Pcarcass fat weight (combined with carcass length, CL; R 2=0.943; Pcarcass composition.
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Directory of Open Access Journals (Sweden)
Fábio M. Pereira
2016-10-01
Full Text Available This paper describes the development of a novel microfluidic platform for multifactorial analysis integrating four label-free detection methods: electrical impedance, refractometry, optical absorption and fluorescence. We present the rationale for the design and the details of the microfabrication of this multifactorial hybrid microfluidic chip. The structure of the platform consists of a three-dimensionally patterned polydimethylsiloxane top part attached to a bottom SU-8 epoxy-based negative photoresist part, where microelectrodes and optical fibers are incorporated to enable impedance and optical analysis. As a proof of concept, the chip functions have been tested and explored, enabling a diversity of applications: (i impedance-based identification of the size of micro beads, as well as counting and distinguishing of erythrocytes by their volume or membrane properties; (ii simultaneous determination of the refractive index and optical absorption properties of solutions; and (iii fluorescence-based bead counting.
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Array of piezoelectric energy harvesting by the equivalent impedance approach
International Nuclear Information System (INIS)
Lien, I C; Shu, Y C
2012-01-01
This article proposes to use the idea of equivalent impedance to investigate the electrical response of an array of piezoelectric oscillators endowed with distinct energy harvesting circuits. Three interface electronics systems are considered including standard AC/DC and parallel/series-SSHI (synchronized switch harvesting on inductor) circuits. Various forms of equivalent load impedance are analytically obtained for different interfaces. The steady-state response of an array system is then shown to be determined by the matrix formulation of generalized Ohm’s law whose impedance matrix is explicitly expressed in terms of the load impedance. A model problem is proposed for evaluating the ability of power harvesting under various conditions. It is shown first that harvested power is increased dramatically for the case of small deviation in the system parameters. On the other hand, if the deviation in mass is relatively large, the result is changed from the power-boosting mode to wideband mode. In particular, the parallel-SSHI array system exhibits much more significant bandwidth improvement than the other two cases. Surprisingly, the series-SSHI array system shows the worst electrical response. Such an observation is opposed to our previous finding that an SSHI technique avails against the standard technique in the case based on a single piezoelectric energy harvester and the explanation is under investigation. (fast track communication)
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Modelling of long High Voltage AC Cables in the Transmission System
DEFF Research Database (Denmark)
Gudmundsdottir, Unnur Stella
: conductor-insulation (with or without SC layers)-conductor-insulation(-conductor-insulation), whereas a transmission line single core XLPE cable will normally have the configuration: conductor-SC layerinsulation-SC layer-conductor-SC layer-conductor-insulation. Furthermore the existing cable models use......, EMTDC/PSCAD is provided. A typical HV AC underground power cable is formed by 4 main layers, namely; Conductor-Insulation-Screen-Insulation. In addition to these main layers, the cable also has semiconductive screens, swelling tapes and metal foil. For high frequency modelling in EMT-based software......-SC layer-solid hollow conductor) is implemented in the model. These improvements result in a more correct series impedance and hence a more correct damping of the simulations. Even though the series impedance is more correct, it does still not include the proximity effect and high frequency oscillations...
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Directory of Open Access Journals (Sweden)
LISTYA UTAMI KARMAWAN
2009-03-01
Full Text Available Musa acuminata cultivar pisang ambon lumut is a native climacteric fruit from Indonesia. Climacteric fruit ripening process is triggered by the gaseous plant hormone ethylene. The rate limiting enzyme involved in ethylene biosynthesis is ACC synthase (ACS which is encoded by ACS gene family. The objective of this study is to identify MA-ACS gene family in M. acuminata cultivar pisang ambon lumut and to study the MA-ACS1 gene expression. The result showed that there were nine M. acuminata ACS gene family members called MA-ACS1–9. Two of them (MA-ACS1 and MA-ACS2 were assessed using reverse transcriptase PCR (RT-PCR for gene expression study and it was only MA-ACS1 correlated with fruit ripening. The MA-ACS1 gene fragment has been successfully isolated and characterized and it has three introns, four exons, and one stop codon. It also shows highest homology with MACS1 gene from M. acuminata cultivar Hsian Jien Chiao (GenBank accession number AF056164. Expression analysis of MA-ACS1 using quantitative PCR (qPCR showed that MA-ACS1 gene expression increased significantly in the third day, reached maximum at the fifth day, and then decreased in the seventh day after harvesting. The qPCR expression analysis result correlated with the result of physical analysis during fruit ripening.
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Directory of Open Access Journals (Sweden)
Karen Cristina Barcellos Ribeiro
2013-12-01
Full Text Available INTRODUCTION: The analysis of urine abnormal constituents and sediment (ACS comprises tests of great diagnostic and prognostic value in clinical practice. When the analysis of ACS cannot be performed within two hours after collection, the sample must be preserved in order to avoid pre-analytical interferences. Refrigeration is the most applied technique due to its cost effectiveness. Moreover, it presents fewer inconveniences when compared to chemical preservation. However, changes in ACS may also occur in samples under refrigeration. OBJECTIVE: To analyze the influence of refrigeration at 2 to 8ºC on the storage of urine samples within 24 hours. MATERIAL AND METHOD: A total of 80 urine samples were selected from patients admitted at Universidade Federal de Juiz de Fora (UFJF university hospital, which were tested for ACS at room temperature and stored under refrigeration for 6, 12 and 24 hours. RESULTS: The results showed that refrigeration proved to be effective when compared to samples kept at room temperature, inasmuch as the physical, chemical, microbial and cellularity features were preserved. Nevertheless, crystalluria was present after a 6- hour storage period. CONCLUSION: The tests revealed that cooling preserved cellularity and chemical characteristics of urine samples for up to 12 hours. Nonetheless, the precipitation of crystals was evident in this storage method. Thus, the possible consequences of storing urine samples for ACS test under these conditions should be included in the analysis report.
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Nguyen, N Q; Holloway, R H; Smout, A J; Omari, T I
2013-03-01
Automated integrated analysis of impedance and pressure signals has been reported to identify patients at risk of developing dysphagia post fundoplication. This study aimed to investigate this analysis in the evaluation of patients with non-obstructive dysphagia (NOD) and normal manometry (NOD/NM). Combined impedance-manometry was performed in 42 patients (27F : 15M; 56.2 ± 5.1 years) and compared with that of 24 healthy subjects (8F : 16M; 48.2 ± 2.9 years). Both liquid and viscous boluses were tested. MATLAB-based algorithms defined the median intrabolus pressure (IBP), IBP slope, peak pressure (PP), and timing of bolus flow relative to peak pressure (TNadImp-PP). An index of pressure and flow (PFI) in the distal esophagus was derived from these variables. Diagnoses based on conventional manometric assessment: diffuse spasm (n = 5), non-specific motor disorders (n = 19), and normal (n = 11). Patients with achalasia (n = 7) were excluded from automated impedance-manometry (AIM) analysis. Only 2/11 (18%) patients with NOD/NM had evidence of flow abnormality on conventional impedance analysis. Several variables derived by integrated impedance-pressure analysis were significantly different in patients as compared with healthy: higher PNadImp (P < 0.01), IBP (P < 0.01) and IBP slope (P < 0.05), and shorter TNadImp_PP (P = 0.01). The PFI of NOD/NM patients was significantly higher than that in healthy (liquid: 6.7 vs 1.2, P = 0.02; viscous: 27.1 vs 5.7, P < 0.001) and 9/11 NOD/NM patients had abnormal PFI. Overall, the addition of AIM analysis provided diagnoses and/or a plausible explanation in 95% (40/42) of patients who presented with NOD. Compared with conventional pressure-impedance assessment, integrated analysis is more sensitive in detecting subtle abnormalities in esophageal function in patients with NOD and normal manometry. © 2012 Blackwell Publishing Ltd.
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Determination of bone mineral volume fraction using impedance analysis and Bruggeman model
Energy Technology Data Exchange (ETDEWEB)
Ciuchi, Ioana Veronica; Olariu, Cristina Stefania, E-mail: oocristina@yahoo.com; Mitoseriu, Liliana, E-mail: lmtsr@uaic.ro
2013-11-20
Highlights: • Mineral volume fraction of a bone sample was determined. • Dielectric properties for bone sample and for the collagen type I were determined by impedance spectroscopy. • Bruggeman effective medium approximation was applied in order to evaluate mineral volume fraction of the sample. • The computed values were compared with ones derived from a histogram test performed on SEM micrographs. -- Abstract: Measurements by impedance spectroscopy and Bruggeman effective medium approximation model were employed in order to determine the mineral volume fraction of dry bone. This approach assumes that two or more phases are present into the composite: the matrix (environment) and the other ones are inclusion phases. A fragment of femur diaphysis dense bone from a young pig was investigated in its dehydrated state. Measuring the dielectric properties of bone and its main components (hydroxyapatite and collagen) and using the Bruggeman approach, the mineral volume filling factor was determined. The computed volume fraction of the mineral volume fraction was confirmed by a histogram test analysis based on the SEM microstructures. In spite of its simplicity, the method provides a good approximation for the bone mineral volume fraction. The method which uses impedance spectroscopy and EMA modeling can be further developed by considering the conductive components of the bone tissue as a non-invasive in situ impedance technique for bone composition evaluation and monitoring.
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Determination of bone mineral volume fraction using impedance analysis and Bruggeman model
International Nuclear Information System (INIS)
Ciuchi, Ioana Veronica; Olariu, Cristina Stefania; Mitoseriu, Liliana
2013-01-01
Highlights: • Mineral volume fraction of a bone sample was determined. • Dielectric properties for bone sample and for the collagen type I were determined by impedance spectroscopy. • Bruggeman effective medium approximation was applied in order to evaluate mineral volume fraction of the sample. • The computed values were compared with ones derived from a histogram test performed on SEM micrographs. -- Abstract: Measurements by impedance spectroscopy and Bruggeman effective medium approximation model were employed in order to determine the mineral volume fraction of dry bone. This approach assumes that two or more phases are present into the composite: the matrix (environment) and the other ones are inclusion phases. A fragment of femur diaphysis dense bone from a young pig was investigated in its dehydrated state. Measuring the dielectric properties of bone and its main components (hydroxyapatite and collagen) and using the Bruggeman approach, the mineral volume filling factor was determined. The computed volume fraction of the mineral volume fraction was confirmed by a histogram test analysis based on the SEM microstructures. In spite of its simplicity, the method provides a good approximation for the bone mineral volume fraction. The method which uses impedance spectroscopy and EMA modeling can be further developed by considering the conductive components of the bone tissue as a non-invasive in situ impedance technique for bone composition evaluation and monitoring
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Impedance spectroscopy of p-ZnGa{sub 2}Te{sub 4}/n-Si nano-HJD
Energy Technology Data Exchange (ETDEWEB)
Fouad, S.S. [Thin film Laboratory, Department of Physics, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Sakr, G.B. [Nano-Science Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Yahia, I.S., E-mail: dr_isyahia@yahoo.com [Nano-Science Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Semiconductor Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia); Abdel-Basset, D.M. [Nano-Science Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Yakuphanoglu, F. [Department of Physics, Faculty of Science, Firat University, Elazig (Turkey)
2013-04-15
The dielectric relaxation and alternating current mechanisms of nano-crystalline p-ZnGa{sub 2}Te{sub 4}/n-Si heterojunction diode (HJD) were investigated by complex impedance spectroscopy over a wide range of temperature (297–473 K) and a frequency range (42 Hz–5 MHz). The bulk resistance R{sub b} as well as the bulk capacitance C{sub b} were found to increase with increasing temperature. The dc conductivity exhibits a typical Arrhenius behavior. The electrical activation energy ΔE{sub σ} was determined to be (0.28 eV). The ac conductivity spectrum was found to obey Jonscher's universal power law. The frequency exponent s decreases slightly with increasing temperature. The temperature dependence of ac conductivity can be reasonably interpreted in terms of the correlated barrier hopping (CBH) model. The dielectric constant ε{sub 1}(ω) and dielectric loss ε{sub 2}(ω) were found to decrease with increasing frequency and to increase with increasing temperature. The mean value of the exponent m decreases with increasing temperature. The dielectric analysis is described by non-Debye type behavior.
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A compact wideband precision impedance measurement system based on digital auto-balancing bridge
International Nuclear Information System (INIS)
Hu, Binxin; Wang, Jinyu; Song, Guangdong; Zhang, Faxiang
2016-01-01
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. (paper)
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Ionic conductivity measurements of zirconia under pressure using impedance spectroscopy
International Nuclear Information System (INIS)
Takebe, H; Sakamoto, D; 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 2 (Y 2 O 3 -ZrO 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
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Entrance and Exit CSR Impedance for Non-Ultrarelativistic Beam
Energy Technology Data Exchange (ETDEWEB)
Li, Rui; Tsai, Cheng Ying [SLAC National Accelerator Lab., Menlo Park, CA (United States); Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
2017-05-01
For a high-brightness electron beam being transported through beamlines involving bending systems, the coherent synchrotron radiation (CSR) and longitudinal space charge (LSC) interaction could often cause microbunching instability. The semi-analytical Vlasov solver for microbunching gain* depends on the impedances for the relevant collective effects. The existing results for CSR impedances are usually obtained for the ultrarelativistic limit. To extend the microbunching analysis to cases of low energies, such as the case of an ERL merger, or to density modulations at extremely small wavelength, it is necessary to extend the impedance analysis to the non-ultrarelativistic regime. In this study, we present the impedance analysis for the transient CSR interaction in the non-ultrarelativistic regime, for transients including both entrance to and exit from a magnetic dipole. These impedance results will be compared to their ultra-relativistic counterparts**, and the corresponding wakefield obtained from the impedance for low-energy beams will be compared with the existing results of transient CSR wakefield for general beam energies***.
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CSR Impedance for Non-Ultrarelativistic Beams
International Nuclear Information System (INIS)
Li, Rui; Tsai, Cheng Y.
2015-09-01
For the analysis of the coherent synchrotron radiation (CSR)-induced microbunching gain in the low energy regime, such as when a high-brightness electron beam is transported through a low-energy merger in an energy-recovery linac (ERL) design, it is necessary to extend the CSR impedance expression in the ultrarelativistic limit to the non-ultrarelativistic regime. This paper presents our analysis of CSR impedance for general beam energies.
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Impedance spectroscopic and dielectric analysis of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} thin films
Energy Technology Data Exchange (ETDEWEB)
Rouahi, A. [Grenoble Electrical Engineering Laboratory (G2E Lab), CNRS, University of Grenoble (UJF), 25 Rue des Martyrs, BP 166, 38042 Grenoble Cedex 9 (France); Laboratory of Materials, Organization and Properties (LMOP), Campus Universities, El Manar, 2092 Tunis (Tunisia); Kahouli, A., E-mail: kahouli.kader@yahoo.fr [Grenoble Electrical Engineering Laboratory (G2E Lab), CNRS, University of Grenoble (UJF), 25 Rue des Martyrs, BP 166, 38042 Grenoble Cedex 9 (France); Laboratory of Materials, Organization and Properties (LMOP), Campus Universities, El Manar, 2092 Tunis (Tunisia); Sylvestre, A., E-mail: alain.sylvestre@grenoble.cnrs.fr [Grenoble Electrical Engineering Laboratory (G2E Lab), CNRS, University of Grenoble (UJF), 25 Rue des Martyrs, BP 166, 38042 Grenoble Cedex 9 (France); Defaye, E. [CEA-LETI, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Yangui, B. [Laboratory of Materials, Organization and Properties (LMOP), Campus Universities, El Manar, 2092 Tunis (Tunisia)
2012-07-15
Highlights: Black-Right-Pointing-Pointer The material exhibits the contribution of both grain and grain boundaries in the electric response of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3}. Black-Right-Pointing-Pointer The plot of normalized complex dielectric modulus and impedance as a function of frequency exhibits both short and long-range conduction in the film. Black-Right-Pointing-Pointer The frequency dependence of ac conductivity exhibits a polaron hopping mechanism with activation energy of 0.38 eV. Black-Right-Pointing-Pointer The complex dielectric modulus analysis confirmed the presence of a non-Debye type of conductivity relaxation deduced from the KWW function. - Abstract: Polycrystalline Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} thin film with Pt/BST/Pt/TiO{sub 2}/SiO{sub 2} structure was prepared by ion beam sputtering. The film was post annealed at 700 Degree-Sign C. The dielectric and electric modulus properties were studied by impedance spectroscopy over a wide frequency range [0.1-10{sup 5} Hz] at different temperatures [175-350 Degree-Sign C]. The Nyquist plots (Z Double-Prime vs . Z Prime ) show the contribution of both grain and grain boundaries at higher temperature on the electric response of BST thin films. Moreover, the resistance of grains decreases with the rise in temperature and the material exhibits a negative temperature coefficient of resistance. The electric modulus plot indicates the non-Debye type of dielectric relaxation. The values of the activation energy computed from both plots of Z Double-Prime and M Double-Prime are 0.86 eV and 0.81 eV respectively, which reveals that the species responsible for conduction are the same. The scaling behavior of M{sup Double-Prime }/M{sup Double-Prime }{sub max} shows the temperature independent nature of relaxation time. The plot of normalized complex dielectric modulus and impedance as a function of frequency exhibits both short and long-range conduction in the film.
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Kinetic mechanism of steel corrosion in clay soils by impedance measurements
International Nuclear Information System (INIS)
Arpaia, M.; Pernice, P.; Costantini, A.
1990-01-01
The corrosion of steel in clay soil at m.c. 15% has been studied for a long exposure time by electrochemical methods. A.c. impedance measurements results show that at a short exposure time the corrosion process is controlled by the diffusion of H + coupled with a rate determining homogeneous reaction, whereas at a long exposure time the process is controlled by pure diffusion. We have hypothesized that the rate determining homogeneous reaction might be the clay particles cations exchange. (orig.)
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Moderately nonlinear diffuse-charge dynamics under an ac voltage.
Stout, Robert F; Khair, Aditya S
2015-09-01
The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of V_{o}/(k_{B}T/e), where V_{o} is the amplitude of the driving voltage and k_{B}T/e is the thermal voltage with k_{B} as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D/λ_{D}L, where D is the ion diffusivity, λ_{D} is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O(V_{o}^{3}) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in V_{o}. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing V_{o}. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.
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Moderately nonlinear diffuse-charge dynamics under an ac voltage
Stout, Robert F.; Khair, Aditya S.
2015-09-01
The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of Vo/(kBT /e ) , where Vo is the amplitude of the driving voltage and kBT /e is the thermal voltage with kB as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D /λDL , where D is the ion diffusivity, λD is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O (Vo3) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in Vo. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing Vo. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.
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FDTD modeling of thin impedance sheets
Luebbers, Raymond J.; Kunz, Karl S.
1991-01-01
Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. In this paper it is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods.
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Havinga-Top, Thamar; Waninge, Aly; van der Schans, Cees; Jager, Harriët
2015-01-01
Background: Body composition measurements provide importanti nformation about physical fitness and nutritional status. People with severe intellectual and visual disabilities (SIVD) have an increased risk for altered body composition. Bioelectrical impedance analysis (BIA) has been evidenced as a
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Havinga-Top, A. M.; Waninge, A.; van der Schans, C. P.; Jager-Wittenaar, H.
2015-01-01
Background: Body composition measurements provide important information about physical fitness and nutritional status. People with severe intellectual and visual disabilities (SIVD) have an increased risk for altered body composition. Bioelectrical impedance analysis (BIA) has been evidenced as a
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Influence of the ac magnetic field frequency on the magnetoimpedance of amorphous wire
International Nuclear Information System (INIS)
Chen, A P; Garcia, C; Zhukov, A; Dominguez, L; Blanco, J M; Gonzalez, J
2006-01-01
Experimental and theoretical studies on the influence of ac magnetic field frequency on the axial diagonal (ζ zz ) and off-diagonal (ζ Φz ) components of the magnetoimpedance (MI) tensor in (Co 0.94 Fe 0.06 ) 72.5 Si 12.5 B 15 amorphous wires have been performed. The frequency (f) of an ac current flowing along the wire was varied from 1 to 20 MHz with the current amplitude less than 15 mA. In order to enhance the ζ Φz component, the amorphous wire was submitted to torsion annealing for developing and preserving a helical magnetic anisotropy in the surface of the wire. The experimental measurements show that the value of the impedance is proportional to the square-root of the ac current frequency, √f, in the vicinity of H ex K and this increase is due to the contribution of the resistance (real part of the impedance). The measurements also indicate that the peaks of the MI curve shift slightly towards higher field values with increasing f. In a theoretical study the magnetoimpedance expressions ζ zz and ζ Φz have been deduced using the Faraday law in combination with the solutions of the Maxwell and Landau-Lifshitz-Gilbert (LLG) equations. By analysing quantitatively the spectra of ζ zz and ζ Φz , the phenomenon of the shift in the peaks of the MI curve with f has been considered as a characteristic of the helical anisotropy in the domain structure of the wire surface
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Directory of Open Access Journals (Sweden)
Sanjeevikumar Padmanaban
2016-03-01
Full Text Available This research article exploits the power management algorithm in post-fault conditions for a six-phase (quad multilevel inverter. The drive circuit consists of four 2-level, three-phase voltage source inverter (VSI supplying a six-phase open-end windings motor or/impedance load, with circumstantial failure of one VSI investigated. A simplified level-shifted pulse-width modulation (PWM algorithm is developed to modulate each couple of three-phase VSI as 3-level output voltage generators in normal operation. The total power of the whole ac drive is shared equally among the four isolated DC sources. The developed post-fault algorithm is applied when there is a fault by one VSI and the load is fed from the remaining three healthy VSIs. In faulty conditions the multilevel outputs are reduced from 3-level to 2-level, but still the system propagates with degraded power. Numerical simulation modelling and experimental tests have been carried out with proposed post-fault control algorithm with three-phase open-end (asymmetrical induction motor/R-L impedance load. A complete set of simulation and experimental results provided in this paper shows close agreement with the developed theoretical background.
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Impedance of the PEP-II DIP screen
Energy Technology Data Exchange (ETDEWEB)
Ng, C -K [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Weiland, T
1996-08-01
The vacuum chamber of a storage ring normally consists of periodically spaced pumping slots. The longitudinal impedance of slots are analyzed in this paper. It is found that although the broad-band impedance is tolerable, the narrow-band impedance, as a consequence of the periodicity of the slots, may exceed the stability limit given by natural damping with no feedback system on. Based on this analysis, the PEP-II distributed-ion-pump (DIP) screen uses long grooves with hidden holes cut halfway to reduce both the broad-band and narrow-band impedances. (author)
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Impedance of the PEP-II DIP screen
International Nuclear Information System (INIS)
Ng, C.K.; Weiland, T.
1995-09-01
The vacuum chamber of a storage ring normally consists of periodically spaced pumping slots. The longitudinal impedance of slots are analyzed in this paper. It is found that although the broad-band impedance is tolerable, the narrow-band impedance, as a consequence of the periodicity of the slots, may exceed the stability limit given by natural damping with no feedback system on. Based on this analysis, the PEP-II distributed-ion-pump (DIP) screen uses long grooves with hidden holes cut halfway to reduce both the broad-band and narrow-band impedances
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International Nuclear Information System (INIS)
García-Chocano, Víctor Manuel; García-Miquel, Héctor
2015-01-01
Giant Magnetoimpedance (GMI) effect has been studied in amorphous glass-coated microwires of composition (Fe 6 Co 94 ) 72.5 Si 12.5 B 15 . The impedance of a 1.5 cm length sample has been characterized by using constant AC currents in the range of 400 µA–4 mA at frequencies from 7 to 15 MHz and DC magnetic fields from −900 to 900 A/m. Double peak responses have been obtained, showing GMI ratios up to 107%. A linear magnetic field sensor for DC and AC field has been designed, using two microwires connected in series with a magnetic bias of 400 A/m with opposite direction in each microwire in order to obtain a linear response from ±70 (A/m) rms for AC magnetic field, and ±100 A/m for DC magnetic field. A closed loop feedback circuit has been implemented to extend the linear range to ±1 kA/m for DC magnetic field. - Highlights: • Giant Magneto Impedance phenomenon has been studied in amorphous microwires. • A combination of two microwires with a bias field has been developed to get a linear response. • An electronic circuit has been developed to obtain a sensor with a linear response. • A feedback coil have been added to increase the measurable range of the sensor
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Multivariate analysis of electrical impedance spectra for relaxed and contracted skeletal muscle
International Nuclear Information System (INIS)
Zagar, T; Krizaj, D
2008-01-01
Four-electrode impedance spectra of relaxed and contracted muscle biceps brachii were analyzed in an adult human subject over the frequency range from 300 Hz to 75 kHz. A feasibility of the principal component analysis of bioimpedance measurement for the evaluation of skeletal muscle contractile state was examined. The principal components score plots show a data grouping of the impedance spectra from the two muscle groups. The classification was performed using a soft independent modeling of class analogy (SIMCA) method. The data set comprised 32 samples (16 samples of contracted muscle and 16 samples of relaxed muscle). The leave-one-out test of the classification yields about 80% of correctly classified samples (11 samples for contracted and 15 samples for relaxed muscle)
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Energy Technology Data Exchange (ETDEWEB)
Gazzarri, J.I.; Kesler, O. [Department of Mechanical Engineering, University of British Columbia, 2054-6250 Applied Science Lane, Vancouver, BC V6T 1Z4 (Canada)
2007-05-01
A finite element model of the impact of diverse degradation mechanisms on the impedance spectrum of a solid oxide fuel cell is presented as a tool for degradation mode identification. Among the degradation mechanisms that cause electrode active area loss, the attention is focused on electrode delamination and uniformly distributed surface area loss, which were found to cause distinct and specific changes in the impedance spectrum. Degradation mechanisms resulting in uniformly distributed reactive surface area loss include sintering, sulphur poisoning, and possibly incipient coke formation at the anode, and chromium deposition at the cathode. Parametric studies reveal the extent and limits of applicability of the model and detectability of the different degradation modes, as well as the influence of different cell geometries on the change in impedance behaviour resulting from the loss of active area. It is expected that this technique could form the basis of a useful diagnostic tool for both solid oxide fuel cell developers and users. (author)
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International Nuclear Information System (INIS)
Castro, E.B.; Vilche, J.R.; Milocco, R.H.
1984-01-01
An impedance measurement system based on the spectral analysis of excitation and response signals was implemented using a pseudo-random binary sequence in the generation of the electrical perturbation signal. The spectral density functions were estimated through finite Fourier transforms of the original time history records by fast computation of Fourier series. Experimental results obtained using the FFT algorithm in the developed impedance measurement system which covers a wide frequency range, 10 KHz >= f >= 1 mHz, are given both for dummy cells representing conventional electric circuits in electrochemistry and corrosion systems and for the Fe/acidic chloride solution interfaces under different polarization conditions. (C.L.B.) [pt
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Structural, dielectric and impedance properties of Ca(Fe2/3W1/3)O3 nanoceramics
International Nuclear Information System (INIS)
Choudhary, R.N.P.; Pradhan, Dillip K.; Tirado, C.M.; Bonilla, G.E.; Katiyar, R.S.
2007-01-01
The polycrystalline nanoceramics (∼60 nm) of Ca(Fe 2/3 W 1/3 )O 3 (CFW) were synthesized by mechanochemical and solid-state reaction techniques. Preliminary X-ray structural analysis of CFW suggested the formation of single-phase compound in tetragonal crystal system (distorted structure of ideal perovskite). The large distortion (∼16%) is supported by a large deviation of tolerance factor t=0.86 from unity (for ideal perovskite). The SEM micrograph shows the polycrystalline nature of the sample with different grain sizes, which are inhomogeneously distributed through the sample surface. Detailed studies of dielectric and impedance properties of the material in a wide range of frequency (1 kHz-1 MHz) and temperatures (300-630 K) show that these properties are strongly temperature and frequency dependent. The nature of variation of AC conductivity exhibits a progressive increase in AC conductivity on increasing temperature. The oxygen vacancies, space charge and mobile charge carriers play an important role in relaxation and conduction process. The relaxation process in the material was found to be of non-Debye type
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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...
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Deletion of the AcMNPV core gene ac109 results in budded virions that are non-infectious
International Nuclear Information System (INIS)
Fang Minggang; Nie, Yingchao; Theilmann, David A.
2009-01-01
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) ac109 is a core gene and its function in the virus life cycle is unknown. To determine its role in the baculovirus life cycle, we used the AcMNPV bacmid system to generate an ac109 deletion virus (vAc 109KO ). Fluorescence and light microscopy showed that transfection of vAc 109KO results in a single-cell infection phenotype. Viral DNA replication is unaffected and the development of occlusion bodies in vAc 109KO -transfected cells evidenced progression to the very late phases of viral infection. Western blot and confocal immunofluorescence analysis showed that AC109 is expressed in the cytoplasm and nucleus throughout infection. In addition, AC109 is a structural protein as it was detected in both budded virus (BV) and occlusion derived virus in both the envelope and nucleocapsid fractions. Titration assays by qPCR and TCID 50 showed that vAc 109KO produced BV but the virions are non-infectious. The vAc 109KO BV were indistinguishable from the BV of repaired and wild type control viruses as determined by negative staining and electron microscopy.
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The Peltier driven frequency domain approach in thermal analysis.
De Marchi, Andrea; Giaretto, Valter
2014-10-01
The merits of Frequency Domain analysis as a tool for thermal system characterization are discussed, and the complex thermal impedance approach is illustrated. Pure AC thermal flux generation with negligible DC component is possible with a Peltier device, differently from other existing methods in which a significant DC component is intrinsically attached to the generated AC flux. Such technique is named here Peltier Driven Frequency Domain (PDFD). As a necessary prerequisite, a novel one-dimensional analytical model for an asymmetrically loaded Peltier device is developed, which is general enough to be useful in most practical situations as a design tool for measurement systems and as a key for the interpretation of experimental results. Impedance analysis is possible with Peltier devices by the inbuilt Seebeck effect differential thermometer, and is used in the paper for an experimental validation of the analytical model. Suggestions are then given for possible applications of PDFD, including the determination of thermal properties of materials.
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Schrabback, T.; Erben, T.; Simon, P.; Miralles, J.-M.; Schneider, P.; Heymans, C.; Eifler, T.; Fosbury, R. A. E.; Freudling, W.; Hetterscheidt, M.; Hildebrandt, H.; Pirzkal, N.
2007-06-01
Context: This is the first paper of a series describing our measurement of weak lensing by large-scale structure, also termed “cosmic shear”, using archival observations from the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). Aims: In this work we present results from a pilot study testing the capabilities of the ACS for cosmic shear measurements with early parallel observations and presenting a re-analysis of HST/ACS data from the GEMS survey and the GOODS observations of the Chandra Deep Field South (CDFS). Methods: We describe the data reduction and, in particular, a new correction scheme for the time-dependent ACS point-spread-function (PSF) based on observations of stellar fields. This is currently the only technique which takes the full time variation of the PSF between individual ACS exposures into account. We estimate that our PSF correction scheme reduces the systematic contribution to the shear correlation functions due to PSF distortions to MUSIC sample, we determine a local single field estimate for the mass power spectrum normalisation σ8, CDFS=0.52+0.11-0.15 (stat) ± 0.07(sys) (68% confidence assuming Gaussian cosmic variance) at a fixed matter density Ω_m=0.3 for a ΛCDM cosmology marginalising over the uncertainty of the Hubble parameter and the redshift distribution. We interpret this exceptionally low estimate to be due to a local under-density of the foreground structures in the CDFS. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archives at the Space Telescope European Coordinating Facility and the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
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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
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Impedance analysis of nanostructured iridium oxide electrocatalysts
International Nuclear Information System (INIS)
Sunde, Svein; Lervik, Ingrid Anne; Tsypkin, Mikhail; Owe, Lars-Erik
2010-01-01
Impedance data were collected for nanostructured iridium oxide (NIROF) at potentials below those at which the oxygen evolution reaction commences. The measurements included thin oxide films covered by a protective Nafion TM layer and thicker composite Nafion TM -oxide electrodes. The time constants for the low-frequency diffusion process were approximately the same for both types of electrodes, indicating diffusion in individual particles in the porous electrode rather than across the film. The diffusion process involves trapping of the diffusion species. The impedance data indicated that there were no significant variations in conductivity of the oxides with potential, as opposed to what appears to be the case for anodically formed iridium oxide films (AIROF). This is interpreted to reflect differences in electronic structure between NIROF and AIROF.
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Bioelectrical impedance analysis for the prediction of hot carcass weight in buffalo calf
Directory of Open Access Journals (Sweden)
Leopoldo Iannuzzi
2010-01-01
Full Text Available Twenty young buffalo male calves were fed ad libitum with a total mix ration and with vitamin-mineral integration for 14 months. Seven days before slaughter, the animals were weighed and bioelectrical impedance measurements were collected in live animals. Physical and chemical characteristics were assessed on the Longissimus dorsi muscle after slaughter. Correlations and regression equations were calculated to determine the possible use of bioelectrical impedance for evaluating hot carcass weight. Bioelectrical impedance analysis at different frequencies, simple correlation and analysis of regression were examined for all the data collected, supporting the possibility of hot carcass weight prediction with equation at multifrequency. The results show that, probably due to the variability in animal live weight, the distribution of the colour parameters was not normally distributed. Moreover, using different frequencies of resistance and reactance, hot carcass weight in buffalo may be predicted with the following equation: Y=98.47–8.84(Rs100KHz+4.41(Rs1000 KHz-116.27(Xc5 KHz+51.04(Xc50 KHz+20.30(Xc100 KHz-33.92(Xc500 KHz+9.01(Xc1000 KHz±ε (Adjusted R Square value of .907 and SE of 5.728 However, further studies are required to improve the technique also in buffalo, after standardization of the method.
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Systémový pohled na klub AC Sparta
Čečák, František
2015-01-01
Title: The system approach of the club AC Sparta Praha Objectives: Elaboration of financial analysis of the club AC Sparta Praha in season 2010/2011.Comparing the results of the financial analysis with the results of clubs FC Viktoria Plzeň and SK Slavia Praha. Prognosis of the club AC Sparta Praha until year 2020. Methods: In the elaboration of the analysis have been used these methods: vertical analysis, horizontal analysis and analysis of the financial ratios. For forecasting have been use...
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Bera, Tushar Kanti
2016-12-05
impedance analysis for electrical impedance-based tissue characterization, health analysis and disease diagnosis.
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Bera, Tushar Kanti; Jampana, Nagaraju; Lubineau, Gilles
2016-01-01
impedance analysis for electrical impedance-based tissue characterization, health analysis and disease diagnosis.
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Energy Technology Data Exchange (ETDEWEB)
Wong, Y.J., E-mail: yjeng_86@hotmail.com [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hassan, J., E-mail: jumiah@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hashim, M., E-mail: mansor@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia)
2013-09-15
Highlights: •A single phase orthorhombic CaTiO{sub 3} structure with sub-micron grains is produced. •The frequency exponent ‘s’ is temperature dependent and explained by CBH model. •The dielectric constant and loss tangent are frequency and temperature dependent. •The modulus plot reveals the presence of thermally activated dielectric relaxation. •Cole-cole plot reveals two primary relaxation processes exist in the sample. -- Abstract: Calcium titanate (CaTiO{sub 3}) with the general formula for perovskites, ABO{sub 3}, is of technological importance, particularly with regard to dielectric properties. In this work, CaTiO{sub 3} ceramic material was prepared by the conventional solid state reaction method. The dielectric properties, impedance characteristics and modulus behavior of the CaTiO{sub 3} ceramic material sintered at 1240 °C were investigated in the frequency range of 10{sup −2}–10{sup 6} Hz and temperature range of 100–250 °C. The XRD analysis of the sintered CaTiO{sub 3} shows that it is an orthorhombic structure with lattice parameters a = 5.4398 Å, b = 7.6417 Å, and c = 5.3830 Å. The FESEM micrograph shows a significant difference in grain size distribution ranging from 0.26 to 2.32 μm. The AC conductivity, σ{sub AC}, is found to increase with increasing temperature within the frequency range of 10{sup −2}–10{sup 6} Hz confirming the hopping of electrons to be the conduction mechanism. Due to the decreasing values of the frequency exponent s with increasing temperature, the results of the σ{sub AC} are discussed using the correlated barrier height (CBH) model. For dielectric studies, the dielectric constant, ε′ is found to decrease with increasing frequency. In the whole temperature range of 100–250 °C, high and low frequency plateau are observed. Each converges at high frequency (>10{sup 5} Hz) for all the temperatures. The frequency dependence of loss tangent, tan δ, decreases with rise in temperature, with the
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Performance Analysis of Phase Controlled Unidirectional and Bidirectional AC Voltage Controllers
Directory of Open Access Journals (Sweden)
Abdul Sattar Larik
2011-01-01
Full Text Available AC voltage controllers are used to vary the output ac voltage from a fixed ac input source. They are also commonly called ac voltage regulators or ac choppers. The output voltage is either controlled by PAC (Phase Angle Control method or on-off control method. Due to various advantages of ac voltage controllers, such as high efficiency, simplicity, low cost and ability to control large amount of power they efficiently control the speed of ac motors, light dimming and industrial heating, etc. These converters are variable structure systems and generate harmonics during the operation which will affect the power quality when connected to system network. During the last couple of years, a number of new semiconductor devices and various power electronic converters has been introduced. Accordingly the subject of harmonics and its problems are of great concern to power industry and customers. In this research work, initially the simulation models of single phase unidirectional and bidirectional ac voltage controllers were developed by using MATLAB software. The harmonics of these models are investigated by simulation. In the end, the harmonics were also analyzed experimentally. The simulated as well as experimental results are presented.
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International Nuclear Information System (INIS)
Osman, Z.; Zainol, N.H.; Samin, S.M.; Chong, W.G.; Md Isa, K.B.; Othman, L.; Supa’at, I.; Sonsudin, F.
2014-01-01
Magnesium-based rechargeable batteries might be an interesting future alternative to lithium-based batteries since magnesium compounds are highly abundant in the earth and are environmental friendly. In this work, we have prepared polymethylmethacrylate (PMMA) based gel polymer electrolyte (GPE) films containing two different magnesium salts, which is magnesium triflate, Mg(CF 3 SO 3 ) 2 and magnesium perchlorate, Mg(ClO 4 ) 2 using solution casting technique . The ionic conductivity of both gel polymer electrolyte systems was evaluated using a.c impedance spectroscopy. Results show that at room temperature, GPE-Mg(CF 3 SO 3 ) 2 system exhibits the highest conductivity value at 1.27 × 10 −3 S cm −1 for the film containing 20 wt.% of Mg(CF 3 SO 3 ) 2 salt, while the highest conductivity value for the GPE-Mg(ClO 4 ) 2 system is 3.13 × 10 −3 S cm −1 for the film containing 15 wt.% of Mg(ClO 4 ) 2 salt. The conductivity-temperature studies of both GPE systems follow the Arrhenius behavior. The activation energies for ionic conduction were determined to be in the range of 0.18–0.26 eV. The transport numbers of magnesium ions in both GPE systems were evaluated using the combination of a.c impedance spectroscopy and d.c polarization techniques. The results obtained indicate that the charge carriers in the GPE films for both systems are predominantly due to ions
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Final design of the Korean AC/DC converters for the ITER coil power supply system
Energy Technology Data Exchange (ETDEWEB)
Oh, Jong-Seok, E-mail: jsoh@nfri.re.kr [ITER Korea, National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of); Choi, Jungwan; Suh, Jae-Hak; Choi, Jihyun [ITER Korea, National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of); Lee, Lacksang; Kim, Changwoo; Park, Hyungjin; Jo, Seongman; Lee, Seungyun; Hwang, Kwangcheol; Liu, Hyoyol [Dawonsys Corp., Siheung 429-450 (Korea, Republic of); Hong, Ki-Don; Sim, Dong-Joon; Lee, Jang-Soo [Hyosung Corp., Gongdeok-Dong, Seoul 121-720 (Korea, Republic of); Lee, Eui-Jae; Kwon, Yang-Hae; Lee, Dae-Yeol; Ko, Ki-Won; Kim, Jong-Min [Mobiis Corp., Yangjae-dong, Seoul 137-888 (Korea, Republic of); Song, Inho [ITER Organization, Route de Vinon sur Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); and others
2015-10-15
The final design of the ITER TF, CS, CC and VS AC/DC converters has been completed to implement ITER requirements following the detailed design and refinements of the preliminary design. The number of parallel thyristors and the rating of fuses are coordinated to keep those devices within the explosion limit even under most severe fault conditions. The impedance of the converter transformer has been optimized taking into account the energization inrush current, short circuit current, reactive power consumption and the available DC voltage. To ensure system integrity, AC/DC converters are mechanically divided into transformers, AC busbars, 6-pulse bridges, DC interconnecting busbars and DC reactors, and then all subsystems are decoupled by flexible links. To provide stable real time network communication down to the converters, a one GbE link is deployed between master controllers and local controllers. IEEE 1588 is implemented to the embedded controllers for precision time synchronization. This paper describes the detailed solutions implemented in the final design for the ITER AC/DC converters with R&D results of converter prototypes.
