Aircraft power system harmonics involving single-phase PFC converters
Jian Sun; Min Chen; KAMIAR J. KARIMI
2008-01-01
AC-DC converters with active power factor correction (PFC) are replacing uncontrolled diode rectification circuits on commercial jet airplanes in order to meet harmonic distortion limits imposed by new airborne electrical system power quality standards. The high line frequency of airborne AC power systems presents a major challenge for the design of PFC converters capable of meeting these standards. This paper
Harness processes and harmonic crystals
Pablo A. Ferrari; Beat M. Niederhauser
2006-01-04
In the Hammersley harness processes the real-valued height at each site i in Z^d is updated at rate 1 to an average of the neighboring heights plus a centered random variable (the noise). We construct the process "a la Harris" simultaneously for all times and boxes contained in Z^d. With this representation we compute covariances and show L^2 and almost sure time and space convergence of the process. In particular, the process started from the flat configuration and viewed from the height at the origin converges to an invariant measure. In dimension three and higher, the process itself converges to an invariant measure in L^2 at speed t^{1-d/2} (this extends the convergence established by Hsiao). When the noise is Gaussian the limiting measures are Gaussian fields (harmonic crystals) and are also reversible for the process.
Harmonic Loss Due to Operation of Induction Machines From Matrix Converters
Patrick W. Wheeler; Jon C. Clare; Maurice Apap; Keith J. Bradley
2008-01-01
This paper quantifies the extra harmonic losses in an induction motor that are associated with the use of a matrix converter topology as a motor drive. These extra losses are compared to the harmonic losses associated with an inverter-based motor drive. The technique employed in the determination of the harmonic losses is described. For the matrix converter, the extra harmonic
Phosphorus Removal Characteristics in Hydroxyapatite Crystallization Using Converter Slag
EUNG-HO KIM; HWAN-KOOK HWANG; SOO-BIN YIM
2006-01-01
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
Second harmonic generation from the ‘centrosymmetric’ crystals
Nalla, Venkatram; Medishetty, Raghavender; Wang, Yue; Bai, Zhaozhi; Sun, Handong; Wei, Ji.; Vittal, Jagadese J.
2015-01-01
Second harmonic generation (SHG) is a well known non-linear optical phenomena which can be observed only in non-centrosymmetric crystals due to non-zero hyperpolarizability. In the current work we observed SHG from a Zn(II) complex which was originally thought to have crystallized in the centrosymmetric space group C2/c. This has been attributed to the unequal antiparallel packing of the metal complexes in the non-symmetric space group Cc or residual non-centrosymmetry in C2/c giving rise to polarizability leading to strong SHG. The enhancement of SHG by UV light has been attributed to the increase in non-centrosymmetry and hence polarity of packing due to strain induced in the crystals. The SHG signals measured from these crystals were as large as potassium dihydrogen phosphate crystals, KH2PO4 (KDP), and showed temperature dependence. The highest SHG efficiency was observed at 50?K. The SHG phenomenon was observed at broad wavelengths ranging from visible to below-red in these crystals. PMID:25995840
A Newton solution for the harmonic phasor analysis of ac\\/dc converters
B. C. Smith; N. R. Watson; A. R. Wood; J. Arrillaga
1996-01-01
The steady state equations that describe the converter and dc system in the harmonic domain are solved by means of Newton`s method, in a manner suitable for embedding in an iterative harmonic analysis of the complete power system. The solution includes the interaction of the converter with the dc system, and the effect of variation in the firing and end
Cerenkov third-harmonic generation in ,,2... nonlinear photonic crystal
Arie, Ady
generation THG and fourth-harmonic generation if the polarization phase velocity v does exceed the velocityCerenkov third-harmonic generation in ,,2... nonlinear photonic crystal Yan Sheng,1,a Wenjie Wang,1 create such an emission via a quadratic nonlinear process such as Cerenkov second-harmonic generation SHG
Performance of Three-Millimeter Harmonic Generators and Crystal Detectors
R. B. Riley; J. M. Richardson
1957-01-01
Because of growing applications of millimeter wave measurements, a fairly thorough investigation of what could be expected from sources and detectors in the 3 mm region was made. The sources consisted of fourth-harmonic generators from a 1.25 cm fundamental. A type of crystal holder for both harmonic generators and detectors in which a small crystal wafer is positioned in the
Reactive power compensation and harmonics elimination at Medium-Voltage using Hexagram converter
Jun Wen; Liang Zhou; Keyue Smedley
2010-01-01
This paper introduced Hexagram converter - a new type of multilevel converter for reactive power compensation and harmonics elimination at Medium-Voltage (MV) grids to improve the power quality. The Hexagram converter is composed of six three-phase two-level Voltage Source Converters (VSCs) interconnected through the inductors, and has the advantages of modular structure with easy construction, even and much reduced voltage
Second harmonic generation from KBBF crystal in the deep ultraviolet
C. Chen; J. Lu; T. Togashi; T. Suganuma; T. Kanai; T. Sekikawa; S. Watanabe; Z. Xu; J. Wang
2002-01-01
The simplest way to produce deep UV coherent light is to use the fourth harmonic generation of a Ti:sapphire laser. So far, only KBe2BO3F (KBBF) crystals can be used to achieve this. We succeeded in growing platelike KBBF crystals. The platelike crystals can be polished but is still too thin to be cut along the phase-matching direction for fourth harmonic
A Newton solution for the harmonic phasor analysis of ac/dc converters
Smith, B.C.; Watson, N.R.; Wood, A.R.; Arrillaga, J. [Univ. of Canterbury, Christchurch (New Zealand)] [Univ. of Canterbury, Christchurch (New Zealand)
1996-04-01
The steady state equations that describe the converter and dc system in the harmonic domain are solved by means of Newton`s method, in a manner suitable for embedding in an iterative harmonic analysis of the complete power system. The solution includes the interaction of the converter with the dc system, and the effect of variation in the firing and end of commutation angles caused by ac voltage and dc current harmonics. The convergence of Newton`s method is investigated, and methods for accelerating the solution are implemented. Finally, the solution obtained is validated by means of time domain simulation.
MSA Comparative Crystal Chemistry The Analysis of Harmonic Displacement Factors
Downs, Robert T.
1 MSA Comparative Crystal Chemistry Chapter 7 The Analysis of Harmonic Displacement Factors R of the displacement ellipsoids for a Si2O7 group in - quartz, SiO2, at 298 K and 838 K (Kihara, 1990). The ellipsoids be mathematically defined with a probability distribution function (p.d.f.). If we assume harmonic restoring forces
A harmonic filter installation to reduce voltage distortion from static power converters
P. W. Hammond
1988-01-01
Voltage distortion on plant distribution systems is becoming an increasingly serious problem as sources of harmonic currents (primarily static power converters) proliferate. The use of interference-prone control and instrumentation equipment is also rapidly expanding. The problem is well defined by IEEE Standard 519, which proposes a 5% limit to voltage distortion for general applications. IEEE 519 is frequently cited in
Reduction of the input current harmonic content in matrix converters under input\\/output unbalance
Domenico Casadei; Giovanni Serra; Angelo Tani
1998-01-01
This paper deals with the performance evaluation of space-vector-modulated matrix power converters under input and output unbalanced conditions. Two control strategies of the input current displacement angle are presented and compared in order to emphasize their influence on the input current harmonic content. The first is based on keeping the input current vector in phase with the input voltage vector.
Phosphorus removal characteristics in hydroxyapatite crystallization using converter slag.
Kim, Eung-Ho; Hwang, Hwan-Kook; Yim, Soo-Bin
2006-01-01
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 removal efficiencies of the batch reactor system were found to increase with increases in the iron and fluoride ion concentrations, and to decrease with increases in the alkalinity and magnesium ion concentration. A column reactor system for HAP crystallization using converter slag was found to achieve high, stable levels of phosphorus elimination: the average PO4-P removal efficiency over 414 days of operation was 90.4%, in which the effluent phosphorus concentration was maintained at less than 0.5 mg/L under the appropriate phosphorus crystallization conditions. The X-ray diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra of the crystalline material deposited on the seed particles exhibited peaks consistent with HAP. Scanning electron micrograph (SEM) images showed that finely distributed crystalline material was formed on the surfaces of the seed particles. Energy dispersive X-ray spectroscopy (EDS) mapping analysis revealed that the molar Ca/P composition ratio of the crystalline material was 1.72. PMID:17000544
de Rooij, Michael Andrew (Clifton Park, NY); Steigerwald, Robert Louis (Burnt Hills, NY); Delgado, Eladio Clemente (Burnt Hills, NY)
2008-12-16
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.
Design Optimization of Broadband Linear Polarization Converter Using Twisted Nematic Liquid Crystal
Wu, Shin-Tson
converter, twisted liquid crystal film, optimization method, Jones matrix, PoincareÂ´ Sphere Most liquidDesign Optimization of Broadband Linear Polarization Converter Using Twisted Nematic Liquid Crystal converters using a twisted nematic liquid crystal film and two uniaxial compensation films. As compared
Hooper, B A; Gauthier, D J; Madey, J M
1994-10-20
Tunable second- and fourth-harmonic radiation was generated in a single 1-cm-long lithium niobate (LiNbO(3)) crystal with the Mark III infrared free electron laser at Duke University. The fundamental laser radiation was tuned from 2 to 2.5 µm, yielding 1-1.25-µm radiation (second harmonic) and 0.5-0.625-µm radiation (fourth harmonic). A fundamental-second-harmonic energy conversion efficiency of 66% and a fundamental-fourth-harmonic energy conversion efficiency of 3.3 × 10(-6) were measured. The maximum energy in the fourth harmonic was 3.3 nJ. PMID:20941245
Second harmonic generation from KBBF crystal in the deep ultraviolet
Chuangtian Chen; Junhua Lu; T. Togashi; T. Suganuma; T. Sekikawa; S. Watanabe; Zuyan Xu; Jiyang Wang
2001-01-01
By using a KBe2BO3F2 (KBBF) crystal with a size of 10 × 10 × 1.2 mm3 and a special prism coupling technique (PCT), the fourth-harmonic generation of Ti:sapphire laser systems from 200 nm to 179.4-nm has been achieved for the first time. Moreover, by a Ti:sapphire laser with a 50-fs pulse duration and a 1-kHz repetition rate. A conversion efficiency
Cascaded fourth-harmonic generation in a single nonlinear crystal
Rosen Ivanov; Solomon Saltiel
2005-01-01
We investigate theoretically the process of phase-matched fourth-harmonic generation in a single quadratic crystal. In the case of a plane-wave fundamental or weak focusing, the results have an analytical form. The optimal focusing position of the fundamental beam depends on the values of the mismatches for each of the two steps of the second-order cascading: doubling of the fundamental frequency
Enhancement of third-harmonic generation in a polymer-dispersed liquid-crystal grating
Cartwright, Alexander N.
enhancement of one-step third-harmonic generation in a one-dimensional photonic crystal pumped by a near9 Third- harmonic generation in one-dimensional 1D photonic crys- tals via a two-step parametric process on a significant enhancement of one-step third-harmonic generation in a 1D photonic crystal, with the fundamental
Chen, Ray
Optimization of Highly Efficient Mode Converter for Coupling Light into Large-slot Photonic Crystal efficient mode converter for coupling light into a silicon slotted photonic crystal waveguide with slot width as large as 320nm. The loss of the mode converter is measured to be 0.08dB. Slotted photonic
Duan Jin-ming; Cao Yin-lan; He Bi-yan
2010-01-01
With powdered converter slag used as a seed crystal, the effects of slag dosage, pH, temperature, and Ca2+ concentration on phosphate removal from synthetic solution through crystallization were investigated in batch experiments. The results indicated that slag concentration of 1.7 g\\/L, pH value of 9-10, reaction time of 3h , reaction temperature of 20-25°C, Ca\\/P molar ratio of 2, seemed
Sampled-Data and Harmonic Balance Analyses of Average Current-Mode Controlled Buck Converter
Chung-Chieh Fang
2012-02-21
Dynamics and stability of average current-mode control of buck converters are analyzed by sampled-data and harmonic balance analyses. An exact sampled-data model is derived. A new continuous-time model "lifted" from the sampled-data model is also derived, and has frequency response matched with experimental data reported previously. Orbital stability is studied and it is found unrelated to the ripple size of the current-loop compensator output. An unstable window of the current-loop compensator pole is found by simulations, and it can be accurately predicted by sampled-data and harmonic balance analyses. A new S plot accurately predicting the subharmonic oscillation is proposed. The S plot assists pole assignment and shows the required ramp slope to avoid instability.
Third-harmonic and fourth-harmonic generations of CO2 laser radiation in a GaSe crystal
Yanzhao Lu; Xinbing Wang; Liang Miao; Duluo Zuo; Zuhai Cheng
2011-01-01
Tunable third-harmonic and fourth-harmonic generations of pulsed CO2 laser radiation in a GaSe crystal were demonstrated. The optical properties of GaSe and phase-matching conditions in harmonic generations were investigated. The output peak powers for 3.2 mum and 2.4 mum were measured to be 1500 W and 320 W, with corresponding conversion efficiency from 9.6 mum of 0.1% and 0.02%, respectively.
Third-harmonic and fourth-harmonic generations of CO 2 laser radiation in a GaSe crystal
Yanzhao Lu; Xinbing Wang; Liang Miao; Duluo Zuo; Zuhai Cheng
2011-01-01
Tunable third-harmonic and fourth-harmonic generations of pulsed CO2 laser radiation in a GaSe crystal were demonstrated. The optical properties of GaSe and phase-matching conditions in harmonic generations were investigated. The output peak powers for 3.2?m and 2.4?m were measured to be 1500W and 320W, with corresponding conversion efficiency from 9.6?m of 0.1% and 0.02%, respectively.
Resonant second harmonic generation in a gallium nitride two-dimensional photonic crystal on silicon
NASA Astrophysics Data System (ADS)
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
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.
M. Suzuki; H. Kiriyama; Y. Nakai; H. Okada; I. Daito; P. R. Bolton; H. Daido; K. Kondo; S. Kawanishi; Y. Kagebayashi; T. Yokota
2010-01-01
Frequency doubling of high-energy Nd-doped laser emission yields harmonically converted laser energy (532-nm) of 1.2-J with 60 % conversion efficiency using a high optical quality top-seeded solution growth CsB3O5 crystal.
Brett A. Hooper; Daniel J. Gauthier; John M. Madey
1994-01-01
Second harmonic generation (SHG) and fourth harmonic generation (FHG) in single 1 cm long lithium niobate crystal pumped by 2-2.5 micron photons from Mark III free-electron laser and type I phase matched for first stage SHG. Energy conversion efficiencies of 66% for SHG and 3.3 x 10(exp -6) for FHG are observed.
Second and Fourth Harmonic Frequencies in Electric Field-Induced Liquid Crystal Reorientations
Wu, Shin-Tson
that the second and fourth harmonic frequencies are generated depending on the biased voltage. Let us define d0Second and Fourth Harmonic Frequencies in Electric Field-Induced Liquid Crystal Reorientations of Central Florida, Orlando, Florida, USA The second and fourth harmonics of low frequency electric field
On the uniqueness of heat flow of harmonic maps and hydrodynamic flow of nematic liquid crystals
Wang, Changyou
On the uniqueness of heat flow of harmonic maps and hydrodynamic flow of nematic liquid crystals manifold (N, h), we establish the unique- ness of the heat flow of harmonic maps from M to N in the class C still remain largely open. The second example is the heat flow of harmonic maps. It is well
Efficient fourth harmonic generation of Nd: glass lasers in ADP and DKDP crystals
NASA Astrophysics Data System (ADS)
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
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.
Grating-assisted phase matching of high harmonic generation in hollow core photonic crystal fiber
Haizhen Ren
2009-01-01
We supposed to use the hollow core photonic crystal fiber as the gas cell for grating-assisted phase matching of high harmonic generation below 1 keV. The conversion efficiency is expected to be dramatically improved.
Grechin, Sergey S; Pryalkin, Vladimir I [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)
2003-08-31
The results of calculation of group-velocity matching for the generation of second harmonic of femtosecond laser pulses in 62 nonlinear-optical crystals are presented. The angular, spectral, and temperature widths of matching as well as the effective nonlinearity are calculated. The crystals providing the efficient generation of second, third, fourth, and fifth harmonics of the femtosecond Cr:forsterite laser radiation are found. (nonlinear optical phenomena)
NASA Astrophysics Data System (ADS)
Parvini, T. S.; Tehranchi, M. M.; Hamidi, S. M.
2015-03-01
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.
Reflected fourth-harmonic radiation from a centrosymmetric crystal.
Lee, Y S; Downer, M C
1998-06-15
We present measurements of fourth-harmonic generation in reflection from the interface between two centrosymmetric media [Si(001)- SiO(2)] , using femtosecond pulses well below damage threshold. Analyses of signal amplitudes, rotational anisotropy, and sensitivity to surface roughening reveal that the surface dipole fourth-harmonic contribution dominates the bulk quadrupole contribution much more strongly than for second-harmonic generation. PMID:18087383
Reflected fourth-harmonic radiation from a centrosymmetric crystal
Y.-S. Lee; M. C. Downer
1998-01-01
We present measurements of fourth-harmonic generation in reflection from the interface between two centrosymmetric media [Si(001) SiO] , using femtosecond pulses well below damage threshold. Analyses of signal amplitudes, rotational anisotropy, and sensitivity to surface roughening reveal that the surface dipole fourth-harmonic contribution dominates the bulk quadrupole contribution much more strongly than for second-harmonic generation. {copyright} {ital 1998} {ital Optical
Reflected fourth-harmonic radiation from a centrosymmetric crystal
Lee, Y.; Downer, M.C. [Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States)
1998-06-01
We present measurements of fourth-harmonic generation in reflection from the interface between two centrosymmetric media [Si(001){endash} SiO{sub 2}] , using femtosecond pulses well below damage threshold. Analyses of signal amplitudes, rotational anisotropy, and sensitivity to surface roughening reveal that the surface dipole fourth-harmonic contribution dominates the bulk quadrupole contribution much more strongly than for second-harmonic generation. {copyright} {ital 1998} {ital Optical Society of America}
Xia, Jinan
2009-10-26
A numerical iteration technique starting from the analytical solution of the fundamental wave and the second harmonic wave propagation equations in undepleted-pump approximation is presented for analysis of second harmonic generation in one-dimensional nonlinear photonic-crystal microcavities under pump light incidence at an arbitrary angle, accounting for pump depletion. Numerical results are in good agreement with experimental observation and theoretical predication by transfer matrix method. Analysis of the conversion efficiency of second harmonic generation in nonlinear photonic-crystal microcavities shows that dramatic enhancement of second harmonic generation occurs in the microcavities which have the optimal numbers of distributed Bragg reflector layers. The enhancement of nonlinear interactions is ascribed to mode resonance and localization of high intensity fundamental field, corresponding to the defect mode within the forbidden band of the photonic-crystal microcavities. PMID:19997231
Highly Efficient Mode Converter for Coupling Light into Wide Slot Photonic Crystal Waveguide
Zhang, Xingyu; Hosseini, Amir; Chen, Ray T
2014-01-01
We design, fabricate and experimentally demonstrate a highly efficient adiabatic mode converter for coupling light into a silicon slot waveguide with a slot width as large as 320nm. This strip-to-slot mode converter is optimized to provide a measured insertion loss as low as 0.08dB. Our mode converter provides 0.1dB lower loss compared to a conventional V-shape mode converter. This mode converter is used to couple light into and out of a 320nm slot photonic crystal waveguide, and it is experimentally shown to improve the coupling efficiency up to 3.5dB compared to the V-shape mode converter, over the slow-light wavelength region.
Low-loss mode converter for coupling light into slotted photonic crystal waveguide
Zhang, Xingyu; Hosseini, Amir; Pan, Zeyu; Yan, Hai; Chung, Chi-jui; Chen, Ray T
2015-01-01
We design, fabricate and experimentally demonstrate a highly efficient adiabatic mode converter for coupling light into a silicon slot waveguide with a slot width as large as 320nm. This strip-to-slot mode converter is optimized to provide a measured insertion loss as low as 0.08dB. Our mode converter provides 0.1dB lower loss compared to a conventional V-shape mode converter. This mode converter is used to couple light into and out of a 320nm slot photonic crystal waveguide, and it is experimentally shown to improve the coupling efficiency up to 3.5dB compared to the V-shape mode converter, over the slow-light wavelength region.
Fourth-harmonic generation of picosecond glass laser pulses with cesium lithium borate crystals
Lalit B. Sharma; H. Daido; Y. Kato; S. Nakai; T. Zhang; Y. Mori; T. Sasaki
1996-01-01
We report the fourth-harmonic generation of 1.5 ps, 1.053 ?m glass laser pulses, where group velocity mismatch plays a significant role, at intensities up to 100 GW\\/cm2 using newly developed crystal, cesium lithium borate (CsLiB6O10). Type-I doubler and type-I quadrupler were used in the fourth harmonic generation experimental scheme. Energy conversion efficiencies of 24% and 53% have been achieved for
Quasi-phase-matched high harmonic generation in hollow core photonic crystal fibers.
Ren, H; Nazarkin, A; Nold, J; Russell, P St J
2008-10-13
The potential of hollow core photonic crystal fiber as a nonlinear gas cell for efficient high harmonic generation is discussed. The feasibility of phase-matching this process by modulating the phase of ionization electrons using a counter-propagating laser field is shown. In this way, harmonics with energies of several hundreds of eV can be produced using fs-laser pump pulses of microJ energy. PMID:18852815
F. Hamdad; A. K. S. Bhat
1998-01-01
A high-frequency transformer isolated, fixed-frequency, 3-? single-stage AC-to-DC converter using a boost-integrated bridge converter is proposed. This converter enjoys natural power factor correction with low line current harmonic distortion and symmetric high frequency voltage and current waveforms while ensuring zero voltage switching for all the switches for a wide variation in load and line voltage. Various operating modes of the
Converting Ceria Polyhedral Nanoparticles into Single-Crystal Nanospheres
Xiangdong Feng; Dean C. Sayle; Zhong Lin Wang; M. Sharon Paras; Brian Santora; Anthony C. Sutorik; Thi X. T. Sayle; Yi Yang; Yong Ding; Xudong Wang; Yie-Shein Her
2006-01-01
Ceria nanoparticles are one of the key abrasive materials for chemical-mechanical planarization of advanced integrated circuits. However, ceria nanoparticles synthesized by existing techniques are irregularly faceted, and they scratch the silicon wafers and increase defect concentrations. We developed an approach for large-scale synthesis of single-crystal ceria nanospheres that can reduce the polishing defects by 80% and increase the silica removal
Eung-Ho Kim; Soo-Bin Yim; Ho-Chan Jung; Eok-Jae Lee
2006-01-01
A system for recovering phosphorus from membrane-filtrate from a sludge reduction process containing high phosphorus concentrations was developed. In this system, referred to as the completely mixed phosphorus crystallization reactor, powdered converter slag was used as a seed material. In a preliminary experiment, the optimal pH range for metastable crystallization of phosphorus from membrane-filtrate containing about 100mg\\/L PO4-P was found
Second harmonic generation in photonic crystal cavities in (111)-oriented GaAs
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
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.
NASA Astrophysics Data System (ADS)
Tatematsu, Yoshinori; Yamaguchi, Yuusuke; Idehara, Toshitaka; Kawase, Tatsuru; Ichioka, Ryoichi; Ogawa, Isamu; Saito, Teruo; Fujiwara, Toshimichi
2014-01-01
Second harmonic gyrotrons, Gyrotron FU CW GII and Gyrotron FU CW GIII, were developed at the Research Center for Development of Far-Infrared Region, University of Fukui, Japan to achieve two goals. Each gyrotron was equipped with an internal quasi-optical mode converter. Using Gyrotron FU CW GII allowed the design of the cavity and mode converter to be validated, which was the first goal. After that, Gyrotron FU CW GIII, which is an improved version of Gyrotron FU CW GII, allowed us to achieve a high power output of up to 420 W, which was the second goal, with a cathode voltage setting of -21 kV and a beam current of 0.57 A. This was achieved using a newly developed electron gun and with the careful sitting of the gyrotron on the magnet.
Operation of a modular multilevel converter with selective harmonic elimination PWM
Georgios S. Konstantinou; Mihai Ciobotaru; Vassilios G. Agelidis
2011-01-01
The modular multilevel converter (MMC) is based on the cascaded interconnection of half-bridge switching sub- modules and features modular characteristics that allow its expandability while providing high quality voltage and current output waveforms and removing the need for filtering. The switching frequency of each of the individual converter sub modules being maintained low and the balancing of the capacitor voltages
A POSITRON SOURCE USING AN AXIALLY ORIENTED CRYSTAL ASSOCIATED TO A GRANULAR AMORPHOUS CONVERTER
Boyer, Edmond
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
High-efficiency fourth-harmonic generation of KBBF crystal
Junhua Lu; Guiling Wang; Zuyan Xu; Chuangtian Chen; Jiyang Wang; Chengqian Zhang; Yaogang Liu
2001-01-01
A prism-coupled technique (PCT) was introduced in the SHG experiment of KBe2BO3F2 (KBBF) crystal. 266-nm ultraviolet energy of 0.28 mJ was obtained by using this method in a KBBF crystal at the input energy of 2.6 mJ, corresponding to a conversion efficiency of 10.8%.
Influence of the temperature distribution in KDP crystal on the second-harmonic generation
Wei Li; Guoying Feng; Qiuhui Zhang; Tianxiang Zhang; Hai Liao
2008-01-01
Using split-step algorithm based on the fast Fourier transform and a fourth-order Runge-Kutta(R-K) method, we studied the second-harmonic generation(SHG) of high power laser with KDP crystal. The transverse walk-off effect, diffraction, the second-order and the third-order nonlinear effects of KDP crystal have been taken into consideration. Special attention has been paid to the influences of a kind of self-induced thermal
Yang, X L; Xie, S W
1995-09-20
Third-harmonic-generation processes in crystals are governed by the fourth-rank tensor ((3))(Xijkl), which reflects the crystal symmetry. In this case, the third-order nonlinear susceptibility tensor can be contracted to the compact matrix form ((3))(Xim). The matrices ((3))(Xim) for isotropic media and all 32 crystallographic point groups are presented. With these matrices, the analytic expressions of third-order effective nonlinear susceptibility can be easily derived. PMID:21060454
B. Corcoran; C. Monat; C. Grillet; T. P. White; L. O'Faolain; T. F. Krauss; B. J. Eggleton; D. J. Moss
2009-01-01
We report optical performance monitoring via slow-light enhanced third harmonic generation in a 2D silicon photonic crystal waveguide. We achieve all-optical in-band OSNR monitoring of a 40Gb\\/s Return-to-Zero signal with significantly better performance than methods based on quadratic response functions.
Efficient fourth harmonic generation of Nd:YAG laser in DKDP crystals
G. Kruglik; N. Kondratyuk; A. A. Shagov
2002-01-01
In the present work we investigated the conditions of the 4th harmonic stable high effective pulse generation with the energy up to 100 mJ, efficiency approximately 50 percent and pulse repetition rate 10 Hz in DKDP crystals with noncritical phase matching. On the basis of experimental data we carried out the numerical modeling of thermal self- action effects influencing on
Deep Ultraviolet Harmonic Generation with KBe2BO3F2 Crystal
Chen Chuang-Tian; Lü Jun-Hua; Wang Gui-Ling; Xu Zu-Yan; Wang Ji-Yang; Zhang Cheng-Qian; Liu Yao-Gang
2001-01-01
A special prism coupling technique with the KBe2BO3F2 crystal is adopted to produce deep ultraviolet light including the fourth harmonic from an Nd:YAG laser, for which a conversion efficiency as high as 10% has been obtained.
Third-harmonic pulse generation in one-dimensional photonic crystal structures
NASA Astrophysics Data System (ADS)
Wicharn, Surawut; Buranasiri, Prathan
2014-01-01
Enhanced third-harmonic generation in a one-dimensional photonic crystal doped with third-order nonlinear medium was numerically investigated using the multiple-scale method and the split-step Fourier transform. The optimal fundamental frequency for third-harmonic wave generation was determined from the transmission spectrum. The third-harmonic pulse intensities grow, depending on the structure thickness and the fundamental-frequency detuning parameter, which determines the band-edge phase matching condition. Furthermore, the total energy output of third-harmonic pulses, depending on the fundamental-frequency pulse width, may be more than 1000 times the energy produced by a phase-matched bulk medium. A narrow pulse with bandwidth less than the band-edge transmission peak enables high conversion efficiency. The maximum conversion efficiency of the forward component may be 12 to 13 orders of magnitude greater than that of the backward component.
Eung-Ho Kim; Dong-Woo Lee; Hwan-Kook Hwang; Soobin Yim
2006-01-01
A phosphorus crystallization process for recovering phosphates was developed using a completely mixed reactor and powdered converter slag as a seed crystal. This completely mixed phosphorus crystallization process achieved a stable and high phosphorus recovery: the average PO4-P removal efficiency during 200 d of operation was 87%, with a range of 70–98%. The apparent volume of the slag doubled due
Fourth-harmonic generation of picosecond glass laser pulses with cesium lithium borate crystals
Sharma, L.B.; Daido, H.; Kato, Y.; Nakai, S. [Institute of Laser Engineering, Osaka University, 2-6, Yamada-Oka, Suita 565 (Japan)] [Institute of Laser Engineering, Osaka University, 2-6, Yamada-Oka, Suita 565 (Japan); Zhang, T. [Yamanashi University, Faculty of Engineering, 4-3-11 Takeda, Kofu, Yamanashi 400 (Japan)] [Yamanashi University, Faculty of Engineering, 4-3-11 Takeda, Kofu, Yamanashi 400 (Japan); Mori, Y.; Sasaki, T. [Department of Electrical Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565 (Japan)] [Department of Electrical Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565 (Japan)
1996-12-01
We report the fourth-harmonic generation of 1.5 ps, 1.053 {mu}m glass laser pulses, where group velocity mismatch plays a significant role, at intensities up to 100 GW/cm{sup 2} using newly developed crystal, cesium lithium borate (CsLiB{sub 6}O{sub 10}). Type-I doubler and type-I quadrupler were used in the fourth harmonic generation experimental scheme. Energy conversion efficiencies of 24{percent} and 53{percent} have been achieved for frequency quadrupling and doubling of the fundamental glass laser pulses, respectively. {copyright} {ital 1996 American Institute of Physics.}
Terahertz-field-induced second harmonic generation through Pockels effect in zinc telluride crystal.
