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1

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

Microsoft Academic Search

Potassium dihydrogen phosphate (KDP) crystals have been used as harmonic converters on the Nova laser at LLNL for more than six years. All crystals were coated with a single layer, quarterwave AR coating of porous silica with a refractive index of 1.22. This was prepared by a sol-gel process and was applied from a colloidal suspension by spin coating at

Ian M. Thomas

1991-01-01

2

Converter-connected distributed generation units with integrated harmonic voltage damping and harmonic current compensation function  

Microsoft Academic Search

The steadily growing share of converter-connected distributed generators, combined with a large amount of nonlinear and unbalanced loads connected to the electric power system, has led to a degraded power quality. Both harmonic voltage and harmonic current distortion may cause many unfavourable effects on the power system. However, the converter-connected distributed generators can be redesigned to have a positive effect

Bert Renders; Koen De Gussemé; Wouter R. Ryckaert; Lieven Vandevelde

2009-01-01

3

Generation of harmonics and supercontinuum in nematic liquid crystals  

SciTech Connect

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

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

2013-02-28

4

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

Microsoft Academic Search

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

Li Qiang; He Zhiyuan; Tang Guangfu

2010-01-01

5

Phosphorus Removal Characteristics in Hydroxyapatite Crystallization Using Converter Slag  

Microsoft Academic Search

This study was performed to investigate the phosphorus removal characteristics in hydroxyapatite (HAP) crystallization using converter slag as a seed crystal and the usefulness of a slag column reactor system. The effects of alkalinity, and the isomorphic-substitutable presence of ionic magnesium, fluoride, and iron on HAP crystallization seeded with converter slag, were examined using a batch reactor system. The phosphorus

EUNG-HO KIM; HWAN-KOOK HWANG; SOO-BIN YIM

2006-01-01

6

Elimination of sub-harmonic oscillation of digital average current control buck converter  

Microsoft Academic Search

The sub-harmonic oscillation of digital average current (DAC) control buck converter with single-edge modulation (trailing-edge modulation and leading-edge modulation) is investigated in this paper. It has been shown that both digital slope compensation (DSC) and digital reposition compensation (DRC) of duty ratio ac component can not be used to eliminate the sub-harmonic oscillation of DAC control buck converter with single-edge

Guohua Zhou; Jianping Xu; Jinping Wang; Qingbo Mu

2008-01-01

7

A New Harmonic Analysis Method for AC\\/DC\\/AC Converters  

Microsoft Academic Search

A new direct harmonic analysis approach for AC\\/DC\\/AC conversion system is presented and discussed. It uses the characteristic of the vectors and their sequence characteristic to obtain the voltage and current transfer rules of the converters in conversion system, and then get the direct harmonic analysis method of the whole AC\\/DC\\/AC. The method can deduce the expression of AC harmonic

Zhaorui Lv; Li Xia; Zhengguo Wu

2008-01-01

8

Converting Gravity-Bin Parameters To Spherical Harmonics  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

9

A Multisampling SVM Scheme for Current Source Converters With Superior Harmonic Performance  

Microsoft Academic Search

The device switching frequency of current source converters (CSCs) in high-power medium-voltage applications is usually several hundred Hz. Selective harmonic elimination (SHE) has been the dominant modulation scheme because of its capability to eliminate unwanted low-order harmonics at low switching frequencies. Conventional space vector modulation (SVM), as another CSC modulation scheme, provides variable modulation index control but its output contains

Jingya Dai; Yongqiang Lang; Bin Wu; Navid R. Zargari

2009-01-01

10

Dynamics of anharmonic surfaces in harmonic crystals  

NASA Astrophysics Data System (ADS)

Explicit expressions are given for the effective equations of motion for surface atoms placed in a general anharmonic potential and attached to semi-infinite harmonic bulk substrates. Three types of one-dimensional substrates are considered: i) continuous dispersionless, ii) discrete with nearest neighbours harmonic interactions, and iii) a substrate showing a strong spatial dispersion due to next-nearest neighbours interactions. The elimination of the harmonic degrees of freedom of the dispersionless substrate i) reduces the problem to the damped Duffing oscillator in the case of an external force applied to the surface atom, and to an extended Duffing oscillator with time-dependent coefficients in the case of scattering of a phonon incoming from the bulk. In both remaining cases [ ii) and iii)]the resulting equations of motion are Volterra integro-differential equations. The equations of motion obtained allow for the study of transitive regimes, of higher harmonics generation and of chaotic behaviour, due to the surface anharmonicity.

Zieli?ski, P.; ?odziana, Z.; Srokowski, T.

1998-12-01

11

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

12

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

Microsoft Academic Search

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

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

2006-01-01

13

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

14

Second harmonic generation in periodic and aperiodic transversely poled crystals  

Microsoft Academic Search

One of the greatest advances in the field of second-harmonic generation (SHG) has been brought about by the use of multi-domain crystals with periodic or aperiodic alteration of the sign of the quadratic nonlinearity. All applications involving the SHG process, however, rely on the propagation of the fundamental beam in the plane perpendicular to the ferroelectric domain walls. In this

S. M. Saltiel; Y. Sheng; N. Voloch; D. N. Neshev; W. Krolikowski; K. Koynov; B. Ma; A. Arie; Yu. S. Kivshar

2009-01-01

15

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

16

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

17

Quartz crystal microbalance based on passive frequency to voltage converter  

NASA Astrophysics Data System (ADS)

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

Burda, Ioan; Tunyagi, Arthur

2012-02-01

18

Resonant second harmonic generation in a gallium nitride two-dimensional photonic crystal on silicon  

NASA Astrophysics Data System (ADS)

We demonstrate second harmonic generation in a gallium nitride photonic crystal cavity embedded in a two-dimensional free-standing photonic crystal platform on silicon. The photonic crystal nanocavity is optically pumped with a continuous-wave laser at telecom wavelengths in the transparency window of the nitride material. The harmonic generation is evidenced by the spectral range of the emitted signal, the quadratic power dependence vs. input power, and the spectral dependence of second harmonic signal. The harmonic emission pattern is correlated to the harmonic polarization generated by the second-order nonlinear susceptibilities ?zxx (2 ), ?zyy (2 ) and the electric fields of the fundamental cavity mode.

Zeng, Y.; Roland, I.; Checoury, X.; Han, Z.; El Kurdi, M.; Sauvage, S.; Gayral, B.; Brimont, C.; Guillet, T.; Mexis, M.; Semond, F.; Boucaud, P.

2015-02-01

19

Design and performance of the Beamlet laser third harmonic frequency converter  

SciTech Connect

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

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

1995-09-12

20

Efficient fourth harmonic generation of Nd: glass lasers in ADP and DKDP crystals  

NASA Astrophysics Data System (ADS)

Experimental research on non-critical phase-matching fourth harmonic generation with ADP and DKDP crystals are reported. The characteristics of 2?-to-4? efficiency as function of incident angle, crystal temperature and input 2? intensity have been investigated in detail, and the 2?-to-4? conversion efficiency has been demonstrated up to 84.1% with ADP crystal and 85.1% with DKDP crystal, respectively. Nevertheless, the spatial non-uniformity of rapid grown DKDP crystal has to be improved while the temperature control uniformity should be upgraded for ADP crystal to realize large aperture high efficiency fourth harmonic generation.

Wang, Fang; Li, Fu-quan; Chai, Xiang-xu; Wang, Li-quan; Han, Wei; Jia, Huai-ting; Zhou, Li-dan; Feng, Bin; Xiang, Yong

2015-02-01

21

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.

2015-03-01

22

Superposed second-harmonic Talbot self-image from a PPLT crystal  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate the superposed second-harmonic Talbot self-image in a z-cut periodically-poled LiTaO3 crystal. The generated second-harmonic (SH) waves in the positive and negative domains have the same intensity but different phases (a phase shift of ?) due to the opposite poling directions, i.e. a second-harmonic phase pattern is generated from the crystal. By introducing a reference SH wave, we can selectively study the self-imaging originating from the SH patterns with different phases. In the integer and fractional Talbot planes, the two patterns interfere with each other and form superposed self-imaging patterns.

Wei, Dunzhao; Liu, Dongmei; Hu, Xiaopeng; Zhang, Yong; Xiao, Min

2014-09-01

23

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

NASA Astrophysics Data System (ADS)

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

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

1993-11-01

24

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

PubMed

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

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

2014-04-15

25

Highly efficient mode converter for coupling light into wide slot photonic crystal waveguide.  

PubMed

We design, fabricate and experimentally demonstrate a highly efficient adiabatic mode converter for coupling light into a silicon slot waveguide with a slot width as large as 320 nm. This strip-to-slot mode converter is optimized to provide a measured insertion loss as low as 0.08 dB. Our mode converter provides 0.1 dB lower loss compared to a conventional V-shape mode converter. This mode converter is used to couple light into and out of a 320 nm slot photonic crystal waveguide, and it is experimentally shown to improve the coupling efficiency up to 3.5 dB compared to the V-shape mode converter, over the slow-light wavelength region. PMID:25321272

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

2014-08-25

26

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

27

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

28

Digital Test Method for Embedded Converters with Unknown-Phase Harmonics  

E-print Network

. INTRODUCTION The popularity of portable data and communication applications like smart phones, laptops, or MP3 to the input phase. This assumption is not valid for all converter architectures, where filtering effects may

Paris-Sud XI, Université de

29

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

30

Converter  

NSDL National Science Digital Library

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

2010-01-01

31

Semiclassical analysis of high harmonic generation in bulk crystals  

NASA Astrophysics Data System (ADS)

High harmonic generation (HHG) in solids is investigated. We find that interband emission is dominant for the midinfrared laser driver frequencies, whereas intraband emission dominates the far-infrared range. Interband HHG is similar to atomic HHG and therewith opens the possibility to apply atomic attosecond technology to the condensed matter phase. Interband emission is investigated with a quasiclassical method, by which HHG can be modeled based on the classical trajectory analysis of electron-hole pairs. This analysis yields a simple approximate cutoff law for HHG in solids. Differences between HHG in atoms and solids are identified that are important for adapting atomic attosecond technology to make it applicable to condensed matter.

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

2015-02-01

32

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

E-print Network

. Tolbert, Keith J. McKenzie and Zhong Du ECE Department, The University of Tennessee, Knoxville, TN 37996/Battelle contract no. 4000007596. ABSTRACT A method is presented to compute the switching angles in a multilevel be converted to polynomial equations which are then solved using the method of resultants from elimination

Tolbert, Leon M.

33

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

34

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

35

A POSITRON SOURCE USING AN AXIALLY ORIENTED CRYSTAL ASSOCIATED TO A GRANULAR AMORPHOUS CONVERTER  

E-print Network

1 A POSITRON SOURCE USING AN AXIALLY ORIENTED CRYSTAL ASSOCIATED TO A GRANULAR AMORPHOUS CONVERTER, Russia Abstract A non conventional positron source using the intense radiation from an axially oriented for this kind of positron source allow its consideration for unpolarized positrons for the ILC. 1- INTRODUCTION

Boyer, Edmond

36

Magnetic-coupled high power factor converter with low line current harmonic distortions for power factor correction and fast output response  

Microsoft Academic Search

A new magnetic-coupled high power factor converter (MCHPFC) with a single switch\\/single stage is proposed. The proposed converter gives good power factor correction, low current harmonic distortions, and tight output voltage regulation. The prototype shows that the IEC555-2 requirements are met satisfactorily with nearly unity power factor. A proposed MCHPFC is particularly suited for low-power-level power supply applications

Gun-Woo Moon; Chung-Wook Roh; Jun-Young Lee; Myung-Joon Choo

1998-01-01

37

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

38

Investigation of a metallic photonic crystal high power microwave mode converter  

NASA Astrophysics Data System (ADS)

It is demonstrated that an L band metallic photonic crystal TEM-TE11 mode converter is suitable for narrow band high power microwave application. The proposed mode converter is realized by partially filling metallic photonic crystals along azimuthal direction in a coaxial transmission line for phase-shifting. A three rows structure is designed and simulated by commercial software CST Microwave Studio. Simulation results show that its conversion efficiency is 99% at the center frequency 1.58 GHz. Over the frequency range of 1.56-1.625 GHz, the conversion efficiency exceeds 90 %, with a corresponding bandwidth of 4.1 %. This mode converter has a gigawatt level power handling capability which is suitable for narrow band high power microwave application. Using magnetically insulated transmission line oscillator(MILO) as a high power microwave source, particle-in-cell simulation is carried out to test the performance of the mode converter. The expected TE11 mode microwave output is obtained and the MILO works well. Mode conversion performance of the converter is tested by far-field measurement method. And the experimental result confirms the validity of our design. Then, high power microwave experiment is carried out on a Marx-driven Blumlein water line pulsed power accelerator. Microwave frequency, radiated pattern and power are measured in the far-field region and the results agree well with simulation results. The experiment also reveals that no microwave breakdown or pulse shortening took place in the experimental setup.

Wang, Dong; Qin, Fen; Xu, Sha; Yu, Aimin; Wu, Yong

2015-02-01

39

National Ignition Facility frequency converter development  

SciTech Connect

A preliminary error budget for the third harmonic converter for the National Ignition Facility (NIF) laser driver has been developed using a root-sum-square-accumulation of error sources. Such a budget sets an upper bound on the allowable magnitude of the various effects that reduce conversion efficiency. Development efforts on crystal mounting technology and crystal quality studies are discussed.

Barker, C.E.; Auerbach, J.M.; Adams, C.H. [and others

1996-12-09

40

Mode converter based on mode coupling in an asymmetric dual-core photonic crystal fibre  

NASA Astrophysics Data System (ADS)

A novel mode converter which is realized by mode coupling between a large core and a small core in an asymmetric dual-core photonic crystal fibre is proposed in this paper. The mode indexes of the individual cores are index matched to produce effective mode coupling. Numerical investigations demonstrate that an LP01 to LP02 mode converter with a bandwidth of 14 nm for the loss of 1 dB and polarization-dependent loss lower than 0.14 dB can be realized in a fibre with a length of 12.7 mm.

Chen, Ming-Yang; Zhou, Jun

2008-11-01

41

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

PubMed Central

The potential of second-harmonic generation (SHG) microscopy for automated crystal centering to guide synchrotron X-­ray diffraction of protein crystals was explored. These studies included (i) comparison of microcrystal positions in cryoloops as determined by SHG imaging and by X-ray diffraction rastering and (ii) X-ray structure determinations of selected proteins to investigate the potential for laser-induced damage from SHG imaging. In studies using ?2 adrenergic receptor membrane-protein crystals prepared in lipidic mesophase, the crystal locations identified by SHG images obtained in transmission mode were found to correlate well with the crystal locations identified by raster scanning using an X-­ray minibeam. SHG imaging was found to provide about 2?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.

2013-01-01

42

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

43

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

44

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

45

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

46

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

PubMed

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

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

2013-02-11

47

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

NASA Astrophysics Data System (ADS)

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

Wicharn, S.; Buranasiri, P.

2014-09-01

48

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

49

Structural light focusing phenomenon and enhanced second harmonic generation in NaNO2-infiltrated opal photonic crystal  

NASA Astrophysics Data System (ADS)

We report new experimental results on enhanced second harmonic generation using a structural light focusing phenomenon in photonic crystals (PCs). We use opal-based PC, infiltrated with NaNO2 and pumped with femtosecond laser pulses at various incidence angles, in order to examine the dependence of second harmonic generation efficiency on the pumping wavelength location toward the PC band-gap. We demonstrate one order enhancement of second harmonic generation in case of PC band-gap pumping in comparison to non-band- gap pumping. Second harmonic generation is performed in reflection mode with the maximum of generation in the direction of mirror reflection. We demonstrate that the spectrum of second harmonic does not narrow with the quasi-phase matching condition in case of band-gap generation, and second harmonic spectrum corresponding to non-band-gap generation undergoes 1.5 times narrowing due to the quasi-phase matching.

Zaytsev, Kirill I.; Katyba, Gleb M.; Yakovlev, Egor V.; Aliev, Ismail N.; Khorokhorov, Alexey M.; Yurchenko, Stanislav O.

2015-01-01

50

Second harmonic generation microscopic observations of a multiferroic BiFeO3 single crystal  

NASA Astrophysics Data System (ADS)

Anisotropy of the optical second harmonic generation (SHG) in a multiferroic BiFeO3 single crystal is observed by an SHG microscope. Polarization dependences of SH intensities are measured in several polarization configurations of the incident and SH waves to determine the magnitude and sign of polar i-type SHG tensor components. To obtain proper values of these SHG tensors, the effects of the interference term and wave number mismatch are taken into account in these analyses. d24 component is 15 times larger than d32 and this result is essentially different from the thin film case.

Yokota, Hiroko; Haumont, Raphael; Kiat, Jean-Michel; Matsuura, Hiroto; Uesu, Yoshiaki

2009-08-01

51

Polar structure of disclination loops in nematic liquid crystals probed by second-harmonic-light scattering  

NASA Astrophysics Data System (ADS)

Angle-resolved, second-harmonic-light scattering (SHLS) measurements are reported for three different classes of thermotropic nematic liquid crystals (NLCs): polar and nonpolar rodlike compounds and a bent-core compound. Results revealing well-defined scattering peaks are interpreted in terms of the electric polarization induced by distortions of the nematic orientational field ("flexopolarity") associated with inversion wall defects, nonsingular disclinations, analogous to Neel walls in ferromagnets, that often exhibit a closed loop morphology in NLCs. Analysis of the SHLS patterns based on this model provides a "proof-of-concept" for a potentially useful method to probe the flexopolar properties of NLCs.

Pardaev, Shokir A.; Williams, J. C.; Twieg, R. J.; Jakli, A.; Gleeson, J. T.; Ellman, B.; Sprunt, S.

2015-03-01

52

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

PubMed

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

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

2012-12-17

53

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

54

Analysis of Second Harmonic Generation of a KDP crystal based on multi-scale topography simulation  

NASA Astrophysics Data System (ADS)

The surface topography of the supporting frame of a KDP crystal is studied, as well as its influence on the deformation and stress of the KDP crystal, together with the Second Harmonic Generation (SHG). A comprehensive model incorporating principles of multi-scale surface analysis, mechanics, and optics is proposed, and it is applied to investigate the surface topography of the supporting frame, the deformation and stress of the KDP crystal, as well as the SHG efficiency. The surface topography is analyzed using fractural theory, and then classified according to its multi-scale specifics. Based on the surface analysis results, the mounting configuration of the KDP crystal is modeled and analyzed in global and local modes, respectively, using the Finite Element Method (FEM). Moreover, deformation and stress of the KDP crystal that is induced by the mechanical mounting is studied using the FEM, together with the effects of the surface topography on them. Furthermore, the change of the refractive index that induced by the deformation and stress are calculated, respectively, the results of which is applied to studied the phase mismatch, and the SHG efficiency considering the phase mismatch is eventually obtained. The numerical results demonstrate that the frame surface with multi-scale dimensions has diverse influences on the distortion and stress, as well as the SHG efficiency.

Liu, Hai Tao; Su, Rui Feng; Sun, Ya Zhou; Wang, He Ran

2015-04-01

55

Crystallization and second harmonic generation in thermally poled niobium borophosphate glasses  

NASA Astrophysics Data System (ADS)

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

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

2005-06-01

56

Characterization of salt interferences in second-harmonic generation detection of protein crystals  

PubMed Central

Studies were undertaken to assess the merits and limitations of second-harmonic generation (SHG) for the selective detection of protein and polypeptide crystal formation, focusing on the potential for false positives from SHG-active salts present in crystallization media. The SHG activities of salts commonly used in protein crystallization were measured and quantitatively compared with reference samples. Out of 19 salts investigated, six produced significant background SHG and 15 of the 96 wells of a sparse-matrix screen produced SHG upon solvent evaporation. SHG-active salts include phosphates, hydrated sulfates, formates and tartrates, while chlorides, acetates and anhydrous sulfates resulted in no detectable SHG activity. The identified SHG-active salts produced a range of signal intensities spanning nearly three orders of magnitude. However, even the weakest SHG-active salt produced signals that were several orders of magnitude greater than those produced by typical protein crystals. In general, SHG-active salts were identifiable through characteristically strong SHG and negligible two-photon-excited ultraviolet fluorescence (TPE-UVF). Exceptions included trials containing either potassium dihydrogen phosphate or ammonium formate, which produced particularly strong SHG, but with residual weak TPE-UVF signals that could potentially complicate discrimination in crystallization experiments using these precipitants. PMID:24282335

Closser, R. G.; Gualtieri, E. J.; Newman, J. A.; Simpson, G. J.

2013-01-01

57

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

58

Type-II second-harmonic-generation properties of YCOB and GdCOB single crystals.  

