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1

Harmonic reduction in thyristor converters by harmonic current injection  

Microsoft Academic Search

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

A. Ametani

1976-01-01

2

Active harmonic elimination in multilevel converters using FPGA control  

Microsoft Academic Search

This paper presents an optimal total harmonic distortion (THD) control algorithm referred to as active harmonic elimination method for cascaded H-bridges multilevel converter control with unequal DC sources. First, the multilevel converter is decoupled into unipolar converters, the low order harmonics, such as the 5th, 7th, 11th and 13th are eliminated by using elimination theory, and the minimum THD combination

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

2004-01-01

3

Active Harmonic Elimination in Multilevel Converters Using FPGA Control  

E-print Network

for cascaded H-bridges multilevel converter control with unequal DC sources. First, the multilevel converter H- bridge multilevel converter with a real-time controller based on Altera FLEX 10K fieldActive Harmonic Elimination in Multilevel Converters Using FPGA Control Zhong Du, Leon M. Tolbert

Tolbert, Leon M.

4

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

5

Reduced Switching-Frequency Active Harmonic Elimination for Multilevel Converters  

Microsoft Academic Search

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

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

2008-01-01

6

Harmonic Elimination for Multilevel Converter with Programmed PWM Method  

E-print Network

wave is produced. An experimental 11-level H-bridge multilevel converter with a first- on, first. An experimental 11-level H-bridge multilevel converter with a first-on, first-off switching strategy (usedHarmonic Elimination for Multilevel Converter with Programmed PWM Method Zhong Du, Leon M. Tolbert

Tolbert, Leon M.

7

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

8

Aircraft power system harmonics involving single-phase PFC converters  

Microsoft Academic Search

AC-DC converters with active power factor correction (PFC) are replacing uncontrolled diode rectification circuits on commercial jet airplanes in order to meet harmonic distortion limits imposed by new airborne electrical system power quality standards. The high line frequency of airborne AC power systems presents a major challenge for the design of PFC converters capable of meeting these standards. This paper

Jian Sun; Min Chen; KAMIAR J. KARIMI

2008-01-01

9

Harmonically Pumped Stripline Down-Converter  

Microsoft Academic Search

A novel thin-film down-converter which is pumped at a submultiple of the local-oscillator frequency has given a conversion loss which is comparable to the performance of conventional balanced mixers. The converter consists of two stripline filters and two Schottky-barrier diodes which are shunt mounted in a strip transmission line. The conversion loss measured at a signal frequency of 3.5 GHz

MARTIN V. SCHNEIDER; W. W. Snell Jr.

1975-01-01

10

Elimination of Harmonics in a Multilevel Converter for HEV Applications  

E-print Network

- tions are found. II. Cascaded H-bridges The cascade multilevel inverter consists of a series of H-phase structure of a multilevel cascaded H-bridges inverter. to a single-phase full-bridge inverter. Each inverter1 Elimination of Harmonics in a Multilevel Converter for HEV Applications Leon M. Tolbert1,2 , John

Tolbert, Leon M.

11

Low Switching Frequency Active Harmonic Elimination in Multilevel Converters with Unequal DC Voltages  

E-print Network

method for the cascaded H-bridges multilevel converter when supplied by unequal DC sources. FirstLow Switching Frequency Active Harmonic Elimination in Multilevel Converters with Unequal DC, the multilevel converter is decoupled into individual unipolar converters, and the low order harmonics (such

Tolbert, Leon M.

12

Reactive Compensation and Harmonic Suppression for Industrial Power Systems Using Thyristor Converters  

Microsoft Academic Search

This paper discusses the problems and solutions of applying reactive compensation, either static or dynamic, to industrial power systems supplying large blocks of dc power from diode or thyristor converters. The resonance between power capacitors and system reactance can produce high harmonic voltages caused by the harmonic currents generated by converters. The interaction between these harmonic voltages and regulating systems

D. E. Steeper; R. P. Stratford

1976-01-01

13

Low switching frequency active harmonic elimination in multilevel converters with unequal DC voltages  

Microsoft Academic Search

This paper presents an active harmonic elimination modulation control method for the cascaded H-bridges multilevel converter when supplied by unequal DC sources. First, the multilevel converter is decoupled into individual unipolar converters, and the low order harmonics (such as the 5th, 7th, 11th, and 13th) are eliminated by using resultant theory while at the same time the minimum specified harmonic

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

2005-01-01

14

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

E-print Network

was implemented with an 11-level H-bridge multilevel converter and an 8µs control resolution to demonstrateModulation Extension Control for Multilevel Converters Using Triplen Harmonic Injection with Low@utk.edu Abstract--This paper presents a modulation extension control method for multilevel converters with low

Tolbert, Leon M.

15

Balancing and harmonic analysis of flying capacitor multilevel converters  

Microsoft Academic Search

To supply medium-voltage AC machines, DC-AC converters working with a high bus voltage are required. By using multilevel converters, these high voltages can be supplied without the need for switches with a high voltage rating. Moreover, the output voltage waveform can be improved considerably. The flying capacitor multilevel converter is a recently developed converter topology assuring a flexible control and

Steven Thielemans; Thomas Vyncke; Jan Melkebeek

2008-01-01

16

Modulation extension control for multilevel converters using triplen harmonic injection with low switching frequency  

Microsoft Academic Search

This paper presents a modulation extension control method for multilevel converters with low switching frequency. The disadvantage of the fundamental frequency switching control method for multilevel converters is its narrow range of modulation indices where solutions exist. To address this problem, a triplen harmonic compensation method is proposed. First, the resultant method and\\/or Newton climbing method are used to find

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

2005-01-01

17

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

E-print Network

multilevel inverter consists of a series of H- bridge (single-phase full-bridge) inverter units. The genElimination of Harmonics in a Multilevel Converter using the Theory of Symmetric Polynomials to compute the switch- ing angles in a multilevel converter so as to produce the required fundamental voltage

Tolbert, Leon M.

18

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

E-print Network

. Cascaded H-bridges A cascade multilevel inverter consists of a series of H- bridge (single-phase full-bridgeA New Approach to Solving the Harmonic Elimination Equations for a Multilevel Converter John N is presented to compute the switch- ing angles in a multilevel converter so as to produce the required

Tolbert, Leon M.

19

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

E-print Network

], the approach here produces all possible solutions. II. Cascaded H-bridges The cascade multilevel inverter1 Harmonic Elimination in Multilevel Converters John Chiasson, Leon Tolbert, Keith Mc in a multilevel converter so as to produce the re- quired fundamental voltage while at the same time not gen

Tolbert, Leon M.

20

Fabrications of liquid-crystal polarization converters and their applications  

Microsoft Academic Search

This study presents a simple but accurate method for measuring the helical twisting power of chiral doped liquid crystals using axially symmetrical photo-alignment in azo dye-doped liquid crystal films. As reported in our previous paper1, the discontinuous twisting effect produces a disclination line in photo-aligned axially symmetrical liquid crystal films, which can be applied for use as a polarization converter.

Shih-Wei Ko; Shu-Hao Huang; Andy Y.-G. Fuh; Tsung-Hsien Lin

2009-01-01

21

Gamma-telescope with crystal converter.  

NASA Astrophysics Data System (ADS)

Two gamma-telescope constructions with high angular resolution are described. They are based on the orientational effect of electromagnetic shower development in a crystal. Some features of the telescope operation under realistic conditions are considered.

Baskov, V. A.; Kim, V. V.; Luchkov, B. I.; Sergienko, V. I.; Tugaenko, V. Yu.; Khablo, V. A.

1996-12-01

22

An autonomous harmonic filtering strategy for distributed energy resources converters in microgrid  

Microsoft Academic Search

Distributed generation based on emerging energy technologies has become an attractive alternative to the conventional centralized power stations, and has drawn much interest due to the increasing demand of premium electric power. The microgrid is a great example of integrating distributed energy resources through power electronics interface converters for grid-connected or islanding operation. This paper presents a cooperative harmonic filtering

Tzung-Lin Lee; Chia-Tse Lee; Po-Tai Cheng

2009-01-01

23

A metallic photonic crystal high power microwave mode converter  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

24

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

DOEpatents

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

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

2008-12-16

25

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

26

Quartz crystal microbalance based on passive frequency to voltage converter  

SciTech Connect

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

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

2012-02-15

27

Liquid Crystal Polarization Converters Using Circular-Buffed Polystyrene Film  

Microsoft Academic Search

Polystyrene is well known to align liquid crystal (LC) perpendicular to the rubbing direction. Based on this unique feature, we prepared two cells with special LC alignments using circular-buffed polystyrene as the alignment layer. For the cell with hybrid-radial LC alignment, it can convert a linear polarization light to axial polarization light; for the cell with twisted-radial LC alignment, it

Miao Xu; Changwoon Nah; Myong-Hoon Lee; Hongwen Ren

2011-01-01

28

Abstract--This paper presents the harmonic analysis of offshore wind farm (OWF) models with full converters  

E-print Network

Abstract--This paper presents the harmonic analysis of offshore wind farm (OWF) models with full will be discussed based on measurements from offshore wind farm. Index Terms--full-rating converters, harmonic analysis, offshore wind farm, wind turbine, validation with measurements I. INTRODUCTION HE tendency

Bak, Claus Leth

29

Heat transport and current fluctuations in harmonic crystals  

NASA Astrophysics Data System (ADS)

The approach of studying heat conduction in harmonic crystals, using generalized Langevin equations and phonon Green's functions, is explained in this review. We present the detailed derivation of the Landauer formula for phonon heat transfer using this approach. Some applications of the Landauer formula to understanding heat conduction in one-dimensional ordered and mass-disordered harmonic chains are given. It is explained how different boundary conditions lead to completely different system-size dependence of the average current in disordered chains. Finally we discuss the fluctuations in the total heat transferred in a fixed large interval of time and show how the Langevin approach is also useful in computing properties of these fluctuations in a harmonic system. In particular we derive the general formula for the cumulant generating function of these fluctuations.

Dhar, Abhishek; Dandekar, Rahul

2015-01-01

30

Experimental measurement of non-characteristic harmonic power generated by thyristor pulse-controlled AC\\/DC three phase converters  

Microsoft Academic Search

This paper presents an experimental investigation to measure the noncharacteristic harmonic power caused by network asymmetries in the AC source feeding thyristor-controlled AC\\/DC three-phase power converters. The experimental measurements were made in an AC\\/DC\\/AC transmission link physical model. Two three-phase power converters linked by a lumped parameters transmission line operate in rectifying and inverting modes, respectively. The converter acting in

Alfriedo Nava Segura; P. B. Sanchez

1996-01-01

31

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

E-print Network

A cascade multilevel inverter consists of a series of H-bridge (sin- gle-phase full-bridge) inverter unitsThe Use of Power Sums to Solve the Harmonic Elimination Equations for Multilevel Converters EPE an 11-level inverter. A preliminary version of this work was presented in [17]. Cascaded H-bridges

Tolbert, Leon M.

32

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

E-print Network

of Harmonics in a Multilevel Converter With Nonequal DC Sources Leon M. Tolbert, Senior Member, IEEE, John N Abstract--Eliminating harmonics in a multilevel converter in which the separate dc sources vary. Work was re- ported in [1] and [2] that presented a method to compute the switching angles for the H-bridges

Tolbert, Leon M.

33

Second-Harmonic Generation from an Interfacial Layer between Orientation Films and Liquid Crystal Layers of Nematic Liquid Crystal Cell  

Microsoft Academic Search

A second-harmonic generation (SHG) has been observed in a nematic liquid crystal cell containing highly polarized liquid crystal and orientation films with high polarization. No SHG is observed when a nonpolar liquid crystal is used regardless of the polarities of the orientation films used. The observed SHG is thought to originate from the ferroelectriclike layer, which comprises decomposed polar liquid

Akihiro Mochizuki; Wataru Sotoyama; Satoshi Tatsuura; Takeshi Ishitsuka; Katsusada Motoyoshi; Shunsuke Kobayashi

1991-01-01

34

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

Microsoft Academic Search

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

FANG-ZHANG PENG; HIROFUMI AKAGI; AKIRA NABAE

1990-01-01

35

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

36

Optical properties of liquid crystal polarization converting devices and their application to optical wavelet transforms  

Microsoft Academic Search

The optical properties of the liquid crystal (LC) polarization-converting device, which can convert a uniformly-distributed polarization state to a radially- distributed one (a radially polarized light), are measured. The availability of such the unique device for optical wavelet transforms is discussed experimentally and theoretically. It is found from the observation of Fourier images that the radially polarized light can be

Michinori Honma; Toshiaki Nose; Susumu Sato

1999-01-01

37

Giant enhancement of second harmonic generation in one-dimensional defective nonlinear photonic crystals  

NASA Astrophysics Data System (ADS)

In this paper, the second harmonic generations in finite size one-dimensional defective nonlinear photonic crystals have been investigated. To calculate the conversion efficiency, fundamental and second harmonic wave propagation among four proposed structures, we use the transfer matrix method. In the designed defective nonlinear photonic crystal structures, the linear and nonlinear optical parameters are both periodically modulated and thus the second harmonic generation efficiency can be several orders of magnitude larger than in a conventional quasi-phase-matched nonlinear structure with the same sample length.

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

2014-12-01

38

Polarization-Independent Optical Properties of Liquid Crystal Polarization-Converting Devices  

Microsoft Academic Search

The transmitted light intensity of liquid crystal (LC) polarization-converting devices is measured in detail and found to be independent of the polarization state of the incident light and the rotation angle of the analyzer thetaA. The focusing properties of the light transmitted through two types of LC polarization-converting devices (±90\\\\circ and ±180\\\\circ twist modes) and the fiber coupling properties are

Michinori Honma; Susumu Sato

2000-01-01

39

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

Microsoft Academic Search

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

Hossein Sepahvand; Mostafa Khazarei; Mehdi Ferdowsi; Keith Corzine

2010-01-01

40

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

41

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

42

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

43

Higher harmonics of converter currents in energy conversion system of small water plants  

Microsoft Academic Search

Energy in small water plants is produced by PM synchronous generators which quite often work at variable rotation speed. This energy has to be converted by means of a power electronic unit to fit to the three-phase power grid parameters (3 x 400 V, 50 Hz). The main purpose of the control strategy is to transfer maximum possible amount of

Tadeusz Sobczyk; Witold Mazgaj; Zbigniew Szular; Tomasz Wegiel

2011-01-01

44

A four legs matrix converter based ground power unit with selective harmonic control  

Microsoft Academic Search

In this paper a three phase four leg matrix converter is proposed to implement a 400Hz Aircraft Ground Power Supply unit. A parallel structure resonant controller is used to regulate the power supply output voltage providing very good tracking of the output voltage reference even in the presence of a non linear load. Simulations results and experimental validation from a

Wesam M. Rohouma; Lee Empringham; Pericle Zanchetta; Patrick W Wheeler

2011-01-01

45

Feature extraction properties in optical wavelet transforms using liquid crystal polarization-converting devices  

Microsoft Academic Search

Liquid crystal (LC) molecular orientations and optical properties of LC polarization-converting devices are discussed. It is found that two stable LC molecular orientation states appear (we define them at the +\\/- 90 degree(s) and +\\/- 180 degree(s) twist modes), and the switching method between the two modes are discussed. Fourier transforms (FT) of the transmitted light of the LC polarization-

Michinori Honma; Toshiaki Nose; Susumu Sato

2001-01-01

46

Third-harmonic pulse generation in one-dimensional photonic crystal structures  

NASA Astrophysics Data System (ADS)

Enhanced third-harmonic generation in a one-dimensional photonic crystal doped with third-order nonlinear medium was numerically investigated using the multiple-scale method and the split-step Fourier transform. The optimal fundamental frequency for third-harmonic wave generation was determined from the transmission spectrum. The third-harmonic pulse intensities grow, depending on the structure thickness and the fundamental-frequency detuning parameter, which determines the band-edge phase matching condition. Furthermore, the total energy output of third-harmonic pulses, depending on the fundamental-frequency pulse width, may be more than 1000 times the energy produced by a phase-matched bulk medium. A narrow pulse with bandwidth less than the band-edge transmission peak enables high conversion efficiency. The maximum conversion efficiency of the forward component may be 12 to 13 orders of magnitude greater than that of the backward component.

Wicharn, Surawut; Buranasiri, Prathan

2014-01-01

47

Some Newly Developed Crystals for Measurement of Ultrafast Laser Pulses by Second Harmonic Generation  

NASA Astrophysics Data System (ADS)

Second harmonic generation in nonlinear optical crystal is a well-established technique for the characterization of ultrafast laser pulses. However, only selected nonlinear crystalline materials can be used due to their limitations in transparency cut-off and limited phase-matching range. It is observed that some newly discovered crystals, such as CLBO, KABO, LB4, and KBBF, have suitable characteristics for use in ultrafast nonlinear optical applications. We have calculated several linear and nonlinear optical parameters including phase-matching angle, angular and spectral acceptance bandwidths, walk-off angle, nonlinear coupling coefficient, and group-velocity mismatch for the generation of vacuum ultraviolet laser radiation in these crystals by type-I and type-II second harmonic generation techniques.

Kumbhakar, Pathik; Chatterjee, Sunanda; Kobayashi, Takayoshi

48

A High-Speed Measurement Method for Reflective Liquid Crystal Cells Using a Liquid Crystal Polarization-Converting Device  

Microsoft Academic Search

We propose a novel measurement method for determining cell parameters, such as a cell thickness and twist angle in reflective liquid crystal (LC) cells, by using a unique polarization-converting device prepared with a circularly and homogeneously aligned LC (CH-LC) cell. The light intensity distributions from the reflective LC cell transmitted twice through the CH-LC cell are measured by a charge-coupled

Marenori Kawamura; Susumu Sato

2007-01-01

49

CsLiB6O10 crystal: forth and fifth-harmonic generation in Nd:YAP laser  

NASA Astrophysics Data System (ADS)

An area of CsLiB6O10 (CLBO) phase equilibrium in the (Cs2O-Li2O) -- B2O3 -- MoO3 system was determined with spontaneous crystallization method. Crystals of 75 X 60 X 40 mm3 size have been growth in [100] direction with Kiropulos method. The forth-harmonic generation (270 nm) was achieved through the doubling of second-harmonic frequency in a multi-mode Nd:YAP laser in the type 1 collinear phase-matched geometry. The second-harmonic radiation in the technological laser of 3 mrad divergence was focused onto the input face of the crystal by a long-focus quartz lens. The input power density of the second harmonic was 300 MW/cm2. Using a 11.5 mm crystal, we showed that the highest efficiency of the forth-harmonic generation is 30%. The fifth harmonic (216 nm) in CLBO crystal was generated by composing the main laser beam and the forth-harmonic beam under the type 1 collinear phase-matching. Both beams were converged with dichroic and turning mirrors and then focused by a long-focus quartz lens. Our experiments showed that the fifth-harmonic generation in a multi-mode technological laser of 3 mrad divergence is possible in a 10 mm CLBO crystal of 23% optical conversion efficiency. The input power density of the forth harmonic was 100 MW/cm2. The use of longer CLBO crystal is less effective due to the nonlinear UV absorption and the walk off between the pump beam (1079 nm) and the harmonic beam.

Kokh, Alexandr E.; Kononova, Nadegda G.; Lisova, Irina A.; Muraviov, Sergey V.

2001-05-01

50

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

SciTech Connect

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

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

2007-07-15

51

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

PubMed

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?µm 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. PMID:23633594

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

2013-05-01

52

Three-dimensional electric field visualization utilizing electric-field-induced second-harmonic generation in nematic liquid crystals  

Microsoft Academic Search

An electric-field-induced second-harmonic-generation signal in a nematic liquid crystal is used to map the electric field in an integrated-circuit-like sample. Since the electric-field-induced second-harmonic-generation signal intensity exhibits a strong dependence on the polarization of the incident laser beam, both the amplitude and the orientation of the electric field vectors can be measured. Combined with scanning second-harmonic-generation microscopy, three-dimensional electric field

I.-Hsiu Chen; Shi-Wei Chu; Francois Bresson; Ming-Chun Tien; Jin-Wei Shi; Chi-Kuang Sun

2003-01-01

53

Mid-infrared second-harmonic generation in chalcogenide photonic crystal fiber  

NASA Astrophysics Data System (ADS)

This study theoretically investigated a feasible modal phase-matching second-harmonic generation (SHG) in chalcogenide photonic crystal fiber. SHG is a technique that enables the acquisition of the mid-infrared resource at 5.3 ?m with the use of a 10.6 ?m commercial laser. The phase-matching condition between two low-order modes can be realized simply by modifying the air hole size and lattice pitch in the designed photonic crystal fiber. Numerical results showed that the confinement loss of the second-harmonic wave was 4.15×10-4 dB/m at 5.3 ?m, and the effective phase-matched fiber length reached as long as 6.382 m.

Cao, Fengzhen; Zhang, Peiqing; Dai, Shixun; Wang, Xunsi; Xu, Tiefeng; Nie, Qiuhua

2015-01-01

54

Crystal lattice determination of ZnSe nanowires with polarization-dependent second harmonic generation microscopy  

NASA Astrophysics Data System (ADS)

We demonstrate a noninvasive optical microscopy technique based on polarization-dependent second harmonic generation for determining the crystal lattice structure and microscopic heterogeneities within individual nanostructures. Differentiation between periodically twinned and wurtzite ZnSe nanowires (NWs) was demonstrated, and measurement of the cubic lattice rotation orientation around the NW axis was determined within 1° accuracy. Zinc blende NWs were differentiated from wurtzite. The technique can be used for quality inspection and optimization of growth conditions for nanostructures.

Cisek, Richard; Tokarz, Danielle; Hirmiz, Nehad; Saxena, Ankur; Shik, Alexander; Ruda, Harry E.; Barzda, Virginijus

2014-12-01

55

“Triggering” effect of second harmonic generation in centrosymmetric ?-BaB 2O 4 crystals  

Microsoft Academic Search

We have discovered an occurrence of optical second harmonic generation at 1064nm fundamental wavelength for the ?-BaB2O4 (ABO) crystal illuminated by 7ns nanosecond nitrogen laser of 337nm. The effect is observed only during illumination and achieves the maximum SHG output after 15–20min of treatment. After switching off of the UV laser treatment the SHG decreases during about 5min. The maximum

V. T. Adamiv; J. Ebothe; M. Piasecki; Ya. V. Burak; I. M. Teslyuk; K. J. Plucinski; Ali H. Reshak; I. V. Kityk

2009-01-01

56

Crystal lattice determination of ZnSe nanowires with polarization-dependent second harmonic generation microscopy.  

PubMed

We demonstrate a noninvasive optical microscopy technique based on polarization-dependent second harmonic generation for determining the crystal lattice structure and microscopic heterogeneities within individual nanostructures. Differentiation between periodically twinned and wurtzite ZnSe nanowires (NWs) was demonstrated, and measurement of the cubic lattice rotation orientation around the NW axis was determined within 1° accuracy. Zinc blende NWs were differentiated from wurtzite. The technique can be used for quality inspection and optimization of growth conditions for nanostructures. PMID:25431947

Cisek, Richard; Tokarz, Danielle; Hirmiz, Nehad; Saxena, Ankur; Shik, Alexander; Ruda, Harry E; Barzda, Virginijus

2014-12-19

57

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

PubMed

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

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

2011-05-15

58

Cherenkov second-harmonic Talbot effect in one-dimension nonlinear photonic crystal.  

PubMed

We demonstrate a new method to generate second-harmonic Talbot effect through degenerate Cherenkov radiation in one-dimension anomalous-dispersion-like nonlinear photonic crystals. In anomalous-dispersion-like medium, the degenerated nonlinear Cherenkov radiation can be achieved and is parallel to domain walls, of which the intensity is adjusted by the second-order nonlinear coefficient. In this system the one-dimension nonlinear photonic crystal can be regarded as a nonlinear grating, which is necessary for nonlinear Talbot effect. This is a new method to generate enhanced nonlinear Talbot effect in addition to the quasi-phase-matching technique reported previously. PMID:25361110

Zhao, Xiaohui; Zheng, Yuanlin; Ren, Huaijin; An, Ning; Chen, Xianfeng

2014-10-15

59

Electric field-induced optical second harmonic generation in nematic liquid crystal 5CB  

NASA Astrophysics Data System (ADS)

Electric field-induced second harmonic generation (EFISH) was studied for the liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) (a nematic phase material at room temperature). The intensity of coherent SHG from 5CB cells upon DC electric field was measured for various initial orientations of the liquid crystal. The dependence of the SHG intensity on the pump beam incidence angle was obtained in transmission geometry using sample rotation method. The experimental results (the registered light intensity in the output SHG interference patterns) were theoretically modelled and analyzed.

Torgova, S. I.; Shigorin, V. D.; Maslyanitsyn, I. A.; Todorova, L.; Marinov, Y. G.; Hadjichristov, G. B.; Petrov, A. G.

2014-12-01

60

Ethylenediaminium di(2-nitrophenolate) single crystals as materials for optical second harmonic generation  

NASA Astrophysics Data System (ADS)

An organic second harmonic generation (SHG) active material, ethylenediaminium di(2-nitrophenolate) (EDA2NP) was synthesized through proton transfer reaction. Good quality single crystals of dimension 6×4×2 mm3 were grown by solvent evaporation method using ethanol as a solvent for the first time in literature. The lattice parameters of the grown crystals were determined by X-ray diffraction studies. Fourier Transform Infra Red (FT-IR) spectrum was recorded to identify the presence of various functional groups and the molecular structure was confirmed by nuclear magnetic resonance (NMR) spectrum. Thermal analyses of the grown crystal were carried out using thermo gravimetric-differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC) curves. Optical (UV-vis-NIR) analysis shows that the grown crystals were found to be transparent (450-2500 nm) in the entire visible region. The existence of second harmonic generation signals was observed by using Nd:YAG laser with fundamental wavelength of 1064 nm.

Thangaraj, M.; Ravi, G.; Sabari Girisun, T. C.

2014-09-01

61

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

62

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

63

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

SciTech Connect

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

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

2012-03-31

64

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

65

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

66

Calculation of optical second-harmonic susceptibilities and optical activity for crystals  

SciTech Connect

A new generation of nearly first-principles calculations predicts both the linear and second-harmonic susceptibilities for a variety of insulating crystals, including GaAs, GaP, AlAs, AlP, Se, {alpha}-quartz, and c-urea. The results are typically in agreement with experimental measurements. The calculations have been extended to optical activity, with somewhat less success to date. The theory, based on a simple self-energy correction to the local density approximation, and results are reviewed herein.

Levine, Z.H. [Ohio State Univ., Columbus, OH (United States)

1994-12-31

67

Multi-direction high-efficiency second harmonic generation in ellipse structure nonlinear photonic crystals  

NASA Astrophysics Data System (ADS)

We have designed and fabricated a lithium niobate (LN) nonlinear photonic crystal (NPC) with a two-dimensional (2D) ellipse structure of inverse poling domains. The structure can offer continuously varying reciprocal lattice vectors in different directions to compensate the phase-mismatching during the second harmonic generation (SHG) for diverse pump wavelengths. We consider three propagation directions with large effective nonlinear susceptibility and measure the nonlinear conversion efficiency of SHG. The experimental data are in good agreement with the quantitative calculation results using the effective susceptibility model with pump depletion. With high-efficiency SHG in multiple propagation direction, the 2D ellipse structure of LN NPC has the potential to realize various broadband nonlinear frequency conversion processes in different propagation direction with a single crystal.

Chen, Bao-Qin; Zhang, Chao; Liu, Rong-Juan; Li, Zhi-Yuan

2014-10-01

68

Deglycosylation, processing and crystallization of human testis angiotensin-converting enzyme.  

PubMed Central

Angiotensin I-converting enzyme (ACE) is a highly glycosylated type I integral membrane protein. A series of underglycosylated testicular ACE (tACE) glycoforms, lacking between one and five N-linked glycosylation sites, were used to assess the role of glycosylation in tACE processing, crystallization and enzyme activity. Whereas underglycosylated glycoforms showed differences in expression and processing, their kinetic parameters were similar to that of native tACE. N-glycosylation of Asn-72 or Asn-109 was necessary and sufficient for the production of enzymically active tACE but glycosylation of Asn-90 alone resulted in rapid intracellular degradation. All mutants showed similar levels of phorbol ester stimulation and were solubilized at the same juxtamembrane cleavage site as the native enzyme. Two mutants, tACEDelta36-g1234 and -g13, were successfully crystallized, diffracting to 2.8 and 3.0 A resolution respectively. Furthermore, a truncated, soluble tACE (tACEDelta36NJ), expressed in the presence of the glucosidase-I inhibitor N -butyldeoxynojirimycin, retained the activity of the native enzyme and yielded crystals belonging to the orthorhombic P2(1)2(1)2(1) space group (cell dimensions, a=56.47 A, b=84.90 A, c=133.99 A, alpha=90 degrees, beta=90 degrees and gamma=90 degrees ). These crystals diffracted to 2.0 A resolution. Thus underglycosylated human tACE mutants, lacking O-linked oligosaccharides and most N-linked oligosaccharides or with only simple N-linked oligosaccharides attached throughout the molecule, are suitable for X-ray diffraction studies. PMID:12542396

Gordon, Kerry; Redelinghuys, Pierre; Schwager, Sylva L U; Ehlers, Mario R W; Papageorgiou, Anastassios C; Natesh, Ramanathan; Acharya, K Ravi; Sturrock, Edward D

2003-01-01

69

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

70

Electrooptic switch for unpolarized radiation in a laser with intracavity second harmonic generation in crystals exhibiting the aperture effect  

SciTech Connect

The average output power of the second harmonic can be increased and the construction of a laser can be simplified by using a nonlinear crystal not only for second harmonic generation, but also as an electrooptic switch for the separation of rays with different polarizations at the fundamental frequency. By way of example, the results are given of a continuously pumped YAG laser in which a switch for unpolarized radiation is in the form of a Pockels cell and a nonlinear lithium iodate crystal cut at an angle of 29/sup 0/ to the optic axis. It was found that such a laser configuration could ensure 77% conversion of the fundamental frequency radiation to the second harmonic at the wavelength of 0.53 ..mu.. and with an average power of 2.4 W.

