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Sample records for dielectric dispersion study

  1. An experimental study of dielectric dispersion in porous media and its dependence on pore geometry

    Energy Technology Data Exchange (ETDEWEB)

    Haslund, E.

    1996-12-31

    Understanding water saturated composite media are important in the study of oil reservoirs. This doctoral thesis discusses measurements of the frequency dependent permittivity and conductivity of water saturated porous glass specimens. The experiments are designed to investigate the dispersion resulting from the geometrical properties of the pore space. Measurements are presented of the effective complex dielectric constant of water saturated porous glass specimens for frequencies below 13 MHz. The specimens are made from sintered glass spheres, and in some specimens thin plates are mixed in with the spheres. Low-conductivity water is used to saturate the pore space in order to scale the frequency range of the Maxwell-Wagner dispersion into the measurement range. The experiments are compared with two different effective medium approaches. One approach is the Mendelson and Cohen theory with randomly oriented spheroidal grains in addition to spherical grains, the other the Local porosity theory due to Hilfer. Both theories were found to be in good agreement with the experimental observations. 175 refs., 59 figs., 1 table

  2. Dielectric Dispersion Studies Indicate Change in Structure of Water by Potentised Homeopathic Medicines

    Science.gov (United States)

    Mahata, C. R.

    2012-12-01

    Response of living bodies to different vastly `diluted' homeopathic medicines are different (rejecting the sceptic's view of `placebo' effect), though they are chemically same. Till now there is no satisfactory answer to how one such medicine differs from another in terms of scientifically measurable parameters. This paper tries to address this basic issue by taking two medicines of the same potency and two different potencies of the same medicine, namely, Arnica Mont 30c, 200c and Anacardium Orient 30c, 200c. These potencies are well above the Avogadro limit. The investigation reported here proceeds with the concept of `induced molecular structure' advanced by a number of scientists. Dielectric dispersion is used as the tool for experimental verification. It is based on the fact that when the exciting frequency of applied electric field equals the characteristic frequency, then macromolecules resonate leading to anomalous dielectric dispersion associated with sharp increase in dielectric loss, the resonance frequencies being different for macromolecules of different structures or dimensions. The results suggest that medicine- and potency-specific attributes are acquired by the vehicle (i.e. water) in the form of macromolecules generated by the potentization process of homeopathy making one medicine structurally different from another.

  3. Dielectric dispersion, relaxation dynamics and thermodynamic studies of Beta-Alanine in aqueous solutions using picoseconds time domain reflectometry

    Science.gov (United States)

    Vinoth, K.; Ganesh, T.; Senthilkumar, P.; Sylvester, M. Maria; Karunakaran, D. J. S. Anand; Hudge, Praveen; Kumbharkhane, A. C.

    2017-09-01

    The aqueous solution of beta-alanine characterised and studied by their dispersive dielectric properties and relaxation process in the frequency domain of 10×106 Hz to 30×109 Hz with varying concentration in mole fractions and temperatures. The molecular interaction and dielectric parameters are discussed in terms of counter-ion concentration theory. The static permittivity (ε0), high frequency dielectric permittivity (ε∞) and excess dielectric parameters are accomplished by frequency depended physical properties and relaxation time (τ). Molecular orientation, ordering and correlation factors are reported as confirmation of intermolecular interactions. Ionic conductivity and thermo dynamical properties are concluded with the behaviour of the mixture constituents. Solute-solvent, solute-solute interaction, structure making and breaking abilities of the solute in aqueous medium are interpreted. Fourier Transform Infrared (FTIR) spectra of beta- alanine single crystal and liquid state have been studied. The 13C Nuclear Magnetic Resonance (NMR) spectral studies give the signature for resonating frequencies and chemical shifts of beta-alanine.

  4. Dielectric dispersion in pure and doped lithium rubidium sulphate

    Science.gov (United States)

    Kassem, M. E.; El-Muraikhi, M.; Al-Houty, L.; Mohamed, A. A.

    The frequency (102 - 105 Hz) dependence of the dielectric properties of lithium rubidium sulphate (LRS) are reported in the vicinity of the transition temperature Tc = 477 K. The a.c. conductivity σ(ω) shows a strong temperature dependence and weak frequency response. The dielectric constant in this region shows a strong frequency dispersion. A Cole-Cole diagram was used to determine the distribution parameter and the molecular relaxation time. The effect of doping with Dy+3, Sm+3 and V+3, was also studied. It was found that doping gives rise to localized states which produce a disorder in the structure of LiRbSO4.

  5. Dispersion characteristics of two-dimensional unmagnetized dielectric plasma photonic crystal

    International Nuclear Information System (INIS)

    Li-Mei, Qi; Zi-Qiang, Yang; Feng, Lan; Xi, Gao; Da-Zhi, Li

    2010-01-01

    This paper studies dispersion characteristics of the transverse magnetic (TM) mode for two-dimensional unmagnetized dielectric plasma photonic crystal by a modified plane wave method. First, the cutoff behaviour is made clear by using the Maxwell–Garnett effective medium theory, and the influences of dielectric filling factor and dielectric constant on effective plasma frequency are analysed. Moreover, the occurence of large gaps in dielectric plasma photonic crystal is demonstrated by comparing the skin depth with the lattice constant, and the influence of plasma frequency on the first three gaps is also studied. Finally, by using the particle-in-cell simulation method, a transmission curve in the Γ – X direction is obtained in dielectric plasma photonic crystal, which is in accordance with the dispersion curves calculated by the modified plane wave method, and the large gap between the transmission points of 27 GHz and 47 GHz is explained by comparing the electric field patterns in particle-in-cell simulation

  6. Quantum optics of dispersive dielectric media

    International Nuclear Information System (INIS)

    Lenac, Z.

    2003-01-01

    We quantize the electromagnetic field in a polar medium starting with the fundamental equations of motion. In our model the medium is described by a Lorenz-type dielectric function ε(r,ω) appropriate, e.g., for ionic crystals, metals, and inert dielectrics. There are no restrictions on the spatial behavior of the dielectric function, i.e., there can be many different polar media with arbitrary shapes. We assume no losses in our system so the dielectric function for the whole space is assumed as real. The quantization procedure is based on an expansion of the total field (transverse and longitudinal) in terms of the coupled (polariton) eigenmodes, and this approach incorporates all previous results derived for similar but restricted systems (e.g., without spatial or frequency dependence of coupled modes). Within the same model, we also quantize the Hamiltonian of a nonretarded electromagnetic field in polar media. Particular attention is paid to the derivation of the orthogonality and closure relations, which are used in a discussion of the fundamental (equal-time) commutation relations between the conjugate field operators

  7. Polarization waves in dielectric films with spatial dispersion

    International Nuclear Information System (INIS)

    Jardin, Jean-Pierre; Moch, Philippe; Dvorak, Vladimir

    2002-01-01

    The polarization waves propagating in a slab-shaped or in a semi-infinite dielectric medium with spatial dispersion characterized by a volume free-energy density and by a boundary-surface energy density are studied, taking into account Maxwell's equations, in the framework of the Landau-Ginzburg formalism. It is shown that two independent extrapolation lengths providing for the required additional boundary conditions need to be specified at each surface limiting the medium. Complete calculations are performed in the electrostatic approximation: they provide evidence of the differences between the transverse in-plane polarized modes (s modes) and the sagittal plane polarized modes (p modes). True surface modes exist only in the case of negative extrapolation lengths. A detailed analysis of the symmetry properties of the surface and of the guided bulk modes in a slab is developed. Finally, our results are compared with those from previous models describing the boundary conditions in media where spatial dispersion is present. (author)

  8. Center for dielectric studies

    Science.gov (United States)

    Cross, L. E.; Newnham, R. E.; Biggers, J. V.

    1984-05-01

    This report focuses upon the parts of the Center program which have drawn most extensively upon Navy funds. In the basic study of polarization processes in high K dielectrics, major progress has been made in understanding the mechanisms in relaxor ferroelectric in the perovskite structure families. A new effort is also being mounted to obtain more precise evaluation of the internal stress effects in fine grained barium titanate. Related to reliability, studies of the effects of induced macro-defects are described, and preparation for the evaluation of space charge by internal potential distribution measurements discussed. To develop new processing methods for very thin dielectric layers, a new type of single barrier layer multilayer is discussed, and work on the thermal evaporation of oriented crystalline antimony sulphur iodide describe.

  9. Dielectric dispersion of porous media as a fractal phenomenon

    Science.gov (United States)

    Thevanayagam, S.

    1997-09-01

    It is postulated that porous media is made up of fractal solid skeleton structure and fractal pore surface. The model thus developed satisfies measured anomalous dielectric behavior of three distinctly different porous media: kaolin, montmorillonite, and shaly sand rock. It is shown that the underlying mechanism behind dielectric dispersion in the kHz range to high MHz range is indeed Maxwell-Wagner mechanism but modified to take into account the multiphase nature of the porous media as opposed to the traditional two-phase Maxwell-Wagner charge accumulation effect. The conductivity of the surface water associated with the solid surface and charge accumulation across the surface irregularities, asperity, and bridging between particles at the micro-scale-level pores are shown to contribute to this modified Maxwell-Wagner mechanism. The latter is dominant at low frequencies. The surface water thickness is calculated to be about 2-6 nm for a variety of porous media.

  10. Exact Dispersion Study of an Asymmetric Thin Planar Slab Dielectric Waveguide without Computing {d^2}β/{d{k^2}} Numerically

    Science.gov (United States)

    Raghuwanshi, Sanjeev Kumar; Palodiya, Vikram

    2017-08-01

    Waveguide dispersion can be tailored but not the material dispersion. Hence, the total dispersion can be shifted at any desired band by adjusting the waveguide dispersion. Waveguide dispersion is proportional to {d^2}β/d{k^2} and need to be computed numerically. In this paper, we have tried to compute analytical expression for {d^2}β/d{k^2} in terms of {d^2}β/d{k^2} accurately with numerical technique, ≈ 10^{-5} decimal point. This constraint sometimes generates the error in calculation of waveguide dispersion. To formulate the problem we will use the graphical method. Our study reveals that we can compute the waveguide dispersion enough accurately for various modes by knowing - β only.

  11. Relativistic plasma dielectric tensor evaluation based on the exact plasma dispersion functions concept

    International Nuclear Information System (INIS)

    Castejon, F.; Pavlov, S. S.

    2006-01-01

    The fully relativistic plasma dielectric tensor for any wave and plasma parameter is estimated on the basis of the exact plasma dispersion functions concept. The inclusion of this concept allows one to write the tensor in a closed and compact form and to reduce the tensor evaluation to the calculation of those functions. The main analytical properties of these functions are studied and two methods are given for their evaluation. The comparison between the exact dielectric tensor with the weakly relativistic approximation, widely used presently in plasma waves calculations, is given as well as the range of plasma temperature, harmonic number, and propagation angle in which the weakly relativistic approximation is valid

  12. Quantum-optical input-output relations for dispersive and lossy multilayer dielectric plates

    International Nuclear Information System (INIS)

    Gruner, T.; Welsch, D.

    1996-01-01

    Using the Green-function approach to the problem of quantization of the phenomenological Maxwell theory, the propagation of quantized radiation through dispersive and absorptive multilayer dielectric plates is studied. Input-output relations are derived, with special emphasis on the determination of the quantum noise generators associated with the absorption of radiation inside the dielectric matter. The input-output relations are used to express arbitrary correlation functions of the outgoing field in terms of correlation functions of the incoming field and those of the noise generators. To illustrate the theory, photons at dielectric tunneling barriers are considered. It is shown that inclusion in the calculations of losses in the photonic band gaps may substantially change the barrier traversal times. copyright 1996 The American Physical Society

  13. Dispersion of Dielectric Permittivity in a Nanocrystalline Cellulose-Triglycine Sulfate Composite at Low and Ultralow Frequencies

    Science.gov (United States)

    Thu'o'ng, Nguyen Hoai; Sidorkin, A. S.; Milovidova, S. D.

    2018-03-01

    The dispersion of dielectric permittivity in nanocrystalline cellulose-triglycine sulfate composites is studied in the range of frequencies from 10-3 to 106 Hz, at temperatures varying from room temperature to the temperature of phase transition in this composite (54°C), in weak electric fields (1 V cm-1). Two behaviors for the dielectric dispersion are identified in the studied frequency range: at ultralow frequencies (10-3-10 Hz), the dispersion is due to Maxwell-Wagner polarization, while at higher frequencies (10-106 Hz), the dispersion is due to the movement of domain walls in the embedded triglycine sulfate crystallites. An additional peak in the temperature-dependent profiles of dielectric permittivity is detected at lower temperatures in freshly prepared samples of the considered composite; we associate it with the presence of residual water in these samples.

  14. Frequency dispersion analysis of thin dielectric MOS capacitor in a five-element model

    Science.gov (United States)

    Zhang, Xizhen; Zhang, Sujuan; Zhu, Huichao; Pan, Xiuyu; Cheng, Chuanhui; Yu, Tao; Li, Xiangping; Cheng, Yi; Xing, Guichao; Zhang, Daming; Luo, Xixian; Chen, Baojiu

    2018-02-01

    An Al/ZrO2/IL/n-Si (IL: interface layer) MOS capacitor has been fabricated by metal organic decomposition of ZrO2 and thermal deposition Al. We have measured parallel capacitance (C m) and parallel resistance (R m) versus bias voltage curves (C m, R m-V) at different AC signal frequency (f), and C m, R m-f curves at different bias voltage. The curves of C m, R m-f measurements show obvious frequency dispersion in the range of 100 kHz-2 MHz. The energy band profile shows that a large voltage is applied on the ZrO2 layer and IL at accumulation, which suggests possible dielectric polarization processes by some traps in ZrO2 and IL. C m, R m-f data are used for frequency dispersion analysis. To exclude external frequency dispersion, we have extracted the parameters of C (real MOS capacitance), R p (parallel resistance), C IL (IL capacitance), R IL (IL resistance) and R s (Si resistance) in a five-element model by using a three-frequency method. We have analyzed intrinsic frequency dispersion of C, R p, C IL, R IL and R s by studying the dielectric characteristics and Si surface layer characteristics. At accumulation, the dispersion of C and R p is attributed to dielectric polarization such as dipolar orientation and oxide traps. The serious dispersion of C IL and R IL are relative to other dielectric polarization, such as border traps and fixed oxide traps. The dispersion of R s is mainly attributed to contact capacitance (C c) and contact resistance (R c). At depletion and inversion, the frequency dispersion of C, R p, C IL, R IL, and R s are mainly attributed to the depletion layer capacitance (C D). The interface trap capacitance (C it) and interface trap resistance (R it) are not dominant for the dispersion of C, R p, C IL, R IL, and R s.

  15. First-principles study of paraelectric and ferroelectric CsH2PO4 including dispersion forces: Stability and related vibrational, dielectric, and elastic properties

    Science.gov (United States)

    Van Troeye, Benoit; van Setten, Michiel Jan; Giantomassi, Matteo; Torrent, Marc; Rignanese, Gian-Marco; Gonze, Xavier

    2017-01-01

    Using density functional theory (DFT) and density functional perturbation theory (DFPT), we investigate the stability and response functions of CsH2PO4 , a ferroelectric material at low temperature. This material cannot be described properly by the usual (semi)local approximations within DFT. The long-range e--e- correlation needs to be properly taken into account, using, for instance, Grimme's DFT-D methods, as investigated in this work. We find that DFT-D3(BJ) performs the best for the members of the dihydrogenated alkali phosphate family (KH2PO4 , RbH2PO4 , CsH2PO4 ), leading to experimental lattice parameters reproduced with an average deviation of 0.5%. With these DFT-D methods, the structural, dielectric, vibrational, and mechanical properties of CsH2PO4 are globally in excellent agreement with the available experiments (<2 % MAPE for Raman-active phonons). Our study suggests the possible existence of a new low-temperature phase of CsH2PO4 , not yet reported experimentally. Finally, we report the implementation of DFT-D contributions to elastic constants within DFPT.

  16. Investigation of beta dielectric dispersion in Bovine yellow bone ...

    African Journals Online (AJOL)

    This technique makes use of a marconi magnification meter TF 1245 working in conjunction with a radio frequently oscillator TF 1246. In general the tissue exhibited a decrease in dielectric constant, ε΄ with increase in frequency until a lower steady value was attained at high frequency. JONAMP Vol. 11 2007: pp. 461-466 ...

  17. Mathematical Modeling of Electrical Conductivity of Dielectric with Dispersed Metallic Inclusions

    Directory of Open Access Journals (Sweden)

    V. S. Zarubin

    2015-01-01

    Full Text Available Composites are increasingly used for application in engineering as structural, thermal protection and functional materials, including dielectrics, because of a wide variety of properties. The relative dielectric constant and the dielectric loss tangent are basic functional characteristics of a composite used as a dielectric. The quantitative level of these characteristics is mainly affected by the properties of the composite matrix and inclusions as well as their shape and volume concentration. Metallic inclusions in a dielectric, which serves as a function of the composite matrix, expand electrical properties of the composite in particular increase its dielectric constant and dielectric loss tangent and thereby greatly expand its application field. Dielectric losses are defined by the imaginary component of the complex value of the relative dielectric constant of the dielectric. At a relatively low vibration frequency of electromagnetic field affecting the dielectric, this value is proportional to the electrical conductivity of the dielectric and inversely proportional to the frequency. In order to predict the expected value of the electric conductivity of the dielectric with metallic inclusions, a mathematical model that properly describes the structure of the composite and the electrical interaction of the matrix and inclusions is required.In the paper, a mathematical model of the electrical interaction of the representative element of the composite structure and a homogeneous isotropic medium with electrical conductivity, which is desired characteristics of the composite, is constructed. Globular shape of the metallic inclusions as an average statistical form of dispersed inclusions with a comparable size in all directions is adopted. The inclusion is covered with a globular layer of electrical insulation to avoid percolation with increasing volume concentration of inclusions. Outer globular layer of representative structure of composite

  18. Characterization of a dielectric microdroplet thermal interface material with dispersed nanoparticles

    International Nuclear Information System (INIS)

    Hamdan, A.; Sahli, F.; Richards, R.; Richards, C.

    2012-01-01

    This work presents the fabrication and characterization of a dielectric microdroplet thermal interface material (TIM). Glycerin droplets, 1 μL, were tested as TIMs in this study. Copper nanoparticles having a diameter of 25 nm were dispersed in glycerin at different volume fractions to enhance its thermal conductivity. An increase of 57.5% in the thermal conductivity of glycerin was measured at a volume fraction of 15%. A minimum thermal interface resistance of 30.37 mm 2 K/W was measured for the glycerin microdroplets at a deformed droplet height of 10.2 μm. Good agreement between experimental measurements and the predictions of a model based on Maxwell’s equation of rules of mixtures was obtained. The effect of nanoparticles' size on the effective thermal conductivity of glycerin was studied. Nanoparticles with diameters of 60–80 and 300 nm were dispersed in glycerin at a volume fraction of 5%, and their results were compared to those of the 25 nm particles.

  19. Efficient reconstruction of dispersive dielectric profiles using time domain reflectometry (TDR

    Directory of Open Access Journals (Sweden)

    P. Leidenberger

    2006-01-01

    Full Text Available We present a numerical model for time domain reflectometry (TDR signal propagation in dispersive dielectric materials. The numerical probe model is terminated with a parallel circuit, consisting of an ohmic resistor and an ideal capacitance. We derive analytical approximations for the capacitance, the inductance and the conductance of three-wire probes. We couple the time domain model with global optimization in order to reconstruct water content profiles from TDR traces. For efficiently solving the inverse problem we use genetic algorithms combined with a hierarchical parameterization. We investigate the performance of the method by reconstructing synthetically generated profiles. The algorithm is then applied to retrieve dielectric profiles from TDR traces measured in the field. We succeed in reconstructing dielectric and ohmic profiles where conventional methods, based on travel time extraction, fail.

  20. Dielectric matrix, dynamical matrix and phonon dispersion in hcp transition metal scandium

    International Nuclear Information System (INIS)

    Singh, Joginder; Singh, Natthi; Prakash, S.

    1976-01-01

    Complete dielectric matrix is evaluated for hcp transition metal scandium using the non-interacting s- and d-band model. The local field corrections which are consequence of the non-diagonal part of the dielectric matrix are calculated explicitly. The free electron approximation is used for the s-electrons and the simple tight-binding approximation is used for the d-electrons. The theory developed by Singh and others is used to invert the dielectric matrix and the explicit expressions for the dynamical matrix are obtained. The phonon dispersion relations are investigated by using the renormalized Animalu transition metal model potential (TMMP) for bare ion potential. The contribution due to non-central forces which arise due to local fields is found to be 20%. The results are found in resonably good agreement with the experimental values. (author)

  1. Control of the hyperbolic dispersion of dielectrics by an ultrashort laser pulse

    Science.gov (United States)

    Zhang, Xiaoqin; Wang, Feng; Zhang, Fengshou; Yao, Yugui

    2018-01-01

    An idea of controlling hyperbolic dispersion of dielectric materials by an ultrashort laser pulse is proposed. Taking the diamond as a concrete example and using time-dependent density functional theory calculations, we show that the permittivity tensor of the material can be effectively tuned by an ultrashort laser pulse, serving as a transient hyperbolic medium with wide working frequency window. With easily tunable laser parameters, the material can even be switched by reversal of both elliptic and hyperbolic for a particular light frequency. Our result points out a route toward transient hyperbolic materials, and it offers methods to achieve tunable hyperbolic dispersion with great potential for ultrafast device applications.

  2. imide, crystal structure, thermal and dielectric studies

    Indian Academy of Sciences (India)

    methyl imidazolium methylidene bis(trifluoromethanesulfonyl)imide, crystal structure, thermal and dielectric studies. BOUMEDIENE HADDAD1,2,3,∗, TAQIYEDDINE MOUMENE2, DIDIER VILLEMIN1,. JEAN-FRANÇOIS LOHIER1 and EL-HABIB ...

  3. Dispersion relation and electron acceleration in the combined circular and elliptical metallic-dielectric waveguide filled by plasma

    Science.gov (United States)

    Abdoli-Arani, A.; Montazeri, M. M.

    2018-04-01

    Two special types of metallic waveguide having dielectric cladding and plasma core including the combined circular and elliptical structure are studied. Longitudinal and transverse field components in the different regions are obtained. Applying the boundary conditions, dispersion relations of the electromagnetic waves in the structures are obtained and then plotted. The acceleration of an injected external relativistic electron in the considered waveguides is studied. The obtained differential equations related to electron motion are solved by the fourth-order Runge-Kutta method. Numerical computations are made, and the results are graphically presented.

  4. Studies on metal-dielectric plasmonic structures.

    Energy Technology Data Exchange (ETDEWEB)

    Chettiar, Uday K. (Purdue University, West Lafayette, IN); Liu, Zhengtong (Purdue University, West Lafayette, IN); Thoreson, Mark D. (Purdue University, West Lafayette, IN); Shalaev, Vladimir M. (Purdue University, West Lafayette, IN); Drachev, Vladimir P. (Purdue University, West Lafayette, IN); Pack, Michael Vern; Kildishev, Alexander V. (Purdue University, West Lafayette, IN); Nyga, Piotr (Purdue University, West Lafayette, IN)

    2010-01-01

    The interaction of light with nanostructured metal leads to a number of fascinating phenomena, including plasmon oscillations that can be harnessed for a variety of cutting-edge applications. Plasmon oscillation modes are the collective oscillation of free electrons in metals under incident light. Previously, surface plasmon modes have been used for communication, sensing, nonlinear optics and novel physics studies. In this report, we describe the scientific research completed on metal-dielectric plasmonic films accomplished during a multi-year Purdue Excellence in Science and Engineering Graduate Fellowship sponsored by Sandia National Laboratories. A variety of plasmonic structures, from random 2D metal-dielectric films to 3D composite metal-dielectric films, have been studied in this research for applications such as surface-enhanced Raman sensing, tunable superlenses with resolutions beyond the diffraction limit, enhanced molecular absorption, infrared obscurants, and other real-world applications.

  5. Broadband Terahertz Refraction Index Dispersion and Loss of Polymeric Dielectric Substrate and Packaging Materials

    Science.gov (United States)

    Motaharifar, E.; Pierce, R. G.; Islam, R.; Henderson, R.; Hsu, J. W. P.; Lee, Mark

    2018-01-01

    In the effort to push the high-frequency performance of electronic circuits and signal interconnects from millimeter waves to beyond 1 THz, a quantitative knowledge of complex refraction index values and dispersion in potential dielectric substrate, encapsulation, waveguide, and packaging materials becomes critical. Here we present very broadband measurements of the real and imaginary index spectra of four polymeric dielectric materials considered for use in high-frequency electronics: benzocyclobutene (BCB), polyethylene naphthalate (PEN), the photoresist SU-8, and polydimethylsiloxane (PDMS). Reflectance and transmittance spectra from 3 to 75 THz were made using a Fourier transform spectrometer on freestanding material samples. These data were quantitatively analyzed, taking into account multiple partial reflections from front and back surfaces and molecular bond resonances, where applicable, to generate real and imaginary parts of the refraction index as a function of frequency. All materials showed signatures of infrared active organic molecular bond resonances between 10 and 50 THz. Low-loss transmission windows as well as anti-window bands of high dispersion and loss can be readily identified and incorporated into high-frequency design models.

  6. High-frequency dielectric study of proustite crystals Ag3AsS3

    Science.gov (United States)

    Bordovsky, V. A.; Gunia, N. Yu; Castro, R. A.

    2014-12-01

    The dielectric properties of the crystals proustite in the frequency of 106-109 Hz and a temperature range of 173 to 473 K were studied. The dispersion of the dielectric parameters indicates the existence of non-Debye relaxation mechanism correlates with structural changes in the phase transition region. The charge transfer is temperature activated with an activation energy of 2.40 ± 0.01 eV.

  7. Progress in urban dispersion studies

    DEFF Research Database (Denmark)

    Batchvarova, E.; Gryning, Sven-Erik

    2006-01-01

    The present Study addresses recent achievements in better representation Of the urban area structure in meteorology and dispersion parameterisations. The setup and Main Outcome of several recent dispersion experiments in Urban areas and their use in model validation are discussed. The maximum con...

  8. Low Frequency Dispersion Mechanism of Dielectric Response for Oil-paper Insulation Diagnosis

    Institute of Scientific and Technical Information of China (English)

    ZHOU Lijun; LI Xianlang; WU Guangning

    2013-01-01

    Both the real part and imaginary part of complex permittivity approximately have a log-linear frequency dependency at low frequencies,especially at ultra-low frequencies under conditions of different moisture concentrations and temperatures,which is recognized as the low frequency dispersion (LFD).In order to explain this dispersion,a new mechanism of dielectric response of LFD of oil-paper insulation is proposed.A simplified one-dimensional mathematical model of concentration polarization carrier caused by slow migration is developed and solved,which indicates that ion mobility is closely related to the size of gap and the adsorption capacity of cellulose molecular chains to ions.A stochastic statistical model of the carrier mobility induced LFD is also developed.Moreover,actual tests under 50 ℃and 2% moisture content were put forward,as well as simulations with according current waveforms.The simulation results agreed well with the experimental data in that concentration polarization of carriers caused by slow migration is the probable cause of low frequency dispersion ofdielectric response for oil-paper insulation diagnosis.

  9. Visible-Frequency Dielectric Metasurfaces for Multiwavelength Achromatic and Highly Dispersive Holograms.

    Science.gov (United States)

    Wang, Bo; Dong, Fengliang; Li, Qi-Tong; Yang, Dong; Sun, Chengwei; Chen, Jianjun; Song, Zhiwei; Xu, Lihua; Chu, Weiguo; Xiao, Yun-Feng; Gong, Qihuang; Li, Yan

    2016-08-10

    Dielectric metasurfaces built up with nanostructures of high refractive index represent a powerful platform for highly efficient flat optical devices due to their easy-tuning electromagnetic scattering properties and relatively high transmission efficiencies. Here we show visible-frequency silicon metasurfaces formed by three kinds of nanoblocks multiplexed in a subwavelength unit to constitute a metamolecule, which are capable of wavefront manipulation for red, green, and blue light simultaneously. Full phase control is achieved for each wavelength by independently changing the in-plane orientations of the corresponding nanoblocks to induce the required geometric phases. Achromatic and highly dispersive meta-holograms are fabricated to demonstrate the wavefront manipulation with high resolution. This technique could be viable for various practical holographic applications and flat achromatic devices.

  10. Polaron-electron assisted giant dielectric dispersion in SrZrO{sub 3} high-k dielectric

    Energy Technology Data Exchange (ETDEWEB)

    Borkar, Hitesh; Barvat, Arun; Pal, Prabir; Kumar, Ashok, E-mail: ashok553@nplindia.org [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-National Physical Laboratory (CSIR-NPL) Campus, Dr. K S Krishnan Marg, New Delhi 110012 (India); Shukla, A. K. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Pulikkotil, J. J. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-National Physical Laboratory (CSIR-NPL) Campus, Dr. K S Krishnan Marg, New Delhi 110012 (India); Computation and Networking Facility, CSIR-National Physical Laboratory, New Delhi 110012 (India)

    2016-06-07

    The SrZrO{sub 3} is a well known high-k dielectric constant (∼22) and high optical bandgap (∼5.8 eV) material and one of the potential candidates for future generation nanoelectronic logic elements (8 nm node technology) beyond silicon. Its dielectric behavior is fairly robust and frequency independent till 470 K; however, it suffers a strong small-polaron based electronic phase transition (T{sub e}) linking 650 to 750 K. The impedance spectroscopy measurements revealed the presence of conducting grains and grain boundaries at elevated temperature which provide energetic mobile charge carriers with activation energy in the range of 0.7 to 1.2 eV supporting the oxygen ions and proton conduction. X-ray photoemission spectroscopy measurements suggest the presence of weak non-stoichiometric O{sup 2−} anions and hydroxyl species bound to different sites at the surface and bulk. These thermally activated charge carriers at elevated temperature significantly contribute to the polaronic based dielectric anomaly and conductivity. Our dielectric anomaly supports pseudo phase transition due to high degree of change in ZrO{sub 6} octahedral angle in the temperature range of 650–750 K, where electron density and phonon vibration affect the dielectric and conductivity properties.

  11. Resonance dielectric dispersion of TEA-CoCl2Br2 nanocrystals incorporated into the PMMA matrix

    Science.gov (United States)

    Kapustianyk, V.; Shchur, Ya; Kityk, I.; Rudyk, V.; Lach, G.; Laskowski, L.; Tkaczyk, S.; Swiatek, J.; Davydov, V.

    2008-09-01

    The dielectric properties of TEA-CoCl2Br2 nanocrystals incorporated into the polymethylmethacrylate matrix within the frequency range of 3 × 105-2.6 × 109 Hz in the temperature region of 90-300 K were investigated. The considerable difference in the dielectric spectra of the nanocomposite compared to those of the bulk crystal and the pure polymer matrix was observed. The dielectric dispersion of the composite material reveals a resonance type (resonance frequency was found to be near 1.3 GHz) and may be qualitatively explained as the result of piezoelectric resonance on the nanocrystals. The model interpretation of this phenomenon based on the forced-dumped oscillator is presented.

  12. Dielectric and gravimetric studies of water binding to lysozyme

    International Nuclear Information System (INIS)

    Bone, S.

    1996-01-01

    Time domain dielectric spectroscopy and hydration isotherm measurements as a function of temperature have been applied to hydrated lysozyme powder. Two dielectric dispersions were identified, the first centred at approximately 8 MHz and a second above 1 GHz. The higher dispersion is considered to be the result of rotational relaxation of water molecules bound to the enzyme. In this case the results indicate the existence of a population of 32 water molecules per lysozyme molecule which are irrotationally bound to the lysozyme structure. A larger population of water molecules is relatively free to respond to the electric field and exhibits a dipole moment close to that of vapour phase water molecules. Multi-temperature hydration isotherm measurements are used to calculate enthalpies and entropies associated with the binding of water to lysozyme. Discontinuities both in dielectric and in thermodynamic characteristics in the range 10-14% hydration are interpreted as a re-ordering of the water structure on the enzyme surface

  13. Dispersion of dielectric permittivity and magnetic properties of solid solution PZT–PFT

    Directory of Open Access Journals (Sweden)

    Skulski Ryszard

    2015-09-01

    Full Text Available In this paper we present the results of investigations into ceramic samples of solid solution (1-x(PbZr0.53Ti0.47O3- x(PbFe0.5Ta0.503 (i.e. (1-xPZT-xPFT with x = 0.25, 0.35 and 0.45. We try to find the relation between the character of dielectric dispersion at various temperatures and the composition of this solution. We also describe the magnetic properties of investigated samples. With increasing the content of PFT also mass magnetization and mass susceptibility increase (i.e. magnetic properties are more pronounced at every temperature. The temperature dependences of mass magnetization and re­ciprocal of mass susceptibility have similar runs for all the compositions. However, our magnetic investigations exhibit weak antiferromagnetic ordering instead of the ferromagnetic one at room temperature. We can also say that up to room tempera­ture any magnetic phase transition has not occurred. It may be a result of the conditions of the technological process during producing our PZT-PFT ceramics.

  14. Artificial dispersion via high-order homogenization: magnetoelectric coupling and magnetism from dielectric layers

    Science.gov (United States)

    Liu, Yan; Guenneau, Sébastien; Gralak, Boris

    2013-01-01

    We investigate a high-order homogenization (HOH) algorithm for periodic multi-layered stacks. The mathematical tool of choice is a transfer matrix method. Expressions for effective permeability, permittivity and magnetoelectric coupling are explored by frequency power expansions. On the physical side, this HOH uncovers a magnetoelectric coupling effect (odd-order approximation) and artificial magnetism (even-order approximation) in moderate contrast photonic crystals. Comparing the effective parameters' expressions of a stack with three layers against that of a stack with two layers, we note that the magnetoelectric coupling effect vanishes while the artificial magnetism can still be achieved in a centre-symmetric periodic structure. Furthermore, we numerically check the effective parameters through the dispersion law and transmission property of a stack with two dielectric layers against that of an effective bianisotropic medium: they are in good agreement throughout the low-frequency (acoustic) band until the first stop band, where the analyticity of the logarithm function of the transfer matrix () breaks down. PMID:24101891

  15. Low percolation transitions in carbon nanotube networks dispersed in a polymer matrix: dielectric properties, simulations and experiments.

    Science.gov (United States)

    Simoes, Ricardo; Silva, Jaime; Vaia, Richard; Sencadas, Vítor; Costa, Pedro; Gomes, João; Lanceros-Méndez, Senentxu

    2009-01-21

    The low concentration behaviour and the increase of the dielectric constant in carbon nanotubes/polymer nanocomposites near the percolation threshold are still not well understood. In this work, a numerical model has been developed which focuses on the effect of the inclusion of conductive fillers in a dielectric polymer matrix on the dielectric constant and the dielectric strength. Experiments have been carried out in carbon nanotubes/poly(vinylidene fluoride) nanocomposites in order to compare to the simulation results. This work shows how the critical concentration is related to the formation of capacitor networks and that these networks give rise to high variations in the electrical properties of the composites. Based on numerical studies, the dependence of the percolation transition on the preparation of the nanocomposite is discussed. Finally, based on numerical and experimental results, both ours and from other authors, the causes of anomalous percolation behaviour of the dielectric constant are identified.

  16. Dielectric dispersion and thermodynamic behavior of stearic acid binary mixtures with alcohol as co-solvent using time domain reflectometry

    Directory of Open Access Journals (Sweden)

    M. Maria Sylvester

    2017-08-01

    Full Text Available Dielectric permittivity and relaxation dynamics of binary and ternary mixture of stearic acid on various concentration and their thermodynamic effects are studied. The static dielectric constant (ε0, dielectric permittivity (ε′ and dielectric loss (ε′′ are found by bilinear calibration. The relaxation time (τ, dielectric strength (Δε and the excess permittivity (εE are found. The thermodynamic parameters such as enthalpy (ΔH, entropy (ΔS and Gibb’s free energy (ΔG are evolved. The significant changes in dielectric parameters are due to the intramolecular and intermolecular interactions in response to the applied frequency. The permittivity spectra of stearic acid–alcohol in the frequency range of 10MHz to 30GHz have been measured using picoseconds Time Domain Reflectometry (TDR. The dielectric parameters (ε0, ε′, ε′′ are found by bilinear calibration method. Influence of temperature in intermolecular interaction and the relaxation process are also studied. The FT-IR spectral analysis reveals that the conformation of functional groups and formation for hydrogen bonding are present in both binary and ternary mixtures of stearic acid.

  17. High dielectric permittivity elastomers from well-dispersed expanded graphite in low concentrations

    DEFF Research Database (Denmark)

    Daugaard, Anders Egede; Hassouneh, Suzan Sager; Kostrzewska, Malgorzata

    2013-01-01

    The development of elastomer materials with a high dielectric permittivity has attracted increased interest over the last years due to their use in for example dielectric electroactive polymers. For this particular use, both the electrically insulating properties - as well as the mechanical...

  18. Mechanistic study of plasma damage to porous low-k: Process development and dielectric recovery

    Science.gov (United States)

    Shi, Hualiang

    Low-k dielectrics with porosity are being introduced to reduce the RC delay of Cu/low-k interconnect. However, during the O2 plasma ashing process, the porous low-k dielectrics tend to degrade due to methyl depletion, moisture uptake, and densification, increasing the dielectric constant and leakage current. This dissertation presents a study of the mechanisms of plasma damage and dielectric recovery. The kinetics of plasma interaction with low-k dielectrics was investigated both experimentally and theoretically. By using a gap structure, the roles of ion, photon, and radical in producing damage on low-k dielectrics were differentiated. Oxidative plasma induced damage was proportional to the oxygen radical density, enhanced by VUV photon, and increased with substrate temperature. Ion bombardment induced surface densification, blocking radical diffusion. Two analytical models were derived to quantify the plasma damage. Based on the radical diffusion, reaction, and recombination inside porous low-k dielectrics, a plasma altered layer model was derived to interpret the chemical effect in the low ion energy region. It predicted that oxidative plasma induced damage can be reduced by decreasing pore radius, substrate temperature, and oxygen radical density and increasing carbon concentration and surface recombination rate inside low-k dielectrics. The model validity was verified by experiments and Monte-Carlo simulations. This model was also extended to the patterned low-k structure. Based on the ion collision cascade process, a sputtering yield model was introduced to interpret the physical effect in the high ion energy region. The model validity was verified by checking the ion angular and energy dependences of sputtering yield using O2/He/Ar plasma, low-k dielectrics with different k values, and a Faraday cage. Low-k dielectrics and plasma process were optimized to reduce plasma damage, including increasing carbon concentration in low-k dielectrics, switching plasma

  19. The set valued unified model of dispersion and attenuation for wave propagation in dielectric (and anelastic media

    Directory of Open Access Journals (Sweden)

    M. Caputo

    1998-06-01

    Full Text Available Since the dispersion and attenuation properties of dielectric and anelastic media, in the frequency domain, are expressed by similar formulae, as shown experimentally by Cole and Cole (1941 and Bagley and Torvik (1983, 1986 respectively, we note that the same properties may be represented in the time domain by means of an equation of the same form; this is obtained by introducing derivatives of fractional order into the system functions of the media. The Laplace Transforms (LT of such system functions contain fractional powers of the imaginary frequency and are, therefore, multivalued functions defined in the Riemann Sheets (RS of the function. We determine the response of the medium (dielectric o anelastic to a generic signal summing the time domain representation due to the branches of the solutions in the RSs of the LT. It is found that, if the initial conditions are equal in all the RSs, the solution is a sum of two exponentials with complex exponents, if the initial conditions are different in some of the RSs, then a transient for each of those RSs is added to the exponentials. In all cases a monochromatic wave is split into a set of waves with the same frequency and slightly different wavelengths which interfere and disperse. As a consequence a monochromatic electromagnetic wave with frequency around 1 MHz in water has a relevant dispersion and beats generating a tunnel effect. In the atmosphere of the Earth the dispersion of a monochromatic wave with frequency around 1 GHz, like those used in tracking artificial satellites, has a negligible effect on the accuracy of the determination of the position of the satellites and the positioning of the bench marks on the Earth. We also find the split eigenfunctions of the free modes of infinite plates and shells made of dielectric and anelastic media.

  20. Photoconductivity and dielectric studies of potassium pentaborate

    Indian Academy of Sciences (India)

    Single crystal of potassium pentaborate (KB5) has been grown by solution growth ... equipped with the Gunn Oscillator guided with rectangular wave-guide. ... its dielectric behaviour with the change of frequency has also been investigated.

  1. Development of accurate UWB dielectric properties dispersion at CST simulation tool for modeling microwave interactions with numerical breast phantoms

    International Nuclear Information System (INIS)

    Maher, A.; Quboa, K. M.

    2011-01-01

    In this paper, a reformulation for the recently published dielectric properties dispersion models of the breast tissues is carried out to be used by CST simulation tool. The reformulation includes tabulation of the real and imaginary parts versus frequency on ultra-wideband (UWB) for these models by MATLAB programs. The tables are imported and fitted by CST simulation tool to second or first order general equations. The results have shown good agreement between the original and the imported data. The MATLAB programs written in MATLAB code are included in the appendix.

  2. Electron depletion via cathode spot dispersion of dielectric powder into an overhead plasma

    International Nuclear Information System (INIS)

    Gillman, Eric D.; Foster, John E.

    2013-01-01

    The effectiveness of cathode spot delivered dielectric particles for the purpose of plasma depletion is investigated. Here, cathode spot flows kinetically entrain and accelerate dielectric particles originally at rest into a background plasma. The time variation of the background plasma density is tracked using a cylindrical Langmuir probe biased approximately at electron saturation. As inferred from changes in the electron saturation current, depletion fractions of up to 95% are observed. This method could be exploited as a means of communications blackout mitigation for manned and unmanned reentering spacecraft as well as any high speed vehicle enveloped by a dense plasma layer

  3. Dispersive dielectric and conductive effects in 2D resistor-capacitor networks.

    Science.gov (United States)

    Hamou, R F; Macdonald, J R; Tuncer, E

    2009-01-14

    How to predict and better understand the effective properties of disordered material mixtures has been a long-standing problem in different research fields, especially in condensed matter physics. In order to address this subject and achieve a better understanding of the frequency-dependent properties of these systems, a large 2D L × L square structure of resistors and capacitors was used to calculate the immittance response of a network formed by random filling of binary conductor/insulator phases with 1000 Ω resistors and 10 nF capacitors. The effects of percolating clusters on the immittance response were studied statistically through the generation of 10 000 different random network samples at the percolation threshold. The scattering of the imaginary part of the immittance near the dc limit shows a clear separation between the responses of percolating and non-percolating samples, with the gap between their distributions dependent on both network size and applied frequency. These results could be used to monitor connectivity in composite materials. The effects of the content and structure of the percolating path on the nature of the observed dispersion were investigated, with special attention paid to the geometrical fractal concept of the backbone and its influence on the behavior of relaxation-time distributions. For three different resistor-capacitor proportions, the appropriateness of many fitting models was investigated for modeling and analyzing individual resistor-capacitor network dispersed frequency responses using complex-nonlinear-least-squares fitting. Several remarkable new features were identified, including a useful duality relationship and the need for composite fitting models rather than either a simple power law or a single Davidson-Cole one. Good fits of data for fully percolating random networks required two dispersive fitting models in parallel or series, with a cutoff at short times of the distribution of relaxation times of one of

  4. Microstructure Study For Optimization Of Dielectric Property Of Electrical Porcelain

    International Nuclear Information System (INIS)

    Tak, S. K.; Shekhawat, M. S.; Mangal, R.

    2010-01-01

    Five sample mixtures of kaolin, ball clay, feldspar and Quartz were formulated and porcelain samples fabricated. Crystalline phases and mullite morphology were studied using XRD and SEM respectively. A composition of 30% kaolin, 15% ball clay, 30% feldspar and 25% quartz yielded a body with high dielectric strength of 19 kV/mm compare to an ISO graded product having dielectric strength 14.6 KV/mm after firing at 1225 deg. C.

  5. Sedimentation in Particulate Aqueous Suspensions as studied by means of Dielectric Time Domain Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pettersen, Bjoernar Hauknes

    1997-12-31

    Many problems in offshore oil production and multiphase transport are related to surface and colloid chemistry. This thesis applies dielectric spectroscopy as an experimental technique to study the behaviour of particle suspensions in polar media. The thesis opens with an introduction to suspensions and time domain dielectric spectroscopy. It then investigates the dielectric properties of silica and alumina dispersed in polar solvents. It is found that theoretical models can be used to calculate the volume fraction disperse phase in the suspension and that the particle sedimentation depends on the wetting of the particles, charge on the particle surface and viscosity of the solvent, and that this dependency can be measured by time domain dielectric spectroscopy. When the surface properties of silica and alumina particles were modified by coating them with a non-ionic polymer and a non-ionic surfactant, then different degrees of packing in the sedimented phase at the bottom of the sedimentation vessel occurred. Chemometrical methods on the synthesis of monodisperse silica particles were used to investigate what factors influence the particle size. It turned out that it is insufficient to consider only main variables when discussing the results of the synthesis. By introducing interaction terms, the author could explain the variation in the size of particles synthesized. The difference in the sedimentation rate of monodisperse silica particles upon variation of volume fraction particles, pH, salinity, amount of silanol groups at the particle surface and temperature was studied. The cross interactions play an important role and a model explaining the variation in sedimentation is introduced. Finally, magnetic particles dispersed in water and in an external magnetic field were used to study the impact on the sedimentation due to the induced flocculation. 209 refs., 90 figs., 9 tabs.

  6. Metallic nanoparticles in dielectrics: A comparative study

    KAUST Repository

    Agambayev, Agamyrat; Farhat, Mohamed; Bagci, Hakan; Salama, Khaled N.

    2017-01-01

    The Maxwell-Garnett method is used to predict the effective dielectric constant and the tangent loss of various composites consisting of a PVDF-TrFE-CFE-matrix and metallic microsphere fillers made of Cu, Ni, W, Zn, or Fe. Simulation results demonstrate that for small filler fraction values and at low frequencies, the electrical properties of the resulting composite do not depend on the conductivity of the filler. These findings show that composites fabricated using cheaper metal nanoparticle fillers are as effective as those fabricated using expensive ones.

  7. Metallic nanoparticles in dielectrics: A comparative study

    KAUST Repository

    Agambayev, Agamyrat

    2017-10-25

    The Maxwell-Garnett method is used to predict the effective dielectric constant and the tangent loss of various composites consisting of a PVDF-TrFE-CFE-matrix and metallic microsphere fillers made of Cu, Ni, W, Zn, or Fe. Simulation results demonstrate that for small filler fraction values and at low frequencies, the electrical properties of the resulting composite do not depend on the conductivity of the filler. These findings show that composites fabricated using cheaper metal nanoparticle fillers are as effective as those fabricated using expensive ones.

  8. Fractional-calculus-based FDTD algorithm for ultrawideband electromagnetic characterization of arbitrary dispersive dielectric materials

    NARCIS (Netherlands)

    Caratelli, Diego; Mescia, Luciano; Bia, Pietro; Stukach, Oleg V.

    2016-01-01

    A novel finite-difference time-domain algorithm for modeling ultrawideband electromagnetic pulse propagation in arbitrary multirelaxed dispersive media is presented. The proposed scheme is based on a general, yet computationally efficient, series representation of the fractional derivative operators

  9. Dielectric behaviour of the composite system: multiwall carbon nanotubes dispersed in ferroelectric liquid crystalline material

    Czech Academy of Sciences Publication Activity Database

    Shukla, R.K.; Raina, K.K.; Hamplová, Věra; Kašpar, Miroslav; Bubnov, Alexej

    2011-01-01

    Roč. 84, 9-10 (2011), 850-857 ISSN 0141-1594 R&D Projects: GA AV ČR IAA100100911; GA AV ČR(CZ) GA202/09/0047; GA ČR(CZ) GAP204/11/0723 Grant - others:RFASI(RU) 02.740.11.5166 Institutional research plan: CEZ:AV0Z10100520 Keywords : ferroelectric liquid crystal * multiwall carbon nanotube * composite * mesomorphic property * dielectric spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.006, year: 2011

  10. Structural, photoconductivity, and dielectric studies of polythiophene-tin oxide nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Murugavel, S., E-mail: starin85@gmail.com; Malathi, M., E-mail: mmalathi@vit.ac.in

    2016-09-15

    Highlights: • Synthesis of polythiophene-tin oxide nanocomposites confirmed by FTIR and EDAX. • SEM shows SnO{sub 2} nanoparticles embedded within polythiophene matrix. • Stability and isoelectric point suggest nanoparticle–matrix interaction. • High dielectric constant due to high Maxwell–Wagner interfacial polarization. - Abstract: Polythiophene-tinoxide (PT-SnO{sub 2}) nanocomposites were prepared by in situ chemical oxidative polymerization, in the presence of various concentrations of SnO{sub 2} nanoparticles. Samples were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and Zeta potential measurements. Morphologies and elemental compositions were investigated by transmission electron microscopy, field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The photoconductivity of the nanocomposites was studied by field-dependent dark and photo conductivity measurements. Their dielectric properties were investigated using dielectric spectroscopy, in the frequency range of 1kHz–1 MHz. The results indicated that the SnO{sub 2} nanoparticles in the PT-SnO{sub 2} nanocomposite were responsible for its enhanced dielectric performance.

  11. Multilayer cladding with hyperbolic dispersion for plasmonic waveguides

    DEFF Research Database (Denmark)

    Babicheva, Viktoriia; Shalaginov, Mikhail Y.; Ishii, Satoshi

    2015-01-01

    We study the properties of plasmonic waveguides with a dielectric core and multilayer metal-dielectric claddings that possess hyperbolic dispersion. The waveguides hyperbolic multilayer claddings show better performance in comparison to conventional plasmonic waveguides. © OSA 2015....

  12. Low-frequency dielectric dispersion and magnetic properties of La, Gd modified Pb(Fe1/2Ta1/2)O3 multiferroics

    International Nuclear Information System (INIS)

    Choudhury, R.N.P.; Rodriguez, C.; Bhattacharya, P.; Katiyar, R.S.; Rinaldi, C.

    2007-01-01

    Pb(Fe 1/2 Ta 1/2 )O 3 (PFT) modified by rare-earth (La and Gd) ions has been synthesized in a single phase using a double-stage synthesis (i.e., Columbite) technique. Scanning electron micrographs (SEM) of the pellet samples have shown a significant change in their grain size and uniform distribution of Gd/La at the Fe-sites. The room temperature X-ray structural analysis shows that the reported cubic (or tetragonal) structure of PFT has been distorted to a monoclinic system on substitution of La/Gd at the Fe-site. Detailed studies of dielectric properties of the above compound on La/Gd substitution have shown strong dielectric dispersion at low frequency (i.e. relaxor behavior) with drastic change in transition temperature. Magnetic characterization shows that though the PFT sample displays an antiferromagnetic transition at ∼150 K, the rare-earth ions-substituted samples do not. Furthermore, temperature dependence of magnetization measurements shows that spin glass transition observed in PFT at low temperatures (5-20 K) does not exist in the La and Gd substituted PFT. Doping of Gd in PFT increases the sample magnetization, especially at low temperature

  13. Studies on conductivity and dielectric properties of polyaniline–zinc ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. In the present paper, we report electrical conductivity and dielectric studies on the composites of conducting polyaniline (PANI) with crystalline semiconducting ZnS powder, wherein PANI has been taken as inclusion and ZnS crystallites as the host matrix. From the studies, it has been observed that the value of.

  14. Dielectric studies of fluids with reentrant resonators

    International Nuclear Information System (INIS)

    Goodwin, A.R.H.; Moldover, M.R.

    1993-01-01

    The authors have used a reentrant radio-frequency (rf) cavity as a resonator operating near 375 MHz to measure changes in the dielectric constant of fluids within it. The utility of these measurements was demonstrated by determining the dipole moment of 1,1,1,2,3,3-hexafluoropropane, a candidate replacement refrigerant (denoted R236ea) and by detecting the phase boundaries in the mixture [(1-x)C 2 H 6 + xCO 2 ], for the mole fraction x = 0.492. The densities of the coexisting phases of the mixture were determined using the Clausius-Mossotti relation which has errors on the order of 0.5% in this application. To test the accuracy of the present techniques, the rf resonator was calibrated with helium and then used to redetermine the molar polarizability A e of argon. The results were in excellent agreement with published values. The design of the reentrant resonator makes it suitable for use with corrosive fluids at temperature up to 400 degrees C

  15. Dielectric and thermal studies on gel grown strontium tartrate ...

    Indian Academy of Sciences (India)

    Administrator

    frequencies (110–700 kHz) of the applied a.c. field. It increases ... lytical studies. It is explained that crystallographic change due to polymorphic phase transition may be occur- ... inexpensive and unique method for growing crystals that show poor ... on dielectric and thermal characteristics of this material are described. 2.

  16. Structural, dielectric and piezoelectric study of Ca-, Zr-modified ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 40; Issue 5. Structural, dielectric and piezoelectric study of Ca-, Zr-modified BaTiO 3 lead-free ceramics. H MSOUNI A TACHAFINE M EL AATMANI D FASQUELLE J C CARRU M EL HAMMIOUI M RGUITI A ZEGZOUTI A OUTZOURHIT M DAOUD. Volume 40 Issue 5 ...

  17. Toward a unified description of nonlinearity and frequency dispersion of piezoelectric and dielectric responses in Pb(Zr,Ti)O3

    International Nuclear Information System (INIS)

    Damjanovic, D.; Bharadwaja, S.S.N.; Setter, N.

    2005-01-01

    A phenomenological approach is proposed describing both nonlinearity and frequency dispersion in dielectric and piezoelectric properties of lead zirconate titanate, Pb(Zr,Ti)O 3 (PZT), thin films and ceramics. The approach couples the frequency dependent response in form of the power law, 1/ω β , with the rate-independent nonlinear response described by the Rayleigh law. The main experimental trends are well described by the model

  18. Role of electron swarm studies in the development of gaseous dielectrics

    International Nuclear Information System (INIS)

    Christophorou, L.G.

    1981-01-01

    Recent knowledge provided by swarm studies allowing control of the number densities and energies of free electrons in electrically stressed gases is highlighted. This knowledge aided the discovery of new gas dielectrics and the tailoring of gas dielectric mixtures. The role of electron attachment in the choice of unitary gas dielectrics or electronegative components in dielectric gas mixtures, and the role of electron scattering at low energies in the choice of buffer gases for mixtures is outlined

  19. Dielectric properties of isolated clusters beam deflection studies

    CERN Document Server

    Heiles, Sven

    2013-01-01

    A broad range of state-of-the-art methods to determine properties of clusters are presented. The experimental setup and underlying physical concepts of these experiments are described. Furthermore, existing theoretical models to explain the experimental observations are introduced and the possibility to deduce structural information from measurements of dielectric properties is discussed. Additional case studies are presented in the book to emphasize the possibilities but also drawbacks of the methods.

  20. Study of dielectric and piezoelectric properties of CNT reinforced PZT-PVA 0-3 composite

    Science.gov (United States)

    Vyas, Prince; Prajapat, Rampratap; Manmeeta, Saxena, Dhiraj

    2016-05-01

    Ferroelectric ceramic/polymer composites have the compliance of polymers which overcome the problems of brittleness in ceramics. By imbedding piezoelectric ceramic powder into a polymer matrix, 0-3 composites with good mechanical properties and high dielectric breakdown strength can be developed. The obtained composites of 0-3 connectivity exhibit the piezoelectric properties of ceramics and flexibility, strength and lightness of polymer. These composites can be used in vibration sensing and transducer applications specially as piezoelectric sensors. A potential way to improve piezoelectric& dielectric properties of theses composites is by inclusion of another conductive phase in these composites as reported in the literature. In present work, we prepared PZT-PVA 0-3 composites with 60% ceramic volume fraction reinforced with CNTs with volume ranging from 0 to 1.5 vol%. These CNT reinforced composites were obtained using hot press method with thickness of 200 µm having 0-3 conductivity. These composites were poled applying DC voltage. Dielectric properties of these samples were obtained in a wide frequency range (100 Hz to 1 Mhz) at room temperature. The piezoelectric properties of these composites were analyzed by measuring piezoelectric charge constants (d33). The dielectric and piezoelectric properties of these composites were studied as a function of CNT volume content. In these reinforced composites, CNTs act as a conductive filler dispersed in the matrix which in turn facilitates poling and results in an increase of the piezoelectric properties of the composite due to formation of percolation path through the composites. With a CNT content of 0.3 vol.% in PZT/PVA/CNTs, an increase of 61.3 % was observed in piezoelectric strain factors (d33). In these CNT reinforced composites, a substantial increase (approx. 67%) was also observed in dielectric constant and approximately 89% increase was observed in dielectric loss factor. Results so obtained are in the good

  1. Study of Dielectric Breakdown Performance of Transformer Oil Based Magnetic Nanofluids

    Directory of Open Access Journals (Sweden)

    Yuzhen Lv

    2017-07-01

    Full Text Available Research on the transformer oil-based nanofluids (NFs has been raised expeditiously over the past decade. Although, there is discrepancy in the stated results and inadequate understanding of the mechanisms of improvement of dielectric nanofluids, these nanofluids have emerged as a potential substitute of mineral oils as insulating and heat removal fluids for high voltage equipment. The transformer oil (TO based magnetic fluids (ferrofluids may be regarded as the posterity insulation fluids as they propose inspiring unique prospectus to improve dielectric breakdown strength, as well as heat transfer efficiency, as compared to pure transformer oils. In this work, transformer oil-based magnetic nanofluids (MNFs are prepared by dispersal of Fe3O4 nanoparticles (MNPs into mineral oil as base oil, with various NPs loading from 5 to 80% w/v. The lightning impulse breakdown voltages (BDV measurement was conducted in accordance with IEC 60897 by using needle to sphere electrodes geometry. The test results showed that dispersion of magnetic NPs may improve the insulation strength of MO. With the increment of NPs concentrations, the positive lightning impulse (LI breakdown strength of TO is first raised, up to the highest value at 40% loading, and then tends to decrease at higher concentrations. The outcomes of negative LI breakdown showed that BDV of MNFs, with numerous loadings, were inferior to the breakdown strength of pure MO. The 40% concentration of nanoparticles (optimum concentration was selected, and positive and negative LI breakdown strength was also further studied at different sizes (10 nm, 20 nm, 30 nm and 40 nm of NPs and different electrode gap distances. Augmentation in the BDV of the ferrofluids (FFs is primarily because of dielectric and magnetic features of Fe3O4 nanoaprticles, which act as electron scavengers and decrease the rate of free electrons produced in the ionization process. Research challenges and technical difficulties

  2. Growth, characterization and dielectric property studies of gel grown ...

    Indian Academy of Sciences (India)

    Administrator

    chemical reaction method. Plate-like single ... Barium succinate; gel growth; single crystals; dielectric constant; dielectric loss. 1. .... The chemical reaction involved in the birth of a new .... due to the displacement of electrons and ions, respec-.

  3. Atmospheric tracer experiments for regional dispersion studies

    International Nuclear Information System (INIS)

    Heffter, J.L.; Ferber, G.J.

    1980-01-01

    Tracer experiments are being conducted to verify atmospheric transport and dispersion calculations at distances from tens to hundreds of km from pollutant sources. In one study, a 2 1/2 year sampling program has been carried out at 13 sites located 30 to 140 km from a source of 85 Kr at the Savannah River Plant in South Carolina. Average weekly concentrations as well as twice-daily concentrations were obtained. Sampling data and meteorological data, including surface, tower, and rawinsonde observations are available on magnetic tape for model verification studies. Some verification results for the Air Resources Laboratories Atmospheric Transort and Dispersion Model (ARL-ATAD) are shown for averaging periods from one week to two years

  4. On the definition of dielectric permittivity for media with temporal dispersion in the presence of free charge carriers

    International Nuclear Information System (INIS)

    Bordag, M; Geyer, B; Klimchitskaya, G L; Mostepanenko, V M

    2010-01-01

    We show that in the presence of free charge carriers the definition of the frequency-dependent dielectric permittivity requires additional regularization. As an example, the dielectric permittivity of the Drude model is considered and its time-dependent counterpart is derived and analyzed. The respective electric displacement cannot be represented in terms of the standard Fourier integral. The regularization procedure allowing the circumvention of these difficulties is suggested. For the purpose of comparison it is shown that the frequency-dependent dielectric permittivity of insulators satisfies all rigorous mathematical criteria. This permits us to conclude that in the presence of free charge carriers the concept of dielectric permittivity is not as well defined as for insulators and we make a link to widely discussed puzzles in the theory of thermal Casimir force which might be caused by the use of this kind of permittivities.

  5. On the definition of dielectric permittivity for media with temporal dispersion in the presence of free charge carriers

    Energy Technology Data Exchange (ETDEWEB)

    Bordag, M; Geyer, B; Klimchitskaya, G L; Mostepanenko, V M [Institute for Theoretical Physics, Leipzig University, Postfach 100920, D-04009, Leipzig (Germany)

    2010-01-08

    We show that in the presence of free charge carriers the definition of the frequency-dependent dielectric permittivity requires additional regularization. As an example, the dielectric permittivity of the Drude model is considered and its time-dependent counterpart is derived and analyzed. The respective electric displacement cannot be represented in terms of the standard Fourier integral. The regularization procedure allowing the circumvention of these difficulties is suggested. For the purpose of comparison it is shown that the frequency-dependent dielectric permittivity of insulators satisfies all rigorous mathematical criteria. This permits us to conclude that in the presence of free charge carriers the concept of dielectric permittivity is not as well defined as for insulators and we make a link to widely discussed puzzles in the theory of thermal Casimir force which might be caused by the use of this kind of permittivities.

  6. Numerical studies on the electromagnetic properties of the nonlinear Lorentz Computational model for the dielectric media

    International Nuclear Information System (INIS)

    Abe, H.; Okuda, H.

    1994-06-01

    We study linear and nonlinear properties of a new computer simulation model developed to study the propagation of electromagnetic waves in a dielectric medium in the linear and nonlinear regimes. The model is constructed by combining a microscopic model used in the semi-classical approximation for the dielectric media and the particle model developed for the plasma simulations. It is shown that the model may be useful for studying linear and nonlinear wave propagation in the dielectric media

  7. A preliminary study on the dielectric constant of WPC based on some tropical woods

    International Nuclear Information System (INIS)

    Chia, L.H.L.; Chua, P.H.; Hon, Y.S.; Lee, E.

    1986-01-01

    The use of WPC as an important insulating material is studied by determining its dielectric constant. The variation of dielectric constant with moisture content is also investigated. Preliminary results show that all untreated woods studied have a higher dielectric constant than their polymer composites with the exception of Kapur and Keruing. It is therefore postulated that the presence of polymers has led to a decrease in the number of polarizable units. Such a material may be useful commercially. (author)

  8. Numerical studies on soliton propagation in the dielectric media by the nonlinear Lorentz computational model

    International Nuclear Information System (INIS)

    Abe, H.; Okuda, H.

    1994-06-01

    Soliton propagation in the dielectric media has been simulated by using the nonlinear Lorentz computational model, which was recently developed to study the propagation of electromagnetic waves in a linear and a nonlinear dielectric. The model is constructed by combining a microscopic model used in the semi-classical approximation for dielectric media and the particle model developed for the plasma simulations. The carrier wave frequency is retained in the simulation so that not only the envelope of the soliton but also its phase can be followed in time. It is shown that the model may be useful for studying pulse propagation in the dielectric media

  9. Powder diffraction studies using anomalous dispersion

    International Nuclear Information System (INIS)

    Cox, D.E.; Wilkinson, A.P.

    1993-01-01

    With the increasing availability and accessibility of high resolution powder diffractometers at many synchrotron radiation sources throughout the world, there is rapidly-growing interest in the exploitation of anomalous dispersion techniques for structural studies of polycrystalline materials. In conjunction with the Rietveld profile method for structure refinement, such studies are especially useful for the determination of the site distributions of two or more atoms which are near neighbors in the periodic table, or atoms which are distributed among partially occupied sites. Additionally, it is possible to (1) determine the mean-square displacements associated with different kinds of atoms distributed over a single set of sites, (2) distinguish between different oxidation states and coordination geometries of a particular atom in a compound and (3) to determine f' for a wide range of atomic species as a function of energy in the vicinity of an absorption edge. Experimental methods for making anomalous dispersion measurements are described in some detail, including data collection strategies, data analysis and correlation problems, possible systematic errors, and the accuracy of the results. Recent work in the field is reviewed, including cation site-distribution studies (e.g. doped high T c superconductors, ternary alloys, FeCo 2 (PO 4 ) 3 , FeNi 2 BO 5 ), oxidation-state contrast (e.g. YBa 2 Cu 3 O 6+x , Eu 3 O 4 , GaCl 2 , Fe 2 PO 5 ), and the effect of coordination geometry (e.g. Y 3 Ga 5 O l2 )

  10. Dielectric property study of poly(4-vinylphenol)-graphene oxide nanocomposite thin film

    Science.gov (United States)

    Roy, Dhrubojyoti

    2018-05-01

    Thin film capacitor device having a sandwich structure of indium tin oxide (ITO)-coated glass/polymer or polymer nanocomposite /silver has been fabricated and their dielectric and leakage current properties has been studied. The dielectric properties of the capacitors were characterized for frequencies ranging from 1 KHz to 1 MHz. 5 wt% Poly(4-vinylphenol)(PVPh)-Graphene (GO) nanocomposite exhibited an increase in dielectric constant to 5.6 and small rise in dielectric loss to around˜0.05 at 10 KHz w.r.t polymer. The DC conductivity measurements reveal rise of leakage current in nanocomposite.

  11. Study of Super Dielectric Material for Novel Paradigm Capacitors

    Science.gov (United States)

    2018-03-01

    density, power density, dielectric constant, constant current, constant voltage, electric field minimization, dipole 15. NUMBER OF PAGES 85 16. PRICE... Technology and Strategies for Improvement ..................................................................................6 4. Super Dielectric...ds infinitesimal displacement dt infinitesimal time DT discharge time dV infinitesimal voltage E electric field Etot total energy EC Lab

  12. Optical constants, dispersion energy parameters and dielectric properties of ultra-smooth nanocrystalline BiVO4 thin films prepared by rf-magnetron sputtering

    Science.gov (United States)

    Sarkar, S.; Das, N. S.; Chattopadhyay, K. K.

    2014-07-01

    BiVO4 thin films have been prepared through radio frequency (rf) magnetron sputtering of a pre-fabricated BiVO4 target on ITO coated glass (ITO-glass) substrate and bare glass substrates. BiVO4 target material was prepared through solid-state reaction method by heating Bi2O3 and V2O5 mixture at 800 °C for 8 h. The films were characterized by X-ray diffraction, UV-Vis spectroscopy, LCR meter, field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. BiVO4 thin films deposited on the ITO-glass substrate are much smoother compared to the thin films prepared on bare glass substrate. The rms surface roughness calculated from the AFM images comes out to be 0.74 nm and 4.2 nm for the films deposited on the ITO-glass substrate and bare glass substrate for the deposition time 150 min respectively. Optical constants and energy dispersion parameters of these extra-smooth BiVO4 thin films have been investigated in detail. Dielectric properties of the BiVO4 thin films on ITO-glass substrate were also investigated. The frequency dependence of dielectric constant of the BiVO4 thin films has been measured in the frequency range from 20 Hz to 2 MHz. It was found that the dielectric constant increased from 145 to 343 at 20 Hz as the film thickness increased from 90 nm to 145 nm (deposition time increased from 60 min to 150 min). It shows higher dielectric constant compared to the literature value of BiVO4.

