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1

A practical method of harmonic analysis for power converter  

Microsoft Academic Search

The converter is one important harmonic source in power systems. For the knowledge of harmonic characteristics of a converter, it is very important to evaluate the harmonic situations of AC and DC sides, and also it is very helpful to design the harmonic filters and to suppress harmonic propagation. A practical method of harmonic evaluation for a power converter is

Jianguo Jiang; Weimin Xie; Juan Zhou

2000-01-01

2

Converting gravity bins to spherical harmonic coefficients  

NASA Technical Reports Server (NTRS)

The gravity bin technique as originally formulated recovers the local gravity field from the bin parameters by finite differencing. The spherical harmonic coefficients of the gravity field are then computed by an orthogonal transformation of the local gravity field. The result differs from that of the traditional method. This paper discusses the difference and proposes a new algorithm to convert the bin parameters to spherical harmonic coefficients. It is shown that the new method produces the same gravity field as the traditional method and maintains the high computational efficiency of the basic gravity bin technique.

Wu, J. T.; Bertiger, W. I.; Wu, S. C.

1990-01-01

3

Harmonic current reduction of a six-pulse thyristor converter  

Microsoft Academic Search

This paper presents a line injection technique in order to reduce line current harmonics generated by AC\\/DC three-phase thyristor converters. The principle of this technique is to modify the current waveforms on the DC side windings of the converter transformer by injecting every harmonic components of the rectified current with an opposite phase. The proposed technique consists of an interconnection

B. M. Saied; H. I. Zynal

2007-01-01

4

A Mechanism for Converting Revolute Motion into Harmonic Rotating Motion  

Microsoft Academic Search

In this paper, we describe the design and construction of a cam mechanism to convert a revolute motion into a symmetrical oscillating harmonic movement. The mechanism consists of a harmonic cam driven by a revolute electric motor joined to a follower by a desmodromic constraint. The linear reciprocating motion of the follower was then transmitted, by a rack-pinion mechanism, to

A. Diana; A. Manuello Bertetto; M. Ruggiu

2008-01-01

5

Elimination of harmonics in a multilevel converter using the theory of symmetric polynomials and resultants  

Microsoft Academic Search

A method is presented to compute the switching angles in a multilevel converter so as to produce the required fundamental voltage while at the same time not generate higher order harmonics. Previous work has shown that the transcendental equations characterizing the harmonic content can be converted to polynomial equations which are then solved using the method of resultants from elimination

John N. Chiasson; Leon M. Tolbert; Keith J. McKenzie; Zhong Du

2005-01-01

6

Mitigation of harmonic disturbance at pumped storage power station with static frequency converter  

Microsoft Academic Search

This paper investigates the harmonic distortion problem and mitigation method at the Mingtan pumped storage power station in Taiwan, where six 300 MVA synchronous generator\\/motors are started by a static frequency converter (SFC) before the pumping stage. Since the SFC uses a 6-pulse rectifier technique, a large amount of harmonic currents are produced during the starting period. The harmonic distortion

Jung-Chen Chiang; Chi-Jui Wu; Shih-Shong Yen

1997-01-01

7

Sum frequency and second harmonics generation of copper vapor laser by nonlinear crystals.  

National Technical Information Service (NTIS)

We have demonstrated sum frequency and second harmonic generation using green (510 nm) and yellow (578 nm) laser light of copper vapor lasers (CVL) by nonlinear crystals of KDP and BBO. The beam patterns of the converted UV laser light become stripe due t...

A. Sugiyama, A. Ohzu, M. Kato, Y. Maruyama

1996-01-01

8

Converting Gravity-Bin Parameters To Spherical Harmonics  

NASA Technical Reports Server (NTRS)

New method of computation of gravitational field of Earth provides for conversion of gravity-bin parameters to coefficients of spherical harmonics. Traditional representation of gravitational field recovered by new method.

Wu, Jiun-Tsong; Bertiger, William I.; Wu, Sien-Chong

1993-01-01

9

Voltage harmonics generated by 3-level converters using PWM natural sampling  

Microsoft Academic Search

This paper presents a detailed analysis on how the independent choice of the branch carrier phase shift angles in 3-level three-phase converters using PWM natural sampling can offer some extra degrees of freedom to establish rules to optimize the line voltage harmonic content. The study developed in this paper is only valid for converters that can be considered as an

O. Alonso Sadaba; P. Sanchis Gurpide; J. Lopez Taberna; I. Munoz Morales; L. Marroyo Palomo

2001-01-01

10

Modulation Extension Control for Multilevel Converters Using Triplen Harmonic Injection with Low Switching Frequency  

E-print Network

-based PWM methods to help to optimize or balance the switch utilization in multilevel inverters [12, 13Modulation Extension Control for Multilevel Converters Using Triplen Harmonic Injection with Low@utk.edu Abstract--This paper presents a modulation extension control method for multilevel converters with low

Tolbert, Leon M.

11

Harmonic optimization of multilevel converters using genetic algorithms  

Microsoft Academic Search

In this paper, a genetic algorithm (GA) optimization technique is applied to multilevel inverter to determine optimum switching angles for cascaded multilevel inverters for eliminating some higher order harmonics while maintaining the required fundamental voltage. This technique can be applied to multilevel inverters with any number of levels; as an example in this paper, a 7-level inverter is considered, and

B. Ozpineci; L. M. Tolbert; J. N. Chiasson

2004-01-01

12

Harmonic Generation in Nanostructures: Metal Nanoparticles and Photonic Crystals  

Microsoft Academic Search

The potential of nonlinear optical phenomena in adding functionality to nanostructures like nanoparticles or photonic crystal\\u000a waveguides are presented. The role of field localization and system resonances is discussed in the light of few examples in\\u000a which harmonic generation is being drastically enhanced by these effects. In particular the results on single nanoparticle\\u000a harmonic response are discussed as the basic

Andrea Marco Malvezzi

13

Higher Harmonic Imaging of Tight Cracks in Glass Plates and Weld Interface with Mode-Converted Transverse Waves  

NASA Astrophysics Data System (ADS)

Higher harmonic imaging technique is applied for delineate the weld interface of thin metal plates and detecting tight cracks in glass plates. The technique of mode-converted shear wave is used for extracting higher harmonics and imaging the harmonic amplitudes. The backscattered higher harmonic wave is captured by a focused transducer in water immersion. High-pass filters of different cut-off frequencies are inserted in the reception circuit to extract higher harmonics and reduce the fundamental frequency component.

Kawashima, Koichiro; Sekino, Kouichi; Ichigo, Kazuyoshi

2008-06-01

14

A 3-point PWM converter with less low order harmonics  

SciTech Connect

It is well understood that pulse width modulation offers several advantages over other methods when used for the control of power (especially for the control of Induction motors). The advantages being that a nearly sinusoidal voltage may be generated and applied to the load. Depending on the switching frequency, higher frequency harmonics are generated which may be filtered out (if desired) with a low rating filter. Single pulse width modulation is obtained by a single pulse bridge inverter with voltage levels of 0, +V, 0, {minus}V volts (also called a 2-point inverter). Multiple pulse width modulation is obtained by a combination of two, single pulse width modulation inverter wave forms suitably shifted with each other using a transformer which results in a waveform of 0, +V, +2V, + V, 0, {minus}2V, {minus}V, 0 volts. Further, in the proposed investigation, a single bridge inverter with a string of switching devices is suggested to be used thereby avoiding the use of transformer for combining the wave forms. Experimental verification is made to verify the satisfactory working of the 3-point inverter in the generation of the pulse width modulation waveform without using a transformer. Due to the absence of the transformer, the circuit suggested for the purpose is light and efficient.

Venkatesha, M.K.; Krishnamurthy, K.A. [Malnad Coll. of Engineering, Hassan (India). Dept. of E and C Engineering

1995-12-31

15

Ferroelectricity in liquid crystals probed by second harmonic generation  

Microsoft Academic Search

Summary form only given. Ferroelectric liquid crystals (FLC) attract significant attention as promising materials for different applications and rare examples of two-dimensional (2D) ferroelectrics. It has been shown previously that a nonlinear optical probe of second harmonic generation (SHG) can be applied to study the structure and switching behaviour of FLC. In this study, ferroelectric properties and switching behaviour of

Yu. G. Fokin; T. V. Murzina; O. A. Aktsipetrov; S. Soria; G. Marowsky

2002-01-01

16

Multiphase semiclassical approximation of the one-dimensional harmonic crystal  

E-print Network

of the harmonic crystal 2 1. Introduction 1.1. Preliminaries It is a familiar fact that electrons are able to move's theory which explains how valence/conduction electrons can move rather freely and have a well principle doesn't have very sensible effects). These electrons move according to the energy bands thus can

Boyer, Edmond

17

A metallic photonic crystal high power microwave mode converter  

NASA Astrophysics Data System (ADS)

A compact metallic photonic crystal mode converter that converts TEM to TE11 mode for a high power transmission system is presented. Metallic photonic crystal is partially filled along azimuthal direction in the device to divide a single coaxial transmission line into two different partitions with different phase propagation constants for phase-shifting. A three row structure is designed and simulated by commercial software cst microwave studio. Simulation results show that it has high conversion efficiency and the bandwidth is 4.1%. Far-field measurement experiment is carried out and get a typical TE11 mode pattern. The result confirms the validity of the design.

Wang, Dong; Qin, Fen; Xu, Sha; Shi, Meiyou

2013-06-01

18

IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 41, NO. 1, JANUARY/FEBRUARY 2005 75 Elimination of Harmonics in a Multilevel Converter  

E-print Network

multilevel inverter is to ensure that the total harmonic distortion (THD) in the voltage output waveform of Harmonics in a Multilevel Converter With Nonequal DC Sources Leon M. Tolbert, Senior Member, IEEE, John N Abstract--Eliminating harmonics in a multilevel converter in which the separate dc sources vary

Tolbert, Leon M.

19

Quartz crystal microbalance based on passive frequency to voltage converter  

SciTech Connect

In dynamics of evaporation or drying of microdrops from a solid surface, a faster and precise quartz crystal microbalance (QCM) is needed. The fast QCM based on frequency to voltage converter is an attractive and powerful tool in the investigation of the dynamic regime of evaporation to translate the frequency shift in terms of a continuous voltage change. The frequency shift monitoring in fast QCM applications is a real challenge for electronic processing interface. Originally developed as a frequency shift processing interface, this novel passive frequency to voltage converter can produce faster, stable, and accurate results in regard to the QCM sensor behavior. In this article, the concept and circuit of passive frequency to voltage converter will be explained followed by static and dynamic characterization. Experimental results of microdrops evaporation will be given.

Burda, Ioan; Tunyagi, Arthur [Department of Physics, Babes-Bolyai University, Cluj-Napoca, 400084 (Romania)

2012-02-15

20

On two-temperature problem for harmonic crystals  

E-print Network

We consider the dynamics of a harmonic crystal in $d$ dimensions with $n$ components,$d,n \\ge 1$. The initial date is a random function with finite mean density of the energy which also satisfies a Rosenblatt- or Ibragimov-Linnik-type mixing condition. The random function converges to different space-homogeneous processes as $x_d\\to\\pm\\infty$, with the distributions $\\mu_\\pm$. We study the distribution $\\mu_t$ of the solution at time $t\\in\\R$. The main result is the convergence of $\\mu_t$ to a Gaussian translation-invariant measure as $t\\to\\infty$. The proof is based on the long time asymptotics of the Green function and on Bernstein's `room-corridor' argument. The application to the case of the Gibbs measures $\\mu_\\pm=g_\\pm$ with two different temperatures $T_{\\pm}$ is given. Limiting mean energy current density is $- (0,...,0,C(T_+ - T_-))$ with some positive constant $C>0$ what corresponds to Second Law.

T. V. Dudnikova; A. I. Komech; N. J. Mauser

2002-11-11

21

Exact iterative solution of simultaneous second-harmonic and third-harmonic generation in nonlinear photonic crystals  

NASA Astrophysics Data System (ADS)

A computational study on simultaneous second-harmonic and third-harmonic generation and enhancement through a ? three-wave mixing process in one-dimensional nonlinear photonic crystals is presented. The mathematical model partly overcomes the shortcoming of some existing models based on the undepleted pump approximation, which is derived from a nonlinear system of Maxwell equations. We introduce not only a variational approach that combined the finite element method and the fixed-point iteration to study the nonlinear frequency conversion but also a continuation technique depends on the weak formulation of the incremental fields to ensure the convergence of the iterative procedure when the nonlinearity is very strong. Two designed photonic crystals matched the phase by utilizing and balancing the interplay of material dispersion and the geometrical dispersion are reported, as well as a tested photonic crystal to show the validity and efficiency of our approaches. Numerical experiments indicate that the conversion efficiencies of SH and TH generation can be significantly enhanced when the frequencies of fundamental and harmonic waves are tuned at the photonic band edges or are located to the defect states.

Yuan, Jianhua; Yang, Jian; Ai, Wenbao; Shuai, Tianping

2014-03-01

22

Deep-UV 236.5??nm laser by fourth-harmonic generation of a single-crystal fiber Nd:YAG oscillator.  

PubMed

We demonstrate a deep-UV laser at 236.5 nm based on extracavity fourth-harmonic generation of a Q-switched Nd:YAG single-crystal fiber laser at 946 nm. We first compare two nonlinear crystals available for second-harmonic generation: LBO and BiBO. The best results at 473 nm are obtained with a BiBO crystal, with an average output power of 3.4 W at 20 kHz, corresponding to a second-harmonic generation efficiency of 38%. This blue laser is frequency-converted to 236.5 nm in a BBO crystal with an overall fourth-harmonic generation yield of 6.5%, corresponding to an average output power of 600 mW at 20 kHz. This represents an order of magnitude increase in average power and energy compared to previously reported pulsed lasers at 236.5 nm. This work opens the possibility of LIDAR detection of dangerous compounds for military or civilian applications. PMID:24978960

Deyra, Loïc; Martial, Igor; Didierjean, Julien; Balembois, François; Georges, Patrick

2014-04-15

23

Second harmonic generation in photonic crystal cavities in (111)-oriented GaAs  

SciTech Connect

We demonstrate second harmonic generation at telecommunications wavelengths in photonic crystal cavities in (111)-oriented GaAs. We fabricate 30 photonic crystal structures in both (111)- and (100)-oriented GaAs and observe an increase in generated second harmonic power in the (111) orientation, with the mean power increased by a factor of 3, although there is a large scatter in the measured values. We discuss possible reasons for this increase, in particular, the reduced two photon absorption for transverse electric modes in (111) orientation, as well as a potential increase due to improved mode overlap.

Buckley, Sonia, E-mail: bucklesm@stanford.edu; Radulaski, Marina; Vu?kovi?, Jelena [E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States)] [E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305 (United States); Biermann, Klaus [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)] [Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)

2013-11-18

24

Huge enhancement of backward second-harmonic generation with slow light in photonic crystals  

SciTech Connect

We study theoretically forward and backward second-harmonic generation in a two-dimensional photonic crystal structure made of lithium niobate. The aim of this article is twofold: First, we propose a reliable modal algorithm for describing the light propagation taking into account the vectorial character of the interacting fields as well as the tensorial character of the nonlinearity and verify it by means of the nonlinear finite-difference time-domain method. Second, we propose a photonic crystal where we obtain a giant efficiency increase for backward second-harmonic generation with slow light.

Iliew, Rumen [Nonlinear Physics Center, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Institute of Condensed Matter Theory and Solid State Optics, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Etrich, Christoph; Pertsch, Thomas [Institute of Applied Physics/Ultra Optics, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Lederer, Falk [Institute of Condensed Matter Theory and Solid State Optics, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Kivshar, Yuri S. [Nonlinear Physics Center, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2010-02-15

25

Solution to the problem of low order harmonic resonance from HVDC converters  

SciTech Connect

The paper identifies a severe form of low order harmonic resonance problem in an HVdc/ac system. It then seeks solutions to the problem by HVdc control means. This is achieved by a proper design of the voltage dependent current order limiter (VDCOL), the current regulator and timing pulse generator. Supplementary control loops have also been introduced to result in a satisfactory performance as compared to that obtained with the use of uncharacteristic harmonic filter on the ac side. Robustness of all the options has been demonstrated through recovery performance of the dc link in response to 3-phase 5 cycle faults on both rectifier and inverter commutating buses.

Kaul, N.; Mathur, R.M. (Western Ontario Univ., London, ON (Canada))

1990-11-01

26

A New Approach to Solving the Harmonic Elimination Equations for a Multilevel Converter  

E-print Network

possible solutions. I. Introduction A multilevel inverter is a power electronic device built to synthesize is required. A multilevel inverter is ideal for connecting such distributed dc energy sources (solar cells to control a multilevel inverter in such a way that it is an e cient, low total harmonic distortion (THD

Tolbert, Leon M.

27

A New Approach to the Elimination of Harmonics in a Multilevel Converter  

E-print Network

, the approach here produces all possible solutions. 1 Introduction A multilevel inverter is a power electronic one to control a multilevel inverter in such a way that it is an efficient, low total harmonic an 11-level inverter. 2 Cascade Multilevel Inverter A cascade multilevel inverter consists of a series

Tolbert, Leon M.

28

Coloured Conical Emission in BBO Crystal Pumped by Second Harmonic Femtosecond Pulses  

Microsoft Academic Search

Coloured conical emission (CCE) is investigated experimentally in a beta-barium borate crystal excited by intense second harmonic femtosecond pulses. Contrary sequences of green and red conical emission with variable diameters are observed at different incidence angles, which is consistent with the calculation results based on the phase matching condition. As its broad range spectrum, CCE offers an alternative means to

Jie Bi; Yu-Hua Li; Juan-Juan Yin; Pei-Xiang Lu

2009-01-01

29

A new control strategy for distributed generation interface converters to compensate microgrid harmonics  

Microsoft Academic Search

Distributed generation has attracted great attention in recent years, thanks to the progress in new-generation technologies and advanced power electronics. The microgrid has been a successful example by integrating various generation sources with the existing power distribution network through power electronic converters. On the other hand, due to rapid penetration of power electronics equipment, many of the loads within microgrid

M. Savaghebi; A. Jalilian

2010-01-01

30

Coded output photonic A/D converter based on photonic crystal slow-light structures  

E-print Network

Coded output photonic A/D converter based on photonic crystal slow-light structures Sunkyu Yu) utilizing a slow- light photonic crystal Mach-Zehnder interferometer (MZI) is proposed, to enable Resonator Optical Waveguides: toward the slowing and storage of light," Opt. Photon. News 16, 36-40 (2005

Park, Namkyoo

31

Probing Alignment of Liquid Crystals on Silane Derivatives by Second Harmonic Generation  

NASA Astrophysics Data System (ADS)

We studied surface second-harmonic generation from thin films of 4'-n-pentyl-4-cyano-biphenyl (5CB) nematic liquid crystal (NLC) deposited onto layers of several silanes dipped on conductive glasses. We also studied a new liquid crystalline polymer deposited onto silanized substrates. The cinnamoyl side groups of this polymer can be aligned by linearly polarized UV light. The average orientation and surface order of the nematic were determined by Fourier analysis of the reflected and transmitted angular dependent second harmonic signal. The aim was to check the possible use of these materials as a control layer for the anchoring properties of nematics.

Soria, S.; Schuhmacher, D.; Marowsky, G.; Barberi, R.; Ciuchi, F.; Paus, S.; Rasing, T.

32

Highly Efficient Mode Converter for Coupling Light into Wide Slot Photonic Crystal Waveguide  

E-print Network

We design, fabricate and experimentally demonstrate a highly efficient adiabatic mode converter for coupling light into a silicon slot waveguide with a slot width as large as 320nm. This strip-to-slot mode converter is optimized to provide a measured insertion loss as low as 0.08dB. Our mode converter provides 0.1dB lower loss compared to a conventional V-shape mode converter. This mode converter is used to couple light into and out of a 320nm slot photonic crystal waveguide, and it is experimentally shown to improve the coupling efficiency up to 3.5dB compared to the V-shape mode converter, over the slow-light wavelength region.

Zhang, Xingyu; Hosseini, Amir; Chen, Ray T

2014-01-01

33

AC susceptibility harmonic response in YBCO single crystals with different oxygen contents  

NASA Astrophysics Data System (ADS)

We measured up to the seventh harmonic response of the complex ac susceptibility ( ?n?-j ?? n; n=1-7) vs. temperature, in YB 2C 3O x single crystals with different oxygen contents (6.5? x?7). The ac field was applied in presence of an external dc field both parallel to the c-axis of the crystals. We show evidence that deoxygenation leads to a reduction of bulk pinning strength evidenced by a decrease in the value of the third, fifth and seventh harmonics. We compare our measurements with a numerical model that includes effects of flux creep and sample geometry where the activation barrier depends explicitly on temperature.

Moreno, A. J.; Valenzuela, S. O.; Bekeris, V.

34

In-Plane Second Harmonic Generations in Photonic Crystal Slabs of LiNbO3  

Microsoft Academic Search

We have fabricated two-dimensional photonic crystal slabs (2D PhCS) of LiNbO3 by 150 fs laser pulses at 767 nm. The mean diameter of air holes in the 2D PhCS is about 800 nm and is realized in submicron dimensions. We have detected in-plane second harmonic generations (SHGs) in the 2D hexagonal PhCS of 4 mum periodicity and examined the dependence

Masashi Ishikawa; Masanobu Iwanaga

2008-01-01

35

Converter  

NSDL National Science Digital Library

In this activity, students enter in a fraction and the applet calculates the decimal representation of the fraction and vice versa. This activity allows students to explore converting fractions from decimals and from decimals to fractions. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

2010-01-01

36

Lossless backward second-harmonic generation of extremely narrow subdiffractive beams in two-dimensional photonic crystals  

SciTech Connect

We report efficient second harmonic generation using extremely narrow beams (with diameter of the order of the wavelength) that propagate in the self-collimation (or nondiffractive) regime in a two-dimensional photonic crystal. We design and numerically test an AlGaAs photonic crystal membrane, where both fundamental and generated second harmonic beams propagate without diffraction and without out-of-plane losses. The characteristics of the generated second harmonic that is mainly propagating in the backward direction and the conversion efficiency of the proposed scheme are obtained by nonlinear finite-difference time-domain numerical simulations.

Nistor, C.; Cojocaru, C.; Trull, J. [Universitat Politecnica de Catalunya, Departament de Fisica i Enginyeria Nuclear, Colom 11, E-08222 Terrassa (Spain); Karle, T. J.; Raj, R. [Laboratoire de Photonique et de Nanostructures, Route de Nozay, F-91460 Marcoussis (France); Raineri, F. [Laboratoire de Photonique et de Nanostructures, Route de Nozay, F-91460 Marcoussis (France); Universite Paris Diderot, Paris (France); Staliunas, K. [Universitat Politecnica de Catalunya, Departament de Fisica i Enginyeria Nuclear, Colom 11, E-08222 Terrassa (Spain); Institucio Catalana de Reserca i Estudis Avancats (ICREA), Barcelona (Spain)

2010-09-15

37

Third-harmonic generation enhancement in polymer-dispersed liquid crystal grating  

NASA Astrophysics Data System (ADS)

In this paper, the enhancement of third-harmonic generation in one-dimensional periodic grating structure with lowindex contrast, which is produced by holographic illuminated liquid crystal droplets and called polymer-dispersed liquid crystal grating, with near-infrared pumping has been demonstrated. The observed enhancement process is theoretically explained and modeled with a multi-scale perturbation analysis and split-step Fourier transform technique, respectively. We show that the third-harmonic generation has been enhanced by setting the fundamental frequency wavelength to the long-wavelength band-edge of the first photonic band-gap of this periodic structure and satisfying band-edge phasematched condition. The numerical results show that a dramatic enhancement of the third-harmonic field is observed near the long-wavelength band-edge of the second photonic band-gap. Furthermore, the conversion efficiency of thirdharmonic field of forward-propagating direction is more than of backward-propagating direction by a factor of 600.

Wicharn, S.; Buranasiri, P.

2014-09-01

38

An azo-bridged ferroelectric liquid crystal with highly enhanced second and third harmonic generation.  

PubMed

A laterally azo-bridged trimer ferroelectric liquid crystal (FLC) incorporating a strong chromophore along its polar axis was synthesized and characterized by polarized-light optical microscopy, differential scanning calorimetry, two-dimensional X-ray diffraction analysis, electro-optical measurements, and nonlinear optical (NLO) investigations. This mesogen exhibits a thermodynamically stable enantiotropic SmC* phase and a bistable ferroelectric switching in a surface stabilized cell with bookshelf geometry. It gives the resonance-enhanced d(22) coefficient of 28 pm V(-1) (? = 1.369 ?m) for second harmonic generation (SHG), the largest NLO susceptibility reported to date for all FLCs. At the same wavelength, a new type of helicoidal phase matching assisted by the helical SmC* structure was identified. When the second harmonic wavelength of 780 nm is far away from the resonance wavelength (?(max) = 572 nm), the d(22) coefficient is reduced to 6.8 pm V(-1) (? = 1.56 ?m). In addition to a strong SHG activity, the trimer also shows a strong third harmonic generation (THG) with an estimated third-order nonlinear susceptibility of ?((3)) = ~3 × 10(-11) esu (? = 1.56 ?m), among the largest ?((3)) value reported from THG measurements for liquid crystals. This work enables viable applications of FLCs in nonlinear optics and offers an innovative approach to develop new FLCs with larger NLO strength. PMID:22909407

Zhang, Yongqiang; Ortega, Josu; Baumeister, Ute; Folcia, César L; Sanz-Enguita, Gerardo; Walker, Christopher; Rodriguez-Conde, Sofía; Etxebarria, Jesus; O'Callaghan, Michael J; More, Kundalika

2012-10-01

39

Third harmonic frequency generation by type-I critically phase-matched LiB3O5 crystal by means of optically active quartz crystal.  

PubMed

We present a method of third harmonic generation at 355 nm by frequency mixing of fundamental and second harmonic radiation of an ytterbium nanosecond pulsed all-fiber laser in a type-I phase-matched LiB(3)O(5) (LBO) crystal where originally orthogonal polarization planes of the fundamental and second harmonic beams are aligned by an optically active quartz crystal. 8 W of ultraviolet light at 355 nm were achieved with 40% conversion efficiency from 1064 nm radiation. The conversion efficiency obtained in a type-I phase-matched LBO THG crystal was 1.6 times higher than the one achieved in a type-II LBO crystal at similar experimental conditions. In comparison to half-wave plates traditionally used for polarization alignment the optically active quartz crystal has much lower temperature dependence and requires simpler optical alignment. PMID:23481827

Gapontsev, Valentin P; Tyrtyshnyy, Valentin A; Vershinin, Oleg I; Davydov, Boris L; Oulianov, Dmitri A

2013-02-11

40

Imaging Ripples on Phononic Crystals Reveals Acoustic Band Structure and Bloch Harmonics  

NASA Astrophysics Data System (ADS)

Broadband surface phonon wave packets on a phononic crystal made up of a microstructured line pattern are tracked in two dimensions and in real time with an ultrafast optical technique. The eigenmode distribution and the 2D acoustic band structure are obtained from spatiotemporal Fourier transforms of the data up to 1 GHz. We find stop bands at the zone boundaries for both leaky-longitudinal and Rayleigh waves, and show how the structure of individual acoustic eigenmodes in k space depends on Bloch harmonics and on mode coupling.

Profunser, Dieter M.; Wright, Oliver B.; Matsuda, Osamu

2006-08-01

41

Liquid crystal spatial light modulator with very large phase modulation operating in high harmonic orders.  

PubMed

Unusually large phase modulation in a commercial liquid crystal spatial light modulator (LCSLM) is reported. Such a situation is obtained by illuminating with visible light a device designed to operate in the infrared range. The phase modulation range reaches 6? radians in the red region of the visible spectrum and 10? radians in the blue region. Excellent diffraction efficiency in high harmonic orders is demonstrated despite a concomitant and non-negligible Fabry-Perot interference effect. This type of SLM opens the possibility to implement diffractive elements with reduced chromatic dispersion or chromatic control. PMID:24322100

Calero, Venancio; García-Martínez, Pascuala; Albero, Jorge; Sánchez-López, María M; Moreno, Ignacio

2013-11-15

42

Harmonic Crystals in the Half-Space, I. Convergence to Equilibrium  

E-print Network

We consider the dynamics of a harmonic crystal in the half-space with zero boundary condition. It is assumed that the initial date is a random function with zero mean, finite mean energy density which also satisfies a mixing condition of Rosenblatt or Ibragimov type. We study the distribution $\\mu_t$ of the solution at time $t\\in\\R$. The main result is the convergence of $\\mu_t$ to a Gaussian measure as $t\\to\\infty$ which is time stationary with a covariance inherited from the initial (in general, non-Gaussian) measure.

T. V. Dudnikova

2009-05-21

43

Crystallization and second harmonic generation in thermally poled niobium borophosphate glasses  

NASA Astrophysics Data System (ADS)

Crystallization of glasses with compositions (1- x)(0.95 NaPO 3+0.05 Na 2B 4O 7)+ xNb 2O 5, x=0.4, 0.43, 0.45, 0.48 was investigated by differential scanning calorimetry and X-ray powder diffraction. Crystallization of two phases was observed in the glasses with x=0.43-0.48. First phase is a sodium niobate with the structure of tetragonal tungsten bronze ( T˜720-760 °C) and second phase is Na 4Nb 8P 4O 32 ( T˜830-850 °C). The crystallization of sodium niobate is correlated with increasing of nonlinear optical efficiency reported for thermally poled glasses with x>0.4. The results of Raman spectroscopy show the formation of three-dimensional (3D) niobium oxide framework in the glasses with increase of niobium concentration. This framework is supposed to have tetragonal tungsten bronze structure and to be responsible for nonlinear optical properties of the glass. Second harmonic generation signals of as prepared and crystallized glass after thermal poling are compared. The nucleation and crystallization do not improve the NLO properties of the glasses under study.

Malakho, Artem; Dussauze, Marc; Fargin, Evelyne; Lazoryak, Bogdan; Rodriguez, Vincent; Adamietz, Frederic

2005-06-01

44

Efficient second-harmonic generation of a broadband radiation by control of the temperature distribution along a nonlinear crystal.  

PubMed

We demonstrate an efficient technique for the second harmonic generation (SHG) of the broadband radiation based on the temperature gradient along a nonlinear crystal. The characteristics of Type I non-critical phase-matched SHG of broadband radiation in the LiB(3)O(5) (LBO) crystal with the temperature gradient imposed along the crystal were investigated both numerically and experimentally. The frequency doubling efficiency of the broadband pulsed fiber laser radiation as high as 68% has been demonstrated. PMID:23263092

Regelskis, K; Želudevi?ius, J; Gavrilin, N; Ra?iukaitis, G

2012-12-17

45

New frequency/voltage converters for ac-electrogravimetric measurements based on fast quartz crystal microbalance.  

PubMed

A better understanding of the mechanisms located at the solid/electrolyte interface is becoming essential to the development of new applications in the electrochemical fields. The fast quartz crystal microbalance is an attractive and powerful gravimetric sensor which can be used in the dynamic regime to determine a mass/potential transfer function. The principle is equivalent to classical electrochemical impedance measurements; the only difference is the determination of mass changes given by the quartz crystal microbalance rather than current changes following sine wave modulations of the applied potential. This function appears very well adapted to characterize ionic exchanges at the electrochemical interface. Frequency/voltage converters are the key devices in translating the microbalance frequency response in terms of a continuous voltage change. The latter allows the transfer function to be obtained via a frequency response analyzer. Different converters were tested in this work in order to improve the performances of the experimental setup. PMID:17672777

Gabrielli, C; Perrot, H; Rose, D; Rubin, A; Toqué, J P; Pham, M C; Piro, B

2007-07-01

46

Crystal growth and second harmonic generation efficiency of a chalcone derivative  

NASA Astrophysics Data System (ADS)

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 Å3. 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 (?) values.

Meenatchi, V.; Muthu, K.; Rajasekar, M.; Meenakshisundaram, SP.

2013-06-01

47

The study of polarization converter with photo-induced ripple structure on dye-doped liquid crystal cell.  

E-print Network

??In this research, the polarization converters were manufactured by impinging intensity-gradient-distribution laser on DDLC (dye-doped liquid crystal) samples, which the gradient distributed light intensity was… (more)

Chiang, Chun-Pin

2011-01-01

48

Enhanced third harmonic generation by organic materials on high-Q plasmonic photonic crystals.  

PubMed

The enhanced optical nonlinearity enabled by localized plasmonic fields has been well studied for all-optical switching processing (AOSP) devices for future optical communication systems. In this work, plasmonic photonic crystals with a nonlinear polycarbonate/polymethine blend cladding layer are designed to enhance the third harmonic generation (THG) at the telecom wavelengths (~1550 nm). Due to the presence of he two-dimensional (2-D) gold nano-patch arrays with improved Q-factor and high local fields, more than 20 × of enhanced THG signals in the hybrid organic-plasmonic nanostructure are experimentally observed. The enhanced THG in the hybrid organic-plasmonic materials suggested that such extraordinary nonlinear effects can be used for AOSP devices and wavelength conversion. PMID:25321239

Ren, Fanghui; Wang, Xiangyu; Li, Zhong'an; Luo, Jingdong; Jang, Sei-Hum; Jen, Alex K-Y; Wang, Alan X

2014-08-25

49

Polarization-resolved second-harmonic generation microscopy as a method to visualize protein-crystal domains  

PubMed Central

Polarization-resolved second-harmonic generation (PR-SHG) microscopy is described and applied to identify the presence of multiple crystallographic domains within protein-crystal conglomerates, which was confirmed by synchrotron X-ray diffraction. Principal component analysis (PCA) of PR-SHG images resulted in principal component 2 (PC2) images with areas of contrasting negative and positive values for conglomerated crystals and PC2 images exhibiting uniformly positive or uniformly negative values for single crystals. Qualitative assessment of PC2 images allowed the identification of domains of different internal ordering within protein-crystal samples as well as differentiation between multi-domain conglomerated crystals and single crystals. PR-SHG assessments of crystalline domains were in good agreement with spatially resolved synchrotron X-ray diffraction measurements. These results have implications for improving the productive throughput of protein structure determination through early identification of multi-domain crystals. PMID:23275165

DeWalt, Emma L.; Begue, Victoria J.; Ronau, Judith A.; Sullivan, Shane Z.; Das, Chittaranjan; Simpson, Garth J.

2013-01-01

50

Characteristics of the mode converter of Gyrotron FU CW GII radiating Gaussian beams in both the fundamental and second harmonic frequency bands  

NASA Astrophysics Data System (ADS)

Gyrotron FU CW GII, the second gyrotron of the Gyrotron FU CW G-series with an internal quasi-optical mode converter, was recently developed at the Research Center for Development of Far-Infrared Region, University of Fukui (FIR FU) [Y. Tatematsu et al., J. Infrared, Millimeter, Terahertz Waves 35, 169 (2014)]. The design oscillation mode of this gyrotron is TE8,3 with a corresponding frequency of 393.4 GHz in the second harmonic cyclotron resonance. We observed oscillations of different modes including fundamental harmonic modes in the 200-GHz band upon varying the strength of the magnetic field in the cavity. Radiation patterns corresponding to these modes emitted from the window were Gaussian although the internal mode converter was designed for the TE8,3 mode. The directions of the radiated Gaussian beams were found to depend on the oscillation modes with a relation similar to that obtained for another gyrotron that was also equipped with a mode converter. This relation is explained based on geometrical optics. Moreover, numerical calculation with the electromagnetic wave code developed in FIR FU confirmed the same relation. The observed features of the Gyrotron FU CW GII show that it can serve as a unique power source with two frequency bands at 200 and 400 GHz. This result provides a way of developing multiple-frequency gyrotrons.

Tatematsu, Yoshinori; Yamaguchi, Yuusuke; Idehara, Toshitaka; Kawase, Tatsuru; Ogawa, Isamu; Saito, Teruo; Fujiwara, Toshimichi

2014-07-01

51

Conical Second Harmonic Generation in a Two-Dimensional chi(2) Photonic Crystal: A Hexagonally Poled LiTaO3 Crystal  

Microsoft Academic Search

A new type of conical second-harmonic generation was discovered in a 2D chi(2) photonic crystal---a hexagonally poled LiTaO3 crystal. It reveals the presence of another type of nonlinear interaction---a scattering involved optical parametric generation in a nonlinear medium. Such a nonlinear interaction can be significantly enlarged in a modulated chi(2) structure by a quasi-phase-matching process. The conical beam records the

P. Xu; S. H. Ji; S. N. Zhu; X. Q. Yu; J. Sun; H. T. Wang; J. L. He; Y. Y. Zhu; N. B. Ming

2004-01-01

52

Non-critical phase-matching fourth harmonic generation of a 1053-nm laser in an ADP crystal.  

PubMed

In current inertial confinement fusion (ICF) facilities, KDP and DKDP crystals are the second harmonic generation (SHG) and third harmonic generation (THG) materials for the Nd:glass laser (1053?nm). Based on the trend for the development of short wavelengths for ICF driving lasers, technical solutions for fourth harmonic generation (FHG) will undoubtedly attract more and more attention. In this paper, the rapid growth of an ADP crystal and non-critical phase-matching (NCPM) FHG of a 1053-nm laser using an ADP crystal are reported. The NCPM temperature is 33.7°C. The conversion efficiency from 526 to 263?nm is 70%, and the angular acceptance range is 55.4?mrad; these results are superior to those for the DKDP crystals. This research has shown that ADP crystals will be a competitive candidate in future ICF facilities when the utilisation of high-energy, high-efficiency UV lasers at wavelengths shorter than the present 351?nm is of interest. PMID:23549389

Ji, Shaohua; Wang, Fang; Zhu, Lili; Xu, Xinguang; Wang, Zhengping; Sun, Xun

2013-01-01

53

Quasiresonant Excitation of InP/InGaP Quantum Dots Using Second Harmonic Generated in a Photonic Crystal Cavity  

E-print Network

Indistinguishable single photons are necessary for quantum information processing applications. Resonant or quasiresonant excitation of single quantum dots provides greater single photon indistinguishability than incoherent pumping, but is also more challenging experimentally. Here, we demonstrate high signal to noise quasiresonant excitation of InP/InGaP quantum dots. The excitation is provided via second harmonic generated from a telecommunications wavelength laser resonant with the fundamental mode of a photonic crystal cavity, fabricated at twice the quantum dot transition wavelength. The second harmonic is generated using the \\chi(2) nonlinearity of the InGaP material matrix.

Sonia Buckley; Kelley Rivoire; Fariba Hatami; Jelena Vuckovic

2012-10-03

54

The Use of Power Sums to Solve the Harmonic Elimination Equations for Multilevel Converters EPE Journal Vol. 15 no  

E-print Network

], a genetic algorithm approach is used to solve for the switching angles. In Kato [10], a homotopy technique. A key issue in the fundamental switching scheme is to determine the switching angles (times) so as to produce the fundamental voltage and not generate specific higher order harmonics. The recent book [7

Tolbert, Leon M.

55

Abstract--A strategy is presented to minimize the voltage total harmonic distortion when controlling a multilevel converter to act  

E-print Network

the complete set of solutions to be found for switching a multilevel inverter's power electronic devices the voltage levels of the multilevel inverter so that it operates in an optimum amplitude modulation index regime. Index Terms--static var compensation, multilevel inverter, resultants, harmonic elimination. I

Tolbert, Leon M.

56

Harmonic Optimization of Multilevel Converters Using Genetic Algorithms Abstract--In this paper, a genetic algorithm (GA) optimization  

E-print Network

, a genetic algorithm (GA) optimization technique is applied to multilevel inverter to determine optimum switching angles for cascaded multilevel inverters for eliminating some higher order harmonics while maintaining the required fundamental voltage. This technique can be applied to multilevel inverters with any

Tolbert, Leon M.

57

Conical second harmonic generation in a two-dimensional chi(2) photonic crystal: a hexagonally poled LiTaO3 crystal.  

PubMed

A new type of conical second-harmonic generation was discovered in a 2D chi((2)) photonic crystal-a hexagonally poled LiTaO3 crystal. It reveals the presence of another type of nonlinear interaction-a scattering involved optical parametric generation in a nonlinear medium. Such a nonlinear interaction can be significantly enlarged in a modulated chi((2)) structure by a quasi-phase-matching process. The conical beam records the spatial distribution of the scattering signal and discloses the structure information and symmetry of the 2D chi((2)) photonic crystal. PMID:15524722

Xu, P; Ji, S H; Zhu, S N; Yu, X Q; Sun, J; Wang, H T; He, J L; Zhu, Y Y; Ming, N B

2004-09-24

58

Third-harmonic generation and growth mechanism of vanadyl-phthalocyanine single crystals prepared on KBr substrate by molecular beam epitaxy  

Microsoft Academic Search

Vanadyl-phthalocyanine (VOPc) single crystals were prepared on KBr (100) substrate by molecular beam epitaxy (MBE). The second and third-harmonic generations of nonlinear optical thin films are proportional to the square of the thickness. Therefore, it is important to prepare a large nonlinear optical single crystal. However, the conditions to prepare a large nonlinear optical single crystal are not well understood

A. Maeda; N Okumura; H Furuhashi; T Yoshikawa; Y Uchida; K Kojima; A Ohashi; S Ochiai; M Ieda; T Mizutani

1999-01-01

59

Absolute non-linear optical coefficients measurements of BBO single crystal and determination of angular acceptance by second harmonic generation  

Microsoft Academic Search

We report second harmonic generation measurements of a continuous Nd-YAG laser beam propagating in a ? barium metaborate (?-BaB2O4) crystals cut in the type I and type II phase matching directions. The absolute values of the effective non-linear optical coefficients deffI and deffII are determined by measuring conversion efficiency and the d22 and d31 coefficients involved in deff developments coefficients

R. S Klein; G. E Kugel; A. Maillard; A. Sifi; K. Polgar

2003-01-01

60

Wavelength tunability of second-harmonic generation from two-dimensional ?(2) nonlinear photonic crystals with a tetragonal lattice structure  

NASA Astrophysics Data System (ADS)

The wavelength tunability of second-harmonic generation (SHG) in a two-dimensional nonlinear photonic crystal (2D NPC) on lithium niobate is examined by using a 1.55 ?m-band optical parametric oscillator. We observed SHG signals that were generated off-axis from the fundamental pump beam and a multiple number of quasi-phase-matchable (QPM) wavelengths for a given crystal setting. The spacing between the phase-matched wavelengths increases with the azimuthal rotation angle (?) in the x-y plane of the crystal. The peak intensity and propagation direction of the SHG signals are found to vary with the pump wavelength and crystal rotation angle. These observations are ascribed to a 2D distribution of high-order reciprocal lattice vectors Gmn(?) and the corresponding ?(2)(Gmn) nonlinearities in 2D NPC having a tetragonal structural symmetry.