PubMed

As excellent nonlinear optical (NLO) crystals, YCa4O(BO3)3 (YCOB) and GdCa4O(BO3)3 (GdCOB) have been paid much attention since their first appearance in 1990's. From that time to now, almost all of related researches and applications have focused on their type-I phase-matching (PM) configurations which possess large effective NLO coefficient (deff). In this paper, type-II second-harmonic-generation (SHG) properties of these two crystals are reported, including PM curve, deff, angular acceptance and walk-off angle. Both of the type-II SHG experiments for 1064 and 1320 nm have indicated that the optimum directions which have maximum deff locate in the second octant, i.e. (90° < ?< 180°, 0° < ? < 90°). For a (112°, 81.3°)-cut, 24 mm long YCOB crystal, the largest type-II SHG conversion efficiency of a 1064 nm Nd:YAG pico-second laser is 55%, which reaches the same level of the optimum type-I sample. To our knowledge this is the first time that type-II SHG performance of YCOB and GdCOB crystals is investigated intensively. Our research has shown that the smaller deff of type-II PM can be compensated by its larger angular acceptance and less beam walk-off. The same level SHG conversion efficiency implies for such type crystals the type-II components have the potential to replace type-I ones and obtain important NLO applications in the future. PMID:25836087

Liu, Yanqing; Qi, Hongwei; Lu, Qingming; Yu, Fapeng; Wang, Zhengping; Xu, Xinguang; Zhao, Xian

2015-02-01

59

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

SciTech Connect

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

Naumov, A N; Zheltikov, Aleksei M [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2002-02-28

60

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

61

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

62

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

PubMed Central

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

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

2013-01-01

63

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

E-print Network

. The inverter synthesizes a desired voltage from several separate dc sources (SDCSs), which may be obtained from is used to solve the harmonic elimination equations for a single DC source inverter. Previous work in [11-bridge inverter. Each inverter level can generate three different voltage outputs, + Vdc, 0 and ­ Vdc

Tolbert, Leon M.

64

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

PubMed Central

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

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

2011-01-01

65

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

66

Diode-pumped efficient slab laser with two Nd:YLF crystals and second-harmonic generation by slab LBO.  

PubMed

We demonstrate a diode-pumped electro-optical Q-switched slab laser with a high optical efficiency, high pulse energy, and short pulse width with two Nd:YLF crystals inside one resonator. The single compact slab resonator can generate a 1D top-hat beam at both the far field and the near field. With a slab-geometry-design lithium triborate (LBO) crystal, efficient critical phase-matching second-harmonic generation for a 1D top-hat beam with multiple transverse modes is achieved. PMID:17440558

Li, Daijun; Ma, Zhe; Haas, Rüdiger; Schell, Alexander; Simon, Janosch; Diart, Robert; Shi, Peng; Hu, Peixin; Loosen, Peter; Du, Keming

2007-05-15

67

Octupolar molecules for nonlinear optics: from molecular design to crystals and films with large second-harmonic generation.  

PubMed

We summarize the nonlinear optical (NLO) properties of octupolar molecules, crystals, and films developed in our laboratory. We present the design strategy, structure-property relationship, and second-order NLO properties of 1,3,5-trinitro- and 1,3,5-tricyano-2,4,6-tris(p-diethylaminostyryl)benzene (TTB) derivatives, TTB crystals, and films prepared by free-casting TTB in poly(methyl methacrylate) (PMMA). The first hyperpolarizability of TTB was fivefold larger than that of the dipolar analogue. Moreover, the TTB crystal showed unprecedentedly large second-harmonic generation (SHG). While TTB crystal films (20 wt% TTB/PMMA) on various substrates showed appreciable SHG values, the cylinder film exhibited much larger SHG values and large electro-optic (EO) coefficients. The large SHG values and EO coefficients, as well as the high thermal stability of the cylinder film, will make it a potential candidate for NLO device applications. PMID:25315898

Jeong, Mi-Yun; Cho, Bong Rae

2015-02-01

68

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

69

Electronic structure of second harmonic generation crystal Li3VO4  

NASA Astrophysics Data System (ADS)

The origin of second harmonic generation (SHG) of Li3VO4 was investigated from the viewpoint of the band structure by using the tight-binding method. The tight-binding parameters were optimized to reproduce the density of states (DOS) obtained from x ray photoelectron spectroscopy and the optical band gap. Although Li3PO4 has the same crystal structure as Li3VO4, it shows no SHG. To explain the difference in optical nonlinearity we compared the electronic structures of Li3VO4 and Li3PO4, in particular at the bottom of conduction band (CB) and the top of valence band (VB), since they are known to play a primary role in SHG. In Li3PO4, the bottom of CB consists of P 3s and O 2p orbitals and the top of VB is composed of O 2p orbitals. These electronic structures result in a relatively low DOS at the bottom of CB and a wide band gap in Li3PO4. On the other hand, in Li3VO4, both bottom of CB and top of VB are composed of V 3d and O 2p. The preferential contribution of V 3d orbitals to the band edge states leads to a high DOS at the bottom of CB, a narrow band gap and delocalization of electrons on V-O bonds. We conclude that these electronic structures are responsible for the high optical-nonlinearity of Li3VO4.

Sakata, S.; Nagoshi, Y.; Nii, H.; Ueda, N.; Kawazoe, H.

1996-10-01

70

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

NASA Astrophysics Data System (ADS)

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

Matinfar, Mehdi D.; Salehi, Jawad A.

2009-11-01

71

Second harmonic generation and sum frequency mixing of Nd:YAlO3 laser in flux grown 7.5 mol% Nb KTP crystals  

Microsoft Academic Search

KTiOPO4 (KTP) crystals doped with Nb (Nb:KTP) can not only largely blue-shift the cut-off wavelength for the type II second harmonic generation (SHG) phase matching of KTP crystals, but can also change the optimum phase matching angle of Nd:YAG 1.0642 ?m laser which has a noncritical phase matching direction

D. Y. Zhang; H. Y. Shen; G. Zhang; W. Z. Chen; W. Liu; R. R. Zeng; C. H. Huang; W. X. Lin; J. K. Liang

2001-01-01

72

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

73

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

74

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

NASA Astrophysics Data System (ADS)

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

Muthu, K.; Meenakshisundaram, SP.

2012-09-01

75

Versatile temperature-insensitive second-harmonic generation by compensating thermally induced phase-mismatch in a two-crystal design Versatile temperature-insensitive second-harmonic generation  

NASA Astrophysics Data System (ADS)

We propose and experimentally demonstrate a novel second-harmonic-generation (SHG) scheme capable of supporting temperature-insensitive phase-matching (PM) at various laser wavelengths. This versatile temperature-insensitive PM is designed by using two cascaded crystals with opposite signs of temperature derivation of phase-mismatch, in which the temperature-induced phase-mismatch in the first crystal is well compensated in the second crystal. Two application examples are studied at the typical wavelengths of ~ 1.0 and 1.5 ?m, respectively. The proof-of-principle experiment, using two crystals of LiB3O5 (LBO) and KH2PO4 (KDP), demonstrates that the temperature-acceptance of PM can be 2 – 3 times larger than that of using a traditional single crystal. The proposed two-crystal design may provide a promising route to high-average-power SHG at various laser wavelengths.

Zhong, H. Z.; Yuan, P.; Zhu, H. Y.; Qian, L. J.

2012-06-01

76

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

PubMed

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

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

2013-03-15

77

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

78

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

Microsoft Academic Search

A better understanding of the mechanisms located at the solid\\/electrolyte interface is becoming essential to the development of new applications in the electrochemical fields. The fast quartz crystal microbalance is an attractive and powerful gravimetric sensor which can be used in the dynamic regime to determine a mass\\/potential transfer function. The principle is equivalent to classical electrochemical impedance measurements; the

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

2007-01-01

79

In-plane time-harmonic elastic wave motion and resonance phenomena in a layered phononic crystal with periodic cracks.  

PubMed

This paper presents an elastodynamic analysis of two-dimensional time-harmonic elastic wave propagation in periodically multilayered elastic composites, which are also frequently referred to as one-dimensional phononic crystals, with a periodic array of strip-like interior or interface cracks. The transfer matrix method and the boundary integral equation method in conjunction with the Bloch-Floquet theorem are applied to compute the elastic wave fields in the layered periodic composites. The effects of the crack size, spacing, and location, as well as the incidence angle and the type of incident elastic waves on the wave propagation characteristics in the composite structure are investigated in details. In particular, the band-gaps, the localization and the resonances of elastic waves are revealed by numerical examples. In order to understand better the wave propagation phenomena in layered phononic crystals with distributed cracks, the energy flow vector of Umov and the corresponding energy streamlines are visualized and analyzed. The numerical results demonstrate that large energy vortices obstruct elastic wave propagation in layered phononic crystals at resonance frequencies. They occur before the cracks reflecting most of the energy transmitted by the incoming wave and disappear when the problem parameters are shifted from the resonant ones. PMID:25618055

Golub, Mikhail V; Zhang, Chuanzeng

2015-01-01

80

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

PubMed

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

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

2014-05-01

81

Enhancement of second harmonic generation in NaNO{sub 2}-infiltrated opal photonic crystal using structural light focusing  

SciTech Connect

Experimental and numerical results for second harmonic generation (SHG) in photonic crystal (PC) based on NaNO{sub 2}-infiltrated opal matrix are presented. SHG is performed in reflection mode; thus, the direction of the SHG maximum is equal to the angle of mirror reflection. The PC was pumped with femtosecond optical pulses at different angles of incidence, allowing the dependence of the SHG efficiency on the location of the fundamental wavelength toward the PC band gap (BG) to be examined. The most efficient SHG was observed when pumping the BG of the PC. To interpret the experimental results, finite-difference time-domain numerical simulations of the light interaction with the PC were conducted. The observed effect of highly efficient SHG is associated with structural light focusing, and, as a consequence, with strong optical field localization within certain near-surface PC regions. Thus, SHG enhancement based on structural light focusing in PC was demonstrated.

Zaytsev, Kirill I., E-mail: kirzay@gmail.com; Yurchenko, Stanislav O., E-mail: st.yurchenko@mail.ru [Bauman Moscow State Technical University, 105005, 2nd Baumanskaya str. 5, Moscow (Russian Federation)

2014-08-04

82

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

PubMed

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

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

2014-08-10

83

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

SciTech Connect

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

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

2007-11-30

84

Growth and second-harmonic-generation of Bi 3+- or Li +-doped GdCa 4O(BO 3) 3 crystals  

Microsoft Academic Search

The bismuth and lithium cations doped GdGa4O(BO3)3 (GdCOB) crystals were successfully grown for the first time. The X-ray powder diffraction (XRPD) shows that the cell parameters of the doped crystals are slightly larger than that of GdCOB. Intracavity second-harmonic-generation (SHG) experiments were carried out on 3×3×6mm3 GdCOB and doped GdCOB crystals along the phase-matching (PM) direction (?=66.8°,?=132.6°). The results show

Shujun Zhang; Zhenxiang Cheng; Junhai Liu; Jianru Han; Zongshu Shao; Huanchu Chen

2000-01-01

85

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

86

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

87

Down Converter Device Combining Rare-Earth Doped Thin Layer and Photonic Crystal for c-Si Based Solar Cell  

E-print Network

The aim of the study is to develop ultra-compact structures enabling an efficient conversion of single high energy photon (UV) to two lower energy photons (IR). The proposed structure combines rare-earths doped thin layer allowing the down-conversion process with a photonic crystal (PhC), in order to control and enhance the down-conversion using optical resonances. On the top of the rare-earths doped layer, a silicon nitride (SiN) 2D planar PhC is synthesized. For that, SiN is first deposited by PECVD. After holographic lithography and reactive ion etching, a periodic square lattice of holes is generated on the SiN layer. The PhC topographical parameters as well as the layers thickness are optimized using Finite-Difference-Time-Domain simulations. The design and realization of such PhC-assisted down-converter structures is presented. Optical simulations demonstrate that the PhC leads to the establishment of resonant modes located in the underneath doped layer, allowing a drastic enhancement of the absorption ...

Deschamps, Thierry; Peretti, Romain; Lalouat, Loïc; Fourmond, Erwann; Fave, Alain; Guille, Antoine; Pereira, António; Moine, Bernard; Seassal, Christian

2013-01-01

88

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

89

Investigation of the vortex dynamics of Fe1.02Se crystals by fundamental and 3rd harmonic ac magnetic susceptibility analysis  

NASA Astrophysics Data System (ADS)

The superconducting properties of mm-sized Fe1.02Se crystals grown by a flux method are investigated. The structural and morphological features are studied by x-ray diffraction (XRD) and by scanning electron microscopy-energy dispersive x-ray spectroscopy SEM-EDX analysis, which identified a co-growth of a dominant superconducting tetragonal phase, with the minority of a non-superconducting hexagonal phase. The ac magnetic response is analyzed using a combined method of the fundamental and the 3rd harmonic ac magnetic susceptibility as a function of the temperature at different ac magnetic field amplitudes and frequencies and with various superimposed dc fields. The variation of the ac magnetic field and frequency in different ranges especially affects the 3rd harmonic components, which are more sensitive to the changes in the flux dynamic regimes. This allows a fine observation of the evolution of the different linear and non-linear processes responsible for the ac magnetic response of the Fe1.02Se crystals. At low enough ac amplitudes and frequencies, and even in high imposed dc magnetic fields, the Fe1.02Se crystals show a typical critical state behavior, marking a high stability of the pinning, with very small influence of the vortex dynamical processes. With the change of ac field amplitude and frequency a gradual crossover is observed from the initial stable pinning state through the domination of the intermediate regimes as flux creep and finally to the complete dominance of flux flow. The ac magnetic response is also influenced by geometric edge barrier effects arising from the plate-like geometry of the Fe1.02Se crystals. The changes of the dominant irreversible (non-linear) mechanism from surface pinning to bulk pinning or to prevailing dynamical regimes is also identified by analyzing the behavior of the 3rd harmonic components.

Buchkov, K.; Polichetti, M.; Nenkov, K.; Nazarova, E.; Mancusi, D.; Balchev, N.; Kovacheva, D.; Zahariev, A.; Pace, S.

2015-03-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

91

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

92

Continuous-wave, double-pass second-harmonic generation with 60% efficiency in a single MgO:PPSLT crystal.  

PubMed

We present a double-pass scheme for high-efficiency, high-power, second-harmonic generation (SHG) in a single MgO-doped periodically poled stoichiometric lithium tantalate (MgO:PPSLT) crystal. The device is pumped by a single-frequency, continuous-wave fiber amplifier laser system at a wavelength of 1091 nm. For the double-pass scheme, a conversion efficiency of 60% and a harmonic power of 12.8 W at a wavelength of 545.5 nm with a high beam quality of (M2<1.2) is achieved. Compared to single-pass SHG, a double-pass enhancement factor of more than two is observed at the highest fundamental pump power. PMID:24978245

Stappel, Matthias; Kolbe, Daniel; Walz, Jochen

2014-05-15

93

crystal  

NASA Astrophysics Data System (ADS)

An eye-safe Raman laser is realized with BaTeMo2O9 (BTM) nonlinear crystal for the first time. By using a diode-end-pumped acousto-optically Q-switched Nd:YVO4 laser as the pumping source, the BTM crystal converts the fundamental laser at 1,342 nm to first-Stokes laser at 1,531 nm successfully. With an incident power of 10.8 W and a pulse repetition rate of 25 kHz, the average output power at 1,531 nm is obtained to be 0.83 W, corresponding to a diode-to-Stokes conversion efficiency of 7.7 %. The pulse width is 11 ns, and the peak power is 3.0 kW.

Bai, Fen; Wang, Qingpu; Tao, Xutang; Li, Ping; Zhang, Xingyu; Liu, Zhaojun; Shen, Hongbin; Lan, Weixia; Gao, Liang; Gao, Zeliang; Zhang, Junjie; Fang, Jiaxiong

2014-08-01

94

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

Microsoft Academic Search

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

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

2009-01-01

95

Pulse pattern modulated soft commutation inverter-type AC-DC power converter with harmonic current components reduction in utility power side  

Microsoft Academic Search

In this paper, a circuit topology of a half bridge quasi-resonant ZVS-PWM high frequency inverter type AC-DC converter using IGBTs for the consumer magnetron drive is presented, which can use the high frequency high voltage transformer, voltage doubler and power semiconductor switching devices (IGBTs) used in active voltage clamped quasi-resonant PWM inverters suitable for 100 V utility AC power systems.

Hidenori Shirai; Takayuki Matsushige; Manabu Ishitobi; Takeshi Myoui; Mutsuo Nakaoka; Daisuke Bessyo; Hideki Omori

2002-01-01

96

On how differently the quasi-harmonic approximation works for two isostructural crystals: thermal properties of periclase and lime.  

PubMed

Harmonic and quasi-harmonic thermal properties of two isostructural simple oxides (periclase, MgO, and lime, CaO) are computed with ab initio periodic simulations based on the density-functional-theory (DFT). The more polarizable character of calcium with respect to magnesium cations is found to dramatically affect the validity domain of the quasi-harmonic approximation that, for thermal structural properties (such as temperature dependence of volume, V(T), bulk modulus, K(T), and thermal expansion coefficient, ?(T)), reduces from [0 K-1000 K] for MgO to just [0 K-100 K] for CaO. On the contrary, thermodynamic properties (such as entropy, S(T), and constant-volume specific heat, CV(T)) are described reliably at least up to 2000 K and quasi-harmonic constant-pressure specific heat, CP(T), up to about 1000 K in both cases. The effect of the adopted approximation to the exchange-correlation functional of the DFT is here explicitly investigated by considering five different expressions of three different classes (local-density approximation, generalized-gradient approximation, and hybrids). Computed harmonic thermodynamic properties are found to be almost independent of the adopted functional, whereas quasi-harmonic structural properties are more affected by the choice of the functional, with differences that increase as the system becomes softer. PMID:25637976

Erba, A; Shahrokhi, M; Moradian, R; Dovesi, R

2015-01-28

97

On how differently the quasi-harmonic approximation works for two isostructural crystals: Thermal properties of periclase and lime  

NASA Astrophysics Data System (ADS)

Harmonic and quasi-harmonic thermal properties of two isostructural simple oxides (periclase, MgO, and lime, CaO) are computed with ab initio periodic simulations based on the density-functional-theory (DFT). The more polarizable character of calcium with respect to magnesium cations is found to dramatically affect the validity domain of the quasi-harmonic approximation that, for thermal structural properties (such as temperature dependence of volume, V(T), bulk modulus, K(T), and thermal expansion coefficient, ?(T)), reduces from [0 K-1000 K] for MgO to just [0 K-100 K] for CaO. On the contrary, thermodynamic properties (such as entropy, S(T), and constant-volume specific heat, CV(T)) are described reliably at least up to 2000 K and quasi-harmonic constant-pressure specific heat, CP(T), up to about 1000 K in both cases. The effect of the adopted approximation to the exchange-correlation functional of the DFT is here explicitly investigated by considering five different expressions of three different classes (local-density approximation, generalized-gradient approximation, and hybrids). Computed harmonic thermodynamic properties are found to be almost independent of the adopted functional, whereas quasi-harmonic structural properties are more affected by the choice of the functional, with differences that increase as the system becomes softer.

Erba, A.; Shahrokhi, M.; Moradian, R.; Dovesi, R.

2015-01-01

98

Second-harmonic generation at 532??nm in K3B6O10Br crystal.  

