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Sample records for vo broad band

  1. Negative thermal expansion and broad band photoluminescence in a novel material of ZrScMo2VO12.

    Science.gov (United States)

    Ge, Xianghong; Mao, Yanchao; Liu, Xiansheng; Cheng, Yongguang; Yuan, Baohe; Chao, Mingju; Liang, Erjun

    2016-04-21

    In this paper, we present a novel material with the formula of ZrScMo2VO12 for the first time. It was demonstrated that this material exhibits not only excellent negative thermal expansion (NTE) property over a wide temperature range (at least from 150 to 823 K), but also very intense photoluminescence covering the entire visible region. Structure analysis shows that ZrScMo2VO12 has an orthorhombic structure with the space group Pbcn (No. 60) at room temperature. A phase transition from monoclinic to orthorhombic structure between 70 and 90 K is also revealed. The intense white light emission is tentatively attributed to the n- and p-type like co-doping effect which creates not only the donor- and acceptor-like states in the band gap, but also donor-acceptor pairs and even bound exciton complexes. The excellent NTE property integrated with the intense white-light emission implies a potential application of this material in light emitting diode and other photoelectric devices.

  2. Broad-band beam buncher

    International Nuclear Information System (INIS)

    Goldberg, D.A.; Flood, W.S.; Arthur, A.A.; Voelker, F.

    1986-01-01

    This patent describes a broad-band beam buncher. This beam buncher consists of: a housing adapted to be eacuated, an electron gun in the housing for producing a beam of electrons, buncher means in the housing forming a buncher cavity which has an entrance opening for receiving the electron beam and an exit opening through which the electron beam passes out of the buncher cavity, a drift tube electrode in the buncher cavity and disposed between the entrance opening and the exit opening with first and second gaps between the drift tube electrode and the entrance and exit openings, the drift tube electrode which has a first drift space through which the electron beam passes in traveling between the entrance and exit openings, modulating means for supplying an ultrahigh frequeny modulating signal to the drift tube electrode for producing velocity modulation of the electrons in the electron beam as the electrons pass through the buncher cavity and the drift tube electrode between the entrance opening and the exit opening, drift space means in the housing forming a second drift space for receiving the velocity modulated electron beam from the exit opening, the velocity modulated electron beam being bunched as it passes along the second drift space, the drift space means has a discharge opening through which the electron beam is discharged from the second drift space after being bunched therein, the modulating means containing a signal source for producing an ultrahigh frequency signal, a transmission line connected between the signal source and the drift tube electrode, and terminating means connected to the drift tube electrode for terminating the transmission line in approximately its characteristic impedance to afford a broad response band with minimum 6 variations therein

  3. Broad band exciplex dye lasers

    International Nuclear Information System (INIS)

    Dienes, A.; Shank, C.V.; Trozzolo, A.M.

    1975-01-01

    The disclosure is concerned with exciplex dye lasers, i.e., lasers in which the emitting species is a complex formed only from a constituent in an electronically excited state. Noting that an exciplex laser, favorable from the standpoint of broad tunability, results from a broad shift in the peak emission wavelength for the exciplex relative to the unreacted species, a desirable class resulting in such broad shift is described. Preferred classes of laser media utilizing specified resonant molecules are set forth. (auth)

  4. Comprehensive picture of VO2 from band theory

    KAUST Repository

    Zhu, Zhiyong; Schwingenschlö gl, Udo

    2012-01-01

    The structural, electronic, and magnetic features of the metal-insulator transition from the tetragonal rutile (R) to the monoclinic (M1) phase of VO2 are well reproduced by band theory using the modified Becke-Johnson exchange potential. Based

  5. Comprehensive picture of VO2 from band theory

    KAUST Repository

    Zhu, Zhiyong

    2012-08-28

    The structural, electronic, and magnetic features of the metal-insulator transition from the tetragonal rutile (R) to the monoclinic (M1) phase of VO2 are well reproduced by band theory using the modified Becke-Johnson exchange potential. Based on this description, we identify a tendency for monoclinic charge ordering in the R phase due to electronic correlations as the origin of the phase transition. Whereas, the structural changes are crucial for the gap opening in the M1 phase, spin degeneracy in both phases is stabilized by correlation-induced delocalization of the V3d electrons.

  6. Manta A New BroadBand OBS

    Science.gov (United States)

    Hello, Y.; Yegikyan, M.; Charvis, P.; Philippe, O.

    2017-12-01

    Manta is a new BroadBand OBS developed at Geoazur and commercialized by Osean. The design is inspired by 3-years autonomy MUG-OBS a Multiparameter Ocean Bottom System which carry a lot of sort of sensor types. As Mug-OBS, Manta-OBS rated 6000m is designed to resist a trawling. All the components are non corrosive such polyethylene, titanium and buoyancy is ensured by syntactic foam. Equipped in standard version with a Trillium compact OBS Manta has an autonomy of 18 months, but can accept on its 4 input channels any kind of signal as low as from an hydrophone or larger from other type of a seismometer or accelerometer. Tri-axial geophones unit (2 Hz or 4.5 Hz ) can replace the seismometer and will expend the lifespan for the instrument. The seismometer is encapsulated in a central well established by four panels of the main structure to protect it from sea current convection and is decoupled from main chassis. An health bulletin is recoverable by acoustic any time to facilitate the installation and during a visit when instrument is deployed. Main parameters for acquisition can be changed by acoustics command from surface at any time. Once at the bottom, release for the main sensor installation is programmed on a timer but controlled by the tilt of the OBS. If the tilt is too important based on programmed limits, sensor will not released automatically, but this can be forced by acoustic command after returning the tilt informations to the boat operator. Manta is equipped with flash light and AIS system for easy location at recovery, and can also send it's position by Iridium satellite in case of an unexpected ascent such caused by a possible trawling if deployed in shallow water. Clock drift calculation is automatically made against GPS time signal once the OBS return at the surface. The recovery of the OBS is initiated by an acoustic command. These new features made Manta a very versatile instrument for monitoring earthquakes.

  7. Instantaneous band gap collapse in VO{sub 2} caused by photocarrier doping

    Energy Technology Data Exchange (ETDEWEB)

    Herzog, Marc; Wegkamp, Daniel; Wolf, Martin; Staehler, Julia [Fritz-Haber-Institut der MPG, Berlin (Germany); Xian, Lede; Cudazzo, Pierluigi [Univ. del Pais Vasco, San Sebastian (Spain); European Theoretical Spectroscopy Facility (ETSF) (France); Gatti, Matteo [European Theoretical Spectroscopy Facility (ETSF) (France); Ecole Polytechnique, Palaiseau (France); McGahan, Christina L.; Marvel, Robert E.; Haglund, Richard F. [Vanderbilt Univ., Nashville, Tennessee (United States); Rubio, Angel [Fritz-Haber-Institut der MPG, Berlin (Germany); Univ. del Pais Vasco, San Sebastian (Spain); European Theoretical Spectroscopy Facility (ETSF) (France); MPI for the Structure and Dynamics of Matter, Hamburg (Germany)

    2015-07-01

    We have investigated the controversially discussed mechanism of the insulator-to-metal transition (IMT) in VO{sub 2} by means of femtosecond time-resolved photoelectron spectroscopy (trPES). Our data show that photoexcitation transforms insulating monoclinic VO{sub 2} quasi-instantaneously into a metal without an 80 fs structural bottleneck for the photoinduced electronic phase transition. First-principles many-body perturbation theory calculations reveal an ultrahigh sensitivity of the VO{sub 2} band gap to variations of the dynamically screened Coulomb interaction thus supporting the fully electronically driven isostructural IMT indicated by our trPES results. We conclude that the ultrafast band structure renormalization is caused by photoexcitation of carriers from localized V 3d valence states, strongly changing the screening before significant hot-carrier relaxation or ionic motion has occurred.

  8. Broad-band hard X-ray reflectors

    DEFF Research Database (Denmark)

    Joensen, K.D.; Gorenstein, P.; Hoghoj, P.