Andreyanov, Y.P.; Minaev, V.P.; Semenov, A.V.

1983-10-01

71

Liquid crystal polarization-converting devices for edge and corner extractions of images using optical wavelet transforms  

Microsoft Academic Search

Optical properties of radially polarized light generated by liquid crystal (LC) polarization-converting devices with two LC molecular orientations (±180° and ±90° twist modes) are measured and the applicability to optical wavelet transforms (WTs) are discussed. It is found that the radially polarized lights in both the ±180° and ±90° twist modes can be regarded as wavelets. Based on the principle

Michinori Honma; Toshiaki Nose; Susumu Sato

2006-01-01

72

Photonic band structure in one-dimensional nonlinear crystal: Analysis of harmonic stability  

NASA Astrophysics Data System (ADS)

We consider a one-dimensional nonlinear photonic crystal consisting of an infinite set of concentrated equidistant scatterers inserted in a linear dielectric medium. Each of the scatterers is made by a very thin layer of a nonlinear medium with high refractive index that we model by a delta function. We show that the nonlinear optical exact solutions of this system form an intensity dependent band structure. To analyze the stability of these solutions we consider a modulation harmonic perturbation of these solutions whose amplitudes are slightly above the instability threshold. We demonstrate that the nonlinearity gives rise to an oscillatory instability of the solutions, which is a localized version of the well-known modulational instability of the nonlinear Schrodinger equation. We show that the linear harmonic perturbation forms as well a band structure whose allowed bands coincide for some intervals with those of the nonlinear band structure of the solutions for which case the structures are unstable whereas in the region where both the linear and nonlinear bands do not coincide, the nonlinear waves are indeed stable so that they conform spatial solitons.

Avendaño, Carlos G.; Reyes, J. Adrián

2015-01-01

73

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

PubMed

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

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

2014-08-25

74

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

75

Improved frequency/voltage converters for fast quartz crystal microbalance applications  

SciTech Connect

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

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

2008-04-15

76

Organic salts of biguanide - An attempt to crystal engineering of novel materials for second harmonic generation  

NASA Astrophysics Data System (ADS)

Three organic salts of biguanide with oxalic, succinic and L-tartaric acids have been prepared and X-ray structural analysis has been performed. Biguanidium(1+) oxalate hemihydrate ( a = 6.8330(2) Å, b = 10.0430(2) Å, c = 14.6230(4) Å, ? = 90.236(1) , ? = 90.333(1) , ? = 105.605(2) , V = 966.46(4) Å 3, Z = 1, R = 0.0393 for 3704 observed reflections) and biguanidium(1+) hydrogen succinate ( a = 6.4600(1) Å, b = 6.7670(2) Å, c = 11.4150(3) Å, ? = 91.822(1) , ? = 105.312(1) , ? = 90.922(1) , V = 480.89(2) Å 3, Z = 2, R = 0.0357 for 1880 observed reflections) belong to the triclinic space group P 1¯. Their crystal structures are based on biguanidium(1+) pairs connected by intermolecular N-H⋯N hydrogen bonds. The remaining ions (eventually water molecules) form a 3D structural network with these pairs. Furthermore, the formation of the cationic and anionic layers interconnected by intermolecular N-H⋯O hydrogen bonds was observed in the crystal structure of biguanidium(1+) hydrogen succinate. Biguanidium(2+) L-tartrate crystallizes in the orthorhombic space group P 2 12 12 1 ( a = 6.7170(2) Å, b = 9.2740(2) Å, c = 16.1500(4) Å, V = 1006.04(4) Å 3, Z = 4, R = 0.0432 for 2193 observed reflections). The crystal structure is based on L-tartrate chains, which are interconnected by isolated biguanidium(2+) cations via several types of N-H⋯O hydrogen bonds. The formation of L-tartrate chains is mediated by two types of intermolecular O-H⋯O hydrogen bonds connecting the hydroxyl and carboxylate groups. The FTIR and FT Raman spectra of all the compounds were recorded and discussed. The theoretical values of the first hyperpolarizability components were calculated for biguanidium(1+) and biguanidium(2+) cations at the B3LYP level with the 6-311G(d,p) basis set. Quantitative measurements of the second harmonic generation of powdered biguanidium(2+) L-tartrate at 800 nm were performed and a relative efficiency of 2% (compared to KDP) was observed. The thermal behaviour of all the prepared compounds was studied by the DSC method in the temperature interval from 90 K up to a temperature close to the melting points of the crystals. The FTIR and FT Raman spectra of biguanidium(2+) L-tartrate were investigated down to 130 K.

Matulková, Irena; N?mec, Ivan; Císa?ová, Ivana; N?mec, Petr; Van?k, P?emysl

2010-03-01

77

Cost effective PWM soft switching high voltage converter with utility AC side harmonic current reduction strategy for microwave oven  

Microsoft Academic Search

This paper presents a new topology of the voltage clamped ZVS-PWM high-frequency inverter-fed DC-DC converter designed for a consumer microwave oven to improve line current distortion and power factor in utility AC power side. Its operation principle in steady state is described. The pulse modulation pattern control implementation is discussed under a condition of allowable magnetron current 1.2 A and

T. Matsushige; S. Chandhaket; S. Moisseev; E. Hiraki; M. Nakaoka; H. Terai; D. Bessyo; K. Yasui; H. Omori

2000-01-01

78

Wide Color Gamut Backlight for Liquid Crystal Displays Using Three-Band Phosphor-Converted White Light-Emitting Diodes  

Microsoft Academic Search

This work reports a wide color gamut backlight for liquid crystal display (LCD) utilizing a three-band white light-emitting diodes (LED). The LED backlight was fabricated by combining a blue LED chip with beta-sialon:Eu (green) and CaAlSiN3:Eu (red) phosphors. This 2-phosphor-converted white LED shows a discrete spectrum with distinct separation of red, green, and blue primary colors due to a narrow

Rong-Jun Xie; Naoto Hirosaki; Takashi Takeda

2009-01-01

79

Optical second-harmonic generation from two-dimensional hexagonal crystals with broken space inversion symmetry  

NASA Astrophysics Data System (ADS)

We propose a microscopic theory of the optical second-harmonic generation (SHG) from ? electrons in two-dimensional (2D) honeycomb lattice structures with broken space inversion symmetry, such as graphene epitaxially grown on a SiC substrate and boronitrene (a single sheet of hexagonal boron nitride (h-BN)). The approach developed is based on a simple two-band ?-electron tight-binding model combined with the original Genkin-Mednis formalism of the second-order nonlinear optical response theory, detailed in our recent paper (2010 Phys. Rev. B 82 235426). Within the framework of the approach, we derive an explicit expression for the SHG susceptibility {\\chi }_{{SHG}}^{(2)}(\\omega ), which involves two distinct contributions originating from a mixture of interband and intraband motion of ? electrons. Both the contributions, and, hence, the {\\chi }_{{SHG}}^{(2)}(\\omega ) on the whole, are found to tend to zero when the ?-electron energy bands involved are treated at the simplest level of approximation, neglecting the effect of their trigonal warping around the corners of the Brillouin zone of the 2D hexagonal lattice. Through numerical calculations, it is shown that this effect, though rather small, leads to a fairly large magnitude of the SHG susceptibility, reaching the order of 10-4 esu for the graphene/SiC overlayer system and 10-7 esu for monolayer h-BN, when the pump photon energy ?? approaches half the bandgap energy Eg of those structures. These theoretical findings suggest that SHG can be used as a sensitive optical probe of the electronic structure of the examined 2D hexagonal crystals and simultaneously demonstrate that those crystals may be an appropriate material for practical uses in future optoelectronic nano-devices.

Margulis, Vl A.; Muryumin, E. E.; Gaiduk, E. A.

2013-05-01

80

Backward emission angle of microscopic second-harmonic generation from crystallized type I collagen fiber  

NASA Astrophysics Data System (ADS)

A theoretical model that deals with SHG from crystallized type I collagen fiber formed by a bundle of fibrils is established. By introducing a density distribution function of dipoles within fibrils assembly into the dipole theory and combining with structural order (m,l) parameters revealed by quasi-phase-matching (QPM) theory, our established theoretical model comprehensively characterizes both biophysical features of collagen dipoles and the crystalline characteristics of collagen fiber. This new model quantitatively reveals the 3-D distribution of second-harmonic generation (SHG) emission angle (?,J) in accordance with the emission power. Results show that fibrils diameter d1 and structural order m, which describes the structural characteristics of collagen fiber along the incident light propagation direction has significant influence on backward/forward SHG emission. The decrease of fibrils diameter d1 induces an increase of the peak SHG emission angle ?max. As d1 decreases to a threshold value, in our case it is around d1 = 150 nm when (m,l) = (1,0), ?max > 90 deg, indicating that backward SHG emission appears. The SHG may have two symmetrical emission distribution lobes or may have only one or two unsymmetrical emission lobes with unequal emission power, depending on the functional area of (m,l) on d1.

Tian, Long; Wei, Huajiang; Jin, Ying; Liu, Hanping; Guo, Zhouyi; Deng, Xiaoyuan

2011-07-01

81

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

PubMed

In this paper, we report the successful growth of pure, Cu(2+) ions and Cd(2+) ions doped on ninhydrin single crystals by slow solvent evaporation technique. The presence of Cu(2+) and Cd(2+) ions in the specimen of ninhydrin single crystal has been determined by atomic absorption spectroscopy. The powder X-ray diffraction analysis was done to calculate the lattice parameters of the pure and doped crystals. The percentage of transmittance of the crystal was recorded using the UV-Vis Spectrophotometer. Thermal behaviors of the grown crystals have been examined by the thermal gravimetric/differential thermal analysis. The hardness of the grown crystals was assessed and the results show the minor variation in the hardness value for the pure and doped ninhydrin samples. The value of the work hardening coefficient n was found to be 2.0, 1.0 and 1.06 for pure, copper and cadmium doped ninhydrin crystals respectively. The second harmonic generation efficiency of Cd(2+) and Cu(2+) doped ninhydrin is 8.3 and 6.3 times greater than well known nonlinear crystal of potassium dihydrogen phosphate respectively. The antibacterial and antifungal activities of the title compound were performed by disk diffusion method against the standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillis niger and Aspergillus flavus. PMID:23266683

Prasanyaa, T; Jayaramakrishnan, V; Haris, M

2013-03-01

82

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. PMID:19547487

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

2010-01-01

83

Temperature dependences of the second-harmonic generation in LiKB 4 O 7 single crystals  

Microsoft Academic Search

We have discovered interesting temperature anomalies of the second-harmonic generation (SHG) in novel LiKB4O7 single crystals. We have found that the maximal SHG signal exists at a temperature equal to about 230–240 K. The maximally\\u000a achieved second-order susceptibility was equal to about 1.4 pm\\/V at a 1064-nm laser wavelength and was achieved at the sizes\\u000a of crystallites of less than

K. Nouneh; I. V. Kityk; K. Michalska-Malecka; K. Ozga; V. T. Adamiv; Ya. V. Burak; I. M. Teslyuk

2008-01-01

84

Restriction of the phase matching condition on refractive index modulation of 1D photonic crystals in second harmonic generation  

NASA Astrophysics Data System (ADS)

Phase and group velocity matching equations of second harmonic generation are reconsidered for 1D photonic crystals to analyze an induced structure restriction. A multiplicity of solutions is found through a numerical computation, which separates the restricted structure parameters into infinite units. The local and global characteristics of the restriction on refractive indices and material lengths are discussed in detail as well. The analysis shows that increasing either the dispersion of the nonlinear material or the thickness of a single layer will require a larger refractive index contrast.

Wu, Huinan; Huang, Jinjer; Pu, Shaozhi; Zhang, Liuyang; Yang, Zhongying

2015-01-01

85

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

DOEpatents

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

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

1987-01-01

86

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

87

Strategy and tactics in the search for new harmonic generating crystals  

SciTech Connect

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

Velsko, S.P.

1990-09-01

88

Wide Color Gamut Backlight for Liquid Crystal Displays Using Three-Band Phosphor-Converted White Light-Emitting Diodes  

NASA Astrophysics Data System (ADS)

This work reports a wide color gamut backlight for liquid crystal display (LCD) utilizing a three-band white light-emitting diodes (LED). The LED backlight was fabricated by combining a blue LED chip with ?-sialon:Eu (green) and CaAlSiN3:Eu (red) phosphors. This 2-phosphor-converted white LED shows a discrete spectrum with distinct separation of red, green, and blue primary colors due to a narrow and asymmetric emission band of the green phosphor. By applying typical color filters of LCDs and color-matching functions, a wide color gamut of 91.9% of the National Television Standard Committee standard is attained, compared to 71.6% for the conventional two-band white LED.

Xie, Rong-Jun; Hirosaki, Naoto; Takeda, Takashi

2009-02-01

89

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

E-print Network

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

Chen, Zhongping

90

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

Microsoft Academic Search

High harmonic generation (HHG) of intense infrared laser radiation (Ferray et al., J. Phys. B: At. Mol. Opt. Phys. 21:L31,\\u000a 1988; McPherson et al., J. Opt. Soc. Am. B 4:595, 1987) enables coherent vacuum-UV (VUV) to soft-X-ray sources. In the usual setup, energetic femtosecond laser pulses are strongly\\u000a focused into a gas jet, restricting the interaction length to the Rayleigh

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

2009-01-01

91

Enhancement in second harmonic generation efficiency, laser damage threshold and optical transparency of Mn2+ doped L-alanine crystals: A correlation with crystalline perfection  

Microsoft Academic Search

Effect on crystalline perfection, second harmonic generation (SHG) efficiency, laser damage threshold (LDT) and optical transparency due to Mn2+ doping in L-alanine crystals has been investigated. The crystalline perfection of pure and doped crystals was evaluated by high-resolution X-ray diffractometry, which revealed the improvement in the crystalline perfection at low and moderate doping concentrations. At moderate and high concentrations, the

S. K. Kushwaha; S. P. Rathee; K. K. Maurya; G. Bhagavannarayana

2011-01-01

92

Enhancement in second harmonic generation efficiency, laser damage threshold and optical transparency of Mn 2+ doped L-alanine crystals: A correlation with crystalline perfection  

Microsoft Academic Search

Effect on crystalline perfection, second harmonic generation (SHG) efficiency, laser damage threshold (LDT) and optical transparency due to Mn2+ doping in L-alanine crystals has been investigated. The crystalline perfection of pure and doped crystals was evaluated by high-resolution X-ray diffractometry, which revealed the improvement in the crystalline perfection at low and moderate doping concentrations. At moderate and high concentrations, the

S. K. Kushwaha; S. P. Rathee; K. K. Maurya; G. Bhagavannarayana

2011-01-01

93

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

94

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

PubMed Central

Second Harmonic Generation (SHG) microscopy coupled with polarization analysis has great potential for use in tissue characterization, as molecular and supramolecular structural details can be extracted. Such measurements are difficult to perform quickly and accurately. Here we present a new method that uses a liquid crystal modulator (LCM) located in the infinity space of a SHG laser scanning microscope that allows the generation of any desired linear or circular polarization state. As the device contains no moving parts, polarization can be rotated accurately and faster than by manual or motorized control. The performance in terms of polarization purity was validated using Stokes vector polarimetry, and found to have minimal residual polarization ellipticity. SHG polarization imaging characteristics were validated against well-characterized specimens having cylindrical and/or linear symmetries. The LCM has a small footprint and can be implemented easily in any standard microscope and is cost effective relative to other technologies. PMID:24156059

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

2013-01-01

95

Two-photon-absorption of frequency converter crystals at 248 nm  

NASA Astrophysics Data System (ADS)

The two-photon-absorption coefficient of KDP, BBO, LTB, and CLBO crystals has been determined from the measurement of the intensity dependent transmission through long samples. The intensity of the sub-picosecond KrF excimer laser pulses on the samples was varied from 0.2-80 GW/cm2. The linear absorption of the samples was determined by using a low intensity, long pulse KrF laser. The first-principle simulations to the experimental data show a TPA value of 0.48 cm/GW for KDP, 0.5 cm/GW (o-ray) and 0.34 cm/GW (e-ray) in BBO, 0.22 cm/GW in LTB and 0.53 cm/GW in CLBO.

Divall, M.; Osvay, K.; Kurdi, G.; Divall, E. J.; Klebniczki, J.; Bohus, J.; Péter, Á.; Polgár, K.

2005-12-01

96

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

97

Non-equilibrium stationary state of a harmonic crystal with alternating masses  

E-print Network

We analyze the non-equilibrium steady states (NESS) of a one dimensional harmonic chain of $N$ atoms with alternating masses connected to heat reservoirs at unequal temperatures. We find that the temperature profile defined through the local kinetic energy $T(j) \\equiv {}/{m_j}$, oscillates with period two in the bulk of the system. Depending on boundary conditions, either the heavier or the lighter particles in the bulk are hotter. We obtain exact expressions for the bulk temperature profile and steady state current in the limit $N \\rightarrow \\infty$. These depend on whether $N$ is odd or even. We also study similar temperature oscillations in the NESS of systems with noise in the dynamics. These die out as $N \\rightarrow \\infty$.

Venkateshan Kannan; Abhishek Dhar; J. L. Lebowitz

2012-02-22

98

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

99

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

PubMed

Angiotensin converting enzyme (ACE) plays a pivotal role in blood pressure regulation, and its interaction with an ACE inhibitor (ACEI) is an important research topic for treatment of hypertension. Herein, a low reagent consumption, multiparameter and highly sensitive quartz crystal microbalance (QCM) at 35-MHz fundamental frequency was utilized to monitor in situ the binding process of solution lisinopril (LIS, a carboxylic third-generation ACEI) to ACE adsorbed at a 1-dodecanethiol (C12SH)-modified Au electrode. From the QCM data, the binding molar ratio (r) of LIS to adsorbed ACE was estimated to be 2.3:1, and the binding and dissociation rate constants (k(1) and k(-1)) and the binding equilibrium constant (K(a)) were estimated to be k(1)=4.1×10(6) L mol(-1) s(-1), k(-1)=7.3×10(-3) s(-1) and K(a)=5.62×10(8) L mol(-1), respectively. Comparable qualitative and quantitative results were also obtained from separate experiments of cyclic voltammetry, electrochemical impedance spectroscopy and surface plasmon resonance measurements. PMID:21255995

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

2011-03-15

100

Third harmonic generation in LiKB 4O 7 single crystal  

Microsoft Academic Search

The third order nonlinear optical properties of the lithium potassium borate (LiKB4O7) single crystal have been investigated by means of the rotational Maker fringe technique using Nd:YAG laser at 1064nm working in picosecond regime. The value of the third order nonlinear optical susceptibility was calculated using the theoretical model of Kajzar et al. and was found to be about 1.4×10?21m2V?2

B. Kulyk; V. Kapustianyk; Ya. Burak; V. Adamiv; B. Sahraoui

2010-01-01

101

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

102

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

PubMed

The ability to use coherent light for material science and applications is linked to our ability to measure short optical pulses. While free-space optical methods are well established, achieving this on a chip would offer the greatest benefit in footprint, performance and cost, and allow the integration with complementary signal-processing devices. A key goal is to achieve operation at sub-watt peak power levels and on sub-picosecond timescales. Previous integrated demonstrations require either a temporally synchronized reference pulse, an off-chip spectrometer or long tunable delay lines. Here we report a device capable of achieving single-shot time-domain measurements of near-infrared picosecond pulses based on an ultra-compact integrated CMOS-compatible device, which could operate without any external instrumentation. It relies on optical third-harmonic generation in a slow-light silicon waveguide. Our method can also serve as an in situ diagnostic tool to map, at visible wavelengths, the propagation dynamics of near-infrared pulses in photonic crystals. PMID:24496243

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

2014-01-01

103

Technique for locking a second-harmonic generation cavity with an electro-optic active nonlinear crystal  

SciTech Connect

A new technique for generating an error signal for locking a second-harmonic generation (SHG) enhancement cavity is presented. The calculations are developed within a linear system framework treated with a Laplace transform. The error-signal generation is based on FM sidebands, but it differs from the Pound--Drever--Hall technique by performing the modulation on the (assumed) electro-optic active nonlinear crystal in the cavity. This new technique for generating the error signal has some advantages over the former one in that (i) the shape of the error signal is independent of the relative phase of the rf signal between the photodiode and the local oscillator; (ii) it provides a handy, high-bandwidth actuator to improve the cavity lock, which can improve the average SHG power; and (iii) it decreases cost and complexity by not requiring an external electro-optical modulator. The specific case of SHG in KNbO{sub 3} is treated as an example of the feasibility of the technique. {copyright} 2001 Optical Society of America

Cesar, Claudio L.

2001-08-01

104

Fourth harmonic generation of a high-repetition rate Nd:YAG laser in CsLiB6O10 crystal  

Microsoft Academic Search

We have used as a fundamental source a diode-pumped high-repetition rate Nd:YAG laser (Spectra-Physics T40-X30-106Q) which has a pulse width of 25 ns at 4 kHz and a beam waist of 500 ?m nonlinear optical (NLO) crystal for second harmonic generation (SHG) was a noncritically phase-matched type-1 LiB3O5 (LBO) crystal with AR coating at 148°C and its length was 12

K. Murse; M. Yoshimura; T. Kamimura; K. Nakai; Y. Mori; T. Sasaki; Y. Matsumoto; Y. Okada

1999-01-01

105

A Musical Scale in Simple Ratios of the Harmonic Series Converted to Cents of Twelve-tone Equal Temperament for Digital Synthesis  

Microsoft Academic Search

Intervals between harmonics in the frequency spectra of pitched sounds occur in a pattern of simple ratios. New musical scales have now been invented with intervals in these ratios, and series of scales sharing common tones allowing for musical modulation. Twelve-tone equal temperament (12Tet) is standard for Euro- genic musical instruments. It divides the octave—the interval between frequencies having a

PETER LUCAS HULEN

106

Reduced Switching Frequency Computed PWM Method for Multilevel Converter Control  

Microsoft Academic Search

This paper presents two computed PWM methods for 11-level multilevel converters to eliminate the specified harmonics in the output voltage to decrease total harmonic distortion (THD). The first method uses the fundamental switching scheme to eliminate low order harmonics, and uses the active harmonic elimination method to eliminate higher order harmonics. The second method uses these schemes in the reverse

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

2005-01-01

107

Absolute non-linear optical coefficients measurements of CsLiB 6O 10 single crystals by second harmonic generation  

NASA Astrophysics Data System (ADS)

We present absolute measurements of the effective non-linear optical coefficients deff of cesium lithium borate crystals (CsLiB 6O 10, CLBO) by second harmonic generation using a continuous Nd-YAG laser source. The experiments were carried out at room temperature, on crystals cut perpendicular to type I or type II phase matching directions, with two different crystal lengths along the propagation direction. The d36 and d14 non-linear coefficients involved in deff developments are deduced and are shown to be equal as it is predicted by the Kleinman symmetry. Two different compositions prepared by the Czochralski technique from melt with compositions of 1:1:6 and 1:1:5.5 molar ratios of Cs 2O, Li 2O and B 2O 3 are comparatively studied.

Sifi, A.; Klein, R. S.; Maillard, A.; Kugel, G. E.; Péter, A.; Polgár, K.

2003-10-01

108

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

109

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

NASA Astrophysics Data System (ADS)

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 CaF2 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

2013-11-01

110

Efficient Frequency Converters Based on Stimulated Raman Scattering in Hollow Core Photonic Crystal Fibres Filled with Nonlinear Liquids  

Microsoft Academic Search

Recent developments in the field of nonlinear optics with photonic crystal fibers have led to the realization of supercontinuum spectra or parametric sources of correlated photons. However the nonlinearities were still limited by the use of silica. Hollow core photonic crystal fibers (HCPCF) filled with highly nonlinear liquids or gases enable the implementation of more performing nonlinear devices and open

Sylvie Lebrun; Philippe Delaye; Robert Frey; Gérald Roosen

2009-01-01

111

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

112

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

NASA Astrophysics Data System (ADS)

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.

1995-03-01

113

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

114

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

115

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

116

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

Microsoft Academic Search

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

R. B. Lal

1995-01-01

117

APPLICATIONS OF LASERS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Generation of the second harmonic of ultrashort pulses as a result of multiple phase-matched interaction in a nonlinear crystal  

NASA Astrophysics Data System (ADS)

A study was made of the interaction of ultrashort second harmonic pulses in a nonlinear crystal placed inside a resonator with a train of ultrashort pulses from a YAG:Nd laser with active mode locking. It was found that at low radiation intensities, insufficient for significant phase modulation in the course of frequency conversion, it was possible to generate strong ultrashort pulses of the second harmonic as a result of multiple interaction of the harmonic radiation with a train of ultrashort pump pulses in an external resonator containing a nonlinear crystal. The experimental setup made it possible also to obtain information on the correlation between the phases in the laser radiation spectrum over periods which were a multiple of the period of intermode resonator beats.

Zaporozhchenko, V. A.; Zaporozhchenko, R. G.; Pilipovich, I. V.; Tylets, N. A.

1988-05-01

118

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

PubMed

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

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

2012-11-01

119

Enhanced second-harmonic generation from nonlinear optical metamagnetics.  

PubMed

We present a numerical simulation of second-harmonic generation (SHG) from a nonlinear magnetic metamaterial. By inserting a second-order nonlinear material in the high local field area of magnetic metamaterial, which consists of periodic arrays of paired thin silver strips, the convertion efficiency of SHG has been significantly enhanced by almost four orders of magnitude. The corresponding field patterns and further studies on dependance between SHG and symmetry of nonlinear crystal show that the increase of the conversion efficiency is attributed to the local field enhancement caused by the magnetic resonnance of the structure. Our researches provide an additional way to further improve the optical nonlinearity in nanostructures. PMID:25401811

Sun, Shang; Yi, Ningbo; Yao, Wenjiao; Song, Qinghai; Xiao, Shumin

2014-11-01

120

Consecutive quasi-phase-matched generation of the third harmonic of the radiation from an Nd:YAG laser in a periodicaly poled Y:LiNbO{sub 3} crystal  

SciTech Connect

Consecutive generation of the third harmonic (i.e. generation of radiation with the doubled frequency followed by frequency summation) radiation from a Q-switched Nd:YAG laser ({lambda} = 1.064 {mu}m) was observed in a Y:LiNbO{sub 3} crystal polarised periodically along the z axis. The modulation period of the nonlinear susceptibility was {approx} 60 {mu}m. The second and third harmonics of the radiation were generated respectively in the ninth and thirty-third quasi-phase-matching orders. (nonlinear optical phenomena and devices)

Volkov, V V; Laptev, G D [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation); Morozov, E Yu; Naumova, I I; Chirkin, Anatolii S [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

1998-11-30

121

Novel multi-element resonant converters for front-end dc\\/dc converters  

Microsoft Academic Search

This paper proposes novel multi-element resonant converters for front-end dc\\/dc converters. The superior performance of the proposed resonant converters is to provide inherent current protection and very low circulating energy. With the optimized design, the proposed resonant converters can operate under short output circuit. Based on the third order harmonic injection, the circulating energy of the resonant tank can be

Dianbo Fu; Fred C. Lee; Ya Liu; Ming Xu

2008-01-01

122

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

123

Insightful analysis of carrier PWM algorithms for direct AC-AC matrix converter based on voltage-source converter modules  

Microsoft Academic Search

This paper discusses the carrier PWM algorithms suitable for the direct AC-AC matrix converter composed of three three-phase voltage source converter modules. The relationship between the conjugated and nonconjugated terms from the dyadic matrix control theory and the harmonic performance of input current and output voltage are outlined through extended harmonic analysis. Furthermore, two algorithms that result in a larger

D. O. Neacsu; A. Alistar; M. Kazerani

2002-01-01

124

Optical properties of the second harmonic generation for nonlinear crystal CsLiB6O10  

NASA Astrophysics Data System (ADS)

According to Sellmeier equation, the detailed theoretical study using a computer stimulation on the nonlinear optical properties of CLBO (CsLiB6O10) frequency doubling are presented as compared to that of BBO in type I and type II phase matching (PM). We obtained the advantage of both a large acceptance angle and a small effective nonlinear coefficient of CLBO versus BBO. The curves of the effective nonlinear coefficient, phase matching angle, walk- off angle, permitted angle and wavelength versus the fundamental wavelength and SHG conversion efficiency versus the crystal length are plotted according to the formulas we derived in type I and type II from the PM. The theoretical guiding to experiments band application in CLBO is presented.

Wang, Li; Chen, Shaohua; Xue, Jianhua; Men, Yanbin

2001-11-01

125

Thermionic converter  

DOEpatents

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

Fitzpatrick, G.O.

1987-05-19

126

Crystals  

NSDL National Science Digital Library

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

Science, Lawrence H.