Peng, L.-H.; Hsu, C.-C.; Ng, Jimmy; Kung, A. H.

2004-04-01

61

Antimicrobial activity and second harmonic studies on organic non-centrosymmetric pure and doped ninhydrin single crystals.  

PubMed

In this paper, we report the successful growth of pure, Cu(2+) ions and Cd(2+) ions doped on ninhydrin single crystals by slow solvent evaporation technique. The presence of Cu(2+) and Cd(2+) 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 Cd(2+) and Cu(2+) 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. PMID:23266683

Prasanyaa, T; Jayaramakrishnan, V; Haris, M

2013-03-01

62

Antimicrobial activity and second harmonic studies on organic non-centrosymmetric pure and doped ninhydrin single crystals  

NASA Astrophysics Data System (ADS)

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.

Prasanyaa, T.; Jayaramakrishnan, V.; Haris, M.

2013-03-01

63

Simultaneous self-collimation of fundamental and second-harmonic in sonic crystals  

Microsoft Academic Search

Simultaneous self-collimation of sound beams with different frequencies, corresponding to fundamental wave and to its second harmonic, is proposed theoretically and demonstrated experimentally. The result is obtained when the isofrequency contours for each harmonics, corresponding to different propagation bands, develop flat segments along the same direction. The effect can be utilized for managing (enhancement and control) of nonlinear frequency mixing

E. Soliveres; I. Pérez-Arjona; R. Picó; V. Espinosa; V. J. Sánchez-Morcillo; K. Staliunas

2011-01-01

64

35 MHz quartz crystal microbalance and surface plasmon resonance studies on the binding of angiotensin converting enzyme with lisinopril  

Microsoft Academic Search

Angiotensin converting enzyme (ACE) plays a pivotal role in blood pressure regulation, and its interaction with an ACE inhibitor (ACEI) is an important research topic for treatment of hypertension. Herein, a low reagent consumption, multiparameter and highly sensitive quartz crystal microbalance (QCM) at 35-MHz fundamental frequency was utilized to monitor in situ the binding process of solution lisinopril (LIS, a

Zhaohong Su; Li Chen; Ying Liu; Xiuhui He; Yaping Zhou; Qingji Xie; Shouzhuo Yao

2011-01-01

65

Mathematical modeling and statistical analysis of SPE-OCDMA systems utilizing second harmonic generation effect in thick crystal receivers  

NASA Astrophysics Data System (ADS)

In this paper we analytically study and evaluate the performance of a Spectral-Phase-Encoded Optical CDMA system for different parameters such as the user's code length and the number of users in the network. In this system an advanced receiver structure in which the Second Harmonic Generation effect imposed in a thick crystal is employed as the nonlinear pre-processor prior to the conventional low speed photodetector. We consider ASE noise of the optical amplifiers, effective in low power conditions, besides the multiple access interference (MAI) noise which is the dominant source of noise in any OCDMA communications system. We use the results of the previous work which we analyzed the statistical behavior of the thick crystals in an optically amplified digital lightwave communication system to evaluate the performance of the SPE-OCDMA system with thick crystals receiver structure. The error probability is evaluated using Saddle-Point approximation and the approximation is verified by Monte-Carlo simulation.

Matinfar, Mehdi D.; Salehi, Jawad A.

2009-11-01

66

Growth and characterization of crystals for IR detectors and second harmonic gereration devices  

NASA Astrophysics Data System (ADS)

Two types of materials, L-arginine phosphate (LAP) and doped triglycine sulfate (TGS), are examined for their growth characteristics and relevant properties for second harmonic generation and IR detector applications, respectively.

Lal, Ravi B.; Batra, Ashok K.; Rao, Sistla M.; Bhatia, S. S.; Chunduru, Kunar P.; Paulson, Ron; Moorkherji, Tripty K.

67

Growth and characterization of crystals for IR detectors and second harmonic gereration devices  

NASA Technical Reports Server (NTRS)

Two types of materials, L-arginine phosphate (LAP) and doped triglycine sulfate (TGS), are examined for their growth characteristics and relevant properties for second harmonic generation and IR detector applications, respectively.

Lal, Ravi B.; Batra, Ashok K.; Rao, Sistla M.; Bhatia, S. S.; Chunduru, Kunar P.; Paulson, Ron; Moorkherji, Tripty K.

1989-01-01

68

Simultaneous self-collimation of fundamental and second-harmonic in sonic crystals  

NASA Astrophysics Data System (ADS)

Simultaneous self-collimation of sound beams with different frequencies, corresponding to fundamental wave and to its second harmonic, is proposed theoretically and demonstrated experimentally. The result is obtained when the isofrequency contours for each harmonics, corresponding to different propagation bands, develop flat segments along the same direction. The effect can be utilized for managing (enhancement and control) of nonlinear frequency mixing of narrow sound beams.

Soliveres, E.; Pérez-Arjona, I.; Picó, R.; Espinosa, V.; Sánchez-Morcillo, V. J.; Staliunas, K.

2011-10-01

69

Crystal Structures of Protein Glutaminase and Its Pro Forms Converted into Enzyme-Substrate Complex*  

PubMed Central

Protein glutaminase, which converts a protein glutamine residue to a glutamate residue, is expected to be useful as a new food-processing enzyme. The crystal structures of the mature and pro forms of the enzyme were refined at 1.15 and 1.73 ? resolution, respectively. The overall structure of the mature enzyme has a weak homology to the core domain of human transglutaminase-2. The catalytic triad (Cys-His-Asp) common to transglutaminases and cysteine proteases is located in the bottom of the active site pocket. The structure of the recombinant pro form shows that a short loop between S2 and S3 in the proregion covers and interacts with the active site of the mature region, mimicking the protein substrate of the enzyme. Ala-47 is located just above the pocket of the active site. Two mutant structures (A47Q-1 and A47Q-2) refined at 1.5 ? resolution were found to correspond to the enzyme-substrate complex and an S-acyl intermediate. Based on these structures, the catalytic mechanism of protein glutaminase is proposed. PMID:21926168

Hashizume, Ryota; Maki, Yukiko; Mizutani, Kimihiko; Takahashi, Nobuyuki; Matsubara, Hiroyuki; Sugita, Akiko; Sato, Kimihiko; Yamaguchi, Shotaro; Mikami, Bunzo

2011-01-01

70

Improved frequency/voltage converters for fast quartz crystal microbalance applications.  

PubMed

The monitoring of frequency changes in fast quartz crystal microbalance (QCM) applications is a real challenge in today's instrumentation. In these applications, such as ac electrogravimetry, small frequency shifts, in the order of tens of hertz, around the resonance of the sensor can occur up to a frequency modulation of 1 kHz. These frequency changes have to be monitored very accurately both in magnitude and phase. Phase-locked loop techniques can be used for obtaining a high performance frequency/voltage converter which can provide reliable measurements. Sensitivity higher than 10 mVHz, for a frequency shift resolution of 0.1 Hz, with very low distortion in tracking both the magnitude and phase of the frequency variations around the resonance frequency of the sensor are required specifications. Moreover, the resonance frequency can vary in a broad frequency range from 5 to 10 MHz in typical QCM sensors, which introduces an additional difficulty. A new frequency-voltage conversion system based on a double tuning analog-digital phase-locked loop is proposed. The reported electronic characterization and experimental results obtained with conducting polymers prove its reliability for ac-electrogravimetry measurements and, in general, for fast QCM applications. PMID:18447558

Torres, R; García, J V; Arnau, A; Perrot, H; Kim, L To Thi; Gabrielli, C

2008-04-01

71

Improved frequency/voltage converters for fast quartz crystal microbalance applications  

SciTech Connect

The monitoring of frequency changes in fast quartz crystal microbalance (QCM) applications is a real challenge in today's instrumentation. In these applications, such as ac electrogravimetry, small frequency shifts, in the order of tens of hertz, around the resonance of the sensor can occur up to a frequency modulation of 1 kHz. These frequency changes have to be monitored very accurately both in magnitude and phase. Phase-locked loop techniques can be used for obtaining a high performance frequency/voltage converter which can provide reliable measurements. Sensitivity higher than 10 mV/Hz, for a frequency shift resolution of 0.1 Hz, with very low distortion in tracking both the magnitude and phase of the frequency variations around the resonance frequency of the sensor are required specifications. Moreover, the resonance frequency can vary in a broad frequency range from 5 to 10 MHz in typical QCM sensors, which introduces an additional difficulty. A new frequency-voltage conversion system based on a double tuning analog-digital phase-locked loop is proposed. The reported electronic characterization and experimental results obtained with conducting polymers prove its reliability for ac-electrogravimetry measurements and, in general, for fast QCM applications.

Torres, R.; Kim, L. To Thi [GIBEC-Escuela de Ingenieria de Antioquia, Universidad CES, Calle 25, Sur No. 42-73, Envigado (Colombia); Garcia, J. V.; Arnau, A. [Departamento Ingenieria Electronica. ETSI de Telecomunicacion, Universidad Politecnica de Valencia, Camino de Vera s/n, Valencia 46022 (Spain); Perrot, H.; Gabrielli, C. [Universite Pierre et Marie Curie-Paris 6, Laboratoire Interfaces et Systemes Electrochemiques, CNRS, UPR15-LISE, 4 place Jussieu, Paris 75252 (France)

2008-04-15

72

Quasi-phase-matched second-harmonic Talbot self-imaging in a 2D periodically-poled LiTaO3 crystal.  

PubMed

We demonstrate the improved second-harmonic Talbot self-imaging through the quasi-phase-matching technique in a 2D periodically-poled LiTaO(3) crystal. The domain structure not only composes a nonlinear optical grating which is necessary to realize nonlinear Talbot self-imaging, but also provides reciprocal vectors to satisfy the phase-matching condition for second-harmonic generation. Our experimental results show that quasi-phase-matching can improve the intensity of the second-harmonic Talbot self-imaging by a factor of 21. PMID:23787586

Liu, Dongmei; Wei, Dunzhao; Zhang, Yong; Zou, Jiong; Hu, X P; Zhu, S N; Xiao, Min

2013-06-17

73

Crystalline perfection, optical and third harmonic generation analyses of non-linear optical single crystal of L-lysine acetate.  

PubMed

The potential organic non-linear optical single crystal of L-lysine acetate has been grown by slow evaporation solution growth technique (SEST) at room temperature. It crystallizes in the monoclinic system with space group of P2(1). The crystalline perfection of the grown single crystal has been examined by high resolution X-ray diffraction analysis (HRXRD). The functional groups of the synthesized compound have been identified by (13)C NMR, (1)H NMR and FTIR analyses. The optical absorption studies show that the crystal is transparent in the entire visible region with a cut-off wavelength of 236 nm. The optical band gap is found to be 5.29 eV. The steady-state PL spectra was recorded for pure L-lysine acetate crystal at room temperature. The third harmonic generation efficiency of the crystal has been evaluated by Z-scan technique and its non-linear optical coefficient has been calculated. Birefringence measurement has been carried out in order to see the optical homogeneity of the grown specimen. Its electrical properties has been assessed by dielectric measurement at different temperatures. The calculated optical band gap is 5.29 eV. Its thermal parameters like thermal diffusivity (?), thermal effusivity (e), thermal conductivity (k) and heat capacity (C(p)) have been determined by photopyroelectric technique. Vickers micro hardness studies were carried out using a Vickers hardness tester equipped with a diamond square indenter. The piezoelectric measurement for L-lysine acetate has been also been carried at ambient condition. PMID:23305871

Rani, Neelam; Vijayan, N; Thukral, Kanika; Maurya, K K; Haranath, D; Bhagavannarayana, G; Verma, S; Wahab, M A

2013-03-15

74

Second-harmonic generation from regeneratively amplified femtosecond laser pulses in BBO and LBO crystals  

Microsoft Academic Search

The spectral and temporal characteristics and optical-conversion efficiency of ;150-fs laser pulses at 400 nm generated by second-harmonic generation (SHG) of a regeneratively amplified mode-locked Ti:sapphire laser were investigated both theoretically and experimentally. The theoretical investigation was done by taking into account cubic nonlinearity, pulse walk-off, group-velocity dispersion, Kerr nonlinearity, quadratic broad- ening, frequency chirping of the fundamental pulse, and

Jing-Yuan Zhang; Jung Y. Huang; H. Wang; K. S. Wong; G. K. Wong

1998-01-01

75

Characterization of Cholesterol Crystals in Atherosclerotic Plaques Using Stimulated Raman Scattering and Second-Harmonic Generation  

E-print Network

Characterization of Cholesterol Crystals in Atherosclerotic Plaques Using Stimulated Raman ABSTRACT Cholesterol crystals (ChCs) have been identified as a major factor of plaque vulnerability cholesterol in its native tissue environment, the physiochemical role of ChCs in atherosclerotic progression

Chen, Zhongping

76

Electro-optic harmonic conversion to switch a laser beam out of a cavity  

DOEpatents

The invention is a switch to permit a laser beam to escape a laser cavity through the use of an externally applied electric field across a harmonic conversion crystal. Amplification takes place in the laser cavity, and then the laser beam is switched out by the laser light being harmonically converted with dichroic or polarization sensitive elements present to alter the optical path of the harmonically converted laser light. Modulation of the laser beam can also be accomplished by varying the external electric field.

Haas, Roger A. (Pleasanton, CA); Henesian, Mark A. (Livermore, CA)

1987-01-01

77

Crystallization and second harmonic generation in thermally poled niobium borophosphate glasses  

Microsoft Academic Search

Crystallization of glasses with compositions (1?x)(0.95 NaPO3+0.05 Na2B4O7)+xNb2O5, x=0.4, 0.43, 0.45, 0.48 was investigated by differential scanning calorimetry and X-ray powder diffraction. Crystallization of two phases was observed in the glasses with x=0.43–0.48. First phase is a sodium niobate with the structure of tetragonal tungsten bronze (Tc?720–760°C) and second phase is Na4Nb8P4O32 (Tc?830–850°C). The crystallization of sodium niobate is correlated

Artem Malakho; Marc Dussauze; Evelyne Fargin; Bogdan Lazoryak; Vincent Rodriguez; Frederic Adamietz

2005-01-01

78

Temperature nonuniformity occurring during the cooling process of a KDP crystal and its effects on second-harmonic generation.  

PubMed

The temperature nonuniformity occurring during the cooling process of a KDP crystal is studied, along with its effects on the second-harmonic generation (SHG) of a high-average-power laser. A comprehensive model is proposed incorporating principles of thermodynamics, mechanics, and optics, and it is applied to investigate the temperature nonuniformity and its effects. The temperature rise caused by linear absorption is calculated, while the temperature nonuniformity occurring during the cooling process is analyzed using the finite-element method (FEM). The stress induced by the nonuniformity is then studied using the FEM, and the trend of its change is determined. Moreover, the changes in refractive index caused by the stress are calculated, the results of which are used to determine the variations in the induced phase mismatch. The SHG efficiency considering the phase mismatch is eventually obtained by solving the coupling wave equations. The results demonstrate that the temperature nonuniformity has negative effects on the SHG efficiency. PMID:25320918

Liang, Yingchun; Su, Ruifeng; Lu, Lihua; Liu, Haitao

2014-08-10

79

Enhancement of second harmonic generation in NaNO2-infiltrated opal photonic crystal using structural light focusing  

NASA Astrophysics Data System (ADS)

Experimental and numerical results for second harmonic generation (SHG) in photonic crystal (PC) based on NaNO2-infiltrated opal matrix are presented. SHG is performed in reflection mode; thus, the direction of the SHG maximum is equal to the angle of mirror reflection. The PC was pumped with femtosecond optical pulses at different angles of incidence, allowing the dependence of the SHG efficiency on the location of the fundamental wavelength toward the PC band gap (BG) to be examined. The most efficient SHG was observed when pumping the BG of the PC. To interpret the experimental results, finite-difference time-domain numerical simulations of the light interaction with the PC were conducted. The observed effect of highly efficient SHG is associated with structural light focusing, and, as a consequence, with strong optical field localization within certain near-surface PC regions. Thus, SHG enhancement based on structural light focusing in PC was demonstrated.

Zaytsev, Kirill I.; Yurchenko, Stanislav O.

2014-08-01

80

Growth and investigation of BBO crystals with improved characteristics for UV harmonic generation  

Microsoft Academic Search

BBO crystals were grown by the top-seeded solution growth technique from a Na2-O melt-solution. Optimization of heating conditions and technological growth parameters allowed us to produce high-quality optic crystals. Their main morphological feature is the facing of a boule side surface. The area of hexagonal prism face {1120} can reach several square centimeters. Non-linear-optical elements which are produced from a

Alexandr E. Kokh; Valentin Mishchenko; Valery D. Antsigin; Alexander M. Yurkin; Nadezhda G. Kononova; Victor A. Guets; Yury K. Nizienko; Alexandr I. Zakharchenko

1999-01-01

81

Consideration of angular acceptance angle in BBO crystal on a highly efficient second harmonic generation  

Microsoft Academic Search

The angular acceptance angle (phase matching acceptance angle) ?? in BBO crystal is theoretically calculated in milli-radian magnitude. To satisfy a fully phase matching condition of a laser beam and obtain efficient conversion of SHG, an intracavity frequency doubled (IFD) Nd:YAP mode-locked laser with a confocal unstable resonator and a BBO crystal as an SH generator is designed. Thus, fully

Feng-Tie Wu; Wen-Zhen Zhang

1998-01-01

82

BBO-crystal optical parametric oscillator tunable over the 300 — 2340 nm range and pumped by the 4th harmonic of a Nd:YAG laser  

Microsoft Academic Search

An investigation was made of the lasing characteristics of a BBO-crystal Type-I optical parametric oscillator pumped by the 4th harmonic of a multimode Nd:YAG laser. The output was tunable over the range 300 — 2340 nm. The efficiency ranged up to 15% near the peak of the tunability curve at double the oscillation threshold.

N V Kondratyuk; A A Shagov; K L Demidchik; A M Yurkin; Aleksandr E Kokh

2000-01-01

83

Nonlinear optical response of the collagen triple helix and second harmonic microscopy of collagen liquid crystals  

NASA Astrophysics Data System (ADS)

Collagen is characterized by triple helical domains and plays a central role in the formation of fibrillar and microfibrillar networks, basement membranes, as well as other structures of the connective tissue. Remarkably, fibrillar collagen exhibits efficient Second Harmonic Generation (SHG) and SHG microscopy proved to be a sensitive tool to score fibrotic pathologies. However, the nonlinear optical response of fibrillar collagen is not fully characterized yet and quantitative data are required to further process SHG images. We therefore performed Hyper-Rayleigh Scattering (HRS) experiments and measured a second order hyperpolarisability of 1.25 10-27 esu for rat-tail type I collagen. This value is surprisingly large considering that collagen presents no strong harmonophore in its amino-acid sequence. In order to get insight into the physical origin of this nonlinear process, we performed HRS measurements after denaturation of the collagen triple helix and for a collagen-like short model peptide [(Pro-Pro-Gly)10]3. It showed that the collagen large nonlinear response originates in the tight alignment of a large number of weakly efficient harmonophores, presumably the peptide bonds, resulting in a coherent amplification of the nonlinear signal along the triple helix. To illustrate this mechanism, we successfully recorded SHG images in collagen liquid solutions by achieving liquid crystalline ordering of the collagen triple helices.

Deniset-Besseau, A.; De Sa Peixoto, P.; Duboisset, J.; Loison, C.; Hache, F.; Benichou, E.; Brevet, P.-F.; Mosser, G.; Schanne-Klein, M.-C.

2010-02-01

84

Integrated optical auto-correlator based on third-harmonic generation in a silicon photonic crystal waveguide  

NASA Astrophysics Data System (ADS)

The ability to use coherent light for material science and applications is 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 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. Here we report a device capable of achieving single-shot time-domain measurements of near-infrared picosecond pulses based on an ultra-compact integrated CMOS-compatible device, which could operate without any external instrumentation. It relies on optical third-harmonic generation in a slow-light silicon waveguide. Our method can also serve as an in situ diagnostic tool to map, at visible wavelengths, the propagation dynamics of near-infrared pulses in photonic crystals.

Monat, Christelle; Grillet, Christian; Collins, Matthew; Clark, Alex; Schroeder, Jochen; Xiong, Chunle; Li, Juntao; O'Faolain, Liam; Krauss, Thomas F.; Eggleton, Benjamin J.; Moss, David J.

2014-02-01

85

BBO-crystal optical parametric oscillator tunable over the 300 - 2340 nm range and pumped by the 4th harmonic of a Nd:YAG laser  

SciTech Connect

An investigation was made of the lasing characteristics of a BBO-crystal Type-I optical parametric oscillator pumped by the 4th harmonic of a multimode Nd:YAG laser. The output was tunable over the range 300 - 2340 nm. The efficiency ranged up to 15% near the peak of the tunability curve at double the oscillation threshold. (nonlinear optical phenomena and devices)

Kondratyuk, N V [Inter-branch Institute of advanced training Belorussian Polytechnic academy Minsk-107 (Belarus); Shagov, A A; Demidchik, K L [Stock Company 'Solar Laser Systems', Minsk-107 (Belarus); Yurkin, A M; Kokh, Aleksandr E [Institute of Mineralogy and Petrography, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

2000-03-31

86

Second harmonic generation and optical parametric amplification in the mid-IR with orthorhombic biaxial crystals LiGaS2 and LiGaSe2  

NASA Astrophysics Data System (ADS)

By second harmonic generation in and out of the principal planes we estimated the three nonlinear coefficients of the Li-containing mid-IR crystals LiGaS2 and LiGaSe2 which are isostructural to LiInS2 and LiInSe2 and possess even larger bandgaps. First results on optical parametric amplification reveal their advantages for direct down conversion to the mid-IR.

Petrov, V.; Yelisseyev, A.; Isaenko, L.; Lobanov, S.; Titov, A.; Zondy, J.-J.

87

Voltage-clamped soft switching PWM inverter-type DC-DC converter for microwave oven and its utility AC side harmonics evaluations  

Microsoft Academic Search

A single-ended quasi-resonant zero voltage soft-switching inverter type DC-DC converter is used to drive the magnetron for a microwave oven. This converter is simple, downsizing, high efficiency and low cost in addition to simple control scheme. However, this power conversion circuit has to control its input power under a condition of ZVS in accordance with the variable frequency regulation. The

T. Matsushige; E. Miyata; M. Ishitobi; M. Nakaoka; D. Bessyo; K. Yasui; I. Hirota; H. Omori

2000-01-01

88

Optical breakdown threshold in nanosecond high repetition second harmonic generation by periodically poled Mg-doped LiTaO{sub 3} crystal  

SciTech Connect

Our study shows that a local temperature increase of ?1 K in the crystal lattice caused by second harmonic generation (SHG) and two-photon absorption of 532 nm radiation at the rear of periodically poled stoichiometric LiTaO{sub 3} crystal by changing spontaneous polarization induces a pyroelectric field ?10 kV/cm, accelerating free electrons to an energy of ?10 eV, followed by optical breakdown and crystal damage. Theoretical analysis leads to an explicit expression for the threshold laser fluence of optical breakdown giving ?1.2 J/cm{sup 2} for 1064 nm input radiation in 6.8 kHz pulsed SHG operation, agreeing well with the experimentally found value ?1.32 J/cm{sup 2}.

Louchev, Oleg A.; Wada, Satoshi [Center for Advanced Photonics, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)] [Center for Advanced Photonics, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Hatano, Hideki; Kitamura, Kenji [Division of Environment and Energy Materials, National Institute for Materials Science (NIMS) 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [Division of Environment and Energy Materials, National Institute for Materials Science (NIMS) 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2013-08-26

89

Optical breakdown threshold in nanosecond high repetition second harmonic generation by periodically poled Mg-doped LiTaO3 crystal  

NASA Astrophysics Data System (ADS)

Our study shows that a local temperature increase of ?1 K in the crystal lattice caused by second harmonic generation (SHG) and two-photon absorption of 532 nm radiation at the rear of periodically poled stoichiometric LiTaO3 crystal by changing spontaneous polarization induces a pyroelectric field ?10 kV/cm, accelerating free electrons to an energy of ?10 eV, followed by optical breakdown and crystal damage. Theoretical analysis leads to an explicit expression for the threshold laser fluence of optical breakdown giving ?1.2 J/cm2 for 1064 nm input radiation in 6.8 kHz pulsed SHG operation, agreeing well with the experimentally found value ?1.32 J/cm2.

Louchev, Oleg A.; Hatano, Hideki; Wada, Satoshi; Kitamura, Kenji

2013-08-01

90

Design and characterization of a rugged and compact setup for widely tunable harmonic generation in the ultraviolet  

Microsoft Academic Search

Design and experimental characterization of a nonlinear optical converter module for the generation of widely tunable UV radiation is presented. The module combines units for second, third and fourth harmonic generation of tunable Ti:Sapphire lasers. A modified conversion scheme based on the combination of BIBO and BBO crystals reduces the complexity of our former published UV setup - resulting in

B. Jungbluth; M. Vierkoetter; M. Hoefer; J. Loehring; D. Oberbeckmann; D. Hoffmann

2007-01-01

91

Optical harmonic generator  

DOEpatents

A pair of uniaxial birefringent crystal elements are fixed together to form a serially arranged, integral assembly which, alternatively, provides either a linearly or elliptically polarized second-harmonic output wave or a linearly polarized third-harmonic output wave. The extraordinary or e directions of the crystal elements are oriented in the integral assembly to be in quadrature (90/sup 0/). For a second-harmonic generation in the Type-II-Type-II angle tuned case, the input fundamental wave has equal amplitude o and e components. For a third-harmonic generation, the input fundamental wave has o and e components whose amplitudes are in a ratio of 2:1 (o:e reference first crystal). In the typical case of a linearly polarized input fundamental wave this can be accomplished by simply rotating the crystal assembly about the input beam direction by 10/sup 0/. For both second and third harmonic generation input precise phase-matching is achieved by tilting the crystal assembly about its two sensitive axeses (o).

Summers, M.A.; Eimerl, D.; Boyd, R.D.

1982-06-10

92

Integrated quasi-phase-matched second-harmonic generator and electrooptic scanner on LiTaO3 single crystals  

Microsoft Academic Search

We report the first integrated quasi-phase-matched second-harmonic generator and electrooptic scanner on ferroelectric Z-cut LiTaO3. The quasi-phase-matched second-harmonic generation device frequency doubles the infrared light at 829.7 nm into blue at 414.85 nm with a bulk conversion efficiency of 0.52%\\/W-cm. The blue light generated in the bulk then passes through an electrooptic scanner, consisting of a series of lithographically defined

Venkatraman Gopalan; M. J. Kawas; M. C. Gupta; T. E. Schlesinger; Daniel D. Stancil

1996-01-01

93

Quasiresonant excitation of InP/InGaP quantum dots using second harmonic generated in a photonic crystal cavity  

E-print Network

harmonic generated from a telecommunications wavelength laser resonant with the fundamental mode are beneficial for implementing single photon sources for quantum applications, since Si avalanche photo- diodes downconverted to telecommunications wave- lengths using readily available lasers,2 in contrast to InAs/ GaAs QDs

Vuckovic, Jelena

94

The interaction between a single two-level atom and the combination of a frequency converter and the sub-harmonic generation  

NASA Astrophysics Data System (ADS)

The problem of a time-dependent quantum system, which consists of coupled sub-harmonic generation with the parametric down conversion injected within a single cavity containing an atom, is considered. The problem is transformed into the interaction between the su(1,1) quantum system and a single two-level atom. The wave function is calculated and the expectation values for the dynamical operators are obtained. It is shown that the phenomenon of collapses and revivals are sensitive to the variation of the Bargmann index k and the Perelomov parameter ?; moreover, a coherent trapping behavior is seen at the atomic coherence angle ? = ?/2. The phenomena of bunching and anti-bunching are reported where the atomic angle ? and the phase angle ? as well as ? are the most effective parameters. They are also effective for the variance squeezing, however the Bargmann index k increases the fluctuations and decreases the amount of squeezing. For the linear entropy we have observed that the index k has no effect, but the main effective parameters are ?, ? and ? in addition to the ratio between the atomic frequency and the coupling parameter.

Sebawe Abdalla, M.; Ahmed, M. M. A.; Obada, A. S.-F.; Khalil, E. M.

2014-09-01

95

Properties of a harmonic lattice  

Microsoft Academic Search

Elastic and thermal properties of crystals depend upon anharmonic behaviour of the atomic bonds that hold them together. In extrapolating these properties to pressures of the Earth's deep interior, an idealized reference material, a harmonic crystal, is often referred to. However, the discussions are often clouded by misunderstanding of what the properties of such a crystal would be. It is

Frank Stacey

1993-01-01

96

Harmonic Analysis of Rail Transportation Systems with Probabilistic Techniques  

Microsoft Academic Search

Harmonics in rail transportation systems are an important design aspect. The overall load in these systems consists of a few large traction motors, often supplied by thyristor controlled choppers or PWM converters. These converters produce high levels of harmonic currents, which may extend into the kHz range. Recognizing harmonic problems in an early stage of development is important in order

J. van Casteren; F. Groeman

2006-01-01

97

Improvement and formation of UV-induced damage on LBO crystal surface during long-term high-power third-harmonic generation.  

PubMed

We demonstrate the improvement and formation of UV-induced damage on LBO crystal output surface during long-term (130 h) high-power (20 W) high-repetition-rate (80 kHz) third-harmonic generation. The output surface was super-polished (RMS surface roughness <0.6 nm) to sub-nanometer scale super smooth roughness. The surface lifetime has been improved more than 20-fold compared with the as-polished ones (RMS surface roughness 4.0~8.0 nm). The damage could be attributed to the consequence of thermal effects resulted from impurity absorptions. Simultaneously, it was verified that the impurities originated in part from the UV-induced deposition. PMID:23546112

Hong, Hailong; Liu, Qiang; Huang, Lei; Gong, Mali

2013-03-25

98

Second-harmonic generation in a laterally azo-bridged trimer ferroelectric liquid crystal: phase matching in the presence of a helicoidal structure.  

PubMed

Optical second-harmonic generation (SHG) has been studied in a trimer smectic C* liquid crystal especially designed for nonlinear optical applications. The molecule has a long conjugated donor-acceptor unit that transversally links three parallel rod-shaped moieties. A strong SHG signal has been observed at a fundamental wavelength of 1369 nm even in the presence of the spontaneous helicoidal structure of the smectic C* phase. This unusual behavior has been interpreted as due to the existence of phase matching, in which the wave vector mismatch is compensated by the wave vector of the helix. This point has been confirmed by the study of the SHG intensity versus sample thickness and light polarization characteristics. The main coefficient of the second-order susceptibility tensor of the material has been estimated to be d(22) = 28 pm/V. PMID:23214805

Etxebarria, J; Ortega, J; Folcia, C L; Zhang, Y; Walker, C

2012-11-01

99

Noncritically phase-matched second-harmonic generation and optical parametric amplification in a lithium triborate crystal  

SciTech Connect

We evaluate the potential of lithium triborate (LBO) temperature-tuned to achieve type-I noncritical phase matching, for picosecond high-power second-harmonic generation (SHG) and tunable optical parametric amplification (OPA). Pumped by 35 ps, 1.064 {mu}m laser pulses, a conversion efficiency of 65% was obtained from SHG. The output of OPA, pumped by 0.532 {mu}m was tunable from 0.75 to 1.8 {mu}m with an efficiency better than 20%.

Huang, J.Y.; Shen, Y.R. (Department of Physics, University of California and Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (US)); Chen, C.; Wu, B. (Fujian Institute of Research on the Structure of Matter, Chinese Academic of Sciences, Fuzhou, Fujian, People's Republic of China (CH))

1991-04-15

100

Second harmonic generation in CdI2 single crystals doped with CuI and NiI2  

Microsoft Academic Search

The effect of doping with CuI and NiI2 on non-linear optical properties of CdI2 crystals was studied. The change of non-linear optical properties of these crystals caused by the ordering of admixture centers was investigated. The ordering was achieved by the interaction of the orienting magnetic field and the membrane oscillations of the lattice with the admixture ions located in

O. N. Yurchenko; I. D. Olekseyuk; S. A. Pyroha

2004-01-01

101

NONLINEAR OPTICAL PHENOMENA AND DEVICES: BBO-crystal optical parametric oscillator tunable over the 300 --- 2340 nm range and pumped by the 4th harmonic of a Nd:YAG laser  

Microsoft Academic Search

An investigation was made of the lasing characteristics of a BBO-crystal Type-I optical parametric oscillator pumped by the 4th harmonic of a multimode Nd:YAG laser. The output was tunable over the range 300 --- 2340 nm. The efficiency ranged up to 15% near the peak of the tunability curve at double the oscillation threshold.

N. V. Kondratyuk; A. A. Shagov; K. L. Demidchik; A. M. Yurkin; Aleksandr E. Kokh

2000-01-01

102

Design of polarity-preserved or polarity-inverted wavelength converters using cross-phase modulation in a highly nonlinear photonic crystal fiber with flat dispersion  

NASA Astrophysics Data System (ADS)

In this paper, we propose the design of tunable and robust wavelength converters which can perform the polarity-preserved or polarity-inverted wavelength conversion by using the cross-phase modulation (XPM) in a dispersion-flattened highly nonlinear photonic crystal fiber (DF-HNL-PCF). The newly designed wavelength converter consists of a DF-HNL-PCF and an optical band-pass filter in the simple straight-line configuration, where XPM leads to broadening the spectrum of a continuous-wave probe light and the polarity-preserved, tunable wavelength conversion is then implemented by filtering out the blue-chirped or red-chirped spectral component of a probe light. The experimental results show that the polarity-preserved wavelength converter using a DF-HNL-PCF can achieve the error-free conversion of 10 Gbit s-1 optical data signals with the maximum power penalty of less than 2.1 dB over a wavelength range of nearly 34 nm. This wavelength tunability is actually limited by an operational wavelength range of the tunable optical band-pass filter that is used to extract the wavelength-converted signal in our experiment. Moreover, the polarity-inverted wavelength conversion is observed at the XPM-based wavelength converter using a DF-HNL-PCF, for the first time. This is achieved by tuning the central wavelength of an optical band-pass filter to coincide with that of a chirped probe light. This work is supported by the Chinese Academy of Sciences (CAS) within the framework of the CAS/SAFEA International Partnership Program for Creative Research Teams. This work was carried out while ZQH was a PhD candidate at the State Key Laboratory of Transient Optics and Photonics and the CAS Graduate University.

Hui, Zhan-Qiang; Zhang, Jian-Guo

2012-06-01

103

The art for broad-bandwidth direct third-harmonic generation focusing beams in a single crystal of BBO  

Microsoft Academic Search

By third-order nonlinear coupling and tightly focusing the beams in a single crystal of BBO, high intensity broad-bandwidth femtosecond pulses are used to generate 50muJ of light at 270nm (up to 1% THG efficiency). It is proved that the major contribution to the THG observed is the third-order process, not the cascaded second-order process. And the primary reasons why THG

Keyu Li; Kun Li; Xiaoming Zeng; Yiqiu Gu; Wei Hang; Bin Zhang; Kainan Zhou; Bin Feng; Fuquan Li; Huaiting Jia; Yong Xiang; Wei Zhong; Bing Xu; Tian'en Li; Liquan Wang; Xu Diao; Xiaojun Huang; Qihua Zhu; Feng Jing; Xiaofeng Wei

2008-01-01

104

An Investigation of Method to Reduce Harmonic Components using Specific Harmonic Control Method  

NASA Astrophysics Data System (ADS)

Low Harmonic Components Elimination Method is effective to suppress the Harmonics of self-commutated converter. But this method can't control the harmonic voltage. Recently the technique have been proposed to control self-commutated converter as shunt active filter to suppress the harmonics voltage of power system, but this method can't be used for this purpose. In this paper, a new PWM method is proposed to control specific low harmonic component. The proposed method uses the approximate equation that was led from theoretical value. The proposed method turned out decreasing the total harmonic distortion of the power system more than conventional Low Harmonic Component Elimination Method by some experimental results employing STATCOM.

Harimoto, Tsuyoshi; Hayashi, Hidemi; Murata, Katsuaki

105

Harmonic Convergence  

NSDL National Science Digital Library

Harmonic convergence refers to a day back in 1987 where there was a particular planetary alignment. New Agers went crazy over the event, and if you want to get a taste of what it was like, enter harmonic convergence into your favorite Internet search engine and sit back and enjoy. This chapter adds to the previous discussion of resonance by expanding the list of vibrating things to metal rods and columns of air.

Robertson, William C.

2003-01-01

106

Modeling of large aperture third harmonic frequency conversion of high power Nd:glass laser systems  

SciTech Connect

To provide high-energy, high-power beams at short wavelengths for inertial-confinement-fusion experiments, we routinely convert the 1.053-{mu}m output of the Nova, Nd:phosphate-glass, laser system to its third-harmonic wavelength. We describe performance and conversion efficiency modeling of the 3 {times} 3 arrays potassium-dihydrogen-phosphate crystal plates used for type II/type II phase-matched harmonic conversion of Nova 0.74-m diameter beams, and an alternate type I/type II phase-matching configuration that improves the third-harmonic conversion efficiency. These arrays provide energy conversion of up to 65% and intensity conversion to 70%. 19 refs., 11 figs.

Henesian, M.A.; Wegner, P.J.; Speck, D.R.; Bibeau, C.; Ehrlich, R.B.; Laumann, C.W.; Lawson, J.K.; Weiland, T.L.

1991-03-13

107

Measures of Suppressing Harmonic Pollution generated by Power Electronic Equipment  

Microsoft Academic Search

Firstly, harmonic generated by power electronic equipments and harmonic hazards are reviewed. In order to improve the quality of power supply, basic operation principles of four techniques which raise the power factor are analyzed, such as active power filter, power factor correction, PWM rectifier and matrix converter. Simultaneously, some new technologies of improving the power factor and harmonic suppression are

Zheng Zheng; Wang Cong

2009-01-01

108

The Harmonic Domain: A frame of reference for power system harmonic analysis  

SciTech Connect

The Harmonic Domain is a general frame of reference for power system analysis in the steady state which models the coupling between phases and between harmonics. In this frame of reference the non-linear components, converted into harmonic Norton equivalents, are combined with the rest of the system and solved iteratively by the Newton-Raphson technique. This paper describes the structure of the new domain and illustrates its potential applications in a small power system with multiple non-linearities.

Arrillaga, J.; Medina, A.; Lisboa, M.L.V. [Univ. of Canterbury (New Zealand)] [Univ. of Canterbury (New Zealand); Cavia, M.A.; Sanchez, P. [Univ. of Cantabria (Spain)] [Univ. of Cantabria (Spain)

1995-02-01

109

Harmonic engine  

SciTech Connect

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.

Bennett, Charles L. (Livermore, CA)

2009-10-20

110

Bookmark Converter  

NSDL National Science Digital Library

This windows utility enables user to convert their bookmarks from Netscape Navigator to Internet explorer and vice versa. It is small, fast, and simple to use. The latest version has been tested up to Netscape 4.6 and IE 5.0. Bookmark Converter is shareware and can be registered for $8.

Broding, Magnus.

111

Thermionic converter  

DOEpatents

A thermionic converter is set forth which includes an envelope having an electron collector structure attached adjacent to a wall. An electron emitter structure is positioned adjacent the collector structure and spaced apart from opposite wall. The emitter and collector structures are in a common chamber. The emitter structure is heated substantially only by thermal radiation. Very small interelectrode gaps can be maintained utilizing the thermionic converter whereby increased efficiency results. 10 figs.

Fitzpatrick, G.O.

1987-05-19

112

Thermionic converter  

DOEpatents

A thermionic converter (10) is set forth which includes an envelope (12) having an electron collector structure (22) attached adjacent to a wall (16). An electron emitter structure (24) is positioned adjacent the collector structure (22) and spaced apart from opposite wall (14). The emitter (24) and collector (22) structures are in a common chamber (20). The emitter structure (24) is heated substantially only by thermal radiation. Very small interelectrode gaps (28) can be maintained utilizing the thermionic converter (10) whereby increased efficiency results.

Fitzpatrick, Gary O. (Livermore, CA)

1987-05-19

113

Second-harmonic generation in nonlinear left-handed metamaterials  

E-print Network

Second-harmonic generation in nonlinear left-handed metamaterials Ilya V. Shadrivov, Alexander A August 21, 2005 We study the second-harmonic generation (SHG) in left-handed metamaterials that this novel parametric process can convert a surface of the left-handed metamaterial into an effective mirror

114

Spontaneous and field-induced mesomorphism of a silyl-terminated bent-core liquid crystal as determined from second-harmonic generation and resonant X-ray scattering.  

PubMed

The polarity and structure of the phases of a liquid crystal constituted by thiophene-based bent-core molecules is investigated by means of optical second-harmonic generation (SHG), and resonant and conventional X-ray diffraction. The material studied is representative of a wide family of mesogens that contain silyl groups at the ends of the chains. These bulky terminal groups have been reported to give rise to smectic phases showing ferroelectric switching. However, the analysis of the SHG signal before and after application of electric fields has allowed us to establish unambiguously that the reported ferroelectricity is not intrinsic to the material but stabilized by the cell substrates once an electric field has been applied. In addition, the results obtained from resonant X-ray diffraction indicate that virgin samples have antiferroelectric undulated synclinic smectic structures. PMID:24651598

Folcia, C L; Ortega, J; Etxebarria, J; Rodríguez-Conde, S; Sanz-Enguita, G; Geese, K; Tschierske, C; Ponsinet, V; Barois, P; Pindak, R; Pan, LiDong; Liu, Z Q; McCoy, B K; Huang, C C

2014-01-01

115

crystal  

NASA Astrophysics Data System (ADS)

A Nd3+:Na2La4(WO4)7 crystal with dimensions of ? 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for ?-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for ?-polarization. The emission cross sections are 3.19 × 10-20 cm2 for ?-polarization and 2.67 × 10-20 cm2 for ?-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.

Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu

2014-07-01

116

A Three-Phase Adaptive Notch Filter-Based Approach to Harmonic\\/Reactive Current Extraction and Harmonic Decomposition  

Microsoft Academic Search

This paper introduces a new three-phase adaptive notch filtering approach for the extraction of harmonic and reactive current components for use in grid-connected converters. The main function of this phase-locked loop-less method is to provide synchronized harmonic and reactive current components for control purposes. Moreover, this method is capable of detecting a selective order of harmonics. This feature is useful

Davood Yazdani; Alireza Bakhshai; Praveen K. Jain

2010-01-01

117

Second-harmonic conical refraction in GUHP  

NASA Astrophysics Data System (ADS)

A comparison of linear and second-harmonic conical refractions in guanylurea(1 +) hydrogen phosphite (GUHP) single crystal is reported. The favorable material properties of GUHP allowed us to observe well resolved second-harmonic conical refraction rings including the Poggendorff division. Study of the refraction patterns confirmed that the spatial distributions of the electromagnetic field behind the sample compare well in the linear and quadratic cases.

Kroupa, J.

2010-04-01

118

Frequency mixing crystal  

DOEpatents

In a laser system for converting infrared laser light waves to visible light comprising a source of infrared laser light waves and means of harmoic generation associated therewith for production of light waves at integral multiples of the frequency of the original wave, the improvement of said means of harmonic generation comprising a crystal having the chemical formula X.sub.2 Y(NO.sub.3).sub.5 .multidot.2 nZ.sub.2 o wherein X is selected from the group consisting of Li, Na, K, Rb, Cs, and Tl; Y is selected from the group consisting of Sc, Y, La, Ce, Nd, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, and In; Z is selected from the group consisting of H and D; and n ranges from 0 to 4.

Ebbers, Christopher A. (Livermore, CA); Davis, Laura E. (Manteca, CA); Webb, Mark (Salida, CA)

1992-01-01

119

X-Ray Second Harmonic Generation  

NASA Astrophysics Data System (ADS)

We report clear experimental evidence for second harmonic generation at hard x-ray wavelengths. Using a 1.7 Å pumping beam generated by a free electron laser, we observe second harmonic generation in diamond. The generated second harmonic is of order 10 times the background radiation, scales quadratically with pump pulse energy, and is generated over a narrow phase-matching condition. Of importance for future experiments, our results indicate that it is possible to observe nonlinear x-ray processes in crystals at pump intensities exceeding 1016 W/cm2.

Shwartz, S.; Fuchs, M.; Hastings, J. B.; Inubushi, Y.; Ishikawa, T.; Katayama, T.; Reis, D. A.; Sato, T.; Tono, K.; Yabashi, M.; Yudovich, S.; Harris, S. E.

2014-04-01

120

Unified approach to ?erenkov second harmonic generation.  

PubMed

We discuss the effect of second harmonic generation via the ?erenkov-like process in nonlinear bulk media and waveguides. We show that in both schemes the ?erenkov harmonic emission represents in fact a nonlinear Bragg diffraction process. It is therefore possible, for the first time, to describe the bulk and waveguide ?erenkov emission uniformly by considering the spatial modulation of the second-order nonlinear polarization. This is also experimentally illustrated by studying the ?erenkov second harmonic generation at the boundary of a nonlinear quadratic medium via the total internal reflection inside the nonlinear crystal. PMID:24216797

Roppo, Vito; Kalinowski, Ksawery; Sheng, Yan; Krolikowski, Wieslaw; Cojocaru, Crina; Trull, Jose

2013-11-01

121

Spectroscopic investigation, nucleation, growth, optical, thermal and second harmonic studies of novel semi-organic nonlinear optical crystal - thiourea urea zinc sulfate.  

PubMed

A new nonlinear optical crystal thiourea urea zinc sulfate (TUZS) has been grown by slow evaporation technique in equimolar ratio. Solubility and metastable zone width measurements have been determined for the grown crystal. Single crystal XRD revealed that the crystal system belongs to orthorhombic with cell parameters a=7.78Å, b=11.15Å and c=15.47Å. The sharp and well defined Bragg peaks observed in the powder XRD pattern confirm the crystalline nature of the TUZS compound. The grown mechanism and surface features were investigated by optical microscopic techniques such as scanning electron microscopy (SEM). The presence of zinc in the grown crystal was detected by atomic absorption spectroscopy and EDAX analysis. The compound has been confirmed by (1)H NMR, mass and FTIR spectral studies. The transmittance spectrum of TUZS has been used to calculate the extinction coefficient K, reflectance R, as functions of photon energy. The optical band gap of TUZS is 4.046 eV. The SHG efficiency has been tested by the Kurtz powder technique using Nd: YAG laser and KDP sample has been used as a standard reference material. PMID:22820345

Rao, Redrothu Hanumantha; Kalainathan, S

2012-11-01

122

crystal  

NASA Astrophysics Data System (ADS)

The polarized absorption, emission spectra and decay time measurements of Pr3+-doped CaYAlO4 single crystal have been performed at room temperature. Based on the Judd-Ofelt theory, the spectroscopic parameters , radiative transition probabilities, radiative lifetimes and branching ratios were obtained. The stimulated emission cross-section, fluorescence lifetimes and the quantum efficiency of the promising laser transition were also calculated and compared with other reported crystals. The results show that Pr3+:CaYAlO4 is a promising candidate for visible solid-state laser emission.

Lv, Shaozhen; Wang, Yan; Zhu, Zhaojie; You, Zhenyu; Li, Jianfu; Gao, Shufang; Wang, Hongyan; Tu, Chaoyang

2014-07-01

123

Modulation of Indirect Matrix Converter under unbalanced source voltage condition  

Microsoft Academic Search

This paper deals with the effects of unbalanced source voltages on Indirect Matrix Converter (IMC). A detailed theoretical analysis is presented for the harmonic content of input and output currents when unbalanced voltages are applied at IMC input. A control strategy is proposed, where the modulation index of inverter section of IMC is dynamically varied to eliminate the harmonic components

Vishal Vekhande; B. B. Pimple; B. G. Fernandes

2011-01-01

124

On The Significance Of An Accurate Evaluation Of Harmonic Amplitudes And Phases In Electrical Plant Design  

Microsoft Academic Search

- The paper shows a comparison of the results provided by approximate and correct estimates of amplitudes and phase angles of the harmonic currents and voltages present in electrical plants supplying static power converters. It comes out that since the ~ctangular current waveshape may not correspond to the worst condition for the harmonic amplitudes and, moreover, the harmonic amplitude and

G. C. Montanari; M. Loggini; A. Cavallini

1992-01-01

125

Design and characterization of a rugged and compact setup for widely tunable harmonic generation in the ultraviolet  

NASA Astrophysics Data System (ADS)

Design and experimental characterization of a nonlinear optical converter module for the generation of widely tunable UV radiation is presented. The module combines units for second, third and fourth harmonic generation of tunable Ti:Sapphire lasers. A modified conversion scheme based on the combination of BIBO and BBO crystals reduces the complexity of our former published UV setup - resulting in a significant increase of performance and long-term stability of the system. Experimental characterization of the former and the improved UV setup are compared. The investigations of the converter module are carried out with a widely tunable Ti:Sapphire laser with nanosecond pulses and a repetition rate of 1 kHz. This laser provides a continuous tuning range of 690 nm to 1010 nm with pulse energies up to 2.0 mJ and a spectral line width of less than 10 GHz resulting in an output power of the converter module of 1000 mW, 400 mW and 200 mW respectively for the second, third and fourth harmonic generation. The new converter module is a decisive step in the development of a hands-off solid-state laser system with a continuous tuning range from the UV to the NIR - 200 nm to 1000 nm.

Jungbluth, B.; Vierkoetter, M.; Hoefer, M.; Loehring, J.; Oberbeckmann, D.; Hoffmann, D.

2007-02-01

126

A design of PWM converter inverter system for building air conditioner compressor  

Microsoft Academic Search

Many countries are making strong harmonic current regulations for high power consuming equipments to reduce power loss and voltage distortion in power distribution. To comply with the regulation, the PWM converter is receiving more interest due to the low harmonic current generation compared with diode rectifier and unity power factor. This paper introduces a design of PWM converter inverter system

Bon-Gwan Gu; Joon Sung Park; Jun-Hyuk Choi; In-Soung Jung

2009-01-01

127

Third-harmonic performance of the Beamlet prototype laser  

SciTech Connect

The Beamlet laser is a nearly full-scale, single-aperture prototype of the driver design for the National Ignition Facility (NIF). As part of a test and validation plan for the NIF design, Beamlet was recently equipped with final focusing optics and diagnostics for the purpose of evaluating integrated component performance and equivalent target-plane irradiance conditions at the 0.351-{mu}m output wavelength specified for NIF targets. A 37-cm aperture two-crystal converter scheme generates the third harmonic of the Nd:glass 1.053-{mu}m wavelength with high efficiency. The efficiency of the converter has been characterized and is reported, along with detailed measurements of the near-field and far-field UV irradiance distributions at operating conditions up to and exceeding red-line levels for the NIF. Dependences of observed beam quality on critical laser parameters including output power, B-integral, and spatial filtering are discussed and compared with numerical simulations.

Wegner, P.J.; Barker, C.E.; Caird, J.A.; Dixit, S.N.; Henesian, M.A.; Seppala, L.G.; Thompson, C.E.; Van Wonterghem, B.V.

1997-01-31

128

On configurable oversampled A/D converters  

SciTech Connect

This abstract presents a configurable oversampled A/D converter that can be either configured as a sigma-delta converter or an incremental converter. The latter refers to oversampled instrumentation converters that cancel offset and 1/f noise. The converter architecture is based on a new concept called mixed analog-digital integrator (MADI). As will be demonstrated in this paper, this concept leads to a very simple and modular architecture. In addition to the configurability as a sigma-delta or incremental converter, the implemented converter allows selection of the converter order and the decimation factor in order to find the best trade-off between resolution, conversion time or bandwidth, and power consumption. As the converter architecture is completely modular, it can rapidly be tailored for a specific application with minimized silicon area. The circuit achieves a resolution of 16 b on a range of [plus minus]650 mV and compensates the offset and the even-order harmonics to a nonobservable level.

Nys, O.J.; Dijkstra, E. (Swiss Center for Electronics and Microtechnology, Neuchatel (Switzerland))

1993-07-01

129

crystals  

NASA Astrophysics Data System (ADS)

A novel combined interferometric-mask method for the formation of micro- and nanometric scale three-dimensional (3D) rotational symmetry quasi-crystalline refractive lattice structures in photorefractive materials is demonstrated experimentally. The method is based on micrometric scale spatial modulation of the light by amplitude mask in the radial directions and along the azimuthal angle and the use of counter-propagating beam geometry building up Gaussian standing wave, which defines the light modulation in the axial direction with half-wavelength periodicity. 3D intensity pattern can be represented as numerous mask-generated 2D quasi-periodic structures located in each anti-node of the standing wave. The formed 3D intensity distributions of the optical beams can be imparted into the photorefractive medium thus creating the micro- and sub-micrometric scale 3D refractive index volume lattices. The used optical scheme allows also the formation of 2D lattices by removing the back-reflecting mirror. 2D and 3D refractive lattices were recorded with the use of 532 nm laser beam and rotational symmetry mask in doped lithium niobate crystals and were tested by the probe beam far-field diffraction pattern imaging and direct observation by phase microscope. The formed rotational symmetry 3D refractive structures have the periods of 20-60 ?m in the radial directions, 60 ?m along the azimuthal angle and half-wavelength 266 nm in the axial direction.

Badalyan, A.; Hovsepyan, R.; Mantashyan, P.; Mekhitaryan, V.; Drampyan, R.

2014-07-01

130

Controlling Second Harmonic Efficiency of Laser Beam Interactions  

NASA Technical Reports Server (NTRS)

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.

Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)

2011-01-01

131

Single Phase Harmonic Limits  

Microsoft Academic Search

The International Electrotechnical Commission (IEC) sets limits for harmonics in the current of small single-phase or three-phase loads, less than 16 A per phase, in Electromagnetic compatibility (EMC) - Part 3-2: Limits - Limits for harmonic current emissions (IEC 61000-3-2). The IEEE Single Phase Harmonics Task Force (P1495) is developing a similar standard for single phase loads of less than

Ward Jewell; Daniel J. Ward; Principal Engineer; Dominion Virginia Power

2002-01-01

132

Workshop on Harmonic Oscillators  

NASA Technical Reports Server (NTRS)

Proceedings of a workshop on Harmonic Oscillators held at the College Park Campus of the University of Maryland on March 25 - 28, 1992 are presented. The harmonic oscillator formalism is playing an important role in many branches of physics. This is the simplest mathematical device which can connect the basic principle of physics with what is observed in the real world. The harmonic oscillator is the bridge between pure and applied physics.

Han, D. (editor); Kim, Y. S. (editor); Zachary, W. W. (editor)

1993-01-01

133

VSC Based D-STATCOM with Selective Harmonic Elimination  

Microsoft Academic Search

This paper describes the design, implementation and performance of a medium-size distribution type static synchronous compensator (D-STATCOM) with the simplest 2- level, 3-leg VSC topology. Reactive power control is achieved by phase-shift-angle control, and voltage source converter (VSC) harmonics are eliminated by selective harmonic elimination method (SHEM) technique. VSC has been designed at the highest low-voltage level of 1 kV,

A. Cetin; M. Ermis

2007-01-01

134

VSC-Based D-STATCOM With Selective Harmonic Elimination  

Microsoft Academic Search

This paper describes the design, implementation, and performance of a medium-size distribution-type static synchronous compensator (D-STATCOM) with the simplest two-level three-leg voltage-source converter (VSC) topology. Reactive-power control is achieved by phase-shift-angle control, and VSC harmonics are eliminated by selective harmonic elimination method (SHEM). VSC has been designed at the highest low-voltage level of 1 kV and connected to a medium-voltage

Alper Cetin; Muammer Ermis

2009-01-01

135

Spontaneous noncollinear second harmonic generation in GUHP  

NASA Astrophysics Data System (ADS)

A detailed experimental investigation of the spontaneous noncollinear second harmonic generation in biaxial guanylurea(1 +) hydrogen phosphite (GUHP) crystal is reported. The number and shape of the resulting second harmonic hollow cones depend explicitly on the direction of propagation of the fundamental beam with respect to the optical axes and the type I or type II phase-matching lines, in agreement with theory and simple calculations. Spontaneous SHG allows an easy adjustment of the two-beam noncollinear SHG. Due to the large nonlinearity of GUHP, Fabry-Perot enhanced noncollinear SHG has been observed as well.

Kroupa, J.; Fridrichová, M.

2011-03-01

136

Voltage and current sensing in power electronic converters using sigma-delta A\\/D conversion  

Microsoft Academic Search

This paper presents a novel approach to voltage and current measurement in power electronics using a sigma-delta A\\/D converter. The system converts the analog input signal into a digital stream of data. By averaging the digital data stream over a switching period of the power converter, the required measurement is obtained. Harmonic distortion of the input waveform and noise caused

A. Mertens; D. Eckardt

1996-01-01

137

Fault Detection on Multicell Converter Based on Output Voltage Frequency Analysis  

Microsoft Academic Search

Multilevel converters use a large amount of semiconductors, allowing the reconfigurate of the converter to work even on internal fault condition. This paper presents a method to detect faulty cells in a cascaded multicell converter requiring just one voltage measurement per output phase. The method is based on high-frequency harmonic analysis, using a dynamic prediction of their behavior, avoiding erroneous

Pablo Lezana; Ricardo Aguilera; José Rodríguez

2009-01-01

138

Covariant harmonic oscillators and coupled harmonic oscillators  

NASA Technical Reports Server (NTRS)

It is shown that the system of two coupled harmonic oscillators shares the basic symmetry properties with the covariant harmonic oscillator formalism which provides a concise description of the basic features of relativistic hadronic features observed in high-energy laboratories. It is shown also that the coupled oscillator system has the SL(4,r) symmetry in classical mechanics, while the present formulation of quantum mechanics can accommodate only the Sp(4,r) portion of the SL(4,r) symmetry. The possible role of the SL(4,r) symmetry in quantum mechanics is discussed.

Han, Daesoo; Kim, Young S.; Noz, Marilyn E.

1995-01-01

139

IEEE POWER ELECTRONICS LETTERS 1 Harmonic Optimization of Multilevel Converters  

E-print Network

to determine the switching angles for a cascaded multilevel inverter which eliminates specified higher order, multilevel in- verters, optimization. I. INTRODUCTION MULTILEVEL inverters have drawn increasing attention reduced switching losses. The output waveforms of multilevel inverters are in a stepped form resulting

Tolbert, Leon M.

140

Elimination of Harmonics in a Multilevel Converter for HEV Applications  

E-print Network

times (angles) in a multilevel inverter can be chosen to achieve a required fundamental voltage multilevel inverters are particularly suited for this applica- tion because of the high VA ratings possible with these in- verters [6]. The multilevel voltage source inverter's unique structure allows it to reach high

Tolbert, Leon M.

141

System and methods for reducing harmonic distortion in electrical converters  

DOEpatents

Systems and methods are provided for delivering energy using an energy conversion module. An exemplary method for delivering energy from an input interface to an output interface using an energy converison module coupled between the input interface and the output interface comprises the steps of determining an input voltage reference for the input interface based on a desired output voltage and a measured voltage and the output interface, determining a duty cycle control value based on a ratio of the input voltage reference and the measured voltage, operating one or more switching elements of the energy conversion module to deliver energy from the input interface to the output interface to the output interface with a duty cycle influenced by the dute cycle control value.

Kajouke, Lateef A; Perisic, Milun; Ransom, Ray M

2013-12-03

142

Second-Harmonic Generation of Light with Double Refraction  

Microsoft Academic Search

Experimental and theoretical investigations are reported on the second-harmonic generation (SHG) of light in crystals long enough so that SHG is limited by double refraction. This effect has been called the aperture effect. SHG has been observed in ammonium dihydrogen phosphate (ADP) under matching conditions using the highly parallel beam from a gas laser. Crystals of lengths 5 and 10

G. D. Boyd; A. Ashkin; J. M. Dziedzic; D. A. Kleinman

1965-01-01

143

Feasibility study for convertible engine torque converter  

NASA Technical Reports Server (NTRS)

The feasibility study has shown that a dump/fill type torque converter has excellent potential for the convertible fan/shaft engine. The torque converter space requirement permits internal housing within the normal flow path of a turbofan engine at acceptable engine weight. The unit permits operating the engine in the turboshaft mode by decoupling the fan. To convert to turbofan mode, the torque converter overdrive capability bring the fan speed up to the power turbine speed to permit engagement of a mechanical lockup device when the shaft speed are synchronized. The conversion to turbofan mode can be made without drop of power turbine speed in less than 10 sec. Total thrust delivered to the aircraft by the proprotor, fan, and engine during tansient can be controlled to prevent loss of air speed or altitude. Heat rejection to the oil is low, and additional oil cooling capacity is not required. The turbofan engine aerodynamic design is basically uncompromised by convertibility and allows proper fan design for quiet and efficient cruise operation. Although the results of the feasibility study are exceedingly encouraging, it must be noted that they are based on extrapolation of limited existing data on torque converters. A component test program with three trial torque converter designs and concurrent computer modeling for fluid flow, stress, and dynamics, updated with test results from each unit, is recommended.

1985-01-01

144

Illustration: The Harmonic Oscillator  

NASA Astrophysics Data System (ADS)

To illustrate the formalism on a simple prototype problem, one may look at the harmonic oscillator. In the spirit of this picture, in fact, one can eschew solving the Schrödinger problem and plugging the wavefunctions into (4)...

Curtright, Thomas L.; Fairlie, David B.; Zachos, Cosmas K.

2014-11-01

145

Simple Harmonic Motion  

NSDL National Science Digital Library

This simulation offers two examples of simple harmonic motion, a mass on a spring and a simple pendulum. The applet allows you to adjust variables and observe the effects these changes have on the movement of the systems.

Pfaff, Raman

2008-07-15

146

Simple Harmonic Motion  

NSDL National Science Digital Library

This site from HyperPhysics presents an introduction to simple harmonic motion. It is explained using a concept map that features equations and diagrams. Links to other concepts involved are also included.

Nave, C. R.; University, Department O.

147

Simple microprocessor implementation of new regular-sampled harmonic elimination PWM techniques  

Microsoft Academic Search

Harmonic elimination PWM strategies for electric drives and static power converters have recently been developed using modified regular sampling techniques. These new PWM strategies can be generated online in real time using a simple microprocessor software algorithm without resorting to the usual offline mainframe computer harmonic elimination numerical techniques. The implementation and generation of these new PWM techniques are presented

Sidney R. Bowes; Paul R. Clark

1992-01-01

148

Intelligent torque sensing and robust torque control of harmonic drive under free-motion  

Microsoft Academic Search

A harmonic drive is a compact, light-weight and high-ratio torque transmission device which is used in many electrically actuated robot manipulators. In many robotic control strategies it is assumed that the actuator is an ideal torque source. However, converting harmonic drive systems to ideal torque sources is still a challenging control problem for researchers. In this paper the torque control

H. D. Taghirad; P. R. Belanger

1997-01-01

149

A simple fuzzy logic based robust active power filter for harmonics minimization under random load variation  

Microsoft Academic Search

Widespread applications of power electronic-based loads continue to increase concerns over harmonic distortion. However, it is desired to draw purely sinusoidal current from the distribution network, but this is no longer the case with new generation loads, consisting of power electronic converters. The current harmonics produced by these non-linear loads further result in voltage distortion and leads to various power

G. K. Singh; Asheesh Kumar Singh; R. Mitra

2007-01-01

150

On-line grid impedance estimation based on harmonic injection for grid-connected PV inverter  

Microsoft Academic Search

The paper presents an on-line software method for impedance estimation of the energized impedances such as power system grid. The proposed method is based on producing a perturbation on the output of the power converter that is in the form of periodical injection of one or two voltage harmonic signals. The single harmonic injection uses a 600 Hz signal and

Mihai Ciobotaru; Remus Teodorescu; Frede Blaabjerg

2007-01-01

151

Simulation of non-linear loads for harmonic studies  

Microsoft Academic Search

Recently, more attention is given to harmonic assessment of nonlinear loads due to the penetration of such devices on power systems which cause detrimental effects to the power system and other users. In order to quantify these distortions precisely, two commonly used topologies for implementation in Personal Computers (PCs) are modeled and accurately assessed. These are forward and flyback converters.

M. J. H. Rawa; D. W. P. Thomas; M. Sumner

2011-01-01

152

Digital Filter Design with Harmonics Estimation for Power Supplies  

NASA Astrophysics Data System (ADS)

The quality of voltage waveforms is nowadays an issue of the utmost importance for power utilities and electronic equipment. Modern frequency power converters generate a wide spectrum of harmonic components, which deteriorate the quality of the delivered energy, increase the energy losses as well as decrease their liability of a power supplies. In large converters systems not only harmonics, but also considerable interharmonics strongly deteriorate the quality of the power supply voltage. The estimation of the components parameters is very important for control and protection tasks. Digital low pass filter overcome the voltage drift, temperature drift and time drift problems and can be used for harmonic detection for better utilization in real-time. Real-time detection of harmonics can be implemented using MATLAB software and developing simulation circuit set up. With the appropriate cutoff frequency f c and nth order of filter, low pass filter and band-pass filter for real-time harmonic detection can be analyzed. In this paper the aim is to design filters using different methods including Prony analysis. The monitoring of power system harmonics an important issue in the frame of modern power system management and control can be achieved easily using digital filters.

Shah, P. J.; Saxena, R.; Chawla, M. P. S.

2012-06-01

153

Voltage-Distortion Compensation in Electrical Plants Supplying Static Power Converters  

Microsoft Academic Search

Voltage distortion compensation is a problem that must often be tackled in electrical plants supplying nonlinear loads, such as static power converters, both to ensure reliable behavior of apparatus sensible to harmonics and to comply with standard limits. Analysis of the compensation system constituted by harmonic filters and protection reactance is carried out, to clarify their contribution to voltage distortion

Gian Carlo Montanari; Mauro Loggini

1987-01-01

154

An improved Flyback converter  

Microsoft Academic Search

This paper presents a modified Flyback converter able to operate with higher efficiency and smaller size, overcoming most of the conventional flyback converter drawbacks, and also keeping its low cost and simplicity. In particular, the proposed converter allows the mosfet off voltage to be reduced and clamped to the input, thus recovering the transformer leakage energy. As a consequence, the

G. M. Ponzo; G. Capponi; P. Scalia; V. Boscaino

2009-01-01

155

Voltage source ac-to-dc converters for high-power transmitters  

NASA Technical Reports Server (NTRS)

This work was done to optimize the design of the components used for the beam power supply, which is a component of the transmitters in the Deep Space Network (DSN). The major findings are: (1) the difference in regulation between a six-pulse and a twelve-pulse converter is at most 7 percent worse for the twelve-pulse converter; (2) the commutation overlap angle of a current source converter equals that of a voltage source converter with continuous line currents; (3) the sources of uncharacteristic harmonics are identified with SPICE simulation; (4) the use of an imperfect phase-shifting transformer for the twelve-pulse converter generates a harmonic at six times the line frequency; and (5) the assumptions usually made in analyzing converters can be relaxed with SPICE simulation. The results demonstrate the suitability of using SPICE simulation to obtain detailed performance predictions of ac-to-dc converters.

Cormier, R.

1990-01-01

156

Practical medium voltage converter topologies for high power applications  

Microsoft Academic Search

Multilevel power conversion has been receiving increasing attention in the past few years for high power applications. Numerous topologies and modulation strategies have been introduced and studied extensively for utility and drive applications in the recent literature. These converters are suitable in high voltage and high power applications due to their ability to synthesize waveforms with better harmonic spectrum and

Peter K. Steimer; Madhav D. Manjrekar

2001-01-01

157

Rotorcraft convertible engine study  

NASA Technical Reports Server (NTRS)

The objective of the Rotorcraft Convertible Engine Study was to define future research and technology effort required for commercial development by 1988 of convertible fan/shaft gas turbine engines for unconventional rotorcraft transports. Two rotorcraft and their respective missions were defined: a Fold Tilt Rotor aircraft and an Advancing Blade Concept (ABC) rotorcraft. Sensitivity studies were conducted with these rotorcraft to determine parametrically the influence of propulsion characteristics on aircraft size, mission fuel requirements, and direct operating costs (DOC). The two rotorcraft were flown with conventional propulsion systems (separate lift/cruise engines) and with convertible propulsion systems to determine the benefits to be derived from convertible engines. Trade-off studies were conducted to determine the optimum engine cycle and staging arrangement for a convertible engine. Advanced technology options applicable to convertible engines were studied. Research and technology programs were identified which would ensure technology readiness for commercial development of convertible engines by 1988.

Gill, J. C.; Earle, R. V.; Mar, H. M.

1982-01-01

158

Harmonics and instabilities in switching circuits  

SciTech Connect

Over the last couple of years there has been significant activity in the development of Flexible AC Transmission Systems (FACTS). Much of this work has been directed towards advanced series compensation (ASC) systems based on a Thyristor Controlled Reactor (TCR) connected in parallel with a fixed capacitor. This results in a controllable series impedance element for use in transmission systems. FACTS devices generate harmonics which interact with the transmission system causing voltage distortions. These distortions can change the operation of such circuits. The authors have found new instabilities in both FACTS and static VAR circuits in which switching times change suddenly, or bifurcate as a system parameter varies slowly. The switching time bifurcation instabilities are explained and their mechanisms are illustrated by both analysis and simulation. The TCR is a periodically operated, nonlinear circuit which may be studied using a Poincare map. The Poincare map is computed and a simple formula for its Jacobian matrix is derived. This formula which describes the stability of the steady state periodic operation of the circuit is used to demonstrate that conventional bifurcations do not occur in this TCR example. The harmonic coupling solution method as developed by Bohmann and Lasseter has been extensively used to compute the steady state solutions of the TCR circuits. In this method, Fourier techniques are used to calculate the system harmonics. By expressing the TCR voltage and current as a Fourier series, a TCR harmonic admittance matrix is constructed and incorporated into a power system providing a general method of computing the power system harmonics. The authors have extended this method to single phase line commutated converters and shown how much circuit may have highly nonlinear and unexpected behavior.

Lasseter, R.H.; Dobson, I.; Jalali, S.G. (Univ. of Wisconsin, Madison, WI (United States). Coll. of Engineering)

1993-05-01

159

Nonlinear generation of a neat semi-Gaussian laser beam with a transversely varying periodically-poled LiTaO3 crystal.  

PubMed

We experimentally demonstrate a compact, all-solid-state 532 nm semi-Gaussian laser beam (SGB) source based on a 1064 nm laser and a transversely varying periodically-poled LiTaO3 (TPPLT) crystal as the laser beam shaper as well as the nonlinear frequency converter. We have used the designed TPPLT crystal to obtain a neat 532nm SGB with the quality of QSGB=1:17.5 by a single-pass second harmonic generation. The dependence of the generated SGB quality on the designed TPPLT parameter and the potential applications of the neat SGB are also discussed. PMID:21445167

Yin, Yaling; Lv, Xinjie; Zhao, Lina; Cao, Jingxiao; Yuan, Ye; Zhang, Chao; Leng, Hanyang; Xie, Zhenda; Xu, Ping; Zhao, Gang; Zhu, Shining

2011-03-14

160

IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 21, NO. 2, MARCH 2006 459 Active Harmonic Elimination  

E-print Network

of polynomial equations using resultants [11]. Another method to eliminate harmonics in multilevel inverters for Multilevel Converters Zhong Du, Student Member, IEEE, Leon M. Tolbert, Senior Member, IEEE, and John N to eliminate any number of specific higher order har- monics of multilevel converters with equal or unequal dc

Tolbert, Leon M.

161

Univalent ?-Harmonic Mappings  

NASA Astrophysics Data System (ADS)

We study mappings from 2 into 2 whose components are weak solutions to the elliptic equation in divergence form, div (??u)= 0, which we call ?-harmonic mappings. We prove sufficient conditions for the univalence, i.e., injectivity, of such mappings. Moreover we prove local bounds in BMO on the logarithm of the Jacobian determinant of such univalent mappings, thus obtaining the a.e. nonvanishing of their Jacobian. In particular, our results apply to ?-harmonic mapping associated with any periodic structure and therefore they play an important role in homogenization.

Alessandrini, Giovanni; Nesi, Vincenzo

162

Magnetization-induced second harmonic generation in a polar ferromagnet.  

PubMed

Second harmonic generation (SHG) induced by spontaneous magnetization has been investigated for a polar ferromagnetic crystal of GaFeO3. The Kerr rotation of the second harmonic light becomes gigantic with decreasing temperature below the magnetic transition temperature (approximately =205 K), e.g., as large as 73 degrees at 100 K. The magnetic domains can be visualized by using that large nonlinear Kerr rotation. The spectrum of the magnetization-induced SHG as measured indicates the two-photon resonant electronic process on a Fe3+ ion in the crystal. PMID:14995401

Ogawa, Y; Kaneko, Y; He, J P; Yu, X Z; Arima, T; Tokura, Y

2004-01-30

163

Magnetization-Induced Second Harmonic Generation in a Polar Ferromagnet  

NASA Astrophysics Data System (ADS)

Second harmonic generation (SHG) induced by spontaneous magnetization has been investigated for a polar ferromagnetic crystal of GaFeO3. The Kerr rotation of the second harmonic light becomes gigantic with decreasing temperature below the magnetic transition temperature (?205 K), e.g., as large as 73° at 100K. The magnetic domains can be visualized by using that large nonlinear Kerr rotation. The spectrum of the magnetization-induced SHG as measured indicates the two-photon resonant electronic process on a Fe3+ ion in the crystal.

Ogawa, Y.; Kaneko, Y.; He, J. P.; Yu, X. Z.; Arima, T.; Tokura, Y.

2004-01-01

164

A digitalized voltage-to-frequency converter  

Microsoft Academic Search

A new voltage-to-frequency converter, controlled by a quartz crystal oscillator, is described. The principle of operation is based on comparing the input voltage and the mean value of the output pulses, whose magnitude and duration are constant. As the duration of the output pulses is a multiple of the quartz oscillator period for any value of the input voltage, the

B. Ž DJORDJEVICH

1975-01-01

165

Harmonic Superspaces of Extended Supersymmetry. The Calculus of Harmonic Variables.  

National Technical Information Service (NTIS)

The main technical apparatus of the harmonic superspace approach to extended SUSY, the calculus of harmonic variables on homogeneous spaces of the SUSY automorphism groups, is presented in detail for N=2, 3, 4. The basic harmonics for the coset manifolds ...

E. Ivanov, S. Kalitzin Nguyen Ai Viet, V. Ogievetsky

1984-01-01

166

Introducing Simple Harmonic Motion.  

ERIC Educational Resources Information Center

Explains the origin and significance of harmonic motion which is an important topic that has wide application in the world. Describes the phenomenon by using an auxiliary circle to help illustrate the key relationships between acceleration, displacement, time, velocity, and phase. (Contains 16 references.) (Author/YDS)

Roche, John

2002-01-01

167

A harmonic motion experiment  

NASA Astrophysics Data System (ADS)

We present a unit comprising theory, simulation and experiment for a body oscillating on a vertical spring, in which the simultaneous use of a force probe and an ultrasonic range finder enables one to explore quantitatively and understand many aspects of simple and damped harmonic motions.

Gluck, P.; Krakower, Zeev

2010-11-01

168

Power line carrier interference from HVDC converter terminals  

SciTech Connect

Power line carrier (PLC) equipment typically operates in the frequency range from 25 kHz to 300 kHz. Interference studies for HVDC converters usually concentrate on interference from noise sources within this frequency range. However, operating experience at the Sandy Pond converter terminal has indicated that PLC equipment is also susceptible to interference from sources of power system harmonics below the PLC frequency range. Extensive field testing and analytical studies have shown that each PLC circuit has a resonant frequency below the operating frequency. If excited at this resonant frequency, high voltages may exist within the PLC circuit. The resulting saturation of PLC components leads to local generation of radio frequency (RF) noise that interferes with proper operation of PLC circuits. Sources of power system harmonics in the 3-10 kHz range, such as line commutated dc converters, are potential sources of this type of interference.

Tatro, P.J.; Adamson, K.A. (New England Power Service Co., Westborough, MA (United States)); Eitzmann, M.A.; Smead, M. (GE Industrial and Power Systems, Schenectady, NY (United States). Power Systems Engineering Dept.)

1993-07-01

169

Interleaved power converter  

DOEpatents

A power converter architecture interleaves full bridge converters to alleviate thermal management problems in high current applications, and may, for example, double the output power capability while reducing parts count and costs. For example, one phase of a three phase inverter is shared between two transformers, which provide power to a rectifier such as a current doubler rectifier to provide two full bridge DC/DC converters with three rather than four high voltage inverter legs.

Zhu, Lizhi (Canton, MI)

2007-11-13

170

Noncritically phase-matched second-harmonic generation in cesium lithium borate  

NASA Astrophysics Data System (ADS)

Efficient generation of 236-nm light was demonstrated by use of noncritically phase-matched second-harmonic generation in cesium lithium borate. Noncritical phase matching provided approximately 20× the nonlinear drive for second-harmonic generation than ?-barium borate for 236-nm generation. The 236-nm wavelength is the fourth harmonic of a 946-nm Nd:YAG laser. Phase matching was accomplished at a crystal temperature of -15 °C.

Gerstenberger, David C.; Trautmann, Thomas M.; Bowers, Mark S.

2003-07-01

171

Far and near-field second-harmonic imaging of ferroelectric domain walls  

Microsoft Academic Search

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 ?0.5 ?m in width (as measured with a near-field microscope) for the polarization of the second harmonic radiation perpendicular

Sergey I. Bozhevolnyi; Kjeld Pedersen; Torben Skettrup; Xiangsu Zhang; Michele Belmonte

1998-01-01

172

Application of beryllium plasma for the harmonic generation of Ti:sapphire laser radiation  

SciTech Connect

We report the studies of the low- and high-order harmonic generation (HHG) in beryllium plasma using the Ti:sapphire laser radiation (790 nm) and its second harmonic (395 nm). We achieved the tuning of HHG spectra by tuning the nonlinear optical crystal used for the second harmonic generation of fundamental radiation. The role of restricting factors during the HHG in a beryllium plume is discussed.

Ganeev, Rashid A.; Suzuki, Masayuki; Baba, Motoyoshi; Kuroda, Hiroto [The Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)

2008-12-15

173

New, zero voltage switching, high frequency boost converter topology for power factor correction  

Microsoft Academic Search

This paper introduces a technique for combining zero-voltage-switching with boost converter technology to enable high frequency, high efficiency operation of the converter. The combination creates a new topology which is effective to meet the power factor correction and harmonic reduction requirements of new EMC standards. The unique topology provides limitation of the recovery current of the boost diode and uses

John A Bassett

1995-01-01

174

A three-phase utility power supply based on the matrix converter  

Microsoft Academic Search

A matrix converter and variable-speed diesel generator are integrated to create a three-phase utility power supply. The matrix converter is designed to meet tight harmonic and transient response requirements while allowing variable voltage and frequency input from the generator's permanent magnet alternator; This enables the generator to provide stable power over a range of engine speeds and load conditions. Test

Dimosthenis Katsis; Patrick Wheeler; Jon Clare; Pericle Zanchetta

2004-01-01

175

Artificial intelligent controller for current source converter-based modular active power filters  

Microsoft Academic Search

The control methodology of the active power-line filter is the key element for its successful performance in mitigating the line current harmonics. The control system processes the distorted line current signal and forces the converter to inject the proper compensating current. At the same time, it regulates the dc term, i.e., the dc current in the current source converter topology

Ramadan El Shatshat; M. M. A. Salama; Mehrdad Kazerani

2004-01-01

176

A Closed-Loop Control System for the Reduction of Reactive Power Required by Electronic Converters  

Microsoft Academic Search

A closed-loop control system to reduce the reactive power required by electronic converters is proposed. The instantaneous reactive power which consists of both displacement of fundamental current and harmonic distortion current is measured and compensated by a reactive power source connected parallel between the power lines and the converter. A combination of a dc choke and a forced-commutated inverter is

Fumio Harashima; Hiroshi Inaba; Kunio Tsuboi

1976-01-01

177

GraphicConverter  

NSDL National Science Digital Library

GraphicConverter goes beyond the ability to convert a large number of graphic file formats. It provides tools for the creation and/or editing of graphics, animations, movies, and slide presentations; it also supports Adobe Photoshop compatible plug-ins. Currently, GraphicConverter can import 96 different graphic file formats and export 38. Conversion of several files (graphic or text) at a time is also possible through the "convert more..." feature. The tools offered for graphic editing are Photoshop-like. Detailed documentation is provided. This Macintosh shareware is provided by Lemke Software.

178

Arc regime of a thermionic converter with different tungsten emitters  

Microsoft Academic Search

Thermionic converters operating in the arc regime are studied experimentally with the <110>, <112>, <100>, and <111> faces of tungsten single crystals and with a polycrystalline tungsten surface as emitters. The experiments are carried out under comparable conditions, and the electrode surfaces are monitored directly. In general, there is no clear correspondence between the output characteristics of the converter and

B. P. Varaksin; A. S. Titkov

1976-01-01

179

Study of narrow-band second harmonic generation from a broad-band fundamental pulse  

NASA Astrophysics Data System (ADS)

This paper studies the type-I phase-matched second harmonic generation using 25-fs input laser pulses in a thick BBO crystal. The harmonic signal exhibits a narrow spectrum bandwidth, even though the input pulse has a broad bandwidth. The energy transfer efficiency and modulation of the fundamental spectrum are investigated.

Wen, Jing; Jiang, Hong-Bing; Deng, Yong-Kai; Gong, Qi-Huang

2010-12-01

180

Second and third harmonic generation in BBO by femtosecond Ti: sapphire laser pulses  

Microsoft Academic Search

Harmonic generation in barium metaborate (BBO) by femtosecond Ti: sapphire laser pulses is studied, taking into account both the group velocity mismatch and the lowest and second order group velocity dispersion (GVD). The lowest and second order GVD is calculated as a function of wavelength in the BBO crystal. Second and third harmonic radiation using femtosecond Ti: sapphire laser pulses

Hang Liu; Jianguan Yao; Ashok Puri

1994-01-01

181

Boost Converter Animation  

NSDL National Science Digital Library

This animation, created by faculty at Dartmouth University, is a boost converter. The resource features other animations such as buck and discontinuous converters. They also add simple diode, bridge and half-wave rectifiers. Although simple in design, this can still be a useful resource for those interested in electrical engineering.

2009-11-06

182

Discontinuous Buck Converter  

NSDL National Science Digital Library

This animation, created by faculty at Dartmouth University, is a discontinuous buck converter. The resource features other animations such as boost and discontinuous converters. They also add simple diode, bridge and half-wave rectifiers. Although simple in design, this can still be a useful resource for those interested in electrical engineering.

2009-11-19

183

Generation of octave-spanning multiple harmonics for ultrafast waveform synthesis  

E-print Network

Up to seven laser harmonics covering more than two octaves in frequency have been generated efficiently in a single PPLT crystal, permitting the synthesis of 1.5 femtosecond pulses in a stable and compact setting.

Hsu, Wei-Chun

184

General Theory of Harmonics Generation thru Energy Transformation  

NASA Astrophysics Data System (ADS)

Energy, whatever its form, can be converted into an electrical signal. When analyzed is found to be comprised of a continuum of sinusoidal frequencies called a harmonic spectrum H/S. This paper addresses the question of how/why, in general, are these sinusoidal frequencies (harmonics) generated and in particular how they are produced in electronic circuits. To address this question many varied experiments were performed. Some experiments used just batteries while others used mechanical, acoustic, pneumatic, thermal, magnetic, hydraulic or photonic devices. All these devices were used to investigate the nature of harmonic generation from the perspective of the en masse movement of conduction electrons. Primarily performing electronic experiments on the envelope of a single pulse revealed that a pulse of one wavelength can be separated into basic individual segments. The energy of each individual segment, when absorbed by conduction electrons, is transformed into a unique H/S. Recombining all the individual segments that comprise a pulse envelope, involves the constructive or destructive interactions of their harmonic spectrums leading to the amplitudes of some harmonics being increased and others reduced or eliminated. The result is a pulse envelope with a different harmonic series.