    1997-01-01

    Interest in optics for hard X-ray broad-band application is growing. In this paper, we compare the hard X-ray (20-100 keV) reflectivity obtained with an energy-dispersive reflectometer, of a standard commercial gold thin-film with that of a 600 bilayer W/Si X-ray supermirror. The reflectivity...... of the multilayer is found to agree extraordinarily well with theory (assuming an interface roughness of 4.5 Angstrom), while the agreement for the gold film is less, The overall performance of the supermirror is superior to that of gold, extending the band of reflection at least a factor of 2.8 beyond...... that of the gold, Various other design options are discussed, and we conclude that continued interest in the X-ray supermirror for broad-band hard X-ray applications is warranted....

  9. Broad-Band Analysis of Polar Motion Excitations

    Science.gov (United States)

    Chen, J.

    2016-12-01

    Earth rotational changes, i.e. polar motion and length-of-day (LOD), are driven by two types of geophysical excitations: 1) mass redistribution within the Earth system, and 2) angular momentum exchange between the solid Earth (more precisely the crust) and other components of the Earth system. Accurate quantification of Earth rotational excitations has been difficult, due to the lack of global-scale observations of mass redistribution and angular momentum exchange. The over 14-years time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) have provided a unique means for quantifying Earth rotational excitations from mass redistribution in different components of the climate system. Comparisons between observed Earth rotational changes and geophysical excitations estimated from GRACE, satellite laser ranging (SLR) and climate models show that GRACE-derived excitations agree remarkably well with polar motion observations over a broad-band of frequencies. GRACE estimates also suggest that accelerated polar region ice melting in recent years and corresponding sea level rise have played an important role in driving long-term polar motion as well. With several estimates of polar motion excitations, it is possible to estimate broad-band noise variance and noise power spectra in each, given reasonable assumptions about noise independence. Results based on GRACE CSR RL05 solutions clearly outperform other estimates with the lowest noise levels over a broad band of frequencies.

  10. The broad-band overlap problem in atmospheric trace gases

    International Nuclear Information System (INIS)

    Subasilar, B.

    1991-01-01

    In relation to a better understanding of climate change and the related greenhouse problem, one way of projecting for the next decades is through general circulation models (GCMs). The only input as a driving force in the changing atmospheric and oceanic circulation patterns is the amount of heat perturbation either due to natural or man-caused activities. Among these, CO 2 concentrations resulting from the latter has been observed to be accelerating at alarmingly high rates especially after the advent of the industrialization which just began in the last century. In addition to that, collective effects of other greenhouse gases (freons, SO 2 , H 2 O, CH 4 , etc.) are as important as CO 2 . Hence, it is evident from the above considerations that, in the predictions of climate models, the heat input which triggers changes in the atmospheric patterns, should be formulated accurately. In order to realize this objective, in this research, beginning with the available line parameter data, the problems of absorption have been investigated and attacked in the frame known as the broad band modeling since that is the only best and fastest manageable representation for GCMs. The first step was the construction of a full broad band (intra band overlap) model that was also flexible enough to accommodate the individual peculiarities of the bands. Before, the well known and very useful Ramanathan model had a limited applicability in the concentration scale, and it was also not systematically or successfully incorporated into an inter band overlap picture. Then, the established ideas that served as bases up to present, have been employed but found to have a limited practical applicability when it came to predict the inter band overlaps

  11. Broad-band spectrophotometry of HAT-P-32 b

    DEFF Research Database (Denmark)

    Mallonn, M.; Bernt, I.; Herrero, E.

    2016-01-01

    Multicolour broad-band transit observations offer the opportunity to characterize the atmosphere of an extrasolar planet with small- to medium-sized telescopes. One of the most favourable targets is the hot Jupiter HAT-P-32 b. We combined 21 new transit observations of this planet with 36 previou...... makes a recent tentative detection of a scattering feature less likely. Instead, the available spectral measurements of HAT-P-32 b favour a completely flat spectrum from the near-UV to the near-IR. A plausible interpretation is a thick cloud cover at high altitudes....

  12. Broad-Band Spectroscopy of Hercules X-1 with Suzaku

    Science.gov (United States)

    Asami, Fumi; Enoto, Teruaki; Iwakiri, Wataru; Yamada, Shin'ya; Tamagawa, Toru; Mihara, Tatehiro; Nagase, Fumiaki

    2014-01-01

    Hercules X-1 was observed with Suzaku in the main-on state from 2005 to 2010. The 0.4- 100 keV wide-band spectra obtained in four observations showed a broad hump around 4-9 keV in addition to narrow Fe lines at 6.4 and 6.7 keV. The hump was seen in all the four observations regardless of the selection of the continuum models. Thus it is considered a stable and intrinsic spectral feature in Her X-1. The broad hump lacked a sharp structure like an absorption edge. Thus it was represented by two different spectral models: an ionized partial covering or an additional broad line at 6.5 keV. The former required a persistently existing ionized absorber, whose origin was unclear. In the latter case, the Gaussian fitting of the 6.5-keV line needs a large width of sigma = 1.0-1.5 keV and a large equivalent width of 400-900 eV. If the broad line originates from Fe fluorescence of accreting matter, its large width may be explained by the Doppler broadening in the accretion flow. However, the large equivalent width may be inconsistent with a simple accretion geometry.

  13. Broad-Band Variability in Accreting Compact Objects

    Directory of Open Access Journals (Sweden)

    S. Scaringi

    2015-02-01

    Full Text Available Cataclysmic variable stars are in many ways similar to X-ray binaries. Both types of systems possess an accretion disk, which in most cases can reach the surface (or event horizon of the central compact object. The main difference is that the embedded gravitational potential well in X-ray binaries is much deeper than those found in cataclysmic variables. As a result, X-ray binaries emit most of their radiation at X-ray wavelengths, as opposed to cataclysmic variables which emit mostly at optical/ultraviolet wavelengths. Both types of systems display aperiodic broad-band variability which can be associated to the accretion disk. Here, the properties of the observed X-ray variability in XRBs are compared to those observed at optical wavelengths in CVs. In most cases the variability properties of both types of systems are qualitatively similar once the relevant timescales associated with the inner accretion disk regions have been taken into account. The similarities include the observed power spectral density shapes, the rms-flux relation as well as Fourier-dependant time lags. Here a brief overview on these similarities is given, placing them in the context of the fluctuating accretion disk model which seeks to reproduce the observed variability.

  14. SKS splitting observed at Romanian broad-band seismic network

    Science.gov (United States)

    Ivan, Marian; Popa, Mihaela; Ghica, Daniela

    2008-12-01

    Shear-wave splitting results are presented for the broad-band stations of the Romanian seismic network. For stations BUC1 and CRAR (located in Moesian Platform), IAS (in East-European Platform), TIRR and CVD (in Central Dobrudja-Black Sea microplate), TIM and DRGR (in Dacia-Tisza plate, including Apuseni Mts.), BURAR, BZS and GZR (in, or very close to the Carpathian Arc), the fast directions ( φ) are around 135°. The mean delay values ( δt) of the slow wave are slightly greater for the stations placed in platform areas ( δt ~ 1.5 s) than for the stations situated in the (proximity) of Carpathians ( δt ~ 1.2 s). For the MLR station located in the South-Western part of Vrancea area, at the Carpathian Bend, the fast direction is 48°, similar to VOIR station (located in Southern Carpathians, 70 km West of MLR). At VRI and PLOR, located in the North-Eastern part of Vrancea, the fast axis is oriented approximately on North-South direction, with a possible dependence of the splitting parameters with back azimuth. At least for some stations, the splitting results are not consistent with vertical coherent lithospheric anisotropy.

