Solid-state three-step model for high-harmonic generation from periodic crystals
Ikemachi, Takuya; Sato, Takeshi; Yumoto, Junji; Kuwata-Gonokami, Makoto; Ishikawa, Kenichi L
2016-01-01
We study high-harmonic generation (HHG) from solids driven by intense laser pulses using the time-dependent Schrodinger equation for a one-dimensional model periodic crystal. Based on the simulation results, we propose a simple model that can quantitatively explain many aspects of solid- state HHG, some of which have been experimentally observed. Incorporating interband tunneling, intraband acceleration, and recombination with the valence-band hole, our model can be viewed as a solid-state counterpart of the familiar three-step model highly successful for gas-phase HHG and provides a unified basis to understand HHG from gaseous media and solid-state materials. The solid-state three-step model describes how, by repeating intraband acceleration and interband tunneling, electrons climb up across multiple conduction bands. The key parameter in predicting the HHG spectrum structure from the band-climbing process is the peak-to-valley (or valley-to-peak) full amplitude of the pulse vector potential $A(t)$. When the...
Second harmonic generation from the `centrosymmetric' crystals
Directory of Open Access Journals (Sweden)
Venkatram Nalla
2015-05-01
Full Text Available Second harmonic generation (SHG is a well known non-linear optical phenomena which can be observed only in non-centrosymmetric crystals due to non-zero hyperpolarizability. In the current work we observed SHG from a Zn(II complex which was originally thought to have crystallized in the centrosymmetric space group C2/c. This has been attributed to the unequal antiparallel packing of the metal complexes in the non-symmetric space group Cc or residual non-centrosymmetry in C2/c giving rise to polarizability leading to strong SHG. The enhancement of SHG by UV light has been attributed to the increase in non-centrosymmetry and hence polarity of packing due to strain induced in the crystals. The SHG signals measured from these crystals were as large as potassium dihydrogen phosphate crystals, KH2PO4 (KDP, and showed temperature dependence. The highest SHG efficiency was observed at 50 K. The SHG phenomenon was observed at broad wavelengths ranging from visible to below-red in these crystals.
Second harmonic generation in Te crystal using free electron laser
Yamauchi, T; Minehara, E J
2002-01-01
The second harmonic generation signal converted from the fundamental wavelength of 22 mu m of a free electron laser was observed for the first time using a birefringent Te crystal. The experimental conversion efficiency of Te crystal for second harmonic generation is 0.53%, which is equivalent to the theoretical value within a factor of 2. The Te crystal has been incorporated into an autocorrelator system to measure the micro-pulse width of infrared free electron laser successfully. (author)
Second Harmonic Generation in Subdiffractive Two-Dimensional Photonic Crystals
Nistor, Cristian
2013-01-01
The PhD thesis is devoted to the study of second harmonic generation of narrow beams in photonic crystals. The basic idea is that if both frequencies, the fundamental and second harmonics are in the region of self-collimation, then the second harmonics of narrow beams can be very efficient. The beams do not spread diffractively during propagation and interaction. The phase matching is ensured for all components of the interacting beams. This allows to enhance the nonlinear interaction efficiency several times. The thesis rewises the theory of self-collimation of narrow beams in photonic crystals, and presents the theory of second harmonics in photonic crystals. Calculations in photonic crystals of different configurations are presented, and the recommendations to experimental realisations are given.
Second harmonic chalcone crystal: Synthesis, growth and characterization
Energy Technology Data Exchange (ETDEWEB)
D' Silva, E.D., E-mail: deepak.dsilva@gmail.co [Department of studies in Physics, Mangalore University, Mangalagangotri, Mangalore 574199 (India); Narayan Rao, D. [School of Physics, University of Hyderabad, Hyderabad 500046 (India); Philip, Reji [Light and Matter Physics Group, Raman Research Institute, Bangalore 560080 (India); Butcher, Ray J. [Department of Chemistry, Howard University, Washington, DC 20059 (United States); Rajnikant [Department of Physics and Electronics, University of Jammu, Jammu Tawi 180006 (India); Dharmaprakash, S.M. [Department of studies in Physics, Mangalore University, Mangalagangotri, Mangalore 574199 (India)
2011-05-15
The novel nonlinear optical chalcone derivative (2E)-3-[4-(methylsulfanyl)phenyl]-1-(3-bromophenyl)prop-2-en-1-one (3Br4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The crystal was subjected to different types of characterization method in order to study its possible application in nonlinear optics. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. The morphology of the crystal is studied. The crystal was subjected to thermal analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique. The laser damage threshold for 3Br4MSP crystal was determined using Q-switched Nd:YAG laser.
Probabilistic Harmonic Modeling of Wind Power Plants
DEFF Research Database (Denmark)
Guest, Emerson; Jensen, Kim H.; Rasmussen, Tonny Wederberg
2017-01-01
A probabilistic sequence domain (SD) harmonic model of a grid-connected voltage-source converter is used to estimate harmonic emissions in a wind power plant (WPP) comprised of Type-IV wind turbines. The SD representation naturally partitioned converter generated voltage harmonics into those...... with deterministic phase and those with probabilistic phase. A case study performed on a string of ten 3MW, Type-IV wind turbines implemented in PSCAD was used to verify the probabilistic SD harmonic model. The probabilistic SD harmonic model can be employed in the planning phase of WPP projects to assess harmonic...
Data harmonization and model performance
The Joint Committee on Urban Storm Drainage of the International Association for Hydraulic Research (IAHR) and International Association on Water Pollution Research and Control (IAWPRC) was formed in 1982. The current committee members are (no more than two from a country): B. C. Yen, Chairman (USA); P. Harremoes, Vice Chairman (Denmark); R. K. Price, Secretary (UK); P. J. Colyer (UK), M. Desbordes (France), W. C. Huber (USA), K. Krauth (FRG), A. Sjoberg (Sweden), and T. Sueishi (Japan).The IAHR/IAWPRC Joint Committee is forming a Task Group on Data Harmonization and Model Performance. One objective is to promote international urban drainage data harmonization for easy data and information exchange. Another objective is to publicize available models and data internationally. Comments and suggestions concerning the formation and charge of the Task Group are welcome and should be sent to: B. C. Yen, Dept. of Civil Engineering, Univ. of Illinois, 208 N. Romine St., Urbana, IL 61801.
Input Harmonic Analysis on the Slim DC-Link Drive Using Harmonic State Space Model
DEFF Research Database (Denmark)
Yang, Feng; Kwon, Jun Bum; Wang, Xiongfei
2017-01-01
variation according to the switching instant, the harmonics at the steady-state condition, as well as the coupling between the multiple harmonic impedances. By using this model, the impaction on the harmonics performance by the film capacitor and the grid inductance is derived. Simulation and experimental......The harmonic performance of the slim dc-link adjustable speed drives has shown good performance in some studies but poor in some others. The contradiction indicates that a feasible theoretical analysis is still lacking to characterize the harmonic distortion for the slim dc-link drive. Considering...... the shortcomings of the present harmonic analysis methods, such as the time-domain simulation, or the Fourier analysis, this paper proposes a Harmonic State Space model to study the harmonics performance for this type of drive. In this study, this model is utilized to describe the behavior of the harmonic...
Thirring model partition functions and harmonic differentials
Freedman, D. Z.; Pilch, K.
1988-10-01
The partition function of the Thirring model on a Riemann surface is calculated using the representation of the model as a fermion interacting with an auxiliary vector potential. The Hodge decomposition of the potential is used and the integral over the harmonic forms is shown to reproduce exactly the soliton sum in the bosonic version of the theory.
Harmonic Interaction Analysis in Grid Connected Converter using Harmonic State Space (HSS) Modeling
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth
2015-01-01
An increasing number of power electronics based Distributed Generation (DG) systems and loads generate coupled harmonic as well as non-characteristic harmonic with each other. Several methods like impedance based analysis, which is derived from conventional small signal- and average...... during the modeling process. This paper investigates grid connected converter by means of Harmonic State Space (HSS) small signal model, which is modeled from Linear Time varying Periodically (LTP) system. Further, a grid connected converter harmonic matrix is investigated to analyze the harmonic...
Resonant second harmonic generation in a gallium nitride two-dimensional photonic crystal on silicon
Energy Technology Data Exchange (ETDEWEB)
Zeng, Y.; Roland, I.; Checoury, X.; Han, Z.; El Kurdi, M.; Sauvage, S.; Boucaud, P., E-mail: philippe.boucaud@ief.u-psud.fr [Institut d' Electronique Fondamentale, CNRS - Univ. Paris Sud 11, Bâtiment 220, F-91405 Orsay (France); Gayral, B. [Univ. Grenoble Alpes, INAC-SP2M, CEA-CNRS group Nanophysique et Semiconducteurs, F-38000 Grenoble (France); CEA, INAC-SP2M, CEA-CNRS group Nanophysique et Semiconducteurs, F-38000 Grenoble (France); Brimont, C.; Guillet, T. [Université Montpellier 2, Laboratoire Charles Coulomb UMR 5221, F-34905 Montpellier (France); Mexis, M.; Semond, F. [CRHEA-CNRS, Rue Bernard Grégory, F-06560 Valbonne (France)
2015-02-23
We demonstrate second harmonic generation in a gallium nitride photonic crystal cavity embedded in a two-dimensional free-standing photonic crystal platform on silicon. The photonic crystal nanocavity is optically pumped with a continuous-wave laser at telecom wavelengths in the transparency window of the nitride material. The harmonic generation is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second harmonic signal. The harmonic emission pattern is correlated to the harmonic polarization generated by the second-order nonlinear susceptibilities χ{sub zxx}{sup (2)}, χ{sub zyy}{sup (2)} and the electric fields of the fundamental cavity mode.
Modelling the harmonized tertiary Institutions Salary Structure ...
African Journals Online (AJOL)
This paper analyses the Harmonized Tertiary Institution Salary Structure (HATISS IV) used in Nigeria. The irregularities in the structure are highlighted. A model that assumes a polynomial trend for the zero step salary, and exponential trend for the incremental rates, is suggested for the regularization of the structure.
Sequence Domain Harmonic Modeling of Type-IV Wind Turbines
DEFF Research Database (Denmark)
Guest, Emerson; Jensen, Kim Høj; Rasmussen, Tonny Wederberg
2017-01-01
A sequence domain (SD) harmonic model of a gridconnected voltage-source converter is developed for decoupling converter generated voltage harmonics from voltage harmonics in the external grid. The modeling procedure includes a derivation of the baseband frequency response for regular......-sampled pulsewidth modulation and an analysis of converter generated voltage harmonics due to compensated dead-time. The decoupling capabilities of the proposed the SD harmonic model are verified through a power quality (PQ) assessment of a 3MW Type-IV wind turbine. The assessment shows that the magnitude and phase...... of low-order odd converter generated voltage harmonics are dependent on the converter operating point and the phase of the fundamental component of converter current respectively. The SD harmonic model can be used to make PQ assessments of Type-IV wind turbines or incorporated into harmonic load flows...
Concept for power scaling second harmonic generation using a cascade of nonlinear crystals
DEFF Research Database (Denmark)
Hansen, Anders Kragh; Tawfieq, Mahmoud; Jensen, Ole Bjarlin
2015-01-01
Within the field of high-power second harmonic generation (SHG), power scaling is often hindered by adverse crystal effects such as thermal dephasing arising from the second harmonic (SH) light, which imposes limits on the power that can be generated in many crystals. Here we demonstrate a concept...... for efficient power scaling of single-pass SHG beyond such limits using a cascade of nonlinear crystals, in which the first crystal is chosen for high nonlinear efficiency and the subsequent crystal(s) are chosen for power handling ability. Using this highly efficient singlepass concept, we generate 3.7 W...... of continuous-wave diffraction-limited 2 ( 1.25) M = light at 532 nm from 9.5 W of non-diffraction-limited 2 ( 7.7) M = light from a tapered laser diode, while avoiding significant thermal effects. Besides constituting the highest SH power yet achieved using a laser diode, this demonstrates that the concept...
Harmonic Interaction Analysis in Grid-connected Converter using Harmonic State Space (HSS) Modeling
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
. Furthermore, a harmonic matrix of the grid-connected converter is developed to analyze the harmonic interaction at the steady-state behavior. Besides, the frequency-domain results are compared with time-domain simulation results by using HSS modeling to verify the theoretical analysis. Experimental results...... research about the harmonic interaction. However, it is found that the Linear Time Invariant (LTI) based model analysis makes it difficult to analyze these phenomena because of the time-varying properties of the power electronic based systems. This paper investigates grid-connected converter by using...
Atomically Phase-Matched Second-Harmonic Generation in a 2D Crystal
2016-08-26
OPEN ORIGINAL ARTICLE Atomically phase-matched second-harmonic generation in a 2D crystal Mervin Zhao1,2,*, Ziliang Ye1,2,*, Ryuji Suzuki3,4,*, Yu...arising from a single atomic layer, where the SH light elucidated important information such as the grain boundaries and electronic structure in these ultra...intensity on layer number as a result of atomically phase-matched nonlinear dipoles in layers of the 3R crystal that constructively interfere. By
Third harmonic generation of CO2 laser radiation in AgGaSe2 crystal
Indian Academy of Sciences (India)
September 2000 physics pp. 405–412. Third harmonic generation of CO2 laser radiation in. AgGaSe2 crystal. GOPAL C BHAR, PATHIK KUMBHAKAR. ½. , D V SATYANARAYANA. ¾. ,. N S N BANERJEE. ¾. , U NUNDY. ¾ and C G CHAO. ¿. Laser Laboratory, Physics Department, Burdwan University, Burdwan 713 104, ...
LED lamp modelling for harmonic studies in distribution systems
Molina, Julio; Mesas García, Juan José; Mesbahi, Nadhir; Sainz Sapera, Luis
2017-01-01
Energy saving policies have boosted the use of light emitting diode (LED) lamps in distribution networks. These lamps are non-linear loads which inject harmonic currents into the distribution system, which has led to a decrease in the system power quality. Study of the modelling of these lamps would allow the prediction of harmonic emissions into distribution systems. This study presents a frequency-domain LED lamp model for harmonic emission calculation, together with a simple estimation pro...
Terahertz-field-induced second harmonic generation through Pockels effect in zinc telluride crystal.
Cornet, Marion; Degert, Jérôme; Abraham, Emmanuel; Freysz, Eric
2014-10-15
We report on the second harmonic generation (SHG) of a near-infrared pulse in a zinc telluride crystal through the Pockels effect induced by an intense terahertz pulse. The temporal and angular behaviors of the SHG have been measured and agree well with theoretical predictions. This phenomenon, so far overlooked, makes it possible to generate second harmonic through cascading of two second-order nonlinear phenomena in the near-infrared and terahertz ranges. We also show how this cascading process can be used to sample terahertz pulses.
Energy Technology Data Exchange (ETDEWEB)
Trull, J.; Wang, B.; Parra, A.; Vilaseca, R.; Cojocaru, C. [Departament de Física i Enginyeria Nuclear, Universitat Politècnica Catalunya, Terrassa 08222 (Spain); Sola, I. [Grupo de Investigación en Óptica Extrema (GIOE), Departamento de Física Aplicada, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain); Krolikowski, W. [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Science Program, Texas A and M University at Qatar, Doha (Qatar); Sheng, Y. [Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)
2015-06-01
Pulse compression in dispersive strontium barium niobate crystal with a random size and distribution of the anti-parallel orientated nonlinear domains is observed via transverse second harmonic generation. The dependence of the transverse width of the second harmonic trace along the propagation direction allows for the determination of the initial chirp and duration of pulses in the femtosecond regime. This technique permits a real-time analysis of the pulse evolution and facilitates fast in-situ correction of pulse chirp acquired in the propagation through an optical system.
Fourth-harmonic generation of picosecond glass laser pulses with cesium lithium borate crystals
Energy Technology Data Exchange (ETDEWEB)
Sharma, L.B.; Daido, H.; Kato, Y.; Nakai, S. [Institute of Laser Engineering, Osaka University, 2-6, Yamada-Oka, Suita 565 (Japan); Zhang, T. [Yamanashi University, Faculty of Engineering, 4-3-11 Takeda, Kofu, Yamanashi 400 (Japan); Mori, Y.; Sasaki, T. [Department of Electrical Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565 (Japan)
1996-12-01
We report the fourth-harmonic generation of 1.5 ps, 1.053 {mu}m glass laser pulses, where group velocity mismatch plays a significant role, at intensities up to 100 GW/cm{sup 2} using newly developed crystal, cesium lithium borate (CsLiB{sub 6}O{sub 10}). Type-I doubler and type-I quadrupler were used in the fourth harmonic generation experimental scheme. Energy conversion efficiencies of 24{percent} and 53{percent} have been achieved for frequency quadrupling and doubling of the fundamental glass laser pulses, respectively. {copyright} {ital 1996 American Institute of Physics.}
Trajectory analysis of high-order-harmonic generation from periodic crystals
Ikemachi, Takuya; Shinohara, Yasushi; Sato, Takeshi; Yumoto, Junji; Kuwata-Gonokami, Makoto; Ishikawa, Kenichi L.
2017-04-01
We theoretically study high-order-harmonic generation (HHG) from solids driven by intense laser pulses using a one-dimensional model periodic crystal. By numerically solving the time-dependent Schrödinger equation directly on a real-space grid, we successfully reproduce experimentally observed unique features of solid-state HHG such as the linear cutoff-energy scaling and the sudden transition from a single- to multiple-plateau structure. Based on the simulation results, we propose a simple model that incorporates vector-potential-induced intraband displacement, interband tunneling, and recombination with the valence-band hole. One key parameter is the peak-to-valley amplitude of the pulse vector potential, which determines the crystal momentum displacement during the half cycle. When the maximum peak-to-valley amplitude Apeak reaches the half width π/a of the Brillouin zone with a being the lattice constant, the HHG spectrum exhibits a transition from a single- to multiple-plateau structure, and even further plateaus appear at Apeak=2/π a ,3/π a ,⋯ . The multiple cutoff positions are given as functions of Apeak and the second maximum Apeak', in terms of the energy difference between different bands. Using our recipe, one can draw electron trajectories in the momentum space, from which one can deduce, for example, the time-frequency structure of HHG without elaborate quantum-mechanical calculations. Finally, we reveal that the cutoff positions depend on not only the intensity and wavelength of the pulse, but also its duration, in marked contrast to the gas-phase case. Our model can be viewed as a solid-state and momentum-space counterpart of the familiar three-step model, highly successful for gas-phase HHG, and provide a unified basis to understand HHG from solid-state materials and gaseous media.
DEFF Research Database (Denmark)
Wiechowski, Wojciech Tomasz; Lykkegaard, Jan; Bak, Claus Leth
2007-01-01
In this paper two methods of validation of transmission network harmonic models are introduced. The methods were developed as a result of the work presented in [1]. The first method allows calculating the transfer harmonic impedance between two nodes of a network. Switching a linear, series network...... are used for calculation of the transfer harmonic impedance between the nodes. The determined transfer harmonic impedance can be used to validate a computer model of the network. The second method is an extension of the fist one. It allows switching a series element that contains a shunt branch...... component that links the nodes causes a variation of the background harmonic voltage distortion at the nodes. Harmonic current in the series element is measured together with the harmonic voltages at both nodes, before and after the switching. Obtained incremental values of harmonic voltages and the current...
Second harmonic generation studies in L-alanine single crystals grown from solution
Energy Technology Data Exchange (ETDEWEB)
Boomadevi, Shanmugam, E-mail: sboomi@gmail.com [Department of Physics, Periyar Maniammai University, Thanjavur-613 403, Tamil Nadu (India); Pandiyan, Krishnamoorthy [School of Electrical and Electronics Engineering, SASTRA University, Thanjavur-613 401, Tamil Nadu (India)
2014-01-01
Single crystals of L-alanine of dimensions 2×1.1×0.5 cm{sup 3} were grown by evaporation method using deionised water as a solvent. The morphology of the grown crystals had (1 2 0) and (0 1 1) as their prominent faces. UV–vis-near IR spectrum shows the transparency range of L-alanine crystal available for frequency doubling from 250 to 1400 nm. Phase-matched second harmonic generation was observed in L-alanine sample by using 7 ns Q-switched Nd:YAG laser with OPO set up. In the present work, phase matching was achieved by angle and wavelength tuning. The angular and spectral phase-matching bandwidths were determined experimentally for a 1.5 mm thick L-alanine crystal and the results have been compared with their theoretical results. Further the possible reasons for the broadening of SHG spectrum have been discussed.
Godiksen, R. H.; Aunsborg, T. S.; Kristensen, P. K.; Pedersen, K.
2017-11-01
Unintentionally doped and semi-insulating Fe-doped GaN crystals grown by hydride vapor phase epitaxy have been investigated with two-photon photoluminescence and second-harmonic generation spectroscopy to reveal doping effects on the nonlinear optical properties and thus indirectly on crystal properties. Like for linear luminescence, it is found that Fe doping strongly reduces nonlinear luminescence. Recording of second-harmonic generation spectra in transmission probing bulk properties shows no significant difference between doped and un-doped crystals. Reflected second-harmonic generation probing 50-100 nm at the surface, on the other hand, shows significantly lower signal from the doped sample. Secondary ion mass spectroscopy shows that the Fe concentration is higher at the surface than in the bulk of the doped crystal. It is suggested that this causes higher defect density and degraded order in the surface region, thus reducing the second-harmonic signal.
Near- and far-field second-harmonic imaging of quasi-phase-matching crystals.
Vohnsen, B; Bozhevolnyi, S I
2001-04-01
Second-harmonic scanning near- and far-field optical microscopy of an electric-field poled KTiOPO4 quasi-phase-matching crystal has been accomplished. This has been done in order to reveal the walls that form the intersections between inverted and non-inverted crystal domains. The domain walls are seen clearly only in images recorded by means of second-harmonic generation because of a large nonlinear contrast, and they appear as bright stripes when studied in a reflection geometry but they are dark when studied in transmission. The images show that the duty cycle of the quasi-phase-matching crystal differs from the ideal and that the walls are not completely smooth. These effects, in combination with the observed scattering from the domain walls, are expected to lower the output of the crystal when used for frequency doubling. We conclude that the wall thickness is no more than approximately 100 nm, which makes it a suitable test object for the resolution capabilities of scanning near-field optical microscopes that are used for nonlinear imaging.
Real-time observation of interfering crystal electrons in high-harmonic generation.
Hohenleutner, M; Langer, F; Schubert, O; Knorr, M; Huttner, U; Koch, S W; Kira, M; Huber, R
2015-07-30
Acceleration and collision of particles has been a key strategy for exploring the texture of matter. Strong light waves can control and recollide electronic wavepackets, generating high-harmonic radiation that encodes the structure and dynamics of atoms and molecules and lays the foundations of attosecond science. The recent discovery of high-harmonic generation in bulk solids combines the idea of ultrafast acceleration with complex condensed matter systems, and provides hope for compact solid-state attosecond sources and electronics at optical frequencies. Yet the underlying quantum motion has not so far been observable in real time. Here we study high-harmonic generation in a bulk solid directly in the time domain, and reveal a new kind of strong-field excitation in the crystal. Unlike established atomic sources, our solid emits high-harmonic radiation as a sequence of subcycle bursts that coincide temporally with the field crests of one polarity of the driving terahertz waveform. We show that these features are characteristic of a non-perturbative quantum interference process that involves electrons from multiple valence bands. These results identify key mechanisms for future solid-state attosecond sources and next-generation light-wave electronics. The new quantum interference process justifies the hope for all-optical band-structure reconstruction and lays the foundation for possible quantum logic operations at optical clock rates.
Application of enthalpy model for floating zone silicon crystal growth
Krauze, A.; Bergfelds, K.; Virbulis, J.
2017-09-01
A 2D simplified crystal growth model based on the enthalpy method and coupled with a low-frequency harmonic electromagnetic model is developed to simulate the silicon crystal growth near the external triple point (ETP) and crystal melting on the open melting front of a polycrystalline feed rod in FZ crystal growth systems. Simulations of the crystal growth near the ETP show significant influence of the inhomogeneities of the EM power distribution on the crystal growth rate for a 4 in floating zone (FZ) system. The generated growth rate fluctuations are shown to be larger in the system with higher crystal pull rate. Simulations of crystal melting on the open melting front of the polycrystalline rod show the development of melt-filled grooves at the open melting front surface. The distance between the grooves is shown to grow with the increase of the skin-layer depth in the solid material.
Crystal growth and second harmonic generation efficiency of a chalcone derivative
Energy Technology Data Exchange (ETDEWEB)
Meenatchi, V.; Muthu, K.; Rajasekar, M.; Meenakshisundaram, SP., E-mail: aumats2009@gmail.com
2013-06-15
Single crystals of (2E,6E)-2-(4-fluorobenzylidine)-6-(4-methoxybenzylidine)cyclohexanone (FBMBC) have been grown by a slow evaporation solution growth technique from ethanol at room temperature. The single crystal X-ray diffraction study reveals that the FBMBC belongs to triclinic system and the cell parameters are a=9.790(6) Å, b=12.08(7) Å, c=14.09(9) Å and V=1577 Å{sup 3}. The structure and the crystallinity of the material were further confirmed by powder X-ray diffraction analysis. The various functional groups present in the molecule are confirmed by Fourier transform infrared spectral analysis. The scanning electron microscopy study reveals the surface morphology of the as-grown crystal. Thermogravimetric/differential thermal analysis studies reveal the purity of the material and the crystals are transparent in the visible region having a low optical cut-off at ∼475 nm. The second harmonic generation efficiency of FBMBC is estimated by the Kurtz and Perry technique. Theoretical calculations were performed using the Hartree–Fock method with 6-31 G(d,p) as the basis set to derive the optimized geometry and the first-order molecular hyperpolarizability (β) values.
The Tax harmonization in open regionalism ; The European model
Directory of Open Access Journals (Sweden)
Mouloud MELIKAOUI
2014-06-01
Full Text Available This research examines the subject of alternative regionalism or open regionalism and reality within the multilateral trading system, based on growing liberalization of trade, and the problem of compatibility between them, as well as the limits of economic policy harmonization in the framework of Open regionalism, special tax harmonization, in the light of economic and tax disparities of the Member States, with an overview of the European tax harmonization and limits. The Study concluded the importance of tax harmonization as a tool by activation of the concept of open regionalism, through facilitating capitals flows and investments between member states and reduction of the négatives phenomena of tax. It recommended the need to emphasizing on the importance of gradually harmonization for tax policy, and expand the rule of tax treaties and exchange of tax information and experiences between countries, This is in light a holistic approach to other economic policies as a the exchange rate policy and monetary policy, just as is the case in the European model.
A Comprehensive and Harmonized Digital Forensic Investigation Process Model.
Valjarevic, Aleksandar; Venter, Hein S
2015-11-01
Performing a digital forensic investigation (DFI) requires a standardized and formalized process. There is currently neither an international standard nor does a global, harmonized DFI process (DFIP) exist. The authors studied existing state-of-the-art DFIP models and concluded that there are significant disparities pertaining to the number of processes, the scope, the hierarchical levels, and concepts applied. This paper proposes a comprehensive model that harmonizes existing models. An effort was made to incorporate all types of processes proposed by the existing models, including those aimed at achieving digital forensic readiness. The authors introduce a novel class of processes called concurrent processes. This is a novel contribution that should, together with the rest of the model, enable more efficient and effective DFI, while ensuring admissibility of digital evidence. Ultimately, the proposed model is intended to be used for different types of DFI and should lead to standardization. © 2015 American Academy of Forensic Sciences.
Silicon photonic crystal cavity enhanced second-harmonic generation from monolayer WSe2
Fryett, Taylor K; Zheng, Jiajiu; Liu, Chang-Hua; Xu, Xiaodong; Majumdar, Arka
2016-01-01
Nano-resonator integrated with two-dimensional materials (e.g. transition metal dichalcogenides) have recently emerged as a promising nano-optoelectronic platform. Here we demonstrate resonatorenhanced second-harmonic generation (SHG) in tungsten diselenide using a silicon photonic crystal cavity. By pumping the device with the ultrafast laser pulses near the cavity mode at the telecommunication wavelength, we observe a near visible SHG with a narrow linewidth and near unity linear polarization, originated from the coupling of the pump photon to the cavity mode. The observed SHG is enhanced by factor of ~200 compared to a bare monolayer on silicon. Our results imply the efficacy of cavity integrated monolayer materials for nonlinear optics and the potential of building a silicon-compatible second-order nonlinear integrated photonic platform.
Directory of Open Access Journals (Sweden)
Yu-Shan Chen
2015-04-01
Full Text Available We reported that the photonic crystal fiber (PCF filled with TI:Bi2Te3 nanosheets solution could act as an effective saturable absorber (SA. Employing this TI-PCF SA device; we constructed an ytterbium-doped all-fiber laser oscillator and achieved the evanescent wave mode-locking operation. Due to the large cavity dispersion; the fundamental mode-locking pulse had the large full width at half maximum (FWHM of 2.33 ns with the repetition rate of ~1.11 MHz; and the radio frequency (RF spectrum with signal-to-noise ratio (SNR of 61 dB. In addition; the transition dynamics from a bunched state of pulses to harmonic mode-locking (HML was also observed; which was up to 26th order.
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth
2015-01-01
As the number of power electronics based systems are increasing, studies about overall stability and harmonic problems are rising. In order to analyze harmonics and stability, most research is using an analysis method, which is based on the Linear Time Invariant (LTI) approach. However, this can...... change compared to the conventional operation. In this paper, a Harmonic State Space modeling method, which is based on the Linear Time varying theory, is used to analyze different operating points of the parallel connected converters. The analyzed results show that the HSS modeling approach explicitly...
Monat, Christelle; Grillet, Christian; Corcoran, Bill; Moss, David J; Eggleton, Benjamin J; White, Thomas P; Krauss, Thomas F
2010-03-29
Using Fourier optics, we retrieve the wavevector dependence of the third-harmonic (green) light generated in a slow light silicon photonic crystal waveguide. We show that quasi-phase matching between the third-harmonic signal and the fundamental mode is provided in this geometry by coupling to the continuum of radiation modes above the light line. This process sustains third-harmonic generation with a relatively high efficiency and a substantial bandwidth limited only by the slow light window of the fundamental mode. The results give us insights into the physics of this nonlinear process in the presence of strong absorption and dispersion at visible wavelengths where bandstructure calculations are problematic. Since the characteristics (e.g. angular pattern) of the third-harmonic light primarily depend on the fundamental mode dispersion, they could be readily engineered.
DEFF Research Database (Denmark)
Sánchez-García, Laura; Tserkezis, Christos; Ramírez, Mariola O
2016-01-01
We demonstrate a 60–fold enhancement of the second harmonic generation (SHG) response at the nanoscale in a hybrid metal-dielectric system. By using complex silver nanostructures photochemically deposited on the polar surface of a ferroelectric crystal, we tune the plasmonic resonances from the v...
Policy harmonized approach for the EU agricultural sector modelling
Directory of Open Access Journals (Sweden)
G. SALPUTRA
2008-12-01
Full Text Available Policy harmonized (PH approach allows for the quantitative assessment of the impact of various elements of EU CAP direct support schemes, where the production effects of direct payments are accounted through reaction prices formed by producer price and policy price add-ons. Using the AGMEMOD model the impacts of two possible EU agricultural policy scenarios upon beef production have been analysed full decoupling with a switch from historical to regional Single Payment scheme or alternatively with re-distribution of country direct payment envelopes via introduction of EU-wide flat area payment. The PH approach, by systematizing and harmonizing the management and use of policy data, ensures that projected differential policy impacts arising from changes in common EU policies reflect the likely actual differential impact as opposed to differences in how common policies are implemented within analytical models. In the second section of the paper the AGMEMOD models structure is explained. The policy harmonized evaluation method is presented in the third section. Results from an application of the PH approach are presented and discussed in the papers penultimate section, while section 5 concludes.;
Pulsed Bessel-Gauss beams: a depleted wave model for type II second-harmonic generation.
Sabaeian, Mohammad; Motazedian, Alireza; Mohammad Rezaee, Mostafa; Jalil-Abadi, Fatemeh Sedaghat
2014-11-10
In this work, a three-dimensional and time-dependent nonlinear wave model to describe the generation of pulsed Bessel-Gauss second-harmonic waves (SHWs) is presented. Three coupled equations, two for ordinary and extraordinary fundamental waves and one for extraordinary SHWs, describing type II second-harmonic generation (SHG) in a KTiOPO4 (KTP) crystal were solved by considering the depletion of fundamental waves (FWs). The results examined the validity of nondepleted wave approximation against the energy of pulses, beam spot size, and interaction length. It was shown that for pulses with spot sizes of ωf=80 μm and energy of 0.8j, the nonlinear interaction was accomplished over a distance of ∼5 mm. Therefore, for KTP crystals with lengths longer than 5 mm, the nondepleted wave approximation can no longer be valid. To be valid, the crystal must be shorter than the interaction length, i.e., 5 mm.
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede
2016-01-01
The increasing number of renewable energy sources in the distribution grid is becoming a major issue for utility companies since grid-connected converters are operating at different operating points due to the probabilistic characteristics of the renewable energy. Usually, the harmonics and imped...... the harmonic coupling characteristic as well as different dynamic characteristics. The theoretical modeling and analysis are verified by simulations as well as experimental results.......The increasing number of renewable energy sources in the distribution grid is becoming a major issue for utility companies since grid-connected converters are operating at different operating points due to the probabilistic characteristics of the renewable energy. Usually, the harmonics...... and impedance from other renewable energy sources are not taken carefully into account in the installation and design of the systems. It can bring an unknown harmonic instability into a multiple power sourced system and makes the analysis difficult due to the complexity of the grid network. This paper proposes...
Modeling of photonic Crystal Fibres
DEFF Research Database (Denmark)
Bjarklev, Anders Overgaard; Broeng, Jes; Barkou, Stig Eigil
1999-01-01
Diferent theoretical models for analysis of photonic crystal fibres are reviewed and compaired. The methods span from simple scalar approaches to full-vectorial models using different mode-field decompositions. The specific advantages of the methods are evaluated.......Diferent theoretical models for analysis of photonic crystal fibres are reviewed and compaired. The methods span from simple scalar approaches to full-vectorial models using different mode-field decompositions. The specific advantages of the methods are evaluated....
Modeling and Identification of Harmonic Instability Problems In Wind Farms
DEFF Research Database (Denmark)
Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei
2016-01-01
to identify harmonic instability problems in wind farms, where many wind turbines, cables, transformers, capacitor banks, shunt reactors, etc, typically are located. This methodology introduces the wind farm as a Multi-Input Multi-Outpur (MIMO) control system, where the linearized models of fast inner control...... loops of the grid-side converters are considered. Therefore, instability problems of the whole wind farm are predicted based on the poles of the introduced MIMO system. In order to confirm the effectiveness of the proposed analytical approach, time-domain simulations are performed in the PSCAD......In power electronics based power systems like wind farms, the interactions between the inner control systems of the power converters and the passive components may lead to high frequency oscillations, which can be called harmonic instability. In this paper, a simple methodology is presented...
Modeling Flow-Induced Crystallization
Roozemond, Peter C.; van Drongelen, Martin; Peters, Gerrit W.M.; Auriemma, Finizia; Alfonso, Giovanni Carlo; de Rosa, Claudio
2017-01-01
A numerical model is presented that describes all aspects of flow-induced crystallization of isotactic polypropylene at high shear rates and elevated pressures. It incorporates nonlinear viscoelasticity, including viscosity change as a result of formation of oriented fibrillar crystals (shish),
Harmonic current prediction by impedance modeling of grid-tied inverters
DEFF Research Database (Denmark)
Pereira, Heverton A.; Freijedo, Francisco D.; Silva, M. M.
2017-01-01
and harmonic voltage profiles. Results reinforce that impedance models can represent with relatively accuracy the harmonic current emitted by the PV plants at the point of common coupling (PCC). Lastly, a stress test is performed to show how a variation in the harmonic voltage phase angle impacts the PV plant...... impedance models when used in harmonic integration studies. It is aimed to estimate the harmonic current contribution as a function of the background harmonic voltages components. Time domain simulations based on detailed and average models are compared with the impedance model developed in frequency domain....... In grids with harmonic voltages, impedance models can predict the current distortion for all active power injection scenarios. Furthermore, measurements in a 1.4 MW PV plant connected in a distributed grid are used to validate the simulation based on impedance models during different power injections...
harmonic load modeling: a case study of 33 kv abuja steel mill feeder
African Journals Online (AJOL)
HOD
An in-depth study of the harmonic orders inherent in a power system network is required before mitigation techniques are adopted. This paper studied the harmonic orders of the 33 kV Abuja Steel Feeder modeled as a harmonic source using measured data. Readings of kW, kVar, kV and Hz were obtained using power ...
Third harmonic generation of CO2 laser radiation in AgGaSe2 crystal
Indian Academy of Sciences (India)
... for second harmonic and third harmonic generations are 6.3% and 2.4% respectively with the input fundamental pump power density of 5.9 MW/cm2 only. The wavelength of the fundamental CO2 laser radiation used for the generation of harmonics is 10.6 m, (20) line. A compact TEA CO2 laser source has been built in ...
Crystal study and econometric model
1975-01-01
An econometric model was developed that can be used to predict demand and supply figures for crystals over a time horizon roughly concurrent with that of NASA's Space Shuttle Program - that is, 1975 through 1990. The model includes an equation to predict the impact on investment in the crystal-growing industry. Actually, two models are presented. The first is a theoretical model which follows rather strictly the standard theoretical economic concepts involved in supply and demand analysis, and a modified version of the model was developed which, though not quite as theoretically sound, was testable utilizing existing data sources.
Modeling stock return distributions with a quantum harmonic oscillator
Ahn, K.; Choi, M. Y.; Dai, B.; Sohn, S.; Yang, B.
2017-11-01
We propose a quantum harmonic oscillator as a model for the market force which draws a stock return from short-run fluctuations to the long-run equilibrium. The stochastic equation governing our model is transformed into a Schrödinger equation, the solution of which features “quantized” eigenfunctions. Consequently, stock returns follow a mixed χ distribution, which describes Gaussian and non-Gaussian features. Analyzing the Financial Times Stock Exchange (FTSE) All Share Index, we demonstrate that our model outperforms traditional stochastic process models, e.g., the geometric Brownian motion and the Heston model, with smaller fitting errors and better goodness-of-fit statistics. In addition, making use of analogy, we provide an economic rationale of the physics concepts such as the eigenstate, eigenenergy, and angular frequency, which sheds light on the relationship between finance and econophysics literature.
Prasanyaa, T.; Jayaramakrishnan, V.; Haris, M.
2013-03-01
In this paper, we report the successful growth of pure, Cu2+ ions and Cd2+ ions doped on ninhydrin single crystals by slow solvent evaporation technique. The presence of Cu2+ and Cd2+ ions in the specimen of ninhydrin single crystal has been determined by atomic absorption spectroscopy. The powder X-ray diffraction analysis was done to calculate the lattice parameters of the pure and doped crystals. The percentage of transmittance of the crystal was recorded using the UV-Vis Spectrophotometer. Thermal behaviors of the grown crystals have been examined by the thermal gravimetric/differential thermal analysis. The hardness of the grown crystals was assessed and the results show the minor variation in the hardness value for the pure and doped ninhydrin samples. The value of the work hardening coefficient n was found to be 2.0, 1.0 and 1.06 for pure, copper and cadmium doped ninhydrin crystals respectively. The second harmonic generation efficiency of Cd2+ and Cu2+ doped ninhydrin is 8.3 and 6.3 times greater than well known nonlinear crystal of potassium dihydrogen phosphate respectively. The antibacterial and antifungal activities of the title compound were performed by disk diffusion method against the standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillis niger and Aspergillus flavus.
The two capacitor problem revisited: simple harmonic oscillator model approach
Lee, Keeyung
2012-01-01
The well-known two-capacitor problem, in which exactly half the stored energy disappears when a charged capacitor is connected to an identical capacitor is discussed based on the mechanical harmonic oscillator model approach. In the mechanical harmonic oscillator model, it is shown first that \\emph {exactly half} the work done by a constant applied force is dissipated irrespective of the form of dissipation mechanism when the system comes to a new equilibrium after a constant force is abruptly applied. This model is then applied to the energy loss mechanism in the capacitor charging problem or the two-capacitor problem. This approach allows a simple explanation of the energy dissipation mechanism in these problems and shows that the dissipated energy should always be \\emph {exactly half} the supplied energy whether that is caused by the Joule heat or by the radiation. This paper which provides a simple treatment of the energy dissipation mechanism in the two-capacitor problem is suitable for all undergraduate...
Harmonization of detailed clinical models with clinical study data standards.
Jiang, G; Evans, J; Oniki, T A; Coyle, J F; Bain, L; Huff, S M; Kush, R D; Chute, C G
2015-01-01
This article is part of the Focus Theme of METHODS of Information in Medicine on "Managing Interoperability and Complexity in Health Systems". Data sharing and integration between the clinical research data management system and the electronic health record system remains a challenging issue. To approach the issue, there is emerging interest in utilizing the Detailed Clinical Model (DCM) approach across a variety of contexts. The Intermountain Healthcare Clinical Element Models (CEMs) have been adopted by the Office of the National Coordinator awarded Strategic Health IT Advanced Research Projects for normalization (SHARPn) project for normalizing patient data from the electronic health records (EHR). The objective of the present study is to describe our preliminary efforts toward harmonization of the SHARPn CEMs with CDISC (Clinical Data Interchange Standards Consortium) clinical study data standards. We were focused on three generic domains: demographics, lab tests, and medications. We performed a panel review on each data element extracted from the CDISC templates and SHARPn CEMs. We have identified a set of data elements that are common to the context of both clinical study and broad secondary use of EHR data and discussed outstanding harmonization issues. We consider that the outcomes would be useful for defining new requirements for the DCM modeling community and ultimately facilitating the semantic interoperability between systems for both clinical study and broad secondary use domains.
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth
2015-01-01
The increasing number of renewable energy sources at the distribution grid is becoming a major issue for utility companies, since the grid connected converters are operating at different operating points due to the probabilistic characteristics of renewable energy. Besides, typically, the harmoni...... impedance matrixes, where that represents the harmonic coupling characteristic as well as the different instability characteristics. The theoretical modeling and analysis are verified by simulations and also experimental results.......The increasing number of renewable energy sources at the distribution grid is becoming a major issue for utility companies, since the grid connected converters are operating at different operating points due to the probabilistic characteristics of renewable energy. Besides, typically, the harmonics...... and impedance from other renewable energy sources are not taken carefully into account in the installation and design. However, this may bring an unknown harmonic instability into the multiple power sourced system and also make the analysis difficult due to the complexity of the grid network. This paper...
Ma, Xiaohua
2011-03-01
Achiral nonlinear optical (NLO) chromophores 1,3-diazaazulene derivatives, 2-(4â€-aminophenyl)-6-nitro-1,3-diazaazulene (APNA) and 2-(4â€-N,N-diphenylaminophenyl)-6-nitro-1,3-diazaazulene (DPAPNA), were synthesized with high yield. Despite the moderate static first hyperpolarizabilities (β0) for both APNA [(136 Â± 5) Ã - 10-30 esu] and DPAPNA [(263 Â± 20) Ã - 10-30 esu], only APNA crystal shows a powder efficiency of second harmonic generation (SHG) of 23 times that of urea. It is shown that the APNA crystallization driven cooperatively by the strong H-bonding network and the dipolar electrostatic interactions falls into the noncentrosymmetric P2 12121 space group, and that the helical supramolecular assembly is solely responsible for the efficient SHG response. To the contrary, the DPAPNA crystal with centrosymmetric P-1 space group is packed with antiparalleling dimmers, and is therefore completely SHG-inactive. 1,3-Diazaazulene derivatives are suggested to be potent building blocks for SHG-active chiral crystals, which are advantageous in high thermal stability, excellent near-infrared transparency and high degree of designing flexibility. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 Optical crystals based on 1,3-diazaazulene derivatives are reported as the first example of organic nonlinear optical crystal whose second harmonic generation activity is found to originate solely from the chirality of their helical supramolecular orientation. The strong H-bond network forming between adjacent choromophores is found to act cooperatively with dipolar electrostatic interactions in driving the chiral crystallization of this material. Copyright © 2011 Wiley Periodicals, Inc.
Global GPS Ionospheric Modelling Using Spherical Harmonic Expansion Approach
Directory of Open Access Journals (Sweden)
Byung-Kyu Choi
2010-12-01
Full Text Available In this study, we developed a global ionosphere model based on measurements from a worldwide network of global positioning system (GPS. The total number of the international GPS reference stations for development of ionospheric model is about 100 and the spherical harmonic expansion approach as a mathematical method was used. In order to produce the ionospheric total electron content (TEC based on grid form, we defined spatial resolution of 2.0 degree and 5.0 degree in latitude and longitude, respectively. Two-dimensional TEC maps were constructed within the interval of one hour, and have a high temporal resolution compared to global ionosphere maps which are produced by several analysis centers. As a result, we could detect the sudden increase of TEC by processing GPS observables on 29 October, 2003 when the massive solar flare took place.
Marx-Glowna, Berit; Schulze, Kai S; Uschmann, Ingo; Kämpfer, Tino; Weber, Günter; Hahn, Christoph; Wille, Hans Christian; Schlage, Kai; Röhlsberger, Ralf; Förster, Eckhart; Stöhlker, Thomas; Paulus, Gerhard G
2015-09-01
The spectrum of the undulator radiation of beamline P01 at Petra III has been measured after passing a multiple reflection channel-cut polarimeter. Odd and even harmonics up to the 15th order, as well as Compton peaks which were produced by the high harmonics in the spectrum, could been measured. These additional contributions can have a tremendous influence on the performance of the polarimeter and have to be taken into account for further polarimeter designs.
Crystallization Kinetics within a Generic Modelling Framework
DEFF Research Database (Denmark)
Meisler, Kresten Troelstrup; von Solms, Nicolas; Gernaey, Krist
2013-01-01
An existing generic modelling framework has been expanded with tools for kinetic model analysis. The analysis of kinetics is carried out within the framework where kinetic constitutive models are collected, analysed and utilized for the simulation of crystallization operations. A modelling...... procedure is proposed to gain the information of crystallization operation kinetic model analysis and utilize this for faster evaluation of crystallization operations....
DEFF Research Database (Denmark)
Glasdam, Jakob Bærholm; Bak, Claus Leth; Kocewiak, Lukasz Hubert
2017-01-01
system with 201 voltage levels, without loss of accuracy compared to conventional modelling of the converter. Harmonic stability is a core concern for both existing and future offshore wind power plants (OWPPs). A harmonic stability study will be undertaken with focus on the number of wind turbine...... generators in service, as this is known to influence the harmonic stability in OWPPs. The paper demonstrates the necessity of the inclusion of a detailed equivalent model of the HVDC converter for harmonic stability studies in the time domain. By implementation of active filtering in the converters...
Modelling of UWB Antenna Perturbed by Human Phantom in Spherical Harmonics Space
DEFF Research Database (Denmark)
Mhedhbi, Meriem; Avrillon, Stephane; Pedersen, Troels
2014-01-01
In this paper we study how the antenna radiation pattern is perturbed in the presence of a human phantom in terms of changes in the coefficients of the spherical harmonic antenna representation. The spherical harmonic basis allows for a compact representation of the antenna pattern which is attra......In this paper we study how the antenna radiation pattern is perturbed in the presence of a human phantom in terms of changes in the coefficients of the spherical harmonic antenna representation. The spherical harmonic basis allows for a compact representation of the antenna pattern which...... is attractive for simulation purposes. We propose a simple model for the spherical harmonics coefficients allowing to predict the antenna behavior perturbed by a human phantom. The model is based on knowledge of the spherical harmonic coefficients of antenna in free space and the antenna-phantom distance....
Harmonizing Social and Environmental Dynamics in Earth Systems Modeling
Evans, T. P.; Estes, L. D.; Caylor, K. K.; McCord, P. F.; Gower, D.; Konar, M.; Baylis, K.; Waldman, K.; Blekking, J.; Schlachter, T.
2016-12-01
The promotion of the Anthropocene has led to new awareness of the role of complex natural-human interactions in environmental change processes. This includes efforts to find causal relationships in empirical studies as well as science to understand how best to incorporate both human and environmental dynamics in models of earth systems spanning fine scale forest ecology models to GCMs. This presentation will discuss challenges and opportunities in integrating social and environmental dynamics in models and recent advances in coupled natural-human systems modeling. The core of this presentation will focus on whether it is possible to harmonize social and environmental dynamics by considering disparities in spatial scale, spatial extent, temporal scale and temporal extent. In the process this presentation will address fundamental questions such as whether social data necessarily entail greater uncertainty than environmental data and the implications for data uncertainty and model design as they relate to the ability to make forecasts and predictions from coupled natural-human systems models. It is imperative that social scientists and environmental scientists collaborate in the development of the data and models needed to understand how environmental systems may change in the future and how human decisions result in or avert environmental degradation. This presentation will argue that the limitations do not lie with data constraints or computational constraints but rather in the tendency for models to be developed without addressing the criticality of environmental vs. social dynamics. This can lead to the somewhat tired conclusion that social scientists and environmental scientists need to collaborate more… But this has been recognized for the last 20-30 years (and arguably longer…). But this is an unsatisfying conclusion. Thus this presentation will discuss new developments in data resources and computational infrastructure that raise the potential for new
West Coast Swing Dancing as a Driven Harmonic Oscillator Model
Ferrara, Davon; Holzer, Marie; Kyere, Shirley
The study of physics in sports not only provides valuable insight for improved athletic performance and injury prevention, but offers undergraduate students an opportunity to engage in both short- and long-term research efforts. In this project, conducted by two non-physics majors, we hypothesized that a driven harmonic oscillator model can be used to better understand the interaction between two west coast swing dancers since the stiffness of the physical connection between dance partners is a known factor in the dynamics of the dance. The hypothesis was tested by video analysis of two dancers performing a west coast swing basic, the sugar push, while changing the stiffness of the physical connection. The difference in stiffness of the connection from the ideal was estimated by the leader; the position with time data from the video was used to measure changes in the amplitude and phase difference between the leader and follower. While several aspects of our results agree with the proposed model, some key characteristics do not, possibly due to the follower relying on visual leads. Corresponding author and principal investigator.
Jeong, Mi-Yun; Cho, Bong Rae
2015-02-01
We summarize the nonlinear optical (NLO) properties of octupolar molecules, crystals, and films developed in our laboratory. We present the design strategy, structure-property relationship, and second-order NLO properties of 1,3,5-trinitro- and 1,3,5-tricyano-2,4,6-tris(p-diethylaminostyryl)benzene (TTB) derivatives, TTB crystals, and films prepared by free-casting TTB in poly(methyl methacrylate) (PMMA). The first hyperpolarizability of TTB was fivefold larger than that of the dipolar analogue. Moreover, the TTB crystal showed unprecedentedly large second-harmonic generation (SHG). While TTB crystal films (20 wt% TTB/PMMA) on various substrates showed appreciable SHG values, the cylinder film exhibited much larger SHG values and large electro-optic (EO) coefficients. The large SHG values and EO coefficients, as well as the high thermal stability of the cylinder film, will make it a potential candidate for NLO device applications. Copyright © 2014 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Modelling of photonic crystal fibres
DEFF Research Database (Denmark)
Knudsen, Erik
2003-01-01
In the presenta ph.d. work a theoretical study of aspects of modelling photonic crystal fibres was carried out. Photonic crystal fibres form a class of optical waveguides where guidance is no longer provided by a difference in refractive index between core and cladding. Instead, guidance...... is provided by an arrangement of air-holes running along the length of the fibre. Depending on the geometry of the fibre, the guiding mechanism may be either arising from the formation of a photonic bandgap in the cladding structure (photonic bandgap fibre), or by an effect resembling total internal...... reflection, which may described by an effective refractive index which is lower in the cladding than in the core (index guiding fibre). By solving Maxwell's equations, under the conditions defined by the geometry of the fibre structure, we may predict the properties of the fibre. In all but rare cases...
Saranraj, A.; Sahaya Jude Dhas, S.; Vinitha, G.; Britto Dhas, S. A. Martin
2017-10-01
A well crystallized Benzophenone single crystal was successfully grown by vertical semi transparent Bridgman technique. The lattice parameters of the grown crystal were established by single crystal x-ray diffraction technique. Fourier transform infrared spectroscopy was performed to determine the functional groups. The UV-NIR analysis revealed that the Benzophenone crystal has high transmittance in the entire visible region and the lower cutoff wavelength has been found to be 381 nm. The optical band gap energy was calculated and it is found to be 3.08 eV. The various linear optical parameters such as, Extinction coefficient (k), Refractive index (n), Reflectance, Complex dielectric constant, Optical susceptibility, Electrical conductivity and Optical polarization of the grown crystal were estimated and its variation with respect to incident photon energy was examined. Furthermore, the third order nonlinear optical properties were investigated by the z-scan technique using continuous wave Nd-YAG laser. The obtained thermophysical properties making use of photoacoustic spectroscopy show the superiority of the crystal over few other standard NLO materials.
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
. Through this method, the required computation time and CPU memory can be reduced, where this faster simulation can be an advantage of a large network simulation. Besides, the achieved results show the same results as the non-linear time-domain simulation. Furthermore, the HSS modeling can describe how...... with different switching frequency or harmonics from ac-dc converters makes that harmonics and frequency coupling are both problems of ac system and challenges of dc system. This paper presents a modeling and simulation method for a large dc power electronic system by using Harmonic State Space (HSS) modeling...
Modeling of higher harmonics formation in medical ultrasound systems
DEFF Research Database (Denmark)
Taylor, Louise Kold; Schlaikjer, Malene; Jensen, Jørgen Arendt
2002-01-01
The pressure eld emitted from multi-element medical ultrasound transducers can be simulated with Field II in the linear regime. By expanding this program's application to the nonlinear regime, beamforming schemes can be studied under strong focusing and high pressure levels as well, providing...... of the approach is demonstrated by comparing results from simulations and measurements from a convex array transducer. The new simulation tool is capable of simulating the formation of higher harmonics in water on the acoustical axis. The generation of nonlinear higher harmonic components can be predicted...
Lien, Chi-Hsiang; Tilbury, Karissa; Chen, Shean-Jen; Campagnola, Paul J
2013-01-01
Second Harmonic Generation (SHG) microscopy coupled with polarization analysis has great potential for use in tissue characterization, as molecular and supramolecular structural details can be extracted. Such measurements are difficult to perform quickly and accurately. Here we present a new method that uses a liquid crystal modulator (LCM) located in the infinity space of a SHG laser scanning microscope that allows the generation of any desired linear or circular polarization state. As the device contains no moving parts, polarization can be rotated accurately and faster than by manual or motorized control. The performance in terms of polarization purity was validated using Stokes vector polarimetry, and found to have minimal residual polarization ellipticity. SHG polarization imaging characteristics were validated against well-characterized specimens having cylindrical and/or linear symmetries. The LCM has a small footprint and can be implemented easily in any standard microscope and is cost effective relative to other technologies.
Photonic Crystals Physics and Practical Modeling
Sukhoivanov, Igor A
2009-01-01
The great interest in photonic crystals and their applications in the past decade requires a thorough training of students and professionals who can practically apply the knowledge of physics of photonic crystals together with skills of independent calculation of basic characteristics of photonic crystals and modelling of various photonic crystal elements for application in all-optical communication systems. This book combines basic backgrounds in fiber and integrated optics with detailed analysis of mathematical models for 1D, 2D and 3D photonic crystals and microstructured fibers, as well as with descriptions of real algorithms and codes for practical realization of the models.
Coupled Person Orientation Estimation and Appearance Modeling using Spherical Harmonics
Liem, M.C.; Gavrila, D.M.
2014-01-01
We present a novel approach for the estimation of a person's overall body orientation, 3D shape and texture, from overlapping cameras. A distinguishing aspect of our approach is the use of spherical harmonics for 3D shape- and texture-representation; it offers a compact, low-dimensional
Computational-Model-Based Analysis of Context Effects on Harmonic Expectancy.
Directory of Open Access Journals (Sweden)
Satoshi Morimoto
Full Text Available Expectancy for an upcoming musical chord, harmonic expectancy, is supposedly based on automatic activation of tonal knowledge. Since previous studies implicitly relied on interpretations based on Western music theory, the underlying computational processes involved in harmonic expectancy and how it relates to tonality need further clarification. In particular, short chord sequences which cannot lead to unique keys are difficult to interpret in music theory. In this study, we examined effects of preceding chords on harmonic expectancy from a computational perspective, using stochastic modeling. We conducted a behavioral experiment, in which participants listened to short chord sequences and evaluated the subjective relatedness of the last chord to the preceding ones. Based on these judgments, we built stochastic models of the computational process underlying harmonic expectancy. Following this, we compared the explanatory power of the models. Our results imply that, even when listening to short chord sequences, internally constructed and updated tonal assumptions determine the expectancy of the upcoming chord.
DEFF Research Database (Denmark)
Bozhevolnyi, Sergey I.; Volkov, V.S.; Søndergaard, Thomas
2002-01-01
We employ a collection scanning near-field optical microscope (SNOM) to image the propagation of light at telecommunication wavelengths along straight and bent regions of silicon-on-insulator photonic crystal waveguides (PCWs) formed by removing a single row of holes in the triangular 410-nm...
