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1

Active harmonic elimination for multilevel converters  

Microsoft Academic Search

This paper presents an active harmonic elimination method to eliminate any number of specific higher order harmonics of multilevel converters with equal or unequal dc voltages. First, resultant theory is applied to transcendental equations characterizing the harmonic content to eliminate low order harmonics and to determine switching angles for the fundamental frequency switching scheme and a unipolar switching scheme. Next,

Zhong Du; L. M. Tolbert; J. N. Chiasson

2006-01-01

2

Study of harmonic cancellation between AC\\/DC converter currents  

Microsoft Academic Search

In this paper, cancellation between the harmonic currents of AC\\/DC converters is analyzed. The converter behavior is univocally characterized by two normalized parameters, and therefore their influence on the harmonic current phase angles is studied. This study allows harmonic cancellation to be determined as a function of the normalized parameters. The results of the study suggest that harmonic cancellation is

L. Sainz; J. J. Mesas; S. Herraiz

2004-01-01

3

Harmonic elimination for multilevel converter with programmed PWM method  

Microsoft Academic Search

This work presents a programmed PWM method to eliminate specific higher order harmonics of multilevel converters. First, resultant theory is applied to transcendental equations to eliminate low order harmonics and to determine switching angles for the fundamental frequency switching techniques. Next the magnitudes and phases of the residual higher order harmonics are computed, generated, and subtracted from the original voltage

Zhong Du; Leon M. Tolbert; John N. Chiasson

2004-01-01

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

Eliminating harmonics in a multilevel converter using resultant theory  

Microsoft Academic Search

A method is given to determine conditions for which the switching angles in a multilevel converter can be chosen to produce the required fundamental voltage while at the same time cancel out higher order harmonics. A complete analysis is given for a 7- level converter where it is shown that for a range of the modulation index mI, the switching

John Chiasson; Leon Tolbert; Keith McKenzie; Zhong Du

2002-01-01

6

Phase-Matched Third-Harmonic Generation in a Nematic Liquid Crystal Cell  

Microsoft Academic Search

We show the generation of a strong phase-matched third harmonic in a simple parallel nematic liquid crystal cell. A single laser beam of femtosecond pulses is used to deform the internal structure of the molecular orientation distribution, and to generate the third harmonic from the twisted structure that is formed. Up to 10-5 of the laser power was converted to

D. Yelin; Y. Silberberg; Y. Barad; J. S. Patel

1999-01-01

7

Generation of harmonics and supercontinuum in nematic liquid crystals  

NASA Astrophysics Data System (ADS)

Nonlinear optical properties of nematic liquid crystals (NLC) have been investigated. A technique for efficient laser frequency conversion in a microscopic NLC volume deposited on an optical fibre end face is experimentally demonstrated. An efficient design of a compact NLC-based IR frequency converter with a fibre input and achromatic collimator is proposed and implemented. Simultaneous generation of the second and third harmonics is obtained for the first time under pumping NLC by a 1.56-mm femtosecond fibre laser. The second-harmonic generation efficiency is measured to be about 1 %, while the efficiency of third-harmonic generation is several tenths of percent. A strong polarisation dependence of the third-harmonic generation efficiency is revealed. When pumping NLC by a cw laser, generation of spectral supercontinua (covering the visible and near-IR spectral ranges) is observed. The nonlinear effects revealed can be due to the light-induced change in the orientational order in liquid crystals, which breaks the initial symmetry and leads to formation of disclination structures. The NLC optical nonlinearity is believed to be of mixed orientationalelectronic nature as a whole.

Nyushkov, B. N.; Trashkeev, S. I.; Klementyev, Vasilii M.; Pivtsov, V. S.; Kobtsev, Sergey M.

2013-02-01

8

Generation of harmonics and supercontinuum in nematic liquid crystals  

SciTech Connect

Nonlinear optical properties of nematic liquid crystals (NLC) have been investigated. A technique for efficient laser frequency conversion in a microscopic NLC volume deposited on an optical fibre end face is experimentally demonstrated. An efficient design of a compact NLC-based IR frequency converter with a fibre input and achromatic collimator is proposed and implemented. Simultaneous generation of the second and third harmonics is obtained for the first time under pumping NLC by a 1.56-mm femtosecond fibre laser. The second-harmonic generation efficiency is measured to be about 1 %, while the efficiency of third-harmonic generation is several tenths of percent. A strong polarisation dependence of the third-harmonic generation efficiency is revealed. When pumping NLC by a cw laser, generation of spectral supercontinua (covering the visible and near-IR spectral ranges) is observed. The nonlinear effects revealed can be due to the light-induced change in the orientational order in liquid crystals, which breaks the initial symmetry and leads to formation of disclination structures. The NLC optical nonlinearity is believed to be of mixed orientationalelectronic nature as a whole. (laser optics 2012)

Nyushkov, B N; Trashkeev, S I; Klementyev, Vasilii M; Pivtsov, V S; Kobtsev, Sergey M

2013-02-28

9

Investigation of the Harmonic Optimization Approaches in the New Modular Multilevel Converters  

Microsoft Academic Search

Modular multilevel converter (MMC) is a new type of multilevel converter. Similar to cascaded multilevel converters, each arm consists of several submodules and each submodule includes one separate DC source in parallel. Based on the analysis of its structure and working mechanism, this paper presents two harmonic optimization techniques, known as optimized harmonic stepped-waveform (OHSW) technique and optimal minimization of

Li Qiang; He Zhiyuan; Tang Guangfu

2010-01-01

10

Second Harmonic Light Generation in Crystals with Natural Optical Activity.  

National Technical Information Service (NTIS)

Whenever a circularly polarized laser beam propagates along an axis of three-fold symmetry in a piezoelectric crystal, the second harmonic polarization is circularly polarized in the opposite sense. Rabin and Bey have discussed the theory of second harmon...

H. J. Simon N. Bloembergen

1968-01-01

11

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

Microsoft Academic Search

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

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

2005-01-01

12

A new approach to solving the harmonic elimination equations for a multilevel converter  

Microsoft Academic Search

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

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

2003-01-01

13

Fuzzy Model Reference Adaptive Control of power converter for unity power factor and harmonics minimization  

Microsoft Academic Search

The absorbed current by the converter is rich in harmonics. This provokes the disruption of the network and influences on the consumers joined to the same node. On the other hand, because of its structure and of the absence of the degree of liberty in the control, the converter consummates a reactive power. In order to minimize the harmonics of

M. T. Benchouia; A. Ghamri; M. E. H. Benbouzid; A. Golea; S. E. Zouzou

2007-01-01

14

Current harmonic compensation by three-phase converters controlled by space vector modulation  

Microsoft Academic Search

This paper deals with the application of a method developed for the compensation of harmonic currents generated by nonlinear loads, connected to the utility grid, using three phase dc\\/ac converters. The converters are supplied by renewable power sources, i.e. they are part of a distributed generation system. Nonlinear load current harmonics are compensated by a voltage oriented control (VOC). Current

Damien Paire; Maurizio Cirrincione; Marcello Pucci; Rafael k. Jardan; Istvan Nagy; Abdellatif Miraoui

2009-01-01

15

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

16

Operation of the LCC-type parallel resonant converter as a low harmonic rectifier  

Microsoft Academic Search

A single-phase high frequency transformer isolated AC-to-DC controlled rectifier with low line current harmonic distortion using a variable frequency controlled LCC-type (or series-parallel) resonant power converter (SPRC) is presented. A simple analysis and design procedure is used for designing the power converter for low line current harmonic distortion and high power factor operation. The converter performance characteristics have been verified

V. Belaguli; A. K. S. Bhat

1996-01-01

17

Elimination of harmonics in a multilevel converter with nonequal DC sources  

Microsoft Academic Search

The problem of eliminating harmonics in a multilevel converter in which the separate DC sources vary is considered. That is, given a desired fundamental output voltage, the problem is to find the switching times (angles) that produce the fundamental while not generating specifically chosen harmonics. Assuming that the separate DC sources can be measured, a procedure is given to find

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

2003-01-01

18

Elimination of harmonics in a multilevel converter with nonequal DC sources  

Microsoft Academic Search

Eliminating harmonics in a multilevel converter in which the separate dc sources vary is considered. That is, given a desired fundamental output voltage, the problem is to find the switching times (angles) that produce the fundamental while not generating specifically chosen harmonics. Assuming that the separate dc sources can be measured, a procedure is given to find all sets of

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

2005-01-01

19

Converting Gravity-Bin Parameters To Spherical Harmonics  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

20

An optimal selective harmonic mitigation for cascaded H-bridge converters  

Microsoft Academic Search

In recent years, due to more intransigent regulations in the area of power quality and appearance of new grid codes which limit the maximum allowable harmonic levels, paying attention to the quality of power converters' output signal has become more important. Moreover, in order to achieve high efficiency in medium voltage and high power converters, the switching frequency has to

A. Marzoughi; H. Imaneini

2012-01-01

21

Harmonic optimization of multilevel converters using genetic algorithms  

Microsoft Academic Search

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

Burak Ozpineci; Leon M. Tolbert; John N. Chiasson

2005-01-01

22

Harmonic optimization of multilevel converters using genetic algorithms  

Microsoft Academic Search

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

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

2004-01-01

23

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

SciTech Connect

PWM controlled line-side 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 the high-voltage transformer to produce a harmonic counter MMF. The transformer main flux is then forced to be sinusoidal, and so is the induced voltage in the primary. The line current, being low-pass filtered by the transformer leakage inductance, assumes a pure sinusoidal waveform. The compensator operates in the low switching frequency range of the main power converters. Its installed power is only 1% of the traction power. Operation, control, and design considerations are described. Results from laboratory tests at full power level are presented.

Krah, J.O.; Holtz, J. [Univ. of Wuppertal (Germany)] [Univ. of Wuppertal (Germany)

1995-11-01

24

Harmonic analysis of the DC capacitor voltage in modular multilevel converter based STATCOM  

Microsoft Academic Search

The floating dc capacitor voltage of modular multilevel converter based STATCOM (M-STATCOM) contains a large amount of low-order harmonic components, which produce current ripple in leg currents, and then greatly affect the output performance and safe operation of M-STATCOM. However, fewer papers have made explicit harmonic analysis on the floating capacitor voltage of M-STATCOM. Detailed floating capacitor voltage computation has

Xiaofeng Yang; Jianghong Li; Xiaopeng Wang; Wenbao Fan; Trillion Q. Zheng

2011-01-01

25

Selective Harmonic Elimination PWM Control for Cascaded Multilevel Voltage Source Converters: A Generalized Formula  

Microsoft Academic Search

This paper proposes a generalized formulation for selective harmonic elimination pulse-width modulation (SHE-PWM) control suitable for high-voltage high-power cascaded multilevel voltage source converters (VSC) with both equal and nonequal dc sources used in constant frequency utility applications. This formulation offers more degrees of freedom for specifying the cost function without any physical changes to the converter circuit, as compared to

Mohamed S. A. Dahidah; Vassilios G. Agelidis

2008-01-01

26

Second harmonic chalcone crystal: Synthesis, growth and characterization  

NASA Astrophysics Data System (ADS)

The novel nonlinear optical chalcone derivative (2 E)-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

27

A unified approach to solving the harmonic elimination equations in multilevel converters  

Microsoft Academic Search

A method is presented to compute the switching angles in a multilevel converter so as to produce the required fundamental voltage while at the same time not generate higher order harmonics. Using a staircase fundamental switching scheme, previous work has shown that this is possible only for specific ranges of the modulation index. Here it is shown that, by considering

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

2004-01-01

28

Optimum harmonic reduction with a wide range of modulation indexes for multilevel converters  

Microsoft Academic Search

This paper proposes a novel modulation technique applying in multilevel voltage source converters suitable for high voltage power supplies and flexible AC transmission system (FACTS) devices. The proposed technique can generate output stepped-waveforms with a wide range of modulation indexes and minimized total voltage harmonic distortion. The main power devices switch only one time per cycle, suitable for high power

Siriroj Sirisukprasert; Jih-Sheng Lai; Tian-Hua Liu

2000-01-01

29

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

30

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 behaviour

M. Banta; M. Grotzbach

1998-01-01

31

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

32

Pulse multiplication in AC-DC converters for harmonic mitigation in vector-controlled induction motor drives  

Microsoft Academic Search

In this paper, an autotransformer with reduced kilovoltampere rating for 24-pulse ac-dc converter fed vector controlled induction motor drives (VCIMDs) is presented for harmonic current reduction. The 24-pulse operation is achieved using dc ripple reinjection technique in 12-pulse ac-dc converters. The proposed novel harmonic mitigator is found capable of suppressing up to 21st harmonic in the supply current. The procedure

Bhim Singh; G. Bhuvaneswari; Vipin Garg; Sanjay Gairola

2006-01-01

33

Temperature-insensitive phase-matched optical harmonic conversion crystal  

DOEpatents

Temperature-insensitive, phase-matched harmonic 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. 12 figures.

Barker, C.E.; Eimerl, D.; Velsko, S.P.; Roberts, D.

1993-11-23

34

Optimum harmonic reduction with a wide range of modulation indexes for multilevel converters  

Microsoft Academic Search

This paper proposes a novel modulation technique to be applied to multilevel voltage-source converters suitable for high-voltage power supplies and flexible AC transmission system devices. The proposed technique can generate output stepped waveforms with a wide range of modulation indexes and minimized total voltage harmonic distortion. The main power devices switch only once per cycle, as is suitable for high-power

Siriroj Sirisukprasert; Jih-Sheng Lai; Tian-Hua Liu

2002-01-01

35

Reduced harmonics PWM controlled line-side converter for electric drives  

Microsoft Academic Search

A reduced-harmonics pulse-width modulator and its application to the control of a three-level line-side power converter for a speed-variable AC drive are described. The pulse-width modulation scheme for the voltage source inverter determines each individual switching instant on the basis of a continuously updated volt-second balance between the reference vector and the actual switching state vector. The generated pulse sequence

Joachim Holtz; Lothar Springob

1990-01-01

36

Reduced harmonics PWM controlled line-side converter for electric drives  

Microsoft Academic Search

The concept for a reduced-harmonics PWM modulator, as applied for the control of a line-side power converter for a variable speed AC motor drive, is described. The PWM algorithm determines the on-state duration of each switching vector based on the observation of the time-variable voltage reference vector. Since there is no reference made to a constant-frequency carrier signal, the generated

Joachim Holtz; Lothar Springob

1993-01-01

37

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

38

Quartz crystal microbalance based on passive frequency to voltage converter.  

PubMed

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. PMID:22380125

Burda, Ioan; Tunyagi, Arthur

2012-02-01

39

Efficiency of nonlinear radiation conversion by phase-matched third harmonic generation in a cholesteric liquid crystal  

Microsoft Academic Search

An investigation was made of the efficiency of third harmonic generation in a cholesteric liquid crystal as a function of the thickness of a nonlinear layer of this crystal. The phase-matching conditions in third harmonic generation were satisfied using the temperature dependence of the helix pitch of the crystal. The maximum third harmonic power was obtained using liquid-crystal cells about

S A Akopyan; S M Arakelyan; R V Kochikyan; S Ts Nersisyan; Yu S Chilingaryan

1977-01-01

40

Intracavity testing of KTiOPO4 crystals for second-harmonic generation at 532 nm.  

PubMed

We have developed a diode-pumped Nd:YVO4 cw laser for testing KTiOPO4 crystals designed for intracavity second-harmonic generation at 532 nm. We demonstrate that this source is extremely sensitive to defects inside the crystal, inducing losses at 1064 nm and an index mismatch between fundamental and harmonic waves. PMID:18319823

Albrecht, H; Balembois, F; Lupinski, D; Georges, P; Brun, A

1999-04-20

41

Implementation of three-level AC\\/DC\\/AC converter with power factor correction and harmonic reduction  

Microsoft Academic Search

This paper proposes a three-level AC\\/DC\\/AC converter. A single-phase double-voltage power factor correction circuit to improve the power quality and provide two capacitor voltages in the input side of the AC\\/DC\\/AC converter and a three-level PWM inverter to reduce the harmonic contents of the inverter output voltages for induction motor drive are presented. In the rectifier side, the hysteresis current

Bor-Ren Lin; Hsin-Hung Lu; Yaow-Ming Chen

1998-01-01

42

Suppression of the input current harmonics and output voltage ripple using the novel multiple-input AC-DC converter  

Microsoft Academic Search

This paper presents a novel method to suppress the input current harmonics and low frequency output voltage ripple using a multiple-input AC-DC power converter. The proposed circuit is fundamentally composed of the multiple-input DC-DC power converter, which is divided broadly into two circuit types; i.e., buck-boost and forward. From view points of the relatively small power application and simple circuit

H. Matsuo; F. Kurokawa; Byunghoon Lee; K. Akise

1997-01-01

43

SubHarmonic Problem in Multi-Converter Vehicular Power Systems  

Microsoft Academic Search

Power electronics is an inevitable part of vehicular multi-converter power systems. In a multi-converter power system, various buses and loads are connected through different power electronic converters and inverters. These systems consist of a few to tens of converters in electric and hybrid electric vehicles to hundreds of converters in more electric aircraft, sea vehicles, and international space station. A

A. M. Rahimi; A. Khalilgh; A. Emadi

2006-01-01

44

Grating-assisted phase matching of high harmonic generation in hollow core photonic crystal fiber  

Microsoft Academic Search

We supposed to use the hollow core photonic crystal fiber as the gas cell for grating-assisted phase matching of high harmonic generation below 1 keV. The conversion efficiency is expected to be dramatically improved.

Haizhen Ren

2009-01-01

45

A power-equalized harmonic-elimination scheme for utility-connected cascaded H-bridge multilevel converters  

Microsoft Academic Search

Although fundamental frequency switching has been the preferred method for high-power medium-voltage multilevel converters, the technology of current generation power semiconductors has made it possible to use higher rates. In utility-connected applications, where a restricted modulation index range is usually sufficient, a main requirement is for very tight control over individual harmonics. For these reasons, this paper considers the application

Joseph Vassallo; Jon C. Clare; Patrick W. Wheeler

2003-01-01

46

Effects of voltage unbalance and harmonics on three-phase SPWM AC-to-DC converters with instantaneous power feedback  

Microsoft Academic Search

A PWM three-phase AC-to-DC converter with unity input power factor can be approached by setting the required active power and setting reactive power to zero in the instantaneous reactive power theory. The instantaneous reactive power theory, proposed by Akagi, is usually used to design reactive power and harmonic compensators, and it is based on a balanced three-phase voltage source. But,

Wen-Inne Tsai; Ming-Tsung Tsai; York-Yih Sun

1993-01-01

47

Harmonics  

NSDL National Science Digital Library

This simulation illustrates the behavior of standing waves in situation where one end fixed, both ends are fixed, and both ends are free. The simulation allows the user to examine the standing wave behavior at the fundamental frequency and when the first three harmonics are added. The user can control the amplitude of each of the harmonics and observe the resulting pattern.

Renault, Pascal

2009-01-22

48

Polarization converting textures of nematic liquid crystal in glass cavities  

NASA Astrophysics Data System (ADS)

When a nematic liquid crystal (LC) is filled in a glass cavity, the LC molecules present azimuthal orientations in the cavity. If the surface of the cavity is coated with a homeotropic polyimide, then the LC molecules exhibit radial orientations. By treating the LC on one side of the cavity with homogeneous alignment, the former orientations change to a twisted-azimuthal texture, while the latter orientations change to a twisted-radial texture. Both textures are verified experimentally, and they can convert a linearly polarization light to an azimuthal and/or radial polarization light, depending on the polarization direction of the incident light. In contrast to previous approaches, various LC textures can be easily formed in a cavity, and the fabrication procedure is simple. Since the LC texture is confined in a cavity, an array pattern of the texture can be obtained, if the employed substrate has multiple cavities. A LC with twisted-azimuthal and/or twisted-radial textures in a cavity array has potential applications in phase modulation, polarization compensating, sharp focus, and material processing.

Wang, Xiahui; Xu, Miao; Ren, Hongwen

2014-01-01

49

Intervening Firing Method and Passive Filter Design for Harmonic Elimination and Reactive Power Compensation in Three-Phase Thyristor Phase-Controlled Converters Supplying a DC Motor  

Microsoft Academic Search

This paper presents a method for harmonic elimination and reactive power compensation using an intervening firing method and passive power filter with is suitable to compensate rapidly changing loads and reactive power. The proliferation of three-phase thyristor phase-controlled converter of DC motor drives into a power system has the potential to increase the harmonic levels in the power system. The

Artite Pattanapongchai; Piphat Laohasongkram

50

Theoretical Framework for Minimizing Converter Losses and Harmonics in a Multilevel STATCOM  

Microsoft Academic Search

In this paper, an analytical framework for minimizing losses and harmonics is presented for the cascaded-type-based multilevel static synchronous compensator (STATCOM) with ldquosquare-wave control.rdquo The focus lays on low losses, low-voltage total harmonic distortion (THD), and low dc voltage ripple. All of the system parameters are studied, including buffer reactance, dc capacitance, transformer ratio, and transformer leakage inductance. The equivalent

Ronny Sternberger; Dragan Jovcic

2008-01-01

51

Multimode anharmonic third-order harmonic generation in a photonic-crystal fiber.  

PubMed

While the third harmonic of a monochromatic pump field with a frequency omega0 is generated exactly at the frequency 3omega0, frequency tripling of broadband ultrashort pump pulses in extended nonlinear media tends to generate isolated spectral peaks substantially shifted from 3omega0. We demonstrate this phenomenon by studying nonlinear spectral transformations of femtosecond Cr:forsterite laser pulses in multimode photonic-crystal fibers. Third-harmonic generation is shown to map adjacent guided modes of the third harmonic onto a manifold of spectral peaks within a 150-THz range around 3omega0. The spectral shifts and the widths of these peaks are controlled by the phase and group-velocity mismatch between the pump field and third-harmonic modes, as well as the length of nonlinear-optical interaction and broadening of the pump spectrum, allowing the spectral content of the third-harmonic signal to be engineered by tailoring the fiber dispersion. PMID:16486298

Ivanov, A A; Lorenc, D; Bugar, I; Uherek, F; Serebryannikov, E E; Konorov, S O; Alfimov, M V; Chorvat, D; Zheltikov, A M

2006-01-01

52

Quasi-phase-matched high harmonic generation in hollow core photonic crystal fibers.  

PubMed

The potential of hollow core photonic crystal fiber as a nonlinear gas cell for efficient high harmonic generation is discussed. The feasibility of phase-matching this process by modulating the phase of ionization electrons using a counter-propagating laser field is shown. In this way, harmonics with energies of several hundreds of eV can be produced using fs-laser pump pulses of microJ energy. PMID:18852815

Ren, H; Nazarkin, A; Nold, J; Russell, P St J

2008-10-13

53

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

54

Tailoring ?erenkov second-harmonic generation in bulk nonlinear photonic crystal.  

PubMed

We investigate theoretically the ?erenkov-type second-harmonic generation in two-dimensional bulk nonlinear photonic crystal with longitudinal modulation of the ?((2)) nonlinearity. We show that in this scheme the ?erenkov radiation can be achieved simultaneously at multiple directions with comparable intensities. The angles of emission are controllable by the spatial modulation of the nonlinearity. We propose a design of the periodically poled domain pattern, which maximizes the efficiency of the second-harmonic emission. PMID:21725490

Sheng, Yan; Roppo, Vito; Kong, Qian; Kalinowski, Ksawery; Wang, Qi; Cojocaru, Crina; Trull, Jose; Krolikowski, Wieslaw

2011-07-01

55

Third-harmonic generation in one-dimensional photonic crystal with graphene-based defect  

NASA Astrophysics Data System (ADS)

Third-harmonic generation may be dramatically enhanced in monolayer graphene by inserting it in a properly designed structure. In addition, placing graphene within the defect layer of an asymmetric, one-dimensional photonic crystal triggers nearly 100% narrowband absorption. We demonstrate that the improved field localization within the defect state enhances third-harmonic generation by nearly five orders of magnitude compared with bare monolayer graphene. Saturation of the third-order susceptibility plays a role at both fundamental and third-harmonic frequencies. We discuss the benefits of including graphene within the structure for both signals.

Vincenti, M. A.; de Ceglia, D.; Grande, M.; D'Orazio, A.; Scalora, M.

2014-04-01

56

Optimization of the modular multilevel converters performance using the second harmonic of the module current  

Microsoft Academic Search

At the design framework, in this Thesis s the modular multilevel converter (MMC) is analysed and proposed for connecting the power grids. In order to mathematically describe the converter behaviour, the linear time-varying model (LTV) is developed. The system is considered linear between two switching instants. Since the switching functions have a periodical nature, the steady state of the system

A. Rasic; U. Krebs; H. Leu; Gerhard Herold

2009-01-01

57

Multivariable current control of Modular Multilevel Converters with disturbance rejection and harmonics compensation  

Microsoft Academic Search

Voltage Source Converter (VSC) technology is very common in high-voltage direct current (HVDC) transmission systems. Compared to conventional VSC technology Modular Multilevel Converters (MMCs) offer advantages such as higher voltage levels, modular construction, longer maintenance intervals and improved reliability. For power transmission, stability, robustness of the control and especially the behavior during grid failures are important economic issues. Furthermore, compensation

Philipp Münch; Steven Liu; Günter Ebner

2010-01-01

58

Operation of a modular multilevel converter with selective harmonic elimination PWM  

Microsoft Academic Search

The modular multilevel converter (MMC) is based on the cascaded interconnection of half-bridge switching sub- modules and features modular characteristics that allow its expandability while providing high quality voltage and current output waveforms and removing the need for filtering. The switching frequency of each of the individual converter sub modules being maintained low and the balancing of the capacitor voltages

Georgios S. Konstantinou; Mihai Ciobotaru; Vassilios G. Agelidis

2011-01-01

59

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

SciTech Connect

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

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

2010-02-15

60

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

SciTech Connect

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

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

2013-11-18

61

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

62

Cherenkov high-order harmonic generation by multistep cascading in {chi}{sup (2)} nonlinear photonic crystal  

SciTech Connect

We propose a scheme for efficient Cherenkov high-order harmonic generation. Second to fifth order harmonic wave are observed in a single periodically poled ferroelectric crystal in our experiment. The noncollinear high-order harmonic generation is produced via enhanced Cherenkov second harmonic cascaded with successive multistep sum-frequency generation with simultaneously longitudinal phase-matching. The emission angle and power dependencies are analyzed in detail experimentally, which coincide with theoretical predictions.

An Ning; Ren Huaijin [Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); State Key Laboratory on Fiber Optic Local Area Communication Networks and Advanced Optical Communication Systems, Shanghai 200240 (China); Zheng Yuanlin [Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Key Laboratory for Laser Plasmas (Ministry of Education), Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Deng Xuewei [Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Chen Xianfeng [Department of Physics, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); State Key Laboratory on Fiber Optic Local Area Communication Networks and Advanced Optical Communication Systems, Shanghai 200240 (China); Key Laboratory for Laser Plasmas (Ministry of Education), Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)

2012-05-28

63

Visible-to-infrared dynamic image-converting system with a liquid crystal light valve  

NASA Astrophysics Data System (ADS)

A kind of liquid crystal light valve (LCLV) based on a CdS-CdSe photoconductor that can convert visible image to infrared at video rate is introduced in this paper. A prototype of a visible to infrared dynamic image converting system using a CO2 laser as the infrared source is built with this device. Results of the converter are presented in this paper.

Mei, Ting; Xia, Monghua; Gu, Peifu; Zhao, Dekang; Li, Haifeng; Liu, Xu; Tang, Jinfa

1993-11-01

64

Optical bistability and second-harmonic generation in thin film coupled cavity photonic crystal structures  

Microsoft Academic Search

This thesis deals with design, fabrication and modeling of bistable and multi-stable switching dynamics and second-harmonic generation in two groups of thin film coupled cavity photonic crystal structures. The first component studies optical bistability and multistability in such structures. Optical bistability and multistability are modelled by a nonlinear transfer matrix method. The second component is focused on the modelling and

Liyong Diao

2009-01-01

65

Optical second harmonic generation of oblique incident light in transmission in potassium dihydrogen phosphate crystal  

NASA Astrophysics Data System (ADS)

The Bloembergen and Pershan theory stated that in a nonlinear crystal there are reflected harmonic beams and two transmitted beams. In this study, the BP theory is verified experimentally by quantitative analysis of the second harmonic generation in transmission with different crystallographic cuts of the potassium dihydrogen phosphate (KDP) crystal. The SHG in transmission is studied in the range of the normal incidence to critical angle of incidence and conditions of null SHG in transmission with both normal and oblique incidence of the fundamental beam. It was observed that for a certain particular crystallographic orientation of the KDP crystal, there can be no SHG in both transmission and reflection at normal incidence. These experimental results correlated well with the BP theory.

Bhanthumnavin, V.; Lee, Chi H.

1994-04-01

66

Second-harmonic parametric scattering in ferroelectric crystals with disordered nonlinear domain structures.  