Czyzyk, Don

2013-04-01

185

Spherical Harmonics YLM Explorer  

NSDL National Science Digital Library

This is a Java applet that creates surface plots of the spherical harmonics. The user can set the L and m indices and the resolution of the plot. There is a restriction that L must be less than or equal to 5. Results are shown as either the amplitude of the function colored by the complex phase or the real part of the function illuminated by an external light source. Plots may be rotated in three dimensions.

Kraus, Martin

2005-04-16

186

Computing prime harmonic sums  

NASA Astrophysics Data System (ADS)

We discuss a method for computing sum_{p le x} 1/p , using time about x^{2/3} and space about x^{1/3} . It is based on the Meissel-Lehmer algorithm for computing the prime-counting function pi(x) , which was adapted and improved by Lagarias, Miller, and Odlyzko. We used this algorithm to determine the first point at which the prime harmonic sum first crosses 4.

Bach, Eric; Klyve, Dominic; Sorenson, Jonathan P.

2009-12-01

187

Metrics with harmonic spinors  

Microsoft Academic Search

We show that every closed spin manifold of dimensionn ? 3 mod 4 with a fixed spin structure can be given a Riemannian metric with harmonic spinors, i.e. the corresponding Dirac operator has a non-trivial kernel (Theorem A). To prove this we first compute the Dirac spectrum of the Berger spheresSn,n odd (Theorem 3.1). The second main ingredient is Theorem

Christian Bär

1996-01-01

188

Photocapacitive image converter  

NASA Technical Reports Server (NTRS)

An apparatus for converting a radiant energy image into corresponding electrical signals including an image converter is described. The image converter includes a substrate of semiconductor material, an insulating layer on the front surface of the substrate, and an electrical contact on the back surface of the substrate. A first series of parallel transparent conductive stripes is on the insulating layer with a processing circuit connected to each of the conductive stripes for detecting the modulated voltages generated thereon. In a first embodiment of the invention, a modulated light stripe perpendicular to the conductive stripes scans the image converter. In a second embodiment a second insulating layer is deposited over the conductive stripes and a second series of parallel transparent conductive stripes perpendicular to the first series is on the second insulating layer. A different frequency current signal is applied to each of the second series of conductive stripes and a modulated image is applied to the image converter.

Miller, W. E.; Sher, A.; Tsuo, Y. H. (inventors)

1982-01-01

189

Tracking harmonic notch filter  

SciTech Connect

An electronic filter for automatically tracking and removing harmonically related interfering electrical signals such as power-line interference harmonics without attenuating other signals of interest even though the signals are frequency stable and/or near the interference signal frequencies. The filter comprises a very narrow band electronic commutated capacitor-bank comb-notch filter driven by a counter/decoder circuit which is in turn driven by a phase locked loop. The filter also comprises two narrow-band analog filters tuned to the two lowest harmonics of the interfering signal. The summed output of these two filters is applied to the input of the phase-locked loop. The phase-locked loop locks to the proper multiple of the interfering signal and drives the comb notch filter at a frequency which causes it to generate notches at unit multiples of the fundamental of the interference frequency. This action is continuous such that center frequencies of the notches are automatically adjusted to compensate for small variations in the interference frequency.

Eno, F.

1989-03-20

190

Improved power quality converter fed permanent magnet AC motor for air-conditioning  

Microsoft Academic Search

This paper presents the performance analysis of interior permanent magnet synchronous motor (IPMSM) fed from improved power quality converter–inverter system as a variable speed drive for air-conditioning (Air-Con). The improved power quality converter (IPQC) makes the input power factor unity and also reduces the total harmonic distortion (THD) of input supply current. This converter consists of two uncontrolled unidirectional and

Bhim Singh; S. S. Murthy; Manoj Kumar

2003-01-01

191

Single-Phase Four Switches Z-Source AC-AC Converter  

Microsoft Academic Search

A new family of single-phase four switches Z-source AC-AC converter are proposed, including voltage-fed and current-fed. Compared to the traditional ac-ac converters, they have unique features: providing a larger range of output ac voltage with buck-boost, reversing or maintaining phase angle, reducing in-rush and harmonic current. A new commutation strategy for single-phase four switches Z-source AC-AC converters is proposed to

Yu Tang; Chaohua Zhang; Shaojun Xie

2007-01-01

192

Heat Flow in Regular and Disordered Harmonic Chains.  

National Technical Information Service (NTIS)

In the report, the authors investigate the steady state heat flux J in a large harmonic crystal containing different masses whose ends are in contact with heat baths at different temperatures. Calling Delta T the temperature difference and L the distance ...

A. Casher, J. L. Lebowitz

1971-01-01

193

Second harmonic generation in nanometer thin films and polar structures  

Microsoft Academic Search

The strengths of the second-order nonlinear optical (NLO) effects in various organic, inorganic materials and structures are important for nanotechnology, sensing and nonlinear microscopy. We analysed factors affecting second harmonic generation (SHG) in noncentrosymmetric materials, polar crystals of addition complexes and electrically poled polymer films. We used a SESAM mode-locked, amplified picosecond pulse laser system to measure SHG in 80

Anna Samoc; Marek Samoc; Vesselin Z. Kolev; Barry Luther-Davies

194

Enhancement of Relativistic Harmonic Generation by An Optically  

E-print Network

Enhancement of Relativistic Harmonic Generation by An Optically Preformed Periodic Plasma Waveguide coherent x-rays. However, hollow fiber and corrugated hollow capillary are not suitable for relativistic fabrication of spatial structures in a gas by laser machining wiht liquid-crystal spatial light modulator

195

Operation of fixed frequency Class-D series-parallel resonant converter on utility line with active control  

Microsoft Academic Search

A single-phase high-frequency transformer-isolated Class-D series parallel (LCC type) resonant power converter (SPRC) with fixed frequency is presented. The results of AC analysis are used to design the converter for low harmonic distortion and near unity power factor (PF) operation. The designed converter is studied through simulation (using SABER) and verified experimentally. For reliable operation of the converter at light

V. R. Durgesh; A. Muthuramalingam; V. V. Sastry

1999-01-01

196

Dot patterns from second-harmonic and sum-frequency generation in polycrystalline ZnSe  

Microsoft Academic Search

During a comparative study of second-harmonic generation (SHG) and sum-frequency generation (SFG) in single-crystal and polycrystalline ZnSe, the polycrystalline material showed a dot pattern in the SHG as well as in the SFG output. No such pattern was found in the output from the single-crystal ZnSe sample. The second-harmonic and also the sum-frequency dot pattern, resembling a diffraction pattern, could

Tran Duc Chinh; Wolfgang Seibt; Kai Siegbahn

2001-01-01

197

Fractional second-harmonic Talbot effect.  

PubMed

We demonstrate the fractional second-harmonic (SH) Talbot effect in a hexagonally poled LiTaO3 crystal. We carefully record the SH Talbot images at 1/2, 1/3, and 1/4 Talbot lengths, which are well matched with the simulated images by using the modified Rayleigh-Sommerfeld diffraction formula. A simplified model with a hexagonal array is adopted in the simulations. Also, we use a modified reciprocal vector theory to analytically explain the evolution of the SH array at fractional Talbot lengths. Our results show that the images are sensitive to the duty circle and the background of the array. PMID:22344149

Chen, Zhenhua; Liu, Dongmei; Zhang, Yong; Wen, Jianming; Zhu, S N; Xiao, Min

2012-02-15

198

IR Bandwidth and Crystal Thickness Effects on THG Efficiency and Temporal Shaping of Quasi-Rectangular UV Pulses: Part II - Incident IR Ripple.  

National Technical Information Service (NTIS)

We have investigated the effect of incident IR spectral bandwidth and crystal thickness, on uv pulses produced by third harmonic generation (THG) in a crystal pair. Our focus is on the third harmonic generation efficiency and longitudinal uv intensity pro...

2010-01-01

199

A new control strategy to improve the performance of PWM ac to dc converter under unbalanced operating condition  

E-print Network

and balanced. However, their studies do not include unbalanced operating condition. %1. H. Rashid and A. . I. VIaswood analyzed the phase controlled converter performance for supply unbalances and its effect on the power factor, harmonic factor. distortion... and balanced. However, their studies do not include unbalanced operating condition. %1. H. Rashid and A. . I. VIaswood analyzed the phase controlled converter performance for supply unbalances and its effect on the power factor, harmonic factor. distortion...

Choudhury, Shamim A.

2012-06-07

200

Multiresonant broadband optical antennas as efficient tunable nanosources of second harmonic light.  

PubMed

We report the experimental realization of efficient tunable nanosources of second harmonic light with individual multiresonant log-periodic optical antennas. By designing the nanoantenna with a bandwidth of several octaves, simultaneous enhancement of fundamental and harmonic fields is observed over a broad range of frequencies, leading to a high second harmonic conversion efficiency, together with an effective second order susceptibility within the range of values provided by widespread inorganic crystals. Moreover, the geometrical configuration of the nanoantenna makes the generated second harmonic signal independent from the polarization of the fundamental excitation. These results open new possibilities for the development of efficient integrated nonlinear nanodevices with high frequency tunability. PMID:22916834

Aouani, Heykel; Navarro-Cia, Miguel; Rahmani, Mohsen; Sidiropoulos, Themistoklis P H; Hong, Minghui; Oulton, Rupert F; Maier, Stefan A

2012-09-12

201

Robust perfect compensation of load harmonics in shunt active filters  

Microsoft Academic Search

In this paper an advanced control strategy is proposed for shunt active filter (SAF) used in three-phases three-wires current harmonic compensation. The SAF considered are based on AC\\/DC three-phase boost converter topology. The robust solution presented by the authors previously is used as a starting point to develop the stabilizing controller of the DC-MA voltage dynamics. SAF resistive power losses

Lorenzo Marconi; Fabio Ronchi; Andrea Tilli

2004-01-01

202

Thermionic photovoltaic energy converter  

NASA Technical Reports Server (NTRS)

A thermionic photovoltaic energy conversion device comprises a thermionic diode mounted within a hollow tubular photovoltaic converter. The thermionic diode maintains a cesium discharge for producing excited atoms that emit line radiation in the wavelength region of 850 nm to 890 nm. The photovoltaic converter is a silicon or gallium arsenide photovoltaic cell having bandgap energies in this same wavelength region for optimum cell efficiency.

Chubb, D. L. (inventor)

1985-01-01

203

Gallium phosphide energy converters  

Microsoft Academic Search

Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need

P. E. Sims; L. C. Dinetta; M. A. Goetz

1995-01-01

204

Towards automated biomedical ontology harmonization.  

PubMed

The use of biomedical ontologies is increasing, especially in the context of health systems interoperability. Ontologies are key pieces to understand the semantics of information exchanged. However, given the diversity of biomedical ontologies, it is essential to develop tools that support harmonization processes amongst them. Several algorithms and tools are proposed by computer scientist for partially supporting ontology harmonization. However, these tools face several problems, especially in the biomedical domain where ontologies are large and complex. In the harmonization process, matching is a basic task. This paper explains the different ontology harmonization processes, analyzes existing matching tools, and proposes a prototype of an ontology harmonization service. The results demonstrate that there are many open issues in the field of biomedical ontology harmonization, such as: overcoming structural discrepancies between ontologies; the lack of semantic algorithms to automate the process; the low matching efficiency of existing algorithms; and the use of domain and top level ontologies in the matching process. PMID:24851964

Uribe, Gustavo A; Lopez, Diego M; Blobel, Bernd

2014-01-01

205

Damped quantum harmonic oscillator  

E-print Network

In the framework of the Lindblad theory for open quantum systems the damping of the harmonic oscillator is studied. A generalization of the fundamental constraints on quantum mechanical diffusion coefficients which appear in the master equation for the damped quantum oscillator is presented; the Schr\\"odinger and Heisenberg representations of the Lindblad equation are given explicitly. On the basis of these representations it is shown that various master equations for the damped quantum oscillator used in the literature are particular cases of the Lindblad equation and that the majority of these equations are not satisfying the constraints on quantum mechanical diffusion coefficients. Analytical expressions for the first two moments of coordinate and momentum are also obtained by using the characteristic function of the Lindblad master equation. The master equation is transformed into Fokker-Planck equations for quasiprobability distributions. A comparative study is made for the Glauber $P$ representation, the antinormal ordering $Q$ representation and the Wigner $W$ representation. It is proven that the variances for the damped harmonic oscillator found with these representations are the same. By solving the Fokker-Planck equations in the steady state, it is shown that the quasiprobability distributions are two-dimensional Gaussians with widths determined by the diffusion coefficients. The density matrix is represented via a generating function, which is obtained by solving a time-dependent linear partial differential equation derived from the master equation. Illustrative examples for specific initial conditions of the density matrix are provided.

A. Isar; A. Sandulescu

2006-02-17

206

Simple Harmonic Oscillator Model  

NSDL National Science Digital Library

The Ejs Simple Harmonic Oscillator model displays the dynamics of a ball attached to an ideal spring. The spring is initially stretched and the ball has zero initial velocity. The initial position of the ball can be changed by click-dragging the ball when the simulation is paused. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Simple Harmonic Oscillator model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_osc_SHO.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for Newtonian mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang

2008-07-05

207

Strange Harmonic Oscillator Model  

NSDL National Science Digital Library

The Ejs Strange Harmonic Oscillator model displays the motion of two masses connected by a massless rigid rod and the masses may move without friction along two perpendicular rails in a horizontal table. The energy of the oscillator system can be changed via a slider. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Strange Harmonic Oscillator model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_oscillations_strange.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for classical mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-11-11

208

Molecular germanium selenophosphate salts: phase-change properties and strong second harmonic generation.  

PubMed

A new series of germanium chalcophosphates with the formula A(4)GeP(4)Q(12) (A = K, Rb, Cs; Q = S, Se) have been synthesized. The selenium compounds are isostructural and crystallize in the polar orthorhombic space group Pca2(1). The sulfur analogues are isostructural to one another but crystallize in the centrosymmetric monoclinic space group C2/c. All structures contain the new molecular anion [GeP(4)Q(12)](4-); however, the difference between the sulfides and selenides arises from the change in crystal packing. Each discrete molecule is comprised of two ethane-like P(2)Q(6) units that chelate to a central tetrahedral Ge(4+) ion in a bidentate fashion. The selenides were synthesized pure by stoichiometric reaction of the starting materials, whereas the sulfides contained second phases. The band gaps of the molecular salts are independent of the alkali metal counterions and have a value of 2.0 eV for the selenides and 3.0-3.1 eV for the sulfides. All A(4)GeP(4)Se(12) compounds melt congruently, and the potassium analogue can be quenched to give a glassy phase that retains its short-range order as shown by Raman spectroscopy and powder X-ray diffraction. Interestingly, K(4)GeP(4)Se(12) is a phase-change material that reversibly converts between glassy and crystalline states and passes through a metastable crystalline state upon heating just before crystallizing into its slow-cooled form. Initial second harmonic generation (SHG) experiments showed crystalline K(4)GeP(4)Se(12) outperforms the other alkali metal analogues and exhibits the strongest second harmonic generation response among reported quaternary chalcophosphates, ~30 times that of AgGaSe(2) at 730 nm. A more thorough investigation of the nonlinear optical (NLO) properties was performed across a range of wavelengths that is almost triple that of previous reports (? = 1200-2700 nm) and highlights the importance of broadband measurements. Glassy K(4)GeP(4)Se(12) also exhibits a measurable SHG response with no poling. PMID:23157167

Morris, Collin D; Chung, In; Park, Sungoh; Harrison, Connor M; Clark, Daniel J; Jang, Joon I; Kanatzidis, Mercouri G

2012-12-26

209

Sound velocity anisotropy in cubic crystals  

NASA Technical Reports Server (NTRS)

Simple analytical expressions may be derived for sound velocities in cubic crystals by using lattice harmonics or functions which are invariant under the crystal symmetry operations. These expressions are in good agreement with the exact results for typical crystals such as metallic iron and potassium fluoride.

Tsang, T.; Park, H. Y.

1983-01-01

210

Harmonic spinors on Riemann surfaces  

Microsoft Academic Search

We calculate the dimension of the space of harmonic spinors on hyperelliptic Riemann surfaces for all spin structures. Furthermore, we present non-hype relliptic examples of genus 4 and 6 on which the maximal possible number of linearly independent harmonic spinors is achieved.

Christian Bär; Paul Schmutz

1992-01-01

211

Harmonic Series Meets Fibonacci Sequence  

ERIC Educational Resources Information Center

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?

Chen, Hongwei; Kennedy, Chris

2012-01-01

212

MODEL HARMONIZATION POTENTIAL AND BENEFITS  

EPA Science Inventory

The IPCS Harmonization Project, which is currently ongoing under the auspices of the WHO, in the context of chemical risk assessment or exposure modeling, does not imply global standardization. Instead, harmonization is thought of as an effort to strive for consistency among appr...

213

Vector generator scan converter  

DOEpatents

High printing speeds for graphics data are achieved with a laser printer by transmitting compressed graphics data from a main processor over an I/O (input/output) channel to a vector generator scan converter which reconstructs a full graphics image for input to the laser printer through a raster data input port. The vector generator scan converter includes a microprocessor with associated microcode memory containing a microcode instruction set, a working memory for storing compressed data, vector generator hardward for drawing a full graphic image from vector parameters calculated by the microprocessor, image buffer memory for storing the reconstructed graphics image and an output scanner for reading the graphics image data and inputting the data to the printer. The vector generator scan converter eliminates the bottleneck created by the I/O channel for transmitting graphics data from the main processor to the laser printer, and increases printer speed up to thirty fold.

Moore, James M. (Livermore, CA); Leighton, James F. (Livermore, CA)

1990-01-01

214

Vector generator scan converter  

DOEpatents

High printing speeds for graphics data are achieved with a laser printer by transmitting compressed graphics data from a main processor over an I/O channel to a vector generator scan converter which reconstructs a full graphics image for input to the laser printer through a raster data input port. The vector generator scan converter includes a microprocessor with associated microcode memory containing a microcode instruction set, a working memory for storing compressed data, vector generator hardware for drawing a full graphic image from vector parameters calculated by the microprocessor, image buffer memory for storing the reconstructed graphics image and an output scanner for reading the graphics image data and inputting the data to the printer. The vector generator scan converter eliminates the bottleneck created by the I/O channel for transmitting graphics data from the main processor to the laser printer, and increases printer speed up to thirty fold. 7 figs.

Moore, J.M.; Leighton, J.F.

1988-02-05

215

Galilean covariant harmonic oscillator  

NASA Technical Reports Server (NTRS)

A Galilean covariant approach to classical mechanics of a single particle is described. Within the proposed formalism, all non-covariant force laws defining acting forces which become to be defined covariantly by some differential equations are rejected. Such an approach leads out of the standard classical mechanics and gives an example of non-Newtonian mechanics. It is shown that the exactly solvable linear system of differential equations defining forces contains the Galilean covariant description of harmonic oscillator as its particular case. Additionally, it is demonstrated that in Galilean covariant classical mechanics the validity of the second Newton law of dynamics implies the Hooke law and vice versa. It is shown that the kinetic and total energies transform differently with respect to the Galilean transformations.

Horzela, Andrzej; Kapuscik, Edward

1993-01-01

216

Thermionic energy converter investigations  

NASA Technical Reports Server (NTRS)

This paper presents evaluation of a variety of thermionic converter configurations to obtain improved efficiency. A variable-spacing diode using an iridium emitter gave emission properties comparable to platinum, but the power output from a sintered LaB6 collector diode was not consistent with its work function. Reflectivities above 0.5 were measured at thermal energies on oxygenated-cesiated surfaces using a field emission retarding potential gun. Performance of converters with structured electrodes and the characteristics of a pulsed triode were studied as a function of emitter, collector, cesium reservoir, interelectrode spacing, xenon pressure, and pulsing parameters.

Goodale, D. B.; Lee, C.; Lieb, D.; Oettinger, P. E.

1979-01-01

217

Modular voltage source converter  

US Patent & Trademark Office Database

Voltage source converter based on a chain-link cell topology including one or more phases, each of the phases having one or more series-connected chain-link cell modules connected to each other. The output voltage of the voltage source converter is controlled by control signals applied to the series-connected chain-link cell modules. In case of failure of a chain-link cell module, that module is controlled, by the control signals, such that zero output voltage is provided at its output voltage AC terminal.

2013-08-06

218

Frequency doubling crystals  

DOEpatents

A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a "harmonic generating unit" which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyl hydroxyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

Wang, Francis (Danville, CA); Velsko, Stephan P. (Livermore, CA)

1989-01-01

219

Multilevel inverter, based on multi-stage connection of three-level converters scaled in power of three  

Microsoft Academic Search

A multi-stage inverter using three-state converters is being analyzed for multipurpose applications, such as active power filters, static VAr compensators and machine drives for sinusoidal and trapezoidal current applications. The great advantage of this kind of converter is the minimum harmonic distortion obtained. The drawbacks are the isolated power supplies required for each one of the stages of the multiconverter.

Juan Dixon; Luis Moran

2002-01-01

220

Catalytic Converters and Nanocatalysts  

NSDL National Science Digital Library

This lab, presented by the National Nanotechnology Infrastructure Network, covers the concept of chemical reactions. Students will learn about "the reactions involved in catalytic converters and the importance of nanocatalysts in the reactions." Teacher Preparation Guides, Student Guides, and Next Generation Science Standards applicable to the lesson are included.

2014-09-08

221

Muslim Converts in Prison  

Microsoft Academic Search

Abstract: There has been something of a moral panic about individuals converting to Islam whilst incarcerated. A number of newspaper articles have suggested that within prisons there is a potentially toxic mix of extremist ideology and a criminal past. This article presents the results of a study exploring conversion to Islam within two prisons in England. The main findings suggest

BASIA SPALEK; SALAH EL-HASSAN

2007-01-01

222

Efficient broadband second-harmonic generation by dispersive achromatic nonlinear conversion using only prisms  

SciTech Connect

Using a lossless dispersive apparatus consisting of six prisms, optimized to match a second-harmonic crystal phase-matching angle vs. wavelength to second order, we efficiently doubled tunable fundamental light near 660 nm over a range of 80 nm using a 4-mm-long type-I {beta}-Barium Borate (BBO) crystal. Another lossless set of six prisms after the crystal realigned the propagation directions of the various second-harmonic frequencies to be collinear to within 1/4 spot diameter in position and 200 {mu}rad in angle. The measured conversion efficiency of a 40-mJ, 5-ns fundamental pulse was 10%.

Richman, B.A.; Bisson, S.E.; Trebino, R.

1997-12-01

223

Liquid metal thermal electric converter  

DOEpatents

A liquid metal thermal electric converter which converts heat energy to electrical energy. The design of the liquid metal thermal electric converter incorporates a unique configuration which directs the metal fluid pressure to the outside of the tube which results in the structural loads in the tube to be compressive. A liquid metal thermal electric converter refluxing boiler with series connection of tubes and a multiple cell liquid metal thermal electric converter are also provided.

Abbin, Joseph P. (Albuquerque, NM); Andraka, Charles E. (Albuquerque, NM); Lukens, Laurance L. (Albuquerque, NM); Moreno, James B. (Albuquerque, NM)

1989-01-01

224

Relativistic harmonic oscillator revisited  

SciTech Connect

The familiar Fock space commonly used to describe the relativistic harmonic oscillator, for example, as part of string theory, is insufficient to describe all the states of the relativistic oscillator. We find that there are three different vacua leading to three disconnected Fock sectors, all constructed with the same creation-annihilation operators. These have different spacetime geometric properties as well as different algebraic symmetry properties or different quantum numbers. Two of these Fock spaces include negative norm ghosts (as in string theory), while the third one is completely free of ghosts. We discuss a gauge symmetry in a worldline theory approach that supplies appropriate constraints to remove all the ghosts from all Fock sectors of the single oscillator. The resulting ghost-free quantum spectrum in d+1 dimensions is then classified in unitary representations of the Lorentz group SO(d,1). Moreover, all states of the single oscillator put together make up a single infinite dimensional unitary representation of a hidden global symmetry SU(d,1), whose Casimir eigenvalues are computed. Possible applications of these new results in string theory and other areas of physics and mathematics are briefly mentioned.

Bars, Itzhak [Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089-2535 (United States)

2009-02-15

225

Spherical harmonics as a shape descriptor for hyperspectral image classification  

NASA Astrophysics Data System (ADS)

Hyperspectral images have traditionally been analyzed by pixel based methods. Invariant methods that consider surface and shape geometry have not been used with these images. However, there is a need for such methods due to the spectral and spatial variability present in these images. In this paper, we develop a method for classifying these images invariant to translation and rotation. The method is based on developing shape descriptors using spherical harmonics. These orthogonal functions have been widely used as a powerful tool for 3D shape recognition and are better suited for hyperspectral images due to its inherent dimensionality. A spherical function defined on the surface of a shape extracts rotation invariant features. In this case, the hyperspectral image is converted to spherical coordinates, decomposed as a sum of its harmonics and then converted to Cartesian coordinates. A classifier is trained with spherical harmonic descriptors computed from training samples. Support vector machines and Maximum Likelihood are considered for classification. The method is tested with hyperspectral image from AISA, AVIRIS and HYDICE sensors. The results show that the descriptors are effective in improving the accuracy of classification.

Nina-Paravecino, Fanny; Manian, Vidya

2010-04-01

226

Thermionic energy converters  

NASA Technical Reports Server (NTRS)

The efficiency of thermionic energy converters is improved by internal distribution of tiny sorted cesium diodes driven by the thermal gradient between the primary emitter and the collector. The tiny, sorted diode distribution comprises protrusions of the emitter material from the main emitter face which contact the main collector face thermally but not electrically. The main collector ends of the protrusions are separated from the main collector by a thin layer of insulation, such as aluminum oxide. The shorted tiny diode distribution augments cesium ionization through internal thermal effects only within the main diode. No electrical inputs are required. This ionization enhancement by the distribution of the tiny shorted diodes not only reduces the plasma voltage drop but also increases the power output and efficiency of the overall thermionic energy converter.

Morris, J. F. (inventor)

1983-01-01

227

Power electronic converter technology  

Microsoft Academic Search

The present state of the art in DC-DC, AC-DC, DC-AC, and AC-AC converter technology is presented along with their typical areas of applications. Advances made in the last decade that are finding use in industrial, commercial, and military applications are emphasized. Soft switching, in which power device switching stresses are reduced due to circuit resonances, has dominated DC-DC power conversion

ROBERT L. STEIGERWALD

2001-01-01

228

Free FLV Converter  

NSDL National Science Digital Library

Taking Flash files from the web can be a bit cumbersome, so this application will definitely be a most welcome find. This free Flash converter (the second to last link on the left) allows users to take Flash files and transfer them to formats appropriate for portable devices and other items. The site is available in both French and English and this particular version is compatible with computers running Windows 2000, XP, 2003, and Vista.

2007-01-01

229

Purplemath: Cancelling / Converting Units  

NSDL National Science Digital Library

This page contains a step-by-step tutorial in converting between units. It begins with one-step conversions, progressing to problems requiring multiple unit conversion. Areas of frequent student difficulty are given extra attention by the author, who presents the tutorial in an informal writing style designed to engage high school students. This tutorial is part of an award-winning collection of free resources developed to promote understanding and confidence in algebra.

Stapel, Elizabeth

230

Digital to synchro converter  

NASA Technical Reports Server (NTRS)

A digital-to-synchro converter is provided where a binary input code specifies a desired shaft angle and where an resolver type position transducer is employed with additional circuitry to generate a shaft position error signal indicative of the angular difference between the desired shaft angle and the actual shaft angle. The additional circuitry corrects for known and calculated errors in the shaft position detection process and equipment.

Predina, Joseph P. (Inventor)

1989-01-01

231

Luke J. Harmon Curriculum Vitae  

E-print Network

University, St. Louis, MO Ph. D. in Evolution, Ecology, and Population Biology Advisor: Dr. Jonathan Losos in action examined over a phylogeny" (co-PI Joe Felsenstein; total $132,794, Harmon lab budget $65,306) 2009

Harmon, Luke

232

Second harmonic generation in potassium niobate thin films  

Microsoft Academic Search

Green light produced by second harmonic generation has been observed in an epitaxial orthorhombic KNbO3 thin film planar waveguide produced by ion-beam sputter deposition on a (100)-oriented MgO single crystal substrate. A Nd:YLF laser beam, with a wavelength of 1.053 ?m and ?80 ps, 100 MHz pulses under mode-locked operation, was coupled into the waveguide using a rutile prism, and

A. F. Chow; D. J. Lichtenwalner; O. Auciello; A. I. Kingon; J. R. Busch; V. E. Wood

1995-01-01

233

Second-harmonic imaging of ferroelectric domain walls  

Microsoft Academic Search

Domain walls in periodically poled ferroelectric KTiOPO4 and LiNbO3 crystals are observed by making use of second-harmonic (SH) generation enhancement in the transition regions between neighboring domains. SH images of domain walls obtained with various samples for different polarization configurations are presented. The SH generation enhancement is found especially pronounced for the polarization of the SH radiation being perpendicular to

Sergey I. Bozhevolnyi; Jørn M. Hvam; Kjeld Pedersen; Fredrik Laurell; Kan; Torben Skettrup; Michele Belmonte

1998-01-01

234

Multilevel converters -- A new breed of power converters  

SciTech Connect

Multilevel voltage source converters are emerging as a new breed of power converter options for high-power applications. The multilevel voltage source converters typically synthesize the staircase voltage wave from several levels of dc capacitor voltages. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. The techniques to balance the voltage between different levels normally involve voltage clamping or capacitor charge control. There are several ways of implementing voltage balance in multilevel converters. Without considering the traditional magnetic coupled converters, this paper presents three recently developed multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded-inverters with separate dc sources. The operating principle, features, constraints, and potential applications of these converters will be discussed.

Lai, J.S. [Oak Ridge National Lab., TN (United States). Div. of Engineering Technology; Peng, F.Z. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Electrical and Computer Engineering

1996-05-01

235

Multilevel converters -- A new breed of power converters  

SciTech Connect

Multilevel voltage source converters are emerging as a new breed of power converter options for high-power applications. The multilevel voltage source converters typically synthesize the staircase voltage wave from several levels of dc capacitor voltages. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. The techniques to balance the voltage between different levels normally involve voltage clamping or capacitor charge control. There are several ways of implementing voltage balance in multilevel converters. Without considering the traditional magnetic coupled converters, this paper presents three recently developed multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded-inverters with separate dc sources. The operating principle, features, constraints, and potential applications of these converters will be discussed.

Lai, J.S. [Oak Ridge National Lab., TN (United States). Engineering Technology Div.; Peng, F.Z. [Univ. of Tennessee, Knoxville, TN (United States)]|[Oak Ridge National Lab., TN (United States)

1995-09-01

236

Helical harmonics for static fields.  

PubMed

Helical harmonic solutions of Laplace's equation are derived using a right-handed nonorthogonal helical coordinate system and a modified separation of variables technique. Unlike the Cartesian or cylindrical coordinate systems, in the helical system, two different sets of solutions are admitted, one right handed and one left handed. Consequently, the helical harmonics are used to solve the boundary value problem of two nested helices with different radii set to different potential values. PMID:11580458

Overfelt, P L

2001-09-01

237

Echo-Enabled Harmonic Generation  

SciTech Connect

A recently proposed concept of the Echo-Enabled Harmonic Generation (EEHG) FEL uses two laser modulators in combination with two dispersion sections to generate a high-harmonic density modulation in a relativistic beam. This seeding technique holds promise of a one-stage soft x-ray FEL that radiates not only transversely but also longitudinally coherent pulses. Currently, an experimental verification of the concept is being conducted at the SLAC National Accelerator Laboratory aimed at the demonstration of the EEHG.

Stupakov, Gennady; /SLAC

2012-06-28

238

Real-time incoherent-to-coherent optical converter  

NASA Technical Reports Server (NTRS)

Description of a real-time incoherent-to-coherent optical converter designed for application in image processing systems. The converter utilizes the photoconductivity effect of the compound Bi(12)SiO(20) for spatial modulation of electrical polarization in the compound. An optically absorbed write-in image is stored as an image polarization pattern in the device. Readout is effectuated electrooptically by using phase retardation in a polarized coherent light beam during the passage through the crystal. The operating mode required for achieving continuous image conversion with a high-speed recyclability is discussed. The performance characteristics of the converter are given and the fabrication technology is described.

Vohl, P.; Nisenson, P.; Oliver, D. S.

1973-01-01

239

Three-Phase Phase-Locked Loop Control of a New Generation Power Converter  

Microsoft Academic Search

This paper describes the development of a new generation of power converter, used to power telecommunications equipment. A telecommunications converter must comply with the psophometric noise standard CCIF-1951 and the IEC1000-3-2 harmonic standard. While the IEC1000-3-2 standard is easily met with active power factor correction techniques, a high degree of effort is usually required to meet with the psophometric standard.

W. Phipps; M. J. Harrison; R. M. Duke

2006-01-01

240

Implementation of a controlled rectifier using AC-AC matrix converter theory  

Microsoft Academic Search

It is well known that a PWM-controlled rectifier can offer advantages of reduced low-order harmonics and unity input power factor when compared to a conventional thyristor converter. However, theoretically optimum PWM strategies are often difficult to implement physically or are not easily extended to regenerative operation. The authors propose an alternative PWM strategy based on AC-AC matrix converter theory, which

Donald G. Holmes; Thomas A. Lipo

1992-01-01

241

Grid-side converter control of DFIG wind turbines to enhance power quality of distribution network  

Microsoft Academic Search

A doubly fed induction generator wind turbine (DFIG-WT) with FACTS capabilities is presented. It is suggested to make use of the grid-side converter as a shunt active filter in order to support the grid with power factor correction as well as harmonic compensation. A vector control scheme is used to control the grid-side converter with a priority level feature to

E. Tremblay; A. Chandra; P. J. Lagace

2006-01-01

242

Theory and optical implementation of the geometrical approach of multiple circular harmonic filters  

NASA Astrophysics Data System (ADS)

The circular harmonic filter contains only one component of the image. Its discrimination capability has been questionable. The geometrical approach of multiple circular harmonic filters uses relative locations of the correlation peaks as the rotation-, shift-, and intensity-invariant features for pattern recognition. Each feature depends on the entire image. This approach has a good discrimination capability. Optical real-time implementation of the on-axis continuous phase-only circular harmonic filters by the use of a commercial liquid-crystal television is shown. A harmonic analysis shows that the phase-mostly filter can tolerate coupled amplitude modulation at the acceptable expense of the output signal-to-noise ratio. An optical experiment of the geometrical approach of multiple circular harmonic filters for a multiple-image input is described. The cross-correlation peaks between the individual filters and the clutter are eliminated, because they are not in good locations.

Shen, Lixin; Sheng, Yunlong; Prémont, Guy

1995-07-01

243

Analysis of harmonic transfer in an AC excited generator including speed ripple  

Microsoft Academic Search

AC excited generators are favoured in some applications due to their features including generation at a constant frequency but a variable speed. With the rotor windings supplied from a static power electronic converter, harmonics are one of the major concerns in such systems. Based on a mathematical model of the AC excited machine, a method is developed to analyze the

Y. Liao; D. Xiang; L. Ran; G. A. Putrus

2002-01-01

244

Crystal Notes The Crystal  

E-print Network

Crystal Notes The Crystal The crystal is defined as an ordered set of atoms (molecules) arranged. Ordered crystals exist because in their formation they must disorder their surroundings more than they are ordered. The key to growing a crystal is to cause in the disorder of the surroundings to be more than

Meagher, Mary

245

Using the self-filtering property of a femtosecond filament to improve second harmonic generation.  

PubMed

In this paper we demonstrate the use of NIR femtosecond filament for improving the generation of second harmonic using a type I BBO crystal. Using this method the beam propagation factor (M(2)) of the second harmonic was improved significantly; which led to enhancement of the attainable SH intensity by up to two orders of magnitude. This method can be beneficial for applications demanding high intensities, small spot size or long interaction lengths. PMID:19365469

Shwa, David; Eisenmann, Shmuel; Marcus, Gilad; Zigler, Arie

2009-04-13

246

Relation of squeezed states between damped harmonic and simple harmonic oscillators  

NASA Technical Reports Server (NTRS)

The minimum uncertainty and other relations are evaluated in the framework of the coherent states of the damped harmonic oscillator. It is shown that the coherent states of the damped harmonic oscillator are the squeezed coherent states of the simple harmonic oscillator. The unitary operator is also constructed, and this connects coherent states with damped harmonic and simple harmonic oscillators.

Um, Chung-In; Yeon, Kyu-Hwang; George, Thomas F.; Pandey, Lakshmi N.

1993-01-01

247

Conversion of the 'Iskra-5' iodine laser to second-harmonic operating mode  

SciTech Connect

The conversion of the 'Iskra-5' iodine laser to the regime of fusion target irradiation by second harmonic radiation at 657.5 nm is reported. The laser upgrading enabled obtaining from 12 channels a total second-harmonic energy yield of 2.5 kJ, which corresponds to an output power of 5 TW. The conversion efficiency was equal to {approx}50% in experiments with DKDP crystals with an aperture of 35 cm. A series of 12-channel experiments was conducted involving second-harmonic irradiation of microtargets. (lasers)

Annenkov, V I; Vinogradskiy, L M; Gaidash, V A; Galakhov, I V; Garanin, Sergey G; Zhidkov, N V; Zubkov, A V; Kalipanov, S V; Kargin, V A; Kirillov, G A; Kovalenko, V P; Kochemasov, G G; Kravchenko, A G; Krotov, V A; Lazarchuk, V P; Lapin, S G [Institute of Laser Physics Research, Russian Federal Nuclear Center 'All-Russian Scientific Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod region (Russian Federation); Bespalov, V I; Bredikhin, V I; Ershov, V P; Zil'berberg, V V [Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

2005-11-30

248

Low pressure solar thermal converter  

Microsoft Academic Search

The current development of solar power converters with air as working fluid focuses mostly on concentrating collectors combined with hot-air engines, and on very low temperature solar tower concepts. Whilst concentrating collectors and Stirling engines need complex technology, solar tower converters have very low efficiencies and require large installations. Pressurized containers as energy converters offer the advantage of simplicity, but

Gerald Muller

249

164 Currencies Converter  

NSDL National Science Digital Library

Olsen and Associates of Zurich, Switzerland, a "developer of online forecasting technology for business and finance" has made this simple and fun service available. Simply enter the amount of currency for any of 164 currencies, the currency to be converted to, and the date of the exchange rate (back to January 1, 1990, in day/month/year format) into an online form, and presto, an exchange rate (which is then reversible) is obtained. As this is a demonstration product, neither multiple currencies nor multiple dates are allowed. Users should also read the FAQ to understand why the rate they get might be slightly different from the one their bank advertises.

1997-01-01

250

Universal Currency Converter  

NSDL National Science Digital Library

The Universal Currency Converter site was developed by Xenon Laboratories. It provides currency conversion for most of the currencies in the world. The conversion rates for the currency are provided by The Bank of Montreal's Treasury Group. Visitors can also obtain a currency table for a selected base currency. The site also provides prices for silver, gold and platinum in the various currencies. Visitors can sign-up for the Currency Update Service which provides free currency table updates specified in the user-selected base currency once every business day.

1998-01-01

251

Cycloidal Wave Energy Converter  

SciTech Connect

This program allowed further advancing the development of a novel type of wave energy converter, a Cycloidal Wave Energy Converter or CycWEC. A CycWEC consists of one or more hydrofoils rotating around a central shaft, and operates fully submerged beneath the water surface. It operates under feedback control sensing the incoming waves, and converts wave power to shaft power directly without any intermediate power take off system. Previous research consisting of numerical simulations and two dimensional small 1:300 scale wave flume experiments had indicated wave cancellation efficiencies beyond 95%. The present work was centered on construction and testing of a 1:10 scale model and conducting two testing campaigns in a three dimensional wave basin. These experiments allowed for the first time for direct measurement of electrical power generated as well as the interaction of the CycWEC in a three dimensional environment. The Atargis team successfully conducted two testing campaigns at the Texas A&M Offshore Technology Research Center and was able to demonstrate electricity generation. In addition, three dimensional wave diffraction results show the ability to achieve wave focusing, thus increasing the amount of wave power that can be extracted beyond what was expected from earlier two dimensional investigations. Numerical results showed wave cancellation efficiencies for irregular waves to be on par with results for regular waves over a wide range of wave lengths. Using the results from previous simulations and experiments a full scale prototype was designed and its performance in a North Atlantic wave climate of average 30kW/m of wave crest was estimated. A full scale WEC with a blade span of 150m will deliver a design power of 5MW at an estimated levelized cost of energy (LCOE) in the range of 10-17 US cents per kWh. Based on the new results achieved in the 1:10 scale experiments these estimates appear conservative and the likely performance at full scale will exceed this initial performance estimates. In advancing the Technology Readiness Level (TRL) of this type of wave energy converter from 3 to 4, we find the CycWEC to exceed our initial estimates in terms of hydrodynamic performance. Once fully developed and optimized, it has the potential to not just outperform all other WEC technologies, but to also deliver power at a lower LCOE than competing conventional renewables like wind and solar. Given the large wave power resource both domestically and internationally, this technology has the potential to lead to a large improvement in our ability to produce clean electricity at affordable cost.

Stefan G. Siegel, Ph.D.

2012-11-30

252

Bidirectional buck boost converter  

DOEpatents

A bidirectional buck boost converter and method of operating the same allows regulation of power flow between first and second voltage sources in which the voltage level at each source is subject to change and power flow is independent of relative voltage levels. In one embodiment, the converter is designed for hard switching while another embodiment implements soft switching of the switching devices. In both embodiments, first and second switching devices are serially coupled between a relatively positive terminal and a relatively negative terminal of a first voltage source with third and fourth switching devices serially coupled between a relatively positive terminal and a relatively negative terminal of a second voltage source. A free-wheeling diode is coupled, respectively, in parallel opposition with respective ones of the switching devices. An inductor is coupled between a junction of the first and second switching devices and a junction of the third and fourth switching devices. Gating pulses supplied by a gating circuit selectively enable operation of the switching devices for transferring power between the voltage sources. In the second embodiment, each switching device is shunted by a capacitor and the switching devices are operated when voltage across the device is substantially zero.

