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1

Optical and environmentally protective coatings for potassium dihydrogen phosphate (KDP) harmonic converter crystals  

SciTech Connect

Potassium dihydrogen phosphate (KDP) crystals have been used as harmonic converters on the Nova laser at LLNL for over six years. All crystals were coated with a single layer, quarterwave AR coating of porous silica with a refractive index of 1.22. This was prepared by a sol-gel process and was applied from a colloidal suspension by spin coating at room temperature. A few crystals were also coated with a methyl silicone coating prior to the application of the AR coating for environmental protection. The initial optical performance of all crystals was very good but there has been some deterioration over the years because of environmental and laser damage degradation. The deterioration in the silicone samples was, however, much less than the others. We are now in the process of replacing all ten KDP arrays with new crystals and will apply the silicone undercoat to all samples. Recently we have been evaluating a new perfluorinated organic polymer coating which has a refractive index of 1.29. This material is soluble in fluorinated solvents and can be applied by dip coating from solution at room temperature. We hope that this can provide environmental protection when applied to KDP and also act as an AR coating at the same time. The optical performance is not as good as our porous silica because of the higher index; about 0.3% reflection per surface is obtained. 4 refs., 10 figs., 1 tab.

Thomas, I.M.

1991-06-24

2

Harmonic reduction in thyristor converters by harmonic current injection  

Microsoft Academic Search

The paper describes analytical and experimental results for a new method of current harmonic reduction in thyristor converters. The principle of the method is to modify the current waveforms on the d.c. windings of the converter transformer by injecting harmonic currents at a particular frequency. In practice, third harmonic currents of the power frequency is most efficient. Experimental results carried

A. Ametani

1976-01-01

3

General analysis of harmonic transfer through converters  

Microsoft Academic Search

Harmonic transfer from DC-side to AC-side and vice-versa through a three-phase bridge power converter is treated by using space vectors. The dependency of the relative frequency of a harmonic and its sequence (positive\\/negative) is illustrated. It is shown that the derived relationships are valid for both voltage-source and current-source power converters. Thereby, the relationships for the frequency transformation through power

Ying Jiang; A. Ekstrom

1997-01-01

4

Reduced Switching Frequency Active Harmonic Elimination for Multilevel Converters  

SciTech Connect

This paper presents a reduced switching-frequency active-harmonic-elimination method (RAHEM) to eliminate any number of specific order harmonics of multilevel converters. First, resultant theory is applied to transcendental equations to eliminate low-order harmonics and to determine switching angles for a fundamental frequency-switching scheme. Next, based on the number of harmonics to be eliminated, Newton climbing method is applied to transcendental equations to eliminate high-order harmonics and to determine switching angles for the fundamental frequency-switching scheme. Third, the magnitudes and phases of the residual lower order harmonics are computed, generated, and subtracted from the original voltage waveform to eliminate these low-order harmonics. Compared to the active-harmonic-elimination method (AHEM), which generates square waves to cancel high-order harmonics, RAHEM has lower switching frequency. The simulation results show that the method can effectively eliminate all the specific harmonics, and a low total harmonic distortion (THD) near sine wave is produced. An experimental 11-level H-bridge multilevel converter with a field-programmable gate-array controller is employed to experimentally validate the method. The experimental results show that RAHEM does effectively eliminate any number of specific harmonics, and the output voltage waveform has low switching frequency and low THD.

Du, Zhong [ORNL; Tolbert, Leon M [ORNL; Chiasson, John N [ORNL; Ozpineci, Burak [ORNL

2008-01-01

5

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

6

Clarification and measurements of high frequency harmonic resonance by a voltage sourced converter  

Microsoft Academic Search

This work presents the clarification and measurements of a high-order harmonic resonance phenomenon for voltage sourced converters. When a voltage sourced converter is connected to a power system through a cable, there is a possibility that small, high frequency, harmonic voltages due to the converter are magnified by series and parallel resonances. The cause of the high-order harmonic resonance is

Koji Temma; Fujio Ishiguro; Naohiro Toki; Isao Iyoda; John J. Paserba

2005-01-01

7

Decoupled Newton Algorithms in the Harmonic Domain for the Harmonic Interaction of Line Commutated Converters With AC Systems  

Microsoft Academic Search

Under certain nonideal conditions, the harmonic interaction of line commutated converters with the ac network must be represented by suitable models with high level of detail. A complex and robust solution of this problem is achieved in previous works by means of an iterative procedure in the harmonic domain, where ac and dc harmonics and switching instants are updated simultaneously.

Julio G. Mayordomo; Ángel Carbonero; Luis F. Beites; Wilsun Xu

2010-01-01

8

Clarification and Measurements of High Frequency Harmonic Resonance by a Voltage Sourced Converter  

Microsoft Academic Search

Summary form only given. This paper presents the clarification and measurements of a high-order harmonic resonance phenomenon for voltage sourced converters. When a voltage sourced converter is connected to a power system through a cable, there is a possibility that small, high frequency, harmonic voltages due to the converter are magnified by series and parallel resonances. The cause of the

K. Temma; F. Ishiguro; N. Toki; I. Iyoda; J. Paserba

2006-01-01

9

A Study for High-Order Harmonic Resonance Phenomena of Voltage Sourced Converter in Cable System  

Microsoft Academic Search

This paper presents high-order harmonic resonance phenomena of voltage sourced converter (VSC). When a voltage sourced converter is connected to power system with cables, there is possibility that minute high-order harmonic voltages of a voltage sourced converter are magnified by a series resonance and a parallel resonance, and high-order harmonic resonance phenomena are found by this study. The cause of

Tatsuhito Nakajima; Hirokazu Suzuki; Koji Temma; Isao Iyoda

2004-01-01

10

Harmonic Propagation in Power Lines due to Converter Loads and Nonlinear Resistors  

Microsoft Academic Search

This paper describes the propagation of harmonic voltages and currents, generated by solid state power converters and nonlinear resistive loads in power systems. After establishing accurate harmonic models for a six pulse bridge rectifier and a nonlinear resistor supplied from non sinusoidal sources, a harmonic power flow technique, \\

J. P. Tamby; V. I. John

1986-01-01

11

Total compensation of line-side switching harmonics in converter-fed AC locomotives  

Microsoft Academic Search

PWM-controlled line-side power converters of modern AC traction locomotives inject harmonic currents into the feeding overhead line. This causes problems of electromagnetic interference. Passive or active filters are usually provided for a partial reduction of the line harmonics. A novel and superior approach employs a switched electronic compensator. It generates an exact replica of the harmonic current, feeding it to

Jew-Onno Krah; Joachim Holtz

1994-01-01

12

Harmonic analysis of nondeterministic switching methods for DC-DC power converters  

Microsoft Academic Search

The authors present a rigorous theoretical harmonic analysis of random pulse width modulation (RPWM) method and random pulse position modulation (RPPM) method for dc-dc converters. The theoretical relationships of discrete harmonics, continuous noise and output voltage ripple of the RPWM and RPPM schemes are established and compared with those of a standard deterministic PWM scheme in a buck converter. Limitations

Yash Shrivastava; S. Y. Hui; S. Sathiakumar; H. Shu-Hung Chung; K. K. Tse

2000-01-01

13

Temperature-noncritical third harmonic generation in an LBO crystal  

SciTech Connect

Temperature-noncritical third harmonic generation is studied theoretically and experimentally in an LBO crystal by compensating for the temperature-induced deviation of the phase-matching direction due to thermal strains in the crystal. The width of the phase-matching temperature curve obtained experimentally in a 14.1-mm-long LBO crystal for the third harmonic generation of the 1.064-{mu}m radiation is 73 {sup 0}C. (nonlinear optical phenomena)

Grechin, Sergei G [Scientific-Research Institute of Radioelectronics and Laser Technology at the N.E. Bauman Moscow State Technical University, Moscow (Russian Federation); Dmitriev, Valentin G [M.F. Stel'makh Polyus Research and Development Institute, Moscow (Russian Federation); Dyakov, Vladimir A [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation); Pryalkin, Vladimir I

2004-06-30

14

An X-band even harmonic type direct converter for CDMA satellite communications  

Microsoft Academic Search

This paper describes an X-band even harmonic type direct converter(EH-DC) used in earth stations for CDMA satellite communications. Technical features of this EH-DC are as follows: (a) Carrier leakage of a modulator is extremely low by employing an even harmonic mixer(EH-MIX). (b) High accuracy of a demodulator(low amplitude error and phase error) is achieved by employing an even harmonic quadrature

Hiroshi Ikematsu; Ken'ichi Tajima; Kenji Kawakami; Kenji Itoh; Yoji Isota; Osami Ishida

1998-01-01

15

Generalized techniques of selective harmonic elimination and current control in current source inverters\\/converters  

Microsoft Academic Search

This paper presents generalized techniques for realizing PWM patterns which provide selective harmonic elimination and current magnitude modulation (SHEM) for current source inverters\\/power converters (CSI\\/C). A combination of chops and short circuit pulses are positioned in such a way that lower order harmonics are eliminated selectively besides current magnitude modulation with minimum switching frequency. Generalized equations and tables which show

Hamid R. Karshenas; Hassan Ali Kojori; Shashi B. Dewan

1995-01-01

16

Properties of a Harmonic Crystal in a Stationary Nonequilibrium State.  

National Technical Information Service (NTIS)

The stationary nonequilibrium Gibbsian ensemble representing a harmonic crystal in contact with several idealized heat reservoirs at different temperatures is shown to have a Gaussian Gamma space distribution for the case where the stochastic interaction ...

Z. Rieder J. L. Lebowitz E. Lieb

1966-01-01

17

Superconducting microwave cavity parametric converter transducer sensitive to 10⁻¹⁹ M harmonic motion  

Microsoft Academic Search

Toward the development of a transducer suitable for the detection of high frequency gravitational effects, a superconducting microwave coupled-cavity parametric converter transducer has been analyzed, developed and tested. An analysis is presented of the intermodal parametric conversion which is produced by harmonic perturbaton of the length of a 10 GHz TEâââ mode cylindrical resonant cavity. The converter is examined as

Reece

1984-01-01

18

A power converter as an active filter for the reduction of harmonic oscillations in supply network  

NASA Astrophysics Data System (ADS)

An active filter is considered with regard to a harmonic oscillation compensation for a supply network. Self compensated converters with load independent current are used for the production of harmonic oscillations required for the compensation. Control design for single phase and three phase converters are presented. For single phase converters, the dynamics of flicker control are improved with an additional back coupling. A phased flicker control design is developed. A modulation process is implemented for the conversion of variance in pulse pattern. The control allows not only an increase of the bandwidth of the distance, but also a high reduction of the resonance step up.

Choe, Song-Yul

1991-05-01

19

Simulated Study of Three-Phase Single-Switch PFC Converter with Harmonic Injected PWM by MATLAB  

Microsoft Academic Search

This paper describes the operation and simulation of a three-phase single-switch PFC converter with a sixth-order harmonic-injection PWM. The PFC converter operates in a discontinuous current mode (DCM). In proposed method, the sixth-order harmonic is injected in PWM so that the harmonic content of the input current meet IEC555-2(A) requirement. The theoretical analysis of the harmonic-injection is discussed. Furthermore, the

Zhanlong Li; Yupeng Tang

2006-01-01

20

Second harmonic chalcone crystal: Synthesis, growth and characterization  

NASA Astrophysics Data System (ADS)

The novel nonlinear optical chalcone derivative (2E)-3-[4-(methylsulfanyl)phenyl]-1-(3-bromophenyl)prop-2-en-1-one (3Br4MSP) crystals have been grown by slow evaporation technique at ambient temperature. The crystal was subjected to different types of characterization method in order to study its possible application in nonlinear optics. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. The morphology of the crystal is studied. The crystal was subjected to thermal analysis to find its thermal stability. The grown crystals were characterized for their optical transmission and mechanical hardness. The second harmonic generation (SHG) efficiency of the crystal is obtained by classical powdered technique. The laser damage threshold for 3Br4MSP crystal was determined using Q-switched Nd:YAG laser.

D'Silva, E. D.; Narayan Rao, D.; Philip, Reji; Butcher, Ray J.; Rajnikant; Dharmaprakash, S. M.

2011-05-01

21

A Flexible Harmonic Control Approach Through Voltage-Controlled DG–Grid Interfacing Converters  

Microsoft Academic Search

The increased penetration of nonlinear loads and power-electronics-based distributed generation (DG) systems may introduce power quality issues to the distribution power system. However, if controlled and regulated properly, the DG-grid in- terfacing converters are able to improve the distribution system efficiency and power quality. This paper focuses on the distrib- ution system harmonic control through the DG-grid interfacing converters. Two

Jinwei He; Yun Wei Li

2012-01-01

22

Noncharacteristic line harmonics of AC\\/DC converters with high DC current ripple  

Microsoft Academic Search

To investigate the basic mechanisms generating noncharacteristic line current harmonics of AC\\/DC converters with high DC ripple, the assumption of negligible small commutation is used. Thus, simple analytical models can be derived describing the effect of voltage unbalance in case of equidistant phase angle control and control angle asymmetry, respectively. By means of superposition of both components, the according behavior

Michael Bauta; Manfred Grötzbach

2000-01-01

23

Second harmonic generation in GaP photonic crystal waveguides  

NASA Astrophysics Data System (ADS)

We demonstrate enhanced second harmonic generation in a gallium phosphide photonic crystal waveguide with a measured external conversion efficiency of 5 × 10-7/W. Our results are promising for frequency conversion of on-chip integrated emitters having broad spectra or large inhomogeneous broadening, as well as for frequency conversion of ultrashort pulses.

Rivoire, Kelley; Buckley, Sonia; Hatami, Fariba; Vu?kovi?, Jelena

2011-06-01

24

Photovoltaic power converter system with a controller configured to actively compensate load harmonics  

DOEpatents

Photovoltaic power converter system including a controller configured to reduce load harmonics is provided. The system comprises a photovoltaic array and an inverter electrically coupled to the array to generate an output current for energizing a load connected to the inverter and to a mains grid supply voltage. The system further comprises a controller including a first circuit coupled to receive a load current to measure a harmonic current in the load current. The controller includes a second circuit to generate a fundamental reference drawn by the load. The controller further includes a third circuit for combining the measured harmonic current and the fundamental reference to generate a command output signal for generating the output current for energizing the load connected to the inverter. The photovoltaic system may be configured to compensate harmonic currents that may be drawn by the load.

de Rooij, Michael Andrew (Clifton Park, NY); Steigerwald, Robert Louis (Burnt Hills, NY); Delgado, Eladio Clemente (Burnt Hills, NY)

2008-12-16

25

Thermal problems caused by harmonic frequency leakage fluxes in three-phase, three-winding converter transformers  

Microsoft Academic Search

Harmonic frequency leakage flux can be a limiting factor in three-phase, three-winding HVDC converter transformers. Investigation of a three-phase, three-winding 240-MVA converter transformer failure indicated the failure was caused by harmonic fluxes. Calculations indicated that the magnitudes of these harmonic fluxes to be approximately 45% of the power frequency leakage flux for the transformer, and are little affected by the

J. A. C. Forrest; B. Allard

2004-01-01

26

AC-DC converter minimizing induced harmonics in industrial power systems  

SciTech Connect

Conventional ac-dc converters present two important disadvantages: they create harmonic currents and require reactive power. To reduce these drawbacks, a diode rectifier is directly connected in series with a chopper controlled by pulsewidth modulation. Both are preceded by a series inductance (added to the equivalent one of the power system) and a shunt capacitor. This study is applied to single-phase powerful electric locomotives. Equivalent three-phase systems are not so interesting.

Destobbeleer, E.; Seguier, G.; Castelain, A.

1987-10-01

27

Second harmonic generation and crystal growth of new chalcone derivatives  

NASA Astrophysics Data System (ADS)

We report on the synthesis, crystal structure and optical characterization of chalcone derivatives developed for second-order nonlinear optics. The investigation of a series of five chalcone derivatives with the second harmonic generation powder test according to Kurtz and Perry revealed that these chalcones show efficient second-order nonlinear activity. Among them, high-quality single crystals of 3-Br-4?-methoxychalcone (3BMC) were grown by solvent evaporation solution growth technique. Grown crystals were characterized by X-ray powder diffraction (XRD), laser damage threshold, UV vis NIR and refractive index measurement studies. Infrared spectroscopy, thermogravimetric analysis and differential thermal analysis measurements were performed to study the molecular vibration and thermal behavior of 3BMC crystal. Thermal analysis does not show any structural phase transition.

Patil, P. S.; Dharmaprakash, S. M.; Ramakrishna, K.; Fun, Hoong-Kun; Sai Santosh Kumar, R.; Narayana Rao, D.

2007-05-01

28

Photoinduced second harmonic generation in molecular crystals caused by defects  

NASA Astrophysics Data System (ADS)

We have found optical photoinduced second harmonic generation in pyrene molecular crystals photoinduced by intrinsic defects. A correlation between the number of macro-vacancies (defects) measured by positron annihilation and second-order nonlinear optical susceptibilities indicates the appearance of additional non-centrosymmetry in the electron charge density distribution caused by the defects. Simultaneously, changes in the kinetics of phenomena in the picosecond time regime are demonstrated. The latter indicate the essential role of intra- and intermolecular contributions in the observed phenomena.

Kityk, I. V.; Marciniak, B.; Mefleh, A.

2001-01-01

29

On the convergence to statistical equilibrium for harmonic crystals  

NASA Astrophysics Data System (ADS)

We consider the dynamics of a harmonic crystal in d dimensions with n components, d,n arbitrary, d,n>=1, and study the distribution ?t of the solution at time t?R. The initial measure ?0 has a translation-invariant correlation matrix, zero mean, and finite mean energy density. It also satisfies a Rosenblatt-resp. Ibragimov-Linnik type mixing condition. The main result is the convergence of ?t to a Gaussian measure as t-->?. The proof is based on the long time asymptotics of the Green's function and on Bernstein's ``room-corridors'' method.

Dudnikova, T. V.; Komech, A. I.; Spohn, H.

2003-06-01

30

A superconducting microwave parametric converter transducer sensitive to 10 to the minus nineteenth power m harmonic motion  

Microsoft Academic Search

Toward the development of a transducer suitable for the detection of high frequency gravitational effects, a superconducting microwave coupled-cavity parametric converter transducer was analyzed, developed and tested. An analysis is presented of the intermodal parametric conversion which is produced by harmonic perturbation of the length of a 10 GHz TE(011) mode cylindrical resonant cavity. The converter is examined as a

C. E. Reece

1984-01-01

31

Design and performance of the Beamlet laser third harmonic frequency converter  

SciTech Connect

The Beamlet laser is a full-scale, single-aperture scientific prototype of the frequency-tripled Nd:glass laser for the proposed National Ignition Facility. At aperture sizes of 30 cm x 30 cm and 34 cm x 34 cm using potassium dihydrogen phosphate crystals of 32 cm x 32 cm and 37 cm x 37 cm, respectively, the authors have obtained up to 8.3 kJ of third harmonic energy at 70%--80% whole beam conversion efficiency.

Barker, C.E.; Wonterghem, B.M. Van; Auerbach, J.M.; Foley, R.J.; Murray, J.R.; Campbell, J.H.; Caird, J.A.; Speck, D.R.; Woods, B.

1995-09-12

32

Diffractive-refractive optics: (+,-,-,+) X-ray crystal monochromator with harmonics separation.  

PubMed

A new kind of two channel-cut crystals X-ray monochromator in dispersive (+,-,-,+) position which spatially separates harmonics is proposed. The diffracting surfaces are oriented so that the diffraction is inclined. Owing to refraction the diffracted beam is sagittally deviated. The deviation depends on wavelength and is much higher for the first harmonics than for higher harmonics. This leads to spatial harmonics separation. The idea is supported by ray-tracing simulation. PMID:21335920

Hrdý, Jaromír; Mikulík, Petr; Oberta, Peter

2011-01-08

33

Effect of DC ripple and commutation on the line harmonics of current-controlled AC\\/DC converters  

Microsoft Academic Search

Line harmonics are usually predetermined under the simplified assumption that the DC current is sufficiently smoothed. But in practical operation of controlled converters, e.g., feeding medium-sized DC drives, DC ripple often cannot be neglected. For the predetermination of line harmonics, this means that the operating point is specified by the EMF and the mean value of the DC current, i.e.,

Manfred Grotzbach; Bertram Draxler

1993-01-01

34

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

35

Quartz crystal microbalance based on passive frequency to voltage converter  

NASA Astrophysics Data System (ADS)

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

2012-02-01

36

Boresight checking techniques using second-harmonic generating /SHG/ crystals and corner cubes  

NASA Astrophysics Data System (ADS)

A simple, low cost, reliable and non-electronic boresight tester was developed for use with military laser designators and range finders. Boresight testing is accomplished by attaching this device to the output end of a laser designator and checking the position of crossed green lines projected on the reticle pattern of the sighting telescope. The device uses a second harmonic generation (SHG) crystal and a corner cube reflector to convert a small portion of the infrared energy to visible green energy. This green energy forms a cross pattern imaged on the reticle by the objective lens of the laser systems under test. Cesium dihydrogen arsenate (CDA) was chosen as the best SHG for this application. Initial tests have shown the green cross pattern to be clearly visible and sufficiently bright far below the eye-safe level.

Priddy, R. W.; Irelan, V. G.; Bellar, D. R.

1980-01-01

37

A current-fed HF link direct DC\\/AC converter with active harmonic filter for fuel cell power systems  

Microsoft Academic Search

This paper describes a current-fed high frequency (HF) link direct DC\\/AC converter suitable for fuel cell power source. The proposed current-fed HF link direct DC\\/AC converter consists of a current-fed full-bridge inverter with an active harmonic filter, a HF link transformer, and a simple cycloconverter. The high frequency full-bridge inverter at the primary generates sinusoidally PWM modulated current pulses with

Yu Jin Song; Se-Kyo Chung; Prasad N. Enjeti

2004-01-01

38

A study of active power filters using quad-series voltage-source PWM converters for harmonic compensation  

Microsoft Academic Search

An active power filter using quad-series voltage-source pulse-width-modulated (PWM) converters to suppress AC harmonics by injecting compensating currents into the AC system is described. The circuit used to calculate the compensating current references, the compensation characteristics, and the capability of the DC capacitor are discussed theoretically and experimentally. A control circuit for the DC capacitor voltage is proposed. The discussions

FANG-ZHANG PENG; HIROFUMI AKAGI; AKIRA NABAE

1990-01-01

39

Effect of bit-threshold errors on the harmonic and intermodulation performance of successive approximation A\\/D converters  

Microsoft Academic Search

A simple approach is described for predicting the harmonic and intermodulation performance of a real successive approximation analog-to-digital converter (ADC) with bit-threshold errors. The real ADC characteristic is split into an ideal staircase characteristic, representing the ideal ADC characteristic, minus a train of pulses, representing the bit-threshold errors. Series expressions are obtained for the output spectra of the real ADC

M. T. Abuelma'atti

1993-01-01

40

Second harmonic generation in gallium phosphide photonic crystal nanocavities with ultralow continuous wave pump power  

Microsoft Academic Search

We demonstrate second harmonic generation in photonic crystal nanocavities fabricated in the semiconductor gallium phosphide. We observe second harmonic radiation at 750 nm with input powers of only nanowatts coupled to the cavity and conversion efficiency $P_{\\\\rm out}\\/P_{\\\\rm in, coupled}^2 = 430%\\/{\\\\rm W}$. The large electronic band gap of GaP minimizes absorption loss, allowing efficient conversion. Our results are promising

Kelley Rivoire; Ziliang Lin; Fariba Hatami; W. Ted Masselink; Jelena Vuckovic

2009-01-01

41

High-efficiency single-crystal third-harmonic generation in BiB?O?.  

PubMed

Third-harmonic generation of high-intensity, sub-100-fs idler pulses from a Ti:sapphire-laser-pumped optical parametric amplifier is demonstrated by using a single nonlinear crystal of BiB?O? (BIBO). Maximum internal energy conversion as high as 11% from the fundamental to the third harmonic is achieved by phase- and group-velocity matching for the direct cubic nonlinear process together with the velocity-mismatched cascading quadratic processes. PMID:21931413

Miyata, Kentaro; Petrov, Valentin; Noack, Frank

2011-09-15

42

Temperature-insensitive phase-matched optical harmonic conversion crystal  

DOEpatents

Temperature-insensitive, phase-matched harmomic frequency conversion of laser light at a preferred wavelength of 1.064 microns can be achieved by use of a crystal of deuterated l-arginine phosphate. The crystal is cut and oriented so that the laser light propagates inside the crystal along one of several required directions, which correspond to a temperature-insensitive, phase-matching locus. The method of measuring and calculating the temperature-insensitive, phase-matching angles can be extended to other fundamental wavelengths and other crystal compositions.

Barker, Charles E. (Sunnyvale, CA); Eimerl, David (Livermore, CA); Velsko, Stephan P. (Livermore, CA); Roberts, David (Sagamore Hills, OH)

1993-01-01

43

Radial state space vector modulation-a new space vector technique for reducing DC link capacitor harmonic currents in three level converters  

Microsoft Academic Search

Three level diode clamped converters exhibit significant low frequency harmonics in the neutral point current with classical modulation methods. A new space vector strategy that eliminates low frequency ripple from the DC link capacitors of a three level converter is proposed in this paper. The strategy redistributes the duty cycles of six states in the three level switching state diagram

Ashish Bendre; G. Venkataramanan

2003-01-01

44

Calculation of thermo-optical distortions of some nonlinear crystals during second-harmonic generation  

SciTech Connect

Numerical calculations are reported of thermooptical distortions of nonlinear ADP, LiNbO{sub 3}, KDP nonlinear crystals used in second-harmonic generation. The elasto-optical effect is taken into account. The calculations are made for crystalline samples in the form of circular cylinders in which a steady-state parabolic temperature field is established. (nonlinear optical phenomena and devices)

Dmitriev, Valentin G [M.F. Stel'makh Polyus Research and Development Institute, Moscow (Russian Federation); Yur'ev, Yu V [Moscow Physicotechnical Institute (State University), Moscow (Russian Federation)

1998-11-30

45

Temperature-independent phase matching for second-harmonic generation in a KTP crystal  

SciTech Connect

Theoretical and experimental investigations were made of temperature-independent ('uncritical') phase matching for second-harmonic generation. It was found experimentally that the bandwidth of the temperature phase-matching tuning curve for a potassium titanyl phosphate (KTP) crystal 7.7 mm long was 210{sup 0}C at the fundamental radiation wavelength of 1064.2 nm. (nonlinear optical phenomena)

Grechin, Sergei G [Scientific-Research Institute of Radioelectronics and Laser Technology at the N.E. Bauman Moscow State Technical University, Moscow (Russian Federation); Dmitriev, Valentin G [M.F. Stel'makh Polyus Research and Development Institute, Moscow (Russian Federation); Dyakov, Vladimir A [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation); Pryalkin, Vladimir I [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation)

1999-01-31

46

Feasibility of capacitor voltage regulation and output voltage harmonic minimization in cascaded H-bridge converters  

Microsoft Academic Search

Multilevel converters have found popularity in electric-drive vehicles. In cascaded H-bridge multilevel converters, it is advantageous to use only one DC voltage source for the main H-bridge cell and supply the rest of the cells with capacitors. However, regulating the capacitors' voltage level becomes a challenging issue. This paper studies the existing constraints on regulating the capacitor voltage levels especially

Hossein Sepahvand; Mostafa Khazarei; Mehdi Ferdowsi; Keith Corzine

2010-01-01

47

Second harmonic generation in gallium phosphide photonic crystal nanocavities with ultralow continuous wave pump power.  

PubMed

We demonstrate second harmonic generation in photonic crystal nanocavities fabricated in the semiconductor gallium phosphide. We observe second harmonic radiation at 750 nm with input powers of only nanowatts coupled to the cavity and conversion effciency P(out)/P(2)(in,coupled)=430%/W. The large electronic band gap of GaP minimizes absorption loss, allowing effcient conversion. Our results are promising for integrated, low-power light sources and on-chip reduction of input power in other nonlinear processes. PMID:20052186

Rivoire, Kelley; Lin, Ziliang; Hatami, Fariba; Masselink, W Ted; Vuckovi?, Jelena

2009-12-01

48

Conical second harmonic generation in one-dimension nonlinear photonic crystal  

NASA Astrophysics Data System (ADS)

We observed conical second-harmonic generation in a one-dimension anomalous-dispersion-like medium, which manifests itself as scattering-assisted nonlinear interaction via quasi-phase-matching sum frequency process. The parameters for the ring-shaped second harmonic beam are analyzed experimentally and theoretically, which disclose the structure information of the nonlinear photonic crystal and imply potential applications as characterization methods. Furthermore, by varying the angles of incident beam, the conical beam can be significantly enhanced owing to collinear nonlinear coupling between the input beam and the scattering light.

An, Ning; Zheng, Yuanlin; Ren, Huaijin; Deng, Xuewei; Chen, Xianfeng

2013-05-01

49

Switching harmonics in the DC link current in a PWM AC-DC-AC converter  

Microsoft Academic Search

A novel method for determining the DC link current drawn by a PWM inverter is described. The equations derived are simple to apply and yield considerable analytical insight into the DC link current waveform. The method enables the RMS current flowing in the DC link capacitor in a back-to-back power converter to be calculated, allowing the capacitor to be specified

H. Zhang; N. Wheeler; D. Grant

1995-01-01

50

How a silver dendritic mesocrystal converts to a single crystal  

Microsoft Academic Search

In this paper, we demonstrate how a silver dendrite transforms from mesocrystal into single crystal and the stability for a dendritic silver mesocrystal within a Sn\\/AgNO3 galvanic replacement reaction. Our findings provide the direct evidence and visible picture of the transformation from mesocrystal to single crystalline structure and further confirm the particle-mediated crystallization mechanism. At the initial stage of the

Jixiang Fang; Bingjun Ding; Xiaoping Song; Yong Han

2008-01-01

51

Highly efficient nanojoule second harmonic generation of a femtosecond Cr:forsterite laser radiation in a lithium niobate crystal  

SciTech Connect

Highly efficient ({approx}70%) second harmonic generation of tightly focused femtosecond radiation from a Cr:forsterite laser is obtained in a LiNbO{sub 3} crystal. The pulse energy amounts to 10 nJ, the spatial and spectral quality of second harmonic radiation being preserved. (nonlinear optical phenomena)

Gordienko, Vyacheslav M; Dyakov, Vladimir A; Mikheev, Pavel M [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation); Syrtsov, Vladimir S [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation)

2006-11-30

52

Simultaneous generation of spectrally distinct third harmonics in a photonic crystal fiber.  

PubMed

By coupling femtosecond pulses at lambda - 1.55mum in a short length (Z - 95 cm) of photonic crystal fiber, we observe the simultaneous generation of two visible radiation components. Frequency-resolved optical gating experiments combined with analysis and modal simulations suggest that the mechanism for their generation is third-harmonic conversion of the fundamental pulse and its split Raman self-shifted component. PMID:18049548

Omenetto, F G; Taylor, A J; Moores, M D; Arriaga, J; Knight, J C; Wadsworth, W J; Russell, P S

2001-08-01

53

Noncritically phase-matched fourth harmonic generation of Nd:glass lasers in partially deuterated KDP crystals.  

PubMed

Noncritically phase-matched (NCPM) fourth harmonic generation (FHG) of Nd:glass laser radiation in partially deuterated dihydrogen phosphate (KD*P) crystals has been demonstrated. At an Nd:glass laser wavelength of 1053.0 nm, NCPM FHG is achieved in 70% deuterated KD*P at a crystal temperature of 18.5±0.1 °C. Tuning the fundamental laser wavelength from 1052.9 to 1053.2 nm, FHG in KD*P is NCPM by changing the crystal temperature from 17.9 °C to 20.5 °C. When driven with 2.4 J of second harmonic radiation in a 3 ns flat-top pulse, corresponding to 1 GW/cm(2) 2? drive intensity, 1.9 J of fourth harmonic radiation was generated in a 6 mm long KD*P crystal, yielding a second to fourth harmonic energy conversion efficiency of 79%. PMID:21593903

Yang, Steven T; Henesian, Mark A; Weiland, Timothy L; Vickers, James L; Luthi, Ronald L; Bielecki, John P; Wegner, Paul J

2011-05-15

54

Phase-sensitive second-harmonic microscopy reveals polarity of topologically centrosymmetric molecular crystals  

NASA Astrophysics Data System (ADS)

Phase-sensitive second-harmonic microscopy is applied to reveal grow-in polarity in topologically centrosymmetric crystals of 4-chloro-4'-nitrostilben. As predicted by the Markow model of layer-by-layer polarity formation, growth along + and -b-direction in P21/c is producing optical nonlinearity in both sectors associated with the b axis. Present experiments show that formation of a pyroelectric symmetry class is a stochastic property of molecular crystals grown from dipolar compounds and near to thermodynamic equilibrium.

Kluge, S.; Budde, F.; Dohnke, I.; Rechsteiner, P.; Hulliger, J.

2002-07-01

55

Study of the second harmonic generation and optical rectification in a cBN crystal  

SciTech Connect

Cubic boron nitride (cBN) - a kind of an artificial (synthetic) crystal with the band gap of {approx}6.3 eV, which has the zinc blende structure and the 4-bar 3m symmetry, is studied. The optical rectification is obtained and the second harmonic generation (SHG) is observed in the cBN crystal for the first time by using a 1064-nm Q-switched Nd:YAG laser. The green light at 532 nm from the cBN sample can be seen with a naked eye. (nonlinear optical phenomena)

Dou Qingping; Ma Haitao; Jia Gang; Chen Zhanguo; Cao Kun [College of Electronic Science and Engineering, State Key Laboratory on Integrated Optoelectronics, Jilin Iniversity, Changchun (China); Zhang Tiechen [State Key Laboratory on Superhard Materials, Jilin University, Changchun (China)

2007-02-28

56

Third harmonic generation of Nd:glass laser with novel composite deuterated KDP crystals  

NASA Astrophysics Data System (ADS)

A novel composite partially deuterated KDP crystal used for frequency tripling is experimentally demonstrated for the first time in this paper. The deuteration level is used as a degree of freedom to alter the phase matching wavelength so as to increase the bandwidth acceptance. The results show that the acceptance bandwidth based on such crystal can be increased by a factor of 3 comparing with the conventional method. The obtained results are very useful to develop frequency tripling components in broadband third harmonic generation.

Wang, W.; Wang, J.; Wang, F.; Feng, B.; Li, K.; Jia, H.; Han, W.; Xiang, Y.; Li, F.; Wang, L.; Zhong, W.; Zhang, X.; Zhao, S.

2010-10-01

57

How a silver dendritic mesocrystal converts to a single crystal  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate how a silver dendrite transforms from mesocrystal into single crystal and the stability for a dendritic silver mesocrystal within a Sn/AgNO3 galvanic replacement reaction. Our findings provide the direct evidence and visible picture of the transformation from mesocrystal to single crystalline structure and further confirm the particle-mediated crystallization mechanism. At the initial stage of the transformation, there is a crystallographic fusion process, dominated by oriented attachment mechanism. Ostwald ripening also plays an important role in forming smooth surface and regular shape of the final nanocrystal.

Fang, Jixiang; Ding, Bingjun; Song, Xiaoping; Han, Yong

2008-04-01

58

How a silver dendritic mesocrystal converts to a single crystal  

SciTech Connect

In this paper, we demonstrate how a silver dendrite transforms from mesocrystal into single crystal and the stability for a dendritic silver mesocrystal within a Sn/AgNO3 galvanic replacement reaction. Our findings provide the direct evidence and visible picture of the transformation from mesocrystal to single crystalline structure and further confirm the particle-mediated crystallization mechanism. At the initial stage of the transformation, there is a crystallographic fusion process, dominated by oriented attachment mechanism. Ostwald ripening also plays an important role in forming smooth surface and regular shape of the final nanocrystal.

Fang, J.; Ding, B.; Song, X.; Han, Y.

2008-05-02

59

Efficient intracavity second-harmonic generation at 1063 nm in a GdCOB crystal  

NASA Astrophysics Data System (ADS)

We report an efficient intracavity second-harmonic generation (SHG) at 1063 nm in a non-linear optical crystal, GdCa4O(BO3)3 (GdCOB), performed with a diode end pumped continuous-wave (CW) Nd:GdVO4 laser. In the case of a laser with an a-cut 0.4 at % Nd:GdVO4 crystal frequency-doubled with a GdCOB crystal cut for Type I frequency doubling. A CW SHG output power of 2.25 W has been obtained using a 15 mm long GCOB crystal. The optical conversion efficiency with respect to the incident pump power was 12.4%.

Wu, Z. C.; Liu, W. M.