PubMed

We study the second-harmonic (SH) parametric processes in unpoled crystals of Strontium Barium Niobate (SBN) with disordered structures of ferroelectric domains. Such crystals allow for the simultaneous phase matching of several second-order nonlinear processes. We analyze the polarization properties of these parametric processes using two types of generation schemes: quasi-collinear SH generation and transverse SH generation. From our experimental data we determine the ratio of d(32) and d(33) components of the second order susceptibility tensor and also the statistical properties of the random structure of the SBN crystal. PMID:19550873

Trull, Jose; Cojocaru, Crina; Fischer, Robert; Saltiel, Solomon M; Staliunas, Kestutis; Herrero, Ramon; Vilaseca, Ramon; N Neshev, Dragomir; Krolikowski, Wieslaw; Kivshar, Yuri S

2007-11-26

67

Fourth-harmonic generation of picosecond glass laser pulses with cesium lithium borate crystals  

SciTech Connect

We report the fourth-harmonic generation of 1.5 ps, 1.053 {mu}m glass laser pulses, where group velocity mismatch plays a significant role, at intensities up to 100 GW/cm{sup 2} using newly developed crystal, cesium lithium borate (CsLiB{sub 6}O{sub 10}). Type-I doubler and type-I quadrupler were used in the fourth harmonic generation experimental scheme. Energy conversion efficiencies of 24{percent} and 53{percent} have been achieved for frequency quadrupling and doubling of the fundamental glass laser pulses, respectively. {copyright} {ital 1996 American Institute of Physics.}

Sharma, L.B.; Daido, H.; Kato, Y.; Nakai, S. [Institute of Laser Engineering, Osaka University, 2-6, Yamada-Oka, Suita 565 (Japan)] [Institute of Laser Engineering, Osaka University, 2-6, Yamada-Oka, Suita 565 (Japan); Zhang, T. [Yamanashi University, Faculty of Engineering, 4-3-11 Takeda, Kofu, Yamanashi 400 (Japan)] [Yamanashi University, Faculty of Engineering, 4-3-11 Takeda, Kofu, Yamanashi 400 (Japan); Mori, Y.; Sasaki, T. [Department of Electrical Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565 (Japan)] [Department of Electrical Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565 (Japan)

1996-12-01

68

Giant microcavity enhancement of second-harmonic generation in all-silicon photonic crystals  

NASA Astrophysics Data System (ADS)

Second-harmonic generation (SHG) spectra of single and coupled porous silicon-based photonic crystal microcavities are studied in both frequency and wave vector domains. For the fundamental field resonant to the microcavity mode the second-harmonic intensity is enhanced by 102 times in comparison with that outside the photonic band gap. SHG spectroscopy in identical microcavities coupled through the intermediate Bragg reflector reveals two SHG peaks if the fundamental field is in resonance with the splitted mode of coupled microcavities. The spatial confinement of the resonant fundamental radiation is directly probed at the microcavity cleavage by scanning near-field optical microscopy.

Dolgova, T. V.; Maidykovski, A. I.; Martemyanov, M. G.; Fedyanin, A. A.; Aktsipetrov, O. A.; Marowsky, G.; Yakovlev, V. A.; Mattei, G.

2002-10-01

69

Parameters for efficient growth of second harmonic field in nonlinear photonic crystals  

NASA Astrophysics Data System (ADS)

The ultrashort pulse propagation and nonlinear second harmonic generation under the undepleted pump approximation in a quadratic nonlinear photonic crystal (NPC) structure is theoretically investigated and the optimized parameters for high second harmonic generation conversion efficiency are extracted. The transfer matrix method is used for the numerical formulation for oblique angle of incidence. A unique set of material combination GaInP/InAlP is selected as alternating nonlinear and linear layers. The NPC parameters like incident angle and layer thickness are manipulated to obtain the exact phase matching using double resonance condition for a fixed number of layers with known experimental material parameters.

Joseph, Shereena; Khan, Mohd. Shahid; Hafiz, Aurangzeb Khurram

2014-03-01

70

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

71

Heat transport and phonon localization in mass-disordered harmonic crystals  

Microsoft Academic Search

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

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

2010-01-01

72

Multi-directional ?erenkov second harmonic generation in two-dimensional nonlinear photonic crystal.  

PubMed

We study ?erenkov-type second-harmonic generation in a two-dimensional quasi-periodically poled LiNbO3 crystal. We employ a new geometry of interaction to observe simultaneous emission of multi-directional nonlinear ?erenkov radiation with comparable intensities. This opens a way to control the angle of ?erenkov emission by tailoring the nonlinearity of the material, which is otherwise intrinsically defined by dielectric constants of the medium and their dispersion. PMID:22418151

Sheng, Yan; Roppo, Vito; Ren, Mingliang; Kalinowski, Ksawery; Cojocaru, Crina; Trull, Jose; Li, Zhiyuan; Koynov, Kaloian; Krolikowski, Wieslaw

2012-02-13

73

Towards protein-crystal centering using second-harmonic generation (SHG) microscopy  

PubMed Central

The potential of second-harmonic generation (SHG) microscopy for automated crystal centering to guide synchrotron X-­ray diffraction of protein crystals was explored. These studies included (i) comparison of microcrystal positions in cryoloops as determined by SHG imaging and by X-ray diffraction rastering and (ii) X-ray structure determinations of selected proteins to investigate the potential for laser-induced damage from SHG imaging. In studies using ?2 adrenergic receptor membrane-protein crystals prepared in lipidic mesophase, the crystal locations identified by SHG images obtained in transmission mode were found to correlate well with the crystal locations identified by raster scanning using an X-­ray minibeam. SHG imaging was found to provide about 2?ľm spatial resolution and shorter image-acquisition times. The general insensitivity of SHG images to optical scatter enabled the reliable identification of microcrystals within opaque cryocooled lipidic mesophases that were not identified by conventional bright-field imaging. The potential impact of extended exposure of protein crystals to five times a typical imaging dose from an ultrafast laser source was also assessed. Measurements of myoglobin and thaumatin crystals resulted in no statistically significant differences between structures obtained from diffraction data acquired from exposed and unexposed regions of single crystals. Practical constraints for integrating SHG imaging into an active beamline for routine automated crystal centering are discussed.

Kissick, David J.; Dettmar, Christopher M.; Becker, Michael; Mulichak, Anne M.; Cherezov, Vadim; Ginell, Stephan L.; Battaile, Kevin P.; Keefe, Lisa J.; Fischetti, Robert F.; Simpson, Garth J.

2013-01-01

74

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

75

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

NASA Astrophysics Data System (ADS)

Coloured conical emission (CCE) is investigated experimentally in a ?-barium borate crystal excited by intense second harmonic femtosecond pulses. Contrary sequences of green and red conical emission with variable diameters are observed at different incidence angles, which is consistent with the calculation results based on the phase matching condition. As its broad range spectrum, CCE offers an alternative means to produce an ultrafast broadband light source. It is found that the spectrum of green CE shifts toward longer wavelengths as the length of BBO crystal increased.

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

2009-01-01

76

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 18.5ą0.1 °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

77

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

SciTech Connect

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

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

2010-09-15

78

Phase-matching solutions for high-order harmonic generation in hollow-core photonic-crystal fibers  

NASA Astrophysics Data System (ADS)

Hollow-core photonic-crystal fibers are shown to allow phase-matched high-order harmonic generation by an isolated guided mode of pump radiation. Regimes of phase matching are analyzed for the fundamental guided mode of pump field with a wavelength around 800nm , generating harmonics within the wavelength range of 25-50nm in hollow photonic-crystal fibers filled with argon, krypton, and helium. Geometric parameters of the fiber structure and the pressure of the gas filling the fiber core are shown to serve as important, often orthogonal, control knobs, allowing a fine adjustment of the phase matching for high-order harmonic generation.

Serebryannikov, E. E.; von der Linde, D.; Zheltikov, A. M.

2004-12-01

79

Phase-matching solutions for high-order harmonic generation in hollow-core photonic-crystal fibers.  

PubMed

Hollow-core photonic-crystal fibers are shown to allow phase-matched high-order harmonic generation by an isolated guided mode of pump radiation. Regimes of phase matching are analyzed for the fundamental guided mode of pump field with a wavelength around 800 nm, generating harmonics within the wavelength range of 25-50 nm in hollow photonic-crystal fibers filled with argon, krypton, and helium. Geometric parameters of the fiber structure and the pressure of the gas filling the fiber core are shown to serve as important, often orthogonal, control knobs, allowing a fine adjustment of the phase matching for high-order harmonic generation. PMID:15697538

Serebryannikov, E E; von der Linde, D; Zheltikov, A M

2004-12-01

80

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

PubMed

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

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

2012-10-01

81

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

PubMed

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

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

2013-11-15

82

Spectral phase correlation of coded femtosecond pulses by second-harmonic generation in thick nonlinear crystals.  

PubMed

We demonstrate a novel all-optical scheme for measuring the correlation of spectrally phase-coded ultrashort optical waveforms that uses second-harmonic generation (SHG) in long, periodically poled lithium niobate crystals. The SHG yield can be controlled over a range of ~30 dB, depending on the correlation of the applied phase codes. Such a spectral phase correlator has applications for ultrashort-pulse optical code-division multiple-access networking and could serve as a nonlinear optical but classical analog for certain schemes for coherent quantum control of multiphoton processes. PMID:18064248

Zheng, Z; Weiner, A M

2000-07-01

83

Second-harmonic generation in a silicon-carbide-based photonic crystal nanocavity.  

PubMed

We demonstrate second-harmonic generation (SHG) in a silicon-carbide (SiC)-based heterostructure photonic crystal nanocavity by using a pulsed laser. We observe SHG light radiated from the SiC nanocavity and estimate the conversion efficiency in the cavity to be 2.59×10(-5) (=0.15??W(-1)) at an average input power of 0.17 mW. The near-field patterns and polarization characteristics of the SHG light are investigated experimentally and theoretically, and the results are in qualitatively good agreement. PMID:24686600

Yamada, Shota; Song, Bong-Shik; Jeon, Seungwoo; Upham, Jeremy; Tanaka, Yoshinori; Asano, Takashi; Noda, Susumu

2014-04-01

84

A general microscopic theory of bulk second-harmonic generation from molecular crystals  

NASA Astrophysics Data System (ADS)

Expressions are derived for bulk second-harmonic generation from molecular crystals including electric dipole, electric quadrupole, magnetic dipole, electric field, electric field gradient and magnetic field contributions. Terms bilinear in the electric field and the electric field gradient or magnetic field depend on differences of molecular response coefficients at different frequencies. The results can be written in terms of non-local hyperpolarizabilities that are significantly generalized through self-consistent and indirect responses, modified by three local field tensors or by two local field tensors and one local field gradient tensor. A previous result for linear optical activity is extended by incorporating the quadrupole field gradient polarizability. Overall, the treatment provides a rigorous basis for numerical calculations of SHG from insulating molecular crystals.

Munn, R. W.

85

Evaluation of 3Phase to 9Phase Transformer, 18Pulse Converter, and Adjustable Speed Drive, Including Novel Third Harmonic Calculations  

Microsoft Academic Search

In the past 14 years, several patented 18-pulse converter methods have been accepted in the marketplace and successfully applied in various practical applications. In this paper, a widely used 18-pulse clean power converter, with \\

Kevin Lee; James E. Armes; Derek A. Paice

2007-01-01

86

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) Ĺ, b=12.08(7) Ĺ, c=14.09(9) Ĺ and V=1577 Ĺ3. 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

87

Temperature-Frequency Converter Using a Liquid Crystal Cell as a Sensing Element  

PubMed Central

A new temperature-frequency converter based on the variation of the dielectric permittivity of the Liquid Crystal (LC) material with temperature has been demonstrated. Unlike other temperature sensors based on liquid crystal processing optical signals for determining the temperature, this work presents a system that is able to sense temperature by using only electrical signals. The variation of the dielectric permittivity with temperature is used to modify the capacitance of a plain capacitor using a LC material as non-ideal dielectric. An electric oscillator with an output frequency depending on variable capacitance made of a twisted-nematic (TN) liquid crystal (LC) cell has been built. The output frequency is related to the temperature of LC cell through the equations associated to the oscillator circuit. The experimental results show excellent temperature sensitivity, with a variation of 0.40% of the initial frequency per degree Celsius in the temperature range from ?6 °C to 110 °C.

Marcos, Carlos; Sanchez Pena, Jose M.; Torres, Juan C.; Santos, Jose Isidro

2012-01-01

88

High efficiency 12.5 J second-harmonic generation from CsLiB6O10 nonlinear crystal by diode-pumped Nd:glass laser.  

PubMed

A 12.5 J second-harmonic generation with 71.5% conversion efficiency at 0.6 Hz repetition rate from a diode-pumped Nd:glass laser system has been demonstrated by using a CsLiB(6)O(10) (CLBO) nonlinear optical crystal as a frequency doubler. The CLBO has aperture of 40 mm x 40 mm and thickness of 14 mm with Type-II phase matching. The CLBO is mounted into a housing which flows dry nitrogen gas on the CLBO's face. There is no significant reduction of conversion efficiency by exposing of over 600,000 shots for intermissive experiment during 3 years. In our knowledge, these experimental results of output energy and conversion efficiency are highest performance as second-harmonic generation of a diode-pumped solid state laser by using one CLBO nonlinear crystal. In this paper, potential of the CLBO as a frequency converter for repetitive kJ class laser is discussed. PMID:23571928

Sekine, Takashi; Sakai, Hiroshi; Takeuchi, Yasuki; Hatano, Yuma; Kawashima, Toshiyuki; Kan, Hirofumi; Kawanaka, Junji; Miyanaga, Noriaki; Norimatsu, Takayoshi

2013-04-01

89

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

91

Harmonic rayleigh scattering from nonlinear octupolar molecular media: the case of crystal violet  

NASA Astrophysics Data System (ADS)

Experimental evidence is provided to supplement earlier molecular engineering propositions as to the high nonlinearities of octupolar origin. The absence of dipole moment in such structures precludes the utilization of electric-field-induced second-harmonic generation (EFISH) in solution: harmonic light scattering (HLS), which does not require dipolar electric field poling, is shown to provide quantitative access to the quadratic nonlinearity of octupolar nonlinear molecules. Crystal violet, a trigonal conjugated cationic dye with electronic charge transfer from peripheral dimethylamino donor groups to an electron deficient sp 2 hybridized central carbon atom, is chosen to illustrate the relevance of HLS in this context as well as provide an experimental estimate of the ? magnitude of a prototypical octupolar system. A resonantly enhanced ? value of 580 × 10 -30 esu is found at 1.064 ?m, in acetone solution (? max = 590 nm). Due care is taken of solvent calibration while a detailed account of symmetry considerations and tensorial averaging in solution are provided for various molecular point groups of relevance (D 3, D 3h, C 2v and T d). It is shown that besides the exploration of the new family of octupolar nonlinear systems, the HLS experiment should be also used to revisit the more traditional dipolar molecular systems: it complements EFISH experiments in providing a measure of the anisotropy of molecular quadratic hyperpolarizabilities.

Zyss, Joseph; Van, Thai Chau; Dhenaut, Christophe; Ledoux, Isabelle

1993-11-01

92

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

PubMed Central

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

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

2013-01-01

93

Two-dimensional GIWAXS reveals a transient crystal phase in solution-processed thermally converted tetrabenzoporphyrin.  

PubMed

Thermally convertible organic materials are useful for the fabrication of multilayered thin film electronic devices such as solar cells. However, substantial changes in molecular ordering can occur during the conversion process that may lead to multiple polymorphs having differing electronic properties. In-situ grazing incidence wide-angle X-ray scattering with 2-D detection (2-D GIWAXS) was used to study the changes in the thin film crystal structure, texture, and crystallite size of a convertible small-molecule electron donor, tetrabenzoporphyrin (BP), during thermal conversion from the precursor bicycloporphyrin (CP) and the resulting crystal-crystal phase transition from a metastable phase (phase I) to a stable phase (phase II). The annealing temperature and the presence of an underlying BP layer both affect the phase-transition behavior. Phase II has a much weaker degree of crystalline texture than phase I, attributed to changes in molecular packing to achieve a herringbone arrangement. The unit cell for phase I was determined by electron diffraction and GIWAXS, and the thin film structure of phase II matched the previously determined bulk structure. The texture of crystallites in phase II was characterized by the simulation of the GIWAXS pattern. Transmission electron microscopy revealed differences in the morphology, grain size, and film coverage of the two polymorphs. Peak shape analysis with corrections for geometric smearing and paracrystalline disorder showed an increase in crystallite size from phase I to phase II. These results demonstrate the utility of in-situ 2-D GIWAXS in revealing polymorphic phases during the structural transition of thermally convertible organic semiconductors, the presence of which may impact the performance of solar cells. PMID:24195584

Liman, Christopher D; Choi, Soohyung; Breiby, Dag W; Cochran, Justin E; Toney, Michael F; Kramer, Edward J; Chabinyc, Michael L

2013-11-21

94

Minimize Low-Order Harmonics in Low-Switching-Frequency Space-Vector-Modulated Current Source Converters With Minimum Harmonic Tracking Technique  

Microsoft Academic Search

Gate turnoffs (GTOs) are usually used in high-power current source converters (CSCs), i.e., rectifiers and inverters. Space vector modulation (SVM) technique for CSC is established by dividing ac-side line current cycle into six sectors. Each sector is divided into a certain number of SV cycles. SV cycle is divided into three states: two active and one zero state. For low

M. F. Naguib; Luiz A. C. Lopes

2009-01-01

95

Neutron transfer kernels in the resonance domain in the harmonic crystal model.  

SciTech Connect

To describe neutron scattering the resonance domain of the nuclear fuel isotopes, the static model is widely in use in nuclear data processing codes. With this model the influence of chemical binding on the transfer cross section is not taken into account since the nucleus is considered to be in rest and isolated in the laboratory system. Further, the application of the free gas model to the resonant scattering of neutrons shows that the up-scattering probability is strongly dependent on the incident neutron energy. If the latter is smaller than the resonance energy then the free gas model predicts an enormous chance for the neutron to gain energy after collision. Neither the static nor free gas model is adequate to describe the resonant scattering of neutrons in a crystal. This fact can induce non-negligible errors in reactor calculations and, in particular, in the estimation of the Doppler coefficient. In the present paper the author proposes the theoretical study of the possibility to estimate the neutron transfer cross sections in the harmonic crystal approximation.

Naberejnev, D. G.

1999-12-21

96

Photonic crystal surface-emitting lasers as a pumping light source for second harmonic generation  

NASA Astrophysics Data System (ADS)

Photonic crystal surface emitting lasers (PCSELs) have recently been achieved with both a single spectrum and narrow spot beam pattern under several hundred mW of output power. Even though the high coherence properties of PCSELs are expected to be used for various applications, we have focused on a pumping light source for a wavelength conversion system in this work. We fabricated a 1.06 ?m PCSEL with a square lattice 2D photonic crystal in which the lattice period corresponded to the lasing wavelength to obtain green light. The fabricated device had a narrow spot beam pattern of less than 0.5 degrees and a single spectrum at 1068 nm under CW output power of more than 200 mW despite the broad emitting area of 200 × 200 ?m2. The wavelength conversion system used single pass second-harmonic generation (SHG) that consisted of only the PCSEL and 50 mm long bulk MgO doped periodically with poled lithium niobate (MgO:PPLN) as a nonlinear medium, i.e., it was a lens-free system. It was important to maintain the high brightness of the pumping light in this system with a single spectrum through the MgO:PPLN. As a result, SHG light was obtained at 534 nm with a narrow spot beam pattern, which followed the beam quality of the PCSEL under CW operation.

Watanabe, Akiyoshi; Hirose, Kazuyoshi; Kurosaka, Yoshitaka; Sugiyama, Takahiro; Liang, Yong; Noda, Susumu

2014-02-01

97

A detailed instantaneous harmonic and reactive compensation analysis of three-phase AC\\/DC converters, in abc and ?? coordinates  

Microsoft Academic Search

This paper presents a digital simulation of an active filter, in which the instantaneous harmonic and reactive compensating currents are desegregated in their different ?? space-trajectories, and in their time-domain waveforms of both the abc and the ?? system of coordinates. Departing from Akagi's generalized instantaneous reactive power theory, a complete analysis is presented, in which the counterharmonic compensating current

Alfredo Nava-Segura; M. Carmona-Hernandez

1998-01-01

98

A detailed instantaneous harmonic and reactive compensation analysis of three-phase AC\\/DC converters, in abc and ?? coordinates  

Microsoft Academic Search

Summary form only as given. This paper presents a digital simulation of an active filter, in which the instantaneous harmonic and reactive compensating currents are desegregated in their different ?? space-trajectories, and in their time-domain waveforms of both the abc and the ?? system of coordinates. Departing from Akagi's generalized instantaneous reactive power theory, a complete analysis is presented, in

A. Nava-Segura; M. Carmona-Hernandez

1999-01-01

99

New marine harmonic standards  

Microsoft Academic Search

To address concerns associated with electrical power system harmonic distortion on ships and offshore oil rigs and platforms, marine regulating bodies have introduced strict new harmonic standards. These standards define the acceptable level of harmonic voltage distortion allowed on the vessels they certify. High-harmonic distortion levels are appearing as a result of the increased use of power-electronic drive converters for

Tony Hoevenaars; Ian Evans; Andy Lawson

2010-01-01

100

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

101

Chirped photonic crystal mode converters for broad-band coupling with highly dispersive photonic crystal microring resonators  

NASA Astrophysics Data System (ADS)

We demonstrate evanescent coupling between a photonic crystal (PhC) waveguide and a PhC embedded microring resonator on the silicon-on-insulator platform. The mode converter comprises 6 linearly chirped air holes that adiabatically couple the light between the silicon waveguide mode and the PhC mode. Three-dimensional finitedifference time-domain simulations reveal a coupling bandwidth of >100nm. From our experiment, the optical spectra show a photonic bandgap located below ~1590nm. At the resonances in the slow-light regime, a loaded quality factor as high as ~2500 was measured and a group index of ~16 in the PhC embedded microring resonator was estimated from the non-uniform free spectral ranges.

Lo, Stanley M.; Lee, Jonathan Y.; Weiss, Sharon M.; Fauchet, Philippe M.

2014-03-01

102

Optically switchable second harmonic generation in a liquid crystal thin film within femtoliter volume  

NASA Astrophysics Data System (ADS)

Nematic liquid crystal (NLC) is one of most useful soft matters. Because the molecular orientation can be controlled electrically, NLC is widely applied to display devices. It is known that NLC exhibits strong second-harmonic-generation (SHG) due to its orderly arranged molecules. The strength of SHG is strongly dependent on the angle between the incident beam polarization and the NLC molecular orientation, so the SHG in NLC can be switched on/off by rotating the NLC director. However, it is very difficult to control the orientation of NLC director electrically within a micrometer spatial domain. In this report, we demonstrated the orientation control of NLC with sub-micrometer spatial resolution based on optical Freedericksz transition (OFT) combined with a high-numerical-aperture objective. We used azo-dye doped NLC to reduce the intensity threshold of OFT with 473-nm excitation. Interestingly, we found that the threshold of OFT increases with tighter focuses. This effect can be explained by the intermolecular forces from the NLC molecules around the focal spot. By incorporating both the blue laser and a femtosecond near-infrared laser into an optical scanning microscope, we have successfully demonstrated switch of SHG inside a NLC thin film. Note that SHG is confined within femtoliter focal volume due to its intrinsic nonlinearity. That is, we have achieved an ultrasmall switch of nonlinear optical signal in NLC. This work will find applications in optical communication as well as optical-base storage system.

Chen, Kuan-Chieh; Zhuo, Guan-Yu; Chu, Shi-Wei

2013-03-01

103

Special phase matching of second-harmonic generation in helical ferroelectric liquid crystal cells  

NASA Astrophysics Data System (ADS)

The helical structures in ferroelectric liquid crystals can be utilized to realize a special phase matching for second-harmonic generation (SHG) when two counter fundamental waves propagate along the helical axis and the wavelength of SHG is near the photonic (selective reflection) band edge. On the basis of the exact theory [Drevensek-Olenik and Copic, Phys. Rev. E 56, 581 (1997)], a simple analytical description is derived and some characteristic features of the special phase matching are shown. (1) Special phase matching is definitely achieved under particular combinations of polarization. (2) The SH spectrum is related to a subsidiary oscillating structure in the selective reflection spectrum. The maximum SH intensity is realized at the first dip of the oscillation near one of the edges in the selective reflection band. (3) The thickness (d) dependence of the maximum SH intensity is d4 in thick cells, while it is d2 for conventional phase matching. (4) The linewidth for the SH peak is d-3 dependent, which is much narrower than in conventional phase matching.

Hoshi, Hajime; Chung, Doo-Han; Ishikawa, Ken; Takezoe, Hideo

2001-05-01

104

Multifrequency third-harmonic generation by red-shifting solitons in a multimode photonic-crystal fiber.  

PubMed

While the standard scenario of third-harmonic generation (THG) by a dispersive-wave pump involves the emission of light with a frequency 3omega, thrice the frequency omega of the input pump field, solitons undergoing a continuous shift of their central frequency omega due to the Raman effect in a multimode optical fiber can generate the third harmonic in a different fashion. In the experiments reported here, we provide the first direct experimental evidence of THG by a continuously red-shifting soliton pump by studying the third-harmonic buildup in relation to the spectral evolution of the soliton pump field in a silica photonic-crystal fiber (PCF). We show that solitons excited in a PCF by unamplified femtosecond pulses of a Cr:forsterite laser sweep through the spectral range from 1.25 to 1.63 microm , scanning through a manifold of THG phase-matching resonances with 3omega dispersive waves in PCF modes. As a result, intense third-harmonic peaks build up in the range of wavelengths from 370 to 550 nm at the output of the fiber, making PCF a convenient fiber-format multifrequency source of short-wavelength radiation. Time-resolved fluorescence measurements with photoexcitation provided by the third-harmonic PCF output are presented, demonstrating the high potential of PCF sources for an ultrafast photoexcitation of fluorescent molecular systems in physics, chemistry, and biology. PMID:17358282

Fedotov, A B; Voronin, A A; Serebryannikov, E E; Fedotov, I V; Mitrofanov, A V; Ivanov, A A; Sidorov-Biryukov, D A; Zheltikov, A M

2007-01-01

105

Multifrequency third-harmonic generation by red-shifting solitons in a multimode photonic-crystal fiber  

NASA Astrophysics Data System (ADS)

While the standard scenario of third-harmonic generation (THG) by a dispersive-wave pump involves the emission of light with a frequency 3? , thrice the frequency ? of the input pump field, solitons undergoing a continuous shift of their central frequency ? due to the Raman effect in a multimode optical fiber can generate the third harmonic in a different fashion. In the experiments reported here, we provide the first direct experimental evidence of THG by a continuously red-shifting soliton pump by studying the third-harmonic buildup in relation to the spectral evolution of the soliton pump field in a silica photonic-crystal fiber (PCF). We show that solitons excited in a PCF by unamplified femtosecond pulses of a Cr:forsterite laser sweep through the spectral range from 1.25to1.63?m , scanning through a manifold of THG phase-matching resonances with 3? dispersive waves in PCF modes. As a result, intense third-harmonic peaks build up in the range of wavelengths from 370to550nm at the output of the fiber, making PCF a convenient fiber-format multifrequency source of short-wavelength radiation. Time-resolved fluorescence measurements with photoexcitation provided by the third-harmonic PCF output are presented, demonstrating the high potential of PCF sources for an ultrafast photoexcitation of fluorescent molecular systems in physics, chemistry, and biology.

Fedotov, A. B.; Voronin, A. A.; Serebryannikov, E. E.; Fedotov, I. V.; Mitrofanov, A. V.; Ivanov, A. A.; Sidorov-Biryukov, D. A.; Zheltikov, A. M.

2007-01-01

106

Terahertz-field-induced second-harmonic generation in a beta barium borate crystal and its application in terahertz detection  

NASA Astrophysics Data System (ADS)

We report the observation of terahertz-field-induced second-harmonic (TFISH) generation in a beta barium borate (?-BBO) crystal based on a four-wave-mixing process. Using the conventional second-harmonic generation in the ?-BBO crystal as a local oscillator, the crossed term between the TFISH and the local oscillator is proportional to the terahertz field. This phenomenon is used for coherent detection of intense terahertz waves, where a good linear response is observed for terahertz fields up to 160 kV/cm. In comparison, deviation from linear response and strong waveform distortion are observed when a 0.5-mm-thick ZnTe detector is used to characterize the same terahertz field.

Chen, Jian; Han, Pengyu; Zhang, X.-C.