Cornet, Marion; Degert, Jérôme; Abraham, Emmanuel; Freysz, Eric
2014-10-15
We report on the second harmonic generation (SHG) of a near-infrared pulse in a zinc telluride crystal through the Pockels effect induced by an intense terahertz pulse. The temporal and angular behaviors of the SHG have been measured and agree well with theoretical predictions. This phenomenon, so far overlooked, makes it possible to generate second harmonic through cascading of two second-order nonlinear phenomena in the near-infrared and terahertz ranges. We also show how this cascading process can be used to sample terahertz pulses. PMID:25361120
Conical second harmonic generation in one-dimension nonlinear photonic crystal
NASA Astrophysics Data System (ADS)
An, Ning; Zheng, Yuanlin; Ren, Huaijin; Deng, Xuewei; Chen, Xianfeng
2013-05-01
We observed conical second-harmonic generation in a one-dimension anomalous-dispersion-like medium, which manifests itself as scattering-assisted nonlinear interaction via quasi-phase-matching sum frequency process. The parameters for the ring-shaped second harmonic beam are analyzed experimentally and theoretically, which disclose the structure information of the nonlinear photonic crystal and imply potential applications as characterization methods. Furthermore, by varying the angles of incident beam, the conical beam can be significantly enhanced owing to collinear nonlinear coupling between the input beam and the scattering light.
Measuring parameters of large-aperture crystals used for generating optical harmonics
Auerbach, J M; English, R E, Jr; Hibbard, R L; Michie, R B; Norton, M A; Perfect, S A; Summers, M D; Wegner, P J
1999-02-23
The purpose of this project was to develop tools for understanding the influence of crystal quality and crystal mounting on harmonic-generation efficiency at high irradiance. Measuring the homogeneity of crystals interferometrically, making detailed physics calculations of conversion efficiency, performing finite- element modeling of mounted crystals, and designing a new optical metrology tool were key elements in obtaining that understanding. For this work, we used the following frequency-tripling scheme: type I second- harmonic generation followed by type II sum-frequency mixing of the residual fundamental and the second harmonic light. The doubler was potassium dihydrogen phosphate (KDP), and the tripler was deuterated KDP (KD*P). With this scheme, near-infrared light (1053 nm) can be frequency tripled (to 351 nm) at high efficiency (theoretically >90%) for high irradiance (>3 GW/cm²). Spatial variations in the birefringence of the large crystals studied here (37 to 41 cm square by about 1 cm thick) imply that the ideal phase-matching orientation of the crystal with respect to the incident laser beam varies across the crystal. We have shown that phase-measuring interferometry can be used to measure these spatial variations. We observed transmitted wavefront differences between orthogonally polarized interferograms of {lambda}/50 to {lambda}/100, which correspond to index variations of order 10^{-6}. On some plates that we measured, the standard deviation of angular errors is 22-23 µrad; this corresponds to a 1% reduction in efficiency. Because these conversion crystals are relatively thin, their surfaces are not flat (deviate by k2.5 urn from flat). A crystal is mounted against a precision-machined surface that supports the crystal on four edges. This mounting surface is not flat either (deviates by +2.5 µm from flat). A retaining flange presses a compliant element against the crystal. The load thus applied near the edges of the crystal surface holds it in place. We performed detailed finite-element modeling to predict the resulting shape of the mounted crystal. The prediction agreed with measurements of mounted crystals. We computed the physics of the frequency-conversion process to better quantify the effects on efficiency of variation in the crystal? s axis, changes in the shape of the crystal, and mounting-induced stress. We were able to accurately predict the frequency-conversion performance of 37-cm square crystals on Beamlet, a one-beam scientific prototype of the NIF laser architecture, using interferometric measurements of the mounted crystals and the model. In a 2{omega} measurement campaign, the model predicted 64.9% conversion efficiency; 64.1% was observed. When detuned by 640 µrad, the model and measurement agreement is even better (both were 10.4%). Finally, we completed the design and initial testing of a new optical metrology tool to measure the spatial variation of frequency conversion. This system employs a high-power subaperture beam from a commercial laser oscillator and rod amplifier. The beam interrogates the crystal? s aperture by moving the crystal horizontally on a translation stage and translating the laser beam vertically on an optical periscope. Precision alignment is maintained by means of a full-aperture reference mirror, a precision-machined surface on the crystal mount, and autocollimators (the goal for angular errors is 10 µrad). The autocollimators track the mounting angle of the crystal and the direction of the laser beam with respect to the reference mirror. The conversion efficiency can be directly measured by recording l{omega}, 2{omega}, 3{omega} energy levels during the scan and by rocking (i.e., tilting) the crystal mount over an angular range.
Towards protein-crystal centering using second-harmonic generation (SHG) microscopy
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
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
Mid-infrared second-harmonic generation in chalcogenide photonic crystal fiber
NASA Astrophysics Data System (ADS)
Cao, Fengzhen; Zhang, Peiqing; Dai, Shixun; Wang, Xunsi; Xu, Tiefeng; Nie, Qiuhua
2015-01-01
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.
Yang, Steven T; Henesian, Mark A; Weiland, Timothy L; Vickers, James L; Luthi, Ronald L; Bielecki, John P; Wegner, Paul J
2011-05-15
Noncritically phase-matched (NCPM) fourth harmonic generation (FHG) of Nd:glass laser radiation in partially deuterated dihydrogen phosphate (KD*P) crystals has been demonstrated. At an Nd:glass laser wavelength of 1053.0 nm, NCPM FHG is achieved in 70% deuterated KD*P at a crystal temperature of 18.5±0.1 °C. Tuning the fundamental laser wavelength from 1052.9 to 1053.2 nm, FHG in KD*P is NCPM by changing the crystal temperature from 17.9 °C to 20.5 °C. When driven with 2.4 J of second harmonic radiation in a 3 ns flat-top pulse, corresponding to 1 GW/cm(2) 2? drive intensity, 1.9 J of fourth harmonic radiation was generated in a 6 mm long KD*P crystal, yielding a second to fourth harmonic energy conversion efficiency of 79%. PMID:21593903
Influence of the temperature distribution in KDP crystal on the second-harmonic generation
NASA Astrophysics Data System (ADS)
Li, Wei; Feng, Guoying; Zhang, Qiuhui; Zhang, Tianxiang; Liao, Hai
2008-08-01
Using split-step algorithm based on the fast Fourier transform and a fourth-order Runge-Kutta(R-K) method, we studied the second-harmonic generation(SHG) of high power laser with KDP crystal. The transverse walk-off effect, diffraction, the second-order and the third-order nonlinear effects of KDP crystal have been taken into consideration. Special attention has been paid to the influences of a kind of self-induced thermal effect. The phase mismatching quantity, the intensity distribution of output beam and the frequency conversion efficiency varying with the crystal temperature distribution have been analyzed. The calculated results indicate that self-induced thermal effects results in the temperature distribution in KDP crystal and the phase mismatching, then the phase mismatching leads to the decreasion of the conversion efficiency.
Temperature-Frequency Converter Using a Liquid Crystal Cell as a Sensing Element
Marcos, Carlos; Sánchez Pena, José M.; Torres, Juan C.; Santos, José Isidro
2012-01-01
A new temperature-frequency converter based on the variation of the dielectric permittivity of the Liquid Crystal (LC) material with temperature has been demonstrated. Unlike other temperature sensors based on liquid crystal processing optical signals for determining the temperature, this work presents a system that is able to sense temperature by using only electrical signals. The variation of the dielectric permittivity with temperature is used to modify the capacitance of a plain capacitor using a LC material as non-ideal dielectric. An electric oscillator with an output frequency depending on variable capacitance made of a twisted-nematic (TN) liquid crystal (LC) cell has been built. The output frequency is related to the temperature of LC cell through the equations associated to the oscillator circuit. The experimental results show excellent temperature sensitivity, with a variation of 0.40% of the initial frequency per degree Celsius in the temperature range from ?6 °C to 110 °C. PMID:22737002
High-efficiency second-harmonic generation with ultrashort pulses in potassium niobate crystals
Dorel Iosif Guzun
2000-01-01
The second-harmonic generation (SHG) of type- I with ultrashort pulses was studied experimentally and theoretically in case of KNbO 3 crystal. The results of the observation of a high-efficiency SHG are presented together with a numerical fit of this data. The dependence of the SHG efficiency on input pump power and its focusing were studied. The observation of SHG efficiency
Widely tunable fourth harmonic generation of a Ti:sapphire laser based on RBBF crystal
X. Zhang; Z. M. Wang; S. Y. Luo; G. L. Wang; Y. Zhu; Z. Y. Xu; C. T. Chen
2011-01-01
Fourth harmonic generation of a tunable Ti:sapphire laser with a repetition rate of 80 MHz and pulse duration ˜150 fs has been realized in a single pass with an RbBe2BO3F2 crystal for the first time. A high average power was obtained which was tunable throughout a wide range from 180 to 232.5 nm. The output power over the whole range
Simultaneous generation of spectrally distinct third harmonics in a photonic crystal fiber.
Omenetto, F G; Taylor, A J; Moores, M D; Arriaga, J; Knight, J C; Wadsworth, W J; Russell, P S
2001-08-01
By coupling femtosecond pulses at lambda - 1.55mum in a short length (Z - 95 cm) of photonic crystal fiber, we observe the simultaneous generation of two visible radiation components. Frequency-resolved optical gating experiments combined with analysis and modal simulations suggest that the mechanism for their generation is third-harmonic conversion of the fundamental pulse and its split Raman self-shifted component. PMID:18049548
Kim, Eung-Ho; Yim, Soo-Bin; Jung, Ho-Chan; Lee, Eok-Jae
2006-08-25
A system for recovering phosphorus from membrane-filtrate from a sludge reduction process containing high phosphorus concentrations was developed. In this system, referred to as the completely mixed phosphorus crystallization reactor, powdered converter slag was used as a seed material. In a preliminary experiment, the optimal pH range for metastable crystallization of phosphorus from membrane-filtrate containing about 100mg/L PO(4)-P was found to be 6.6-7.0. The laboratory scale completely mixed phosphorus crystallization reactor, actually operated in pH range of 6.8-7.6 for influent 72.9 mg/L PO(4)-P, achieved an average efficiency of phosphorus removal from the membrane-filtrate of 52.4% during a 30-day experiment. Mixed-liquor suspended solids (MLSS) measurements revealed that, out of 0.24 kg PO(4)-P in the original membrane-filtrate fed into the reactor, 0.12 kg PO(4)-P was recovered on the seed particles after 30 days. X-ray diffraction (XRD) pattern and Fourier transform infrared (FT-IR) spectra of the crystalline material deposited on the seed particles showed peaks consistent with hydroxyapatite. Scanning electron micrograph (SEM) images exhibited that finely distributed crystalline material was formed on the surfaces of seed particles. Energy dispersive X-ray spectroscopy (EDS) mapping analysis revealed that the molar composition ratio of Ca/P of the crystalline material was 1.84. The Ca/P molar ratio>1.67 for crystalline substance might result from the presence of CaCO(3) on the crystalline surfaces. A particle size distribution analysis showed that the average particle size increased from 22 microm for the original converter slag seed particles, to 94 microm after 30 days of phosphorus crystallization. Collectively, the present results suggest that the proposed phosphorus crystallization recovery system is an effective tool for recycling phosphorus from phosphate solution. PMID:16504382
Second Harmonic Light Scattering Study of a Twist-Bend Nematic Liquid Crystal
NASA Astrophysics Data System (ADS)
Pardaev, Shokir; Gleeson, James; Jakli, Antal; Sprunt, Samuel
2015-03-01
The twist-bend nematic phase exhibited by certain liquid crystalline dimers has been the subject of intensive recent investigation. In this report we present the results of angle-resolved second harmonic (SH) light scattering measurements from a twist-bend (TB) nematic liquid crystal for various combinations of the fundamental and second harmonic polarizations. These measurements reveal a polarization-dependent pretransitional temperature dependence of the SH signal, as well as an evolution of the SH scattering pattern below the transition (in the TB phase). We will discuss our results in terms of other recent experiments, as well as the current theoretical understanding of the nematic to TB transition and the nature of the TB phase. We thank O. Parri at Merck Chemicals Ltd., Southampton, UK for providing the studied material for us. Acknowledgement: NSF DMR-0964765 and DMR-1307674.
Second-Harmonic Generation in a Phase-Match Free Nonlinear 2D Crystal
NASA Astrophysics Data System (ADS)
Zhao, Mervin; Ye, Ziliang; Ye, Yu; Zhu, Hanyu; Wang, Yuan; Zhang, Xiang
2015-03-01
The second harmonic generation (SHG) produced from two-dimensional atomic crystals have been utilized to great effect in studying the grain boundaries and electronic structure of such crystals. However, the SHG in many transition metal dichalcogenides (TMDCs) only occur in odd numbered layers due to their noncentrosymmetric nature, limiting the applicability of their SHG. Here, we probe the SHG from the bulk noncentrosymmetric molybdenum disulfide (MoS2). Whereas the commonly studied 2H crystal phase's antiparallel dipoles in adjacent layers give an oscillatory SH response, the parallel dipoles of each atomic layer in the 3R phase constructively interfere to amplify the second harmonic intensity. Due to this interference, we observed the phase-match free condition yielding a quadratic dependence between the intensity and layer number. Additionally, we probed the layer evolution of the A and B excitonic transitions in 3R-MoS2 using SHG spectroscopy. We find exciton splittings distinct from 2H-MoS2, resulting from the different interlayer interactions of the two polytypes.
High efficiency second-harmonic generation in KNbO3 crystals
J.-C. Baumert; P. Günter; H. Melchior
1983-01-01
Second-harmonic generation in KNbO3 crystals has been studied with CW and pulsed AlxGa1-xAs and dye lasers. High conversion efficiencies were obtained by noncritical Type I phase-matching at room temperature for the wavelength lambdaPM = (860+\\/-2) nm using the nonlinear optical coefficient d32 = 21 pm\\/V. The measured peak power was P2omega=13.6 muW for a fundamental power Pomega=21 mW with a
Widely tunable fourth harmonic generation of a Ti:sapphire laser based on RBBF crystal
X. Zhang; Z. M. Wang; S. Y. Luo; G. L. Wang; Y. Zhu; Z. Y. Xu; C. T. Chen
2011-01-01
Fourth harmonic generation of a tunable Ti:sapphire laser with a repetition rate of 80 MHz and pulse duration ?150 fs has\\u000a been realized in a single pass with an RbBe2BO3F2 crystal for the first time. A high average power was obtained which was tunable throughout a wide range from 180 to 232.5 nm.\\u000a The output power over the whole range exceeded 2 mW,
Calculation of optical second-harmonic susceptibilities and optical activity for crystals
Levine, Z.H. [Ohio State Univ., Columbus, OH (United States)
1994-12-31
A new generation of nearly first-principles calculations predicts both the linear and second-harmonic susceptibilities for a variety of insulating crystals, including GaAs, GaP, AlAs, AlP, Se, {alpha}-quartz, and c-urea. The results are typically in agreement with experimental measurements. The calculations have been extended to optical activity, with somewhat less success to date. The theory, based on a simple self-energy correction to the local density approximation, and results are reviewed herein.
Characterization of salt interferences in second-harmonic generation detection of protein crystals
Closser, R. G.; Gualtieri, E. J.; Newman, J. A.; Simpson, G. J.
2013-01-01
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
Characterization of salt interferences in second-harmonic generation detection of protein crystals.
Closser, R G; Gualtieri, E J; Newman, J A; Simpson, G J
2013-12-01
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
Chen, Bao-Qin; Zhang, Chao; Liu, Rong-Juan; Li, Zhi-Yuan, E-mail: lizy@aphy.iphy.ac.cn [Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China)
2014-10-13
We have designed and fabricated a lithium niobate (LN) nonlinear photonic crystal (NPC) with a two-dimensional (2D) ellipse structure of inverse poling domains. The structure can offer continuously varying reciprocal lattice vectors in different directions to compensate the phase-mismatching during the second harmonic generation (SHG) for diverse pump wavelengths. We consider three propagation directions with large effective nonlinear susceptibility and measure the nonlinear conversion efficiency of SHG. The experimental data are in good agreement with the quantitative calculation results using the effective susceptibility model with pump depletion. With high-efficiency SHG in multiple propagation direction, the 2D ellipse structure of LN NPC has the potential to realize various broadband nonlinear frequency conversion processes in different propagation direction with a single crystal.
DeWalt, Emma L.; Begue, Victoria J.; Ronau, Judith A.; Sullivan, Shane Z.; Das, Chittaranjan; Simpson, Garth J.
2013-01-01
Polarization-resolved second-harmonic generation (PR-SHG) microscopy is described and applied to identify the presence of multiple crystallographic domains within protein-crystal conglomerates, which was confirmed by synchrotron X-ray diffraction. Principal component analysis (PCA) of PR-SHG images resulted in principal component 2 (PC2) images with areas of contrasting negative and positive values for conglomerated crystals and PC2 images exhibiting uniformly positive or uniformly negative values for single crystals. Qualitative assessment of PC2 images allowed the identification of domains of different internal ordering within protein-crystal samples as well as differentiation between multi-domain conglomerated crystals and single crystals. PR-SHG assessments of crystalline domains were in good agreement with spatially resolved synchrotron X-ray diffraction measurements. These results have implications for improving the productive throughput of protein structure determination through early identification of multi-domain crystals. PMID:23275165
NASA Astrophysics Data System (ADS)
Singh, O. P.; Singh, Y. P.; Singh, Namwar; Singh, N. B.
2001-05-01
Vanillin also known as 4-hydroxy 3-methoxy benzaldehyde, is an excellent candidate for second harmonic generation for ultra-violet and near infrared wavelength region because of its higher effective conversion efficiency. We have grown centimeter sized single crystals from solution by lowering the temperature of the bath. We used a mixture of methanol, chloroform as the solvents and a temperature region of 35°C-40°C was used for growing the crystals. A qualitative comparative study was performed for its effective conversion efficiency to compare vanillin with m. nitroaniline (m.NA) a well known organic crystal. We observed that the output intensity for second harmonic conversion was very high for vanillin in comparison to any other commercially available crystal.
Martijn de Sterke; Solomon M. Saltiel; Yuri S. Kivshar
2001-01-01
We investigate efficient fourth-harmonic generation in a single two-dimensional (2D) quadratically nonlinear photonic crystal. We propose a novel parametric process that starts with phase-matched generation of a pair of symmetric second-harmonic waves, which then interact to produce a fourth-harmonic wave that is collinear to the fundamental. We show that this process is more efficient than conventional fourth-harmonic-generation schemes by a
P. Xu; S. H. Ji; S. N. Zhu; X. Q. Yu; J. Sun; H. T. Wang; J. L. He; Y. Y. Zhu; N. B. Ming
2004-01-01
A new type of conical second-harmonic generation was discovered in a 2D chi(2) photonic crystal---a hexagonally poled LiTaO3 crystal. It reveals the presence of another type of nonlinear interaction---a scattering involved optical parametric generation in a nonlinear medium. Such a nonlinear interaction can be significantly enlarged in a modulated chi(2) structure by a quasi-phase-matching process. The conical beam records the
Christopher D. Brooks; Fabio di Teodoro
2007-01-01
We report on the use of a single-polarization, 41 mum core-diameter, intrinsically single-mode photonic crystal fiber (PCF) to obtain high peak power (up to ˜800 kW), 1 ns-duration pulses in a 100:1 linearly polarized, intrinsically single-mode (M2 ˜ 1.2) output. By transmitting the PCF output through nonlinear crystals, we also obtained efficient second, third, and fourth harmonic generation resulting in
W. Chen; M. B. Feller; Y. R. Shen
1989-01-01
We show that optical second-harmonic generation can be used to determine the anisotropic orientational distribution of a surface monolayer of molecules. The technique applied to liquid-crystal monolayers on rubbed and unrubbed substrates indicates that two different surface-originated mechanisms are effective in aligning a liquid-crystal film: One is based on molecular interaction and the other on elastic interaction.
B. W. van der Meer; F. Postma; A. J. Dekker; W. H. de Jeu
1982-01-01
The stiffness constants of a nematic liquid crystal are calculated for the situation of perfect orientational order with the aid of a model of distributed harmonic forces. Both attractive and repulsive forces are taken as distributed along the molecules, and thus are only important for the parts of two molecules that are in close proximity. For small deviations between the
Enhanced third harmonic generation by organic materials on high-Q plasmonic photonic crystals.
Ren, Fanghui; Wang, Xiangyu; Li, Zhong'an; Luo, Jingdong; Jang, Sei-Hum; Jen, Alex K-Y; Wang, Alan X
2014-08-25
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
Photonic band structure in one-dimensional nonlinear crystal: Analysis of harmonic stability
NASA Astrophysics Data System (ADS)
Avendaño, Carlos G.; Reyes, J. Adrián
2015-01-01
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.
Xu, P; Ji, S H; Zhu, S N; Yu, X Q; Sun, J; Wang, H T; He, J L; Zhu, Y Y; Ming, N B
2004-09-24
A new type of conical second-harmonic generation was discovered in a 2D chi((2)) photonic crystal-a hexagonally poled LiTaO3 crystal. It reveals the presence of another type of nonlinear interaction-a scattering involved optical parametric generation in a nonlinear medium. Such a nonlinear interaction can be significantly enlarged in a modulated chi((2)) structure by a quasi-phase-matching process. The conical beam records the spatial distribution of the scattering signal and discloses the structure information and symmetry of the 2D chi((2)) photonic crystal. PMID:15524722
Ji, Shaohua; Wang, Fang; Xu, Miaomiao; Zhu, Lili; Xu, Xinguang; Wang, Zhengping; Sun, Xun
2013-05-15
High-efficiency frequency conversion into the deep ultraviolet in a partially deuterated ammonium dihydrogen phosphate (ADP) crystal is reported. For a 60% deuterated ADP crystal, the spontaneous Raman scattering intensity decreased by 38% compared with that of a pristine ADP crystal. At room temperature (24°C), noncritical phase-matching fourth harmonic generation of a 1053 nm laser was realized. The angular acceptance was 55.7 mrad, and the external conversion efficiency from 526 to 263 nm reached 85.3%. PMID:23938909
Non-critical phase-matching fourth harmonic generation of a 1053-nm laser in an ADP crystal.
Ji, Shaohua; Wang, Fang; Zhu, Lili; Xu, Xinguang; Wang, Zhengping; Sun, Xun
2013-01-01
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
de Sterke, M; Saltiel, S M; Kivshar, Y S
2001-04-15
We investigate efficient fourth-harmonic generation in a single two-dimensional (2D) quadratically nonlinear photonic crystal. We propose a novel parametric process that starts with phase-matched generation of a pair of symmetric second-harmonic waves, which then interact to produce a fourth-harmonic wave that is collinear to the fundamental. We show that this process is more efficient than conventional fourth-harmonic-generation schemes by a factor that reaches 4 at low intensities and discuss how to design and optimize the nonlinear 2D photonic crystals that are implemented in LiNbO(3) and LiTaO(3) . PMID:18040378
Tolbert, Leon M.
. 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
Bak, Claus Leth
Abstract--This paper presents the harmonic analysis of offshore wind farm (OWF) models with full analysis, offshore wind farm, wind turbine, validation with measurements I. INTRODUCTION HE tendency. Nowadays wind turbines are often grouped in large wind farms, installed offshore and connected directly
Won K. Ng; E. J. Woodbury
1971-01-01
We have observed simultaneous generation of the second, third, and fourth harmonics of a 1.06-? fundamental in Ba2NaNb5O15, LiNbO3, and LiIO3 crystals. Experimental results reveal that the third harmonic is generated through the process of mixing the fundamental with the second harmonic; the fourth harmonic arises as a result of doubling the second harmonic. Strong absorption of the fourth harmonic
NASA Astrophysics Data System (ADS)
Brooks, Christopher D.; Di Teodoro, Fabio
2007-12-01
We report on the use of a single-polarization, 41 ?m core-diameter, intrinsically single-mode photonic crystal fiber (PCF) to obtain high peak power (up to ˜800 kW), 1 ns-duration pulses in a 100:1 linearly polarized, intrinsically single-mode ( M2 ˜ 1.2) output. By transmitting the PCF output through nonlinear crystals, we also obtained efficient second, third, and fourth harmonic generation resulting in peak power >400 kW in the visible (green, 531 nm) and ˜200 kW in the UV (265.5 nm). To our knowledge these results represent the highest peak power obtained in a linearly polarized output from a fiber and the highest peak power in the visible and UV obtained through harmonic generation of the direct fiber output.
Jeong, Mi-Yun; Cho, Bong Rae
2015-02-01
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
Christopher D. Brooks; Fabio Di Teodoro
2007-01-01
We report on the use of a single-polarization, 41?m core-diameter, intrinsically single-mode photonic crystal fiber (PCF) to obtain high peak power (up to ?800kW), 1ns-duration pulses in a 100:1 linearly polarized, intrinsically single-mode (M2?1.2) output. By transmitting the PCF output through nonlinear crystals, we also obtained efficient second, third, and fourth harmonic generation resulting in peak power >400kW in the
Second-harmonic generation from a KBe2BO3F2 crystal in the deep ultraviolet
Chuangtian Chen; Junhua Lu; T. Togashi; T. Suganuma; T. Sekikawa; S. Watanabe; Zuyan Xu; Jiyang Wang
2002-01-01
By use of KBe2BO3F2 (KBBF) crystal with a size of 10 mm x 10 mm x 1.2 mm and a special prism-coupling technique (PCT), fourth-harmonic generation of Ti:sapphire laser systems from 200 to 179.4 nm has been achieved. Moreover, with a Ti:sapphire laser with a 50-fs pulse duration and a 1-kHz repetition rate, conversion efficiency as high as 13% from
High harmonic generation (HHG) in a Kagome-type hollow-core photonic crystal fiber (HC-PCF)
O. H. Heckl; C. R. E. Baer; C. Krankel; S. V. Marchese; F. Schapper; M. Holler; T. Sudmeyer; J. S. Robinson; J. W. G. Tisch; F. Couny; P. Light; F. Benabid; P. S. J. Russell; U. Keller
2009-01-01
Hollow-core photonic crystal fibers (HC-PCF) offer a combination of long effective interaction length and small mode areas which has resulted in several major breakthroughs in low-power nonlinear optics. Recently, it was shown numerically that such fibers offer unique properties in terms of efficiency and low threshold for high harmonic generation. In addition to the substantial decrease in pump threshold, the
Tony Hoevenaars; Ian Evans; Andy Lawson
2010-01-01
To address concerns associated with electrical power system harmonic distortion on ships and offshore oil rigs and platforms, marine regulating bodies have introduced strict new harmonic standards. These standards define the acceptable level of harmonic voltage distortion allowed on the vessels they certify. High-harmonic distortion levels are appearing as a result of the increased use of power-electronic drive converters for
NASA Astrophysics Data System (ADS)
Prasanyaa, T.; Jayaramakrishnan, V.; Haris, M.
2013-03-01
In this paper, we report the successful growth of pure, Cu2+ ions and Cd2+ ions doped on ninhydrin single crystals by slow solvent evaporation technique. The presence of Cu2+ and Cd2+ ions in the specimen of ninhydrin single crystal has been determined by atomic absorption spectroscopy. The powder X-ray diffraction analysis was done to calculate the lattice parameters of the pure and doped crystals. The percentage of transmittance of the crystal was recorded using the UV-Vis Spectrophotometer. Thermal behaviors of the grown crystals have been examined by the thermal gravimetric/differential thermal analysis. The hardness of the grown crystals was assessed and the results show the minor variation in the hardness value for the pure and doped ninhydrin samples. The value of the work hardening coefficient n was found to be 2.0, 1.0 and 1.06 for pure, copper and cadmium doped ninhydrin crystals respectively. The second harmonic generation efficiency of Cd2+ and Cu2+ doped ninhydrin is 8.3 and 6.3 times greater than well known nonlinear crystal of potassium dihydrogen phosphate respectively. The antibacterial and antifungal activities of the title compound were performed by disk diffusion method against the standard bacteria Escherichia coli, Xanthomonas oryzae and against the fungus Aspergillis niger and Aspergillus flavus.
Fedotov, A B; Voronin, A A; Serebryannikov, E E; Fedotov, I V; Mitrofanov, A V; Ivanov, A A; Sidorov-Biryukov, D A; Zheltikov, A M
2007-01-01
While the standard scenario of third-harmonic generation (THG) by a dispersive-wave pump involves the emission of light with a frequency 3omega, thrice the frequency omega of the input pump field, solitons undergoing a continuous shift of their central frequency omega due to the Raman effect in a multimode optical fiber can generate the third harmonic in a different fashion. In the experiments reported here, we provide the first direct experimental evidence of THG by a continuously red-shifting soliton pump by studying the third-harmonic buildup in relation to the spectral evolution of the soliton pump field in a silica photonic-crystal fiber (PCF). We show that solitons excited in a PCF by unamplified femtosecond pulses of a Cr:forsterite laser sweep through the spectral range from 1.25 to 1.63 microm , scanning through a manifold of THG phase-matching resonances with 3omega dispersive waves in PCF modes. As a result, intense third-harmonic peaks build up in the range of wavelengths from 370 to 550 nm at the output of the fiber, making PCF a convenient fiber-format multifrequency source of short-wavelength radiation. Time-resolved fluorescence measurements with photoexcitation provided by the third-harmonic PCF output are presented, demonstrating the high potential of PCF sources for an ultrafast photoexcitation of fluorescent molecular systems in physics, chemistry, and biology. PMID:17358282
Kim, Eung-Ho; Lee, Dong-Woo; Hwang, Hwan-Kook; Yim, Soobin
2006-04-01
A phosphorus crystallization process for recovering phosphates was developed using a completely mixed reactor and powdered converter slag as a seed crystal. This completely mixed phosphorus crystallization process achieved a stable and high phosphorus recovery: the average PO4-P removal efficiency during 200 d of operation was 87%, with a range of 70-98%. The apparent volume of the slag doubled due to crystal growth during the long-term phosphorus-removal experiments. The Ca2+ concentration, slag dosage, and temperature were found to govern the phosphorus recovery system for a given condition of pH and hydraulic retention time. The equations for the rate constant and reaction order were obtained by evaluating the model parameters. The model developed in this study was observed to successfully simulate the behavior of effluent PO4-P in a completely mixed phosphorus crystallization reactor over a wide variety of operating conditions of temperature, Ca2+ concentration, and influent PO4-P. Model investigations of design factors suggest that the completely mixed phosphorus crystallization process with influent PO4-P concentrations of less than 10 mg l(-1) could ensure effluent PO4-P concentrations of less than 0.5 and 1.0 mg l(-1) during summer and winter in Korea, respectively. PMID:16213546
Electronic structure of second harmonic generation crystal Li3VO4
NASA Astrophysics Data System (ADS)
Sakata, S.; Nagoshi, Y.; Nii, H.; Ueda, N.; Kawazoe, H.