2009-01-01

127

Active Harmonic Filtering Using Current Controlled Grid-Connected DG Units with Closed-Loop Power Control  

E-print Network

1 Active Harmonic Filtering Using Current Controlled Grid- Connected DG Units with Closed converters to actively compensate harmonics, this paper proposes an enhanced current control approach, which seamlessly integrates system harmonic mitigation capabilities with the primary DG power generation function

Berning, Torsten

128

Magnetorheological converters  

SciTech Connect

The authors study the problems of constructing an electrohydraulic converter functioning based on the magnetoheological effect: the magnetorheological throttle (MR throttle). Requirements are listed that must be taken into account in developing the MR throttle. The paper attempts to calculate the flow-rate characteristics of the MR throttle. The rheological equation which describes sufficiently the mechanical properties of the magnetoheological suspensions is presented. The paper examines the calculation of the magnetic inductor for the example of a toroidal core with a gap, which simultaneously functions as the slot throttling channel. The use of the designs described enabled the development of bridge converters, which have a flat amplitude-frequency characteristic in the range 200-250 Hz and which have good energy indicators. Typical experimental logarithmic amplitude-frequency and phase-frequency characteristics of a bridge converter are shown.

Zal'tsgendler, E.A.; Kolomentsev, A.V.; Kordonskii, V.I.; Madorskii, L.S.

1986-04-01

129

Sharing of nonlinear load in parallel connected three-phase converters  

Microsoft Academic Search

In this paper a new control method is presented which enables equal sharing of linear and nonlinear loads in paralleled three-phase power converters without communication between the converters. The paper focuses on solving the problem that arises when two converters with harmonic compensation are connected in parallel. Without the new solution they are normally not able to distinguish the harmonic

Uffe Borup Jensen; Frede Blaabjerg; P. N. Enjeti

2000-01-01

130

Ac-dc converter firing error detection  

SciTech Connect

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

Gould, O.L.

1996-07-15

131

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

132

Reduced Switching Frequency Computed PWM Method for Multilevel Converter Control  

E-print Network

. An experimental 11-level H-bridge multilevel converter with a first-on first-off switching strategy (usedReduced Switching Frequency Computed PWM Method for Multilevel Converter Control Zhong Du, Leon M computed PWM methods for 11-level multilevel converters to eliminate the specified harmonics in the output

Tolbert, Leon M.

133

Constant frequency aircraft electric power systems with harmonic reduction  

Microsoft Academic Search

The ever-increasing number of power electronic converters connected to the aircraft electric power system significantly increases harmonic levels and voltage transients in that system. Stringent limits on harmonic current distortion and perturbation of the aircraft electric power supply demands accurate simulation and development of high performance filters for the mitigation of harmonics and minimization of system transients. This paper presents

A. Eid; H. El-Kishky; M. Abdel-Salam; T. El-Mohandes

2008-01-01

134

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

SciTech Connect

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

Hibbard, R.L., LLNL

1998-03-30

135

Transient of modified HVDC converters  

Microsoft Academic Search

The bridge circuit used in high voltage direct current (HVDC) converters may be modified by including by-pass thyristor valves connected to tapping points on the secondary windings of the transformer to give a reduction in both harmonic generation and reactive volt–ampere absorption for the rectifier and inverter modes of operation.In this paper, control strategies for the transient response of the

Hussein. D. Al-Majali; Sulaiman. M. Al-Dhalaan

2007-01-01

136

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

SciTech Connect

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

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

1995-02-01

137

Second-harmonic optical coherence tomography  

Microsoft Academic Search

Second-harmonic optical coherence tomography, which uses coherence gating of second-order nonlinear optical responses of biological tissues for imaging, is described and demonstrated. Femtosecond laser pulses were used to excite second-harmonic waves from collagen harvested from rat tail tendon and a reference nonlinear crystal. Second-harmonic interference fringe signals were detected and used for image construction. Because of the strong dependence of

Yi Jiang; Ivan Tomov; Yimin Wang; Zhongping Chen

2004-01-01

138

Organometallic Salts Generate Optical Second Harmonics  

NASA Technical Reports Server (NTRS)

Series of organometallic salts exhibit large second-order dielectric susceptibilities, as evidenced by generation of second harmonics when illuminated at visible and near-infrared wavelengths. Investigations of these and related compounds continue with view toward development of materials for use as optical second-harmonic generators, electro-optical modulators, optical switches, piezoelectric sensors, and parametric crystals.

Marder, Seth R.; Perry, Joseph W.

1991-01-01

139

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

140

Optical Second-Harmonic Generation in Single Crystals of Thiosemicarbazide Cadmium Bromide Hydrate (Cd(NH2NHCSNH2)Br2\\cdotH2O)  

NASA Astrophysics Data System (ADS)

A new nonlinear optical organic-inorganic crystal, thiosemicarbazide cadmium bromide hydrate (TSCCB), with crystal class m has been grown by a temperature-lowering technique (TLT) and a temperature-difference technique (TDT). The crystal structure of TSCCB is reported. Its linear and nonlinear optical properties have been investigated. The highest measured nonlinear optical susceptibility is dmax{=}2.8 pm/V.

Wang, W. S.; Sutter, K.; Bosshard, Ch.; Pan, Z.; Arend, H.; Günter, P.; Chapuis, G.; Nicolo, F.

1988-07-01

141

A new real-time non-coherent to coherent light image converter - The hybrid field effect liquid crystal light valve  

NASA Technical Reports Server (NTRS)

A new, high-performance device has been developed for application to real-time coherent optical data processing. The new device embodies a CdS photoconductor, a CdTe light-absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The noncoherent image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the ac voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The liquid crystal is operated in a hybrid field effect mode. It utilizes the twisted nematic effect to create a dark off-state and the optical birefringence effect to create the bright on-state. The liquid crystal modulates the polarization of the coherent read-out light so an analyzer must be used to create an intensity modulated output beam.

Grinberg, J.; Jacobson, A.; Bleha, W.; Miller, L.; Fraas, L.; Boswell, D.; Myer, G.

1975-01-01

142

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

143

Efficient polarization converter for projection displays  

E-print Network

Efficient polarization converter for projection displays W. C. Yip, H. C. Huang, and H. S. Kwok In the waveguiding limit, a twisted nematic liquid crystal cell behaves as an achromatic polarization rotator. We propose and demonstrate the application of such a polarization rotator to convert unpolar- ized light

144

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

145

High efficiency, high energy second-harmonic generation of Nd glass laser radiation in large aperture CsLiB sub 6 O sub 1 sub 0 crystals  

E-print Network

We have demonstrated the generation of a high-energy green laser pulse using large aperture CsLiB sub 6 O sub 1 sub 0 (CLBO) crystals. A pulsed energy of 25 J at 532-nm was generated using the 1064-nm incident Nd:glass laser radiation with an energy of 34 J. High conversion efficiency of 74% at intensities of only 370 MW/cm sup 2 was obtained using a two-stage crystal architecture. This result represents the highest green pulse energy ever reported using the CLBO crystals. We discuss in detail the design and performance of SHG using CLBO crystals.

Kiriyama, H; Yamakawa, K

2002-01-01

146

Frequency converter design and manufacturing considerations for the National Ignition Facility  

SciTech Connect

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

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

1998-03-25

147

Design and Analysis of the Main AC/DC Converter System for ITER  

NASA Astrophysics Data System (ADS)

A design of the main AC/DC converter system for ITER is described and the configuration of the main AC/DC converters is presented. To reduce the reactive power absorbed from the converter units, the main AC/DC converters are designed to be series-connected and work in a sequential mode. The structure of the regulator of the converter system is described. A simulation model was built up for the PSCAD/EMTDC code, and the design was validated accordingly. Harmonic analysis and reactive power calculation of the converters units are presented. The results reveal the advantage of sequential control in reducing reactive power and harmonics.

Sheng, Zhicai; Xu, Liuwei; Fu, Peng

2012-04-01

148

crystals  

NASA Astrophysics Data System (ADS)

We present the crystal growth, optical spectroscopy, and room temperature continuous-wave (CW) laser operation of monoclinic Ho:KLu(WO4)2 crystals. Macro defect-free crystals of several dopant concentrations were grown by top-seeded solution growth slow-cooling method. The evolution of unit cell parameters with holmium doping level and temperature was studied using X-ray powder diffraction. The spectroscopic properties were characterized in terms of room- and low-temperature optical absorption and photoluminescence. From low-temperature optical absorption measurements, the energy of the Stark levels was determined. Calculation of the emission and gain cross sections is presented. CW laser action was realized for 3 and 5 at. % Ho-doped KLu(WO4)2 by in-band pumping using a Tm:KLu(WO4)2 pump laser. A maximum output power of 507 mW with a slope efficiency of ~38 % with respect to the incident power was achieved at 2,080 nm with the Ho:KLu(WO4)2 laser.

Jambunathan, V.; Mateos, X.; Pujol, M. C.; Carvajal, J. J.; Zaldo, C.; Griebner, U.; Petrov, V.; Aguiló, M.; Díaz, F.

2014-08-01

149

IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 55, NO. 4, APRIL 2008 1761 Reduced Switching-Frequency Active Harmonic  

E-print Network

) near sine wave is produced. An experimental 11-level H-bridge multilevel converter with a field-Frequency Active Harmonic Elimination for Multilevel Converters Zhong Du, Member, IEEE, Leon M. Tolbert, Senior number of specific order harmonics of multilevel converters. First, resultant theory is applied

Tolbert, Leon M.

150

High energy second-harmonic generation of Nd:glass laser radiation with large aperture CsLiB6O10 crystals  

NASA Astrophysics Data System (ADS)

We have demonstrated the generation of a high-energy green laser pulse using large aperture CsLiB6O10 (CLBO) crystals for the first time to our knowledge. A pulsed energy of 25 J at 532-nm was generated using the 1064-nm incident Nd:glass laser radiation with an energy of 34 J. High conversion efficiency of 74 % at intensities of only 370 MW/cm2 was obtained using a two-stage crystal architecture. This result represents the highest green pulse energy ever reported using the CLBO crystals.

Kiriyama, Hiromitsu; Inoue, Norihiro; Yamakawa, Koichi

2002-09-01

151

High energy second-harmonic generation of Nd:glass laser radiation with large aperture CsLiB6O10 crystals.  

PubMed

We have demonstrated the generation of a high-energy green laser pulse using large aperture CsLiB6O10 (CLBO) crystals for the first time to our knowledge. A pulsed energy of 25 J at 532-nm was generated using the 1064-nm incident Nd:glass laser radiation with an energy of 34 J. High conversion efficiency of 74 % at intensities of only 370 MW/cm2 was obtained using a two-stage crystal architecture. This result represents the highest green pulse energy ever reported using the CLBO crystals. PMID:19451960

Kiriyama, Hiromitsu; Inoue, Norihiro; Yamakawa, Koichi

2002-09-23

152

Second-harmonic generation in nonlinear left-handed metamaterials  

E-print Network

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

153

Harmonic engine  

DOEpatents

An engine based on a reciprocating piston engine that extracts work from pressurized working fluid. The engine includes a harmonic oscillator inlet valve capable of oscillating at a resonant frequency for controlling the flow of working fluid into of the engine. In particular, the inlet valve includes an inlet valve head and a spring arranged together as a harmonic oscillator so that the inlet valve head is moveable from an unbiased equilibrium position to a biased closed position occluding an inlet. Upon releasing the inlet valve the inlet valve head undergoes a single oscillation past the equilibrium positio to a maximum open position and returns to a biased return position close to the closed position to choke the flow and produce a pressure drop across the inlet valve causing the inlet valve to close. Protrusions carried either by the inlet valve head or piston head are used to bump open the inlet valve from the closed position and initiate the single oscillation of the inlet valve head, and protrusions carried either by the outlet valve head or piston head are used to close the outlet valve ahead of the bump opening of the inlet valve.

Bennett, Charles L.; Sewall, Noel; Boroa, Carl

2014-08-19

154

SHE-PWM control for asymmetrical hybrid multilevel flying capacitor and H-bridge converter  

Microsoft Academic Search

This paper presents a new asymmetrical hybrid voltage source multilevel converter controlled with selective harmonic elimination pulse width modulation (SHE-PWM) technique. The proposed hybrid multilevel converter combines the separate flying capacitor (FC) converter in series with an H-bridge converter with distinct DC voltage supply. The DC-link voltage of the FC is twice that of the H-bridge converter and the flying

Mohamed S. A. Dahidah; Georgios S. Konstantinou; Vassilios G. Agelidis

2011-01-01

155

Numerical Analysis of Fifth-Harmonic Conversion of Low-Power Pulsed Nd:YAG Laser with Resonance of Second Harmonic  

NASA Astrophysics Data System (ADS)

A model for the fifth-harmonic generation of pulsed IR lasers involving an external ring cavity resonating at the second harmonic has been developed. Numerical analysis is performed to show the relative effects of the pulse delay, input polarization, and orientation of the nonlinear crystals on the fifth harmonic power. The results are validated by published experimental results. The model is used to analyze and obtain the optimal combination of nonlinear optical crystals for the fifth-harmonic generation. Our calculation shows that the combination of LiB3O5 (LBO), CsLiB6O10 (CLBO), and CLBO crystals for the second-harmonic, fourth-harmonic, and fifth-harmonic generation steps respectively gives an approximate conversion of 30% from the fundamental to the fifth harmonic power, resulting in 2 W at 213 nm for an input of 7 W at 1064 nm.

Chang, Lien-Bee; Wang, S. C.; Kung, A. H.

2003-07-01

156

Optimal design of LLC series resonant converter with enhanced controllability characteristic  

Microsoft Academic Search

This paper proposes an optimization model for the determination of LLC resonant converter design parameters. The optimization model is developed based on the fundamental harmonic approximation (FHA) analysis and variable reluctance control method. The objective of the optimal design is to reach the maximum controllability characteristics by the resonant converter. The reluctance control strategy is used as converter controller because

Ehsan Khoobroo; Mahdi Akhbari

2012-01-01

157

Sharing of nonlinear load in parallel-connected three-phase converters  

Microsoft Academic Search

In this paper, a new control method is presented which enables equal sharing of linear and nonlinear loads in three-phase power converters connected in parallel, without communication between the converters. The paper focuses on solving the problem that arises when two converters with harmonic compensation are connected in parallel. Without the new solution, they are normally not able to distinguish

Uffe Borup; Frede Blaabjerg; Prasad N. Enjeti

2001-01-01

158

Harmonic and Anharmonic Properties of Diamond Structure Crystals with Application to the Calculation of the Thermal Expansion of Silicon. Ph.D. Thesis. Final Report  

NASA Technical Reports Server (NTRS)

Silicon has interesting harmonic and anharmonic properties such as the low lying transverse acoustic modes at the X and L points of the Brillouin zone, negative Gruneisen parameters, negative thermal expansion and anomalous acoustic attenuation. In an attempt to understand these properties, a lattice dynamical model employing long range, nonlocal, dipole-dipole interactions was developed. Analytic expression for the Gruneisen parameters of several modes are presented. These expressions explain how the negative Gruneisen parameters arise. This model is applied to the calculation of the thermal expansion of silicon from 5K to 1700K. The thermoelastic contribution to the acoustic attenuation of silicon is computed from 1 to 300 K. Strong attenuation anomalies associated with negative thermal expansion are found in the vicinity of 17K and 125K.

Wanser, K. H.

1981-01-01

159

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

160

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

161

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

162

Third-harmonic performance of the Beamlet prototype laser  

SciTech Connect

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

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

1997-01-31

163

Spectrum of second-harmonic radiation generated from incoherent light  

SciTech Connect

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

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

2011-10-15

164

Measurement: Converting Distances  

NSDL National Science Digital Library

This lesson helps students understand and practice converting measurements in both English and metric systems. The 8-page pdf begins with a brief introduction to measuring length, English measurement systems, and metric measurement. Students then learn to convert measurements within each system. At the end of the lesson, there are 18 review problems for students to convert measurements on their own. Answers are provided.

2006-01-01

165

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

166

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

167

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

168

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

169

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

170

Polynomial Harmonic Morphisms Martin Svensson  

E-print Network

Polynomial Harmonic Morphisms Martin Svensson Examensarbete, 20 poang Lunds Universitet November Chapter 2. Harmonic Maps 13 1. The Second Fundamental Form 13 2. Harmonic Maps 18 3. Harmonic Functions 25 Chapter 3. Harmonic Morphisms 29 1. Horizontal Conformality 29 2. Harmonic Morphisms 33 3. The Existence

Gudmundsson, Sigmundur

171

A closed-loop selective harmonic compensation for active filters  

Microsoft Academic Search

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

Paolo Mattavelli

2001-01-01

172

High Power Machine Drive, Based on Three-Stage Connection of "H" Converters, and Active Front End Rectifiers.  

E-print Network

High Power Machine Drive, Based on Three-Stage Connection of "H" Converters, and Active Front End "H" converters is being analyzed for high power machine drive applications. The great advantage of this kind of converter is the minimum harmonic distortion obtained at the machine side. The drawbacks

Catholic University of Chile (Universidad Católica de Chile)

173

Floating gate power supply of multilevel converters for circuit integration  

Microsoft Academic Search

There is the possibility of the intrinsic elimination of harmonics and electromagnetic interference (EMI) by introducing multilevel converters with a large number of levels. As the number of levels increases, the number of the main switching devices on their higher side increases, and their floating gate power supplies become larger scale circuits. Because it is necessary to integrate the floating

Masamu Kamaga; Kyungmin Sung; Jin Xu; Yukihiko Sato; Hiromichi Ohashi

2009-01-01

174

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.

175

Harmonic generation in 2D layered materials  

NASA Astrophysics Data System (ADS)

Two-Dimensional (2D) layered materials have garnered interest due to their novel optical and electronic properties. In this work, we investigate Second Harmonic Generation (SHG) in Tungsten Disulfide (WS2) monolayers grown on SiO2/Si substrates and suspended on a transmission electron microscopy grid; we find an unusually large second order susceptibility, which is nearly three orders of magnitude larger than common nonlinear crystals. We have also developed a Green's function based formalism to model the harmonic generation from a 2D layer .

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

2014-09-01

176

Second-Harmonic Generation of Light with Double Refraction  

Microsoft Academic Search

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

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

1965-01-01

177

Control of Cascaded Multilevel Converters with Unequal Voltage Sources for HEVs  

E-print Network

The cascade multilevel inverter consists of a series of H- bridge (single-phase full-bridge) inverter unitsControl of Cascaded Multilevel Converters with Unequal Voltage Sources for HEVs Leon M. Tolbert1 2 possible solu- tions are found. Keywords­ Hybrid Electric Vehicles, Multilevel Convert- ers, Harmonic

Tolbert, Leon M.

178

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

179

When is the product of two planar harmonic mappings harmonic?  

E-print Network

When is the product of two planar harmonic mappings harmonic? Raymond Mortini Lecturas Matem´aticas Volumen 23 (2002), p´aginas 5­10 Abstract. We determine all complex-valued harmonic functions u and v defined on a planar domain for which uv, respectively u2 - v2 is harmonic Key words and phrases. Harmonic

Mortini, Raymond

180

Active Harmonic Filters  

Microsoft Academic Search

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

HIROFUMI AKAGI

2005-01-01

181

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

182

HARMONIC AMPLIFIER FREE ELECTRON LASER  

Microsoft Academic Search

The harmonic optical klystron (HOK) in which the second undulator is resonant on the higher harmonic of the first undulator is analysed as a harmonic amplifier. The optical field evolution equation of the HOK is derived analytically for both CHG mode (Coherent Harmonic Generation, the quadratic gain regime) and HGHG mode (High Gain Harmonic Generation, the exponential gain regime), the

Jia Qika

183

GaxIn1-xAs thermophotovoltaic converters  

Microsoft Academic Search

Preliminary research into the development of single-junction Ga xIn1-xAs thermophotovoltaic (TPV) power converters is reviewed. The devices structures are grown epitaxially on single-crystal InP substrates. Converter band gaps of 0.50 -0.74 eV have been considered in accordance with modeling calculations. A 1-sun, AMO efficiency of 12.8% is reported for a lattice-matched, 0.74-eV converter. Converters with lower band gaps are fabricated

M. W. Wanlass; J. S. Ward; K. A. Emery; T. J. Coutts

1994-01-01

184

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

185

Harmonizing Civil Engineering Education  

Microsoft Academic Search

Uniformity never will be the objective of education, yet some level of compatibility can be useful or even indi spensable. Though academic teachers are rather attached to the idea of University autonomy and freedom than to any form of harmonization, some harmonization is necessary to assure readable and comparable professional degrees, as well as comparable criteria of quality assurance, irrespective

Stanisøaw Majewski

186

Electrodynamic spherical harmonic  

E-print Network

Electrodynamic spherical harmonic is a second rank tensor in three-dimensional space. It allows to separate the radial and angle variables in vector solutions of Maxwell's equations. Using the orthonormalization for electrodynamic spherical harmonic, a boundary problem on a sphere can be easily solved.

Andrey Novitsky

2008-03-28

187

Spatial and energy parameters of laser radiation and second harmonic upon self-frequency doubling  

SciTech Connect

The intracavity second-harmonic generation of laser radiation in an active nonlinear crystal is studied. The spatial distributions of the intensity and power of laser radiation and its second harmonic are calculated by the method of numerical simulations as functions of the parameters of the resonator, active nonlinear crystal, and pump. The analysis is performed for a periodically poled Nd:Mg:LiNbO{sub 3} crystal taking diffraction into account. (active media. lasers)

Laptev, G D [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation); Novikov, Aleksei A; Chirkin, Anatolii S [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2005-01-31

188

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 Lai; Fang Zheng Peng

1996-01-01

189

Vector generator scan converter  

DOEpatents

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

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

1990-01-01

190

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

191

Harmonic conversion of phase-aberrated beam in CLBO  

NASA Astrophysics Data System (ADS)

In this paper, based on the point of the statistical-optics, we have developed a discussion for the Type II second harmonic generation of short pulse laser beams with phase modulations fluctuations in the new crystal such as CLBO. In it, fundamental wave is aberrated beam of which the aberration is assumed to be a Gaussian random variable. The theory on focusing the both characteristics approximate and calculated results of fundamental wave and second harmonic VS phase aberration coefficient have been presented. It is applicable in designs of harmonic generation for high power lasers.

Gao, Yanxia; Fan, Dianyuan

1998-08-01

192

Nonuniversality of entanglement convertibility  

NASA Astrophysics Data System (ADS)

Recently, it has been suggested that operational properties connected to quantum computation can be alternative indicators of quantum phase transitions. In this work we systematically study these operational properties in one-dimensional systems that present phase transitions of different orders. For this purpose, we evaluate the local convertibility between bipartite ground states. Our results suggest that the operational properties, related to nonanalyticities of the entanglement spectrum, are good detectors of explicit symmetries of the model, but not necessarily of phase transitions. We also show that thermodynamically equivalent phases, such as Luttinger liquids, may display different convertibility properties depending on the underlying microscopic model.

Bragança, Helena; Mascarenhas, Eduardo; Luiz, G. I.; Duarte, C.; Pereira, R. G.; Santos, M. F.; Aguiar, M. C. O.

2014-06-01

193

On harmonic binomial series  

E-print Network

We evaluate binomial series with harmonic number coefficients, providing recursion relations, integral representations, and several examples. The results are of interest to analytic number theory, the analysis of algorithms, and calculations of theoretical physics, as well as other applications.

Mark W. Coffey

2008-12-09

194

Illustration: The Harmonic Oscillator  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

195

Harmonic Morphisms -Basics Sigmundur Gudmundsson  

E-print Network

Harmonic Morphisms - Basics Sigmundur Gudmundsson Department of Mathematics Faculty of Science Lund University Sigmundur.Gudmundsson@math.lu.se March 11, 2014 #12;Harmonic Maps in Gaussian Geometry Harmonic Maps in Riemannian Geometry Outline 1 Harmonic Maps in Gaussian Geometry Holomorphic Functions in One

Gudmundsson, Sigmundur

196

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

197

Catalytic Converters and Nanocatalysts  

NSDL National Science Digital Library

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

198

Liquid metal thermal electric converter  

DOEpatents

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

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

1989-01-01

199

Phase regeneration of an M-PSK signal using partial regeneration of its M/2-PSK second phase harmonic  

NASA Astrophysics Data System (ADS)

We propose and numerically investigate a phase regeneration technique that allows an M-PSK signal to be phase regenerated by an M/2-PSK (or even M/4-PSK) phase regenerator (applicable for M=2k, with k an integer). This scheme comprises three main parts; firstly, phase harmonic generation is used to create the second and third phase harmonics, secondly, the second phase harmonic (a down-converted M/2-PSK signal) is partially phase-regenerated, and thirdly and finally, the partially regenerated second phase harmonic and the third phase harmonic are mixed together to re-synthesize a phase regenerated replica of the original signal.

Jones, Liam; Parmigiani, Francesca; Petropoulos, Periklis; Richardson, David J.

2015-01-01

200

Thermionic energy converters  

NASA Technical Reports Server (NTRS)

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

Morris, J. F. (inventor)

1983-01-01

201

Free FLV Converter  

NSDL National Science Digital Library

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

2007-01-01

202

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.

Elizabeth Stapel

203

Multilevel converters -- A new breed of power converters  

SciTech Connect

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

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

1995-09-01

204

Generation of octave-spanning multiple harmonics for ultrafast waveform synthesis  

E-print Network

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

Hsu, Wei-Chun

205

Active front-end converter input filter minimization using sequential sampling space vector modulation for multi-motor drives  

Microsoft Academic Search

Sequential sampling space vector modulation, and its equivalent the phase-shifted carrier PWM, have been used with good results in various multi-level converter structures. However, up to now they have been usually restrained to operation with a power-balanced set of converters in order to assure harmonic cancellation between the parallel or series connected converters. This paper expands the use of sequential

Eduardo P. Wiechmann; Rolando P. Burgos; Dushan Boroyevich

2001-01-01

206

A novel forward AC\\/DC converter with input current shaping and fast output voltage regulation via reset winding  

Microsoft Academic Search

This work presents a novel simple forward AC\\/DC converter with harmonic current correction and fast output voltage regulation. In the proposed AC\\/DC converter, a transformer incorporating reset winding provides two main advantages. First, the bulk inductor used in the conventional boost-based power-factor-correction cell is omitted in the proposed converter, allowing significant volume and weight of magnetic material to be saved.

Lon-Kou Chang; Hsing-Fu Liu

2005-01-01

207

Optical third-harmonic generation using ultrashort laser pulses  

SciTech Connect

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

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

2005-06-15

208

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

209

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.

210

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

Microsoft Academic Search

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

Daolian Chen

2008-01-01

211

Experimental Harmonic Motion  

NASA Astrophysics Data System (ADS)

1. Elementary theory of harmonic motion; 2. Experimental work in harmonic motion; Experiment 1. Determination of g by a simple pendulum; Experiment 2. Harmonic motion of a body suspended by a spring; Experiment 3. Harmonic motion of a rigid body suspended by a torsion wire; Experiment 4. Study of a system with variable moment of inertia; Experiment 5. Dynamical determination of ratio of couple to twist for a torsion wire; Experiment 6. Comparison of the moments of inertia of two bodies; Experiment 7. Experiment with a pair of inertia bars; Experiment 8. Determination of the moment of inertia of a rigid pendulum; Experiment 9. Experiment on a pendulum with variable moment of inertia; Experiment 10. Determination of g by a rigid pendulum; Experiment 11. Pendulum on a yielding support; Experiment 12. Determination of the radius of curvature of a concave mirror by the oscillations of a sphere rolling in it; Experiment 13. Determination of g by the oscillations of a rod rolling on a cylinder; Experiment 14. Study of a vibrating system with two degrees of freedom; Note 1. On the vibration of a body suspended from a light spring; Note 2. Periodic time of a pendulum vibrating through a finite arc; Note 3. Periodic time for finite motion; Note 4. Periodic times of a pendulum with two degrees of freedom.

Searle, G. F. C.

2014-05-01

212

Spherical Harmonic class  

NSDL National Science Digital Library

SphericalHarmonic returns the value of P(theta,phi) where theta and phi are defined in terms of a standard spherical coordinate system (phi measures angle (x,y,z) makes with z axis.) The algorithm is taken from Messiah's Quantum Mechanics, but readers should note that Messiah defines theta and phi in opposite order from this implementation.

Joiner, David; The Shodor Education Foundation, Inc.

213

Stress in Harmonic Serialism  

ERIC Educational Resources Information Center

This dissertation proposes a model of word stress in a derivational version of Optimality Theory (OT) called Harmonic Serialism (HS; Prince and Smolensky 1993/2004, McCarthy 2000, 2006, 2010a). In this model, the metrical structure of a word is derived through a series of optimizations in which the "best" metrical foot is chosen…

Pruitt, Kathryn Ringler

2012-01-01

214

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

215

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

216

Gallium phosphide energy converters  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

217

Harmonic Generation in Thin Films and Multilayers William S. Kolthammer, Dustin Barnard, Nicole Carlson, Aaron D. Edens, Nathan A. Miller, and Peter N. Saeta  

E-print Network

Harmonic Generation in Thin Films and Multilayers William S. Kolthammer, Dustin Barnard, Nicole, Claremont, CA 91711 (Dated: September 6, 2004) A general method for computing harmonic generation in studying the second- and third-harmonic generation properties of thin crystal silicon layers surrounded

Saeta, Peter N.

218

HARMONIC MORPHISMS ON HOMOGENEOUS HADAMARD  

E-print Network

HARMONIC MORPHISMS ON HOMOGENEOUS HADAMARD MANIFOLDS JONAS NORDSTRÃ?M Master's thesis 2010:E14;#12;Abstract In this thesis we investigate the existence of complex-valued harmonic morphisms on Lie groups of their Lie algebra. This decomposi- tion allows us to define harmonic morphisms to Rn , n 2. Any homogeneous

Gudmundsson, Sigmundur

219

Analytic Continuation of Harmonic Sums  

E-print Network

We present a method for calculating any (nested) harmonic sum to arbitrary accuracy for all complex values of the argument. The method utilizes the relation between harmonic sums and (derivatives of) Hurwitz zeta functions, which allows a harmonic sum to be calculated as an expansion valid for large values of its argument. A program for implementing this method is also provided.