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Systémový pohled na klub AC Sparta
Čečák, František
2014-01-01
Title: The system approach of the club AC Sparta Praha Aim of the paper: Elaboration of financial analysis of the club AC Sparta Praha in season 2010/2011.Comparing the results of the financial analysis with the results of clubs FC Viktoria Plzeň and SK Slavia Praha. Prognosis of the club AC Sparta Praha until year 2020. Methods: In the elaboration of the analysis have been used these methods: vertical analysis, horizontal analysis and analysis of the financial ratios. For forecasting have be...
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Czech Academy of Sciences Publication Activity Database
Silver, Barry Richard; Holub, Karel; Mareček, Vladimír
2014-01-01
Roč. 731, OCT 2014 (2014), s. 107-111 ISSN 1572-6657 R&D Projects: GA ČR GA13-04630S Institutional support: RVO:61388955 Keywords : Liquid/liquid interfaces * Ion transport * AC impedance Subject RIV: CG - Electrochemistry Impact factor: 2.729, year: 2014
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Synthesis, characterization and a.c. magnetic analysis of magnetite nanoparticles
International Nuclear Information System (INIS)
Riani, P.; Napoletano, M.; Canepa, F.
2011-01-01
In the last years, the study of Fe-based magnetic nanoparticles (MNP) has attracted increasing interest either for the physical properties shown by nanosized materials (electric and magnetic properties are strongly affected by dimension and surface effects) either for the different technological applications of these materials (catalysis, drug delivery, magnetic resonance imaging, contaminants removal from groundwater, new exchange coupled magnets, soft nanomagnets for high frequency applications, etc.). In this article, the results obtained in the synthesis and characterization of the Fe 3 O 4 MNP is reported. The magnetite nanoparticles were synthesized by a modified Massart method. Structural characterization was performed using X-ray diffraction analysis and a complete morphological and dimensional study was carried out by means of Transmission Electron Microscopy, and a.c. magnetic susceptibility measured as a function of the frequency of the applied magnetic field. Diameters of the superparamagnetic Fe 3 O 4 nanoparticles are ranging from 2 to 10 nm, as evidenced by all the techniques employed. The size distribution of the hydrated aggregates in solution has been obtained by quantitative analysis of the frequency dependence of the a.c. susceptibility. The mathematical approach adopted will be described and all the obtained results will be compared and discussed.
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Stolwijk, Judith A; Matrougui, Khalid; Renken, Christian W; Trebak, Mohamed
2015-10-01
The past 20 years has seen significant growth in using impedance-based assays to understand the molecular underpinning of endothelial and epithelial barrier function in response to physiological agonists and pharmacological and toxicological compounds. Most studies on barrier function use G protein-coupled receptor (GPCR) agonists which couple to fast and transient changes in barrier properties. The power of impedance-based techniques such as electric cell-substrate impedance sensing (ECIS) resides in its ability to detect minute changes in cell layer integrity label-free and in real-time ranging from seconds to days. We provide a comprehensive overview of the biophysical principles, applications, and recent developments in impedance-based methodologies. Despite extensive application of impedance analysis in endothelial barrier research, little attention has been paid to data analysis and critical experimental variables, which are both essential for signal stability and reproducibility. We describe the rationale behind common ECIS data presentation and interpretation and illustrate practical guidelines to improve signal intensity by adapting technical parameters such as electrode layout, monitoring frequency, or parameter (resistance versus impedance magnitude). Moreover, we discuss the impact of experimental parameters, including cell source, liquid handling, and agonist preparation on signal intensity and kinetics. Our discussions are supported by experimental data obtained from human microvascular endothelial cells challenged with three GPCR agonists, thrombin, histamine, and sphingosine-1-phosphate.
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You, J. J.; Ning, W. Y.; Jiang, H.; Dong, Y. X.; Liu, H.; Li, Y.
2017-05-01
Sub-synchronous resonance (SSR) occurred in the power system with both Doubly Fed Induction Generators (DFIGs) and series-compensated lines. There have been several papers focusing on the analysis of such SSR phenomenon. To the authors’ knowledge, the impacts of DFIG numbers are seldom considered in existing papers. In this paper, the impedance characteristics of DFIGs under different numbers are analyzed. Then the relationship between DFIG numbers and SSR characteristics is discussed. The contributions to be included in the paper are as following: 1) the impedance of N DFIGs is roughly equal to 1/N of the impedance of one DFIG. 2) The SSR risk of system is related with both the numbers of DFIGs and the parameters of the series-compensated lines.
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DEFF Research Database (Denmark)
Mosbæk, Rasmus Rode; Hjelm, Johan; Barfod, R.
2013-01-01
As solid oxide fuel cell (SOFC) technology is moving closer to a commercial break through, lifetime limiting factors, and methods to measure the “state-of-health” of operating cells and stacks are becoming of increasing interest. This requires application of advanced methods for detailed...... electrochemical characterization during operation. An experimental stack with low ohmic resistance from Topsoe Fuel Cell A/S was characterized in detail using electrochemical impedance spectroscopy (EIS). An investigation of the optimal geometrical placement of the current feeds and voltage probes was carried out...... with hydrogen as fuel with 52% fuel utilization and constant current load (0.2 A cm–2) at 750 °C. Stack interconnects were coated with six different coatings to prevent chromium poisoning on the cathode side. Four repeating units (RUs) with different coatings were selected for detailed impedance analysis. EIS...
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Time-domain representation of frequency-dependent foundation impedance functions
Safak, E.
2006-01-01
Foundation impedance functions provide a simple means to account for soil-structure interaction (SSI) when studying seismic response of structures. Impedance functions represent the dynamic stiffness of the soil media surrounding the foundation. The fact that impedance functions are frequency dependent makes it difficult to incorporate SSI in standard time-history analysis software. This paper introduces a simple method to convert frequency-dependent impedance functions into time-domain filters. The method is based on the least-squares approximation of impedance functions by ratios of two complex polynomials. Such ratios are equivalent, in the time-domain, to discrete-time recursive filters, which are simple finite-difference equations giving the relationship between foundation forces and displacements. These filters can easily be incorporated into standard time-history analysis programs. Three examples are presented to show the applications of the method.
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International Nuclear Information System (INIS)
Hubrecht, J.; Piens, M.; Vereecken, J.
1984-01-01
The ac impedance measurement has proved to be a useful electrochemical technique for mainly qualitative studies of electrochemical and corrosion systems. Even for complicated systems such as coated metals in corrosive environments this technique has been used with success. The system chosen for the present study is an ARMCO iron plate, coated with a SrCrO 4 -pigmented styrene acrylic polymer, and immersed for several weeks in an aqueous NaCl solution. Impedance measurements analyze a system under test into its constituting phenomena. The dependence of system parameters on coating layer thickness, NaCl concentration, and pigmentation of the coating during the immersion time provides insight into the corrosion and protection mechanisms at the coating/metal interface, besides the behavior of the coating itself
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Surge Protection in Low-Voltage AC Power Circuits: An Anthology
Martzloff, F. D.
2002-10-01
The papers included in this part of the Anthology provide basic information on the propagation of surges in low-voltage AC power circuits. The subject was approached by a combination of experiments and theoretical considerations. One important distinction is made between voltage surges and current surges. Historically, voltage surges were the initial concern. After the introduction and widespread use of current-diverting surge-protective devices at the point-of-use, the propagation of current surges became a significant factor. The papers included in this part reflect this dual dichotomy of voltage versus current and impedance mismatch effects versus simple circuit theory.
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Mahajan, Sandeep; Haridas, Divya; Ali, S. T.; Munirathnam, N. R.; Sreenivas, K.; Thakur, O. P.; Prakash, Chandra
2014-10-01
In present study we have prepared ferroelectric BaZrxTi1-xO3 (x=0.05) ceramic by conventional solid state reaction route and studied its electrical properties as a function of temperature and frequency. X-ray diffraction (XRD) analysis shows single-phase formation of the compound with orthorhombic crystal structure at room temperature. Impedance and electric modulus spectroscopy analysis in the frequency range of 40 Hz-1 MHz at high temperature (200-600 °C) suggests two relaxation processes with different time constant are involved which are attributed to bulk and grain boundary effects. Frequency dependent dielectric plot at different temperature shows normal variation with frequency while dielectric loss (tanδ) peak was found to obey an Arrhenius law with activation energy of 1.02 eV. The frequency-dependent AC conductivity data were also analyzed in a wide temperature range. In present work we have studied the role of grain and grain boundaries on the electrical behaviour of Zr-doped BaTiO3 and their dependence on temperature and frequency by complex impedance and modulus spectroscopy (CIS) technique in a wide frequency (40 Hz-1 MHz) and high temperature range.
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Two port network analysis for three impedance based oscillators
Said, Lobna A.
2011-12-01
Two-port network representations are applied to analyze complex networks which can be dissolved into sub-networks connected in series, parallel or cascade. In this paper, the concept of two-port network has been studied for oscillators. Three impedance oscillator based on two port concept has been analyzed using different impedance structures. The effect of each structure on the oscillation condition and the frequency of oscillation have been introduced. Two different implementations using MOS and BJT have been introduced. © 2011 IEEE.
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Tuan, Nguyen Anh; Anh, Nguyen Tuan; Nga, Nguyen Tuyet; Tue, Nguyen Anh; Van Cuong, Giap
2016-06-01
The alternating-current (ac) electrical properties of granular-type-barrier magnetic tunnel junctions (GBMTJs) based on Co/Co x (Al2O3)1- x ( t)/Co trilayer structures have been studied using complex impedance spectroscopy (CIS). Their CIS characteristics were investigated in external magnetic fields varying from 0 kOe to 3 kOe as a function of Co composition x at 10 at.%, 25 at.%, and 35 at.%, with barrier layer thickness t of 20 nm to 90 nm. The influence of these factors on the behaviors of the ac impedance response of the GBMTJs was deeply investigated and attributed to the dielectric or conducting nature of the Co-Al2O3 barrier layer. The most remarkable typical phenomena observed in these behaviors, even appearing paradoxical, include lower impedance for thicker t for each given x, a declining trend of Z with increasing x, a clear decrease of Z with H, and especially a partition of Z into zones according to the H value. All these effects are analyzed and discussed to demonstrate that diffusion-type and mass-transfer-type phenomena can be inferred from processes such as spin tunneling and Coulomb or spin blockade in the Co-Al2O3 barrier layer.
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Energy Technology Data Exchange (ETDEWEB)
Norouzi, P.; Ganjali, M.R.; Golmohamaddi, M.; Mousavi, S. [Department of Chemistry, Faculty of Science, University of Tehran, Tehran (Iran); Vatankhah, G. [Iranian Organization for Science and Technology (IROST), Isfahan Center, A5 Ghezelbash Avenue, Tohid Street, Isfahan 8173954541 (Iran)
2003-04-01
The effect of coloring condition of Al with Calcon (sodium 2,2'-dihydroxy-azonaphthalene-4-sulfonate), on the corrosion resistance of Al in 0.1 M sulfuric acid solution was studied, using cyclic voltammetry and measurement of impedance noise methods. The changes in the corrosion resistance of colored aluminum electrodes were evaluated by measuring the magnitude of impedance and cyclic voltammetric responses of anodized and colored electrodes. An irreversible corrosion response was observed at the cyclic voltammogram of the colored aluminum electrode. The current and threshold potential of corrosion responses strongly depends on the applied conditions during anodizing, coloring and sealing stages. In addition, significant changes in impedance at the ac voltammogram and noise level at some ac frequencies were observed, when the electrodes were colored under various conditions. In this regard, the surface of the electrode was studied by Scanning Electron Microscopy (SEM). Comparison of SEM images of the colored and uncolored aluminum specimens showed that the colored surface contained a significant numbers of pits. The results indicated that coloring aluminum with Calcon could reduce corrosion resistance of aluminum and increase roughness of the oxide film. (Abstract Copyright [2003], Wiley Periodicals, Inc.) [German] Mit Hilfe zyklischer Voltammetrie und Messungen mit Impedanzrauschmethoden wurde der Einfluss der Faerbungsbedingungen von Aluminium mit Calcon (Natrium 2,2'-Dihydroxyazonaphthalen-4-Sulfonat) auf den Korrosionswiderstand von Aluminium in 0,1 M Schwefelsaeure untersucht. Die Veraenderungen des Korrosionswiderstandes von gefaerbten Aluminiumelektroden wurden durch Messungen der Hoehe der Impedanzreaktion bzw. der Reaktion bei der zyklischen Voltammetrie von anodisierten und gefaerbten Elektroden beurteilt. Eine irreversible Korrosionsreaktion wurde beim zyklischen Voltammogramm der gefaerbten Aluminiumelektrode beobachtet. Der Strom und das
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Energy Technology Data Exchange (ETDEWEB)
Deslouis, C. (LP15 du CNRS, Physique des Liquides et Electrochimie, Lab. de l' Univ. Pierre et Marie Curie, 75252 Paris Cedex 05 (FR)); Musiani, M.M.; Pagura, C.; Tribollet, C. (Inst. di Polarografia de Elettrochimica Preparativa del CNR, Corso Stati Uniti, 4, 35020 Camin, Padova (IT))
1991-09-01
This paper discusses the Fe{sup 3+} reduction reaction studied at Pt and polyaniline rotating disk electrodes by steady-state and impedance methods with the aim of testing the possibility of achieving the charge transfer resistance (R{sub ts}) of a redox reaction mediated by a conducting polymer film by ac impedance R{sub ts} was obtained as a function of electrode potential and rotation rate by nonlinear least squares fitting of a previously developed kinetic equation to the experimental data. These R{sub ts} values were combined with steady-state ones to calculate b{sub c} and k{sup 0}.
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Unified Impedance Model of Grid-Connected Voltage-Source Converters
DEFF Research Database (Denmark)
Wang, Xiongfei; Harnefors, Lennart; Blaabjerg, Frede
2018-01-01
This paper proposes a unified impedance model of grid-connected voltage-source converters for analyzing dynamic influences of the Phase-Locked Loop (PLL) and current control. The mathematical relations between the impedance models in the different domains are first explicitly revealed by means...... of complex transfer functions and complex space vectors. A stationary (αβ-) frame impedance model is then proposed, which not only predicts the stability impact of the PLL, but reveals also its frequency coupling effect explicitly. Furthermore, the impedance shaping effect of the PLL on the current control...... results and theoretical analysis confirm the effectiveness of the stationary-frame impedance model....
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Increased Ac excision (iae): Arabidopsis thaliana mutations affecting Ac transposition
International Nuclear Information System (INIS)
Jarvis, P.; Belzile, F.; Page, T.; Dean, C.
1997-01-01
The maize transposable element Ac is highly active in the heterologous hosts tobacco and tomato, but shows very much reduced levels of activity in Arabidopsis. A mutagenesis experiment was undertaken with the aim of identifying Arabidopsis host factors responsible for the observed low levels of Ac activity. Seed from a line carrying a single copy of the Ac element inserted into the streptomycin phosphotransferase (SPT) reporter fusion, and which displayed typically low levels of Ac activity, were mutagenized using gamma rays. Nineteen mutants displaying high levels of somatic Ac activity, as judged by their highly variegated phenotypes, were isolated after screening the M2 generation on streptomycin-containing medium. The mutations fall into two complementation groups, iae1 and iae2, are unlinked to the SPT::Ac locus and segregate in a Mendelian fashion. The iae1 mutation is recessive and the iae2 mutation is semi-dominant. The iae1 and iae2 mutants show 550- and 70-fold increases, respectively, in the average number of Ac excision sectors per cotyledon. The IAE1 locus maps to chromosome 2, whereas the SPT::Ac reporter maps to chromosome 3. A molecular study of Ac activity in the iae1 mutant confirmed the very high levels of Ac excision predicted using the phenotypic assay, but revealed only low levels of Ac re-insertion. Analyses of germinal transposition in the iae1 mutant demonstrated an average germinal excision frequency of 3% and a frequency of independent Ac re-insertions following germinal excision of 22%. The iae mutants represents a possible means of improving the efficiency of Ac/Ds transposon tagging systems in Arabidopsis, and will enable the dissection of host involvement in Ac transposition and the mechanisms employed for controlling transposable element activity
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Galluzzo, M; Talamonti, M; Perino, F; Servoli, S; Giordano, D; Chimenti, S; De Simone, C; Peris, K
2017-06-01
There is strong evidence that obesity is closely associated with psoriasis. However, data on body composition are lacking in psoriasis. The purpose of this study were to investigate the body composition in psoriasis patients using bioelectrical impedance analysis and to correlate the bioelectrical impedance data with disease severity and laboratory parameters. Anthropometric measurements and bioelectrical impedance analyses were performed on patients with psoriasis, naïve to any systemic treatment, who attended the outpatient clinics of two University centers. Data of 164 adult patients were analyzed. Compared to men, women had several significantly higher bioelectrical impedance parameters including reactance, fat mass% and adipose tissue%. The values of adipose tissue were positively correlated only with patients age (p = .021) and age at disease onset (p = .0006), but not with disease severity. In addition, we observed that the use of BMI cutoffs allowed to categorize 36.7% of women and 19.2% of men as obese, while fat mass% showed that 53.3% of women and 48.1% of men were obese. In our study, psoriasis is been associated with a high fat mass%. We suggest that screening for body fat distribution in psoriatic patients might be useful to identify early obesity-related disease.
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Smart Multi-Frequency Bioelectrical Impedance Spectrometer for BIA and BIVA Applications.
Harder, Rene; Diedrich, Andre; Whitfield, Jonathan S; Buchowski, Macie S; Pietsch, John B; Baudenbacher, Franz J
2016-08-01
Bioelectrical impedance analysis (BIA) is a noninvasive and commonly used method for the assessment of body composition including body water. We designed a small, portable and wireless multi-frequency impedance spectrometer based on the 12 bit impedance network analyzer AD5933 and a precision wide-band constant current source for tetrapolar whole body impedance measurements. The impedance spectrometer communicates via Bluetooth with mobile devices (smart phone or tablet computer) that provide user interface for patient management and data visualization. The export of patient measurement results into a clinical research database facilitates the aggregation of bioelectrical impedance analysis and biolectrical impedance vector analysis (BIVA) data across multiple subjects and/or studies. The performance of the spectrometer was evaluated using a passive tissue equivalent circuit model as well as a comparison of body composition changes assessed with bioelectrical impedance and dual-energy X-ray absorptiometry (DXA) in healthy volunteers. Our results show an absolute error of 1% for resistance and 5% for reactance measurements in the frequency range of 3 kHz to 150 kHz. A linear regression of BIA and DXA fat mass estimations showed a strong correlation (r(2)=0.985) between measures with a maximum absolute error of 6.5%. The simplicity of BIA measurements, a cost effective design and the simple visual representation of impedance data enables patients to compare and determine body composition during the time course of a specific treatment plan in a clinical or home environment.
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Energy Technology Data Exchange (ETDEWEB)
Halder, S.; Bhuyan, S.; Das, S.N.; Sahoo, S.; Choudhary, R.N.P.; Parida, K. [Siksha ' O' Anusandhan University, Bhubaneswar (India); Das, P. [Midnapore College, Department of Physics, Midnapore, West Bengal (India)
2017-12-15
A lead-free dielectric material [Bi(Zn{sub 2/3}Ta{sub 1/3})O{sub 3}] has been prepared using a solid state reaction technique at high-temperature. The resistive, conducting and capacitive characteristics of the prepared electronic material have been studied in different experimental conditions. The determination of basic crystal parameters and reflection indices confirm the development of polycrystalline compound with orthorhombic crystal structure. The study of frequency-temperature dependence of ac conductivity illustrates the nature and conduction mechanism of the material. On the basis of observed impedance data and detailed dielectric analysis, the existence of non-Debye type relaxation has been affirmed. The electronic charge carriers of compound have short range order that has been validated from the complex modulus and impedance spectrum. The detailed studies of resistive, capacitive, microstructural characteristics of the prepared material provide some useful data for considering the material as an electronic component for fabrication of devices. (orig.)
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Impedance spectroscopy studies on lead free (Ba0.85Ca0.15(Ti0.9Zr0.1O3 ceramics
Directory of Open Access Journals (Sweden)
Ahcène Chaouchi
2012-12-01
Full Text Available The AC complex impedance spectroscopy technique has been used to obtain the electrical parameters of polycrystalline sample of (Ba0.85Ca0.15(Ti0.9Zr0.1O3 in a wide frequency range at different temperatures. This sample was prepared by a high temperature solid-state reaction technique and single phase formation was confirmed by X-ray diffraction technique. This study was carried out by the means of simultaneous analysis of impedance, modulus, and electrical conductivity. The Cole-Cole (Nyquist plots suggest that the grains and grain boundaries are responsible in the conduction mechanism of the material at high temperature. The ColeCole (Nyquist plot studies revealed the presence of grain and grain boundary effect at 485 °C. On the other hand, it showed only the presence of grain boundary component of the resistivity at 535 °C. Complex impedance analysis indicated the presence of non-Debye type dielectric relaxation. The bulk resistance of the material decreases with rise in temperature similar to a semiconductor, and the Cole-Cole (Nyquist plot showed the negative temperature coefficient of resistance (NTCR character of (Ba0.85Ca0.15(Ti0.9Zr0.1O3. The value of activation energy is found to be 0.7433 eV, which suggests that the conduction may be the result of defect and charge carriers present in the materials.
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Advanced impedance modeling of solid oxide electrochemical cells
DEFF Research Database (Denmark)
Graves, Christopher R.; Hjelm, Johan
2014-01-01
Impedance spectroscopy is a powerful technique for detailed study of the electrochemical and transport processes that take place in fuel cells and electrolysis cells, including solid oxide cells (SOCs). Meaningful analysis of impedance measurements is nontrivial, however, because a large number...... techniques to provide good guesses for the modeling parameters, like transforming the impedance data to the distribution of relaxation times (DRT), together with experimental parameter sensitivity studies, is the state-of-the-art approach to achieve good EC model fits. Here we present new impedance modeling...... electrode and 2-D gas transport models which have fewer unknown parameters for the same number of processes, (ii) use of a new model fitting algorithm, “multi-fitting”, in which multiple impedance spectra are fit simultaneously with parameters linked based on the variation of measurement conditions, (iii...
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Directory of Open Access Journals (Sweden)
Liu Shuyi
2016-01-01
Full Text Available The hardware design of tuber electrical resistance tomography (TERT system is one of the key research problems of TERT data acquisition system. The TERT system can be applied to the tuber growth process monitoring in agriculture, i.e., the TERT data acquisition system can realize the real imaging of tuber plants in soil. In TERT system, the imaging tuber and soil multiphase medium is quite complexity. So, the impedance test and analysis of soil multiphase medium is very important to the design of sensitive array sensor subsystem and signals processing circuits. In the paper, the soil impedance test experimental is described and the results are analysed. The data acquisition hardware system is designed based on the result of soil medium impedance test and analysis. In the hardware design, the switch control chip ADG508, the instrumentation amplifier AD620 and programmable amplifier AD526 are employed. In the meantime, the phase locked loop technique for signal demodulation is introduced. The initial data collection is given and discussed under the conditions of existing plant tuber and no existing plant tuber. Conclusions of the hardware design of TERT system are presented.
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Dielectric relaxation behavior and impedance studies of Cu2+ ion doped Mg - Zn spinel nanoferrites
Choudhary, Pankaj; Varshney, Dinesh
2018-03-01
Cu2+ substituted Mg - Zn nanoferrites is synthesized by low temperature fired sol gel auto combustion method. The spinel nature of nanoferrites was confirmed by lab x-ray technique. Williamson - Hall (W-H) analysis estimate the average crystallite size (22.25-29.19 ± 3 nm) and micro strain induced Mg0.5Zn0.5-xCuxFe2O4 (0.0 ≤ x ≤ 0.5). Raman scattering measurements confirm presence of four active phonon modes. Red shift is observed with enhanced Cu concentration. Dielectric parameters exhibit a non - monotonous dispersion with Cu concentration and interpreted with the support of hopping mechanism and Maxwell-Wagner type of interfacial polarization. The ac conductivity of nanoferrites increases with raising the frequency. Complex electrical modulus reveals a non - Debye type of dielectric relaxation present in nanoferrites. Reactive impedance (Z″) detected an anomalous behavior and is related with resonance effect. Complex impedance demonstrates one semicircle corresponding to the intergrain (grain boundary) resistance and also explains conducting nature of nanoferrites. For x = 0.2, a large semicircle is observed revealing the ohmic nature (minimum potential drop at electrode surface). Dielectric properties were improved for nanoferrites with x = 0.2 and is due to high dielectric constant, conductivity and minimum loss value (∼0.009) at 1 MHz.
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Performance of an X-ray single pixel TES microcalorimeter under DC and AC biasing
International Nuclear Information System (INIS)
Gottardi, L.; Kuur, J. van der; Korte, P. A. J. de; Den Hartog, R.; Dirks, B.; Popescu, M.; Hoevers, H. F. C.; Bruijn, M.; Borderias, M. Parra; Takei, Y.
2009-01-01
We are developing Frequency Domain Multiplexing (FDM) for the read-out of TES imaging microcalorimeter arrays for future X-ray missions like IXO. In the FDM configuration the TES is AC voltage biased at a well defined frequencies (between 0.3 to 10 MHz) and acts as an AM modulating element. In this paper we will present a full comparison of the performance of a TES microcalorimeter under DC bias and AC bias at a frequency of 370 kHz. In both cases we measured the current-to-voltage characteristics, the complex impedance, the noise, the X-ray responsivity, and energy resolution. The behaviour is very similar in both cases, but deviations in performances are observed for detector working points low in the superconducting transition (R/R N <0.5). The measured energy resolution at 5.89 keV is 2.7 eV for DC bias and 3.7 eV for AC bias, while the baseline resolution is 2.8 eV and 3.3 eV, respectively.
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Oz, Alon; Hershkovitz, Shany; Tsur, Yoed
2014-11-01
In this contribution we present a novel approach to analyze impedance spectroscopy measurements of supercapacitors. Transforming the impedance data into frequency-dependent capacitance allows us to use Impedance Spectroscopy Genetic Programming (ISGP) in order to find the distribution function of relaxation times (DFRT) of the processes taking place in the tested device. Synthetic data was generated in order to demonstrate this technique and a model for supercapacitor ageing process has been obtained.
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Role of radiation damping in the impedance function approach to soil-structure interaction analysis
International Nuclear Information System (INIS)
1980-05-01
This report was prepared at the request of the Lawrence Livermore Laboratory (LLL) to provide background information for analyzing soil-structure interaction by the frequency-independent impedance function approach. LLL is conducting such analyses as part of its seismic review of selected operating plants under the Systematic Evaluation Program for the US Nuclear Regulatory Commission. The analytical background and basic assumptionsof the impedance function theory are briefly reviewed, and the role of radiation damping in soil-structure interaction analysis is discussed. The validity of modeling soil-structure interaction by using frequency-independent functions is evaluated based on data from several field tests. Finally, the recommended procedures for performing soil-structure interaction analyses are discussed with emphasis on the modal superposition method
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Vertical load analysis of cylindrical ACS support structures
International Nuclear Information System (INIS)
Kennedy, J.M.; Belytschko, T.B.
1984-01-01
A new concept in LMFBR design ACS (above-core structures) supports which has generated some interest is to use a single large radius cylinder. The advantages of a single cylinder are reduced cost of fabrication, increased lateral stiffness, which enhances seismic resistance, and easier access to the fuel. However, the performance of these support structures when submitted to vertical loads from the core area may be substantially different, for the buckling and postbuckling behavior of a cylinder differs substantially from that of cylindrical beams. In this paper, a comparative analysis of an old prototypical support by 4 columns is compared with a cylindrical support. It is assumed that the single cylinder replaces the 4 columns in the original design. The dimensions of the two designs are compared
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Solar Dynamic Power System Stability Analysis and Control
Momoh, James A.; Wang, Yanchun
1996-01-01
The objective of this research is to conduct dynamic analysis, control design, and control performance test of solar power system. Solar power system consists of generation system and distribution network system. A bench mark system is used in this research, which includes a generator with excitation system and governor, an ac/dc converter, six DDCU's and forty-eight loads. A detailed model is used for modeling generator. Excitation system is represented by a third order model. DDCU is represented by a seventh order system. The load is modeled by the combination of constant power and constant impedance. Eigen-analysis and eigen-sensitivity analysis are used for system dynamic analysis. The effects of excitation system, governor, ac/dc converter control, and the type of load on system stability are discussed. In order to improve system transient stability, nonlinear ac/dc converter control is introduced. The direct linearization method is used for control design. The dynamic analysis results show that these controls affect system stability in different ways. The parameter coordination of controllers are recommended based on the dynamic analysis. It is concluded from the present studies that system stability is improved by the coordination of control parameters and the nonlinear ac/dc converter control stabilize system oscillation caused by the load change and system fault efficiently.
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An ac initiation system is described which uses three ac transmission signals interlocked for safety by frequency, phase, and power discrimination...The ac initiation system is pre-armed by the application of two ac signals have the proper phases, and activates a load when an ac power signal of the proper frequency and power level is applied. (Author)
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International Nuclear Information System (INIS)
Boissy, Clement; Normand, Bernard
2013-01-01
A review of the published models to describe the passivation of metallic materials is proposed. The objective is to illustrate the importance of the selection of a model considering their complementarity. The discussion is based on an analysis to assess whether the mass transport in the film must be taken into account or not in the modelling of the electrochemical impedance. (authors)
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International Nuclear Information System (INIS)
Stupakov, G.
2009-01-01
We review recent progress in the following areas of the impedance theory: calculation of impedance of tapers and small angle collimators; optical approximation and parabolic equation for the high-frequency impedance; impedance due to resistive inserts in a perfectly conducting pipe.
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Directory of Open Access Journals (Sweden)
Tanmaya Badapanda
2014-09-01
Full Text Available In this work, we report the dielectric, impedance, modulus and conductivity study of BaBi4Ti4O15 ceramic synthesized by solid state reaction. X-ray diffraction (XRD pattern showed orthorhombic structure with space group A21am confirming it to be an m = 4 member of the Aurivillius oxide. The frequency dependence dielectric study shows that the value of dielectric constant is high at lower frequencies and decreases with increase in frequency. Impedance spectroscopy analyses reveal a non-Debye relaxation phenomenon since relaxation frequency moves towards the positive side with increase in temperature. The shift in impedance peaks towards higher frequency side indicates conduction in material and favouring of the long rangemotion of mobile charge carriers. The Nyquist plot from complex impedance spectrum shows only one semicircular arc representing the grain effect in the electrical conduction. The modulus mechanism indicates the non-Debye type of conductivity relaxation in the material, which is supported by impedance data. Relaxation times extracted using imaginary part of complex impedance (Z′′ and modulus (M′′ were also found to follow Arrhenius law. The frequency dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated. The variation of DC conductivity exhibits a negative temperature coefficient of resistance behaviour.
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Energy Technology Data Exchange (ETDEWEB)
Bueno, V.; Lazzari, L.; Ormellesse, M. [Politecnico di Milano, Milan (Italy). Dept. of Chemistry, Materials and Chemical Engineering; Spinelli, P. [Politecnico di Torino, Torino (Italy). Dept. of Materials Science and Chemical Engineering
2008-07-01
Stray AC-currents have been reported to cause many cases of unwanted corrosion on metallic structures. This study characterized the formation and stability of the surface oxide film formed on mild steel under the effect of AC voltage in a very basic environment. The response of the system to DC signals was examined, along with its reversibility to AC perturbations. SEM analysis was used to complement AC-Voltammetry. Reaction mechanisms responsible for the AC-corrosion were formulated. AC-Voltammetry involves the application of a controlled sinusoidal voltage onto a solid working electrode while it is being swept in a DC-voltage range, with the faradaic or capacitative components of the resulting AC-current being recorded. The innovative aspect is the application of AC-V to characterize its nano-surface while it is being affected by AC-signals. It was concluded that the AC-V can be useful for the study of redox processes occurring at the surface of a reactive electrode and for the application of a considerable AC perturbation to the electrode in a potentiostatically controlled way. According to the electrochemistry of the double layer, there are 3 main reactions in the NaOH 1M media that are not reversible to DC nor to AC perturbations in the range of cathodic protection of mild steel. When designing metallic systems susceptible to stray currents, the AC-V could quantify the final faradaic, resistive and capacitative responses. 6 refs., 1 fig.
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Amperometric and impedance monitoring systems for biomedical applications
Punter-Villagrasa, Jaime; del Campo, Francisco J; Miribel, Pere
2017-01-01
The book presents the conception and realization of a pervasive electronic architecture for electrochemical applications, focusing on electronic instrumentation design and device development, particularly in electrochemical Point-of-Care and Lab-on-a-Chip devices, covering examples based on amperometric (DC) and impedance detection (AC) techniques. The presented electronics combine tailored front-end instrumentation and back-end data post-processing, enabling applications in different areas, and across a variety of techniques, analytes, transducers and environments. It addresses how the electronics are designed and implemented with special interest in the flow process: starting from electronic circuits and electrochemical biosensor design to a final validation and implementation for specific applications. Similarly, other important aspects are discussed throughout the book, such as electrochemical techniques, different analytes, targets, electronics reliability and robustness. The book also describes the use ...
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Haverkort, E. B.; Reijven, P. L. M.; Binnekade, J. M.; de van der Schueren, M. A. E.; Earthman, C. P.; Gouma, D. J.; de Haan, R. J.
2015-01-01
Bioelectrical impedance analysis (BIA) is a commonly used method for the evaluation of body composition. However, BIA estimations are subject to uncertainties.The aim of this systematic review was to explore the variability of empirical prediction equations used in BIA estimations and to evaluate
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Impedance Spectroscopy of Dielectrics and Electronic Conductors
DEFF Research Database (Denmark)
Bonanos, Nikolaos; Pissis, Polycarpos; Macdonald, J. Ross
2013-01-01
Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property, such as admi......Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property......, such as admittance or dielectric constant - as a function of frequency and comparing the results with expectations based on physical, chemical, and microstructural models. This article reviews the principles and practical aspects of the technique, the representations of the results, the analysis of data......, and procedures for the correction of measurement errors. The applications of impedance spectroscopy are illustrated with examples from electroceramics and polymer-based dielectric systems. The way in which the technique is applied to the two classes of materials is compared with reference to the different models...
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Study on ac losses of HTS coil carrying ac transport current
International Nuclear Information System (INIS)
Dai Taozhen; Tang Yuejin; Li Jingdong; Zhou Yusheng; Cheng Shijie; Pan Yuan
2005-01-01
Ac loss has an important influence on the thermal performances of HTS coil. It is necessary to quantify ac loss to ascertain its impact on coil stability and for sizing the coil refrigeration system. In this paper, we analyzed in detail the ac loss components, hysteresis loss, eddy loss and flux flow loss in the pancake HTS coil carrying ac transport current by finite element method. We also investigated the distribution of the ac losses in the coil to study the effects of magnetic field distribution on ac losses
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Meso Mechanical Analysis of AC Mixture Response
Woldekidan, M.F.; Huurman, M.; Vaccari, E.; Poot, M.
2012-01-01
Ongoing research into performance modeling of Asphalt Concrete (AC) mixtures using meso mechanics approaches is being undertaken at Delft University of Technology (TUD). The approach has already been successfully employed for evaluating the long term performance of porous asphalt concrete. The work
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Multi-phase AC/AC step-down converter for distribution systems
Aeloiza, Eddy C.; Burgos, Rolando P.
2017-10-25
A step-down AC/AC converter for use in an electric distribution system includes at least one chopper circuit for each one of a plurality of phases of the AC power, each chopper circuit including a four-quadrant switch coupled in series between primary and secondary sides of the chopper circuit and a current-bidirectional two-quadrant switch coupled between the secondary side of the chopper circuit and a common node. Each current-bidirectional two-quadrant switch is oriented in the same direction, with respect to the secondary side of the corresponding chopper circuit and the common node. The converter further includes a control circuit configured to pulse-width-modulate control inputs of the switches, to convert a first multiphase AC voltage at the primary sides of the chopper circuits to a second multiphase AC voltage at the secondary sides of the chopper circuits, the second multiphase AC voltage being lower in voltage than the first multiphase AC voltage.
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Analytic model of Applied-B ion diode impedance behavior
International Nuclear Information System (INIS)
Miller, P.A.; Mendel, C.W. Jr.
1987-01-01
An empirical analysis of impedance data from Applied-B ion diodes used in seven inertial confinement fusion research experiments was published recently. The diodes all operated with impedance values well below the Child's-law value. The analysis uncovered an unusual unifying relationship among data from the different experiments. The analysis suggested that closure of the anode-cathode gap by electrode plasma was not a dominant factor in the experiments, but was not able to elaborate the underlying physics. Here we present a new analytic model of Applied-B ion diodes coupled to accelerators. A critical feature of the diode model is based on magnetic insulation theory. The model successfully describes impedance behavior of these diodes and supports stimulating new viewpoints of the physics of Applied-B ion diode operation
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Elhatimi, Wafaa; Bouragba, Fatima Zahra; Lahkale, Redouane; Sadik, Rachid; Lebbar, Nacira; Siniti, Mostapha; Sabbar, Elmouloudi
2018-05-01
The Cu2Cr-DS-LDH hybrid was successfully prepared by the anion exchange method at room temperature. The structure, the chemical composition and the physico-chemical properties of the sample were determined using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and inductively coupled plasma (ICP). In this work, the electrical and dielectric properties investigated are determined using impedance spectroscopy (IS) in a frequency range of 1 Hz to 1 MHz. Indeed, the Nyquist diagram modelized by an electrical equivalent circuit showed three contributions attributed respectively to the polarization of grains, grains boundaries and interface electrode-sample. This modelization allowed us to determine the intrinsic electrical parameters of the hybrid (resistance, pseudo-capacitance and relaxation time). The presence of the non-Debye relaxation phenomena was confirmed by the frequency analysis of impedance. Moreover, the evolution of the alternating current conductivity (σac) studied obeys the double power law of Jonscher. The ionic conduction of this material was generated through a jump movement by translation of the charge carriers. As for the dielectric behavior of the material, the evolution of dielectric constant as a function of frequency shows relatively high values in a frequency range between 10 Hz and 1 KHz. The low values of the loss tangent obtained in this frequency zone can valorize this LDH hybrid.
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Crawshaw, Jacob; Auyeung, Vivian; Ashworth, Lucy; Norton, Sam; Weinman, John
2017-01-01
We conducted a systematic review and meta-analysis to determine the effectiveness of healthcare provider-led (HCPs) interventions to support medication adherence in patients with acute coronary syndrome (ACS). A systematic search of Cochrane Library, Medline, EMBASE, PsycINFO, Web of Science, IPA, CINAHL, ASSIA, OpenGrey, EthOS, WorldCat and PQDT was undertaken. Interventions were deemed eligible if they included adult ACS patients, were HCP-led, measured medication adherence and randomised participants to parallel groups. Intervention content was coded using the Behaviour Change Technique (BCT) Taxonomy and data were pooled for analysis using random-effects models. Our search identified 8870 records, of which 27 were eligible (23 primary studies). A meta-analysis (n=9735) revealed HCP-led interventions increased the odds of medication adherence by 54% compared to control interventions (k=23, OR 1.54, 95% CI 1.26 to 1.88, I 2 =57.5%). After removing outliers, there was a 41% increase in the odds of medication adherence with moderate heterogeneity (k=21, OR 1.41, 95% CI 1.21 to 1.65, I 2 =35.3%). Interventions that included phone contact yielded (k=12, OR 1.63, 95% CI 1.25 to 2.12, I 2 =32.0%) a larger effect compared to those delivered exclusively in person. A total of 32/93 BCTs were identified across interventions (mean=4.7, SD=2.2) with 'information about health consequences' (BCT 5.1) (19/23) the most common. HCP-led interventions for ACS patients appear to have a small positive impact on medication adherence. While we were able to identify BCTs among interventions, data were insufficient to determine the impact of particular BCTs on study effectiveness. CRD42016037706.