Matsunaga, Ryusuke; Tsuji, Naoto; Makise, Kazumasa; Terai, Hirotaka; Aoki, Hideo; Shimano, Ryo
2017-07-01
Recent advances in time-domain terahertz (THz) spectroscopy have unveiled that resonantly enhanced strong THz third-harmonic generation (THG) mediated by the collective Higgs amplitude mode occurs in s -wave superconductors, where charge-density fluctuations (CDFs) have been shown to also contribute to the nonlinear third-order susceptibility. It has been theoretically proposed that the nonlinear responses of Higgs and CDF exhibit essentially different polarization dependences. Here we experimentally discriminate the two contributions by polarization-resolved intense THz transmission spectroscopy for a single-crystal NbN film. The result shows that the resonant THG in the transmitted light always appears in the polarization parallel to that of the incident light with no appreciable polarization-angle dependence relative to the crystal axis. When we compare this with the theoretical calculation here with the BCS approximation and the dynamical mean-field theory for a model of NbN constructed from first principles, the experimental result strongly indicates that the Higgs mode rather than the CDF dominates the THG resonance in NbN. A possible mechanism for this is the retardation effect in the phonon-mediated pairing interaction beyond BCS.
DEFF Research Database (Denmark)
Bozhevolnyi, Sergey I.; Volkov, V.S.; Søndergaard, Thomas
2002-01-01
We employ a collection scanning near-field optical microscope (SNOM) to image the propagation of light at telecommunication wavelengths along straight and bent regions of silicon-on-insulator photonic crystal waveguides (PCWs) formed by removing a single row of holes in the triangular 410-nm...... PCW bends, bend loss is evaluated and found to noticeably increase with the increase of the light wavelength from similar to1 dB at 1520 nm to similar to6 dB at 1570 nm. We analyze light intensity variations along PCWs measured with the SNOM at different distances from the sample surface. Considering...
Crystallization Kinetics within a Generic Modeling Framework
DEFF Research Database (Denmark)
Meisler, Kresten Troelstrup; von Solms, Nicolas; Gernaey, Krist V.
2014-01-01
A new and extended version of a generic modeling framework for analysis and design of crystallization operations is presented. The new features of this framework are described, with focus on development, implementation, identification, and analysis of crystallization kinetic models. Issues related...... to the modeling of various kinetic phenomena like nucleation, growth, agglomeration, and breakage are discussed in terms of model forms, model parameters, their availability and/or estimation, and their selection and application for specific crystallization operational scenarios under study. The advantages...... of employing a well-structured model library for storage, use/reuse, and analysis of the kinetic models are highlighted. Examples illustrating the application of the modeling framework for kinetic model discrimination related to simulation of specific crystallization scenarios and for kinetic model parameter...
Precise Model Analysis for 3-phase High Power Converter using the Harmonic State Space Modeling
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Blaabjerg, Frede
2015-01-01
This paper presents about the generalized multi-frequency modeling and analysis methodology, which can be used in control loop design and stability analysis. In terms of the switching frequency of high power converter, there can be harmonics interruption if the voltage source converter has a low....... The modeling procedure shows the precision in the analysis of the stability as well as the controller design. The overall results are validated by using not only the non-linear time domain simulation, but also the analytical model....
Andreh, Angga Muhamad; Subiyanto, Sunardiyo, Said
2017-01-01
Development of non-linear loading in the application of industry and distribution system and also harmonic compensation becomes important. Harmonic pollution is an urgent problem in increasing power quality. The main contribution of the study is the modeling approach used to design a shunt active filter and the application of the cascade multilevel inverter topology to improve the power quality of electrical energy. In this study, shunt active filter was aimed to eliminate dominant harmonic component by injecting opposite currents with the harmonic component system. The active filter was designed by shunt configuration with cascaded multilevel inverter method controlled by PID controller and SPWM. With this shunt active filter, the harmonic current can be reduced so that the current wave pattern of the source is approximately sinusoidal. Design and simulation were conducted by using Power Simulator (PSIM) software. Shunt active filter performance experiment was conducted on the IEEE four bus test system. The result of shunt active filter installation on the system (IEEE four bus) could reduce THD current from 28.68% to 3.09%. With this result, the active filter can be applied as an effective method to reduce harmonics.
DEFF Research Database (Denmark)
Kocewiak, Lukasz Hubert; Hjerrild, Jesper; Bak, Claus Leth
2009-01-01
and assess harmonic emission in the point of common coupling. Different modelling methods of power electronic devices installed in wind turbines are presented. Harmonic load flow analysis and impedance frequency characteristics calculation are conducted to present differences between the models. Simulation...... results are compared with measurement data from the Burbo Bank offshore wind farm. The delimitations of both power converter models with referent to harmonic analysis are shown in this paper....
Improved dq-axes Model of PMSM Considering Airgap Flux Harmonics and Saturation
DEFF Research Database (Denmark)
Fasil, Muhammed; Antaloae, Ciprian; Mijatovic, Nenad
The classical dq-axes model of permanent magnet synchronous machines (PMSM) uses linear approximation. This was not an issue in earlier versions of PMSM drives because they mostly used surface magnet motors. With the arrival of interior permanent magnet (IPM) machines, which use reluctance torque......-saturation on constant torque curves of PMSM. Two interior permanent magnet motor with two different rotor topologies and different specifications are designed to evaluate the effect of saturation on synchronous and harmonic inductances, and operating points of the machines....... along with magnet torque, the accuracy of linear models are found to be insufficient. In this work, the effect of air gap flux harmonics is included in the classical model of PMSM using d and q-axes harmonic inductances. Further, a method has been presented to assess the effect of saturation and cross...
Higher harmonics of azimuthal anisotropy in relativistic heavy ion collisions in HYDJET++ model
Bravina, L V; Eyyubova, G. Kh.; Korotkikh, V.L.; Lokhtin, I.P.; Malinina, L.V.; Petrushanko, S.V.; Snigirev, A.M.; Zabrodin, E.E.
2014-01-01
The LHC data on azimuthal anisotropy harmonics from PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed and interpreted in the framework of the HYDJET++ model. The cross-talk of elliptic $v_2$ and triangular $v_3$ flow in the model generates both even and odd harmonics of higher order. Comparison with the experimental data shows that this mechanism is able to reproduce the $p_{\\rm T}$ and centrality dependencies of quadrangular flow $v_4$, and also the basic trends for pentagonal $v_5$ and hexagonal $v_6$ flows.
Improved dq-Axes Model of PMSM Considering Airgap Flux Harmonics and Saturation
DEFF Research Database (Denmark)
Fasil, Muhammed; Antaloae, Ciprian; Mijatovic, Nenad
2016-01-01
In this work, the classical linear model of a permanent magnet synchronous motor (PMSM) is modified by adding d and q-axes harmonic inductances so that the modified model can consider non-linearities present in an interior permanent magnet (IPM) motor. Further, a method has been presented to assess...... the effect of saturation and cross-saturation on constant torque curves of PMSM. Two IPM motors with two different rotor topologies and different specifications are designed to evaluate the effect of saturation on synchronous and harmonic inductances, and on operating points of the machines...
Digital model for harmonic interactions in AC/DC/AC systems
Energy Technology Data Exchange (ETDEWEB)
Guarini, A.P.; Rangel, R.D.; Pilotto, L.A.S.; Pinto, R.J.; Passos Junior, R. [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil)
1994-12-31
The main purpose of this paper is to present a model for calculation of HVdc converter harmonics taking into account the influence of the harmonic interactions between the ac systems in dc link transmissions. The ideas and methodologies used in the model development take into account the dc current ripple and ac voltage distortion in the ac systems. The theory of switching functions is applied to contemplate for the frequency conversions between the ac and dc sides, in an iterative process. It is possible then to obtain, even in balanced situations, non-characteristic harmonics that are produced by frequencies originated in the other terminal, which can be significant in a strongly coupled system, such as back-to-back configuration. (author) 9 refs., 3 figs.
Phase-field-crystal model for ordered crystals.
Alster, Eli; Elder, K R; Hoyt, Jeffrey J; Voorhees, Peter W
2017-02-01
We describe a general method to model multicomponent ordered crystals using the phase-field-crystal (PFC) formalism. As a test case, a generic B2 compound is investigated. We are able to produce a line of either first-order or second-order order-disorder phase transitions, features that have not been incorporated in existing PFC approaches. Further, it is found that the only elastic constant for B2 that depends on ordering is C_{11}. This B2 model is then used to study antiphase boundaries (APBs). The APBs are shown to reproduce classical mean-field results. Dynamical simulations of ordering across small-angle grain boundaries predict that dislocation cores pin the evolution of APBs.
Molecular Models of Liquid Crystal Elastomers
Rajshekhar
Liquid crystal elastomers combine the elastic properties of conventional rubbers with the optical properties of liquid crystals. This dual nature gives rise to unusual physical properties, including the stress induced transition from a polydomain state, consisting of multiple nematic regions with independent orientations, to a monodomain state consisting of a single nematic region with a uniform director. We propose several molecular-scale coarse-grained models of liquid crystal elastomers with varying degrees of resolution. The models employ the Gay-Berne soft potential, and exhibit the chain connectivity of a diamond network. Simulation results show that these models are able to capture the polydomain state exhibited by liquid crystal elastomers in the absence of any external stress. When subjected to uniaxial stress, our models exhibit a polydomain to monodomain transition. We explain that the polydomain state occurs through the aggregation of liquid crystal molecules assisted by crosslinking sites, and conclude that the transition mechanism to the monodomain state is based on the reorientation of nematic domains along the direction of applied stress. Our modeling efforts are primarily focused on three models. The first two models consider the effects of rigid and flexible crosslinkers in liquid crystal elastomers with a diamond topology for chain connectivity. The third model deviates from the diamond network topology and adopts a random network topology.
Yuan, Jinhui; Kang, Zhe; Li, Feng; Zhou, Guiyao; Zhang, Xianting; Mei, Chao; Sang, Xinzhu; Wu, Qiang; Yan, Binbin; Zhou, Xian; Zhong, Kangping; Wang, Kuiru; Yu, Chongxiu; Lu, Chao; Tam, Hwa Yaw; Wai, P K A
2017-08-23
Deep-ultraviolet (UV) second-harmonics (SHs) have important applications in basic physics and applied sciences. However, it still remains challenging to generate deep-UV SHs especially in optical fibers. Here, for the first time, we experimentally demonstrate the deep-UV SH generations (SHGs) by combined degenerate four-wave mixing (FWM) and surface nonlinearity polarization in an in-house designed and fabricated air-silica photonic crystal fiber (PCF). When femtosecond pump pulses with average input power P av of 650 mW and center wavelength λ p of 810, 820, 830, and 840 nm are coupled into the normal dispersion region close to the zero-dispersion wavelength of the fundamental mode of the PCF, the anti-Stokes waves induced by degenerate FWM process are tunable from 669 to 612 nm. Then, they serve as the secondary pump, and deep-UV SHs are generated within the wavelength range of 334.5 to 306 nm as a result of surface nonlinearity polarization at the core-cladding interface of the PCF. The physical mechanism of the SHGs is confirmed by studying the dependences of the output power P SH of the SHs on the PCF length and time. Finally, we also establish a theoretical model to analyze the SHGs.
Novel Harmonic Regularization Approach for Variable Selection in Cox’s Proportional Hazards Model
Directory of Open Access Journals (Sweden)
Ge-Jin Chu
2014-01-01
Full Text Available Variable selection is an important issue in regression and a number of variable selection methods have been proposed involving nonconvex penalty functions. In this paper, we investigate a novel harmonic regularization method, which can approximate nonconvex Lq (1/2model using microarray gene expression data. The harmonic regularization method can be efficiently solved using our proposed direct path seeking approach, which can produce solutions that closely approximate those for the convex loss function and the nonconvex regularization. Simulation results based on the artificial datasets and four real microarray gene expression datasets, such as real diffuse large B-cell lymphoma (DCBCL, the lung cancer, and the AML datasets, show that the harmonic regularization method can be more accurate for variable selection than existing Lasso series methods.
DEFF Research Database (Denmark)
Dowlatabadi, Mohammadkazem Bakhshizadeh; Hjerrild, Jesper; Kocewiak, Łukasz
2016-01-01
be reduced and operational availability and the reliability can be improved. Challenges hereto include lower resonance frequencies due to the long cables, frequency dependent modelling of long submarine cables, passive filtering, and PLL dynamics in the control loops (from a harmonic stability point of view)....
Region Spherical Harmonic Magnetic Modeling from Near-Surface and Satellite-Altitude Anomlaies
Kim, Hyung Rae; von Frese, Ralph R. B.; Taylor, Patrick T.
2013-01-01
The compiled near-surface data and satellite crustal magnetic measured data are modeled with a regionally concentrated spherical harmonic presentation technique over Australia and Antarctica. Global crustal magnetic anomaly studies have used a spherical harmonic analysis to represent the Earth's magnetic crustal field. This global approach, however is best applied where the data are uniformly distributed over the entire Earth. Satellite observations generally meet this requirement, but unequally distributed data cannot be easily adapted in global modeling. Even for the satellite observations, due to the errors spread over the globe, data smoothing is inevitable in the global spherical harmonic presentations. In addition, global high-resolution modeling requires a great number of global spherical harmonic coefficients for the regional presentation of crustal magnetic anomalies, whereas a lesser number of localized spherical coefficients will satisfy. We compared methods in both global and regional approaches and for a case where the errors were propagated outside the region of interest. For observations from the upcoming Swarm constellation, the regional modeling will allow the production a lesser number of spherical coefficients that are relevant to the region of interest
Modeling of VSC-Based Power Systems in The Extended Harmonic Domain
DEFF Research Database (Denmark)
Esparza, Miguel; Segundo-Ramirez, Juan; Kwon, Jun Bum
2017-01-01
Averaged modeling is a commonly used approach used to obtain mathematical representations of VSC-based systems. However, essential characteristics mainly related to the modulation process and the harmonic distortion of the signals are not able to be accurately captured and analyzed. The extended ...
Modelling heating effects in cryocooled protein crystals
Nicholson, J; Fayz, K; Fell, B; Garman, E
2001-01-01
With the application of intense X-ray beams from third generation synchrotron sources, damage to cryocooled macromolecular crystals is being observed more commonly . In order to fully utilize synchrotron facilities now available for studying biological crystals, it is essential to understand the processes involved in radiation damage and beam heating so that, if possible, action can be taken to slow the rate of damage. Finite Element Analysis (FEA) has been applied to model the heating effects of X-rays on cryocooled protein crystals, and to compare the relative cooling efficiencies of nitrogen and helium.
Crystal shape 2D modeling for transient CZ silicon crystal growth
Sabanskis, A.; Bergfelds, K.; Muiznieks, A.; Schröck, Th.; Krauze, A.
2013-08-01
A non-stationary axisymmetric model of Czochralski silicon single crystal growth is presented. The model describes transient behavior of crystal-melt, melt-gas and crystal-gas interfaces in connection with PID-based control of crystal diameter by changing crystal pulling velocity and heater power. To calculate significant crystal shape changes, unstructured finite element mesh is used in crystal and melt together with automatic element size control. Heater temperature changes are modeled with a simplified integral model. A numerical simulation example of start cone growth is given.
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth
2015-01-01
As the increasing of power electronics based systems, not only the component-based analysis but also a systematic interaction analysis with each other systems are being important. Especially studies about the stability and the harmonics interaction are critical in order to establish the required ...... for the AC-DC converters with a low ratio of switching to the fundamental frequency, and it provides an effective way to reveal the harmonic interaction and stability analysis for the future power electronics based power systems.......As the increasing of power electronics based systems, not only the component-based analysis but also a systematic interaction analysis with each other systems are being important. Especially studies about the stability and the harmonics interaction are critical in order to establish the required...... performance in a power network. However, the traditional small-signal modeling approaches are not enough to represent the complexity of the interaction due to the time varying components of such systems. This paper compares the small-signal modeling methods for harmonic analysis of AC - DC converters...
Compact fluorescent lamp modeling for large-scale harmonic penetration studies
Molina, Julio; Sainz Sapera, Luis
2014-01-01
Low-watt compact fluorescent lamps (CFLs) may account for significant energy consumption of power distribution feeders in future years. This can lead to power-quality concerns because these devices consume highly distorted currents. In order to predict CFL harmonic current emissions into networks, CFL models capable of predicting these emissions accurately are being studied. On the other hand, these models require great computational effort in large-scale CFL penetration studies. This paper p...
Energy Technology Data Exchange (ETDEWEB)
Erba, A., E-mail: alessandro.erba@unito.it; Dovesi, R. [Dipartimento di Chimica, Università di Torino and NIS, Nanostructured Interfaces and Surfaces, Centre of Excellence, Via Giuria 5, 10125 Torino (Italy); Shahrokhi, M. [Dipartimento di Chimica, Università di Torino and NIS, Nanostructured Interfaces and Surfaces, Centre of Excellence, Via Giuria 5, 10125 Torino (Italy); Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Moradian, R. [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of)
2015-01-28
Harmonic and quasi-harmonic thermal properties of two isostructural simple oxides (periclase, MgO, and lime, CaO) are computed with ab initio periodic simulations based on the density-functional-theory (DFT). The more polarizable character of calcium with respect to magnesium cations is found to dramatically affect the validity domain of the quasi-harmonic approximation that, for thermal structural properties (such as temperature dependence of volume, V(T), bulk modulus, K(T), and thermal expansion coefficient, α(T)), reduces from [0 K-1000 K] for MgO to just [0 K-100 K] for CaO. On the contrary, thermodynamic properties (such as entropy, S(T), and constant-volume specific heat, C{sub V}(T)) are described reliably at least up to 2000 K and quasi-harmonic constant-pressure specific heat, C{sub P}(T), up to about 1000 K in both cases. The effect of the adopted approximation to the exchange-correlation functional of the DFT is here explicitly investigated by considering five different expressions of three different classes (local-density approximation, generalized-gradient approximation, and hybrids). Computed harmonic thermodynamic properties are found to be almost independent of the adopted functional, whereas quasi-harmonic structural properties are more affected by the choice of the functional, with differences that increase as the system becomes softer.
Directory of Open Access Journals (Sweden)
Manuel Kasper
2016-05-01
Full Text Available We developed an impedance quartz crystal microbalance (QCM approach with the ability to simultaneously record mass changes and calibrated energy dissipation with high sensitivity using an impedance analyzer. This impedance QCM measures frequency shifts and resistance changes of sensing quartz crystals very stable, accurately, and calibrated, thus yielding quantitative information on mass changes and dissipation. Resistance changes below 0.3 Ω were measured with corresponding dissipation values of 0.01 µU (micro dissipation units. The broadband impedance capabilities allow measurements between 20 Hz and 120 MHz including higher harmonic modes of up to 11th order for a 10 MHz fundamental resonance frequency quartz crystal. We demonstrate the adsorbed mass, calibrated resistance, and quantitative dissipation measurements on two biological systems including the high affinity based avidin-biotin interaction and nano-assemblies of polyelectrolyte layers. The binding affinity of a protein-antibody interaction was determined. The impedance QCM is a versatile and simple method for accurate and calibrated resistance and dissipation measurements with broadband measurement capabilities for higher harmonics measurements.
Vector cylindrical harmonics for low-dimensional convection models
Kelley, Douglas H; Knox, Catherine A
2016-01-01
Approximate empirical models of thermal convection can allow us to identify the essential properties of the flow in simplified form, and to produce empirical estimates using only a few parameters. Such "low-dimensional" empirical models can be constructed systematically by writing numerical or experimental measurements as superpositions of a set of appropriate basis modes, a process known as Galerkin projection. For Boussinesq convection in a cylinder, those basis modes should be defined in cylindrical coordinates, vector-valued, divergence-free, and mutually orthogonal. Here we construct two such basis sets, one using Bessel functions in the radial direction, and one using Chebyshev polynomials. We demonstrate that each set has those desired characteristics and demonstrate the advantages and drawbacks of each set. We show their use for representing sample simulation data and point out their potential for low-dimensional convection models.
Heemink, Arnold; de Jong, B.; Prins, Harrie
1991-01-01
In this paper we describe a new approach to the harmonic analysis of the tide. For a number of reasons the harmonic constants are not really constant but vary slowly in time. Therefore, we introduce a narrow-band noise process to model the time-varying behaviour of these harmonic parameters.
Ganeev, Rashid A
2014-01-01
Preface; Why plasma harmonics? A very brief introduction Early stage of plasma harmonic studies - hopes and frustrations New developments in plasma harmonics studies: first successes Improvements of plasma harmonics; Theoretical basics of plasma harmonics; Basics of HHG Harmonic generation in fullerenes using few-cycle pulsesVarious approaches for description of observed peculiarities of resonant enhancement of a single harmonic in laser plasmaTwo-colour pump resonance-induced enhancement of odd and even harmonics from a tin plasmaCalculations of single harmonic generation from Mn plasma;Low-o
Directory of Open Access Journals (Sweden)
Bangcheng Han
2013-01-01
Full Text Available The double-gimbal control moment gyro (DGCMG demands that the gimbal servosystem should have fast response and small overshoot. But due to the low and nonlinear torsional stiffness of harmonic drive, the gimbal servo-system has poor dynamic performance with large overshoot and low bandwidth. In order to improve the dynamic performance of gimbal servo-system, a model reference adaptive control (MRAC law is introduced in this paper. The model of DGCMG gimbal servo-system with harmonic drive is established, and the adaptive control law based on POPOV super stable theory is designed. The MATLAB simulation results are provided to verify the effectiveness of the proposed control algorithm. The experimental results indicate that the MRAC could increase the bandwidth of gimbal servo-system to 3 Hz and improve the dynamic performance with small overshoot.
Modelling of BLDCM with a double 3-phase stator winding and back EMF harmonics
Directory of Open Access Journals (Sweden)
Drozdowski Piotr
2015-03-01
Full Text Available In this paper the mathematical model of the brushless DC motor (BLDCM with a double 3-phase stator winding is analysed. Both the 3-phase windings are mutually displaced by 30 electrical degree. Special care has been sacrificed to influence of higher harmonics of induced electromotive forces (EMF on electromagnetic torque and zero sequence voltages that may be used for sensorless control. The mathematical model has been presented in natural variables and, after transformation to symmetrical components, in a vector form. This allows, from one side, for formulating the equivalent circuit suitable for circuit oriented simulators (e.g.: Spice, SimPowerSystems of Simulink and, from the other point of view, for analysis of higher harmonics influence on control possibilities. These considerations have been illustrated with some results of four quadrant operation obtainded due to simulation at automatic control.
Modeling Tetragonal Lysozyme Crystal Growth Rates
Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.
2003-01-01
Tetragonal lysozyme 110 face crystal growth rates, measured over 5 orders of magnitude in range, can be described using a model where growth occurs by 2D nucleation on the crystal surface for solution supersaturations of c/c(sub eq) less than or equal to 7 +/- 2. Based upon the model, the step energy per unit length, beta was estimated to be approx. 5.3 +/- 0.4 x 10(exp -7) erg/mol-cm, which for a step height of 56 A corresponds to barrier of approx. 7 +/- 1 k(sub B)T at 300 K. For supersaturations of c/c(sub eq) > 8, the model emphasizing crystal growth by 2D nucleation not only could not predict, but also consistently overestimated, the highest observable crystal growth rates. Kinetic roughening is hypothesized to occur at a cross-over supersaturation of c/c(sub eq) > 8, where crystal growth is postulated to occur by a different process such as adsorption. Under this assumption, all growth rate data indicated that a kinetic roughening transition and subsequent crystal growth by adsorption for all solution conditions, varying in buffer pH, temperature and precipitant concentration, occurs for c/c(sub eq)(T, pH, NaCl) in the range between 5 and 10, with an energy barrier for adsorption estimated to be approx. 20 k(sub B)T at 300 K. Based upon these and other estimates, we determined the size of the critical surface nucleate, at the crossover supersaturation and higher concentrations, to range from 4 to 10 molecules.
Monitoring and modeling of ultrasonic wave propagation in crystallizing mixtures
Marshall, T.; Challis, R. E.; Tebbutt, J. S.
2002-05-01
The utility of ultrasonic compression wave techniques for monitoring crystallization processes is investigated in a study of the seeded crystallization of copper II sulfate pentahydrate from aqueous solution. Simple models are applied to predict crystal yield, crystal size distribution and the changing nature of the continuous phase. A scattering model is used to predict the ultrasonic attenuation as crystallization proceeds. Experiments confirm that modeled attenuation is in agreement with measured results.
DEFF Research Database (Denmark)
Bak, Claus Leth; Bak-Jensen, Birgitte; Wiechowski, Wojciech
2008-01-01
This paper demonstrates the results of implementation and verification of an already existing algorithm that allows for calculating saturation characteristics of singlephase power transformers. The algorithm was described for the first time in 1993. Now this algorithm has been implemented using...... the DIgSILENT Programming Language (DPL) as an external script in the harmonic domain calculations of a power system analysis tool PowerFactory [10]. The algorithm is verified by harmonic measurements on a single-phase power transformer. A theoretical analysis of the core nonlinearities phenomena...... in single and three-phase transformers is also presented. This analysis leads to the conclusion that the method can be applied for modelling nonlinearities of three-phase autotransformers....
Frictional-faulting model for harmonic tremor before Redoubt Volcano eruptions
Dmitrieva, Ksenia; Hotovec-Ellis, Alicia J.; Prejean, Stephanie G.; Dunham, Eric M.
2013-01-01
Seismic unrest, indicative of subsurface magma transport and pressure changes within fluid-filled cracks and conduits, often precedes volcanic eruptions. An intriguing form of volcano seismicity is harmonic tremor, that is, sustained vibrations in the range of 0.5–5 Hz. Many source processes can generate harmonic tremor. Harmonic tremor in the 2009 eruption of Redoubt Volcano, Alaska, has been linked to repeating earthquakes of magnitudes around 0.5–1.5 that occur a few kilometres beneath the vent. Before many explosions in that eruption, these small earthquakes occurred in such rapid succession—up to 30 events per second—that distinct seismic wave arrivals blurred into continuous, high-frequency tremor. Tremor abruptly ceased about 30 s before the explosions. Here we introduce a frictional-faulting model to evaluate the credibility and implications of this tremor mechanism. We find that the fault stressing rates rise to values ten orders of magnitude higher than in typical tectonic settings. At that point, inertial effects stabilize fault sliding and the earthquakes cease. Our model of the Redoubt Volcano observations implies that the onset of volcanic explosions is preceded by active deformation and extreme stressing within a localized region of the volcano conduit, at a depth of several kilometres.
Mosaic anisotropy model for magnetic interactions in mesostructured crystals
Directory of Open Access Journals (Sweden)
Abby R. Goldman
2017-10-01
Full Text Available We propose a new model for interpreting the magnetic interactions in crystals with mosaic texture called the mosaic anisotropy (MA model. We test the MA model using hematite as a model system, comparing mosaic crystals to polycrystals, single crystal nanoparticles, and bulk single crystals. Vibrating sample magnetometry confirms the hypothesis of the MA model that mosaic crystals have larger remanence (Mr/Ms and coercivity (Hc compared to polycrystalline or bulk single crystals. By exploring the magnetic properties of mesostructured crystalline materials, we may be able to develop new routes to engineering harder magnets.
Towards an Open Modelling Interface (OpenMI the HarmonIT project
Directory of Open Access Journals (Sweden)
M. Blind
2005-01-01
Full Text Available The Water Framework Directive (WFD poses an immense challenge to water management in Europe. Aiming at a "good ecological status" of surface waters in 2015, integrated river basin management plans need to be in place by 2009, and broadly supported by stakeholders. Information & Communication Technology (ICT tools, such as computational models, are very helpful in designing river basin management plans (rbmp-s. However, many scientists believe that a single integrated modelling system to support the WFD cannot be developed, and integrated systems need to be quite tailored to the local situation and evolve during a collaborative planning process. As a consequence there is an urgent need to increase the flexibility of modelling systems, such that dedicated model systems can be developed from available building blocks. In the recent past a number of initiatives have been started to develop an IT framework for modelling to meet the required flexibility. In Europe the international project HarmonIT, which is sponsored by the European Commission, is developing and implementing a standard interface for modelling components and other relevant tools: The Open Modelling Interface (OpenMI. This paper describes the HarmonIT project and objectives in general. The current progress is described. It describes the roles for different types of stakeholders in modelling, varying from software coders to non-specialized users of decision support systems. It will provide insight in the requirements imposed when using the OpenMI.
Modelling and control of crystallization process
Directory of Open Access Journals (Sweden)
S.K. Jha
2017-03-01
Full Text Available Batch crystallizers are predominantly used in chemical industries like pharmaceuticals, food industries and specialty chemicals. The nonlinear nature of the batch process leads to difficulties when the objective is to obtain a uniform Crystal Size Distribution (CSD. In this study, a linear PI controller is designed using classical controller tuning methods for controlling the crystallizer outlet temperature by manipulating the inlet jacket temperature; however, the response is not satisfactory. A simple PID controller cannot guarantee a satisfactory response that is why an optimal controller is designed to keep the concentration and temperature in a range that suits our needs. Any typical process operation has constraints on states, inputs and outputs. So, a nonlinear process needs to be operated satisfying the constraints. Hence, a nonlinear controller like Generic Model Controller (GMC which is similar in structure to the PI controller is implemented. It minimizes the derivative of the squared error, thus improving the output response of the process. Minimization of crystal size variation is considered as an objective function in this study. Model predictive control is also designed that uses advanced optimization algorithm to minimize the error while linearizing the process. Constraints are fed into the MPC toolbox in MATLAB and Prediction, Control horizons and Performance weights are tuned using Sridhar and Cooper Method. Performances of all the three controllers (PID, GMC and MPC are compared and it is found that MPC is the most superior one in terms of settling time and percentage overshoot.
Mathematical Modeling of Vegetable-Oil Crystallization
DEFF Research Database (Denmark)
Hjorth, Jeppe Lindegaard
be desirable to enhance specific properties such as shelf life, viscosity, texture, sensory aspects and physical appearance. Vegetable oils and fats constitute a considerable part of many food products such as chocolate, margarine, bread, spreads and ice cream. Several attractive properties found...... and specialists drawing on many years of experience and knowledge. With this in mind, the aim of the present project was to develop a transient mathematical model, describing crystallization of vegetable fats and oils, based on physicochemical phenomena. The model itself can provide the industry with a valuable...... tool to design and optimize products. It can also serve as a fundament for testing proposed hypotheses and facilitate realizations with respect to oil and fat crystallization. The research carried out in this project is schematically described in Figure 2. The mathematical model is developed...
Modeling and Simulation of DC Power Electronics Systems Using Harmonic State Space (HSS) Method
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth
2015-01-01
based on the state-space averaging and generalized averaging, these also have limitations to show the same results as with the non-linear time domain simulations. This paper presents a modeling and simulation method for a large dc power electronic system by using Harmonic State Space (HSS) modeling....... Through this method, the required computation time and CPU memory for large dc power electronics systems can be reduced. Besides, the achieved results show the same results as with the non-linear time domain simulation, but with the faster simulation time which is beneficial in a large network....
Systematic Modelling and Crystal Size Distribution Control for Batch Crystallization Processes
DEFF Research Database (Denmark)
Abdul Samad, Noor Asma Fazli; Singh, Ravendra; Sin, Gürkan
morphology by means of model-based approaches, appropriate models covering the effects of the various operational parameters on the behavior of the crystals are necessary. Usually the main difficulty in batch crystallization is to accomplish a uniform CSD. There are many ways to enhance the control of CSD...... such as to use supersaturation control which drives the process within the metastable zone or by determining the amount and size of seeds that should be added into a crystallizer through seed recipe design approach. Therefore, there is a need for a generic crystallization model that can provide a better...... to predict the desired crystal morphology by means of model-based approaches, appropriate models covering the effects of the various operational parameters on the behavior of the crystals are necessary. Usually the main difficulty in batch crystallization is to accomplish a uniform CSD. There are many ways...
Oguz, H Kagan; Olcum, Selim; Senlik, Muhammed N; Taş, Vahdettin; Atalar, Abdullah; Köymen, Hayrettin
2010-01-01
Finite element method (FEM) is used for transient dynamic analysis of capacitive micromachined ultrasonic transducers (CMUT) and is particularly useful when the membranes are driven in the nonlinear regime. One major disadvantage of FEM is the excessive time required for simulation. Harmonic balance (HB) analysis, on the other hand, provides an accurate estimate of the steady-state response of nonlinear circuits very quickly. It is common to use Mason's equivalent circuit to model the mechanical section of CMUT. However, it is not appropriate to terminate Mason's mechanical LC section by a rigid piston's radiation impedance, especially for an immersed CMUT. We studied the membrane behavior using a transient FEM analysis and found out that for a wide range of harmonics around the series resonance, the membrane displacement can be modeled as a clamped radiator. We considered the root mean square of the velocity distribution on the membrane surface as the circuit variable rather than the average velocity. With this definition, the kinetic energy of the membrane mass is the same as that in the model. We derived the force and current equations for a clamped radiator and implemented them using a commercial HB simulator. We observed much better agreement between FEM and the proposed equivalent model, compared with the conventional model.
Energy Technology Data Exchange (ETDEWEB)
Ganesh, V. [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); Shkir, Mohd, E-mail: shkirphysics@gmail.com [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); AlFaify, S.; Algarni, H. [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); Abutalib, M.M. [Faculty of Science-AL Faisaliah, Campus, King Abdulaziz University, P.O. Box 80200, Jeddah 21589 (Saudi Arabia); Yahia, I.S. [Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha 61413 (Saudi Arabia); Nano-Science & Semiconductor Labs., Thin Film Lab., Department of Physics, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt)
2016-06-15
The nonlinear optical single crystals of pure and Ni{sup 2+} doped potassium dihydrogen phosphate (KDP) were successfully grown by slow evaporation solution growth technique. The effects of the addition of Ni{sup 2+} with different molar concentration have been studied by powder X-ray diffraction, FT-Raman, second harmonic generation, microscopic and dielectric studies. Its crystallinity was assessed by the FT-Raman technique and its surface, structural imperfections were recorded using high resolution microscope, which clearly reveals that the doping is showing considerable effect on the samples. The SHG measurements also carried out on pure and doped samples, which reveal the relative SHG efficiency has been enhanced due to doping. The optical activities were studied by UV–vis-NIR technique and reveals high optical transparency in doped samples. The remarkable enhancement in mechanical strength was observed due to doping. The enhanced dielectric constant and low dielectric loss confirms that the grown crystals with doping are superior to pure crystals and may be used in optoelectronic devices.
Solving a fuzzy initial value problem of a harmonic oscillator model
Karim, M. A.; Gunawan, A. Y.; Apri, M.; Sidarto, K. A.
2017-03-01
Modeling in systems biology is often faced with challenges in terms of measurement uncertainty. This is possibly either due to limitations of available data, environmental or demographic changes. One of typical behavior that commonly appears in the systems biology is a periodic behavior. Since uncertainties would get involved into the systems, the change of solution behavior of the periodic system should be taken into account. To get insight into this issue, in this work a simple mathematical model describing periodic behavior, i.e. a harmonic oscillator model, is considered by assuming its initial value has uncertainty in terms of fuzzy number. The system is known as Fuzzy Initial Value Problems. Some methods to determine the solutions are discussed. First, solutions are examined using two types of fuzzy differentials, namely Hukuhara Differential (HD) and Generalized Hukuhara Differential (GHD). Application of fuzzy arithmetic leads that each type of HD and GHD are formed into α-cut deterministic systems, and then are solved by the Runge-Kutta method. The HD type produces a solution with increasing uncertainty starting from the initial condition. While, GHD type produces an oscillatory solution but only until a certain time and above it the uncertainty becomes monotonic increasing. Solutions of both types certainly do not provide the accuracy for harmonic oscillator model during its evolution. Therefore, we propose the third method, so called Fuzzy Differential Inclusions (FDI), to attack the problem. Using this method, we obtain oscillatory solutions during its evolution.
Hadron spectra from a non-relativistic model with confining harmonic potential
Directory of Open Access Journals (Sweden)
Cuervo-Reyes Eduardo
2003-01-01
Full Text Available Hadron spectra and other properties of quark systems are studied in the framework of a non-relativistic spinindependent phenomenological model. The chosen confining potential is harmonic, which allowed us to obtain analytical solutions for both meson and baryon (of equal constituent quarks spectra. The introduced parameters are fixed from the low-lying levels of heavy quark mesons. The requirement of flavor independence is imposed, and it restricts the possible choices of inter-quark potentials. The hyper-spherical coordinates are considered for the solution of the three-body problem.
DEFF Research Database (Denmark)
Schneider, M.; Johnson, T.; Dumont, R.
2016-01-01
Recent JET experiments have been dedicated to the studies of fusion reactions between deuterium (D) and Helium-3 (3He) ions using neutral beam injection (NBI) in synergy with third harmonic ion cyclotron radio-frequency heating (ICRH) of the beam. This scenario generates a fast ion deuterium tail...... ion diagnostics, showing an overall good agreement. Finally, a sawtooth activity for these experiments has been observed and interpreted using SPOT/RFOF simulations in the framework of Porcelli’s theoretical model, where NBI+ICRH accelerated ions are found to have a strong stabilizing effect, leading...
Using Hough harmonics to validate and assess nonlinear shallow-water models
Dee, Dick P.; Moraes Da Silva, Arlindo
1986-01-01
The implementation of a technique for locating programming errors in shallow-water codes, establishing the correctness of the code, and assessing the performance of the numerical model under various flow conditions is described. The right-hand side of the differential equations is modified in such a way that the exact solution of the nonlinear initial-value problem is known, so that the truncation errors of the numerical scheme can be studied in detail. The exact solution is prescribed to be any linear combination of Hough harmonics which propagate in time according to their natural frequencies.
Alhulaimi, B.; van den Hoogen, R. J.; Coley, A. A.
2017-12-01
Inflationary spatially homogeneous cosmological models within an Einstein-aether gravitational framework are investigated. The matter source is assumed to be a scalar field which is coupled to the aether field expansion and shear scalars through the generalized harmonic scalar field potential. The evolution equations are expressed in terms of expansion-normalized variables to produce an autonomous system of ordinary differential equations suitable for numerical and local stability analysis. An analysis of the local stability of the equilibrium points indicates that there exists a range of values of the parameters in which there exists an accelerating expansionary future attractor.
Energy Technology Data Exchange (ETDEWEB)
Nocente, M.; Rebai, M.; Gorini, G. [EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Dipartimento di Fisica “G. Occhialini,” Università degli Studi di Milano-Bicocca, Milano (Italy); Istituto di Fisica del Plasma “P. Caldirola,” Consiglio Nazionale delle Ricerche, Milano (Italy); Cazzaniga, C. [EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Istituto di Fisica del Plasma “P. Caldirola,” Consiglio Nazionale delle Ricerche, Milano (Italy); Rutherford Appleton Laboratory, ISIS Facility, Didcot (United Kingdom); Tardocchi, M.; Giacomelli, L.; Muraro, A. [EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Istituto di Fisica del Plasma “P. Caldirola,” Consiglio Nazionale delle Ricerche, Milano (Italy); Binda, F.; Eriksson, J. [EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Department of Physics and Astronomy, Uppsala University, Uppsala (Sweden); Sharapov, S. [EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); CCFE, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Collaboration: (EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom)
2015-10-15
Neutron spectroscopy measurements with a single crystal diamond detector have been carried out at JET, for the first time in an experiment aimed at accelerating deuterons to MeV energies with radio frequency heating at the third harmonic. Data are interpreted by means of the expected response function of the detector and are used to extract parameters of the highly non-Maxwellian distribution function generated in this scenario. A comparison with observations using a time of flight and liquid scintillator neutron spectrometers is also presented. The results demonstrate the capability of diamond detectors to contribute to fast ion physics studies at JET and are of more general relevance in view of the application of such detectors for spectroscopy measurements in the neutron camera of next step tokamak devices.
Effects of combined harmonic and random excitations on a Brusselator model
Xu, Yong; Ma, Jinzhong; Wang, Haiyan; Li, Yongge; Kurths, Jürgen
2017-10-01
We discuss the constructive role of combined harmonic and random excitation on stochastic resonance (SR) in a Brusselator model. We first numerically investigate SR determined by the Signal-to-Noise Ratio (SNR) in this model. Effects of different parameters on SR are described in detail. Our simulation results show that the intensity of the Gaussian colored noise and the amplitude of the periodic force can enhance SR. Moreover, an analytical framework is presented for the SNR of the Brusselator model, leading to a theoretical expression of SNR. We observe a good agreement between the theoretical and numerical results, and the effectiveness of the proposed theoretical method is verified. This theoretical analysis provides a global view on how the dynamics of a periodically forced system with noise changes in the vicinity of a Hopf bifurcation.
Aksu, Anil; Peter, Diamessis; Wunsch, Scott
2014-11-01
An energetic analysis of the interaction of a numerically simulated IWB with a model ocean pycnocline is presented. The focus is on the nonlinear generation of harmonics. The analysis consists of a) monitoring the transfer of the primary beam's energy into higher harmonics along the beam path and b) evaluating how any energy trapped inside the pycnocline is distributed across different wave frequencies propagating within it. The majority of the analysis is performed on a dataset spanning a wide range of pycnocline strengths and thicknesses restricted to an IWB propagating at 45° from the horizontal. For such an angle, internal wave refraction is the primary driver of nonlinear harmonic generation. Moreover, all resulting harmonics remain trapped within the pycnocline. Preliminary results from additional simulations with shallower angles of IWB incidence are also analyzed. When the incidence angle is less than 30 degrees, IWB reflection is an additional important mechanism of harmonic generation and lower harmonics are able to radiate back out of the pycnocline.
Data-adaptive harmonic spectra and multilayer Stuart-Landau models
Chekroun, Mickaël D.; Kondrashov, Dmitri
2017-09-01
Harmonic decompositions of multivariate time series are considered for which we adopt an integral operator approach with periodic semigroup kernels. Spectral decomposition theorems are derived that cover the important cases of two-time statistics drawn from a mixing invariant measure. The corresponding eigenvalues can be grouped per Fourier frequency and are actually given, at each frequency, as the singular values of a cross-spectral matrix depending on the data. These eigenvalues obey, furthermore, a variational principle that allows us to define naturally a multidimensional power spectrum. The eigenmodes, as far as they are concerned, exhibit a data-adaptive character manifested in their phase which allows us in turn to define a multidimensional phase spectrum. The resulting data-adaptive harmonic (DAH) modes allow for reducing the data-driven modeling effort to elemental models stacked per frequency, only coupled at different frequencies by the same noise realization. In particular, the DAH decomposition extracts time-dependent coefficients stacked by Fourier frequency which can be efficiently modeled—provided the decay of temporal correlations is sufficiently well-resolved—within a class of multilayer stochastic models (MSMs) tailored here on stochastic Stuart-Landau oscillators. Applications to the Lorenz 96 model and to a stochastic heat equation driven by a space-time white noise are considered. In both cases, the DAH decomposition allows for an extraction of spatio-temporal modes revealing key features of the dynamics in the embedded phase space. The multilayer Stuart-Landau models (MSLMs) are shown to successfully model the typical patterns of the corresponding time-evolving fields, as well as their statistics of occurrence.
Blaclard, G.; Vincenti, H.; Lehe, R.; Vay, J. L.
2017-09-01
With the advent of petawatt class lasers, the very large laser intensities attainable on target should enable the production of intense high-order Doppler harmonics from relativistic laser-plasma mirror interactions. At present, the modeling of these harmonics with particle-in-cell (PIC) codes is extremely challenging as it implies an accurate description of tens to hundreds of harmonic orders on a broad range of angles. In particular, we show here that due to the numerical dispersion of waves they induce in vacuum, standard finite difference time domain (FDTD) Maxwell solvers employed in most PIC codes can induce a spurious angular deviation of harmonic beams potentially degrading simulation results. This effect was extensively studied and a simple toy model based on the Snell-Descartes law was developed that allows us to finely predict the angular deviation of harmonics depending on the spatiotemporal resolution and the Maxwell solver used in the simulations. Our model demonstrates that the mitigation of this numerical artifact with FDTD solvers mandates very high spatiotemporal resolution preventing realistic three-dimensional (3D) simulations even on the largest computers available at the time of writing. We finally show that nondispersive pseudospectral analytical time domain solvers can considerably reduce the spatiotemporal resolution required to mitigate this spurious deviation and should enable in the near future 3D accurate modeling on supercomputers in a realistic time to solution.
Energy Technology Data Exchange (ETDEWEB)
Yazdanpannah, M.M.; Dehghanzadeh, M. [Shahid Bahonar University of Kerman, Faculty of Physics, Kerman (Iran, Islamic Republic of); Mirjalili, A. [Yazd University, Physics Department, P.O. Box 89195-741, Yazd (Iran, Islamic Republic of)
2012-11-15
The solution of the Dirac equation with a generalized harmonic oscillator potential is used to extract the constituent bare parton densities. The results are firstly in spatial space which are converted to momentum space, using the Fourier transformation. The final results are presented in terms of the Bjorken x-variable. Employing the effective chiral quark model and the related convolutions, the parton densities inside the proton are obtained. Choosing an appropriate radius of proton, they indicate reasonable behavior. Although the initial framework is completely theoretical, the results for the sea and valence quark densities and also the ratio of d to u valence quarks inside the proton are in good agreement with the available experimental data and some theoretical models. (orig.)
Nakai, Hiromi; Ishikawa, Atsushi
2014-11-01
We propose a novel quantum chemical method, called the harmonic solvation model (HSM), for calculating thermochemical parameters in the condensed phase, particularly in the liquid phase. The HSM represents translational and rotational motions of a solute as vibrations interacting with a cavity wall of solvent molecules. As examples, the HSM and the ideal-gas model (IGM) were used for the standard formation reaction of liquid water, combustion reactions of liquid formic acid, methanol, and ethanol, vapor-liquid equilibration of water and ethanol, and dissolution of gaseous CO2 in water. The numerical results confirmed the reliability and applicability of the HSM. In particular, the temperature dependence of the Gibbs energy of liquid molecules was accurately reproduced by the HSM; for example, the boiling point of water was reasonably determined using the HSM, whereas the conventional IGM treatment failed to obtain a crossing of the two Gibbs energy curves for gaseous and liquid water.
Nakai, Hiromi; Ishikawa, Atsushi
2014-11-07
We propose a novel quantum chemical method, called the harmonic solvation model (HSM), for calculating thermochemical parameters in the condensed phase, particularly in the liquid phase. The HSM represents translational and rotational motions of a solute as vibrations interacting with a cavity wall of solvent molecules. As examples, the HSM and the ideal-gas model (IGM) were used for the standard formation reaction of liquid water, combustion reactions of liquid formic acid, methanol, and ethanol, vapor-liquid equilibration of water and ethanol, and dissolution of gaseous CO2 in water. The numerical results confirmed the reliability and applicability of the HSM. In particular, the temperature dependence of the Gibbs energy of liquid molecules was accurately reproduced by the HSM; for example, the boiling point of water was reasonably determined using the HSM, whereas the conventional IGM treatment failed to obtain a crossing of the two Gibbs energy curves for gaseous and liquid water.
A Review of Flood Loss Models as Basis for Harmonization and Benchmarking.
Directory of Open Access Journals (Sweden)
Tina Gerl
exemplarily presents an approach for a quantitative comparison of disparate models via the reduction to the joint input variables of all models. Harmonization of models for benchmarking and comparison requires profound insight into the model structures, mechanisms and underlying assumptions. Possibilities and challenges are discussed that exist in model harmonization and the application of the inventory in a benchmarking framework.
An ice crystal model for jupiter's moon Europa
DEFF Research Database (Denmark)
Dahl-Jensen, Dorthe; schmidt, Karen Guldbae
2003-01-01
A simple model for crystal growth in the ice shell of Europa has been made in order to estimate the size of ice crystals at Europa's surface. If mass is lost from the surface of Europa due to sputtering processes, and the ice thickness is constant in time, ice crystals will be transported upwards...
Simulating complex crystal structures using the phase-field crystal model
Alster, Eli; Montiel, David; Thornton, Katsuyo; Voorhees, Peter W.
2017-11-01
We introduce a phase-field crystal model that creates an array of complex three- and two-dimensional crystal structures via a numerically tractable three-point correlation function. The three-point correlation function is designed in order to energetically favor the principal interplanar angles of a target crystal structure. This is achieved via an analysis performed by examining the crystal's structure factor. This approach successfully yields energetically stable simple cubic, diamond cubic, simple hexagonal, graphene layers, and CaF2 crystals. To illustrate the ability of the method to yield a particularly complex and technologically important crystal structure, we show how this three-point correlation function method can be used to generate perovskite crystals.
Systematic identification of crystallization kinetics within a generic modelling framework
DEFF Research Database (Denmark)
Abdul Samad, Noor Asma Fazli Bin; Meisler, Kresten Troelstrup; Gernaey, Krist
2012-01-01
A systematic development of constitutive models within a generic modelling framework has been developed for use in design, analysis and simulation of crystallization operations. The framework contains a tool for model identification connected with a generic crystallizer modelling tool-box, a tool...
Yamamoto, Shu; Yamaguchi, Tomonobu; Hirahara, Hideaki; Ara, Takahiro
This paper presents asymmetric circuit models and an inductance parameter measurement method for Permanent Magnet Linear Synchronous Motors (PMLSMs). The reason why the tested PMLSM with surface permanent magnet structure exhibits both asymmetry and salient pole natures is investigated. Asymmetric circuit models considering the saliency and inductance harmonic effects are discussed for PMLSM fed by three-phase three-wire power source systems. All fundamental and harmonic inductance parameters are easily determined by a standstill test using a single-phase commercial source. Experimental and simulation results on a single-sided PMLSM with a 3-phase, 4-pole and 14-slot mover demonstrate the validity of the proposed method.
DEFF Research Database (Denmark)
Chaaban, Joussef Hussein; Dam-Johansen, Kim; Skovby, Tommy
2014-01-01
A mathematical model describing the separation of enantiomers by simultaneous preferential crystallization in a coupled crystallizer configuration is developed. The model was validated against experimental data for a chemical model compound, the conglomerate forming system of asparagine monohydrate...... in water. The kinetic parameters required were taken from available literature sources and simulations compared to experimental data. Simulations were found to be in good agreement with experimental data. Additional model simulations suggest that the separation process can be improved by increasing...... the mean residence time of the liquid phase in the crystallizers, and the mass of seeds supplied. Reducing the size of seed crystals will also lead to an improved separation. The model can also be used to simulate the performance of the crystallization process for a racemic compound forming system...
Harmonic Pollution Produced by Low Power Nonlinear Loads: Mathematical Model and Practical Cases
Directory of Open Access Journals (Sweden)
Mora–Barajas M.A.
2010-04-01
Full Text Available Many household electrical appliances like televisions, video recorders and computers are sources of voltage and current harmonics, which increase power losses and contaminate the AC power line. These harmonics can cause serious problems in both, utilities and electrical equipments connected to the same AC line. This paper shows a mathematical analysis of harmonics content on the electrical current for a circuit representing a non linear residential load. A comparative harmonic distortion study produced by the residential loads on the electrical power lines, measured experimentally, is also shown.
Event-plane dependent di-hadron correlations with harmonic vn subtraction in a hydrodynamic model
Castilho, Wagner M.; Qian, Wei-Liang; Hama, Yogiro; Kodama, Takeshi
2018-02-01
In this work, a hydrodynamic study of the di-hadron azimuthal correlations for the Au+Au collisions at 200 GeV is carried out. The correlations are evaluated using the ZYAM method for the centrality windows as well as the transverse momentum range in accordance with the existing data. Event-plane dependence of the correlation is obtained after the subtraction of contributions from the most dominant harmonic coefficients. In particular, the contribution from the triangular flow, v3, is removed from the proper correlations following the procedure implemented by the STAR collaboration. The resultant structure observed in the correlations was sometimes attributed to the mini-jet dynamics, but the present calculations show that a pure hydrodynamic model gives a reasonable agreement with the main feature of the published data. A brief discussion on the physical content of the present findings is presented.
Lyu, Dandan; Li, Shaofan
2017-10-01
Crystal defects have microstructure, and this microstructure should be related to the microstructure of the original crystal. Hence each type of crystals may have similar defects due to the same failure mechanism originated from the same microstructure, if they are under the same loading conditions. In this work, we propose a multiscale crystal defect dynamics (MCDD) model that models defects by considering its intrinsic microstructure derived from the microstructure or material genome of the original perfect crystal. The main novelties of present work are: (1) the discrete exterior calculus and algebraic topology theory are used to construct a scale-up (coarse-grained) dual lattice model for crystal defects, which may represent all possible defect modes inside a crystal; (2) a higher order Cauchy-Born rule (up to the fourth order) is adopted to construct atomistic-informed constitutive relations for various defect process zones, and (3) an hierarchical strain gradient theory based finite element formulation is developed to support an hierarchical multiscale cohesive (process) zone model for various defects in a unified formulation. The efficiency of MCDD computational algorithm allows us to simulate dynamic defect evolution at large scale while taking into account atomistic interaction. The MCDD model has been validated by comparing of the results of MCDD simulations with that of molecular dynamics (MD) in the cases of nanoindentation and uniaxial tension. Numerical simulations have shown that MCDD model can predict dislocation nucleation induced instability and inelastic deformation, and thus it may provide an alternative solution to study crystal plasticity.
Directory of Open Access Journals (Sweden)
Tiago E. C. de Oliveira
2018-02-01
Full Text Available This paper introduces a brief analysis on hosting capacity and related concepts as applied to distribution network systems. Furthermore, it addresses the applicability of hosting capacity study methodologies to harmonic voltage distortion caused by photovoltaic panels (PV connected at a low-voltage (LV side of a university campus grid. The analysis of the penetration of new distributed generation technologies, such as PV panels, in the distribution grid of the campus was carried out via measurement processes, and later by computer simulations analyzing a new concept of the hosting capacity approach in relation to voltage harmonics distortion. The voltage rise due to harmonic injection is analyzed and discussed with the aim of validating the discussed model and also putting forward recommendations for connecting PV generation across other network systems.
Kersemans, Mathias; Martens, Arvid; Van Den Abeele, Koen; Degrieck, Joris; Pyl, Lincy; Zastavnik, Filip; Sol, Hugo; Van Paepegem, Wim
2015-04-01
Conventionally, the ultrasonic polar scan (UPS) records the amplitude or time-of-flight in transmission using short ultrasonic pulses for a wide range of incidence angles, resulting in a fingerprint of the critical bulk wave angles of the material at the insonified spot. Here, we investigate the use of quasi-harmonic ultrasound (bursts) in a polar scan experiment, both experimentally and numerically. It is shown that the nature of the fingerprint drastically changes, and reveals the positions of the leaky Lamb angles. To compare with experiments, both plane wave and bounded beam simulations have been performed based on the recursive stiffness matrix method. Whereas the plane wave computations yield a pure Lamb wave angle fingerprint, this is no longer valid for the more realistic case of a bounded beam. The experimental recordings are fully supported by the bounded beam simulations. To complement the traditional amplitude measurement, experimental and numerical investigations have been performed to record, predict and analyze the phase of the transmitted ultrasonic beam. This results in the conceptual introduction of the 'phase polar scan', exposing even more intriguing and detailed patterns. In fact, the combination of the amplitude and the phase polar scan provides the complete knowledge about the complex transmission coefficient for every possible angle of incidence. This comprehensive information will be very valuable for inverse modeling of the local elasticity tensor based on a single UPS experiment. Finally, the UPS method has been applied for the detection of an artificial delamination. Compared to the pulsed UPS, the quasi-harmonic UPS (both the amplitude and phase recording) shows a superior sensitivity to the presence of a delamination. Copyright © 2015 Elsevier B.V. All rights reserved.
Modeling of ultrafast THz interactions in molecular crystals
DEFF Research Database (Denmark)
Pedersen, Pernille Klarskov; Clark, Stewart J.; Jepsen, Peter Uhd
2014-01-01
In this paper we present a numerical study of terahertz pulses interacting with crystals of cesium iodide. We model the molecular dynamics of the cesium iodide crystals with the Density Functional Theory software CASTEP, where ultrafast terahertz pulses are implemented to the CASTEP software...... to interact with molecular crystals. We investigate the molecular dynamics of cesium iodide crystals when interacting with realistic terahertz pulses of field strengths from 0 to 50 MV/cm. We find nonlinearities in the response of the CsI crystals at field strengths higher than 10 MV/cm....
DEFF Research Database (Denmark)
Kwon, JunBum; Wang, Xiongfei; Bak, Claus Leth
2014-01-01
This paper addresses the harmonic compensation error problem existing with parallel connected inverter in the same grid interface conditions by means of impedance-based analysis and modeling. Unlike the single grid connected inverter, it is found that multiple parallel connected inverters and grid...
Energy Technology Data Exchange (ETDEWEB)
Li, H.T. [Department of Engineering Mechanics, Northwestern Polytechnical University, Xian (China); Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, Ontario (Canada); Yang, Z.; Zu, J. [Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, Ontario (Canada); Qin, W. Y., E-mail: qinweiyang67@gmail.com [Department of Engineering Mechanics, Northwestern Polytechnical University, Xian (China)
2016-08-15
This paper presents the modeling and parametric analysis of the recently proposed nonlinear compressive-mode energy harvester (HC-PEH) under harmonic excitation. Both theoretical and experimental investigations are performed in this study over a range of excitation frequencies. Specially, a distributed parameter electro-elastic model is analytically developed by means of the energy-based method and the extended Hamilton’s principle. An analytical formulation of bending and stretching forces are derived to gain insight on the source of nonlinearity. Furthermore, the analytical model is validated against with experimental data and a good agreement is achieved. Both numerical simulations and experiment illustrate that the harvester exhibits a hardening nonlinearity and hence a broad frequency bandwidth, multiple coexisting solutions and a large-amplitude voltage response. Using the derived model, a parametric study is carried out to examine the effect of various parameters on the harvester voltage response. It is also shown from parametric analysis that the harvester’s performance can be further improved by selecting the proper length of elastic beams, proof mass and reducing the mechanical damping.
Model-driven harmonic parameterization of the cortical surface: HIP-HOP.