  13. Pigment dispersion syndrome: a clinical study.

    Science.gov (United States)

    Scheie, H G; Cameron, J D

    1981-01-01

    This study involved a group of 407 patients (799 eyes) with pigment dispersion syndrome gathered from a glaucoma population of 9200 patients. The sex distribution was equal. The majority (65%) of patients were myopic. The incidence of retinal detachment was 6.4%. No patients were black, but 5 were mulatto. Approximately one-quarter of the patients wih pigment dispersion syndrome (31% of the men, 19% of the women) had glaucoma. The average age of onset of glaucoma was 15 years less than in control patients with chronic simple glaucoma. When both eyes were affected by glaucoma, the glaucoma was consistently more severe in the eye with the more heavily pigmented angle. The degree of iris transillumination was found to be of no importance in predicting the presence of glaucoma or the severity of trabecular pigmentation. The pressure in 66% of the eyes with pigmentary glaucoma was controlled medically. A higher percentage of patients with pigmentary glaucoma required surgery than patients in the control group with chronic simple glaucoma. Men with pigmentary glaucoma required surgery at a much earlier age than women with pigmentary glaucoma. PMID:7236571

  14. Split-field FDTD method for oblique incidence study of periodic dispersive metallic structures.

    Science.gov (United States)

    Baida, F I; Belkhir, A

    2009-08-15

    The study of periodic structures illuminated by a normally incident plane wave is a simple task that can be numerically simulated by the finite-difference time-domain (FDTD) method. On the contrary, for off-normal incidence, a widely modified algorithm must be developed in order to bypass the frequency dependence appearing in the periodic boundary conditions. After recently implementing this FDTD algorithm for pure dielectric materials, we here extend it to the study of metallic structures where dispersion can be described by analytical models. The accuracy of our code is demonstrated through comparisons with already-published results in the case of 1D and 3D structures.

  15. The study of dielectric properties of the endohedral fullerenes

    Science.gov (United States)

    Bhusal, Shusil

    Dielectric response of the metal nitride fullerenes is studied using the density functional theory at the all-electron level using generalized gradient approximation. The dielectric response is studied by computing the static dipole polarizabilities using the finite field method, i.e. by numerically differentiating the dipole moments with respect to electric field. The endohedral fullerenes studied in this work are Sc3N C68(6140), Sc3N C68(6146), Sc3N C70(7854), Sc3N C70(7960), Sc3N C76(17490), Sc3N C78(22010), Sc3N C80(31923), Sc3N C80(31924), Sc3N C82(39663), Sc3N C90(43), Sc3N C90(44), Sc3N C92(85), Sc3N C94(121), Sc3N C96(186), Sc3N C98(166). Using the Voronoi and Hirschfield approaches as implemented in our NRLMOL code, we determine the atomic contributions to the total polarizability. The site-specific contributions to the polarizability of endohedral fullerenes allowed us to determine the polarizability of two subsystems: the fullerene shell and the encapsulated Sc3N unit. Our results showed that the contributions to the total polarizability from the encapsulated Sc3N units are vanishingly small. Thus, the total polarizability of the endohedral fullerene is almost entirely due to the outer fullerene shell. These fullerenes are excellent molecular models of a Faraday cage.

  16. Optical studies of metallo-dielectric photonic crystals

    Science.gov (United States)

    Kamaev, Vladimir

    2007-12-01

    Metallo-dielectric photonic crystals (MDPCs) are characterized by a large difference between the dielectric constants of the constituents. Owing to their high DC conductivity a broad omnidirectional band gap is formed at low frequencies. At the same time there exist numerous propagating electromagnetic modes at frequencies above a cutoff. This gives a possibility of creating a "transparent" metal: a crystal transparent in the visible spectral range and simultaneously having high DC conductivity. Since the cutoff wavelength linearly scales with the crystal periodicity, in order to make an MDPC with propagating modes in the visible range the crystal periodicity has to be around a quarter micrometer. Fabrication of such a crystal is a challenging task. One of the feasible choices is natural or artificial opals, structures made of silica balls arranged into a close packed fcc lattice. The ball diameters could vary from 200 nm to several microns, allowing the desired optical features to be in the visible spectral range. In the present work we studied metal-infiltrated opals numerically, analytically, and experimentally (Chapters 1 and 4). Both theory and experiment revealed high reflectance of the samples at large wavelengths associated with the low frequency metallic band gap formation, and low reflectance at short wavelengths that has characteristic wiggles. Contrarily, the absorbance is low in the IR region and goes up towards the UV end, which is due to low group velocity of light and high metal absorption in the region. Numerical analysis of thin metal-infiltrated opals (˜3-5 layers) did show a transmission peak around the first reflectance minimum and cutoff frequency. In Chapter 5 we present transmission experiments on thin metal films perforated with periodic arrays of holes or deposited on an opal monolayer. Both types of 2D MDPCs exhibited anomalous transmission peaks associated with surface plasma excitations. It was shown that the phenomenon could be

  17. Dielectric and AC Conductivity Studies in PPy-Ag Nanocomposites

    OpenAIRE

    Praveenkumar, K.; Sankarappa, T.; Ashwajeet, J. S.; Ramanna, R.

    2015-01-01

    Polypyrrole and silver nanoparticles have been synthesized at 277 K by chemical route. Nanoparticles of polypyrrole-silver (PPy-Ag) composites were prepared by mixing polypyrrole and silver nanoparticles in different weight percentages. Dielectric properties as a function of temperature in the range from 300 K to 550 K and frequency in the range from 50 Hz to 1 MHz have been measured. Dielectric constant decreased with increase in frequency and temperature. Dielectric loss decreased with incr...

  18. Studying The Effect of Various Parameters on The Characteristics of The Dielectric and Metallic Photonic Crystals

    International Nuclear Information System (INIS)

    Ismail, M.; Badawy, Z.M.; Abdel-Rahman, E.

    2015-01-01

    Transmittance characteristics of two types of photonic crystals have been analysed using the transfer matrix method. The first one is the dielectric photonic crystal (DPC), and the second is the metallic photonic crystal (MPC). The effect of the most parameters on the transmission spectra of the dielectric and metallic photonic crystals has been studied

  19. Dielectric relaxation studies of dilute solutions of amides

    Energy Technology Data Exchange (ETDEWEB)

    Malathi, M.; Sabesan, R.; Krishnan, S

    2003-11-15

    The dielectric constants and dielectric losses of formamide, acetamide, N-methyl acetamide, acetanilide and N,N-dimethyl acetamide in dilute solutions of 1,4-dioxan/benzene have been measured at 308 K using 9.37 GHz, dielectric relaxation set up. The relaxation time for the over all rotation {tau}{sub (1)} and that for the group rotation {tau}{sub (2)} of (the molecules were determined using Higasi's method. The activation energies for the processes of dielectric relaxation and viscous flow were determined by using Eyring's rate theory. From relaxation time behaviour of amides in non-polar solvent, solute-solvent and solute-solute type of molecular association is proposed.

  20. First-principles study of dielectric properties of cerium oxide

    International Nuclear Information System (INIS)

    Yamamoto, Takenori; Momida, Hiroyoshi; Hamada, Tomoyuki; Uda, Tsuyoshi; Ohno, Takahisa

    2005-01-01

    We have theoretically investigated the dielectric properties of fluorite CeO 2 as well as hexagonal and cubic Ce 2 O 3 by using first-principles pseudopotentials techniques within the local density approximation. Calculated electronic and lattice dielectric constants of CeO 2 are in good agreement with previous theoretical and experimental results. For Ce 2 O 3 , the hexagonal phase has a lattice dielectric constant comparable to that of CeO 2 , whereas the cubic phase has a much smaller one. We have concluded that the enhancement of the dielectric constant in CeO 2 epitaxially grown on Si is not due to its lattice expansion experimentally observed nor regular formation of oxygen vacancies in CeO 2

  1. Ion transport study in polymer-nanocomposite films by dielectric spectroscopy and conductivity scaling

    Science.gov (United States)

    Tripathi, Namrata; Thakur, Awalendra K.; Shukla, Archana; Marx, David T.

    2015-07-01

    The dielectric and conductivity response of polymer nanocomposite electrolytes (films of PMMA4LiClO4 dispersed with nano-CeO2 powder) have been investigated. The dielectric behavior was analyzed via the dielectric permittivity (ε‧) and dissipation factor (tan δ) of the samples. The analysis has shown the presence of space charge polarization at lower frequencies. The real part of ac conductivity spectra of materials obeys the Jonscher power law. Parameters such as dc conductivity, hopping rate, activation energies and the concentration of charge carriers were determined from conductivity data using the Almond West formalism. It is observed that the higher ionic conductivity at higher temperature is due to increased thermally-activated hopping rates accompanied by a significant increase in carrier concentration. The contribution of carrier concentration to the total conductivity is also confirmed from activation energy of migration conduction and from Summerfield scaling. The ac conductivity results are also well correlated with TEM results.

  2. 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.

  3. Dielectric studies of Co3-xMnxO4 (x=0.1-1.0) cubic spinel multiferroic

    Science.gov (United States)

    Meena, P. L.; Kumar, Ravi; Prajapat, C. L.; Sreenivas, K.; Gupta, Vinay

    2009-07-01

    A series of Co3-xMnxO4 (x =0.1-1.0) multiferroic cubic spinel ceramics were prepared to study the effect of Mn substitution at Co site on the crystal structures and dielectric properties. No significant change in the structural symmetry was observed with increasing x up to 1.0. A linear increase in lattice parameter with x is attributed to the substitution of Co3+ by Mn3+ (large ionic radii) at the octahedral sites. An antiferromagnetic-type ordering of Co3O4 changes to ferrimagnetic-type order after incorporation of Mn. The effect of Mn substitution on the dielectric constant and loss tangent was studied over a wide range of frequency (75 kHz-5 MHz) and temperature of 150-450 K. The measured value of room temperature ac conductivity at 1.0 MHz was found to increase from 2.0×10-6 to 4.4×10-4 Ω-1 cm-1 and follows power law (σac=Aωs) behavior. The dielectric constant ɛ'(ω) shows a weak frequency dispersion and small temperature dependence below 250 K for all ceramic samples. However, a strong temperature and frequency dependence on ɛ'(ω) was observed at higher temperature (>250 K). The temperature dependent ɛ'(ω) data show the existence of room temperature ferroelectricity in all prepared samples.

  4. Structural, morphological and dielectric studies of zirconium substituted CoFe2O4 nanoparticles

    Directory of Open Access Journals (Sweden)

    S. Anand

    2017-12-01

    Full Text Available In this work, the influence of zirconium substitution in cubic spinel nanocrystalline CoFe2O4 on the structural, morphological and dielectric properties are reported. Zirconium substituted cobalt ferrite Co1-xZrxFe2O4 (x = 0.7 nanoparticles were synthesized by sol-gel route. The structural and morphological investigations using powder X-ray diffraction and high resolution scanning electron microscope (HRSEM analysis are reported. Scherrer plot, Williamson–Hall analysis and Size-strain plot method were used to calculate the crystallite size and lattice strain of the samples. High purity chemical composition of the sample was confirmed by energy dispersive X-ray analysis. The atoms vibration modes of as synthesized nanoparticles were recorded using Fourier transform infrared (FTIR spectrometer in the range of 4000–400 cm-1. The temperature-dependent dielectric properties of zirconium substituted cobalt ferrite nanoparticles were also carried out. Relative dielectric permittivity, loss tangent and AC conductivity were measured in the frequency range 50 Hz to 5 MHz at temperatures between 323 K and 473 K. The dielectric constant and dielectric loss values of the sample decreased with increasing in the frequency of the applied signal.

  5. Study of nonequilibrium dispersed two phase flow

    International Nuclear Information System (INIS)

    Reyes, J.N. Jr.

    1986-01-01

    Understanding the behavior of liquid droplets in a superheated steam environment is essential to the accurate prediction of nuclear fuel rod surface temperatures during the blowdown and reflood phase of a loss-of-coolant-accident (LOCA). In response to this need, this treatise presents several original and significant contributions to the field of thermofluid physics. The research contained herein presents a statistical derivation of the two-phase mass, momentum, and energy-conservation equations using a droplet continuity equation analogous to that used in the Kinetic Theory of Gases. Unlike the Eulerian volume and time-averaged conservation equations generally used to describe dispersed two-phase flow behavior, this statistical averaging approach results in an additional mass momentum or energy term in each of the respective conservation equations. Further, this study demonstrates that current definitions of the volumetric vapor generation rate used in the mass conservation equation are inappropriate results under certain circumstances. The mass conservation equation derived herein is used to obtain a new definition for the volumetric vapor-generation rate. Last, a simple two phase phenomenological model, based on the statistically averaged conservation equations, is presented and solved analytically. It is shown that the actual quality and vapor temperature, under these circumstances, depend on a single dimensionless group

  6. Free water content and monitoring of healing processes of skin burns studied by microwave dielectric spectroscopy in vivo

    International Nuclear Information System (INIS)

    Hayashi, Yoshihito; Miura, Nobuhiro; Shinyashiki, Naoki; Yagihara, Shin

    2005-01-01

    We have investigated the dielectric properties of human skin in vivo at frequencies up to 10 GHz using a time-domain reflectometry method with open-ended coaxial probes. Since γ-dispersion results from the reorientation of free water molecules, the free water content of skin is quantitatively determined by dielectric measurements. The free water content of finger skin increased by about 10% after soaking in 37 0 C water for 30 min, and it systematically decreased again through the drying process, as expected. Thus this analytical method has been applied to the study of skin burns. The free water content of burned human cheek skin due to hydrofluoric acid was significantly lower than that of normal skin, and the burned skin recovered through the healing process. In the case of a human hand skin burn due to heat, although the free water content was almost the same as that of normal skin at the beginning, it decreased during the healing process for the first 10 days, then began to increase. Although the number of test subjects was one for each experiment, it was shown that free water content is a good indicator for evaluating skin health and can be well monitored by dielectric spectroscopy

  7. Experimental study of dielectric characteristics of rocks in a high-frequency field

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, S.

    1982-01-01

    Dielectric permeability (epsilon) as an electrical property of rocks has been used in recent years as the new parameter of well logging. Consequently a study was made of the dependence of epsilon of rocks on different factors. It was found that epsilon of rocks depends not only on minerals contained in them, their properties and distribution, but also on the frequency of the field, temperature and content of the mineralized water in the bed. It was indicated that for sedimentary rocks with low content of clay, their epsilon depends mainly on the content of water, and between epsilon and water saturation there is an approximately rectilinear relationship. The epsilon of dry and wet rocks differs 3-5-fold, so that with the help of epsilon one can determine flooding of the bed. Since epsilon increases with a rise in the content of clay in the rocks, with dielectric logging of the flooded bed it is necessary to make the corresponding correction. Under conditions of frequency of the field 60 Mz, epsilon in the NaCl solution decreases with an increase in mineralization, but the epsilon of the soda-containing rocks increases with an increase in mineralization. However, with mineralization less than 1 x 10/sup -2/, its influence on epsilon does not exceed 10%. The epsilon of water containing rocks diminishes with a rise in temperature. In addition, the epsilon of rocks drops with an increase in field frequency. With an increase in frequency, there is a decrease in influence of different factors (mineralization, distribution of minerals, content of clay, etc.) on the epsilon of rocks. At high frequencies, a distinct relationship is observed only between the epsilon and the water content of the rocks. Consequently it is expedient to improve the frequency of measurement to reveal the flooded beds. According to the data of dispersion of epsilon with different frequencies, one can determine the content of quality of the bed using electromagnetic logging.

  8. Monodispersed fabrication and dielectric studies on ethylenediamine passivated α-manganese dioxide nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, A. Martin [Research and Development Centre, Bharathiar University, Coimbatore, Tamilnadu (India); Kumar, R. Thilak, E-mail: manojthilak@yahoo.com [Periyar Arts College, Cuddalore-607001, Tamilnadu (India)

    2016-09-15

    Highlights: • Monodispersed ethylenediamine (EDA) passivated α-MnO{sub 2} nanorods were fabricated by inexpensive wet chemical method. • FTIR analysis indicated that surface passivation is strongly influenced by the introduction of the organic ligand. • XRD and HR-SEM revealed the structure and morphology of the fabricated α-MnO{sub 2} nanorods with an average size of about 40 × 200 nm. • Dielectric studies pointed out that the fabricated α-MnO{sub 2} is semiconducting in nature with resistivity, ρ = 1.46 to 5.76 × 10{sup 3} Ωcm. • The optical energy gap for the fabricated α-MnO{sub 2} nanorods is found to be around 1.37 eV. - Abstract: In this present work, pure α-MnO{sub 2} nanorods were fabricated by the reduction of 0.2 m/L of KMnO{sub 4} with 0.2 m/L of Na{sub 2}S{sub 2}O{sub 3}·5H{sub 2}O and by passivating with the organic ligand Ethylenediamine (EDA). The structural, functional, morphological and chemical composition of the nanorods were investigated by X-Ray Diffractometer (XRD), Fourier Transform Infrared Spectrometer (FTIR), High Resolution Scanning Electron Microscope (HR-SEM) and Energy Dispersive X-Ray Spectrometry (EDX). The XRD analysis indicated high crystalline nature of the product and FTIR confirmed the contribution of the organic ligand in surface passivation. HR-SEM image revealed the morphology of the α-MnO{sub 2} nanorods with an average size of about 40 × 200 nm. EDX confirmed the presence of Mn and O in the material. UV–visible spectrophotometery was used to determine the absorption behavior of the nanorods and an indirect band gap of 1.37 eV was acquired by Taucplot. Dielectric studies were carried out using Broadband Dielectric Spectrometer(BDS) and the resistivity was found to be around the semiconductor range (ρ = 1.46 to 5.76 × 10{sup 3} Ωcm).

  9. Numerical study of the lateral resolution in electrostatic force microscopy for dielectric samples

    International Nuclear Information System (INIS)

    Riedel, C; AlegrIa, A; Colmenero, J; Schwartz, G A; Saenz, J J

    2011-01-01

    We present a study of the lateral resolution in electrostatic force microscopy for dielectric samples in both force and gradient modes. Whereas previous studies have reported expressions for metallic surfaces having potential heterogeneities (Kelvin probe force microscopy), in this work we take into account the presence of a dielectric medium. We introduce a definition of the lateral resolution based on the force due to a test particle being either a point charge or a polarizable particle on the dielectric surface. The behaviour has been studied over a wide range of typical experimental parameters: tip-sample distance (1-20) nm, sample thickness (0-5) μm and dielectric constant (1-20), using the numerical simulation of the equivalent charge method. For potential heterogeneities on metallic surfaces expressions are in agreement with the bibliography. The lateral resolution of samples having a dielectric constant of more than 10 tends to metallic behaviour. We found a characteristic thickness of 100 nm, above which the lateral resolution measured on the dielectric surface is close to that of an infinite medium. As previously reported, the lateral resolution is better in the gradient mode than in the force mode. Finally, we showed that for the same experimental conditions, the lateral resolution is better for a polarizable particle than for a charge, i.e. dielectric heterogeneities should always look 'sharper' (better resolved) than inhomogeneous charge distributions. This fact should be taken into account when interpreting images of heterogeneous samples.

  10. Numerical study of the lateral resolution in electrostatic force microscopy for dielectric samples

    Energy Technology Data Exchange (ETDEWEB)

    Riedel, C; AlegrIa, A; Colmenero, J [Departamento de Fisica de Materiales UPV/EHU, Facultad de Quimica, Apartado 1072, 20080 San Sebastian (Spain); Schwartz, G A [Centro de Fisica de Materiales CSIC-UPV/EHU, Paseo Manuel de Lardizabal 5, 20018 San Sebastian (Spain); Saenz, J J, E-mail: riedel@ies.univ-montp2.fr [Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian (Spain)

    2011-07-15

    We present a study of the lateral resolution in electrostatic force microscopy for dielectric samples in both force and gradient modes. Whereas previous studies have reported expressions for metallic surfaces having potential heterogeneities (Kelvin probe force microscopy), in this work we take into account the presence of a dielectric medium. We introduce a definition of the lateral resolution based on the force due to a test particle being either a point charge or a polarizable particle on the dielectric surface. The behaviour has been studied over a wide range of typical experimental parameters: tip-sample distance (1-20) nm, sample thickness (0-5) {mu}m and dielectric constant (1-20), using the numerical simulation of the equivalent charge method. For potential heterogeneities on metallic surfaces expressions are in agreement with the bibliography. The lateral resolution of samples having a dielectric constant of more than 10 tends to metallic behaviour. We found a characteristic thickness of 100 nm, above which the lateral resolution measured on the dielectric surface is close to that of an infinite medium. As previously reported, the lateral resolution is better in the gradient mode than in the force mode. Finally, we showed that for the same experimental conditions, the lateral resolution is better for a polarizable particle than for a charge, i.e. dielectric heterogeneities should always look 'sharper' (better resolved) than inhomogeneous charge distributions. This fact should be taken into account when interpreting images of heterogeneous samples.

  11. Dielectric studies of Graphene and Glass Fiber reinforced composites

    Science.gov (United States)

    Praveen, D.; Shashi Kumar, M. E.; Pramod, R.

    2018-02-01

    Graphene and E-glass fibres are one of the key materials used currently due to their unique chemical and mechanical properties. Lately graphene has attracted many researchers across academic fraternity as it can yield better properties with lesser reinforcement percentages. The current research emphasizes on the development of graphene-based nanocomposites and its investigation on dielectric applications. The composites were fabricated by adding graphene reinforcements from 1%-3% by weight using conventional Hand-lay process. A thorough investigation was carried out to determine the dielectric behaviour of the nano-composites using impedance analyser according to ASTM standards. The dielectric measurements were carried out in the temperature range of 300K to 400K in a step of 20K. The current research proposes the material for application in capacitor industry as the sample of 2.5% weight fraction showed highest value of K with 14 at 26.1 Hz and 403K.

  12. Preparation and study of properties of dispersed graphene oxide

    Directory of Open Access Journals (Sweden)

    Evgeniya Seliverstova

    2015-09-01

    Full Text Available Ability of graphene oxide to form stable dispersion in organic solvents was studied in this work. As it was shown, sonication of graphene leads to the decreas of the particle size. Stability of prepared graphene dispersions was studied upon measurements of distribution of number of the particles via size and change of optical density of the solutions with time. It was found that graphene oxide forms a more stable dispersion in tetrahydrofuran and dimethylformamide than in chloroform and acetone.

  13. Study of dielectric liquids at room temperature for high energy x ray Tomography

    International Nuclear Information System (INIS)

    Lepert, S.

    1989-09-01

    The detection of X rays by means of a dielectric liquid detector system, at room temperature, is discussed. The physico-chemical properties of a dielectric liquid, the construction of a cleaning device and of two electrode configurations, and the utilization of different amplifier models are studied. The results allowed the analysis and characterization of the behavior of the dielectric liquid under X ray irradiation. Data obtained is confirmed by computerized simulation. The choice of Tetramethyl-germanium for the X ray tomography, applied in nondestructive analysis, is explained. The investigation of the system parameters allowed the setting of the basis of a prototype project for a multi-detector [fr

  14. Ultrasonic and dielectric studies of polymer PDMS composites with ZnO and onion-like carbons nanoinclusions

    OpenAIRE

    Samulionis, Vytautas; Macutkevič, Jan; Banys, Jūras; Shenderova, Olga

    2015-01-01

    The ultrasonic and dielectric temperature investigations were performed in polydi-methylsiloxane (PDMS) with zinc oxide (ZnO) and onion-like carbon (OLC) nanocomposites. In the glass transition region, the ultrasonic velocity dispersion and large ultrasonic attenuation maxima were observed. The positions of ultrasonic attenuation peaks were slightly shifted to higher temperatures after doping PDMS with OLC and ZnO nanoparticles. The ultrasonic relaxation was compared to that of dielectric and...

  15. Thermal, FT–IR and dielectric studies of gel grown sodium oxalate ...

    Indian Academy of Sciences (India)

    WINTEC

    Institute of Diploma Studies, Nirma University of Science and Technology, Ahmedabad 384 481, India. MS received 29 ... dielectric response at various frequencies of applied field. ... 1987). Many oxalates exist in nature, for example, copper.

  16. Structural, dielectric and a.c. conductivity study of Sb2O3 thin film ...

    Indian Academy of Sciences (India)

    X-ray diffraction; a.c. conductivity; dielectric properties; complex electric modulus. ... the study disordered systems because of the unusual temper- ..... energy. tunnelling model suggested by Wang et al [31], (s) should decrease with increase in ...

  17. Study of electrical percolation phenomenon from the dielectric and ...

    Indian Academy of Sciences (India)

    pattern of real part of electric modulus (M′) at selected frequencies is similar to dielectric constant. The existence of .... charge carriers have sufficient time to orient in the direction ..... Aziz S B and Abidin Z H Z 2013 J. Soft Matter Article ID.

  18. Dielectric Relaxation Studies of Alkyl Methacrylate–Phenol Mixtures ...

    African Journals Online (AJOL)

    The Kirkwood correlation factor and the excess inverse relaxation time were determined and they yield information on the molecular interactions occurring in the systems. The values of the static permittivity and the relaxation time increase with an increase in the percentage of phenol in the mixtures. KEYWORDS: Dielectric ...

  19. Dielectric studies of molecular motions in glassy and liquid nicotine

    Energy Technology Data Exchange (ETDEWEB)

    Kaminski, K [Institute of Physics, Silesian University, ulica Uniwersytecka 4, 40-007 Katowice (Poland); Paluch, M [Institute of Physics, Silesian University, ulica Uniwersytecka 4, 40-007 Katowice (Poland); Ziolo, J [Institute of Physics, Silesian University, ulica Uniwersytecka 4, 40-007 Katowice (Poland); Ngai, K L [Naval Research Laboratory, Washington DC 20375-5320 (United States)

    2006-06-21

    The dielectric permittivity and loss spectra of glassy and liquid states of nicotine have been measured over the frequency range 10{sup -2}-10{sup 9} Hz. The relaxation spectra are similar to common small molecular glass-forming substances, showing the structural {alpha}-relaxation and its precursor, the Johari-Goldstein {beta}-relaxation. The {alpha}-relaxation is well described by the Fourier transform of the Kohlrausch-Williams-Watts stretched exponential function with an approximately constant stretch exponent that is equal to 0.70 as the glass transition temperature is approached. The dielectric {alpha}-relaxation time measured over 11 orders of magnitude cannot be described by a single Vogel-Fulcher-Tamman-Hesse equation. The most probable Johari-Goldstein {beta}-relaxation time determined from the dielectric spectra is in good agreement with the primitive relaxation time of the coupling model calculated from parameters of the structural {alpha}-relaxation. The shape of the dielectric spectra of nicotine is compared with that of other glass-formers having about the same stretch exponent, and they are shown to be nearly isomorphic. The results indicate that the molecular dynamics of nicotine conform to the general pattern found in other glass-formers, and the presence of the universal Johari-Goldstein secondary relaxation, which plays a role in the crystallization of amorphous pharmaceuticals.

  20. Study of dielectric properties of adulterated milk concentration and freshness

    Science.gov (United States)

    Jitendra Murthy, V.; Sai Kiranmai, N.; Kumar, Sanjeev

    2017-08-01

    The knowledge of dielectric properties may hold a potential to develop a new technique for quality evaluation of milk. The dielectric properties of water diluted cow’s milk with milk concentration from 70 percent to 100 percent stored during 36hour storage at 22°C and 144 hour at 5°C were measured at room temperature for frequencies ranging from 10 to 4500 MHz and at low, high & at microwave frequencies using X band bench and open-ended coaxial-line probe technology, along with electrical conductivity. The raw milk had the lowest dielectric constant (ɛ‧) when the frequency was higher than about 20M.Hz, and had the highest loss (ɛ″) or decepation factor tan (δ) at each frequency. The penetration depth (dp) increased with decreasing frequency, water content and storage time, which was large enough to detect dielectric properties changes in milk samples and provide large scale RF pasteurization processes. The loss factor can be an indicator in predicting milk concentration and freshness.

  1. Structural and dielectric studies on Ag doped nano ZnSnO3

    Science.gov (United States)

    Deepa, K.; Angel, S. Lilly; Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

    2018-04-01

    Undoped and Ag-doped nano Zinc Stannate (ZSO) ternary oxide were prepared by co-precipitation method. The crystallographic, morphological and optical properties of the synthesized nanoparticles were studied using X-ray diffraction (XRD) and UV-Visible spectroscopy (UV-Vis) and Scanning electron microscopy (SEM). The electrical properties of the synthesized samples were studied by dielectric measurements. Higher concentration Ag doped ZSO nanoparticles exhibit higher dielectric constant at low frequency.

  2. Broadening our approaches to studying dispersal in raptors

    Science.gov (United States)

    Morrison, J.L.; Wood, P.B.

    2009-01-01

    Dispersal is a behavioral process having consequences for individual fitness and population dynamics. Recent advances in technology have spawned new theoretical examinations and empirical studies of the dispersal process in birds, providing opportunities for examining how this information may be applied to studies of the dispersal process in raptors. Many raptors are the focus of conservation efforts; thus, reliable data on all aspects of a species' population dynamics, including dispersal distances, movement rates, and mortality rates of dispersers, are required for population viability analyses that are increasingly used to inform management. Here, we address emerging issues and novel approaches used in the study of avian dispersal, and provide suggestions to consider when developing and implementing studies of dispersal in raptors. Clarifying study objectives is essential for selection of an appropriate methodology and sample size needed to obtain accurate estimates of movement distances and rates. Identifying an appropriate study-area size will allow investigators to avoid underestimating population connectivity and important population parameters. Because nomadic individuals of some species use temporary settling areas or home ranges before breeding, identification of these areas is critical for conservation efforts focusing on habitats other than breeding sites. Study designs for investigating raptor dispersal also should include analysis of environmental and social factors influencing dispersal, to improve our understanding of condition-dependent dispersal strategies. Finally, we propose a terminology for use in describing the variety of movements associated with dispersal behavior in raptors, and we suggest this terminology could be used consistently to facilitate comparisons among studies. ?? 2009 The Raptor Research Foundation, Inc.

  3. Dielectric relaxation behavior and impedance studies of Cu2+ ion doped Mg - Zn spinel nanoferrites

    Science.gov (United States)

    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.

  4. Dielectric spectroscopy studies of low-disorder and low-dimensional materials

    OpenAIRE

    Tripathi, Pragya

    2016-01-01

    In this thesis we employ dielectric spectroscopy (in different implementations) to study the dielectric properties of different materials ranging from completely disordered supercooled liquids to low-disorder solids with only ratcheting reorientational motions, to low-dimensional systems such as thin films or needle-like crystals. The probed material properties include the electrical conductivity, the space-charge processes due to sample heterogeneities, molecular dynamics, hydrogen-bond dyna...

  5. Studies on dielectric properties of ferrocenylhydrazone coordinated polymers irradiated by γ-rays

    International Nuclear Information System (INIS)

    Lin Yun; Chen Jie; Lin Zhanru

    2007-01-01

    The three ferrocenylhydrazone coordinated metal polymers were synthesized (PZM). The effect of the 60 Co γ irradiation on microwave dielectric properties and their temperature-dielectric properties were studies. It has been found that the dielectric parameters (ε', tgδ) of coordinated polymers increase along with the absorbed doses and coordinated metals in order Cu, Co, Ni, However, the dependent curves of dielectric parameters on arise-down temperature are universal. On the other hand, the small changes in chemical structure before and after irradiation were confirmed by IR differential spectrometry and SEM. It is possible to make such coordinated polymers as a multifunctional polymeric material with optical, electric and magnetic properties, which may be potentially used in microwave communication. (authors)

  6. High pressure dielectric studies on the structural and orientational glass.

    Science.gov (United States)

    Kaminska, E; Tarnacka, M; Jurkiewicz, K; Kaminski, K; Paluch, M

    2016-02-07

    High pressure dielectric studies on the H-bonded liquid D-glucose and Orientationally Disordered Crystal (ODIC) 1,6-anhydro-D-glucose (levoglucosan) were carried out. It was shown that in both compounds, the structural relaxation is weakly sensitive to compression. It is well reflected in the low pressure coefficient of the glass transition and orientational glass transition temperatures which is equal to 60 K/GPa for both D-glucose and 1,6-anhydro-D-glucose. Although it should be noted that ∂Tg(0)/∂p evaluated for the latter compound seems to be enormously high with respect to other systems forming ODIC phase. We also found that the shape of the α-loss peak stays constant for the given relaxation time independently on the thermodynamic condition. Consequently, the Time Temperature Pressure (TTP) rule is satisfied. This experimental finding seems to be quite intriguing since the TTP rule was shown to work well in the van der Waals liquids, while in the strongly associating compounds, it is very often violated. We have also demonstrated that the sensitivity of the structural relaxation process to the temperature change measured by the steepness index (mp) drops with pressure. Interestingly, this change is much more significant in the case of D-glucose with respect to levoglucosan, where the fragility changes only slightly with compression. Finally, kinetics of ODIC-crystal phase transition was studied at high compression. It is worth mentioning that in the recent paper, Tombari and Johari [J. Chem. Phys. 142, 104501 (2015)] have shown that ODIC phase in 1,6-anhydro-D-glucose is stable in the wide range of temperatures and there is no tendency to form more ordered phase at ambient pressure. On the other hand, our isochronal measurements performed at varying thermodynamic conditions indicated unquestionably that the application of pressure favors solid (ODIC)-solid (crystal) transition in 1,6-anhydro-D-glucose. This result mimics the impact of pressure on the

  7. Study of water mass transfer dynamics in frescoes by dielectric spectroscopy

    International Nuclear Information System (INIS)

    Olmi, R.; Riminesi, C.

    2008-01-01

    The knowledge of moisture content (M C) is essential for determining the state of preservation of various types of hand-work: from building materials such as bricks and concrete, to objects of artistic value, in particular frescoes and mural paintings. In all above, moisture is the primary source of damages, as it affects the durability of porous materials. Dielectric properties of porous materials are strongly affected by the presence of water, suggesting dielectric spectroscopy as a suitable non-invasive diagnostic technique. The development of a quantitative relationship between M C and permittivity requires to investigate the dynamics of water mass transfer in porous media, and to determine its effect on the dielectric properties. In this paper a coupled mass transfer/dielectric problem is introduced and solved numerically, based on a finite element model. Results are compared to experimental dielectric measurements performed on plaster samples by the open coaxial method. The application of the dielectric technique to frescoes monitoring is proposed, showing the results obtained is an on-site study.

  8. Study on niobium carbide dispersed superconducting tapes

    Energy Technology Data Exchange (ETDEWEB)

    Wada, H; Tachikawa, K [National Research Inst. for Metals, Tokyo (Japan); Oh' asa, M [Science Univ. of Tokyo (Japan)

    1977-11-01

    Niobium carbide (NbC) dispersed superconducting tapes have been fabricated by two metallurgical processes. In the first process, Ni-Nb-C alloys are directly arc melted and hot worked in air and the NbC phase is distributed in the form of fine discrete particles. In the second process, Ni-Nb and Ni-Nb-Cu alloys are arc melted, hot worked and subjected to solid-state carburization. NbC then precipitates along the grain boundaries, forming a network. The highest superconducting transition temperature attained is about 11 K. Taken together with the lattice parameter measurement, this indicates that NbC with a nearly perfect NaCl structure is formed in both processes. Measured values of the upper critical field, the critical current density and the volume fraction of the NbC phase are also discussed.

  9. Mechanistic interaction study of thin oxide dielectric with conducting organic electrode

    International Nuclear Information System (INIS)

    Sharma, Himani; Sethi, Kanika; Raj, P. Markondeya; Gerhardt, R.A.; Tummala, Rao

    2012-01-01

    Highlights: ► Thin film-oxide dielectric-organic electrode interface studies for investigating the leakage mechanism. ► XPS to elucidate chemical-structural changes on dielectric oxide surface. ► Correlates structural characterization data with capacitor leakage current and impedance spectroscopy characteristics. - Abstract: This paper aims at understanding the interaction of intrinsic conducting polymer, PEDT, with ALD-deposited Al 2 O 3 and thermally oxidized Ta 2 O 5 dielectrics, and the underlying mechanisms for increase in leakage currents in PEDT-based capacitors. Conducting polymers offer several advantages as electrodes for high surface area capacitors because of their lower resistance, self-healing and enhanced conformality. However, capacitors with in situ polymerized PEDT show poor electrical properties that are attributed to the interfacial interaction between the organic electrode and the oxide dielectric. This study focuses on characterizing these interactions. A combination of compositional, structural and electrical characterization techniques was applied to polymer-solid-state-capacitor to understand the interfacial chemical behavior and dielectric property deterioration of alumina and tantalum-oxide films. XPS and impedance studies were employed to understand the stiochiometric and compositional changes that occur in the dielectric film on interaction with in situ deposited PEDT. Based on the observations from several complimentary techniques, it is concluded that tantalum-pentoxide has more resistance towards chemical interaction with in situ polymerized PEDT. The thermally oxidized Ta 2 O 5 -PEDT system showed leakage current of 280 nA μF −1 at 3 V with a breakdown voltage of 30 V. On the other hand, Al 2 O 3 -PEDT capacitor showed leakage current of 50 μA μF −1 and a breakdown voltage of 40 V. The study reports direct evidence for the mechanism of resistivity drop in alumina dielectric with in situ polymerized PEDT electrode.

  10. Dispersion engineering for integrated nanophotonics

    CERN Document Server

    Vanbésien, Olivier

    2014-01-01

    This book shows how dispersion engineering in two dimensional dielectric photonic crystals can provide new effects for the precise control of light propagation for integrated nanophotonics.Dispersion engineering in regular and graded photonic crystals to promote anomalous refraction effects is studied from the concepts to experimental demonstration via nanofabrication considerations. Self collimation, ultra and negative refraction, second harmonic generation, mirage and invisibility effects which lead to an unprecedented control of light propagation at the (sub-)wavelength scale for the

  11. Dispersion of complex dielectric constant and electronic characteristics of the compounds Nb-Al and Nb-Ge with A15 structure

    International Nuclear Information System (INIS)

    Kuzmichev, N.D.; Levchenko, I.S.; Motulevich, G.P.

    1989-01-01

    This paper reports that the dispersions of complex dielectric constant of the compounds Nb-Al and Nb-Ge with A15 structure, used for determination of electronic characteristics and their variations with temperature, are measured in the 0.177-3.1 eV spectral interval at 295 and 670 K. The squares of the plasma frequencies ω 2 p of conduction electrons are obtained. In both compounds ω 2 p ∼ 19 eV 2 , which is 3.2 times less than for niobium. In this spectral interval, Nb-Al has four interband transition zones at 0.2, 0.35, 1.45, and 3.1 eV, while Nb-Ge has five such bands: 0.21, 0.32, 0.48, 0.95 and 2.0 eV. As the temperature increases ω 2 p of conduction electrons increases somewhat more than for usual metals (in both compounds), and the decrease in the analogous characteristic in the long-wave band for Nb-Ge is unusually great, preserving the sum of the changes, and there is also a significant decrease in the width of the long-wave band. These anomalies can be explained by thermal transfer of electrons from the base state of the long-wave band to the conduction band

  12. Energy dispersive X-Ray fluorescence spectrometric study of ...

    African Journals Online (AJOL)

    Energy dispersive X-Ray fluorescence spectrometric study of compositional differences in trace elements in dried Moringa oleifera leaves grown in two different agro-ecological locations in Ebonyi State, Nigeria.

  13. Experimental Study on High Electrical Breakdown of Water Dielectric

    International Nuclear Information System (INIS)

    Zhang Zicheng; Zhang Jiande; Yang Jianhua

    2005-01-01

    By means of a coaxial apparatus, pressurized water breakdown experiments with microsecond charging have been carried out with different surface roughness of electrodes and different ethylene glycol concentrations of ethylene glycol/water mixture. The experimental results about the breakdown stress and the effective time are presented. The breakdown stress is normalized to the situation that the effective time is transformed to 1 μs and analyzed. The conclusions are as follows: (1) the breakdown stress formula is modified to E = 0.561M A -1/10 t eff -1/N P 1/8 ; (2) the coefficient M is significantly increased by surface polishing and ethylene glycol additive; (3) it is accumulative for the capacity of improving electrical breakdown strength for surface polishing, ethylene glycol additive, and pressurization, of which pressurization is the most effective method; (4) the highest stress of 235.5 kV/cm is observed in ethylene glycol/water mixture with an ethylene glycol concentration of 80% at a hydrostatic pressure of 1215.9 kPa and is about one time greater than that in pure water at constant pressure; (5) for pressurization and surface polishing, the primary mechanism to improve the breakdown strength of water dielectric is the increase in the breakdown time delay. Research results indicate great potential in the application of the high power pulse conditioning system of water dielectric

  14. Study on chitosan film properties as a green dielectric

    Science.gov (United States)

    Nainggolan, I.; Nasution, T. I.; Putri, S. R. E.; Azdena, D.; Balyan, M.; Agusnar, H.

    2018-02-01

    Chitosan film dielectrics to produce an electrostatic capacitor were prepared by the solution cast technique. The charging and discharging of the capacitor were done using RC series circuit with DC voltage supply because chitosan has bipolar properties. First testing was by varying supply voltage of 1, 3, 5, 10 and 15 V, respectively, and could be determined that the most effective voltage for chitosan film can be well polarised is 5 V. The results of second testing for the use of 5 V supply showed that the capacitance of a chitosan film capacitor decreased with the increase in load value. For loads of 100, 1K, 10K, 100K and 1M Ω, the capacitance values of the chitosan film capacitor were 3.1725, 0.4136, 0.05379, 0.007917 and 0.001522 F, respectively. It was also found that the increase in voltage of the capacitor at charging process was faster for the lower load. Therefore, the research result has corresponded to the general formula that used to calculate the capacitance value and thus, the biopolymer chitosan has potential as a sustainable green dielectric.

  15. Dielectric relaxation studies of some primary alcohols and their mixture with water

    International Nuclear Information System (INIS)

    Ahmad, S.S.; Yaqub, M.

    2003-01-01

    The complex dielectric constant of ethyl alcohol, methyl alcohol and 1- propanol and their mixtures with water of different concentration, (0 to 100% by weight) at the temperature of 303K has been evaluated, within the frequency range of (100KHz- 100 MHz). Moreover, the viscosity mu of each alcohol and its mixture with water have been measured at this temperature. The dielectric properties have been evaluated by Hartshorn and Ward apparatus. The purpose of this work is to study the influence of aliphatic group, size and shape on the extent of hydrogen bonding and also to obtain the thermodynamic data on hydrogen bond formation in the pure liquid state and its mixture. The width of the semicircle plot determines the distribution of average relaxation time. Dielectric relaxation time in pure alcohols and their water mixture has been calculated from the respected Cole-Cole plot and dielectric data. A single relaxation time of 117.16ps has been obtained for the molecules of pure methanol, whereas, the dielectric data of prophyl alcohol which indicates the viscosity water have been measured at the temperature 303 K. The dielectric properties in distribution of relaxation time, which is in good agreement with the Davidson-cole representation. The molecules in liquid mixture within frequency range, the mixture has more than one relaxation item, leading to the shortening of main relaxation time as compared with the pure alcohol and broadening of the complex permitivity spectra. The dependence of the dielectric relaxation on composition shows a remarkable behavior. Results are discussed in the light of H-bonded molecules. (author)

  16. Ion transport study in polymer-nanocomposite films by dielectric spectroscopy and conductivity scaling

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, Namrata, E-mail: ntripat@ilstu.edu [Department of Physics, Illinois State University, Normal, IL 61790 (United States); Thakur, Awalendra K. [Department of Physics, Indian Institute of Technology Patna, Bihar 800013 (India); Shukla, Archana [Department of Metallurgical Engineering & Materials Science, Indian Institute of Technology, Bombay 721302 (India); Marx, David T. [Department of Physics, Illinois State University, Normal, IL 61790 (United States)

    2015-07-15

    The dielectric and conductivity response of polymer nanocomposite electrolytes (films of PMMA{sub 4}LiClO{sub 4} dispersed with nano-CeO{sub 2} powder) have been investigated. The dielectric behavior was analyzed via the dielectric permittivity (ε′) and dissipation factor (tan δ) of the samples. The analysis has shown the presence of space charge polarization at lower frequencies. The real part of ac conductivity spectra of materials obeys the Jonscher power law. Parameters such as dc conductivity, hopping rate, activation energies and the concentration of charge carriers were determined from conductivity data using the Almond West formalism. It is observed that the higher ionic conductivity at higher temperature is due to increased thermally-activated hopping rates accompanied by a significant increase in carrier concentration. The contribution of carrier concentration to the total conductivity is also confirmed from activation energy of migration conduction and from Summerfield scaling. The ac conductivity results are also well correlated with TEM results.

  17. Brillouin light scattering studies on the mechanical properties of ultrathin, porous low-K dielectric films

    Science.gov (United States)

    Zhou, Wei; Sooryakumar, R.; King, Sean

    2010-03-01

    Low K dielectrics have predominantly replaced silicon dioxide as the interlayer dielectric material for interconnects in state of the art integrated circuits. To further reduce interconnect resistance-capacitance (RC) delays, additional reductions in the K for these low-K materials is being pursued by the introduction of controlled levels of porosity. The main challenge for porous low-K dielectrics is the substantial reduction in mechanical properties that is accompanied by the increased pore volume content needed to reduce K. We report on the application of the nondestructive Brillouin light scattering technique to monitor and characterize the mechanical properties of these porous films at thicknesses well below 200 nm that are pertinent to present applications. Observation of longitudinal and transverse standing wave acoustic resonances and the dispersion that accompany their transformation into traveling waves with finite in-plane wave vectors provides for the principal elastic constants that completely characterize the mechanical properties of these porous films. The mode amplitudes of the standing waves, their variation within the film, and the calculated Brillouin intensities account for most aspects of the spectra. The resulting elastic constants are compared with corresponding values obtained from other experimental techniques.

  18. A Comprehensive Study on Dielectric Properties of Volcanic Rock/PANI Composites

    Science.gov (United States)

    Kiliç, M.; Karabul, Y.; Okutan, M.; İçelli, O.

    2016-05-01

    Basalt is a very well-known volcanic rock that is dark colored and relatively rich in iron and magnesium, almost located each country in the world. These rocks have been used in the refused rock industry, to produce building tiles, construction industrial, highway engineering. Powders and fibers of basalt rocks are widely used of radiation shielding, thermal stability, heat and sound insulation. This study examined three different basalt samples (coded CM-1, KYZ-13 and KYZ-24) collected from different regions of Van province in Turkey. Polyaniline (PANI) is one of the representative conductive polymers due to its fine environmental stability, huge electrical conductivity, as well as a comparatively low cost. Also, the electrical and thermal properties of polymer composites containing PANI have been widely studied. The dielectric properties of Basalt/Polyaniline composites in different concentrations (10, 25, 50 wt.% PANI) have been investigated by dielectric spectroscopy method at the room temperature. The dielectric parameters (dielectric constants, loss and strength) were measured in the frequency range of 102 Hz-106 Hz at room temperature. The electrical mechanism change with PANI dopant. A detailed dielectrically analysis of these composites will be presented.

  19. Numerical study on flow and pollutant dispersion inside street canyons

    OpenAIRE

    Yunkai, Yang

    2013-01-01

    This thesis analyzes the characteristics of flow pattern and vehicle-emitted pollutant dispersion in roughness surface layer. In an urban environment, wind flow and transported-pollutant source interfere strongly with buildings and other roughness elements on the surface ground, which results in complex characteristics of flow pattern and pollutant dispersion in 3D circumstances. The present study intends to simplify the research domain and investigate the fundamental modeling problems that e...

  20. Dispersion of helically corrugated waveguides: Analytical, numerical, and experimental study

    International Nuclear Information System (INIS)

    Burt, G.; Ronald, K.; Young, A.R.; Phelps, A.D.R.; Cross, A.W.; Konoplev, I.V.; He, W.; Thomson, J.; Whyte, C.G.; Samsonov, S.V.; Denisov, G.G.; Bratman, V.L.

    2004-01-01

    Helically corrugated waveguides have recently been studied for use in various applications such as interaction regions in gyrotron traveling-wave tubes and gyrotron backward-wave oscillators and as a dispersive medium for passive microwave pulse compression. The paper presents a summary of various methods that can be used for analysis of the wave dispersion of such waveguides. The results obtained from an analytical approach, simulations with the three-dimensional numerical code MAGIC, and cold microwave measurements are analyzed and compared

  1. Study of dielectric relaxation and AC conductivity of InP:S single crystal

    Science.gov (United States)

    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.

  2. Numerical study on characteristic of two-dimensional metal/dielectric photonic crystals

    Science.gov (United States)

    Zong, Yi-Xin; Xia, Jian-Bai; Wu, Hai-Bin

    2017-04-01

    An improved plan-wave expansion method is adopted to theoretically study the photonic band diagrams of two-dimensional (2D) metal/dielectric photonic crystals. Based on the photonic band structures, the dependence of flat bands and photonic bandgaps on two parameters (dielectric constant and filling factor) are investigated for two types of 2D metal/dielectric (M/D) photonic crystals, hole and cylinder photonic crystals. The simulation results show that band structures are affected greatly by these two parameters. Flat bands and bandgaps can be easily obtained by tuning these parameters and the bandgap width may reach to the maximum at certain parameters. It is worth noting that the hole-type photonic crystals show more bandgaps than the corresponding cylinder ones, and the frequency ranges of bandgaps also depend strongly on these parameters. Besides, the photonic crystals containing metallic medium can obtain more modulation of photonic bands, band gaps, and large effective refractive index, etc. than the dielectric/dielectric ones. According to the numerical results, the needs of optical devices for flat bands and bandgaps can be met by selecting the suitable geometry and material parameters. Project supported by the National Basic Research Program of China (Grant No. 2011CB922200) and the National Natural Science Foundation of China (Grant No. 605210010).

  3. Numerical study on characteristic of two-dimensional metal/dielectric photonic crystals

    International Nuclear Information System (INIS)

    Zong Yi-Xin; Xia Jian-Bai; Wu Hai-Bin

    2017-01-01

    An improved plan-wave expansion method is adopted to theoretically study the photonic band diagrams of two-dimensional (2D) metal/dielectric photonic crystals. Based on the photonic band structures, the dependence of flat bands and photonic bandgaps on two parameters (dielectric constant and filling factor) are investigated for two types of 2D metal/dielectric (M/D) photonic crystals, hole and cylinder photonic crystals. The simulation results show that band structures are affected greatly by these two parameters. Flat bands and bandgaps can be easily obtained by tuning these parameters and the bandgap width may reach to the maximum at certain parameters. It is worth noting that the hole-type photonic crystals show more bandgaps than the corresponding cylinder ones, and the frequency ranges of bandgaps also depend strongly on these parameters. Besides, the photonic crystals containing metallic medium can obtain more modulation of photonic bands, band gaps, and large effective refractive index, etc. than the dielectric/dielectric ones. According to the numerical results, the needs of optical devices for flat bands and bandgaps can be met by selecting the suitable geometry and material parameters. (paper)

  4. Transport and dielectric studies on silver based molybdo-tungstate quaternary superionic conducting glasses

    International Nuclear Information System (INIS)

    Prasad, P.S.S.; Radhakrishna, S.

    1988-01-01

    The molybdo-tungstate (MoO 3 -WO 3 ) combination of glass formers with silver oxide (Ag 2 O) as glass modifier and silver iodide (AgI) as ionic conductor were prepared to study the transport and dielectric properties of 60% AgI-40% (x Ag 2 O-y(WO 3 -MoO 3 )) for x/y=0.33 to 3.0 and establish the feasibility of using these glasses as electrolytes in the fabrication and characterisation of solid state batteries and potential memory devices. The details of the preparation of glasses and methods of measurement of their capacitance, dielectric loss factor and ac conductivity in the frequency range 100 Hz - 100 kHz from 30-120 C have been reported. The electronic contribution to the total conductivity, the ionic and electronic transport numbers were determined using Wagners dc polarisation technique. The observed high ionic and low electronic conductivities were attributed to the formation of ionic clusters in the glass and the effect of mixing two glass formers. The observed total ionic conductivity and its temperature dependence was explained using Arrhenius relation σ=σ 0 /T exp(-E/RT) and the measured dielectric constant and dielectric loss were explained on the basis of Jonschers theory. The frequency dependence of dielectric constant obeys the theory based on the polarisation of ions. 25 refs.; 8 figs

  5. High temperature dielectric studies of indium-substituted NiCuZn nanoferrites

    Science.gov (United States)

    Hashim, Mohd.; Raghasudha, M.; Shah, Jyoti; Shirsath, Sagar E.; Ravinder, D.; Kumar, Shalendra; Meena, Sher Singh; Bhatt, Pramod; Alimuddin; Kumar, Ravi; Kotnala, R. K.

    2018-01-01

    In this study, indium (In3+)-substituted NiCuZn nanostructured ceramic ferrites with a chemical composition of Ni0.5Cu0.25Zn0.25Fe2-xInxO4 (0.0 ≤ x ≤ 0.5) were prepared by chemical synthesis involving sol-gel chemistry. Single phased cubic spinel structure materials were prepared successfully according to X-ray diffraction and transmission electron microscopy analyses. The dielectric properties of the prepared ferrites were measured using an LCR HiTester at temperatures ranging from room temperature to 300 °C at different frequencies from 102 Hz to 5 × 106 Hz. The variations in the dielectric parameters ε‧ and (tanδ) with temperature demonstrated the frequency- and temperature-dependent characteristics due to electron hopping between the ions. The materials had low dielectric loss values in the high frequency range at all temperatures, which makes them suitable for high frequency microwave applications. A qualitative explanation is provided for the dependences of the dielectric constant and dielectric loss tangent on the frequency, temperature, and composition. Mӧssbauer spectroscopy was employed at room temperature to characterize the magnetic behavior.

  6. Differential Thermal Analysis and Dielectric Studies on 2-Methyl-2-Nitro-Propane under High Pressure

    Science.gov (United States)

    Büsing, D.; Jenau, M.; Reuter, J.; Würflinger, A.; Tamarit, J. Li.

    1995-05-01

    Differential thermal analysis and dielectric studies under pressures up to 300 MPa and temperatures of about 200 to 350 K have been performed on 2-methyl-2-nitro-propane (TBN). TBN displays an orientationally disordered phase (ODIC), solid I, and two non-plastic phases, solids II and III. The coexistence region of the plastic phase I increases with increasing pressure, whereas the low-temperature phase II apparently vanishes at a triple point I, II, III, above 300 MPa. The static permittivity increases on freezing, characterizing the solid I as an ODIC phase. In the frame of the Kirkwood-Onsager-Fröhlich theory the g-factor is about unity, discounting specific dielectric correlations. The dielectric behaviour of TBN is similar to previously studied related compounds, such as 2-chloro-2-methyl-propane or 2-brome- 2-methyl-propane

  7. Gate dielectric strength dependent performance of CNT MOSFET and CNT TFET: A tight binding study

    Directory of Open Access Journals (Sweden)

    Md. Shamim Sarker

    Full Text Available This paper presents a comparative study between CNT MOSFET and CNT TFET taking into account of different dielectric strength of gate oxide materials. Here we have studied the transfer characteristics, on/off current (ION/IOFF ratio and subthreshold slope of the device using Non Equilibrium Greens Function (NEGF formalism in tight binding frameworks. The results are obtained by solving the NEGF and Poisson’s equation self-consistently in NanoTCADViDES environment and found that the ON state performance of CNT MOSFET and CNT TFET have significant dependency on the dielectric strength of the gate oxide materials. The figure of merits of the devices also demonstrates that the CNT TFET is promising for high-speed and low-power logic applications. Keywords: CNT TFET, Subthreshold slop, Barrier width, Conduction band (C.B and Valance band (V.B, Oxide dielectric strength, Tight binding approach

  8. Dielectric and electrical study of PPy doped PVA-PVP films

    Science.gov (United States)

    Jha, Sushma; Tripathi, Deepti

    2018-05-01

    Dielectric parameters of free standing films of pure PVA (PolyvinylAlcohol) and PVA with varying concentrations of PVP(Polyvinylpyrrolidone) and Polypyrrole were prepared and studied in low frequency range (100Hz - 2MHz). The results show that dielectric constant, loss tangent and conductivity increase sharply on increasing the concentration of PVP above 50wt% in polymer matrix. PVA-PVP film with low concentration of PPy showed improvement in the values of complex permittivity, loss tangent and ac conductivity within the experimental frequency range. This eco - friendly polymeric material will be studied for its probable application for RFI/EMI shielding, biosensors, capacitors & insulation purposes.

  9. Temperature-dependent dielectric function of germanium in the UV–vis spectral range: A first-principles study

    International Nuclear Information System (INIS)

    Yang, J.Y.; Liu, L.H.; Tan, J.Y.

    2014-01-01

    The study of temperature dependence of thermophysical parameter dielectric function is key to understanding thermal radiative transfer in high-temperature environments. Limited by self-radiation and thermal oxidation, however, it is difficult to directly measure the high-temperature dielectric function of solids with present experimental technologies. In this work, we implement two first-principles methods, the ab initio molecular dynamics (AIMD) and density functional perturbation theory (DFPT), to study the temperature dependence of dielectric function of germanium (Ge) in the UV–vis spectral range in order to provide data of high-temperature dielectric function for radiative transfer study in high-temperature environments. Both the two methods successfully predict the temperature dependence of dielectric function of Ge. Moreover, the good agreement between the calculated results of the AIMD approach and experimental data at 825 K enables us to predict the high-temperature dielectric function of Ge with the AIMD method in the UV–vis spectral range. - Highlights: • The temperature dependence of dielectric function of germanium (Ge) is investigated with two first-principles methods. • The temperature effect on dielectric function of Ge is discussed. • The high-temperature dielectric function of Ge is predicted

  10. Structural, optical and dielectric properties of graphene oxide

    Science.gov (United States)

    Bhargava, Richa; Khan, Shakeel

    2018-05-01

    The Modified Hummers method has been used to synthesize Graphene oxide nanoparticles. Microstructural analyses were carried out by X-ray diffraction and Fourier transform infrared spectroscopy. Optical properties were studied by UV-visible spectroscopy in the range of 200-700 nm. The energy band gap was calculated with the help of Tauc relation. The frequency dependence of dielectric constant and dielectric loss were studied over a range of the frequency 75Hz to 5MHz at room temperature. The dispersion in dielectric constant can be explained with the help of Maxwell-Wagner model in studied nanoparticles.

  11. Conductivity, dielectric behavior and FTIR studies of high molecular weight poly(vinylchloride)-lithium triflate polymer electrolytes

    International Nuclear Information System (INIS)

    Ramesh, S.; Chai, M.F.

    2007-01-01

    Thin films of high molecular weight polyvinyl chloride (PVC) with lithium triflate (LiCF 3 SO 3 ) salt were prepared by solution casting method. The ionic conductivity and dielectric measurements were carried out on these films over a wide frequency regime at various temperatures. The conductivity-temperature plots were found to obey classical Arrhenius relationship. The dielectric behavior was analysed using dielectric permittivity and dielectric modulus of the samples. FTIR studies show some simple overlapping and shift in peaks between high molecular weight polyvinyl chloride (PVC) with lithium triflate (LiCF 3 SO 3 ) salt in the polymer electrolyte complexes

  12. Conductivity, dielectric behavior and FTIR studies of high molecular weight poly(vinylchloride)-lithium triflate polymer electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Ramesh, S. [Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Setapak, 53300 Kuala Lumpur (Malaysia)]. E-mail: ramesh@mail.utar.edu.my; Chai, M.F. [Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Setapak, 53300 Kuala Lumpur (Malaysia)

    2007-05-15

    Thin films of high molecular weight polyvinyl chloride (PVC) with lithium triflate (LiCF{sub 3}SO{sub 3}) salt were prepared by solution casting method. The ionic conductivity and dielectric measurements were carried out on these films over a wide frequency regime at various temperatures. The conductivity-temperature plots were found to obey classical Arrhenius relationship. The dielectric behavior was analysed using dielectric permittivity and dielectric modulus of the samples. FTIR studies show some simple overlapping and shift in peaks between high molecular weight polyvinyl chloride (PVC) with lithium triflate (LiCF{sub 3}SO{sub 3}) salt in the polymer electrolyte complexes.

  13. Dielectric and electro-optical parameters of two ferroelectric liquid crystals: a comparative study

    International Nuclear Information System (INIS)

    Kumar Misra, Abhishek; Kumar Srivastava, Abhishek; Shukla, J P; Manohar, Rajiv

    2008-01-01

    Dielectric relaxation and an electro-optical study of two ferroelectric liquid crystals having different spontaneous polarizations (Felix 16/100 and Felix 17/000) showing SmC* and SmA phases have been performed in the temperature range 30-80 compfn C. The experimental data have been used to determine different relaxation parameters, viz. distribution parameter, relaxation frequency, dielectric strength and rotational viscosity. The Goldstone mode of dielectric permittivity has been well observed for both the samples under investigation. The activation energy of both the samples has also been determined by the best theoretical fitting of the Arrhenius plot. We have also evaluated the optical response time and anchoring energy coefficients from electro-optical measurement techniques for these samples.

  14. Structural-optical study of high-dielectric-constant oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Losurdo, M. [Institute of Inorganic Methodologies and Plasmas, IMIP-CNR, Department of Chemistry and INSTM Universita di bari, Via Orabona 4, 70126 Bari (Italy)]. E-mail: maria.losurdo@ba.imip.cnr.it; Giangregorio, M.M. [Institute of Inorganic Methodologies and Plasmas, IMIP-CNR, Department of Chemistry and INSTM Universita di bari, Via Orabona 4, 70126 Bari (Italy); Luchena, M. [Institute of Inorganic Methodologies and Plasmas, IMIP-CNR, Department of Chemistry and INSTM Universita di bari, Via Orabona 4, 70126 Bari (Italy); Capezzuto, P. [Institute of Inorganic Methodologies and Plasmas, IMIP-CNR, Department of Chemistry and INSTM Universita di bari, Via Orabona 4, 70126 Bari (Italy); Bruno, G. [Institute of Inorganic Methodologies and Plasmas, IMIP-CNR, Department of Chemistry and INSTM Universita di bari, Via Orabona 4, 70126 Bari (Italy); Toro, R.G. [Dipartimento di Scienze Chimiche, Universita di Catania, and INSTM-UdR Catania, Viale A. Doria 6, I-95125 Catania (Italy); Malandrino, G. [Dipartimento di Scienze Chimiche, Universita di Catania, and INSTM-UdR Catania, Viale A. Doria 6, I-95125 Catania (Italy); Fragala, I.L. [Dipartimento di Scienze Chimiche, Universita di Catania, and INSTM-UdR Catania, Viale A. Doria 6, I-95125 Catania (Italy); Nigro, R. Lo [Istituto di Microelettronica e Microsistemi, IMM-CNR, Stradale Primosole 50, I-95121 Catania (Italy)

    2006-10-31

    High-k polycrystalline Pr{sub 2}O{sub 3} and amorphous LaAlO{sub 3} oxide thin films deposited on Si(0 0 1) are studied. The microstructure is investigated using X-ray diffraction and scanning electron microscopy. Optical properties are determined in the 0.75-6.5 eV photon energy range using spectroscopic ellipsometry. The polycrystalline Pr{sub 2}O{sub 3} films have an optical gap of 3.86 eV and a dielectric constant of 16-26, which increases with film thickness. Similarly, very thin amorphous LaAlO{sub 3} films have the optical gap of 5.8 eV, and a dielectric constant below 14 which also increases with film thickness. The lower dielectric constant compared to crystalline material is an intrinsic characteristic of amorphous films.

  15. Microwave dielectric study of polar liquids at 298 K

    Science.gov (United States)

    Maharolkar, Aruna P.; Murugkar, A.; Khirade, P. W.

    2018-05-01

    Present paper deals with study of microwave dielectric properties like dielectric constant, viscosity, density and refractive index for the binary mixtures of Dimethylsulphoxide (DMSO) and Methanol over the entire concentration range were measured at 298K. The experimental data further used to determine the excess properties viz. excess static dielectric constant, excess molar volume, excess viscosity& derived properties viz. molar refraction&Bruggman factor. The values of excess properties further fitted with Redlich-Kister (R-K Fit) equation to calculate the binary coefficients and standard deviation. The resulting excess parameters are used to indicate the presence of intermolecular interactions and strength of intermolecular interactions between the molecules in the binary mixtures. Excess parameters indicate structure breaking factor in the mixture predominates in the system.

  16. Dispersant testing : a study on analytical test procedures

    International Nuclear Information System (INIS)

    Fingas, M.F.; Fieldhouse, B.; Wang, Z.; Environment Canada, Ottawa, ON

    2004-01-01

    Crude oil is a complex mixture of hydrocarbons, ranging from small, volatile compounds to very large, non-volatile compounds. Analysis of the dispersed oil is crucial. This paper described Environment Canada's ongoing studies on various traits of dispersants. In particular, it describes small studies related to dispersant effectiveness and methods to improve analytical procedures. The study also re-evaluated the analytical procedure for the Swirling Flask Test, which is now part of the ASTM standard procedure. There are new and improved methods for analyzing oil-in-water using gas chromatography (GC). The methods could be further enhanced by integrating the entire chromatogram rather than just peaks. This would result in a decrease in maximum variation from 5 per cent to about 2 per cent. For oil-dispersant studies, the surfactant-dispersed oil hydrocarbons consist of two parts: GC-resolved hydrocarbons and GC-unresolved hydrocarbons. This study also tested a second feature of the Swirling Flask Test in which the side spout was tested and compared with a new vessel with a septum port instead of a side spout. This decreased the variability as well as the energy and mixing in the vessel. Rather than being a variation of the Swirling Flask Test, it was suggested that a spoutless vessel might be considered as a completely separate test. 7 refs., 2 tabs., 4 figs

  17. A study on the optical, structural, electrical conductivity and dielectric properties of a lithium bismuth germanium tungsten glasses

    Energy Technology Data Exchange (ETDEWEB)

    Salem, Shaaban M., E-mail: shaabansalem@gmail.com [Department of Physics, Faculty of Science, Al Azhar University, Nasr City 11884, Cairo (Egypt); Abdel-Khalek, E.K. [Department of Physics, Faculty of Science, Al Azhar University, Nasr City 11884, Cairo (Egypt); Department of Physics, Faculty of Science, Jazan University (Saudi Arabia); Mohamed, E.A. [Department of Physics, Faculty of Science (Girl' s Branch), Al Azhar University, Nasr City, Cairo (Egypt); Department of Physics, Faculty of Science, Jazan University (Saudi Arabia); Farouk, M. [Department of Physics, Faculty of Science, Al Azhar University, Nasr City 11884, Cairo (Egypt); Department of Physics, Faculty of Science, Jazan University (Saudi Arabia)

    2012-02-05

    Highlights: Black-Right-Pointing-Pointer I report, for the first time, the effect of WO{sub 3} on Bi{sub 2}O{sub 3}, Li{sub 2}O, GeO{sub 2} and WO{sub 3} glasses through structural, optical, conductivity and dielectric studies. Black-Right-Pointing-Pointer Optical band gap E{sub op} for all types of electronic transitions, Urbach energy (E{sub r}), and refractive index determined. Black-Right-Pointing-Pointer The WO{sub 3} promotes as bitter constituent the reduction of W{sup 6+} to W{sup 5+} giving the bluish color. Black-Right-Pointing-Pointer Infrared spectra reveal characteristic GeO{sub 4}, GeO{sub 6}, Bi{sub 2}O{sub 3}, BiO{sub 6}, WO{sub 4} and WO{sub 6} units. Black-Right-Pointing-Pointer Based on ac and dc conductivity the conductivity increased and activation energies decreased with increase of WO{sub 3} content at all frequencies. - Abstract: Glasses in the system (65 - x)Bi{sub 2}O{sub 3}-15Li{sub 2}O-20GeO{sub 2}-xWO{sub 3} (where x = 2, 5 and 10 mol%) were prepared by normal melt quenching method. The change in density and molar volume in these glasses indicates the effect of WO{sub 3} on the glass structure. Fourier transform infrared (FT-IR) spectra show that these glasses are made up of GeO{sub 4}, GeO{sub 6}, BiO{sub 6}, BiO{sub 3}, WO{sub 4} and WO{sub 6} basic structural units. The structural units of BiO{sub 6}, GeO{sub 6} and WO{sub 6} increase with the increasing of WO{sub 3} content. The optical constants of these glasses are determined over a spectral range, providing the complex dielectric constant to be calculated. Higher values for the refractive index and dispersion are recorded due to the high polarizability of bismuth and tungsten ions. The values of the optical band gap E{sub g} for all types of electronic transitions and refractive index have been determined and discussed. The dc conductivity measured in the temperature range 423-623 K obeys Arrhenius law. The dielectric constant ({epsilon} Prime ), dielectric loss (tan {delta}) and

  18. Atomization of bismuthane in a dielectric barrier discharge: A mechanistic study

    Czech Academy of Sciences Publication Activity Database

    Kratzer, Jan; Zelina, Ondřej; Svoboda, Milan; Sturgeon, R. E.; Mester, Z.; Dědina, Jiří

    2016-01-01

    Roč. 88, č. 3 (2016), s. 1804-1811 ISSN 0003-2700 R&D Projects: GA ČR GA14-23532S Grant - others:GA AV ČR(CZ) M200311202 Institutional support: RVO:68081715 Keywords : dielectric barrier discharge * hydride generation * mechanistic study Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 6.320, year: 2016

  19. Oscillatory shear and high-pressure dielectric study of 5-methyl-3-heptanol

    DEFF Research Database (Denmark)

    Hecksher, Tina; Jakobsen, Bo; Dyre, J. C.