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Narendran, M; Deole, Satish G; Harkude, Satish; Shirale, Dattatray; Nanote, Asaram; Bihani, Pankaj; Parimi, Srinivas; Char, Bharat R; Zehr, Usha B
2013-08-01
Agrobacterium -mediated transformation system for okra using embryos was devised and the transgenic Bt plants showed resistance to the target pest, okra shoot, and fruit borer ( Earias vittella ). Okra is an important vegetable crop and progress in genetic improvement via genetic transformation has been impeded by its recalcitrant nature. In this paper, we describe a procedure using embryo explants for Agrobacterium-mediated transformation and tissue culture-based plant regeneration for efficient genetic transformation of okra. Twenty-one transgenic okra lines expressing the Bacillus thuringiensis gene cry1Ac were generated from five transformation experiments. Molecular analysis (PCR and Southern) confirmed the presence of the transgene and double-antibody sandwich ELISA analysis revealed Cry1Ac protein expression in the transgenic plants. All 21 transgenic plants were phenotypically normal and fertile. T1 generation plants from these lines were used in segregation analysis of the transgene. Ten transgenic lines were selected randomly for Southern hybridization and the results confirmed the presence of transgene integration into the genome. Normal Mendelian inheritance (3:1) of cry1Ac gene was observed in 12 lines out of the 21 T0 lines. We selected 11 transgenic lines segregating in a 3:1 ratio for the presence of one transgene for insect bioassays using larvae of fruit and shoot borer (Earias vittella). Fruit from seven transgenic lines caused 100 % larval mortality. We demonstrate an efficient transformation system for okra which will accelerate the development of transgenic okra with novel agronomically useful traits.
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Muscle development in healthy children evaluated by bioelectrical impedance analysis.
Uchiyama, Tomoka; Nakayama, Takahiro; Kuru, Satoshi
2017-02-01
This study aimed to use bioelectrical impedance analysis (BIA) to generate a new muscle density index (MDI), the MDI_BIA, to evaluate muscle development, and to demonstrate the changes that occur in the BIA-based muscle cross-sectional area index (MCAI_BIA) that accompany growth. We also sought to determine the traceability of chronological changes in the MDI_BIA and MCAI_BIA. Healthy children (n=112) aged 8.68±3.16years (0.33-14.00years) underwent bioelectrical impedance (BI) measurements of their upper arms, thighs, and lower legs. The MDI_BIA and MCAI_BIA were calculated, and cross-sectional investigations were conducted into the changes in these indices that accompanied growth. Data collected after 1.10±0.08years from 45 participants determined the traceability of the chronological changes in the MDI_BIA and MCAI_BIA. The MDI_BIA and MCAI_BIA were significantly positively correlated with age and height at all locations (Pchildren, and they showed significant chronological increases. Hence, these indices could be used to represent muscle development and muscle mass increases. BIA is non-invasive, convenient, and economical and it may be useful in evaluating muscle development and muscle cross-sectional areas in children. Copyright © 2016 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.
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Nonsynchronous Noncommensurate Impedance Transformers
DEFF Research Database (Denmark)
Zhurbenko, Vitaliy; Kim, K
2012-01-01
Nonsynchronous noncommensurate impedance transformers consist of a combination of two types of transmission lines: transmission lines with a characteristic impedance equal to the impedance of the source, and transmission lines with a characteristic impedance equal to the load. The practical...... advantage of such transformers is that they can be constructed using sections of transmission lines with a limited variety of characteristic impedances. These transformers also provide comparatively compact size in applications where a wide transformation ratio is required. This paper presents the data...... matrix approach and experimentally verified by synthesizing a 12-section nonsynchronous noncommensurate impedance transformer. The measured characteristics of the transformer are compared to the characteristics of a conventional tapered line transformer....
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DNA Based Electrolyte/Separator for Lithium Battery Application (Postprint)
2015-10-07
composite electrolyte as shown by the thermos- gravimetric analysis (TGA). The AC conductivity measurements suggest that the addition of DC to the gel...stability of the composite electrolyte as shown by the thermos- gravimetric analysis (TGA). The AC conductivity measurements suggest that the...2.3. Testing methods and equipment Impedance testing using the Solartron 1260A Impedance/ Gain- phase Analyzer was performed on each cell at
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International Nuclear Information System (INIS)
Liu Guozhi
2003-01-01
The energy spectrum of the electron beam generated by low-impedance diode and the influence of external magnetic field on the impedance of diode are studied numerically in this paper. The results show that the beam generated by the diode has an energy spread, even with constant applied voltage. Additionally, external magnetic field has great but reverse influence on the impedance of low-impedance diode, which is, according to the author's analysis, the result of the change of the electron's track due to external magnetic field. If the beam current is less than the critical one for self-pinch, the impedance will be constant with the variation of external magnetic field
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Törer, Nurkan; Aytaç, Özgür
2017-06-01
Conventional 24-h pH monitoring is the gold standard for the diagnosis of non-erosive, non-acidic gastro-esophageal reflux disease. Multichannel Intraluminal Impedance (MII) analysis markedly improves diagnostic accuracy of non-erosive, non-acidic gastro-esophageal reflux disease. However, MII catheters are more expensive than standard catheters. This study aimed to determine the rates of acid or non-acid reflux and by making a retrospective projection, to predict the costs of two algorithms. We retrospectively reviewed the medical data of 102 patients who presented to our hospital with suspected non-erosive GERD and underwent 24 h impedance/pH-monitoring. Demographic characteristics, Demeester scores, number of reflux episodes, and results of impedance analysis were recorded. According to these data, cost was calculated either for the scenario in which impedance measurement was performed solely or following a negative conventional pH monitoring. Thirty-seven of all 102 patients (36.3 %) had a Demeester score greater than 14.7. These patients were assigned as group 1 (acid reflux). The impedance analysis of the remaining 65 patients detected 34 patients (33.3 %) to have more than 50 reflux episodes over a period of 24 h and assigned as Group 2, and 31 patients (30.4 %) had no reflux (group 3). The cost of the single- step algorithm using MII catheter was calculated as $15,300, while the total cost of two-step scenario would have been predicted as $16,890. Our study showed that an initial conventional pH monitoring can make the diagnosis of GERD in only one third of the patients with suspected non-erosive GERD. In nearly two-thirds of patients, however, repeated procedures and use of impedance catheters are needed. It is clear that this algorithm has certain drawbacks with regard to cost, patient comfort, and workforce loss.
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Nguyen, N. Q.; Holloway, R. H.; Smout, A. J.; Omari, T. I.
2013-01-01
Background Automated integrated analysis of impedance and pressure signals has been reported to identify patients at risk of developing dysphagia post fundoplication. This study aimed to investigate this analysis in the evaluation of patients with non-obstructive dysphagia (NOD) and normal
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Electrical impedance tomography: topology optimization
International Nuclear Information System (INIS)
Miranda, Lenine Campos
2013-01-01
The Electrical Impedance Tomography (EIT) is a study of body parts who use electric current. Is studied through computers resistance or conductivity of these parts, producing an image used for medical diagnosis. A body is wrapped in a blanket placed with small electrodes and receivers of electric current, potential difference. Based on data obtained from a series of measurements at the electrodes, one by one, sending and receiving, you can perform a numerical phantom, where each 'voxel' of the image formed computationally represents the impedance of biological tissue. In Brazil, studies on electrical impedance tomography (EIT) has not yet started. Such equipment are measured tensions - potential difference - between each electrode / sensor one by one, as a way to Simple Combinatorial Analysis. The sequence and the way it is measured strains are in the final image quality. Finite Element Method Interactive, whose algorithm is based on Dialectical Method. We use an initial function with the objective of maximizing the data quantitatively, for better qualitative analysis. Topology Optimization methods are used to improve the image reconstruction. Currently the study is quite primitive related to the theory that shows how to power the new science studied. The high quality images requires a difficulty in obtaining. This work is not intended for detailed for analysis in any tissue or organ specific, but in general terms. And the formation of the 2D image. 3D need a reconstructor to part. (author)
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Impact of ac/dc spark anodizing on the corrosion resistance of Al-Cu alloys
Energy Technology Data Exchange (ETDEWEB)
Alsrayheen, Enam, E-mail: ealsrayh@ucalgary.ca [Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary AB, T2N 1N4 (Canada); McLeod, Eric, E-mail: hmolero@ucalgary.ca [Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary AB, T2N 1N4 (Canada); Rateick, Richard, E-mail: richard.rateick@honeywell.com [Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary AB, T2N 1N4 (Canada); Molero, Hebert, E-mail: Eric.McLeod@stmu.ab.ca [Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary AB, T2N 1N4 (Canada); Birss, Viola, E-mail: birss@ucalgary.ca [Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary AB, T2N 1N4 (Canada)
2011-07-01
An ac/dc spark anodization method was used to deposit an oxide film (6 {+-} 3 {mu}m in thickness) on the Al-Cu alloy AA2219. The oxide films were formed at 10 mA/cm{sup 2} for 30 min in an alkaline silicate solution, showing three main stages of growth. Scanning electron microscopy and electron microprobe analysis revealed that the oxide films are not uniform and consist of three main layers, an inner Al-rich barrier layer ({approx}1 {mu}m), an intermediate Al-Si mixed oxide layer ({approx}2 {+-} 1 {mu}m), and an outer porous Si-rich layer ({approx}3 {+-} 3 {mu}m). In addition, microscopic analysis showed that the Al{sub 2}Cu intermetallics present in the alloy have not been excessively oxidized during the anodization process and thus are retained beneath the oxide film, as desired. The coating passivity and corrosion resistance, evaluated using linear sweep voltammetry (LSV) in pH 7 borate buffer solution and electrochemical impedance spectroscopy (EIS) in 0.86 M NaCl solution, respectively, were both significantly improved after spark-anodization.
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Spectroscopic Observations and Analysis of the Unusual Type Ia SN1999ac
International Nuclear Information System (INIS)
Garavini, G.; Aldering, G.; Amadon, A.; Amanullah, R.; Astier, P.; Balland, C.; Blanc, G.; Conley, A.; Dahlen, T.; Deustua, S.E.; Ellis, R.; Fabbro, S.; Fadeyev, V.; Fan, X.; Folatelli, G.; Frye, B.; Gates, E.L.; Gibbons, R.; Goldhaber, G.; Goldman, B.; Goobar, A.; Groom, D.E.; Haissinski, J.; Hardin, D.; Hook, I.; Howell, D.A.; Kent, S.; Kim, A.G.; Knop, R.A.; Kowalski, M.; Kuznetsova, N.; Lee, B.C.; Lidman, C.; Mendez, J.; Miller, G.J.; Moniez, M.; Mouchet, M.; Mourao, A.; Newberg, H.; Nobili, S.; Nugent, P.E.; Pain, R.; Perdereau, O.; Perlmutter, S.; Quimby, R.; Regnault, N.; Rich, J.; Richards, G.T.; Ruiz-Lapuente, P.; Schaefer, B.E.; Schahmaneche, K.; Smith, E.; Spadafora, A.L.; Stanishev, V.; Thomas, R.C.; Walton, N.A.; Wang, L.; Wood-Vasey, W.M.
2005-01-01
The authors present optical spectra of the peculiar Type Ia supernova (SN Ia) 1999ac. The data extend from -15 to +42 days with respect to B-band maximum and reveal an event that is unusual in several respects. prior to B-band maximum, the spectra resemble those of SN 1999aa, a slowly declining event, but possess stronger Si II and Ca II signatures (more characteristic of a spectroscopically normal SN). Spectra after B-band maximum appear more normal. The expansion velocities inferred from the Iron lines appear to be lower than average; whereas, the expansion velocity inferred from Calcium H and K are higher than average. The expansion velocities inferred from the Iron lines appear to be lower than average; whereas, the expansion velocity inferred from Calcium H and K are higher than average. The expansion velocities inferred from Si II are among the slowest ever observed, though SN 1999ac is not particularly dim. The analysis of the parameters v 10 (Si II), R(Si II), v, and Δm 15 further underlines the unique characteristics of SN 1999ac. They find convincing evidence of C II λ6580 in the day -15 spectrum with ejection velocity v > 16,000 km s -1 , but this signature disappears by day -9. This rapid evolution at early times highlights the importance of extremely early-time spectroscopy
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Impedance analysis of a disk-type SOFC using doped lanthanum gallate under power generation
Kato, Tohru; Nozaki, Ken; Negishi, Akira; Kato, Ken; Monma, Akihiko; Kaga, Yasuo; Nagata, Susumu; Takano, Kiyonami; Inagaki, Toru; Yoshida, Hiroyuki; Hosoi, Kei; Hoshino, Koji; Akbay, Taner; Akikusa, Jun
Impedance measurements were carried out under practical power generation conditions in a disk-type SOFC, which may be utilized as a small-scale power generator. The tested cell was composed of doped lanthanum gallate (La 0.8Sr 0.2Ga 0.8Mg 0.15Co 0.05O 3- δ) as the electrolyte, Sm 0.5Sr 0.5CoO 3 as the cathode electrode and Ni/Ce 0.8Sm 0.2O 2 cermet as the anode electrode. The cell impedance was measured between 10 mHz and 10 kHz by varying the fuel utilization and gas flow rate and plotted in complex impedance diagrams. The observed impedance shows a large semi-circular pattern on the low frequency side. The semi-circular impedance, having a noticeably low characteristic frequency between 0.13 and 0.4 Hz, comes from the change in gas composition, originally caused by the cell reaction. The change in impedance with the fuel utilization (load current) and the gas flow rate agreed qualitatively well with the theoretical predictions from a simulation. This impedance was dominant under high fuel-utilization power-generation conditions. The impedance, which described the activation polarizations in the electrode reactions, was comparatively small and scarcely changed with the change in fuel utilization (load current) and gas flow rate.
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Ikeda, Hideharu; Suda, Hideaki
2013-04-01
The objectives of the present study were to quantitatively evaluate chemical permeability through human enamel/dentine using conductometry and to clarify if alternating current (AC) iontophoresis facilitates such permeability. Electrical impedance of different concentrations of lidocaine hydrochloride was measured using a bipolar platinum impedance probe. A quadratic curve closely fitted to the response functions between conductance and lidocaine hydrochloride. For analysis of the passage of lidocaine hydrochloride through human enamel/dentine, eight premolars that were extracted for orthodontic treatment were sectioned at the cemento-enamel junction. The tooth crowns were held between two chambers with a double O-ring. The enamel-side chamber was filled with lidocaine hydrochloride, and the pulp-side chamber was filled with extrapure water. Two platinum plate electrodes were set at the end of each chamber to pass alternating current. A simulated interstitial pulp pressure was applied to the pulp-side chamber. The change in the concentration of lidocaine hydrochloride in the pulp-side chamber was measured every 2min using a platinum recording probe positioned at the centre of the pulp-side chamber. Passive entry without iontophoresis was used as a control. The level of lidocaine hydrochloride that passed through enamel/dentine against the dentinal fluid flow increased with time. Electrical conductance (G, mho) correlated closely to the concentration (x, mmol/L) of lidocaine hydrochloride (G=2.16x(2)+0.0289x+0.000376, r(2)=0.999). Lidocaine hydrochloride can pass through enamel/dentine. Conductometry showed that the level of lidocaine hydrochloride that passed through enamel/dentine was increased by AC iontophoresis. Copyright © 2012 Elsevier Ltd. All rights reserved.
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Security analysis of interconnected AC/DC systems
DEFF Research Database (Denmark)
Eriksson, Robert
2015-01-01
This paper analyses N-1 security in an interconnected ac/dc transmission system using power transfer distribution factors (PTDFs). In the case of a dc converter outage the power needs to be redistributed among the remaining converter to maintain power balance and operation of the dc grid...... any line or transformer limits. Simulations were performed in a model of the Nordic power system where a dc grid is placed on top. The simulation supports the method as a tool to consider transfer limits in the grid to avoid violate the same and increase the security after a converter outage........ The redistribution of power has a sudden effect on the power-flow in the interconnected ac system. This may cause overloading of lines and transformers resulting in disconnection of equipment, and as a consequence cascading failure. The PTDF is used as a method to analyze and avoid violating limits by in the dc...
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International Nuclear Information System (INIS)
Hu Yixiang; Qiu Aici; Sun Fengju; Huang Tao; Cong Peitian; Wang Liangping; Zeng Jiangtao; Li Yan; Zhang Xinjun; Lei Tianshi
2011-01-01
Based on the transmission line code TLCODE, a 1D circuit model for a transmission-line impedance transformer was developed and the simulation results were compared with those in the literature. The model was used to quantify the efficiencies of voltage-transport, energy-transport and power-transport for a transmission-line impedance transformer as functions of ψ (the ratio of the output impedance to the input impedance of the transformer) and Γ (the ratio of the pulse width to the one-way transit time of the transformer) under a large scale of m (the coefficient of the generalized exponential impedance profile). Simulation results suggest that with the increase in Γ, from 0 to ∞, the power transport efficiency first increases and then decreases. The maximum power transport efficiency can reach 90% or even higher for an exponential impedance profile (m = 1). With a consideration of dissipative loss in the dielectric and electrodes of the transformer, two representative designs of the water-insulated transformer are investigated for the next generation of petawatt-class z-pinch drivers. It is found that the dissipative losses in the electrodes are negligibly small, below 0.1%, but the dissipative loss in the water dielectric is about 1% to 4%. (fusion engineering)
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Electrochemical Impedance Spectroscopic Analysis of RuO2 Based Thick Film pH Sensors
International Nuclear Information System (INIS)
Manjakkal, Libu; Djurdjic, Elvira; Cvejin, Katarina; Kulawik, Jan; Zaraska, Krzysztof; Szwagierczak, Dorota
2015-01-01
The conductimetric interdigitated thick film pH sensors based on RuO 2 were fabricated and their electrochemical reactions with solutions of different pH values were studied by electrochemical impedance spectroscopy (EIS) technique. The microstructural properties and composition of the sensitive films were examined by scanning electron microscopy, X-ray energy dispersive spectroscopy and Raman spectroscopy. The EIS analysis of the sensor was carried out in the frequency range 10 mHz–2 MHz for pH values of test solutions 2–12. The electrical parameters of the sensor were found to vary with changing pH. The conductance and capacitance of the film were distinctly dependent on pH in the low frequency range. The Nyquist and Bode plots derived from the impedance data for the metal oxide thick film pH sensor provided information about the underlying electrochemical reactions
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DEFF Research Database (Denmark)
Sanjeevikumar, P.; Grandi, Gabriele; Blaabjerg, Frede
2016-01-01
sources. The developed post-fault algorithm is applied when there is a fault by one VSI and the load is fed from the remaining three healthy VSIs. In faulty conditions the multilevel outputs are reduced from 3-level to 2-level, but still the system propagates with degraded power. Numerical simulation......This research article exploits the power management algorithm in post-fault conditions for a six-phase (quad) multilevel inverter. The drive circuit consists of four 2-level, three-phase voltage source inverter (VSI) supplying a six-phase open-end windings motor or/impedance load......, with circumstantial failure of one VSI investigated. A simplified level-shifted pulse-width modulation (PWM) algorithm is developed to modulate each couple of three-phase VSI as 3-level output voltage generators in normal operation. The total power of the whole ac drive is shared equally among the four isolated DC...
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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.
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International Nuclear Information System (INIS)
Abo-Elenien, G.M.; Abdel-Salam, O.E.
1987-01-01
Zirconium and its alloys are finding increasing applications especially in water-cooled nuclear reactors. Because of the fact that zirconium is electronegative (E 0 = -1.529V) its corrosion resistance in aqueous solutions is largely determined by the existence of a thin oxide film on its surface. The structure and properties of this film depend in the first place on the method of surface pre-treatment. This paper presents an experimental study of the nature of the oxide film on mechanically polished, chemically etched and anodized zirconium. Ac impedance measurements carried out in various acidic, neutral and alkaline solutions show that the film thickness depends on the method of surface pre-treatment and the type of electrolyte solution. The variation of the potential and impedance during anodization of zirconium at low current density indicates that the initial stages of polarization consist of oxide build-up at a rate dependent on the nature of the electrode surface and the electrolyte. Oxygen evolution commences at a stage where oxide thickening starts to decline. The effect of frequency on the measured impedance indicates that the surface reactivity, and hence the corrosion rate, decreases in the following order: mechanically polished > chemically etched > anodized
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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.
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Performance of AC/graphite capacitors at high weight ratios of AC/graphite
Energy Technology Data Exchange (ETDEWEB)
Wang, Hongyu [IM and T Ltd., Advanced Research Center, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan); Yoshio, Masaki [Advanced Research Center, Department of Applied Chemistry, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan)
2008-03-01
The effect of negative to positive electrode materials' weight ratio on the electrochemical performance of both activated carbon (AC)/AC and AC/graphite capacitors has been investigated, especially in the terms of capacity and cycle-ability. The limited capacity charge mode has been proposed to improve the cycle performance of AC/graphite capacitors at high weight ratios of AC/graphite. (author)
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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.
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Ohta, Megumi; Midorikawa, Taishi; Hikihara, Yuki; Masuo, Yoshihisa; Sakamoto, Shizuo; Torii, Suguru; Kawakami, Yasuo; Fukunaga, Tetsuo; Kanehisa, Hiroaki
2017-02-01
This study examined the validity of segmental bioelectrical impedance (BI) analysis for predicting the fat-free masses (FFMs) of whole-body and body segments in children including overweight individuals. The FFM and impedance (Z) values of arms, trunk, legs, and whole body were determined using a dual-energy X-ray absorptiometry and segmental BI analyses, respectively, in 149 boys and girls aged 6 to 12 years, who were divided into model-development (n = 74), cross-validation (n = 35), and overweight (n = 40) groups. Simple regression analysis was applied to (length) 2 /Z (BI index) for each of the whole-body and 3 segments to develop the prediction equations of the measured FFM of the related body part. In the model-development group, the BI index of each of the 3 segments and whole body was significantly correlated to the measured FFM (R 2 = 0.867-0.932, standard error of estimation = 0.18-1.44 kg (5.9%-8.7%)). There was no significant difference between the measured and predicted FFM values without systematic error. The application of each equation derived in the model-development group to the cross-validation and overweight groups did not produce significant differences between the measured and predicted FFM values and systematic errors, with an exception that the arm FFM in the overweight group was overestimated. Segmental bioelectrical impedance analysis is useful for predicting the FFM of each of whole-body and body segments in children including overweight individuals, although the application for estimating arm FFM in overweight individuals requires a certain modification.
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DEFF Research Database (Denmark)
Nørgaard, Kren Rahbek; Fernandez Grande, Efren
2017-01-01
The ear-canal acoustic impedance and reflectance are useful for assessing conductive hearing disorders and calibrating stimulus levels in situ. However, such probe-based measurements are affected by errors due to the presence of evanescent modes and incorrect estimates or assumptions regarding...... characteristic impedance. This paper proposes a method to compensate for evanescent modes in measurements of acoustic impedance, reflectance, and sound pressure in waveguides, as well as estimating the characteristic impedance immediately in front of the probe. This is achieved by adjusting the characteristic...... impedance and subtracting an acoustic inertance from the measured impedance such that the non-causality in the reflectance is minimized in the frequency domain using the Hilbert transform. The method is thus capable of estimating plane-wave quantities of the sought-for parameters by supplying only...
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Directory of Open Access Journals (Sweden)
Viswanath eSankar
2014-05-01
Full Text Available Changes in biotic and abiotic factors can be reflected in the complex impedance spectrum of the microelectrodes chronically implanted into the neural tissue. The recording surface of the tungsten electrode in vivo undergoes abiotic changes due to recording site corrosion and insulation delamination as well as biotic changes due to tissue encapsulation as a result of the foreign body immune response. We reported earlier that large changes in electrode impedance measured at 1 kHz were correlated with poor electrode functional performance, quantified through electrophysiological recordings during the chronic lifetime of the electrode. There is a need to identity the factors that contribute to the chronic impedance variation. In this work, we use numerical simulation and regression to equivalent circuit models to evaluate both the abiotic and biotic contributions to the impedance response over chronic implant duration. COMSOL® simulation of abiotic electrode morphology changes provide a possible explanation for the decrease in the electrode impedance at long implant duration while biotic changes play an important role in the large increase in impedance observed initially.
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Gastric emptying patterns of a liquid meal in newborn infants, measured by epigastric impedance
DEFF Research Database (Denmark)
Lange, Aksel; Funch-Jensen, Peter; Thommesen, Peter
1997-01-01
time (T50) was calculated. For mature infants it was found to be 6.9 mins. For a second meal given within an hour after the first meal the half emptying time was 5.5 mins (p times were not significant different from mature infants, but the number examined was small...... Epigastric impedance was used to measure patterns of the gastric emptying of a liquid non-caloric meal (5 ml water/kg) in newborn infants. The emptying patterns consisted of two components, theemptying signal - the DC component - and a phasic 3 cycle per minutes (CPM) signal - the AC component.......A periodic change of the impedance signal, the phasic 3 CPM signal, was observed after a meal in 24 of the infants. The median frequency was 3.03 CPM in 20 mature and 2.93 CPM in 4 preterminfants. In 9 infants a phasic 3 CPM signal was observed during fasting state. The median frequency was 2.9 CPM...
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Marketingová komunikace AC Sparta Praha
Fanta, Jan
2016-01-01
Title: Marketing communications of AC Sparta Praha Objectives: The main objective of this thesis is to analyze contemporary state of marketing communications with the audience of AC Sparta Praha, identify deficiencies and develop a proposal to improve the marketing communications with fans of this club. Methods: In this thesis have been used methods of case study, analysis of available documents and texts, structured interview with director od marketing, and director of communications and pub...
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Characterisation of AC1: a naturally decaffeinated coffee
Directory of Open Access Journals (Sweden)
Luciana Benjamim Benatti
2012-01-01
Full Text Available We compared the biochemical characteristics of the beans of a naturally decaffeinated Arabica coffee (AC1 discovered in 2004 with those of the widely grown Brazilian Arabica cultivar "Mundo Novo" (MN. Although we observed differences during fruit development, the contents of amino acids, organic acids, chlorogenic acids, soluble sugars and trigonelline were similar in the ripe fruits of AC1 and MN. AC1 beans accumulated theobromine, and caffeine was almost entirely absent. Tests on the supply of [2-14C] adenine and enzymatic analysis of theobromine synthase and caffeine synthase in the endosperm of AC1 confirmed that, as in the leaves, caffeine synthesis is blocked during the methylation of theobromine to caffeine. The quality of the final coffee beverage obtained from AC1 was similar to that of MN.
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Rae, L S; Vankan, D M; Rand, J S; Flickinger, E A; Ward, L C
2016-06-01
Thirty-five healthy, neutered, mixed breed dogs were used to determine the ability of multifrequency bioelectrical impedance analysis (MFBIA) to predict accurately fat-free mass (FFM) in dogs using dual energy X-ray absorptiometry (DXA)-measured FFM as reference. A second aim was to compare MFBIA predictions with morphometric predictions. MFBIA-based predictors provided an accurate measure of FFM, within 1.5% when compared to DXA-derived FFM, in normal weight dogs. FFM estimates were most highly correlated with DXA-measured FFM when the prediction equation included resistance quotient, bodyweight, and body condition score. At the population level, the inclusion of impedance as a predictor variable did not add substantially to the predictive power achieved with morphometric variables alone; in individual dogs, impedance predictors were more valuable than morphometric predictors. These results indicate that, following further validation, MFBIA could provide a useful tool in clinical practice to objectively measure FFM in canine patients and help improve compliance with prevention and treatment programs for obesity in dogs. Copyright © 2016. Published by Elsevier Ltd.
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Performance Analysis of Three-Phase Induction Motor with AC Direct and VFD
Kumar, Dinesh
2018-03-01
The electrical machine analysis and performance calculation is a very important aspect of efficient drive system design. The development of power electronics devices and power converters provide smooth speed control of Induction Motors by changing the frequency of input supply. These converters, on one hand are providing a more flexible speed control that also leads to problems of harmonics and their associated ailments like pulsating torque, distorted current and voltage waveforms, increasing losses etc. This paper includes the performance analysis of three phase induction motor with three-phase AC direct and variable frequency drives (VFD). The comparison has been concluded with respect to various parameters. MATLAB-SIMULINKTM is used for the analysis.
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Chang, Kuo-Chu; Hsu, Kwan-Lih; Tseng, Yung-Zu
2003-01-01
We determined the effects of diabetes and gender on the physical properties of the vasculature in streptozotocin (STZ)-treated rats based on the aortic input impedance analysis. Rats given STZ 65 mg/kg i.v. were compared with untreated age-matched controls. Pulsatile aortic pressure and flow signals were measured and were then subjected to Fourier transformation for the analysis of aortic input impedance. Wave transit time was determined using the impulse response function of the filtered aortic input impedance spectra. Male but not female diabetic rats exhibited an increase in cardiac output in the absence of any significant changes in arterial blood pressure, resulting in a decline in total peripheral resistance. However, in each gender group, diabetes contributed to an increase in wave reflection factor, from 0.47 +/- 0.04 to 0.84 +/- 0.03 in males and from 0.46 +/- 0.03 to 0.81 +/- 0.03 in females. Diabetic rats had reduced wave transit time, at 18.82 +/- 0.60 vs 21.34 +/- 0.51 msec in males and at 19.63 +/- 0.37 vs 22.74 +/- 0.57 msec in females. Changes in wave transit time and reflection factor indicate that diabetes can modify the timing and magnitude of the wave reflection in the rat arterial system. Meanwhile, diabetes produced a fall in aortic characteristic impedance from 0.023 +/- 0.002 to 0.009 +/- 0.001 mmHg/min/kg/ml in males and from 0.028 +/- 0.002 to 0.014 +/- 0.001 mmHg/min/kg/ml in females. With unaltered aortic pressure, both the diminished aortic characteristic impedance and wave transit time suggest that the muscle inactivation in diabetes may occur in aortas and large arteries and may cause a detriment to the aortic distensibility in rats with either sex. We conclude that only rats with male gender diabetes produce a detriment to the physical properties of the resistance arterioles. In spite of male or female gender, diabetes decreases the aortic distensibility and impairs the wave reflection phenomenon in the rat arterial system.
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Chen, Jian; Xue, Chengcheng; Zhao, Yang; Chen, Deyong; Wu, Min-Hsien; Wang, Junbo
2015-01-01
This article reviews recent developments in microfluidic impedance flow cytometry for high-throughput electrical property characterization of single cells. Four major perspectives of microfluidic impedance flow cytometry for single-cell characterization are included in this review: (1) early developments of microfluidic impedance flow cytometry for single-cell electrical property characterization; (2) microfluidic impedance flow cytometry with enhanced sensitivity; (3) microfluidic impedance and optical flow cytometry for single-cell analysis and (4) integrated point of care system based on microfluidic impedance flow cytometry. We examine the advantages and limitations of each technique and discuss future research opportunities from the perspectives of both technical innovation and clinical applications. PMID:25938973
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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.
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Synthesis of adaptive impedance control for bipedal robot mechanisms
Petrović Milena; Rodić Aleksandar
2008-01-01
The paper describes the impedance algorithm in locomotion of humanoid robot with proposed parameter modulation depending on the gate phase. The analysis shows influence of walking speed and foot elevation on regulator's parameters. Chosen criterion cares for footpath tracking and needed energy for that way of walking. The experiments give recommendation for impedance regulator tuning.
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Ac-electrical conductivity of poly(propylene) before and after X-ray irradiation
International Nuclear Information System (INIS)
Gaafar, M.
2001-01-01
Study on the ac-electrical conductivity of poly(propylene), before and after X-ray irradiation within the temperature range 300-360 K are reported. The measurements have been performed in a wide range of frequencies (from 0 to 10 5 Hz) and under the effect of different X-ray irradiation doses (from 0 to 15 Gy). Cole-Cole diagrams have been used to show the frequency dependence of the complex impedance at different temperatures. The results exhibit semicircles which are consistent with existing equivalent circuit model. Analysis of the results reveal semiconducting features based mainly on a hopping mechanism. The study shows a pronounced effect of X-ray irradiation on the electrical conductivity at zero frequency σ DC . At the early stage of irradiation, σ DC increased as a result of free radical formation. As the irradiation progressed, it decreased as a result of crosslinking, then it increased again due to irradiation induced degradation, which motivates the generation of mobile free radicals. The study shows that this polymer is one among other polymers which its electrical conductivity is modified by irradiation
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Ac-electrical conductivity of poly(propylene) before and after X-ray irradiation
Gaafar, M.
2001-05-01
Study on the ac-electrical conductivity of poly(propylene), before and after X-ray irradiation within the temperature range 300-360 K are reported. The measurements have been performed in a wide range of frequencies (from 0 to 10 5 Hz) and under the effect of different X-ray irradiation doses (from 0 to 15 Gy). Cole-Cole diagrams have been used to show the frequency dependence of the complex impedance at different temperatures. The results exhibit semicircles which are consistent with existing equivalent circuit model. Analysis of the results reveal semiconducting features based mainly on a hopping mechanism. The study shows a pronounced effect of X-ray irradiation on the electrical conductivity at zero frequency σDC. At the early stage of irradiation, σDC increased as a result of free radical formation. As the irradiation progressed, it decreased as a result of crosslinking, then it increased again due to irradiation induced degradation, which motivates the generation of mobile free radicals. The study shows that this polymer is one among other polymers which its electrical conductivity is modified by irradiation.
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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...
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The use of bioelectrical impedance analysis for body composition in epidemiological studies
DEFF Research Database (Denmark)
Böhm, A; Heitmann, B L
2013-01-01
BACKGROUND/OBJECTIVES: Bioelectrical impedance analysis (BIA) is a relatively simple, inexpensive and non-invasive technique to measure body composition and is therefore suitable in field studies and larger surveys. SUBJECTS/METHODS: We performed an overview of BIA-derived body fat percentages (BF......%) from 55 published studies of healthy populations aged 6-80 years. In addition, the relationship between body mass index (BMI) and body composition is documented in the context of BIA as a good alternative to closely differentiate which composition of the body better relates to the risk...
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Modeling and analysis of harmonic resonance in a power electronics based AC power system
DEFF Research Database (Denmark)
Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe
2013-01-01
The dynamic interactions among the interconnected power converters may bring in harmonic resonance in a power electronics based power system. This paper addresses this issue in a power system dominated by multiple current- and voltage-controlled inverters with LCL- and LC-filters. The impedance...... stability criterion. To validate the theoretical analysis, the time domain simulations and experimental tests on a three-inverter-based system are presented....
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Impedance computations and beam-based measurements: A problem of discrepancy
Smaluk, Victor
2018-04-01
High intensity of particle beams is crucial for high-performance operation of modern electron-positron storage rings, both colliders and light sources. The beam intensity is limited by the interaction of the beam with self-induced electromagnetic fields (wake fields) proportional to the vacuum chamber impedance. For a new accelerator project, the total broadband impedance is computed by element-wise wake-field simulations using computer codes. For a machine in operation, the impedance can be measured experimentally using beam-based techniques. In this article, a comparative analysis of impedance computations and beam-based measurements is presented for 15 electron-positron storage rings. The measured data and the predictions based on the computed impedance budgets show a significant discrepancy. Three possible reasons for the discrepancy are discussed: interference of the wake fields excited by a beam in adjacent components of the vacuum chamber, effect of computation mesh size, and effect of insufficient bandwidth of the computed impedance.
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Brandriet, Alexandra; Holme, Thomas
2015-01-01
The American Chemical Society Examinations Institute (ACS-EI) has recently developed the Exams Data Analysis Spread (EDAS) as a tool to help instructors conduct customizable analyses of their student data from ACS exams. The EDAS calculations allow instructors to analyze their students' performances both at the total score and individual item…
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VLF surface-impedance modelling techniques for coal exploration
Energy Technology Data Exchange (ETDEWEB)
Wilson, G.; Thiel, D.; O' Keefe, S. [Central Queensland University, Rockhampton, Qld. (Australia). Faculty of Engineering and Physical Systems
2000-10-01
New and efficient computational techniques are required for geophysical investigations of coal. This will allow automated inverse analysis procedures to be used for interpretation of field data. In this paper, a number of methods of modelling electromagnetic surface impedance measurements are reviewed, particularly as applied to typical coal seam geology found in the Bowen Basin. At present, the Impedance method and the finite-difference time-domain (FDTD) method appear to offer viable solutions although both have problems. The Impedance method is currently slightly inaccurate, and the FDTD method has large computational demands. In this paper both methods are described and results are presented for a number of geological targets. 17 refs., 14 figs.
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Chen, Qi; Wang, Dan; Cai, Gaozhe; Xiong, Yonghua; Li, Yuntao; Wang, Maohua; Huo, Huiling; Lin, Jianhan
2016-12-15
Early screening of pathogenic bacteria is a key to prevent and control of foodborne diseases. In this study, we developed a fast and sensitive bacteria detection method integrating electrochemical impedance analysis, urease catalysis with microfluidics and using Listeria as model. The Listeria cells, the anti-Listeria monoclonal antibodies modified magnetic nanoparticles (MNPs), and the anti-Listeria polyclonal antibodies and urease modified gold nanoparticles (AuNPs) were incubated in a fluidic separation chip with active mixing to form the MNP-Listeria-AuNP-urease sandwich complexes. The complexes were captured in the separation chip by applying a high gradient magnetic field, and the urea was injected to resuspend the complexes and hydrolyzed under the catalysis of the urease on the complexes into ammonium ions and carbonate ions, which were transported into a microfluidic detection chip with an interdigitated microelectrode for impedance measurement to determine the amount of the Listeria cells. The capture efficiency of the Listeria cells in the separation chip was ∼93% with a shorter time of 30min due to the faster immuno-reaction using the active magnetic mixing. The changes on both impedance magnitude and phase angle were demonstrated to be able to detect the Listeria cells as low as 1.6×10(2)CFU/mL. The detection time was reduced from original ∼2h to current ∼1h. The recoveries of the spiked lettuce samples ranged from 82.1% to 89.6%, indicating the applicability of this proposed biosensor. This microfluidic impedance biosensor has shown the potential for online, automatic and sensitive bacteria separation and detection. Copyright © 2016 Elsevier B.V. All rights reserved.
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An electrode polarization impedance based flow sensor for low water flow measurement
International Nuclear Information System (INIS)
Yan, Tinghu; Sabic, Darko
2013-01-01
This note describes an electrode polarization impedance based flow sensor for low water flow measurement. It consists of two pairs of stainless steel electrodes set apart and inserted into a non-conductive flow tube with each pair of electrodes placed diametrically at the opposite sides. The flow sensor is modeled as a typical four-electrode system of which two electrodes are current-carrying and the other two serve as output pick ups. The polarization impedances of the two current carrying electrodes are affected by water flows resulting in changes of differential potential between the two pick-up electrodes which are separated by the same fluid. The interrogation of the two excitation electrodes with dc biased ac signals offers significantly higher sensor sensitivities to flow. The prototype flow sensor constructed for a 20 mm diameter pipeline was able to measure water flow rate as low as tested at 1.06 l h −1 and remained sensitive at a flow rate of 25.18 l h −1 when it was driven with a sinusoidal voltage at 1000 Hz with a peak ac amplitude of 2 V and a dc offset of +8 V. The nonlinear characteristics of the sensor response indicate that the sensor is more sensitive at low flows and will not be able to measure at very high flows. Additional experiments are needed to evaluate the influences of impurities, chemical species, ions constituents, conductivity and temperature over a practical range of residential water conditions, the effects of fluctuating ground signals, measurement uncertainty, power consumption, compensation of effects and practical operations. The flow sensor (principle) presented may be used as (in) a secondary sensor in combination with an existing electronic water meter to extend the low end of measurement range in residential water metering. (technical design note)
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Bedogni, Giorgio; Grugni, Graziano; Tringali, Gabriella; Agosti, Fiorenza; Sartorio, Alessandro
2015-01-01
Fat-free mass (FFM) is lower in obese subjects with Prader-Willi syndrome (PWS) than in obese subjects without PWS. FFM prediction equations developed in non-PWS subjects may, thus, not work in PWS subjects. To test whether the estimation of FFM from bioelectrical impedance analysis (BIA) in PWS subjects requires population-specific equations. Using dual-energy X-ray absorptiometry, this study measured FFM in 27 PWS and 56 non-PWS obese women and evaluated its association with the impedance index at 50 kHz (ZI50), i.e. the ratio between squared height and whole-body impedance at 50 kHz. At the same level of ZI50, PWS women had a lower FFM than non-PWS women. However, when PWS-specific equations were used, FFM was accurately estimated at the population level. An equation employing a dummy variable coding for PWS status was able to explain 85% of the variance of FFM with a root mean squared error of 3.3 kg in the pooled sample (n = 83). Population-specific equations are needed to estimate FFM from BIA in obese PWS women.
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High transmission acoustic focusing by impedance-matched acoustic meta-surfaces
Al Jahdali, Rasha
2016-01-19
Impedance is an important issue in the design of acoustic lenses because mismatched impedance is detrimental to real focusing applications. Here, we report two designs of acoustic lenses that focus acoustic waves in water and air, respectively. They are tailored by acoustic meta-surfaces, which are rigid thin plates decorated with periodically distributed sub-wavelength slits. Their respective building blocks are constructed from the coiling-up spaces in water and the layered structures in air. Analytic analysis based on coupled-mode theory and transfer matrix reveals that the impedances of the lenses are matched to those of the background media. With these impedance-matched acoustic lenses, we demonstrate the acoustic focusing effect by finite-element simulations.