Auzias, G; Lefèvre, J; Le Troter, A; Fischer, C; Perrot, M; Régis, J; Coulon, O
2013-05-01
In the context of inter subject brain surface matching, we present a parameterization of the cortical surface constrained by a model of cortical organization. The parameterization is defined via an harmonic mapping of each hemisphere surface to a rectangular planar domain that integrates a representation of the model. As opposed to previous landmark-based registration methods we do not match folds between individuals but instead optimize the fit between cortical sulci and specific iso-coordinate axis in the model. This strategy overcomes some limitation to sulcus-based registration techniques such as topological variability in sulcal landmarks across subjects. Experiments on 62 subjects with manually traced sulci are presented and compared with the result of the Freesurfer software. The evaluation involves a measure of dispersion of sulci with both angular and area distortions. We show that the model-based strategy can lead to a natural, efficient and very fast (less than 5 min per hemisphere) method for defining inter subjects correspondences. We discuss how this approach also reduces the problems inherent to anatomically defined landmarks and open the way to the investigation of cortical organization through the notion of orientation and alignment of structures across the cortex.
Modeling nuclear volume isotope effects in crystals
Schauble, Edwin A.
2013-01-01
Mass-independent isotope fractionations driven by differences in volumes and shapes of nuclei (the field shift effect) are known in several elements and are likely to be found in more. All-electron relativistic electronic structure calculations can predict this effect but at present are computationally intensive and limited to modeling small gas phase molecules and clusters. Density functional theory, using the projector augmented wave method (DFT-PAW), has advantages in greater speed and compatibility with a three-dimensional periodic boundary condition while preserving information about the effects of chemistry on electron densities within nuclei. These electron density variations determine the volume component of the field shift effect. In this study, DFT-PAW calculations are calibrated against all-electron, relativistic Dirac–Hartree–Fock, and coupled-cluster with single, double (triple) excitation methods for estimating nuclear volume isotope effects. DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used. Nuclear volume contributions to vapor–crystal isotope fractionation are calculated for elemental cadmium and mercury, showing good agreement with experiments. The nuclear-volume component of mercury and cadmium isotope fractionations between atomic vapor and montroydite (HgO), cinnabar (HgS), calomel (Hg2Cl2), monteponite (CdO), and the CdS polymorphs hawleyite and greenockite are calculated, indicating preferential incorporation of neutron-rich isotopes in more oxidized, ionically bonded phases. Finally, field shift energies are related to Mössbauer isomer shifts, and equilibrium mass-independent fractionations for several tin-bearing crystals are calculated from 119Sn spectra. Isomer shift data should simplify calculations of mass-independent isotope fractionations in other elements with Mössbauer isotopes, such as platinum and uranium
Modeling nuclear volume isotope effects in crystals.
Schauble, Edwin A
2013-10-29
Mass-independent isotope fractionations driven by differences in volumes and shapes of nuclei (the field shift effect) are known in several elements and are likely to be found in more. All-electron relativistic electronic structure calculations can predict this effect but at present are computationally intensive and limited to modeling small gas phase molecules and clusters. Density functional theory, using the projector augmented wave method (DFT-PAW), has advantages in greater speed and compatibility with a three-dimensional periodic boundary condition while preserving information about the effects of chemistry on electron densities within nuclei. These electron density variations determine the volume component of the field shift effect. In this study, DFT-PAW calculations are calibrated against all-electron, relativistic Dirac-Hartree-Fock, and coupled-cluster with single, double (triple) excitation methods for estimating nuclear volume isotope effects. DFT-PAW calculations accurately reproduce changes in electron densities within nuclei in typical molecules, when PAW datasets constructed with finite nuclei are used. Nuclear volume contributions to vapor-crystal isotope fractionation are calculated for elemental cadmium and mercury, showing good agreement with experiments. The nuclear-volume component of mercury and cadmium isotope fractionations between atomic vapor and montroydite (HgO), cinnabar (HgS), calomel (Hg2Cl2), monteponite (CdO), and the CdS polymorphs hawleyite and greenockite are calculated, indicating preferential incorporation of neutron-rich isotopes in more oxidized, ionically bonded phases. Finally, field shift energies are related to Mössbauer isomer shifts, and equilibrium mass-independent fractionations for several tin-bearing crystals are calculated from (119)Sn spectra. Isomer shift data should simplify calculations of mass-independent isotope fractionations in other elements with Mössbauer isotopes, such as platinum and uranium.
Directory of Open Access Journals (Sweden)
Guohong Zou
2016-04-01
Full Text Available Crystals of congruently melting noncentrosymmetric (NCS mixed alkali metal nitrate, Rb2Na(NO33, have been grown through solid state reactions. The material possesses layers with NaO8 hexagonal bipyramids and NO3 triangular units. Rb+ cations are residing in the interlayer space. Each NaO8 hexagonal bipyramid shares its corners and edges with two and three NO3 units, respectively, in order to fulfill a highly dense stacking in the unit cell. The NaO8 groups share their six oxygen atoms in equatorial positions with three different NO3 groups to generate a NaO6-NO3 layer with a parallel alignment. The optimized arrangement of the NO3 groups and their high density in the structure together produce a strong second-harmonic generation (SHG response. Powder SHG measurements indicate that Rb2Na(NO33 has a strong SHG efficiency of five times that of KH2PO4 (KDP and is type I phase-matchable. The calculated average nonlinear optical (NLO susceptibility of Rb2Na(NO33 turns out to be the largest value among the NLO materials composed of only [NO3]− anion. In addition, Rb2Na(NO33 exhibits a wide transparency region ranging from UV to near IR, which suggests that the compound is a promising NLO material.
Zhong, Yin; Liu, Yu; Luo, Hong-Gang
2017-10-01
The periodic Anderson model (PAM), where local electron orbitals interplay with itinerant electronic carriers, plays an essential role in our understanding of heavy fermion materials. Motivated by recent proposals for simulating the Kondo lattice model (KLM) in terms of alkaline-earth metal atoms, we take another step toward the simulation of PAM, which includes the crucial charge/valence fluctuation of local f-electrons beyond purely low-energy spin fluctuation in the KLM. To realize PAM, a transition induced by a suitable laser between the electronic excited and ground state of alkaline-earth metal atoms (1 S 0⇌3 P 0) is introduced. This leads to effective hybridization between local electrons and conduction electrons in PAM. Generally, the SU( N) version of PAM can be realized by our proposal, which gives a unique opportunity to detect large- N physics without complexity in realistic materials. In the present work, high-temperature physical features of standard [ SU(2)] PAM with harmonic trapping potential are analyzed by quantum Monte Carlo and dynamic mean-field theory, where the Mott/orbital-selective Mott state was found to coexist with metallic states. Indications for near-future experiments are provided. We expect our theoretical proposal and (hopefully) forthcoming experiments will deepen our understanding of heavy fermion systems. At the same time, we hope these will trigger further studies on related Mott physics, quantum criticality, and non-trivial topology in both the inhomogeneous and nonequilibrium realms.
Brigham, John C.; Aquino, Wilkins; Aguilo, Miguel A.; Diamessis, Peter J.
2010-01-01
An approach for efficient and accurate finite element analysis of harmonically excited soft solids using high-order spectral finite elements is presented and evaluated. The Helmholtz-type equations used to model such systems suffer from additional numerical error known as pollution when excitation frequency becomes high relative to stiffness (i.e. high wave number), which is the case, for example, for soft tissues subject to ultrasound excitations. The use of high-order polynomial elements allows for a reduction in this pollution error, but requires additional consideration to counteract Runge's phenomenon and/or poor linear system conditioning, which has led to the use of spectral element approaches. This work examines in detail the computational benefits and practical applicability of high-order spectral elements for such problems. The spectral elements examined are tensor product elements (i.e. quad or brick elements) of high-order Lagrangian polynomials with non-uniformly distributed Gauss-Lobatto-Legendre nodal points. A shear plane wave example is presented to show the dependence of the accuracy and computational expense of high-order elements on wave number. Then, a convergence study for a viscoelastic acoustic-structure interaction finite element model of an actual ultrasound driven vibroacoustic experiment is shown. The number of degrees of freedom required for a given accuracy level was found to consistently decrease with increasing element order. However, the computationally optimal element order was found to strongly depend on the wave number. PMID:21461402
The evolution of applied harmonic analysis models of the real world
Prestini, Elena
2016-01-01
A sweeping exploration of the development and far-reaching applications of harmonic analysis such as signal processing, digital music, optics, radio astronomy, crystallography, medical imaging, spectroscopy, and more. Featuring a wealth of illustrations, examples, and material not found in other harmonic analysis books, this unique monograph skillfully blends together historical narrative with scientific exposition to create a comprehensive yet accessible work. While only an understanding of calculus is required to appreciate it, there are more technical sections that will charm even specialists in harmonic analysis. From undergraduates to professional scientists, engineers, and mathematicians, there is something for everyone here. The second edition of The Evolution of Applied Harmonic Analysis contains a new chapter on atmospheric physics and climate change, making it more relevant for today’s audience. Praise for the first edition: "…can be thoroughly recommended to any reader who is curious about the ...
Phase field crystal modeling of ternary solidification microstructures
Berghoff, Marco; Nestler, Britta
2015-01-01
In the present work, we present a free energy derivation of the multi-component phase-field crystal model [1] and illustrate the capability to simulate dendritic and eutectic solidification in ternary alloys. Fast free energy minimization by a simulated annealing algorithm of an approximated crystal is compared with the free energy of a fully simulated phase field crystal structure. The calculation of ternary phase diagrams from these free energies is described. Based on the free energies rel...
Modeling the Mechanical Response of Tetragonal Lysozyme Crystals
Zamiri, Amir; De, Suvranu
2010-01-01
In this paper we investigate the mechanical response of tetragonal lysozyme crystals based on existing experimental data and a continuum-based crystal plasticity model. Compression analyses along different crystallographic directions reveal that the mechanical response of lysozyme crystals is highly anisotropic and orientation dependent. While the response is purely elastic along the [110] direction, it is elasto-plastic along the [100] and [2̄ 12] directions. The yield stress and critical re...
Energy Technology Data Exchange (ETDEWEB)
Eliazar, Iddo, E-mail: eliazar@post.tau.ac.il
2017-05-15
The exponential, the normal, and the Poisson statistical laws are of major importance due to their universality. Harmonic statistics are as universal as the three aforementioned laws, but yet they fall short in their ‘public relations’ for the following reason: the full scope of harmonic statistics cannot be described in terms of a statistical law. In this paper we describe harmonic statistics, in their full scope, via an object termed harmonic Poisson process: a Poisson process, over the positive half-line, with a harmonic intensity. The paper reviews the harmonic Poisson process, investigates its properties, and presents the connections of this object to an assortment of topics: uniform statistics, scale invariance, random multiplicative perturbations, Pareto and inverse-Pareto statistics, exponential growth and exponential decay, power-law renormalization, convergence and domains of attraction, the Langevin equation, diffusions, Benford’s law, and 1/f noise. - Highlights: • Harmonic statistics are described and reviewed in detail. • Connections to various statistical laws are established. • Connections to perturbation, renormalization and dynamics are established.
Energy Technology Data Exchange (ETDEWEB)
Davis, R.; Fishman, D.; Frank, E. D.; Wigmosta, M. S.; Aden, A.; Coleman, A. M.; Pienkos, P. T.; Skaggs, R. J.; Venteris, E. R.; Wang, M. Q.
2012-06-01
The U.S. Department of Energy's Biomass Program has begun an initiative to obtain consistent quantitative metrics for algal biofuel production to establish an 'integrated baseline' by harmonizing and combining the Program's national resource assessment (RA), techno-economic analysis (TEA), and life-cycle analysis (LCA) models. The baseline attempts to represent a plausible near-term production scenario with freshwater microalgae growth, extraction of lipids, and conversion via hydroprocessing to produce a renewable diesel (RD) blendstock. Differences in the prior TEA and LCA models were reconciled (harmonized) and the RA model was used to prioritize and select the most favorable consortium of sites that supports production of 5 billion gallons per year of RD. Aligning the TEA and LCA models produced slightly higher costs and emissions compared to the pre-harmonized results. However, after then applying the productivities predicted by the RA model (13 g/m2/d on annual average vs. 25 g/m2/d in the original models), the integrated baseline resulted in markedly higher costs and emissions. The relationship between performance (cost and emissions) and either productivity or lipid fraction was found to be non-linear, and important implications on the TEA and LCA results were observed after introducing seasonal variability from the RA model. Increasing productivity and lipid fraction alone was insufficient to achieve cost and emission targets; however, combined with lower energy, less expensive alternative technology scenarios, emissions and costs were substantially reduced.
Harmonics in transmission power systems
DEFF Research Database (Denmark)
Wiechowski, Wojciech Tomasz
Some time ago, Energinet.dk, the Transmission System Operator of the 150 kV and 400 kV transmission network in Denmark, had experienced operational malfunctions of some of the measuring and protection equipment. Also an overloading of a harmonic filter has been reported, and therefore, a need...... to perform more detailed harmonic studies emerged. Since the transmission network has a complex structure and its impedance varies with frequency in a nonlinear fashion, such harmonic study would require a detailed computer model of the network. Consequently, a PhD project proposal titled "Harmonics......, provided that background harmonic distortion, and the network configuration, are not changing during the measurement. It is shown that switching of a shunt linear power system component can result in variation of the harmonic levels that can be measured and used to verify the harmonic model of the network...
Directory of Open Access Journals (Sweden)
Niancheng Zhou
2014-08-01
Full Text Available The influence of electric vehicle charging stations on power grid harmonics is becoming increasingly significant as their presence continues to grow. This paper studies the operational principles of the charging current in the continuous and discontinuous modes for a three-phase uncontrolled rectification charger with a passive power factor correction link, which is affected by the charging power. A parameter estimation method is proposed for the equivalent circuit of the charger by using the measured characteristic AC (Alternating Current voltage and current data combined with the charging circuit constraints in the conduction process, and this method is verified using an experimental platform. The sensitivity of the current harmonics to the changes in the parameters is analyzed. An analytical harmonic model of the charging station is created by separating the chargers into groups by type. Then, the harmonic current amplification caused by the shunt active power filter is researched, and the analytical formula for the overload factor is derived to further correct the capacity of the shunt active power filter. Finally, this method is validated through a field test of a charging station.
Photonic crystal fiber modelling and applications
DEFF Research Database (Denmark)
Bjarklev, Anders Overgaard; Broeng, Jes; Libori, Stig E. Barkou
2001-01-01
Photonic crystal fibers having a microstructured air-silica cross section offer new optical properties compared to conventional fibers for telecommunication, sensor, and other applications. Recent advances within research and development of these fibers are presented.......Photonic crystal fibers having a microstructured air-silica cross section offer new optical properties compared to conventional fibers for telecommunication, sensor, and other applications. Recent advances within research and development of these fibers are presented....
Miller, Christopher A; Borg, Alex; Clark, David; Steadman, Christopher D; McCann, Gerry P; Clarysse, Patrick; Croisille, Pierre; Schmitt, Matthias
2013-08-01
To compare local sine-wave modeling (SinMod) with harmonic phase analysis (HARP), for assessment of left ventricular (LV) circumferential strain (εcc) from tagged cardiovascular magnetic resonance images. Mid-ventricular spatial modulation of magnetization was performed in 60 participants (15 each with hypertrophic, dilated or ischemic cardiomyopathy and 15 healthy controls) at 1.5 Tesla. Global and segmental peak transmural εcc were measured using HARP and SinMod. Repeated measurements were performed on 25% of examinations to assess observer variability. Effect of contrast was assessed in 10 additional patients. SinMod showed a high level of agreement with HARP for global εcc (mean difference -0.02, 95% limits of agreement -6.46 to 6.43%). Agreement was much lower for segmental εcc. Both methods showed excellent observer agreement for global εcc (intraclass correlation coefficient >0.75). Observer agreement for segmental εcc was also excellent with SinMod, but was significantly lower with HARP. Analysis time was significantly shorter using SinMod. Pre- and postcontrast εcc measurements were not significantly different using either technique, although postcontrast measurements showed greater variability with HARP. SinMod and HARP-based measurements of global εcc have a high level of agreement, but segmental agreement is substantially lower. SinMod has generally lower observer variability, is faster and is less affected by contrast, but requires further validation. Copyright © 2012 Wiley Periodicals, Inc.
Practical analysis and mathematical modelling of harmonic distortions caused by electronic loads
Energy Technology Data Exchange (ETDEWEB)
Jabbar, R.A.; Akmal, M.; Qureshi, W.A.; Ahmad, A. [Rachna College of Engineering and Technology, Gujranwala (Pakistan); Qureshi, S.A. [Univ. of Engineering and Technology, Lahore (Pakistan)
2007-07-01
Power supply systems have no control over the currents that particular loads may draw upon, and standards in power quality tend to focus on maintaining supply voltage within certain limits. This study examined the impact of personal computers (PCs) connected to a single power supply on voltage and current waveforms. Total harmonic distortion in current and voltage was measured using a power quality analyzer. Distorted waveforms of current and voltage in time and frequency domains for the 23 personal computers were presented. Mathematical expressions were then developed using the data. The analysis demonstrated that voltage distortions increased with the addition of more PCs, while current distortions decreased. The power factor also increased when additional PCs were added. The study showed that there is a linear relationship between the number of PCs and the number of total voltage distortions. An approximate linear relationship between the number of PCs and the number of total current distortions was also observed. It was concluded that the model can be used to evaluate anticipated voltage distortions in power distribution networks as well as to improve performance and power quality. 14 refs., 2 tabs., 10 figs.
Microscopic kinetic model for polymer crystal growth
Hu, Wenbing
2011-03-01
Linear crystal growth rates characterize the net result of competition between growth and melting at the liquid-solid interfaces. The rate equation for polymer crystal growth can be derived with a barrier term for crystal growth and with a driving force term of excess lamellar thickness, provided that growth and melting share the same rate-determining steps at the growth front. Such an ansatz can be verified by the kinetic symmetry between growth and melting around the melting point of lamellar crystals, as made in our recent dynamic Monte Carlo simulations. The profile of the growth/melting front appears as wedge-shaped, with the free energy barrier for intramolecular secondary crystal nucleation at its top, and with the driving force gained via instant thickening at its bottom. Such a scenario explains unique phenomena on polymer crystal growth, such as chain folding, regime transitions, molecular segregation of polydisperse polymers, self-poisoning with integer-number chain-folding of short chains, and colligative growth rates of binary mixtures of two chain lengths. Financial support from NNSFC No. 20825415 and NBRPC No. 2011CB606100 is acknowledged.
Steinschneider, Mitchell; Micheyl, Christophe
2014-01-01
The ability to attend to a particular sound in a noisy environment is an essential aspect of hearing. To accomplish this feat, the auditory system must segregate sounds that overlap in frequency and time. Many natural sounds, such as human voices, consist of harmonics of a common fundamental frequency (F0). Such harmonic complex tones (HCTs) evoke a pitch corresponding to their F0. A difference in pitch between simultaneous HCTs provides a powerful cue for their segregation. The neural mechanisms underlying concurrent sound segregation based on pitch differences are poorly understood. Here, we examined neural responses in monkey primary auditory cortex (A1) to two concurrent HCTs that differed in F0 such that they are heard as two separate “auditory objects” with distinct pitches. We found that A1 can resolve, via a rate-place code, the lower harmonics of both HCTs, a prerequisite for deriving their pitches and for their perceptual segregation. Onset asynchrony between the HCTs enhanced the neural representation of their harmonics, paralleling their improved perceptual segregation in humans. Pitches of the concurrent HCTs could also be temporally represented by neuronal phase-locking at their respective F0s. Furthermore, a model of A1 responses using harmonic templates could qualitatively reproduce psychophysical data on concurrent sound segregation in humans. Finally, we identified a possible intracortical homolog of the “object-related negativity” recorded noninvasively in humans, which correlates with the perceptual segregation of concurrent sounds. Findings indicate that A1 contains sufficient spectral and temporal information for segregating concurrent sounds based on differences in pitch. PMID:25209282
Yants, A. Yu.; Trusov, P. V.; Teplyakova, L. A.
2017-12-01
The mathematical formulation and the results of solving a boundary value problem of uniaxial loading of single-crystal aluminum samples are reported. A first-type direct model was used for the solution of the boundary value problem. The material response is determined within the crystal elastoviscoplasticity theory. The fragmentation of the initially homogeneous sample into zones with different internal structure evolution is shown.
Trap effects and the continuum limit of the Hubbard model in the presence of a harmonic potential
Nigro, Davide
2017-09-01
We discuss how to perform the continuum limit of the d -dimensional Hubbard model in the presence of a harmonic confining potential at zero temperature and fixed particle number. While for d ≥3 the system can be mapped into a noninteracting two-component Fermi gas in a harmonic trap, for d =1 and 2 the two-body interaction is described by a Dirac δ . We show that the properties of this continuum limit can be put in one-to-one correspondence with those obtained by applying the trap-size scaling formalism to the confined Hubbard model in the so called dilute regime (fixed number of particles and weak confinement). The correspondence for d <3 has been tested, in the case of two particles with opposite spin, by comparing numerical exact-diagonalization results of the lattice system with those obtained in the continuum limit.
DEFF Research Database (Denmark)
Nielsen, Jesper Kjær; Jensen, Tobias Lindstrøm; Jensen, Jesper Rindom
2017-01-01
The harmonic chirp signal model has only very recently been in- troduced for modelling approximately periodic signals with a time- varying fundamental frequency. A number of estimators for the pa- rameters of this model have already been proposed, but they are ei- ther inaccurate, non-robust to n......The harmonic chirp signal model has only very recently been in- troduced for modelling approximately periodic signals with a time- varying fundamental frequency. A number of estimators for the pa- rameters of this model have already been proposed, but they are ei- ther inaccurate, non......-robust to noise, or very computationally inten- sive. In this paper, we propose a fast algorithm for the harmonic chirp summation method which has been demonstrated in the liter- ature to be accurate and robust to noise. The proposed algorithm is orders of magnitudes faster than previous algorithms which is also...
Directory of Open Access Journals (Sweden)
El Korso Mohammed
2011-01-01
Full Text Available Abstract The statistical resolution limit (SRL, which is defined as the minimal separation between parameters to allow a correct resolvability, is an important statistical tool to quantify the ultimate performance for parametric estimation problems. In this article, we generalize the concept of the SRL to the multidimensional SRL (MSRL applied to the multidimensional harmonic retrieval model. In this article, we derive the SRL for the so-called multidimensional harmonic retrieval model using a generalization of the previously introduced SRL concepts that we call multidimensional SRL (MSRL. We first derive the MSRL using an hypothesis test approach. This statistical test is shown to be asymptotically an uniformly most powerful test which is the strongest optimality statement that one could expect to obtain. Second, we link the proposed asymptotic MSRL based on the hypothesis test approach to a new extension of the SRL based on the Cramér-Rao Bound approach. Thus, a closed-form expression of the asymptotic MSRL is given and analyzed in the framework of the multidimensional harmonic retrieval model. Particularly, it is proved that the optimal MSRL is obtained for equi-powered sources and/or an equi-distributed number of sensors on each multi-way array.
Multi-dimensional population balance models of crystallization processes
DEFF Research Database (Denmark)
Meisler, Kresten Troelstrup; von Solms, Nicolas
A generic and model-based framework for batch cooling crystallization operations has been extended to incorporate continuous and fed-batch processes. Modules for the framework have been developed, including a module for reactions, allowing the study of reactive crystallization within the framework......, analyzed, used for simulation and stored again. The model library facilitates comparison of expressions for kinetic phenomena and is tightly integrated with the model analysis tools of the framework.Through the framework, a model for a crystallization operation may be systematically generated...... applied to case studies involving inorganic and organic compounds, including an active pharmaceutical ingredient (paracetamol) crystallized from different solvents. The case studies have been used to demonstrate the versatility of the framework....
Comprehensive FDTD modelling of photonic crystal waveguide components
DEFF Research Database (Denmark)
Lavrinenko, Andrei; Borel, Peter Ingo; Frandsen, Lars Hagedorn
2004-01-01
Planar photonic crystal waveguide structures have been modelled using the finite-difference-time-domain method and perfectly matched layers have been employed as boundary conditions. Comprehensive numerical calculations have been performed and compared to experimentally obtained transmission spec...
Three-dimensional simulations of harmonic radiation and harmonic lasing
Energy Technology Data Exchange (ETDEWEB)
Schmitt, M.J.; McVey, B.D.
1990-01-01
Characteristics of the harmonic emission from free-electron lasers (FELs) are examined in the spontaneous, coherent-spontaneous and stimulated emission regimes. The radiation at both odd and even harmonic frequencies is treated for electron beams with finite emittance and energy spread. In the spontaneous emission regime, the transverse radiation patterns including the transverse frequency dependences, are given. How this expression is modified to include energy spread and emittance is described. In the coherent-spontaneous emission and stimulated emission regimes, the interaction of the radiation fields with the electrons must be treated self-consistently. Here, a single-frequency distributed transverse source function for each electron is used in the harmonic version of the 3-D code FELEX to model the harmonic radiation. The code has recently been modified to simultaneously model the fundamental and harmonic interactions for multiple-pass oscillator simulations. These modifications facilitate the examination of FELs under various operating conditions. When the FEL is lasing at the fundamental, the evolution of the harmonic fields can be examined. This evolution is unique in the sense that the electron beam radiates at the harmonic frequencies in the presence of the harmonic radiation circulating in the cavity. As a result, enhancements of the harmonic emission can be observed. Finally, harmonic lasing can occur in cases where there is sufficient gain to overcome cavity losses and lasing at the fundamental can be suppressed. The characteristics and efficiency of these interactions are explored. 11 refs., 9 figs.
Edge loss of high-harmonic fast-wave heating power in NSTX: a cylindrical model
Perkins, R. J.; Hosea, J. C.; Bertelli, N.; Taylor, G.; Wilson, J. R.
2017-11-01
Efficient high-harmonic fast-wave (HHFW) heating in the National Spherical Torus Experiment Upgrade (NSTX-U) would facilitate experiments in turbulence, transport, fast-ion studies, and more. However, previous HHFW operation in NSTX exhibited a large loss of fast-wave power to the divertor along the scrape-off layer field lines for edge densities above the fast-wave cutoff. It was postulated that the wave amplitude is enhanced in the scrape-off layer due to cavity-like modes, and that these enhanced fields drive sheath losses through RF rectification. As part of ongoing work to confirm this hypothesis, we have developed a cylindrical cold-plasma model to identify and understand scenarios where a substantial fraction of wave power is confined to the plasma periphery. We previously identified a peculiar class of modes, named annulus resonances, that conduct approximately half of their wave power in the periphery and can also account for a significant fraction of the total wave power. Here, we study the influence of annulus resonances on wave field reconstructions and find instances where annulus-resonant modes dominate the spectrum and trap over half of the total wave power at the edge. The work is part of an ongoing effort to determine the mechanism underlying these scrape-off layer losses in NSTX, identify optimal conditions for operation in NSTX-U, and predict whether similar losses occur for the ion-cyclotron minority heating scheme for both current experiments and future devices such as ITER.
Numerical modeling in photonic crystals integrated technology: the COPERNICUS Project
DEFF Research Database (Denmark)
Malaguti, Stefania; Armaroli, Andrea; Bellanca, Gaetano
2011-01-01
Photonic crystals will play a fundamental role in the future of optical communications. The relevance of the numerical modeling for the success of this technology is assessed by using some examples concerning the experience of the COPERNICUS Project.......Photonic crystals will play a fundamental role in the future of optical communications. The relevance of the numerical modeling for the success of this technology is assessed by using some examples concerning the experience of the COPERNICUS Project....
Monte Carlo Modeling of Crystal Channeling at High Energies
Schoofs, Philippe; Cerutti, Francesco
Charged particles entering a crystal close to some preferred direction can be trapped in the electromagnetic potential well existing between consecutive planes or strings of atoms. This channeling effect can be used to extract beam particles if the crystal is bent beforehand. Crystal channeling is becoming a reliable and efficient technique for collimating beams and removing halo particles. At CERN, the installation of silicon crystals in the LHC is under scrutiny by the UA9 collaboration with the goal of investigating if they are a viable option for the collimation system upgrade. This thesis describes a new Monte Carlo model of planar channeling which has been developed from scratch in order to be implemented in the FLUKA code simulating particle transport and interactions. Crystal channels are described through the concept of continuous potential taking into account thermal motion of the lattice atoms and using Moliere screening function. The energy of the particle transverse motion determines whether or n...
Modeling the Mechanical Response of Tetragonal Lysozyme Crystals
Zamiri, Amir; De, Suvranu
2011-01-01
In this paper we investigate the mechanical response of tetragonal lysozyme crystals based on existing experimental data and a continuum-based crystal plasticity model. Compression analyses along different crystallographic directions reveal that the mechanical response of lysozyme crystals is highly anisotropic and orientation dependent. While the response is purely elastic along the [110] direction, it is elasto-plastic along the [100] and [2̄ 12] directions. The yield stress and critical resolved shear stress are observed to be sensitive to temperature and the amount of intracrystalline water. An increase in temperature and the amount of intracrystalline water molecules leads to a decrease in the critical resolved shear stress of the slip systems and makes the crystal softer. The analysis presented in this paper may be applied to the study of other protein crystal systems as well as their optimal design for biotechnological applications. PMID:20039601
DEFF Research Database (Denmark)
Schneider, M.; Johnson, T.; Dumont, R.
2016-01-01
Recent JET experiments have been dedicated to the studies of fusion reactions between deuterium (D) and Helium-3 (3He) ions using neutral beam injection (NBI) in synergy with third harmonic ion cyclotron radio-frequency heating (ICRH) of the beam. This scenario generates a fast ion deuterium tail...
Harness processes and harmonic crystals
Ferrari, Pablo A.; Niederhauser, Beat M.
2003-01-01
In the Hammersley harness processes the real-valued height at each site i in Z^d is updated at rate 1 to an average of the neighboring heights plus a centered random variable (the noise). We construct the process "a la Harris" simultaneously for all times and boxes contained in Z^d. With this representation we compute covariances and show L^2 and almost sure time and space convergence of the process. In particular, the process started from the flat configuration and viewed from the height at ...
Spatial mode discrimination using second harmonic generation
DEFF Research Database (Denmark)
Delaubert, Vincent; Lassen, Mikael Østergaard; Pulford, David
2007-01-01
-Kleinmann analysis, taking into account the full description of the multi-mode field inside the nonlinear crystal in a type I phase-maching condition. The good agreement between experiments and theory shows that the effect is well understood and that we have reliable models required for the design of novel photonics......Second harmonic generation can be used as a technique for controlling the spatial mode structure of optical beams. We demonstrate experimentally the generation of higher order spatial modes, and that it is possible to use nonlinear phase matching as a predictable and robust technique...... for the conversion of transverse electric modes of the second harmonic output. For a given TEMn0 pump mode the output mode can be altered continuously by adjusting the laser wavelength, the focusing of the pump or the temperature of the nonlinear medium. We make quantitative comparisons with a generalized Boyd...
Thin film modeling of crystal dissolution and growth in confinement
Gagliardi, Luca; Pierre-Louis, Olivier
2018-01-01
We present a continuum model describing dissolution and growth of a crystal contact confined against a substrate. Diffusion and hydrodynamics in the liquid film separating the crystal and the substrate are modeled within the lubrication approximation. The model also accounts for the disjoining pressure and surface tension. Within this framework, we obtain evolution equations which govern the nonequilibrium dynamics of the crystal interface. Based on this model, we explore the problem of dissolution under an external load, known as pressure solution. We find that in steady state, diverging (power-law) crystal-surface repulsions lead to flat contacts with a monotonic increase of the dissolution rate as a function of the load. Forces induced by viscous dissipation then surpass those due to disjoining pressure at large enough loads. In contrast, finite repulsions (exponential) lead to sharp pointy contacts with a dissolution rate independent of the load and the liquid viscosity. Ultimately, in steady state, the crystal never touches the substrate when pressed against it. This result is independent from the nature of the crystal-surface interaction due to the combined effects of viscosity and surface tension.
Directory of Open Access Journals (Sweden)
Yang Yu
2013-01-01
Full Text Available Based on a brief review on current harmonics generation mechanism for grid-connected inverter under distorted grid voltage, the harmonic disturbances and uncertain items are immersed into the original state-space differential equation of grid-connected inverter. A new algorithm of global current harmonic rejection based on nonlinear backstepping control with multivariable internal model principle is proposed for grid-connected inverter with exogenous disturbances and uncertainties. A type of multivariable internal model for a class of nonlinear harmonic disturbances is constructed. Based on application of backstepping control law of the nominal system, a multivariable adaptive state feedback controller combined with multivariable internal model and adaptive control law is designed to guarantee the closed-loop system globally uniformly bounded, which is proved by a constructed Lyapunov function. The presented algorithm extends rejection of nonlinear single-input systems to multivariable globally defined normal form, the correctness and effectiveness of which are verified by the simulation results.
Indian Academy of Sciences (India)
Harish-Chandra, Gelfand and several other mathematicians and physicists, group-theoretic harmonic analysis is a flourishing industry today paving the way to new developments in the con- text of noncompact Lie groups as well as quantum groups. Since B(n, z) = zn the expansion (3) suggests a link between Fourier series.
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 1; Issue 10. Harmonic Analysis Fourier Series and Beyond. K R Parthasarathy. Book Review Volume 1 Issue 10 October 1996 pp 87-91. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/001/10/0087-0091 ...
Energy Technology Data Exchange (ETDEWEB)
Hernandez-Tenorio, C. [Benemerita Universidad Autonoma de Puebla, 7200 Puebla (Mexico) and Universidad Autonoma del Estado de Mexico (Mexico)]. E-mail: celso1@hotmail.com; Belyaeva, T.L. [Universidad Autonoma del Estado de Mexico (Mexico); Serkin, V.N. [Benemerita Universidad Autonoma de Puebla, 7200 Puebla (Mexico)
2007-09-01
The dynamics of nonlinear solitary waves is studied in the framework of the nonlinear Schroedinger equation model with time-dependent harmonic oscillator potential. The model allows one to analyse on general basis a variety of nonlinear phenomena appearing both in Bose-Einstein condensate, condensed matter physics, nonlinear optics, and biophysics. The soliton parametric resonance is investigated by using two complementary methods: the adiabatic perturbation theory and direct numerical experiments. Conditions for reversible and irreversible denaturation of soliton bound states are also considered.
Theoretical modeling of zircon's crystal morphology according to data of atomistic calculations
Gromalova, Natalia; Nikishaeva, Nadezhda; Eremin, Nikolay
2017-04-01
Zircon is an essential mineral that is used in the U-Pb dating. Moreover, zircon is highly resistant to radioactive exposure. It is of great interest in solving both fundamental and applied problems associated with the isolation of high-level radioactive waste. There is significant progress in forecasting of the most energetically favorable crystal structures at the present time. Unfortunately, the theoretical forecast of crystal morphology at high technological level is under-explored nowadays, though the estimation of crystal equilibrium habit is extremely important in studying the physical and chemical properties of new materials. For the first time, the thesis about relation of the equilibrium shape of a crystal with its crystal structure was put forward in the works by O.Brave. According to it, the idealized habit is determined in the simplest case by a correspondence with the reticular densities Rhkl of individual faces. This approach, along with all subsequent corrections, does not take into account the nature of atoms and the specific features of the chemical bond in crystals. The atomistic calculations of crystal surfaces are commonly performed using the energetic characteristics of faces, namely, the surface energy (Esurf), which is a measure of the thermodynamic stability of the crystal face. The stable crystal faces are characterized by small positive values of Esurf. As we know from our previous research (Gromalova et al.,2015) one of the constitutive factors affecting the value of the surface energy in calculations is a choice of potentials model. In this regard, we studied several sets of parameters of atomistic interatomic potentials optimized previously. As the first test model («Zircon 1») were used sets of interatomic potentials of interaction Zr-O, Si-O and O-O in the form of Buckingham potentials. To improve playback properties of zircon additionally used Morse potential for a couple of Zr-Si, as well as the three-particle angular harmonic
Energy Technology Data Exchange (ETDEWEB)
Doyle, Paul; Burke, Orla; Phang, Willian [ESB International (Ireland)
2010-11-15
Due to extending of a big industrial plant, with the exchange of synchronous motors of 2 MW for asynchronous of 4 MW, the impacts of the increase in load and the introduction of capacitors to provide the reactive power lost with the removal of synchronous motors were evaluated, as contribution for the current harmonics and voltage in the plant. The possible resonances and the use of the capacitors as filters were also evaluated.
Directory of Open Access Journals (Sweden)
P. A. Deymier
2016-12-01
Full Text Available We illustrate the concept of geometric phase in the case of two prototypical elastic systems, namely the one-dimensional harmonic oscillator and a one-dimensional binary superlattice. We demonstrate formally the relationship between the variation of the geometric phase in the spectral and wave number domains and the parallel transport of a vector field along paths on curved manifolds possessing helicoidal twists which exhibit non-conventional topology.
Model of Cu-Al-Fe-Ni Bronze Crystallization
Directory of Open Access Journals (Sweden)
Pisarek B. P.
2013-09-01
Full Text Available According to the analysis of the current state of the knowledge shows that there is little information on the process of phase transformations that occur during the cooling Cu-Al-Fe-Ni hypo-eutectoid bronzes with additions of Cr, Mo and/or W, made additions individually or together, for the determination of: the type of crystallizing phases, crystallizing phases, order and place of their nucleation. On the basis of recorded using thermal and derivative analysis of thermal effects phases crystallization or their systems, analysis of the microstructure formed during crystallization - observed on the metallographic specimen casting ATD10-PŁ probe, analysis of the existing phase equilibrium diagrams forming elements tested Cu-Al-Fe-Ni bronze, with additions of Cr, Mo, W and/or Si developed an original model of crystallization and phase transformation in the solid state, the casting of high quality Cu-Al-Fe-Ni bronze comprising: crystallizing type phase, crystallizing phase sequence, place of nucleation.
Crystal Structure of a Model Spider Silk Peptide
Chen, Shujun; Gido, Samuel; Valluzzi, Regina; Kaplan, David
2001-03-01
Crystallization study on a novel model silk peptide has been carried out using optical microscopy, AFM, TEM and electron diffraction. The sequence of the peptide, (E)5(GDVGGAGATGGS)2(E)5, is based on the GXYGGZ motif in the less repetitive amorphous blocks of Nephila clavipes spider dragline silk. When the peptide was crystallized out of aqueous solution, spherulites as well as dendritic crystals on the order of several to tens of microns in diameter were observed under polarizing optical microscope, depending on drying speed, volume of the droplet and concentration. The same crystals were collected and sonicated in methanol, a non-solvent, to yield individual crystals that were later examined in the electron microscope. Regular-shaped lamellar crystals of micron size were observed in the TEM. The lamellar thickness as determined by Pt/Pd shadowing and AFM is 50 Å. Selected area electron diffraction showed single crystal diffraction patterns indicating a possible orthorhombic unit cell of 9.91 x 5.57 x 20.40 Å.
Directory of Open Access Journals (Sweden)
Kalamatiev Todor
2014-01-01
Full Text Available The European integration process accompanied by the harmonization of the EU member states' legislation will inevitably lead to the establishment of a European social model which has a 'sui generis' legal nature. European social model forms a part of the common legal heritage of the European countries and it can be defined as a system of values that include democracy and individual rights, free collective bargaining, market economy, equal opportunities for all, and social protection and solidarity. Subject of analysis in this paper are both, the essential components of the European social model such as: the social 'acquis communautaire' and the European industrial relations. The social 'acquis communautaire' is an integral part of the general 'acquis communautaire' and it encompasses the regulations arising from the primary and secondary labour law legislation of the EU, decisions of the European Court of Justice and other legal measures of the European Union with a binding or non-binding legal nature. European industrial relations encompass the key features of the European trade union models as well as the types of social dialogue in different EU member states. This paper pays attention to a profound elaboration of the harmonization of two EU labour law directives with the Macedonian employment legislation. The first Directive (Directive 91/533/EEC of 14 October 1991 on an employers' obligation to inform employees of the conditions applicable to the contract or employment relationship may be classified in the field of individual employment relations, while the second one (Directive 2002/14/EC of 11 March 2002 establishing a general framework for informing and consulting employees in the European Community can be subsumed within the field of collective employment relations. Finally, the authors illustrate the advantages and disadvantages of the Macedonian labour legislation in the process of harmonization with the relevant EU directives
Directory of Open Access Journals (Sweden)
Saeid Haghbin
2014-10-01
Full Text Available Closed-form analytical formulas are provided to calculate the dc bus harmonics of a three-phase sinusoidal pulse width modulation (SPWM inverter. The harmonic analysis is performed by using a double Fourier series approach to determine the dc bus current frequency spectrum. For an arbitrary modulation index and load power factor, the full harmonic components of the inverter dc side current are calculated. Based on the developed analytical model, an equivalent circuit is proposed for the inverter harmonic analysis towards the dc bus. Moreover, the impacts of line harmonics and zero sequence injection in controller towards the dc bus are presented. The results show that the 5th and 7th ac line harmonics on the dc side current is appearance of the 6th harmonic in the dc side. The impact of zero sequence injection to the controller on the dc side is negligible. In addition to analytical formulation, different simulations and extensive measurements performed which the results verified the presented analytical framework.
On the formulation of a crystal plasticity model.
Energy Technology Data Exchange (ETDEWEB)
Marin, Esteban B.
2006-08-01
This report presents the formulation of a crystal elasto-viscoplastic model and the corresponding integration scheme. The model is suitable to represent the isothermal, anisotropic, large deformation of polycrystalline metals. The formulation is an extension of a rigid viscoplastic model to account for elasticity effects, and incorporates a number of changes with respect to a previous formulation [Marin & Dawson, 1998]. This extension is formally derived using the well-known multiplicative decomposition of the deformation gradient into an elastic and plastic components, where the elastic part is additionally decomposed into the elastic stretch V{sup e} and the proper orthogonal R{sup e} tensors. The constitutive equations are written in the intermediate, stress-free configuration obtained by unloading the deformed crystal through the elastic stretch V{sup e-}. The model is framed in a thermodynamic setting, and developed initially for large elastic strains. The crystal equations are then specialized to the case of small elastic strains, an assumption typically valid for metals. The developed integration scheme is implicit and proceeds by separating the spherical and deviatoric crystal responses. An ''approximate'' algorithmic material moduli is also derived for applications in implicit numerical codes. The model equations and their integration procedure have been implemented in both a material point simulator and a commercial finite element code. Both implementations are validated by solving a number of examples involving aggregates of either face centered cubic (FCC) or hexagonal close-packed (HCP) crystals subjected to different loading paths.
Blaclard, G; Lehe, R; Vay, J L
2016-01-01
With the advent of PW class lasers, the very large laser intensities attainable on-target should enable the production of intense high order Doppler harmonics from relativistic laser-plasma mirrors interactions. At present, the modeling of these harmonics with Particle-In-Cell (PIC) codes is extremely challenging as it implies an accurate description of tens of harmonic orders on a a broad range of angles. In particular, we show here that standard Finite Difference Time Domain (FDTD) Maxwell solvers used in most PIC codes partly fail to model Doppler harmonic generation because they induce numerical dispersion of electromagnetic waves in vacuum which is responsible for a spurious angular deviation of harmonic beams. This effect was extensively studied and a simple toy-model based on Snell-Descartes law was developed that allows us to finely predict the angular deviation of harmonics depending on the spatio-temporal resolution and the Maxwell solver used in the simulations. Our model demonstrates that the miti...
Lastre, Arlys; Torriente, Ives; Méndez, Erik F.; Cordovés, Alexis
2017-06-01
In the present investigation, the authors propose a conceptual model for the analysis and the decision making of the corrective models to use in the mitigation of the harmonic distortion. The authors considered the setting of conventional models, and such adaptive models like the filters incorporation to networks neuronal artificial (RNA's) for the mitigating effect. In addition to the present work is a showing of the experimental model that learns by means of a flowchart denoting the need to use artificial intelligence skills for the exposition of the proposed model. The other aspect considered and analyzed are the adaptability and usage of the same, considering a local reference of the laws and lineaments of energy quality that demands the Department of Electricity and Energy Renewable (MEER) of Equator.
Bennett, Charles L [Livermore, CA
2009-10-20
A high efficiency harmonic engine based on a resonantly reciprocating piston expander that extracts work from heat and pressurizes working fluid in a reciprocating piston compressor. The engine preferably includes harmonic oscillator valves capable of oscillating at a resonant frequency for controlling the flow of working fluid into and out of the expander, and also preferably includes a shunt line connecting an expansion chamber of the expander to a buffer chamber of the expander for minimizing pressure variations in the fluidic circuit of the engine. The engine is especially designed to operate with very high temperature input to the expander and very low temperature input to the compressor, to produce very high thermal conversion efficiency.
Slenders, Eli; vandeVen, Martin; Hooyberghs, Jef; Ameloot, Marcel
2015-07-15
We present a general analytical model for the intensity fluctuation autocorrelation function for second and third harmonic generating point scatterers. Expressions are derived for a stationary laser beam and for scanning beam configurations for specific correlation methodologies. We discuss free translational diffusion in both three and two dimensions. At low particle concentrations, the expressions for fluorescence are retrieved, while at high particle concentrations a rescaling of the function parameters is required for a stationary illumination beam, provided that the phase shift per unit length of the beam equals zero.
Trasi, N. S.; de Oliveira, C. R. E.; Haigh, J. D.
2004-11-01
We present a new numerical radiative transfer model for application to solar radiation transport in three-dimensional (3D) cloudy atmospheres. The code uses the finite element-spherical harmonics (FE- PN) approximation to solve the second-order even-parity form of the transport equation. It is validated by comparison with solutions from two well-established, deterministic radiative transfer models, the one-dimensional (1D) DISORT code and the spherical harmonics discrete ordinates method (SHDOM). The cases solved show generally good agreement, but also reveal some differences. EVEn-parity Neutral particle Transport (EVENT) is very efficient at performing 1D calculations quickly and, even for quite high angular resolutions, is faster. EVENT also has a competitive speed for the simpler, less-heterogeneous multidimensional cases but it is slower than SHDOM for more variable cases. However, there is significant potential to improve the performance of EVENT; it has not yet been optimised for speed and, as such, is not a finished product. Even as it is, EVENT could be used to produce fast, lower-resolution estimates for applications where this would be sufficient, or at lower-spatial resolutions with partial homogenisation. Another difference between the models is that the SHDOM algorithm is designed for small-scale inhomogeneous cloud fields in which the grid spacing is comparable to the mean free path. Problems arise from the use of larger grid cell optical depths, with an increase in the number of iterations required and a lack of flux conservation. Neither of the models is specifically constrained to conserve flux, but the conservation of flux gives an indication of the accuracy of the solution. Increasing the spatial and angular resolution can improve the accuracy but this is not always possible for very large 3D scenes. The grid-point method of property definition in SHDOM means that it performs best for cases with a continuous variation in extinction as this
Czochralski silicon crystal growth: Modeling and simulation study
Javidi, Massoud
Czochralski (CZ) crystal growth process is a widely used technique in the manufacturing of silicon crystals and other semiconductor materials such as germanium (Ge) and gallium arsenide (GaAs). The ultimate goal for the Integrated Circuit (IC) industry is to have the highest quality substrate. There is a huge interest to manipulate the thermal field in both the melt and crystal and control the melt convection and crystal-annealing rate in order to reduce growth striations, impurity and dopant inhomogeneity concentrations, excess point defects generation at interface, and micro defects nucleation and growth within the growing crystal. The objective of this investigation has been to facilitate and spearhead the development of a simple/efficient simulation tool for the accurate prediction of global thermal and flow fields and the melt-crystal interface position in the CZ process. The numerical algorithm employs a rectangular (fixed or non-uniform) mesh for enhanced computational efficiency and an enthalpy-based technique for interface tracking. Turbulent flow in the melt is accounted for by utilizing a K-ε model. Radiative heat transfer is modeled in a lumped parameter sense without appreciably compromising on solution accuracy to further allow for CPU times savings. The simulation tool is validated in a number of benchmark flows such as Wheeler's problem. For the CZ crystal growth process, an entire growth cycle has been computed and reliable predictions for the evolution of interface position, and flow/thermal field characteristics have been obtained. The enhanced CPU efficiency of the approach developed here could help integrate it into on-line control strategies.
Phase-field-crystal model for fcc ordering
Wu, Kuo-An; Adland, Ari; Karma, Alain
2010-06-01
We develop and analyze a two-mode phase-field-crystal model to describe fcc ordering. The model is formulated by coupling two different sets of crystal density waves corresponding to ⟨111⟩ and ⟨200⟩ reciprocal lattice vectors, which are chosen to form triads so as to produce a simple free-energy landscape with coexistence of crystal and liquid phases. The feasibility of the approach is demonstrated with numerical examples of polycrystalline and (111) twin growth. We use a two-mode amplitude expansion to characterize analytically the free-energy landscape of the model, identifying parameter ranges where fcc is stable or metastable with respect to bcc. In addition, we derive analytical expressions for the elastic constants for both fcc and bcc. Those expressions show that a nonvanishing amplitude of [200] density waves is essential to obtain mechanically stable fcc crystals with a nonvanishing tetragonal shear modulus (C11-C12)/2 . We determine the model parameters for specific materials by fitting the peak liquid structure factor properties and solid-density wave amplitudes following the approach developed for bcc [K.-A. Wu and A. Karma, Phys. Rev. B 76, 184107 (2007)]. This procedure yields reasonable predictions of elastic constants for both bcc Fe and fcc Ni using input parameters from molecular dynamics simulations. The application of the model to two-dimensional square lattices is also briefly examined.
Intermittent dislocation density fluctuations in crystal plasticity from a phase-field crystal model
DEFF Research Database (Denmark)
Tarp, Jens M.; Angheluta, Luiza; Mathiesen, Joachim
2014-01-01
Plastic deformation mediated by collective dislocation dynamics is investigated in the two-dimensional phase-field crystal model of sheared single crystals. We find that intermittent fluctuations in the dislocation population number accompany bursts in the plastic strain-rate fluctuations....... Dislocation number fluctuations exhibit a power-law spectral density 1/f2 at high frequencies f. The probability distribution of number fluctuations becomes bimodal at low driving rates corresponding to a scenario where low density of defects alternates at irregular times with high populations of defects. We...... propose a simple stochastic model of dislocation reaction kinetics that is able to capture these statistical properties of the dislocation density fluctuations as a function of shear rate....
Tarp, Jens M; Angheluta, Luiza; Mathiesen, Joachim; Goldenfeld, Nigel
2014-12-31
Plastic deformation mediated by collective dislocation dynamics is investigated in the two-dimensional phase-field crystal model of sheared single crystals. We find that intermittent fluctuations in the dislocation population number accompany bursts in the plastic strain-rate fluctuations. Dislocation number fluctuations exhibit a power-law spectral density 1/f2 at high frequencies f. The probability distribution of number fluctuations becomes bimodal at low driving rates corresponding to a scenario where low density of defects alternates at irregular times with high populations of defects. We propose a simple stochastic model of dislocation reaction kinetics that is able to capture these statistical properties of the dislocation density fluctuations as a function of shear rate.
Ikuma, Takeshi; Kunduk, Melda; McWhorter, Andrew J.
2014-01-01
Purpose: The model-based quantitative analysis of high-speed videoendoscopy (HSV) data at a low frame rate of 2,000 frames per second was assessed for its clinical adequacy. Stepwise regression was employed to evaluate the HSV parameters using harmonic models and their relationships to the Voice Handicap Index (VHI). Also, the model-based HSV…
Discrete dislocation plasticity modeling of short cracks in single crystals
Deshpande, VS; Needleman, A; Van der Giessen, E
2003-01-01
The mode-I crack growth behavior of geometrically similar edge-cracked single crystal specimens of varying size subject to both monotonic and cyclic axial loading is analyzed using discrete dislocation dynamics. Plastic deformation is modeled through the motion of edge dislocations in an elastic
Modelling of transport phenomena and defects in crystal growth ...
Indian Academy of Sciences (India)
... transport and defect phenomena involoved in the growth process with the ultimate aim of integrating them into a comprehensive numerical model. The sources of dislocation nucleation in the growing crystal are discussed, and the propagation and multiplication of these under the action of thermal stresses is discussed.
A three-body force model for the harmonic and anharmonic oscillator
Directory of Open Access Journals (Sweden)
A. A. Rajabi
2005-06-01
Full Text Available We present a mathematical method to describe motion of a system based on 3 identical body forces. The 3-body forces are more easily introduced and treated within the hyperspherical harmonics. We have obtained an exact solution of the radial Schrödinger equation for a 3- body system in three dimensions. The interact potential V is assumed to depend on the hyperradius X only where X is a function of the Jacobi relative coordinates ρ and λ which are functions of the three identical particles, relative positions r12 , r23 and r31 . This method has been extensively used in nuclear and molecular physics. This work is interesting to those who are studying hadronic and bosonics physics and problems consisting three - body systems.
Bennett, Charles L.; Sewall, Noel; Boroa, Carl
2014-08-19
An engine based on a reciprocating piston engine that extracts work from pressurized working fluid. The engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into of the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. Upon releasing the inlet valve the inlet valve head undergoes a single oscillation past the equilibrium positio to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. Protrusions carried either by the inlet valve head or piston head are used to bump open the inlet valve from the closed position and initiate the single oscillation of the inlet valve head, and protrusions carried either by the outlet valve head or piston head are used to close the outlet valve ahead of the bump opening of the inlet valve.
Wang, Cheng; He, Yue; Lu, Bin; Jiang, Jun; Miao, Li; Deng, Xian-Jin; Xiong, Yong-zhong; Zhang, Jian
2017-11-01
This paper presents a sub-harmonic mixer at 340 GHz based on anti-parallel Schottky diodes (SBDs). Intrinsic resonances in low-pass hammer-head filter have been adopted to enhance the isolation for different harmonic components, while greatly minimizing the transmission loss. The application of new DC grounding structure, impedance matching structure, and suspended micro-strip mitigates the negative influences of fabrication errors from metal cavity, quartz substrate, and micro-assembly. An improved lumped element equivalent circuit model of SBDs guarantees the accuracy of simulation, which takes current-voltage (I/V) behavior, capacitance-voltage (C/V) behavior, carrier velocity saturation, DC series resistor, plasma resonance, skin effect, and four kinds of noise generation mechanisms into consideration thoroughly. The measurement indicates that with local oscillating signal of 2 mW, the lowest double sideband conversion loss is 5.5 dB at 339 GHz; the corresponding DSB noise temperature is 757 K. The 3 dB bandwidth of conversion loss is 50 GHz from 317 to 367 GHz.
Microwave Diffraction Techniques from Macroscopic Crystal Models
Murray, William Henry
1974-01-01
Discusses the construction of a diffractometer table and four microwave models which are built of styrofoam balls with implanted metallic reflecting spheres and designed to simulate the structures of carbon (graphite structure), sodium chloride, tin oxide, and palladium oxide. Included are samples of Bragg patterns and computer-analysis results.…
Lumped model for rotational modes in phononic crystals
Peng, Pai
2012-10-16
We present a lumped model for the rotational modes induced by the rotational motion of individual scatterers in two-dimensional phononic crystals comprised of square arrays of solid cylindrical scatterers in solid hosts. The model provides a physical interpretation of the origin of the rotational modes, reveals the important role played by the rotational motion in determining the band structure, and reproduces the dispersion relations in a certain range. The model increases the possibilities of manipulating wave propagation in phononic crystals. In particular, expressions derived from the model for eigenfrequencies at high symmetry points unambiguously predict the presence of a new type of Dirac-like cone at the Brillouin center, which is found to be the result of accidental degeneracy of the rotational and dipolar modes.
Helson, Henry
2010-01-01
This second edition has been enlarged and considerably rewritten. Among the new topics are infinite product spaces with applications to probability, disintegration of measures on product spaces, positive definite functions on the line, and additional information about Weyl's theorems on equidistribution. Topics that have continued from the first edition include Minkowski's theorem, measures with bounded powers, idempotent measures, spectral sets of bounded functions and a theorem of Szego, and the Wiener Tauberian theorem. Readers of the book should have studied the Lebesgue integral, the elementary theory of analytic and harmonic functions, and the basic theory of Banach spaces. The treatment is classical and as simple as possible. This is an instructional book, not a treatise. Mathematics students interested in analysis will find here what they need to know about Fourier analysis. Physicists and others can use the book as a reference for more advanced topics.
Models of protein-ligand crystal structures: trust, but verify
Deller, Marc C.; Rupp, Bernhard
2015-09-01
X-ray crystallography provides the most accurate models of protein-ligand structures. These models serve as the foundation of many computational methods including structure prediction, molecular modelling, and structure-based drug design. The success of these computational methods ultimately depends on the quality of the underlying protein-ligand models. X-ray crystallography offers the unparalleled advantage of a clear mathematical formalism relating the experimental data to the protein-ligand model. In the case of X-ray crystallography, the primary experimental evidence is the electron density of the molecules forming the crystal. The first step in the generation of an accurate and precise crystallographic model is the interpretation of the electron density of the crystal, typically carried out by construction of an atomic model. The atomic model must then be validated for fit to the experimental electron density and also for agreement with prior expectations of stereochemistry. Stringent validation of protein-ligand models has become possible as a result of the mandatory deposition of primary diffraction data, and many computational tools are now available to aid in the validation process. Validation of protein-ligand complexes has revealed some instances of overenthusiastic interpretation of ligand density. Fundamental concepts and metrics of protein-ligand quality validation are discussed and we highlight software tools to assist in this process. It is essential that end users select high quality protein-ligand models for their computational and biological studies, and we provide an overview of how this can be achieved.