    2014-01-01

    The monohydroxy alcohol 5-methyl-3-heptanol is studied using rheology at ambient pressure and using dielectric spectroscopy at elevated pressures up to 1.03 GPa. Both experimental techniques reveal that the relaxational behavior of this liquid is intermediate between those that show a large Debye...

  20. Atomization of bismuthane in a dielectric barrier discharge: A mechanistic study

    Czech Academy of Sciences Publication Activity Database

    Kratzer, Jan; Zelina, Ondřej; Svoboda, Milan; Sturgeon, R. E.; Mester, Z.; Dědina, Jiří

    2016-01-01

    Roč. 88, č. 3 (2016), s. 1804-1811 ISSN 0003-2700 R&D Projects: GA ČR GA14-23532S Grant - others:GA AV ČR(CZ) M200311202 Institutional support: RVO:68081715 Keywords : dielectric barrier discharge * hydride generation * mechanistic study Subject RIV: CB - Analytical Chemistry , Separation Impact factor: 6.320, year: 2016

  1. NUMERICAL STUDY OF ELECTROMAGNETIC WAVES GENERATED BY A PROTOTYPE DIELECTRIC LOGGING TOOL

    Science.gov (United States)

    To understand the electromagnetic waves generated by a prototype dielectric logging tool, a numerical study was conducted using both the finite-difference, time-domain method and a frequency- wavenumber method. When the propagation velocity in the borehole was greater than th...

  2. Dielectrics in electric fields

    CERN Document Server

    Raju, Gorur G

    2003-01-01

    Discover nontraditional applications of dielectric studies in this exceptionally crafted field reference or text for seniors and graduate students in power engineering tracks. This text contains more than 800 display equations and discusses polarization phenomena in dielectrics, the complex dielectric constant in an alternating electric field, dielectric relaxation and interfacial polarization, the measurement of absorption and desorption currents in time domains, and high field conduction phenomena. Dielectrics in Electric Fields is an interdisciplinary reference and text for professionals and students in electrical and electronics, chemical, biochemical, and environmental engineering; physical, surface, and colloid chemistry; materials science; and chemical physics.

  3. Study of the dielectric properties of barium titanate-polymer composites

    Energy Technology Data Exchange (ETDEWEB)

    Pant, H.C. [R and D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace, Jodhpur 342011, Rajasthan (India); Patra, M.K. [R and D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace, Jodhpur 342011, Rajasthan (India); Verma, Aditya [R and D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace, Jodhpur 342011, Rajasthan (India); Vadera, S.R. [R and D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace, Jodhpur 342011, Rajasthan (India); Kumar, N. [R and D Laboratory, Defence Laboratory, Camouflage Division, Defence Laboratory Ratanada Palace, Jodhpur 342011, Rajasthan (India)]. E-mail: nkjainjd@yahoo.com

    2006-07-15

    A comparative study of complex dielectric properties has been carried out at the X-band of microwave frequencies of composites of barium titanate (BaTiO{sub 3}) with two different polymer matrices: insulating polyaniline (PANI) powder (emeraldine base) and maleic resin. From these studies, it is observed that the composites of BaTiO{sub 3} with maleic resin show normal composite behavior and the dielectric constant follows the asymmetric Bruggeman model. In contrast, the composites of BaTiO{sub 3} with PANI show an unusual behavior wherein even at a low concentration of PANI (5 wt.%) there is a drastic reduction in the dielectric constant of BaTiO{sub 3}. This behavior of the dielectric constant is explained on the basis of coating of BaTiO{sub 3} particles by PANI which in turn is attributed to the highly surface adsorbing character. The materials have also been characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and optical microscopy studies.

  4. Study of the dielectric properties of barium titanate-polymer composites

    International Nuclear Information System (INIS)

    Pant, H.C.; Patra, M.K.; Verma, Aditya; Vadera, S.R.; Kumar, N.

    2006-01-01

    A comparative study of complex dielectric properties has been carried out at the X-band of microwave frequencies of composites of barium titanate (BaTiO 3 ) with two different polymer matrices: insulating polyaniline (PANI) powder (emeraldine base) and maleic resin. From these studies, it is observed that the composites of BaTiO 3 with maleic resin show normal composite behavior and the dielectric constant follows the asymmetric Bruggeman model. In contrast, the composites of BaTiO 3 with PANI show an unusual behavior wherein even at a low concentration of PANI (5 wt.%) there is a drastic reduction in the dielectric constant of BaTiO 3 . This behavior of the dielectric constant is explained on the basis of coating of BaTiO 3 particles by PANI which in turn is attributed to the highly surface adsorbing character. The materials have also been characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and optical microscopy studies

  5. Dielectric and complex impedance studies of BaTi0·85W0·15O3+δ ...

    Indian Academy of Sciences (India)

    Keywords. Ferroelectrics; grain boundaries; dielectric response; X-ray diffraction. 1. Introduction. Since the discovery of BaTiO3, these materials have been extensively studied owing to their interesting dielectric, ferroelectric, piezoelectric and pyroelectric properties. (Goodman and Buchanan 1986; Hench and West 1990;.

  6. Mord studies in IR region by new dispersion relation

    International Nuclear Information System (INIS)

    Murthy, V.R.; Kumar, R. Jeevan

    1994-01-01

    This is the continuation of the series reporting MORD studies to typical problem in Chemistry and Polymer Science. In our earlier papers the MORDsup1.2 studied only in visible region. In this present investigation we extended the application of the New Dispersion Relation in IR region to determine the MORD and tested to some simple systems

  7. Reliability of in vivo measurements of the dielectric properties of anisotropic tissue: a simulative study

    International Nuclear Information System (INIS)

    Huo Xuyang; Shi Xuetao; You Fusheng; Fu Feng; Liu Ruigang; Tang Chi; Dong Xiuzhen; Lu Qiang

    2013-01-01

    A simulative study was performed to measure the dielectric properties of anisotropic tissue using several in vivo and in vitro probes. COMSOL Multiphysics was selected to carry out the simulation. Five traditional probes and a newly designed probe were used in this study. One of these probes was an in vitro measurement probe and the other five were in vivo. The simulations were performed in terms of the minimal tissue volume for in vivo measurements, the calibration of a probe constant, the measurement performed on isotropic tissue and the measurement performed on anisotropic tissue. Results showed that the in vitro probe can be used to measure the in-cell dielectric properties of isotropic and anisotropic tissues. When measured with the five in vivo probes, the dielectric properties of isotropic tissue were all measured accurately. For the measurements performed on anisotropic tissue, large errors were observed when the four traditional in vivo probes were used, but only a small error was observed when the new in vivo probe was used. This newly designed five-electrode in vivo probe may indicate the dielectric properties of anisotropic tissue more accurately than these four traditional in vivo probes. (paper)

  8. Static dielectric constant of water within a bilayer using recent water models: a molecular dynamics study

    Science.gov (United States)

    Meneses-Juárez, Efrain; Rivas-Silva, Juan Francisco; González-Melchor, Minerva

    2018-05-01

    The water confined within a surfactant bilayer is studied using different water models via molecular dynamics simulations. We considered four representative rigid models of water: the SPC/E and the TIP4P/2005, which are commonly used in numerical calculations and the more recent TIP4Q and SPC/ε models, developed to reproduce the dielectric behaviour of pure water. The static dielectric constant of the confined water was analyzed as a function of the temperature for the four models. In all cases it decreases as the temperature increases. Additionally, the static dielectric constant of the bilayer-water system was estimated through its expression in terms of the fluctuations in the total dipole moment, usually applied for isotropic systems. The estimated dielectric was compared with the available experimental data. We found that the TIP4Q and the SPC/ε produce closer values to the experimental data than the other models, particularly at room temperature. It was found that the probability of finding the sodium ion close to the head of the surfactant decreases as the temperature increases, thus the head of the surfactant is more exposed to the interaction with water when the temperature is higher.

  9. The experimental study of seed dispersal by fish (ichthyochory)

    NARCIS (Netherlands)

    Pollux, B.J.A.

    2011-01-01

    1.The last few years have seen an increased interest in the experimental study of seed dispersal by fish (ichthyochory). This paper reviews such experiments, aiming to determine what functional aspects of ichthyochory have been investigated, what experimental designs have been used and what the

  10. Dielectric silicone elastomers with mixed ceramic nanoparticles

    International Nuclear Information System (INIS)

    Stiubianu, George; Bele, Adrian; Cazacu, Maria; Racles, Carmen; Vlad, Stelian; Ignat, Mircea

    2015-01-01

    Highlights: • Composite ceramics nanoparticles (MCN) with zirconium dioxide and lead zirconate. • Dielectric elastomer films wDith PDMS matrix and MCN as dielectric filler. • Hydrophobic character—water resistant and good flexibility specific to siloxanes. • Increased value of dielectric constant with the content of MCN in dielectric films. • Increased energy output from uniaxial deformation of the dielectric elastomer films. - Abstract: A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles

  11. Dielectric silicone elastomers with mixed ceramic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Stiubianu, George, E-mail: george.stiubianu@icmpp.ro [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Bele, Adrian; Cazacu, Maria; Racles, Carmen; Vlad, Stelian [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Ignat, Mircea [National R& D Institute for Electrical Engineering ICPE-CA Bucharest, Splaiul Unirii 313, District 3, Bucharest 030138 (Romania)

    2015-11-15

    Highlights: • Composite ceramics nanoparticles (MCN) with zirconium dioxide and lead zirconate. • Dielectric elastomer films wDith PDMS matrix and MCN as dielectric filler. • Hydrophobic character—water resistant and good flexibility specific to siloxanes. • Increased value of dielectric constant with the content of MCN in dielectric films. • Increased energy output from uniaxial deformation of the dielectric elastomer films. - Abstract: A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles.

  12. Changes in the dielectric properties of medaka fish embryos during development, studied by electrorotation

    Energy Technology Data Exchange (ETDEWEB)

    Shirakashi, Ryo, E-mail: aa21150@iis.u-tokyo.ac.jp [Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505 (Japan); Mischke, Miriam [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Fischer, Peter [Physiologische Chemie, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Memmel, Simon [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Krohne, Georg [Abteilung fuer Elektronenmikroskopie, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Fuhr, Guenter R. [Lehrstuhl fuer Biotechnologie und Medizintechnik, Universitaet des Saarlandes, Saarbruecken (Germany); Zimmermann, Heiko [Lehrstuhl fuer Molekulare und Zellulaere Biotechnologie, Universitaet des Saarlandes, Saarbruecken (Germany); Sukhorukov, Vladimir L., E-mail: sukhorukov@biozentrum.uni-wuerzburg.de [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany)

    2012-11-09

    Highlights: Black-Right-Pointing-Pointer Electrorotation offers a non-invasive tool for dielectric analysis of fish embryos. Black-Right-Pointing-Pointer The three-shell dielectric model matches the rotation spectra of medaka eggs. Black-Right-Pointing-Pointer The capacitance value suggests a double-membrane structure of yolk envelope. -- Abstract: The Japanese medaka fish, Oryzias latipes, has become a powerful vertebrate model organism in developmental biology and genetics. The present study explores the dielectric properties of medaka embryos during pre-hatching development by means of the electrorotation (ROT) technique. Due to their layered structure, medaka eggs exhibited up to three ROT peaks in the kHz-MHz frequency range. During development from blastula to early somite stage, ROT spectra varied only slightly. But as the embryo progressed to the late-somite stage, the ROT peaks underwent significant changes in frequency and amplitude. Using morphological data obtained by light and electron microscopy, we analyzed the ROT spectra with a three-shell dielectric model that accounted for the major embryonic compartments. The analysis yielded a very high value for the ionic conductivity of the egg shell (chorion), which was confirmed by independent osmotic experiments. A relatively low capacitance of the yolk envelope was consistent with its double-membrane structure revealed by transmission electron microscopy. Yolk-free dead eggs exhibited only one co-field ROT peak, shifted markedly to lower frequencies with respect to the corresponding peak of live embryos. The dielectric data may be useful for monitoring the development and changes in fish embryos' viability/conditions in basic research and industrial aquaculture.

  13. Changes in the dielectric properties of medaka fish embryos during development, studied by electrorotation

    International Nuclear Information System (INIS)

    Shirakashi, Ryo; Mischke, Miriam; Fischer, Peter; Memmel, Simon; Krohne, Georg; Fuhr, Günter R.; Zimmermann, Heiko; Sukhorukov, Vladimir L.

    2012-01-01

    Highlights: ► Electrorotation offers a non-invasive tool for dielectric analysis of fish embryos. ► The three-shell dielectric model matches the rotation spectra of medaka eggs. ► The capacitance value suggests a double-membrane structure of yolk envelope. -- Abstract: The Japanese medaka fish, Oryzias latipes, has become a powerful vertebrate model organism in developmental biology and genetics. The present study explores the dielectric properties of medaka embryos during pre-hatching development by means of the electrorotation (ROT) technique. Due to their layered structure, medaka eggs exhibited up to three ROT peaks in the kHz–MHz frequency range. During development from blastula to early somite stage, ROT spectra varied only slightly. But as the embryo progressed to the late-somite stage, the ROT peaks underwent significant changes in frequency and amplitude. Using morphological data obtained by light and electron microscopy, we analyzed the ROT spectra with a three-shell dielectric model that accounted for the major embryonic compartments. The analysis yielded a very high value for the ionic conductivity of the egg shell (chorion), which was confirmed by independent osmotic experiments. A relatively low capacitance of the yolk envelope was consistent with its double-membrane structure revealed by transmission electron microscopy. Yolk-free dead eggs exhibited only one co-field ROT peak, shifted markedly to lower frequencies with respect to the corresponding peak of live embryos. The dielectric data may be useful for monitoring the development and changes in fish embryos’ viability/conditions in basic research and industrial aquaculture.

  14. Studies of emulsification, emulsion prevention and underwater dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Celius, H.K.; Vassbotn, T.

    1985-03-01

    This is a report from the work performed under task 2: ''Effect of demulsifiers and despersants injected into a blowing oil stream'' of the research program ''Dispersion of oil on sea''. Three ad hoc experiments have been carried out involving laboratory studies in a small turbulent oil plume, tests with revolving flasks, and a small scale field test with a combined gas/oil plume. The results show that emulsion is formed in plume from underwater blowouts, and that this formation is prevented by small amounts (250 ppM) of demulsifiers or dispersants. Larger concentrations of dispersants (ca 2%) disperse the oil, and the oil is transported to the upper water layer in the gas/oil plume. None of the experiments have been designed as true scale tests, and the results cannot be directly transferred to operational, full scale conditions. The experiments have however narroved the necessary extent of studies, and allows for a simpler experimental procedure in the full scale field test planned for June 1985. 19 references.

  15. High Explosive Radiological Dispersion Device: Time and Distance Multiscale Study

    International Nuclear Information System (INIS)

    Sharon, A.; Sattinger, I.; Halevy, D.; Banaim, P.; Yaar, I.; Krantz, L.

    2014-01-01

    A wide range of explosion tests imitates different explosive RDD scenarios were conducted and aimed at increasing the preparedness for possible terrorism events, where radioactive (RA) materials disperse via an explosive charge. About 20 atmospheric dispersion tests were conducted using6-8 Ci of 99mTc which were coupled to TNT charges within the range of 0.2525 kg. Tests performed above different typical urban ground surfaces (in order to study the surface effect on the activity ground deposition pattern due to different in particles size distribution). We have used an efficient aerosolizing devices, means that most of the RA particles were initially created within the size of fine aerosols, mostly respirable. Ground activity measurements were performed both, around the dispersion point and up to few hundred meters downwind. Micrometeorology parameters (wind intensity and direction, potential temperature, relative humidity, solar radiation and atmospheric stability) were collected allowing comparisons topredictions of existing atmospheric dispersion models’1. Based on the experimental results, new model parameterizations were performed. Improvements in the models’ predictions were achieved and a set of thumb rules for first responders was formulated. This paper describes the project objectives, some of the experimental setups and results obtained. Post detonation nuclear forensic considerations can be made based upon results achieved

  16. Stability studies of colloidal silica dispersions in binary solvent mixtures

    International Nuclear Information System (INIS)

    Bean, Keith Howard

    1997-01-01

    A series of monodispersed colloidal silica dispersions, of varying radii, has been prepared. These particles are hydrophilic in nature due to the presence of surface silanol groups. Some of the particles have been rendered hydrophobic by terminally grafting n-alkyl (C 18 ) chains to the surface. The stability of dispersions of these various particles has been studied in binary mixtures of liquids, namely (i) ethanol and cyclohexane, and (ii) benzene and n-heptane. The ethanol - cyclohexane systems have been studied using a variety of techniques. Adsorption excess isotherms have been established and electrophoretic mobility measurements have been made. The predicted stability of the dispersions from D.V.L.O. calculations is compared to the observed stability. The hydrophilic silica particles behave as predicted by the calculations, with the zeta potential decreasing and the van der Waals attraction increasing with increasing cyclohexane concentration. The hydrophobic particles behave differently than expected, and the stability as a function of solvent mixture composition does not show a uniform trend. The effect of varying the coverage of C 18 chains on the surface and the effect of trace water in the systems has also been investigated. Organophilic silica dispersions in benzene - n-heptane solvent mixtures show weak aggregation and phase separation into a diffuse 'gas-like' phase and a more concentrated 'liquid-like' phase, analogous to molecular condensation processes. Calculations of the van der Waals potential as a function of solvent mixture composition show good agreement with the observed stability. Determination of the number of particles in each phase at equilibrium allows the energy of flocculation to be determined using a simple thermodynamic relationship. Finally, the addition of an AB block copolymer to organophilic silica particles in benzene n-heptane solvent mixtures has been shown to have a marked effect on the dispersion stability. This stability

  17. Single crystal magnetic, dielectric and thermal studies of the relaxor ferroelectric Pb(Fe2/3W1/3)O3

    International Nuclear Information System (INIS)

    Ye, Z.G.; Sato, M.; Kita, E.; Bursill, L.A.; Schmid, H.

    1998-01-01

    The magnetic, dielectric and thermal properties of the complex perovskite Pb(Fe 2/3 W 1/3 )O 3 [PFW] have been studied on single crystals by means of a SQUID magnetometer, dielectric measurements and thermal analysis. Anomalies in the temperature dependence of the magnetization have revealed magnetic phase transitions at T N1 =350 K and T N2 =20 K. These two steps of antiferromagnetic ordering are attributed to the microstructural feature of the complex perovskite, characterized by ordered and disordered arrangements on the B-site, giving rise to a strong superexchange interaction of - Fe 3 + - O - Fe 3+ - type with a higher ordering temperature, and to a weak superexchange interaction of the B-site ordered elpasolite type - Fe 3+ + - O - W - O - Fe 3+ - with a lower Neel temperature. The low temperature antiferromagnetic phase exhibits a weak ferromagnetism. The dielectric properties of PFW show a relaxor ferroelectric behaviour with a dispersive maximum of permittivity at Tm (170 -190 K). The magnetic phase transition at T N2 =20 K results in anomalies both of the real part of permittivity and the dissipation factor, suggesting a magneto-electric coupling via magneto-structural interactions

  18. Theoretical and Experimental Studies of New Polymer-Metal High-Dielectric Constant Nanocomposites

    Science.gov (United States)

    Ginzburg, Valeriy; Elwell, Michael; Myers, Kyle; Cieslinski, Robert; Malowinski, Sarah; Bernius, Mark

    2006-03-01

    High-dielectric-constant (high-K) gate materials are important for the needs of electronics industry. Most polymers have dielectric constant in the range 2 materials with K > 10 it is necessary to combine polymers with ceramic or metal nanoparticles. Several formulations based on functionalized Au-nanoparticles (R ˜ 5 -— 10 nm) and PMMA matrix polymer are prepared. Nanocomposite films are subsequently cast from solution. We study the morphology of those nanocomposites using theoretical (Self-Consistent Mean-Field Theory [SCMFT]) and experimental (Transmission Electron Microscopy [TEM]) techniques. Good qualitative agreement between theory and experiment is found. The study validates the utility of SCMFT as screening tool for the preparation of stable (or at least metastable) polymer/nanoparticle mixtures.

  19. Molecular interactions in ethyl acetate-chlorobenzene binary solution: Dielectric, spectroscopic studies and quantum chemical calculations

    Science.gov (United States)

    Karthick, N. K.; Kumbharkhane, A. C.; Joshi, Y. S.; Mahendraprabu, A.; Shanmugam, R.; Elangovan, A.; Arivazhagan, G.

    2017-05-01

    Dielectric studies using Time Domain Reflectometry method has been carried out on the binary solution of Ethyl acetate (EA) with Chlorobenzene (CBZ) over the entire composition range. Spectroscopic (FTIR and 13C NMR) signatures of neat EA, CBZ and their equimolar binary solution have also been recorded. The results of the spectroscopic studies favour the presence of (CBZ) Csbnd H ⋯ Odbnd C (EA), (EA) methylene Csbnd H ⋯ π electrons (CBZ) and (EA) methyl Csbnd H ⋯ Cl (CBZ) contacts which have been validated using quantum chemical calculations. Dimerization of CBZ has been identified. Presence of β-clusters has been identified in all the solutions. Although EA and CBZ molecules have nearly equal molar volumes, CBZ molecules experience larger hindrance for the rotation than EA molecules. Very small excess dielectric constant (εE) values may be correlated with weak heteromolecular forces and/or closed heteromolecular association.

  20. Barium ferrite/epoxy resin nanocomposite system: Fabrication, dielectric, magnetic and hydration studies

    Directory of Open Access Journals (Sweden)

    A. Kanapitsas

    2016-03-01

    Full Text Available Composite systems of epoxy resin and barium ferrite nanoparticles have been prepared, and studied varying the content of the inclusions. Morphology of prepared samples has been examined via scanning electron microscopy and X-ray diffraction spectra, while electrical and magnetic properties were investigated by means of broadband dielectric spectroscopy, and magnetization tests respectively. Finally, water vapor sorption measurements were conducted in order to study the water sorption dynamics of the system. Electron microscopy images revealed the successful fabrication of nanocomposites. Dielectric permittivity increases with filler content, while three relaxation processes were detected in the relative spectra. These processes are attributed to interfacial polarization, glass to rubber transition of the matrix, and re-orientation of polar side groups of the polymer’s chain. Magnetization and magnetic saturation increase with magnetic nano-powder content. Nanocomposites absorb a small amount of water, not exceeding 1.7 wt%, regardless filler content, indicating their hydrophobic character.

  1. Dielectric and modulus studies of polycrystalline BaZrO3 ceramic

    Science.gov (United States)

    Saini, Deepash S.; Singh, Sunder; Kumar, Anil; Bhattacharya, D.

    2018-05-01

    In the present work, dielectric and modulus studies of polycrystalline BaZrO3 ceramic, prepared by modified combustion method followed by conventional sintering, are investigated over the frequency range of 100 Hz to 106 Hz at different temperatures from 250 to 500 °C in air. The high value of dielectric constant (ɛ' ˜ 103) of BaZrO3 at high temperature and low frequency can be attributed to the Maxwell-Wagner polarization mechanism as well as to the thermally activated mechanism of charge carriers. Electric modulus reveal two type relaxations in the 250 °C to 800 °C temperature region as studied at different frequencies over 100 Hz to 106 Hz in air.

  2. Morphological studies of polymer dispersed liquid crystal materials

    International Nuclear Information System (INIS)

    Han, Jin-Woo

    2006-01-01

    In this work, we have studied the morphologies of polymer dispersed liquid crystals (PDLCs) based on E7/NOA61. Scanning electron microscope studies show that the PDLC morphology is strongly affected by the LC concentration and the cure temperature. A typical PDLC morphology with isolated LC droplets dispersed in a polymer matrix is only observed at low LC compositions and at low cure temperatures. Increasing either the LC composition or the cure temperature results in a polymer ball morphology, in which LCs exist in irregularly shaped voids in the polymer network structure. It is shown that the transition between these two morphologies can be qualitatively explained using a pseudo-binary phase diagram.

  3. Dielectric and physiochemical study of binary mixture of nitrobenzene with toluene

    Science.gov (United States)

    Mohod, Ajay G.; Deshmukh, S. D.; Pattebahadur, K. L.; Undre, P. B.; Patil, S. S.; Khirade, P. W.

    2018-05-01

    This paper presents the study of binary mixture of Nitrobenzene (NB) with Toluene (TOL) for eleven different concentrations at room temperature. The determined Dielectric Constant (ɛ0) Density (ρ) and Refractive index (nD) values of binary mixture are used to calculate the excess properties i.e. Excess Dielectric Constant (ɛ0E), Excess Molar Volume (VmE), Excess Refractive Index (nDE) and Excess Molar Refraction (RmE) of mixture over the entire composition range and fitted to the Redlich-Kister equation. The Kirkwood Correlation Factor (geff) and other parameters were used to discuss the information about the orientation of dipoles and the solute-solvent interaction of binary mixture at molecular level over the entire range of concentration.

  4. Dielectric and conformational studies of hydrogen bonded 2-ethoxyethanol and ethyl methyl ketone system

    Science.gov (United States)

    Pattebahadur, Kanchan. L.; Deshmukh, S. D.; Mohod, A. G.; Undre, P. B.; Patil, S. S.; Khirade, P. W.

    2018-05-01

    The Dielectric constant, density and refractive index of binary mixture of 2-ethoxy ethanol (2-EE) with ethyl methyl ketone (EMK) including those of the pure liquids were measured for 11 concentrations at 25°C temperature. The experimental data is used to calculate the Excess molar volume, Excess dielectric constant, Kirkwood correlation factor and Bruggemann factor. The excess parameters results were fitted to the Redlich-Kister type polynomial equation to derive its fitting coefficient. The Kirkwood correlation factor of the mixture has been discussed to yield information about solute solvent interaction. The Bruggeman plot shows a deviation from linearity. The FT-IR spectra of pure and their binary mixtures are also studied.

  5. Studies of permittivity and permeability of dielectric matrix with cuboid metallic inclusions in different orientations

    Directory of Open Access Journals (Sweden)

    W. M. Wu

    2014-10-01

    Full Text Available In this paper, we investigate the possibility of using the heterogeneous materials, with cuboid metallic inclusions inside a dielectric substrate (host to control the effective permittivity. We find that in the gigahertz range, such a material demonstrates a significantly larger permittivity compared to the pure dielectric substrate. Three principal orientations of microscale cuboid inclusions have been taken into account in this study. The highest permittivity is observed when the orientation provides the largest polarization (electric dipole moment. The detrimental side effect of the metallic inclusion, which leads to the decrease of the effective magnetic permeability, can be suppressed by the proper choice of shape and orientation of the inclusions. This choice can in fact reduce the induced current and hence maximize the permeability. The dissipative losses are shown to be negligible in the relevant range of frequencies and cuboid dimensions.

  6. Numerical study of the characteristics of a dielectric barrier discharge plasma actuator

    Science.gov (United States)

    Shi, C. A.; Adamiak, K.; Castle, G. S. P.

    2018-03-01

    A dielectric barrier discharge actuator to control airflow along a flat dielectric plate has been numerically investigated in this paper. In order to avoid large computing times, streamers, Trichel pulses and the ionic reactions involving photons and electrons are neglected. The numerical model assumes two types of generic ions, one positive and one negative, whose drift in the electric field produces the electrohydrodynamic flow. This study provides detailed insights into the physical mechanisms of DBD that include the electric field, space charge transport, surface charge accumulation and air flow motion. The results show the V-I characteristics, velocity profiles and drag force estimates. In addition, the effects of the voltage level, frequency and inlet air velocity on the actuator performance are presented and interpreted. The simulation results show a good agreement with theoretical expectations and experimental data available in literature.

  7. STRUCTURAL AND DIELECTRIC STUDIES ON Sr0.5-3y/2LayBa0.5Nb2O6 CERAMIC SYSTEMS WITH VARIED SINTERING TIME AND La CONCENTRATION

    Directory of Open Access Journals (Sweden)

    Zahariman S. R.

    2013-12-01

    Full Text Available Sr0.5Ba0.5Nb2O6 (SBN50 ceramic doped with different concentration of Lanthanum, La according to stoichiometric formulation of Sr0.5-3y/2LayBa0.5Nb2O6 (LSBN with y = 0.01, 0.03, 0.05 and 0.07 prepared using traditional ceramic method at the calcination temperature of 1200°C and sintered at 1300°C at varied sintering time. The effects of the sintering time and La3+ substitution on the morphological, compositional, structural and electrical properties of the LSBN is presented using scanning electronic microscopy (SEM, energy dispersive spectroscopy (EDS, X-ray diffraction (XRD and dielectric analysis. The XRD spectra confirm the presence of TTB structure in the ceramics. The Curie temperature (Tc of the ceramic identified from the dielectric studies performed in the temperature range of 28°C to 300°C. The temperature dependent dielectric exhibits broad peaks indicating a diffuse phase transition and relaxor behavior of the ceramic. The measured density of the samples is proportional to the sintering time and inversely proportional to the amount of the La3+ substitution. The solubility limit of La3+ ions in the SBN solid solution is at y ~ 0.05. This observation is also supported by the dielectric results where the dielectric properties of the ceramic deteriorate for y > 0.05 La substitution.

  8. Dielectric properties of ligand-modified gold nanoparticles/SU-8 photopolymer based nanocomposites

    KAUST Repository

    Toor, Anju; So, Hongyun; Pisano, Albert P.

    2017-01-01

    This article reports the enhanced dielectric properties of a photodefinable nanocomposite material containing sub–10 nm coated metal nanoparticles (NPs). The surface morphology of the synthesized dodecanethiol-functionalized gold NPs was characterized using the transmission electron microscopy (TEM). We investigated the particle agglomeration and dispersion during the various stages of the nanocomposite synthesis using TEM. Physical properties such as dielectric permittivity and dielectric loss were measured experimentally. The dependence of dielectric permittivity and loss tangent on particle concentration and frequency was studied. Nanocomposite films showed an approximately three times enhancement in average dielectric constant over the polymer base value and an average dielectric loss of 0.09 at 1 kHz, at a filler loading of 10% w/w.

  9. Dielectric properties of ligand-modified gold nanoparticles/SU-8 photopolymer based nanocomposites

    KAUST Repository

    Toor, Anju

    2017-04-15

    This article reports the enhanced dielectric properties of a photodefinable nanocomposite material containing sub–10 nm coated metal nanoparticles (NPs). The surface morphology of the synthesized dodecanethiol-functionalized gold NPs was characterized using the transmission electron microscopy (TEM). We investigated the particle agglomeration and dispersion during the various stages of the nanocomposite synthesis using TEM. Physical properties such as dielectric permittivity and dielectric loss were measured experimentally. The dependence of dielectric permittivity and loss tangent on particle concentration and frequency was studied. Nanocomposite films showed an approximately three times enhancement in average dielectric constant over the polymer base value and an average dielectric loss of 0.09 at 1 kHz, at a filler loading of 10% w/w.

  10. Curcumin containing monoolein aqueous dispersions: A preformulative study

    Energy Technology Data Exchange (ETDEWEB)

    Esposito, Elisabetta, E-mail: ese@unife.it [Department of Life Sciences and Biotechnology, University of Ferrara, I-44121 Ferrara (Italy); Ravani, Laura [Department of Life Sciences and Biotechnology, University of Ferrara, I-44121 Ferrara (Italy); Mariani, Paolo [Department of Life and Environmental Sciences and CNISM, Università Politecnica delle Marche, I-60100 Ancona (Italy); Contado, Catia [Department of Chemistry, University of Ferrara, I-44121 Ferrara (Italy); Drechsler, Markus [Macromolecular Chemistry II, University of Bayreuth (Germany); Puglia, Carmelo [Department of Drug Sciences, University of Catania, I-95125 Catania (Italy); Cortesi, Rita [Department of Life Sciences and Biotechnology, University of Ferrara, I-44121 Ferrara (Italy)

    2013-12-01

    The present study describes the production and characterization of monoolein aqueous dispersions (MAD) as drug delivery systems for curcumin (CR). MAD based on monoolein and different emulsifiers have been produced and characterized. Morphology and dimensional distribution have been investigated by Cryogenic Transmission Electron Microscopy (cryo-TEM), X-ray and Photon Correlation Spectroscopy (PCS). Monoolein in different mixtures with sodium cholate, sodium caseinate, bentonite and poloxamer resulted in heterogeneous dispersions constituted of unilamellar vesicles, cubosomes and sponge type phases, depending on the employed components, as found by cryo-TEM and X-ray studies. CR was encapsulated with entrapment efficiencies depending on the MAD composition, particularly the highest was reached in the case of monoolein/poloxamer/sodium cholate mixture. The same mixture was able to maintain CR stability also after 6 months. CR release modalities were in vitro investigated in order to mimic a possible subcutaneous administration of MAD. It was found that MAD constituted of monoolein/poloxamer and monoolein/poloxamer/sodium cholate mixtures were able to sustain CR release. MAD viscous vehicles were produced by xanthan gum. CR percutaneous absorption has been studied in vitro using excised human skin membranes [stratum corneum epidermis (SCE)] mounted into Franz cells. It was found that fluxes (F{sub n}) of CR incorporated in MAD are influenced by the presence of monoolein based nanosystems. In particular xanthan gum based MAD better control CR diffusion from MAD. - Highlights: • Curcumin (CR) can be solubilized in monoolein aqueous dispersions (MAD). • Different emulsifiers result in different inner structures in the disperse phase. • Monoolein/poloxamer/sodium cholate mixture (MCP) results in the highest CR encapsulation. • MCP maintains CR stability for 6 months. • Xanthan gum based MAD better control CR fluxes with respect to plain gel and liquid MAD.

  11. Curcumin containing monoolein aqueous dispersions: A preformulative study

    International Nuclear Information System (INIS)

    Esposito, Elisabetta; Ravani, Laura; Mariani, Paolo; Contado, Catia; Drechsler, Markus; Puglia, Carmelo; Cortesi, Rita

    2013-01-01

    The present study describes the production and characterization of monoolein aqueous dispersions (MAD) as drug delivery systems for curcumin (CR). MAD based on monoolein and different emulsifiers have been produced and characterized. Morphology and dimensional distribution have been investigated by Cryogenic Transmission Electron Microscopy (cryo-TEM), X-ray and Photon Correlation Spectroscopy (PCS). Monoolein in different mixtures with sodium cholate, sodium caseinate, bentonite and poloxamer resulted in heterogeneous dispersions constituted of unilamellar vesicles, cubosomes and sponge type phases, depending on the employed components, as found by cryo-TEM and X-ray studies. CR was encapsulated with entrapment efficiencies depending on the MAD composition, particularly the highest was reached in the case of monoolein/poloxamer/sodium cholate mixture. The same mixture was able to maintain CR stability also after 6 months. CR release modalities were in vitro investigated in order to mimic a possible subcutaneous administration of MAD. It was found that MAD constituted of monoolein/poloxamer and monoolein/poloxamer/sodium cholate mixtures were able to sustain CR release. MAD viscous vehicles were produced by xanthan gum. CR percutaneous absorption has been studied in vitro using excised human skin membranes [stratum corneum epidermis (SCE)] mounted into Franz cells. It was found that fluxes (F n ) of CR incorporated in MAD are influenced by the presence of monoolein based nanosystems. In particular xanthan gum based MAD better control CR diffusion from MAD. - Highlights: • Curcumin (CR) can be solubilized in monoolein aqueous dispersions (MAD). • Different emulsifiers result in different inner structures in the disperse phase. • Monoolein/poloxamer/sodium cholate mixture (MCP) results in the highest CR encapsulation. • MCP maintains CR stability for 6 months. • Xanthan gum based MAD better control CR fluxes with respect to plain gel and liquid MAD

  12. Dielectric properties: A gateway to antibacterial assay-A case study of low-density polyethylene/chitosan composite films.

    Digital Repository Service at National Institute of Oceanography (India)

    Sunilkumar, M.; Gafoor, A.A.; Anas, A.; Haseena, A.P.; Sujith, A.

    anhydride and dicumyl peroxide were used as a coupling agent and a free radical initiator, respectively. The dielectric properties of the composite films were studied as a function of chitosan loading, presence of plasticizer and variable applied frequency...

  13. On gel electrophoresis of dielectric charged particles with hydrophobic surface: A combined theoretical and numerical study.

    Science.gov (United States)

    Majee, Partha Sarathi; Bhattacharyya, Somnath; Gopmandal, Partha Pratim; Ohshima, Hiroyuki

    2018-03-01

    A theoretical study on the gel electrophoresis of a charged particle incorporating the effects of dielectric polarization and surface hydrophobicity at the particle-liquid interface is made. A simplified model based on the weak applied field and low charge density assumption is also presented and compared with the full numerical model for a nonpolarizable particle to elucidate the nonlinear effects such as double layer polarization and relaxation as well as surface conduction. The main motivation of this study is to analyze the electrophoresis of the surface functionalized nanoparticle with tunable hydrophobicity or charged fluid drop in gel medium by considering the electrokinetic effects and hydrodynamic interactions between the particle and the gel medium. An effective medium approach, in which the transport in the electrolyte-saturated hydrogel medium is governed by the Brinkman equation, is adopted in the present analysis. The governing electrokinetic equations based on the conservation principles are solved numerically. The Navier-slip boundary condition along with the continuity condition of dielectric displacement are imposed on the surface of the hydrophobic polarizable particle. The impact of the slip length on the electrophoresis is profound for a thinner Debye layer, however, surface conduction effect also becomes significant for a hydrophobic particle. Impact of hydrophobicity and relaxation effects are higher for a larger particle. Dielectric polarization creates a reduction in its electrophoretic propulsion and has negligible impact at the thinner Debye length as well as lower gel screening length. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. An experimental study of electrical and dielectric properties of consolidated clayey materials

    International Nuclear Information System (INIS)

    Comparon, L.

    2005-06-01

    This study is devoted to the electrical and dielectric properties of consolidated clays. A better understanding of the conduction and polarization phenomena in clays is necessary to better interpret in situ measurements in terms of water saturation and texture. An experimental study was carried out on synthetic clay samples (kaolinite and smectite) compacted with various water contents, porosities and mineralogical compositions, on a large frequency range, using three laboratory setups. The electrical properties of natural argillites (from ANDRA) were then investigated. We found that the response of the synthetic samples is mainly controlled by water content on the whole frequency range; two polarization phenomena were observed, which were related to the Maxwell-Wagner polarization and the electrical double layer polarization around the clay particles. The electrical response of argillites is more complex; it is controlled by water content but also by the microstructure of the rock. In these rocks, the electrical and dielectric anisotropies are high; anisotropy was also measured for the synthetic clays. The existing models explain the high frequency limit of the dielectric permittivity of the clayey materials, but the low frequency part of the spectra (≤1 MHz) needs theoretical developments. (author)

  15. Dispersant effectiveness: Studies into the causes of effectiveness variations

    International Nuclear Information System (INIS)

    Fingas, M.F.; Kyle, D.; Tennyson, E.

    1995-01-01

    Effectiveness, a key issue of using dispersants, is affected by many interrelated factors. The principal factors involved are the oil composition, dispersant formulation, sea surface turbulence and dispersant quantity. Oil composition is a very strong determinant. Current dispersant formulation effectiveness correlates strongly with the amount of saturate component in the oil. The other components of the oil, the asphaltenes, resins or polars and aromatic fractions show a negative correlation with the dispersant effectiveness. Viscosity is also a predictor of dispersant effectiveness and may have an effect because it is in turn determined by oil composition. Dispersant composition is significant and interacts with oil composition. Dispersants show high effectiveness at HLB values near 10. Sea turbulence strongly affects dispersant effectiveness.Effectiveness rises with increasing turbulence to a maximum value. Effectiveness for current commercial dispersants is gaussian around a peak salinity value. Peak effectiveness is achieved at very high dispersant quantities--at a ratio of 1:5, dispersant-to-oil volume. Dispersant effectiveness for those oils tested and under the conditions measured, is approximately logarithmic with dispersant quantity and will reach about 50% of its peak value at a dispersant to oil ratio of about 1:20 and near zero at a ratio of about 1:50

  16. Studies of Tracer Dispersion and Fluid Flow in Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Rage, T.

    1996-12-31

    This doctoral thesis explores the connection between the topology of a porous medium and its macroscopic transport properties and is based on computerized simulation. In porous media, both diffusion and convection contribute to the dispersion of a tracer and their combined effect is emphasized. The governing equations are solved numerically, using finite differences and Monte Carlo technique. The influence of finite Reynolds number on the outcome of echo-experiments is discussed. Comparing experiments and simulations it is found that nonlinear inertial forces lead to a visible deformation of a returned tracer at surprisingly small Reynolds numbers. In a study of tracer dispersion and fluid flow in periodic arrays of discs it is demonstrated that the mechanisms of mechanical dispersion in periodic media and in natural (non-periodic) porous media are essentially different. Measurements of the percolation probability distribution of a sandstone sample is presented. Local porosity theory predicts that this simple geometric function of a porous medium is of dominant importance for its macroscopic transport properties. It is demonstrated that many aspects of transport through fractures can be studied by using simple but realistic models and readily available computer resources. An example may be the transport of hydrocarbon fluids from the source rock to a reservoir. 165 refs., 44 figs., 1 table

  17. Electrowetting on dielectric: experimental and model study of oil conductivity on rupture voltage

    Science.gov (United States)

    Zhao, Qing; Tang, Biao; Dong, Baoqin; Li, Hui; Zhou, Rui; Guo, Yuanyuan; Dou, Yingying; Deng, Yong; Groenewold, Jan; Henzen, Alexander Victor; Zhou, Guofu

    2018-05-01

    Electrowetting on dielectric devices uses a conducting (water) and insulating (oil) liquid phase in conjunction on a dielectric layer. In these devices, the wetting properties of the liquid phases can be manipulated by applying an electric field. The electric field can rupture the initially flat oil film and promotes further dewetting of the oil. Here, we investigate a problem in the operation of electrowetting on dielectric caused by a finite conductivity of the oil. In particular, we find that the voltage at which the oil film ruptures is sensitive to the application of relatively low DC voltages prior to switching. Here, we systematically investigate this dependence using controlled driving schemes. The mechanism behind these history effects point to charge transport processes in the dielectric and the oil, which can be modeled and characterized by a decay time. To quantify the effects the typical response timescales have been measured with a high-speed video camera. The results have been reproduced in simulations. In addition, a simplified yet accurate equivalent circuit model is developed to analyze larger data sets more conveniently. The experimental data support the hypothesis that each pixel can be characterized by a single decay time. We studied an ensemble of pixels and found that they showed a rather broad distribution of decay times with an average value of about 440 ms. This decay time can be interpreted as a discharge timescale of the oil, not to be confused with discharge of the entire system which is generally much faster (<1 ms). Through the equivalent circuit model, we also found that variations in the fluoropolymer (FP) conductivity cannot explain the distribution of decay times, while variations in oil conductivity can.

  18. Dielectric and electrical conductivity studies of bulk lead (II) oxide (PbO)

    Energy Technology Data Exchange (ETDEWEB)

    Darwish, A.A.A., E-mail: aaadarwish@gmail.com [Department of Physics, Faculty of Education at Al-Mahweet, Sana’a University, Al-Mahwit (Yemen); Department of Physics, Faculty of Science, University of Tabuk, P.O. Box 741, Tabuk 71491, Tabuk (Saudi Arabia); El-Zaidia, E.F.M.; El-Nahass, M.M. [Department of Physics, Faculty of Education, Ain Shams University, Rorxy, Cairo 11757 (Egypt); Hanafy, T.A. [Department of Physics, Faculty of Science, University of Tabuk, P.O. Box 741, Tabuk 71491, Tabuk (Saudi Arabia); Department of Physics, Faculty of Science, Fayoum University, 63514 El Fayoum (Egypt); Al-Zubaidi, A.A. [Department of Physics, Faculty of Science, University of Tabuk, P.O. Box 741, Tabuk 71491, Tabuk (Saudi Arabia)

    2014-03-15

    Highlights: • The AC measurements of PbO were measured at temperature range 313–523 K. • The dielectric constants increased with temperature. • The mechanism responsible for AC conduction is electronic hopping. -- Abstract: The dielectric properties, the impedance spectroscopy and AC conductivity of bulk PbO have been investigated as a function of frequency and temperature. The measurements were carried out in the frequency range from 40 to 5 × 10{sup 6} Hz and in temperature range from 313 to 523 K. The frequency response of dielectric constant, ε{sub 1}, and dielectric loss index, ε{sub 2}, as a function of temperature were studied. The values of ε{sub 1} and ε{sub 2} were found to decrease with the increase in frequency. However, they increase with the increase in temperature. The presence of a single arc in the complex modulus spectrum at different temperatures confirms the single-phase character of the PbO. The AC conductivity exhibited a universal dynamic response: σ{sub AC} = Aω{sup s}. The AC conductivity was also found to increase with increasing temperature and frequency. The correlation barrier hopping (CBH) model was found to apply to the AC conductivity data. The calculated values of s were decreased with temperature. This behavior reveals that the conduction mechanism for PbO samples is CBH. The activation energy for AC conductivity decreases with increasing frequency. This confirms that the hopping conduction to the dominant mechanism for PbO samples.

  19. Interest in broadband dielectric spectroscopy to study the electronic transport in materials for lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Badot, Jean-Claude, E-mail: jc.badot@chimie-paristech.fr [Institut de Recherche de Chimie Paris, UMR CNRS 8247, Réseau sur le Stockage Electrochimique de l' Energie (RS2E), Chimie Paris Tech, PSL*, 11 rue P. et M. Curie, 75231 Cedex 05 Paris (France); Lestriez, Bernard [Institut des Matériaux Jean Rouxel, UMR CNRS 6502, Université de Nantes, 2 rue de la Houssinière, BP32229, 44322 Nantes (France); Dubrunfaut, Olivier [GeePs | Group of electrical engineering – Paris, UMR CNRS 8507, CentraleSupélec, Univ. Paris-Sud, Université Paris-Saclay, Sorbonne Universités, UPMC Univ Paris 06, 3 & 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette CEDEX, Paris (France)

    2016-11-15

    Highlights: • Broadband dielectric spectroscopy measures the multiscale electronic conductivity from macroscopic to interatomic sizes. • There is an influence of the surface states on the electronic transfer of powdered materials (e.g. thin insulating layer of Li{sub 2}CO{sub 3} on LiNiO{sub 2} and carbon coating on LiFePO{sub 4}). • Electrical relaxations resulting from the interfacial polarizations at the different scales of the carbon black network are evidenced. - Abstract: Broadband dielectric spectroscopy (BDS) is used to measure complex permittivity and conductivity of conducting materials for lithium batteries at frequencies from a few Hz to several GHz with network and impedance analysers. Under the influence of an electric field, there will be charge density fluctuations in the conductor mainly due to electronic transfer. These fluctuations result in dielectric relaxations for frequencies below 100 GHz. The materials are compacted powders in which each element (particles, agglomerates of particles) can have different sizes and morphologies. In the present review, studies are reported on the influence of surface states in LiNiO{sub 2} (ageing and degradation in air) and LiFePO{sub 4} (carbon coating thin layer), and on a composite electrode based on the lithium trivanadate (Li{sub 1.1}V{sub 3}O{sub 8}) active material. The results have shown that the BDS technique is very sensitive to the different scales of materials architectures involved in electronic transport, from interatomic distances to macroscopic sizes.

  20. Electronic polarizability of light crude oil from optical and dielectric studies

    Science.gov (United States)

    George, A. K.; Singh, R. N.

    2017-07-01

    In the present paper we report the temperature dependence of density, refractive indices and dielectric constant of three samples of crude oils. The API gravity number estimated from the temperature dependent density studies revealed that the three samples fall in the category of light oil. The measured data of refractive index and the density are used to evaluate the polarizability of these fluids. Molar refractive index and the molar volume are evaluated through Lorentz-Lorenz equation. The function of the refractive index, FRI , divided by the mass density ρ, is a constant approximately equal to one-third and is invariant with temperature for all the samples. The measured values of the dielectric constant decrease linearly with increasing temperature for all the samples. The dielectric constant estimated from the refractive index measurements using Lorentz-Lorentz equation agrees well with the measured values. The results are promising since all the three measured properties complement each other and offer a simple and reliable method for estimating crude oil properties, in the absence of sufficient data.

  1. Experimental study for the use of sulfur hexafluoride as dielectric gas in particle accelerators

    International Nuclear Information System (INIS)

    Candanedo y Bernabe, C.

    1993-01-01

    The sulfur hexafluoride is the better dielectric gas in the world. It is used in particle accelerator, power stations and high voltage transformators. This is a high stable gas, but when is used as dielectric is degraded in toxic and corrosive fluorides this degradation of sulfur hexafluoride is a function of the voltaic arc, crown effect, pressure, temperature and radiation. The purification of the sulfur fluoride permitted to work in safe form and without the risks as contaminant. The objective of the work is the development of a process for the separation of the wastes from the fabrication of sulphur fluoride and the products of degradation. This process used adsorbents when this gas is used as dielectric. The methodology employed was bibliography research, experimental design of the equipment, construction of the experimental equipment, selection and use of adsorbents, installation of the adsorption columns for the experimentation, flow of the sulfur hexafluoride through the adsorbents, searching of the fluoride hexafluoride before and after of the step through the adsorption columns and writing of the results. In base to the results we conclude that the process is good. The work could be advantage using chromatographic techniques with adequate standards. Is possible to extend the study using an additional number of adsorbents. (Author). 34 refs, 7 graphs, 3 tabs

  2. Comprehensive Study of Lanthanum Aluminate High-Dielectric-Constant Gate Oxides for Advanced CMOS Devices

    Directory of Open Access Journals (Sweden)

    Masamichi Suzuki

    2012-03-01

    Full Text Available A comprehensive study of the electrical and physical characteristics of Lanthanum Aluminate (LaAlO3 high-dielectric-constant gate oxides for advanced CMOS devices was performed. The most distinctive feature of LaAlO3 as compared with Hf-based high-k materials is the thermal stability at the interface with Si, which suppresses the formation of a low-permittivity Si oxide interfacial layer. Careful selection of the film deposition conditions has enabled successful deposition of an LaAlO3 gate dielectric film with an equivalent oxide thickness (EOT of 0.31 nm. Direct contact with Si has been revealed to cause significant tensile strain to the Si in the interface region. The high stability of the effective work function with respect to the annealing conditions has been demonstrated through comparison with Hf-based dielectrics. It has also been shown that the effective work function can be tuned over a wide range by controlling the La/(La + Al atomic ratio. In addition, gate-first n-MOSFETs with ultrathin EOT that use sulfur-implanted Schottky source/drain technology have been fabricated using a low-temperature process.

  3. Interest in broadband dielectric spectroscopy to study the electronic transport in materials for lithium batteries

    International Nuclear Information System (INIS)

    Badot, Jean-Claude; Lestriez, Bernard; Dubrunfaut, Olivier

    2016-01-01

    Highlights: • Broadband dielectric spectroscopy measures the multiscale electronic conductivity from macroscopic to interatomic sizes. • There is an influence of the surface states on the electronic transfer of powdered materials (e.g. thin insulating layer of Li_2CO_3 on LiNiO_2 and carbon coating on LiFePO_4). • Electrical relaxations resulting from the interfacial polarizations at the different scales of the carbon black network are evidenced. - Abstract: Broadband dielectric spectroscopy (BDS) is used to measure complex permittivity and conductivity of conducting materials for lithium batteries at frequencies from a few Hz to several GHz with network and impedance analysers. Under the influence of an electric field, there will be charge density fluctuations in the conductor mainly due to electronic transfer. These fluctuations result in dielectric relaxations for frequencies below 100 GHz. The materials are compacted powders in which each element (particles, agglomerates of particles) can have different sizes and morphologies. In the present review, studies are reported on the influence of surface states in LiNiO_2 (ageing and degradation in air) and LiFePO_4 (carbon coating thin layer), and on a composite electrode based on the lithium trivanadate (Li_1_._1V_3O_8) active material. The results have shown that the BDS technique is very sensitive to the different scales of materials architectures involved in electronic transport, from interatomic distances to macroscopic sizes.

  4. Comparative Study on Atmospheric Dispersion Module of Level 3 PSA

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Dahye; Jang, Misuk; Kang, Hyun Sik; Kim, Seoung Rae [NESS, Daejeon (Korea, Republic of)

    2016-10-15

    Some regulation documents such as Regulatory Guides and NUREG publications from the U.S. Nuclear Regulatory Commission (NRC) have influences on domestic radiation environmental analyses. As renewal versions of NUREG-0800 and NUREG-1555 have issued lately, the assessment for Severe Accident (SA) with Probabilistic Safety Assessment (PSA) should be added to Safety Analysis Report (SAR) and Radiation Environmental Report (RER). Because these reports are the required documents for obtaining the construction permit and operating license, it is important to understand the PSA methodology and it needs to improve the site-specific input data of L3PSA codes for SA. First, our review focuses on the atmospheric dispersion and deposition related input data of L3PSA code in this paper. Then we will continue to review the improvements of other input data. Two atmospheric dispersion models, which are PAVAN developed for design basis accident and ATMOS of MACCS2 code developed for SA, were reviewed in this paper. L3PSA deals with the effects of severe accidents and basically includes the evaluation of both short- and long-term effects. Therefore, both the deposition effects and nuclide information(type, amount, and chemical characteristics of released radionuclide) would be considered as the input parameters of atmospheric dispersion model for L3PSA. Additionally, the meteorological data would be sampled randomly to meet the purpose of probabilistic method. However, the sampling method would be selected according to analysis purpose. After review, ATMOS module and its input data are suitably developed for the atmospheric dispersion analysis of L3PSA. However, ATMOS module was developed using the site-specific terrain and environment characteristics. For the domestic application, it needs to study the input data reflecting the Korean terrain and environment characteristics. It would be also continuously improved in response to the time- and site-specific changes of weather

  5. Dielectric track detectors and their applications in boron studies

    International Nuclear Information System (INIS)

    Mysak, F.; Krejci, M.

    1982-01-01

    Examples are presented of the applications of autoradiography using plastic films in the study of the distribution of boron in metal materials and its translocation owing to diffusion annealing. Alpha radiation is induced in the material by thermal neutrons while the reaction 10 B(n,α) 7 Li is used. Diffusion processes were studied in the transition zone between the base material and the overlay in hard alloy surfacing. The metallographically treated samples were placed on cellulose nitrate films and irradiated in a reactor. Autoradiograms showed that up to an annealing temperature of 800 degC there was no notable diffusion. Only at 900 degC migration occurred of boron from the transition zone to the base material. Also studied was the distribution of boron in soldered joints of nickel heat resisting alloys. The joints were subjected to homogenization annealing and the gradual disintegration was monitored of boride phases in dependence on the temperature and duration of annealing. Inside the joint boron practically disappeared and it finally appeared in the base material outside of the initial interface. (M.D.)

  6. Analytical study of the relativistic dispersion: Application to the generation of the auroral kilometric radiation

    International Nuclear Information System (INIS)

    Le Queau, D.; Louarn, P.

    1989-01-01

    The measurements recently performed by the Viking spacecraft have shown that, in addition to being cold plasma depleted, the source regions of the Auroral Kilometric Radiation (A.K.R.) are characterized by a relatively denser, more energetic electron component. In order to properly study the Cyclotron Maser Instability (C.M.I.) which is thought to be responsible for the A.K.R. generation, it is thus necessary to include relativistic corrections in both the hermitian and the antihermitian parts of the dielectric tensor characterizing the linear properties of the plasma. Here one presents an analytical study of the corresponding dispersion equation which aims to describe stable and unstable waves having frequencies lying very close to the electronic gyrofrequency and propagating across the geomagnetic field with a perpendicular refractive index less than a few units (n perpendicular 1 and χ small), the growth rate could maximize at the cut-off frequency of the relativistic X mode. Moreover, for small χ, the relativistic X mode is connected to freely propagating modes which guarantees an easy access of the electromagnetic energy to free space

  7. A compare study on dielectric behaviors of Au/(Zn-doped PVA)/n-4H ...

    Indian Academy of Sciences (India)

    55

    thickness effect of Zn-doped PVA on the dielectric constant (ε′), dielectric .... In order to formation MPS structures, the prepared PVA (Zn-nanoparticle doped) ..... MacCallumand J R and Vincent C A 1989 Polymer Electrolyte Reviews (London:.

  8. Critical review of studies on atmospheric dispersion in coastal regions

    International Nuclear Information System (INIS)

    Shearer, D.L.; Kaleel, R.J.

    1982-09-01

    This study effort was required as a preliminary step prior to initiation of field measurements of atmospheric dispersion in coastal regions. The Nuclear Regulatory Commission (NRC) is in the process of planning an extensive field measurement program to generate data which will serve as improved data bases for licensing decisions, confirmation of regulations, standards, and guides, and for site characterizations. The study being reported here is an effort directed to obtaining as much information as is possible from existing studies that is relevant toward NRC's objectives. For this study, reports covering research and meteorological measurements conducted for industrial purposes, utility needs, military objectives, and academic studies were obtained and critically reviewed in light of NRC's current data needs. This report provides an interpretation of the extent of existing usable information, an indication of the potential for tailoring existing research toward current NRC information needs, and recommendations for several follow-on studies which could provide valuable additional information through reanalysis of the data. Recommendations are also offered regarding new measurement programs. Emphasis is placed on the identification and acquisition of data from atmospheric tracer studies conducted in coastal regions. A total of 225 references were identified which deal with the coastal atmosphere, including meteorological and tracer measurement programs, theoretical descriptions of the relevant processes, and dispersion models

  9. Studying the factors affecting urban dispersion in mashhad metropolis

    African Journals Online (AJOL)

    economic, social, and physical aspects including increased air pollution, potential deterioration within ... solutions to control this problem. The tools used in ... Key words: urban dispersion, technology, roots of Mashhad dispersion, the price of

  10. Dielectric spectroscopy technique applied to study the behaviour of irradiated polymer

    International Nuclear Information System (INIS)

    Saoud, R.; Soualmia, A.; Guerbi, C.A.; Benrekaa, N.

    2006-01-01

    Relaxation spectroscopy provides an excellent method for the study of motional processes in materials and has been widely applied to macromolecules and polymers. The technique is potentially of most interest when applied to irradiated systems. Application to the study of the structure beam-irradiated Teflon is thus an outstanding opportunity for the dielectric relaxation technique, particularly as this material exhibits clamping problems when subjected to dynamic mechanical relaxation studies. A very wide frequency range is necessary to resolve dipolar effects. In this paper, we discuss some significant results about the behavior and the modification of the structure of Teflon submitted to weak energy radiations

  11. Millimeter wave and terahertz dielectric properties of biological materials

    Science.gov (United States)

    Khan, Usman Ansar

    Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to 1.2 THz. This is an extremely difficult portion of the frequency spectrum to obtain a material's dielectric properties since neither optical nor microwave-based techniques provide accurate data. The dielectric characteristics of liquids such as cyclohexane, chlorobenzene, benzene, ethanol, methanol, 1,4 dioxane, and 10% formalin were obtained using the liquid interferometer. Subsequently the solid interferometer was utilized to determine the dielectric properties of human breast tissues, which are fixed and preserved in 10% formalin. This joint collaboration with the Tufts New England Medical Center demonstrated a significant difference between the dielectric response of tumorous and non-tumorous breast tissues across the spectrum. Powders such as anthrax, flour, talc, corn starch, dry milk, and baking soda have been involved in a number of security threats and false alarms around the globe in the last decade. To be able to differentiate hoax attacks and serious security threats, the dielectric properties of common household powders were also examined using the solid interferometer to identify the powders' unique resonance peaks. A new sample preparation kit was designed to test the powder specimens. It was anticipated that millimeter wave and terahertz dielectric characterization will enable one to clearly distinguish one powder from the other; however most of the powders had relatively close dielectric responses and only Talc had a resonance signature recorded at 1.135 THz. Furthermore, due to

  12. Ultrasonic and dielectric studies of polymer PDMS composites with ZnO and onion-like carbons nanoinclusions

    International Nuclear Information System (INIS)

    Samulionis, V; Macutkevic, J; Banys, J; Belovickis, J; Shenderova, O

    2015-01-01

    The ultrasonic and dielectric temperature investigations were performed in polydi- methylsiloxane (PDMS) with zinc oxide (ZnO) and onion-like carbon (OLC) nanocomposites. In the glass transition region, the ultrasonic velocity dispersion and large ultrasonic attenuation maxima were observed. The positions of ultrasonic attenuation peaks were slightly shifted to higher temperatures after doping PDMS with OLC and ZnO nanoparticles. The ultrasonic relaxation was compared to that of dielectric and such behaviour was described by Vogel- Fulcher law. The upshift of the glass transition temperature with addition of nanoparticles was confirmed by both methods. The additional increase of ultrasonic attenuation in composites doped with OLC and ZnO was observed at room temperature and such behaviour we attributed to ultrasound-nanofiller interaction in polymer matrix. (paper)

  13. Ultrasonic and dielectric studies of polymer PDMS composites with ZnO and onion-like carbons nanoinclusions

    Science.gov (United States)

    Samulionis, V.; Macutkevic, J.; Banys, J.; Belovickis, J.; Shenderova, O.

    2015-07-01

    The ultrasonic and dielectric temperature investigations were performed in polydi- methylsiloxane (PDMS) with zinc oxide (ZnO) and onion-like carbon (OLC) nanocomposites. In the glass transition region, the ultrasonic velocity dispersion and large ultrasonic attenuation maxima were observed. The positions of ultrasonic attenuation peaks were slightly shifted to higher temperatures after doping PDMS with OLC and ZnO nanoparticles. The ultrasonic relaxation was compared to that of dielectric and such behaviour was described by Vogel- Fulcher law. The upshift of the glass transition temperature with addition of nanoparticles was confirmed by both methods. The additional increase of ultrasonic attenuation in composites doped with OLC and ZnO was observed at room temperature and such behaviour we attributed to ultrasound-nanofiller interaction in polymer matrix.

  14. A Study on Fluid Dispersion after Liquid Filled Missile Impact

    International Nuclear Information System (INIS)

    Shin, Sang Shup; Hahm, Daegi; Choi, In-Kil

    2015-01-01

    In order to fire damage evaluations by fuel included transportation crash, the fire duration should be analyzed that consider the fuel spread range, amount of leaked fuel, and various ignition sources. The water slug impact test performed in Sandia National Laboratory (SNL) in 2002 was representative. The cloud of mist dispersion range of the dyed red water and ejection velocity of water after impact were analyzed using Particle Image Velocimetry (PIV) method and numerical simulation. In this study, the included fluid was modeled by using smooth particle hydrodynamics (SPH) technique. The fluid dispersion range following impact was analyzed by considering the particle velocity and flying distance. The result values obtained through this study were compared to the water slug (WS) test results. And the applicability of an analysis method was verified by comparing the WS test results. The results and methodology obtained through this study can be utilized to damage assessment, fuel spread and fire risk for large infrastructures such as nuclear power plants following an aircraft impact. In this study, the included fluid was modeled by using smooth particle hydrodynamics (SPH) technique; the fluid spread range following an impact was analyzed. The radius of fluid spread on the numerical analysis became conservative than the WS test results. However, the shape of the cloud is similar to the WS test results

  15. A Study on Fluid Dispersion after Liquid Filled Missile Impact

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Sang Shup; Hahm, Daegi; Choi, In-Kil [KAERI, Daejeon (Korea, Republic of)

    2015-05-15

    In order to fire damage evaluations by fuel included transportation crash, the fire duration should be analyzed that consider the fuel spread range, amount of leaked fuel, and various ignition sources. The water slug impact test performed in Sandia National Laboratory (SNL) in 2002 was representative. The cloud of mist dispersion range of the dyed red water and ejection velocity of water after impact were analyzed using Particle Image Velocimetry (PIV) method and numerical simulation. In this study, the included fluid was modeled by using smooth particle hydrodynamics (SPH) technique. The fluid dispersion range following impact was analyzed by considering the particle velocity and flying distance. The result values obtained through this study were compared to the water slug (WS) test results. And the applicability of an analysis method was verified by comparing the WS test results. The results and methodology obtained through this study can be utilized to damage assessment, fuel spread and fire risk for large infrastructures such as nuclear power plants following an aircraft impact. In this study, the included fluid was modeled by using smooth particle hydrodynamics (SPH) technique; the fluid spread range following an impact was analyzed. The radius of fluid spread on the numerical analysis became conservative than the WS test results. However, the shape of the cloud is similar to the WS test results.

  16. Trajectory and Relative Dispersion Case Studies and Statistics from the Green River Mesoscale Deformation, Dispersion, and Dissipation Program

    Science.gov (United States)

    Niemann, Brand Lee

    A major field program to study beta-mesoscale transport and dispersion over complex mountainous terrain was conducted during 1969 with the cooperation of three government agencies at the White Sands Missile Range in central Utah. The purpose of the program was to measure simultaneously on a large number of days the synoptic and mesoscale wind fields, the relative dispersion between pairs of particle trajectories and the rate of small scale turbulence dissipation. The field program included measurements during more than 60 days in the months of March, June, and November. The large quantity of data generated from this program has been processed and analyzed to provide case studies and statistics to evaluate and refine Lagrangian variable trajectory models. The case studies selected to illustrate the complexities of mesoscale transport and dispersion over complex terrain include those with terrain blocking, lee waves, and stagnation, as well as those with large vertical wind shears and horizontal wind field deformation. The statistics of relative particle dispersion were computed and compared to the classical theories of Richardson and Batchelor and the more recent theories of Lin and Kao among others. The relative particle dispersion was generally found to increase with travel time in the alongwind and crosswind directions, but in a more oscillatory than sustained or even accelerated manner as predicted by most theories, unless substantial wind shears or finite vertical separations between particles were present. The relative particle dispersion in the vertical was generally found to be small and bounded even when substantial vertical motions due to lee waves were present because of the limiting effect of stable temperature stratification. The data show that velocity shears have a more significant effect than turbulence on relative particle dispersion and that sufficient turbulence may not always be present above the planetary boundary layer for "wind direction shear

  17. Contribution to the thermal study of a dielectric barrier discharge reactor

    International Nuclear Information System (INIS)

    Dubus, Nicolas

    2009-01-01

    This thesis aims to study the thermal behaviour of a laboratory Dielectric Barrier Discharge (DBD) reactor. An experimental study was first realized to measure temperatures at different points of the reactor by using optic fibers. These measurements were performed in transient and steady states. To examine the influence of heat losses, not insulated and insulated reactors were considered. The influence of the nature and the form of the applied voltage was else considered. Experiments were conducted with a sinusoidal voltage and a pulsed power supply. (author) [fr

  18. A large-scale study of the ultrawideband microwave dielectric properties of normal breast tissue obtained from reduction surgeries.