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High transmission acoustic focusing by impedance-matched acoustic meta-surfaces
Al Jahdali, Rasha; Wu, Ying
2016-01-01
Impedance is an important issue in the design of acoustic lenses because mismatched impedance is detrimental to real focusing applications. Here, we report two designs of acoustic lenses that focus acoustic waves in water and air, respectively. They are tailored by acoustic meta-surfaces, which are rigid thin plates decorated with periodically distributed sub-wavelength slits. Their respective building blocks are constructed from the coiling-up spaces in water and the layered structures in air. Analytic analysis based on coupled-mode theory and transfer matrix reveals that the impedances of the lenses are matched to those of the background media. With these impedance-matched acoustic lenses, we demonstrate the acoustic focusing effect by finite-element simulations.
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DEFF Research Database (Denmark)
Araya, Samuel Simon; Vang, Jakob Rabjerg; Andreasen, Søren Juhl
2013-01-01
This work analyses the conditioning of single fuel cell assemblies based on different membrane electrode assembly (MEA) types, produced by different methods. The analysis was done by means of electrochemical impedance spectroscopy, and the changes in the fitted resistances of the all the tested...
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AC Loss Analysis of MgB2-Based Fully Superconducting Machines
Feddersen, M.; Haran, K. S.; Berg, F.
2017-12-01
Superconducting electric machines have shown potential for significant increase in power density, making them attractive for size and weight sensitive applications such as offshore wind generation, marine propulsion, and hybrid-electric aircraft propulsion. Superconductors exhibit no loss under dc conditions, though ac current and field produce considerable losses due to hysteresis, eddy currents, and coupling mechanisms. For this reason, many present machines are designed to be partially superconducting, meaning that the dc field components are superconducting while the ac armature coils are conventional conductors. Fully superconducting designs can provide increases in power density with significantly higher armature current; however, a good estimate of ac losses is required to determine the feasibility under the machines intended operating conditions. This paper aims to characterize the expected losses in a fully superconducting machine targeted towards aircraft, based on an actively-shielded, partially superconducting machine from prior work. Various factors are examined such as magnet strength, operating frequency, and machine load to produce a model for the loss in the superconducting components of the machine. This model is then used to optimize the design of the machine for minimal ac loss while maximizing power density. Important observations from the study are discussed.
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Frazzoni, M; Conigliaro, R; Mirante, V G; Melotti, G
2012-02-01
By analysis of symptom-reflux association, endoscopy-negative refractory heartburn can be related to acid/non-acid refluxes with impedance-pH monitoring. Unfortunately, patients frequently do not report symptoms during the test. We aimed to assess the contribution of quantitative analysis of impedance-pH parameters added to symptom-reflux association in evaluating patients with endoscopy-negative heartburn refractory to high-dose proton pump inhibitor therapy. The symptom association probability (SAP), the symptom index (SI), the esophageal acid exposure time and the number of distal and proximal refluxes were assessed at on-therapy impedance-pH monitoring. Relationships with hiatal hernia and manometric findings were also evaluated. Eighty patients were prospectively studied. Refractory heartburn was more frequently related to reflux by a positive SAP/SI and/or abnormal impedance-pH parameters (52/80 cases) (65%) than by a positive SAP/SI only (38/80 cases) (47%) (P = 0.038). In patients with refractory non-erosive reflux disease (NERD) defined by a positive SAP/SI and/or abnormal impedance-pH parameters, the prevalence of hiatal hernia was significantly higher (56%vs 21%, P = 0.007) and the mean lower esophageal sphincter tone was significantly lower (18.7 vs 25.8 mmHg, P = 0.005) than in those (35%) with reflux-unrelated, i.e., functional heartburn (FH). On the contrary, no significant difference was observed subdividing patients according to a positive SAP/SI only. Quantitative analysis of impedance-pH parameters added to symptom-reflux association allows a subdivision of refractory-heartburn patients into refractory NERD and FH which is substantiated by pathophysiological findings and which restricts the diagnosis of FH to one third of cases. © 2011 Blackwell Publishing Ltd.
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Noise and ac impedance analysis of ion transfer kinetics at the micro liquid/liquid interface
Czech Academy of Sciences Publication Activity Database
Josypčuk, Oksana; Holub, Karel; Mareček, Vladimír
2015-01-01
Roč. 56, JUL 2015 (2015), s. 43-45 ISSN 1388-2481 R&D Projects: GA ČR GA13-04630S Institutional support: RVO:61388955 Keywords : noise analysis * liquid/liquid interface * ion transfer kinetics Subject RIV: CG - Electrochemistry Impact factor: 4.569, year: 2015
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Energy Technology Data Exchange (ETDEWEB)
Kopp, Joachim; Liu, Jia [PRISMA Cluster of Excellence & Mainz Institute for Theoretical Physics,Johannes Gutenberg University,Staudingerweg 7, 55099 Mainz (Germany); Slatyer, Tracy R. [Center for Theoretical Physics, Massachusetts Institute of Technology,Cambridge, MA 02139 (United States); Wang, Xiao-Ping [PRISMA Cluster of Excellence & Mainz Institute for Theoretical Physics,Johannes Gutenberg University,Staudingerweg 7, 55099 Mainz (Germany); Xue, Wei [Center for Theoretical Physics, Massachusetts Institute of Technology,Cambridge, MA 02139 (United States)
2016-12-12
We consider dark matter models 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. To emphasize this modification, we dub our scenario “Impeded Dark Matter”. We demonstrate that Impeded Dark Matter 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 suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden SU(2) sector, and a composite dark matter scenario based on a QCD-like dark sector.
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International Nuclear Information System (INIS)
Kopp, Joachim; Liu, Jia; Slatyer, Tracy R.; Wang, Xiao-Ping; Xue, Wei
2016-01-01
We consider dark matter models 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. To emphasize this modification, we dub our scenario “Impeded Dark Matter”. We demonstrate that Impeded Dark Matter 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 suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden SU(2) sector, and a composite dark matter scenario based on a QCD-like dark sector.
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Ac-conductivity and dielectric response of new zinc-phosphate glass/metal composites
Energy Technology Data Exchange (ETDEWEB)
Maaroufi, A., E-mail: maaroufi@fsr.ac.ma [University of Mohammed V, Laboratory of Composite Materials, Polymers and Environment, Department of Chemistry, Faculty of Sciences, P.B. 1014, Rabat-Agdal (Morocco); Oabi, O. [University of Mohammed V, Laboratory of Composite Materials, Polymers and Environment, Department of Chemistry, Faculty of Sciences, P.B. 1014, Rabat-Agdal (Morocco); Lucas, B. [XLIM UMR 7252 – Université de Limoges/CNRS, 123 avenue Albert Thomas, 87060 Limoges Cedex (France)
2016-07-01
The ac-conductivity and dielectric response of new composites based on zinc-phosphate glass with composition 45 mol%ZnO–55 mol%P{sub 2}O{sub 5}, filled with metallic powder of nickel (ZP/Ni) were investigated by impedance spectroscopy in the frequency range from 100 Hz to 1 MHz at room temperature. A high percolating jump of seven times has been observed in the conductivity behavior from low volume fraction of filler to the higher fractions, indicating an insulator – semiconductor phase transition. The measured conductivity at higher filler volume fraction is about 10{sup −1} S/cm and is frequency independent, while, the obtained conductivity for low filler volume fraction is around 10{sup −8} S/cm and is frequency dependent. Moreover, the elaborated composites are characterized by high dielectric constants in the range of 10{sup 5} for conductive composites at low frequencies (100 Hz). In addition, the distribution of the relaxation processes was also evaluated. The Debye, Cole-Cole, Davidson–Cole and Havriliak–Negami models in electric modulus formalism were used to model the observed relaxation phenomena in ZP/Ni composites. The observed relaxation phenomena are fairly simulated by Davidson–Cole model, and an account of the interpretation of results is given. - Highlights: • Composites of ZnO-P{sub 2}O{sub 5}/metal were investigated by impedance spectroscopy. • Original ac-conductivity behavior was discovered in ZnO-P{sub 2}O{sub 5}/metal composites. • High dielectric constant is measured in ZnO-P{sub 2}O{sub 5}/metal composites. • Dielectric constant as filler function is well interpreted with percolation theory. • Observed relaxation processes are well described using electric modulus formalism.
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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)
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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.
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Directory of Open Access Journals (Sweden)
Jung-Chuan Chou
2016-01-01
Full Text Available The internal impedances of different dye-sensitized solar cell (DSSC models were analyzed by electrochemical impedance spectrometer (EIS with an equivalent circuit model. The Nyquist plot was built to simulate the redox reaction of internal device at the heterojunction. It was useful to analyze the component structure and promote photovoltaic conversion efficiency of DSSC. The impedance of DSSC was investigated and the externally connected module assembly was constructed utilizing single cells on the scaled-up module. According to the experiment results, the impedance was increased with increasing cells connected in series. On the contrary, the impedance was decreased with increasing cells connected in parallel.
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Theoretical interpretation of Warburg's impedance in unsupported electrolytic cells.
Barbero, G
2017-12-13
We discuss the origin of Warburg's impedance in unsupported electrolytic cells containing only one group of positive and one group of negative ions. Our analysis is based on the Poisson-Nernst-Planck model, where the generation-recombination phenomenon is neglected. We show that to observe Warburg-like impedance the diffusion coefficient of the positive ions has to differ from that of the negative ones, and furthermore the electrodes have to be not blocking. We assume that the non-blocking properties of the electrodes can be described by means of an Ohmic model, where the charge exchange between the cell and the external circuit is described by means of an electrode conductivity. For simplicity we consider a symmetric cell. However, our analysis can be easily generalized to more complicated situations, where the cell is not symmetric and the charge exchange is described by the Chang-Jaffe model, or by a linearized version of the Butler-Volmer equation. Our analysis allows justification of the expression for Warburg's impedance proposed previously by several groups, based on wrong assumptions.
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Digital model for harmonic interactions in AC/DC/AC systems
Energy Technology Data Exchange (ETDEWEB)
Guarini, A P; Rangel, R D; Pilotto, L A.S.; Pinto, R J; Passos, Junior, R [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil)
1994-12-31
The main purpose of this paper is to present a model for calculation of HVdc converter harmonics taking into account the influence of the harmonic interactions between the ac systems in dc link transmissions. The ideas and methodologies used in the model development take into account the dc current ripple and ac voltage distortion in the ac systems. The theory of switching functions is applied to contemplate for the frequency conversions between the ac and dc sides, in an iterative process. It is possible then to obtain, even in balanced situations, non-characteristic harmonics that are produced by frequencies originated in the other terminal, which can be significant in a strongly coupled system, such as back-to-back configuration. (author) 9 refs., 3 figs.
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International Nuclear Information System (INIS)
Bogónez-Franco, P; Nescolarde, L; Bragós, R; Rosell-Ferrer, J; Yandiola, I
2009-01-01
The purpose of this study is to compare measurement errors in two commercially available multi-frequency bioimpedance analyzers, a Xitron 4000B and an ImpediMed SFB7, including electrode impedance mismatch. The comparison was made using resistive electrical models and in ten human volunteers. We used three different electrical models simulating three different body segments: the right-side, leg and thorax. In the electrical models, we tested the effect of the capacitive coupling of the patient to ground and the skin–electrode impedance mismatch. Results showed that both sets of equipment are optimized for right-side measurements and for moderate skin–electrode impedance mismatch. In right-side measurements with mismatch electrode, 4000B is more accurate than SFB7. When an electrode impedance mismatch was simulated, errors increased in both bioimpedance analyzers and the effect of the mismatch in the voltage detection leads was greater than that in current injection leads. For segments with lower impedance as the leg and thorax, SFB7 is more accurate than 4000B and also shows less dependence on electrode mismatch. In both devices, impedance measurements were not significantly affected (p > 0.05) by the capacitive coupling to ground
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Single stage buck-boost DC-AC neutral point clamped inverter
DEFF Research Database (Denmark)
Mo, Wei; Loh, Poh Chiang; Andrew, A.
2012-01-01
This paper proposes a new single stage buck-boost DC-AC neutral point clamped inverter topology which integrates the cascaded configurations of recently introduced inductor-capacitor-capacitor-transformer impedance source network (by Adamowicz) and classic NPC configuration. As a consequence......, it has enhanced buck-boost functionality and low output voltage distortions compared to the traditional Z-source inverter; it has continuous input current which reduces the source stress and inverter noise; it also contains two built-in capacitors which can block the DC current in the transformer...... windings thus preventing the core from saturation; lowers the voltage stresses and power losses of inverter switches and reduces the sizes of filtering devices and as well as obtains better output performance compared to the original two-level Z-source inverters. A phase disposition pulse width modulation...
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A dielectrophoresis-impedance method for protein detection and analysis
Directory of Open Access Journals (Sweden)
Ahmad Sabry Mohamad
2017-01-01
Full Text Available 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.
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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.
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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.
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Impedance and modulus spectroscopic study of nano hydroxyapatite
Jogiya, B. V.; Jethava, H. O.; Tank, K. P.; Raviya, V. R.; Joshi, M. J.
2016-05-01
Hydroxyapatite (Ca10 (PO4)6 (OH)2, HAP) is the main inorganic component of the hard tissues in bones and also important material for orthopedic and dental implant applications. Nano HAP is of great interest due to its various bio-medical applications. In the present work the nano HAP was synthesized by using surfactant mediated approach. Structure and morphology of the synthesized nano HAP was examined by the Powder XRD and TEM. Impedance study was carried out on pelletized sample in a frequency range of 100Hz to 20MHz at room temperature. The variation of dielectric constant, dielectric loss, and a.c. conductivity with frequency of applied field was studied. The Nyquist plot as well as modulus plot was drawn. The Nyquist plot showed two semicircle arcs, which indicated the presence of grain and grain boundary effect in the sample. The typical behavior of the Nyquist plot was represented by equivalent circuit having two parallel RC combinations in series.
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Applications for Electrical Impedance Tomography (EIT) and Electrical Properties of the Human Body.
Lymperopoulos, Georgios; Lymperopoulos, Panagiotis; Alikari, Victoria; Dafogianni, Chrisoula; Zyga, Sofia; Margari, Nikoletta
2017-01-01
Electrical Impedance Tomography (EIT) is a promising application that displays changes in conductivity within a body. The basic principle of the method is the repeated measurement of surface voltages of a body, which are a result of rolling injection of known and small-volume sinusoidal AC current to the body through the electrodes attached to its surface. This method finds application in biomedicine, biology and geology. The objective of this paper is to present the applications of Electrical Impedance Tomography, along with the method's capabilities and limitations due to the electrical properties of the human body. For this purpose, investigation of existing literature has been conducted, using electronic databases, PubMed, Google Scholar and IEEE Xplore. In addition, there was a secondary research phase, using paper citations found during the first research phase. It should be noted that Electrical Impedance Tomography finds use in a plethora of medical applications, as the different tissues of the body have different conductivities and dielectric constants. Main applications of EIT include imaging of lung function, diagnosis of pulmonary embolism, detection of tumors in the chest area and diagnosis and distinction of ischemic and hemorrhagic stroke. EIT advantages include portability, low cost and safety, which the method provide, since it is a noninvasive imaging method that does not cause damage to the body. The main disadvantage of the method, which blocks its wider spread, appears in the image composition from the voltage measurements, which are conducted by electrodes placed on the periphery of the body, because the injected currents are affected nonlinearly by the general distribution of the electrical properties of the body. Furthermore, the complex impedance of the skin-electrode interface can be modelled by using a capacitor and two resistor, as a result of skin properties. In conclusion, Electrical Impedance Tomography is a promising method for the
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Nwosu, Amara Callistus; Mayland, Catriona R; Mason, Stephen R; Khodabukus, Andrew F; Varro, Andrea; Ellershaw, John E
2013-09-01
Decisions surrounding the administration of clinically assisted hydration to patients dying of cancer can be challenging because of the limited understanding of hydration in advanced cancer and a lack of evidence to guide health care professionals. Bioelectrical impedance analysis (BIA) has been used to assess hydration in various patient groupings, but evidence for its use in advanced cancer is limited. To critically appraise existing methods of hydration status assessment in advanced cancer and review the potential for BIA to assess hydration in advanced cancer. Searches were carried out in four electronic databases. A hand search of selected peer-reviewed journals and conference abstracts also was conducted. Studies reporting (de)hydration assessment (physical examination, biochemical measures, symptom assessment, and BIA) in patients with advanced cancer were included. The results highlight how clinical examination and biochemical tests are standard methods of assessing hydration, but limitations exist with these methods in advanced cancer. Furthermore, there is disagreement over the evidence for some commonly associated symptoms with dehydration in cancer. Although there are limitations with using BIA alone to assess hydration in advanced cancer, analysis of BIA raw measurements through the method of bioelectrical impedance vector analysis may have a role in this population. The benefits and burdens of providing clinically assisted hydration to patients dying of cancer are unclear. Bioelectrical impedance vector analysis shows promise as a hydration assessment tool but requires further study in advanced cancer. Innovative methodologies for research are required to add to the evidence base and ultimately improve the care for the dying. Copyright © 2013 U.S. Cancer Pain Relief Committee. Published by Elsevier Inc. All rights reserved.
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Historical Analysis of the Inorganic Chemistry Curriculum Using ACS Examinations as Artifacts
Srinivasan, Shalini; Reisner, Barbara A.; Smith, Sheila R.; Stewart, Joanne L.; Johnson, Adam R.; Lin, Shirley; Marek, Keith A.; Nataro, Chip; Murphy, Kristen L.; Raker, Jeffrey R.
2018-01-01
ACS Examinations provide a lens through which to examine historical changes in topic coverage via analyses of course-specific examinations. This study is an extension of work completed previously by the ACS Exams Research Staff and collaborators in general chemistry, organic chemistry, and physical chemistry to explore content changes in the…
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Choi, Jongwan; Kim, Felix Sunjoo
2018-03-01
We studied the influence of photoanode thickness on the photovoltaic characteristics and impedance responses of the dye-sensitized solar cells based on a ruthenium dye containing a hexyloxyl-substituted carbazole unit (Ru-HCz). As the thickness of photoanode increases from 4.2 μm to 14.8 μm, the dye-loading amount and the efficiency increase. The device with thicker photoanode shows a decrease in the efficiency due to the higher probability of recombination of electron-hole pairs before charge extraction. We also analyzed the electron-transfer and recombination characteristics as a function of photoanode thickness through detailed electrochemical impedance spectroscopy analysis.
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Low profile conformal antenna arrays on high impedance substrate
Singh, Hema; Jha, Rakesh Mohan
2016-01-01
This book presents electromagnetic (EM) design and analysis of dipole antenna array over high impedance substrate (HIS). HIS is a preferred substrate for low-profile antenna design, owing to its unique boundary conditions. Such substrates permit radiating elements to be printed on them without any disturbance in the radiation characteristics. Moreover HIS provides improved impedance matching, enhanced bandwidth, and increased broadside directivity owing to total reflection from the reactive surface and high input impedance. This book considers different configurations of HIS for array design on planar and non-planar high-impedance surfaces. Results are presented for cylindrical dipole, printed dipole, and folded dipole over single- and double-layered square-patch-based HIS and dogbone-based HIS. The performance of antenna arrays is analyzed in terms of performance parameters such as return loss and radiation pattern. The design presented shows acceptable return loss and mainlobe gain of radiation pattern. Thi...
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Determination of beam coupling impedance in the frequency domain
Energy Technology Data Exchange (ETDEWEB)
Niedermayer, Uwe
2016-07-01
simulations always contain simplifications, therefore they have to be confirmed by dedicated measurements. However, the beam coupling impedance of a single accelerator component cannot be measured directly. Therefore, a dedicated RF-laboratory was established at GSI, in order to measure broadband beam coupling impedances on the bench by means of the wire method, i.e. without beam. A detailed analysis of measurement methods is given by comparison of analytical, numerical, and measurement results for simplified accelerator devices. One conclusion is, that also the bench measurements have to be validated by dedicated electromagnetic simulations. The thesis closes with selected impedance induced effects on the beam revolving in the synchrotron and relevant impedance results for the future SIS-100 synchrotron for the FAIR project at GSI.
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Dolphin, Andrew
2005-07-01
The uncertainties in the photometric zero points create a fundamental limit to the accuracy of photometry. The current state of the ACS calibration is surprisingly poor, with zero point uncertainties of 0.03 magnitudes. The reason for this is that the ACS calibrations are based primarily on semi-emprical synthetic zero points and observations of fields too crowded for accurate ground-based photometry. I propose to remedy this problem by obtaining ACS images of the omega Cen standard field with all nine broadband ACS/WFC filters. This will permit the direct determination of the ACS zero points by comparison with excellent ground-based photometry, and should reduce their uncertainties to less than 0.01 magnitudes. A second benefit is that it will facilitate the comparison of the WFPC2 and ACS photometric systems, which will be important as WFPC2 is phased out and ACS becomes HST's primary imager. Finally, three of the filters will be repeated from my Cycle 12 observations, allowing for a measurement of any change in sensitivity.
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Nonlinear Impedance of Whole Cells Near an Electrode as a Probe of Mitochondrial Activity
Directory of Open Access Journals (Sweden)
John H. Miller Jr.
2011-04-01
Full Text Available By simultaneously measuring the bulk media and electrode interface voltages of a yeast (Saccharomyces cerevisiae suspension subjected to an AC voltage, a yeast-dependent nonlinear response was found only near the current injection electrodes. Computer simulation of yeast near a current injection electrode found an enhanced voltage drop across the yeast near the electrode due to slowed charging of the electrode interfacial capacitance. This voltage drop is sufficient to induce conformation change in membrane proteins. Disruption of the mitochondrial electron transport chain is found to significantly change the measured nonlinear current response, suggesting nonlinear impedance can be used as a non-invasive probe of cellular metabolic activity.
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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.
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Applications of Nonlinear Electrochemical Impedance Spectroscopy (NLEIS)
Adler, S. B.
2013-01-01
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
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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.
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Directory of Open Access Journals (Sweden)
Yongling FU
2018-03-01
Full Text Available Electrohydrostatic actuator (EHA is a type of power-by-wire actuator that is widely implemented in the aerospace industry for flight control, landing gears, thrust reversers, thrust vector control, and space robots. This paper presents the development and evaluation of position-based impedance control (PBIC for an EHA. Impedance control provides the actuator with compliance and facilitates the interaction with the environment. Most impedance control applications utilize electrical or valve-controlled hydraulic actuators, whereas this work realizes impedance control via a compact and efficient EHA. The structures of the EHA and PBIC are firstly introduced. A mathematical model of the actuation system is established, and values of its coefficients are identified by particle swarm optimization. This model facilitates the development of a position controller and the selection of target impedance parameters. A nonlinear proportional-integral position controller is developed for the EHA to achieve the accurate positioning requirement of PBIC. The controller compensates for the adverse effect of stiction, and a position accuracy of 0.08 mm is attained. Various experimental results are presented to verify the applicability of PBIC to the EHA. The compliance of the actuator is demonstrated in an impact test. Keywords: Actuation system, Aerospace, Electrohydrostatic actuator, Force control, Nonlinear dynamics, Particle swarm optimization, Position control
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The influence of a delaminated layer on the impedance spectrum of an operating solid oxide fuel cell
Energy Technology Data Exchange (ETDEWEB)
Gazzarri, J.I. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Mechanical Engineering; Kesler, O. [National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation
2005-07-01
The development of a 2-dimensional finite element model of Solid Oxide Fuel Oxide (SOFC) AC impedance behavior was discussed. The model was developed to simulate the frequency response of a single cell with and without mechanical damage. Impedance spectroscopy was used in the development of a diagnostic technique to identify a delamination failure within a working SOFC. Changes in the impedance spectrum of a working cell were observed on the appearance of a delamination between 2 adjacent layers. The intent was to identify distinctive patterns in the cracked cell spectra that provide enough information about the degradation process so that it can be recognized and distinguished from other electrochemical processes and degradation modes. It was anticipated that the method will provide a useful tool for both maintenance and research purposes, providing insight into the causes of inadequate functioning. Results indicate that the presence of mechanically induced damage within the components of an SOFC can be detected by comparing the frequency response of the undamaged cell with that of a cell in which in-plane cracking or delamination has occurred. The presence of such defects manifests itself as a new semicircle in the Nyquist impedance diagram of the full cell, with a relaxation frequency of approximately 35 kHz. It was concluded that the ability to distinguish the crack-induced semicircle from the semicircles induced by electrochemical reactions depended on the difference between the characteristic relaxation times and their relative sizes. 17 refs., 1 tab.,10 figs.
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Characterization of Bi4Ge3O12 single crystal by impedance spectroscopy
Directory of Open Access Journals (Sweden)
Zélia Soares Macedo
2003-12-01
Full Text Available Bi4Ge3O12 (bismuth germanate - BGO single crystals were produced by the Czochralski technique and their electrical and dielectric properties were investigated by impedance spectroscopy. The isothermal ac measurements were performed for temperatures from room temperature up to 750 °C, but only the data taken above 500 °C presented a complete semicircle in the complex impedance diagrams. Experimental data were fitted to a parallel RC equivalent circuit, and the electrical conductivity was obtained from the resistivity values. Conductivity values from 5.4 × 10(9 to 4.3 × 10-7 S/cm were found in the temperature range of 500 to 750 °C. This electrical conductivity is thermally activated, following the Arrhenius law with an apparent activation energy of (1.41 ± 0.04 eV. The dielectric properties of BGO single crystal were also studied for the same temperature interval. Permittivity values of 20 ± 2 for frequencies higher than 10³ Hz and a low-frequency dispersion were observed. Both electric and dielectric behavior of BGO are typical of systems in which the conduction mechanism dominates the dielectric response.
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Superconductive AC current limiter
International Nuclear Information System (INIS)
Bekhaled, M.
1987-01-01
This patent describes an AC current limiter for a power transport line including a power supply circuit and feeding a load circuit via an overload circuit-breaker member. The limiter comprises a transformer having a primary winding connected in series between the power supply circuit and the load circuit and at least one secondary winding of superconductor material contained in a cryogenic enclosure and short-circuited on itself. The leakage reactance of the transformer as seen from the primary winding is low, and the resistance of the at least one secondary winding when in the non-superconducting state and as seen from the primary is much greater than the nominal impedance of the transformer. The improvement whereby the at least one secondary winding of the transformer comprises an active winding in association with a set of auxiliary windings. The set of auxiliary windings is constituted by an even number of series-connected auxiliary windings wound in opposite directions, with the total number of turns in one direction being equal to the total number of turns in the opposite direction, and with the thermal capacity of the secondary winding as a whole being sufficiently high to limit the expansion thereof to a value which remains small during the time it takes the circuit-breaking member to operate
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Impedance Characterisation of the SPS Wire Scanner
AUTHOR|(CDS)2091911; Prof. Sillanpää, Mika
As a beam diagnostic tool, the SPS wire scanner interacts with the proton bunches traversing the vacuum pipes of the Super Proton Synchrotron particle accelerator. Following the interaction, the bunches decelerate or experience momentum kicks off-axis and couple energy to the cavity walls, resonances and to the diagnostic tool, the scanning wire. The beam coupling impedance and, in particular, the beam induced heating of the wire motivate the characterisation and redesign of the SPS wire scanner. In this thesis, we characterise RF-wise the low frequency modes of the SPS wire scanner. These have the highest contribution to the impedance. We measure the cavity modes in terms of resonance frequency and quality factor by traditional measurement techniques and data analysis. We carry out a 4-port measurement to evaluate the beam coupling to the scanning wire, that yields the spectral heating power. If combined with the simulations, one is able to extract the beam coupling impedance and deduce the spectral dissipa...
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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
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Analysis of Human Fibroadenomas Using Three-Dimensional Impedance Maps
Dapore, Alexander J.; King, Michael R.; Harter, Josephine; Sarwate, Sandhya; Oelze, Michael L.; Zagzebski, James A.; Do, Minh N.; Hall, Timothy J.
2012-01-01
Three-dimensional impedance maps (3DZMs) are virtual volumes of acoustic impedance values constructed from histology to represent tissue microstructure acoustically. From the 3DZM, the ultrasonic backscattered power spectrum can be predicted and model based scatterer properties, such as effective scatterer diameter (ESD), can be estimated. Additionally, the 3DZM can be exploited to visualize and identify possible scattering sites, which may aid in the development of more effective scattering models to better represent the ultrasonic interaction with underlying tissue microstructure. In this study, 3DZMs were created from a set of human fibroadenoma samples. ESD estimates were made assuming a fluid-filled sphere form factor model from 3DZMs of volume 300 × 300 × 300 µm. For a collection of 33 independent human fibroadenoma tissue samples, the ESD was estimated to be 111 ± 40.7 µm. The 3DZMs were then investigated visually to identify possible scattering sources which conformed to the estimated model scatterer dimensions. This estimation technique allowed a better understanding of the spatial distribution and variability of the estimates throughout the volume. PMID:21278015
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The measurement of skin impedance for the diagnosis of skin cancer
International Nuclear Information System (INIS)
Menzies, S.; Crook, B.; McCarthy, W.
1996-01-01
Full text: In vivo skin impedance measurements have been reported to be diagnostic in differentiating benign from malignant skin tumours (Kiss G et al. Borgyogy Vener Szle 45: 164,1969; Melczer N. In: Cancer of the Skin. Saunders Co. Philadelphia, 1976, pp293-313). However, in contrast to non-melanoma skin cancer, only, a small sample of malignant melanomas were reported in these previous studies. We performed skin impedance measurements on a larger sample of melanomas in order to assess the potential use of such instrumentation for clinical diagnosis. The diagnostic method described by Kiss and Horvath was reproduced with only minor modifications. Low voltage impedance measurements at 1600 Hz were taken over each lesion and on nearby surrounding normal skin. Filter paper (4mm diameter) soaked in 0.1 M KCl was used at the skin-probe interface. A minimum of 2 skin and 1 lesion measurements were taken. All lesions were taken from relatively hairless sites and were non abraded or ulcerated. With the exception of 6 seborrhoeic keratoses all lesions were excised for histological diagnosis. The lesions tested were 27 invasive melanomas, 3 in situ melanomas, 27 basal cell carcinomas (BCC), 70 benign melanocytic lesions, 19 seborrhoeic keratoses, 5 Bowens disease (in situ SCC), 1 squamous cell carcinoma (SCC) and 25 other benign lesions. Results were interpreted as previously (Melczer) by the quotient of skin impedance / lesion impedance > 1.5 indicating malignancy. Analysis of total melanocytic lesions gave a sensitivity of 44% and specificity of 83% for the diagnosis of invasive melanoma (p < 0.05). Fifty two percent of BCCs were positively diagnosed. Analysis of all benign versus all invasive malignancy gave a sensitivity of 47% and specificity of 77% for the diagnosis of invasive malignancy (p < 0.01). While impedance measurements at 1600 Hz provide a statistically significant differentiation of melanoma versus non-melanoma and invasive malignancy versus benign lesions
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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......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...
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Stolarski, J.T.; Margraf, F.J.; Carlson, J.G.; Sutton, T.M.
2014-01-01
The physiological well-being or condition of fish is most commonly estimated from aspects of individual morphology. However, these metrics may be only weakly correlated with nutritional reserves stored as lipid, the primary form of accumulated energy in fish. We constructed and evaluated bioelectrical impedance analysis (BIA) models as an alternative method of assessing condition in amphidromous Dolly Varden Salvelinus malma collected from nearshore estuarine and lotic habitats of the Alaskan Arctic. Data on electrical resistance and reactance were collected from the lateral and ventral surfaces of 192 fish, and whole-body percent lipid and moisture content were determined using standard laboratory methods. Significant inverse relationships between temperature and resistance and reactance prompted the standardization of these data to a constant temperature using corrective equations developed herein. No significant differences in resistance or reactance were detected among spawning and nonspawning females after accounting for covariates, suggesting that electrical pathways do not intersect the gonads. Best-fit BIA models incorporating electrical variables calculated from the lateral and ventral surfaces produced the strongest associations between observed and model-predicted estimates of proximate content. These models explained between 6% and 20% more of the variability in laboratory-derived estimates of proximate content than models developed from single-surface BIA data and 32% more than models containing only length and weight data. While additional research is required to address the potential effects of methodological variation, bioelectrical impedance analysis shows promise as a way to provide high-quality, minimally invasive estimates of Dolly Varden lipid or moisture content in the field with only small increases in handling time.
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Hybrid-Source Impedance Networks
DEFF Research Database (Denmark)
Li, Ding; Gao, Feng; Loh, Poh Chiang
2010-01-01
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...... for current-type inverters. These impedance networks can in principle be combined into two generic network entities, before multiple of them can further be connected together by applying any of the two proposed generalized cascading concepts. The resulting two-level and three-level inverters implemented using...
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This patent describes a low offset AC correlator avoids DC offset and low frequency noise by frequency operating the correlation signal so that low...noise, low level AC amplification can be substituted for DC amplification. Subsequently, the high level AC signal is demodulated to a DC level. (Author)
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International Nuclear Information System (INIS)
Law, H.
1987-01-01
An ac power supply system includes a rectifier fed by a normal ac supply, and an inverter connected to the rectifier by a dc link, the inverter being effective to invert the dc output of the receiver at a required frequency to provide an ac output. A dc backup power supply of lower voltage than the normal dc output of the rectifier is connected across the dc link such that the ac output of the rectifier is derived from the backup supply if the voltage of the output of the inverter falls below that of the backup supply. The dc backup power may be derived from a backup ac supply. Use in pumping coolant in nuclear reactor is envisaged. (author)
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Tian, Zhang; Yanfeng, Gong
2017-05-01
In order to solve the contradiction between demand and distribution range of primary energy resource, Ultra High Voltage (UHV) power grids should be developed rapidly to meet development of energy bases and accessing of large-scale renewable energy. This paper reviewed the latest research processes of AC/DC transmission technologies, summarized the characteristics of AC/DC power grids, concluded that China’s power grids certainly enter a new period of large -scale hybrid UHV AC/DC power grids and characteristics of “strong DC and weak AC” becomes increasingly pro minent; possible problems in operation of AC/DC power grids was discussed, and interaction or effect between AC/DC power grids was made an intensive study of; according to above problems in operation of power grids, preliminary scheme is summarized as fo llows: strengthening backbone structures, enhancing AC/DC transmission technologies, promoting protection measures of clean energ y accessing grids, and taking actions to solve stability problems of voltage and frequency etc. It’s valuable for making hybrid UHV AC/DC power grids adapt to operating mode of large power grids, thus guaranteeing security and stability of power system.
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Droop-free Distributed Control for AC Microgrids
DEFF Research Database (Denmark)
Nasirian, Vahidreza; Shafiee, Qobad; Guerrero, Josep M.
2016-01-01
A cooperative distributed secondary/primary control paradigm for AC microgrids is proposed. This solution replaces the centralized secondary control and the primary-level droop mechanism of each inverter with three separate regulators: voltage, reactive power, and active power regulators. A sparse...... guidelines are provided. Steady-state performance analysis shows that the proposed controller can accurately handle the global voltage regulation and proportional load sharing. An AC microgrid prototype is set up, where the controller performance, plug-and-play capability, and resiliency to the failure...
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Autographa californica multiple nucleopolyhedrovirus ac53 plays a role in nucleocapsid assembly
International Nuclear Information System (INIS)
Liu Chao; Li Zhaofei; Wu Wenbi; Li Lingling; Yuan Meijin; Pan Lijing; Yang Kai; Pang Yi
2008-01-01
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) orf53 (ac53) is a highly conserved gene existing in all sequenced Lepidoptera and Hymenoptera baculoviruses, but its function remains unknown. To investigate its role in the baculovirus life cycle, an ac53 deletion virus (vAc ac53KO-PH-GFP ) was generated through homologous recombination in Escherichia coli. Fluorescence and light microscopy and titration analysis revealed that vAc ac53KO-PH-GFP could not produce infectious budded virus in infected Sf9 cells. Real-time PCR demonstrated that the ac53 deletion did not affect the levels of viral DNA replication. Electron microscopy showed that many lucent tubular shells devoid of the nucleoprotein core are present in the virogenic stroma and ring zone, indicating that the ac53 knockout affected nucleocapsid assembly. With a recombinant virus expressing an Ac53-GFP fusion protein, we observed that Ac53 was distributed within the cytoplasm and nucleus at 24 h post-infection, but afterwards accumulated predominantly near the nucleus-cytoplasm boundary. These data demonstrate that ac53 is involved in nucleocapsid assembly and is an essential gene for virus production
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DEFF Research Database (Denmark)
Bak, Christen Kjeldahl; Dalsgaard, Erik
1967-01-01
An ac measuring technique devised primarily for measuring galvanomagnetic effects in metals is presented. The instrument may, however, be useful whenever it is desired to measure and record continuously impedances in the range 10−3 to 10−8 Omega. The sample assembly is disscussed in some detail....... Measurements with the bridge show that in the temperature range 300°K to 4.2°K the noise level changes from 30×10−11 V to 10−11 V without any zero shift, and as a result the lower limit for the impedance range changes from 10−6 Omega to less than 5×10−8 Omega. ©1967 The American Institute of Physics...
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Energy Technology Data Exchange (ETDEWEB)
Rout, S.K. [Department of Chemical and Biomolecular Engineering, KAIST (Korea, Republic of); Department of Applied Physics, BIT, Mesra, Ranchi (India)], E-mail: drskrout@gmail.com; Hussian, Ali; Lee, J.S. [School of Materials Science and Engineering University of Ulsan (Korea, Republic of); Kim, I.W. [Department of Physics, University of Ulsan (Korea, Republic of); Woo, S.I. [Department of Chemical and Biomolecular Engineering, KAIST (Korea, Republic of)], E-mail: siwoo@kaist.ac.kr
2009-05-27
In this work, we have synthesized polycrystalline SrBi{sub 4}Ti{sub 4}O{sub 15} (SBiT) ceramics by soft chemical method. These ceramics were structurally characterized by analysis of X-ray diffraction (XRD) patterns, indicates that SBiT ceramics present an orthorhombic structure. Scanning electron micrograph shows that the grains exhibit a plate like morphology. Dielectric relaxations of the SBiT ceramics were investigated in the temperature range 100-700 deg. C. Using the Cole-Cole model, an analysis of the dielectric loss with frequency was performed, assuming a distribution of relaxation time. The presence of the peaks in temperature dependent dielectric loss indicates that the hoping of charge carriers is responsible for the relaxation. Impedance studies shows a non-Debye type relaxation, and relaxation frequency shift to higher side with increase in temperature. A significant shift in impedance loss peaks towards higher frequency side indicates conduction in material and favoring the long range motion of mobile charge carriers. The Nyquist plot shows overlapping semicircles, for grain and grain boundary of SBiT ceramics. The frequency dependent ac conductivity at different temperatures indicates that the conduction process is thermally activated process and the spectra follow the universal power law. The hopping frequency shifts towards higher frequency side with increase of temperature, below which the conductivity is frequency independent. The variation of dc conductivity confirms that the SBiT ceramics exhibits negative temperature coefficient of resistance behavior in high temperature.
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Harne, Ryan L.; Goodpaster, Benjamin A.
2018-01-01
Structural components susceptible to adverse, post-buckled dynamic behaviors have long challenged the success of applications requiring lightweight, slender curved structures, while researchers have begun to leverage such bistable systems in emerging applications for novel energy attenuation and shape-changing properties. To expedite development and deployment of these built-up platforms containing post-buckled constituents, efficient approaches are required to complement time-consuming full-field models in the prediction of the near- and far-from-equilibrium dynamics. This research meets the need by introducing a semi-analytical model framework to enable the characterization of steady-state responses in multi degree-of-freedom (DOF) and multistable structural systems subjected to harmonic excitation. In so doing, the pathway for assessing impedance measures is created here so as to identify how energy travels and returns within built-up multistable structures. Verified by simulations and qualitatively validated by experiments, the analysis is shown to accurately reproduce both near- and far-from-equilibrium responses including different classes of energetic snap-through dynamics that only exist in such multistable structures. A first look at the impedance measures of different dynamic regimes reveals a connection between damping in multistable structures and the sustainability of far-from-equilibrium oscillations.