2011-12-01

60

Influence of the temperature distribution in KDP crystal on the second-harmonic generation  

NASA Astrophysics Data System (ADS)

Using split-step algorithm based on the fast Fourier transform and a fourth-order Runge-Kutta(R-K) method, we studied the second-harmonic generation(SHG) of high power laser with KDP crystal. The transverse walk-off effect, diffraction, the second-order and the third-order nonlinear effects of KDP crystal have been taken into consideration. Special attention has been paid to the influences of a kind of self-induced thermal effect. The phase mismatching quantity, the intensity distribution of output beam and the frequency conversion efficiency varying with the crystal temperature distribution have been analyzed. The calculated results indicate that self-induced thermal effects results in the temperature distribution in KDP crystal and the phase mismatching, then the phase mismatching leads to the decreasion of the conversion efficiency.

Li, Wei; Feng, Guoying; Zhang, Qiuhui; Zhang, Tianxiang; Liao, Hai

2008-08-01

61

Converting Ceria Polyhedral Nanoparticles into Single-Crystal Nanospheres  

Microsoft Academic Search

Ceria nanoparticles are one of the key abrasive materials for chemical-mechanical planarization of advanced integrated circuits. However, ceria nanoparticles synthesized by existing techniques are irregularly faceted, and they scratch the silicon wafers and increase defect concentrations. We developed an approach for large-scale synthesis of single-crystal ceria nanospheres that can reduce the polishing defects by 80% and increase the silica removal

Xiangdong Feng; Dean C. Sayle; Zhong Lin Wang; M. Sharon Paras; Brian Santora; Anthony C. Sutorik; Thi X. T. Sayle; Yi Yang; Yong Ding; Xudong Wang; Yie-Shein Her

2006-01-01

62

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

2012-09-18

63

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

64

Second-harmonic dielectric response of an antiferroelectric liquid crystal under dc electric fields.  

PubMed

Second-harmonic dielectric response under dc fields in an antiferroelectric liquid-crystal 4-(1-methyl-heptyloxycarbonyl)phenyl 4-octylcarbonyloxybiphenyl- 4-carboxylate (MHPOCBC) has been investigated. The second-harmonic response from the amplitude mode in the smectic- Calpha* phase was observed due to the symmetry breaking by the application of dc electric fields. A Landau theory was developed in order to analyze experimentally obtained frequency dispersions. From the analysis we found a softening of the amplitude mode with increasing the dc field at a temperature close to the smectic- Calpha*-smectic- A phase transition point. It was turned out that the relaxation frequency of the amplitude mode decreases linearly with the applied electric field. PMID:20365754

Fajar, Andika; Orihara, Hiroshi

2010-03-24

65

Resonance in the Presence of Harmonics Produced by Power Converters and Arc Furnaces Associated with Compensation Devices.  

National Technical Information Service (NTIS)

Capacitors and harmonic filters are associated with arc furnaces and power rectifiers, particularly in connection with rolling mills. By producing reactive energy and absorbing harmonic distortions, they present definite advantages for industry and EDF. O...

M. Lemoine

1978-01-01

66

The applicability of second harmonic generation for in situ measurement of induction time of selected crystallization systems  

Microsoft Academic Search

The nonlinear optical technique of second harmonic generation (SHG) is introduced as a novel technique for monitoring particle formation in batch crystallizations. SHG is more sensitive and is less prone to interference than turbidometric methods. The studies presented show the applicability of SHG as a method for in situ measuring the induction time of a number of noncentrosymmetric crystal systems.

Dale J. LeCaptain; Kris A. Berglund

1999-01-01

67

Nuclear motion effects on the density matrix of crystals: an ab initio Monte Carlo harmonic approach.  

PubMed

In the frame of the Born-Oppenheimer approximation, nuclear motions in crystals can be simulated rather accurately using a harmonic model. In turn, the electronic first-order density matrix (DM) can be expressed as the statistically weighted average over all its determinations each resulting from an instantaneous nuclear configuration. This model has been implemented in a computational scheme which adopts an ab initio one-electron (Hartree-Fock or Kohn-Sham) Hamiltonian in the CRYSTAL program. After selecting a supercell of reasonable size and solving the corresponding vibrational problem in the harmonic approximation, a Metropolis algorithm is adopted for generating a sample of nuclear configurations which reflects their probability distribution at a given temperature. For each configuration in the sample the "instantaneous" DM is calculated, and its contribution to the observables of interest is extracted. Translational and point symmetry of the crystal as reflected in its average DM are fully exploited. The influence of zero-point and thermal motion of nuclei on such important first-order observables as x-ray structure factors and Compton profiles can thus be estimated. PMID:22852604

Pisani, Cesare; Erba, Alessandro; Ferrabone, Matteo; Dovesi, Roberto

2012-07-28

68

Generation of tunable mid-IR radiation by second harmonic in a CdGeAs{sub 2} crystal  

SciTech Connect

Tunable mid-IR radiation is obtained during second harmonic generation of tunable CO{sub 2}-laser radiation using a CdGeAs{sub 2} crystal. Its angular tuning characteristics at the CO{sub 2}- laser wavelength, angular acceptance angle and spectral acceptance are measured. For second harmonic generation at 10.6 {mu}m, the conversion efficiency in the CdGeAs{sub 2} crystal is 90 times higher than that in the ZnGeP{sub 2} crystal.

Das, S [Laser Laboratory, Department of Physics, Burdwan University, Burdwan (India)

2012-03-31

69

Blue light second harmonic generation in the organic crystal ortho-Dicyanovinyl-anisole  

SciTech Connect

Type I phase matched second harmonic generation (SHG) in the organic crystal ortho-Dicyanovinyl-anisole (DIVA) has been measured for a range of near infrared fundamental wavelengths (855{endash}960 nm). Turning curves for type I phase matched SHG were derived from measured refractive index values and show noncritical phase matching at 860. Measured type I phase matched SHG is in close agreement with the calculated results and gives effective SHG coefficients ranging from 1.9 to 5.9 times as large as d{sub 32} of potassium niobate. {copyright} {ital 1997 American Institute of Physics.}

Grossman, C.H.; Schulhofer-Wohl, S.; Thoen, E.R. [Department of Physics and Astronomy, Swarthmore College, Swarthmore, Pennsylvania 19081 (United States)

1997-01-01

70

On the asymptotical normality of statistical solutions for harmonic crystals in half-space  

NASA Astrophysics Data System (ADS)

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 µ t of the solution at time t ? ?. The main result is the convergence of µ t as t ? ? to a Gaussian measure which is time stationary with a covariance inherited from the initial measure (non-Gaussian in general).

Dudnikova, T. V.

2008-12-01

71

A positron source using an axially oriented crystal associated to a granular amorphous converter  

NASA Astrophysics Data System (ADS)

A non-conventional positron source using the intense ? radiation from an axially oriented monocrystal which materializes into e+e- pairs in a granular amorphous converter is described. The enhancement of photon radiation by multi-GeV electrons crossing a tungsten crystal along its <111> axis is reported. The resulting enhancement of pair production in an amorphous converter placed 2 meters downstream, is also reported. Sweeping off the charged particles from the crystal by a bending magnet upstream of the converter allows a significant reduction of the deposited energy density. Substituting a granular target made of small spheres for the usual compact one, makes the energy dissipation easier. The deposited energy and corresponding heating are analyzed and solutions for cooling are proposed. The configurations studied here for this kind of positron source allow its consideration for unpolarized positrons for the ILC.

Xu, Cheng-Hai; Robert, Chehab; Peter, Sievers; Xavier, Artru; Michel, Chevallier; Olivier, Dadoun; Pei, Guo-Xi; Vladimir, M. Strakhovenko; Alessandro, Variola

2012-09-01

72

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

73

Phase-matched magnetization-induced second-harmonic generation in yttrium-iron-garnet magnetophotonic crystals  

Microsoft Academic Search

Magnetization-induced second-harmonic generation (MSHG) is studied in one-dimensional magnetophotonic crystals formed from a stack of ferromagnetic Bi-substituted yttrium-iron-garnet layers alternating with dielectric films. The resonance enhancement of reflected MSHG due to the phase-mismatch compensation is observed for longitudinal dc-magnetic-field application if the fundamental radiation is tuned across the photonic band gap edge. The high-contrast magnetization-induced variations in the second-harmonic intensity

Andrey A. Fedyanin; Oleg A. Aktsipetrov; Daisuke Kobayashi; Kazuhiro Nishimura; Hironaga Uchida; Mitsuteru Inoue

2004-01-01

74

Switchable circular-to-point converter based on holographic polymer-dispersed liquid-crystal technology  

NASA Astrophysics Data System (ADS)

We demonstrate the use of a switchable circular-to-point converter (SCPC) device based on holographic polymer-dispersed liquid-crystal technology for application in lidar detection and optical telecommunication. A SCPC device converts the Fabry-Perot ring pattern into a single point or an array of points, while an external electrical field on the SCPC deactivates the conversion. Stacking different SCPC elements gives a random optical switch for applications in lidar detection and optical telecommunication. Two types of SCPC designs are analyzed and one is chosen and built for testing.

Zhang, Hailiang; Xianyu, Haiqing; Liang, Jianhua; Bétrémieux, Yan; Crawford, Gregory P.; Noto, John; Kerr, Robert

2007-01-01

75

Laser-Induced Damage in DKDP Crystals under Simultaneous Exposure to Laser Harmonics  

SciTech Connect

While KDP and DKDP crystals remain the only viable solution for frequency conversion in large aperture laser systems in the foreseeable future, our understanding of damage behavior in the presence of multiple colors is very limited. Such conditions exist during normal operation where, for third harmonic generation, 1{omega}, 2{omega} and 3{omega} components are present with different energy ratios as they propagate inside the crystal. The objective of this work is to shed light into the damage behavior of frequency conversion crystals during operational conditions as well as probe the fundamental mechanisms of damage initiation. We have performed a series of experiments to quantify the damage performance of pristine (unconditioned) DKDP material under simultaneous exposure to 2{omega} and 3{omega} laser pulses from a 3-ns Nd:YAG laser system as a function of the laser influences at each frequency. Results show that simultaneous dual wavelength exposure leads to a much larger damage density as compared to the total damage resulting from separate exposure at each wavelength. Furthermore, under such excitation conditions, the damage performance is directly related to and can be predicted from the damage behavior of the crystal at each wavelength separately while the mechanism and type of defects responsible for damage initiation are shown to be the same at both 2{omega} and 3{omega} excitation.

Negres, R A; DeMange, P; Radousky, H B; Demos, S G

2005-10-28

76

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

77

Spectral properties of second-harmonic generation at 800 nm in a BiB3O6 crystal  

NASA Astrophysics Data System (ADS)

We have investigated spectral distribution and walk-off effect of second-harmonic generation in a 3-mm-long type I BiB3O6 crystal. Linearly turning ability of the BiB3O6 crystal is confirmed for wavelengths around 800 nm. In addition, the walk-off effect of fundamental beams is quantitatively measured by introducing a little vertical polarization component into pumping fundamental pulses. A conversion efficiency of 28% from fundamental to second harmonic is achieved at a 3.2-GW/cm2 fundamental intensity.

Harimoto, Tetsuo; Takeuchi, Yasuki; Fujita, Masayuki

2004-03-01

78

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

SciTech Connect

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.

Gabrielli, C.; Perrot, H.; Rose, D.; Rubin, A.; Toque, J. P.; Pham, M. C.; Piro, B. [LISE--UPR 15 du CNRS, Universite Pierre et Marie Curie-Paris 6, 4, place Jussieu (case 133), 75252 Paris Cedex 05 (France); LISE-UPR 15 du CNRS, Universite Pierre et Marie Curie-Paris 6, 4, place Jussieu (case 133), 75252 Paris Cedex 05, France and ITODYS, Universite Denis Diderot-Paris 7, 1, rue Guy de la Brosse, 75005 Paris (France); LISE-UPR 15 du CNRS, Universite Pierre et Marie Curie-Paris 6, 4, place Jussieu (case 133), 75252 Paris Cedex 05 (France); ITODYS, Universite Denis Diderot-Paris 7, 1, rue Guy de la Brosse, 75005 Paris (France)

2007-07-15

79

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

NASA Astrophysics Data System (ADS)

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.

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

2007-07-01

80

Numerical analysis of near and far field patterns of second-harmonic generation with tiling nonlinear optical crystals  

NASA Astrophysics Data System (ADS)

We report numerical analysis of near- and far-field patterns of the second-harmonic wave in a large-scale high-power laser used in the laser fusion with type I KDP crystals arranged in a tiling style. The thickness and phase-matching angle of the tiling crystals are designed based on the near-field pattern of the second-harmonic wave. The tilting angle error and thickness difference of the tiling crystals are evaluated by the energy distribution included in the Airy spot of the far-field pattern at the focal point. The parallelism and flatness of the tiling crystals can also be estimated with the same method.

Harimoto, T.; Shiraga, H.

2008-05-01

81

Period-doubling bifurcation in two-stage power factor correction converters using the method of incremental harmonic balance and Floquet theory  

NASA Astrophysics Data System (ADS)

In this paper, period-doubling bifurcation in a two-stage power factor correction converter is analyzed by using the method of incremental harmonic balance (IHB) and Floquet theory. A two-stage power factor correction converter typically employs a cascade configuration of a pre-regulator boost power factor correction converter with average current mode control to achieve a near unity power factor and a tightly regulated post-regulator DC—DC Buck converter with voltage feedback control to regulate the output voltage. Based on the assumption that the tightly regulated post-regulator DC—DC Buck converter is represented as a constant power sink and some other assumptions, the simplified model of the two-stage power factor correction converter is derived and its approximate periodic solution is calculated by the method of IHB. And then, the stability of the system is investigated by using Floquet theory and the stable boundaries are presented on the selected parameter spaces. Finally, some experimental results are given to confirm the effectiveness of the theoretical analysis.

Wang, Fa-Qiang; Zhang, Hao; Ma, Xi-Kui

2012-02-01

82

Simultaneous generation of second to fifth harmonic conical beams in a two dimensional nonlinear photonic crystal.  

PubMed

Broadly tunable multiple high-harmonic conical beams have been generated by means of a multistep ?(2) cascade processes in a two dimensional nonlinear photonic crystal. The nonlinear structure consists of a square lattice of inverted hexagonal domains with diameters and distances between domains as low as 1 ?m. The large number of reciprocal lattice vectors provided by both the square nonlinear structure and the hexagonal shaped domains, along with imperfections on the size and shape of the individual domains make possible the simultaneous generation of second up to fifth harmonic conical beams in a single nonlinear structure by using different types of phase matching geometries. The frequency response can be tuned in an extremely large spectral range, and continuous generation of nonlinear conical beams covering the whole visible spectral region can be achieved. Further, the same photon energy can be generated at different orders, so that concentrically emitted conical beams with angular dispersion as large as ?? = 50° can be observed. The results highlight the significance of highly controlled engineered 2D nonlinear structures to generate advanced multi-photon devices with large spatial and spectral tunable response. PMID:23388820

Mateos, Luis; Molina, Pablo; Galisteo, Juan; López, Cefe; Bausá, Luisa E; Ramírez, Mariola O

2012-12-31

83

Photoinduced second harmonic generation in partially crystallized BiB3O6 glass  

NASA Astrophysics Data System (ADS)

Photoinduced second harmonic generation was found in BiB3O6 (BiBO) glass having different degree of crystallinity. We have revealed that an increasing degree of crystallinity of BiBO glass leads to increase of the output second-order optical susceptibility. We have used a pulsed 35 MW nitrogen laser (?=337nm; ?=50ps) as a source of photoinducing laser beam. Fundamental laser beam was generated by pulsed Nd:YAG laser (?=1.06?m time duration about 25 ps). Maximal value of the photoinduced second-order non-linear optical susceptibility d222 was equal to about 5 pm/V, what is substantially higher than in case of BiBO single crystals (~3pm/V).

Kityk, I. V.; Imiolek, W.; Majchrowski, A.; Michalski, E.

2003-04-01

84

Well-posedness for the heat flow of harmonic maps and the liquid crystal flow with rough initial data  

NASA Astrophysics Data System (ADS)

We investigate the well-posedness of (1) the heat flow of harmonic maps from {mathbb R^n} to a compact Riemannian manifold N without boundary for initial data in BMO; and (2) the hydrodynamic flow (u, d) of nematic liquid crystals on {mathbb R^n} for initial data in BMO-1 × BMO.

Wang, Changyou

2010-07-01

85

Well-posedness for the heat flow of harmonic maps and the liquid crystal flow with rough initial data  

NASA Astrophysics Data System (ADS)

We investigate the well-posedness of (1) the heat flow of harmonic maps from {mathbb R^n} to a compact Riemannian manifold N without boundary for initial data in BMO; and (2) the hydrodynamic flow ( u, d) of nematic liquid crystals on {mathbb R^n} for initial data in BMO-1 × BMO.

Wang, Changyou

2011-04-01

86

A harmonic transition state theory model for defect initiation in crystals  

NASA Astrophysics Data System (ADS)

We outline here a model for the initiation of defects in crystals based upon harmonic transition state theory (hTST). This model combines a previously developed model for zero-temperature defect initiation with a multi-dimensional hTST model that is capable of accurately predicting the effects of temperature and loading rate upon defect initiation. The model has several features that set it apart from previous efforts along these lines, most notably a straightforward method of determining the energy barrier between adjacent equilibrium states that does not depend upon a priori information concerning the nature of the defect. We apply the model to two examples, triaxial stretching of a perfect fcc crystal and nanoindentation of a gold substrate. Very good agreement is found between the predictions of the model and independent molecular dynamics (MD) simulations. Among other things, the model predicts a strong dependence of the defect initiation behavior upon the loading parameter. A very attractive feature of this model is that it is valid for arbitrarily slow loading rates, in particular loading rates achievable in the laboratory, and suffers from none of the limitations in this regard inherent in MD simulations.

Delph, T. J.; Cao, P.; Park, H. S.; Zimmerman, J. A.

2013-03-01

87

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

88

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

89

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

PubMed Central

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.

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

2013-01-01

90

Efficient collinear fourth-harmonic generation by two-channel multistep cascading in a single two-dimensional nonlinear photonic crystal.  

PubMed

We investigate efficient fourth-harmonic generation in a single two-dimensional (2D) quadratically nonlinear photonic crystal. We propose a novel parametric process that starts with phase-matched generation of a pair of symmetric second-harmonic waves, which then interact to produce a fourth-harmonic wave that is collinear to the fundamental. We show that this process is more efficient than conventional fourth-harmonic-generation schemes by a factor that reaches 4 at low intensities and discuss how to design and optimize the nonlinear 2D photonic crystals that are implemented in LiNbO(3) and LiTaO(3) . PMID:18040378

de Sterke, M; Saltiel, S M; Kivshar, Y S

2001-04-15

91

Room temperature, high-efficiency, noncritical phase-matching fourth harmonic generation in partially deuterated ADP crystal.  

PubMed

High-efficiency frequency conversion into the deep ultraviolet in a partially deuterated ammonium dihydrogen phosphate (ADP) crystal is reported. For a 60% deuterated ADP crystal, the spontaneous Raman scattering intensity decreased by 38% compared with that of a pristine ADP crystal. At room temperature (24°C), noncritical phase-matching fourth harmonic generation of a 1053 nm laser was realized. The angular acceptance was 55.7 mrad, and the external conversion efficiency from 526 to 263 nm reached 85.3%. PMID:23938909

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

2013-05-15

92

Tunable-wavelength second harmonic generation from GaP photonic crystal cavities coupled to fiber tapers.  

PubMed

We demonstrate up to 30 nm tuning of gallium phosphide photonic crystal cavities resonances at aproximately 1.5 microm using a tapered optical fiber. The tuning is achieved through a combination of near-field perturbations and mechanical deformation of the membrane, both induced by the fiber probe. By exploiting this effect, we show fiber-coupled second harmonic generation with a tuning range of nearly 10 nm at the second harmonic wavelength of approximately 750 nm. By scaling cavity parameters, the signal could easily be shifted into other parts of the visible spectrum. PMID:20588341

Shambat, Gary; Rivoire, Kelley; Lu, Jesse; Hatami, Fariba; Vuckovi?, Jelena

2010-06-01

93

Design of a compact mode and polarization converter in three-dimensional photonic crystals.  

PubMed

A mode and polarization converter is proposed and optimized for 3D photonic integrated circuits based on photonic crystals (PhCs). The device converts the index-guided TE mode of a W1 solid-core (SC) waveguide to the band-gap-guided TM mode of a W1 hollow-core (HC) waveguide in 3D PhCs, and vice versa. The conversion is achieved based on contra-directional mode coupling. For a 25 ?m-long device, simulations show that the power conversion efficiency is over 98% across a wavelength range of 16 nm centered at 1550 nm, whereas the reflection remains below -20 dB. The polarization extinction ratio of the conversion is in principle infinitely high because both W1 waveguides operate in the single-mode regimes in this wavelength range. PMID:23037086

Wang, Jian; Qi, Minghao

2012-08-27

94

Heat transport and phonon localization in mass-disordered harmonic crystals  

NASA Astrophysics Data System (ADS)

We investigate the steady-state heat current in two- and three-dimensional disordered harmonic crystals in a slab geometry connected at the boundaries to stochastic white-noise heat baths at different temperatures. The disorder causes short-wavelength phonon modes to be localized so the heat current in this system is carried by the extended phonon modes which can be either diffusive or ballistic. Using ideas both from localization theory and from kinetic theory we estimate the contribution of various modes to the heat current and from this we obtain the asymptotic system size dependence of the current. These estimates are compared with results obtained from a numerical evaluation of an exact formula for the current, given in terms of a frequency-transmission function, as well as from direct nonequilibrium simulations. These yield a strong dependence of the heat flux on boundary conditions. Our analytical arguments show that for realistic boundary conditions the conductivity is finite in three dimensions but we are not able to verify this numerically, except in the case where the system is subjected to an external pinning potential. This case is closely related to the problem of localization of electrons in a random potential and here we numerically verify that the pinned three-dimensional system satisfies Fourier’s law while the two-dimensional system is a heat insulator. We also investigate the inverse participation ratio of different normal modes.

Chaudhuri, Abhishek; Kundu, Anupam; Roy, Dibyendu; Dhar, Abhishek; Lebowitz, Joel L.; Spohn, Herbert

2010-02-01

95

Guided-wave second-harmonic generation in a LiNbO3 nonlinear photonic crystal.  

PubMed

We demonstrate twin-beam second-harmonic generation from telecommunications wavelengths in an optimized buried reverse proton exchanged planar waveguide made in 2D hexagonally poled LiNbO3. Experiments carried out with a nanosecond narrow-bandwidth, high-power fiber source thoroughly explored the response of the nonlinear photonic crystal device in terms of its power, wavelength, and angle tunability. PMID:16642069

Gallo, Katia; Codemard, Christophe; Gawith, Corin B E; Nilsson, Johan; Smith, Peter G R; Broderick, Neil G R; Richardson, David J

2006-05-01

96

Simultaneous generation of a second harmonic of laser radiation by three types of interaction in nonlinear crystals with a regular domain structure  

SciTech Connect

Conditions for continuous generation of the second harmonic of laser radiation are determined for three types of interaction in nonlinear crystals with a regular domain structure. (nonlinear optical phenomena)

Grechin, Sergei G [Scientific-Research Institute of Radioelectronics and Laser Technology at the N.E. Bauman Moscow State Technical University, Moscow (Russian Federation); Dmitriev, Valentin G [M.F. Stel'makh Polyus Research and Development Institute, Moscow (Russian Federation)

1999-02-28

97

Coherent multistep anti-Stokes and stimulated Raman scattering associated with third harmonics in YFeO3 crystals  

NASA Astrophysics Data System (ADS)

Multicolored light pulses are generated with high efficiency in the visible region by injecting two ultrashort light pulses with infrared frequencies into orthoferrite YFeO3 single crystals. The spectrum of the multicolored light pulses consists of third harmonics of two beams and higher-order coherent anti-Stokes Raman scattering. This is generated by the excitation of a phonon in the crystal resonating to the frequency difference of two incident beams. The spectrum of the emitted light signals covers a frequency region wider than 5000 cm-1 with the same frequency separation equal to that of the coherently driven phonons.

Takahashi, Jun-Ichi; Matsubara, Eiichi; Arima, Takahisa; Hanamura, Eiichi

2003-10-01

98

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

2012-11-29

99

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

100

High harmonic generation in a gas-filled hollow-core photonic crystal fiber  

NASA Astrophysics Data System (ADS)

High harmonic generation (HHG) of intense infrared laser radiation (Ferray et al., J. Phys. B: At. Mol. Opt. Phys. 21:L31, 1988; McPherson et al., J. Opt. Soc. Am. B 4:595, 1987) enables coherent vacuum-UV (VUV) to soft-X-ray sources. In the usual setup, energetic femtosecond laser pulses are strongly focused into a gas jet, restricting the interaction length to the Rayleigh range of the focus. The average photon flux is limited by the low conversion efficiency and the low average power of the complex laser amplifier systems (Keller, Nature 424:831, 2003; Südmeyer et al., Nat. Photonics 2:599, 2008; Röser et al., Opt. Lett. 30:2754, 2005; Eidam et al., IEEE J. Sel. Top. Quantum Electron. 15:187, 2009) which typically operate at kilohertz repetition rates. This represents a severe limitation for many experiments using the harmonic radiation in fields such as metrology or high-resolution imaging. Driving HHG with novel high-power diode-pumped multi-megahertz laser systems has the potential to significantly increase the average photon flux. However, the higher average power comes at the expense of lower pulse energies because the repetition rate is increased by more than a thousand times, and efficient HHG is not possible in the usual geometry. So far, two promising techniques for HHG at lower pulse energies were developed: external build-up cavities (Gohle et al., Nature 436:234, 2005; Jones et al., Phys. Rev. Lett. 94:193, 2005) and resonant field enhancement in nanostructured targets (Kim et al., Nature 453:757, 2008). Here we present a third technique, which has advantages in terms of ease of HHG light extraction, transverse beam quality, and the possibility to substantially increase conversion efficiency by phase-matching (Paul et al., Nature 421:51, 2003; Ren et al., Opt. Express 16:17052, 2008; Serebryannikov et al., Phys. Rev. E (Stat. Nonlinear Soft Matter Phys.) 70:66611, 2004; Serebryannikov et al., Opt. Lett. 33:977, 2008; Zhang et al., Nat. Phys. 3:270, 2007). The interaction between the laser pulses and the gas occurs in a Kagome-type Hollow-Core Photonic Crystal Fiber (HC-PCF) (Benabid et al., Science 298:399, 2002), which reduces the detection threshold for HHG to only 200 nJ. This novel type of fiber guides nearly all of the light in the hollow core (Couny et al., Science 318:1118, 2007), preventing damage even at intensities required for HHG. Our fiber guided 30-fs pulses with a pulse energy of more than 10 ?J, which is more than five times higher than for any other photonic crystal fiber (Hensley et al., Conference on Lasers and Electro-Optics (CLEO), IEEE Press, New York, 2008).

Heckl, O. H.; Baer, C. R. E.; Kränkel, C.; Marchese, S. V.; Schapper, F.; Holler, M.; Südmeyer, T.; Robinson, J. S.; Tisch, J. W. G.; Couny, F.; Light, P.; Benabid, F.; Keller, U.

2009-10-01

101

Spatial-temporal structure of the femtosecond third harmonic generation in photonic-crystal fibers  

PubMed Central

We analyze the third harmonic generation by the supercontinuum at 1.5 ?m in nonlinear-glass microstructured fibers. The numerical model includes the real field dynamics and allows analyzing the spectral as well as the temporal structure of the generated field. The calculated third harmonic and supercontinuum spectra are compared with the experiment in the SF6 glass PCF pumped by a femtosecond Cr4+:YAG oscillator. The spectral structure of the third harmonic is composed of the 10–20 high-order modes excited at the phase matching points around 500–550 nm. The individual third harmonic modes have spectral widths of 2–4 nm. In the time domain, the third harmonic signal is a ~10-ps pulse with ps-scale slow modulation, containing subpicosecond ripples at its trailing edge.

Kalashnikov, Vladimir L.; Sorokin, Evgeni; Sorokina, Irina T.

2010-01-01

102

Roughness-induced acoustic second-harmonic generation during electrochemical metal deposition on the quartz-crystal microbalance.  

PubMed

This paper reports on the relation between the surface roughness and emission of compressional waves from the surface of an electrochemical quartz-crystal microbalance. The detection of the compressional waves took place with an ultrasonic microphone and the quartz crystal itself. As a model process, the electrochemical deposition of copper from an acidic copper sulfate solution has been chosen. For this system, the roughness of the layer can be tuned via the current density. Roughness may be a source of the longitudinal waves at twice the frequency of the exciting shear wave (acoustic second-harmonic generation, ASHG) if the flow profile above the quartz-crystal surface is not entirely laminar. Slight deviations from the laminar flow can be reached at high amplitudes of oscillation. Comparing the ASHG efficiency of a rough and smooth surface, we find that the rough surface is more efficient in generating second-harmonic waves. This suggests that ASHG can be used to obtain a roughness parameter independent from the resonance frequency or bandwidth (damping) of a quartz-crystal resonator. Such an independent determination of roughness should be very interesting in practical applications. PMID:15835696

Wehner, Susanne; Wondraczek, Katrin; Johannsmann, Diethelm; Bund, Andreas

2004-03-16

103

Second-harmonic generation under conditions of simultaneous phase-matched and quasi-phase-matched interactions in nonlinear crystals with a regular domain structure  

SciTech Connect

Characteristic features of simultaneous generation under conditions of phase-matched and quasi-phase-matched interactions in crystals with a regular domain structure were investigated. Under such conditions the efficiency of second- harmonic generation may prove higher than the generation in homogeneous crystals. (nonlinear optical phenomena)

Grechin, Sergei G [Scientific-Research Institute of Radioelectronics and Laser Technology at the N.E. Bauman Moscow State Technical University, Moscow (Russian Federation); Dmitriev, Valentin G [M.F. Stel'makh Polyus Research and Development Institute, Moscow (Russian Federation); Yur'ev, Yu V [Moscow Physicotechnical Institute (State University), Moscow (Russian Federation)

1999-02-28

104

Nonlinear optical conversion of Nd:glass laser multimode radiation into the second harmonic in KDP crystal  

NASA Astrophysics Data System (ADS)

The second-harmonic generation (SHG) of Nd:glass multimode laser radiation in a 3 cm long KDP crystal has been studied both experimentally and theoretically for type I doubling at power densities of up to 2.5 GW cm-2, radiation divergence of 0.5-3.5 mrad and between 100-1000 transverse modes. The theoretical calculations of SHG were performed in the fixed-field approximation, fixed-intensity approximation and in the nonlinear regime. The maximum experimental conversion efficiency of 52% was obtained for the case of partially polarized radiation with divergence of 0.5 mrad and 100 transverse modes.

Dmitriev, V. G.; Osipov, M. V.; Puzyrev, V. N.; Sahakyan, A. T.; Starodub, A. N.; Vasin, B. L.

2012-08-01

105

LETTER TO THE EDITOR: Second-harmonic generation in highly anisotropic molecular crystals for the depleted fundamental beam  

NASA Astrophysics Data System (ADS)

The theory required for the description of the effect of large beam walk-off angles has been developed and applied to the biaxial molecular crystals (-)2-?-(methylbenzylamino)-5-nitropyridine (MBANP) and 4-(N, N- dimethylamino)-3-acetamidonitrobenzene (DAN). It is shown that for the range of the parameters considered, the large beam-walk angles are not critical in assessing these materials. The dependence of the second-harmonic efficiency on the beam walk-off angles and the crystal length is discussed. Maximum efficiencies of 68 and 82% were calculated for MBANP and DAN, respectively, for the input peak power of 12.6 kW with a beam radius of 0.2 mm.

Kerkoc, P.

2002-07-01

106

Efficient second harmonic conversion of broad-band high-peak-power Nd:glass laser radiation using large-aperture KDP crystals in quadrature  

Microsoft Academic Search

The authors have investigated the second-harmonic conversion efficiency of broadband Nd:glass laser light (??\\/c<30 cm-1 FWHM). Using two KDP crystals in a quadrature arrangement, they obtain energy conversion efficiencies of ≈55% with an initial bandwidth for the fundamental of ??\\/c≈17 cm-1 FWHM. For these conditions, a modest increase (≈70%) was observed in the harmonic bandwidth (FWHM) relative to the fundamental.

MARK S. PRONKO; ROBERT H. LEHMBERG; S. Obenschain; CARL J. PAWLEY; CHARLES K. MANKA; R. Eckardt

1990-01-01

107

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.

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

2011-01-01

108

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

PubMed Central

Cholesterol crystals (ChCs) have been identified as a major factor of plaque vulnerability and as a potential biomarker for atherosclerosis. Yet, due to the technical challenge of selectively detecting cholesterol in its native tissue environment, the physiochemical role of ChCs in atherosclerotic progression remains largely unknown. In this work, we demonstrate the utility of hyperspectral stimulated Raman scattering (SRS) microscopy combined with second-harmonic generation (SHG) microscopy to selectively detect ChC. We show that despite the polarization sensitivity of the ChC Raman spectrum, cholesterol monohydrate crystals can be reliably discriminated from aliphatic lipids, from structural proteins of the tissue matrix and from other condensed structures, including cholesteryl esters. We also show that ChCs exhibit a nonvanishing SHG signal, corroborating the noncentrosymmetry of the crystal lattice composed of chiral cholesterol molecules. However, combined hyperspectral SRS and SHG imaging reveals that not all SHG-active structures with solidlike morphologies can be assigned to ChCs. This study exemplifies the merit of combining SRS and SHG microscopy for an enhanced label-free chemical analysis of crystallized structures in diseased tissue.

Suhalim, Jeffrey L.; Chung, Chao-Yu; Lilledahl, Magnus B.; Lim, Ryan S.; Levi, Moshe; Tromberg, Bruce J.; Potma, Eric O.

2012-01-01

109

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

NASA Astrophysics Data System (ADS)

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 P21. 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 13C NMR, 1H 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 (Cp) 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.

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

2013-03-01

110

Strategy and tactics in the search for new harmonic generating crystals  

SciTech Connect

Three basic questions must be answered to ensure success in the search for an optimized nonlinear crystal for a particular application: What are the most important optical properties which determine the crystal's figure of merit for the intended application What is the best methodology for characterizing those optical properties so that materials of interest can be identified efficiently Where in materials space'' can crystals with such properties be found with the highest probability Answers to these questions will be discussed in the context of a program to find improved frequency conversion crystals for high power lasers. 27 refs., 9 figs.

Velsko, S.P.

1990-09-01

111

Precise, motion-free polarization control in Second Harmonic Generation microscopy using a liquid crystal modulator in the infinity space  

PubMed Central

Second Harmonic Generation (SHG) microscopy coupled with polarization analysis has great potential for use in tissue characterization, as molecular and supramolecular structural details can be extracted. Such measurements are difficult to perform quickly and accurately. Here we present a new method that uses a liquid crystal modulator (LCM) located in the infinity space of a SHG laser scanning microscope that allows the generation of any desired linear or circular polarization state. As the device contains no moving parts, polarization can be rotated accurately and faster than by manual or motorized control. The performance in terms of polarization purity was validated using Stokes vector polarimetry, and found to have minimal residual polarization ellipticity. SHG polarization imaging characteristics were validated against well-characterized specimens having cylindrical and/or linear symmetries. The LCM has a small footprint and can be implemented easily in any standard microscope and is cost effective relative to other technologies.

Lien, Chi-Hsiang; Tilbury, Karissa; Chen, Shean-Jen; Campagnola, Paul J.

2013-01-01

112

Generation of vacuum-ultraviolet light below 160 nm in a KBBF crystal by the fifth harmonic of a single-mode Ti:sapphire laser  

Microsoft Academic Search

We have generated a vacuum-ultraviolet light below 160 nm by sum-frequency mixing in an optically contacted, prism-coupled KBe2BO3F2 crystal. The vacuum-ultraviolet light was generated as the fifth harmonic of a tunable, single-mode, 1-kHz Ti:sapphire laser system. The wavelength of 156 nm, to our knowledge, is the shortest ever obtained by use of nonlinear crystals in a phase-matched process. In addition,

Teruto Kanai; Takeshi Kanda; Taro Sekikawa; Shuntaro Watanabe; Tadashi Togashi; Chuangtian Chen; Chengqian Zhang; Zuyan Xu; Jiyang Wang

2004-01-01

113

Second harmonic generation of femtosecond radiation from a Cr:forsterite laser in a nonlinear-optical crystal at the plasma-formation threshold  

SciTech Connect

The second harmonic generation in KDP and LiNbO{sub 3} crystals exposed to tightly focused radiation from a Cr:forsterite laser is studied. The negative influence exerted on this process by a plasma produced due to multiphoton ionisation in the focal region at laser pulse intensities above 10{sup 13} W cm{sup -2} is discussed. (nonlinear optical phenomena)

Gordienko, V M; Dyakov, V A; Mikheev, P M; Syrtsov, V S [M. V. Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation)

2007-11-30

114

Crystallization and second harmonic generation in potassium-sodium niobiosilicate glasses  

SciTech Connect

Transparent glasses having molar composition (23-x)K{sub 2}O.xNa{sub 2}O.27Nb{sub 2}O{sub 5}.50SiO{sub 2} (x=0, 5, 10, 15 and 23) have been synthesized by the melt-quenching technique and their devitrification behaviour has been investigated by DTA and XRD. Depending on the composition, the glasses showed a glass transition temperature in the range 660-680 deg. C and devitrified in several steps. XRD measurements showed that the replacement of K{sub 2}O by Na{sub 2}O strongly affects the crystallization behaviour. Particularly, in the glasses with only potassium or low sodium content the first devitrification step is related to the crystallization of an unidentified phase, while in the glass containing only sodium, NaNbO{sub 3} crystallizes. For an intermediate sodium content (x=10 and 15) a potassium sodium niobate crystalline phase, belonging to the tungsten-bronze family, is formed by bulk nucleation. This system looks promising to produce active nanostructured glasses as the tungsten-bronze type crystals have ferroelectric, electro-optical and non-linear optical properties. Preliminary measurements evidenced SHG activity in the crystallized glasses containing this phase. - Graphical abstract: Synthesis of glasses (23-x)K{sub 2}O.xNa{sub 2}O.27Nb{sub 2}O{sub 5}.50SiO{sub 2} (x=0, 5, 10, 15 and 23) from which SHG active phases crystallize by bulk nucleation for non-linear optical nanostructured glasses.