    Science.gov (United States)

    Lazebnik, Mariya; McCartney, Leah; Popovic, Dijana; Watkins, Cynthia B; Lindstrom, Mary J; Harter, Josephine; Sewall, Sarah; Magliocco, Anthony; Booske, John H; Okoniewski, Michal; Hagness, Susan C

    2007-05-21

    The efficacy of emerging microwave breast cancer detection and treatment techniques will depend, in part, on the dielectric properties of normal breast tissue. However, knowledge of these properties at microwave frequencies has been limited due to gaps and discrepancies in previously reported small-scale studies. To address these issues, we experimentally characterized the wideband microwave-frequency dielectric properties of a large number of normal breast tissue samples obtained from breast reduction surgeries at the University of Wisconsin and University of Calgary hospitals. The dielectric spectroscopy measurements were conducted from 0.5 to 20 GHz using a precision open-ended coaxial probe. The tissue composition within the probe's sensing region was quantified in terms of percentages of adipose, fibroconnective and glandular tissues. We fit a one-pole Cole-Cole model to the complex permittivity data set obtained for each sample and determined median Cole-Cole parameters for three groups of normal breast tissues, categorized by adipose tissue content (0-30%, 31-84% and 85-100%). Our analysis of the dielectric properties data for 354 tissue samples reveals that there is a large variation in the dielectric properties of normal breast tissue due to substantial tissue heterogeneity. We observed no statistically significant difference between the within-patient and between-patient variability in the dielectric properties.

  19. A large-scale study of the ultrawideband microwave dielectric properties of normal breast tissue obtained from reduction surgeries

    International Nuclear Information System (INIS)

    Lazebnik, Mariya; McCartney, Leah; Popovic, Dijana; Watkins, Cynthia B; Lindstrom, Mary J; Harter, Josephine; Sewall, Sarah; Magliocco, Anthony; Booske, John H; Okoniewski, Michal; Hagness, Susan C

    2007-01-01

    The efficacy of emerging microwave breast cancer detection and treatment techniques will depend, in part, on the dielectric properties of normal breast tissue. However, knowledge of these properties at microwave frequencies has been limited due to gaps and discrepancies in previously reported small-scale studies. To address these issues, we experimentally characterized the wideband microwave-frequency dielectric properties of a large number of normal breast tissue samples obtained from breast reduction surgeries at University of Wisconsin and University of Calgary hospitals. The dielectric spectroscopy measurements were conducted from 0.5 to 20 GHz using a precision open-ended coaxial probe. The tissue composition within the probe's sensing region was quantified in terms of percentages of adipose, fibroconnective and glandular tissues. We fit a one-pole Cole-Cole model to the complex permittivity data set obtained for each sample and determined median Cole-Cole parameters for three groups of normal breast tissues, categorized by adipose tissue content (0-30%, 31-84% and 85-100%). Our analysis of the dielectric properties data for 354 tissue samples reveals that there is a large variation in the dielectric properties of normal breast tissue due to substantial tissue heterogeneity. We observed no statistically significant difference between the within-patient and between-patient variability in the dielectric properties

  20. Generalized dielectric permittivity tensor

    International Nuclear Information System (INIS)

    Borzdov, G.N.; Barkovskii, L.M.; Fedorov, F.I.

    1986-01-01

    The authors deal with the question of what is to be done with the formalism of the electrodynamics of dispersive media based on the introduction of dielectric-permittivity tensors for purely harmonic fields when Voigt waves and waves of more general form exist. An attempt is made to broaden and generalize the formalism to take into account dispersion of waves of the given type. In dispersive media, the polarization, magnetization, and conduction current-density vectors of point and time are determined by the values of the electromagnetic field vectors in the vicinity of this point (spatial dispersion) in the preceding instants of time (time dispersion). The dielectric-permittivity tensor and other tensors of electrodynamic parameters of the medium are introduced in terms of a set of evolution operators and not the set of harmonic function. It is noted that a magnetic-permeability tensor and an elastic-modulus tensor may be introduced for an acoustic field in dispersive anisotropic media with coupling equations of general form

  1. Dielectric properties of ligand-modified gold nanoparticle/SU-8 photopolymer based nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Toor, Anju, E-mail: atoor@berkeley.edu [Department of Mechanical Engineering, University of California, Berkeley, CA 94720 (United States); So, Hongyun, E-mail: hyso@berkeley.edu [Department of Mechanical Engineering, University of California, Berkeley, CA 94720 (United States); Pisano, Albert P. [Department of Mechanical Engineering, University of California, Berkeley, CA 94720 (United States); Department of Mechanical and Aerospace Engineering, University of California, San Diego, CA 92093 (United States)

    2017-08-31

    Highlights: • Ligand-modified gold NP/SU-8 nanocomposites were synthesized and demonstrated. • Particle agglomeration and dispersion were characterized with different NPs concentration. • Nanocomposites showed higher average dielectric permittivity compared to SU-8 only. • Relatively lower dielectric loss (average 0.09 at 1 kHz) was achieved with 10 % w/w NPs. - Abstract: This article reports the enhanced dielectric properties of a photodefinable polymer nanocomposite material containing sub–10 nm coated metal nanoparticles (NPs). The surface morphology of the synthesized dodecanethiol-functionalized gold NPs was characterized using the transmission electron microscopy (TEM). We investigated the particle agglomeration and dispersion during the various stages of the nanocomposite synthesis using TEM. Physical properties such as dielectric permittivity and dielectric loss were measured experimentally. The dependence of the dielectric permittivity and loss tangent on the particle concentration, and frequency was studied. Nanocomposite films showed an approximately three times enhancement in average dielectric constant over the polymer base value and an average dielectric loss of 0.09 at 1 kHz, at a filler loading of 10% w/w.

  2. Brillouin light scattering studies of the mechanical properties of ultrathin low-k dielectric films

    Science.gov (United States)

    Link, A.; Sooryakumar, R.; Bandhu, R. S.; Antonelli, G. A.

    2006-07-01

    In an effort to reduce RC time delays that accompany decreasing feature sizes, low-k dielectric films are rapidly emerging as potential replacements for silicon dioxide (SiO2) at the interconnect level in integrated circuits. The main challenge in low-k materials is their substantially weaker mechanical properties that accompany the increasing pore volume content needed to reduce k. We show that Brillouin light scattering is an excellent nondestructive technique to monitor and characterize the mechanical properties of these porous films at thicknesses well below 200nm that are pertinent to present applications. Observation of longitudinal and transverse standing wave acoustic resonances and the dispersion that accompany their transformation into traveling waves with finite in-plane wave vectors provides for a direct measure of the principal elastic constants that completely characterize the mechanical properties of these ultrathin films. The mode amplitudes of the standing waves, their variation within the film, and the calculated Brillouin intensities account for most aspects of the spectra. We further show that the values obtained by this method agree well with other experimental techniques such as nanoindentation and picosecond laser ultrasonics.

  3. FTIR and dielectric studies of molecular interaction between alkyl methacrylates and primary alcohols

    International Nuclear Information System (INIS)

    Dharmalingam, K.; Ramachandran, K.; Sivagurunathan, P.

    2007-01-01

    The molecular interaction between alkyl methacrylates (methyl methacrylate, ethyl methacrylate and butyl methacrylate) and primary alcohols (1-propanol, 1-butanol, 1-pentanol, 1-heptanol, 1-octanol and 1-decanol) has been studied in carbon tetrachloride by FTIR spectroscopic and dielectric methods. The results show that the most likely association between alcohol and ester is 1:1 complex through the free hydroxyl group of the alcohol and the carbonyl group of ester, and the alkyl chain length of both the alcohols and esters plays an important role in the determination of the strength of hydrogen bond (O-H:O=C) formed

  4. Study of observed broad dielectric relaxation and compatibility of polysulfone - Polyvinylidenefluoride blends

    Science.gov (United States)

    Patel, Swarnim; Shrivas, Sandhya; Dubey, R. K.; Keller, J. M.

    2018-05-01

    Short circuit thermally stimulated depolarization current measurement techniques has been employed to investigate the dielectric relaxation behavior of PSF: PVDF blends. The samples taken were blends of composition PSF: PVDF:: 80:20; 85:15; 90:10 and 95:05 percent by weight. The thermograms were characterized by a high value of initial current, a low temperature peak around 75-80°C and a prominent broad peak in the temperature interval 130 to 160°C. The two polymers are found to form compatible blend in the studied composition range.

  5. Computational study of textured ferroelectric polycrystals: Dielectric and piezoelectric properties of template-matrix composites

    Science.gov (United States)

    Zhou, Jie E.; Yan, Yongke; Priya, Shashank; Wang, Yu U.

    2017-01-01

    Quantitative relationships between processing, microstructure, and properties in textured ferroelectric polycrystals and the underlying responsible mechanisms are investigated by phase field modeling and computer simulation. This study focuses on three important aspects of textured ferroelectric ceramics: (i) grain microstructure evolution during templated grain growth processing, (ii) crystallographic texture development as a function of volume fraction and seed size of the templates, and (iii) dielectric and piezoelectric properties of the obtained template-matrix composites of textured polycrystals. Findings on the third aspect are presented here, while an accompanying paper of this work reports findings on the first two aspects. In this paper, the competing effects of crystallographic texture and template seed volume fraction on the dielectric and piezoelectric properties of ferroelectric polycrystals are investigated. The phase field model of ferroelectric composites consisting of template seeds embedded in matrix grains is developed to simulate domain evolution, polarization-electric field (P-E), and strain-electric field (ɛ-E) hysteresis loops. The coercive field, remnant polarization, dielectric permittivity, piezoelectric coefficient, and dissipation factor are studied as a function of grain texture and template seed volume fraction. It is found that, while crystallographic texture significantly improves the polycrystal properties towards those of single crystals, a higher volume fraction of template seeds tends to decrease the electromechanical properties, thus canceling the advantage of ferroelectric polycrystals textured by templated grain growth processing. This competing detrimental effect is shown to arise from the composite effect, where the template phase possesses material properties inferior to the matrix phase, causing mechanical clamping and charge accumulation at inter-phase interfaces between matrix and template inclusions. The computational

  6. Urban Dispersion Program Overview and MID05 Field Study Summary

    Energy Technology Data Exchange (ETDEWEB)

    Allwine, K Jerry; Flaherty, Julia E.

    2007-07-31

    The Urban Dispersion Program (UDP) was a 4-year project (2004–2007) funded by the U.S. Department of Homeland Security with additional support from the Defense Threat Reduction Agency. The U.S. Environmental Protection Agency (EPA) also contributed to UDP through funding a human-exposure component of the New York City (NYC) field studies in addition to supporting an EPA scientist in conducting modeling studies of NYC. The primary goal of UDP was to improve the scientific understanding of the flow and diffusion of airborne contaminants through and around the deep street canyons of NYC. The overall UDP project manager and lead scientist was Dr. Jerry Allwine of Pacific Northwest National Laboratory. UDP had several accomplishments that included conducting two tracer and meteorological field studies in Midtown Manhattan.

  7. A terahertz study of taurine: Dispersion correction and mode couplings

    Science.gov (United States)

    Dai, Zelin; Xu, Xiangdong; Gu, Yu; Li, Xinrong; Wang, Fu; Lian, Yuxiang; Fan, Kai; Cheng, Xiaomeng; Chen, Zhegeng; Sun, Minghui; Jiang, Yadong; Yang, Chun; Xu, Jimmy

    2017-03-01

    The low-frequency characteristics of polycrystalline taurine were studied experimentally by terahertz (THz) absorption spectroscopy and theoretically by ab initio density-functional simulations. Full optimizations with semi-empirical dispersion correction were performed in spectral computations and vibrational mode assignments. For comparison, partial optimizations with pure density functional theory were conducted in parallel. Results indicate that adding long-range dispersion correction to the standard DFT better reproduces the measured THz spectra than the popular partial optimizations. The main origins of the observed absorption features were also identified. Moreover, a coupled-oscillators model was proposed to explain the experimental observation of the unusual spectral blue-shift with the increase of temperature. Such coupled-oscillators model not only provides insights into the temperature dynamics of non-bonded interactions but also offers an opportunity to better understand the physical mechanisms behind the unusual THz spectral behaviors in taurine. Particularly, the simulation approach and novel coupled-oscillators model presented in this work are applicable to analyze the THz spectra of other molecular systems.

  8. Noise Studies of Externally Dispersed Interferometry for Doppler Velocimetry

    International Nuclear Information System (INIS)

    Erskine, D J; Edelstein, J; Lloyd, J; Muirhead, P

    2006-01-01

    Externally Dispersed Interferometry (EDI) is the series combination of a fixed-delay field-widened Michelson interferometer with a dispersive spectrograph. This combination boosts the spectrograph performance for both Doppler velocimetry and high resolution spectroscopy. The interferometer creates a periodic comb that multiplies against the input spectrum to create moire fringes, which are recorded in combination with the regular spectrum. Both regular and high-frequency spectral components can be recovered from the data--the moire component carries additional information that increases the signal to noise for velocimetry and spectroscopy. Here we present simulations and theoretical studies of the photon limited Doppler velocity noise in an EDI. We used a model spectrum of a 1600K temperature star. For several rotational blurring velocities 0, 7.5, 15 and 25 km/s we calculated the dimensionless Doppler quality index (Q) versus wavenumber v. This is the normalized RMS of the derivative of the spectrum and is proportional to the photon-limited Doppler signal to noise ratio

  9. Surface plasmon polariton Akhmediev Breather in a dielectric-metal-dielectric geometry with subwavelength thickness

    Science.gov (United States)

    Devi, Koijam Monika; Porsezian, K.; Sarma, Amarendra K.

    2018-05-01

    We report Akhmediev Breather solutions in a nonlinear multilayer structure comprising of a metal sandwiched between two semi-infinite dielectric layers with subwavelength thickness. These nonlinear solutions inherit the properties of Surface plasmon polaritons and its dynamics is governed by the Nonlinear Schrodinger equation. The breather evolution is studied for specific values of nonlinear and dispersion parameters. An experimental scheme to observe these breathers is also proposed.

  10. Study of PECVD films containing flourine and carbon and diamond like carbon films for ultra low dielectric constant interlayer dielectric applications

    Science.gov (United States)

    Sundaram, Nandini Ganapathy

    precursors. Pre and post-anneal structural properties of the deposited thin film were studied using laser excitation of 633 nm in a Jobin Yvon Labram high-resolution micro-Raman spectrometer. The film was further characterized using AFM, FTIR, XRD, goniometry and electrical testing. Average film roughness as measured by AFM was less than 1 nm, the k-value was 2.5, and the contact angle with water was 42°. Lastly, layered dielectric films comprising of Diamond like Carbon (DLC) and Amorphous Fluorocarbon (a:C-F) were generated using three different stack configurations and subsequently evaluated. Seven unique process conditions generated promising stacks with k-values between 1.69 and 1.95. Of these, only one film exhibited very low shrinkage rates acceptable for semiconductor device processing. Annealed a:C-F films with DLC top coat are similar in bonding structure to as deposited FC films proving that DLC deposition significantly modified the bonding structure of the underlying annealed a:C-F film. Stacks comprised of a:C-F films with higher oxygen content, deposited using high FRRs exhibited both macro and microbuckling to a larger degree and extent. Film integrity was preserved by annealing the Fluorocarbon component or by providing a DLC base coat.

  11. Structural, optical, dielectric and magnetic studies of gadolinium-added Mn-Cu nanoferrites

    Science.gov (United States)

    Kanna, R. Rajesh; Lenin, N.; Sakthipandi, K.; Kumar, A. Senthil

    2018-05-01

    Spinel ferrite with the general formula Mn1-xCuxFe1.85Gd0.15O4 (x = 0.2, 0.4, 0.6 and 0.8) was synthesized using the standard sonochemical method. The structure, optical, morphology, dielectric and magnetic properties of the prepared Mn1-xCuxFe1.85Gd0.15O4 nanoferrites were exhaustively investigated using various characterization techniques. The phase purity, secondary phase and crystallite parameters were studied from X-ray diffraction patterns. Fourier transform infrared spectra showed two absorption bands of transition metal oxides in the frequency range from 400 to 650 cm-1, which are related to asymmetric stretching modes of the spinel ferrites (AB2O4). Raman spectra have five active modes illustrating the vibration of O2- ions at both tetrahedral (A) site and octahedral (B) site ions. The wide and narrow scan spectrum from X-ray photoelectron spectroscopy results confirmed the presence of Mn, Cu, Gd, Fe, C and O elements in the composition. The oxidation state and core level of the photo electron peaks of Mn 2p, Cu 2p, Gd 3d, Fe 2p and O 1s were analyzed. The influence of the Cu2+ concentration in Mn1-xCuxFe1.85Gd0.15O4 on the morphology, varying from nanorods, nanoflakes to spherical, was explored on the basis of scanning electron microscopy images. Ultraviolet diffuse reflectance spectroscopy studies indicated that the optical bandgap (5.12-5.32 eV) of the nanoferrites showed an insulating behavior. The dielectric constant, loss tangent and complex dielectric constant values decreased with an increase in frequency with the addition of Gd3+ content. A vibrating sample magnetometer showed that the prepared nanoferrites had a soft ferromagnetic nature. The magnetic parameter changed markedly with an increase in the Cu content in Mn1-xCuxFe1.85Gd0.15O4 nanoferrites. The optical, dielectric and magnetic properties were considerably enhanced with the addition of Gd3+ ions in the spinel nanoferrites.

  12. Studies of low current back-discharge in point-plane geometry with dielectric layer

    International Nuclear Information System (INIS)

    Jaworek, A.; Rajch, E.; Czech, T.; Lackowski, M

    2005-01-01

    The paper presents results of spectroscopic investigations of back-discharge generated in the point-plane electrode geometry in air at atmospheric pressure, with the plane covered with fly ash layer. Four forms of the discharges were studied: onset streamers, glow, breakdown streamers and low-current back-arc discharge. Both polarities of the active discharge electrode, positive and negative, were tested. The back discharge is a type of DC electrical discharge, which take place when the passive plane electrode is covered with a dielectric layer. The layer can be made of solid material or a packed bed of dust or powder of low conductivity. The charge produced due to ionisation processes in the vicinity of the active point electrode is accumulated on the dielectric surface, and generates high electric field through this layer. When critical electric field through the layer is attained an electrical breakdown of the layer take place. The point of breakdown becomes a new source of ions of polarity opposite to those generated by the active electrode. The dielectric layer on the passive electrode causes that gaseous discharges such as breakdown streamers or arc start at lower voltages than they could in the case of normal corona discharge. The visual forms of the discharge were recorded and correlated with the current-voltage characteristics and optical emission spectra. Emission spectra of the discharge were measured in the light wavelength range of 200 to 600 nm to get information about excitation and ionisation processes. The light spectra were analysed by monochromator SPM-2 Karl-Zeiss-Jena with diffraction grating of 1302 grooves/mm and photomultiplier R375 (Hamamatsu) and signal preamplifier unit C7319 (Hamamatsu). The spectral analysis showed that the nitrogen molecular bands were dominant, but the emission of negative ions from the dielectric layer material were also detected. The most noticeable light emission in the range from 280 to 490 nm due to second

  13. Magnetic and dielectric studies of Fe substituted sillenite phase bismuth cobaltite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ray, J.; Biswal, A.K.; Kuila, S.; Vishwakarma, P.N., E-mail: prakashn@nitrkl.ac.in

    2015-06-05

    Highlights: • The samples prepared under ambient conditions, crystalizes in sillenite phase. • Ferrimagnetic ordering in BCO occurs at 30 K, with no bifurcation in ZFC and FC. • BCFO shows large bifurcation in ZFC and FC data as the sample is cooled down. • Dielectric loss improves by one order when 50% of cobalt is replaced with Fe. • Well distinguished extrinsic and intrinsic contributions in BCO and BCFO are seen. - Abstract: (Bi{sub 13}Co{sub 12})CoO{sub 40} (BCO) and (Bi{sub 13}Co{sub 5.5}Fe{sub 6.5})CoO{sub 40} (BCFO) nanoparticles are prepared by sol–gel auto combustion method. The X-ray diffraction study (XRD) reveals cubic crystal structure with space group I23. Surface scanning via atomic force microscopy shows the particle size decreases from 100 nm to 75 nm on partially substituting Fe at Co site. At room temperature, BCO is paramagnetic and shows signature of magnetic ordering at 30 K, which seems to be competing paramagnetic and antiferromagnetic behavior. No sign of magnetic disorder is seen, though indication of magnetic frustration is seen. Interestingly, the Fe substituted BCFO shows large magnetic disorder (even at room temperature) with strengthening ferromagnetic ordering as the temperature is lowered. The low temperature dielectric and magnetodielectric measurement shows dominance of extrinsic contributions, through-out the temperature range for BCO. For BCFO, the behavior may be divided under two regions viz., intrinsic (<260 K) and extrinsic (>260 K). Relaxation in both the regions is described by Arrhenius behavior with activation energies 0.25 eV and 0.04 eV in the extrinsic and intrinsic regions respectively. Most interestingly, the dielectric loss decreases by one order for Fe substituted sample. The Haverliak–Negami equation is found to better describe the observed relaxation data.

  14. Magnetic and dielectric studies of Fe substituted sillenite phase bismuth cobaltite nanoparticles

    International Nuclear Information System (INIS)

    Ray, J.; Biswal, A.K.; Kuila, S.; Vishwakarma, P.N.

    2015-01-01

    Highlights: • The samples prepared under ambient conditions, crystalizes in sillenite phase. • Ferrimagnetic ordering in BCO occurs at 30 K, with no bifurcation in ZFC and FC. • BCFO shows large bifurcation in ZFC and FC data as the sample is cooled down. • Dielectric loss improves by one order when 50% of cobalt is replaced with Fe. • Well distinguished extrinsic and intrinsic contributions in BCO and BCFO are seen. - Abstract: (Bi 13 Co 12 )CoO 40 (BCO) and (Bi 13 Co 5.5 Fe 6.5 )CoO 40 (BCFO) nanoparticles are prepared by sol–gel auto combustion method. The X-ray diffraction study (XRD) reveals cubic crystal structure with space group I23. Surface scanning via atomic force microscopy shows the particle size decreases from 100 nm to 75 nm on partially substituting Fe at Co site. At room temperature, BCO is paramagnetic and shows signature of magnetic ordering at 30 K, which seems to be competing paramagnetic and antiferromagnetic behavior. No sign of magnetic disorder is seen, though indication of magnetic frustration is seen. Interestingly, the Fe substituted BCFO shows large magnetic disorder (even at room temperature) with strengthening ferromagnetic ordering as the temperature is lowered. The low temperature dielectric and magnetodielectric measurement shows dominance of extrinsic contributions, through-out the temperature range for BCO. For BCFO, the behavior may be divided under two regions viz., intrinsic (<260 K) and extrinsic (>260 K). Relaxation in both the regions is described by Arrhenius behavior with activation energies 0.25 eV and 0.04 eV in the extrinsic and intrinsic regions respectively. Most interestingly, the dielectric loss decreases by one order for Fe substituted sample. The Haverliak–Negami equation is found to better describe the observed relaxation data

  15. Construction of electron accelerator for studying secondary emission in dielectric materials

    International Nuclear Information System (INIS)

    Hessel, R.

    1990-01-01

    An acelerator for the generation of low energy electrons (in the 0.4 to 20 keV range) was constructed. The accelerator is equipped with some devices especially designed for the investigation of the electrical properties of electron-irradiated dielectrics. In this work we have employed it for the study of the secondary electron emission of irradiated polymers. Reference is made to a method proposed by H. von Seggern (IEEE Trans. Nucl. Sci. NS-32, p.1503 (1985)] which was intended for the determination of the electron emission yield especially between the two cross-over points in a single run, here called the dynamical method. We have been able to prove that, contrary to expectation, this method does not give correct results over the entire emission curve. Rather it gives yield values which are too low by 25% in the region where the emission exhibits a maximum, due to the interaction between the electron emission process and the positive surface charge of the dielectric. However the method needs not to be dismissed entirely. As it is, it can be used advantageously for the precise determination of the energy of the second cross-over point. In addition, with the same set up, the method could be improved by replacing the continuous irradiation of the sample by a pulsed irradiation, leading to results essentially the same as those shown in the literature. Finally analysing the process of interaction between the positive charge of the dielectric and the mechanism of electron emission in several situations, we were able: I) to determine the maximum value and the average value of the escape depth of the emitted electrons; II) for a sample with a net positive charge, to show that the positive charge resides very near the surface of incidence; III) for a sample with a net negative charge, to show that the positive charge also resides near the surface while the (prevalent) negative charge resides in the bulk of the material. (author)

  16. In vitro Dissolution Studies on Solid Dispersions of Mefenamic Acid.

    Science.gov (United States)

    Rao, K R S Sambasiva; Nagabhushanam, M V; Chowdary, K P R

    2011-03-01

    Solid dispersions of mefanamic acid with a water-soluble polymer polyvinyl pyrrolidine and a super disintegrant, primojel were prepared by common solvent and solvent evaporation methods employing methanol as the solvent. The dissolution rate and dissolution efficiency of the prepared solid dispersions were evaluated in comparison to the corresponding pure drug. Solid dispersions of mefenamic acid showed a marked enhancement in dissolution rate and dissolution efficiency. At 1:4 ratio of mefenamic acid-primojel a 2.61 fold increase in the dissolution rate of mefenamic acid was observed with solid dispersion. The solid dispersions in combined carriers gave much higher rates of dissolution than super disintegrants alone. Mefanamic acid-primojel-polyvinyl pyrrolidine (1:3.2:0.8) solid dispersion gave a 4.11 fold increase in the dissolution rate of mefenamic acid. Super disintegrants alone or in combination with polyvinyl pyrrolidine could be used to enhance the dissolution rate of mefenamic acid.

  17. THE STUDYING OF COLLOIDAL-CHEMICAL PROPERTIES OF CLAY MINERALS DISPERSIONS

    Directory of Open Access Journals (Sweden)

    A. F. Tymchuk

    2015-02-01

    Full Text Available The element structure is studied, the microscopic analysis of fine-dispersed min­eral systems (ground sediments of a mouth of the river Danube is carried out. The sedimentation process of clay minerals dispersions in solutions of surfactants and macromolecular substances is studied. Concentration intervals of stabilization of investigating dispersions were defined.

  18. Study of memory effects in polymer dispersed liquid crystal films

    International Nuclear Information System (INIS)

    Han, Jinwoo

    2006-01-01

    In this work, we have studied the memory effects in polymer dispersed liquid crystal films. We found that optical responses, such as the memory effects, of the films depended strongly on the morphology. For example, memory effects were observed for films with polymer ball morphologies; however, only weak hysteresis effects were observed for films with droplet morphologies. In particular, a stronger memory effect was observed for films with more complicated polymer ball structures. Coincidentally, T TE , the temperature at which the memory state is thermally erased, was generally higher for the films exhibiting a stronger memory effect. In addition, studies of the temporal evolution of the films show that the memory effects become stronger after films have been kept on the shelf for a period of time. This change is likely to be associated with a modification of surface anchoring properties at the LC-polymer interface.

  19. Theoretical study of liquid droplet dispersion in a venturi scrubber.

    Science.gov (United States)

    Fathikalajahi, J; Talaie, M R; Taheri, M

    1995-03-01

    The droplet concentration distribution in an atomizing scrubber was calculated based on droplet eddy diffusion by a three-dimensional dispersion model. This model is also capable of predicting the liquid flowing on the wall. The theoretical distribution of droplet concentration agrees well with experimental data given by Viswanathan et al. for droplet concentration distribution in a venturi-type scrubber. The results obtained by the model show a non-uniform distribution of drops over the cross section of the scrubber, as noted by the experimental data. While the maximum of droplet concentration distribution may depend on many operating parameters of the scrubber, the results of this study show that the highest uniformity of drop distribution will be reached when penetration length is approximately equal to one-fourth of the depth of the scrubber. The results of this study can be applied to evaluate the removal efficiency of a venturi scrubber.

  20. Multi-Dielectric Brownian Dynamics and Design-Space-Exploration Studies of Permeation in Ion Channels.

    Science.gov (United States)

    Siksik, May; Krishnamurthy, Vikram

    2017-09-01

    This paper proposes a multi-dielectric Brownian dynamics simulation framework for design-space-exploration (DSE) studies of ion-channel permeation. The goal of such DSE studies is to estimate the channel modeling-parameters that minimize the mean-squared error between the simulated and expected "permeation characteristics." To address this computational challenge, we use a methodology based on statistical inference that utilizes the knowledge of channel structure to prune the design space. We demonstrate the proposed framework and DSE methodology using a case study based on the KcsA ion channel, in which the design space is successfully reduced from a 6-D space to a 2-D space. Our results show that the channel dielectric map computed using the framework matches with that computed directly using molecular dynamics with an error of 7%. Finally, the scalability and resolution of the model used are explored, and it is shown that the memory requirements needed for DSE remain constant as the number of parameters (degree of heterogeneity) increases.

  1. Growth, spectral, dielectric and antimicrobial studies on 4-piperidinium carboxylamide picrate crystals

    Science.gov (United States)

    Dhanabal, T.; Tharanitharan, V.; Amirthaganesan, G.; Dhandapani, M.

    2014-07-01

    Single crystal of 4-piperidinium carboxylamide picrate was grown by slow evaporation solution growth technique at ambient temperature. The average dimensions of grown crystal were 0.7 × 0.3 × 0.2 cm3. The solubility of the compound was analyzed using methanol and acetone. Optical property of the compound was ascertained by UV-visible absorption spectral study. The sharp and well defined Bragg peaks observed in the powder X-ray diffraction pattern confirm its crystallinity. The different kinds of protons and carbons in the compound were confirmed by 1H and 13C NMR spectral analyses. The presence of various functional groups in the compound was assigned through polarized Raman spectral study. The mechanical property of the crystal was measured by Vicker's microhardness test and the compound was found to be soft material. The dielectric constant and dielectric loss of the crystal decrease with increase in frequency. The antibacterial and antifungal activities of the crystal were studied by disc diffusion method and found that the compound shows good inhibition efficiency against various bacteria and fungi species.

  2. Studies on nitric oxide removal in simulated gas compositions under plasma-dielectric/catalytic discharges

    International Nuclear Information System (INIS)

    Rajanikanth, B.S.; Rout, Satyabrata

    2001-01-01

    Application of pulsed electrical discharges for gas cleaning is gaining prominence, mainly from the energy consideration point of view. This present paper presents recent work on applying the electrical discharge plasma technology for treating gaseous pollutants, in general, and nitric oxide, in particular, as this is one of the major contributors to air pollution. The present work focuses attention on pulsed electrical discharge technique for nitric oxide removal from simulated gas compositions and study of effect of packed dielectric pellets, with and without a coating of catalyst, on the removal process. Experiments were conducted in a cylindrical corona reactor energized by repetitive high voltage pulses. The effects of various parameters, viz. pulse voltage magnitude, pulse frequency, initial nitric oxide concentration and gas mixture composition on nitric oxide removal efficiency, are discussed. When the reactors were filled with different dielectric pellets like, barium titanate, alumina, and alumina coated with palladium catalyst, the improvement in nitric oxide removal efficiency is studied and discussed. The power dissipated in the reactor and the energy consumed per nitric oxide molecule removed was calculated. Further results and comparative study of various cases are presented in the paper

  3. Study of the aging processes in polyurethane adhesives using thermal treatment and differential calorimetric, dielectric, and mechanical techniques ; 1, identifying the aging processes ; 2, quantifying the aging effect

    CERN Document Server

    Althouse, L P

    1979-01-01

    Study of the aging processes in polyurethane adhesives using thermal treatment and differential calorimetric, dielectric, and mechanical techniques ; 1, identifying the aging processes ; 2, quantifying the aging effect

  4. Comparative study on nitridation and oxidation plasma interface treatment for AlGaN/GaN MIS-HEMTs with AlN gate dielectric

    Science.gov (United States)

    Zhu, Jie-Jie; Ma, Xiao-Hua; Hou, Bin; Chen, Li-Xiang; Zhu, Qing; Hao, Yue

    2017-02-01

    This paper demonstrated the comparative study on interface engineering of AlN/AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) by using plasma interface pre-treatment in various ambient gases. The 15 nm AlN gate dielectric grown by plasma-enhanced atomic layer deposition significantly suppressed the gate leakage current by about two orders of magnitude and increased the peak field-effect mobility by more than 50%. NH3/N2 nitridation plasma treatment (NPT) was used to remove the 3 nm poor-quality interfacial oxide layer and N2O/N2 oxidation plasma treatment (OPT) to improve the quality of interfacial layer, both resulting in improved dielectric/barrier interface quality, positive threshold voltage (V th) shift larger than 0.9 V, and negligible dispersion. In comparison, however, NPT led to further decrease in interface charges by 3.38 × 1012 cm-2 and an extra positive V th shift of 1.3 V. Analysis with fat field-effect transistors showed that NPT resulted in better sub-threshold characteristics and transconductance linearity for MIS-HEMTs compared with OPT. The comparative study suggested that direct removing the poor interfacial oxide layer by nitridation plasma was superior to improving the quality of interfacial layer by oxidation plasma for the interface engineering of GaN-based MIS-HEMTs.

  5. Molecular dynamics of amorphous pharmaceutical fenofibrate studied by broadband dielectric spectroscopy

    Directory of Open Access Journals (Sweden)

    U. Sailaja

    2016-06-01

    Full Text Available Fenofibrate is mainly used to reduce cholesterol level in patients at risk of cardiovascular disease. Thermal transition study with the help of differential scanning calorimetry (DSC shows that the aforesaid active pharmaceutical ingredient (API is a good glass former. Based on our DSC study, the molecular dynamics of this API has been carried out by broadband dielectric spectroscopy (BDS covering wide temperature and frequency ranges. Dielectric measurements of amorphous fenofibrate were performed after its vitrification by fast cooling from a few degrees above the melting point (Tm=354.11 K to deep glassy state. The sample does not show any crystallization tendency during cooling and reaches the glassy state. The temperature dependence of the structural relaxation has been fitted by single Vogel–Fulcher–Tamman (VFT equation. From VFT fit, glass transition temperature (Tg was estimated as 250.56 K and fragility (m was determined as 94.02. This drug is classified as a fragile glass former. Deviations of experimental data from Kohlrausch–Williams–Watts (KWW fits on high-frequency flank of α-peak indicate the presence of an excess wing in fenofibrate. Based on Ngai׳s coupling model, we identified the excess wing as true Johari–Goldstein (JG process. Below the glass transition temperature one can clearly see a secondary relaxation (γ with an activation energy of 32.67 kJ/mol.

  6. Trapping-charging ability and electrical properties study of amorphous insulator by dielectric spectroscopy

    International Nuclear Information System (INIS)

    Mekni, Omar; Arifa, Hakim; Askri, Besma; Yangui, Béchir; Raouadi, Khaled; Damamme, Gilles

    2014-01-01

    Usually, the trapping phenomenon in insulating materials is studied by injecting charges using a Scanning Electron Microscope. In this work, we use the dielectric spectroscopy technique for showing a correlation between the dielectric properties and the trapping-charging ability of insulating materials. The evolution of the complex permittivity (real and imaginary parts) as a function of frequency and temperature reveals different types of relaxation according to the trapping ability of the material. We found that the space charge relaxation at low frequencies affects the real part of the complex permittivity ε ′ and the dissipation factor Tan(δ). We prove that the evolution of the imaginary part of the complex permittivity against temperature ε ″ =f(T) reflects the phenomenon of charge trapping and detrapping as well as trapped charge evolution Q p (T). We also use the electric modulus formalism to better identify the space charge relaxation. The investigation of trapping or conductive nature of insulating materials was mainly made by studying the activation energy and conductivity. The conduction and trapping parameters are determined using the Correlated Barrier Hopping (CBH) model in order to confirm the relation between electrical properties and charge trapping ability.

  7. Direct Effect of Dielectric Surface Energy on Carrier Transport in Organic Field-Effect Transistors.

    Science.gov (United States)

    Zhou, Shujun; Tang, Qingxin; Tian, Hongkun; Zhao, Xiaoli; Tong, Yanhong; Barlow, Stephen; Marder, Seth R; Liu, Yichun

    2018-05-09

    The understanding of the characteristics of gate dielectric that leads to optimized carrier transport remains controversial, and the conventional studies applied organic semiconductor thin films, which introduces the effect of dielectric on the growth of the deposited semiconductor thin films and hence only can explore the indirect effects. Here, we introduce pregrown organic single crystals to eliminate the indirect effect (semiconductor growth) in the conventional studies and to undertake an investigation of the direct effect of dielectric on carrier transport. It is shown that the matching of the polar and dispersive components of surface energy between semiconductor and dielectric is favorable for higher mobility. This new empirical finding may show the direct relationship between dielectric and carrier transport for the optimized mobility of organic field-effect transistors and hence show a promising potential for the development of next-generation high-performance organic electronic devices.

  8. A Molecular Dynamics Study of Crosslinked Phthalonitrile Polymers: The Effect of Crosslink Density on Thermomechanical and Dielectric Properties

    Directory of Open Access Journals (Sweden)

    Janel Chua

    2018-01-01

    Full Text Available In this work, molecular dynamics (MD and molecular mechanics (MM simulations are used to study well-equilibrated models of 4,4′-bis(3,4-dicyanophenoxybiphenyl (BPh–1,3-bis(3-aminophenoxybenzene (m-APB phthalonitrile (PN system with a range of crosslink densities. A cross-linking technique is introduced to build a series of systems with different crosslink densities; several key properties of this material, including thermal expansion, mechanical properties and dielectric properties are studied and compared with experimental results. It is found that the coefficient of linear thermal expansion predicted by the model is in good agreement with experimental results and indicative of the good thermal stability of the PN polymeric system. The simulation also shows that this polymer has excellent mechanical property, whose strength increases with increasing crosslink density. Lastly and most importantly, the calculated dielectric constant—which shows that this polymer is an excellent insulating material—indicates that there is an inverse relation between cross-linking density and dielectric constant. The trend gave rise to an empirical quadratic function which can be used to predict the limits of attainable dielectric constant for highly crosslinked polymer systems. The current computational work provides strong evidence that this polymer is a promising material for aerospace applications and offers guidance for experimental studies of the effect of cross-linking density on the thermal, mechanical and dielectric properties of the material.

  9. Laboratory Study of Dispersion of Buoyant Surface Plumes

    DEFF Research Database (Denmark)

    Petersen, Ole; Larsen, Torben

    1990-01-01

    -differences. Other methods as infra-red sensing are used for visualizing purpose. The results are used to calibrate an integral model of the dispersion. Conclusions are that the dispersion of a buoyant surface plume can be treated the superposition of a buoyancy induced stretching and turbulent diffusion, reduced...

  10. Spontaneous dispersion of PdO onto acid sites of zeolites studied by in situ DXAFS

    CERN Document Server

    Okumura, K; Niwa, M; Yokota, S; Kato, K; Tanida, H; Uruga, T

    2003-01-01

    The generation of highly dispersed PdO over zeolite supports was studied using in situ energy-dispersive XAFS (DXAFS) technique. From the comparison with the Na-ZSM-5, it was found that the oxidation as well as the spontaneous dispersion of Pd was promoted through the interaction between PdO and acid sites of H-form zeolites. (author)

  11. A Numerical Study of the Sour Gas Reforming in a Dielectric Barrier Discharge Reactor

    Directory of Open Access Journals (Sweden)

    Sajedeh Shahsavari

    2016-10-01

    Full Text Available In this paper, using a one-dimensional simulation model, the reforming process of sour gas, i.e. CH4, CO2, and H2S, to the various charged particles and syngas in a dielectric barrier discharge (DBD reactor is studied. An electric field is applied across the reactor radius, and thus a non-thermal plasma discharge is formed within the reactor. Based on the space-time coupled finite element method, the governing equations are solved, and the temporal and spatial profiles of different formed charged species from sour gas inside the plasma reactor are verified. It is observed that the electric field increases radially towards the cathode electrode. Moreover, the electron density growth rate at the radial positions closer to the cathode surface is smaller than the one in the anode electrode region. Furthermore, as time progresses, the positive ions density near the anode electrode is higher. In addition, the produced syngas density is mainly concentrated in the proximity of anode dielectric electrode.

  12. Study on the changes in blood plasma electroconductivity and dielectric constant in irradiated mammals

    International Nuclear Information System (INIS)

    Paskalev, Z.; Bancheva, E.

    1975-01-01

    Blood plasma electroconductivity and dielectric constant were measured in C57BL mice exposed to an uncontaminated gamma or neutron field or a mixed gamma-neutron field at a total dose of 5, 10, 15, 20, or 25 rad. Measurements were also made with blood plasma from Wistar rats given 200, 400, or 600 R X-rays. The results obtained revealed a characteristic pattern of radiation-induced changes in electroconductivity and dielectric constant, these end-points being indicative, respectively, or shifts in saline concentrations and in conformation of protein fractions of blood plasma. Analysis of the data showed that within a few days after exposure there were changes occurring in cellular and tissue water-salt metabolism, followed by enhancement or recovery to norm, depending on the dose. A possibility is thus rendered to use the blood plasma parameters studied as a test for detecting early shifts in cellular water-salt metabolism and in conformation of protein fractions at a time when no characteristic changes are yet to be observed in amounts of individual types of protein fractions from blood plasma of irradiated organisms. (author)

  13. Experimental study of the complex resistivity and dielectric constant of chrome-contaminated soil

    Science.gov (United States)

    Liu, Haorui; Yang, Heli; Yi, Fengyan

    2016-08-01

    Heavy metals such as arsenic and chromium often contaminate soils near industrialized areas. Soil samples, made with different water content and chromate pollutant concentrations, are often needed to test soil quality. Because complex resistivity and complex dielectric characteristics of these samples need to be measured, the relationship between these measurement results and chromium concentration as well as water content was studied. Based on soil sample observations, the amplitude of the sample complex resistivity decreased with an increase of contamination concentration and water content. The phase of complex resistivity takes on a tendency of initially decrease, and then increase with the increasing of contamination concentration and water content. For a soil sample with the same resistivity, the higher the amplitude of complex resistivity, the lower the water content and the higher the contamination concentration. The real and imaginary parts of the complex dielectric constant increase with an increase in contamination concentration and water content. Note that resistivity and complex resistivity methods are necessary to adequately evaluate pollution at various sites.

  14. Thermal and Dielectric Behavior Studies of Poly(Arylene Ether Sulfones with Sulfonated and Phosphonated Pendants

    Directory of Open Access Journals (Sweden)

    Shimoga D. Ganesh

    2016-01-01

    Full Text Available The present paper discusses the aspects of the synthesizing valeric acid based poly(ether sulfones with active carboxylic acid pendants (VALPSU from solution polymerization technique via nucleophilic displacement polycondensation reaction among 4,4′-dichlorodiphenyl sulfone (DCDPS and 4,4′-bis(4-hydroxyphenyl valeric acid (BHPA. The conditions necessary to synthesize and purify the polymer were investigated in some detail. The synthesized poly(ether sulfones comprise sulfone and ether linkages in addition to reactive carboxylic acid functionality; these active carboxylic acid functional groups were exploited to hold the phenyl sulphonic acid and phenyl phosphonic acid pendants. The phenyl sulphonic acid pendants in VALPSU were easily constructed by altering active carboxylic acid moieties by sulfanilic acid using N,N′-dicyclohexylcarbodiimide (DCC mediated mild synthetic route, whereas the latter one was built in two steps. Initially, polyphosphoric acid condensation with VALPSU by 4-bromoaniline and next straightforward palladium catalyzed synthetic route, in both of which acidic pendants are clenched by polymer backbone via amide linkage. Without impairing the primary polymeric backbone modified polymers were prepared by varying the stoichiometric ratios of respective combinations. All the polymers were physicochemically characterized and pressed into tablets; electrical contacts were established to study the dielectric properties. Finally, the influence of the acidic pendants on the dielectric properties was examined.

  15. A systematic study of the isothermal crystallization of the mono-alcohol n-butanol monitored by dielectric spectroscopy

    DEFF Research Database (Denmark)

    Jensen, Mikkel Hartmann; Hecksher, Tina; Niss, Kristine

    2015-01-01

    Isothermal crystallization of the mono-hydroxyl alcohol n-butanol was studied with dielectric spectroscopy in real time. The crystallization was carried out using two different sample cells at 15 temperatures between 120 K and 134 K. Crystallization is characterized by a decrease of the dielectric...... intensity. In addition, a shift in relaxation times to shorter times was observed during the crystallization process for all studied temperatures. The two different sample environments induced quite different crystallization behaviors, consistent and reproducible over all studied temperatures...... that a microscopic interpretation of crystallization measurements requires multiple probes, sample cells, and protocols....

  16. Ferroelectric BaTiO3 and LiNbO3 Nanoparticles Dispersed in Ferroelectric Liquid Crystal Mixtures: Electrooptic and Dielectric (Postprint)

    Science.gov (United States)

    2016-10-14

    strength for non- doped LF4 and LiNbO3/LF4 nanocolloids at temperature 30C. 146 R. K . SHUKLA ET AL. 6 Distribution A. Approved for public release (PA...AFRL-RX-WP-JA-2017-0210 FERROELECTRIC BaTiO3 AND LiNbO3 NANOPARTICLES DISPERSED IN FERROELECTRIC LIQUID CRYSTAL MIXTURES: ELECTROOPTIC...COMMAND UNITED STATES AIR FORCE Ferroelectric BaTiO3 and LiNbO3 nanoparticles dispersed in ferroelectric liquid crystal mixtures: Electrooptic and

  17. Synthesis and Characterization of High-Dielectric-Constant Nanographite-Polyurethane Composite

    Science.gov (United States)

    Mishra, Praveen; Bhat, Badekai Ramachandra; Bhattacharya, B.; Mehra, R. M.

    2018-05-01

    In the face of ever-growing demand for capacitors and energy storage devices, development of high-dielectric-constant materials is of paramount importance. Among various dielectric materials available, polymer dielectrics are preferred for their good processability. We report herein synthesis and characterization of nanographite-polyurethane composite with high dielectric constant. Nanographite showed good dispersibility in the polyurethane matrix. The thermosetting nature of polyurethane gives the composite the ability to withstand higher temperature without melting. The resultant composite was studied for its dielectric constant (ɛ) as a function of frequency. The composite exhibited logarithmic variation of ɛ from 3000 at 100 Hz to 225 at 60 kHz. The material also exhibited stable dissipation factor (tan δ) across the applied frequencies, suggesting its ability to resist current leakage.

  18. Photoacoustic and dielectric spectroscopic studies of 4-dimethylamino-n-methyl-4-stilbazolium tosylate single crystal: An efficient terahertz emitter

    Science.gov (United States)

    Manivannan, M.; Martin Britto Dhas, S. A.; Jose, M.

    2016-12-01

    Bulk terahertz emitting single crystal of 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) was synthesized by condensation method and grown by slow solvent evaporation technique from methanol. The structure and cell parameters of the grown crystals were derived from single crystal and powder X-ray diffraction analyses and the optical properties of the crystal were analyzed by UV-Vis Spectrophotometer. The presence of functional groups was identified by FTIR and FT-Raman spectroscopic studies. We demonstrated that in DAST crystal, the thermal transport properties such as thermal conductivity, thermal diffusivity and thermal effusivity are better than several well recognized standard materials using photoacoustic spectrophotometer. The dielectric measurement was made as a function of frequency (1 Hz-35 MHz) at different temperatures (30-200 °C). The dielectric constant and dielectric loss were found to be strongly dependent on temperature and frequency of the applied electric field. The semicircle in the cole-cole plot showed the presence of dielectric relaxation in the crystal with its diameter representing the resistance of the crystal. The resistivity and ac conductivity were calculated from the measured dielectric data.

  19. Silver Nanowire/MnO2 Nanowire Hybrid Polymer Nanocomposites: Materials with High Dielectric Permittivity and Low Dielectric Loss.

    Science.gov (United States)

    Zeraati, Ali Shayesteh; Arjmand, Mohammad; Sundararaj, Uttandaraman

    2017-04-26

    This study reports the fabrication of hybrid nanocomposites based on silver nanowire/manganese dioxide nanowire/poly(methyl methacrylate) (AgNW/MnO 2 NW/PMMA), using a solution casting technique, with outstanding dielectric permittivity and low dielectric loss. AgNW was synthesized using the hard-template technique, and MnO 2 NW was synthesized employing a hydrothermal method. The prepared AgNW:MnO 2 NW (2.0:1.0 vol %) hybrid nanocomposite showed a high dielectric permittivity (64 at 8.2 GHz) and low dielectric loss (0.31 at 8.2 GHz), which are among the best reported values in the literature in the X-band frequency range (8.2-12.4 GHz). The superior dielectric properties of the hybrid nanocomposites were attributed to (i) dimensionality match between the nanofillers, which increased their synergy, (ii) better dispersion state of AgNW in the presence of MnO 2 NW, (iii) positioning of ferroelectric MnO 2 NW in between AgNWs, which increased the dielectric permittivity of nanodielectrics, thereby increasing dielectric permittivity of the hybrid nanocomposites, (iv) barrier role of MnO 2 NW, i.e., cutting off the contact spots of AgNWs and leading to lower dielectric loss, and (v) AgNW aligned structure, which increased the effective surface area of AgNWs, as nanoelectrodes. Comparison of the dielectric properties of the developed hybrid nanocomposites with the literature highlights their great potential for flexible capacitors.

  20. Dielectric properties of gadolinium molybdate in low- and infralow frequency electric fields

    International Nuclear Information System (INIS)

    Galiyarova, N.M.; Gorin, S.V.; Dontsova, L.I.; Shil'nikov, A.V.; Shuvalov, L.A.; AN SSSR, Moscow

    1992-01-01

    Temperature dependences of complex dielectric permittivity of gadolinium molybdate (GMO) in low- (LF) and infralow-frequency (ILF) electric fields with 0.1 V·cm -1 amplitude within 0.25-10 4 Hz frequency range are studied. Substantial effect of the crystal prehistory on LF and ILF dielectric properties and domain structure state is revealed. An anomalous reduction of complex dielectric permittivity accompanied by the occurrence of the Debye LF-dispersion of permittivity is detected under the sample cooling from a nonpolar phase

  1. Study on evaluation methods for Rayleigh wave dispersion characteristic

    Science.gov (United States)

    Shi, L.; Tao, X.; Kayen, R.; Shi, H.; Yan, S.

    2005-01-01

    The evaluation of Rayleigh wave dispersion characteristic is the key step for detecting S-wave velocity structure. By comparing the dispersion curves directly with the spectra analysis of surface waves (SASW) method, rather than comparing the S-wave velocity structure, the validity and precision of microtremor-array method (MAM) can be evaluated more objectively. The results from the China - US joint surface wave investigation in 26 sites in Tangshan, China, show that the MAM has the same precision with SASW method in 83% of the 26 sites. The MAM is valid for Rayleigh wave dispersion characteristic testing and has great application potentiality for site S-wave velocity structure detection.

  2. Theoretical study of the electromechanical efficiency of a loaded tubular dielectric elastomer actuator

    DEFF Research Database (Denmark)

    Rechenbach, Björn; Willatzen, Morten; Lassen, Benny

    2016-01-01

    The electromechanical efficiency of a loaded tubular dielectric elastomer actuator (DEA) is investigated theoretically. In previous studies, the external system, on which the DEA performs mechanical work, is implemented implicitly by prescribing the stroke of the DEA in a closed operation cycle....... Here, a more generic approach, modelling the external system by a frequency-dependent mechanical impedance which exerts a certain force on the DEA depending on its deformation, is chosen. It admits studying the dependence of the electromechanical efficiency of the DEA on the external system. A closed...... operation cycle is realized by exciting the DEA electrically by a sinusoidal voltage around a bias voltage. A detailed parametric study shows that the electromechanical efficiency is highly dependent on the frequency, amplitude, and bias of the excitation voltage and the mechanical impedance of the external...

  3. Photoluminescence intermittency of semiconductor quantum dots in dielectric environments

    Energy Technology Data Exchange (ETDEWEB)

    Isaac, A.

    2006-08-11

    The experimental studies presented in this thesis deal with the photoluminescence intermittency of semiconductor quantum dots in different dielectric environments. Detailed analysis of intermittency statistics from single capped CdSe/ZnS, uncapped CdSe and water dispersed CdSe/ZnS QDs in different matrices provide experimental evidence for the model of photoionization with a charge ejected into the surrounding matrix as the source of PL intermittency phenomenon. We propose a self-trapping model to explain the increase of dark state lifetimes with the dielectric constant of the matrix. (orig.)

  4. Thermoluminescence study of the trapped charge at an alumina surface electrode in different dielectric barrier discharge regimes

    Energy Technology Data Exchange (ETDEWEB)

    Ambrico, P F; Ambrico, M; Dilecce, G; De Benedictis, S [Consiglio Nazionale delle Ricerche, Istituto di Metodologie Inorganiche e dei Plasmi UOS Bari-c/o Dipartimento di Chimica, Universita degli Studi di Bari ' Aldo Moro' , via Orabona, 4, 70126 Bari (Italy); Colaianni, A [Dipartimento di Geologia e Geofisica, Universita degli Studi di Bari ' Aldo Moro' , via Orabona, 4, 70126 Bari (Italy); Schiavulli, L, E-mail: paolofrancesco.ambrico@cnr.i [Dipartimento Interateneo di Fisica, Universita degli Studi di Bari ' Aldo Moro' , via Orabona, 4, 70126 Bari (Italy)

    2010-08-18

    In this study, the charge trapping effect in alumina dielectric surfaces has been deeply investigated by means of a dedicated dielectric barrier discharge apparatus in different discharge regimes and gas mixtures. This work further validates our previous findings in the case of air discharges in a filamentary regime. Long lasting charge trapping has been evidenced by ex situ thermoluminescence characterizations of alumina dielectric barrier plates exposed to a plasma. The density of trapped surface charges was found to be higher in the glow discharge with respect to pseudo-glow and filamentary regimes, and for all regimes the minimum trap activation temperature was 390 K and the trap energy was less than or around 1 eV. This implies that in the case of glow discharges a higher reservoir of electrons is present. Also, the effect was found to persist for several days after running the discharge.

  5. Thermoluminescence study of the trapped charge at an alumina surface electrode in different dielectric barrier discharge regimes

    International Nuclear Information System (INIS)

    Ambrico, P F; Ambrico, M; Dilecce, G; De Benedictis, S; Colaianni, A; Schiavulli, L

    2010-01-01

    In this study, the charge trapping effect in alumina dielectric surfaces has been deeply investigated by means of a dedicated dielectric barrier discharge apparatus in different discharge regimes and gas mixtures. This work further validates our previous findings in the case of air discharges in a filamentary regime. Long lasting charge trapping has been evidenced by ex situ thermoluminescence characterizations of alumina dielectric barrier plates exposed to a plasma. The density of trapped surface charges was found to be higher in the glow discharge with respect to pseudo-glow and filamentary regimes, and for all regimes the minimum trap activation temperature was 390 K and the trap energy was less than or around 1 eV. This implies that in the case of glow discharges a higher reservoir of electrons is present. Also, the effect was found to persist for several days after running the discharge.

  6. 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 ...

  7. In-vitro Study of the Dielectric Effects of X-Ray on Whole Human Blood

    International Nuclear Information System (INIS)

    Bernal-Alvarado, Jesus; Sanchez, Antonio; Gutierrez, Gilberto; Sosa, Modesto; Hernandez, Francisco; Marquez, Sergio; Sotelo, Fernando; Palomares, Pascual

    2006-01-01

    A comparative study was done to investigate the effects of the x-radiation on the electric properties of whole human blood, from healthy people. The x-ray source was set to 55 kV and 75 kV, in order to investigate power level effects on the samples. Short and long time effects were also investigated. This experiment used a Solartron spectrometer to obtain the impedance response. No differences were found when samples were studied in the order of days (from one to five days), independently of the power level. Only in the case of 75 kV, in the power of the x-ray source, were detected significant differences between the dielectric properties of the blood, exposed to radiation, and its control sample, provided that the impedance spectrum were registered immediately after the exposure (after 15 or less minutes)

  8. Dielectric Relaxation Studies of 2-Butoxyethanol with Aniline and Substituted Anilines Using Time Domain Reflectometry

    Directory of Open Access Journals (Sweden)

    P. Jeevanandham

    2014-01-01

    Full Text Available The complex dielectric spectra of 2-butoxyethanol with aniline and substituted anilines like aniline, o-chloroaniline, m-chloroaniline, o-anisidine and m-anisidine binary mixtures in the composition of different volumes of percent (0%, 25%, 50%, 75%, and 100% have been measured as a function of frequency between 10 MHz and 30 GHz at 298.15 K. The dielectric parameters like static dielectric constant ε0 and relaxation time τ have been obtained by using least square fit method. By using these parameters ε0,τ, effective Kirkwood correlation factor geff, corrective Kirkwood correlation factor gf, Bruggeman factor fB, excess dielectric constant εE, and excess inverse relaxation time 1/τE values are calculated and discussed to yield information on the dipolar alignment and molecular rotation of the binary liquid mixtures. From all the derived dielectric parameters, molecular interactions are interpreted through hydrogen bonding.

  9. Studies on the structural, optical and dielectric properties of samarium coordinated with salicylic acid single crystal

    Science.gov (United States)

    Singh, Harjinder; Slathia, Goldy; Gupta, Rashmi; Bamzai, K. K.

    2018-04-01

    Samarium coordinated with salicylic acid was successfully grown as a single crystal by low temperature solution technique using mixed solvent of methanol and water in equal ratio. Structural characterization was carried out by single crystal X-ray diffraction analysis and it crystallizes in centrosymmetric space group P121/c1. FTIR and UV-Vis-NIR spectroscopy confirmed the compound formation and help to determine the mode of binding of the ligand to the rare earth-metal ion. Dielectric constant and dielectric loss have been measured over the frequency range 100 Hz - 30MHz. The decrease in dielectric constant with increases in frequency is due to the transition from interfacial polarization to dipolar polarization. The small value of dielectric constant at higher frequency ensures that the crystal is good candidate for NLO devices. Dielectric loss represents the resistive nature of the material.

  10. DNA fingerprinting validates seed dispersal curves from observational studies in the neotropical legume parkia.

    Science.gov (United States)

    Heymann, Eckhard W; Lüttmann, Kathrin; Michalczyk, Inga M; Saboya, Pedro Pablo Pinedo; Ziegenhagen, Birgit; Bialozyt, Ronald

    2012-01-01

    Determining the distances over which seeds are dispersed is a crucial component for examining spatial patterns of seed dispersal and their consequences for plant reproductive success and population structure. However, following the fate of individual seeds after removal from the source tree till deposition at a distant place is generally extremely difficult. Here we provide a comparison of observationally and genetically determined seed dispersal distances and dispersal curves in a Neotropical animal-plant system. In a field study on the dispersal of seeds of three Parkia (Fabaceae) species by two Neotropical primate species, Saguinus fuscicollis and Saguinus mystax, in Peruvian Amazonia, we observationally determined dispersal distances. These dispersal distances were then validated through DNA fingerprinting, by matching DNA from the maternally derived seed coat to DNA from potential source trees. We found that dispersal distances are strongly right-skewed, and that distributions obtained through observational and genetic methods and fitted distributions do not differ significantly from each other. Our study showed that seed dispersal distances can be reliably estimated through observational methods when a strict criterion for inclusion of seeds is observed. Furthermore, dispersal distances produced by the two primate species indicated that these primates fulfil one of the criteria for efficient seed dispersers. Finally, our study demonstrated that DNA extraction methods so far employed for temperate plant species can be successfully used for hard-seeded tropical plants.

  11. DNA Fingerprinting Validates Seed Dispersal Curves from Observational Studies in the Neotropical Legume Parkia

    Science.gov (United States)

    Heymann, Eckhard W.; Lüttmann, Kathrin; Michalczyk, Inga M.; Saboya, Pedro Pablo Pinedo; Ziegenhagen, Birgit; Bialozyt, Ronald

    2012-01-01

    Background Determining the distances over which seeds are dispersed is a crucial component for examining spatial patterns of seed dispersal and their consequences for plant reproductive success and population structure. However, following the fate of individual seeds after removal from the source tree till deposition at a distant place is generally extremely difficult. Here we provide a comparison of observationally and genetically determined seed dispersal distances and dispersal curves in a Neotropical animal-plant system. Methodology/Principal Findings In a field study on the dispersal of seeds of three Parkia (Fabaceae) species by two Neotropical primate species, Saguinus fuscicollis and Saguinus mystax, in Peruvian Amazonia, we observationally determined dispersal distances. These dispersal distances were then validated through DNA fingerprinting, by matching DNA from the maternally derived seed coat to DNA from potential source trees. We found that dispersal distances are strongly right-skewed, and that distributions obtained through observational and genetic methods and fitted distributions do not differ significantly from each other. Conclusions/Significance Our study showed that seed dispersal distances can be reliably estimated through observational methods when a strict criterion for inclusion of seeds is observed. Furthermore, dispersal distances produced by the two primate species indicated that these primates fulfil one of the criteria for efficient seed dispersers. Finally, our study demonstrated that DNA extraction methods so far employed for temperate plant species can be successfully used for hard-seeded tropical plants. PMID:22514748

  12. Study on guided-mode resonance characteristic of multilayer dielectric grating with broadband and wide using-angle

    International Nuclear Information System (INIS)

    Jian-Peng, Wang; Yun-Xia, Jin; Jian-Yong, Ma; Jian-Da, Shao; Zheng-Xiu, Fan

    2010-01-01

    Guided-mode resonance in a diffraction band of multilayer dielectric gratings may lead to a catastrophic result in laser system, especially in the ultrashort pulse laser system, so the inhibition of guided-mode resonance is very important. In this paper the characteristics of guided-mode resonance in multilayer dielectric grating are studied with the aim of better understanding the physical process of guided-mode resonance and designing a broadband multilayer dielectric grating with no guided-mode resonance. By employing waveguide theory, all guided-wave modes appearing in multilayer dielectric grating are found, and the incident conditions, separately, corresponding to each guided-wave mode are also obtained. The electric field enhancement in multilayer dielectric grating is shown obviously. Furthermore, from the detailed analyses on the guided-mode resonance conditions, it is found that the reduction of the grating period would effectively avoid the appearing of guided-mode resonance. And the expressions for calculating maximum periods, which ensure that no guided-mode resonance occurs in the requiring broad angle or wavelength range, are first reported. The above results calculated by waveguide theory and Fourier mode method are compared with each other, and they are coincident completely. Moreover, the method that relies on waveguide theory is more helpful for understanding the guided-mode resonance excited process and analyzing how each parameter affects the characteristic of guided-mode resonance. Therefore, the effects of multilayer dielectric grating parameters, such as period, fill factor, thickness of grating layer, et al., on the guided-mode resonance characteristic are discussed in detail based on waveguide theory, and some meaningful results are obtained. (classical areas of phenomenology)

  13. Quantitative approach to relate dielectric constant studies with TSDC studies of 50 MeV Si ion irradiated kapton-H polymide

    International Nuclear Information System (INIS)

    Quamara, J.K.; Garg, Maneesha; Sridharbabu, Y.; Prabhavathi, T.

    2003-01-01

    Temperature and frequency dependent dielectric behaviour has been investigated for pristine and swift heavy ion irradiated (Si ion, 50 MeV energy) kapton-H polyimide in the temperature range of 30 to 250 deg C at frequencies 120 Hz, 1 kHz, 10 kHz and 100 kHz respectively. The dielectric relaxation behaviour of the same samples was also studied using thermally stimulated discharge current (TSDC) technique. A quantitative approach is developed using a well-known Clausius Mossotti equation to relate the TSDC findings to the dielectric constant studies. An overall increase in the dielectric constant of the irradiated samples are also in conformity to the TSDC findings. (author)

  14. Experimental study on the dispersion properties of cusptron structure

    International Nuclear Information System (INIS)

    Choe, J.Y.; Crosby, H.; Jablon, D.G.; Krall, A.D.; Namkung, W.

    1984-01-01

    One of the promising devices that generates high frequency microwaves is the cusptron, where the fast rotating electron beam interacts with the high muthal (iota>1) waveguide mode, thereby producing multiples of the cyclotron frequency (iotaω/sub c/). In order to encourage the chosen azimuthal perturbation, it is necessary to structure the wall in a magnetron-like shape. In particular, the authors consider the structure where the outer wall is radially cut out to make multiple vane-like resonators. With these interruptions, it obvious that there exist strong couplings among the muthal space harmonics, iota n in the cusptron device. The mode is characterized by the axial wave number, k, the primary azimuthal mode number iota, which indicates the phase difference between adjacent segments, and whether it is TE or TM. Recently, a rigorous numerical method has been devised to determine the cusptron structure. This method uses the orthonormal mode expansions both in the interaction space and the resonators to assure the point-by-point match of the fields. The method also finds the distribution of the harmonics iota n as well, that serves as a signature of the particular mode. In the present study, the authors experimentally investigate the dispersion characteristics of the cusptron, and compare the results with the theory

  15. Experimental study of ERT monitoring ability to measure solute dispersion.

    Science.gov (United States)

    Lekmine, Grégory; Pessel, Marc; Auradou, Harold

    2012-01-01

    This paper reports experimental measurements performed to test the ability of electrical resistivity tomography (ERT) imaging to provide quantitative information about transport parameters in porous media such as the dispersivity α, the mixing front velocity u, and the retardation factor R(f) associated with the sorption or trapping of the tracers in the pore structure. The flow experiments are performed in a homogeneous porous column placed between two vertical set of electrodes. Ionic and dyed tracers are injected from the bottom of the porous media over its full width. Under such condition, the mixing front is homogeneous in the transverse direction and shows an S-shape variation in the flow direction. The transport parameters are inferred from the variation of the concentration curves and are compared with data obtained from video analysis of the dyed tracer front. The variations of the transport parameters obtained from an inversion performed by the Gauss-Newton method applied on smoothness-constrained least-squares are studied in detail. While u and R(f) show a relatively small dependence on the inversion procedure, α is strongly dependent on the choice of the inversion parameters. Comparison with the video observations allows for the optimization of the parameters; these parameters are found to be robust with respect to changes in the flow condition and conductivity contrast. © 2011, The Author(s). Ground Water © 2011, National Ground Water Association.

  16. Positron annihilation lifetime study of oxide dispersion strengthened steels

    International Nuclear Information System (INIS)

    Krsjak, V.; Szaraz, Z.; Hähner, P.

    2012-01-01

    A comparative positron annihilation lifetime study has been performed on various commercial ferritic and ferritic/martensitic oxide dispersion strengthened (ODS) steels. Both as-extruded and recrystallized materials were investigated. In the materials with recrystallized coarse-grained microstructures, only the positron trapping at small vacancy clusters and yttria nanofeatures was observed. Materials which had not undergone recrystallization treatment clearly showed additional positron trapping which is associated with dislocations. Dislocation densities were calculated from a two-component decomposition of the positron lifetime spectra by assuming the first component to be a superposition of the bulk controlled annihilation rate and the dislocation controlled trapping rate. The second component (which translates into lifetimes of 240–260 ps) was found to be well separated in all those ODS materials. This paper presents the potentialities and limitations of the positron annihilation lifetime spectroscopy, and discusses the results of the experimental determination of the defect concentrations and sensitivity of this technique to the material degradation due to thermally induced precipitation of chromium-rich α′ phases.

  17. Microscopic theoretical study of frequency dependent dielectric constant of heavy fermion systems

    Science.gov (United States)

    Shadangi, Keshab Chandra; Rout, G. C.

    2017-05-01

    The dielectric polarization and the dielectric constant plays a vital role in the deciding the properties of the Heavy Fermion Systems. In the present communication we consider the periodic Anderson's Model which consists of conduction electron kinetic energy, localized f-electron kinetic energy and the hybridization between the conduction and localized electrons, besides the Coulomb correlation energy. We calculate dielectric polarization which involves two particle Green's functions which are calculated by using Zubarev's Green's function technique. Using the equations of motion of the fermion electron operators. Finally, the temperature and frequency dependent dielectric constant is calculated from the dielectric polarization function. The charge susceptibility and dielectric constant are computed numerically for different physical parameters like the position (Ef) of the f-electron level with respect to fermi level, the strength of the hybridization (V) between the conduction and localized f-electrons, Coulomb correlation potential temperature and optical phonon wave vector (q). The results will be discussed in a reference to the experimental observations of the dielectric constants.

  18. Infrared gas phase study on plasma-polymer interactions in high-current diffuse dielectric barrier discharge

    NARCIS (Netherlands)

    Liu, Y.; Welzel, S.; Starostin, S. A.; van de Sanden, M. C. M.; Engeln, R.; de Vries, H. W.

    2017-01-01

    A roll-to-roll high-current diffuse dielectric barrier discharge at atmospheric pressure was operated in air and Ar/N2/O2 gas mixtures. The exhaust gas from the discharge was studied using a high-resolution Fourier-transform infrared spectrometer in the range from 3000 to 750?cm-1 to unravel the

  19. Comparative calculations and validation studies with atmospheric dispersion models

    International Nuclear Information System (INIS)

    Paesler-Sauer, J.