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Pumping slots: impedances and power losses
Energy Technology Data Exchange (ETDEWEB)
Kurennoy, S [Maryland Univ., College Park, MD (United States). Dept. of Physics
1996-08-01
Contributions of pumping slots to the beam coupling impedances and power losses in a B-factory ring are considered. While their leading contribution is to the inductive impedance, for high-intensity machines with short bunches like e{sup +}e{sup -} B-factories the real part of the impedance and related loss factors are also important. Using an analytical approach we calculate the coupling impedances and loss factors due to slots in a ring with an arbitrary cross section of the vacuum chamber. Effects of the slot tilt on the beam impedance are also considered, and restrictions on the tilt angle are derived from limitations on the impedance increase. The power leakage through the slots is discussed briefly. The results are applied to the KEK B-factory. (author)
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Voltage Stability Bifurcation Analysis for AC/DC Systems with VSC-HVDC
Directory of Open Access Journals (Sweden)
Yanfang Wei
2013-01-01
Full Text Available A voltage stability bifurcation analysis approach for modeling AC/DC systems with VSC-HVDC is presented. The steady power model and control modes of VSC-HVDC are briefly presented firstly. Based on the steady model of VSC-HVDC, a new improved sequential iterative power flow algorithm is proposed. Then, by use of continuation power flow algorithm with the new sequential method, the voltage stability bifurcation of the system is discussed. The trace of the P-V curves and the computation of the saddle node bifurcation point of the system can be obtained. At last, the modified IEEE test systems are adopted to illustrate the effectiveness of the proposed method.
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Briffa, Thomas G; Hammett, Christopher J; Cross, David B; Macisaac, Andrew I; Rankin, James M; Board, Neville; Carr, Bridie; Hyun, Karice K; French, John; Brieger, David B; Chew, Derek P
2015-09-01
The aim of the present study was to explore the association of health insurance status on the provision of guideline-advocated acute coronary syndrome (ACS) care in Australia. Consecutive hospitalisations of suspected ACS from 14 to 27 May 2012 enrolled in the Snapshot study of Australian and New Zealand patients were evaluated. Descriptive and logistic regression analysis was performed to evaluate the association of patient risk and insurance status with the receipt of care. In all, 3391 patients with suspected ACS from 247 hospitals (23 private) were enrolled in the present study. One-third of patients declared private insurance coverage; of these, 27.9% (304/1088) presented to private facilities. Compared with public patients, privately insured patients were more likely to undergo in-patient echocardiography and receive early angiography; furthermore, in those with a discharge diagnosis of ACS, there was a higher rate of revascularisation (P fee-for-service. In contrast, proportionately fewer privately insured ACS patients were discharged on selected guideline therapies and were referred to a secondary prevention program (P = 0.056), neither of which directly attracts a fee. Typically, as GRACE (the Global Registry of Acute Coronary Events) risk score rose, so did the level of ACS care; however, propensity-adjusted analyses showed lower in-hospital adverse events among the insured group (odds ratio 0.68; 95% confidence interval 0.52-0.88; P = 0.004). Fee-for-service reimbursement may explain differences in the provision of selected guideline-advocated components of ACS care between privately insured and public patients.
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Impedance Synthesis Based Vibration Analysis of Geared Transmission System
Directory of Open Access Journals (Sweden)
Yafeng Ren
2017-01-01
Full Text Available The severity of gear noise response depends on the sensitivity of geared rotor system dynamics to the transmission error. As gearbox design trending towards lighter weight and lower noise, the influence of housing compliance on system dynamic characteristics cannot be ignored. In this study, a gear-shaft-bearing-housing coupled impedance model is proposed to account for the effect of housing compliance on the vibration of geared transmission system. This proposed dynamic model offers convenient modeling, efficient computing, and ability to combine computed parameters with experimental ones. The numerical simulations on system dynamic characteristics are performed for both a rigid housing configuration and a flexible one. Natural frequencies, dynamic mesh forces, and dynamic bearing reaction loads are computed, and the housing compliance contribution on system dynamic characteristics is analyzed. Results show that increasing housing compliance will decrease the system natural frequencies and will affect the dynamic bearing reaction loads significantly but have very little influence on the dynamic mesh force. Also, the analysis shows that bearing stiffness has significant influence on the degree of housing contribution on system dynamic characteristics.
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Numerical Simulation of Electro-Mechanical Impedance Response in Cable-Anchor Connection Interface
International Nuclear Information System (INIS)
Nguyen, Khac Duy; Kim, Jeong Tae
2011-01-01
In this study, a finite element(FE) analysis on electro-mechanical impedance response of cable-anchor connection interface under various anchor force is presented. In order to achieve the objective, the following approaches are implemented. Firstly, an interface washer coupled with piezoelectric(PZT) material is designed for monitoring cable-force loss. The interface washer is a small aluminum plate on which a PZT patch is surface-bonded. Cable-force loss could be monitored by installing the interface washer between the anchor plate and the anchorage of cable-anchor connection and examining the changes of impedance of the interface washer. Secondly, a FE model for cable-anchor connection is established to examine the effect of cable-force on impedance response of interface washer. Also, the effects of geometrical and material properties of the interface washer on impedance responses under various cable-forces are investigated. Finally, validation of the FE analysis is experimentally evaluated by a lab-scale cable-anchor connection
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Chen, Piaojuan; Li, Yi; Zhao, Lihua; Hou, Zhimin; Yan, Maokai; Hu, Bingyan; Liu, Yanhui; Azam, Syed Muhammad; Zhang, Ziyan; Rahman, Zia Ur; Liu, Liping; Qin, Yuan
2017-01-01
Pineapple ( Ananas comosus L .) cultivation commonly relies on asexual reproduction which is easily impeded by many factors in agriculture production. Sexual reproduction might be a novel approach to improve the pineapple planting. However, genes controlling pineapple sexual reproduction are still remain elusive. In different organisms a conserved superfamily proteins known as ATP binding cassette (ABC) participate in various biological processes. Whereas, till today the ABC gene family has not been identified in pineapple. Here 100 ABC genes were identified in the pineapple genome and grouped into eight subfamilies (5 ABCAs , 20 ABCB s, 16 ABCCs , 2 ABCDs , one ABCEs , 5 ABCFs , 42 ABCGs and 9 ABCIs ). Gene expression profiling revealed the dynamic expression pattern of ABC gene family in various tissues and different developmental stages. AcABCA5, AcABCB6, AcABCC4 , AcABCC7 , AcABCC9 , AcABCG26 , AcABCG38 and AcABCG42 exhibited preferential expression in ovule and stamen. Over-expression of AcABCG38 in the Arabidopsis double mutant abcg1-2abcg16-2 partially restored its pollen abortion defects, indicating that AcABCG38 plays important roles in pollen development. Our study on ABC gene family in pineapple provides useful information for developing sexual pineapple plantation which could be utilized to improve pineapple agricultural production.
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DEFF Research Database (Denmark)
Hou, Xiaochao; Sun, Yao; Yuan, Wenbin
2016-01-01
-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......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...
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International Nuclear Information System (INIS)
Jung, Kyu-Nam; Pyun, Su-Il
2007-01-01
The mechanism transition of lithium transport through a Li 1-δ Mn 2 O 4 composite electrode caused by the surface-modification and temperature variation was investigated using the galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS) and the potentiostatic current transient technique. From the analyses of the ac-impedance spectra, experimentally measured from unmodified Li 1-δ Mn 2 O 4 and surface-modified Li 1-δ Mn 2 O 4 with MgO composite electrodes, the internal cell resistance of the MgO-modified Li 1-δ Mn 2 O 4 electrode was determined to be much smaller in value than that of the unmodified electrode over the whole potential range. Moreover, from the analysis of the anodic current transients measured on the MgO-modified Li 1-δ Mn 2 O 4 electrode, it was found that the cell-impedance-controlled constraint at the electrode surface is changed to a diffusion-controlled constraint, which is characterised by a large potential step and simultaneously by a small amount of lithium transferred during lithium transport. This strongly suggests that the internal cell resistance plays a significant role in determining the cell-impedance-controlled lithium transport through the MgO-modified Li 1-δ Mn 2 O 4 electrode. Furthermore, from the temperature dependence of the internal cell resistance and diffusion resistance in the unmodified Li 1-δ Mn 2 O 4 composite electrode measured by GITT and EIS, it was concluded that which mechanism of lithium transport will be operative strongly depends on the diffusion resistance as well as on the internal cell resistance
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A Unified Impedance Model of Voltage-Source Converters with Phase-Locked Loop Effect
DEFF Research Database (Denmark)
Wang, Xiongfei; Harnefors, Lennart; Blaabjerg, Frede
2016-01-01
This paper proposes a unified impedance model for analyzing the effect of Phase-Locked Loop (PLL) on the stability of grid-connected voltage-source converters. In the approach, the dq-frame impedance model is transformed into the stationary αβ-frame by means of complex transfer functions...... and complex space vectors, which not only predicts the stability impact of the PLL, but reveals also its frequency coupling effect in the phase domain. Thus, the impedance models previously developed in the different domains can be unified. Moreover, the impedance shaping effects of PLL are structurally...... characterized for the current control in the rotating dq-frame and the stationary αβ-frame. Case studies based on the unified impedance model are presented, which are then verified in the time-domain simulations and experiments. The results closely correlate with the impedance-based analysis....
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ACS Photometric Zero Point Verification
Dolphin, Andrew
2003-07-01
The uncertainties in the photometric zero points create a fundamental limit to the accuracy of photometry. The current state of the ACS calibration is surprisingly poor, with zero point uncertainties of 0.03 magnitudes in the Johnson filters. The reason for this is that ACS observations of excellent ground-based standard fields, such as the omega Cen field used for WFPC2 calibrations, have not been obtained. Instead, the ACS photometric calibrations are based primarily on semi-emprical synthetic zero points and observations of fields too crowded for accurate ground-based photometry. I propose to remedy this problem by obtaining ACS broadband images of the omega Cen standard field with both the WFC and HRC. This will permit the direct determination of the ACS transformations, and is expected to double the accuracy to which the ACS zero points are known. A second benefit is that it will facilitate the comparison of the WFPC2 and ACS photometric systems, which will be important as WFPC2 is phased out and ACS becomes HST's primary imager.
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Using impedance cardiography with postural change to stratify patients with hypertension.
DeMarzo, Arthur P
2011-06-01
Early detection of cardiovascular disease in patients with hypertension could initiate appropriate treatment to control blood pressure and prevent the progression of cardiovascular disease. The goal of this study was to show how impedance cardiography waveform analysis with postural change can be used to detect subclinical cardiovascular disease in patients with high blood pressure. Patients with high blood pressure had impedance cardiography data obtained in two positions, standing upright and supine. In 50 adults, impedance cardiography indicated that all patients had abnormal data, with 44 (88%) having multiple abnormalities. Impedance cardiography showed 32 (64%) had ventricular dysfunction, 48 (96%) had vascular load abnormalities, 34 (68%) had hemodynamic abnormalities, 2 (4%) had hypovolemia, and 3 (6%) had hypervolemia. Hypertensive patients have diverse cardiovascular abnormalities that can be quantified by impedance cardiography. By stratifying patients with ventricular, vascular, and hemodynamic abnormalities, treatment could be customized based on the abnormal underlying mechanisms with the potential to rapidly control blood pressure, prevent progression of cardiovascular disease, and possibly reverse remodeling.
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Electrochemical impedance spectroscopy: An effective tool for a fast microbiological diagnosis
International Nuclear Information System (INIS)
Ramirez, Nardo; Regueiro, Angel; Arias, Olimpia; Contreras, Rolando
2009-01-01
Dielectric spectroscopy, also called electrochemical impedance spectroscopy, is traditionally used in monitoring corrosion and electro-deposition processes in the coating and characterization assessment of many kinds of sensors and semi-conductors. Its application in biotechnology for the characterization of cell cultures has, however, been notably expanded in the last decade. As a transductional principle, impedance has been applied in the field of microbiology as a means of detecting and quantifying pathogenic bacteria. This paper reviews the state-of-the-art of Impedance Microbiology, its progress and its applications for the detection of foodborne pathogenic bacteria, including the use of interdigitated microelectrodes, the development of chip-based impedance microbiology and the integration of impedance biosensors along with other techniques such as dielectrophoresis and electropermeabilization. Reference is made to basic components, definitions and principles of this technique, as well as to the explanation of the components and principles for cell culture design and the use of equivalent circuits for the analysis of the systems based on this alternative. (Author)
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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.
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Kim, Hye Jin; Kang, Dong-Hoon; Lee, Eunji; Hwang, Kyo Seon; Shin, Hyun-Joon; Kim, Jinsik
2018-02-01
We propose a simple fluorescent bio-chip based on two types of alternative current-dielectrophoretic (AC-DEP) force, attractive (positive DEP) and repulsive (negative DEP) force, for simultaneous nano-molecules analysis. Various radius of micro-holes on the bio-chip are designed to apply the different AC-DEP forces, and the nano-molecules are concentrated inside the micro-hole arrays according to the intensity of the DEP force. The bio-chip was fabricated by Micro Electro Mechanical system (MEMS) technique, and was composed of two layers; a SiO2 layer and Ta/Pt layer were accomplished for an insulation layer and a top electrode with micro-hole arrays to apply electric fields for DEP force, respectively. Each SiO2 and Ta/Pt layers were deposited by thermal oxidation and sputtering, and micro-hole arrays were fabricated with Inductively Coupled Plasma (ICP) etching process. For generation of each positive and negative DEP at micro-holes, we applied two types of sine-wave AC voltage with different frequency range alternately. The intensity of the DEP force was controlled by the radius of the micro-hole and size of nano-molecule, and calculated with COMSOL multi-physics. Three types of nano-molecules labelled with different fluorescent dye were used and the intensity of nano-molecules was examined by the fluorescent optical analysis after applying the DEP force. By analyzing the fluorescent intensities of the nano-molecules, we verify the various nano-molecules in analyte are located successfully inside corresponding micro-holes with different radius according to their size.
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Da, J J; Peng, H Y; Lin, X; Shen, Y; Zhao, J Q; He, S; Zha, Y
2018-03-27
Objective: To explore the level of resting energy expenditure (REE) estimated by bioelectrical impedance analysis and the association of resting metabolic rate (RMR) with clinical related factors, and provide new ideas for improving protein energy wasting (PEW) in maintenance hemodialysis (MHD) patients. Methods: Seven hundred and sixty-five subjects receiving MHD between July 2015 and September 2016 in 11 hemodialysis centers in Guizhou province were enrolled in this cross-sectional study. Bioelectrical impedance analysis was used to measure RMR and body composition, such as lean body mass, fat mass and body cell mass (BCM). Baseline characteristics, routine blood test indexes and biochemical data of hemodialysis patients were collected. The level of RMR and body composition in hemodialysis patients was compared by gender grouping. Then the patients were divided into four groups according to the cutoff value of RMR quartile. Spearman correlation analysis and multiple linear regression analysis were used to analyze the relationships between RMR and clinical related factors. Results: The average age of MHD patients was (54.96±15.78) years and the duriation of dialysis was (42.3±9.0) months. The level of RMR in male patients (474 cases, 61.96%) was significantly higher than that in female patients [1 591(1 444, 1 764) kcal/d vs 1 226 (1 104, 1 354) kcal/d, P lean body mass ( P =0.193). Multiple linear regression analysis showed that RMR was positively correlated with body surface area (β=0.817) and lactate dehydrogenase (LDH) (β=0.198), and negatively correlated with age (β=-0.141), all P maintenance hemodialysis are associated with lactate dehydrogenase level, which may become a new index to evaluate energy consumption.
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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...
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Frequency effects on charge ordering in Y0.5Ca0.5MnO3 by impedance spectroscopy
Sarwar, Tuba; Qamar, Afzaal; Nadeem, Muhammad
2015-02-01
In this work, structural and electrical properties of Y0.5Ca0.5MnO3 are investigated by employing X-ray diffraction and impedance spectroscopy, respectively. Applied ac electric field showed the charge ordering transition temperature around 265 K and below this temperature the heteromorphic behavior of the sample is discussed in the proximity of TCO. With frequency effects the volume of robust charge orbital ordering (COO) domains diminishes due to different competing phases along with Jahn Teller distortions. Comprehensive melting and collapse of charge orbital ordering occurs below TN(125 K), where a colossal drop in the value of impedance is observed. The change in profile of modulus plane plots determines the spreading of relaxation time of intermingled phases. Hopping mechanism is elaborated in terms of strong electron phonon coupling. Variable range hopping model and Arrhenius model are used to discuss the short and long range hopping between Mn3+ and Mn4+ channels assessing the activation energy Ea.
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Jager-Wittenaar, Harriët; Dijkstra, Pieter; Earthman, Carrie; Krijnen, Wim; Langendijk, Johannes A.; van der Laan, Bernard; Pruim, Jan; Roodenburg, Jan
2013-01-01
Assessment and monitoring of fat-free mass (FFM) is of clinical importance, because FFM is reflective of body cell mass, the total mass of protein-rich, metabolically active cells which is affected during malnutrition and therefore related to clinical outcome. Bioelectrical impedance analysis (BIA)
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Effects of tissue impedance on heat generation during RF delivery with the Thermage system
Tomkoria, Sara; Pope, Karl
2005-04-01
The Thermage ThermaCool TC system is a non-ablative RF device designed to promote tissue tightening and contouring. The system delivers RF energy to a target area under the skin, with volumetric tissue heating in that area. While the amount of energy delivered to a patient can be controlled by ThermaCool system settings, the distribution of energy to the treatment area and underlying layers is variable from individual to individual due to differences in body composition. The present study investigated how local tissue impedance affects the amount of discomfort experienced by patients during RF energy delivery. Discomfort results from heat generation in the treatment area. By using features of the ThermaCool TC System, local impedance (impedance of the treatment area), bulk impedance (impedance of the underlying tissue layers), and total impedance (the sum of local and bulk impedance) were measured for 35 patients. For each patient, impedance measurements were compared to discomfort levels expressed during treatment. Analysis of whole body, local, and bulk impedance values indicate that the percent of total body impedance in the local treatment area contributes to discomfort levels expressed by patients during treatment.
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Impedance and instability threshold estimates in the main injector I
International Nuclear Information System (INIS)
Martens, M.A.; Ng, K.Y.
1994-03-01
One of the important considerations in the design of the Main Injector is the beam coupling impedances in the vacuum chamber and the stability of the beam. Along with the higher intensities comes the possibility of instabilities which lead to growth in beam emittances and/or the loss of beam. This paper makes estimations of the various impedances and instability thresholds based on impedance estimations and measurements. Notably missing from this paper is any analysis of transition crossing and its potential limitations on beam intensity and beam emittance. Future work should consider this issue. The body of the work contains detailed analysis of the various impedance estimations and instability threshold calculations. The calculations are based on the Main Injector beam intensity of 6 x 10 10 protons per bunch, 95% normalized transverse emittances of 20π mm-mrad, and 95% normalized longitudinal emittance of 0.1 eV-s at 8.9 GeV injection energy and 0.25 eV-s at 150 GeV flattop energy. The conclusions section summarizes the results in the paper and is meant to be readable by itself without referring to the rest of the paper. Also in the conclusion section are recommendations for future investigations
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Harada, Taro; Murakoshi, Yuino; Torii, Yuka; Tanase, Koji; Onozaki, Takashi; Morita, Shigeto; Masumura, Takehiro; Satoh, Shigeru
2011-04-01
Carnation (Dianthus caryophyllus) flowers exhibit climacteric ethylene production followed by petal wilting, a senescence symptom. DcACS1, which encodes 1-aminocyclopropane-1-carboxylate synthase (ACS), is a gene involved in this phenomenon. We determined the genomic DNA structure of DcACS1 by genomic PCR. In the genome of 'Light Pink Barbara', we found two distinct nucleotide sequences: one corresponding to the gene previously shown as DcACS1, designated here as DcACS1a, and the other novel one designated as DcACS1b. It was revealed that both DcACS1a and DcACS1b have five exons and four introns. These two genes had almost identical nucleotide sequences in exons, but not in some introns and 3'-UTR. Analysis of transcript accumulation revealed that DcACS1b is expressed in senescing petals as well as DcACS1a. Genomic PCR analysis of 32 carnation cultivars showed that most cultivars have only DcACS1a and some have both DcACS1a and DcACS1b. Moreover, we found two DcACS1 orthologous genes with different nucleotide sequences from D. superbus var. longicalycinus, and designated them as DsuACS1a and DsuACS1b. Petals of D. superbus var. longicalycinus produced ethylene in response to exogenous ethylene, accompanying accumulation of DsuACS1 transcripts. These data suggest that climacteric ethylene production in flowers was genetically established before the cultivation of carnation.
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Structure and electrochemical impedance of LiNi_xMn_2_-_xO_4
International Nuclear Information System (INIS)
Ta Anh Tan; Nguyen Si Hieu; Le Ha Chi; Pham Duy Long; Dang Tran Chien; Le Dinh Trong
2016-01-01
Ni-substitution spinel LiNi_xMn_2_-_xO_4 (x = 0, 0.1, 0.2) materials were synthesized by the sol--gel method. The structure and morphology of the samples were characterized by the X-ray diffraction (XRD) and the scanning electron microscopy. The ac conduction of the materials was investigated by electrochemical impedance spectroscopy (EIS) measurements. The refinement results showed that the substitution of Ni decreased the lattice constant and Mn--O distance, while increased Li--O bond length and 16c octahedral volume. The EIS results confirmed the decrease of conductivity with increasing Ni substitution content. Based on XRD and EIS results, the relationship between the crystal structure and electrochemical behavior of the materials was discussed and explained. (author)
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Energy Technology Data Exchange (ETDEWEB)
Saravanan, R. Sakthi Sudar, E-mail: rsakthiss@yahoo.com [Physics Research Centre, S.T. Hindu College, Nagercoil 629 002 (India); Mahadevan, C.K. [Physics Research Centre, S.T. Hindu College, Nagercoil 629 002 (India)
2012-11-15
Highlights: Black-Right-Pointing-Pointer High yield synthesis of Zn-Cd-S QDs. is achieved by solvothermal-microwave heating. Black-Right-Pointing-Pointer The samples are highly crystalline and the average particle size is {approx}3.5 nm. Black-Right-Pointing-Pointer High luminescent quantum yield and narrow emission spectral widths are obtained. Black-Right-Pointing-Pointer High conduction activation energy is observed in the case of Zn-Cd coexisting QDs. - Abstract: A series of wurtzite Zn{sub (1-x)}Cd{sub x}S (x = 0, 0.25, 0.5, 0.75 and 1) nanocrystals with average crystallite size of 1.98, 1.82, 1.80, 2.04 and 2.51 nm, respectively, have been synthesized by simple solvothermal microwave heating method. The photoluminescence yield is found to be higher in the case of alloyed nanocrystals (x = 0.25, 0.5, 0.75) as compared to ZnS (x = 0) and CdS (x = 1). The optical emission is tuned from blue (440 nm) to orange (575 nm) with the increase of Cd composition in Zn{sub (1-x)}Cd{sub x}S nanocrystal. The impedance analysis for Zn{sub (1-x)}Cd{sub x}S nanocrystals has been measured as a function of frequency and temperature. The real and imaginary part of complex impedance plots exhibit semicircle behavior in the complex plane. The AC activation energies of ZnS, Zn{sub 0.75}Cd{sub 0.25}S, Zn{sub 0.5}Cd{sub 0.5}S, Zn{sub 0.25}Cd{sub 0.75}S and CdS nanocrystals were calculated from electrical conductivity analysis and are found to be 0.188, 0.378, 0.456, 0.284 and 0.255 eV, respectively. The conductivity of the alloyed nanocrystals was higher than that of ZnS and CdS.
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Wave impedance selection for passivity-based bilateral teleoperation
D'Amore, Nicholas John
instantaneous conditions encountered. A Lyapunov-like analysis is presented demonstrating that time variation in wave impedance will not violate the passivity of the system. Experimental trials, both in simulation and on a haptic feedback device, are presented validating the technique. Consideration is also given to the case of an uncertain environment, in which an a priori impedance choice may not be possible.
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Several fluidic tuned AC Amplifiers were designed and tested. Interstage tuning and feedback designs are considered. Good results were obtained...corresponding Q’s as high as 12. Element designs and test results of one, two, and three stage amplifiers are presented. AC Modulated Carrier Systems
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Quantitative impedance analysis of solid ionic conductors: Effects of electrode polarization
Czech Academy of Sciences Publication Activity Database
Patil, D.; Shimakawa, K.; Zima, Vítězslav; Wágner, T.
2014-01-01
Roč. 115, č. 14 (2014), "143707-1"-"143707-6" ISSN 0021-8979 Institutional support: RVO:61389013 Keywords : impedance * conductivity * ion conductors Subject RIV: CA - Inorganic Chemistry Impact factor: 2.183, year: 2014
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Superconducting fault current-limiter with variable shunt impedance
Llambes, Juan Carlos H; Xiong, Xuming
2013-11-19
A superconducting fault current-limiter is provided, including a superconducting element configured to resistively or inductively limit a fault current, and one or more variable-impedance shunts electrically coupled in parallel with the superconducting element. The variable-impedance shunt(s) is configured to present a first impedance during a superconducting state of the superconducting element and a second impedance during a normal resistive state of the superconducting element. The superconducting element transitions from the superconducting state to the normal resistive state responsive to the fault current, and responsive thereto, the variable-impedance shunt(s) transitions from the first to the second impedance. The second impedance of the variable-impedance shunt(s) is a lower impedance than the first impedance, which facilitates current flow through the variable-impedance shunt(s) during a recovery transition of the superconducting element from the normal resistive state to the superconducting state, and thus, facilitates recovery of the superconducting element under load.
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Reliability of emergency ac power systems at nuclear power plants
International Nuclear Information System (INIS)
Battle, R.E.; Campbell, D.J.
1983-07-01
Reliability of emergency onsite ac power systems at nuclear power plants has been questioned within the Nuclear Regulatory Commission (NRC) because of the number of diesel generator failures reported by nuclear plant licensees and the reactor core damage that could result from diesel failure during an emergency. This report contains the results of a reliability analysis of the onsite ac power system, and it uses the results of a separate analysis of offsite power systems to calculate the expected frequency of station blackout. Included is a design and operating experience review. Eighteen plants representative of typical onsite ac power systems and ten generic designs were selected to be modeled by fault trees. Operating experience data were collected from the NRC files and from nuclear plant licensee responses to a questionnaire sent out for this project
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Preliminary design of reactor coolant pump canned motor for AC600
International Nuclear Information System (INIS)
Deng Shaowen
1998-01-01
The reactor coolant pump canned motor of AC600 PWR is the kind of shielded motors with high moment of inertia, high reliability, high efficiency and nice starting performance. The author briefly presents the main feature, design criterion and technical requirements, preliminary design, computation results and analysis of performance of AC600 reactor coolant pump canned motor, and proposes some problems to be solved for study and design of AC600 reactor coolant pump canned motor
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78 FR 49318 - Availability of Draft Advisory Circular (AC) 90-106A and AC 20-167A
2013-08-13
...] Availability of Draft Advisory Circular (AC) 90-106A and AC 20- 167A AGENCY: Federal Aviation Administration... of draft Advisory Circular (AC) 90-106A, Enhanced Flight Vision Systems and draft AC 20- 167A... Federal holidays. FOR FURTHER INFORMATION CONTACT: For technical questions concerning draft AC 90-106A...
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Longitudinal coupling impedance of a hole in the accelerator beam pipe
International Nuclear Information System (INIS)
Chae, Yong-Chul.
1993-12-01
In the design of modern accelerators, an accurate estimate of coupling impedance is very important. The sources which give rise to coupling impedance are the geometric discontinuities in the accelerator beam pipe. In various discontinuities such as RF cavities, bellows, and collimators, the coupling impedance of the holes has not been well understood. Although coupling impedance can be obtained in general from the Fourier transform of the corresponding wake potential which may be obtained numerically, this is time consuming and requires a large amount of computer storage when applied to a small dimension of a discontinuity in a typical beam pipe, often imposing a fundamental limitation of the numerical approach. More fundamentally, however, numerical calculation does not have the predictive power because of limited understanding of how the coupling impedance of a hole should behave over a wide frequency range. This question was studied by developing a theoretical analysis based on a variational method. An analytical formula for the coupling impedance of a hole is developed in this work using a variational method. The result gives good qualitative agreements with the coupling impedances evaluated numerically from the Fourier transform of the wake potential which is obtained from the computer code MAFIA-T3. The author shows that the coupling impedance of a hole behaves quite similar to the impedance of an RLC-resonator circuit. Important parameters used to describe such a resonator circuit are the resonant frequency and bandwidth. The author provides a theoretical insight on how to parameterize properly the numerical impedance of a hole when data exhibit complicated dependence on frequency. This is possible because one can show that the parameters are a function of the dimensionless quantity kd alone, with k the free-space wave number and d the radius of hole
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Rf Discharge Impedance Measurements Using a New Method to Determine the Stray Impedances
Bakker, L.P.; Kroesen, G.M.W.; Hoog, de F.J.
1999-01-01
The impedance of a capacitively coupled radio frequency discharge in a tubular fluorescent lamp filled with neon and mercury is measured. The stray impedances in the electrical network are determined using a new method that requires no extra instruments. The reflection of power is used to determine
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Development of a hardware-based AC microgrid for AC stability assessment
Swanson, Robert R.
As more power electronic-based devices enable the development of high-bandwidth AC microgrids, the topic of microgrid power distribution stability has become of increased interest. Recently, researchers have proposed a relatively straightforward method to assess the stability of AC systems based upon the time-constants of sources, the net bus capacitance, and the rate limits of sources. In this research, a focus has been to develop a hardware test system to evaluate AC system stability. As a first step, a time domain model of a two converter microgrid was established in which a three phase inverter acts as a power source and an active rectifier serves as an adjustable constant power AC load. The constant power load can be utilized to create rapid power flow transients to the generating system. As a second step, the inverter and active rectifier were designed using a Smart Power Module IGBT for switching and an embedded microcontroller as a processor for algorithm implementation. The inverter and active rectifier were designed to operate simultaneously using a synchronization signal to ensure each respective local controller operates in a common reference frame. Finally, the physical system was created and initial testing performed to validate the hardware functionality as a variable amplitude and variable frequency AC system.
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Hybrid silicon mode-locked laser with improved RF power by impedance matching
Tossoun, Bassem; Derickson, Dennis; Srinivasan, Sudharsanan; Bowers, John
2015-02-01
We design and discuss an impedance matching solution for a hybrid silicon mode-locked laser diode (MLLD) to improve peak optical power coming from the device. In order to develop an impedance matching solution, a thorough measurement and analysis of the MLLD as a function of bias on each of the laser segments was carried out. A passive component impedance matching network was designed at the operating frequency of 20 GHz to optimize RF power delivery to the laser. The hybrid silicon laser was packaged together in a module including the impedance matching circuit. The impedance matching design resulted in a 6 dB (electrical) improvement in the detected modulation spectrum power, as well as approximately a 10 dB phase noise improvement, from the MLLD. Also, looking ahead to possible future work, we discuss a Step Recovery Diode (SRD) driven impulse generator, which wave-shapes the RF drive to achieve efficient injection. This novel technique addresses the time varying impedance of the absorber as the optical pulse passes through it, to provide optimum optical pulse shaping.
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A THREE-PHASE BOOST DC-AC CONVERTER
African Journals Online (AJOL)
dc-ac converter (inverter) based on the dc-dc boost converters. ... Sliding mode controllers are designed to perform a robust control for the ... Computer simulations and spectral analysis demon- ... the conventional three-phase buck inverter,.
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Analysis of Magnetically-Coupled Impedance Source Three-Phase Four-Switch Inverters
DEFF Research Database (Denmark)
Li, Kerui; Abdelhakim, Ahmed; Yang, Yongheng
2017-01-01
In this paper, magnetically-coupled impedance source (MCIS) three-phase four-switch inverters are introduced for renewable energy applications. This inverter utilizes two single-phase MCIS inverters to obtain a three-phase output, where less component-count is achieved in order to reduce the inve......In this paper, magnetically-coupled impedance source (MCIS) three-phase four-switch inverters are introduced for renewable energy applications. This inverter utilizes two single-phase MCIS inverters to obtain a three-phase output, where less component-count is achieved in order to reduce...... the inverter volume. On the other hand, as a result of the reduced number of switches, the proposed inverter suffers from higher voltage stresses. The MCIS inverters are first reviewed. Then, the modulation and operation principle of the MCIS three-phase inverter topology are introduced before sizing...
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International Nuclear Information System (INIS)
Greffet, Jean-Jacques; Laroche, Marine; Marquier, Francois
2009-01-01
We introduce a generalized definition of the impedance of a nanoantenna that can be applied to any system. We also introduce a definition of the impedance of a two level system. Using this framework, we establish a link between the electrical engineering and the quantum optics picture of light emission.
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Stability of Grid-Connected PV Inverters with Large Grid Impedance Variation
DEFF Research Database (Denmark)
Liserre, Marco; Teodorescu, Remus; Blaabjerg, Frede
2004-01-01
Photovoltaic (PV) inverters used in dispersed power generation of houses in the range of 1-5 kW are currently available from several manufactures. However, large grid impedance variation is challenging the control and the grid filter design in terms of stability. In fact the PV systems are well...... suited for loads connected in a great distance to the transformer (long wires) and the situation becomes even more difficult in low-developed remote areas characterized by low power transformers and long distribution wires with high grid impedance. Hence a theoretical analysis is needed because the grid...... impedance variation leads to dynamic and stability problems both in the low frequency range (around the current controller bandwidth frequency) as well as in the high frequency range (around the LCL-filter resonance frequency). In the low frequency range the possible variation of the impedance challenges...
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Rossi, Paolo; Isoldi, Sara; Mallardo, Saverio; Papoff, Paola; Rossetti, Danilo; Dilillo, Anna; Oliva, Salvatore
2018-04-05
Gastro-oesophageal reflux is very common in the paediatric age group. There is no single and reliable test to distinguish between physiologic and pathological gastro-oesophageal reflux, and this lack of clear distinction between disease and normal can have a negative impact on the management of children. To evaluate the usefulness of 24-h oesophageal pH-impedance study in infants and children with suspected gastro-oesophageal reflux disease. Patients were classified by age groups (A-C) and reflux-related symptoms (typical and atypical). All underwent pH-impedance study. If the latter suggested an abnormal reflux, patients received therapy in accordance with NASPGHAN/ESPGHAN recommendations, while those with normal study had an additional diagnostic work-up. The efficacy of therapy was evaluated with a specific standardized questionnaire for different ages. The study was abnormal in 203/428 patients (47%) while normal in 225/428 (53%). Of those with abnormal study, 109 exhibited typical symptoms (54%), and 94 atypical (46%). The great majority of the patients with abnormal study were responsive to medical anti-reflux therapy. We confirm the utility of prolonged oesophageal pH-impedance study in detecting gastro-oesophageal reflux disease in children and in guiding therapy. Performing oesophageal pH-impedance monitoring in children with suspected gastro-oesophageal reflux disease is helpful to establish the diagnosis and avoid unnecessary therapy. Copyright © 2018 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.
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A Switched Capacitor Based AC/DC Resonant Converter for High Frequency AC Power Generation
Directory of Open Access Journals (Sweden)
Cuidong Xu
2015-09-01
Full Text Available A switched capacitor based AC-DC resonant power converter is proposed for high frequency power generation output conversion. This converter is suitable for small scale, high frequency wind power generation. It has a high conversion ratio to provide a step down from high voltage to low voltage for easy use. The voltage conversion ratio of conventional switched capacitor power converters is fixed to n, 1/n or −1/n (n is the switched capacitor cell. In this paper, A circuit which can provide n, 1/n and 2n/m of the voltage conversion ratio is presented (n is stepping up the switched capacitor cell, m is stepping down the switching capacitor cell. The conversion ratio can be changed greatly by using only two switches. A resonant tank is used to assist in zero current switching, and hence the current spike, which usually exists in a classical switching switched capacitor converter, can be eliminated. Both easy operation and efficiency are possible. Principles of operation, computer simulations and experimental results of the proposed circuit are presented. General analysis and design methods are given. The experimental result verifies the theoretical analysis of high frequency AC power generation.
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Dielectric and impedance study of praseodymium substituted Mg-based spinel ferrites
Energy Technology Data Exchange (ETDEWEB)
Farid, Hafiz Muhammad Tahir, E-mail: tahirfaridbzu@gmail.com [Department of Physics, Bahauddin Zakariya, University Multan, 60800 (Pakistan); Ahmad, Ishtiaq; Ali, Irshad [Department of Physics, Bahauddin Zakariya, University Multan, 60800 (Pakistan); Ramay, Shahid M. [College of Science, Physics and Astronomy Department, King Saud University, P.O. Box 2455, 11451 Riyadh (Saudi Arabia); Mahmood, Asif [Chemical Engineering Department, College of Engineering, King Saud University, Riyadh (Saudi Arabia); Murtaza, G. [Centre for Advanced Studies in Physics, GC University, Lahore 5400 (Pakistan)
2017-07-15
Highlights: • Magnesium based spinel ferrites were successfully synthesized by sol-gel method. • Dielectric constant shows the normal spinel ferrites behavior. • The dc conductivity are found to decrease with increasing temperature. • The samples with low conductivity have high values of activation energy. • The Impedance decreases with increasing frequency of applied field. - Abstract: Spinel ferrites with nominal composition MgPr{sub y}Fe{sub 2−y}O{sub 4} (y = 0.00, 0.025, 0.05, 0.075, 0.10) were prepared by sol-gel method. Temperature dependent DC electrical conductivity and drift mobility were found in good agreement with each other, reflecting semiconducting behavior. The dielectric properties of all the samples as a function of frequency (1 MHz–3 GHz) were measured at room temperature. The dielectric constant and complex dielectric constant of these samples decreased with the increase of praseodymium concentration. In the present spinel ferrite, Cole–Cole plots were used to separate the grain and grain boundary’s effects. The substitution of praseodymium ions in Mg-based spinel ferrites leads to a remarkable rise of grain boundary’s resistance as compared to the grain’s resistance. As both AC conductivity and Cole–Cole plots are the functions of concentration, they reveal the dominant contribution of grain boundaries in the conduction mechanism. AC activation energy was lower than dc activation energy. Temperature dependence normalized AC susceptibility of spinel ferrites reveals that MgFe{sub 2}O{sub 4} exhibits multi domain (MD) structure with high Curie temperature while on substitution of praseodymium, MD to SD transitions occurs. The low values of conductivity and low dielectric loss make these materials best candidate for high frequency application.
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International Nuclear Information System (INIS)
Sumi, S.; Prabhakar Rao, P.; Mahesh, S.K.; Koshy, Peter
2012-01-01
Graphical abstract: DC conductivity variation of CaCe 1−x Mn x SnNbO 7−δ (x = 0, 0.2, 0.4 and 0.6) with inverse of temperature. Variation of conductivity with Mn concentration at 600 °C is shown in the inset. Display Omitted Highlights: ► We have observed that the structural ordering as well as grain size increase with Mn substitution. ► Impedance analysis proved that a correlated barrier hopping type conduction mechanism is involved in the materials. ► Activation energy as well as electrical conductivity increases with increase in Mn substitution. ► Localization of electrons associated with Mn 2+ and structural ordering are the key factors for the increased activation energy with Mn substitution. ► All the materials showed good NTC thermistor properties. -- Abstract: A new series of manganese containing pyrochlore type semiconducting oxides CaCe 1−x Mn x SnNbO 7−δ (x = 0, 0.2, 0.4 and 0.6) have been synthesized to study the effect of Mn substitution on the structure, microstructure and electrical properties of these samples. X-ray diffraction and scanning electron microscopy studies revealed an increase of structural ordering and grain size respectively with increase of Mn substitution. Rietveld analysis and Raman spectroscopy were also employed to corroborate the XRD results. The bulk resistance measurements with temperature exhibit negative temperature coefficient behavior. The impedance analysis of the samples revealed a non-Debye type relaxation existed in the materials. The ac conductivity variation with temperature and frequency indicates a correlated barrier hopping type conduction mechanism in these materials. The barrier height and the intersite separation for hopping influence the electrical conductivity of these samples and are found to be a function of localization of electrons associated with the Mn 2+ ions and the unit cell volume respectively. The Mn substitution increases both electrical conductivity and activation energy
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Structural, dielectric and impedance characteristics of CoTiO{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Acharya, Truptimayee, E-mail: truptiacharya18@gmail.com; Choudhary, R.N.P.