Aronne, Antonio, E-mail: anaronne@unina.i [Dipartimento di Ingegneria dei Materiali e della Produzione, Universita di Napoli Federico II, Piazzale V. Tecchio, I-80125 Napoli (Italy); Fanelli, Esther; Pernice, Pasquale [Dipartimento di Ingegneria dei Materiali e della Produzione, Universita di Napoli Federico II, Piazzale V. Tecchio, I-80125 Napoli (Italy); Peli, Simone; Giannetti, Claudio; Ferrini, Gabriele [Dipartimento di Matematica e Fisica, Universita Cattolica del Sacro Cuore, Via dei Musei, 41, I-25121 Brescia (Italy)

2009-10-15

115

Investigation on intracavity second-harmonic generation of a new Li-doped GdCa 4O(BO 3) 3 crystal  

Microsoft Academic Search

Efficient intracavity second-harmonic generation (SHG) has been realized in a new Li-doped GdCa4O(BO3)3 (GdCOB) crystal. 2.55W CW SHG output power was obtained with an optical conversion efficiency of 19.6%, while the effective intracavity SHG efficiency was determined to be 44%. Compared to that of undoped GdCOB crystal, the effective SHG efficiency of the Li-doped GdCOB crystal was found to increase

Junhai Liu; Zhenyi Fei; Shujun Zhang; Chenlin Du; Jiyang Wang; Huanchu Chen; Zongshu Shao

2001-01-01

116

Coefficients of Second Harmonic Generation of Light (SHG) of Noncentrosymmetric Crystals.  

National Technical Information Service (NTIS)

The piezoelectric and SHG effects, both described by a second-order matrix and denoted by the same symbol, are independent of each other. They are defined differently, however, and for the trigonal and hexagonal crystal classes lead to incorrect schemes f...

A. Ballato R. Bechmann

1972-01-01

117

Near-field imaging of light propagation in photonic crystal waveguides: Explicit role of Bloch harmonics  

Microsoft Academic Search

We employ a collection scanning near-field optical microscope (SNOM) to image the propagation of light at telecommunication wavelengths along straight and bent regions of silicon-on-insulator photonic crystal waveguides (PCWs) formed by removing a single row of holes in the triangular 410-nm-period lattice along the GammaM direction of the irreducible Brillouin zone. We obtain high quality SNOM images of PCWs excited

Sergey I. Bozhevolnyi; Valentyn S. Volkov; Thomas Søndergaard; Alexandra Boltasseva; Peter I. Borel; Martin Kristensen

2002-01-01

118

Ionic Radical Theory of Crystal Electro-Optical and Nonlinear Optical Effects. I. Computation of BaTiO sub 3 Crystal Electro-Optical and Harmonic Generation Coefficients by Using a Distortion Model of the Oxygen Octahedron.  

National Technical Information Service (NTIS)

An MO sub 6 ionic radical model is proposed for the mechanism of electro-optical (EO) and Second Harmonic Generation (SHG) effects of BaTiO sub 3 type crystals. Starting with the ionic bond orbital of the TiO sub 6 radical under the interaction between th...

C. Chungtian

1976-01-01

119

UPFC modeling in the harmonic domain  

Microsoft Academic Search

This paper outlines the extension of harmonic domain modeling to flexible ac transmission system (FACTS) devices which contain series voltage injection elements. The proposed iterative technique is capable of modeling generic combinations of series and shunt converters; representing these elements as harmonic current and voltage sources, respectively. The harmonic performance of these converter combinations is characterized in terms of dc

Christopher Collins; N. Watson; A. Wood

2006-01-01

120

High-power intracavity second-harmonic generation of 1.34 ?m in BiB3O6 crystal  

NASA Astrophysics Data System (ADS)

The phase-matching curve and effective nonlinear optical coefficient distribution for the second-harmonic generation of 1342 nm in BiB3O6 crystal were calculated. High-power intracavity second-harmonic generation of 1.34 ?m in BiB3O6 crystals, at a type-I phase-matching direction of (?, ø)=(9.07°, 0°), was performed with a LD-end-pumped Nd:YVO4 laser. The maximum continuous-wave (CW) and quasi-CW output powers at 671 nm were obtained to be 1.22 W and 4.38 W, with the corresponding optical conversion efficiency of 4.9% and 9.5%, respectively.

Du, Chenlin; Ruan, Shuangchen; Yu, Yongqin; Wang, Zhengping

2005-10-01

121

High-power intracavity second-harmonic generation of 1.34 microm in BiB3O6 crystal.  

PubMed

The phase-matching curve and effective nonlinear optical coefficient distribution for the second-harmonic generation of 1342 nm in BiB3O6 crystal were calculated. High-power intracavity second-harmonic generation of 1.34 microm in BiB3O6 crystals, at a type-I phase-matching direction of (theta, ø)=(9.07 degrees , 0 degrees ), was performed with a LD-end-pumped Nd:YVO4 laser. The maximum continuous-wave (CW) and quasi-CW output powers at 671 nm were obtained to be 1.22 W and 4.38 W, with the corresponding optical conversion efficiency of 4.9% and 9.5%, respectively. PMID:19498889

Du, Chenlin; Ruan, Shuangchen; Yu, Yongqin; Wang, Zhengping

2005-10-17

122

Application of the optical second harmonic generation method in the study of the crystallization of noncetrosymmetric phases in glasses  

SciTech Connect

The theoretical and experimental foundations of the optical-radiation second harmonic generation (SHG) method are briefly reported. The optimum conditions for applying the SHG method both to an investigation of glasses and glass-ceramics at the early stages of the glass crystallization and to an analysis of the well-formed glass-ceramic structure are determined. The exceptionally high informative capabilities of the SHG method in studies of phase transformations of the {open_quotes}glass-acentric phase{close_quotes} type is demonstrated by the example of glass-forming systems containing the acentric phases [Li{sub 2}SiO{sub 3}, Li{sub 2}GeO{sub 3}, LiB{sub 3}O{sub 5}, Li{sub 2}B{sub 4}O{sub 7}, PbTiO{sub 3}, Pb{sub 5}Ge{sub 3}O{sub 11}, LnBXO{sub 5} (Ln=La, Ce, and Pr; X=Si and Ge), and others].

Stefanovich, S.Yu. [Karpov Institute of Physical Chemistry, Moscow (Russian Federation); Sigaev, V.N. [Mendeleev Univ. of Chemical Tecnology, Moscow (Russian Federation)

1995-07-01

123

Exploring a photonic quasi-crystal fiber for enhancing the efficiency of second harmonic generation: Modeling and analysis  

NASA Astrophysics Data System (ADS)

In this paper, we explore the possibility of using a new type of microstructured optical fiber called photonic quasi-crystal fiber (PQF) for enhancing the efficiency of second harmonic generation (SHG). We model a six-fold, index guided, silica core PQF with a relative air hole diameter ranging from 0.1-0.5. We compute the various factors related to SHG, namely, phase mismatch factor, wave-vector mismatch, coherence length, quasi-phase matching length and overlap area. Of the various factors, we focus more on the role of wave-vector mismatch and overlap area as these parameters are highly sensitive to the variations in the geometrical arrangement of air holes in the cladding. Further, these parameters are required to be as minimum as possible for enhancing the efficiency of SHG. We find that the wave-vector mismatch factor does decrease for higher values of pitch and for lower values of relative air hole diameter. However, the overlap area increases for higher values of pitch and for lower values of relative air hole diameter. Therefore, we optimize the hitherto mentioned parameters such that the wave-vector mismatch is 0.145 ?m-1 and the overlap area is 3.48 ?m2. With these values, we demonstrate a relative efficiency of 62.96% W-1 cm-2 with the proposed PQF.

Bhattacharjee, Ritapa; Senthilnathan, K.; Sivabalan, S.; Ramesh Babu, P.

2013-10-01

124

Angular phase-matching bandwidths in biaxial nonlinear crystals for frequency converters  

SciTech Connect

It is shown that the angular phase-matching bandwidths in biaxial nonlinear crystals in the general case must be calculated in the coordinate system in which the angular deviations of the crystal and the laser beam divergence are determined consistently. The angular phase-matching bandwidths in this coordinate system may considerably differ from the conventionally determined values. The optimum orientation of the coordinate system for determining the angular phase-matching bandwidths is found. It is established that, in the general case in biaxial crystals, as in uniaxial ones, phase matching is always angle-critical along one coordinate and noncritical along the other and that it is possible to realise angle-noncritical phase matching of the fourth order. (nonlinear optical phenomena)

Grechin, Sergei G [Scientific-Research Institute of Radioelectronics and Laser Technology at the N.E. Bauman Moscow State Technical University, Moscow (Russian Federation)

2010-11-13

125

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

Microsoft Academic Search

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

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

2008-01-01

126

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

Microsoft Academic Search

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

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

2007-01-01

127

Second harmonic generation of spectrally broadened femtosecond ytterbium laser radiation in a gas-filled capillary  

SciTech Connect

A 300-fs radiation pulse of an ytterbium laser with a wavelength of 1030 nm and energy of 150 {mu}J were converted to a 15-fs pulse with a wavelength of 515 nm by broadening the emission spectrum in a capillary filled with xenon and by generating the second harmonic in a KDP crystal. The energy efficiency of the conversion was 30 %.

Didenko, N V; Konyashchenko, Aleksandr V; Kostryukov, P V; Losev, Leonid L; Tenyakov, S Yu

2011-09-30

128

Timing jitter measurement of transmitted laser pulse relative to the reference using type II second harmonic generation in two nonlinear crystals.  

PubMed

A new method is proposed and analyzed for measuring the timing jitter of the transmitted pulse relative to the reference pulse using two type II phase-matched nonlinear crystals for second harmonic generation (SHG). The polarizations of the two pulses are exchanged in two crystals and the difference between two detected second harmonic signals can reflect the transmitted jitter. This new method provides a high sensitivity and timing resolution compared with the conventional RF (radio frequency) method. Since the overlapping levels in the two crystals are the same, the final output is zero when there is no time delay between the two pulses. Thus no offset is necessary to be subtracted from the final output and no time delay adjustment is required between the two pulses, compared with the previous optical method using one crystal and two dichroic beamsplitters. The jitter measuring performance is studied theoretically using non-stationary nonlinear wave-coupled equations for type II SHG of two pulses. The theoretical computation and analysis show that the sensitivity and the dynamic range of this new method depend on pulse width, crystal pulses and group velocity difference between two fundamental pulses. PMID:20372647

Ma, Xuelian; Liu, Lu; Tang, Junxiong

2009-10-12

129

Convertible holograms in CaF2 crystals with color centers  

NASA Astrophysics Data System (ADS)

When recording hologram in ionic CaF2 crystal with color centers, the center conversion is accompanied with their spatial redistribution. The peculiar diffusion-drift mechanism of the recording is responsible for the extremely high hologram stability to both heating and illumination of the sample with a hologram by non-coherent radiation. However such photo-thermal treatment of the sample results in partial or total transformation of the center type and modification in their space distribution. Thus, keeping the hologram, such treatment influences its character of diffraction response, diffraction efficiency and profile. This work describes the mechanism and the character of these changes. It is shown that photo-thermal treatment can be used for fabrication of thick (up to 10 mm thickness) high stable holograms when reading out both in visible and infrared ranges of the spectrum.

Angervaks, Alexandr E.; Shcheulin, Aleksandr S.; Ryskin, Aleksandr I.

2013-05-01

130

Efficient intracavity second-harmonic generation at 1.06 ?m in a BiB3O6 (BIBO) crystal  

NASA Astrophysics Data System (ADS)

We report, for the first time, efficient intracavity second-harmonic generation (SHG) at 1.06 ?m in a non-linear optical crystal, BiB3O6 (BIBO), at a type-I phase-matching direction of (?,?)=(168.9°,90°), performed with a LD end-pumped cw Nd:YVO4 laser. A cw SHG output power of 364 mW has been obtained using a 1.9-mm-thick BIBO crystal. The optical conversion efficiency was 12.2% and the corresponding effective intracavity SHG efficiency was determined to be 32.4%. It was found that the intracavity SHG efficiency is greater than that obtained with a type-II phase-matching KTiOPO4 (KTP) crystal with a thickness of 3 mm. The effective non-linear optical coefficient (deff) ratio of BIBO to that of KTP, determined experimentally, is 1.23:1.

Du, C.; Wang, Z.; Liu, J.; Xu, X.; Teng, B.; Fu, K.; Wang, J.; Liu, Y.; Shao, Z.

131

Efficient second harmonic generation of pulsed laser radiation in BiB3O6 (BIBO) crystal with different phase matching directions  

NASA Astrophysics Data System (ADS)

The transmission spectra of BiB3O6 (BIBO) crystals are compared with KTP. With BIBO samples cut in different phase matching (PM) directions in (010) plane, we obtain efficient second harmonic generation (SHG) of pulsed laser radiation in this low symmetric crystal. For BIBO crystal, the direction (168.9°, 90°) exhibits a larger efficient nonlinear optical (NLO) coefficient than the direction (11.1°, 90°). For a 2.4 mm long, (168.9°, 90°)-cut BIBO, the SHG conversion efficiency can reach 67.7%, while at the same conditions the efficiency of a 4.7 mm long, (11.1°, 90°)-cut BIBO is 58% or so.

Wang, Zhengping; Teng, Bing; Fu, Kun; Xu, Xinguang; Song, Renbo; Du, Chenlin; Jiang, Huaidong; Wang, Jiyang; Liu, Yaogang; Shao, Zongshu

2002-02-01

132

Harmonic and Anharmonic Properties of Diamond Structure Crystals with Application to the Calculation of the Thermal Expansion of Silicon.  

National Technical Information Service (NTIS)

Silicon has interesting harmonic and anharmonic properties such as the low lying transverse acoustic modes at the X and L points of the Brillouin zone, negative Gruneisen parameters, negative thermal expansion and anomalous acoustic attenuation. In an att...

K. H. Wanser

1981-01-01

133

Liquid crystal modulator as diffraction pattern converter used to exhibit the average droplet diameter of fuel aerosol  

NASA Astrophysics Data System (ADS)

Measurement of the fuel aerosol droplet diameter is very important in the course of construction of new types of sprayers (burners, carburettors, injectors) and diagnostic processes as well. Diffraction method is one of the most useful measuring procedures in this case. The droplet size of monodispersion medium is easy to recognize (Airy rings). Analysis of the diffraction pattern of polydispersion medium is considerably more difficult. After recording the diffraction pattern I(r) of an aerosol stream one of the numerical procedures is used. The registration process and data processing are usually separated. The final result of the investigation -- average droplet diameter D(rho ) of distribution (rho) (D) -- is obtained after some time. The most useful procedure in the diagnostic is real-time measuring. The diffraction light intensity curve I(r) depends on the type of droplet diameter statistical distribution (rho) (D) and relative standard deviation d equals (sigma) /D(rho ) as well. Precise analysis in nondimensional units [z equals (pi) Dr/(lambda) f and Iw(z) equals I(z)/Imax] shows the point [z0 equals 1.47, Iw(Z0) equals 0.57] which may be used to display average droplet diameter D(rho ). The position of point [z0, I(z0)] is independent of relative standard deviation d and the type of distribution function (rho) (D) as well. After finding the value of radius-vector r0.57 that I(r0.57) equals 0.57 it is possible to evaluate average droplet diameter from relation D(rho ) equals (0.47 (lambda) f)/r0.57. After using an image converter with a rectangular optical response OR(I), the Airy picture I(r) becomes a ring. The radius of that ring depends on threshold light intensity Ip of characteristic OR(I). If Ip equals 0.57Imax, the radius of the converted Airy picture will be r equals r0.57. After introducing non-linear scale D equals f(r0.57) the image converter becomes an analogue measuring instrument. This idea has been tested with TV and CCD cameras. Making use of threshold effects of liquid crystal displays it is possible to reduce the volume of the measuring stand and its price as well.

Opara, Tadeusz

1995-04-01

134

Liquid crystal modulator as a diffraction pattern converter used to exhibit the average droplet diameter of fuel aerosol  

NASA Astrophysics Data System (ADS)

Measurement of the fuel aerosol droplet diameter is very important in the course of construction of new type sprayers (burners, carburettors, injectors), a diagnostic process. Diffraction method is one of the most useful measuring procedures in this case. The droplet size of monodispersion medium is easy to recognize (Airy rings). Analysis of a diffraction pattern of polydispersion medium is more difficult, however. After recording the diffraction pattern I(r) of an aerosol stream, one of the numerical procedures is used. Registration process and data processing are usually separated. The final result of investigation--average droplet diameter Drho of distribution (rho) (D) is obtained after some time. The most useful procedure in a diagnostic is real-time measuring. Diffraction light intensity curve I(r) depends on the type of droplet diameter statistical distribution (rho) (D) and relative standard deviation d equals (sigma) /Drho as well. Precise analysis in nondimensional units (z equals (pi) Dr/(lambda) f and Iw(z) equals I(z)/Imax) shows the point (z0 equals 1.47, Iw(z0) equals 0.57) which may be used to display average droplet diameter Drho. The position of the point [z0,I(z0)] is independent on relative standard deviation d and type of distribution function (rho) (D) as well. After finding the value of radius-vector r0.57 equal I (r0.57) equals 0.57, it is possible to evaluate the average droplet diameter from the relation D(rho ) equals (0.47(lambda) f)/r0.57. After using image converter with a rectangular optical response OR(I), the Airy picture I(r) becomes a ring. The radius of that ring depends on the threshold light intensity Ip of characteristic OR(I). The radius of converted Airy picture will be r equals r0.57 if Ip equals 0.57Imax. After introducing a nonlinear scale, D equals f(r0.57) image converter becomes an analogue measuring instrument. This idea has been tested with TV and CCD cameras. Using threshold effects of liquid crystal displays it is possible to reduce volume of measuring stand and its price.

Opara, Tadeusz

1995-08-01

135

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.degree.). 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.degree.. For both second and third harmonic generation input precise phase-matching is achieved by tilting the crystal assembly about its two sensitive axes ("o").

Summers, Mark A. (Livermore, CA); Eimerl, David (Pleasanton, CA); Boyd, Robert D. (Livermore, CA)

1985-01-01

136

The Influence of the Orientation of the Collagen Dipoles on Second Harmonic Generation (shg) with High NA Under Crystallized Type i Collagen Fiber Model  

NASA Astrophysics Data System (ADS)

In this paper, for the first time, we consider theoretically all the potential orientations of dipoles for second harmonic generation (SHG) under crystallized type I collagen fiber. With high numerical aperture (NA = 14), the effect of dipole orientation angle ? on the SHG intensity, on the maximum SHG emergence angles (?max, ?max) and the action of these dipole sources on the ratio of forward to backward (F/B) SHG have been studied under different cases of fibrils diameter d1 and the QPM order (m, l) in the crystallized collagen fiber, and it is found that the influential patterns of the same ? on SHG at different fibrils diameter d1 and the QPM order (m, l) are different. The dipoles arrangement is related to the characteristic changes in biological tissue so that our work may provide a helpful theoretical tool for pathological status detecting.

Wang, Fei Fei; Liu, Jian Mei; Deng, Xiao Yuan

2012-11-01

137

Investigation of organic nonlinear optical crystals for harmonic frequency conversion and electro-optics. Final technical report  

SciTech Connect

The authors are conducting a detailed study of the crystal growth of different organic materials and their physical, optical and morphological properties. The crystals are grown by a novel solution crystal growth technique developed by the principal investigator at Alabama A and M University (AAMU). The studies included the measurement of solubility of organic NLO materials in different solvents, growth of crystals by solution growth technique, and the characterization of optical properties and damage threshold of crystals for high power laser applications. Two different NLO crystals of 4-Aminobenzophenone (ABP) and 3-methoxy-4-hydroxy-benzaldehyde (MHBA) were investigated during the course of this investigation. A paper on ABP crystals was published in Journal of Crystal Growth in 1997.

NONE

1998-01-01

138

Harmonics in multiple light dimmer systems  

Microsoft Academic Search

Static power converters have found a wide range of applications in all kind of industries. Even ships do not escape this technology and, consequently, to the problem of harmonics. The harmonic disturbances are very critical on a ship supply network because it is a local one and its impedance has a finite value. Therefore, the prediction of the harmonics level

P. Guerin; M. MACIIMOUM; M. F. Benkhoris; R. Le Doeuff

1994-01-01

139

Structural, spectroscopic and nonlinear optical studies on a new efficient organic donor-acceptor crystal for second harmonic generation: L-Threoninium picrate.  

PubMed

A new and efficient organic nonlinear optical (NLO) crystal from the amino acid family, viz., l-threoninium picrate (LTHP), has been grown by solvent evaporation technique from aqueous solution. The structure of LTHP was elucidated using single crystal X-ray diffraction data. The compound crystallized in the non-centrosymmetric space group P2(1) and the unit cell contains two l-threoninium cations and two picrate anions. The backbone conformation angles Psi(1) and Psi(2) are in cis and trans configurations for both the picrate and the threoninium residues. An intra-molecular hydrogen bond between the amine N atom and the nearby oxygen atom, viz., N1-H1B(...)O3 is observed, with a graph set motif R(1)(1)(5). The second harmonic generation (SHG) efficiency of this material was measured using Kurtz and Perry method and found to be about 43 times that of standard potassium dihydrogen phosphate (KDP) crystals. Fourier transform infrared (FTIR) and ultraviloet-visible-near infrared spectral studies were also carried out. The details are discussed. PMID:20537939

Natarajan, S; Umamaheswaran, M; Kalyana Sundar, J; Suresh, J; Martin Britto Dhas, S A

2010-05-07

140

Structural, spectroscopic and nonlinear optical studies on a new efficient organic donor-acceptor crystal for second harmonic generation: L-Threoninium picrate  

NASA Astrophysics Data System (ADS)

A new and efficient organic nonlinear optical (NLO) crystal from the amino acid family, viz., L-threoninium picrate (LTHP), has been grown by solvent evaporation technique from aqueous solution. The structure of LTHP was elucidated using single crystal X-ray diffraction data. The compound crystallized in the non-centrosymmetric space group P2 1 and the unit cell contains two L-threoninium cations and two picrate anions. The backbone conformation angles ?1 and ?2 are in cis and trans configurations for both the picrate and the threoninium residues. An intra-molecular hydrogen bond between the amine N atom and the nearby oxygen atom, viz., N1-H1B …O3 is observed, with a graph set motif R 11(5). The second harmonic generation (SHG) efficiency of this material was measured using Kurtz and Perry method and found to be about 43 times that of standard potassium dihydrogen phosphate (KDP) crystals. Fourier transform infrared (FTIR) and ultraviloet-visible-near infrared spectral studies were also carried out. The details are discussed.

Natarajan, S.; Umamaheswaran, M.; Kalyana Sundar, J.; Suresh, J.; Martin Britto Dhas, S. A.

2010-09-01

141

Remarkable enhancement in crystalline perfection, second harmonic generation efficiency, optical transparency, and laser damage threshold in potassium dihydrogen phosphate crystals by L-threonine doping  

SciTech Connect

Effect of L-threonine (LT) doping on crystalline perfection, second harmonic generation (SHG) efficiency, optical transparency, and laser damage threshold (LDT) in potassium dihydrogen phosphate (KDP) crystals grown by slow evaporation solution technique (SEST) has been investigated. The influence of doping on growth rate and morphology of the grown crystals has also been studied. Powder x-ray diffraction data confirms the crystal structure of KDP and shows a systematic variation in intensity of diffraction peaks in correlation with morphology due to varying LT concentration. No extra phase formation was observed which is further confirmed by Fourier transform Raman (FT-Raman) studies. High-resolution x-ray diffraction curves indicate that crystalline perfection has been improved to a great extent at low concentrations with a maximum perfection at 1 mol % doping. At higher concentrations (5 to 10 mol %), it is slightly reduced due to excess incorporation of dopants at the interstitial sites of the crystalline matrix. LDT has been increased considerably with increase in doping concentration, whereas SHG efficiency was found to be maximum at 1 mol % in correlation with crystalline. The optical transparency for doped crystals has been increased as compared to that of pure KDP with a maximum value at 1 mol % doping.

Kushwaha, S. K.; Maurya, K. K.; Bhagavannarayana, G. [Materials Characterization Division, National Physical Laboratory, Council of Scientific and Industrial Research, New Delhi 110 012 (India); Shakir, Mohd. [Materials Characterization Division, National Physical Laboratory, Council of Scientific and Industrial Research, New Delhi 110 012 (India) and Department of Physics, Crystal growth Laboratory, Jamia Millia Islamia, New Delhi 110 025 (India); Shah, A. L. [Solid State Laser Division, LASTEC, Metcalfe House, New Delhi 110 054 (India); Wahab, M. A. [Department of Physics, Crystal growth Laboratory, Jamia Millia Islamia, New Delhi 110 025 (India)

2010-08-15

142

Ultrathin harmonic generators  

SciTech Connect

In second-harmonic generation in optical materials with extremely large nonlinearity (about 1,000 that in KDP), efficient conversion may be expected for gain lengths of just a few micrometers. If the gain length is less than the coherence length, the phase-matching condition normally invoked for KDP and other common nonlinear materials may not apply. Devices based on such ultrathin media are potentially insensitive to wavelength, bandwidth, temperature, and poor beam quality. The authors have analyzed harmonic generation in ultrathin media to evaluate their materials requirements. They show that in such devices the conversion efficiency to the second harmonic is necessarily limited to about 25%, because higher harmonics are also necessarily generated with significant efficiencies. Ultrathin devices are therefore subject to large thermal loads, and perhaps optical damage arising from the generation of strong ultraviolet or soft X-ray harmonics. Whereas ultrathin media are not as efficient as conventional phase-matched crystals for second-harmonic generation, they do generate phase-coherent, multiple higher harmonics. As a consequence, they can generate optical square waves electromagnetic shock waves, and may find application as coherent soft X-ray generators.

Eimerl, D. (Lawrence Livermore National Lab., CA (United States). Nonlinear Optical Materials Group)

1991-09-01

143

Growth and ultraviolet application of Li{sub 2}B{sub 4}O{sub 7} crystals: Generation of the fourth and fifth harmonics of Nd:Y{sub 3}Al{sub 5}O{sub 12} lasers  

SciTech Connect

A 2 in. diam single crystal of lithium tetraborate (Li{sub 2}B{sub 4}O{sub 7}) was successfully grown by the Czochralski method. The crystal was free from macrodefects and had a dislocation density as low as 100/cm{sup 2}. It had an excellent homogeneity of the refractive index and a wide transparency down to 170 nm. The optical damage threshold was 40 GW/cm{sup 2}. Second-harmonic generation and sum frequency generation were investigated in association with the generation of the fourth and fifth harmonics of a Q-switched Nd:YAG laser. The conversion efficiency of the second-harmonic generation from the green (532 nm) light was 20{percent}. {copyright} {ital 1997 American Institute of Physics.}

Komatsu, R.; Sugawara, T.; Sassa, K. [Advanced Technology Research Laboratories, Central Research Institute, Mitsubishi Materials Corporation, 1-297 Kitabukuro-cho, Omiya, Saitama 330 (Japan); Sarukura, N.; Liu, Z.; Izumida, S. [Institute for Molecular Science, Okazaki National Research Institute, 38 Nishigonaka, Myodaiji, Okazaki 444 (Japan); Segawa, Y. [Photodynamics Research Center, The Institute of Physical and Chemical Research, Nagamachi Koeji 19-1399, Aoba-ku, Sendai, Miyagi 980 (Japan); Uda, S.; Fukuda, T. [Institute for Material Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, Miyagi 980 (Japan); Yamanouchi, K. [Research Institute for Electric Communication, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, Miyagi 980 (Japan)

1997-06-01

144

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

145

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

NASA Astrophysics Data System (ADS)

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 d22=28 pm/V.

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

2012-11-01

146

Orthorhombic ferroelectric and ferroelastic Gd 2(MoO 4) 3 crystal — a new many-purposed nonlinear and optical material: efficient multiple stimulated Raman scattering and CW and tunable second harmonic generation  

Microsoft Academic Search

The nonlinear optical properties of a ferroelectric and ferroelastic ??-Gd2(MoO4)3 laser crystal-host were studied by second harmonic generation (SHG) and stimulated Raman scattering (SRS) experiments using different laser sources for excitation. It is shown that the investigated crystals are very attractive for SHG with IR CW lasers as well as for continuously tunable SHG under illumination with a femtosecond hyper-continuum

A. A. Kaminskii; A. V. Butashin; H.-J. Eichler; D. Grebe; R. Macdonald; K. Ueda; H. Nishioka; W. Odajima; M. Tateno; J. Song; M. Musha; S. N. Bagaev; A. A. Pavlyuk

1997-01-01

147

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

148

Growth and Characterization of Crystals for Room Temperature I.R. Detectors and Second Harmonic Generation Devices.  

National Technical Information Service (NTIS)

One of the major objectives of this program was to modify the triglycine sulfate (TGS) crystals with suitable dopants and variants to achieve better pyroelectric properties and improved infrared detectivities (D(sup *)), and higher Curie transition temper...

R. B. Lal

1995-01-01

149

Second-harmonic generation of TEA CO2 10. 6-micrometer laser light in AgGaS2 crystals  

SciTech Connect

Characteristics of AgGaS2 crystal for frequency doubling of TEA CO2 10.6 micrometer laser light were investigated. When the crystal was 4.3mm long, the maximum conversion frequency was 0.122 percent. In recent years, much progress was made in expanding the range of laser wavebands by utilizing the nonlinear effects. In the medium-infrared waveband, the CO2 laser is a relatively ideal light source and can output tens of laser spectral lines within the range 8.7 to 11.8 micrometers. With double frequency, tunable output can be obtained within the range 4.3 to 5.9 micrometers. Since the advent of CO2 lasers, researchers have conducted numerous research tasks in this area. However, since it is relatively difficult to obtain high-quality and large infrared nonlinear optical crystals, such work still remains at the laboratory research stage without practical applications.

Bangmin, Z.; Dinghua, W.

1991-05-03

150

Efficient intracavity second-harmonic generation at 930 nm in a BiB3O6 crystal  

NASA Astrophysics Data System (ADS)

It is reported that efficient continuous-wave (CW) blue laser generation at 465 nm in a BiB3O6 (BiBO) crystal at type-I phase matching direction performed with a diode-pumped Nd3+:YAlO3 (Nd:YAP) laser. With incident pump power of 18.4 W, output power of 823 mW at 465 nm has been obtained using a 10 mm-long BiBO crystal. At the output power level of 823 mW, the output stability is better than 2.3%.

Shi, L. X.; Liu, T. T.

2012-03-01

151

Generation of single frequency blue light by highly efficient harmonic generation of IR laser diodes in resonance build-up cavities using nonlinear crystals  

NASA Astrophysics Data System (ADS)

Blue and UV lasers have a wide variety of applications, including atomic spectroscopy. We are particularly interested in 486 nm and 243 nm for hydrogen spectroscopy. Blue and UV laser diodes are at the early stages of development. At this time, harmonic generations (HG) is a viable technique to produce blue and UV light with well developed fiber coupled IR laser diodes. We recently reported a polarization maintaining (PM) fiber to fiber conversion efficiency of 71 percent overall. We used a PPKTP (Periodically Poled Potassium Titanyl Phosphate) crystal in an external build-up cavity. The 600 mW of blue at 486 nm was generated from second HG of a 972 nm PM fiber coupled laser diode [1]. PPKTP presents blue absorption (BA) and blue light induced IR absorption (BLIIRA) which cause thermal instability and inefficiency in the buildup cavity. Another crystal, PPSLT (Periodically Poled Lithium Tantalite) promises less BA and less BLIIRA. Our latest results for producing 486 nm using PPSLT and comparison with PPKTP will be presented. [4pt] [1] Koustrubh Danekar, Ali Khademian, and David Shiner, Opt. Lett. 36, 294 (2011)

Khademian, Ali; Danekar, Koustubh; Aflakian, Nafiseh; Shiner, David

2012-06-01

152

Optical second harmonic generation as a probe of electrostatic fields and flatband potential at single-crystal TiO[sub 2] electrodes  

SciTech Connect

The surface-sensitive technique of optical second harmonic generation (SHG) is applied to the measurement of dc electrostatic fields and the flatband potential at the TiO[sub 2] semiconductor electrode-electrolyte interface. A large SHG response is observed from n-type single-crystal TiO[sub 2](001) electrodes at potentials for which a depletion layer exists at the surface. This response is attributed to the electric field-induced SHG from the polarized TiO[sub 2] lattice in the space charge layer at the semiconductor surface. The SHG from the interface varies linearly with the applied potential and reaches a minimum at the flatband potential of the electrode. The potential at which this minimum occurs shifts with pH at the expected rate of 60 mV/pH unit. A simple model of the electrostatic fields as a function of the band bending at the interface can be used to explain the observed dependence of the SHG on applied potential. These experiments suggest that SHG can be used as a local, time-resolved spectroscopic measurement of the electrostatic fields and surface charge density at single-crystal TiO[sub 2] electrodes. 36 refs., 3 figs.

Lantz, J.M.; Corn, R.M. (Univ. of Wisconsin, Madison (United States)); Baba, Ryo (Univ. of Tokyo (Japan))

1993-07-22

153

Regulatory Harmonization  

Center for Biologics Evaluation and Research (CBER)

. The Agency engages in a range of explicit harmonization initiatives, a subset of which includes the participation of CBER. ... More results from www.fda.gov/biologicsbloodvaccines/internationalactivities

154

Second harmonic generation in periodically domain-inverted Sr{sub 0.6}Ba{sub 0.4}Nb{sub 2}O{sub 6} crystal plate  

SciTech Connect

Quasiphase-matched second harmonic generation (SHG) has been realized in periodically domain-inverted strontium barium niobate (Sr{sub 0.6}Ba{sub 0.4}Nb{sub 2}O{sub 6}, so-called SBN) crystal plate induced by an external electric field. Both the coercive field and Curie temperature have been determined through {ital in situ} observation of the second harmonic signals. The measured SHG conversion efficiency is about 10{percent} at a fundamental wavelength of 977.8 nm. {copyright} {ital 1997 American Institute of Physics.}

Zhu, Y.Y.; Fu, J.S.; Xiao, R.F.; Wong, G.K. [Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

1997-04-01

155

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

156

The effect of an infinite plane-wave approximation on calculations for second-harmonic generation in a one-dimensional nonlinear crystal  

NASA Astrophysics Data System (ADS)

In this paper, the second-harmonic generation (SHG) in a one-dimensional nonlinear crystal that is embedded in air is investigated. Previously, the identical configuration was studied in Li Z. Y. et al., Phys. Rev. B, 60 (1999) 10644, without the use of the slowly varying amplitude approximation (SVAA), but by adopting the infinite plane-wave approximation (PWA), despite the fact that this approximation is not quite applicable to such a system. We calculate the SHG conversion efficiency without a PWA, and compare the results with those from the quoted reference. The investigation reveals that conversion efficiencies of SHG as calculated by the two methods appear to exhibit significant differences, and that the SHG may be modulated by the field of a fundamental wave (FW). The ratio between SHG conversion efficiencies as produced by the two methods shows a periodic variation, and this oscillatory behavior is fully consistent with the variation in transmittance of the FW. Quasi-phase matching (QPM) is also studied, and we find that the location of the peak for SHG conversion efficiency deviates from ?d=0, which differs from the conventional QPM results.