S. Albino

2009-03-06

220

Second harmonic inversion for ultrasound contrast harmonic imaging  

NASA Astrophysics Data System (ADS)

Ultrasound contrast agents (UCAs) are small micro-bubbles that behave nonlinearly when exposed to an ultrasound wave. This nonlinear behavior can be observed through the generated higher harmonics in a back-scattered echo. In past years several techniques have been proposed to detect or image harmonics produced by UCAs. In these proposed works, the harmonics generated in the medium during the propagation of the ultrasound wave played an important role, since these harmonics compete with the harmonics generated by the micro-bubbles. We present a method for the reduction of the second harmonic generated during nonlinear-propagation-dubbed second harmonic inversion (SHI). A general expression for the suppression signals is also derived. The SHI technique uses two pulses, p' and p'', of the same frequency f0 and the same amplitude P0 to cancel out the second harmonic generated by nonlinearities of the medium. Simulations show that the second harmonic is reduced by 40 dB on a large axial range. Experimental SHI B-mode images, from a tissue-mimicking phantom and UCAs, show an improvement in the agent-to-tissue ratio (ATR) of 20 dB compared to standard second harmonic imaging and 13 dB of improvement in harmonic power Doppler.

Pasovic, Mirza; Danilouchkine, Mike; Faez, Telli; van Neer, Paul L. M. J.; Cachard, Christian; van der Steen, Antonius F. W.; Basset, Olivier; de Jong, Nico

2011-06-01

221

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

PubMed

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

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

2012-12-26

222

Generating Second Harmonics In Nonlinear Resonant Cavities  

NASA Technical Reports Server (NTRS)

Single-axial-mode lasers pump very-low-loss doubling crystals. Important advance in making resonant generation of second harmonics possible for diode-laser-pumped solid-state lasers is recent development of monolithic nonplanar ring geometries in neodymium:yttrium aluminum garnet (Nd:YAG) lasers that produce frequency-stable single-mode outputs. Other advance is development of high-quality MgO:LiNbO3 as electro-optically nonlinear material. Series of experiments devised to improve doubling efficiency of low-power lasers, and particularly of diode-laser-pumped continuous-wave Nd:YAG lasers.

Kozlovsky, William J.; Nabors, C. David; Byer, Robert L.

1990-01-01

223

Laser boresighting by second-harmonic generation  

NASA Astrophysics Data System (ADS)

Weapons delivery systems frequently use laser designators which require boresighting with the visual line of sight. For systems based on the Nd .YAG laser (A = 1 . O6jnrt) , this may be achieved by a boresight collimator with a second harmonic generating crystal in its focal plane which reradiates collimated, visible light (A 0 . 53/nfl) . The conception, design and testing of such a device will be described along with a comparison with alternative technologies which demonstrates its superiority in terms of conversion efficiency, damage threshold and design versatility.

Adel, Michael E.; Buckwald, Robert A.; Cabib, Dario

1991-04-01

224

Harmonic entanglement in a degenerate parametric down conversion  

E-print Network

We study the harmonic entanglement and squeezing in a two-mode radiation produced in a degenerate parametric down conversion process coupled to a two-mode vacuum reservoir employing the linearization procedure. It is found that there is a quadrature entanglement between the harmonically related fundamental and second-harmonic modes and the superimposed radiation exhibits a significant two-mode squeezing. The entanglement exits even when there is no two-mode squeezing, since the correlation leading to these phenomena are essentially different. In addition, the more the external coherent light is down converted, the more stronger the entanglement and mean photon number of the two-mode radiation would be which is not generally true for squeezing.

Sintayehu Tesfa

2007-07-25

225

A new approach to harmonic compensation in power systems  

Microsoft Academic Search

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

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

1988-01-01

226

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

227

Wave energy converter  

SciTech Connect

A power generation system for converting the motion of waves on a body of water such as a lake or sea to drive pumps, electrical generators or the like. A weighted float rides on the waves. A cable and pulley arrangement changes the direction, travel and force of the wave energy action imparted on the float and drives a hydraulic circuit. The hydraulic circuit includes an accumulator for temporary energy storage and release to assist in maintaining constant flow and pressure of hydraulic fluid to one or more hydraulic motors during each wave cycle. The hydraulic motor drives a load such as an electric generator. An automatically actuated device adjusts for high and low tides.

Taylor, R.N.

1984-02-28

228

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

Microsoft Academic Search

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

Steven Moran

1989-01-01

229

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

230

Harmonic multiplication using resonant tunneling  

NASA Technical Reports Server (NTRS)

This paper demonstrates the use of resonant-tunneling diodes as varistors for harmonic multiplication. It is shown that efficient odd-harmonic conversion is possible and that even harmonics do not appear because of the antisymmetry of the current-voltage (I-V) curve. It is also shown that, with the proper choice of resonant-tunneling structure and pump amplitude, most of the harmonic output power can be confined to a single odd-harmonic frequency. Fifth-harmonic multiplication was demonstrated with an output at 21.75 GHz and a power conversion efficiency of 0.5 percent, and a fifth-harmonic efficiency of 2.7 percent was achieved in a circuit simulation using an improved I-V curve.

Sollner, T. C. L. G.; Brown, E. R.; Goodhue, W. D.; Correa, C. A.

1988-01-01

231

Three-dimensional simulations of harmonic radiation and harmonic lasing  

SciTech Connect

Characteristics of the harmonic emission from free-electron lasers (FELs) are examined in the spontaneous, coherent-spontaneous and stimulated emission regimes. The radiation at both odd and even harmonic frequencies is treated for electron beams with finite emittance and energy spread. In the spontaneous emission regime, the transverse radiation patterns including the transverse frequency dependences, are given. How this expression is modified to include energy spread and emittance is described. In the coherent-spontaneous emission and stimulated emission regimes, the interaction of the radiation fields with the electrons must be treated self-consistently. Here, a single-frequency distributed transverse source function for each electron is used in the harmonic version of the 3-D code FELEX to model the harmonic radiation. The code has recently been modified to simultaneously model the fundamental and harmonic interactions for multiple-pass oscillator simulations. These modifications facilitate the examination of FELs under various operating conditions. When the FEL is lasing at the fundamental, the evolution of the harmonic fields can be examined. This evolution is unique in the sense that the electron beam radiates at the harmonic frequencies in the presence of the harmonic radiation circulating in the cavity. As a result, enhancements of the harmonic emission can be observed. Finally, harmonic lasing can occur in cases where there is sufficient gain to overcome cavity losses and lasing at the fundamental can be suppressed. The characteristics and efficiency of these interactions are explored. 11 refs., 9 figs.

Schmitt, M.J.; McVey, B.D.

1990-01-01

232

APPLICATIONS OF LASERS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Second harmonic generators as a new class of light polarizers and analyzers  

NASA Astrophysics Data System (ADS)

Crystals capable of second harmonic generation can be used effectively as analyzers and polarizers of laser radiation in the visible and infrared parts of the spectrum. Experimental results show that the extinction coefficient of a system comprising a polarizer in the form of a Glan prism an an analyzer representing a KDP crystal capable of second harmonic generation reached 6×10-9.

Zheludev, N. I.; Saltiel, S. M.; Yankov, P.

1987-07-01

233

Harmonically trapped jellium  

E-print Network

We discuss the model of a $D$-dimensional confined electron gas in which the particles are trapped by a harmonic potential. In particular, we study the non-interacting kinetic and exchange energies of finite-size inhomogeneous systems, and compare the resulting Thomas-Fermi and Dirac coefficients with various uniform electron gas paradigms. We show that, in the thermodynamic limit, the properties of this model are identical to those of the $D$-dimensional Fermi gas.

Loos, Pierre-François

2012-01-01

234

WAVE PROPAGATION IN CATALYTIC CONVERTERS: FORMULATION OF THE PROBLEM AND FINITE ELEMENT TO SOLUTION SCHEME  

Microsoft Academic Search

The fluid-dynamical equations governing wave propagation in catalytic converter elements containing isothermal mean flow are linearized, approximated and written in appropriate forms to act as the basis for a finite element solution scheme involving time harmonic variation. This solution scheme is described and numerical results are presented and compared—where possible—to other published data; favourable agreement is noted.

R. J. Astley; A. Cummings

1995-01-01

235

A Randomized Wrapped-Around Pulse Position Modulation Scheme for DC–DC Converters  

Microsoft Academic Search

We present a novel randomized wrapped-around pulse position modulation (RWAPPM) scheme for digital modulators of dc-dc converters. Unlike the reported modulation schemes that require a varying switching period (thereby resulting in high attenuation or complete elimination of discrete harmonics), the proposed RWAPPM conversely requires only a constant switching period (thereby advantageous in terms of easy realization in hardware), and yet,

Victor Adrian; Joseph S. Chang; Bah-Hwee Gwee

2010-01-01

236

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

Microsoft Academic Search

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

M. Calais; V. G. Agelidis

1998-01-01

237

Wide adjustable range LLC resonant converter's maximum switching frequency for realizing the ZVS operation  

Microsoft Academic Search

In this paper, the FHA and a simple TDA approaches have been used to derive the normalized maximum switching frequency of wide adjustable range LLC resonant converter for realizing the ZVS operation even under the worst-case conditions. By accounting the resonant current higher harmonics, more accurate expressions are derived. These analyses demonstrate that the normalized maximum switching frequency depends on

Reza Beiranvand; Bizhan Rashidian; Mohammad Reza Zolghadri; Mohammad Hossein Alavi

2010-01-01

238

Design-oriented steady-state analysis of LLC resonant converters based on FHA  

Microsoft Academic Search

The aim of this paper is to present a comprehensive design methodology for an LLC resonant converter, based on a detailed quantitative analysis of the steady-state operation of the circuit. This analysis follows the first harmonic approximation (FHA) approach, which tremendously simplifies the system model, leading to a linear circuit, which can be dealt with through the classical complex AC-circuit

S. De Simone; C. Adragna; C. Spini; G. Gattavari

2006-01-01

239

Multilevel converters control for renewable energy integration to the power grid  

Microsoft Academic Search

The paper deals with the multilevel converters control strategy for renewable energy resources integration in distribution grids. The proposed control scheme ensures the injection of the generated power in the distribution grid with fast dynamic response, while providing an additional active power filtering capability providing the required harmonic and reactive currents to the considered non-linear loads. The proposed control scheme

Edris Pouresmaeil; Oriol Gomis-Bellmunt; Daniel Montesinos-Miracle; Joan Bergas-Jané

2011-01-01

240

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

241

Surface plasma wave assisted second harmonic generation of laser over a metal film  

NASA Astrophysics Data System (ADS)

Second harmonic generation of laser mode converted surface plasma wave (SPW) over a corrugated metal film is studied. The laser, impinged on the metal film, under attenuated total reflection configuration, excites SPW over the metal-vacuum interface. The excited SPW extends over a much wider surface area than the laser spot cross-section. It exerts a second harmonic ponderomotive force on metal electrons, imparting them velocity that beats with the surface ripple to produce a nonlinear current, driving resonant second harmonic surface plasma wave.

Chauhan, Santosh; Parashar, J.

2015-01-01

242

Cost-effective segmented scintillating converters for hard x rays  

NASA Astrophysics Data System (ADS)

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

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

1996-07-01

243

Ocean wave energy converter  

SciTech Connect

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 within the tube receptacles approximately forming trimetric edge elements of a right conical frustum; a separable buoyancy device affixed to the upper portions of the tubular members above the lower structural support means, the buoyancy device having upper and lower surfaces and an enclosed space therein; an annulated receptacle plate affixed to the upper surface of the buoyancy device; truncated right circular cylinders connected to the annulated receptacle plate extending outwardly in coaxial alignment with respective tubular members; articulated brackets connected to the annulated receptacle plate in radial extension; upper structural support means connected to the articulated brackets in radial extension for connection to other receptacle plate articulated brackets of a module array; and dual rolling contact support means comprising open linear slide bearings operatively positioned within the tube upper portions and the truncated cylinders.

Ames, P.F.

1987-06-09

244

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.

245

Efficient second harmonic generation of 10-micron radiation in AgGaSe2  

NASA Technical Reports Server (NTRS)

AgGaSe2 crystals for nonlinear infrared applications are being grown reproducibly. Using high-quality, 2-cm-long crystals, 14 percent energy and 60 percent peak intensity conversion efficiency have been demonstrated for second harmonic generation of the pulsed output of a CO2 miniature transversely excited atmospheric laser.

Eckardt, R. C.; Fan, Y. X.; Byer, R. L.; Route, R. K.; Feigelson, R. S.

1985-01-01

246

Towards automated biomedical ontology harmonization.  

PubMed

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

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

2014-01-01

247

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

248

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

249

Fuzzy Controller for Matrix Converter System to Improve its Quality of Output  

E-print Network

In this paper, Fuzzy Logic controller is developed for ac/ac Matrix Converter. Furthermore, Total Harmonic Distortion is reduced significantly. Space Vector Algorithm is a method to improve power quality of the converter output. But its quality is limited to 86.7%.We are introduced a Cross coupled DQ axis controller to improve power quality. The Matrix Converter is an attractive topology for High voltage transformation ratio. A Matlab / Simulink simulation analysis of the Matrix Converter system is provided. The design and implementation of fuzzy controlled Matrix Converter is described. This AC-AC system is proposed as an effective replacement for the conventional AC-DC-AC system which employs a two-step power conversion.

Mahendran, Nagalingam; 10.5121/ijaia.2010.1402

2010-01-01

250

The Effect of the Phosphor Particle Sizes on the Angular Homogeneity of Phosphor-Converted High-Power White LED Light Sources  

Microsoft Academic Search

Based on optical ray tracing, we discuss the effect of the phosphor particle sizes on the angular homogeneity of the light emitted from phosphor-converted LEDs. Since the blue LED and the yellow-converted light have rather different emission characteristics, which have to be harmonized to one another by the scattering processes within the color conversion element, the phosphor particle size turns

Christian Sommer; Joachim R. Krenn; Paul Hartmann; Peter Pachler; Marko Schweighart; Stefan Tasch; Franz P. Wenzl

2009-01-01

251

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

252

.../Chorum Technologies' Dr. J.C. Chiao to Present Paper On Liquid-Crystal Optical HarmonicPage 1 of 4 http://biz.yahoo.com/bw/010730/0446.html 8/22/2001  

E-print Network

of 4 http://biz.yahoo.com/bw/010730/0446.html 8/22/2001 Shell Platinum MasterCard [ Latest Headlines Finance Home - Yahoo! - Help Related Quotes ^DJI ^IXIC ^SPC ^IIX ^PSE 10206.87 1830.89 1160.08 138.03 632. J.C. Chiao to Present Paper On Liquid-Crystal Optical Harmoni Page 2 of 4 http://biz.yahoo

Chiao, Jung-Chih

253

Thermionic converters with microcavity electrodes in the cesium arc regime  

NASA Astrophysics Data System (ADS)

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

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

1990-06-01

254

can significantly improve the performance of colour-conversion In addition to applications as efficient colour converters, nano-  

E-print Network

as efficient colour converters, nano- crystals have been considered promising building blocks for colour in the regime of electrical injection by combining nano- crystals with an electrically driven InGaN quantum well of high-efficiency, electrically driven, hybrid nano- crystal/quantum-well devices. A Received 9 February

Pierrehumbert, Raymond

255

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

256

Harmonic sources and filtering approaches  

Microsoft Academic Search

This article presents 22 configurations of power filters for the harmonic compensation of nonlinear loads. Some of these configurations are novel and result from the newly discovered characteristics of nonlinear loads and circuitry duality, while the others are well known and used in practice. Nonlinear loads can be characterized into two types of harmonic sources: current-source nonlinear loads and voltage-source

F. Z. Peng

2001-01-01

257

High resolution switching mode inductance-to-frequency converter with temperature compensation.  

PubMed

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

Matko, Vojko; Milanovi?, Miro

2014-01-01

258

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

Microsoft Academic Search

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

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

2006-01-01

259

CRIME BULLETIN INCIDENT: Catalytic Converter Thefts  

E-print Network

CRIME BULLETIN C R I M E INCIDENT: Catalytic Converter Thefts DATE/TIME: 2/20/2013-2/27/2013, Various Times CONTACT: UCIPD Corporal B. Green (949) 824-5223 Catalytic converter Catalytic converter converters were stolen from various locations on the UC Irvine campus. The catalytic converters came from

Barrett, Jeffrey A.

260

High-field harmonic generation in helium  

SciTech Connect

We observe harmonics of 526-nm laser light up to the 45th order, 11.7 nm, in helium. We discuss the extension of the harmonic plateau with increasing laser intensity. The data suggest that the highest harmonic order produced depends on the highest intensity seen by the atom before photoionization. Harmonics are generated predominantly from neutrals. Harmonic generation from ions is weak owing to poor phase matching between the fundamental and harmonic fields at high electron densities.

Crane, J.K.; Perry, M.D.; Herman, S. (Laser Program, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States)); Falcone, R.W. (Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States))

1992-09-15

261

Converting Petroleum Coke to Electricity  

E-print Network

. This paper presents the operating history of US based plants converting petroleum coke to electricity, and presents generic economics for the conversion process utilizing three primary technologies available: conventional pulverized coke combustion...

Pavone, A.

262

Radiant energy to electric energy converter  

NASA Technical Reports Server (NTRS)

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

Sher, Arden (Inventor)

1980-01-01

263

Third-harmonic generation of intense laser pulses  

NASA Astrophysics Data System (ADS)

In this thesis, third harmonic generation of ultrashort pulses and the related phenomena have been studied experimentally and theoretically. The third harmonic conversion of 1.6 ps pulses at 1053 nm were performed with the Chirped-Pulse-Amplification (CPA) laser system using two type II KDP crystals, one for frequency doubling and another one for frequency tripling. Conversion efficiencies of 60-65% was achieved from frequency doubling and that of 45-50% was achieved for frequency tripling at input pulse intensities of 50-100 GW/cm2. Our experimental study also showed the importance of the self- and cross-phase modulation effects in the frequency tripling process. The self-phase modulation coefficients in KDP crystals at wavelengths of 1.053 ?m, 0.527 ?m and 0.351 ?m were measured using single beam Z-scan technique. The cross-phase modulation coefficients between 1.053 ?m and 0.527 ?m were also measured by a two color z-scan. These coefficients are used in the theoretical simulation of frequency conversion of ultrafast pulses. It is important to know the direction of the crystals axis relative to the propagation direction of the laser to optimize the phase matching for harmonic generations. The orientation of the optical axis in the crystal determines the spatial and temporal walk-off between the ordinary (o) and extraordinary (e) waves. Frequency domain interferometry has been used to measure the group velocity walk-off (GVW) between the ordinary and extraordinary waves in uniaxial crystals. The dependence of the interference fringe spacing and the walk-off on incident angle with respect to the birefringent crystal were measured in KDP and the direction of the optical axis was determined.

Zheng, Lily Li

1997-07-01

264

Thermoionic converter for space Reactor  

Microsoft Academic Search

Thermionic converters offer many advantages for use as space reactors. Over the last several years, six experiments were performed, of which four were in-pile experiments and two out-pile experiments. Of the four in-pile experiments, three involved the use of three converters linked in series. The use of nuclear reactors as the power source for an electrical system in space is

Shengquan Cao; Jicai Yang

1990-01-01

265

Synchronous Discrete Harmonic Oscillator  

SciTech Connect

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

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

2008-10-17

266

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

267

Energy-Sampled Data Modeling of a Cascade H-Bridge Multilevel Converter for Grid-connected PV Systems  

Microsoft Academic Search

This paper presents an energy-sampled data model of a cascade H-bridge multilevel converter for single-phase multi-string grid-connected photovoltaic systems. Based on this model a control scheme for the power converter is obtained. The achievement of the DC-AC conversion with an efficient PV energy extraction, low harmonic distortion and output unity power factor is validated with simulation results

J. J. Negroni; F. Guinjoan; C. Meza; D. Biel; P. Sanchis

2006-01-01

268

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

Microsoft Academic Search

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

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

2008-01-01

269

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

E-print Network

the origin and causes of harmonics, the bad effects of harmonics, the acceptable harmonic distortion limits in the telecommunication power system and the best methods for harmonic detection and mitigation. DEFINING THE PROBLEM Harmonics are currents...POWER QUALITY/HARMONIC DETECTION: HARMoNIc CONTROL IN ELECTRIC POWER SYSTEMS FOR THE TELECOMMUNICATIONS INDUSTRY J. L. "Jim" Felkner Power Equipment Engineer MCI Communications Corporation Richardson, Texas 75082 ABSTRACT The control...

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

270

Growth, characterization, vibrational spectroscopic and thermal studies of a new metallorganic non-linear optical crystal—Bisthiourea cadmium bromide  

NASA Astrophysics Data System (ADS)

Single crystals of bisthiourea cadmium bromide (BTCB), a new metallorganic material crystallizing in orthorhombic system were grown from slow evaporation solution growth. The grown crystals were characterized by X-ray diffraction, FTIR and FT-Raman spectral studies. The crystals were also subjected to TGA/DTA analysis and second harmonic generation test. The transmission characteristics of the crystal was also studied.

Ramachandraraja, C.; Sundararajan, R. S.

2008-12-01

271

Approximations to toroidal harmonics  

SciTech Connect

Toroidal harmonics P/sub n-1/2/ (cosh ) and Q/sub n-1/2/ (cosh ) are useful in solutions to Maxwell's equations in toroidal coordinates. In order to speed their computation, a set of approximations has been developed that is valid over the range 0 < < infinity. The functional form used for these approximations is dictated by their behavior as 0 and as infinity, and is similar to that used by Hastings in his approximations to the elliptic integrals K and E. This report lists approximations of several mathematical forms with varying numbers of terms; approximations to the above Legendre functions are given for n = 0 through 6. Coefficients of each expansion have been adjusted to distribute the relative error in equi-amplitude peaks over some range, typically .05 < < 5, and in the best cases these peaks are less than 10 . The simple method used to determine the approximations is described. Relative error curves are also presented, obtained by comparing approximations to the more accurate values computed by direct summation of the hypergeometric series.

Pribyl, P.A.

1985-10-01

272

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

273

Harmonic analysis of electrical distribution systems  

SciTech Connect

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

NONE

1996-03-01

274

Harmonic functions over group actions Renato Feres  

E-print Network

Harmonic functions over group actions Renato Feres Washington University Renato Feres Washington University () Harmonic functions over group actions 1 / 25 #12;Topics: Harmonic functions and random walks on discrete groups The Liouville property and Poisson boundary Harmonic functions over group actions Examples

Feres, Renato

275

HARMONIC TWOSPHERES IN COMPACT SYMMETRIC SPACES, REVISITED  

E-print Network

HARMONIC TWO­SPHERES IN COMPACT SYMMETRIC SPACES, REVISITED F. E. Burstall and M. A. Guest Introduction The purpose of this article is to give a new description of harmonic maps from the two­sphere S 2 of such harmonic maps occur when G=K = S n or CP n . In 1967, E. Calabi gave a construction of all harmonic maps

Bath, University of

276

Harmonic Broadcasting Is Optimal Lars Engebretsen  

E-print Network

Harmonic Broadcasting Is Optimal Lars Engebretsen Madhu Sudan Abstract Harmonic broadcasting-on-demand broadcasting. In this paper, we note that harmonic broadcasting is actually a special case of the priority argument--that it is impossible to achieve the design goals of harmonic broadcasting using a shorter

Sudan, Madhu

277

High Harmonic Generation Physics 208A Presentation  

E-print Network

High Harmonic Generation Physics 208A Presentation October 11, 2004 Tom Allison UC Berkeley #12 to Fourier components of the polarization at harmonics of the laser frequency, creating radiation at harmonics of the laser frequency. #12;· First demonstration of second harmonic generation by P.A. Franken et

Budker, Dmitry

278

On The Harmonic Oscillator Group  

E-print Network

We discuss the maximum kinematical invariance group of the quantum harmonic oscillator from a view point of the Ermakov-type system. A six parameter family of the square integrable oscillator wave functions, which seems cannot be obtained by the standard separation of variables, is presented as an example. The invariance group of generalized driven harmonic oscillator is shown to be isomorphic to the corresponding Schroedinger group of the free particle.

Raquel M. Lopez; Sergei K. Suslov; Jose M. Vega-Guzman

2011-12-04

279

Echo-Enabled Harmonic Generation  

SciTech Connect

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

Stupakov, Gennady; /SLAC

2012-06-28

280

Azimuthal anisotropy: The higher harmonics  

SciTech Connect

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

Poskanzer, Arthur M.; STAR Collaboration

2004-03-12

281

High efficiency thermionic converter studies  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

282

Stirling Converters For Solar Power  

NASA Technical Reports Server (NTRS)

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

Shaltens, Richard K.; Schreiber, Jeffrey G.

1993-01-01

283

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

284

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

285

Topological constraints on basic PWM converters  

Microsoft Academic Search

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

Kwang-Hwa Liu; F. C. Lee

1988-01-01

286

Integrated magnetic for LLC resonant converter  

Microsoft Academic Search

A new LLC resonant converter is proposed for front end DC\\/DC conversion in a distributed power system. This converter shows some potential benefits in this application. This paper proposes several integrated magnetic designs for LLC resonant converter. This converter has three magnetic components. With magnetic integration, first, a number of components can be reduced; secondly, flux ripple cancellation is achieved

Bo Yang; Rengang Chen; Fred C. Lee

2002-01-01

287

PWM Resonant Single-Switch Isolated Converter  

Microsoft Academic Search

The flyback converter is one of the most attractive isolated converters in small power applications because of its simple structure. However, it suffers from a high device stress and a large transformer size. To relieve these drawbacks, a high-efficient pulsewidth modulation resonant single-switch isolated converter is proposed. The proposed converter derives the power using the resonance between transformer leakage inductor

Ki-Bum Park; Chong-Eun Kim; Gun-Woo Moon; Myung-Joong Youn

2009-01-01

288

Harmonic Contribution Evaluation using Independent Component Analysis  

NASA Astrophysics Data System (ADS)

The widespread use of power electronic devices caused the harmonic pollution in power systems. However, it is difficult to determine customer and utility responsibility for harmonic distortion at the point of common coupling (PCC). In this letter, we propose a method to evaluate harmonic contribution at the PCC using independent component analysis (ICA). This method can evaluate the true harmonic contribution of utility and customer without estimating the harmonic impedance.

Lian, Suo; Ito, Daisuke; Takayama, Satoshi; Ishigame, Atsushi; Kitagawa, Masahiro; Katayama, Kousaku; Nakatani, Hideyuki; Takeuchi, Masayasu

289

Solid oxygen as converter for the production of ultra-cold neutrons  

E-print Network

We have investigated solid oxygen as a converter material for the production of ultra-cold neutrons. In a first series of experiments the crystal preparation was examined. An optically semi-transparent solid $\\alpha$-oxygen crystal has been prepared. In a second series of experiments such a crystal prepared indentically as in the first series of experiments has been exposed to the cold neutron flux of the MEPHISTO beam line of the FRM II. Ultra-cold neutrons produced inside the oxygen crystal have been extracted and the count rates have been measured at different converter temperatures. The results of these measurements give a clear signal of the superthermal UCN production mechanism in $\\alpha$-oxygen. The mean free loss length of UCN inside the crystal at a temperature of 5\\,K was determined to be in the order of $20\\,\\mathrm{cm}$.

A. Frei; F. Böhle; R. Bozhanova; E. Gutsmiedl; T. Huber; J. Klenke; S. Paul; S. Wlokka

2011-07-11

290

Multilevel converters for power system applications  

SciTech Connect

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

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

1995-09-01

291

A novel modular approach to active power-line harmonic filtering in distribution systems  

NASA Astrophysics Data System (ADS)

The objective of this research is to develop an efficient and reliable modular active harmonic filter system to realize a cost-effective solution to the harmonic problem. The proposed filter system consists of a number CSC modules, each dedicated to filter a specific harmonic of choice (Frequency-Splitting Approach). The power rating of the modules will decrease and their switching frequency will increase as the order of the harmonic to be filtered is increased. The overall switching losses are minimized due to the selected harmonic elimination and balanced a "power rating"-"switching frequency" product. Two ADALINEs are proposed as a part of the filter controller for processing the signals obtained from the power-line. One ADALINE (the Current ADALINE) extracts the fundamental and harmonic components of the distorted current. The other ADALINE (the Voltage ADALINE) estimates the line voltage. The outputs of both ADALINEs are used to construct the modulating signals of the filter modules. The proposed controller decides which CSC filter module(s) is connected to the electric grid. The automated connection of the corresponding filter module(s) is based on decision-making rules in such a way that the IEEE 519-1992 limits are not violated. The information available on the magnitude of each harmonic component allows us to select the active filter bandwidth (i.e., the highest harmonic to be suppressed). This will result in more efficiency and higher performance. The proposed controller adjusts the I dc in each CSC module according to the present magnitude of the corresponding harmonic current. This results in optimum dc-side current value and minimal converter losses. The comparison of the proposed modular active filter scheme and the conventional one converter scheme on practical use in industry is presented. This comparison shows that the proposed solution is more economical, reliable and flexible compared to conventional one. High speed and accuracy of ADALINE, self-synchronizing harmonic tracking, intelligence and robustness of the controller, optimum Idc value, minimal converter losses, and high speed and low dc energy requirement of the CSC, are the main features of the proposed active filter system. Simulation results using the EMTDC simulation package are presented to validate the effectiveness of the proposed modular active filter system. (Abstract shortened by UMI.)