1996-10-01
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.
NASA Astrophysics Data System (ADS)
Kaltenbach, André; Schönau, Thomas; Lauritsen, Kristian; Tränkle, Günther; Erdmann, Rainer
2015-02-01
Third harmonic 355nm picosecond pulses are generated by sum frequency mixing in a periodically poled magnesium doped stoichiometric lithium tantalate (PPMgSLT) crystal. The third harmonic generation is based on the 1064nm radiation of a gain-switched distributed feedback (DFB) diode laser which is amplified by a two-stage fiber amplifier. The diode laser is freely triggerable at variable repetition rates up to 80MHz and provides optical pulses of 65 ps FWHM duration and pulse energies in the range of 5 pJ. The 355nm third harmonic generation is realized in a two-step conversion process. First, the 1064nm fundamental radiation is frequency-doubled to 532 nm, afterwards both frequencies are mixed in the PPMgSLT crystal to 355 nm. The UV-radiation shows a pulse width of 60 ps, a good beam profile and stable pulse energy over a wide range of repetition rates by proprietary pump power management. At 355nm a pulse peak power of 5.3W was achieved with 192W pulse peak power of the fundamental radiation.
Zhenlin Liu; T. Kozeki; Y. Suzuki; N. Sarukura; M. Hirano; H. Hosono
2001-01-01
Long-term stability of the fourth harmonic generation of Nd:YAG lasers is confirmed by use of the nonlinear crystal, Li2B4O7. Using four Li2B4O7 crystals, 264-mJ, 266-nm pulses are obtained from a 10-Hz Nd:YAG laser with a total conversion efficiency of 31%.
Kuyken, B; Leo, F; Mussot, A; Kudlinski, A; Roelkens, G
2015-05-18
We demonstrate a two-stage wavelength converter that uses compact near-infrared sources to amplify and convert short-wave infrared signals. The first stage consists of a photonic crystal fiber wavelength converter pumped by a Q-switched 1064 nm pump source, while the second stage consists of a silicon photonic wire waveguide wavelength converter. The system enables on-chip amplification and conversion of up to 30 dB . We demonstrate amplification in a broad wavelength range around 2344 nm using temporally long pulses (>300ps). PMID:26074555
Nold, J; Hölzer, P; Joly, N Y; Wong, G K L; Nazarkin, A; Podlipensky, A; Scharrer, M; Russell, P St J
2010-09-01
We report tunable third-harmonic generation (THG) in an Ar-filled hollow-core photonic crystal fiber, pumped by broadband <2 microJ, 30 fs pulses from an amplified Ti:sapphire laser system. The overall dispersion is precisely controlled by balancing the negative dielectric susceptibility of the waveguide against the positive susceptibility of the gas. We demonstrate THG to a higher-order guided mode and show that the phase-matched UV wavelength is tunable by adjusting the gas pressure. PMID:20808370
Growth and characterization of crystals for IR detectors and second harmonic gereration devices
NASA Technical Reports Server (NTRS)
Lal, Ravi B.; Batra, Ashok K.; Rao, Sistla M.; Bhatia, S. S.; Chunduru, Kunar P.; Paulson, Ron; Moorkherji, Tripty K.
1989-01-01
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.
Second-harmonic generation from a KBe(2) BO(3)F(2) crystal in the deep ultraviolet.
Chen, Chuangtian; Lu, Junhua; Togashi, T; Suganuma, T; Sekikawa, T; Watanabe, S; Xu, Zuyan; Wang, Jiyang
2002-04-15
By use of KBe(2)BO(3)F(2) (KBBF) crystal with a size of 10 mmx10 mm x1.2 mm and a special prism-coupling technique (PCT), fourth-harmonic generation of Ti:sapphire laser systems from 200 to 179.4 nm has been achieved. Moreover, with a Ti:sapphire laser with a 50-fs pulse duration and a 1-kHz repetition rate, conversion efficiency as high as 13% from 400 to 200 nm without any surface-loss correction has also been obtained. The data show that with the PCT a KBBF crystal can produce deep-UV coherent light with measurable power output. PMID:18007887
G. C. Bhar; A. K. Chaudhary; P. Kumbhakar; A. M. Rudra
2001-01-01
A type-I walk-off compensation (WOC) arrangement has been made for the second harmonic generation (SHG) and the fourth harmonic generation (FOHG) of commercially available Q-switched Nd:YAG laser radiation, for the first time, using two identically cut Li2B4O7 crystals. The enhancement of the conversion efficiencies has been realized in the WOC arrangement by a factor of 2.71 for the SHG and
Electro-optic harmonic conversion to switch a laser beam out of a cavity
Haas, Roger A. (Pleasanton, CA); Henesian, Mark A. (Livermore, CA)
1987-01-01
The invention is a switch to permit a laser beam to escape a laser cavity through the use of an externally applied electric field across a harmonic conversion crystal. Amplification takes place in the laser cavity, and then the laser beam is switched out by the laser light being harmonically converted with dichroic or polarization sensitive elements present to alter the optical path of the harmonically converted laser light. Modulation of the laser beam can also be accomplished by varying the external electric field.
Quasi-phase-matched second-harmonic Talbot self-imaging in a 2D periodically-poled LiTaO3 crystal.
Liu, Dongmei; Wei, Dunzhao; Zhang, Yong; Zou, Jiong; Hu, X P; Zhu, S N; Xiao, Min
2013-06-17
We demonstrate the improved second-harmonic Talbot self-imaging through the quasi-phase-matching technique in a 2D periodically-poled LiTaO(3) crystal. The domain structure not only composes a nonlinear optical grating which is necessary to realize nonlinear Talbot self-imaging, but also provides reciprocal vectors to satisfy the phase-matching condition for second-harmonic generation. Our experimental results show that quasi-phase-matching can improve the intensity of the second-harmonic Talbot self-imaging by a factor of 21. PMID:23787586
Passive Polarization Converters Based on Photonic Crystal Fiber With L-Shaped Core Region
Mohamed Farhat O. Hameed; S. S. A. Obayya; H. A. El-Mikati
2012-01-01
In this paper, novel designs of single and multiple sectioned passive polarization rotators (PRs) based on silica photonic crystal fiber (PCF) are studied and analyzed. The suggested PCF PRs have an L-shaped core region which offers nearly 100% polarization conversion ratio. The simulation results are obtained using the full vectorial finite difference method along with the full vectorial finite difference
NASA Astrophysics Data System (ADS)
Xie, Rong-Jun; Hirosaki, Naoto; Takeda, Takashi
2009-02-01
This work reports a wide color gamut backlight for liquid crystal display (LCD) utilizing a three-band white light-emitting diodes (LED). The LED backlight was fabricated by combining a blue LED chip with ?-sialon:Eu (green) and CaAlSiN3:Eu (red) phosphors. This 2-phosphor-converted white LED shows a discrete spectrum with distinct separation of red, green, and blue primary colors due to a narrow and asymmetric emission band of the green phosphor. By applying typical color filters of LCDs and color-matching functions, a wide color gamut of 91.9% of the National Television Standard Committee standard is attained, compared to 71.6% for the conventional two-band white LED.
Watanabe, L; Vieira, D F; Bortoleto, R K; Arni, R K
2002-06-01
Bothrombin, a snake-venom serine protease, specifically cleaves fibrinogen, releasing fibrinopeptide A to form non-crosslinked soft clots, aggregates platelets in the presence of exogenous fibrinogen and activates blood coagulation factor VIII. Bothrombin shares high sequence homology with other snake-venom proteases such as batroxobin (94% identity), but only 30 and 34% identity with human alpha-thrombin and trypsin, respectively. Single crystals of bothrombin have been obtained and X-ray diffraction data have been collected at the Laboratorio Nacional de Luz Sincrotron to a resolution of 2.8 A. The crystals belong to the space group P2(1)2(1)2(1), with unit-cell parameters a = 94.81, b = 115.68, c = 155.97 A. PMID:12037309
Golub, Mikhail V; Zhang, Chuanzeng
2015-01-01
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
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
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)
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
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.
Convertible holograms in CaF2 crystals with color centers
NASA Astrophysics Data System (ADS)
Angervaks, Alexandr E.; Shcheulin, Aleksandr S.; Ryskin, Aleksandr I.
2013-05-01
When recording hologram in ionic CaF2 crystal with color centers, the center conversion is accompanied with their spatial redistribution. The peculiar diffusion-drift mechanism of the recording is responsible for the extremely high hologram stability to both heating and illumination of the sample with a hologram by non-coherent radiation. However such photo-thermal treatment of the sample results in partial or total transformation of the center type and modification in their space distribution. Thus, keeping the hologram, such treatment influences its character of diffraction response, diffraction efficiency and profile. This work describes the mechanism and the character of these changes. It is shown that photo-thermal treatment can be used for fabrication of thick (up to 10 mm thickness) high stable holograms when reading out both in visible and infrared ranges of the spectrum.
Crystallization and second harmonic generation in potassium-sodium niobiosilicate glasses
Aronne, Antonio, E-mail: anaronne@unina.i [Dipartimento di Ingegneria dei Materiali e della Produzione, Universita di Napoli Federico II, Piazzale V. Tecchio, I-80125 Napoli (Italy); Fanelli, Esther; Pernice, Pasquale [Dipartimento di Ingegneria dei Materiali e della Produzione, Universita di Napoli Federico II, Piazzale V. Tecchio, I-80125 Napoli (Italy); Peli, Simone; Giannetti, Claudio; Ferrini, Gabriele [Dipartimento di Matematica e Fisica, Universita Cattolica del Sacro Cuore, Via dei Musei, 41, I-25121 Brescia (Italy)
2009-10-15
Transparent glasses having molar composition (23-x)K{sub 2}O.xNa{sub 2}O.27Nb{sub 2}O{sub 5}.50SiO{sub 2} (x=0, 5, 10, 15 and 23) have been synthesized by the melt-quenching technique and their devitrification behaviour has been investigated by DTA and XRD. Depending on the composition, the glasses showed a glass transition temperature in the range 660-680 deg. C and devitrified in several steps. XRD measurements showed that the replacement of K{sub 2}O by Na{sub 2}O strongly affects the crystallization behaviour. Particularly, in the glasses with only potassium or low sodium content the first devitrification step is related to the crystallization of an unidentified phase, while in the glass containing only sodium, NaNbO{sub 3} crystallizes. For an intermediate sodium content (x=10 and 15) a potassium sodium niobate crystalline phase, belonging to the tungsten-bronze family, is formed by bulk nucleation. This system looks promising to produce active nanostructured glasses as the tungsten-bronze type crystals have ferroelectric, electro-optical and non-linear optical properties. Preliminary measurements evidenced SHG activity in the crystallized glasses containing this phase. - Graphical abstract: Synthesis of glasses (23-x)K{sub 2}O.xNa{sub 2}O.27Nb{sub 2}O{sub 5}.50SiO{sub 2} (x=0, 5, 10, 15 and 23) from which SHG active phases crystallize by bulk nucleation for non-linear optical nanostructured glasses.
Stimulated Raman scattering of the second harmonic of a neodymium laser in nitrate crystals
A S Eremenko; S N Karpukhin; A I Stepanov
1980-01-01
An investigation was made of the efficiency of stimulated Raman scattering in sodium, barium, and lead nitrates, compared with that in calcite. Measurements were made of the energies of two Stokes components of stimulated Raman scattering. The suitability of nitrate crystals for Raman stimulated emission was demonstrated.
Control of visible harmonic generation using polarization in photonic crystal fibers
F. G. Omenetto; Anatoly Efimov; Antoinette I. Taylor; J. C. Knight; W. Wadsworth; P. S. J. Russell
2002-01-01
We present the dependence of the generated visible radiation on the polarization state of the input pulse coupled into the photonic crystal fiber. We experimentally observe that the propagation of a pulse of fixed energy, yet polarized along different directions, yields different visible components at the output, suggesting polarization-dependent selectivity for phase-matching according to the input polarization state.
Simultaneous generation of spectrally distinct third harmonic in photonic crystal fibers
F. G. Omenetto; M. D. Moores; D. H. Reitze; J. C. Knight; W. J. Wadsworth; P.St.J. Russell; A. J. Taylor
2001-01-01
Summary form only given. Recently, photonic crystal fibers have attracted considerable interest for their unique structure and optical properties. These fibers contain an ordered array of air holes which form a low-index cladding around a solid silica core. Other examples include fibers with hollow cores where light is guided by a photonic bandgap effect. Understanding the propagation of fs pulses
NASA Astrophysics Data System (ADS)
Jiang, Yi; Ding, Yujie J.
2009-04-01
Second, 3rd, and 4th order harmonics from a Fourier-transform-limited nanosecond CO 2 laser beam at 10.6 ?m were efficiently generated within one or two GaSe crystals. The peak output powers were determined to be 443, 23, and 2 W, respectively, corresponding to conversion efficiencies of 3.0%, 0.13% and 0.0093%, which were significantly improved, compared with all the previous results. The linewidths of the harmonic beams were estimated to be 80, 104, and 116 MHz, respectively.
NASA Astrophysics Data System (ADS)
Oka, Toshiharu; Suhara, Toshiaki
2015-07-01
A heavily (8 mol %) MgO-doped congruent LiTaO3 crystal (MgO:cLT) has a wider transparency range and a higher photorefractive damage resistance than LiNbO3 or a non-doped LiTaO3 crystal. We have found that annealing the crystal at 550 °C for 8 h in O2 atmosphere before applying voltage leads to the remarkable improvement for fabricating periodically-poled (PP) structures of good quality in the MgO:cLT crystal. We obtained the uniform PP structure with a period of 7.6 µm and demonstrated quasi-phase-matched second-harmonic generation (SHG) experiments by pumping at 1.064 µm wavelength for the first time. The temperature acceptance bandwidth 4.3 °C and the normalized SHG efficiency 0.30%/W were in good agreement with the calculated value.
Fourth harmonic generation of a high-repetition rate Nd:YAG laser in CsLiB6O10 crystal
K. Murse; M. Yoshimura; T. Kamimura; K. Nakai; Y. Mori; T. Sasaki; Y. Matsumoto; Y. Okada
1999-01-01
We have used as a fundamental source a diode-pumped high-repetition rate Nd:YAG laser (Spectra-Physics T40-X30-106Q) which has a pulse width of 25 ns at 4 kHz and a beam waist of 500 ?m nonlinear optical (NLO) crystal for second harmonic generation (SHG) was a noncritically phase-matched type-1 LiB3O5 (LBO) crystal with AR coating at 148°C and its length was 12
S. O. Konorov; A. A. Ivanov; M. V. Alfimov; A. M. Zheltikov
2005-01-01
Femtosecond Cr: forsterite laser pulses coupled into small-diameter birefringent channel waveguides off the central core of a photonic-crystal fiber are shown to generate multiple narrowband spectral peaks within the 380 460 nm wavelength region through multimode-phase-matched third-harmonic generation. Some of these peaks are shifted by tens of terahertz from the tripled frequency of the pump field, dictated by standard energy
S. O. Konorov; A. A. Ivanov; M. V. Alfimov; A. M. Zheltikov
2005-01-01
Femtosecond Cr: forsterite laser pulses coupled into small-diameter birefringent channel waveguides off the central core of a photonic-crystal fiber are shown to generate multiple narrowband spectral peaks within the 380–460 nm wavelength region through multimode-phase-matched third-harmonic generation. Some of these peaks are shifted by tens of terahertz from the tripled frequency of the pump field, dictated by standard energy conservation
Stefanovich, S.Yu. [Karpov Institute of Physical Chemistry, Moscow (Russian Federation); Sigaev, V.N. [Mendeleev Univ. of Chemical Tecnology, Moscow (Russian Federation)
1995-07-01
The theoretical and experimental foundations of the optical-radiation second harmonic generation (SHG) method are briefly reported. The optimum conditions for applying the SHG method both to an investigation of glasses and glass-ceramics at the early stages of the glass crystallization and to an analysis of the well-formed glass-ceramic structure are determined. The exceptionally high informative capabilities of the SHG method in studies of phase transformations of the {open_quotes}glass-acentric phase{close_quotes} type is demonstrated by the example of glass-forming systems containing the acentric phases [Li{sub 2}SiO{sub 3}, Li{sub 2}GeO{sub 3}, LiB{sub 3}O{sub 5}, Li{sub 2}B{sub 4}O{sub 7}, PbTiO{sub 3}, Pb{sub 5}Ge{sub 3}O{sub 11}, LnBXO{sub 5} (Ln=La, Ce, and Pr; X=Si and Ge), and others].
A. K. S. Bhat; R. Venkatraman
2005-01-01
A single-phase high-frequency transformer-isolated soft-switching single-stage ac-to-dc converter with low-line-current distortion is presented. The circuit configuration is obtained by integrating two discontinuous current mode (DCM) boost converters with a DCM full-bridge buck converter. The zero-voltage switching for the top switches is achieved automatically, whereas bottom switches are aided by zero-voltage transition circuits. The output voltage is regulated by duty-cycle control
B. Jungbluth; M. Vierkoetter; M. Hoefer; J. Loehring; D. Oberbeckmann; D. Hoffmann
2007-01-01
Design and experimental characterization of a nonlinear optical converter module for the generation of widely tunable UV radiation is presented. The module combines units for second, third and fourth harmonic generation of tunable Ti:Sapphire lasers. A modified conversion scheme based on the combination of BIBO and BBO crystals reduces the complexity of our former published UV setup - resulting in
Louchev, Oleg A.; Wada, Satoshi [Center for Advanced Photonics, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)] [Center for Advanced Photonics, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Hatano, Hideki; Kitamura, Kenji [Division of Environment and Energy Materials, National Institute for Materials Science (NIMS) 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)] [Division of Environment and Energy Materials, National Institute for Materials Science (NIMS) 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)
2013-08-26
Our study shows that a local temperature increase of ?1 K in the crystal lattice caused by second harmonic generation (SHG) and two-photon absorption of 532 nm radiation at the rear of periodically poled stoichiometric LiTaO{sub 3} crystal by changing spontaneous polarization induces a pyroelectric field ?10 kV/cm, accelerating free electrons to an energy of ?10 eV, followed by optical breakdown and crystal damage. Theoretical analysis leads to an explicit expression for the threshold laser fluence of optical breakdown giving ?1.2 J/cm{sup 2} for 1064 nm input radiation in 6.8 kHz pulsed SHG operation, agreeing well with the experimentally found value ?1.32 J/cm{sup 2}.
Rosen Ivanov; Kaloian Koynov; Solomon Saltiel
2005-01-01
The role of the ratio of the two design periods for phase reversed QPM structure is theoretically investigated. It is found that the efficiency of third and fourth harmonic generation strongly depends on this ratio. The results for third harmoic generation and fourth harmonic generation in LiTaO3, LiNbO3 and KTP are shown in graphical form.
Stappel, Matthias; Kolbe, Daniel; Walz, Jochen
2014-05-15
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
NASA Astrophysics Data System (ADS)
Liu, Weimin; Wang, Liang; Han, Fangyuan; Fang, Chong
2013-11-01
Coherent phonon dynamics in condensed-phase medium are responsible for important material properties including thermal and electrical conductivities. We report a structural dynamics technique, time-resolved surface third-harmonic generation (TRSTHG) spectroscopy, to capture transient phonon propagation near the surface of polycrystalline CaF2 and amorphous borosilicate (BK7) glass. Our approach time-resolves the background-free, high-sensitivity third harmonic generation (THG) signal in between the two crossing near-IR pulses. Pronounced intensity quantum beats reveal the impulsively excited low-frequency Raman mode evolution on the femtosecond to picosecond timescale. After amplified laser irradiation, danburite-crystal-like structure units form at the glass surface. This versatile TRSTHG setup paves the way to mechanistically study and design advanced thermoelectrics and photovoltaics.
Liu, Weimin; Wang, Liang; Han, Fangyuan; Fang, Chong [Department of Chemistry, Oregon State University, Corvallis, Oregon 97331 (United States)] [Department of Chemistry, Oregon State University, Corvallis, Oregon 97331 (United States)
2013-11-11
Coherent phonon dynamics in condensed-phase medium are responsible for important material properties including thermal and electrical conductivities. We report a structural dynamics technique, time-resolved surface third-harmonic generation (TRSTHG) spectroscopy, to capture transient phonon propagation near the surface of polycrystalline CaF{sub 2} and amorphous borosilicate (BK7) glass. Our approach time-resolves the background-free, high-sensitivity third harmonic generation (THG) signal in between the two crossing near-IR pulses. Pronounced intensity quantum beats reveal the impulsively excited low-frequency Raman mode evolution on the femtosecond to picosecond timescale. After amplified laser irradiation, danburite-crystal-like structure units form at the glass surface. This versatile TRSTHG setup paves the way to mechanistically study and design advanced thermoelectrics and photovoltaics.
High-Efficiency Second Harmonic Generation of a Pulsed Ti: Al2O3 Laser with beta-BaB2O4 Crystal
Xiang Liu; Daoqun Deng; Yufei Zhang; Zuyan Xu
1994-01-01
Tunable blue radiation with a tuning range of 340-460 nm has been generated using a beta-BaB2O4 crystal for external frequency doubling of a ns-pulsed Ti: Al2O3 laser. By pumping the Ti: sapphire with 94 mJ\\/pulse of energy from the second harmonic of a Q-switched Nd: YAG laser, as much as 5.4 mJ\\/pulse at 390 nm with a bandwidth of 0.02
Erba, A; Shahrokhi, M; Moradian, R; Dovesi, R
2015-01-28
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
NASA Astrophysics Data System (ADS)
Erba, A.; Shahrokhi, M.; Moradian, R.; Dovesi, R.
2015-01-01
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.
Serebryannikov, Evgenii E; von der Linde, Dietrich; Zheltikov, Aleksei M
2008-05-01
Hollow-core photonic-crystal fibers are shown to enable dynamically phase-matched high-order harmonic generation by a gigawatt soliton pump field. With a careful design of the waveguide structure and an appropriate choice of input-pulse and gas parameters, a remarkably broadband phase matching can be achieved for a soliton pump field and a large group of optical harmonics in the soft-x-ray-extreme-ultraviolet spectral range. PMID:18451958
Tunnel-diode converter analysis
C. S. Kim
1961-01-01
An analysis of tunnel-diode converters is presented for two different conditions of operation. In the first, the converter is self-oscillating; in the second, the local oscillator (LO) voltage is provided from an external source. Two classes of self-oscillating converters are presented. The first operates on the fundamental of the oscillation frequency and the other operates on the second harmonic. Assuming
NASA Technical Reports Server (NTRS)
Lal, R. B.
1995-01-01
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.
Venkatraman Gopalan; M. J. Kawas; M. C. Gupta; T. E. Schlesinger; Daniel D. Stancil
1996-01-01
We report the first integrated quasi-phase-matched second-harmonic generator and electrooptic scanner on ferroelectric Z-cut LiTaO3. The quasi-phase-matched second-harmonic generation device frequency doubles the infrared light at 829.7 nm into blue at 414.85 nm with a bulk conversion efficiency of 0.52%\\/W-cm. The blue light generated in the bulk then passes through an electrooptic scanner, consisting of a series of lithographically defined
Attaccalite, C; Nguer, A; Cannuccia, E; Grüning, M
2015-04-14
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
NASA Astrophysics Data System (ADS)
Zhuo, Guan-Yu; Chen, Kuan-Chieh; Lai, Kai-Wen; Wang, Chao-Ran; Chao, Chih-Yu; Chu, Shi-Wei
2015-02-01
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.
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
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.}
Enhanced second-harmonic generation from nonlinear optical metamagnetics.
Sun, Shang; Yi, Ningbo; Yao, Wenjiao; Song, Qinghai; Xiao, Shumin
2014-11-01
We present a numerical simulation of second-harmonic generation (SHG) from a nonlinear magnetic metamaterial. By inserting a second-order nonlinear material in the high local field area of magnetic metamaterial, which consists of periodic arrays of paired thin silver strips, the convertion efficiency of SHG has been significantly enhanced by almost four orders of magnitude. The corresponding field patterns and further studies on dependance between SHG and symmetry of nonlinear crystal show that the increase of the conversion efficiency is attributed to the local field enhancement caused by the magnetic resonnance of the structure. Our researches provide an additional way to further improve the optical nonlinearity in nanostructures. PMID:25401811
NSDL National Science Digital Library
Lawrence Hall of Science
2009-01-01
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.
NASA Astrophysics Data System (ADS)
Ren, Ming-Liang; Li, Zhi-Yuan
2012-04-01
Second harmonic generation (SHG) in a short nonlinear photonic bandgap (PBG) structure coated with distributed Bragg reflector (DBR) mirrors is theoretically investigated by means of an iteration approach that fully considers pump depletion. A total conversion efficiency of about 96% can be obtained in an optimized structure with a size scale of about 0.2 mm and at the modest pump intensity of about 0.133 MW/cm2, which is four orders of magnitude more than that in a quasi-phase-matching (QPM) structure with the same sample length. Such a high conversion efficiency of SHG will greatly facilitate the success of short frequency conversion devices and all-optical integration in nanostructures.
High-efficiency fourth harmonic generation
Jeffrey W. Pierce; Raymond G. Beausoleil
1995-01-01
The technique of Type I quadrature doubling has been used to generate 266 nm output from 532 nm input. Using a simple flashlamp pumped Nd:YAG laser doubled in KTP, the best conversion efficiency from the second harmonic to the fourth harmonic was 42% using two KDP crystals. With a second harmonic conversion efficiency of 60%, the total conversion efficiency from
NASA Astrophysics Data System (ADS)
Garmash, V. M.; Ermakov, G. A.; Pavlova, N. I.; Tarasov, A. V.
1986-10-01
Experiments are reported in which KTP crystals were used to achieve efficient doubling of the emission frequency of lasers based on Nd-alloyed yttrium orthoaluminate (wavelength, 1.0796 micron) under conditions of 90-deg synchronism characterized by an exceptionally large angular width of synchronism in comparison with critical synchronism and by the absence of the diaphragm aperture effect. It is thus possible to achieve a high mean power of laser emission in the green region of the visible spectrum by using the pair YA:Nd(3+)-KTP in the optical circuit of the laser.
P. W. Wheeler; J. C. Clare; L. Empringham; M. Bland; K. G. Kerris
2004-01-01
This paper deals with the vector-controlled MCT matrix converter induction motor drive with minimized commutation time and enchanced waveform quality. It also deals with the design, construction, and testing of a 10-kVA three-phase to three-phase matrix converter induction motor drive. The converter has been built using discrete 65 A metal-oxide-semiconductor (MOS) controlled thyristors (MCTs). The commutation time has been minimized
CAVE: the design of a precision metrology instrument for studying performance of KDP crystals
Hibbard, R.L., LLNL
1998-03-30
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.
Modeling of large aperture third harmonic frequency conversion of high power Nd:glass laser systems
Henesian, M.A.; Wegner, P.J.; Speck, D.R.; Bibeau, C.; Ehrlich, R.B.; Laumann, C.W.; Lawson, J.K.; Weiland, T.L.
1991-03-13
To provide high-energy, high-power beams at short wavelengths for inertial-confinement-fusion experiments, we routinely convert the 1.053-{mu}m output of the Nova, Nd:phosphate-glass, laser system to its third-harmonic wavelength. We describe performance and conversion efficiency modeling of the 3 {times} 3 arrays potassium-dihydrogen-phosphate crystal plates used for type II/type II phase-matched harmonic conversion of Nova 0.74-m diameter beams, and an alternate type I/type II phase-matching configuration that improves the third-harmonic conversion efficiency. These arrays provide energy conversion of up to 65% and intensity conversion to 70%. 19 refs., 11 figs.
In-phased second harmonic wave array generation with intra-Talbot-cavity frequency-doubling.
Hirosawa, Kenichi; Shohda, Fumio; Yanagisawa, Takayuki; Kannari, Fumihiko
2015-03-23
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:YVO? array laser. PMID:25837108
Fitzpatrick, G.O.
1987-05-19
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.
Application of the matrix converter to induction motor drives
Takayoshi Matsuo; Steffen Bernet; R. S. Colby; T.A. Lipo
1996-01-01
This paper presents the technical issues of applying the matrix power converter to field-oriented induction motor drives. A newly developed matrix power converter switching sequence combination is described in detail, the purpose of which is to minimize harmonic components of the matrix power converter input currents. It is demonstrated that small size capacitors work efficiently as input filters. Matrix power
H. J. Scott; L. J. Black
1938-01-01
When plate current in a vacuum-tube amplifier flows for only a portion of the grid-excitation cycle, harmonics appear in the output circuit. The magnitude of any one of these harmonics depends upon the fraction of the fundamental cycle during which plate current flows. In the gradual transition from perfect class A to extreme class C operation, the magnitude of the
Fitzpatrick, Gary O. (Livermore, CA)
1987-05-19
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.
Ebbers, Christopher A. (Livermore, CA); Davis, Laura E. (Manteca, CA); Webb, Mark (Salida, CA)
1992-01-01
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.
AC-DC converter with an improved input current waveform
Yuvarajan, S.; Weng, D.F.; Chen, M.S. [North Dakota State Univ., Fargo, ND (United States). Electrical Engineering Dept.
1995-12-31
The paper proposes a new control scheme for an ac-dc converter that will reduce the total harmonic distortion in the input current while operating at an improved power factor. The circuit uses a diode rectifier whose output is varied by a boost regulator with a second-harmonic injected PWM. An approximate analysis shows that the addition of a second harmonic component in the PWM helps to reduce the third harmonic in the input current. The design parameters are obtained using digital simulation. The results obtained on an experimental converter are compared with the ones obtained from a conventional scheme.