Zhao, Jing; Zhao, Li-Ming

2012-05-01

157

Third harmonic generation of high-energy large-aperture one microlaser and its spatial beam property investigation  

NASA Astrophysics Data System (ADS)

In this paper we report on the design and performance of the large KDP crystal plates that were constructed to convert 1.054 micrometer laser beam to its third harmonic. The KDP crystals were AR-coated by sol-gel films. Type II/type II phase-matching configurations for cascade frequency doubling and tripling have been implemented at 250 mm aperture. High conversion efficiencies approaching to 70% were achieved. Focusing properties of harmonic beam are also investigated in the paper. Based on the transfer of electric-field amplitude and phase ripple in frequency tripling, simple formulas are derived for the harmonic laser beam-quality factor, M3(omega )2, with an arbitrary fundamental beam incident to ideal nonlinear crystals. Harmonic beam-quality is generally degraded, while the beam divergence is similar to that of the fundamental after a nonlinear frequency-conversion process. For practical crystals with periodic surface ripples due to their machining, a multi-order diffractive model is presented to study the focusing properties of harmonic beam. Predictions of the theories are shown to be in excellent agreement with full numerical simulations of tripling.

Zhu, Baoqiang; Zhan, Tingyu; Gu, Zhen; Wang, Tao; Qian, Liejia

2001-05-01

158

BRIEF COMMUNICATIONS: Generation of ultraviolet radiation in an LiIO3 crystal at the frequency of the third harmonic of a mode-locked YAG:Nd3+ laser  

Microsoft Academic Search

The third harmonic of a mode-locked YAG:Nd3+ (lambda = 355 nm) solid-state laser was generated for the first time. A crystal of LiIO3 was found to be promising for the generation of near-ultraviolet radiation in the cw and quasi-cw regimes. An average ultraviolet radiation power of 4.5 mW was obtained in the mode-locking regime. Bibtex entry for this abstract Preferred

S. F. Bogdanov; P. G. Konvisar; S. R. Rustamov

1985-01-01

159

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 harmonic 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} {center dot} 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, C.A.; Davis, L.E.; Webb, M.

1990-10-16

160

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 harmonic 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} {center_dot} 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, C.A.; Davis, L.E.; Webb, M.

1990-10-16

161

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

162

Harmonic models of shape transformations in digital images and patterns  

Microsoft Academic Search

A harmonic model of shape transformations is presented. In this model, harmonic functions are governed by the Laplace equation. This model can convert all image or a pattern to another with arbitrary shapes. The transformation process is harmonic, without abruptness and discontinuity. This model can be used to generate and recognize handwritten Roman letters and Chinese characters, fingerprints, and other

Z. C. Li; C. Y. Suen; T. D. Bui; Q. L. Gu

1990-01-01

163

Multichannel Measuring Converter for Temperature Control.  

National Technical Information Service (NTIS)

Described is the multichannel measuring normalizing converter constructed on the base of magnetic second harmonic modulators and intended for preliminary voltage amplification of thermocouples controlling the unit discharge chamber temperature. The conver...

M. P. Vasil'ev V. G. Ivkin Y. M. Fedorishin

1979-01-01

164

First-principles study of crystal structure, electronic structure, and second-harmonic generation in a polar double perovskite Bi2ZnTiO6.  

PubMed

Within the density functional theory with the generalized gradient approximation, we present a systematic ab initio investigation of crystal structure, electronic structure, and linear and nonlinear optical responses in a polar double perovskite Bi(2)ZnTiO(6). The effect of B-site ordering is explored by comparing three possible configurations: A-type with alternative Zn and Ti layers stacking along the c axis; C-type with Zn and Ti c axis chains; and G-type with every Zn(Ti) atoms is surrounded by its nearby six Ti(Zn) atoms. It is found that the system with G-type B-site ordering is energetically favorable, which is lower in the total energies of 0.055 and 0.133 eV/formula unit than C-type and A-type, respectively. Optical calculations indicate that all the three configurations show large second-harmonic generation (SHG) coefficients, and the largest static SHG observed in the C-type system reaches 123 (10(-9) esu), the value of which is much larger than ever known polar oxides, e.g., 72 (10(-9) esu) in LiNbO(3). The predicted significant nonlinear optical properties are consistent with the calculated high tetragonality as well as the large off-center displacement of Zn, Ti, and Bi atoms. In particular, a large off-center displacement greater than 0.5 A in Zn atoms is revealed for the first time. A further microscopic picture is presented via the successful connection of the prominent feature of SHG in Bi(2)ZnTiO(6) with that of the linear optical dielectric function in terms of single-photon and double-photon resonances. Our calculations demonstrate the promising application of Bi(2)ZnTiO(6) in optoelectronics. PMID:19026078

Ju, Sheng; Guo, Guang-Yu

2008-11-21

165

Advances in spectral conversion for photovoltaics: up-converting Er3+ doped YF3 nano-crystals in transparent glass ceramic  

NASA Astrophysics Data System (ADS)

Up- and down-conversion (UC, DC) constitute two singular routes to achieve improved energy harvesting of sunlight by changing its shape of the solar spectrum. To obtain a significant conversion rate two main challenges have to be overcome: i) the excited lanthanide ions have to emit efficiently, a target which has been better accomplished for DC materials; ii) the absorption in the lanthanide-based UC and DC layers has to be high to ensure a sizeable fraction of photons can be harvested. In this paper, we review such materials and their use as spectral converters for photovoltaics (PV), paying special attention to the UC and DC processes in lanthanide glasses in fluoride matrices. We discuss the challenges that need to be overcome in order to implement these materials in real PV devices. Finally, we will present the synthesis of erbium (Er3+) doped YF3 nano-crystals embedded in transparent glass ceramic (TGC) by melt quenching. This material presents a low phonon energy environment for the Er3+ ions due to the fluoride crystals, while the silica glass provides chemical and mechanical stability to the compound.

Marques-Hueso, Jose; Chen, Daqin; MacDougall, Sean K. W.; Wang, Yuansheng; Richards, Bryce S.

2011-09-01

166

Power pollution due to grid connected wind electric converter  

Microsoft Academic Search

Analyses the harmonic behaviour of a wind electric converter in a grid connected mode under varying wind speed condition. The power quality of interconnected grid-windmill system performance is specified in terms of harmonic orders and total harmonic distortion. The fluctuations in wind reflect in the output power. The voltage and current wave forms are observed in reference to power quality

W. Z. Gandhare; G. R. Bhagwatikar

2000-01-01

167

Harness processes and harmonic crystals  

Microsoft Academic Search

In the Hammersley harness processes the R-valued height at each site i?Zd is updated at rate 1 to an average of the neighboring heights plus a centered random variable (the noise). We construct the process “a la Harris” simultaneously for all times and boxes contained in Zd. With this representation we compute covariances and show L2 and almost sure time

Pablo A. Ferrari; Beat M. Niederhauser

2006-01-01

168

Harmonic engine  

DOEpatents

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

169

Crystals  

NSDL National Science Digital Library

In this earth science/math/art activity, learners use simple ingredients to grow crystals and examine the repeating geometric shapes and patterns. Learners compare the growth of crystals from four types of crystal-starters (table salt, Borax, sand, and Epsom salt) to see which starter grows the most crystals in 14 days. Learners report their results online and find out what other learners discovered. Afterward, learners can use the crystals they grew to create works of art.

Science, Lawrence H.

2009-01-01

170

LASERS: Neodymium-doped yttrium aluminate laser with a pulse repetition frequency of 12.5 Hz and efficient second and third harmonic generation  

Microsoft Academic Search

A pulse-periodic yttrium aluminate (YAlO3:Nd3+) laser consisting of an oscillator and two amplifiers is described. At a fixed pulse repetition frequency of 12.5 Hz, the first harmonic was converted to the second with a 30% efficiency and to the third with a 6% conversion efficiency using KDP crystals. This efficiency was achieved by selecting an unstable resonator configuration in the

T. V. Plakhotnik; A. M. Pyndyk

1987-01-01

171

CAVE: the design of a precision metrology instrument for studying performance of KDP crystals  

SciTech Connect

A device has been developed to measure the frequency conversion performance of large aperture potassium dihydrogen phosphate (KDP) crystals. Third harmonic generation using ICDP is critical to the function of the National Ignition Facility (NIF) laser. The crystals in the converter can be angularly or thermally tuned but are subject to larger aperture inhomogeneities that are functions of growth manufacturing and - mounting. The CAVE (Crystal Alignment Verification Equipment) instrument scans the crystals in a thermally and mechanically controlled environment to determine the local peak tuning angles. The CAVE can then estimate the optimum tuning angle and conversion efficiency over the entire aperture. Coupled with other metrology techniques, the CAVE will help determine which crystal life-cycle components most affect harmonic conversion.

Hibbard, R.L., LLNL

1998-03-30

172

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.

173

Catalytic converter  

Microsoft Academic Search

A catalytic converter for oxidation of internal combustion engine exhausts is described which overcomes problems resulting from thermal expansion of core members and casings at a relatively low cost as compared to prior art solutions. The converter consists of pairs of circular and generally frusto-conical or funnel-shaped and concentric metal housings or casings forming a container surrounding a circularly cylindrical

1974-01-01

174

A high frequency link direct dc-ac converter for residential fuel cell power systems  

Microsoft Academic Search

This paper describes a boost converter cascaded high frequency link direct dc-ac converter suitable for fuel cell power sources. A new multi-loop control for a boost converter to reduce the low frequency input current harmonics drawn from the fuel cell is proposed. A new PWM technique for the cycloconverter at the secondary to reject the low order harmonics in the

Yu Jin Song; Prasad N. Enjeti

2004-01-01

175

New harmonic materials: index engineering. Thin-thick quadrature frequency conversion  

SciTech Connect

The quadrature conversion scheme is a method of generating the second harmonic. The scheme, which uses two crystals in series, has several advantages over single-crystal or other two crystal schemes. The most important is that it is capable of high conversion efficiency over a large dynamic range of drive intensity and detuning angle. Consider a pair of KDP crystals cut for type-II phase matching. In the quadrature scheme, the optic axes of the crystals are arranged so that the plans containing the direction of the laser beam and their optic axes (the kz planes) are mutually perpendicular. This arrangement has two important properties. First, in type-II phase matching, the incident wave is polarized at 45 deg to the kz plane of the crystal. This, in the quadrature scheme, if the incident wave is correctly polarized for efficient conversion in the first crystal, it is also correctly polarized for efficient conversion in the second crystal. Both crystals can therefore convert efficiently.

Eimerl, D.

1985-02-07

176

Ac-dc converter firing error detection  

SciTech Connect

Each of the twelve Booster Main Magnet Power Supply modules consist of two three-phase, full-wave rectifier bridges in series to provide a 560 VDC maximum output. The harmonic contents of the twelve-pulse ac-dc converter output are multiples of the 60 Hz ac power input, with a predominant 720 Hz signal greater than 14 dB in magnitude above the closest harmonic components at maximum output. The 720 Hz harmonic is typically greater than 20 dB below the 500 VDC output signal under normal operation. Extracting specific harmonics from the rectifier output signal of a 6, 12, or 24 pulse ac-dc converter allows the detection of SCR firing angle errors or complete misfires. A bandpass filter provides the input signal to a frequency-to-voltage converter. Comparing the output of the frequency-to-voltage converter to a reference voltage level provides an indication of the magnitude of the harmonics in the ac-dc converter output signal.

Gould, O.L.

1996-07-15

177

Covariant Harmonic Oscillators and Coupled Harmonic Oscillators.  

National Technical Information Service (NTIS)

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 ...

D. Han Y. S. Kim M. E. Noz

1995-01-01

178

Analysis of sub-harmonics in power systems  

Microsoft Academic Search

With a wide range of power electronics-related applications in power systems, harmonic currents are increasing at an alarming rate which has greatly deteriorated the power quality in electrical power networks. Moreover, some of electronic controlled equipments used in power systems, such as power converters, produce sub-harmonics, a type of waveform distortion, which can severely degrade the power system performance. Therefore,

Zbigniew Leonowicz

2010-01-01

179

High Dinamic Control of a PWM Rectifier using Harmonic Elimination  

Microsoft Academic Search

In this paper the problem of current control in high power converters using low frequency, precalculated switching patterns is addressed. To overcome the problem of switching harmonics feeding through the current controllers a harmonic prediction and compensation method is devised. The good performance of the method is tested extensively through simulation of an three level PWM rectifier modulated with a

C. Silva; J. Oyarzun

2006-01-01

180

Electrostatic field measurements and band flattening during electron-transfer processes at single-crystal TiO[sub 2] electrodes by electric field-induced optical second harmonic generation  

SciTech Connect

Optical second harmonic generation (SHG) is employed as a local, time-resolved measurement of the electrostatic fields at the surface of single-crystal TiO[sub 2] electrodes in contact with aqueous electrolyte solutions. The interfacial SHG at a fundamental wavelength of 584 nm is dominated by the electric field-induced second harmonic (EFISH) response from the first 20 nm of the space charge layer at the surface of the semiconductor. A substantial decrease in the amount of SHG from the electrode while under potentiostatic control is observed upon illumination of the surface with UV light (320 nm) whose energy is above the bandgap for TiO[sub 2] (3.0 eV or 410 nm). Comparisons of the drop in SHG upon UV illumination with photovoltage measurements for TiO[sub 2] electrodes at open circuit verify that this decrease is due to a reduction in the strength of the electrostatic fields ([open quotes]band flattening[close quotes]) within the space charge region upon UV illumination. The EFISH response from the surface decreases with increasing power of the UV illumination, corresponding to a band flattening of up to 70% for the highest power densities. Upon termination of the UV illumination, a slow (10-12 s) rise time is observed for the return of the surface SHG to its normal levels. 50 refs., 8 figs.

Lantz, J.M.; Corn, R.M. (Univ. of Wisconsin, Madison, WI (United States))

1994-05-05

181

Radiating dipoles in photonic crystals  

Microsoft Academic Search

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

Kurt Busch; Nipun Vats; Sajeev John; Barry C. Sanders

2000-01-01

182

Photothermophotovoltaic converter  

SciTech Connect

A photothermophotovoltaic energy conversion system for converting solar energy to electrical energy is described comprising: a radiator; and photovoltaic cell means for receiving incoming electromagnetic radiant energy including the solar energy and converting a first portion of the incoming energy to electrical energy and having reflecting means for reflecting a second portion of the incoming energy to the radiation. The radiator is disposed to receive the second portion of the energy from at least one photovoltaic cell and be heated thereby for radiating energy back to the photovoltaic cell means for subsequent energy conversion therein.

Woolf, L.D.

1988-05-24

183

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

184

Measurement Converter  

NSDL National Science Digital Library

Many online calculators require a Java-capable browser. Here's one that doesn't, and will perform over 500 different unit conversions for distance, area, volume, mass, speed, temperature, pressure, energy, power, force, etc. And when you convert, say, 5 kilometers to miles, you not only get the conversion result, but a wealth of related measurements and sample conversions.

2007-12-13

185

Color harmonization for images  

NASA Astrophysics Data System (ADS)

Color harmonization is an artistic technique to adjust a set of colors in order to enhance their visual harmony so that they are aesthetically pleasing in terms of human visual perception. We present a new color harmonization method that treats the harmonization as a function optimization. For a given image, we derive a cost function based on the observation that pixels in a small window that have similar unharmonic hues should be harmonized with similar harmonic hues. By minimizing the cost function, we get a harmonized image in which the spatial coherence is preserved. A new matching function is proposed to select the best matching harmonic schemes, and a new component-based preharmonization strategy is proposed to preserve the hue distribution of the harmonized images. Our approach overcomes several shortcomings of the existing color harmonization methods. We test our algorithm with a variety of images to demonstrate the effectiveness of our approach.

Tang, Zhen; Miao, Zhenjiang; Wan, Yanli; Wang, Zhifei

2011-04-01

186

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

NASA Astrophysics Data System (ADS)

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 = 7.78 Å, b = 11.15 Å and c = 15.47 Å. 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 1H 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.

Rao, Redrothu Hanumantha; Kalainathan, S.

2012-11-01

187

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

2012-06-30

188

Second-harmonic generation in transparent surface crystallized glasses in the BaO-B{sub 2}O{sub 3}-TeO{sub 2} system  

SciTech Connect

A transparent glass-ceramic containing borate crystallites in tellurite glass is reported. Controlled heat treatment resulted in surface crystallization of BaB{sub 4}O{sub 7} in the BaO-B{sub 2}O{sub 3}-TeO{sub 2} glass system. The second-order optical nonlinearities observed in these surface crystallized glasses were attributed to the distortion present in the BaB{sub 4}O{sub 7} unit cell as evidenced by x-ray powder diffraction studies. A d{sub 33} value of 0.08 pm/V was obtained from the Maker fringe analysis for a surface crystallized glass.

Murugan, G. Senthil; Suzuki, Takenobu; Ohishi, Yasutake; Takahashi, Yoshihiro; Benino, Yasuhiko; Fujiwara, Takumi; Komatsu, Takayuki [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511 (Japan); Department of Chemistry, Nagaoka University of Technology, Nagaoka 940-2188 (Japan)

2004-10-18

189

Second-harmonic generation in substoichiometric silicon nitride layers  

NASA Astrophysics Data System (ADS)

Harmonic generation in optical circuits offers the possibility to integrate wavelength converters, light amplifiers, lasers, and multiple optical signal processing devices with electronic components. Bulk silicon has a negligible second-order nonlinear optical susceptibility owing to its crystal centrosymmetry. Silicon nitride has its place in the microelectronic industry as an insulator and chemical barrier. In this work, we propose to take advantage of silicon excess in silicon nitride to increase the Second Harmonic Generation (SHG) efficiency. Thin films have been grown by reactive magnetron sputtering and their nonlinear optical properties have been studied by femtosecond pumping over a wide range of excitation wavelengths, silicon nitride stoichiometry and thermal processes. We demonstrate SHG in the visible range (375 - 450 nm) using a tunable 150 fs Ti:sapphire laser, and we optimize the SH emission at a silicon excess of 46 at.% demonstrating a maximum SHG efficiency of 4x10-6 in optimized films. Polarization properties, generation efficiency, and the second order nonlinear optical susceptibility are measured for all the investigated samples and discussed in terms of an effective theoretical model. Our findings show that the large nonlinear optical response demonstrated in optimized Si-rich silicon nitride materials can be utilized for the engineering of nonlinear optical functions and devices on a Si chip.

Pecora, Emanuele Francesco; Capretti, Antonio; Miano, Giovanni; Dal Negro, Luca

2013-03-01

190

Crystals  

NSDL National Science Digital Library

This page contains four documents explaining crystals. The topic is covered at an advanced level in relation to nanotechnology and requires background knowledge in eight grade science. A powerpoint with illustrations and instructor guide containing activities are included to aid in teaching this subject. Additionally, links to related videos, a lab handout, and discussion questions are available.

2012-10-16

191

On the effect of structural and symmetrical features of potassium titanyl phosphate crystals with different contents of niobium, antimony, and zirconium on the second-harmonic intensity  

SciTech Connect

A model is proposed, which shows that, at small deviations from the centrosymmetric state of the atomic structure, the quadratic nonlinear susceptibility of a crystal monotonically decreases with approach of the degree of central symmetry {eta} {sub 1}[{phi}(r)] of the electric potential function of the crystal structure to unity. The quadratic nonlinear susceptibility of K{sub 1-x}Ti{sub 1-x}Nb{sub x}OPO{sub 4} (x = 0, 0.02, 0.04, 0.11), K{sub 1} {sub -x}Ti{sub 1-x}Sb{sub x}OPO{sub 4} (x = 0.01, 0.07, 0.17), and KTi{sub 1-x}Zr{sub x}OPO{sub 4} (x = 0.03, 0.04) crystals has been measured. The degree of central symmetry {eta} {sub 1}[{phi}(r)] has been calculated for the structures of K{sub 1-x}Ti{sub 1-x}Nb{sub x}OPO{sub 4} (x = 0, 0.04, 0.11), K{sub 1-x}Ti{sub 1-x}Sb{sub x}OPO{sub 4} (x = 0.01, 0.07, 0.17), and KTi{sub 1} {sub -x}Zr{sub x}OPO{sub 4} (x = 0.03, 0.04) crystals. It is shown that, at {eta} {sub 1}[{phi}(r)] > 0.7, the relationship between the quadratic nonlinear susceptibility of the investigated crystals and the degree of their central symmetry {eta} {sub 1}[{phi}(r)] is in qualitative agreement with the proposed model.

Ivanov, V. A., E-mail: iv-vlad@yandex.ru; Burdov, V. A.; Marychev, M. O.; Titaev, D. N.; Faddeev, M. A.; Chuprunov, E. V. [Nizhni Novgorod State University (Russian Federation)

2008-07-15

192

Spectrum of second-harmonic radiation generated from incoherent light  

SciTech Connect

We report on the development of the theory of second-harmonic generation by an incoherent pump with broad angular and frequency spectra. We show that spatial as well as temporal walk-off effects in a nonlinear crystal result in angular dispersion of the second-harmonic radiation. We demonstrate that the acceptance angle in second-harmonic generation by incoherent light is caused by the width of the pump angular spectrum and the resulting angular dispersion of second-harmonic radiation but does not depend on crystal length. In this case the frequency spectrum of second-harmonic radiation is determined by its angular dispersion and the pump angular spectrum. The theory is supported by an experiment in which a LiIO{sub 3} crystal was pumped by a tungsten halogen lamp.

Stabinis, A.; Pyragaite, V.; Tamosauskas, G.; Piskarskas, A. [Department of Quantum Electronics, Vilnius University, Sauletekio Avenue 9, Building 3, LT-10222 Vilnius (Lithuania)

2011-10-15

193

Simple Harmonic Motion in Harmonic Plane Waves.  

ERIC Educational Resources Information Center

Discusses the distribution of kinetic and potential energy in transverse and longitudinal waves and examines the transmission of power and momentum. This discussion is intended to aid in understanding the simple harmonic motion of a particle involved in the propagation of a harmonic mechanical plane wave. (HM)

Benumof, Reuben

1980-01-01

194

Simple Harmonic Motion in Harmonic Plane Waves.  

ERIC Educational Resources Information Center

|Discusses the distribution of kinetic and potential energy in transverse and longitudinal waves and examines the transmission of power and momentum. This discussion is intended to aid in understanding the simple harmonic motion of a particle involved in the propagation of a harmonic mechanical plane wave. (HM)|

Benumof, Reuben

1980-01-01

195

Multiple harmonic plasma emission  

SciTech Connect

A generalized weak turbulence theory for electromagnetic emission at multiple harmonics of the plasma frequency is developed. In the literature, the electromagnetic emission at the plasma frequency and/or its second harmonic has been intensively studied. However, the emission at harmonics higher than the second harmonic is scarcely discussed. In the present paper, the higher harmonic plasma emission is explained by taking the interactions between the transverse mode and electrostatic nonlinear eigenmodes into consideration. The present analysis incorporates electrostatic nonlinear harmonic Langmuir waves into the fully electromagnetic weak turbulence formalism recently reformulated on the basis of the statistical mechanical Klimontovich approach. The wave kinetic equations for the transverse electromagnetic and Langmuir waves interacting with the harmonic Langmuir waves are derived, on the basis of which the emission of electromagnetic waves near multiple harmonics of the plasma frequency is qualitatively discussed.

Yi, Sumin; Yoon, Peter H.; Ryu, Chang-Mo [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of)

2007-01-15

196

The resonance damping effect associated with linear shunt loads and single-phase converters  

Microsoft Academic Search

The possibility of circuit resonance due to the application of capacitors in a harmonic rich environment is well understood. A converter is a source of distortion, which may excite a resonance. However a converter may also contribute to the damping of resonance. A method is described to calculate the harmonic impedance of a system from simulated capacitor switching. The effect

M. J. Bridgeman; N. MacLeod; S. B. Tennakoon; R. E. Morrison

2000-01-01

197

Harmonization of Biodiesel Specifications  

SciTech Connect

Worldwide biodiesel production has grown dramatically over the last several years. Biodiesel standards vary across countries and regions, and there is a call for harmonization. For harmonization to become a reality, standards have to be adapted to cover all feedstocks. Additionally, all feedstocks cannot meet all specifications, so harmonization will require standards to either tighten or relax. For harmonization to succeed, the biodiesel market must be expanded with the alignment of test methods and specification limits, not contracted.

Alleman, T. L.

2008-02-01

198

MR harmonic quad study  

SciTech Connect

To understand the effect of Main Ring harmonic quadruple correctors. Previous data taken with the harmonic quads did not agree well with the SYNCH calculation. The ultimate goal of this study was to be able to change the harmonic quads and verify the changes in lattice function.

Yang, M.-J.; /Fermilab

1995-01-01

199

Enhancement of third harmonics generation during ultrashort pulse diffraction in multi-layer volume grating  

NASA Astrophysics Data System (ADS)

Successful phase-matching methods for Third Harmonics Generation (THG) include phase-matching in birefringent crystal and quasi-phase-matching (QPM) in crystal with periodically poled domains. However, these methods are not feasible in some isotropic materials (e.g. fused silica and photosensitive silicate glass). It was known that volume-grating in isotropic materials can independently generate frequency-converted waves. One of disadvantages of single-layer volumegrating is that the brightness of harmonic emission can not be enhanced by increasing the grating thickness. In this paper, a THG device with stratified sub-gratings was designed to enhance THG in isotropic materials: several sub-gratings were arranged parallel, and the grating-figures misalignment between neighboring sub-gratings was pre-fabricated. In terms of extension of interaction length in THG, our multi-layer sub-grating is formally equivalent to the multi-layer periodically poled crystal (e.g. lithium niobate) in conventional QPM approach. According to the calculation results, the N-layer (N <2) can, in principle, generate TH output intensity of N2 times stronger than single-layer volume-grating does, also compared to N times stronger than N-layer without figures-misalignment. The effect of random fabrication error in grating thickness on normalized conversion efficiency was discussed.

Tan, Yizhou; Yang, Yisheng; Liao, Jiali; Zhang, Ming

2013-09-01

200

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

201

Power system applications for PASC converter systems  

SciTech Connect

This paper shows, using computer EMTP simulations, some preliminary results of applying pulse amplitude synthesis and control (PASC) technology to single-source level voltage converter system. The method can be applied to any single terminal pair source with appropriate modifications in power extraction interface and computer control program to match source and load impedance characteristics. The PASC realization as discussed here employs banks of transformers, one bank per phase, in which the primaries are connected in parallel through a switch matrix to the dc source. Two opposite polarity primaries per transformer are pulsed alternatively in time to produce an oscillatory sinusoidal output waveform. PASC conversion system capabilities to produce both leading and lagging power factor power output in single-phase and three-phase {Delta} or Y configurations are illustrated. EMTP simulations are used to demonstrate the converter capabilities. Also included are discussions regarding harmonics and potential control strategies to adapt the converter to an application or to minimize harmonics.

Donnelly, M.K. [Pacific Northwest Lab., Richland, WA (United States); Johnson, R.M. [Montana State Univ., Bozeman, MT (United States)

1994-04-01

202

Power system applications for PASC converter systems  

SciTech Connect

This paper shows, using computer EMTP simulations, some preliminary results of applying pulse amplitude synthesis and control (PASC) technology to single-source voltage converter systems. The method can be applied to any single terminal pair source with appropriate modifications in power extraction interface and computer control program to match source and load impedance characteristics. The PASC realization as discussed here employs banks of transformers, one bank per phase, in which the primary are connected in parallel through a switch matrix to the dc source. Two opposite polarity primaries per transformer are pulsed alternatively in time to produce an oscillatory sinusoidal output waveform. PASC conversion system capabilities to produce both leading and lagging power factor power output in single-phase and three-phase {Delta} or Y configurations are illustrated. EHTP simulations are used to demonstrate the converter capabilities. Also included are discussions regarding harmonics and potential control strategies to adapt the converter to an application or to minimize harmonics.

Donnelly, M.K. [Pacific Northwest Lab., Richland, WA (United States); Johnson, R.M. [Montana State Univ., Bozeman, MT (United States)

1995-01-01

203

Power system applications for PASC converter systems  

NASA Astrophysics Data System (ADS)

This paper shows, using computer EMTP simulations, some preliminary results of applying pulse amplitude synthesis and control (PASC) technology to single-source level voltage converter system. The method can be applied to any single terminal pair source with appropriate modifications in power extraction interface and computer control program to match source and load impedance characteristics. The PASC realization as discussed here employs banks of transformers, one bank per phase, in which the primaries are connected in parallel through a switch matrix to the dc source. Two opposite polarity primaries per transformer are pulsed alternatively in time to produce an oscillatory sinusoidal output waveform. PASC conversion system capabilities to produce both leading and lagging power factor power output in single-phase and three-phase (Delta) or Y configurations are illustrated. EMTP simulations are used to demonstrate the converter capabilities. Also included are discussions regarding harmonics and potential control strategies to adapt the converter to an application or to minimize harmonics.

Donnelly, M. K.; Johnson, R. M.

1994-04-01

204

Frequency converter design and manufacturing considerations for the National Ignition Facility  

SciTech Connect

The National Ignition Facility (NIF), being constructed at Lawrence Livermore National Laboratory (LLNL), comprises 192 laser beams, Figure 1. The lasing medium is neodymium in phosphate glass with a fundamental frequency (1{omega}) of 1.053 {micro}m. Sum frequency generation in a pair of conversion crystals (KDP/KD*P) produces 1.8 Mj of the third harmonic light (3{omega} or {lambda}=0.35). On NIF the frequency conversion crystals are part of the Final Optics Assembly (FOA), whose two principal functions are to convert the laser light to 3{omega} and focus it on target. In addition, the FOA provides a vacuum window to the target chamber, smoothes the on- target irradiance profile, moves the unconverted light away from the target, and provides signals for alignment and diagnostics. The FOA has four Integrated Optics Modules (IOM), Figure 4, each of which contains two 41 cm square crystals are mounted with the full edge support to micro radian angular and micron flatness tolerances. This paper is intended to be an overview of the important factors that affect frequency conversion on NIF. Chief among these are angular errors arising from crystal growth, finishing, and mounting. The general nature of these errors and how they affect frequency conversion, and finally the importance of a frequency conversion metrology tool in assessing converter performance before opto-mechanical assemblies are installed on NIF will be discussed.

Hibbard, R.L.; English, R.E., Jr.; De Yoreo, J.J.; Montesanti, R.C.

1998-03-25

205

A voltage source three phase PWM converter with chopper circuit  

Microsoft Academic Search

This paper presents a novel strategy of a PWM power converter to control output voltage using a chopper circuit. Voltage source PWM converters are unsuitable for general purposes with wide adjustable voltage range. However, the surge voltage at switching becomes small and the input current waveforms have low harmonics and less resonant oscillations as compared with the current source power

Keiju Matsui; Tomohiro Katayama; Shinichi Takase; Yue Yang

1997-01-01

206

A flying capacitor multilevel PWM converter based UPFC  

Microsoft Academic Search

The paper presents a unified power flow controller (UPFC) based on the flying capacitor (FC) multilevel voltage source converter (VSC) with phase-shifted sinusoidal PWM control. The topology allows high power handling, low power loss, low harmonic distortion and hence less filtering requirement. The series converter injects a voltage with controlled magnitude and phase to control the active\\/reactive power flow in

Lie Xu; Vassilios G. Agelidis

2001-01-01

207

H? repetitive control of DC-AC converters in microgrids  

Microsoft Academic Search

This paper proposes a voltage controller design method for DC-AC converters supplying power to a microgrid, which is also connected to the power grid. This converter is meant to operate in conjunction with a small power generating unit. The design of the output voltage controller is based on H? and repetitive control techniques. This leads to a very low harmonic

George Weiss; Qing-Chang Zhong; Tim C. Green; Jun Liang

2004-01-01

208

Optical Second Harmonic Generation from Surfaces.  

National Technical Information Service (NTIS)

Optical second harmonic generation (SHG) from centro-symmetric crystals is restricted to the surface. A free electron model is used to derive the relevant source terms in the nonlinear polarization. Results of SHG from alkali metal covered surfaces of GE,...

J. M. Chen J. R. Bower C. S. Wang

1974-01-01

209

Measurement of submilliwatt, picosecond terahertz emission from a femtosecond-laser-pumped solid-state dc to ac radiation converter based on a ZnSe crystal  

SciTech Connect

We measured the terahertz pulse emission from a femtosecond-laser-pumped solid-state dc to ac radiation converter using a 150 fs Ti:sapphire laser pulse for dense plasma diagnostics. The laser-produced ionization front was directly modulated from a periodic electrostatic field to pulsed emission. The central frequency of the emission was measured to be 0.13 THz having a bandwidth of 0.1 THz and a peak power of 0.2 mW. This emission source is suitable for use in various novel diagnostic techniques, such as dense plasma diagnostics.

Yugami, Noboru; Ohata, Nobuo; Yaegashi, Kenta; Kawanago, Hiroshi [Department of Energy and Environmental Science, Graduate School of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585, Japan and Japan Science and Technology Agency, CREST, 4-1-8 Honcho, Kanagawa, Saitama 332-0012 (Japan); Department of Energy and Environmental Science, Graduate School of Engineering, Utsunomiya University, 7-1-2 Yoto, Utsunomiya, Tochigi 321-8585 (Japan)

2006-11-15

210

A Series-Connected Hybrid Triple Converter System  

NASA Astrophysics Data System (ADS)

A hybrid converter system aims at a large capacity high voltage high efficiency converter system with being free from harmonics in the output. The system can consist of n GTO converters and a single NPC IGBT converter connected series by n+1 output transformers. It is proved that a triple converter system consists of two GTO converters and one IGBT converter is most feasible based on the performance evaluation. Thus, this paper treats a triple converter system in detail. The GTO converters operate in a square-wave switching mode, while the IGBT converter operates in a PWM switching mode. The former produces a base part of the total output voltage. The latter not only produces an additional part of the total output, but offsets the harmonic components generated by the GTO converters. The control strategy for the system is proposed, and the experiments on inverter, rectifier and STATCOM operation are demonstrated. The experimental results verified the validity of the proposed hybrid triple converter configuration and its control strategy.

Li, Dongsheng; Fukuda, Shoji; Kubo, Yusuke

211

Nonlinear harmonic generation in the STARS FEL  

Microsoft Academic Search

BESSY proposes to build STARS, an FEL to demonstrate cascaded High Gain Harmonic Generation (HGHG). In two HGHG stages, a laser source of 700–900nm is converted down to a wavelength of 40–70nm. The STARS facility consists of a normal-conducting RF photoinjector, three superconducting TESLA-type acceleration modules, a magnetic bunch compressor and two stages of HGHG, each consisting of a modulator,

M. Abo-Bakr; K. Goldammer; T. Kamps; J. Knobloch; B. Kuske; T. Leitner; A. Meseck

2008-01-01

212

Active Harmonic Filters  

Microsoft Academic Search

Unlike traditional passive harmonic filters, modern active harmonic filters have the following multiple functions: harmonic filtering, damping,isolation and termination, reactive-power control for power factor correction and voltage regulation, load balancing, voltage-flicker reduction, and\\/or their combinations. Significant cost reductions in both power semiconductor devices and signal processing devices have inspired manufactures to put active filters on the market. This paper deals

HIROFUMI AKAGI

2005-01-01

213

Bernstein mode coupling to cyclotron harmonic radiation in a plasma  

SciTech Connect

An electron Bernstein wave in the presence of an ion-acoustic wave of suitable wave number converts itself into cyclotron harmonic electromagnetic radiation in a plasma. The Bernstein wave imparts oscillatory velocity to electrons that couples with the density perturbation associated with the sound wave to produce a nonlinear current, driving the electromagnetic wave at sum (or difference) frequency. Conversely a large amplitude electromagnetic wave at a cyclotron harmonic can parametrically excite an electron Bernstein wave that may effectively heat the electrons.

Kumar, Asheel; Tripathi, V.K. [Department of Physics, University of Allahabad, Allahabad-211002 (India); Department of Physics, Indian Institute of Technology, New Delhi-110016 (India)

2006-05-15

214

A closed-loop selective harmonic compensation for active filters  

Microsoft Academic Search

This paper proposes a control algorithm for parallel active power filters, based on current-controlled pulsewidth-modulated converters, which allows precise compensation of selected harmonic currents produced by distorting loads. The approach is based on the measurement of line currents and performs the compensation of the selected harmonics using closed-loop synchronous frame controllers. Thanks to the closed-loop operation, full compensation of the

Paolo Mattavelli

2001-01-01

215

Harmonic generation in multiresonant plasma films  

NASA Astrophysics Data System (ADS)

We investigate second- and third-harmonic generation in a slab of material that displays plasma resonances at the pump and its harmonic frequencies. Near-zero refractive indices and local field enhancement can deplete the pump for kW/cm2 incident powers, without resorting to other resonant photonic mechanisms. We show that low-threshold, highly efficient nonlinear processes are possible in the presence of losses and phase mismatch in structures that are 104 times shorter than typical nonlinear crystals, for relatively low irradiance values.

Vincenti, M. A.; de Ceglia, D.; Haus, J. W.; Scalora, M.