Iwamoto, Mitsumasa; Manaka, Takaaki; Taguchi, Dai
2014-10-01
By probing dielectric polarization originating from dipoles and electrons in materials, we can study dynamical carrier behaviors in materials and also in devices. Maxwell displacement current (MDC) measurement allows us to directly probe orientational dipolar motion in monolayers, while electric-field-induced optical second-harmonic generation (EFISHG) measurement allows dynamical electron and hole transport in solids to be probed directly. By probing nonlinear polarization induced in solids by coupling with incident electromagnetic waves of laser beam and dc electric field that originate from moving carriers, long-range carrier motion is visualized. Experiments using a time-resolved EFISHG technique reveal carrier transfer in organic devices such as organic field-effect transistors, organic light-emitting diodes, organic memory devices, and organic solar cells, and thus enable us to model the carrier transport mechanism. We anticipate that this novel technique using EFISHG can be a powerful tool for studying carrier behaviors in organic devices as well as in organic materials.
Second Harmonic of Laser Radiation for IR-Range in Mixed AgGa0.6In0.4Se2 Crystals
Directory of Open Access Journals (Sweden)
Rena J. Kasumova
2014-01-01
Full Text Available The results of investigations of the influence of different parameters on conversion efficiency in mixed AgGa0.6In0.4Se2 crystal in conditions of existing experiments are cited. The angular dispersion coefficients for three versions of crystal AgGaxIn1-xSe2, differing by a content of indium, have been calculated. A comparison was made of the obtained results on conversion efficiency with analogous results in case of other crystals and with corresponding experimentally measured values. The applied analytical method makes it possible to calculate the optimum parameters of both crystal-converter and a source of radiation for conditions of uncritical phase matching in the concrete experiment.
Phononic High Harmonic Generation
Ganesan, Adarsh; Do, Cuong; Seshia, Ashwin A.
2016-01-01
This paper reports the first experimental evidence for phononic low-order to high-order harmonic conversion leading to high harmonic generation. Similar to parametric resonance, phononic high harmonic generation is also mediated by a threshold dependent instability of a driven phonon mode. Once the threshold for instability is met, a cascade of harmonic generation processes is triggered. Firstly, the up-conversion of first harmonic phonons into second harmonic phonons is established. Subseque...
X-ray wavefront modeling of Bragg diffraction from crystals
Sutter, John P.
2011-09-01
The diffraction of an X-ray wavefront from a slightly distorted crystal can be modeled by the Takagi-Taupin theory, an extension of the well-known dynamical diffraction theory for perfect crystals. Maxwell's equations applied to a perturbed periodic medium yield two coupled differential equations in the incident and diffracted amplitude. These equations are discretized for numerical calculation into the determination of the two amplitudes on the points of an integration mesh, beginning with the incident amplitudes at the crystal's top surface. The result is a set of diffracted amplitudes on the top surface (in the Bragg geometry) or the bottom surface (in the Laue geometry), forming a wavefront that in turn can be propagated through free space using the Fresnel- Huygens equations. The performance of the Diamond Light Source I20 dispersive spectrometer has here been simulated using this method. Methods are shown for transforming displacements calculated by finite element analysis into local lattice distortions, and for efficiently performing 3-D linear interpolations from these onto the Takagi-Taupin integration mesh, allowing this method to be extended to crystals under thermal load or novel mechanical bender designs.
Kaminski, Adam
2017-08-22
A method and apparatus to generate harmonically related laser wavelengths includes a pair of lenses at opposing faces of a non-linear optical material. The lenses are configured to promote incoming and outgoing beams to be normal to each outer lens surface over a range of acceptance angles of the incoming laser beam. This reduces reflection loss for higher efficiency operation. Additionally, the lenses allow a wider range of wavelengths for lasers for more universal application. Examples of the lenses include plano-cylindrical and plano-spherical form factors.
Mathematical modeling and numerical simulation of Czochralski Crystal Growth
Energy Technology Data Exchange (ETDEWEB)
Jaervinen, J.; Nieminen, R. [Center for Scientific Computing, Espoo (Finland)
1996-12-31
A detailed mathematical model and numerical simulation tools based on the SUPG Finite Element Method for the Czochralski crystal growth has been developed. In this presentation the mathematical modeling and numerical simulation of the melt flow and the temperature distribution in a rotationally symmetric crystal growth environment is investigated. The temperature distribution and the position of the free boundary between the solid and liquid phases are solved by using the Enthalpy method. Heat inside of the Czochralski furnace is transferred by radiation, conduction and convection. The melt flow is governed by the incompressible Navier-Stokes equations coupled with the enthalpy equation. The melt flow is numerically demonstrated and the temperature distribution in the whole Czochralski furnace. (author)
Icosahedral symmetry described by an incommensurately modulated crystal structure model
DEFF Research Database (Denmark)
Wolny, Janusz; Lebech, Bente
1986-01-01
A crystal structure model of an incommensurately modulated structure is presented. Although six different reciprocal vectors are used to describe the model, all calculations are done in three dimensions making calculation of the real-space structure trivial. Using this model, it is shown that both...... the positions of the bragg reflections and information about the relative intensities of these reflections are in full accordance with the diffraction patterns reported for microcrystals of the rapidly quenched Al86Mn14 alloy. It is also shown that at least the local structure possesses full icosahedral...
Numerical methods for modeling photonic-crystal VCSELs
DEFF Research Database (Denmark)
Dems, Maciej; Chung, Il-Sug; Nyakas, Peter
2010-01-01
We show comparison of four different numerical methods for simulating Photonic-Crystal (PC) VCSELs. We present the theoretical basis behind each method and analyze the differences by studying a benchmark VCSEL structure, where the PC structure penetrates all VCSEL layers, the entire top-mirror DBR......, a fraction of the top-mirror DBR or just the VCSEL cavity. The different models are evaluated by comparing the predicted resonance wavelengths and threshold gains for different hole diameters and pitches of the PC. The agreement between the models is relatively good, except for one model, which corresponds...
Orbifold melting crystal models and reductions of Toda hierarchy
Takasaki, Kanehisa
2015-05-01
Orbifold generalizations of the ordinary and modified melting crystal models are introduced. They are labelled by a pair a,b of positive integers, and geometrically related to {{{Z}}a}× {{{Z}}b} orbifolds of local {C}{{{P}}1} geometry of the {O}(0)\\oplus {O}(-2) and {O}(-1)\\oplus {O}(-1) types. The partition functions have a fermionic expression in terms of charged free fermions. With the aid of shift symmetries in a fermionic realization of the quantum torus algebra, one can convert these partition functions to tau functions of the 2D Toda hierarchy. The powers {{L}a},{{\\bar{L}}-b} of the associated Lax operators turn out to take a special factorized form that defines a reduction of the 2D Toda hierarchy. The reduced integrable hierarchy for the orbifold version of the ordinary melting crystal model is the bi-graded Toda hierarchy of bi-degree (a,b). That of the orbifold version of the modified melting crystal model is the rational reduction of bi-degree (a,b). This result seems to be in accord with recent work of Brini et al on a mirror description of the genus-zero Gromov-Witten theory on a {{{Z}}a}× {{{Z}}b} orbifold of the resolved conifold.
Modeling the Growth Rates of Tetragonal Lysozyme Crystal Faces
Li, Meirong; Nadarajah, Arunan; Pusey, Marc L.
1998-01-01
with respect to its concentration at saturation in order to apply growth rate models to this process. The measured growth rates were then compared with the predicted ones from several dislocation and 2D nucleation growth models, employing tetramer and octamer growth units in polydisperse solutions and monomer units in monodisperse solutions. For the (110) face, the calculations consistently showed that the measured growth rates followed the expected model relations with octamer growth units. For the (101) face, it is not possible to obtain a clear agreement between the predicted and measured growth rates for a single growth unit as done for the (110) face. However, the calculations do indicate that the average size of the growth unit is between a tetramer and an octamer. This suggests that tetramers, octamers and other intermediate size growth units all participate in the growth process for this face. These calculations show that it is possible to model the macroscopic protein crystal growth rates if the molecular level processes can be account for, particularly protein aggregation processes in the bulk solution. Our recent investigations of tetragonal lysozyme crystals employing high resolution atomic force microscopy scans have further confirmed the growth of these crystals by aggregate growth units corresponding to 4(sub 3) helices.
Oettel, M; Dorosz, S; Berghoff, M; Nestler, B; Schilling, T
2012-08-01
In materials science the phase-field crystal approach has become popular to model crystallization processes. Phase-field crystal models are in essence Landau-Ginzburg-type models, which should be derivable from the underlying microscopic description of the system in question. We present a study on classical density functional theory in three stages of approximation leading to a specific phase-field crystal model, and we discuss the limits of applicability of the models that result from these approximations. As a test system we have chosen the three-dimensional suspension of monodisperse hard spheres. The levels of density functional theory that we discuss are fundamental measure theory, a second-order Taylor expansion thereof, and a minimal phase-field crystal model. We have computed coexistence densities, vacancy concentrations in the crystalline phase, interfacial tensions, and interfacial order parameter profiles, and we compare these quantities to simulation results. We also suggest a procedure to fit the free parameters of the phase-field crystal model. Thereby it turns out that the order parameter of the phase-field crystal model is more consistent with a smeared density field (shifted and rescaled) than with the shifted and rescaled density itself. In brief, we conclude that fundamental measure theory is very accurate and can serve as a benchmark for the other theories. Taylor expansion strongly affects free energies, surface tensions, and vacancy concentrations. Furthermore it is phenomenologically misleading to interpret the phase-field crystal model as stemming directly from Taylor-expanded density functional theory.
The effect of harmonized emissions on aerosol properties in global models – an AeroCom experiment
Directory of Open Access Journals (Sweden)
C. Textor
2007-08-01
Full Text Available The effects of unified aerosol sources on global aerosol fields simulated by different models are examined in this paper. We compare results from two AeroCom experiments, one with different (ExpA and one with unified emissions, injection heights, and particle sizes at the source (ExpB. Surprisingly, harmonization of aerosol sources has only a small impact on the simulated inter-model diversity of the global aerosol burden, and consequently global optical properties, as the results are largely controlled by model-specific transport, removal, chemistry (leading to the formation of secondary aerosols and parameterizations of aerosol microphysics (e.g., the split between deposition pathways and to a lesser extent by the spatial and temporal distributions of the (precursor emissions.
The burdens of black carbon and especially sea salt become more coherent in ExpB only, because the large ExpA diversities for these two species were caused by a few outliers. The experiment also showed that despite prescribing emission fluxes and size distributions, ambiguities in the implementation in individual models can lead to substantial differences.
These results indicate the need for a better understanding of aerosol life cycles at process level (including spatial dispersal and interaction with meteorological parameters in order to obtain more reliable results from global aerosol simulations. This is particularly important as such model results are used to assess the consequences of specific air pollution abatement strategies.
Madu, B. C.
2012-01-01
The study explored the efficacy of four-step (4-E) learning cycle approach on students understanding of concepts related to Simple Harmonic Motion (SHM). 124 students (63 for experimental group and 61 for control group) participated in the study. The students' views and ideas in simple Harmonic Achievement test were analyzed qualitatively. The…
Energy Technology Data Exchange (ETDEWEB)
Muthu, K. [Department of Chemistry, Annamalai University, Annamalainagar-608 002 (India); Bhagavannarayana, G. [Crystal Growth and X-ray Analysis Activity, Council of Scientific and Industrial Research, National Physical Laboratory, New Delhi-110 012 (India); Meenakshisundaram, S.P., E-mail: aumats2009@gmail.com [Department of Chemistry, Annamalai University, Annamalainagar-608 002 (India)
2013-01-25
Highlights: Black-Right-Pointing-Pointer A small quantity incorporation of Mg(II)- enhances the SHG efficiency of ZTS. Black-Right-Pointing-Pointer Crystal stress is observed. Black-Right-Pointing-Pointer Structure of Mg(II)-incorporated ZTS is elucidated. Black-Right-Pointing-Pointer Crystalline perfection is evaluated by HRXRD. - Abstract: Single crystals of Mg(II)-incorporated tris(thiourea)Zn(II) sulfate (MZTS) have been grown from aqueous solution at room temperature by slow evaporation solution growth technique. The incorporation of Mg(II)- into the crystalline lattice was well confirmed by energy dispersive X-ray spectroscopy (EDS) and by single crystal X-ray diffraction technique. The reduction in the intensities observed in powder X-ray diffraction patterns of doped specimen and slight shifts in vibrational frequencies in FT-IR indicate the lattice stress as a result of doping. Thermal studies reveal the purity of the material and no decomposition is observed up to the melting point. High transmittance is observed in the visible region and the band gap energy is estimated by Kubelka-Munk algorithm. Surface morphology of doped material was observed by scanning electron microscopy (SEM). Decreased crystalline perfection by doping observed by high-resolution X-ray diffraction (HRXRD) analysis is justified by the crystal stress. Even a small quantity incorporation of Mg(II)- enhances the SHG efficiency significantly. The as-grown crystal is further characterized by microhardness and dielectric studies.
Energy Technology Data Exchange (ETDEWEB)
Park, Byung Heung [Korea National University of Transportation, Chungju (Korea, Republic of); Jeong, Seong-Uk [Korea Institute of Energy Research, Daejeon (Korea, Republic of); Kang, Jeong Won [Korea University, Seoul (Korea, Republic of)
2014-12-15
SI process is a thermochemical process producing hydrogen by decomposing water while recycling sulfur and iodine. Various technologies have been developed to improve the efficiency on Section III of SI process, where iodine is separated and recycled. EED(electro-electrodialysis) could increase the efficiency of Section III without additional chemical compounds but a substantial amount of I{sub 2} from a process stream is loaded on EED. In order to reduce the load, a crystallization technology prior to EED is considered as an I{sub 2} removal process. In this work, I{sub 2} particle sinking behavior was modeled to secure basic data for designing an I{sub 2} crystallizer applied to I{sub 2}-saturated HI{sub x} solutions. The composition of HI{sub x} solution was determined by thermodynamic UVa model and correlation equations and pure properties were used to evaluate the solution properties. A multiphysics computational tool was utilized to calculate particle sinking velocity changes with respect to I{sub 2} particle radius and temperature. The terminal velocity of an I{sub 2} particle was estimated around 0.5 m/s under considered radius (1.0 to 2.5 mm) and temperature (10 to 50 .deg. C) ranges and it was analyzed that the velocity is more dependent on the solution density than the solution viscosity.
Neutron total cross section calculation within the framework of quasi-harmonic approximation
DEFF Research Database (Denmark)
Cai, Xiao Xiao; Klinkby, Esben Bryndt
2017-01-01
The accuracy of neutron scattering cross sections is the gauge for the realistic outcome of a neutron transport simulation. To improve the traditional harmonic physics model used in such simulations, we revisit the slow neutron transport theory in crystalline materials and aim to develop a unified...... model that has good performance for neutron transport problems in crystals in a wide range of temperatures and pressures. The quasi-harmonic approximation (QHA) correlates phonon evolution explicitly with unit cell volume. Therefore, it is capable of evaluating a variety of material properties at finite...
Implementation and application of a gradient enhanced crystal plasticity model
Soyarslan, C.; Perdahcıoǧlu, E. S.; Aşık, E. E.; van den Boogaard, A. H.; Bargmann, S.
2017-10-01
A rate-independent crystal plasticity model is implemented in which description of the hardening of the material is given as a function of the total dislocation density. The evolution of statistically stored dislocations (SSDs) is described using a saturating type evolution law. The evolution of geometrically necessary dislocations (GNDs) on the other hand is described using the gradient of the plastic strain tensor in a non-local manner. The gradient of the incremental plastic strain tensor is computed explicitly during an implicit FE simulation after each converged step. Using the plastic strain tensor stored as state variables at each integration point and an efficient numerical algorithm to find the gradients, the GND density is obtained. This results in a weak coupling of the equilibrium solution and the gradient enhancement. The algorithm is applied to an academic test problem which considers growth of a cylindrical void in a single crystal matrix.
Plasticity and dislocation dynamics in a phase field crystal model.
Chan, Pak Yuen; Tsekenis, Georgios; Dantzig, Jonathan; Dahmen, Karin A; Goldenfeld, Nigel
2010-07-02
The critical dynamics of dislocation avalanches in plastic flow is examined using a phase field crystal model. In the model, dislocations are naturally created, without any ad hoc creation rules, by applying a shearing force to the perfectly periodic ground state. These dislocations diffuse, interact and annihilate with one another, forming avalanche events. By data collapsing the event energy probability density function for different shearing rates, a connection to interface depinning dynamics is confirmed. The relevant critical exponents agree with mean field theory predictions.
Pal, J.; Cramer, A.; Grants, I.; Eckert, S.; Gerbeth, G.
2015-12-01
A low temperature liquid metal model of the Czochralski (CZ) crystal growth process is considered experimentally for a high aspect ratio. Temperature fluctuations close to the edge of the model crystal are studied under the action of a rotating magnetic field (RMF) and/or rotation of the model crystal. A rotation of thermal structures is observed which loses its periodicity at sufficiently high strengths of the RMF. This finding is in qualitative agreement with previous findings in Rayleigh-Bénard (RB) cells. Opposing to that more generic case, the remaining amplitude of the temperature fluctuations stays significantly higher. I.e., the suppression of the fluctuations, which are detrimental to the growth of a mono-crystal, is weaker in the model under investigation.
Bovine gallbladder mucin accelerates cholesterol monohydrate crystal growth in model bile.
Afdhal, N H; Niu, N; Gantz, D; Small, D M; Smith, B F
1993-05-01
Gallbladder mucin accelerates cholesterol crystal nucleation, an early step in the pathogenesis of gallstones. To examine the role of gallbladder mucin in postnucleation gallstone maturation, the influence of mucin on cholesterol monohydrate crystal growth was studied in a novel model system. Cholesterol crystals of a uniform size were incubated in model biles at 37 degrees C with varying cholesterol saturation indices. Crystal size was quantitated by measuring the width and length of individual crystals under polarizing light microscopy and calculating average crystal area. Crystal growth was dependent on the degree of cholesterol supersaturation of bile. Bovine gallbladder mucin (0.5-8 mg/mL) accelerated crystal growth in supersaturated model bile in a concentration- and time-dependent fashion compared with control incubations with bovine serum albumin or model bile alone (P < 0.05). Cholesterol crystal growth was accompanied by a progressive decrease in cholesterol saturation and an increase in total cholesterol crystal mass. Crystal growth was also accompanied by a decrease in total crystal number, suggesting net transfer of cholesterol to larger crystals. The acceleration of cholesterol crystal growth by gallbladder mucin may be of pathophysiological importance in the postnucleation maturation of cholesterol gallstones.
A thermomechanical crystal plasticity constitutive model for ultrasonic consolidation
Siddiq, Amir
2012-01-01
We present a micromechanics-based thermomechanical constitutive model to simulate the ultrasonic consolidation process. Model parameters are calibrated using an inverse modeling approach. A comparison of the simulated response and experimental results for uniaxial tests validate and verify the appropriateness of the proposed model. Moreover, simulation results of polycrystalline aluminum using the identified crystal plasticity based material parameters are compared qualitatively with the electron back scattering diffraction (EBSD) results reported in the literature. The validated constitutive model is then used to simulate the ultrasonic consolidation process at sub-micron scale where an effort is exerted to quantify the underlying micromechanisms involved during the ultrasonic consolidation process. © 2011 Elsevier B.V. All rights reserved.
Harmonic Domain Modeling of a Distribution System Using the DIgSILENT PowerFactory Software
DEFF Research Database (Denmark)
Wasilewski, J.; Wiechowski, Wojciech Tomasz; Bak, Claus Leth
The first part of this paper presents the comparison between two models of distribution system created in computer simulation software PowerFactory (PF). Model A is an exciting simplified equivalent model of the distribution system used by Transmission System Operator (TSO) Eltra for balenced load...
Morin, Stéphane; Ahmaïdi, Saïd; Leprêtre, Pierre-Marie
2016-10-01
Positive and negative effects of training induce apparent oscillations of performance, suggesting that the delayed cumulative effects of training on daily performance capacity (DPC) are best fitted by sine waves damped over time. To compare the criterion validity of the impulse-response (IR) model of Banister et al and the damped harmonic oscillation (DHO) model for quantifying the training load (TL)-DPC relationship. Six female professional volleyball players (20.8 ± 2.4 y) were monitored using the session rating of perceived exertion (sRPE) for 9 mo to quantify TL. Countermovement-jump (CMJ) and 4-step-approach-CMJ (4sCMJ) performances were recorded once a month. Parameters of models were determined by minimizing residual-sum squares between predicted and real performances with a nonlinear regression. DPC was best fitted by the DHO model rather than the IR model (CMJ, R(2) = .80 ±.08 and.69 ±.20, respectively; 4sCMJ, R(2) = .86 ± .09 and .67 ± .29, respectively). The damping parameter θ and the period T were positively correlated with age (ρ = 0.81, P training and recovery days. DPC could be considered the expression of the individual process of accumulation and dissipation of fatigue induced by training. DHO-model parameters were correlated with age, which prompts one to postulate that expertise has a major influence on DPC. The DHO model will help coaches develop a greater understanding of training effects and make monitoring of the training process more effective.
Modeling Commercial Turbofan Engine Icing Risk With Ice Crystal Ingestion
Jorgenson, Philip C. E.; Veres, Joseph P.
2013-01-01
The occurrence of ice accretion within commercial high bypass aircraft turbine engines has been reported under certain atmospheric conditions. Engine anomalies have taken place at high altitudes that have been attributed to ice crystal ingestion, partially melting, and ice accretion on the compression system components. The result was degraded engine performance, and one or more of the following: loss of thrust control (roll back), compressor surge or stall, and flameout of the combustor. As ice crystals are ingested into the fan and low pressure compression system, the increase in air temperature causes a portion of the ice crystals to melt. It is hypothesized that this allows the ice-water mixture to cover the metal surfaces of the compressor stationary components which leads to ice accretion through evaporative cooling. Ice accretion causes a blockage which subsequently results in the deterioration in performance of the compressor and engine. The focus of this research is to apply an engine icing computational tool to simulate the flow through a turbofan engine and assess the risk of ice accretion. The tool is comprised of an engine system thermodynamic cycle code, a compressor flow analysis code, and an ice particle melt code that has the capability of determining the rate of sublimation, melting, and evaporation through the compressor flow path, without modeling the actual ice accretion. A commercial turbofan engine which has previously experienced icing events during operation in a high altitude ice crystal environment has been tested in the Propulsion Systems Laboratory (PSL) altitude test facility at NASA Glenn Research Center. The PSL has the capability to produce a continuous ice cloud which are ingested by the engine during operation over a range of altitude conditions. The PSL test results confirmed that there was ice accretion in the engine due to ice crystal ingestion, at the same simulated altitude operating conditions as experienced previously in
Stelian, C.; Nehari, A.; Lasloudji, I.; Lebbou, K.; Dumortier, M.; Cabane, H.; Duffar, T.
2017-10-01
Single La3Ga5.5Ta0.5O14 (LGT) crystals have been grown by using the Czochralski technique with inductive heating. Some ingots exhibit imperfections such as cracks, dislocations and striations. Numerical modeling is applied to investigate the factors affecting the shape of the crystal-melt interface during the crystallization of ingots having 3 cm in diameter. It was found that the conical shape of the interface depends essentially on the internal radiative exchanges in the semi-transparent LGT crystal. Numerical results are compared to experimental visualization of the growth interface, showing a good agreement. The effect of the forced convection produced by the crystal and crucible rotation is numerically investigated at various rotation rates. Increasing the crystal rotation rate up to 50 rpm has a significant flattening effect on the interface shape. Applying only crucible rotation enhances the downward flow underneath the crystal, leading to an increased interface curvature. Counter rotation between the crystal and the crucible results in a distorted shape of the interface.
Energy Technology Data Exchange (ETDEWEB)
Mitzschke, Kerstin
2007-11-01
Nonlinear optical spectroscopy is a powerful method to study surface or bulk properties of condensed matter. In centrosymmetric materials like silicon even order nonlinear optical processes are forbidden. Besides self-focussing or self phase modulation third-harmonic-generation (THG) is the simplest process that can be studied. This work demonstrates that THG is a adapted non-contact and non-invasive optical method to get information about bulk structures of silicon and Photonic crystals (PC), consisting of silicon. Until now most studies are done in the visible spectral range being limited by the linear absorption losses. So the extension of THG to the IR spectral range is extremely useful. This will allow the investigation of Photonic Crystals, where frequencies near a photonic bandgap are of special interest. 2D- photonic structures under investigation were fabricated via photoelectrochemical etching of the Si (100) wafer (thickness 500 {mu}m) receiving square and hexagonal arranged pores. The typical periodicity of the structures used is 2 {mu}m and the length of the pores reached to 400 {mu}m. Because of stability the photonic structures were superimposed on silicon substrate. The experimental set-up used for the THG experiments generates tuneable picosecond IR pulses (tuning range 1500-4000 cm{sup -1}). The IR-pulse hit the sample either perpendicular to the sample surface or under an angle {theta}. The sample can be rotated (f) around the surface normal. The generated third harmonic is analysed by a polarizer, spectrally filtered by a polychromator and registered by a CCD camera. The setup can be used either in transmission or in reflection mode. Optical transmission and reflection spectra of the Si bulk correspond well with the theoretical description, a 4-fold and a 8-fold dependencies of the azimuth angle resulting in the structure of the x{sup (3)}-tensor of (100)-Si. The situation changes dramatically if the PC with hexagonal structure is investigated
Directory of Open Access Journals (Sweden)
Piotr FOLĘGA
2014-03-01
Full Text Available The variety of types and sizes currently in production harmonic drive is a problem in their rational choice. Properly selected harmonic drive must meet certain requirements during operation, and achieve the anticipated service life. The paper discusses the problems associated with the selection of the harmonic drive. It also presents the algorithm correct choice of harmonic drive. The main objective of this study was to develop a computer program that allows the correct choice of harmonic drive by developed algorithm.
Four-quadrant propeller modeling: A low-order harmonic approximation
Digital Repository Service at National Institute of Oceanography (India)
Haeusler, A.J.; Saccon, A.; Hauser, J.; Pascoal, A.M.; Aguiar, A.P.
- els mentioned in this work. In van Lammeren et al. (1969), the authors plot the efficiency η against the ratio kT/J2o , i.e. related to the first-quadrant model. The equations of the momentum theory and four-quadrant models can be rewritten in such a... way that they become compatible with that plot (Oosterveld, 1970, Fig. 31), which is shown next. Ideal propulsion efficiency. The momentum theory propeller model is an idealized model which can be used to compute the so-called ideal efficiency. Stated...
Crystal Plasticity Model of Reactor Pressure Vessel Embrittlement in GRIZZLY
Energy Technology Data Exchange (ETDEWEB)
Chakraborty, Pritam [Idaho National Laboratory (INL), Idaho Falls, ID (United States); Biner, Suleyman Bulent [Idaho National Laboratory (INL), Idaho Falls, ID (United States); Zhang, Yongfeng [Idaho National Laboratory (INL), Idaho Falls, ID (United States); Spencer, Benjamin Whiting [Idaho National Laboratory (INL), Idaho Falls, ID (United States)
2015-07-01
The integrity of reactor pressure vessels (RPVs) is of utmost importance to ensure safe operation of nuclear reactors under extended lifetime. Microstructure-scale models at various length and time scales, coupled concurrently or through homogenization methods, can play a crucial role in understanding and quantifying irradiation-induced defect production, growth and their influence on mechanical behavior of RPV steels. A multi-scale approach, involving atomistic, meso- and engineering-scale models, is currently being pursued within the GRIZZLY project to understand and quantify irradiation-induced embrittlement of RPV steels. Within this framework, a dislocation-density based crystal plasticity model has been developed in GRIZZLY that captures the effect of irradiation-induced defects on the flow stress behavior and is presented in this report. The present formulation accounts for the interaction between self-interstitial loops and matrix dislocations. The model predictions have been validated with experiments and dislocation dynamics simulation.
An Application of the Harmonic Oscillator Model to Verify Dunning’s Theory of the Economic Growth
Directory of Open Access Journals (Sweden)
Marcin Salamaga
2013-09-01
Full Text Available Analogies with mechanisms ruling the natural world have oft en been sought in the course of economic phenomena.Th is paper is also an attempt to combine the physical phenomenon of a harmonious oscillator withthe theory of economic growth by J. H. Dunning (1981. In his theory, Dunning distinguished stages of economicgrowth of countries that imply the dependency between the investment position of countries and theirGDP per capita, while the graph presenting this dependency reminds a trajectory of oscillating motion of adamped harmonic oscillator. Th is analogy has given inspiration to reinterpret the theory of economy on thegrounds of the mechanism of a physical model. In this paper, the harmonious oscillator motion equation wasadapted to the description of dependencies shown in the theory of economic growth by J. H. Dunning. Th emathematical solution of this equation is properly parameterised and parameters are estimated with the useof the Gauss-Newton algorithm. Th e main objective of this paper is to allocate a specifi c stage in the economicgrowth to each country on the basis of the values of parameter estimations of the proposed cyclical models ofchanges in the net investment indicator.
Harmonic polynomials, hyperspherical harmonics, and atomic spectra
Avery, John Scales
2010-01-01
The properties of monomials, homogeneous polynomials and harmonic polynomials in d-dimensional spaces are discussed. The properties are shown to lead to formulas for the canonical decomposition of homogeneous polynomials and formulas for harmonic projection. Many important properties of spherical harmonics, Gegenbauer polynomials and hyperspherical harmonics follow from these formulas. Harmonic projection also provides alternative ways of treating angular momentum and generalised angular momentum. Several powerful theorems for angular integration and hyperangular integration can be derived in this way. These purely mathematical considerations have important physical applications because hyperspherical harmonics are related to Coulomb Sturmians through the Fock projection, and because both Sturmians and generalised Sturmians have shown themselves to be extremely useful in the quantum theory of atoms and molecules.
Computational Modeling of Photonic Crystal Microcavity Single-Photon Emitters
Saulnier, Nicole A.
Conventional cryptography is based on algorithms that are mathematically complex and difficult to solve, such as factoring large numbers. The advent of a quantum computer would render these schemes useless. As scientists work to develop a quantum computer, cryptographers are developing new schemes for unconditionally secure cryptography. Quantum key distribution has emerged as one of the potential replacements of classical cryptography. It relics on the fact that measurement of a quantum bit changes the state of the bit and undetected eavesdropping is impossible. Single polarized photons can be used as the quantum bits, such that a quantum system would in some ways mirror the classical communication scheme. The quantum key distribution system would include components that create, transmit and detect single polarized photons. The focus of this work is on the development of an efficient single-photon source. This source is comprised of a single quantum dot inside of a photonic crystal microcavity. To better understand the physics behind the device, a computational model is developed. The model uses Finite-Difference Time-Domain methods to analyze the electromagnetic field distribution in photonic crystal microcavities. It uses an 8-band k · p perturbation theory to compute the energy band structure of the epitaxially grown quantum dots. We discuss a method that combines the results of these two calculations for determining the spontaneous emission lifetime of a quantum dot in bulk material or in a microcavity. The computational models developed in this thesis are used to identify and characterize microcavities for potential use in a single-photon source. The computational tools developed are also used to investigate novel photonic crystal microcavities that incorporate 1D distributed Bragg reflectors for vertical confinement. It is found that the spontaneous emission enhancement in the quasi-3D cavities can be significantly greater than in traditional suspended slab
Molecular Dynamics Modeling of PPTA Crystals in Aramid Fibers
Energy Technology Data Exchange (ETDEWEB)
Mercer, Brian Scott [Univ. of California, Berkeley, CA (United States)
2016-05-19
In this work, molecular dynamics modeling is used to study the mechanical properties of PPTA crystallites, which are the fundamental microstructural building blocks of polymer aramid bers such as Kevlar. Particular focus is given to constant strain rate axial loading simulations of PPTA crystallites, which is motivated by the rate-dependent mechanical properties observed in some experiments with aramid bers. In order to accommodate the covalent bond rupture that occurs in loading a crystallite to failure, the reactive bond order force eld ReaxFF is employed to conduct the simulations. Two major topics are addressed: The rst is the general behavior of PPTA crystallites under strain rate loading. Constant strain rate loading simulations of crystalline PPTA reveal that the crystal failure strain increases with increasing strain rate, while the modulus is not a ected by the strain rate. Increasing temperature lowers both the modulus and the failure strain. The simulations also identify the C N bond connecting the aromatic rings as weakest primary bond along the backbone of the PPTA chain. The e ect of chain-end defects on PPTA micromechanics is explored, and it is found that the presence of a chain-end defect transfers load to the adjacent chains in the hydrogen-bonded sheet in which the defect resides, but does not in uence the behavior of any other chains in the crystal. Chain-end defects are found to lower the strength of the crystal when clustered together, inducing bond failure via stress concentrations arising from the load transfer to bonds in adjacent chains near the defect site. The second topic addressed is the nature of primary and secondary bond failure in crystalline PPTA. Failure of both types of bonds is found to be stochastic in nature and driven by thermal uctuations of the bonds within the crystal. A model is proposed which uses reliability theory to model bonds under constant strain rate loading as components with time-dependent failure rate
Liquid Crystal Photonic bandgap Fibers: Modeling and Devices
DEFF Research Database (Denmark)
Weirich, Johannes
In this PhD thesis an experimental and numerical investigation of liquid crystal infiltrated photonic bandgap fibers (LCPBGs) is presented. A simulation scheme for modeling LCPBG devices including electrical tunability is presented. New experimental techniques, boundary coating and the applications...... of monomer added LCs, are investigated. Waveplates based on LCPBGs and a tunable polarization maintaining filter are developed. An on-chip tunable notch filter based on long period gratings is presented. Furthermore, the application of a LCPBG device for the electrical control of a fiber laser...
Finite Element Modeling of Acoustic Shielding via Phononic Crystal structures
Lipp, Clémentine Sophie Sarah; Lozzi, Andrea
2016-01-01
Quality factor of Contour Mode Resonators (CMR) are mainly affected by energy losses due to acoustic waves leaving the resonator through the anchors. An engineering of the anchors in order to create a periodic variation in the acoustic impedance of the material, structures known as Phononic Crystals (PnCs), can help improve the Q factor by reflecting part of the acoustic waves. During this project, FEM models have been validated for both 1D and 2D PnCs. The behavior of the band diagram and qu...
Diamessis, P. J.; Wunsch, S.; Delwiche, I.; Richter, M. P.
2014-06-01
The interaction of an internal wave beam (IWB) with an idealized oceanic pycnocline is examined using two-dimensional fully nonlinear direct numerical simulations based on a spectral multidomain penalty method in the vertical direction. The phenomenon of focus is the nonlinear generation of harmonics. A total of 24 simulations have been performed, varying the normalized pycnocline thickness and the ratio of peak pycnocline Brunt-Väisälä frequency to that of the stratified lower layer. Harmonics at the point of IWB entry into the pycnocline increase in amplitude and number with a measure of the maximum gradient of the Brunt-Väisälä frequency, suggesting refraction as an important factor in harmonic generation. Among the simulations performed, two distinct limits of pycnocline thickness are identified. For thin pynoclines, whose thickness is 10% of the incident IWB's horizontal wavelength, harmonics trapped within the pycnocline have maximum amplitude when their frequency and wavenumber match those of the natural pycnocline interfacial wave mode. Results in this case are compared with weakly nonlinear theory for harmonic generation by plane wave refraction. For thicker pycnoclines, whose thickness is equal the incident IWB's horizontal wavelength, IWB refraction results in harmonic generation at multiple locations in addition to pycnocline entry, giving rise to complex flow structure inside the pycnocline.
Modeling the Shape of Ions in Pyrite-Type Crystals
Directory of Open Access Journals (Sweden)
Mario Birkholz
2014-09-01
Full Text Available The geometrical shape of ions in crystals and the concept of ionic radii are re-considered. The re-investigation is motivated by the fact that a spherical modelling is justified for p valence shell ions on cubic lattice sites only. For the majority of point groups, however, the ionic radius must be assumed to be an anisotropic quantity. An appropriate modelling of p valence ions then has to be performed by ellipsoids. The approach is tested for pyrite-structured dichalcogenides MX2, with chalcogen ions X = O, S, Se and Te. The latter are found to exhibit the shape of ellipsoids being compressed along the <111> symmetry axes, with two radii r|| and r⊥ describing their spatial extension. Based on this ansatz, accurate interatomic M–X distances can be derived and a consistent geometrical model emerges for pyrite-structured compounds. Remarkably, the volumes of chalcogen ions are found to vary only little in different MX2 compounds, suggesting the ionic volume rather than the ionic radius to behave as a crystal-chemical constant.
Q-tensor model for electrokinetics in nematic liquid crystals
Tovkach, O. M.; Conklin, Christopher; Calderer, M. Carme; Golovaty, Dmitry; Lavrentovich, Oleg D.; Viñals, Jorge; Walkington, Noel J.
2017-05-01
We use a variational principle to derive a mathematical model for a nematic electrolyte in which the liquid crystalline component is described in terms of a second-rank order parameter tensor. The model extends the previously developed director-based theory and accounts for the presence of disclinations and possible biaxiality. We verify the model by considering a simple but illustrative example of liquid crystal-enabled electro-osmotic flow around a stationary dielectric spherical particle placed at the center of a large cylindrical container filled with a nematic electrolyte. Assuming homeotropic anchoring of the nematic on the surface of the particle and uniform distribution of the director on the surface of the container, we consider two configurations with a disclination equatorial ring and with a hyperbolic hedgehog, respectively. The computed electro-osmotic flows show a strong dependence on the director configurations and on the anisotropies of dielectric permittivity and electric conductivity of the nematic, characteristic of liquid crystal-enabled electrokinetics. Further, the simulations demonstrate space charge separation around the dielectric sphere, even in the case of isotropic permittivity and conductivity. This is in agreement with the induced-charge electroosmotic effect that occurs in an isotropic electrolyte when an applied field acts on the ionic charge it induces near a polarizable surface.
Wannier-Bloch Approach to Localization in High-Harmonics Generation in Solids
Directory of Open Access Journals (Sweden)
Edyta N. Osika
2017-05-01
Full Text Available Emission of high-order harmonics from solids provides a new avenue in attosecond science. On the one hand, it allows us to investigate fundamental processes of the nonlinear response of electrons driven by a strong laser pulse in a periodic crystal lattice. On the other hand, it opens new paths toward efficient attosecond pulse generation, novel imaging of electronic wave functions, and enhancement of high-order harmonic-generation (HHG intensity. A key feature of HHG in a solid (as compared to the well-understood phenomenon of HHG in an atomic gas is the delocalization of the process, whereby an electron ionized from one site in the periodic lattice may recombine in any other. Here, we develop an analytic model, based on the localized Wannier wave functions in the valence band and delocalized Bloch functions in the conduction band. This Wannier-Bloch approach assesses the contributions of individual lattice sites to the HHG process and hence precisely addresses the question of localization of harmonic emission in solids. We apply this model to investigate HHG in a ZnO crystal for two different orientations, corresponding to wider and narrower valence and conduction bands, respectively. Interestingly, for narrower bands, the HHG process shows significant localization, similar to harmonic generation in atoms. For all cases, the delocalized contributions to HHG emission are highest near the band-gap energy. Our results pave the way to controlling localized contributions to HHG in a solid crystal.
Monat, Christelle; Collins, Matthew; Clark, Alex; Schroeder, Jochen; Xiong, Chunle; Li, Juntao; O'Faolain, Liam; Krauss, Thomas F; Eggleton, Benjamin J; Moss, David J
2014-01-01
The ability to use coherent light for material science and applications is directly linked to our ability to measure short optical pulses. While free-space optical methods are well-established, achieving this on a chip would offer the greatest benefit in footprint, performance, flexibility and cost, and allow the integration with complementary signal processing devices. A key goal is to achieve operation at sub-Watt peak power levels and on sub-picosecond timescales. Previous integrated demonstrations require either a temporally synchronized reference pulse, an off-chip spectrometer, or long tunable delay lines. We report the first device capable of achieving single-shot time-domain measurements of near-infrared picosecond pulses based on an ultra-compact integrated CMOS compatible device, with the potential to be fully integrated without any external instrumentation. It relies on optical third-harmonic generation in a slow-light silicon waveguide. Our method can also serve as a powerful in-situ diagnostic to...
Phase-field-crystal models and mechanical equilibrium.
Heinonen, V; Achim, C V; Elder, K R; Buyukdagli, S; Ala-Nissila, T
2014-03-01
Phase-field-crystal (PFC) models constitute a field theoretical approach to solidification, melting, and related phenomena at atomic length and diffusive time scales. One of the advantages of these models is that they naturally contain elastic excitations associated with strain in crystalline bodies. However, instabilities that are diffusively driven towards equilibrium are often orders of magnitude slower than the dynamics of the elastic excitations, and are thus not included in the standard PFC model dynamics. We derive a method to isolate the time evolution of the elastic excitations from the diffusive dynamics in the PFC approach and set up a two-stage process, in which elastic excitations are equilibrated separately. This ensures mechanical equilibrium at all times. We show concrete examples demonstrating the necessity of the separation of the elastic and diffusive time scales. In the small-deformation limit this approach is shown to agree with the theory of linear elasticity.
Signell, Richard; Camossi, E.
2016-01-01
Work over the last decade has resulted in standardised web services and tools that can significantly improve the efficiency and effectiveness of working with meteorological and ocean model data. While many operational modelling centres have enabled query and access to data via common web services, most small research groups have not. The penetration of this approach into the research community, where IT resources are limited, can be dramatically improved by (1) making it simple for providers to enable web service access to existing output files; (2) using free technologies that are easy to deploy and configure; and (3) providing standardised, service-based tools that work in existing research environments. We present a simple, local brokering approach that lets modellers continue to use their existing files and tools, while serving virtual data sets that can be used with standardised tools. The goal of this paper is to convince modellers that a standardised framework is not only useful but can be implemented with modest effort using free software components. We use NetCDF Markup language for data aggregation and standardisation, the THREDDS Data Server for data delivery, pycsw for data search, NCTOOLBOX (MATLAB®) and Iris (Python) for data access, and Open Geospatial Consortium Web Map Service for data preview. We illustrate the effectiveness of this approach with two use cases involving small research modelling groups at NATO and USGS.
Harmonic generation in the generalized Sagdeev pseudopotential
Akbari-Moghanjoughi, M.
2017-09-01
In this paper, we study the nonlinear harmonic generation effect in different oscillator models. For weakly nonlinear systems, we use the generalized forced Korteweg de Vries Burgers (KdVB) and modified KdVB (mKdVB) models in order to classify three fundamentally different harmonic structures in a nonlinear dynamical system. The first is called the internal harmonic structure which exists due to the self oscillation of the system in the absence of dissipation effect and is shown to follow either relations of nf or (2n - 1)f depending on the symmetry of oscillator potential in which n is an integer number and f is the fundamental frequency which is exactly obtained for the Helmholtz oscillator. The second structure is the resonant harmonics which appears in the presence of damping and follows the harmonic structure nf0 in which f0 is the linear resonance frequency. Finally, the last harmonic structure appears in the presence of dissipation and external periodic forcing effects which we call the external harmonic pattern. It is shown that the external harmonic pattern, in which f1 is the driving frequency, always follows the nf1 rule regardless of the potential symmetry. We then extend our analysis to study the harmonic generation in the fully nonlinear generalized Sagdeev potential for real plasmas with isothermal and adiabatic ion fluids and investigate the effects of different plasma parameters such as the fractional ion temperature and normalized ion acoustic speed on all three kinds of harmonic generation.
Signell, R. P.; Camossi, E.
2015-11-01
Work over the last decade has resulted in standardized web-services and tools that can significantly improve the efficiency and effectiveness of working with meteorological and ocean model data. While many operational modelling centres have enabled query and access to data via common web services, most small research groups have not. The penetration of this approach into the research community, where IT resources are limited, can be dramatically improved by: (1) making it simple for providers to enable web service access to existing output files; (2) using technology that is free, and that is easy to deploy and configure; and (3) providing tools to communicate with web services that work in existing research environments. We present a simple, local brokering approach that lets modelers continue producing custom data, but virtually aggregates and standardizes the data using NetCDF Markup Language. The THREDDS Data Server is used for data delivery, pycsw for data search, NCTOOLBOX (Matlab®1) and Iris (Python) for data access, and Ocean Geospatial Consortium Web Map Service for data preview. We illustrate the effectiveness of this approach with two use cases involving small research modelling groups at NATO and USGS.1 Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the US Government.
Parameter identification in a generalized time-harmonic Rayleigh damping model for elastography.
Directory of Open Access Journals (Sweden)
Elijah E W Van Houten
Full Text Available The identifiability of the two damping components of a Generalized Rayleigh Damping model is investigated through analysis of the continuum equilibrium equations as well as a simple spring-mass system. Generalized Rayleigh Damping provides a more diversified attenuation model than pure Viscoelasticity, with two parameters to describe attenuation effects and account for the complex damping behavior found in biological tissue. For heterogeneous Rayleigh Damped materials, there is no equivalent Viscoelastic system to describe the observed motions. For homogeneous systems, the inverse problem to determine the two Rayleigh Damping components is seen to be uniquely posed, in the sense that the inverse matrix for parameter identification is full rank, with certain conditions: when either multi-frequency data is available or when both shear and dilatational wave propagation is taken into account. For the multi-frequency case, the frequency dependency of the elastic parameters adds a level of complexity to the reconstruction problem that must be addressed for reasonable solutions. For the dilatational wave case, the accuracy of compressional wave measurement in fluid saturated soft tissues becomes an issue for qualitative parameter identification. These issues can be addressed with reasonable assumptions on the negligible damping levels of dilatational waves in soft tissue. In general, the parameters of a Generalized Rayleigh Damping model are identifiable for the elastography inverse problem, although with more complex conditions than the simpler Viscoelastic damping model. The value of this approach is the additional structural information provided by the Generalized Rayleigh Damping model, which can be linked to tissue composition as well as rheological interpretations.
Bokarev, Valery P.; Krasnikov, Gennady Ya
2018-02-01
Based on the evaluation of the properties of crystals, such as surface energy and its anisotropy, the surface melting temperature, the anisotropy of the work function of the electron, and the anisotropy of adsorption, were shown the advantages of the model of coordination melting (MCM) in calculating the surface properties of crystals. The model of coordination melting makes it possible to calculate with an acceptable accuracy the specific surface energy of the crystals, the anisotropy of the surface energy, the habit of the natural crystals, the temperature of surface melting of the crystal, the anisotropy of the electron work function and the anisotropy of the adhesive properties of single-crystal surfaces. The advantage of our model is the simplicity of evaluating the surface properties of the crystal based on the data given in the reference literature. In this case, there is no need for a complex mathematical tool, which is used in calculations using quantum chemistry or modeling by molecular dynamics.
Modeling a nanocantilever based biosensor using a stochastically perturbed harmonic oscillator
Snyder, Patrick; Serna, Juan D
2013-01-01
A nanoscale biosensor most suitable for clinical purposes could be based on the use of nanocantilevers. These microscopic `diving boards' are coated with binding probes that have an affinity to a specific amino acid, enzyme or protein in the body. The binding probes on the silicon cantilever attract target particles, and as target biomolecules bind to the cantilever, it changes the vibrating frequency of the cantilever. The process of target binding is a random process and hence creates fluctuations in the frequency and damping mechanism of the cantilever. The effect of such fluctuations are given in our model calculations to provide a broader quantitative understanding of nanocantilever biosensors.
Singh, Amit Raj; Granek, Rony
2016-10-01
We study DNA denaturation by integrating elasticity — as described by the Gaussian network model — with bond binding energies, distinguishing between different base pairs and stacking energies. We use exact calculation, within the model, of the Helmholtz free-energy of any partial denaturation state, which implies that the entropy of all formed "bubbles" ("loops") is accounted for. Considering base pair bond removal single events, the bond designated for opening is chosen by minimizing the free-energy difference for the process, over all remaining base pair bonds. Despite of its great simplicity, for several known DNA sequences our results are in accord with available theoretical and experimental studies. Moreover, we report free-energy profiles along the denaturation pathway, which allow to detect stable or meta-stable partial denaturation states, composed of bubble, as local free-energy minima separated by barriers. Our approach allows to study very long DNA strands with commonly available computational power, as we demonstrate for a few random sequences in the range 200-800 base-pairs. For the latter, we also elucidate the self-averaging property of the system. Implications for the well known breathing dynamics of DNA are elucidated.
Spherical model provides visual aid for cubic crystal study
Bacigalupi, R. J.; Spakowski, A. E.
1965-01-01
Transparent sphere of polymethylmethacrylate with major zones and poles of cubic crystals is used to make crystallographic visualizations and to interpret Laue X ray diffraction of single cubic crystals.
HARMONIZED EUROPE OR EUROPEAN HARMONY?
Directory of Open Access Journals (Sweden)
Cosmin Marinescu
2007-07-01
Full Text Available Recent evolutions in Europe raise questions on the viability of the present economic and social model that defines the European construction project. In this paper, the author will try to explain the viability of institutional European model that sticks between free market mechanisms and protectionism. The main challenge for the EU is about the possibility to bring together the institutional convergence and the welfare for all Europeans. This is the result of the view, still dominant, of European politics elite, according to which institutional harmonization is the solution of a more dynamic and prosper Europe. But, economic realities convince us that, more and more, a harmonized, standardized Europe is not necessarily identical with a Europe of harmony and social cooperation. If „development through integration” seems to be harmonization through „institutional transplant”, how could then be the European model one sufficiently wide open to market, which creates the prosperity so long waited for by new member countries?
Belda, Santiago; Heinkelmann, Robert; Ferrándiz, José M.; Karbon, Maria; Nilsson, Tobias; Schuh, Harald
2017-10-01
Very Long Baseline Interferometry (VLBI) is the only space geodetic technique capable of measuring all the Earth orientation parameters (EOP) accurately and simultaneously. Modeling the Earth's rotational motion in space within the stringent consistency goals of the Global Geodetic Observing System (GGOS) makes VLBI observations essential for constraining the rotation theories. However, the inaccuracy of early VLBI data and the outdated products could cause non-compliance with these goals. In this paper, we perform a global VLBI analysis of sessions with different processing settings to determine a new set of empirical corrections to the precession offsets and rates, and to the amplitudes of a wide set of terms included in the IAU 2006/2000A precession-nutation theory. We discuss the results in terms of consistency, systematic errors, and physics of the Earth. We find that the largest improvements w.r.t. the values from IAU 2006/2000A precession-nutation theory are associated with the longest periods (e.g., 18.6-yr nutation). A statistical analysis of the residuals shows that the provided corrections attain an error reduction at the level of 15 μas. Additionally, including a Free Core Nutation (FCN) model into a priori Celestial Pole Offsets (CPOs) provides the lowest Weighted Root Mean Square (WRMS) of residuals. We show that the CPO estimates are quite insensitive to TRF choice, but slightly sensitive to the a priori EOP and the inclusion of different VLBI sessions. Finally, the remaining residuals reveal two apparent retrograde signals with periods of nearly 2069 and 1034 days.
Modelling the acoustical response of lossy lamella-crystals
DEFF Research Database (Denmark)
Christensen, Johan; Mortensen, N. Asger; Willatzen, Morten
2014-01-01
The sound propagation properties of lossy lamella-crystals are analysed theoretically utilizing a rig- orous wave expansion formalism and an effective medium approach. We investigate both sup- ported and free-standing crystal slab structures and predict high absorption for a broad range...... only makes sense if the crystal filling fraction is sufficiently large to satisfy an effective medium approach....
Modeling of Photonic Band Gap Crystals and Applications
Energy Technology Data Exchange (ETDEWEB)
El-Kady, Ihab Fathy [Iowa State Univ., Ames, IA (United States)
2002-01-01
In this work, the authors have undertaken a theoretical approach to the complex problem of modeling the flow of electromagnetic waves in photonic crystals. The focus is to address the feasibility of using the exciting phenomena of photonic gaps (PBG) in actual applications. The authors start by providing analytical derivations of the computational electromagnetic methods used in their work. They also present a detailed explanation of the physics underlying each approach, as well as a comparative study of the strengths and weaknesses of each method. The Plane Wave expansion, Transfer Matrix, and Finite Difference time Domain Methods are addressed. They also introduce a new theoretical approach, the Modal Expansion Method. They then shift the attention to actual applications. They begin with a discussion of 2D photonic crystal wave guides. The structure addressed consists of a 2D hexagonal structure of air cylinders in a layered dielectric background. Comparison with the performance of a conventional guide is made, as well as suggestions for enhancing it. The studies provide an upper theoretical limit on the performance of such guides, as they assumed no crystal imperfections and non-absorbing media. Next, they study 3D metallic PBG materials at near infrared and optical wavelengths. The main objective is to study the importance of absorption in the metal and the suitability of observing photonic band gaps in such structures. They study simple cubic structures where the metallic scatters are either cubes or interconnected metallic rods. Several metals are studied (aluminum, gold, copper, and silver). The effect of topology is addressed and isolated metallic cubes are found to be less lossy than the connected rod structures. The results reveal that the best performance is obtained by choosing metals with a large negative real part of the dielectric function, together with a relatively small imaginary part. Finally, they point out a new direction in photonic crystal
Harmonic Morphisms Projecting Harmonic Functions to Harmonic Functions
Mustafa, M. T.
2012-01-01
For Riemannian manifolds $M$ and $N$ , admitting a submersion $\\varphi $ with compact fibres, we introduce the projection of a function via its decomposition intohorizontal and vertical components. By comparing the Laplacians on $M$ and $N$ , we determine conditions under which a harmonic function on $U={\\varphi }^{-1}(V)\\subset M$ projects down, via its horizontal component, to a harmonic function on $V\\subset N$ .
Directory of Open Access Journals (Sweden)
Ogbagaber Semhar
2012-05-01
Full Text Available Abstract Background Physical activity as measured by activity counts over short time intervals across a 24 h period are often used to assess circadian variation. We are interested in characterizing circadian patterns in activity among adolescents and examining how these patterns vary by obesity status. New statistical approaches are needed to examine how factors affect different features of the circadian pattern and to make appropriate covariate adjustments when the outcomes are longitudinal count data. Methods We develop a statistical model for longitudinal or repeated activity count data that is used to examine differences in the overall activity level, amplitude (defined as the difference between the lowest and highest activity level over a 24 hour period, and phase shift. Using seven days of continuous activity monitoring, we characterize the circadian patterns and compare them between obese and non-obese adolescent girls. Results We find a statistically significant phase delay in adolescent girls who were obese compared with their non-obese counterparts. After the appropriate adjustment for measured potential confounders, we did not find differences in mean activity level between the two groups. Conclusion New statistical methodology was developed to identify a phase delay in obese compared with non-obese adolescents. This new approach for analyzing longitudinal circadian rhythm count data provides a useful statistical technique to add to the repertoire for those analyzing circadian rhythm data.
Predicting crystal growth via a unified kinetic three-dimensional partition model
Anderson, Michael W.; Gebbie-Rayet, James T.; Hill, Adam R.; Farida, Nani; Attfield, Martin P.; Cubillas, Pablo; Blatov, Vladislav A.; Proserpio, Davide M.; Akporiaye, Duncan; Arstad, Bjørnar; Gale, Julian D.
2017-04-01
Understanding and predicting crystal growth is fundamental to the control of functionality in modern materials. Despite investigations for more than one hundred years, it is only recently that the molecular intricacies of these processes have been revealed by scanning probe microscopy. To organize and understand this large amount of new information, new rules for crystal growth need to be developed and tested. However, because of the complexity and variety of different crystal systems, attempts to understand crystal growth in detail have so far relied on developing models that are usually applicable to only one system. Such models cannot be used to achieve the wide scope of understanding that is required to create a unified model across crystal types and crystal structures. Here we describe a general approach to understanding and, in theory, predicting the growth of a wide range of crystal types, including the incorporation of defect structures, by simultaneous molecular-scale simulation of crystal habit and surface topology using a unified kinetic three-dimensional partition model. This entails dividing the structure into ‘natural tiles’ or Voronoi polyhedra that are metastable and, consequently, temporally persistent. As such, these units are then suitable for re-construction of the crystal via a Monte Carlo algorithm. We demonstrate our approach by predicting the crystal growth of a diverse set of crystal types, including zeolites, metal-organic frameworks, calcite, urea and L-cystine.
Samad, Noor Asma Fazli Abdul; Sin, Gürkan; Gernaey, Krist V; Gani, Rafiqul
2013-11-01
This paper presents the application of uncertainty and sensitivity analysis as part of a systematic model-based process monitoring and control (PAT) system design framework for crystallization processes. For the uncertainty analysis, the Monte Carlo procedure is used to propagate input uncertainty, while for sensitivity analysis, global methods including the standardized regression coefficients (SRC) and Morris screening are used to identify the most significant parameters. The potassium dihydrogen phosphate (KDP) crystallization process is used as a case study, both in open-loop and closed-loop operation. In the uncertainty analysis, the impact on the predicted output of uncertain parameters related to the nucleation and the crystal growth model has been investigated for both a one- and two-dimensional crystal size distribution (CSD). The open-loop results show that the input uncertainties lead to significant uncertainties on the CSD, with appearance of a secondary peak due to secondary nucleation for both cases. The sensitivity analysis indicated that the most important parameters affecting the CSDs are nucleation order and growth order constants. In the proposed PAT system design (closed-loop), the target CSD variability was successfully reduced compared to the open-loop case, also when considering uncertainty in nucleation and crystal growth model parameters. The latter forms a strong indication of the robustness of the proposed PAT system design in achieving the target CSD and encourages its transfer to full-scale implementation. Copyright © 2013 Elsevier B.V. All rights reserved.
Metzger, Bernd; Gui, Lili; Fuchs, Jaco; Floess, Dominik; Hentschel, Mario; Giessen, Harald
2015-06-10
We perform second harmonic spectroscopy of aluminum nanoantenna arrays that exhibit plasmonic resonances at the second harmonic wavelength between 450 and 570 nm by focusing sub-30 fs laser pulses tunable from 900 to 1140 nm onto the nanoantenna arrays. We find that a plasmonic resonance at the second harmonic wavelength boosts the overall nonlinear process by more than an order of magnitude. In particular, in the measurement the resonant second harmonic polarization component is a factor of about 70 stronger when compared to the perpendicular off-resonant second harmonic polarization. Furthermore, the maximum of the second harmonic conversion efficiency is found to be slightly blue-shifted with respect to the peak of the linear optical far-field spectrum. This fact can be understood from a simple model that accounts for the almost off-resonant absorption at the fundamental wavelength and the resonant emission process at the second harmonic.