Radiating dipoles in photonic crystals
Kurt Busch; Nipun Vats; Sajeev John; Barry C. Sanders
2000-01-01
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
Harmonics and Resonance Issues with Wind Plants
Bradt, M. [IEEE PES Wind Plant Collector System Design Working Group; Badrzadeh, Babak [IEEE PES Wind Plant Collector System Design Working Group; Camm, E H [IEEE PES Wind Plant Collector System Design Working Group; Castillo, Nestor [IEEE PES Wind Plant Collector System Design Working Group; Mueller, David [IEEE PES Wind Plant Collector System Design Working Group; Siebert, T. [IEEE PES Wind Plant Collector System Design Working Group; Schoene, Jens [IEEE PES Wind Plant Collector System Design Working Group; Smith, Travis M [ORNL; Starke, Michael R [ORNL; Walling, R. [IEEE PES Wind Plant Collector System Design Working Group
2011-01-01
Wind plants are susceptible to lightly-damped resonances which can attract and amplify ambient grid harmonic distortion and magnify wind turbine harmonic generation. Long-accepted harmonic modeling assumptions and practices are not appropriate for wind plants. VSCs are not ideal current sources and grid impedance is important. Attention to modeling detail and thorough evaluation over range of conditions is critical to meaningful analysis. In general, wind turbines are very slight sources of harmonics. Most harmonic issues are a result of resonance, caused by capacitor banks (for reactive power compensation) or from the extensive underground cabling in a collector system. Converter controls instability can be exacerbated by power system resonances. In some cases this has caused severe voltage distorDon and other problems. The IEEE 519 recommended guidelines are very restrictive. I recommend that they are used to resolve serious harmonic issues, and not to create petty problems.
Compounds Generate Optical Second Harmonics
NASA Technical Reports Server (NTRS)
Marder, Seth R.; Perry, Joseph W.
1990-01-01
Newly synthesized organic salts found to generate relatively large second-harmonic signals when illuminated by fundamental signals in near-infrared spectrum. Made by crystallizing, with appropriate counterions, organic ions having large molecular hyperpolarizibilities. Large second-order nonlinear susceptibilities observed. These and other compounds having large nonlinear optical properties used in electro-optical modulators, switches, and signal-processing equipment.
Phase effects in the cascade generation of the fourth harmonic
Z. A. Tagiev; Sh. Sh. Amirov
1992-01-01
The cascade mechanism of fourth harmonic generation is investigated analytically using the approximation of specified intensity, with allowance made for the reverse response of the fourth harmonic to the fundamental emission phase. It is shown that the efficiency of a cascade fourth harmonic oscillator can be substantially increased by selecting optimal crystal lengths.
Michael, J. Robert; Volkov, Anatoliy
2015-01-23
The widely used pseudoatom formalism [Stewart (1976). Acta Cryst. A32, 565–574; Hansen & Coppens (1978). Acta Cryst. A34, 909–921] in experimental X-ray charge-density studies makes use of real spherical harmonics when describing the angular component of aspherical deformations of the atomic electron density in molecules and crystals. The analytical form of the densitynormalized Cartesian spherical harmonic functions for up to l 7 and the corresponding normalization coefficients were reported previously by Paturle & Coppens [Acta Cryst. (1988), A44, 6–7]. It was shown that the analytical form for normalization coefficients is available primarily for l 4 [Hansen & Coppens, 1978; Paturlemore »& Coppens, 1988; Coppens (1992). International Tables for Crystallography, Vol. B, Reciprocal space, 1st ed., edited by U. Shmueli, ch. 1.2. Dordrecht: Kluwer Academic Publishers; Coppens (1997). X-ray Charge Densities and Chemical Bonding. New York: Oxford University Press]. Only in very special cases it is possible to derive an analytical representation of the normalization coefficients for 4 4 the density normalization coefficients were calculated numerically to within seven significant figures. In this study we review the literature on the density-normalized spherical harmonics, clarify the existing notations, use the Paturle–Coppens (Paturle & Coppens, 1988) method in the Wolfram Mathematica software to derive the Cartesian spherical harmonics for l 20 and determine the density normalization coefficients to 35 significant figures, and computer-generate a Fortran90 code. The article primarily targets researchers who work in the field of experimental X-ray electron density, but may be of some use to all who are interested in Cartesian spherical harmonics.« less
Long-term operation of CsLiB6O10 crystal in fourth-harmonic generation of Nd:YAG laser
K. Deki; Y. Kagebayashi; N. Kitatochi; Y. Ohsako; M. Horiguchi; Y. K. Yap; Y. Mori; T. Sasaki; K. Yoshida
1998-01-01
Long-term operation of fourth-harmonic generation by CLBO was evaluated by two types of lasers. One type of laser produces a high peak power beam at low repetition rate, and the other type of laser produces low peak power but can run at a high repetition rate. Using the high peak power laser, more than 1000 h of stable operation was
Displacement angle control of matrix converter
Jun Oyama; Xiarong Xia; Tsuyoshi Higuchi; Eiji Yamada
1997-01-01
The authors previously proposed and discussed a control method for matrix power converters in which instantaneous input voltages are used. The method can generate output voltages of 0.866 times the supply voltage. Control input current and output voltage of sinusoidal waveform can be obtained and can compensate the effect of fluctuation, asymmetry or harmonics in both the output voltage and
NASA Astrophysics Data System (ADS)
Badalyan, A.; Hovsepyan, R.; Mantashyan, P.; Mekhitaryan, V.; Drampyan, R.
2014-07-01
A novel combined interferometric-mask method for the formation of micro- and nanometric scale three-dimensional (3D) rotational symmetry quasi-crystalline refractive lattice structures in photorefractive materials is demonstrated experimentally. The method is based on micrometric scale spatial modulation of the light by amplitude mask in the radial directions and along the azimuthal angle and the use of counter-propagating beam geometry building up Gaussian standing wave, which defines the light modulation in the axial direction with half-wavelength periodicity. 3D intensity pattern can be represented as numerous mask-generated 2D quasi-periodic structures located in each anti-node of the standing wave. The formed 3D intensity distributions of the optical beams can be imparted into the photorefractive medium thus creating the micro- and sub-micrometric scale 3D refractive index volume lattices. The used optical scheme allows also the formation of 2D lattices by removing the back-reflecting mirror. 2D and 3D refractive lattices were recorded with the use of 532 nm laser beam and rotational symmetry mask in doped lithium niobate crystals and were tested by the probe beam far-field diffraction pattern imaging and direct observation by phase microscope. The formed rotational symmetry 3D refractive structures have the periods of 20-60 ?m in the radial directions, 60 ?m along the azimuthal angle and half-wavelength 266 nm in the axial direction.
ON THE UNIQUENESS OF HEAT FLOW OF HARMONIC MAPS AND HYDRODYNAMIC FLOW OF
ON THE UNIQUENESS OF HEAT FLOW OF HARMONIC MAPS AND HYDRODYNAMIC FLOW OF NEMATIC LIQUID CRYSTALS of harmonic maps and hydrodynamic flow of nematic liquid crystals Fanghua Lin Changyou Wang Dedicated- ness of the heat flow of harmonic maps from M to N in the class C([0, T), W1,n ). For the hydrodynamic
Neil G. R. Broderick; Radu T. Bratfalean; Tanya M. Monro; David J. Richardson; C. Martijn de Sterke
2002-01-01
Using high-power nanosecond pulses, we measured the second-harmonic conversion efficiency of two-dimensional hexagonally poled lithium niobate as a function of temperature and wavelength. These results were compared with theoretical estimates and with measurements in one-dimensional periodically poled lithium niobate. We found that for a substantial range of parameters a two-dimensional noncollinear interaction has a broader tuning response than a one-dimensional
Wiggler magnetic field assisted second harmonic generation in clusters
NASA Astrophysics Data System (ADS)
Aggarwal, Munish; Vij, Shivani; Kant, Niti
2015-06-01
Wiggler magnetic field assisted second harmonic generation in clusters has been investigated theoretically. An intense short-pulse laser propagating through a gas embedded with atomic clusters, converts it into hot plasma balls. For clusters with radius less than one tenth of the laser wavelength, the nonlinear restoration force dominates, which leads to second harmonic generation. The magnetic wiggler provides the uncompensated momentum to second harmonic photon, to make the process of harmonic generation resonant. We explore the impact of laser intensity and cluster size on the efficiency of second harmonic generation. Pulse slippage of second harmonic pulse out of the domain of fundamental laser pulse has been observed on account of group velocity mismatch between the fundamental and second harmonic pulse. Enhancement in the efficiency of the second harmonic is seen for the optimum values of wiggler magnetic field.
Experimental evaluation of losses in magnetic components for power converters
J. A. Ferreira; J. D. van Wyk
1988-01-01
Optimization of copper and core losses is an important aspect of converter technology in the trend towards high frequency and high power density, ranging from high-frequency high-Q inductors in resonant converters, to high-power thyristor converters that impress complex current waveforms with significant harmonic content on line frequency transformers and electric machines. Core materials are obtained from manufacturers, so that a
Vladimir I Clue; William Kelleher; Anatoly Levin
2005-01-01
This paper describes a method of calculating the transforms, currently\\u000aobtained via Fourier and reverse Fourier transforms. The method allows\\u000acalculating efficiently the transforms of a signal having an arbitrary\\u000adimension of the digital representation by reducing the transform to a\\u000avector-to-circulant matrix multiplying. There is a connection between harmonic\\u000aequations in rectangular and polar coordinate systems. The connection\\u000aestablished
Harmonic analysis of current waveforms using optical current sensor
W. C. Michie; A. Cruden; P. Niewczas; W. I. Madden; J. R. McDonald; M. Gauduin
2001-01-01
This work reports on the research and development of an optical current sensor for harmonic analysis within the electricity supply network. The device has a measurement capability, limited by the sampling frequency of the A\\/D converter, to around 20 kHz. We report on experimental verification of these measurements up to the 80th harmonic (4 kHz)
Harmonic analysis of current waveforms using optical current sensor
W. C. Michie; A. Cruden; P. Niewczas; W. I. Madden; J. R. McDonald; M. Gauduin
2002-01-01
This paper reports on the research and development of an optical current sensor for harmonic analysis within the electricity supply network. The device has a measurement capability, limited by the sampling frequency of the analog-to-digital converter, to around 20 kHz. We report on experimental verification of these measurements up to the 60th harmonic (3 kHz).
Second-harmonic generation in nonlinear left-handed metamaterials
Second-harmonic generation in nonlinear left-handed metamaterials Ilya V. Shadrivov, Alexander A August 21, 2005 We study the second-harmonic generation (SHG) in left-handed metamaterials that this novel parametric process can convert a surface of the left-handed metamaterial into an effective mirror
Kino-Dynamic, Harmonic, Potential-based Motion Planning
Ahmad A. Masoud
2006-01-01
This paper extends the capabilities of the harmonic potential field (HPF) approach to planning to cover both the kinematic and dynamic aspects of a robot's motion. The suggested approach converts the gradient guidance field from a harmonic potential to a control signal by augmenting it with a novel type of dampening forces suggested in this paper called: nonlinear, anisotropic, dampening
Switching Power Converter A/D Converters
Controller Health Monitoring Efficiency Monitoring Frequency Response Monitoring Health Monitoring Sensing Points Figure 1. System architecture for health monitoring test-bed. Converter parameters are sensed then displays processed data concerning the converter health status. Online Health Monitoring in Digitally
G. P. Srivastava; S. Mohan; S. C. Gupta
1976-01-01
The behaviour of optical second harmonic due to crystal inhomogeneity and self-induced thermal effect has been considered for a focused laser beam. Temperature profile created due to a fundamental laser beam along the crystal length shows an increase in temperature band width for various values of focusing parameter (). Normalized second harmonic power in inhomogeneous crystals increases up to an
Boyer, Edmond
LINEAR TIME PERIODIC MODELLING OF POWER ELECTRONIC DEVICES FOR POWER SYSTEM HARMONIC ANALYSIS for modelling and analysis of multi-converter systems. In order to take the harmonic interactions into account by better precision, but are too complicated for being applied for harmonic analysis when the system
P. W. Lehn; K. L. Lian
2007-01-01
When a power-electronic converter is introduced into a linear network, voltage and current harmonics of differing orders become coupled (through the modulation effect of the converter). The interharmonic coupling introduced by the modulation effect of a converter may be mathematically represented through a frequency coupling matrix (FCM). Given that the source of the coupling is a modulation process, researchers have,
Conducted RFI emission from an AC-DC converter with sinusoidal line current
J. Mahdavi; J. Roudet; R. Scheich; J. P. Rognon
1993-01-01
The authors discuss the generation and modeling of conducted electromagnetic interference (EMI) in a single-phase AC\\/DC power converter with sinusoidal line current at unity power factor. The converter is composed of a diode rectifier and a conventional boost converter with pulsewidth modulation (PWM) control. Due to this control mode the input current has a very low content of harmonics (the
Bennett, Charles L.; Sewall, Noel; Boroa, Carl
2014-08-19
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.
X-ray second harmonic generation.
Shwartz, S; Fuchs, M; Hastings, J B; Inubushi, Y; Ishikawa, T; Katayama, T; Reis, D A; Sato, T; Tono, K; Yabashi, M; Yudovich, S; Harris, S E
2014-04-25
We report clear experimental evidence for second harmonic generation at hard x-ray wavelengths. Using a 1.7 Å pumping beam generated by a free electron laser, we observe second harmonic generation in diamond. The generated second harmonic is of order 10 times the background radiation, scales quadratically with pump pulse energy, and is generated over a narrow phase-matching condition. Of importance for future experiments, our results indicate that it is possible to observe nonlinear x-ray processes in crystals at pump intensities exceeding 1016??W/cm2. PMID:24815649
Third-harmonic performance of the Beamlet prototype laser
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
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.
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.
Analysis and Design of New Harmonic Mitigation Approaches
Aeloiza Matus, Eddy 1972-
2012-11-01
-pulse rectifiers are based on the principle of harmonic cancellation through phase shifting and are the preferred solution to eliminate harmonics in high power converters in large motor drives, electro-winning rectifiers and HVDC transmission systems [23...-voltage systems can have up to 2.0% THD where the cause is an HVDC terminal that will attenuate by the time it is tapped for user. Individual Harmonic Order (Odd Harmonics) Isc / IL <11 11 ? h"? 17 17 ? h"? 23 23 ? h"? 35 h"? 35 TDD <20 * 4.0 2...
Harmonic analysis of spacecraft power systems using a personal computer
NASA Technical Reports Server (NTRS)
Williamson, Frank; Sheble, Gerald B.
1989-01-01
The effects that nonlinear devices such as ac/dc converters, HVDC transmission links, and motor drives have on spacecraft power systems are discussed. The nonsinusoidal currents, along with the corresponding voltages, are calculated by a harmonic power flow which decouples and solves for each harmonic component individually using an iterative Newton-Raphson algorithm. The sparsity of the harmonic equations and the overall Jacobian matrix is used to an advantage in terms of saving computer memory space and in terms of reducing computation time. The algorithm could also be modified to analyze each harmonic separately instead of all at the same time.
Zhang, Yun; Sato, Yusuke; Watanabe, Nobuyoshi; Ananda, Riskey; Okada-Shudo, Yoshiko; Watanabe, Masayoshi; Hyodo, Masaharu; Wang, Xiaoyang; Chen, Chuangtian; Kanai, Teruto; Watanabe, Shuntaro
2009-05-11
We report the generation of quasi-continuous-wave vacuum-ultraviolet (VUV) coherent light based on a Ti:sapphire laser with two successive frequency doubling stages. In the first stage, UV light at 399 nm with power of 1.1 W was obtained by exploiting an enhanced cavity. With a KBBF crystal as nonlinear material, quasi-continuous-wave VUV coherent light with power of about 25 mW at 199.5 nm and 4.7 mW at 193.5 nm were achieved through a single-pass SHG configuration, respectively, in the second stage. PMID:19434143
RTP as an effective frequency doubling crystal for the radiation of yttrium ortoaluminat laser
NASA Astrophysics Data System (ADS)
Pisarevsky, A. I.; Prosvirnin, A. L.; Oseledchik, Yuriy S.; Osadchuk, V. V.; Belokris, S. P.; Starshenko, V. V.; Kasjan, M. M.
1992-11-01
Efficiency of conversion to second harmonics of the radiation at (lambda) equals 1079 nm from the rubidium titanil phosphate crystal and of conversion to high harmonics on BBO crystals is investigated.
Wang, F.; Velsko, S.P.
1989-10-24
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.
Nd-laser installation for effective fourth harmonic generation
I. A. Bufetov; S. B. Kravtsov; V. B. Fedorov
1996-01-01
The process of fourth harmonic generation in multicascade laser installation is experimentally investigated. The operative correction of phase synchronism in nonlinear crystals permits to compensate an installation parameters drift and provides stable radiation conversion to the 4th harmonic with efficiency 0.4 divided by 0.5 at E4 approximately 10 J.
Fourth harmonic generation in a resonant ring cavity
Joachim Knittel; A. H. Kung
1997-01-01
We have analyzed the generation of the fourth harmonic of pulsed laser radiation in a ring cavity that resonates at the second harmonic wavelength. With the help of numerical simulation, the dependence of the conversion efficiency on input laser power as well as cavity loss and nonlinear crystal coefficient is obtained. The model predicts over 50% conversion from the fundamental
A Submillimeter Measurement System Using a Harmonic Mixing Superheterodyne Receiver
J. M. Cotton
1963-01-01
A measurement system for use in the submillimeter wavelength region has been assembled and evaluated. This system utilizes two 70-Gc klystron sources and operates as high as the sixth harmonic. One of these sources provides the fundamental input power for a crystal harmonic generator which serves as the transmitter. The other klystron serves as a fundamental local oscillator for the
NASA Astrophysics Data System (ADS)
Aouani, Heykel; Rahmani, Mohsen; Navarro-Cía, Miguel; Maier, Stefan A.
2014-04-01
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
The ability to convert low-energy quanta into a quantum of higher energy is of great interest for a variety of applications, including bioimaging, drug delivery and photovoltaics. Although high conversion efficiencies can be achieved using macroscopic nonlinear crystals, upconverting light at the nanometre scale remains challenging because the subwavelength scale of materials prevents the exploitation of phase-matching processes. Light-plasmon interactions that occur in nanostructured noble metals have offered alternative opportunities for nonlinear upconversion of infrared light, but conversion efficiency rates remain extremely low due to the weak penetration of the exciting fields into the metal. Here, we show that third-harmonic generation from an individual semiconductor indium tin oxide nanoparticle is significantly enhanced when coupled within a plasmonic gold dimer. The plasmonic dimer acts as a receiving optical antenna, confining the incident far-field radiation into a near field localized at its gap; the indium tin oxide nanoparticle located at the plasmonic dimer gap acts as a localized nonlinear transmitter upconverting three incident photons at frequency ? into a photon at frequency 3?. This hybrid nanodevice provides third-harmonic-generation enhancements of up to 10(6)-fold compared with an isolated indium tin oxide nanoparticle, with an effective third-order susceptibility up to 3.5 × 10(3) nm V(-2) and conversion efficiency of 0.0007%. We also show that the upconverted third-harmonic emission can be exploited to probe the near-field intensity at the plasmonic dimer gap. PMID:24608232
Enhanced ?erenkov second-harmonic emission in nonlinear photonic structures.
Kalinowski, K; Roedig, P; Sheng, Y; Ayoub, M; Imbrock, J; Denz, C; Krolikowski, W
2012-06-01
We study experimentally and theoretically the ?erenkov-type second-harmonic generation in a one-dimensional nonlinear photonic crystal. We demonstrate that the power of emitted second-harmonic can be enhanced 270 times by varying the angle of incidence of the fundamental beam such that the reciprocal lattice vector of the crystal can be used to compensate for the phase mismatch in the transverse direction enabling interaction in the nonlinear Bragg diffraction regime. PMID:22660044
Yin, Yaling; Lv, Xinjie; Zhao, Lina; Cao, Jingxiao; Yuan, Ye; Zhang, Chao; Leng, Hanyang; Xie, Zhenda; Xu, Ping; Zhao, Gang; Zhu, Shining
2011-03-14
We experimentally demonstrate a compact, all-solid-state 532 nm semi-Gaussian laser beam (SGB) source based on a 1064 nm laser and a transversely varying periodically-poled LiTaO3 (TPPLT) crystal as the laser beam shaper as well as the nonlinear frequency converter. We have used the designed TPPLT crystal to obtain a neat 532nm SGB with the quality of QSGB=1:17.5 by a single-pass second harmonic generation. The dependence of the generated SGB quality on the designed TPPLT parameter and the potential applications of the neat SGB are also discussed. PMID:21445167
Efficient polarization converter for projection displays
to achieve a high level of conversion of unpolarized to polarized light, including the use of cholesteric LCEfficient polarization converter for projection displays W. C. Yip, H. C. Huang, and H. S. Kwok In the waveguiding limit, a twisted nematic liquid crystal cell behaves as an achromatic polarization rotator. We
Thermoacoustic Space Power Converter
Emanuel Tward; Michael Petach; Scott Backhaus
2003-01-01
A thermoacoustic power converter for use in space in the conversion of radioisotope-generated heat to electricity is under development. The converter incorporates a thermoacoustic driver that converts heat to acoustic power without any moving parts. The acoustic power is used to drive a pair of flexure bearing supported pistons connected to voice coils in a vibrationally balanced pair of moving
Jeremy C. Stein
1992-01-01
This paper argues that corporations may use convertible bonds as an indirect (albeit possibly risky) method for getting equity into their capital structures in situations where adverse selection problems make a conventional stock issue unattractive. Unlike other theories of convertible bond issuance, the model of this paper highlights: 1) the importance of call provisions on convertibles; and 2) the significance
Color harmonization for images
NASA Astrophysics Data System (ADS)
Tang, Zhen; Miao, Zhenjiang; Wan, Yanli; Wang, Zhifei
2011-04-01
Color harmonization is an artistic technique to adjust a set of colors in order to enhance their visual harmony so that they are aesthetically pleasing in terms of human visual perception. We present a new color harmonization method that treats the harmonization as a function optimization. For a given image, we derive a cost function based on the observation that pixels in a small window that have similar unharmonic hues should be harmonized with similar harmonic hues. By minimizing the cost function, we get a harmonized image in which the spatial coherence is preserved. A new matching function is proposed to select the best matching harmonic schemes, and a new component-based preharmonization strategy is proposed to preserve the hue distribution of the harmonized images. Our approach overcomes several shortcomings of the existing color harmonization methods. We test our algorithm with a variety of images to demonstrate the effectiveness of our approach.
NONLINEAR OPTICAL EFFECTS AND INSTRUMENTS: Phase effects in multistage fourth-harmonic generation
Z. A. Tagiev; Sh Sh Amirov
1992-01-01
An analysis is made of the process of multistage fourth-harmonic generation. Use is made of the approximation of a constant intensity and an allowance is made for the reaction of the fourth harmonic on the phase of the fundamental (first-harmonic) radiation. It is shown that selection of the optimal lengths of crystals can ensure a considerable increase in the efficiency
Voltage source ac-to-dc converters for high-power transmitters
NASA Technical Reports Server (NTRS)
Cormier, R.
1990-01-01
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.
Rotorcraft convertible engine study
NASA Technical Reports Server (NTRS)
Gill, J. C.; Earle, R. V.; Mar, H. M.
1982-01-01
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.
Visible quasi-phase-matched harmonic generation by electric-field-poled lithium niobate
NASA Astrophysics Data System (ADS)
Miller, Gregory D.; Batchko, Robert G.; Fejer, Martin M.; Byer, Robert L.
1996-05-01
Laser-based displays and illumination systems are applications which can capitalize on the brightness and efficiency of semiconductor lasers, provided that there is a means for converting their output into the visible spectrum. Semiconductor laser manufacturers can adjust their processes to achieve desired wavelengths in several near-infrared bands; an equally agile conversion technology is needed to permit display and illumination system manufacturers to choose visible wavelengths appropriate to their products. Quasi- phasematched second harmonic generation has the potential to convert high-power semiconductor laser output to the visible with 50% optical-to-optical conversion efficiency in a single-pass bulk configuration, using electric-field-poled lithium niobate. Lithographically- defined electrode structures on the positive or negative polar faces of this crystal are used to control the formation of domains under the influence of electric fields applied using those electrode structures. The quality of the resulting domain patterns not only controls the efficiency of quasi-phasematched second harmonic generation, but also controls the degree of resistance to photorefractive damage. We present a model which is used to identify the optimum electrode duty cycle and applied poling field for domain patterning and compare the predicted domain duty cycle with experimental results. We discuss factors which contribute to inhomogeneous domain pattern quality for samples poled under otherwise ideal conditions and our progress in limiting their influence. Finally, we present optical characterization of a 2.4 mm long 500 micrometers thick sample which produced an average second harmonic power of 1.3 W of 532 nm green from a 9 W average power Q-switched 1064 nm Nd:YAG laser in a loose- focus single-pass configuration.
A general approach for the analysis of the input power quality in matrix converters
Domenico Casadei; Giovanni Serra; Angelo Tani
1998-01-01
In this paper, a general approach based on a linearized analysis is employed in order to determine the matrix converter performance in terms of input-current quality. Considering input disturbances such as voltage unbalance and voltage distortion as a linear deviation from the fundamental harmonic component, it is possible to evaluate analytically the input-current harmonic content. It is emphasized that the
Simple Harmonic Motion in Harmonic Plane Waves.
ERIC Educational Resources Information Center
Benumof, Reuben
1980-01-01
Discusses the distribution of kinetic and potential energy in transverse and longitudinal waves and examines the transmission of power and momentum. This discussion is intended to aid in understanding the simple harmonic motion of a particle involved in the propagation of a harmonic mechanical plane wave. (HM)
P. S. Howe
1998-12-15
A short survey of some aspects of harmonic superspace is given. In particular, the $d=3, N=8$ scalar supermultiplet and the $d=6, N=(2,0)$ tensor multiplet are described as analytic superfields in appropriately defined harmonic superspaces.
Harmonization of Biodiesel Specifications
Alleman, T. L.
2008-02-01
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.
IEEE POWER ELECTRONICS LETTERS 1 Harmonic Optimization of Multilevel Converters
Tolbert, Leon M.
by a contractor of the U.S. Government under Contract no. DE-AC05-00OR22725. Accordingly, the U.S. Government inverter to feed a load or interconnect to the ac grid without voltage balancing problems. In addition. This solves the same problem with a simpler Manuscript received February 2, 2005; revised June 10, 2005
Harmonic synchronizations of spacetime
Bona, C.; Masso, J.
1988-10-15
The spacetime slicings associated with a harmonic time coordinate (harmonic synchronizations) are considered and their usefulness in the field of numerical relativity is studied. Harmonic synchronizations are shown to avoid singularities in the same way that the widely used maximal slicings do. Both kinds of slicing are compared in stationary axisymmetric spacetimes, homogeneous cosmological models, and Kerr-Newman black holes.
Michalakis A. Averkiou
2000-01-01
Harmonic imaging was originally developed for microbubble contrast agents in the early 90s under the assumption that tissue is linear and all harmonic echoes are generated by the bubbles. In fact, tissue, like bubbles, is a nonlinear medium. Whereas the harmonic echoes from bubbles have their origins in nonlinear scattering, those from tissue are a result of nonlinear propagation. The
Tissue harmonic ultrasonic imaging
Michalakis A. Averkiou
2001-01-01
Harmonic imaging was originally developed for microbubble contrast agents in the early 90s under the assumption that tissue is linear and all harmonic echoes are generated by the bubbles. In fact, tissue, like bubbles, is a nonlinear medium. Whereas the harmonic echoes from bubbles have their origins in nonlinear scattering, those from tissue are a result of nonlinear propagation. The
Tao, Terence
HARMONIC ANALYSIS TERENCE TAO Analysis in general tends to revolve around the study of general functions as input, and return some other function as output). Harmonic analysis1 focuses in particular Strictly speaking, this sentence describes the field of real-variable harmonic analysis. There is another
Zhu, Lizhi (Canton, MI)
2007-11-13
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.
ITER convertible blanket evaluation
Wong, C.P.C.; Cheng, E.
1995-09-01
Proposed International Thermonuclear Experimental Reactor (ITER) convertible blankets were reviewed. Key design difficulties were identified. A new particle filter concept is introduced and key performance parameters estimated. Results show that this particle filter concept can satisfy all of the convertible blanket design requirements except the generic issue of Be blanket lifetime. If the convertible blanket is an acceptable approach for ITER operation, this particle filter option should be a strong candidate.
NSDL National Science Digital Library
GraphicConverter goes beyond the ability to convert a large number of graphic file formats. It provides tools for the creation and/or editing of graphics, animations, movies, and slide presentations; it also supports Adobe Photoshop compatible plug-ins. Currently, GraphicConverter can import 96 different graphic file formats and export 38. Conversion of several files (graphic or text) at a time is also possible through the "convert more..." feature. The tools offered for graphic editing are Photoshop-like. Detailed documentation is provided. This Macintosh shareware is provided by Lemke Software.
Tertiary side resonant DC/DC converter with integrated magnetics
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
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.
Harmonic generation in 2D layered materials
NASA Astrophysics Data System (ADS)
Janisch, Corey; Ma, Ding; Mehta, Nikhil; Laura-Elias, Ana; Perea-Lopez, Nestor; Terrones, Mauricio; Liu, Zhiwen
2014-09-01
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 .
Direct power control of PWM converter without power-source voltage sensors
Toshihiko Noguchi; Hiroaki Tomiki; Seiji Kondo; Isao Takahashi
1998-01-01
This paper proposes a novel control strategy of a pulsewidth modulation (PWM) converter with no power-source voltage sensors. The strategy has two main features to improve a total power factor and efficiency, taking harmonic components into account without detecting the voltage waveforms. One feature is a direct instantaneous power control technique for the converter, which has been developed to control
Characterization of differential-mode filter for grid-side converters
W.-T. Franke; J. Dannehl; F. W. Fuchs; M. Liserre
2009-01-01
Pulse width modulated voltage source converters (PWM-VSC) could be the universal interface for distributed power producers, loads, storage, power conditioning and transmission systems to the future smart grid. The differential mode filter used to connect the PWM-VSC to the electric grid has a crucial role in the proper operation of the converter and in filtering PWM switching harmonics. The paper
Design and simulation of a matrix converter-fed scalar controlled synchronous motor drive
Prasad Kulkarni; Meharegzi Tewolde Abraham; Shyama P Das
2008-01-01
Matrix converter is an ac\\/ac converter without a dc link. It acts much the same way as a cycloconverter, but with better harmonic profile, large range of output frequency and controllable input displacement factor. A synchronous motor is used in many industrial applications such as cement kilns, mine winders, etc. Although synchronous motors are mostly used for high power applications,
Comparison of conducted RFI emission from different unity power factor AC\\/DC converters
J. Mahdavi; M. Tabandeh; A. K. Shahriari
1996-01-01
Low frequency harmonics injection into AC power supply and small power factor are the main disadvantages of conventional AC\\/DC converters. By using current mode control, the converter can be designed such that its input current have a sinusoidal form and in phase with the power supply voltage. By solving the problem of power factor with high frequency switching current mode
A matrix converter using reverse blocking NPT-IGBTs and optimized pulse patterns
Steffen Bernet; Takayoshi Matsuo; T.A. Lipo
1996-01-01
The paper compares three-phase to three-phase IGBT matrix converters in which required four-quadrant switches are realized by conventional common collector configurations and a sophisticated semiconductor loss model is used to compute the converter losses for both switch configurations. New pulse patterns are derived to minimize the input current harmonics
Linking high harmonics from gases and solids.