2009-07-01

107

Modeling optical properties of liquid-crystal devices by numerical solution of time-harmonic Maxwell equations  

Microsoft Academic Search

We consider numerical modeling of the optical properties of devices typical of beam-steering devices based on liquid-crystal materials: two-dimensional, anisotropic and inhomogeneous dielectric properties, periodic in one dimension. A mathematical formulation of the system of second-order partial differential equations for the components of the time-harmonic electric field is discretized by using a finite-element method based on curl-conforming edge elements. The

Nandana D. Amarasinghe; Eugene C. Gartland; Jack R. Kelly

2004-01-01

108

Ferroelectric phases in a chiral bent-core smectic liquid crystal: Dielectric and optical second-harmonic generation measurements  

NASA Astrophysics Data System (ADS)

We report unambiguous evidence for ferroelectricity in a chiral bent-core liquid crystal. This evidence includes (i) a single current peak in the polarization reversal current, (ii) a strong dielectric response that is suppressed by applying a bias electric field, and (iii) strong optical second-harmonic generation in the absence of electric field even at normal incidence. We propose a phase structure that is anticlinic in tilt and ferroelectric in polar order, i.e., smectic-CAP*F.

Gorecka, E.; Pociecha, D.; Araoka, F.; Link, D. R.; Nakata, M.; Thisayukta, J.; Takanishi, Y.; Ishikawa, K.; Watanabe, J.; Takezoe, H.

2000-10-01

109

Crystallization, texture and second-harmonic generation in TiO 2-BaO-B 2O 3 glasses  

NASA Astrophysics Data System (ADS)

Partially crystallized glasses containing non-centrosymmetric ?-BaB 2O 4 (?-BBO) and/or BaTi(BO 3) 2 crystals were prepared by controlled surface crystallization of x1TiO 2- x2BaO- x3B 2O 3 glasses, where x1 = 4%, 8%, 15% and x2/ x3 = 8/9 (mol%). Differential thermal analyses were made to select appropriate heat treatments to partially crystallize some samples. The resulting crystalline phases were determined by X-ray diffraction and micro-Raman spectroscopy. Spontaneous preferred orientation (texture) occurred on the surface of all these glasses. Samples with x1 = 4% and 8% heat-treated from 1 to 32 h showed only ?-BaB 2O 4 precipitated on the glass surfaces, while the glass with x1 = 15% only had BaTi(BO 3) 2 in samples heat-treated for less than 8 h. Longer treatments also led to crystallization of ?-BaB 2O 4, occurring preferentially between the arms or underneath the BaTi(BO 3) 2 crystals, but present on the glass surface as well, and this became the predominant crystalline phase. Some surface crystallized glasses yielded a reasonable second-harmonic generation. The non-linear optical coefficient, deff, in the x1 = 15% crystallized sample was 1.1 pm/V, which corresponds to approximately 50% of that observed in the ?-BBO single crystal.

Feitosa, C. A. C.; Mastelaro, V. R.; Zanatta, A. R.; Hernandes, A. C.; Zanotto, E. D.

2006-06-01

110

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

111

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

112

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

113

Manifestation of quantum disordered wave functions with weak localization from conical second harmonic generation in ferroelectric crystal  

NASA Astrophysics Data System (ADS)

The spatial structure of two-dimensional quantum disordered wave functions with weak localization (WL) is experimentally observed using a calcium barium niobate Ca0.28Ba0.72Nb2O6 (CBN-28) ferroelectric crystal illuminated by a pulsed laser beam. Non-collinear phase-matching in CBN-28 produces conical second harmonic pattern in the far-field. The probability density distribution of the experimental near-field pattern agrees very well with the theoretical predictions. The localization degree, within the error limits, is the same at different transverse positions due to the periodicity of the crystal and the eigenfunctions are degenerated. We conclude that a ferroelectric crystal represents an ideal model system for investigation of WL.

Yu, H. H.; Zhang, H. J.; Wang, Z. P.; Xu, H. H.; Wang, Y. C.; Wang, J. Y.; Petrov, V.

2012-02-01

114

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

115

Ferroelectric Properties and Second Harmonic Intensities of Stillwellite-Type (La,Ln)BGeO5 Crystallized Glasses  

NASA Astrophysics Data System (ADS)

Glasses with compositions corresponding to stillwellite-type (La,Ln)BGeO5 (Ln: Nd, Gd, Eu and Tm) crystalline phases have been prepared, and the effect of lanthanide substitutions on ferroelectric properties and second harmonic (SH) intensities of stillwellite-type crystalline phases formed by crystallization of glasses has been examined. The substitution of \\textit{Ln}3+ for La3+ ions in the LaBGeO5 phase has been confirmed from the results of X-ray diffraction (XRD) analysis and fluorescence spectra of Eu3+ ions. The substitution of \\textit{Ln}3+ for La3+ ions causes a decrease not only in the lattice constants but also in the a/c axis ratio. The amount of substitutions depends on the \\textit{Ln}3+ ionic radius. The Curie temperature of crystallized glasses increases almost linearly with decreasing mean ionic radius of lanthanides estimated from the composition of base glasses. A similar trend is observed in the SH intensity for crystallized glasses (powdered form), indicating the presence of a close relationship between Curie temperature and SH intensity. It is proposed from Raman spectra that the enhancement of SH intensities is caused by the change in the arrangements of BO4 and GeO4 tetrahedra in the (La,Ln)BGeO5 crystals due to the substitution of \\textit{Ln}3+ ions having stronger \\textit{Ln}3+-O bonds. A clear second harmonic generation is observed in transparent surface crystallized glasses of the Nd2O3- or Gd2O3-substituted system.

Takahashi, Yoshihiro; Iwasaki, Akihisa; Benino, Yasuhiko; Fujiwara, Takumi; Komatsu, Takayuki

2002-06-01

116

Pressure-controlled phase matching to third harmonic in Ar-filled hollow-core photonic crystal fiber.  

PubMed

We report tunable third-harmonic generation (THG) in an Ar-filled hollow-core photonic crystal fiber, pumped by broadband <2 microJ, 30 fs pulses from an amplified Ti:sapphire laser system. The overall dispersion is precisely controlled by balancing the negative dielectric susceptibility of the waveguide against the positive susceptibility of the gas. We demonstrate THG to a higher-order guided mode and show that the phase-matched UV wavelength is tunable by adjusting the gas pressure. PMID:20808370

Nold, J; Hölzer, P; Joly, N Y; Wong, G K L; Nazarkin, A; Podlipensky, A; Scharrer, M; Russell, P St J

2010-09-01

117

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

118

Enhancement of second harmonic generation efficiency: Cs(I)-doped tris(thiourea)zinc(II) sulphate crystals  

NASA Astrophysics Data System (ADS)

The effect of dopant cesium (Cs(I)) over a concentration range from 1 to 10 mol% on the growth process, morphology, thermal and optical properties of tri(thiourea)zinc(II) sulfate (ZTS) single crystals grown by slow evaporation solution growth technique has been investigated. Incorporation of Cs(I) into the crystal lattice was well confirmed by energy dispersive X-ray spectroscopy (EDS). The lattice parameters of the as-grown crystals were obtained by single crystal X-ray diffraction analysis. The reduction in the intensities observed in powder X-ray diffraction patterns of doped specimen and slight shifts in vibrational frequencies in fourier transform infrared spectra (FT-IR) indicate the lattice stress as a result of doping. Thermal studies reveal the purity of the material and no decomposition is observed up to the melting point. High transmittance is observed in the visible region and the cut-off ? is ?280 nm. The surface morphology of the as-grown specimens was studied by scanning electron microscopy (SEM). The second harmonic generation (SHG) efficiency of the host crystal is enhanced greatly in the presence of high concentrations of the dopant.

Muthu, K.; Meenakshisundaram, SP.

2012-09-01

119

Exploring metastability via third harmonic measurements in single crystals of 2H- NbSe2 showing an anomalous peak effect  

NASA Astrophysics Data System (ADS)

We explore the metastability effects across the order-disorder transition pertaining to the peak effect phenomenonon in critical current density ( Jc ) via the first and the third harmonic ac susceptibility measurements in the weakly pinned single crystals of 2H- NbSe2 . An analysis of our data suggests that an imprint of the limiting (spinodal) temperature above which Jc is path independent can be conveniently located in the third harmonic data ( ? '3? ) .

Thakur, A. D.; Banerjee, S. S.; Higgins, M. J.; Ramakrishnan, S.; Grover, A. K.

2005-10-01

120

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

121

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

122

Giant optical second-harmonic generation in single and coupled microcavities formed from one-dimensional photonic crystals  

NASA Astrophysics Data System (ADS)

The nonlinear optical properties of one-dimensional all-solid-state photonic-crystal microcavities (MCs) are experimentally studied by second-harmonic generation (SHG) spectroscopy in both the frequency and the wave-vector domains. The studied single and coupled MCs are formed by the alternating of mesoporous silicon layers of different porosities. When the fundamental radiation is in resonance with the MC mode the second-harmonic intensity is enhanced by a factor of approximately 102. The resonant SHG response is compared with the off-resonance response, as the fundamental wavelength is outside the photonic bandgap. The splitting of the modes of two identical coupled MCs is observed in the wave-vector domain spectrum of enhanced SHG. The SHG enhancement is attributed to the combined effects of the spatial localization of the fundamental field in the MC spacer and the fulfillment of the phase-matching conditions. The confinement of the resonant fundamental field is probed directly at the MC cleavage by a scanning near-field optical microscope. The role of the phase matching that is associated with the giant effective dispersion in the spectral vicinity of the MC mode is deduced from a comparison with the SHG peaks at both edges of the photonic bandgap.

Dolgova, Tatyana V.; Maidykovski, Anton I.; Martemyanov, Michail G.; Fedyanin, Andrey A.; Aktsipetrov, Oleg A.; Marowsky, Gerd; Yakovlev, Vladimir A.; Mattei, Giorgio; Ohta, Narumi; Nakabayashi, Seiichiro

2002-09-01

123

Theoretical and Experimental Studies of Type I and Type II Phase Matched Second Harmonic Generation in Organic Single Crystals.  

NASA Astrophysics Data System (ADS)

The conditions for phase matched second harmonic generation (SHG) in the organic molecular crystal dicyanovinyl-anisole (DIVA) were calculated from frequency dependent refractive index values. The Type I and Type II phase matched SHG tuning curves show non critical phase matching at 880 and 967 nm, respectively. These calculated results are in reasonable agreement with SHG measurements in the fundamental wavelength range of 850 to 970 nm. Non critical Type I phase matching is observed at 860 nm with a calculated bandwidth of 1.43/length GHz-cm. Because of an absorption band edge near 430 nm, Type I phase matched SHG is largely absorbed at the non critical wavelength. Experiments are underway to measure the Type II phase matched SHG tuning curve and condition of non criticality.

Schulhofer-Wohl, Samuel; Grossman, Carl

1996-03-01

124

OPTICAL FIBRES: Optical harmonic generation in hollow-core photonic-crystal fibres: analysis of optical losses and phase-matching conditions  

NASA Astrophysics Data System (ADS)

We consider hollow-core fibres with a microstructure photonic-crystal cladding, which open a unique opportunity of implementing nonlinear-optical interactions of waveguide modes with transverse sizes on the order of several microns in the gas phase. Phase-matching conditions for optical harmonic generation can be improved in higher waveguide modes of hollow-core photonic-crystal fibres by optimising parameters of the gas medium filling the fibre and characteristics of the fibre.

Naumov, A. N.; Zheltikov, Aleksei M.

2002-02-01

125

Second harmonic generation and sum frequency mixing of dual wavelength Nd:YALO3 laser in flux grown KTiOPO4 crystal  

Microsoft Academic Search

On the basis of accurately measured refractive indexes, the authors have obtained the Sellmeier's equations for flux grown KTiOPO4 (KTP) crystal and used them to calculate the phase matched angles (theta sub m, phi sub m) and effective nonlinear coefficients (d sub eff) for type I and III second harmonic generation (SHG) and sum frequency mixing (SFM) of radiations at

H. Y. Shen; Y. P. Zhou; W. X. Lin; Z. D. Zeng; R. R. Zeng; G. F. Yu; C. H. Huang; A. D. Jiang; S. Q. Jia; D. Z. Shen

1992-01-01

126

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

127

Analysis of a novel stator winding structure minimizing harmonic current and torque ripple for dual six-step converter-fed high power AC machines  

Microsoft Academic Search

The authors study the causes of degraded converter current when dual six-step power converters feed a dual winding induction machine drive. They proposed an end winding structure and corresponding control strategy to solve the converter current problem while retaining the advantages of the dual winding induction machine drive. Principles associated with the stator winding are discussed, and a practical implementation

Lurong Ye; Longya Xu

1993-01-01

128

Green light source by single-pass second harmonic generation with laser and crystal in a tilted butt joint setup  

NASA Astrophysics Data System (ADS)

In this work a compact green laser light source is presented based on a single-pass second harmonic generation (SHG) in non-linear material. The green light source consists of a distributed feedback (DFB) laser with a monolithically integrated power amplifier (PA) and a periodically poled lithium niobate (PPLN) crystal with a ridge waveguide. To achieve the smallest size and to reduce the number of parts to be assembled, a direct coupling approach is implemented without using any lens. The waveguide of the laser is bent and the facet of the crystal is tilted and AR-coated in order to reduce undesired reflections and to increase the stability of operation. By varying the injection current of the amplifier the infrared output power of the laser changes proportionally. The wavelength remains stable during current variation and in that way the green optical output power can also be modulated. No additional external modulator is required for the generation of distinct green light levels. At a wavelength of 530 nm, a green optical output power of more than 35 mW is achieved for injection currents of 93 mA and 400 mA through the DFB section and amplifier section respectively.

Wiedmann, J.; Scholz, F.; Tekin, T.; Marx, S.; Lang, G.; Schröder, H.; Brox, O.; Erbert, G.

2009-02-01

129

Study of Second Harmonic Generation Coefficients and Ultraviolet Absorption Edge of Barium Borate Crystal.  

National Technical Information Service (NTIS)

Barium borate (beta-BaB2O4) is a new type of non-linear optical crystal. In this paper the authors report one-electron energies and wave functions of barium borate by use of EHMO theory. Both the calculated values of SHG coefficient and ultraviolet absorp...

J. K. Zhu B. Zhang S. H. Liu

1985-01-01

130

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

131

Analysis of a novel stator winding structure minimizing harmonic current and torque ripple for dual six-step converter-fed high power AC machines  

Microsoft Academic Search

Many attempts have been made to expand the application of AC motor drives to high-power levels. One way to use AC motor drives at high-power levels is to use multiple power converters together to supply power to a large machine. For a multiple converter combination scheme, the six-step power converter is competitive due to its robust structure and simplicity of

Longya Xu; Lurong Ye

1995-01-01

132

Direct Observation of Bloch Harmonics and Negative Phase Velocity in Photonic Crystal Waveguides  

NASA Astrophysics Data System (ADS)

The eigenfield distribution and the band structure of a photonic crystal waveguide have been measured with a phase-sensitive near-field scanning optical microscope. Bloch modes, which consist of more than one spatial frequency, are visualized in the waveguide. In the band structure, multiple Brillouin zones due to zone folding are observed, in which positive and negative dispersion is seen. The negative slopes are shown to correspond to a negative phase velocity but a positive group velocity. The lateral mode profile for modes separated by one reciprocal lattice vector is found to be different.

Gersen, H.; Karle, T. J.; Engelen, R. J.; Bogaerts, W.; Korterik, J. P.; van Hulst, N. F.; Krauss, T. F.; Kuipers, L.

2005-03-01

133

Minimizing the current harmonics RMS value of three-phase PWM converter systems by optimal and suboptimal transition between continuous and discontinuous modulation  

Microsoft Academic Search

A given converter voltage space vector can be realized by a three-phase PWM converter system by switching only two bridge legs. There, the third phase is clamped to the positive or negative DC link voltage. This method is called discontinuous modulation, due to the discontinuous shape of the generating phase modulation functions. As a closer analysis shows, the discontinuous method

JOHANN W. KOLAR; HANS ERTL; FRANZ C. ZACH

1991-01-01

134

Designing photonic quasi-crystal fibers of various folds: onto optimization of efficiency and bandwidth of second harmonic generation.  

PubMed

We design photonic quasi-crystal fibers (PQFs) of six-, eight-, ten-, and twelve-folds for determining the optimized efficiency as well as the bandwidth of second harmonic generation (SHG). We report a maximum SHG relative efficiency of 941.36?%??W-1??cm-2 for a twelve-fold PQF of 2 ?m pitch. The detailed numerical results reveal that, while the relative efficiency increases appreciably, the phase-matching bandwidth increases marginally, as and when the number of folds increases. As the primary interest of this work is to enhance the relative efficiency, we focus our analysis with a twelve-fold PQF for which the efficiency turns a maximum. In line with the practical feasibility of poling, we keep the pitch at 7 ?m and report an optimized relative efficiency and phase-matching bandwidth as 95.28?%??W-1??cm-2 and 50.51 nm.cm, respectively. PMID:24921878

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

2014-05-01

135

Collimating properties of an axicon for the ?erenkov-radiation-type second-harmonic light from a crystal-cored fiber.  

PubMed

The optical second-harmonic wave generated from a crystal-cored fiber from the ?erenkov-radiation-type phase matching can be collimated by an axicon and then can be focused by a spherical lens to a diffraction-limited spot. Tolerance of the optical system to meet the Maréchal criterion is analyzed; tolerable maximum errors in alignment and fabrication of the axicon lens are evaluated. PMID:20885688

Chikuma, K; Okamoto, S; Tohma, T; Umegaki, S

1994-05-20

136

Second Harmonic Generation of Self-Mode-Locked ??2-Laser Radiation in GaSe and GaSeS Crystals  

NASA Astrophysics Data System (ADS)

A TEA CO2 laser generating at the wavelength ? = 10.6 ?m in the modes of free lasing and self-mode-locking was used to obtain and compare second harmonic generation (SHG) in GaSe and GaSe0.7S0.3 crystals. With the self-mode-locked laser, a 5-times higher energy efficiency of SHG was obtained. The efficiency of SHG in the GaSe0.7S0.3 crystal and its second-order nonlinear susceptibility were estimated and compared with their values for undoped GaSe.

Genin, D. E.; Beloplotov, D. V.; Sitnikov, A. G.; Panchenko, A. N.; Sarkisov, S. Yu.; Chernyshov, A. I.

2014-03-01

137

Harmonic State Space model of power electronics  

Microsoft Academic Search

This paper presents a technique for deriving the linearized Harmonic State Space model of a power electronic converter. The Harmonic State Space model, in which harmonics of state variables, inputs and outputs are posed separately in a State Space form, can be used for dynamic small signal studies, and for harmonic steady state studies. The technique can handle autonomous switches

G. N. Love; A. R. Wood

2008-01-01

138

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

139

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

SciTech Connect

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

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

2013-08-26

140

In-situ characterization of femtosecond laser-induced crystallization in borosilicate glass using time-resolved surface third-harmonic generation  

SciTech Connect

Coherent phonon dynamics in condensed-phase medium are responsible for important material properties including thermal and electrical conductivities. We report a structural dynamics technique, time-resolved surface third-harmonic generation (TRSTHG) spectroscopy, to capture transient phonon propagation near the surface of polycrystalline CaF{sub 2} and amorphous borosilicate (BK7) glass. Our approach time-resolves the background-free, high-sensitivity third harmonic generation (THG) signal in between the two crossing near-IR pulses. Pronounced intensity quantum beats reveal the impulsively excited low-frequency Raman mode evolution on the femtosecond to picosecond timescale. After amplified laser irradiation, danburite-crystal-like structure units form at the glass surface. This versatile TRSTHG setup paves the way to mechanistically study and design advanced thermoelectrics and photovoltaics.

Liu, Weimin; Wang, Liang; Han, Fangyuan; Fang, Chong [Department of Chemistry, Oregon State University, Corvallis, Oregon 97331 (United States)] [Department of Chemistry, Oregon State University, Corvallis, Oregon 97331 (United States)

2013-11-11

141

All-optical wavelength converter based on self-phase modulation in highly nonlinear photonic crystal fiber  

NASA Astrophysics Data System (ADS)

A simple architecture of all-optical wavelength conversion in a highly nonlinear bismuth oxide-based photonic crystal fiber (PCF) is proposed, which consists of an erbium-doped fiber amplifier, a polarization controller, a nonlinear medium PCF, two tunable fiber Fabry-Perot filters and an optical isolator. Self-phase modulation is utilized to induce spectral broadening for all-optical wavelength conversion. The desired dispersion properties can be tailored by the parameters of bismuth oxide-based PCF microstructure. The propagation loss at 1550nm is about 0.8dB/m. The nonlinear coefficient is expected to be 1100W -1km -1 by using bismuth oxide-based glass and reducing the effective core area. The mode-field diameter of PCF is estimated to be 1.98?m and the predicted effective core area is 3.3?m2. The intermediate high numerical aperture fibers between bismuth oxide-based PCF and single-mode fibers are considered to reduce the splicing loss. The obtained results show that the all-optical wavelength converter has a potential of high conversion efficiency, wide conversion bandwidth, ultrafast response time, compact configuration and low insertion loss etc.

Yan, Huangping; Huang, Yuanqing; Weng, Zihua; Wang, Yiju; Ye, Ruifang; Wu, Zhaoxi; Wan, Jin

2008-03-01

142

Output voltage switching noise peaks and utility AC input harmonic current characteristics of delta-sigma modulated AC-DC converter with boost-buck circuit topologies  

Microsoft Academic Search

A high frequency carrier PWM regulator used for various types of switch-mode power converters are based on the digital or analog signal comparison processing. The voltage-mode or current-mode PWM strategies due to comparison signal processing between voltage\\/current reference and periodic carrier signals cause the switching noise peaks dependent on the multiple numbers of carrier signal frequency. In general, the switching

Atsushi Hirota; Sang-Pil Mun; Soon-Kurl Kwon; M. Nakaoka

2009-01-01

143

Single-Phase Back-To-Back Converter for Active Power Balancing, Reactive Power Compensation, and Harmonic Filtering in Traction Power System  

Microsoft Academic Search

An active power compensator (APC) based on single- phase back-to-back power converter is proposed in this paper to solve problems of power quality of electric railway power sup- ply system. This system adopts a single-phase feeding connection, which is called cophase power supply scheme. In this scheme, APC connects the balance transformer between feeding phase for power supply and another

Zeliang Shu; Shaofeng Xie; Qunzhan Li

2011-01-01

144

Optical harmonic generator  

DOEpatents

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

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

1982-06-10

145

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

146

Liquid Crystal Display (LCD) Supplied by Highly Integrated Dual-Side Dual-Output Switched-Capacitor DC-DC Converter With Only Two Flying Capacitors  

Microsoft Academic Search

This paper proposes a highly integrated dual-side dual-output (DSDO) switched-capacitor (SC) converter with only two flying capacitors. Generally, a dual-phase voltage doubler and an inverter are used to supply positive and negative voltages for thin film transistor-liquid crystal display (TFT-LCD) gate drivers, respectively. Four flying capacitors, eight pin-outs for the four flying capacitors, and 16 power switches are necessary for

Yang-Ching Lin; Yean-Kuo Luo; Ke-Horng Chen; Wei-Chou Hsu

2012-01-01

147

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

148

Broadband dynamic phase matching of high-order harmonic generation by a high-peak-power soliton pump field in a gas-filled hollow photonic-crystal fiber.  

PubMed

Hollow-core photonic-crystal fibers are shown to enable dynamically phase-matched high-order harmonic generation by a gigawatt soliton pump field. With a careful design of the waveguide structure and an appropriate choice of input-pulse and gas parameters, a remarkably broadband phase matching can be achieved for a soliton pump field and a large group of optical harmonics in the soft-x-ray-extreme-ultraviolet spectral range. PMID:18451958

Serebryannikov, Evgenii E; von der Linde, Dietrich; Zheltikov, Aleksei M

2008-05-01

149

Broadband Frequency Mixing and Second-Harmonic Generation in 2-METHYL-4-NITROANILINE Thin Crystal from 250 FS Pulses  

NASA Astrophysics Data System (ADS)

In this paper, we present the experimental proof that even for highly nonlinear (NL), such as 2-methyl-4-nitroaniline (MNA), wave mixing has negligible effect on the second-harmonic generation (SHG) using 250 fs fundamental pulses. We explain our experimental results with a simple formalism based on monochromatic plane wave (MPW).

Ben-Messaoud, T.; Desforges, J.; Gauvin, S.

150

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

151

Growth and characterization of crystals for room temperature I.R. detectors and second harmonic generation devices  

NASA Technical Reports Server (NTRS)

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 temperature compared to undoped TGS crystals. Towards these objectives, many promising dopants, both inorganic and organic, were investigated in the last few years. These dopants gave significant improvement in the D(sup *) value of the infrared detectors fabricated from the grown crystals with no significant increase in the Curie temperature (49 C). The IR detectors were fabricated at EDO/Barnes Engineering Division, Shelton, CT. In the last one year many TGS crystals doped with urea were grown using the low temperature solution crystal growth facility. It is found that doping with urea, the normalized growth yield increased significantly compared to pure TGS crystals and there is an improvement in the pyroelectric and dielectric constant values of doped crystals. This gave a significant increase in the materials figure of merits. The Vicker's hardness of 10 wt percent urea doped crystals is found to be about three times higher in the (010) direction compared to undoped crystals. This report describes in detail the results of urea doped TGS crystals.

Lal, R. B.

1995-01-01

152

Harmonic Drive.  

National Technical Information Service (NTIS)

The harmonic drive has utility in optical tracking telescopes, radar antenna drives, aircraft control surface actuators, and high precision X-Y plotting equipment. Two harmonic drive units, each having its own input motor, are coupled together. One of the...

R. H. Lapp

1965-01-01

153

Harmonic Analysis of Rail Transportation Systems with Probabilistic Techniques  

Microsoft Academic Search

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

J. van Casteren; F. Groeman

2006-01-01

154

Bandwidth considerations for multilevel converters  

Microsoft Academic Search

Multilevel converters can achieve an overall effective switch frequency multiplication and consequent ripple reduction through the cancellation of the lowest order switch frequency terms. This paper investigates the harmonic content and the frequency response of these multimodulator converters. It is shown that the transfer function of uniformly sampled modulators is a bessel function associated with the inherent sampling process. Naturally

Geoff Walker; Gerard Ledwich

1999-01-01

155

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

156

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

157

Role of Acentric Displacements on the Crystal Structure and Second-Harmonic Generating Properties of RbPbCO3F and CsPbCO3F.  

PubMed

Two lead fluorocarbonates, RbPbCO3F and CsPbCO3F, were synthesized and characterized. The materials were synthesized through solvothermal and conventional solid-state techniques. RbPbCO3F and CsPbCO3F were structurally characterized by single-crystal X-ray diffraction and exhibit three-dimensional (3D) crystal structures consisting of corner-shared PbO6F2 polyhedra. For RbPbCO3F, infrared and ultraviolet-visible spectroscopy and thermogravimetric and differential thermal analysis measurements were performed. RbPbCO3F is a new noncentrosymmetric material and crystallizes in the achiral and nonpolar space group P6?m2 (crystal class 6?m2). Powder second-harmonic generation (SHG) measurements on RbPbCO3F and CsPbCO3F using 1064 nm radiation revealed an SHG efficiency of approximately 250 and 300 × ?-SiO2, respectively. Charge constants d33 of approximately 72 and 94 pm/V were obtained for RbPbCO3F and CsPbCO3F, respectively, through converse piezoelectric measurements. Electronic structure calculations indicate that the nonlinear optical response originates from the distorted PbO6F2 polyhedra, because of the even-odd parity mixing of the O 2p states with the nearly spherically symmetric 6s electrons of Pb(2+). The degree of inversion symmetry breaking is quantified using a mode-polarization vector analysis and is correlated with cation size mismatch, from which it is possible to deduce the acentric properties of 3D alkali-metal fluorocarbonates. PMID:24867361

Tran, T Thao; Halasyamani, P Shiv; Rondinelli, James M

2014-06-16

158

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

159

Conversion efficiency analysis of second harmonic generation of the novel nonlinear crystal RbBe2BO3F2  

NASA Astrophysics Data System (ADS)

For the first time, the SHG efficiency of RBBF crystal in type-I and type-II phase matching has been simulated. RBBF crystal is pumped by the fundamental radiation of a Q-switched Nd:YAG laser with the wavelength of 1064nm and the shape of plane wave or Gaussian beam. When the pumped radiation is of plane wave, the conversion efficiency of RBBF in type-I and type-II could be as high as 100% and 78%. When the pumped radiation is of Gaussian beam, the conversion efficiency shows a monotonically increasing trend in the type-I phase matching, and in the type-II phase matching the conversion efficiency varies periodically.

Sun, Rui; Wang, Li; Bao, Chuanchen

2012-11-01

160

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)] [Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

1997-04-01

161

Second-harmonic generation of blue light in LiNbO3 crystal with periodic ferroelectric domain structures  

Microsoft Academic Search

Optical pulse generation of blue light (430 and 435 nm) was demonstrated in a bulk yttrium-doped LiNbO3 crystal with periodic ferroelectric domain structures, under the condition of quasi-phase matching. Blue light output of 0.2 microJ energy was measured for input energy 5 microJ of fundamental wave in pulse operation. The average efficiency was 4.2 percent, and the maximal point pulse

Ya-Lin Lu; Lun Mao; Shi-De Cheng; Nai-Ben Ming; Yu-Tian Lu

1991-01-01

162

Direct observation of transient Ostwald crystallization ordering from racemic serine solutions.  