Analytic model of bunched beams for harmonic generation in the low-gain free electron laser regime
Directory of Open Access Journals (Sweden)
G. Penn
2006-06-01
Full Text Available One scheme for harmonic generation employs free electron lasers (FELs with two undulators: the first uses a seed laser to modulate the energy of the electron beam; following a dispersive element which acts to bunch the beam, the second undulator radiates at a higher harmonic. These processes are currently evaluated using extensive calculations or simulation codes which can be slow to evaluate and difficult to set up. We describe a simple algorithm to predict the output of a harmonic generation beam line in the low-gain FEL regime, based on trial functions for the output radiation. Full three-dimensional effects are included. This method has been implemented as a Mathematica® package, named CAMPANILE, which runs rapidly and can be generalized to include effects such as asymmetric beams and misalignments. This method is compared with simulation results using the FEL code GENESIS, both for single stages of harmonic generation and for the LUX project, a design concept for an ultrafast x-ray facility, where multiple stages upshift the input laser frequency by factors of up to 200.
Axler, Sheldon; Ramey, Wade
2013-01-01
This is a book about harmonic functions in Euclidean space. Readers with a background in real and complex analysis at the beginning graduate level will feel comfortable with the material presented here. The authors have taken unusual care to motivate concepts and simplify proofs. Topics include: basic properties of harmonic functions, Poisson integrals, the Kelvin transform, spherical harmonics, harmonic Hardy spaces, harmonic Bergman spaces, the decomposition theorem, Laurent expansions, isolated singularities, and the Dirichlet problem. The new edition contains a completely rewritten chapter on spherical harmonics, a new section on extensions of Bocher's Theorem, new exercises and proofs, as well as revisions throughout to improve the text. A unique software package-designed by the authors and available by e-mail - supplements the text for readers who wish to explore harmonic function theory on a computer.
Synthesis and ultrastructure of plate-like apatite single crystals as a model for tooth enamel
Energy Technology Data Exchange (ETDEWEB)
Zhuang, Zhi, E-mail: zhuang@meiji.ac.jp [Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan); Yoshimura, Hideyuki, E-mail: hyoshi@isc.meiji.ac.jp [Department of Physics, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan); Aizawa, Mamoru, E-mail: mamorua@isc.meiji.ac.jp [Department of Applied Chemistry, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa 214-8571 (Japan)
2013-07-01
Hydroxyapatite (HAp) is an inorganic constituent compound of human bones and teeth, with superior biocompatibility and bioactivity characteristics. Its crystal structure is hexagonal, characterized by a(b)- and c-planes. In vertebrate long bones, HAp crystals have a c-axis orientation, while in tooth enamel, they have an a(b)-axis orientation. Many methods can be used to synthesize c-axis oriented HAp single crystals; however, to the best of our knowledge, there have been no reports on a synthesis method for a(b)-axis oriented HAp single crystals. In this study, we successfully synthesized plate-like HAp crystals at the air–liquid interface of a starting solution via an enzyme reaction of urea with urease. Crystal phase analysis and ultrastructure observations were carried out, and the results indicated that the particles were single crystals, with almost the same a(b)-axis orientation as tooth enamel. It is hoped that by utilizing their unique surface charge and atomic arrangement, the resulting particles can be used as a high-performance biomaterial, capable of adsorbing bio-related substances and a model for tooth enamel. - Highlights: ► Synthesis of plate-like hydroxyapatite crystals at air–liquid interface ► Ultrastructural analysis of plate-like hydroxyapatite crystals ► Plate-like hydroxyapatite single crystals with a high a(b)-axis orientation ► Plate-like hydroxyapatite single crystals as a model for tooth enamel.
Renormalization for free harmonic oscillators
Sonoda, H.
2013-01-01
We introduce a model of free harmonic oscillators that requires renormalization. The model is similar to but simpler than the soluble Lee model. We introduce two concrete examples: the first, resembling the three dimensional $\\phi^4$ theory, needs only mass renormalization, and the second, resembling the four dimensional $\\phi^4$ theory and the Lee model, needs additional renormalization of a coupling and a wave function.
Derewenda, Zygmunt S; Godzik, Adam
2017-01-01
Crystallization of macromolecules has long been perceived as a stochastic process, which cannot be predicted or controlled. This is consistent with another popular notion that the interactions of molecules within the crystal, i.e., crystal contacts, are essentially random and devoid of specific physicochemical features. In contrast, functionally relevant surfaces, such as oligomerization interfaces and specific protein-protein interaction sites, are under evolutionary pressures so their amino acid composition, structure, and topology are distinct. However, current theoretical and experimental studies are significantly changing our understanding of the nature of crystallization. The increasingly popular "sticky patch" model, derived from soft matter physics, describes crystallization as a process driven by interactions between select, specific surface patches, with properties thermodynamically favorable for cohesive interactions. Independent support for this model comes from various sources including structural studies and bioinformatics. Proteins that are recalcitrant to crystallization can be modified for enhanced crystallizability through chemical or mutational modification of their surface to effectively engineer "sticky patches" which would drive crystallization. Here, we discuss the current state of knowledge of the relationship between the microscopic properties of the target macromolecule and its crystallizability, focusing on the "sticky patch" model. We discuss state-of-the-art in silico methods that evaluate the propensity of a given target protein to form crystals based on these relationships, with the objective to design variants with modified molecular surface properties and enhanced crystallization propensity. We illustrate this discussion with specific cases where these approaches allowed to generate crystals suitable for structural analysis.
Critical Points and Bifurcations of the Three-Dimensional Onsager Model for Liquid Crystals
Vollmer, Michaela A. C.
2017-11-01
We study the bifurcation diagram of the Onsager free-energy functional for liquid crystals with orientation parameter on the sphere. In particular, we concentrate on the bifurcations from the isotropic solution for a general class of two-body interaction potentials including the Onsager kernel. Reformulating the problem as a non-linear eigenvalue problem for the kernel operator, we prove that spherical harmonics are the corresponding eigenfunctions and we present a direct relationship between the coefficients of the Taylor expansion of this class of interaction potentials and their eigenvalues. We find explicit expressions for all bifurcation points corresponding to bifurcations from the isotropic state of the Onsager free-energy functional equipped with the Onsager interaction potential. A substantial amount of our analysis is based on the use of spherical harmonics and a special algorithm for computing expansions of products of spherical harmonics in terms of spherical harmonics is presented. Using a Lyapunov-Schmidt reduction, we derive a bifurcation equation depending on five state variables. The dimension of this state space is further reduced to two dimensions by using the rotational symmetry of the problem and the invariant theory of groups. On the basis of these results, we show that the first bifurcation from the isotropic state of the Onsager interaction potential is a transcritical bifurcation and that the corresponding solution is uniaxial. In addition, we prove some global properties of the bifurcation diagram such as the fact that the trivial solution is the unique local minimiser if the bifurcation parameter is high, that it is not a local minimiser if the bifurcation parameter is small, the boundedness of all equilibria of the functional and that the bifurcation branches are either unbounded or that they meet another bifurcation branch.
Kugele, Daniel; Dörr, Dominik; Wittemann, Florian; Hangs, Benjamin; Rausch, Julius; Kärger, Luise; Henning, Frank
2017-10-01
The combination of thermoforming processes of continuous-fiber reinforced thermoplastics and injection molding offers a high potential for cost-effective use in automobile mass production. During manufacturing, the thermoplastic laminates are initially heated up to a temperature above the melting point. This is followed by continuous cooling of the material during the forming process, which leads to crystallization under non-isothermal conditions. To account for phase change effects in thermoforming simulation, an accurate modeling of the crystallization kinetics is required. In this context, it is important to consider the wide range of cooling rates, which are observed during processing. Consequently, this paper deals with the experimental investigation of the crystallization at cooling rates varying from 0.16 K/s to 100 K/s using standard differential scanning calorimetry (DSC) and fast scanning calorimetry (Flash DSC). Two different modeling approaches (Nakamura model, modified Nakamura-Ziabicki model) for predicting crystallization kinetics are parameterized according to DSC measurements. It turns out that only the modified Nakamura-Ziabicki model is capable of predicting crystallization kinetics for all investigated cooling rates. Finally, the modified Nakamura-Ziabicki model is validated by cooling experiments using PA6-CF laminates with embedded temperature sensors. It is shown that the modified Nakamura-Ziabicki model predicts crystallization at non-isothermal conditions and varying cooling rates with a good accuracy. Thus, the study contributes to a deeper understanding of the non-isothermal crystallization and presents an overall method for modeling crystallization under process conditions.
Controlling Second Harmonic Efficiency of Laser Beam Interactions
Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)
2011-01-01
A method is provided for controlling second harmonic efficiency of laser beam interactions. A laser system generates two laser beams (e.g., a laser beam with two polarizations) for incidence on a nonlinear crystal having a preferred direction of propagation. Prior to incidence on the crystal, the beams are optically processed based on the crystal's beam separation characteristics to thereby control a position in the crystal along the preferred direction of propagation at which the beams interact.
Martelli, Nicolas; Devaux, Capucine; van den Brink, Hélène; Billaux, Mathilde; Pineau, Judith; Prognon, Patrice; Borget, Isabelle
2017-01-01
The number of new medical devices for individual use that are launched annually exceeds the assessment capacity of the French national health technology assessment (HTA) agency. This has resulted in hospitals, and particularly university hospitals (UHs), developing hospital-based HTA initiatives to support their decisions for purchasing innovative devices. However, the methodologies used in such hospitals have no common basis. The aim of this study was to assess a mini-HTA model as a potential solution to harmonize HTA methodology in French UHs. A systematic review was conducted on Medline, Embase, Health Technology Assessment database, and Google Scholar to identify published articles reporting the use of mini-HTA tools and decision support-like models. A survey was also carried out in eighteen French UHs to identify in-house decision support tools. Finally, topics evaluated in the Danish mini-HTA model and in French UHs were compared using Jaccard similarity coefficients. Our findings showed differences between topics evaluated in French UHs and those assessed in decision support models from the literature. Only five topics among the thirteen most evaluated in French UHs were similar to those assessed in the Danish mini-HTA model. The organizational and ethical/social impacts were rarely explored among the surveyed models used in French UHs when introducing new medical devices. Before its widespread and harmonized use in French UHs, the mini-HTA model would first require adaptations to the French context.
Neutron total cross section calculation within the framework of quasi-harmonic approximation
Cai, Xiao-Xiao; Klinkby, Esben
2017-10-01
The accuracy of neutron scattering cross sections is the gauge for the realistic outcome of a neutron transport simulation. To improve the traditional harmonic physics model used in such simulations, we revisit the slow neutron transport theory in crystalline materials and aim to develop a unified model that has good performance for neutron transport problems in crystals in a wide range of temperatures and pressures. The quasi-harmonic approximation (QHA) correlates phonon evolution explicitly with unit cell volume. Therefore, it is capable of evaluating a variety of material properties at finite temperatures. In this work, we show numerically that it is a very effective tool for our application as well. Within the framework of QHA, we calculate the temperature dependent characteristics of phonons in three elemental crystals, namely Be, Mg and Al. Based on the obtained results, our calculated neutron total cross sections agree closely with experimental transmission cross sections in a large temperature range below the melting point. We show that as the harmonic cross section model ignores the effects of phonon softening in these crystals, it underestimates the total inelastic cross sections at high temperatures. In the case of Al, we observe that such underestimation is up to 7% at room temperature. In addition, we study the phonon–phonon scatterings in Al. We observe that the cross section is insensitive to the finite phonon lifetimes even at 800 K.
A lamellar model for the X-ray rocking curves of sagittally bent Laue crystals.
Zhong, Z; Kao, C C; Siddons, D P; Zhong, H; Hastings, J B
2003-01-01
The use of sagittally bent asymmetric Laue crystals in horizontally focusing monochromators for high-energy synchrotron X-rays necessitates simulation of the X-ray reflectivity by such crystals. Based on the theory of the lattice distortion in the diffraction plane of sagittally bent Laue crystals, a lamellar model was developed to predict their rocking curves. The model was experimentally verified by rocking-curve measurements from various reflections on silicon crystals of four representative orientations, sagittally bent to various radii, using X-rays of 67 keV energy.
Nonlinear modeling of crystal system transition of black phosphorus using continuum-DFT model.
Setoodeh, AliReza; Farahmand, Hamed
2017-11-13
In this paper, nonlinear behavior of black phosphorus crystals is investigated in tandem with dispersion corrected density functional theory (DFT-D) analysis under uniaxial loading. According to the distinguished anisotropic behavior of black phosphorus due to its morphological anisotropy, a hyperelastic anisotropic (HA) model named continuum-DFT is established to predict nonlinear behavior of the material. In this respect, uniaxial tensile Cauchy stresses are employed on both the DFT-D and HA models along zig-zag direction. Simultaneously, the transition of crystal system is recognized in about 4.5 GPa of the applied uniaxial tensile stress on the DFT-D simulation in the nonlinear region. In order to develop the nonlinear continuum model, unknown constants are surveyed with optimized least square technique. In this regard, the continuum model is obtained to reproduce the Cauchy stress-stretch and density of strain energy-stretch results of the DFT-D simulation. Consequently, the modified HA model is introduced to characterize the nonlinear behavior of black phosphorus. More importantly, the specific transition of crystal system is successfully predicted in the new modified continuum-DFT model. The results reveal that the modified continuum model is well defined to replicate the nonlinear behavior of black phosphorus. © 2017 IOP Publishing Ltd.
Glenn, Autumn L.; Seagrave, Sarah L.; Bulusu, Kartik V.; Plesniak, Michael W.
2011-11-01
Inward centrifuging of fluid in a 180 degree curved pipe leads to development of secondary flow vortical structures. These Dean's vortices have been widely studied in steady flows. Complex secondary flow structures were observed under (unsteady) physiological flow forcing associated with the cardiac cycle, as well as simple harmonic forcing. These structures were investigated under several simple harmonic inflow conditions with phase-locked 2-D PIV measurements to examine the formation of coherent structures in the secondary flow. Experimental velocity field data were acquired at various cross-sectional planes along the bend. Multiple vortex pairs were observed at 90 degrees into the bend for all waveforms investigated. The overarching goal of this study is to understand the effect of driving waveform characteristics, i.e. period, flow acceleration, etc. on secondary flow morphologies and to characterize these morphologies in terms of dimensionless parameters describing the flow. Supported by the National Science Foundation under Grant No. CBET-0828903.
Messner, Mark C.; Rhee, Moono; Arsenlis, Athanasios; Barton, Nathan R.
2017-06-01
This work develops a method for calibrating a crystal plasticity model to the results of discrete dislocation (DD) simulations. The crystal model explicitly represents junction formation and annihilation mechanisms and applies these mechanisms to describe hardening in hexagonal close packed metals. The model treats these dislocation mechanisms separately from elastic interactions among populations of dislocations, which the model represents through a conventional strength-interaction matrix. This split between elastic interactions and junction formation mechanisms more accurately reproduces the DD data and results in a multi-scale model that better represents the lower scale physics. The fitting procedure employs concepts of machine learning—feature selection by regularized regression and cross-validation—to develop a robust, physically accurate crystal model. The work also presents a method for ensuring the final, calibrated crystal model respects the physical symmetries of the crystal system. Calibrating the crystal model requires fitting two linear operators: one describing elastic dislocation interactions and another describing junction formation and annihilation dislocation reactions. The structure of these operators in the final, calibrated model reflect the crystal symmetry and slip system geometry of the DD simulations.
Harmonics mitigation on industrial loads using series and parallel ...
African Journals Online (AJOL)
This work compared the use of series and parallel resonant harmonic filters in suppressing harmonics using Simulink model of the power system of NICHEMTEX, a Textile industry in Nigeria as a case study. Mathematical analysis representing current harmonics distributions on industrials loads with and without capacitor ...
A Micro-Mechanically Based Continuum Model for Strain-Induced Crystallization in Natural Rubber
Mistry, Sunny Jigger
Recent experimental results show that strain-induced crystallization can substantially improve the crack growth resistance of natural rubber. While this might suggest superior designs of tires or other industrial applications where elastomers are used, a more thorough understanding of the underlying physics of strain-induced crystallization in natural rubber has to be developed before any design process can be started. The objective of this work is to develop a computationally-accessible micro-mechanically based continuum model, which is able to predict the macroscopic behavior of strain crystallizing natural rubber. While several researchers have developed micro-mechanical models of partially crystallized polymer chains, their results mainly give qualitative agreement with experimental data due to a lack of good micro-macro transition theories or the lack of computational power. However, recent developments in multiscale modeling in polymers provide new tools to continue this early work. In this thesis, a new model is proposed to model strain-induced crystallization in natural rubber. To this end, a micro-mechanical model of a constrained partially crystallized polymer chain with an extended-chain crystal is derived and connected to the macroscopic level using the non-affine micro-sphere model. On the macroscopic level, a thermodynamically consistent framework for strain-crystallizing materials is developed, and a description of the crystallization kinetics is introduced. For that matter, an evolution law for crystallization based on the gradient of the macroscopic Helmholtz free energy function (chemical potential) in combination with a simple threshold function is used. A numerical implementation of the model is proposed and its predictive performance assessed using published data.
Rigorous modeling of cladding modes in photonic crystal fibers
DEFF Research Database (Denmark)
Rindorf, Lars Henning; Bang, Ole
We study the cladding modes of a photonic crystal fiber (PCF) with a finite size cladding using a finite element method. The cladding consists of seven rings of air holes with bulk silica outside.......We study the cladding modes of a photonic crystal fiber (PCF) with a finite size cladding using a finite element method. The cladding consists of seven rings of air holes with bulk silica outside....
Hysteresis behaviors of the crystal field diluted general spin-S Ising model
Akıncı, Ümit
2017-10-01
Hysteresis characteristics of the crystal field diluted general Spin-S (S > 1) Blume-Capel model have been studied within the effective field approximation. Particular emphasis has been paid on the large negative valued crystal field and low temperature region and it has been demonstrated for this region that, rising dilution of the crystal field results in decreasing number of windowed hysteresis loops. The evolution of the multiple hysteresis loop with the dilution of the crystal field has been investigated and physical mechanism behind this evolution has been given.
High order harmonic generation in rare gases
Energy Technology Data Exchange (ETDEWEB)
Budil, Kimberly Susan [Univ. of California, Davis, CA (United States)
1994-05-01
The process of high order harmonic generation in atomic gases has shown great promise as a method of generating extremely short wavelength radiation, extending far into the extreme ultraviolet (XUV). The process is conceptually simple. A very intense laser pulse (I ~10^{13}-10^{14} W/cm^{2}) is focused into a dense (~10^{17} particles/cm^{3}) atomic medium, causing the atoms to become polarized. These atomic dipoles are then coherently driven by the laser field and begin to radiate at odd harmonics of the laser field. This dissertation is a study of both the physical mechanism of harmonic generation as well as its development as a source of coherent XUV radiation. Recently, a semiclassical theory has been proposed which provides a simple, intuitive description of harmonic generation. In this picture the process is treated in two steps. The atom ionizes via tunneling after which its classical motion in the laser field is studied. Electron trajectories which return to the vicinity of the nucleus may recombine and emit a harmonic photon, while those which do not return will ionize. An experiment was performed to test the validity of this model wherein the trajectory of the electron as it orbits the nucleus or ion core is perturbed by driving the process with elliptically, rather than linearly, polarized laser radiation. The semiclassical theory predicts a rapid turn-off of harmonic production as the ellipticity of the driving field is increased. This decrease in harmonic production is observed experimentally and a simple quantum mechanical theory is used to model the data. The second major focus of this work was on development of the harmonic "source". A series of experiments were performed examining the spatial profiles of the harmonics. The quality of the spatial profile is crucial if the harmonics are to be used as the source for experiments, particularly if they must be refocused.
Scafetta, Nicola
2013-01-01
Power spectra of global surface temperature (GST) records reveal major periodicities at about 9.1, 10-11, 19-22 and 59-62 years. The Coupled Model Intercomparison Project 5 (CMIP5) general circulation models (GCMs), to be used in the IPCC (2013), are analyzed and found not able to reconstruct this variability. From 2000 to 2013.5 a GST plateau is observed while the GCMs predicted a warming rate of about 2 K/century. In contrast, the hypothesis that the climate is regulated by specific natural oscillations more accurately fits the GST records at multiple time scales. The climate sensitivity to CO2 doubling should be reduced by half, e.g. from the IPCC-2007 2.0-4.5 K range to 1.0-2.3 K with 1.5 C median. Also modern paleoclimatic temperature reconstructions yield the same conclusion. The observed natural oscillations could be driven by astronomical forcings. Herein I propose a semi empirical climate model made of six specific astronomical oscillations as constructors of the natural climate variability spanning ...
Harmonic Distortion in CMOS Current Mirrors
DEFF Research Database (Denmark)
Bruun, Erik
1998-01-01
One of the origins of harmonic distortion in CMOS current mirrors is the inevitable mismatch between the MOS transistors involved. In this paper we examine both single current mirrors and complementary class AB current mirrors and develop an analytical model for the mismatch induced harmonic...... distortion. This analytical model is verified through simulations and is used for a discussion of the impact of mismatch on harmonic distortion properties of CMOS current mirrors. It is found that distortion levels somewhat below 1% can be attained by carefully matching the mirror transistors but ultra low...
Directory of Open Access Journals (Sweden)
Yufei Liu
2015-01-01
Full Text Available This paper investigates the dynamic of a flexible robotic manipulator (FRM which consists of rigid driving base, flexible links, and flexible joints. With considering the motion fluctuations caused by the coupling effect, such as the motor parameters and mechanism inertias, as harmonic disturbances, the system investigated in this paper remains a parametrically excited system. An elastic restraint model of the FRM with elastic joints (FRMEJ is proposed, which considers the elastic properties of the connecting joints between the flexible arm and the driving base, as well as the harmonic disturbances aroused by the electromechanical coupling effect. As a consequence, the FRMEJ accordingly remains a flexible multibody system which conveys the effects of rigid-flexible couple and electromechanical couple. The Lagrangian function and Hamilton’s principle are used to establish the dynamic model of the FRMEJ. Based on the dynamic model proposed, the vibration power flow is introduced to show the vibration energy distribution. Numerical simulations are conducted to investigate the effect of the joint elasticities and the disturbance excitations, and the influences of the structure parameters and motion parameters on the vibration power flow are studied. The results obtained in this paper contribute to the structure design, motion optimization, and vibration control of FRMs.
Vibrational properties of model monatomic crystals under pressure
Wolf, George H.; Jeanloz, Raymond
1985-12-01
The roles of the attractive and repulsive forces in controlling the vibrational properties of monatomic crystals are systematically evaluated as a function of compression. Face-centered-cubic, hexagonal, and body-centered-cubic structures are considered with Lennard-Jones and Buckingham-type interatomic potentials. At zero pressure, the phonon frequencies and their mode-Grüneisen parameters deviate strongly from those of a reference state where the atoms interact solely through the corresponding purely repulsive potential. In detail, the degree of deviation depends on the structure, relative range of the repulsive and attractive forces, and the vibrational wavelength. With increasing pressure, the phonon frequencies asymptotically approach values of the purely repulsive reference state. Higher-order properties such as the mode-Grüneisen parameters and their logarithmic volume derivatives approach the repulsive limiting values more rapidly than do the frequencies, provided the associated modes do not become unstable. The close-packed lattices are dynamically stable at all positive pressures and display only a small variation among different orders of the frequency spectra Debye moments. However, this variation can be quite large for any structure at strains near that where the lattice is dynamically unstable. We find that the thermal Grüneisen parameter decreases with pressure, but the commonly assumed power-law relation of the thermal Grüneisen parameter with volume is violated. Average anharmonic vibrational properties are well described by a cell model in these monatomic systems at both low and high pressures. In addition, a strong correlation is found between the static-lattice compressional properties and the average vibrational properties; free-volume relations give good estimates of the high-temperature thermal properties, especially at high pressures.
Czochralski growth of crystals - Simple models for growth rate and interface shape
Srivastava, R. K.; Ramachandran, P. A.; Dudukovic, M. P.
1986-01-01
A simple model for the crystal growth by the Czochralski (CZ) process has been proposed based on semiquantitative arguments. The model provides empirical relationships for the dependence of the pulling rate and the interface shape on the important process variables such as crystal radius, crucible temperature, height of the melt level, and the height of the exposed portion of the crucible wall. The parameters of the model can be evaluated by matching the results obtained from a detailed mathematical model of the CZ process or from extensive experimental data. The model has, therefore, the potential application for determining the best process conditions and for on-line control and optimization of the crystal puller to grow crystals with constant diameter and nearly planar interface.
Simone, Colucci; Mattia, de'Michieli Vitturi; Patrizia, Landi
2017-12-01
Nucleation and growth of crystals, and the resulting crystal size distribution, play a fundamental role in controlling the physical properties of magmas and consequently the dynamics of the eruptions. In the past decades, laboratory experiments demonstrated that size and shape of crystals strongly control the physical properties of magma and lava. Additionally, natural and experimental samples are usually characterized in terms of their crystal size distribution to link it with physical processes that are not directly observable, such as cooling or decompression mechanisms. In this paper, we present CrystalMoM, a new predictive model, based on the quadrature-based method of moments, developed for studying the kinetic of crystallization in volcanic systems. The quadrature-based method of moments, well established in the field of chemical engineering, represents a mesoscale modelling approach that rigorously simulates the space-time evolution of a distribution of particles, by considering its moments. The method is applied here, for the first time, for studying the equilibrium/disequilibrium crystallization in magma, modelling the temporal evolution of the moments of a crystal size distribution. The model, verified against numerical and experimental data, represents a valuable tool to infer the cooling and decompression rates from the crystal size distribution observed in natural samples.
Raman, AFM and SNOM high resolution imaging of carotene crystals in a model carrot cell system.
Rygula, Anna; Oleszkiewicz, Tomasz; Grzebelus, Ewa; Pacia, Marta Z; Baranska, Malgorzata; Baranski, Rafal
2018-02-02
Three non-destructive and complementary techniques, Raman imaging, Atomic Force Microscopy and Scanning Near-field Optical Microscopy were used simultaneously to show for the first time chemical and structural differences of carotenoid crystals. Spectroscopic and microscopic scanning probe measurements were applied to the released crystals or to crystals accumulated in a unique, carotenoids rich callus tissue growing in vitro that is considered as a new model system for plant carotenoid research. Three distinct morphological crystal types of various carotenoid composition were identified, a needle-like, rhomboidal and helical. Raman imaging using 532 and 488 nm excitation lines provided evidence that the needle-like and rhomboidal crystals had similar carotenoid composition and that they were composed mainly of β-carotene accompanied by α-carotene. However, the presence of α-carotene was not identified in the helical crystals, which had the characteristic spatial structure. AFM measurements of crystals identified by Raman imaging revealed the crystal topography and showed the needle-like and rhomboidal crystals were planar but they differed in all three dimensions. Combining SNOM and Raman imaging enabled indication of carotenoid rich structures and visualised their distribution in the cell. The morphology of identified subcellular structures was characteristic for crystalline, membraneous and tubular chromoplasts that are plant organelles responsible for carotenoid accumulation in cells. Copyright © 2018 Elsevier B.V. All rights reserved.
On Regularity Criteria for the Two-Dimensional Generalized Liquid Crystal Model
Directory of Open Access Journals (Sweden)
Yanan Wang
2014-01-01
Full Text Available We establish the regularity criteria for the two-dimensional generalized liquid crystal model. It turns out that the global existence results satisfy our regularity criteria naturally.
Harmonic Aspects of Offshore Wind Farms
DEFF Research Database (Denmark)
Kocewiak, Lukasz Hubert; Bak, Claus Leth; Hjerrild, Jesper
2010-01-01
This paper presents the aim, the work and the findings of a PhD project entitled "Harmonics in Large Offshore Wind Farms". It focuses on the importance of harmonic analysis in order to obtain a better performance of future wind farms. The topic is investigated by the PhD project at Aalborg...... University (AAU) and DONG Energy. The objective of the project is to improve and understand the nature of harmonic emission and propagation in wind farms (WFs), based on available information, measurement data and simulation tools. The aim of the project is to obtain validated models and analysis methods...... of offshore wind farm (OWF) systems....
Selective harmonic control for power converters
DEFF Research Database (Denmark)
Zhou, Keliang; Yang, Yongheng; Blaabjerg, Frede
2014-01-01
This paper proposes an Internal Model Principle (IMP) based Selective Harmonic Controller (SHC) for power converters. The proposed SHC offers an optimal control solution for power converters to mitigate power harmonics. It makes a good trade-off among cost, complexity and performance. It has high...... accuracy and fast transient response, and it is cost-effective, easy for real-time implementation, and compatible for design rules-of-thumb. An application on a three-phase PWM converter has confirmed the effectiveness of the proposed control scheme in terms of harmonic mitigation....
Crystal structures and atomic model of NADPH oxidase
Magnani, Francesca; Nenci, Simone; Fananas, Elisa Millana; Ceccon, Marta; Romero, Elvira; Fraaije, Marco W.; Mattevi, Andrea
2017-01-01
NADPH oxidases (NOXs) are the only enzymes exclusively dedicated to reactive oxygen species (ROS) generation. Dysregulation of these polytopic membrane proteins impacts the redox signaling cascades that control cell proliferation and death. We describe the atomic crystal structures of the catalytic
Kinetic characteristics of the crystallization from model solutions of blood plasma
Golovanova, O. A.; Solodyankina, A. A.
2017-05-01
The kinetic regularities of crystallization (growth order and constants) in a model solution of blood plasma have been investigated. The particular order and crystallization constant are determined to be n magnesium ions > alanine, glycine, glucose, and citric acid. It is shown that the impurities affect to a greater extent the nucleation rather than the growth stage. It is also established that a change in pH within 7.0-8.0 does not affect the crystallization parameters of the system modeling the composition of human blood plasma.
Investigation of the cluster formation in lithium niobate crystals by computer modeling method
Energy Technology Data Exchange (ETDEWEB)
Voskresenskii, V. M.; Starodub, O. R., E-mail: ol-star@mail.ru; Sidorov, N. V.; Palatnikov, M. N. [Russian Academy of Sciences, Tananaev Institute of Chemistry and Technology of Rare Earth Elements and Mineral Raw Materials, Kola Science Centre (Russian Federation)
2017-03-15
The processes occurring upon the formation of energetically equilibrium oxygen-octahedral clusters in the ferroelectric phase of a stoichiometric lithium niobate (LiNbO{sub 3}) crystal have been investigated by the computer modeling method within the semiclassical atomistic model. An energetically favorable cluster size (at which a structure similar to that of a congruent crystal is organized) is shown to exist. A stoichiometric cluster cannot exist because of the electroneutrality loss. The most energetically favorable cluster is that with a Li/Nb ratio of about 0.945, a value close to the lithium-to-niobium ratio for a congruent crystal.
Derewenda, Zygmunt S.; Godzik, Adam
2017-01-01
Crystallization of macromolecules has long been perceived as a stochastic process, which cannot be predicted or controlled. This is consistent with another popular notion that the interactions of molecules within the crystal, i.e. crystal contacts, are essentially random and devoid of specific physicochemical features. In contrast, functionally relevant surfaces, such as oligomerization interfaces and specific protein-protein interaction sites, are under evolutionary pressures so their amino acid composition, structure and topology are distinct. However, current theoretical and experimental studies are significantly changing our understanding of the nature of crystallization. The increasingly popular ‘sticky patch’ model, derived from soft matter physics, describes crystallization as a process driven by interactions between select, specific surface patches, with properties thermodynamically favorable for cohesive interactions. Independent support for this model comes from various sources including structural studies and bioinformatics. Proteins that are recalcitrant to crystallization can be modified for enhanced crystallizability through chemical or mutational modification of their surface to effectively engineer ‘sticky patches’ which would drive crystallization. Here, we discuss the current state of knowledge of the relationship between the microscopic properties of the target macromolecule and its crystallizability, focusing on the ‘sticky patch’ model. We discuss state-of-art in silico methods that evaluate the propensity of a given target protein to form crystals based on these relationships, with the objective to design of variants with modified molecular surface properties and enhanced crystallization propensity. We illustrate this discussion with specific cases where these approaches allowed to generate crystals suitable for structural analysis. PMID:28573570
Third Harmonic Mechanism in Complex Plasmonic Fano Structures.
Metzger, Bernd; Schumacher, Thorsten; Hentschel, Mario; Lippitz, Markus; Giessen, Harald
2014-06-18
We perform third harmonic spectroscopy of dolmen-type nanostructures, which exhibit plasmonic Fano resonances in the near-infrared. Strong third harmonic emission is predominantly radiated close to the low energy peak of the Fano resonance. Furthermore, we find that the third harmonic polarization of the subradiant mode interferes destructively and diminishes the nonlinear signal in the far-field. By comparing the experimental third harmonic spectra with finite element simulations and an anharmonic oscillator model, we find strong indications that the source of the third harmonic is the optical nonlinearity of the bare gold enhanced by the resonant plasmonic polarization.
W.H. van Boom (Willem)
2009-01-01
textabstractThis paper presents a review of the literature on comparative tort law and economics. It pays special attention to the economics arguments against and in favour of harmonization of tort law in Europe.
Chen, Shigao; Kinnick, Randall R; Greenleaf, James F; Fatemi, Mostafa
2007-07-01
Vibro-acoustography is an imaging method that uses the radiation force of two interfering ultrasound beams of slightly different frequency to probe an object. An image is made using the acoustic emission resulted from the object vibration at the difference frequency. In this paper, the feasibility of imaging objects at twice the difference frequency (harmonic acoustic emission) is studied. Several possible origins of harmonic acoustic emission are explored. As an example, it is shown that microbubbles close to resonance can produce significant harmonic acoustic emission due to its high nonlinearity. Experiments demonstrate that, compared to the fundamental acoustic emission, harmonic acoustic emission greatly improves the contrast between microbubbles and other objects in vibro-acoustography (an improvement of 17-23 dB in these experiments). Applications of this technique include imaging the nonlinearity of the object and selective detection of microbubbles for perfusion imaging. The impact of microbubble destruction during the imaging process also is discussed.
Saether, Erik; Hochhalter, Jacob D.; Glaessgen, Edward H.
2012-01-01
A multiscale modeling methodology that combines the predictive capability of discrete dislocation plasticity and the computational efficiency of continuum crystal plasticity is developed. Single crystal configurations of different grain sizes modeled with periodic boundary conditions are analyzed using discrete dislocation plasticity (DD) to obtain grain size-dependent stress-strain predictions. These relationships are mapped into crystal plasticity parameters to develop a multiscale DD/CP model for continuum level simulations. A polycrystal model of a structurally-graded microstructure is developed, analyzed and used as a benchmark for comparison between the multiscale DD/CP model and the DD predictions. The multiscale DD/CP model follows the DD predictions closely up to an initial peak stress and then follows a strain hardening path that is parallel but somewhat offset from the DD predictions. The difference is believed to be from a combination of the strain rate in the DD simulation and the inability of the DD/CP model to represent non-monotonic material response.
Scafetta, N.
2012-12-01
We show that the Schwabe frequency band of the Zurich sunspot record since 1749 is made of three major cycles that are closely related to the spring tidal period of Jupiter and Saturn (~9.93 year), to the tidal sidereal period of Jupiter (about 11.86 years) and to a central cycle that may be associated to a quasi-11-year solar dynamo cycle. The central harmonic is approximately synchronized to the average of the two planetary frequencies. A harmonic model based on the above two planetary tidal frequencies and on the exact dates of Jupiter and Saturn planetary tidal phases, plus a theoretically deduced 10.87-year central cycle reveals major beat periods occurring at about 115, 61 and 130 years, plus a quasi-millennial large beat cycle around 983 years. Equivalent synchronized cycles are found in cosmogenic solar proxy records used to reconstruct solar activity and in proxy climate records throughout the Holocene (last 12,000 years) up to now. The quasi-secular beat oscillations hindcast reasonably well the known prolonged periods of low solar activity during the last millennium such as the Oort, Wolf, Sporer, Maunder and Dalton minima, as well as the 17 115-year long oscillations found in a detailed temperature reconstruction of the Northern Hemisphere covering the last 2000 years. The millennial three-frequency beat cycle hindcasts equivalent solar and climate cycles for 12,000 years. Finally, the harmonic model herein proposed reconstructs the prolonged solar minima around 1900-1920 and 1960-1980, the secular solar maxima around 1870-1890, 1940-1950 and 1995-2005, and a secular upward trending during the 20th century. The latter modulated trending agrees well with some solar proxy model, with the ACRIM TSI satellite composite and with the global surface temperature modulation since 1850. The model forecasts a new prolonged solar minimum during 2020-2045, which is produced by the minima of both the 61 and 115-year reconstructed cycles. Finally, the model predicts
Energy Technology Data Exchange (ETDEWEB)
Breitzke, M.
1990-02-09
A normal mode summation process and a frequency harmonic process for the modelling, recomposition and migration of dispersive seismic surveys. The use of underground seismic surveys to locate seams and to position small techtonic or atechtonic faults predominantly used in coal mining requires, because of the dispersive seismic waves, special computer processing. This work is concerned with two such techniques. The first is a normal mode summation process for modelling and recompression, this means the time-dependent deconvolution of dispersive waves from underground transmission data with any number of superimposed modes. The second is a recursive frequency harmonics migration process for dispersive waves from underground reflexion data. (orig.).
Tremblay, Jean Christophe
2013-06-28
A model for treating excitation and relaxation of adsorbates at metallic surfaces induced by non-adiabatic coupling is developed. The derivation is based on the concept of resonant electron transfer, where the adsorbate serves as a molecular bridge for the inelastic transition between an electron source and a sink. In this picture, energy relaxation and scanning tunneling microscopy (STM) at metallic surfaces are treated on an equal footing as a quasi-thermal process. The model goes beyond the local harmonic approximation and allows for an unbiased description of floppy systems with multiple potential wells. Further, the limitation of the product ansatz for the vibronic wave function to include the position-dependence of the non-adiabatic couplings is avoided by explicitly enforcing detailed balance. The theory is applied to the excitation of hydrogen on palladium, which has multiple local potential minima connected by low energy barriers. The main aspects investigated are the lifetimes of adsorbate vibrations in different adsorption sites, as well as the dependence of the excitation, response, and transfer rates on an applied potential bias. The excitation and relaxation simulations reveal intricate population dynamics that depart significantly from the simplistic tunneling model in a truncated harmonic potential. In particular, the population decay from an initially occupied local minimum induced by the contact with an STM tip is found to be better described by a double exponential. The two rates are interpreted as a response to the system perturbation and a transfer rate following the perturbation. The transfer rate is found to obey a power law, as was the case in previous experimental and theoretical work.
Kinetic modeling of multi‐component crystallization of industrial‐grade oils and fats
DEFF Research Database (Denmark)
Hjorth, Jeppe L.; Miller, Rasmus L.; Woodley, John M.
2015-01-01
. Growth is modeled using a modified Burton‐Cabrera‐Frank (BCF) model. Surface tensions and growth constants have been determined using focused‐beam‐reflectance measurements (FBRM). The required adjustable parameters in the model have been fitted to overall crystallization curves obtained by solid‐fat...
Forcher, Francesco; Redaelli, Stefano; Zanetti, Marco; CERN. Geneva. ATS Department
2018-01-01
The planes in crystalline solids can constrain the directions that charged particles take as they pass through. Physicists can use this "channelling" property of crystals to steer particle beams. In a bent crystal, for example, channelled particles follow the bend and can change their direction. Several studies are on-going at CERN to verify the possibility of using bent crystals as primary collimators in high energy hadron colliders like the LHC. Simulations have been developed to model the coherent interaction with crystalline planes. The goal of this note is to analyze the data collected on extracted beam from the SPS and develop an improved model to simulate the data’s subtleties, in particular the transition between the volume reﬂection and amorphous interactions of the beam with crystals.
Atomistic modeling of different loading paths in single crystal copper and aluminum
Directory of Open Access Journals (Sweden)
R. Pezer
2016-10-01
Full Text Available Utilizing molecular dynamics (MD integration model we have investigated some of the relevant physical processes caused by different loading paths at the atomic level in Cu and Al monocrystal specimen. Interactions among the atoms in the bulk are modeled with the standard realistic Embedded Atom Method (EAM potentials. MD simulation gives us the detailed information about non-equilibrium dynamics including crystal structure defects, vacancies and dislocations. In particular, we have obtained result that indicate increase in the total energy of the crystal during loading (especially cyclic that provides us direct quantitative evidence of the metal weakening. For the basic response, we have deformed copper and aluminum single crystal according to the simple loading path and a series of multiaxial loading-paths including cyclic repetition. We compute equivalent stress-strain diagrams as well as dislocation total length vs time graphs to describe signatures of the anisotropic response of the crystal
Mixed spin Ising model with four-spin interaction and random crystal field
Energy Technology Data Exchange (ETDEWEB)
Benayad, N., E-mail: n.benayad@fsac.ac.ma [Groupe de Mecanique Statistique, Laboratoire de physique theorique et appliquee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco); Laboratoire de physique des hautes energies et de la matiere condensee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco); Ghliyem, M. [Groupe de Mecanique Statistique, Laboratoire de physique theorique et appliquee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco); Laboratoire de physique des hautes energies et de la matiere condensee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco)
2012-01-01
The effects of fluctuations of the crystal field on the phase diagram of the mixed spin-1/2 and spin-1 Ising model with four-spin interactions are investigated within the finite cluster approximation based on a single-site cluster theory. The state equations are derived for the two-dimensional square lattice. It has been found that the system exhibits a variety of interesting features resulting from the fluctuation of the crystal field interactions. In particular, for low mean value D of the crystal field, the critical temperature is not very sensitive to fluctuations and all transitions are of second order for any value of the four-spin interactions. But for relatively high D, the transition temperature depends on the fluctuation of the crystal field, and the system undergoes tricritical behaviour for any strength of the four-spin interactions. We have also found that the model may exhibit reentrance for appropriate values of the system parameters.
Tehrani, Kayvan; Kner, Peter; Mortensen, Luke J.
2017-02-01
Multiphoton imaging through the bone to image into the bone marrow or the brain is an emerging need in the scientific community. Due to the highly scattering nature of bone, bone thinning or removal is typically required to enhance the resolution and signal intensity at the imaging plane. The optical aberrations and scattering in the bone significantly affect the resolution and signal to noise ratio of deep tissue microscopy. Multiphoton microscopy uses long wavelength (nearinfrared and infrared) excitation light to reduce the effects of scattering. However, it is still susceptible to optical aberrations and scattering since the light propagates through several layers of media with inhomogeneous indices of refraction. Mechanical removal of bone is highly invasive, laborious, and cannot be applied in experiments where imaging inside of the bone is desired. Adaptive optics technology can compensate for these optical aberrations and potentially restore the diffraction limited point spread function of the system even in deep tissue. To design an adaptive optics system, a priori knowledge of the sample structure assists selection of the proper correction element and sensing methods. In this work we present the characterization of optical aberrations caused by mouse cranial bone, using second harmonic generation imaging of bone collagen. We simulate light propagation through the bone, calculate aberrations and determine the correction that can be achieved using a deformable mirror.
On conformal supergravity and harmonic superspace
Energy Technology Data Exchange (ETDEWEB)
Butter, Daniel [Nikhef Theory Group,Science Park 105, 1098 XG Amsterdam (Netherlands)
2016-03-16
This paper describes a fully covariant approach to harmonic superspace. It is based on the conformal superspace description of conformal supergravity and involves extending the supermanifold M{sup 4|8} by the tangent bundle of ℂP{sup 1}. The resulting superspace M{sup 4|8}×TℂP{sup 1} can be identified in a certain gauge with the conventional harmonic superspace M{sup 4|8}×S{sup 2}. This approach not only makes the connection to projective superspace transparent, but simplifies calculations in harmonic superspace significantly by eliminating the need to deal directly with supergravity prepotentials. As an application of the covariant approach, we derive from harmonic superspace the full component action for the sigma model of a hyperkähler cone coupled to conformal supergravity. Further applications are also sketched.
The second order phase transition in Sn2P2S6 crystals: anharmonic oscillator model
Directory of Open Access Journals (Sweden)
Yu.M. Vysochanskii
2008-09-01
Full Text Available Statistical theory for ferroelectrics based on triple well anharmonic potential was used for the case of structural second order phase transition in Sn2P2S6 crystals. Parameters of effective Hamiltonian of the model were estimated using available experimental data. These findings confirm the assumption that the phase transition in these crystals is located in crossover region between order-disorder and displacive type, and very closely to tricritical point.
Modeling Nonlinear Elastic-plastic Behavior of RDX Single Crystals During Indentation
2012-01-01
single crystals has also been probed using shock experiments (6, 12) and molecular dynamics simulations (12–14). RDX undergoes a polymorphic phase... HMX ) (19) and pentaerythritol tetranitrate (PETN) (20, 21). Aims of the present work are to develop and implementent a crystal plasticity model for...which is the stable polymorph for pressures under ≈ 3.8 GPa and temperatures under ≈ 480 K. High pressure phases with different structures (γ , β ) and
MSET modeling of Crystal River-3 venturi flow meters.
Energy Technology Data Exchange (ETDEWEB)
Bockhorst, F. K.; Gross, K. C.; Herzog, J. P.; Wegerich, S. W.
1998-01-05
The analysis of archived Crystal River-3 feedwater flow data reveals a slow and steady degradation of the flow meter measurements during the 1992/1993 operating cycle. MSET can reliably estimate the true flow rate and quantify the degree of departure between the indicated signal and the true flow rate with high accuracy. The MSET computed flow rate could, in principle, be used to provide an improved estimate of the reactor power and hence avoid the revenue loss associated with derating the reactor based on a faulty feedwater flow rate indication.
A High-Rate, Single-Crystal Model including Phase Transformations, Plastic Slip, and Twinning
Energy Technology Data Exchange (ETDEWEB)
Addessio, Francis L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Bronkhorst, Curt Allan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Bolme, Cynthia Anne [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Explosive Science and Shock Physics Division; Brown, Donald William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Cerreta, Ellen Kathleen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Lebensohn, Ricardo A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Lookman, Turab [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Luscher, Darby Jon [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Mayeur, Jason Rhea [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Morrow, Benjamin M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division; Rigg, Paulo A. [Washington State Univ., Pullman, WA (United States). Dept. of Physics. Inst. for Shock Physics
2016-08-09
An anisotropic, rate-dependent, single-crystal approach for modeling materials under the conditions of high strain rates and pressures is provided. The model includes the effects of large deformations, nonlinear elasticity, phase transformations, and plastic slip and twinning. It is envisioned that the model may be used to examine these coupled effects on the local deformation of materials that are subjected to ballistic impact or explosive loading. The model is formulated using a multiplicative decomposition of the deformation gradient. A plate impact experiment on a multi-crystal sample of titanium was conducted. The particle velocities at the back surface of three crystal orientations relative to the direction of impact were measured. Molecular dynamics simulations were conducted to investigate the details of the high-rate deformation and pursue issues related to the phase transformation for titanium. Simulations using the single crystal model were conducted and compared to the high-rate experimental data for the impact loaded single crystals. The model was found to capture the features of the experiments.
DEFF Research Database (Denmark)
Abdul Samad, Noor Asma Fazli Bin
A generic and systematic model-based framework for the design of a process monitoring and control system to achieve the desired crystal size distribution (CSD) and crystal shape for a wide range of crystallization processes has been developed. This framework combines a generic multi-dimensional m...
Microwave harmonic generation and nonlinearity in microplasmas
Gregório, José; Parsons, Stephen; Hopwood, Jeffrey
2016-06-01
Nonlinearities in microplasmas excited by microwaves are described both experimentally and through a 2D fluid model. A split-ring resonator generates a microplasma in a 150 μm discharge gap at 1 GHz. Nonlinearity generates both radiated and conducted harmonics which are measured from 0.2-760 Torr (Ar) for power levels between 0.5 and 3 W. Asymmetric electrode configurations produce the highest 3rd harmonic power (>10 mW) at an optimal pressure of the order of 0.3 Torr. The microplasma is also demonstrated as a mixer. The experimental results are explained with the aid of a fluid model of the microplasma. The model shows that the smaller electrode in an asymmetric device is forced to attain a large microwave potential that strongly modulates the sheath thickness and the local electron energy. The voltage-dependent sheath width gives rises to a nonlinear sheath capacitance as well as short pulses of hot electron flux to the electrode. The modeled 3rd harmonic current is converted to an extractable harmonic power by a microwave circuit model. Using this technique the modeled and measured harmonic production of the microplasma are found to compare favorably.
Cascading nonlinearities in an organic single crystal core fiber: The Cerenkov regime
Torruellas, William E.; Krijnen, Gijsbertus J.M.; Kim, Dug Y.; Schiek, Roland; Stegeman, George J.; Vidakovic, Petar; Zyss, Joseph
1994-01-01
The large nonlinear phase shifts imparted to the fundamental beam during Cerenkov second harmonic generation (SHG) in a DAN, 4-(N,N-dimethylamino)-3-acetamidonitrobenzene, single crystal core fiber are explained and modelled numerically. Cascading upconversion and downconversion processes leads to
Harmonic Analysis of Offshore Wind Farms with Full Converter Wind Turbines
DEFF Research Database (Denmark)
Kocewiak, Lukasz Hubert; Hjerrild, Jesper; Bak, Claus Leth
2009-01-01
This paper presents the harmonic analysis of offshore wind farm (OWF) models with full converters represented as harmonic sources and measurement data on the point of common coupling (PCC) during normal operation. The model describes a wind farm (WF) with full rated converters installed connected...... to a shore with a long HV cable. The way of propagation and effects of harmonics are presented for different study cases. Modeling strategies of harmonic sources for harmonic analysis are described and compared. Different results dependent on applied harmonic models are shown and discussed in this paper...
Bennett, Charles L.
2016-03-22
A reciprocating-piston uniflow engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. When released, the inlet valve head undergoes a single oscillation past the equilibrium position to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. In other embodiments, the harmonic oscillator arrangement of the inlet valve enables the uniflow engine to be reversibly operated as a uniflow compressor.
Second harmonic generation imaging
2013-01-01
Second-harmonic generation (SHG) microscopy has shown great promise for imaging live cells and tissues, with applications in basic science, medical research, and tissue engineering. Second Harmonic Generation Imaging offers a complete guide to this optical modality, from basic principles, instrumentation, methods, and image analysis to biomedical applications. The book features contributions by experts in second-harmonic imaging, including many pioneering researchers in the field. Written for researchers at all levels, it takes an in-depth look at the current state of the art and possibilities of SHG microscopy. Organized into three sections, the book: Provides an introduction to the physics of the process, step-by-step instructions on how to build an SHG microscope, and comparisons with related imaging techniques Gives an overview of the capabilities of SHG microscopy for imaging tissues and cells—including cell membranes, muscle, collagen in tissues, and microtubules in live cells—by summarizing experi...
Jin, Lihua; Zeng, Zhi; Huo, Yongzhong
2010-11-01
Liquid crystal elastomer is a kind of anisotropic polymeric material, with complicated micro-structures and thermo-order-mechanical coupling behaviors. In this paper, we propose a method to systematically model these coupling behaviors. We derive the constitutive model in full tensor structure according to the Clausius-Duhem inequality. Two of the constitutive equations represent the mechanical equilibrium and the other two represent the phase equilibrium. Choosing the total free energy as the combination of the neo-classical free energy and the Landau-de Gennes nematic free energy, we obtain the Cauchy stress-deformation gradient relation and the order-mechanical coupling equations. We find the analytical homogeneous solutions of the deformation for the typical mechanical loadings, such as uniaxial stretch, and simple shear in any directions. We also compare the compression behavior of prolate liquid crystal elastomers with the stretch behavior of oblate liquid crystal elastomers. As a result, the stress, strain, temperature, order parameter, biaxiality and the direction of the director of liquid crystal elastomers couple with each other. When the prolate liquid crystal elastomer sample is stretched in the direction parallel to its director, the deviatoric stress makes the mesogens more order and increase the transition temperature. When the sample is sheared or stretched in the direction non-parallel to the director, the director of the liquid crystal elastomer will rotate, and the biaxiality will be induced. Because of the order-mechanical coupling, under infinitesimal deformation, liquid crystal elastomer has anisotropic Young's modulus and zero shear modulus in the direction parallel or perpendicular to the director. While for the oblate liquid crystal elastomers, the stretch parallel to the director will cause the rotation of the director and induce the biaxiality.
DEFF Research Database (Denmark)
Abdul Samad, Noor Asma Fazli; Singh, Ravendra; Sin, Gürkan
2011-01-01
A generic multi-dimensional modeling framework for studying batch cooling crystallization processes under generated operational policies is presented. The generic nature of the modeling allows the study of a wide range of chemical systems under different operational scenarios, enabling thereby, t...
General Criterion for Harmonicity
Proesmans, Karel; Vandebroek, Hans; Van den Broeck, Christian
2017-10-01
Inspired by Kubo-Anderson Markov processes, we introduce a new class of transfer matrices whose largest eigenvalue is determined by a simple explicit algebraic equation. Applications include the free energy calculation for various equilibrium systems and a general criterion for perfect harmonicity, i.e., a free energy that is exactly quadratic in the external field. As an illustration, we construct a "perfect spring," namely, a polymer with non-Gaussian, exponentially distributed subunits which, nevertheless, remains harmonic until it is fully stretched. This surprising discovery is confirmed by Monte Carlo and Langevin simulations.
Harmonic arbitrary waveform generator
Energy Technology Data Exchange (ETDEWEB)
Roberts, Brock Franklin
2017-11-28
High frequency arbitrary waveforms have applications in radar, communications, medical imaging, therapy, electronic warfare, and charged particle acceleration and control. State of the art arbitrary waveform generators are limited in the frequency they can operate by the speed of the Digital to Analog converters that directly create their arbitrary waveforms. The architecture of the Harmonic Arbitrary Waveform Generator allows the phase and amplitude of the high frequency content of waveforms to be controlled without taxing the Digital to Analog converters that control them. The Harmonic Arbitrary Waveform Generator converts a high frequency input, into a precision, adjustable, high frequency arbitrary waveform.
Quantum harmonically kicked environments
Custódio, M. S.; Strunz, W. T.; Beims, M. W.
2017-11-01
In this work we derive a generalized map which describes the time evolution of a quantum system coupled to a quantum environment composed by a finite number of free particles kicked harmonically at periodic times. Dissipation is introduced via the interaction between system and environment, which is switched on and off simultaneously at regular time intervals. The dynamics of the environmental particles occurs along rotated ellipsis in phase space and can be described by unrotated harmonic oscillators with a new frequency which depends on the kicking time. With the definition of a thermal bath we show that our quantum kicked environment induces an unusual fluctuation-dissipation relation.
Booster Double Harmonic Setup Notes
Energy Technology Data Exchange (ETDEWEB)
Gardner, C. J. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.
2015-02-17
The motivation behind implementing a booster double harmonic include the reduced transverse space charge force from a reduced peak beam current and reduced momentum spread of the beam, both of which can be achieved from flattening the RF bucket. RF capture and acceleration of polarized protons (PP) is first set up in the single harmonic mode with RF harmonic h=1. Once capture and acceleration have been set up in the single harmonic mode, the second harmonic system is brought on and programmed to operate in concert with the single harmonic system.
Simulations of micro-bending of thin foils using a scale dependent crystal plasticity model
DEFF Research Database (Denmark)
Kuroda, Mitsutoshi; Tvergaard, Viggo; Ohashi, T.
2007-01-01
In this paper, we perform crystal plasticity analyses of micro-bending of thin f.c.c. metal foils having thicknesses ranging from 10 to 50 mu m. The scale dependent crystal plasticity model used here is a viscoplastic finite strain version of the model proposed by Ohashi (2005 Int. J. Plast. 21...... 2071-88), in which the mean free path of moving dislocations is determined by a function of the densities of statistically stored dislocations (SSDs) and geometrically necessary dislocations (GNDs), while the slip resistance for each slip system is determined only by the density of SSDs through...... a Bailey-Hirsch type relation. The computational results are compared with the experimental results for Ni foils, reported in Stolken and Evans (1998 Acta Mater. 46 5109-15). The validity of the current model and the direction of future development of the 'physically-based' scale dependent crystal...
Nucleation of crystals from solution: classical and two-step models.