    1986-11-01

    This report presents the results of an intercomparison of different mesoscale dispersion models and measured data of tracer experiments. The types of models taking part in the intercomparison are Gaussian-type, numerical Eulerian, and Lagrangian dispersion models. They are suited for the calculation of the atmospherical transport of radionuclides released from a nuclear installation. For the model intercomparison artificial meteorological situations were defined and corresponding arithmetical problems were formulated. For the purpose of model validation real dispersion situations of tracer experiments were used as input data for model calculations; in these cases calculated and measured time-integrated concentrations close to the ground are compared. Finally a valuation of the models concerning their efficiency in solving the problems is carried out by the aid of objective methods. (orig./HP) [de

  20. Parametric study of guided waves dispersion curves for composite plates

    Science.gov (United States)

    Predoi, Mihai Valentin; Petre, Cristian Cǎtǎlin; Kettani, Mounsif Ech Cherif El; Leduc, Damien

    2018-02-01

    Nondestructive testing of composite panels benefit from the relatively long range propagation of guided waves in sandwich structures. The guided waves are sensitive to delamination, air bubbles inclusions and cracks and can thus bring information about hidden defects in the composite panel. The preliminary data in all such inspections is represented by the dispersion curves, representing the dependency of the phase/group velocity on the frequency for the propagating modes. In fact, all modes are more or less attenuated, so it is even more important to compute the dispersion curves, which provide also the modal attenuation as function of frequency. Another important aspect is the sensitivity of the dispersion curves on each of the elastic constant of the composite, which are orthotropic in most cases. All these aspects are investigated in the present work, based on our specially developed finite element numerical model implemented in Comsol, which has several advantages over existing methods. The dispersion curves and modal displacements are computed for an example of composite plate. Comparison with literature data validates the accuracy of our results.

  1. Energy Dispersive X-Ray Fluorescence Spectrometric Study of ...

    African Journals Online (AJOL)

    MBI

    2017-06-11

    Jun 11, 2017 ... Compositional Differences in Trace Elements in Dried Moringa oleifera ... Ti, Cu, Mo, Fe, Zn, Ni, Re, Eu and Pb using Energy Dispersive X-ray fluorescence ... Africa, Southeast Asia (Valdez-Solana et al., 2015). ... vegetable in many countries, including Nigeria .... of other elements in environmental samples.

  2. Study of the determination method of the river dispersion coefficient

    International Nuclear Information System (INIS)

    Carvalho, M.A.G. de.

    1982-01-01

    An application of the method introduced by 'Fischer, H.B. - 1968 - Dispersion prediction in natural streams Journal of the Sanitary Engineering Division, ACSE, vol. 94 n 5A5. Proc. Paper 6169 pp 927-943.', for the calculation of the dispersion coefficient, based on Taylor's model is made. The aim is to develop a method which avoids the necessity of having an instantaneous impulse at the entrance section (1st section) of the system being measured. The dispersion coefficient is determined by curve fitting the experimental response in the 2nd secton and that obtained with the model by means of the non-linear least-squares method. The same method is applied with the residence time distribution function. The theoretical differences between these two function and their results are discussed. By adjusting the two model parameters in all these calculations, the dispersion coefficient and the mean velocity are determined, simultaneously. A comparison between the moment's method and Fischer's formulation is also done using the same experimental data. (E.G.) [pt

  3. Studies on dispersive stabilization of porous media flows

    Energy Technology Data Exchange (ETDEWEB)

    Daripa, Prabir, E-mail: prabir.daripa@math.tamu.edu; Gin, Craig [Department of Mathematics, Texas A& M University, College Station, Texas 77843 (United States)

    2016-08-15

    Motivated by a need to improve the performance of chemical enhanced oil recovery (EOR) processes, we investigate dispersive effects on the linear stability of three-layer porous media flow models of EOR for two different types of interfaces: permeable and impermeable interfaces. Results presented are relevant for the design of smarter interfaces in the available parameter space of capillary number, Peclet number, longitudinal and transverse dispersion, and the viscous profile of the middle layer. The stabilization capacity of each of these two interfaces is explored numerically and conditions for complete dispersive stabilization are identified for each of these two types of interfaces. Key results obtained are (i) three-layer porous media flows with permeable interfaces can be almost completely stabilized by diffusion if the optimal viscous profile is chosen, (ii) flows with impermeable interfaces can also be almost completely stabilized for short time, but become more unstable at later times because diffusion flattens out the basic viscous profile, (iii) diffusion stabilizes short waves more than long waves which leads to a “turning point” Peclet number at which short and long waves have the same growth rate, and (iv) mechanical dispersion further stabilizes flows with permeable interfaces but in some cases has a destabilizing effect for flows with impermeable interfaces, which is a surprising result. These results are then used to give a comparison of the two types of interfaces. It is found that for most values of the flow parameters, permeable interfaces suppress flow instability more than impermeable interfaces.

  4. Dielectric properties study of surface engineered nanoTiO2/epoxy ...

    Indian Academy of Sciences (India)

    2018-02-02

    Feb 2, 2018 ... 2Department of Physics, Sri Sathya Sai Institute of Higher Learning, Vidyagiri, ... the surface modifiers were not successful in obtaining the improved dielectric .... lent Technologies Inc., Santa Clara, CA) at a frequency range.

  5. Dielectric nanoresonators for light manipulation

    Science.gov (United States)

    Yang, Zhong-Jian; Jiang, Ruibin; Zhuo, Xiaolu; Xie, Ya-Ming; Wang, Jianfang; Lin, Hai-Qing

    2017-07-01

    Nanostructures made of dielectric materials with high or moderate refractive indexes can support strong electric and magnetic resonances in the optical region. They can therefore function as nanoresonators. In addition to plasmonic metal nanostructures that have been widely investigated, dielectric nanoresonators provide a new type of building blocks for realizing powerful and versatile nanoscale light manipulation. In contrast to plasmonic metal nanostructures, nanoresonators made of appropriate dielectric materials are low-cost, earth-abundant and have very small or even negligible light energy losses. As a result, they will find potential applications in a number of photonic devices, especially those that require low energy losses. In this review, we describe the recent progress on the experimental and theoretical studies of dielectric nanoresonators. We start from the basic theory of the electromagnetic responses of dielectric nanoresonators and their fabrication methods. The optical properties of individual dielectric nanoresonators are then elaborated, followed by the coupling behaviors between dielectric nanoresonators, between dielectric nanoresonators and substrates, and between dielectric nanoresonators and plasmonic metal nanostructures. The applications of dielectric nanoresonators are further described. Finally, the challenges and opportunities in this field are discussed.

  6. Slow light based on material and waveguide dispersion

    DEFF Research Database (Denmark)

    Nielsen, Torben Roland; Lavrinenko, Andrei; Mørk, Jesper

    2009-01-01

    We study slow light pulse propagation in a photonic crystal structure consisting of a dispersive and absorptive dielectric material and compare it with the constant wave case. The group index and the trasmission are investigated for the example of an ensemble of semiconductor quantum dots embedded...

  7. Dielectric loss of strontium titanate thin films

    Science.gov (United States)

    Dalberth, Mark Joseph

    1999-12-01

    Interest in strontium titanate (STO) thin films for microwave device applications continues to grow, fueled by the telecommunications industry's interest in phase shifters and tunable filters. The optimization of these devices depends upon increasing the phase or frequency tuning and decreasing the losses in the films. Currently, the dielectric response of thin film STO is poorly understood through lack of data and a theory to describe it. We have studied the growth of STO using pulsed laser deposition and single crystal substrates like lanthanum aluminate and neodymium gallate. We have researched ways to use ring resonators to accurately measure the dielectric response as a function of temperature, electric field, and frequency from low radio frequencies to a few gigahertz. Our films grown on lanthanum aluminate show marked frequency dispersion in the real part of the dielectric constant and hints of thermally activated loss behavior. We also found that films grown with conditions that optimized the dielectric constant showed increased losses. In an attempt to simplify the system, we developed a technique called epitaxial lift off, which has allowed us to study films removed from their growth substrates. These free standing films have low losses and show obvious thermally activated behavior. The "amount of tuning," as measured by a figure of merit, KE, is greater in these films than in the films still attached to their growth substrates. We have developed a theory that describes the real and imaginary parts of the dielectric constant. The theory models the real part using a mean field description of the ionic motion in the crystal and includes the loss by incorporating the motion of charged defects in the films.

  8. Dielectric properties of binary solutions a data handbook

    CERN Document Server

    Akhadov, Y Y

    1980-01-01

    Dielectric Properties of Binary Solutions focuses on the investigation of the dielectric properties of solutions, as well as the molecular interactions and mechanisms of molecular processes that occur in liquids. The book first discusses the fundamental formulas describing the dielectric properties of liquids and dielectric data for binary systems of non-aqueous solutions. Topics include permittivity and dielectric dispersion parameters of non-aqueous solutions of organic and inorganic compounds. The text also tackles dielectric data for binary systems of aqueous solutions, including permittiv

  9. Dielectric properties of Zea mays kernels - studies for microwave power processing applications

    Energy Technology Data Exchange (ETDEWEB)

    Surducan, Emanoil; Neamtu, Camelia; Surducan, Vasile, E-mail: emanoil.surducan@itim-cj.r [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)

    2009-08-01

    Microwaves absorption in biological samples can be predicted by their specific dielectrical properties. In this paper, the dielectric properties ({epsilon}' and {epsilon}'') of corn (Zea mays) kernels in the 500 MHz - 20 GHz frequencies range are presented. A short analysis of the microwaves absorption process is also presented, in correlation with the specific thermal properties of the samples, measured by simultaneous TGA-DSC method.

  10. Numerical study of the influence of dielectric tube on propagation of atmospheric pressure plasma jet based on coplanar dielectric barrier discharge

    Science.gov (United States)

    Haixin, HU; Feng, HE; Ping, ZHU; Jiting, OUYANG

    2018-05-01

    A 2D fluid model was employed to simulate the influence of dielectric on the propagation of atmospheric pressure helium plasma jet based on coplanar dielectric barrier discharge (DBD). The spatio-temporal distributions of electron density, ionization rate, electrical field, spatial charge and the spatial structure were obtained for different dielectric tubes that limit the helium flow. The results show that the change of the relative permittivity of the dielectric tube where the plasma jet travels inside has no influence on the formation of DBD itself, but has great impact on the jet propagation. The velocity of the plasma jet changes drastically when the jet passes from a tube of higher permittivity to one of lower permittivity, resulting in an increase in jet length, ionization rate and electric field, as well as a change in the distribution of space charges and discharge states. The radius of the dielectric tube has a great influence on the ring-shaped or solid bullet structure. These results can well explain the behavior of the plasma jet from the dielectric tube into the ambient air and the hollow bullet in experiments.

  11. Performance of dielectric nanocomposites: matrix-free, hairy nanoparticle assemblies and amorphous polymer-nanoparticle blends.

    Science.gov (United States)

    Grabowski, Christopher A; Koerner, Hilmar; Meth, Jeffrey S; Dang, Alei; Hui, Chin Ming; Matyjaszewski, Krzysztof; Bockstaller, Michael R; Durstock, Michael F; Vaia, Richard A

    2014-12-10

    Demands to increase the stored energy density of electrostatic capacitors have spurred the development of materials with enhanced dielectric breakdown, improved permittivity, and reduced dielectric loss. Polymer nanocomposites (PNCs), consisting of a blend of amorphous polymer and dielectric nanofillers, have been studied intensely to satisfy these goals; however, nanoparticle aggregates, field localization due to dielectric mismatch between particle and matrix, and the poorly understood role of interface compatibilization have challenged progress. To expand the understanding of the inter-relation between these factors and, thus, enable rational optimization of low and high contrast PNC dielectrics, we compare the dielectric performance of matrix-free hairy nanoparticle assemblies (aHNPs) to blended PNCs in the regime of low dielectric contrast to establish how morphology and interface impact energy storage and breakdown across different polymer matrices (polystyrene, PS, and poly(methyl methacrylate), PMMA) and nanoparticle loadings (0-50% (v/v) silica). The findings indicate that the route (aHNP versus blending) to well-dispersed morphology has, at most, a minor impact on breakdown strength trends with nanoparticle volume fraction; the only exception being at intermediate loadings of silica in PMMA (15% (v/v)). Conversely, aHNPs show substantial improvements in reducing dielectric loss and maintaining charge/discharge efficiency. For example, low-frequency dielectric loss (1 Hz-1 kHz) of PS and PMMA aHNP films was essentially unchanged up to a silica content of 50% (v/v), whereas traditional blends showed a monotonically increasing loss with silica loading. Similar benefits are seen via high-field polarization loop measurements where energy storage for ∼15% (v/v) silica loaded PMMA and PS aHNPs were 50% and 200% greater than respective comparable PNC blends. Overall, these findings on low dielectric contrast PNCs clearly point to the performance benefits of

  12. Dielectric and acoustical high frequency characterisation of PZT thin films

    International Nuclear Information System (INIS)

    Conde, Janine; Muralt, Paul

    2010-01-01

    Pb(Zr, Ti)O 3 (PZT) is an interesting material for bulk acoustic wave resonator applications due to its high electromechanical coupling constant, which would enable fabrication of large bandwidth frequency filters. The major challenge of the PZT solid solution system is to overcome mechanical losses generally observed in PZT ceramics. To increase the understanding of these losses in textured thin films, thin film bulk acoustic resonators (TFBAR's) based on PZT thin films with compositions either in the tetragonal region or at the morphotropic phase boundary and (111) or {100} textures were fabricated and studied up to 2 GHz. The dielectric and elastic materials coefficients were extracted from impedance measurements at the resonance frequency. The dispersion of the dielectric constant was obtained from impedance measurements up to 2 GHz. The films with varying compositions, textures and deposition methods (sol-gel or sputtering) were compared in terms of dielectric and acoustical properties.

  13. Dielectric and acoustical high frequency characterisation of PZT thin films

    Science.gov (United States)

    Conde, Janine; Muralt, Paul

    2010-02-01

    Pb(Zr, Ti)O3 (PZT) is an interesting material for bulk acoustic wave resonator applications due to its high electromechanical coupling constant, which would enable fabrication of large bandwidth frequency filters. The major challenge of the PZT solid solution system is to overcome mechanical losses generally observed in PZT ceramics. To increase the understanding of these losses in textured thin films, thin film bulk acoustic resonators (TFBAR's) based on PZT thin films with compositions either in the tetragonal region or at the morphotropic phase boundary and (111) or {100} textures were fabricated and studied up to 2 GHz. The dielectric and elastic materials coefficients were extracted from impedance measurements at the resonance frequency. The dispersion of the dielectric constant was obtained from impedance measurements up to 2 GHz. The films with varying compositions, textures and deposition methods (sol-gel or sputtering) were compared in terms of dielectric and acoustical properties.

  14. Study on the dielectric properties of Al2O3/TiO2 sub-nanometric laminates: effect of the bottom electrode and the total thickness

    Science.gov (United States)

    Ben Elbahri, M.; Kahouli, A.; Mercey, B.; Lebedev, O.; Donner, W.; Lüders, U.

    2018-02-01

    Dielectrics based on amorphous sub-nanometric laminates of TiO2 and Al2O3 are subject to elevated dielectric losses and leakage currents, in large parts due to the extremely thin individual layer thickness chosen for the creation of the Maxwell-Wagner relaxation and therefore the high apparent dielectric constants. The optimization of performances of the laminate itself being strongly limited by this contradiction concerning its internal structure, we will show in this study that modifications of the dielectric stack of capacitors based on these sub-nanometric laminates can positively influence the dielectric losses and the leakage, as for example the nature of the electrodes, the introduction of thick insulating layers at the laminate/electrode interfaces and the modification of the total laminate thickness. The optimization of the dielectric stack leads to the demonstration of a capacitor with an apparent dielectric constant of 90, combined with low dielectric loss (tan δ) of 7 · 10-2 and with leakage currents smaller than 1  ×  10-6 A cm-2 at 10 MV m-1.

  15. Study of the physical mechanisms involved in the femtosecond laser optical breakdown of dielectric materials

    International Nuclear Information System (INIS)

    Mouskeftaras, Alexandros

    2013-01-01

    We have carried out detailed time resolved experimental studies of the mechanism of electron excitation-relaxation, when an ultrashort (60 fs -1 ps) laser (UV and IR) pulse interacts with a wide band gap dielectric material. The studies cover a range of different dielectric materials and the investigated regimes span from nondestructive ionization of the material at the low power end (∼TW/cm 2 ) to ablative domain at a higher laser power (∼10 TW/cm 2 ). This gives fundamental insight into the understanding of the laser damaging process taking place under our irradiation conditions. The usage of time-resolved spectral interferometry technique allows to directly measure the electron density of the irradiated material under different excitation conditions and hence leads to quantification of the process. The measurements, carried out at the optical breakdown threshold utilizing different pulse durations, raise questions regarding the usage of critical excitation density as a universal ablation criterion. A new criterion related to the exchanged energy is proposed. Additionally, the use of an experimental setup implementing a double pump pulse allows the identification of different excitation mechanisms taking place at time scales of the order of the pulse duration used. Electronic avalanche is observed in some materials (SiO 2 , NaCl) while this is not the case for others (Al 2 O 3 , MgO). These differences are discussed in detail. Next, we measure the energy spectrum of excited electrons with a complementary technique: the photoemission spectroscopy. These results allow us on one hand to show a crossed effect between the two 'pump' pulses and on the other hand to measure electron relaxation characteristic times, as a function of their kinetic energy. Finally, a morphological study of craters resulting from ablation in the case of a single pulse has been carried out for different irradiation parameters: number of shots, energy and pulse duration. This work has

  16. Dielectric and conduction mechanism studies of PEMA/ENR-50 blend with LiCF3SO3 salt

    Science.gov (United States)

    Sukri, N.; Mohamed, N. S.; Subban, R. H. Y.

    2017-09-01

    Solid polymer electrolytes (SPEs) composed of a blend of Poly(ethyl methacrylate) (PEMA) and Epoxidized Natural Rubber-50 (ENR-50) and Lithium triflate (LiCF3SO3) were prepared by solution casting technique. The conductivity was measured by using electrical impedance spectroscopy (EIS). Measurement of conductivity was carried out as a function of frequency at various concentrations of salt. The SPE exhibit high conductivity of ˜10-5 S/cm at ambient temperature when 40 wt% of LiCF3SO3 was added. Increase in conductivity is attributed to increasing number of charge carriers due to dissociation of salt when the concentration of salt increased. Dielectric properties and ac conductivity of the samples were analyzed. The values of dielectric constant were found to increase with increasing conductivity of the samples. The electrical modulus shows the formation of dispersion peaks. Relaxation time of ionic charge carriers were extracted from the maximum peak of loss tangent at various concentrations of LiCF3SO3 salt. The temperature dependence of the power law exponent s is explained by the overlapping large polaron-tunnelling (OLPT) model.

  17. Characterization and study of dielectric and electrical properties of CaBi4Ti4O_1_5 (CBT) added with Bi_2O_3

    International Nuclear Information System (INIS)

    Freitas, D.B.; Campos Filho, M.C.; Sales, J.C.; Silva, P.M.O.; Sombra, A.S.

    2011-01-01

    The ceramic perovskite CaBi_4Ti_4O_1_5 (CBT) of space group A21am, Aurivillius family with deficiency A_5B_4O_1_5 cation has been prepared by solid state method in a planetary ball mill of high energy. The reagents samples were ground and calcined and then added with Bi_2O_3 (2% wt.) This work aims to characterize by X-ray diffraction to study the electrical properties and dielectric properties of (CBT). The x-ray diffraction revealed the formation of single orthorhombic phase. As for the dielectric properties (dielectric constant and dielectric loss) were measured at 30 deg C to 450 deg C, through which can be verified the presence of thermally activated processes. This phase has properties very relevant for possible use in capacitive devices, miniaturized filters, dielectric resonators antennas and oscillators. (author)

  18. Energy dispersive X-ray diffractometry in texture studies

    International Nuclear Information System (INIS)

    Szpunar, J.A.

    1983-01-01

    Information about texture is traditionally obtained from the two-dimensional distributions of crystallographic directions in the reference frame of the specimen. The distributions can be measured using the angular dispersive diffractometry. In such measurements the rotation of the specimen brings the crystallographic planes of differently oriented crystals into the diffraction position. The distribution (pole figure) can be measured continuously or alternatively the angular space can be scanned in different directions and with required accuracy. The subject is discussed, with examples. (author)

  19. [Study on A White-Eye Pattern in Dielectric Barrier Discharge by Optical Emission Spectrum].

    Science.gov (United States)

    Zhu, Ping; Dong, Li-fang; Yang, Jing; Zhang, Yu; Zhang, Chao

    2015-06-01

    The white-eye pattern was firstly observed and investigated in a dielectric barrier discharge system in the mixture of argon and air whose content can be varied whenever necessary, and the study shows that the white-eye cell is an interleaving of three different hexagonal sub-structures: the center spot, the halo, and the ambient spots. The white-eye pattern is observed at a lower applied voltage. In this experiment, the heat capacity of water is high so that the water in water electrode is good at absorbing heat. In the process of pattern discharging the gas gap didn't increase its temperature, and the discharging phenomenon of this pattern has not changed. The temperature of the water electrodes almost keeps unchanged during the whole experiment, which is advantageous for the long-term stable measurement. Pictures recorded by ordinary camera with long exposure time in the same argon content condition show that the center spot, the halo, and the ambient spots og the white-eye pattern have different brightness, which may prove that their plasma states are different. And, it is worth noting that there are obvious differences of brightness not only on the center spot, the halo, and the ambient spots at the same pressure but also at the different pressure, which shows that its plasma state also changed with the variation of the pressure. Given this, in this experiment plasma temperatures of the central spot, halo, and ambient spots in a white-eye pattern at different gas pressure were studied by using optical emission spectra. The molecular vibration temperature is investigated by the emission spectra of nitrogen band of second positive system ( C3Πu --> B3Πg ). The electron excitation temperature is researched by the relative intensity ratio method of spectral lines of Ar I 763. 51 nm (2P6 --> 1S5) and Ar I 772. 42 nm (2P2 --> 1S3). The electronic density is investigated by the broadening of spectral line 696.5 nm. Through the analysis of experimental results, it

  20. Dielectric, optical and mechanical studies of phenolic polyene OH1 organic electrooptic crystal

    Science.gov (United States)

    Bharath, D.; Kalainathan, S.

    2014-11-01

    2-{3-[2-(4-Hydroxyphenyl) vinyl]-5, 5-dimethylcyclo-hex-2-en-1-ylidene}malononitrile (OH1) phenolic locked polyene organic material has been synthesized by the Knoevenagel condensation method. OH1 single crystals were grown in methanol by a slow evaporation method. In order to avoid the multinucleation and reduce the metastable zone width, phosphoric acid is added in different concentrations. The linear optical property of OH1 crystal has been studied using UV-vis-NIR spectroscopy in the wavelength range 190-1100 nm and optical constants are calculated theoretically. The magnitude of nonlinear refractive index (10-12 m2/W), nonlinear absorption (10-6 m/W) and third order nonlinear susceptibility (10-6 esu) has been studied using a Z-scan technique. Dielectric property of OH1 crystal has been studied in frequency range 50 Hz-5 MHz. Photoluminescence spectrum was recorded using a xenon lamp in the range of 450-700 nm. Laser optical damage threshold of OH1 crystal was obtained (0.62 GW/cm2) using a pulsed Nd-YAG laser (1064 nm) of repetition rate 10 ns.

  1. Improved Dielectric Properties of Polyvinylidene Fluoride Nanocomposite Embedded with Poly(vinylpyrrolidone)-Coated Gold Nanoparticles

    KAUST Repository

    Toor, Anju

    2017-01-25

    A novel nanocomposite dielectric was developed by embedding polyvinylpyrrolidone (PVP)-encapsulated gold (Au) nanoparticles in the polyvinylidene fluoride (PVDF) polymer matrix. The surface functionalization of Au nanoparticles with PVP facilitates favorable interaction between the particle and polymer phase, enhancing nanoparticle dispersion. To study the effect of entropic interactions on particle dispersion, nanocomposites with two different particle sizes (5 and 20 nm in diameter) were synthesized and characterized. A uniform particle distribution was observed for nanocomposite films consisting of 5 nm Au particles, in contrast to the film with 20 nm particles. The frequency-dependent dielectric permittivity and the loss tangent were studied for the nanocomposite films. These results showed the effectiveness of PVP ligand in controlling the agglomeration of Au particles in the PVDF matrix. Moreover, the study showed the effect of particle concentration on their spatial distribution in the polymer matrix and the dielectric properties of nanocomposite films.

  2. Improved Dielectric Properties of Polyvinylidene Fluoride Nanocomposite Embedded with Poly(vinylpyrrolidone)-Coated Gold Nanoparticles

    KAUST Repository

    Toor, Anju; So, Hongyun; Pisano, Albert P.

    2017-01-01

    A novel nanocomposite dielectric was developed by embedding polyvinylpyrrolidone (PVP)-encapsulated gold (Au) nanoparticles in the polyvinylidene fluoride (PVDF) polymer matrix. The surface functionalization of Au nanoparticles with PVP facilitates favorable interaction between the particle and polymer phase, enhancing nanoparticle dispersion. To study the effect of entropic interactions on particle dispersion, nanocomposites with two different particle sizes (5 and 20 nm in diameter) were synthesized and characterized. A uniform particle distribution was observed for nanocomposite films consisting of 5 nm Au particles, in contrast to the film with 20 nm particles. The frequency-dependent dielectric permittivity and the loss tangent were studied for the nanocomposite films. These results showed the effectiveness of PVP ligand in controlling the agglomeration of Au particles in the PVDF matrix. Moreover, the study showed the effect of particle concentration on their spatial distribution in the polymer matrix and the dielectric properties of nanocomposite films.

  3. Liquid argon dielectric breakdown studies with the MicroBooNE purification system

    Energy Technology Data Exchange (ETDEWEB)

    Acciarri, R.; Carls, B.; James, C.; Johnson, B.; Jostlein, H.; Lockwitz, S.; Lundberg, B.; Raaf, J. L.; Rameika, R.; Rebel, B.; Zeller, G. P.; Zuckerbrot, M.

    2014-11-01

    The proliferation of liquid argon time projection chamber detectors makes the characterization of the dielectric properties of liquid argon a critical task. To improve understanding of these properties, a systematic study of the breakdown electric field in liquid argon was conducted using a dedicated cryostat connected to the MicroBooNE cryogenic system at Fermilab. An electrode sphere-plate geometry was implemented using spheres with diameters of 1.3 mm, 5.0 mm, and 76 mm. The MicroBooNE cryogenic system allowed measurements to be taken at a variety of electronegative contamination levels ranging from a few parts-per-million to tens of parts-per-trillion. The cathode-anode distance was varied from 0.1 mm to 2.5 cm. The results demonstrate a geometric dependence of the electric field strength at breakdown. This study is the first time that the dependence of the breakdown field on stressed cathode area has been shown for liquid argon.

  4. A numerical study on charging mechanism in leaky dielectric liquids inside the electrostatic atomizers

    Science.gov (United States)

    Kashir, Babak; Perri, Anthony; Yarin, Alexander L.; Mashayek, Farzad

    2017-11-01

    The charging of leaky dielectric liquids inside an electrostatic atomizer is studied numerically by developed codes based on OpenFOAM platform. Faradaic reactions are taken into account as the electrification mechanism. The impact of ionic finite size (steric terms) in high voltages is also investigated. The fundamental electrohydrodynamic understanding of the charging mechanism is aimed in the present work where the creation of polarized near-electrode layer and the movement of charges due to hydrodynamic flow are studied in conjunction with the solution of the Navier-Stokes equations. The case of a micro channel electrohydrodynamic flow subjected to two electrodes of the opposite polarity is considered as an example, with the goal to predict the resulting net charge at the exit. Even though the electrodes constitute a small portion of the channel wall, otherwise insulated, it is indicated that the channel length plays a dominant role in the discharging net charge. The ionic fluxes at the electrode surfaces are accounted through the Frumkin-Butler-Volmer relation found from the concurrent in-house experimental investigations. This projects was supported by National science Foundation (NSF) GOALI Grant CBET-1505276.

  5. The Study of Electrical Properties for Multilayer La2O3/Al2O3 Dielectric Stacks and LaAlO3 Dielectric Film Deposited by ALD.

    Science.gov (United States)

    Feng, Xing-Yao; Liu, Hong-Xia; Wang, Xing; Zhao, Lu; Fei, Chen-Xi; Liu, He-Lei

    2017-12-01

    The capacitance and leakage current properties of multilayer La 2 O 3 /Al 2 O 3 dielectric stacks and LaAlO 3 dielectric film are investigated in this paper. A clear promotion of capacitance properties is observed for multilayer La 2 O 3 /Al 2 O 3 stacks after post-deposition annealing (PDA) at 800 °C compared with PDA at 600 °C, which indicated the recombination of defects and dangling bonds performs better at the high-k/Si substrate interface for a higher annealing temperature. For LaAlO 3 dielectric film, compared with multilayer La 2 O 3 /Al 2 O 3 dielectric stacks, a clear promotion of trapped charges density (N ot ) and a degradation of interface trap density (D it ) can be obtained simultaneously. In addition, a significant improvement about leakage current property is observed for LaAlO 3 dielectric film compared with multilayer La 2 O 3 /Al 2 O 3 stacks at the same annealing condition. We also noticed that a better breakdown behavior for multilayer La 2 O 3 /Al 2 O 3 stack is achieved after annealing at a higher temperature for its less defects.

  6. Filamentation and light bullet formation dynamics in solid-state dielectric media with weak, moderate and strong anomalous group velocity dispersion

    International Nuclear Information System (INIS)

    Gražulevičiūtė, I; Garejev, N; Majus, D; Tamošauskas, G; A Dubietis; Jukna, V

    2016-01-01

    We present a series of measurements, which characterize filamentation dynamics of intense ultrashort laser pulses in the space–time domain, as captured by means of three-dimensional imaging technique in sapphire and fused silica, in the wavelength range of 1.45–2.25 μm, accessing the regimes of weak, moderate and strong anomalous group velocity dispersion (GVD). In the regime of weak anomalous GVD (at 1.45 μm), pulse splitting into two sub-pulses producing a pair of light bullets with spectrally shifted carrier frequencies in both nonlinear media is observed. In contrast, in the regimes of moderate (at 1.8 μm) and strong (at 2.25 μm) anomalous GVD we observe notably different transient dynamics, which however lead to the formation of a single self-compressed quasistationary light bullet with an universal spatiotemporal shape comprised of an extended ring-shaped periphery and a localized intense core that carries the self-compressed pulse. (paper)

  7. Filamentation and light bullet formation dynamics in solid-state dielectric media with weak, moderate and strong anomalous group velocity dispersion

    Science.gov (United States)

    Gražulevičiūtė, I.; Garejev, N.; Majus, D.; Jukna, V.; Tamošauskas, G.; Dubietis, A.

    2016-02-01

    We present a series of measurements, which characterize filamentation dynamics of intense ultrashort laser pulses in the space-time domain, as captured by means of three-dimensional imaging technique in sapphire and fused silica, in the wavelength range of 1.45-2.25 μm, accessing the regimes of weak, moderate and strong anomalous group velocity dispersion (GVD). In the regime of weak anomalous GVD (at 1.45 μm), pulse splitting into two sub-pulses producing a pair of light bullets with spectrally shifted carrier frequencies in both nonlinear media is observed. In contrast, in the regimes of moderate (at 1.8 μm) and strong (at 2.25 μm) anomalous GVD we observe notably different transient dynamics, which however lead to the formation of a single self-compressed quasistationary light bullet with an universal spatiotemporal shape comprised of an extended ring-shaped periphery and a localized intense core that carries the self-compressed pulse.

  8. An experimental investigation of the dielectric properties of electrorheological fluids

    International Nuclear Information System (INIS)

    Sun, Y; Thomas, M; Masounave, J

    2009-01-01

    A home-made electrorheological (ER) fluid, known as ETSERF, has been created with suspension-based powders dispersed in silicone oil. Because of the special structure of their particles, ETSERF suspensions present a complex behavior. In the absence of an electric field, the ETSERF fluid manifests a near-Newtonian behavior, but when an electric field is applied, it exhibits a pseudoplastic behavior with yield stress. The ER effect under DC electric fields has been experimentally investigated using both hydrous and anhydrous ER fluids. The ER properties are strongly dependent on the dielectric properties of ETSERF suspensions, and hydrous ER fluids have a high dielectric constant and a high relaxation frequency which show a strong electrorheological effect. The relationship between the electrorheological effect and the permittivity of ER fluids has also been extensively studied. Experimental results show that the interfacial polarization plays an important role in the electrorheological phenomenon. The ageing of ETSERF fluids was also studied and it was found that the dielectric properties (mainly the dielectric loss tangent) and ER properties are strongly related to the duration of ageing. A fresh ETSERF suspension exhibits high relaxation frequency and high dielectric constant. These results are mainly explained by the effect of interfacial polarizations

  9. Optical and dielectric studies of KH2PO4 crystal influenced by organic ligand of citric acid and l-valine: A single crystal growth and comparative study

    Directory of Open Access Journals (Sweden)

    Mohd Anis

    Full Text Available In the present study pure, citric acid (CA and l-valine (LV doped potassium dihydrogen phosphate (KDP crystals have been grown with the aim to investigate the nonlinear optical applications facilitated by UV–visible, third order nonlinear optical (TONLO and dielectric properties. The structural parameters of grown crystals have been confirmed by single crystal X-ray diffraction analysis. The enhancement in optical transparency of KDP crystal due to addition of CA and LV has been examined within 200–900 nm by means of UV–visible spectral analysis. In addition, the transmittance data have been used to evaluate the effect of dopants on reflectance, refractive index and extinction coefficient of grown crystals in the visible region. The Z-scan analysis has been performed at 632.8 nm to identify the nature of photoinduced nonlinear refraction and nonlinear absorption in doped KDP crystals. The influence of π-bonded ligand of dopant CA and LV on TONLO susceptibility (χ3, refractive index (n2 and absorption coefficient (β of KDP crystals has been evaluated to discuss laser assisted device applications. The decrease in dielectric constant and dielectric loss of KDP crystal due to addition of CA and LV has been explored using the temperature dependent dielectric studies. Keywords: Crystal growth, Nonlinear optical materials, UV–visible studies, Z-scan analysis, Dielectric studies

  10. A Simplified Numerical Study of the Kr/Cl2 Plasma Chemistry in Dielectric Barrier Discharge

    International Nuclear Information System (INIS)

    Bachir, N. Larbi Daho; Belasri, A.

    2013-01-01

    In this paper, the generation of excimers and exciplexe radiation in mixtures of rare gas with halogen by homogeneous dielectric barrier discharge (DBD) is investigated. The typical characteristics of an excilamp based on KrCl* exciplexe molecules and the kinetic processes for the formation and the decay of this molecules in the Kr/Cl 2 mixture are studied. The computer model developed is based on the Kr/Cl 2 mixture chemistry, the equivalent electric circuit and the Boltzmann equations. The importance in the kinetic processes of some species such as the metastable state of Krypton (Kr*( 3 P 0,2 )) and the negative ion of chloride (Cl − ) is considered. The results illustrate the time variations of charged species (n e , Kr + , Cl − , Cl + , Cl + 2 , Kr + 2 ), excited atoms and molecules (Kr*( 3 P 0,2 ), Kr*( 3 P 1 ), Cl*, Cl* 2 ), the excimers (Kr* 2 , KrCl*(B), KrCl*(C), Kr 2 Cl*) and the UV photon concentrations (in 222 nm, 235 nm, 258 nm and 325 nm range). The effects of chlorine concentration and the total gas pressure in the Kr-Cl 2 discharge on the electric parameters and radiation emissions are investigated. (low temperature plasma)

  11. Experimental study of surface dielectric barrier discharge in air and its ozone production

    International Nuclear Information System (INIS)

    Pekárek, Stanislav

    2012-01-01

    For surface dielectric barrier discharge in air we studied the effects of frequency of the driving voltage on dissipated power, asymmetry of amplitudes of the discharge voltage, discharge UV emission, ozone production, ozone production of the discharge with TiO 2 and of the discharge in magnetic field. We found that for a particular voltage the dissipated power is higher for the frequency of the driving voltage of 26.3 kHz than for the frequency of 10.9 kHz; peak values of the positive half-periods of the discharge voltage are higher than peak values of the negative half-periods; intensity of the discharge UV emissions for wavelengths of 320-420 nm is for both frequencies a linear function of power; maximum ozone concentration for the frequency of the driving voltage of 26.3 kHz is obtained with smaller power than for the frequency of 10.9 kHz; placement of TiO 2 particles into the discharge chamber increases for both frequencies of the driving voltage maximum ozone concentration produced by the discharge and for the frequency of the driving voltage of 26.3 kHz increases ozone production yield. Finally, there is no observable effect of magnetic field on concentration of ozone produced by the discharge as well as on production yield. (paper)

  12. Study of strained-Si p-channel MOSFETs with HfO2 gate dielectric

    Science.gov (United States)

    Pradhan, Diana; Das, Sanghamitra; Dash, Tara Prasanna

    2016-10-01

    In this work, the transconductance of strained-Si p-MOSFETs with high-K dielectric (HfO2) as gate oxide, has been presented through simulation using the TCAD tool Silvaco-ATLAS. The results have been compared with a SiO2/strained-Si p-MOSFET device. Peak transconductance enhancement factors of 2.97 and 2.73 has been obtained for strained-Si p-MOSFETs in comparison to bulk Si channel p-MOSFETs with SiO2 and high-K dielectric respectively. This behavior is in good agreement with the reported experimental results. The transconductance of the strained-Si device at low temperatures has also been simulated. As expected, the mobility and hence the transconductance increases at lower temperatures due to reduced phonon scattering. However, the enhancements with high-K gate dielectric is less as compared to that with SiO2.

  13. Structure-property relationship in dielectric mixtures: application of the spectral density theory

    International Nuclear Information System (INIS)

    Tuncer, Enis

    2005-01-01

    This paper presents numerical simulations performed on dielectric properties of two-dimensional binary composites. The influence of structural differences and intrinsic electrical properties of constituents on the composite's overall electrical properties is investigated. The structural differences are resolved by fitting the dielectric data with an empirical formula and by the spectral density representation approach. At low concentrations of inclusions (concentrations lower than the percolation threshold), the spectral density functions are delta-sequences, which corresponds to the predictions of the general Maxwell-Garnett (MG) mixture formula. At high concentrations of inclusions (close to the percolation threshold) systems exhibit non-Debye-type dielectric dispersions, and the spectral density functions differ from each other and that predicted by the MG expression. The analysis of the dielectric dispersions with an empirical formula also brings out the structural differences between the considered geometries, however, the information is not qualitative. The empirical formula can only be used to compare structures. The spectral representation method on the other hand is a concrete way of characterizing the structures of the dielectric mixtures. Therefore, as in other spectroscopic techniques, a look-up table might be useful to classify/characterize structures of composite materials. This can be achieved by generating dielectric data for known structures by using ab initio calculations, as presented and emphasized in this study. The numerical technique presented here is not based on any a priori assumption methods

  14. Theoretical study of the attenuation of a gaussian beam penetrating into a dielectric circular wave guide

    International Nuclear Information System (INIS)

    Crenn, J.P.

    1981-07-01

    It is proposed to draw up an approximate formula directly giving the attenuation of a gaussian beam penetrating into a superdimensioned dielectric circular wave guide. This formula is derived from optical laws, i.e. Fresnel's formulae of the reflexion of a wave on a dielectric to which a correcting term due to diffraction has been added. The results given by this formula are compared with the existing results, based on the breakdown of a gaussian beam into propagation modes, thereby enabling their validity and the field of use to be checked. An application is then made to the wave guides that will be employed in the infrared interferometer fitted in JET [fr

  15. A large-scale study of the ultrawideband microwave dielectric properties of normal, benign and malignant breast tissues obtained from cancer surgeries

    Energy Technology Data Exchange (ETDEWEB)

    Lazebnik, Mariya [Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI (United States); Popovic, Dijana [Department of Electrical and Computer Engineering, University of Calgary, Calgary, AB (Canada); McCartney, Leah [Department of Electrical and Computer Engineering, University of Calgary, Calgary, AB (Canada); Watkins, Cynthia B [Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI (United States); Lindstrom, Mary J [Department of Biostatistics and Medical Informatics, University of Wisconsin, Madison, WI (United States); Harter, Josephine [Department of Pathology, University of Wisconsin, Madison, WI (United States); Sewall, Sarah [Department of Pathology, University of Wisconsin, Madison, WI (United States); Ogilvie, Travis [Department of Pathology, University of Calgary, Calgary, AB (Canada); Magliocco, Anthony [Department of Pathology, University of Calgary, Calgary, AB (Canada); Breslin, Tara M [Department of Surgery, University of Wisconsin, Madison, WI (United States); Temple, Walley [Department of Surgery and Oncology, University of Calgary, Calgary, AB (Canada); Mew, Daphne [Department of Surgery and Oncology, University of Calgary, Calgary, AB (Canada); Booske, John H [Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI (United States); Okoniewski, Michal [Department of Electrical and Computer Engineering, University of Calgary, Calgary, AB (Canada); Hagness, Susan C [Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI (United States)

    2007-10-21

    The development of microwave breast cancer detection and treatment techniques has been driven by reports of substantial contrast in the dielectric properties of malignant and normal breast tissues. However, definitive knowledge of the dielectric properties of normal and diseased breast tissues at microwave frequencies has been limited by gaps and discrepancies across previously published studies. To address these issues, we conducted a large-scale study to experimentally determine the ultrawideband microwave dielectric properties of a variety of normal, malignant and benign breast tissues, measured from 0.5 to 20 GHz using a precision open-ended coaxial probe. Previously, we reported the dielectric properties of normal breast tissue samples obtained from reduction surgeries. Here, we report the dielectric properties of normal (adipose, glandular and fibroconnective), malignant (invasive and non-invasive ductal and lobular carcinomas) and benign (fibroadenomas and cysts) breast tissue samples obtained from cancer surgeries. We fit a one-pole Cole-Cole model to the complex permittivity data set of each characterized sample. Our analyses show that the contrast in the microwave-frequency dielectric properties between malignant and normal adipose-dominated tissues in the breast is considerable, as large as 10:1, while the contrast in the microwave-frequency dielectric properties between malignant and normal glandular/fibroconnective tissues in the breast is no more than about 10%.

  16. A large-scale study of the ultrawideband microwave dielectric properties of normal, benign and malignant breast tissues obtained from cancer surgeries

    Science.gov (United States)

    Lazebnik, Mariya; Popovic, Dijana; McCartney, Leah; Watkins, Cynthia B.; Lindstrom, Mary J.; Harter, Josephine; Sewall, Sarah; Ogilvie, Travis; Magliocco, Anthony; Breslin, Tara M.; Temple, Walley; Mew, Daphne; Booske, John H.; Okoniewski, Michal; Hagness, Susan C.

    2007-10-01

    The development of microwave breast cancer detection and treatment techniques has been driven by reports of substantial contrast in the dielectric properties of malignant and normal breast tissues. However, definitive knowledge of the dielectric properties of normal and diseased breast tissues at microwave frequencies has been limited by gaps and discrepancies across previously published studies. To address these issues, we conducted a large-scale study to experimentally determine the ultrawideband microwave dielectric properties of a variety of normal, malignant and benign breast tissues, measured from 0.5 to 20 GHz using a precision open-ended coaxial probe. Previously, we reported the dielectric properties of normal breast tissue samples obtained from reduction surgeries. Here, we report the dielectric properties of normal (adipose, glandular and fibroconnective), malignant (invasive and non-invasive ductal and lobular carcinomas) and benign (fibroadenomas and cysts) breast tissue samples obtained from cancer surgeries. We fit a one-pole Cole-Cole model to the complex permittivity data set of each characterized sample. Our analyses show that the contrast in the microwave-frequency dielectric properties between malignant and normal adipose-dominated tissues in the breast is considerable, as large as 10:1, while the contrast in the microwave-frequency dielectric properties between malignant and normal glandular/fibroconnective tissues in the breast is no more than about 10%.

  17. A large-scale study of the ultrawideband microwave dielectric properties of normal, benign and malignant breast tissues obtained from cancer surgeries

    International Nuclear Information System (INIS)

    Lazebnik, Mariya; Popovic, Dijana; McCartney, Leah; Watkins, Cynthia B; Lindstrom, Mary J; Harter, Josephine; Sewall, Sarah; Ogilvie, Travis; Magliocco, Anthony; Breslin, Tara M; Temple, Walley; Mew, Daphne; Booske, John H; Okoniewski, Michal; Hagness, Susan C

    2007-01-01

    The development of microwave breast cancer detection and treatment techniques has been driven by reports of substantial contrast in the dielectric properties of malignant and normal breast tissues. However, definitive knowledge of the dielectric properties of normal and diseased breast tissues at microwave frequencies has been limited by gaps and discrepancies across previously published studies. To address these issues, we conducted a large-scale study to experimentally determine the ultrawideband microwave dielectric properties of a variety of normal, malignant and benign breast tissues, measured from 0.5 to 20 GHz using a precision open-ended coaxial probe. Previously, we reported the dielectric properties of normal breast tissue samples obtained from reduction surgeries. Here, we report the dielectric properties of normal (adipose, glandular and fibroconnective), malignant (invasive and non-invasive ductal and lobular carcinomas) and benign (fibroadenomas and cysts) breast tissue samples obtained from cancer surgeries. We fit a one-pole Cole-Cole model to the complex permittivity data set of each characterized sample. Our analyses show that the contrast in the microwave-frequency dielectric properties between malignant and normal adipose-dominated tissues in the breast is considerable, as large as 10:1, while the contrast in the microwave-frequency dielectric properties between malignant and normal glandular/fibroconnective tissues in the breast is no more than about 10%

  18. Dielectric properties of calicum and barium-doped strontium titanate

    Science.gov (United States)

    Tung, Li-Chun

    Dielectric properties of high quality polycrystalline Ca- and Ba-doped SrTiO3 perovskites are studied by means of dielectric constant, dielectric loss and ferroelectric hysteresis measurements. Low frequency dispersion of the dielectric constant is found to be very small and a simple relaxor model may not be able to explain its dielectric behavior. Relaxation modes are found in these samples, and they are all interpreted as thermally activated Bipolar re-orientation across energy barriers. In Sr1- xCaxTiO3 (x = 0--0.3), two modes are found associated with different relaxation processes, and the concentration dependence implies a competition between these processes. In Sr1-xBa xTiO3 (x = 0--0.25), relaxation modes are found to be related to the structural transitions, and the relaxation modes persist at low doping levels (x Barret formula is discussed and two of the well-accepted models, anharmonic oscillator model and transverse Ising model, are found to be equivalent. Both of the Ca and Ba systems can be understood qualitatively within the concept of transverse Ising model.

  19. Study of spatiotemporal dynamics of a nanosecond atmospheric-pressure dielectric barrier discharge in millimeter-long air gaps

    Energy Technology Data Exchange (ETDEWEB)

    Malashin, M. V.; Moshkunkov, S. I.; Khomich, V. Yu.; Shershunova, E. A., E-mail: eshershunova@gmail.com [Russian Academy of Sciences, Institute for Electrophysics and Electric Power (Russian Federation)

    2017-02-15

    The spatiotemporal dynamics of a nanosecond atmospheric-pressure dielectric barrier discharge in 1- to 3-mm-long air gaps was studied experimentally. By using a segmented electrode, data on the time evolution of the discharge in different regions of the discharge gap were obtained. The uniformity of the discharge over the cross section is estimated by analyzing the spatial distribution of its glow.

  20. Study of the pressure dependence of dielectric properties of ionic crystals with the exchange-charge model

    Energy Technology Data Exchange (ETDEWEB)

    Batana, A; Faour, J

    1987-03-01

    The formalism of the exchange-charge model (ECM) is extended for studying the pressure dependence of the static dielectric constant and the volume dependence of the effective ionic charge for b.c.c. lattices. Calculated values for CsCl, CsBr, CsI, and TlBr together with the simple shell model values and experimental values are listed and discussed.

  1. Study on characteristics of high frequency dielectric barrier discharge for the removal of organic pollutant adsorbed on activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Qu, G.Z.; Li, G.F. [Dalian Univ. of Technology, Dalian (China). Inst. of Electrostatics and Special Power; Li, J.; Lu, N.; Wu, Y.; Li, D. [Dalian Univ. of Technology, Dalian (China). Inst. of Electrostatics and Special Power; Key Lab of Industrial Ecology and Environmental Engineering, Ministry of Education, Dalian (China)

    2010-07-01

    Advanced oxidation technologies such as photocatalysis, electrochemical degradation, Fenton oxidation, hydrogen peroxide oxidation, and plasma oxidation are increasingly being used to degrade refractory biodegradable organic contaminants. The plasma oxidation method has the advantage of direct in situ production of multiple types of high-reactive chemical species, including molecules and radicals that facilitate the degradation reaction. In addition, plasma oxidation does not produce any secondary pollution. Compared to other plasma technologies, the dielectric barrier discharge (DBD) plasma has been considered as a promising technology for removing toxic compounds because of its stability and its treatability property of biologically recalcitrant compounds in wastewater. However, the energy efficiency of DBD requires improvement for economic reasons. This paper reported on an experimental study that investigated the electrical characteristics of a parallel plate DBD reactor using a high frequency power supply for the removal of pentachlorophenol (PCP) adsorbed on activated carbon (AC). This study examined the effects of AC with different mass on discharge characteristics and compared the voltage and current waveforms, and discharge images of DBD reactors with different dielectric configurations. When the DBD reactor filled with AC, the applied voltage of discharge decreased regardless of the DBD reactor configuration in terms of having a single barrier or two barriers. The discharge characteristics had no significant change with AC mass increasing. The discharge images and current waveforms showed that DBD reactor configuration consisting of two dielectrics is more homogeneous and stable than the one consisting of a single dielectric. Under the same electric field condition, the degradation efficiency of PCP in two barriers reactor is higher than that in single barrier reactor. It was concluded that the findings from this study may be instrumental in treating

  2. Dielectric relaxation studies in super-cooled liquid and glassy phases of anti-cancerous alkaloid: Brucine

    Science.gov (United States)

    Afzal, Aboothahir; Shahin Thayyil, M.; Sulaiman, M. K.; Kulkarni, A. R.

    2018-05-01

    Brucine has good anti-tumor effects, on both liver cancer and breast cancer. It has bioavailability of 40.83%. Since the bioavailability of the drug is low, an alternative method to increase its bioavailability and solubility is by changing the drug into glassy form. We used Differential Scanning Calorimetry (DSC) for studying the glass forming ability of the drug. Brucine was found to be a very good glass former glass transition temperature 365 K. Based on the DSC analysis we have used broadband dielectric spectroscopy (BDS) for studying the drug in the super cooled and glassy state. BDS is an effective tool to probe the molecular dynamics in the super cooled and glassy state. Molecular mobility is found to be present even in the glassy state of this active pharmaceutical ingredient (API) which is responsible for the instability. Our aim is to study the factors responsible for instability of this API in amorphous form. Cooling curves for dielectric permittivity and dielectric loss revealed the presence of structural (α) and secondary relaxations (β and γ). Temperature dependence of relaxation time is fitted by Vogel-Fulcher-Tammann equation and found the values of activation energy of the α relaxation, fragility and glass transition temperature. Paluch's anti correlation is also verified, that the width of the α-loss peak at or near the glass transition temperature Tg is strongly anticorrelated with the polarity of the molecule. The larger the dielectric relaxation strength Δɛ (Tg) of the system, the narrower is the α-loss peak (higher value of βKWW).

  3. Charge accumulation in lossy dielectrics: a review

    DEFF Research Database (Denmark)

    Rasmussen, Jørgen Knøster; McAllister, Iain Wilson; Crichton, George C

    1999-01-01

    At present, the phenomenon of charge accumulation in solid dielectrics is under intense experimental study. Using a field theoretical approach, we review the basis for charge accumulation in lossy dielectrics. Thereafter, this macroscopic approach is applied to planar geometries such that the mat......At present, the phenomenon of charge accumulation in solid dielectrics is under intense experimental study. Using a field theoretical approach, we review the basis for charge accumulation in lossy dielectrics. Thereafter, this macroscopic approach is applied to planar geometries...

  4. Studies of the thermal properties of horn keratin by dielectric spectroscopy, thermogravimetric analysis and differential thermal analysis

    International Nuclear Information System (INIS)

    Marzec, E.; Piskunowicz, P.; Jaroszyk, F.

    2002-01-01

    The dielectric and thermal properties of horn keratin have been studied bu dielectric spectroscopy in the frequency range 10 1 -10 5 Hz, thermogravimetric analysis (TG) and different thermal analysis (DTA). Measurement of non-irradiated and g amma - irradiated keratin with doses 5, 50 kGy were performed at temperature from 22 to 260 o C. The results revealed the occurrence of phase transitions related to release of loosely bound water and bound water up to 200 o Cand the denaturation of the crystalline structure above this temperature. The influence of γ-irradiation on the thermal behaviour of keratin is significant only in the temperature range of denaturation. The decrease in the temperature of denaturation would suggest that γ-irradiation initiates main-chain degradation. (authors)

  5. Study of surface plasmon resonance of core-shell nanogeometry under the influence of perovskite dielectric environment: Electrostatic approximation

    Energy Technology Data Exchange (ETDEWEB)

    Pathak, Nilesh Kumar; Sharma, R. P. [Centre for Energy Studies, Indian Institute of Technology, Delhi-110016 (India)

    2016-05-23

    We have systematically study the nano-plasmonic coupling to the perovskite (CH{sub 3}NH{sub 3}PbI{sub 3}) dielectric media in terms of surface plasmon resonance. The surface plasmon resonances are exhibited by the metal nanoparticles which is the electromagnetic excitation conduction electron when it is irradiated by incident light photon. Tunable behaviour of SPRs can be utilized to enhance the absorption of photon inside the surrounding environment in the wavelength range 300 to 800 nm. We have been selected two different types of nanogeometry such as coated and non-coated metal nanoparticles (radii ranges from 10 to 15 nm) to understand the plasmonic interaction to the dielectric media. Finally, we have observed that the coated nanogeometry is more preferable as compared to non-coated system to analyse the tunability of SPR peaks.

  6. QT and JT dispersion and cardiac performance in children with neonatal Bartter syndrome: a pilot study.

    Science.gov (United States)

    Hacihamdioglu, Duygu Ovunc; Fidanci, Kursat; Kilic, Ayhan; Gok, Faysal; Topaloglu, Rezan

    2013-10-01

    QT dispersion and JT dispersion are simple noninvasive arrhythmogenic markers that can be used to assess the homogeneity of cardiac repolarization. The aim of this study was to assess QT and JT dispersion and their relation with left ventricular systolic and diastolic functions in children with Bartter syndrome (BS). Nine neonatal patients with BS (median age 9.7 years) and 20 controls (median age 8 years) were investigated at rest. Both study and control subjects underwent electrocardiography (ECG) in which the interval between two R waves and QT intervals, corrected QT, QT dispersion, corrected QT dispersion, JT, corrected JT, JT dispersion and corrected JT dispersion were measured with 12-lead ECG. Two-dimensional, Doppler echocardiographic examinations were performed. Patients and controls did not differ for gender and for serum levels of potassium, magnesium, and calcium (p > 0.05). Both study and control subjects had normal echocardiographic examination and baseline myocardial performance indexes. The QT dispersion and JT dispersion were significantly prolonged in patients with BS compared to those of the controls {37.5 ms [interquartile range (IQR) 32.5-40] vs. 25.5 ms (IQR 20-30), respectively, p = 0.014 and 37.5 ms (IQR 27.5-40) vs. 22.5 ms (IQR 20-30), respectively, p = 0.003}. Elevated QT and JT dispersion during asymptomatic and normokalemic periods may be risk factors for the development of cardiac complications and arrhythmias in children with BS. In these patients the need for systematic cardiac screening and management protocol is extremely important for effective prevention.

  7. Modelling and tracer studies of atmospheric dispersion and deposition in regions of complex topography

    International Nuclear Information System (INIS)

    Norden, C.E.

    1981-11-01

    An indium tracer aerosol generating apparatus based on an alcohol/oxygen burner, and an analytical procedure by which filter samples containing tracer material could be analysed quantitatively by means of neutron activation analysis, were developed for use in atmospheric dispersion and deposition studies. A number of series of atmospheric dispersion experiments were conducted in the Richards Bay and Koeberg- Cape Town areas. The results are given, comparing the airbone tracer concentrations measured at ground level with values predicted by means of a numerical model, utilising two to three schemes, varying in sophistication, for calculating the dispersion coefficients. Recommendations are given regarding a dispersion model and dispersion coefficients for regular use in the Koeberg area, and ways for estimating plume trajectories

  8. studies dielectric behaviour of some long chain alcohols and their mixtures with a non-polar solvent at various concentration

    International Nuclear Information System (INIS)

    Yaqub, M.; Ahmed, S.S.; Hussain, A.

    2006-01-01

    Dielectric constant, refractive index and the Kirkwood linear correlation factor of 1-propanol, 1-butanol and 1-pentanol in mixtures with carbon tetrachloride at various concentration have been measured at fixed frequency (100 KHz) at 303.15 K. For the study of dielectric properties of polar molecules in a non-polar solvent at different concentrations, polarization per unit volume and excess free-energy of mixing were evaluated at this temperature. In order to study the association of polar molecules in such a non-polar solvent, the Kirkwood correlation factor (g) between molecular pairs, which exists due to the hydrogen bond association suggesting the presence of some dimension in the liquid phase with a number of dimmers, was determined. The refractive index and dielectric constant measurements are expected to shed some light on the configuration of molecules in various mixtures, and give some idea about the specific interactions between components, which decrese with the increase in the concentration of alcohol. All the three mixtures showed different behaviour for the value of correlation factor (g) as a function of concentration. The response of 1-pentanol was broadly identical to that of small chain alcohols. The different behaviour of the correlation factor (g) was interpreted in terms of the Kirkwood-Frohlich theory, as it takes into account, explicitly, such type of short and long range interactions of a mixture of polar molecules with non-polar solvents. (author)

  9. Dielectric relaxation studies in 5CB nematic liquid crystal at 9 GHz ...

    Indian Academy of Sciences (India)

    Resonance width, shift in resonance frequency, relaxation time and activation energy of 5CB nematic liquid crystal are measured using microwave cavity technique under the influence of an external magnetic field at 9 GHz and at different temperatures. The dielectric response in liquid crystal at different temperatures and ...

  10. A first-principles study of the dielectric properties of TiO{sub 2} polymorphs

    Energy Technology Data Exchange (ETDEWEB)

    Thilagam, A; Simpson, D J; Gerson, A R, E-mail: Thilagam.Lohe@unisa.edu.au, E-mail: Darren.Simpson@unisa.edu.au, E-mail: Andrea.Gerson@unisa.edu.au [Minerals and Materials Science and Technology, Mawson Institute, Division of IEEE, University of South Australia, Mawson Lakes Campus, South Australia 5095 (Australia)

    2011-01-19

    We present an analysis of the dielectric properties of the three polymorphs of TiO{sub 2} (rutile, anatase and brookite phases), using ab initio time-dependent density functional perturbation theory based on the Vignale-Kohn functional. We implement this functional, which incorporates many-body effects, using the periodic program BAND. The improved result for the density of states spectra for brookite is suggestive of increased titanium ion Jahn-Teller effects for this phase. The imaginary and real components of the frequency-dependent dielectric functions show notable dielectric anisotropies, with implications for excitonic interactions, for all three common phases of TiO{sub 2}. Comparison of the electron energy-loss spectrum for undoped and doped rutile and anatase reveals the critical role of collective charge excitations in photocatalytic mechanisms. The correlation between plasmon peaks present at lower energies and decreased photocatalytic activity due to substitutional aluminum doping in combination with oxygen vacancies in rutile and anatase is highlighted. Moreover, there is clear correlation between dielectric properties and the microstructure of the TiO{sub 2} polymorphs as suggested via the framework of the Born effective charge and Hirshfeld charge distribution schemes.

  11. A first-principles study of the dielectric properties of TiO2 polymorphs

    International Nuclear Information System (INIS)

    Thilagam, A; Simpson, D J; Gerson, A R

    2011-01-01

    We present an analysis of the dielectric properties of the three polymorphs of TiO 2 (rutile, anatase and brookite phases), using ab initio time-dependent density functional perturbation theory based on the Vignale-Kohn functional. We implement this functional, which incorporates many-body effects, using the periodic program BAND. The improved result for the density of states spectra for brookite is suggestive of increased titanium ion Jahn-Teller effects for this phase. The imaginary and real components of the frequency-dependent dielectric functions show notable dielectric anisotropies, with implications for excitonic interactions, for all three common phases of TiO 2 . Comparison of the electron energy-loss spectrum for undoped and doped rutile and anatase reveals the critical role of collective charge excitations in photocatalytic mechanisms. The correlation between plasmon peaks present at lower energies and decreased photocatalytic activity due to substitutional aluminum doping in combination with oxygen vacancies in rutile and anatase is highlighted. Moreover, there is clear correlation between dielectric properties and the microstructure of the TiO 2 polymorphs as suggested via the framework of the Born effective charge and Hirshfeld charge distribution schemes.

  12. Ab-initio study of the dielectric response of high-permittivity perovskites for energy storage

    International Nuclear Information System (INIS)

    Do-Amaral-De-Andrade-Sophia, Gustavo

    2014-01-01

    Many of materials based on transition metals have a wide range of applications, such as the storage of energy, due to their peculiar properties (high-dielectric constants, ferro-electricity,...). The knowledge of their bulk properties is essential in designing targeted devices with high performance. For instance, ABO 3 perovskites are peculiarly interesting for their atomic structural flexibility, allowing high number of atoms substitution and giving them specific chemical and electrical properties compared to the pure compounds. In this context, first principles calculations can be useful to understand the structural and electronic properties of these materials. The pressure-induced giant dielectric anomaly of ABO 3 perovskites has been investigated at the ab initio level. Its mechanism has been analyzed in terms of thermodynamic phase stability, structural and phonon contributions and Born effective charges. It is shown that the IR-active soft phonon is responsible for the anomaly. This mode always involves a displacement and a deformation of the oxygen octahedra, while the roles of A and B ions vary among the materials and between high- and low-pressure phase transitions. A sharp increase in the phonon amplitude near the phase transition gives rise to the dielectric anomaly. The use of hybrid functionals is required for agreement with experimental data. The calculations show that the dielectric anomaly in the pressure-induced phase transitions of these perovskites is a property of the bulk material. (author)

  13. Study made of dielectric properties of promising materials for cryogenic capacitors

    Science.gov (United States)

    Mathes, K. N.; Minnich, S. H.

    1967-01-01

    Experimental investigations were conducted to determine dielectric properties of promising materials for cryogenic capacitors to be used in energy storage and pulse applications. The three classes of materials investigated were inorganic bonded ferroelectric materials, anodic coatings on metal foils, and polar low temperature liquids.

  14. 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.

  15. Ab initio molecular dynamics study of temperature and pressure-dependent infrared dielectric functions of liquid methanol

    Directory of Open Access Journals (Sweden)

    C. C. Wang

    2017-03-01

    Full Text Available The temperature and pressure-dependent dielectric functions of liquids are of great importance to the thermal radiation transfer and the diagnosis and control of fuel combustion. In this work, we apply the state-of-the-art ab initio molecular dynamics (AIMD method to calculate the infrared dielectric functions of liquid methanol at 183–573 K and 0.1–160 MPa in the spectral range 10−4000 cm−1, and study the temperature and pressure effects on the dielectric functions. The AIMD approach is validated by the Infrared Variable Angle Spectroscopic Ellipsometry (IR-VASE experimental measurements at 298 K and 0.1 MPa, and the proposed IR-VASE method is verified by comparison with paper data of distilled water. The results of the AIMD approach agrees well with the experimental values of IR-VASE. The experimental and theoretical analyses indicate that the temperature and pressure exert a noticeable influence on the infrared dielectric functions of liquid methanol. As temperature increases, the average molecular dipole moment decreases. The amplitudes of dominant absorption peaks reduce to almost one half as temperature increases from 183 to 333 K at 0.1 MPa and from 273 to 573 K at 160 MPa. The absorption peaks below 1500 cm–1 show a redshift, while those centered around 3200 cm–1 show a blueshift. Moreover, larger average dipole moments are observed as pressure increases. The amplitudes of dominant absorption peaks increase to almost two times as pressure increases from 1 to 160 MPa at 373 K.

  16. A comparative study on thermal, mechanical and dielectric characteristics of low density polyethylene crosslinked by radiation and chemical methods

    International Nuclear Information System (INIS)

    Kim, B.H.; Ling, D.Y.; Kim, J.S.

    1976-01-01

    A comparative study on thermal, static mechanical and dielectric characteristics were made over a temperature range of ca. 20 0 C to 320 0 C and a frequency range of KHZ band on low density polyethylene specimens crosslinked, respectively, by radiation and chemical method. The thermal property of both specimens shows that softening point appears to unchange by crosslinking however, melting and liquidizing temperatures attain rapid increase at the imitation of crosslinking. Mechanical properties show little difference to both specimens crosslinked by different method, further the behaviors were discussed in connection with the relaxation of molecular segments in amorphous phase. Dose dependent dielectric characteristics observed at ambient temperature under several fixed frequencies exhibit extremities at ca. 20 Mrad and the behaviors also were interpreted qualitatively by taking into consideration of dipole concentration change in amorphous phase together with the role of specimen geometry to the depth of oxidative layer. Observing frequency dependent dielectric characteristics, it was also proved that ionic conduction loss is appreciably greater in the specimen prepared by chemical method than that by radiation. (author)

  17. Cluster synthesis of monodisperse rutile-TiO2 nanoparticles and dielectric TiO2-vinylidene fluoride oligomer nanocomposites

    International Nuclear Information System (INIS)

    Balasubramanian, Balamurugan; Kraemer, Kristin L; Valloppilly, Shah R; Ducharme, Stephen; Sellmyer, David J

    2011-01-01

    The embedding of oxide nanoparticles in polymer matrices produces a greatly enhanced dielectric response by combining the high dielectric strength and low loss of suitable host polymers with the high electric polarizability of nanoparticles. The fabrication of oxide-polymer nanocomposites with well-controlled distributions of nanoparticles is, however, challenging due to the thermodynamic and kinetic barriers between the polymer matrix and nanoparticle fillers. In the present study, monodisperse TiO 2 nanoparticles having an average particle size of 14.4 nm and predominant rutile phase were produced using a cluster-deposition technique without high-temperature thermal annealing and subsequently coated with uniform vinylidene fluoride oligomer (VDFO) molecules using a thermal evaporation source, prior to deposition as TiO 2 -VDFO nanocomposite films on suitable substrates. The molecular coatings on TiO 2 nanoparticles serve two purposes, namely to prevent the TiO 2 nanoparticles from contacting each other and to couple the nanoparticle polarization to the matrix. Parallel-plate capacitors made of TiO 2 -VDFO nanocomposite film as the dielectric exhibit minimum dielectric dispersion and low dielectric loss. Dielectric measurements also show an enhanced effective dielectric constant in TiO 2 -VDFO nanocomposites as compared to that of pure VDFO. This study demonstrates for the first time a unique electroactive particle coating in the form of a ferroelectric VDFO that has high-temperature stability as compared to conventionally used polymers for fabricating dielectric oxide-polymer nanocomposites.

  18. Dielectric function of semiconductor superlattice

    International Nuclear Information System (INIS)

    Qin Guoyi.