El Shatshat, Ramadan A.

292

Charge-pump voltage converter  

DOEpatents

A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

Brainard, John P. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2009-11-03

293

A novel interferometric wavelength converter  

Microsoft Academic Search

The fiber Kerr effect employment in a wavelength conversion version, owing to low silica nonlinearity, has been prevented by the lack of an efficient interferometric architecture. A novel all-fiber wavelength converter is presented and characterized. The proposed scheme while taking advantage of the Kerr effect properties in standard communication optical fiber overcomes classical interferometric structure limitations, such as high environmental

Pierpaolo Boffi; Lucia Marazzi; Mario Martinelli

1999-01-01

294

State controller for buck converter  

Microsoft Academic Search

The average state space model of the buck converter has been used in order to design the PI and state controller. Simple analytical expressions in terms of the circuit components are derived for frequency responses of time averaged (continuous) power-stage for use in designing and understanding the behavior of corresponding switched power stage. Such obtained models enable the designing of

Suzana Uran; M. Milanovic

2003-01-01

295

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

Microsoft Academic Search

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

J. S. Kim; S. K. Sul

1993-01-01

296

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

Microsoft Academic Search

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

Andrew C. Wang; Seth R. Sanders

1993-01-01

297

Design and Implementation of a Single-Stage LLC Resonant Converter with High Power Factor  

Microsoft Academic Search

A zero voltage switching (ZVS) based on LLC resonant topology is proposed to implement a single-stage ac\\/dc converter which performs both input-current harmonics reduction and power factor correction (PFC). By integrating a boost-PFC cell and an LLC resonant dc\\/dc cell into a single power conversion stage, the power losses in the secondary rectifier diodes and the primary switches can be

Ching-Ming Lai; Rong-Chyang Lee; Te-Wei Wang; Kuo-Kai Shyu

2007-01-01

298

Analysis, modeling, and simulation of series-parallel resonant converter circuits  

Microsoft Academic Search

This paper presents a SPICE macromodel for a generic series-parallel resonant converter circuit. The model is derived from the averaged time-invariant state-space equations obtained from a Fourier transform. The conditions are derived under which all but the fundamental harmonic may be discarded, and the model developed based solely on the fundamental Fourier component. The single macromodel developed has a wide

Siu-Chung Wong; Andrew D. Brown

1995-01-01

299

A novel class of multipulse converters based on high-frequency-operated transformers  

Microsoft Academic Search

This paper presents a novel class of multipulse converter based on high-frequency-operated multipulse transformers. Utility line currents are 12-pulse in nature with the cancellation of 5th and 7th harmonic components. The method demonstrates a considerable reduction in size and weight of the multipulse transformer, due to higher frequency operation. Furthermore, the magnetic components on the rectifier dc sides are also

Sheng Zheng; Dong Chen; Hai Lin; Yousheng Wang; Zhaoming Qian; Fang Z. Peng

2010-01-01

300

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

301

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

302

Portable convertible blast effects shield  

DOEpatents

A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more frusto-conically-tapered telescoping rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration by the friction fit of adjacent pairs of frusto-conically-tapered rings to each other.

Pastrnak, John W. (Livermore, CA); Hollaway, Rocky (Modesto, CA); Henning, Carl D. (Livermore, CA); Deteresa, Steve (Livermore, CA); Grundler, Walter (Hayward, CA); Hagler, Lisle B. (Berkeley, CA); Kokko, Edwin (Dublin, CA); Switzer, Vernon A. (Livermore, CA)

2011-03-15

303

Reducing catalytic converter pressure loss  

SciTech Connect

This article examines why approximately 30--40% of total exhaust-system pressure loss occurs in the catalytic converter and what can be done to reduce pressure loss. High exhaust-system backpressure is of concern in the design of power trains for passenger cars and trucks because it penalizes fuel economy and limits peak power. Pressure losses occur due to fluid shear and turning during turbulent flow in the converter headers and in entry separation and developing laminar-flow boundary layers within the substrate flow passages. Some of the loss mechanisms are coupled. For example, losses in the inlet header are influenced by the presence of the flow resistance of a downstream substrate. Conversely, the flow maldistribution and pressure loss of the substrate(s) depend on the design of the inlet header.

NONE

1996-06-01

304

Portable convertible blast effects shield  

SciTech Connect

A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more telescoping cylindrical rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration, such as by click locks.

Pastrnak, John W. (Livermore, CA); Hollaway, Rocky (Modesto, CA); Henning, Carl D. (Livermore, CA); Deteresa, Steve (Livermore, CA); Grundler, Walter (Hayward, CA); Hagler,; Lisle B. (Berkeley, CA); Kokko, Edwin (Dublin, CA); Switzer, Vernon A (Livermore, CA)

2010-10-26

305

Portable convertible blast effects shield  

DOEpatents

A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more telescoping cylindrical rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration, such as by click locks.

Pastrnak, John W. (Livermore, CA); Hollaway, Rocky (Modesto, CA); Henning, Carl D. (Livermore, CA); Deteresa, Steve (Livermore, CA); Grundler, Walter (Hayward, CA); Hagler, Lisle B. (Berkeley, CA); Kokko, Edwin (Dublin, CA); Switzer, Vernon A (Livermore, CA)

2007-05-22

306

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

307

Microenergy Converter Using Insect Wings  

Microsoft Academic Search

This paper is concerned with the development of novel type of micro wind energy converter using insect wings. A series of\\u000a experimental studies are made on the function of wing apparatus of flying insects. In the first place, the structural properties\\u000a of insect wings are studied through measurements of certain morphological parameters. The scanning electron microscopic observation\\u000a of an insect

Seiichi Sudo; Kazumasa Nashimoto; Koji Tsuyuki; Tetsuya Yano; Muneo Futamura

308

Green phosphor-converted LED  

Microsoft Academic Search

Green phosphor-converted LEDs using a blue pump InGaN diodes have advantages over the direct green InGaN LED with regards to color stability with drive and\\/or temperature. Added manufacturing steps are outweighed by higher color yield, as a range of pump colors can be used without changing the final chromaticity. The conversion losses can be smaller than the decrease in wall-plug

Regina Mueller-Mach; Gerd O. Mueller; Troy A. Trottier; Michael R. Krames; A. Kim; Dan A. Steigerwald

2002-01-01

309

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

310

Harmonic Balance Computations of Fan Aeroelastic Stability  

NASA Technical Reports Server (NTRS)

A harmonic balance (HB) aeroelastic analysis, which has been recently developed, was used to determine the aeroelastic stability (flutter) characteristics of an experimental fan. To assess the numerical accuracy of this HB aeroelastic analysis, a time-domain aeroelastic analysis was also used to determine the aeroelastic stability characteristics of the same fan. Both of these three-dimensional analysis codes model the unsteady flowfield due to blade vibrations using the Reynolds-averaged Navier-Stokes (RANS) equations. In the HB analysis, the unsteady flow equations are converted to a HB form and solved using a pseudo-time marching method. In the time-domain analysis, the unsteady flow equations are solved using an implicit time-marching approach. Steady and unsteady computations for two vibration modes were carried out at two rotational speeds: 100 percent (design) and 70 percent (part-speed). The steady and unsteady results obtained from the two analysis methods compare well, thus verifying the recently developed HB aeroelastic analysis. Based on the results, the experimental fan was found to have no aeroelastic instability (flutter) at the conditions examined in this study.

Bakhle, Milind A.; Reddy, T. S. R.

2010-01-01

311

Growth and characterization of large CLBO crystals  

NASA Astrophysics Data System (ADS)

A high optical quality Cesium lithium borate (CLBO) crystal with dimensions of 146×132×118 mm was grown by the Kyropoulos method. The 4th harmonic generation of a frequency doubled Nd:YAG laser, from 532 to 266 nm, was carried out with a CLBO crystal doubler, and an average output power of 28.4 W was achieved at 266 nm. Polished surfaces were etched to reveal the cracking mechanism of CLBO crystals. Through observation and comparison of the surface etching patterns, it is proved that CLBO crystals crack under chemical attack by water molecules penetrating from the (1 0 0) and (0 1 0) crystallographic planes.

Yuan, Xin; Shen, Guangqiu; Wang, Xiaoqing; Shen, Dezhong; Wang, Guiling; Xu, Zuyan

2006-07-01

312

High efficiency thermionic converter studies  

NASA Technical Reports Server (NTRS)

The objective is to improve thermionic converter performance by means of reduced interelectrode losses, greater emitter capabilities, and lower collector work functions until the converter performance level is suitable for out-of-core space reactors and radioisotope generators. Electrode screening experiments have identified several promising collector materials. Back emission work function measurements of a ZnO collector in a thermionic diode have given values less than 1.3 eV. Diode tests were conducted over the range of temperatures of interest for space power applications. Enhanced mode converter experiments have included triodes operated in both the surface ionization and plasmatron modes. Pulsed triodes were studied as a function of pulse length, pulse potential, inert gas fill pressure, cesium pressure, spacing, emitter temperature and collector temperature. Current amplifications (i.e., mean output current/mean grid current) of several hundred were observed up to output current densities of one amp/sq cm. These data correspond to an equivalent arc drop less than 0.1 eV.

Huffman, F. N.; Sommer, A. H.; Balestra, C. L.; Briere, D. P.; Oettinger, P. E.

1976-01-01

313

Ga{sub x}In{sub 1{minus}x}As thermophotovoltaic converters  

SciTech Connect

Preliminary research into the development of single-junction Ga{sub x}In{sub 1{minus}x}As thermophotovoltaic (TPV) power converters is reviewed. The devices structures are grown epitaxially on single-crystal InP substrates. Converter band gaps of 0.50--0.74 eV have been considered in accordance with modeling calculations. A 1-sun, AMO efficiency of 12.8% is reported for a lattice-matched, 0.74-eV converter. Converters with lower band gaps are fabricated using lattice-mismatched, compositionally graded structures. Functional TPV converters with good performance characteristics have been demonstrated for band gaps as low as 0.5 eV.

Wanlass, M.W.; Ward, J.S.; Emery, K.A.; Coutts, T.J. [National Renewable Energy Lab., Golden, CO (United States)

1994-12-31

314

Sharp bounds for harmonic numbers  

E-print Network

In the paper, we first survey some results on inequalities for bounding harmonic numbers or Euler-Mascheroni constant, and then we establish a new sharp double inequality for bounding harmonic numbers as follows: For $n\\in\\mathbb{N}$, the double inequality -\\frac{1}{12n^2+{2(7-12\\gamma)}/{(2\\gamma-1)}}\\le H(n)-\\ln n-\\frac1{2n}-\\gamma<-\\frac{1}{12n^2+6/5} is valid, with equality in the left-hand side only when $n=1$, where the scalars $\\frac{2(7-12\\gamma)}{2\\gamma-1}$ and $\\frac65$ are the best possible.

Qi, Feng

2010-01-01

315

Synthesis, crystal growth and characterization of glycine lithium sulphate  

NASA Astrophysics Data System (ADS)

Glycine lithium sulphate (GLS) single crystals of size 12 mm×6 mm×4 mm have been grown by slow evaporation technique at ambient temperature from aqueous solution of glycine and lithium sulphate. The grown crystals were characterized by FTIR, single crystal X-ray diffraction and powder X-ray diffraction techniques. The GLS crystallizes in noncetrosymmetric structure, which is an essential criterion for second harmonic generation. The GLS crystal is thermally stable up to 283 °C. The GLS crystal shows better hardness value compared to ?-glycine. The lower optical cutoff for this crystal was observed at 228 nm. The second harmonic conversion efficiency of GLS was determined using Kurtz and Perry technique and was found to be two times greater than that of KDP.

Suresh Kumar, M. R.; Ravindra, H. J.; Dharmaprakash, S. M.

2007-08-01

316

Resonant third harmonic generation of KrF laser in Ar gas.  

PubMed

Investigations of emission of harmonics from argon gas jet irradiated by 700 fs, 5 mJ pulses from a KrF laser are presented. Harmonics conversion was optimized by varying the experimental geometry and the nozzle size. For the collection of the harmonic radiation silicon and solar-blind diamond semiconductor detectors equipped with charge preamplifiers were applied. The possibility of using a single-crystal CVD diamond detector for separate measurement of the 3rd harmonic in the presence of a strong pumping radiation was explored. Our experiments show that the earlier suggested 0.7% conversion efficiency can really be obtained, but only in the case when phase matching is optimized with an elongated gas target length corresponding to the length of coherence. PMID:25554270

Rakowski, R; Barna, A; Suta, T; Bohus, J; Földes, I B; Szatmári, S; Miko?ajczyk, J; Bartnik, A; Fiedorowicz, H; Verona, C; Verona Rinati, G; Margarone, D; Nowak, T; Rosi?ski, M; Ry?, L

2014-12-01

317

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

PubMed

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

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

2011-11-21

318

Resonant third harmonic generation of KrF laser in Ar gas  

NASA Astrophysics Data System (ADS)

Investigations of emission of harmonics from argon gas jet irradiated by 700 fs, 5 mJ pulses from a KrF laser are presented. Harmonics conversion was optimized by varying the experimental geometry and the nozzle size. For the collection of the harmonic radiation silicon and solar-blind diamond semiconductor detectors equipped with charge preamplifiers were applied. The possibility of using a single-crystal CVD diamond detector for separate measurement of the 3rd harmonic in the presence of a strong pumping radiation was explored. Our experiments show that the earlier suggested 0.7% conversion efficiency can really be obtained, but only in the case when phase matching is optimized with an elongated gas target length corresponding to the length of coherence.

Rakowski, R.; Barna, A.; Suta, T.; Bohus, J.; Földes, I. B.; Szatmári, S.; Miko?ajczyk, J.; Bartnik, A.; Fiedorowicz, H.; Verona, C.; Verona Rinati, G.; Margarone, D.; Nowak, T.; Rosi?ski, M.; Ry?, L.

2014-12-01

319

Active optoelectronic system for stabilizing pulsed laser output energy at the fourth-harmonic frequency  

NASA Astrophysics Data System (ADS)

A feedback loop using an optoelectronic system has been tested successfully for the stabilization of the output energy at the fourth-harmonic frequency of a Nd-YAG laser (266 nm). The system presented includes an optical device to monitor the laser output energy at the nonconverted wavelengths and an electronic circuitry to optimize the laser output energy at the fourth-harmonic frequency, via real-time correction of the frequency quadrupling laser crystal angle with respect to the input beam. Results show that the present system provides a laser output energy stability better than +/- 15 percent for a long-term operation at the fourth-harmonic frequency, and keeps the locking even during the warming phase, immediately after the laser turning on. This system was designed for automatic lidar operations in field experiments, but its principle of operation is applicable to any type of harmonic generator for either solid-state or dye laser.

Papayannis, A.; Ancellet, G.; Conrad, J. L.; Laqui, C.; Pelon, J.

1993-03-01

320

Experimental results of two stage harmonic generation with picosecond pulses on the Stanford Mark III FEL  

NASA Astrophysics Data System (ADS)

We report experimental results on upper harmonic conversion using a lithium niobate and a beta barium borate crystal to quadruple the FEL light up into the visible and near infrared. The effects of finite linewidth, birefingent walk-off, and group velocity walk-off on conversion efficiency will be discussed with reference to the experimental results.

Hooper, Brett A.; Benson, Stephen V.; Cutolo, Antonello; Madey, John M. J.

1988-10-01

321

Experimental results of two stage harmonic generation with picosecond pulses on the Stanford Mark III FEL  

Microsoft Academic Search

We report experimental results on upper harmonic conversion using a lithium niobate and a beta barium borate crystal to quadruple the FEL light up into the visible and near infrared. The effects of finite linewidth, birefingent walk-off, and group velocity walk-off on conversion efficiency will be discussed with reference to the experimental results.

Brett A. Hooper; Stephen V. Benson; Antonello Cutolo; John M. J. Madey

1988-01-01

322

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

323

Design, Control, and Modeling of a New Voltage Source Converter for HVDC System  

NASA Astrophysics Data System (ADS)

Abstract: A New Voltage Source Converter (VSC) based on neutral clamped three-level circuit is proposed for High Voltage DC (HVDC) system. The proposed VSC is designed in a multipulse configuration. The converter is operated by Fundamental Frequency Switching (FFS). A new control method is developed for achieving all the necessary control aspects of HVDC system such as independent real and reactive power control, bidirectional real and reactive power control. The basic of the control method is varying the pulse width and by keeping the dc link voltage constant. The steady state and dynamic performances of HVDC system interconnecting two different frequencies network are demonstrated for active and reactive power control. Total number of transformers used in this system are reduced to half in comparison with the two-level VSCs for both active and reactive power control. The performance of the HVDC system is improved in terms of reduced harmonics level even at fundamental frequency switching. The harmonic performance of the designed converter is also studied for different value of the dead angle (?), and the optimized range of the dead angle is achieved for varying reactive power requirement. Simulation results are presented for the designed three level multipulse voltage source converters with the proposed control algorithm.

Mohan, Madhan; Singh, Bhim; Ketan Panigrahi, Bijaya

2013-05-01

324

Photoresponsive Polymers: Converting Light to Mechanical Work  

NASA Astrophysics Data System (ADS)

The ability to remotely control the creation of mechanical work, rapidly, with high spatial precision, and over long distances, offers many intriguing possibilities. Whether driving direct conformational changes, initiating reversible chemical reactions to release stored strain, or converting the photon to a local temperature increase, combinations of photoactive units, nanoparticles, ordered mesophases and polymeric networks are providing an expansive array of photo-responsive polymer options. By combining these material responses with kinematic concepts, mechanical devices can be demonstrated that exhibiting tunable and controllable macroscopic deformation, high-frequency oscillation or directional motion. Specifically, we will discuss recent investigation of liquid crystal polymer networks containing main chain and pendent azobenzene moieties (azo-LCN) with modulus ˜1.3GPa that are actuated at the absorptive overlap of the cis and trans confirmers (442 nm). Cantilevers and unconstrained beams of these azo-LCNs can be controlled by polarization angle of the source, as well as by a specific optical exposure history (on-off), with responses ranging from lateral motion to oscillations in excess of 30Hz. These phenomena reflect an underlying interaction between the mesophase order, the network architecture and kinematic constraints of the exposed material. In collaboration with Timothy Bunning, Timothy White, Hilmar Koerner, Air Force Research Laboratory; and Nelson Tabiryan, BEAM Co.

Vaia, Richard A.

2009-03-01

325

Large wind energy converter: Growian 3 MW  

NASA Technical Reports Server (NTRS)

The main features of the Growian wind energy converter are presented. Energy yield, environmental impact, and construction of the energy converter are discussed. Reliability of the windpowered system is assessed.

Koerber, F.; Thiele, H. A.

1979-01-01

326

Harmonic algebraic curves and noncrossing partitions  

E-print Network

Motivated by Gauss’s first proof of the fundamental Theorem of Algebra, we study the topology of harmonic algebraic curves. By the maximum principle, a harmonic curve has no bounded components; its topology is determined by the combinatorial data...

Martin, Jeremy L.; Savitt, David; Singer, Ted

2007-02-01

327

Low work function silicon collector for thermionic converters  

NASA Technical Reports Server (NTRS)

To improve the efficiency of present thermionic converters, single crystal silicon was investigated as a low work function collector material. The experiments were conducted in a test vehicle which resembled an actual thermionic converter. Work function as low as 1.0eV was obtained with an n-type silicon. The stabilities of the activated surfaces at elevated temperatures were tested by raising the collector temperature up to 829 K. By increasing the Cs arrival rate, it was possible to restore the originally activated low work function of the surface at elevated surface temperatures. These results, plotted in the form of Rasor-Warner curve, show a behavior similar to that of metal electrode except that the minimum work function was much lower with silicon than with metals.

Chang, K. H.; Shimada, K.

1976-01-01

328

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

329

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

330

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

331

Reduced Harmonic Representation of Partitions  

E-print Network

In the present article the reduced integral representation of partitions in terms of harmonic products has been derived first by using hypergeometry and the new concept of fractional sum and secondly by studying the Fourier series of the kernel function appearing in the integral representation. Using the method of induction, a generalization of the theory has also been obtained.

Michalis Psimopoulos

2011-03-08

332

Web Assignments: Harmonic Oscillator I  

NSDL National Science Digital Library

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

Walkup, John

2008-11-23

333

Strings, standing waves and harmonics  

NSDL National Science Digital Library

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

Wolfe, Joe

2009-11-16

334

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

335

Harmonic filtering for offshore industry  

Microsoft Academic Search

The application of a large number of Adjustable Speed Drives (ASDs) operating Electric Submersible Pumps (ESPs) on two separate offshore platforms, connected to a limited electrical power system on a tanker feeding power to the platforms via subsea power cables, presents technical problems involving high levels of harmonic distortions that experience shows can impact the overall system reliability. Here such

S. J. Merhej; W. H. Nichols

2009-01-01

336

Harmonic undulator radiations with constant magnetic field  

NASA Astrophysics Data System (ADS)

Harmonic undulators has been analysed in the presence of constant magnetic field along the direction of main undulator field. The spectrum modifications in harmonic undulator radiations and intensity degradation as a function of constant magnetic field magnitude at fundamental and third harmonics have been evaluated with a numerical integration method and generalised Bessel function. The role of harmonic field to overcome the intensity reduction due to constant magnetic field and energy spread in electron beam has also been demonstrated.

Jeevakhan, Hussain; Mishra, G.

2015-01-01

337

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

338

Harmonic Morphisms from Homogeneous Spaces -Some Existence Theory -  

E-print Network

Harmonic Morphisms from Homogeneous Spaces - Some Existence Theory - Sigmundur Gudmundsson 2014 #12;Harmonic Morphisms Eigenfamilies - Constructions Orthogonal Harmonic Families - Constructions Low-Dimensional Classifications References Outline 1 Harmonic Morphisms Basics Geometric Motivation

Gudmundsson, Sigmundur

339

A Carrier-Phase Control Suitable for Conducted EMI Noise Reduction in a Multiple-Converter System  

NASA Astrophysics Data System (ADS)

Conducted EMI noise flowing from the power converters to AC utility line is regulated by international commissions such as International Electrotechnical Commission (IEC). For adherence to the IEC regulations, EMI filters should be used in power electronics equipment. This paper proposes a method for analyzing the conducted EMI noise in multiple power converters connected to the same power line. In this method, the phase difference between sub-harmonic modulated carrier signals at each power converter is taken into account. The phase difference among the power converters determines the EMI noise level in a multiple-converter system, as is evident from the analysis of the waveform of the common-mode current. In addition, EMI noise suppression using a carrier-phase control is a proposed. In order to reduce volume of the EMI filter effectively, the phase difference ? should be set to 360/nN° here, n is a high-order harmonic component at around 150kHz, and N is the number of power converters. Therefore, the conducted EMI noise can be reduced effectively with the help of the proposed phase control.

Tamate, Michio; Toba, Akio; Matsumoto, Yasushi; Wada, Keiji; Shimizu, Toshihisa

340

Poisson harmonic forms, Kostant harmonic forms, and the S 1 equivariant cohomology of K/T  

E-print Network

Poisson harmonic forms, Kostant harmonic forms, and the S 1 ­equivariant cohomology of K/T Sam Abstract We characterize the harmonic forms on a flag manifold K/T defined by Kostant in 1963 in terms of a Poisson structure. Namely, they are ``Poisson harmonic'' with respect to the so­called Bruhat Poisson

Evens, Sam

341

Crystal Creations.  

ERIC Educational Resources Information Center

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

Whipple, Nona; Whitmore, Sherry

1989-01-01

342

Light-off behavior of catalytic converters  

Microsoft Academic Search

This paper studies a system of partial differential equations modeling the behavior of an automotive catalytic converter. The particular phenomenon considered in detail is light-off, when the temperature of the converter changes dramatically from cold to hot somewhere within the converter. The initial position of light-off and the subsequent movement of this steep jump in temperature toward the inlet of

P. S. Hagan; D. W. Schwendeman

1994-01-01

343

COMMUNITY ALERT INCIDENT: Catalytic Converter Thefts  

E-print Network

COMMUNITY ALERT C R I M E INCIDENT: Catalytic Converter Thefts DETAILS: There has been a recent series of catalytic converter thefts from vehicles in parking lots adjacent to campus housing communities. The suspect(s) typically go underneath the victim's vehicle to steal the catalytic converter. A catalytic

Rose, Michael R.

344

Compact HVDC converter station design considerations  

Microsoft Academic Search

In this paper, the possible means to reduce HVDC converter station land area requirements are shown. The split-up of real estate between the different kinds of equipment in present-day terminals is analysed. From this, a priority list for suitable action to be taken is deducted. Three concepts of converter valves suitable for compact converter stations are briefly discussed. By example

P. Lips

1976-01-01

345

Acoustics of automotive catalytic converter assemblies  

Microsoft Academic Search

In an automotive exhaust system, the purpose of the catalytic converter is to reduce pollutant emissions. However, catalytic converters also affect the engine and exhaust system breathing characteristics; they increase backpressure, affect exhaust system acoustic characteristics, and contribute to exhaust manifold tuning. Thus, radiated sound models should include catalytic converters since they can affect both the source characteristics and the

Nolan S. Dickey; Ahmet Selamet; Steve J. Parks; Kevin V. Tallio; Keith D. Miazgowicz; Paul M. Radavich

2003-01-01

346

Auxiliary resonant DC tank converter  

DOEpatents

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

Peng, Fang Z. (Knoxville, TN)

2000-01-01

347

Thermodynamic integration at constant pressure from the nonlocal Einstein crystal  

NASA Astrophysics Data System (ADS)

The Gibbs free energy of a periodic, d-dimensional crystalline assembly can be estimated using thermodynamic integration at constant pressure from a nonlocal Einstein crystal. The method is demonstrated using a two-dimensional, harmonic crystal with hexagonal symmetry for which the isobaric Gibbs function can be derived analytically.

Lusk, Mark T.

2004-12-01

348

Harmonic bundles, topological-antitopological fusion  

E-print Network

Harmonic bundles, topological-antitopological fusion and the related pluriharmonic maps Lars Sch generalize the notion of a harmonic bundle of Simpson [Si] to the case of indefinite metrics. We show, that harmonic bundles are solutions of tt-geometry. Further we analyze the relation between metric tt

Paris-Sud XI, Université de

349

Harmonic knots P. -V. Koseleff, D. Pecker  

E-print Network

Harmonic knots P. -V. Koseleff, D. Pecker Universit´e Pierre et Marie Curie 4, place Jussieu, F-75252 Paris Cedex 05 e-mail: {koseleff,pecker}@math.jussieu.fr March 20, 2012 Abstract The harmonic knot integers and Tn is the degree n Chebyshev polynomial of the first kind. We classify the harmonic knots H

Paris-Sud XI, Université de

350

HARMONIC FUNCTIONS ON HYPERBOLIC GRAPHS CAMILLE PETIT  

E-print Network

HARMONIC FUNCTIONS ON HYPERBOLIC GRAPHS CAMILLE PETIT Abstract. We consider admissible random walks on hyperbolic graphs. For a given harmonic function on such a graph, we prove that asymptotic proper- ties and infinite trees. It involves geometric and probabilitistic methods. Contents 1. Introduction 1 2. Harmonic

Paris-Sud XI, Université de

351

HARMONIC MORPHISMS, HERMITIAN STRUCTURES AND SYMMETRIC SPACES  

E-print Network

HARMONIC MORPHISMS, HERMITIAN STRUCTURES AND SYMMETRIC SPACES In this text we refer to the following papers by capital letters as indicated. [A] M. Svensson, On holomorphic harmonic morphisms, Manuscripta Math. 107 (2002), 1­13. [B] M. Svensson, Harmonic morphisms from even-dimensional hyper- bolic

Gudmundsson, Sigmundur

352

HARMONIC AND SUPERHARMONIC MAJORANTS ON THE DISK  

E-print Network

HARMONIC AND SUPERHARMONIC MAJORANTS ON THE DISK function on the unit disk admits * *a harmonic majorant if and only if a certain explicit upper D denote the open unit disk in the complex plane, and H+ (D) the cone of positive harmonic

Thomas, Pascal J.

353

Method for Controlling a Multilevel Cascade BTB System Using Bidirectional Isolated DC/DC Converters  

NASA Astrophysics Data System (ADS)

This paper discusses a 6.6-kV next-generation BTB system in which bidirectional isolated dc/dc converters are combined with modular multilevel cascade converters. The system consists of N converter cells cascaded in each phase at both front ends. Each converter cell consists of a bidirectional isolated dc/dc converter and two voltage-source H-bridge PWM converters. This circuit configuration can be adopted to significantly reduce harmonic voltages and currents because the voltage steps are extremely low. In a conventional power conversion system, bulky line-frequency transformers are employed. On the other hand, in the present system, light and compact high-frequency transformers are used for providing galvanic isolation. Thus, the overall physical size and weight are reduced. The authors design, construct, and test a single-phase 120-V, 3.3-kW downscaled model with N=3, in order to verify the feasibility and effectiveness. The downscaled model helps to develop an operable 6.6-kV system with focus on control and performance.

Kitada, Ryohei; Akagi, Hirofumi

354

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

355

Efficient second harmonic generation of picosecond laser pulses.  

NASA Technical Reports Server (NTRS)

Efficient conversion to the second harmonic (SH) using KD2PO4 and CsH2AsO4 crystals inside a folded cavity of a high-power-dye mode-locked neodymium-glass laser is reported. For the first time, frequency-doubled picosecond light pulses have been obtained in CsH2AsO4 with peak powers of the order of 1 GW/sq cm at 0.531 micron for an effective pump power density of 4 GW/sq cm.