  15. Designing broad phononic band gaps for in-plane modes

    Science.gov (United States)

    Li, Yang Fan; Meng, Fei; Li, Shuo; Jia, Baohua; Zhou, Shiwei; Huang, Xiaodong

    2018-03-01

    Phononic crystals are known as artificial materials that can manipulate the propagation of elastic waves, and one essential feature of phononic crystals is the existence of forbidden frequency range of traveling waves called band gaps. In this paper, we have proposed an easy way to design phononic crystals with large in-plane band gaps. We demonstrated that the gap between two arbitrarily appointed bands of in-plane mode can be formed by employing a certain number of solid or hollow circular rods embedded in a matrix material. Topology optimization has been applied to find the best material distributions within the primitive unit cell with maximal band gap width. Our results reveal that the centroids of optimized rods coincide with the point positions generated by Lloyd's algorithm, which deepens our understandings on the formation mechanism of phononic in-plane band gaps.

  16. Free space optical networks for ultra-broad band services

    CERN Document Server

    Kartalopoulos, Stamatios V

    2011-01-01

    "Free Space Optical Network is a next generation communication network which uses optical waves instead of microwaves, potentially offering faster communication with ultra band width, meaning more complex communication services can be simultaneously offered. This book describes the network concepts in simple language starting with point-to-point free space optics basics and discusses networking, interoperability with existing communication network, and security. An ideal resource for communication professionals just entering the free space optical communication field and graduate students majoring in optical communications"--Provided by publisher.

  17. System Realization of Broad Band Digital Beam Forming for Digital Array Radar

    Directory of Open Access Journals (Sweden)

    Wang Feng

    2013-09-01

    Full Text Available Broad band Digital Beam Forming (DBF is the key technique for the realization of Digital Array Radar (DAR. We propose the method of combination realization of the channel equalization and DBF time delay filter function by using adaptive Sample Matrix Inversion algorithm. The broad band DBF function is realized on a new DBF module based on parallel fiber optic engines and Field Program Gate Array (FPGA. Good performance is achieved when it is used to some radar products.

  18. Estimating carbon dioxide fluxes from temperate mountain grasslands using broad-band vegetation indices

    Directory of Open Access Journals (Sweden)

    G. Wohlfahrt

    2010-02-01

    Full Text Available The broad-band normalised difference vegetation index (NDVI and the simple ratio (SR were calculated from measurements of reflectance of photosynthetically active and short-wave radiation at two temperate mountain grasslands in Austria and related to the net ecosystem CO2 exchange (NEE measured concurrently by means of the eddy covariance method. There was no significant statistical difference between the relationships of midday mean NEE with narrow- and broad-band NDVI and SR, measured during and calculated for that same time window, respectively. The skill of broad-band NDVI and SR in predicting CO2 fluxes was higher for metrics dominated by gross photosynthesis and lowest for ecosystem respiration, with NEE in between. A method based on a simple light response model whose parameters were parameterised based on broad-band NDVI allowed to improve predictions of daily NEE and is suggested to hold promise for filling gaps in the NEE time series. Relationships of CO2 flux metrics with broad-band NDVI and SR however generally differed between the two studied grassland sites indicting an influence of additional factors not yet accounted for.

  19. Broad-band near-field ground motion simulations in 3-dimensional scattering media

    KAUST Repository

    Imperatori, W.; Mai, Paul Martin

    2012-01-01

    examine scattering phenomena, related to the loss of radiation pattern and the directivity breakdown. We first simulate broad-band ground motions for a point-source characterized by a classic ω2 spectrum model. Fault finiteness is then introduced by means

  20. Broad-Band Spectral Indices Variability of BL Lacertae by Wavelet ...

    Indian Academy of Sciences (India)

    by Wavelet Method. Hao-Jing Zhang1,2,∗, Jing-Ming Bai1, Yu-Ying Bao3 & Xiong Zhang2. 1Yunnan Astronomical Observatory, National Astronomical Observatory, ... 3Department of Physics, Yuxi Teachers' College, Yuxi, Yunnan 653100, China. ∗ ... broad-band spectral indices—periodic variation—methods: numerical:.

  1. Screened coulomb hybrid DFT investigation of band gap and optical absorption predictions of CuVO3, CuNbO3 and Cu 5Ta11O30 materials

    KAUST Repository

    Harb, Moussab

    2014-01-01

    We present a joint theoretical and experimental investigation of the optoelectronic properties of CuVO3, CuNbO3 and Cu 5Ta11O30 materials for potential photocatalytic and solar cell applications. In addition to the experimental results obtained by powder X-ray diffraction and UV-Vis spectroscopy of the materials synthesized under flowing N2 gas at atmospheric pressure via solid-state reactions, the electronic structure and the UV-Vis optical absorption coefficient of these compounds are predicted with high accuracy using advanced first-principles quantum methods based on DFT (including the perturbation theory approach DFPT) within the screened coulomb hybrid HSE06 exchange-correlation formalism. The calculated density of states are found to be in agreement with the UV-Vis diffuse reflectance spectra, predicting a small indirect band gap of 1.4 eV for CuVO3, a direct band gap of 2.6 eV for CuNbO3, and an indirect (direct) band gap of 2.1 (2.6) eV for Cu5Ta 11O30. It is confirmed that the Cu(i)-based multi-metal oxides possess a strong contribution of filled Cu(i) states in the valence band and of empty d0 metal states in the conduction band. Interestingly, CuVO3 with its predicted small indirect band gap of 1.4 eV shows the highest absorption coefficient in the visible range with a broad absorption edge extending to 886 nm. This novel result offers a great opportunity for this material to be an excellent candidate for solar cell applications. © the Partner Organisations 2014.

  2. Band offsets of novel CoTiO{sub 3}/Ag{sub 3}VO{sub 4} heterojunction measured by X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wangkawong, Kanlayawat [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Tantraviwat, Doldet [Thai Microelectronics Center (TMEC), National Electronics and Computer Technology Center (NECTEC), Chachoengsao 24000 (Thailand); Phanichphant, Sukon [Materials Science Research Centre, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Inceesungvorn, Burapat, E-mail: binceesungvorn@gmail.com [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2015-01-01

    Highlights: • Band lineup of novel CoTiO{sub 3}/Ag{sub 3}VO{sub 4} composite is determined by semidirect XPS method. • The composite forms a type-II staggered heterojunction. • Valence and conduction-band offsets are 0.2 ± 0.3 and −0.6 ± 0.3 eV, respectively. • Band lineup determination is needed for understanding charge transfer at interfaces. - Abstract: The energy band diagram and band offsets of the novel CoTiO{sub 3}/Ag{sub 3}VO{sub 4} heterojunction photocatalyst are investigated by X-ray photoelectron spectroscopy for the first time. Excluding the strain effect, the valence-band and conduction-band offsets are determined to be 0.2 ± 0.3 eV and −0.6 ± 0.3 eV, respectively. The CoTiO{sub 3}/Ag{sub 3}VO{sub 4} composite forms a type-II heterojunction, for which the photogenerated charge carriers could be effectively separated. The results suggest that determination of the energy band structure is crucial for understanding the photogenerated charge transfer mechanism at the interfaces, hence the corresponding photocatalytic activity and would also be beneficial to the design of new and efficient heterostructure-based photocatalysts.

  3. Broad-Band Visually Evoked Potentials: Re(convolution in Brain-Computer Interfacing.

    Directory of Open Access Journals (Sweden)

    Jordy Thielen

    Full Text Available Brain-Computer Interfaces (BCIs allow users to control devices and communicate by using brain activity only. BCIs based on broad-band visual stimulation can outperform BCIs using other stimulation paradigms. Visual stimulation with pseudo-random bit-sequences evokes specific Broad-Band Visually Evoked Potentials (BBVEPs that can be reliably used in BCI for high-speed communication in speller applications. In this study, we report a novel paradigm for a BBVEP-based BCI that utilizes a generative framework to predict responses to broad-band stimulation sequences. In this study we designed a BBVEP-based BCI using modulated Gold codes to mark cells in a visual speller BCI. We defined a linear generative model that decomposes full responses into overlapping single-flash responses. These single-flash responses are used to predict responses to novel stimulation sequences, which in turn serve as templates for classification. The linear generative model explains on average 50% and up to 66% of the variance of responses to both seen and unseen sequences. In an online experiment, 12 participants tested a 6 × 6 matrix speller BCI. On average, an online accuracy of 86% was reached with trial lengths of 3.21 seconds. This corresponds to an Information Transfer Rate of 48 bits per minute (approximately 9 symbols per minute. This study indicates the potential to model and predict responses to broad-band stimulation. These predicted responses are proven to be well-suited as templates for a BBVEP-based BCI, thereby enabling communication and control by brain activity only.