PubMed

We demonstrate that an average power of 45.5 W at 532 nm is obtained with a 13 mm length K3B6O10Br (KBB) crystal corresponding to a conversion efficiency of 36.5% for the first time. The power stability of the 532 nm output power measurement indicates that the standard deviation jitters of the average power are 1.46% and 1.50% at 24.8 and 43.8 W, respectively. The effective nonlinear optical coefficient deff is also obtained as 0.92 pm/V by the phase-matching (PM) method. The angle and temperature bandwidths of second-harmonic generation (SHG) for 1064 nm pump light are also investigated. Therefore, KBB crystal can be a promising nonlinear optical material for visible laser generation. PMID:25768185

Xu, Bo; Xia, Mingjun; Wang, Xiaoyang; Li, Rukang; Chen, Chuangtian

2015-03-15

99

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

SciTech Connect

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

NONE

1998-01-01

100

Spectroscopic and second harmonic generation properties of a new crystal: Yb-doped RbTiOPO 4  

Microsoft Academic Search

RbTiOPO4 single crystals doped with a concentration of 1.96×1020 ionscm?3 of Yb3+ have been grown. These crystals exhibit a large splitting of the 2F5\\/2 sublevels of Yb3+ of about 70 nm, which is one of the largest crystal fields ever known for Yb-doped crystals. The larger compensation is ensured by a Nb-co-doping. As expected from the large splitting, a broadband

J. J. Carvajal; R. Sole; Jna Gavaldà; J. Massons; P. Segonds; B. Boulanger; A. Brenier; G. Boulon; J. Zaccaro; M. Aguilo; F D??az

2004-01-01

101

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

102

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

103

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

104

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

NASA Astrophysics Data System (ADS)

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

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

105

High-Resolution Crystal Structures of Drosophila melanogaster Angiotensin-Converting Enzyme in Complex with Novel Inhibitors and Antihypertensive Drugs  

Microsoft Academic Search

Angiotensin I-converting enzyme (ACE), one of the central components of the renin–angiotensin system, is a key therapeutic target for the treatment of hypertension and cardiovascular disorders. Human somatic ACE (sACE) has two homologous domains (N and C). The N- and C-domain catalytic sites have different activities toward various substrates. Moreover, some of the undesirable side effects of the currently available

Mohd Akif; Dimitris Georgiadis; Aman Mahajan; Vincent Dive; Edward D. Sturrock; R. Elwyn Isaac; K. Ravi Acharya

2010-01-01

106

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

107

Optimization of single-layer sol-gel antireflection coatings on potassium dihydrogen phosphate crystals in quadrature geometry for second-harmonic conversion of high-power Nd:glass lasers  

NASA Astrophysics Data System (ADS)

Quadrature geometry of two potassium dihydrogen phosphate crystals is a standard configuration to achieve efficient second-harmonic conversion of Nd:glass high-power lasers. Antireflection coatings on the entrance face of the first crystal and on the exit face of the second one are easily designed using quarterwave optical thicknesses adjusted separately for minimum reflectivity at the fundamental wavelength and at its second harmonic. It is however not possible to simultaneously obtain the lowest reflectivity for both the wavelengths on the inner faces. We describe a theoretical optimization of a single-layer sol-gel silica coating that allows maximum transmission of energy in the fundamental and second harmonic, taken together, across the inner faces of the two crystals. The optimum thickness is a function of the conversion efficiency to the second harmonic, and hence of the incident intensity of the fundamental wave. We have deposited sol-gel silica single-layer coatings of this optimum thickness, and the total reflectivity at fundamental and second-harmonic wavelengths taken together was measured and compared with the theoretically calculated values.

Pareek, Rakesh; Kumbhare, Mohan; Joshi, Anandvardhan; Banerjee, Arup; Gupta, Parshottam

2010-09-01

108

Reversible suppression of second harmonic generation in dye-doped liquid crystal by light-induced thermal phase transition on sub-micrometer scale  

NASA Astrophysics Data System (ADS)

Optically controllable signals are fundamental to various applications from communication to super-resolution imaging. However, literature on non-fluorescent, nonlinear optical signals that can be reversibly turned on/off on a sub-micrometer scale is scant. In this work, we experimentally demonstrate a scheme for the reversible suppression of second harmonic generation (SHG) based on dye-doped nematic liquid crystal molecules. Under a pump (suppressing SHG) and probe (generating SHG) setup with a tightly focusing microscope and a time-gated detection, outstanding modulation depth (>80%) has been realized. Surprisingly, the mechanism of liquid crystal SHG switch on a sub-micrometer scale was found to be light-induced thermal phase transition as against optical Frederick's transition. Quantitative analysis of the optical nonlinearity ? ( 2 ) versus local heating shows an excellent agreement of SHG signal suppression as well as its dependence on the liquid crystal molecular order and phase change. Our work provides an innovative example of applying nonlinear optical properties of soft materials, and can be further optimized for all-optical modulation applications.

Zhuo, Guan-Yu; Chen, Kuan-Chieh; Lai, Kai-Wen; Wang, Chao-Ran; Chao, Chih-Yu; Chu, Shi-Wei

2015-02-01

109

Strong second harmonic generation in SiC, ZnO, GaN two-dimensional hexagonal crystals from first-principles many-body calculations.  

PubMed

The second harmonic generation (SHG) intensity spectrum of SiC, ZnO, GaN two-dimensional hexagonal crystals is calculated by using a real-time first-principles approach based on Green's function theory [Attaccalite et al., Phys. Rev. B: Condens. Matter Mater. Phys. 2013 88, 235113]. This approach allows one to go beyond the independent particle description used in standard first-principles nonlinear optics calculations by including quasiparticle corrections (by means of the GW approximation), crystal local field effects and excitonic effects. Our results show that the SHG spectra obtained using the latter approach differ significantly from their independent particle counterparts. In particular they show strong excitonic resonances at which the SHG intensity is about two times stronger than within the independent particle approximation. All the systems studied (whose stabilities have been predicted theoretically) are transparent and at the same time exhibit a remarkable SHG intensity in the range of frequencies at which Ti:sapphire and Nd:YAG lasers operate; thus they can be of interest for nanoscale nonlinear frequency conversion devices. Specifically the SHG intensity at 800 nm (1.55 eV) ranges from about 40-80 pm V(-1) in ZnO and GaN to 0.6 nm V(-1) in SiC. The latter value in particular is 1 order of magnitude larger than values in standard nonlinear crystals. PMID:25766901

Attaccalite, C; Nguer, A; Cannuccia, E; Grüning, M

2015-04-14

110

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

SciTech Connect

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

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

1997-06-01

111

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

PubMed

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

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

2013-03-25

112

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

113

Role of acentric displacements on the crystal structure and second-harmonic generating properties of RbPbCO3F and CsPbCO3F.  

PubMed

Two lead fluorocarbonates, RbPbCO3F and CsPbCO3F, were synthesized and characterized. The materials were synthesized through solvothermal and conventional solid-state techniques. RbPbCO3F and CsPbCO3F were structurally characterized by single-crystal X-ray diffraction and exhibit three-dimensional (3D) crystal structures consisting of corner-shared PbO6F2 polyhedra. For RbPbCO3F, infrared and ultraviolet-visible spectroscopy and thermogravimetric and differential thermal analysis measurements were performed. RbPbCO3F is a new noncentrosymmetric material and crystallizes in the achiral and nonpolar space group P6m2 (crystal class 6m2). Powder second-harmonic generation (SHG) measurements on RbPbCO3F and CsPbCO3F using 1064 nm radiation revealed an SHG efficiency of approximately 250 and 300 × ?-SiO2, respectively. Charge constants d33 of approximately 72 and 94 pm/V were obtained for RbPbCO3F and CsPbCO3F, respectively, through converse piezoelectric measurements. Electronic structure calculations indicate that the nonlinear optical response originates from the distorted PbO6F2 polyhedra, because of the even-odd parity mixing of the O 2p states with the nearly spherically symmetric 6s electrons of Pb(2+). The degree of inversion symmetry breaking is quantified using a mode-polarization vector analysis and is correlated with cation size mismatch, from which it is possible to deduce the acentric properties of 3D alkali-metal fluorocarbonates. PMID:24867361

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

2014-06-16

114

Controlling the disorder properties of quadratic nonlinear photonic crystals.  

PubMed

We experimentally demonstrate a modulation scheme for disordered nonlinear crystals that combines periodic modulation and disordered sections. The crystal is divided into a set of identical periodically poled building blocks, whereby each block is followed by a short section of random length. We use this scheme to achieve broadband second harmonic generation in KTiOPO4 nonlinear crystals while independently controlling the bandwidth and the center of the converted wavelengths as well as the efficiency of conversion. The trade-off between bandwidth and efficiency is improved in comparison with periodically poled crystals. PMID:22002358

Varon, Idith; Porat, Gil; Arie, Ady

2011-10-15

115

Crystal Growth of Four Oxovanadium(IV) Tartrates Prepared via a Mild Two-Step Hydrothermal Method: Observation of Spin-Dimer Behavior and Second Harmonic Generation.  

PubMed

Four new oxovanadium(IV) tartrates, namely, A2[(VO)2(C4H4O6)(C4H2O6)(H2O)2]·(H2O)2, where A = Cs, 1, Rb, 2; K2[(VO)2(C4H2O6)2(H2O)2]·(H2O)2, 3; and Na2[(VO)2(C4H4O6)(C4H2O6)(H2O)7]·(H2O)2, 4, were prepared utilizing a two-step, mild hydrothermal route involving l-(+)-tartaric acid as the reducing agent. All four compounds were structurally characterized by single-crystal and powder X-ray diffraction methods and were found to crystallize in the non-centrosymmetric orthorhombic space groups P212121 for 1, 2, and 4 and C2221 for 3. The temperature dependence of the magnetic susceptibility of these compounds was measured, and 1, 2, and 4 were found to be paramagnetic down to 2 K, while 3 was found to exhibit spin-dimer behavior. Compounds 1, 2, and 3 were found to be second harmonic generation active. All compounds were further characterized by IR and UV-vis spectroscopies. PMID:25823416

Cortese, Anthony J; Wilkins, Branford; Smith, Mark D; Yeon, Jeongho; Morrison, Gregory; Tran, T Thao; Halasyamani, P Shiv; Zur Loye, Hans-Conrad

2015-04-20

116

PHYSICAL REVIEW A 81, 023820 (2010) Huge enhancement of backward second-harmonic generation with slow light in photonic crystals  

E-print Network

mixing process 1 + 2 = 3 is defined through the wave vector difference k = k3 - k1 - k2 of the three, the anisotropy of the common nonlinear crystals can be utilized to obtain phase matching between waves and Yuri S. Kivshar1 1 Nonlinear Physics Center, Research School of Physics and Engineering, The Australian

2010-01-01

117

High-resolution crystal structures of Drosophila melanogaster angiotensin-converting enzyme in complex with novel inhibitors and antihypertensive drugs.  

PubMed

Angiotensin I-converting enzyme (ACE), one of the central components of the renin-angiotensin system, is a key therapeutic target for the treatment of hypertension and cardiovascular disorders. Human somatic ACE (sACE) has two homologous domains (N and C). The N- and C-domain catalytic sites have different activities toward various substrates. Moreover, some of the undesirable side effects of the currently available and widely used ACE inhibitors may arise from their targeting both domains leading to defects in other pathways. In addition, structural studies have shown that although both these domains have much in common at the inhibitor binding site, there are significant differences and these are greater at the peptide binding sites than regions distal to the active site. As a model system, we have used an ACE homologue from Drosophila melanogaster (AnCE, a single domain protein with ACE activity) to study ACE inhibitor binding. In an extensive study, we present high-resolution structures for native AnCE and in complex with six known antihypertensive drugs, a novel C-domain sACE specific inhibitor, lisW-S, and two sACE domain-specific phosphinic peptidyl inhibitors, RXPA380 and RXP407 (i.e., nine structures). These structures show detailed binding features of the inhibitors and highlight subtle changes in the orientation of side chains at different binding pockets in the active site in comparison with the active site of N- and C-domains of sACE. This study provides information about the structure-activity relationships that could be utilized for designing new inhibitors with improved domain selectivity for sACE. PMID:20488190

Akif, Mohd; Georgiadis, Dimitris; Mahajan, Aman; Dive, Vincent; Sturrock, Edward D; Isaac, R Elwyn; Acharya, K Ravi

2010-07-16

118

Frequency converter development for the National Ignition Facility  

SciTech Connect

The design of the National Ignition Facility (NIF) incorporates a type I/type II third harmonic generator to convert the 1.053-{micro}m fundamental wavelength of the laser amplifier to a wavelength of 0.351 {micro}m for target irradiation. To understand and control the tolerances in the converter design, we have developed a comprehensive error budget that accounts for effects that are known to influence conversion efficiency, including variations in amplitude and phase of the incident laser pulse, temporal bandwidth of the incident laser pulse, crystal surface figure and bulk non-uniformities, angular alignment errors, Fresnel losses, polarization errors and crystal temperature variations. The error budget provides specifications for the detailed design of the NIF final optics assembly (FOA) and the fabrication of optical components. Validation is accomplished through both modeling and measurement, including full-scale Beamlet tests of a 37-cm aperture frequency converter in a NIF prototype final optics cell. The prototype cell incorporates full-perimeter clamping to support the crystals, and resides in a vacuum environment as per the NIF design.

Auerbach, J M; Barker, C E; Burkhart, S C; Couture, S A; DeYoreo, J J; Hackel, L A; Hibbard, R L; Liou, L W; Norton, M A; Wegner, P J; Whitman, P A

1998-10-30

119

Double-crystal RbTiOPO4 for simultaneous 200 kHz Q-switching and second-harmonic generation in a direct-pumped Nd:YVO4 laser  

NASA Astrophysics Data System (ADS)

We report on electro-optic (EO) Q-switched intracavity second-harmonic generation (SHG) based on double-crystal RbTiOPO4 (RTP) in an 880 nm diode-end-pumped Nd:YVO4 laser for the first time. The double-crystal RTP performed simultaneously as a high repetition rate laser Q switch and a second-harmonic generator. At a repetition rate of 200 kHz, a maximum average output power of 2.51 W at 532 nm wavelength ({M}x2=1.2 4 3, {M}y2=1.1 31) and a shortest pulse width of 15.7 ns were achieved under an absorbed pump power of 21 W, corresponding to an optical–optical conversion efficiency of 11.9% and a slope efficiency of 12.8%, respectively.

Yu, Y. J.; Chen, X. Y.; Wang, C.; Wu, C. T.; Liu, R.; Jin, G. Y.

2013-01-01

120

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

121

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.

Lawrence Hall of Science

2009-01-01

122

Bookmark Converter  

NSDL National Science Digital Library

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

Broding, Magnus.

123

Harmonic engine  

Microsoft Academic Search

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

Charles L

2009-01-01

124

In-phased second harmonic wave array generation with intra-Talbot-cavity frequency-doubling.  

PubMed

The Talbot cavity is one promising method to synchronize the phase of a laser array. However, it does not achieve the lowest array mode with the same phase but the highest array mode with the anti-phase between every two adjacent lasers, which is called out-phase locking. Consequently, their far-field images exhibit 2-peak profiles. We propose intra-Talbot-cavity frequency-doubling. By placing a nonlinear crystal in a Talbot cavity, the Talbot cavity generates an out-phased fundamental wave array, which is converted into an in-phase-locked second harmonic wave array at the nonlinear crystal. We demonstrate numerical calculations and experiments on intra-Talbot-cavity frequency-doubling and obtain an in-phase-locked second harmonic wave array for a Nd:YVO4 array laser. PMID:25837108

Hirosawa, Kenichi; Shohda, Fumio; Yanagisawa, Takayuki; Kannari, Fumihiko

2015-03-23

125

Discriminating harmonicity  

NASA Astrophysics Data System (ADS)

Simultaneous tones that are harmonically related tend to be grouped perceptually to form a unitary auditory image. A partial that is mistuned stands out from the other tones, and harmonic complexes with different fundamental frequencies can readily be perceived as separate auditory objects. These phenomena are evidence for the strong role of harmonicity in perceptual grouping and segregation of sounds. This study measured the discriminability of harmonicity directly. In a two interval, two alternative forced-choice (2I2AFC) paradigm, the listener chose which of two sounds, signal or foil, was composed of tones that more closely matched an exact harmonic relationship. In one experiment, the signal was varied from perfectly harmonic to highly inharmonic by adding frequency perturbation to each component. The foil always had 100% perturbation. Group mean performance decreased from greater than 90% correct for 0% signal perturbation to near chance for 80% signal perturbation. In the second experiment, adding a masker presented simultaneously with the signals and foils disrupted harmonicity. Both monaural and dichotic conditions were tested. Signal level was varied relative to masker level to obtain psychometric functions from which slopes and midpoints were estimated. Dichotic presentation of these audible stimuli improved performance by 3-10 dB, due primarily to a release from ``informational masking'' by the perceptual segregation of the signal from the masker.

Kidd, Gerald; Mason, Christine R.; Brughera, Andrew; Chiu, Chung-Yiu Peter

2003-08-01

126

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

127

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

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

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

130

Measurement Converter  

NSDL National Science Digital Library

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

131

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

132

crystal  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

133

Frequency mixing crystal  

DOEpatents

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

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

1992-01-01

134

Radiating dipoles in photonic crystals  

Microsoft Academic Search

The radiation dynamics of a dipole antenna embedded in a photonic crystal are modeled by an initially excited harmonic oscillator coupled to a non-Markovian bath of harmonic oscillators representing the colored electromagnetic vacuum within the crystal. Realistic coupling constants based on the natural modes of the photonic crystal, i.e., Bloch waves and their associated dispersion relation, are derived. For simple

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

2000-01-01

135

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

136

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

137

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

138

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

139

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

140

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

PubMed

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

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

2014-01-01

141

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

142

Drive System for Traction Applications Using 81-Level Converter  

E-print Network

by harmonics is minimized, and power losses into the machine are also reduced. Another advantage of this kind. Normally, voltage (or current in dual devices) moves to discrete values, forcing the design of machines of the multi-stage converter. It is based on the simple, four switches converter, used for single

Catholic University of Chile (Universidad Católica de Chile)

143

Hybrid-integrated polarization mode converters and low-voltage electro-optic modulators using crystal-ion-sliced LiNbO3 films  

Microsoft Academic Search

Lithium Niobate (LiNbO3) films produced by the crystal ion slicing (CIS) method are introduced in various components in use in the optical telecommunications market. The CIS technique employs high-energy ion implantation to create a narrow (~0.2 micrometers ) planar layer of localized damage, buried ~10 micrometers beneath the surface of the implanted LiNbO3 wafers. This sacrificial layer allows for slicing

Antonije M. Radojevic; Junichiro Fujita; Louay A. Eldada

2002-01-01

144

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

NASA Astrophysics Data System (ADS)

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

Rao, Redrothu Hanumantha; Kalainathan, S.

2012-11-01

145

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

SciTech Connect

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

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

2004-10-18

146

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

147

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

148

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

149

Development of Large Capacity Programmable Harmonic Current Generator Based on Three-phase-four-wire Configuration  

Microsoft Academic Search

The large capacity harmonic current generator based on three-phase four-wire configuration uses four-leg converter as its main circuit. So it is different from the traditional small capacity linear current source. The whole equipment can output steady harmonic current include the selective order harmonic (below 25th order), reactive current and unbalanced current. Besides, dynamic change process of harmonic current can also

Liu Tao; Zhuo Fang; Chen Bo; Zhai Xi; Wang Zhao-an

2006-01-01

150

Three-phase-four-wire Inverter Used in Large Capacity Programmable Harmonic Current Generator  

Microsoft Academic Search

The large capacity harmonic current generator based on three-phase-four-wire configuration uses four-leg converter as its main circuit. So it is different from the traditional small capacity linear current source. The whole equipment can output steady harmonic current include the selective order harmonic (below 25th order), reactive current and unbalanced current. Besides, dynamic change process of harmonic current can also be

Xian'wei Wang; Fang Zhuo; Hao Yi; Yan'hui Qiu; Xiang Shen; Guo'chun Xiao; Zhao'an Wang

2009-01-01

151

Study on the second-harmonic-generation of GdCa 4O(BO 3) 3 crystals along various phase-matching directions  

Microsoft Academic Search

In this paper, the theoretical calculations of deff of GdCa4O(BO3)3 (GdCOB) along various phase-matching (PM) directions are reported. It is shown that the maximum deff is out of the main planes and the deff in the range of (0crystal has

Shujun Zhang; Zhenxiang Cheng; Junhai Liu; Guangming Li; Jianru Han; Zongshu Shao; Huanchu Chen

2000-01-01

152

Buck Converter Animation  

NSDL National Science Digital Library

This website from the Thayer School of Engineering at Dartmouth College features an animation of a buck converter. A buck converter is a step-down DC to DC converter. Its design is similar to the step-up boost converter, and like the boost converter it is a switched-mode power supply that uses two switches (a transistor and a diode), an inductor and a capacitor.

153

Broadband second harmonic generation in a tapered isotropic semiconductor slab using total internal reflection quasi phase matching  

NASA Astrophysics Data System (ADS)

This paper analytically describes the concept of enhancing the bandwidth of second-harmonic generation in the mid-infrared region in an isotropic tapered semiconductor slab configuration. In this slab geometry, the lengths between successive reflection points due to total internal reflection of the incident laser radiation increase when it propagates through the slab. A computer aided simulation has been carried out to determine the possibility of generating broadband second harmonic intensity for broadband fundamental laser radiations as they are allowed to undergo total internal reflection inside the tapered isotropic semiconductor crystal slab made of either gallium arsenide (GaAs) or zinc selenide (ZnSe). The simulated results indicate wide 3 dB bandwidths of 187 nm and 196 nm in a 30 mm long tapered slab of GaAs and ZnSe respectively. The conversion efficiency, after considering the absorption and reflection losses, is quite satisfactory (? 1%). The effects of variations in temperature, incident angle of the fundamental laser radiations at the air-slab interface, length and tapering angle of the semiconductor slab have been studied for generated second harmonic radiations in both GaAs and ZnSe crystals. Optimising these parameters a wider broadband frequency converter with appreciable conversion efficiency can be designed.