Vampa, G; Hammond, T J; Thiré, N; Schmidt, B E; Légaré, F; McDonald, C R; Brabec, T; Corkum, P B
2015-06-25
When intense light interacts with an atomic gas, recollision between an ionizing electron and its parent ion creates high-order harmonics of the fundamental laser frequency. This sub-cycle effect generates coherent soft X-rays and attosecond pulses, and provides a means to image molecular orbitals. Recently, high harmonics have been generated from bulk crystals, but what mechanism dominates the emission remains uncertain. To resolve this issue, we adapt measurement methods from gas-phase research to solid zinc oxide driven by mid-infrared laser fields of 0.25 volts per ångström. We find that when we alter the generation process with a second-harmonic beam, the modified harmonic spectrum bears the signature of a generalized recollision between an electron and its associated hole. In addition, we find that solid-state high harmonics are perturbed by fields so weak that they are present in conventional electronic circuits, thus opening a route to integrate electronics with attosecond and high-harmonic technology. Future experiments will permit the band structure of a solid to be tomographically reconstructed. PMID:26108855
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.
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.
The microminiature thermionic converter
Donald Bryan King
2000-01-01
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
NASA Astrophysics Data System (ADS)
Linke, Heiner
2013-03-01
An overview is given of the types of energy converters considered by this symposium: systems that make use of nanoscale phenomena and nanotechnology to achieve higher conversion efficiency, to achieve qualitatively enhanced performance, or to access new energy resources. The focus is on general concepts and principles, and approaches used by several nanoscale energy converters are identified.
Photocapacitive image converter
NASA Technical Reports Server (NTRS)
Miller, W. E.; Sher, A.; Tsuo, Y. H. (inventors)
1982-01-01
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.
Cascaded resonant bridge converters
NASA Technical Reports Server (NTRS)
Stuart, Thomas A. (Inventor)
1989-01-01
A converter for converting a low voltage direct current power source to a higher voltage, high frequency alternating current output for use in an electrical system where it is desired to use low weight cables and other circuit elements. The converter has a first stage series resonant (Schwarz) converter which converts the direct current power source to an alternating current by means of switching elements that are operated by a variable frequency voltage regulator, a transformer to step up the voltage of the alternating current, and a rectifier bridge to convert the alternating current to a direct current first stage output. The converter further has a second stage series resonant (Schwarz) converter which is connected in series to the first stage converter to receive its direct current output and convert it to a second stage high frequency alternating current output by means of switching elements that are operated by a fixed frequency oscillator. The voltage of the second stage output is controlled at a relatively constant value by controlling the first stage output voltage, which is accomplished by controlling the frequency of the first stage variable frequency voltage controller in response to second stage voltage. Fault tolerance in the event of a load short circuit is provided by making the operation of the first stage variable frequency voltage controller responsive to first and second stage current limiting devices. The second stage output is connected to a rectifier bridge whose output is connected to the input of the second stage to provide good regulation of output voltage wave form at low system loads.
Multipulse AC–DC Converters for Improving Power Quality: A Review
Bhim Singh; Sanjay Gairola; Brij N. Singh; Ambrish Chandra; Kamal Al-Haddad
2008-01-01
Three-phase multipulse AC-DC converters (MPC) are developed for improving power quality to reduce harmonics in AC mains and ripples in DC output. This paper deals with the multipulse AC-DC converter configurations, state of art, their performance, power quality aspects, components selection considerations, latest trends, future developments, and potential applications. It is targeted to provide broad perspective on multipulse converter technology
Harmonic leakage and image quality degradation in tissue harmonic imaging
Che-Chou Shen; Pai-Chi Li
2001-01-01
Image quality degradation caused by harmonic leakage was studied for finite amplitude distortion-based harmonic imaging. Various sources of harmonic leakage, including transmit waveform, signal bandwidth, and system nonlinearity, were investigated using both simulations and hydrophone measurements. Effects of harmonic leakage in the presence of sound velocity inhomogeneities were also considered. Results indicated that sidelobe levels of the harmonic beam pattern
Lab 5: Damped simple harmonic motion Simple harmonic oscillation
Glashausser, Charles
Lab 5: Damped simple harmonic motion · Simple harmonic oscillation · Damped harmonic oscillation;Friction: retarding motion (energy dissipation) Damped simple harmonic oscillation 1 2 Hooke's law: Damping 381 Mechanics #12;Ideal case: no friction Simple harmonic oscillation Hooke's law: Newton's 2nd law: F
Yokotani, A.; Sasaki, T.; Yoshida, K.; Nakai, S. (Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565, Japan (JP))
1989-12-25
L-arginine phosphate monohydrate (LAP) and deuterated LAP (DLAP) are new organic nonlinear optical materials useful for higher harmonics of radiation from high-power lasers. We measured the bulk laser damage threshold of these crystals using light from a 1.05 {mu}m laser with 1 and 25 ns pulse widths and 0.53 {mu}m laser light with 0.6 and 20 ns pulse widths. In every case, these crystals show much higher thresholds than potassium dihydrogen phosphate (KDP) and fused silica. These crystals are very interesting not only as a frequency converter but also as other optical components of high-power lasers, because of their extremely high damage threshold.
Thermoacoustic Space Power Converter
NASA Astrophysics Data System (ADS)
Tward, Emanuel; Petach, Michael; Backhaus, Scott
2003-01-01
A thermoacoustic power converter for use in space in the conversion of radioisotope-generated heat to electricity is under development. The converter incorporates a thermoacoustic driver that converts heat to acoustic power without any moving parts. The acoustic power is used to drive a pair of flexure bearing supported pistons connected to voice coils in a vibrationally balanced pair of moving coil alternators. Initial tests of the small ~100W thermoacoustic driver have demonstrated good efficiency. An alternator matched to the driver is now under construction. A description of the system and the results of development tests are presented.
Microminiature thermionic converters
King, Donald B. (Albuquerque, NM); Sadwick, Laurence P. (Salt Lake City, UT); Wernsman, Bernard R. (Clairton, PA)
2001-09-25
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.
Fluorescent radiation converter
NASA Technical Reports Server (NTRS)
Viehmann, W.
1980-01-01
Fluorescent radiation converter used optically transparent substrate. One side of substrate is coated with plastic film containing fluorescent organic dyes that absorb optical radiation at one wavelength and emit it at longer one. Coating is formulated to respond to specific wavelengths. Emitted radiation is reflected internally inside substrate, amplifying intensity that reaches radiation detector. Converter can be made in several shapes and size; round and square bars coated all round their lengths are useful in converting relatively intense radiation and transmitting it through substrate over lengthy distances.
Schmitt, M.J.
1991-01-01
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.
Thermionic photovoltaic energy converter
NASA Technical Reports Server (NTRS)
Chubb, D. L. (inventor)
1985-01-01
A thermionic photovoltaic energy conversion device comprises a thermionic diode mounted within a hollow tubular photovoltaic converter. The thermionic diode maintains a cesium discharge for producing excited atoms that emit line radiation in the wavelength region of 850 nm to 890 nm. The photovoltaic converter is a silicon or gallium arsenide photovoltaic cell having bandgap energies in this same wavelength region for optimum cell efficiency.
Gallium phosphide energy converters
P. E. Sims; L. C. Dinetta; M. A. Goetz
1995-01-01
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
Multistep cascading and fourth-harmonic generation
Andrey A. Sukhorukov; Tristram J. Alexander; Yuri S. Kivshar
2001-01-01
A concept of multistep cascading is applied to the problem of fourth-harmonic generation (FHG) in a single quadratic crystal, and a new model of parametric wave mixing is analyzed in detail. Important applications to the optical frequency division and efficient FHG as well as the realization of the double-phase-matching multistep cascading processes in engineered QPM structures with phase-reversal sequences are
C. K. Duffey; R. P. Stratford
1988-01-01
The authors present the changes in IEEE STD 519-1981, titled IEEE Guide for Harmonic Control and Reactive Compensation of Static Power Converters, that are to be made in 1988 as the result of a two-year review. The voltage distortion criteria in the 1981 edition could not be used to distribute among users, the ability of the utility system to absorb
Spatiotemporal toroidal waves from the transverse second-harmonic generation.
Saltiel, Solomon M; Neshev, Dragomir N; Fischer, Robert; Krolikowski, Wieslaw; Arie, Ady; Kivshar, Yuri S
2008-03-01
We study the second-harmonic generation via transversely matched interaction of two counterpropagating ultrashort pulses in chi(2) photonic structures. We show that the emitted second-harmonic wave attains the form of spatially expanding toroid with the initial thickness given by the cross correlation of the pulses. We demonstrate the formation of such toroidal waves in crystals with random ferroelectric domains as well as in annularly poled nonlinear photonic structures. PMID:18311314
Selection rules for harmonic generation in solids
NASA Astrophysics Data System (ADS)
Moiseyev, Nimrod
2015-05-01
High-order harmonic generation (HHG) in a bulk crystal was first observed in 2011 [S. Ghimire, A. D. DiChiara, E. Sistrunk, P. Agostini, L. F. DiMauro, and D. A. Reis, Nat. Phys. 7, 138 (2011), 10.1038/nphys1847]. Only odd-order harmonics were observed as expected on the basis of the selection rules in solids, which were derived when only the interband currents were taken into consideration. Here we study HHG in solids when the intraband currents are taken into consideration as well. We show that the dynamical selection rules are broken in solids and the possibility of generation of even-order harmonics cannot be excluded on the basis of the dynamical symmetry analysis. However, a simple analysis of the expression we obtained for the amplitude of the emitted high-order harmonics shows, without the need to carry out numerical calculations, that the even-order harmonics are suppressed due to the localization of the field-free one-electron density probability on the atoms in the solids.
HARMONIC FUNCTIONS WITH POLYNOMIAL GROWTH
Minicozzi, William
HARMONIC FUNCTIONS WITH POLYNOMIAL GROWTH TOBIAS 1 1. Harmonic functions with polynomial growth on cones 5 2. Tools to study the growth of harmonic functions on manifolds 13 3. Lower bound of the frequency
Quadripartite entangled state from cascaded second-harmonic generation
NASA Astrophysics Data System (ADS)
Yang, Rui; Zhai, Shu-Qin; Yang, Rong-Guo
2014-04-01
A generation system of continuous-variable (CV) quadripartite entangled state based on two cascaded second-harmonic generation (SHG) cavities below the threshold is investigated. Two reflected fundamental beams of the first cavity, the reflected second-harmonic beam and the output fourth-harmonic beam of the second cavity are proved to be entangled, and the dependence of the entanglement degree on the normalized frequency, pump parameter, fourth-harmonic loss parameter, and second-harmonic loss parameter is also analyzed. Due to the fact that the cavity parameters and the nonlinear crystals of the two SHG cavities can be freely chosen, the practicality of the proposed protocol is relatively perfect and the system can also be extended to the preparation of multicolor entangled states for a quantum network.
Development of AC and DC Power Supply Direct Interface Converter
NASA Astrophysics Data System (ADS)
Kato, Koji; Itoh, Jun-Ichi
This paper proposes a novel control method for a direct interface converter for management of the energy flow in either an AC or DC supply. The proposed converter is constructed based on an indirect matrix converter. Therefore a proposed control strategy is based on an indirect control method with a triangular carrier wave. The basic operation of the proposed control method is confirmed by experimental results. In addition, this paper also proposes a commutation error compensation method of an output voltage error and an input current error for an indirect matrix converter. In the proposed method, the output voltage and input current error by the commutation can be compensated at the same time, because the PWM pulse of each switch is directly compensated. The validity of the proposed method is confirmed by experimental results. Those results prove that the proposed compensation method can decrease total harmonic distortion (THD) of the input and output current.
Mikhail Slepchenkov; Keyue Smedley
2009-01-01
This paper addresses some major problems in steel plant power systems such as voltage fluctuations and flicker, load unbalance, current harmonics and reactive power and demonstrates the significance of reactive power management for steel plants power system. Two One-Cycle Control techniques for Hexagram Converter based STATCOM are presented. The first technique effectively achieves load balancing, harmonic filtering and reactive power
D. F. Chen; K. C. Yao
2006-01-01
The matrix converter is a single stage ac-ac power conversion device without dc-link energy storage elements. Any disturbance in the input voltages will be immediately reflected to the output voltages. Line voltage source unbalances can result in unwanted input harmonic currents. In order to eliminate the harmonic contents of the input current, the paper proposes a new switching strategy for
Multilevel converters-a new breed of power converters
Jih-Sheng Lai; Fang Zheng Peng
1996-01-01
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
L. A. Golovan’; A. M. Zheltikov; P. K. Kashkarov; N. I. Koroteev; M. G. Lisachenko; A. N. Naumov; D. A. Sidorov-Biryukov; V. Yu. Timoshenko; A. B. Fedotov
1999-01-01
Efficient generation of the second optical harmonic is observed experimentally in a multilayer periodic structure based on\\u000a porous silicon. The second-harmonic signal is much stronger than the signal from a uniform porous silicon layer or from the\\u000a single-crystal silicon substrate. The orientational dependence of the second-harmonic signal is isotropic. The second-harmonic\\u000a intensity as a function of the reflection angle reaches
Wang, F.; Velsko, S.P.
1988-08-15
A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a harmonic generating unit'' which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyle hydroxyyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.
Wang, Francis (Danville, CA); Velsko, Stephan P. (Livermore, CA)
1989-01-01
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.
Rotorcraft convertible engine study
NASA Technical Reports Server (NTRS)
Goldstein, D. N.; Hirschkron, R.; Smith, C. E.
1983-01-01
Convertible propulsion systems for advanced rotorcraft are evaluated in terms of their impact on aircraft operating economics and fuel consumption. A variety of propulsion system concepts, including separate thrust and power producing engines, convertible fan/shaft engines, and auxiliary propeller configurations are presented. The merits of each are evaluated in two different rotorcraft missions: an intercity, commercial transport of the ABC(TM) type, and an offshore oil ring supply ship of the X-wing type. The variable inlet guide vane fan/shaft converting engine and auxiliary propeller configurations are shown to offer significant advantages over all the other systems evaluated, in terms of both direct operating cost and fuel consumption.
Transformation of spherical harmonic coefficients to ellipsoidal harmonic coefficients
D. Dechambre; D. J. Scheeres
2002-01-01
Analytical expressions linking spherical harmonics gravity field expansions with ellipsoidal harmonics gravity field expansions are developed. Certain symmetries and simplifications for the transformation between the two are noted. Using the expressions, a numerical approach is developed and applied for the computation of ellipsoidal harmonic gravity coefficients using spherical harmonics coefficients as inputs. This method can be used to transform a
Transformation of spherical harmonic coecients to ellipsoidal harmonic coecients
D. Dechambre; D. J. Scheeres
2002-01-01
Analytical expressions linking spherical harmonics gravity eld expansions with ellipsoidal harmonics gravity eld expansions are developed. Certain symmetries and simplications for the transformation between the two are noted. Using the expressions, a numerical approach is developed and applied for the computation of ellipsoidal harmonic gravity coecients using spherical harmonics coecients as inputs. This method can be used to transform a
Thermionic energy converter investigations
NASA Technical Reports Server (NTRS)
Goodale, D. B.; Lee, C.; Lieb, D.; Oettinger, P. E.
1979-01-01
This paper presents evaluation of a variety of thermionic converter configurations to obtain improved efficiency. A variable-spacing diode using an iridium emitter gave emission properties comparable to platinum, but the power output from a sintered LaB6 collector diode was not consistent with its work function. Reflectivities above 0.5 were measured at thermal energies on oxygenated-cesiated surfaces using a field emission retarding potential gun. Performance of converters with structured electrodes and the characteristics of a pulsed triode were studied as a function of emitter, collector, cesium reservoir, interelectrode spacing, xenon pressure, and pulsing parameters.
Converting triangulations to quadrangulations
Suneeta Ramaswamia; Pedro Ramos; Godfried Toussaint
1995-01-01
We study the problem of converting triangulated domains to quadrangulations, under a variety of constraints. We obtain a variety of characterizations for when a triangulation (of some structure such as a polygon, set of points, line segments or planar subdivision) admits a quadrangulation without the use of Steiner points, or with a bounded number of Steiner points. We also investigate
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.
Hydro current energy converter
Rauch
1985-01-01
A hydro-dynamic device for capturing the energy of a natural stream of flowing water, and converting such current or flow of water energy into electric power for user consumption. The device has a primary tubular housing, a sealed, conical, secondary housing containing an electrical generator. The secondary housing has a conical end portion, and is disposed within and along the
Noncritically phase-matched second-harmonic generation in cesium lithium borate
David C. Gerstenberger; Thomas M. Trautmann; Mark S. Bowers
2003-01-01
Efficient generation of 236-nm light was demonstrated by use of noncritically phase-matched second-harmonic generation in cesium lithium borate. Noncritical phase matching provided approximately 20× the nonlinear drive for second-harmonic generation than beta-barium borate for 236-nm generation. The 236-nm wavelength is the fourth harmonic of a 946-nm Nd:YAG laser. Phase matching was accomplished at a crystal temperature of -15 °C.
Generation of octave-spanning multiple harmonics for ultrafast waveform synthesis
Hsu, Wei-Chun
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.
NASA Astrophysics Data System (ADS)
Kaminskii, A. A.; Bagayev, S. N.; Dolbinina, V. V.; Voloshin, A. E.; Rhee, H.; Eichler, H. J.; Hanuza, J.
2009-07-01
Raman-induced many-phonons Stokes and anti-Stokes generation in a orthorhombic crystals KHC6H4(COO)2 and (NH4)HC6H4(COO)2 under picosecond pumping has been observed. All recorded nonlinear lasing lines in the visible and near-IR regions are identified and attributed to the ?(3)-promoting vibration modes of these orthorhombic phthalates.
Reflected optical fourth harmonic generation at crystalline surfaces
Y.-S. Lee; M. C. Downer
2000-01-01
We present a systematic analysis of the intensity anisotropy of fourth harmonic generation (FHG) in reflection from centrosymmetric crystals of classes m3m (e.g. diamond structure) and 6\\/mmm (e.g. graphite) and non-centrosymmetric crystals of class 4?3m (e.g. zincblende structure). Surface dipole FH contributions are analyzed for six symmetry classes (2mm, 4mm, 3m, m, 6mm, 5-fold) which encompass the (001), (111), and
Fourth harmonic generation of a large-aperture Nd:glass laser
D. Bruneau; A. M. Tournade; E. Fabre
1985-01-01
Basic properties of the fourth harmonic conversion of 1.053-..mu..m laser radiation with KDP crystals are experimentally determined. Optimization of crystal thickness, based on numerical simulations is discussed. A large aperture conversion cell combining second and fourth harmonic generators has been designed. Overall conversion efficiencies (..omega.. ..-->.. 4..omega..) in excess of 40% have been achieved for incident laser intensities between 1
Multilevel converters -- A new breed of power converters
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
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.
NASA Technical Reports Server (NTRS)
Morris, J. F. (inventor)
1983-01-01
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.
Converting Informix 4GLApplications to Informix Genero Why Convert?
Converting Informix 4GLApplications to Informix Genero Why Convert? Your Informix 4GL applications. This is normal; your forms layouts respect the structure of IBM® Informix® 4GL. With a few minor modifications will be a state-of-the-art graphical application. Considerations for Converting I-4GL/D-4GL to Informix Genero
Hong He; Xiufeng Song; Renli Fu; Zhengwei Pan; Xinran Zhao; Zhonghua Deng; Yongge Cao
2010-01-01
The crystal structure and photoluminescence properties of Eu2+ doped Li2Ca0.7Sr0.3SiO4 phosphors were investigated. The Li2Ca0.7Sr0.3SiO4 is not an alloy between the tetragonal Li2CaSiO4 and hexagonal Li2SrSiO4 but crystallizes in orthorhombic structure similar to Li2(CaSr)SiO4. Photoluminescence properties of the Li2Ca0.7Sr0.3SiO4:Eu2+ phosphors, summarized in effective excitation in the UV region, strong emission in the blue light range (with a peak at 427nm)
Second harmonic generation in nanometer thin films and polar structures
Anna Samoc; Marek Samoc; Vesselin Z. Kolev; Barry Luther-Davies
The strengths of the second-order nonlinear optical (NLO) effects in various organic, inorganic materials and structures are important for nanotechnology, sensing and nonlinear microscopy. We analysed factors affecting second harmonic generation (SHG) in noncentrosymmetric materials, polar crystals of addition complexes and electrically poled polymer films. We used a SESAM mode-locked, amplified picosecond pulse laser system to measure SHG in 80
Implementation of a controlled rectifier using AC-AC matrix converter theory
Donald G. Holmes; Thomas A. Lipo
1992-01-01
It is well known that a PWM-controlled rectifier can offer advantages of reduced low-order harmonics and unity input power factor when compared to a conventional thyristor converter. However, theoretically optimum PWM strategies are often difficult to implement physically or are not easily extended to regenerative operation. The authors propose an alternative PWM strategy based on AC-AC matrix converter theory, which
Lehn, Peter W.
distribution system. It is therefore essential to predict the harmonic levels these converters produce as a variable resistor, one can convert Fig. 1 to Fig. 2, where Rd= Ron when the diode turns on, and Rd- Rff= blkdiag{K? 00}[2? 0 0'[n j} Note that: 1. A is a time varying matrix because Rd changes its values
Spherical and Ellipsoidal Harmonic Field Transformation based on FFT
NASA Astrophysics Data System (ADS)
Gruber, Christian; Abrykosov, Oleh
2013-04-01
High resolution transformations (synthesis and analysis) between regular geophysical data and harmonic model coefficients can be most efficiently computed by fast Fourier methods (FFT). Prerequisite however is the data to be given in the corresponding geometrical domain. If the data are e.g. situated on the ellipsoid at equiv-spaced, reduced latitudes ellipsoidal harmonics can be employed and subsequently converted by Jekeli's transformation into spherical harmonic coefficients in the domain of geocentric latitudes. But the data are most likely given at geodetic latitudes where the FFT base would then need to be shifted by latitude dependent phase lags. This results in (appropriate) re-sampling that demands for Fourier summation and cannot be treated by FFT. Alternatively, the linearization about the derivatives of the respective geopotential functional w.r.t. latitude can be used, that preserves the computational advances of FFT, but does not always converge quickly enough. Another solution is discussed instead. The data are given on the ellipsoid at regular geocentric latitudes. They can be directly transformed by means of spherical harmonics if the variable heights to the reference sphere and the resulting signal attenuation are directly convolved into the constituents of the spherical harmonic base functions by means of a fast convergent series of Tschebysev polynomials. By subtracting this solution from the solution obtained in ellipsoidal harmonics the differential from the changeover between geocentric and reduced latitudes is obtained. A similar step, now being from reduced to geodetic latitudes, then resembles in an equivalent difference.
Spherical Harmonic Transform Algorithms
Drake, John B [ORNL; Worley, Patrick H [ORNL; D'Azevedo, Eduardo [ORNL
2008-01-01
A collection of MATLAB classes for computing spherical harmonic transforms are presented and used to solve simple partial differential equations on the sphere. The spectral synthesis and analysis using fast Fourier transforms and Legendre transforms with the associated Legendre functions are presented in depth. A set of methods associated with a spectral\\_field class provides spectral approximation to the $\\DIV$, $\\CURL$, $\\GRAD$, and $\\LAPL$ in spherical geometr y. Laplace inversion and Helmholtz equation solvers are also methods for this clas s. Investigation of algorithms and analysis for spherical harmonic transform optio ns for parallel high performance computers are discussed in the context of global climate and weather models.
Radiating dipoles in photonic crystals
Busch, K; John, S; Sanders, B C; Busch, Kurt; Vats, Nipun; John, Sajeev; Sanders, Barry C.
2000-01-01
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.
Radiating dipoles in photonic crystals
Kurt Busch; Nipun Vats; Sajeev John; Barry C. Sanders
2000-06-02
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.
Radiating dipoles in photonic crystals
Busch; Vats; John; Sanders
2000-09-01
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
Electrothermodynamic (etd) power converter
Marks, A.M.
1983-07-26
These inventions relate to novel advances in Electrothermodynamics (ETD), also known as charged aerosol, heat/electric power generators: (1) A new more efficient, compact converging/diverging configuration comprising a torus of revolution (TORON) used with a gas flywheel. (2) A ''Method II'' two-fluid mixed flow ejector/converter in a gas flywheel loop employing a primary steam or a high molecular weight driver jet such as a fluorocarbon containing charged aerosol water droplets and a low molecular weight carrier gas such as hydrogen or helium with an electro-negative gas additive, in a Rankine cycle including a vapor/gas and liquid separator with a bypass to the ejector/converter loop. (3) A ''Method III'' two-fluid mixed flow comprising a supersonic jet expanding conically within a subsonic flow, separated by a boundary layer in which the charged aerosol forms downstream of the orifice, at a cross section of at least 100 times the orifice section; and in which the electric charge density of the charged aerosol decreases along the jet axis, whereby substantially all of the kinetic power of the jet is converted to electric power within the jet, there being no ejector. (4) An array of supersonic jets utilizing Method III. (5) An array of supersonic jets utilizing Method III without separating duct walls in which ''convection cells'' provide return flows, forming a plurality of TORON configurations. (6) A supercritical Rankline cycle in a single stage employing Method III. (7) A method IV two-fluid cycle uses charged aerosols in an inert gas and operates on an Ericsson-type cycle. (8) Optimum operating conditions are defined for Methods II, III, and IV. (9) A high potential emitter is employed with a grounded body, and a sapphire tube sealed to metal by a new technique provides an insulating duct for the high temperature, high pressure vapor.
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.
Cycloidal Wave Energy Converter
Stefan G. Siegel, Ph.D.
2012-11-30
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.
Fractional second-harmonic Talbot effect.
Chen, Zhenhua; Liu, Dongmei; Zhang, Yong; Wen, Jianming; Zhu, S N; Xiao, Min
2012-02-15
We demonstrate the fractional second-harmonic (SH) Talbot effect in a hexagonally poled LiTaO3 crystal. We carefully record the SH Talbot images at 1/2, 1/3, and 1/4 Talbot lengths, which are well matched with the simulated images by using the modified Rayleigh-Sommerfeld diffraction formula. A simplified model with a hexagonal array is adopted in the simulations. Also, we use a modified reciprocal vector theory to analytically explain the evolution of the SH array at fractional Talbot lengths. Our results show that the images are sensitive to the duty circle and the background of the array. PMID:22344149
Polynomial Harmonic Morphisms Martin Svensson
Gudmundsson, Sigmundur
Polynomial Harmonic Morphisms Martin Svensson Examensarbete, 20 poang Lunds Universitet November- agement. Martin Svensson 3 #12;4 #12;CHAPTER 1 Introduction 1. Motivation The study of harmonic morphisms
ent Harmonics in Thruster AC Dr Rig Platforms
Parikshit Yadav; C. W. Cheah
2009-01-01
The paper investigates the ef harmonics in oil-rig's thruster drives, whi variable frequency AC induction motor driv system in the oil rig consists of two 12 pu transformers having a relative phase shift of converter and an induction motor. The exhibits clean energy characteristics accord 519.1992 with I-THD of 2.48% and harmoni 24n±1 at the busbar when both transform loaded.Due
Gallium phosphide energy converters
NASA Technical Reports Server (NTRS)
Sims, P. E.; Dinetta, L. C.; Goetz, M. A.
1995-01-01
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.
Bidirectional buck boost converter
Esser, A.A.M.
1998-03-31
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.
Gallium phosphide energy converters
NASA Astrophysics Data System (ADS)
Sims, P. E.; Dinetta, L. C.; Goetz, M. A.
1995-10-01
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.
Gallium phosphide energy converters
Sims, P.E.; Dinetta, L.C.; Goetz, M.A.
1995-10-01
Gallium phosphide (GaP) energy converters may be successfully deployed to provide new mission capabilities for spacecraft. Betavoltaic power supplies based on the conversion of tritium beta decay to electricity using GaP energy converters can supply long term low-level power with high reliability. High temperature solar cells, also based on GaP, can be used in inward-bound missions greatly reducing the need for thermal dissipation. Results are presented for GaP direct conversion devices powered by Ni-63 and compared to the conversion of light emitted by tritiarated phosphors. Leakage currents as low as 1.2 x 10(exp {minus}17) A/sq cm have been measured and the temperature dependence of the reverse saturation current is found to have ideal behavior. Temperature dependent IV, QE, R(sub sh), and V(sub oc) results are also presented. These data are used to predict the high-temperature solar cell and betacell performance of GaP devices and suggest appropriate applications for the deployment of this technology.
Ian Rice; Gordon Smith
2005-01-01
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
ERIC Educational Resources Information Center
Gluck, P.; Krakower, Zeev
2010-01-01
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.)
Harmonically excited orbital variations
Morgan, T.
1985-08-06
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.
Qun Chen; Juergen Jost; Jiayu Li; Guofang Wang
2004-01-01
We introduce a functional that couples the nonlinear sigma model with a spinor field: $L=\\\\int_M[|d\\\\phi|^2+(\\\\psi,\\\\D\\\\psi)]$. In two dimensions, it is conformally invariant. The critical points of this functional are called Dirac-harmonic maps. We study some geometric and analytic aspects of such maps, in particular a removable singularity theorem.
P. Gluck; Zeev Krakower
2010-01-01
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.
Introducing Simple Harmonic Motion.