2013-10-01

216

Nonlinear harmonic generation in the STARS FEL  

NASA Astrophysics Data System (ADS)

BESSY proposes to build STARS, an FEL to demonstrate cascaded High Gain Harmonic Generation (HGHG). In two HGHG stages, a laser source of 700 900 nm is converted down to a wavelength of 40 70 nm. The STARS facility consists of a normal-conducting RF photoinjector, three superconducting TESLA-type acceleration modules, a magnetic bunch compressor and two stages of HGHG, each consisting of a modulator, dispersive chicane and a radiator. At the entrance of the undulator section, the beam energy is 325 MeV and the peak current is about 500 A. With these parameters, the STARS FEL reaches saturation with a peak power of 100 350 MW. A superradiant mode is also foreseen which boosts the radiation power to the GW-level. Due to nonlinear harmonic generation (NHG), free electron lasers also radiate coherently at higher harmonics of the FEL resonant frequency. STARS can hence extend its output range to even shorter wavelengths. This paper presents studies of the STARS harmonic content in the wavelength range of 6 20 nm. Seeding with high harmonic generation pulses at 32 nm is also discussed.

Abo-Bakr, M.; Goldammer, K.; Kamps, T.; Knobloch, J.; Kuske, B.; Leitner, T.; Meseck, A.

2008-08-01

217

Harmonic synchronization of nonlinear oscillators  

Microsoft Academic Search

The locking range of a harmonic synchronized oscillator is calculated, and it is shown to be proportional to the relative harmonic amplitude produced by the nonlinearity. For completeness a simple method is given for calculating the harmonic output produced.

I. Schmideg

1971-01-01

218

A generalized capacitor voltage balancing scheme for flying capacitor multilevel converters  

Microsoft Academic Search

Multilevel power electronic converters are the converter of choice in medium-voltage applications due to their reduced switch voltage stress, better harmonic performance, and lower switching losses. Although it has received little attention, the flying-capacitor multilevel converter has a distinct advantage in terms of its ease of capacitor voltage balancing. A number of techniques have been presented in the literature for

Mostafa Khazraei; Hossein Sepahvand; Keith Corzine; Mehdi Ferdowsi

2010-01-01

219

A novel multipass scheme for enhancement of second harmonic generation.  

PubMed

We present experimental evidence of enhancement of the second-harmonic generation by using a multipass non-collinear phase-matching configuration for a Q-switched nanosecond-kilohertz Nd:YVO4 laser. In comparison with the single-pass configuration, the enhancement factor of the second-harmonic laser with the two-pass configuration is up to 2.5 in a type I beta-barium borate crystal, which can be further increased by adding the third-pass through the crystal. In addition, we provide a general relationship between the phase-matching angle and tilting azimuth angles of the unconverted fundamental and second-harmonic lasers. The multipass non-collinear phase-matching configuration is capable of reducing a thermal effect due to the absorption in the crystal and effectively avoiding damages on the crystal surfaces. PMID:22109150

Harimoto, Tetsuo; Yo, Boku; Uchida, Kosuke

2011-11-01

220

Harmonic analysis of multi-phase electric-power distribution systems  

Microsoft Academic Search

This study presents a computer program as a tool for the harmonic analysis of multi-phase electric power distribution systems. In the program, the source of harmonics can be any number of multi-phase harmonic currents and\\/or voltages, or up to 10 three-phase converts. Frequency-dependent models of ac network elements are assembled into a sparse admittance matrix. Then, sparsity techniques are employed

Hosseini

1988-01-01

221

The Effect of Harmonic Currents on the Noise of a Three-Phase Induction Motor  

Microsoft Academic Search

The magnetic air gap radial force waves in a three-phase induction motor excited with a nonsinusoidal supply from a solid-state converter are investigated analytically, taking into account the interaction between the flux density waves due to the harmonic currents. A simple method for the prediction of the frequencies and origins of the magnetic force components paused by the harmonic currents

S. J. Yang; P. L. Timar

1980-01-01

222

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.

223

Lasing on higher harmonics  

SciTech Connect

Lasing at short wavelengths with an accelerator of modest energy can only be achieved with a wiggler of short period and high field operating, perhaps, at a high harmonic of the fundamental frequency. We discuss the characteristics of wigglers of this kind, designed to lase with harmonic numbers as large as fifty or so, emphasizing their gain, efficiency, and sensitivity to emittance and energy spread. 5 refs., 3 figs.

Warren, R.W.

1990-01-01

224

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

225

NONLINEAR OPTICS PHENOMENA: Second harmonic generation from DF laser radiation in ZnGeP2  

Microsoft Academic Search

We have succeeded in generating the second harmonic of the radiation from a DF laser for the first time, using single crystals of ZnGeP2. For crystals with lengths of 10.1 and 13.6 mm, the overall external efficiencies of the entire oscillator system were 4 and 6.2%. The internal efficiencies of second-harmonic generation in the crystals were 7.6 and 11.8%, respectively.

Yu M. Andreev; S. D. Velikanov; A. S. Yerutin; A. F. Zapol'skii; D. V. Konkin; S. N. Mishkin; S. V. Smirnov; Yu N. Frolov; V. V. Shchurov

1992-01-01

226

Zero current switching cuk converter for power factor correction  

Microsoft Academic Search

A new cuk resonant high power factor single-phase ac to dc converter for power factor correction is proposed in this paper which employs the zero-current switching (ZCS) technique. Merits of the proposed converter include power factor of unity, less harmonic control contents, zero switch loss, simpler control stage, higher power density and unidirectional power flow. Optional principles, design analysis, small-signal

Bor-ren Lin; Tsang-sum Huang

1997-01-01

227

Nonlinear optical effects in liquid crystals  

NASA Astrophysics Data System (ADS)

Direct current field induced optical second harmonic generation in nematic and cholesteric liquid crystals is investigated. In addition, flexoelectric induced second harmonic generation in nematic MBBA is studied. The experiments involve the detection of optical radiation at second harmonic frequency when aligned thin film liquid crystals samples are irradiated with laser beam at the fundamental frequency. The laser used is a Q switched Nd YAG laser. Sample alignment is achieved either with rubbing technique or by coating glass spacers with 100 A thick of SiO2. Experiments on nematic liquid crystals show that the temperature dependence of nematic order parameters is obtained from the measurement of dc induced second harmonic generation. Flexoelectric effect gives rise to second harmonic generation in nematic liquid crystal and the birefringence of nematic crystal is used to achieve phase matching.

Saha, S. K.

228

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

229

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

230

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

NASA Astrophysics Data System (ADS)

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.

1990-02-01

231

An investigation of voltage balancing circuit for DC capacitors in diode-clamped multilevel inverters to realize high output power density converters  

Microsoft Academic Search

Output power density of power converters has been increasing. At the same time, the power converters with lower harmonics and lower electromagnetic interference are required in many applications. To satisfy these requirements, the volume of filters and heat sinks should be reduced. As a solution to realize higher output power density and lower harmonics, diode-clamped multilevel inverters are investigated. In

Takumi Ito; M. Kamaga; Y. Sato; H. Ohashi

2010-01-01

232

PWM Converter Topologies.  

National Technical Information Service (NTIS)

Dc to dc converters using an electrical switch to control power flow between a dc source and a dc load are discussed. Only Pulse Width Modulation (PWM) type converter topologies are considered. A basic three element, three terminal converter topology is d...

E. R. W. Meerman H. J. N. Spruyt

1989-01-01

233

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

234

Harmonic analysis of multi-phase electric-power distribution systems  

SciTech Connect

This study presents a computer program as a tool for the harmonic analysis of multi-phase electric power distribution systems. In the program, the source of harmonics can be any number of multi-phase harmonic currents and/or voltages, or up to 10 three-phase converts. Frequency-dependent models of ac network elements are assembled into a sparse admittance matrix. Then, sparsity techniques are employed to determine the current flow in all elements and voltages at all busses throughout the system at any harmonic frequency up to 3 KHz. Voltage distortion factors that represent the overall effects of the harmonics of the system voltages are also calculated. The digital program was then applied to a multi-phase distribution system in order to observe the response of the system to the various changes that were made in the system. It was found that the converter size and location, the capacitor bank sizes and locations, and the representation of the system loads are factors in determining in harmonic current flows and the level of voltage-distortion factors. Also, the response of the system to single-phase harmonic sources was investigated, and it was discovered that the effects of single-phase harmonic sources can be serious enough that they should not be ignored in the harmonic analysis of multi-phase systems.

Hosseini, S.H.

1988-01-01

235

Design of precision mounts for optimizing the conversion efficiency of KDP crystals for the National Ignition Facility  

SciTech Connect

A key design challenge for the National Ignition Facility (NIF), being constructed at Lawrence Livermore National Laboratory (LLNL), [Hibbard, R L , 1998], is the frequency converter consisting of two KDP crystals and a focusing lens Frequency conversion is a critical performance factor for NIF and the optical mount design for this plays a key role in meeting design specifications The frequency converter is a monolithic cell that mounts the optics and is the point on the beamline where the frequency conversion crystals are optimally aligned and the cell is focused on target The lasing medium is neodymium in phosphate glass with a fundamental frequency (1{omega}) of 1 053 {micro}m Sum frequency generation in a pair of conversion crystals (KDP/KD*P) produces 1 8 MJ of the third harmonic light (3{omega} or {lambda}=O 35 pm). The phase-matching scheme on NIF is type I second harmonic generation followed by type II sum-frequency-mixing of the residual fundamental and the second harmonic light This laser unlike previous laser system designs, must achieve high conversion efficiency, 85%, which is close to the 90 8% theoretical maximum As a result, this design is very sensitive to angular variations in beam propagation and in the crystal axes orientation. Factors that influence the phase matching angle include crystal inhomogeneity, residual and induced stress in the crystals, the crystals` natural and mounted surface figure, mounting imperfections and gravity sag These angular variations need to be controlled within a 40 {micro}rad error budget. The optical mount contributions to the angular error budget are 20 {micro}rad and are what make the frequency converter in the Final Optics Cell (FOC) such a challenging precision design. The premise of using full edge support in the FOC design is primarily driven by the spherical target chamber design that has optics mounted at multiple longitudinal angles and thus gravity sag in the crystals that needs to be minimized To meet the angular performance requirements, a precision monolithic cell with full edge support for mounting the optics to 10 {micro}rad angular and 1-5 {micro}m flatness tolerances is required The NIF frequency converter design is a major step in improving both conversion efficiency and precision of the mount design Another major consideration in the FOC design is the trade-off between cost of manufacturing the cell and the performance of the mount An interesting balance of what can be accomplished with a conventional machine tool in a commercial shop to produce prototype FOC` s will be discussed Metrology issues involved in qualifying the FOC are also discussed.

Hibbard, R.L., LLNL

1998-03-30

236

Harmonically excited orbital variations  

SciTech Connect

Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs.

Morgan, T.

1985-08-06

237

A Harmonic Motion Experiment  

ERIC Educational Resources Information Center

|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. (Contains 14 figures.)|

Gluck, P.; Krakower, Zeev

2010-01-01

238

Harmonic Multiplication Using Resonant Tunneling,  

National Technical Information Service (NTIS)

We propose and demonstrate an odd-harmonic resistive multiplier that exploits the unique current-voltage (I-V) relation of resonant-tunneling diodes. It is shown that efficient odd-harmonic conversion is possible and that even harmonics do not appear beca...

T. C. Sollner E. R. Brown W. D. Goodhue C. A. Correa

1988-01-01

239

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

240

Optical third-harmonic generation using ultrashort laser pulses  

SciTech Connect

To better predict optical third-harmonic generation (THG) in transparent dielectrics, we model a typical ultrashort pulsed Gaussian beam, including both group velocity mismatch and phase mismatch of the fundamental and harmonic fields. We find that competition between the group velocity mismatch and phase mismatch leads to third-harmonic generation that is sensitive only to interfaces. In this case, the spatial resolution is determined by the group velocity walk-off length. THG of modern femtosecond lasers in optical solids is a bulk process, without a surface susceptibility, but bears the signature of a surface enhancement effect in z-scan measurements. We demonstrate the accuracy of the model, by showing the agreement between the predicted spectral intensity and the measured third-harmonic spectrum from a thin sapphire crystal.

Stoker, D.; Keto, J.W. [Department of Physics, University of Texas at Austin, 1 University Station C1600, Austin, Texas 78712-0264 (United States); Center for Nano and Molecular Science and Technology and Texas Materials Institute, University of Texas at Austin, Building ETC, Room 8.102, Campus Mail Code C2201, Austin, Texas 78712-1063 (United States); Becker, M.F. [Center for Nano and Molecular Science and Technology and Texas Materials Institute, University of Texas at Austin, Building ETC, Room 8.102, Campus Mail Code C2201, Austin, Texas 78712-1063 (United States); Electrical and Computer Engineering, University of Texas at Austin, 1 University Station C0803, Austin, Texas 78712-0240 (United States)

2005-06-15

241

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

242

Cascaded H-bridge with bidirectional boost converters for energy storage  

Microsoft Academic Search

This paper presents the design and control of a cascaded H-bridge converter for energy storage with bidirectional boost converter as charge\\/discharge unit. The disadvantage of the second harmonic on the main energy storage unit as well as its voltage variation with the state of charge is solved by this structure. The independent phase grid control is proposed for this topology.

Ionut Trintis; Stig Munk-Nielsen; Remus Teodorescu

2011-01-01

243

A matrix converter using reverse blocking NPT-IGBTs and optimized pulse patterns  

Microsoft Academic Search

The paper compares three-phase to three-phase IGBT matrix converters in which required four-quadrant switches are realized by conventional common collector configurations and a sophisticated semiconductor loss model is used to compute the converter losses for both switch configurations. New pulse patterns are derived to minimize the input current harmonics

Steffen Bernet; Takayoshi Matsuo; T.A. Lipo

1996-01-01

244

An Optimal Combination Modulation Strategy for a Seven-level Cascade Multilevel Converter Based STATCOM  

Microsoft Academic Search

This paper proposes an optimal modulation strategy for a static synchronous compensation (STATCOM) using a seven-level cascade multilevel converter without any filter. Cascade multilevel converters have been used in STATCOM application due to its ability to reduce harmonics and increase output power by increasing the level of output voltages for a given semiconductor device without device series connection. Challenges in

Yu Liu; Zhong Du; A. Q. Huang; S. Bhattacharya

2006-01-01

245

Complete harmonic-domain modeling and performance evaluation of an optimal-PWM-modulated STATCOM in a realistic distribution network  

Microsoft Academic Search

Power systems use STATCOM for compensating purposes that is subjected to the high switching frequencies. Various PWM techniques make selective harmonic elimination possible, which effectively control the harmonic content of voltage source inverters. On the other hand, distribution systems have to supply unbalanced nonlinear loads, transferring oscillations to the DC-side of the converter in a realistic operating condition. Thus, additional

H. Valizadeh Haghi; M. Tavakoli Bina

2008-01-01

246

Second-harmonic generation in a laser cavity  

SciTech Connect

We study the process of second-harmonic generation when the nonlinear crystal is in an active laser cavity. This system is characterized by isolated bifurcations (steady and Hopf) but also by interacting bifurcations. They are studied both analytically and numerically.

Mandel, P.; Wu, X.

1986-07-01

247

KTP second-harmonic generator for high-power lasers  

NASA Astrophysics Data System (ADS)

The analysis of the problems arising when the KTP crystals are used for the second harmonic generation in the case of the high peak and high average power laser radiation is presented. The main attention is paid for the investigation of the radiation absorption including the induced one.

Pavlova, Nina; Sidoryuk, Oleg E.; Astapenko, Valerie A.

1996-03-01

248

Second Harmonic Generation in Porous Silicon Multilayer Periodic Structures.  

National Technical Information Service (NTIS)

In tne paper second harmonic (SH) generation in a photonic bandgap structure was investigated. The intensity of SH from a multilayer structure exceeds the intensity of SH from both homogeneous layer of porous silicon and a single crystal silicon (100) sub...

A. B. Fedotov L. A. Golovan M. G. Lisachenko N. I. Koroteev P. K. Kashkarov

1999-01-01

249

Hypercomplete circular harmonic pyramids  

NASA Astrophysics Data System (ADS)

In this contribution we present a steerable pyramid based on a particular set of complex wavelets named circular harmonic wavelets (CHW). The proposed CHWs set constitutes a generalization of the smoothed edge wavelets introduced by Mallat, consisting of extending the local differential representation of a signal image from the first order to a generic n-th order. The key feature of the proposed representation is the use of complex operators leading to an expansion in series of polar separable complex functions, which are shown to possess the space-scale representability of the wavelets. The resulting tool is highly redundant, and for this reason is called hypercomplete circular harmonic pyramid (HCHP), but presents some interesting aspects in terms of flexibility, being suited for many image processing applications. In the present contribution the main theoretical aspects of the HCHPs are discussed along with some introductory applications.

Jacovitti, Giovanni; Manca, A.; Neri, Alessandro

1996-10-01

250

Tertiary side resonant DC/DC converter with integrated magnetics  

SciTech Connect

This paper presents a constant frequency tertiary side resonant dc/dc converter topology. The proposed converter topology gives the opportunity to integrate all the resonant inductors with the output transformer and provides greater flexibility in selecting the resonant capacitors. The harmonic equivalent circuit model and frequency domain analysis, which incorporates the effect of the leakage inductance of the high frequency transformer are presented. Steady state characteristics curves are presented to describe the effect of the leakage inductance and resonant circuit parameters on the performance of the converter. It is shown that with a tuned parallel resonant circuit on the tertiary winding the converter can be operated at higher frequencies. Finally, the experimental results show a higher than 80% efficiency for a 500 W, 48V to 5V dc/dc converter operating at 128 kHz.

Jain, P. [Concordia Univ., Montreal, Quebec (Canada); Jain, P.; Quaicoe, J. [Memorial Univ. of Newfoundland, St. John`s, Newfoundland (Canada)

1996-09-01

251

Simple Harmonic Motion - Example  

NSDL National Science Digital Library

This website contains a detailed development and comparison of a classical and a quantum mechanical description of motion in a simple harmonic potential "spring force", complete with figures. This example is a part of a larger collection of examples in which the classical and quantum mechanical descriptions are compared. (Note that there are thirteen pages, and that the user must use the navigation buttons at the bottom of the page)

Kirkman, Tom

2005-07-26

252

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.

253

PWM converter topologies  

NASA Astrophysics Data System (ADS)

Dc to dc converters using an electrical switch to control power flow between a dc source and a dc load are discussed. Only Pulse Width Modulation (PWM) type converter topologies are considered. A basic three element, three terminal converter topology is defined followed by two universal rules allowing for derivation of a wide variety of different topologies. A summary of different topology types is provided with steady state and small signal relations given for each. The survey shows 46 converter topologies of which 18 are known and 28 are new (under, patent application). The number of topologies could be increased to 68 if negative input voltages are considered.

Meerman, E. R. W.; Spruyt, H. J. N.

1989-08-01

254

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

255

On a new harmonic selection technique for harmonic balance method  

NASA Astrophysics Data System (ADS)

This paper is intended to present a new harmonic selection technique when solving nonlinear dynamic systems with the harmonic balance method. This technique belongs to the class of method called the adaptive harmonic balance method (AHBM). The harmonic selection is based on the use of a tangent predictor and relies on a stepwise regression procedure that allows for a dynamic management of the number of selected harmonics via an addition or removal procedure. The efficiency of this method relative to the classical harmonic balance method (HBM) is then evaluated through examples; this later step will indicate that AHBM can significantly reduce the number of variables, thus leading to computational time savings without deteriorating solution quality.

Grolet, Aurélien; Thouverez, Fabrice

2012-07-01

256

Resonant fluorescent lamp converter provides efficient and compact solution  

Microsoft Academic Search

A zero voltage switched (ZVS) resonant power converter for driving cold cathode fluorescent lamps is described. Primarily intended for liquid crystal display (LCD) back lighting, the circuit features minimal component count and size. A specially designed integrated circuit provides all control functions for a current fed push-pull ZVS converter, and also contains an auxiliary pulse width modulated (PWM) controller to

M. Jordan; J. A. O'Connor

1993-01-01

257

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

258

Three-phase Series-Connected Hybrid Converter System  

NASA Astrophysics Data System (ADS)

In this paper, a 3-phase series-connected hybrid converter system is introduced. The converter system is constructed by a GTO converter and an IGBT converter connected in series by two output transformers aiming at a high voltage high efficiency converter. The GTO converter operates in a square-wave switching mode at the same switching rate as a reference output voltage in order to minimize the device switching losses. The IGBT converter is built in an NPC (neutral-point-clamped) arrangement and operates in a PWM switching mode at a high switching rate. The former produces a base part of the total output voltage. The latter not only produces an additional part of the total output, but also offsets the harmonic components generated by the GTO converter. The control strategy for the system is proposed, and the experiment on an inverter, rectifier and STATCOM operation is demonstrated using the proposed hybrid converter. The experimental results verified the validity of the proposed hybrid configuration and its control strategy.

Li, Dongsheng; Fukuda, Shoji; Kubo, Yusuke; Kitano, Masayuki

259

Thermionic converters for ISUS  

Microsoft Academic Search

Eight alkali metal thermionic power converters were produced for a ground-based design verification test of a bimodal power and propulsion system. The effort provided a significant development step toward a spaceflight demonstration of the Integrated Solar Upper Stage (ISUS). The converters are electrically connected in series to produce a nominal eight (8) volt, 250 Watt output. In the power mode

Edmund L. James; William D. Ramsey; Gregory J. Talbot

1997-01-01

260

Analog to Digital Converter.  

National Technical Information Service (NTIS)

An analog-to-digital converters, finding particular application in a multichannel pulse height analyzer, with a means for digitizing the analog input in two conversion steps is presented. To digitize the input to 13 bits, a 7-bit digital to analog convert...

C. H. Lucas

1974-01-01

261

Respectful Type Converters  

Microsoft Academic Search

In converting an object of one type to another, we expect some of the original object's behavior to remain the same and some to change. How can we state the relationship between the original object and converted object to characterize what information is preserved and what is lost after the conversion takes place? We answer this question by introducing the

Jeannette M. Wing; John Ockerbloom

2000-01-01

262

A new approach to harmonic compensation in power systems  

Microsoft Academic Search

A novel approach to compensate for harmonics in power systems is proposed. The approach differs from conventional passive and active filters in its compensation principle. A practical system configuration to implement the approach is presented. It consists of a small-VA-rating PWM (pulsewidth-modulated) converter and a passive filter. The compensation principle is described, and compensation characteristics are examined theoretically and experimentally.

F. Z. Peng; H. Akagi; A. Nabae

1988-01-01

263

Design of dispersion section for the ATF harmonic generation FEL  

SciTech Connect

We present an analysis of the dispersion magnet for the high gain harmonic generation experiment to be carried out at the Accelerator Test Facility at BNL. The purpose of the dispersion magnet is to convert energy modulation of the electron beam into spatial bunching. For the dispersion magnet, we discuss the physical requirements, analyze the magnetic design, determine the focusing properties, and consider the effect on the FEL gain of departures from idea behavior on the FEL gain.

Zhang, X.; Ben-Zvi, I.; Ingold, G.; Krinsky, S.; Yu, L.H.

1992-10-01

264

Design of dispersion section for the ATF harmonic generation FEL  

SciTech Connect

We present an analysis of the dispersion magnet for the high gain harmonic generation experiment to be carried out at the Accelerator Test Facility at BNL. The purpose of the dispersion magnet is to convert energy modulation of the electron beam into spatial bunching. For the dispersion magnet, we discuss the physical requirements, analyze the magnetic design, determine the focusing properties, and consider the effect on the FEL gain of departures from idea behavior on the FEL gain.

Zhang, X.; Ben-Zvi, I.; Ingold, G.; Krinsky, S.; Yu, L.H.

1992-01-01

265

Harmonic generation in optical fibers  

SciTech Connect

This patent describes an apparatus for providing second harmonic generated radiation. It comprises: an optical fiber disposed in a laser cavity, the optical fiber having a substantially single-mode core which is doped with an active laser material, the laser material being self-organizable to produce radiation by second harmonic generation, the laser material further being substantially transparent to the second harmonic generated radiation; and means for pumping the core of the optical fiber to produce laser radiation therein and the laser cavity further comprising means for extracting at least a portion of the second harmonic generated radiation.

Sherborn, H.P.

1990-05-01

266

A line voltage regulator\\/conditioner for harmonic-sensitive load isolation  

Microsoft Academic Search

A technique is presented for the isolation of harmonic-sensitive loads from harmonic-producing loads, such as rectifiers and power converters. The solution, referred to as a line voltage regulator\\/conditioner (LVRC), utilizes a combination of a series and a parallel active power filter. The series filter isolates the sensitive loads on the output side of the LVRC from the nonlinear, distortion-producing loads

Steven Moran

1989-01-01

267

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

268

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

269

Harmonic generation at high intensities  

SciTech Connect

Atomic electrons subject to intense laser fields can absorb many photons, leading either to multiphoton ionization or the emission of a single, energetic photon which can be a high multiple of the laser frequency. The latter process, high-order harmonic generation, has been observed experimentally using a range of laser wavelengths and intensities over the past several years. Harmonic generation spectra have a generic form: a steep decline for the low order harmonics, followed by a plateau extending to high harmonic order, and finally an abrupt cutoff beyond which no harmonics are discernible. During the plateau the harmonic production is a very weak function of the process order. Harmonic generation is a promising source of coherent, tunable radiation in the XUV to soft X-ray range which could have a variety of scientific and possibly technological applications. Its conversion from an interesting multiphoton phenomenon to a useful laboratory radiation source requires a complete understanding of both its microscopic and macroscopic aspects. We present some recent results on the response of single atoms at intensities relevant to the short pulse experiments. The calculations employ time-dependent methods, which we briefly review in the next section. Following that we discuss the behavior of the harmonics as a function of laser intensity. Two features are notable: the slow scaling of the harmonic intensities with laser intensity, and the rapid variation in the phase of the individual harmonics with respect to harmonic order. We then give a simple empirical formula that predicts the extent of the plateau for a given ionization potential, wavelength and intensity.

Schafer, K.J.; Krause, J.L.; Kulander, K.C.

1993-06-01

270

Extremely high damage threshold of a new nonlinear crystal L-arginine phosphate and its deuterium compound  

SciTech Connect

L-arginine phosphate monohydrate (LAP) and deuterated LAP (DLAP) are new organic nonlinear optical materials useful for higher harmonics of radiation from high-power lasers. We measured the bulk laser damage threshold of these crystals using light from a 1.05 {mu}m laser with 1 and 25 ns pulse widths and 0.53 {mu}m laser light with 0.6 and 20 ns pulse widths. In every case, these crystals show much higher thresholds than potassium dihydrogen phosphate (KDP) and fused silica. These crystals are very interesting not only as a frequency converter but also as other optical components of high-power lasers, because of their extremely high damage threshold.

Yokotani, A.; Sasaki, T.; Yoshida, K.; Nakai, S. (Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565, Japan (JP))

1989-12-25

271

Direct AC-AC converter and its applications to induction motor drives  

SciTech Connect

Several modulation schemes are used to reduce the harmonic content in a direct ac-ac converter. A new modulation scheme using a clipped sine reference is proposed and the harmonic content with this scheme is found to be lower. The performance of a three-phase induction motor fed by a direct ac-ac converter is analyzed using the equivalent-circuit model as well as the dynamic equations referred to a frame fixed to the stator. Operation of a bipolar direct ac-ac converter with high input utilization is studied. The performance of a single-phase induction motor fed by such a converter is analyzed using an equivalent-circuit model. The direct ac-ac converter makes us of several bilateral switches which enable both motoring and regeneration. A practical realization using power MOSFETs is given.

Khoei, A.

1989-01-01

272

Catalytic converter efficiency monitoring  

SciTech Connect

This patent describes a method for monitoring an internal combustion engine on-board catalytic converter efficiency. It comprises: establishing predetermined test entry conditions; transferring fuel control system input to an EGO sensor located downstream of a converter; measuring a characteristic of a first air/fuel ratio limit cycle with a first set of fuel controller parameters; changing fuel controller parameters; measuring a characteristic of a second air/fuel ratio limit cycle with a second set of fuel controller parameters; calculating a transport time delay and a time constant of a converter as a function of the first and second limit cycles; and determining catalytic converter efficiency from a predetermined catalytic efficiency characterized as a function of a transport time delay and a time constant.

Gopp, A.Y.

1992-10-27

273

Template Converter Program.  

National Technical Information Service (NTIS)

The computer program represents one of three FORTRAN IV programs necessary to generate perspective views of highways from design data. The Template Converter Program performs essentially a bookkeeping function for the Perspective Plot Program. It accepts ...

J. P. Penzien

1971-01-01

274

Wirephoto Standards Converter.  

National Technical Information Service (NTIS)

A standards converter that translates simultaneously between the United States and European wirephoto networks has been developed. Items of noncompatibility include picture duration, lines per minute, lines per inch, and scanning direction. The system ope...

D. E. Troxel W. F. Schreiber C. L. Seitz

1968-01-01

275

Harmonics from compact fluorescent lamps  

Microsoft Academic Search

The measured performance of compact fluorescent lamps (CFLs) and some rectified incandescent lamps, which can cause considerable harmonic distortion of the input power, is discussed. These include both the electronically and magnetically ballasted CFLs with poor power factors and\\/or high harmonics. Using the model of a building's electrical load, it is shown that there is little cause for concern for

R. R. Verderber; O. C. Morse; W. R. Alling

1993-01-01

276

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

277

Cascaded thermionic converters  

NASA Astrophysics Data System (ADS)

A combination of experimental results and analytical work indicates the feasibility of a cascaded thermionic converter comprised of a barium-cesium stage with an emitter temperature of 2000 K and a cesium close-spaced stage with a collector temperature of 740 K having an overall lead efficiency of 27%. This cascaded converter has potential beneficial applications to space nuclear power, space terrestrial solar power and topping cycles in fossil or nuclear central stations.

Fitzpatrick, Gary O.; Allen, Daniel T.; McVey, John B.

1992-01-01

278

PDF to HTML Converter  

NSDL National Science Digital Library

If you're looking for a way to convert pdf files to html, this helpful application can do just that. Visitors just need to click the browse button here to locate the pdf that they wish to transfer. After doing this, they will supply their own email, and seconds later, they will have the converted file. This version is compatible with all operating systems.

2010-01-01

279

Analog to digital converter  

Microsoft Academic Search

An analog-to-digital converter, finding particular application in a multichannel pulse height analyzer, includes means for digitizing the analog input in two conversion steps. To digitize the input to 13 bits, a 7-bit digital to analog converter with a 7-bit up-down counter is used. During the first conversion step which is a coarse conversion, the input V sub i is compared

C. H. Lucas

1976-01-01

280

Nonlinear cyclotron harmonic absorption  

SciTech Connect

Nonlinear oscillations of particle's energy occur when a particle stays in a resonance zone. In this work, we found that collisionless heating of particles occurs when they pass the microwave beam at first, second, and third harmonic resonances. It is found that the net energy gain of particles from the microwaves is inversely proportional to the wave frequency. It is also found that the net energy gain is dependent on the microwave beam width. The energy gain of particles from a single pass through a resonance zone has been formulated analytically. A numerical calculation has been performed and the results are in good agreement with the analytic calculation. Both analytic and numerical calculations show a strong frequency dependence and a beam width dependence of nonlinear cyclotron resonance heating.

Seol, Jae Chun [National Fusion Research Institute, Yuseong, Daejeon 555-333 (Korea, Republic of); Hegna, C. C.; Callen, J. D. [Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706-1609 (United States)

2009-05-15

281

Synchronous Discrete Harmonic Oscillator  

SciTech Connect

We introduce the synchronous discrete harmonic oscillator, and present an analytical, numerical and graphical study of its characteristics. The oscillator is synchronous when the time T for one revolution covering an angle of 2{pi} in phase space, is an integral multiple N of the discrete time step {delta}t. It is fully synchronous when N is even. It is pseudo-synchronous when T/{delta}t is rational. In the energy conserving hyperincursive representation, the phase space trajectories are perfectly stable at all time scales, and in both synchronous and pseudo-synchronous modes they cycle through a finite number of phase space points. Consequently, both the synchronous and the pseudo-synchronous hyperincursive modes of time-discretization provide a physically realistic and mathematically coherent, procedure for dynamic, background independent, discretization of spacetime. The procedure is applicable to any stable periodic dynamical system, and provokes an intrinsic correlation between space and time, whereby space-discretization is a direct consequence of background-independent time-discretization. Hence, synchronous discretization moves the formalism of classical mechanics towards that of special relativity. The frequency of the hyperincursive discrete harmonic oscillator is ''blue shifted'' relative to its continuum counterpart. The frequency shift has the precise value needed to make the speed of the system point in phase space independent of the discretizing time interval {delta}t. That is the speed of the system point is the same on the polygonal (in the discrete case) and the circular (in the continuum case) phase space trajectories.

Antippa, Adel F. [Departement de Physique Universite du Quebec a Trois-Rivieres Trois-Rivieres, Quebec, G9A 5H7 (Canada); Dubois, Daniel M. [Centre for Hyperincursion and Anticipation in Ordered Systems, CHAOS asbl, Institute of Mathematics, B37, University of Liege Grande Traverse 12, B-4000 LIEGE 1 (Belgium)

2008-10-17

282

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

283

High-performance front-end converter for avionics applications [aircraft power systems  

Microsoft Academic Search

The distributed power systems of future commercial aircraft will adopt variable frequency generation (360 to 800 Hz). Front-end converters in the system will be required to have a high efficiency and a low total harmonic distortion (THD) of the input current. This paper explains the design of a zero-voltage-switching (ZVS) active-clamped isolated low-harmonic SEPIC rectifier for such applications. Utilization of

Praneet Athalye; DRAGAN MAKSIMOVIC; ROBERT ERICKSON

2003-01-01

284

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

285

Glycine lithium nitrate crystals  

NASA Astrophysics Data System (ADS)

Crystals of glycine lithium nitrate with non-linear optical properties have been grown in a solution by slow evaporation at room temperature. The crystal shows a good thermal stability from room temperature to 175 °C where the crystal begins to degrade. This property is desirable for future technological applications. Also, a good performance on the second harmonic generation was found, characterizing the emitted dominant wavelength by a customized indirect procedure using luminance and chromaticity measured data based on the CIE-1931 standard. Additionally, the 532 nm signal was detected by using a variant to the Kurtz and Perry method.

González-Valenzuela, R.; Hernández-Paredes, J.; Medrano-Pesqueira, T.; Esparza-Ponce, H. E.; Jesús-Castillo, S.; Rodriguez-Mijangos, R.; Terpugov, V. S.; Alvarez-Ramos, M. E.; Duarte-Möller, A.

286

Ionic Radical Theory of Crystalline Electro-Optical and Nonlinear Optical Effects. II. Calculation of Second Harmonic Generation Coefficient of alpha -LiIO sub 3 Crystal Using (IO Sub 3 ) exp -1 Radical Molecular Orbitals.  

National Technical Information Service (NTIS)

An (IO sub 3 ) exp -1 ionic radical model is proposed for the SHG effect of iodate crystals. The SHG coefficient for alpha LiIO sub 3 is calculated using (IO sub 3 ) exp -1 radical molecular orbitals and the calculated value agrees well with experimental ...

C. Chen

1977-01-01

287

Influence of filter parameters\\/topologies on stability of matrix converter-fed permanent magnet brushless motor drive systems  

Microsoft Academic Search

This paper analyses the stability of matrix converter-fed permanent-magnet brushless AC motor drive systems. The dynamic interaction between the input filter and the motor drive system are fully represented and the characteristics of the matrix converter are derived based on the commonly adopted modulation strategies by neglecting the effect of switching harmonics and taking average voltage and current over a

Jiabin Wang; M. Bouazdia

2009-01-01

288

Optimization of Input and Output Filters in Matrix Converter Drive System  

NASA Astrophysics Data System (ADS)

This paper presents an AC-AC power converter integrated with techniques that provide environmental harmony. The voltage source PWM inverter has been established as the major motor drive equipment. However, it is associated with issues pertaining to PWM switching as well as issues related to the input harmonics caused by capacitor input type rectification. Hence, there is need for a converter that addresses these problems and provides an environmentally harmonious solution. The matrix converter has a topology that inherently exhibits sinusoidal input current waveforms and less stressful output voltage waveforms. Combining the matrix converter with certain filter topologies is shown to provide an environmentally harmonious solution.

Yamada, Kenji; Higuchi, Tsuyoshi; Hara, Hidenori; Yamamoto, Eiji; Kume, Tsuneo; Swamy, Mahesh M.

289

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

290

Evaluation of third harmonic component effects in five-phase synchronous reluctance motor drive using time-stepping finite-element method  

Microsoft Academic Search

Interaction of the third harmonic magnetic field with the third harmonic current in a five-phase synchronous reluctance motor (SynRM) can produce additional torque. However, it is still not clear about the SynRM power factor and its impact on the associated power converter because of the third harmonic components. Using time-stepping finite-element method, a mathematical model of the SynRM, which allows

Longya Xu; Weinong N. Fu

2002-01-01

291

Highly efficient third harmonic generation of 1.32-um radiation of a Nd:YAG laser in KTP  

NASA Astrophysics Data System (ADS)

We report highly efficient cascade tripling of 1.32 micrometers Nd:YAG laser emission using combination of LiIO3 and KTP crystals. The generation of 0.44 micrometers radiation in KTP has been shown to occur at the purely noncritical phase-matching condition at slightly elevated temperature. Conversion efficiency of third harmonic generation in relation to second harmonic energy was approximately 60% in 4 mm long KTP crystal. The temperature and angular characteristics of conversion are presented.