Saha, Ardhendu; Deb, Sumita

2011-09-01

154

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

155

Full bridge converter Transformers and isolated converters  

E-print Network

control. 2. High power factor PFC - discussed previously. 3. Isolation 4. Multiple outputs IsolatedFull bridge converter Transformers and isolated converters Most DC power supplies have the following requirements: 1. Regulated output voltage Solved by a large capacitor at the output, and feedback

Knobloch,Jürgen

156

Switching Power Converter A/D Converters  

E-print Network

" monitoring capable of measuring system performance and detecting faults or anomalies in the operation using A/D converters and the data is sent to a digital controller for processing. A system interface then displays processed data concerning the converter health status. Online Health Monitoring in Digitally

157

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

158

Harmonization of Biodiesel Specifications  

SciTech Connect

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

Alleman, T. L.

2008-02-01

159

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

160

An improved approach to reduce harmonics in the utility interface of wind, photovoltaic and fuel cell power systems  

Microsoft Academic Search

In this paper, an improved approach to reduce harmonics in the utility interface of wind, photovoltaic and fuel cells power systems is presented. The approach is based on circulating third harmonic current injection to reduce utility line current harmonics in SCR converters. In this paper, a new injected current shape is computed from analysis to achieve sinusoidal utility line currents.

Ali M. El-Tamaly; P. N. Enjeti; H. H. El-Tamaly

2000-01-01

161

Bidirectional dc-ac conversion topology using matrix converter technique  

Microsoft Academic Search

The matrix converter is a power conversion topology, directly connecting the input and output with bidirectional switches. It has advantages such as high reliability and long life, bidirectional power flow and reduced current harmonics. This paper proposes a bidirectional dc-ac conversion topology with step-up and step-down capabilities using matrix converter technique. Detail of circuit operation and experimental results for various

Sadao Ishii; Hidenori Hara; Tsuyoshi Higuchi; Tomohiro Kawachi; Katsutoshi Yamanaka; Noritaka Koga; Tsuneo Kume; Jun-Koo Kang

2010-01-01

162

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

163

System and methods for reducing harmonic distortion in electrical converters  

DOEpatents

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

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

2013-12-03

164

Elimination of Harmonics in a Multilevel Converter for HEV Applications  

E-print Network

with these in- verters [6]. The multilevel voltage source inverter's unique structure allows it to reach high multilevel inverter is then 2s + 1, where s is the number of #12;2 dc sources. An example phase voltage times (angles) in a multilevel inverter can be chosen to achieve a required fundamental voltage

Tolbert, Leon M.

165

Noncollinear second-harmonic generation in sub-micrometer-poled RbTiOPO4  

E-print Network

Noncollinear second-harmonic generation in sub-micrometer-poled RbTiOPO4 S. Moscovich, A. Arie, R generated noncollinear quasi-phase-matched second harmonic wave in an RbTiOPO4 crystal that was poled using. Svitanko, "Nonlinear optical properties of the flux grown RbTiOPO4 crystal," Opt..Mat. 3, 237-242 (1994). 7

Arie, Ady

166

Design of MOS transconductors with low noise and low harmonic distortion for minimum current consumption  

Microsoft Academic Search

This paper describes a method for analysis and design of MOS voltage-to-current converters (V–I converters or transconductors) and introduces a novel V–I converter circuit with significantly improved linearity performance. The proposed method uses harmonic compensation for the linearization of the V–I characteristics and introduces a normalized representation of the converter equations. The analysis is applied for several circuit topologies based

Sotir Ouzounov; Engel Roza; Hans Hegt; Gerard V. D. Weide; Arthur H. M. Van Roermund

2007-01-01

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

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

169

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

170

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

Microsoft Academic Search

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

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

2011-01-01

171

A Space Vector Modulation Approach for a Multimodule HVDC Converter System  

Microsoft Academic Search

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

Maryam Saeedifard; Hassan Nikkhajoei; Reza Iravani; Alireza Bakhshai

2007-01-01

172

Nonlinear harmonic generation in the STARS FEL  

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

173

Workshop on Harmonic Oscillators  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

174

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

SciTech Connect

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

Hibbard, R.L., LLNL

1998-03-30

175

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

176

Interleaved power converter  

DOEpatents

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

Zhu, Lizhi (Canton, MI)

2007-11-13

177

Accurate tracking of harmonic signals in VSC-HVDC systems using PSO based unscented transformation  

Microsoft Academic Search

This paper presents the estimation of harmonics in a voltage source converter based HVDC (VSC-HVDC) system for designing AC side filters. The extended Kalman filter (EKF) is well known for estimating amplitude, phase, frequency, and harmonic content of a signal corrupted with noise. However, the EKF algorithm suffers from instability due to linearization and costly calculation of Jacobian matrices, and

P. K. Dash; R. K. Mallick

2011-01-01

178

Tertiary side resonant DC/DC converter with integrated magnetics  

SciTech Connect

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

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

1996-09-01

179

Covariant harmonic oscillators and coupled harmonic oscillators  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

180

Evaluation of converter topologies for improved power quality in DC traction substations  

Microsoft Academic Search

A high power converter is developed for improved power quality in DC traction substation applications. The proposed converter can be used as both an inverter and an active power filter (APF). As an inverter, it can recycle regenerative energy caused by decelerating trains and as an APF, it can compensate for harmonic distortion produced by the rectifier substations. This paper

A. Horn; R. H. Wilkinson; T. H. R. Enslin

1996-01-01

181

Wave-energy converter  

Microsoft Academic Search

The invention provides a device for converting wave energy into useful work, and comprises a body adapted to be moved to and fro by waves on a liquid, and means such as a hydraulic piston in a cylinder for converting this movement of the body into a power output. The body may be disposed about a horizontal cable along which

1985-01-01

182

Wave-energy converter  

Microsoft Academic Search

The invention provides a device for converting wave energy into useful work, and comprises a body adapted to be moved to and fro by waves on a liquid, and means such as a hydraulic piston in a cylinder for converting this movement of the body into a power output. The body may be disposed about a horizontal cable along which

1982-01-01

183

The microminiature thermionic converter  

Microsoft Academic Search

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

Donald Bryan King

2000-01-01

184

Discontinuous Buck Converter  

NSDL National Science Digital Library

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

185

Boost Converter Animation  

NSDL National Science Digital Library

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

186

Third harmonic generation in phase-matched alkali metal vapors  

NASA Technical Reports Server (NTRS)

We report improvements in conversion efficiency for third harmonic generation in sodium and rubidium vapor. 30-psec pulses of radiation at 1.064 micron have been converted to 0.3547 micron with an energy conversion efficiency of 10%. Factors limiting conversion efficiency are discussed.

Bloom, D. M.; Young, J. F.; Harris, S. E.; Bekkers, G. W.

1975-01-01

187

Photocapacitive image converter  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

188

Polarization anisotropy in fiber-optic second harmonic generation microscopy.  

PubMed

We report the investigation and implementation of a compact second harmonic generation microscope that uses a single-mode fiber coupler and a double-clad photonic crystal fiber. Second harmonic polarization anisotropy through the fiber-optic microscope systems is quantitatively measured with KTP microcrystals, fish scale and rat tail tendon. It is demonstrated that the polarized second harmonic signals can be excited and collected through the single-mode fiber coupler to analyze the molecular orientations of structural proteins. It has been discovered that a double-clad photonic crystal fiber can preserve the linear polarization in the core, although a depolarization effect is observed in the inner cladding region. The feasibility of polarization anisotropy measurements in fiber-optic second harmonic generation microscopy will benefit the in vivo study of collagen-related diseases with a compact imaging probe. PMID:18542600

Fu, Ling; Gu, Min

2008-03-31

189

A New Harmonic Mitigation Scheme for MMC - An Experimental Approach  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

190

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

191

Microminiature thermionic converters  

DOEpatents

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

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

2001-09-25

192

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

193

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

194

Coupled Harmonics in Nonlinear Coplanar Waveguide Resonators  

NASA Astrophysics Data System (ADS)

The coplanar waveguide resonator has become a ubiquitous design element in superconducting quantum information experiments. By necessity, many of these resonators are loaded with nonlinear elements and, as such, incorporate a mechanism for coupling power between harmonic modes of the system. In this talk, we will present a specific example in which a dc SQUID terminates a quarter wave resonator and how the mode coupling via this nonlinear element can both enhance and degrade the performance of this device as a parametric amplifier and frequency converter.

Aumentado, Jose; Lee, Minhyea; Spietz, Lafe

2010-03-01

195

A novel SVM-DPC control method for grid connected AC-DC converters under asymmetrical fault  

Microsoft Academic Search

A Space Vector Modulated based on Direct Power Control (SVM-DPC) method applied to a AC-DC Converter connected to the unbalanced input voltages was present in this paper. Asymmetrical grid fault is the main reason caused large 2nd harmonic DC voltage ripple and 3nd harmonic Current in AC side, which severely threaten the safety of the power converter. By using three

Lei Xiao; Shoudao Huang; Ting Liu; Qiong Xu; Keyuan Huang

2011-01-01

196

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

197

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

198

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

199

DC-induced generation of the reflected second harmonic in silicon  

Microsoft Academic Search

DC-induced generation of the reflected second harmonic is experimentally observed on the surface of a centrosymmetric silicon single crystal. A direct current with a surface density of j max ˜ 103 A\\/cm2 violates the symmetry of the electron distribution function and induces the optical second harmonic with an intensity corresponding to the dipole quadratic susceptibility chi(2) d ( j max)

O. A. Aktsipetrov; V. O. Bessonov; A. A. Fedyanin; V. O. Val'Dner

2009-01-01

200

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

201

Metallurgical study of thermionic converters  

Microsoft Academic Search

This paper describes some of the observations made as a result of the test of 180 thermionic converters and of the postmortem metallographic examination of approximately 50 converters. The causes and effects of converter abnormal performance are related to the results of the metallographic examinations. The materials and fabrication methods utilized in converter construction are discussed together with areas of

PETER ROUKLOVE

1969-01-01

202

Dual switched mode power converter  

Microsoft Academic Search

A dual power converter is introduced which addresses the problem of output ripple and switching losses in a switched power converter. One stage of the power converter is a conventional PWM (pulse-width modulated) converter, and the other stage is a linear source. The linear source controls the voltage directly, and the output current of the linear stage is used to

PALLAB MIDYA; FRED H. SCHLERETH

1989-01-01

203

Optimization of Input and Output Filters in Matrix Converter Drive System  

NASA Astrophysics Data System (ADS)

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

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

204

Harmonic prime movers  

NASA Astrophysics Data System (ADS)

Western Kentucky University is undertaking the development of a thermoacoustically powered acoustic agglomerator as a means of pretreating exhaust from coal generators before entering standard industrial electrostatic precipitators. In order to fulfill the design requirement of maintaining a clean, isolated environment for the thermoacoustic components, it will be necessary to operate a thermoacoustic prime mover in a harmonic mode, which normally is not a desirable feature in typical devices. Details of a harmonic-mode prime mover will be presented. [Work supported by KY EPSCoR and the Western Kentucky Office of Sponsored Programs.

Rice, Ian; Smith, Gordon

2005-09-01

205

HEAT DIODE CONVERTER  

Microsoft Academic Search

Experimental and theoretical investigations were made on several aspects ; of the cesium plasma thermionic converter. Data were taken on the electron ; emission properties of tungsten, tantalum, molybdenum, niobium, rhenium, iridium, ; and tantalum carbide. Two methods were used in this study; one was the ; measurement of the I-V characteristics of diodes using eminers of these materials ;

M. Gottlieb; R. J. Zollweg; L. S. Richardson; A. E. Fein; J. G. DeSteese

1963-01-01

206

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.

207

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

208

Current Phase Lead Compensation in Single-Phase PFC Boost Converters With a Reduced Switching Frequency to Line Frequency Ratio  

Microsoft Academic Search

Traditional design of the current loop controller in a single-phase power factor correction boost converter is not suitable for applications with higher line frequencies (up to 800 Hz) because of the zero-crossing distortion and high harmonic content due to the current phase lead effect. Increasing the control bandwidth and switching frequency in order to avoid this effect would reduce converter

Konstantin P. Louganski

2007-01-01

209

Current phase lead compensation in single-phase PFC boost converters with a reduced switching frequency to line frequency ratio  

Microsoft Academic Search

Traditional design of the current loop controller in a single-phase PFC boost converter is not suitable for applications with higher line frequencies (up to 800 Hz) because of the zero-crossing distortion and high harmonic content due to the current phase lead effect. Increasing the control bandwidth and switching frequency in order to avoid this effect would reduce converter efficiency and

Konstantin P. Louganski; Jih-Sheng Lai

2006-01-01

210

NONEQUILIBRIUM STATIONARY STATES OF HARMONIC CHAINS WITH BULK NOISES  

E-print Network

-equilibrium sta- tionary states (NESS) of systems in contact, at their boundaries, with ther- mal reservoirs for which NESS are known are harmonic crystals [1, 2]. These are described by specifying the positions and to produce NESS with normal transport one may add bulk noise to the system [3]­[8]. The new NESS will, we

211

NONEQUILIBRIUM STATIONARY STATES OF HARMONIC CHAINS WITH BULK NOISES  

E-print Network

-equilibrium sta- tionary states (NESS) of systems in contact, at their boundaries, with ther- mal reservoirs for which NESS are known are harmonic crystals [1, 2]. These are described by specifying the positions and to produce NESS with normal transport one may add bulk noise to the system [3]­[8]. The new NESS will, we

Paris-Sud XI, Université de

212

Frequency doubling crystals  

DOEpatents

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

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

1989-01-01

213

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.

David Joiner

214

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

215

Harmonically excited orbital variations  

SciTech Connect

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

Morgan, T.

1985-08-06

216

A Harmonic Motion Experiment  

ERIC Educational Resources Information Center

We present a unit comprising theory, simulation and experiment for a body oscillating on a vertical spring, in which the simultaneous use of a force probe and an ultrasonic range finder enables one to explore quantitatively and understand many aspects of simple and damped harmonic motions. (Contains 14 figures.)

Gluck, P.; Krakower, Zeev

2010-01-01

217

Harmonic operation of STW filters  

Microsoft Academic Search

The physical mechanism causing the propagation loss of surface transverse wave (STW) devices during harmonic operation is modeled and analyzed. It is found that as the mode frequency is pushed beyond the fundamental, the dominant Bloch component of the STW solution passes through the higher spatial harmonics. In these frequency regions, the lower harmonic components which contribute (perhaps weakly) to

R. L. Baer; C. A. FLory

1988-01-01

218

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

219

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

220

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

221

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.

2009-08-14

222

Advanced thermionic converter development  

Microsoft Academic Search

Recent progress at Thermo Electron in developing advanced thermionic converters is summarized with particular attention paid to the development of electrodes, diodes, and triodes. It is found that one class of materials (ZnO, BaO and SrO) provides interesting cesiated work functions (1.3-1.4 eV) without additional oxygen. The second class of materials studied (rare earth oxides and hexaborides) gives cesiated\\/oxygenated work

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

1976-01-01

223

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

224

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

Microsoft Academic Search

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

Weihao Hu; Yue Wang; Xianwen Song; Zhaoan Wang

2009-01-01

225

Thermionic energy converters  

SciTech Connect

This invention is concerned with improving the efficiency of thermionic energy converters. The invention is particularly directed to the reduction of plasma losses in these converters. This beneficial technical effect is achieved by internal distribution of tiny shorted cesium diodes driven by the thermal gradient between the primary emitter and the collector. Specifically, the tiny, shorted 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 diode effect will increase with the use of metals that adsorb cesium less readily for the main emitter ends of the tiny protrusions and metals that adsorb cesium more readily for the main collector ends of the protrusions. By way of example, the main emitter can be made of rhenium or irridium; the main emitter ends of the protrusions can be made of tantalum or niobium; and the main collector ends of the protrusions can be made of platinum or irridium. 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.

1983-02-08

226

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

Microsoft Academic Search

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

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

2006-01-01

227

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

Microsoft Academic Search

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

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

228

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

229

Cycloidal Wave Energy Converter  

SciTech Connect

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

Stefan G. Siegel, Ph.D.

2012-11-30

230

The microminiature thermionic converter  

NASA Astrophysics Data System (ADS)

The design, fabrication, testing, and analysis of the microminiature thermionic converter (MTC) is discussed. MTCs are two electrode devices that convert heat energy into electrical energy. The electrodes are spaced opposite each other in a vacuum environment with one electrode heated and the second cooled. Electrons are emitted from the hot electrode to the cool electrode creating electrical power. The fabrication of the MTC uses micromachining and semiconductor integrated circuit fabrication methods. These fabrication techniques allow the MTC to have an inter-electrode spacing of 20 microns or less with electrode materials having work functions ranging from 0.75 to 3 eV. The small gap size and low work function features of the MTC give it the potential to produce electricity at relatively high conversion efficiencies (20--25%). MTC designs may be tailored to function for different heat sources (combustion, solar, advanced nuclear reactors, radioisotopes, waste heat) over broad temperature regimes. The MTC diode prototype has been successfully fabricated, operated, and analyzed over a wide range of emitter and collector temperatures in the power production mode as well as power consumption mode. The emitter temperatures of interest ranged from 770 through 1220K. Maximum power output densities of 2mW/cm2 have been produced, and maximum output voltages approaching 1 Volt have also been produced. The MTC has been used to power an external load consisting of a Motorola 1N4004 diode. Models have been developed to characterize thermionic surface emission and electron transport across the gap. The MTC diode current-voltage characteristics and features have been successfully modeled over all five operational modes that characterize a thermionic converter. Power production has not been as high as expected. The shortcomings are due to the low work function material, (Ba,Sr,Ca)O, used in the diode. The tests and models indicate that the irregularities in work function across the emission material are detrimental to power production that occurs at low voltage in all thermionic converters. Modest improvements in surface homogeneity could increase the power output density by at least three orders of magnitude.

King, Donald Bryan

231

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.

232

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.

233

Theory of high-harmonic generation in solids  

NASA Astrophysics Data System (ADS)

High-harmonic generation (HHG) in bulk crystals exposed to intense mid-infrared lasers with photon energies below the bandgap is investigated theoretically. A three dimensional, two-band model that considers both interband and intraband currents is used. It is shown that the interband current is the dominant mechanism for HHG in solids. A physical interpretation of interband HHG – similar to atomic HHG – is provided by saddle point analysis. The effects of dephasing time and driving field wavelength on the harmonic specrum are investigated.

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

2015-03-01

234

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

235

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

236

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

237

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

238

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

239

Frequency Doubling Broadband Light in Multiple Crystals  

SciTech Connect

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

ALFORD,WILLIAM J.; SMITH,ARLEE V.

2000-07-26

240

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

241

Harmonic behavior of variable-speed wind turbines during a control fault  

Microsoft Academic Search

This paper is concerned with the harmonic behavior of variable-speed wind turbines during a control fault. Different topologies for the power-electronic converters are considered, namely two-level and multilevel converters. A three- mass drive train model is considered, and a fractional-order control strategy is proposed for the wind turbines. The performance of disturbance attenuation and system robustness is ascertained. Finally, conclusions

R. Melicio; V. M. F. Mendes; J. P. S. Catalao

2011-01-01

242

Radiating dipoles in photonic crystals  

E-print Network

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

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

2000-01-01

243

Radiating dipoles in photonic crystals  

PubMed

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

Busch; Vats; John; Sanders

2000-09-01

244

Radiating dipoles in photonic crystals  

E-print Network

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

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

2000-06-02

245

Spiked harmonic oscillators  

NASA Astrophysics Data System (ADS)

A complete variational treatment is provided for a family of spiked-harmonic oscillator Hamiltonians H=-d2/dx2+Bx2+?/x?(B>0,?>0), for arbitrary ?>0. A compact topological proof is presented that the set S={?n} of known exact solutions for ?=2 constitutes an orthonormal basis of the Hilbert space L2(0,?). Closed-form expressions are derived for the matrix elements of H with respect to S. These analytical results, and the inclusion of a further free parameter, facilitate optimized variational estimation of the eigenvalues of H to high accuracy.

Hall, Richard L.; Saad, Nasser; von Keviczky, Attila B.

2002-01-01

246

Electromagnetic wave energy converter  

NASA Technical Reports Server (NTRS)

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

Bailey, R. L. (inventor)

1973-01-01

247

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

248

Converting Biomass to Products  

SciTech Connect

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

Graybeal, Judith W.