PubMed

The Ostwald rule of stages describes the conjectured transitioning through metastable polymorphic crystal structures during crystallization. Direct observation of the Ostwald rule of stages using was performed using solutions of simple amino acids by second-order nonlinear optical imaging of chiral crystals (SONICC). SONICC, which is based on second-harmonic generation (SHG) imaging, enabled detection of homochiral microcrystals that survived only a few seconds before being converted to the more stable SHG-inactive polymorphic forms. PMID:20828149

Hall, Victoria J; Simpson, Garth J

2010-10-01

163

a Study of New Optical Materials. I. Crystal-Chemical Development of New Optical Frequency Converters. I. New Hosts for Chromium  

NASA Astrophysics Data System (ADS)

The emphasis of this work has been in two areas of optical materials--the crystal-chemical development of new optical frequency converters and the synthesis and study of the new hosts for Cr^{3+} luminescence and lasing. A simple method has been developed to identify promising frequency-doubling materials containing triangular oxoanions by estimation of nonlinear susceptibilities. Implementation of this method and its results have generated predictive capabilities in determining the relationships among crystal structure, nonlinear properties, and threshold powers. The new noncentrosymmetric borate SrLiB_9O _{15} is discussed; its structure is built from a 3-dimensional condensation of B_3O_7 units with channels alternately filled with Sr and Li atoms. From these studies, a prescription for new pyroborate frequency converters has been developed. The material CdCl _2C_3H_7 NO_2, has been synthesized and structurally characterized by single-crystal X-ray diffraction. Three new alkaline-earth beryllium borates, built from unique 2- and 3-dimensional networks and frameworks, have been identified. The structure of SrBe_2 (BO_3)_2 consists of layers of composition (Be_2(BO _3)_2]^{2- } interleaved by Sr atoms. CaBeB_2 O_5 is constructed from a CaO_9 polyhedral network and a beryllium borate network. In BaBe_2(BO _3)_2 the structure is composed of a beryllium borate framework intermingled with a Ba-centered dodecahedral framework. Several materials with potential as hosts for Cr^{3+} lasing have been analyzed. The structural study of the laser host LiSrAlF _6 revealed the distortions at the Al site that contribute to the unique optical properties of the Cr^{3+}-doped crystals. The family of solid state oxide A_6MM ^'(BO_3) _6 is one of the largest families of oxide reported to date. Metal site preferences, disorder, solid solubility, and the interrelationship between this structure and the layered structure type of Ba_3Sc(BO _3)_3 are detailed. An optimal synthetic procedure has been developed for these materials to provide pure, highly crystalline phases. Also, the structural and optical features of (Cr^ {3+}:) Sr_3In(BO _3)_3 with A = Sr and M = M^' = In have been studied. The material Sr_2LiInB _4O_{10}, was discovered while searching for a suitable lithium borate flux for crystal growth of the compound Sr _3In(BO_3)_3..

Schaffers, Kathleen Irene

164

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

165

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

166

Harmonic conversion of large-aperture 1. 05-. mu. m laser beams for inertial-confinement fusion research  

Microsoft Academic Search

To provide high-energy, high-power beams at short wavelengths for inertial-confinement fusion experiments, we routinely convert the 1.05-Îźm output of the Nova, Nd:phosphate-glass, laser system to its second- or third-harmonic wavelength. We describe the design and performance of the 3 Ă 3 arrays of potassium dihydrogen phosphate crystal plates used for type-II--type-II phase-matched harmonic conversion of the Nova 0.74-m diameter beams.

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

1992-01-01

167

Harmonic compensator for 50Hz fed AC railway vehicles  

Microsoft Academic Search

AC railway vehicles controlled by PWM line-side power converters inject harmonic current into the feeding overhead line. This causes problems such as resonance expansions which produce malfunctions or overcurrents at substations and electromagnetic interference with signalling systems. Normal active filters only shift the harmonic frequencies to a higher range. A novel harmonic compensator produces an exact counter-MMF of which in

M. Ogasa; J. O. Krah; J. Holtz

1997-01-01

168

An Investigation of Capacitors for Flying Capacitor Converters  

NASA Astrophysics Data System (ADS)

Multi-level converters can essentially reduce harmonics even when their switching frequency is low. Among the various topologies of the multi-level converters, flying capacitor converters are considered to be promising converters for realizing high power density. However, the main circuit of the flying capacitor converters has many capacitors. Therefore, in this study, the volume of the capacitors in the flying capacitor converters is determined by taking into consideration the allowable ripple voltage and temperature rise in the capacitor.

Obara, Hidemine; Kamaga, Masamu; Ito, Takumi; Sato, Yukihiko

169

Harmonic modelling of offshore wind farms  

Microsoft Academic Search

The combination of extensive cable networks and wind turbine converters has been identified as a potential cause of resonances. A modelling approach for a doubly fed induction generator and a full power converter fed generator for harmonic penetration studies is developed and discussed. An example offshore wind farm is then studied in the simulation package IPSA using the detailed wind

R. King; J. B. Ekanayake

2010-01-01

170

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

NASA Astrophysics Data System (ADS)

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 Bi2ZnTiO6. 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 LiNbO3. 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 Bi2ZnTiO6 with that of the linear optical dielectric function in terms of single-photon and double-photon resonances. Our calculations demonstrate the promising application of Bi2ZnTiO6 in optoelectronics.

Ju, Sheng; Guo, Guang-Yu

2008-11-01

171

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

172

Three-phase, power quality improvement ac\\/dc converters  

Microsoft Academic Search

The generation of harmonics and reactive power flow in a power system is greatly influenced by the widespread use of power electronic converters in addition to other sources of harmonics and reactive power. The design, development and successful application of single-phase, power quality improvement converters in domestic, commercial and industrial environment has made possible the design and development of three-phase,

Abdul Hamid Bhat; Pramod Agarwal

2008-01-01

173

Second harmonic generation in single-crystal thin membranes of LiNbO3 fabricated by patterned He+ ion implantation  

Microsoft Academic Search

We demonstrate room-temperature phase matching of second-harmonic generation by waveguide dispersion (WGD) in 3-mum-thick LiNbO3 membranes. The membranes were made using patterned deep-ion-implantation-guided etching.

O. Gaathon; A. Ofan; D. Djukic; J. I. Dadap; R. M. Osgood; S. Bakhru; H. Bakhru

2008-01-01

174

Low-cost frequency-converted laser light sources  

NASA Astrophysics Data System (ADS)

We report a fast-switching two-component frequency-converted laser with reduced speckle visibility. A bottom-emitting passively Q-switched laser with integrated electroabsorber, folding mirror and coupling lens was successfully applied with a waveguide-type periodically poled magnesium oxide doped lithium niobate crystal to generate second harmonic light at 532 nm. Reduced speckle visibility was demonstrated when operating the laser in self-pulsating mode when compared to continuous-wave operation even when using a nonlinear crystal with narrow acceptance bandwidth of 0.24 nm @ 1064 nm. The spectral width of the infrared light was 0.33 nm in pulsed mode and 0.08 nm in continuous-wave mode resulting in visible light spectral width of 0.12 nm and 0.03 nm in self-pulsating and continuous-wave mode.

Konttinen, J.; Tuomisto, P.; Vallius, T.; Pietilä, P.; Jouhti, T.

2010-02-01

175

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

176

An algorithm of the harmonics on traction power system of the electrified railway  

Microsoft Academic Search

The authors explore harmonic calculations for Chinese electrified railway systems. One of the branches of the electrified railway power system in operation was emulated and calculated with special purpose software for analyzing harmonic currents. The multiple harmonic sources and the asymmetry of the system make the harmonic analysis complicated. The three-phase power system is converted into a single-phase network with

Pan Yinxuan; Sun Shugin; Li Chunhua

1990-01-01

177

Thermophotovoltaic converter  

SciTech Connect

A thermophotovoltaic converter of the type comprising a concentrating optical system and a transducer for solar radiation provided with at least one lens and with at least one photovoltaic cell is described. The principal feature of this converter is that the aforementioned transducer comprises at least a radiator having an irradiating surface substantially facing the sensitive surface of the photovoltaic cell and a selective filter disposed between the photovoltaic cell and the aforementioned radiator.

Boero, A.; Demichelis, F.; Ferrari, G.; Minetti-mezetti, E.; Palazzetti, M.

1982-05-25

178

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

179

Thermionic converter  

DOEpatents

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

Fitzpatrick, Gary O. (Livermore, CA)

1987-05-19

180

High-Gain Harmonic-Generation Free-Electron Laser Seeded by Harmonics Generated in Gas  

NASA Astrophysics Data System (ADS)

The injection of a seed in a free-electron laser (FEL) amplifier reduces the saturation length and improves the longitudinal coherence. A cascaded FEL, operating in the high-gain harmonic-generation regime, allows us to extend the beneficial effects of the seed to shorter wavelengths. We report on the first operation of a high-gain harmonic-generation free-electron laser, seeded with harmonics generated in gas. The third harmonics of a Ti:sapphire laser, generated in a gas cell, has been amplified and up-converted to its second harmonic (?rad=133nm) in a FEL cascaded configuration based on a variable number of modulators and radiators. We studied the transition between coherent harmonic generation and superradiant regime, optimizing the laser performances with respect to the number of modulators and radiators.

Labat, M.; Bellaveglia, M.; Bougeard, M.; Carré, B.; Ciocci, F.; Chiadroni, E.; Cianchi, A.; Couprie, M. E.; Cultrera, L.; Del Franco, M.; di Pirro, G.; Drago, A.; Ferrario, M.; Filippetto, D.; Frassetto, F.; Gallo, A.; Garzella, D.; Gatti, G.; Giannessi, L.; Lambert, G.; Mostacci, A.; Petralia, A.; Petrillo, V.; Poletto, L.; Quattromini, M.; Rau, J. V.; Ronsivalle, C.; Sabia, E.; Serluca, M.; Spassovsky, I.; Surrenti, V.; Vaccarezza, C.; Vicario, C.

2011-11-01

181

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

182

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

PubMed

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

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

2014-01-01

183

Selection of the PWM algorithm for 3-phase interleaved converters  

Microsoft Academic Search

One solution for high current applications consists of paralleling power stages of lower power. This paper analyzes and justifies the selection of the PWM algorithm used within interleaved three-phase power inverters with respect to the resulting phase current harmonics, DC link current harmonics, neutral point voltage and inter-converter circulation currents. Analytical aspects of different current control structures used within interleaved

Dorin O. Neacsu; Edward Wagner; Bogdan Borowy

2002-01-01

184

Effects of High Power Electronics Converters on PLC Signals  

Microsoft Academic Search

The harmonics are generated by the switching operation of large power converters, such as Static Compensator (STATCOM), Static Reactive Power Controller (SVC) and UPFC. These harmonics may cover a wide range of frequencies and it can cause problems of interference with communication systems. Power Line Carrier (PLC) system is one of the systems used in transmission of signals for Tele-potations,

S. M. Bashi; A. U. M. Al-Abulaziz; N. F. Mailah

2006-01-01

185

Shaping the Noise Spectrum in Power Electronic Converters  

Microsoft Academic Search

The operation of switch-mode converters results in electromagnetic noise propagating throughout the power elec- tronic system. Pulsewidth modulation (PWM) strategies with fixed switching frequency generate harmonics in the spectra of con- verter voltages and currents. Random PWM techniques allow the elimination of the harmonics, resulting in a continuous spectrum of noise, i.e., a spectrum retaining all frequency components. As a

R. Lynn Kirlin; Cristian Lascu; Andrzej M. Trzynadlowski

2011-01-01

186

crystal  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

187

X-Ray Second Harmonic Generation  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

188

Unified approach to ?erenkov second harmonic generation.  

PubMed

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

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

2013-11-01

189

X-ray second harmonic generation.  

PubMed

We report clear experimental evidence for second harmonic generation at hard x-ray wavelengths. Using a 1.7 Ĺ pumping beam generated by a free electron laser, we observe second harmonic generation in diamond. The generated second harmonic is of order 10 times the background radiation, scales quadratically with pump pulse energy, and is generated over a narrow phase-matching condition. Of importance for future experiments, our results indicate that it is possible to observe nonlinear x-ray processes in crystals at pump intensities exceeding 1016??W/cm2. PMID:24815649

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

2014-04-25

190

Voltage-source active power filter based on multilevel converter and ultracapacitor DC link  

Microsoft Academic Search

A new topology for active power filters (APF) using an 81-level converter is analyzed. Each phase of the converter is composed of four three-state converters, all of them connected to the same capacitor dc link voltage and their output connected in series through output transformers. The main advantages of this kind of converter are the negligible harmonic distortion obtained and

Micah E. Ortúzar; Rodrigo E. Carmi; Juan W. Dixon; Luis Morán

2006-01-01

191

A Signal-Processing Adaptive Algorithm for Selective Current Harmonic Cancellation in Active Power Filters  

Microsoft Academic Search

Selective harmonic cancellation has become of primary importance in a wide range of power electronics applications, for example, uninterrupted power systems, regenerative converters, and active power filters (APFs). In such applications, the primary objectives are an accurate cancellation of selected harmonics and a quick speed of response under transients. This paper provides a novel signal-processing algorithm for selective harmonic identification

Francisco D. Freijedo; JesÚs Doval-Gandoy; Óscar Lopez; Pablo Fernandez-Comesana; Carlos Martinez-Penalver

2009-01-01

192

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 Ĺ, b = 11.15 Ĺ and c = 15.47 Ĺ. 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

193

Comparison of multilevel converter-based STATCOMs  

Microsoft Academic Search

Multilevel converters have become the real option for high voltage and current applications for power systems, especially for FACTS controllers. The Static Compensator (STATCOM) is a shunt-type device which can be used to control reactive power in a network as of its many advantages such as fast speed, compact footprint and small harmonics. In this work a comparison between two

J. H. Vivas; G. Bergna; M. Boyra

2011-01-01

194

Power converter  

NASA Technical Reports Server (NTRS)

A dc-to-dc converter employs four transistor switches in a bridge to chop dc power from a source, and a voltage multiplying diode rectifying ladder network to rectify and filter the chopped dc power for delivery to a load. The bridge switches are cross coupled in order for diagonally opposite pairs to turn on and off together using RC networks for the cross coupling to achieve the mode of operation of a free running multivibrator, and the diode rectifying ladder is configured to operate in a push-pull mode driven from opposite sides of the multivibrator outputs of the ridge switches. The four transistor switches provide a square-wave output voltage which as a peak-to-peak amplitude that is twice the input dc voltage, and is thus useful as a dc-to-ac inverter.

Black, J. M. (inventor)

1981-01-01

195

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

196

crystal  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

197

A Comparative Evaluation of Three-Phase High Power Factor Boost Converters for Power Quality Improvement  

Microsoft Academic Search

The generation of harmonics and reactive power flow in a power system is greatly influenced by the widespread use of Power Electronic converters in addition to other sources of harmonics and reactive power generation. This paper gives a comparative evaluation of some improved power quality three-phase Boost converters based on their performance, specifically from the point of view of improved

A. H. Bhat; P. Agarwal

2006-01-01

198

Control Strategies of a Hybrid Multilevel Converter for Expanding Adjustable Output Voltage Range  

Microsoft Academic Search

This paper proposes a new arrangement and new control strategies for a hybrid multilevel converter aiming at a high power high efficiency converter system with being free from harmonic distortion of the output. The strategies enable one to expand the adjustable output voltage range up to 100% with keeping very low harmonic distortion of the output voltages. The triangular-carrier based

Shoji Fukuda; Takatsugu Yoshida; S. Ueda

2007-01-01

199

A Simple, Passive 24Pulse AC–DC Converter With Inherent Load Balancing  

Microsoft Academic Search

A new converter topology for a three-phase multipulse rectifier circuit is described. This converter draws almost sinusoidal currents from the ac system with very low harmonic content and typically less than 3% total harmonic distortion. The topology uses only passive components and has a lower component count than other rectifier circuits with similar performance. Two six-pulse rectifier bridges are connected

F. Javier Chivite-Zabalza; Andrew J. Forsyth; David R. Trainer

2006-01-01

200

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

201

Harmonic analysis of spacecraft power systems using a personal computer  

NASA Technical Reports Server (NTRS)

The effects that nonlinear devices such as ac/dc converters, HVDC transmission links, and motor drives have on spacecraft power systems are discussed. The nonsinusoidal currents, along with the corresponding voltages, are calculated by a harmonic power flow which decouples and solves for each harmonic component individually using an iterative Newton-Raphson algorithm. The sparsity of the harmonic equations and the overall Jacobian matrix is used to an advantage in terms of saving computer memory space and in terms of reducing computation time. The algorithm could also be modified to analyze each harmonic separately instead of all at the same time.

Williamson, Frank; Sheble, Gerald B.

1989-01-01

202

Room-temperature particle detectors based on purified InP single-crystals converted to semi-insulating state by annealing  

Microsoft Academic Search

InP were grown by Czochralski technique. They were purified by admixture of Ta into the growth melt and then converted to semi-insulating state by annealing. Temperature dependent Hall measurements were carried out in the range from 300 K to 430 K and the activation energy of the impurity responsible for the semi-insulating state was determined from the slope of the

Karel Zdansky; Vladyslav Gorodynskyy; Ladislav Pekarek; Halyna Kozak

2005-01-01

203

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

204

Convertible Stadium  

NASA Technical Reports Server (NTRS)

Air flotation technology used in NASA's Apollo program has found an interesting application in Hawaii's Aloha Stadium near Honolulu. The stadium's configuration can be changed, by moving entire 7,000-seat sections on a cushion of air, for best accommodation of spectators and participants at different types of events. In most stadiums, only a few hundred seats can be moved, by rolling sections on wheels or rails. At Aloha Stadium, 28,000 of the 50,000 seats can be repositioned for better spectator viewing and, additionally, for improved playing conditions. For example, a stadium designed primarily for football may compromise the baseball diamond by providing only a shallow outfield. Aloha's convertibility allows a full-size baseball field as well as optimum configurations for many other types of sports and special events. The photos show examples. The stadium owes its versatility to air flotation technology developed by General Motors. Its first large-scale application was movement of huge segments of the mammoth Saturn V moonbooster during assembly operations at Marshall Space Flight Center.

1978-01-01

205

Control of a multilevel converter using resultant theory  

Microsoft Academic Search

In this work, a method is given to compute the switching angles in a multilevel converter to produce the required fundamental voltage while at the same time cancel out specified higher order harmonics. Specifically, a complete analysis is given for a seven-level converter (three dc sources), where it is shown that for a range of the modulation index mI, the

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

2003-01-01

206

Multilevel converters for high power AC drives: a review  

Microsoft Academic Search

The multilevel approach appears to be very promising in AC motor drives, especially when both reduced harmonic contents and high power are required. Several topologies of multilevel voltage source power converters structures are presented and discussed, with particular reference to the modulation techniques which rule the power converters interfacing with the AC drives processes.

M. Marchesoni; M. Mazzucchelli

1993-01-01

207

Power line carrier interference from HVDC converter terminals  

Microsoft Academic Search

Power line carrier (PLC) equipment typically operates in the frequency range from 25 kHz to 300 kHz. Interference studies for HVDC converters usually concentrate on interference from noise sources within this frequency range. However, operating experience at the Sandy Pond converter terminal has indicated that PLC equipment is also susceptible to interference from sources of power system harmonics below the

P. J. Tatro; K. A. Adamson; M. A. Eitzmann; M. Smead

1993-01-01

208

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

Microsoft Academic Search

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 Bi2ZnTiO6. 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

Sheng Ju; Guang-Yu Guo

2008-01-01

209

Space Vector Modulation for High-Power Three-Level NPC Rectifiers Without Even Order Harmonics  

Microsoft Academic Search

Space vector modulation (SVM) is a preferred PWM scheme for multilevel converters mainly due to its flexibility, easy digital implementation and good harmonic profile. However, the conventional SVM scheme normally produces even-order voltage\\/current harmonics at the rectifier inputs. The even-order harmonic currents are strictly regulated by the harmonic guidelines such as the IEEE Standards 519-1992 in North America. In this

D. Feng; B. Wu; C. Liu; D. Xu; R. Cheung

2005-01-01

210

Harmonic synchronizations of spacetime  

SciTech Connect

The spacetime slicings associated with a harmonic time coordinate (harmonic synchronizations) are considered and their usefulness in the field of numerical relativity is studied. Harmonic synchronizations are shown to avoid singularities in the same way that the widely used maximal slicings do. Both kinds of slicing are compared in stationary axisymmetric spacetimes, homogeneous cosmological models, and Kerr-Newman black holes.

Bona, C.; Masso, J.

1988-10-15

211

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

212

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

213

Enhanced ?erenkov second-harmonic emission in nonlinear photonic structures.  

PubMed

We study experimentally and theoretically the ?erenkov-type second-harmonic generation in a one-dimensional nonlinear photonic crystal. We demonstrate that the power of emitted second-harmonic can be enhanced 270 times by varying the angle of incidence of the fundamental beam such that the reciprocal lattice vector of the crystal can be used to compensate for the phase mismatch in the transverse direction enabling interaction in the nonlinear Bragg diffraction regime. PMID:22660044

Kalinowski, K; Roedig, P; Sheng, Y; Ayoub, M; Imbrock, J; Denz, C; Krolikowski, W

2012-06-01

214

Domain structure analysis of Pb(Zn1/3Nb2/3)O3-9%PbTiO3 single crystals using optical second harmonic generation microscopy  

NASA Astrophysics Data System (ADS)

The domain structures of relaxor-ferroelectric Pb(Zn1/3Nb2/3)O3-9%PbTiO3 (PZN-9PT) single crystals with a morphotropic phase boundary (MPB) composition are observed with a scanning second harmonic generation (SHG) microscope. Three-dimensional domain structures are obtained from sectional SH images along the axial direction. The domain structures are explained well by the strain compatibility theory that is based on the ferroelectric/ferroelastic phase transition of m3ŻmFm(p) with the monoclinic space group Pm . The SHG images are divided into several parts, and the light-polarization dependence (PolD) at each site is calculated by minimizing the least-squares errors of the nonlinear susceptibilities. The PolDs are fitted well by theoretical formulas of the SH intensities for the Pm symmetry, and the two-dimensional map of the PolD coincides well with the corresponding SHG image of the domain structures. The monoclinic Pm symmetry at the MPB of PZN-9PT is determined at the optical diffraction limit of 460 nm.

Kaneshiro, Junichi; Uesu, Yoshiaki

2010-11-01

215

Third-harmonic-upconversion enhancement from a single semiconductor nanoparticle coupled to a plasmonic antenna.  

PubMed

The ability to convert low-energy quanta into a quantum of higher energy is of great interest for a variety of applications, including bioimaging, drug delivery and photovoltaics. Although high conversion efficiencies can be achieved using macroscopic nonlinear crystals, upconverting light at the nanometre scale remains challenging because the subwavelength scale of materials prevents the exploitation of phase-matching processes. Light-plasmon interactions that occur in nanostructured noble metals have offered alternative opportunities for nonlinear upconversion of infrared light, but conversion efficiency rates remain extremely low due to the weak penetration of the exciting fields into the metal. Here, we show that third-harmonic generation from an individual semiconductor indium tin oxide nanoparticle is significantly enhanced when coupled within a plasmonic gold dimer. The plasmonic dimer acts as a receiving optical antenna, confining the incident far-field radiation into a near field localized at its gap; the indium tin oxide nanoparticle located at the plasmonic dimer gap acts as a localized nonlinear transmitter upconverting three incident photons at frequency ? into a photon at frequency 3?. This hybrid nanodevice provides third-harmonic-generation enhancements of up to 10(6)-fold compared with an isolated indium tin oxide nanoparticle, with an effective third-order susceptibility up to 3.5 × 10(3) nm V(-2) and conversion efficiency of 0.0007%. We also show that the upconverted third-harmonic emission can be exploited to probe the near-field intensity at the plasmonic dimer gap. PMID:24608232

Aouani, Heykel; Rahmani, Mohsen; Navarro-Cía, Miguel; Maier, Stefan A

2014-04-01

216

Third-harmonic-upconversion enhancement from a single semiconductor nanoparticle coupled to a plasmonic antenna  

NASA Astrophysics Data System (ADS)

The ability to convert low-energy quanta into a quantum of higher energy is of great interest for a variety of applications, including bioimaging, drug delivery and photovoltaics. Although high conversion efficiencies can be achieved using macroscopic nonlinear crystals, upconverting light at the nanometre scale remains challenging because the subwavelength scale of materials prevents the exploitation of phase-matching processes. Light-plasmon interactions that occur in nanostructured noble metals have offered alternative opportunities for nonlinear upconversion of infrared light, but conversion efficiency rates remain extremely low due to the weak penetration of the exciting fields into the metal. Here, we show that third-harmonic generation from an individual semiconductor indium tin oxide nanoparticle is significantly enhanced when coupled within a plasmonic gold dimer. The plasmonic dimer acts as a receiving optical antenna, confining the incident far-field radiation into a near field localized at its gap; the indium tin oxide nanoparticle located at the plasmonic dimer gap acts as a localized nonlinear transmitter upconverting three incident photons at frequency ? into a photon at frequency 3?. This hybrid nanodevice provides third-harmonic-generation enhancements of up to 106-fold compared with an isolated indium tin oxide nanoparticle, with an effective third-order susceptibility up to 3.5 × 103 nm V-2 and conversion efficiency of 0.0007%. We also show that the upconverted third-harmonic emission can be exploited to probe the near-field intensity at the plasmonic dimer gap.

Aouani, Heykel; Rahmani, Mohsen; Navarro-Cía, Miguel; Maier, Stefan A.

2014-04-01

217

crystals  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

218

Modeling of electric railway vehicle for harmonic analysis of traction power-supply system using spline interpolation in frequency domain  

Microsoft Academic Search

It is essential to model nonlinear traction power converter loads for the harmonic analysis of traction systems. A behavioral model in the frequency domain to represent electric railway vehicles based on testing and measurements is proposed for harmonic analysis. The harmonic current characteristics are represented by a set of polynomials generated from cubic smoothing spline interpolation. The purpose of this

K. H. Yuen; M. H. Pong; W. C. Lo; Z. M. Ye

1999-01-01

219

Frequency Coupling Matrix of a Voltage-Source Converter Derived From Piecewise Linear Differential Equations  

Microsoft Academic Search

When a power-electronic converter is introduced into a linear network, voltage and current harmonics of differing orders become coupled (through the modulation effect of the converter). The interharmonic coupling introduced by the modulation effect of a converter may be mathematically represented through a frequency coupling matrix (FCM). Given that the source of the coupling is a modulation process, researchers have,

P. W. Lehn; K. L. Lian

2007-01-01

220

Harmonic radar literature  

NASA Astrophysics Data System (ADS)

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 radar has an extremely low range of detection. Natural objects in the target area do not disturb the high frequency harmonics. The radar becomes clutter free. The principals of generating high frequency harmonics cover tunneling, semiconductor and microwave effects. Signal generation is most powerful when f sub o is between 100 and 1000 MHz.

Jansson, B.

1980-07-01

221

Even harmonic lasing  

SciTech Connect

Operation of a free-electron laser at harmonics of the fundamental frequency is explored with the numerical simulation code HELEX. This code includes coupling to the harmonics caused by misalignment of the electrons with the optical beam and coupling due to transverse gradients. Albeit weak, the transverse gradients produce the dominant coupling of the electrons to the even-harmonic light. Even-harmonic lasing occurs in a TEM{sub 0,2m+1}-like mode where the field on axis is zero. As bunching of the electron beam progresses, radiation at the higher odd harmonics is suppressed owing to the absence of higher-order odd-harmonic Fourier components in the bunch. Growth of the even-harmonic power from small signal requires suppression of competing harmonics (including the fundamental) that have higher gain. Lasing at an even harmonic has yet to be experimentally demonstrated in an open resonator (i.e. optical cavity). Strategies to make such an experiment possible are discussed. 9 refs., 5 figs., 1 tab.

Schmitt, M.J.

1991-01-01

222

Laser third harmonic generation in organic dye vapors  

Microsoft Academic Search

The phenomenon of nonlinear optical conversion of a YAG:Nd laser radiation frequency from IR to UV spectral range in naphthalene\\u000a vapors was studied. The optimum temperature of naphthalene vapors (170C) was found at which the pumping radiation is synchronously\\u000a converted into the third harmonic emission. A mechanism of the third harmonic generation is proposed based on the difference\\u000a frequency generation

R. A. Ganeev; Sh. R. Kamalov; M. K. Kodirov; M. R. Malikov; A. I. Ryasnyanskii; R. I. Tugushev; Sh. U. Umidullaev; T. Usmanov

2000-01-01

223

Controlling Second Harmonic Efficiency of Laser Beam Interactions  

NASA Technical Reports Server (NTRS)

A method is provided for controlling second harmonic efficiency of laser beam interactions. A laser system generates two laser beams (e.g., a laser beam with two polarizations) for incidence on a nonlinear crystal having a preferred direction of propagation. Prior to incidence on the crystal, the beams are optically processed based on the crystal's beam separation characteristics to thereby control a position in the crystal along the preferred direction of propagation at which the beams interact.