ERIC Educational Resources Information Center
Roche, John
2002-01-01
Explains the origin and significance of harmonic motion which is an important topic that has wide application in the world. Describes the phenomenon by using an auxiliary circle to help illustrate the key relationships between acceleration, displacement, time, velocity, and phase. (Contains 16 references.) (Author/YDS)
Harmonic operation of STW filters
R. L. Baer; C. A. FLory
1988-01-01
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
Physics 116 Simple Harmonic Motion
Glashausser, Charles
Physics 116 Simple Harmonic Motion Any Simple Harmonic Oscillator (SHO) has the following features Harmonic Motion (SHM). If the system is a SHO, then the following is true: MASS-SPRING system of the motion. Because of (3) above, we characterize SH oscillators based on their oscillation frequencies
Hydrodynamic interactions in colloidal crystals
J. M. A. Hofman; H. J. H. Clercx; P. P. J. M. Schram
1999-01-01
Wavevector dependent friction factors, which together with the elastic properties determine the hydrodynamic damping of harmonic lattice waves in colloidal crystals, are calculated for cubic arrays of rigid spheres at low, intermediate and high sphere volume fractions, including simple cubic (SC), body-centred cubic (BCC) and face-centred cubic (FCC) lattices. Exact numerical data are presented for the rheological coefficient appropriate to
Monitoring and Diagnosis for the DC–DC Converter Using the Magnetic Near Field Waveform
Yu Chen; Xuejun Pei; Songsong Nie; Yong Kang
2011-01-01
A new diagnostic method for the dc-dc converter, which utilizes the magnetic near field as the diagnostic criterion, is proposed in this paper. The magnetic near field of the con- verter is captured using a loop magnetic near field probe. The frequency information in the measured waveform is extracted by the fast Fourier transfer; the interested low-order harmonic com- ponents
R. J. Astley; A. Cummings
1995-01-01
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.
A Novel Polygon Based 15Phase AC-DC Converter for Vector Controlled Induction Motor Drives
Bhim Singh; G. Bhuvaneswari; Vipin Garg
2007-01-01
In this article, a new approach to improve power quality at AC mains in a vector controlled induction motor drive (VCIMD) is proposed. The novel multi-phase AC-DC converter, consisting of a reduced rating autotransformer, leading to savings in weight, size, and cost, results in reduction in harmonic current at AC mains. The resulting supply current is near sinusoidal in shape
RF propagation in finite thickness unidirectional magnetic photonic crystals
Gokhan Mumcu; Kubilay Sertel; John L. Volakis; Ilya Vitebskiy; Alexander Figotin
2005-01-01
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
Electromagnetic wave energy converter
NASA Technical Reports Server (NTRS)
Bailey, R. L. (inventor)
1973-01-01
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.
Harmonic multiplication using resonant tunneling
NASA Technical Reports Server (NTRS)
Sollner, T. C. L. G.; Brown, E. R.; Goodhue, W. D.; Correa, C. A.
1988-01-01
This paper demonstrates the use of resonant-tunneling diodes as varistors for harmonic multiplication. It is shown that efficient odd-harmonic conversion is possible and that even harmonics do not appear because of the antisymmetry of the current-voltage (I-V) curve. It is also shown that, with the proper choice of resonant-tunneling structure and pump amplitude, most of the harmonic output power can be confined to a single odd-harmonic frequency. Fifth-harmonic multiplication was demonstrated with an output at 21.75 GHz and a power conversion efficiency of 0.5 percent, and a fifth-harmonic efficiency of 2.7 percent was achieved in a circuit simulation using an improved I-V curve.
Frequency response of resonant converters
K. Siri; C. Q. Lee; S. J. Fang
1990-01-01
The general theory of the discrete small-signal analyses of resonant converters has been formulated in a closed form. For simplicity and verification, the state-plane diagram technique is used for the analysis. This theory is applicable to converters in half-bridge or full-bridge configurations when operated in the continuous conduction mode. Using a series resonant converter (SRC) as an example, the analytic
Harmonic behavior of variable-speed wind turbines during a control fault
R. Melicio; V. M. F. Mendes; J. P. S. Catalao
2011-01-01
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
Pierrehumbert, Raymond
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
Three-dimensional simulations of harmonic radiation and harmonic lasing
Schmitt, M.J.; McVey, B.D.
1990-01-01
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.
Digital regulation of a phase controlled power converter
Schultheiss, C.; Haque, T.
1995-12-01
The Relativistic Heavy Ion Collider, now in construction at Brookhaven National Laboratory, will use phase controlled power converters for the main dipole and quadrupole magnet strings. The rectifiers in these power supplies will be controlled by a digital regulator based on the TI 320C30 Digital Signal Processor (DSP). The DSP implements the current loop, the voltage loop, and a system to actively reduce the sub-harmonic ripple components. Digital firing circuits consisting of a phase locked lop and counters are used to fire the SCRs. Corrections for the sub-harmonic reduction are calculated by the DSP and stored in registers in the firing circuit. These corrections are added in hardware, to the over-all firing count provided by the DSP. the resultant count is compared to a reference counter to fire the SCRs. This combination of a digital control system and the digital firing circuits allows the correction of the sub-harmonics in a real-time sense. A prototype of the regulator has been constructed, and the preliminary testing indicates a sub-harmonic reduction of 60 dB.
Fuzzy Controller for Matrix Converter System to Improve its Quality of Output
Mahendran, Nagalingam; 10.5121/ijaia.2010.1402
2010-01-01
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.
On Cyclic Harmonic Oscillators
Konishi, K; Konishi, Kenichi; Paffuti, Giampiero
2004-01-01
It is proven that the energy of a quantum mechanical harmonic oscillator with a generically time-dependent but cyclic frequency, $\\omega_{0}(t_{0})= \\omega_{0}(0)$, cannot decrease on the average if the system is originally in a stationary state, after the system goes through a full cycle. The energy exchange always takes place in the direction from the macroscopic system (environment) to the quantum microscopic system.
NASA Astrophysics Data System (ADS)
Zakrzewski, Wojtek
2000-05-01
We describe some relations between solitonic solutions of various models in different dimensions. We present some examples and then concentrate on some of our recent work (performed in collaboration with Ioannidou and Piette) te{IPZ} te{us2} which shows how some harmonic maps from S2 to CPN-1 can be used to find nontrivial spherically symmetric static solutions of the SU(N) Skyrme model in 3 dimensions and to generate some of its low energy field configurations.
High resolution switching mode inductance-to-frequency converter with temperature compensation.
Matko, Vojko; Milanovi?, Miro
2014-01-01
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
High Resolution Switching Mode Inductance-to-Frequency Converter with Temperature Compensationti
Matko, Vojko; Milanovi?, Miro
2014-01-01
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
Ashim K. Chakravorti; Alexander E. Emanuel
1993-01-01
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.
Microfabricated multijunction thermal converters
NASA Astrophysics Data System (ADS)
Wunsch, Thomas Franzen
2001-12-01
In order to develop improved standards for the measurement of ac voltages and currents, a new thin-film fabrication technique for the multijunction thermal converter has been developed. The ability of a thermal converter to relate an rms ac voltage or current to a dc value is characterized by a quantity called `ac-dc difference' that is ideally zero. The best devices produced using the new techniques have ac-dc differences below 1 × 10-6 in the range of frequencies from 20 Hz to 10 kHz and below 7.5 × 10-6 in the range of frequencies from 20 kHz to 300 kHz. This is a reduction of two orders of magnitude in the lower frequency range and one order of magnitude in the higher frequency range over devices produced at the National Institute of Standards and Technology in 1996. The performance achieved is competitive with the best techniques in the world for ac measurements and additional evaluation is therefore warranted to determine the suitability of the devices for use as national standards that form the legal basis for traceable rms voltage measurements of time varying waveforms in the United States. The construction of the new devices is based on thin-film fabrication of a heated wire supported by a thermally isolated thin-film membrane. The membrane is produced utilizing a reactive ion plasma etch. A photoresist lift- off technique is used to pattern the metal thin-film layers that form the heater and the multijunction thermocouple circuit. The etching and lift-off allow the device to be produced without wet chemical etches that are time consuming and impede the investigation of structures with differing materials. These techniques result in an approach to fabrication that is simple, inexpensive, and free from the manual construction techniques used in the fabrication of conventional single and multijunction thermoelements. Thermal, thermoelectric, and electrical models have been developed to facilitate designs that reduce the low- frequency error. At high frequencies, from 300 kHz to 1 MHz, the performance of the device is degraded by a capacitive coupling effect that produces an ac-dc difference of approximately -90 × 10-6 at 1 MHz. A model is developed that explains this behavior. The model shows that an improvement in performance in the high-frequency range is possible through the use of very high or very low resistivity silicon substrates.
Numerical study of fourth-harmonic generation of a picosecond laser pulse with time predelay
Tiejun Zhang; Yoshiaki Kato; Hiroyuki Daido
1996-01-01
We describe fourth-harmonic generation of a picosecond laser pulse with KDP crystals. The coupled nonlinear equations for the parametric process including the third-order nonlinear susceptibility have been solved. Applying a time predelay in the doubling crystal between the extraordinary and the ordinary waves of the fundamental pulse causes the group-velocity mismatch and the nonlinear phase shift in the doubling crystal
Diamond turning of L-arginine phosphate, a new organic crystal
Fuchs, B.A.; Syn, K.; Velsko, S.P. (Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (US))
1989-10-15
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.
NSDL National Science Digital Library
First published in 1727, the remarkable book "Indian Converts, or Some account of the lives and dying speeches of a considerable number of the Christianized Indians of Martha's Vineyard" is now available in full online. Written by Experience Mayhew, the book provides remarkable insights into the lives and culture of four generations of Native Americans in colonial America. This digitized version was created at Reed College, and visitors can look through all four sections of the work, which include "Indian Ministers" and "Pious Children." Throughout the work, Mayhew details the books that different age groups were reading, provides insights into early New England pedagogy and childrearing practices, and also describes each individual in terms of their own genealogy and personal history. The truly fantastic thing about the site is that it also contains an archive with over 600 images and documents that further contextualize the work. Also, the site contains study guides designed for classroom use that cover artifact analysis, genealogy, and reading gravestones.
Proposed electromagnetic wave energy converter
NASA Technical Reports Server (NTRS)
Bailey, R. L.
1973-01-01
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.
PWM Converter Power Density Barriers
J. W. Kolar; U. Drofenik; J. Biela; M. L. Heldwein; H. Ertl; T. Friedli; S. D. Round
2007-01-01
Power density of power electronic converters in different applications has roughly doubled every 10 years since 1970. Behind this trajectory was the continuous advancement of power semiconductor device technology allowing an increase of converter switching frequencies by a factor of 10 every decade. However, today's cooling concepts, and passive components and wire bond interconnection technologies could be major barriers for
Matrix converters: a technology review
Patrick W. Wheeler; José Rodríguez; Jon C. Clare; Lee Empringham; Alejandro Weinstein
2002-01-01
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
Towards automated biomedical ontology harmonization.
Uribe, Gustavo A; Lopez, Diego M; Blobel, Bernd
2014-01-01
The use of biomedical ontologies is increasing, especially in the context of health systems interoperability. Ontologies are key pieces to understand the semantics of information exchanged. However, given the diversity of biomedical ontologies, it is essential to develop tools that support harmonization processes amongst them. Several algorithms and tools are proposed by computer scientist for partially supporting ontology harmonization. However, these tools face several problems, especially in the biomedical domain where ontologies are large and complex. In the harmonization process, matching is a basic task. This paper explains the different ontology harmonization processes, analyzes existing matching tools, and proposes a prototype of an ontology harmonization service. The results demonstrate that there are many open issues in the field of biomedical ontology harmonization, such as: overcoming structural discrepancies between ontologies; the lack of semantic algorithms to automate the process; the low matching efficiency of existing algorithms; and the use of domain and top level ontologies in the matching process. PMID:24851964
Imaging and quality assessment of high-harmonic focal spots.
Valentin, C; Douillet, D; Kazamias, S; Lefrou, Th; Grillon, G; Augé, F; Mullot, G; Balcou, Ph; Mercère, P; Zeitoun, Ph
2003-06-15
We present a direct method of studying the focusability of an intense, short-pulse extreme-ultraviolet (XUV) beam obtained by high-harmonic generation. We perform near-field imaging of the focal spot of five high-harmonic orders strongly focused by a broadband toroidal mirror. To visualize the focal spot directly, we image the fluorescence induced by an XUV beam on a cerium-doped YAG crystal on a visible CCD camera. We can thus measure the harmonic spot size on a single image, together with the Strehl ratio, to evaluate the quality of focusing. Such techniques should become instrumental in optimizing the focusing conditions and reaching intensities required for exploring attosecond nonlinear optics in the XUV range. PMID:12836775
Algal Supply System Design - Harmonized Version
Abodeely, Jared; Stevens, Daniel; Ray, Allison; Newby, Deborah; Schaller, Kastli
2013-03-01
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.
Ablamowicz, Rafal
Function: Cliplus:-`convert/dwedge_to_wedge`, Cliplus:-`convert/dwedge_to_wedge` - converting between wedge and dotted wedge Calling Sequence: c1 := convert(p1,wedge_to_dwedge,F) c2 := convert(p2 Grassmann wedge monomials) Â· F, FT - argument of type name, symbol, matrix, array, or `&*`(numeric,{name,symbol,matrix
Ultrabroadband single crystal composite transducers for underwater ultrasound
S. Cochran; M. Parker; P. Marin-Franch
2005-01-01
Through the use of complex piezoelectric structures, it is possible to obtain resonant harmonics not observed in the usual odd- harmonic response of a conventional structure. When combined with inherently broadband components, such as composites made with PMN- PT single crystal material, this permits the realisation of ultrabroadband devices. In the work reported here, results from modelling indicate that a
On Cyclic Harmonic Oscillators
Kenichi Konishi; Giampiero Paffuti
2004-01-01
It is proven that the energy of a quantum mechanical harmonic oscillator with\\u000aa generically time-dependent but cyclic frequency, $\\\\omega_{0}(t_{0})=\\u000a\\\\omega_{0}(0)$, cannot decrease on the average if the system is originally in a\\u000astationary state, after the system goes through a full cycle. The energy\\u000aexchange always takes place in the direction from the macroscopic system\\u000a(environment) to the quantum
Branko Dragovich
2004-04-21
Using the Weyl quantization we formulate one-dimensional adelic quantum mechanics, which unifies and treats ordinary and $p$-adic quantum mechanics on an equal footing. As an illustration the corresponding harmonic oscillator is considered. It is a simple, exact and instructive adelic model. Eigenstates are Schwartz-Bruhat functions. The Mellin transform of a simplest vacuum state leads to the well known functional relation for the Riemann zeta function. Some expectation values are calculated. The existence of adelic matter at very high energies is suggested.
Richard L. Hall; Nasser Saad; Attila B. von Keviczky
2001-09-18
A complete variational treatment is provided for a family of spiked-harmonic oscillator Hamiltonians H = -d^2/dx^2 + B x^2 + lambda/x^alpha, B > 0, lambda > 0, for arbitrary alpha > 0. A compact topological proof is presented that the set S = {psi_n} of known exact solutions for alpha = 2 constitutes an orthonormal basis for the Hilbert space L_2(0, infinity). 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.
A multilevel active front-end rectifier with current harmonic compensation capability
Franco Hernández; Luis Morán; José Espinoza; Juan Dixon
2004-01-01
This paper presents a multilevel active front-end rectifier that can absorb current harmonics generated by nonlinear loads connected to the same power distribution bus. That is, the proposed active front-end converter can operate as an active power filter and simultaneously as a rectifier. The control scheme is simple and forces the power system line current to be sinusoidal and in
Investigation of current harmonics in thruster AC drives in oilrig platforms
Parikshit Yadav; C. W. Cheah; A. S. Allana; T. Lye; C. S. Chang; S. K. Panda; S. K. Sahoo
2009-01-01
The paper investigates the effect of current harmonics in oil-rig's thruster drives, which are based on variable frequency AC induction motor drives. The electrical system in the oil rig consists of two 12 pulse phase shifting transformers having a relative phase shift of 15°, a frequency converter and an induction motor. The electrical system exhibits clean energy characteristics according to
Power system harmonic mitigation of an offshore oil rig using passive shunt filter
Shib Sankar Saha; Ramesh Suryavanshi
2010-01-01
Offshore oil rigs use large dc drives, usually fed from a.c. utility services through ac\\/dc converters, thus distorting current and voltage waveforms. Passive filters have been very effective solution for the harmonic mitigation as well as reactive VAR compensation. However, improper choice of filter components may lead to severe voltage and current stress to power system components or even sometimes
CRIME BULLETIN INCIDENT: Catalytic Converter Thefts
Barrett, Jeffrey A.
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
A low-power CMOS time-to-digital converter
E. Raisanen-Ruotsalainen; T. Rahkonen; J. Kostamovaara
1995-01-01
A time-to-digital converter, TDC, with 780 ps lsb and 10-?s input range has been integrated in a 1.2-?m CMOS technology. The circuit is based on the interpolation time interval measurement principle and contains an amplitude regulated crystal oscillator, a counter, two pulse-shrinking delay lines, and a delay-locked loop for stabilization of the delay. The TDC is designed for a portable,
Harmonic generation at high intensities
Schafer, K.J.; Krause, J.L.; Kulander, K.C.
1993-06-01
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.
Control Design of a Three-Phase Matrix-Converter-Based AC–AC Mobile Utility Power Supply
Pericle Zanchetta; Patrick W. Wheeler; Jon C. Clare; Michael Bland; Lee Empringham; Dimosthenis Katsis
2008-01-01
This paper describes the control analysis and design of an ac-to-ac three-phase mobile utility power supply using a matrix converter capable of high-quality 50-, 60-, and 400-Hz output voltage and reduced input harmonic distortion. Instead of the traditional structure employing a diode bridge rectifier, a dc link and a pulsewidth-modulated inverter, a three-phase-to-three-phase direct ac-ac (matrix) converter has been used
High-energy, high-efficiency second-harmonic generation of 1064-nm radiation in KTP
Andrew J. W. Brown; Mark S. Bowers; Ken W. Kangas; Charles H. Fisher
1992-01-01
An energy conversion efficiency of 80 percent for second-harmonic generation of 532-nm radiation from 1064-nm radiation has been achieved with a single KTP crystal and a commercial injection-seeded Q-switched Nd:YAG laser. A second-harmonic output of 720 mJ was generated with 900 mJ of incident 1064-nm radiation at 10 Hz.
Hippocampal Surface Analysis using Spherical Harmonic Functions
Wang, Yalin
Hippocampal Surface Analysis using Spherical Harmonic Functions Applied to Surface Conformal Laplacian is Spherical harmonic analysis applied to conforaml mapping Let be a conformal homeomorphism of Neurology, UCLA School of Medicine, Los Angeles, CA, USA. The spherical harmonic descriptors should
LOCALIZED HARMONIC MOTION IMAGING: THEORY, SIMULATIONSAND EXPERIMENTS
Konofagou, Elisa E.
LOCALIZED HARMONIC MOTION IMAGING: THEORY, SIMULATIONSAND EXPERIMENTS Elisa E. Konofagou typically estimate static or harmonic motion resulting from an externally or internally applied mechanical signaltraclung in orderto estimate the localized oscillatory motion resulting from the harmonic radiation force
Coherence convertibility for mixed states
Xiaofei Qi; Zhaofang Bai; Shuanping Du
2015-05-27
In this paper, by providing a class of coherence measures in finite dimensional systems, a sufficient and necessary condition for the existence of coherence transformations that convert one probability distribution of any pure states into another one is obtained.
NASA Technical Reports Server (NTRS)
Paulkovich, J.
1979-01-01
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.
Ellipsoidal harmonic (Lame) MRI shims
S. Crozier; L. K. Forbes; M. Brideson
2002-01-01
Ellipsoidal harmonics are presented as a basis function set for the design of shim coils for magnetic resonance imaging (MRI) or spectroscopy. MR shim coils may be either superconductive or resistive. Ellipsoidal harmonics form an orthogonal set over an ellipsoid and hence are appropriate in circumstances where the imaging or spectroscopic region of a magnet more closely conforms to an
Exploration method using harmonic functions
Edson Prestes e Silva Jr.; Paulo Martins Engel; Marcelo Trevisan; Marco Aurélio Pires Idiart
2002-01-01
Harmonic functions provide optimal potential maps for robot navigation in a previously explored static environment. Here we investigate the performance of an algorithm for exploration based on partial updates of a harmonic potential in an occupancy grid. We consider that while the robot moves it carries along an activation window whose size is of the order of the sensor's range.
Azimuthal anisotropy: the higher harmonics
Poskanzer, Arthur M
2004-01-01
We report the first observations of the fourth harmonic (v_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_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.
Azimuthal anisotropy: the higher harmonics
Arthur M. Poskanzer
2004-03-12
We report the first observations of the fourth harmonic (v_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_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.
Harmonic Series Meets Fibonacci Sequence
ERIC Educational Resources Information Center
Chen, Hongwei; Kennedy, Chris
2012-01-01
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?
Harmonic behaviour of HVDC cables
Roberto Benato; Michele Forzan; Marco Marelli; Ambrogio Orini; Ernesto Zaccone
2010-01-01
The paper deals with harmonic analysis of HVDC submarine cables. The longitudinal series impedance matrix is computed with reference to armoured cables. The results are also compared with Finite Element models showing a very good agreement. This investigation can be considered the first step of more detailed further analysis about the propagation of harmonics on the d.c. and a.c. sides.
Numerical study of fourth-harmonic generation of a picosecond laser pulse with time predelay
Zhang, T.; Kato, Y.; Daido, H. [Institute of Laser Engineering, Osaka University, Yamada-oka 2-6, Suita, Osaka 565 (Japan)
1996-06-01
We describe fourth-harmonic generation of a picosecond laser pulse with KDP crystals. The coupled nonlinear equations for the parametric process including the third-order nonlinear susceptibility have been solved. Applying a time predelay in the doubling crystal between the extraordinary and the ordinary waves of the fundamental pulse causes the group-velocity mismatch and the nonlinear phase shift in the doubling crystal to be compensated for each other, resulting in pulse duration compression at the fourth-harmonic wavelength. It is shown that the reduction from a 1-ps fundamental pulse to a 0.25-ps fourth-harmonic pulse can be achieved at an incident intensity of 50 GW/cm{sup 2}. {copyright} {ital 1996 Optical Society of America.}
Radiation tolerant power converter controls
NASA Astrophysics Data System (ADS)
Todd, B.; Dinius, A.; King, Q.; Uznanski, S.
2012-11-01
The Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) is the world's most powerful particle collider. The LHC has several thousand magnets, both warm and super-conducting, which are supplied with current by power converters. Each converter is controlled by a purpose-built electronic module called a Function Generator Controller (FGC). The FGC allows remote control of the power converter and forms the central part of a closed-loop control system where the power converter voltage is set, based on the converter output current and magnet-circuit characteristics. Some power converters and FGCs are located in areas which are exposed to beam-induced radiation. There are numerous radiation induced effects, some of which lead to a loss of control of the power converter, having a direct impact upon the accelerator's availability. Following the first long shut down (LS1), the LHC will be able to run with higher intensity beams and higher beam energy. This is expected to lead to significantly increased radiation induced effects in materials close to the accelerator, including the FGC. Recent radiation tests indicate that the current FGC would not be sufficiently reliable. A so-called FGClite is being designed to work reliably in the radiation environment in the post-LS1 era. This paper outlines the concepts of power converter controls for machines such as the LHC, introduces the risks related to radiation and a radiation tolerant project flow. The FGClite is then described, with its key concepts and challenges: aiming for high reliability in a radiation field.
HIGH EFFICIENCY AUXILIARY POWER CONVERTERS
Geoff Walker
The auxiliary load DC-DC converters of the Sunshark solar car have never been examined. An analysis of the current design reveals it is complicated, and inefficient. Some simple measures to greatly improve the efficiency are present which will achieve an overall worthwhile power saving. Two switch-mode power supply DC-DC converter designs are presented. One is a constant current supply for
AMTEC cells challenge energy converters
Henry Oman
1999-01-01
Sodium-base alkali-metal-thermal-to-electric conversion (AMTEC) cells have been receiving attention. Recently they were selected for the next generation deep-space missions, which need a converter that makes electricity from radioisotope heat. The AMTEC cell, being an electrochemical converter of heat to electricity, has no moving parts and is not limited to Carnot-cycle efficiency. However, its heat source and sink have to be
Power converters and amplifiers (review of \\
Marian Kazmierkowski
2009-01-01
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
Solid oxygen as converter for the production of ultra-cold neutrons
A. Frei; F. Böhle; R. Bozhanova; E. Gutsmiedl; T. Huber; J. Klenke; S. Paul; S. Wlokka
2011-07-11
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 $20\\,\\mathrm{cm}$.
NSDL National Science Digital Library
Kenneth Libbrecht
1999-02-01
This site is all about snow crystals and snowflakes. The many facets of snow crystals are described here, along with attempts to understand their formation. This site includes collections of super-high-resolution snow crystal photos, as well as links to learn about snow crystal classifications and how to make snow crystal fossils. Included in the study of how snow crystals form, these researchers have created snow crystals in the laboratory. Their snow crystal galleries include selections of images and movies of laboratory-grown snow crystals, as well as information on how to make your own snow crystals. The snow crystal primer describes what snow crystals are, how they form, and why they form the way they do. There is also a section on snow crystal physics.
Nonlinear cyclotron harmonic absorption
Seol, Jae Chun [National Fusion Research Institute, Yuseong, Daejeon 555-333 (Korea, Republic of); Hegna, C. C.; Callen, J. D. [Department of Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706-1609 (United States)
2009-05-15
Nonlinear oscillations of particle's energy occur when a particle stays in a resonance zone. In this work, we found that collisionless heating of particles occurs when they pass the microwave beam at first, second, and third harmonic resonances. It is found that the net energy gain of particles from the microwaves is inversely proportional to the wave frequency. It is also found that the net energy gain is dependent on the microwave beam width. The energy gain of particles from a single pass through a resonance zone has been formulated analytically. A numerical calculation has been performed and the results are in good agreement with the analytic calculation. Both analytic and numerical calculations show a strong frequency dependence and a beam width dependence of nonlinear cyclotron resonance heating.
Galilean covariant harmonic oscillator
NASA Technical Reports Server (NTRS)
Horzela, Andrzej; Kapuscik, Edward
1993-01-01
A Galilean covariant approach to classical mechanics of a single particle is described. Within the proposed formalism, all non-covariant force laws defining acting forces which become to be defined covariantly by some differential equations are rejected. Such an approach leads out of the standard classical mechanics and gives an example of non-Newtonian mechanics. It is shown that the exactly solvable linear system of differential equations defining forces contains the Galilean covariant description of harmonic oscillator as its particular case. Additionally, it is demonstrated that in Galilean covariant classical mechanics the validity of the second Newton law of dynamics implies the Hooke law and vice versa. It is shown that the kinetic and total energies transform differently with respect to the Galilean transformations.
Generalized spiked harmonic oscillator
Richard L. Hall; Nasser Saad; Attila B. von Keviczky
2001-01-05
A variational and perturbative treatment is provided for a family of generalized spiked harmonic oscillator Hamiltonians H = -(d/dx)^2 + B x^2 + A/x^2 + lambda/x^alpha, where B > 0, A >= 0, and alpha and lambda denote two real positive parameters. The method makes use of the function space spanned by the solutions |n> of Schroedinger's equation for the potential V(x)= B x^2 + A/x^2. Compact closed-form expressions are obtained for the matrix elements , and a first-order perturbation series is derived for the wave function. The results are given in terms of generalized hypergeometric functions. It is proved that the series for the wave function is absolutely convergent for alpha <= 2.
Harmonicity and submanifold maps
Udriste, Constantin; Bejenaru, Andreea
2011-01-01
The aim of this paper is fourfold. Firstly, we introduce and study the f-ultra-harmonic maps. Secondly, we recall the geometric dynamics generated by a first order normal PDE system and we give original results regarding the geometric dynamics generated by other first order PDE systems. Thirdly, we determine the Gauss PDEs and the fundamental forms associated to integral manifolds of first order PDE systems. Fourthly, we change the Gauss PDEs into a geometric dynamics on the jet bundle of order one, showing that there exist an infinity of Riemannian metrics such that the lift of a submanifold map into the first order jet bundle to be an ultra-potential map.
Caspi, S.; Helm, M.; Laslett, L.J.
1991-03-30
We have developed an harmonic representation for the three dimensional field components within the windings of accelerator magnets. The form by which the field is presented is suitable for interfacing with other codes that make use of the 3D field components (particle tracking and stability). The field components can be calculated with high precision and reduced cup time at any location (r,{theta},z) inside the magnet bore. The same conductor geometry which is used to simulate line currents is also used in CAD with modifications more readily available. It is our hope that the format used here for magnetic fields can be used not only as a means of delivering fields but also as a way by which beam dynamics can suggest correction to the conductor geometry. 5 refs., 70 figs.
Efficient 266 nm Ultraviolet Beam Generation in K2Al2B2O7 Crystal
Jun-Hua Lu; Gui-Ling Wang; Zu-Yan Xu; Chuang-Tian Chen; Ji-Yang Wang; Cheng-Qian Zhang; Yao-Gang Liu
2002-01-01
The ultraviolet beam at 266 nm was obtained by fourth harmonic generation of 1064 nm Nd:YAG laser radiation through a nonlinear crystal K2Al2B2O7 (KABO). The fundamental frequency of a flash-lamp pumped Nd:YAG laser was doubled in a beta-Ba2B2O4 crystal to generate a second harmonic output at the wavelength of 532 nm, and then doubled again in the KABO crystal to
Topology of Platonic Spherical Manifolds: From Homotopy to Harmonic Analysis
Kramer, Peter
2015-01-01
We carry out the harmonic analysis on four Platonic spherical three-manifolds with different topologies. Starting out from the homotopies (Everitt 2004), we convert them into deck operations, acting on the simply connected three-sphere as the cover, and obtain the corresponding variety of deck groups. For each topology, the three-sphere is tiled into copies of a fundamental domain under the corresponding deck group. We employ the point symmetry of each Platonic manifold to construct its fundamental domain as a spherical orbifold. While the three-sphere supports an~orthonormal complete basis for harmonic analysis formed by Wigner polynomials, a given spherical orbifold leads to a selection of a specific subbasis. The resulting selection rules find applications in cosmic topology, probed by the cosmic microwave background.
Analysis of harmonic spline gravity models for Venus and Mars
NASA Technical Reports Server (NTRS)
Bowin, Carl
1986-01-01
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.