Esser, Albert Andreas Maria (Niskayuna, NY)

1998-03-31

253

Gallium phosphide energy converters  

NASA Technical Reports Server (NTRS)

Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need for thermal dissipation. Results are presented for GaP direct conversion devices powered by Ni-63 and compared to the conversion of light emitted by tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp -17) A/sq cm have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. Temperature dependent IV, QE, R(sub sh), and V(sub oc) results are also presented. These data are used to predict the high-temperature solar cell and betacell performance of GaP devices and suggest appropriate applications for the deployment of this technology.

Sims, P. E.; Dinetta, L. C.; Goetz, M. A.

1995-01-01

254

Gallium phosphide energy converters  

SciTech Connect

Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need for thermal dissipation. Results are presented for GaP direct conversion devices powered by Ni-63 and compared to the conversion of light emitted by tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp {minus}17) A/sq cm have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. Temperature dependent IV, QE, R(sub sh), and V(sub oc) results are also presented. These data are used to predict the high-temperature solar cell and betacell performance of GaP devices and suggest appropriate applications for the deployment of this technology.

Sims, P.E.; Dinetta, L.C.; Goetz, M.A.

1995-10-01

255

Gallium phosphide energy converters  

NASA Astrophysics Data System (ADS)

Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need for thermal dissipation. Results are presented for GaP direct conversion devices powered by Ni-63 and compared to the conversion of light emitted by tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp -17) A/sq cm have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. Temperature dependent IV, QE, R(sub sh), and V(sub oc) results are also presented. These data are used to predict the high-temperature solar cell and betacell performance of GaP devices and suggest appropriate applications for the deployment of this technology.

Sims, P. E.; Dinetta, L. C.; Goetz, M. A.

1995-10-01

256

Frequency Doubling Broadband Light in Multiple Crystals  

SciTech Connect

The authors compare frequency doubling of broadband light in a single nonlinear crystal with doubling in five crystals with intercrystal temporal walk off compensation, and with doubling in five crystals adjusted for offset phase matching frequencies. Using a plane-wave, dispersive numerical model of frequency doubling they study the bandwidth of the second harmonic and the conversion efficiency as functions of crystal length and fundamental irradiance. For low irradiance the offset phase matching arrangement has lower efficiency than a single crystal of the same total length but gives a broader second harmonic bandwidth. The walk off compensated arrangement gives both higher conversion efficiency and broader bandwidth than a single crystal. At high irradiance, both multicrystal arrangements improve on the single crystal efficiency while maintaining broad bandwidth.

ALFORD,WILLIAM J.; SMITH,ARLEE V.

2000-07-26

257

Multilevel hysteresis controller of the novel seven-level packed U cells converter  

Microsoft Academic Search

In this paper, authors propose a six-band hysteresis vector controller based on the seven level packed U cells (PUC) converter to alleviate harmonics contents of stator voltages and currents of the induction machine. Active and passive filters rating can thus be significantly reduced resulting on a high energetic efficiency and a reduced installation cost. The PUC topology was first introduced

Y. Ounejjar; K. Al-Haddad

2010-01-01

258

Direct Space Vector PWM Strategies for Three-Phase to Three-Phase Matrix Converter  

Microsoft Academic Search

This paper proposes 3 types of new direct space vector modulation methods for three-phase to three-phase matrix converters. The space vector modulation method allows a direct understanding of switching patterns and their characteristics from the viewpoint of analysis and control. Output voltage harmonics and switching losses can be reduced across the entire voltage region by making use of the direct

Y. Tadano; S. Urushibata; M. Nomura; Y. Sato; M. Ishida

2007-01-01

259

Multilevel converters for single-phase grid connected photovoltaic systems-an overview  

Microsoft Academic Search

Multilevel voltage source inverters offer several advantages compared to their conventional counterparts. By synthesising the AC output terminal voltage from several levels of voltages, staircase waveforms can be produced, which approach the sinusoidal waveform with low harmonic distortion, thus reducing filter requirements. The need of several sources on the DC side of the converter makes multilevel technology attractive for photovoltaic

M. Calais; V. G. Agelidis

1998-01-01

260

Virtual stage pulse-width modulation technique for multilevel inverter\\/converter  

Microsoft Academic Search

The main theme of this paper is to present a new pulse-width modulation (PWM) technique for multilevel inverter\\/converter control, which provides more degrees of freedom for specifying the cost function than that for step modulation technique, for a given hardware. Therefore, the presented technique eliminates more specified low order harmonics without resorting to the increase of hardware. In comparison with

Fu-San Shyu; Yen-Shin Lai

2002-01-01

261

Radiating dipoles in photonic crystals  

PubMed

The radiation dynamics of a dipole antenna embedded in a photonic crystal are modeled by an initially excited harmonic oscillator coupled to a non-Markovian bath of harmonic oscillators representing the colored electromagnetic vacuum within the crystal. Realistic coupling constants based on the natural modes of the photonic crystal, i.e., Bloch waves and their associated dispersion relation, are derived. For simple model systems, well-known results such as decay times and emission spectra are reproduced. This approach enables direct incorporation of realistic band structure computations into studies of radiative emission from atoms and molecules within photonic crystals. We therefore provide a predictive and interpretative tool for experiments in both the microwave and optical regimes. PMID:11088954

Busch; Vats; John; Sanders

2000-09-01

262

Harmonic nanoparticles for regenerative research.  

PubMed

In this visualized experiment, protocol details are provided for in vitro labeling of human embryonic stem cells (hESC) with second harmonic generation nanoparticles (HNPs). The latter are a new family of probes recently introduced for labeling biological samples for multi-photon imaging. HNPs are capable of doubling the frequency of excitation light by the nonlinear optical process of second harmonic generation with no restriction on the excitation wavelength. Multi-photon based methodologies for hESC differentiation into cardiac clusters (maintained as long term air-liquid cultures) are presented in detail. In particular, evidence on how to maximize the intense second harmonic (SH) emission of isolated HNPs during 3D monitoring of beating cardiac tissue in 3D is shown. The analysis of the resulting images to retrieve 3D displacement patterns is also detailed. PMID:24836220

Ronzoni, Flavio; Magouroux, Thibaud; Vernet, Remi; Extermann, Jérôme; Crotty, Darragh; Prina-Mello, Adriele; Ciepielewski, Daniel; Volkov, Yuri; Bonacina, Luigi; Wolf, Jean-Pierre; Jaconi, Marisa

2014-01-01

263

Second harmonic generation of optical ellipse fields  

NASA Astrophysics Data System (ADS)

Frequency doubling of polarization singularities is studied for elliptically polarized light. Phase matching requirements are briefly considered for birefringent and for periodic structures, while non-phase matched second harmonic generation (SHG) is discussed in detail. General expressions are presented for all the symmetry classes of uniaxial crystals for propagation parallel and perpendicular to the optic axis. For propagation parallel to the optic axis, the critical points of ellipse fields transform under SHG as follows: The singularity indices of all C-points (isolated points of circular polarization) are doubled in magnitude and reversed in sign. Also the handedness (right/left) of all C-points, as well as of all other regions of the ellipse field, are reversed. All azimuthal maxima become minima, and vice versa, and directions of steepest ascent and descent of all azimuthal saddle points are interchanged. All L-lines (lines of linear polarization) are preserved unchanged, and no new L-lines are produced. Similar results are found for linearly polarized vector fields, and the winding numbers (topological charges) of the point singularities of these fields are doubled in magnitude and reversed in sign. SHG for propagation perpendicular to the optic axis depends sensitively on dispersion, birefringence, and crystal thickness, and is found to give rise to a host of peculiar effects, including the generation of "dark" polarization singularities.

Freund, Isaac

2002-11-01

264

Thermionic converters with microcavity electrodes in the cesium arc regime  

Microsoft Academic Search

The volt-ampere characteristics of thermionic converters with microcavity electrodes are investigated theoretically and experimentally. A mathematical model is presented which makes it possible to analyze plasma parameter distribution in thermionic conversion systems of this kind. It is shown that cathodes with a microcavity surface structure have better emission properties than smooth cathodes of single-crystal tungsten with a vacuum output energy

V. D. Atamasov; N. A. Ivanova

1990-01-01

265

Simple Harmonic Oscillator JS Model  

NSDL National Science Digital Library

The Simple Harmonic Oscillator JS Model displays the dynamics of a ball attached to an ideal spring. The spring is initially stretched and the ball has zero initial velocity. The initial position of the ball can be changed by click-dragging the ball when the simulation is paused. The Simple Harmonic Oscillator JS Model was developed using the Easy Java/JavaScript Simulations (EjsS) version 5. It is distributed as a ready-to-run html page and requires only a browser with JavaScript support. This model runs on tablets.

Christian, Wolfgang; Franciscouembre

2014-01-01

266

Radially polarized annular beam generated through a second-harmonic-generation process.  

PubMed

A radially polarized beam with an annular intensity pattern was generated through a second-harmonic-generation process by focusing an azimuthally polarized Ti:sapphire pulsed laser beam to a c-cut beta-barium borate (BBO) crystal. The annular intensity pattern of the second-harmonic wave had a nearly sixfold symmetry as a result of the nonlinear susceptibility tensor of the BBO crystal. The width of the annulus was as narrow as less than 1/40th of its radius. PMID:19838261

Sato, Shunichi; Kozawa, Yuichi

2009-10-15

267

Simple method of detecting ferroelectric domains with non-phase-matched second-harmonic generation  

SciTech Connect

We demonstrate a new method of detecting the presence of ferroelectric domains based on non-phase-matched second-harmonic generation. If a domain boundary is tilted relative to the input and output faces of the crystal, the far-field second-harmonic light consists of multiple beams, in contrast to the single beam generated in a single-domain crystal. The angular separation of the beams provide a measure of the tilt of the domain wall if the refractive-index difference n{sub 2{omega}}{minus}n{sub {omega}} is known. {copyright} 1998 Optical Society of America

Gehr, R.J.; Alford, W.J.; Smith, A.V. [Department of Lasers, Optics, and Remote Sensing, Sandia National Laboratories, Albuquerque, New Mexico 87185-1423 (United States)

1998-05-01

268

Resistive anode image converter  

NASA Technical Reports Server (NTRS)

The invention of an apparatus for imaging soft X-ray and ultraviolet electromagnetic radiation and charged particles was described. The apparatus includes a pair of microchannel electron multiplier plates connected in a cascaded chevron configuration which intercepts an incident beam of radiation or charged particles. Incident photons or charged particles strike the front surface of the chevron configuration causing emission of electrons. The electrons are accelerated by a voltage gradient and strike the inner side walls of the individual channels, causing emission of secondary electrons. Accelerated and multiplied secondary electrons impinge upon a resistive anode after they transverse the chevron configuration. A pulse position circuit converts the magnitude or transit time of the currents flowing from the point of impact of the electrons on the resistive anode to four contact electrodes mounted on their periphery of the resistive anode into the spatial coordinates of electron impact.

Lampton, M. L.; Paresce, F. (inventors)

1976-01-01

269

Electromagnetic wave energy converter  

NASA Technical Reports Server (NTRS)

Electromagnetic wave energy is converted into electric power with an array of mutually insulated electromagnetic wave absorber elements each responsive to an electric field component of the wave as it impinges thereon. Each element includes a portion tapered in the direction of wave propagation to provide a relatively wideband response spectrum. Each element includes an output for deriving a voltage replica of the electric field variations intercepted by it. Adjacent elements are positioned relative to each other so that an electric field subsists between adjacent elements in response to the impinging wave. The electric field results in a voltage difference between adjacent elements that is fed to a rectifier to derive dc output power.

Bailey, R. L. (inventor)

1973-01-01

270

Positron Source Using Channeling with a Granular Converter  

NASA Astrophysics Data System (ADS)

A new kind of positron source is presented. It uses the intense radiation emitted by channeled electrons in axially oriented crystals to generate positrons in a granular amorphous converter. A distance of 2 meters between the crystal radiator and the amorphous converter is used to put a bending magnet which sweeps off the charged particles allowing only to the photons to hit the converter. The simulation results on photon production, and positron generation are reported. A particular attention is brought to the energy deposition and Peak Energy Deposition Density (PEDD) in the targets. Emphasis is put on the problems of heating, cooling and on different methods and devices to handle the power dissipation in the targets. An application for the case of ILC (International Linear Collider) is worked out.

Sievers, P.; Xu, C.; Chehab, R.; Artru, X.; Chevallier, M.; Dadoun, O.; Pei, G.; Strakhovenko, V. M.; Variola, A.

2013-10-01

271

Harmonic Phasors and Fourier Series  

NSDL National Science Digital Library

This resource from Johns Hopkins University has audio and interactive components. Various forms of the Fourier series description for periodic signals are based on alternate ways of writing a cosine signal. This resource goes over Phasors, Phasor Sums, Harmonic Phasor Sums, Gibbs Effect, Windowing, Fejer Window, and Hamming Window.

2012-07-13

272

Foliated stochastic calculus: Harmonic measures  

Microsoft Academic Search

In this article we present an intrinsec construction of foliated Brownian motion via stochastic calculus adapted to foliation. The stochastic approach together with a proposed foliated vector calculus provide a natural method to work on harmonic measures. Other results include a decomposition of the Laplacian in terms of the foliated and basic Laplacians, a characterization of totally invariant measures and

Pedro J. Catuogno; Diego S. Ledesma; Paulo R. Ruffino

2010-01-01

273

Agglomeration, Integration and Tax Harmonization  

Microsoft Academic Search

This paper considers tax competition and tax harmonization in the presence of agglomeration forces and falling trade costs. With agglomerative forces operating, industry is not indifferent to location in equilibrium, so perfectly mobile capital becomes a quasi-fixed factor. This suggests that the tax game is something subtler than a race to the bottom. Advanced 'core' nations may act like limit-pricing

2001-01-01

274

Agglomeration, Integration and Tax Harmonization  

Microsoft Academic Search

This Paper considers tax competition and tax harmonization in the presence of agglomeration forces and falling trade costs. With agglomerative forces operating, industry is not indifferent to location in equilibrium, so perfectly mobile capital becomes a quasi-fixed factor. This suggests that the tax game is something subtler than a race to the bottom. Advanced 'core' nations may act like limit-pricing

Richard E. Baldwin; Paul Krugman

2000-01-01

275

Covariant harmonic oscillators: 1973 revisited  

NASA Technical Reports Server (NTRS)

Using the relativistic harmonic oscillator, a physical basis is given to the phenomenological wave function of Yukawa which is covariant and normalizable. It is shown that this wave function can be interpreted in terms of the unitary irreducible representations of the Poincare group. The transformation properties of these covariant wave functions are also demonstrated.

Noz, M. E.

1993-01-01

276

Web Assignments: Harmonic Oscillator I  

NSDL National Science Digital Library

This student activity uses a Java applet to show the relationship between simple harmonic motion and constant velocity circular motion. The applet is broken into three major parts. The first shows a particle undergoing circular motion at a constant rate. The second shows the same particle on a vertical spring. Finally, the third plots the time evolution of the system, resulting in a sine wave. Instructions for using the applet, which is in Spanish, are included. The applet includes several questions relating to the applet and the physics of harmonic motion. This is part of a larger collection of applet-based learning activities.This student activity uses a Java applet to show the relationship between simple harmonic motion and constant circular motion. The applet is broken into three major parts. The first shows a particle undergoing circular motion at a constant rate. The second shows the same particle on a vertical spring. Finally, the third plots the time evolution of the system -- the result is a sine wave. The amplitude, frequency, and initial phase of the harmonic motion can be changed by typing in new values in the "Amplitud", "Frequencia", and "Fase Inicial" text windows, respectively. To start the applet, press the "Empiaza" button. To pause the motion, press "Pausa," and to stop the applet press "Paso." The user is asked to answer several questions relating to the applet. This is part of a larger collection of applet-based learning activities.

Walkup, John

2008-11-23

277

Harmonization of company taxation systems  

Microsoft Academic Search

The author of the following article gives a survey of the different corporation tax systems and rates in the individual EC-member\\u000a countries, explains the need for a harmonization of direct company taxation within the Community, and discusses the Commission’s\\u000a recent proposal as compared with other possible approaches.

Heinrich Hölzler

1976-01-01

278

Standing Waves: Harmonics and Patterns  

NSDL National Science Digital Library

This high school physics tutorial provides an introduction to standing waves. The site contains a description of such waves and related features such as nodes, antinodes, and interference. The site presents several simulations that demonstrate harmonics and their associated wave patterns.

Henderson, Tom

2010-08-27

279

Lasing on the third harmonic  

SciTech Connect

The Los Alamos Free-Electron Laser has recently lased near 4 {mu}m on the third harmonic of the fundamental frequency of about 12 {mu}m. By choice of intercavity apertures and cavity length, lasing can be forced to occur on both frequencies simultaneously or on either one alone. 8 refs., 3 figs., 1 tab.

Warren, R.W.; Haynes, L.C.; Feldman, D.W.; Stein, W.E.; Gitomer, S.J.

1989-01-01

280

Harmonic resolution as a holographic quantum number  

SciTech Connect

The Bekenstein bound takes the holographic principle into the realm of flat space, promising new insights on the relation of non-gravitational physics to quantum gravity. This makes it important to obtain a precise formulation of the bound. Conventionally, one specifies two macroscopic quantities, mass and spatial width, which cannot be simultaneously diagonalized. Thus, the counting of compatible states is not sharply defined. The resolution of this and other formal difficulties leads naturally to a definition in terms of discretized light-cone quantization. In this form, the area difference specified in the covariant bound converts to a single quantum number, the harmonic resolution K. The Bekenstein bound then states that the Fock space sector with K units of longitudinal momentum contains no more than exp(2 pi^2 K) independent discrete states. This conjecture can be tested unambiguously for a given Lagrangian, and it appears to hold true for realistic field theories, including models arising from string compactifications. For large K, it makes contact with more conventional but less well-defined formulations.

Bousso, Raphael

2004-01-31

281

Design, analysis and limitations of a DC-to-AC converter usable for interface alternative energy sources and energy storage systems with the utility grid  

Microsoft Academic Search

A DC-AC power converter design that can be used to interface any type of alternative energy source or energy storage system with the utility grid is presented. The converter is capable of real and reactive power exchanges between the utility grid and the alternative energy source(s). The control philosophy is very simple and allows for the synthesis of useful harmonics.

Ashim K. Chakravorti; Alexander E. Emanuel

1993-01-01

282

Harmonic ratcheting for fast acceleration  

NASA Astrophysics Data System (ADS)

A major challenge in the design of rf cavities for the acceleration of medium-energy charged ions is the need to rapidly sweep the radio frequency over a large range. From low-power medical synchrotrons to high-power accelerator driven subcritical reactor systems, and from fixed focus alternating gradient accelerators to rapid cycling synchrotrons, there is a strong need for more efficient, and faster, acceleration of protons and light ions in the semirelativistic range of hundreds of MeV/u. A conventional way to achieve a large, rapid frequency sweep (perhaps over a range of a factor of 6) is to use custom-designed ferrite-loaded cavities. Ferrite rings enable the precise tuning of the resonant frequency of a cavity, through the control of the incremental permeability that is possible by introducing a pseudoconstant azimuthal magnetic field. However, rapid changes over large permeability ranges incur anomalous behavior such as the "Q-loss" and "f-dot" loss phenomena that limit performance while requiring high bias currents. Notwithstanding the incomplete understanding of these phenomena, they can be ameliorated by introducing a "harmonic ratcheting" acceleration scheme in which two or more rf cavities take turns accelerating the beam—one turns on when the other turns off, at different harmonics—so that the radio frequency can be constrained to remain in a smaller range. Harmonic ratcheting also has straightforward performance advantages, depending on the particular parameter set at hand. In some typical cases it is possible to halve the length of the cavities, or to double the effective gap voltage, or to double the repetition rate. This paper discusses and quantifies the advantages of harmonic ratcheting in general. Simulation results for the particular case of a rapid cycling medical synchrotron ratcheting from harmonic number 9 to 2 show that stability and performance criteria are met even when realistic engineering details are taken into consideration.

Cook, N.; Brennan, J. M.; Peggs, S.

2014-04-01

283

Harmonic generation from indium-rich plasmas  

SciTech Connect

An experimental study of high-order harmonic generation in In, InSb, InP, and InGaP plasmas using femtosecond laser radiation with variable chirp is presented. Intensity enhancement of the 13th and 21st harmonics compared to the neighboring harmonics by a factor of 200 and 10, respectively, is observed. It is shown that the harmonic spectrum from indium-containing plasma plumes can be considerably modified by controlling the chirp of the driving laser pulse.

Ganeev, R. A.; Kulagin, I. A. [Akadempribor Scientific Association, Academy of Sciences of Uzbekistan, Tashkent 700125 (Uzbekistan); Singhal, H.; Naik, P. A.; Arora, V.; Chakravarty, U.; Chakera, J. A.; Khan, R. A.; Raghuramaiah, M.; Gupta, P. D. [Laser Plasma Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Redkin, P. V. [Samarkand State University, Samarkand 703004 (Uzbekistan)

2006-12-15

284

A multilevel converter-based universal power conditioner  

SciTech Connect

This paper presents the development of a control scheme for a multilevel diode-clamped converter connected in a series-parallel fashion to the electrical system such that it can compensate for deviations in utility voltage (sag, surge, and unbalance) and act as a harmonic and/or reactive current source for a load. New carrier-based multilevel pulsewidth modulation techniques are identified to maximize switch utilization of the two back-to-back diode-clamped inverters that constitute the universal power conditioner. An experimental verification for a six-level power conditioner is given.

Tolbert, L.M.; Peng, F.Z.; Habetler, T.G.

2000-04-01

285

Pulsed thermionic converter study  

NASA Technical Reports Server (NTRS)

A nuclear electric propulsion concept using a thermionic reactor inductively coupled to a magnetoplasmadynamic accelerator (MPD arc jet) is described, and the results of preliminary analyses are presented. In this system, the MPD thruster operates intermittently at higher voltages and power levels than the thermionic generating unit. A typical thrust pulse from the MPD arc jet is characterized by power levels of 1 to 4 MWe, a duration of 1 msec, and a duty cycle of approximately 20%. The thermionic generating unit operates continuously but with a lower power level of approximately 0.4 MWe. Energy storage between thrust pulses is provided by building up a large current in an inductor using the output of the thermionic converter array. Periodically, the charging current is interrupted, and the energy stored in the magnetic field of the inductor is utilized for a short duration thrust pulse. The results of the preliminary analysis show that a coupling effectiveness of approximately 85 to 90% is feasible for a nominal 400 KWe system with an inductive unit suitable for a flight vehicle.

1976-01-01

286

Indian Converts Collection  

NSDL National Science Digital Library

First published in 1727, the remarkable book "Indian Converts, or Some account of the lives and dying speeches of a considerable number of the Christianized Indians of Martha's Vineyard" is now available in full online. Written by Experience Mayhew, the book provides remarkable insights into the lives and culture of four generations of Native Americans in colonial America. This digitized version was created at Reed College, and visitors can look through all four sections of the work, which include "Indian Ministers" and "Pious Children." Throughout the work, Mayhew details the books that different age groups were reading, provides insights into early New England pedagogy and childrearing practices, and also describes each individual in terms of their own genealogy and personal history. The truly fantastic thing about the site is that it also contains an archive with over 600 images and documents that further contextualize the work. Also, the site contains study guides designed for classroom use that cover artifact analysis, genealogy, and reading gravestones.

287

Cost-effective segmented scintillating converters for hard x rays  

NASA Astrophysics Data System (ADS)

Thick segmented scintillating converters coupled to optical imaging detectors offer the advantage of large area, high stopping power sensors for high energy x-ray digital imaging. The recent advent of high resolution and solid state optical sensors such as amorphous silicon arrays and CCD optical imaging detectors makes it feasible to build large, cost effective imaging arrays. This technology, however, shifts the sensor cost burden to the segmented scintillators needed for imaging. The required labor intensive fabrication of high resolution, large area hard x- ray converters results in high cost and questionable manufacturability on a large scale. We report on recent research of a new segmented x-ray imaging converter. This converter is fabricated using vacuum injection and crystal growth methods to induce defect free, high density scintillating fibers into a collimator matrix. This method has the potential to fabricate large area, thick segmented scintillators. Spatial resolution calculations of these scintillator injected collimators show that the optical light spreading is significantly reduced compared to single crystalline scintillators and sub-millimeter resolution x- ray images acquired with the segmented converter coupled to a cooled CCD camera provided the resolution to characterize the converter efficiency and noise. The proposed concept overcomes the above mentioned limitations by producing a cost-effective technique of fabricating large area x-ray scintillator converters with high stopping power and high spatial resolution. This technology will readily benefit diverse fields such as particle physics, astronomy, medicine, as well as industrial nuclear and non-destructive testing.

Vasile, Stefan A.; Gordon, Jeffrey S.; Klugerman, Mikhail; Nagarkar, Vivek V.; Squillante, Michael R.; Entine, Gerald; Watson, Scott; Kauppila, Todd J.

1996-07-01

288

Optimal control subsumes harmonic control Amine Boumaza  

E-print Network

Optimal control subsumes harmonic control Amine Boumaza LORIA Campus Scientifique B.P. 239 54506 planning within the frame- works of optimal control and harmonic control. We present a formal evidence, in the continuous domain and in a stan- dard discretization, that harmonic control is the limit case of some optimal

Paris-Sud XI, Université de

289

Optimal control subsumes harmonic control Amine Boumaza  

E-print Network

Optimal control subsumes harmonic control Amine Boumaza LORIA Campus Scientifique B.P. 239 54506 planning within the frame- works of optimal control and harmonic control. We present a formal evidence, in continuous domain and in a standard discretization, that harmonic control is the limit case of a some optimal

Paris-Sud XI, Université de

290

Modeling a Harmonic Drive Gear Transmission  

Microsoft Academic Search

In order to capture the dynamic behavior of harmonic drives, dynamic models must include accurate representations of transmission friction, compliance, and kinematic error. Experimental observations are used to guide the development of a model to describe harmonic-drive operation. This model is able to replicate many of the features observed in actual harmonic-drive dynamic response. Valuable insights are gained about the

Timothy D. Tuttle; Warren P. Seering

1993-01-01

291

Face recognition in global harmonic subspace  

Microsoft Academic Search

In this paper, a novel pattern recognition scheme, global harmonic subspace analysis (GHSA), is developed for face recognition. In the proposed scheme, global harmonic features are extracted at the semantic scale to capture the 2-D semantic spatial structures of a face image. Laplacian Eigenmap is applied to discriminate faces in their global harmonic subspace. Experimental results on the Yale and

Richard M. Jiang; Danny Crookes; Nie Luo

2010-01-01

292

Experimental study of a thermionic converter in the arc regime with different tungsten emitters  

Microsoft Academic Search

A thermionic converter operating in the arc regime with single crystal tungsten edges and a polycrystal tungsten surface serving as emitters was examined experimentally under operating conditions. It was revealed that there is no single-valued correspondence between the output characteristics of the converter and the vacuum work function of the emitter, and that therefore the work function cannot act as

B. P. Varaksin; A. S. Titkov

1976-01-01

293

Efficiency Investigation of Electrical Generator-Converter Set  

NASA Astrophysics Data System (ADS)

The efficiency of the electrical GEN-SET (EGS) for speeds with diesel generator (?3000rpm) and feasibility of high-speed generator with gas turbine (?30000rpm) and permanent magnet synchronous generator is investigated. Three different configurations of power converter are considered. The paper given an answer to the question if a a full controlled rectifier should be employed or a version with diode rectifier is satisfactory? This is investigated also for high-speed generation. Different current forms for the three defined configurations with their harmonics and influence on generator is given. The efficiency of the overall system is here investigated and an optimal topology is selected. Since the EGS operates very often under low load which does not exceed in average more than 30% of the rated permanent load, a new topology of converter of EGS with high efficiency and low cost is suggested and studied theoretically and experimentally in the paper.

Leuchter, Jan; Bauer, Pavol

294

Theoretical and experimental study of second harmonic generation from the surface of the topological insulator Bi2Se3  

NASA Astrophysics Data System (ADS)

We develop a theoretical model that describes the second harmonic generation of light from the surface of the topological insulator Bi2Se3 and experimentally demonstrate that the technique is sensitive to the surface electrons. By performing a crystal symmetry analysis of Bi2Se3(111) we determine the nonlinear electric susceptibility tensor elements that give rise to second harmonic generation. Using these results, we present a phenomenological model that shows that the relative magnitudes of these tensor elements can be determined by measuring the polarization and intensity of the radiated second harmonic light as a function of the in-plane crystal orientation and incident laser polarization. We describe optical techniques capable of isolating second harmonic light and, using these techniques, we measure the first-order linear optical and second-order nonlinear optical responses as a function of crystal orientation and laser polarization on bulk single crystals of Bi2Se3(111). The experimental results are consistent with our theoretical description. By comparing the data to our theoretical model we determine that a portion of the measured second harmonic light originates from the accumulation region of Bi2Se3(111), which we confirm by performing surface doping-dependent studies. Our results show that second harmonic generation is a promising tool for spectroscopic studies of topological surfaces and buried interfaces.

McIver, J. W.; Hsieh, D.; Drapcho, S. G.; Torchinsky, D. H.; Gardner, D. R.; Lee, Y. S.; Gedik, N.

2012-07-01

295

Lorentz Harmonics, Squeeze Harmonics, and their Physical Applications  

E-print Network

Among the symmetries in physics, the rotation symmetry is most familiar to us. It is known that the spherical harmonics serve useful purposes when the world is rotated. Squeeze transformations are also becoming more prominent in physics, particularly in optical sciences and in high-energy physics. As can be seen from Dirac's light-cone coordinate system, Lorentz boosts are squeeze transformations. Thus the squeeze transformation is one of the fundamental transformations in Einstein's Lorentz-covariant world. It is possible to define a complete set of orthonormal functions defined for one Lorentz frame. It is shown that the same set can be used for other Lorentz frames. Transformation properties are discussed. Physical applications are discussed in both optics and high-energy physics. It is shown that the Lorentz harmonics provide the mathematical basis for squeezed states of light. It is shown also that the same set of harmonics can be used for understanding Lorentz-boosted hadrons in high-energy physics. It is thus possible to transmit physics from one branch of physics to the other branch using the mathematical basis common to them.

Young S. Kim; Marilyn E. Noz

2011-02-19

296

Proposed electromagnetic wave energy converter  

NASA Technical Reports Server (NTRS)

Device converts wave energy into electric power through array of insulated absorber elements responsive to field of impinging electromagnetic radiation. Device could also serve as solar energy converter that is potentially less expensive and fragile than solar cells, yet substantially more efficient.

Bailey, R. L.

1973-01-01

297

PWM Converter Power Density Barriers  

Microsoft Academic Search

Power density of power electronic converters in different applications has roughly doubled every 10 years since 1970. Behind this trajectory was the continuous advancement of power semiconductor device technology allowing an increase of converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts, and passive components and wire bond interconnection technologies could be major barriers for

J. W. Kolar; U. Drofenik; J. Biela; M. L. Heldwein; H. Ertl; T. Friedli; S. D. Round

2007-01-01

298

Continuous-wave ultraviolet emission through fourth-harmonic generation in a whispering-gallery resonator.  

PubMed

We experimentally demonstrate continuous-wave ultraviolet emission through forth-harmonic generation in a millimeter-scale lithium niobate whispering-gallery resonator pumped with a telecommunication-compatible infrared source. The whispering-gallery resonator provides four spectral lines at ultraviolet, visible, near-infrared and infrared, which are equally spaced in frequency via the cascaded-harmonic process and span a 2-octave frequency band. Our technique relies on a variable crystal poling and high transverse order of the modes for phase-matching and a resonator quality factor of over 10(7) to allow cascaded-harmonic generation up to the fourth-harmonic at input pump powers as low as 200 mW. The compact size of the whispering gallery resonator pumped at telecommunication-compatible infrared wavelengths and the low pump power requirement make our device a promising ultraviolet light source for information storage, microscopy, and chemical analysis. PMID:22109440

Moore, Jeremy; Tomes, Matthew; Carmon, Tal; Jarrahi, Mona

2011-11-21

299

Bandwidth enhancement of electro-optic sensing using high-even-order harmonic sidebands.  

PubMed

We demonstrate that the bandwidth of an electro-optic sensing system can be significantly enhanced by the use of even-order harmonic sidebands (order > 2) produced on an optical-carrier probe beam with two cascaded electro-optic modulators. The sensing frequency range may be routinely expanded by at least four times, with respect to the use of fundamental-harmonic sidebands, by enhancing the nonlinearity of high-order-harmonic electro-optic modulation. The creation of harmonic modulation sidebands up to the sixth order of the drive frequency on a laser-diode output is described analytically, as is photonic heterodyne down-conversion of microwave signals using these high-order even harmonics within an electro-optic sensor crystal. The nonlinear harmonics serve as beneficial local-oscillator modulations for broadband electro-optic detection of microwave fields without nonlinear distortion. Transverse near-field distributions from an 18.5 GHz patch antenna are extracted using the fourth- (sixth-) order-harmonic sidebands at the output of the cascaded electro-optic modulators driven with a 4.6- (3.1-) GHz continuous-wave input. PMID:19687970

Lee, Dong-Joon; Whitaker, John F

2009-08-17

300

Highly efficient continuous-wave single-pass second-harmonic generation using multicrystal scheme  

Microsoft Academic Search

We report a simple, compact and novel implementation for single-pass second-harmonic-generation (SP-SHG) of continuous-wave laser radiation based on a cascaded multi-crystal scheme, which can provide the highest conversion efficiency at any given fundamental power. By deploying a suitable number of identical 30-mm-long MgO:sPPLT crystals in a cascade, and a 30-W cw Yb-fiber laser at 1064 nm as the fundamental source,

Kavita Devi; S. Chaitanya Kumar; G. K. Samanta; M. Ebrahim-Zadeh

2010-01-01

301

Voltage and Frequency Control for a Self-Excited Induction Generator Using a Three-Phase Four-Wire Electronic Converter  

Microsoft Academic Search

This work proposes a system, based on a self-excited induction generator (SEIG) with a shunt electronic converter, to feed isolated three-phase and single-phase linear or nonlinear loads. The electronic converter is composed by a three-phase four-wire shunt active filter and a DC chopper attached to its DC bus. The converter compensates the current harmonics, the reactive power and the load

JoseAntonio Barrado; R. Grino

2006-01-01

302

Axisymmetric generalized harmonic evolution code  

SciTech Connect

We describe the first axisymmetric numerical code based on the generalized harmonic formulation of the Einstein equations, which is regular at the axis. We test the code by investigating gravitational collapse of distributions of complex scalar field in a Kaluza-Klein spacetime. One of the key issues of the harmonic formulation is the choice of the gauge source functions, and we conclude that a damped-wave gauge is remarkably robust in this case. Our preliminary study indicates that evolution of regular initial data leads to formation both of black holes with spherical and cylindrical horizon topologies. Intriguingly, we find evidence that near threshold for black hole formation the number of outcomes proliferates. Specifically, the collapsing matter splits into individual pulses, two of which travel in the opposite directions along the compact dimension and one which is ejected radially from the axis. Depending on the initial conditions, a curvature singularity develops inside the pulses.

Sorkin, Evgeny [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Muehlenberg 1, D-14476, Golm (Germany)

2010-04-15

303

Third harmonic generation in graphene  

NASA Astrophysics Data System (ADS)

We report the measurement of optical third harmonic generation from single-layer graphene and few-layer graphite flakes produced by exfoliation. In the measurements, femtosecond near-infrared laser pulses were used to irradiate the samples. The emission observed scales with the cube of the intensity of the incident near-infrared pulse and with one third of the incident wavelength - both are clear evidences of third harmonic generation. We deduced an effective third-order susceptibility for single layer graphene to be on the order of 10-16 m^2/V^2. By measuring a set of flakes with different numbers of atomic layers, we found that for a few layers, the emission scales with the square of the number of atomic layers.

Kumar, Nardeep; Kumar, Jatinder; Gerstenkorn, Chris; Wang, Rui; Chiu, Hsin-Ying; Smirl, Arthur; Zhao, Hui

2013-03-01

304

Harmon Craig (1926-2003)  

NASA Astrophysics Data System (ADS)

Harmon Craig, one of the great pioneers of isotope geochemistry died on 14 March after suffering a massive heart attack at his home in La Jolla, California. He was one day shy of his 77th birthday. Through an academic career of more than fifty years, Craig—or simply “Harmon,” as he was known throughout the world of geochemistry—made a remarkable number of fundamental and far-reaching contributions in a wide range of important areas concerned with the chemical and physical processes by which the solid Earth, the oceans, the atmosphere, and the solar system interact. While his research was broad in scope, it was also characterized by a strong emphasis on meticulous field and laboratory work, and on original and insightful interpretations of the resulting observations.

Weiss, Ray

305

Foliated stochastic calculus: Harmonic measures  

Microsoft Academic Search

In this article we present an intrinsec construction of foliated Brownian\\u000amotion via stochastic calculus adapted to foliation. The stochastic approach\\u000atogether with a proposed foliated vector calculus provide a natural method to\\u000awork on harmonic measures. Other results include a decomposition of the\\u000aLaplacian in terms of the foliated and basic Laplacians, a characterization of\\u000atotally invariant measures and

Pedro J. Catuogno; Diego S. Ledesma; Paulo R. Ruffino

2010-01-01

306

Intramolecular Dynamics Probed using High Harmonic Generation  

NASA Astrophysics Data System (ADS)

We observed intramolecular dynamics as a modulation in high harmonic emission. We excite coherent vibrations in CF3Cl using impulsive Raman scattering with a short laser pulse. A second laser pulse generates high harmonics. The harmonic yield is observed to oscillate at frequencies corresponding to three vibrational modes of CF3Cl. In a second experiment, we used UV light to excite and dissociate CF3I, and follow the dynamic evolution by monitoring the harmonic yield. We observe a large modulation of the harmonic yield, likely due to resonance excitation and subsequent dissociation of the molecule. We speculate that the less-than full baseline recovery after the UV pulse is due to ionization, and that the harmonic yield is sensitive to the bond length during dissociation. By these two experiments, we confirm that high harmonic generation is a sensitive probe of intramolecular dynamics and may yield more information simultaneously than conventional ultrafast spectroscopic techniques.

Hooper, Robynne; Zhou, Xibin; Li, Wen; Wagner, Nick; Kapteyn, Henry; Murnane, Margaret

2007-06-01

307

The designated harmonic suppression for SPWM  

NASA Astrophysics Data System (ADS)

SPWM is a critical method used in asynchronous motor-driven area. But harmonic components of inverter output wave impair its application in motor speed control. A new mixed algorithm was proposed for SPWM, which was a designated harmonic suppression technology by way of improved regular sampling in low voltage and low frequency and harmonic elimination in high voltage and high frequency. This algorithm was based on both analysis of sampled SPWM and Fourier series transform method and aimed at eliminating some odd harmonic components to obtain an identical sine wave. After explication of the harmonic elimination procedure and real time calculation process, an effective control mode and its control circuit were put forward so that the designated harmonic suppression made a reality. Applied it in whole speed adjusting range, the voltage can be conveniently controlled and high frequency harmonic components of SPWM are also improved.

Ping, Yang; Yang, Shi-ping

2005-12-01

308

Efficient broadband second-harmonic generation by dispersive achromatic nonlinear conversion using only prisms.  

National Technical Information Service (NTIS)

Using a lossless dispersive apparatus consisting of six prisms, optimized to match a second-harmonic crystal phase-matching angle vs. wavelength to second order, we efficiently doubled tunable fundamental light near 660 nm over a range of 80 nm using a 4-...

B. A. Richman, S. E. Bisson, R. Trebino

1997-01-01

309

Free-space propagation of second harmonic Laguerre Gaussian beams carrying phase singularity  

Microsoft Academic Search

The vorticity of a free propagating second harmonic (SH) beam produced in a nonlinear quadratic crystal by a combined beam composed of two coaxial Laguerre-Gaussian vortex beams is analysed. In the near field of the SH radiation an aligned vortical structure with a number of double-charge vortices is created. The diffraction of the SH beam under free propagation is also

S. Orlov; K. Regelskis; V. Smilgevicius; A. Stabinis

2004-01-01

310

Femtosecond second-harmonic pulse compression in aperiodically poled lithium niobate: a  

E-print Network

-doubled components to exit the crystal simulta- neously, in the form of a transform-limited pulse. Com- pressionFemtosecond second-harmonic pulse compression in aperiodically poled lithium niobate: a systematic detailed experimental results of simultaneous frequency doubling and pulse compression of chirped pulses

311

Thermionic converters with microcavity electrodes in the cesium arc regime  

NASA Astrophysics Data System (ADS)

The volt-ampere characteristics of thermionic converters with microcavity electrodes are investigated theoretically and experimentally. A mathematical model is presented which makes it possible to analyze plasma parameter distribution in thermionic conversion systems of this kind. It is shown that cathodes with a microcavity surface structure have better emission properties than smooth cathodes of single-crystal tungsten with a vacuum output energy of 5.0 eV. It is estimated that the use of a microcavity cathode makes it possible to increase the output power of the converter by about 10-60 percent, depending on the surface development.

Atamasov, V. D.; Ivanova, N. A.

1990-06-01

312

Control scheme of three-level H-bridge converter for interfacing between renewable energy resources and AC grid  

Microsoft Academic Search

This paper presents a control strategy of multilevel converters for integration of renewable energy resources into power grid. The proposed technique provides compensation for active, reactive, and harmonic current components of grid-connected loads. A three-level H-bridge converter is proposed as the interfacing system between renewable energy resources and utility grid. High performance of the proposed technique is indicated with injection

Edris Pouresmaeil; Daniel Montesinos-Miracle; Oriol Gomis-Bellmunt

2011-01-01

313

Control Design of a Three-Phase Matrix-Converter-Based AC–AC Mobile Utility Power Supply  

Microsoft Academic Search

This paper describes the control analysis and design of an ac-to-ac three-phase mobile utility power supply using a matrix converter capable of high-quality 50-, 60-, and 400-Hz output voltage and reduced input harmonic distortion. Instead of the traditional structure employing a diode bridge rectifier, a dc link and a pulsewidth-modulated inverter, a three-phase-to-three-phase direct ac-ac (matrix) converter has been used

Pericle Zanchetta; Patrick W. Wheeler; Jon C. Clare; Michael Bland; Lee Empringham; Dimosthenis Katsis

2008-01-01

314

On Attaining the Multiple Solutions of Selective Harmonic Elimination PWM Three-Level Waveforms Through Function Minimization  

Microsoft Academic Search

Selective harmonic elimination pulsewidth modulation techniques are some of the control methods used in voltage\\/current source converters. However, challenges such as the task of finding all the multiple sets of solutions of the switching angles for a given problem may be difficult to deal with. In this paper, a direct minimization of the nonlinear transcendental trigonometric Fourier functions in combination

Vassilios G. Agelidis; Anastasios I. Balouktsis; Calum Cossar

2008-01-01

315

High Resolution Switching Mode Inductance-to-Frequency Converter with Temperature Compensation.  