2016-07-01
The present work reports the synthesis and characterization of the ilmenite-type rhombohedral structured CoTiO{sub 3} ceramic. The polycrystalline powder of CoTiO{sub 3} was prepared by the mixed-oxide technique. X-ray structural analysis of the compound confirmed the formation of a single-phase compound. The study of microstructure by scanning electron microscopy shows that the compound has well defined grains which are distributed uniformly throughout the surface. It shows that the grain size lies in the range of 8–10 μm. The Fourier transform infrared spectroscopy (FTIR) studies confirm the presence of Ti−O, Ti−O−Ti, Ti−O−O, Co−O bond in the studied compound. The frequency dependence of dielectric constant was explained on the basis of Maxwell–Wagner mechanism and Koop's phenomenological theory. The frequency-temperature dependence of impedance analysis shows that the bulk effect dominates up to 250 °C, and the appearance of second semicircular arc above 280 °C indicates the presence of grain boundary effect in the sample. The depressed semicircles in Nyquist plot with depression angles clearly indicate the distribution of relaxation times in the ceramic samples. It also shows that the material has negative temperature co-efficient of resistance similar to that of semiconductors. Similar behavior has also been observed in the study of I−V characteristics of the material. Through the study of dc conductivity of CoTiO{sub 3} and using the relation; ln σ{sub dc} α E{sub a}/K{sub B}T, activation energy of the compound was calculated. The frequency dependence of ac conductivity is explained on the basis of Correlated barrier Hopping Model. - Highlights: • The lattice parameters of CoTiO{sub 3} were determined by using Rietveld refinement method. • The frequency dependence of ε{sub r} was explained on the basis of Maxwell–Wagner model. • The depressed semicircles in Nyquist plot indicate the Non Debye-type response. • The
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International Nuclear Information System (INIS)
Makhnovskiy, D. P.; Panina, L. V.; Mapps, D. J.
2001-01-01
This article concerns the investigation of the magnetic behavior of the surface impedance tensor cflx var-sigma in CoSiB amorphous wires having a residual torsion stress and a helical anisotropy. The full tensor cflx var-sigma involving three different components is found by measuring the S 21 parameter at a required excitation with a Hewlett-Packard network/spectrum analyzer at MHz frequencies. In general, the impedance plots versus axial magnetic field H ex exhibit a hysteresis related to that for the case of static magnetization. The diagonal components of cflx var-sigma (longitudinal var-sigma zz and circular var-sigma v ar-phi v ar-phi) show a sharp peak in a narrow field interval where the domain walls form and contribute to the ac magnetization dynamics. This peak is not seen for the off-diagonal component var-sigma zv ar-phi (var-sigma v ar-phi z ) since the existence of the domain structure suppresses it. Applying a dc bias current results in a gradual transition to a nonhysteretic asymmetrical behavior with an enhanced sensitivity. The portions of the experimental plots associated with the rotational dynamic process are in qualitative agreement with the theory based on a single-domain model. [copyright] 2001 American Institute of Physics
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Cascaded impedance networks for NPC inverter
DEFF Research Database (Denmark)
Li, Ding; Gao, Feng; Loh, Poh Chiang
2010-01-01
they are subject to the renewable sources. To date, three distinct types of impedance networks can be summarized for implementing a hybrid source impedance network, which can in principle be combined and cascaded before connected to a NPC inverter by proposed two ways. The resulting cascaded impedance network NPC...
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Energy Technology Data Exchange (ETDEWEB)
Tian, Yahui [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Xue, Fei [Center of Collaboration and Innovation, Jiangxi University of Technology, Nanchang, Jiangxi 330098 (China); Fu, Qiuyun, E-mail: fuqy@mail.hust.edu.cn [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhou, Dongxiang; Hu, Yunxiang; Zhou, Ling; Zheng, Zhiping; Xin, Zengnian [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China)
2017-08-01
Highlights: • BGFO ceramics exhibited high density, strong ferroelectricity, and good magnetism. • BGFO ceramics exhibited typical relaxor behavior. • There are different conductivity mechanisms at different temperatures for BGFO. - Abstract: Multiferroic Bi{sub 0.8}Gd{sub 0.2}FeO{sub 3} (BGFO) ceramics were prepared by a rapid-liquid phase sintering process. BGFO ceramics can be sintered at a sintering temperature range of 875 °C–940 °C and shown a pure orthorhombic (space group, Pnma) structure. The crystal symmetry and lattice parameters were determined from the Rietveld analysis for the experimental data. BGFO ceramics sintered at 900 °C exhibited high theoretical relative density (∼98%), strong ferroelectricity and good magnetism. BGFO ceramics exhibited the similar dielectric relaxation properties to the typical relaxor ferroelectrics. The role of oxygen vacancies at high temperature in dielectric and ac conductivity behavior was also discussed. The diffusing of structure defects between the grain and grain boundary was established using Impedance Spectroscopy (IS).
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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)
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Impedance of finite length resistive cylinder
Directory of Open Access Journals (Sweden)
S. Krinsky
2004-11-01
Full Text Available We determine the impedance of a cylindrical metal tube (resistor of radius a, length g, and conductivity σ attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency (k≫1/a. In the equilibrium regime, ka^{2}≪g, the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity σ. In the transient regime, ka^{2}≫g, where the contribution of transition radiation arising from the discontinuity in conductivity is important, we derive an analytic expression for the impedance and compute the short-range wakefield. The analytic results are shown to agree with numerical evaluation of the impedance.
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Iwakuma, M; Funaki, K
2002-01-01
The ac loss properties of two-strand parallel conductors composed of superconducting multifilamentary strands were theoretically investigated. The constituent strands generally need to be insulated and transposed for the sake of uniform current distribution and low ac loss. In case the transposition points deviate from the optimum ones, shielding current is induced according to the interlinkage magnetic flux of the twisted loop enclosed by the insulated strands and the contact resistances at the terminals. It produces an additional ac loss. Supposing a simple situation where a two-strand parallel conductor with one-point transposition is exposed to a uniform ac magnetic field, the basic equations for the magnetic field were proposed and the theoretical expressions of the additional ac losses derived. As a result, the following features were shown. The additional ac loss in the non-saturation case, where the induced shielding current is less than the critical current of a strand, is proportional to the square ...
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AC conductivity of a quantum Hall line junction
International Nuclear Information System (INIS)
Agarwal, Amit; Sen, Diptiman
2009-01-01
We present a microscopic model for calculating the AC conductivity of a finite length line junction made up of two counter- or co-propagating single mode quantum Hall edges with possibly different filling fractions. The effect of density-density interactions and a local tunneling conductance (σ) between the two edges is considered. Assuming that σ is independent of the frequency ω, we derive expressions for the AC conductivity as a function of ω, the length of the line junction and other parameters of the system. We reproduce the results of Sen and Agarwal (2008 Phys. Rev. B 78 085430) in the DC limit (ω→0), and generalize those results for an interacting system. As a function of ω, the AC conductivity shows significant oscillations if σ is small; the oscillations become less prominent as σ increases. A renormalization group analysis shows that the system may be in a metallic or an insulating phase depending on the strength of the interactions. We discuss the experimental implications of this for the behavior of the AC conductivity at low temperatures.
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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.
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AC-Induced Bias Potential Effect on Corrosion of Steels
2009-02-05
induction, variable conduction Experimental Setup Super- martensitic stainless steel composition Analysis: C Mn Si Cr Ni Mo Cu N Typical 13 Cr ɘ.01 0.6... stainless steel used in pipelines. •Low carbon (ɘ.01): allows the formation of a “soft” martensite that is more resistant than standard martensitic ...Proposed AC Corrosion Models AC Simulated Corrosion testing Stainless steel pipe and coating Cathodic protection Experimental Setup Preliminary
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Energy Technology Data Exchange (ETDEWEB)
Ranjan, Rajiv [Department of Physics, J. Co-operative College, Kolhan University, Jharkhand 831036 (India); Kumar, Rajiv [Department of Physics, J. Worker' s College, Kolhan University, Jharkhand 831012 (India); Kumar, Nawnit [Department of Physics and Meteorology, IIT Kharagpur, West Bengal 721302 (India); Behera, Banarji [School of Physics, Sambalpur University, Jyoti Vihar, Bula 768019, Orissa (India); Choudhary, R.N.P., E-mail: crnpfl@gmail.com [Department of Physics, ITER, S.O.A. University, Bhubaneswar 751 013, Orissa (India)
2011-06-02
Highlights: > The PSZT ceramics with samarium were prepared by solid-state reaction technique. > Bulk resistive contribution is found to decrease with the increase in temperature. > PSZT ceramics exhibit NTCR type behavior usually found in semiconductors. > Modulus plots show the presence of grain boundary along with bulk contributions. > Impedance analysis has confirmed the presence of non-Debye type of relaxation. - Abstract: The polycrystalline ceramic samples of Pb{sub 1-x}Sm{sub x}(Zr{sub 0.55}Ti{sub 0.45}){sub 1-x/4}O{sub 3} (x = 0.00, 0.03, 0.06 and 0.09) were prepared by solid-state reaction technique at high temperature. Electric impedance (Z) and modulus (M) properties of the materials have been investigated within a wide range of temperature and frequency using complex impedance spectroscopy (CIS) technique. The complex impedance analysis has suggested the presence of mostly bulk resistive (grain) contributions in the materials. This bulk resistance is found to decrease with the increase in temperature. It indicates that the PSZT compounds exhibit a typical negative temperature coefficient of resistance (NTCR) behavior. The bulk contribution also exhibits an increasing trend with the increase in Sm{sup 3+} substitution to PZT. The complex modulus plots have confirmed the presence of grain (bulk) as well as grain boundary contributions in the materials. Both the complex impedance and modulus studies have suggested the presence of non-Debye type of relaxation in the materials.
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RHIC injection kicker impedance
International Nuclear Information System (INIS)
Mane, V.; Peggs, S.; Trbojevic, D.; Zhang, W.
1995-01-01
The longitudinal impedance of the RHIC injection kicker is measured using the wire method up to a frequency of 3 GHz. The mismatch between the 50 ohm cable and the wire and pipe system is calibrated using the TRL calibration algorithm. Various methods of reducing the impedance, such as coated ceramic pipe and copper strips are investigated
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Luczak, Susan E; Rosen, I Gary
2014-08-01
Transdermal alcohol sensor (TAS) devices have the potential to allow researchers and clinicians to unobtrusively collect naturalistic drinking data for weeks at a time, but the transdermal alcohol concentration (TAC) data these devices produce do not consistently correspond with breath alcohol concentration (BrAC) data. We present and test the BrAC Estimator software, a program designed to produce individualized estimates of BrAC from TAC data by fitting mathematical models to a specific person wearing a specific TAS device. Two TAS devices were worn simultaneously by 1 participant for 18 days. The trial began with a laboratory alcohol session to calibrate the model and was followed by a field trial with 10 drinking episodes. Model parameter estimates and fit indices were compared across drinking episodes to examine the calibration phase of the software. Software-generated estimates of peak BrAC, time of peak BrAC, and area under the BrAC curve were compared with breath analyzer data to examine the estimation phase of the software. In this single-subject design with breath analyzer peak BrAC scores ranging from 0.013 to 0.057, the software created consistent models for the 2 TAS devices, despite differences in raw TAC data, and was able to compensate for the attenuation of peak BrAC and latency of the time of peak BrAC that are typically observed in TAC data. This software program represents an important initial step for making it possible for non mathematician researchers and clinicians to obtain estimates of BrAC from TAC data in naturalistic drinking environments. Future research with more participants and greater variation in alcohol consumption levels and patterns, as well as examination of gain scheduling calibration procedures and nonlinear models of diffusion, will help to determine how precise these software models can become. Copyright © 2014 by the Research Society on Alcoholism.
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Stability Analysis for Isolated AC Microgrids Based on PV-Active Generators
DEFF Research Database (Denmark)
Aldana, Nelson Leonardo Diaz; Coelho, Ernane A. A.; Quintero, Juan Carlos Vasquez
2015-01-01
The current trend in isolated microgrids is oriented to distributed renewable energy generators, such as photovoltaic (PV) generators and their corresponding distributed energy storage systems (ESS) as an unit denoted as active generator (PV+ESS). In an isolated microgrid, every distributed...... for all the distributed generators. In particular, ESS’s based on batteries require at least two different mode of charge. As consequence, the topological operation mode of the microgrid is affected by the changes of the operation mode of each distributed generator. Typically, droop control loops are used...... for interconnecting several different distributed generators in parallel to a common bus, whose parameters determine the stability and damping of the microgrid operation. In this paper, a small-signal stability analysis is applied to an isolated AC microgrid composed of (PV+ESS) active generators, regarding three...
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Impedance-based analysis and study of phase sensitivity in slow-wave two-beam accelerators
International Nuclear Information System (INIS)
Wurtele, J.S.; Whittum, D.H.; Sessler, A.M.
1992-06-01
This paper presents a new formalism which makes the analysis and understanding of both the relativistic klystron (RK) and the standing-wave free-electron laser (SWFEL) two-beam accelerator (TBA) available to a wide audience of accelerator physicists. A ''coupling impedance'' for both the RK and SWFEWL is introduced, which can include realistic cavity features, such as beam and vacuum ports, in a simple manner. The RK and SWFEL macroparticle equations, which govern the energy and phase evolution of successive bunches in the beam, are of identical form, differing only by multiplicative factors. Expressions are derived for the phase and amplitude sensitivities of the TBA schemes to errors (shot-to-shot jitter) in current and energy. The analysis allows, for the first time, relative comparisons of the RK and the SWFEL TBAs
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Impedance studies of a green blend polymer electrolyte based on PVA and Aloe-vera
Selvalakshmi, S.; Mathavan, T.; Vijaya, N.; Selvasekarapandian, Premalatha, M.; Monisha, S.
2016-05-01
The development of polymer electrolyte materials for energy generating and energy storage devices is a challenge today. A new type of blended green electrolyte based on Poly-vinyl alcohol (PVA) and Aloe-vera has been prepared by solution casting technique. The blending of polymers may lead to the increase in stability due to one polymer portraying itself as a mechanical stiffener and the other as a gelled matrix supported by the other. The prepared blend electrolytes were subjected to Ac impedance studies. It has been found out that the polymer film in which 1 gm of PVA was dissolved in 40 ml of Aloe-vera extract exhibits highest conductivity and its value is 3.08 × 10-4 S cm-1.
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Detection of high-impedance fault in low-voltage DC distribution system via mathematical morphology
Directory of Open Access Journals (Sweden)
Yun-Sik Oh
2016-01-01
Full Text Available This study presents a method for high-impedance fault (HIF detection in a low-voltage DC (LVDC distribution system via mathematical morphology (MM, which is composed of two elementary transformations, namely, dilation and erosion. Various MM-based filters are used to detect abnormal signals of current waveform. The LVDC distribution system, including power conversion devices, such as AC/DC and DC/DC converters, is modelled with electromagnetic transient program (EMTP software to verify the proposed method. The HIF arc model in the DC system is also implemented with EMTP/MODELS, which is a symbolic language interpreter for EMTP. Simulation results show that the proposed method can be applied to detect HIF effectively in the LVDC distribution system.
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Concentric artificial impedance surface for directional sound beamforming
Directory of Open Access Journals (Sweden)
Kyungjun Song
2017-03-01
Full Text Available Utilizing acoustic metasurfaces consisting of subwavelength resonant textures, we design an artificial impedance surface by creating a new boundary condition. We demonstrate a circular artificial impedance surface with surface impedance modulation for directional sound beamforming in three-dimensional space. This artificial impedance surface is implemented by revolving two-dimensional Helmholtz resonators with varying internal coiled path. Physically, the textured surface has inductive surface impedance on its inner circular patterns and capacitive surface impedance on its outer circular patterns. Directional receive beamforming can be achieved using an omnidirectional microphone located at the focal point formed by the gradient-impeding surface. In addition, the uniaxial surface impedance patterning inside the circular aperture can be used for steering the direction of the main lobe of the radiation pattern.
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Tapping mode microwave impedance microscopy
Lai, K.; Kundhikanjana, W.; Peng, H.; Cui, Y.; Kelly, M. A.; Shen, Z. X.
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
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THE ACS NEARBY GALAXY SURVEY TREASURY
International Nuclear Information System (INIS)
Dalcanton, Julianne J.; Williams, Benjamin F.; Rosema, Keith; Gogarten, Stephanie M.; Christensen, Charlotte; Gilbert, Karoline; Hodge, Paul; Seth, Anil C.; Dolphin, Andrew; Holtzman, Jon; Skillman, Evan D.; Weisz, Daniel; Cole, Andrew; Girardi, Leo; Karachentsev, Igor D.; Olsen, Knut; Freeman, Ken; Gallart, Carme; Harris, Jason; De Jong, Roelof S.
2009-01-01
The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D 4 in luminosity and star formation rate. The survey data consist of images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST), supplemented with archival data and new Wide Field Planetary Camera 2 (WFPC2) imaging taken after the failure of ACS. Survey images include wide field tilings covering the full radial extent of each galaxy, and single deep pointings in uncrowded regions of the most massive galaxies in the volume. The new wide field imaging in ANGST reaches median 50% completenesses of m F475W = 28.0 mag, m F606W = 27.3 mag, and m F814W = 27.3 mag, several magnitudes below the tip of the red giant branch (TRGB). The deep fields reach magnitudes sufficient to fully resolve the structure in the red clump. The resulting photometric catalogs are publicly accessible and contain over 34 million photometric measurements of >14 million stars. In this paper we present the details of the sample selection, imaging, data reduction, and the resulting photometric catalogs, along with an analysis of the photometric uncertainties (systematic and random), for both ACS and WFPC2 imaging. We also present uniformly derived relative distances measured from the apparent magnitude of the TRGB.
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Development of a real-time, semi-capacitive impedance phlebography device
Directory of Open Access Journals (Sweden)
Sören Niklas Weyer
2015-04-01
Full Text Available Chronic venous insufficiency of the lower limbs is a disease which is caused by an increased blood pressure inside the veins of the leg and the resulting increase of the contained blood volume.This work focuses on developing a device which uses impedance plethysmography to obtain information about the blood volume in the lower leg and provides the possibility to measure the impedance semi contact-less, e.g. through compression stockings. Furthermore a real-time beat-to-beat interval detection algorithm was implemented. Finally, the function of the developed impedance measuring system and the whole system was verified by comparing it with a gold standard.In comparison to the conductive coupling, the system performed similarly. The analysis showed that the developed system is suitable for semi-capacitive IPG. The algorithm was implemented conservatively since it provided a good false-positive rate of 0%, but only a moderate sensitivity of about 68%.Reliable and continuous measurement of the pulse signal was only possible in periods of immobility.Chronic venous insufficiency of the lower limbs is a disease which is caused by an increased blood pressure inside the veins of the leg and the resulting increase of the contained blood volume.\\\\ This work focuses on developing a device which uses impedance plethysmography to obtain information about the blood volume in the lower leg and provides the possibility to measure the impedance semi contact-less, e.g. through compression stockings. Furthermore a real-time beat-to-beat interval detection algorithm was implemented. Finally, the function of the developed impedance measuring system and the whole system was verified by comparing it with a gold standard.\\\\ In comparison to the conductive coupling, the system performed similarly. The analysis showed that the developed system is suitable for semi-capacitive IPG. The algorithm was implemented conservatively since it provided a good false-positive rate
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Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes
International Nuclear Information System (INIS)
Liu, F. B.; Jing, B.; Cui, Y.; Di, J. J.; Qu, M.
2015-01-01
The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond film are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed
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Energy Technology Data Exchange (ETDEWEB)
Sarwar, T., E-mail: sarwartuba@gmail.com [EMMG, Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Qamar, A., E-mail: afzaal.qamar@griffithuni.edu.au [Queensland Micro-Nanotechnology Centre, Griffith University, Nathan, QLD 4111 (Australia); Nadeem, M. [EMMG, Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)
2017-07-15
Highlights: • Electronic & magnetic behavior of Nd{sub 0.5}Ca{sub 0.5}MnO{sub 3} is explored using impedance spectroscopy. • Under ac field, possible signature of suppression of robust CO/OO antiferromagnetism is studied. • We propose the existence of spin glass state at low temperature. • A novel tactic is used to estimate the existence of weak ferromagnetism at high temperature. - Abstract: Dynamics of spin ordering in the manganite Nd{sub 0.5}Ca{sub 0.5}MnO{sub 3} have been investigated in this paper. It was observed that the complex mixed magnetic ordering in pellets is comprised of antiferromagnetic ordering at 160 K (T{sub N}) and complete charge ordering at 250 K (T{sub CO}). Under ac field, appearance of unstable ferromagnetic correlations is observed above T{sub CO}, which is badly frustrated due to strong spin disorder induced by Jahn Teller distortions. Impedance measurements reveal the spin glass like scenario, suppressing the strong antiferromagnetic and charge ordering states below T{sub N}.
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Antifriction coatings based on a-C for biomedicine applications
International Nuclear Information System (INIS)
Yurjev, Y N; Kiseleva, D V; Zaitcev, D A; Sidelev, D V; Korneva, O S
2016-01-01
This article reports on the investigation of mechanical properties of carbon films deposited by dual magnetron sputtering system with closed and mirror magnetic field. There is shown that a-C films with predominantly sp 2 -phase have relatively high hardness (up to 20 GPa) and low friction index (∼0.01). The influence of magnetic field on friction index is determined. The analysis of experimental data shows the obtained a-C samples can be used for biomedicine applications. (paper)
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Magneto-Impedance behavior of Co-Fe-Nb-Si-B-based ribbons
Energy Technology Data Exchange (ETDEWEB)
Sarkar, Partha; Mohanta, O.; Pal, S.K.; Panda, A.K. [National Metallurgical Laboratory, Council of Scientific and Industrial Research, Jamshedpur 831007 (India); Mitra, A., E-mail: amitra@nmlindia.or [National Metallurgical Laboratory, Council of Scientific and Industrial Research, Jamshedpur 831007 (India)
2010-04-15
The giant magneto-impedance of melt spun Co{sub x}Fe{sub 72-x}Nb{sub 4}Si{sub 4}B{sub 20}(x=10, 20, 36, 50) amorphous and nanostructured ribbons have been investigated. Alloys have been optimized at the driving current amplitude, frequency and found that amorphous ribbon of nominal composition of Co{sub 36}Fe{sub 36}Nb{sub 4}Si{sub 4}B{sub 20} shown maximum GMI ratio of 13%. The behaviour of the driving current amplitude on the GMI behaviour was studied and the sample was optimized for driving current amplitude, I{sub ac}=10 mA. The frequency dependence of the GMI behaviour was studied for the ribbon sample Co{sub 36}Fe{sub 36}Nb{sub 4}Si{sub 4}B{sub 20} at frequency in the range of 100 kHz-1.2 MHz of the optimized driving current amplitude and it was found that the sample showed the maximum GMI behaviour at f=700 kHz. The optimized samples were Joule heated at the current density J=0-35 A/m{sup 2} for a period of 1 min. The GMI ratio initially increased then progressively deteriorated with J, but after a certain range it shows up to 16% of improvement in the magneto-impedance value due the increase of nanocrystalline volume fraction. The asymmetry in the GMI profile was observed for the sample Joule heated at J=1-5 A/m{sup 2} for 1 min.
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Bera, Tushar Kanti
2016-03-18
Abstract: Electrical impedance tomography (EIT) phantoms are essential for the calibration, comparison and evaluation of the EIT systems. In EIT, the practical phantoms are typically developed based on inhomogeneities surrounded by a homogeneous background to simulate a suitable conductivity contrast. In multifrequency EIT (Mf-EIT) evaluation, the phantoms must be developed with the materials which have recognizable or distinguishable impedance variations over a wide range of frequencies. In this direction the impedance responses of the saline solution (background) and a number vegetable and fruit tissues (inhomogeneities) are studied with electrical impedance spectroscopy (EIS) and the frequency responses of bioelectrical impedance and conductivity are analyzed. A number of practical phantoms with different tissue inhomogeneities and different inhomogeneity configurations are developed and the multifrequency impedance imaging is studied with the Mf-EIT system to evaluate the phantoms. The conductivity of the vegetable inhomogeneities reconstructed from the EIT imaging is compared with the conductivity values obtained from the EIS studies. Experimental results obtained from multifrequency EIT reconstruction demonstrate that the electrical impedance of all the biological tissues inhomogenity decreases with frequency. The potato tissue phantom produces better impedance image in high frequency ranges compared to the cucumber phantom, because the cucumber impedance at high frequency becomes lesser than that of the potato at the same frequency range. Graphical Abstract: [Figure not available: see fulltext.] © 2016 The Visualization Society of Japan
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Directory of Open Access Journals (Sweden)
Zhong Chen
2017-08-01
Full Text Available A conventional steady-state power flow security check only implements point-by-point assessment, which cannot provide a security margin for system operation. The concept of a steady-state security region is proposed to effectively tackle this problem. Considering that the commissioning of the increasing number of HVDC (High Voltage Direct Current and the fluctuation of renewable energy have significantly affected the operation and control of a conventional AC system, the definition of the steady-state security region of the AC/DC power system is proposed in this paper based on the AC/DC power flow calculation model including LCC/VSC (Line Commutated Converter/Voltage Sourced Converter-HVDC transmission and various AC/DC constraints, and hence the application of the security region is extended. In order to ensure that the proposed security region can accurately provide global security information of the power system under the fluctuations of renewable energy, this paper presents four methods (i.e., a screening method of effective boundary surfaces, a fitting method of boundary surfaces, a safety judging method, and a calculation method of distances and corrected distance between the steady-state operating point and the effective boundary surfaces based on the relation analysis between the steady-state security region geometry and constraints. Also, the physical meaning and probability analysis of the corrected distance are presented. Finally, a case study is demonstrated to test the feasibility of the proposed methods.
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Energy Technology Data Exchange (ETDEWEB)
Pyun, Su Il; Moon, S. M.; Orr, S. J.; Kim, D. J.; Lee, W. J.; Jeong, I. J.; Shin, H. C.; Han, J. N.; Lee, M. H.; Lee, S. B. [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)
1998-01-01
Pitting corrosion of sensitized 316L stainless steel has been investigated as a function of the degree of sensitization in aqueous NaCl solution with various Cl{sup -} ion concentrations ([Cl{sup -}] = 0.005 (177.25 ppm); 0.01 (354.50 ppm); 0.05 (1772.5 ppm); 0.1 (3545 ppm); 0.5 M (17725 ppm)) at room temperature. The squared rod specimens of 316L stainless steel were thermally annealed at 700 C for various durations (0 h : non-sensitized specimen A; 8 h : moderately sensitized specimen B; 96 h : severely sensitized specimen C). The pitting corrosion resistance of the three kinds of specimens was evaluated by the potentio dynamic anodic polarization method, abrading electrode technique and ac{sup -}impedance spectroscopy. The measured potentiostatic decay current transient obtained just after interrupting the abrading action showed that the repassivation rate of the oxide film on the fresh bare surface of the specimen decreased in the order of specimens A, B and C in the early stage of the film formation. From the results of ac{sup -}impedance spectroscopy, the oxide film resistance R{sub ox} and oxide film capacitance C{sub ox} of specimens B and C in value were evaluated to be lower and higher, respectively, than those of specimen A and the repassivation rate and resistance value of the oxide film on the three kinds could be quantitatively calculated. 10 refs., 8 tabs., 31 figs.(author)
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RHIC spin flipper AC dipole controller
Energy Technology Data Exchange (ETDEWEB)
Oddo, P.; Bai, M.; Dawson, C.; Gassner, D.; Harvey, M.; Hayes, T.; Mernick, K.; Minty, M.; Roser, T.; Severino, F.; Smith, K.
2011-03-28
The RHIC Spin Flipper's five high-Q AC dipoles which are driven by a swept frequency waveform require precise control of phase and amplitude during the sweep. This control is achieved using FPGA based feedback controllers. Multiple feedback loops are used to and dynamically tune the magnets. The current implementation and results will be presented. Work on a new spin flipper for RHIC (Relativistic Heavy Ion Collider) incorporating multiple dynamically tuned high-Q AC-dipoles has been developed for RHIC spin-physics experiments. A spin flipper is needed to cancel systematic errors by reversing the spin direction of the two colliding beams multiple times during a store. The spin flipper system consists of four DC-dipole magnets (spin rotators) and five AC-dipole magnets. Multiple AC-dipoles are needed to localize the driven coherent betatron oscillation inside the spin flipper. Operationally the AC-dipoles form two swept frequency bumps that minimize the effect of the AC-dipole dipoles outside of the spin flipper. Both AC bumps operate at the same frequency, but are phase shifted from each other. The AC-dipoles therefore require precise control over amplitude and phase making the implementation of the AC-dipole controller the central challenge.
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Structural and impedance spectroscopic studies of samarium modified lead zirconate titanate ceramics
Energy Technology Data Exchange (ETDEWEB)
Ranjan, Rajiv [Department of Physics, Jamshedpur Co-operative College, Jamshedpur 831036 (India); Kumar, Rajiv [Department of Physics, Jamshedpur Worker' s College, Jamshedpur 831012 (India); Behera, Banarji [Department of Physics and Meteorology, I.I.T. Kharagpur 721302 (India); Choudhary, R.N.P., E-mail: crnpfl@phy.iitkgp.ernet.i [Department of Physics and Meteorology, I.I.T. Kharagpur 721302 (India)
2009-11-01
The polycrystalline samples of Pb{sub 1-x}Sm{sub x}(Zr{sub 0.60}Ti{sub 0.40}){sub 1-x/4}O{sub 3} (PSZT) where x=0.00, 0.03, 0.06 and 0.09 were prepared by a high-temperature solid-state reaction technique. The preliminary structural analysis using X-ray diffraction (XRD) data collected at room temperature has confirmed the formation of single-phase compounds in tetragonal crystal system. The morphological study of each sample using scanning electron microscope (SEM) has revealed that the grains are uniformly distributed through out the surfaces of the samples. Using complex impedance spectroscopy (CIS) technique, the electrical impedance and modulus properties of the materials were studied in a wide range of temperatures at different frequencies. The impedance analysis indicates the presence of bulk resistive contributions in the materials which is found to decrease on increasing temperature. The nature of variation of resistances with temperature suggests a typical negative temperature coefficient of resistance (NTCR) type behavior of the materials. The complex modulus plots clearly exhibits the presence of grain boundaries along with the bulk contributions in the PSZT materials. The presence of non-Debye type of relaxation has been confirmed by the complex impedance analysis. The variation of dc conductivity (bulk) with temperature demonstrates that the compounds exhibit Arrhenius type of electrical conductivity.
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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.
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Evaluation of electrical impedance ratio measurements in accuracy of electronic apex locators.
Kim, Pil-Jong; Kim, Hong-Gee; Cho, Byeong-Hoon
2015-05-01
The aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL). The literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC) in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions. Among the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model. Using the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC.
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Bera, Tushar Kanti; Nagaraju, J.; Lubineau, Gilles
2016-01-01
. In this direction the impedance responses of the saline solution (background) and a number vegetable and fruit tissues (inhomogeneities) are studied with electrical impedance spectroscopy (EIS) and the frequency responses of bioelectrical impedance and conductivity
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Liu Shuyi; Deng Xiang; Jiang Zili; Tang Yu
2016-01-01
The hardware design of tuber electrical resistance tomography (TERT) system is one of the key research problems of TERT data acquisition system. The TERT system can be applied to the tuber growth process monitoring in agriculture, i.e., the TERT data acquisition system can realize the real imaging of tuber plants in soil. In TERT system, the imaging tuber and soil multiphase medium is quite complexity. So, the impedance test and analysis of soil multiphase medium is very important to the desi...
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Impedance function of a group of vertical piles
International Nuclear Information System (INIS)
Wolf, J.P.; Arx, G.A. von
1978-01-01
Impedance and transfer functions of a group of vertical piles located in any desired configuration in plan in a horizontally stratified soil layer are derived. Hysteretic and radiation damping are accounted for. The method separates the piles and the soil, introducing unknown interaction forces. The total flexibility matrix of the soil is constructed, superposing the (complex) flexibility coefficients caused by the interaction forces of a single pile only. The dependence of the impedance and transfer functions on the oscllating frequency for foundations with different numbers of piles is investigated. Pile-soil-pile interaction is shown to be very important for all modes of vibration. The procedure is used in the seismic analysis of a reactor building. (Author)
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Intraesophageal impedance monitoring: clinical studies
Conchillo Armendáriz, J.M.
2007-01-01
Electrical impedance (Z) between two electrodes is the ratio between applied voltage (U) and resulting current (I). In electrical impedance monitoring the resistance to electrical flow in an alternating current circuit is measured. Multichannel esophageal monitoring can be measured by using an
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Plasma antennas driven by 5–20 kHz AC power supply
Energy Technology Data Exchange (ETDEWEB)
Zhao, Jiansen, E-mail: 67093058@qq.com; Chen, Yuli; Sun, Yang; Wu, Huafeng; Liu, Yue; Yuan, Qiumeng [Merchant Marine College, Shanghai Maritime University, Shanghai, 201306 (China)
2015-12-15
The experiments described in this work were performed with the aim of introducing a new plasma antenna that was excited by a 5–20 kHz alternating current (AC) power supply, where the antenna was transformed into a U-shape. The results show that the impedance, voltage standing-wave ratio (VSWR), radiation pattern and gain characteristics of the antenna can be controlled rapidly by varying not only the discharge power, but also by varying the discharge frequency in the range from 5 to 20 kHz. When the discharge frequency is adjusted from 10 to 12 kHz, the gain is higher within a relatively broad frequency band and the switch-on time is less than 1 ms when the discharge power is less than 5 W, meaning that the plasma antenna can be turned on and off rapidly.
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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 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...... through a RLS-algorithm. The algorithms have been tested and implemented on a PC at a 132 kV substation supplying a rolling mill. Knowing the short-circuit impedance gives the rolling mill an opportunity to adjust the arc furnace operation to keep flicker below a certain level. Therefore, the PC performs...
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Journal bearing impedance descriptions for rotordynamic applications
Childs, D.W.; Moes, H.; Leeuwen, van H.J.
1977-01-01
Bearing impedance vectors are introduced for plain journal bearings which define the bearing reaction force components as a function of the bearing motion. Impedance descriptions are developed directly for the approximate Ocvirk (short) and Sommerfeld (long) bearing solutions. The impedance vector
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Impedance of porous IT-SOFC LSCF:CGO composite cathodes
DEFF Research Database (Denmark)
Nielsen, Jimmi; Jacobsen, Torben; Wandel, Marie
2011-01-01
The impedance of technological relevant LSCF:CGO composite IT-SOFC cathodes was studied over a very wide performance range. This was experimentally achieved by impedance measurements on symmetrical cells with three different microstructures in the temperature range 550–850 °C. In order to account...... for the impedance spectra of the poor performing cathodes the Finite-Length-Gerischer (FLG) impedance was derived and applied to the impedance data. The FLG impedance describes for a given microstructure the situation where the cathode is made too thin from a cathode development point of view. The moderate...... performing cathodes showed a slightly suppressed Gerischer impedance, while the impedance spectra of the well performing cathodes showed the presence of an arc due to oxygen gas diffusion. The overall impedance of the well performing cathodes could be described with a slightly suppressed Gerischer impedance...
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Energy Technology Data Exchange (ETDEWEB)
United States. Bonneville Power Administration.
1994-01-01
Bonneville Power Administration (BPA) is considering action in two areas: (1) non-Federal access to the AC Intertie, and, (2) BPA Intertie marketing. BPA`s preferred alternative for non-Federal access is the Capacity Ownership alternative combined with the Increased Assured Delivery -- Access for Non-Scheduling Utilities alternative; the preferred alternative for BPA Intertie marketing is the Federal Marketing and Joint Ventures alternative. BPA considered these two areas previously in its Intertie Development and Use EIS of April 1988. The EIS resulted in BPA decisions to participate in the construction of the Third AC Intertie, to allow non-Federal access to BPA`s share of the Pacific Northwest-Pacific Southwest (PNW-PSW) Intertie (AC and DC lines) pursuant to a Long-Term Intertie Access Policy (LTIAP), and to pursue BPA`s export marketing alternative. The decision on allowing direct financial non-Federal participation in the Third AC line was deferred to a later, separate process, examined here. Also, BPA`s export marketing objectives must now be examined in view of changed operations of Columbia River hydro facilities for improved fish survival.
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Real-time impedance analysis of silica nanowire toxicity on epithelial breast cancer cells.
Alexander, Frank A; Huey, Eric G; Price, Dorielle T; Bhansali, Shekhar
2012-12-21
Silica nanowires have great potential for usage in the development of highly sensitive in vivo biosensors used for biomarker monitoring. However, careful analysis of nanowire toxicity is required prior to placing these sensors within the human body. This paper describes a real-time and quantitative analysis of nanowire cytotoxicity using impedance spectroscopy; improving upon studies that have utilized traditional endpoint assays. Silica nanowires were grown using the vapor liquid solid (VLS) method, mixed with Dulbecco's Modified Eagle Medium (DMEM) and exposed to Hs578T epithelial breast cancer cells at concentrations of 0 μg ml(-1), 1 μg ml(-1), 50 μg ml(-1) and 100 μg ml(-1). Real-time cellular responses to silica nanowires confirm that while not cytotoxic, silica nanowires at high concentrations (≥50 μg ml(-1)) are toxic to cells, and also suggest that cell death is due to mechanical disturbances of high numbers of nanowires.
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Study of dielectric relaxation and AC conductivity of InP:S single crystal
El-Nahass, M. M.; Ali, H. A. M.; El-Shazly, E. A.
2012-07-01
The dielectric relaxation and AC conductivity of InP:S single crystal were studied in the frequency range from 100 to 5.25 × 105 Hz and in the temperature range from 296 to 455 K. The dependence of the dielectric constant (ɛ1) and the dielectric loss (ɛ2) on both frequency and temperature was investigated. Since no peak was observed on the dielectric loss, we used a method based on the electric modulus to evaluate the activation energy of the dielectric relaxation. Scaling of the electric modulus spectra showed that the charge transport dynamics is independent of temperature. The AC conductivity (σAC) was found to obey the power law: Aωs. Analysis of the AC conductivity data and the frequency exponent showed that the correlated barrier hopping (CBH) model is the dominant mechanism for the AC conduction. The variation of AC conductivity with temperature at different frequencies showed that σAC is a thermally activated process.
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Perry, Nicola H; Kim, Jae Jin; Tuller, Harry L
2018-01-01
We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi 0.65 Fe 0.35 O 3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe 4+ ) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The k chem values obtained by OTR were significantly lower than the AC-IS derived k chem values and k q values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in k chem and k q values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived k chem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ , and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films.
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Perry, Nicola H.; Kim, Jae Jin; Tuller, Harry L.
2018-01-01
Abstract We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi0.65Fe0.35O3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe4+) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The kchem values obtained by OTR were significantly lower than the AC-IS derived kchem values and kq values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in kchem and kq values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived kchem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ, and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films. PMID:29511391
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Energy Technology Data Exchange (ETDEWEB)
Zhao, Yanlin [Department of Thermal Energy Engineering, College of Mechanical and Transportation Engineering, China University of Petroleum, Beijing, 102249 (China); Wang, Mi [Institute of Particle Science and Engineering, School of Process, Environmental and Materials Engineering, University of Leeds, Leeds LS2 9JT (China); Yao, Jun [School of Energy Research, Xiamen University, Xiamen 361005 (China)
2014-04-11
Electrical impedance tomography (EIT) is one of the process tomography techniques to provide an on-line non-invasive imaging for multiphase flow measurement. With EIT measurements, the images of impedance real part, impedance imaginary part, phase angle, and magnitude can be obtained. However, most of the applications of EIT in the process industries rely on the conductivity difference between two phases in fluids to obtain the concentration profiles. It is not common to use the imaginary part or phase angle due to the dominant change in conductivity or complication in the use of other impedance information. In a solid-liquid two phases system involving nano- or submicro-particles, characterisation of particles (e.g. particle size and concentration) have to rely on the measurement of impedance phase angle or imaginary part. Particles in a solution usually have an electrical double layer associated with their surfaces and can form an induced electrical dipole moment due to the polarization of the electrical double layer under the influence of an alternating electric field. Similar to EIT, electrical impedance spectroscopy (EIS) measurement can record the electrical impedance data, including impedance real part, imaginary part and phase angle (θ), which are caused by the polarization of the electrical double layer. These impedance data are related to the particle characteristics e.g. particle size, particle and ionic concentrations in the aqueous medium, therefore EIS method provides a capability for characterising the particles in suspensions. Electrical impedance tomography based on EIS measurement or namely, electrical impedance tomography spectroscopy (EITS) could image the spatial distribution of particle characteristics. In this paper, a new method, including test set-up and data analysis, for characterisation of particles in suspensions are developed through the experimental approach. The experimental results on tomographic imaging of colloidal particles
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Design and AC loss analysis of a superconducting synchronous motor
Energy Technology Data Exchange (ETDEWEB)
Jiang, Q [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom); Majoros, M [Department of Materials Science and Engineering, Ohio State University (United States); Hong, Z [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom); Campbell, A M [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom); Coombs, T A [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)
2006-11-15
This paper gives a conceptual design of a superconducting synchronous motor consisting of both high-temperature superconducting rotating field winding and armature winding. The AC losses of the armature winding of the motor have been investigated experimentally and numerically, by considering the self-field of the superconducting coils and the rotating magnetic field exposed on the armature winding. The recent developments of YBCO-coated conductors present the possibility of achieving a wholly superconducting machine of significantly smaller size and weight than a conventional machine. Both the rotating field winding and the armature winding are composed of YBCO high-temperature superconducting (HTS) coils. A low AC loss armature winding design has been developed for this superconducting synchronous motor. The performance of the machine was investigated by modelling with the finite-element method. The machine's torque is calculated from first principles by considering the angle between the field and the armature main flux lines.