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

2011-01-01

224

System and methods for reducing harmonic distortion in electrical converters  

DOEpatents

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

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

2013-12-03

225

Coherent combining of SHG converters through active phase control of the fundamental waves  

NASA Astrophysics Data System (ADS)

Coherent beam combining (CBC) by active phase control has proven to be an efficient and scalable way to increase the output power delivered by fiber laser systems. This study investigates the potential of this technique when applied to another type of laser sources: nonlinear optical frequency converters. Given that the efficiency of nonlinear conversion processes, here Second Harmonic Generation (SHG), relies on a phase-matching condition between the fundamental and the harmonic waves, an indirect control of the phase of an SHG beam through the fundamental wave is theoretically possible. This paper experimentally demonstrates such indirect phase control and its application to CBC of frequency converters. Two continuous-wave 1.55-?m fiber amplifiers are frequency doubled in PPLN crystals to generate 775-nm beams. These SH beams are coherently combined using frequency-tagging active phase control. A standard fibered electro-optic modulator (EOM) is used to control the phase of one of the 1.55-?m fiber amplifiers. This EOM provides both phase modulation for frequency-tagging and proper phase shifts to compensate for the phase fluctuations of the other 1.55-?m amplifier. Efficient coherent combining of these two 775-nm beams is successfully achieved: a ?/19.5 residual phase error is measured.

Durécu, A.; Aubert, C.; Canat, G.; Le Gouët, J.; Lombard, L.; Bourdon, P.

2014-03-01

226

New hybrid control methods based on multi-carrier PWM techniques and charge balance control methods for cascaded multilevel converters  

Microsoft Academic Search

In this paper, the elimination of low order harmonics in a cascaded multilevel converter by considering the charge balance control methods is proposed. Reduction of the total harmonics distortion (THD) and improvement of the harmonic spectrum of the output voltage are some advantages of the proposed hybrid control methods. Due to the use of the charge balance methods, the lifetime

Sara Laali; Karim Abbaszade; Hamid Lesani

2011-01-01

227

Covariant harmonic oscillators and coupled harmonic oscillators  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

228

Harmonic radar literature  

Microsoft Academic Search

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 radar has an extremely low range of detection. Natural objects in the target

B. Jansson

1980-01-01

229

Singular spin harmonics  

Microsoft Academic Search

The definition of the spin-weighted spherical harmonics, sYlm, is extended so that all integral spin weights, s, are allowed. We then discuss a set of spin-weighted functions, sZlm, which are analogous to the spherical harmonics of the second kind.

G. J. Weir

1979-01-01

230

Harmonic ScalpelŽ Hemorrhoidectomy  

Microsoft Academic Search

PURPOSE: The aim of this study was to evaluate the incidence of postoperative complications after Harmonic ScalpelŽ hemorrhoidectomy and to identify any predisposing factors leading to postoperative complications. METHODS: Five hundred consecutive cases of Harmonic ScalpelŽ hemorrhoidectomy were studied in a prospective manner. Postoperative complications were recorded, and any predisposing factors were evaluated. RESULTS: Three hundred fifty-five patients (71 percent)

David N. Armstrong; Charles Frankum; Marion E. Schertzer; Wayne L. Ambroze; Guy R. Orangio

2002-01-01

231

Fast Polar Harmonic Transforms  

Microsoft Academic Search

Polar Harmonic Transform (PHT) is termed to represent a set of transforms those kernels are basic waves and harmonic in nature. PHTs consist of Polar Complex Exponential Transform (PCET), Polar Cosine Transform (PCT) and Polar Sine Transform (PST). They are proposed to represent invariant image patterns for two dimensional image retrieval and pattern recognition tasks. They are demonstrated to show

Zhuo Yang; Sei-ichiro Kamata

2010-01-01

232

Feasibility study for convertible engine torque converter  

NASA Technical Reports Server (NTRS)

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

1985-01-01

233

A 16-bit 4'th order noise-shaping D\\/A converter  

Microsoft Academic Search

A 16-bit oversampling D\\/A (digital-to-analog) converter has been designed using a fourth-order all-digital noise-shaping loop followed by a 3-bit D\\/A converter. The 3-bit D\\/A converter, which uses a novel form of dynamic element matching achieves high accuracy and long-term stability without requiring precision matching of components. The harmonic distortion of the untrimmed monolithic CMOS prototype D\\/A converter is less than

L. Richard Carley; John Kenney

1988-01-01

234

Optimized Modulation for AC–DC Harmonic Immunity in VSC HVDC Transmission  

Microsoft Academic Search

Control methods based on selective harmonic elimination pulse-width modulation (SHE-PWM) techniques offer the lowest possible number of switching transitions. This feature also results in the lowest possible level of converter switching losses. For this reason, they are very attractive techniques for the voltage-source-converter-(VSC) based high-voltage dc (HVDC) power transmission systems. The paper discusses optimized modulation patterns which offer controlled harmonic

Nikolas Flourentzou; Vassilios. G. Agelidis

2010-01-01

235

Relationship between monopole harmonics and spin-weighted spherical harmonics  

SciTech Connect

We compare two independent generalizations of the usual spherical harmonics, namely monopole harmonics and spin-weighted spherical harmonics, and make precise the sense in which they can be considered to be the same. By analogy with the spin-gauge language, raising and lowering operators for the monopole index of the monopole harmonics can immediately be written down.

Dray, T.

1985-05-01

236

A Theoretical Analysis of the Harmonic Content of PWM Waveforms for Multiple-Frequency Modulators  

Microsoft Academic Search

This paper theoretically identifies the harmonic components of a carrier-based pulsewidth-modulated (PWM) voltage-source converter (VSC) output voltage when the modulating wave includes fundamental and baseband harmonic components. This occurs, for example, when a VSC is used as an active power filter. The general analytical solution provided can be applied with a minimum additional mathematical effort to any harmonic combination in

Milijana Odavic; Mark Sumner; Pericle Zanchetta; Jon C. Clare

2010-01-01

237

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

238

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

Microsoft Academic Search

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

H. D. Taghirad; P. R. Belanger

1997-01-01

239

Harmonics and powers of doubly fed induction generators at balanced sinusoidal voltages  

Microsoft Academic Search

Wind energy converters feeding into the power grid must comply with standards for harmonics. In practice harmonics or subharmonics caused by the generator are difficult to measure, because the grid itself is also distorted. This paper describes test-bench measurements that are performed with an ideal balanced and sinusoidal voltage source instead of a grid. The results show, which significant frequencies

Steffen Schostan; Klaus-Dieter Dettmann; Ilir Purellku; Detlef Schulz

2010-01-01

240

Study of the multilevel converters in DC-DC applications  

Microsoft Academic Search

Multilevel converters have been demonstrated to have many advantages such as low harmonic, low voltage stress, and high power capability. However, most of the researches are focused on high power AC-DC and DC-AC applications. This paper presents several multilevel DC-DC converters, which can be used in automotive applications as well as in high power applications. Based on the diode-clamp, flying-capacitor,

Fan Zhang; Fang Z. Peng; Zhaoming Qian

2004-01-01

241

The PWM control of modular multi-level converter  

Microsoft Academic Search

MMC (modular multilevel converter) is a voltage converter with good character, such as low harmonic, no additional filters and transformers, suitable for modular produce etc. However, due to the bridge arm of MMC cascading multiple sub-modules, balance control of the sub-module is needed, and the balance between the various sub-module control systems affect the normal operation of MMC largely. This

Jiahu Guo; Qi-yan Liao

2011-01-01

242

An Interleaved AC–DC Converter Based on Current Tracking  

Microsoft Academic Search

In this paper, an interleaved AC-DC converter based on current tracking without any current sharing required is presented and applied to a two-phase flyback converter. This is realized using two critical-conduction-mode (CRM) pulsewidth-modulated chips, together with a field-programmable gate array technique. By doing so, not only are the total harmonic distortion and the power factor improved but the output power

K. I. Hwu; Y. T. Yau

2009-01-01

243

HARMONIC OSCILLATOR PROPAGATOR  

Microsoft Academic Search

We show how the pre-exponential factor of the Feynman propagator for the harmonic oscillator can be computed by the generalized ?-function method. Besides, we establish a direct equivalence between this method and Schwinger's propertime method.

F. A. Barone; C. Farina

244

Simple Harmonic Motion  

NSDL National Science Digital Library

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

Pfaff, Raman

2008-07-15

245

Harmonically Excited Orbital Variations.  

National Technical Information Service (NTIS)

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...

T. Morgan

1985-01-01

246

Harmonic mappings onto stars  

NASA Astrophysics Data System (ADS)

A general version of the Radó-Kneser-Choquet theorem implies that a piecewise constant sense-preserving mapping of the unit circle onto the vertices of a convex polygon extends to a univalent harmonic mapping of the unit disk onto the polygonal domain. This paper discusses similarly generated harmonic mappings of the disk onto nonconvex polygonal regions in the shape of regular stars. Calculation of the Blaschke product dilatation allows a determination of the exact range of parameters that produce univalent mappings.

Duren, Peter; McDougall, Jane; Schaubroeck, Lisbeth

2005-07-01

247

Modeling of multilevel converters  

Microsoft Academic Search

In this paper, the imbricated cells multilevel converters are studied and modeled from a control viewpoint. These converters make use of several switches connected in a series, which allows using switches with reduced voltage ratings; these low voltage switches have lower conduction losses and can switch at higher frequency. In addition to this feature common to all converters using series

T. A. Meynard; M. Fadel; N. Aouda

1997-01-01

248

A Space Vector Modulation Approach for a Multimodule HVDC Converter System  

Microsoft Academic Search

This paper presents the application of a space vector modulation (SVM) strategy for a multimodule converter system that 1) enables low switching frequency, 2) eliminates\\/minimizes ac-side voltage harmonics, particularly low-order harmonics, and 3) provides maximum ac-side fundamental voltage component. The SVM strategy is based on a sequential sampling technique. The SVM provides harmonic cancellation\\/minimization by introducing appropriate phase shift for

Maryam Saeedifard; Hassan Nikkhajoei; Reza Iravani; Alireza Bakhshai

2007-01-01

249

Second-harmonic generation in centro-symmetric semiconductors  

Microsoft Academic Search

Summary  The crystallographic dependence of optical-second-harmonic generation (SHG) in Si and Ge single crystals is obtained with\\u000a 10 ps pulses at 527 nm and at incident fluences above the threshold for laser melting of the crystal lattice. We find that\\u000a the experimentally observed dependence of SHG on crystal orientation remains unchanged up to the damage limit. Observed selection\\u000a rules are analysed

D. Guidotti; T. A. Driscoll

1986-01-01

250

Losses in three-phase induction machines fed by PWM converter  

Microsoft Academic Search

The paper deals with the analysis and evaluation of test results of PWM converter-fed induction motors. The test results presented point out the dependency of the harmonic losses on the pulse frequency. The measured values were obtained by means of a novel high precision power-analyzer capable of measuring the harmonics of voltage, current and power. Following a detailed investigation regarding

E. Nicol Hildebrand; Hagen Roehrdanz

2001-01-01

251

Coordinated control of grid-connected three-level NPC converter under distorted grid voltage  

Microsoft Academic Search

This paper presents complete control algorithm for grid-connected Pulse Width Modulated (PWM) AC\\/DC converter intended for industrial drives and renewable energy applications. The objective of control is to limit current harmonics distortion and provide ride through capability during voltage dips. Following improvements to Voltage Oriented Control are presented: synchronization loop with positive sequence extraction, resonant current controllers for higher harmonics

Krzysztof Rafal; Malgorzata Bobrowska-Rafal; Szymon Piasecki; Marek Jasinski

2011-01-01

252

Second-harmonic generation spectroscopy on organic nanofibers  

NASA Astrophysics Data System (ADS)

Optical second-harmonic generation upon nanosecond laser irradiation of nanofibers grown from nonsymmetrically functionalized para-quarter-phenylene molecules on mica surfaces is investigated in the spectral region around electronic resonances. Strong multiphoton excited luminescence appears together with the second-harmonic signal in the spectra. It is demonstrated how the two components can be separated by analyzing emission spectra recorded over a broad range of wavelengths around the second-harmonic energy. Spectra of the absolute values of the second-harmonic signals are obtained for three differently functionalized molecules. Together with supplementary measurements of the structure of the nanofiber films this forms the basis for estimation of the second-harmonic susceptibility of the fiber materials. Values of the nonlinear susceptibilities are obtained, which are comparable to those of well-known inorganic nonlinear optical crystals.

Pedersen, K.; Schiek, M.; Rafaelsen, J.; Rubahn, H.-G.

2009-09-01

253

Quadripartite entangled state from cascaded second-harmonic generation  

NASA Astrophysics Data System (ADS)

A generation system of continuous-variable (CV) quadripartite entangled state based on two cascaded second-harmonic generation (SHG) cavities below the threshold is investigated. Two reflected fundamental beams of the first cavity, the reflected second-harmonic beam and the output fourth-harmonic beam of the second cavity are proved to be entangled, and the dependence of the entanglement degree on the normalized frequency, pump parameter, fourth-harmonic loss parameter, and second-harmonic loss parameter is also analyzed. Due to the fact that the cavity parameters and the nonlinear crystals of the two SHG cavities can be freely chosen, the practicality of the proposed protocol is relatively perfect and the system can also be extended to the preparation of multicolor entangled states for a quantum network.

Yang, Rui; Zhai, Shu-Qin; Yang, Rong-Guo

2014-04-01

254

A New Harmonic Mitigation Scheme for MMC – An Experimental Approach  

NASA Astrophysics Data System (ADS)

A multilevel converter has been brought into limelight in this article, however, particular attention has been provided to the form and function of modular multilevel converter (MMC) with new design, control and harmonic mitigation schemes. A new controller scheme has been proposed to mitigate the lower and higher order harmonics. The proposed scheme shows its effectiveness by theoretical calculations, verified by simulation and experimental results. Till date, research in this field is very limited with circulating currents and harmonics as the major problem. This article effectively addresses the problem with prototype 1 kVA implementation and attempts to make a detailed analysis with their functions in comprehensive manner with high-voltage DC application under different conditions. Also, the applicability of zero voltage switching at turn ON and zero current transition at turn OFF has been verified experimentally. The strategic conclusions on MMC have been made in order to make the system more robust in operation, less complexity in design and control.

Madichetty, S.; Dasgupta, A.; Jinka, S.

2014-06-01

255

Frequency doubling crystals  

SciTech Connect

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, F.; Velsko, S.P.

1989-10-24

256

Rotorcraft convertible engine study  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

257

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

NASA Technical Reports Server (NTRS)

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

Cormier, R.

1990-01-01

258

A SVM3D generalized algorithm for multilevel converters  

Microsoft Academic Search

A novel three dimensional space vector algorithm of multilevel converters for compensating harmonics and homopolar component in system with neutral is presented. This generalized method provides an online computation of the nearest switching vectors sequence to the reference vector and calculates the on-state durations of the respective switching state vectors without involving trigonometric functions, look-up tables or coordinate system transformations

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

2003-01-01

259

Prediction of core saturation instability at an HVDC converter  

SciTech Connect

Core saturation instability has occurred on several HVDC schemes resulting from interactions between second harmonic and dc quantities (voltages and currents) on the ac side of the converter and fundamental frequency quantities on the dc side of the converter. The instability can be reinforced by unbalanced saturation of the converter transformers. The paper presents an analytical method which can be used to quickly screen ac and dc system operating conditions to predict where core saturation instability is likely to occur. Analytical results have been confirmed using the digital transients simulation program PSCAD/EMTDC.

Burton, R.S. [Teshmont Consultants, Inc., Winnipeg, Manitoba (Canada)] [Teshmont Consultants, Inc., Winnipeg, Manitoba (Canada); Fuchshuber, C.F. [Alberta Power Ltd., Edmonton, Alberta (Canada)] [Alberta Power Ltd., Edmonton, Alberta (Canada); Woodford, D.A. [Manitoba HVDC Research Centre, Winnipeg, Manitoba (Canada)] [Manitoba HVDC Research Centre, Winnipeg, Manitoba (Canada); Gole, A.M. [Univ. of Manitoba, Winnipeg, Manitoba (Canada)] [Univ. of Manitoba, Winnipeg, Manitoba (Canada)

1996-10-01

260

Expressing Crystallographic Textures through the Orientation Distribution Function: Conversion between Generalized Spherical Harmonic and Hyperspherical Harmonic Expansions  

NASA Astrophysics Data System (ADS)

In the analysis of crystallographic texture, the orientation distribution function (ODF) of the grains is generally expressed as a linear combination of the generalized spherical harmonics. Recently, an alternative expansion of the ODF, as a linear combination of the hyperspherical harmonics, has been proposed, with the advantage that this is a function of the angles that directly describe the axis and angle of each grain rotation, rather than of the Euler angles. This article provides the formulas required to convert between the generalized spherical harmonics and the hyperspherical harmonics, and between the coefficients appearing in their respective expansions of the ODF. A short discussion of the phase conventions surrounding these expansions is also presented.

Mason, J. K.; Schuh, C. A.

2009-11-01

261

Multitone harmonic radar  

NASA Astrophysics Data System (ADS)

Nonlinear radar exploits the electronic response from a target whose reflected frequencies are different from those transmitted. Reception of frequencies that are not part of the transmitted probe distinguishes the received signal from a linear return produced by clutter and indicates the presence of electronics. Presented in this paper is a type of nonlinear radar that transmits multiple frequencies and listens for a harmonic of these frequencies as well as other frequencies near that harmonic. A laboratory test-bed has been constructed to demonstrate the multitone radar concept. Measurements of nonlinear responses from RF devices probed by multiple tones are reported.

Mazzaro, Gregory J.; Martone, Anthony F.

2013-05-01

262

Chromatic second harmonic imaging.  

PubMed

We report a non-axial-scanning second harmonic imaging technique, in which the chromatic aberration of a Fresnel lens is exploited to focus different wavelengths of a fundamental beam into different axial positions to effectively realize axial scanning. Since the second harmonic signals at different axial positions are generated by different fundamental wavelengths and hence accordingly have different center wavelengths, they can be resolved and detected in parallel by using a spectrometer without axial mechanical scanning. We have demonstrated a system capable of achieving about 8 ?m effective axial scanning range. Proof-of-concept imaging results are also presented. PMID:21164728

Yang, Chuan; Shi, Kebin; Li, Haifeng; Xu, Qian; Gopalan, Venkatraman; Liu, Zhiwen

2010-11-01

263

Interleaved power converter  

DOEpatents

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

Zhu, Lizhi (Canton, MI)

2007-11-13

264

Convertible Exchangeable Preferred Stock  

Microsoft Academic Search

Convertible exchangeable preferred stock includes an option for the issuer to exchange the preferred for convertible bonds with identical pre-tax cash flows and conversion terms. In other respects this innovative corporate security is identical to traditional convertible preferred stock. The exchange feature provides the issuer with a potentially valuable option to swap a non-tax-deductible expense for a tax-deductible one. The

Arnold R. Cowan

1996-01-01

265

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.

266

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

267

Low-frequency components in the switch currents of Matrix Converter  

Microsoft Academic Search

The paper is focused on analysis of harmonics component content in the switch currents of Matrix Converter and the effect of modulation method and conversion parameters such as the matrix converter output frequency and input shift phase angle on these components. There are two sources of the switch current distortion components: PWM process resulting in high-frequency components and direct energy

Rzasa Janina

2011-01-01

268

An analytical frequency-domain modeling of a Modular Multilevel Converter  

Microsoft Academic Search

The Modular Multilevel Converter (MMC) is a new topology for multilevel converters with potential for medium voltage and high voltage applications. This paper focuses on the modeling technique in the frequency domain of an MMC. Using this frequency domain modeling it is possible to analyze and predict the harmonic content in the arm current and capacitor voltages. In MMC, a

Hamed Nademi; Anandarup Das; Lars Norum

2012-01-01

269

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

270

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

271

Optimal firing-angle control of cascaded HVDC converters for minimum reactive power demand  

Microsoft Academic Search

An asymmetrical firing strategy for the cascaded converters of a HVDC link is proposed, resulting in minimum reactive power compensation at both ends of the DC link. Both 6- and 12-pulse converters, in unipolar and bipolar operation, are considered. In addition to reactive power reduction, AC and DC harmonics are greatly reduced

D. A. Deib; H. W. Hill

1993-01-01

272

Phase locked oscillator: a new control system for controlled static converters  

Microsoft Academic Search

Static converters for high voltage direct current transmission links, whether based on mercury arc valves or thyristors, are controlled by accurately timed firing pulses from a control system. With conventional control systems, it has not so far been practicable to operate a converter on a very weak ac system, one principal reason being inherent harmonic instability caused by the direct

1967-01-01

273

Improved power quality AC-DC converter for electric multiple units in electric traction  

Microsoft Academic Search

This paper presents the performance analysis of an improved power quality AC-DC converter (IPQC) fed vector controlled induction motor drive (VCIMD) for electric multiple units (EMU) application in electric traction of Indian railways. The IPQC enhances the input power factor close to unity and also reduces the total harmonic distortion (THD) of AC mains current. The converter provides bi-directional power

Bhim Singh; G. Bhuvaneswari; Vipin Garg

2006-01-01

274

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

1996-09-01

275

Harmonic Drive Adjusting Means.  

National Technical Information Service (NTIS)

An expansible, elliptical disk, in which the major axis may be minutely varied, is provided for spreading the flexible ball bearing arrangement of a conventional harmonic drive unit. The spreading of the ball bearings maintains the various parts of the un...

R. H. Lapp

1965-01-01

276

Hypercomplete circular harmonic pyramids  

Microsoft Academic Search

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

Giovanni Jacovitti; A. Manca; Alessandro Neri

1996-01-01

277

Extended range harmonic filter  

NASA Technical Reports Server (NTRS)

Two types of filters, leaky-wall and open-guide, are combined into single component. Combination gives 10 db or greater additional attenuation to fourth and higher harmonics, at expense of increasing loss of fundamental frequency by perhaps 0.05 to 0.08 db. Filter is applicable to all high power microwave transmitters, but is especially desirable for satellite transmitters.

Jankowski, H.; Geia, A. J.; Allen, C. C.

1973-01-01

278

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

279

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

280

Harmonic generation in clusters  

Microsoft Academic Search

A model is presented for the nonlinear response of a small cluster, with a size much smaller than the wavelength, at the third harmonic of the laser frequency. The model involves collective modes of a cold electron core confined within a positively charged ion background. The response of the electron core to the laser field is similar to that of

Mykhailo V. Fomyts’kyi; Boris N. Breizman; Alexey V. Arefiev; Charles Chiu

2004-01-01

281

Spherical harmonic molecular surfaces  

Microsoft Academic Search

Starlike surfaces can be defined in spherical coordinates by a function r(?, ?) on the unit sphere, which can be expanded in spherical harmonics to give a consequence of smooth approximations to the surface. This method has been used to approximate the solvent-accessible surface of a molecule. The coefficients in the expansion provide a small collection of numbers that characterize

Nelson L. Max; Elizabeth D. Getzoff

1988-01-01

282

Advanced Control Strategy for Single-Phase Voltage-Source Active Rectifier with Low Harmonic Emission  

NASA Astrophysics Data System (ADS)

This paper introduces the advanced control of single-phase voltage-source active rectifier. This control provide direct control of trolley-wire current and active damping of low-frequency disturbances at the converter ac side. Our proposed control strategy combines PR controller with feed-forward model and low-frequency harmonic compensator based on resonant controllers. Achieved experimental results show excellent converter behavior, where converter is fed by strongly distorted supply voltage.

Blahník, Vojt?ch; Peroutka, Zden?k; Talla, Jakub

2014-03-01

283

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

284

Parametric energy converter  

Microsoft Academic Search

A method and apparatus for converting thermal energy into mechanical energy by parametric pumping of rotary inertia. In a preferred embodiment, a modified tesla turbine rotor is positioned within a rotary boiler along its axis of rotation. An external heat source, such as solar radiation, is directed onto the outer casing of the boiler to convert the liquid to steam.

Johnson

1981-01-01

285

Discontinuous Buck Converter  

NSDL National Science Digital Library

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

2009-11-19

286

Boost Converter Animation  

NSDL National Science Digital Library

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

2009-11-06

287

The microminiature thermionic converter  

Microsoft Academic Search

The design, fabrication, testing, and analysis of the microminiature thermionic converter (MTC) is discussed. MTCs are two electrode devices that convert heat energy into electrical energy. The electrodes are spaced opposite each other in a vacuum environment with one electrode heated and the second cooled. Electrons are emitted from the hot electrode to the cool electrode creating electrical power. The

Donald Bryan King

2000-01-01

288

Variable Geometry Torque Converter.  

National Technical Information Service (NTIS)

Program objective was to design and evaluate a breadboard variable reactor system using the B-1 secondary power system torque converter. Results of the evaluation indicate that a variable reactor can be used in a small, high-speed torque converter to cont...

K. W. Benn G. L. Perrone

1978-01-01

289

Carrier frequency noise from HVDC converters  

NASA Astrophysics Data System (ADS)

The development of an ac and dc side carrier frequency noise model for incorporation in the Bonneville Power Administration's ElectroMagnetic Transient Program (EMTP) is described. This model of an HVDC Station generates the characteristic wave shapes of voltages and currents in the time plane on which a Fast Fourier Transformer (FFT) is applied. The model representation of HVDC equipment such as converter transformers, smoothing reactors and harmonic filters is compared with de-energized impedance measurements of similar equipment in an HVDC Station. The carrier frequency range for the model covered is 10 kHz - 300 kHz. The measurements were obtained on the valve side and line side of the converter for both ac and dc sides. The calculated and measured noise were compared. The different measuring methods are described. A preferred measurement program is suggested and guidelines are indicated for power line carrier (plc) signal to noise ratios.

Fisher, F. A.; Griess, L. D.; Laforest, J. J.; Lindh, C. B.

1982-08-01

290

Measurement of the nonlinear susceptibility of certain molecular crystals using the method of frequency interference fringes  

NASA Astrophysics Data System (ADS)

The feasibility of measuring the components of the nonlinear susceptibility tensor by observing the intensity fluctuations of the second harmonic as a function of the converted-signal frequency is considered. If the refractive-index dispersion is known, then the components of the nonlinear susceptibility can be measured with the same accuracy as with the use of 'Meiker fringes'. The present method is less sensitive to the quality of the samples and light beam divergence. The components of the nonlinear susceptibility tensor were measured for several molecular crystals.

Kochikian, R. V.; Markushev, V. M.; Iakovlev, Iu. O.; Belan, V. R.; Zolin, V. F.

1987-03-01

291

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

292

Cascaded resonant bridge converters  

NASA Technical Reports Server (NTRS)

A converter for converting a low voltage direct current power source to a higher voltage, high frequency alternating current output for use in an electrical system where it is desired to use low weight cables and other circuit elements. The converter has a first stage series resonant (Schwarz) converter which converts the direct current power source to an alternating current by means of switching elements that are operated by a variable frequency voltage regulator, a transformer to step up the voltage of the alternating current, and a rectifier bridge to convert the alternating current to a direct current first stage output. The converter further has a second stage series resonant (Schwarz) converter which is connected in series to the first stage converter to receive its direct current output and convert it to a second stage high frequency alternating current output by means of switching elements that are operated by a fixed frequency oscillator. The voltage of the second stage output is controlled at a relatively constant value by controlling the first stage output voltage, which is accomplished by controlling the frequency of the first stage variable frequency voltage controller in response to second stage voltage. Fault tolerance in the event of a load short circuit is provided by making the operation of the first stage variable frequency voltage controller responsive to first and second stage current limiting devices. The second stage output is connected to a rectifier bridge whose output is connected to the input of the second stage to provide good regulation of output voltage wave form at low system loads.

Stuart, Thomas A. (Inventor)

1989-01-01

293

Harmonic Golay coded excitation based on harmonic quadrature demodulation method.  