2006-06-01

249

Applied Averaging Theory to Power Converters Fabiola Angulo, Enric Fossas, Tere M. Seara  

E-print Network

in the implementa- tion of power converters. As a consequence of the switch- ing action, chattering, high order], while chattering and harmonic dis- tortion, inherent to switching, can be reduced, but not avoided, using fixed switching frequency. To achieve this reduction, some techniques have been reported

Politècnica de Catalunya, Universitat

250

A novel high-efficiency single-stage PFC converter with reduced voltage stress  

Microsoft Academic Search

In this paper, a novel single-stage power-factor-correction converter is proposed, which employs two auxiliary windings to achieve low input current total harmonic distortion, low voltage stress across the bulk capacitor, and high efficiency. The improved performance was experimentally verified

Miaosen Shen; Zhaoming Qian

2002-01-01

251

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

Microsoft Academic Search

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

Z. Chen

2004-01-01

252

Monte Carlo simulation of AC\\/DC\\/AC power converter distortion  

Microsoft Academic Search

Probabilistic analyses of AC\\/DC\\/AC power converter harmonic and interharmonic distortion are performed by using the Monte Carlo simulation. Starting from previous experiences of some of the authors, an analytical and simplified conversion system model recently proposed is recalled and discussed. A new model of the control system is presented. Different tests considering both mechanical working condition variability and supplying voltage

Rosario Carbone; Daniele Castaldo; Francesco De Rosa; Roberto Langella; Alfkedo Testa

2001-01-01

253

Medium-Voltage Multilevel Converters—State of the Art, Challenges, and Requirements in Industrial Applications  

Microsoft Academic Search

This paper gives an overview of medium-voltage (MV) multilevel converters with a focus on achieving minimum harmonic distortion and high efficiency at low switching frequency operation. Increasing the power rating by minimizing switching frequency while still maintaining reasonable power quality is an important requirement and a persistent challenge for the industry. Existing solutions are discussed and analyzed based on their

Haitham Abu-Rub; Joachim Holtz; Jose Rodriguez; Ge Baoming

2010-01-01

254

PWM control of three-phase series resonant DC link converters for UPS applications  

Microsoft Academic Search

This paper present a novel PWM control strategy that can be used for general 3 phase AC\\/AC series resonant DC link converters in uninterruptible power supplies (UPS) applications. The algorithm can achieve control over unity input power factor and provide low total harmonic distortions of input and output line currents. The control is performed in the DQ rotating reference frame

M. N. Marwali; A. Keyhani

1999-01-01

255

Novel PLL scheme for grid connection of three-phase power converters  

Microsoft Academic Search

Basic phase-locked loop (PLL) schemes used for the grid connection of three-phase static converters suffer from line voltage harmonics and unbalance. To overcome this shortcoming, the operation of the basic PLL schemes is improved by supplementing them with blocks that pre or post- processes the line voltages. This paper presents a novel improved PLL scheme that, in spite of its

Osley Lopez Gonzalez; Giuseppe Buja

2011-01-01

256

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

257

Analytical Modeling of Static Converters for optimal sizing of on-board electrical systems  

E-print Network

- 1 - Analytical Modeling of Static Converters for optimal sizing of on-board electrical systems Hieu NGUYEN HUU, Laurent GERBAUD, Nicolas RETIERE, James ROUDET, Frederic WURTZ GRENOBLE ELECTRICAL-board electrical systems (planes, ships, road vehicles...). For the optimal sizing of these systems, harmonics must

Paris-Sud XI, Université de

258

Algal Supply System Design - Harmonized Version  

SciTech Connect

The objective of this design report is to provide an assessment of current technologies used for production, dewatering, and converting microalgae cultivated in open-pond systems to biofuel. The original draft design was created in 2011 and has subsequently been brought into agreement with the DOE harmonized model. The design report extends beyond this harmonized model to discuss some of the challenges with assessing algal production systems, including the ability to (1) quickly assess alternative algal production system designs, (2) assess spatial and temporal variability, and (3) perform large-scale assessments considering multiple scenarios for thousands of potential sites. The Algae Logistics Model (ALM) was developed to address each of these limitations of current modeling efforts to enable assessment of the economic feasibility of algal production systems across the United States. The (ALM) enables (1) dynamic assessments using spatiotemporal conditions, (2) exploration of algal production system design configurations, (3) investigation of algal production system operating assumptions, and (4) trade-off assessments with technology decisions and operating assumptions. The report discusses results from the ALM, which is used to assess the baseline design determined by harmonization efforts between U.S. DOE national laboratories. Productivity and resource assessment data is provided by coupling the ALM with the Biomass Assessment Tool developed at PNNL. This high-fidelity data is dynamically passed to the ALM and used to help better understand the impacts of spatial and temporal constraints on algal production systems by providing a cost for producing extracted algal lipids annually for each potential site.

Abodeely, Jared; Stevens, Daniel; Ray, Allison; Newby, Deborah; Schaller, Kastli

2013-03-01

259

Harmonic generation at high intensities  

SciTech Connect

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

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

1993-06-01

260

Self-powered microthermionic converter  

DOEpatents

A self-powered microthermionic converter having an internal thermal power source integrated into the microthermionic converter. These converters can have high energy-conversion efficiencies over a range of operating temperatures. Microengineering techniques are used to manufacture the converter. The utilization of an internal thermal power source increases potential for mobility and incorporation into small devices. High energy efficiency is obtained by utilization of micron-scale interelectrode gap spacing. Alpha-particle emitting radioisotopes can be used for the internal thermal power source, such as curium and polonium isotopes.

Marshall, Albert C.; King, Donald B.; Zavadil, Kevin R.; Kravitz, Stanley H.; Tigges, Chris P.; Vawter, Gregory A.

2004-08-10

261

Generation of Second-Harmonic Bessel Beams by Transverse Phase-Matching in Annular Periodically Poled Structures  

NASA Astrophysics Data System (ADS)

We demonstrate experimentally the generation of second-harmonic conical waves via parametric frequency doubling in a two-dimensional annular periodically poled nonlinear photonic structure fabricated in a stoichiometric lithium tantalate crystal. We apply the concept of nonlinear Bragg diffraction for explaining this effect, and show theoretically that in low-symmetry crystals this process results in generated second-harmonic waves being a superposition of the Bessel beams.

Saltiel, Solomon M.; Neshev, Dragomir N.; Fischer, Robert; Krolikowski, Wieslaw; Arie, Ady; Kivshar, Yuri S.

2008-08-01

262

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

263

MODEL HARMONIZATION POTENTIAL AND BENEFITS  

EPA Science Inventory

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

264

Luke J. Harmon Curriculum Vitae  

E-print Network

, Chelsea Specht, Curtis Lisle, and Jorge Soberon; total $4,000,000, Harmon lab budget $921,602; Start date in action examined over a phylogeny" (co-PI Joe Felsenstein; total $132,794, Harmon lab budget $65,306) 2009

Harmon, Luke

265

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

266

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

267

RF propagation in finite thickness unidirectional magnetic photonic crystals  

Microsoft Academic Search

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

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

2005-01-01

268

Spatial control of second-harmonic light from a disordered structure  

NASA Astrophysics Data System (ADS)

The second harmonic light generated in crystals with a random distribution of nonlinear domains is usually emitted in a broad range of directions. When the fundamental light has good coherence, the intensity of the second harmonic shows a speckle pattern even when the crystal is transparent. We explain that with the interference at the detection point of the second harmonic generated by the different domains. Using a phase-only spatial light modulator in the fundamental beam, it is possible to concentrate the second harmonic intensity in one direction at the same time that the intensity is reduced in the other directions. In our experiments we measured enhancements in the selected direction up of 700 times over the average intensity in other directions.

Rodríguez, Francisco J.; Yao, Can; Bravo-Abad, Jorge; Martorell, Jordi

2012-06-01

269

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

270

Proposed electromagnetic wave energy converter  

NASA Technical Reports Server (NTRS)

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

Bailey, R. L.

1973-01-01

271

Matrix converters: a technology review  

Microsoft Academic Search

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

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

2002-01-01

272

Observation of optical vortex streets in walking second-harmonic generation.  

PubMed

We report what is believed to be the first experimental observation of spontaneous nucleation of arrays of optical vortices in the process of second-harmonic generation in a crystal with moderate Poynting vector walk-off, pumped with focused beams containing screw phase dislocations. Our experiments were conducted in lithium triborate under conditions of small-efficiency second-harmonic generation pumped by nanosecond pulses at 1064 nm. PMID:18007883

Molina-Terriza, Gabriel; Petrov, Dmitri V; Recolons, Jaume; Torner, Lluis

2002-04-15

273

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

Microsoft Academic Search

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

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

1999-01-01

274

Noncollinear second-harmonic generation in sub-micrometer-poled RbTiOPO4  

Microsoft Academic Search

We have generated noncollinear quasi-phase-matched second harmonic wave in an RbTiOPO4 crystal that was poled using the high-voltage atomic force microscope (HV-AFM). To the best of our knowledge, this is the first systematic nonlinear frequency conversion study of samples produced by the HV-AFM method. The short poling period of 1.18 µm enabled us to observe second harmonic generation at very

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

2004-01-01

275

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

276

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

277

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

PubMed Central

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

Matko, Vojko; Milanovi?, Miro

2014-01-01

278

Magnetic Dirac-harmonic maps  

NASA Astrophysics Data System (ADS)

We study a functional, whose critical points couple Dirac-harmonic maps from surfaces with a two form. The critical points can be interpreted as coupling the prescribed mean curvature equation to spinor fields. On the other hand, this functional also arises as part of the supersymmetric sigma model in theoretical physics. In two dimensions it is conformally invariant. We call critical points of this functional magnetic Dirac-harmonic maps. We study geometric and analytic properties of magnetic Dirac-harmonic maps including their regularity and the removal of isolated singularities.

Branding, Volker

2015-03-01

279

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

SciTech Connect

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

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

1989-10-15

280

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

PubMed

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

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

1989-10-15

281

Analysis of harmonic spline gravity models for Venus and Mars  

NASA Technical Reports Server (NTRS)

Methodology utilizing harmonic splines for determining the true gravity field from Line-Of-Sight (LOS) acceleration data from planetary spacecraft missions was tested. As is well known, the LOS data incorporate errors in the zero reference level that appear to be inherent in the processing procedure used to obtain the LOS vectors. The proposed method offers a solution to this problem. The harmonic spline program was converted from the VAX 11/780 to the Ridge 32C computer. The problem with the matrix inversion routine that improved inversion of the data matrices used in the Optimum Estimate program for global Earth studies was solved. The problem of obtaining a successful matrix inversion for a single rev supplemented by data for the two adjacent revs still remains.

Bowin, Carl

1986-01-01

282

Optical-damage-free guided second-harmonic generation in 1% MgO-doped stoichiometric lithium tantalate  

NASA Astrophysics Data System (ADS)

Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W-1 cm-2 efficiency and second-harmonic power levels up to 41 mW, was achieved in buried waveguides fabricated by reverse-proton exchange in 1% MgO-doped stoichiometric lithium tantalate without any evidence of optical damage. The technology proves suitable for the realization of efficient nonlinear frequency converters and all-optical devices.

Lobino, M.; Marangoni, M.; Ramponi, R.; Cianci, E.; Foglietti, V.; Takekawa, S.; Nakamura, M.; Kitamura, K.

2006-01-01

283

Optical-damage-free guided second-harmonic generation in 1% MgO-doped stoichiometric lithium tantalate.  

PubMed

Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W(-1) cm(-2) efficiency and second-harmonic power levels up to 41 mW, was achieved in buried waveguides fabricated by reverse-proton exchange in 1% MgO-doped stoichiometric lithium tantalate without any evidence of optical damage. The technology proves suitable for the realization of efficient nonlinear frequency converters and all-optical devices. PMID:16419885

Lobino, M; Marangoni, M; Ramponi, R; Cianci, E; Foglietti, V; Takekawa, S; Nakamura, M; Kitamura, K

2006-01-01

284

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.

285

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

286

Analysis of the novel soft-switching buck-boost type AC-DC converter using magnetic coupling  

Microsoft Academic Search

This paper presents the design-oriented analysis of the novel soft-switching buck-boost type AC-DC converter with high power efficiency and high power factor. In this AC-DC converter, the power factor and input current harmonic distortion are improved by using the third winding of the energy-storage reactor, and the high power efficiency is achieved by the soft-switching operation of the main power

H. Matsuo; H. Watanabe; F. Kurokawa; Lishan Tu

2000-01-01

287

A combined approach using phase-controlled rectifiers and high-frequency converters for magnet-load power supplies  

Microsoft Academic Search

In this paper, a control technique for a hybrid large-power high-precision magnet power supply is presented. The system consists of a phase controlled rectifier and a high-frequency PWM converter. The rectifier is designed to handle the main output power and the PWM converter is designed only for harmonics cancellation and error compensation. A feedforward control scheme is proposed to ensure

H. Jin; Y. Wang; G. Joos

1994-01-01

288

Current-fed three-phase PWM converter with sinewave line current shaping and power factor correction scheme  

Microsoft Academic Search

This paper describes a new method to select the optimum pulse-width modulation (PWM) patterns and a procedure to design a low-pass filter in a large-capacity current-source-fed active PWM power converter which is used to suppress higher harmonics flowing into the utility-grid power source. A feasible test is carried out using a 500 kVA active PWM power converter designed for unique

Y. Konishi; N. Arai; Y. Matsumoto; M. Kurokawa; M. Nakaoka

1997-01-01

289

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

290

Echo-Enabled Harmonic Generation  

SciTech Connect

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

Stupakov, Gennady

2010-08-25

291

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

292

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.

293

Wind/water energy converter  

NASA Technical Reports Server (NTRS)

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

Paulkovich, J.

1979-01-01

294

Relation of squeezed states between damped harmonic and simple harmonic oscillators  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

295

Improved technique for picosecond pulse duration measurement based on second harmonic generation  

NASA Astrophysics Data System (ADS)

In present paper we demonstrated an improved technique for characterization of ultra-short pulse duration (PD) based on second harmonic generation (SHG). We utilized Yb- doped fiber laser with picosecond duration of pulses as implementation of proposed technique and for estimating the accuracy of pulse duration measurement. KTiOPO4 crystal was used for the purpose of second harmonic generation. We determined the duration of laser pulses by analysing the combination of signal intensities on input and output of SHG crystal. We observed experimentally error of pulse duration measurement less then 2%. We showed strong dependence between the average power of SHG and the duration of picosecond pulses.

Shelestov, D. A.; Karasik, V. E.; Koshelev, K. I.; Lazarev, V. A.; Pnev, A. B.

2015-01-01

296

Transformerless dc-Isolated Converter  

NASA Technical Reports Server (NTRS)

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

Rippel, Wally E.

1987-01-01

297

Crystal growth, structural and optical characterization of a semi-organic single crystal for frequency conversionapplications  

NASA Astrophysics Data System (ADS)

Single crystals of semi-organic L-histidine hydrobromide have been grown by slow evaporation technique from a mixture of L-histidine and hydrobromic acid in aqueous solution at ambient temperature. From high-resolution X-ray diffraction analysis, the crystalline perfection of the grown crystal has been studied. Single crystal X-ray diffraction analyses, Nuclear Magnetic Resonance spectral analysis, Thermo-Gravimetry (TG), Differential Thermal Analysis (DTA) and hardness test have been employed to characterize the as-grown crystals. The UV cutoff wavelength of the grown crystal is below 300 nm and has a wide transparency window, which is suitable for second harmonic generation of laser in the blue region. Nonlinear optical characteristics have been studied using Q switched Nd:YAG laser ( ?=1064 nm). The second harmonic generation conversion efficiency of the grown crystals confirms their suitability for frequency conversion applications.

Anandan, P.; Parthipan, G.; Saravanan, T.; Mohan Kumar, R.; Bhagavannarayana, G.; Jayavel, R.

2010-12-01

298

Binary/BCD-to-ASCII data converter  

NASA Technical Reports Server (NTRS)

Converter inputs multiple precision binary words, converts data to multiple precision binary-coded decimal, and routes data back to computer. Converter base can be readily changed without need for new gate structure for each base changeover.

Miller, A. J.

1977-01-01

299

High-order harmonic generation in plasmas from nanoparticle and mixed metal targets at 1-kHz repetition rate  

NASA Astrophysics Data System (ADS)

High-order harmonic generation in laser-produced plasmas from nanoparticle and mixed metal targets is studied using a femtosecond Ti:sapphire laser operating at 1-kHz repetition rate. Mixed plasmas from brass and plasmas from nanoparticles (Al, carbon) are investigated and compared to their monatomic counterparts of Zn, Cu, and Al. The dependence on the delay between the heating ablation pulse and the driving converting pulse is studied for a light (carbon) and a heavy atom (silver) target. Further, we report on a comparative measurement of the efficiencies and the photon flux from argon gas harmonics and carbon plasma harmonics. For our conditions, the 13th harmonic is generated in a carbon plasma with an efficiency of ? = 5.3 × 10-7 and yields a flux of about 9.8 × 1010 photons s-1, about 40 % higher than the corresponding harmonic flux in Ar gas under otherwise identical conditions.

Wöstmann, Michael; Redkin, Pavel V.; Zheng, Jiaan; Witte, Henrik; Ganeev, Rashid A.; Zacharias, Helmut

2015-02-01

300

Power converters and amplifiers (review of \\  

Microsoft Academic Search

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

Marian Kazmierkowski

2009-01-01

301

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

NASA Astrophysics Data System (ADS)

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

Boopathi, K.; Ramasamy, P.

302

Growth, spectral and crystallization perfection studies of semi organic non linear optical crystal - L-alanine lithium chloride  

NASA Astrophysics Data System (ADS)

Single crystals of L-alanine lithium chloride single crystals were successfully grown using slow evaporation solution growth technique at constant temperature (303K). The formation of the new crystal has been confirmed by single-crystal X-ray diffraction, FT-IR studies. The crystalline perfection was analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. The powder second harmonic generation (SHG) has been confirmed by Nd: YAG laser. The results have been discussed in detail.

Redrothu, Hanumantharao; Kalainathan, S.; Bhagavannarayana, G.

2012-06-01

303

Crystal growth, X-ray diffraction and nonlinear optical properties of Nb : KTiOPO 4 crystal  

Microsoft Academic Search

The crystal growth experiment of Nb:KTP crystal has been reported. The effect of Nb concentration and seed crystal on the Nb:KTP crystal growth has also been studied. The type II phase-matched (PM) second harmonic generation (SHG) cut-off wavelength and optimal SHG PM angle of Nd:YAG 1.0642?m laser and Nd:YAlO31.0795?m laser have been measured. It shows that Nb concentration has a

D. Y Zhang; H. Y Shen; W Liu; W. Z Chen; G. F Zhang; R. R Zeng; C. H Huang; W. X Lin; J. K Liang

2000-01-01

304

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

305

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

306

A hybrid structure using phase-controlled rectifiers and high-frequency converters for magnet-load power supplies  

Microsoft Academic Search

Thyristor rectifiers are still the preferred choice for large magnet power supplies. However, large harmonic voltages, resulting in large current ripple, and slow dynamic response are major drawbacks of these converters. This paper presents a topology and a control technique for hybrid large-power high-precision magnet power supplies. The system consists of a phase controlled rectifier connected in series with a

H. Jin; Y. Wang; G. Joos

1996-01-01

307

High quality input current waveform on soft-switching DCM boost converter applying pulse-space-modulation  

Microsoft Academic Search

To reduce the switching-loss and the switching-noise, a single-phase soft-switching discontinuous-conduction-mode (SSDCM) boost-type AC-to-DC power converter utilizing the lossless-snubber has proposed. The SSDCM power converter performs zero-voltage-switching and zero-current-switching with a simple topology and control scheme. However, the SSDM boost power converter has significant input-current harmonic distortion in the higher output-voltage range. In this paper, the authors propose a novel

Shin-ichi MOTEGI; Akeshi MAEDA

1998-01-01

308

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

309

Annular symmetry nonlinear frequency converters  

NASA Astrophysics Data System (ADS)

We present a new type of two-dimensional nonlinear structure for quasi-phase matching. This structure has continuous rotational symmetry, and in contrary to the commonly used periodic structures, is not lattice shaped and has no translation symmetry. It is shown that this annular symmetry structure possesses interesting phase matching attributes that are significantly different than those of periodic structures. In particular, it enables simultaneous phase-matched frequency doubling of the same pump into several different directions. Moreover, it has extremely wide phase-mismatch tolerance, since a change in the phase matching conditions does not change the second harmonic power, but only changes its propagation direction. Several structures were fabricated using either the indirect e-beam method in LiNbO3 or the electric field poling method in stoichiometric LiTaO3, and their conversion efficiencies, as well as angular and thermal dependencies, were characterized by second harmonic generation.

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

2006-10-01

310

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

311

Second Harmonic Breakdown in KSTAR  

SciTech Connect

An 84-GHz electron cyclotron heating (ECH) system is being installed on the KSTAR tokamak. KSTAR adopts ECH-assisted start-up for the flexibility and reliability of the KSTAR operation with the plasma breakdown voltage reduced. The available maximum power of the 84 GHz ECH system is presently 500 kW with maximum duration of 2 s. Currently, the second harmonic ECH-assisted start-up is under consideration because a low toroidal field of B{sub T}{approx}1.5 T is desirable for safety and also for the high-beta experiments in the initial operation phase. The studies in this paper are on the effectiveness of the second harmonic breakdown using a 0-D time dependent plasma evolution code and the comparison with the recent DIII-D experimental results on the second harmonic pre-ionization.