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Grid impedance detection via excitation of LCL-filter resonance
DEFF Research Database (Denmark)
Liserre, Marco; Blaabjerg, Frede; Teodorescu, Remus
2005-01-01
Inverters adopted in distributed power generation, active filter and UPS are often connected to the grid through an LCL-fiIter. The impedance of the LCL-fiIter has a typical frequency spectrum with a resonance peak. Hence the LCL-fiIter has to be damped in order to avoid instability. However...... the resonance of the LCL-fiIter can be also excited in a controlled way in order to individuate the resonance frequency in the spectrum (using for example the FFn. This paper proposes to use a controlled excitation to measure the grid impedance, since this one influences also the resonance frequency. This paper...... will address some possible limits, some solutions and some implementation issues (e.g. how to obtain a controlled resonance in the filter without damaging the system) in order to use the resonant peak for grid impedance detection. The analysis is validated both by simulations and experimental results....
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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)
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Fast FPGA Implementation of an Original Impedance Analyser
Directory of Open Access Journals (Sweden)
Abdulrahman HAMED
2011-02-01
Full Text Available This article describes in detail the design and rapid prototyping of an embedded impedance analyzer. The measurement principle is based on the feedback control of the excitation voltage VD during a fast frequency sweeping. This function is carried out by a high precision synthesizer whose output resistance RG is digitally adjustable. Real and imaginary parts of the dipole impedance are determined from RG and the phase of VD. The digital architecture design uses the hardware-in-the-loop simulation in which the dipole is modeled using an RLC parallel circuit and a Butterworth Van Dyke structure. All digital functions are implemented on a Stratix II FPGA board with a 100 MHz frequency clock. The parameters taken into account are the frequency range (0 to 5 MHz, speed and resolution of the analysis and the quality factor of the resonant dipole. To reduce the analysis duration, the frequency sweeping rate is adjusted in real time.
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The AC photovoltaic module is here!
Strong, Steven J.; Wohlgemuth, John H.; Wills, Robert H.
1997-02-01
This paper describes the design, development, and performance results of a large-area photovoltaic module whose electrical output is ac power suitable for direct connection to the utility grid. The large-area ac PV module features a dedicated, integrally mounted, high-efficiency dc-to-ac power inverter with a nominal output of 250 watts (STC) at 120 Vac, 60 H, that is fully compatible with utility power. The module's output is connected directly to the building's conventional ac distribution system without need for any dc wiring, string combiners, dc ground-fault protection or additional power-conditioning equipment. With its advantages, the ac photovoltaic module promises to become a universal building block for use in all utility-interactive PV systems. This paper discusses AC Module design aspects and utility interface issues (including islanding).
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Impedance Changes Indicate Proximal Ventriculoperitoneal Shunt Obstruction In Vitro.
Basati, Sukhraaj; Tangen, Kevin; Hsu, Ying; Lin, Hanna; Frim, David; Linninger, Andreas
2015-12-01
Extracranial cerebrospinal fluid (CSF) shunt obstruction is one of the most important problems in hydrocephalus patient management. Despite ongoing research into better shunt design, robust and reliable detection of shunt malfunction remains elusive. The authors present a novel method of correlating degree of tissue ingrowth into ventricular CSF drainage catheters with internal electrical impedance. The impedance based sensor is able to continuously monitor shunt patency using intraluminal electrodes. Prototype obstruction sensors were fabricated for in-vitro analysis of cellular ingrowth into a shunt under static and dynamic flow conditions. Primary astrocyte cell lines and C6 glioma cells were allowed to proliferate up to 7 days within a shunt catheter and the impedance waveform was observed. During cell ingrowth a significant change in the peak-to-peak voltage signal as well as the root-mean-square voltage level was observed, allowing the impedance sensor to potentially anticipate shunt malfunction long before it affects fluid drainage. Finite element modeling was employed to demonstrate that the electrical signal used to monitor tissue ingrowth is contained inside the catheter lumen and does not endanger tissue surrounding the shunt. These results may herald the development of "next generation" shunt technology that allows prediction of malfunction before it affects patient outcome.
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Road Impedance Model Study under the Control of Intersection Signal
Directory of Open Access Journals (Sweden)
Yunlin Luo
2015-01-01
Full Text Available Road traffic impedance model is a difficult and critical point in urban traffic assignment and route guidance. The paper takes a signalized intersection as the research object. On the basis of traditional traffic wave theory including the implementation of traffic wave model and the analysis of vehicles’ gathering and dissipating, the road traffic impedance model is researched by determining the basic travel time and waiting delay time. Numerical example results have proved that the proposed model in this paper has received better calculation performance compared to existing model, especially in flat hours. The values of mean absolute percentage error (MAPE and mean absolute deviation (MAD are separately reduced by 3.78% and 2.62 s. It shows that the proposed model has feasibility and availability in road traffic impedance under intersection signal.
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Directory of Open Access Journals (Sweden)
Marcela C. Quevedo
2018-04-01
Full Text Available The effect of flow on the corrosion of Al–14 wt% Zn–8 wt% Mg alloy in aerated synthetic seawater at ambient temperature was studied using a rotating cylinder electrode (RCE under turbulent regime conditions by means of electrochemical impedance spectroscopy (EIS. The overall electrochemical corrosion process was found to be strongly influenced by the oxygen mass transfer process under turbulent flow conditions on the cathodic kinetics, driving to a significant increase in corrosion rate.At corrosion potential, Ecorr value, contributions from the anodic and cathodic processes involved were observed in the impedance diagrams. Instead, at a cathodic potential of −1.2 V (sce, impedance measurements proved the predominance of the mass-transfer process for oxygen. A primary analysis of the impedance plots allowed to confirm such situation. Keywords: Aluminum alloy, Corrosion, EIS, Flow, Oxygen, Mass transfer, Rotating cylinder electrode, Seawater
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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 traditional tapered line transformers. This flexibility of the broadband nonsynchronous noncommensurate impedance transformers is experimentally demonstrated in this article allowing the length reduction by almost three times. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1832–1835, 2012; View...
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DEFF Research Database (Denmark)
Nielsen, Jimmi; Hjelm, Johan
2014-01-01
It was shown through a comprehensive impedance spectroscopy study that the impedance of the classic composite LSM:YSZ (lanthanum strontium manganite and yttria stabilized zirconia) solid oxide fuel cell (SOFC) cathode can be described well with porous electrode theory. Furthermore, it was illustr......It was shown through a comprehensive impedance spectroscopy study that the impedance of the classic composite LSM:YSZ (lanthanum strontium manganite and yttria stabilized zirconia) solid oxide fuel cell (SOFC) cathode can be described well with porous electrode theory. Furthermore......, it was illustrated through a literature review on SOFC electrodes that porous electrode theory not only describes the classic LSM:YSZ SOFC cathode well, but SOFC electrodes in general. The extensive impedance spectroscopy study of LSM:YSZ cathodes consisted of measurements on cathodes with three different sintering...... temperatures and hence different microstructures and varying degrees of LSM/YSZ solid state interactions. LSM based composite cathodes, where YSZ was replaced with CGO was also studied in order to acquire further knowledge on the chemical compatibility between LSM and YSZ. All impedance measurements were...
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Impedance models in time domain
Rienstra, S.W.
2005-01-01
Necessary conditions for an impedance function are derived. Methods available in the literature are discussed. A format with recipe is proposed for an exact impedance condition in time domain on a time grid, based on the Helmholtz resonator model. An explicit solution is given of a pulse reflecting
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Directory of Open Access Journals (Sweden)
Hazem K. Khanfar
2017-01-01
Full Text Available In the current study, an Au/BN/C microwave back-to-back Schottky device is designed and characterized. The device morphology and roughness were evaluated by means of scanning electron and atomic force microscopy. As verified by the Richardson–Schottky current conduction transport mechanism which is well fitted to the experimental data, the temperature dependence of the current-voltage characteristics of the devices is dominated by the electric field assisted thermionic emission of charge carriers over a barrier height of ~0.87 eV and depletion region width of ~1.1 μm. Both the depletion width and barrier height followed an increasing trend with increasing temperature. On the other hand, the alternating current conductivity analysis which was carried out in the frequency range of 100–1400 MHz revealed the domination of the phonon assisted quantum mechanical tunneling (hopping of charge carriers through correlated barriers (CBH. In addition, the impedance and power spectral studies carried out in the gigahertz-frequency domain revealed a resonance-antiresonance feature at frequency of ~1.6 GHz. The microwave power spectra of this device revealed an ideal band stop filter of notch frequency of ~1.6 GHz. The ac signal analysis of this device displays promising characteristics for using this device as wave traps.
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Evaluation of electrical impedance ratio measurements in accuracy of electronic apex locators
Directory of Open Access Journals (Sweden)
Pil-Jong Kim
2015-05-01
Full Text Available Objectives The aim of this paper was evaluating the ratios of electrical impedance measurements reported in previous studies through a correlation analysis in order to explicit it as the contributing factor to the accuracy of electronic apex locator (EAL. Materials and Methods The literature regarding electrical property measurements of EALs was screened using Medline and Embase. All data acquired were plotted to identify correlations between impedance and log-scaled frequency. The accuracy of the impedance ratio method used to detect the apical constriction (APC in most EALs was evaluated using linear ramp function fitting. Changes of impedance ratios for various frequencies were evaluated for a variety of file positions. Results Among the ten papers selected in the search process, the first-order equations between log-scaled frequency and impedance were in the negative direction. When the model for the ratios was assumed to be a linear ramp function, the ratio values decreased if the file went deeper and the average ratio values of the left and right horizontal zones were significantly different in 8 out of 9 studies. The APC was located within the interval of linear relation between the left and right horizontal zones of the linear ramp model. Conclusions Using the ratio method, the APC was located within a linear interval. Therefore, using the impedance ratio between electrical impedance measurements at different frequencies was a robust method for detection of the APC.
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Andrade, Marco Aurélio Brizzotti; Pérez, Nicolás; Adamowski, Julio Cezar
2015-01-01
A levitação acústica pode ser uma ferramenta valiosa para auxiliar estudantes de graduação a aprender conceitos básicos de física, tais como movimento harmônico simples, ondas acústicas estacionárias, e energia potencial. Neste artigo, apresentamos o princípio de funcionamento de um levitador acústico e explicamos como aplicar as equações básicas da acústica para determinar a força de radiação acústica que atua numa esfera em uma onda estacionária. Acoustic levitation can be a valuable too...
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International Nuclear Information System (INIS)
Jung, Kyu-Nam; Pyun, Su-Il
2006-01-01
The effect of pore structure on anomalous behaviour of the lithium intercalation into porous V 2 O 5 film electrode has been investigated in terms of fractal geometry by employing ac-impedance spectroscopy combined with N 2 gas adsorption method and atomic force microscopy (AFM). For this purpose, porous V 2 O 5 film electrodes with different pore structures were prepared by the polymer surfactant templating method. From the analysis of N 2 gas adsorption isotherms and the triangulation analysis of AFM images, it was found that porous V 2 O 5 surfaces exhibited self-similar scaling properties with different fractal dimensions depending upon amount of the polymer surfactant in solution and the spatial cut-off ranges. All the ac-impedance spectra measured on porous V 2 O 5 film electrodes showed the non-ideal behaviour of the charge-transfer reaction and the diffusion reaction, which resulted from the interfacial capacitance dispersion and the frequency dispersion of the diffusion impedance, respectively. From the comparison between the surface fractal dimensions by using N 2 gas adsorption method and AFM, and the analysis of ac-impedance spectra by employing a constant phase element (CPE), it is experimentally confirmed that the lithium intercalation into porous V 2 O 5 film electrode is crucially influenced by the pore surface irregularity and the film surface irregularity
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Approaches to building single-stage AC/AC conversion switch-mode audio power amplifiers
DEFF Research Database (Denmark)
Ljusev, Petar; Andersen, Michael Andreas E.
2004-01-01
This paper discusses the possible topologies and promising approaches towards direct single-phase AC-AC conversion of the mains voltage for audio applications. When compared to standard Class-D switching audio power amplifiers with a separate power supply, it is expected that direct conversion...
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Introduction to AC machine design
Lipo, Thomas A
2018-01-01
AC electrical machine design is a key skill set for developing competitive electric motors and generators for applications in industry, aerospace, and defense. This book presents a thorough treatment of AC machine design, starting from basic electromagnetic principles and continuing through the various design aspects of an induction machine. Introduction to AC Machine Design includes one chapter each on the design of permanent magnet machines, synchronous machines, and thermal design. It also offers a basic treatment of the use of finite elements to compute the magnetic field within a machine without interfering with the initial comprehension of the core subject matter. Based on the author's notes, as well as after years of classroom instruction, Introduction to AC Machine Design: * Brings to light more advanced principles of machine design--not just the basic principles of AC and DC machine behavior * Introduces electrical machine design to neophytes while also being a resource for experienced designers * ...
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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
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Determination of input/output characteristics of full-bridge AC/DC/DC converter for arc welding
Stefanov, Goce; Karadzinov, Ljupco; Sarac, Vasilija; Cingoski, Vlatko; Gelev, Saso
2016-01-01
This paper describes the design and practical implementation of AC/DC/DC converter in mode of arc welding. An analysis of the operation of AC/DC/DC converter and its input/output characteristics are determined with computer simulations. The practical part is consisted of AC/DC/DC converter prototype for arc welding with output power of 3 kW and switching frequency of 64 kHz. The operation of AC/DC/DC converter is validated with experimental measurements.
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Mechanical Impedance Modeling of Human Arm: A survey
Puzi, A. Ahmad; Sidek, S. N.; Sado, F.
2017-03-01
Human arm mechanical impedance plays a vital role in describing motion ability of the upper limb. One of the impedance parameters is stiffness which is defined as the ratio of an applied force to the measured deformation of the muscle. The arm mechanical impedance modeling is useful in order to develop a better controller for system that interacts with human as such an automated robot-assisted platform for automated rehabilitation training. The aim of the survey is to summarize the existing mechanical impedance models of human upper limb so to justify the need to have an improved version of the arm model in order to facilitate the development of better controller of such systems with ever increase in complexity. In particular, the paper will address the following issue: Human motor control and motor learning, constant and variable impedance models, methods for measuring mechanical impedance and mechanical impedance modeling techniques.
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Srivastava, Abhishek; McMahon, Katherine D; Stepanauskas, Ramunas; Grossart, Hans-Peter
2015-12-01
The National Center for Biotechnology Information [http://www.ncbi.nlm.nih.gov/guide/taxonomy/] database enlists more than 15,500 bacterial species. But this also includes a plethora of uncultured bacterial representations. Owing to their metabolism, they directly influence biogeochemical cycles, which underscores the the important status of bacteria on our planet. To study the function of a gene from an uncultured bacterium, we have undertaken a de novo gene synthesis approach. Actinobacteria of the acI-B subcluster are important but yet uncultured members of the bacterioplankton in temperate lakes of the northern hemisphere such as oligotrophic Lake Stechlin (NE Germany). This lake is relatively poor in phosphate (P) and harbors on average ~1.3 x 10 6 bacterial cells/ml, whereby Actinobacteria of the ac-I lineage can contribute to almost half of the entire bacterial community depending on seasonal variability. Single cell genome analysis of Actinobacterium SCGC AB141-P03, a member of the acI-B tribe in Lake Stechlin has revealed several phosphate-metabolizing genes. The genome of acI-B Actinobacteria indicates potential to degrade polyphosphate compound. To test for this genetic potential, we targeted the exoP-annotated gene potentially encoding polyphosphatase and synthesized it artificially to examine its biochemical role. Heterologous overexpression of the gene in Escherichia coli and protein purification revealed phosphatase activity. Comparative genome analysis suggested that homologs of this gene should be also present in other Actinobacteria of the acI lineages. This strategic retention of specialized genes in their genome provides a metabolic advantage over other members of the aquatic food web in a P-limited ecosystem. [Int Microbiol 2016; 19(1):39-47]. Copyright© by the Spanish Society for Microbiology and Institute for Catalan Studies.
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Ac-driven vortex-antivortex dynamics in nanostructured superconductor-ferromagnetic hybrids
Energy Technology Data Exchange (ETDEWEB)
Lima, Clessio L.S., E-mail: clsl@df.ufpe.br [Nucleo de Tecnologia, Centro Academico do Agreste, Universidade Federal de Pernambuco, 55002-970 Caruaru-PE (Brazil); Souza Silva, Clecio C. de; Aguiar, J. Albino [Departamento de Fisica, Universidade Federal de Pernambuco, 50670-901 Recife-PE (Brazil)
2012-09-15
The dynamics of ac-driven vortices and antivortices in a superconducting film interacting with an array of magnetic dipoles on top is investigated via hybrid molecular dynamics-Monte Carlo simulations. The dipole array considered in this study is capable to stabilize in equilibrium vortex-antivortex pairs. The appearance of a net electric field out of the ac excitation demonstrates that this system behaves as a voltage rectifier. Because of the asymmetric nature of the effective pinning potential generated by the dipole array, the ac-driven vortices and antivortices are ratcheted in opposite directions, thereby contributing additively to the observed net voltage. In addition, for high frequency values, the dc electric field-ac amplitude curves present a series of steps. A careful analysis of the time series of the electric field and number of vortex-antivortex (v-av) pairs reveals that these steps are related to mode-locking between the drive frequency and the number of v-av creation-annihilation events.
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Low ac loss geometries in YBCO coated conductors and impact on conductor stability
Energy Technology Data Exchange (ETDEWEB)
Duckworth, Robert C [ORNL; List III, Frederick Alyious [ORNL; Paranthaman, Mariappan Parans [ORNL; Rupich, M. W. [American Superconductor Corporation, Westborough, MA; Zhang, W. [American Superconductor Corporation, Westborough, MA; Xie, Y. Y. [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York
2007-01-01
Reduction of ac losses in applied ac fields can be accomplished through either the creation of filaments and bridging in YBCO coated conductors or an assembly of narrow width YBCO tapes. The ac losses for each of these geometries were measured at 77 K in perpendicular ac fields up to 100 mT. While ac loss reduction was achieved with YBCO filaments created through laser scribing and inkjet deposition, the assembly of stacked YBCO conductor provides an alternative method of ac loss reduction. When compared to a 4-mm wide YBCO coated conductor with a critical current of 60 A, the ac loss in a stack of 2-mm wide YBCO coated conductors with a similar total critical current was reduced. While the reduction in ac loss in a 2-mm wide stack coincided with the reduction in the engineering current density of the conductor, further reduction of ac loss was obtained through the splicing of the 2-mm wide tapes with low resistance solders. To better determine the practicality of these methods from a stability point of view, a numerical analysis was carried out to determine the influence of bridging and splicing on stability of a YBCO coated conductor for both liquid nitrogen-cooled and conduction cooled geometries.
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Hauschild, Daniela Barbieri; Barbosa, Eliana; Moreira, Emilia Addison Machado; Ludwig Neto, Norberto; Platt, Vanessa Borges; Piacentini Filho, Eduardo; Wazlawik, Elisabeth; Moreno, Yara Maria Franco
2016-06-01
(1) To compare nutrition and hydration status between a group of children/adolescents with cystic fibrosis (CFG; n = 46; median age, 8.5 years) and a control group without cystic fibrosis (CG). (2) To examine the association of nutrition and hydration status with lung function in the CFG. A cross-sectional study. Nutrition screening, anthropometric parameters, and bioelectrical impedance analysis (BIA) were assessed. The z scores for body mass index for age, height for age, mid upper arm circumference, triceps and subscapular skinfold thickness, mid upper arm muscle area, resistance/height, and reactance/height were calculated. Bioelectrical impedance vector analysis was conducted. Forced expiratory volume in 1 second hydration status were associated with lung function. © 2016 American Society for Parenteral and Enteral Nutrition.
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The validity and accuracy in foot-to-foot bioelectrical impedance ...
African Journals Online (AJOL)
owner
2011-04-18
Apr 18, 2011 ... impedance analysis measuring models referenced by dual-energy ... The ZF-F value was 481.85 ± 63.37 ohm in male and ... BIA method to predict the body composition such as ... position have been published, the comparison of various ..... Bioimpedance analysis: evaluation of leg-to-leg system based.
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Dielectric relaxation and AC conductivity studies of Se90Cd10−xInx glassy alloys
Directory of Open Access Journals (Sweden)
Nitesh Shukla
2016-06-01
Full Text Available Chalcogenide glassy alloys of Se90Cd10−xInx (x = 2, 4, 6, 8 are synthesized by melt quench technique. The prepared glassy alloys have been characterized by techniques such as differential scanning calorimetry (DSC, scanning electron microscopy (SEM and energy dispersive X-ray (EDAX. Dielectric properties of Se90Cd10−xInx (x = 2, 4, 6, 8 chalcogenide glassy system have been studied using impedance spectroscopic technique in the frequency range 42 Hz to 5 MHz at room temperature. It is found that the dielectric constants ɛ′, dielectric loss factor ɛ″ and loss angle Tan δ depend on frequency. ɛ′, ɛ″ and loss angle Tan δ are found to be decreasing with the In content in Se90Cd10−xInx glassy system. AC conductivity of the prepared sample has also been studied. It is found that AC conductivity increases with frequency where as it has decreasing trend with increasing In content in Se–Cd matrix. The semicircles observed in the Cole–Cole plots indicate a single relaxation process.
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Non-Characteristic Harmonics Analysis of the ITER Pulsed Power Supply
International Nuclear Information System (INIS)
Yang Wei; Xu Liuwei; Fu Peng; Lu Huawei; Sheng Zhicai
2009-01-01
The ITER pulsed power supply system will be operated in non-ideal conditions including an asymmetric firing angle, an unbalanced AC supply and an unbalanced AC side impedance of the transformer. In this study the switching functions approach is used to calculate non-characteristic harmonics in ITER, possibly caused by an AC-DC convertor in non-ideal conditions. A PSCAD simulation model is set up to study the non-characteristic harmonics in those non-ideal conditions. It is found that the non-characteristic harmonic does appear and the simulation result is in accordance with the calculating strategy. (fusion engineering)
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Improved transistorized AC motor controller for battery powered urban electric passenger vehicles
Peak, S. C.
1982-01-01
An ac motor controller for an induction motor electric vehicle drive system was designed, fabricated, tested, evaluated, and cost analyzed. A vehicle performance analysis was done to establish the vehicle tractive effort-speed requirements. These requirements were then converted into a set of ac motor and ac controller requirements. The power inverter is a three-phase bridge using power Darlington transistors. The induction motor was optimized for use with an inverter power source. The drive system has a constant torque output to base motor speed and a constant horsepower output to maximum speed. A gear shifting transmission is not required. The ac controller was scaled from the base 20 hp (41 hp peak) at 108 volts dec to an expanded horsepower and battery voltage range. Motor reversal was accomplished by electronic reversal of the inverter phase sequence. The ac controller can also be used as a boost chopper battery charger. The drive system was tested on a dynamometer and results are presented. The current-controlled pulse width modulation control scheme yielded improved motor current waveforms. The ac controller favors a higher system voltage.
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Czech Academy of Sciences Publication Activity Database
Jurák, Pavel; Halámek, Josef; Vondra, Vlastimil; Viščor, Ivo; Lipoldová, J.; Plachý, M.
2010-01-01
Roč. 37, - (2010), s. 1051-1054 ISSN 0276-6574 R&D Projects: GA AV ČR IAA200650801 Institutional research plan: CEZ:AV0Z20650511 Keywords : respiratory effect * thoracic impedance signal * impedance cardiography Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering http://cinc.mit.edu/archives/2010/pdf/1051.pdf
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The Effect of the Feedback Controller on Superconducting Tokamak AC Losses + AC-CRPP user manual
International Nuclear Information System (INIS)
Schaerz, B.; Bruzzone, P.; Favez, J.Y.; Lister, J.B.; Zapretilina, E.
2001-11-01
Superconducting coils in a Tokamak are subject to AC losses when the field transverse to the coil current varies. A simple model to evaluate the AC losses has been derived and benchmarked against a complete model used in the ITER design procedure. The influence of the feedback control strategy on the AC losses is examined using this model. An improved controller is proposed, based on this study. (author)
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Impedance characteristics of nanoparticle-LiCoO{sub 2}+PVDF
Energy Technology Data Exchange (ETDEWEB)
Panjaitan, Elman, E-mail: elmanp@batan.go.id; Kartini, Evvy, E-mail: kartini@batan.go.id; Honggowiranto, Wagiyo [Center for Science and Technology for Advanced Materials, National Nuclear Energy Agency Kawasan Puspiptek Serpong, Tangerang Selatan15314 (Indonesia)
2016-02-08
The impendance of np-LiCoO{sub 2}+xPVDF, as a cathode material candidate for lithium-ion battery (LIB), has been characterized using impedance spectroscopy for x = 0, 5, 10, 15 and 20 volume percentage (%v/v) and for frequencies in the 42 Hz to 5 MHz range. Both real and imaginary components of the impedance were found to be frequency dependent, and both tend to increase for increasing PVDF (polyvinyilidene fluoride) concentration, except that for 10% PVDF both real and imaginary components of impedance are smaller than for 5%. The mechanism for relaxation time for each addition of PVDF was analyzed using Cole-Cole plots. The analysis showed that the relaxation times of the nanostructured LiCoO{sub 2} with PVDF additive is relatively constant. Further, PVDF addition increases the bulk resistance and decreases the bulk capacitance of the nanostructured LiCoO{sub 2}.
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AC losses in horizontally parallel HTS tapes for possible wireless power transfer applications
Shen, Boyang; Geng, Jianzhao; Zhang, Xiuchang; Fu, Lin; Li, Chao; Zhang, Heng; Dong, Qihuan; Ma, Jun; Gawith, James; Coombs, T. A.
2017-12-01
This paper presents the concept of using horizontally parallel HTS tapes with AC loss study, and the investigation on possible wireless power transfer (WPT) applications. An example of three parallel HTS tapes was proposed, whose AC loss study was carried out both from experiment using electrical method; and simulation using 2D H-formulation on the FEM platform of COMSOL Multiphysics. The electromagnetic induction around the three parallel tapes was monitored using COMSOL simulation. The electromagnetic induction and AC losses generated by a conventional three turn coil was simulated as well, and then compared to the case of three parallel tapes with the same AC transport current. The analysis demonstrates that HTS parallel tapes could be potentially used into wireless power transfer systems, which could have lower total AC losses than conventional HTS coils.
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The Effects of Theta and Gamma tACS on Working Memory and Electrophysiology
Directory of Open Access Journals (Sweden)
Anja Pahor
2018-01-01
Full Text Available A single blind sham-controlled study was conducted to explore the effects of theta and gamma transcranial alternating current stimulation (tACS on offline performance on working memory tasks. In order to systematically investigate how specific parameters of tACS affect working memory, we manipulated the frequency of stimulation (theta frequency vs. gamma frequency, the type of task (n-back vs. change detection task and the content of the tasks (verbal vs. figural stimuli. A repeated measures design was used that consisted of three sessions: theta tACS, gamma tACS and sham tACS. In total, four experiments were conducted which differed only with respect to placement of tACS electrodes (bilateral frontal, bilateral parietal, left fronto-parietal and right-fronto parietal. Healthy female students (N = 72 were randomly assigned to one of these groups, hence we were able to assess the efficacy of theta and gamma tACS applied over different brain areas, contrasted against sham stimulation. The pre-post/sham resting electroencephalogram (EEG analysis showed that theta tACS significantly affected theta amplitude, whereas gamma tACS had no significant effect on EEG amplitude in any of the frequency bands of interest. Gamma tACS did not significantly affect working memory performance compared to sham, and theta tACS led to inconsistent changes in performance on the n-back tasks. Active theta tACS significantly affected P3 amplitude and latency during performance on the n-back tasks in the bilateral parietal and right-fronto parietal protocols.
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An NPV and AC Analysis of a Stochastic Inventory System with Joint Manufacturing and Remanufacturing
E.A. van der Laan (Erwin)
2000-01-01
textabstractWhile the net present value (NPV) approach is widely accepted as the right framework for studying production and inventory control systems, average cost (AC) models are more widely used. For the well known EOQ model it can be veri_ed that (under certain conditions) the AC approach gives
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Identification of irradiated potatoes by impedance
International Nuclear Information System (INIS)
Singh, Rita; Singh, Antaryami; Wadhawan, A.K.
1997-01-01
The electrical impedance of potatoes irradiated at 60, 90, 150 and 1000 Gy was measured using various frequencies of alternating current. The impedance of the irradiated potatoes was higher than the unirradiated potatoes particularly in the frequency range of 100 Hz to 10 kHz. The ratio of the impedance at 5 kHz to that at 50 Hz (Z5k/Z50) was found to be the best indicator for detection of radiation treatment. (author). 4 refs., 2 figs
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SPATIAL VARIABILITY OF PEDOZEMS MECHANICAL IMPEDANCE
Directory of Open Access Journals (Sweden)
Zhukov A.V.
2013-04-01
Full Text Available We studied the spatial variability of pedozem mechanical impedance in ResearchRemediation Center of the Dnipropetrovsk State Agrarian University in Ordzhonikidze. Thestatistical distribution of the soil mechanical impedance within the studied area is characterized by deviation from the normal law in 0–10 and 30–50 cm layers from the surface. 2D and 3D modeling shows the structural design of the soil as locations of high mechanical impedance which found in the soils with less hardness.
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International Nuclear Information System (INIS)
McCarthy, Christina B.; Theilmann, David A.
2008-01-01
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) ac143 (odv-e18) is a late gene that encodes for a predicted 9.6 kDa structural protein that locates to the occlusion derived viral envelope and viral induced intranuclear microvesicles [Braunagel, S.C., He, H., Ramamurthy, P., and Summers, M.D. (1996). Transcription, translation, and cellular localization of three Autographa californica nuclear polyhedrosis virus structural proteins: ODV-E18, ODV-E35, and ODV-EC27. Virology 222, 100-114.]. In this study we demonstrate that ac143 is actually a previously unrecognized core gene and that it is essential for mediating budded virus production. To examine the role of ac143 in the baculovirus life cycle, we used the AcMNPV bacmid system to generate an ac143 knockout (KO) virus (AcBAC ac142REP-ac143KO ). Fluorescence and light microscopy showed that infection by AcBAC ac142REP-ac143KO is limited to a single cell and titration assays confirmed that AcBAC ac142REP-ac143KO was unable to produce budded virus (BV). Progression to very late phases of the viral infection was evidenced by the development of occlusion bodies in the nuclei of transfected cells. This correlated with the fact that viral DNA replication was unaffected in AcBAC ac142REP-ac143KO transfected cells. The entire ac143 promoter, which includes three late promoter motifs, is contained within the ac142 open reading frame. Different deletion mutants of this region showed that the integrity of the ac142-ac143 core gene cluster was required for the bacmids to display wild-type patterns of viral replication, BV production and RNA transcription
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Energy Technology Data Exchange (ETDEWEB)
Mora-Sero, Ivan; Luo, Yan; Garcia-Belmonte, Germa; Bisquert, Juan [Departament de Fisica, Universitat Jaume I, E-12071 Castello (Spain); Munoz, Delfina; Voz, Cristobal; Puigdollers, Joaquim; Alcubilla, Ramon [Departament d' Enginyeria Electronica, Universitat Politecnica de Catalunya, E-08034 Barcelona (Spain)
2008-04-15
Impedance spectroscopy (at forward bias and under illumination) of solar cells comprised thin hydrogenated amorphous silicon (a-Si:H) films deposited on crystalline silicon (c-Si) wafers was analyzed in terms of ac equivalent circuits. Shockley-Read-Hall recombination at states on the device interfaces governs the cell dynamic response. Recombination process was modeled by means of simple RC circuits which allow to determine the capture rate of electrons and holes. Carrier lifetime is found to be stated by the electron capture time {tau}{sub SRH}{approx}{tau}{sub n}, and it results in the range of 300 {mu}s. The Al-annealed back contact was regarded as the dominating recombination interface. (author)
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Hofsteenge, G.H.; Chin A Paw, M.J.M.; Weijs, P.J.M.
2015-01-01
Background: In clinical practice, patient friendly methods to assess body composition in obese adolescents are needed. Therefore, the bioelectrical impedance analysis (BIA) related fat-free mass (FFM) prediction equations (FFM-BIA) were evaluated in obese adolescents (age 11-18 years) compared to
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Impedance Method for Leak Detection in Zigzag Pipelines
Lay-Ekuakille, A.; Vergallo, P.; Trotta, A.
2010-01-01
Transportation of liquids is a primary aspect of human life. The most important infrastructure used accordingly is the pipeline. It serves as an asset for transporting different liquids and strategic goods. The latter are for example: chemical substances, oil, gas and water. Thus, it is necessary to monitor such infrastructures by means of specific tools. Leakage detection methods are used to reveal liquid leaks in pipelines for many applications, namely, waterworks, oil pipelines, industry heat exchangers, etc. The configuration of pipelines is a key issue because it impacts on the effectiveness of the method to be used and, consequently, on the results to be counterchecked. This research illustrated an improvement of the impedance method for zigzag pipeline by carrying out an experimental frequency analysis that has been compared with other methods based on frequency response. Hence, the impedance method is generally used for simple (straight) pipeline configurations because complicated pipelines with many curves introduce difficulties and major uncertainties in the calculation of characteristic impedance and in the statement of boundary conditions. The paper illustrates the case of a water pipeline where the leakage is acquired thanks to pressure transducers.
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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...... from driver to driver. Therefore, a loudspeaker emulator capable of adjusting its impedance to that of a given driver is desired for measurement purposes. This paper proposes a loudspeaker emulator circuit for small signals. Simulations and experimental results are compared and show that it is possible...... to emulate the loudspeaker impedance with an electric circuit and that its resonance frequency can be changed by tuning two resistors....
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Small-signal Loudspeaker Impedance Emulator
DEFF Research Database (Denmark)
Knott, Arnold; Iversen, Niels Elkjær
2014-01-01
Specifying the performance of audio ampliers is typically done by playing sine waves into a pure ohmic load. However real loudspeaker impedances are not purely ohmic but characterised by the mechanical resonance between the mass of the diaphragm and the compliance of its' suspension which vary from...... driver to driver. Therefore a loudspeaker emulator capable of adjusting its' impedance to a given driver is in need for measurement purposes. This paper proposes a loudspeaker emulator circuit for small signals. Simulations and experimental results are compared and show that it is possible to emulate...... the loudspeaker impedance with an electric circuit and that its' resonance frequency can be changed by tuning two resistors....
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Impedance budget and beam stability analysis of the Fermilab Main Injector
International Nuclear Information System (INIS)
Martens, M.A.; Ng, K.Y.
1993-05-01
The impedance budget of the Fermilab Main Injector (MI) is estimated, which includes the contributions from the resistive walls, bellows, rf cavities, steps, Lambertsons, etc. Beam stability during ramping and bunch coalescence is analyzed. The transverse resistive-wall coupled bunch growth is found to be somewhat worse than the situation in the Main Ring (MR)
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Mathematical modeling of the electrochemical impedance spectroscopy in lithium ion battery cycling
International Nuclear Information System (INIS)
Xie, Yuanyuan; Li, Jianyang; Yuan, Chris
2014-01-01
Electrochemical impedance spectroscopy (EIS) has been widely utilized as an experimental method for understanding the internal mechanisms and aging effect of lithium ion battery. However, the impedance interpretation still has a lot of difficulties. In this study, a multi-physics based EIS simulation approach is developed to study the cycling effect on the battery impedance responses. The SEI film growth during cycling is coherently coupled with the complicated charge, mass and energy transport processes. The EIS simulation is carried out by applying a perturbation voltage on the electrode surface, and the numerical results on cycled cells are compared with the corresponding experimental data. The effect of electrical double layer, electrode open circuit potential as well as the diffusivity of binary electrolyte are simulated on battery impedance responses. The influence of different SEI growth rate, thermal conditions and charging-discharging rate during cycling are also studied. This developed method can be potentially utilized for interpretation and analysis of experimental EIS results
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Harmonic Active Filtering and Impedance-based Stability Analysis in Offshore Wind Power Plants
DEFF Research Database (Denmark)
Dhua, Debasish; Yang, Guangya; Zhang, Zhe
2017-01-01
installation and provides effectively similar functionality as passive filters. This work is focused on harmonic propagation studies in wind power plants, power quality evaluation at the point of connection and harmonic mitigation by active filtering. Finally, an impedance-based stability analysis......Nowadays, to eliminate harmonics injected by the wind turbines in offshore wind power plants there is a need to install passive filters. Moreover, the passive filters are not adaptive to harmonic profile changes due to topology changes, grid loading etc. Therefore, active filters in wind turbines...... are proposed as a flexible harmonic mitigation measure. The motivation of this study is to explore the possibility of embedding active filtering in wind turbine grid-side converters without having to change the system electrical infrastructure. The active filtering method can prevent additional equipment...
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Impedance Modeling of Solid Oxide Fuel Cell Cathodes
DEFF Research Database (Denmark)
Mortensen, Jakob Egeberg; Søgaard, Martin; Jacobsen, Torben
2010-01-01
A 1-dimensional impedance model for a solid oxide fuel cell cathode is formulated and applied to a cathode consisting of 50/50 wt% strontium doped lanthanum cobaltite and gadolinia doped ceria. A total of 42 impedance spectra were recorded in the temperature range: 555-852°C and in the oxygen...... partial pressure range 0.028-1.00 atm. The recorded impedance spectra were successfully analyzed using the developed impedance model in the investigated temperature and oxygen partial pressure range. It is also demonstrated that the model can be used to predict how impedance spectra evolve with different...
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Abbas, Qamar; Béguin, François
2016-06-01
We demonstrate that an activated carbon (AC)-based electrochemical capacitor implementing aqueous lithium sulfate electrolyte in 7:3 vol:vol water/methanol mixture can operate down to -40 °C with good electrochemical performance. Three-electrode cell investigations show that the faradaic contributions related with hydrogen chemisorption in the negative AC electrode are thermodynamically unfavored at -40 °C, enabling the system to work as a typical electrical double-layer (EDL) capacitor. After prolonged floating of the AC/AC capacitor at 1.6 V and -40°C, the capacitance, equivalent series resistance and efficiency remain constant, demonstrating the absence of ageing related with side redox reactions at this temperature. Interestingly, when temperature is increased back to 24 °C, the redox behavior due to hydrogen storage reappears and the system behaves as a freshly prepared one.
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International Nuclear Information System (INIS)
Brown, R.; Alias, M.N.
1994-01-01
Ac impedance and dc polarization tests of 304 stainless steels coated by cathodic arc plasma deposition (CAPD) titanium nitride and zirconium nitride were conducted in aqueous chloride solution. Cyclic polarization data suggested passive films were formed over the nitride coatings which are most likely hydrated titanium oxide and zirconium oxides. ESCA analysis of fresh samples and samples exposed during impedance tests indicated a layer rich in oxygen over the ZrN coating after exposure but not over TiN coating. Chemical shifts in the Zr 3d 5/2 core electrons indicate transformation from ZrN to its oxide; the shifts in Ti 2P 3/2 did not support the change from TiN to its oxide. The influence of these shifts on corrosion protection is documented
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International Nuclear Information System (INIS)
Cho, Eu-Kyeong; Park, Jung-Il; Lee, Jong-Rim
1995-01-01
A new analytic scheme to resolve the liquid-soil-structure interaction problem in cylindrical liquid storage tanks on the deformable soil is presented. Boundary elements and finite elements are combined to simulate the liquid-structure coupling effect while tuned foundation impedance functions (TFIF's) are representing the motion of the rigid foundation block on the flexible soil. Because the coupled dynamic system is expressed explicitly in terms of mass and stiffness, the developed scheme is applicable to any standard dynamic analysis methodologies. (author)
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Transverse impedance measurement in RHIC and the AGS
Energy Technology Data Exchange (ETDEWEB)
Biancacci, Nicolo [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Dutheil, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Liu, C. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Mernick, M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; Minty, M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.; White, S. M. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.