Rabson, T. A.; Ruiz, H. J.; Shah, P. L.; Tittel, F. K.

1972-01-01

356

Theoretical Analysis of High-Harmonic Generation in Solids  

NASA Astrophysics Data System (ADS)

We investigate theoretically high-harmonic generation (HHG) in bulk crystals exposed to intense midinfrared lasers with photon energies smaller than the band gap. The two main mechanisms, interband and intraband HHG, are explored. Our analysis indicates that the interband current neglected so far is the dominant mechanism for HHG. Saddle point analysis in the Keldysh limit yields an intuitive picture of interband HHG in solids similar to atomic HHG. Interband and intraband HHG exhibit a fundamentally different wavelength dependence. This signature can be used to experimentally distinguish between the two mechanisms in order to verify their importance.

Vampa, G.; McDonald, C. R.; Orlando, G.; Klug, D. D.; Corkum, P. B.; Brabec, T.

2014-08-01

357

Harmonics in DC to AC converters of single phase uninterruptible power supplies  

Microsoft Academic Search

Single phase uninterruptible power supplies (UPS) employ an inverter for DC to AC conversion. Advanced inverters consist of a full bridge transistor topology and an LC filter. An optimal inverter performance can be achieved if the output voltage is controlled by unipolar pulse width modulation (PWM). The paper describes the influence of the unipolar PWM on the voltages and the

H. Van der Broeck; M. Miller

1995-01-01

358

Wind Turbine Current-Source Converter Providing Reactive Power Control and Reduced Harmonics  

Microsoft Academic Search

This paper presents a current-source inverter topology that is suitable for multi-megawatt wind turbines. The proposed scheme utilizes two series-connected three-phase inverters that employ fully controllable switches and a proper interconnection transformer with the mains. In order to improve the efficiency and to allow the use of high-power devices, the inverters are switched at the mains frequency. The axial-flux permanent-magnet

Pierluigi Tenca; Andrew A. Rockhill; Thomas A. Lipo

2007-01-01

359

A 36Pulse AC-DC Converter for Line Current Harmonic Reduction  

Microsoft Academic Search

In this paper, a novel transformer for 36-pulse AC-DC conversion is designed, modeled and developed to feed isolated varying DC loads. The proposed transformer is normally used for large current rating rectifiers such as electric-aircraft power supply, electrowinning, electrochemical processes, induction heating, drives, plasma torches, etc., where isolation is required mainly for stepping down the supply voltage. It consists of

B. Singh; S. Gairola

2006-01-01

360

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

SciTech Connect

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 ?{sub i}=k{sub ?}{sup 2}?{sub i}{sup 2}/2?1 (where k{sub ?} is the perpendicular wave number and ?{sub 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, E-mail: swcho@kgu.ac.kr [Department of Physics, Kyonggi University, Suwon, Kyonggi-Do 443-760 (Korea, Republic of)] [Department of Physics, Kyonggi University, Suwon, Kyonggi-Do 443-760 (Korea, Republic of); Kwak, Jong-Gu [National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of)] [National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of)

2014-04-15

361

A study of the fundamental principles to power system harmonic  

Microsoft Academic Search

This paper is to present the harmonic phenomenon. The Fourier series is the tool for harmonic analysis in order to interpret waveforms behavior due to nonlinear loads is carried out. Some harmonics measurements for nonlinear loads are also observed. The harmonics theory, definition of harmonic quantities, related harmonics problems in power distribution systems are explained. Also, filter applications such as

M. Izhar; C. M. Hadzer; S. Masri; S. Idris

2003-01-01

362

Active filtering of harmonic currents in three-phase, four-wire systems with three-phase and single-phase nonlinear loads  

Microsoft Academic Search

A novel active harmonic-neutralizing filter is proposed which eliminates current harmonic effects, caused by any configuration of nonlinear loads in a three-phase, four-wire systems. The authors present proposed filter topologies and simulation results verifying the concept. Theoretical analysis of the circuit is included to facilitate a detailed converter design. The proposed topology is shown to have distinct advantages over traditional

Conor A. Quinn; Ned Mohan

1992-01-01

363

Structural ordering and glass forming of soft spherical particles with harmonic repulsions  

SciTech Connect

We carry out dissipative particle dynamics simulations to investigate the dynamic process of phase transformation in the system with harmonic repulsion particles. Just below the melting point, the system undergoes liquid state, face-centered cubic crystallization, body-centered cubic crystallization, and reentrant melting phase transition upon compression, which is in good agreement with the phase diagram constructed previously via thermodynamic integration. However, when the temperature is decreased sufficiently, the system is trapped into an amorphous and frustrated glass state in the region of intermediate density, where the solid phase and crystal structure should be thermodynamically most stable.

Sun, Bin [School of Materials and Chemical Engineering, Zhongyuan University of Technology, Zhengzhou 450007 (China)] [School of Materials and Chemical Engineering, Zhongyuan University of Technology, Zhengzhou 450007 (China); Sun, Zhiwei; Ouyang, Wenze, E-mail: oywz@imech.ac.cn; Xu, Shenghua, E-mail: xush@imech.ac.cn [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China)] [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China)

2014-04-07

364

Intramolecular Dynamics Probed using High Harmonic Generation  

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

365

Self-consistent theory of the thermal softening and instability of simple crystals  

Microsoft Academic Search

We consider the thermal softening of crystals due to anharmonicity. Self-consistent methods find a maximum temperature for a stable crystal, which gives an upper bound to the melting temperature. Previous workers have shown that the self-consistent harmonic approximation (SCHA) gives misleading results for the thermal stability of crystals. The reason is that the most important diagrams in the perturbation expansion

M. J. W. Dodgson; V. B. Geshkenbein; M. V. Feigel'man; G. Blatter

2000-01-01

366

Axisymmetric generalized harmonic evolution code  

SciTech Connect

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

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

2010-04-15

367

Crystal Monochromator based Emittance Measurements at the PETRA Undulator Beamline  

SciTech Connect

The synchrotron radiation beamline at the PETRA storage ring at DESY with two end stations uses a 4 m-long undulator delivering hard X-ray photons up to 300 keV at a storage ring energy of 12 GeV. The spatial photon intensity distribution at the first undulator harmonic (21.23 keV) was used to determine the horizontal emittance of the storage ring. The set-up installed at 107.7 m from the source point consists of a vacuum chamber with a cryogenically cooled silicon crystal in Laue geometry. The monochromatized radiation is converted to visible light by a fluorescent screen on the back of an aluminum plate and observed by a digital camera. Gaussian fits to horizontal lines through the centre of mass of the images provide the standard deviations of the measured intensity distributions in the horizontal plane. The corresponding emittance values were derived by modeling the whole setup with the SPECTRA code using the emittance as a free parameter and by using machine physics formulas neglecting photon source size effects.

Hahn, U.; Schulte-Schrepping, H. [Hamburger Synchrotronstrahlungslabor HASYLAB at Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22603 Hamburg (Germany)

2004-05-12

368

D-Deformed Harmonic Oscillators  

NASA Astrophysics Data System (ADS)

We analyze systematically several deformations arising from two-dimensional harmonic oscillators which can be described in terms of D-pseudo bosons. They all give rise to exactly solvable models, described by non self-adjoint hamiltonians whose eigenvalues and eigenvectors can be found adopting the quite general framework of the so-called D-pseudo bosons. In particular, we show that several models previously introduced in the literature perfectly fit into this scheme.

Bagarello, F.; Gargano, F.; Volpe, D.

2015-01-01

369

Hyperspherical harmonic formalism for tetraquarks  

E-print Network

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.

J. Vijande; N. Barnea; A. Valcarce

2006-10-11

370

Wood stove having catalytic converter  

SciTech Connect

A wood burning stove is formed with double front and rear side walls of heat conductive metal spaced apart by heat conductive spacer fins and providing air passageways by which room air is heated by conduction from the walls which are heated by the burning of wood deposited on a firebox floor supported in heat conducting relationship with the inner side walls. A catalytic converter is disposed over the fire area in the upper portion of the stove, and is arranged to receive preheated fresh secondary air which mixes with hot, incompletely combusted compounds from the fire and, in the presence of the catalyst, induces a secondary combustion of the substances. This mixture is channeled into a heat extraction chamber where the secondary combustion is completed and the resultant heat is transferred to the metal body of the stove. An exhaust passageway is provided for releasing the products of complete combustion into the atmosphere.

Willson, A.C.

1982-12-14

371

Thermionic converter emitter support arrangement  

DOEpatents

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

Allen, Daniel T. (La Jolla, CA)

1990-01-01

372

Thermionic converter emitter support arrangement  

DOEpatents

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

Allen, Daniel T. (La Jolla, CA)

1990-01-01

373

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

SciTech Connect

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

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

2011-11-30

374

175 GHz, 400-fs-pulse harmonically mode-locked surface emitting semiconductor laser.  

PubMed

We report a harmonically mode-locked vertical external cavity surface emitting laser (VECSEL) producing 400 fs pulses at a repetition frequency of 175 GHz with an average output power of 300 mW. Harmonic mode-locking was established using a 300 µm thick intracavity single crystal diamond heat spreader in thermal contact with the front surface of the gain sample using liquid capillary bonding. The repetition frequency was set by the diamond microcavity and stable harmonic mode locking was achieved when the laser cavity length was tuned so that the laser operated on the 117th harmonic of the fundamental cavity. When an etalon placed intracavity next to the gain sample, but not in thermal contact was used pulse groups were observed. These contained 300 fs pulses with a spacing of 5.9 ps. We conclude that to achieve stable harmonic mode locking at repetition frequencies in the 100s of GHz range in a VECSEL there is a threshold pulse energy above which harmonic mode locking is achieved and below which groups of pulses are observed. PMID:22453384

Wilcox, Keith G; Quarterman, Adrian H; Apostolopoulos, Vasilis; Beere, Harvey E; Farrer, Ian; Ritchie, David A; Tropper, Anne C

2012-03-26

375

Fully phosphor-converted LEDs with Lumiramic phosphor technology  

NASA Astrophysics Data System (ADS)

Fully phosphor-converted LEDs (FpcLeds) with saturated emission have been realized in the green and amber spectral region. With the Lumiramic phosphor technology it is possible to achieve high package efficiency with minimum transmission of blue light from the primary LED source. This is done by keeping the scattering properties of the phosphor layer low while the phosphor thickness is chosen to fully convert all blue LED emission. It is shown that this can be done not only for optically isotropic Lumiramic materials like garnets, but also for oxonitridosilicate materials like the green emitting Europium doped SrSi2O2N2, crystallizing in a triclinic lattice with three optical axes. The scattering power of the Lumiramic can be decreased to acceptable levels by increasing the size of the crystallites in the densely sintered ceramics. Light propagation is found to be described well with Mie scattering of mono-sized SrSi2O2N2 spheres with refraction index differing by 0.07 to the refractive index of a SrSi2O2N2 matrix material. Using this technology, the green-yellow gap of visible light emitting LEDs can be bridged and color tunable lamps with the efficiency and flux of today's white phosphor-converted LEDs become feasible.

Bechtel, Helmut; Schmidt, Peter J.; Tücks, Andreas; Heidemann, Matthias; Chamberlin, Danielle; Müller-Mach, Regina; Müller, Gerd O.; Shchekin, Oleg

2010-08-01

376

Radiation-Tolerant DC-DC Converters  

NASA Technical Reports Server (NTRS)

A document discusses power converters suitable for space use that meet the DSCC MIL-PRF-38534 Appendix G radiation hardness level P classification. A method for qualifying commercially produced electronic parts for DC-DC converters per the Defense Supply Center Columbus (DSCC) radiation hardened assurance requirements was developed. Development and compliance testing of standard hybrid converters suitable for space use were completed for missions with total dose radiation requirements of up to 30 kRad. This innovation provides the same overall performance as standard hybrid converters, but includes assurance of radiation- tolerant design through components and design compliance testing. This availability of design-certified radiation-tolerant converters can significantly reduce total cost and delivery time for power converters for space applications that fit the appropriate DSCC classification (30 kRad).

Skutt, Glenn; Sable, Dan; Leslie, Leonard; Graham, Shawn

2012-01-01

377

Performance of Power Converters at Cryogenic Temperatures  

NASA Technical Reports Server (NTRS)

Power converters capable of operation at cryogenic temperatures are anticipated to play an important role in the power system architecture of future NASA deep space missions. Design of such converters to survive cryogenic temperatures will improve the power system performance and reduce development and launch costs. Aerospace power systems are mainly a DC distribution network. Therefore, DC/DC and DC/AC converters provide the outputs needed to different loads at various power levels. Recently, research efforts have been performed at the NASA Glenn Research Center (GRC) to design and evaluate DC/DC converters that are capable of operating at cryogenic temperatures. This paper presents a summary of the research performed to evaluate the low temperature performance of five DC/DC converters. Various parameters were investigated as a function of temperature in the range of 20 to -196 C. Data pertaining to the output voltage regulation and efficiency of the converters is presented and discussed.

Elbuluk, Malik E.; Gerber, Scott; Hammoud, Ahmad; Patterson, Richard L.

2001-01-01

378

Development of a Modular Power Converter  

NASA Astrophysics Data System (ADS)

This report describes the most important details of elaboration of a versatile power module that can be utilized as a part of various converters. Two or more modules connected together can form a frequency converter or multilevel converter or 3-phase inverter/rectifier etc. Initially the module was developed for fast prototyping of uninterruptible power supplies and energy systems with alternative energy sources. The module can be used also as a basis for laboratory equipment of the power electronics course.

Stepanov, A.; Biesenieks, L.; Sokolovs, A.; Galkin, I.

2009-01-01

379

Low Frequency Characterization of PWM Converters  

Microsoft Academic Search

Low frequency components of states or outputs in pulse-width modulation (PWM) dc and ac converters can be characterized by differential equations called describing state-space equations. These equations are derived by inspection of converter topology and use of switching functions and duty ratios. Their steady-state and small-signal dynamic solutions show how energy-storage elements in a converter\\/load system shape the frequency response

Khai D. T. Ngo

1986-01-01

380

Vacuum-insulated catalytic converter  

DOEpatents

A catalytic converter has an inner canister that contains catalyst-coated substrates and an outer canister that encloses an annular, variable vacuum insulation chamber surrounding the inner canister. An annular tank containing phase-change material for heat storage and release is positioned in the variable vacuum insulation chamber a distance spaced part from the inner canister. A reversible hydrogen getter in the variable vacuum insulation chamber, preferably on a surface of the heat storage tank, releases hydrogen into the variable vacuum insulation chamber to conduct heat when the phase-change material is hot and absorbs the hydrogen to limit heat transfer to radiation when the phase-change material is cool. A porous zeolite trap in the inner canister absorbs and retains hydrocarbons from the exhaust gases when the catalyst-coated substrates and zeolite trap are cold and releases the hydrocarbons for reaction on the catalyst-coated substrate when the zeolite trap and catalyst-coated substrate get hot.

Benson, David K. (Golden, CO)

2001-01-01

381

Extra Harmonic Vowel in Chicahuaxtla Trique  

E-print Network

Extra Harmonic Vowel in Chicahuaxtla Trique1 Kosuke Matsukawa State University of New York at Albany 1. Introduction Chicahuaxtla Trique is spoken in Oaxaca, Mexico and belongs to the Trique language group of the Mixtecan family...). In Chicahuaxtla Trique, an extra harmonic vowel is added after a laryngealized vowel (either a glottalized vowel or an aspirated vowel) in a final syllable. The extra harmonic vowel does not exist in Copala Trique or Itunyoso Trique and is attached mostly...

Matsukawa, Kosuke

2008-01-01

382

Relativistic Harmonic Oscillator with Spin Symmetry  

E-print Network

The eigenfunctions and eigenenergies for a Dirac Hamiltonian with equal scalar and vector harmonic oscillator potentials are derived. Equal scalar and vector potentials may be applicable to the spectrum of an antinucleion imbedded in a nucleus. Triaxial, axially deformed, and spherical oscillator potentials are considered. The spectrum has a spin symmetry for all cases and, for the spherical harmonic oscillator potential, a higher symmetry analogous to the SU(3) symmetry of the non-relativistic harmonic oscillator is discussed.

Joseph N. Ginocchio

2005-03-25

383

Effect of undulator harmonics field on free-electron laser harmonic generation  

NASA Astrophysics Data System (ADS)

The harmonics field effect of a planar undulator on free-electron laser (FEL) harmonic generation has been analyzed. For both the linear case and the nonlinear case, the harmonic fraction of the radiation can be characterized by the coupling coefficients. The modification of the coupling coefficients is given when the third harmonics magnetic field component exists, thus the enhancement of the harmonic radiation can be predicted. The numerical results show that with the third harmonics magnetic field component that has the opposite sign to the fundamental, the intensity of third-harmonic radiation can be increased distinctly for both the small signal gain and the nonlinear harmonic generation. The increase is larger for the smaller undulator deflecting parameter.

Jia, Qika

2011-06-01

384

High voltage photovoltaic power converter  

DOEpatents

An array of independently connected photovoltaic cells on a semi-insulating substrate contains reflective coatings between the cells to enhance efficiency. A uniform, flat top laser beam profile is illuminated upon the array to produce electrical current having high voltage. An essentially wireless system includes a laser energy source being fed through optic fiber and cast upon the photovoltaic cell array to prevent stray electrical signals prior to use of the current from the array. Direct bandgap, single crystal semiconductor materials, such as GaAs, are commonly used in the array. Useful applications of the system include locations where high voltages are provided to confined spaces such as in explosive detonation, accelerators, photo cathodes and medical appliances.

Haigh, Ronald E. (Arvada, CO); Wojtczuk, Steve (Cambridge, MA); Jacobson, Gerard F. (Livermore, CA); Hagans, Karla G. (Livermore, CA)

2001-01-01

385

A Transformerless Hybrid Filter Using a Three-Level Diode-Clamped PWM Converter  

NASA Astrophysics Data System (ADS)

This paper deals with a transformerless hybrid active filter integrated into a medium-voltage three-phase diode rectifier used as the front end of an adjustable-speed motor drive. The hybrid filter is formed by a single LC filter tuned to the 7th-harmonic frequency per phase and a small-rated active filter based on a three-phase three-level diode-clamped PWM converter. A three-phase downscaled system rated at 400V and 15kW is designed, constructed, and tested to verify the filtering performance of the hybrid filter. Experimental results show that the current THD (total harmonic distortion) gets less than 5%, and that the voltage-balancing control proposed in this paper works properly even in transient states.

Hatada, Takaaki; Akagi, Hirofumi

386

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

387

Harmonic potential and hadron spectroscopy  

E-print Network

The quark-gluon sea in the hadrons is considered as periodically correlated. Energy levels of Shrodinger equation with harmonic potential is used for describing of the spectrum of hadron masses. In the considered cases the effective potential operating on each particle of ensemble, under certain conditions becomes square-law on displacement from a equilibrium point. It can become an explanation of popularity of oscillator potential for the description of a spectrum of masses of elementary particles. The analysis shows that levels of periodic potential better agreed to the spectrum of hadron masses, than levels of other potentials used for an explanation of a spectrum of masses.

Rafael Tumanyan

2009-05-28

388

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

389

A model-based controller for the cascade h-bridge multilevel converter used as a shunt active filter  

Microsoft Academic Search

This paper presents the modeling and control processes of the cascade h-bridge multilevel converter used as a shunt active filter. The single-phase five-level topology is studied, however, it can be easily scaled to more levels. Based on the model, a controller is proposed to compensate harmonic distortion and reactive power due to a nonlinear load which is equivalent to guarantee

G. Escobar; M. F. Martinez-Montejano; P. R. Martinez-Rodriguez; M. Hernandez-Gomez

2006-01-01

390

Temperature Fluctuations During Crystal Growth  

NASA Technical Reports Server (NTRS)

Technique developed to deconvolve period and relative amplitude of fluctuations of heat flow inBridgman crystal growth. Temperature-measuring device with enough sensitivity and frequency response to make desired measurements inserted close as possible to substance monitored. Time-dependent temperature response recorded, and time domain response converted to frequency domain for further analysis. Fast fourier transform (FFT) of data on temperature oscillations shows particular behavior at some specific frequencies corresponding with striations, or defects observed on crystal. Useful procedure to help determine sources of some growth-induced crystalline defects. Other processes sensitive to small temperature fluctuations, such as diffusion, precipitation, and corrsion, benefit from technique.

Fripp, Archibald L., Jr.; Clark, Ivan O.; Debnam, William J., Jr.; Barber, Patrick G.; Crouch, Roger K.; Simchick, Richard T.

1988-01-01

391

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

Microsoft Academic Search

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

HASMUKH S. PATELAND; Richard G. Hoft

1973-01-01

392

Echo-Enabled Harmonic Generation for Seeded FELs  

SciTech Connect

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

Stupakov, G.; /SLAC

2011-05-19

393

Ray tracing study for a detuned nondispersed double crystal monochromator  

SciTech Connect

The properties of a detuned nondispersive Si(111) double crystal monochromator were studied by using the ray tracing method. The program used was the PC version of shadow V2.3.3 with gui V1.2. This article concentrates on detuning of the second crystal since detuning of the first crystal causes a larger shift of the energy center of the transmitted beam than detuning of the second one does. The results indicate that for a large detuning angle of the second crystal, the transmitted spectrum splits into two bands with equal bandwidth, which is delayed at a large vertical divergence of the incident beam. With increasing detuning angle of the second crystal, both the fundamental bandwidth (for a well collimated beam) and the harmonic contamination decrease until they reach the minimum at a detuning angle of roughly half the full width at half maximum of the rocking curve, where the left fundamental flux is about 50%. The capability of harmonic suppression by detuning the second crystal is limited, with the harmonic contamination reduced by about two orders of magnitude at most, which implies that other methods, such as double mirror system, must be adopted when smaller harmonic contamination is required.

Hou Zhengchi [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800 (China)

2005-01-01

394

Efficient Third Harmonic Generation for Wind Lidar Applications  

NASA Technical Reports Server (NTRS)

The characterization of atmospheric winds on a global basis is a key parameter required for accurate weather prediction. The use of a space based lidar system for remote measurement of wind speed would provide detailed and highly accurate data for future weather prediction models. This paper reports the demonstration of efficient third harmonic conversion of a 1 micrometer laser to provide an ultraviolet (UV) source suitable for a wind lidar system based on atmospheric molecular scattering. Although infrared based lidars using aerosol scattering have been demonstrated to provide accurate wind measurement, a UV based system using molecular or Rayleigh scattering will provide accurate global wind measurements, even in those areas of the atmosphere where the aerosol density is too low to yield good infrared backscatter signals. The overall objective of this work is to demonstrate the maturity of the laser technology and its suitability for a near term flight aboard the space shuttle. The laser source is based on diode-pumped solid-state laser technology which has been extensively demonstrated at TRW in a variety of programs and internal development efforts. The pump laser used for the third harmonic demonstration is a breadboard system, designated the Laser for Risk Reduction Experiments (LARRE), which has been operating regularly for over 5 years. The laser technology has been further refined in an engineering model designated as the Compact Advanced Pulsed Solid-State Laser (CAPSSL), in which the laser head was packaged into an 8 x 8 x 18 inch volume with a weight of approximately 61 pounds. The CAPSSL system is a ruggedized configuration suitable for typical military applications. The LARRE and CAPSSL systems are based on Nd:YAG with an output wavelength of 1064 nm. The current work proves the viability of converting the Nd:YAG fundamental to the third harmonic wavelength at 355 nm for use in a direct detection wind lidar based on atmospheric Rayleigh scattering.

Mordaunt, David W.; Cheung, Eric C.; Ho, James G.; Palese, Stephen P.

1998-01-01

395

Virtual Crystallizer  

SciTech Connect

Large dihydrogen phosphate (KDP) crystals are grown in large crystallizers to provide raw material for the manufacture of optical components for large laser systems. It is a challenge to grow crystal with sufficient mass and geometric properties to allow large optical plates to be cut from them. In addition, KDP has long been the canonical solution crystal for study of growth processes. To assist in the production of the crystals and the understanding of crystal growth phenomena, analysis of growth habits of large KDP crystals has been studied, small scale kinetic experiments have been performed, mass transfer rates in model systems have been measured, and computational-fluid-mechanics tools have been used to develop an engineering model of the crystal growth process. The model has been tested by looking at its ability to simulate the growth of nine KDP boules that all weighed more than 200 kg.

Land, T A; Dylla-Spears, R; Thorsness, C B

2006-08-29

396

Crystal Systems.  

ERIC Educational Resources Information Center

Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)

Schomaker, Verner; Lingafelter, E. C.

1985-01-01

397

On harmonic measures and group actions Alberto Candel  

E-print Network

On harmonic measures and group actions Alberto Candel CSUN I Congreso Hispano-Franc´es de Matem´aticas Zaragoza, 13 Julio del 2007 #12;Harmonic measures Harmonic measures for foliated spaces were introduced in foliation theory by Lucy Garnett. #12;Harmonic measures Harmonic measures for foliated spaces were

Candel, Alberto

398

A direct AC\\/AC converter based on current-source converter modules  

Microsoft Academic Search

The research on direct AC\\/AC conversion in the past twenty years has been following two major directions: improving the performance of the original nine-bidirectional-switch matrix converter topology; and using converter topologies composed of unidirectional switches only. In this paper, a direct AC\\/AC converter topology based on current-source converter modules is proposed. It is shown, through analysis and simulation, that the

Mehrdad Kazerani

2003-01-01

399

Crystal growth of organics for nonlinear optical applications  

NASA Technical Reports Server (NTRS)

The crystal growth and characterization of organic and inorganic nonlinear optical materials were extensively studied. For example, inorganic crystals such as thallium arsenic selenide were studied in our laboratory for several years and crystals in sizes over 2.5 cm in diameter are available. Organic crystals are suitable for the ultraviolet and near infrared region, but are relatively less developed than their inorganic counterparts. Very high values of the second harmonic conversion efficiency and the electro-optic coefficient were reported for organic compounds. Single crystals of a binary organic alloy based on m.NA and CNA were grown and higher second harmonic conversion efficiency than the values reported for m.NA were observed.

Singh, N. B.; Mazelsky, R.

1993-01-01

400

Celilo Converter Station mercury arc valve replacement  

Microsoft Academic Search

The Pacific HVDC Intertie (PDCI) is the most complicated HVDC Scheme in the world. Decisions about changing the PDCI are further complicated by a complex ownership arrangement. The Intertie has the a capacity of 3100 MW and runs from the Celilo Converter Station in The Dalles, Oregon to the Sylmar Converter Station in Sylmar, California. After an earthquake damaged the

Wayne Litzenberger

2002-01-01

401

The auxiliary resonant commutated pole converter  

Microsoft Academic Search

The auxiliary resonant commutated pole (ARCP), a new power converter topology that fully achieves soft switching without increasing primary device voltage or current ratings, is discussed. The ARCP converter is capable of true pulse-width modulation (PWM) control of each phase. The power circuit relies on the addition of an auxiliary triggered resonant commutation circuit or snubber to commutate the inductive

R. W. De Doncker; J. P. Lyons

1990-01-01

402

RF digital-to-analog converter  

DOEpatents

A digital-to-analog converter is disclosed for producing an RF output signal proportional to a digital input word of N bits from an RF reference input, N being an integer greater or equal to 2. The converter comprises a plurality of power splitters, power combiners and a plurality of mixers or RF switches connected in a predetermined configuration. 18 figs.

Conway, P.H.; Yu, D.U.L.

1995-02-28

403

RF digital-to-analog converter  

DOEpatents

A digital-to analogue converter for producing an RF output signal proportional to a digital input word of N bits from an RF reference input, N being an integer greater or equal to 2. The converter comprises a plurality of power splitters, power combiners and a plurality of mixers or RF switches connected in a predetermined configuration.

Conway, Patrick H. (Rancho Palos Verdes, CA); Yu, David U. L. (Rancho Palos Verdes, CA)

1995-01-01

404

Directivity of parametric converters with biharmonic pumping  

Microsoft Academic Search

The conditions of stable amplification and ideal directivity of amplification are obtained for different types of three-frequency parametric converters with biharmonic pumping. The equivalent circuit of the converter incorporates a parametric diode whose elastance varies time-dependently under the action of voltages from two pumping sources and an oscillatory system containing resonant chains for three different working frequencies. A system of

Iu. K. Tarabrin

1976-01-01

405

Firing angle optimisation for chain cell converters  

Microsoft Academic Search

Firing angles for chain cell multi-level converters can be optimised to reduce waveform distortion. Optimisation techniques have previously been developed that calculate the required firing angles, but these techniques fall short of accurate optimisation due to over-simplification of the problem. Established optimisation routines often only work on a subset of possible converter modes, hence optimal solutions are not produced for

D. W. Sandells; T. C. Green

2001-01-01

406

Generation of Triggering Signals for Multilevel Converter  

Microsoft Academic Search

Multilevel converter has become attractive in the power industries and it can be applied in many applications especially on improvement of the power quality. This paper presents the generation of triggering signals used to control the cascaded H-bridge (CHB) multilevel converter. One of the carrier based pulse width modulation scheme which is level shifted multicarrier modulation has been chosen to

S. A. Bashi; N. F. Mailah; M. Z. Kadir; K. H. Leong

407

Optimal design methodology for LLC resonant converter  

Microsoft Academic Search

Although LLC resonant converter can achieve wide operation range with high efficiency, lack of design methodology makes it difficult to be implemented. In this paper, based on the theoretical analysis on the operation principles during normal condition and holdup time, the relationship between converter efficiency and operation range with different circuit parameters has be revealed. An optimal design methodology has

Bing Lu; Wenduo Liu; Yan Liang; Fred C. Lee; Jacobus D. van Wyk

2006-01-01

408

Multilevel converters for 10 MW Wind Turbines  

Microsoft Academic Search

Several promising multi-level converter configurations for 10 MW Wind Turbines both with direct drive and one-stage gear box drive using Permanent Magnet Synchronous Generator (PMSG) are proposed, designed and compared. Reliability is a crucial indicator for large scale wind power converters, therefore the evaluations are mainly focused on the power device thermal performances, which are closely related to the life

Ke Ma; Frede Blaabjerg

2011-01-01

409

Time interleaved counter analog to digital converters   

E-print Network

The work explores extending time interleaving in A/D converters, by applying a high-level of parallelism to one of the slowest and simplest types of data-converters, the counter ADC. The motivation for the work is to ...

