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Electric Conductivity (electric + conductivity)
Selected AbstractsAnalyzing Bank Filtration by Deconvoluting Time Series of Electric ConductivityGROUND WATER, Issue 3 2007Olaf A. Cirpka Knowing the travel-time distributions from infiltrating rivers to pumping wells is important in the management of alluvial aquifers. Commonly, travel-time distributions are determined by releasing a tracer pulse into the river and measuring the breakthrough curve in the wells. As an alternative, one may measure signals of a time-varying natural tracer in the river and in adjacent wells and infer the travel-time distributions by deconvolution. Traditionally this is done by fitting a parametric function such as the solution of the one-dimensional advection-dispersion equation to the data. By choosing a certain parameterization, it is impossible to determine features of the travel-time distribution that do not follow the general shape of the parameterization, i.e., multiple peaks. We present a method to determine travel-time distributions by nonparametric deconvolution of electric-conductivity time series. Smoothness of the inferred transfer function is achieved by a geostatistical approach, in which the transfer function is assumed as a second-order intrinsic random time variable. Nonnegativity is enforced by the method of Lagrange multipliers. We present an approach to directly compute the best nonnegative estimate and to generate sets of plausible solutions. We show how the smoothness of the transfer function can be estimated from the data. The approach is applied to electric-conductivity measurements taken at River Thur, Switzerland, and five wells in the adjacent aquifer, but the method can also be applied to other time-varying natural tracers such as temperature. At our field site, electric-conductivity fluctuations appear to be an excellent natural tracer. [source] Synthesis and characterization of a ,-conjugated hybrid of oligothiophene and porphyrinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2006Kenichi Oyaizu Abstract 5-(3-Thienyl)-10,15,20-triethyl-21H,23H -porphine (H2(ttep)) was synthesized and characterized. Oxidative polymerization of H2(ttep) gave a novel oligomeric porphyrin linked at the 2,5-positions of the thienyl group. Electric conductivity of 4 × 10,1 S/cm after I2 doping indicated that the oligomer had a ,-conjugated structure with a delocalization of , electrons over the thienylene backbone. PM3 calculations revealed a low HOCO-LUCO gap, which was consistent with the relatively high electric conductivity. Regioregular (head-to-tail) structure was inferred from spectroscopic and calculational results. The pendant porphyrin groups formed a regular J-type array along the thienylene backbone, which was indicated by a significant red shift of the Soret band maximum. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5403,5412, 2006 [source] Preparation and properties of the single-walled carbon nanotube/cellulose nanocomposites using N -methylmorpholine- N -oxide monohydrateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Dong-Hun Kim Abstract Single-walled carbon nanotube (SWNT)/cellulose nanocomposite films were prepared using N -methylmorpholine- N -oxide (NMMO) monohydrate as a dispersing agent for the acid-treated SWNTs (A-SWNTs) as well as a cellulose solvent. The A-SWNTs were dispersed in both NMMO monohydrate and the nanocomposite film (as confirmed by scanning electron microscopy) because of the strong hydrogen bonds of the A-SWNTs with NMMO and cellulose. The mechanical properties, thermal properties, and electric conductivity of the nanocomposite films were improved by adding a small amount of the A-SWNTs to the cellulose. For example, by adding 1 wt % of the A-SWNTs to the cellulose, tensile strain at break point, Young's modulus, and toughness increased , 5.4, , 2.2, and , 6 times, respectively, the degradation temperature increased to 9°C as compared with those of the pure cellulose film, and the electric conductivities at , (the wt % of A-SWNTs in the composite) = 1 and 9 were 4.97 × 10,4 and 3.74 × 10,2 S/cm, respectively. Thus, the A-SWNT/cellulose nanocomposites are a promising material and can be used for many applications, such as toughened Lyocell fibers, transparent electrodes, and soforth. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Numerical simulation of a permittivity probe for measuring the electric properties of planetary regolith and application to the near-surface region of asteroids and cometsMETEORITICS & PLANETARY SCIENCE, Issue 6 2008Klaus SPITZER Our simulation techniques aim at accompanying hardware development and conducting virtual experiments, e.g., to assess the response of arbitrary heterogeneous conductivity and permittivity distributions or to scrutinize possibilities for spatial reconstruction methods using inverse schemes. In a first step, we have developed a finite element simulation code on the basis of unstructured, adaptive triangular grids for arbitrary two-dimensional axisymmetric distributions of conductivity and permittivity. The code is able to take into account the spatial geometry of the probe and allows for possible inductive effects. In previous studies, the non-inductive approach has been used to convert potential and phase data into apparent material properties. By our simulations, we have shown that this approach is valid for the frequency range from 102 Hz to 107 Hz and electric conductivities of 10,8 S/m that are typical for the near-surface region of asteroids and comets composed of chondritic materials and/or frozen volatiles such as H2O and CO2 ice. We prove the accuracy of our code to be better than 10%, using mixed types of boundary conditions and present a simulated vertical log through a horizontally stratified subsurface layer as a representative example of a heterogeneous distribution of the electrical properties. Resolution studies for the given electrode separation reveal that the material parameters of layers having thicknesses of less than about half the electrode spread are not reconstructible if only apparent quantities are considered. Therefore, spatial distributions of the complex sensitivity are presented having in mind a future data inversion concept that will permit the multi-dimensional reconstruction of material parameters in heterogeneous environments. [source] Low-voltage electroosmosis pump for stand-alone microfluidics devicesELECTROPHORESIS, Issue 1-2 2003Yuzuru Takamura Abstract Two types of low-voltage electroosmosis pumps were developed using microfabrication technology for usage in handy or stand-alone applications of the micrototal analysis systems (,-TAS) and the lab-on-a-chip. This was done by making a thin (<,1 ,m) region in the flow path and by only applying voltages near this thin region using electrodes inserted into the flow path. The inserted electrodes must be free from bubble formation and be gas-tight in order to avoid pressure leakage. For these electrodes, Ag/AgCl or a gel salt bridge was used. For patterning the gel on the chip, a hydrophilic photopolymerization gel and a photolithographic technique were optimized for producing a gel with higher electric conductivity and higher mechanical strength. For high flow rate application, wide (33.2 mm) and thin (400 nm) pumping channels were compacted into a 1 mm×6 mm area by folding. This pump achieves an 800 Pa static pressure and a flow of 415 nL/min at 10 V. For high-pressure application, a pump was designed with the thin and thick regions in series and positive and negative electrodes were inserted between them alternatively. This pump could increase the pumping pressure without increasing the supply voltage. A pump with 10-stage connections generated a pressure of 25 kPa at 10 V. [source] Czochralski-grown Single Crystals with Acentric Symmetry Group 32,ADVANCED ENGINEERING MATERIALS, Issue 7 2004R.B. Heimann Single crystals with calcium gallium germanate (Ca3Ga2Ge4O14, CGG) structure such as langasite La3Ga5SiO14 (LGS), its niobium (,langanite', La3Ga5.5Nb0.5O14, LGN) and tantalum (,langataite', La3Ga5.5Ta0.5O14, LGT) analogs as well as strontium niobium gallium silicate (Sr3NbGa3Si2O14, SNGS) and strontium tantalum gallium silicate (Sr3TaGa3Si2O14, STGS) were grown with high perfection by the Czochralski pulling technique. Specific electric conductivity, optical activity, and dielectric, piezoelectric, bulk and surface acoustic, elastic, and electro-optic properties were measured. [source] Design and Synthesis of Hierarchical Nanowire Composites for Electrochemical Energy StorageADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Zheng Chen Abstract Nanocomposites of interpenetrating carbon nanotubes and vanadium pentoxide (V2O5) nanowires networks are synthesized via a simple in situ hydrothermal process. These fibrous nanocomposites are hierarchically porous with high surface area and good electric conductivity, which makes them excellent material candidates for supercapacitors with high energy density and power density. Nanocomposites with a capacitance up to 440 and 200,F g,1 are achieved at current densities of 0.25 and 10 A g,1, respectively. Asymmetric devices based on these nanocomposites and aqueous electrolyte exhibit an excellent charge/discharge capability, and high energy densities of 16,W h kg,1 at a power density of 75,W kg,1 and 5.5,W h kg,1 at a high power density of 3,750,W kg,1. This performance is a significant improvement over current electrochemical capacitors and is highly competetive with Ni,MH batteries. This work provides a new platform for high-density electrical-energy storage for electric vehicles and other applications. [source] Synthesis and Thermoelectric Characterization of Bi2Te3 NanoparticlesADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Marcus Scheele Abstract Here, a novel synthesis for near monodisperse, sub-10,nm