2014-05-12
The RHIC luminosity upgrade program aims for an increase of the polarized proton luminosity by a factor 2. To achieve this goal a significant increase in the beam intensity is foreseen. The beam coupling impedance could therefore represent a source of detrimental effects for beam quality and stability at high bunch intensities. For this reason it is essential to quantify the accelerator impedance budget and the major impedance sources, and possibly cure them. In this MD note we summarize the results of the 2013 transverse impedance measurements in the AGS and RHIC. The studies have been performed measuring the tune shift as a function of bunch intensity and deriving the total accelerator machine transverse impedance. For RHIC, we could obtain first promising results of impedance localization measurements as well.
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FEM Analysis of Beam-coupling Impedance and RF Contacts Criticality on the LHC UA9 Piezo Goniometer
Danisi, A; Passarelli, A; Masi, A; Losito, R; Salvant, B
2014-01-01
The UA9 piezo-goniometer has been designed to guarantee micro-radians-accuracy angular positioning of a silicon crystal for a crystal collimation experiment in the LHC, and to minimize the impact on the LHC beam coupling impedance. This paper presents a Finite Element Method (FEM) study of the device, in both parking and operational positions, to evaluate its impact on the LHC impedance budget. In addition, the shielding contribution of the RF gaskets has been carefully evaluated, with the objective to assess the consequences for operation in case of their failure. A final word is drawn on the overall device impedance criticality.
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Lifescience Database Archive (English)
Full Text Available in 5-4 OS=Homo sap... 33 1.1 sp|Q9DBY1|SYVN1_MOUSE E3 ubiquitin-protein ligase synoviolin OS=... 33 1.4 sp|Q...86TM6|SYVN1_HUMAN E3 ubiquitin-protein ligase synoviolin OS=... 33 1.4 sp|O55188|DMP1_MOUSE Dentin matrix ac
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21 CFR 886.4440 - AC-powered magnet.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and remove...
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Beam pipe impedances in the TRIUMF KAON factory
International Nuclear Information System (INIS)
Baartman, R.; Oram, C.J.
1989-09-01
The standard formalism for estimating longitudinal beam pipe impedances is given. Estimates of realistically obtainable impedances are developed. We show that where the impedance is critical an impedance divided by mode number of 1-2 Ω should be the design goal for the beam pipe group. However for machine design criteria and planning purposes 5 Ω should continue to be adopted so that sufficient contingency is present in the design
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Piccoli, Antonio; Codognotto, Marta; Piasentin, Paola; Naso, Agostino
2014-08-01
Body hydration changes continuously in hemodialysis patients. The Subjective Global Assessment (SGA) is used for the nutritional evaluation but it does not allow a direct evaluation of hydration. Bioelectrical impedance vector analysis (BIVA) is very sensitive to hydration. The potential of the combined evaluation of hydration and nutrition with SGA and BIVA is still lacking. Observational cross-sectional study on 130 (94 Male) uremic patients undergoing chronic hemodialysis three times a week. Nutritional status was evaluated with the SGA. Each subject was classified as SGA-A (normal nutritional status), SGA-B (moderate malnutrition), or SGA-C (severe malnutrition). Body hydration was evaluated with BIVA. The two vector components resistance (R) and reactance (Xc) were normalized by the subject's height and standardized as bivariate Z-score, i.e. Z(R) and Z(Xc). Undernutrition influenced impedance vector distribution both before and after a dialysis session. In pre-dialysis, the mean vector of SGA A was inside the 50% tolerance ellipse. In SGA B and C, Z(R) was increased and Z(Xc) decreased, indicating a progressive loss of soft tissue mass. Fluid removal with dialysis increased both Z(R) and Z(Xc) in SGA A and B but not in C. With ROC curve analysis on the slope of increase, we found the cutoff value of 27.8° below which undernutrition was present, either moderate or severe. The area under the ROC curve was 77.7° (95% CI 69.5-84.5, P hydration in each SGA category can be detected with BIVA. Copyright © 2013 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.
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Rababah, A S; Walsh, S J; Manoharan, G; Walsh, P R; Escalona, O J
2016-07-01
Intracardiac impedance (ICI) is a major determinant of success during internal cardioversion of atrial fibrillation (AF). However, there have been few studies that have examined the dynamic behaviour of atrial impedance during internal cardioversion in relation to clinical outcome. In this study, voltage and current waveforms captured during internal cardioversion of acute AF in ovine models using novel radiofrequency (RF) generated low-tilt rectilinear and conventional capacitor-discharge based shock waveforms were retrospectively analysed using a digital signal processing algorithm to investigate the dynamic behaviour of atrial impedance during cardioversion. The algorithm was specifically designed to facilitate the simultaneous analysis of multiple impedance parameters, including: mean intracardiac impedance (Z M), intracardiac impedance variance (ICIV) and impedance amplitude spectrum area (IAMSA) for each cardioversion event. A significant reduction in ICI was observed when comparing two successive shocks of increasing energy where cardioversion outcome was successful. In addition, ICIV and IAMSA variables were found to inversely correlate to the magnitude of energy delivered; with a stronger correlation found to the former parameter. In conclusion, ICIV and IAMSA have been evidenced as two key dynamic intracardiac impedance variables that may prove useful in better understanding of the cardioversion process and that could potentially act as prognostic markers with respect to clinical outcome.
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The IMPACT shirt: textile integrated and portable impedance cardiography
International Nuclear Information System (INIS)
Ulbrich, Mark; Wan, Tingting; Leonhardt, Steffen; Walter, Marian; Mühlsteff, Jens; Sipilä, Auli; Kamppi, Merja; Koskela, Anne; Myry, Manu
2014-01-01
Measurement of hemodynamic parameters such as stroke volume (SV) via impedance cardiography (ICG) is an easy, non-invasive and inexpensive way to assess the health status of the heart. We present a possibility to use this technology for monitoring risk patients at home. The IMPACT Shirt (IMPedAnce Cardiography Textile) has been developed with integrated textile electrodes and textile wiring, as well as with portable miniaturized hardware. Several textile materials were characterized in vitro and in vivo to analyze their performance with regard to washability, and electrical characteristics such as skin-electrode impedance, capacitive coupling and subjective tactile feeling. The small lightweight hardware measures ECG and ICG continuously and transmits wireless data via Bluetooth to a mobile phone (Android) or PC for further analysis. A lithium polymer battery supplies the circuit and can be charged via a micro-USB. Results of a proof-of-concept trial show excellent agreement between SV assessed by a commercial device and the developed system. The IMPACT Shirt allows monitoring of SV and ECG on a daily basis at the patient’s home. (paper)
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Aperture measurements with AC dipole
Fuster Martinez, Nuria; Dilly, Joschua Werner; Nevay, Laurence James; Bruce, Roderik; Tomas Garcia, Rogelio; Redaelli, Stefano; Persson, Tobias Hakan Bjorn; CERN. Geneva. ATS Department
2018-01-01
During the MDs performed on the 15th of September and 29th of November 2017, we measured the LHC global aperture at injection with a new AC dipole method as well as using the Transverse Damper (ADT) blow-up method used during the 2017 LHC commissioning for benchmarking. In this note, the MD procedure is presented as well as the analysis of the comparison between the two methods. The possible benefits of the new method are discussed.
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International Nuclear Information System (INIS)
Andrade, C.; Alonso, C.; Gonzalez, J.A.
1989-01-01
Laboratory results of the corrosion rate of steel embedded in carbonated concrete contaminated with chlorides determined through the Polarization Resistance method are presented here as examples of the possibilities offered by this technique in order to monitor the reinforcement corrosion process. The Rp technique has the advantages of fast response, simple and relatively accurate. Contrasts with gravimetric losses are presented. The A.C. Impedance measurements determined on the same specimens are also presented. The difficulties found in the interpretation of the results are stressed. R T values cannot easily be obtained. Several electrical circuits which may model the behaviour of the steel/concrete system are discussed. Finally, comments on the basic criteria to interpret results of both techniques are given. (author) 4 refs., 6 figs
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Modeling degradation in SOEC impedance spectra
DEFF Research Database (Denmark)
Jensen, Søren Højgaard; Hauch, Anne; Knibbe, Ruth
2013-01-01
Solid oxide cell (SOC) performance is limited by various processes. One way to investigate these processes is by electrochemical impedance spectroscopy. In order to quantify and characterize the processes, an equivalent circuit can be used to model the SOC impedance spectra (IS). Unfortunately......, the optimal equivalent circuit is often unknown and to complicate matters further, several processes contribute to the SOC impedance - making detailed process characterization difficult. In this work we analyze and model a series of IS measured during steam electrolysis operation of an SOC. During testing......, degradation is only observed in the Ni/YSZ electrode and not in the electrolyte or the LSM/YSZ electrode. A batch fit of the differences between the IS shows that a modified Gerischer element provides a better fit to the Ni/YSZ electrode impedance than the frequently used RQ element - albeit neither...
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Directory of Open Access Journals (Sweden)
N. Murali
2017-12-01
Full Text Available Layered structure LiNi0.45M0.1Mn0.45O2 (MCu and Al cathode materials for lithium-ion batteries are synthesized by solâgel auto combustion method. The structural, morphological, electrical and magnetic properties are examined by X-ray diffraction (XRD, field effect scanning electron microscope FESEM, FT-IR, EIS and ESR. XRD data revealed the rhombohedral and α-NaFeO2 structure with a space group R-3m. The electrical conductivity, dielectric constant, and dielectric loss are measured in the room temperature at a frequency ranging from 20 Hz to 1 MHz. The electrical conductivity of the compound is measured by AC impedance. An effective improvement in the electrical conductivity of order 5.42 Ã 10â6 S/cm is observed for the copper doped LNMO compounds. ESR spectra is recorded at room temperature on a Bruker EMX model X-band spectrometer operating at a frequency of 9.50 GHz. The critical dopants of Cu, with minimum g-factor and maximum line-width (W are observed. Keywords: Solâgel, FESEM, AC impedance, ESR
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Geometric beam coupling impedance of LHC secondary collimators
Frasciello, Oscar; Tomassini, Sandro; Zobov, Mikhail; Salvant, Benoit; Grudiev, Alexej; Mounet, Nicolas
2016-02-01
The High Luminosity LHC project is aimed at increasing the LHC luminosity by an order of magnitude. One of the key ingredients to achieve the luminosity goal is the beam intensity increase. In order to keep beam instabilities under control and to avoid excessive power losses a careful design of new vacuum chamber components and an improvement of the present LHC impedance model are required. Collimators are among the major impedance contributors. Measurements with beam have revealed that the betatron coherent tune shifts were higher by about a factor of 2 with respect to the theoretical predictions based on the LHC impedance model up to 2012. In that model the resistive wall impedance has been considered as the dominating impedance contribution for collimators. By carefully simulating also their geometric impedance we have contributed to the update of the LHC impedance model, reaching also a better agreement between the measured and simulated betatron tune shifts. During the just ended LHC Long Shutdown I (LSI), TCS/TCT collimators were replaced by new devices embedding BPMs and TT2-111R ferrite blocks. We present here preliminary estimations of their broad-band impedance, showing that an increase of about 20% is expected in the kick factors with respect to previous collimators without BPMs.
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Design of current source for multi-frequency simultaneous electrical impedance tomography
Han, Bing; Xu, Yanbin; Dong, Feng
2017-09-01
Multi-frequency electrical impedance tomography has been evolving from the frequency-sweep approach to the multi-frequency simultaneous measurement technique which can reduce measuring time and will be increasingly attractive for time-varying biological applications. The accuracy and stability of the current source are the key factors determining the quality of the image reconstruction. This article presents a field programmable gate array-based current source for a multi-frequency simultaneous electrical impedance tomography system. A novel current source circuit was realized by combining the classic current mirror based on the feedback amplifier AD844 with a differential topology. The optimal phase offsets of harmonic sinusoids were obtained through the crest factor analysis. The output characteristics of this current source were evaluated by simulation and actual measurement. The results include the following: (1) the output impedance was compared with one of the Howland pump circuit in simulation, showing comparable performance at low frequencies. However, the proposed current source makes lower demands for resistor tolerance but performs even better at high frequencies. (2) The output impedance in actual measurement below 200 kHz is above 1.3 MΩ and can reach 250 KΩ up to 1 MHz. (3) An experiment based on a biological RC model has been implemented. The mean error for the demodulated impedance amplitude and phase are 0.192% and 0.139°, respectively. Therefore, the proposed current source is wideband, biocompatible, and high precision, which demonstrates great potential to work as a sub-system in the multi-frequency electrical impedance tomography system.
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Characterization of the mechanical behavior of human skin by means of impedance spectroscopy
Pavšelj, N.; Mitar, M.; Hart, F. X.; Miklavčič, D.
2010-04-01
There is increased interest for the use of impedance spectroscopy to measure skin dielectric properties in vivo. The aim of such measurements can be either to evaluate the hydration state of the skin, to detect diseased states such as skin cancer, to follow the progress of transdermal drug delivery, or simply to gather data on skin tissue impedance to be used in theoretical studies. However, obtaining reliable data can be difficult. Namely, skin is a highly nonhomogeneous multi-layered structure whose composition and dimensions differ depending on the location on the body and interindividual variations. Also, impedance measurements on skin are accompanied by a number of artefacts. We performed a series of impedance measurements using an Agilent/HP 4284A precision LCR meter with parallel plate electrodes pressed on the skin, at different locations on the body. We observed substantial impedance changes over the course of the measurement. These changes can be mainly attributed to skin deformation caused by the electrodes pressing against skin. The analysis showed that skin mechanical properties and layer thicknesses can be inferred from these temporal changes. Such data on mechanical properties of skin tissue give valuable extra information, crucial for successful estimation of the impedance of different skin layers.
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Sound Propagation An impedance Based Approach
Kim, Yang-Hann
2010-01-01
In Sound Propagation: An Impedance Based Approach , Professor Yang-Hann Kim introduces acoustics and sound fields by using the concept of impedance. Kim starts with vibrations and waves, demonstrating how vibration can be envisaged as a kind of wave, mathematically and physically. One-dimensional waves are used to convey the fundamental concepts. Readers can then understand wave propagation in terms of characteristic and driving point impedance. The essential measures for acoustic waves, such as dB scale, octave scale, acoustic pressure, energy, and intensity, are explained. These measures are
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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.
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Directory of Open Access Journals (Sweden)
Sumedha Mahajan
2017-04-01
Full Text Available This paper proposes a Capacitor Excited Induction Generator (CEIG-Matrix Converter (MC system for feeding stand-alone AC loads. The variable output voltage magnitude and frequency from CEIG is converted into a constant voltage magnitude and frequency at the load terminals by controlling MC using Space Vector Modulation (SVM technique. This single-stage MC is turned up as a good alternative for the proposed system against commonly used AC/DC/AC two stage power converters. The configuration and implementation of the closed-loop control scheme employing dSPACE 1103 real time controller have been fully described in the paper. The proposed closed-loop controller regulates the AC load voltage irrespective of changes in the prime mover speed and load. A method for predetermining the steady-state performance of the proposed system has been developed and described with relevant analytical expressions. The effectiveness of the proposed system is exemplified through simulation results for various operating conditions. The proposed control technique is further validated using an experimental setup developed in the laboratory.
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Impedance spectroscopy study of Na{sub 1/2}Sm{sub 1/2}TiO{sub 3} ceramic
Energy Technology Data Exchange (ETDEWEB)
Barik, S K; Choudhary, R N.P. [I.I.T., Department of Physics and Meteorology, Kharagpur (India); Mahapatra, P K [Vidyasagar University, Department of Physics and Technophysics, Midnapur, West Bengal (India)
2007-07-15
Complex impedance analysis of a valence-compensated perovskite ceramic oxide Na{sub 1/2}Sm{sub 1/2}TiO{sub 3}, prepared by a mixed oxide (solid-state reaction) method, has been carried out. The formation of single-phase material was confirmed by X-ray diffraction studies, and it was found to be an orthorhombic phase at room temperature. In a scanning electron microscope, grains separated by well-defined boundaries are visible, which is in good agreement with that of impedance analysis. Alternating current impedance measurements were made over a wide temperature range (31-400 C) in an air atmosphere. Complex impedance and modulus plots helped to separate out the contributions of grain and grain boundaries to the overall polarization or electrical behavior. The physical structure of the samples was visualized most prominently at higher temperatures (275 C) from the Nyquist plots showing inter- and intragranular impedance present in the material. The frequency dependence of electrical data is also analyzed in the framework of the conductivity and modulus formalisms. The bulk resistance, evaluated from the impedance spectrum, was observed to decrease with rise in temperature, showing a typical negative temperature coefficient of resistance-type behavior like that of semiconductors. The modulus mechanism indicates the non-Debye type of conductivity relaxation in the materials, which is supported by the impedance data. (orig.)
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Hu, Hejing; Zhang, Yannan; Shi, Yanfeng; Feng, Lin; Duan, Junchao; Sun, Zhiwei
2017-10-01
With rapid development of nanotechnology and growing environmental pollution, the combined toxic effects of SiNPs and pollutants of heavy metals like lead have received global attentions. The aim of this study was to explore the cardiovascular effects of the co-exposure of SiNPs and lead acetate (PbAc) in zebrafish using microarray and bioinformatics analysis. Although there was no other obvious cardiovascular malformation except bleeding phenotype, bradycardia, angiogenesis inhibition and declined cardiac output in zebrafish co-exposed of SiNPs and PbAc at NOAEL level, significant changes were observed in mRNA and microRNA (miRNA) expression patterns. STC-GO analysis indicated that the co-exposure might have more toxic effects on cardiovascular system than that exposure alone. Key differentially expressed genes were discerned out based on the Dynamic-gene-network, including stxbp1a, ndfip2, celf4 and gsk3b. Furthermore, several miRNAs obtained from the miRNA-Gene-Network might play crucial roles in cardiovascular disease, such as dre-miR-93, dre-miR-34a, dre-miR-181c, dre-miR-7145, dre-miR-730, dre-miR-129-5p, dre-miR-19d, dre-miR-218b, dre-miR-221. Besides, the analysis of miRNA-pathway-network indicated that the zebrafish were stimulated by the co-exposure of SiNPs and PbAc, which might cause the disturbance of calcium homeostasis and endoplasmic reticulum stress. As a result, cardiac muscle contraction might be deteriorated. In general, our data provide abundant fundamental research clues to the combined toxicity of environmental pollutants and further in-depth verifications are needed. Copyright © 2017 Elsevier Ltd. All rights reserved.
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Directory of Open Access Journals (Sweden)
Elin Ericsson
Full Text Available Ventilator-induced or ventilator-associated lung injury (VILI/VALI is common and there is an increasing demand for a tool that can optimize ventilator settings. Electrical impedance tomography (EIT can detect changes in impedance caused by pulmonary ventilation and perfusion, but the effect of changes in the position of the body and in the placing of the electrode belt on the impedance signal have not to our knowledge been thoroughly evaluated. We therefore studied ventilation-related and perfusion-related changes in impedance during spontaneous breathing in 10 healthy subjects in five different body positions and with the electrode belt placed at three different thoracic positions using a 32-electrode EIT system. We found differences between regions of interest that could be attributed to changes in the position of the body, and differences in impedance amplitudes when the position of the electrode belt was changed. Ventilation-related changes in impedance could therefore be related to changes in the position of both the body and the electrode belt. Perfusion-related changes in impedance were probably related to the interference of major vessels. While these findings give us some insight into the sources of variation in impedance signals as a result of changes in the positions of both the body and the electrode belt, further studies on the origin of the perfusion-related impedance signal are needed to improve EIT further as a tool for the monitoring of pulmonary ventilation and perfusion.
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Directory of Open Access Journals (Sweden)
Resnanti Utami Handayani
2014-07-01
Full Text Available Ethylene has an important function in plant growth and development. Ethylene production generally increases in response to pathogen attacks and other environmental stress conditions. The synthesis of this phytohormone is regulated by two enzymes, ACC synthase (ACS and ACC oxidase (ACO. ACC synthase is encoded by a multigene that regulates the production of ACC, after which this precursor is converted into ethylene by ACO. Pisang Ambon (Musa sp. AAA group, a banana cultivar originating from Indonesia, has nine ACS genes (MaACS 1-9 and one ACO gene (MaACO. One of the banana ACS genes, MaACS2, is stress-inducible. In this research, we have investigated the expression profile of MaACS2 in the roots and leaf tissues of infected tissue culture plants. Quantification of gene expression was analyzed using Real-Time PCR (qPCR using Ma18srRNA and MaGAPDH as reference genes. The results showed nine-to ten fold higher MaACS2 expression levels in the infected roots tissues compared to the uninfected roots tissues. However, MaACS2 expression in the leaves was only detected in infected tissue.
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Directory of Open Access Journals (Sweden)
Jiao Jiao
2016-11-01
Full Text Available Explored in this paper is the grid impedance effect on the stability of a single-phase grid connected inverter with an LC filter based on an analysis of the inverter output impedance. For a single-phase grid connected inverter, a PI controller is often used to regulate the current injected into the grid. However, the control performance can be influenced when the inverter is connected to a weak grid. Also, the utility grid has background harmonic noise, which can make the injected current distorted. Therefore, analysis of the output impedance of a single-phase grid connected inverter is important for the robustness and stability of the system. By modeling the output impedance of inverter, it can be determined that the proportional gain and integral gain of the controller have an effect on the output impedance. Analytical results show that by adjusting the PI controller parameters, the ability for harmonic reduction and stability of the system can be improved. Simulation and experiments using a 1 kW single-phase grid connected inverter verify the effectiveness of the theoretical analysis.
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Impedance interactions in bidirectional cascaded converter
DEFF Research Database (Denmark)
Tian, Yanjun; Loh, Poh Chiang; Chen, Zhe
2016-01-01
A cascaded converter is built by connecting one elementary converter to another. Output impedance of one converter will therefore interact with input impedance of the other converter. This interaction will change when power flow reverses. To compare this difference, an investigation is performed...
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Impedance of accelerator components
International Nuclear Information System (INIS)
Corlett, J.N.
1996-05-01
As demands for high luminosity and low emittance particle beams increase, an understanding of the electromagnetic interaction of these beams with their vacuum chamber environment becomes more important in order to maintain the quality of the beam. This interaction is described in terms of the wake field in time domain, and the beam impedance in frequency domain. These concepts are introduced, and related quantities such as the loss factor are presented. The broadband Q = 1 resonator impedance model is discussed. Perturbation and coaxial wire methods of measurement of real components are reviewed
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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...
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The validity and accuracy in foot-to-foot bioelectrical impedance ...
African Journals Online (AJOL)
The validity and accuracy in foot-to-foot bioelectrical impedance analysis measuring models referenced by dual-energy X-ray absorptiometry in body composition in standing position. KC Hsieh, HK Lu, CH Chen, TR Jang, YY Chen, MF Kao ...
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Energy Technology Data Exchange (ETDEWEB)
Yadav, Pankaj [Department of Physics, Marwadi Education Foundation, Rajkot 360003 (India); Pandey, Kavita; Bhatt, Parth [School of Solar Energy, Pandit Deendayal Petroleum University, Gandhinagar 382007 (India); Tripathi, Brijesh, E-mail: brijesh.tripathi@sse.pdpu.ac.in [School of Technology, Pandit Deendayal Petroleum University, Gandhinagar 382007 (India); Pandey, Manoj Kumar; Kumar, Manoj [School of Technology, Pandit Deendayal Petroleum University, Gandhinagar 382007 (India)
2016-04-15
Highlights: • Role of TiO{sub 2}/graphene composite in charge transport within supercapacitors. • DC and AC characterization to investigate voltage dependence of charge transport. • Physical insight into the electrochemistry of electrode–electrolyte interface. - Abstract: This work describes the role of graphene in charge transport and diffusion mechanism at TiO{sub 2}/graphene electrode–electrolyte interface. To explore the mechanism, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used. The CV results depict that TiO{sub 2} and TiO{sub 2}/graphene electrodes behave differently in terms of charge transport and ion adsorption under the steady state conditions. The performance of TiO{sub 2} electrode–electrolyte interface is mainly limited by the charge transport and pseudo-capacitive effects while the response of TiO{sub 2}/graphene electrode–electrolyte interface is mainly dominated by the double layer capacitive effects. The EIS measurement leads to the direct determination of broad range of parameters, i.e. series resistance, charge transport, rate capability and ion diffusion. The experimental results and their analysis will have a significant impact on understanding the role of graphene in the electrochemical response of an electrode–electrolyte interface.
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Assessing the immediate impact of botulinum toxin injection on impedance of spastic muscle.
Li, Xiaoyan; Shin, Henry; Li, Le; Magat, Elaine; Li, Sheng; Zhou, Ping
2017-05-01
This study aimed to investigate the immediate impacts of Botulinum Toxin A (BoNT-A) injections on the inherent electrical properties of spastic muscles using a newly developed electrical impedance myography (EIM) technique. Impedance measures were performed before and after a BoNT-A injection in biceps brachii muscles of 14 subjects with spasticity. Three major impedance variables, resistance (R), reactance (X) and phase angle (θ) were obtained from three different configurations, and were evaluated using the conventional EIM frequency at 50kHz as well as multiple frequency analysis. Statistical analysis demonstrated a significant decrease of resistance in the injected muscles (Multiple-frequency: R pre =25.17±1.94Ohm, R post =23.65±1.63Ohm, ptoxin effects on the muscle. This study demonstrated high sensitivity of the EIM technique in the detection of alterations to muscle composition. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.
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International Nuclear Information System (INIS)
Kim, Eun-San
2003-01-01
This paper shows the results of a numerical study of the impedance in the Accelerator Test Facility damping ring. The longitudinal impedance in the damping ring is shown to be inductive. It is shown that the total impedance |Z || /n| is 0.23 Ω and the inductance is L = 14 nH. In the extremely low emittance beam of the damping ring, bunch lengthening is caused by both the effects of potential-well distortion and intra-beam scattering. In this paper, the bunch-lengthening due to the ring impedance is numerically investigated, and the result shows qualitative agreement with the result of an analysis performed using the bunch-length measurement. With the calculated longitudinal impedance, the instability threshold in the damping ring is estimated to be a bunch population of 3.3 x 10 10 by using both a Vlasov equation approach and a multi-particle tracking method.
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Directory of Open Access Journals (Sweden)
M. Egginger
2012-12-01
Full Text Available Polyvinylalcohol (PVA is a water soluble polymer frequently applied in the field of organic electronics for insulating thin film layers. By-products of PVA synthesis are sodium acetate ions which contaminate the polymer material and can impinge on the electronic performance when applied as interlayer dielectrics in thin film transistors. Uncontrollable voltage instabilities and unwanted hysteresis effects are regularly reported with PVA devices. An understanding of these effects require knowledge about the electronic dynamics of the ionic impurities and their influence on the dielectric properties of PVA. Respective data, which are largely unknown, are being presented in this work. Experimental investigations were performed from room temperature to 125°C on drop-cast PVA films of three different quality grades. Data from thermal discharge current (TDC measurements, polarization experiments, and dielectric impedance spectroscopy concurrently show evidence of mobile ionic carriers. Results from TDC measurements indicate the existence of an intrinsic, build-in electric field of pristine PVA films. The field is caused by asymmetric ionic double layer formation at the two different film-interfaces (substrate/PVA and PVA/air. The mobile ions cause strong electrode polarization effects which dominate dielectric impedance spectra. From a quantitative electrode polarization analysis of isothermal impedance spectra temperature dependent values for the concentration, the mobility and conductivity together with characteristic relaxation times of the mobile carriers are given. Also shown are temperature dependent results for the dc-permittivity and the electronic resistivity. The obtained results demonstrate the feasibility to partly remove contaminants from a PVA solution by dialysis cleaning. Such a cleaning procedure reduces the values of ion concentration, conductivity and relaxation frequency.
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Directory of Open Access Journals (Sweden)
Olga Mizera
2018-03-01
Full Text Available Introduction: Regular assessment of body composition in athletes is a key element of their nutritional status and general condition monitoring. Purpose: Analysis of differences in the impedance (I and body composition measurements performed by the use of analyzers with a constant current frequency of 50 kHz with steel and gel electrodes. Material and methods: Analysis were performed in experienced fencers by the use of analyzers: Tanita BC418MA (aT with steel electrodes (eT and Akern BIA101ASE (aA with gel electrodes (eA, eL, eT. During the first stage of the study in 48 athletes I, fat mass (FM and fat free mass (FFM were measured using aA with eB in a supine position and after 3 min using aT with eT in a standing position. Then 10 fencers were randomly selected. For them measurements were performed after 10, 13 and 16 min in a supine position using eA, eL, eB and then after 3 min in a standing one using eT. Intrinsic impedance of the 3 types of gel electrodes (eA, eL, eB were measured using aA. Results: The first stage. Differences in I, FM and FFM between eT and aA were observed (women: 101.4±52.2Ω, 1.2±2.1kg, -1.2±2.1kg, men: 98.8±27.5Ω, 1.1±1.5kg, -1.1±1.5kg, respectively. The second stage. In the subsequent measurements, differences in I were observed (women: eL-eA 3.8±1.8Ω, eB-eA 26.1±8.0Ω, eT-eA 154.4±40.6Ω;, men: of -0.7±9.4Ω, 11.1±9.2Ω, 107±36.3Ω, respectively. In both subgroups along with the increase in I, FM also increased, while FFM decreased. Intrinsic impedance of the applied gel electrodes was measured and the differences between the results were reported (eL-eA 41.1±22.0Ω, eB-eL 138.4±20.7Ω, eB-eA 179.5Ω. As the intrinsic impedance of gel electrodes increased, an increase in the whole body I was observed. Conclusion: It seems that the observed differences in the whole body impedance were not only a simple effect of changes in a body position but they might have also been related to the intrinsic
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Numerical analysis on effective electric field penetration depth for interdigital impedance sensor
International Nuclear Information System (INIS)
Kim, Chon-ung; Jong, Hakchol; Ro, Cholwu; Pak, Gilhung; Im, Songil; Li, Guofeng; Li, Jie; Song, Yunho
2013-01-01
Interdigital (finger-like) electrodes are widely used for electrical impedance and capacitance tomography of composite dielectric materials and complex insulating structures. Because of their advantages, they are now effectively introduced as capacitance sensors into a variety of industrial branches, agriculture, medical science, biological engineering, military branches, etc. In order to effectively apply the so-called interdigital impedance sensors in practice, of great importance is to optimize the sensor design parameters such as the electric field penetration depth, signal strength and so on. The general design principles of the interdigital capacitance sensor have been discussed for a long time by many researchers. However, there is no consensus on the definition of the effective electric field penetration depth of interdigital electrode. This paper discusses how to determine the effective electric field penetration depth of interdigital sensor on the basis of the refractive principle of electric field intensity and the FEM analyses of electric field distribution and capacitance for the sensor model.
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AC Conductivity and Dielectric Properties of Borotellurite Glass
Taha, T. A.; Azab, A. A.
2016-10-01
Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF- xTeO2 ( x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density ( ρ) was determined by the Archimedes method at room temperature. The density ( ρ) and molar volume ( V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity ( σ ac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.
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Simultaneous distribution of AC and DC power
Polese, Luigi Gentile
2015-09-15
A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.
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Ferreira, J; Seoane, F; Lindecrantz, K
2013-01-01
Personalised Health Systems (PHS) that could benefit the life quality of the patients as well as decreasing the health care costs for society among other factors are arisen. The purpose of this paper is to study the capabilities of the System-on-Chip Impedance Network Analyser AD5933 performing high speed single frequency continuous bioimpedance measurements. From a theoretical analysis, the minimum continuous impedance estimation time was determined, and the AD5933 with a custom 4-Electrode Analog Front-End (AFE) was used to experimentally determine the maximum continuous impedance estimation frequency as well as the system impedance estimation error when measuring a 2R1C electrical circuit model. Transthoracic Electrical Bioimpedance (TEB) measurements in a healthy subject were obtained using 3M gel electrodes in a tetrapolar lateral spot electrode configuration. The obtained TEB raw signal was filtered in MATLAB to obtain the respiration and cardiogenic signals, and from the cardiogenic signal the impedance derivative signal (dZ/dt) was also calculated. The results have shown that the maximum continuous impedance estimation rate was approximately 550 measurements per second with a magnitude estimation error below 1% on 2R1C-parallel bridge measurements. The displayed respiration and cardiac signals exhibited good performance, and they could be used to obtain valuable information in some plethysmography monitoring applications. The obtained results suggest that the AD5933-based monitor could be used for the implementation of a portable and wearable Bioimpedance plethysmograph that could be used in applications such as Impedance Cardiography. These results combined with the research done in functional garments and textile electrodes might enable the implementation of PHS applications in a relatively short time from now.
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Universality of ac conduction in disordered solids
DEFF Research Database (Denmark)
Dyre, Jeppe; Schrøder, Thomas
2000-01-01
The striking similarity of ac conduction in quite different disordered solids is discussed in terms of experimental results, modeling, and computer simulations. After giving an overview of experiment, a macroscopic and a microscopic model are reviewed. For both models the normalized ac conductivity...... as a function of a suitably scaled frequency becomes independent of details of the disorder in the extreme disorder limit, i.e., when the local randomly varying mobilities cover many orders of magnitude. The two universal ac conductivities are similar, but not identical; both are examples of unusual non......-power-law universalities. It is argued that ac universality reflects an underlying percolation determining dc as well as ac conductivity in the extreme disorder limit. Three analytical approximations to the universal ac conductivities are presented and compared to computer simulations. Finally, model predictions...
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PHEMT Distributed Power Amplifier Adopting Broadband Impedance Transformer
DEFF Research Database (Denmark)
Narendra, K.; Limiti, E.; Paoloni, C.
2013-01-01
A non-uniform drain line distributed power amplifier (DPA) employing a broadband impedance transformer is presented. The DPA is based on GaAs PHEMT technology. The impedance transformer employs asymmetric coupled lines and transforms a low output impedance of the amplifier to a standard 50 Ω...
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Optical approximation in the theory of geometric impedance
International Nuclear Information System (INIS)
Stupakov, G.; Bane, K.L.F.; Zagorodnov, I.
2007-02-01
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. (orig.)
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Transport ac losses in Bi-2223 multifilamentary tapes - conductor materials aspect
Energy Technology Data Exchange (ETDEWEB)
Glowacki, B A [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge BC2 3QZ (United Kingdom); Majoros, M [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Institute of Electrical Engineering, SAS, Bratislava (Slovakia)
2000-05-01
Transport ac losses in technical superconductors based on Bi-2223 tape material are influenced by many parameters. The major factors that define the ac performance of such conductors are the following: the size and number of filaments, their geometrical arrangement in the cross-section of the conductor, the twist pitch length, the resistivity of the matrix, the presence of oxide barriers around the filaments and deformation procedures such as sequential pressing or rolling followed by appropriate thermal treatment. In the present paper the above aspects are addressed from the viewpoint of the materials science of technical conductor design. Transport ac losses at power frequencies in different types of Bi-2223 conductor are presented and analysed. The results of conductor design analysis with respect to the coexistence of the superconductor with other materials in the conductor structure are presented. New concepts for minimization of the transport ac losses are discussed in detail. (author)
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A new approach to electrical impedance imaging technique
International Nuclear Information System (INIS)
Afroj Quadir, K.; Nasir, F.; Rahman, M.; Rabbani, K.S.
2004-09-01
It is possible to obtain a 2 dimensional (2D) image of a volume conductor, to locate a few widely separated objects, by driving ac constant currents through two orthogonal pairs of electrodes and measuring the resulting potential differences between several diagonally placed electrodes at the centre and back-projecting their impedance values along equi-potential lines. This has been termed as Pigeon Hole Imaging (PHI). Experimental verification has been attempted using a small insulating object placed at different locations in a saline filled 2D phantom. For a 6 x 6 matrix, the image in 16 pixels in close proximity of the diagonal along which electrodes are arranged, coincide with the object positions, while they do nt for the remaining 20 pixels. We applied a new technique where image smearing patterns have been used to correct the images in 14 of these pixels while 6 pixels near the two opposite comers still remain uncertain. Thus 30 pixels out of 36 give the right object position which may be termed a success. The concept may be extended further to higher order matrices by increasing the number of diagonal electrodes. The present work mainly concentrates on the feasibility of localization of a single small object in one matrix position of the image. (author)
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Quadratic Boost A-Source Impedance Network
DEFF Research Database (Denmark)
Siwakoti, Yam Prasad; Blaabjerg, Frede; Chub, Andrii
2016-01-01
A novel quadratic boost A-source impedance network is proposed to realize converters that demand very high voltage gain. To satisfy the requirement, the network uses an autotransformer where the obtained gain is quadratically dependent on the duty ratio and is unmatched by any existing impedance...
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Flow reversal at low voltage and low frequency in a microfabricated ac electrokinetic pump
DEFF Research Database (Denmark)
Gregersen, Misha Marie; Olesen, Laurits Højgaard; Brask, Anders
2007-01-01
measured in a regime, where both the applied voltage and the frequency are low, Vrms1.5 V and f20 kHz, compared to previously investigated parameter ranges. The impedance spectrum has been thoroughly measured and analyzed in terms of an equivalent circuit diagram to rule out trivial circuit explanations......Microfluidic chips have been fabricated in Pyrex glass to study electrokinetic pumping generated by a low-voltage ac bias applied to an in-channel asymmetric metallic electrode array. A measurement procedure has been established and followed carefully resulting in a high degree of reproducibility...... of the measurements over several days. A large coverage fraction of the electrode array in the microfluidic channels has led to an increased sensitivity allowing for pumping measurements at low bias voltages. Depending on the ionic concentration a hitherto unobserved reversal of the pumping direction has been...
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Microfluidic device for cell capture and impedance measurement.
Jang, Ling-Sheng; Wang, Min-How
2007-10-01
This work presents a microfluidic device to capture physically single cells within microstructures inside a channel and to measure the impedance of a single HeLa cell (human cervical epithelioid carcinoma) using impedance spectroscopy. The device includes a glass substrate with electrodes and a PDMS channel with micro pillars. The commercial software CFD-ACE+ is used to study the flow of the microstructures in the channel. According to simulation results, the probability of cell capture by three micro pillars is about 10%. An equivalent circuit model of the device is established and fits closely to the experimental results. The circuit can be modeled electrically as cell impedance in parallel with dielectric capacitance and in series with a pair of electrode resistors. The system is operated at low frequency between 1 and 100 kHz. In this study, experiments show that the HeLa cell is successfully captured by the micro pillars and its impedance is measured by impedance spectroscopy. The magnitude of the HeLa cell impedance declines at all operation voltages with frequency because the HeLa cell is capacitive. Additionally, increasing the operation voltage reduces the magnitude of the HeLa cell because a strong electric field may promote the exchange of ions between the cytoplasm and the isotonic solution. Below an operating voltage of 0.9 V, the system impedance response is characteristic of a parallel circuit at under 30 kHz and of a series circuit at between 30 and 100 kHz. The phase of the HeLa cell impedance is characteristic of a series circuit when the operation voltage exceeds 0.8 V because the cell impedance becomes significant.
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Low Impedance Carbon Adhesive Electrodes with Long Shelf Life.
Posada-Quintero, Hugo F; Reyes, Bersaín A; Burnham, Ken; Pennace, John; Chon, Ki H
2015-10-01
A novel electrocardiogram (ECG) electrode film is developed by mixing carbon black powder and a quaternary salt with a visco-elastic polymeric adhesive. Unlike traditional wet gel-based electrodes, carbon/salt/adhesive (CSA) electrodes should theoretically have an infinite shelf life as they do not dehydrate even after a prolonged period of storage. The CSA electrodes are electrically activated for use through the process of electrophoresis. Specifically, the activation procedure involves sending a high voltage and current through the electrode, which results in significant reduction of impedance so that high fidelity ECG signals can be obtained. Using the activation procedure, the ideal concentration of carbon black powder in the mixture with the adhesive was examined. It was determined that the optimum concentration of carbon black which minimized post-activation impedance was 10%. Once the optimal carbon black powder concentration was determined, extensive signal analysis was performed to compare the performance of the CSA electrodes to the standard silver-silver chloride (Ag/AgCl) electrodes. As a part of data analysis, electrode-skin contact impedance of the CSA was measured and compared to the standard Ag/AgCl electrodes; we found consistently lower impedance for CSA electrodes. For quantitative data analysis, we simultaneously collected ECG data with CSA and Ag/AgCl electrodes from 17 healthy subjects. Heart rate variability (HRV) indices and ECG morphological waveforms were calculated to compare CSA and Ag/AgCl electrodes. Non-significant differences for most of the HRV indices between CSA and Ag/AgCl electrodes were found. Of the morphological waveform metrics consisting of R-wave peak amplitude, ST-segment elevation and QT interval, only the first index was found to be significantly different between the two media. The response of CSA electrodes to motion artifacts was also tested, and we found in general no difference in the quality of the ECG signal