  4. Electrostatic probes driven by broad band high power and propagation of the turbulent perturbation

    International Nuclear Information System (INIS)

    Wang Zhijiang; Sun Xuan; Wan Shude; Wen Yizhi; Yu Changxuan; Liu Wandong; Wang Cheng; Pan Gesheng

    2003-01-01

    A high dynamic output, broad-band power source for driving electrostatic probes in the investigation on propagation of turbulent perturbation has been built and used successfully in experiments on the KT-5C tokamak. The details of the experiment setup as well as some preliminary results are presented. Detections both from the small size magnetic probes and electrostatic probes indicate that the modified perturbation excited by the power source may propagate electrostatically, and electromagnetically as well

  5. C.A.D for broad-band multistage microwave transimpedance amplifier.

    OpenAIRE

    Olomo Ngongo, A.; Perennec, A.; Soares, R.; Jarry, P.

    1992-01-01

    In high data rate optical-fiber, it is necessary to employ an ultra broad-band transimpedance amplifier. In this paper, we present a technique for the design of a transimpedance amplifiers. It can be applied as well to the design of interstage equalizers for microwave transimpedance amplifiers. In the version described in this paper, the optimisation process is applied to the transimpedance gain and noise which is adjusted. Based on the load charge matching technique, a sequential procedure t...

  6. Broad-band linear polarization and magnetic intensification in rotating magnetic stars

    International Nuclear Information System (INIS)

    Degl'Innocenti, M.L.; Calamai, G.; Degl'Innocenti, E.L.; Patriarchi, P.

    1981-01-01

    Magnetic intensification is proposed as a mechanism to explain the general features of the variable broad-band linear polarization emerging from rotating magnetic stars. This mechanism is studied in detail, and some efforts are made to investigate the wide variety of polarization diagrams that can result from it. Theoretical results are compared with direct observations of the variable magnetic star 53 Cam to determine its geometric and magnetic configuration

  7. The status of the search for muonless events in the broad band neutrino beam at NAL

    International Nuclear Information System (INIS)

    Aubert, B.; Benvenuti, A.; Cline, D.; Ford, W.T.; Imlay, R.; Ling, T.Y.; Mann, A.K.; Messing, F.; Piccioni, R.; Pilcher, J.; Reeder, D.D.; Rubbia, C.; Stefanski, R.; Sulak, L.

    The current status and results of the search for muonless events in the broad band neutrino beam at NAL are presented. An excess of events unaccompanied by muon is observed which cannot be explained by instrumental effects. The ratio of the unaccompanied events to the customary charged current events is 0.20+-0.05 for the mixture of ν and anti ν in this beam

  8. A novel approach for characterizing broad-band radio spectral energy distributions

    Science.gov (United States)

    Harvey, V. M.; Franzen, T.; Morgan, J.; Seymour, N.

    2018-05-01

    We present a new broad-band radio frequency catalogue across 0.12 GHz ≤ ν ≤ 20 GHz created by combining data from the Murchison Widefield Array Commissioning Survey, the Australia Telescope 20 GHz survey, and the literature. Our catalogue consists of 1285 sources limited by S20 GHz > 40 mJy at 5σ, and contains flux density measurements (or estimates) and uncertainties at 0.074, 0.080, 0.119, 0.150, 0.180, 0.408, 0.843, 1.4, 4.8, 8.6, and 20 GHz. We fit a second-order polynomial in log-log space to the spectral energy distributions of all these sources in order to characterize their broad-band emission. For the 994 sources that are well described by a linear or quadratic model we present a new diagnostic plot arranging sources by the linear and curvature terms. We demonstrate the advantages of such a plot over the traditional radio colour-colour diagram. We also present astrophysical descriptions of the sources found in each segment of this new parameter space and discuss the utility of these plots in the upcoming era of large area, deep, broad-band radio surveys.

  9. Study of LEO-SAT microwave link for broad-band mobile satellite communication system

    Science.gov (United States)

    Fujise, Masayuki; Chujo, Wataru; Chiba, Isamu; Furuhama, Yoji; Kawabata, Kazuaki; Konishi, Yoshihiko

    1993-01-01

    In the field of mobile satellite communications, a system based on low-earth-orbit satellites (LEO-SAT's) such as the Iridium system has been proposed. The LEO-SAT system is able to offer mobile telecommunication services in high-latitude areas. Rain degradation, fading and shadowing are also expected to be decreased when the system is operated at a high elevation angle. Furthermore, the propagation delay generated in the LEO-SAT system is less pronounced than that in the geostationary orbit satellite (GEO-SAT) system and, in voice services, the effect of the delay is almost negligible. We proposed a concept of a broad-band mobile satellite communication system with LEO-SAT's and Optical ISL. In that system, a fixed L-band (1.6/1.5 GHz) multibeam is used to offer narrow band service to the mobile terminals in the entire area covered by a LEO-SAT and steerable Ka-band (30/20 GHz) spot beams are used for the wide band service. In this paper, we present results of a study of LEO-SAT microwave link between a satellite and a mobile terminal for a broad-band mobile satellite communication system. First, the results of link budget calculations are presented and the antennas mounted on satellites are shown. For a future mobile antenna technology, we also show digital beamforming (DBF) techniques. DBF, together with modulation and/or demodulation, is becoming a key technique for mobile antennas with advanced functions such as antenna pattern calibration, correction, and radio interference suppression. In this paper, efficient DBF techniques for transmitting and receiving are presented. Furthermore, an adaptive array antenna system suitable for this LEO-SAT is presented.

  10. Room Temperature Optical Constants and Band Gap Evolution of Phase Pure M1-VO2 Thin Films Deposited at Different Oxygen Partial Pressures by Reactive Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Meng Jiang

    2014-01-01

    Full Text Available Spectroscopic ellipsometry study was employed for phase pure VO2(M1 thin films grown at different oxygen partial pressures by reactive magnetron sputtering. The optical constants of the VO2(M1 thin films have been determined in a photon energy range between 0.73 and 5.05 eV. The near-infrared extinction coefficient and optical conductivity of VO2(M1 thin films rapidly increase with decreasing O2-Ar ratios. Moreover, two electronic transitions can be uniquely assigned. The energy gaps correlated with absorption edge (E1 at varied O2-Ar ratios are almost the same (~2.0 eV; consequently, the absorption edge is not significantly changed. However, the optical band gap corresponding to semiconductor-to-metal phase transition (E2 decreases from 0.53 to 0.18 eV with decreasing O2-Ar ratios.

  11. Broad-band near-field ground motion simulations in 3-dimensional scattering media

    KAUST Repository

    Imperatori, W.