Danesh, Seyed Amir Ali

2011-11-22

410

Component technology for Stirling power converters  

Microsoft Academic Search

NASA Lewis Research Center has organized a component technology program as part of the efforts to develop Stirling converter technology for space power applications. The Stirling Space Power Program is part of the NASA High Capacity Power Project of the Civil Space Technology Initiative (CSTI). NASA Lewis is also providing technical management for the DOE\\/Sandia program to develop Stirling converters

Lanny G. Thieme

1991-01-01

411

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

SciTech Connect

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

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

1999-05-01

412

Generation of green frequency comb from chirped ?(2) nonlinear photonic crystals  

NASA Astrophysics Data System (ADS)

Spectrally broad frequency comb generation over 510-555 nm range was reported on chirped quasi-phase-matching (QPM) ?(2) nonlinear photonic crystals of 12 mm length with periodicity stepwise increased from 5.9 ?m to 7.1 ?m. When pumped with nanosecond infrared (IR) frequency comb derived from a QPM optical parametric oscillator (OPO) and spanned over 1040 nm to 1090 nm wavelength range, the 520 nm to 545 nm up-converted green spectra were shown to consist of contributions from (a) second-harmonic generation among the signal or the idler modes, and (b) sum-frequency generation (SFG) from the neighboring pairs of the signal or the idler modes. These mechanisms led the up-converted green frequency comb to have the same mode spacing of 450 GHz as that in the IR-OPO pump comb. As the pump was further detuned from the aforementioned near-degeneracy point and moved toward the signal (1020-1040 nm) and the idler (1090-1110 nm) spectral range, the above QPM parametric processes were preserved in the chirped QPM devices to support up-converted green generation in the 510-520 nm and the 545-555 nm spectral regime. Additional 530-535 nm green spectral generation was also observed due to concurrence of multi-wavelength SFG processes between the (signal, idler) mode pairs. These mechanisms facilitate the chirped QPM device to support a single-pass up-conversion efficiency ˜10% when subject to an IR-OPO pump comb with 200 mW average power operated near- or off- the degeneracy point.

Lai, C.-M.; Chang, K.-H.; Yang, Z.-Y.; Fu, S.-H.; Tsai, S.-T.; Hsu, C.-W.; Yu, N. E.; Boudrioua, A.; Kung, A. H.; Peng, L.-H.

2014-12-01

413

Evaluations of uranium-nitride fueled converters.  

NASA Technical Reports Server (NTRS)

Evaluation of two uranium-nitride (UN) fueled converters was initiated at the Jet Propulsion Laboratory to investigate the effect of fuel on the converter performance while being operated out-of-core. The initial tests were performed with the dynamic data acquisition system that was developed at the Laboratory. Parametric tests of these converters were to obtain: (1) static volt-ampere curves, (2) dynamic volt-ampere curves, and (3) the electrode work functions. The power outputs were 9.3 W/sq cm for the rhenium converter and 3.8 W/sq cm for the tungsten converter at 0.6 V when the emitter surface temperature was 2000 K, according to the static volt-ampere curves.

Shimada, K.; Cassell, P. L.

1971-01-01

414

Modelling, analyses and design of switching converters  

NASA Technical Reports Server (NTRS)

A state-space averaging method for modelling switching dc-to-dc converters for both continuous and discontinuous conduction mode is developed. In each case the starting point is the unified state-space representation, and the end result is a complete linear circuit model, for each conduction mode, which correctly represents all essential features, namely, the input, output, and transfer properties (static dc as well as dynamic ac small-signal). While the method is generally applicable to any switching converter, it is extensively illustrated for the three common power stages (buck, boost, and buck-boost). The results for these converters are then easily tabulated owing to the fixed equivalent circuit topology of their canonical circuit model. The insights that emerge from the general state-space modelling approach lead to the design of new converter topologies through the study of generic properties of the cascade connection of basic buck and boost converters.

Cuk, S. M.; Middlebrook, R. D.

1978-01-01

415

Boost matrix converters in clean energy systems  

NASA Astrophysics Data System (ADS)

This dissertation describes an investigation of novel power electronic converters, based on the ultra-sparse matrix topology and characterized by the minimum number of semiconductor switches. The Z-source, Quasi Z-source, Series Z-source and Switched-inductor Z-source networks were originally proposed for boosting the output voltage of power electronic inverters. These ideas were extended here on three-phase to three-phase and three-phase to single-phase indirect matrix converters. For the three-phase to three-phase matrix converters, the Z-source networks are placed between the three-switch input rectifier stage and the output six-switch inverter stage. A brief shoot-through state produces the voltage boost. An optimal pulse width modulation technique was developed to achieve high boosting capability and minimum switching losses in the converter. For the three-phase to single-phase matrix converters, those networks are placed similarly. For control purposes, a new modulation technique has been developed. As an example application, the proposed converters constitute a viable alternative to the existing solutions in residential wind-energy systems, where a low-voltage variable-speed generator feeds power to the higher-voltage fixed-frequency grid. Comprehensive analytical derivations and simulation results were carried out to investigate the operation of the proposed converters. Performance of the proposed converters was then compared between each other as well as with conventional converters. The operation of the converters was experimentally validated using a laboratory prototype.

Karaman, Ekrem

416

Growth, characterization, vibrational spectroscopic and thermal studies of a new metallorganic non-linear optical crystal-Bisthiourea cadmium bromide.  

PubMed

Single crystals of bisthiourea cadmium bromide (BTCB), a new metallorganic material crystallizing in orthorhombic system were grown from slow evaporation solution growth. The grown crystals were characterized by X-ray diffraction, FTIR and FT-Raman spectral studies. The crystals were also subjected to TGA/DTA analysis and second harmonic generation test. The transmission characteristics of the crystal was also studied. PMID:18487082

Ramachandraraja, C; Sundararajan, R S

2008-12-15

417

The harmonic organization of auditory cortex  

PubMed Central

A fundamental structure of sounds encountered in the natural environment is the harmonicity. Harmonicity is an essential component of music found in all cultures. It is also a unique feature of vocal communication sounds such as human speech and animal vocalizations. Harmonics in sounds are produced by a variety of acoustic generators and reflectors in the natural environment, including vocal apparatuses of humans and animal species as well as music instruments of many types. We live in an acoustic world full of harmonicity. Given the widespread existence of the harmonicity in many aspects of the hearing environment, it is natural to expect that it be reflected in the evolution and development of the auditory systems of both humans and animals, in particular the auditory cortex. Recent neuroimaging and neurophysiology experiments have identified regions of non-primary auditory cortex in humans and non-human primates that have selective responses to harmonic pitches. Accumulating evidence has also shown that neurons in many regions of the auditory cortex exhibit characteristic responses to harmonically related frequencies beyond the range of pitch. Together, these findings suggest that a fundamental organizational principle of auditory cortex is based on the harmonicity. Such an organization likely plays an important role in music processing by the brain. It may also form the basis of the preference for particular classes of music and voice sounds. PMID:24381544

Wang, Xiaoqin

2013-01-01

418

Radiation reaction and quantum damped harmonic oscillator  

E-print Network

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

F. Kheirandish; M. Amooshahi

2005-07-19

419

Practical Tools to Foster Harmonic Understanding  

ERIC Educational Resources Information Center

Among the elements required to develop a comprehensive understanding of music is students' ability to perceive, recognize, and label the harmonies they hear. Harmonic dictation is among the strategies that teachers have traditionally chosen to help students develop harmonic awareness. However, the highly idiosyncratic ways that students approach…

Johnson, Erik

2013-01-01

420

The Harmonic Series Diverges Again and Again  

ERIC Educational Resources Information Center

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

Kifowit, Steven J.; Stamps, Terra A.

2006-01-01

421

CHAPLIN - Complex Harmonic Polylogarithms in Fortran  

E-print Network

We present a new Fortran library to evaluate all harmonic polylogarithms up to weight four numerically for any complex argument. The algorithm is based on a reduction of harmonic polylogarithms up to weight four to a minimal set of basis functions that are computed numerically using series expansions allowing for fast and reliable numerical results.

Stephan Buehler; Claude Duhr

2011-06-28

422

High-order harmonic generation in plasmas  

Microsoft Academic Search

The phenomenon of harmonic generation by electrons oscillating in high-intensity laser fields is surveyed and assessed as a means of producing short-wavelength radiation. Starting from the seminal early work by Sarachik and Schappert (1970), simple motivatory examples are given of incoherent harmonic generation via nonlinear scattering from single electrons. More recent studies aimed at observing the coherent version of this

Paul Gibbon

1997-01-01

423

Sunspots and Their Simple Harmonic Motion  

ERIC Educational Resources Information Center

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

Ribeiro, C. I.

2013-01-01

424

Spherical harmonic analysis of wavefields using multiple circular sensor arrays  

E-print Network

Spherical harmonic analysis of wavefields using multiple circular sensor arrays Thushara D. Abhayapala, Senior Member, IEEE and Aastha Gupta Student Member, IEEE Abstract Spherical harmonic of sensors to decompose a wavefield into spherical harmonic components. The new structure presented here

Abhayapala, Thushara D.

425

HARMONIC MAPPINGS BETWEEN RIEMANNIAN MANIFOLDS Anand Arvind Joshi  

E-print Network

HARMONIC MAPPINGS BETWEEN RIEMANNIAN MANIFOLDS by Anand Arvind Joshi A Thesis Presented ii Abstract iv 1 Harmonic Mappings 1 1.1 Space of Maps Variation Formula . . . . . . . . . . . . . . . . . . . . . . . . 11 1.4 Harmonic Maps

Leahy, Richard M.

426

Acoustoelectric Harmonic Generation in a Photoconductive Piezoelectric Semiconductor  

E-print Network

Acoustoelectric Harmonic Generation in a Photoconductive Piezoelectric Semiconductor W. Arthur, R harmonics in the low frequency regime (. Piezoelectric semiconductors can exhibit harmonic generation because of interactions between the acoustic

427

Harmonic relationships influence auditory brainstem encoding of chords  

E-print Network

Harmonic relationships influence auditory brainstem encoding of chords Frederic Marmela processing of musical sounds would be sensitive to harmonic relationships. We examined auditory brainstem brainstem response, harmonic relationships, implicit learning, music perception, subcortical encoding

428

Studies on the growth aspects of semi-organic cadmium zinc thiourea acetate: A promising new NLO crystal  

Microsoft Academic Search

Single crystals of a new nonlinear optical material, cadmium zinc thiourea acetate (CZTA), were successfully grown by slow evaporation of the aqueous solution at room temperature. Single crystal X-ray diffraction pattern and FTIR spectrum analysis have confirmed the formation of the new crystal. The optical transmission studies and second harmonic generation (SHG) efficiency studies justified the device quality of the

K. Kirubavathi; K. Selvaraju; R. Valluvan; N. Vijayan; S. Kumararaman

2008-01-01

429

Growth and characterization of new organic nonlinear optical crystal (R)-2-cyano-N-(1-phenylethyl) acetamide  

SciTech Connect

(R)-2-Cyano-N-(1-phenylethyl) acetamide (RCNPA) single crystals were grown by slow evaporation of the aqueous solution at room temperature (300K) using ethanol. The grown crystals were characterized by single crystal X-ray diffraction, powder X-ray diffraction, FTIR, UV-Vis-NIR transmittance, scanning electron microscopy (SEM) and powder second harmonic generation (SHG)

Hemaraju, B. C.; Gnana Prakash, A. P., E-mail: gnanaprakash@physics.uni-mysore.ac.in [Department of Studies in Physics, University of Mysore, Mysore-570006, Karnataka (India); Madhukar, B. S.; Bhadregowda, D. G. [Department of Chemistry, Yuvaraja's College Mysore-570005, Karnataka (India)

2014-04-24

430

Acoustics of automotive catalytic converter assemblies  

NASA Astrophysics Data System (ADS)

In an automotive exhaust system, the purpose of the catalytic converter is to reduce pollutant emissions. However, catalytic converters also affect the engine and exhaust system breathing characteristics; they increase backpressure, affect exhaust system acoustic characteristics, and contribute to exhaust manifold tuning. Thus, radiated sound models should include catalytic converters since they can affect both the source characteristics and the exhaust system acoustic behavior. A typical catalytic converter assembly employs a ceramic substrate to carry the catalytically active noble metals. The substrate has numerous parallel tubes and is mounted in a housing with swelling mat or wire mesh around its periphery. Seals at the ends of the substrate can be used to help force flow through the substrate and/or protect the mat material. Typically, catalytic converter studies only consider sound propagation in the small capillary tubes of the substrate. Investigations of the acoustic characteristics of entire catalytic converter assemblies (housing, substrate, seals, and mat) do not appear to be available. This work experimentally investigates the acoustic behavior of catalytic converter assemblies and the contributions of the separate components to sound attenuation. Experimental findings are interpreted with respect to available techniques for modeling sound propagation in ceramic substrates.

Dickey, Nolan S.; Selamet, Ahmet; Parks, Steve J.; Tallio, Kevin V.; Miazgowicz, Keith D.; Radavich, Paul M.

2003-10-01

431

Probing polar molecules with high harmonic spectroscopy.  

PubMed

We bring the methodology of orienting polar molecules together with the phase sensitivity of high harmonic spectroscopy to experimentally compare the phase difference of attosecond bursts of radiation emitted upon electron recollision from different ends of a polar molecule. This phase difference has an impact on harmonics from aligned polar molecules, suppressing emission from the molecules parallel to the driving laser field while favoring the perpendicular ones. For oriented molecules, we measure the amplitude ratio of even to odd harmonics produced when intense light irradiates CO molecules and determine the degree of orientation and the phase difference of attosecond bursts using molecular frame ionization and recombination amplitudes. The sensitivity of the high harmonic spectrum to subtle phase differences in the emitted radiation makes it a detailed probe of polar molecules and will drive major advances in the theory of high harmonic generation. PMID:23368205

Frumker, E; Kajumba, N; Bertrand, J B; Wörner, H J; Hebeisen, C T; Hockett, P; Spanner, M; Patchkovskii, S; Paulus, G G; Villeneuve, D M; Naumov, A; Corkum, P B

2012-12-01

432

Second-Harmonic Generation Induced by Electric Currents in GaAs  

NASA Astrophysics Data System (ADS)

We demonstrate a new, nonlinear optical effect of electric currents. First, a steady current is generated by applying a voltage on a doped GaAs crystal. We demonstrate that this current induces second-harmonic generation of a probe laser pulse. Second, we optically inject a transient current in an undoped GaAs crystal by using a pair of ultrafast laser pulses and demonstrate that it induces the same second-harmonic generation. In both cases, the induced second-order nonlinear susceptibility is proportional to the current density. This effect can be used for nondestructive, noninvasive, and ultrafast imaging of currents. These advantages are illustrated by the real-time observations of a coherent plasma oscillation and spatial resolution of current distribution in a device. This new effect also provides a mechanism for electrical control of the optical response of materials.

Ruzicka, Brian A.; Werake, Lalani K.; Xu, Guowei; Khurgin, Jacob B.; Sherman, E. Ya.; Wu, Judy Z.; Zhao, Hui

2012-02-01

433

Second-harmonic generation efficiency for multifrequency ytterbium-doped fibre laser radiation  

SciTech Connect

The second-harmonic generation (SHG) efficiency for cw Yb-doped fibre laser radiation, which is characterised by many longitudinal modes with random phases, is compared with the SHG efficiency for amplified single-frequency Nd : YAG laser radiation in ppLN and KTP crystals, characterised by the type-I and type-IIphase matching, respectively. It is shown that the conversion efficiency into the second harmonic in the multifrequency regime for both crystals is higher by a factor of about 1.6, a value close to the calculated enhancement (2 for the Gaussian mode statistics). This difference is explained by possible deviation of the statistics of the Yb-doped fibre laser radiation from Gaussian, which is confirmed by measurements of the laser temporal dynamics. (laser optics 2012)

Politko, M O; Kablukov, S I; Nemov, I N; Babin, Sergei A

2013-02-28

434

High order harmonic generation in rare gases  

SciTech Connect

The process of high order harmonic generation in atomic gases has shown great promise as a method of generating extremely short wavelength radiation, extending far into the extreme ultraviolet (XUV). The process is conceptually simple. A very intense laser pulse (I {approximately}10{sup 13}-10{sup 14} W/cm{sup 2}) is focused into a dense ({approximately}10{sup l7} particles/cm{sup 3}) atomic medium, causing the atoms to become polarized. These atomic dipoles are then coherently driven by the laser field and begin to radiate at odd harmonics of the laser field. This dissertation is a study of both the physical mechanism of harmonic generation as well as its development as a source of coherent XUV radiation. Recently, a semiclassical theory has been proposed which provides a simple, intuitive description of harmonic generation. In this picture the process is treated in two steps. The atom ionizes via tunneling after which its classical motion in the laser field is studied. Electron trajectories which return to the vicinity of the nucleus may recombine and emit a harmonic photon, while those which do not return will ionize. An experiment was performed to test the validity of this model wherein the trajectory of the electron as it orbits the nucleus or ion core is perturbed by driving the process with elliptically, rather than linearly, polarized laser radiation. The semiclassical theory predicts a rapid turn-off of harmonic production as the ellipticity of the driving field is increased. This decrease in harmonic production is observed experimentally and a simple quantum mechanical theory is used to model the data. The second major focus of this work was on development of the harmonic {open_quotes}source{close_quotes}. A series of experiments were performed examining the spatial profiles of the harmonics. The quality of the spatial profile is crucial if the harmonics are to be used as the source for experiments, particularly if they must be refocused.

Budil, K.S.

1994-05-01

435

Lunar gravity - A harmonic analysis  

NASA Technical Reports Server (NTRS)

A sixteenth-degree and sixteenth-order spherical harmonic lunar gravity field has been derived from the long-term Keplerian variations in the orbits of the Apollo subsatellites and Lunar Orbiter 5. This model resolves the major mascon gravity anomalies of the lunar near side and is in very good agreement with line-of-sight acceleration results. The far-side map shows the major ringed basins to be strong localized negative anomalies located in broad regions of positive gravity which correspond closely to the highlands. The rms pressure levels calculated from equivalent-surface height variations show that the moon and earth support nearly equal pressures, whereas Mars is appreciably stronger. The moon appears to support larger loads than earth owing to its weaker central gravity field and perhaps a colder upper lithosphere. Significant differences between the low-degree gravity and topography spectra indicate that the longer-wavelength topographic features are isostatically compensated.

Ferrari, A. J.

1977-01-01

436

Electron cyclotron harmonic wave acceleration  

NASA Technical Reports Server (NTRS)

A nonlinear analysis of particle acceleration in a finite bandwidth, obliquely propagating electromagnetic cyclotron wave is presented. It has been suggested by Sprangle and Vlahos in 1983 that the narrow bandwidth cyclotron radiation emitted by the unstable electron distribution inside a flaring solar loop can accelerate electrons outside the loop by the interaction of a monochromatic wave propagating along the ambient magnetic field with the ambient electrons. It is shown here that electrons gyrating and streaming along a uniform, static magnetic field can be accelerated by interacting with the fundamental or second harmonic of a monochromatic, obliquely propagating cyclotron wave. It is also shown that the acceleration is virtually unchanged when a wave with finite bandwidth is considered. This acceleration mechanism can explain the observed high-energy electrons in type III bursts.

Karimabadi, H.; Menyuk, C. R.; Sprangle, P.; Vlahos, L.

1987-01-01

437

Optical Cherenkov radiation in ultrafast cascaded second-harmonic generation  

SciTech Connect

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

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

2010-12-15

438

28th European Photovoltaic Solar Energy Conference and Exhibition 1.BO11.2 DOWN CONVERTER DEVICE COMBINING RARE-EARTH DOPED THIN LAYER AND PHOTONIC  

E-print Network

28th European Photovoltaic Solar Energy Conference and Exhibition 1.BO11.2 DOWN CONVERTER DEVICE COMBINING RARE-EARTH DOPED THIN LAYER AND PHOTONIC CRYSTAL FOR C-SI BASED SOLAR CELL Thierry Deschamps1 structure combines rare-earths doped thin layer allowing the down-conversion process with a photonic crystal

Paris-Sud XI, Université de

439

How spherical plasma crystals form.  

PubMed

The correlation buildup and the formation dynamics of the shell structure in a spherically confined one-component plasma are studied. Using Langevin dynamics simulations the relaxation processes and characteristic time scales and their dependence on the pair interaction and dissipation in the plasma are investigated. While in systems with Coulomb interaction (e.g., trapped ions) in a harmonic confinement shell formation starts at the plasma edge and proceeds inward, this trend is significantly weakened for dusty plasmas with Yukawa interaction. With a suitable change of the confinement conditions the crystallization scenario can be externally controlled. PMID:20366366

Kählert, H; Bonitz, M

2010-01-01

440

Modified Perfect Harmonics Cancellation Control of a Grid Interfaced SPV Power Generation  

NASA Astrophysics Data System (ADS)

This paper deals with a grid interfaced solar photo voltaic (SPV) power generating system with modified perfect harmonic cancellation (MPHC) control for power quality improvement in terms of mitigation of the current harmonics, power factor correction, control of point of common coupling (PCC) voltage with reactive power compensation and load balancing in a three phase distribution system. The proposed grid interfaced SPV system consists of a SPV array, a dc-dc boost converter and a voltage source converter (VSC) used for the compensation of other connected linear and nonlinear loads at PCC. The reference grid currents are estimated using MPHC method and control signals are derived by using pulse width modulation (PWM) current controller of VSC. The SPV power is fed to the common dc bus of VSC and dc-dc boost converter using maximum power point tracking (MPPT). The dc link voltage of VSC is regulated by using dc voltage proportional integral (PI) controller. The analysis of the proposed SPV power generating system is carried out under dc/ac short circuit and severe SPV-SX and SPV-TX intrusion.

Singh, B.; Shahani, D. T.; Verma, A. K.

2014-07-01

441

Oriented single-crystal-to-single-crystal phase transition with dramatic changes in the dimensions of crystals.  

PubMed

We report here a new polymorph of cocrystal CuQ2-TCNQ that shows an oriented single-crystal-to-single-crystal phase transition along its a-axis at ambient conditions. Upon mechanical stimulation, it converts into another polymorph accompanied by almost doubling its length and halving its thickness. Our crystallographic studies indicate the dramatic changes in crystal dimensions resulted from the prominent changes of molecular stacking patterns. A reasonable mechanism for the phenomenon was proposed on the basis of the structural, microscopic, and thermal analysis. PMID:24372005

Liu, Guangfeng; Liu, Jie; Liu, Yang; Tao, Xutang

2014-01-15

442

Rotorcraft convertible engines for the 1980s  

NASA Technical Reports Server (NTRS)

Two rotorcraft studies were executed. The goal was to identify attractive techniques for implementing convertible powerplants for the ABC, Folded Tilt Rotor, and X-wing type high speed, high-L/D rotorcraft; to determine the DOC and fuel savings benefits achieved thereby; and to define research required to bring these powerplants into existence by the 1990's. These studies are reviewed herein and the different methods of approach are pointed out as well as the key findings. Fan shaft engines using variable inlet guide vanes or torque converters, and turboprop powerplants appear attractive. Savings in DOC and fuel consumption of over 15 percent are predicted in some cases as a result of convertible engine use rather than using separate engines for the thrust and the shaft functions. Areas of required research are fan performance (including noise), integrated engine/rotorcraft control, torque converters, turbine design, airflow for rotorcraft torque control, bleed for lift flow, and transmissions and clutches.

Eisenberg, J. D.

1982-01-01

443

Radio frequency digital to analog converter  

E-print Network

Dynamic performance of high speed, high resolution digital-to-analog converters (DACs) is limited by distortion at the data switching instants. Inter-symbol interference (ISI), imperfect timing synchronization and clock ...

Luschas, Susan, 1975-

2003-01-01

444

Integrated photonic analog-to-digital converters  

E-print Network

Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical ...

Khilo, Anatol (Anatol M.)

2011-01-01

445

Waveguide mode converter and method using same  

DOEpatents

A waveguide mode converter converts electromagnetic power being transmitted in a TE.sub.0n or a TM.sub.0n mode, where n is an integer, to an HE.sub.11 mode. The conversion process occurs in a single stage without requiring the power to pass through any intermediate modes. The converter comprises a length of circular corrugated waveguide formed in a multiperiod periodic curve. The period of the curve is selected to couple the desired modes and decouple undesired modes. The corrugation depth is selected to control the phase propagation constant, or wavenumbers, of the input and output modes, thereby preventing coherent coupling to competing modes. In one embodiment, both the period and amplitude of the curve may be selectively adjusted, thereby allowing the converter to be tuned to maximize the conversion efficiency.

Moeller, Charles P. (Del Mar, CA)

1990-01-01

446

Converting a Motorcycle to Electric Power  

E-print Network

Research was conducted to determine how simple and practical it would be to convert a standard gasoline powered motorcycle to electric power. The research involved background investigation of useful concepts in electric powered motorcycles...

Simcoe, Christopher M.

2009-12-18

447

Improvements in solid state radiographic converter screens.  

NASA Technical Reports Server (NTRS)

Description of two different kinds of solid-state radiographic converter screens which have been developed. After briefly reviewing the working principles of the solid-state image converter - a sandwich type structure consisting of a photoconductive layer and an electroluminescent layer with a semiconductive layer and a black layer between them, two different kinds of radiographic converter screens are described - a radiographic amplifier screen that can be used as a substitute for the fluoroscopic screen, and a radiographic storage screen that can be used instead of radiographic films. The construction of both kinds of converters is fundamentally the same, the only difference being in the sensing photoconductive material. The radiographic amplifier screen has a moderately fast response, while the radiographic storage screen displays the image long after the irradiation is stopped.

Szepesi, Z.

1972-01-01

448

100kW Energy Transfer Multiplexer Power Converter Prototype Development Project  

SciTech Connect

Project Final Report for "100kW Energy Transfer Multiplexer Power Converter Prototype Development Project" prepared under DOE grant number DE-FG36-03GO13138. This project relates to the further development and prototype construction/evaluation for the Energy Transfer Multiplexer (ETM) power converter topology concept. The ETM uses a series resonant link to transfer energy from any phase of a multiphase input to any phase of a multiphase output, converting any input voltage and frequency to any output voltage and frequency. The basic form of the ETM converter consists of an eight (8)-switch matrix (six phase power switches and two ground power switches) and a series L-C resonant circuit. Electronic control of the switches allows energy to be transferred in the proper amount from any phase to any other phase. Depending upon the final circuit application, the switches may be either SCRs or IGBTs. The inherent characteristics of the ETM converter include the following: Power processing in either direction (bidirectional); Large voltage gain without the need of low frequency magnetics; High efficiency independent of output load and frequency; Wide bandwidth with fast transient response and; Operation as a current source. The ETM is able to synthesize true sinusoidal waveforms with low harmonic distortions. For a low power PM wind generation system, the ETM has the following characteristics and advantages: It provides voltage gain without the need of low frequency magnetics (DC inductors) and; It has constant high efficiency independent of the load. The ETM converter can be implemented into a PM wind power system with smaller size, reduced weight and lower cost. As a result of our analyses, the ETM offers wind power generation technology for the reduction of the cost and size as well as the increase in performance of low power, low wind speed power generation. This project is the further theoretical/analytical exploration of the ETM converter concept in relationship to PM wind power generator applications in the 100kW and under power range. The theoretical/analytical and bench scale work focuses on simplifying the basic ETM converter topology (in terms of parts count and complexity) for the specific application of the low power PM system. The project goals and objectives were for Spellman HV will develop a 100kW prototype ETM power converter based on paralleled lower ratings converters. The proposed configuration of this prototype is a 100kW rated converter comprised of four (4) 34kW rated modules connected in parallel (the fourth converter is included to demonstrate N+1 fault tolerance). This approach is more viable as there is lower technological risk involved in developing a 34kW-rated converter than a single 100kW unit. The modular system approach should have a lower deployment and service cost over a single unit system, because of the economics of scale (smaller units at a higher volume means lower manufacturing cost) and because of improved serviceability (a non-redundant power system with one failed module will still operate at a lower power level). There is also the added benefit that greater commercial application and acceptance should be achieved by having a modular system available in which fault tolerance (N+1 or 2N) is a feature. This modular approach would allow the output power to be increased by adding more paralleled converters. Thus, the maximum output power of the overall power system is a function of the interconnection medium (the hot swap connection subsystem), rather than the ratings of a single module. The project was implemented with Spellman HV acting as the program management and production assembly and test facility; The Baker Company acting as a technical consultant and resource when required; and dtm Associates acting as the design/development resource for the hardware development of the 100kW ETM converter prototype.

S. Merrill Skeist; Richard H. (Dick) Baker; Anthony G.P. Marini; DOE Project Officer - Keith Bennett

2006-03-21

449

Intermediate-Frequency-to-Video-Band Converter  

NASA Technical Reports Server (NTRS)

Analog and digital circuits combined to frequency-convert from intermediate frequencies directly to video-band frequencies to meet stringent requirements. IF-to-video-band converter operates on principle of signal-band cancellation in phase-quadrature circuits. Downconverts intermediate frequencies directly to video-band frequencies to near-zero frequency with good image-band rejection and low phase variation within passband.