Bae, Y. S.; England, A. C.; Kwon, M.; Lee, G. S. [National Fusion Research Center, 52 Eoeun-dong, Yuseong-gu, Daejeon (Korea, Republic of)

2007-09-28

312

Evaluation of harmonic suppression devices  

SciTech Connect

An assessment has been conducted of five commercially available devices to determine their ability to provide clean sinusoidal voltage to nonlinear loads and to eliminate harmonic currents demanded by nonlinear loads. The devices tested were a passive series-shunt filter, a delta-wye isolation transformer, a ferroresonant magnetic synthesizer, an active power line conditioner, and an active injection mode filter. These devices were installed in existing Department of Energy facilities that had substantial non-linear loads which drew a significant harmonic current. These devices were then compared in the following categories: cancellation of harmonic currents, supply of nondistorted voltage, supply of regulated voltage, elimination of transients and impulses, efficiency, reliability, and cost.

Tolbert, L.M. [Oak Ridge National Lab., TN (United States); Hollis, H.D.; Hale, P.S. Jr. [Army Center for Public Works, Alexandria, VA (United States)

1996-09-01

313

The Geography of European Convertible Bonds: Why Firms Issue Convertibles?  

E-print Network

the global convertible market, suggesting that country-specific factors may play an important role in the use share of about 40% of the global market whereas most other countries have experienced dramatic changes to about 25% of the global market by the end of 2005. Why CBs find a more conducive growth environment

Saskatchewan, University of

314

Luminescent up-converting nanocrystals for in vivo imaging  

NASA Astrophysics Data System (ADS)

Luminescent nanoparticles are increasingly used as emitting labels in the design of fluorescence imaging probes, because of their outstanding optical properties, such as in the case of quantum dots, or their role in nano-assembling different functionalities, such as imaging, drug delivery, and therapy. In this work, the potentiality of up-converting nano-crystals for non invasive fluorescence imaging of small animal is explored. These up-converting nano-crystals are lanthanide doped oxide matrices, such as Y IIO 3:Er,Yb compositions. They are produced by a bottom-up process and a thermal treatment. They are functionalized by the coating of a thin polysiloxane shell layer, which can be further derivatized in order to graft biomolecules such as antibodies, peptides, or DNA. Contrary to classical luminescent particles for which light emission occurs at a wavelength superior to that of excitation, these materials emit at 564 and 661 nm upon excitation at 980 or 815 nm. These unique emission properties, due to a multi-photonic process, can allow imaging without any auto-fluorescence from the tissues in the wavelength detection window. Experiments in phantoms mimicking the optical absorption and diffusion of tissues show that these crystals can be detected 4 mm deep at a 10 mg/mL concentration. Luminescence measurements in mouse and the potentiality of these nano-crystals for in vivo imaging are discussed.

Texier, Isabelle; Heinrich, Emilie; Berger, Michel; Tillement, O.; Louis, C.; Peltié, Philippe

2007-02-01

315

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

316

A thermionic converter success story  

SciTech Connect

This paper summarizes the advanced out-of-core thermionic technology program being managed at Wright Laboratory: The Thermionic Critical Technology (TCT) Investigation. This program has been supported primarily by the United State Air Force for design and fabrication, and supported by Strategic Defense Initiative Organization (SDIO) for performance and life testing efforts. Converter design parameters, specifications, and performance testing data is summarized. Converters fabricated by Loral Electro Optical Systems (Loral EOS) under this program have exceeding performance requirements, and have demonstrated efficiencies as high as 14%.

Donovan, B.D.; Lamp, T.R. (Aerospace Power Division, Wright Laboratory Wright-Patterson AFB, OH 45433-6563 (United States)); Ramaligam, M.L. (UES, Inc. 4401 Dayton-Xenia Road, Dayton, OH 45432-1894 (United States))

1993-01-20

317

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

318

Harmonic resolution as a holographic quantum number  

SciTech Connect

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

Bousso, Raphael

2004-01-31

319

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

320

Analytic signals and harmonic measures  

NASA Astrophysics Data System (ADS)

We prove that a sufficient and necessary condition for Hei[Theta](s)=-iei[Theta](s), where H is Hilbert transformation, [Theta] is a continuous and strictly increasing function with [Theta](R)=2[pi], is that d[Theta](s) is a harmonic measure on the line. The counterpart result for the periodic case is also established. The study is motivated by, and has significant impact to time-frequency analysis, especially to aspects of analytic signals inducing instantaneous amplitude and frequency. As a by-product we introduce the theory of Hardy-space-preserving weighted trigonometric series and Fourier transformations induced by harmonic measures in the respective contexts.

Qian, Tao

2006-02-01

321

Current sharing in multiphase ZVT boost converter  

Microsoft Academic Search

Paralleling converters is a good choice for designing high frequency and high power converters. Nevertheless there must be a mechanism to share the load among phases to achieve all the benefits of parallel operation. A simple method to achieve current sharing is paralleling converters with high impedance. The ZVT Boost converter has interesting properties: Zero Voltage Transition, less semiconductors stress

Esther de Jódar; José A. Villarejo; Jacinto Jiménez; Miguel Moreno

2010-01-01

322

Damping assembly for a torque converter clutch  

Microsoft Academic Search

This patent describes a turbine damped torque converter and clutch. It comprises: a pressure plate; a torque converter turbine; a torque converter impeller; means including a control chamber for the pressure plate means for controlling the apply and release of the clutch for engaging the clutch with the impeller; a torque converter output shaft; a planetary gear arrangement including an

Dull

1989-01-01

323

Characteristics of an equidistant firing system in 12-pulse converter bridges for HVDC  

NASA Astrophysics Data System (ADS)

The construction of a simulation model for a twelve pulse HVDC transmission line is discussed. The realized equidistant pulse phase control system is suitable for the operation in weak or strongly unbalanced ac systems from the viewpoint of harmonic instability and suppression of abnormal harmonic currents. The phase of the firing pulses is proportional to an absolute level of the control voltage, and the operation with a constant control angle is possible. The synchronism with an ac system is guaranteed by a phase-locked loop, not by the main control loop. Thus quick and ideal response is obtaind. The measurements show that this kind of grid conrol is stable also in many faulty conditions. Abnormal harmonic generation of the converter is very small compared with the traditional systems by utilizing this kind of grid control.

Juslin, K.; Laiho, Y.; Vauhkonen, V.

1981-05-01

324

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

325

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

326

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

327

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

328

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

329

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

330

Modeling of medium voltage power electronics converters utilizing advanced simulation tools  

Microsoft Academic Search

This paper addresses the steady-state and dynamic modeling of a three-level, neutral-point-clamped (NPC) voltage source converter (VSC) with active front-end (AFE) in a commercial 2.5 MW variable speed motor drive (VSD). The AFE of the modeled VSD adopts the selective harmonic elimination SHE-PWM technique with the optimization of inverter power capacity and power source quality for a wide- range VSD

Oleg Vodyakho; Tim Chiocchio; Michael Steurer; Chris Edrington; Mike Sloderbeck

2011-01-01

331

Reversible AC Drive Systems Based on Parallel AC–AC DC-Link Converters  

Microsoft Academic Search

In this paper, two reversible single-phase-to-three-phase ac drive systems are proposed. They are composed of an induction motor fed by two parallel single-phase-to-three-phase dc-link converters without isolation transformers. Suitable modeling and control strategy of the systems based on odq approach, including the unbalanced case, are developed. The proposed topologies permit reducing the harmonic distortion and presents fault tolerance characteristics. Even

Cursino Brandão Jacobina; Euzeli Cipriano dos Santos; Nady Rocha; Bernard de S Gouveia; Edison Roberto Cabral da Silva

2010-01-01

332

Potentials of LiGa(S 1-xSe x) 2 mixed crystals for optical frequency conversion  

NASA Astrophysics Data System (ADS)

Phase-matching conditions are considered for second harmonic generation (SHG) and optical parametric generation in LiGa(S 1-xSe x) 2 mixed crystals as a function of chemical composition under the supposition of linear dependence of refractive indices on x. It has been shown that by tuning x over the range 0-1 the SHG can be realized in XY plane for ?=2.1-7.8 ?m pumping at ?=43-90°, in YZ plane for ?=2.1-2.2 and 4.8-7.8 ?m pumping at ?=0-90°, and in XZ plane for ?=1.6-11.7 ?m pumping at ?=0-57°. The LiGa(S 1-xSe x) 2 solid solutions are also attractive for design of tunable femtosecond pulse frequency converters with saving of pump pulse duration.

Huang, J.-J.; Atuchin, V. V.; Andreev, Yu. M.; Lanskii, G. V.; Pervukhina, N. V.

2006-07-01

333

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

PubMed

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

Lee, Dong-Joon; Whitaker, John F

2009-08-17

334

Curious Crystals  

NSDL National Science Digital Library

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

James H. Kessler

2007-01-01

335

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

Microsoft Academic Search

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

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

2004-01-01

336

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

337

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

338

Hybrid-mode thermionic converter  

NASA Technical Reports Server (NTRS)

Converter's collector electrode has uniform low work-function surface and operates at sufficiently low temperature to produce negligible electron emission. Emitter electrode has main region which has intermediate work-function and auxiliary region which has relatively high work-function surface.

Rasor, N. S.; Britt, E. J.

1976-01-01

339

Converting Work into College Credits  

ERIC Educational Resources Information Center

The Cooperative Education Program conducted by the New Jersey Department of Labor and Industry and Thomas A. Edison College enables State labor department employees to work toward college degrees by attending free classes, taking college-level examinations for college credit, and converting work and life experiences into college credits.…

Hoffman, Joseph A.

1976-01-01

340

Direct Drive Wave Energy Converters  

Microsoft Academic Search

Over the last 25 years there have been numerous proposals for the conversion of energy contained within sea waves into electricity. Despite this fact, there is not yet one definitive wave energy device that stands out from the rest and developments in several concepts still continues. One aspect of a wave energy converter is the manner in which the physical

N. J. Baker; M. A. Mueller

2001-01-01

341

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

342

Parametric study of laser photovoltaic energy converters  

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

343

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

SciTech Connect

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

Jay L. Hirshfield

2012-07-26

344

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

345

Limits of long wavelength High Harmonic Generation  

E-print Network

Many researchers are pushing for long wavelength driver pulses for High Harmonic Generation (HHG). The advantage of longer wavelengths is that the cut-off of the harmonic spectrum can be increased without the need for large ...

Bhardwaj, Siddharth

2010-01-01

346

A novel, empirical equation — Based shunt active filter for harmonic elimination and power factor correction, using a modified PSO algorithm  

Microsoft Academic Search

This paper presents a novel approach for harmonic elimination and power factor correction (PFC) in a single phase AC-DC rectifier system using a shunt Active Power Filter (APF). The DC output of the rectifier is further regulated using a Buck Converter. The active filter topology is based on a single-phase voltage source inverter with four IGBT switches. The proposed approach

Harish S. Krishnamoorthy; Manoj K. Vadali; Prahlad Supeda

2011-01-01

347

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

E-print Network

Research Centre, University of Southampton, Southampton, SO17 1BJ, UK *orc.jones@soton.ac.uk Keywords: All, secondly, the second phase harmonic (a down-converted M/2-PSK signal) is partially phase through four-wave mixing (FWM) can be limited by the fiber parameters and input power constraints. Very

348

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

349

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

350

Algorithms for spherical harmonic lighting  

Microsoft Academic Search

Spherical harmonic (SH) lighting models require efficient and general libraries for evaluation of SH functions and of Wigner matrices for rotation. We introduce an efficient algebraic recurrence for evaluation of SH functions, and also implement SH rotation via Wigner matrices constructed for the real SH basis by a recurrence. Using these algorithms, we provide a freely distributable C \\/ OpenGL

Ian G. Lisle; S.-L. Tracy Huang

2007-01-01

351

Quantum Damped Harmonic Oscillator Revisited  

E-print Network

In this paper we revisit the quantum damped harmonic oscillator and construct an interesting approximate solution in the operator algebra level. Namely, we first give the general solution to the Lindblad form (equation) and next construct an approximate solution to the full equation by use of it. Our method is a milestone to construct the general solution.

Fujii, Kazuyuki

2007-01-01

352

Standing Waves: Harmonics and Patterns  

NSDL National Science Digital Library

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

Henderson, Tom

353

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

354

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

355

Electromagnetic space-time crystals. II. Fractal computational approach  

E-print Network

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

G. N. Borzdov

2014-10-20

356

Spherical Harmonic Solutions of Fiber Orientation Probability Distributions for Composite Processes  

NASA Astrophysics Data System (ADS)

This paper presents a method to numerically solve partial differential equations such as the Jeffery's equation, which calculates the orientation of fiber in a slow moving fluid. Our method relies on spherical harmonics. This method is equivalent to using the higher order moment tensors with the linear closure, but using tensors of very high order, even as high as 400. However, using spherical harmonics and its related theory, it is possible to create methods that compute surprisingly quickly. In fact we created a general process, whereby many kinds of partial differential equation that describes a distribution of directions of fibers, can be automatically converted into a computer program capable of solving the differential equation. This automated process is carried out using a script, which converts the partial differential equation into a threaded C program.

Montgomery-Smith, Stephen; Jack, David; Smith, Douglas

2008-07-01

357

Improved picosecond laser ablation with second harmonic seeding  

NASA Astrophysics Data System (ADS)

We report on recent results of laser ablation in semiconductors obtained by simultaneous irradiation of the sample with a superposition of the fundamental beam of a picosecond-Neodymium-Vanadate (Nd:VAN) laser (1064 nm, 10 ps pulse duration) and a small fraction of its second harmonic (SH) produced in a thin nonlinear crystal. In this fashion, the ablation yield could be increased by 70%. In addition, the ablation quality was improved in terms of surface smoothness. The underlying mechanism can be attributed to a 'seeding' of the target area with free carriers by the 532 nm radiation.

Zoppel, S.; Zehetner, J.; Reider, G. A.

2006-03-01

358

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

359

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

360

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

361

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)

2010-10-26

362

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

363

Method for reducing energy losses in laser crystals  

DOEpatents

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

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

1992-03-24

364

Method for reducing energy losses in laser crystals  

DOEpatents

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

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

1992-01-01

365

The method of separating harmonic signals from multiplicative and additive noises  

Microsoft Academic Search

This paper focuses on the extraction of a harmonic signal from multiplicative and additive noises. A method is proposed in\\u000a two stages: (1) to square the original discrete time series, which includes both signals and noises, and form a new time series.\\u000a By this means, the multiplicative noise is converted to additive noise; and (2) to filter out the noise

Yangyu Fan; Zhengwei Zhang; Xiaorong Wei; Li Zeng; Wei Wei

2007-01-01

366

Dynamic Trajectory Generation for Spatially Constrained Mechanical Systems Using Harmonic Potential Fields  

Microsoft Academic Search

The harmonic potential field (HPF) approach to motion planning is shown to provide an efficient and provably-correct basis for building intelligent, context-sensitive, and goal-oriented controllers. In the paper by the author (2006) a novel type of dampening forces called: nonlinear, anisotropic, dampening forces (NADFs) are used to convert the guidance signal from an HPF into a navigation control signal with

Ahmad A. Masoud

2007-01-01

367

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

368

Modular packaging of VSCF converters  

NASA Astrophysics Data System (ADS)

The use of modular building blocks to configure VSCF converters of ratings varying from 40 to 110 kVA with an unvarying geometry for uniform circuit impedances is demonstrated. The various modules are described and means of implementating rating changes are considered. Alternate cooling methods such as air and oil are discussed and a description is given of the physical adjustments necessary for cooling compatibility. Weight, size, and efficiency data are provided for all ratings and cooling methods.

Pollard, David D.

1987-10-01

369

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

370

Split-mode-enhanced second-harmonic generation in porous silicon-coupled microcavities  

NASA Astrophysics Data System (ADS)

The enhancement of the second-harmonic generation (SHG) in all-silicon coupled microcavities (CMC) based on one-dimensional photonic crystals is experimentally studied. CMC are fabricated from alternating layers of electrochemically grown mesoporous silicon and consist of two identical half-wavelength-thick cavity spacers separated by additional porous silicon photonic crystal. The enhancement of the second-harmonic response of CMC in the vicinity of splitted cavity modes is experimentally observed in both angular (wave vector) and frequency domain spectra. The variation of transmission of the intermediate photonic crystal, which controls the interaction between coupled cavity spacers, leads to monotonic dependence of the SHG resonances splitting on the number of pairs of the intermediate Bragg reflector.

Dolgova, Tatyana V.; Martemyanov, Michail G.; Kim, Evgenia M.; Gusev, D. G.; Fedyanin, Andrew A.

2002-11-01

371

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

372

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

373

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

374

Data harmonization and model performance  

NASA Astrophysics Data System (ADS)

The Joint Committee on Urban Storm Drainage of the International Association for Hydraulic Research (IAHR) and International Association on Water Pollution Research and Control (IAWPRC) was formed in 1982. The current committee members are (no more than two from a country): B. C. Yen, Chairman (USA); P. Harremoes, Vice Chairman (Denmark); R. K. Price, Secretary (UK); P. J. Colyer (UK), M. Desbordes (France), W. C. Huber (USA), K. Krauth (FRG), A. Sjoberg (Sweden), and T. Sueishi (Japan).The IAHR/IAWPRC Joint Committee is forming a Task Group on Data Harmonization and Model Performance. One objective is to promote international urban drainage data harmonization for easy data and information exchange. Another objective is to publicize available models and data internationally. Comments and suggestions concerning the formation and charge of the Task Group are welcome and should be sent to: B. C. Yen, Dept. of Civil Engineering, Univ. of Illinois, 208 N. Romine St., Urbana, IL 61801.

375

Harmon Craig (1926-2003)  

NASA Astrophysics Data System (ADS)

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

Weiss, Ray

376

A mathematical model of the class D converter for compact fluorescent ballasts  

SciTech Connect

The time-harmonic analysis is often used to design the class D converter. Since the Q of the resonant network is often low, this analysis, in the form of the sinusoidal approximation, begins to lose accuracy. This paper explores an improved method of designing compact fluorescent ballasts via the square wave approximation (SWA), where the time domain equations are solved for the general case of arbitrary Q, duty ratio, and frequency. A precise mathematical model of the Class D converter is developed that predicts the currents and voltages of the converter and these solutions are compared with computer simulation. Nonlinear programming (NLP) is introduced as a means to design the ballast for the lowest conduction losses. The equations developed in the mathematical model are formulated into a NLP format that includes the self-oscillating case.

Nerone, L.R. [Reliance Research Center, Euclid, OH (United States)] [Reliance Research Center, Euclid, OH (United States)

1995-11-01

377

Zigzag Connected Autotransformer-Based 24-pulse AC-DC Converter  

NASA Astrophysics Data System (ADS)

In this paper, a zigzag connected autotransformer-based 24-pulse AC-DC converter is designed, modeled and simulated to feed direct torque controlled induction motor drives. Winding arrangements and parameters of the autotransformer and interphase reactor are given. Moreover, the design procedure of the autotransformer is modified to make it suitable for retrofit applications. Simulation results indicate that the system is capable of eliminating up to 21st harmonics in the ac mains current. The effect of load variation and load character is also studied to demonstrate the performance and effectiveness of the proposed 24-pulse converters. A set of power quality indices at ac mains and dc side are presented to compare the performance of 6-, 12- and 24-pulse converters.

Xiao-qiang, Chen; Hao, Qiu

2015-02-01

378

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

379

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

E-print Network

possible with these inverters [4]. The multi- level voltage source inverter's unique structure allows of this multilevel inverter is to synthesize a desired voltage from several separate dc sources (SDCSs), which may]. The general function of the multilevel inverter is to syn- thesize a desired ac voltage from several levels

Tolbert, Leon M.

380

Crystal Notes The Crystal  

E-print Network

. Ordered crystals exist because in their formation they must disorder their surroundings more than Diamond Octahedron octahedral 8 faces Truncated Octahedron octahedral > 8 faces Tetrahedron tetrahedral 35O4 9 2000 corundum Al2O3 10 10,000 diamond C #12;

Meagher, Mary

381

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

382

Thermionic converter studies at Thermo Electron  

Microsoft Academic Search

The Thermionic Energy Converter (TEC) development program includes theoretical and experimental surface studies, diode evaluation, enhanced mode converter investigations and system studies, as well as materials fabrication and testing. The primary effort has been concentrated on increasing converter performance via improved electrodes. Diodes with oxide collectors (i.e., tungsten oxide, titanium oxide, zinc oxide and barium oxide) have provided the best

F. N. Huffman; D. Lieb; F. Rufeh

1977-01-01

383

Agilent 11982A Amplified Lightwave Converter  

E-print Network

Agilent 11982A Amplified Lightwave Converter Product Overview Wide bandwidth, sensitive O/E converter for characterizing lightwave systems and components Agilent's lightwave converter, the Agilent-end for lightwave frequency- and time- domain measurements. It can be used with Agilent spectrum analyzers

Park, Namkyoo

384

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

385

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.