Damazyan, G. S.; Sanamyan, T. V.

1999-12-01

292

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

293

Turnable Second Harmonic Generation from an Organic Dye Laser  

Microsoft Academic Search

Ultraviolet light has been generated from a Rhodamine 60 organic dye laser by frequency doubling with a KDP crystal. The second harmonic was tuned from 2900Å to 3000Å with peak powers of 40 watts.Organic dye lasers have now been reported with output wave-lengths extending throughout the visible and near infrared. The tunability and output energies now available in the visible

B. G. Huth; G. I. Farmer; L. M. Taylor; M. R. Kagan

1968-01-01

294

Second-harmonic generation in solar-pumped laser  

Microsoft Academic Search

Summary form only given. Solar-pumped lasers are candidates for wireless power transmission in space, free space optical communication, and photochemistry. The broad variety of applications necessitates a spectral coverage between the UV and the IR. Here, we report on second-harmonic generation (SHG) of a solar-pumped laser using a type II KTP crystal in an intracavity Q-switched resonator. Q-switching was obtained

M. Lando; Y. Shimony; R. M. J. Benmair; I. Vishnevetsky; A. Yogev

1998-01-01

295

Geodesic spaces and harmonic maps.  

National Technical Information Service (NTIS)

This brief summary contains discussions of smooth geometry, metric geometry, first applications of tensor calculus, geometry in geodesic spaces, and harmonic maps. 6 refs. (Atomindex citation 27:026727)

J. Eells

1995-01-01

296

Harmonic detection by using neural network  

Microsoft Academic Search

A methodology of harmonic detection in active power filter from the power line by using neural network is presented. Harmonic detection by using Fourier transformation is an advantageous method to compensate a specific harmonic component. However, it needs input data for each cycle of the current waveform and needs time for the analysis in each cycle. Therefore, the harmonic compensation

N. Pecharanin; H. Mitsui; M. Sone

1995-01-01

297

Harmonic analysis of electrical distribution systems  

SciTech Connect

This report presents data pertaining to research on harmonics of electric power distribution systems. Harmonic data is presented on RMS and average measurements for determination of harmonics in buildings; fluorescent ballast; variable frequency drive; georator geosine harmonic data; uninterruptible power supply; delta-wye transformer; westinghouse suresine; liebert datawave; and active injection mode filter data.

NONE

1996-03-01

298

Azimuthal anisotropy: The higher harmonics  

SciTech Connect

We report the first observations of the fourth harmonic (v{sub 4}) in the azimuthal distribution of particles at RHIC. The measurement was done taking advantage of the large elliptic flow generated at RHIC. The integrated v{sub 4} is about a factor of 10 smaller than v{sub 2}. For the sixth (v{sub 6}) and eighth (v{sub 8}) harmonics upper limits on the magnitudes are reported.

Poskanzer, Arthur M.; STAR Collaboration

2004-03-12

299

Limits: Geometric and Harmonic Series  

NSDL National Science Digital Library

A geometric series is a sum of numbers such that the ratio between consecutive terms is constant. For instance, 1/2 + 1/4 + 1/8 + … is a geometric series. The harmonic series is the sum of all numbers 1/n for nn = 1, 2, 3, …. In this activity, you can see a representation of three geometric series and the harmonic series.

Mathematics, Illuminations N.

2010-05-26

300

Fluorometer to spectrophotometer converter  

Microsoft Academic Search

A simple accessory has been constructed that will convert a standard laboratory spectrofluorometer into a spectrophotometer. This attachment fits within the sample compartment of a spectrofluorometer and consists of a cuvette holder, two mirrors, and two collimators. Light is redirected from the excitation lamp through the cuvette and then into the emission detector to measure absorbance instead of fluorescence. One

H. R. Garner

1996-01-01

301

An Improved DC-Link Voltage Control Method for Multiple Grid Connected Converter in Direct Drive Wind Power Generation System  

Microsoft Academic Search

In order to reduce the current of each IGBT and reduce the harmonic current into the grid, a multiple AC-DC-AC full-scale converter which is suitable for high power direct drive wind power generation systems is adopted. The reasons of DC-link voltage fluctuation of the grid connected converter are analyzed. An improved DC-link voltage control method for multiple grid connected converter

Weihao Hu; Yue Wang; Xianwen Song; Zhaoan Wang

2009-01-01

302

A simple pulsed laser design for high harmonics generation  

NASA Astrophysics Data System (ADS)

We demonstrate a simple pulsed laser design with a potentially high efficiency for high harmonics generation. The basic idea is to generate pulsed laser operation with a resonantly oscillating piezo-electric crystal made of LiTaO3 or LiNbO3, i.e. Q-switching with a Single Crystal Photo-Elastic Modulators (SCPEM). The pulsed mode operation shows 30 (internal SHG) to 50 (external SHG) times higher green power than the cw-mode operation with a maximum green output of 290mW.

Bachmair, J.; Gómez Vázquez, R.; Bammer, F.

2012-01-01

303

Strong second-harmonic generation in silicon nitride films  

NASA Astrophysics Data System (ADS)

We observe strong second-harmonic generation from silicon nitride films prepared on fused silica substrates by plasma enhanced chemical vapor deposition. The components of the second-order nonlinear optical susceptibility tensor of the films are calibrated against quartz crystal. The dominant component has the magnitude of 2.5 pm/V, almost two orders of magnitude larger than reported for Si3N4, and about three times larger than for the traditional nonlinear crystal of potassium dihydrogen phosphate. The results indicate that silicon nitride has great potential for second-order nonlinear optical devices, especially in on-chip nanophotonics.

Ning, Tingyin; Pietarinen, Henna; Hyvärinen, Outi; Simonen, Janne; Genty, Goëry; Kauranen, Martti

2012-04-01

304

Second-harmonic generation frequency-resolved optical gating in the single-cycle regime  

Microsoft Academic Search

The problem of measuring broad-band femtosecond pulses by the technique of second-harmonic generation frequency-resolved optical gating (SHG FROG) is addressed. We derive the full equation for the FROG signal, which is valid even for single-optical-cycle pulses. The effect of the phase mismatch in the second-harmonic crystal, the implications of the beam geometry, and the frequency-dependent variation of the nonlinearity are

A. Baltuska; Maxim S. Pshenichnikov; Douwe A. Wiersma

1999-01-01

305

Impact of wind turbine generators on network resonance and harmonic distortion  

Microsoft Academic Search

Distributed generators (DGs) are being increasingly connected at medium voltage level distribution networks. It is likely that different types of DGs, i.e. wind turbine generators (WTGs), photovoltaic solar systems, etc, may be connected on the same feeder. Most of the modern DGs are equipped with power electronic converters at their terminals, which act as sources of harmonic injection into the

Dhaval Patel; Rajiv K. Varma; Ravi Seethapathy; Michael Dang

2010-01-01

306

High-order-harmonic generation and superradiance in a seeded free-electron laser.  

PubMed

Higher order harmonic generation in a free-electron laser amplifier operating in the superradiant regime [R. H. Dicke, Phys. Rev. 93, 99 (1954).] has been observed. Superradiance has been induced by seeding a single-pass amplifier with the second harmonic of a Ti:sapphire laser, generated in a ?-Barium borate crystal, at seed intensities comparable to the free-electron laser saturation intensity. Pulse energy and spectral distributions of the harmonics up to the 11th order have been measured and compared with simulations. PMID:22680723

Giannessi, L; Artioli, M; Bellaveglia, M; Briquez, F; Chiadroni, E; Cianchi, A; Couprie, M E; Dattoli, G; Di Palma, E; Di Pirro, G; Ferrario, M; Filippetto, D; Frassetto, F; Gatti, G; Labat, M; Marcus, G; Mostacci, A; Petralia, A; Petrillo, V; Poletto, L; Quattromini, M; Rau, J V; Rosenzweig, J; Sabia, E; Serluca, M; Spassovsky, I; Surrenti, V

2012-04-19

307

High-Order-Harmonic Generation and Superradiance in a Seeded Free-Electron Laser  

NASA Astrophysics Data System (ADS)

Higher order harmonic generation in a free-electron laser amplifier operating in the superradiant regime [R. H. Dicke, Phys. Rev. 93, 99 (1954).PHRVAO0031-899X10.1103/PhysRev.93.99] has been observed. Superradiance has been induced by seeding a single-pass amplifier with the second harmonic of a Ti:sapphire laser, generated in a ?-Barium borate crystal, at seed intensities comparable to the free-electron laser saturation intensity. Pulse energy and spectral distributions of the harmonics up to the 11th order have been measured and compared with simulations.

Giannessi, L.; Artioli, M.; Bellaveglia, M.; Briquez, F.; Chiadroni, E.; Cianchi, A.; Couprie, M. E.; Dattoli, G.; Di Palma, E.; Di Pirro, G.; Ferrario, M.; Filippetto, D.; Frassetto, F.; Gatti, G.; Labat, M.; Marcus, G.; Mostacci, A.; Petralia, A.; Petrillo, V.; Poletto, L.; Quattromini, M.; Rau, J. V.; Rosenzweig, J.; Sabia, E.; Serluca, M.; Spassovsky, I.; Surrenti, V.

2012-04-01

308

Second-harmonic generation with free-running Nd:YAG laser  

NASA Astrophysics Data System (ADS)

First results and analysis of second harmonic generation with a Nd:YAG laser working in the long pulse, free running mode are presented in this paper. Second harmonic generation conversion efficiencies of up to 17.5% and pulse powers of 162W have been generated with a free running Nd:YAG laser and a KTP non-linear crystal. The conversion efficiency is limited by a saturation effect and optical damage occurring at ~50 times lower peak intensities than in the Q-switch mode. The saturation and damage mechanism involves creation of temporary 'color centers' induced by the second harmonic radiation and subsequent increased fundeamental wave absorption.

Favre, Sebastian; Sidler, Thomas C.; Salathé, Rene-Paul

2003-11-01

309

Multipolar second harmonic generation from planar arrays of Au nanoparticles.  

PubMed

We demonstrate optical Second Harmonic Generation (SHG) in planar arrays of cylindrical Au nanoparticles arranged in periodic and deterministic aperiodic geometries. In order to understand the respective roles of near-field plasmonic coupling and long-range photonic interactions on the SHG signal, we systematically vary the interparticle separation from 60 nm to distances comparable to the incident pump wavelength. Using polarization-resolved measurements under femtosecond pumping, we demonstrate multipolar SHG signal largely tunable by the array geometry. Moreover, we show that the SHG signal intensity is maximized by arranging Au nanoparticles in aperiodic spiral arrays. The possibility to engineer multipolar SHG in planar arrays of metallic nanoparticles paves the way to the development of novel optical elements for nanophotonics, such as nonlinear optical sensors, compact frequency converters, optical mixers, and broadband harmonic generators on a chip. PMID:22772269

Capretti, Antonio; Walsh, Gary F; Minissale, Salvatore; Trevino, Jacob; Forestiere, Carlo; Miano, Giovanni; Dal Negro, Luca

2012-07-01

310

A comparison of nondeterministic and deterministic switching methods for DC-DC power converters  

Microsoft Academic Search

An analysis and experimental results of the random pulsewidth modulation (RPWM) and random pulse-position modulation (RPPM) methods for DC-DC converters are presented. The characteristics and performance of power converters under two randomized modulations are evaluated. The theoretical relationships of discrete harmonics, continuous noise, and output-voltage ripple of the RPWM and RPPM schemes are established and compared with those of a

S. Y. Hui; Y. Shrivastava; S. Sathiakumar; K. K. Tse; Henry Shu-Hung Chun

1998-01-01

311

A 3-D space vector modulation generalized algorithm for multilevel converters  

Microsoft Academic Search

A three-dimensional (3-D) space vector algorithm of multilevel converters for compensating harmonics and zero sequence in three-phase four-wire systems with neutral is presented. The low computational cost of the proposed method is always the same and it is independent of the number of levels of the converter. The conventional two-dimensional (2-D) space vector algorithms are particular cases of the proposed

M. M. Prats; L. G. Franquelo; R. Portillo; J. I. Leon; E. Galvan; J. M. Carrasco

2003-01-01

312

Space vector modulation for a capacitor clamped multi-level matrix converter  

Microsoft Academic Search

As an array of controlled bi-directional semiconductor switches, the matrix converter allows direct AC-AC conversion without an intermediate DC link. The matrix converter has several attractive advantages that have been investigated in the last twenty years. Multilevel topologies have become increasingly popular in recent years due to high power quality, high-voltage capability, low harmonics and low EMI issues. This paper

Xu Lie; Jon C. Clare; Patrick W. Wheeler; Lee Empringham

2008-01-01

313

Novel Current-Mode AC\\/AC Converters With High-Frequency AC Link  

Microsoft Academic Search

A novel circuit-topology family of the current-mode AC\\/AC converter with high-frequency AC link, based on a Flyback converter, is proposed. These circuit topologies, which can transfer one unregulated sinusoidal voltage with high total harmonic distortion (THD) into another regulated constant-frequency sinusoidal voltage with low THD, are composed of input cycloconverter, high-frequency storage transformer, and output cycloconverter. The circuit-topology family includes

Daolian Chen

2008-01-01

314

A review of three-phase improved power quality AC-DC converters  

Microsoft Academic Search

Three-phase AC-DC converters have been developed to a matured level with improved power quality in terms of power-factor correction, reduced total harmonic distortion at input AC mains, and regulated DC output in buck, boost, buck-boost, multilevel, and multipulse modes with unidirectional and bidirectional power flow. This paper presents an exhaustive review of three-phase improved power quality AC-DC converters (IPQCs) configurations,

Bhim Singh; Brij N. Singh; Ambrish Chandra; Kamal Al-Haddad; Ashish Pandey; Dwarka P. Kothari

2004-01-01

315

Control strategies for multiple parallel current-source converters of SMES system  

Microsoft Academic Search

Multiple structured current-source converters are applied for a superconducting magnetic energy storage (SMES) system. Suitable control method and control block diagram are proposed by taking much use of the advantage of this multiple structure. A multi-modular pulse width modulation (PWM) control strategy of current-source converters for the purpose of higher efficiency and less harmonic distortion is developed with an idea

Kazuhiro Imaie; Osami Tsukamoto; Yoshiaki Nagai

2000-01-01

316

Multifrequency Small-Signal Model for Buck and Multiphase Buck Converters  

Microsoft Academic Search

To investigate the high-frequency behaviors of buck and multiphase buck converters, this paper develops a modeling method based on the harmonic-balance approach. Because the nonlinear pulse-width modulator generates sideband components, the sideband effect occurs in a closed-loop converter. Taking this effect into account, the multifrequency small-signal model is proposed, which is applicable beyond half of the switching frequency. In a

Yang Qiu; Ming Xu; Kaiwei Yao; Juanjuan Sun; Fred C. Lee

2006-01-01

317

Fiber optic power converter  

NASA Astrophysics Data System (ADS)

High-efficiency, narrow-band fiber optic power converters have been produced under pilot line conditions. Power conversion efficiencies as high as 30 percent are obtained for devices illuminated with 50 mw from a 1060 nm Nd:YAG laser. The devices have an average power conversion efficiency in excess of 23 percent and fill factor greater than 74 percent. These devices can be used in remote locations to provide power for a variety of uses.

Eide, John; Mueller, Chip; Leonard, Ted

1989-09-01

318

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

319

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

320

Electrothermodynamic (etd) power converter  

Microsoft Academic Search

These inventions relate to novel advances in Electrothermodynamics (ETD), also known as charged aerosol, heat\\/electric power generators: (1) A new more efficient, compact converging\\/diverging configuration comprising a torus of revolution (TORON) used with a gas flywheel. (2) A ''Method II'' two-fluid mixed flow ejector\\/converter in a gas flywheel loop employing a primary steam or a high molecular weight driver jet

1983-01-01

321

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

322

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

323

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

324

Operation of the unified power flow controller as harmonic isolator  

SciTech Connect

The unified power flow controller (UPFC) is a tool in the implementation of Flexible AC Transmission Systems (FACTS). It provides for the equivalent of static VAr compensation and series injection using back-to-back force commutated converters. This paper proposes a control strategy to extend UPFC operation to allow for the isolation of harmonics due to nonlinear loads. Simulation results based on the Electromagnetic Transients Program (EMTP) are used to illustrate device performance in a power system environment. Experimental results based on a single phase laboratory implementation verify the proposed control algorithm.

Enslin, J.H.R.; Zhao, J. [Univ. of Stellenbosch (South Africa). Dept. of Electrical and Electronic Engineering; Spee, R. [Oregon State Univ., Corvallis, OR (United States). Dept. of Electrical and Computer Engineering

1996-11-01

325

Thyristor converter simulation and analysis.  

National Technical Information Service (NTIS)

In this paper we present a simulation on thyristor converters. The simulation features nonlinearity, non-uniform firing, and the commutations. Several applications such as a current regulation, a converter frequency characteristics analysis, and a power l...

S. Y. Zhang

1991-01-01

326

Synthesized Energy Converting Materials.  

National Technical Information Service (NTIS)

Octahedra and rod shaped crystals of semiconducting ferromagnetic chalcogenide spinel (Cu(x)Cd(1-x)Cr2Se4) have been grown from molten CdCl2 by slow cooling or by the travelling heater method (THM). Slow cooling of its solution in molten CdCl2 resulted in...

1971-01-01

327

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

328

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 DC 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

Martina Calais; Vassilios G. Agelidis; Mike Meinhardt

1999-01-01

329

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

330

PR-controller in a 2MW grid side windpower converter  

Microsoft Academic Search

To regulate the current in grid connected power converters mostly proporional integral (PI) controller in synchronous reference frame are used. To improve their known drawbacks such as complexity of control structure because of the dq-transformation and the poor behavior concerning low order harmonics compensation, proportional resonant (PR) controller gained a large popularity. This paper describes the differences between using PI-controller

Andreas Uphues; Kilian Notzold; Ralf Wegener; Stefan Soter

2012-01-01

331

Influence of the modulation method on the conduction and switching losses of a PWM converter system  

Microsoft Academic Search

The authors explore the dependency of the conduction losses of a bridge leg of a pulsewidth modulation (PWM) power converter system with a high pulse rate on the shape of the phase modulation functions. This is done for modulation methods that are optimized with respect to minimum harmonic current RMS values. The results are compared to the results gained for

Johann W. Kolar; Hans Ertl; Franz C. Zach

1991-01-01

332

Compensation schemes for a SCR converter in variable speed wind power systems  

Microsoft Academic Search

This paper presents the performance study of several compensation schemes for a line-commutated SCR converter operating under a wide range of dc voltage. The studied reactive power and harmonic compensation schemes include passive filters, active filters, and hybrid compensation methods for a SCR interfaced permanent magnet generator based variable speed wind turbine. The effectiveness of the compensation schemes has been

Z. Chen

2004-01-01

333

First-order pseudo dead-beat current controller for buck converter  

Microsoft Academic Search

Analysis and current control using pseudo deadbeat controller (PDC) for the buck dc-dc converter is proposed in this paper. The conventional deadbeat current controller, reported in the literature, exhibit sub-harmonic oscillations and it may lead to instability in the event of parameter changes. To avoid such problems a pseudo deadbeat controller is proposed in this paper, which gives almost first

Mummadi Veerachary; Gundu Satish

2009-01-01

334

Natural capacitor voltage balancing for a flying capacitor converter induction motor drive  

Microsoft Academic Search

This paper presents an analysis of the natural voltage balancing dynamics of a three phase flying capacitor converter when supplying an induction motor. The approach substitutes Double Fourier harmonic series for the PWM switching waveforms and the frequency response of the motor, to create a linear state space model of this type of load. The model requires the mid-frequency response

Brendan Peter McGrath; Donald Grahame Holmes

2008-01-01

335

Electrothermodynamic (etd) power converter  

SciTech Connect

These inventions relate to novel advances in Electrothermodynamics (ETD), also known as charged aerosol, heat/electric power generators: (1) A new more efficient, compact converging/diverging configuration comprising a torus of revolution (TORON) used with a gas flywheel. (2) A ''Method II'' two-fluid mixed flow ejector/converter in a gas flywheel loop employing a primary steam or a high molecular weight driver jet such as a fluorocarbon containing charged aerosol water droplets and a low molecular weight carrier gas such as hydrogen or helium with an electro-negative gas additive, in a Rankine cycle including a vapor/gas and liquid separator with a bypass to the ejector/converter loop. (3) A ''Method III'' two-fluid mixed flow comprising a supersonic jet expanding conically within a subsonic flow, separated by a boundary layer in which the charged aerosol forms downstream of the orifice, at a cross section of at least 100 times the orifice section; and in which the electric charge density of the charged aerosol decreases along the jet axis, whereby substantially all of the kinetic power of the jet is converted to electric power within the jet, there being no ejector. (4) An array of supersonic jets utilizing Method III. (5) An array of supersonic jets utilizing Method III without separating duct walls in which ''convection cells'' provide return flows, forming a plurality of TORON configurations. (6) A supercritical Rankline cycle in a single stage employing Method III. (7) A method IV two-fluid cycle uses charged aerosols in an inert gas and operates on an Ericsson-type cycle. (8) Optimum operating conditions are defined for Methods II, III, and IV. (9) A high potential emitter is employed with a grounded body, and a sapphire tube sealed to metal by a new technique provides an insulating duct for the high temperature, high pressure vapor.

Marks, A.M.

1983-07-26

336

Unidirectional energy converter  

SciTech Connect

Thermal energy is converted into rotational energy by using the expansion of a fluid medium to propel a plurality of pistons within at least one continuous, closed-loop passageway mounted on a rotatable platform. In at least one region of the passageway, the pistons must move inwardly against centrifugal force as the platform rotates. In at least one other region of the passageway, the pistons are moved outwardly under the influence of centrifugal force. Means are provided for imparting force to successive ones of the pistons to propel them against centrifugal force in said one region; while means are provided for converting the energy of pistons moving outwardly under the influence of centrifugal force in said other region into rotational energy. This rotational energy is used to drive gears mounted on the platform which mesh with a stationary gear carried beneath the platform to cause rotation of the platform about its rotational axis. The energy used to accelerate the pistons is thereby converted into rotational energy of the platform. In one embodiment of the invention, at least two continuous, closed-loop passageways are used on the platform in order to prevent an unbalanced condition. In another embodiment of the invention, a single passageway is used on the platform comprising two essentially straight portions on opposite sides of the axis of rotation of the platform interconnected at their opposite ends by curved portions, also on opposite sides of the axis of rotation of the platform. By forcibly rotating the platform in reverse, the invention can be used as a compressor.

Anno, J.N.; Fawcett, S.L.

1981-07-28

337

Plastic molded torque converter turbine  

Microsoft Academic Search

A turbine disposed within a torque converter is described, the torque converter disposed between an engine and a transmission within a vehicle, the turbine rotatively fixed to a converter output element, the turbine comprising: a hub, formed of ferrous material, including: a flange portion, having a first side and a second side, having a complement of projections protruding from the

R. R; T. E. Hojna

1993-01-01

338

Rupee Convertibility and Exit Policy  

Microsoft Academic Search

The successful of partial convertibility of rupee and adequate foreign reserves have boosted confidence of the government. It is more than likely that we are going to see a convertible rupee on trade account before the end of this year. In official quarters it is believed that fiscal imbalance is only stumbling block in the path of a fully convertible

Rastogi A B

339

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

340

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

341

Design of high voltage DC power supply based on LCC resonant converter  

NASA Astrophysics Data System (ADS)

The aim of this paper is to design a small size, light weight high frequency high voltage (HFHV) power supply. It presents a comprehensive procedure for designing a high output voltage power supply based on series-parallel (LCC) resonant converter, aiming to realize the soft-switching. Through mathematical calculation based on an extensive of the first harmonic analysis, the paper derives the approach of determining the resonant parameters of the LCC converter. Then, a 35 kV power supply featuring a series-parallel resonant converter topology to compensate the distributed parameter is built to verify the correctness of the theory.

Wang, Z. Q.; Liu, Z. G.; Wang, J. J.; Li, G. F.

2013-03-01

342

Harmonizing national growth references for multi-centre surveys, drug monitoring and international postmarketing surveillance  

PubMed Central

Aim National European growth references differ. We aimed to convert (harmonize) currently used charts into a single unified interchangeable LMS format for each European nation. Methods Nine currently used national European growth references from Belgium (2009), France (1979), Poland (2001), Sweden (2002), Switzerland (1989), the UK (1990), Italy (2006) and Germany (1979 and 1997) were harmonized and compared with the international WHO child growth standards and WHO growth reference data for 5–19 years. Results European growth charts can be harmonized. The approach appears useful as height, and body mass index (BMI) is inappropriately represented by WHO references. European height references exhibit warping when plotted against the WHO reference. The French appears too short, the other Europeans too tall. Also, the BMI is not appropriately represented by the WHO references. Conclusions Harmonizing references is a novel, convenient and cost-effective approach for converting historic and/or incomplete local or national growth reference charts into a unified interchangeable LMS format. Harmonizing facilitates producing growth references ‘on demand’, for limited regional purposes, for ethnically, socio-economically or politically defined minorities, but also for matching geographically different groups of children and adolescents for international growth and registry studies.

Hermanussen, M; Assmann, C; Wohling, H; Zabransky, M

2012-01-01

343

Computer aided conceptual design based on harmonics  

Microsoft Academic Search

In order to improve the intelligent level of computer aided conceptual design system, and the creative design is supported effectively, man-computer harmonization principle in harmonics is used in product conceptual design. According to the rule of \\

Shao-zhong Cao; Guo-wei Yang; Xu-yan Tu

2005-01-01

344

Propagators for driven coupled harmonic oscillators  

Microsoft Academic Search

The path-integral method is used for the exact evaluation of propagators for coupled and driven coupled harmonic oscillators. The energy expectation values are then obtained explicitly on the basis of the propagators for coupled harmonic oscillators.

Kyu-Hwang Yeon; Chung-In Um; Woo-Hyung Kahng; Thomas F. George

1988-01-01

345

A transformerless hybrid active filter using a three-level PWM converter for a medium-voltage motor drive  

Microsoft Academic Search

This paper presents a transformerless hybrid active filter integrated into a medium-voltage motor drive for energy savings. This hybrid filter is intended for harmonic-current mitigation of the three-phase diode rectifier used as the front end of the motor drive. It consists of a passive filter tuned to the seventh-harmonic frequency and an active filter using a three-level PWM converter. This

Hirofumi Akagi; Ryota Kondo

2009-01-01

346

Harmonic Analysis of Stream Temperatures.  

National Technical Information Service (NTIS)

Computer program B260 is one of a series of programs in the SYSLAB system for data analysis of water-quality records. This special-purpose program was developed for harmonic analysis of water-quality constituent records, primarily stream-temperature data....

T. D. Steele

1974-01-01

347

Second harmonic microscopy of axonemes.  

PubMed

We performed Second Harmonic Microscopy of axonemes obtained from sea urchin sperm. Using polarization analysis and a trade-off between signal and photodamage, we were able to determine, for the first time to our knowledge, the nonlinear susceptibility chizxx/chixzx = 1.1+/-0.2 and chizzz/chixzx = 4+/-0.5 of axonemes. PMID:19466174

Odin, Christophe; Heichette, Claire; Chretien, Denis; Le Grand, Yann

2009-05-25

348

Strings, standing waves and harmonics  

NSDL National Science Digital Library

This website from the University of New South Wales contains basic information about how stringed instruments produce sound. The site discusses plucked string sound and bowed string sound, standing waves, and harmonics. There are many helpful animations and pictures to illustrate concepts.

Wolfe, Joe

2009-11-16

349

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

350

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

351

Stupid Spherical Harmonics (SH) Tricks  

Microsoft Academic Search

This paper is a companion to a GDC 2008 Lecture with the same title. It provides a brief overview of spherical harmonics (SH) and discusses several ways they can be used in interactive graphics and problems that might arise. In particular it focuses on the following issues: How to evaluate lighting models efficiently using SH, what \\

Peter-Pike Sloan

352

Data Compression and Harmonic Analysis  

Microsoft Academic Search

In this paper we review some recent interactions between harmonic analysis and data compression. The story goes back of course to Shannon's theory in the case of Gaussian stationary processes, which says that transforming into a Fourier basis followed by block coding gives an optimal lossy compression technique; practical developments like transform- based image compression have been inspired by this

David L. Donoho; Martin Vetterli; Ronald A. Devore; Ingrid Daubechies

1998-01-01

353

Load harmonics analysis and mitigation  

Microsoft Academic Search

Load harmonics in electrical submersible pump (ESP) systems could interact with the inductance of the transformers and shunt capacitance of the downhole cable creating a severe resonance condition. Although load filters are developed by some drive manufacturers as standard products or even integrated as part of the drive, such filters might not work well for ESP systems. In this paper,

Xiaodong Liang; Rotimi Adedun

2012-01-01

354

Harmonization and homogenization on fractals  

Microsoft Academic Search

This paper suggests a direct approach to define the Laplacian, the spectral dimension of nested fractals and the pre-Sierpinski carpet conductivity. We find a geometric construction of the harmonic functions on the gasket and therefore can describe effectively the dense set of functions having finite energy. The paper is mostly aimed at the homogenization on the pre-Sierpinski gasket, whose horizontal

Serguei M. Kozlov

1993-01-01

355

RF propagation in finite thickness unidirectional magnetic photonic crystals  

Microsoft Academic Search

This paper presents an analysis of a new class of magnetic photonic crystals (MPCs) constructed from periodic arrangements of available (possibly anisotropic) homogeneous material layers. Earlier, analytical studies of semi-infinite versions of these crystals demonstrated that they exhibit the phenomena of minimal reflection at their interface, large amplitude growth of the harmonic wave within the crystal, and concurrent group velocity

Gokhan Mumcu; Kubilay Sertel; John L. Volakis; Ilya Vitebskiy; Alexander Figotin

2005-01-01

356

Generalized Ellipsoidal and Sphero-Conal Harmonics  

NASA Astrophysics Data System (ADS)

Classical ellipsoidal and sphero-conal harmonics are polynomial solutions of the Laplace equation that can be expressed in terms of Lamé polynomials. Generalized ellipsoidal and sphero-conal harmonics are polynomial solutions of the more general Dunkl equation that can be expressed in terms of Stieltjes polynomials. Niven's formula connecting ellipsoidal and sphero-conal harmonics is generalized. Moreover, generalized ellipsoidal harmonics are applied to solve the Dirichlet problem for Dunkl's equation on ellipsoids.

Volkmer, Hans

2006-10-01

357

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

358

ac/dc converter topologies for the Space Station  

NASA Astrophysics Data System (ADS)

A new class of ac/dc converter topologies (Type-1 converters) is described, suitable for use in an advanced single-phase sine-wave voltage, high-frequency power distribution system, of the type that was proposed for a 20 kHz Space Station primary electrical power distribution system. The converter comprises a transformer, a resonant network, a current controller, a diode rectifier, and an output filter. The input ac voltage source is converted into a sinusoidal current source using the resonant network. The output of this current source is rectified by the diode rectifier and is controlled by the current controller. The controlled rectified current is then filtered by the output filter to obtain a constant voltage across the load. Three distinct converter topologies, Type-1A, type-1B, and Type-1C, are described and their performance characteristics presented. All three types have close-to-unity rated power factor (greater than 0.98), low total harmonic distortion in input current (less than 5 percent), and high conversion efficiency (greater than 96 percent).

Jain, Praveen K.; Tanju, Mehmet Celal; Bottrill, John

1993-04-01

359

Harmonic signals in Saudi Arabia industrial plants  

Microsoft Academic Search

Results of a preliminary survey of harmonic levels within the Saudi Arabian power network and industrial facilities are presented. The major industries are petrochemical related and a number of arc furnaces. The voltage and current harmonic levels are within the IEEE 519-1992 standard. The results indicate a growing level of harmonics as more and more petrochemical industries are connected to

Ibrahim El-Amin; A. Al-Shehri

1999-01-01

360

Power System Harmonics Estimation and Monitoring  

Microsoft Academic Search

The existence of harmonics in power systems and their effects have led to numerous issues of electric power quality. The IEEE Standard 519 is being revised and upgraded from a guide to a recommended practice in order to set limits on harmonic distortion and to ensure a high power quality. Thus, the measurement of harmonics in power system has assumed

Husam M. Beides; G. T. Heydt

1992-01-01

361

Dynamic state estimation of power system harmonics  

Microsoft Academic Search

The application of solid state drives in power systems has led to numerous issues of electric power quality. Many of these issues are related to harmonics in power systems which threaten the quality of electric power supplied to the consumer. The upgrading of the IEEE guide that set limits on harmonic injections added additional focus to the subject of harmonic

Husam Mohamed Beides

1991-01-01

362

Guelph Physics Tutorials: Simple Harmonic Motion  

NSDL National Science Digital Library

This website offers a tutorial on harmonic motion. The tutorial includes an introduction to the properties that describe harmonic motion, the connection between simple harmonic and uniform circular motions, and provides students with self-paced questions to test their understanding. This is part of series of tutorials on physics and mathematics to be used in physics classes.

2004-12-19

363

HARMONIC EFFECTS ON ELECTROMECHANICAL OVERCURRENT RELAYS  

Microsoft Academic Search

The electromechanical overcurrent protection relays are designed to operate with sinusoidal current. The operation of protective relay with harmonic currents is not reliable. The literature on harmonics and relays covers mostly the theoretical studies. In this paper, the harmonic effects on operation of electromechanical inverse time overcurrent relay (ITOCR) were examined. Not common in existing studies, the behaviour of ITOCR

HARMONKLERN ELEKTROMEKANK; AIRI AKIM; K. Burak DALCI; Recep YUMURTACI

364

Thermally driven acoustic oscillations: Second-harmonic  

Microsoft Academic Search

A second-harmonic is observed in a pipe closed at both ends with steep temperature gradients. The stability curves of the fundamental and the second-harmonic are experimentally determined, and the unstable region of the second-harmonic is estimated.

T. Yazaki; A. Tominaga; Y. Narahara

1980-01-01

365

Ultrabroadband single crystal composite transducers for underwater ultrasound  

Microsoft Academic Search

Through the use of complex piezoelectric structures, it is possible to obtain resonant harmonics not observed in the usual odd- harmonic response of a conventional structure. When combined with inherently broadband components, such as composites made with PMN- PT single crystal material, this permits the realisation of ultrabroadband devices. In the work reported here, results from modelling indicate that a

S. Cochran; M. Parker; P. Marin-Franch

2005-01-01

366

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

367

Converting Biomass to Products  

SciTech Connect

For nearly 30 years, PNNL has been developing and applying novel thermal, chemical and biological processes to convert biomass to industrial and consumer products, fuels and energy. Honors for technologies resulting from this research include the Presidential Green Chemistry Award and several Federal Laboratory Consortium and R&D 100 Awards. PNNL’s research and development activities address the complete processing scheme, from feedstock pretreatment to purified product recovery. The laboratory applies fundamental science and advanced engineering capabilities to biomass conversion and processing to ensure effective recovery of optimal value from biomass; carbohydrate polymer systems to maximize energy efficiencies; and micro-technology systems for separation and conversion processes. For example, bioproducts researchers in the laboratory’s Institute for Interfacial Catalysis develop and demonstrate the utility of new catalyst formulations for production of bio-based chemicals. This article describes a sampling of current and recent catalysis projects for biomass conversion.

Graybeal, Judith W.

2006-06-01

368

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

369

Surface Dipole and Electric Quadrupole Contributions to the Anisotropic Second Harmonic Generation from Noble-Metal Surfaces. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Azimuthal anisotropy in the optical second-harmonic response from various crystal faces of Ag, Cu, and Au has been measured. Comparing the relative magnitude of the isotropic and anisotropic signals indicates that the strong anisotropy observed from the (...

D. A. Koos V. L. Shannon G. L. Richmond

1993-01-01

370

Waveguide harmonic damper for klystron amplifier.  

SciTech Connect

A waveguide harmonic damper was designed for removing the harmonic frequency power from the klystron amplifiers of the APS linac. Straight coaxial probe antennas are used in a rectangular waveguide to form a damper. A linear array of the probe antennas is used on a narrow wall of the rectangular waveguide for damping klystron harmonics while decoupling the fundamental frequency in dominent TE{sub 01} mode. The klystron harmonics can exist in the waveguide as waveguide higher-order modes above cutoff. Computer simulations are made to investigate the waveguide harmonic damping characteristics of the damper.

Kang, Y.