PubMed

This article proposes a novel method for the temperature-compensated inductance-to-frequency converter with a single quartz crystal oscillating in the switching oscillating circuit to achieve better temperature stability of the converter. The novelty of this method lies in the switching-mode converter, the use of additionally connected impedances in parallel to the shunt capacitances of the quartz crystal, and two inductances in series to the quartz crystal. This brings a considerable reduction of the temperature influence of AT-cut crystal frequency change in the temperature range between 10 and 40 °C. The oscillator switching method and the switching impedances connected to the quartz crystal do not only compensate for the crystal's natural temperature characteristics but also any other influences on the crystal such as ageing as well as from other oscillating circuit elements. In addition, the method also improves frequency sensitivity in inductance measurements. The experimental results show that through high temperature compensation improvement of the quartz crystal characteristics, this switching method theoretically enables a 2 pH resolution. It converts inductance to frequency in the range of 85-100 µH to 2-560 kHz. PMID:25325334

Matko, Vojko; Milanovi?, Miro

2014-01-01

316

High Resolution Switching Mode Inductance-to-Frequency Converter with Temperature Compensationti  

PubMed Central

This article proposes a novel method for the temperature-compensated inductance-to-frequency converter with a single quartz crystal oscillating in the switching oscillating circuit to achieve better temperature stability of the converter. The novelty of this method lies in the switching-mode converter, the use of additionally connected impedances in parallel to the shunt capacitances of the quartz crystal, and two inductances in series to the quartz crystal. This brings a considerable reduction of the temperature influence of AT-cut crystal frequency change in the temperature range between 10 and 40 °C. The oscillator switching method and the switching impedances connected to the quartz crystal do not only compensate for the crystal's natural temperature characteristics but also any other influences on the crystal such as ageing as well as from other oscillating circuit elements. In addition, the method also improves frequency sensitivity in inductance measurements. The experimental results show that through high temperature compensation improvement of the quartz crystal characteristics, this switching method theoretically enables a 2 pH resolution. It converts inductance to frequency in the range of 85–100 ?H to 2–560 kHz. PMID:25325334

Matko, Vojko; Milanovi?, Miro

2014-01-01

317

Wind/water energy converter  

NASA Technical Reports Server (NTRS)

Device will convert wind, water, tidal or wave energy into electrical or mechanical energy. Is comprised of windmill-like paddles or blades synchronously geared to orient themselves to wind direction for optimum energy extraction.

Paulkovich, J.

1979-01-01

318

Converting Technology into a Company  

E-print Network

;2 Science-Driven Disruptive Technology Development and Marketplace Realization Science BreakthroughPlasmasol: Converting Technology into a Company Christos Chrisodoulatos, Ph.D. Vice Provost #12 Technology Chemistry/ Materials Sensors EnviroSense? Engineering Technology Chemistry/ Materials Met

Yang, Eui-Hyeok

319

Radiant energy to electric energy converter  

NASA Technical Reports Server (NTRS)

Radiant energy is converted into electric energy by irradiating a capacitor including an ionic dielectric. The dielectric is a sintered crystal superionic conductor, e.g., lanthanum trifluoride, lanthanum trichloride, or silver bromide, so that a multiplicity of crystallites exist between electrodes of the capacitor. The radiant energy cyclically irradiates the dielectric so that the dielectric exhibits a cyclic photocapacitive like effect. Adjacent crystallites have abutting surfaces that enable the crystallites to effectively form a multiplicity of series capacitor elements between the electrodes. Each of the capacitor elements has a dipole layer only on or near its surface. The capacitor is initially charged to a voltage just below the dielectric breakdown voltage by connecting it across a DC source causing a current to flow through a charging resistor to the dielectric. The device can be utilized as a radiant energy detector or as a solar energy cell.

Sher, Arden (Inventor)

1980-01-01

320

Growth and characterization of L-tryptophan doped KDP crystals  

NASA Astrophysics Data System (ADS)

Potassium Dihydrogen Phosphate crystals are one of the most popular crystals used for Non-linear Optical applications. Most of the amino acids also exhibit NLO properties. The effect of doping of one of the amino acids, L-tryptophan in KDP crystals has been investigated. Pure and L-tryptophan doped KDP crystals were grown by slow solvent evaporation solution growth technique. Good quality transparent crystals were obtained. Doping of L-tryptophan in KDP crystal was confirmed by FT-IR spectroscopy studies. The value of second harmonic generation efficiency and optical transmission in UV-Vis spectra increased as doping of L-tryptophan increased in KDP crystals.

Parikh, K. D.; Dave, D. J.; Parekh, B. B.; Joshi, M. J.

2013-06-01

321

HIGH EFFICIENCY AUXILIARY POWER CONVERTERS  

Microsoft Academic Search

The auxiliary load DC-DC converters of the Sunshark solar car have never been examined. An analysis of the current design reveals it is complicated, and inefficient. Some simple measures to greatly improve the efficiency are present which will achieve an overall worthwhile power saving. Two switch-mode power supply DC-DC converter designs are presented. One is a constant current supply for

Geoff Walker

322

A Binary Coded Decimal Converter  

Microsoft Academic Search

Of the many different coding schemes possible, the 8-4-2-1 binary decimal code was felt to be the most useful for data handling systems. A transducer wes developed for converting shaft positions to digital numbers in this code. The converter is small, light weight, and produces 10,000 binary coded decimal numbers in 100 revolutions of the input shaft. No ambiguity of

Martin Ziserman

1956-01-01

323

Radiation effects on DC-DC Converters  

NASA Technical Reports Server (NTRS)

DC-DC switching converters are circuits that can be used to convert a DC voltage of one value to another by switching action. They are increasing being used in space systems. Most of the popular DC-DC switching converters utilize power MOSFETs. However power MOSFETs, when subjected to radiation, are susceptible to degradation of device characteristics or catastrophic failure. This work focuses on the effects of total ionizing dose on converter performance. Four fundamental switching converters (buck converter, buck-boost converter, cuk converter, and flyback converter) were built using Harris IRF250 power MOSFETs. These converters were designed for converting an input of 60 volts to an output of about 12 volts with a switching frequency of 100 kHz. The four converters were irradiated with a Co-60 gamma source at dose rate of 217 rad/min. The performances of the four converters were examined during the exposure to the radiation. The experimental results show that the output voltage of the converters increases as total dose increases. However, the increases of the output voltage were different for the four different converters, with the buck converter and cuk converter the highest and the flyback converter the lowest. We observed significant increases in output voltage for cuk converter at a total dose of 24 krad (si).

Zhang, Dexin; Attia, John O.; Kankam, Mark D. (Technical Monitor)

2000-01-01

324

Synthesis, crystal growth and physical characterizations of organic nonlinear optical crystal: Ammonium hydrogen L-malate.  

PubMed

An organic nonlinear optical crystal ammonium hydrogen l-malate (AHM) has been synthesized. Single crystals of AHM have successfully been grown by the slow evaporation solution method. Optically clear single crystals having dimensions up to 23×9×4mm(3) have been grown. Single crystal X-ray diffraction study confirms that the AHM crystallizes in orthorhombic crystal system with space group P212121. The powder X-ray diffraction pattern of the grown crystal has been recorded. FT-IR spectrum was recorded to identify the various functional groups of AHM. The UV-vis-NIR transmission was analyzed for grown crystal. Thermal analysis was performed to find out thermal stability of the compound. Vickers microhardness measurements were carried and also work hardening coefficient has been found. The crystalline perfection of the grown crystal has been analyzed by HRXRD measurements. The second harmonic efficiency of AHM was found to be 1.2 times that of KDP. PMID:24583470

Boopathi, K; Ramasamy, P

2014-05-21

325

Synthesis, crystal growth and physical characterizations of organic nonlinear optical crystal: Ammonium hydrogen L-malate  

NASA Astrophysics Data System (ADS)

An organic nonlinear optical crystal ammonium hydrogen L-malate (AHM) has been synthesized. Single crystals of AHM have successfully been grown by the slow evaporation solution method. Optically clear single crystals having dimensions up to 23 × 9 × 4 mm3 have been grown. Single crystal X-ray diffraction study confirms that the AHM crystallizes in orthorhombic crystal system with space group P212121. The powder X-ray diffraction pattern of the grown crystal has been recorded. FT-IR spectrum was recorded to identify the various functional groups of AHM. The UV-vis-NIR transmission was analyzed for grown crystal. Thermal analysis was performed to find out thermal stability of the compound. Vickers microhardness measurements were carried and also work hardening coefficient has been found. The crystalline perfection of the grown crystal has been analyzed by HRXRD measurements. The second harmonic efficiency of AHM was found to be 1.2 times that of KDP.

Boopathi, K.; Ramasamy, P.

326

Noncollinear second-harmonic generation in sub-micrometer-poled RbTiOPO(4).  

PubMed

We have generated noncollinear quasi-phase-matched second harmonic wave in an RbTiOPO(4) crystal that was poled using the high-voltage atomic force microscope (HV-AFM). To the best of our knowledge, this is the first systematic nonlinear frequency conversion study of samples produced by the HV-AFM method. The short poling period of 1.18 microm enabled us to observe second harmonic generation at very large angles with respect to the fundamental wave. The setup was used to optically explore the homogeneity of the poled area. The measurements are in a reasonable agreement with an analytic calculations. PMID:19475059

Moscovich, S; Arie, A; Urneski, R; Agronin, A; Rosenman, G; Rosenwaks, Y

2004-05-17

327

Harmonic Elimination in Multilevel Converters John Chiasson, Leon Tolbert, Keith McKenzie and Zhong Du  

E-print Network

multilevel inverter that, by modifying the switching scheme, one can extend the range of modulation indices]. The general function of the multilevel inverter is to syn- thesize a desired ac voltage from several levels of dc volt- ages. For this reason, multilevel inverters are ideal for con- necting either in series

Tolbert, Leon M.

328

Elimination of Harmonics in a Multilevel Converter using the Theory of Symmetric  

E-print Network

possible solutions. Keywords­ Multilevel Inverter, Symmetric Polynomials, Resultants. I. Introduction A multilevel inverter is a power electronic device built to synthesize a desired ac voltage from several levels into an ac power grid, a power electronic interface is required. A multilevel inverter is ideal

Tolbert, Leon M.

329

New converter circuitry for PV applications using multilevel converters  

Microsoft Academic Search

This paper presents an analysis and the design of an off grid PV system for providing electricity for remote area. The system composed of dc-dc multilevel boost converter (MLBC) which is used for extracting maximum power from the cell. It has been chosen to generate three dc voltages at its output terminal. In addition to, a multilevel dc link inverter

Mostafa Mousa; Mahrous E. Ahmed; M. Orabi

2009-01-01

330

High efficiency thermionic converter studies  

NASA Technical Reports Server (NTRS)

Research in thermionic energy conversion technology is reported. The objectives were to produce converters suitable for use in out of core space reactors, radioisotope generators, and solar satellites. The development of emitter electrodes that operate at low cesium pressure, stable low work function collector electrodes, and more efficient means of space charge neutralization were investigated to improve thermionic converter performance. Potential improvements in collector properties were noted with evaporated thin film barium oxide coatings. Experiments with cesium carbonate suggest this substance may provide optimum combinations of cesium and oxygen for thermionic conversion.

Huffman, F. N.; Sommer, A. H.; Balestra, C. L.; Briere, T. R.; Lieb, D.; Oettinger, P. E.; Goodale, D. B.

1977-01-01

331

Convertible Gas-Turbine Engines  

NASA Technical Reports Server (NTRS)

Convertible engine aircraft gas-turbine is two engines in one. Produces turbofan thrust, turboshaft power, or any combined thrust and shaftpower continously while operating up to full speed. Used to power vertical/short-takeoff-and-landing (V/STOL) airplanes and advanced high-speed rotorcraft. Rotorcraft shows use of convertible engines rather than separate engines for rotor power and forward thrust affords advantages in installation and save 16 percent in fuel and 20 percent in direct operating costs. Engine used for propulsion of new high-speed rotorcraft that needs both thrust and shaft power. Also used to cross-couple fans of two-engine V/STOL aircraft.

Abdalla, K. L.; Mcardle, J. G.; Lindsay, H.

1988-01-01

332

Stirling Converters For Solar Power  

NASA Technical Reports Server (NTRS)

Two designs expected to meet long-term goals for performance and cost. Proposed for advanced systems to convert solar thermal power to electrical power. Each system, designed to operate with 11-m-diameter paraboloidal reflector, includes solar-energy receiver, liquid-metal heat-transport subsystem, free-piston Stirling engine, cooling subsystem, alternator or generator coupled directly or indirectly to commercial electric-power system, and control and power-conditioning circuitry. System converts approximately 75 kW of input solar thermal power falling on collector to about 25 kW of output electrical power.

Shaltens, Richard K.; Schreiber, Jeffrey G.

1993-01-01

333

Physics 321 Simple and Damped Harmonic Oscillators  

E-print Network

Physics 321 Hour 11 Simple and Damped Harmonic Oscillators Mass on a Massless Spring 1) Find U) x y z Example Lissajous.nb Damped Oscillator The equation: A little rearranging: 0 A trial Driven Harmonic Oscillators #12;Driven Oscillator The equation: 0 Let The oscillator wants

Hart, Gus

334

Radiation reaction and quantum damped harmonic oscillator  

E-print Network

By taking a Klein-Gordon field as the environment of an harmonic oscillator and using a new method for dealing with quantum dissipative systems (minimal coupling method), the quantum dynamics and radiation reaction for a quantum damped harmonic oscillator investigated. Applying perturbation method, some transition probabilities indicating the way energy flows between oscillator, reservoir and quantum vacuum, obtained

F. Kheirandish; M. Amooshahi

2005-07-19

335

Sunspots and their simple harmonic motion  

NASA Astrophysics Data System (ADS)

In this paper an example of a simple harmonic motion, the apparent motion of sunspots due to the Sun’s rotation, is described, which can be used to teach this subject to high-school students. Using real images of the Sun, students can calculate the star’s rotation period with the simple harmonic motion mathematical expression.

Ribeiro, C. I.

2013-09-01

336

Harmonic oscillator states in aberration optics  

NASA Technical Reports Server (NTRS)

The states of the three-dimensional quantum harmonic oscillator classify optical aberrations of axis-symmetric systems due to the isomorphism between the two mathematical structures. Cartesian quanta and angular momentum classifications have their corresponding aberration classifications. The operation of concatenation of optical elements introduces a new operation between harmonic oscillator states.

Wolf, Kurt Bernardo

1993-01-01

337

Sunspots and Their Simple Harmonic Motion  

ERIC Educational Resources Information Center

In this paper an example of a simple harmonic motion, the apparent motion of sunspots due to the Sun's rotation, is described, which can be used to teach this subject to high-school students. Using real images of the Sun, students can calculate the star's rotation period with the simple harmonic motion mathematical expression.

Ribeiro, C. I.

2013-01-01

338

Quantum wormholes and harmonic oscillators  

NASA Technical Reports Server (NTRS)

The quantum state of a wormhole can be represented by a path integral over all asymptotically Euclidean four-geometries and all matter fields which have prescribed values, the arguments of the wave function, on a three-surface which divides the space time manifold into two disconnected parts. Minisuperspace models which consist of a homogeneous massless scalar field coupled to a Friedmann-Robertson-Walker space time are considered. Once the path integral over the lapse function is performed, the requirement that the space time be asymptotically Euclidean can be accomplished by fixing the asymptotic gravitational momentum in the remaining path integral. It is argued that there does not exist any wave function which corresponds to asymptotic field configurations such that the effective gravitational constant is negative in the asymptotic region. Then, the wormhole wave functions can be written as linear combinations of harmonic oscillator wave functions.

Garay, Luis J.

1993-01-01

339

Point-based manifold harmonics.  

PubMed

This paper proposes an algorithm to build a set of orthogonal Point-Based Manifold Harmonic Bases (PB-MHB) for spectral analysis over point-sampled manifold surfaces. To ensure that PB-MHB are orthogonal to each other, it is necessary to have symmetrizable discrete Laplace-Beltrami Operator (LBO) over the surfaces. Existing converging discrete LBO for point clouds, as proposed by Belkin et al., is not guaranteed to be symmetrizable. We build a new point-wisely discrete LBO over the point-sampled surface that is guaranteed to be symmetrizable, and prove its convergence. By solving the eigen problem related to the new operator, we define a set of orthogonal bases over the point cloud. Experiments show that the new operator is converging better than other symmetrizable discrete Laplacian operators (such as graph Laplacian) defined on point-sampled surfaces, and can provide orthogonal bases for further spectral geometric analysis and processing tasks. PMID:22879345

Liu, Yang; Prabhakaran, Balakrishnan; Guo, Xiaohu

2012-10-01

340

Characterization of Second Harmonic Afterburner Radiation at the LCLS  

SciTech Connect

During commissioning of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Laboratory it was shown that saturation lengths much shorter than the installed length of the undulator line can routinely be achieved. This frees undulator segments that can be used to provide enhanced spectral properties and at the same time, test the concept of FEL Afterburners. In December 2009 a project was initiated to convert undulator segments at the down-beam end of the undulator line into Second Harmonic Afterburners (SHAB) to enhance LCLS radiation levels in the 10-20 keV energy range. This is being accomplished by replacement of gap-shims increasing the fixed gaps from 6.8 mm to 9.9 mm, which reduces their K values from 3.50 to 2.25 and makes the segments resonant at the second harmonic of the upstream unmodified undulators. This paper reports experimental results of the commissioning of the SHAB extension to LCLS.

Nuhn, Heinz-Dieter

2010-09-14

341

High order harmonic generation in rare gases  

SciTech Connect

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 {approximately}10{sup 13}-10{sup 14} W/cm{sup 2}) is focused into a dense ({approximately}10{sup l7} particles/cm{sup 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 {open_quotes}source{close_quotes}. 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.

Budil, K.S.

1994-05-01

342

Multilevel converters for power system applications  

SciTech Connect

Multilevel converters are emerging as a new breed of power converter options for power system applications. These converters are most suitable for high voltage high power applications because they connect devices in series without the need for component matching. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. To avoid voltage unbalance between different levels, several techniques have been proposed for different applications. Excluding magnetic-coupled converters, this paper introduces three multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded inverters with separate dc sources. The operation principle, features, constraints, and potential applications of these converters will be discussed.

Lai, J.S.; Stovall, J.P. [Oak Ridge National Lab., TN (United States); Peng, F.Z. [Univ. of Tennessee, Knoxville, TN (United States)]|[Oak Ridge National Lab., TN (United States)

1995-09-01

343

New ?-? voltage to frequency converter  

Microsoft Academic Search

The voltage to frequency converter (VFC) is an oscillator whose frequency is linearly proportional to the control voltage. There are two common VFC architectures: the current steering multivibrator and the charge-balance VFC. For higher linearity, the charge-balancing method is preferred. The charge balanced VFC may be made in asynchronous or synchronous (clocked) forms. The synchronous charge balanced VFC or \\

Milan Stork

2002-01-01

344

ELSEVIER Journal of Crystal Growth 143 (1994) 317--333 The influence of oscillatory and steady shears on interfacial  

E-print Network

~N~H CRYSTAL GROWTH ELSEVIER Journal of Crystal Growth 143 (1994) 317--333 The influence reserved SSDI 0022-0248(94)00418-L #12;315 T.P. Schuize, S.H. Divis/Journal of Crystal Growth 143 (1994) 3 by a simple harmonic, lateral oscillation of the crystal, resulting in solidification into a compressed Stokes

Schulze, Tim

345

Snow Crystals  

NSDL National Science Digital Library

This site is all about snow crystals and snowflakes. The many facets of snow crystals are described here, along with attempts to understand their formation. This site includes collections of super-high-resolution snow crystal photos, as well as links to learn about snow crystal classifications and how to make snow crystal fossils. Included in the study of how snow crystals form, these researchers have created snow crystals in the laboratory. Their snow crystal galleries include selections of images and movies of laboratory-grown snow crystals, as well as information on how to make your own snow crystals. The snow crystal primer describes what snow crystals are, how they form, and why they form the way they do. There is also a section on snow crystal physics.

Libbrecht, Kenneth

1999-02-01

346

Curious Crystals  

NSDL National Science Digital Library

Learners carefully look at four known household crystals. After observing and describing the crystals, learners are given an unknown crystal, which is chemically the same as one of the four known crystals but looks different. When learners realize that they cannot identify this crystal by its appearance alone, they will suggest other tests and ways to compare the crystals to eventually identify the unknown crystal. The related activities are examples of tests learners can conduct on the crystals. After a series of these tests, learners will gather enough evidence to identify the unknown crystal.

Kessler, James H.; Galvan, Patricia M.

2007-01-01

347

Electromagnetic space-time crystals. II. Fractal computational approach  

E-print Network

A fractal approach to numerical analysis of electromagnetic space-time crystals, created by three standing plane harmonic waves with mutually orthogonal phase planes and the same frequency, is presented. Finite models of electromagnetic crystals are introduced, which make possible to obtain various approximate solutions of the Dirac equation. A criterion for evaluating accuracy of these approximate solutions is suggested.

G. N. Borzdov

2014-10-20

348

Parametric study of laser photovoltaic energy converters  

NASA Technical Reports Server (NTRS)

Photovoltaic converters are of interest for converting laser power to electrical power in a space-based laser power system. This paper describes a model for photovoltaic laser converters and the application of this model to a neodymium laser silicon photovoltaic converter system. A parametric study which defines the sensitivity of the photovoltaic parameters is described. An optimized silicon photovoltaic converter has an efficiency greater than 50 percent for 1000 W/sq cm of neodymium laser radiation.

Walker, G. H.; Heinbockel, J. H.

1987-01-01

349

All-prism achromatic phase matching for tunable second-harmonic generation.  

PubMed

Achromatic phase matching (APM) involves dispersing the light entering a nonlinear optical crystal so that a wide range of wavelengths is simultaneously phase matched. We constructed an APM apparatus consisting of six prisms, the final dispersion angle of which was optimized to match to second order in wavelength the type I phase-matching angle of beta barium borate (BBO). With this apparatus, we doubled tunable fundamental light from 620 to 700 nm in wavelength using a 4-mm-long BBO crystal. An analogous set of six prisms after the BBO crystal, optimized to second order in second-harmonic wavelength, realigned the output second-harmonic beams. Computer simulations predict that adjustment of a single prism can compensate angular misalignment of any or all the prisms before the crystal, and similarly for the prisms after the crystal. We demonstrated such compensation with the experimental device. The simulations also indicate that the phase-matching wavelength band can be shifted and optimized for different crystal lengths. PMID:18319927

Richman, B A; Bisson, S E; Trebino, R; Sidick, E; Jacobson, A

1999-05-20

350

All-prism achromatic phase matching for tunable second-harmonic generation  

SciTech Connect

Achromatic phase matching (APM) involves dispersing the light entering a nonlinear optical crystal so that a wide range of wavelengths is simultaneously phase matched. We constructed an APM apparatus consisting of six prisms, the final dispersion angle of which was optimized to match to second order in wavelength the type I phase-matching angle of {beta} barium borate (BBO). With this apparatus, we doubled tunable fundamental light from 620 to 700 nm in wavelength using a 4-mm-long BBO crystal. An analogous set of six prisms after the BBO crystal, optimized to second order in second-harmonic wavelength, realigned the output second-harmonic beams. Computer simulations predict that adjustment of a single prism can compensate angular misalignment of any or all the prisms before the crystal, and similarly for the prisms after the crystal. We demonstrated such compensations with the experimental device. The simulations also indicate that the phase-matching wavelength band can be shifted and optimized for different crystal lengths. {copyright} 1999 Optical Society of America

Richman, Bruce A.; Bisson, Scott E.; Trebino, Rick [Combustion Research Facility, Sandia National Laboratories, MS 9051, Livermore, California 94551-0969 (United States); Jacobson, Alexander [CVI Laser Corporation, 361 Lindbergh Avenue, Livermore, California 94550 (United States)

1999-05-01

351

Harmonic analysis of industrial power systems  

SciTech Connect

When large harmonic producing loads are added to an industrial plant power system it is good engineering practice to analyze the impact on the power system by performing harmonic modeling analysis of the system at the design stage. Such a study can identify any potentially harmful resonances or other harmonic levels that are predicted to be in excess of IEEE 519 recommended limits and suggest corrective measures (if necessary). This paper discusses the impact of the harmonic limits of IEEE 519-1992 on the industrial power consumer and addresses the differences between the 1992 and 1981 versions of the standard. Harmonics produced by variable frequency drives are discussed. The data required to conduct a harmonic study, the types of analyses that can be performed, and some of the mitigating measures that can be taken to alleviate a potential harmonic problem are detailed. A case study is presented based on a typical paper mill where a large variable frequency drive was added to the power system.

Ellis, R.G. [Allen-Bradley Canada Ltd., Cambridge, Ontario (Canada)] [Allen-Bradley Canada Ltd., Cambridge, Ontario (Canada)

1996-03-01

352

A high-fidelity harmonic drive model.  

SciTech Connect

In this paper, a new model of the harmonic drive transmission is presented. The purpose of this work is to better understand the transmission hysteresis behavior while constructing a new type of comprehensive harmonic drive model. The four dominant aspects of harmonic drive behavior - nonlinear viscous friction, nonlinear stiffness, hysteresis, and kinematic error - are all included in the model. The harmonic drive is taken to be a black box, and a dynamometer is used to observe the input/output relations of the transmission. This phenomenological approach does not require any specific knowledge of the internal kinematics. In a novel application, the Maxwell resistive-capacitor hysteresis model is applied to the harmonic drive. In this model, sets of linear stiffness elements in series with Coulomb friction elements are arranged in parallel to capture the hysteresis behavior of the transmission. The causal hysteresis model is combined with nonlinear viscous friction and spectral kinematic error models to accurately represent the harmonic drive behavior. Empirical measurements are presented to quantify all four aspects of the transmission behavior. These measurements motivate the formulation of the complete model. Simulation results are then compared to additional measurements of the harmonic drive performance.

Preissner, C.; Royston, T. J.; Shu, D. (APS Engineering Support Division); ( MCS); (Univ. of Illinois)

2012-01-01

353

Crystal Creations.  

ERIC Educational Resources Information Center

Presents a many-faceted learning approach to the study of crystals. Provides instructions for performing activities including crystal growth and patterns, creating miniature simulations of crystal-containing rock formations, charcoal and sponge gardens, and snowflakes. (RT)

Whipple, Nona; Whitmore, Sherry

1989-01-01

354

Crystal Meth  

MedlinePLUS

... Navigation Home / Stories of Hope / Crystal meth Crystal meth Story Of Hope By giovanni January 3rd, 2013 ... my drug addiction having to deal with Crystal meth. I am now in recovery and fighting my ...

355

Harmonic power flow for unbalanced systems  

SciTech Connect

In this paper a harmonic power flow that analyzes harmonics in unbalanced systems is presented. The developed algorithm has two steps which are executed successively: the first is a fundamental frequency power flow for the ac linear network in which non-linear loads are represented by current sources. The second is a frequency-domain iterative Newton-Raphson method to calculate the harmonics generated by non-linear loads. In this second step, the ac linear network is represented by a generalized Thevenin equivalent with respect to the non-linear loads, obtained from the power flow solution. Both linear and non-linear loads are considered in terms of power.

Valcarcel, M.; Mayordomo, J.G. (Univ. Politecnica de Madrid (Spain). Dept. de Ingenieria Electrica)

1993-10-01

356

High-average power second harmonic generation of femtosecond fiber lasers  

NASA Astrophysics Data System (ADS)

We present second harmonic generation of a high average power, high energy femtosecond Yb doped fiber chirped pulse amplifier. This system is operated at various repetition rates at a central wavelength of 1040 nm. After two pre-amplification stages a main amplifier is used to achieve the required pulse energy for efficient second harmonic generation. It is comprised of a 1.2 m long photonic crystal fiber with a mode field diameter of 45 ?m. A dielectric grating based compressor is used for compression to a pulse duration of about 406 fs. Second harmonic generation is then achieved in a 500 ?m thick BBO crystal. The conversion efficiency of the second harmonic generation remained almost constant at >60 % for all repetition rates and average power levels. At 5.25 MHz the highest average power of 135 W at 520 nm was achieved. In addition this comes with an excellent beam quality which is validated by a measured M2 < 1.2.

Hädrich, S.; Rothhardt, J.; Eidam, T.; Gottschall, T.; Limpert, J.; Tünnermann, A.

2011-02-01

357

Harmonic regression and scale stability.  

PubMed

Monitoring a very frequently administered educational test with a relatively short history of stable operation imposes a number of challenges. Test scores usually vary by season, and the frequency of administration of such educational tests is also seasonal. Although it is important to react to unreasonable changes in the distributions of test scores in a timely fashion, it is not a simple matter to ascertain what sort of distribution is really unusual. Many commonly used approaches for seasonal adjustment are designed for time series with evenly spaced observations that span many years and, therefore, are inappropriate for data from such educational tests. Harmonic regression, a seasonal-adjustment method, can be useful in monitoring scale stability when the number of years available is limited and when the observations are unevenly spaced. Additional forms of adjustments can be included to account for variability in test scores due to different sources of population variations. To illustrate, real data are considered from an international language assessment. PMID:24092490

Lee, Yi-Hsuan; Haberman, Shelby J

2013-10-01

358

A 400 W flyback converter  

Microsoft Academic Search

It is demonstrated that it is possible to manufacture a very compact high-power switch-mode power supply based on the flyback technique using standard components, with no sacrifice in performance and operation at 80 kHz. A superior flyback converter can be designed on the basis of the following criteria: (1) choosing a pulse ratio to optimize the switching transistor\\/diode; (2) assuring

B. Assow

1989-01-01

359

Optical Cherenkov radiation in ultrafast cascaded second-harmonic generation  

SciTech Connect

We show through theory and numerics that when few-cycle femtosecond solitons are generated through cascaded (phase-mismatched) second-harmonic generation, these broadband solitons can emit optical Cherenkov radiation in the form of linear dispersive waves located in the red part of the spectrum. The beating between the dispersive wave and the soliton generates trailing temporal oscillations on the compressed soliton. Insertion of a simple short-wave pass filter after the crystal can restore a clean soliton. On the other hand, bandpass filtering around the dispersive wave peak results in near-transform-limited ultrashort mid-IR pulses with pulse durations much shorter than the input near-IR pulse. The Cherenkov radiation for the crystal considered ({beta}-barium borate) is found for pump wavelengths in the range {lambda}=0.95-1.45 {mu}m, and is located in the regime {lambda}=1.5-3.5 {mu}m. For shorter pump wavelengths, the phase-matching point is located in the absorption region of the crystal, effectively absorbing the generated dispersive wave. By calculating the phase-matching curves for typically used frequency conversion crystals, we point out that the mid-IR absorption in the crystal in many cases automatically will filter away the dispersive wave. Finally, an investigation of recent experimental results uncovers a four-wave-mixing phenomenon related to Cherenkov radiation that is an additional generation mechanism of long-wavelength radiation that can occur during soliton compression. We discuss the conditions that lead to this alternative dynamics rather than generation of Cherenkov radiation.

Bache, M.; Bang, O.; Zhou, B. B. [DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); Moses, J. [Optics and Quantum Electronics Group, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Wise, F. W. [Department of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853 (United States)

2010-12-15

360

High-order harmonics with frequency-varying polarization within each harmonic  

E-print Network

We predict high-order harmonics in which the polarization within the spectral bandwidth of each harmonic varies continuously and significantly. For example, the interaction of counter-rotating circularly-polarized bichromatic drivers having close central frequencies with isotropic gas leads to the emission of polarization-fan harmonics which are nearly circularly-polarized in one tail of the harmonic peak, linear in the center of the peak and nearly circular with the opposite helicity in the opposite tail. Polarization fan harmonics are obtained as a result of multiple (at least two) head-on recollisions of electrons with their parent ions occurring from different angles. The process can be phase-matched using standard methods (e.g. pressure tuning phase matching) and maintains the single-atom polarization property through propagation. These polarization-fan harmonics may be used for exploring non-repetitive ultrafast chiral phenomena, e.g. dynamics of magnetic domains, in a single shot

Fleischer, Avner; Sidorenko, Pavel; Cohen, Oren

2014-01-01

361

Dye laser pumped by radiation from a cw YAG:Nd/sup 3 +/ laser with intracavity second harmonic generation  

SciTech Connect

An experimental study was made of lasing in dyes pumped by radiation from a cw YAG:Nd/sup 3 +/ laser with intracavity second harmonic generation in an LiIO/sub 3/ crystal. The parameters of the tunable dye laser radiation were not inferior to those obtained by pumping dyes with high-power argon laser radiation.

Konvisar, P.G.; Lokhnygin, V.D.; Rustamov, S.R.; Fomichev, A.A.

1982-08-01

362

21 CFR 26.48 - Harmonization.  

Code of Federal Regulations, 2010 CFR

...MEDICAL DEVICE QUALITY SYSTEM AUDIT REPORTS, AND CERTAIN MEDICAL DEVICE PRODUCT EVALUATION REPORTS: UNITED STATES AND THE EUROPEAN COMMUNITY Specific Sector Provisions for Medical Devices § 26.48 Harmonization. During both the transitional...

2010-04-01

363

Motion in a Harmonic Central Force Model  

NSDL National Science Digital Library

The Motion in a Harmonic Central Force model displays the dynamics of an orbiting mass due to a harmonic force (a quadratic potential energy function). The simulation displays the motion of the mass as well as the effective potential energy. The initial conditions can be changed by dragging the mass or dragging the pink circle in the effect potential energy diagram. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item. The Motion in a Harmonic Central Force model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_central_forces_harmonic.jar file will run the program if Java is installed.

Aguirregabiria, Juan

2011-09-08

364

Tracking Comb Filter Suppresses Welder Harmonics  

NASA Technical Reports Server (NTRS)

Tracking comb filter includes charge-coupled-device delay line and phase-locked loop. Filter removes harmonics of frequency of repetition of welding-current pulses from acoustic-emission signal. Spurious signals reduced almost to fundamental limit.

Delcher, Ray C.

1992-01-01

365

Limits of High Harmonic Generation conversion efficiency  

E-print Network

High Harmonic Generation (HHG) is a fascinating phenomenon from both fundamental and technological point of view. It enables the generation of attosecond pulses and can have applications in EUV lithography and bio-microscopy. ...

Gkortsas, Vasileios-Marios

2013-01-01

366

Dirac-harmonic maps with torsion  

E-print Network

We study Dirac-harmonic maps from surfaces to manifolds with torsion, which is motivated from the superstring action considered in theoretical physics. We discuss analytic and geometric properties of such maps and outline an existence result for uncoupled solutions.

Volker Branding

2014-05-20

367

Improved Efficiency Type II Second Harmonic Generation  

NASA Technical Reports Server (NTRS)

Second harmonic efficiency is limited by lateral and temporal separation of the ordinary and extraordinary components of the fundamental. A mode locked dual beam laser demonstrated these effects and a novel method to minimize them.

Barnes, Norman P.; Walsh, Brian M.; Reichle, Donald J., Jr.

2009-01-01

368

Parametric Estimation of Harmonically Related Sinusoids  

E-print Network

algorithm proves quite robust and successfully tracks both stationary and slowly varying frequency signals. Later, we propose an algorithm for fundamental frequency estimation which relies on the initial harmonic frequency estimate. The results of tests...

Dixit, Richa

2010-04-01

369

Human Lung Angiotensin Converting Enzyme  

PubMed Central

To enable its immunohistologic localization, angiotensin converting enzyme (EC 3.4.15.1) from human lung was solubilized by trypsinization and purified ?2,660-fold to apparent homogeneity from a washed lung particulate fraction. The specific activity of pure enzyme was estimated to be 117 ?mol/min per mg protein with the substrate hippuryl-l-histidyl-l-leucine. Consistent with previously described lung enzyme studies, catalytic activity was strongly inhibited by EDTA, O-phenanthroline, SQ 20,881, and SQ 14,225 and increased by CoCl2. SQ 20,881 was a somewhat more potent inhibitor than SQ 14,225, unlike rabbit lung enzyme. The Michaelis constant (Km) with hippuryl-l-histidyl-l-leucine was 1.6 mM. The molecular weight was estimated at 150,000 from sucrose density gradient centrifugation. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed a single polypeptide chain estimated at 130,000 daltons. Rabbit antibody to human lung enzyme was prepared by parenteral administration of pure angiotensin-converting enzyme in Freund's adjuvant. Rabbit antibody to human lung angiotensin-converting enzyme appeared to crossreact weakly with the rabbit enzyme and strongly inhibited the catalytic activity of the enzymes from human serum, lung, and lymph node. The specificity of the rabbit antibody and purity of the final human lung enzyme preparation was suggested by the single precipitin lines obtained by radial double immunodiffusion, and by the coincidence of enzyme catalytic activity and immunoreactivity on polyacrylamide gel electrophoresis, with both relatively pure and highly impure enzymes. Generally applicable sensitive analysis of acrylamide gels for immunoreactivity (and subsequently for any other activity) by use of intact gel slices in radial double immunodiffusion was devised. Human lung enzyme was very tightly bound to and catalytically active on anti-human enzyme antibody covalently bound to Sepharose 4B, and could not be readily dissociated without inactivation. Antibody to human lung angiotensin converting enzyme has permitted tissue localization of the enzyme, which appears to be clinically useful in diseases associated with abnormal abundance of angiotensin-converting enzyme in tissues, such as sarcoidosis. Images PMID:6259212

Friedland, Joan; Silverstein, Emanuel; Drooker, Martin; Setton, Charlotte

1981-01-01

370

Power Quality/Harmonic Detection: Harmonic Control in Electric Power Systems for the Telecommunications Industry  

E-print Network

if harmonics are present both in the voltage and current waveforms. There are a range of instruments that can be used to indicate harmonic distortion from a general purpose Oscilloscope to a specially designed Harmonic Analyzer. A general purpose low...-Linear Components Some Motors DC drives/power supplies Incandescent Variable frequency drives lighting Programmable controllers Heating loads Induction furnaces Solid-state uninterrupt ible power supplies (UPS) Arc furnaces and Arc welders Electronic power...

Felkner, L. J.; Waggoner, R. M.

371

Second harmonic generation in a low-loss orientation-patterned GaAs waveguide.  

PubMed

The technology of low-loss orientation-patterned gallium arsenide (OP-GaAs) waveguided crystals was developed and realized by reduction of diffraction scattering on the waveguide pattern. The propagation losses in the OP-GaAs waveguide were estimated to be as low as 2.1 dB/cm, thus demonstrating the efficient second harmonic generation at 1621 nm under an external pumping. PMID:23938493

Fedorova, K A; McRobbie, A D; Sokolovskii, G S; Schunemann, P G; Rafailov, E U

2013-07-15

372

Coherent states for the nonlinear harmonic oscillator  

SciTech Connect

Wave packets for the quantum nonlinear oscillator are considered in the generalized coherent state framework. To first order in the nonlinearity parameter the coherent state behaves very similar to its classical counterpart. The position expectation value oscillates in a simple harmonic manner. The energy-momentum uncertainty relation is time independent as in a harmonic oscillator. Various features (such as the squeezed state nature) of the coherent state have been discussed.

Ghosh, Subir [Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 B. T. Road, Kolkata 700108 (India)

2012-06-15

373

Fast Analysis\\/Synthesis of Harmonic Signals  

Microsoft Academic Search

Harmonic models are commonly used in signal processing. The analysis of harmonic signals requires the solution of a symmetric Toeplitz system of equations. Levinson-based Toeplitz solvers have a O(n 2) complexity. This paper proposes an O(n) algorithm by encoding the inverse matrices required for the solution of the linear system to a few parameters in order to obtain an approximate

M. Vasilakis; Y. Agiomyrgiannakis; Y. Stylianou

2006-01-01

374

Spectral characterization of some second harmonic generation materials from the amino acid family: L-Threonine and L-prolinium tartrate  

NASA Astrophysics Data System (ADS)

Single crystals of the organic non-linear optical materials L-threonine (I) and L-prolinium tartrate (II) were grown using a home-made crystal growth setup (MKN setup). The grown crystals were characterized using X-ray diffraction, Infrared (IR), UV-vis-NIR and Circular dichroism (CD) spectroscopy. Measurements of Vicker’s microhardness, laser damage threshold (LDT) values and second harmonic generation (SHG) efficiencies are reported. Thermal and dielectric studies were also carried out.

Moovendaran, K.; Natarajan, S.

2014-08-01

375

Higher-Order Harmonic Generation from Fullerene by Means of the Plasma Harmonic Method  

SciTech Connect

We demonstrate, for the first time, high-order harmonic generation from C{sub 60} by an intense femtosecond Ti:sapphire laser. Laser-produced plasmas from C{sub 60}-rich epoxy and C{sub 60} films were used as the nonlinear media. Harmonics up to the 19th order were observed. The harmonic yield from fullerene-rich plasma is about 25 times larger compared with those produced from a bulk carbon target. Structural studies of plasma debris confirm the presence and integrity of fullerenes within the plasma plume, indicating fullerenes as the source of high-order harmonics.