    1990-08-01

    We present a calculation of the dielectric function for semiconductor GaAs/Ga 1-x Al x As superlattice taking account of the extension of the electron envelope function and the difference of both the dielectric constant and width between GaAs and Ga 1-x Al x As layers. In the appropriate limits, our results exactly reduce to the well-known results of the quasi two-dimensional electron gas obtained by Lee and Spector and of the period array of two-dimensional electron layers obtained by Das Sarma and Quinn. By means of the dielectric function of the superlattice, the dispersion relation of the collective excitation and the screening property of semiconductor superlattice are discussed and compared with the results of the quasi two-dimensional system and with the results of the periodic array of the two-dimensional electron layers. (author). 4 refs, 3 figs

  19. Injector and beam transport simulation study of proton dielectric wall accelerator

    International Nuclear Information System (INIS)

    Zhao, Quantang; Yuan, P.; Zhang, Z.M.; Cao, S.C; Shen, X.K.; Jing, Y.; Ma, Y.Y.; Yu, C.S.; Li, Z.P.; Liu, M.; Xiao, R.Q.; Zhao, H.W.

    2012-01-01

    A simulation study of a short-pulsed proton injector for, and beam transport in, a dielectric wall accelerator (DWA) has been carried out using the particle-in-cell (PIC) code Warp. It was shown that applying “tilt pulse” voltage waveforms on three electrodes enables the production of a shorter bunch by the injector. The fields in the DWA beam tube were simulated using Computer Simulation Technology’s Microwave Studio (CST MWS) package, with various choices for the boundary conditions. For acceleration in the DWA, the beam transport was simulated with Warp, using applied fields obtained by running CST MWS. Our simulations showed that the electric field at the entrance to the DWA represents a challenging issue for the beam transport. We thus simulated a configuration with a mesh at the entrance of the DWA, intended to improve the entrance field. In these latter simulations, a proton bunch was successfully accelerated from 130 keV to about 36 MeV in a DWA with a length of 36.75 cm. As the beam bunch progresses, its transverse dimensions diminish from (roughly) 0.5×0.5 cm to 0.2×0.4 cm. The beam pulse lengthens from 1 cm to 2 cm due to lack of longitudinal compression fields. -- Highlights: ► A pulse proton injector with tilt voltages on the three electrodes was simulated. ► The fields in different part of the DWA were simulated with CST and analyzed. ► The proton beam transport in DWA was simulated with Warp successfully. ► The simulation can help for designing a real DWA.

  20. Conductivity percolation in loosely compacted microcrystalline cellulose: An in situ study by dielectric spectroscopy during densification.

    Science.gov (United States)

    Nilsson, Martin; Frenning, Göran; Gråsjö, Johan; Alderborn, Göran; Strømme, Maria

    2006-10-19

    The present study aims at contributing to a complete understanding of the water-induced ionic charge transport in cellulose. The behavior of this transport in loosely compacted microcrystalline cellulose (MCC) powder was investigated as a function of density utilizing a new type of measurement setup, allowing for dielectric spectroscopy measurement in situ during compaction. The ionic conductivity in MCC was found to increase with increasing density until a leveling-out was observed for densities above approximately 0.7 g/cm3. Further, it was shown that the ionic conductivity vs density followed a percolation type behavior signifying the percolation of conductive paths in a 3D conducting network. The density percolation threshold was found to be between approximately 0.2 and 0.4 g/cm3, depending strongly on the cellulose moisture content. The observed percolation behavior was attributed to the forming of interparticulate bonds in the MCC and the percolation threshold dependence on moisture was linked to the moisture dependence of particle rearrangement and plastic deformation in MCC during compaction. The obtained results add to the understanding of the density-dependent water-induced ionic transport in cellulose showing that, at given moisture content, the two major parameters determining the magnitude of the conductivity are the connectedness of the interparticluate bonds and the connectedness of pores with a diameter in the 5-20 nm size range. At densities between approximately 0.7 and 1.2 g/cm3 both the bond and the pore networks have percolated, facilitating charge transport through the MCC compact.

  1. Hydrothermal assisted growth of CdSe nanoparticles and study on its dielectric properties

    Science.gov (United States)

    Jamble, Shweta N.; Ghoderao, Karuna P.; Kale, Rohidas B.

    2017-11-01

    In this work, we have synthesized cadmium selenide (CdSe) nanoparticles by using cadmium chloride (CdCl2) as cadmium ion and sodium selenosulfate (Na2SeSO3) as selenium ion sources through a simple, convenient and cost-effective hydrothermal route at 180 °C temperature for 24 h. Aqueous ammonia was employed as a complex reagent to adjust the pH of the solution. Structural analysis of the obtained product was carried out by using x-ray diffractometer, which revealed that the final product has a cubic structure of CdSe with average crystallite size 13.15 nm. The cauliflower-like CdSe nanostructures were confirmed from the scanning electron microscopy and high-resolution transmission electron microscopy. EDS analysis indicates that the obtained product has a good elemental stoichiometric ratio. The electron diffraction pattern reveals the polycrystalline nature of CdSe. From UV-visible absorption spectral analysis, the optical energy bandgap of CdSe nanoparticles was found to be 1.90 eV. XPS spectra presented Cd 3d3/2, Cd 3d5/2 and Se 3d3/2 peaks at 411.04, 404.29 and 53.52 eV respectively. The CdSe nanoparticles exhibit photoluminescence with two distinct emission bands at 632 nm and 720 nm. FTIR study was used towards the understanding of the formation mechanism and bonding on the surface of the resulting nanoparticles. The dielectric properties of a pelletized sample of CdSe nanoparticles were carried out at room temperature.

  2. Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Zhang, Meiyun; Long, Shibing [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Lian, Xiaojuan; Miao, Feng [National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Larcher, Luca [DISMI, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (Italy); Wu, Ernest [IBM Research Division, Essex Junction, Vermont 05452 (United States)

    2016-01-04

    Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.

  3. Marine radioactivity studies in the Suez Canal: Modelling hydrodynamics and dispersion

    International Nuclear Information System (INIS)

    Abril, J.M.; Abdel-Aal, M.M.

    1999-01-01

    This paper comprises the work carried out under the IAEA Technical Co-operation Project EGY/07/002. The main goal was to develop a modelling study on the dispersion of radioactive pollution in the Suez Canal

  4. Dielectric relaxation study of the dynamics of monosaccharides: D-ribose and 2-deoxy-D-ribose

    Energy Technology Data Exchange (ETDEWEB)

    Kaminski, K; Kaminska, E; Wlodarczyk, P; Paluch, M; Ziolo, J [Institute of Physics, Silesian University, ulica Uniwersytecka 4, 40-007 Katowice (Poland); Ngai, K L [Naval Research Laboratory, Washington, DC 20375-5320 (United States)

    2008-08-20

    The dielectric loss spectra of two closely related monosaccharides, D-ribose and 2-deoxy-D-ribose, measured at ambient and elevated pressures are presented. 2-deoxy-D-ribose and D-ribose are respectively the building blocks of the backbone chains in the nucleic acids DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Small differences in the structure between D-ribose and 2-deoxy-D-ribose result in changes of the glass transition temperature T{sub g}, as well as the dielectric strength and activation enthalpy of the secondary relaxations. However, the frequency dispersion of the structural {alpha}-relaxation for the same relaxation time remains practically the same. Two secondary relaxations are present in both sugars. The slower secondary relaxation shifts to lower frequencies with increasing applied pressure, but not the faster one. This pressure dependence indicates that the slower secondary relaxation is the important and 'universal' Johari-Goldstein {beta}-relaxation of both sugars according to one of the criteria set up to classify secondary relaxations. Additional confirmation of this conclusion comes from good agreement of the observed relaxation time of the slower secondary relaxation with the primitive relaxation time calculated from the coupling model. All the dynamic properties of D-ribose and 2-deoxy-D-ribose are similar to the other monosaccharides, glucose, fructose, galactose and sorbose, except for the much larger relaxation strength of the {alpha}-relaxation of the former compared to the latter. The difference may distinguish the chemical and biological functions of D-ribose and 2-deoxy-D-ribose from the other monosaccharides.

  5. Studies on Dissolution Enhancement of Prednisolone, a Poorly Water-Soluble Drug by Solid Dispersion Technique

    Directory of Open Access Journals (Sweden)

    Parvin Zakeri-Milani

    2011-06-01

    Full Text Available Introduction: Prednisolone is a class II substance according to the Biopharmaceutics Classification System. It is a poorly water soluble agent. The aim of the present study was to improve dissolution rate of a poorly water-soluble drug, prednisolone, by a solid dispersion technique. Methods: Solid dispersion of prednisolone was prepared with PEG 6000 or different carbohydrates such as lactose and dextrin with various ratios of the drug to carrier i.e., 1:10, 1:20 and 1:40. Solid dispersions were prepared by coevaporation method. The evaluation of the properties of the dispersions was performed using dissolution studies, Fourier-transform infrared spectroscopy and x-ray powder diffractometery. Results: The results indicated that lactose is suitable carriers to enhance the in vitro dissolution rate of prednisolone. The data from the x-ray diffraction showed that the drug was still detectable in its solid state in all solid dispersions except solid dispersions prepared by dextrin as carrier. The results from infrared spectroscopy showed no well-defined drug–carrier interactions for coevaporates. Conclusion: Solid dispersion of a poorly water-soluble drug, prednisolone may alleviate the problems of delayed and inconsistent rate of dissolution of the drug.

  6. The effect of organo-clay on the dielectric properties of silicone rubber

    International Nuclear Information System (INIS)

    Razzaghi-Kashani, M; Gharavi, N; Javadi, S

    2008-01-01

    Dielectric elastomers are highly deformable and fast response smart materials capable of actuation under electric fields. Among commercially available dielectric elastomers, silicone rubber can be compounded with different fillers in order to modify its electrical and mechanical properties. To study the effect of organically modified montmorillonite (OMMT) on the dielectric properties of silicone rubber, OMMT was added to this rubber at two levels, 2% and 5%, using two methods, low-shear and high-shear mixing. Composites were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The XRD patterns showed different crystallite structures for silicate platelets in the rubber matrix as a result of the two different mixing methods. In low-shear mixing, the ordered crystallite structure of the clay remains almost unchanged, whereas in high-shear mixing it loses its ordered structure, leading to the disappearance of the diffraction peaks. SEM and AFM micrographs depicted better dispersion and more uniform distribution of the organo-clay under high-shear mixing compared to those obtained by low-shear mixing. The tensile properties also confirmed the different degree of dispersion of the nano-clay resulting from the two different methods of mixing. The dielectric properties of the composites were measured under AC electric fields, and the results were compared with reference silicone rubbers with no OMMT. It was shown that the order of organo-clay layers in the less dispersed structure of the clay imparts an additional ionic polarization and higher dielectric permittivity compared to the case where the clay layers are more dispersed and lost their order. The storage and loss dielectric constants of base silicone rubber increase when it is compounded with OMMT

  7. Numerical study on general dispersion relation of anisotropic and weakly relativistic plasma

    International Nuclear Information System (INIS)

    Ke Fujiu; Chen Yanping

    1987-01-01

    The key problem in heating and instability studies in plasma physics is to obtain dispersive equation and its solution. This paper presents the general dispersive equation and corresponding procedure for electromagnetic wave which nearly poloidally impinges on anisotropic, weakly relativistic Maxwellian plasma with inhomogeneous density in nonuniform magnetic field (such as plasma in TOKAMAK). The double index function F ij , significant in plasma physics, was expanded as single index function F 1 , and then the values were calculated by means of dispersive function. It was also pointed out that the severe error would be involved in the calculation of F ij from recurrence relation of F 11

  8. Radiotracer study to investigate the dilution and dispersion of sewage off Worli coast

    International Nuclear Information System (INIS)

    Yelgaonkar, V.N.; Pendharkar, A.S.; Agashe, S.M.; Kumar, U.S.; Kulkarni, U.P.; Mendhekar, G.N.; Navada, S.V.

    1998-01-01

    Radiotracer experiments were carried out off Worli Coast, Mumbai to study the dilution and dispersion of sewage from the proposed out fall at 3000 m and existing out fall at 500 m from the shore. Dilutions observed were 2.3 x 10 7 at 3.3 km from the injection point for the disposal at 3,000 m and 6.9 x 10 5 at 5 km for the disposal at 500 m. Dispersion coefficients obtained from two dimensional advection dispersion model for the experiment off 500 m are Dx 15-18 m 2 /s and Dy = 0.5-2 m 2 /s. (author)

  9. Numerical study of the Kadomtsev-Petviashvili equation and dispersive shock waves

    Science.gov (United States)

    Grava, T.; Klein, C.; Pitton, G.

    2018-02-01

    A detailed numerical study of the long time behaviour of dispersive shock waves in solutions to the Kadomtsev-Petviashvili (KP) I equation is presented. It is shown that modulated lump solutions emerge from the dispersive shock waves. For the description of dispersive shock waves, Whitham modulation equations for KP are obtained. It is shown that the modulation equations near the soliton line are hyperbolic for the KPII equation while they are elliptic for the KPI equation leading to a focusing effect and the formation of lumps. Such a behaviour is similar to the appearance of breathers for the focusing nonlinear Schrödinger equation in the semiclassical limit.

  10. Study of line source characteristics for 2-D physical modelling of pollutant dispersion in street canyons

    Energy Technology Data Exchange (ETDEWEB)

    Meroney, Robert N. [Fluid Mechanics and Wind Engineering Program, Civil Engineering Department, Colorado State University Fort Collins, CO (United States); Pavageau, Michel; Rafailidis, Stilianos; Schatzmann, Michael [Meteorologisches Institut, Universitaet Hamburg, Hamburg (Germany)

    1996-08-01

    The University of Hamburg initiated a wind tunnel study of car exhaust dispersion from street canyons in an urban environment to investigate how pollution dispersion is affected by street geometry. Particular emphasis at the beginning of this work was put on the design of a line source to represent traffic exhaust. Pollution dispersion was studied in two dimensions (i.e., infinite-length streets were assumed). The case of an isolated street canyon in open country was examined first. The same street canyon geometry was subsequently studied in an urban environment, i.e., with additional canyons of similar geometry upstream and downstream of the test street. The dynamic and dispersion characteristics of the flow in the two cases were quite different. In the canyon amidst open country we observed better canyon ventilation than in the urban roughness case

  11. Theoretical Study of Local Surface Plasmon Resonances on a Dielectric-Ag Core-Shell Nanosphere Using the Discrete-Dipole Approximation Method

    International Nuclear Information System (INIS)

    Ma Ye-Wan; Wu Zhao-Wang; Zhang Li-Hua; Liu Wan-Fang; Zhang Jie

    2015-01-01

    The local surface plasmon resonances (LSPRs) of dielectric-Ag core-shell nanospheres are studied by the discretedipole approximation method. The result shows that LSPRs are sensitive to the surrounding medium refractive index, which shows a clear red-shift with the increasing surrounding medium refractive index. A dielectric-Ag core-shell nanosphere exhibits a strong coupling between the core and shell plasmon resonance modes. LSPRs depend on the shell thickness and the composition of dielectric-core and metal-shell. LSPRs can be tuned over a longer wavelength range by changing the ratio of core to shell value. The lower energy mode ω_− shows a red-shift with the increasing dielectric-core value and the inner core radius, while blue-shifted with the increasing outer shell thickness. The underlying mechanisms are analyzed with the plasmon hybridization theory and the phase retardation effect. (paper)

  12. Dielectric studies on cerium doped BaLa2Ti3O10

    Directory of Open Access Journals (Sweden)

    Parshuram B. Abhange

    2015-12-01

    Full Text Available The BaLa2-xCexTi3O10 samples (with x = 0.2, 0.4, 0.6 and 0.8 were prepared by hydroxide co-precipitation method and finally sintered at 1150 °C. The structure of the prepared samples was characterized by XRD and SEM. The single phase material was confirmed only for the BaLa1.8Ce0.2Ti3O10 ceramics. However, at higher cerium concentration secondary phase was observed. The characteristic plate-like structure, having grains with submicrometer thickness and high aspect ratio, was clearly observed by SEM. The results of dielectric measurement suggest that the appropriate adjustment of doping (with x between 0.2 and 0.8 will give sufficient high dielectric constant at very low loss. The resistivity of samples decreases with increase in temperature indicating the normal semiconducting electrical behaviour.

  13. Study of high-k gate dielectrics by means of positron annihilation

    International Nuclear Information System (INIS)

    Uedono, A.; Naito, T.; Otsuka, T.; Ito, K.; Shiraishi, K.; Yamabe, K.; Miyazaki, S.; Watanabe, H.; Umezawa, N.; Hamid, A.; Chikyow, T.; Ohdaira, T.; Suzuki, R.; Ishibashi, S.; Inumiya, S.; Kamiyama, S.; Akasaka, Y.; Nara, Y.; Yamada, K.

    2007-01-01

    High-dielectric constant (high-k) gate materials, such as HfSiO x and HfAlO x , fabricated by atomic-layer-deposition techniques were characterized using monoenergetic positron beams. Measurements of the Doppler broadening spectra of annihilation radiation and the lifetime spectra of positrons indicated that positrons annihilated from the trapped state by open volumes that exist intrinsically in amorphous structures of the films. The size distributions of the open volumes and the local atomic configurations around such volumes can be discussed using positron annihilation parameters, and they were found to correlate with the electrical properties of the films. We confirmed that the positron annihilation is useful technique to characterize the matrix structure of amorphous high-k materials, and can be used to determine process parameters for the fabrication of high-k gate dielectrics. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Study of a Modified AC Bridge Technique for Loss Angle Measurement of a Dielectric Material

    Directory of Open Access Journals (Sweden)

    S. C. BERA

    2008-09-01

    Full Text Available A Wheatstone’s bridge network like Schering Bridge, DeSauty Bridge etc measures the loss angle or tangent of loss angle (tanδ of a dielectric material. In high voltage application this loss angle is generally measured by high voltage Schering Bridge. But continuous measurement of tan δ is not possible by these techniques. In the present paper a modified operational amplifiers based Schering Bridge network has been proposed for continuous measurement of tanδ in the form of a bridge network output voltage. Mathematical analysis of the proposed bridge network has been discussed in the paper and experimental work has been performed assuming the lossy dielectric material as a series combination of loss less capacitor and a resistor. Experimental results are reported in the paper. From the mathematical analysis and experimental results it is found that the output of the proposed bridge network is almost linearly related with tanδ.

  15. Raman spectroscopy and dielectric Studies of multiple phase transitions in ZnO:Ni

    Science.gov (United States)

    Yadav, Harish Kumar; Sreenivas, K.; Gupta, Vinay; Scott, J. F.; Katiyar, R. S.

    2008-03-01

    We present Raman and dielectric data on Ni-doped ZnO (Zn1-xNixO) ceramics as a function of Ni concentration (x =0.03, 0.06, and 0.10) and temperature. A mode (around 130cm-1) is identified as TA(M) [J. M. Calleja and M. Cardona, Phys. Rev. B 16, 3753 (1977)] and appears due to an antiferromagnetic phase transition at low temperatures (100K) via the spin-orbit mechanism [P. Moch and C. Dugautier, Phys. Lett. A 43, 169 (1973)]. A strong dielectric anomaly occurs at around 430-460K, depending on Ni concentration, and is due to extrinsic electret effects (Ni ionic conduction) and not to a ferroelectric phase transition.

  16. Dielectric, electrical and infrared studies of γ-Fe2O3 prepared by ...

    Indian Academy of Sciences (India)

    Unknown

    Murthy V R K 1990 Low frequency dielectric properties of ferrites (eds) V R K Murthy and B Viswanatham (New. Delhi: Narosa Publication) Ch. IV, ed. 1. Murthy V R K and Sobhanadri J 1976 J. Phys. Status Solidi. (a)36k 133. Rahman M M and Venkataraman A 2002 J. Therm. Anal. Cal. 68 91. Rane K S, Verenkar V M S and ...

  17. Second harmonic generation and dielectric study of the fine and coarse grain PMN-35PT ceramics

    Czech Academy of Sciences Publication Activity Database

    Kroupa, Jan; Bovtun, Viktor; Nuzhnyy, Dmitry; Savinov, Maxim; Vaněk, Přemysl; Kamba, Stanislav; Petzelt, Jan; Holc, J.; Kosec, M.; Amorin, H.; Alguero, M.

    2008-01-01

    Roč. 81, 11-12 (2008), s. 1059-1064 ISSN 0141-1594 R&D Projects: GA ČR(CZ) GA202/06/0403; GA MŠk OC 101 Institutional research plan: CEZ:AV0Z10100520 Keywords : relaxor ferroelectrics * phase transitions * PMN-PT * SHG * dielectric Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.201, year: 2008

  18. Dielectric study on hierarchical water structures restricted in cement and wood materials

    International Nuclear Information System (INIS)

    Abe, Fumiya; Nishi, Akihiro; Saito, Hironobu; Asano, Megumi; Watanabe, Seiei; Kita, Rio; Shinyashiki, Naoki; Yagihara, Shin; Fukuzaki, Minoru; Sudo, Seiichi; Suzuki, Youki

    2017-01-01

    Dielectric relaxation processes for mortar observed by broadband dielectric spectroscopy were analyzed in the drying and hydration processes for an aging sample in the frequency region from 1 MHz up to 2 MHz. At least two processes for structured water in the kHz frequency region and another mHz relaxation process affected by ionic behaviors were observed. Comparison of the relaxation parameters obtained for the drying and hydration processes suggests an existence of hierarchical water structures in the exchange of water molecules, which are originally exchanged from free water observed at around 20 GHz. The water molecules reflected in the lower frequency process of the two kHz relaxation processes are more restricted and take more homogeneous structures than the higher kHz relaxation process. These structured water usually hidden in large ionic behaviors for wood samples was observed by electrodes covered by a thin Teflon film, and hierarchical water structures were also suggested for wood samples. Dielectric spectroscopy technique is an effective tool to analyze the new concept of hierarchical water structures in complex materials. (paper)

  19. Survey of literature on dispersion ratio and collection ratio of radioisotopes in animal study using radioisotopes

    International Nuclear Information System (INIS)

    Tozuka, Zenzaburo; Doi, Masahiro; Miyazawa, Eiji; Kawakami, Takeo

    1998-01-01

    A survey of literature in the title was performed to know the actual status of the dispersion from excretion and expiration studies of radioisotopes since, at present, the probable dispersion ratio is assumed to be 100% in calculation for legally permitted use of radioisotopes which conceivably being far from the real status and being incompatible with the guideline for pharmacokinetic studies requiring the recovery of >95% of dosed radioactivity in balance study. There are two interpretations for the dispersion; it is the expiration ratio and it is the fraction unrecovered. Survey was done on 11 Japanese and foreign journals in 1985-1996 publishing most of pharmacokinetic studies and on 650 compounds in 358 facilities with 1,975 experiments in total. In those experiments, the total recovery of radioactivity was 95% in average, unrecovered fraction, 5% and expiration ratio, 2%. As for unclide, 14 C, 3 H, 125 I and 35 S were surveyed since they occupied 99.4% of the experiments and their dispersion was <5%. Rats were used in 70% of the experiments and the dispersion in all animal experiments was about 5%. Administration route was regardless of the dispersion. (K.H.)

  20. A dielectric approach to high temperature superconductivity

    International Nuclear Information System (INIS)

    Mahanty, J.; Das, M.P.

    1989-01-01

    The dielectric response of an electron-ion system to the presence of a pair of charges is investigated. From the nature of the dielectric function, it is shown that a strong attractive pair formation is possible depending on the dispersion of the ion branches. The latter brings a reduction to the sound velocity which is used as a criterion for the superconductivity. By solving the BCS equation with the above dielectric function, we obtain a reasonable value of T/sub c/. 17 refs., 1 fig

  1. High Dielectric Constant Study of TiO2-Polypyrrole Composites with Low Contents of Filler Prepared by In Situ Polymerization

    Directory of Open Access Journals (Sweden)

    Khalil Ahmed

    2016-01-01

    Full Text Available TiO2/polypyrrole composites with high dielectric constant have been synthesized by in situ polymerization of pyrrole in an aqueous dispersion of low concentration of TiO2, in the presence of small amount of HCl. Structural, optical, surface morphological, and thermal properties of the composites were investigated by X-ray diffractometer, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, and thermogravimetric analysis, respectively. The data obtained from diffractometer and thermal gravimetric analysis confirmed the crystalline nature and thermal stability of the prepared composites. The dielectric constant of 5 wt% TiO2 increased with filler content up to 4.3 × 103 at 1 kHz and then decreased to 1.25 × 103 at 10 kHz.

  2. Ionic Structure at Dielectric Interfaces

    Science.gov (United States)

    Jing, Yufei

    The behavior of ions in liquids confined between macromolecules determines the outcome of many nanoscale assembly processes in synthetic and biological materials such as colloidal dispersions, emulsions, hydrogels, DNA, cell membranes, and proteins. Theoretically, the macromolecule-liquid boundary is often modeled as a dielectric interface and an important quantity of interest is the ionic structure in a liquid confined between two such interfaces. The knowledge gleaned from the study of ionic structure in such models can be useful in several industrial applications, such as biosensors, lithium-ion batteries double-layer supercapacitors for energy storage and seawater desalination. Electrostatics plays a critical role in the development of such functional materials. Many of the functions of these materials, result from charge and composition heterogeneities. There are great challenges in solving electrostatics problems in heterogeneous media with arbitrary shapes because electrostatic interactions remains unknown but depend on the particular density of charge distributions. Charged molecules in heterogeneous media affect the media's dielectric response and hence the interaction between the charges is unknown since it depends on the media and on the geometrical properties of the interfaces. To determine the properties of heterogeneous systems including crucial effects neglected in classical mean field models such as the hard core of the ions, the dielectric mismatch and interfaces with arbitrary shapes. The effect of hard core interactions accounts properly for short range interactions and the effect of local dielectric heterogeneities in the presence of ions and/or charged molecules for long-range interactions are both analyzed via an energy variational principle that enables to update charges and the medium's response in the same simulation time step. In particular, we compute the ionic structure in a model system of electrolyte confined by two planar dielectric

  3. Experimental and computational study of dielectric barrier discharges for environmental applications

    Science.gov (United States)

    Aerts, Robby

    Air pollution has become a major global concern which affects all inhabitants of our precious earth. Nowadays it is fact that our climate is changing and the sea level is rising. Moreover, we are facing an energy crisis because all our fossil fuel resources will sooner or later be running empty. It is clear that drastic measures are needed to keep our planet as it is today for generations to come. One of these measures is the 20-20-20 targets imposed by the European Commission, which stimulates the research for environmental energy applications. In this PhD dissertation two environmental applications of plasma technology are investigated. The first one is the abatement of flue gases, and more specifically the destruction of volatile organic compounds (VOCs). The second one is the conversion of CO2 into valuable chemicals. Both of these applications suffer from a large energy cost under classical (thermodynamic) conditions, due to the chemical stability of these molecules. Plasma technology is quite promising to overcome these thermodynamic barriers. Plasmas allow reactions at different time-scales with different species, such as electrons, ions, radicals, molecules and excited species, creating new chemical pathways. Indeed, in a plasma the applied electrical energy is directly transferred to the electrons, which activate the gas by ionization, excitation and dissociation, hence creating reactive species (ions, excited species, radicals), that can further easily undergo other chemical reactions. Especially gas discharges, which are low temperature plasmas, show promising results in the destruction of pollutants at mild conditions. A common type of gas discharge is the dielectric barrier discharge (DBD) which has been successfully scaled up for industrial ozone generation and is widely investigated in the field of environmental applications. The complexity of DBDs creates difficulties for experimental diagnostics and therefore numerical studies can help to improve

  4. Visualization Study of Melt Dispersion Behavior for SFR with a Metallic Fuel under Severe Accidents

    Energy Technology Data Exchange (ETDEWEB)

    Heo, Hyo Heo; Park, Seong Dae; Bang, In Cheol [Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of); Jerng, Dong Wook [Jungang Univ., Seoul (Korea, Republic of)

    2015-05-15

    The safety strategy provides negative reactivity driven by the melt dispersal, so it could reduce the possibility of the recriticality event under a severe triple or more fault scenario for SFR. Since the behavior of the melt dispersion is unpredictable, it depends on the accident condition, particularly core region. While the voided coolant channel region is usually developed in the inner core, the unvoided coolant channel region is formed in the outer core. It is important to confirm the fuel dispersion with the core region, but there are not sufficient existing studies for them. From the existing studies, the coolant vapor pressure is considered as one of driving force to move the melt towards outside of the core. There is a complexity of the phenomena during intermixing of the melt with the coolant after the horizontal melt injections. It is too difficult to understand the several combined mechanisms related to the melt dispersion and the fragmentation. The specific conditions to be well dispersed for the molten metallic fuel were discussed in the experiments with the simulant materials. The each melt behavior was compared to evaluate the melt dispersion under the coolant void condition and the boiling condition.

  5. Synthesis, spectral, thermal, optical dispersion and dielectric ...

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... ... fast atom bombardment-mass spectrometry, thermogravimetric/ differential thermal analysis, and ... In UV spectrum, the transmittance increases followed by a sharp decrease at wavelength 700–750 nm within visible range.

  6. Synthesis, spectral, thermal, optical dispersion and dielectric ...

    Indian Academy of Sciences (India)

    of nanocrystalline dimer complex (PEPyr–diCd) thin films as novel organic semiconductor .... iments were obtained by diethyl ether diffusion to a solution in CH2Cl2. Pale brown ...... A F 2004 Phosphorus Sulfur Silicon Relat. Elem. 179 1251.

  7. Investigation of the dielectric properties of shale

    International Nuclear Information System (INIS)

    Martemyanov, Sergey M.

    2011-01-01

    The article is dedicated to investigation of the dielectric properties of oil shale. Investigations for samples prepared from shale mined at the deposit in Jilin Province in China were done. The temperature and frequency dependences of rock characteristics needed to calculate the processes of their thermal processing are investigated. Frequency dependences for the relative dielectric constant and dissipation factor of rock in the frequency range from 0,1 Hz to 1 MHz are investigated. The temperature dependences for rock resistance, dielectric capacitance and dissipation factor in the temperature range from 20 to 600°C are studied. Key words: shale, dielectric properties, relative dielectric constant, dissipation factor, temperature dependence, frequency dependence

  8. Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications

    Science.gov (United States)

    Kádár, Roland; Abbasi, Mahdi; Figuli, Roxana; Rigdahl, Mikael; Wilhelm, Manfred

    2017-01-01

    The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate) (EBA) nanocomposite hybrids containing graphite nanoplatelets (GnP) and carbon black (CB). The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix. Evidence of the influence of dispersion properties was found in linear viscoelastic dynamic frequency sweeps, while the percolation of the nanocomposites was detected in nonlinearities developed in dynamic strain sweeps. Using extensional rheology, hybrid samples with better dispersion properties lead to a more pronounced strain hardening behavior, while samples with a higher volume percentage of fillers caused a drastic reduction in strain hardening. The rheo-dielectric time-dependent response showed that in the case of nanocomposites containing only GnP, the orientation dynamics leads to non-conductive samples. However, in the case of hybrids, the orientation of the GnP could be offset by the dispersing of the CB to bridge the nanoplatelets. The results were interpreted in the framework of a dual PE-BA model, where the fillers would be concentrated mainly in the BA regions. Furthermore, better dispersed hybrids obtained using mixing screws at the expense of filler distortion via extrusion processing history were emphasized through the rheo-dielectric tests. PMID:28336857

  9. Spectral, structural, optical and dielectrical studies of UV irradiated Rose Bengal thin films prepared by spin coating technique

    Energy Technology Data Exchange (ETDEWEB)

    Zeyada, H.M., E-mail: hzeyada@gmail.com [Department of Physics, Faculty of Science at New Damietta, University of Damietta, 34517 (Egypt); Youssif, M.I.; El-Ghamaz, N.A. [Department of Physics, Faculty of Science at New Damietta, University of Damietta, 34517 (Egypt); Aboderbala, M.E.O. [Department of Physics, Faculty of Science at New Damietta, University of Damietta, 34517 (Egypt); Department of Physics, Faculty of Science, AlJabl Al Gharbi University (Libya)

    2017-02-01

    Optical properties of pristine and UV irradiated Rose Bengal (RB) films have been investigated using transmittance and reflectance methods. The refractive index(n) and extinction coefficient (k) have been calculated from the absolute values of transmission and reflection spectrum. Single oscillator parameters and Drude model of free carrier absorption have been applied for analysis of the refractive index dispersion. Within the frame work of the band-to-band electron transitions theory; the fundamental absorption edge data were analyzed. Our results suggest that thickness of RB films has no effect on the absorption or the refractive indices in the investigated thicknesses range and within the experimental error. Structural transformation of films from amorphous to polycrystalline has been observed upon UV irradiation. Accordingly, the decreases of all of the absorption coefficient, the energy gap and the refractive index of RB films have been detected. Furthermore, the dependence of the optical functions on UV exposure times has been discussed based on the spectral distribution of the dielectric constant.

  10. Study on the dipole moment of asphaltene molecules through dielectric measuring

    KAUST Repository

    Zhang, Long Li; Yang, Chao He; Wang, Ji Qian; Yang, Guo Hua; Li, Li; Li, Yan Vivian; Cathles, Lawrence

    2015-01-01

    The polarity of asphaltenes influences production, transportation, and refining of heavy oils. However, the dipole moment of asphaltene molecules is difficult to measure due to their complex composition and electromagnetic opaqueness. In this work, we present a convenient and efficient way to determine the dipole moment of asphaltene in solution by dielectric measurements alone without measurement of the refractive index. The dipole moment of n-heptane asphaltenes of Middle East atmospheric residue (MEAR) and Ta-He atmospheric residue (THAR) are measured within the temperature range of -60°C to 20°C. There is one dielectric loss peak in the measured solutions of the two types of asphaltene at the temperatures of -60°C or -40°C, indicating there is one type of dipole in the solution. Furthermore, there are two dielectric loss peaks in the measured solutions of the two kinds of asphaltene when the temperature rises above -5°C, indicating there are two types of dipoles corresponding to the two peaks. This phenomenon indicates that as the temperature increases above -5°C, the asphaltene molecules aggregate and present larger dipole moment values. The dipole moments of MEAR C7-asphaltene aggregates are up to 5 times larger than those before aggregation. On the other hand, the dipole moments of the THAR C7-asphaltene aggregates are only 3 times larger than those before aggregation. It will be demonstrated that this method is capable of simultaneously measuring multi dipoles in one solution, instead of obtaining only the mean dipole moment. In addition, this method can be used with a wide range of concentrations and temperatures.

  11. Dielectric properties of gadolinium molybdate in low- and infralow frequency electric fields. Diehlektricheskie svojstva molibdata gadoliniya v nizko- i infranizkochastotnykh ehlektricheskikh polyakh

    Energy Technology Data Exchange (ETDEWEB)

    Galiyarova, N M; Gorin, S V; Dontsova, L I; Shil' nikov, A V; Shuvalov, L A [Volgogradskij Inzhenerno-Stroitel' nyj Inst., Volgograd (Russian Federation) AN SSSR, Moscow (Russian Federation). Inst. Kristallografii

    1992-10-01

    Temperature dependences of complex dielectric permittivity of gadolinium molybdate (GMO) in low- (LF) and infralow-frequency (ILF) electric fields with 0.1 V[center dot]cm[sup -1] amplitude within 0.25-10[sup 4] Hz frequency range are studied. Substantial effect of the crystal prehistory on LF and ILF dielectric properties and domain structure state is revealed. An anomalous reduction of complex dielectric permittivity accompanied by the occurrence of the Debye LF-dispersion of permittivity is detected under the sample cooling from a nonpolar phase.

  12. Structural and dielectric studies of Ce doped BaSnO3 perovskite nanostructures

    Science.gov (United States)

    Angel, S. Lilly; Deepa, K.; Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

    2018-04-01

    Undoped and Cerium (Ce) doped BaSnO3(BSO) nanostructures were synthesized by co-precipitation method. The cubic structure and perovskite phase were confirmed by X-ray diffraction (XRD). The crystallite size of BSO is 41nm and when Ce ion concentration is increased, the crystallite sizesdecreased. The nanocube, nanocuboids and nanorods are observed from SEM analysis. The purity of the undoped and doped samples are confirmed by EDS spectrum. For larger defects, wide band gap was obtained from UV-Vis and PL spectrum. The dielectric constants are increased at low frequencies when Ce impurities are introduced in the BSO matrix at Sn site.

  13. Structural and dielectric studies of Co doped MgTiO3 thin films fabricated by RF magnetron sputtering

    Directory of Open Access Journals (Sweden)

    T. Santhosh Kumar

    2014-06-01

    Full Text Available We report the structural, dielectric and leakage current properties of Co doped MgTiO3 thin films deposited on platinized silicon (Pt/TiO2/SiO2/Si substrates by RF magnetron sputtering. The role of oxygen mixing percentage (OMP on the growth, morphology, electrical and dielectric properties of the thin films has been investigated. A preferred orientation of grains along (110 direction has been observed with increasing the OMP. Such evolution of the textured growth is explained on the basis of the orientation factor analysis followed the Lotgering model. (Mg1-xCoxTiO3 (x = 0.05 thin films exhibits a maximum relative dielectric permittivity of ɛr = 12.20 and low loss (tan δ ∼ 1.2 × 10−3 over a wide range of frequencies for 75% OMP. The role of electric field frequency (f and OMP on the ac-conductivity of (Mg0.95Co0.05TiO3 have been studied. A progressive increase in the activation energy (Ea and relative permittivity ɛr values have been noticed up to 75% of OMP, beyond which the properties starts deteriorate. The I-V characteristics reveals that the leakage current density decreases from 9.93 × 10−9 to 1.14 × 10−9 A/cm2 for OMP 0% to 75%, respectively for an electric field strength of 250 kV/cm. Our experimental results reveal up to that OMP ≥ 50% the leakage current mechanism is driven by the ohmic conduction, below which it is dominated by the schottky emission.

  14. Development of a dielectric ceramic based on diatomite-titania part two: dielectric properties characterization

    Directory of Open Access Journals (Sweden)

    Medeiros Jamilson Pinto

    1998-01-01

    Full Text Available Dielectric properties of sintered diatomite-titania ceramics are presented. Specific capacitance, dissipation factor, quality factor and dielectric constant were determined as a function of sintering temperature, titania content and frequency; the temperature coefficient of capacitance was measured as a function of frequency. Besides leakage current, the dependence of the insulation resistance and the dielectric strength on the applied dc voltage were studied. The results show that diatomite-titania compositions can be used as an alternative dielectric.

  15. Microwave dielectric characterization of binary mixture of formamide ...

    Indian Academy of Sciences (India)

    are fitted to the three different relaxation models [24–27] by the non-linear least squares fit method. It is observed that the Davidson–Cole model is adequate to describe major dispersion of the various solute and solvent mixtures over this fre- quency range. Static dielectric constant and dielectric relaxation time could be.

  16. A Study of Dip-Coatable, High-Capacitance Ion Gel Dielectrics for 3D EWOD Device Fabrication

    Directory of Open Access Journals (Sweden)

    Carlos E. Clement

    2017-01-01

    Full Text Available We present a dip-coatable, high-capacitance ion gel dielectric for scalable fabrication of three-dimensional (3D electrowetting-on-dielectric (EWOD devices such as an n × n liquid prism array. Due to the formation of a nanometer-thick electric double layer (EDL capacitor, an ion gel dielectric offers two to three orders higher specific capacitance (c ≈ 10 μF/cm2 than that of conventional dielectrics such as SiO2. However, the previous spin-coating method used for gel layer deposition poses several issues for 3D EWOD device fabrication, particularly when assembling multiple modules. Not only does the spin-coating process require multiple repetitions per module, but the ion gel layer also comes in risks of damage or contamination due to handling errors caused during assembly. In addition, it was observed that the chemical formulation previously used for the spin-coating method causes the surface defects on the dip-coated gel layers and thus leads to poor EWOD performance. In this paper, we alternatively propose a dip-coating method with modified gel solutions to obtain defect-free, functional ion gel layers without the issues arising from the spin-coating method for 3D device fabrication. A dip-coating approach offers a single-step coating solution with the benefits of simplicity, scalability, and high throughput for deposition of high-capacitance gel layers on non-planar EWOD devices. An ion gel solution was prepared by combining the [EMIM][TFSI] ionic liquid and the [P(VDF-HFP] copolymer at various wt % ratios in acetone solvent. Experimental studies were conducted to fully understand the effects of chemical composition ratios in the gel solution and how varying thicknesses of ion gel and Teflon layers affects EWOD performance. The effectiveness and potentiality of dip-coatable gel layers for 3D EWOD devices have been demonstrated through fabricating 5 × 1 arrayed liquid prisms using a single-step dip-coating method. Each prism module has

  17. Positron and positronium annihilation in low-dielectric-constant films studied by a pulsed positron beam

    International Nuclear Information System (INIS)

    Suzuki, R.; Ohdaira, T.; Kobayashi, Y.; Ito, K.; Yu, R.S.; Shioya, Y.; Ichikawa, H.; Hosomi, H.; Ishikiriyama, K.; Shirataki, H.; Matsuno, S.; Xu, J.

    2004-01-01

    Positron and positronium annihilation in porous low-dielectric-constant (low-k) films deposited by plasma-enhanced chemical vapor deposition (PECVD) and spin-on dielectric (SOD) have been investigated by means of positron annihilation lifetime spectroscopy (PALS) and age-momentum correlation (AMOC) spectroscopy with a pulsed slow positron beam. The ortho-positronium (o-Ps) lifetime strongly depends on the deposition condition. In general, PECVD low-k films have shorter o-Ps lifetimes than SOD low-k films, indicating PECVD low-k films have smaller pores. Since o-Ps diffusion and escaping from the surface occurs in most of porous SOD films, three-gamma annihilation measurement is important. To investigate o-Ps behavior in SOD films, we have carried out two-dimensional (2D) PALS measurement, which measures annihilation time and pulse-height of the scintillation detector simultaneously. Monte-Carlo simulation of the o-Ps diffusion and escaping in porous films has been carried out to simulate the 2D-PALS results. (orig.)

  18. The non-separability of ''dielectric'' and ''mechanical'' friction in molecular systems: A simulation study

    International Nuclear Information System (INIS)

    Kumar, P. V.; Maroncelli, M.

    2000-01-01

    Simulations of the time-dependent friction controlling rotational, translational, and vibrational motions of dipolar diatomic solutes in acetonitrile and methanol have been used to examine the nature of ''dielectric'' friction. The way in which electrical interactions increase the friction beyond that present in nonpolar systems is found to be rather different than what is anticipated by most theories of dielectric friction. Long-range electrostatic forces do not simply add an independent contribution to the friction due to short-ranged or ''mechanical'' sources (modeled here in terms of Lennard-Jones forces). Rather, the electrical and Lennard-Jones contributions are found to be strongly anticorrelated and not separable in any useful way. For some purposes, the mechanism by which electrical interactions increase friction is better viewed as a static electrostriction effect: electrical forces cause a subtle increase in atomic density in the solute's first solvation shell, which increases the amplitude of the force fluctuations derived from the Lennard-Jones interactions, i.e., the mechanical friction. However, electrical interactions also modify the dynamics of the friction, typically adding a long-time tail, which significantly increases the integral friction. Both of these effects must be included in a correct description of friction in the presence of polar interactions. (c) 2000 American Institute of Physics

  19. [Study on formation process of honeycomb pattern in dielectric barrier discharge by optical emission spectrum].

    Science.gov (United States)

    Dong, Li-Fang; Zhu, Ping; Yang, Jing; Zhang, Yu

    2014-04-01

    The authors report on the first investigation of the variations in the plasma parameters in the formation process of the honeycomb pattern in a dielectric barrier discharge by optical emission spectrum in argon and air mixture. The discharge undergoes hexagonal lattice, concentric spot-ring pattern and honeycomb pattern with the applied voltage increasing. The molecular vibration temperature, electron excitation temperature and electronic density of the three kinds of patterns were investigated by the emission spectra of nitrogen band of second positive system (C3pi(u) --> B3 pi(g)), the relative intensity ratio method of spectral lines of Ar I 763.51 nm (2P(6) --> 1S(5)) and Ar I 772.42 nm (2P(2) -->1S(3)) and the broadening of spectral line 696.5 nm respectively. It was found that the molecular vibration temperature and electron excitation temperature of the honeycomb pattern are higher than those of the hexagonal lattice, but the electron density of the former is lower than that of the latter. The discharge powers of the patterns were also measured with the capacitance method. The discharge power of the honeycomb pattern is much higher than that of the hexagonal lattice. These results are of great importance to the formation mechanism of the patterns in dielectric barrier discharge.

  20. Temperature dependent dielectric relaxation and ac-conductivity of alkali niobate ceramics studied by impedance spectroscopy

    Science.gov (United States)

    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.

  1. Magnetic and dielectric study of Fe-doped CdSe nanoparticles

    Science.gov (United States)

    Das, Sayantani; Banerjee, Sourish; Bandyopadhyay, Sudipta; Sinha, Tripurari Prasad

    2018-01-01

    Nanoparticles of cadmium selenide (CdSe) and Fe (5% and 10%) doped CdSe have been synthesized by soft chemical route and found to have cubic structure. The magnetic field dependent magnetization measurement of the doped samples indicates the presence of anti-ferromagnetic order. The temperature dependent magnetization (M-T) measurement under zero field cooled and field cooled conditions has also ruled out the presence of ferromagnetic component in the samples at room temperature as well as low temperature. In order to estimate the anti-ferromagnetic coupling among the doped Fe atoms, an M-T measurement at 500 Oe has been carried out, and the Curie-Weiss temperature θ of the samples has been estimated from the inverse of susceptibility versus temperature plots. The dielectric relaxation peaks are observed in the spectra of imaginary part of dielectric constant. The temperature dependent relaxation time is found to obey the Arrhenius law having activation energy 0.4 eV for Fe doped samples. The frequency dependent conductivity spectra are found to obey the power law. [Figure not available: see fulltext.

  2. Theoretical Study of the Transverse Dielectric Constant of Superlattices and Their Alloys. Ph.D Thesis

    Science.gov (United States)

    Kahen, K. B.

    1986-01-01

    The optical properties of III to V binary and ternary compounds and GaAs-Al(x)Ga(1-x)As superlattices are determined by calculating the real and imaginary parts of the transverse dielectric constant. Emphasis is given to determining the influence of different material and superlattice parameters on the values of the index of refraction and absorption coefficient. In order to calculate the optical properties of a material, it is necessary to compute its electronic band structure. This was accomplished by introducing a partition band structure approach based on a combination of the vector k x vector p and nonlocal pseudopotential techniques. The advantages of this approach are that it is accurate, computationally fast, analytical, and flexible. These last two properties enable incorporation of additional effects into the model, such as disorder scattering, which occurs for alloy materials and excitons. Furthermore, the model is easily extended to more complex structures, for example multiple quantum wells and superlattices. The results for the transverse dielectric constant and absorption coefficient of bulk III to V compounds compare well with other one-electron band structure models and the calculations show that for small frequencies, the index of refraction is determined mainly by the contibution of the outer regions of the Brillouin zone.

  3. Dielectric, ferroelectric and impedance spectroscopic studies of Mn and W modified AgNbO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Muduli, Rakesh; Kumar, Pawan, E-mail: pawankumar@nitrkl.ac.in; Panda, Ranjit Kumar; Panigrahi, Simanchal

    2016-09-01

    In the present study, the effect of heterovalent ion doping on the dielectric and ferroelectric behaviour of AgNbO{sub 3}/AN system was investigated. 0.04 mol of manganese (Mn{sup 4+}) and tungsten (W{sup 6+}) ions of smaller ionic radii were substituted in place of niobium (Nb{sup 5+}) ions in the AN system for generating hole and electron rich compounds, respectively. Better dielectric properties with improved saturation polarisations were observed in the heterovalent ions modified AN ceramics. The relaxation behaviour of the modified AN ceramics was investigated by impedance spectroscopy study and intrinsic grain conduction was found to be dominating in the chosen frequency and temperature ranges. The reduced resistivity of the modified AN ceramics was discussed in terms of calculated activation energy. The significant reduction of the activation energy was proposed as the possible cause of early arrival of relaxation peak in the electron doped AN system. - Highlights: • Holes and electrons doping effect on electrical properties of AN system. • Doping of holes significantly enhanced the ferroelectricity. • Doping of electrons reduced activation energy. • Reduced activation energy was related with grains relaxation process.

  4. Dispersion Forces

    CERN Document Server

    Buhmann, Stefan Yoshi

    2012-01-01

    In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

  5. Mechanical reliability of porous low-k dielectrics for advanced interconnect: Study of the instability mechanisms in porous low-k dielectrics and their mediation through inert plasma induced re-polymerization of the backbone structure

    Science.gov (United States)

    Sa, Yoonki

    Continuous scaling down of critical dimensions in interconnect structures requires the use of ultralow dielectric constant (k) films as interlayer dielectrics to reduce resistance-capacitance delays. Porous carbon-doped silicon oxide (p-SiCOH) dielectrics have been the leading approach to produce these ultralow-k materials. However, embedding of porosity into dielectric layer necessarily decreases the mechanical reliability and increases its susceptibility to adsorption of potentially deleterious chemical species during device fabrication process. Among those, exposure of porous-SiCOH low-k (PLK) dielectrics to oxidizing plasma environment causes the increase in dielectric constant and their vulnerability to mechanical instability of PLKs due to the loss of methyl species and increase in moisture uptake. These changes in PLK properties and physical stability have been persisting challenges for next-generation interconnects because they are the sources of failure in interconnect integration as well as functional and physical failures appearing later in IC device manufacturing. It is therefore essential to study the fundamentals of the interactions on p-SiCOH matrix induced by plasma exposure and find an effective and easy-to-implement way to reverse such changes by repairing damage in PLK structure. From these perspectives, the present dissertation proposes 1) a fundamental understanding of structural transformation occurring during oxidative plasma exposure in PLK matrix structure and 2) its restoration by using silylating treatment, soft x-ray and inert Ar-plasma radiation, respectively. Equally important, 3) as an alternative way of increasing the thermo-mechanical reliability, PLK dielectric film with an intrinsically robust structure by controlling pore morphology is fabricated and investigated. Based on the investigations, stability of PLK films studied by time-dependent ball indentation tester under the elevated temperature, variation in film thickness and

  6. Dielectric properties of single wall carbon nanotubes-based gelatin phantoms

    Science.gov (United States)

    Altarawneh, M. M.; Alharazneh, G. A.; Al-Madanat, O. Y.

    In this work, we report the dielectric properties of Single wall Carbon Nanotubes (SWCNTs)-based phantom that is mainly composed of gelatin and water. The fabricated gelatin-based phantom with desired dielectric properties was fabricated and doped with different concentrations of SWCNTs (e.g., 0%, 0.05%, 0.10%, 0.15%, 0.2%, 0.4% and 0.6%). The dielectric constants (real ɛ‧ and imaginary ɛ‧‧) were measured at different positions for each sample as a function of frequency (0.5-20GHz) and concentrations of SWCNTs and their averages were found. The Cole-Cole plot (ɛ‧ versus ɛ‧‧) was obtained for each concentration of SWCNTs and was used to obtain the static dielectric constant ɛs, the dielectric constant at the high limit of frequency ɛ∞ and the average relaxation time τ. The measurements showed that the fabricated samples are in good homogeneity and the SWCNTs are dispersed well in the samples as an acceptable standard deviation is achieved. The study showed a linear increase in the static dielectric constant ɛs and invariance of the average relaxation time τ and the value of ɛ∞ at room temperature for the investigated concentrations of SWCNTs.

  7. A structure study of copper oxide for monolayer dispersion of anatase supported

    International Nuclear Information System (INIS)

    Zi Fenlan; Yu Xiaofeng; Guo Hongyou; Cai Xiaohai; Yang Pengcheng; Wu Nianzu; Xie Yaning; Zang Jing; Hu Tiandou

    2002-01-01

    The monolayer dispersion of copper oxide on the surface of anatase and its effect on the properties have been studied by X-ray photoelectron spectroscopy (XPS) and X-ray extended absorption fine structure (EXAFS). XPS results give an utmost dispersion capacity of 7.2 mg/gTiO 2 . Strong interactions between copper oxide and anatase can be seen from EXAFS results. The structure of the supported CuO species is strongly dependent on the amount of CuO loading. When the content of CuO loading is below the utmost dispersion capacity, the surface of CuO/TiO 2 is dominated by the highly dispersed CuO species having no -Cu-O-Cu- chains. The copper ion is located in an octahedral coordination environment, and the Cu-O coordination distance is much longer than that in pure crystalline CuO. When CuO loading is exceeds the utmost dispersion capacity, crystalline CuO is formed on the surface of CuO/TiO 2 . From the result of the structure study, it is Cu-O octahedral coordination and coordination distance change in comparison with pure crystalline CuO on the surface CuO/TiO 2 that have catalytic activity

  8. Contaminant dispersion and bacterial declination studies ate the bay of Chimbote - Peru

    International Nuclear Information System (INIS)

    Sebastian, C.; Maghella, G.; Mamani, E.

    2000-02-01

    A review of both, the dispersion studies and preliminary determination of T-90 performed at the bay of Chimbote - Peru, has been made. As for the dispersion studies, a fundamental partial differential equation and its solution for three-dimensional case is presented. The shape and characteristics of the tracer plume is determined as well as the decrease rate of peak concentrations. The method considers a point injection with Rhodamine B and Iodine-131 as tracers, in order to determine the longitudinal, lateral and vertical dispersion coefficients that govern the dispersion rates of industrial and waste waters to be discharged through a submarine outfall that will be installed at the sea of Chimbote. The method presented herein allows the estimation of the dispersion coefficients and predicts the influence of the future diffuser as well, regardless of the nature of the body of water in which the tests were conducted. With regard to T-90 determinations, they were better performed by the use of a combined tracer technique, using I-131 for dilution measurement and Rhodamine B as a visual aid. Dilution and decrease in bacterial concentrations were taken into consideration as well as continuous radiotracer injection. The values of T-90 estimated from experiments should be reconfirmed in future experiments under different oceanographic conditions. (authors)

  9. Investigation of dielectric relaxation in systems with hierarchical organization: From time to frequency domain and back again

    Energy Technology Data Exchange (ETDEWEB)

    Yokoi, Koki [Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI (United States); Raicu, Valerică, E-mail: vraicu@uwm.edu [Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI (United States); Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI (United States)

    2017-06-28

    Relaxation in fractal structures was investigated theoretically starting from a simple model of a Cantorian tree and kinetic equations linking the change in the number of particles (e.g., electrical charges) populating each branch of the tree and their transfer to other branches or to the ground state. We numerically solved the system of differential equations obtained and determined the so-called cumulative distribution function of particles, which, in dielectric or mechanical relaxation parlance, is the same as the relaxation function of the system. As a physical application, we studied the relationship between the dielectric relaxation in time-domain and the dielectric dispersion in the frequency-domain. Upon choosing appropriate rate constants, our model described accurately well-known non-exponential and non-Debye time- and frequency-domain functions, such as stretched exponentials, Havrilliak–Negami, and frequency power law. Our approach opens the door to applying kinetic models to describe a wide array of relaxation processes, which traditionally have posed great challenges to theoretical modeling based on first principles. - Highlights: • Relaxation was investigated for a system of particles flowing through a Cantorian tree. • A set of kinetic equations was formulated and used to compute the relaxation function of the system. • The dispersion function of the system was computed from the relaxation function. • An analytical method was used to recover the original relaxation function from the dispersion function. • This formalism was used to study dielectric relaxation and dispersion in fractal structures.

  10. Case Study of Airborne Pathogen Dispersion Patterns in Emergency Departments with Different Ventilation and Partition Conditions.

    Science.gov (United States)

    Cheong, Chang Heon; Lee, Seonhye

    2018-03-13

    The prevention of airborne infections in emergency departments is a very important issue. This study investigated the effects of architectural features on airborne pathogen dispersion in emergency departments by using a CFD (computational fluid dynamics) simulation tool. The study included three architectural features as the major variables: increased ventilation rate, inlet and outlet diffuser positions, and partitions between beds. The most effective method for preventing pathogen dispersion and reducing the pathogen concentration was found to be increasing the ventilation rate. Installing partitions between the beds and changing the ventilation system's inlet and outlet diffuser positions contributed only minimally to reducing the concentration of airborne pathogens.

  11. Discrete element method study of fuel relocation and dispersal during loss-of-coolant accidents

    Science.gov (United States)

    Govers, K.; Verwerft, M.

    2016-09-01

    The fuel fragmentation, relocation and dispersal (FFRD) during LOCA transients today retain the attention of the nuclear safety community. The fine fragmentation observed at high burnup may, indeed, affect the Emergency Core Cooling System performance: accumulation of fuel debris in the cladding ballooned zone leads to a redistribution of the temperature profile, while dispersal of debris might lead to coolant blockage or to debris circulation through the primary circuit. This work presents a contribution, by discrete element method, towards a mechanistic description of the various stages of FFRD. The fuel fragments are described as a set of interacting particles, behaving as a granular medium. The model shows qualitative and quantitative agreement with experimental observations, such as the packing efficiency in the balloon, which is shown to stabilize at about 55%. The model is then applied to study fuel dispersal, for which experimental parametric studies are both difficult and expensive.

  12. Sensitivity model study of regional mercury dispersion in the atmosphere

    Science.gov (United States)

    Gencarelli, Christian N.; Bieser, Johannes; Carbone, Francesco; De Simone, Francesco; Hedgecock, Ian M.; Matthias, Volker; Travnikov, Oleg; Yang, Xin; Pirrone, Nicola

    2017-01-01

    bogs, etc., is highlighted in this study.

  13. Simulation Studies of the Dielectric Grating as an Accelerating and Focusing Structure

    International Nuclear Information System (INIS)

    Soong, Ken; Peralta, E.A.; Byer, R.L.; Colby, E.

    2011-01-01

    A grating-based design is a promising candidate for a laser-driven dielectric accelerator. Through simulations, we show the merits of a readily fabricated grating structure as an accelerating component. Additionally, we show that with a small design perturbation, the accelerating component can be converted into a focusing structure. The understanding of these two components is critical in the successful development of any complete accelerator. The concept of accelerating electrons with the tremendous electric fields found in lasers has been proposed for decades. However, until recently the realization of such an accelerator was not technologically feasible. Recent advances in the semiconductor industry, as well as advances in laser technology, have now made laser-driven dielectric accelerators imminent. The grating-based accelerator is one proposed design for a dielectric laser-driven accelerator. This design, which was introduced by Plettner, consists of a pair of opposing transparent binary gratings, illustrated in Fig. 1. The teeth of the gratings serve as a phase mask, ensuring a phase synchronicity between the electromagnetic field and the moving particles. The current grating accelerator design has the drive laser incident perpendicular to the substrate, which poses a laser-structure alignment complication. The next iteration of grating structure fabrication seeks to monolithically create an array of grating structures by etching the grating's vacuum channel into a fused silica wafer. With this method it is possible to have the drive laser confined to the plane of the wafer, thus ensuring alignment of the laser-and-structure, the two grating halves, and subsequent accelerator components. There has been previous work using 2-dimensional finite difference time domain (2D-FDTD) calculations to evaluate the performance of the grating accelerator structure. However, this work approximates the grating as an infinite structure and does not accurately model a

  14. Analysis of photonic band gap in dispersive properties of tunable three-dimensional photonic crystals doped by magnetized plasma

    International Nuclear Information System (INIS)

    Zhang HaiFeng; Liu Shaobin; Yang Huan; Kong Xiangkun

    2013-01-01

    In this paper, the magnetooptical effects in dispersive properties for two types of three-dimensional magnetized plasma photonic crystals (MPPCs) containing homogeneous dielectric and magnetized plasma with diamond lattices are theoretically investigated for electromagnetic (EM) wave based on plane wave expansion (PWE) method, as incidence EM wave vector is parallel to the external magnetic field. The equations for two types of MPPCs with diamond lattices (dielectric spheres immersed in magnetized plasma background or vice versa) are theoretically deduced. The influences of dielectric constant, plasma collision frequency, filling factor, the external magnetic field, and plasma frequency on the dispersive properties for both types of structures are studied in detail, respectively, and some corresponding physical explanations are also given. From the numerical results, it has been shown that the photonic band gaps (PBGs) for both types of MPPCs can be manipulated by plasma frequency, filling factor, the external magnetic field, and the relative dielectric constant of dielectric, respectively. Especially, the external magnetic field can enlarge the PBG for type-2 structure (plasma spheres immersed in dielectric background). However, the plasma collision frequency has no effect on the dispersive properties of two types of three-dimensional MPPCs. The locations of flatbands regions for both types of structures cannot be tuned by any parameters except for plasma frequency and the external magnetic field. The analytical results may be informative and of technical use to design the MPPCs devices.

  15. Numerical study of the dielectric liquid around an electrical discharge generated vapor bubble in ultrasonic assisted EDM.

    Science.gov (United States)

    Shervani-Tabar, Mohammad T; Mobadersany, Nima

    2013-07-01

    In electrical discharge machining due to the electrical current, very small bubbles are created in the dielectric fluid between the tool and the workpiece. Increase of the number of bubbles and their growth in size generate a single bubble. The bubble has an important role in electrical discharge machining. In this paper the effect of ultrasonic vibration of the tool and the velocity fields and pressure distribution in the dielectric fluid around the bubble in the process of electrical discharge machining are studied numerically. The boundary integral equation method is applied for the numerical solution of the problem. It is shown that ultrasonic vibration of the tool has great influence on the evolution of the bubble, fluid behavior and the efficiency of the machining in EDM. At the last stages of the collapse phase of the bubble, a liquid jet develops on the bubble which has different shapes. Due to the different cases, and a high pressure region appears just near the jet of the bubble. Also the fluid particles have the highest relative velocity just near the liquid jet of the bubble. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Dielectric properties of liquid systems: study of interactions in the systems carbon tetrachloride with benzene, toluene, and p-xylene

    Directory of Open Access Journals (Sweden)

    Adrián H. Buep

    2014-12-01

    Full Text Available Intermolecular associations in liquid systems of non-polar and slightly polar compounds were studied through excess molar volumes (VEM and excess dielectric properties (εE and n2ED for mixtures of carbon tetrachloride (CCl4 with benzene (C6H6, toluene (C6H5CH3, and p-xylene (p-(CH32C6H4. These excess properties were calculated from measurements of density (ρ, static permittivity (ε, and refractive index (nD over the whole range of concentrations at 298.15 K. The values of the excess dielectric properties for these mixtures were fitted in two different ways, one through least squares using the Redlich–Kister equation and the other using a model developed to explain deviations from ideality. The first fit was found to be descriptive while the second gave the equilibrium constant values for the interaction products actually formed in the mixtures and the respective electronic polarizabilities and dipole moments, indicating the existence of interaction products.

  17. Contaminant dispersion and bacterial declination studies ate the bay of Chimbote - Peru; Estudios de dispersion de contaminantes y declinacion bacteriana en la bahia del mar de Chimbote - Peru

    Energy Technology Data Exchange (ETDEWEB)

    Sebastian, C; Maghella, G; Mamani, E [Instituto Peruano de Energia Nuclear, Lima (Peru)

    2000-02-01

    A review of both, the dispersion studies and preliminary determination of T-90 performed at the bay of Chimbote - Peru, has been made. As for the dispersion studies, a fundamental partial differential equation and its solution for three-dimensional case is presented. The shape and characteristics of the tracer plume is determined as well as the decrease rate of peak concentrations. The method considers a point injection with Rhodamine B and Iodine-131 as tracers, in order to determine the longitudinal, lateral and vertical dispersion coefficients that govern the dispersion rates of industrial and waste waters to be discharged through a submarine outfall that will be installed at the sea of Chimbote. The method presented herein allows the estimation of the dispersion coefficients and predicts the influence of the future diffuser as well, regardless of the nature of the body of water in which the tests were conducted. With regard to T-90 determinations, they were better performed by the use of a combined tracer technique, using I-131 for dilution measurement and Rhodamine B as a visual aid. Dilution and decrease in bacterial concentrations were taken into consideration as well as continuous radiotracer injection. The values of T-90 estimated from experiments should be reconfirmed in future experiments under different oceanographic conditions. (authors)

  18. Experimental study on behaviors of dielectric elastomer based on acrylonitrile butadiene rubber

    Science.gov (United States)

    An, Kuangjun; Chuc, Nguyen Huu; Kwon, Hyeok Yong; Phuc, Vuong Hong; Koo, Jachoon; Lee, Youngkwan; Nam, Jaedo; Choi, Hyouk Ryeol

    2010-04-01

    Previously, the dielectric elastomer based on Acrylonitrile Butadiene Rubber (NBR), called synthetic elastomer has been reported by our group. It has the advantages that its characteristics can be modified according to the requirements of performances, and thus, it is applicable to a wide variety of applications. In this paper, we address the effects of additives and vulcanization conditions on the overall performance of synthetic elastomer. In the present work, factors to have effects on the performances are extracted, e.g additives such as dioctyl phthalate (DOP), barium titanium dioxide (BaTiO3) and vulcanization conditions such as dicumyl peroxide (DCP), cross-linking times. Also, it is described how the performances can be optimized by using DOE (Design of Experiments) technique and experimental results are analyzed by ANOVA (Analysis of variance).

  19. Synthesis, growth, structural, optical, thermal, dielectric and mechanical studies of an organic guanidinium p-nitrophenolate crystal

    Science.gov (United States)

    Dhavamurthy, M.; Peramaiyan, G.; Mohan, R.

    2014-08-01

    Guanidinium p-nitrophenolate (GUNP), a novel organic compound, was synthesized and crystals were grown from methanol solution by a slow evaporation solution growth technique. A single crystal X-ray diffraction study elucidated the crystal structure of GUNP belonging to the orthorhombic crystal system with space group Pnma. Thermal studies revealed that the GUNP crystal is thermally stable up to 192 °C. The lower cut-off wavelength of GUNP was found to be 505 nm by UV-vis-NIR spectral studies. The luminescence properties of the GUNP crystal were investigated. The three independent tensor coefficients ε11, ε22 and ε33 of the dielectric permittivity were calculated. The mechanical properties of the grown crystal were studied by Vickers' microhardness hardness technique.

  20. Growth and dielectric, mechanical, thermal and etching studies of an organic nonlinear optical L-arginine trifluoroacetate (LATF) single crystal

    International Nuclear Information System (INIS)

    Arjunan, S.; Mohan Kumar, R.; Mohan, R.; Jayavel, R.

    2008-01-01

    L-arginine trifluoroacetate, an organic nonlinear optical material, has been synthesized from aqueous solution. Bulk single crystal of dimension 57 mm x 5 mm x 3 mm has been grown by temperature lowering technique. Powder X-ray diffraction studies confirmed the monoclinic structure of the grown L-arginine trifluoroacetate crystal. Linear optical property of the grown crystal has been studied by UV-vis spectrum. Dielectric response of the L-arginine trifluoroacetate crystal was analysed for different frequencies and temperatures in detail. Microhardness study on the sample reveals that the crystal possesses relatively higher hardness compared to many organic crystals. Thermal analyses confirmed that the L-arginine trifluoroacetate material is thermally stable upto 212 deg. C. The etching studies have been performed to assess the perfection of the L-arginine trifluoroacetate crystal. Kurtz powder second harmonic generation test confirms the nonlinear optical properties of the as-grown L-arginine trifluoroacetate crystal

  1. Numerical Study on Sensitivity of Pollutant Dispersion on Turbulent Schmidt Number in a Street Canyon

    Science.gov (United States)

    WANG, J.; Kim, J.

    2014-12-01

    In this study, sensitivity of pollutant dispersion on turbulent Schmidt number (Sct) was investigated in a street canyon using a computational fluid dynamics (CFD) model. For this, numerical simulations with systematically varied Sct were performed and the CFD model results were validated against a wind‒tunnel measurement data. The results showed that root mean square error (RMSE) was quite dependent on Sct and dispersion patterns of non‒reactive scalar pollutant with different Sct were quite different among the simulation results. The RMSE was lowest in the case of Sct = 0.35 and the apparent dispersion pattern was most similar to the wind‒tunnel data in the case of Sct = 0.35. Also, numerical simulations using spatially weighted Sct were additionally performed in order for the best reproduction of the wind‒tunnel data. Detailed method and procedure to find the best reproduction will be presented.

  2. The study of atmospheric dispersion of radionuclide near nuclear power plant using CFD approach

    International Nuclear Information System (INIS)

    Nagrale, Dhanesh B.; Bera, Subrata; Deo, Anuj K.; Gaikwad, Avinash J.