386

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

387

Noncollinear second-harmonic generation in sub-micrometer-poled RbTiOPO4  

NASA Astrophysics Data System (ADS)

We have generated noncollinear quasi-phase-matched second harmonic wave in an RbTiOPO4 crystal that was poled using the high-voltage atomic force microscope (HV-AFM). To the best of our knowledge, this is the first systematic nonlinear frequency conversion study of samples produced by the HV-AFM method. The short poling period of 1.18 µm enabled us to observe second harmonic generation at very large angles with respect to the fundamental wave. The setup was used to optically explore the homogeneity of the poled area. The measurements are in a reasonable agreement with an analytic calculations.

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

2004-05-01

388

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

389

Evaluation of the input current quality by three different modulation strategies for SVM controlled matrix converters with input voltage unbalance  

SciTech Connect

A new input current modulation strategy for a matrix converter is presented. The performance of the new strategy during input voltage unbalance is compared to two other strategies. The difference of the three modulations only concerns the detection of the reference angle for the input current vector. The input current quality is evaluated using four different criteria. It is concluded that depending upon the modulation strategy, the distortion of the input current may appear either as a series of positive sequence harmonics or a negative sequence fundamental component or a positive and a negative series of harmonic components with reduced amplitudes. Good accordance is found between the analytical solutions and numerical simulation.

Nielsen, P. [Danfoss A/S, Graasten (Denmark). Transmission Div.; Casadei, D.; Serra, G.; Tani, A. [Univ. degli Studi di Bologna (Italy). Ist. di Elettrotecnica

1995-12-31

390

Recent progresses in INNOSLAB lasers and their harmonic generation  

NASA Astrophysics Data System (ADS)

Through an optimal combination of crystal shape, cooling and resonator design, InnoSlab lasers possess unified advantageous features of short pulse duration and high peak output power, high pulse repetition rate, high beam quality and high flexibility in beam profile, from circular beam profile, through line shaped one dimensional Top-hat, to two dimensional Top-hat with rectangular cross section. We report diode end pumped, electrooptically q-switched Nd:YLF, Nd:YAG and Nd:YVO4 slab laser and their efficient harmonic generation in near field. Using oscillator/amplifier with Nd:YAG slabs over 50mJ pulse energy at 6kHz was obtained. The pulse length is 7ns and the peak power is as high as 7MW. With Nd:YVO4 slabs 400W average power at 50kHz was obtained. The pulse length is as short as 8ns. Because of the high peak power over 300W second harmonic is achieved by two LBO crystals.

Li, Daijun; Fu, Shaojun; Liu, Xiaomeng; Shi, Peng; Chen, Jun; Shell, Alexander; Qi, Bingsong; Haas, Claus-Rüdiger; Wang, Jingxiong; Du, Keming

2010-02-01

391

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

NASA Astrophysics Data System (ADS)

Nonlinear optical (NLO) organic compound, 4-bromobenzaldehyde-4?-N?-methylstilbazolium tosylate was synthesized by reflux method. The formation of molecular complex was confirmed from 1H NMR, FT-IR and FT-Raman spectral analyses. The single crystals were grown by slow evaporation solution growth method and the crystal structure and atomic packing of grown crystal was identified. The morphology and growth axis of grown crystal were determined. The crystal perfection was analyzed using high resolution X-ray diffraction study on (0 0 1) plane. Thermal stability, decomposition stages and melting point of the grown crystal were analyzed. The optical absorption coefficient (?) and energy band gap (Eg) of the crystal were determined using UV-visible absorption studies. Second harmonic generation efficiency of the grown crystal was examined by Kurtz powder method with different particle size using 1064 nm laser. Laser induced damage threshold study was carried out for the grown crystal using Nd:YAG laser.

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

392

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

PubMed

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

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

2014-05-01

393

Harmonic retrieval of regenerative machining chatter responses  

NASA Astrophysics Data System (ADS)

Based on cross fourth-order cumulants, a total least square ESPRIT approach to jointly estimating harmonic parameters in hybrid colored noises is presented, which is applied to investigate the harmonic retrieval of regenerative machining chatter responses. Taking into consideration the multiple-regenerative effect, the delayed machining dynamics under the excitation of stochastic noises is modeled, and a recursive algorithm of the solution to the delayed machining dynamics is proposed. The harmonic parameter estimation of regenerative chatter responses is detailed, which include the harmonic frequencies, cross powers, and phase shifts between successive cuts. The results demonstrate that the presented harmonic parameter estimation approach can eliminate the hybrid colored noises, retrieve the harmonic parameters with excellent estimation performance, and extract the evolution features of regenerative machining chatter.

Zhou, Xiaoqin; Wang, Wencai; Lin, Jieqiong

2013-12-01

394

Killing vector fields and harmonic superfield theories  

NASA Astrophysics Data System (ADS)

The harmonic action functional allows a natural generalisation to semi-Riemannian supergeometry, also referred to as harmonic, which resembles the supersymmetric sigma models studied in high energy physics. We show that Killing vector fields are infinitesimal supersymmetries of this harmonic action and prove three different Noether theorems in this context. En passant, we provide a homogeneous treatment of five characterisations of Killing vector fields on semi-Riemannian supermanifolds, thus filling a gap in the literature.

Groeger, Josua

2014-09-01

395

High power density dc\\/dc converter: Selection of converter topology  

Microsoft Academic Search

The work involved in the identification and selection of a suitable converter topology is described. Three new dc\\/dc converter topologies are proposed: Phase-Shifted Single Active Bridge DC\\/DC Converter; Single Phase Dual Active Bridges DC\\/DC Converter; and Three Phase Dual Active Bridges DC\\/DC Converter (Topology C). The salient features of these topologies are: (1) All are minimal in structure, i.e., each

Deepakraj M. Divan

1990-01-01

396

Modeling and space vector control of a novel multilevel matrix converter for variable-speed wind power generators  

NASA Astrophysics Data System (ADS)

A novel multilevel matrix converter is developed to efficiently transfer energy between a three-phase variable-speed generator of a wind turbine and a three-phase ac utility network. Optimizing the energy transfer efficiency at light load is critical in variable-speed wind generators. Laboratory experiment suggests that converter efficiency at light load may be increased via soft-switching and multilevel switching techniques. The new converter includes the advantages of multilevel converters, such as reduced harmonic content, increased power handling capability without additional switching loss, and high efficiency at low machine voltages. It also features the characteristics of conventional matrix converters, such as space vector control and improved efficiency via auxiliary resonant commutation soft-switching techniques. Similar to a conventional matrix converter, the novel multilevel matrix converter uses a nine-switch matrix with four-quadrant switches to connect input phases at one side of the converter with output phases at the other side of the converter. However, the switches of the new converter are configured differently from those used in the conventional matrix converter. Each switch of the new converter is a cell that resembles a full-bridge inverter topology and can assume three voltage levels while used. Semiconductor devices in a switch cell are always clamped to a known constant do voltage of a capacitor. This is a typical characteristic of multilevel converters where device voltage stresses are reduced by clamping the main transistor voltages to low levels. With reduced voltage stresses, switching frequency can be increased to allow for reduced size of filter magnetics. Unlike conventional matrix converter, the multilevel matrix converter uses inductors on both input and output sides of the converter. This symmetry allows for both step up and step down operations. Each switch cell features double the power handling capability compared to the four-quadrant switches used in a conventional matrix converter. This increase in power handling capability is due to the doubling of the number of devices in a multilevel matrix converter switch cell. Scaling up the power handling capability is accomplished by cascading more than one switch cell per branch. Control of the new converter is achieved through space vector modulation in which three-phase ac voltages are transformed to the d-q reference frame and compared with a set of space vectors prior to modulation. Since it has 19683 different switching combinations, control can be difficult and complex. Nevertheless, the multilevel matrix converter has been modeled and controlled through simulation. Simulation results show the possibility of operating the converter to produce the desired voltage waveforms with universal input and output power factors and maintain constant capacitor voltages simultaneously. Also in this dissertation is the derivation of an analytical averaged equivalent circuit model of a PWM converter. This model reveals how dominant loss mechanisms vary with converter operating point. The model is based on the operational characteristics of power diodes and IGBTs. Laboratory experiments support the derived model and confirm that IGBT current tailing and diode reverse-recovery are indeed the most critical losses in a PWM converter. These losses are more significant at light load, hence reducing the energy capture capability of converters used in wind generation. The results suggest that multilevel conversion, which has been employed in the novel multilevel matrix converter, could improve the low-wind converter efficiency.

Al-Naseem, Osama Abdulrahman

397

Constructing Buildings and Harmonic Maps  

E-print Network

In a continuation of our previous work, we outline a theory which should lead to the construction of a universal pre-building and versal building with a $\\phi$-harmonic map from a Riemann surface, in the case of two-dimensional buildings for the group $SL_3$. This will provide a generalization of the space of leaves of the foliation defined by a quadratic differential in the classical theory for $SL_2$. Our conjectural construction would determine the exponents for $SL_3$ WKB problems, and it can be put into practice on examples.

Katzarkov, Ludmil; Pandit, Pranav; Simpson, Carlos

2015-01-01

398

Constructing Buildings and Harmonic Maps  

E-print Network

In a continuation of our previous work, we outline a theory which should lead to the construction of a universal pre-building and versal building with a $\\phi$-harmonic map from a Riemann surface, in the case of two-dimensional buildings for the group $SL_3$. This will provide a generalization of the space of leaves of the foliation defined by a quadratic differential in the classical theory for $SL_2$. Our conjectural construction would determine the exponents for $SL_3$ WKB problems, and it can be put into practice on examples.

Ludmil Katzarkov; Alexander Noll; Pranav Pandit; Carlos Simpson

2015-03-03

399

Snow Crystals  

NSDL National Science Digital Library

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

Kenneth Libbrecht

400

Characterization of Second Harmonic Afterburner Radiation at the LCLS  

SciTech Connect

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

Nuhn, Heinz-Dieter

2010-09-14

401

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

402

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

403

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

404

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

405

Catalytic converter for an automobile  

SciTech Connect

A catalytic converter is described for an automobile comprising a single strip of metal folded back and forth upon itself, the strip having at least one slot along each line of folding, the slots being aligned with each other across adjacent layers of the strip, each folded slot defining a notch. The notches together define at least one groove along the periphery of the folded strip, and at least one canister section, the canister section being shaped to coincide with the shape of the folded strip, the canister section having at least one ridge shaped to mate with the groove, the canister section being wrapped around the folded strip so as to maintain the strip in a fixed position.

Retallick, W.B.

1986-03-18

406

Quasi-harmonic approximation of thermodynamic properties of ice Ih, II, and III  

E-print Network

Several thermodynamic properties of ice Ih, II, and III are studied by a quasi-harmonic approximation and compared to results of quantum path integral and classical simulations. This approximation allows to obtain thermodynamic information at a fraction of the computational cost of standard simulation methods, and at the same time permits studying quantum effects related to zero point vibrations of the atoms. Specifically we have studied the crystal volume, bulk modulus, kinetic energy, enthalpy and heat capacity of the three ice phases as a function of temperature and pressure. The flexible q-TIP4P/F model of water was employed for this study, although the results concerning the capability of the quasi-harmonic approximation are expected to be valid independently of the employed water model. The quasi-harmonic approximation reproduces with reasonable accuracy the results of quantum and classical simulations showing an improved agreement at low temperatures (T < 100 K). This agreement does not deteriorate ...

Ramirez, R; Fernandez-Serra, M -V; Herrero, C P; 10.1063/1.4737862

2012-01-01

407

Functional facets for nonlinear crystals  

NASA Astrophysics Data System (ADS)

We report on a new optical device allowing to efficiently add desired functionalities to a nonlinear interaction. This is achieved by focused ion beam patterning of a nano-layer of gold sputtered at the exit facet of a nonlinear crystal. The functionality is experimentally demonstrated with three examples: spatial filtering where a fundamental beam with a poor mode quality and its' frequency-doubled beam are filtered thereby providing high mode quality beams, focusing of a generated second harmonic beam and beam shaping where a fundamental Gaussian beam is transformed into any arbitrary desired frequency-doubled beam. For the latter two examples, the functional facet also provides angular separation of the fundamental and second harmonic beams.

Shapira, Asia; Libster, Ana; Lilach, Yigal; Arie, Ady

2013-07-01

408

Crystal Movies  

NSDL National Science Digital Library

This site, maintained by the Geosciences Department at the University of Arizona, contains animated gif files of common mineral crystals. The movies show crystal structures evolving as a function of pressure, temperature, chemistry, or orientation. The movies are an excellent aid for visualizing the structure of various crystals.

R.T. Downs

409

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

410

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

411

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

PubMed

Single crystals of the organic non-linear optical materials L-threonine (I) and L-prolinium tartrate (II) were grown using a home-made crystal growth setup (MKN setup). The grown crystals were characterized using X-ray diffraction, Infrared (IR), UV-vis-NIR and Circular dichroism (CD) spectroscopy. Measurements of Vicker's microhardness, laser damage threshold (LDT) values and second harmonic generation (SHG) efficiencies are reported. Thermal and dielectric studies were also carried out. PMID:24747852

Moovendaran, K; Natarajan, S

2014-08-14

412

Thermionic converter studies at Thermo Electron  

NASA Technical Reports Server (NTRS)

The Thermionic Energy Converter (TEC) development program includes theoretical and experimental surface studies, diode evaluation, enhanced mode converter investigations and system studies, as well as materials fabrication and testing. The primary effort has been concentrated on increasing converter performance via improved electrodes. Diodes with oxide collectors (i.e., tungsten oxide, titanium oxide, zinc oxide and barium oxide) have provided the best performance. Emitters requiring reduced cesium pressure (such as oxygenated tungsten, lanthanum hexaboride, platinum and graphite) are being tested. Converter configurations using particle spacing are under investigation. Experiments with auxiliary electrode thermionic converters are in progress. Both silicon carbide and alloy hot shells (i.e., barriers to isolate the converter from the combustion environment) have been fabricated and tested.

Huffman, F. N.; Lieb, D.; Rufeh, F.

1977-01-01

413

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

414

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

415

Continuous-wave cascaded-harmonic generation and multi-photon Raman lasing in lithium niobate whispering-gallery resonators  

NASA Astrophysics Data System (ADS)

We report experimental demonstration of continuous-wave cascaded-harmonic generation and Raman lasing in a millimeter-scale lithium niobate whispering-gallery resonator pumped at a telecommunication-compatible infrared wavelength. Intensity enhancement through multiple recirculations in the whispering-gallery resonator and quasi phase-matching through a nonuniform crystal poling enable simultaneous cascaded-harmonic generation up to the fourth-harmonic accompanied by stimulated Raman, two-photon, three-photon, and four-photon Raman scattering corresponding the molecular vibrational wavenumbers 632 and 255 cm-1 in z-cut lithium niobate at pump power levels as low as 200 mW. We demonstrate simultaneous cascaded-harmonic generation and Raman lasing by observing the spectrum of the scattered light from the resonator and by capturing the image of the decoupled light from the resonator on a camera.

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

2011-11-01

416

Disappearing Crystals  

NSDL National Science Digital Library

Learners experiment with water gel crystals, or sodium polyacrylate crystals, which absorb hundreds of times their weight in water. When in pure water, the water gel crystals cannot be seen. However, when learners place the crystals in solutions of Splenda and water, the crystals can be seen. Learners use this property to determine how much Splenda is in 4 different cups of water. This is one of four activities learners can complete related to PhysicsQuest 2008. Each activity gives a clue to solve a puzzle in the accompanying comic book, "Nikola Tesla and the Electric Fair."

2012-06-26

417

Thermographic Analysis of a Bridge Power Converter  

NASA Astrophysics Data System (ADS)

Any loss of power in converters is dissipated as heat in the components of the circuit. The article presents a new approach to measuring heat dissipation in a bridge power converter with hard switches using infrared thermography. Parallel measurements by thermocouples have been carried out. The experimental results are compared and used from the both cases. The proposed approach can be used for various circuit implementations of the converters in a similar manner.

Anna, V. Andonova; Nikolay, L. Hinov

2015-01-01

418

A Novel Lossless Snubber for Boost Converters  

Microsoft Academic Search

Advanced transportation technologies, such as hybrid-electric vehicles, battery-electric vehicles, and fuel cell vehicles, rely on high-power DC\\/DC converters to interconnect and manage their power systems. Boost converters are especially useful in stepping-up the voltage from a battery or fuel cell to match the electric motor voltage range. However, conventional high-power boost converters are very large and heavy, partly due to

J. Marshall; M. Kazerani

2006-01-01

419

Dynamics and control of instrumented harmonic drives  

NASA Technical Reports Server (NTRS)

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

Kazerooni, H.; Ellis, S. R. (Principal Investigator)

1995-01-01

420

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

421

Harmonic maps as models for physical theories  

Microsoft Academic Search

Harmonic maps are an aesthetically appealing class of nonlinear field equations of which only a few nontrivial examples have as yet appeared in physical theories. These fields appear well suited for describing broken symmetries either in conjunction with or instead of the Yang-Mills equations. The harmonic mapping equation is quite similar in many respects to the Einstein equations for gravitation,

Charles Misner

1978-01-01

422

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

423

HARMONIC CYCLOTRON HEATING IN THE TOROIDAL OCTUPOLE  

E-print Network

HARMONIC CYCLOTRON HEATING IN THE TOROIDAL OCTUPOLE J. C. Sprott October 1976 Plasma Studies PLP without consent of the author and maj or professor. #12;-2- Previous calculations of cyclotron resonance the harmonic cyclotron heating of both electrons and ions. It is well known (see, for example, O. Eldridge

Sprott, Julien Clinton

424

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

425

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

426

AC-DC-AC Power Converters with Novel Approach to Power Factor Correction in Three-Phase Systems  

Microsoft Academic Search

The main goal of this paper is to propose three new three-phase to three-phase ac-dc-ac converters, in which the input side is implemented with three-phase three-level PFC rectifier. This rectifier presents some advantages when compared to the two-level rectifier, i.e.: a) operation with high power level; b) reduced voltage harmonics while operating at lower frequency; and c) better quality in

E. C. dos Santos; E. R. C. da Silva; A. A. M. Bento

2009-01-01

427

DC/DC Converter Stability Testing Study  

NASA Technical Reports Server (NTRS)

This report presents study results on hybrid DC/DC converter stability testing methods. An input impedance measurement method and a gain/phase margin measurement method were evaluated to be effective to determine front-end oscillation and feedback loop oscillation. In particular, certain channel power levels of converter input noises have been found to have high degree correlation with the gain/phase margins. It becomes a potential new method to evaluate stability levels of all type of DC/DC converters by utilizing the spectral analysis on converter input noises.

Wang, Bright L.

2008-01-01

428

PHYSICAL REVIEW E 88, 062142 (2013) Reaction-diffusion theory in the presence of an attractive harmonic potential  

E-print Network

, an atom, a molecule, a biological object such as a receptor cluster, a cell, or even an animal and photosynthesis. Funneling phenomena attract excitations in photosynthetic antennae and molecular crystals and aggre- gates. Particle diffusion in a harmonic field occurs also in biophysical studies on DNA

Kenkre, V.M.

2013-01-01

429

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

430

Realizing the frequency quality factor product limit in silicon via compact phononic crystal resonators  

NASA Astrophysics Data System (ADS)

High-Q (quality factor) resonators are a versatile class of components for radio frequency micro-electromechanical systems . Phononic crystals provide a promising method of producing these resonators. In this article, we present a theoretical study of the Q factor of a cavity resonator in a two-dimensional phononic crystal comprised of tungsten rods in a silicon matrix. One can optimize the Q of a phononic crystal resonator by varying the number of inclusions or the cavity harmonic number. We conclude that using higher harmonics marginally increases Q while increasing crystal length via additional inclusions causes Q to increase by orders of magnitude. Incorporating loss into the model shows that the silicon material limit on Q is achievable using a two-dimensional phononic crystal design with a reasonable length. With five layers of inclusions on either side of the cavity, the material limit on Q is achieved, regardless of the harmonic number.

Goettler, Drew; Su, Mehmet; Leseman, Zayd; Soliman, Yasser; Olsson, Roy; El-Kady, Ihab

2010-10-01

431

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

432

Point-based manifold harmonics.  