Ganeev, R. A. [Institut National de la Recherche Scientifique, Energie, Materiaux et Telecommunications, 1650 Lionel-Boulet, Varennes, Quebec J3X 1S2 (Canada); Scientific Association Akadempribor, Academy of Sciences of Uzbekistan, Akademgorodok, Tashkent 100125 (Uzbekistan); Bom, L. B. Elouga; Abdul-Hadi, J.; Ozaki, T. [Institut National de la Recherche Scientifique, Energie, Materiaux et Telecommunications, 1650 Lionel-Boulet, Varennes, Quebec J3X 1S2 (Canada); Wong, M. C. H.; Brichta, J. P.; Bhardwaj, V. R. [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada)

2009-01-09

376

Harmonic Oscillators as Bridges between Theories  

SciTech Connect

Other than scattering problems where perturbation theory is applicable, there are basically two ways to solve problems in physics. One is to reduce the problem to harmonic oscillators, and the other is to formulate the problem in terms of two-by-two matrices. If two oscillators are coupled, the problem combines both two-by-two matrices and harmonic oscillators. This method then becomes a powerful research tool to cover many different branches of physics. Indeed, the concept and methodology in one branch of physics can be translated into another through the common mathematical formalism. It is noted that the present form of quantum mechanics is largely a physics of harmonic oscillators. Special relativity is the physics of the Lorentz group which can be represented by the group of by two-by-two matrices commonly called SL(2, c). Thus the coupled harmonic oscillators can therefore play the role of combining quantum mechanics with special relativity. Both Paul A. M. Dirac and Richard P. Feynman were fond of harmonic oscillators, while they used different approaches to physical problems. Both were also keenly interested in making quantum mechanics compatible with special relativity. It is shown that the coupled harmonic oscillators can bridge these two different approaches to physics.

Kim, Y.S. [Department of Physics, University of Maryland College Park, Maryland 20742 (United States); Noz, Marilyn E. [Department of Radiology, New York University, New York, New York 10016 (United States)

2005-03-31

377

High order harmonics from relativistic electron spikes  

NASA Astrophysics Data System (ADS)

A new regime of relativistic high-order harmonic generation has been discovered (Pirozhkov 2012 Phys. Rev. Lett. 108 135004). Multi-terawatt relativistic-irradiance (>1018 W cm?2) femtosecond (?30–50 fs) lasers focused to underdense (few × 1019 cm?3) plasma formed in gas jet targets produce comb-like spectra with hundreds of even and odd harmonic orders reaching the photon energy of 360 eV, including the ‘water window’ spectral range. Harmonics are generated either by linearly or circularly polarized pulses from the J-KAREN (KPSI, JAEA) and Astra Gemini (CLF, RAL, UK) lasers. The photon number scalability has been demonstrated with a 120 TW laser, producing 40 ?J sr?1 per harmonic at 120 eV. The experimental results are explained using particle-in-cell simulations and catastrophe theory. A new mechanism of harmonic generation by sharp, structurally stable, oscillating electron spikes at the joint of the boundaries of the wake and bow waves excited by a laser pulse is introduced. In this paper, detailed descriptions of the experiments, simulations and model are provided and new features are shown, including data obtained with a two-channel spectrograph, harmonic generation by circularly polarized laser pulses and angular distribution.

Pirozhkov, Alexander S.; Kando, Masaki; Esirkepov, Timur Zh; Gallegos, Pablo; Ahmed, Hamad; Ragozin, Eugene N.; Faenov, Anatoly Ya; Pikuz, Tatiana A.; Kawachi, Tetsuya; Sagisaka, Akito; Koga, James K.; Coury, Mireille; Green, James; Foster, Peta; Brenner, Ceri; Dromey, Brendan; Symes, Dan R.; Mori, Michiaki; Kawase, Keigo; Kameshima, Takashi; Fukuda, Yuji; Chen, Liming; Daito, Izuru; Ogura, Koichi; Hayashi, Yukio; Kotaki, Hideyuki; Kiriyama, Hiromitsu; Okada, Hajime; Nishimori, Nobuyuki; Imazono, Takashi; Kondo, Kiminori; Kimura, Toyoaki; Tajima, Toshiki; Daido, Hiroyuki; Rajeev, Pattathil; McKenna, Paul; Borghesi, Marco; Neely, David; Kato, Yoshiaki; Bulanov, Sergei V.

2014-09-01

378

Dual aperture dipole magnet with second harmonic component  

SciTech Connect

An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

Praeg, Walter F. (Palos Park, IL)

1985-01-01

379

Dual aperture dipole magnet with second harmonic component  

DOEpatents

An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

Praeg, W.F.

1983-08-31

380

Second harmonic generation of a new nonlinear optical material: urea L-malic acid  

NASA Astrophysics Data System (ADS)

Second harmonic generation (SHG) of a new organic optical crystal-urea L-malic acid (ULMA) was studied. A comparison of SHG efficiency of ULMA and KDP at a fundamental wavelength of 1064 nm using the Kurtz powder method demonstrated that the second order nonlinear coefficient of ULMA is 1.57 times of that of KDP, and the damage threshold of ULMA is relatively higher. Finally, both Type I and Type II phase match angles of the biaxial crystal ULMA were calculated.

Chen, Ding-An; Zhu, Li; Hu, Yong-Hong; Xu, Ling-Ling; Cui, Yi-Ping

2006-03-01

381

Method for reducing energy losses in laser crystals  

DOEpatents

A process for reducing energy losses in crystals is disclosed which comprises: a. heating a crystal to a temperature sufficiently high as to cause dissolution of microscopic inclusions into the crystal, thereby converting said inclusions into point-defects, and b. maintaining said crystal at a given temperature for a period of time sufficient to cause said point-defects to diffuse out of said crystal. Also disclosed are crystals treated by the process, and lasers utilizing the crystals as a source of light. 12 figs.

Atherton, L.J.; DeYoreo, J.J.; Roberts, D.H.

1992-03-24

382

Method for reducing energy losses in laser crystals  

DOEpatents

A process for reducing energy losses in crystals is disclosed which comprises: a. heating a crystal to a temperature sufficiently high as to cause dissolution of microscopic inclusions into the crystal, thereby converting said inclusions into point-defects, and b. maintaining said crystal at a given temperature for a period of time sufficient to cause said point-defects to diffuse out of said crystal. Also disclosed are crystals treated by the process, and lasers utilizing the crystals as a source of light.

Atherton, L. Jeffrey (Pleasanton, CA); DeYoreo, James J. (Livermore, CA); Roberts, David H. (Pleasanton, CA)

1992-01-01

383

Cell modulated DC/DC converter  

E-print Network

A very high frequency converter roughly based on a class E topology is investigated for replacing a conventional boost converter circuit. The loss mechanisms in class E inverters are characterized, and metrics are developed ...

Warren, James Raymond, III

2005-01-01

384

The harmonic oscillator and the position dependent mass Schroedinger equation: isospectral partners and factorization operators  

SciTech Connect

One of the most important scientific contributions of Professor Marcos Moshinsky has been his study on the harmonic oscillator in quantum theory vis a vis the standard Schroedinger equation with constant mass [1]. However, a simple description of the motion of a particle interacting with an external environment such as happen in compositionally graded alloys consist of replacing the mass by the so-called effective mass that is in general variable and dependent on position. Therefore, honoring in memoriam Marcos Moshinsky, in this work we consider the position-dependent mass Schrodinger equations (PDMSE) for the harmonic oscillator potential model as former potential as well as with equi-spaced spectrum solutions, i.e. harmonic oscillator isospectral partners. To that purpose, the point canonical transformation method to convert a general second order differential equation (DE), of Sturm-Liouville type, into a Schroedinger-like standard equation is applied to the PDMSE. In that case, the former potential associated to the PDMSE and the potential involved in the Schroedinger-like standard equation are related through a Riccati-type relationship that includes the equivalent of the Witten superpotential to determine the exactly solvable positions-dependent mass distribution (PDMD)m(x). Even though the proposed approach is exemplified with the harmonic oscillator potential, the procedure is general and can be straightforwardly applied to other DEs.

Morales, J.; Ovando, G.; Pena, J. J. [Universidad Autonoma Metropolitana-Azcapotzalco, CBI-Area de Fisica Atomica Molecular Aplicada, Av. San Pablo 180, Reynosa Azcapotzalco, 02200 Mexico, D. F. (Mexico)

2010-12-23

385

CMB map derived from the WMAP data through harmonic internal linear combination  

SciTech Connect

We are presenting an internal linear combination CMB map, in which the foreground is reduced through harmonic variance minimization. We have derived our method by converting a general form of pixel-space approach into spherical harmonic space, maintaining full correspondence. By working in spherical harmonic space, spatial variability of linear weights is incorporated in a self-contained manner and our linear weights are continuous functions of position over the entire sky. The full correspondence to pixel-space approach enables straightforward physical interpretation on our approach. In variance minimization of a linear combination map, the existence of a cross term between residual foregrounds and CMB makes the linear combination of minimum variance differ from that of minimum foreground. We have developed an iterative foreground reduction method, where perturbative correction is made for the cross term. Our CMB map derived from the WMAP data is in better agreement with the WMAP best-fit {lambda}CDM model than the WMAP team's internal linear combination map. We find that our method's capacity to clean foreground is limited by the availability of enough spherical harmonic coefficients of good signal-to-noise ratio.

Kim, Jaiseung; Naselsky, Pavel; Christensen, Per Rex [Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark)

2008-05-15

386

Auxiliary resonant DC tank converter  

DOEpatents

An auxiliary resonant dc tank (ARDCT) converter is provided for achieving soft-switching in a power converter. An ARDCT circuit is coupled directly across a dc bus to the inverter to generate a resonant dc bus voltage, including upper and lower resonant capacitors connected in series as a resonant leg, first and second dc tank capacitors connected in series as a tank leg, and an auxiliary resonant circuit comprising a series combination of a resonant inductor and a pair of auxiliary switching devices. The ARDCT circuit further includes first clamping means for holding the resonant dc bus voltage to the dc tank voltage of the tank leg, and second clamping means for clamping the resonant dc bus voltage to zero during a resonant period. The ARDCT circuit resonantly brings the dc bus voltage to zero in order to provide a zero-voltage switching opportunity for the inverter, then quickly rebounds the dc bus voltage back to the dc tank voltage after the inverter changes state. The auxiliary switching devices are turned on and off under zero-current conditions. The ARDCT circuit only absorbs ripples of the inverter dc bus current, thus having less current stress. In addition, since the ARDCT circuit is coupled in parallel with the dc power supply and the inverter for merely assisting soft-switching of the inverter without participating in real dc power transmission and power conversion, malfunction and failure of the tank circuit will not affect the functional operation of the inverter; thus a highly reliable converter system is expected.

Peng, Fang Z. (Knoxville, TN)

2000-01-01

387

Heat flow in a pyroelectric converter  

Microsoft Academic Search

A simulated pyroelectric converter has been constructed. The heat flow and temperature profiles within the converter have been measured. Computer simulations of the heat flow compare well with the measurements and predict an efficiency of 12 percent of the Carnot limit for a real pyroelectric converter with the operating configuration of the simulation. These heat flow results are useful in

R. B. Olsen; W. F. Butler; J. E. Drummond; D. A. Bruno; J. M. Briscoe

1985-01-01

388

Electromagnetic Compatibility of Matrix Converter System  

Microsoft Academic Search

Abstract. The presented paper ,deals with matrix converters pulse width modulation strategies design with emphasis on the ,electromagnetic compatibility. Matrix converters provide an all-silicon solution to the problem of converting AC power from one frequency to another, offering almost all the features required of an ideal static frequency changer. They possess many ,advantages compared to the conventional voltage or current

Ji?í Lettl; Stanislav Flígl

389

Nonlinear-optic IR radiation converters  

NASA Astrophysics Data System (ADS)

A new class of instruments, nonlinear-optic (parametric) IR-visible converters, is described. A geometrical optics approximation and the diffraction theory are presented, and an analysis is made of the converter efficiency, noise characteristics, and threshold sensitivity of IR nonlinear-optic IR detection schemes. The theoretically derived converter parameters are compared with experimental data.

Gainer, Aleksandr V.

390

Harmonic current emission of photovoltaic installations under system conditions  

Microsoft Academic Search

Harmonic currents of PV-inverters show a significant dependency on the harmonic voltage content of the AC-system voltage. Measurements of harmonic currents were carried out in LV-systems and under laboratory test conditions with adjustable harmonic content of the AV-voltage. Two PV-inverters, one with coupling transformer and one without transformer were tested. The results indicated that the emitted harmonic currents depend strongly

J. Schlabbach

2008-01-01

391

High-order-harmonic generation driven by metal nanotip photoemission: Theory and simulations  

NASA Astrophysics Data System (ADS)

We present theoretical predictions of high-order-harmonic generation resulting from the interaction of short femtosecond laser pulses with metal nanotips. It is demonstrated that high-energy electrons can be generated using nanotips as sources; furthermore, the recollision mechanism is proven to be intrinsically linked to this high-energy tail. If recollision exists, it should be possible to convert the energy gained by the electron in the continuum in a high-energy photon. Consequently, the emission of harmonic radiation appears to be viable. We employ a quantum mechanical time-dependent approach to model the electron dipole moment including both the laser experimental conditions and the bulk matter properties. The use of metal tips should provide an alternative way of generating coherent XUV light with a femtosecond laser field.

Ciappina, M. F.; Pérez-Hernández, J. A.; Shaaran, T.; Lewenstein, M.; Krüger, M.; Hommelhoff, P.

2014-01-01

392

Highly efficient deep ultraviolet generation by sum-frequency mixing in a BBO crystal pair  

Microsoft Academic Search

Generation of deep ultraviolet radiation at 210 nm by Type-I third harmonic generation is achieved in a pair of BBO crystals\\u000a with conversion efficiency as high as 36%. The fundamental source is the dye laser radiation pumped by the second harmonic\\u000a of a Q-switched Nd: YAG laser. A walk-off compensated configuration with the BBO crystal pair has enabled us to

Gopal C Bhar; Pathik Kumbhakar; Udit Chatterjee; Anil K Chaudhary; Alexander Kokh

2002-01-01

393

Crystallization of soft crystals.  

PubMed

The crystallization of micelles formed by surfactant F127 solvated by 20% in water was investigated in the vicinity of a hydrophilic interface. Upon entering the crystalline phase from low temperature, a large correlation length develops without preferential texture. Upon heating, the correlation length decreases and Oswald ripening is observed with crystallites orienting with respect to each other while retaining long-range and textured correlation. PMID:19115865

Wolff, Max; Magerl, Andreas; Zabel, Hartmut

2009-01-01

394

Crystal growth, spectral, structural and optical studies of ?-conjugated stilbazolium crystal: 4-bromobenzaldehyde-4'-N'-methylstilbazolium tosylate.  

PubMed

Nonlinear optical (NLO) organic compound, 4-bromobenzaldehyde-4'-N'-methylstilbazolium tosylate was synthesized by reflux method. The formation of molecular complex was confirmed from (1)H NMR, FT-IR and FT-Raman spectral analyses. The single crystals were grown by slow evaporation solution growth method and the crystal structure and atomic packing of grown crystal was identified. The morphology and growth axis of grown crystal were determined. The crystal perfection was analyzed using high resolution X-ray diffraction study on (001) plane. Thermal stability, decomposition stages and melting point of the grown crystal were analyzed. The optical absorption coefficient (?) and energy band gap (E(g)) of the crystal were determined using UV-visible absorption studies. Second harmonic generation efficiency of the grown crystal was examined by Kurtz powder method with different particle size using 1064 nm laser. Laser induced damage threshold study was carried out for the grown crystal using Nd:YAG laser. PMID:24531108

Krishna Kumar, M; Sudhahar, S; Bhagavannarayana, G; Mohan Kumar, R

2014-05-01

395

repulsion and quantization in almost-harmonic maps, and asymptotics of the harmonic map flow  

E-print Network

.5.3 Neck surgery and energy quantization . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 2 a surface, their energy is precisely the area of their image, and thus E(u) = 4#25;j deg(u)j 2 4#25;Z, it is known that u will resemble a harmonic `body' map h : S 2 ! S 2 with a #12;nite number of harmonic

Mitchener, Paul

396

Photovoltaic converters for solar-pumped lasers  

NASA Technical Reports Server (NTRS)

The authors describe a mathematical parametric study of converters used to convert laser radiation to electricity for space-based laser power systems. Two different lasers, the 1.06-micron Nd laser and the 1.315-micron iodine laser, are used in the vertical junction converter. The calculated efficiency is 50 percent for a 100-junction Si photovoltaic converter when used with a Nd laser. The calculated efficiency for a 1000-junction Ga(0.53)In(0.47)As photovoltaic converter is 43 percent when used with an iodine laser.

Walker, Gilbert H.; Heinbockel, John H.

1988-01-01

397

Radicalization of Homegrown Sunni Militants in the United States: Comparing Converts and Non-Converts  

Microsoft Academic Search

Are the mechanisms and processes that lead to radicalization different for Muslim converts and non-converts in the United States? While many scholars attempt to explain why people violently radicalize, the theories are diverse and most treat converts and non-converts the same. This study answers this question by categorizing the many radicalization theories into three levels of analysis so that cases

Scott Matthew Kleinmann

2012-01-01

398

Improved fourth harmonic generation in ?-BaB 2O 4 by tight elliptical focusing perpendicular to walk-off plane  

NASA Astrophysics Data System (ADS)

We present a scheme using beta-barium borate (BBO) crystal to maximize fourth-harmonic ultraviolet (UV) generation from high-power, kHz-range repetition rate Nd lasers by reducing thermal dephasing during the phase matching process. Thermal dephasing due to nonlinear absorption (NLA) induced by two-photon absorption of high peak power fourth-harmonic UV radiation is reduced by minimizing second- and fourth-harmonic beam overlap through tight elliptical focusing perpendicular to the walk-off plane, leading to multi-watt, kHz-range repetition rate UV generation in BBO crystal. With such beam shaping, nearly 5 W at 10 kHz of 262-nm UV radiation is generated using an 8-mm long BBO crystal. The results of our investigation show an efficient way of achieving multi-watt UV generation at kHz-range repetition rate.

Takahashi, Masakuni; Osada, Akira; Dergachev, Alex; Moulton, Peter F.; Cadatal-Raduban, Marilou; Shimizu, Toshihiko; Sarukura, Nobuhiko

2011-03-01

399

Abstract--The offshore wind farm with installed back-to-back power converter in wind turbines is studied. As an  

E-print Network

Abstract--The offshore wind farm with installed back-to- back power converter in wind turbines is studied. As an example the Burbo Bank offshore wind farm with Siemens Wind Power wind turbines is taken installed in wind turbines are presented. Harmonic load flow analysis and impedance frequency

Bak, Claus Leth

400

Snow Crystals  

NSDL National Science Digital Library

This site describes snow crystals and snowflakes. Although a common meteorological phenomenon, snow crystal growth is a fascinating and poorly understood process, in which remarkably complex and beautifully symmetric structures appear, quite literally, out of thin air. The many facets of snow crystals are described here, along with the attempts to understand their formation. Site highlights include research on creating designer snow crystals in the laboratory, the history of early snow crystal observations, snow crystal photography, properties of frozen precipitation, and a snow crystal primer for a short course in snow crystal physics - what snow crystals are, how they form, and why they form the way they do. Information is offered on snow crystal classification, preservation, and unusual crystal forms. An extensive image gallery of lab-created crystal forms is available, with enlargeable thumbnail images. There are even instructions for users on how to create crystals. This could be made into a classroom activity, as the science of the growth is explained. Snowflake Physics discusses diffusion, dendrite growth, ice surface physics, electric growth, and ice properties. A vast list of related links is also provided.

Libbrecht, Kenneth

401

Second harmonic generation in isotropic media: six-wave mixing of optical vortices.  

PubMed

Optical vortex light can be up-converted into a second harmonic output in an isotropic medium, in which such conversion is normally forbidden, through six-wave mixing. The involvement of orbital angular momentum is tackled for the case of a Laguerre-Gaussian pump comprising l = 1 photons. By calculating quantum amplitudes for the emergent radiation states, utilizing a state-sequence method, the analysis identifies the characteristics of the emission and an entangled distribution of conserved orbital momentum. A distinctive conical spread affords a potential means of resolving the individual angular momentum content. PMID:23736496

Coles, Matt M; Williams, Mathew D; Andrews, David L

2013-05-20

402

A flash analog to digital converter on stainless steel foil substrate  

Microsoft Academic Search

In an effort to increase the integration level of large area digital and mixed-signal systems on flexible substrate, we designed and successfully fabricated and characterized a 3-bit flash analog to digital converter on stainless steel foil substrate. High quality laser crystallized polysilicon Thin Film Transistors (TFT) as well as carefully designed comparator circuit made it possible for a high performance

Abbas Jamshidi-Roudbari; Po-Chin Kuo; Miltiadis K. Hatalis

2010-01-01

403

Microcomputer control of power converters  

SciTech Connect

Thyristor power converters are charac terized by an inherent discrete control action and are, therefore, particularly well suited to on - line control by microcomputers. The paper presents a new design of digital controllers based upon powerful 16-bit or bit -slice microprocessors, which provide high firing time resolution and enough computing power to implement sophis ticated control strategies. Both hardware and software are discussed, with special emphasis on the firing con trol algorithms. The properties of Pulse Frequency Con trol (PFC) and Pulse Phase Control (PPC) are examined and small-signal discrete models are presented. These models are used in the analysis of constant current and constant extinction angle control through the z-transform method.

Alegria, C.M.; Freris, L.L.; Paiva, J.P.

1984-08-01

404

Thermionic converter emitter support arrangement  

DOEpatents

A support is provided for use in a therminonic converter to support an end of an emitter to keep it out of contact with a surrounding collector while allowing the emitter end to move axially as its temperature changes. The emitter end (34) is supported by a spring structure (44) that includes a pair of Belleville springs, and the spring structure is supported by a support structure (42) fixed to the housing that includes the collector. The support structure is in the form of a sandwich with a small metal spring-engaging element (74) at the front end, a larger metal main support (76) at the rear end that is attached to the housing, and with a ceramic layer (80) between them that is bonded by hot isostatic pressing to the metal element and metal main support. The spring structure can include a loose wafer (120) captured between the Belleville springs.

Allen, Daniel T. (La Jolla, CA)

1990-01-01

405

Thermionic converter emitter support arrangement  

DOEpatents

A support is provided for use in a thermionic converter to support an end an emitter to keep it out of contact with a surrounding collector while allowing the emitter end to move axially at its temperatures changes. The emitter end (34) is supported by a spring structure (44) that includes a pair of Belleville springs, and the spring structure is supported by a support structure (42) fixed to the housing that includes the collector. The support structure is in the form of a sandwich with a small metal spring-engaging element (74) at the front end, a larger metal main support (76) at the rear end that is attached to the housng, and with a ceramic layer (80) between them that is bonded by hot isostatic pressing to the metal element and metal main support. The spring structure can include a loose wafer (120) captured between the Belleville springs.

Allen, Daniel T. (La Jolla, CA)

1990-01-01

406

High harmonic phase in molecular nitrogen  

SciTech Connect

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.

McFarland, Brian K.

2009-10-17

407

The harmonic oscillator and nuclear physics  

NASA Technical Reports Server (NTRS)

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.

Rowe, D. J.

1993-01-01

408

GRACE Harmonic and Mascon Solutions at JPL  

NASA Astrophysics Data System (ADS)

Gravity field solutions at JPL over the past few years have explored use of range, range-rate, and range-acceleration K/Ka-band satellite-satellite data types (with and without GPS), and with both spherical harmonic and mascon-type local mass representations. Until recently, resource and computing limitations have limited the scope of our mascon and other local solutions to a few months and/or small spatial regions and the standard GRACE products have remained spherical harmonic fields. The use of a new very large (~500 node) beowulf machine at JPL is now enabling a wider range of solutions over longer time spans and deeper understanding of their characteristics. These include much higher spherical harmonic degrees, mascons, and hybrids of the two. We will present the current status for several solution types, strengths and weaknesses of each, and our assessments of limiting errors including data noise and aliasing sensitivity.

Watkins, M. M.; Yuan, D.; Kuang, D.; Bertiger, W.; Kim, M.; Kruizinga, G. L.

2005-12-01

409

Second International Workshop on Harmonic Oscillators  

NASA Technical Reports Server (NTRS)

The Second International Workshop on Harmonic Oscillators was held at the Hotel Hacienda Cocoyoc from March 23 to 25, 1994. The Workshop gathered 67 participants; there were 10 invited lecturers, 30 plenary oral presentations, 15 posters, and plenty of discussion divided into the five sessions of this volume. The Organizing Committee was asked by the chairman of several Mexican funding agencies what exactly was meant by harmonic oscillators, and for what purpose the new research could be useful. Harmonic oscillators - as we explained - is a code name for a family of mathematical models based on the theory of Lie algebras and groups, with applications in a growing range of physical theories and technologies: molecular, atomic, nuclear and particle physics; quantum optics and communication theory.

Han, Daesoo (editor); Wolf, Kurt Bernardo (editor)

1995-01-01

410

Optical Third-Harmonic Generation in Graphene  

We report strong third-harmonic generation in monolayer graphene grown by chemical vapor deposition and transferred to an amorphous silica (glass) substrate; the photon energy is in three-photon resonance with the exciton-shifted van Hove singularity at the M point of graphene. The polarization selection rules are derived and experimentally verified. In addition, our polarization- and azimuthal-rotation-dependent third-harmonic-generation measurements reveal in-plane isotropy as well as anisotropy between the in-plane and out-of-plane nonlinear optical responses of graphene. Since the third-harmonic signal exceeds that from bulk glass by more than 2 orders of magnitude, the signal contrast permits background-free scanning of graphene and provides insight into the structural properties of graphene.

Hong, Sung-Young; Dadap, Jerry I.; Petrone, Nicholas; Yeh, Po-Chun; Hone, James; Osgood, Richard M.

2013-06-01

411

Influence of small-scale self-focusing on second harmonic generation in an intense laser field  

SciTech Connect

Linearised equations for the amplitudes of harmonic perturbations of strong waves in quadratic and cubic nonlinear media are obtained within the model of plane monochromatic waves. The dependences of the gains of noise components of the first and second harmonic waves upon frequency doubling on the B integral are found. The maximally admissible noise level in the fundamental radiation beam is calculated by the example of a 0.5-mm-long KDP crystal at the peak intensity of 4.5 TW cm{sup -2}. (nonlinear-optics phenomena)

Ginzburg, V N; Lozhkarev, V V; Mironov, S Yu; Potemkin, A K; Khazanov, Efim A [Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

2010-08-27

412

Efficient second-harmonic generation of continuous-wave Yb fiber lasers coupled with an external resonant cavity  

NASA Astrophysics Data System (ADS)

Efficient second-harmonic generation of continuous-wave Yb fiber lasers is reported. A simple bow-tie external resonant cavity incorporating a type I LBO nonlinear optical crystal was employed for second harmonic frequency conversion of a multi-longitudinal-mode Yb fiber laser. It is shown that strong coupling was formed between the Yb fiber laser and the external cavity and, as a result, the laser produced 9.1 W of green output at 535 nm for 43 W of absorbed diode pump power at 975 nm corresponding to an optical conversion efficiency of 21 % with respect to absorbed diode pump power. The prospects for further improvement are discussed.

Kim, J. W.; Jeong, J.; Lee, K.; Lee, S. B.

2012-09-01

413

Visible femtosecond pulses by second-harmonic generation of a cw mode-locked KTP optical parametric oscillator  

NASA Astrophysics Data System (ADS)

Efficient generation of femtosecond pulses in the wavelength range from 520 to 675 nm by external frequency doubling the signal wave of a non-critically phase-matched picosecond KTP Optical Parametric Oscillator (OPO) in a non-critically phase-matched temperature tuned LiB3O5(LBO) crystal is demonstrated. An average power of the second harmonic as high as 310 mW at 575 nm was generated. In the absence of group velocity mismatch of LBO for a wavelength of the OPO at about 1.3 µm the minimum second-harmonic pulse width was 400 fs at 645 nm.

Nebel, A.; Frost, H.; Beigang, R.; Wallenstein, R.

1995-05-01

414

Extraordinary Second Harmonic Generation in Tungsten Disulfide Monolayers  

NASA Astrophysics Data System (ADS)

We investigate Second Harmonic Generation (SHG) in monolayer WS2 both deposited on a SiO2/Si substrate or suspended using transmission electron microscopy grids. We find unusually large second order nonlinear susceptibility, with an estimated value of deff ~ 4.5 nm/V nearly three orders of magnitude larger than other common nonlinear crystals. In order to quantitatively characterize the nonlinear susceptibility of two-dimensional (2D) materials, we have developed a formalism to model SHG based on the Green's function with a 2D nonlinear sheet source. In addition, polarized SHG is demonstrated as a useful method to probe the structural symmetry and crystal orientation of 2D materials. To understand the large second order nonlinear susceptibility of monolayer WS2, density functional theory based calculation is performed. Our analysis suggests the origin of the large nonlinear susceptibility in resonance enhancement and a large joint density of states, and yields an estimate of the nonlinear susceptibility value deff = 0.77 nm/V for monolayer WS2, which shows good order-of-magnitude agreement with the experimental result.

Janisch, Corey; Wang, Yuanxi; Ma, Ding; Mehta, Nikhil; Elías, Ana Laura; Perea-López, Néstor; Terrones, Mauricio; Crespi, Vincent; Liu, Zhiwen

2014-07-01

415

Extraordinary Second Harmonic Generation in tungsten disulfide monolayers.  

PubMed

We investigate Second Harmonic Generation (SHG) in monolayer WS? both deposited on a SiO?/Si substrate or suspended using transmission electron microscopy grids. We find unusually large second order nonlinear susceptibility, with an estimated value of d(eff) ~ 4.5?nm/V nearly three orders of magnitude larger than other common nonlinear crystals. In order to quantitatively characterize the nonlinear susceptibility of two-dimensional (2D) materials, we have developed a formalism to model SHG based on the Green's function with a 2D nonlinear sheet source. In addition, polarized SHG is demonstrated as a useful method to probe the structural symmetry and crystal orientation of 2D materials. To understand the large second order nonlinear susceptibility of monolayer WS?, density functional theory based calculation is performed. Our analysis suggests the origin of the large nonlinear susceptibility in resonance enhancement and a large joint density of states, and yields an estimate of the nonlinear susceptibility value d(eff) = 0.77?nm/V for monolayer WS?, which shows good order-of-magnitude agreement with the experimental result. PMID:24984953

Janisch, Corey; Wang, Yuanxi; Ma, Ding; Mehta, Nikhil; Elías, Ana Laura; Perea-López, Néstor; Terrones, Mauricio; Crespi, Vincent; Liu, Zhiwen

2014-01-01

416

Extraordinary Second Harmonic Generation in Tungsten Disulfide Monolayers  

PubMed Central

We investigate Second Harmonic Generation (SHG) in monolayer WS2 both deposited on a SiO2/Si substrate or suspended using transmission electron microscopy grids. We find unusually large second order nonlinear susceptibility, with an estimated value of deff ~ 4.5?nm/V nearly three orders of magnitude larger than other common nonlinear crystals. In order to quantitatively characterize the nonlinear susceptibility of two-dimensional (2D) materials, we have developed a formalism to model SHG based on the Green's function with a 2D nonlinear sheet source. In addition, polarized SHG is demonstrated as a useful method to probe the structural symmetry and crystal orientation of 2D materials. To understand the large second order nonlinear susceptibility of monolayer WS2, density functional theory based calculation is performed. Our analysis suggests the origin of the large nonlinear susceptibility in resonance enhancement and a large joint density of states, and yields an estimate of the nonlinear susceptibility value deff = 0.77?nm/V for monolayer WS2, which shows good order-of-magnitude agreement with the experimental result. PMID:24984953

Janisch, Corey; Wang, Yuanxi; Ma, Ding; Mehta, Nikhil; Elias, Ana Laura; Perea-Lopez, Nestor; Terrones, Mauricio; Crespi, Vincent; Liu, Zhiwen

2014-01-01

417

Application of a Series-Connected Hybrid Multi-Converter System to STATCOM  

NASA Astrophysics Data System (ADS)

This paper gives an analysis and design of a static synchronous compensator (STATCOM) using a series-connected hybrid multi-converter system. The hybrid multi-converter system consists of two GTO converters and an IGBT converter connected in series by transformers. The proposed STATCOM has advantages that the harmonic components of the output voltage/current would be less than a conventional configuration STATCOM composed of a 12-, 24-, or 48-pulse converter; the total switching losses would be less than a PWM STATCOM; and the response would be as rapid as a PWM STATCOM. One problem of the hybrid configuration STATCOM is that it tends to operate in an over-modulation range if a considerable compensating reference change occurs. To solve this problem, this paper also proposes a variable DC voltage control strategy, where the DC voltage is adaptively adjusted in accordance with the required reactive power. The validity of the proposed configuration STATCOM and control strategies are verified by simulation and experimental results.

Li, Dongsheng; Fukuda, Shoji

418

Intermediate Mechanics Tutorials: Simple Harmonic Motion  

NSDL National Science Digital Library

This set of tutorial materials covers the topic of simple harmonic motion. Students examine qualitatively and quantitatively the motion of a simple harmonic oscillator, as exemplified by a mass attached to an ideal spring. There are two tutorials, one using motion graphs and one using vectors, to describe the motion. Students analyze and solve the differential equations of motion to develop an understanding of the physical parameters in the problem. This material also includes a pretest, example homework, and test questions. This is part of a large collection of similar tutorial materials in intermediate classical mechanics.

Wittmann, Michael C.; Ambrose, Bradley S.

2009-03-31

419

Spin conservation in high harmonic generation  

E-print Network

We present an alternative theoretical model for a recent experiment [A. Fleischer et al., arXiv:1310.1206] which used bichromatic, counter-rotating high intensity laser pulses to probe the conservation of spin angular momentum in high harmonic generation. We separate elliptical polarizations into independent circular fields with definite angular momentum, instead of using the expectation value of spin for each photon in the conservation equation, and we find good agreement with the experimental results. In our description the generation of each individual harmonic conserves spin angular momentum, in contrast to the model proposed by Fleischer et al. Our model also correctly describes analogous processes in standard perturbative optics.

Pisanty, Emilio

2014-01-01

420

Crystal Movies  

NSDL National Science Digital Library

This site, maintained by the Geosciences Department at the University of Arizona, contains animated gif files of common mineral crystals. The movies show crystal structures evolving as a function of pressure, temperature, chemistry, or orientation. The movies are an excellent aid for visualizing the structure of various crystals.

Downs, R. T.; Arizona, University O.

421

Extraction of small boat harmonic signatures from passive sonar.  

PubMed

This paper investigates the extraction of acoustic signatures from small boats using a passive sonar system. Noise radiated from a small boats consists of broadband noise and harmonically related tones that correspond to engine and propeller specifications. A signal processing method to automatically extract the harmonic structure of noise radiated from small boats is developed. The Harmonic Extraction and Analysis Tool (HEAT) estimates the instantaneous fundamental frequency of the harmonic tones, refines the fundamental frequency estimate using a Kalman filter, and automatically extracts the amplitudes of the harmonic tonals to generate a harmonic signature for the boat. Results are presented that show the HEAT algorithms ability to extract these signatures. PMID:21682400

Ogden, George L; Zurk, Lisa M; Jones, Mark E; Peterson, Mary E

2011-06-01

422

Growth and characterization of organometallic l-alanine cadmium chloride single crystal by slow evaporation technique  

Microsoft Academic Search

Single crystals of l-alanine cadmium chloride (LACC), an organometallic nonlinear optical material, have been grown by the slow evaporation technique. The grown crystals were subjected to various characterization techniques, such as single crystal and powder XRD, FTIR, UV–vis and TGA-DTA. The mechanical properties of the crystals show that this material belongs to the category of hard materials. Second harmonic generation

K. C. Bright; T. H. Freeda

2010-01-01

423

Growth and characterization of organometallic L-alanine cadmium chloride single crystal by slow evaporation technique  

Microsoft Academic Search

Single crystals of L-alanine cadmium chloride (LACC), an organometallic nonlinear optical material, have been grown by the slow evaporation technique. The grown crystals were subjected to various characterization techniques, such as single crystal and powder XRD, FTIR, UV-vis and TGA-DTA. The mechanical properties of the crystals show that this material belongs to the category of hard materials. Second harmonic generation

K. C. Bright; T. H. Freeda

2010-01-01

424

Growth and characterization of new organic nonlinear optical crystal (R)-2-cyano-N-(1-phenylethyl) acetamide  

NASA Astrophysics Data System (ADS)

(R)-2-Cyano-N-(1-phenylethyl) acetamide (RCNPA) single crystals were grown by slow evaporation of the aqueous solution at room temperature (300K) using ethanol. The grown crystals were characterized by single crystal X-ray diffraction, powder X-ray diffraction, FTIR, UV-Vis-NIR transmittance, scanning electron microscopy (SEM) and powder second harmonic generation (SHG).

Hemaraju, B. C.; Madhukar, B. S.; Bhadregowda, D. G.; Gnana Prakash, A. P.

2014-04-01

425

Growth and characterization of hexamethylenetetramine crystals grown from solution  

NASA Astrophysics Data System (ADS)

Organic nonlinear optical single crystals of hexamethylenetetramine (HMT; 10 × 10 × 5 mm3) were prepared by crystallization from methanol solution. The grown crystals were subjected to various characterization techniques such as single crystal XRD, powder XRD, UV-Vis and electrical studies. Single crystal XRD analysis confirmed the crystalline structure of the grown crystals. Their crystalline nature was also confirmed by powder XRD technique. The optical transmittance property was identified from UV-Vis spectrum. Dielectric measurements were performed as a function of frequency at different temperatures. DC conductivity and photoconductivity studies were also carried out for the crystal. The powder second harmonic generation efficiency (SHG) of the crystal was measured using Nd:YAG laser and the efficiency was found to be two times greater than that of potassium dihydrogen phosphate (KDP).

Babu, B.; Chandrasekaran, J.; Balaprabhakaran, S.

2014-06-01

426

Temperature Fluctuations During Crystal Growth  

NASA Technical Reports Server (NTRS)

Technique developed to deconvolve period and relative amplitude of fluctuations of heat flow inBridgman crystal growth. Temperature-measuring device with enough sensitivity and frequency response to make desired measurements inserted close as possible to substance monitored. Time-dependent temperature response recorded, and time domain response converted to frequency domain for further analysis. Fast fourier transform (FFT) of data on temperature oscillations shows particular behavior at some specific frequencies corresponding with striations, or defects observed on crystal. Useful procedure to help determine sources of some growth-induced crystalline defects. Other processes sensitive to small temperature fluctuations, such as diffusion, precipitation, and corrsion, benefit from technique.

Fripp, Archibald L., Jr.; Clark, Ivan O.; Debnam, William J., Jr.; Barber, Patrick G.; Crouch, Roger K.; Simchick, Richard T.

1988-01-01

427

Observation of strong second harmonic generation in monolayer MoS2  

E-print Network

We show that the lack of inversion symmetry in monolayer MoS2 allows strong optical second harmonic generation. Monolayer and few layer MoS2 samples are fabricated by mechanical exfoliation. Strong second harmonic of a normal incident 810-nm pulse is observed, with the central wavelength of 405 nm and the expected quadratic dependence on the fundamental power. The magnitude of the second order nonlinear susceptibility is on the order of 1E-7 m/V. The parallel and perpendicular components of the second harmonic are measured as we rotate the crystal with respect to the fundamental polarization. The results are consistent with the lattice structure of monolayer MoS2. The susceptibility reduces by a factor of seven in trilayers, and reduced by about two orders of magnitude in flakes with even numbers of layers. Since the second harmonic generation is very sensitive to crystalline orientation and layer number, it can be used as a non-invasive tool to characterize MoS2 thin films.

Kumar, Nardeep; Ceballos, Frank; Zhao, Hui

2013-01-01

428

Bandwidth enhancement of electro-optic field sensing using photonic down-mixing with harmonic sidebands.  

PubMed

We demonstrate that harmonic sidebands of an electro-optic modulator's driving frequency can be used as the local oscillator in a photonic down-mixing process in order to significantly enhance the bandwidth of near-field, electro-optic, microwave measurements. The creation of second- and third-order-harmonic modulation sidebands on a laser-diode output are described, with heterodyne down-conversion of microwave signals taking place within an electro-optic sensor crystal. The measurement bandwidth of an electro-optic microwave probe can thus be enhanced by as much as a factor of three with respect to the use of conventional, fundamental-harmonic sidebands. Carrier-sideband analysis from the measured optical spectrum indicates that millimeter-wave-frequency local-oscillator sidebands can be created using a Ku-band electro-optic modulator and that the electro-optic-signal-modulation depth can be enhanced by suppressing the light-beam carrier component. Transverse near-field distributions from high frequency patch antennas are extracted using both second- and third-order-harmonic sidebands. PMID:18795014

Lee, Dong-Joon; Whitaker, John F

2008-09-15

429

Thermionic converter studies at Thermo Electron  

NASA Technical Reports Server (NTRS)

The Thermionic Energy Converter (TEC) development program includes theoretical and experimental surface studies, diode evaluation, enhanced mode converter investigations and system studies, as well as materials fabrication and testing. The primary effort has been concentrated on increasing converter performance via improved electrodes. Diodes with oxide collectors (i.e., tungsten oxide, titanium oxide, zinc oxide and barium oxide) have provided the best performance. Emitters requiring reduced cesium pressure (such as oxygenated tungsten, lanthanum hexaboride, platinum and graphite) are being tested. Converter configurations using particle spacing are under investigation. Experiments with auxiliary electrode thermionic converters are in progress. Both silicon carbide and alloy hot shells (i.e., barriers to isolate the converter from the combustion environment) have been fabricated and tested.

Huffman, F. N.; Lieb, D.; Rufeh, F.

1977-01-01

430

Performance of Power Converters at Cryogenic Temperatures  

NASA Technical Reports Server (NTRS)

Power converters capable of operation at cryogenic temperatures are anticipated to play an important role in the power system architecture of future NASA deep space missions. Design of such converters to survive cryogenic temperatures will improve the power system performance and reduce development and launch costs. Aerospace power systems are mainly a DC distribution network. Therefore, DC/DC and DC/AC converters provide the outputs needed to different loads at various power levels. Recently, research efforts have been performed at the NASA Glenn Research Center (GRC) to design and evaluate DC/DC converters that are capable of operating at cryogenic temperatures. This paper presents a summary of the research performed to evaluate the low temperature performance of five DC/DC converters. Various parameters were investigated as a function of temperature in the range of 20 to -196 C. Data pertaining to the output voltage regulation and efficiency of the converters is presented and discussed.

Elbuluk, Malik E.; Gerber, Scott; Hammoud, Ahmad; Patterson, Richard L.