Ham, N. C.; Chavez, V. M.; Chen, V. S.; Sato, T.

1986-01-01

450

Extended modelling for time-encoding converters  

Microsoft Academic Search

Amplitude-quantized time-encoding is beneficial in terms of Shannon capacity, a.o. for data converters. In case of asynchronous, it can be used too for power converters and amplifiers, with extra advantages in terms of power efficiency, power control, in-band quantizer distortion, and absence of both clock-induced noise and power dissipation. This paper fills in the lack of analysis and synthesis tools,

Arthur H. M. van Roermund; Foad Arfaei Malekzadeh; Mehdi Sarkeshi; Reza Mahmoudi

2010-01-01

451

Designing LLC resonant converters for optimum efficiency  

Microsoft Academic Search

This paper presents a novel design methodology for the tank circuit of LLC resonant converters, based on a simplified yet accurate model of the steady-state operation in the ldquobelow-resonancerdquo region. This model is used in a design strategy that aims to design a converter capable of operating with soft-switching in the specified input voltage range, with a load varying from

C. Adragna; S. De Simone; C. Spini

2009-01-01

452

Multiloop control for quasi-resonant converters  

Microsoft Academic Search

A multiloop control scheme for quasi-resonant converters (QRCs) is described. Like current-mode control for pulse width modulation (PWM) converters, this control offers excellent transient response and replaces the voltage-controlled oscillator (VCO) with a simple comparator. In this method, referred to as current-sense frequency modulation (CSFM), a signal proportional to the output-inductor current is compared with an error voltage signal to

Raymond B. Ridley; Wojciech A. Tabisz; Fred C. Y. Lee; V. Vorperian

1991-01-01

453

Multilevel converters for large electric drives  

Microsoft Academic Search

This paper presents transformerless multilevel power converters as an application for high-power and\\/or high-voltage electric motor drives. Multilevel converters: (1) can generate near-sinusoidal voltages with only fundamental frequency switching; (2) have almost no electromagnetic interference or common-mode voltage; and (3) are suitable for large voltampere-rated motor drives and high voltages. The cascade inverter is a natural fit for large automotive

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

1999-01-01

454

SP100 thermoelectric converter technology development  

Microsoft Academic Search

The SP-100 thermoelectric power converter utilizes reactor-delivered heat and transforms it into usable electric power by purely static means. The converter features conduction coupling of TE cells to both the heat source and the heat rejection elements. The conduction coupling technique offers significant improvement in the system specific power since it avoids the losses associated with parasitic Delta(T)s across the

D. N. Matteo; J. A. Bond; R. J. Rosko

1992-01-01

455

Protein Crystallization  

NASA Technical Reports Server (NTRS)

Nucleation, growth and perfection of protein crystals will be overviewed along with crystal mechanical properties. The knowledge is based on experiments using optical and force crystals behave similar to inorganic crystals, though with a difference in orders of magnitude in growing parameters. For example, the low incorporation rate of large biomolecules requires up to 100 times larger supersaturation to grow protein, rather than inorganic crystals. Nucleation is often poorly reproducible, partly because of turbulence accompanying the mixing of precipitant with protein solution. Light scattering reveals fluctuations of molecular cluster size, its growth, surface energies and increased clustering as protein ages. Growth most often occurs layer-by-layer resulting in faceted crystals. New molecular layer on crystal face is terminated by a step where molecular incorporation occurs. Quantitative data on the incorporation rate will be discussed. Rounded crystals with molecularly disordered interfaces will be explained. Defects in crystals compromise the x-ray diffraction resolution crucially needed to find the 3D atomic structure of biomolecules. The defects are immobile so that birth defects stay forever. All lattice defects known for inorganics are revealed in protein crystals. Contribution of molecular conformations to lattice disorder is important, but not studied. This contribution may be enhanced by stress field from other defects. Homologous impurities (e.g., dimers, acetylated molecules) are trapped more willingly by a growing crystal than foreign protein impurities. The trapped impurities induce internal stress eliminated in crystals exceeding a critical size (part of mni for ferritin, lysozyme). Lesser impurities are trapped from stagnant, as compared to the flowing, solution. Freezing may induce much more defects unless quickly amorphysizing intracrystalline water.

Chernov, Alexander A.

2005-01-01

456

A high-fidelity harmonic drive model.  

SciTech Connect

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

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

2012-01-01

457

Harmonization in laboratory medicine: the complete picture.  

PubMed

Evidence of the acute lack of interchangeable laboratory results and consensus in current practice among clinical laboratories has underpinned greater attention to standardization and harmonization projects. Although the focus is mainly on the standardization of measurement procedures, the scope of harmonization goes beyond method and analytical results: it includes all other aspects of laboratory testing, including terminology and units, report formats, reference intervals and decision limits, as well as test profiles and criteria for the interpretation of results. This review provides further insight on the issue of harmonization in laboratory medicine in view of the urgent need for a complete picture now that old and new drivers are calling for more effective efforts in this field. The main drivers for standardization and harmonization projects are first and foremost patient safety, but also the increasing trends towards consolidation and networking of clinical laboratories, accreditation programs, clinical governance, and advances in Information Technology (IT), including the electronic patient record. The harmonization process, which should be considered a three-tier approach involving local, national and international fronts, must go beyond the harmonization of methods and analytical results to include all other aspects of laboratory testing. A pertinent example of the importance of a complete picture in harmonization programs is given by the National Bone Health Alliance working in the field of bone turnover markers in cooperation with scientific societies including the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). PMID:23435100

Plebani, Mario

2013-04-01

458

Generation of ultraviolet radiation with wide angular tolerance in cesium lithium borate crystal  

NASA Astrophysics Data System (ADS)

Tangential phase-matching has been realised in cesium lithium borate (CLBO) crystal for the first time for the generation of fourth harmonic (266 nm) of Nd:YAG and third harmonic (226.7 nm) of a dye laser radiation by second harmonic generation and sum-frequency mixing with the angular tolerance as large as 22 mrad and 21 mrad respectively, over one of the interacting beams. An energy conversion efficiency of 15% for fourth harmonic generation is obtained with a 5.5 mm thick crystal and with the average pump powers only 170 and 70 mW. A set of Sellmeier dispersion equations for the CLBO crystal have also been formulated.

Bhar, Gopal C.; Kumbhakar, Pathik; Chaudhary, Anil K.

2000-09-01

459

Growing Crystals  

NSDL National Science Digital Library

In this activity, students grow crystals of the same substance over different periods of time to determine the relationship between time of growth and the size of the crystal. Students should understand that in this investigation evaporation of water is analogous to heat loss in a large body of rock. They learn that small crystals grow in igneous rocks that cool relatively quickly while larger crystals take more time, so they grow in igneous rocks that cool slowly. Students also learn that diamonds are found in a matrix of kimberlite, a vein or pipe of molten rock formed deep underground, and that over millions of years, heat and pressure transform carbon into diamonds.

460

An Isolated DC\\/DC Converter Using High-Frequency Unregulated $LLC$ Resonant Converter for Fuel Cell Applications  

Microsoft Academic Search

This paper suggests an isolated dc\\/dc converter using an unregulated LLC converter for fuel cell applications. The LLC converter operates as an isolated voltage amplifier with a constant voltage gain, and a nonisolated converter installed in the input stage regulates the output voltage under a wide variation of fuel cell stack voltage. By separating the functions, the unregulated LLC converter

Jun-Young Lee; Yu-Seok Jeong; Byung-Moon Han

2011-01-01

461

31 CFR 363.164 - Is a converted savings bond eligible to be converted back into a definitive bond?  

Code of Federal Regulations, 2010 CFR

...converted savings bond eligible to be converted back into a definitive bond? 363.164 ...converted savings bond eligible to be converted back into a definitive bond? Once a definitive...book-entry bond, it may not be converted back into a definitive...

2010-07-01

462

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

463

Constructing analysis-suitable parameterization of computational domain from CAD boundary by variational harmonic method  

NASA Astrophysics Data System (ADS)

In isogeometric analysis, parameterization of computational domain has great effects as mesh generation in finite element analysis. In this paper, based on the concept of harmonic mapping from the computational domain to parametric domain, a variational harmonic approach is proposed to construct analysis-suitable parameterization of computational domain from CAD boundary for 2D and 3D isogeometric applications. Different from the previous elliptic mesh generation method in finite element analysis, the proposed method focuses on isogeometric version, and converts the elliptic PDE into a nonlinear optimization problem, in which a regular term is integrated into the optimization formulation to achieve more uniform and orthogonal iso-parametric structure near convex (concave) parts of the boundary. Several examples are presented to show the efficiency of the proposed method in 2D and 3D isogeometric analysis.

Xu, Gang; Mourrain, Bernard; Duvigneau, Régis; Galligo, André

2013-11-01

464

Harmonic power flow for unbalanced systems  

SciTech Connect

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

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

1993-10-01

465

Synthesis, crystal growth and physiochemical characterization of organic NLO crystal: L-ornithinium dipicrate (LODP)  

NASA Astrophysics Data System (ADS)

L-ornithinium dipicrate (LODP) has been synthesized and good quality single crystals were grown by slow evaporation method at room temperature. Single crystal XRD confirms that the grown crystal belongs to the monoclinic system with the noncentrosymmetric space group P21. Powder X-ray diffraction study confirms the crystalline nature of the compound. FTIR spectral analysis confirms the functional group in the synthesized compound. Thermogravimetric and differential thermal analyses reveal the thermal stability of the crystal. The optical absorption spectrum shows the absence of absorption between 475 nm and 800 nm. The dielectric measurements were carried out to estimate the dielectric parameters of the grown crystal in the frequency range from 50 Hz to 5 MHz at various temperatures. The second harmonic property has been investigated by Kurtz-Perry powder technique. The relative SHG efficiency of LODP is found to be 14.57 times greater than that of the reference material KDP.

Balaprabhakaran, S.; Chandrasekaran, J.; Babu, B.; Thirumurugan, R.; Anitha, K.

2015-02-01

466

Synthesis, crystal growth and physiochemical characterization of organic NLO crystal: L-ornithinium dipicrate (LODP).  

PubMed

L-ornithinium dipicrate (LODP) has been synthesized and good quality single crystals were grown by slow evaporation method at room temperature. Single crystal XRD confirms that the grown crystal belongs to the monoclinic system with the noncentrosymmetric space group P21. Powder X-ray diffraction study confirms the crystalline nature of the compound. FTIR spectral analysis confirms the functional group in the synthesized compound. Thermogravimetric and differential thermal analyses reveal the thermal stability of the crystal. The optical absorption spectrum shows the absence of absorption between 475 nm and 800 nm. The dielectric measurements were carried out to estimate the dielectric parameters of the grown crystal in the frequency range from 50 Hz to 5 MHz at various temperatures. The second harmonic property has been investigated by Kurtz-Perry powder technique. The relative SHG efficiency of LODP is found to be 14.57 times greater than that of the reference material KDP. PMID:25448969

Balaprabhakaran, S; Chandrasekaran, J; Babu, B; Thirumurugan, R; Anitha, K

2015-02-01

467

Harmonic Lasing Characterization at Jefferson Lab  

SciTech Connect

Harmonic lasing is normally suppressed because of lasing at the fundamental wavelength. It can, however, be achieved by using any of several methods that suppress fundamental lasing. In this paper we discuss two methods used at Jefferson Lab. The first is to use the characteristics of dielectric coatings to allow harmonic lasing at cavity lengths longer than the synchronous length for the fundamental. The second is to use a dielectric coating that has little reflectivity at the fundamental. This allows us to directly compare fundamental and harmonic lasing with the same optical resonator and electron beam. We present measurement carried out at Jefferson Lab using the IR Upgrade FEL operating at 0.53, 0.94, 1.04, 1.6, and 2.8 microns in which both schemes are used to produce lasing at both the 3rd and 5th harmonic of the fundamental.

Stephen Benson; Michelle D. Shinn

2006-08-27

468

Geomagnetic local and regional harmonic analyses.  

USGS Publications Warehouse

Procedures are developed for using rectangular and cylindrical harmonic analyses in local and regional areas. Both the linear least squares analysis, applicable when component data are available, and the nonlinear least squares analysis, applicable when only total field data are available, are treated. When component data are available, it is advantageous to work with residual fields obtained by subtracting components derived from a harmonic potential from the observed components. When only total field intensity data are available, they must be used directly. Residual values cannot be used. Cylindrical harmonic analyses are indicated when fields tend toward cylindrical symmetry; otherwise, rectangular harmonic analyses will be more advantageous. Examples illustrating each type of analysis are given.-Author

Alldredge, L.R.

1982-01-01

469

Dirac-harmonic maps with torsion  

E-print Network

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

Volker Branding

2014-05-20

470

Limits of High Harmonic Generation conversion efficiency  

E-print Network

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

Gkortsas, Vasileios-Marios

2013-01-01

471

SEVENTH HARMONIC 20 GHz CO-GENERATOR  

SciTech Connect

To satisfy the need for multi-MW rf sources in frequency ranges where commercial sources do not exist, a study was undertaken on a class of devices based on gyro-harmonic frequency multiplication. This mechanism relies upon adding energy in gyrating motion to a linear electron beam that traverses a rotating-mode TE111-mode drive cavity in a dc magnetic field. The beam then drifts along the magnetic field into a second cavity, operating in the TEn11-mode tuned to the nth harmonic of the drive cavity. Studies of this configuration have been carried out for 2 < n < 7. Results are given for multi-MW, efficient operation of a 7th harmonic device operating at 20 GHz, and a 2nd harmonic device operating at 22.4 GHz.

Hirshfield, Jay L

2014-04-08

472

Harmonic superconformal maps of surfaces in Hn  

NASA Astrophysics Data System (ADS)

The class of harmonic superconformal maps from Riemann surfaces into real hyperbolic spaces is considered and harmonic sequences are constructed for these maps. They are used to obtain a rigidity result for such maps and to construct primitive lifts into an auxiliary flag space Fm. It is also shown that superconformal harmonic maps into H2 m and H2 m-1 are locally described by 2D-affine Toda fields associated to the pair ( so(2m+1,C),?) , where ? is the involution determined by the non-compact real form so(1,2m) . Applying the Adler-Kostant-Symes integration scheme to appropriate loop algebras we construct finite type primitive maps ?:H 2? Fm, and harmonic superconformal maps f: H2? H2 m and hence finite type Toda fields.

Hulett, Eduardo

2002-05-01

473

Improved Efficiency Type II Second Harmonic Generation  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

474

Harmonic Representation of Combinations and Partitions  

E-print Network

In the present article a new method of deriving integral representations of combinations and partitions in terms of harmonic products has been established. This method may be relevant to statistical mechanics and to number theory.

Michalis Psimopoulos

2011-03-01

475

Harmonic Control Based on Fuzzy Logic  

NASA Astrophysics Data System (ADS)

Proliferation of nonlinear loads in power systems has increased harmonic pollution and deteriorated power quality. Passive filtering has typically been the standard technology for harmonic and reactive power compensation .With the advancements in power electronics, active filtering is being more widely considered given its flexibility and precise control. However, cost, complexity, and reliability are considered the major drawbacks of active filters. In this paper a new fuzzy logic is introduced to control the harmonic in the power system, which has more advantages such as simplicity, ease of application, flexibility, speed and ability to deal with imprecision and uncertainties .The introduction of fuzzy logic can not only reduce harmonic,but also correct the power factor.

Wu, Shihong; Dang, Gang; Wang, Jun; Li, Xiaohui; Zhang, Zhixia; Jiang, Fengli

476

Second harmonic generation in transition metamaterials  

NASA Astrophysics Data System (ADS)

We show that the resonant field enhancement of light obliquely incident on a quadratically nonlinear metamaterial with refractive index gradually changing from positive to negative values enables ultracompact geometry for second harmonic generation at significantly reduced input powers.

Kudyshev, Zhaxylyk A.; Gabitov, Ildar R.; Maimistov, Andrei I.; Sagdeev, Roald Z.; Litchinitser, Natalia M.

2014-11-01

477

Harmonizing Systems and Software Cost Estimation  

E-print Network

The objective of this paper is to examine the gaps and overlaps between software and systems engineering cost models with intent to harmonize the estimates in engineering engineering estimation. In particular, we evaluate ...

Wang, Gan

2009-07-19

478

Dual aperture dipole magnet with second harmonic component  

DOEpatents

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

Praeg, W.F.

1983-08-31

479

Dual aperture dipole magnet with second harmonic component  

DOEpatents

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

Praeg, Walter F. (Palos Park, IL)

1985-01-01

480

Harmonic bundle solutions of Topological-antitopological fusion  

E-print Network

Harmonic bundle solutions of Topological-antitopological fusion in para-complex geometry Lars Sch@math.uni-hamburg.de September 14, 2006 Abstract In this work we introduce the notion of a para-harmonic bundle, i.e. the general- ization of a harmonic bundle [Si] to para-complex differential geometry. We show that para-harmonic

Paris-Sud XI, Université de

481

High harmonic generation in the relativistic *, A. GOPAL2  

E-print Network

LETTERS High harmonic generation in the relativistic limit B. DROMEY1 , M. ZEPF1 *, A. GOPAL2 , K, measurements with unprecedented temporal resolution1­6 . Harmonics from laser­solid target interactions have of harmonic efficiency to high orders by driving harmonic production to the relativistic limit1 . Here we

482

Local Harmonic Estimation in Musical Sound Rafael A. IRIZARRY  

E-print Network

Local Harmonic Estimation in Musical Sound Signals Rafael A. IRIZARRY Statistical modeling so a local harmonic model that tracks changes in pitch and in the amplitudes of the harmonics is fit estimates of the harmonic signal and of the noise signal. Different musical composition applications may

Irizarry, Rafael A.

483

2. LOOKING NORTH ON COMMERCE ST. SHOWING HARMON MATTRESS FACTORY. ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

2. LOOKING NORTH ON COMMERCE ST. SHOWING HARMON MATTRESS FACTORY. BRIDGE CONNECTS HARMON MATTRESS FACTORY WITH HARMON WAREHOUSE (SEE PHOTO HABS WA-165-15). BUILDING IN LEFT FOREGROUND IS LINDSTROM-BERG CABINET FACTORY (SEE PHOTO HABS WA-165-36). - Union Depot Area Study, F. S. Harmon Mattress Company, 1953 South C Street, Tacoma, Pierce County, WA

484

Distributed Active Filters for Harmonic Resonance Suppression in Industrial Facilities  

Microsoft Academic Search

Significant harmonics amplification in industry facilities has been reported. This phenomenon is identified as harmonic resonance between power factor correction capacitor banks and system inductors. Conventional active filter techniques aimed at harmonic current compensation are not effective under this resonance situation. This paper proposes a distributed active filter design for harmonics damping within industry facility. In this system, the active

Shen-Yuan Kuo; Tzung-Lin Lee; Chien-An Chen; Po-Tai Cheng; Ching-Tsai Pan

2007-01-01

485

Efficient Harmonic Filter Allocation in an Industrial Distribution System  

Microsoft Academic Search

In order to properly suppress the harmonic current in a power system, the harmonic similarity metric is developed in this paper and used to establish an efficient strategy for harmonic filter placement. To validate the strategy, an industrial distribution system is analyzed under two harmonic current injection scenar- ios. It is demonstrated that the proposed strategy has a robust ability

Philip E. C. Stone; Jingjiang Wang; Yong-June Shin; Roger A. Dougal

2012-01-01

486

The influence of thermal deformation processes on frequency conversion in an LBO crystal  

NASA Astrophysics Data System (ADS)

The influence of the thermal deformation process on frequency conversion in an LBO crystal is considered. The different temperature bandwidths at the harmonic generation of YAG:Nd laser radiation were obtained experimentally three times at different types of crystal fixation.

Arapov, Yu D.; Dyakov, V. A.; Grechin, S. G.; Kasyanov, I. V.

2014-12-01

487

Harmonic Noise-Induced Resonant Passing in an Inverse Harmonic Potential  

NASA Astrophysics Data System (ADS)

The problem of a Brownian particle driven by harmonic noise passing over the saddle point in an inverse harmonic potential is studied. The passing probability over the saddle point is obtained analytically. The stationary passing probability is found to arrive at its maximal value when the frequency parameter of the harmonic noise is close to the frequency of the inverse harmonic potential, which results in a resonance phenomenon. With an increase in the frequency parameter of noise, the Brownian particle will recross the barrier, thereby increasing the escape rate and resulting in a decrease in the passing probability.

Han, Jie; Bao, Jing-Dong

2014-12-01

488

Supersymmetric partners of the truncated harmonic oscillator  

NASA Astrophysics Data System (ADS)

First and second order supersymmetric transformations are applied to the truncated harmonic oscillator to generate new Hamiltonians with known spectra. We also study the effect of these transformations on the eigenfunctions of the initial Hamiltonian. Finally the link between first and the second order supersymmetric partners of the truncated harmonic oscillator which possess third-order differential ladder operators with the Painlevé IV equation is used to obtain several solutions of this non-linear second-order differential equation.

Fernández C, David J.; Morales-Salgado, V. S.

2014-05-01

489

Object recognition using cylindrical harmonic filter.  

PubMed

We present the cylindrical harmonic filter for three-dimensional (3D) discrete correlation between range data. The filter guarantees invariance of the correlation peak intensity under target rotation around z-axis. It can be considered a harmonic decomposition, in cylindrical coordinates, of the 3D Fourier spectrum of the target. Some simulation results confirm the in-plane rotation invariance and the discrimination of the filter. PMID:19483822

Guerrero Bermúdez, Jáder

2004-06-28

490

Nonlinearly driven harmonics of Alfvén modes  

SciTech Connect

In order to study the leading order nonlinear magneto-hydrodynamic (MHD) harmonic response of a plasma in realistic geometry, the AEGIS code has been generalized to account for inhomogeneous source terms. These source terms are expressed in terms of the quadratic corrections that depend on the functional form of a linear MHD eigenmode, such as the Toroidal Alfvén Eigenmode. The solution of the resultant equation gives the second order harmonic response. Preliminary results are presented here.

Zhang, B., E-mail: bozhang@austin.utexas.edu; Breizman, B. N.; Zheng, L. J.; Berk, H. L. [Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States)] [Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States)

2014-01-15

491

Shock Waves in Falling Coupled Harmonic Oscillators  

NASA Astrophysics Data System (ADS)

Shock waves propagate in falling coupled harmonic oscillators. The bottom end of coupled harmonic oscillators does not fall downwards until a shock wave reaches the bottom end. The exact solution can be expressed by the Fourier series expansion, and an approximate solution can be expressed by the integral of the Airy function. The width of the shock wave increases slowly in accordance with a power law.

Sakaguchi, Hidetsugu

2013-07-01

492

Effective ATI channels in high harmonic generation  

NASA Astrophysics Data System (ADS)

Harmonic generation by an atom in a laser field is described by the three-step mechanism as proceeding via above-threshold ionization (ATI) followed by electron propagation in the laser-dressed continuum and subsequent laser-assisted recombination (LAR). The amplitude of the harmonic production is given by the coherent sum of contributions from different intermediate ATI channels labelled by the number, m, of absorbed laser photons. The range of m-values that give a substantial contribution is explored and found to be rather broad for high harmonic generation. The coherence effects are of crucial importance as they are responsible for the characteristic pattern of harmonic intensities with a plateau domain followed by a cut-off region. Due to the multiphoton nature of the process, an efficient summation of m-contributions can be carried out within the framework of the saddle-point method. The saddle points correspond to some complex-valued labels m = mc associated with the intermediate effective ATI channels in the three-step harmonic generation process. The advantage of this approach stems from the fact that summation over a large number of conventional ATI m-channels is replaced by summation over a small number of effective mc-channels. The equation governing mc has a transparent physical meaning: the electron ejected from the atom on the first (ATI) stage should return to the core to make LAR possible. The effective channel labels m move along characteristic trajectories in the complex plane as the system parameters vary. In the cut-off region of the harmonic spectrum a single effective channel contributes. For lower harmonics, in the plateau domain, two effective ATI channels become essential. The interference of their contributions leads to an oscillatory pattern in the harmonic generation rates. The calculated rates are in good agreement with the results obtained by other approaches.

Kuchiev, M. Yu; Ostrovsky, V. N.

2001-02-01

493

Coherent states for the nonlinear harmonic oscillator  

SciTech Connect

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

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

2012-06-15

494

HARMONIC CAVITY PERFORMANCE FOR NSLS-II  

SciTech Connect

NSLS-II is a 3 GeV ultra-high brightness storage ring planned to succeed the present NSLS rings at BNL. Ultralow emittance combined with short bunch length means that it is critical to minimize the effects of Touschek scattering and coherent instabilities. Improved lifetime and stability can be achieved by including a third-harmonic RF cavity in the baseline design. This paper describes the required harmonic RF parameters and the expected system performance.

BLEDNYKH, A.; KRINSKY, S.; PODOBEDOV, B.; ROSE, J.; TOWNE, N.; WANG, J.M.

2005-05-15

495

The Case of the Missing Harmonic Structure  

SciTech Connect

Classical synchrotron radiation theory predicts emission in harmonics of the revolution frequency of the radiating particles. The Synchrotron Ultraviolet Radiation Facility SURF is an electron storage ring based on the weak focusing principle. The particles travel on a near perfect circular path, which makes SURF an ideal test-bed for synchrotron radiation theory. The harmonic structure of the radiation emitted by the electrons stored in SURF will be explored.

Arp, U. [Electron and Optical Physics Division, National Institute of Standards and Technology, 100 Bureau Dr, MS 8410, Gaithersburg, MD 20899-8410 (United States)

2007-01-19

496

Isolated and soft-switched power converter  

DOEpatents

An isolated and soft-switched power converter is used for DC/DC and DC/DC/AC power conversion. The power converter includes two resonant tank circuits coupled back-to-back through an isolation transformer. Each resonant tank circuit includes a pair of resonant capacitors connected in series as a resonant leg, a pair of tank capacitors connected in series as a tank leg, and a pair of switching devices with anti-parallel clamping diodes coupled in series as resonant switches and clamping devices for the resonant leg. The power converter is well suited for DC/DC and DC/DC/AC power conversion applications in which high-voltage isolation, DC to DC voltage boost, bidirectional power flow, and a minimal number of conventional switching components are important design objectives. For example, the power converter is especially well suited to electric vehicle applications and load-side electric generation and storage systems, and other applications in which these objectives are important. The power converter may be used for many different applications, including electric vehicles, hybrid combustion/electric vehicles, fuel-cell powered vehicles with low-voltage starting, remote power sources utilizing low-voltage DC power sources, such as photovoltaics and others, electric power backup systems, and load-side electric storage and generation systems.

Peng, Fang Zheng (Knoxville, TN); Adams, Donald Joe (Knoxville, TN)

2002-01-01

497

Materials technology for Stirling space power converters  

NASA Technical Reports Server (NTRS)

This program was conducted in support of the NASA LeRC development of the Stirling power converter (SPC) for space power applications. The objectives of this contract were: (1) to perform a technology review and analyses to support the evaluation of materials issues for the SPC; (2) to evaluate liquid metal compatibility issues of the SPC; (3) to evaluate and define a transient liquid phase diffusion bonding (TLPDB) process for the SPC joints to the Udimet 720 heater head; and (4) to evaluate alternative (to the TLPDB) joining techniques. In the technology review, several aspects of the current Stirling design were examined including the power converter assembly process, materials joining, gas bearings, and heat exchangers. The supporting analyses included GLIMPS power converter simulation in support of the materials studies, and system level analysis in support of the technology review. The liquid metal compatibility study evaluated process parameters for use in the Stirling power converter. The alternative joining techniques study looked at the applicability of various joining techniques to the Stirling power converter requirements.

Baggenstoss, William; Mittendorf, Donald

1992-01-01

498

Harmonic Functions are Real Analytic1 On this very short note we prove that harmonic functions are real analytic functions.  

E-print Network

Harmonic Functions are Real Analytic1 On this very short note we prove that harmonic functions prove Lemma 1 using the mean value property of harmonic functions, Green's theorem and the maximum principle. Lemma 1 (estimate on first derivative) Suppose w is harmonic in Rn , > 0, y and B

Cabral, Marco

499

Kinetics : CatalyticConverters (4 Variations)  

NSDL National Science Digital Library

The following table illustrates the changes in emissions requirements for automobiles: Pollutant 1970 Emissions 1990 Emissions CA ultra-low emissions C x H y 1.5 g/mile 0.25 g/mile 0.04 g/mile CO 15 g/mile 3.4 g/mile 1.7 g/mile NO x 3.1 g/mile 0.4 g/mile 0.2 g/mile Catalytic converters are used in automobiles to convert pollutants in engine emissions to benign products. Catalytic converters in today's automobiles are made of a porous ceramic brick that has been coated with catalysts, additives, stabilizers, and support materials. Corning has developed bricks that have very thin-walled channels with 600 channels per square inch. Which of the following research goals did they target?

500

Design of high power density DC Bus Converter based on LLC resonant converter with synchronous rectifier  

Microsoft Academic Search

The LLC resonant converter can easily achieve soft-switching and magnetic components integration that makes it an excellent candidate for DC bus converter. In low voltage high output current applications, the design of synchronous rectifier (SR) and transformer is the key issue. A SR driving scheme with less circuit complexity is adopted for switching frequency at the resonant frequency in this

Niu Huapeng; Pei Yunqing; Yang Xu; Wang Laili; Wang Zhaoan

2009-01-01