Topology of Platonic Spherical Manifolds: From Homotopy to Harmonic Analysis
Peter Kramer
2015-04-05
We carry out the harmonic analysis on four Platonic spherical three-manifolds with different topologies. Starting out from the homotopies (Everitt 2004), we convert them into deck operations, acting on the simply connected three-sphere as the cover, and obtain the corresponding variety of deck groups. For each topology, the three-sphere is tiled into copies of a fundamental domain under the corresponding deck group. We employ the point symmetry of each Platonic manifold to construct its fundamental domain as a spherical orbifold. While the three-sphere supports an~orthonormal complete basis for harmonic analysis formed by Wigner polynomials, a given spherical orbifold leads to a selection of a specific subbasis. The resulting selection rules find applications in cosmic topology, probed by the cosmic microwave background.
Improved technique for picosecond pulse duration measurement based on second harmonic generation
NASA Astrophysics Data System (ADS)
Shelestov, D. A.; Karasik, V. E.; Koshelev, K. I.; Lazarev, V. A.; Pnev, A. B.
2015-01-01
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.
Generation of ultraviolet light by using new nonlinear optical crystal CsLiB{sub 6}O{sub 10}
Mori, Y.; Nakajima, S.; Miyamoto, A.; Inagaki, M.; Sasaki, T.; Yoshida, H.; Nakai, S. [Osaka Univ., Suita, Osaka (Japan)
1995-12-31
A new nonlinear optical crystal, CsLiB{sub 6}O{sub 10} (CLBO), is described, which is a congruently melting crystal and can realize fourth harmonic and fifth harmonic generations of the 1.064 {micro}m Nd:YAG laser radiation with type-1 phase matching. A large and high quality single crystal with dimensions of 14 x 11 x 11 cm{sup 3} was obtained by the top-seeded Kyropoulos method. CLBO showed higher fourth harmonic generation efficiency from the second harmonic of ND:YAG laser output compared to {beta}-BaB{sub 2}O{sub 4}.
ERIC Educational Resources Information Center
Whipple, Nona; Whitmore, Sherry
1989-01-01
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)
Method for reducing energy losses in laser crystals
Atherton, L. Jeffrey (Pleasanton, CA); DeYoreo, James J. (Livermore, CA); Roberts, David H. (Pleasanton, CA)
1992-01-01
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.
Analysis and Design of New Harmonic Mitigation Approaches
Aeloiza Matus, Eddy 1972-
2012-11-01
is proposed to reduce the HF circulating current and a zero-sequence control loop to mitigate the low frequency circulating current is also proposed [56]-[58]. 5 Power Quality Standards 1.2. IEEE 519-1981 [67] 1.2.1 In 1981... to determine whether or not the new converters were going to be a problem. It was impractical and not economical to mitigate the harmonics for each non-linear load. Therefore, the IEEE 519-1981 was designed to help these users with the application...
NASA Astrophysics Data System (ADS)
Branding, Volker
2015-03-01
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.
Donald Grahame Holmes
1992-01-01
A unified pulse width modulation (PWM) algorithm is presented that is derived from AC-AC matrix power converter theory. The algorithm can be used to implement either a voltage source or a current source inverter, using only conventional bridge topologies. The resultant modulation strategy produces minimal low-order AC harmonics, yet it is readily capable of being computed online in a single
EMI Reduction by Spread-Spectrum Clocking in Digitally-Controlled DC-DC Converters
NASA Astrophysics Data System (ADS)
Mori, Ibuki; Yamada, Yoshihisa; Wibowo, Santhos A.; Kono, Masashi; Kobayashi, Haruo; Fujimura, Yukihiro; Takai, Nobukazu; Sugiyama, Toshio; Fukai, Isao; Onishi, Norihisa; Takeda, Ichiro; Matsuda, Jun-Ichi
This paper proposes spread-spectrum clock modulation algorithms for EMI reduction in digitally-controlled DC-DC converters. In switching regulators using PWM, switching noise and harmonic noise concentrated in a narrow spectrum around the switching frequency can cause severe EMI. Spread-spectrum clock modulation can be used to minimize EMI. In conventional switching regulators using analog control it is very difficult to realize complex spread-spectrum clocking, however this paper shows that it is relatively easy to implement spread-spectrum EMI-reduction using digital control. The proposed algorithm was verified using a power converter simulator (SCAT).
Schulze, Tim
1994-01-01
~N~H CRYSTAL GROWTH ELSEVIER Journal of Crystal Growth 143 (1994) 317--333 The influence reserved SSDI 0022-0248(94)00418-L #12;315 T.P. Schuize, S.H. Divis/Journal of Crystal Growth 143 (1994) 3 by a simple harmonic, lateral oscillation of the crystal, resulting in solidification into a compressed Stokes
Ultra-compact photonic crystal waveguide spatial mode converter and
Miller, David A. B.
and optimization process that allows these types of devices to be designed in a matter of minutes. We also present conversion in multimode waveguides using computer-generated planar holograms," IEEE Photon. Technol. Lett. 22
NASA Astrophysics Data System (ADS)
Wöstmann, Michael; Redkin, Pavel V.; Zheng, Jiaan; Witte, Henrik; Ganeev, Rashid A.; Zacharias, Helmut
2015-07-01
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.
Hexagram converter for static VAR compensation
Jun Wen; K. M. Smedley
2008-01-01
A new multilevel converter - Hexagram converter is proposed for static VAR compensation in high-voltage high- power applications. The new converter is composed of six three- phase two-level standard voltage source converter (VSC) modules interconnected through inductors. It has the advantages of modular structure leading to easy construction and maintenance, no voltage unbalance, low voltage stress, low dc energy storage,
Configuration Interaction in Crystal Field Theory
K. Rajnak; B. G. Wybourne
1964-01-01
The effect of configuration interaction on the validity of the usual method of expanding the crystal field potential in terms of spherical harmonics is examined using second-order perturbation theory. It is found that for a configuration of equivalent electrons lN most mechanisms of configuration interaction lead to a simple scaling of the crystal field parameters Bqk. However, one-electron excitations, either
Applied and Numerical Harmonic Analysis Series Editor
O'Brien, James F.
#12;Applied and Numerical Harmonic Analysis Series Editor John J. Benedetto University of Maryland and Numerical Harmonic Analysis (ANHA) book series aims to provide the engineering, mathematical, and scientific communities with significant develop- ments in harmonic analysis, ranging from abstract harmonic analysis
REALIZING STEP FUNCTIONS AS HARMONIC MEASURE DISTRIBUTIONS
Ward, Lesley A.
motion and harmonic measure, h(r) is equal to the harmonic measure in D at z0 of the part of the boundary, Brownian motion, step functions, harmonic measure distribution functions. Research supported in partREALIZING STEP FUNCTIONS AS HARMONIC MEASURE DISTRIBUTIONS OF PLANAR DOMAINS MARIE A. SNIPES
Stirling Converters For Solar Power
NASA Technical Reports Server (NTRS)
Shaltens, Richard K.; Schreiber, Jeffrey G.
1993-01-01
Two designs expected to meet long-term goals for performance and cost. Proposed for advanced systems to convert solar thermal power to electrical power. Each system, designed to operate with 11-m-diameter paraboloidal reflector, includes solar-energy receiver, liquid-metal heat-transport subsystem, free-piston Stirling engine, cooling subsystem, alternator or generator coupled directly or indirectly to commercial electric-power system, and control and power-conditioning circuitry. System converts approximately 75 kW of input solar thermal power falling on collector to about 25 kW of output electrical power.
Multilevel converters for power system applications
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
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.
Soft-switching techniques in PWM converters
Guichao Hua; Fred C. Lee
1995-01-01
A number of soft-switching pulse-width-modulated (PWM) converter techniques have been proposed, aimed at combining the desirable features of both the conventional PWM and resonant converters while avoiding their respective limitations. In this paper, three classes of zero-voltage soft-switching (PWM) converters (namely the zero-voltage-switched (ZVS) quasi-square-wave converters, ZVS-PWM converters, and zero-voltage-transition PWM converters) and two classes of zero-current soft-switching PWM converters
Masakuni Takahashi; Akira Osada; Alex Dergachev; Peter F. Moulton; Marilou Cadatal-Raduban; Toshihiko Shimizu; Nobuhiko Sarukura
2011-01-01
We present a scheme using beta-barium borate (BBO) crystal to maximize fourth-harmonic ultraviolet (UV) generation from high-power, kHz-range repetition rate Nd lasers by reducing thermal dephasing during the phase matching process. Thermal dephasing due to nonlinear absorption (NLA) induced by two-photon absorption of high peak power fourth-harmonic UV radiation is reduced by minimizing second- and fourth-harmonic beam overlap through tight
Michel Poulin; Normand Cyr; Christine Latrasse; M. Tetu
1997-01-01
Second harmonic generation of a 192.1 THz semiconductor distributed feedback (DFB) laser is achieved using a KNbO3 crystal in a resonant ring cavity. Optical feedback from this cavity is used to stabilize the laser frequency and reduce its linewidth. A second harmonic power of 5.5 ?W is generated with 38 mW incident on the cavity. We use the second harmonic
Pythagorean Triples from Harmonic Sequences.
ERIC Educational Resources Information Center
DiDomenico, Angelo S.; Tanner, Randy J.
2001-01-01
Shows how all primitive Pythagorean triples can be generated from harmonic sequences. Use inductive and deductive reasoning to explore how Pythagorean triples are connected with another area of mathematics. (KHR)
Electromagnetic space-time crystals. II. Fractal computational approach
G. N. Borzdov
2014-10-20
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.
Structure and Elasticity of Nematic and Isotropic Liquid Crystals
liquid crystals consisting of softellipsoidal particles. (2) The correla tion functions in the bulk calculations. We model the nematic liquid crystals molecules as softellipsoidal particles interacting through in spherical harmonics, taking the dependence of these functions on the orientation of the director
Structure and Elasticity of Nematic and Isotropic Liquid Crystals
liquid crystals consisting of soft-ellipsoidal particles. (2) The correla- tion functions in the bulk calculations. We model the nematic liquid crystals molecules as soft-ellipsoidal particles interacting through correlation function. We expand all these functions in spherical harmonics, taking the dependence
Cylindrical Harmonic Galaxy Classification
NASA Astrophysics Data System (ADS)
Riess, Jeff; Kutzner, Mickey
2008-04-01
In this study, we investigate the use of features in the Spherical Harmonic power spectra to aid in the classification of galaxies. Let I(r,?) represent a galaxy image function in polar coordinates. The image function may be represented as a two-dimensional Fourier-Bessel series. The coefficients in the expansion, An,i and Bn,i, multiply the radial Bessel functions of order n, Jn(?n,ir/R) and the polar functions cos(n?) and sin(n?), respectively. The coefficients are known as the Fourier-Bessel Transform (FBT) of I(r,?). The parameter ?n,i is the ith root of the Bessel function of the first kind of order n, Jn(x), and R is the radius to the edge of the galaxy image. We have computed the coefficients An,i and Bn,i for a number of representative FBT spectra. Spectra are presented as 3D plots of the modulus of An,i and Bn,i versus the root number, i, and the order n. Radial structures (such as spiral arms) are manifested in the spectra as peaks in amplitude at certain values of i, whereas, azimuthal variations are seen as amplitude peaks at particular values of n. Since each galaxy type will have a unique spectrum type due to its distinct matter distributions, we investigate the possibility of automatically classifying galaxies by minimizing the Euclidean distance of the galaxy's FBT spectrum to typical spectra of each morphological type.
Relativistic harmonic oscillator revisited
Bars, Itzhak [Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089-2535 (United States)
2009-02-15
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.
Relation of squeezed states between damped harmonic and simple harmonic oscillators
NASA Technical Reports Server (NTRS)
Um, Chung-In; Yeon, Kyu-Hwang; George, Thomas F.; Pandey, Lakshmi N.
1993-01-01
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.
Azimuthal anisotropy: The higher harmonics
Poskanzer, Arthur M.; STAR Collaboration
2004-03-12
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.
Echo-Enabled Harmonic Generation
Stupakov, Gennady; /SLAC
2012-06-28
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.
Echo-Enabled Harmonic Generation
Stupakov, Gennady
2010-08-25
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.
Parametric study of laser photovoltaic energy converters
NASA Technical Reports Server (NTRS)
Walker, G. H.; Heinbockel, J. H.
1987-01-01
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.
Analysis, modeling, and simulation of series-parallel resonant converter circuits
Siu-Chung Wong; Andrew D. Brown
1995-01-01
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
A new single phase AC to DC zero voltage soft switching converter
R. W. De Doncker; G. Venkataramanan
1990-01-01
A resonant boost rectifier is analyzed. The primary goal of the circuit is to produce single-phase AC line currents with very low harmonic distortion at unity power factor, thereby eliminating or reducing the size of filter components. The single-phase AC-to-DC converter consists of a boost-rectifier line conditioner connected to a resonant DC link bus. This enables zero-voltage soft switching operation
Implementation of a controlled rectifier using AC-AC matrix converter theory
D. G. Holmes; T.A. Lipo
1989-01-01
Current optimum PWM (pulse-width-modulation) strategies are often difficult to physically implement or not easily extended to regenerative operation. The authors propose an alternative PWM strategy based on current AC-AC matrix converter theory, which generates only high-order switching harmonics, presents a unity power factor load to the supply, implicitly extends to regeneration (and operation with a center-tapped DC output), and is
NASA Astrophysics Data System (ADS)
Elshin, A. S.; Firsova, N. Yu.; Marchenkova, M. A.; Emel'yanov, V. I.; Pronin, I. P.; Senkevich, S. V.; Mishina, E. D.; Sigov, A. S.
2015-05-01
Features of crystallization of microstructures to the perovskite-like phase in a lead zirconate titanate film are studied using multiple near-IR femtosecond laser pulse radiation. The kinetics of crystallization is in situ investigated using the second-harmonic generation technique. It is established that the crystallization is divided into high-temperature ultrafast (explosive) crystallization, which occurs right after the start of irradiation, and low-temperature slow (self-induced) crystallization, which starts after termination of irradiation of a strained multilayer structure. The advantages of the second-harmonic generation microscopy in studying annealed microstructures are demonstrated.
A quick convertible agitating system
Liu Ying; Song Biao; Ni Xiao-yu; Li Jia; Wang Li-jie; Fei Ye-qi; Wang Chang-qin
2010-01-01
Experiments of agitator properties are required a lot in process industry. A more efficient, practical and lower cost experimental system is demanded. In this research, a new type of quick convertible agitating system was designed which had a unique structure combined turning bracket with available impeller to enhance the prosperities and efficiency of the agitator experiment. Consisted of one driven
Brainard, John P. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)
2009-11-03
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.
Power converters for parabolic dishes
V. C. Truscello; A. N. Williams
1981-01-01
The development status of receivers and power conversion units to be used with parabolic dish concentrators is presented. Applications are identified, and the key role played by the power converter element of the collector module is emphasized. The electrical output of the 11-meter-diameter dish modules which are being developed varies up to a maximum of about 25 kilowatts, depending on
CONVERTING ABANDONED LANDS TO CROPLAND
Technology Transfer Automated Retrieval System (TEKTRAN)
Because of economic conditions, areas of cropland in Ukraine have been left unused for several years. These abandoned lands are now infested with perennial weeds. Producers are interested in converting these lands back to cropland with no-till systems to preserve soil benefits gained by not tillin...
Mesoscopic harmonic mapping of electromechanical response in a relaxor ferroelectric
NASA Astrophysics Data System (ADS)
Vasudevan, Rama K.; Zhang, Shujun; Ding, Jilai; Okatan, M. Baris; Jesse, Stephen; Kalinin, Sergei V.; Bassiri-Gharb, Nazanin
2015-06-01
Relaxor-ferroelectrics are renowned for very large electrostrictive response, enabling applications in transducers, actuators, and energy harvesters. However, insight into the dissimilar contributions (polarization rotation, wall motion) to the electromechanical response from electrostrictive strain, and separation of such contributions from linear piezoelectric response are largely ignored at the mesoscale. Here, we employ a band-excitation piezoresponse force microscopy (BE-PFM) technique to explore the first and second harmonics of the piezoelectric response in prototypical relaxor-ferroelectric 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-0.28PT) single crystals. Third order polynomial fitting of the second harmonic reveals considerable correlation between the cubic coefficient map and the first harmonic piezoresponse amplitude. These results are interpreted under a modified Rayleigh framework, as evidence for domain wall contributions to enhanced electromechanical response. These studies highlight the contribution of domain wall motion in the electromechanical response of relaxor ferroelectrics, and further show the utility of harmonic BE-PFM measurements in spatially mapping the mesoscopic variability inherent in disordered systems.
Experimental Investigation of Laser Emission of Dye-Doped Cholesteric Liquid Crystals with a
Wu, Shin-Tson
like a one-dimensional photo- nic crystal laser when pumped by a second harmonic Nd-YAG pulsed laser; laser enhancement 1. INTRODUCTION Cholesteric liquid crystal (CLC) is a promising chiral photonic mediumExperimental Investigation of Laser Emission of Dye-Doped Cholesteric Liquid Crystals
repulsion and quantization in almost-harmonic maps, and asymptotics of the harmonic map flow
Mitchener, Paul
map flow Peter Topping of the harmonic map flow; we find uniform exponential convergence in time, in the case und* *er repulsion and quantization in almost-harmonic maps, and asymptotics of the harmonic
Solid state eyesafe converter for multimode YAG lasers
NASA Astrophysics Data System (ADS)
Grabon, Glenn A.; Moon, William L.; Witt, Gregory A.; Jones, Larry G.
1994-06-01
We have developed and demonstrated a solid state wavelength converter that has potential for upgrading current military laser designator/rangefinders to include an eyesafe operating mode. To provide high repetition rate, compact design, and low weight in a unit that will perform under demanding environmental conditions, a KTP OPO was developed that can be pumped by the multi-axial and transverse-mode Nd:YAG lasers. Two resonator configurations were tested: forward and reverse coupling geometries. Neither configuration used 1.06-micrometers feedback, which eliminated any feedback problems into the pump resonator yet achieved GRT25% conversion. An increased margin of eyesafety was realized in the reverse coupled OPO by dumping the residual pump. Sensitivity to the pump's polarization was found to be 10% greater for hydrothermally grown crystals while flux grown crystals exhibited higher conversion efficiency. The beam quality of the converted signal tracked with the pump and scaled with the ratio of the wavelengths. OPO output coupling and resonator length were optimized for conversion efficiency. The final configuration using a 20 x 5 x 5 mm crystal was 3 to 4 inches in length, used a 50% signal reflector, and achieved greater than 35mJ output with a beam quality of 8.5 mm*mrads. Testing is currently underway to complete environmental characterization.
Efficiency and Reliability Improvement in Wind Turbine Converters by Grid Converter Adaptive Control
Munk-Nielsen, Stig
Efficiency and Reliability Improvement in Wind Turbine Converters by Grid Converter Adaptive test setup. Keywords >, >, >, >>. Abstract This paper presents a control method that reduces the losses in wind turbine converters adaptively
Broadband second harmonic generation in whispering gallery mode resonators
Lin, Guoping; Strekalov, Dmitry V; Yu, Nan
2013-01-01
Optical frequency conversion processes in nonlinear materials are limited in wavelength by the accessible phase matching and the required high pump powers. In this letter, we report a novel broadband phase matching (PM) technique in high quality factor (Q) whispering gallery mode (WGM) resonators made of birefringent crystalline materials. This technique relies on two interacting WGMs, one with constant and the other with spatially oscillating phase velocity. Thus, phase matching occurs cyclically. The technique can be implemented with a WGM resonator with its disk plane parallel to the optic axis of the crystal. With a single beta barium borate (BBO) resonator in that configuration, we experimentally demonstrated efficient second harmonic generation (SHG) to harmonic wavelengths from 780 nm in the near infrared to 317 nm in the ultraviolet (UV). The observed SHG conversion efficiency is as high as 4.6% (mW)-1. This broadband PM technique opens a new way for nonlinear optics applications in WGM resonators. Th...
Brett A. Hooper; Stephen V. Benson; Antonello Cutolo; John M. J. Madey
1988-01-01
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.
NASA Astrophysics Data System (ADS)
Hooper, Brett A.; Benson, Stephen V.; Cutolo, Antonello; Madey, John M. J.
1988-10-01
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.
Nonclassical states of the second optical harmonic in the presence of self-action
NASA Technical Reports Server (NTRS)
Chirkin, A. S.; Korolkova, N. V.
1993-01-01
The quantum theory of coherent radiation frequency doubling in crystals with quadratic and cubic optical nonlinearities is developed. The possibility of producing the quadrature-squeezed state of the second harmonic (SH) field is shown. The nonclassical SH states arise due to self-action effect.
Low work function silicon collector for thermionic converters
NASA Technical Reports Server (NTRS)
Chang, K. H.; Shimada, K.
1976-01-01
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.
Moore, Jeremy; Tomes, Matthew; Carmon, Tal; Jarrahi, Mona
2011-11-21
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
Harmonic resolution as a holographic quantum number
Bousso, Raphael
2004-01-31
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.
Portable convertible blast effects shield
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
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.
Portable convertible blast effects shield
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
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.
Design, Control, and Modeling of a New Voltage Source Converter for HVDC System
NASA Astrophysics Data System (ADS)
Mohan, Madhan; Singh, Bhim; Ketan Panigrahi, Bijaya
2013-05-01
Abstract: A New Voltage Source Converter (VSC) based on neutral clamped three-level circuit is proposed for High Voltage DC (HVDC) system. The proposed VSC is designed in a multipulse configuration. The converter is operated by Fundamental Frequency Switching (FFS). A new control method is developed for achieving all the necessary control aspects of HVDC system such as independent real and reactive power control, bidirectional real and reactive power control. The basic of the control method is varying the pulse width and by keeping the dc link voltage constant. The steady state and dynamic performances of HVDC system interconnecting two different frequencies network are demonstrated for active and reactive power control. Total number of transformers used in this system are reduced to half in comparison with the two-level VSCs for both active and reactive power control. The performance of the HVDC system is improved in terms of reduced harmonics level even at fundamental frequency switching. The harmonic performance of the designed converter is also studied for different value of the dead angle (?), and the optimized range of the dead angle is achieved for varying reactive power requirement. Simulation results are presented for the designed three level multipulse voltage source converters with the proposed control algorithm.
Third- and fifth-harmonic generation in transparent solids with few-optical-cycle midinfrared pulses
NASA Astrophysics Data System (ADS)
Garejev, N.; Gražulevi?iÅ«tÄ--, I.; Majus, D.; Tamošauskas, G.; Jukna, V.; Couairon, A.; Dubietis, A.
2014-03-01
We report an experimental and numerical investigation of third- and fifth-harmonic generation in a CaF2 crystal with 20 fs (three-optical-cycle), 2 ?m driving pulses. The double-peaked temporal profile of the third-harmonic pulse and its propagation dynamics was captured by means of the cross-correlation technique, showing that the third-harmonic pulse naturally consists of free and driven components propagating with different group velocities, and which occur without the splitting of the driving pulse at the fundamental frequency. Relevant characteristics of the harmonics generation process, such as the harmonics spectra, energy oscillations, and conversion efficiency, were measured as functions of propagation length and input-pulse energy and intensity. Our results demonstrate that the fifth harmonic is generated solely via cascaded four-wave mixing between the fundamental and third-harmonic frequency pulses due to cubic nonlinearity, without any detectable contribution of six-wave mixing due to quintic nonlinearity in the process.
High efficiency thermionic converter studies
NASA Technical Reports Server (NTRS)
Huffman, F. N.; Sommer, A. H.; Balestra, C. L.; Briere, D. P.; Oettinger, P. E.
1976-01-01
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.
Evaluation of harmonic suppression devices
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
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.
Zigzag Connected Autotransformer-Based 24-pulse AC-DC Converter
NASA Astrophysics Data System (ADS)
Xiao-qiang, Chen; Hao, Qiu
2015-02-01
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.
Cell modulated DC/DC converter
Warren, James Raymond, III
2005-01-01
A very high frequency converter roughly based on a class E topology is investigated for replacing a conventional boost converter circuit. The loss mechanisms in class E inverters are characterized, and metrics are developed ...
Novel zero-voltage-transition PWM converters
Guichao Hua; Ching-Shan Leu; Fred C. Lee
1992-01-01
A class of zero voltage transition (ZVT) power converters is proposed in which both the transistor and the rectifier operate with zero voltage switching and are subjected to minimum voltage and current stresses. The boost ZVT-PWM converter is used as an example to illustrate the operation of these converters. A 300 kHz, 600 W ZVT-PWM boost, DC-DC converter, and a
Integrated converters for switched reluctance motor drives
Z. Nie; A. Emadi
2004-01-01
Switched reluctance motors (SRM) are relatively inexpensive and robust. The proportional cost of the power electronics is large especially for lower power drives. It is therefore important to optimize the power converter for the practical applications. This work presents the concept of integrated converters for SRM drives. Basic converters based on the sub-integrated concept are also discussed for the purpose
Light-off behavior of catalytic converters
P. S. Hagan; D. W. Schwendeman
1994-01-01
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
COMMUNITY ALERT INCIDENT: Catalytic Converter Thefts
Rose, Michael R.
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
Digital scan converters in diagnostic ultrasound imaging
JONATHAN OPHIR; N. F. Maklad
1979-01-01
The use of digital scan converters in ultrasonic imaging is presented. The basic principles of ultrasound physics and imaging are briefly reviewed. A detailed description of the components and principles of operation of digital scan converters follows. The capabilities of current digital scan converters in terms of resolution, writing speed, pre-processing and postprocessing, and new rapid scanning techniques are discussed.
Structural ordering and glass forming of soft spherical particles with harmonic repulsions
Sun, Bin [School of Materials and Chemical Engineering, Zhongyuan University of Technology, Zhengzhou 450007 (China)] [School of Materials and Chemical Engineering, Zhongyuan University of Technology, Zhengzhou 450007 (China); Sun, Zhiwei; Ouyang, Wenze, E-mail: oywz@imech.ac.cn; Xu, Shenghua, E-mail: xush@imech.ac.cn [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China)] [Key Laboratory of Microgravity (National Microgravity Laboratory), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China)
2014-04-07
We carry out dissipative particle dynamics simulations to investigate the dynamic process of phase transformation in the system with harmonic repulsion particles. Just below the melting point, the system undergoes liquid state, face-centered cubic crystallization, body-centered cubic crystallization, and reentrant melting phase transition upon compression, which is in good agreement with the phase diagram constructed previously via thermodynamic integration. However, when the temperature is decreased sufficiently, the system is trapped into an amorphous and frustrated glass state in the region of intermediate density, where the solid phase and crystal structure should be thermodynamically most stable.
Theoretical analysis of high-harmonic generation in solids.
Vampa, G; McDonald, C R; Orlando, G; Klug, D D; Corkum, P B; Brabec, T
2014-08-15
We investigate theoretically high-harmonic generation (HHG) in bulk crystals exposed to intense midinfrared lasers with photon energies smaller than the band gap. The two main mechanisms, interband and intraband HHG, are explored. Our analysis indicates that the interband current neglected so far is the dominant mechanism for HHG. Saddle point analysis in the Keldysh limit yields an intuitive picture of interband HHG in solids similar to atomic HHG. Interband and intraband HHG exhibit a fundamentally different wavelength dependence. This signature can be used to experimentally distinguish between the two mechanisms in order to verify their importance. PMID:25170708
Theoretical Analysis of High-Harmonic Generation in Solids
NASA Astrophysics Data System (ADS)
Vampa, G.; McDonald, C. R.; Orlando, G.; Klug, D. D.; Corkum, P. B.; Brabec, T.
2014-08-01
We investigate theoretically high-harmonic generation (HHG) in bulk crystals exposed to intense midinfrared lasers with photon energies smaller than the band gap. The two main mechanisms, interband and intraband HHG, are explored. Our analysis indicates that the interband current neglected so far is the dominant mechanism for HHG. Saddle point analysis in the Keldysh limit yields an intuitive picture of interband HHG in solids similar to atomic HHG. Interband and intraband HHG exhibit a fundamentally different wavelength dependence. This signature can be used to experimentally distinguish between the two mechanisms in order to verify their importance.
LARGE DEVIATIONS AND VARIATIONAL PRINCIPLE FOR HARMONIC CRYSTALS
on the interactions such as super- stability, [26]. Assuming superstability and other regularity properties, a version free #12;eld in dimension d > 3 - which violate superstability, it is interesting to see how far
LARGE DEVIATIONS AND VARIATIONAL PRINCIPLE FOR HARMONIC CRYSTALS
Caputo, Pietro
on the interactions such as superstability, [26]. Assuming superstability and other regularity properties, a version free #12;eld in dimension d > 3 - which violate superstability, it is interesting to see how far
Optical Performance Monitoring in DWDM Networks Using Channels 2nd Harmonics Generation
Moncef B. Tayahi; SivaKumar Lanka; Banmali S. Rawat; Chandrasekhar Roychoudhuri
Optical second harmonic generation in dense wavelength division multiplexing was used to monitor the performance of each channel in all dense wavelength division multiplexing (DWDM) optical networks. A poled Lithium-Niobate (PP-LNO3) device is used to convert C and L- band optical DWDM channels into half wavelength channels where silicon arrayed detectors and CMOS electronics were used to perform advanced digital
Jeremy Moore; Matthew Tomes; Tal Carmon; Mona Jarrahi
2011-01-01
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
Karvonen, Lasse; Säynätjoki, Antti; Mehravar, Soroush; Rodriguez, Raul D.; Hartmann, Susanne; Zahn, Dietrich R. T.; Honkanen, Seppo; Norwood, Robert A.; Peyghambarian, N.; Kieu, Khanh; Lipsanen, Harri; Riikonen, Juha
2015-01-01
Gallium selenide (GaSe) is a layered semiconductor and a well-known nonlinear optical crystal. The discovery of graphene has created a new vast research field focusing on two-dimensional materials. We report on the nonlinear optical properties of few-layer GaSe using multiphoton microscopy. Both second- and third-harmonic generation from few-layer GaSe flakes were observed. Unexpectedly, even the peak at the wavelength of 390?nm, corresponding to the fourth-harmonic generation or the sum frequency generation from third-harmonic generation and pump light, was detected during the spectral measurements in thin GaSe flakes. PMID:25989113
Karvonen, Lasse; Säynätjoki, Antti; Mehravar, Soroush; Rodriguez, Raul D; Hartmann, Susanne; Zahn, Dietrich R T; Honkanen, Seppo; Norwood, Robert A; Peyghambarian, N; Kieu, Khanh; Lipsanen, Harri; Riikonen, Juha
2015-01-01
Gallium selenide (GaSe) is a layered semiconductor and a well-known nonlinear optical crystal. The discovery of graphene has created a new vast research field focusing on two-dimensional materials. We report on the nonlinear optical properties of few-layer GaSe using multiphoton microscopy. Both second- and third-harmonic generation from few-layer GaSe flakes were observed. Unexpectedly, even the peak at the wavelength of 390?nm, corresponding to the fourth-harmonic generation or the sum frequency generation from third-harmonic generation and pump light, was detected during the spectral measurements in thin GaSe flakes. PMID:25989113
NASA Astrophysics Data System (ADS)
Cho, Suwon; Kwak, Jong-Gu
2014-04-01
The propagation and absorption of high harmonic fast waves is of interest for non-inductive current drives in fusion experiments. The fast wave can be coupled with the ion Bernstein wave that propagates in the high magnetic field side of an ion cyclotron harmonic resonance layer. This coupling and the absorption are analyzed using the hot plasma dispersion relation and a wave equation that was converted from an approximate dispersion relation for the case where ?i=k?2?i2/2?1 (where k? is the perpendicular wave number and ?i is the ion Larmor radius). It is found that both reflection and conversion may occur near the harmonic resonance layer but that they decrease rapidly, giving rise to a sharp increase in the absorption as the parallel wave number increases.