1998-10-27

371

High intensity solar energy converter  

Microsoft Academic Search

A photovoltaic energy converter is described for converting incident radiant energy, such as solar energy, to electrical energy. The converter comprises a cell formed from integrally interconnected p-n junction-containing semiconductor wafers. The wafers are stacked end-to-end so that the respective junctions in each wafer are parallel to each other. The efficiency and performance of the cell is improved, upon exposure

R. E. House; R. A. Irvin; D. F. Kane

1978-01-01

372

A ZCS bidirectional flyback converter  

Microsoft Academic Search

This paper addresses the design and analysis of a zero-current-switched (ZCS) bi-directional flyback dc\\/dc converter. The converter is based on extending a previously developed unidirectional ZCS flyback converter and replacing the output diode with a controlled switch, which acts as either a rectifier or a power control switch in the corresponding power flow direction. By adding an auxiliary winding in

H. S. H. Chung; Wai-leung Cheung; Kam-shing Tang

2004-01-01

373

Noncollinear second-harmonic generation in BiB3O6  

NASA Astrophysics Data System (ADS)

Noncollinear second-harmonic generation (SHG) in a BiB3O6 crystal was investigated. Using a picosecond Nd:YAG laser as the fundamental light source, we achieved two efficient types of noncritical noncollinear SHG. A total reflection technique was employed to make the experimental setup quite simple. The noncollinear SHG efficiency could be as high as 49.2%.

Wang, Zhengping; Xu, Guibao; Liu, Junhai; Hu, Dawei; Xu, Xinguang; Wang, Jiyang; Shao, Zongshu

2004-07-01

374

Hydrogen-bonding contributions to the lattice energy of salts for second harmonic generation  

Microsoft Academic Search

The lattice energies of a series of organic dihydrogenphosphate salts capable of second harmonic generation (SHG) have been calculated. These calculations, coupled with empirical data, indicate that a minimum of 20–25% of the lattice energy arises from hydrogen-bond interactions. Hydrogen bonding is shown to be a strong enough force to have a profound effect on the overall packing and crystal

Christer B. Aakeröy; Kenneth R. Seddon; Maurice Leslie

1992-01-01

375

Optical Second-Harmonic Generation from Submonolayer Na-Covered Ge Surfaces.  

National Technical Information Service (NTIS)

Optical second harmonic generation (SHG) from centro-symmetric crystals is restricted to the surface. It is found that submonolayers of Na on Ge caused drastic increases in SHG. The different effects of Na on SHG of Ge(111) and Ge(100) were correlated wit...

C. H. Lee C. S. Wang J. M. Chen J. R. Bower

1973-01-01

376

Dislocation Detection Through Harmonic Generation  

NASA Astrophysics Data System (ADS)

A fundamental goal of ultrasonic nondestructive evaluation is to characterize material defects before failure. During material fatigue, dislocations tend to nucleate, becoming sources of stress concentration. Eventually, cracks start to form and lead to material failure. Recent research has indicated that nonlinear harmonic generation can be used to distinguish between materials of high and low dislocation densities. This research reports nonlinear harmonic generation measurements to distinguish between those areas of high and low dislocation densities in copper bars. The copper bars were subjected to flexural fatigue. Periodic scans were taken in order to track dislocation development during the fatigue life of the material. We show that this technique provides improved early detection for critical components of failure.

Reinhardt, B. T.; Kropf, M.; Boudraeu, K.; Guers, M. J.; Tittmann, B. R.

2010-02-01

377

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

378

Diamond turning of L-arginine phosphate, a new organic nonlinear crystal.  

PubMed

We have demonstrated that single point diamond turning can be used to generate high optical quality finished surfaces on a new organic nonlinear crystal, L-arginine phosphate (LAP). The proper choice of cutting conditions can produce surfaces with <5-A rms local roughness. Local softening or melting near the cutting tool tip may play a key role in the machining process by ensuring that material is removed by ductile cutting rather than brittle fracture. At the same time, the low melting temperature of LAP makes lubrication and cooling especially important to prevent extensive melting and tool fouling. In spite of the presence of a weak cleavage plane in LAP, the surface quality is relatively insensitive to crystallographic orientation. Tool wear is apparently negligible, so that surface flatness is governed by the stability of the diamond turning machine. These results suggest that it may be possible to fabricate large aperture LAP harmonic converters for use in inertial confinement fusion lasers. PMID:20555896

Fuchs, B A; Syn, C K; Velsko, S P

1989-10-15

379

Diamond turning of L-arginine phosphate, a new organic crystal  

SciTech Connect

We have demonstrated that single point diamond turning can be used to generate high optical quality finished surfaces on a new organic nonlinear crystal, L-arginine phosphate (LAP). The proper choice of cutting conditions can produce surfaces with {lt}5-A rms local roughness. Local softening or melting near the cutting tool tip may play a key role in the machining process by ensuring that material is removed by ductile cutting rather than brittle fracture. At the same time, the low melting temperature of LAP makes lubrication and cooling especially important to prevent extensive melting and tool fouling. In spite of the presence of a weak cleavage plane in LAP, the surface quality is relatively insensitive to crystallographic orientation. Tool wear is apparently negligible, so that surface flatness is governed by the stability of the diamond turning machine. These results suggest that it may be possible to fabricate large aperture LAP harmonic converters for use in inertial confinement fusion lasers.

Fuchs, B.A.; Syn, K.; Velsko, S.P. (Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (US))

1989-10-15

380

Venus topography - A harmonic analysis  

Microsoft Academic Search

A model of Venusian global topography has been obtained by fitting an eighteenth-degree harmonic series to Pioneer Venus orbiter radar altimeter data. The mean radius is (6051.45 + or - 0.04) km. The corresponding mean density is (5244.8 + or 0.5) kg\\/cu m. The center of figure is displaced from the center of mass by (0.339 + or - 0.088)

B. G. Bills; Michael Kobrick

1985-01-01

381

Effects of harmonics on equipment  

SciTech Connect

The purpose of this paper is to summarize the state-of-knowledge of the effects of power system harmonics on equipment. The general mechanisms presented are thermal overloading, disruption, and dielectric stressing. Quantitative effects are presented or referenced whenever possible. However, many of the effects can only be qualitatively described. The equipment considered are adjustable speed drives, capacitors, circuit breakers, fuses, conductors, electronic equipment, lighting, metering, protective relays, rotating machines, telephones, and transformers.

Wagner, V.E.; Balda, J.C.; Barnes, T.M.; Emannuel, A.E.; Ferraro, R.J.; Griffith, D.C.; Hartmann, D.P.; Horton, W.F.; Jewell, W.T.; McEachern, A.; Phileggi, D.J.; Reid, W.E.

1993-04-01

382

Lunar gravity - A harmonic analysis  

Microsoft Academic Search

A sixteenth-degree and sixteenth-order spherical harmonic lunar gravity field has been derived from the long-term Keplerian variations in the orbits of the Apollo subsatellites and Lunar Orbiter 5. This model resolves the major mascon gravity anomalies of the lunar near side and is in very good agreement with line-of-sight acceleration results. The far-side map shows the major ringed basins to

A. J. Ferrari

1977-01-01

383

LUNAR GRAVITY: A HARMONIC ANALYSIS  

Microsoft Academic Search

A sixteenth-degree and sixteenth- ing a selenopotential usable for global geophysi- order spherical harmonic lunar gravity field has cal analysis, errors still exist in the locations been derived from the long-term KeplerJan varia- of some prominent nearside anomalies. Errors of tions in the orbits of the Apollo subsatellites this type cause considerable problems when the and Lunar Orbiter 5. This

Alfred J. Ferrari

1977-01-01

384

Multi-MW 22.8 GHz Harmonic Multiplier - RF Power Source for High-Gradient Accelerator R&D  

SciTech Connect

Electrodynamic and particle simulation studies have been carried out to optimize design of a two-cavity harmonic frequency multiplier, in which a linear electron beam is energized by rotating fields near cyclotron resonance in a TE111 cavity in a uniform magnetic field, and in which the beam then radiates coherently at the nth harmonic into a TEn11 output cavity. Examples are worked out in detail for 7th and 2nd harmonic converters, showing RF-to-RF conversion efficiencies of 45% and 88%, respectively at 19.992 GHz (K-band) and 5.712 GHz (C-band), for a drive frequency of 2.856 GHz. Details are shown of RF infrastructure (S-band klystron, modulator) and harmonic converter components (drive cavity, output cavities, electron beam source and modulator, beam collector) for the two harmonic converters to be tested. Details are also given for the two-frequency (S- and C-band) coherent multi-MW test stand for RF breakdown and RF gun studies.

Jay L. Hirshfield

2012-07-26

385

Parallel Power Flow AC\\/DC Converter with High Input Power Factor and Tight Output Voltage Regulation for Universal Voltage Application  

Microsoft Academic Search

In this paper, a new parallel-connected single phase power factor correction (PFC) topology using flyback converter in parallel with forward converter is proposed to improve the input power factor with simultaneously output voltage regulation taking consideration of current harmonic norms. Paralleling of converter modules is a well-known technique that is often used in medium-power applications to achieve the desired output

A. K. Jha; K. H. Babu; B. M. Karan

2006-01-01

386

Narrow Pulse Elimination PWM for Multilevel Digital Audio Power Amplifiers Using Two Cascaded H-Bridges as a Nine-Level Converter  

Microsoft Academic Search

This paper presents a methodology to reduce total harmonic distortion (THD) in digital audio power amplifiers, using two new approaches: 1) a multilevel converter made of two cascaded full-bridges, with suitable power supplies to operate as a nine-level hybrid type converter and 2) a new pulsewidth modulation (PWM) technique called narrow pulse elimination (NPE) PWM. The proposed nine-level converter uses

Victor M. E. Antunes; V. Fernão Pires; J. Fernando A. Silva

2007-01-01

387

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.

388

Second-harmonic imaging from a modulated domain structure.  

PubMed

We present a new second-harmonic (SH) imaging technique to study the domains in a hexagonally poled LiTaO(3) nonlinear photonic crystal by using a femtosecond laser. By detecting the SH images at different planes, the distribution of the 180 degrees -inverted ferroelectric domains can be characterized, and the contributions of different nonlinear tensor components, modulated differently in the domain structure, can be selectively determined. Fundamental understanding and potential applications of such SH imaging techniques for the inverted nonlinear domain structures are presented and discussed. PMID:20081960

Zhang, Yong; Wang, Fuming; Geren, Katrina; Zhu, S N; Xiao, Min

2010-01-15

389

Inverse problem of cascaded third-harmonic generation  

NASA Astrophysics Data System (ADS)

Based on some numerical techniques such as split-step Fourier transformation, fourth-order Runge-Kutta and successive iteration method, the fundamental field was calculated from the known third-harmonic (TH) field in the process of TH generation (THG) using one doubling and one mixing KDP crystals. The effects of the monochromatic initial fields on the iteration numbers and the calculation precision were discussed. The inverse solution of the broadband laser pulse with linear frequency chirp was also carried out. The results show that the method proposed in this paper is available and efficient, which gives a new way to design and optimize the process of THG.

Li, Kun; Zhang, Bin

2008-01-01

390

Optical properties of rapidly grown KDP crystal improved by thermal conditioning  

Microsoft Academic Search

The medium-size crystal (64 × 63 × 43 mm) of potassium dihydrogen phosphate (KDP) was grown for one day from the 8 mm cubic seed crystal with a growth rate over 30 mm\\/day. The spectral transmittance, second-harmonic generation (SHG) property and laser damage threshold of the rapidly grown crystals were measured. The comparison with those of conventionally grown KDP crystal

K. Fujioka; S. Matsuo; T. Kanabe; H. Fujita; M. Nakatsuka

1997-01-01

391

Nonlinear-optical brain anatomy by harmonic-generation and coherent Raman microscopy on a compact femtosecond laser platform  

NASA Astrophysics Data System (ADS)

An extended-cavity Cr:forsterite laser is integrated with a photonic-crystal fiber soliton frequency shifter and a periodically poled lithium niobate spectrum compressor for simultaneous harmonic-generation and coherent Raman brain imaging. Adapting the laser beam focusing geometry to the tissue morphology is shown to enable complementarity enhancement in tissue imaging by second- and third-harmonic generation, as well as coherent Raman scattering, facilitating quantitative image analysis.

Doronina-Amitonova, Lyubov V.; Lanin, Aleksandr A.; Ivashkina, Olga I.; Zots, Marina A.; Fedotov, Andrei B.; Anokhin, Konstantin V.; Zheltikov, Aleksei M.

2011-12-01

392

Improvement of Input Current Waveform for Soft-Switching Boost DCM Converter with Unity Power Factor  

NASA Astrophysics Data System (ADS)

In this paper, a soft-switching discontinuous mode (DCM) power factor corrected (PFC) converter is analyzed by applying the double Fourier series expansion. It is found that the fundamental component and higher-order harmonics included in the input current waveform are obtained by the Fourier series expansion of the mean value of the inductor current. From the theoretical analysis, a new method removing the distortion of the input current waveform is proposed. In spite of an open loop system, the proposed method makes a great improvement of the total harmonic distortion even if the ratio of output voltage to input voltage is very low.

Taniguchi, Katsunori; Morizane, Toshimitsu; Kimura, Noriyuki

393

Matrix converters: a technology review  

Microsoft Academic Search

The matrix converter is an array of controlled semiconductor switches that connects directly the three-phase source to the three-phase load. This converter has several attractive features that have been investigated in the last two decades. In the last few years, an increase in research work has been observed, bringing this topology closer to the industrial application. This paper presents the

Patrick W. Wheeler; José Rodríguez; Jon C. Clare; Lee Empringham; Alejandro Weinstein

2002-01-01

394

Thyristor converter simulation and analysis  

NASA Astrophysics Data System (ADS)

In this paper we present a simulation on thyristor converters. The simulation features nonlinearity, non-uniform firing, and the commutations. Several applications such as a current regulation, a converter frequency characteristics analysis, and a power line disturbance analysis will be presented.

Zhang, S. Y.

1991-05-01

395

The Angiotensin I Converting Enzyme.  

National Technical Information Service (NTIS)

The angiotensin I converting enzyme (kininase II; peptidyl dipeptidase; EC 3.4. 15.1) has a dual function: it converts angiotensin I to angiotensin II and it inactivates bradykinin. Lung, kidney, guinea pig plasma and testicles are among the richest sourc...

E. G. Erdos

1977-01-01

396

High Efficiency Flyback Converter Technology  

Microsoft Academic Search

Technologies are discussed to realize a DC\\/DC Flyback converter with high power conversion efficiency. The focus is on efficiency because of its high value in the application to process electricity generated by photovoltaic modules. Experiments with a 200 W active-clamped bidirectional Flyback converter prototype demonstrate power train efficiencies above 90% between 10% and 100% of the rated power and peak

U. Boeke

2007-01-01

397

Broadband second harmonic generation in GaAs nanowires by femtosecond laser sources  

NASA Astrophysics Data System (ADS)

Nonlinear optical property of semiconductor nanowires plays a key role in nanoscale optoelectronics. In this paper, we demonstrate an excellent frequency converter based on GaAs nanowires (NWs), in which second harmonic generation (SHG) is excited by femtosecond lasers from 800 nm to 1800 nm. Simultaneous SHG with a bandwidth of 300-nm is excited by a super-continuum source at 1000-1600 nm. Broadband SHG can also be acquired from an isolated single NW and the process is coherent. The experimental results suggest that GaAs NWs are potential broadband optical nonlinear converters in nanoscale optoelectronics.

He, Hao; Zhang, Xiaoqing; Yan, Xin; Huang, Lili; Gu, Chenglin; Hu, Ming-lie; Zhang, Xia; Ren, Xiao min; Wang, Chingyue

2013-09-01

398

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

399

Converter-fed subsea motor drives  

SciTech Connect

A subsea adjustable-speed motor fed via a long cable in range of several tens of kilometers between the converter and the motor are analyzed by simulations. Due to resonance, one critical frequency range occurs where significant generation of harmonics from the inverter should be avoided. A voltage source inverter is more feasible than a current source inverter since it is easier to modify the output waveform in order to avoid resonance problems. The resistive voltage drop in the long cable reduces the air-gap torque of the motor particular at low frequencies. This causes a problem for the start-up of the motor due to stiction torque. A start-up strategy is envisaged which is a compromise between voltage boost, inverter current, and transformer core dimensions. In normal operation mode the inverter voltage is proportional to the frequency. An open speed lop is used which keeps the system stable for potential load variations. The results from a 1-MW full-scale system test are summarized.

Raad, R.O.; Raphael, H.B. [Statoil, Stavanger (Norway); Henriksen, T. [Norwegian Electric Power Research Inst., Trondheim (Norway); Hadler-Jacobsen, A. [Framo Engineering AS, Nesttun (Norway)

1996-09-01

400

Lowand high frequency harmonic reduction in a PWM inverter using dithered sigma-delta modulation  

Microsoft Academic Search

This paper presents the use of dithered sigma-delta modulation (??M) to mitigate low and high frequency harmonics of pulse-width modulated (PWM) inverters without increasing switching losses. A PWM bit stream generated by a 1 bit- 1st-order discrete ??M is converted into a continuous pulse train which controls the inverter operation. The minimum pulse width of the pulse train is strictly

Wonjin Cho; Edward J. Powers; Surya Santoso

2010-01-01

401

Control of 3-level shunt active power filter using harmonic selective controller  

Microsoft Academic Search

In this paper the control of 3-level shunt active power filter is proposed using frequency selective proportional plus multiple resonant controllers. The voltage source converter (VSC) is operated using ramp-comparison current control method. The method provides fixed switching frequency operation, and unipolar modulation of a control function yields three-level PWM output. The resonant controllers are tuned near the harmonic frequencies

Rajesh Gupta; Arindam Ghosh; Avinash Joshi

2006-01-01

402

Modeling of frequency doubling and tripling with converter refractive index spatial non-uniformities due to gravitational sag  

SciTech Connect

Accurate predictions of the performance of frequency conversion requires knowledge of the spatial variation of departures from the phase-matching condition in the converter crystals. This variation is caused by processes such as crystal growth and crystal surface finishing. Gravitational sag and mounting configurations also lead to deformation and stresses which cause spatially varying departures from the phase-matching condition. We have modeled the effect of gravitational forces on conversion efficiency performance of horizontal converter crystals and have shown for the NIF mounting configurations that gravity has very little effect on conversion efficiency. Keywords: Frequency conversion, ICF, Nonlinear optics, KDP crystals

De Yoreo, J J; Auerbach, J M; Barker, C E; Couture, S A; Eimerl, D; Hackel, L A; Hibbard, R L; Liou, L W; Norton, M; Wegner, P J

1998-08-03

403

GaN doped with beryllium--An effective light converter for white light emitting diodes  

NASA Astrophysics Data System (ADS)

So far, most of the studies on GaN doped with beryllium have mainly concentrated on possible p-type doping. Unfortunately, realization of p-type conductivity in such a way appeared to be very difficult. It seems, however, that bulk crystals doped with beryllium can be used as white light converters in the monolithic white light emitting diodes. To realize monolithic white light emitting diode, we used blue light emitting diodes and a single GaN:Be crystal as converter. High value of the Color Rendering Index gives hope for obtaining an effective light converter based on gallium nitride doped with beryllium.

Teisseyre, Henryk; Bockowski, Michal; Grzegory, Izabella; Kozanecki, Adrian; Damilano, Benjamin; Zhydachevskii, Yaroslav; Kunzer, Michael; Holc, Katarzyna; Schwarz, Ulrich T.

2013-07-01

404

Harmonic analysis of Fermilab main ring quadrupoles  

SciTech Connect

The Main Ring Quadrupoles have been used in the Fermilab Main Ring and will be utilized in the proposed Fermilab Main Injector. Utilizing a rotating coil harmonic measurement system, a sample of more than 35 Fermilab Main Ring Quadrupoles have been measured. The asymmetric design of these magnets provides many easily measured harmonic coefficients. Results for harmonic coefficients at various excitation levels are presented. 5 refs., 3 figs., 1 tab.

Brown, B.C.; Mazur, P.O.; Ostiguy, J.F.; Pruss, S.M.; Turkot, F.

1991-05-01

405

Deriving projective hyperspace from harmonic  

SciTech Connect

We derive actions for projective N=2 superspace ('hyperspace') from those for harmonic hyperspace, including that for non-Abelian Yang-Mills theory (a new result). The method uses Wick rotation of the sphere from complex conjugate coordinates to real, null ones, which can be treated as independent. The result can be considered 'holographic' in that the dimension of the internal (R symmetry) space is reduced from 2 to 1, by solving equations of motion or gauge conditions for dependence on the other coordinate. The auxiliary nature of the redundant dimension makes the hypergraph rules and evaluation almost identical.

Jain, Dharmesh; Siegel, Warren [C. N. Yang Institute for Theoretical Physics, State University of New York, Stony Brook, New York 11794-3840 (United States)

2009-08-15

406

Making space for harmonic oscillators  

SciTech Connect

If we restrict the number of harmonic oscillator energy eigenstates to some finite value, N, then the discrete spectrum of the corresponding position operator comprise the roots of the Hermite polynomial H{sub N+1}. Its range is just large enough to accommodate classical motion at high energy. A negative energy term must be added to the Hamiltonian which affects only the last eigenstate, |N>, suggesting it is concentrated at the extrema of this finite ''space''. Calculations support a conjecture that, in the limit of large N, the global distribution of points approaches the differential form for classical action.

Michelotti, Leo; /Fermilab

2004-11-01

407

Deriving projective hyperspace from harmonic  

NASA Astrophysics Data System (ADS)

We derive actions for projective N=2 superspace (“hyperspace”) from those for harmonic hyperspace, including that for non-Abelian Yang-Mills theory (a new result). The method uses Wick rotation of the sphere from complex conjugate coordinates to real, null ones, which can be treated as independent. The result can be considered “holographic” in that the dimension of the internal (R symmetry) space is reduced from 2 to 1, by solving equations of motion or gauge conditions for dependence on the other coordinate. The auxiliary nature of the redundant dimension makes the hypergraph rules and evaluation almost identical.

Jain, Dharmesh; Siegel, Warren

2009-08-01

408

Comment on: The Magnus expansion for the harmonically driven harmonic oscillator  

Microsoft Academic Search

The exponential time-evolution operator for the harmonically driven harmonic oscillator is exactly obtained from the equations of motion for the coordinate and momentum in the Heisenberg representation. The convergence of the Magnus expansion is discussed.

Francisco M. Ferna´ndez

1988-01-01

409

Scintillation gamma Spectrometry with a Stilbene Crystal.  

National Technical Information Service (NTIS)

A method of converting apparatus for amplitude dispersion to energy dispersion of gamma quanta measured with a single stilbene crystal gamma spectrometer is described. One of the main advantages of this spectrometer is the possibility of practically simul...

Y. I. Kolevatov V. I. Kukhtevich I. V. Goryachev

1969-01-01

410

Measurement of harmonic currents and evaluation of the dc filter performance of the New England - Hydro-Quebec Phase I HVDC Project  

SciTech Connect

Measurements of harmonic currents in the New England-Hydro-Quebec Phase I HVDC Project de transmission line are presented in this paper. Measurements were conducted to determine the cause of increased telephone interference and to evaluate the dc filter performance. The measurements revealed unexpected high levels of 3-pulse harmonic currents in the dc pole conductors. The cause is attributed to imbalances within the 6-pulse bridges caused by the converter transformer and valve stray capacitances to ground. The conventional model of the converter power circuit used as the basis for the dc filter design does not reproduce the measured 3-pulse harmonics. Modification to this model is required to account for the effect of the converter transformer and valve stray capacitances to ground.

Garrity, T.F.; Hassan, I.D.; Donahue, J.A.

1989-01-01

411

Monochromator harmonic content measurements and calculations at energies above 20 keV  

SciTech Connect

Measurements of the harmonic content from single and double crystal silicon monochromators have been made in the 20 to 100 keV at the X17 Superconducting Wiggler Beamline at the NSLS. These measurements are compared with calculations which estimate the monochromatic beam harmonic content and the detection system efficiency with good agreement. At high photon energies ( > 20keV), the scattering of x-rays from an amorphous scatterer is dominated by the inelastic Compton process. At large scattering angles this will completely overwhelm the more forward directed elastic scattering. The Compton x-ray energy shift is large enough to make the distinction between elastic and Compton scattering unambiguous when a spectrum is acquired with a solid state detector. This shift, which is energy dependent, allows the measurement of the relative harmonic intensity in a way that is not affected by pulse pileup in the detector and electronics. The present measurements were done to assess the level of harmonic contamination from two monochromator systems both used on the X17 beamline: the single crystal type monochromator for the Digital Subtraction Coronary Angiography project; and the double crystal monochromator being developed for the Multiple Energy Computed Tomography (MECT) project and the Materials Science program. 5 refs.

Chapman, D.; Moulin, H.; Garrett, R.F.

1991-01-01

412

Generalized Techniques of Harmonic Elimination and Voltage Control in Thyristor Inverters: Part I--Harmonic Elimination  

Microsoft Academic Search

This paper considers the theoretical problem of eliminating harmonics in inverter-output waveforms. Generalized methods are developed for eliminating a fixed number of harmonics in the half-bridge and full-bridge inverter-output waveforms, and solutions are presented for eliminating up to five harmonics. Numerical techniques are applied to solve the nonlinear equations of the problem on the computer. The uneliminated higher order harmonics

HASMUKH S. PATELAND; Richard G. Hoft

1973-01-01

413

The current state of accounting harmonization: impediments to and benefits from harmonization  

Microsoft Academic Search

Although the EU has made progress towards harmonization of accounting law, this cannot hide the fact that the harmonization of the financial accounting information across Europe, through the accounting directives did not reach the intended level of comparability and transparency. Through the adoption of IFRS a higher level of harmonization has been pursued. Up to the present, the implementation of

V. VANSTEEGER

2005-01-01

414

Hybrid LCI\\/VSI Power Circuit—A Universal High-Power Converter Solution for Wound Field Synchronous Motor Drives  

Microsoft Academic Search

Load commutated inverter (LCI)-fed wound field synchronous motor drives are used for medium-voltage high- power drive applications. This drive suffers from drawbacks such as complex starting procedure, sixth harmonic torque pulsations, quasi square wave motor current, notches in the terminal voltages, etc. In this paper, a hybrid converter circuit, consisting of an LCI and a voltage source inverter (VSI), is

Amit Kumar Jain; V. T. Ranganathan

2011-01-01

415

High power GTO AC\\/DC current source converter with minimum switching frequency and maximum power factor  

Microsoft Academic Search

This paper presents a unique PWM switching pattern and a novel power factor control scheme for high power GTO AC\\/DC converters. This switching pattern has a switching frequency of 360 Hz, which is the lowest possible frequency to achieve 5th and 7th harmonic elimination and an adjustable DC output current simultaneously. Using both feedback and feedforward control techniques, the proposed

Y. Xiao; B. Wu; F. DeWinter; R. Sotudeh

1996-01-01

416

Mapping of the organization of p-nitroaniline in SAPO-5 by second-harmonic generation microscopy.  

PubMed

Second-harmonic generation microscopy (SHGM) has been employed to study crystals of zeolite-like material SAPO-5 filled with p-nitroaniline (PNA). The SHG and 2-photon fluorescence response of PNA in the one-dimensional channels readily reveals the pore accessibility; intergrown crystallites containing hexagonal pyramidal components and internal diffusion barriers are found next to seemingly perfect crystals. The sensitivity of second-harmonic generation to molecular orientation allowed for mapping of the domains of differently organized PNA. Dense domains of highly aligned PNA alternate with dilute zones with loosely aligned PNA. PMID:20714583

van der Veen, Monique A; Van Noyen, Jasper; Sels, Bert F; Jacobs, Pierre A; Verbiest, Thierry; De Vos, Dirk E

2010-08-16

417

Highly efficient second-harmonic generation of intense femtosecond pulses with a significant effect of cubic nonlinearity  

SciTech Connect

A highly efficient (73%) second-harmonic generation of femtosecond pulses in a 1-mm-thick KDP crystal at a fundamentalharmonic peak intensity of 2 TW cm{sup -2} has been demonstrated experimentally. In a 0.5-mm-thick KDP crystal, a 50% efficiency has been reached at a peak intensity of 3.5 TW cm{sup -2}. We examine the key factors that limit the conversion efficiency and present numerical simulation results on further temporal compression of second-harmonic pulses.

Mironov, S Yu; Ginzburg, V N; Lozhkarev, V V; Luchinin, G A; Kirsanov, Aleksei V; Yakovlev, I V; Khazanov, Efim A; Shaykin, A A [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod (Russian Federation)

2011-11-30

418

Bidirectional control of inverse KY converter  

Microsoft Academic Search

An inverse KY converter, derived from the KY converter, is proposed herein. And such a converter can be used as a bidirectional converter, whose operating modes are classified into two modes. One is the buck mode and the other is the boost mode. This converter can operate stably between these two modes. In this paper, the detailed illustration of the

K. I. Hwu; Y. H. Chen

2009-01-01

419

A Multichannel Airborne Coding Converter.  

National Technical Information Service (NTIS)

The paper describes an eight-channel aircraft coding converter designed for conversion of signals from transducers sensing pulsation meteorological parameters to a form suitable for subsequent magnetic recording. (Author)

N. K. Vinnichenko G. N. Shur

1967-01-01

420

Thermionic-photovoltaic energy converter  

SciTech Connect

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 galium arsenide photovoltaic cell having bandgap energies in this same wavelength region for optimum cell efficiency.

Chubb, D. L.

1985-07-09

421

Radiation tolerant power converter controls  

NASA Astrophysics Data System (ADS)

The Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) is the world's most powerful particle collider. The LHC has several thousand magnets, both warm and super-conducting, which are supplied with current by power converters. Each converter is controlled by a purpose-built electronic module called a Function Generator Controller (FGC). The FGC allows remote control of the power converter and forms the central part of a closed-loop control system where the power converter voltage is set, based on the converter output current and magnet-circuit characteristics. Some power converters and FGCs are located in areas which are exposed to beam-induced radiation. There are numerous radiation induced effects, some of which lead to a loss of control of the power converter, having a direct impact upon the accelerator's availability. Following the first long shut down (LS1), the LHC will be able to run with higher intensity beams and higher beam energy. This is expected to lead to significantly increased radiation induced effects in materials close to the accelerator, including the FGC. Recent radiation tests indicate that the current FGC would not be sufficiently reliable. A so-called FGClite is being designed to work reliably in the radiation environment in the post-LS1 era. This paper outlines the concepts of power converter controls for machines such as the LHC, introduces the risks related to radiation and a radiation tolerant project flow. The FGClite is then described, with its key concepts and challenges: aiming for high reliability in a radiation field.

Todd, B.; Dinius, A.; King, Q.; Uznanski, S.

2012-11-01

422

Harmonic considerations for electrical distribution feeders  

NASA Astrophysics Data System (ADS)

Harmonics on the electric power distribution system can cause motor overheating, capacitor failures,watt-hour meter error, and relay malfunctions. The degree of problems caused by harmonics is greatly dependent on the characteristics of the distribution feeder, which can absorb a considerable percentage of its capacity in harmonic currents without ill effects. However, power factor correction capacitors can cause resonances near harmonic voltages that can result in intolerable distortion. Both motor loads and resistive loads can decrease the effect of resonance significantly. This report describes useful techniques to analyze, suppress, and measure harmonics on distribution feeders. Applicable areas for manual analysis and computer analysis are explained. The basic formulae are presented as well as sophisticated computer methods. Emphasis is placed on the fundamental principle. Models of harmonic-producing devices are presented and their limitations discussed. Most distribution feeder harmonics analyses can be performed using simple current source models. Filtering of specific loads and general, dispersed load is discussed. The fundamental principle in filtering distribution feeders is to shorten the harmonic current path. 3-dimensional plots enhance the understanding of the filtering action. Equipment and procedures for making measurements are described.

1988-03-01

423

High harmonic currents in fluorescent lamp circuits  

Microsoft Academic Search

Some formulae associated with the percentage of high harmonics in the current in fluorescent lamp fixtures are derived for the cases of L and LC ballasts. The third harmonic is analyzed most carefully, and the theoretically predicted values are compared with those found experimentally. The agreement appears to be quite satisfactory. To meet the requirement of a standard, the power

EMANUEL GLUSKIN

1990-01-01

424

The Harmonic Series Diverges Again and Again  

ERIC Educational Resources Information Center

The harmonic series is one of the most celebrated infinite series of mathematics. A quick glance at a variety of modern calculus textbooks reveals that there are two very popular proofs of the divergence of the harmonic series. In this article, the authors survey these popular proofs along with many other proofs that are equally simple and…

Kifowit, Steven J.; Stamps, Terra A.

2006-01-01

425

Harmonic management in mv distribution systems  

Microsoft Academic Search

With many distribution customer loads being sensitive to excessive harmonic voltage distortion, electricity distribution network service providers should now be looking towards preventative measures to ensure that voltage distortion levels remain within limits set by the appropriate standards. Measures will need to be taken at the planning stage to ensure distribution systems are able to meet harmonic limits recommended by

Duane Robinson

2003-01-01

426

Harmonic Radar Literature Harmonisk Radar - en Litteraturstudie.  

National Technical Information Service (NTIS)

A harmonic radar sends on a given frequency f sub o and receives on another frequency usually 3 f sub o. The overtone is generated on joints between the metal parts of the radar target. The generated high harmonic frequency is very weak, which is why this...

B. Jansson

1980-01-01

427

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

428

Lattice Vibrations and Harmonic Forces in Solids  

Microsoft Academic Search

A discussion is given of the interpretation in terms of harmonic forces between atoms of the phonon frequency against wave vector data which is provided by the results of both X-ray and neutron scattering experiments. A knowledge of the phonon polarization vectors is required before a calculation of the components of the interatomic harmonic force tensors between all neighbour atom

A J E Foreman; W M Lomer

1957-01-01

429

Dynamics and control of instrumented harmonic drives.  

PubMed

Since torque in harmonic drives is transmitted by a pure couple, harmonic drives do not generate radial forces and therefore can be instrumented with torque sensors without interference from radial forces. The installation of torque sensors on the stationary component of harmonic drives (the Flexipline cup in this research work) produce backdrivability needed for robotic and telerobotic compliant maneuvers. Backdrivability of a harmonic drive, when used as torque increaser, means that the output shaft can be rotated via finite amount of torque. A high ratio harmonic drive is non-backdrivable because its output shaft cannot be turned by applying a torque on it. This article first develops the dynamic behavior of a harmonic drive, in particular the non-backdrivability, in terms of a sensitivity transfer function. The instrumentation of the harmonic drive with torque sensor is then described. This leads to a description of the control architecture which allows modulation of the sensitivity transfer function within the limits established by the closed-loop stability. A set of experiments on an active hand controller, powered by a DC motor coupled to an instrumented harmonic drive, is given to exhibit this method's limitations. PMID:11540398

Kazerooni, H

1995-03-01

430

Representation Discovery in Planning using Harmonic Analysis  

Microsoft Academic Search

This paper summarizes ongoing research on a frame- work for representation learning using harmonic analy- sis, a subeld of mathematics. Harmonic analysis in- cludes Fourier analysis, where new eigenvector rep- resentations are constructed by diagonalization of op- erators, and wavelet analysis, where new representa- tions are constructed by dilation. The approach is pre- sented specically in the context of Markov

Jeff Johns; Sarah Osentoski; Sridhar Mahadevan

431

The Not-So-Simple Harmonic Oscillator  

Microsoft Academic Search

The study of simple harmonic oscillators is a staple of physics courses and laboratories at the introductory level. We consider a system consisting of a vertical spring with a suspended mass. One typical laboratory experiment is the demonstration of Hooke's law using static measurements of extension vs. force. Another is the demonstration of simple harmonic motion using dynamic measurements of

William Sears; G. Whitmore Hancock

2007-01-01

432

Harmonic considerations for electrical distribution feeders  

SciTech Connect

Harmonics on the electric power distribution system can cause motor overheating, capacitor failures, watthour meter error, and relay malfunctions. The degree of problems caused by harmonics is greatly dependent on the characteristics of the distribution feeder. A typical distribution feeder can absorb a considerable percentage of its capacity in harmonic currents without ill effects. However, power factor correction capacitors can cause resonances near harmonic voltages that can result in intolerable distortion. Both motor loads and resistive loads can decrease the effet of resonance significatnly. This report describes useful techniques to analyze, suppress, and measure harmonics on distribution feeders. Applicable areas for manual analysis and computer analysis are explained. The basic formulae are presented as well as sophisticated omputer methods. Emphasis is placed on the fundamental principle. Models of harmonic-producing devices are presented and their limitations discussed. Most distribution feeder harmonics analyses can be performed using simple current source models. Filtering of specific loads and general, dispersed load is discussed. The fundamental principle in filtering distribution feeders is to shorten the harmonic current path. 3-dimensional plots enhance the understanding of the filtering action. Equipment and procedures for making measurements are described.

Not Available

1988-03-01

433

Annular symmetry nonlinear frequency converters.  