    2012-12-06

    The heterogeneous nature of Earth\\'s crust is manifested in the scattering of propagating seismic waves. In recent years, different techniques have been developed to include such phenomenon in broad-band ground-motion calculations, either considering scattering as a semi-stochastic or purely stochastic process. In this study, we simulate broad-band (0–10 Hz) ground motions with a 3-D finite-difference wave propagation solver using several 3-D media characterized by von Karman correlation functions with different correlation lengths and standard deviation values. Our goal is to investigate scattering characteristics and its influence on the seismic wavefield at short and intermediate distances from the source in terms of ground motion parameters. We also examine scattering phenomena, related to the loss of radiation pattern and the directivity breakdown. We first simulate broad-band ground motions for a point-source characterized by a classic ω2 spectrum model. Fault finiteness is then introduced by means of a Haskell-type source model presenting both subshear and super-shear rupture speed. Results indicate that scattering plays an important role in ground motion even at short distances from the source, where source effects are thought to be dominating. In particular, peak ground motion parameters can be affected even at relatively low frequencies, implying that earthquake ground-motion simulations should include scattering also for peak ground velocity (PGV) calculations. At the same time, we find a gradual loss of the source signature in the 2–5 Hz frequency range, together with a distortion of the Mach cones in case of super-shear rupture. For more complex source models and truly heterogeneous Earth, these effects may occur even at lower frequencies. Our simulations suggests that von Karman correlation functions with correlation length between several hundred metres and few kilometres, Hurst exponent around 0.3 and standard deviation in the 5–10 per cent

  12. Characteristics of temporal modulation in nonlinear propagation of broad-band lasers stacked by chirped pulses

    International Nuclear Information System (INIS)

    Wang Youwen; Chen Liezun; Zhang Lifu; Deng Jianqin; Zhang Jin; Wen Shuangchun; Fu Xiquan; Fan Dianyuan

    2010-01-01

    Characteristics of the temporal modulation riding on broad-band lasers stacked by chirped pulses are numerically investigated in nonlinear propagation. For the case of normal dispersion, the temporal modulations induced by interference among pulses and added artificially to simulate the noise weaken gradually with the increase of the propagation distance. For the case of anomalous dispersion, the temporal modulations induced by interference among pulses grow slowly at first, and start to grow rapidly after a long propagation distance; in contrast, the temporal modulations added artificially grow rapidly from the begin, indicating that the temporal peak of damage risk to the optics can be formed easily. (authors)

  13. Dual-etalon cavity ring-down frequency-comb spectroscopy with broad band light source

    Science.gov (United States)

    Chandler, David W; Strecker, Kevin E

    2014-04-01

    In an embodiment, a dual-etalon cavity-ring-down frequency-comb spectrometer system is described. A broad band light source is split into two beams. One beam travels through a first etalon and a sample under test, while the other beam travels through a second etalon, and the two beams are recombined onto a single detector. If the free spectral ranges ("FSR") of the two etalons are not identical, the interference pattern at the detector will consist of a series of beat frequencies. By monitoring these beat frequencies, optical frequencies where light is absorbed may be determined.

  14. The diverse broad-band light-curves of Swift GRBs reproduced with the cannonball model

    CERN Document Server

    Dado, Shlomo; De Rújula, A

    2009-01-01

    Two radiation mechanisms, inverse Compton scattering (ICS) and synchrotron radiation (SR), suffice within the cannonball (CB) model of long gamma ray bursts (LGRBs) and X-ray flashes (XRFs) to provide a very simple and accurate description of their observed prompt emission and afterglows. Simple as they are, the two mechanisms and the burst environment generate the rich structure of the light curves at all frequencies and times. This is demonstrated for 33 selected Swift LGRBs and XRFs, which are well sampled from early time until late time and well represent the entire diversity of the broad band light curves of Swift LGRBs and XRFs. Their prompt gamma-ray and X-ray emission is dominated by ICS of glory light. During their fast decline phase, ICS is taken over by SR which dominates their broad band afterglow. The pulse shape and spectral evolution of the gamma-ray peaks and the early-time X-ray flares, and even the delayed optical `humps' in XRFs, are correctly predicted. The canonical and non-canonical X-ra...

  15. Estimate of the atmospheric turbidity from three broad-band solar radiation algorithms. A comparative study

    Directory of Open Access Journals (Sweden)

    G. López

    2004-09-01

    Full Text Available Atmospheric turbidity is an important parameter for assessing the air pollution in local areas, as well as being the main parameter controlling the attenuation of solar radiation reaching the Earth's surface under cloudless sky conditions. Among the different turbidity indices, the Ångström turbidity coefficient β is frequently used. In this work, we analyse the performance of three methods based on broad-band solar irradiance measurements in the estimation of β. The evaluation of the performance of the models was undertaken by graphical and statistical (root mean square errors and mean bias errors means. The data sets used in this study comprise measurements of broad-band solar irradiance obtained at eight radiometric stations and aerosol optical thickness measurements obtained at one co-located radiometric station. Since all three methods require estimates of precipitable water content, three common methods for calculating atmospheric precipitable water content from surface air temperature and relative humidity are evaluated. Results show that these methods exhibit significant differences for low values of precipitable water. The effect of these differences in precipitable water estimates on turbidity algorithms is discussed. Differences in hourly turbidity estimates are later examined. The effects of random errors in pyranometer measurements and cloud interferences on the performance of the models are also presented. Examination of the annual cycle of monthly mean values of β for each location has shown that all three turbidity algorithms are suitable for analysing long-term trends and seasonal patterns.

  16. Estimate of the atmospheric turbidity from three broad-band solar radiation algorithms. A comparative study

    Directory of Open Access Journals (Sweden)

    G. López

    2004-09-01

    Full Text Available Atmospheric turbidity is an important parameter for assessing the air pollution in local areas, as well as being the main parameter controlling the attenuation of solar radiation reaching the Earth's surface under cloudless sky conditions. Among the different turbidity indices, the Ångström turbidity coefficient β is frequently used. In this work, we analyse the performance of three methods based on broad-band solar irradiance measurements in the estimation of β. The evaluation of the performance of the models was undertaken by graphical and statistical (root mean square errors and mean bias errors means. The data sets used in this study comprise measurements of broad-band solar irradiance obtained at eight radiometric stations and aerosol optical thickness measurements obtained at one co-located radiometric station. Since all three methods require estimates of precipitable water content, three common methods for calculating atmospheric precipitable water content from surface air temperature and relative humidity are evaluated. Results show that these methods exhibit significant differences for low values of precipitable water. The effect of these differences in precipitable water estimates on turbidity algorithms is discussed. Differences in hourly turbidity estimates are later examined. The effects of random errors in pyranometer measurements and cloud interferences on the performance of the models are also presented. Examination of the annual cycle of monthly mean values of β for each location has shown that all three turbidity algorithms are suitable for analysing long-term trends and seasonal patterns.

  17. High-power broad-band tunable microwave oscillator, driven by REB in plasma

    Energy Technology Data Exchange (ETDEWEB)

    Kuzelev, M V; Loza, O T; Ponomarev, A V; Rukhadze, A A; Strel` kov, P S; Shkvarunets, A G; Ulyanov, D K [General Physics Inst. of Russian Academy of Sciences, Moscow (Russian Federation)

    1997-12-31

    The radiation spectra of a plasma relativistic broad-band microwave oscillator were measured. A hollow relativistic electron beam (REB) was injected into the plasma waveguide, consisting of annular plasma in a circular metal waveguide. The radiation spectra were measured by means of a calorimeter-spectrometer with a large cross section in the band of 3-39 GHz. The mean frequency was tunable in the band of 20-27 GHz, the spectrum width was 5-25 GHz with a power level of 40-85 MW. Calculations were carried out based on non-linear theory, taking into account electromagnetic noise amplification due to REB injection into the plasma waveguide. According to the theory the radiation regime should change from the single-particle regime to the collective regime when the plasma density and the gap between the annular plasma and REB are increased. Comparison of the experimental results with the non-linear theory explains some peculiarities of the measured spectrum. (author). 4 figs., 2 refs.

  18. 11th International Conference On Broad-Band Wireless Computing, Communication and Applications

    CERN Document Server

    Xhafa, Fatos; Yim, Kangbin

    2017-01-01

    The success of all-IP networking and wireless technology has changed the ways of living the people around the world. The progress of electronic integration and wireless communications is going to pave the way to offer people the access to the wireless networks on the fly, based on which all electronic devices will be able to exchange the information with each other in ubiquitous way whenever necessary. The aim of the volume is to provide latest research findings, innovative research results, methods and development techniques from both theoretical and practical perspectives related to the emerging areas of broadband and wireless computing. This proceedings volume presents the results of the 11th International Conference on Broad-Band Wireless Computing, Communication And Applications (BWCCA-2016), held November 5-7, 2016, at Soonchunhyang University, Asan, Korea. .