PubMed

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

Liu, Yang; Prabhakaran, Balakrishnan; Guo, Xiaohu

2012-10-01

433

Terahertz harmonic generation in graphene  

NASA Astrophysics Data System (ADS)

We show that charge carrier transport in graphene exhibits sharp resonances in the presence of spatially and temporarily modulated scattering. Resonances occur when the period of an applied a-c field corresponds to the time taken by quasi-ballistic carriers to drift over a spatial scattering period, provided the latter is shorter than the distance taken by carriers to emit an optic phonon. We show that such system can be achieved with interdigitated gates energized with an a-c bias on graphene layers. Gate separation and fields to achieve ballistic transport would result in resonances in the terahertz range, with the generation of higher harmonics characterized by large Q-factors, which are tunable with gate spacing.

Sekwao, Samwel; Leburton, Jean-Pierre

2015-02-01

434

Quantum wormholes and harmonic oscillators  

NASA Technical Reports Server (NTRS)

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

Garay, Luis J.

1993-01-01

435

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

436

Constraining topology in harmonic space  

E-print Network

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

M. Kunz; N. Aghanim; L. Cayon; O. Forni; A. Riazuelo; J. P. Uzan

2006-01-28

437

Libsharp - spherical harmonic transforms revisited  

NASA Astrophysics Data System (ADS)

We present libsharp, a code library for spherical harmonic transforms (SHTs), which evolved from the libpsht library and addresses several of its shortcomings, such as adding MPI support for distributed memory systems and SHTs of fields with arbitrary spin, but also supporting new developments in CPU instruction sets like the Advanced Vector Extensions (AVX) or fused multiply-accumulate (FMA) instructions. The library is implemented in portable C99 and provides an interface that can be easily accessed from other programming languages such as C++, Fortran, Python, etc. Generally, libsharp's performance is at least on par with that of its predecessor; however, significant improvements were made to the algorithms for scalar SHTs, which are roughly twice as fast when using the same CPU capabilities. The library is available at http://sourceforge.net/projects/libsharp/ under the terms of the GNU General Public License.

Reinecke, M.; Seljebotn, D. S.

2013-06-01

438

A closely regulated TWT converter.  

NASA Technical Reports Server (NTRS)

The design concept for the TWT amplifier converter for possible use in the Thermoelectric Outer Planet Spacecraft (TOPS) is presented. An unusual combination of semiconductors and magnetics was utilized to achieve very stable voltage regulation on a number of separate outputs to satisfy the requirements of a high-power TWT, and at the same time operate at an efficiency of better than 90% from a 30-V source. The circuitry consists of an output filter, an auxiliary Jensen oscillator driving a high-reactance transformer to provide current limiting to the heater, a variable time delay, a main Jensen oscillator driving the power transformer with a maximum step-up ratio of 120 to 1, and series transistorized post regulators to provide precise voltage adjustment and low output impedance. This paper discusses the design of the high-reactance transformer and the high step-up ratio transformer, as well as the high-voltage series regulators that are limited in range and operate at the top of the unregulated output voltage. Test data are presented, and details of current transients caused by charging the filter circuits, input current ripple, and output voltage ripples are considered.

Hopper, D. J.; Andryczyk, R. W.

1971-01-01

439

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

440

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

441

Digital control for phase shift converter  

Microsoft Academic Search

The development of intelligent microgrids with renewable energy sources increased significantly nowadays. The present paper examines and compares analog and digital control of a bidirectional phase shift converter in order to find out which is best suited to be used in intelligent microgrid applications. New small signal models for the direct and reverse power flow transfer modes of the converter

R. Etz; T. Patarau; D. Petreus; S. Daraban; D. Moga

2012-01-01

442

Control strategy for a Teniente Converter  

Microsoft Academic Search

A diagnosis of the actual distributed control and measurements system for a Teniente Converter, processing copper concentrates, is presented. Besides the importance of this converter in Caletones Smelter, there is a number of unsolved problems related to lack of instrumentation, lack of process knowledge, odd operating practices, and lack of procedures to process data to aid management and operating decisions.

L. G. Bergh; P. Chacana; C. Carrasco

2005-01-01

443

Distributed electrical leads for thermionic converter  

DOEpatents

In a thermionic converter, means are provided for coupling an electrical lead to at least one of the electrodes thereof. The means include a bus bar and a plurality of distributed leads coupled to the bus bar each of which penetrates through one electrode and are then coupled to the other electrode of the converter in spaced apart relation.

Fitzpatrick, Gary O. (Livermore, CA); Britt, Edward J. (Cupertino, CA)

1979-01-01

444

Power Converters Secure Electronics in Harsh Environments  

NASA Technical Reports Server (NTRS)

In order to harden power converters for the rigors of space, NASA awarded multiple SBIR contracts to Blacksburg, Virginia-based VPT Inc. The resulting hybrid DC-DC converters have proven valuable in aerospace applications, and as a result the company has generated millions in revenue from the product line and created four high-tech jobs to handle production.

2013-01-01

445

Passive Resonant Bidirectional Converter with Galvanic Barrier  

NASA Technical Reports Server (NTRS)

A passive resonant bidirectional converter system that transports energy across a galvanic barrier includes a converter using at least first and second converter sections, each section including a pair of transfer terminals, a center tapped winding; a chopper circuit interconnected between the center tapped winding and one of the transfer terminals; an inductance feed winding interconnected between the other of the transfer terminals and the center tap and a resonant tank circuit including at least the inductance of the center tap winding and the parasitic capacitance of the chopper circuit for operating the converter section at resonance; the center tapped windings of the first and second converter sections being disposed on a first common winding core and the inductance feed windings of the first and second converter sections being disposed on a second common winding core for automatically synchronizing the resonant oscillation of the first and second converter sections and transferring energy between the converter sections until the voltage across the pairs of transfer terminals achieves the turns ratio of the center tapped windings.

Rosenblad, Nathan S. (Inventor)

2014-01-01

446

DC current sensor for PWM converters  

Microsoft Academic Search

A sensor for inductor current in PWM converters which offers improved performance over presently available sensors is presented. The sensor is based on a saturable transformer, derives power from existing converter waveforms, provides DC isolation, and has inherently wide bandwidth. The sensor is compared to available current sensors. A theory of operation for the sensor is presented, the results of

Arthur W. Kelley; John E. Titus

1991-01-01

447

Laser energy converted into electric power  

NASA Technical Reports Server (NTRS)

Apparatus verifies concepts of converting laser energy directly into electric energy. Mirror, placed in beam and inclined at angle to it, directs small amount of incident radiation to monitor which establishes precise power levels and other beam characteristics. Second mirror and condensing lens direct bulk of laser energy into laser plasmadynamic converter.

Shimada, K.

1973-01-01

448

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

449

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

450

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

451

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.

2015-03-01

452

Experimental thermionic energy converter without enclosure: A molecular beam supplied converter  

Microsoft Academic Search

Experimental thermionic energy converters of an open type, i.e. with no closely located surrounding walls, as proposed here, have many advantages compared to conventional enclosed converters. Interactions with and problems of the enclosure do not interfere with the fundamental plasma and surface processes, which can be studied efficiently in an open converter, for example by mass spectrometry, optical spectroscopy, electron

L. Holmlid; K. Möller

1984-01-01

453

Radiation Effects on DC-DC Converters  

NASA Technical Reports Server (NTRS)

In this work, several DC-DC converters were designed and built. The converters are Buck Buck-Boost, Cuk, Flyback, and full-bridge zero-voltage switched. The total ionizing dose radiation and single event effects on the converters were investigated. The experimental results for the TID effects tests show that the voltages of the Buck Buck-Boost, Cuk, and Flyback converters increase as total dose increased when using power MOSFET IRF250 as a switching transistor. The change in output voltage with total dose is highest for the Buck converter and the lowest for Flyback converter. The trend of increase in output voltages with total dose in the present work agrees with those of the literature. The trends of the experimental results also agree with those obtained from PSPICE simulation. For the full-bridge zero-voltage switch converter, it was observed that the dc-dc converter with IRF250 power MOSFET did not show a significant change of output voltage with total dose. In addition, for the dc-dc converter with FSF254R4 radiation-hardened power MOSFET, the output voltage did not change significantly with total dose. The experimental results were confirmed by PSPICE simulation that showed that FB-ZVS converter with IRF250 power MOSFET's was not affected with the increase in total ionizing dose. Single Event Effects (SEE) radiation tests were performed on FB-ZVS converters. It was observed that the FB-ZVS converter with the IRF250 power MOSFET, when the device was irradiated with Krypton ion with ion-energy of 150 MeV and LET of 41.3 MeV-square cm/mg, the output voltage increased with the increase in fluence. However, for Krypton with ion-energy of 600 MeV and LET of 33.65 MeV-square cm/mg, and two out of four transistors of the converter were permanently damaged. The dc-dc converter with FSF254R4 radiation hardened power MOSFET's did not show significant change at the output voltage with fluence while being irradiated by Krypton with ion energy of 1.20 GeV and LET of 25.97 MeV-square cm/mg. This might be due to fact that the device is radiation hardened.

Zhang, De-Xin; AbdulMazid, M. D.; Attia, John O.; Kankam, Mark D. (Technical Monitor)

2001-01-01

454

Harmonic analysis of industrial power systems  

SciTech Connect

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

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

1996-03-01

455

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

456

RNA Crystallization  

NASA Technical Reports Server (NTRS)

RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.

Golden, Barbara L.; Kundrot, Craig E.

2003-01-01

457

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

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

CMB map derived from the WMAP data through Harmonic Internal Linear Combination  

E-print Network

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

Jaiseung Kim; Pavel Naselsky; Per Rex Christensen

2008-05-28

460

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

461

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

462

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.

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

Mechanical phase matching of birefringent non-linear crystals.  

PubMed

Second-order nonlinear processes such as second harmonic generation or parametric amplification have found numerous applications in the scientific and industrial world, from micromachining to petawatt laser facilities. These nonlinear interactions are mostly carried out in birefringent crystals because of their low cost and the possibility to operate at high powers Phase-matching configurations in birefringent crystals are determined by their refractive indexes. Here, we show that an important mechanical stress can be used to significantly change the phase-matching properties of a birefringent crystal. As an example, we demonstrate the shift of second harmonic non-critical phase matching wavelength of LiB3O5 (LBO) crystal at room temperature from 1200 nm to 1120 nm by applying compressive forces up to 100 MPa. We believe that this mechanical phase matching can be used as an additional degree of freedom to optimize nonlinear optical frequency mixing geometries. PMID:25321800

Deyra, Loïc; Balembois, François; Guilbaud, André; Villeval, Philippe; Georges, Patrick

2014-09-22

465

Investigation of thermally-induced phase mismatching in continuous-wave second harmonic generation: a theoretical model.  

PubMed

A fraction of the fundamental beam energy deposited into nonlinear crystals to generate second harmonic waves (SHW) causes a temperature gradient within the crystal. This temperature inhomogeneity can alter the refractive index of the medium leading to a well-known effect called thermal dispersion. Therefore, the generated SHW suffers from thermal lensing and a longitudinal thermal phase mismatching. In this work by coupling the heat equation with second harmonic generation (SHG) formalism applied to type-II configuration along with walk-off effect, we investigate the continuous wave (CW) SHW beam profile and conversion efficiency when a non-linear KTP crystal is under induced thermal load. We have demonstrated for average and high powers, the thermal de-phasing lead to considerable reduction in SHG compared to an ideal case in which induced heat is neglected. PMID:20940766

Sabaeian, Mohammad; Mousave, Laleh; Nadgaran, Hamid

2010-08-30

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 Analysis on Quantum Tori  

NASA Astrophysics Data System (ADS)

This paper is devoted to the study of harmonic analysis on quantum tori. We consider several summation methods on these tori, including the square Fejér means, square and circular Poisson means, and Bochner-Riesz means. We first establish the maximal inequalities for these means, then obtain the corresponding pointwise convergence theorems. In particular, we prove the noncommutative analogue of the classical Stein theorem on Bochner-Riesz means. The second part of the paper deals with Fourier multipliers on quantum tori. We prove that the completely bounded L p Fourier multipliers on a quantum torus are exactly those on the classical torus of the same dimension. Finally, we present the Littlewood-Paley theory associated with the circular Poisson semigroup on quantum tori. We show that the Hardy spaces in this setting possess the usual properties of Hardy spaces, as one can expect. These include the quantum torus analogue of Fefferman's H1-BMO duality theorem and interpolation theorems. Our analysis is based on the recent developments of noncommutative martingale/ergodic inequalities and Littlewood-Paley-Stein theory.

Chen, Zeqian; Xu, Quanhua; Yin, Zhi

2013-09-01

468

Ab initio lattice dynamics of nonconducting crystals by systematic fragmentation  

NASA Astrophysics Data System (ADS)

A systematic method for approximating the ab initio electronic energy of crystal lattices has been improved by the incorporation of long range electrostatic and dispersion interactions. The effect of these long range interactions on the optimization of the crystal structure is reported. The harmonic lattice dynamics have been evaluated to give phonon frequencies and neutron scattering intensities. Exemplary results are reported for diamond, silicon, and ?-quartz using Hartree-Fock, Möller-Plesset perturbation, and coupled-cluster levels of ab initio theory.

Collins, Michael A.

2011-04-01

469

Crystal Structure of L-Histidinium 2-Nitrobenzoate  

PubMed Central

A new nonlinear optical organic compound, namely, L-histidinium 2-nitrobenzoate (abbreviated as LH2NB (I); ([C6H10N3O2]+ [C7H4NO4]?)), was synthesized. The molecular structure of LH2NB (I) was elucidated using single crystal X-ray diffraction technique. The second harmonic generation (SHG) efficiency of this compound is about two times that of the standard potassium dihydrogen phosphate crystals. PMID:22536482

Natarajan, Subramanian; Moovendaran, Kalimuthu; Kalyana Sundar, Jeyaperumal; Ravikumar, Krishnan

2012-01-01

470

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

471

A harmonic oscillator having “volleyball damping”  

NASA Astrophysics Data System (ADS)

Volleyball damping corresponds to linear damping up to a certain critical velocity, with zero damping above this value. The dynamics of a linear harmonic oscillator is investigated with this damping mechanism.

Mickens, R. E.; Oyedeji, K.; Rucker, S. A.

2006-05-01

472

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

473

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

474

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

475

New ladder operators for the monopole harmonics  

SciTech Connect

Using the ladder operators shifting the index m of the associated Jacobi functions, for a given n, the monopole harmonics and their corresponding angular momentum operators are, respectively, extracted as the irreducible representation space and generators of su(2) Lie algebra. The indices n and m play the role of principal and azimuthal quantum numbers. By introducing the ladder operators shifting the index n of the same associated Jacobi functions, we also get a new type of the raising and lowering relations which are realized by the operators shifting only the index n of the monopole harmonics. Moreover, other symmetries, including the transformation of the irreducible representation spaces into each other, are derived based on the operators that shift the indices n and m of the monopole harmonics simultaneously and agreeably as well as simultaneously and inversely. Our results are reduced to spherical harmonics by eliminating magnetic charge of the monopole.

Fakhri, H.; Dehghani, A.; Jafari, A. [Research Institute for Fundamental Sciences, Tabriz (Iran, Islamic Republic of); Institute for Studies in Theoretical Physics and Mathematics IPM, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Department of Theoretical Physics and Astrophysics, Faculty of Physics, University of Tabriz, P.O. Box 51666-16471, Tabriz (Iran, Islamic Republic of); Department of Theoretical Physics and Astrophysics, Faculty of Physics, University of Tabriz, P.O. Box 51666-16471, Tabriz (Iran, Islamic Republic of)

2007-02-15

476

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

477

Dual aperture dipole magnet with second harmonic component  

SciTech Connect

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

Praeg, Walter F. (Palos Park, IL)

1985-01-01

478

Making Crystals  

NSDL National Science Digital Library

In this lab, students work in groups to grow crystals in different conditions, and then make conclusions about how and why crystals form. This site contains a detailed procedure and materials list, as well as follow-up questions. A teacher's guide contains extension ideas and information for conducting this lab.

Michael Davidson

479

Crystal Growing  

NSDL National Science Digital Library

These lab activities are designed to exhibit how crystals grow. Students will distinguish living from nonliving matter, measure crystal growth using the metric system, explain three industrial uses of minerals, and learn to take notes from lecture by filling in an outline of main points covered.

1998-01-01

480

Analysis and Implementation of Real Number Extended Sliding Surface with Integral Compensation for DC-AC Converters  

NASA Astrophysics Data System (ADS)

This paper proposes a real number extended sliding surface (RNESS) with integral compensation (IC) for the application of DC-AC converters. Classic sliding surface (CSS) is insensitive to system uncertainties, but in sliding action its system dynamics becomes a reduced-order dimension and thus lost the partial system dynamics. For recovering incomplete system response, the RNESS is designed and can retrieve incomplete system response of the CSS. However, steady-state errors still exist in system dynamics of the RNESS and cause high converter voltage harmonics. To overcome steady-state errors, a modified RNESS by the addition of IC is proposed. With the proposed method, the system yields a DC-AC converter with high-quality AC output voltage. Experiments are performed in support of the proposed method.

Chang, E. C.; Wu, R. C.; Liao, K. Y.

2014-11-01

481

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

SciTech Connect

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

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

2009-01-09

482

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

483

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

484

Frequency domain second harmonic optical coherence tomography  

NASA Astrophysics Data System (ADS)

We report the development of a frequency domain second harmonic OCT system. The system uses a 170 fs pulses from Yb fiber laser and second harmonic spectrum is recorded by a 0.17 nm resolution spectrometer and thermoelectric cooled CCD detector. The system is applied to image biological tissue of the fish scales. Highly organized collagen fibrils can be visualized in the recorded images. The axial resolution of the frequency domain SH-OCT is 30 ?m.

Su, Jianping; Tomov, I. V.; Jiang, Y.; Chen, Zhongping

2006-02-01

485

Generation mechanism of power line harmonic radiation  

Microsoft Academic Search

The questions concerning the generation of power line harmonic radiation (PLHR) and magne-tospheric line radiation (MLR) are discussed, including the effective source of high harmonics of 50\\/60 Hz, and fine dynamic structure of the frequency spectrum of PLHR and MLR. It is shown, that thyristor-based power regulators used by large electrical power consumers produce the periodic sequences of current pulses

Alexander Kostrov; Mikhail Gushchin; Sergei Korobkov

2010-01-01

486

Temporal coherence of high-order harmonics  

Microsoft Academic Search

Systematic studies of the temporal coherence properties of high-order harmonic radiation are presented. These complement our previous investigations [Bellini et al., Phys. Rev. Lett. 81, 297 (1998)], where we showed the separation of the far-field pattern of high-order harmonics into two distinct spatial regions with different coherence times. Here we show how the coherence time of the inner and outer

C. Lyngå; M. B. Gaarde; C. Delfin; M. Bellini; T. W. Hänsch; A. L' Huillier; C.-G. Wahlström

1999-01-01

487

Nonconvective and convective electron cyclotron harmonic instabilities  

Microsoft Academic Search

The article discusses nonconvective and convective electron-cyclotron harmonic instabilities. Particularly, the spatial growth rates of electrostatic waves in an electron plasma having hot and cold components and a weak loss cone perpendicular velocity distribution are investigated. It is found that the cold-electron density controls which harmonic band may be excited and that the cold-electron temperature controls spatial amplification. The nonconvective

M. Ashour-Abdalla; C. F. Kennel

1978-01-01

488

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

489

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

490

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

491

RGB source based on simultaneous quasi-phasematched second and third harmonic generation in periodically poled lithium niobate  

NASA Astrophysics Data System (ADS)

We present a pulsed RGB source based on cascaded nonlinear processes that occur inside a single crystal of PPLN with two poling periodicities placed in tandem. The first periodicity produces a ~1.43 ?m signal through optical parametric generation and the last section simultaneously produces the second (near - IR) and third harmonic (blue). The green is produced by second harmonic generation of the pump and the red is produced by non-phase-matched sum-frequency generation between the signal and pump beam.

Cudney, R. S.; Robles-Agudo, M.; Ríos, L. A.

2006-10-01

492

Converted Phase Elastic Migration Velocity Analysis  

E-print Network

Multi-component elastic seismic data collected at large offsets have the potential to be used in seismic imaging and velocity analysis. In this study, we present an approach for converted-phase elastic-transmission migration ...

Shabelansky, Andrey Hanan

2013-01-01

493

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

494

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

495

Process for converting oxygenates to hydrocarbons  

SciTech Connect

A process is described for converting oxygenate feedstock to liquid hydrocarbons comprising: converting oxygenate feedstock predominantly to gasoline range hydrocarbons in a first reactor zone, in contact with ZSM-5 zeolite catalyst thereby producing a minor amount of excess isobutane; separating isobutane from the first reactor effluent; converting oxygenate feedstock predominantly to C/sub 2/-C/sub 5/ lower olefins in a second reactor zone in contact with zeolite