PubMed

Harmonic coded excitation techniques have been used to increase SNR of harmonic imaging with limited peak voltage. Harmonic Golay coded excitation, in particular, generates each scan line using four transmit-receive cycles, unlike conventional Golay coded excitation method, thus resulting in low frame rates. In this paper we propose a method of increasing the frame rate of said method without impacting the image quality. The proposed method performs two transmit-receive cycles using QPSK code to ensure that the harmonic components of incoming signals are Golay coded and uses harmonic quadrature demodulation to extract compressed second harmonic component only. The proposed method has been validated through mathematical analysis and MATLAB simulation, and has been verified to yield a limited error of -52.08dB compared to the ideal case. Therefore, the proposed method doubles the frame rate compared to the existing harmonic Golay coded excitation method without significantly deteriorating the image quality. PMID:19164018

Kim, Sang-Min; Song, Jae-Hee; Song, Tai-Kyong

2008-01-01

294

Broadband linearly polarized beat-wave TE{sub m1}\\/TEââ mode converters  

Microsoft Academic Search

Broadband linearly polarized waveguide mode converters have been developed to transform the high-order cylindrical TE{sub m1} output wave from harmonic gyrotron amplifiers into the more useful TEââ fundamental waveguide mode. The converter`s corrugation period is equal to the beat between the two waves and the bandwidth is predicted to be inversely proportional to the number of periods. Four-period TEââ\\/TEââ and

D. B. McDermott; C. K. Chong; M. M. Razeghi; N. C. Jr. Luhmann; J. Pretterebner; C. F. Kinney

1996-01-01

295

Study and implementation of a single-phase isolated AC-DC converter  

Microsoft Academic Search

A single-phase isolated AC-DC converter is presented in this paper. The front semi-stage, which is a modified buck-boost converter, is used for power factor correction and is operated in discontinuous conduction mode (DCM) to achieve high power factor and low total harmonic distortion of input current. The rear semi-stage, which is a forward converter, is operated in DCM for step-down

Lung-Sheng Yang; Chia-Ching Lin; Ming-Rong Lee

2012-01-01

296

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

297

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

298

Second-harmonic generation in disordered quadratic media: Role of a ferroelectric domain structure  

Microsoft Academic Search

We study theoretically the second harmonic generation in a nonlinear quadratic crystal with random distribution of ferroelectric domains. We show that the specific features of disordered domain structure greatly affect the emission pattern of the generated harmonics. This phenomenon can be used to characterize the degree of disorder in nonlinear photonic structures.

V. Roppo; K. Kalinowski; W. Wang; C. Cojocaru; J. Trull; R. Vilaseca; M. Scalora; W. Krolikowski; Y. Kivshar

2010-01-01

299

The role of ferroelectric domain structure in second harmonic generation in random quadratic media.  

PubMed

We study theoretically and numerically the second harmonic generation in a nonlinear crystal with random distribution of ferroelectric domains. We show that the specific features of disordered domain structure greatly affect the emission pattern of the generated harmonics. This phenomena can be used to characterize the degree of disorder in nonlinear photonic structures. PMID:20389416

Roppo, Vito; Wang, W; Kalinowski, K; Kong, Y; Cojocaru, C; Trull, J; Vilaseca, R; Scalora, M; Krolikowski, W; Kivshar, Yu

2010-03-01

300

Depth-resolved structural imaging by third-harmonic generation microscopy  

Microsoft Academic Search

Third harmonic generation microscopy is shown to be a robust method for obtaining structural information on a variety of biological specimens. Its nature allows depth-resolved imaging of inhomogeneities with virtually no background from surrounding homogeneous media. With an appropriate illumination geometry, third harmonic generation microscopy is shown to be particularly suitable for imaging of biogenic crystals, enabling extraction of the

Dan Oron; Dvir Yelin; Eran Tal; Sefi Raz; Rachel Fachima; Yaron Silberberga

2003-01-01

301

Enhancement of second harmonic generation by double-pass configuration in barium borate  

Microsoft Academic Search

Double-pass type-I second harmonic generation (SHG) external to a laser cavity is reported for the first time in a BBO crystal resulting in an enhancement of the generated harmonic intensity by a factor of 3.4 from that obtained in the single-pass generation.

G. C. Bhar; U. Chatterjee; P. Datta

1990-01-01

302

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

303

Microminiature thermionic converters  

DOEpatents

Microminiature thermionic converts (MTCs) having high energy-conversion efficiencies and variable operating temperatures. Methods of manufacturing those converters using semiconductor integrated circuit fabrication and micromachine manufacturing techniques are also disclosed. The MTCs of the invention incorporate cathode to anode spacing of about 1 micron or less and use cathode and anode materials having work functions ranging from about 1 eV to about 3 eV. Existing prior art thermionic converter technology has energy conversion efficiencies ranging from 5-15%. The MTCs of the present invention have maximum efficiencies of just under 30%, and thousands of the devices can be fabricated at modest costs.

King, Donald B. (Albuquerque, NM); Sadwick, Laurence P. (Salt Lake City, UT); Wernsman, Bernard R. (Clairton, PA)

2001-09-25

304

Advanced thermionic converter development  

NASA Technical Reports Server (NTRS)

Recent progress at Thermo Electron in developing advanced thermionic converters is summarized with particular attention paid to the development of electrodes, diodes, and triodes. It is found that one class of materials (ZnO, BaO and SrO) provides interesting cesiated work functions (1.3-1.4 eV) without additional oxygen. The second class of materials studied (rare earth oxides and hexaborides) gives cesiated/oxygenated work functions of less than 1.2 eV. Five techniques of oxygen addition to thermionic converters are discussed. Vapor deposited tungsten oxide collector diodes and the reflux converter are considered.

Huffman, F. N.; Lieb, D.; Briere, T. R.; Sommer, A. H.; Rufeh, F.

1976-01-01

305

Fluorescent radiation converter  

NASA Technical Reports Server (NTRS)

Fluorescent radiation converter used optically transparent substrate. One side of substrate is coated with plastic film containing fluorescent organic dyes that absorb optical radiation at one wavelength and emit it at longer one. Coating is formulated to respond to specific wavelengths. Emitted radiation is reflected internally inside substrate, amplifying intensity that reaches radiation detector. Converter can be made in several shapes and size; round and square bars coated all round their lengths are useful in converting relatively intense radiation and transmitting it through substrate over lengthy distances.

Viehmann, W.

1980-01-01

306

A Practical Guide to Harmonic Frequency Interference Affecting High-Voltage Power-Line Carrier Coupling Systems  

Microsoft Academic Search

Power-line carrier (PLC) systems have proven to be susceptible to interference caused by harmonics produced by loads, such as HVDC converters, DC electric arc furnaces, static var compensators, and motor speed controllers. Previous work in this area has provided information regarding the nature and origin of harmonic frequency interference affecting PLC systems as well as discussion of problem mitigation. However,

Gregory A. Franklin

2009-01-01

307

Harmonic N=2 mechanics  

SciTech Connect

N=2 superconformal many-body quantum mechanics in arbitrary dimensions is governed by a single scalar prepotential which determines the bosonic potential and the boson-fermion couplings. We present a special class of such models, for which the bosonic potential is absent. They are classified by homogeneous harmonic functions subject to physical symmetry requirements, such as translation, rotation and permutation invariance. The central charge is naturally quantized. We provide some examples for systems of identical particles in any dimension.

Galajinsky, Anton [Laboratory of Mathematical Physics, Tomsk Polytechnic University, 634050 Tomsk, Lenin Avenue 30 (Russian Federation); Lechtenfeld, Olaf [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany)

2009-09-15

308

Spherical Harmonics YLM Explorer  

NSDL National Science Digital Library

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

Kraus, Martin

2005-04-16

309

Nonclassical States of the Second Optical Harmonic in the Presence of Self-Action.  

National Technical Information Service (NTIS)

The quantum theory of coherent radiation frequency doubling in crystals with quadratic and cubic optical nonlinearities is developed. The possibility of producing the quadrature-squeezed state of the second harmonic (SH) field is shown. The nonclassical S...

A. S. Chirkin N. V. Korolkova

1993-01-01

310

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

311

Multilevel converters -- A new breed of power converters.  

National Technical Information Service (NTIS)

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....

J. S. Lai F. Z. Peng

1995-01-01

312

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

313

Thermionic photovoltaic energy converter  

NASA Technical Reports Server (NTRS)

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

Chubb, D. L. (inventor)

1985-01-01

314

X-ray converter  

US Patent & Trademark Office Database

An X-RAY CONVERTER having a light-proof housing with an X-ray-transparent wall behind which there are fastened an X-ray-to-optical converter, a filter of residual X-radiation, an objective lenses unit, and a photodetector containing at least two optoelectronic converters with partly overlapping fields of view and separated electrical outputs for connection to a system for processing of fragmentary video signals and generating an integral output video signal. For improving the efficiency of suppression of internal interferences in optical channels and the operating reliability, within the housing, parallel to the X-ray-to-optical converter, there is rigidly fastened an additional light- and X-ray-opaque partition with through-holes which in the number and placement correspond to objective lenses and optoelectronic converters and are blocked by washers of the filter of residual X-radiation, and ahead of the washers there are installed blinds, length A of each of which and distance D from the front surface of the X-ray-to-optical converter to the plane of front end faces of objective lenses are related by the ratio A/D=(0.50 . . . 0.95).

2009-02-24

315

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

316

Development of AC and DC Power Supply Direct Interface Converter  

NASA Astrophysics Data System (ADS)

This paper proposes a novel control method for a direct interface converter for management of the energy flow in either an AC or DC supply. The proposed converter is constructed based on an indirect matrix converter. Therefore a proposed control strategy is based on an indirect control method with a triangular carrier wave. The basic operation of the proposed control method is confirmed by experimental results. In addition, this paper also proposes a commutation error compensation method of an output voltage error and an input current error for an indirect matrix converter. In the proposed method, the output voltage and input current error by the commutation can be compensated at the same time, because the PWM pulse of each switch is directly compensated. The validity of the proposed method is confirmed by experimental results. Those results prove that the proposed compensation method can decrease total harmonic distortion (THD) of the input and output current.

Kato, Koji; Itoh, Jun-Ichi

317

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

318

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

319

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

320

On 1-Harmonic Functions  

NASA Astrophysics Data System (ADS)

Characterizations of entire subsolutions for the 1-harmonic equation of a constant 1-tension field are given with applications in geometry via transformation group theory. In particular, we prove that every level hypersurface of such a subsolution is calibrated and hence is area-minimizing over R; and every 7-dimensional SO(2) × SO(6)-invariant absolutely area-minimizing integral current in R8 is real analytic. The assumption on the SO(2) × SO(6)-invariance cannot be removed, due to the first counter-example in R8, proved by Bombieri, De Girogi and Giusti.

Wei, Shihshu Walter

2007-12-01

321

A Ka Band Balanced Third LO-Harmonic Mixer Using a Lumped-Elements Quadrature Hybrid  

Microsoft Academic Search

A novel configuration of a subharmonic mixer utilizing third local oscillation (LO) harmonic is presented. The mixer is capable of down-converting a Ka-Band radio frequency (RF) signal with the third harmonic of an X-band LO signal to produce a 2 GHz intermediate frequency signal. It is fabricated on a 4 mil substrate using a 0.15 mum GaAs PHEMT process. A

Jian-An Hou; Yeong-Her Wang

2008-01-01

322

Multilevel converters-a new breed of power converters  

Microsoft Academic Search

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

Jih-Sheng Lail; Fang Zheng Peng

1995-01-01

323

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

324

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

325

E\\/O Tunable Second-Harmonic-Generation Gratings in Ion-Exfoliated Thin Films of Periodically Poled LiNbO3  

Microsoft Academic Search

We demonstrate for the first time that thin, single-crystal films fabricated by ion- exfoliation of a bulk PPLN crystal will reduce tuning voltage for electro-optically tunable harmonic generation in PPLN devices.

D. Djukic; G. Cerda-Pons; R. M. Roth; R. M. Osgood; S. Bakhru; H. Bakhru

2007-01-01

326

A multilevel converter-based universal power conditioner  

Microsoft Academic Search

This paper presents the development of a control scheme for a multilevel diode-clamped converter connected in a series-parallel fashion to the electrical system such that it can compensate for deviations in utility voltage (sag, surge, and unbalance) and act as a harmonic and\\/or reactive current source for a load. New carrier-based multilevel pulsewidth modulation techniques are identified to maximize switch

Leon M. Tolbert; Fang Zheng Peng; Thomas G. Habetler

2000-01-01

327

A new multi carrier based PWM for multilevel converter  

Microsoft Academic Search

This paper addresses a new multi-carrier modulation technique called wave shift multi-carrier modulation (WSHM), which used to control the cascade multilevel converter (CMC). The proposed switching technique generates lower voltage total harmonic distortion (THD) in comparison with conventional multi-carrier based pulse width modulation (PWM) schemes, phase-shift (PSHM) and level-shift (LSHM) modulations. To compare the performance of proposed method with PSHM

Bahr Eldin S. Mohammed; K. S. Rama Rao

2011-01-01

328

A new scheme for power factor correction and active filtering for six-pulse converters loads  

Microsoft Academic Search

This paper presents a novel harmonic-free power factor correction (PFC) topology based on T-type active power filter (APF), which is dedicated for power factor improvement and harmonic filtering for six-pulse converter loads. The cascaded controller structure is adopted for the proposed system, namely, the inner current loop and outer voltage loop. The current-loop control scheme is based on a decoupled

Y. HAN; M. M. KHAN; L. XU; G. YAO; L. ZHOU; C. CHEN

329

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

330

Analog to Digital Converter.  

National Technical Information Service (NTIS)

A device for converting a signal voltage into a multibit digital word that defines that voltage magnitude and polarity. The input voltage V to be digitized is used to control the frequency of a voltage controlled oscillator, whose output is defined to be ...

B. L. Lewis

1981-01-01

331

Heat flux converter  

Microsoft Academic Search

(usually by means of glue or putty). The operation of such a converter is based upon measurement of the entire quantity of heat which enters it from the start of the process. Strict fulfillment of the latter condition is guaranteed by a choice of thickness of the calorimeter such that its inner surface is heated just so much during the

B. I. Bakum; L. V. Novikov; Yu. V. Yakhlakov

1968-01-01

332

How to Convert Temperatures  

NSDL National Science Digital Library

This elementary school classroom activity has students measure water temperature, use formulas to convert between Fahrenheit, Celsius, and Kelvin, and use a conversion tool to check their answers between the three systems. It is part of the Atmospheric Visualization Collection (AVC), which focuses on data from the Atmospheric Radiation Measurement (ARM) program.

2003-05-09

333

Fractional Watt AMTEC Converter  

NASA Astrophysics Data System (ADS)

We report here the long term performance of a small, multi-tube AMTEC converter. This converter was designed to operate and produce approximately 12 watt of electrical output from a small, 4 to 6 watt radioisotope heat source for remote power applications. It was built and put on test in 1999 using electrical heaters as stand-ins for the radioisotope capsule. Since that time it has accumulated more than 5 years of run time at an input heater temperature of 700 °C, with numerous thermal cycles to ambient that were generally related to grid power failures or physical moves of the test apparatus. The power output has remained, with variations due to orientation changes and minor variations due to small temperature changes, essentially constant at 0.40 W to 0.60 W over the test period and operation is ongoing. The converter casing and mechanical structure was fabricated from 316 SS and the electrodes are sputtered titanium nitride films. Separate static tests of a multilayer insulation package suitable for use with the converter showed the capability to reach 700 °C with a thermal input of < 4 watts.

Hunt, T. K.; Rasmussen, J. R.

2006-01-01

334

Ocean wave energy converter  

Microsoft Academic Search

A device for converting the energy of ocean waves into electricity, comprises a buoyant body that floats on the surface of the water and rises and falls with the waves. Fixedly secured to the buoyant body at a depth in the region of still water not affected by the waves, is a bucket wheel or bucket chain which will accordingly

1982-01-01

335

Ocean wave energy converter  

Microsoft Academic Search

This patent describes apparatus for converting the energy of wave motion on the surface of a body of water to electricity comprising: lower structural support means approximately forming edge elements of an equilateral triangle; lower tube receptacles connected to the lower structural support means approximately forming vertex elements of an equilateral triangle; tubular members having upper and lower portions positioned

1987-01-01

336

Converting industrial boilers  

Microsoft Academic Search

Based on the limitations of retrofit applications, a summary is presented of means by which existing oil or gas fired boilers can be converted to coal utilization. Boiler capacity is discussed as well as space limitations, particulate emissions, ash and cinder formation, air pollution, and effectiveness. Specifically, the following modes of firing are discussed: (1) spreader stoker firing; (2) pulverized

D. F. Dunphy; V. S. Ramapriya

1981-01-01

337

Converting Bookmobiles to Paperbacks  

ERIC Educational Resources Information Center

The Oklahoma County Libraries System in Oklahoma City converted its five bookmobiles from hardbound to paperbound materials in 1975. The conversion has been a notable success, proving popular with patrons and proving low cost and efficient for the library system. (Author)

Little, Paul

1976-01-01

338

Digitise this: converting content  

Microsoft Academic Search

This paper describes and illustrates the new processes that CAVAL is using to convert content into digital form. The research and development process began with the purchase of a Kirtas 2400 RA Book Digitising device in 2008. This Kirtas with its page-turning technology now underpins the provision of high quality digitisation services for books and bound volumes. Issues discussed include

Cathie Jilovsky; George Panagiotidis

339

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

340

Exploration method using harmonic functions  

Microsoft Academic Search

Harmonic functions provide optimal potential maps for robot navigation in a previously explored static environment. Here we investigate the performance of an algorithm for exploration based on partial updates of a harmonic potential in an occupancy grid. We consider that while the robot moves it carries along an activation window whose size is of the order of the sensor's range.

Edson Prestes e Silva Jr.; Paulo Martins Engel; Marcelo Trevisan; Marco Aurélio Pires Idiart

2002-01-01

341

International Harmonization of Economic Regulation  

Microsoft Academic Search

With the advancing globalization of the world economy, domestic economic regulations are becoming more and more subject to efforts at international harmonization. This book presents an analysis of this worldwide phenomenon from both a legal and a politico-economic perspective by focusing on (1) the backgrounds and objectives of international harmonization, (2) the negotiating processes involved, and (3) the impact of

Junji Nakagawa

342

Selection of dead angle of a three-level multipulse voltage source converter for power quality improvement in HVDC system  

Microsoft Academic Search

This paper deals with the optimum dead angle operation of a three level 18-pulse voltage source converter (VSC) for power quality improvement in High Voltage DC (HVDC) transmission system. The harmonics level of VSC is optimized by selecting proper dead angle (??) of a three level 18-pulse voltage source converter operated at fundamental frequency switching. The effect of varying dead

D. Madhan Mohan; Bhim Singh; B. K. Panigrahi

2009-01-01

343

Liquid metal thermal electric converter  

DOEpatents

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

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

1989-01-01

344

Parametric energy converter  

SciTech Connect

A method and apparatus for converting thermal energy into mechanical energy by parametric pumping of rotary inertia. In a preferred embodiment, a modified tesla turbine rotor is positioned within a rotary boiler along its axis of rotation. An external heat source, such as solar radiation, is directed onto the outer casing of the boiler to convert the liquid to steam. As the steam spirals inwardly toward the discs of the rotor, the moment of inertia of the mass of steam is reduced to thereby substantially increase its kinetic energy. The laminar flow of steam between the discs of the rotor transfers the increased kinetic energy to the rotor which can be coupled out through an output shaft to perform mechanical work. A portion of the mechanical output can be fed back to maintain rotation of the boiler.

Johnson, R.N.

1981-10-20

345

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

346

Digital to synchro converter  

NASA Technical Reports Server (NTRS)

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

Predina, Joseph P. (Inventor)

1989-01-01

347

Evading surface and detector frequency noise in harmonic oscillator measurements of force gradients  

PubMed Central

We introduce and demonstrate a method of measuring small force gradients acting on a harmonic oscillator in which the force-gradient signal of interest is used to parametrically up-convert a forced oscillation below resonance into an amplitude signal at the oscillator’s resonance frequency. The approach, which we demonstrate in a mechanically detected electron spin resonance experiment, allows the force-gradient signal to evade detector frequency noise by converting a slowly modulated frequency signal into an amplitude signal.

Moore, Eric W.; Lee, SangGap; Hickman, Steven A.; Harrell, Lee E.; Marohn, John A.

2010-01-01

348

Frequency doubling crystals  

SciTech Connect

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

349

Frequency doubling crystals  

SciTech Connect

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-acetyle hydroxyyproline. 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, F.; Velsko, S.P.

1988-08-15

350

Correlation Effects in Quantum Crystals  

Microsoft Academic Search

Correlation effects in the quantum crystals He3 and He4 are studied in detail. The single-particle wave function is obtained in the harmonic effective-field approximation; the parameters of the harmonic-oscillator potential are determined self-consistently from the two-body correlation function and the bare interatomic potential. We determine the two-body correlation function by solving numerically an equation derived by decoupling the three-body correlation

C. Ebner; C. C. Sung

1971-01-01

351

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

352

Characteristics of fixed frequency series-parallel resonant converter operating on the utility line with and without active control  

Microsoft Academic Search

A 1-? high-frequency transformer isolated AC-to-DC controlled rectifier using a fixed-frequency series-parallel (or LCC type) resonant converter (SPRC) is presented. A simple analysis and design procedure is used for designing the converter for low line current harmonic distortion and high power-factor (PF) operation. The converter performance characterstics have been verified with SPICE simulations and an experimental prototype SPRC, without using

V. Belaguli; A. K. S. Bhat

1995-01-01

353

Multilevel converters -- A new breed of power converters  

SciTech Connect

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

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

1996-05-01

354

Luminescent dye-doped KAP nanorods obtained by template assisted crystallization.  

PubMed

Luminescent nanorods of potassium acid phthalate (KAP) doped with rhodamine 6G (Rh 6G) dye molecules were grown by template assisted crystallization. Pores with diameters ranging from tens of nanometers to few micrometers were obtained in polycarbonate foils after heavy-ion irradiation and subsequent chemical etching of the damage trails along the ion trajectories. Crystallization from solution was employed for filling of the pores with the dye-doped KAP rods. These nanostructures were characterized using scanning electron microscopy, optical absorption spectroscopy and photoluminescence detection. X-ray diffraction was used for structural analysis. The luminescence of the dye-doped rods undergoes a redshift when the diameter of the structures decreases. This shift is probably caused by increasing dye concentration in the rods with decreasing pore diameter. The luminescence originating from the Rh 6G presence is up-converted due to the second-harmonic generation in KAP. PMID:21780390

Enculescu, M; Neumann, R

2011-05-01

355

Harmonic Measure of Critical Curves  

SciTech Connect

Fractal geometry of critical curves appearing in 2D critical systems is characterized by their harmonic measure. For systems described by conformal field theories with central charge c{<=}1, scaling exponents of the harmonic measure have been computed by Duplantier [Phys. Rev. Lett. 84, 1363 (2000)] by relating the problem to boundary two-dimensional gravity. We present a simple argument connecting the harmonic measure of critical curves to operators obtained by fusion of primary fields and compute characteristics of the fractal geometry by means of regular methods of conformal field theory. The method is not limited to theories with c{<=}1.

Bettelheim, E.; Rushkin, I.; Gruzberg, I.A.; Wiegmann, P. [James Frank Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637 (United States)

2005-10-21

356

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

357

Symmetric functions and BN-invariant spherical harmonics  

NASA Astrophysics Data System (ADS)

The wavefunctions of a quantum isotropic harmonic oscillator modified by reflecting barriers at the coordinate planes in N-dimensional space can be expressed in terms of certain generalized spherical harmonics. These are associated with a product-type weight function on the sphere. Their analysis is carried out by means of differential-difference operators. The symmetries of this system involve the Weyl group of type B, generated by permutations and changes of sign of the coordinates. A new basis for symmetric functions as well as an explicit transition matrix to the monomial basis is constructed. This basis leads to a basis for invariant spherical harmonics. The determinant of the Gram matrix for the basis in the natural inner product over the sphere is evaluated. When the underlying parameter is specialized to zero, the basis consists of ordinary spherical harmonics with cube group symmetry, as used for wavefunctions of electrons in crystals. The harmonic oscillator can also be considered as a degenerate interaction-free spin Calogero model.

Dunkl, Charles F.

2002-12-01

358

STATCOM based on multimodules of multilevel converters under multiple regulation feedback control  

Microsoft Academic Search

This paper describes a STATCOM based on diode-damped multilevel power converters. The current rating is increased by parallel connections of multiple power converter modules. The gate-turn-off thyristor (GTO) switching angles of the fundamental switching strategy are exploited in the design to accomplish three objectives: (1) low total harmonic distortion (THD) in voltages and currents; (2) equal sharing of the currents

Yiqiang Chen; Boon-Teck Ooi

1999-01-01

359

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

360

Research on the Amplitude Coefficient for Multilevel Matrix Converter Space Vector Modulation  

Microsoft Academic Search

This paper presents an improved space vector modulation (SVM) using amplitude coefficient on a capacitor-clamped multilevel matrix converter (MMC). The MMC utilizes a multilevel structure on a conventional matrix converter, which allows direct ac–ac power conversion without large energy store elements. This structure features, in high-voltage application, staircase output voltage with less voltage step, better harmonic issue, and compact design.

Xu Lie; Li Yongdong; Wang Kui; Jon C. Clare; Patrick W. Wheeler

2012-01-01

361

Control of a two-phase bi-directional interleaved converter for maximum power point tracking  

Microsoft Academic Search

The paper presents realization and control of a two-phase bi-directional interleaved converter for a photovoltaic (PV) system. Harmonic contents due to switching action in a dc-dc converter are reduced by the interleaving technique. A nonlinear function is used for predicting the maximum power point (MPP). A novel multi-loop control scheme is developed to achieve maximum PV power generation under all

Niphat Jantharamin; Li Zhang

2008-01-01

362

Comparison of Power Quality Improvement techniques in AC-DC Cuk Converter  

Microsoft Academic Search

The Improved Power Quality AC-DC Converters (IPQCs) provides enhanced power quality in terms of improved power factor and reduced Total Harmonic Distortion (THD) at the utility interface. This paper addresses comparison of power factor correction techniques for high frequency isolation based single phase Buck-Boost AC-DC Cuk Converter, which consists of only one switch resulting in reduced THD and improved power

J. Gnanavadivel; Vidhya Chellappa; N. Senthil Kumar

2011-01-01

363

Polygon Connected 15Phase AC-DC Converter for Power Quality Improvement  

Microsoft Academic Search

This paper presents a polygon connected autotransformer based 15-phase AC-DC converter for power quality improvement in vector controlled induction motor drives (VCIMD's). The proposed multi-phase AC-DC converter is based on a polygon connected autotransformer, designed for producing 15-phase voltages for effective harmonic reduction. The effect of load variation on drive is also studied to demonstrate the effectiveness of the proposed

Bhim Singh; Vipin Garg; G. Bhuvaneswari

2006-01-01

364

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

Microsoft Academic Search

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

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

2006-01-01

365

Bus-voltage ripple optimization method for automotive multiphase DC\\/DC-converters  

Microsoft Academic Search

Phase interleaving is a well known technique to increase output power, power density, and efficiency of DC\\/DC-converters. If the n-phase converter is ideal (symmetrical), the first n-1 harmonics of the ripple are canceled in the bus-capacitors and the cut-off frequency of the EMI-filters can be increased. But tolerances of real components and control circuit can seriously limit this theoretical benefit.

Tomas Reiter; Dieter Polenov; H. Probstle; H.-G. Herzog

2009-01-01

366

A review of single-phase PFC topologies based on the boost converter  

Microsoft Academic Search

The need for solid-state ac-dc converters to improve power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input ac mains, and precisely regulated dc output have motivated the proposal of several topologies based on classical converters such as buck, boost, and buck-boost. Additionally, novel control techniques dedicated to PFC have also been introduced, motivating the manufacturing

J. P. M. Figueiredo; F. L. Tofoli; B. L. A. Silva

2010-01-01

367

A Sensorless AC-DC-AC Converter with Sliding Mode Controller for Induction Motors Drives  

Microsoft Academic Search

In this paper, a high power factor three-phase AC-DC-AC converter is presented. The driver includes a sensorless indirect field-oriented induction motor drive with a sliding-mode controller and a line-voltage- sensorless PWM synchronous rectifier with a nearly unity power factor. The mean targets have been basically: reduction in harmonic contamination produced by AC driver converters in the electric power supply network,

F. J. Maseda; O. Barambones; A. J. Garrido; I. Martija

368

A Novel Phase-shift Control Scheme for Interleaved Boost Converters Operating in Critical Conduction Mode  

Microsoft Academic Search

Interleaving techniques are adopted to reduce input\\/output current or voltage ripples for converters with critical conduction mode. The paper studies and implements two types of phase-shift control schemes for critical interleaved boost PFC converters. Sub-harmonic oscillation phenomena occur at high line voltage when one of them is adopted. So this paper presents a quantitative analysis on the phenomena and proposes

Yanping Yin; Xu Yang; Yongjiang Bai; Qiaoliang Chen; Li Jin; Zhaoan Wang

2009-01-01

369

Real-time incoherent-to-coherent optical converter  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

370

Thin Film Image Converter.  

National Technical Information Service (NTIS)

The epitaxial growth of Ge on GaAs has been studied. Although both open-tube and closed-tube growth methods were attempted, only by the former could single crystal layers be prepared. The Ge layers were invariably n-type regardless of the type of the sour...