  19. Laser induced broad band anti-Stokes white emission from LiYbF4 nanocrystals

    Institute of Scientific and Technical Information of China (English)

    L. Marciniak; R. Tomala; M. Stefanski; D. Hreniak; W. Strek

    2016-01-01

    Spectroscopic properties of tetragonal LiYbF4 nanocrystals under high dense NIR excitation at vacuum condition were in-vestigated. White, broad band emission covering whole visible part of the spectrum from LiYbF4 nanocrystals was observed. Its in-tensity strongly depended on the excitation power, excitation wavelength and ambient pressure. Temperature of the nanocrystals un-der 975 nm excitation was determined as a function of excitation power. Strong photo-induced current was observed from LiYbF4 pallet. The emission kinetic was analyzed. The mechanism of the anti-Stokes white emission was discussed in terms of the la-ser-induced charge transfer emission from Yb2+ states.

  20. How to adapt broad-band gravitational-wave searches for r-modes

    International Nuclear Information System (INIS)

    Owen, Benjamin J.

    2010-01-01

    Up to now there has been no search for gravitational waves from the r-modes of neutron stars in spite of the theoretical interest in the subject. Several oddities of r-modes must be addressed to obtain an observational result: The gravitational radiation field is dominated by the mass current (gravitomagnetic) quadrupole rather than the usual mass quadrupole, and the consequent difference in polarization affects detection statistics and parameter estimation. To astrophysically interpret a detection or upper limit it is necessary to convert the gravitational-wave amplitude to an r-mode amplitude. Also, it is helpful to know indirect limits on gravitational-wave emission to gauge the interest of various searches. Here I address these issues, thereby providing the ingredients to adapt broad-band searches for continuous gravitational waves to obtain r-mode results. I also show that searches of existing data can already have interesting sensitivities to r-modes.

  1. Applicability of Broad-Band Photometry for Determining the Properties of Stars and Interstellar Extinction

    Science.gov (United States)

    Sichevskij, S. G.

    2018-01-01

    The feasibility of the determination of the physical conditions in star's atmosphere and the parameters of interstellar extinction from broad-band photometric observations in the 300-3000 nm wavelength interval is studied using SDSS and 2MASS data. The photometric accuracy of these surveys is shown to be insufficient for achieving in practice the theoretical possibility of estimating the atmospheric parameters of stars based on ugriz and JHK s photometry exclusively because such determinations result in correlations between the temperature and extinction estimates. The uncertainty of interstellar extinction estimates can be reduced if prior data about the temperature are available. The surveys considered can nevertheless be potentially valuable sources of information about both stellar atmospheric parameters and the interstellar medium.

  2. Broad-band time-resolved near infrared spectroscopy in the TJ-II stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, M.C.; Pastor, I.; Cal, E. de la; McCarthy, K.J. [Laboratorio Nacional de Fusion, CIEMAT, Madrid (Spain); Diaz, D. [Universidad Autonoma de Madrid, Dept Quimica Fisica Aplicada, Madrid (Spain)

    2014-11-15

    First experimental results on broad-band, time-resolved Near Infrared (NIR;here loosely defined as covering from 750 to 1650 nm) passive spectroscopy using a high sensitivity InGaAs detector are reported for the TJ-II Stellarator. Experimental set-up is described together with its main characteristics, the most remarkable ones being its enhanced NIR response, broadband spectrum acquisition in a single shot, and time-resolved measurements with up to 1.8 kHz spectral rate. Prospects for future work and more extended physics studies in this newly open spectral region in TJ-II are discussed. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Broad band seismology in the Scotia region. The base Esperanza seismological observatory

    International Nuclear Information System (INIS)

    Russi, M.; Costa, G.; Febrer, J.

    1995-08-01

    The lithospheric study and the identification of relevant lateral heterogeneities in the Antarctic continent and borderlands, is essential to understand the geodynamic evolution both of the continental and oceanic bordering regions. The complexity of the geological evolution and the structural properties of the lithosphere in the Scotia area have been stressed by many authors. The present setting of the area is the result of the mutual interaction among the Antarctic, South American and several minor plants whose geodynamic history and actual boundaries are still partially unknown. The intense seismic activity that characterizes the region encourages the use of the seismological approach to investigate the lithospheric structure of the area. Since January 1992 a broad band three components station is operating at the Antarctic base Esperanza in the NE area of Antarctic Peninsula. The station has been installed with financial support of the Italian Programma Nazionale di Ricerche in Antartide (PNRA) by Osservatorio Geofisico Sperimentale (OGS) and Instituto Antartico Argentino (IAA). Russi et al. (1994) have analyzed selected recordings using the frequency-time analysis (FTAN) method obtaining some relevant information on the large scale structure of the lithosphere in the Scotia region even if data recorded by a single station were available. The extension of our analysis to further events and to horizontal component records is here presented. Within the framework of the international co-operation to the Antarctic Seismographic Network, the OGS and the IAA are upgrading the Esperanza station and installing an additional broad band station near the town of Ushuaia (Tierra del Fuego, Argentina) with the financial support of PNRA. The inversion of the dispersion curves through the FTAN of the signals recorded by an increased number of stations and generated by events with source-station paths spanning the region will allow us to extract the elastic and anelastic

  4. Mednet: the very broad-band seismic network for the Mediterranean

    International Nuclear Information System (INIS)

    Boschi, E.; Giardini, D.; Morelli, A.

    1991-01-01

    Mednet is the very broad-band seismic network installed by the Istituto Nazionale di Geofisica (ING) in countries of the mediterranean area, with a final goal of 12-15 stations and a spacing of about 1000 km between stations. The project started in 1987 and will be completed within 1992. Mednet is motivated both by research interest and by seismic hazard monitoring; it will allow to define the structure of the mediterranean region to a high detail, to study properties of the seismic source for intermediate and large events, and to apply this knowledge to procedures of civil protection. To reach its goals, the network has been designed following the highest technical standards: STS-1/VBB sensors, Quanterra 24 bits A/D converters with 140 dB dynamic range, real-time telemetry. Five sites are now operational in Italy (L'Aquila, Bardonecchia and Villasalto) and in northern african countries (Midelt, Morocco; Gafsa, Tunisia); other sites are under construction in Pakistan (Islamabad), Irak (Rutba) and Egypt (Kottamya), while locations are examined for stations in Greece, Jugoslavia and Algeria. The centre of the mednet network is the data center (MDC) in Rome; its tasks include data collection, verification, quality control, archivial and dissemination, monitoring of station performance, event detection, routine determination of source parameters. Data distribution will follow the guidelines set by FDSN, and will be coordinated with other international network projects

  5. Design and construction of a broad-band electric field probe

    International Nuclear Information System (INIS)

    Bahrami, A.; Sohrabi, M.; Farvadin, D.