    2015-01-01

    Most of the studies on atmospheric dispersion of radioactive material released from nuclear power plants are based on Gaussian plume models which fail to take account turbulence generated. The Fire Dynamic Simulator (FDS) code is one such flow model that uses a form of Navier-Stokes equation for low mach number applications. In the 0-2 km range near nuclear power plant, mainly near the source of emission of radionuclides, obstructions like natural draft cooling towers, plant building and structures are located. The stability class 'F' conditions and temperature of surrounding atmosphere, 15°C are considered in analysis. Main constituents of radionuclides released from stack mainly xenon, krypton. Two cases are carried out a) dispersion of gases without obstruction of cooling tower and b) dispersion of gases with obstruction of cooling tower. It is observed that mass fraction of radionuclides near the cooling tower ground increased to certain extent due to obstruction and wake effect. (author)

  3. Topography and its effects on atmospheric dispersion in a risk study for nuclear facilities

    International Nuclear Information System (INIS)

    Wittek, P.

    1985-07-01

    In the consequence assessment model, applied in the German Reactor Risk Study (GRRS), atmospheric dispersion of radioactive substances is beeing treated with a straight line Gaussian dispersion model. But some of the German nuclear power plants are located in complex terrain. In this report, the 19 sites which are considered in the GRRS, are described and classified by two different methods in respect to terrain complexity. The relevant effects of the terrain on the dispersion are commented. Two modifications of the GRRS consequence assessment code UFOMOD take into account in a simple way the terrain elevation and the enhanced turbulence effected eventually by the terrain structure. Sample calculations for two release categories of the GRRS demonstrate the effect of these modifications on the calculated number of early fatalities. (orig.) [de

  4. Dielectric inspection of erythrocyte morphology

    International Nuclear Information System (INIS)

    Hayashi, Yoshihito; Oshige, Ikuya; Katsumoto, Yoichi; Omori, Shinji; Yasuda, Akio; Asami, Koji

    2008-01-01

    We performed a systematic study of the sensitivity of dielectric spectroscopy to erythrocyte morphology. Namely, rabbit erythrocytes of four different shapes were prepared by precisely controlling the pH of the suspending medium, and their complex permittivities over the frequency range from 0.1 to 110 MHz were measured and analyzed. Their quantitative analysis shows that the characteristic frequency and the broadening parameter of the dielectric relaxation of interfacial polarization are highly specific to the erythrocyte shape, while they are insensitive to the cell volume fraction. Therefore, these two dielectric parameters can be used to differentiate erythrocytes of different shapes, if dielectric spectroscopy is applied to flow-cytometric inspection of single blood cells. In addition, we revealed the applicability and limitations of the analytical theory of interfacial polarization to explain the experimental permittivities of non-spherical erythrocytes

  5. Dielectric inspection of erythrocyte morphology

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Yoshihito; Oshige, Ikuya; Katsumoto, Yoichi; Omori, Shinji; Yasuda, Akio [Life Science Laboratory, Materials Laboratories, Sony Corporation, Sony Bioinformatics Center, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510 (Japan); Asami, Koji [Laboratory of Molecular Aggregation Analysis, Division of Multidisciplinary Chemistry, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan)], E-mail: Yoshihito.Hayashi@jp.sony.com

    2008-05-21

    We performed a systematic study of the sensitivity of dielectric spectroscopy to erythrocyte morphology. Namely, rabbit erythrocytes of four different shapes were prepared by precisely controlling the pH of the suspending medium, and their complex permittivities over the frequency range from 0.1 to 110 MHz were measured and analyzed. Their quantitative analysis shows that the characteristic frequency and the broadening parameter of the dielectric relaxation of interfacial polarization are highly specific to the erythrocyte shape, while they are insensitive to the cell volume fraction. Therefore, these two dielectric parameters can be used to differentiate erythrocytes of different shapes, if dielectric spectroscopy is applied to flow-cytometric inspection of single blood cells. In addition, we revealed the applicability and limitations of the analytical theory of interfacial polarization to explain the experimental permittivities of non-spherical erythrocytes.

  6. Studies of migration and dispersion of radionuclides from the storage of radioactive wastes

    International Nuclear Information System (INIS)

    Dlouhy, Z.

    1976-08-01

    Conditions were tested under which fixed low level liquid radioactive wastes could be safely stored in geological formations of Czechoslovakia. Geological models were constructed to yield relatively accurate information on the migration and dispersion properties of some soils and rock formation in both static and dynamic conditions. Based on results of the models further testing was conducted under field conditions. The principal radionuclides used during the tests were 90 Sr and 137 Cs. Relative transport and dispersion data are provided for various of the earth studied groups and an assessment of the various sites provided in the report

  7. Evaluation of twin-head electrospray nanoparticle disperser for nanotoxicity study

    Science.gov (United States)

    Liu, Qiaoling; Budiman, Thomas; Chen, Da-Ren

    2014-08-01

    With the rapid development of nanotechnology, nanoparticles with various sizes and compositions have been synthesized and proposed for industrial applications. At the same time, the health effects and environmental impacts of nanoparticles become an emerging concern to be addressed. Both in vitro and in vivo studies are of importance to better understand the toxicity of nanoparticles. It is thus essential to have a nanoparticle disperser capable of dispersing individual nanoparticles for these studies. A twin-head electrospray (THES) nanoparticle disperser for animal inhalation exposure studies has recently become commercially available from TSE Systems Inc. Different from the cone-jet electrospray method used in the majority of literature, this particular disperser operates at the multi-jet mode. In this study, we reported our finding on the performance evaluation of the THES disperser with respect to its mass throughput and quality of size distribution of aerosol produced. Three different nanomaterials (TiO2, ZnO, and NiO) were used in this study. It is found that the maximal mass throughput of the studied disperser was achieved by keeping the distance between two opposite spray capillary tips at 3.0 cm, operating the primary carrier-to-capillary sheath flow rates at the ratio of 4:3, and feeding spray suspensions at a flow rate of 20 µl/min. Under the above settings and operations, the highest mass concentration for nano-ZnO was measured at 14.56 mg/m3. Nanoparticle streams with higher concentrations can be further produced by lowering the total carrier gas flow rate and spraying suspensions of higher nanomaterial concentrations. Our study also found that the particle mass throughput of the studied disperser had a good linear relationship with the mass concentration of spray suspension. In addition, the spatial uniformity of nano aerosol distribution in a TSE head-nose-only exposure chamber was investigated. An acceptable nano aerosol uniformity result was

  8. Enhanced performance in capacitive force sensors using carbon nanotube/polydimethylsiloxane nanocomposites with high dielectric properties

    Science.gov (United States)

    Jang, Hyeyoung; Yoon, Hyungsuk; Ko, Youngpyo; Choi, Jaeyoo; Lee, Sang-Soo; Jeon, Insu; Kim, Jong-Ho; Kim, Heesuk

    2016-03-01

    Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased dielectric properties of elastomers and simple sensor structure. We rationally design dielectric elastomers based on alkylamine modified-multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composites, which have a higher dielectric constant than pure PDMS. The alkylamine-MWCNTs show excellent dispersion in a PDMS matrix, thus leading to enhanced and reliable dielectric properties of the composites. A force sensor array fabricated with alkylamine-MWCNT/PDMS composites presents an enhanced response due to the higher dielectric constant of the composites than that of pure PDMS. This study is the first to report enhanced performance of capacitive force sensors by modulating the dielectric properties of elastomers. We believe that the disclosed strategy to improve the sensor performance by increasing the dielectric properties of elastomers has great potential in the development of capacitive force sensor arrays that respond to various input forces.Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased

  9. Field studies of transport and dispersion of atmospheric tracers in nocturnal drainage flows

    Science.gov (United States)

    Paul H. Gudiksen; Gilbert J. Ferber; Malcolm M. Fowler; Wynn L. Eberhard; Michael A. Fosberg; William R. Knuth

    1984-01-01

    A series of tracer experiments were carried out as part of the Atmospheric Studies in Complex Terrain (ASCOT) program to evaluate pollutant transport and dispersion characteristics of nocturnal drainage flows within a valley in northern California. The results indicate that the degree of interaction of the drainage flows with the larger scale regional flows are...

  10. Study of the interaction of Tb (III) with dextran through fluorescence spectroscopy and optical rotatory dispersion

    International Nuclear Information System (INIS)

    Vasconcelos, Sandra S.; Rodrigues, J.F.

    1984-01-01

    A study of the interaction of Tb(III) with dextran in aqueous solution was perform using fluorescence spectroscopy and optical rotatory dispersion. The results indicate the formation of a complex with the displacent of water from the cation coordinated sphere by hydroxyl groups at the second and third carbon atoms of the monomer unit. (Author) [pt

  11. Study of abrasive wear process of lining of grinding chamber of vortex-acoustic disperser

    Science.gov (United States)

    Perelygin, D. N.

    2018-03-01

    The theoretical and experimental studies of the process of gas-abrasive wear of the lining of a vortex-acoustic disperser made it possible to establish the conditions and patterns of their occurrence and also to develop proposals for its reduction.

  12. Characterization of size, surface charge, and agglomeration state of nanoparticle dispersions for toxicological studies

    International Nuclear Information System (INIS)

    Jiang Jingkun; Oberdoerster, Guenter; Biswas, Pratim

    2009-01-01

    Characterizing the state of nanoparticles (such as size, surface charge, and degree of agglomeration) in aqueous suspensions and understanding the parameters that affect this state are imperative for toxicity investigations. In this study, the role of important factors such as solution ionic strength, pH, and particle surface chemistry that control nanoparticle dispersion was examined. The size and zeta potential of four TiO 2 and three quantum dot samples dispersed in different solutions (including one physiological medium) were characterized. For 15 nm TiO 2 dispersions, the increase of ionic strength from 0.001 M to 0.1 M led to a 50-fold increase in the hydrodynamic diameter, and the variation of pH resulted in significant change of particle surface charge and the hydrodynamic size. It was shown that both adsorbing multiply charged ions (e.g., pyrophosphate ions) onto the TiO 2 nanoparticle surface and coating quantum dot nanocrystals with polymers (e.g., polyethylene glycol) suppressed agglomeration and stabilized the dispersions. DLVO theory was used to qualitatively understand nanoparticle dispersion stability. A methodology using different ultrasonication techniques (bath and probe) was developed to distinguish agglomerates from aggregates (strong bonds), and to estimate the extent of particle agglomeration. Probe ultrasonication performed better than bath ultrasonication in dispersing TiO 2 agglomerates when the stabilizing agent sodium pyrophosphate was used. Commercially available Degussa P25 and in-house synthesized TiO 2 nanoparticles were used to demonstrate identification of aggregated and agglomerated samples.

  13. A contribution from dielectric analysis to the study of the formation of multi-wall carbon nanotubes percolated networks in epoxy resin under an electric field

    International Nuclear Information System (INIS)

    Risi, Celso L.S.; Hattenhauer, Irineu; Ramos, Airton; Coelho, Luiz A.F.; Pezzin, Sérgio H.

    2015-01-01

    The formation of percolation networks in epoxy matrix nanocomposites reinforced with multi-wall carbon nanotubes (MWNT) during the curing process, at different MWNT contents, was studied by using a parallel plate cell subjected to a 300 V/cm AC electric field at 1 kHz. The percolation was verified by the electrical current output measured during and after the resin curing. The behavior of electric dipoles was characterized by impedance spectroscopy and followed the Debye first order dispersion model, by which an average relaxation time of 6.0 × 10 −4 s and a cut-off frequency of 1.7 kHz were experimentally found. By applying the theory of percolation, a critical probability, p c , equal to 0.038 vol% and an exponent of conductivity of 2.0 were found. Both aligned and random samples showed dipole relaxation times typical of interfacial and/or charge-hopping polarization, while the permittivity exhibited an exponential decrease with frequency. This behavior can be related to the increased ability to trap electrical charges due to the formation of the carbon nanotubes network. Optical and electron microscopies confirm the theoretical prediction that the application of an electric field during cure helps the process of MWNT debundling in epoxy resin. - Highlights: • We report the formation of percolating networks of MWNTs under AC electric field. • MWNT/epoxy dielectric properties were measured by impedance spectroscopy. • Lower percolation thresholds were obtained for composites with aligned CNTs. • Application of AC electric field helps the debundling of CNTs. • CNT/Epoxy with percolated networks presents interfacial and hopping polarizations

  14. Dispersants in an organic medium: synthesis and physicochemical study of dispersants for fuels and lubricants; Dispersants en milieu organique: synthese et etude physicochimique de dispersants pour carburants et lubrifiants

    Energy Technology Data Exchange (ETDEWEB)

    Dubois-Clochard, M.C.

    1998-11-19

    Carbonaceous deposits coming from the fuel and the lubricant are known to form over time at critical locations in an engine. In general, the deposits have an adverse effect on four functional areas which are the fuel metering system, the intake system, the lubrication system and the combustion chambers. These deposits can degrade vehicle performance and drive-ability, reduce fuel economy, increase fuel consumption and pollutant emissions and may lead to the destruction of the engine. In order to remedy these problems, detergent-dispersant additives are used in fuels and lubricants to avoid or decrease deposit adhesion on metallic surfaces and prevent from deposit aggregation. These products are mainly polymer surfactants and in this work, poly-iso-butenyl-succinimide of different structures have been studied. Firstly, 'comb like' polymers have been synthesized. Then they have been compared to classical di-bloc additives in terms of performance and action mechanism. These additives are adsorbed from their hydrophilic polyamine part on the acidic functions of the carbon black surface chosen as an engine deposit model and on the aluminium oxide function of an aluminium powder chosen as an engine wall model. The adsorption increases with temperature on the two solids. Their affinity with the solid surface increases with the length of the hydrophilic part. In the same way, changing the di-bloc structure for a comb like one lead to a better adsorption. At low concentration, it has been shown that the adsorption phenomenon was irreversible, due to the polymer structure of the polar part. Depending on the space required by the hydrophilic part on the solid surface, a more of less dense monolayer is formed. At higher concentrations, an important increase of the adsorbed amount appears. This phenomenon is totally reversible showing that the interactions additive / additive are weak. The dispersing efficiency of a comb like structure is better than a di-bloc one as

  15. Super dielectric capacitor using scaffold dielectric

    OpenAIRE

    Phillips, Jonathan

    2018-01-01

    Patent A capacitor having first and second electrodes and a scaffold dielectric. The scaffold dielectric comprises an insulating material with a plurality of longitudinal channels extending across the dielectric and filled with a liquid comprising cations and anions. The plurality of longitudinal channels are substantially parallel and the liquid within the longitudinal channels generally has an ionic strength of at least 0.1. Capacitance results from the migrations of...

  16. Study of dielectric materials irradiated with electron beam by using the Pulsed Electro-Acoustic (PEA) method

    International Nuclear Information System (INIS)

    Nguyen, Xuan Truong

    2014-01-01

    Dielectric materials are frequently used as electrical insulators in spatial applications. Due to their dielectric nature, these dielectrics are likely to accumulate electric charges during their service. Under certain critical conditions, these internal or surface space charges can lead to an electrostatic surface discharge. To understand these phenomena, an experimental device has been developed in the laboratory. This device allows us to simulate the electronic irradiation conditions encountered in space. The aim of our study is to characterize the electrical behavior of insulating materials irradiated by electron beam, to investigate charge storage and transport phenomena and anticipate electrostatic discharges. In this work, the device based on the Pulsed Electro-Acoustic (PEA) technique has been chosen. It has been implanted in the irradiation chamber. It allows us to obtain the spatial distribution of charges injected between two periods of irradiation and during relaxation. However the PEA method offers a limited resolution and does not allow the detection of injected charges when they are too close to the surface. First, we performed a parameters signal processing analysis that we will call the spreading factor and the resolution factor. The preliminary study post-irradiation in air of experimental measurements showed that the resolution factor choice is important for the analysis and interpretation of the signal when the space charge is localized near the surface. Then, a comparison to the spreading parameter used in some deconvolution technique was established. In the second time, space charge distribution measurements in vacuum have been carried out on Poly Tetra Fluoro Ethylene (PTFE) films irradiated by an electron beam in the range [10-100] keV. Results from irradiation periods with increasing energies [10 keV → 100 keV] of the electron beam have been compared with results from irradiation periods with decreasing energies [100 keV → 10 keV]. In

  17. Three-dimensional periodic dielectric structures having photonic Dirac points

    Science.gov (United States)

    Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin

    2015-06-02

    The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.

  18. Three-dimensional periodic dielectric structures having photonic Dirac points

    Energy Technology Data Exchange (ETDEWEB)

    Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin

    2015-06-02

    The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.

  19. The use of dielectric spectroscopy for the characterization of polymer-induced flocculation of polystyrene particles

    DEFF Research Database (Denmark)

    Christensen, Peter Vittrup; Keiding, Kristian

    2008-01-01

    in dilute suspensions. Thus, techniques usable for flocculation characterization in high-solids suspensions are desirable. This study investigates the use of dielectric spectroscopy to monitor the flocculation of polystyrene particles with a cationic polymer. The frequency-dependent permittivity is modeled......The flocculation of colloidal suspensions is an important unit operation in many industries, as it greatly improves the performance of solid separation processes. The number of available techniques for evaluating flocculation processes on line is limited, and most of these are only functional...... as a decrease in the magnitude of the dielectric dispersion. The use of dielectric spectroscopy is found to be valuable for assessing flocculation processes in high-solids suspensions, as changes in parameters Such as floc size and charge can be detected....

  20. Dielectric Losses and Charge Transfer in Antimony-Doped TlGaS2 Single Crystal

    Science.gov (United States)

    Asadov, S. M.; Mustafaeva, S. N.

    2018-03-01

    Effect of semimetallic antimony (0.5 mol % Sb) on the dielectric properties and ac-conductivity of TlGaS2-based single crystals grown by the Bridgman-Stockbarger method has been studied. The experimental results on the frequency dispersion of dielectric coefficients and the conductivity of TlGa0.995Sb0.005S2 single crystals allowed the revealing of the dielectric loss nature, the charge transfer mechanism, and the estimation of the parameters of the states localized in the energy gap. The antimony-doping of the TlGaS2 single crystal leads to an increase in the density of states near the Fermi level and a decrease in the average time and average distance of hopes.

  1. Study of phenomena of tracer transport and dispersion in fractured media

    International Nuclear Information System (INIS)

    Ippolito, Irene

    1993-01-01

    The objective of this research thesis is to present some transport phenomena according to two different approaches: firstly, the study of flows and tracing in a natural crack within a granitic site, and secondly, the study of flows of different geometries in model cracks, mainly by using techniques of tracer dispersion. The author first presents some properties of fractured media and elements of the theory of the phenomenon of dispersion. She notably discusses the reversibility of the Taylor dispersion which is the prevailing mechanism for simply connected geometries such as in the case of a flow between two continuous solid surfaces limiting a fracture. In the next chapters, the author reports the analysis of characteristics of local structures (mouths, roughnesses) of a single fracture by using echo dispersion. She reports experiments as well as Monte Carlo simulations performed on well defined geometries. In a parallel way, some characteristics measurements (rate-pressure, distribution of flows and tracing in transmission) and mechanical measurements of fracture deformation have been performed on a natural fracture in a granitic site [fr

  2. Discrete element method study of fuel relocation and dispersal during loss-of-coolant accidents

    International Nuclear Information System (INIS)

    Govers, K.; Verwerft, M.

    2016-01-01

    The fuel fragmentation, relocation and dispersal (FFRD) during LOCA transients today retain the attention of the nuclear safety community. The fine fragmentation observed at high burnup may, indeed, affect the Emergency Core Cooling System performance: accumulation of fuel debris in the cladding ballooned zone leads to a redistribution of the temperature profile, while dispersal of debris might lead to coolant blockage or to debris circulation through the primary circuit. This work presents a contribution, by discrete element method, towards a mechanistic description of the various stages of FFRD. The fuel fragments are described as a set of interacting particles, behaving as a granular medium. The model shows qualitative and quantitative agreement with experimental observations, such as the packing efficiency in the balloon, which is shown to stabilize at about 55%. The model is then applied to study fuel dispersal, for which experimental parametric studies are both difficult and expensive. - Highlights: • We performed Discrete Element Methods simulation for fuel relocation and dispersal during LOCA transients. • The approach provides a mechanistic description of these phenomena. • The approach shows the ability of the technique to reproduce experimental observations. • The packing fraction in the balloon is shown to stabilize at 50–60%.

  3. Dielectric lattice gauge theory

    International Nuclear Information System (INIS)

    Mack, G.

    1983-06-01

    Dielectric lattice gauge theory models are introduced. They involve variables PHI(b)epsilong that are attached to the links b = (x+esub(μ),x) of the lattice and take their values in the linear space g which consists of real linear combinations of matrices in the gauge group G. The polar decomposition PHI(b)=U(b)osub(μ)(x) specifies an ordinary lattice gauge field U(b) and a kind of dielectric field epsilonsub(ij)proportionalosub(i)osub(j)sup(*)deltasub(ij). A gauge invariant positive semidefinite kinetic term for the PHI-field is found, and it is shown how to incorporate Wilson fermions in a way which preserves Osterwalder Schrader positivity. Theories with G = SU(2) and without matter fields are studied in some detail. It is proved that confinement holds, in the sense that Wilson loop expectation values show an area law decay, if the Euclidean action has certain qualitative features which imply that PHI = 0 (i.e. dielectric field identical 0) is the unique maximum of the action. (orig.)

  4. Dielectric lattice gauge theory

    International Nuclear Information System (INIS)

    Mack, G.

    1984-01-01

    Dielectric lattice gauge theory models are introduced. They involve variables PHI(b)element ofG that are attached to the links b = (x+esub(μ), x) of the lattice and take their values in the linear space G which consists of real linear combinations of matrices in the gauge group G. The polar decomposition PHI(b)=U(b)sigmasub(μ)(x) specifies an ordinary lattice gauge field U(b) and a kind of dielectric field epsilonsub(ij)proportional sigmasub(i)sigmasub(j)sup(*)deltasub(ij). A gauge invariant positive semidefinite kinetic term for the PHI-field is found, and it is shown how to incorporate Wilson fermions in a way which preserves Osterwalder-Schrader positivity. Theories with G = SU(2) and without matter fields are studied in some detail. It is proved that confinement holds, in the sense that Wilson-loop expectation values show an area law decay, if the euclidean action has certain qualitative features which imply that PHI=0 (i.e. dielectric field identical 0) is the unique maximum of the action. (orig.)

  5. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil

  6. Study of influence of fuel on dielectric and ferroelectric properties of bismuth titanate ceramics synthesized using solution based combustion technique

    International Nuclear Information System (INIS)

    Subohi, Oroosa; Malik, M M; Kurchania, Rajnish; Kumar, G S

    2015-01-01

    The effect of fuel characteristics on the processing and properties of bismuth titanate (BIT) ceramics obtained by solution combustion route using different fuels are reported in this paper. Dextrose, urea and glycine were used as fuel in this study. The obtained bismuth titanate ceramics were characterized by using XRD, SEM at different stages of sample preparation. It was observed that BIT obtained by using dextrose as fuel shows higher dielectric constant and higher remnant polarization due to smaller grain size and lesser c-axis growth as compared to the samples with urea and glycine as fuel. The electrical behavior of the samples with respect to temperature and frequency was also investigated to understand relaxation phenomenon. (paper)

  7. Synthesis and study of the optical properties of dielectric Bragg reflectors infiltrated with 6G-Rhodamine

    International Nuclear Information System (INIS)

    Gómez-Barojas, E; Aca-López, V; Luna-López, J A; Sánchez-Mora, E; Silva-González, R

    2014-01-01

    We report the study of the optical properties of 6G-Rhodamine (Rhd) infiltrated porous silicon dielectric Bragg reflectors (DBRs) with 31 constituent periods. The DBRs were obtained by an electrochemical anodizing process of Si in a two electrodes Teflon cell. The porosity was determined by gravimetric measurements on single Porous silicon (PSi) layers. Based on the characterization results of single layers the DBRs were synthesized. After anodizing, the DBRs were silanized with a 3-mercaptopropyltrimethoxysilane solution and functionalized with Rhd solutions at different concentrations. Cross section scanning electron micrographs show that the DBRs synthesis was successful. After each preparation step, Reflectance and Fluorescence (FL) spectra were recorded. These spectra show that as the Rhd concentration in solution is increased the stop band intensity as well as the FL intensity are enhanced due to constructive interference effects

  8. Dispersive photonic crystals from the plane wave method

    Energy Technology Data Exchange (ETDEWEB)

    Guevara-Cabrera, E.; Palomino-Ovando, M.A. [Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Apdo. Post. 165, Puebla, Pue. 72000, México (Mexico); Flores-Desirena, B., E-mail: bflores@fcfm.buap.mx [Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Apdo. Post. 165, Puebla, Pue. 72000, México (Mexico); Gaspar-Armenta, J.A. [Departamento de Investigación en Física de la Universidad de Sonora Apdo, Post 5-088, Hermosillo Sonora 83190, México (Mexico)

    2016-03-01

    Nowadays photonic crystals are widely used in many different applications. One of the most used methods to compute their band structure is the plane wave method (PWM). However, it can only be applied directly to non-dispersive media and be extended to systems with a few model dielectric functions. We explore an extension of the PWM to photonic crystals containing dispersive materials, that solves an eigenvalue equation for the Bloch wave vectors. First we compare our calculation with analytical results for one dimensional photonic crystals containing Si using experimental values of its optical parameters, and obtainig very well agreement, even for the spectrum region with strong absorption. Then, using the same method, we computed the band structure for a two dimensional photonic crystal without absorption, formed by an square array of MgO cylinders in air. The optical parameters for MgO were modeled with the Lorentz dielectric function. Finally, we studied an array of MgO cylinders in a metal, using Drude model without absorption, for the metal dielectric function. For this last case, we study the gap–midgap ratio as a function of the filling fraction for both the square and triangular lattice. The gap–midgap ratio is larger for the triangular lattice, with a maximum value of 10% for a filling fraction of 0.6. Our results show that the method can be applied to dispersive materials, and then to a wide range of applications where photonic crystals can be used.

  9. Structure and dynamics of hyaluronic acid semidilute solutions: a dielectric spectroscopy study.

    Science.gov (United States)

    Vuletić, T; Dolanski Babić, S; Ivek, T; Grgicin, D; Tomić, S; Podgornik, R

    2010-07-01

    Dielectric spectroscopy is used to investigate fundamental length scales describing the structure of hyaluronic acid sodium salt (Na-HA) semidilute aqueous solutions. In salt-free regime, the length scale of the relaxation mode detected in MHz range scales with HA concentration as c(HA)(-0.5) and corresponds to the de Gennes-Pfeuty-Dobrynin correlation length of polyelectrolytes in semidilute solution. The same scaling was observed for the case of long, genomic DNA. Conversely, the length scale of the mode detected in kilohertz range also varies with HA concentration as c(HA)(-0.5) which differs from the case of DNA (c(DNA)(-0.25)). The observed behavior suggests that the relaxation in the kilohertz range reveals the de Gennes-Dobrynin renormalized Debye screening length, and not the average size of the chain, as the pertinent length scale. Similarly, with increasing added salt the electrostatic contribution to the HA persistence length is observed to scale as the Debye length, contrary to scaling pertinent to the Odijk-Skolnick-Fixman electrostatic persistence length observed in the case of DNA. We argue that the observed features of the kilohertz range relaxation are due to much weaker electrostatic interactions that lead to the absence of Manning condensation as well as a rather high flexibility of HA as compared to DNA.

  10. Rigorous numerical study of strong microwave photon-magnon coupling in all-dielectric magnetic multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Maksymov, Ivan S., E-mail: ivan.maksymov@uwa.edu.au [School of Physics M013, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); ARC Centre of Excellence for Nanoscale BioPhotonics, School of Applied Sciences, RMIT University, Melbourne, VIC 3001 (Australia); Hutomo, Jessica; Nam, Donghee; Kostylev, Mikhail [School of Physics M013, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)

    2015-05-21

    We demonstrate theoretically a ∼350-fold local enhancement of the intensity of the in-plane microwave magnetic field in multilayered structures made from a magneto-insulating yttrium iron garnet (YIG) layer sandwiched between two non-magnetic layers with a high dielectric constant matching that of YIG. The enhancement is predicted for the excitation regime when the microwave magnetic field is induced inside the multilayer by the transducer of a stripline Broadband Ferromagnetic Resonance (BFMR) setup. By means of a rigorous numerical solution of the Landau-Lifshitz-Gilbert equation consistently with the Maxwell's equations, we investigate the magnetisation dynamics in the multilayer. We reveal a strong photon-magnon coupling, which manifests itself as anti-crossing of the ferromagnetic resonance magnon mode supported by the YIG layer and the electromagnetic resonance mode supported by the whole multilayered structure. The frequency of the magnon mode depends on the external static magnetic field, which in our case is applied tangentially to the multilayer in the direction perpendicular to the microwave magnetic field induced by the stripline of the BFMR setup. The frequency of the electromagnetic mode is independent of the static magnetic field. Consequently, the predicted photon-magnon coupling is sensitive to the applied magnetic field and thus can be used in magnetically tuneable metamaterials based on simultaneously negative permittivity and permeability achievable thanks to the YIG layer. We also suggest that the predicted photon-magnon coupling may find applications in microwave quantum information systems.

  11. Dielectric functions and energy band gap variation studies of manganese doped Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12} thin films using spectroscopic ellipsometry

    Energy Technology Data Exchange (ETDEWEB)

    Gautam, Prikshit, E-mail: pgautam.phy.du@gmail.com [Department of Physics and Astrophysics, University of Delhi (DU), Delhi 110007 (India); Department of Physics Kirori Mal College, University of Delhi, Delhi 110007 (India); Sachdeva, Anupama [Department of Physics and Astrophysics, University of Delhi (DU), Delhi 110007 (India); Singh, Sushil K. [Functional Materials Division, SSPL, Timarpur, New Delhi 110054 (India); Tandon, R.P., E-mail: ram_tandon@hotmail.com [Department of Physics and Astrophysics, University of Delhi (DU), Delhi 110007 (India)

    2014-12-25

    Highlights: • Mn Doped Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12} (BLT) thin films prepared by chemical solution deposition technique. • Raman spectroscopy of these films shows that Mn{sup 3+} is well substituted at Ti{sup 4+} site. • The optical properties of BLT and Mn modified BLT thin films were investigated by using spectroscopic ellipsometry. • A double Tauc–Lorentz (DTL) dispersion relation was successfully used to model the dielectric functions. • The direct optical band gap (Eg{sup d}) is found to decrease with increase in Mn content. - Abstract: Single phase polycrystalline Mn-modified Bi{sub 3.25}La{sub 0.75}Ti{sub 3}O{sub 12} (BLT) thin films were prepared by chemical solution deposition method using spin coating technique on Pt/Ti/SiO{sub 2}/Si (1 0 0) substrates. Raman spectroscopy of these films shows that Mn{sup 3+} is well substituted at Ti{sup 4+} site. The optical properties of BLT and Mn modified BLT thin films were investigated at room temperature by using spectroscopic ellipsometry (SE) in the energy range 0.72–6.2 eV. A double Tauc–Lorentz (DTL) dispersion relation was successfully used to model the dielectric functions of these films where a shift to the lower energy side with Mn doping is seen. The full width at half maxima (FWHM) (Γ) of dielectric function is found to increase with Mn doping. This increase in FWHM may be attributed to the increase in the trap density in forbidden band which consequently decreases the value of direct optical band gap (Eg{sup d}). The direct optical band gap (Eg{sup d}) is found to decrease with increase in Mn content in the studied composition range. This decrease in Eg{sup d} with doping may be attributed to the variation in the defect concentration present in the structure.

  12. UV response on dielectric properties of nano nematic liquid crystal

    Directory of Open Access Journals (Sweden)

    Kamal Kumar Pandey

    2018-03-01

    Full Text Available In this work, we investigate the effect of UV light irradiation on the dielectric parameters of nematic liquid crystal (5CB and ZnO nanoparticles dispersed liquid crystal. With addition of nanoparticles in nematic LC are promising new materials for a variety of application in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however we optimize the properties of liquid crystal and understand how the UV light irradiation interact the nanoparticles and LC molecules in dispersed/doped LC. The dielectric permittivity and loss factor have discussed the pure nematic LC and dispersed/doped system after, during and before UV light exposure. The dielectric relaxation spectroscopy was carried out in the frequency range 100 Hz–10 MHz in the nematic mesophase range. Keywords: Dielectric permittivity, Relaxation frequency, Nematic liquid crystal, UV light irradiation

  13. Radiotracer study on dispersion of sewerage off Mumbai Coast in Western India

    International Nuclear Information System (INIS)

    Kumar, U.S.; Yelgaonkar, V.N.; Navada, S.V.

    1997-01-01

    Municipal Corporation of Greater Mumbai discharges the treated sewage at various locations off Mumbai coast. One such discharge point is located near Colaba near South Mumbai. Screened, degritted and aerated sewage is discharged through a 1 m diameter steel pipe by gravity to the diffuser installed on the sea bed at 1.1 km away from the shore. A radiotracer study was carried out to evaluate the dilution and dispersion pattern of the sewage at different points from the disposal point. The experiment was carried out during high tide. About 110 GBq of 82 Br was used as the tracer. A dilution factor of about 5.5 x 10 3 was obtained at a distance of 4.3 km from the outfall. The dilution downshore was small even for a long distance due to strong unidirectional currents. Comparable dilution factors were also obtained by Brooks' model. Vertical tracer profiles showed that the waste plume was well mixed over a depth of 2 to 3 m from the surface. A 2-D advection simulation model was employed to simulate the spatial and temporal distribution of the radiotracer data. From the model simulation best fit was obtained for dispersion coefficients Dx = 15 m 2 .s -1 and Dy = 2m 2 .s -1 . The dispersion coefficients can be used for predicting the effluent dispersion under different outfall and disposal conditions. The tracer pattern at Colaba and Malad indicated no possibility of contamination of the beaches

  14. 30 years of the Goiania Accident: a comparative study with other radioactivity dispersion events

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Ricardo Bastos; Vicente, Roberto, E-mail: rbsmith@ipen.br, E-mail: rvicente@ipen.br [Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil)

    2017-07-01

    The year 2017 marks 30 years since the radioactive accident that occurred in the city of Goiania, capital of the state of Goias. It was the largest radiological accident in Brazil, and one of the largest in the world occurring outside nuclear facilities. Regarding the accidents at nuclear power plants, two of the biggest were Chernobyl in Ukraine, a year and a half before Goiania, and the Fukushima accident in Japan, in 2011. Different amounts of radioactive material were dispersed in the environment in each of these events. However, each one’s main pathway of dispersion was different: the accident of Goiania was terrestrial, Chernobyl was at the atmosphere, and Fukushima was mainly in the ocean. This work aims to study these different amounts, comparing such activities. In addition, it proposes to compare the sea dispersion of Fukushima with the amount of radioactive waste dumped in the oceans, when the release of radioactive waste at sea was permitted. It also proposes to compare the Chernobyl aerial dispersion with the radioactive material dissipated in the atmosphere, resulting from the more than 500 atmospheric nuclear tests conducted between 1945 and 1962 by the United States, the former Soviet Union, England, France and China. (author)

  15. 30 years of the Goiania Accident: a comparative study with other radioactivity dispersion events

    International Nuclear Information System (INIS)

    Smith, Ricardo Bastos; Vicente, Roberto

    2017-01-01

    The year 2017 marks 30 years since the radioactive accident that occurred in the city of Goiania, capital of the state of Goias. It was the largest radiological accident in Brazil, and one of the largest in the world occurring outside nuclear facilities. Regarding the accidents at nuclear power plants, two of the biggest were Chernobyl in Ukraine, a year and a half before Goiania, and the Fukushima accident in Japan, in 2011. Different amounts of radioactive material were dispersed in the environment in each of these events. However, each one’s main pathway of dispersion was different: the accident of Goiania was terrestrial, Chernobyl was at the atmosphere, and Fukushima was mainly in the ocean. This work aims to study these different amounts, comparing such activities. In addition, it proposes to compare the sea dispersion of Fukushima with the amount of radioactive waste dumped in the oceans, when the release of radioactive waste at sea was permitted. It also proposes to compare the Chernobyl aerial dispersion with the radioactive material dissipated in the atmosphere, resulting from the more than 500 atmospheric nuclear tests conducted between 1945 and 1962 by the United States, the former Soviet Union, England, France and China. (author)

  16. Stability and generalization in seed dispersal networks: a case study of frugivorous fish in Neotropical wetlands.

    Science.gov (United States)

    Correa, Sandra Bibiana; Arujo, Joisiane K; Penha, Jerry; Nunes da Cunha, Catia; Bobier, Karen E; Anderson, Jill T

    2016-08-31

    When species within guilds perform similar ecological roles, functional redundancy can buffer ecosystems against species loss. Using data on the frequency of interactions between fish and fruit, we assessed whether co-occurring frugivores provide redundant seed dispersal services in three species-rich Neotropical wetlands. Our study revealed that frugivorous fishes have generalized diets; however, large-bodied fishes had greater seed dispersal breadth than small species, in some cases, providing seed dispersal services not achieved by smaller fish species. As overfishing disproportionately affects big fishes, the extirpation of these species could cause larger secondary extinctions of plant species than the loss of small specialist frugivores. To evaluate the consequences of frugivore specialization for network stability, we extracted data from 39 published seed dispersal networks of frugivorous birds, mammals and fish (our networks) across ecosystems. Our analysis of interaction frequencies revealed low frugivore specialization and lower nestedness than analyses based on binary data (presence-absence of interactions). In that case, ecosystems may be resilient to loss of any given frugivore. However, robustness to frugivore extinction declines with specialization, such that networks composed primarily of specialist frugivores are highly susceptible to the loss of generalists. In contrast with analyses of binary data, recently developed algorithms capable of modelling interaction strengths provide opportunities to enhance our understanding of complex ecological networks by accounting for heterogeneity of frugivore-fruit interactions. © 2016 The Author(s).

  17. Effect of Compatibilization on Interfacial Polarization and Intrinsic Length Scales in Biphasic Polymer Blends of PαMSAN and PMMA : A Combined Experimental and Modeling Dielectric Study

    NARCIS (Netherlands)

    Bharati, A.; Wübbenhorst, M.; Moldenaers, Paula; Cardinaels, Ruth

    2016-01-01

    We describe an approach to tailor the dielectric interfacial properties of polymer blends by the interplay of compatibilizer effects on blend morphology and on blocking of charge carriers. A systematic study of the effect of the concentration of the compatibilizer, a random copolymer of

  18. Dielectric Property Enhancement in Polymer Composites with Engineered Interfaces

    Science.gov (United States)

    Krentz, Timothy Michael

    This thesis reports studies into the dielectric behavior of polymer composites filled with silica nanoparticles. The permittivity and dielectric breakdown strength (DBS) of these materials are critical to their performance in insulating applications such as high voltage power transmission. Until now, the mechanisms which lead to improvements in DBS in these systems have been poorly understood, in part because the effects of dispersion of the filler and the filler's surface electronic characteristics have been confused. The new surface modifications created in this thesis permit these two parameters to be addressed independently, leading to the hypothesis that nanocomposite dielectric materials exhibit DBS enhancement when electron avalanches are prevented from proceeding to reach a critical size capable of causing failure. The same control of dispersion and surface properties also lead to changes in the permittivity of the composite based upon the polarizability and trapping behavior of the filler. In this work, the dispersion and surface states of silica nanoparticles were independently controlled with two separate populations of surface molecules. Two matrix materials were studied, and in each system, a different, matrix-compatible long chain polymer is required to control dispersion. Conversely, a second population of short molecules is shown to be capable of creating electronic traps associated with the silica nanoparticle surface which lead to DBS enhancements largely independent of the matrix, indicating that the same failure mechanism is operating in both epoxy and polypropylene. Progressive variation in dispersion quality is attained with this surface modification scheme. This creates progressively smaller volumes of matrix polymer unaffected by the filler. This work shows that when these volumes approach and become smaller than the same scale as predicted for electron avalanches, the greatest changes in DBS are seen. Likewise, the plateau behavior of this

  19. Peculiarities of low-frequency dielectric spectra and domain wall motion in gadolinium molybdate

    International Nuclear Information System (INIS)

    Galiyarova, N.M.; Gorin, S.V.; Dontsova, L.I.; Shil'nikov, A.V.; Shuvalov, L.A.

    1994-01-01

    Low-frequency Debye dispersion of dielectric permeability in GMO with the low values of high-frequency limit ε ∞ was investigated in a wide temperature range as well as in fields of variable amplitude. The features of domain boundaries motion were studied at the partial repolarization in monopolar P-pulsed fields. The model of cooperationrelaxation motion brifing in parallel with positive to negative contribution to polarization that explained the low values of ε ∞ was suggested

  20. Extrinsic and Intrinsic Frequency Dispersion of High-k Materials in Capacitance-Voltage Measurements

    Directory of Open Access Journals (Sweden)

    S. Taylor

    2012-06-01

    Full Text Available In capacitance-voltage (C-V measurements, frequency dispersion in high-k dielectrics is often observed. The frequency dependence of the dielectric constant (k-value, that is the intrinsic frequency dispersion, could not be assessed before suppressing the effects of extrinsic frequency dispersion, such as the effects of the lossy interfacial layer (between the high-k thin film and silicon substrate and the parasitic effects. The effect of the lossy interfacial layer on frequency dispersion was investigated and modeled based on a dual frequency technique. The significance of parasitic effects (including series resistance and the back metal contact of the metal-oxide-semiconductor (MOS capacitor on frequency dispersion was also studied. The effect of surface roughness on frequency dispersion is also discussed. After taking extrinsic frequency dispersion into account, the relaxation behavior can be modeled using the Curie-von Schweidler (CS law, the Kohlrausch-Williams-Watts (KWW relationship and the Havriliak-Negami (HN relationship. Dielectric relaxation mechanisms are also discussed.

  1. A study on the evolution of dielectric function of ZnO thin films with decreasing film thickness

    International Nuclear Information System (INIS)

    Li, X. D.; Chen, T. P.; Liu, P.; Liu, Y.; Liu, Z.; Leong, K. C.

    2014-01-01

    Dielectric function, band gap, and exciton binding energies of ultrathin ZnO films as a function of film thickness have been obtained with spectroscopic ellipsometry. As the film thickness decreases, both real (ε 1 ) and imaginary (ε 2 ) parts of the dielectric function decrease significantly, and ε 2 shows a blue shift. The film thickness dependence of the dielectric function is shown related to the changes in the interband absorption, discrete-exciton absorption, and continuum-exciton absorption, which can be attributed to the quantum confinement effect on both the band gap and exciton binding energies

  2. Inertial polarization of dielectrics

    OpenAIRE

    Zavodovsky, A. G.

    2011-01-01

    It was proved that accelerated motion of a linear dielectric causes its polarization. Accelerated translational motion of a dielectric's plate leads to the positive charge of the surface facing the direction of motion. Metal plates of a capacitor were used to register polarized charges on a dielectric's surface. Potential difference between the capacitor plates is proportional to acceleration, when acceleration is constant potential difference grows with the increase of a dielectric's area, o...

  3. Study of structural, electrical, and dielectric properties of phosphate-borate glasses and glass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Melo, B. M. G.; Graça, M. P. F., E-mail: mpfg@ua.pt; Prezas, P. R.; Valente, M. A. [Physics Department (I3N), Aveiro University, Campus Universitário de Santiago, Aveiro (Portugal); Almeida, A. F.; Freire, F. N. A. [Mechanics Engineering Department, Ceará Federal University, Fortaleza (Brazil); Bih, L. [Equipe Physico-Chimie la Matière Condensée, Faculté des Sciences de Meknès, Meknès (Morocco)

    2016-08-07

    In this work, phosphate-borate based glasses with molar composition 20.7P{sub 2}O{sub 5}–17.2Nb{sub 2}O{sub 5}–13.8WO{sub 3}–34.5A{sub 2}O–13.8B{sub 2}O{sub 3}, where A = Li, Na, and K, were prepared by the melt quenching technique. The as-prepared glasses were heat-treated in air at 800 °C for 4 h, which led to the formation of glass-ceramics. These high chemical and thermal stability glasses are good candidates for several applications such as fast ionic conductors, semiconductors, photonic materials, electrolytes, hermetic seals, rare-earth ion host solid lasers, and biomedical materials. The present work endorses the analysis of the electrical conductivity of the as-grown samples, and also the electrical, dielectric, and structural changes established by the heat-treatment process. The structure of the samples was analyzed using X-Ray powder Diffraction (XRD), Raman spectroscopy, and density measurements. Both XRD and Raman analysis confirmed crystals formation through the heat-treatment process. The electrical ac and dc conductivities, σ{sub ac} and σ{sub dc}, respectively, and impedance spectroscopy measurements as function of the temperature, varying from 200 to 380 K, were investigated for the as-grown and heat-treated samples. The impedance spectroscopy was measured in the frequency range of 100 Hz–1 MHz.

  4. Dielectric study of Poly(styrene- co -butadiene) Composites with Carbon Black, Silica, and Nanoclay

    KAUST Repository

    Vo, Loan T.

    2011-08-09

    Dielectric spectroscopy is used to measure polymer relaxation in styrene-butadiene rubber (SBR) composites. In addition to the bulk polymer relaxation, the SBR nanocomposites also exhibit a slower relaxation attributed to polymer relaxation at the polymer-nanoparticle interface. The glass transition temperature associated with the slower relaxation is used as a way to quantify the interaction strength between the polymer and the surface. Comparisons were made among composites containing nanoclay, silica, and carbon black. The interfacial relaxation glass transition temperature of SBR-clay nanocomposites is more than 80 °C higher than the SBR bulk glass transition temperature. An interfacial mode was also observed for SBR-silica nanocomposites, but the interfacial glass transition temperature of SBR-silica nanocomposite is somewhat lower than that of clay nanocomposites. An interfacial mode is also seen in the carbon black filled system, but the signal is too weak to analyze quantitatively. The interfacial polymer relaxation in SBR-clay nanocomposites is stronger compared to both SBR-carbon black and SBR-silica composites indicating a stronger interfacial interaction in the nanocomposites containing clay. These results are consistent with dynamic shear rheology and dynamic mechanical analysis measurements showing a more pronounced reinforcement for the clay nanocomposites. Comparisons were also made among clay nanocomposites using different SBRs of varying styrene concentration and architecture. The interfacial glass transition temperature of SBR-clay nanocomposites increases as the amount of styrene in SBR increases indicating that styrene interacts more strongly than butadiene with clay. © 2011 American Chemical Society.

  5. Ac conductivity and dielectric spectroscopy studies on tin oxide thin films formed by spray deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Barış, Behzad, E-mail: behzadbaris@gmail.com

    2014-04-01

    Au/tin oxide/n-Si (1 0 0) structure has been created by forming a tin oxide (SnO{sub 2}) on n-type Si by using the spray deposition technique. The ac electrical conductivity (σ{sub ac}) and dielectric properties of the structure have been investigated between 30 kHz and 1 MHz at room temperature. The values of ε', ε″, tanδ, σ{sub ac}, M' and M″ were determined as 1.404, 0.357, 0.253, 1.99×10{sup −7} S/cm, 0.665 and 0.168 for 1 MHz and 6.377, 6.411, 1.005, 1.07×10{sup −7} S/cm, 0.077 and 0.078 for 30 kHz at zero bias, respectively. These changes were attributed to variation of the charge carriers from the interface traps located between semiconductor and metal in the band gap. It is concluded that the values of the ε', ε″ and tanδ increase with decreasing frequency while a decrease is seen in σ{sub ac} and the real (M') and imaginary (M″) components of the electrical modulus. The M″ parameter of the structure has a relaxation peak as a function of frequency for each examined voltage. The relaxation time of M″(τ{sub M″}) varies from 0.053 ns to 0.018 ns with increasing voltage. The variation of Cole–Cole plots of the sample shows that there is one relaxation.

  6. Marine radioactivity studies in the Suez Canal. A modelling study on radionuclide dispersion

    International Nuclear Information System (INIS)

    Abril, J.M.; Abdel-Aal, M.M.

    2000-01-01

    This paper describes work carried out under the IAEA Project EGY/07/002 to study the dispersion of radioactive material in the Suez Canal and the Bitter Lakes. This effort is linked with increased public concern about radiation safety through this important trade route. We apply a sequence of related modelling approaches, covering: (1) hydrodynamics, (2) transport of dissolved pollutants, (3) suspended loads and sediment dynamics, and (4) electrolytic reactions in aqueous suspension and in-sediment water pores. The final stage is a kinetic-reactive transport model for these tidal waters. The hydrodynamics have been studied using both 1D and 2D modelling approaches, and a reasonable calibration has been possible from the data set prepared with the collaboration of the Suez Canal Authority. Diffusion coefficients are calibrated from field tracing experiments included in the IAEA Project. They have been implemented in 1D and 2D models. Suspended matter dynamics and electrolytic reactions are documented from the available literature. Finally, different scenarios of discharges for both conservative and non-conservative radionuclides have been investigated

  7. Parametric study of the dispersion aspects in a street-canyon area

    Energy Technology Data Exchange (ETDEWEB)

    Koutsourakis, N.; Neofytou, P.; Venetsanos, A.G.; Bartzis, J.G. [NCSR Demokritos (Greece). Environmental Research Lab.

    2004-07-01

    Continuously increasing vehicles' fleet is still considered to be the main emission factor in urban environments, despite the enormous progress of modern catalytic technology. Under that perspective, calculation of transportation induced pollutant dispersion is of augmented importance, especially within street canyons, where poor ventilation can result in awkward concentration levels. Computational Fluid Dynamics (CFD) studies have been conducted in the past by Neofytou, P. et al, so as to define appropriate locations for measuring-instrument placement by numerically simulating the flow and pollution dispersion fields in the vicinity of the measuring site taking into account the wind rose of the area and selecting locations of high pollution concentrations so that non-zero indications are assured. Vardoulakis, S. et al, provides a general overview of the street-canyon studies concerning both modelling and experimental investigations and offers plenty of references on air quality within street canyons. Besides air-quality, street canyon CFD studies have also been performed to evaluate accident consequences and hydrogen safety, Venetsanos A. et al. The current study examines a real street canyon in Thessaloniki, Greece. It was performed in order to examine dispersion patterns for different parameters' scenarios and help deciding where to place actual pollutant measurement instruments to better capture traffic pollution data. Various wind directions and speeds are examined and height influence on concentration levels is investigated. Complex area geometry is a key factor of the whole study. (orig.)

  8. Experimental and numerical study of light gas dispersion in a ventilated room

    Energy Technology Data Exchange (ETDEWEB)

    Gelain, Thomas, E-mail: thomas.gelain@irsn.fr; Prévost, Corinne

    2015-11-15

    Highlights: • Presentation of many experimental local data for different configurations. • Highlight of the influence of numerical parameters used in the CFD code. • Validation of the CFD code ANSYS CFX on the basis of experimental data. - Abstract: The objective of this study is to validate the ANSYS CFX version 12 computational code on the basis of light gas dispersion tests performed in two ventilated rooms. It follows an initial study on heavy gas dispersion carried out by Ricciardi et al. (2008). First, a study of sensitivity to various numerical parameters allows a set of reference data to be developed and the influence of the numerical scheme of advection to be revealed. Second, two helium (simulating hydrogen) dispersion test grids are simulated for the two rooms studied, and the results of the calculations are compared with experimental results. The very good agreement between these results allows the code and its dataset to be validated for this application. In future, a study with higher levels of helium (on the order of 4% vol at equilibrium) is envisaged in the context of safety analyses related to the hydrogen risk, these levels representing the lower explosive limit (LEL) of hydrogen.

  9. Optimal Super Dielectric Material

    Science.gov (United States)

    2015-09-01

    plate capacitor will reduce the net field to an unprecedented extent. This family of materials can form materials with dielectric values orders of... Capacitor -Increase Area (A)............8 b. Multi-layer Ceramic Capacitor -Decrease Thickness (d) .......10 c. Super Dielectric Material-Increase...circuit modeling, from [44], and B) SDM capacitor charge and discharge ...................................................22 Figure 15. Dielectric

  10. Structural, dielectric and ferroelectric properties of (Bi,Na)TiO{sub 3}–BaTiO{sub 3} system studied by high throughput screening

    Energy Technology Data Exchange (ETDEWEB)

    Hayden, Brian E. [Ilika Technologies Plc., Kenneth Dibben House, Enterprise Road, University of Southampton Science Park, Chilworth, Southampton SO16 7NS (United Kingdom); Department of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Yakovlev, Sergey, E-mail: sergey.yakovlev@ilika.com [Ilika Technologies Plc., Kenneth Dibben House, Enterprise Road, University of Southampton Science Park, Chilworth, Southampton SO16 7NS (United Kingdom)

    2016-03-31

    Thin-film materials libraries of the Bi{sub 2}O{sub 3}–Na{sub 2}O–TiO{sub 2}–BaO system in a broad composition range have been deposited in ultra-high vacuum from elemental evaporation sources and an oxygen plasma source. A high throughput approach was used for systematic compositional and structural characterization and the screening of the dielectric and ferroelectric properties. The perovskite (Bi,Na)TiO{sub 3}–BaTiO{sub 3} phase with a Ba concentration near the morphotropic phase boundary (ca. 6 at.%) exhibited a relative dielectric permittivity of 180, a loss tangent of 0.04 and remnant polarization of 19 μC/cm{sup 2}. Compared to published data, observed remnant polarization is close to that known for epitaxially grown films but higher than the values reported for polycrystalline films. The high throughput methodology and systematic nature of the study allowed us to establish the composition boundaries of the phase with optimal dielectric and ferroelectric characteristics. - Highlights: • Bi{sub 2}O{sub 3}–Na{sub 2}O–TiO{sub 2}–BaO high throughput materials library was deposited using PVD method. • Materials were processed from individual molecular beam epitaxy sources of elements. • High throughput approach was used for structural, dielectric and ferroelectric study. • Composition boundaries of perovskite compounds with optimum properties are reported.

  11. Structural, dielectric and ferroelectric properties of (Bi,Na)TiO3–BaTiO3 system studied by high throughput screening

    International Nuclear Information System (INIS)

    Hayden, Brian E.; Yakovlev, Sergey

    2016-01-01

    Thin-film materials libraries of the Bi 2 O 3 –Na 2 O–TiO 2 –BaO system in a broad composition range have been deposited in ultra-high vacuum from elemental evaporation sources and an oxygen plasma source. A high throughput approach was used for systematic compositional and structural characterization and the screening of the dielectric and ferroelectric properties. The perovskite (Bi,Na)TiO 3 –BaTiO 3 phase with a Ba concentration near the morphotropic phase boundary (ca. 6 at.%) exhibited a relative dielectric permittivity of 180, a loss tangent of 0.04 and remnant polarization of 19 μC/cm 2 . Compared to published data, observed remnant polarization is close to that known for epitaxially grown films but higher than the values reported for polycrystalline films. The high throughput methodology and systematic nature of the study allowed us to establish the composition boundaries of the phase with optimal dielectric and ferroelectric characteristics. - Highlights: • Bi 2 O 3 –Na 2 O–TiO 2 –BaO high throughput materials library was deposited using PVD method. • Materials were processed from individual molecular beam epitaxy sources of elements. • High throughput approach was used for structural, dielectric and ferroelectric study. • Composition boundaries of perovskite compounds with optimum properties are reported.

  12. Improvement of CBR and compaction characteristics of bauxite rich dispersive soils available in pakistan: a case study of khushab soil

    International Nuclear Information System (INIS)

    Batool, S.

    2016-01-01

    Dispersion of dispersive soil occurs when it comes in contact with water and clay particles deflocculate and disperse away from each other. Thus dispersive soils undergo erosion under low seepage velocity leading to instability problems of slopes and earth retaining structures. The amount of dispersion depends upon the mineralogy and geochemistry of clayey soil as well as the dissolved salts of the pore fluid. The dispersivity of the soil mainly depends on the amount of exchangeable sodium present in its formation. Under saturated conditions, the attractive forces are less than the repulsive forces and this will help the particles to disperse and go into colloidal suspension. The use of chemical stabilizers such as lime and cement to bind the clay particles and reduce the dispersivity of soil and to improve the compaction and CBR characteristics of bauxite rich dispersive soil present in Khushab district have been studied in this research. Soil behavior was studied after addition of 2%, 4%, 6% and 8% Lime and Cement, at optimum level of 6% for Lime and Cement; it has been observed that the CBR and compaction characteristics of Khushab soil have been improved. (author)

  13. Dispersion relation of electromagnetic waves in one-dimensional plasma photonic crystals

    International Nuclear Information System (INIS)

    Hojo, Hitoshi; Mase, Atsushi

    2004-01-01

    The dispersion relation of electromagnetic waves in one-dimensional plasma photonic crystals is studied. The plasma photonic crystal is a periodic array composed of alternating thin plasma and dielectric material. The dispersion relation is obtained by solving a Maxwell wave equation using a method analogous to Kronig-Penny's problem in quantum mechanics, and it is found that the frequency gap and cut-off appear in the dispersion relation. The frequency gap is shown to become larger with the increase of the plasma density as well as plasma width. (author)

  14. Study of Phonon Dispersion Relations in Cuprous Oxide by Inelastic Neutron Scattering

    DEFF Research Database (Denmark)

    Beg, M. M.; Shapiro, S. M.

    1976-01-01

    Phonon dispersion relations in Cu2O have been studied at 20°C using inelastic neutron scattering. Seven acoustic branches and twelve optical branches have been studied in detail in the three symmetry directions [00ζ], [ζζ0], and [ζζζ] of the cubic lattice. Four of the six zone-center phonons have...... been observed and the assignments and energies are confirmed as Γ25=87±2 cm-1, Γ12′=105±3 cm-1, Γ15=146±1 cm-1, and Γ2′≈347 cm-1. The dispersion relations agree only qualitatively with the rigid-ion-model calculations. It is suggested that more detailed calculations may be performed in the light...

  15. Numerical Study of Traffic Pollutant Dispersion within Different Street Canyon Configurations

    Directory of Open Access Journals (Sweden)

    Yucong Miao

    2014-01-01

    Full Text Available The objective of this study is to numerically study flow and traffic exhaust dispersion in urban street canyons with different configurations to find out the urban-planning strategies to ease the air pollution. The Computational Fluid Dynamics (CFD model used in this study—Open Source Field Operation and Manipulation (OpenFOAM software package—was firstly validated against the wind-tunnel experiment data by using three different k-ε turbulence models. And then the patterns of flow and dispersion within three different kinds of street canyon configuration under the perpendicular approaching flow were numerically studied. The result showed that the width and height of building can dramatically affect the pollution level inside the street canyon. As the width or height of building increases, the pollution at the pedestrian level increases. And the asymmetric configuration (step-up or step-down street canyon could provide better ventilation. It is recommended to design a street canyon with nonuniform configurations. And the OpenFOAM software package can be used as a reliable tool to study flows and dispersions around buildings.

  16. Structural, dielectric and magnetic studies of magnetoelectric trirutile Fe{sub 2}TeO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Kaushik, S. D., E-mail: sdkaushik@csr.res.in [UGC-DAE-Consortium for Scientific Research Mumbai Centre, R-5 Shed, BARC, Mumbai-400085 (India); Sahu, B.; Mohapatra, S. R.; Singh, A. K. [Department of Physics and Astronomy, National Institute of Technology, Rourkela-769008, Odisha (India)

    2016-05-23

    We have investigated structural, magnetic and dielectric properties of Fe{sub 2}TeO{sub 6} which is a magnetoelectric antiferromagnet with the trirutile lattice. Rietveld analysis of room temperature X-ray diffraction data shows the phase purity of the sample with tetragonal trirutile structure (space group P4{sub 2}/mnm). The DC susceptibility measurement performed on polycrystalline powders exhibits antiferromagnetic ordering below transition temperature ~ 210K. The employment of Curie-Weiss law to inverse magnetic susceptibility only in the temperature range 350-260 K indicates the magnetic ordering starts developing before the transition temperature. The temperature dependent dielectric measurements show an intrinsic behavior of dielectric constant below 150 K while a continuous increase in dielectric constant with temperature above 150 K may be attributed to a small increase in electrical conduction, known commonly in the literatures.

  17. Dielectric spectroscopy platform to measure MCF10A epithelial cell aggregation as a model for spheroidal cell cluster analysis.

    Science.gov (United States)

    Heileman, K L; Tabrizian, M

    2017-05-02

    3-Dimensional cell cultures are more representative of the native environment than traditional cell cultures on flat substrates. As a result, 3-dimensional cell cultures have emerged as a very valuable model environment to study tumorigenesis, organogenesis and tissue regeneration. Many of these models encompass the formation of cell aggregates, which mimic the architecture of tumor and organ tissue. Dielectric impedance spectroscopy is a non-invasive, label free and real time technique, overcoming the drawbacks of established techniques to monitor cell aggregates. Here we introduce a platform to monitor cell aggregation in a 3-dimensional extracellular matrix using dielectric spectroscopy. The MCF10A breast epithelial cell line serves as a model for cell aggregation. The platform maintains sterile conditions during the multi-day assay while allowing continuous dielectric spectroscopy measurements. The platform geometry optimizes dielectric measurements by concentrating cells within the electrode sensing region. The cells show a characteristic dielectric response to aggregation which corroborates with finite element analysis computer simulations. By fitting the experimental dielectric spectra to the Cole-Cole equation, we demonstrated that the dispersion intensity Δε and the characteristic frequency f c are related to cell aggregate growth. In addition, microscopy can be performed directly on the platform providing information about cell position, density and morphology. This platform could yield many applications for studying the electrophysiological activity of cell aggregates.

  18. Aging of Dielectric Properties below Tg

    DEFF Research Database (Denmark)

    Olsen, Niels Boye; Dyre, Jeppe; Christensen, Tage Emil

    The dielectric loss at 1Hz in TPP is studied during a temperature step from one equilibrium state to another. In the applied cryostate the temperature can be equilibrated on a timescale of 1 second. The aging time dependence of the dielectric loss is studied below Tg applying temperature steps...

  19. A Molecular Dynamics Study of Single-Walled Carbon Nanotubes (SWCNTs) Dispersed in Bile Salt Surfactants

    Science.gov (United States)

    Phelan, Frederick, Jr.; Sun, Huai

    2014-03-01

    Single-walled carbon nanotubes (SWNCTs) are materials with structural, electronic and optical properties that make them attractive for a myriad of advanced technology applications. A practical barrier to their use is that SWCNT synthesis techniques produce heterogeneous mixtures of varying lengths and chirality, whereas applications generally require tubes with narrow size distributions and individual type. Most separation techniques currently in use to obtain monodisperse tube fractions rely on dispersion of these materials in aqueous solution using surfactants. The dispersion process results in a mixture of colloidal structures in which individual tubes are dispersed and contained in a surfactant shell. Understanding the structure and properties of the SWCNT-surfactant complex at the molecular level, and how this is affected by chirality, is key to understanding and improving separations processes. In this study, we use molecular dynamics (MD) simulations to study the structure and properties of SWCNT-surfactant colloidal complexes. We tested a number of methods and protocols in order to build an accurate model for simulating SWCNT systems for a variety of bile salt surfactants as well as anionic co-surfactants, components that are widely used and important in experimental separation studies at NIST. The custom force field parameters used here will be stored in WebFF, a Web-hosted smart force-field repository for polymeric and organic materials being developed at NIST for the Materials Genome Initiative.

  20. Dielectric Study of the Phase Transitions in [P(CH3)4]2CuY4 (Y = Cl, Br)

    Science.gov (United States)

    Gesi, Kazuo

    2002-05-01

    Phase transitions in [P(CH3)4]2CuY4 (Y = Cl, Br) have been studied by dielectric measurements. In [P(CH3)4]2CuCl4, a slight break and a discontinuous jump on the dielectric constant vs. temperature curve are seen at the normal-incommensurate and the incommensurate-commensurate phase transitions, respectively. A small peak of dielectric constant along the b-direction exists just above the incommensurate-to-commensurate transition temperature. The anisotropic dielectric anomalies of [P(CH3)4]2CuBr4 at phase transitions were measured along the three crystallographic axes. The pressure-temperature phase diagram of [P(CH3)4]2CuCl4 was determined. The initial pressure coefficients of the normal-to-incommensurate and the incommensurate-to-commensurate transition temperatures are 0.19 K/MPa and 0.27 K/MPa, respectively. The incommensurate phase in [P(CH3)4]2CuCl4 disappears at a triple point which exists at 335 MPa and 443 K. The stability and the pressure effects of the incommensurate phases are much different among the four [Z(CH3)4]2CuY4 crystals (Z = N, P; Y = Cl, Br).

  1. Study on the microstructure and dielectric properties of X9R ceramics based on BaTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Gao Shunqi, E-mail: shunqigao@163.com [Institute of Electronics and Information Engineering, Tianjin University, Weijin Road, Tianjin 300072 (China); Wu Shunhua; Zhang Yonggang; Yang Hongxing; Wang Xinru [Institute of Electronics and Information Engineering, Tianjin University, Weijin Road, Tianjin 300072 (China)

    2011-01-15

    This paper investigated the microstructure and dielectric properties of BaTiO{sub 3}-Pb(Sn, Ti)O{sub 3} system ceramics. The Curie point of BaTiO{sub 3} is 130 deg. C. When the temperature is higher than 130 deg. C, the dielectric constant of BaTiO{sub 3} drops severely according to Curie-Weiss law. Pb(Ti, Sn)O{sub 3}(PTS) was selected to compensate the dielectric constant doping of BaTiO{sub 3} since it has high Curie temperature (Tc) point that is about 296 deg. C. The Curie temperature (Tc) point of BaTiO{sub 3} was broadened and shifted to higher temperature because of the doping of PTS, so the temperature coefficient of capacitance (TCC) curves of the ceramics based on BaTiO{sub 3} was flattened. When 2 wt% Pb(Ti{sub 0.55}Sn{sub 0.45})O{sub 3} was added, the sample showed super dielectric properties that the dielectric constant was >1750 at 25 deg. C, dielectric loss was lower than 2.0% and TCC was <{+-}10% from -55 deg. C to 200 deg. C. Therefore the materials satisfied EIA X9R specifications.

  2. Study of SrBi4Ti4O15 (SBTi) dielectric properties of doped PbO

    International Nuclear Information System (INIS)

    Rodrigues Junior, C.A.; Silva Filho, J.M.; Freitas, D.B.; Oliveira, R.G.M.; Sombra, B.; Sales, J.C.

    2012-01-01

    The ceramic SrBi 4 Ti 4 O 15 (SBTI), cation-deficient perovskite A 5 B 4 O 15 , was prepared by the method of solid state reaction and then doped with PbO (in the range 2-10% by weight). The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy at room temperature. The X-ray analysis was performed by the Rietveld refinement. The micrographs of the samples show globular-shaped grains (doped PbO). The dielectric properties: dielectric constant (Κ' or έ) and dielectric loss tangent (tan δ), were measured at room temperature in the frequency range 100 Hz - 1 MHz dielectric properties of these 1 MHz sample doped with 10 % PbO showed the dielectric constant Κ'= 168.34 and dielectric loss tangent tanδ, = 7,1.10 -2 . These results show a good possibility of miniaturization of electronic devices such as capacitors. (author)

  3. Noise study of all-normal dispersion supercontinuum sources for potential application in optical coherence tomography

    DEFF Research Database (Denmark)

    Bravo Gonzalo, Ivan; Engelsholm, Rasmus Dybbro; Bang, Ole

    2017-01-01

    bandwidths, such sources are characterized by large intensity fluctuations, limiting their performance for applications in imaging such as optical coherence tomography (OCT). An approach to eliminate the influence of noise sensitive effects is to use a so-called all-normal dispersion (ANDi) fiber, in which...... the dispersion is normal for all the wavelengths of interest. Pumping these types of fibers with short enough femtosecond pulses allows to suppress stimulated Raman scattering (SRS), which is known to be as noisy process as modulation instability (MI), and coherent SC is generated through self-phase modulation...... (SPM) and optical wave breaking (OWB). In this study, we show the importance of the pump laser and fiber parameters in the design of low-noise ANDi based SC sources, for application in OCT. We numerically investigate the pulse-to-pulse fluctuations of the SC, calculating the relative intensity noise...