P. W. Kruse F. C. Pribble S. B. Schuldt R. G. Schulze

1965-01-01

371

Spin-Weighted Cylindrical Harmonics  

Microsoft Academic Search

\\u000a As shown in Chapter 3, the spin-weighted spherical harmonics are very useful in the solution of linear nonscalar equations\\u000a and in the derivation of general expressions for the solutions of such equations. The usefulness of the spin-weighted spherical\\u000a harmonics is related to the appearance of the operators đ and \\u000a , when the equations are written in terms of spin-weighted components.

G. F. Torres Castillo

372

Echo-Enabled Harmonic Generation  

SciTech Connect

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

Stupakov, Gennady

2010-08-25

373

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

374

The convertible flywheel  

NASA Astrophysics Data System (ADS)

The design and testing of a new twin-disk composite flywheel is described. It is the first flywheel to store 2 kW-hr of energy and the first to successfully combine the advantages of composite materials with metal hubs, thus providing a system-ready flywheel with high energy storage and high torque capabilities. The use of flywheels in space for energy storage in satellites and space stations is examined. The convertibility of the present flywheel to provide the next generation Annular Momentum Control Device or Annular Suspension and Pointing System is discussed.

Ginsburg, B. R.

375

Universal Currency Converter  

NSDL National Science Digital Library

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

1998-01-01

376

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

377

A Three-Phase Neutral-Point Clamped AC\\/DC Converter Based On Modified Space Vector Modulation for Power Quality Improvement  

Microsoft Academic Search

The generation of harmonics and reactive power flow in a power system is greatly influenced by the widespread use of power electronic converters in addition to other sources of harmonics and reactive power. This paper presents a space-vector modulated three-level neutral-point clamped converter in rectification and regeneration modes for the power quality improvement. Specifically, this paper identifies the unbalance generated

A. H. Bhat; P. Agarwal

2006-01-01

378

Array antenna for body-worn automotive harmonic radar tag  

Microsoft Academic Search

A W-band four-by-four microstrip patch array antenna for body-worn automotive harmonic radar tag is presented in this paper. The antenna is fabricated on 100 mum thick liquid crystal polymer flex foil, using commercially available printed circuit board manufacturing processes. Port impedance and radiation patterns of the antenna are studied numerically and experimentally. The measured results are in good agreements with

S. Cheng; P. Hallbjorner; A. Rydberg

2009-01-01

379

Harmonics and Fourier Series Model  

NSDL National Science Digital Library

The Ejs Harmonics and Fourier Series model displays the sum of harmonics via a Fourier series to yield a new wave. The amplitude of each harmonic as well as the phase of that harmonic can be changed via sliders. In addition, several pre-set functions can be chosen to display. 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 Harmonics and Fourier Series 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_harmonics.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

380

dq-control of high-power current source rectifiers utilizing Selective Harmonic Elimination  

Microsoft Academic Search

Selective harmonic elimination (SHE) is usually the preferred modulation technique for high power converters. When such modulation is used with current source rectifiers (CSR), control of the DC-link current and of the input displacement power factor is typically achieved by adjusting the amplitude and phase of the CSR modulation index. In this paper control of an SHE modulated CSR is

Matteo Tomasini; Ralph Feldman; Patrick Wheeler; Jon Clare; Christian Klumpner; Ushe Mupambireyi

2009-01-01

381

Power system harmonic mitigation of an offshore oil rig using passive shunt filter  

Microsoft Academic Search

Offshore oil rigs use large dc drives, usually fed from a.c. utility services through ac\\/dc converters, thus distorting current and voltage waveforms. Passive filters have been very effective solution for the harmonic mitigation as well as reactive VAR compensation. However, improper choice of filter components may lead to severe voltage and current stress to power system components or even sometimes

Shib Sankar Saha; Ramesh Suryavanshi

2010-01-01

382

Electro-optically tunable second-harmonic-generation gratings in ion-exfoliated thin films of periodically poled lithium niobate  

Microsoft Academic Search

The authors demonstrate that thin, single-crystal films fabricated by ion exfoliation of a bulk periodically poled LiNbO3 (PPLN) crystal reduced the tuning voltages for electro-optically tunable harmonic generation in PPLN devices. The tuning voltage of +\\/-150 V resulted in 0.5 nm total tuning of the second harmonic signal in the authors' 10-mum-thick device, compared to an order of magnitude higher

Djordje Djukic; Guiem Cerda-Pons; Ryan M. Roth; Richard M. Osgood; Sasha Bakhru; Hassaram Bakhru

2007-01-01

383

Bidirectional buck boost converter  

DOEpatents

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

Esser, Albert Andreas Maria (Niskayuna, NY)

1998-03-31

384

Bidirectional buck boost converter  

DOEpatents

A bidirectional buck boost converter and method of operating the same allows regulation of power flow between first and second voltage sources in which the voltage level at each source is subject to change and power flow is independent of relative voltage levels. In one embodiment, the converter is designed for hard switching while another embodiment implements soft switching of the switching devices. In both embodiments, first and second switching devices are serially coupled between a relatively positive terminal and a relatively negative terminal of a first voltage source with third and fourth switching devices serially coupled between a relatively positive terminal and a relatively negative terminal of a second voltage source. A free-wheeling diode is coupled, respectively, in parallel opposition with respective ones of the switching devices. An inductor is coupled between a junction of the first and second switching devices and a junction of the third and fourth switching devices. Gating pulses supplied by a gating circuit selectively enable operation of the switching devices for transferring power between the voltage sources. In the second embodiment, each switching device is shunted by a capacitor and the switching devices are operated when voltage across the device is substantially zero. 20 figs.

Esser, A.A.M.

1998-03-31

385

Generation of a coherent second-harmonic beam from incoherent conical beams  

NASA Astrophysics Data System (ADS)

Second-harmonic generation from incoherent conical beams is investigated. A theoretical description of an incoherent conical beam is provided. It is demonstrated that in the case of noncollinear phase matching, the spectrum of the second-harmonic beam narrows with the propagation in a nonlinear crystal. A simplified experiment with two intersecting fundamental beams is described. Numerical simulations of the nonlinear coupling equations are performed and good agreement with the theory is obtained.

Stanislovaitis, P.; Narmontas, A.; Pyragaite, V.; Smilgevi?ius, V.

2014-04-01

386

Cerenkov-type second-harmonic generation with fundamental beams of different polarizations.  

PubMed

We analyze the conical second-harmonic generation via Cerenkov-type phase matching in two-dimensional decagonal nonlinear photonic quasi-crystals for linear, circular, and elliptical polarized fundamental beams. Depending on the polarization state, we observe either centrosymmetric or noncentrosymmetric intensity modulation of the second-harmonic rings. We explain this effect by employing the concept of effective quadratic nonlinearity combined with the hexagonal symmetry of the individual ferroelectric domains. PMID:20436554

Sheng, Yan; Saltiel, Solomon M; Krolikowski, Wieslaw; Arie, Ady; Koynov, Kaloian; Kivshar, Yuri S

2010-05-01

387

Cerenkov-Type Second-Harmonic Generation in Two-Dimensional Nonlinear Photonic Structures  

Microsoft Academic Search

We study the Cerenkov-type second-harmonic gen- eration in several different two-dimensional nonlinear photonic structures formed in birefringent crystals with the 3m symmetry. Depending on the degree of birefringence, we observe either single or double Cerenkov-like second-harmonic rings. We discuss the properties of these parametrically generated rings and show that their sixfold azimuthal modulation is associated with the hexagonal symmetry of

Solomon Mois Saltiel; Yan Sheng; Noa Voloch-Bloch; Dragomir N. Neshev; Wieslaw Krolikowski; Ady Arie; Kaloian Koynov; Yuri S. Kivshar

2009-01-01

388

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

389

Modeling and current control of modular multilevel converters considering actuator and sensor delays  

Microsoft Academic Search

Voltage source converter (VSC) technology becomes more and more common in high-voltage direct current (HVDC) transmission systems. Compared to conventional VSC technology modular multilevel design offers advantages such as higher voltage levels, modular construction, longer maintenance intervals and improved reliability. A multilevel approach can also help to reduce harmonics due to sinusoidal output voltages so that grid filters become dispensable.

Philipp Munch; Steven Liu; Mike Dommaschk

2009-01-01

390

A Pulse Width Modulation technique for reducing switching frequency for modular multilevel converter  

Microsoft Academic Search

In this paper, a Pulse Width Modulation (PWM) technique for modular multilevel converter has been explored. The PWM technique is implemented using carrier based level shifted PWM strategy. It does not necessitate the calculation of duty cycles, and can be easily implemented in a DSP. With the proposed technique, harmonics in the phase voltage is shifted to twice the switching

Anandarup Das; Hamed Nademi; Lars Norum

2011-01-01

391

Improvements in Power Quality and Efficiency with a new AC\\/DC High Current Converter  

Microsoft Academic Search

A bstract: - A very flexible AC\\/DC converter featuring high-output current, reduced voltage ripple and highly adjustable current control is described. The whole system consists of four stages and uses a proper switching technique in conjunction with a feedback control performed by means of a PID regulator. Moreover, the built prototype exhibits high efficiency and reduced harmonic pollution. In order

F RANCESCO MUZI; LUIGI PASSACANTANDO; Francesco Muzi

2008-01-01

392

Control of cascaded multilevel converters with unequal voltage sources for HEVs  

Microsoft Academic Search

One promising technology to interface battery packs in electric and hybrid electric vehicles is the multilevel converter. In the work presented here, it is shown how the switching times (angles) in a multilevel inverter can be chosen to achieve a required fundamental voltage and not generate specific higher order harmonics. The method gives a complete solution to the problem in

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

2003-01-01

393

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

Microsoft Academic Search

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

JOHANN W. KOLAR; HANS ERTL; FRANZ C. ZACH

1990-01-01

394

Interleaving Impact on AC Passive Components of Paralleled Three-Phase Voltage-Source Converters  

Microsoft Academic Search

This paper presents a comprehensive analysis studying the impact of interleaving on harmonic currents and voltages on AC side of parallel three-phase voltage source converters (VSCs). The analysis performed considers the effects of modulation index and the interleaving angle. Based on the analysis, the impact of interleaving on the design of AC passive components such as AC line inductor and

Di Zhang; Fred Wang; Rolando Burgos; Rixin Lai; Dushan Boroyevich

2008-01-01

395

A New Modulation Method with Low Switching Frequency for Cascade Multilevel Current Controlled Converter  

Microsoft Academic Search

Recently cascade multilevel converters have attracted attention for many applications in medium voltage levels, such as STATCOMs and active power filters. The main challenges in these applications are limitation of the switching frequency of semiconductor devices and low harmonic distortion requirement of the current supplied by the current injection device. In this paper a new modulation method is proposed which

Omid Alizadeh; Shahrokh Farhangi; Saeid Afsharnia

2007-01-01

396

High power AC\\/DC converter and DC\\/AC inverter for high speed train applications  

Microsoft Academic Search

New developments in the design of high-speed electric trains are discussed, with particular reference to the induction motor drive system. A new high power three level converter-inverter system applying advanced insulated gate bipolar transistors (IGBTs) is described. Advanced control techniques lead to a unity power factor seen by the AC supply as well as minimising the line harmonics, power loss,

Adrian David Cheok; Shoichi Kawamoto; Takeo Matsumoto; Hideo Obi

2000-01-01

397

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

398

Theory of the Quantum Breathing Mode in Harmonic Traps and its Use as a Diagnostic Tool  

NASA Astrophysics Data System (ADS)

An analytical expression for the quantum breathing frequency ?b of harmonically trapped quantum particles with inverse power-law repulsion is derived. It is verified by ab initio numerical calculations for electrons confined in a lateral (2D) quantum dot. We show how this relation can be used to express the ground state properties of harmonically trapped quantum particles as functions of the breathing frequency by presenting analytical results for the kinetic, trap, and repulsive energy and for the linear entropy. Measurement of ?b together with these analytical relations represents a tool to characterize the state of harmonically trapped interacting particles—from the Fermi gas to the Wigner crystal regime.

McDonald, C. R.; Orlando, G.; Abraham, J. W.; Hochstuhl, D.; Bonitz, M.; Brabec, T.

2013-12-01

399

Theory of the quantum breathing mode in harmonic traps and its use as a diagnostic tool.  

PubMed

An analytical expression for the quantum breathing frequency ?b of harmonically trapped quantum particles with inverse power-law repulsion is derived. It is verified by ab initio numerical calculations for electrons confined in a lateral (2D) quantum dot. We show how this relation can be used to express the ground state properties of harmonically trapped quantum particles as functions of the breathing frequency by presenting analytical results for the kinetic, trap, and repulsive energy and for the linear entropy. Measurement of ?b together with these analytical relations represents a tool to characterize the state of harmonically trapped interacting particles--from the Fermi gas to the Wigner crystal regime. PMID:24483751

McDonald, C R; Orlando, G; Abraham, J W; Hochstuhl, D; Bonitz, M; Brabec, T

2013-12-20

400

Digital regulation of a phase controlled power converter  

SciTech Connect

The Relativistic Heavy Ion Collider, now in construction at Brookhaven National Laboratory, will use phase controlled power converters for the main dipole and quadrupole magnet strings. The rectifiers in these power supplies will be controlled by a digital regulator based on the TI 320C30 Digital Signal Processor (DSP). The DSP implements the current loop, the voltage loop, and a system to actively reduce the sub-harmonic ripple components. Digital firing circuits consisting of a phase locked lop and counters are used to fire the SCRs. Corrections for the sub-harmonic reduction are calculated by the DSP and stored in registers in the firing circuit. These corrections are added in hardware, to the over-all firing count provided by the DSP. the resultant count is compared to a reference counter to fire the SCRs. This combination of a digital control system and the digital firing circuits allows the correction of the sub-harmonics in a real-time sense. A prototype of the regulator has been constructed, and the preliminary testing indicates a sub-harmonic reduction of 60 dB.

Schultheiss, C.; Haque, T.

1995-12-01

401

Two new methanol converters  

SciTech Connect

Two novel converter systems were developed for the manufacture of methanol from synthesis gas: the Gas-Solid-Solid Trickle Flow Reactor (GSSTFR) and the Reactor System with Interstage Product Removal (RSIPR). In the GSSTFR version, the product formed at the catalyst surface is directly removed from the reaction zone by means of a solid adsorbent. This adsorbent continuously trickles over the catalyst bed. High reactant conversions up to 100% can be achieved in a single pass so that the usual recycle loop for the unconverted reactants is absent or greatly reduced in size. In the RSIPR version, high conversions per pass are achieved in a series of adiabatic or isothermal fixed bed reactors with selective product removal in absorbers between the reactor stages. The feasibility and economics of the two systems are discussed on the basis of 1,000 tpd methanol plants compared with a low-pressure Lurgi system.

Westerterp, K.R.; Bodewes, T.N.; Vrijiand, M.S.A.; Kuczynski, M. (Twente Univ. of Technology, Enschede (NL))

1988-11-01

402

Converting industrial boilers  

SciTech Connect

Based on the limitations of retrofit applications, a summary is presented of means by which existing oil or gas fired boilers can be converted to coal utilization. Boiler capacity is discussed as well as space limitations, particulate emissions, ash and cinder formation, air pollution, and effectiveness. Specifically, the following modes of firing are discussed: (1) spreader stoker firing; (2) pulverized coal firing; (3) producer gas firing; and (4) fluidized bed coal firing. Outputs in the range of 20,000 to 500,000 pph are considered. Auxillary equipment, particulate emissions, SO/sub 2/ emissions, and nitrogen oxide emissions are discussed briefly. A listing of all design factors to be considered (if coal firing is used) is included. (MJJ)

Dunphy, D.F.; Ramapriya, V.S.

1981-03-01

403

Fluorescent radiation converter  

NASA Technical Reports Server (NTRS)

A fluorescence radiation converter is described which includes a substantially undoped optically transparent substrate and a waveshifter coating deposited on at least one portion of the substrate for absorption of radiation and conversion of fluorescent radiation. The coating is formed to substantially 1000 g/liter of a solvent, 70 to 200 g/liter of an organic polymer, and 0.2 to 25 g/liter of at least one organic fluorescent dye. The incoming incident radiation impinges on the coating. Radiation is absorbed by the fluorescent dye and is re-emitted as a longer wavelength radiation. Radiation is trapped within the substrate and is totally internally reflected by the boundary surface. Emitted radiation leaves the substrate ends to be detected.

Viehmann, W. (inventor)

1981-01-01

404

Electromagnetic wave energy converter  

NASA Technical Reports Server (NTRS)

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

Bailey, R. L. (inventor)

1973-01-01

405

Unity power factor converter  

NASA Technical Reports Server (NTRS)

A unity power factor converter capable of effecting either inversion (dc-to-dc) or rectification (ac-to-dc), and capable of providing bilateral power control from a DC source (or load) through an AC transmission line to a DC load (or source) for power flow in either direction, is comprised of comparators for comparing the AC current i with an AC signal i.sub.ref (or its phase inversion) derived from the AC ports to generate control signals to operate a switch control circuit for high speed switching to shape the AC current waveform to a sine waveform, and synchronize it in phase and frequency with the AC voltage at the AC ports, by selectively switching the connections to a series inductor as required to increase or decrease the current i.

Wester, Gene W. (Inventor)

1980-01-01

406

Asymmetric Gaussian harmonic steering in second-harmonic generation  

NASA Astrophysics Data System (ADS)

Intracavity second-harmonic generation is one of the simplest of the quantum optical processes and is well within the expertise of most optical laboratories. It is well understood and characterized, both theoretically and experimentally. We show that it can be a source of continuous-variable asymmetric Gaussian harmonic steering with fields which have a coherent excitation, hence combining the important effects of harmonic entanglement and asymmetric steering in one easily controllable device, adjustable by the simple means of tuning the cavity loss rates at the fundamental and harmonic frequencies. We find that whether quantum steering is available via the standard measurements of the Einstein-Podolsky-Rosen correlations can depend on which quadrature measurements are inferred from output spectral measurements of the fundamental and the harmonic. Altering the ratios of the cavity loss rates can be used to tune the regions where symmetric steering is available, with the results becoming asymmetric over all frequencies as the cavity damping at the fundamental frequency becomes significantly greater than at the harmonic. This asymmetry and its functional dependence on frequency is a potential new tool for experimental quantum information science, with possible utility for quantum key distribution. Although we show the effect here for Gaussian measurements of the quadratures, and cannot rule out a return of the steering symmetry for some class of non-Gaussian measurements, we note here that the system obeys Gaussian statistics in the operating regime investigated and Gaussian inference is at least as accurate as any other method for calculating the necessary correlations. Perhaps most importantly, this system is simpler than any other methods we are aware of which have been used or proposed to create asymmetric steering.

Olsen, M. K.

2013-11-01

407

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

408

Harmonic and Inter-harmonic Signal Analysis Based on Hilbert-Huang Transform  

Microsoft Academic Search

Because of the extensive application of the non- linear electrical equipment, aircraft power system contains a number of harmonic and inter-harmonic components. Aiming at the situation that Fourier transform and wavelet transform method could not effectively extract and analyze these harmonic and inter-harmonic signal, made use of Hilbert- Huang Transform (HHT) to extract and analyze harmonic and inter-harmonic components for

Wei Fu; Yan Zhu

2011-01-01

409

Harmonic nanoparticles for regenerative research.  

PubMed

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

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

2014-01-01

410

Harmonic Analysis of the Output Voltage of a Third-Harmonic-Injected Inverter for LSM Drives  

NASA Astrophysics Data System (ADS)

The superconducting magnetic levitation railway system (MAGLEV) under development in Japan uses a pulse-width-modulation (PWM) inverter for driving a linear synchronous motor (LSM). The inverter output voltage contains non-negligible harmonics which cause harmonic resonances in the LSM system, and therefore harmonics of the output voltage have been analyzed in order to control such harmonic resonances. This paper applies a third-harmonic injection method to the inverter for the purpose of enhancing the output voltage without changing the circuit configuration. It performs harmonic analysis of the output voltage of the inverter based on the third-harmonic injection. Validity of the harmonic analysis is verified by computer simulation.

Shigeeda, Hidenori; Okui, Akinobu; Akagi, Hirofumi

411

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

412

Thermionic Converter Life and Repeatability Investigation.  

National Technical Information Service (NTIS)

This report covers work on thermionic converters, generators, and thermionic converter additives. Efforts included emitter work function measurements of seven converters which are on life-test and collector work function measurements of these converters. ...

C. Z. Kamien L. van Someren

1966-01-01

413

Radiating dipoles in photonic crystals  

NASA Astrophysics Data System (ADS)

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.

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

2000-09-01

414

Four quadrant operating Luo-converters  

Microsoft Academic Search

Classical DC-DC converters usually perform in single quadrant operation, such as buck converter, boost converter, buck-boost converter, Cuk-converter and Luo-converters. In industrial applications four-quadrant operation is required, e.g. a DC motor runs forward and reverse in motoring and regenerative braking states. This paper introduces a new converter that can perform four-quadrant DC\\/DC conversion. Because this converter implements dual-direction energy transference

Fang L. Luo; Hong Ye; Muhammad H. Rashid

2000-01-01

415

Photovoltaic energy converters  

NASA Astrophysics Data System (ADS)

The operational principles and numerical models for various significant parameters of solar cell performance are explored. Photovoltaics are semiconductor materials which experience quantum electronic trannsitions when a photon is absorbed. Electron hole pairs produced have a potential that can be converted into electrical energy. The photon energy must exceed the band-band transition energy band gap of the material for the absorption to occur. Each semiconductor material, e.g., Si, GaAs, CdS, etc., used for solar cells features a particular absorption coefficient, and production economies are partially dependent on the development of cells which are thinner and have a broad spectral response, such as found with amorphous Si. The functional characteristics of the junction between layers of a photovoltaic cell are also significant for the cell efficiency, as are the cell temperature and wiring interconnection with other cells. The maximum power delivered is a function of the fill factor, short circuit current, and open circuit voltage. The total efficiency can be augmented through concentrating configurations and by manufacturing tandem cells, which permit efficiencies of 30 percent.

Bloss, W. H.

416

Wind power converter  

SciTech Connect

A high torque windmill is provided for use in converting wind power to usable energy, having a vertical axis about which a plurality of flexible vanes are journaled for rotation and spaced radially therefrom. The vanes are circumferentially spaced and mounted on a rigid circular, multi-sided support member which comprises the rotor journaled for rotation about the vertical mounting axis. Each vane comprises a conical member made of a dacron material and open at opposed ends thereof. A plurality of rods are held in pockets located about the conical surface for maintaining the desired conical configuration. These rods extend beyond each pocket at the smaller end of the cone, for fitting into tubular members fastened to the rotor to hold the vanes in place. Adjacent vanes are offset from the plane of rotation by 15 degrees in opposite directions (That is, up and down) in order to maximize the amount of captured wind power. The foregoing design provides a low speed high torque multi-directional windmill unit.

Tornquist, A.

1982-12-21

417

Pulsed thermionic converter study  

NASA Technical Reports Server (NTRS)

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

1976-01-01

418

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.

419

Planar second-harmonic generation with noncollinear pumps in disordered media.  

PubMed

We study experimentally the process of the second harmonic generation by two noncollinear beams in quadratic nonlinear crystals with a disordered structure of ferroelectric domains. We show that the second-harmonic radiation is emitted in the form of two cones as well as in a plane representing the cross-correlation of the two fundamental pulses. We demonstrate the implementation of this parametric process for characterisation of femtosecond pulses, enabling the estimation of pulse width, chirp, and front tilt. This is achieved through monitoring the evolution of the autocorrelation trace inside the nonlinear crystal. PMID:18773029

Roppo, Vito; Dumay, David; Trull, Jose; Cojocaru, Crina; Saltiel, Solomon M; Staliunas, Kestutis; Vilaseca, Ramon; Neshev, Dragomir N; Krolikowski, Wieslaw; Kivshar, Yuri S

2008-09-01

420

NOVEL topology of traction converter with single phase Matrix converter  

Microsoft Academic Search

This paper presents research motivated by industrial demand for special traction drive topology devoted to minimization of traction transformer weight of traction vehicles. The main attention has been given to the special traction drive topology for AC power systems: input high voltage trolley converter (single phase) - middle frequency transformer (single phase) - output converter (single phase voltage-source active rectifier

PITTERMANN Martin; DRÁBEK Pavel; CÉDL Marek

2009-01-01

421

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

422

A multilevel converter-based universal power conditioner  

SciTech Connect

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

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

2000-04-01

423

Multifunctional interleaved boost converter for PV systems  

Microsoft Academic Search

In this study, an interleaved boost converter cascaded with a battery charger buck converter is designed and implemented. The converter also has maximum power point tracking capability and the battery charge operation is designed for purpose of long life requirements of batteries. Proposed interleaved boost converter operates in conventional converter mode and in interleaved boost converter mode with different switching

I. Sefa; S. O?zdemir

2010-01-01

424

Buck-boost integrated forward converter  

Microsoft Academic Search

An integrated converter is a synthesized converter based on the overall system integration, which is simplified by the system objective and can implement the system functions similar to the discrete converters. An integrated converter consists of converter sets; each converter set has a special function defined by the designer. A family of DC\\/DC buck boost based integrated rectifier with two

Z. Nie; A. Emadi

2005-01-01

425

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

426

Directional harmonics in Doppler effect  

NASA Astrophysics Data System (ADS)

A mathematical theory is presented which shows that a moving reflector of waves gives rise to harmonics of the Doppler shift in the input impedance of the transmission medium. The analysis can be used to explain new 'direction of motion' detection phenomena.

Lazarus, M. J.; Somekh, M. G.; Novak, S.; Pantoja, F. R.

1981-01-01

427

Adaptive control of harmonic drives  

Microsoft Academic Search

In this paper, an adaptive control algorithm is designed for controlling the harmonic drives used to drive robot manipulators. Direct torque measurement is available by using the flexspline mounted strain-gauges. The torque error is added to the required velocity. Adaptive friction compensation and flexspline dynamics based control are the two main contributions in the paper. The L2\\/L? stability and the

Wen-Hong Zhu; Michel Doyon

2004-01-01

428

Covariant harmonic oscillators: 1973 revisited  

NASA Technical Reports Server (NTRS)

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

Noz, M. E.

1993-01-01

429

Spin-Weighted Spherical Harmonics  

Microsoft Academic Search

\\u000a The spherical harmonics can be defined in various ways; they are eigenfunctions of the Laplace-Beltrami operator of the sphere\\u000a and they are the angular part of the separable solutions in spherical coordinates of the Laplace equation in Euclidean space.\\u000a Another useful characterization is given by the following result.

G. F. Torres Castillo

430

Radiative transfer via spherical harmonics  

Microsoft Academic Search

It is shown that several approximate treatments of radiative transfer (classic diffusion; diffusion with temperature jump boundary conditions; differential approximation) have a common origin in the spherical harmonic expansion of the equation of transfer. Comparisons with exact results, computed numerically with a discrete ordinates computer code (ANISN), are made for several problems, with and without heat sources, for the standard

G. C. Pomraning

1979-01-01

431

Renormalization for free harmonic oscillators  

NASA Astrophysics Data System (ADS)

We introduce a model of free harmonic oscillators that requires renormalization. The model is similar to but simpler than the soluble Lee model. We introduce two concrete examples: the first, resembling the three dimensional ?4 theory, needs only mass renormalization, and the second, resembling the four dimensional ?4 theory and the Lee model, needs additional renormalization of a coupling and a wave function.

Sonoda, H.

2014-02-01

432

Lasing on the third harmonic  

SciTech Connect

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

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

1989-01-01

433

Harmonic Oscillator Model for Baryons.  

National Technical Information Service (NTIS)

Attention is drawn to a possible band structure displayed by the known N* resonances. The observed spectrum is similar to that predicted by a paraquark harmonic oscillator shell model. Exact three-body Schrodinger wave functions are used to compute the N-...

D. Faiman A. W. Hendry

1968-01-01

434

Agglomeration, Integration and Tax Harmonization  

Microsoft Academic Search

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

Richard E. Baldwin; Paul Krugman

2000-01-01

435

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

436

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

437

A harmonic analysis of lunar gravity  

NASA Technical Reports Server (NTRS)

An improved model of lunar global gravity has been obtained by fitting a sixteenth-degree harmonic series to a combination of Doppler tracking data from Apollo missions 8, 12, 15, and 16, and Lunar Orbiters 1, 2, 3, 4, and 5, and laser ranging data to the lunar surface. To compensate for the irregular selenographic distribution of these data, the solution algorithm has also incorporated a semi-empirical a priori covariance function. Maps of the free-air gravity disturbance and its formal error are presented, as are free-air anomaly and Bouguer anomaly maps. The lunar gravitational variance spectrum has the form V(G; n) = O(n to the -4th power), as do the corresponding terrestrial and martian spectra. The variance spectra of the Bouguer corrections (topography converted to equivalent gravity) for these bodies have the same basic form as the observed gravity; and, in fact, the spectral ratios are nearly constant throughout the observed spectral range for each body. Despite this spectral compatibility, the correlation between gravity and topography is generally quite poor on a global scale.