    1996-01-01

    The design of a broad-band electric field probe based on a resistive film diode antenna on RT/Duroid substrate to measure the electric RF/MW fields as constructed at the National Radiation Protection Department (NRPD) of the Atomic Energy Organization of Iran (AEOI) are described in this paper. A square law diode detector with a matching circuit and also low pass filter have been used to produce a dc current proportional to the square RF voltage across the resistive antenna gap. A double-strip coplanar waveguide has also been designed to transfer this dc current to an amplifier with an output signal showing the electric field intensity in one direction. By using three mutually orthogonal resistive antennas, an isotropic electric field probe was made. All parts of this probe have been completely modeled and solved by the MATLAB computer program to determine the optimum values of the elements of the probe. The frequency response of the probe has also been theoretically found to be flat in the range 0.8 to 3 GHz. It was found to be quite satisfactory compared with those of similar probes commercially available. The probe is being used routinely in practice. (author)

  6. Estimate of the atmospheric turbidity from three broad-band solar radiation algorithms. A comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, G.; Batlles, F.J. [Dept. de Ingenieria Electrica y Termica, EPS La Rabida, Univ. de Huelva, Huelva (Spain)

    2004-07-01

    Atmospheric turbidity is an important parameter for assessing the air pollution in local areas, as well as being the main parameter controlling the attenuation of solar radiation reaching the Earth's surface under cloudless sky conditions. Among the different turbidity indices, the Aangstroem turbidity coefficient {beta} is frequently used. In this work, we analyse the performance of three methods based on broadband solar irradiance measurements in the estimation of {beta}. The evaluation of the performance of the models was undertaken by graphical and statistical (root mean square errors and mean bias errors) means. The data sets used in this study comprise measurements of broad-band solar irradiance obtained at eight radiometric stations and aerosol optical thickness measurements obtained at one co-located radiometric station. Since all three methods require estimates of precipitable water content, three common methods for calculating atmospheric precipitable water content from surface air temperature and relative humidity are evaluated. Results show that these methods exhibit significant differences for low values of precipitable water. The effect of these differences in precipitable water estimates on turbidity algorithms is discussed. Differences in hourly turbidity estimates are later examined. The effects of random errors in pyranometer measurements and cloud interferences on the performance of the models are also presented. Examination of the annual cycle of monthly mean values of {beta} for each location has shown that all three turbidity algorithms are suitable for analysing long-term trends and seasonal patterns. (orig.)

  7. Ultra-Broad Band Radar Cross Section Reduction of Waveguide Slot Antenna with Metamaterials

    Directory of Open Access Journals (Sweden)

    Qiang Fu

    2016-06-01

    Full Text Available To reduce the radar cross section of a waveguide slot antenna, a three-layer metamaterial is presented based on orthogonal double split-ring resonators. The absorption characteristics of three-layer metamaterial are demonstrated by simulation. Moreover, the metamaterials have been loaded on common waveguide slot antenna according to the surface current distribution. The ultra-broad band radar cross section reduction of the antenna with metamaterials had been theoretically and experimentally investigated by radiating and scattering performances. Experimental and simulated results showed that the proposed antenna with metamaterials performed broadband radar cross section reduction from 3.9 GHz to 18 GHz and the gain had been improved due to the coupling effect between slot and the period structure. The maximal radar cross section reduction achieved 17.81 dB at 8.68 GHz for x-polarized incidence and 21.79 dB at 6.25 GHz for y-polarized waves.

  8. Numerical experiments to investigate the accuracy of broad-band moment magnitude, Mwp

    Science.gov (United States)

    Hara, Tatsuhiko; Nishimura, Naoki

    2011-12-01

    We perform numerical experiments to investigate the accuracy of broad-band moment magnitude, Mwp. We conduct these experiments by measuring Mwp from synthetic seismograms and comparing the resulting values to the moment magnitudes used in the calculation of synthetic seismograms. In the numerical experiments using point sources, we have found that there is a significant dependence of Mwp on focal mechanisms, and that depths phases have a large impact on Mwp estimates, especially for large shallow earthquakes. Numerical experiments using line sources suggest that the effects of source finiteness and rupture propagation on Mwp estimates are on the order of 0.2 magnitude units for vertical fault planes with pure dip-slip mechanisms and 45° dipping fault planes with pure dip-slip (thrust) mechanisms, but that the dependence is small for strike-slip events on a vertical fault plane. Numerical experiments for huge thrust faulting earthquakes on a fault plane with a shallow dip angle suggest that the Mwp estimates do not saturate in the moment magnitude range between 8 and 9, although they are underestimates. Our results are consistent with previous studies that compared Mwp estimates to moment magnitudes calculated from seismic moment tensors obtained by analyses of observed data.

  9. The Low Band Observatory (LOBO): Expanding the VLA Low Frequency Commensal System for Continuous, Broad-band, sub-GHz Observations

    Science.gov (United States)

    Kassim, Namir E.; Clarke, Tracy E.; Helmboldt, Joseph F.; Peters, Wendy M.; Brisken, Walter; Hyman, Scott D.; Polisensky, Emil; Hicks, Brian

    2015-01-01

    The Naval Research Laboratory (NRL) and the National Radio Astronomy Observatory (NRAO) are currently commissioning the VLA Low Frequency Ionosphere and Transient Experiment (VLITE) on a subset of JVLA antennas at modest bandwidth. Its bounded scientific goals are to leverage thousands of JVLA on-sky hours per year for ionospheric and transient studies, and to demonstrate the practicality of a prime-focus commensal system on the JVLA. Here we explore the natural expansion of VLITE to a full-antenna, full-bandwidth Low Band Observatory (LOBO) that would follow naturally from a successful VLITE experience. The new Low Band JVLA receivers, coupled with the existing primary focus feeds, can access two frequency bands: 4 band (54 - 86 MHz) and P band (236-492 MHz). The 4 band feeds are newly designed and now undergoing testing. If they prove successful then they can be permanently mounted at the primary focus, unlike their narrow band predecessors. The combination of Low Band receivers and fixed, primary-focus feeds could provide continuous, broad-band data over two complimentary low-frequency bands. The system would also leverage the relatively large fields-of-view of ~10 degrees at 4 band, and ~2.5 degrees at P band, coupling an excellent survey capability with a natural advantage for serendipitous discoveries. We discuss the compelling science case that flows from LOBO's robust imaging and time domain capabilities coupled with thousands of hours of wide-field, JVLA observing time each year. We also touch on the possibility to incorporate Long Wavelength Array (LWA) stations as additional 'dishes' through the LOBO backend, to improve calibration and sensitivity in LOBO's 4 band.

  10. Enhanced surface area, high Zn interstitial defects and band gap reduction in N-doped ZnO nanosheets coupled with BiVO{sub 4} leads to improved photocatalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Sonal [Deen Dayal Upadhyaya College, Dwarka, University of Delhi, New Delhi 110078 (India); Sharma, Rishabh, E-mail: rishabh.rammstien@gmail.com [Thin Film Laboratory, Department of Physics, Indian Institute of Technology, New Delhi 110016 (India); Mehta, Bodh Raj [Thin Film Laboratory, Department of Physics, Indian Institute of Technology, New Delhi 110016 (India)

    2017-07-31

    Highlights: • In this study, we report novel nitrogen doped ZnO (nanosheet)/BiVO{sub 4} nanocomposite with enhanced visible light photocatalytic activity tested on methylene blue dye. • In a typical composite synthesis process, individual metal oxides synthesized by chemical route were mixed through ultrasonication followed by annealing at the temperature of 400 °C. • To understand mechanism of action we carried out XRD, TEM, UV–vis spectroscopy, XPS, BET & PL of the samples. • Enhancement in photocatalytic performance of the composite was due to increased light absorption due to band gap reduction and formation intermediate band. • Also, charge exchange as per Z-scheme at the hetrojunction between N-ZnO and BiVO{sub 4} resulted in reduced charge recombination rate which is further responsible for enhancement in photocatalytic activity. - Abstract: For the first time, a series of Nitrogen-doped-ZnO nanosheet coupled with BiVO{sub 4} (N-ZnO/BiVO{sub 4}) heterojunctioned photocatalysts have been synthesized. The new N-ZnO/BiVO{sub 4} material has been prepared via a simple and effective method of precipitation followed by high temperature annealing process. The photocatalytic activities of the N-ZnO/BiVO{sub 4} composites were evaluated for the degradation of methylene blue (MB) a common organic pollutant under visible-light irradiation. The results revealed that photocatalytic activity of the coupled system was directly influenced by the percentage amount of BiVO{sub 4} in N-ZnO which affected the available exposed surface area for photoreactions. 30% N-ZnO/BiVO{sub 4} system exhibited remarkable performance than 10%N-ZnO/BiVO{sub 4}, 50%N-ZnO/BiVO{sub 4}, and also to their pristine counterparts. The composite demonstrated the degradation efficiency of 90% in 90 min which is 1.76 times the efficiency of pure ZnO for same time duration. This pronounced photocatalytic effect is ascribed to the reduced band gap and lowered recombination rate of ZnO due to

  11. Precision Column CO2 Measurement from Space Using Broad Band LIDAR

    Science.gov (United States)

    Heaps, William S.