Generalized Ellipsoidal and Sphero-Conal Harmonics
Hans Volkmer
2006-10-24
Classical ellipsoidal and sphero-conal harmonics are polynomial solutions of the Laplace equation that can be expressed in terms of Lame polynomials. Generalized ellipsoidal and sphero-conal harmonics are polynomial solutions of the more general Dunkl equation that can be expressed in terms of Stieltjes polynomials. Niven's formula connecting ellipsoidal and sphero-conal harmonics is generalized. Moreover, generalized ellipsoidal harmonics are applied to solve the Dirichlet problem for Dunkl's equation on ellipsoids.
Generalized Ellipsoidal and Sphero-Conal Harmonics
Hans Volkmer
2006-01-01
Classical ellipsoidal and sphero-conal harmonics are polynomial solutions of the Laplace equation that can be expressed in terms of Lame polynomials. Generalized ellipsoidal and sphero-conal harmonics are polynomial solutions of the more general Dunkl equation that can be expressed in terms of Stieltjes polynomials. Niven's formula connecting ellipsoidal and sphero-conal harmonics is generalized. Moreover, generalized ellipsoidal harmonics are applied to
Effects of harmonics on equipment
V. E. Wagner; J. C. Balda; T. M. Barnes; A. E. Emannuel; R. J. Ferraro; D. C. Griffith; D. P. Hartmann; W. F. Horton; W. T. Jewell; A. McEachern; D. J. Phileggi; W. E. Reid
1993-01-01
The purpose of this paper is to summarize the state-of-knowledge of the effects of power system harmonics on equipment. The general mechanisms presented are thermal overloading, disruption, and dielectric stressing. Quantitative effects are presented or referenced whenever possible. However, many of the effects can only be qualitatively described. The equipment considered are adjustable speed drives, capacitors, circuit breakers, fuses, conductors,
Standing Waves: Harmonics and Patterns
NSDL National Science Digital Library
Henderson, Tom
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.
Harmonic Phasors and Fourier Series
NSDL National Science Digital Library
This resource from Johns Hopkins University has audio and interactive components. Various forms of the Fourier series description for periodic signals are based on alternate ways of writing a cosine signal. This resource goes over Phasors, Phasor Sums, Harmonic Phasor Sums, Gibbs Effect, Windowing, Fejer Window, and Hamming Window.
Harmonic Analysis of Neural Networks
Emmanuel J. Candès
1999-01-01
It is known that superpositions of ridge functions (single hidden-layer feedforward neural networks) may give good approximations to certain kinds of multivariate functions. It remains unclear, however, how to effectively obtain such approximations. In this paper, we use ideas from harmonic analysis to attack this question. We introduce a special admissibility condition for neural activation functions. The new condition is
Harmonic piezodrive — miniaturized servo motor
Oliver Barth
2000-01-01
Miniaturised dc-motors used in servomotor applications show some disadvantages like very high speed and therefore are combined with gearsets of a high gear ratio which introduce backlash and low efficiency. This article proposed a different kind of motor principle by the combination of a harmonic drive gearbox and stack piezoactuators. The actuators replace the functionality of the wave generator generating
Harmonic Superspaces and Superconformal Fields
P. Heslop; P. S. Howe
2000-09-27
Representations of four-dimensional superconformal groups on harmonic superfields are discussed. It is argued that any representation can be given as a superfield on many superflag manifolds. Representations on analytic superspaces do not require constraints. We discuss short representations and how to obtain them as explicit products of fundamental fields. We also discuss superfields that transform under supergroups.
Auxiliary resonant DC tank converter
Peng, Fang Z. (Knoxville, TN)
2000-01-01
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.
Converting Petroleum Coke to Electricity
Pavone, A.
as compared to soft coal, has also created flame stability problems for both initial ignition, and sustained ignition. Lastly, ash deposition in the form of slagging on heat transfer surface walls has sometimes been a problem in utility scale boilers... (250 psig) slagging gasifier that introduces both oxygen and steam. The reaction is designed to convert coke to a synthesis gas mixture of CO and H2. Sulfur in the form of H2S is removed ESL-IE-92-04-47 Proceedings from the 14th National Industrial...
Crystal growth of organics for nonlinear optical applications
NASA Technical Reports Server (NTRS)
Singh, N. B.; Mazelsky, R.
1993-01-01
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.
Optical High Harmonic Generation in C60
Guoping Zhang
2005-01-01
C60 et al. Physical Review Letters Physical Review B High harmonic generation (HHG) requires a strong laser field, but in a relatively weak laser field is sufficient. Numerical results presented here show while its low order harmonics result from the laser field, its high order ones are mainly from the multiple excitations. Since high order harmonics directly correlate electronic transitions,
Simple Harmonic Motion and Newton's 3rd
Yu, Jaehoon
until outside forces changes its motion or bring it to a stop. The period of the motion can be predicted Newton's 3rd Law using two Force sensors. Procedure: Simple Harmonic Motion Getting the data 1. OpenSimple Harmonic Motion and Newton's 3rd Law Theory Simple Harmonic Motion is not as simple
Optimal control subsumes harmonic control Amine Boumaza
Paris-Sud XI, Université de
Optimal control subsumes harmonic control Amine Boumaza LORIA Campus Scientifique B.P. 239 54506 planning within the frame- works of optimal control and harmonic control. We present a formal evidence, in the continuous domain and in a stan- dard discretization, that harmonic control is the limit case of some optimal
An Introduction of Infinity Harmonic Changyou Wang
Wang, Changyou
An Introduction of Infinity Harmonic Functions Changyou Wang University of Kentucky Lexington, KY on the analysis of infinity harmonic functions, a subject that has received considerable interests very recently characterizations of infinity harmonic functions. He presents the celebrated theorem by R. Jensen [17
Bayesian harmonic models for musical signal analysis
Godsill, Simon
Bayesian harmonic models for musical signal analysis Simon Godsill and Manuel Davy June 2, 2002 harmonic models 4. Computations 5. Results 6. Discussion 5 #12;Overview 1. Music modelling issues 2. Other work 3. Bayesian harmonic models 4. Computations 5. Results 6. Discussion 5 #12;Overview 1. Music
Harmonic oscillator: an analysis via Fourier series
A. S. de Castro
2013-09-30
The Fourier series method is used to solve the homogeneous equation governing the motion of the harmonic oscillator. It is shown that the general solution to the problem can be found in a surprisingly simple way for the case of the simple harmonic oscillator. It is also shown that the damped harmonic oscillator is susceptible to the analysis.
Quantum harmonic oscillator state synthesis and analysis
Quantum harmonic oscillator state synthesis and analysis W. M. Itano, C. Monroe, D. M. Meekhof, D to the ground (n = 0) quantum harmonic oscillator state with greater than 90% probability. From this starting single, trapped, 9 Be+ ions in various quantum harmonic oscillator states and performed measurements
Motion Planning with Gamma-Harmonic Potential
Masoud, Ahmad A.
Motion Planning with Gamma-Harmonic Potential Fields AHMAD A. MASOUD, Member, IEEE King Fahad University of Petroleum and Minerals This paper extends the capabilities of the harmonic potential field (HPF flowing in a nonhomogeneous conducting medium. The resulting potential field is known as the gamma-harmonic
NASA Astrophysics Data System (ADS)
Al-Naseem, Osama Abdulrahman
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.
Harmonic ratcheting for fast acceleration
NASA Astrophysics Data System (ADS)
Cook, N.; Brennan, J. M.; Peggs, S.
2014-04-01
A major challenge in the design of rf cavities for the acceleration of medium-energy charged ions is the need to rapidly sweep the radio frequency over a large range. From low-power medical synchrotrons to high-power accelerator driven subcritical reactor systems, and from fixed focus alternating gradient accelerators to rapid cycling synchrotrons, there is a strong need for more efficient, and faster, acceleration of protons and light ions in the semirelativistic range of hundreds of MeV/u. A conventional way to achieve a large, rapid frequency sweep (perhaps over a range of a factor of 6) is to use custom-designed ferrite-loaded cavities. Ferrite rings enable the precise tuning of the resonant frequency of a cavity, through the control of the incremental permeability that is possible by introducing a pseudoconstant azimuthal magnetic field. However, rapid changes over large permeability ranges incur anomalous behavior such as the "Q-loss" and "f-dot" loss phenomena that limit performance while requiring high bias currents. Notwithstanding the incomplete understanding of these phenomena, they can be ameliorated by introducing a "harmonic ratcheting" acceleration scheme in which two or more rf cavities take turns accelerating the beam—one turns on when the other turns off, at different harmonics—so that the radio frequency can be constrained to remain in a smaller range. Harmonic ratcheting also has straightforward performance advantages, depending on the particular parameter set at hand. In some typical cases it is possible to halve the length of the cavities, or to double the effective gap voltage, or to double the repetition rate. This paper discusses and quantifies the advantages of harmonic ratcheting in general. Simulation results for the particular case of a rapid cycling medical synchrotron ratcheting from harmonic number 9 to 2 show that stability and performance criteria are met even when realistic engineering details are taken into consideration.
NASA Astrophysics Data System (ADS)
Sederberg, S.; Elezzabi, A. Y.
2015-06-01
We report visible third-harmonic conversion at ? =517 nm in subwavelength silicon-based nanoplasmonic waveguides at an unprecedented conversion efficiency of 2.3 ×10-5 . This marks both the highest third-harmonic conversion efficiency in a silicon-based or nanoplasmonic structure and the smallest silicon waveguide structure demonstrated to date. The high conversion efficiency is attributed to tight electric field confinement and strong light-matter coupling arising from surface plasmon modes in the nanoplasmonic waveguide, enabling efficient nonlinear optical mixing over micrometer length scales. The nonresonant geometry of the waveguide enables the entire ? =1550 nm femtosecond pulse spectrum to be converted to its third harmonic, which may be easily extended to the entire visible spectrum. We envisage that third-harmonic generation in silicon-based nanoplasmonic waveguides could provide a platform for integrated, broadband visible light sources and entangled triplet photons on future hybrid electronic-silicon photonic chips.
The myosin converter domain modulates muscle performance.
Swank, Douglas M; Knowles, Aileen F; Suggs, Jennifer A; Sarsoza, Floyd; Lee, Annie; Maughan, David W; Bernstein, Sanford I
2002-04-01
Myosin is the molecular motor that powers muscle contraction as a result of conformational changes during its mechanochemical cycle. We demonstrate that the converter, a compact structural domain that differs in sequence between Drosophila melanogaster myosin isoforms, dramatically influences the kinetic properties of myosin and muscle fibres. Transgenic replacement of the converter in the fast indirect flight muscle with the converter from an embryonic muscle slowed muscle kinetics, forcing a compensatory reduction in wing beat frequency to sustain flight. Conversely, replacing the embryonic converter with the flight muscle converter sped up muscle kinetics and increased maximum power twofold, compared to flight muscles expressing the embryonic myosin isoform. The substitutions also dramatically influenced in vitro actin sliding velocity, suggesting that the converter modulates a rate-limiting step preceding cross-bridge detachment. Our integrative analysis demonstrates that isoform-specific differences in the myosin converter allow different muscle types to meet their specific locomotion demands. PMID:11901423
Generation of green frequency comb from chirped ?(2) nonlinear photonic crystals
NASA Astrophysics Data System (ADS)
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
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.
NASA Technical Reports Server (NTRS)
Willis, A. E.; Gould, J. M.; Matheney, J. L.; Garrett, H. (inventors)
1984-01-01
The object of the invention is to provide an improved converter for converting one direct current voltage to another. A plurality of phased square wave voltages are provided from a ring counter through amplifiers to a like plurality of output transformers. Each of these transformers has two windings, and S(1) winding and an S(2) winding. The S(1) windings are connected in series, then the S(2) windings are connected in series, and finally, the two sets of windings are connected in series. One of six SCRs is connected between each two series connected windings to a positive output terminal and one of diodes is connected between each set of two windings of a zero output terminal. By virtue of this configuration, a quite high average direct current voltage is obtained, which varies between full voltage and two-thirds full voltage rather than from full voltage to zero. Further, its variation, ripple frequency, is reduced to one-sixth of that present in a single phase system. Application to raising battery voltage for an ion propulsion system is mentioned.
Monochromator harmonic content measurements and calculations at energies above 20 keV
Chapman, D.; Moulin, H.; Garrett, R.F.
1991-01-01
Measurements of the harmonic content from single and double crystal silicon monochromators have been made in the 20 to 100 keV at the X17 Superconducting Wiggler Beamline at the NSLS. These measurements are compared with calculations which estimate the monochromatic beam harmonic content and the detection system efficiency with good agreement. At high photon energies ( > 20keV), the scattering of x-rays from an amorphous scatterer is dominated by the inelastic Compton process. At large scattering angles this will completely overwhelm the more forward directed elastic scattering. The Compton x-ray energy shift is large enough to make the distinction between elastic and Compton scattering unambiguous when a spectrum is acquired with a solid state detector. This shift, which is energy dependent, allows the measurement of the relative harmonic intensity in a way that is not affected by pulse pileup in the detector and electronics. The present measurements were done to assess the level of harmonic contamination from two monochromator systems both used on the X17 beamline: the single crystal type monochromator for the Digital Subtraction Coronary Angiography project; and the double crystal monochromator being developed for the Multiple Energy Computed Tomography (MECT) project and the Materials Science program. 5 refs.
Tolbert, Leon M.
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
Waveguide harmonic damper for klystron amplifier.
Kang, Y.
1998-10-27
A waveguide harmonic damper was designed for removing the harmonic frequency power from the klystron amplifiers of the APS linac. Straight coaxial probe antennas are used in a rectangular waveguide to form a damper. A linear array of the probe antennas is used on a narrow wall of the rectangular waveguide for damping klystron harmonics while decoupling the fundamental frequency in dominent TE{sub 01} mode. The klystron harmonics can exist in the waveguide as waveguide higher-order modes above cutoff. Computer simulations are made to investigate the waveguide harmonic damping characteristics of the damper.
A comparative study of seed crystals for the phosphorus crystallization process.
Yim, S; Kim, E-H
2004-07-01
This study was performed to select a preferred seed crystal material for the phosphorus crystallization process through a comparative study of four materials: electron arc furnace, blast furnace and converter slag, and phosphate rock. Leaching and phosphorus removal tests were conducted to evaluate the efficacy of the four materials as seeding agents. Converter slag demonstrated a much larger leaching capacity with respect to calcium and hydroxide ions than did either electron arc furnace or blast furnace slag. The average phosphorus removal efficiencies of phosphorus rock, and the electron arc furnace, blast furnace and converter slag were 35.9%, 74.2%, 99.1%, and 94.5% following 20, 17, 32, and 175 days of leach time, respectively. Consideration of both technical and cost factors suggests that converter slag may have competitive advantages over the other three seed materials. X-ray diffraction (XRD) analysis showed that peak patterns for hydroxyapatite increased slightly as the hydrous flow time was extended. Scanning electron micrograph (SEM) images revealed that finely distributed cubic crystals were deposited on the surfaces of converter slag. When analyzed by energy dispersive x-ray spectrometer (EDS) mapping, the crystals gave a composition mole ratio (Ca/P) of 1.97 and they were determined to be hydroxyapatite. PMID:15346854
Tsung-Tsong Wu; Zi-Gui Huang; S. Lin
2004-01-01
Successful application of photonic crystals has led recently to a rapidly growing interest in the analogous acoustic effects in periodic elastic structures called phononic crystals. This study is aimed at developing a theory for two-dimensional phononic crystal consisting of materials with general anisotropy. Explicit formulations of the plane harmonic bulk wave and the surface wave dispersion relations in such a
Hemaraju, B. C.; Gnana Prakash, A. P., E-mail: gnanaprakash@physics.uni-mysore.ac.in [Department of Studies in Physics, University of Mysore, Mysore-570006, Karnataka (India); Madhukar, B. S.; Bhadregowda, D. G. [Department of Chemistry, Yuvaraja's College Mysore-570005, Karnataka (India)
2014-04-24
(R)-2-Cyano-N-(1-phenylethyl) acetamide (RCNPA) single crystals were grown by slow evaporation of the aqueous solution at room temperature (300K) using ethanol. The grown crystals were characterized by single crystal X-ray diffraction, powder X-ray diffraction, FTIR, UV-Vis-NIR transmittance, scanning electron microscopy (SEM) and powder second harmonic generation (SHG)
A new time-to-digital converter for the 3D imaging Lidar
NASA Astrophysics Data System (ADS)
Hu, Chunsheng; Huang, Zongsheng; Qin, Shiqiao; Hu, Feng
2012-10-01
In order to reduce the negative influence caused by the temperature and voltage variations of the FPGA (Field Programmable Gate Array), we propose a new FPGA-based time-to-digital converter. The proposed converter adopts a high-stability TCXO (Temperature Compensated Crystal Oscillator), a FPGA and a new algorithm, which can significantly decrease the negative influence due to the FPGA temperature and voltage variations. This paper introduces the principle of measurement, main framework, delayer chain structure and delay variation compensation method of the proposed converter, and analyzes its measurement precision and the maximum measurement frequency. The proposed converter is successfully implemented with a Cyclone I FPGA chip and a TCXO. And the implementation method is discussed in detail. The measurement precision of the converter is also validated by experiments. The results show that the mean measurement error is less than 260 ps, the standard deviation is less than 300 ps, and the maximum measurement frequency is above 10 million times per second. The precision and frequency of measurement for the proposed converter are adequate for the 3D imaging lidar (light detection and ranging). As well as the 3D imaging lidar, the converter can be applied to the pulsed laser range finder and other time interval measuring areas.
Beam shaping to suppress phase mismatch in high power second-harmonic generation
NASA Astrophysics Data System (ADS)
Hon, D. T.; Bruesselbach, H.
1980-12-01
A set of guidelines is presented for designing high-power second-harmonic generation experiments or systems which are based on beam shaping techniques such as beam fanning and beam scanning. Performance limits imposed by existing crystal quality and growth technology are defined using cesium di-hydrogen arsenate as an example. A flow chart summarizing a step-by-step design approach for high-power second-harmonic generation, starting with laser and ending with the shape of the beam, is given.
Retrieving squeezing from classically noisy light in second-harmonic generation
NASA Astrophysics Data System (ADS)
Ralph, T. C.; White, A. G.
1995-05-01
We report the results of a study of the quantum noise properties of a squeezing system involving a three-level laser pumping two similar second-harmonic-generating crystals. We show that squeezing that has been obscured by intensity and phase noise from the pump laser may be retrieved by difference detection of both second-harmonic outputs. Similarly, the squeezed vacuum formed by combining the two outputs on a 50/50 beam splitter will be squeezed at frequencies that are classically noisy in the individual beams.
Intramolecular Dynamics Probed using High Harmonic Generation
NASA Astrophysics Data System (ADS)
Hooper, Robynne; Zhou, Xibin; Li, Wen; Wagner, Nick; Kapteyn, Henry; Murnane, Margaret
2007-06-01
We observed intramolecular dynamics as a modulation in high harmonic emission. We excite coherent vibrations in CF3Cl using impulsive Raman scattering with a short laser pulse. A second laser pulse generates high harmonics. The harmonic yield is observed to oscillate at frequencies corresponding to three vibrational modes of CF3Cl. In a second experiment, we used UV light to excite and dissociate CF3I, and follow the dynamic evolution by monitoring the harmonic yield. We observe a large modulation of the harmonic yield, likely due to resonance excitation and subsequent dissociation of the molecule. We speculate that the less-than full baseline recovery after the UV pulse is due to ionization, and that the harmonic yield is sensitive to the bond length during dissociation. By these two experiments, we confirm that high harmonic generation is a sensitive probe of intramolecular dynamics and may yield more information simultaneously than conventional ultrafast spectroscopic techniques.
Chang Hsin Chien; Richard W. G. Bucknall
2007-01-01
Subsea power cables are a critical component of a voltage-source converter-high-voltage direct current (VSC-HVDC) transmission system in any offshore electrical power scheme. Subsea cables have complicated structures consisting of many different layers: conductor, insulation, sheath, and armor. Harmonic performance of the system depends upon the interactions between the subsea cable, the power converters, and other system components, such as smoothing
Infrared diagnosis using liquid crystal detectors
NASA Technical Reports Server (NTRS)
Hugenschmidt, M.; Vollrath, K.
1986-01-01
The possible uses of pulsed carbon dioxide lasers for analysis of plasmas and flows need appropriate infrared image converters. Emphasis was placed on liquid crystal detectors and their operational modes. Performance characterstics and selection criteria, such as high sensitivity, short reaction time, and high spatial resolution are discussed.
Bak, Claus Leth
Abstract--The offshore wind farm with installed back-to- back power converter in wind turbines is studied. As an example the Burbo Bank offshore wind farm with Siemens Wind Power wind turbines is taken installed in wind turbines are presented. Harmonic load flow analysis and impedance frequency
NASA Astrophysics Data System (ADS)
Goettler, Drew; Su, Mehmet; Leseman, Zayd; Soliman, Yasser; Olsson, Roy; El-Kady, Ihab
2010-10-01
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.
Method for measuring temperature of crystals during elastic and plastic deformation
D. Ronnpagel; H. Neuhauser
1972-01-01
A method of measurement developed for the investigation of energy relations during plastic deformation of metal crystals is described. The energy stored in the crystal is obtained from the difference in work expended and energy converted into heat. The heat evolved per unit of time is determined by measuring the crystal temperature during plastic deformation by means of small thermistors.
Thermionic converter emitter support arrangement
Allen, Daniel T. (La Jolla, CA)
1990-01-01
A support is provided for use in a therminonic converter to support an end of an emitter to keep it out of contact with a surrounding collector while allowing the emitter end to move axially as its temperature changes. The emitter end (34) is supported by a spring structure (44) that includes a pair of Belleville springs, and the spring structure is supported by a support structure (42) fixed to the housing that includes the collector. The support structure is in the form of a sandwich with a small metal spring-engaging element (74) at the front end, a larger metal main support (76) at the rear end that is attached to the housing, and with a ceramic layer (80) between them that is bonded by hot isostatic pressing to the metal element and metal main support. The spring structure can include a loose wafer (120) captured between the Belleville springs.
Thermionic converter emitter support arrangement
Allen, Daniel T. (La Jolla, CA)
1990-01-01
A support is provided for use in a thermionic converter to support an end an emitter to keep it out of contact with a surrounding collector while allowing the emitter end to move axially at its temperatures changes. The emitter end (34) is supported by a spring structure (44) that includes a pair of Belleville springs, and the spring structure is supported by a support structure (42) fixed to the housing that includes the collector. The support structure is in the form of a sandwich with a small metal spring-engaging element (74) at the front end, a larger metal main support (76) at the rear end that is attached to the housng, and with a ceramic layer (80) between them that is bonded by hot isostatic pressing to the metal element and metal main support. The spring structure can include a loose wafer (120) captured between the Belleville springs.
Axisymmetric generalized harmonic evolution code
Sorkin, Evgeny [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Am Muehlenberg 1, D-14476, Golm (Germany)
2010-04-15
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.
Harmonic Analysis of Neural Networks
Emmanuel J. Candès
1998-01-01
It is known that superpositions of ridge functions (single hidden-layer feedforward neuralnetworks) may give good approximations to certain kinds of multivariate functions. It remainsunclear, however, how to eectively obtain such approximations.In this paper, we use ideas from harmonic analysis to attack this question. We introduce aspecial admissibility condition for neural activation functions. The new condition is not satis-ed by the
Performance of Power Converters at Cryogenic Temperatures
NASA Technical Reports Server (NTRS)
Elbuluk, Malik E.; Gerber, Scott; Hammoud, Ahmad; Patterson, Richard L.
2001-01-01
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.
Venus topography - A harmonic analysis
NASA Technical Reports Server (NTRS)
Bills, B. G.; Kobrick, M.
1985-01-01
A model of Venusian global topography has been obtained by fitting an eighteenth-degree harmonic series to Pioneer Venus orbiter radar altimeter data. The mean radius is (6051.45 + or - 0.04) km. The corresponding mean density is (5244.8 + or 0.5) kg/cu m. The center of figure is displaced from the center of mass by (0.339 + or - 0.088) km towards (6.6 + or 10.1) deg N, (148. 8 + or - 7.7) deg. The figure of Venus is distinctly triaxial, but the orientation and magnitudes of the principal topographic axes correlate rather poorly with the gravitational principal axes. However, the higher-degree harmonics of topography and gravity are significantly correlated. The topographic variance spectrum of Venus is very similar in form to those of the moon, Mars, and especially earth. It is suggested that this spectral similarity simply reflects a statistical balance between constructional and degradational geomorphic proceses. Venus and earth are particularly similar (and differ from the moon and Mars) in that the larger bodies both exhibit a significant low degree deficit (relative to the extrapolated trend of the higher harmonics).
NSDL National Science Digital Library
James Kessler
2010-01-01
In this activity, students will carefully look at four known household crystals. After observing and describing the crystals, students will be given an unknown crystal, which is chemically the same as one of the four known crystals but looks different. There is a downloadable activity sheet that will be very helpful to educators, and will help students stay on track. An assessment sheet is also available on the activity page to keep track of students progress. There is also a step by step guide as to how to perform the experiment, and how to introduce it to the students.
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.
Converted-wave seismology for coal exploration
Natasha Hendrick
Despite the success of multi-component seismology and asso- ciated converted-wave (PS-wave) imaging methods in the petroleum industry, there has been relatively little effort devoted to shallow, high-resolution converted-wave imaging in the coal sector. By analogy to petroleum-scale applications, converted-wave seismic imaging in the coal environment offers interesting possibilities for independent validation of mapped stru c t u res, clearer imaging
Novel zero-current-transition PWM converters
Guichao Hua; Eric X. Yang; Yimin Jiang; Fred C. Lee
1993-01-01
A new family of zero-current-transition (ZCT) pulse-width-modulated (PWM) converters are proposed. The new family of converters implements zero-current turn-off for power transistor(s) without increasing voltage\\/current stresses and operates at a fixed frequency. The proposed converters are deemed most suitable for high-power applications where the minority-carrier semiconductor devices (such as IGBTs, BJTs, and MCTs) are predominantly used as the power switches.
Novel zero-current-transition PWM converters
Guichao Hua; Eric X. Yang; Yimin Jiang; Fred C. Lee
1994-01-01
A new family of zero-current-transition (ZCT) pulsewidth-modulated (PWM) converters is proposed. The new family of converters implements zero-current turn-off for power transistor(s) without increasing voltage\\/current stresses and operates at a fixed frequency. The proposed converters are deemed most suitable for high-power applications where the minority-carrier semiconductor devices (such as IGBTs, BJTs, and MCTs) are predominantly used as the power switches.
Inverting ZCS Switched-Capacitor Bidirectional Converter
Yaung-Shung Lee; Yin-Yuan Chiu; Ming-Wang Cheng
2006-01-01
The proposed inverting type zero-current switching switched-capacitor (ZCS SC) DC\\/DC converters are a new type of bi-directional power flow control conversion schemes. They possess high efficiency, low EMI emission and current stress features for the proposed quasi-resonant switched-capacitor inverting converters. A family of inverting type zero-current switching switched-capacitor bi-directional converters is presented, which can improve the current stress problem during
A Novel Lossless Snubber for Boost Converters
J. Marshall; M. Kazerani
2006-01-01
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
A theoretical study of photovoltaic converters
NASA Technical Reports Server (NTRS)
Heinbockel, John H.
1987-01-01
Mathematical models for the photovoltaic conversion of laser power were developed. These models simulate the operation of planar and vertical junction photovoltaic converters and are described in detail.
A variable parameter thermionic energy converter
Bragg, Bobby Joe
1967-01-01
. In describing the electron energy gain and loss pro- cesses in the interelectrode region, he notes that, at a particular point in the interelectrode plasma, the rates of energy gain and loss for the electron gas balance, and the electron kinetic energy flux... LIST OF FIGURES FIGURE 1. SIMPLE SCHEMATIC OF A THERMIONIC CONVERTER PAGE 2. POWER VS SPACING WITH A MINIMUM POWER POINT 3. POWER VS SPACING WITH NO MINIMUM POWER POINT 4. CONVERTER MOTIVE DIAGRAM~ O'E = 5. CONVERTER MOTIVE DIAGRAM~ 6. CONVERTER...
DC/DC Converter Stability Testing Study
NASA Technical Reports Server (NTRS)
Wang, Bright L.
2008-01-01
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.
Distributed interleaving of paralleled power converters
Kassakian, J.G.
This paper introduces a distributed approach to interleaving paralleled power converter cells. Unlike conventional methods, the distributed approach requires no centralized control, automatically accommodates varying numbers ...
Moovendaran, K; Natarajan, S
2014-08-14
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
P. L. Ramazza; S. Ducci; A. Zavatta; M. Bellini; F. T. Arecchi
2002-01-01
. We report an experimental study of the second harmonic generated in type I interaction by a Ti:Sa laser operating in the picosecond\\u000a regime at 786 nm in LBO crystals. A joint characterization of the dependence of conversion efficiency and spatial beam quality\\u000a on crystal length and degree of pump focusing is given. A simple heuristic formula, reproducing over a broad