Erdemir, Deniz; Lee, Alfred Y; Myerson, Allan S
2009-05-19
Crystallization is vital to many processes occurring in nature and in the chemical, pharmaceutical, and food industries. Notably, crystallization is an attractive isolation step for manufacturing because this single process combines both particle formation and purification. Almost all of the products based on fine chemicals, such as dyes, explosives, and photographic materials, require crystallization in their manufacture, and more than 90% of all pharmaceutical products contain bioactive drug substances and excipients in the crystalline solid state. Hence control over the crystallization process allows manufacturers to obtain products with desired and reproducible properties. We judge the quality of a crystalline product based on four main properties: size, purity, morphology, and crystal structure. The pharmaceutical industry in particular requires production of the desired crystal form (polymorph) to assure the bioavailability and stability of the drug substance. In solution crystallization, nucleation plays a decisive role in determining the crystal structure and size distribution. Therefore, understanding the fundamentals of nucleation is crucial to achieve control over these properties. Because of its analytical simplicity, researchers have widely applied classical nucleation theory to solution crystallization. However, a number of differences between theoretical predictions and experimental results suggest that nucleation of solids from solution does not proceed via the classical pathway but follows more complex routes. In this Account, we discuss the shortcomings of classical nucleation theory and review studies contributing to the development of the modern two-step model. In the two-step model that was initially proposed for protein crystallization, a sufficient-sized cluster of solute molecules forms first, followed by reorganization of that cluster into an ordered structure. In recent experimental and theoretical studies, we and other researchers have
Scafetta, Nicola
2012-05-01
The Schwabe frequency band of the Zurich sunspot record since 1749 is found to be made of three major cycles with periods of about 9.98, 10.9 and 11.86 years. The side frequencies appear to be closely related to the spring tidal period of Jupiter and Saturn (range between 9.5 and 10.5 years, and median 9.93 years) and to the tidal sidereal period of Jupiter (about 11.86 years). The central cycle may be associated to a quasi-11-year solar dynamo cycle that appears to be approximately synchronized to the average of the two planetary frequencies. A simplified harmonic constituent model based on the above two planetary tidal frequencies and on the exact dates of Jupiter and Saturn planetary tidal phases, plus a theoretically deduced 10.87-year central cycle reveals complex quasi-periodic interference/beat patterns. The major beat periods occur at about 115, 61 and 130 years, plus a quasi-millennial large beat cycle around 983 years. We show that equivalent synchronized cycles are found in cosmogenic records used to reconstruct solar activity and in proxy climate records throughout the Holocene (last 12,000 years) up to now. The quasi-secular beat oscillations hindcast reasonably well the known prolonged periods of low solar activity during the last millennium such as the Oort, Wolf, Spörer, Maunder and Dalton minima, as well as the 17 115-year long oscillations found in a detailed temperature reconstruction of the Northern Hemisphere covering the last 2000 years. The millennial three-frequency beat cycle hindcasts equivalent solar and climate cycles for 12,000 years. Finally, the harmonic model herein proposed reconstructs the prolonged solar minima that occurred during 1900-1920 and 1960-1980 and the secular solar maxima around 1870-1890, 1940-1950 and 1995-2005 and a secular upward trending during the 20th century: this modulated trending agrees well with some solar proxy model, with the ACRIM TSI satellite composite and with the global surface temperature
Squeezing and entanglement in doubly resonant, type II, second-harmonic generation
DEFF Research Database (Denmark)
Andersen, Ulrik Lund; Buchhave, Preben
2003-01-01
We investigate, theoretically, the generation of bright and vacuum-squeezed light as well as entanglement in intracavity, type II, phase-matched second-harmonic generation. The cavity in which the crystal is embedded is resonant at the fundamental frequency but not at the second-harmonic frequency....... A simple model for the process using semiclassical theory is derived, and quadrature-squeezing spectra of the involved fundamental fields are deduced. The analysis shows that vacuum squeezing reminiscent of subthreshold optical parametric oscillator squeezing is present and, in the ideal case, perfect....... Under slight modifications of the operational conditions, the system is shown to produce efficient bright, squeezed light. Furthermore, we investigate the degree of polarization squeezing and find that three Stokes parameters can be squeezed simultaneously. Finally, we gauge the process for possible...
Effect of transition dipole phase on high-order-harmonic generation in solid materials
Jiang, Shicheng; Wei, Hui; Chen, Jigen; Yu, Chao; Lu, Ruifeng; Lin, C. D.
2017-11-01
High-order harmonic spectra from solid materials driven by single-color multicycle laser fields sometimes contain even harmonics. In this work we attribute the appearance of even harmonics to the nonzero transition dipole phase (TDP) when the solid system has broken symmetry. By calculating the harmonic efficiency from graphene and gapped graphene by using the semiconductor Bloch equations under the tight-binding approximation, we demonstrate the role of the TDP, which has been ignored for a long time. When the crystal has inversion symmetry, or reflection symmetry with the symmetry plane perpendicular to the laser polarization direction, the TDP can be neglected. Without such symmetry, however, the TDP will lead to the appearance of even harmonics. We further show that the TDP is sensitive to the crystal geometry. To extract the structure information from the harmonic spectra of a solid the TDP cannot be ignored.
A modelling and experimental study of the bubble trajectory in a non-Newtonian crystal suspension
Energy Technology Data Exchange (ETDEWEB)
Hassan, N M S [Process Engineering and Light Metals (PELM) Centre, Faculty of Sciences, Engineering and Health, CQUniversity, Rockhampton, QLD 4702 (Australia); Khan, M M K; Rasul, M G, E-mail: m.rasul@cqu.edu.a [School of Engineering and Built Environment, Faculty of Sciences, Engineering and Health, CQUniversity, Rockhampton, QLD 4702 (Australia)
2010-12-15
This paper presents an experimental and computational study of air bubbles rising in a massecuite-equivalent non-Newtonian crystal suspension. The bubble trajectory inside the stagnant liquid of a 0.05% xanthan gum crystal suspension was investigated and modelled using the computational fluid dynamics (CFD) model to gain an insight into the bubble flow characteristics. The CFD code FLUENT was used for numerical simulation, and the bubble trajectory calculations were performed through a volume of fluid (VOF) model. The influences of the Reynolds number (Re), the Weber number (We) and the bubble aspect ratio (E) on the bubble trajectory are discussed. The conditions for the bubbles' path oscillations are identified. The experimental results showed that the path instability for the crystal suspension was less rapid than in water. The trajectory analysis indicated that 5.76 mm diameter bubbles followed a zigzag motion in the crystal suspension. Conversely, the smaller bubbles (5.76 mm) followed a path of least horizontal movement and larger bubbles (21.21 mm) produced more spiral motion within the crystal suspension. Path instability occurred for bubbles of 15.63 and 21.21 mm diameter, and they induced both zigzag and spiral trajectories within the crystal suspension. At low Re and We, smaller bubbles (5.76 mm) produced a zigzag trajectory, whereas larger bubbles (15.63 and 21.21 mm) showed both zigzag and spiral trajectories at intermediate and moderately high Re and We in the crystal suspension. The simulation results illustrated that a repeating pattern of swirling vortices was created for smaller bubbles due to the unstable wake and unsteady flow of these bubbles. This is the cause of the smaller bubbles moving in a zigzag way. Larger bubbles showed two counter-rotating trailing vortices at the back of the bubble. These vortices induced a velocity component to the gas-liquid interface and caused a deformation. Hence, the larger bubbles produced a path
A modelling and experimental study of the bubble trajectory in a non-Newtonian crystal suspension
Hassan, N. M. S.; Khan, M. M. K.; Rasul, M. G.
2010-12-01
This paper presents an experimental and computational study of air bubbles rising in a massecuite-equivalent non-Newtonian crystal suspension. The bubble trajectory inside the stagnant liquid of a 0.05% xanthan gum crystal suspension was investigated and modelled using the computational fluid dynamics (CFD) model to gain an insight into the bubble flow characteristics. The CFD code FLUENT was used for numerical simulation, and the bubble trajectory calculations were performed through a volume of fluid (VOF) model. The influences of the Reynolds number (Re), the Weber number (We) and the bubble aspect ratio (E) on the bubble trajectory are discussed. The conditions for the bubbles' path oscillations are identified. The experimental results showed that the path instability for the crystal suspension was less rapid than in water. The trajectory analysis indicated that 5.76 mm diameter bubbles followed a zigzag motion in the crystal suspension. Conversely, the smaller bubbles (5.76 mm) followed a path of least horizontal movement and larger bubbles (21.21 mm) produced more spiral motion within the crystal suspension. Path instability occurred for bubbles of 15.63 and 21.21 mm diameter, and they induced both zigzag and spiral trajectories within the crystal suspension. At low Re and We, smaller bubbles (5.76 mm) produced a zigzag trajectory, whereas larger bubbles (15.63 and 21.21 mm) showed both zigzag and spiral trajectories at intermediate and moderately high Re and We in the crystal suspension. The simulation results illustrated that a repeating pattern of swirling vortices was created for smaller bubbles due to the unstable wake and unsteady flow of these bubbles. This is the cause of the smaller bubbles moving in a zigzag way. Larger bubbles showed two counter-rotating trailing vortices at the back of the bubble. These vortices induced a velocity component to the gas-liquid interface and caused a deformation. Hence, the larger bubbles produced a path transition.
Energy Technology Data Exchange (ETDEWEB)
Nanev, C.N.; Dimitrov, I.L.; Hodzhaoglu, F.V. [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia (Bulgaria)
2011-02-15
Insulin is the only protein that is secreted in a crystalline form in a human healthy body. To mimic the secretion process we used NaCl salting-out to growing tiny rhombohedral Zn-insulin crystals. The dissolution of the insulin crystals is of special interest for the therapeutical praxis, because the human body is supplied with the physiologically active monomers of the insulin through dissolution of the crystalline granules secreted in the pancreatic {beta}-cells. Sets of tiny rhombohedral Zn-insulin crystals, which resembled the granules secreted in the {beta}-cells, were subjected to dissolution in blood plasma and model solutions. The impacts of the solution composition, flow rate, pH and ionic strength on the insulin crystal dissolution were investigated. The effect of the blood plasma was determinant because it dissolved the rhombohedral Zn-insulin crystals almost instantly, while the effects of solution's physicochemical characteristics were of minor importance. In addition, we found that the presence of abundant zinc ions suppressed the dissolution of the insulin crystals. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Directory of Open Access Journals (Sweden)
Ahmad Soni
2014-12-01
Full Text Available Kidney stones is a disease that characterized by a disturbance in the bladder. The main constituent of kidney stones namely Calcium Oxalate Monohydrate (COM crystals. The presence of a COM crystal adhesion to renal tubular cells, will initiate the internalization which will further lead to the formation of crystals retention in the kidney. In Indonesia, there are many herbal products are considered able to cope the complaints due to the kidney stone disease. One of the herbal product is Calcusol „¢, which is the main constituent of those herbal product was the leaf extract of tempuyung. This study observed the effectiveness of Calcusol „¢ in reducing crystals retention that was formed in kidney epithelial cells model of nephrolithiasis. The result showed that Calcusol „¢ is able to reduce the average number of calcium crystals retention in the renal epithelial cells. It indicate that Calcusol „¢ has the ability to reduce crystals retention that already formed in renal epithelial cells. Furthermore, the results of this study are expected to be one of the considerations for further research on the potential of overcoming Calcusol „¢ in kidney stone disease
Harmonic Intravascular Ultrasound
M.E. Frijlink (Martijn)
2006-01-01
textabstractMedical ultrasound is a popular imaging modality in cardiology. Harmonic Imaging is a technique that has been shown to increase the image quality of diagnostic ultrasound at frequencies below 10 MHz. However, Intravascular Ultrasound, which is a technique to acoustically investigate
Interfacial free energy adjustable phase field crystal model for homogeneous nucleation.
Guo, Can; Wang, Jincheng; Wang, Zhijun; Li, Junjie; Guo, Yaolin; Huang, Yunhao
2016-05-18
To describe the homogeneous nucleation process, an interfacial free energy adjustable phase-field crystal model (IPFC) was proposed by reconstructing the energy functional of the original phase field crystal (PFC) methodology. Compared with the original PFC model, the additional interface term in the IPFC model effectively can adjust the magnitude of the interfacial free energy, but does not affect the equilibrium phase diagram and the interfacial energy anisotropy. The IPFC model overcame the limitation that the interfacial free energy of the original PFC model is much less than the theoretical results. Using the IPFC model, we investigated some basic issues in homogeneous nucleation. From the viewpoint of simulation, we proceeded with an in situ observation of the process of cluster fluctuation and obtained quite similar snapshots to colloidal crystallization experiments. We also counted the size distribution of crystal-like clusters and the nucleation rate. Our simulations show that the size distribution is independent of the evolution time, and the nucleation rate remains constant after a period of relaxation, which are consistent with experimental observations. The linear relation between logarithmic nucleation rate and reciprocal driving force also conforms to the steady state nucleation theory.
Young children's harmonic perception.
Costa-Giomi, Eugenia
2003-11-01
Harmony and tonality are two of the most difficult elements for young children to perceive and manipulate and are seldom taught in the schools until the end of early childhood. Children's gradual harmonic and tonal development has been attributed to their cumulative exposure to Western tonal music and their increasing experiential knowledge of its rules and principles. Two questions that are relevant to this problem are: (1) Can focused and systematic teaching accelerate the learning of the harmonic/tonal principles that seem to occur in an implicit way throughout childhood? (2) Are there cognitive constraints that make it difficult for young children to perceive and/or manipulate certain harmonic and tonal principles? A series of studies specifically addressed the first question and suggested some possible answers to the second one. Results showed that harmonic instruction has limited effects on children's perception of harmony and indicated that the drastic improvement in the perception of implied harmony noted approximately at age 9 is due to development rather than instruction. I propose that young children's difficulty in perceiving implied harmony stems from their attention behaviors. Older children have less memory constraints and more strategies to direct their attention to the relevant cues of the stimulus. Younger children focus their attention on the melody, if present in the stimulus, and specifically on its concrete elements such as rhythm, pitch, and contour rather than its abstract elements such as harmony and key. The inference of the abstract harmonic organization of a melody required in the perception of implied harmony is thus an elusive task for the young child.
Energy Technology Data Exchange (ETDEWEB)
Matyáš, Josef; Gervasio, Vivianaluxa; Sannoh, Sulaiman E.; Kruger, Albert A.
2017-11-01
The effectiveness of HLW vitrification is limited by precipitation/accumulation of spinel crystals [(Fe, Ni, Mn, Zn)(Fe, Cr)2O4] in the glass discharge riser of Joule-heated ceramic melters during idling. These crystals do not affect glass durability; however, if accumulated in thick layer, they can clog the melter and prevent discharge of molten glass into canisters. To address this problem, an empirical model was developed that can predict thicknesses of accumulated layers as a function of glass composition. This model predicts well the accumulation of single crystals and/or small-scale agglomerates, but, excessive agglomeration observed in high-Ni-Fe glass resulted in an under-prediction of accumulated layers, which gradually worsen over time as an increased number of agglomerates formed. Accumulation rate of ~53.8 ± 3.7 µm/h determined for this glass will result in ~26 mm thick layer in 20 days of melter idling.
Harmonic Patterns in Forex Trading
Nemček, Sebastian
2013-01-01
This diploma thesis is committed to examination of validity of Harmonic Patterns in Forex trading. Scott Carney described existing and introduced new Harmonic Patterns in 1999 in his book Harmonic Trader. These patterns use the Fibonacci principle to analyze price action and to provide both bullish and bearish trading signals. The goal of this thesis is to find out whether harmonic trading strategy on selected pairs is profitable in FX market, which patterns are the most profitable and what i...
Thermodynamic consistency and fast dynamics in phase field crystal modeling
Cheng, Mowei; Cottenier, Stefaan; Emmerich, Heike
2008-01-01
A general formulation is presented to derive the equation of motion and to demonstrate thermodynamic consistency for several classes of phase field models at once. It applies to models with a conserved phase field, describing either uniform or periodic stable states, and containing slow as well as fast thermodynamic variables. The approach is based on an entropy functional formalism previously developed in the context of phase field models for uniform states [P. Galenko and D. Jou, Phys. Rev....
Modelling of ion implantation in SiC crystals
Energy Technology Data Exchange (ETDEWEB)
Chakarov, Ivan [SILVACO International, 4701 Patrick Henry Drive, Building 2, Santa Clara, CA 95054 (United States)]. E-mail: ivan.chakarov@silvaco.com; Temkin, Misha [SILVACO International, 4701 Patrick Henry Drive, Building 2, Santa Clara, CA 95054 (United States)
2006-01-15
An advanced electronic stopping model for ion implantation in SiC has been implemented within the binary collision approximation. The model has been thoroughly tested and validated for Al implantation into 4H-, 6H-SiC under different initial implant conditions. A very good agreement between calculated and experimental profiles has been achieved. The model has been integrated in an industrial technology CAD process simulator.
Coherent harmonic production using a two-section undulator FEL
Energy Technology Data Exchange (ETDEWEB)
Jaroszynski, D.A. [Commissariat a l`Energie, Bruyeres-le-Chatel (France); Prazeres, R.; Glotin, F. [Centre Universitaire Paris-Sud (France)] [and others
1995-12-31
We present measurements and a theoretical analysis of a new method of generating harmonic radiation in a free-electron laser oscillator with a two section undulator in a single optical cavity. To produce coherent harmonic radiation the undulator is arranged so that the downstream undulator section resonance frequency matches a harmonic of the upstream undulator. Both the fundamental and the harmonic optical fields evolve in the same optical cavity and are coupled out with different extraction fractions using a hole in one of the cavity mirrors. We present measurements that show that the optical power at the second and third harmonic can be enhanced by more than an order of magnitude in this fundamental/harmonic configuration. We compare the production of harmonic radiation of a two sectioned fundamental/harmonic undulator with that produced from a FEL operating at its highest efficiency with a step-tapered undulator, where the bunching at the end of the first section is very large. We examine, the dependence of the harmonic power on the intracavity power by adjusting the optical cavity desynchronism, {delta}L. We also examine the evolution of the fundamental and harmonic powers as a function of cavity roundtrip number to evaluate the importance of the small signal gain at the harmonic. We compare our measurements with predictions of a multi-electron numerical model that follows the evolution of fundamental and harmonic power to saturation. This fundamental/harmonic mode, of operation of the FEL may have useful applications in the production of coherent X-ray and VUV radiation, a spectral range where high reflectivity optical cavity mirrors are difficult or impossible to manufacture.
Dual-time scale crystal plasticity FE model for cyclic deformation of Ti alloys
Manchiraju, Sivom; Kirane, Kedar; Ghosh, Somnath
2007-12-01
A dual-time scale finite element model is developed in this paper for simulating cyclic deformation in a Titanium alloy Ti-6242. The material is characterized by crystal plasticity constitutive relations. Modeling cyclic deformation using conventional time integration algorithms in a single time scale can be prohibitive for crystal plasticity computations. Typically 3D crystal plasticity based fatigue simulations found in the literature are in the range of 100 cycles. Results are subsequently extrapolated to thousands of cycles, which can lead to considerable error in fatigue predictions. However, the dual-time scale model enables simulations up to a significantly high number of cycles to reach local states of damage initiation leading to fatigue crack growth. This formulation decomposes the governing equations into two sets of problems, corresponding to a coarse time scale (low frequency) cycle-averaged problem and a fine time scale (high frequency) oscillatory problem. A statistically equivalent 3D polycrystalline model of Ti-6242 is simulated by the crystal plasticity finite element model to study the evolution of local stresses and strains in the microstructure with cyclic loading. The comparison with the single time scale reference solution shows excellent accuracy while the efficiency gained through time-scale compression can be enormous.
Characterization of a plasma photonic crystal using a multi-fluid plasma model
Thomas, W. R.; Shumlak, U.; Wang, B.; Righetti, F.; Cappelli, M. A.; Miller, S. T.
2017-10-01
Plasma photonic crystals have the potential to significantly expand the capabilities of current microwave filtering and switching technologies by providing high speed (μs) control of energy band-gap/pass characteristics in the GHz through low THz range. While photonic crystals consisting of dielectric, semiconductor, and metallic matrices have seen thousands of articles published over the last several decades, plasma-based photonic crystals remain a relatively unexplored field. Numerical modeling efforts so far have largely used the standard methods of analysis for photonic crystals (the Plane Wave Expansion Method, Finite Difference Time Domain, and ANSYS finite element electromagnetic code HFSS), none of which capture nonlinear plasma-radiation interactions. In this study, a 5N-moment multi-fluid plasma model is implemented using University of Washington's WARPXM finite element multi-physics code. A two-dimensional plasma-vacuum photonic crystal is simulated and its behavior is characterized through the generation of dispersion diagrams and transmission spectra. These results are compared with theory, experimental data, and ANSYS HFSS simulation results. This research is supported by a Grant from United States Air Force Office of Scientific Research.
Harmonic Analysis and Active Filtering in Offshore Wind Power Plants
DEFF Research Database (Denmark)
Chaudhary, Sanjay Kumar; Freijedo Fernandez, Francisco Daniel; Guerrero, Josep M.
2015-01-01
at the point of common coupling (PCC). The resonance conditions should be avoided in all cases. This paper describes the harmonic analysis techniques applied on an OWPP network model. A method is proposed to estimate the harmonic current compensation from a shunt-connected active power filter to mitigate......Due to presence of long high voltage cable networks, and power transformers for the grid connection, the offshore wind power plants (OWPPs) are susceptible to harmonic distortion and resonances. The grid connection of OWPP should not cause the harmonic distortion beyond the permissible limits...... the harmonic voltage distortion at the PCC. Finally the harmonic distortions in the compensated and the uncompensated systems are compared to demonstrate the efficacy of the compensation....
Recursive Harmonic Numbers and Binomial Coefficients
Maw, Aung Phone; Kyaw, Aung
2017-01-01
We define recursive harmonic numbers as a generalization of harmonic numbers. The table of recursive harmonic numbers, which is like Pascal's triangle, is constructed. A formula for recursive harmonic numbers containing binomial coefficients is also presented.
Buchheit, T. E.; Wert, J. A.
1994-11-01
A model that combines the phenomenological theory of martensite with a generalized Schmid’s law has been used to predict the principal stress combinations required to induce the martensitic transformation in unconstrained NiTi shape memory alloy (SMA) single crystals. The transformation surfaces prescribed by the model are anisotropic and asymmetric, reflecting the unidirectional character of shear on individual martensite habit planes. Model predictions of the transformation strain as a function of stress axis orientation for a uniaxial applied stress further demonstrate the anisotropy of the stress-induced transformation in NiTi single crystals. Model results for the uniaxial stress case compare favorably with previously published experimental observations for aged NiTi single crystals.
Oxygen isotope trajectories of crystallizing melts: Insights from modeling and the plutonic record
Bucholz, Claire E.; Jagoutz, Oliver; VanTongeren, Jill A.; Setera, Jacob; Wang, Zhengrong
2017-06-01
Elevated oxygen isotope values in igneous rocks are often used to fingerprint supracrustal alteration or assimilation of material that once resided near the surface of the earth. The δ18O value of a melt, however, can also increase through closed-system fractional crystallization. In order to quantify the change in melt δ18O due to crystallization, we develop a detailed closed-system fractional crystallization mass balance model and apply it to six experimentally- and naturally-determined liquid lines of descent (LLDs), which cover nearly complete crystallization intervals (melt fractions of 1 to Igneous Complex (Mongolia). These two sequences were chosen as their major and trace element compositions appear to have been predominantly controlled by closed-system fractional crystallization and their LLDs have been modeled in detail. We calculated equilibrium melt δ18O values using the measured mineral δ18O values and calculated mineral-melt fractionation factors. Increases of 2-3‰ and 1-1.5‰ in the equilibrium melts are observed for the Dariv Igneous Complex and the UUMZ of the Bushveld Complex, respectively. Closed-system fractional crystallization model results reproduce the 1‰ increase observed in the equilibrium melt δ18O for the Bushveld UUMZ, whereas for the Dariv Igneous Complex assimilation of high δ18O material is necessary to account for the increase in melt δ18O values. Assimilation of evolved supracrustal material is also confirmed with Sr and Nd isotope analyses of clinopyroxene from the sequence. Beginning with a range of mantle-derived basalt δ18O values of 5.7‰ ("pristine" mantle) to ∼7.0‰ (heavily subduction-influenced mantle), our model results demonstrated that high-silica melts (i.e. granites) with δ18O of up to 8.5‰ can be produced through fractional crystallization alone. Lastly, we model the zircon-melt δ18O fractionations of different LLDs, emphasizing their dependence on the specific SiO2-T relationships of a given
High harmonic phase in molecular nitrogen
Energy Technology Data Exchange (ETDEWEB)
McFarland, Brian K.
2009-10-17
Electronic structure in atoms and molecules modulates the amplitude and phase of high harmonic generation (HHG). We report measurements of the high harmonic spectral amplitude and phase in N{sub 2}. The phase is measured interferometrically by beating the N{sub 2} harmonics with those of an Ar reference oscillator in a gas mixture. A rapid phase shift of 0.2{pi} is observed in the vicinity of the HHG spectral minimum, where a shift of {pi} had been presumed [J. Itatani et al., Nature 432, 867 (2004)]. We compare the phase measurements to a simulation of the HHG recombination step in N{sub 2} that is based on a simple interference model. The results of the simulation suggest that modifications beyond the simple interference model are needed to explain HHG spectra in molecules.
The harmonic oscillator and nuclear physics
Rowe, D. J.
1993-01-01
The three-dimensional harmonic oscillator plays a central role in nuclear physics. It provides the underlying structure of the independent-particle shell model and gives rise to the dynamical group structures on which models of nuclear collective motion are based. It is shown that the three-dimensional harmonic oscillator features a rich variety of coherent states, including vibrations of the monopole, dipole, and quadrupole types, and rotations of the rigid flow, vortex flow, and irrotational flow types. Nuclear collective states exhibit all of these flows. It is also shown that the coherent state representations, which have their origins in applications to the dynamical groups of the simple harmonic oscillator, can be extended to vector coherent state representations with a much wider range of applicability. As a result, coherent state theory and vector coherent state theory become powerful tools in the application of algebraic methods in physics.
Chattoraj, Sayantan; Bhugra, Chandan; Li, Zheng Jane; Sun, Changquan Calvin
2014-12-01
The nonisothermal crystallization kinetics of amorphous materials is routinely analyzed by statistically fitting the crystallization data to kinetic models. In this work, we systematically evaluate how the model-dependent crystallization kinetics is impacted by variations in the heating rate and the selection of the kinetic model, two key factors that can lead to significant differences in the crystallization activation energy (Ea ) of an amorphous material. Using amorphous felodipine, we show that the Ea decreases with increase in the heating rate, irrespective of the kinetic model evaluated in this work. The model that best describes the crystallization phenomenon cannot be identified readily through the statistical fitting approach because several kinetic models yield comparable R(2) . Here, we propose an alternate paired model-fitting model-free (PMFMF) approach for identifying the most suitable kinetic model, where Ea obtained from model-dependent kinetics is compared with those obtained from model-free kinetics. The most suitable kinetic model is identified as the one that yields Ea values comparable with the model-free kinetics. Through this PMFMF approach, nucleation and growth is identified as the main mechanism that controls the crystallization kinetics of felodipine. Using this PMFMF approach, we further demonstrate that crystallization mechanism from amorphous phase varies with heating rate. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.
Morozova, K.; Jaeger, R.; Balodis, J.; Kaminskis, J.
2017-10-01
Over several years the Institute of Geodesy and Geoinformatics (GGI) was engaged in the design and development of a digital zenith camera. At the moment the camera developments are finished and tests by field measurements are done. In order to check these data and to use them for geoid model determination DFHRS (Digital Finite element Height reference surface (HRS)) v4.3. software is used. It is based on parametric modelling of the HRS as a continous polynomial surface. The HRS, providing the local Geoid height N, is a necessary geodetic infrastructure for a GNSS-based determination of physcial heights H from ellipsoidal GNSS heights h, by H=h-N. The research and this publication is dealing with the inclusion of the data of observed vertical deflections from digital zenith camera into the mathematical model of the DFHRS approach and software v4.3. A first target was to test out and validate the mathematical model and software, using additionally real data of the above mentioned zenith camera observations of deflections of the vertical. A second concern of the research was to analyze the results and the improvement of the Latvian quasi-geoid computation compared to the previous version HRS computed without zenith camera based deflections of the vertical. The further development of the mathematical model and software concerns the use of spherical-cap-harmonics as the designed carrier function for the DFHRS v.5. It enables - in the sense of the strict integrated geodesy approach, holding also for geodetic network adjustment - both a full gravity field and a geoid and quasi-geoid determination. In addition, it allows the inclusion of gravimetric measurements, together with deflections of the vertical from digital-zenith cameras, and all other types of observations. The theoretical description of the updated version of DFHRS software and methods are discussed in this publication.
Perturbative modeling of Bragg-grating-based biosensors in photonic-crystal fibers
DEFF Research Database (Denmark)
Burani, Nicola; Lægsgaard, Jesper
2005-01-01
We present a modeling study carried out to support the design of a novel, to our knowledge, kind of photonic-crystal fiber (PCF)-based sensor. This device, based on a PCF Bragg grating, detects the presence of selected single-stranded DNA molecules, hybridized to a biofilm in the air holes of the...
Directory of Open Access Journals (Sweden)
A. N. Chichko
2006-01-01
Full Text Available The method of calculation and results of computer dynamics modeling of solid ingot skin in a crystallizer are presented in the paper. The paper shows influence of ingot drawing rate on dynamics of solid ingot skin growth in the continuous casting machine at steel grades used at Republic Unitary Enterprise «Belarussian Metallurgical Works» (BMZ.
Virtual and Printed 3D Models for Teaching Crystal Symmetry and Point Groups
Casas, Lluís; Estop, Euge`nia
2015-01-01
Both, virtual and printed 3D crystal models can help students and teachers deal with chemical education topics such as symmetry and point groups. In the present paper, two freely downloadable tools (interactive PDF files and a mobile app) are presented as examples of the application of 3D design to study point-symmetry. The use of 3D printing to…
Modeling of the radiation-induced microstructural evolution in ionic crystals
Dubinko, V.I.; Turkin, A.A.; Vainshtein, D.I.; Hartog, H.W. den
Results of experimental and theoretical investigations are presented on heavily irradiated natural and synthetic NaCl crystals in the temperature range where anion defects are mobile. They give a strong evidence for the formation of vacancy voids, which cannot be explained by the Jain-Lidiard model
Crystal structures of model lithium halides in bulk phase and in clusters
Lanaro, G.; Patey, G. N.
2017-04-01
We employ lattice energy calculations and molecular dynamics simulations to compare the stability of wurtzite and rock salt crystal structures of four lithium halides (LiF, LiCl, LiBr, and LiI) modeled using the Tosi-Fumi and Joung-Cheatham potentials, which are models frequently used in simulation studies. Both infinite crystals and finite clusters are considered. For the Tosi-Fumi model, we find that all four salts prefer the wurtzite structure both at 0 K and at finite temperatures, in disagreement with experiments, where rock salt is the stable structure and wurtzite exists as a metastable state. For Joung-Cheatham potentials, rock salt is more stable for LiF and LiCl, but the wurtzite structure is preferred by LiBr and LiI. It is clear that the available lithium halide force fields need improvement to bring them into better accord with the experiment. Finite-size clusters that are more stable as rock salt in the bulk phase tend to solidify as small rock salt crystals. However, small clusters of salts that prefer the wurtzite structure as bulk crystals tend to form structures that have hexagonal motifs, but are not finite-size wurtzite crystals. We show that small wurtzite structures are unstable due to the presence of a dipole and rearrange into more stable, size-dependent structures. We also show that entropic contributions can act in favor of the wurtzite structure at higher temperatures. The possible relevance of our results for simulation studies of crystal nucleation from melts and/or aqueous solutions is discussed.
Modeling of Thermal Phase Noise in a Solid Core Photonic Crystal Fiber-Optic Gyroscope.
Song, Ningfang; Ma, Kun; Jin, Jing; Teng, Fei; Cai, Wei
2017-10-26
A theoretical model of the thermal phase noise in a square-wave modulated solid core photonic crystal fiber-optic gyroscope has been established, and then verified by measurements. The results demonstrate a good agreement between theory and experiment. The contribution of the thermal phase noise to the random walk coefficient of the gyroscope is derived. A fiber coil with 2.8 km length is used in the experimental solid core photonic crystal fiber-optic gyroscope, showing a random walk coefficient of 9.25 × 10 -5 deg/√h.
Modeling of Thermal Phase Noise in a Solid Core Photonic Crystal Fiber-Optic Gyroscope
Directory of Open Access Journals (Sweden)
Ningfang Song
2017-10-01
Full Text Available A theoretical model of the thermal phase noise in a square-wave modulated solid core photonic crystal fiber-optic gyroscope has been established, and then verified by measurements. The results demonstrate a good agreement between theory and experiment. The contribution of the thermal phase noise to the random walk coefficient of the gyroscope is derived. A fiber coil with 2.8 km length is used in the experimental solid core photonic crystal fiber-optic gyroscope, showing a random walk coefficient of 9.25 × 10−5 deg/√h.
Principles of harmonic analysis
Deitmar, Anton
2014-01-01
This book offers a complete and streamlined treatment of the central principles of abelian harmonic analysis: Pontryagin duality, the Plancherel theorem and the Poisson summation formula, as well as their respective generalizations to non-abelian groups, including the Selberg trace formula. The principles are then applied to spectral analysis of Heisenberg manifolds and Riemann surfaces. This new edition contains a new chapter on p-adic and adelic groups, as well as a complementary section on direct and projective limits. Many of the supporting proofs have been revised and refined. The book is an excellent resource for graduate students who wish to learn and understand harmonic analysis and for researchers seeking to apply it.
Crystallization tendencies of modelled Lennard-Jones liquids with different attractions.
Valdès, L-C; Gerges, J; Mizuguchi, T; Affouard, F
2018-01-07
Molecular dynamics simulations are performed on simple models composed of monoatomic Lennard-Jones atoms for which the repulsive interaction is the same but the attractive part is tuned. We investigate the precise role of the attractive part of the interaction potential on different structural, dynamical, and thermodynamical properties of these systems in the liquid and crystalline states. It includes crystallization trends for which the main physical ingredients involved have been computed: the diffusion coefficient, the Gibbs energy difference between the liquid and the crystalline state, and the crystal-liquid interfacial free energy. Results are compared with predictions from the classical nucleation theory including transient and steady-state regimes at moderate and deeper undercooling. The question of the energetic and entropic impact of the repulsive and attractive part of the interaction potential towards crystallization is also addressed.
REFINED MATHEMATICAL MODEL OF HYDROELECTRIC DRIVE OF THE CRYSTALLIZER ROLLING OF HIGH-SPEED MNLZ
Directory of Open Access Journals (Sweden)
V. V. Bolotskij
2004-01-01
Full Text Available At present time the high emphasis is placed on the problems of the quality improvement and increase of the metal cast speed at the machines of the slugs continuous casting. One of the ways of solving of this task is using of hydroelectric drive of the mechanism of the crystallizer swinging, which allows to vary frequency and amplitude of swinging and also to change the principle of crystallizer. In the work there is presented the improved mathematical model of the crystallizer swinging mechanism in the form of the automatic control system, using of which one can investigate the influence of different parameters of the system on quality and productivity of the machines of the slugs continuous casting.
[HDL inhibit cytokine production in a mouse model of urate crystal-induced inflammation].
Scanu, A; Oliviero, F; Luisetto, R; Sfriso, P; Dayer, J M; Burger, D; Punzi, L
2010-01-01
To evaluate whether high density lipoproteins (HDL) affect monosodium urate (MSU) crystal-induced inflammation in the murine air pouch model. MSU crystals were prepared by Denko's method and sterilized by heating at 180°C for 2 h before each experiment. Human HDL were isolated from peripheral blood of healthy volunteers. MSU crystals (2 mg in 1 ml of PBS) were injected into subcutaneous air pouches in mice in the presence or absence of HDL (0.1 mg). Negative control pouches received 1 ml of PBS. To recover pouch fluid, the pouches were washed with 2 ml of PBS after the animals were sacrificed. The leukocyte count in the lavage fluids was obtained using a hemocytometer and differential leukocyte count was determined by May-Grunwald-Giemsa staining. IL-6, KC, CCL2 and TNF-α levels were measured in exudates by ELISA. MSU crystals increased the number of leukocytes and the neutrophil migration, as well as the concentrations of IL-6, KC and CCL2 in pouch fluids, while the TNF-α levels were not detectable. The treatment with HDL led to a reduction in all inflammatory parameters: the leukocyte count decreased by 73%; the neutrophil density decreased by 35%; the IL-6, KC and CCL2 concentration decreased by 4-, 6- and 5-fold respectively. This study shows that HDL may limit the inflammatory process by inhibiting leukocyte recruitment and cytokine release. HDL are likely to represent a mechanism of control of crystal-induced inflammation.
Evolution of the Bangalore ICT Cluster: The "Crystal Growth" Model
Manimala, Mathew J.
2006-01-01
In about twenty years, starting in 1984, Bangalore has become the fourth best "Global Hub of Technological Innovation", according to Business Week. This article reviews the major milestones in Bangalore's development and the interactive roles of government, universities and private entrepreneurs. The author offers a new model: innovation…
Harmonic and geometric analysis
Citti, Giovanna; Pérez, Carlos; Sarti, Alessandro; Zhong, Xiao
2015-01-01
This book presents an expanded version of four series of lectures delivered by the authors at the CRM. Harmonic analysis, understood in a broad sense, has a very wide interplay with partial differential equations and in particular with the theory of quasiconformal mappings and its applications. Some areas in which real analysis has been extremely influential are PDE's and geometric analysis. Their foundations and subsequent developments made extensive use of the Calderón–Zygmund theory, especially the Lp inequalities for Calderón–Zygmund operators (Beurling transform and Riesz transform, among others) and the theory of Muckenhoupt weights. The first chapter is an application of harmonic analysis and the Heisenberg group to understanding human vision, while the second and third chapters cover some of the main topics on linear and multilinear harmonic analysis. The last serves as a comprehensive introduction to a deep result from De Giorgi, Moser and Nash on the regularity of elliptic partial differen...
Directory of Open Access Journals (Sweden)
Liu Yu-Jen
2016-01-01
Full Text Available Electric arc is a discharge phenomenon caused by particular electrical events and arc produced facilities in power system, for example the occurrence of short-circuit fault in feeders and the use of electric arc furnace for steel-making. All of these electric arcs have a highly nonlinear nature and can be considered as a significant source of power quality problems. To investigate the impacts of the electric arcs on power quality studies the development of the electric arc models for simulation analysis is became necessary. This paper thus presents the use of different one-dimensional interpolation methods for modelling the alternating current electric arc. The performances of different methods are compared by simulation results that are derived from the modelling of an alternating current electric arc furnace load and a low-frequency fluorescent tube.
St-Onge, Guillaume; Barletta, Francesco; Ledu, David; Rochon, André; Channell, James E. T.
2010-05-01
Radiocarbon dating of Holocene sediments is often challenging in the Arctic due to the paucity of datable material, carbonate dissolution and an often poorly constrained reservoir correction, highlighting the need to combine 14C dating with other methods to establish robust Arctic chronologies. Here we illustrate the potential of using Holocene paleomagnetic secular variation records and a time-varying spherical harmonic model of the geomagnetic field (CALS7K.2; Korte and Constable, 2005) in conjunction with radiocarbon dating to establish or improve age models from marine sedimentary records recently recovered on board the CCGS Amundsen in the Beaufort Sea (western Canadian Arctic, core 2004-804-650PC) and Lancaster Sound (eastern Canadian Arctic, core 2004-804-009PC). For both cores, a u-channel-based paleomagnetic study reveals the presence of a strong, stable, well-defined single component magnetization (maximum angular deviation < 5°), with characteristic remanent magnetization (ChRM) inclinations varying around the expected inclination for the latitude of the sites assuming a geocentric axial dipole. For core 650PC (Beaufort Sea), an age model spanning the last ~6 000 cal BP was established from one radiocarbon age in addition to nine paleomagnetic tie points obtained by comparing the ChRM declination profiles of core 650PC and the CALS7k.2 geomagnetic model output. In order to verify the robustness of this correlation, the ChRM inclination record of core 650PC was then compared with other western North American lacustrine and volcanic Holocene paleomagnetic secular variation records. Several common magnetic inclination features are detected among all the considered records during the last ~6 000 cal BP, indicating the same geomagnetic origin as well as the consistency of the derived age model. Similarly, for core 009PC (Lancaster Sound), the initial age model consisting of 4 radiocarbon ages was improved by adding 4 paleomagnetic tie points derived by
Numerical modelling of micro-machining of f.c.c. single crystal: Influence of strain gradients
Demiral, Murat
2014-11-01
A micro-machining process becomes increasingly important with the continuous miniaturization of components used in various fields from military to civilian applications. To characterise underlying micromechanics, a 3D finite-element model of orthogonal micro-machining of f.c.c. single crystal copper was developed. The model was implemented in a commercial software ABAQUS/Explicit employing a user-defined subroutine VUMAT. Strain-gradient crystal-plasticity and conventional crystal-plasticity theories were used to demonstrate the influence of pre-existing and evolved strain gradients on the cutting process for different combinations of crystal orientations and cutting directions. Crown Copyright © 2014.
Bajul, Audrey; Gerbaud, Vincent; Teychene, Sébastien; Devatine, Audrey; Bajul, Gilles
2017-08-01
Instability in bottled wines refer to tartaric salts crystallization such as potassium bitartrate (KHT). It is not desirable as consumers see the settled salts as an evidence of a poor quality control. In some cases, it causes excessive gushing in sparkling wine. We investigate the effect of two oenological carboxymethylcellulose (CMC) for KHT inhibition in a model solution of white wine by studying the impact of some properties of CMC such as the degree of polymerization, the degree of substitution, and the apparent dissociation constant determined by potentiometric titration. Polyelectrolyte adsorption is used for determining the surface and total charge and for providing information about the availability of CMC charged groups for interacting with KHT crystal faces. The inhibitory efficiency of CMC on model solution is evaluated by measuring the induction time with the help of conductimetric methods. Crystals growth with and without CMC are studied by observation with MEB and by thermal analysis using DSC. The results confirm the effectiveness of CMC as an inhibitor of KHT crystallization in a model solution. The main hypothesis of the mechanism lies in the interaction of dissociated anionic carboxymethyl groups along the cellulose backbone with positively charged layers on KHT faces like the {0 1 0} face. Key factors such as pH, CMC chain length and total charge are discusses.
Phase-Field Crystal Modeling of Polcrystalline Pattern Evolution in Hard and Soft Matter
Karma, Alain
2013-03-01
The phase-field crystal (PFC) model has attracted considerable attention during the past decade for its potential application to model the complex defect-mediated dynamics of hard and soft crystalline materials on diffusive time scales. The model is rooted in earlier models of non-equilibrium pattern formation (Swift-Hohenberg equation), and classical density functional theory that expresses the free-energy of a system as a functional of its density. This talk will discuss progress made to investigate the dynamics for both isolated grain boundaries and complex polycrystalline patterns under the driving forces of boundary curvature and applied stress. The results highlight fundamental differences between polycrystalline pattern evolution in soft matter, including colloid crystals and crystalline non-equilibrium patterns described by the standard PFC dynamics, and crystalline solids described by a reformulation of this dynamics presented in this talk. The results also pave the way for a unified theory of polycrystalline pattern evolution in hard and soft matter.
Energy Technology Data Exchange (ETDEWEB)
Lim, Hojun [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Owen, Steven J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Abdeljawad, Fadi F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hanks, Byron [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Battaile, Corbett Chandler [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-09-01
In order to better incorporate microstructures in continuum scale models, we use a novel finite element (FE) meshing technique to generate three-dimensional polycrystalline aggregates from a phase field grain growth model of grain microstructures. The proposed meshing technique creates hexahedral FE meshes that capture smooth interfaces between adjacent grains. Three dimensional realizations of grain microstructures from the phase field model are used in crystal plasticity-finite element (CP-FE) simulations of polycrystalline a -iron. We show that the interface conformal meshes significantly reduce artificial stress localizations in voxelated meshes that exhibit the so-called "wedding cake" interfaces. This framework provides a direct link between two mesoscale models - phase field and crystal plasticity - and for the first time allows mechanics simulations of polycrystalline materials using three-dimensional hexahedral finite element meshes with realistic topological features.
Callahan, Shannon M.; Caldwell, Kirin; Bulusu, Kartik V.; Plesniak, Michael W.
2012-11-01
Secondary flow structures are known to affect wall shear stress, which is closely related to atherogenesis and drug particle deposition. A regime map provides a framework to examine phase-wise variations in secondary flow structures under physiological and multi-harmonic inflow waveforms under conditions of a fixed Womersley number (4.2) and curvature ratio (1/7). Experimental PIV data were acquired at the 90-degree location in a 180-degree curved test section of a bent tube model for curved arteries using a blood analog working fluid. Coherent structure detection was performed using a continuous wavelet transform algorithm (PIVlet 1.2) and further analysis was carried out by grouping similar secondary flow structures at a fixed secondary Reynolds numbers. Phase-locked, planar vorticity fields over one period of inflow waveform revealed size, structure and strength similarities in secondary flow morphologies during the acceleration and deceleration phases. The utility of the new regime map lies in the a priori identification of pulsatile secondary flow structures, eliminating the need for exhaustive experimentation or computing, requiring only flow rate measurements that are easily acquired under clinical conditions. Supported by the National Science Foundation, Grant No. CBET-0828903 and GW Center for Biomimetics and Bioinspired Engineering (COBRE).
DEFF Research Database (Denmark)
Knudsen, Hans
1995-01-01
A model of the 2×3-phase synchronous machine is presented using a new transformation based on the eigenvectors of the stator inductance matrix. The transformation fully decouples the stator inductance matrix, and this leads to an equivalent diagram of the machine with no mutual couplings...
A Simple Harmonic Model for FAPAR Temporal Dynamics in the Wetlands of the Volga-Akhtuba Floodplain
Directory of Open Access Journals (Sweden)
Alexander Kozlov
2016-09-01
Full Text Available The paper reports a technique used to construct a reference time series for the fraction of absorbed photosynthetically-active radiation (FAPAR based on remotely-sensed data in the largest Russian arid wetland territory. For the arid Volga-Akhtuba wetlands, FAPAR appears to be an informative spectral index for estimating plant cover health and its seasonal and annual dynamics. Since FAPAR algorithms are developed for multiple satellite sensors, all FAPAR-based models are suggested to be universal and useful for future studies and long-term monitoring of plant cover, particularly in wetlands. The model developed in the present work for FAPAR temporal dynamics clearly reflects the field-observed seasonal and annual changes of plant cover in the Volga-Akhtuba floodplain wetlands. Various types of wetland plant communities were categorized by the specific parameters of the model seasonal vegetation curve. In addition, the values derived from the model function allow quantitative estimation of wetland plant cover health. This information is particularly important for the Volga-Akhtuba floodplain, because its hydrological regime is regulated by the Volzhskaya hydropower plant. The ecosystem is extremely fragile and sensitive to human impact, and wetland plant cover health is a key indicator of regulatory efficiency. The present study is another step towards developing a methodology focused on arid wetland vegetation monitoring and conservation of its biodiversity and natural conditions.
Development of a CE-QUAL-W2 temperature model for Crystal Springs Lake, Portland, Oregon
Buccola, Norman L.; Stonewall, Adam J.
2016-05-19
During summer 2014, lake level, streamflow, and water temperature in and around Crystal Springs Lake in Portland, Oregon, were measured by the U.S. Geological Survey and the City of Portland Bureau of Environmental Services to better understand the effect of the lake on Crystal Springs Creek and Johnson Creek downstream. Johnson Creek is listed as an impaired water body for temperature by the Oregon Department of Environmental Quality (ODEQ), as required by section 303(d) of the Clean Water Act. A temperature total maximum daily load applies to all streams in the Johnson Creek watershed, including Crystal Springs Creek. Summer water temperatures downstream of Crystal Springs Lake and the Golf Pond regularly exceed the ODEQ numeric criterion of 64.4 °F (18.0 °C) for salmonid rearing and migration. To better understand temperature contributions of this system, the U.S. Geological Survey developed two-dimensional hydrodynamic water temperature models of Crystal Springs Lake and the Golf Pond. Model grids were developed to closely resemble the bathymetry of the lake and pond using data from a 2014 survey. The calibrated models simulated surface water elevations to within 0.06 foot (0.02 meter) and outflow water temperature to within 1.08 °F (0.60 °C). Streamflow, water temperature, and lake elevation data collected during summer 2014 supplied the boundary and reference conditions for the model. Measured discrepancies between outflow and inflow from the lake, assumed to be mostly from unknown and diffuse springs under the lake, accounted for about 46 percent of the total inflow to the lake.
Honeycomb optical lattices with harmonic confinement
DEFF Research Database (Denmark)
Jacobsen, Jens Kusk Block; Nygaard, Nicolai
2010-01-01
We consider the fate of the Dirac points in the spectrum of a honeycomb optical lattice in the presence of a harmonic confining potential. By numerically solving the tight binding model, we calculate the density of states and find that the energy dependence can be understood from analytical...... arguments. In addition, we show that the density of states of the harmonically trapped lattice system can be understood by application of a local density approximation based on the density of states in the homogeneous lattice. The Dirac points are found to survive locally in the trap as evidenced...
Relativistic harmonics for turbulent wakefield diagnostics
Kuramitsu, Yasuhiro; Chen, Shih-Hung
2017-06-01
The propagation properties of relativistic harmonics excited in a plasma with an intense laser pulse is investigated theoretically and numerically. Focusing on the frequency separation, a cold electron fluid model in two spatial dimension is discussed to obtain the harmonic amplitude. The theoretical predictions are verified by performing particle-in-cell simulations in two spatial dimensions. When the laser amplitude is large, the strong ponderomotive force expels the electrons, creating a large amplitude density structures associated with the wakefield. The harmonics propagate obliquely with respect to the laser propagation direction, which is well represented by the structure of the high density layer resulting from the transverse poderomotive force. We also discuss a possible experimental setup to observe the density structures relevant to wakefield.
Optically induced structural phase transitions in ion Coulomb crystals
DEFF Research Database (Denmark)
Horak, Peter; Dantan, Aurelien Romain; Drewsen, Michael
2012-01-01
We investigate numerically the structural dynamics of ion Coulomb crystals confined in a three-dimensional harmonic trap when influenced by an additional one-dimensional optically induced periodical potential. We demonstrate that transitions between thermally excited crystal structures, such as b......We investigate numerically the structural dynamics of ion Coulomb crystals confined in a three-dimensional harmonic trap when influenced by an additional one-dimensional optically induced periodical potential. We demonstrate that transitions between thermally excited crystal structures...
Application of smooth exterior scaling method to calculate the high harmonic generation spectra.
Kalita, Dhruba J; Gupta, Ashish K
2013-02-21
We have calculated the high harmonic generation spectra from Xe atom by imposing different kinds of absorbing potentials. Owing to the center of inversion of the model system, one should get odd harmonics only. However, using negative imaginary potentials as an absorbing boundary condition, we have also got even order harmonics along with the odd order harmonics. These non-odd order harmonics are generated due to the spurious reflections occurring at the grid boundary. On the contrary, when smooth exterior scaling methods are used as an absorbing boundary condition, only odd order harmonics are obtained. Hence, smooth exterior scaling methods impose proper absorbing boundary condition.
Rahaman, Md Saifur; Mavinic, Donald S; Meikleham, Alexandra; Ellis, Naoko
2014-03-15
The cost associated with the disposal of phosphate-rich sludge, the stringent regulations to limit phosphate discharge into aquatic environments, and resource shortages resulting from limited phosphorus rock reserves, have diverted attention to phosphorus recovery in the form of struvite (MAP: MgNH4PO4·6H2O) crystals, which can essentially be used as a slow release fertilizer. Fluidized-bed crystallization is one of the most efficient unit processes used in struvite crystallization from wastewater. In this study, a comprehensive mathematical model, incorporating solution thermodynamics, struvite precipitation kinetics and reactor hydrodynamics, was developed to illustrate phosphorus depletion through struvite crystal growth in a continuous, fluidized-bed crystallizer. A thermodynamic equilibrium model for struvite precipitation was linked to the fluidized-bed reactor model. While the equilibrium model provided information on supersaturation generation, the reactor model captured the dynamic behavior of the crystal growth processes, as well as the effect of the reactor hydrodynamics on the overall process performance. The model was then used for performance evaluation of the reactor, in terms of removal efficiencies of struvite constituent species (Mg, NH4 and PO4), and the average product crystal sizes. The model also determined the variation of species concentration of struvite within the crystal bed height. The species concentrations at two extreme ends (inlet and outlet) were used to evaluate the reactor performance. The model predictions provided a reasonably good fit with the experimental results for PO4-P, NH4-N and Mg removals. Predicated average crystal sizes also matched fairly well with the experimental observations. Therefore, this model can be used as a tool for performance evaluation and process optimization of struvite crystallization in a fluidized-bed reactor. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.
ACCOUNTING HARMONIZATION AND HISTORICAL COST ACCOUNTING
Directory of Open Access Journals (Sweden)
Valentin Gabriel CRISTEA
2017-05-01
Full Text Available There is a huge interest in accounting harmonization and historical costs accounting, in what they offer us. In this article, different valuation models are discussed. Although one notices the movement from historical cost accounting to fair value accounting, each one has its advantages.
Optical second harmonic generation from Wannier excitons
DEFF Research Database (Denmark)
Pedersen, Thomas Garm; Cornean, Horia
2007-01-01
, a simplified three-band Wannier exciton model of cubic semiconductors is applied and a closed form expression for the complex second harmonic response function including broadening is derived. Our calculated spectra are found to be in excellent agreement with the measured response near the band edge...
Hysteresis in Two-Dimensional Liquid Crystal Models
Directory of Open Access Journals (Sweden)
Slavko Buček
2015-01-01
Full Text Available We make a numerical study of hysteresis loop shapes within a generalized two-dimensional Random Anisotropy Nematic (RAN model at zero temperature. The hysteresis loops appear on cycling a static external ordering field. Ordering in these systems is history dependent and involves interplay between the internal coupling constant J, the anisotropy random field D, and the ordering external field H. Here the external field is represented by a traceless tensor, analogous to extension-type fields in continuum mechanics. The calculations use both a mean field approach and full lattice simulations. Our analysis suggests the existence of two qualitatively different solutions, which we denote as symmetric and symmetry breaking. For the set of parameters explored, only the symmetric solutions are stable. Both approaches yield qualitatively similar hysteresis curves, which are manifested either by single or double loops. But the quantitative differences indicate that mean field estimates are only of limited predictive value.
Far- and near-field second harmonic imaging of ferroelectric domain walls
DEFF Research Database (Denmark)
Bozhevolnyi, Sergey I.; Pedersen, Kjeld; Skettrup, Torben
1998-01-01
Domain walls in periodically poled ferroelectric LiNbO3 crystals are observed with both far- and near-field imaging techniques that make use of second harmonic generation in the transition regions between neighbouring domains. Second harmonic images of domain walls represent bright lines of about 0.......5 micrometers in width (as measured with the near-field microscope) for the polarization of the second harmonic radiation perpendicular to the domain walls. Origin and selection rules for the constrast in second harmonic images of domain walls are discussed....
Energy Technology Data Exchange (ETDEWEB)
Barton, N R; Benson, D J; Becker, R; Bykov, Y; Caplan, M
2004-10-18
We present a crystal level model for thermo-mechanical deformation with phase transformation capabilities. The model is formulated to allow for large pressures (on the order of the elastic moduli) and makes use of a multiplicative decomposition of the deformation gradient. Elastic and thermal lattice distortions are combined into a single lattice stretch to allow the model to be used in conjunction with general equation of state relationships. Phase transformations change the mass fractions of the material constituents. The driving force for phase transformations includes terms arising from mechanical work, from the temperature dependent chemical free energy change on transformation, and from interaction energy among the constituents. Deformation results from both these phase transformations and elasto-viscoplastic deformation of the constituents themselves. Simulation results are given for the {alpha} to {epsilon} phase transformation in iron. Results include simulations of shock induced transformation in single crystals and of compression of polycrystals. Results are compared to available experimental data.
One-step model of photoemission from single-crystal surfaces
Karkare, Siddharth; Wan, Weishi; Feng, Jun; Chiang, Tai C.; Padmore, Howard A.
2017-02-01
In this paper, we present a three-dimensional one-step photoemission model that can be used to calculate the quantum efficiency and momentum distributions of electrons photoemitted from ordered single-crystal surfaces close to the photoemission threshold. Using Ag(111) as an example, we show that the model can not only calculate the quantum efficiency from the surface state accurately without using any ad hoc parameters, but also provides a theoretical quantitative explanation of the vectorial photoelectric effect. This model in conjunction with other band structure and wave function calculation techniques can be effectively used to screen single-crystal photoemitters for use as electron sources for particle accelerator and ultrafast electron diffraction applications.
Monte Carlo modelling of germanium crystals that are tilted and have rounded front edges
Energy Technology Data Exchange (ETDEWEB)
Gasparro, Joel [EC-JRC-IRMM, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel (Belgium); Hult, Mikael [EC-JRC-IRMM, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel (Belgium)], E-mail: mikael.hult@ec.europa.eu; Johnston, Peter N. [Applied Physics, Royal Melbourne Institute of Technology, GPO Box 2476V, Melbourne 3001 (Australia); Tagziria, Hamid [EC-JRC-IPSC, Institute for the Protection and the Security of the Citizen, Via E. Fermi 1, I-21020 Ispra (Vatican City State, Holy See,) (Italy)
2008-09-01
Gamma-ray detection efficiencies and cascade summing effects in germanium detectors are often calculated using Monte Carlo codes based on a computer model of the detection system. Such a model can never fully replicate reality and it is important to understand how various parameters affect the results. This work concentrates on quantifying two issues, namely (i) the effect of having a Ge-crystal that is tilted inside the cryostat and (ii) the effect of having a model of a Ge-crystal with rounded edges (bulletization). The effect of the tilting is very small (in the order of per mille) when the tilting angles are within a realistic range. The effect of the rounded edges is, however, relatively large (5-10% or higher) particularly for gamma-ray energies below 100 keV.
High-order harmonic generation from polar molecules
DEFF Research Database (Denmark)
Etches, Adam
When a molecule is submitted to a very intense laser pulse it emits coherent bursts of light in each optical half-cycle of the laser field. This process is known as high-order harmonic generation because the spectrum consists of many peaks at energies corresponding to an integer amount of laser...... photons. The harmonics contain information about the wave function of the loosest bound electron on an Ångström length scale and attosecond time scale. However, accurate theoretical models are needed in order to extract this information. In this thesis the most widely used model of high-order harmonic...... generation is extended to polar molecules by including the laser-induced Stark shift of each molecular orbitals. The Stark shift is shown to have a major influence on the relative strength of harmonic bursts in neighbouring half-cycles, as well as leaving an imprint on the phase of the harmonics...