Bi2Te3 nanoparticles is reported. A new reduction route to bismuth nanoparticles is described, which are then applied as starting materials in the formation of rhombohedral Bi2Te3 nanoparticles. After ligand removal by a novel hydrazine hydrate etching procedure, the nanoparticle powder is spark plasma sintered to a pellet with preserved crystal grain sizes. Unlike previous works on the properties of Bi2Te3 nanoparticles, the full thermoelectric characterization of such sintered pellets shows a highly reduced thermal conductivity and the same electric conductivity as bulk n-type Bi2Te3. [source] In Situ Growth of Mesoporous SnO2 on Multiwalled Carbon Nanotubes: A Novel Composite with Porous-Tube Structure as Anode for Lithium Batteries,ADVANCED FUNCTIONAL MATERIALS, Issue 15 2007Z. Wen Abstract A novel mesoporous-nanotube hybrid composite, namely mesoporous tin dioxide (SnO2) overlaying on the surface of multiwalled carbon nanotubes (MWCNTs), was prepared by a simple method that included in situ growth of mesoporous SnO2 on the surface of MWCNTs through hydrothermal method utilizing Cetyltrimethylammonium bromide (CTAB) as structure-directing agents. Nitrogen adsorption,desorption, X-ray diffraction and transmission electron microscopy analysis techniques were used to characterize the samples. It was observed that a thin layer tetragonal SnO2 with a disordered porous was embedded on the surface of MWCNTs, which resulted in the formation of a novel mesoporous-nanotube hybrid composite. On the base of TEM analysis of products from controlled experiment, a possible mechanism was proposed to explain the formation of the mesoporous-nanotube structure. The electrochemical properties of the samples as anode materials for lithium batteries were studied by cyclic voltammograms and Galvanostatic method. Results showed that the mesoporous-tube hybrid composites displayed higher capacity and better cycle performance in comparison with the mesoporous tin dioxide. It was concluded that such a large improvement of electrochemical performance within the hybrid composites may in general be related to mesoporous-tube structure that possess properties such as one-dimensional hollow structure, high-strength with flexibility, excellent electric conductivity and large surface area. [source] Preparation and properties of the single-walled carbon nanotube/cellulose nanocomposites using N -methylmorpholine- N -oxide monohydrateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Dong-Hun Kim Abstract Single-walled carbon nanotube (SWNT)/cellulose nanocomposite films were prepared using N -methylmorpholine- N -oxide (NMMO) monohydrate as a dispersing agent for the acid-treated SWNTs (A-SWNTs) as well as a cellulose solvent. The A-SWNTs were dispersed in both NMMO monohydrate and the nanocomposite film (as confirmed by scanning electron microscopy) because of the strong hydrogen bonds of the A-SWNTs with NMMO and cellulose. The mechanical properties, thermal properties, and electric conductivity of the nanocomposite films were improved by adding a small amount of the A-SWNTs to the cellulose. For example, by adding 1 wt % of the A-SWNTs to the cellulose, tensile strain at break point, Young's modulus, and toughness increased , 5.4, , 2.2, and , 6 times, respectively, the degradation temperature increased to 9°C as compared with those of the pure cellulose film, and the electric conductivities at , (the wt % of A-SWNTs in the composite) = 1 and 9 were 4.97 × 10,4 and 3.74 × 10,2 S/cm, respectively. Thus, the A-SWNT/cellulose nanocomposites are a promising material and can be used for many applications, such as toughened Lyocell fibers, transparent electrodes, and soforth. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Effect of morphology on the electric conductivity of binary polymer blends filled with carbon blackJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Zhongbin Xu Abstract Several carbon black (CB)-filled binary polymer blends were prepared in Haake rheometer. Distribution states of CB and effect of morphology on the electric conductivity of different ternary composites were investigated. Under our experimental condition CB particles located preferentially at the interface between polymethyl methacrylate (PMMA) and polypropylene (PP) in PMMA/PP/CB composites, in high-density polyethylene (HDPE) phase in PP/HDPE/CB composites, and in Nylon6 (PA6) phase in polystyrene (PS)/PA6/CB, PP/PA6/CB, PMMA/PA6/CB, and polyacrylonitrile (PAN)/PA6/CB composites; the ternary composites in which CB particles locate at the interface of two polymer components have the highest electric conductivity when the mass ratio of the two polymers is near to 1 : 1. The ternary composites in which CB particles located preferentially in one polymer have the highest electric conductivity usually when the amount of the polymer component having CB particles is comparatively less than the amount of the polymer component not having CB particles; if the formulations of PS/PA6/CB, PP/PA6/CB, and PMMA/PA6/CB composites equaled and PA6/CB in them is in dispersed phase, PS/PA6/CB composites have the highest electric conductivity and PP/PA6/CB composites have the lowest electric conductivity; suitable amount of PS or PAN in PA6/CB composites increase the electric conductivity due in the formation of a parallel electrocircuit for electrons to transmit. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Synthesis and characterization of a ,-conjugated hybrid of oligothiophene and porphyrinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2006Kenichi Oyaizu Abstract 5-(3-Thienyl)-10,15,20-triethyl-21H,23H -porphine (H2(ttep)) was synthesized and characterized. Oxidative polymerization of H2(ttep) gave a novel oligomeric porphyrin linked at the 2,5-positions of the thienyl group. Electric conductivity of 4 × 10,1 S/cm after I2 doping indicated that the oligomer had a ,-conjugated structure with a delocalization of , electrons over the thienylene backbone. PM3 calculations revealed a low HOCO-LUCO gap, which was consistent with the relatively high electric conductivity. Regioregular (head-to-tail) structure was inferred from spectroscopic and calculational results. The pendant porphyrin groups formed a regular J-type array along the thienylene backbone, which was indicated by a significant red shift of the Soret band maximum. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5403,5412, 2006 [source] Effect of Thermal Initiator Concentration on the Electrical Behavior of Polymer-Derived Amorphous Silicon CarbonitridesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2008Yansong Wang The electric conductivity of polymer-derived silicon carbonitrides made from a polysilazane modified with different amounts of thermal initiator is measured at room temperature. It is found that the thermal initiator has a significant effect on the electric conductivity, which first increases and then decreases with increasing thermal initiator concentration. The highly conductive sample exhibits a very high piezoresistive coefficient and weak temperature dependence as compared with the low conductive samples. The microstructures of the materials are characterized using a Raman spectroscope. Based on these results, two conducting mechanisms are identified: the highly conductive sample is dominated by the tunneling,percolation mechanism, while the low conductive samples are dominated by matrix phases. The effect of the thermal initiator on the development of the microstructures of the materials is discussed. [source] Facile Fabrication of Functional Polypyrrole Nanotubes via a Reactive Self-Degraded TemplateMACROMOLECULAR RAPID COMMUNICATIONS, Issue 21 2005Xiaoming Yang Abstract Summary: Polypyrrole nanotubes with high electric conductivity and azo function have been fabricated in high yield via an in-situ polymerization. During the process fibrillar complex of FeCl3 and methyl orange (MO), acting as a reactive self-degraded template, directed the growth of polypyrrole on its surface and promoted the assembly into hollow nanotubular structures. TEM image of uncompleted PPy nanotubes synthesized in MO solutions after reaction for 40 min. [source] Effect of aeration in reducing phytotoxicity in anaerobic digestion liquor of swine manureANIMAL SCIENCE JOURNAL, Issue 4 2007Dai HANAJIMA ABSTRACT Numerous reports have accumulated concerning the quality of solid compost. In contrast, there are few for the residue of anaerobic digestion. In this study, the fertilizer value of anaerobic digestion liquor (ADL) was evaluated, and the effect of aeration on the reduction of the phytotoxicity was examined by a germination assay. Low or high aeration (100 or 400 mL/min) was added to 3 L of ADL obtained from a mixture of pig manure and garbage by using 5-L jar fermenters under a controlled temperature of 30°C. During the 14-day aeration period, a high aeration rate improved the germination index (GI) score from 5.7% to nearly 80%, while a low aeration rate did not. Although organic matter decomposition, determined as chemical oxygen demand, did not differ with aeration intensity, remarkable differences were observed in the time course of changes in pH, electric conductivity and ammonium-nitrogen (NH4 -N) and total nitrogen (T-N) content. Among these parameters, the NH4 -N concentration correlated highly with the GI score (r = 0.986). The primary phytotoxic element in ADL was considered to be NH4 -N, and the stripping of ammonia (NH3) by high aeration resulted in the improvement of the GI score. Although the ratio of major nutrients N : P2O5 : K2O (1:0.41:0.94) in ADL was at nearly same level as conventional liquid fertilizer, special attention should be paid to the high concentration of NH3 when drawing up a fertilization plan. [source] Research on synthesis and conductivity of ferrocenyl Schiff base and its saltAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2007Wei-Jun