2001-01-01

431

Radiation-Tolerant DC-DC Converters  

NASA Technical Reports Server (NTRS)

A document discusses power converters suitable for space use that meet the DSCC MIL-PRF-38534 Appendix G radiation hardness level P classification. A method for qualifying commercially produced electronic parts for DC-DC converters per the Defense Supply Center Columbus (DSCC) radiation hardened assurance requirements was developed. Development and compliance testing of standard hybrid converters suitable for space use were completed for missions with total dose radiation requirements of up to 30 kRad. This innovation provides the same overall performance as standard hybrid converters, but includes assurance of radiation- tolerant design through components and design compliance testing. This availability of design-certified radiation-tolerant converters can significantly reduce total cost and delivery time for power converters for space applications that fit the appropriate DSCC classification (30 kRad).

Skutt, Glenn; Sable, Dan; Leslie, Leonard; Graham, Shawn

2012-01-01

432

Disappearing Crystals  

NSDL National Science Digital Library

Learners experiment with water gel crystals, or sodium polyacrylate crystals, which absorb hundreds of times their weight in water. When in pure water, the water gel crystals cannot be seen. However, when learners place the crystals in solutions of Splenda and water, the crystals can be seen. Learners use this property to determine how much Splenda is in 4 different cups of water. This is one of four activities learners can complete related to PhysicsQuest 2008. Each activity gives a clue to solve a puzzle in the accompanying comic book, "Nikola Tesla and the Electric Fair."

Society, American P.

2009-01-01

433

Harmonic segregation through mistuning can improve fundamental frequency discrimination  

PubMed Central

This study investigated the relationship between harmonic frequency resolution and fundamental frequency (f0) discrimination. Consistent with earlier studies, f0 discrimination of a diotic bandpass-filtered harmonic complex deteriorated sharply as the f0 decreased to the point where only harmonics above the tenth were presented. However, when the odd harmonics were mistuned by 3%, performance improved dramatically, such that performance nearly equaled that found with only even harmonics present. Mistuning also improved performance when alternating harmonics were presented to opposite ears (dichotic condition). In a task involving frequency discrimination of individual harmonics within the complexes, mistuning the odd harmonics yielded no significant improvement in the resolution of individual harmonics. Pitch matches to the mistuned complexes suggested that the even harmonics dominated the pitch for f0’s at which a benefit of mistuning was observed. The results suggest that f0 discrimination performance can benefit from perceptual segregation based on inharmonicity, and that poor performance when only high-numbered harmonics are present is not due to limited peripheral harmonic resolvability. Taken together with earlier results, the findings suggest that f0 discrimination may depend on auditory filter bandwidths, but that spectral resolution of individual harmonics is neither necessary nor sufficient for accurate f0 discrimination. PMID:19045656

Bernstein, Joshua G.W.; Oxenham, Andrew J.

2008-01-01

434

Heat flow in a pyroelectric converter  

NASA Astrophysics Data System (ADS)

A simulated pyroelectric converter has been constructed. The heat flow and temperature profiles within the converter have been measured. Computer simulations of the heat flow compare well with the measurements and predict an efficiency of 12 percent of the Carnot limit for a real pyroelectric converter with the operating configuration of the simulation. These heat flow results are useful in considerations of heat engines using active materials other than pyroelectrics, such as Nitinol, when these engines utilize similar heat flow management.

Olsen, R. B.; Butler, W. F.; Drummond, J. E.; Bruno, D. A.; Briscoe, J. M.

1985-12-01

435

Gadolinium sheet converter for neutron radiography.  

PubMed

This work describes a methodology developed for the confection of gadolinium sheet converter for neutron radiography using the gadolinium chloride (GdCl3) as material converter. Though manufactured at a relatively low cost, they are as good as the sheet converter on the market. Here, we present neutron radiography of the penetrameter, the edge spread function, the modulation transfer function and characteristic curves for each set sheet-AA400 Kodak film. PMID:17702586

Lima, C T S; Crispim, V R; Santos, W M S

2007-12-01

436

Simplified Heat-Source/Thermionic Converter  

NASA Technical Reports Server (NTRS)

Radiation coupling of heat from heat-source cylinder to converter cylinder through vacuum gap eliminates need for high-temperature electrical insulators between reactor heat pipes and thermionic converters. In addition no radiatior heat pipe is necessary because collectors of thermionic converters from which excess heat must be removed radiate directly to space. New design concept is also applicable to terrestrial and non-nuclear thermionic power supplies.

Shimada, K.

1983-01-01

437

DC/DC Converter Stability Testing Study  

NASA Technical Reports Server (NTRS)

This report presents study results on hybrid DC/DC converter stability testing methods. An input impedance measurement method and a gain/phase margin measurement method were evaluated to be effective to determine front-end oscillation and feedback loop oscillation. In particular, certain channel power levels of converter input noises have been found to have high degree correlation with the gain/phase margins. It becomes a potential new method to evaluate stability levels of all type of DC/DC converters by utilizing the spectral analysis on converter input noises.

Wang, Bright L.

2008-01-01

438

Adaptive harmonic generation microscopy of mammalian embryos  

E-print Network

the second- and third-harmonic intensity signals are used as the optimization metric. Aber- ration correction is performed to compensate both system- and specimen-induced aberrations by using an efficient optimization and resolution. © 2009 Optical Society of America OCIS codes: 180.0180, 180.4315, 110.1080, 170.3880, 180

Paris-Sud XI, Université de

439

VOLUMETRIC HARMONIC BRAIN MAPPING Yalin Wang1  

E-print Network

VOLUMETRIC HARMONIC BRAIN MAPPING Yalin Wang1 , Xianfeng Gu2 , Tony F. Chan1 , Paul M. Thompson3 and Brain Research Institute, UCLA School of Medicine 4 Department of Mathematics, Harvard University. In this paper, we apply these two techniques to brain mapping problem. We use a tetrahedral mesh to represent

440

Musical Harmonization with Constraints: A Survey  

Microsoft Academic Search

We survey works on the musical problem of automatic harmonization. This problem, which consists in creating musical scores which satisfy given rules of harmony, has been the object of numerous studies, most of them using constraint techniques in one way or another. We outline the main results obtained and the current status of this category of problems.

Francois Pachet; Pierre Roy

2001-01-01

441

Resonant second harmonic generation in potassium vapor  

SciTech Connect

Picosecond pulses are used to study resonant second harmonic generation in potassium vapor. Although the process is both microscopically and macroscopically forbidden, it can readily be observed. The results can be quantitatively understood by a multiphoton-ionization-initiated, dc-field-induced, coherent transient model.

Kim, D.; Mullin, C.S.; Shen, Y.R. [Univ. of California, Berkeley, CA (United States). Dept. of Physics]|[Lawrence Berkeley Lab., CA (United States). Materials Science Div.

1995-06-01

442

Quantization of the damped harmonic oscillator revisited  

NASA Astrophysics Data System (ADS)

We return to the description of the damped harmonic oscillator with an assessment of previous works, in particular the Bateman-Caldirola-Kanai model and a new model proposed by one of the authors. We argue the latter has better high energy behavior and is connected to existing open-systems approaches.

Baldiotti, M. C.; Fresneda, R.; Gitman, D. M.

2011-04-01

443

Quantum nondemolition measurements of harmonic oscillators  

NASA Technical Reports Server (NTRS)

Measuring systems to determine the real component of the complex amplitude of a harmonic oscillator are described. This amplitude is constant in the absence of driving forces, and the uncertainty principle accounts for the fact that only the real component can be measured precisely and continuously ('quantum nondemolition measurement'). Application of the measuring systems to the detection of gravitational waves is considered.

Thorne, K. S.; Caves, C. M.; Zimmermann, M.; Sandberg, V. D.; Drever, R. W. P.

1978-01-01

444

Quantum harmonic oscillator in a thermal bath  

NASA Technical Reports Server (NTRS)

The influence functional path-integral treatment of quantum Brownian motion is briefly reviewed. A newly derived exact master equation of a quantum harmonic oscillator coupled to a general environment at arbitrary temperature is discussed. It is applied to the problem of loss of quantum coherence.

Zhang, Yuhong

1993-01-01

445

Group Theory of Covariant Harmonic Oscillators  

ERIC Educational Resources Information Center

A simple and concrete example for illustrating the properties of noncompact groups is presented. The example is based on the covariant harmonic-oscillator formalism in which the relativistic wave functions carry a covariant-probability interpretation. This can be used in a group theory course for graduate students who have some background in…

Kim, Y. S.; Noz, Marilyn E.

1978-01-01

446

Environmental Health and Safety Global Harmonization System  

E-print Network

Environmental Health and Safety Global Harmonization System for the Classification and Labeling of Chemicals Department of Environmental Health and Safety (412) 624-9505 www.ehs.pitt.edu #12;Environmental (GHS) as a revision to the Hazard Communication Standard (HazCom) · GHS was developed and adopted

Jiang, Huiqiang

447

Power Divider for Waveforms Rich in Harmonics  

NASA Technical Reports Server (NTRS)

A method for dividing the power of an electronic signal rich in harmonics involves the use of an improved divider topology. A divider designed with this topology could be used, for example, to propagate a square-wave signal in an amplifier designed with a push-pull configuration to enable the generation of more power than could be generated in another configuration.

Sims, William Herbert, III

2005-01-01

448

Laguerre polynomials by a harmonic oscillator  

NASA Astrophysics Data System (ADS)

The study of an isotropic harmonic oscillator, using the factorization method given in Ohanian's textbook on quantum mechanics, is refined and some collateral extensions of the method related to the ladder operators and the associated Laguerre polynomials are presented. In particular, some analytical properties of the associated Laguerre polynomials are derived using the ladder operators.

Baykal, Melek; Baykal, Ahmet

2014-09-01

449

221A Lecture Notes Spherical Harmonics  

E-print Network

221A Lecture Notes Spherical Harmonics 1 Oribtal Angular Momentum The orbital angular momentum operator is given just as in the classical mechanics, L = x Ã? p. (1) From this definition and the canonical in this note, it is understood that it acts on a position bra instead of ket. With this caveat in mind, we can

Murayama, Hitoshi

450

Perfusion harmonic imaging of the human brain  

NASA Astrophysics Data System (ADS)

The fast visualisation of cerebral microcirculation supports diagnosis of acute cerebrovascular diseases. However, the commonly used CT/MRI-based methods are time consuming and, moreover, costly. Therefore we propose an alternative approach to brain perfusion imaging by means of ultrasonography. In spite of the low signal/noise-ratio of transcranial ultrasound and the high impedance of the skull, flow images of cerebral blood flow can be derived by capturing the kinetics of appropriate contrast agents by harmonic ultrasound image sequences. In this paper we propose three different methods for human brain perfusion imaging, each of which yielding flow images indicating the status of the patient's cerebral microcirculation by visualising local flow parameters. Bolus harmonic imaging (BHI) displays the flow kinetics of bolus injections, while replenishment (RHI) and diminution harmonic imaging (DHI) compute flow characteristics from contrast agent continuous infusions. RHI measures the contrast agents kinetics in the influx phase and DHI displays the diminution kinetics of the contrast agent acquired from the decay phase. In clinical studies, BHI- and RHI-parameter images were found to represent comprehensive and reproducible distributions of physiological cerebral blood flow. For DHI it is shown, that bubble destruction and hence perfusion phenomena principally can be displayed. Generally, perfusion harmonic imaging enables reliable and fast bedside imaging of human brain perfusion. Due to its cost efficiency it complements cerebrovascular diagnostics by established CT/MRI-based methods.

Metzler, Volker H.; Seidel, Guenter; Wiesmann, Martin; Meyer, Karsten; Aach, Til

2003-05-01

451

Conformation, orientation and interaction in molecular monolayers: A surface second harmonic and sum frequency generation study  

SciTech Connect

We have used sum frequency generation (SFG) to study the order in a silane monolayer before and after the deposition of a coadsorbed liquid crystal monolayer. We observe an increase in the order of the chain of the silane molecule induced by the interpenetration of the liquid crystal molecules. By using second harmonic generation (SHG) and SFG, we have studied the orientation and conformation of the liquid crystal molecule on clean and silane coated glass surfaces. On both surfaces, the biphenyl group is tilted by 70{degree} with the alkyl chain end pointing away from the surface. The shift in the C-H stretch frequencies in the coadsorbed system indicates a significant interaction between molecules. 9 refs., 3 figs.

Superfine, R.; Huang, J.Y.; Shen, Y.R.

1988-12-01

452

Waveform generator for electrical impedance tomography (EIT) using linear interpolation with multiplying D/A converters.  

PubMed

This paper describes the implementation of a multiplying digital-to-analogue (D/A) converter as a programmable waveform generator to be used in an electrical impedance tomography (EIT) system. Different digital techniques of generation waveforms are considered and the advantages and disadvantages of the chosen slope-plus-pedestal technique are presented. A wire-wrapped prototype system has been designed, and from measured frequency spectra the total harmonic distortion can be calculated to values between 1.1 and 2.9% depending on frequency. PMID:7776358

Blad, B; Johannesson, J; Johnsson, G; Bachman, B; Lindström, K

1994-01-01

453

Second harmonic generating (SHG) nanoprobes for in vivo imaging  

PubMed Central

Fluorescence microscopy has profoundly changed cell and molecular biology studies by permitting tagged gene products to be followed as they function and interact. The ability of a fluorescent dye to absorb and emit light of different wavelengths allows it to generate startling contrast that, in the best cases, can permit single molecule detection and tracking. However, in many experimental settings, fluorescent probes fall short of their potential due to dye bleaching, dye signal saturation, and tissue autofluorescence. Here, we demonstrate that second harmonic generating (SHG) nanoprobes can be used for in vivo imaging, circumventing many of the limitations of classical fluorescence probes. Under intense illumination, such as at the focus of a laser-scanning microscope, these SHG nanocrystals convert two photons into one photon of half the wavelength; thus, when imaged by conventional two-photon microscopy, SHG nanoprobes appear to generate a signal with an inverse Stokes shift like a fluorescent dye, but with a narrower emission. Unlike commonly used fluorescent probes, SHG nanoprobes neither bleach nor blink, and the signal they generate does not saturate with increasing illumination intensity. The resulting contrast and detectability of SHG nanoprobes provide unique advantages for molecular imaging of living cells and tissues. PMID:20668245

Pantazis, Periklis; Maloney, James; Wu, David; Fraser, Scott E.

2010-01-01

454

Vacuum-insulated catalytic converter  

DOEpatents

A catalytic converter has an inner canister that contains catalyst-coated substrates and an outer canister that encloses an annular, variable vacuum insulation chamber surrounding the inner canister. An annular tank containing phase-change material for heat storage and release is positioned in the variable vacuum insulation chamber a distance spaced part from the inner canister. A reversible hydrogen getter in the variable vacuum insulation chamber, preferably on a surface of the heat storage tank, releases hydrogen into the variable vacuum insulation chamber to conduct heat when the phase-change material is hot and absorbs the hydrogen to limit heat transfer to radiation when the phase-change material is cool. A porous zeolite trap in the inner canister absorbs and retains hydrocarbons from the exhaust gases when the catalyst-coated substrates and zeolite trap are cold and releases the hydrocarbons for reaction on the catalyst-coated substrate when the zeolite trap and catalyst-coated substrate get hot.

Benson, David K. (Golden, CO)

2001-01-01

455

A subclasses of harmonic functions defined by multiplier transformation  

NASA Astrophysics Data System (ADS)

We investigate some properties of a new subclass of harmonic univalent functions defined by multiplier transformation. We obtain coefficient conditions, extreme points, distortion bounds, convolution, and convex combination for the above subclass of harmonic functions.

Al-Shaqsi, Khalifa Zayid

2014-06-01

456

UNIFORM RECTIFIABILITY, CARLESON MEASURE ESTIMATES, AND APPROXIMATION OF HARMONIC FUNCTIONS  

E-print Network

UNIFORM RECTIFIABILITY, CARLESON MEASURE ESTIMATES, AND APPROXIMATION OF HARMONIC FUNCTIONS STEVE rectifiable set of dimension n. Then bounded harmonic functions in := Rn+1 \\ E satisfy Carleson measure25, 42B37. Key words and phrases. Carleson measures, -approximability, uniform rectifiability

Mayboroda, Svitlana

457

Elements of Postmodern Harmonic Analysis Hans G. Feichtinger  

E-print Network

Elements of Postmodern Harmonic Analysis Hans G. Feichtinger hans.feichtinger@univie.ac.at October to Postmodern Harmonic Analysis, with strong functional analytic aspects, but also incorporating concepts from

Feichtinger, Hans Georg

458

Current Generated Harmonics and Their Effect Upon Electrical Industrial Systems  

E-print Network

equipment; such as cables, meters, capacitors, motors, transformers, emergency generators, etc. are presented. Recommendations for solving harmonic problems are also provided. The paper discusses and analyzes two actual cases where harmonics caused problems...

Alexander, H. R.; Rogge, D. S.

459

Augmenting Second Harmonic Generation Using Fano Resonances in Plasmonic Systems  

E-print Network

Augmenting Second Harmonic Generation Using Fano Resonances in Plasmonic Systems Krishnan ABSTRACT: Significant augmentation of second harmonic generation using Fano resonances in plasmonic in nonlinear and quantum optics. KEYWORDS: Plasmonics, nonlinear optics, Fano resonance, silver nanostructures

Dalang, Robert C.

460

The hydrodynamic flow of nematic liquid crystals in R3  

NASA Astrophysics Data System (ADS)

This manuscript demonstrates the well-posedness (existence, uniqueness, and regularity of solutions) of the Cauchy problem for simplified equations of nematic liquid crystal hydrodynamic flow in three dimensions for initial data that is uniformly locally L3(R 3) integrable (L3U(R 3)). The equations examined are a simplified version of the equations derived by Ericksen and Leslie. Background on the continuum theory of nematic liquid crystals and their flow is provided as are explanations of the related mathematical literature for nematic liquid crystals and the Navier--Stokes equations. KEYWORDS: nematic liquid crystals, Navier--Stokes equations, Ericksen--Leslie equations, harmonic maps.

Hineman, Jay Lawrence

461

Structural and mechanical studies of cadmium manganese thiocyanate crystal  

NASA Astrophysics Data System (ADS)

Single crystals of cadmium manganese thiocyanate (CMTC) have been synthesized successfully and grown by slow evaporation method. The structural perfection of the grown crystals has been analyzed by High resolution X-ray diffraction (HRXRD), which shows the crystalline perfection of the grown crystal is quite good. Optical behavior was assessed by UV-Vis analysis and found that no absorption in the UV visible region and it may be useful for second harmonic applications. The mechanical hardness of the grown crystals was studied and Vicker's microhardness, Stiffness constant was calculated.

Manikandan, M. R.; Vijayaprasath, G.; babu, G. Anandha; Bhagavannarayan, G.; Vijayan, N.; Ravi, G.

2012-06-01

462

Imaging theory of nonlinear second harmonic and third harmonic generations in confocal microscopy  

Microsoft Academic Search

The imaging theory of nonlinear second harmonic generation (SHG) and third harmonic generation (THG) in confocal microscopy\\u000a is presented in this paper. The nonlinear effect of SHG and THG on the imaging properties of confocal microscopy has been\\u000a analyzed in detail by the imaging theory. It is proved that the imaging process of SHG and THG in confocal microscopy, which

Zhilie Tang; Da Xing; Songhao Liu

2004-01-01

463

Real time digital harmonic modeling and simulation: an advanced tool for understanding power system harmonics mechanisms  

Microsoft Academic Search

Off-line computation and sometimes full transient time domain simulation has been the tool of choice for modeling power system harmonic phenomena in the past. Due to significant advances in real-time digital network simulation technologies, both in decreasing time step size and increased model complexity, this tool becomes more attractive for advanced harmonic analysis. This paper proposes the use of hardware-in-loop

M. Steurer; S. Woodruff

2004-01-01

464

Lysozyme Crystal  

NASA Technical Reports Server (NTRS)

To the crystallographer, this may not be a diamond but it is just as priceless. A Lysozyme crystal grown in orbit looks great under a microscope, but the real test is X-ray crystallography. The colors are caused by polarizing filters. Proteins can form crystals generated by rows and columns of molecules that form up like soldiers on a parade ground. Shining X-rays through a crystal will produce a pattern of dots that can be decoded to reveal the arrangement of the atoms in the molecules making up the crystal. Like the troops in formation, uniformity and order are everything in X-ray crystallography. X-rays have much shorter wavelengths than visible light, so the best looking crystals under the microscope won't necessarily pass muster under the X-rays. In order to have crystals to use for X-ray diffraction studies, crystals need to be fairly large and well ordered. Scientists also need lots of crystals since exposure to air, the process of X-raying them, and other factors destroy them. Growing protein crystals in space has yielded striking results. Lysozyme's structure is well known and it has become a standard in many crystallization studies on Earth and in space.

2004-01-01

465

Stokes vector based polarization resolved second harmonic microscopy of starch granules  

PubMed Central

We report on the measurement and analysis of the polarization state of second harmonic signals generated by starch granules, using a four-channel photon counting based Stokes-polarimeter. Various polarization parameters, such as the degree of polarization (DOP), the degree of linear polarization (DOLP), the degree of circular polarization (DOCP), and anisotropy are extracted from the 2D second harmonic Stokes images of starch granules. The concentric shell structure of a starch granule forms a natural photonic crystal structure. By integration over all the solid angle, it will allow very similar SHG quantum efficiency regardless of the angle or the states of incident polarization. Given type I phase matching and the concentric shell structure of a starch granule, one can easily infer the polarization states of the input beam from the resulting SH micrograph. PMID:23577289

Mazumder, Nirmal; Qiu, Jianjun; Foreman, Matthew R.; Romero, Carlos Macias; Torok, Peter; Kao, Fu-Jen

2013-01-01

466

Phase-matched second-harmonic generation in poled polymers by the use of birefringence  

NASA Astrophysics Data System (ADS)

Green light has been observed for the first time to the authors' knowledge by bulk phase-matched second-harmonic generation from a stretched main chain polyurea. The polyurea was synthesized from 4,4'-diphenylmethane diisocyanate and 4,4'-methylene bis(cyclohexylamine). The spin-coated film has an initial positive birefringence. Drawing further increased the birefringence, and the film can be used for phase matching just as in biaxial single crystals. The drawn and poled polymer films belong to the 2mm point group. Three independent nonlinear-optic coefficients were determined. The type I phase-matching characteristics were calculated and confirmed by experiments. We demonstrate that a highly effective second-harmonic-generation device with a long optical path length can be obtained by use of bulk phase-matchable poled polymer.

Tao, X. T.; Watanabe, T.; Zou, D. C.; Ukuda, H.; Miyata, S.

1995-09-01

467

A Look at Damped Harmonic Oscillators through the Phase Plane  

ERIC Educational Resources Information Center

Damped harmonic oscillations appear naturally in many applications involving mechanical and electrical systems as well as in biological systems. Most students are introduced to harmonic motion in an elementary ordinary differential equation (ODE) course. Solutions to ODEs that describe simple harmonic motion are usually found by investigating the…

Daneshbod, Yousef; Latulippe, Joe

2011-01-01

468

Single-channel Mixture Decomposition using Bayesian Harmonic Models  

E-print Network

Single-channel Mixture Decomposition using Bayesian Harmonic Models Emmanuel Vincent and Mark D a mixture into components made of harmonic sinusoidal par- tials. We address this problem in the Bayesian framework by building a probabilistic model of the mixture combining generic priors for harmonic- ity

Plumbley, Mark

469

Transmission characteristics of cyclotron harmonic waves in plasma  

Microsoft Academic Search

In recent years the importance of cyclotron harmonic waves has become apparent in many branches of plasma physics. For example, it has been demonstrated that they are involved in the anomalously high noise radiation near the electron cyclotron harmonic frequencies that has been observed from thermonuclear fusion study devices, and that they can explain the cyclotron harmonic resonances observed in

F. W. Crawford; H. H. Weiss

1966-01-01

470

Anomalies in high-order harmonic generation at relativistic intensities  

SciTech Connect

High-order harmonic generation from a solid target surface has been investigated using femtosecond laser pulses focused to intensities greater than 10{sup 18} W/cm{sup 2}. The experiments show that the harmonics are very intense, with a conversion efficiency that is one or two orders of magnitude larger than that of harmonics generated in gases. Beside the observation of presently the shortest wavelength harmonics from femtosecond-laser solid target interaction, i.e., down to 22 nm, an anomaly has been observed in the harmonic spectrum. In contrast to the expected well-known continuous 'roll off' of the high-harmonic orders, the harmonic intensity decreases with the increase of harmonic order, but in between shows minima which are significantly less intense than the neighboring harmonics. Furthermore, the order of the harmonic minima depend on target material. Additional calculations using numerical kinetic particle simulations and a simpler oscillating mirror model show that the physical origin of these modulations is an intricate interplay of resonance absorption and ponderomotive force which leads to a complex electron density profile evolution. Furthermore, this is emphasized by a spectral line analysis of the harmonics. In agreement with the theory, broad lines have been observed and, in particular for the harmonics in the minima, a complex interference structure is present.

Teubner, U.; Foerster, E. [Abteilung Roentgenoptik, Institut fuer Optik und Quantenelektronik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Pretzler, G.; Eidmann, K.; Witte, K. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Schlegel, Th. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt (Germany)

2003-01-01

471

Harmonic Generation in the Novosibirsk Terahertz Free Electron Laser  

Microsoft Academic Search

At the present time, the radiation of the main first harmonic of the Novosibirsk terahertz free electron laser (FEL) lies in the range of 120-230 mum with power level of up to 400 W. The radiation of second and third harmonics was experimentally found in the FEL. This high harmonic FEL radiation extends its spectral range by a factor of

V. V. Kubarev; N. A. Vinokurov; V. V. Kotenkov; G. N. Kulipanov; A. N. Matveenko; T. V. Salikova; S. S. Serednyakov; M. A. Scheglov

2006-01-01

472

Modified harmonic loss model in PWM fed induction machines  

Microsoft Academic Search

In this paper, a modified harmonic loss model in PWM fed induction machines is proposed for improving the loss prediction. This model is based on the measured harmonic loss characteristics. The method for determining model parameters is given. The core and stray load losses are taken into consideration for a proposed model. The discussion of harmonic loss mechanisms particularly due

V. Kinnares; S. Potivejkul; B. Sawetsakulanond

1998-01-01

473

ASYMPTOTIC BEHAVIOR OF THE NONLINEAR SCHRODINGER EQUATION WITH HARMONIC TRAPPING  

E-print Network

ASYMPTOTIC BEHAVIOR OF THE NONLINEAR SCHR�ODINGER EQUATION WITH HARMONIC TRAPPING ZAHER HANI AND LAURENT THOMANN Abstract. We consider the cubic nonlinear Schr�odinger equation with harmonic trapping of the cubic nonlinear Schr�odinger equation with harmonic trapping given by (it - RD + D j=1 jx2 j )U = 0|U|2

Boyer, Edmond

474

Extraction of Harmonics and Reactive Current for Power Quality Enhancement  

Microsoft Academic Search

A detection technique for extraction of total harmonics, individual harmonics, and reactive current components is introduced and its performance is evaluated. The detection algorithm is then adopted as part of the control system of a single-phase active power filter (APF) to provide the required signals for harmonic filtering and reactive power compensation. Performance of the overall system is evaluated based

M. Karimi-Ghartemani; H. Mokhtari

2006-01-01

475

Measurement, Prediction, and Training of Harmonic Audiation and Performance Skills.  

ERIC Educational Resources Information Center

Investigated music majors' ability to harmonize notated melodies and recorded melodies with chord symbols, and to perform harmonic accompaniments to recorded melodies. Results showed, among other findings, that subjects (n = 45) improved ability to harmonize simple melodic patterns and that melodic echo-playing ability was highly correlated with…

Humphreys, Jere T.

1986-01-01

476

A Novel Control Strategy for Matrix Converter in Over-Modulation Range  

NASA Astrophysics Data System (ADS)

This paper proposes a control strategy for matrix converters to reduce the torque ripple in the over-modulation range. In the over-modulation range, motor drive performance of matrix converters is deteriorated because of the output voltage saturation. Especially, the torque ripple which has lower frequency components than the input voltage frequency is remarkable. In this paper, the theoretical analysis about the causes of the torque ripple and the effect of the proposed control strategy are shown. Experimental examinations including performance comparison with a trapezoidal wave modulation are carried out by a 400V, 22kW experimental system. The experimental results verify the validity of the theoretical analysis and confirm the effectiveness of the proposed control strategy for reducing the torque ripple. Furthermore, the harmonic distortion of the output current is also reduced compared with the trapezoidal wave modulation.

Tamai, Yasuhiro; Sato, Ikuya; Odaka, Akihiro; Mine, Hironori; Itoh, Jun-Ichi

477

Bioimpedance Harmonic Analysis as a Diagnostic Tool to Assess Regional Circulation and Neural Activity  

NASA Astrophysics Data System (ADS)

The novel technique based on harmonic analysis of bioimpedance microvariations with original hard- and software complex incorporating a high-resolution impedance converter was used to assess the neural activity and circulation in human urinary bladder and penis in patients with pelvic pain, erectile dysfunction, and overactive bladder. The therapeutic effects of shock wave therapy and Botulinum toxin detrusor injections were evaluated quantitatively according to the spectral peaks at low 0.1 Hz frequency (M for Mayer wave), respiratory (R) and cardiac (C) rhythms with their harmonics. Enhanced baseline regional neural activity identified according to M and R peaks was found to be presumably sympathetic in pelvic pain patients, and parasympathetic - in patients with overactive bladder. Total pulsatile activity and pulsatile resonances found in the bladder as well as in the penile spectrum characterised regional circulation and vascular tone. The abnormal spectral parameters characteristic of the patients with genitourinary diseases shifted to the norm in the cases of efficient therapy. Bioimpedance harmonic analysis seems to be a potent tool to assess regional peculiarities of circulatory and autonomic nervous activity in the course of patient treatment.

Mudraya, I. S.; Revenko, S. V.; Khodyreva, L. A.; Markosyan, T. G.; Dudareva, A. A.; Ibragimov, A. R.; Romich, V. V.; Kirpatovsky, V. I.

2013-04-01

478

Peak power tracking in parallel connected converters  

Microsoft Academic Search

A control scheme for parallel-connected converter systems that will transfer the maximum available power from a nonideal voltage source is presented. Monitoring the rates of change in both the average input current and the average input power from the source, the proposed control scheme can dynamically regulate the DC-DC converter system to track the peak power point of the source.

K. Siri; V. A. Caliskan; C. Q. Lee; G. C. Agarwal

1992-01-01

479

Converter Design for a Model Solar Car  

Microsoft Academic Search

To provide our students with practical experience in power electronic design they undertake an assignment that involves a model solar car race. The students are required to design, build and demonstrate a dc-dc converter that matches the output from a 10W solar panel to a permanent magnet DC motor. The converter must step down the output voltage from the panel

Richard Duke; Simon Round

480

Radioisotope Thermionic Converters for Space Applications  

Microsoft Academic Search

The recent history of radioisotope thermionics is reviewed, with emphasis on the US. programs, and the prospects for the future are assessed. In radioisotope thermionic converters the emitter heat is generated by the decay of a radioactive isotope. The thermionic converter emitter is mounted directly on a capsule containing the isotope. The rest of the capsule is generally insulated to

Gabor Miskolczy; David P. Lieb

1990-01-01

481

Power Converters Secure Electronics in Harsh Environments  

NASA Technical Reports Server (NTRS)

In order to harden power converters for the rigors of space, NASA awarded multiple SBIR contracts to Blacksburg, Virginia-based VPT Inc. The resulting hybrid DC-DC converters have proven valuable in aerospace applications, and as a result the company has generated millions in revenue from the product line and created four high-tech jobs to handle production.

2013-01-01

482

New control strategy for matrix converter  

Microsoft Academic Search

The authors propose a control strategy for the matrix converter which allows output voltage of 0.866 times the supply voltage to be generated. They discuss how to eliminate voltage and current spikes in the commutation. The system operation is examined and confirmed by experiments using a matrix converter with anti-parallel-connected SITs (static induction thyristors)

Jun Oyama; Tsuyoshi Higuchi; Eiji Yamada; Takashi Koga; Thomas Lipo

1989-01-01

483

Randomized modulation in power electronic converters  

Microsoft Academic Search

This article reviews analytical results and practical experience with randomized modulation in power electronic converters. After providing a brief overview of power electronics and of relevant switching patterns, the authors present performance specifications for converters (in terms of electromagnetic interference, vibrations and acoustic noise), and classify various randomized switching schemes. They review the most directly related references next, and introduce

ALEKSANDAR M. STANKOVIC; HANOCH LEV-ARI

2002-01-01

484

GaN betavoltaic energy converters  

Microsoft Academic Search

Semiconductor betavoltaic converters use energy from radioisotope sources to generate electricity for remote applications requiring power for 5-50 years. To be competitive with thermoelectric devices, they must achieve an efficiency above 20%. This paper presents the design rules and efficiency calculations for such high efficiency GaN betavoltaic converters, and experimentally demonstrates the radiation tolerance of GaN.

C. Honsberg; W. A. Doolittle; M. Allen; C. Wang

2005-01-01

485

Multilevel converters for 10 MW Wind Turbines  

Microsoft Academic Search

Several promising multi-level converter configurations for 10 MW Wind Turbines both with direct drive and one-stage gear box drive using Permanent Magnet Synchronous Generator (PMSG) are proposed, designed and compared. Reliability is a crucial indicator for large scale wind power converters, therefore the evaluations are mainly focused on the power device thermal performances, which are closely related to the life

Ke Ma; Frede Blaabjerg

2011-01-01

486

European Converts to Islam: Mechanisms of Radicalization  

Microsoft Academic Search

While European converts to Islam represent only a tiny percentage of Europe's Muslim population, members of that group have participated in major Islamist terrorist plots and attacks on European soil. Although the radicalization process has not been the same for all individuals, it could be still possible to understand the circumstances under which some European converts turned to violence. Therefore,

Emmanuel Karagiannis

2012-01-01

487

ZETA converter applied in power factor correction  

Microsoft Academic Search

This paper presents the analysis of the ZETA converter operating in discontinuous conduction mode (DCM) for power factor correction. The main attraction of the ZETA converter is that it is a naturally isolated structure, which allows a regulated output voltage with only one power processing stage. The principle of operation, mathematical analysis, design procedure and experimental results obtained from a

ADRIANO PERES; DENIZAR CRUZ MARTINS; I. Barbi

1994-01-01

488

RF digital-to-analog converter  

DOEpatents

A digital-to-analog converter is disclosed for producing an RF output signal proportional to a digital input word of N bits from an RF reference input, N being an integer greater or equal to 2. The converter comprises a plurality of power splitters, power combiners and a plurality of mixers or RF switches connected in a predetermined configuration. 18 figs.

Conway, P.H.; Yu, D.U.L.

1995-02-28

489

The auxiliary resonant commutated pole converter  

Microsoft Academic Search

The auxiliary resonant commutated pole (ARCP), a new power converter topology that fully achieves soft switching without increasing primary device voltage or current ratings, is discussed. The ARCP converter is capable of true pulse-width modulation (PWM) control of each phase. The power circuit relies on the addition of an auxiliary triggered resonant commutation circuit or snubber to commutate the inductive

R. W. De Doncker; J. P. Lyons

1990-01-01

490

Mechanical phase matching of birefringent non-linear crystals.  

PubMed

Second-order nonlinear processes such as second harmonic generation or parametric amplification have found numerous applications in the scientific and industrial world, from micromachining to petawatt laser facilities. These nonlinear interactions are mostly carried out in birefringent crystals because of their low cost and the possibility to operate at high powers Phase-matching configurations in birefringent crystals are determined by their refractive indexes. Here, we show that an important mechanical stress can be used to significantly change the phase-matching properties of a birefringent crystal. As an example, we demonstrate the shift of second harmonic non-critical phase matching wavelength of LiB3O5 (LBO) crystal at room temperature from 1200 nm to 1120 nm by applying compressive forces up to 100 MPa. We believe that this mechanical phase matching can be used as an additional degree of freedom to optimize nonlinear optical frequency mixing geometries. PMID:25321800

Deyra, Loïc; Balembois, François; Guilbaud, André; Villeval, Philippe; Georges, Patrick

2014-09-22

491

RNA Crystallization  

NASA Technical Reports Server (NTRS)

RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.

Golden, Barbara L.; Kundrot, Craig E.

2003-01-01

492

Radiation Effects on DC-DC Converters  

NASA Technical Reports Server (NTRS)

In this work, several DC-DC converters were designed and built. The converters are Buck Buck-Boost, Cuk, Flyback, and full-bridge zero-voltage switched. The total ionizing dose radiation and single event effects on the converters were investigated. The experimental results for the TID effects tests show that the voltages of the Buck Buck-Boost, Cuk, and Flyback converters increase as total dose increased when using power MOSFET IRF250 as a switching transistor. The change in output voltage with total dose is highest for the Buck converter and the lowest for Flyback converter. The trend of increase in output voltages with total dose in the present work agrees with those of the literature. The trends of the experimental results also agree with those obtained from PSPICE simulation. For the full-bridge zero-voltage switch converter, it was observed that the dc-dc converter with IRF250 power MOSFET did not show a significant change of output voltage with total dose. In addition, for the dc-dc converter with FSF254R4 radiation-hardened power MOSFET, the output voltage did not change significantly with total dose. The experimental results were confirmed by PSPICE simulation that showed that FB-ZVS converter with IRF250 power MOSFET's was not affected with the increase in total ionizing dose. Single Event Effects (SEE) radiation tests were performed on FB-ZVS converters. It was observed that the FB-ZVS converter with the IRF250 power MOSFET, when the device was irradiated with Krypton ion with ion-energy of 150 MeV and LET of 41.3 MeV-square cm/mg, the output voltage increased with the increase in fluence. However, for Krypton with ion-energy of 600 MeV and LET of 33.65 MeV-square cm/mg, and two out of four transistors of the converter were permanently damaged. The dc-dc converter with FSF254R4 radiation hardened power MOSFET's did not show significant change at the output voltage with fluence while being irradiated by Krypton with ion energy of 1.20 GeV and LET of 25.97 MeV-square cm/mg. This might be due to fact that the device is radiation hardened.

Zhang, De-Xin; AbdulMazid, M. D.; Attia, John O.; Kankam, Mark D. (Technical Monitor)

2001-01-01

493

Modelling, analyses and design of switching converters  

NASA Technical Reports Server (NTRS)

A state-space averaging method for modelling switching dc-to-dc converters for both continuous and discontinuous conduction mode is developed. In each case the starting point is the unified state-space representation, and the end result is a complete linear circuit model, for each conduction mode, which correctly represents all essential features, namely, the input, output, and transfer properties (static dc as well as dynamic ac small-signal). While the method is generally applicable to any switching converter, it is extensively illustrated for the three common power stages (buck, boost, and buck-boost). The results for these converters are then easily tabulated owing to the fixed equivalent circuit topology of their canonical circuit model. The insights that emerge from the general state-space modelling approach lead to the design of new converter topologies through the study of generic properties of the cascade connection of basic buck and boost converters.

Cuk, S. M.; Middlebrook, R. D.

1978-01-01

494

Physics of tissue harmonic imaging by ultrasound  

NASA Astrophysics Data System (ADS)

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 reverberation; (2) is not immune to aberration effects and (3) suffers less clutter due to reduced side-lobe levels. The results indicate that side lobe suppression is the most significant reason for the improvement of second harmonic imaging.

Jing, Yuan

495

Boost matrix converters in clean energy systems  

NASA Astrophysics Data System (ADS)

This dissertation describes an investigation of novel power electronic converters, based on the ultra-sparse matrix topology and characterized by the minimum number of semiconductor switches. The Z-source, Quasi Z-source, Series Z-source and Switched-inductor Z-source networks were originally proposed for boosting the output voltage of power electronic inverters. These ideas were extended here on three-phase to three-phase and three-phase to single-phase indirect matrix converters. For the three-phase to three-phase matrix converters, the Z-source networks are placed between the three-switch input rectifier stage and the output six-switch inverter stage. A brief shoot-through state produces the voltage boost. An optimal pulse width modulation technique was developed to achieve high boosting capability and minimum switching losses in the converter. For the three-phase to single-phase matrix converters, those networks are placed similarly. For control purposes, a new modulation technique has been developed. As an example application, the proposed converters constitute a viable alternative to the existing solutions in residential wind-energy systems, where a low-voltage variable-speed generator feeds power to the higher-voltage fixed-frequency grid. Comprehensive analytical derivations and simulation results were carried out to investigate the operation of the proposed converters. Performance of the proposed converters was then compared between each other as well as with conventional converters. The operation of the converters was experimentally validated using a laboratory prototype.

Karaman, Ekrem

496

Growth and characterization of L-serine formate nonlinear optical single crystal  

NASA Astrophysics Data System (ADS)

A novel organic nonlinear optical single crystal L-Serine Formate (LSF) was successfully grown by solution growth using the slow evaporation technique. The structure of the grown crystal has been determined by single crystal X-ray diffraction analysis. The presence of functional groups in LSF crystal has been identified by FTIR spectrum. The crystal is transparent over entire visible region. The second harmonic generation efficiency of the grown LSF crystal has been obtained by the Kurtz-Perry powder technique. The laser induced surface damage threshold value 6.836 GW/cm2 indicates that this material can be used for high-power laser applications.

Krishnan, P.; Gayathri, K.; Anbalagan, G.

2013-02-01

497

Efficient 2(nd) and 4(th) harmonic generation of a single-frequency, continuous-wave fiber amplifier.  

PubMed

We demonstrate efficient cavity-enhanced second and fourth harmonic generation of an air-cooled, continuous-wave (cw), single-frequency 1064 nm fiber-amplifier system. The second harmonic generator achieves up to 88% total external conversion efficiency, generating more than 20-W power at 532 nm wavelength in a diffraction-limited beam (M(2) < 1.05). The nonlinear medium is a critically phase-matched, 20-mm long, anti-reflection (AR) coated LBO crystal operated at 25 degrees C. The fourth harmonic generator is based on an AR-coated, Czochralski-grown beta-BaB(2)O(4) (BBO) crystal optimized for low loss and high damage threshold. Up to 12.2 W of 266-nm deep-UV (DUV) output is obtained using a 6-mm long critically phase-matched BBO operated at 40 degrees C. This power level is more than two times higher than previously reported for cw 266-nm generation. The total external conversion efficiency from the fundamental at 1064 nm to the fourth harmonic at 266 nm is >50%. PMID:18542230

Sudmeyer, Thomas; Imai, Yutaka; Masuda, Hisashi; Eguchi, Naoya; Saito, Masaki; Kubota, Shigeo

2008-02-01