PubMed

We present a new type of two-dimensional nonlinear structure for quasi-phase matching. This structure has continuous rotational symmetry, and in contrary to the commonly used periodic structures, is not lattice shaped and has no translation symmetry. It is shown that this annular symmetry structure possesses interesting phase matching attributes that are significantly different than those of periodic structures. In particular, it enables simultaneous phase-matched frequency doubling of the same pump into several different directions. Moreover, it has extremely wide phase-mismatch tolerance, since a change in the phase matching conditions does not change the second harmonic power, but only changes its propagation direction. Several structures were fabricated using either the indirect e-beam method in LiNbO(3) or the electric field poling method in stoichiometric LiTaO(3), and their conversion efficiencies, as well as angular and thermal dependencies, were characterized by second harmonic generation. PMID:19529321

Kasimov, Dror; Arie, Ady; Winebrand, Emil; Rosenman, Gil; Bruner, Ariel; Shaier, Pnina; Eger, David

2006-10-01

434

Destructive interference of high harmonics generated in mixed gases  

Microsoft Academic Search

We demonstrate destructive interference of high harmonics generated in a He-Ne mixed gas, which offers novel methods for observing the underlying attosecond electron dynamics as well as shaping harmonic pulses and measuring harmonic phases.

Tsuneto Kanai; Eiji J. Takahashi; Yasuo Nabekawa; Katsumi Midorikawa

2007-01-01

435

Digital current control of a voltage source converter with active damping of LCL resonance  

Microsoft Academic Search

LCL filters installed at converter outputs offer higher harmonic attenuation than L-filters but careful design is required to damp LCL resonance, which can cause poorly damped oscillations and even instability. A new topology is presented for a discrete-time current controller which damps this resonance, combining deadbeat current control with optimal state-feedback pole assignment. By separating the state feedback gains into

Eric Wu; Peter W. Lehn

2005-01-01

436

Digital Current Control of a Voltage Source Converter With Active Damping of LCL Resonance  

Microsoft Academic Search

Inductance-capacitor-inductance (LCL)-filters installed at converter outputs offer higher harmonic attenuation than L-filters, but careful design is required to damp LCL resonance, which can cause poorly damped oscillations and even instability. A new topology is presented for a discrete-time current controller which damps this resonance, combining deadbeat current control with optimal state-feedback pole assignment. By separating the state feedback gains into

Eric Wu; Peter W. Lehn

2006-01-01

437

Programmed pulsewidth modulated waveforms for electromagnetic interference mitigation in DC-DC converters  

Microsoft Academic Search

The regular switching action of a pulse-width-modulated (PWM) circuit generates conducted and radiated electromagnetic interference (EMI) and may also generate acoustical disturbances. Programmed pulsewidth modulation techniques have been applied using various methods to control harmonics inherent in switched power circuits. A method for generating an optimal programmed switching waveform for a DC-DC converter is presented. This switching waveform is optimized

Andrew C. Wang; Seth R. Sanders

1993-01-01

438

New control scheme for AC-DC-AC converter without DC link electrolytic capacitor  

Microsoft Academic Search

A novel concept for a static three-phase to three-phase power converter for an AC motor drive with unity power factor and reduced harmonics on the utility line is presented. The power circuit consists of two back-to-back connected six-pulse bridges having only a 5-?F ceramic capacitor in the DC link. By controlling the active power balance between two bridges, the DC

J. S. Kim; S. K. Sul

1993-01-01

439

Natural Capacitor Voltage Balancing for a Flying Capacitor Converter Induction Motor Drive  

Microsoft Academic Search

This paper presents an analysis of the natural voltage balancing dynamics of a three-phase flying capacitor converter when supplying an induction motor. The approach substitutes double Fourier harmonic series for the pulsewidth modulation switching waveforms and the frequency response of the motor, to create a linear state-space model of this type of load. The model requires the mid-frequency response (500

Brendan Peter McGrath; Donald Grahame Holmes

2009-01-01

440

Echo-Enabled Harmonic Generation for Seeded FELs  

SciTech Connect

In the x-ray wavelengths, the two leading FEL concepts are the self-amplified spontaneous emission (SASE) configuration and the high-gain harmonic generation (HGHG) scheme. While the radiation from a SASE FEL is coherent transversely, it typically has rather limited temporal coherence. Alternatively, the HGHG scheme allows generation of fully coherent radiation by up-converting the frequency of a high-power seed laser. However, due to the relatively low up-frequency conversion efficiency, multiple stages of HGHG FEL are needed in order to generate x-rays from a UV laser. The up-frequency conversion efficiency can be greatly improved with the recently proposed echo-enabled harmonic generation (EEHG) technique. In this work we will present the concept of EEHG, and address some practically important issues that affect the performance of the seeding. We show how the EEHG can be incorporated in the FEL scheme and what is the expected performance of the EEHG seeded FEL. We will then briefly describe the first proof-of-principle EEHG experiment carried out at the Next Linear Collider Test Accelerator (NLCTA) at SLAC. We will also discuss latest advances in the echo-scheme approach, and refer to subsequent modifications of the original concept.

Stupakov, G.; /SLAC

2011-05-19

441

High-harmonic spectroscopy of molecular isomers  

NASA Astrophysics Data System (ADS)

We demonstrate that high-order-harmonic generation (HHG) spectroscopy can be used to probe stereoisomers of randomly oriented 1,2-dichloroethylene (C2H2Cl2) and 2-butene (C4H8). The high-harmonic spectra of these isomers are distinguishable over a range of laser intensities and wavelengths. Time-dependent numerical calculations of angle-dependent ionization yields for 1,2-dichloroethylene suggest that the harmonic spectra of molecular isomers reflect differences in their strong-field ionization. The subcycle ionization yields for the cis isomer are an order of magnitude higher than those for the trans isomer. The sensitivity in discrimination of the harmonic spectra of cis- and trans- isomers is greater than 8 and 5 for 1,2-dichloroethylene and 2-butene, respectively. We show that HHG spectroscopy cannot differentiate the harmonic spectra of the two enantiomers of the chiral molecule propylene oxide (C3H6O).

Wong, M. C. H.; Brichta, J.-P.; Spanner, M.; Patchkovskii, S.; Bhardwaj, V. R.

2011-11-01

442

Nano-antenna-assisted harmonic generation  

NASA Astrophysics Data System (ADS)

We report on low-order harmonic generation utilising the plasmonic field enhancement in arrays of rod-type gold optical antennae. Furthermore, we examine their suitability to support high-order harmonic generation (HHG). The low-order harmonics are used as a tool to investigate the nonlinear properties of the antennae. Particular attention is paid to the thermal properties, which become significant at the peak intensities necessary for HHG. A theoretical model explains the experimental findings and enables future improvements. In experiments we observe up to the fifth harmonic order and measure a field enhancement sufficient to support high-order harmonic generation. Moreover, we find a damage threshold for the antennae.

Pfullmann, Nils; Waltermann, Christian; Kova?ev, Milutin; Knittel, Vanessa; Bratschitsch, Rudolf; Akemeier, Dieter; Hütten, Andreas; Leitenstorfer, Alfred; Morgner, Uwe

2013-07-01

443

Digitally corrected multi-bit ?? data converters  

Microsoft Academic Search

?? data converters using multibit internal A\\/D and D\\/A converters (noise-shaping converters) have lower quantization noise and are more stable than the usual single-bit systems. However, the required linearity of the internal multibit digital-to-analog converter (DAC) is very difficult to achieve for an untrimmed integrated converter. A description is given of several novel multibit ?? converters which use digital correction

T. Cataltepe; A. R. Kramer; L. E. Larson; G. C. Temes; R. H. Walden

1989-01-01

444

Power converters and amplifiers (review of \\  

Microsoft Academic Search

This book is a comprehensive textbook in the areas of electrical, electronics, and telecommunications engineering. It consists of 17 chapters and two appendices. Some of the topics covered include: buck PWM DC-DC converters; boost PWM DC-DC converters; buck-boost-PWM DC-DC converters; half-bridge and full-bridge converters; push-pull PWM DC-DC converters; open-loop small-signal characteristics of boost converters for CCM; current-mode control of boost

Marian Kazmierkowski

2009-01-01

445

High Efficiency RFID UHF Power Converter  

Microsoft Academic Search

The paper proposes a high efficiency RFID UHF power converter unit to overcome the low efficiency problem. This power converter is mainly composed of an RF-DC converter and a DC-DC converter. In order to overcome the low efficiency problem in low current consuming condition, a DC-DC converter is added to conventional single RF-DC converter rectifier to increase the rectifying efficiency

Zhou Shenghua; Yang Zhichao; Wu Nanjian

2006-01-01

446

Constraining topology in harmonic space  

SciTech Connect

We consider several ways to test for topology directly in harmonic space by comparing the measured a{sub lm} with the expected correlation matrices. Two tests are of a frequentist nature while we compute the Bayesian evidence as the third test. Using correlation matrices for cubic and slab-space tori, we study how these tests behave as a function of the minimal scale probed and as a function of the size of the Universe. We also apply them to different first-year Wilkinson microwave anisotropy probe CMB maps and confirm that the Universe is compatible with being infinitely big for the cases considered. We argue that there is an information theoretical limit (given by the Kullback-Leibler divergence) on the size of the topologies that can be detected.

Kunz, M. [Departement de Physique Theorique, Universite de Geneve, 24 quai Ernest Ansermet, CH-1211 Geneva 4 (Switzerland); Astronomy Centre, SciTech, University of Sussex, Brighton BN1 9QJ (United Kingdom); Aghanim, N.; Forni, O. [Institut d'Astrophysique Spatiale (IAS), Batiment 121, F-91405, Orsay (France); Universite Paris-Sud 11 et CNRS, UMR 8617 (France); Cayon, L. [Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, Indiana 47907-2036 (United States); Riazuelo, A.; Uzan, J. P. [Institut d'Astrophysique de Paris, Universite Pierre et Marie Curie, Paris VI, 98 bis bd Arago, 75014 Paris (France)

2006-01-15

447

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

448

Efficient second harmonic conversion efficiency through one-dimensional coupled resonator poled nonlinear optical waveguide  

NASA Astrophysics Data System (ADS)

In this paper, the second harmonic generation in finite size one-dimensional coupled resonator poled nonlinear optical waveguide has been investigated. To calculate the conversion efficiency, fundamental and second harmonic wave propagation among two proposed structures, we use the transfer matrix method. In the designed nonlinear photonic crystal structure, the linear and nonlinear optical parameters are both periodically modulated, and thus the second harmonic generation efficiency can be several orders of magnitude larger than in a conventional quasi-phase-matched nonlinear structure with the same sample length. In fact, due to the presence of a photonic band gap in a slow wave system, the density of states of the electromagnetic fields is large at the photonic band edge and photonic defect modes, and thus the group velocity is small, and the local field is enhanced. All these factors contribute to significant enhancement of the nonlinear optical interactions.

Hamidi, S. M.; Parvini, T.; Tehranchi, M. M.

2013-05-01

449

Picosecond Internal Conversion in Crystal Violet.  

National Technical Information Service (NTIS)

On the basis of measurements made using the second harmonic of a mode-locked Nd(3+) laser, the authors demonstrate that the efficient quenching of the lowest excited singlet state in the dye, crystal violet involves rapid repopulation of the ground state ...

D. Magde M. W. Windsor

1973-01-01

450

Light generation in silicon photonic crystal cavities  

Microsoft Academic Search

Far-field optimized photonic crystal nanocavities are used to strongly increase light generation from crystalline silicon. Low-power continuous-wave harmonic generation as well as efficient room temperature light-emission from optically-active defects are demonstrated in these devices.

Matteo Galli; Liam O'Faolain; Dario Gerace; Roberto Lo Savio; Simone Luca Portalupi; Abdul Shakoor; Karl Welna; Lucio C. Andreani; Thomas F. Krauss; Alessia Irrera; Giorgia Franzo; Francesco Priolo

2011-01-01

451

Automotive catalytic converter exhaust system  

SciTech Connect

Disclosed is a vehicle exhaust system containing a three-way catalytic converter. An insulated flexible duct connects the outlet of the engine exhaust manifold with the inlet of the three-way catalytic converter to retain the exhaust engine gases at a temperature greater than the ignition temperature of the threeway catalyst in the catalytic converter. The insulated flexible duct is preferably made of an inner flexible metal conduit surrounded by fibrous insulation which in turn is surrounded on the outside by a second flexible metal conduit. The system is economical, contains no active elements which would require maintenance or could get out of order, is adaptable to motor vehicles of all types (especially automobiles, light trucks and vans) including those powered by either gasoline and diesel engines and entirely eliminates the need for expensive and complicated light-off catalysts in the system.

Pallo, J.M.; Previte, S.J.; Schafer, W.

1982-08-24

452

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

453

Harmonic Generation from Common Liquid Phase Systems  

NASA Astrophysics Data System (ADS)

Harmonic generation driven by the fundamental frequency of an intense laser field has been the subject of extensive studies in gas phase atomic and molecular systems. Exciting contributions from this diverse field of study include the production of attosecond (10E-18 s) pulses and molecular orbital tomography. Recently, there has been an interest in scaling strong field processes with wavelengths in the mid-infrared (MIR) region. An advantage is that harmonics of moderate order are transparent in air for driving fields in the MIR region. Here we present an experiment where this transparency is exploited to study the generation of harmonics from a liquid at room temperature. A wire guided fluid jet is used to create thin (100-150 microns) flowing samples of various fluids. The laser is a MIR optical parametric amplifier operating at a center wavelength of 3.6 microns with a repetition rate of 1 kHz, a peak pulse power over 700 MW and is focused to field intensities less than 10 terawatts per-square-centimeter. No evidence of supercontinuum generation is observed. Odd harmonics from samples of water, heavy water and several alcohols, including Isopropyl, are examined. For example, Isopropyl alcohol (water) generated up to the ninth (thirteenth) harmonic. For isopropyl the seventh harmonic is 130 times brighter and the overall efficiency of harmonic production is greater by two orders of magnitude as compared to water.

Dichiara, Anthony; Sistrunk, Emily; Miller, Terry; Agostini, Pierre; Dimauro, Lou

2009-05-01

454

Optical second harmonic generation properties of BiB3O6  

NASA Astrophysics Data System (ADS)

We present studies of the optical properties of the new nonlinear material BiB3O6 for second harmonic generation from the visible to infrared. We have determined the phase-matching conditions and effective nonlinear coefficients in the three principal optical planes, acceptance bandwidths, spatial and temporal walkoff, group velocity dispersion and double phase-matching behaviour. We also report on experimental studies in this material, where efficient, high-average-power second harmonic generation of femtosecond pulses into the blue is demonstrated. Using 130-fs fundamental pulses at 76 MHz, single-pass second harmonic average powers as much as 830 mW at greater than 50% conversion efficiency have been generated over a tunable range of 375-435 nm. Using cross-correlation measurements in a 100-?m ?-BaB2O4 crystal second harmonic pulse durations of 220 fs are obtained. Our theoretical findings are verified by experimental data, where excellent agreement between the calculations and measurements is obtained. Direct comparison of BiB3O6 with ?-BaB2O4 also confirms improved performance of this new material for second harmonic generation of femtosecond pulses.

Ghotbi, Masood; Ebrahim-Zadeh, M.

2004-11-01

455

Optical second harmonic generation properties of BiB3O6.  

PubMed

We present studies of the optical properties of the new nonlinear material BiB3O6 for second harmonic generation from the visible to infrared. We have determined the phase-matching conditions and effective nonlinear coefficients in the three principal optical planes, acceptance bandwidths, spatial and temporal walkoff, group velocity dispersion and double phase-matching behaviour. We also report on experimental studies in this material, where efficient, high-average-power second harmonic generation of femtosecond pulses into the blue is demonstrated. Using 130-fs fundamental pulses at 76 MHz, single-pass second harmonic average powers as much as 830 mW at greater than 50% conversion efficiency have been generated over a tunable range of 375-435 nm. Using cross-correlation measurements in a 100-mum beta-BaB2O4 crystal second harmonic pulse durations of 220 fs are obtained. Our theoretical findings are verified by experimental data, where excellent agreement between the calculations and measurements is obtained. Direct comparison of BiB3O6 with beta-BaB2O4 also confirms improved performance of this new material for second harmonic generation of femtosecond pulses. PMID:19488242

Ghotbi, Masood; Ebrahim-Zadeh, M

2004-11-29

456

XUV harmonic enhancement by magnetic fields  

SciTech Connect

We examine three ways to enhance harmonic output of an XUV planar free-electron laser (FEL) operating in the Compton regime. The first method is to increase the rms static magnetic field, making it as large as possible. The second is by adding effective magnetic fields at the harmonics, thereby increasing the coupling to the harmonics. The third is by phase programming; i.e. programming the magnetic field to introduce jumps in the phase of the electrons as they move through phase space.

Elliott, C.J.; Schmitt, M.J.

1986-09-01

457

Harmonics generated from a DC biased transformer  

SciTech Connect

The paper presents harmonic characteristics of transformer excitation currents under DC bias caused by geomagnetically induced currents (GIC). A newly developed saturation model of a single phase shell form transformer based on 3D finite element analysis is used to calculate the excitation currents. As a consequence, the complete variations of excitation current harmonics with respect to an extended range of GIC bias are revealed. The results of this study are useful in understanding transformers as harmonic sources and the impact on power systems during a solar magnetic disturbance.

Shu Lu; Yilu Liu; Ree, J. De La (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). The Bradley Dept. of Electrical Engineering)

1993-04-01

458

Topological constraints on basic PWM converters  

NASA Astrophysics Data System (ADS)

A modeling and synthesis technique is introduced for single-ended ladder-structured dc-dc converter topologies. Topological constraints are derived that enhance the understanding of structural properties of converter circuits and clarify the roles of inductors and capacitors in various converters using magnetic or capacitive energy storage/transfer mechanisms. The exact duality relationships among the basic converter topologies are established.

Liu, Kwang-Hwa; Lee, Fred C.

459

Multibeam second-harmonic generation by spatiotemporal shaping of femtosecond pulses.  

PubMed

We present a technique for efficient generation of the second-harmonic signal at several points of a nonlinear crystal simultaneously. Multispot operation is performed by using a diffractive optical element that splits the near-infrared light of a mode-locked Ti:sapphire laser into an arbitrary array of beams that are transformed into an array of foci at the nonlinear crystal. We show that, for pulse temporal durations under 100 fs, spatiotemporal shaping of the pulse is mandatory to overcome chromatic dispersion effects that spread both in space and time the foci showing a reduced peak intensity that prevents nonlinear phenomena. We experimentally demonstrate arbitrary irradiance patterns for the second-harmonic signal consisting of more than 100 spots with a multipass amplifier delivering 28 fs, 0.8 mJ pulses at 1 kHz repetition rate. PMID:22378451

Martínez-Cuenca, Raúl; Mendoza-Yero, Omel; Alonso, Benjamín; Sola, Íñigo Juan; Mínguez-Vega, Gladys; Lancis, Jesús

2012-03-01

460

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

461

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

462

Half-Bridge Type Immittance Converter  

NASA Astrophysics Data System (ADS)

The immittance converter has the input impedance that is proportional to the admittance of the load connected across output terminals. Therefore, in this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently, it converts a constant voltage source into a constant current source and a constant current source into a constant voltage source. In this paper, we propose a new type immittance converter, named half-bridge type immittance converter, consists of a tapped transformer and a pair of L, C. The new immittance converter is developed from the hybrid type immittance converter, and has almost same characteristics of that.

Irie, Hisaichi; Takayama, Nobuyuki

463

CONVERTING ABANDONED LANDS TO CROPLAND  

Technology Transfer Automated Retrieval System (TEKTRAN)

Because of economic conditions, areas of cropland in Ukraine have been left unused for several years. These abandoned lands are now infested with perennial weeds. Producers are interested in converting these lands back to cropland with no-till systems to preserve soil benefits gained by not tillin...

464

A novel interferometric wavelength converter  

Microsoft Academic Search

The fiber Kerr effect employment in a wavelength conversion version, owing to low silica nonlinearity, has been prevented by the lack of an efficient interferometric architecture. A novel all-fiber wavelength converter is presented and characterized. The proposed scheme while taking advantage of the Kerr effect properties in standard communication optical fiber overcomes classical interferometric structure limitations, such as high environmental

Pierpaolo Boffi; Lucia Marazzi; Mario Martinelli

1999-01-01

465

Tactical Data Converter Design Study.  

National Technical Information Service (NTIS)

The report contains the studies performed and the systems analysis used to provide design data necessary for construction of a tactically-oriented digital-to-video converter. This study was conducted in two parts: the first was an investigation into the v...

A. W. Brown A. B. Cohen G. G. Strohmeyer

1969-01-01

466

Sea water battery power converter  

Microsoft Academic Search

The invention converts the voltage output of a DC source to a higher voltage. A germanium transistor start-up circuit receives a DC supply voltage input and includes an astable multivibrator which produces a square wave voltage output that is transformed to a substantially DC steady-state voltage output by a transformer and a capacitor. This elevated voltage is provided to an

Russell E. Hammond; John L. Henry

1991-01-01

467

Harmonically forced enclosed swirling flow  

NASA Astrophysics Data System (ADS)

The response of steady state flows in a cylinder driven by a harmonically modulated rotating endwall is investigated experimentally and numerically. Three dynamic regimes are identified. For very low forcing frequency, the synchronous flow approaches quasi-static adjustment, and for very large forcing frequencies the oscillations are localized in the boundary layers on the cylinder. These localized wall oscillations drive the synchronous flow in the interior to the underlying axisymmetric steady basic state. The third regime occurs for forcing frequencies in the range of the most dangerous axisymmetric Hopf eigenfrequencies, with the 1:1 resonances leading to greatly enhanced oscillation amplitudes localized in the axis region where the flow manifests vortex breakdown recirculation zones. By comparing the spatio-temporal structure of the junction vortices produced by the modulations in this range of frequencies with the vorticity eigenfunctions responsible for the self-sustained oscillations in the unmodulated problem, we have identified the mechanism responsible for the large amplitude pulsations of the vortex breakdown recirculations on the axis at mean rotation rates well below critical for the self-sustained vortex breakdown oscillations. An important consequence of this study is that to achieve a strong resonant effect, it is not sufficient to only consider the temporal characteristics of the flow state, but that the imposed forcing must also match the spatial characteristics.

Lopez, J. M.; Marques, F.; Lim, T. T.; Cui, Y. D.

2008-11-01

468

Simultaneous femtosecond-pulsecompression and second-harmonic generationin aperiodically poled KTiOPO4  

Microsoft Academic Search

We report both extracavity and intracavity simultaneous second-harmonic generation and compression of pulses at 1.25 mm from a synchronously pumped RbTiOAsO4-based optical parametric oscillator, using an aperiodically poled crystal of KTiOPO4. The 290-fs input pulses were temporally compressed to 120 fs, with average output powers as great as 120 mW. The experimental results are compared with a numerical model that

P. Loza-Alvarez; D. T. Reid; P. Faller; M. Ebrahimzadeh; W. Sibbett; H. Karlsson; F. Laurell

1999-01-01

469

Limitation of second-harmonic generation of femtosecond Ti:sapphire laser pulses  

Microsoft Academic Search

The second-harmonic generation of 50-fs Ti:sapphire laser pulses in 1- and 2-mm KDP crystals at 350 mJ of incident energy is measured experimentally and analyzed theoretically. A frequency-conversion efficiency of ~40% is reached. The limiting influence of self-phase modulation and fundamental phase modulation is demonstrated. The deep modulation of a frequency-doubled spectrum at a high incident intensity is observed. Methods

Ildar A. Begishev; Mikhail Kalashnikov; Vladimir Karpov; Peter Nickles; Horst Schönnagel; Ilya A. Kulagin; Timurbek Usmanov

2004-01-01

470

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

471

Second-harmonic generation of femtosecond high-intensity Ti:sapphire laser pulses  

Microsoft Academic Search

The second-harmonic generation (SHG) of ultrashort Ti:sapphire laser pulses in potassium dihydrogen phosphate crystal in type-I phase-matching geometry has been investigated theoretically, including the effects of cubic nonlinearity. It is found that the phase mismatch due to the broad bandwidth associated with the short pulse width limits the maximum conversion efficiency to less than 60%, and the temporal shape of

Kurumi Mori; Yusuke Tamaki; Minoru Obara; Katsumi Midorikawa

1998-01-01

472

Propagation of second-harmonic wave in quasi-phase-matching nonlinear medium  

NASA Astrophysics Data System (ADS)

We studied the propagation of the second-harmonic (SH) wave in a quasi-phase-matching (QPM) medium with a slanted nonlinear grating. By solving the electromagnetic boundary value problem for the SH wave, we derived the propagation law for the SH wave, which can be interpreted as a diffraction phenomenon. Such interpretation was supported by a series of SH generation experiments with a periodically-poled lithium niobate crystal with a slanted QPM grating.

Choi, Hee Joo; Kim, Byoung Joo; Cha, Myoungsik

2013-05-01

473

Plasmonic grating as a nonlinear converter-coupler.  

PubMed

The paper introduces a wavelength converter composed of a metallic finite 2-dimensional particle grating on top of an optical waveguide. The particles sustain plasmonic resonances which will result in the near-field enhancement and therefore, high conversion efficiency. Due to near-field interaction of the grating field with the propagating modes of the waveguide, the generated third harmonic wave is phase-matched to a propagating mode of the waveguide, while the fundamental frequency component is not coupled into the output waveguide of the structure. The performance of this structure is numerically investigated using a full-wave transmission line method for the linear analysis and a three-dimensional finite-difference time-domain method for the nonlinear analysis. PMID:22274484

Talebi, Nahid; Shahabadi, Mahmoud; Khunsin, Worawut; Vogelgesang, Ralf

2012-01-16

474

Effects of geomagnetically-induced currents on HVDC converter operation  

SciTech Connect

Electrons and protons emitted by a solar flare can be captured by the Earth's magnetic field. The resulting transient in the geomagnetic field can produce quasi-dc currents in electric power systems. These geomagnetically-induced currents (GIC) in excess of 100 amps have been measured in the transformer neutral leads. With the practice of using EHV and UHV lines for transmitting ac power over long distances and because the systems are more solidly grounded, the problems posed by GIC have become more severe. This paper presents the consequences of transformer halfcycle saturation on the operation of HVDC converter terminals. A detailed computer simulation of the Square Butte HVDC system reveals that the large values of GIC can cause enough distortion in the ac system voltage at the inverter end to prevent normal system operation. Moreover, the amount of harmonics generated could overload the ac as well as the dc-side filters.

Mohan, N.; Albertson, V.D.; Bahrman, M.P.; Kappenman, K.G.; Speak, T.J.

1982-11-01

475

High order harmonic generation in rare gases.  

National Technical Information Service (NTIS)

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 lase...

K. S. Budil

1994-01-01

476

21 CFR 26.48 - Harmonization.  

Code of Federal Regulations, 2010 CFR

...HEALTH AND HUMAN SERVICES GENERAL MUTUAL RECOGNITION OF PHARMACEUTICAL GOOD MANUFACTURING PRACTICE REPORTS, MEDICAL DEVICE QUALITY...intend to continue to participate in the activities of the Global Harmonization Task Force (GHTF) and utilize the results...

2010-04-01

477

21 CFR 26.48 - Harmonization.  

Code of Federal Regulations, 2010 CFR

...HEALTH AND HUMAN SERVICES GENERAL MUTUAL RECOGNITION OF PHARMACEUTICAL GOOD MANUFACTURING PRACTICE REPORTS, MEDICAL DEVICE QUALITY...intend to continue to participate in the activities of the Global Harmonization Task Force (GHTF) and utilize the results...

2009-04-01

478

21 CFR 26.48 - Harmonization.  

Code of Federal Regulations, 2013 CFR

...HEALTH AND HUMAN SERVICES GENERAL MUTUAL RECOGNITION OF PHARMACEUTICAL GOOD MANUFACTURING PRACTICE REPORTS, MEDICAL DEVICE QUALITY...intend to continue to participate in the activities of the Global Harmonization Task Force (GHTF) and utilize the results...

2013-04-01

479

Geomagnetic local and regional harmonic analyses.  

USGS Publications Warehouse

Procedures are developed for using rectangular and cylindrical harmonic analyses in local and regional areas. Both the linear least squares analysis, applicable when component data are available, and the nonlinear least squares analysis, applicable when only total field data are available, are treated. When component data are available, it is advantageous to work with residual fields obtained by subtracting components derived from a harmonic potential from the observed components. When only total field intensity data are available, they must be used directly. Residual values cannot be used. Cylindrical harmonic analyses are indicated when fields tend toward cylindrical symmetry; otherwise, rectangular harmonic analyses will be more advantageous. Examples illustrating each type of analysis are given.-Author

Alldredge, L. R.

1982-01-01

480

Multisite EPR oximetry from multiple quadrature harmonics.  

PubMed

Multisite continuous wave (CW) electron paramagnetic resonance (EPR) oximetry using multiple quadrature field modulation harmonics is presented. First, a recently developed digital receiver is used to extract multiple harmonics of field modulated projection data. Second, a forward model is presented that relates the projection data to unknown parameters, including linewidth at each site. Third, a maximum likelihood estimator of unknown parameters is reported using an iterative algorithm capable of jointly processing multiple quadrature harmonics. The data modeling and processing are applicable for parametric lineshapes under nonsaturating conditions. Joint processing of multiple harmonics leads to 2-3-fold acceleration of EPR data acquisition. For demonstration in two spatial dimensions, both simulations and phantom studies on an L-band system are reported. PMID:22154283

Ahmad, R; Som, S; Johnson, D H; Zweier, J L; Kuppusamy, P; Potter, L C

2011-11-15

481

A Model for Generative Harmonic Dictation.  

National Technical Information Service (NTIS)

This BASIC computer program designed to help music theory students practice harmonic dictation generates examples for students to use in a drill and practice approach in developing aural skills. To facilitate the implementation of effective generative alg...

W. K. Bales

1980-01-01

482

Transformation of Real Spherical Harmonics under Rotations  

NASA Astrophysics Data System (ADS)

The algorithm rotating the real spherical harmonics is presented. The convenient and ready to use formulae for l = 0, 1, 2, 3 are listed. The rotation in R3 space is determined by the rotation axis and the rotation angle; the Euler angles are not used. The proposed algorithm consists of three steps. (i) Express the real spherical harmonics as the linear combination of canonical polynomials. (ii) Rotate the canonical polynomials. (iii) Express the rotated canonical polynomials as the linear combination of real spherical harmonics. Since the three step procedure can be treated as a superposition of rotations, the searched rotation matrix for real spherical harmonics is a product of three matrices. The explicit formulae of matrix elements are given for l = 0, 1, 2, 3, what corresponds to s, p, d, f atomic orbitals.

Romanowski, Z.; Krukowski, St.; Jalbout, A. F.

2008-08-01

483

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

484

Classical harmonic generation in rare gases  

SciTech Connect

The classical microcanonical ensemble approach to high-harmonic generation (HHG) in rare gases subjected to intense laser fields is studied. We show that the ensemble spectrum is a ''sampled'' version of the single trajectory spectrum. Unlike the radiation of the single ensemble member, the total ensemble radiation possesses all the basic HHG features: odd laser harmonics, plateau, and cutoff. The sampling theorem for uniform grids is used to explain why the ensemble spectrum can be computed accurately with a very small number of ensemble members compared to the Monte Carlo method. Furthermore, The phase space relevant to harmonic generation is found to be significantly smaller than the field free microcanonical ensemble. In addition we demonstrate the seeding effect that was predicted and observed in quantum simulation. For circular polarization, we verify that the harmonic generation is highly suppressed even when the argument of the three-step model does not apply. All the findings are numerically calculated for the xenon atom.

Uzdin, Raam; Moiseyev, Nimrod [Department of Physics, Technion, Israel Institute of Technology (Israel)

2010-06-15

485

Satellite Perturbations Due to Zonal Gravitational Harmonics.  

National Technical Information Service (NTIS)

Literal expressions for the first order pertubative effects on the orbital parameters of a satellite orbit due to zonal gravitational harmonics to the tenth degree were derived from the general equations of Kaula. Numerical values from these expressions w...

R. H. Rapp

1964-01-01

486

Harmonic Lasing Characterization at Jefferson Lab  

SciTech Connect

Harmonic lasing is normally suppressed because of lasing at the fundamental wavelength. It can, however, be achieved by using any of several methods that suppress fundamental lasing. In this paper we discuss two methods used at Jefferson Lab. The first is to use the characteristics of dielectric coatings to allow harmonic lasing at cavity lengths longer than the synchronous length for the fundamental. The second is to use a dielectric coating that has little reflectivity at the fundamental. This allows us to directly compare fundamental and harmonic lasing with the same optical resonator and electron beam. We present measurement carried out at Jefferson Lab using the IR Upgrade FEL operating at 0.53, 0.94, 1.04, 1.6, and 2.8 microns in which both schemes are used to produce lasing at both the 3rd and 5th harmonic of the fundamental.

Stephen Benson; Michelle D. Shinn

2006-08-27

487

Guidance for Industry: Harmonized Tariff Schedule Codes ...  

Center for Food Safety and Applied Nutrition (CFSAN)

... The Harmonized Tariff Schedule (HTS) codes listed in the table apply to prior notice submitted via the US Customs and Border Protection's (CBP's ... More results from www.fda.gov/food/guidanceregulation/guidancedocumentsregulatoryinformation

488

2. LOOKING NORTH ON COMMERCE ST. SHOWING HARMON MATTRESS FACTORY. ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. LOOKING NORTH ON COMMERCE ST. SHOWING HARMON MATTRESS FACTORY. BRIDGE CONNECTS HARMON MATTRESS FACTORY WITH HARMON WAREHOUSE (SEE PHOTO HABS WA-165-15). BUILDING IN LEFT FOREGROUND IS LINDSTROM-BERG CABINET FACTORY (SEE PHOTO HABS WA-165-36). - Union Depot Area Study, F. S. Harmon Mattress Company, 1953 South C Street, Tacoma, Pierce County, WA

489

Harmonic source and type identification in a radial distribution system  

Microsoft Academic Search

To aid in locating the source and type of harmonics in a distribution system, a computer program called HARM TRACER has been developed. HARM TRACER is a reverse harmonic power flow study program which traces the flow of harmonics in a radial distribution system from the point of measurement to the harmonic source or sources. It does so by considering

Asrat Teshome

1991-01-01

490

Harmonized strategy for breaking the striations in the fluorescent lamp  

Microsoft Academic Search

A harmonized strategy for breaking the striations in the fluorescent lamp is proposed. The harmonized circuit (HC) presented is a dependent current source and is used to modulate the lamp current by making the amplitudes of the even harmonics nearly the same as the neighboring odd harmonics. The time and frequency responses of the lamp current without and with HC

Guan-Chyun Hsieh; Chang-Hua Lin

2001-01-01

491

Harmonic Distortion Assessment and Minimization for Railway Systems  

Microsoft Academic Search

This article addresses the power quality issues in railway systems. It starts with a distributed parameter approach to the determination of the current and voltage harmonics along a railway feeder. For the assessment of the harmonic distortion, three global indices for the harmonic voltage, current, and power are suggested, which take into account the spatial harmonic distribution (up to the

Mohamed Saied; Meshal Al-Shaher

2009-01-01

492

Multi-Harmonic Cavities for Increasing RF Breakdown Threshold  

SciTech Connect

A multi-harmonic asymmetric cavity is predicted to sustain higher acceleration gradients than a conventional pillbox cavity, 55% higher in one example, when driven by external RF harmonic sources. Simulations of multi-harmonic excitation in such a cavity are described, either by a charged drive beam or by external RF sources. An accelerator structure based on multi-harmonic cavity is proposed.

Jiang, Y. [Beam Physics Laboratory, Yale University, 272 Whitney Ave., New Haven, CT 06511 (United States); Kazakov, S. Yu. [Omega-P, Inc., 258 Bradley St., New Haven, CT 06510 (United States); Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Kuzikov, S. V. [Omega-P, Inc., 258 Bradley St., New Haven, CT 06510 (United States); Institute of Applied Physics, Nizhny Novgorod (Russian Federation); Hirshfield, J. L. [Beam Physics Laboratory, Yale University, 272 Whitney Ave., New Haven, CT 06511 (United States); Omega-P, Inc., 258 Bradley St., New Haven, CT 06510 (United States)

2010-11-04

493

High-frequency harmonic imaging of the eye  

Microsoft Academic Search

Purpose: Harmonic imaging has become a well-established technique for ultrasonic imaging at fundamental frequencies of 10 MHz or less. Ophthalmology has benefited from the use of fundamentals of 20 MHz to 50 MHz. Our aim was to explore the ability to generate harmonics for this frequency range, and to generate harmonic images of the eye. Methods: The presence of harmonics

Ronald H. Silverman; D. Jackson Coleman; Jeffrey A. Ketterling; Frederic L. Lizzi

2005-01-01

494

Accounting harmonization in ASEAN: Benefits, models and policy issues  

Microsoft Academic Search

This paper addresses policy issues on the feasibility and prospects for accounting harmonization within ASEAN countries. It examines the benefits of harmonization for ASEAN countries and discusses issues related to the harmonization of both broad accounting aims as well as detailed accounting regulations within ASEAN. The paper examines institutional choices for pursuing regional harmonization and concludes with five policy recommendations

Joselito G. Diga

1998-01-01