Liu Abstract Ferrocenyl Schiff base was synthesized through the condensation of ferrocenecarboxaldehyde and p -phenylenediamine under neutral conditions, and then a new interesting category of organometallic charge transfer complex was obtained by the doping of ferrocenyl Schiff base with Fe3+, Al3+ and Ti3+ salts. The effects of the dosage of doping agent and doping temperature on the room-temperature electric conductivity of samples were discussed; in addition, the temperature dependence of the electric conductivity of samples was studied, their structures and compositions were characterized by 1H-NMR spectra, infrared spectra, ultraviolet spectra and an electron probe X-ray microanalyser. The results showed that the electric conductivity of sample can increase 4,5 orders of magnitude after doping with a metallic salt, and the electric conductivity has a positive temperature coefficient effect. The electrical activation energies of the complexes in the range 0.09,1.54 eV were calculated from Arrhenius plots, indicating their favourable semiconducting behaviour. Copyright © 2006 John Wiley & Sons, Ltd. [source] Magnetic signal prospecting using multiparameter measurements: the case study of the Gallic Site of LevrouxARCHAEOLOGICAL PROSPECTION, Issue 3 2010M. Pétronille Abstract The ,magnetic signal' that combines both the induced (Ji) and the remanent (Jr) magnetization is widely used in archaeological and pedological prospecting. Magnetic prospecting recording the lateral variations of the total magnetization is the most frequently used measurement before in-phase magnetic susceptibility (Kph) and magnetic viscosity (Kqu) mapping. The work presented here brings together three types of prospecting technique: magnetic field survey and electromagnetic measurements with both frequency and time domain devices that measure magnetic susceptibility and viscosity respectively. The site studied, the Gallic town of Levroux (Indre, France), is particularly interesting because it includes features such as pits and ditches dug into the calcareous substratum partly filled with topsoil and with residues of different metallurgical and fire activities. The field results indicated anomalies with different types of characterization: (i) many compact features filled with magnetic, electrically conductive and minimally viscous materials; and (ii) elongated anomalies characterized by lower magnetic properties and electric conductivity but relatively higher magnetic viscosity than those of the compact features. In addition to the location of the features, the combination of the information brought by the different types of measurements allows us to evaluate the possible erosion of their upper parts by ploughing, to assess their depth (never deeper than 1.30,m) and to precise the nature of the feature's fill. Copyright © 2010 John Wiley & Sons, Ltd. [source] Tetraalkylammonium Salts of Weakly Coordinating Aluminates: Ionic Liquids, Materials for Electrochemical Applications and Useful Compounds for Anion InvestigationCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2009Ines Raabe Dr. Abstract Weak and robust? Tetraalkylammonium salts of weakly coordinating fluorinated alkoxyaluminates are easily accessible, chemically robust materials that show interesting physico-chemical properties like low melting points, high electrochemical stability and electric conductivity in weakly polar solvents such as CH2Cl2, Ph-F and toluene. In this study, we investigated the tetraalkylammonium salts of the weakly coordinating fluorinated alkoxyaluminates [pftb], ([Al(O(C(CF3)3)4],), [hfip], ([Al(OC(H)(CF3)2)4],) and [hftb], ([Al(OC(CH3)(CF3)2)4],) in order to obtain information on their undisturbed spectral and structural properties, as well as to study their electrochemical behavior (i.e., conductivities in non-polar solvents and electrochemical windows). Several of the compounds qualify as ionic liquids with melting points as low as 42,°C for [NBu4]+[hfip],. Simple and almost quantitative metathesis reactions yielding these materials in high purity were developed. These [NR4]+ salts serve as model compounds for undisturbed anions and their vibrational spectra,together with simulated spectra based on quantum chemical DFT calculations,were used for the clear assignment of the anion bands. Besides, the ion volumes of the anions (Vion([pftb],)=0.736,nm3, Vion([hftb],)=0.658,nm3, Vion([hfip],)=0.577,nm3) and their decomposition pathways in the mass spectrometric measurements have been established. The salts are highly soluble in non-polar solvents (up to 1.09,mol,L,1 are possible for [NBu4]+[hftb], in CH2Cl2 and 0.41,mol,L,1 for [NBu4]+[hfip], in CHCl3) and show higher molar conductivities if compared to [NBu4]+[PF6],. The electrochemical windows of CH2Cl2, CH3CN and 1,2-F2C6H4 using the [NBu4]+ aluminate electrolytes are up to +0.5,V/,0.7,V larger than those using the standard [NBu4]+[PF6],. [source] | |||||||||||||||||||||||||||||||