Directory of Open Access Journals (Sweden)
Pavel Masek
2016-11-01
Full Text Available The unprecedented growth of today’s cities together with increased population mobility are fueling the avalanche in the numbers of vehicles on the roads. This development led to the new challenges for the traffic management, including the mitigation of road congestion, accidents, and air pollution. Over the last decade, researchers have been focusing their efforts on leveraging the recent advances in sensing, communications, and dynamic adaptive technologies to prepare the deployed road traffic management systems (TMS for resolving these important challenges in future smart cities. However, the existing solutions may still be insufficient to construct a reliable and secure TMS that is capable of handling the anticipated influx of the population and vehicles in urban areas. Along these lines, this work systematically outlines a perspective on a novel modular environment for traffic modeling, which allows to recreate the examined road networks in their full resemblance. Our developed solution is targeted to incorporate the progress in the Internet of Things (IoT technologies, where low-power, embedded devices integrate as part of a next-generation TMS. To mimic the real traffic conditions, we recreated and evaluated a practical traffic scenario built after a complex road intersection within a large European city.
Masek, Pavel; Masek, Jan; Frantik, Petr; Fujdiak, Radek; Ometov, Aleksandr; Hosek, Jiri; Andreev, Sergey; Mlynek, Petr; Misurec, Jiri
2016-01-01
The unprecedented growth of today’s cities together with increased population mobility are fueling the avalanche in the numbers of vehicles on the roads. This development led to the new challenges for the traffic management, including the mitigation of road congestion, accidents, and air pollution. Over the last decade, researchers have been focusing their efforts on leveraging the recent advances in sensing, communications, and dynamic adaptive technologies to prepare the deployed road traffic management systems (TMS) for resolving these important challenges in future smart cities. However, the existing solutions may still be insufficient to construct a reliable and secure TMS that is capable of handling the anticipated influx of the population and vehicles in urban areas. Along these lines, this work systematically outlines a perspective on a novel modular environment for traffic modeling, which allows to recreate the examined road networks in their full resemblance. Our developed solution is targeted to incorporate the progress in the Internet of Things (IoT) technologies, where low-power, embedded devices integrate as part of a next-generation TMS. To mimic the real traffic conditions, we recreated and evaluated a practical traffic scenario built after a complex road intersection within a large European city. PMID:27834796
Masek, Pavel; Masek, Jan; Frantik, Petr; Fujdiak, Radek; Ometov, Aleksandr; Hosek, Jiri; Andreev, Sergey; Mlynek, Petr; Misurec, Jiri
2016-11-08
The unprecedented growth of today's cities together with increased population mobility are fueling the avalanche in the numbers of vehicles on the roads. This development led to the new challenges for the traffic management, including the mitigation of road congestion, accidents, and air pollution. Over the last decade, researchers have been focusing their efforts on leveraging the recent advances in sensing, communications, and dynamic adaptive technologies to prepare the deployed road traffic management systems (TMS) for resolving these important challenges in future smart cities. However, the existing solutions may still be insufficient to construct a reliable and secure TMS that is capable of handling the anticipated influx of the population and vehicles in urban areas. Along these lines, this work systematically outlines a perspective on a novel modular environment for traffic modeling, which allows to recreate the examined road networks in their full resemblance. Our developed solution is targeted to incorporate the progress in the Internet of Things (IoT) technologies, where low-power, embedded devices integrate as part of a next-generation TMS. To mimic the real traffic conditions, we recreated and evaluated a practical traffic scenario built after a complex road intersection within a large European city.
Energy Technology Data Exchange (ETDEWEB)
Ganeev, R A [Ophthalmology and Advanced Laser Medical Center, Saitama Medical University, Saitama 350-0495 (Japan)
2015-09-30
We discuss the emergence of interest in the high-order harmonic generation (HHG) of ultrashort pulses propagated through laser-produced plasmas. It is shown that, during the last few years, substantial amendments of plasma HHG allowed in some cases the characteristics of gas HHG to be surpassed. The attractiveness of a new approach in coherent extreme ultraviolet radiation generation is demonstrated, which can also be used as a tool for laser-ablation-induced HHG spectroscopy of a giant class of solids. We present general ideas and prospects for this relatively new field of nonlinear optics. (review)
Harmonic analysis and applications
Heil, Christopher
2007-01-01
This self-contained volume in honor of John J. Benedetto covers a wide range of topics in harmonic analysis and related areas. These include weighted-norm inequalities, frame theory, wavelet theory, time-frequency analysis, and sampling theory. The chapters are clustered by topic to provide authoritative expositions that will be of lasting interest. The original papers collected are written by prominent researchers and professionals in the field. The book pays tribute to John J. Benedetto's achievements and expresses an appreciation for the mathematical and personal inspiration he has given to
A study of gradient strengthening based on a finite-deformation gradient crystal-plasticity model
Pouriayevali, Habib; Xu, Bai-Xiang
2017-11-01
A comprehensive study on a finite-deformation gradient crystal-plasticity model which has been derived based on Gurtin's framework (Int J Plast 24:702-725, 2008) is carried out here. This systematic investigation on the different roles of governing components of the model represents the strength of this framework in the prediction of a wide range of hardening behaviors as well as rate-dependent and scale-variation responses in a single crystal. The model is represented in the reference configuration for the purpose of numerical implementation and then implemented in the FEM software ABAQUS via a user-defined subroutine (UEL). Furthermore, a function of accumulation rates of dislocations is employed and viewed as a measure of formation of short-range interactions. Our simulation results reveal that the dissipative gradient strengthening can be identified as a source of isotropic-hardening behavior, which may represent the effect of irrecoverable work introduced by Gurtin and Ohno (J Mech Phys Solids 59:320-343, 2011). Here, the variation of size dependency at different magnitude of a rate-sensitivity parameter is also discussed. Moreover, an observation of effect of a distinctive feature in the model which explains the effect of distortion of crystal lattice in the reference configuration is reported in this study for the first time. In addition, plastic flows in predefined slip systems and expansion of accumulation of GNDs are distinctly observed in varying scales and under different loading conditions.
A study of gradient strengthening based on a finite-deformation gradient crystal-plasticity model
Pouriayevali, Habib; Xu, Bai-Xiang
2017-07-01
A comprehensive study on a finite-deformation gradient crystal-plasticity model which has been derived based on Gurtin's framework (Int J Plast 24:702-725, 2008) is carried out here. This systematic investigation on the different roles of governing components of the model represents the strength of this framework in the prediction of a wide range of hardening behaviors as well as rate-dependent and scale-variation responses in a single crystal. The model is represented in the reference configuration for the purpose of numerical implementation and then implemented in the FEM software ABAQUS via a user-defined subroutine (UEL). Furthermore, a function of accumulation rates of dislocations is employed and viewed as a measure of formation of short-range interactions. Our simulation results reveal that the dissipative gradient strengthening can be identified as a source of isotropic-hardening behavior, which may represent the effect of irrecoverable work introduced by Gurtin and Ohno (J Mech Phys Solids 59:320-343, 2011). Here, the variation of size dependency at different magnitude of a rate-sensitivity parameter is also discussed. Moreover, an observation of effect of a distinctive feature in the model which explains the effect of distortion of crystal lattice in the reference configuration is reported in this study for the first time. In addition, plastic flows in predefined slip systems and expansion of accumulation of GNDs are distinctly observed in varying scales and under different loading conditions.
Empirical Modeling of Heating Element Power for the Czochralski Crystallization Process
Directory of Open Access Journals (Sweden)
Magnus Komperød
2010-01-01
Full Text Available The Czochralski (CZ crystallization process is used to produce monocrystalline silicon. Monocrystalline silicon is used in solar cell wafers and in computers and electronics. The CZ process is a batch process, where multicrystalline silicon is melted in a crucible and later solidifies on a monocrystalline seed crystal. The crucible is heated using a heating element where the power is manipulated using a triode for alternating current (TRIAC. As the electric resistance of the heating element increases by increased temperature, there are significant dynamics from the TRIAC input signal (control system output to the actual (measured heating element power. The present paper focuses on empirical modeling of these dynamics. The modeling is based on a dataset logged from a real-life CZ process. Initially the dataset is preprocessed by detrending and handling outliers. Next, linear ARX, ARMAX, and output error (OE models are identfied. As the linear models do not fully explain the process' behavior, nonlinear system identification is applied. The Hammerstein-Wiener (HW model structure is chosen. The final model identified is a Hammerstein model, i.e. a HW model with nonlinearity at the input, but not at the output. This model has only one more identified parameter than the linear OE model, but still improves the optimization criterion (mean squared ballistic simulation errors by a factor of six. As there is no nonlinearity at the output, the dynamics from the prediction error to the model output are linear, which allows a noise model to be added. Comparison of a Hammerstein model with noise model and the linear ARMAX model, both optimized for mean squared one-step-ahead prediction errors, shows that this optimization criterion is 42% lower for the Hammerstein model. Minimizing the number of parameters to be identified has been an important consideration throughout the modeling work.
Probing energetics with second harmonic generation
Konek, Christopher; Mason, Brian; Stoltz, Chad; Gump, Jared; Wilkinson, John
2009-06-01
We focus on the insensitive high explosive 1,3,5-triamino-2,4,6- trinitrobenzene (TATB) with the goal of obtaining structural information as a function of pressure and temperature. Prior experiments from Los Alamos (Son et al. J. Phys. Chem. B. 1999, 103 (26) 5434) demonstrated that in high temperature environments (approaching 300^o C) TATB increases in efficiency as a nonlinear optical medium, possibly undergoing structural changes which alter the crystal symmetry. We use the nonlinear optical technique second harmonic generation (SHG) to probe TATB in a diamond anvil cell experimental setup to perform measurements at high pressure. Additionally, by exploiting the electronic absorption features of TATB to perform resonantly enhanced second harmonic generation (RE-SHG) experiments, we probe the electronic transitions in the visible range as a function of pressure and temperature, to observe electronic changes that would occur. Polarization resolved SHG experiments allow further insight into changes in crystal structure. These static measurements may have implications for shocked TATB.
Bilayered smectic phase polymorphism in the dipolar Gay-Berne liquid crystal model.
Houssa, Mohammed; Rull, Luis F; Romero-Enrique, Jose M
2009-04-21
We present computer simulations of the Gay-Berne model with a strong terminal dipole. We report the existence of different stable antiferroelectric interdigitated bilayered phases in this model with diverse in-plane organization. The occurrence of these phases depends crucially on the value of the molecular elongation kappa. For kappa=3 we find an interdigitated bilayered smectic-A phase (absent when there is no dipole) and a bilayered smectic-T (or crystal) with positional in-plane tetragonal ordering, different from the hexatic observed in the absence of the molecular dipole. For kappa=4, bilayered smectic-A and in-plane hexatic-ordered smectic-B (or crystal) phases are observed.
Emergence of foams from the breakdown of the phase field crystal model.
Guttenberg, Nicholas; Goldenfeld, Nigel; Dantzig, Jonathan
2010-06-01
The phase field crystal (PFC) model captures the elastic and topological properties of crystals with a single scalar field at small undercooling. At large undercooling, new foamlike behavior emerges. We characterize this foam phase of the PFC equation and propose a modified PFC equation that may be used for the simulation of foam dynamics. This minimal model reproduces von Neumann's rule for two-dimensional dry foams and Lifshitz-Slyozov coarsening for wet foams. We also measure the coordination number distribution and find that its second moment is larger than previously reported experimental and theoretical studies of soap froths, a finding that we attribute to the wetness of the foam increasing with time.
Molecular modelling of the crystallization of polymorphs. Part I: The morphology of HMX polymorphs
ter Horst, J. H.; Kramer, H. J. M.; van Rosmalen, G. M.; Jansens, P. J.
2002-04-01
A molecular modelling procedure for the prediction of interfacial energies between polymorphs and solvents is under development. The first step in such a procedure must be to determine and investigate the structure of the possible morphologically important crystal surfaces. This is done for two of the experimentally readily obtained polymorphs β-HMX and α-HMX (cyclotetramethylene tetramine) by means of a periodic bond chain analysis.
Analytical modeling of the gas-filling dynamics in photonic crystal fibers
Dicaire, Isabelle; Beugnot, Jean-Charles; Thévenaz, Luc
2010-01-01
We present useful expressions predicting the filling time of gaseous species inside photonic crystal fibers. Based on the theory of diffusion, this gas-filling model can be applied to any given fiber geometry or length by calculating diffusion coefficients. This was experimentally validated by monitoring the filling process of acetylene gas in several fiber samples of various geometries and lengths. The measured filling times agree well, within ±15%, with the predicted values for all fiber sa...
Validation of a Crystal Plasticity Model Using High Energy Diffraction Microscopy
Beaudoin, A. J.; Obstalecki, M.; Storer, R.; Tayon, W.; Mach, J.; Kenesei, P.; Lienert, U.
2012-01-01
High energy diffraction microscopy is used to measure the crystallographic orientation and evolution of lattice strain in an Al Li alloy. The relative spatial arrangement of the several pancake-shaped grains in a tensile sample is determined through in situ and ex situ techniques. A model for crystal plasticity with continuity of lattice spin is posed, where grains are represented by layers in a finite element mesh following the arrangement indicated by experiment. Comparison is drawn between experiment and simulation.
Directory of Open Access Journals (Sweden)
I.Stasyuk
2003-01-01
Full Text Available A microscopic model based on the consideration of the proton ordering is proposed for describing the H-bonded ferroelectric crystalline systems with a complex structure of the hydrogen bond network. The model has been used for the investigation of thermodynamics and dielectric properties of the GPI crystal. The symmetry analysis of the order parameters responsible for the mixed (ferro- and antiferroelectric nature of ordering is performed within the model. The phase transition into the ferroelectric state is described. Changes in the dielectric susceptibility of the crystal are studied in the presence of the transverse external electric field acting along the c-axis. The results of measurements of temperature and field dependences of dielectric permittivity εc' in the paraelectric phase are presented. The microscopic mechanism of the observed effects is discussed based on the comparison of theoretical results and experimental data. A conclusion is made about the significant role of the ionic groups connected by hydrogen bonds in the charge transfer. So they make an important contribution into the polarizability of the GPI crystal along the direction of H-bonded chains.
Directory of Open Access Journals (Sweden)
Kryukov Igor Yu.
2017-01-01
Full Text Available Present article is devoted to the development of the mathematical model, which describes thermal state and crystallization process of the rectangular cross-section blank while continious process of extraction from a horysontal continious casting machine (HCCM.The developed model took cue for the heat-transfer properties of non-iron metal teeming; its temperature on entry to the casting mold; cooling conditions of blank in the carbon molds in the presence of a copper water cooler. Besides, has been considered the asymmetry of heat interchange from blank`s head and drag at mold, coming out from fluid contraction and features of the horizontal casting mold. The developed mathematical model allows to determine alterations in crystallizing blank of the following factors with respect to time: temperature pattern of crystallizing blank under different technical working regimes of HCCM; boundaries of solid two-phase field and liquid two-phase filed; blank`s thickness variation under shrinkage of the ingot`s material
Psychoacoustic Approaches for Harmonic Music Mixing
Directory of Open Access Journals (Sweden)
Roman B. Gebhardt
2016-05-01
Full Text Available The practice of harmonic mixing is a technique used by DJs for the beat-synchronous and harmonic alignment of two or more pieces of music. In this paper, we present a new harmonic mixing method based on psychoacoustic principles. Unlike existing commercial DJ-mixing software, which determines compatible matches between songs via key estimation and harmonic relationships in the circle of fifths, our approach is built around the measurement of musical consonance. Given two tracks, we first extract a set of partials using a sinusoidal model and average this information over sixteenth note temporal frames. By scaling the partials of one track over ±6 semitones (in 1/8th semitone steps, we determine the pitch-shift that maximizes the consonance of the resulting mix. For this, we measure the consonance between all combinations of dyads within each frame according to psychoacoustic models of roughness and pitch commonality. To evaluate our method, we conducted a listening test where short musical excerpts were mixed together under different pitch shifts and rated according to consonance and pleasantness. Results demonstrate that sensory roughness computed from a small number of partials in each of the musical audio signals constitutes a reliable indicator to yield maximum perceptual consonance and pleasantness ratings by musically-trained listeners.
DEFF Research Database (Denmark)
Kwon, Jun Bum; Wang, Xiongfei; Bak, Claus Leth
2015-01-01
points and harmonic coupling analysis. Hence, it is critically needed to develop the advanced converter model, which can include almost all the possibilities. This paper develops the advanced Back to Back (BtB) converter model for wind farm application by means of Harmonic State Space (HSS) modeling...... method. The modeling and analysis results are remarkable that this model can include non-linear component and also show different operating points and harmonic coupling point, where this means each wind power converter can show the different impedance characteristics. The developed model can easily......Understanding about harmonic propagation in wind turbine converter is fundamental to research the influence of these on a large network harmonic distortion. Therefore, the analysis of wind turbine converter harmonic spectrum as well as the influence of converter operating point into the network...
HDL inhibit cytokine production in a mouse model of urate crystal-induced inflammation
Directory of Open Access Journals (Sweden)
L. Punzi
2011-06-01
Full Text Available Objectives: To evaluate whether high density lipoproteins (HDL affect monosodium urate (MSU crystal-induced inflammation in the murine air pouch model. Methods: MSU crystals were prepared by Denko’s method and sterilized by heating at 180°C for 2 h before each experiment. Human HDL were isolated from peripheral blood of healthy volunteers. MSU crystals (2 mg in 1 ml of PBS were injected into subcutaneous air pouches in mice in the presence or absence of HDL (0.1 mg. Negative control pouches received 1 ml of PBS. To recover pouch fluid, the pouches were washed with 2 ml of PBS after the animals were sacrificed. The leukocyte count in the lavage fluids was obtained using a hemocytometer and differential leukocyte count was determined by May-Grünwald-Giemsa staining. IL-6, KC, CCL2 and TNF-α levels were measured in exudates by ELISA. Results: MSU crystals increased the number of leukocytes and the neutrophil migration, as well as the concentrations of IL-6, KC and CCL2 in pouch fluids, while the TNF-α levels were not detectable. The treatment with HDL led to a reduction in all inflammatory parameters: the leukocyte count decreased by 73%; the neutrophil density decreased by 35%; the IL-6, KC and CCL2 concentration decreased by 4-, 6- and 5-fold respectively. Conclusions: This study shows that HDL may limit the inflammatory process by inhibiting leukocyte recruitment and cytokine release. HDL are likely to represent a mechanism of control of crystal-induced inflammation.
Wannier-Bloch approach to localization in high harmonics generation in solids
Osika, Edyta N; Ortmann, Lisa; Suárez, Noslen; Pérez-Hernández, Jose Antonio; Szafran, Bartłomiej; Ciappina, Marcelo F; Sols, Fernando; Landsman, Alexandra S; Lewenstein, Maciej
2016-01-01
Emission of high-order harmonics from solids provides a new avenue in attosecond science. On one hand, it allows to investigate fundamental processes of the non-linear response of electrons driven by a strong laser pulse in a periodic crystal lattice. On the other hand, it opens new paths toward efficient attosecond pulse generation, novel imaging of electronic wave functions, and enhancement of high-order harmonic generation (HHG) intensity. A key feature of HHG in a solid (as compared to the well-understood phenomena of HHG in an atomic gas) is the delocalization of the process, whereby an electron ionized from one site in the periodic lattice may recombine with any other. Here, we develop an analytic model, based on the localized Wannier wave functions in the valence band and delocalized Bloch functions in the conduction band. This Wannier-Bloch approach assesses the contributions of individual lattice sites to the HHG process, and hence addresses precisely the question of localization of harmonic emission...
Full quantum trajectories resolved high-order harmonic generation.
Ye, Peng; He, Xinkui; Teng, Hao; Zhan, Minjie; Zhong, Shiyang; Zhang, Wei; Wang, Lifeng; Wei, Zhiyi
2014-08-15
We use a carrier-envelope-phase stabilized sub-2-cycle laser pulse to generate high-order harmonics and study how the two-dimensional spectrum of harmonics, with the resolutions in temporal frequency and spatial frequency, is shaped by the laser phase. An arrowlike spectrum obtained experimentally when the gas cell is located in front of the laser focus point shows a resolution of full quantum trajectories; i.e., harmonics from different trajectories stand on different positions in this spectrum. In particular, due to the laser phase combined with the classical-like action, the harmonics from short and long trajectories differ maximally in their curvatures of wave fronts in the generation area, and so occupy very different ranges of spatial frequency at the far field. The result directly gives a full map of quantum trajectories in high-order harmonic generation. The conclusion is supported by an analytical model and quantum mechanics simulations.
Energy Technology Data Exchange (ETDEWEB)
Mora Barajas, M.A.; Banuelos Sanchez, P. [Universidad de las Americas Puebla (Mexico)]. E-mail: marco.morabs@udlap.mx; pedro.banuelos@udlap.mx
2010-04-15
Many household electrical appliances like televisions, video recorders and computers are sources of voltage and current harmonics, which increase power losses and contaminate the AC power line. These harmonics can cause serious problems in both, utilities and electrical equipment connected to the same AC line. This paper shows a mathematical analysis of harmonics content on the electrical current for a circuit representing a non linear residential load. A comparative harmonic distortion study produced by the residential loads on the electrical power lines, measured experimentally, is also shown. [Spanish] Muchos de los aparatos electricos que tenemos en casa como televisores, videograbadoras y computadoras, generan armonicos de voltaje y de corriente que incrementan las perdidas de potencia y contaminan las lineas de suministro electrico, pudiendo ocasionar severos danos tanto a las redes de energia como a los equipos que de ellas se alimentan. En este articulo se muestra un analisis matematico del contenido armonico en la corriente de un circuito que representa a una carga residencial no lineal. Ademas, a partir de mediciones electricas realizadas de manera experimental, se presente un estudio comparativo de la contaminacion armonica que este tipo de cargas introduce a las lineas de suministro electrico.
MOLA SPHERICAL HARMONICS TOPOGRAPHY MODEL
National Aeronautics and Space Administration — The Mars Global Surveyor spacecraft included a laser altimeter instrument. The primary objective of the Mars Orbiter Laser Altimeter (MOLA) is to determine globally...
DEFF Research Database (Denmark)
Abdul Samad, Noor Asma Fazli Bin; Sin, Gürkan; Gernaey, Krist
2013-01-01
This paper presents the application of uncertainty and sensitivity analysis as part of a systematic modelbased process monitoring and control (PAT) system design framework for crystallization processes. For the uncertainty analysis, the Monte Carlo procedure is used to propagate input uncertainty...
SF-FDTD analysis of a predictive physical model for parallel aligned liquid crystal devices
Márquez, Andrés.; Francés, Jorge; Martínez, Francisco J.; Gallego, Sergi; Alvarez, Mariela L.; Calzado, Eva M.; Pascual, Inmaculada; Beléndez, Augusto
2017-08-01
Recently we demonstrated a novel and simplified model enabling to calculate the voltage dependent retardance provided by parallel aligned liquid crystal devices (PA-LCoS) for a very wide range of incidence angles and any wavelength in the visible. To our knowledge it represents the most simplified approach still showing predictive capability. Deeper insight into the physics behind the simplified model is necessary to understand if the parameters in the model are physically meaningful. Since the PA-LCoS is a black-box where we do not have information about the physical parameters of the device, we cannot perform this kind of analysis using the experimental retardance measurements. In this work we develop realistic simulations for the non-linear tilt of the liquid crystal director across the thickness of the liquid crystal layer in the PA devices. We consider these profiles to have a sine-like shape, which is a good approximation for typical ranges of applied voltage in commercial PA-LCoS microdisplays. For these simulations we develop a rigorous method based on the split-field finite difference time domain (SF-FDTD) technique which provides realistic retardance values. These values are used as the experimental measurements to which the simplified model is fitted. From this analysis we learn that the simplified model is very robust, providing unambiguous solutions when fitting its parameters. We also learn that two of the parameters in the model are physically meaningful, proving a useful reverse-engineering approach, with predictive capability, to probe into internal characteristics of the PA-LCoS device.
Formation of Bragg Band Gaps in Anisotropic Phononic Crystals Analyzed With the Empty Lattice Model
Directory of Open Access Journals (Sweden)
Yan-Feng Wang
2016-05-01
Full Text Available Bragg band gaps of phononic crystals generally, but not always, open at Brillouin zone boundaries. The commonly accepted explanation stems from the empty lattice model: assuming a small material contrast between the constituents of the unit cell, avoided crossings in the phononic band structure appear at frequencies and wavenumbers corresponding to band intersections; for scalar waves the lowest intersections coincide with boundaries of the first Brillouin zone. However, if a phononic crystal contains elastically anisotropic materials, its overall symmetry is not dictated solely by the lattice symmetry. We construct an empty lattice model for phononic crystals made of isotropic and anisotropic materials, based on their slowness curves. We find that, in the anisotropic case, avoided crossings generally do not appear at the boundaries of traditionally defined Brillouin zones. Furthermore, the Bragg “planes” which give rise to phononic band gaps, are generally not flat planes but curved surfaces. The same is found to be the case for avoided crossings between shear (transverse and longitudinal bands in the isotropic case.
Harmonic Series Meets Fibonacci Sequence
Chen, Hongwei; Kennedy, Chris
2012-01-01
The terms of a conditionally convergent series may be rearranged to converge to any prescribed real value. What if the harmonic series is grouped into Fibonacci length blocks? Or the harmonic series is arranged in alternating Fibonacci length blocks? Or rearranged and alternated into separate blocks of even and odd terms of Fibonacci length?
Numerical computation of the linear stability of the diffusion model for crystal growth simulation
Energy Technology Data Exchange (ETDEWEB)
Yang, C.; Sorensen, D.C. [Rice Univ., Houston, TX (United States); Meiron, D.I.; Wedeman, B. [California Institute of Technology, Pasadena, CA (United States)
1996-12-31
We consider a computational scheme for determining the linear stability of a diffusion model arising from the simulation of crystal growth. The process of a needle crystal solidifying into some undercooled liquid can be described by the dual diffusion equations with appropriate initial and boundary conditions. Here U{sub t} and U{sub a} denote the temperature of the liquid and solid respectively, and {alpha} represents the thermal diffusivity. At the solid-liquid interface, the motion of the interface denoted by r and the temperature field are related by the conservation relation where n is the unit outward pointing normal to the interface. A basic stationary solution to this free boundary problem can be obtained by writing the equations of motion in a moving frame and transforming the problem to parabolic coordinates. This is known as the Ivantsov parabola solution. Linear stability theory applied to this stationary solution gives rise to an eigenvalue problem of the form.
Modeling of hydrogen-assisted cracking in iron crystal using a quasi-Newton method.
Telitchev, Igor Ye; Vinogradov, Oleg
2008-07-01
A Quasi-Newton method was applied in the context of a molecular statics approach to simulate the phenomenon of hydrogen embrittlement of an iron lattice. The atomic system is treated as a truss-type structure. The interatomic forces between the hydrogen-iron and the iron-iron atoms are defined by Morse and modified Morse potential functions, respectively. Two-dimensional hexagonal and 3D bcc crystal structures were subjected to tensile numerical tests. It was shown that the Inverse Broyden's Algorithm-a quasi-Newton method-provides a computationally efficient technique for modeling of the hydrogen-assisted cracking in iron crystal. Simulation results demonstrate that atoms of hydrogen placed near the crack tip produce a strong deformation and crack propagation effect in iron lattice, leading to a decrease in the residual strength of numerically tested samples.
Dugar, Sneha; Fu, Riqiang; Dalal, Naresh S
2012-08-02
Octaethyl porphyrin (OEP) and its Ni and Zn derivatives are considered as model compounds in biochemical, photophysical, and fossil fuel chemistry. They have thus been investigated by high-resolution solid-state (13)C NMR using powders, but peak assignment has been difficult because of large line widths. Arguing that a significant cause of broadening might be the anisotropic bulk magnetic susceptibility, we utilized single crystals in our (13)C cross-polarization magic angle spinning (CP-MAS) measurements and observed a nearly 2-fold line narrowing. This enhanced resolution enabled us to assign chemical shifts to each carbon for all the three compounds. The new assignments are now in agreement with X-ray structural data and allowed us to probe the motional dynamics of the methyl and methylene carbons of the OEP side chains. It is apparent that the use of single crystals in (13)C CP-MAS measurements has a significantly wider impact than previously thought.
CuII materials—From crystal chemistry to magnetic model compounds
Directory of Open Access Journals (Sweden)
H. Rosner et al
2007-01-01
Full Text Available Based on electronic structure calculations within the density functional theory, we report a systematic approach for the modelling of low-dimensional CuII materials. Combining concepts of crystal chemistry with ab initio-based magnetic models, we present a systematic study of recently discovered compounds. Our calculation results are in good agreement with thermodynamic and magnetic measurements, suggesting the presented approach as a well-directed route to explore the magnetic phase diagram of low-dimensional CuII systems.
Peng, Xiang-Long; Husser, Edgar; Huang, Gan-Yun; Bargmann, Swantje
2018-03-01
A finite-deformation gradient crystal plasticity theory is developed, which takes into account the interaction between dislocations and surfaces. The model captures both energetic and dissipative effects for surfaces penetrable by dislocations. By taking advantage of the principle of virtual power, the surface microscopic boundary equations are obtained naturally. Surface equations govern surface yielding and hardening. A thin film under shear deformation serves as a benchmark problem for validation of the proposed model. It is found that both energetic and dissipative surface effects significantly affect the plastic behavior.
A soft-core Gay-Berne model for the simulation of liquid crystals by Hamiltonian replica exchange.
Berardi, Roberto; Zannoni, Claudio; Lintuvuori, Juho S; Wilson, Mark R
2009-11-07
The Gay-Berne (GB) potential has proved highly successful in the simulation of liquid crystal phases, although it is fairly demanding in terms of resources for simulations of large (e.g., N>10(5)) systems, as increasingly required in applications. Here, we introduce a soft-core GB model, which exhibits both liquid crystal phase behavior and rapid equilibration. We show that the Hamiltonian replica exchange method, coupled with the newly introduced soft-core GB model, can effectively speed up the equilibration of a GB liquid crystal phase by frequent exchange of configurations between replicas, while still recovering the mesogenic properties of the standard GB potential.
Comparative analysis of harmonized forest area stimates for European countries
DEFF Research Database (Denmark)
Seebach, Lucia Maria; Strobl, P.; Miguel-Ayanz, J. San
2011-01-01
Harmonized forest area information provides an important basis for environmental modelling and policy-making at both national and international levels. Traditionally, this information has been provided by national forest inventory statistics but is now increasingly complemented with remote sensing...
Disclination elastica model of loop collision and growth in confined nematic liquid crystals.
Shams, Alireza; Yao, Xuxia; Park, Jung Ok; Srinivasarao, Mohan; Rey, Alejandro D
2015-07-21
Theory and modeling are used to characterize disclination loop-loop interactions in nematic liquid crystals under capillary confinement with strong homeotropic anchoring. This defect process arises when a mesogen in the isotropic phase is quenched into the stable nematic state. The texture evolution starts with +1/2 disclination loops that merge into a single loop through a process that involves collision, pinching and relaxation. The process is characterized with a combined Rouse-Frank model that incorporates the tension and bending elasticity of disclinations and the rotational viscosity of nematics. The Frank model of disclinations follows the Euler elastica model, whose non-periodic solution, known as Poleni's curve, is shown to locally describe the loop-loop collision and to shed light on why loop-loop merging results in a disclination intersection angle of approximately 60°. Additional Poleni invariants demonstrate how tension and bending pinch the two loops into a single +1/2 disclination ring. The Rouse model of disclination relaxation yields a Cahn-Hilliard equation whose time constant combines the confinement, tension/bending stiffness ratio and disclination diffusivity. Based on predictions made using this three stage process, a practical procedure is proposed to find viscoelastic parameters from defect geometry and defect dynamics. These findings contribute to the evolving understanding of textural transformations in nematic liquid crystals under confinement using the disclination elastica methodology.
Moonage Daydream: Reassessing the Simple Model for Lunar Magma Ocean Crystallization
Rapp, J. F.; Draper, D. S.
2016-01-01
Details of the differentiation of a global-scale lunar magma ocean (LMO) remain enigmatic, as the Moon is not simply composed of highlands anorthosite and a suite of mare basalts as inferred from early studies. Results from recent orbital missions, and the increasingly detailed study of lunar samples, have revealed a much larger range of lithologies, from relatively MgO-rich and "purest anorthosite" discovered on the lunar far side by the M3 instrument on Chandraayan-1 to more exotic lithologies such as Si-rich domes and spinel-rich clasts distributed globally. To understand this increasingly complex geology, we must understand the initial formation and evolution of the LMO, and the composition of the cumulates this differentiation could have produced. Several attempts at modelling such a crystallization sequence have been made, and have raised as many questions as they have answered. We present results from our ongoing experimental simulations of magma ocean crystallization, investigating two end-member bulk compositions (TWM and LPUM) under fully fractional crystallization conditions. These simulations represent melting of the entire silicate portion of the Moon, as an end-member starting point from which to begin assessing the evolution of the lunar interior and formation of the lunar crust.
Modeling Textural Processes during Self-Assembly of Plant-Based Chiral-Nematic Liquid Crystals
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Yogesh K. Murugesan
2010-12-01
Full Text Available Biological liquid crystalline polymers are found in cellulosic, chitin, and DNA based natural materials. Chiral nematic liquid crystalline orientational order is observed frozen-in in the solid state in plant cell walls and is known as a liquid crystal analogue characterized by a helicoidal plywood architecture. The emergence of the plywood architecture by directed chiral nematic liquid crystalline self assembly has been postulated as the mechanism that leads to optimal cellulose fibril organization. In natural systems, tissue growth and development takes place in the presence of inclusions and secondary phases leaving behind characteristic defects and textures, which provide a unique testing ground for the validity of the liquid crystal self-assembly postulate. In this work, a mathematical model, based on the Landau-de Gennes theory of liquid crystals, is used to simulate defect textures arising in the domain of self assembly, due to presence of secondary phases representing plant cells, lumens and pit canals. It is shown that the obtained defect patterns observed in some plant cell walls are those expected from a truly liquid crystalline phase. The analysis reveals the nature and magnitude of the viscoelastic material parameters that lead to observed patterns in plant-based helicoids through directed self-assembly. In addition, the results provide new guidance to develop biomimetic plywoods for structural and functional applications.
Green Fluorescent Protein as a Model for Protein Crystal Growth Studies
Agena, Sabine; Smith, Lori; Karr, Laurel; Pusey, Marc
1998-01-01
Green fluorescent protein (GFP) from jellyfish Aequorea Victoria has become a popular marker for e.g. mutagenesis work. Its fluorescent property, which originates from a chromophore located in the center of the molecule, makes it widely applicable as a research too]. GFP clones have been produced with a variety of spectral properties, such as blue and yellow emitting species. The protein is a single chain of molecular weight 27 kDa and its structure has been determined at 1.9 Angstrom resolution. The combination of GFP's fluorescent property, the knowledge of its several crystallization conditions, and its increasing use in biophysical and biochemical studies, all led us to consider it as a model material for macromolecular crystal growth studies. Initial preparations of GFP were from E.coli with yields of approximately 5 mg/L of culture media. Current yields are now in the 50 - 120 mg/L range, and we hope to further increase this by expression of the GFP gene in the Pichia system. The results of these efforts and of preliminary crystal growth studies will be presented.
Khavasi, Amin; Miri, Mehdi; Rezaei, Mohsen; Mehrany, Khashayar; Rashidian, Bizhan
2012-04-15
A simple and efficient transmission line model is proposed here to study how the transmission characteristics of photonic crystal waveguides are tailored by introduction of stubs patterned in the photonic crystal lattice. It is shown that band-pass and band-stop optical filters can be easily designed and optimized when stubs of appropriate length are brought in. Since the lengths of the designed stubs are not necessarily integer multiples of the photonic crystal lattice constant, a geometric shift in a portion of the photonic crystal structure is shown to be essential. The proposed model is verified by using a rigorous numerical method. An excellent agreement is observed between the numerical results and the transmission characteristics as extracted by the proposed model. © 2012 Optical Society of America
Experimental observation of a theoretically predicted nonlinear sleep spindle harmonic in human EEG.
Abeysuriya, R G; Rennie, C J; Robinson, P A; Kim, J W
2014-10-01
To investigate the properties of a sleep spindle harmonic oscillation previously predicted by a theoretical neural field model of the brain. Spindle oscillations were extracted from EEG data from nine subjects using an automated algorithm. The power and frequency of the spindle oscillation and the harmonic oscillation were compared across subjects. The bicoherence of the EEG was calculated to identify nonlinear coupling. All subjects displayed a spindle harmonic at almost exactly twice the frequency of the spindle. The power of the harmonic scaled nonlinearly with that of the spindle peak, consistent with model predictions. Bicoherence was observed at the spindle frequency, confirming the nonlinear origin of the harmonic oscillation. The properties of the sleep spindle harmonic were consistent with the theoretical modeling of the sleep spindle harmonic as a nonlinear phenomenon. Most models of sleep spindle generation are unable to produce a spindle harmonic oscillation, so the observation and theoretical explanation of the harmonic is a significant step in understanding the mechanisms of sleep spindle generation. Unlike seizures, sleep spindles produce nonlinear effects that can be observed in healthy controls, and unlike the alpha oscillation, there is no linearly generated harmonic that can obscure nonlinear effects. This makes the spindle harmonic a good candidate for future investigation of nonlinearity in the brain. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
Phase-field crystal modeling of equilibrium bcc-liquid interfaces
Wu, Kuo-An; Karma, Alain
2007-11-01
We investigate the equilibrium properties of bcc-liquid interfaces modeled with a continuum phase-field crystal (PFC) approach [K. R. Elder and M. Grant, Phys. Rev. E 70, 051605 (2004)]. A multiscale analysis of the PFC model is carried out which exploits the fact that the amplitudes of crystal density waves decay slowly into the liquid in the physically relevant limit where the freezing transition is weakly first order. This analysis yields a set of coupled equations for these amplitudes that is similar to the set of equations derived from Ginzburg-Landau (GL) theory [K.-A. Wu , Phys. Rev. B 73, 094101 (2006)]. The two sets only differ in the details of higher order nonlinear couplings between different density waves, which is determined by the form of the nonlinearity assumed in the PFC model and by the ansatz that all polygons with the same number of sides have equal weight in GL theory. Despite these differences, for parameters (liquid structure factor and solid density wave amplitude) of Fe determined from molecular dynamics (MD) simulations, the PFC and GL amplitude equations yield very similar predictions for the overall magnitude and anisotropy of the interfacial free-energy and density wave profiles. These predictions are compared with MD simulations as well as numerical solutions of the PFC model.
Modified phase-field-crystal model for solid-liquid phase transitions.
Guo, Can; Wang, Jincheng; Wang, Zhijun; Li, Junjie; Guo, Yaolin; Tang, Sai
2015-07-01
A modified phase-field-crystal (PFC) model is proposed to describe solid-liquid phase transitions by reconstructing the correlation function. The effects of fitting parameters of our modified PFC model on the bcc-liquid phase diagram, numerical stability, and solid-liquid interface properties during planar interface growth are examined carefully. The results indicate that the increase of the correlation function peak width at k=k(m) will enhance the stability of the ordered phase, while the increase of peak height at k=0 will narrow the two-phase coexistence region. The third-order term in the free-energy function and the short wave-length of the correlation function have significant influences on the numerical stability of the PFC model. During planar interface growth, the increase of peak width at k=k(m) will decrease the interface width and the velocity coefficient C, but increase the anisotropy of C and the interface free energy. Finally, the feasibility of the modified phase-field-crystal model is demonstrated with a numerical example of three-dimensional dendritic growth of a body-centered-cubic structure.
Binding site of ABC transporter homology models confirmed by ABCB1 crystal structure
Directory of Open Access Journals (Sweden)
Sager Georg
2009-09-01
Full Text Available Abstract The human ATP-binding cassette (ABC transporters ABCB1, ABCC4 and ABCC5 are involved in resistance to chemotherapeutic agents. Here we present molecular models of ABCB1, ABCC4 and ABCC5 by homology based on a wide open inward-facing conformation of Escherichia coli MsbA, which were constructed in order to elucidate differences in the electrostatic and molecular features of their drug recognition conformations. As a quality assurance of the methodology, the ABCB1 model was compared to an ABCB1 X-ray crystal structure, and with published cross-linking and site directed mutagenesis data of ABCB1. Amino acids Ile306 (TMH5, Ile340 (TMH6, Phe343 (TMH6, Phe728 (TMH7, and Val982 (TMH12, form a putative substrate recognition site in the ABCB1 model, which is confirmed by both the ABCB1 X-ray crystal structure and the site-directed mutagenesis studies. The ABCB1, ABCC4 and ABCC5 models display distinct differences in the electrostatic properties of their drug recognition sites.
Dada, Michael O; Jayeoba, Babatunde; Awojoyogbe, Bamidele O; Uno, Uno E; Awe, Oluseyi E
2017-09-13
Harmonic Phase-Magnetic Resonance Imaging (HARP-MRI) is a tagged image analysis method that can measure myocardial motion and strain in near real-time and is considered a potential candidate to make magnetic resonance tagging clinically viable. However, analytical expressions of radially tagged transverse magnetization in polar coordinates (which is required to appropriately describe the shape of the heart) have not been explored because the physics required to directly connect myocardial deformation of tagged Nuclear Magnetic Resonance (NMR) transverse magnetization in polar geometry and the appropriate harmonic phase parameters are not yet available. The analytical solution of Bloch NMR diffusion equation in spherical geometry with appropriate spherical wave tagging function is important for proper analysis and monitoring of heart systolic and diastolic deformation with relevant boundary conditions. In this study, we applied Harmonic Phase MRI method to compute the difference between tagged and untagged NMR transverse magnetization based on the Bloch NMR diffusion equation and obtained radial wave tagging function for analysis of myocardial motion. The analytical solution of the Bloch NMR equations and the computational simulation of myocardial motion as developed in this study are intended to significantly improve healthcare for accurate diagnosis, prognosis and treatment of cardiovascular related deceases at the lowest cost because MRI scan is still one of the most expensive anywhere. The analysis is fundamental and significant because all Magnetic Resonance Imaging techniques are based on the Bloch NMR flow equations.
The behavior of commensurate-incommensurate transitions using the phase field crystal model
Zhang, Tinghui; Lu, Yanli; Chen, Zheng
2018-02-01
We study the behavior of the commensurate-incommensurate (CI) transitions by using a phase field crystal model. The model is capable of modeling both elastic and plastic deformation and can simulate the evolution of the microstructure of the material at the atomic scale and the diffusive time scale, such as for adsorbed monolayer. Specifically, we study the behavior of the CI transitions as a function of lattice mismatch and the amplitude of substrate pinning potential. The behavior of CI phase transitions is revealed with the increase of the amplitude of pinning potential in some certain lattice mismatches. We find that for the negative lattice mismatch absorbed monolayer undergoes division, reorganization and displacement as increasing the amplitude of substrate pinning potential. In addition, for the positive mismatch absorbed monolayer undergoes a progress of phase transformation after a complete grain is split. Our results accord with simulations for atomic models of absorbed monolayer on a substrate surface.
Harmonic Resonances in Wind Power Plants
DEFF Research Database (Denmark)
Fernandez, Francisco Daniel Freijedo; Chaudhary, Sanjay; Teodorescu, Remus
2015-01-01
This work reviews the state-of-the-art in the field of harmonic resonance problems in Wind Power Plants (WPPs). Firstly, a generic WPP is modeled according to the equivalent circuits of its passive and active components. Main focus is put on modeling active components, i.e. the ones based on power...... converters. Subsequently, pros and cons of frequency and time domain analysis methods are outlined. The next sections are devoted to mitigation methods implemented in the power electronics converters. From the wind turbine perspective, different techniques to enhance the robustness of the controller...... are analyzed. Subsequently, the suitability for active damping of harmonics using STATCOM devices is assessed, with focus both on control techniques and power converter technologies....
Wind Farm Structures’ Impact on Harmonic Emission and Grid Interaction
DEFF Research Database (Denmark)
Kocewiak, Lukasz Hubert; Hjerrild, Jesper; Bak, Claus Leth
The impact of a wind farm’s internal structures on harmonic emission at the point of common coupling and on the whole system frequency characteristic is investigated in this paper. The largest wind farms in the world, Horns Rev 2 Offshore Wind Farm and Polish Karnice Onshore Wind Farm......, are thoroughly analyzed. Different wind farm configurations are taken into consideration in order to entirely describe phenomena associated with harmonics. Some aspects of wind farm modelling for harmonic studies are also presented in this paper. The simulation results are compared with measurement data in order...
Harmonic and attosecond pulse enhancement in the presence of noise
Feng, Li-Qiang; Chu, Tian-Shu
2012-12-01
In this paper, we theoretically investigate the effect of noise on the photoionization, the generation of the high-order harmonic and the attosecond pulse irradiated from a model He+ ion. It shows that by properly adding noise fields, such as Gaussian white noise, random light or colored noise, both the ionization probabilities (IPs) and the harmonic yields can be enhanced by several orders of magnitude. Further, by tuning the noise intensity, a stochastic resonance-like curve is observed, showing the existence of an optimal noise in the ionization enhancement process. Finally, by superposing a properly selected harmonic, an intense attosecond pulse with a duration of 67 as is directly generated.
Power quality issues current harmonics
Mikkili, Suresh
2015-01-01
Power Quality Issues: Current Harmonics provides solutions for the mitigation of power quality problems related to harmonics. Focusing on active power filters (APFs) due to their excellent harmonic and reactive power compensation in two-wire (single phase), three-wire (three-phase without neutral), and four-wire (three-phase with neutral) AC power networks with nonlinear loads, the text:Introduces the APF technology, describing various APF configurations and offering guidelines for the selection of APFs for specific application considerationsCompares shunt active filter (SHAF) control strategi
Energy Technology Data Exchange (ETDEWEB)
Mezani, S.
2004-07-15
This work is interested in the study of the electromagnetic and thermal behaviors of the induction motor. A state of the art is initially drawn up, where we have presented and discussed the current methods dealing with electromagnetic and thermal modeling of induction motors. An electromagnetic model, that uses the 2D complex finite element method to solve the field equations, is developed. The rotor movement is accounted for by coupling the air gap field, for each space harmonic, using the double air gap method. The superposition principle permits the determination of the final solution. To deal with non linear problems, an approach that introduces equivalent reluctivities, is proposed. We have assumed that the saturation is only due to the first space harmonic. A thermal model is elaborated by using the nodal method. The machine is cut up into 11 cylindrical lumped elements, the thermal model represents the juxtaposition of these lumped elements. The electromagnetic and thermal models are, weakly, coupled together for a more precise determination of the temperature distribution inside the motor. In the validation phase of our work, we have designed a test bench that allows specific torque and temperature measurements. The comparison of the calculations and the measurements is satisfactory. (author)
Symmetric functions and B sub N -invariant spherical harmonics
Dunkl, C F
2002-01-01
The wavefunctions of a quantum isotropic harmonic oscillator modified by reflecting barriers at the coordinate planes in N-dimensional space can be expressed in terms of certain generalized spherical harmonics. These are associated with a product-type weight function on the sphere. Their analysis is carried out by means of differential-difference operators. The symmetries of this system involve the Weyl group of type B, generated by permutations and changes of sign of the coordinates. A new basis for symmetric functions as well as an explicit transition matrix to the monomial basis is constructed. This basis leads to a basis for invariant spherical harmonics. The determinant of the Gram matrix for the basis in the natural inner product over the sphere is evaluated. When the underlying parameter is specialized to zero, the basis consists of ordinary spherical harmonics with cube group symmetry, as used for wavefunctions of electrons in crystals. The harmonic oscillator can also be considered as a degenerate in...
Aoyagi, Y.
2017-05-01
In this study, a crystal plasticity model expressing the behavior of the dislocation source and the mobile dislocations is proposed by considering a thermal activation process of dislocations. In order to predict the variation of critical resolved shear stress due to grain boundaries, mobile dislocations, or dislocation sources, information on these crystal defects is introduced into a hardening law of crystal plasticity. The crystal orientation and shape of ultrafine-grained (UFG) aluminum produced by accumulative roll bonding processes are measured by electron backscatter diffraction (EBSD). Mechanical properties of the UFG aluminum are estimated using tensile test and indentation test. Results obtained by EBSD are introduced into a computational model. Finite element simulation for polycrystal of aluminum investigates the effect of microstructure on mechanical properties of UFG aluminum.
Modeling of Commercial Turbofan Engine With Ice Crystal Ingestion: Follow-On
Jorgenson, Philip C. E.; Veres, Joseph P.; Coennen, Ryan
2014-01-01
The occurrence of ice accretion within commercial high bypass aircraft turbine engines has been reported under certain atmospheric conditions. Engine anomalies have taken place at high altitudes that have been attributed to ice crystal ingestion, partially melting, and ice accretion on the compression system components. The result was degraded engine performance, and one or more of the following: loss of thrust control (roll back), compressor surge or stall, and flameout of the combustor. As ice crystals are ingested into the fan and low pressure compression system, the increase in air temperature causes a portion of the ice crystals to melt. It is hypothesized that this allows the ice-water mixture to cover the metal surfaces of the compressor stationary components which leads to ice accretion through evaporative cooling. Ice accretion causes a blockage which subsequently results in the deterioration in performance of the compressor and engine. The focus of this research is to apply an engine icing computational tool to simulate the flow through a turbofan engine and assess the risk of ice accretion. The tool is comprised of an engine system thermodynamic cycle code, a compressor flow analysis code, and an ice particle melt code that has the capability of determining the rate of sublimation, melting, and evaporation through the compressor flow path, without modeling the actual ice accretion. A commercial turbofan engine which has previously experienced icing events during operation in a high altitude ice crystal environment has been tested in the Propulsion Systems Laboratory (PSL) altitude test facility at NASA Glenn Research Center. The PSL has the capability to produce a continuous ice cloud which is ingested by the engine during operation over a range of altitude conditions. The PSL test results confirmed that there was ice accretion in the engine due to ice crystal ingestion, at the same simulated altitude operating conditions as experienced previously in
Nonlinear response and dynamical transitions in a phase-field crystal model for adsorbed overlayers
Energy Technology Data Exchange (ETDEWEB)
Ramos, J A P [Departamento de Ciencias Exatas, Universidade Estadual do Sudoeste da Bahia, 45000-000 Vitoria da Conquista, BA (Brazil); Granato, E [Laboratorio Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, 12245-970 Sao Jose dos Campos, SP (Brazil); Ying, S C; Ala-Nissila, T [Department of Physics, PO Box 1843, Brown University, Providence, RI 02912-1843 (United States); Achim, C V [Department of Applied Physics, Aalto University School of Science and Technology, PO Box 11000, FI-00076 Aalto, Espoo (Finland); Elder, K R, E-mail: Jorge@las.inpe.b [Department of Physics, Oakland University, Rochester, Michigan 48309-4487 (United States)
2010-09-01
The nonlinear response and sliding friction behavior of a phase-field crystal model for driven adsorbed atomic layers is determined numerically. The model describes the layer as a continuous density field coupled to the pinning potential of the substrate and under an external driving force. Dynamical equations which take into account both thermal fluctuations and inertial effects are used for numerical simulations of commensurate and incommensurate layers. At low temperatures, the velocity response of an initially commensurate layer shows hysteresis with dynamical melting and freezing transitions at different critical forces. The main features of the sliding friction behavior are similar to the results obtained previously from molecular dynamics simulations of particle models. However, the dynamical transitions correspond to nucleations of stripes rather than closed domains.
Theoretical modeling of infrared spectra of the hydrogen and deuterium bond in aspirin crystal
Ghalla, Houcine; Rekik, Najeh; Michta, Anna; Oujia, Brahim; Flakus, Henryk T.
2010-01-01
An extended quantum theoretical approach of the ν IR lineshape of cyclic dimers of weakly H-bonded species is proposed. We have extended a previous approach [M.E.-A. Benmalti, P. Blaise, H.T. Flakus, O. Henri-Rousseau, Chem. Phys. 320 (2006) 267] by accounting for the anharmonicity of the slow mode which is described by a "Morse" potential in order to reproduce the polarized infrared spectra of the hydrogen and deuterium bond in acetylsalicylic acid (aspirin) crystals. From comparison of polarized IR spectra of isotopically neat and isotopically diluted aspirin crystals it resulted that centrosymmetric aspirin dimer was the bearer of the crystal main spectral properties. In this approach, the adiabatic approximation is performed for each separate H-bond bridge of the dimer and a strong non-adiabatic correction is introduced into the model via the resonant exchange between the fast mode excited states of the two moieties. Within the strong anharmonic coupling theory, according to which the X-H→⋯Y high-frequency mode is anharmonically coupled to the H-bond bridge, this model incorporated the Davydov coupling between the excited states of the two moieties, the quantum direct and indirect dampings and the anharmonicity for the H-bond bridge. The spectral density is obtained within the linear response theory by Fourier transform of the damped autocorrelation functions. The evaluated spectra are in fairly good agreement with the experimental ones by using a minimum number of independent parameters. The effect of deuteration has been well reproduced by reducing simply the angular frequency of the fast mode and the anharmonic coupling parameter.
Introduction to abstract harmonic analysis
Loomis, Lynn H
2011-01-01
Written by a prominent figure in the field of harmonic analysis, this classic monograph is geared toward advanced undergraduates and graduate students and focuses on methods related to Gelfand's theory of Banach algebra. 1953 edition.
Tissue Harmonic Synthetic Aperture Imaging
DEFF Research Database (Denmark)
Rasmussen, Joachim
The main purpose of this PhD project is to develop an ultrasonic method for tissue harmonic synthetic aperture imaging. The motivation is to advance the field of synthetic aperture imaging in ultrasound, which has shown great potentials in the clinic. Suggestions for synthetic aperture tissue...... system complexity compared to conventional synthetic aperture techniques. In this project, SASB is sought combined with a pulse inversion technique for 2nd harmonic tissue harmonic imaging. The advantages in tissue harmonic imaging (THI) are expected to further improve the image quality of SASB....... The first part of the scientific contribution investigates an implementation of pulse inversion for THI on the experimental ultrasound system SARUS. The technique is initially implemented for linear array transducers and then expanded for convex array transducers. The technique is evaluated based on spatial...
Harmonic structures and intrinsic torsion
DEFF Research Database (Denmark)
Conti, Diego; Madsen, Thomas Bruun
We discuss the construction of 8-manifolds with harmonic Sp(2)Sp(1)-structures. In particular, we find 10 new examples of nilmanifolds that admit a closed 4-form Omega whose stabiliser is Sp(2)Sp(1). Our constructions entail the notion of SO(4)-structures on 7-manifolds. We present a thorough inv...... investigation of the intrinsic torsion of such structures; in addition to the construction of harmonic structures, this analysis leads to explicit Lie group examples with invariant intrinsic torsion....
Rahaman, M S; Mavinic, D S; Ellis, N
2008-01-01
This paper is an attempt to model the UBC (University of British Columbia) MAP (Magnesium Ammonium Phosphate) fluidized bed crystallizer. A mathematical model is developed based on the assumption of perfect size classification of struvitre crystals in the reactor and considering the movement of liquid phase as a plug flow pattern. The model predicts variation of species concentration of struvite along the crystal bed height. The species concentrations at two extreme ends (inlet and outlet) are then used to evaluate the reactor performance. The model predictions provide a reasonable good fit with the experimental results for both PO4-P and NH4-N removals. Another important aspect of this model is its capability of predicting the crystals size and the bed voidage at different height of the reactor. Those predictions also match fairly well with the experimental observations. Therefore, this model can be used as a tool for performance evaluation of the reactor and can also be extended to optimize the struvite crystallization process in the UBC MAP reactor. IWA Publishing 2008.
Evidence from mixed hydrate nucleation for a funnel model of crystallization.
Hall, Kyle Wm; Carpendale, Sheelagh; Kusalik, Peter G
2016-10-25
The molecular-level details of crystallization remain unclear for many systems. Previous work has speculated on the phenomenological similarities between molecular crystallization and protein folding. Here we demonstrate that molecular crystallization can involve funnel-shaped potential energy landscapes through a detailed analysis of mixed gas hydrate nucleation, a prototypical multicomponent crystallization process. Through this, we contribute both: (i) a powerful conceptual framework for exploring and rationalizing molecular crystallization, and (ii) an explanation of phenomenological similarities between protein folding and crystallization. Such funnel-shaped potential energy landscapes may be typical of broad classes of molecular ordering processes, and can provide a new perspective for both studying and understanding these processes.
Ab initio multiscale simulation of high-order harmonic generation in solids
Floss, Isabella; Lemell, Christoph; Wachter, Georg; Smejkal, Valerie; Sato, Shunsuke A.; Tong, Xiao-Min; Yabana, Kazuhiro; Burgdörfer, Joachim
2018-01-01
High-order-harmonic generation by a highly nonlinear interaction of infrared laser fields with matter allows for the generation of attosecond pulses in the XUV spectral regime. This process, well established for atoms, has been recently extended to the condensed phase. Remarkably well-pronounced harmonics up to order ˜30 have been observed for dielectrics. We establish a route toward an ab initio multiscale simulation of solid-state high-order-harmonic generation. We find that mesoscopic effects of the extended system, in particular the realistic sampling of the entire Brillouin zone, the pulse propagation in the dense medium, and the inhomogeneous illumination of the crystal, have a strong effect on the harmonic spectra. Our results provide an explanation for the formation of clean harmonics and have implications for a wide range of nonlinear optical processes in dense media.