  4. A Study On Dispersion Stability Of Nickel Nanoparticles Synthesized By Wire Explosion In Liquid Media

    Directory of Open Access Journals (Sweden)

    Kim C.K.

    2015-06-01

    Full Text Available In this study, nickel nanoparticles were synthesized in ethanol using portable pulsed wire evaporation, which is a one-step physical method. From transmission electron microscopy images, it was found that the Ni nanoparticles exhibited a spherical shape with an average diameter of 7.3 nm. To prevent aggregation of the nickel nanoparticles, a polymer surfactant was added into the ethanol before the synthesis of nickel nanoparticles, and adsorbed on the freshly synthesized nickel nanoparticles during the wire explosion. The dispersion stability of the prepared nickel nanofluids was investigated by zeta-potential analyzer and Turbiscan optical analyzer. As a result, the optimum concentration of polymer surfactant to be added was suggested for the maximized dispersion stability of the nickel nanofluids.

  5. A study of the physical factors affecting air pollution dispersion in Helwan

    International Nuclear Information System (INIS)

    Megahed, A.A.

    1992-01-01

    Air pollution is considered as one of the most important environmental problems facing the humanity. Cement industry, usually, is responsible for building high levels of pollutants. The present research focused on the study of air pollution control of cement industry using mathematical modeling. A mathematical dispersion model was developed based on Gaussian distribution where the dispersion parameters increase with increasing atmospheric turbulence. The Gaussian equation takes in consideration the effect of emission rates. stack height, buoyant plume rise, weather and meteorological parameters. The model was tested for different stack heights, wind speeds. And atmospheric stability classes. Maximum ground level concentration of cement pollutants were measured in different locations of Helwan, south Cairo around the cement factories. Analysis of results shows that the ground level of pollutants concentrations are inversely proportional to wind speed and atmospheric stability classes. Stack height also affects the behaviour of deposition of cement particulates. The model results show satisfactory agreement with the measured concentrations. 6 figs

  6. Ceramic-polymer nanocomposites with increased dielectric permittivity and low dielectric loss

    International Nuclear Information System (INIS)

    Bhardwaj, Sumit; Paul, Joginder; Raina, K. K.; Thakur, N. S.; Kumar, Ravi

    2014-01-01

    The use of lead free materials in device fabrication is very essential from environmental point of view. We have synthesized the lead free ferroelectric polymer nanocomposite films with increased dielectric properties. Lead free bismuth titanate has been used as active ceramic nanofillers having crystallite size 24nm and PVDF as the polymer matrix. Ferroelectric β-phase of the polymer composite films was confirmed by X-ray diffraction pattern. Mapping data confirms the homogeneous dispersion of ceramic particles into the polymer matrix. Frequency dependent dielectric constant increases up to 43.4 at 100Hz, whereas dielectric loss decreases with 7 wt% bismuth titanate loading. This high dielectric constant lead free ferroelectric polymer films can be used for energy density applications

  7. Nanocomposites of TiO2/cyanoethylated cellulose with ultra high dielectric constants

    International Nuclear Information System (INIS)

    Madusanka, Nadeesh; Shivareddy, Sai G; Hiralal, Pritesh; Choi, Youngjin; Amaratunga, Gehan A J; Eddleston, Mark D; Oliver, Rachel A

    2016-01-01

    A novel dielectric nanocomposite containing a high permittivity polymer, cyanoethylated cellulose (CRS) and TiO 2 nanoparticles was successfully prepared with different weight percentages (10%, 20% and 30%) of TiO 2 . The intermolecular interactions and morphology within the polymer nanocomposites were analysed. TiO 2 /CRS nanofilms on SiO 2 /Si wafers were used to form metal–insulator–metal type capacitors. Capacitances and loss factors in the frequency range of 1 kHz–1 MHz were measured. At 1 kHz CRS-TiO 2 nanocomposites exhibited ultra high dielectric constants of 118, 176 and 207 for nanocomposites with 10%, 20% and 30% weight of TiO 2 respectively, significantly higher than reported values of pure CRS (21), TiO 2 (41) and other dielectric polymer-TiO 2 nanocomposite films. Furthermore, all three CRS-TiO 2 nanocomposites show a loss factor <0.3 at 1 kHz and low leakage current densities (10 −6 –10 −7 A cm −2 ). Leakage was studied using conductive atomic force microscopy and it was observed that the leakage is associated with TiO 2 nanoparticles embedded in the CRS polymer matrix. A new class of ultra high dielectric constant hybrids using nanoscale inorganic dielectrics dispersed in a high permittivity polymer suitable for energy management applications is reported. (paper)

  8. Structural and dielectric properties of yttrium-substituted hydroxyapatites

    Energy Technology Data Exchange (ETDEWEB)

    Kaygili, Omer, E-mail: okaygili@firat.edu.tr [Department of Physics, Faculty of Science, Firat University, 23119 Elazig (Turkey); Dorozhkin, Sergey V. [Kudrinskaja sq. 1-155, 123242 Moscow (Russian Federation); Ates, Tankut [Department of Physics, Faculty of Science, Firat University, 23119 Elazig (Turkey); Canan Gursoy, N. [Department of Microbiology and Clinic Microbiology, Inonu University, 44280 Malatya (Turkey); Keser, Serhat [Department of Chemistry, Faculty of Science, Firat University, 23119 Elazig (Turkey); Yakuphanoglu, Fahrettin [Department of Physics, Faculty of Science, Firat University, 23119 Elazig (Turkey); Birkan Selçuk, A. [Technology Department, Saraykoy Nuclear Research and Training Centre, 06983 Ankara (Turkey)

    2015-02-01

    Hydroxyapatite (HAp) samples doped with 0, 2 and 4 at.% of yttrium (Y) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy attached with energy dispersive X-ray (EDX) spectroscopy, antimicrobial activity tests and dielectric studies. The hydroxyl groups observed in FTIR spectra confirmed the formation of HAp phase in the studied samples. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content. The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains. It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content. - Highlights: • The lattice parameters and crystal size are affected by Y content. • The volume of the unit cell was gradually decreased with the addition of Y. • No samples have any antimicrobial effect. • The alternating current conductivity decreases with increasing Y content.

  9. Structural and dielectric properties of yttrium-substituted hydroxyapatites

    International Nuclear Information System (INIS)

    Kaygili, Omer; Dorozhkin, Sergey V.; Ates, Tankut; Canan Gursoy, N.; Keser, Serhat; Yakuphanoglu, Fahrettin; Birkan Selçuk, A.

    2015-01-01

    Hydroxyapatite (HAp) samples doped with 0, 2 and 4 at.% of yttrium (Y) were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy attached with energy dispersive X-ray (EDX) spectroscopy, antimicrobial activity tests and dielectric studies. The hydroxyl groups observed in FTIR spectra confirmed the formation of HAp phase in the studied samples. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content. The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains. It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content. - Highlights: • The lattice parameters and crystal size are affected by Y content. • The volume of the unit cell was gradually decreased with the addition of Y. • No samples have any antimicrobial effect. • The alternating current conductivity decreases with increasing Y content

  10. Lattices of dielectric resonators

    CERN Document Server

    Trubin, Alexander

    2016-01-01

    This book provides the analytical theory of complex systems composed of a large number of high-Q dielectric resonators. Spherical and cylindrical dielectric resonators with inferior and also whispering gallery oscillations allocated in various lattices are considered. A new approach to S-matrix parameter calculations based on perturbation theory of Maxwell equations, developed for a number of high-Q dielectric bodies, is introduced. All physical relationships are obtained in analytical form and are suitable for further computations. Essential attention is given to a new unified formalism of the description of scattering processes. The general scattering task for coupled eigen oscillations of the whole system of dielectric resonators is described. The equations for the  expansion coefficients are explained in an applicable way. The temporal Green functions for the dielectric resonator are presented. The scattering process of short pulses in dielectric filter structures, dielectric antennas  and lattices of d...

  11. Electroactive Phase Induced Bi4Ti3O12-Poly(Vinylidene Difluoride) Composites with Improved Dielectric Properties

    Science.gov (United States)

    Bhardwaj, Sumit; Paul, Joginder; Chand, Subhash; Raina, K. K.; Kumar, Ravi

    2015-10-01

    Lead-free ceramic-polymer composite films containing Bi4Ti3O12 (BIT) nanocrystals as the active phase and poly(vinylidene difluoride) as the passive matrix were synthesized by spin coating. The films' structural, morphological, and dielectric properties were systemically investigated by varying the weight fraction of BIT. Formation of electroactive β and γ phases were strongly affected by the presence of BIT nanocrystals. Analysis was performed by Fourier-transform infrared and Raman spectroscopy. Morphological studies confirmed the homogeneous dispersion of BIT particles within the polymer matrix. The composite films had dielectric constants as high as 52.8 and low dielectric loss of 0.1 at 100 Hz when the BIT content was 10 wt.%. We suggest that the enhanced electroactive phase content of the polymer matrix and interfacial polarization may contribute to the improved dielectric performance of these composite films. Dielectric modulus analysis was performed to enable understanding of the dielectric relaxation process. Non-Debye-type relaxation behavior was observed for the composite films at high temperature.

  12. Disclosed dielectric and electromechanical properties of hydrogenated nitrile–butadiene dielectric elastomer

    International Nuclear Information System (INIS)

    Yang, Dan; Tian, Ming; Dong, Yingchao; Liu, Haoliang; Yu, Yingchun; Zhang, Liqun

    2012-01-01

    This paper presents a comprehensive study of the effects of acrylonitrile content, crosslink density and plasticization on the dielectric and electromechanical performances of hydrogenated nitrile–butadiene dielectric elastomer. It was found that by increasing the acrylonitrile content of hydrogenated nitrile–butadiene dielectric elastomer, the dielectric constant will be improved accompanied with a sharp decrease of electrical breakdown strength leading to a small actuated strain. At a fixed electric field, a high crosslink density increased the elastic modulus of dielectric elastomer, but it also enhanced the electrical breakdown strength leading to a high actuated strain. Adding a plasticizer into the dielectric elastomer decreased the dielectric constant and electrical breakdown strength slightly, but reduced the elastic modulus sharply, which was beneficial for obtaining a large strain at low electric field from the dielectric elastomer. The largest actuated strain of 22% at an electric field of 30 kV mm −1 without any prestrain was obtained. Moreover, the hydrogenated nitrile–butadiene dielectric actuator showed good history dependence. This proposed material has great potential to be an excellent dielectric elastomer. (paper)

  13. Effects of Particle Size and Surface Chemistry on the Dispersion of Graphite Nanoplates in Polypropylene Composites

    Directory of Open Access Journals (Sweden)

    Raquel M. Santos

    2018-02-01

    Full Text Available Carbon nanoparticles tend to form agglomerates with considerable cohesive strength, depending on particle morphology and chemistry, thus presenting different dispersion challenges. The present work studies the dispersion of three types of graphite nanoplates (GnP with different flake sizes and bulk densities in a polypropylene melt, using a prototype extensional mixer under comparable hydrodynamic stresses. The nanoparticles were also chemically functionalized by covalent bonding polymer molecules to their surface, and the dispersion of the functionalized GnP was studied. The effects of stress relaxation on dispersion were also analyzed. Samples were removed along the mixer length, and characterized by microscopy and dielectric spectroscopy. A lower dispersion rate was observed for GnP with larger surface area and higher bulk density. Significant re-agglomeration was observed for all materials when the deformation rate was reduced. The polypropylene-functionalized GnP, characterized by increased compatibility with the polymer matrix, showed similar dispersion effects, albeit presenting slightly higher dispersion levels. All the composites exhibit dielectric behavior, however, the alternate current (AC conductivity is systematically higher for the composites with larger flake GnP.

  14. Dielectric and acoustical high frequency characterisation of PZT thin films

    Energy Technology Data Exchange (ETDEWEB)

    Conde, Janine; Muralt, Paul, E-mail: janine.conde@epfl.ch [Department of Materials Science, EPFL (Switzerland)

    2010-02-15

    Pb(Zr, Ti)O{sub 3} (PZT) is an interesting material for bulk acoustic wave resonator applications due to its high electromechanical coupling constant, which would enable fabrication of large bandwidth frequency filters. The major challenge of the PZT solid solution system is to overcome mechanical losses generally observed in PZT ceramics. To increase the understanding of these losses in textured thin films, thin film bulk acoustic resonators (TFBAR's) based on PZT thin films with compositions either in the tetragonal region or at the morphotropic phase boundary and (111) or {l_brace}100{r_brace} textures were fabricated and studied up to 2 GHz. The dielectric and elastic materials coefficients were extracted from impedance measurements at the resonance frequency. The dispersion of the dielectric constant was obtained from impedance measurements up to 2 GHz. The films with varying compositions, textures and deposition methods (sol-gel or sputtering) were compared in terms of dielectric and acoustical properties.

  15. Marine Radioactivity Studies in the Suez Canal, Part II: Field Experiments and a Modelling Study of Dispersion

    Science.gov (United States)

    Abril, J. M.; Abdel-Aal, M. M.; Al-Gamal, S. A.; Abdel-Hay, F. A.; Zahar, H. M.

    2000-04-01

    In this paper we take advantage of the two field tracing experiments carried out under the IAEA project EGY/07/002, to develop a modelling study on the dispersion of radioactive pollution in the Suez Canal. The experiments were accomplished by using rhodamine B as a tracer, and water samples were measured by luminescence spectrometry. The presence of natural luminescent particles in the canal waters limited the use of some field data. During experiments, water levels, velocities, wind and other physical parameters were recorded to supply appropriate information for the modelling work. From this data set, the hydrodynamics of the studied area has been reasonably described. We apply a 1-D-Gaussian and 2-D modelling approaches to predict the position and the spatial shape of the plume. The use of different formulations for dispersion coefficients is studied. These dispersion coefficients are then applied in a 2-D-hydrodynamic and dispersion model for the Bitter Lake to investigate different scenarios of accidental discharges.

  16. Structural, Raman, and dielectric studies on multiferroic Mn-doped Bi 1-xLax FeO 3 ceramics

    KAUST Repository

    Xing, Zhibiao

    2014-04-03

    Multiferroic Bi1-xLaxFeO3 [BLFO (x)] ceramics with x = 0.10-0.50 and Mn-doped BLFO (x = 0.30) ceramics with different doping contents (0.1-1.0 mol%) were prepared by solid-state reaction method. They were crystallized in a perovskite phase with rhombohedral symmetry. In the BLFO (x) system, a composition (x)-driven structural transformation (R3c→C222) was observed at x = 0.30. The formation of Bi2Fe 4O9 impure phase was effectively suppressed with increasing the x value, and the rhombohedral distortion in the BLFO ceramics was decreased, leading to some Raman active modes disappeared. A significant red frequency shift (~13 cm-1) of the Raman mode of 232 cm-1 in the BLFO ceramics was observed, which strongly perceived a significant destabilization in the octahedral oxygen chains, and in turn affected the local FeO6 octahedral environment. In the Mn-doped BLFO (x = 0.30) ceramics, the intensity of the Raman mode near 628 cm-1 was increased with increasing the Mn-doping content, which was resulted from an enhanced local Jahn-Teller distortions of the (Mn,Fe)O6 octahedra. Electron microscopy images revealed some changes in the ceramic grain sizes and their morphologies in the Mn-doped samples at different contents. Wedge-shaped 71° ferroelectric domains with domain walls lying on the {110} planes were observed in the BLFO (x = 0.30) ceramics, whereas in the 1.0 mol% Mn-doped BLFO (x = 0.30) samples, 71° ferroelectric domains exhibited a parallel band-shaped morphology with average domain width of 95 nm. Dielectric studies revealed that high dielectric loss of the BLFO (x = 0.30) ceramics was drastically reduced from 0.8 to 0.01 (measured @ 104 Hz) via 1.0 mol% Mn-doping. The underlying mechanisms can be understood by a charge disproportion between the Mn4+ and Fe2+ in the Mn-doped samples, where a reaction of Mn4+ + Fe2+→Mn3+ + Fe3+ is taken place, resulting in the reduction in the oxygen vacancies and a suppression of the electron hopping from Fe3+ to Fe2+ ions

  17. Structural, Raman, and dielectric studies on multiferroic Mn-doped Bi 1-xLax FeO 3 ceramics

    KAUST Repository

    Xing, Zhibiao; Zhu, Xinhua; Zhu, Jianmin; Liu, Zhiguo; Al-Kassab, Talaat

    2014-01-01

    Multiferroic Bi1-xLaxFeO3 [BLFO (x)] ceramics with x = 0.10-0.50 and Mn-doped BLFO (x = 0.30) ceramics with different doping contents (0.1-1.0 mol%) were prepared by solid-state reaction method. They were crystallized in a perovskite phase with rhombohedral symmetry. In the BLFO (x) system, a composition (x)-driven structural transformation (R3c→C222) was observed at x = 0.30. The formation of Bi2Fe 4O9 impure phase was effectively suppressed with increasing the x value, and the rhombohedral distortion in the BLFO ceramics was decreased, leading to some Raman active modes disappeared. A significant red frequency shift (~13 cm-1) of the Raman mode of 232 cm-1 in the BLFO ceramics was observed, which strongly perceived a significant destabilization in the octahedral oxygen chains, and in turn affected the local FeO6 octahedral environment. In the Mn-doped BLFO (x = 0.30) ceramics, the intensity of the Raman mode near 628 cm-1 was increased with increasing the Mn-doping content, which was resulted from an enhanced local Jahn-Teller distortions of the (Mn,Fe)O6 octahedra. Electron microscopy images revealed some changes in the ceramic grain sizes and their morphologies in the Mn-doped samples at different contents. Wedge-shaped 71° ferroelectric domains with domain walls lying on the {110} planes were observed in the BLFO (x = 0.30) ceramics, whereas in the 1.0 mol% Mn-doped BLFO (x = 0.30) samples, 71° ferroelectric domains exhibited a parallel band-shaped morphology with average domain width of 95 nm. Dielectric studies revealed that high dielectric loss of the BLFO (x = 0.30) ceramics was drastically reduced from 0.8 to 0.01 (measured @ 104 Hz) via 1.0 mol% Mn-doping. The underlying mechanisms can be understood by a charge disproportion between the Mn4+ and Fe2+ in the Mn-doped samples, where a reaction of Mn4+ + Fe2+→Mn3+ + Fe3+ is taken place, resulting in the reduction in the oxygen vacancies and a suppression of the electron hopping from Fe3+ to Fe2+ ions

  18. Studies on frequency dependent electrical and dielectric properties of sintered zinc oxide pellets: effects of Al-doping

    Science.gov (United States)

    Tewari, S.; Ghosh, A.; Bhattacharjee, A.

    2016-11-01

    Sintered pellets of zinc oxide (ZnO), both undoped and Al-doped are prepared through a chemical process. Dopant concentration of Aluminium in ZnO [Al/Zn in weight percentage (wt%)] is varied from 0 to 3 wt%. After synthesis structural characterisation of the samples are performed with XRD and SEM-EDAX which confirm that all the samples are of ZnO having polycrystalline nature with particle size from 108.6 to 116 nm. Frequency dependent properties like a.c. conductivity, capacitance, impedance and phase angle are measured in the frequency range 10 Hz to 100 kHz as a function of temperature (in the range 25-150 °C). Nature of a.c. conductivity in these samples indicates hopping type of conduction arising from localised defect states. The frequency and temperature dependent properties under study are found to be as per correlated barrier hoping model. Dielectric and impedance properties studied in the samples indicate distributed relaxation, showing decrease of relaxation time with temperature.

  19. Numerical study on the discharge characteristics and nonlinear behaviors of atmospheric pressure coaxial electrode dielectric barrier discharges

    International Nuclear Information System (INIS)

    Zhang Ding-Zong; Wang Yan-Hui; Wang De-Zhen

    2017-01-01

    The discharge characteristics and temporal nonlinear behaviors of the atmospheric pressure coaxial electrode dielectric barrier discharges are studied by using a one-dimensional fluid model. It is shown that the discharge is always asymmetrical between the positive pulses and negative pulses. The gas gap severely affects this asymmetry. But it is hard to acquire a symmetrical discharge by changing the gas gap. This asymmetry is proportional to the asymmetric extent of electrode structure, namely the ratio of the outer electrode radius to the inner electrode radius. When this ratio is close to unity, a symmetrical discharge can be obtained. With the increase of frequency, the discharge can exhibit a series of nonlinear behaviors such as period-doubling bifurcation, secondary bifurcation and chaotic phenomena. In the period-doubling bifurcation sequence the period- n discharge becomes more and more unstable with the increase of n . The period-doubling bifurcation can also be obtained by altering the discharge gas gap. The mechanisms of two bifurcations are further studied. It is found that the residual quasineutral plasma from the previous discharges and corresponding electric field distribution can weaken the subsequent discharge, and leads to the occurrence of bifurcation. (paper)

  20. Growth, optical, thermal and dielectric studies of an amino acid organic nonlinear optical material: L-Alanine

    International Nuclear Information System (INIS)

    Caroline, M. Lydia; Sankar, R.; Indirani, R.M.; Vasudevan, S.

    2009-01-01

    Good transparent bulk single crystals of L-alanine (nonlinear optical material) have been grown successfully by slow cooling technique from aqueous solution at pH value of 2.0. Optically transparent crystals with dimensions 2.4 cm x 1.2 cm x 1.6 cm, were grown by optimizing the growth parameters within a growth period of 2 weeks. The crystallinity of L-alanine crystal was confirmed by the powder X-ray diffraction study and diffraction peaks are indexed. The vibrational structure of the molecule is elucidated from FTIR spectra. The thermal behaviour of the grown crystal was investigated by thermogravimetric (TG) and differential thermal analyses (DTA) techniques in a nitrogen atmosphere. The result showed that the material starts decomposing at 297 deg. C. Its optical behaviour has been examined by UV-vis spectral analysis, which shows the absence of absorbance between the wavelengths ranging from 200 to 1200 nm. The NLO property was confirmed by the powder technique of Kurtz and Perry. The dielectric behaviour of the sample was also studied for the first time

  1. Study of the defect structures produced by heavy ions in dielectrics by means of small angle scattering

    International Nuclear Information System (INIS)

    Albrecht, D.J.

    1983-11-01

    The aim of the present thesis was to study the defects in dielectrics produced by fast ions. For this the small angle scattering was proved as suitable method. By the production by means of the ion beam of an accelerator the defects possess a pronounced preferential direction. In scattering experiments this system of scattering centers is distinguished by its unusually strong dependence of the sample orientation according to the primary beam. This property was studied, described, and illustrated by examples, and it could by shown that from this additional informations about the scattering defects can be derived. For the first time nuclear tracks were detected by means of small angle neutron scattering. It could be shown that here the same results are obtained as by small angle X-ray scattering. The measured intensity distributions could be assigned to a mathematical model description which gives form, width, and density of the tracks in the position space. On the base of this cylinder model computer codes were established which simulate the scattering experiment regarding the main influences and calculate the expected theoretical intensity distribution. The agreement between calculated and measured scattering distributions proves the validity of the model. The parameters determined by this model, maximal change of density in the track, defect length, radial dilatation, distance of the narrowings and there depth were determined. For the main quantities, radial dilatation and maximal change of densities a simple description of the energy dependence could be given via the energy loss. (orig./HSI) [de

  2. Numerical Study of Traffic Pollutant Dispersion within Different Street Canyon Configurations

    OpenAIRE

    Yucong Miao; Shuhua Liu; Yijia Zheng; Shu Wang; Yuan Li

    2014-01-01

    The objective of this study is to numerically study flow and traffic exhaust dispersion in urban street canyons with different configurations to find out the urban-planning strategies to ease the air pollution. The Computational Fluid Dynamics (CFD) model used in this study—Open Source Field Operation and Manipulation (OpenFOAM) software package—was firstly validated against the wind-tunnel experiment data by using three different k-ε turbulence models. And then the patterns of flow and dispe...

  3. A first principle study for the comparison of phonon dispersion of armchair carbon and silicon nanotubes

    International Nuclear Information System (INIS)

    Chandel, Surjeet Kumar; Kumar, Arun; Bharti, Ankush; Sharma, Raman

    2015-01-01

    Using first principles density functional theoretical calculations, the present paper reports a systematic study of phonon dispersion curves in pristine carbon (CNT) and silicon nanotubes (SiNT) having chirality (6,6) in the armchair configuration. Some of the phonon modes are found to have negative frequencies which leads to instability of the systems under study. The number of phonon branches has been found to be thrice as much as the number of atoms. The frequency of the higher optical bands varies from 1690 to 1957 cm −1 for CNT(6,6) while it is 596 to 658 cm −1 for SiNT

  4. Elaboration and dielectric characterization of a doped ferroelectric ...

    African Journals Online (AJOL)

    ... 1150,1180 and 1200 °C successively to optimize the sintering temperature optimal where the density of the sample is maximum (near theoretical density) and therefore the product has better physical quality. The study of dielectric properties of all samples showed a high permittivity dielectric εr = 18018, low dielectric loss: ...

  5. Analyzing the effect of gate dielectric on the leakage currents

    Directory of Open Access Journals (Sweden)

    Sakshi

    2016-01-01

    Full Text Available An analytical threshold voltage model for MOSFETs has been developed using different gate dielectric oxides by using MATLAB software. This paper explains the dependency of threshold voltage on the dielectric material. The variation in the subthreshold currents with the change in the threshold voltage sue to the change of dielectric material has also been studied.

  6. Nonlinear electroelastic deformations of dielectric elastomer composites: II - Non-Gaussian elastic dielectrics

    Science.gov (United States)

    Lefèvre, Victor; Lopez-Pamies, Oscar

    2017-02-01

    This paper presents an analytical framework to construct approximate homogenization solutions for the macroscopic elastic dielectric response - under finite deformations and finite electric fields - of dielectric elastomer composites with two-phase isotropic particulate microstructures. The central idea consists in employing the homogenization solution derived in Part I of this work for ideal elastic dielectric composites within the context of a nonlinear comparison medium method - this is derived as an extension of the comparison medium method of Lopez-Pamies et al. (2013) in nonlinear elastostatics to the coupled realm of nonlinear electroelastostatics - to generate in turn a corresponding solution for composite materials with non-ideal elastic dielectric constituents. Complementary to this analytical framework, a hybrid finite-element formulation to construct homogenization solutions numerically (in three dimensions) is also presented. The proposed analytical framework is utilized to work out a general approximate homogenization solution for non-Gaussian dielectric elastomers filled with nonlinear elastic dielectric particles that may exhibit polarization saturation. The solution applies to arbitrary (non-percolative) isotropic distributions of filler particles. By construction, it is exact in the limit of small deformations and moderate electric fields. For finite deformations and finite electric fields, its accuracy is demonstrated by means of direct comparisons with finite-element solutions. Aimed at gaining physical insight into the extreme enhancement in electrostriction properties displayed by emerging dielectric elastomer composites, various cases wherein the filler particles are of poly- and mono-disperse sizes and exhibit different types of elastic dielectric behavior are discussed in detail. Contrary to an initial conjecture in the literature, it is found (inter alia) that the isotropic addition of a small volume fraction of stiff (semi

  7. Effectiveness of monopolar dielectric transmission of pulsed electromagnetic fields for multiple sclerosis-related pain: A pilot study.

    Science.gov (United States)

    Hochsprung, A; Escudero-Uribe, S; Ibáñez-Vera, A J; Izquierdo-Ayuso, G

    2018-05-08

    Pain is highly prevalent in patients with multiple sclerosis (MS); it is chronic in 50% of cases and is classified as nociceptive, neuropathic, or mixed-type. Pain affects quality of life, sleep, and the activities of daily living. Electrotherapy is an interesting alternative or complementary treatment in the management of pain in MS, with new innovations constantly appearing. This study evaluates the effectiveness of treatment with monopolar dielectric transmission of pulsed electromagnetic fields (PEMF) for pain associated with MS. We performed a randomised, placebo-controlled clinical trial including 24 patients, who were assessed with the Brief Pain Inventory, the Multiple Sclerosis International Quality of Life questionnaire, the Beck Depression Inventory, and the Modified Fatigue Impact Scale. Statistically significant improvements were observed in maximum and mean pain scores, as well as in the impact of pain on work, personal relationships, and sleep and rest. Not significant differences were found between the treatment and placebo groups. Treatment with PEMF may be effective in reducing pain in patients with MS, although further research is necessary to confirm its effectiveness over placebo and to differentiate which type of pain may be more susceptible to this treatment. Copyright © 2018 Sociedad Española de Neurología. Publicado por Elsevier España, S.L.U. All rights reserved.

  8. Near-field study with a photon scanning tunneling microscope: Comparison between dielectric nanostructure and metallic nanostructure

    International Nuclear Information System (INIS)

    Mahmoud, Mahmoud Youcef; Bassou, Ghaouti; Salomon, Laurant; Chekroun, Z.; Djamai, Nesrine

    2007-01-01

    Scanning near-field optical microscopy (SNOM) integrates standard optical methods with scanning probe microscopy (SPM) techniques allowing to collect optical information with resolution well beyond the diffraction limit. We study the influence on image formation of several parameters in scanning near-field microscopy. The numerical calculations have been carried out using the differential method. We investigate a 2D-PSTM configuration with a dielectric rectangular object. We will focus on the collection type SNOM in a constant height scanning mode. Various oscillation patterns are observed from both sides of the nanostructure, which we interpret as interference between the diffracted waves scattered by the nanostructure (with the components of the wave vector parallel to the surface) and the evanescent incident wave above the surface. Using an optical near-field analysis and by calculating the electric field intensity distribution, we investigate the probe-sample distance effect. It is found that the distribution of the intensity related to the electric field is depending on sample-probe distance. We noticed the loss of details in the image and the presence of dramatic oscillations. Also, both of the polarization state of the illuminating light effect and the angle of incidence are investigated. We conclude that a differential method provides physical insight into the main features of the different images

  9. Near-field study with a photon scanning tunneling microscope: Comparison between dielectric nanostructure and metallic nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Mahmoud, Mahmoud Youcef [Laboratoire d' elaboration et caracterisation des materiaux, Groupe de Microscopie et Microanalyse, Universite Djilali Liabes de Sidi Bel-Abbes, Faculte des sciences (Algeria)], E-mail: mahmoudhamoud@yahoo.com; Bassou, Ghaouti [Laboratoire d' elaboration et caracterisation des materiaux, Groupe de Microscopie et Microanalyse, Universite Djilali Liabes de Sidi Bel-Abbes, Faculte des sciences (Algeria); Laboratoire de Physique (LPUB), CNRS UMR 5027, Groupe d' Optique de Champ Proche, Faculte des Sciences Mirande, Universite de Bourgogne, 9 Avenue Alain Savary, BP 47 870, 21078 Dijon Cedex (France); Salomon, Laurant [Laboratoire de Physique (LPUB), CNRS UMR 5027, Groupe d' Optique de Champ Proche, Faculte des Sciences Mirande, Universite de Bourgogne, 9 Avenue Alain Savary, BP 47 870, 21078 Dijon Cedex (France); Chekroun, Z. [Laboratoire d' elaboration et caracterisation des materiaux, Groupe de Microscopie et Microanalyse, Universite Djilali Liabes de Sidi Bel-Abbes, Faculte des sciences (Algeria); Djamai, Nesrine [Laboratoire de telecommunications et de traitement numerique du signal (LTTNS), Universite Djilali Liabes de Sidi Bel-Abbes, Faculte des sciences de l' ingenieur, Departement d' electronique (Algeria)

    2007-08-25

    Scanning near-field optical microscopy (SNOM) integrates standard optical methods with scanning probe microscopy (SPM) techniques allowing to collect optical information with resolution well beyond the diffraction limit. We study the influence on image formation of several parameters in scanning near-field microscopy. The numerical calculations have been carried out using the differential method. We investigate a 2D-PSTM configuration with a dielectric rectangular object. We will focus on the collection type SNOM in a constant height scanning mode. Various oscillation patterns are observed from both sides of the nanostructure, which we interpret as interference between the diffracted waves scattered by the nanostructure (with the components of the wave vector parallel to the surface) and the evanescent incident wave above the surface. Using an optical near-field analysis and by calculating the electric field intensity distribution, we investigate the probe-sample distance effect. It is found that the distribution of the intensity related to the electric field is depending on sample-probe distance. We noticed the loss of details in the image and the presence of dramatic oscillations. Also, both of the polarization state of the illuminating light effect and the angle of incidence are investigated. We conclude that a differential method provides physical insight into the main features of the different images.

  10. Formation and dielectric properties of polyelectrolyte multilayers studied by a silicon-on-insulator based thin film resistor.

    Science.gov (United States)

    Neff, Petra A; Wunderlich, Bernhard K; Klitzing, Regine V; Bausch, Andreas R

    2007-03-27

    The formation of polyelectrolyte multilayers (PEMs) is investigated using a silicon-on-insulator based thin film resistor which is sensitive to variations of the surface potential. The buildup of the PEMs at the silicon oxide surface of the device can be observed in real time as defined potential shifts. The influence of polymer charge density is studied using the strong polyanion poly(styrene sulfonate), PSS, combined with the statistical copolymer poly(diallyl-dimethyl-ammoniumchloride-stat-N-methyl-N-vinylacetamide), P(DADMAC-stat-NMVA), at various degrees of charge (DC). The multilayer formation stops after a few deposition steps for a DC below 75%. We show that the threshold of surface charge compensation corresponds to the threshold of multilayer formation. However, no reversion of the preceding surface charge was observed. Screening of polyelectrolyte charges by mobile ions within the polymer film leads to a decrease of the potential shifts with the number of layers deposited. This decrease is much slower for PEMs consisting of P(DADMAC-stat-NMVA) and PSS as compared to PEMs consisting of poly(allylamine-hydrochloride), PAH, and PSS. From this, significant differences in the dielectric constants of the polyelectrolyte films and in the concentration of mobile ions within the films can be derived.

  11. Study on Relationship between Dielectric Constant and Water Content of Rock-Soil Mixture by Time Domain Reflectometry

    Directory of Open Access Journals (Sweden)

    Daosheng Ling

    2016-01-01

    Full Text Available It is important to test water content of rock-soil mixtures efficiently and accurately to ensure both the quality control of compaction and assessment of the geotechnical engineering properties. To overcome time and energy wastage and probe insertion problems when using the traditional calibration method, a TDR coaxial test tube calibration arrangement using an upward infiltration method was designed. This arrangement was then used to study the influence of dry density, pore fluid conductivity, and soil/rock ratio on the relationship between water content and the dielectric constant of rock-soil mixtures. The results show that the empirical calibration equation forms for rock-soil mixtures can be the same as for soil materials. The effect of dry density on the calibration equation has the most significance and the influence of pore fluid conductivity can be ignored. The impact of variation of the soil/rock ratio can be neutralized by considering the effect of dry density in the calibration equation for the same kind of soil and rock. The empirical equations proposed by Zhao et al. show a good accuracy for rock-soil mixtures, indicating that the TDR method can be used to test gravimetric water content conveniently and efficiently without calibration in the field.

  12. Study of dielectric property on ZrO2 and Al doped ZrO2 nanoparticles

    International Nuclear Information System (INIS)

    Catherine Siriya Pushpa, K.; Mangayarkarasi, K.; Ravichandran, A.T.; Xavier, A. Robert; Nagabushana, B.M.

    2014-01-01

    A solution combustion process was used to synthesize ZrO 2 and Al doped ZrO 2 nanoparticles by using Zirconium nitrate and aluminium nitrate as the oxidizer and glycine as fuel. The prepared samples were characterized by several techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-visible spectroscopy (UV-vis). The dielectric values of the pelletized samples were examined at room temperature as the function of frequency. XRD shows the structure of the prepared and doped samples. The SEM shows the surface morphology of the pure and doped ZrO 2 nanoparticles. The dielectric property enhances with increase of Al concentration, which is useful in dielectric gates. (author)

  13. Interface Study on Amorphous Indium Gallium Zinc Oxide Thin Film Transistors Using High-k Gate Dielectric Materials

    International Nuclear Information System (INIS)

    Lin, Y. H.; Chou, J. C.

    2015-01-01

    We investigated amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFT_s) using different high-Κ gate dielectric materials such as silicon nitride (Si_3N_4) and aluminum oxide (Al_2O_3) at low temperature process (<300 degree) and compared them with low temperature silicon dioxide (SiO_2). The IGZO device with high-Κ gate dielectric material will expect to get high gate capacitance density to induce large amount of channel carrier and generate the higher drive current. In addition, for the integrating process of integrating IGZO device, post annealing treatment is an essential process for completing the process. The chemical reaction of the high-κ/IGZO interface due to heat formation in high-Κ/IGZO materials results in reliability issue. We also used the voltage stress for testing the reliability for the device with different high-Κ gate dielectric materials and explained the interface effect by charge band diagram.

  14. A high resolution complex terrain dispersion study in the Rocky Flats, Colorado vicinity

    International Nuclear Information System (INIS)

    Poulos, G.S.; Bossert, J.E.

    1992-01-01

    In January/February, 1991 an intensive set of measurements was taken around Rocky Flats near Denver, CO under the auspices of the Department of Energy Atmospheric Studies over Complex Terrain (ASCOT) program. This region of the country is known as the Front Range, and is characterized by a transition from the relatively flat terrain of the Great Plains to the highly varied terrain of the Rocky Mountains. One goal of the ASCOT 1991 program was to gain insight into multi-scale meteorological interaction by observing wintertime drainage conditions at the mountain-valley-plains interface. ASCOT data included surface and upper air measurements on approximately a 50km 2 scale. Simultaneously, an SF 6 tracer release study was being conducted around Rocky Flats, a nuclear materials production facility. Detailed surface concentration measurements were completed for the SF 6 plume. This combination of meteorological and tracer concentration data provided a unique data set for comparisons of mesoscale and dispersion modeling results with observations and for evaluating our capability to predict pollutant transport. Our approach is to use the Regional Atmospheric Modeling System (RAMS) mesoscale model to simulate atmospheric conditions and the Lagrangian Particle Dispersion Model (LPDM), a component of the RAMS system, to model the dispersion of the SF 6 . We have chosen the 4--5 February, 1991 overnight period as our case study. This night was characterized by strong drainage flows from the Rocky Mountains to the west of Rocky Flats, southerly winds in a layer about lkm thick above the drainage flows, and northwesterly winds above that layer extending to the tropopause

  15. Dielectric spectroscopy of watermelons for quality sensing

    Science.gov (United States)

    Nelson, Stuart O.; Guo, Wen-chuan; Trabelsi, Samir; Kays, Stanley J.

    2007-07-01

    Dielectric properties of four small-sized watermelon cultivars, grown and harvested to provide a range of maturities, were measured with an open-ended coaxial-line probe and an impedance analyser over the frequency range from 10 MHz to 1.8 GHz. Probe measurements were made on the external surface of the melons and also on tissue samples from the edible internal tissue. Moisture content and soluble solids content (SSC) were measured for internal tissue samples, and SSC (sweetness) was used as the quality factor for correlation with the dielectric properties. Individual dielectric constant and loss factor correlations with SSC were low, but a high correlation was obtained between the SSC and permittivity from a complex-plane plot of dielectric constant and loss factor, each divided by SSC. However, SSC prediction from the dielectric properties by this relationship was not as high as expected (coefficient of determination about 0.4). Permittivity data (dielectric constant and loss factor) for the melons are presented graphically to show their relationships with frequency for the four melon cultivars and for external surface and internal tissue measurements. A dielectric relaxation for the external surface measurements, which may be attributable to a combination of bound water, Maxwell-Wagner, molecular cluster or ion-related effects, is also illustrated. Coefficients of determination for complex-plane plots, moisture content and SSC relationship, and penetration depth are also shown graphically. Further studies are needed for determining the practicality of sensing melon quality from their dielectric properties.

  16. Characterization of dielectric materials

    Energy Technology Data Exchange (ETDEWEB)

    King, Danny J.; Babinec, Susan; Hagans, Patrick L.; Maxey, Lonnie C.; Payzant, Edward A.; Daniel, Claus; Sabau, Adrian S.; Dinwiddie, Ralph B.; Armstrong, Beth L.; Howe, Jane Y.; Wood, III, David L.; Nembhard, Nicole S.

    2017-06-27

    A system and a method for characterizing a dielectric material are provided. The system and method generally include applying an excitation signal to electrodes on opposing sides of the dielectric material to evaluate a property of the dielectric material. The method can further include measuring the capacitive impedance across the dielectric material, and determining a variation in the capacitive impedance with respect to either or both of a time domain and a frequency domain. The measured property can include pore size and surface imperfections. The method can still further include modifying a processing parameter as the dielectric material is formed in response to the detected variations in the capacitive impedance, which can correspond to a non-uniformity in the dielectric material.

  17. Application of energy-dispersive XRF technique in the hydrometallurgy study of local zircon

    International Nuclear Information System (INIS)

    Meor Yusoff Sulaiman; Kamaruddin Hussin; Azizan Aziz

    1996-01-01

    In this study, energy-dispersive X-ray Fluorescence (EDXR-F) was used to analyse the elemental composition of the starting zircon mineral associated elements in the leaching solution. Besides analysing the major elements i.e. of zirconium, silicon and hafnium, trace elemental analysis for iron, titanium and the naturally occurring radioactive element thorium and uranium are important in establishing the grades of Malaysian zircon. The technique was also used in determine the optimum conditions for zirconium and hafnium recovery during the leaching process

  18. Study of electrical properties of Sc doped BaFe12O19 ceramic using dielectric, impedance, modulus spectroscopy and AC conductivity

    Science.gov (United States)

    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.

  19. Synchrotron radiation x-ray photoelectron spectroscopy study on the interface chemistry of high-k PrxAl2-xO3 (x=0-2) dielectrics on TiN for dynamic random access memory applications

    Science.gov (United States)

    Schroeder, T.; Lupina, G.; Sohal, R.; Lippert, G.; Wenger, Ch.; Seifarth, O.; Tallarida, M.; Schmeisser, D.

    2007-07-01

    Engineered dielectrics combined with compatible metal electrodes are important materials science approaches to scale three-dimensional trench dynamic random access memory (DRAM) cells. Highly insulating dielectrics with high dielectric constants were engineered in this study on TiN metal electrodes by partly substituting Al in the wide band gap insulator Al2O3 by Pr cations. High quality PrAlO3 metal-insulator-metal capacitors were processed with a dielectric constant of 19, three times higher than in the case of Al2O3 reference cells. As a parasitic low dielectric constant interface layer between PrAlO3 and TiN limits the total performance gain, a systematic nondestructive synchrotron x-ray photoelectron spectroscopy study on the interface chemistry of PrxAl2-xO3 (x =0-2) dielectrics on TiN layers was applied to unveil its chemical origin. The interface layer results from the decreasing chemical reactivity of PrxAl2-xO3 dielectrics with increasing Pr content x to reduce native Ti oxide compounds present on unprotected TiN films. Accordingly, PrAlO3 based DRAM capacitors require strict control of the surface chemistry of the TiN electrode, a parameter furthermore of importance to engineer the band offsets of PrxAl2-xO3/TiN heterojunctions.

  20. Experimental Study of Dispersion and Deposition of Expiratory Aerosols in Aircraft Cabins and Impact on Infectious Disease Transmission

    DEFF Research Database (Denmark)

    To, G.N.S.; Wan, M.P.; Chao, C.Y.H.

    2009-01-01

    The dispersion and deposition characteristics of polydispersed expiratory aerosols were investigated in an aircraft cabin mockup to study the transmission of infectious diseases. The airflow was characterized by particle image velocimetry (PIV) measurements. Aerosol dispersionwas measured...

  1. Inductive dielectric analyzer

    International Nuclear Information System (INIS)

    Agranovich, Daniel; Popov, Ivan; Ben Ishai, Paul; Feldman, Yuri; Polygalov, Eugene

    2017-01-01

    One of the approaches to bypass the problem of electrode polarization in dielectric measurements is the free electrode method. The advantage of this technique is that, the probing electric field in the material is not supplied by contact electrodes, but rather by electromagnetic induction. We have designed an inductive dielectric analyzer based on a sensor comprising two concentric toroidal coils. In this work, we present an analytic derivation of the relationship between the impedance measured by the sensor and the complex dielectric permittivity of the sample. The obtained relationship was successfully employed to measure the dielectric permittivity and conductivity of various alcohols and aqueous salt solutions. (paper)

  2. Method of making dielectric capacitors with increased dielectric breakdown strength

    Science.gov (United States)

    Ma, Beihai; Balachandran, Uthamalingam; Liu, Shanshan

    2017-05-09

    The invention is directed to a process for making a dielectric ceramic film capacitor and the ceramic dielectric laminated capacitor formed therefrom, the dielectric ceramic film capacitors having increased dielectric breakdown strength. The invention increases breakdown strength by embedding a conductive oxide layer between electrode layers within the dielectric layer of the capacitors. The conductive oxide layer redistributes and dissipates charge, thus mitigating charge concentration and micro fractures formed within the dielectric by electric fields.

  3. Numerical investigation of dielectric barrier discharges

    Science.gov (United States)

    Li, Jing

    1997-12-01

    A dielectric barrier discharge (DBD) is a transient discharge occurring between two electrodes in coaxial or planar arrangements separated by one or two layers of dielectric material. The charge accumulated on the dielectric barrier generates a field in a direction opposite to the applied field. The discharge is quenched before an arc is formed. It is one of the few non-thermal discharges that operates at atmospheric pressure and has the potential for use in pollution control. In this work, a numerical model of the dielectric barrier discharge is developed, along with the numerical approach. Adaptive grids based on the charge distribution is used. A self-consistent method is used to solve for the electric field and charge densities. The Successive Overrelaxation (SOR) method in a non-uniform grid spacing is used to solve the Poisson's equation in the cylindrically-symmetric coordinate. The Flux Corrected Transport (FCT) method is modified to solve the continuity equations in the non-uniform grid spacing. Parametric studies of dielectric barrier discharges are conducted. General characteristics of dielectric barrier discharges in both anode-directed and cathode-directed streamer are studied. Effects of the dielectric capacitance, the applied field, the resistance in external circuit and the type of gases (O2, air, N2) are investigated. We conclude that the SOR method in an adaptive grid spacing for the solution of the Poisson's equation in the cylindrically-symmetric coordinate is convergent and effective. The dielectric capacitance has little effect on the g-factor of radical production, but it determines the strength of the dielectric barrier discharge. The applied field and the type of gases used have a significant role on the current peak, current pulse duration and radical generation efficiency, discharge strength, and microstreamer radius, whereas the external series resistance has very little effect on the streamer properties. The results are helpful in

  4. Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications

    Directory of Open Access Journals (Sweden)

    Roland Kádár

    2017-01-01

    Full Text Available The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate (EBA nanocomposite hybrids containing graphite nanoplatelets (GnP and carbon black (CB. The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix. Evidence of the influence of dispersion properties was found in linear viscoelastic dynamic frequency sweeps, while the percolation of the nanocomposites was detected in nonlinearities developed in dynamic strain sweeps. Using extensional rheology, hybrid samples with better dispersion properties lead to a more pronounced strain hardening behavior, while samples with a higher volume percentage of fillers caused a drastic reduction in strain hardening. The rheo-dielectric time-dependent response showed that in the case of nanocomposites containing only GnP, the orientation dynamics leads to non-conductive samples. However, in the case of hybrids, the orientation of the GnP could be offset by the dispersing of the CB to bridge the nanoplatelets. The results were interpreted in the framework of a dual PE-BA model, where the fillers would be concentrated mainly in the BA regions. Furthermore, better dispersed hybrids obtained using mixing screws at the expense of filler distortion via extrusion processing history were emphasized through the rheo-dielectric tests.

  5. [Study on Square Super-Lattice Pattern with Surface Discharge in Dielectric Barrier Discharge by Optical Emission Spectra].

    Science.gov (United States)

    Niu, Xue-jiao; Dong, Li-fang; Liu, Ying; Wang, Qian; Feng, Jian-yu

    2016-02-01

    Square super-lattice pattern with surface discharge consisting of central spots and dim spots is firstly observed in the mixture of argon and air by using a dielectric barrier discharge device with water electrodes. By observing the image, it is found that the central spot is located at the centriod of its surrounding four dim spots. The short-exposure image recorded by a high speed video camera shows that the dim spot results from the surface discharges (SDs). The brightness of the central spot and is quite different from that of the dim spot, which indicates that the plasma states of the central spot and the dim spot may be differentiated. The optical emission spectrum method is used to further study the several plasma parameters of the central spot and the dim spot in different argon content. The emission spectra of the N₂ second positive band (C³IIu --> B³ IIg) are measured, from which the molecule vibration temperatures of the central spot and the dim spot are calculated respectively. The broadening of spectral line 696.57 nm (2P₂-->1S₅) is used to study the electron densities of the central spot and the dim spot. It is found that the molecule vibration temperature and electron density of the dim spot are higher than those of the central spot in the same argon content The molecule vibration temperature and electron density of the central spot and the dim spot increase with the argon content increasing from 90% to 99.9%. The surface discharge induced by the volume discharge (VD) has the determinative effect on the formation of the dim spot The experimental results above play an important role in studying the formation mechanism of surface discharg&of square super-lattice pattern with surface discharge. In addition, the studies exert an influence on the application of surface discharge and volume discharge in different fields.

  6. Mixing and axial dispersion in Taylor-Couette flow: experimental and numerical study

    International Nuclear Information System (INIS)

    Nemri, M.

    2013-01-01

    Taylor-Couette flows between two concentric cylinders have great potential applications in chemical engineering. They are particularly convenient for two-phase small scale devices enabling solvent extraction operations. An experimental device was designed with this idea in mind. It consists of two concentric cylinders with the inner one rotating and the outer one fixed. Taylor-Couette flows take place in the annular gap between them, and are known to evolve towards turbulence through a sequence of successive instabilities. Macroscopic quantities, such as axial dispersion and mixing index, are extremely sensitive to these flow structures, which may lead to flawed modelling of the coupling between hydrodynamics and mass transfer. This particular point has been studied both experimentally and numerically. The flow and mixing have been characterized by means of flow visualization and simultaneous PIV (Particle Imaging Velocimetry) and PLIF (Planar Laser Induced Fluorescence) measurements. PLIF visualizations showed clear evidences of different transport mechanisms including 'intra-vortex mixing' and 'inter-vortex mixing'. Under WVF and MWVF regimes, intra-vortex mixing is controlled by chaotic advection, due to the 3D nature of the flow, while inter-vortex transport occurs due to the presence of waves between neighboring vortices. The combination of these two mechanisms results in enhanced axial dispersion. We showed that hysteresis may occur between consecutive regimes depending on flow history and this may have a significant effect on mixing for a given Reynolds number. The axial dispersion coefficient Dx evolution along the successive flow states was investigated thanks to dye Residence Time Distribution measurements (RTD) and particle tracking (DNS). Both experimental and numerical results have confirmed the significant effect of the flow structure and history on axial dispersion. Our study confirmed that the commonly used 1-parameter chemical engineering models (e

  7. Noise study of all-normal dispersion supercontinuum sources for potential application in optical coherence tomography

    Science.gov (United States)

    Gonzalo, I. B.; Engelsholm, R. D.; Bang, O.

    2018-03-01

    Commercially available silica-fiber-based and ultra-broadband supercontinuum (SC) sources are typically generated by pumping close to the zero-dispersion wavelength (ZDW) of a photonic crystal fiber (PCF), using high-power picosecond or nanosecond laser pulses. Despite the extremely broad bandwidths, such sources are characterized by large intensity fluctuations, limiting their performance for applications in imaging such as optical coherence tomography (OCT). An approach to eliminate the influence of noise sensitive effects is to use a so-called all-normal dispersion (ANDi) fiber, in which the dispersion is normal for all the wavelengths of interest. Pumping these types of fibers with short enough femtosecond pulses allows to suppress stimulated Raman scattering (SRS), which is known to be as noisy process as modulation instability (MI), and coherent SC is generated through self-phase modulation (SPM) and optical wave breaking (OWB). In this study, we show the importance of the pump laser and fiber parameters in the design of low-noise ANDi based SC sources, for application in OCT. We numerically investigate the pulse-to-pulse fluctuations of the SC, calculating the relative intensity noise (RIN) as a function of the pump pulse duration and fiber length. Furthermore, we experimentally demonstrate the role of the fiber length on the RIN of the ANDi SC, validating the results calculated numerically. In the end, we compare the RIN of a commercial SC source based on MI and the ANDi SC source developed here, which shows better noise performance when it is carefully designed.

  8. Vacancy-fluorine complexes and their impact on the properties of metal-oxide transistors with high-k gate dielectrics studied using monoenergetic positron beams

    Science.gov (United States)

    Uedono, A.; Inumiya, S.; Matsuki, T.; Aoyama, T.; Nara, Y.; Ishibashi, S.; Ohdaira, T.; Suzuki, R.; Miyazaki, S.; Yamada, K.

    2007-09-01

    Vacancy-fluorine complexes in metal-oxide semiconductors (MOS) with high-k gate dielectrics were studied using a positron annihilation technique. F+ ions were implanted into Si substrates before the deposition of gate dielectrics (HfSiON). The shift of threshold voltage (Vth) in MOS capacitors and an increase in Fermi level position below the HfSiON/Si interface were observed after F+ implantation. Doppler broadening spectra of the annihilation radiation and positron lifetimes were measured before and after HfSiON fabrication processes. From a comparison between Doppler broadening spectra and those obtained by first-principles calculation, the major defect species in Si substrates after annealing treatment (1050 °C, 5 s) was identified as vacancy-fluorine complexes (V3F2). The origin of the Vth shift in the MOS capacitors was attributed to V3F2 located in channel regions.

  9. Crystallization studies and dielectric properties of (Ba0.7Sr0.3)TiO3 in bariumaluminosilicate glass

    Science.gov (United States)

    Divya, P. V.; Vignesh, G.; Kumar, V.

    2007-12-01

    Ferroelectric glass-ceramics with a basic composition (1 - y)(Ba0.70Sr0.30)TiO3 : y(BaO : Al2O3 : 2SiO2) have been synthesized by the sol-gel method. The major crystalline phase is the perovskite. The crystallization of the ferroelectric phase in the glass matrix have been studied using differential thermal analysis and x-ray diffraction and the kinetic parameters characterizing the crystallization have been determined using an Arrhenius model. Glass contents <= 5 mol% promoted liquid phase sintering, which reduced the sintering temperature to 1250 °C. The dielectric permittivity of the glass-ceramic samples decreased and the ferroelectric-paraelectric phase transition became more diffuse with increasing glass content. The dielectric connectivity of the ferroelectric phase in the composite have also been investigated and are reported.

  10. Realization of a complementary medium using dielectric photonic crystals.

    Science.gov (United States)

    Xu, Tao; Fang, Anan; Jia, Ziyuan; Ji, Liyu; Hang, Zhi Hong

    2017-12-01

    By exploiting the scaling invariance of photonic band diagrams, a complementary photonic crystal slab structure is realized by stacking two uniformly scaled double-zero-index dielectric photonic crystal slabs together. The space cancellation effect in complementary photonic crystals is demonstrated in both numerical simulations and microwave experiments. The refractive index dispersion of double-zero-index dielectric photonic crystal is experimentally measured. Using pure dielectrics, our photonic crystal structure will be an ideal platform to explore various intriguing properties related to a complementary medium.

  11. Preparation and Characterization of Pure Organic Dielectric Composites for Capacitors

    Directory of Open Access Journals (Sweden)

    Mao Xin

    2018-01-01

    Full Text Available This work reports the excellent dielectric composites were prepared from polyimide (PI and poly(vinylidene fluoride (PVDF via solution blending and thermal imidization or chemical imidization. The dielectric and thermal properties of the composites were studied. Results indicated that the dielectric properties of the composites synthesized by these two methods were enhanced through the introduction of PVDF, and the composites exhibited excellent thermal stability. Compared to the thermal imidization, the composites prepared by chemical imidization exhibited superior dielectric properties. This study demonstrated that the PI/PVDF composites were potential dielectric materials in the field of electronics.

  12. Study on the wind field and pollutant dispersion in street canyons using a stable numerical method.

    Science.gov (United States)

    Xia, Ji-Yang; Leung, Dennis Y C

    2005-01-01

    A stable finite element method for the time dependent Navier-Stokes equations was used for studying the wind flow and pollutant dispersion within street canyons. A three-step fractional method was used to solve the velocity field and the pressure field separately from the governing equations. The Streamline Upwind Petrov-Galerkin (SUPG) method was used to get stable numerical results. Numerical oscillation was minimized and satisfactory results can be obtained for flows at high Reynolds numbers. Simulating the flow over a square cylinder within a wide range of Reynolds numbers validates the wind field model. The Strouhal numbers obtained from the numerical simulation had a good agreement with those obtained from experiment. The wind field model developed in the present study is applied to simulate more complex flow phenomena in street canyons with two different building configurations. The results indicated that the flow at rooftop of buildings might not be assumed parallel to the ground as some numerical modelers did. A counter-clockwise rotating vortex may be found in street canyons with an inflow from the left to right. In addition, increasing building height can increase velocity fluctuations in the street canyon under certain circumstances, which facilitate pollutant dispersion. At high Reynolds numbers, the flow regimes in street canyons do not change with inflow velocity.

  13. Case study of the atmospheric dispersion of emissions from UPPR/CDTN, Brazil

    International Nuclear Information System (INIS)

    Barreto, Alberto A.; Cesar, Raisa H.S.; Maleta, Paulo G.M.; Grossi, Pablo A.

    2015-01-01

    This work presents a study of the atmospheric dispersion of emissions released during activities of production and research of radiopharmaceuticals in the Center of Nuclear Technology Development (CDTN), localized in Belo Horizonte, Minas Gerais - Brazil. The installation, 'Unidade de Producao e Pesquisa de Radiofarmacos' (UPPR), was considered operating full time during a year. The general goal was to evaluate the radiological environmental impact due to these atmospheric emissions. The pollutants studied were the radionuclides F-18, C-11 and N-13. The meteorological view evaluated was a period of 365 days, simulated from the dates of a typical meteorological year. It was applied the dispersion model ARTM (Atmospheric Radionuclide Transport Model). The atmospheric emissions from UPPR were estimated for the simulation based in an extremely conservative operation condition. Others important data raised and analyzed were: topography, obstacles (buildings) and the land occupation around the CDTN. Among the main results, it is important to emphasize the estimate of the radionuclide concentration and the dose value calculated from these concentration. These results were compared with the dose restriction limit set by the standard CNEN 3.01. Areas of higher concentration were identified and are being used as reference for the positioning of the concentration's monitor of the pollutant by the Radiological Environmental Monitoring Program (PMA). (author)

  14. A Study of Dispersion Compensation of Polarization Multiplexing-Based OFDM-OCDMA for Radio-over-Fiber Transmissions.

    Science.gov (United States)

    Yen, Chih-Ta; Chen, Wen-Bin

    2016-09-07

    Chromatic dispersion from optical fiber is the most important problem that produces temporal skews and destroys the rectangular structure of code patterns in the spectra-amplitude-coding-based optical code-division multiple-access (SAC-OCDMA) system. Thus, the balance detection scheme does not work perfectly to cancel multiple access interference (MAI) and the system performance will be degraded. Orthogonal frequency-division multiplexing (OFDM) is the fastest developing technology in the academic and industrial fields of wireless transmission. In this study, the radio-over-fiber system is realized by integrating OFDM and OCDMA via polarization multiplexing scheme. The electronic dispersion compensation (EDC) equalizer element of OFDM integrated with the dispersion compensation fiber (DCF) is used in the proposed radio-over-fiber (RoF) system, which can efficiently suppress the chromatic dispersion influence in long-haul transmitted distance. A set of length differences for 10 km-long single-mode fiber (SMF) and 4 km-long DCF is to verify the compensation scheme by relative equalizer algorithms and constellation diagrams. In the simulation result, the proposed dispersion mechanism successfully compensates the dispersion from SMF and the system performance with dispersion equalizer is highly improved.

  15. A Study of Dispersion Compensation of Polarization Multiplexing-Based OFDM-OCDMA for Radio-over-Fiber Transmissions

    Directory of Open Access Journals (Sweden)

    Chih-Ta Yen

    2016-09-01

    Full Text Available Chromatic dispersion from optical fiber is the most important problem that produces temporal skews and destroys the rectangular structure of code patterns in the spectra-amplitude-coding-based optical code-division multiple-access (SAC-OCDMA system. Thus, the balance detection scheme does not work perfectly to cancel multiple access interference (MAI and the system performance will be degraded. Orthogonal frequency-division multiplexing (OFDM is the fastest developing technology in the academic and industrial fields of wireless transmission. In this study, the radio-over-fiber system is realized by integrating OFDM and OCDMA via polarization multiplexing scheme. The electronic dispersion compensation (EDC equalizer element of OFDM integrated with the dispersion compensation fiber (DCF is used in the proposed radio-over-fiber (RoF system, which can efficiently suppress the chromatic dispersion influence in long-haul transmitted distance. A set of length differences for 10 km-long single-mode fiber (SMF and 4 km-long DCF is to verify the compensation scheme by relative equalizer algorithms and constellation diagrams. In the simulation result, the proposed dispersion mechanism successfully compensates the dispersion from SMF and the system performance with dispersion equalizer is highly improved.

  16. High energy-resolution electron energy-loss spectroscopy study of the dielectric properties of bulk and nanoparticle LaB6 in the near-infrared region

    International Nuclear Information System (INIS)

    Sato, Yohei; Terauchi, Masami; Mukai, Masaki; Kaneyama, Toshikatsu; Adachi, Kenji

    2011-01-01

    The dielectric properties of LaB 6 crystals and the plasmonic behavior of LaB 6 nanoparticles, which have been applied to solar heat-shielding filters, were studied by high energy-resolution electron energy-loss spectroscopy (HR-EELS). An EELS spectrum of a LaB 6 crystal showed a peak at 2.0 eV, which was attributed to volume plasmon excitation of carrier electrons. EELS spectra of single LaB 6 nanoparticles showed peaks at 1.1-1.4 eV depending on the dielectric effect from the substrates. The peaks were assigned to dipole oscillation excitations. These peak energies almost coincided with the peak energy of optical absorption of a heat-shielding filter with LaB 6 nanoparticles. On the other hand, those energies were a smaller than a dipole oscillation energy predicted using the dielectric function of bulk LaB 6 crystal. It is suggested that the lower energy than expected is due to an excitation at 1.2 eV, which was observed for oxidized LaB 6 area. -- Highlights: → The dielectric properties of LaB 6 nanoparticles applied to solar heat-shielding filters were studied by HR-EELS. → Plasmon peak energies of the LaB 6 nanoparticles were almost equal to optical absorption energy of a heat-shielding filter. → From this result, near-infrared optical absorption of the filter is due to the surface dipole mode of the nanoparticles.

  17. Solid binary mixtures of neopentanol with tert-Butyl chloride and carbon tetrachloride studied by thermal, X-ray and dielectric techniques

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Girish; Murthy, S.S.N., E-mail: ssnm0700@gmail.com

    2016-05-10

    Highlights: • DSC, dielectric and X-ray measurements have been done on TBC-NPOH and CTC-NPOH. • The results show the formation of solid solution for concentrations 0.7 ≤ x{sub m} ≤ 0.9. • A primary α-process and two sub-T{sub g} processes are found for TBC-NPOH. • For CTC-NPOH only one sub-T{sub g} process is found. • All the three sub-T{sub g} processes are Johari–Goldstein type. - Abstract: The binary mixtures of Neopentanol (NPOH) with tert-Butyl chloride (TBC) and Carbon tetrachloride (CTC), have been studied using Differential Scanning Calorimetry, Dielectric spectroscopy and X-ray diffraction techniques. The results indicate the formation of the solid solutions. The crystalline solid thus formed is found to be orientationally disordered and supercools easily to form glassy crystal for mole fraction of NPOH in the range of 0.7–0.9. The T{sub g} values are in the range of 140–147 K. In the dielectric study, a primary α-process and two sub-T{sub g} processes are found for TBC-NPOH, whereas for CTC-NPOH only one sub-T{sub g} process is found. The dielectric spectra of α- process follows the Havriliak–Negami equation. The sub-T{sub g} processes follow the Cole–Cole equation, and are found to be of Johari–Goldstein type, indicating intermolecular nature.

  18. A Brief Study on the Ignition of the Non-Thermal Atmospheric Pressure Plasma Jet from a Double Dielectric Barrier Configured Plasma Pencil

    International Nuclear Information System (INIS)

    Begum, Asma; Laroussi, Mounir; Pervez, M. R.

    2013-01-01

    To understand the self sustained propagation of the plasma jet/bullet in air under atmospheric pressure, the ignition of the plasma jet/bullet, the plasma jet/bullet ignition point in the plasma pencil, the formation time and the formation criteria from a dielectric barrier configured plasma pencil were investigated in this study. The results were confirmed by comparing these results with the plasma jet ignition process in the plasma pencil without a dielectric barrier. Electrical, optical, and imaging techniques were used to study the formation of the plasma jet from the ignition of discharge in a double dielectric barrier configured plasma pencil. The investigation results show that the plasma jet forms at the outlet of the plasma pencil as a donut shaped discharge front because of the electric field line along the outlet's surface. It is shown that the required time for the formation of the plasma jet changes with the input voltage of the discharge. The input power calculation for the gap discharge and for the whole system shows that 56% of the average input power is used by the first gap discharge. The estimated electron density inside the gap discharge is in the order of 10 11 cm −3 . If helium is used as a feeding gas, a minimum 1.48×10 −8 C charge is required per pulse in the gap discharge to generate a plasma jet

  19. An experimental study of electrical and dielectric properties of consolidated clayey materials; Etude experimentale des proprietes electriques et dielectriques des materiaux argileux consolides

    Energy Technology Data Exchange (ETDEWEB)

    Comparon, L

    2005-06-15

    This study is devoted to the electrical and dielectric properties of consolidated clays. A better understanding of the conduction and polarization phenomena in clays is necessary to better interpret in situ measurements in terms of water saturation and texture. An experimental study was carried out on synthetic clay samples (kaolinite and smectite) compacted with various water contents, porosities and mineralogical compositions, on a large frequency range, using three laboratory setups. The electrical properties of natural argillites (from ANDRA) were then investigated. We found that the response of the synthetic samples is mainly controlled by water content on the whole frequency range; two polarization phenomena were observed, which were related to the Maxwell-Wagner polarization and the electrical double layer polarization around the clay particles. The electrical response of argillites is more complex; it is controlled by water content but also by the microstructure of the rock. In these rocks, the electrical and dielectric anisotropies are high; anisotropy was also measured for the synthetic clays. The existing models explain the high frequency limit of the dielectric permittivity of the clayey materials, but the low frequency part of the spectra ({<=}1 MHz) needs theoretical developments. (author)

  20. Dielectric Actuation of Polymers

    Science.gov (United States)

    Niu, Xiaofan

    Dielectric polymers are widely used in a plurality of applications, such as electrical insulation, dielectric capacitors, and electromechanical actuators. Dielectric polymers with large strain deformations under an electric field are named dielectric elastomers (DE), because of their relative low modulus, high elongation at break, and outstanding resilience. Dielectric elastomer actuators (DEA) are superior to traditional transducers as a muscle-like technology: large strains, high energy densities, high coupling efficiency, quiet operation, and light weight. One focus of this dissertation is on the design of DE materials with high performance and easy processing. UV radiation curing of reactive species is studied as a generic synthesis methodology to provide a platform for material scientists to customize their own DE materials. Oligomers/monomers, crosslinkers, and other additives are mixed and cured at appropriate ratios to control the stress-strain response, suppress electromechanical instability of the resulting polymers, and provide stable actuation strains larger than 100% and energy densities higher than 1 J/g. The processing is largely simplified in the new material system by removal of the prestretching step. Multilayer stack actuators with 11% linear strain are demonstrated in a procedure fully compatible with industrial production. A multifunctional DE derivative material, bistable electroactive polymer (BSEP), is invented enabling repeatable rigid-to-rigid deformation without bulky external structures. Bistable actuation allows the polymer actuator to have two distinct states that can support external load without device failure. Plasticizers are used to lower the glass transition temperature to 45 °C. Interpenetrating polymer network structure is established inside the BSEP to suppress electromechanical instability, providing a breakdown field of 194 MV/m and a stable bistable strain as large as 228% with a 97% strain fixity. The application of BSEP