Bills, B. G.; Ferrari, A. J.

1980-01-01

438

PWM Converter Power Density Barriers  

Microsoft Academic Search

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

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

2007-01-01

439

Thyristor converter simulation and analysis  

SciTech Connect

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. 4 refs., 4 figs.

Zhang, S.Y.

1991-01-01

440

Magnetic integration for interleaved converters  

Microsoft Academic Search

In this paper several techniques for integration of magnetic components in interleaved converters are analyzed. Magnetic components define the way the energy is transformed. Several opposite approaches can be considered: from decoupled integrated inductors to tightly coupled inductors. The integration of inductors in the same core for multiphase converters is especially analyzed from the point of view of size, losses

P. Zumel; O. Garcia; J. A. Cobos; J. Uceda

2003-01-01

441

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

442

Proposed electromagnetic wave energy converter  

NASA Technical Reports Server (NTRS)

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

Bailey, R. L.

1973-01-01

443

Resonant AC to AC converter  

Microsoft Academic Search

This paper proposes a novel, power electronics system, a series resonant AC to AC converter, capable of converting a single phase AC supply of frequency fi, into a balanced three-phase supply of frequency foc that may he both higher as well as lower to the input frequency. Use of microcontrollers to control the trigger pulses has made it more versatile.

Vineeta Agarwal; Sachin Nema

2005-01-01

444

Improvement of Pulse Pattern for Space Vector Modulated Matrix Converters  

NASA Astrophysics Data System (ADS)

Novel modulation which consists of conventional space vector modulation (SVM) based on a virtual AC/DC/AC conversion and carrier signal modulation for matrix converters is proposed. In this proposed modulation, duties for the switching pattern decided by conventional SVM are changed into those for each switch of matrix converter. The new duties for each output phase are compared with the triangle carrier. By using proposed modulation, switchings between the input phase voltage with minimum value and the voltage with maximum value are eliminated. In this paper, the conventional SVM and proposed modulation are explained. Next, for both conventional and proposed modulations waveforms of input current, output voltage and output current and their frequency spectra are calculated by PSIM simulation program. Simulation results show the proposed modulation can reduce harmonics of output voltage waveforms.

Yamamoto, Kichiro; Shinohara, Katsuji; Mori, Tatsuya

445

Magnetic noise in single-machine rotating frequency converters  

NASA Astrophysics Data System (ADS)

The magnetic noise in rotating frequency converters with two magnetic fields in a common structure of an induction machine, each field having a different number of pole pairs corresponding to the frequency conversion ratio, is evaluated on the basis of harmonic analysis of the resultant magnetic induction in the air gap and the radial forces it generates. The rotor in small and medium-size machines is regarded as a solid cylinder so that the hollow stator cylinder remains the principal source of noise. Constraints on the numbers of stator slots and rotors slots are established so as to ensure minimum higher-frequency tooth noise and vibration, while structural requirements are stipulated for minimizing lower-frequency noise and vibration and avoiding resonances at any frequency. Typical design calculations for a three-phase motor-generator machine operating at 1:3 frequency converter are shown, including the amplitudes of design-controlled vibrations of magnetic origin.

Popov, V. I.

1985-01-01

446

Harmonic ratcheting for fast acceleration  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

447

Harmonic generation from indium-rich plasmas  

SciTech Connect

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

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

2006-12-15

448

Harmonic generation in a UV laser plasma  

Microsoft Academic Search

Second and third harmonic generation in the interaction of a prepulse-free 700-fs, 248-nm laser pulse with solid targets was observed for maximum intensities of ~5.1015 W\\/cm2. Both s- and p-polarized light generated harmonic emission without observable difference. Harmonic generation was shown to prefer the specular direction. The results showed short-pulse ultraviolet lasers to be efficient drivers of harmonics in the

I. B. Foldes; J. S. Bakos; G. Veres; Z. Bakonyi; T. Nagy; S. Szatmari

1996-01-01

449

The relationship between monopole harmonics and spin-weighted spherical harmonics  

Microsoft Academic Search

We compare two independent generalizations of the usual spherical harmonics, namely monopole harmonics and spin-weighted spherical harmonics, and make precise the sense in which they can be considered to be the same. By analogy with the spin-gauge language, raising and lowering operators for the monopole index of the monopole harmonics can immediately be written down.

Tevian Dray

1985-01-01

450

Modeling a Harmonic Drive Gear Transmission  

Microsoft Academic Search

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

Timothy D. Tuttle; Warren P. Seering

1993-01-01

451

High-Harmonic Probing of Electronic Coherence in Dynamically Aligned Molecules  

NASA Astrophysics Data System (ADS)

We introduce and demonstrate a new approach to measuring coherent electron wave packets using high-harmonic spectroscopy. By preparing a molecule in a coherent superposition of electronic states, we show that electronic coherence opens previously unobserved high-harmonic-generation channels that connect distinct but coherently related electronic states. Performing the measurements in dynamically aligned nitric oxide molecules we observe the complex temporal evolution of the electronic coherence under coupling to nuclear motion. Choosing a weakly allowed transition to prepare the wave packet, we demonstrate an unprecedented sensitivity that arises from optical interference between coherent and incoherent pathways. This mechanism converts a 0.1% excitation fraction into a ˜20% signal modulation.

Kraus, P. M.; Zhang, S. B.; Gijsbertsen, A.; Lucchese, R. R.; Rohringer, N.; Wörner, H. J.

2013-12-01

452

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

Microsoft Academic Search

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

JoseAntonio Barrado; R. Grino

2006-01-01

453

Organic nonlinear crystals and high power frequency conversion  

Microsoft Academic Search

We are searching for a new second- and third-harmonic generators among the salts of chiral organic acids and bases. We discuss the relevant properties of crystals from this group of compounds, including their nonlinear and phasematching characteristics, linear absorption, damage threshold and crystal growth. In addition, we summarize what is known concerning other nonlinear optical properties of these crystals, such

S. P. Velsko; L. Davis; F. Wang; S. Monaco; D. Eimerl

1987-01-01

454

Organic nonlinear crystals and high power frequency conversion  

Microsoft Academic Search

We are searching for new second and third harmonic generators among the salts of organic acids and bases. We discuss the relevant properties of crystals from this group of compounds, including their nonlinear and phasematching characteristics, linear absorption, damage threshold and crystal growth. In addition, we summarize what is known concerning other nonlinear optical properties of these crystals, such as

S. P. Velsko; L. Davis; F. Wang; S. Monaco; D. Eimerl

1987-01-01

455

Switched-capacitor DC-DC converters  

Microsoft Academic Search

Novel switched-capacitor (SC) DC-DC converters are derived from three basic SC DC-DC converters. The converter outputs can be regulated by changing the duty ratio of the transistor switch. These converters have features not found in conventional switching regulators (buck, boost, and buck-boost converters). Of these converters, the voltage polarity inverting converter is expected to be widely used for small-size, small-power

K. Kuwabara; E. Hiyachika

1988-01-01

456

Scanning second-harmonic/third-harmonic generation microscopy of gallium nitride  

NASA Astrophysics Data System (ADS)

Scanning second-harmonic generation and third-harmonic generation microscopy of a gallium nitride (GaN) sample was demonstrated using a femtosecond Cr:forsterite laser. Taking advantage of the electric-field enhanced second-harmonic generation effect and bandtail state resonance effect, the obtained second-harmonic and third-harmonic generation microscopic images revealed the piezoelectric field and bandtail state distributions in a GaN sample.

Sun, Chi-Kuang; Chu, Shih-Wei; Tai, Shi-Peng; Keller, Stacia; Mishra, Umesh K.; Denbaars, Steven P.

2000-10-01

457

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 versus wavelength to second order, we efficiently doubled tunable fundamental light near 660nm over a range of 80nm, using a 4-mm-long type I {beta}-barium borate crystal without tuning the crystal angle. Another 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{percent}. {copyright} {ital 1998} {ital Optical Society of America}

Richman, B.A.; Bisson, S.E.; Trebino, R. [Combustion Research Facility, Sandia National Laboratory, M/S 9051, Livermore, California 94551-0969 (United States); Sidick, E.; Jacobson, A. [CVI Laser Corporation, 361 Lindbergh Avenue, Livermore, California 94550 (United States)

1998-04-01

458

High harmonic generation from atom clusters  

NASA Astrophysics Data System (ADS)

High harmonics generation driven by 40 fs laser pulses is investigated in three different noble gases, both in gas and cluster regime depending on gas type and backing pressure. Pressure dependence of the harmonic intensity shows different scaling laws in case of cluster formation compared with monomer gas. Both the higher harmonic yield and the stronger spectral broadening of harmonics in xenon gas show the presence of clusters in the jet. The central wavelength of harmonics has a blue shift increasing with increasing laser intensity which is a consequence of free electron contribution to the phase matching.

Aladi, M.; Földes, I. B.

2014-04-01

459

Spectral analysis of DC link ripple currents in three-phase AC\\/DC\\/AC PWM converters feeding AC machines  

Microsoft Academic Search

In this paper, DC link ripple currents for three-phase AC\\/DC\\/AC PWM converters feeding adjustable speed AC machine drives are analysed in a frequency domain. The expression of the harmonic currents is developed by using switching functions and exponential Fourier series expansion. The effect of the displacement angle between the switching periods of line-side converters and motor-side inverters on the DC

Young-Wook Park; Dong-Choon Lee; Jul-Ki Seok

2001-01-01

460

Nonclassical correlations and entanglement in intracavity second harmonic generation  

NASA Astrophysics Data System (ADS)

Quantum information science is a rapidly growing field of research that combines the techniques developed in quantum optics with those of information science. One primary goal of the field is to implement a quantum information network using non-classical light sources such as entangled photon pairs. The process of parametric down conversion has been widely used to generate entangled photons as well as twin beams that have intensity correlations below the shot noise limit. The complementary process - second harmonic generation (SHG) is less well studied in comparison. This dissertation presents the techniques of generating non-classical optical fields using SHG in the continuous variable regime of quantum mechanics. Using a potassium niobate crystal in a resonator, bright blue light was generated through frequency doubling of an infrared beam. We report an observation of 1 dB noise reduction in the amplitude fluctuations of the harmonic output. By double-passing the nonlinear crystal sitting inside a resonator, we set up a singly resonant system which allows two harmonic beams to escape at two different ports. Using a self-consistent propagation model and solutions of the traveling wave SHG, we show that such a dual ported cavity can be used to generate entangled beams with nonclassical intensity correlations in the harmonic outputs. We obtain 0.9 dB of twin-beam intensity correlation from the resonator and demonstrate the inseparability of the two beams with a balanced Mach-Zehnder interferometer. In addition to the generation of quantum correlated states of light, we also investigate the dynamic of coherent light in SHG such as the generation of optical vortices. We demonstrate generation and frequency doubling of unit charge vortices in a linear astigmatic resonator. Through an appropriate alignment of a near confocal cavity, we couple higher order transverse modes of the fundamental laser beam into a vortex mode. With the presence of a nonlinear crystal, a doubly charged vortex was generated. Topological instability of the double charge harmonic vortices leads to well separated vortex cores that are shown to rotate, and become anisotropic, as the resonator is tuned across resonance.

Lim, Oo-Kaw

461

Orthogonality of spherical harmonic coefficients  

NASA Technical Reports Server (NTRS)

Orthogonality relations are obtained for the spherical harmonic coefficients of functions defined on the surface of a sphere. Following a brief discussion of the orthogonality of Fourier series coefficients, consideration is given to the values averaged over all orientations of the coordinate system of the spherical harmonic coefficients of a function defined on the surface of a sphere that can be expressed in terms of Legendre polynomials for the special case where the function is the sum of two delta functions located at two different points on the sphere, and for the case of an essentially arbitrary function. It is noted that the orthogonality relations derived have found applications in statistical studies of the geomagnetic field.

Mcleod, M. G.

1980-01-01

462

Harmon Craig (1926-2003)  

NASA Astrophysics Data System (ADS)

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

Weiss, Ray

463

Dynamics of second harmonic in nonlinear surface acoustic waves and a proposal of its device application  

NASA Astrophysics Data System (ADS)

Dynamic behavior of nonlinear surface acoustic waves (NLSAWs) generated on a piezoelectric single crystal has been much interested in application to new engineering fields from a viewpoint of the complex system. In this study, characteristics of fundamental and second-order harmonic components in NLSAWs propagating on a LiNbO3 single crystal were investigated, and we proposed a novel photonic signal control device using the NLSAW.

Aizawa, Koji; Tokunaga, Yoshiaki

2012-09-01

464

Higher order quasi-phase matched harmonics in two-dimensional quasiperiodic superlattice  

NASA Astrophysics Data System (ADS)

Two-dimensional LiNbO 3 nonlinear photonic crystal with octagonal quasilattice was fabricated by applying the external electric field. The higher order collinear quasi-phase matched second harmonics, in the red, orange and blue-green areas, along the midline of the two adjacent basic reciprocal vectors were obtained, in which the efficiency of red harmonics reached 17%. And the higher order non-collinear second-harmonic generations with the input beams parallel to the basic reciprocal vectors were studied systematically, in which the related highest-order reciprocal vector pair was (2 2 1 0) and (-2 0 1 2). All the same results can be obtained when the crystal is rotated by the integral multiples of ?/4.

Ma, Boqin; Sheng, Yan; Dou, Junhong; Cheng, Bingying; Zhang, Daozhong

2007-06-01

465

Hyperspherical Harmonic Formalism for Tetraquarks  

NASA Astrophysics Data System (ADS)

We present a generalization of the hyperspherical harmonic formalism to study systems made of quarks and antiquarks of the same flavor. This generalization is based on the symmetrization of the N-body wave function with respect to the symmetric group using the Barnea and Novoselsky algorithm. Our analysis shows that four-quark systems with non-exotic 2++ quantum numbers may be bound independently of the quark mass. 0+- and 1+- states become attractive only for larger quarks masses.

Vijande, J.; Valcarce, A.; Barnea, N.

466

Venus topography - A harmonic analysis  

NASA Technical Reports Server (NTRS)

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) km towards (6.6 + or 10.1) deg N, (148. 8 + or - 7.7) deg. The figure of Venus is distinctly triaxial, but the orientation and magnitudes of the principal topographic axes correlate rather poorly with the gravitational principal axes. However, the higher-degree harmonics of topography and gravity are significantly correlated. The topographic variance spectrum of Venus is very similar in form to those of the moon, Mars, and especially earth. It is suggested that this spectral similarity simply reflects a statistical balance between constructional and degradational geomorphic proceses. Venus and earth are particularly similar (and differ from the moon and Mars) in that the larger bodies both exhibit a significant low degree deficit (relative to the extrapolated trend of the higher harmonics).

Bills, B. G.; Kobrick, M.

1985-01-01

467

Fast generic polar harmonic transforms.  

PubMed

Generic polar harmonic transforms have recently been proposed to extract rotation-invariant features from images and their usefulness has been demonstrated in a number of pattern recognition problems. However, direct computation of these transforms from their definition is inefficient and is usually slower than some efficient computation strategies that have been proposed for other methods. This paper presents a number of novel computation strategies to compute these transforms rapidly. The proposed methods are based on the inherent recurrence relations among complex exponential and trigonometric functions used in the definition of the radial and angular kernels of these transforms. The employment of these relations leads to recursive and addition chain-based strategies for fast computation of harmonic function-based kernels. Experimental results show that the proposed method is about 10× faster than direct computation and 5× faster than fast computation of Zernike moments using the q-recursive strategy. Thus, among all existing rotation-invariant feature extraction methods, polar harmonic transforms are the fastest. PMID:24835224

Hoang, Thai V; Tabbone, Salvatore

2014-07-01

468

High-temperature solar converter  

NASA Technical Reports Server (NTRS)

Converter has parabolic concentrator that directs sunlight on three-dimensional absorber assembly within an evacuated glass cylinder. No tracking mechanism is required. Concentrator aperture is adjustable to modify concentration in direct or diffuse sunlight. Range of adjustment is small.

Ascher, G.

1978-01-01

469

Wind/water energy converter  

NASA Technical Reports Server (NTRS)

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

Paulkovich, J.

1979-01-01

470

Method for Converting Chrysotile Asbestos.  

National Technical Information Service (NTIS)

The patent application discloses a method for converting chrysotile asbestos to a magnesium hydroxide rich composition by subjecting the asbestos to repeated cycles of treatment with a 20 to 60 percent solution of potassium hydroxide heated to a temperatu...

Y. Harada

1973-01-01

471

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

472

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

473

HIGH EFFICIENCY AUXILIARY POWER CONVERTERS  

Microsoft Academic Search

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

Geoff Walker

474

Transformerless dc-Isolated Converter  

NASA Technical Reports Server (NTRS)

Efficient voltage converter employs capacitive instead of transformer coupling to provide dc isolation. Offers buck/boost operation, minimal filtering, and low parts count, with possible application in photovoltaic power inverters, power supplies and battery charges. In photovoltaic inverter circuit with transformerless converter, Q2, Q3, Q4, and Q5 form line-commutated inverter. Switching losses and stresses nil because switching performed when current is zero.

Rippel, Wally E.

1987-01-01

475

Nonclassical states of the second optical harmonic in the presence of self-action  

NASA Technical Reports Server (NTRS)

The quantum theory of coherent radiation frequency doubling in crystals with quadratic and cubic optical nonlinearities is developed. The possibility of producing the quadrature-squeezed state of the second harmonic (SH) field is shown. The nonclassical SH states arise due to self-action effect.

Chirkin, A. S.; Korolkova, N. V.

1993-01-01

476

Second harmonic generation of a copper vapor laser in barium borate  

Microsoft Academic Search

The beam from a Cu-vapor laser with an unstable resonator was focused in a nonlinear crystal, barium borate, for second-harmonic generation. Light at 255.3 nm was generated with a conversion efficiency of 8.9 percent at an average input power of 2.55 W. The characteristics of conversion were investigated.

K. Kuroda; T. Omatsu; T. Shimura; M. Chihara; I. Ogura

1990-01-01

477

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

478

Multi-harmonic detection in wavelength modulation spectroscopy systems  

NASA Astrophysics Data System (ADS)

Two multi-harmonic detection methods for wavelength modulation spectroscopy (WMS) systems are presented and compared. The two possibilities discussed in this paper are: simultaneous curve fitting of multiple harmonic spectra, and reconstruction of the transmission from harmonic coefficients. The optimum number of harmonics is four and 25 harmonics, respectively. Compared with standard single-harmonic curve fitting, the methods give about a factor of 3 better performance than standard second-harmonic curve fitting. Concluding, multi-harmonic detection is better than single-harmonic detection and should be used if the system bandwidth is high enough to allow for proper detection of the higher harmonics.

Hangauer, A.; Chen, J.; Strzoda, R.; Amann, M.-C.

2013-02-01

479

Radiation effects on DC-DC Converters  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

480

Multilevel converters for power system applications.  

National Technical Information Service (NTIS)

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 m...

J. S. Lai J. P. Stovall F. Z. Peng

1995-01-01

481

Mode conversion and absorption of fast waves at high ion cyclotron harmonics in inhomogeneous magnetic fields  

NASA Astrophysics Data System (ADS)

The propagation and absorption of high harmonic fast waves is of interest for non-inductive current drives in fusion experiments. The fast wave can be coupled with the ion Bernstein wave that propagates in the high magnetic field side of an ion cyclotron harmonic resonance layer. This coupling and the absorption are analyzed using the hot plasma dispersion relation and a wave equation that was converted from an approximate dispersion relation for the case where ?i=k?2?i2/2?1 (where k? is the perpendicular wave number and ?i is the ion Larmor radius). It is found that both reflection and conversion may occur near the harmonic resonance layer but that they decrease rapidly, giving rise to a sharp increase in the absorption as the parallel wave number increases.

Cho, Suwon; Kwak, Jong-Gu

2014-04-01

482

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

483

Input power conditioning of a linearized induction motor drive using three level front-end converter and passive filter  

Microsoft Academic Search

This paper proposes a simple three phase, three level IGBT based ac-dc neutral point clamped converter with a shunt passive filter, at the front end of a PWM VSI feeding induction motor drive, to compensate reactive power, reduce harmonics in source current and to regulate dc link voltage. Mathematical model is used to design the control scheme for the front-end

Kanungo Barada Mohanty; Madhu Singh

2011-01-01

484

Influence of the inverter characteristics on the harmonic losses in PWM fed traction motors  

Microsoft Academic Search

The paper focuses on the effects of the inverter characteristics on the losses increment traction motors fed by pulse width modulation (PWM) controlled converters. Using the MATLAB soft, the AC-DC-AC equivalent model is founded on the principle of sinusoidal pulse width modulation (SPWM). The harmonic spectrum of steady-state operation is simulated using this model. In particular, the influence of the

Laisheng Tong I; Giiangriing Wu; Fengxiang Wen Wen Shu; Enguang He

2005-01-01

485

PWM Converter Power Density Barriers  

NASA Astrophysics Data System (ADS)

Power density of power electronic converters has roughly doubled every 10 years since 1970. Behind this trajectory is the continuous advancement of power semiconductor devices, which has increased the converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts and passive components are major barriers for a continuation of this trend. To identify such technological barriers, this paper investigates the volume of the cooling system and passive components as a function of the switching frequency for power electronic converters and determines the switching frequency that minimizes the total volume. A power density limit of 28kW/dm3 at 300kHz is calculated for an isolated DC-DC converter, 44kW/dm3 at 820kHz for a three-phase unity power factor PWM rectifier, and 26kW/dm3 at 21kHz for a sparse matrix converter. For single-phase AC-DC conversion a general limit of 35kW/dm3 results from the DC link capacitor. These power density limits highlight the need to broaden the scope of power electronics research to include cooling systems, high frequency electromagnetics, interconnection and packaging technology, and multi-domain modelling and simulation to ensure further advancement along the power density trajectory.

Kolar, Johann W.; Drofenik, Uwe; Biela, Juergen; Heldwein, Marcelo; Ertl, Hans; Friedli, Thomas; Round, Simon

486

Luminescent up-converting nanocrystals for in vivo imaging  

Microsoft Academic Search

Luminescent nanoparticles are increasingly used as emitting labels in the design of fluorescence imaging probes, because of their outstanding optical properties, such as in the case of quantum dots, or their role in nano-assembling different functionalities, such as imaging, drug delivery, and therapy. In this work, the potentiality of up-converting nano-crystals for non invasive fluorescence imaging of small animal is

Isabelle Texier; Emilie Heinrich; Michel Berger; O. Tillement; C. Louis; Philippe Peltié

2007-01-01

487

Searching for the Second Harmonic  

NASA Technical Reports Server (NTRS)

To mathematically model the oscillations of a spherical bubble, either the time-dependent volume V(t) or the radius R(t) can be used as the dependent variable. A recent exchange between the advocates of the volume approach and the radius approach concerns in apparent discrepancy in the predicted nonlinear acoustic emissions from a bubble subject to a time-periodic external pressure field. This letter attempts to resolve the discrepancy via an examination of the arguments offered by both sides. In addition, some general comments on nonlinear harmonic and subharmonic emissions from acoustically forced bubble oscillations are presented.

Holt, R. Glynn

1994-01-01

488

Symmetries of coupled harmonic oscillators  

NASA Technical Reports Server (NTRS)

It is shown that the system of two coupled harmonic oscillators possesses many interesting symmetries. It is noted that the symmetry of a single oscillator is that of the three-parameter group Sp(2). Thus two uncoupled oscillator exhibits a direct product of two Sp(2) groups, with six parameters. The coupling can be achieved through a rotation in the two-dimensional space of two oscillator coordinates. The closure of the commutation relations for the generators leads to the ten-parameter group Sp(4) which is locally isomorphic to the deSitter group O(3,2).

Han, D.; Kim, Y. S.

1993-01-01

489

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

490

A Proposal of a Power Distortion Compensator Using a Matrix Converter  

NASA Astrophysics Data System (ADS)

Recently, renewable resources supplies, such as fuel cells, photovoltaic cells, wind power and engine generators, for distributed power system have been studied intensely. Conventional compensators with switching devices are constructed based on a voltage source inverter using six arms. Therefore, conventional power quality compensators require a large electrolytic capacitor in the dc link part of the equipment. The use of a large capacitor hinders downsizing efforts and the lowering of equipment costs. Direct converters, which do not have a large electrolytic capacitor and an initial charge circuit, can be used to realize downsizing and lowering of equipment costs, when compared with conventional converters. This paper proposes one of new applications of a matrix converter to a PM generator for power quality compensation, such as reactive power compensation, harmonic current and power interruption. The novel point of this work is that the matrix converter provides reactive power with harmonic current. Simulated and experimental results confirm that the matrix converter can maintain high performance as same as a conventional active filter and an uninterruptible power supply (UPS).

Tamada, Shunsuke; Itoh, Jun-Ichi

491

Infinity-harmonic maps and morphisms  

Microsoft Academic Search

We propose a new notion called \\\\emph{infinity-harmonic maps}between Riemannain manifolds. These are natural generalizations of the well known notion of infinity harmonic functions and are also the limiting case of $p$% -harmonic maps as $p\\\\to \\\\infty $. Infinity harmoncity appears in many familiar contexts. For example, metric projection onto the orbit of an isometric group action from a tubular neighborhood

Ye-Lin Ou; Tiffany Troutman; Frederick Wilhelm

2008-01-01

492

Third-harmonic generation in liquids  

Microsoft Academic Search

Third-order nonlinear susceptibilities of several organic solvents are measured by third-harmonic generation at two laser wavelengths: 1.064 and 1.907 mum. The method used allows a determination of the modulus and phase by interference with the harmonic field generated in the liquid-cell windows. Air contribution to the resulting harmonic intensities is studied in detail. An experimental correction for this effect is

F. Kajzar; J. Messier

1985-01-01

493

Higher harmonic control for rotary wing aircraft  

NASA Technical Reports Server (NTRS)

Higher Harmonic Control reduces helicopter airframe vibration through the exercise of rotor blade pitch control at frequencies that are higher harmonics of rotor rotation. Analysis wind tunnel tests and flight tests of this technology with an OH-6A helicopter have led to vibration reduction levels of the order of more than 80 percent. Blade feathering capability at rotor speed harmonics other than the first also promises the improvement of such rotor characteristics as acoustics, aerodynamic efficiency and ground resonance.

Gupta, B. P.; Logan, A. H.; Wood, E. R.

1984-01-01

494

Thermal optimization of second harmonic generation at high pump powers.  

PubMed

We measure the temperature distribution of a 3 cm long periodically poled LiNbO? crystal in a single-pass second harmonic generation (SHG) setup at 488 nm. By means of three resistance heaters and directly mounted Pt100 sensors the crystal is subdivided in three sections. 9.4 W infrared pump light and 1.3 W of SHG light cause a de-homogenized temperature distribution of 0.2 K between the middle and back section. A sectional offset heating is used to homogenize the temperature in those two sections and thus increasing the conversion efficiency. A 15% higher SHG output power matching the prediction of our theoretical model is achieved. PMID:22109182

Sahm, Alexander; Uebernickel, Mirko; Paschke, Katrin; Erbert, Götz; Tränkle, Günther

2011-11-01

495

Characteristics of an equidistant firing system in 12-pulse converter bridges for HVDC  

NASA Astrophysics Data System (ADS)

The construction of a simulation model for a twelve pulse HVDC transmission line is discussed. The realized equidistant pulse phase control system is suitable for the operation in weak or strongly unbalanced ac systems from the viewpoint of harmonic instability and suppression of abnormal harmonic currents. The phase of the firing pulses is proportional to an absolute level of the control voltage, and the operation with a constant control angle is possible. The synchronism with an ac system is guaranteed by a phase-locked loop, not by the main control loop. Thus quick and ideal response is obtaind. The measurements show that this kind of grid conrol is stable also in many faulty conditions. Abnormal harmonic generation of the converter is very small compared with the traditional systems by utilizing this kind of grid control.

Juslin, K.; Laiho, Y.; Vauhkonen, V.

1981-05-01

496

Angiotensin converting enzyme inhibitor therapy.  

PubMed

Angiotensin converting enzyme inhibitor therapy decreases the production of the vasoconstrictive angiotensin II and reduces the degradation of certain kinines of vasodilatator action. Of captopril, enalapril, and lysinopril marketed abroad, only captopril of shorter action is available in Hungary. Angiotensin converting enzyme inhibitors are new means for the therapy of hypertension and congestive heart failure. Captopril seems to be effective at an early stage of heart failure. It slows down or even inhibits the progression of heart failure. New aspects of therapy have been revealed. It may be successfully used in angina pectoris, for the prevention of reperfusion arrhythmias accompanying myocardial infarction, for the treatment of renoparenchimal renal diseases, diabetic nephropathy. The side-effects, interactions, and dosage of angiotensin converting enzyme inhibitors have also been discussed. PMID:1948779

Róna, G

1991-01-01