Casati, Nicola; Genoni, Alessandro; Meyer, Benjamin; Krawczuk, Anna; Macchi, Piero
2017-08-01
The possibility to determine electron-density distribution in crystals has been an enormous breakthrough, stimulated by a favourable combination of equipment for X-ray and neutron diffraction at low temperature, by the development of simplified, though accurate, electron-density models refined from the experimental data and by the progress in charge density analysis often in combination with theoretical work. Many years after the first successful charge density determination and analysis, scientists face new challenges, for example: (i) determination of the finer details of the electron-density distribution in the atomic cores, (ii) simultaneous refinement of electron charge and spin density or (iii) measuring crystals under perturbation. In this context, the possibility of obtaining experimental charge density at high pressure has recently been demonstrated [Casati et al. (2016). Nat. Commun. 7, 10901]. This paper reports on the necessities and pitfalls of this new challenge, focusing on the species syn-1,6:8,13-biscarbonyl[14]annulene. The experimental requirements, the expected data quality and data corrections are discussed in detail, including warnings about possible shortcomings. At the same time, new modelling techniques are proposed, which could enable specific information to be extracted, from the limited and less accurate observations, like the degree of localization of double bonds, which is fundamental to the scientific case under examination.
Energy Technology Data Exchange (ETDEWEB)
Choi, A. S.; Flach, G. P.; Martino, C. J.; Zamecnik, J. R.; Harris, M. K.; Wilmarth, W. R.; Calloway, T. B.
2005-03-23
In order to accelerate waste treatment and disposal of Hanford tank waste by 2028, the Department of Energy (DOE) and CH2M Hill Hanford Group (CHG), Inc. are evaluating alternative technologies which will be used in conjunction with the Waste Treatment Plant (WTP) to safely pretreat and immobilize the tank waste. Several technologies (Bulk Vitrification and Steam Reforming) are currently being evaluated for immobilizing the pretreated waste. Since the WTP does not have sufficient capacity to pretreat all the waste going to supplemental treatment by the 2028 milestone, two technologies (Selective Dissolution and Fractional Crystallization) are being considered for pretreatment of salt waste. The scope of this task was to: (1) evaluate the recent Savannah River Site (SRS) Tank 41 dissolution campaign and other literature to provide a more complete understanding of selective dissolution, (2) provide an update on the progress of salt dissolution and modeling activities at SRS, (3) investigate SRS experience and outside literature sources on industrial equipment and experimental results of previous fractional crystallization processes, and (4) evaluate recent Hanford AP104 boildown experiments and modeling results and recommend enhancements to the Environmental Simulation Program (ESP) to improve its predictive capabilities. This report provides a summary of this work and suggested recommendations.
General Lp-harmonic Blaschke bodies
Indian Academy of Sciences (India)
Lutwak introduced the harmonic Blaschke combination and the harmonic Blaschke body of a star body. Further, Feng and Wang introduced the concept of the -harmonic Blaschke body of a star body. In this paper, we define the notion of general -harmonic Blaschke bodies and establish some of its properties.
General Lp-harmonic Blaschke bodies
Indian Academy of Sciences (India)
Abstract. Lutwak introduced the harmonic Blaschke combination and the harmonic. Blaschke body of a star body. Further, Feng and Wang introduced the concept of the L p- harmonic Blaschke body of a star body. In this paper, we define the notion of general. L p-harmonic Blaschke bodies and establish some of its ...
Harmonics of circadian gene transcription in mammals.
Directory of Open Access Journals (Sweden)
Michael E Hughes
2009-04-01
Full Text Available The circadian clock is a molecular and cellular oscillator found in most mammalian tissues that regulates rhythmic physiology and behavior. Numerous investigations have addressed the contribution of circadian rhythmicity to cellular, organ, and organismal physiology. We recently developed a method to look at transcriptional oscillations with unprecedented precision and accuracy using high-density time sampling. Here, we report a comparison of oscillating transcription from mouse liver, NIH3T3, and U2OS cells. Several surprising observations resulted from this study, including a 100-fold difference in the number of cycling transcripts in autonomous cellular models of the oscillator versus tissues harvested from intact mice. Strikingly, we found two clusters of genes that cycle at the second and third harmonic of circadian rhythmicity in liver, but not cultured cells. Validation experiments show that 12-hour oscillatory transcripts occur in several other peripheral tissues as well including heart, kidney, and lungs. These harmonics are lost ex vivo, as well as under restricted feeding conditions. Taken in sum, these studies illustrate the importance of time sampling with respect to multiple testing, suggest caution in use of autonomous cellular models to study clock output, and demonstrate the existence of harmonics of circadian gene expression in the mouse.
Energy Technology Data Exchange (ETDEWEB)
Wu Ping; Lingvall, Fredrik; Stepinski, Tadeusz [Uppsala Univ. (Sweden). Dept. of Materials Science
2000-12-01
This report presents the research in the sixth phase that is concerned with ultrasonic techniques for assessing electron beam (EB) welds in copper canisters. The research has been carried out in three main aspects: (1) comparative inspections of EB welds, (2) EB weld evaluation, and (3) quantitative evaluation of attenuation in copper. Comparative inspections of EB welds in two copper canister blocks have been made by means of ultrasound and radiography. Comparison of the inspected results demonstrate that both techniques complement each other very well. The radiographic technique on the whole gives relatively better spatial resolution but low contrast in radiographs. It can reliably detect voids in EB, but cannot provide information about material structure in the EB weld. Ultrasonic technique provides information about flaw locations and shapes similar to the radiographs. Moreover, it can easily distinguish welded and non-welded zones and be used to study weld's macro- and microstructure. The defects in ultrasonic images often show higher contrast, and some flaw indications may be seen in ultrasonic inspection but not in radiographs. But small flaws are hard to distinguish from grain noise. For EB weld evaluation, first, scattering from EB weld has been investigated using three broadband transducers with different center frequencies. The investigation has shown that more information on scattering and attenuation can be exploited in this case so that the EB welds can be better characterized, and that the best frequency range for characterizing welds is 2 - 5 MHz. Secondly, harmonic imaging (HI) of EB welds have been studied using two different sources of harmonics: (i) transducer harmonics, originating from the high-order resonant modes of transmitters excited by a broadband pulse, and (ii) material harmonics, stemming from the nonlinear distortion of waves propagating in materials. The transducer HI exploits additional information due to transducer harmonics
Directory of Open Access Journals (Sweden)
Juan Miguel Astorga Gómez
2015-04-01
Full Text Available En este artículo se evalúan las armónicas individuales de tensión como función de las armónicas individuales de corriente usando los análisis estadísticos de regresión lineal simple, regresión polinomial y regresión lineal múltiple. Para la selección del modelo, se usan el coeficiente de determinación R2 y el criterio de información de Akaike (AIC. Se utiliza como caso de estudio un sistema eléctrico de un proceso minero ubicado en la región de Atacama Copiapó Chile, que ocupa la técnica de electro obtención de cobre como parte principal de su proceso productivo. Se muestran y comparan los resultados para los distintos modelos estadísticos y se discute la información de éstos para el estudio de calidad de energía. Finalmente, usando el modelo que mejor se ajusta a las mediciones de armónicas de tensión y corriente, se muestran algunas predicciones para la componente armónica dominante de tensión. This paper assesses the individual voltage harmonics as a function of the individual current harmonics using the statistical analyses of simple linear regression, polynomial regression and multiple linear regression. For model choice, the coefficient of determination R2 and Akaike information criterion (AIC are used. A mining process electrical system located in the Atacama Copiapó Chile, is used as a case study. This uses the technique copper electrowining as the main part of its production process. The results for different statistical models are shown and their information discussed for the power quality study. Finally, using the model that better fits to the measurements of voltage and current harmonics, some predictions for the dominant voltage harmonic are shown.
Prony Analysis for Power System Transient Harmonics
Directory of Open Access Journals (Sweden)
David Cartes
2007-01-01
Full Text Available Proliferation of nonlinear loads in power systems has increased harmonic pollution and deteriorated power quality. Not required to have prior knowledge of existing harmonics, Prony analysis detects frequencies, magnitudes, phases, and especially damping factors of exponential decaying or growing transient harmonics. In this paper, Prony analysis is implemented to supervise power system transient harmonics, or time-varying harmonics. Further, to improve power quality when transient harmonics appear, the dominant harmonics identified from Prony analysis are used as the harmonic reference for harmonic selective active filters. Simulation results of two test systems during transformer energizing and induction motor starting confirm the effectiveness of the Prony analysis in supervising and canceling power system transient harmonics.
Physics of tissue harmonic imaging by ultrasound
Jing, Yuan
Tissue Harmonic Imaging (THI) is an imaging modality that is currently deployed on diagnostic ultrasound scanners. In THI the amplitude of the ultrasonic pulse that is used to probe the tissue is large enough that the pulse undergoes nonlinear distortion as it propagates into the tissue. One result of the distortion is that as the pulse propagates energy is shifted from the fundamental frequency of the source pulse into its higher harmonics. These harmonics will scatter off objects in the tissue and images formed from the scattered higher harmonics are considered to have superior quality to the images formed from the fundamental frequency. Processes that have been suggested as possibly responsible for the improved imaging in THI include: (1) reduced sensitivity to reverberation, (2) reduced sensitivity to aberration, and (3) reduction in side lobes. By using a combination of controlled experiments and numerical simulations, these three reasons have been investigated. A single element transducer and a clinical ultrasound scanner with a phased array transducer were used to image a commercial tissue-mimicking phantom with calibrated targets. The higher image quality achieved with THI was quantified in terms of spatial resolution and "clutter" signals. A three-dimensional model of the forward propagation of nonlinear sound beams in media with arbitrary spatial properties (a generalized KZK equation) was developed. A time-domain code for solving the KZK equation was validated with measurements of the acoustic field generated by the single element transducer and the phased array transducer. The code was used to investigate the impact of aberration using tissue-like media with three-dimensional variations in all acoustic properties. The three-dimensional maps of tissue properties were derived from the datasets available through the Visible Female project. The experiments and simulations demonstrated that second harmonic imaging (1) suffers less clutter associated with
Energy Technology Data Exchange (ETDEWEB)
Myronchuk, G.L.; Krymus, A.S.; Piasecki, M. [Institute of Physics, J. Dlugosz University, Czestochowa (Poland); Eastern European National University, Physics Department, Lutsk (Ukraine); Lakshminarayana, G. [Universiti Putra Malaysia, Wireless and Photonic Networks Research Centre, Faculty of Engineering, Serdang, Selangor (Malaysia); Kityk, I.V. [Czestochowa University of Technology, Faculty of Electrical Engineering, Czestochowa (Poland); Eastern European National University, Physics Department, Lutsk (Ukraine); Parasyuk, O.V. [Eastern European National University, Department of Chemistry, Lutsk (Ukraine); Rudysh, M.Ya.; Shchepanskyi, P.A. [Institute of Physics, J. Dlugosz University, Czestochowa (Poland); Ivan Franko National University of Lviv, Physics Department, Lviv (Ukraine)
2017-03-15
Spectral features of absorption were studied for novel AgGaGe{sub 3}Se{sub 7.6}Te{sub 0.4} solid-state alloys at different temperatures. The synthesized crystals structure parameters are obtained by the X-ray Rietveld refinement method. During increasing temperature from 100 up to 300 K, the energy gap of AgGaGe{sub 3}Se{sub 7.6}Te{sub 0.4} decreases linearly from 2.05 up to 1.94 eV at a rate 5.7 x 10{sup -4} eV/K. The magnitudes of piezoelectric coefficients are significantly changed and demonstrate substantial anisotropy. At room temperature, these values are equal to 5.2 pm/V (d{sub 11}), 31.5 pm/V (d{sub 22}) and 35.5 pm/V (d{sub 33}). It is crucial that with an increasing temperature the piezoelectric efficiencies are increased. We have explored temperature and laser-induced changes of piezoelectric coefficients. (orig.)
Snyder, Gregory A.; Taylor, Lawrence A.; Neal, Clive R.
1992-01-01
A chemical model for simulating the sources of the lunar mare basalts was developed by considering a modified mafic cumulate source formed during the combined equilibrium and fractional crystallization of a lunar magma ocean (LMO). The parameters which influence the initial LMO and its subsequent crystallization are examined, and both trace and major elements are modeled. It is shown that major elements tightly constrain the composition of mare basalt sources and the pathways to their creation. The ability of this LMO model to generate viable mare basalt source regions was tested through a case study involving the high-Ti basalts.
Harmonic Impact of Plug-In Hybrid Electric Vehicle on Electric Distribution System
Directory of Open Access Journals (Sweden)
A. Aljanad
2016-01-01
Full Text Available This paper presents the harmonic effects of plug-in hybrid electric vehicles (PHEV on the IEEE 37-bus distribution system at different PHEV penetration levels considering a practical daily residential load shape. The PHEV is modeled as a current harmonic source by using the Open-Source Distribution System Simulator (OpenDSS and DSSimpc software. Time series harmonic simulation was conducted to investigate the harmonic impact of PHEV on the system by using harmonic data obtained from a real electric vehicle. Harmonic effects on the system voltage profile and circuit power losses are also investigated by using OpenDSS and MATLAB software. Current/voltage total harmonic distortion (THD produced from the large scale of PHEV is investigated. Test results show that the voltage and current THDs are increased up to 9.5% and 50%, respectively, due to high PHEV penetrations and these THD values are significantly larger than the limits prescribed by the IEEE standards.
Linear and nonlinear modeling of light propagation in hollow-core photonic crystal fiber
DEFF Research Database (Denmark)
Roberts, John; Lægsgaard, Jesper
2009-01-01
Hollow core photonic crystal fibers (HC-PCFs) find applications which include quantum and non-linear optics, gas detection and short high-intensity laser pulse delivery. Central to most applications is an understanding of the linear and nonlinear optical properties. These require careful modeling...... due to the multitude of lengthscales involved and non-standard variations in properties such as the mode-field distribution. Linear mode-solvers require many 100,000's of basis functions to resolve the field variations, and extra terms are often required in descriptions of nonlinear propagation....... The intricacies of modeling various forms of HC-PCF are reviewed. An example of linear dispersion engineering, aimed at reducing and flattening the group velocity dispersion, is then presented. Finally, a study of short high intensity pulse delivery using HC-PCF in both dispersive and nonlinear (solitonic...
Modeling the Color Image and Video Quality on Liquid Crystal Displays with Backlight Dimming
DEFF Research Database (Denmark)
Korhonen, Jari; Mantel, Claire; Burini, Nino
2013-01-01
Objective image and video quality metrics focus mostly on the digital representation of the signal. However, the display characteristics are also essential for the overall Quality of Experience (QoE). In this paper, we use a model of a backlight dimming system for Liquid Crystal Display (LCD......) and show how the modeled image can be used as an input to quality assessment algorithms. For quality assessment, we propose an image quality metric, based on Peak Signal-to-Noise Ratio (PSNR) computation in the CIE L*a*b* color space. The metric takes luminance reduction, color distortion and loss...... of uniformity in the resulting image in consideration. Subjective evaluations of images generated using different backlight dimming algorithms and clipping strategies show that the proposed metric estimates the perceived image quality more accurately than conventional PSNR....
Modeling of photonic crystal fibers with Fibonacci-patterned circular and elliptical air holes
Singh, Ghanshyam; Sahu, Sourabh; Chaurasia, Praveen
2012-11-01
Novel index-guiding photonic crystal fibers (PCF) with rings of cladding holes (circularly or elliptically shaped) arranged in the Fibonacci series are proposed. The dispersion, confinement losses, and generated birefringence in PCFs are evaluated for light signal at 1.55-μm wavelength, by employing alterations in various design parameters. Full-vector analysis using anisotropic perfectly matched layers is performed to validate the accuracy of the modeled PCFs in a finite-difference time-domain environment. For such PCF modeling, the lower value of dispersion is found to be 7.311 ps nm-1 km-1, and the zero-dispersion wavelength is shifted to lower infrared region in accordance with variation in the hole diameter-to-pitch ratio.
Validation of phantom-based harmonization for patient harmonization.
Panetta, Joseph V; Daube-Witherspoon, Margaret E; Karp, Joel S
2017-07-01
To improve the precision of multicenter clinical trials, several efforts are underway to determine scanner-specific parameters for harmonization using standardized phantom measurements. The goal of this study was to test the correspondence between quantification in phantom and patient images and validate the use of phantoms for harmonization of patient images. The National Electrical Manufacturers' Association image quality phantom with hot spheres was scanned on two time-of-flight PET scanners. Whole-body [18 F]-fluorodeoxyglucose (FDG)-PET scans were acquired of subjects on the same systems. List-mode events from spheres (diam.: 10-28 mm) measured in air on each scanner were embedded into the phantom and subject list-mode data from each scanner to create lesions with known uptake with respect to the local background in the phantom and each subject's liver and lung regions, as a proxy to characterize true lesion quantification. Images were analyzed using the contrast recovery coefficient (CRC) typically used in phantom studies and serving as a surrogate for the standardized uptake value used clinically. Postreconstruction filtering (resolution recovery and Gaussian smoothing) was applied to determine if the effect on the phantom images translates equivalently to subject images. Three postfiltering strategies were selected to harmonize the CRCmean or CRCmax values between the two scanners based on the phantom measurements and then applied to the subject images. Both the average CRCmean and CRCmax values for lesions embedded in the lung and liver in four subjects (BMI range 25-38) agreed to within 5% with the CRC values for lesions embedded in the phantom for all lesion sizes. In addition, the relative changes in CRCmean and CRCmax resulting from the application of the postfilters on the subject and phantom images were consistent within measurement uncertainty. Further, the root mean squared percent difference (RMSpd ) between CRC values on the two scanners
Kalbasenka, A.N.
2009-01-01
Crystallization is one of the oldest separation and purification techniques. Batch crystallizers are widely used in production of fine chemicals, food ingredients, specialty chemicals, and active pharmaceutical ingredients. Control of the crystalline material properties is a challenging task due to
Energy Technology Data Exchange (ETDEWEB)
Chao, Ong Zhi; Cheet, Lim Hong; Yee, Khoo Shin [Mechanical Engineering Department, Faculty of EngineeringUniversity of Malaya, Kuala Lumpur (Malaysia); Rahman, Abdul Ghaffar Abdul [Faculty of Mechanical Engineering, University Malaysia Pahang, Pekan (Malaysia); Ismail, Zubaidah [Civil Engineering Department, Faculty of Engineering, University of Malaya, Kuala Lumpur (Malaysia)
2016-08-15
A novel method called Impact-synchronous modal analysis (ISMA) was proposed previously which allows modal testing to be performed during operation. This technique focuses on signal processing of the upstream data to provide cleaner Frequency response function (FRF) estimation prior to modal extraction. Two important parameters, i.e., windowing function and impact force level were identified and their effect on the effectiveness of this technique were experimentally investigated. When performing modal testing during running condition, the cyclic loads signals are dominant in the measured response for the entire time history. Exponential window is effectively in minimizing leakage and attenuating signals of non-synchronous running speed, its harmonics and noises to zero at the end of each time record window block. Besides, with the information of the calculated cyclic force, suitable amount of impact force to be applied on the system could be decided prior to performing ISMA. Maximum allowable impact force could be determined from nonlinearity test using coherence function. By applying higher impact forces than the cyclic loads along with an ideal decay rate in ISMA, harmonic reduction is significantly achieved in FRF estimation. Subsequently, the dynamic characteristics of the system are successfully extracted from a cleaner FRF and the results obtained are comparable with Experimental modal analysis (EMA)
Numerical study of fourth-harmonic generation of a picosecond laser pulse with time predelay
Energy Technology Data Exchange (ETDEWEB)
Zhang, T.; Kato, Y.; Daido, H. [Institute of Laser Engineering, Osaka University, Yamada-oka 2-6, Suita, Osaka 565 (Japan)
1996-06-01
We describe fourth-harmonic generation of a picosecond laser pulse with KDP crystals. The coupled nonlinear equations for the parametric process including the third-order nonlinear susceptibility have been solved. Applying a time predelay in the doubling crystal between the extraordinary and the ordinary waves of the fundamental pulse causes the group-velocity mismatch and the nonlinear phase shift in the doubling crystal to be compensated for each other, resulting in pulse duration compression at the fourth-harmonic wavelength. It is shown that the reduction from a 1-ps fundamental pulse to a 0.25-ps fourth-harmonic pulse can be achieved at an incident intensity of 50 GW/cm{sup 2}. {copyright} {ital 1996 Optical Society of America.}
Frequency Adaptive Selective Harmonic Control for Grid-Connected Inverters
DEFF Research Database (Denmark)
Yang, Yongheng; Zhou, Keliang; Wang, Huai
2015-01-01
In this paper, a Frequency Adaptive Selective Harmonic Control (FA-SHC) scheme is proposed. The FA-SHC method is developed from a hybrid SHC scheme based on the internal model principle, which can be designed for gridconnected inverters to optimally mitigate feed-in current harmonics. The hybrid...... SHC scheme consists of multiple parallel recursive (nk±m)-order (k = 0, 1, 2, . . ., and m ≤ n/2) harmonic control modules with independent control gains, which can be optimally weighted in accordance with the harmonic distribution. The hybrid SHC thus offers an optimal trade-off among cost...... into the FA-SHC, being the proposed fractional order controller, when it is implemented with a fixed sampling rate. The FASHC is implemented by substituting the fractional order elements with the Lagrange polynomial based interpolation filters. The proposed FA-SHC scheme provides fast on-line computation...
Sideband-Harmonic Instability of Paralleled Inverters with Asynchronous Carriers
DEFF Research Database (Denmark)
Yang, Dongsheng; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
Paralleled inverters with asynchronous carriers are increasingly emerging into renewable power plants and other power-electronic-based power systems. The sideband harmonics resulting from the pulse width modulation tend to be different from one inverter to another, which may trigger sideband-harmonic...... resonances among the paralleled inverters. To address the sideband-harmonic instability, the nonlinearity of the digital pulse width modulator is analyzed first in this paper based on the harmonic balance principle. It is revealed that the dynamic sideband components corresponding to a given small......-signal perturbation can be far below the Nyquist frequency, and they may not be effectively attenuated by anti-aliasing filters. A multi-frequency impedance model is then developed for the inverter, which characterizes the dynamic coupling between the perturbed frequency component and the sideband frequency component...
Human brain networks function in connectome-specific harmonic waves.
Atasoy, Selen; Donnelly, Isaac; Pearson, Joel
2016-01-21
A key characteristic of human brain activity is coherent, spatially distributed oscillations forming behaviour-dependent brain networks. However, a fundamental principle underlying these networks remains unknown. Here we report that functional networks of the human brain are predicted by harmonic patterns, ubiquitous throughout nature, steered by the anatomy of the human cerebral cortex, the human connectome. We introduce a new technique extending the Fourier basis to the human connectome. In this new frequency-specific representation of cortical activity, that we call 'connectome harmonics', oscillatory networks of the human brain at rest match harmonic wave patterns of certain frequencies. We demonstrate a neural mechanism behind the self-organization of connectome harmonics with a continuous neural field model of excitatory-inhibitory interactions on the connectome. Remarkably, the critical relation between the neural field patterns and the delicate excitation-inhibition balance fits the neurophysiological changes observed during the loss and recovery of consciousness.
DEFF Research Database (Denmark)
Abdul Samad, Noor Asma Fazli; Singh, Ravendra; Sin, Gürkan
Crystallization processes form an important class of separation methods that are frequently used in the chemical, the pharmaceutical and the food industry. The specifications of the crystal product are usually given in terms of crystal size, shape and purity. In order to predict the desired cryst...
A task based design procedure and modelling approached for industrial crystallization processes
Menon, A.R.
2006-01-01
A synthesis-based approach to the design of crystallizers and industrial crystallization processes is introduced in this thesis. An ontology for a task-based design procedure has been developed which breaks the crystallization process into a subset of basic functions (physical tasks) which transform
Directory of Open Access Journals (Sweden)
Claudia Alicia Castillo-Miranda
2016-01-01
Full Text Available The crystallization of nonsteroidal anti-inflammatory drug [2-(4-isobutyl-phenyl propionic acid] ibuprofen (IBP on a hydroxypropyl cellulose (HPC and polyacrylamide (PAAm gel was studied as well as the release kinetics of the drug. The IBP was crystallized on the gel surface of HPC/PAAm. It had a prismatic shape and the growth was made in an aqueous medium; the crystallinity grade of the gels HPC/PAAm and HPC/PAAm-IBU increased to 68% and to 58%, respectively. The release of IBP is performed by two means: by a non-Fickian diffusion process and by relaxation of the chains of the gel; without regard to temperature and the diffusion media, this correlates with the lower critical solution temperature (LCST of the proposed gel. This polymer matrix provides an option for releasing nonsteroidal anti-inflammatory drugs in a temperature range of 35–39°C. Korsmeyer and Peppas mathematical model was simulated for data releases, statistically significant at 95% confidence level.
Energy Technology Data Exchange (ETDEWEB)
Pallan, Pradeep S.; Marshall, William S.; Harp, Joel; Jewett III, Frederic C.; Wawrzak, Zdzislaw; Brown II, Bernard A.; Rich, Alexander; Egli, Martin (MIT); (Wake Forest); (Dharmacon); (Vanderbilt)
2010-03-08
To understand the role of structural elements of RNA pseudoknots in controlling the extent of -1-type ribosomal frameshifting, we determined the crystal structure of a high-efficiency frameshifting mutant of the pseudoknot from potato leaf roll virus (PLRV). Correlations of the structure with available in vitro frameshifting data for PLRV pseudoknot mutants implicate sequence and length of a stem-loop linker as modulators of frameshifting efficiency. Although the sequences and overall structures of the RNA pseudoknots from PLRV and beet western yellow virus (BWYV) are similar, nucleotide deletions in the linker and adjacent minor groove loop abolish frameshifting only with the latter. Conversely, mutant PLRV pseudoknots with up to four nucleotides deleted in this region exhibit nearly wild-type frameshifting efficiencies. The crystal structure helps rationalize the different tolerances for deletions in the PLRV and BWYV RNAs, and we have used it to build a three-dimensional model of the PRLV pseudoknot with a four-nucleotide deletion. The resulting structure defines a minimal RNA pseudoknot motif composed of 22 nucleotides capable of stimulating -1-type ribosomal frameshifts.
Modeling of the effect of intentionally introduced traps on hole transport in single-crystal rubrene
Dacuña, Javier
2014-06-05
Defects have been intentionally introduced in a rubrene single crystal by means of two different mechanisms: ultraviolet ozone (UVO) exposure and x-ray irradiation. A complete drift-diffusion model based on the mobility edge (ME) concept, which takes into account asymmetries and nonuniformities in the semiconductor, is used to estimate the energetic and spatial distribution of trap states. The trap distribution for pristine devices can be decomposed into two well defined regions: a shallow region ascribed to structural disorder and a deeper region ascribed to defects. UVO and x ray increase the hole trap concentration in the semiconductor with different energetic and spatial signatures. The former creates traps near the top surface in the 0.3-0.4 eV region, while the latter induces a wider distribution of traps extending from the band edge with a spatial distribution that peaks near the top and bottom interfaces. In addition to inducing hole trap states in the transport gap, both processes are shown to reduce the mobility with respect to a pristine crystal. © 2014 American Physical Society.
Modeling surface segregation phenomena in the (111) surface of ordered Pt3Ti crystal.
Duan, Zhiyao; Zhong, Jun; Wang, Guofeng
2010-09-21
We investigated the surface segregation phenomena in the (111) surface of ordered Pt(3)Ti crystal using density functional theory (DFT) calculation (with no configuration sampling) and Monte Carlo (MC) simulation method (employing modified embedded atom method potentials and with extensive configuration sampling). Our DFT study suggested that the off-stoichiometric effect (specifically, a Pt concentration higher than 75 at. %) accounted for the experimentally observed Pt segregation to the outermost layer of the Pt(3)Ti (111). Our MC simulations predicted that in a Pt(3)Ti (111) sample with a Pt concentration slightly above 75 at. %, Pt atoms would segregate to the surface to form a pure Pt outermost layer, while the ordered Pt(3)Ti crystal structure would be maintained in the second layer and below. Moreover, our DFT calculations revealed that the d-band center of the Pt-segregated Pt(3)Ti (111) surface would downshift by 0.21 eV as compared to that of a pure Pt (111) surface. As a result, O adsorption energy on the Pt-segregated Pt(3)Ti (111) surface was found to be at least 0.16 eV weaker than that on the pure Pt (111) surface. Thus, we theoretically modeled the geometric and electronic structures of the Pt-segregated Pt(3)Ti (111) surface and further suggested that the Pt surface segregation could lead to enhanced catalytic activity for oxygen reduction reactions on Pt(3)Ti alloy catalysts.
Harmonic Structure Predicts the Enjoyment of Uplifting Trance Music.
Agres, Kat; Herremans, Dorien; Bigo, Louis; Conklin, Darrell
2016-01-01
An empirical investigation of how local harmonic structures (e.g., chord progressions) contribute to the experience and enjoyment of uplifting trance (UT) music is presented. The connection between rhythmic and percussive elements and resulting trance-like states has been highlighted by musicologists, but no research, to our knowledge, has explored whether repeated harmonic elements influence affective responses in listeners of trance music. Two alternative hypotheses are discussed, the first highlighting the direct relationship between repetition/complexity and enjoyment, and the second based on the theoretical inverted-U relationship described by the Wundt curve. We investigate the connection between harmonic structure and subjective enjoyment through interdisciplinary behavioral and computational methods: First we discuss an experiment in which listeners provided enjoyment ratings for computer-generated UT anthems with varying levels of harmonic repetition and complexity. The anthems were generated using a statistical model trained on a corpus of 100 uplifting trance anthems created for this purpose, and harmonic structure was constrained by imposing particular repetition structures (semiotic patterns defining the order of chords in the sequence) on a professional UT music production template. Second, the relationship between harmonic structure and enjoyment is further explored using two computational approaches, one based on average Information Content, and another that measures average tonal tension between chords. The results of the listening experiment indicate that harmonic repetition does in fact contribute to the enjoyment of uplifting trance music. More compelling evidence was found for the second hypothesis discussed above, however some maximally repetitive structures were also preferred. Both computational models provide evidence for a Wundt-type relationship between complexity and enjoyment. By systematically manipulating the structure of chord
Harmonic Structure Predicts the Enjoyment of Uplifting Trance Music
Agres, Kat; Herremans, Dorien; Bigo, Louis; Conklin, Darrell
2017-01-01
An empirical investigation of how local harmonic structures (e.g., chord progressions) contribute to the experience and enjoyment of uplifting trance (UT) music is presented. The connection between rhythmic and percussive elements and resulting trance-like states has been highlighted by musicologists, but no research, to our knowledge, has explored whether repeated harmonic elements influence affective responses in listeners of trance music. Two alternative hypotheses are discussed, the first highlighting the direct relationship between repetition/complexity and enjoyment, and the second based on the theoretical inverted-U relationship described by the Wundt curve. We investigate the connection between harmonic structure and subjective enjoyment through interdisciplinary behavioral and computational methods: First we discuss an experiment in which listeners provided enjoyment ratings for computer-generated UT anthems with varying levels of harmonic repetition and complexity. The anthems were generated using a statistical model trained on a corpus of 100 uplifting trance anthems created for this purpose, and harmonic structure was constrained by imposing particular repetition structures (semiotic patterns defining the order of chords in the sequence) on a professional UT music production template. Second, the relationship between harmonic structure and enjoyment is further explored using two computational approaches, one based on average Information Content, and another that measures average tonal tension between chords. The results of the listening experiment indicate that harmonic repetition does in fact contribute to the enjoyment of uplifting trance music. More compelling evidence was found for the second hypothesis discussed above, however some maximally repetitive structures were also preferred. Both computational models provide evidence for a Wundt-type relationship between complexity and enjoyment. By systematically manipulating the structure of chord
Aerometric measurement and modeling of the mass of CO2 emissions from Crystal Geyser, Utah
Energy Technology Data Exchange (ETDEWEB)
Gouveia, F J; Johnson, M R; Leif, R N; Friedmann, S J
2005-02-07
Crystal Geyser in eastern Utah is a rare, non-geothermal geyser that emits carbon dioxide gas in periodic eruptions. This geyser is the largest single source of CO{sub 2} originating from a deep reservoir. For this study, the amount of CO{sub 2} emitted from Crystal Geyser is estimated through measurements of downwind CO{sub 2} air concentration applied to an analytical model for atmospheric dispersion. Five eruptions occurred during the 48-hour field study, for a total of almost 3 hours of eruption. Pre-eruption emissions were also timed and sampled. Slow wind during three of the active eruptions conveyed the plume over a grid of samplers arranged in arcs from 25 to 100 m away from the geyser. An analytical, straight-line Gaussian model matched the pattern of concentration measurements. Plume width was determined from least-squares fit of the CO{sub 2} concentrations integrated over time. The CO{sub 2} emission rate was found to be between 2.6 and 5.8 kg/s during the eruption events, and about 0.17 kg/s during the active pre-eruptive events. Our limited field study can be extrapolated to an annual CO{sub 2} emission of 12 kilotonnes from this geyser. As this is the first application of Gaussian dispersion modeling and objective timing to CO{sub 2} emissions from a geyser of any type, the present study demonstrates the feasibility of applying this method more completely in the future.
Energy Technology Data Exchange (ETDEWEB)
Ludden, J.N.; Thompson, G.; Bryan, W.B.; Frey, F.A.
1980-08-10
Ferrobasalts from DSDP sites 214 and 216 on the Ninetyeast Ridge are characterized by high absolute iron (FeO>12.9 wt %), FeO/MgO>1.9, and TiO/sub 2/>2.0 wt %. Their trace element abundances indicate a tholeiitic affinity; however, they are distinct from midocean ridge incompatible element-depleted tholeiites owing to higher contents of Ba, Zr, and Sr and flat to slightly light-REE-enriched, chondrite-normalized REE patterns. Calculations using major and trace element abundances and phase compositions are generally consistent with a model relating most major elements and phase compositions in site 214 and 216 ferrobasalts by fractionation of clinopyroxene and plagio-class. However, some incompatible element abundances for site 216 basalts are not consistent with the fractional crystallization models. Baslats from site 214 can be related to andesitic rocks from the same site by fractionating clinopyroxene, plagioclase and titanomagnetite. Site 254 basalts, at the southern end of the Ninetyeast Ridge, and island tholeiites in the southern Indian Ocean (Amsterdam-St. Paul or Kerguelen-Heard volcanic provinces) possibly represent the most recent activity associated with a hot spot forming the Ninetyeast Ridge. These incompatible-element-enriched tholeiites have major element compositions consistent with those expected for a parental liquid for the site 214 and 216 ferrobasalts. However, differences in the trace element contents of the basalts from the Ninetyeast Ridge sites are not consistent with simple fractional crystallization derivation but require either a complex melting model or a heterogeneous mantle source.
Huang, Jen-Ching; Weng, Yung-Jin
2014-01-01
This study focused on the nanomachining property and cutting model of single-crystal sapphire during nanomachining. The coated diamond probe is used to as a tool, and the atomic force microscopy (AFM) is as an experimental platform for nanomachining. To understand the effect of normal force on single-crystal sapphire machining, this study tested nano-line machining and nano-rectangular pattern machining at different normal force. In nano-line machining test, the experimental results showed that the normal force increased, the groove depth from nano-line machining also increased. And the trend is logarithmic type. In nano-rectangular pattern machining test, it is found when the normal force increases, the groove depth also increased, but rather the accumulation of small chips. This paper combined the blew by air blower, the cleaning by ultrasonic cleaning machine and using contact mode probe to scan the surface topology after nanomaching, and proposed the "criterion of nanomachining cutting model," in order to determine the cutting model of single-crystal sapphire in the nanomachining is ductile regime cutting model or brittle regime cutting model. After analysis, the single-crystal sapphire substrate is processed in small normal force during nano-linear machining; its cutting modes are ductile regime cutting model. In the nano-rectangular pattern machining, due to the impact of machined zones overlap, the cutting mode is converted into a brittle regime cutting model. © 2014 Wiley Periodicals, Inc.
TAX HARMONIZATION VERSUS FISCAL COMPETITION
Directory of Open Access Journals (Sweden)
Florin Alexandru MACSIM
2016-12-01
Full Text Available Recent years have brought into discussion once again subjects like tax harmonization and fiscal competition. Every time the European Union tends to take a step forward critics enter the scene and give contrary arguments to European integration. Through this article we have offered our readers a compelling view over the “battle” between tax harmonization and fiscal competition. While tax harmonization has key advantages as less costs regarding public revenues, leads to higher degree of integration and allows the usage of fiscal transfers between regions, fiscal competition is no less and presents key advantages as high reductions in tax rates and opens a large path for new investments, especially FDI. Choosing tax harmonization or fiscal competition depends on a multitude of variables, of circumstances, the decision of choosing one path or the other being ultimately influenced by the view of central and local authorities. Our analysis indicates that if we refer to a group of countries that are a part of a monetary union or that form a federation, tax harmonization seems to be the best path to choose. Moving the analysis to a group of regions that aren’t taking any kind of correlated actions or that have not signed any major treaties regarding monetary or fiscal policies, the optimal solution is fiscal competition.
Harmonic Coupling Analysis of a Multi-Drive System with Slim DC-link Drive
DEFF Research Database (Denmark)
Yang, Feng; Kwon, Jun Bum; Blaabjerg, Frede
2017-01-01
One of the problems with slim dc-link adjustable speed drive is the difficulties to analyze the harmonic coupling when it is integrated into a multi-drive system. The traditional methods analyze this harmonic issue by neglecting the harmonic coupling, and base on the linear time-invariant methods....... Its disadvantages include the time consumption and large computer memory. This paper proposes to do harmonic analysis by using the harmonic state-space modeling method by using the linear time-periodic theory. By using the proposed model, the harmonic couplings, between dc-link and point of common...... coupling in different drives, are all analyzed in the multi-drive system. In the meantime, the effects of the small film dc-link capacitance and the nonlinear characteristic of the diode rectifier are considered. The detailed modeling procedure, the simulations and the lab experiment on a two-drive system...
Energy Technology Data Exchange (ETDEWEB)
Epishin, Alexander, E-mail: alex_epishin@yahoo.de [Technical University of Berlin, Institute of Material Sciences and Technologies, Metallic Materials, secr. BH18, Ernst-Reuter-Platz 1, 10587 Berlin (Germany); Fedelich, Bernard [Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin (Germany); Link, Thomas [Technical University of Berlin, Institute of Material Sciences and Technologies, Metallic Materials, secr. BH18, Ernst-Reuter-Platz 1, 10587 Berlin (Germany); Feldmann, Titus [Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin (Germany); Svetlov, Igor L. [All-Russian Institute of Aviation Materials (VIAM), Radio Street, 105005 Moscow (Russian Federation)
2013-12-01
Pore annihilation during hot isostatic pressing (HIP) was investigated in the single-crystal nickel-base superalloy CMSX-4 experimentally by interrupted HIP tests at 1288 °C/103 MPa. The kinetics of pore annihilation was determined by density measurement and quantitative metallography. Transmission electron microscopy of a HIPed specimen showed that the pores shrink via dislocation movement on octahedral glide planes. Theoretically pore closure under HIP condition was modelled by the finite element method using crystal plasticity and large strain theories. The modelling gives a similar kinetics of pore annihilation as observed experimentally, however somewhat higher annihilation rate.
Iijima, Mayumi; Tohda, Hisako; Moriwaki, Yutaka
1992-02-01
Lamellar mixed crystals of octacalcium phosphate (OCP) and apatite were synthesized in a model system of enamel formation in the presence of 1 ppm F - at 37°C and at pH 6.5. The crystal has long and thin plate-like morphology and contained a distinct OCP lamella in the center of the apatite matrix. The thickness of the OCP lamella in the a-axis direction is one to several unit cells. Some apatite crystals embed a central layer instead of the distinct OCP lamella. The OCP lamella and the central layer are parallel to the (100) plane of the apatite, while the c-axis of the OCP is parallel to the c-axis of the apatite. Analysis suggests that (1) F - causes the growth of apatite on OCP and regulates the formation of the lamellar mixed crystals of OCP and apatite, (2) the OCP lamella acts as a template for the subsequent epitaxial growth of apatite, and (3) the lamellar mixed crystals grow mainly in the c-axis direction of both the OCP and apatite. These results strongly support the idea that enamel crystals take a thin and long ribbon-like morphology when the initially formed OCP acts as a template for the subsequent growth of apatite in the enamel formation.
Ray, S K; Singh, A K; Kumar, A; Misra, A Mandal S; Mitra, P; Ghosh, N
2016-01-01
We present a simple yet elegant Mueller matrix approach for controlling the Fano interference effect and engineering the resulting asymmetric spectral line shape in anisotropic optical system. The approach is founded on a generalized model of anisotropic Fano resonance, which relates the spectral asymmetry to two physically meaningful and experimentally accessible parameters of interference, namely, the Fano phase shift and the relative amplitudes of the interfering modes. The differences in these parameters between orthogonal linear polarizations in an anisotropic system are exploited to desirably tune the Fano spectral asymmetry using pre- and post-selection of optimized polarization states. Experimental control on the Fano phase and the relative amplitude parameters and resulting tuning of spectral asymmetry is demonstrated in waveguided plasmonic crystals using Mueller matrix-based polarization analysis. The approach enabled tailoring of several exotic regimes of Fano resonance including the complete reve...
Towards an optimal model for a bistable nematic liquid crystal display device
Cummings, L. J.
2013-03-13
Bistable liquid crystal displays offer the potential for considerable power savings compared with conventional (monostable) LCDs. The existence of two stable field-free states that are optically distinct means that contrast can be maintained in a display without an externally applied electric field. An applied field is required only to switch the device from one state to the other, as needed. In this paper we examine a theoretical model of a possible bistable device, originally proposed by Cummings and Richardson (Euro J Appl Math 17:435-463 2006), and explore means by which it may be optimized, in terms of optical contrast, manufacturing considerations, switching field strength, and switching times. The compromises inherent in these conflicting design criteria are discussed. © 2013 Springer Science+Business Media Dordrecht.
A New Approach to the Modeling of Local Defects in Crystals: The Reduced Hartree-Fock Case
Cancès, Éric; Deleurence, Amélie; Lewin, Mathieu
2008-07-01
This article is concerned with the derivation and the mathematical study of a new mean-field model for the description of interacting electrons in crystals with local defects. We work with a reduced Hartree-Fock model, obtained from the usual Hartree-Fock model by neglecting the exchange term. First, we recall the definition of the self-consistent Fermi sea of the perfect crystal, which is obtained as a minimizer of some periodic problem, as was shown by Catto, Le Bris and Lions. We also prove some of its properties which were not mentioned before. Then, we define and study in detail a nonlinear model for the electrons of the crystal in the presence of a defect. We use formal analogies between the Fermi sea of a perturbed crystal and the Dirac sea in Quantum Electrodynamics in the presence of an external electrostatic field. The latter was recently studied by Hainzl, Lewin, Séré and Solovej, based on ideas from Chaix and Iracane. This enables us to define the ground state of the self-consistent Fermi sea in the presence of a defect. We end the paper by proving that our model is in fact the thermodynamic limit of the so-called supercell model, widely used in numerical simulations.
Modeling of stimulated hydrogel volume changes in photonic crystal Pb2+ sensing materials.
Goponenko, Alexander V; Asher, Sanford A
2005-08-03
We modeled the stimulated hydrogel volume transitions of a material which binds Pb2+ and is used as a photonic crystal chemical sensing material. This material consists of a polymerized crystalline colloidal array (PCCA) hydrogel which contains a crown ether molecular recognition group. The PCCA is a polyacrylamide hydrogel which embeds a crystalline colloidal array (CCA) of monodisperse polystyrene spheres of approximately 100 nm. The array spacing is set to diffract light in the visible spectral region. Changes in the hydrogel volume induced by Pb2+ binding alter the array spacing and shift the diffracted wavelength. This system allows us to sensitively follow the hydrogel swelling behavior which results from the immobilization of the Pb2+ by the crown ether chelating groups. Binding of the Pb2+ immobilizes its counterions. This results in a Donnan potential, which results in an osmotic pressure which swells the hydrogel. We continue here our development of a predictive model for hydrogel swelling based on Flory's theory of gel swelling. We are qualitatively able to model the PCCA swelling but cannot correctly model the large responsivity observed at the lowest Pb2+ concentrations which give rise to the experimentally observed low detection limits for Pb2+. These PCCA materials enable stimulated hydrogel volume transitions to be studied.
Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties
Braun, Efrem; Carraro, Carlo; Smit, Berend
2017-01-01
Some nanoporous, crystalline materials possess dynamic constituents, for example, rotatable moieties. These moieties can undergo a conformation change in response to the adsorption of guest molecules, which qualitatively impacts adsorption behavior. We pose and solve a statistical mechanical model of gas adsorption in a porous crystal whose cages share a common ligand that can adopt two distinct rotational conformations. Guest molecules incentivize the ligands to adopt a different rotational configuration than maintained in the empty host. Our model captures inflections, steps, and hysteresis that can arise in the adsorption isotherm as a signature of the rotating ligands. The insights disclosed by our simple model contribute a more intimate understanding of the response and consequence of rotating ligands integrated into porous materials to harness them for gas storage and separations, chemical sensing, drug delivery, catalysis, and nanoscale devices. Particularly, our model reveals design strategies to exploit these moving constituents and engineer improved adsorbents with intrinsic thermal management for pressure-swing adsorption processes. PMID:28049851
Elements of abstract harmonic analysis
Bachman, George
2013-01-01
Elements of Abstract Harmonic Analysis provides an introduction to the fundamental concepts and basic theorems of abstract harmonic analysis. In order to give a reasonably complete and self-contained introduction to the subject, most of the proofs have been presented in great detail thereby making the development understandable to a very wide audience. Exercises have been supplied at the end of each chapter. Some of these are meant to extend the theory slightly while others should serve to test the reader's understanding of the material presented. The first chapter and part of the second give
Harmonic functions with varying coefficients
Directory of Open Access Journals (Sweden)
Jacek Dziok
2016-05-01
Full Text Available Abstract Complex-valued harmonic functions that are univalent and sense preserving in the open unit disk can be written in the form f = h + g ‾ $f=h+\\overline{g}$ , where h and g are analytic. In this paper we investigate some classes of univalent harmonic functions with varying coefficients related to Janowski functions. By using the extreme points theory we obtain necessary and sufficient convolution conditions, coefficients estimates, distortion theorems, and integral mean inequalities for these classes of functions. The radii of starlikeness and convexity for these classes are also determined.
Porru, Marcella; Özkan, Leyla
2017-05-24
This paper develops a new simulation model for crystal size distribution dynamics in industrial batch crystallization. The work is motivated by the necessity of accurate prediction models for online monitoring purposes. The proposed numerical scheme is able to handle growth, nucleation, and agglomeration kinetics by means of the population balance equation and the method of characteristics. The former offers a detailed description of the solid phase evolution, while the latter provides an accurate and efficient numerical solution. In particular, the accuracy of the prediction of the agglomeration kinetics, which cannot be ignored in industrial crystallization, has been assessed by comparing it with solutions in the literature. The efficiency of the solution has been tested on a simulation of a seeded flash cooling batch process. Since the proposed numerical scheme can accurately simulate the system behavior more than hundred times faster than the batch duration, it is suitable for online applications such as process monitoring tools based on state estimators.
Optimal Selective Harmonic Control for Power Harmonics Mitigation
DEFF Research Database (Denmark)
Zhou, Keliang; Yang, Yongheng; Blaabjerg, Frede
2015-01-01
of power harmonics. The proposed optimal SHC is of hybrid structure: all recursive SHC modules with weighted gains are connected in parallel. It bridges the real “nk+-m order RC” and the complex “parallel structure RC”. Compared to other IMP based control solutions, it offers an optimal trade-off among...
Algal Supply System Design - Harmonized Version
Energy Technology Data Exchange (ETDEWEB)
Jared Abodeely; Daniel Stevens; Allison Ray; Debor
2013-03-01
The objective of this design report is to provide an assessment of current technologies used for production, dewatering, and converting microalgae cultivated in open-pond systems to biofuel. The original draft design was created in 2011 and has subsequently been brought into agreement with the DOE harmonized model. The design report extends beyond this harmonized model to discuss some of the challenges with assessing algal production systems, including the ability to (1) quickly assess alternative algal production system designs, (2) assess spatial and temporal variability, and (3) perform large-scale assessments considering multiple scenarios for thousands of potential sites. The Algae Logistics Model (ALM) was developed to address each of these limitations of current modeling efforts to enable assessment of the economic feasibility of algal production systems across the United States. The (ALM) enables (1) dynamic assessments using spatiotemporal conditions, (2) exploration of algal production system design configurations, (3) investigation of algal production system operating assumptions, and (4) trade-off assessments with technology decisions and operating assumptions. The report discusses results from the ALM, which is used to assess the baseline design determined by harmonization efforts between U.S. DOE national laboratories. Productivity and resource assessment data is provided by coupling the ALM with the Biomass Assessment Tool developed at PNNL. This high-fidelity data is dynamically passed to the ALM and used to help better understand the impacts of spatial and temporal constraints on algal production systems by providing a cost for producing extracted algal lipids annually for each potential site.
Ward, Logan; Liu, Ruoqian; Krishna, Amar; Hegde, Vinay I.; Agrawal, Ankit; Choudhary, Alok; Wolverton, Chris
2017-07-01
While high-throughput density functional theory (DFT) has become a prevalent tool for materials discovery, it is limited by the relatively large computational cost. In this paper, we explore using DFT data from high-throughput calculations to create faster, surrogate models with machine learning (ML) that can be used to guide new searches. Our method works by using decision tree models to map DFT-calculated formation enthalpies to a set of attributes consisting of two distinct types: (i) composition-dependent attributes of elemental properties (as have been used in previous ML models of DFT formation energies), combined with (ii) attributes derived from the Voronoi tessellation of the compound's crystal structure. The ML models created using this method have half the cross-validation error and similar training and evaluation speeds to models created with the Coulomb matrix and partial radial distribution function methods. For a dataset of 435 000 formation energies taken from the Open Quantum Materials Database (OQMD), our model achieves a mean absolute error of 80 meV/atom in cross validation, which is lower than the approximate error between DFT-computed and experimentally measured formation enthalpies and below 15% of the mean absolute deviation of the training set. We also demonstrate that our method can accurately estimate the formation energy of materials outside of the training set and be used to identify materials with especially large formation enthalpies. We propose that our models can be used to accelerate the discovery of new materials by identifying the most promising materials to study with DFT at little additional computational cost.
Automatic Functional Harmonic Analysis
de Haas, W.B.|info:eu-repo/dai/nl/304841250; Magalhães, J.P.; Wiering, F.|info:eu-repo/dai/nl/141928034; Veltkamp, R.C.|info:eu-repo/dai/nl/084742984
2013-01-01
Music scholars have been studying tonal harmony intensively for centuries, yielding numerous theories and models. Unfortunately, a large number of these theories are formulated in a rather informal fashion and lack mathematical precision. In this article we present HarmTrace, a functional model of
Ren, Ming-Liang; Agarwal, Rahul; Nukala, Pavan; Liu, Wenjing; Agarwal, Ritesh
2016-07-13
We demonstrate that optical second harmonic generation (SHG) can be utilized to determine the exact nature of nanotwins in noncentrosymmetric crystals, which is challenging to resolve via conventional transmission electron or scanned probe microscopies. Using single-crystalline nanotwinned CdTe nanobelts and nanowires as a model system, we show that SHG polarimetry can distinguish between upright (Cd-Te bonds) and inverted (Cd-Cd or Te-Te bonds) twin boundaries in the system. Inverted twin boundaries are generally not reported in nanowires due to the lack of techniques and complexity associated with the study of the nature of such defects. Precise characterization of the nature of defects in nanocrystals is required for deeper understanding of their growth and physical properties to enable their application in future devices.
Energy Technology Data Exchange (ETDEWEB)
Hamh, S. Y.; Park, S.-H.; Lee, J. S., E-mail: jsl@gist.ac.kr [Department of Physics and Photon Science, School of Physics and Chemistry, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Jerng, S.-K.; Jeon, J. H.; Chun, S. H. [Department of Physics and Graphene Research Institute, Sejong University, Seoul 143-747 (Korea, Republic of); Jeon, J. H.; Kahng, S. J. [Department of Physics, Korea University, Seoul 136-701 (Korea, Republic of); Yu, K.; Choi, E. J. [Department of Physics, University or Seoul, Seoul 130-743 (Korea, Republic of); Kim, S.; Choi, S.-H. [Department of Applied Physics, College of Applied Science, Kyung Hee University, Yongin 446-701 (Korea, Republic of); Bansal, N. [Department of Electrical and Computer Engineering, Rutgers, The state University of New Jersey, Piscataway, New Jersey 08854 (United States); Oh, S. [Department of Physics and Astronomy, Rutgers, The state University of New Jersey, Piscataway, New Jersey 08854 (United States); Park, Joonbum; Kho, Byung-Woo; Kim, Jun Sung [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)
2016-02-01
We investigate the surface and interface states of Bi{sub 2}Se{sub 3} thin films by using the second-harmonic generation technique. Distinct from the surface of bulk crystals, the film surface and interface show the isotropic azimuth dependence of second-harmonic intensity, which is attributed to the formation of randomly oriented domains on the in-plane. Based on the nonlinear susceptibility deduced from the model fitting, we determine that the surface band bending induced in a space charge region occurs more strongly at the film interface facing the Al{sub 2}O{sub 3} substrate or capping layer compared with the interface facing the air. We demonstrate that distinct behavior of the terahertz electric field emitted from the samples can provide further information about the surface electronic state of Bi{sub 2}Se{sub 3}.
Zhuo, G-Y; Lee, H; Hsu, K-J; Huttunen, M J; Kauranen, M; Lin, Y-Y; Chu, S-W
2014-03-01
Chirality is one of the most fundamental and essential structural properties of biological molecules. Many important biological molecules including amino acids and polysaccharides are intrinsically chiral. Conventionally, chiral species can be distinguished by interaction with circularly polarized light, and circular dichroism is one of the best-known approaches for chirality detection. As a linear optical process, circular dichroism suffers from very low signal contrast and lack of spatial resolution in the axial direction. It has been demonstrated that by incorporating nonlinear interaction with circularly polarized excitation, second-harmonic generation circular dichroism can provide much higher signal contrast. However, previous circular dichroism and second-harmonic generation circular dichroism studies are mostly limited to probe chiralities at surfaces and interfaces. It is known that second-harmonic generation, as a second-order nonlinear optical effect, provides excellent optical sectioning capability when combined with a laser-scanning microscope. In this work, we combine the axial resolving power of second-harmonic generation and chiral sensitivity of second-harmonic generation circular dichroism to realize three-dimensional chiral detection in biological tissues. Within the point spread function of a tight focus, second-harmonic generation circular dichroism could arise from the macroscopic supramolecular packing as well as the microscopic intramolecular chirality, so our aim is to clarify the origins of second-harmonic generation circular dichroism response in complicated three-dimensional biological systems. The sample we use is starch granules whose second-harmonic generation-active molecules are amylopectin with both microscopic chirality due to its helical structure and macroscopic chirality due to its crystallized packing. We found that in a starch granule, the second-harmonic generation for right-handed circularly polarized excitation is
Sheth, Swapnil Suhas
Narrow molecular weight fractions of poly(epsilon-caprolactone) were successfully obtained using the successive precipitation fractionation technique with toluene/n-heptane as a solvent/nonsolvent pair. Calorimetric studies of the melting behavior of fractions that were crystallized either isothermally or under constant cooling rate conditions suggested that the isothermal crystallization of the samples should be used for a proper evaluation of the molecular weight dependence of the observed melting temperature and degree of crystallinity in PCL. The molecular weight and temperature dependence of the spherulitic growth rate of fractions was studied in the context of the Lauritzen-Hoffman two-phase model and the Strobl three-phase model of polymer crystallization. The zero-growth rate temperatures, determined from spherulitic growth rates using four different methods, are consistent with each other and increase with chain length. The concomitant increase in the apparent secondary nucleation constant was attributed to two factors. First, for longer chains there is an increase in the probability that crystalline stems belong to loose chain-folds, hence, an increase in fold surface free energy. It is speculated that the increase in loose folding and resulting decrease in crystallinity with increasing chain length are associated with the ester group registration requirement in PCL crystals. The second contribution to the apparent nucleation constant arises from chain friction associated with segmental transport across the melt/crystal interface. These factors were responsible for the much stronger chain length dependence of spherulitic growth rates at fixed undercooling observed here with PCL than previously reported for PE and PEO. In the case of PCL, the scaling exponent associated with the chain length dependence of spherulitic growth rates exceeds the upper theoretical bound of 2 predicted from the Brochard- DeGennes chain pullout model. Observation that zero
Sums of Generalized Harmonic Series
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 9. Sums of Generalized Harmonic Series: For Kids from Five to Fifteen. Zurab Silagadze. General Article Volume 20 Issue 9 September 2015 pp 822-843 ... Keywords. Riemann zeta function; integral representation; Basel problem.
Shi, J.; Turteltaub, S.; Van der Giessen, E.
A discrete dislocation-transformation model is used to analyze the response of an aggregate of ferritic and austenitic grains that can transform into martensite. In particular, the influence of the crystal orientation of the austenitic grains on the plastic and transformation behavior is studied. It
Enhancement of Non-Stationary Speech using Harmonic Chirp Filters
DEFF Research Database (Denmark)
Nørholm, Sidsel Marie; Jensen, Jesper Rindom; Christensen, Mads Græsbøll
2015-01-01
the non-stationarity nature of voiced speech into account via linear constraints. This is facilitated by imposing a harmonic chirp model on the speech signal. As an implicit part of the filter design, the noise statistics are also estimated based on the observed signal and parameters of the harmonic chirp......In this paper, the issue of single channel speech enhancement of non-stationary voiced speech is addressed. The non-stationarity of speech is well known, but state of the art speech enhancement methods assume stationarity within frames of 20–30 ms. We derive optimal distortionless filters that take...... model. Simulations on real speech show that the chirp based filters perform better than their harmonic counterparts. Further, it is seen that the gain of using the chirp model increases when the estimated chirp parameter is big corresponding to periods in the signal where the instantaneous fundamental...