    2009-01-01

    In order to better understand the budget of carbon dioxide in the Earth's atmosphere it is necessary to develop a global high precision understanding of the carbon dioxide column. To uncover the missing sink" that is responsible for the large discrepancies in the budget as we presently understand it, calculation has indicated that measurement accuracy of 1 ppm is necessary. Because typical column average CO2 has now reached 380 ppm this represents a precision on the order of 0.25% for these column measurements. No species has ever been measured from space at such a precision. In recognition of the importance of understanding the CO2 budget to evaluate its impact on global warming the National Research Council in its decadal survey report to NASA recommended planning for a laser based total CO2 mapping mission in the near future. The extreme measurement accuracy requirements on this mission places very strong constraints on the laser system used for the measurement. This work presents an overview of the characteristics necessary in a laser system used to make this measurement. Consideration is given to the temperature dependence, pressure broadening, and pressure shift of the CO2 lines themselves and how these impact the laser system characteristics. We are examining the possibility of making precise measurements of atmospheric carbon dioxide using a broad band source of radiation. This means that many of the difficulties in wavelength control can be treated in the detector portion of the system rather than the laser source. It also greatly reduces the number of individual lasers required to make a measurement. Simplifications such as these are extremely desirable for systems designed to operate from space.

  12. Long-term uvb forecasting on the basis of spectral and broad-band measurements

    Science.gov (United States)

    Bérces, A.; Gáspár, S.; Kovács, G.; Rontó, G.

    2003-04-01

    The stratospheric ozone concentration has been investigated by several methods, e.g. determinations of the ozone layer using a network of ground based spectrophotometers, of the Dobson and the Brewer types. These data indicate significant decrease of the ozone layer superimposed by much larger seasonal changes at specific geographical locations. The stratospheric ozone plays an important role in the attenuation of the short-wavelength components of the solar spectrum, thus the consequence of the decreased ozone layer is an increased UVB level. Various pyranometers measuring the biological effect of environmental UV radiation have been constructed with spectral sensitivities close to the erythema action spectrum defined by the CIE. Using these erythemally weighted broad-band instruments to detect the tendency of UVB radiation controversial data have been found. To quantify the biological risk due to environmental UV radiation it is reasonable to weight the solar spectrum by the spectral sensitivity of the DNA damage taking into account the high DNA-sensitivity at the short wavelength range of the solar spectrum. Various biological dosimeters have been developed e.g. polycrystalline uracil thin layer. These are usually simple biological systems or components of them. Their UV sensitivity is a consequence of the DNA-damage. Biological dosimeters applied for long-term monitoring are promising tools for the assessment of the biological hazard. Simultaneous application of uracil dosimeters and Robertson-Berger meters can be useful to predict the increasing tendency of the biological UV exposure more precisely. The ratio of the biologically effective dose obtained by the uracil dosimeter (a predominately UVB effect) and by the Robertson-Berger meter (insensitive to changes below 300 nm) is a sensitive method for establishing changes in UVB irradiance due to changes in ozone layer.

  13. Constructing Repairable Meta-Structures of Ultra-Broad-Band Electromagnetic Absorption from Three-Dimensional Printed Patterned Shells.

    Science.gov (United States)

    Song, Wei-Li; Zhou, Zhili; Wang, Li-Chen; Cheng, Xiao-Dong; Chen, Mingji; He, Rujie; Chen, Haosen; Yang, Yazheng; Fang, Daining

    2017-12-13

    Ultra-broad-band electromagnetic absorption materials and structures are increasingly attractive for their critical role in competing with the advanced broad-band electromagnetic detection systems. Mechanically soft and weak wax-based materials composites are known to be insufficient to serve in practical electromagnetic absorption applications. To break through such barriers, here we developed an innovative strategy to enable the wax-based composites to be robust and repairable meta-structures by employing a three-dimensional (3D) printed polymeric patterned shell. Because of the integrated merits from both the dielectric loss wax-based composites and mechanically robust 3D printed shells, the as-fabricated meta-structures enable bear mechanical collision and compression, coupled with ultra-broad-band absorption (7-40 and 75-110 GHz, reflection loss  smaller than -10 dB) approaching state-of-the-art electromagnetic absorption materials. With the assistance of experiment and simulation methods, the design advantages and mechanism of employing such 3D printed shells for substantially promoting the electromagnetic absorption performance have been demonstrated. Therefore, such universal strategy that could be widely extended to other categories of wax-based composites highlights a smart stage on which high-performance practical multifunction meta-structures with ultra-broad-band electromagnetic absorption could be envisaged.

  14. Combustion synthesis of Eu 2+ and Dy 3+ activated Sr 3 (VO 4 ) 2 ...

    Indian Academy of Sciences (India)

    2:Eu,Dy phosphors are presented in this paper. PL emission of Sr3(VO4)2:Eu phosphor shows green broad emission band centring at 511 nm and a red sharp band at 614 nm by excitation wavelength of 342 nm. The PL emission spectrum of ...

  15. Receiver function structure beneath a broad-band seismic station in south Sumatra

    Science.gov (United States)

    MacPherson, K. A.; Hidayat, D.; Goh, S.

    2010-12-01

    We estimated the one-dimensional velocity structure beneath a broad-band station in south Sumatra by the forward modeling and inversion of receiver functions. Station PMBI belongs to the GEOFON seismic network maintained by GFZ-Potsdam, and at a longitude of 104.77° and latitude of -2.93°, sits atop the south Sumatran basin. This station is of interest to researchers at the Earth Observatory of Singapore, as data from it and other stations in Sumatra and Singapore will be incorporated into a regional velocity model for use in seismic hazard analyses. Three-component records from 193 events at teleseismic distances and Mw ≥ 5.0 were examined for this study and 67 records were deemed to have sufficient signal to noise characteristics to be retained for analysis. Observations are primarily from source zones in the Bougainville trench with back-azimuths to the east-south-east, the Japan and Kurile trenches with back-azimuths to the northeast, and a scattering of observations from other azimuths. Due to the level of noise present in even the higher-quality records, the usual frequency-domain deconvolution method of computing receiver functions was ineffective, and a time-domain iterative deconvolution was employed to obtain usable wave forms. Receiver functions with similar back-azimuths were stacked in order to improve their signal to noise ratios. The resulting wave forms are relatively complex, with significant energy being present in the tangential components, indicating heterogeneity in the underlying structure. A dip analysis was undertaken but no clear pattern was observed. However, it is apparent that polarities of the tangential components were generally reversed for records that sample the Sunda trench. Forward modeling of the receiver functions indicates the presence of a near-surface low-velocity layer (Vp≈1.9 km/s) and a Moho depth of ~31 km. Details of the crustal structure were investigated by employing time-domain inversions of the receiver

  16. Broad-band tunable visible emission of sol-gel derived SiBOC ceramic thin films

    International Nuclear Information System (INIS)

    Karakuscu, Aylin; Guider, Romain; Pavesi, Lorenzo; Soraru, Gian Domenico

    2011-01-01

    Strong broad band tunable visible emission of SiBOC ceramic films is reported and the results are compared with one of boron free SiOC ceramic films. The insertion of boron into the SiOC network is verified by Fourier-Transform Infrared Spectroscopy. Optical properties are studied by photoluminescence and ultraviolet-visible spectroscopy measurements. Boron addition causes a decrease in the emission intensity attributed to defect states and shifts the emission to the visible range at lower temperatures (800-900 o C) leading to a very broad tunable emission with high external quantum efficiency.

  17. Broad frequency band full field measurements for advanced applications: Point-wise comparisons between optical technologies

    Science.gov (United States)

    Zanarini, Alessandro

    2018-01-01

    The progress of optical systems gives nowadays at disposal on lightweight structures complex dynamic measurements and modal tests, each with its own advantages, drawbacks and preferred usage domains. It is thus more easy than before to obtain highly spatially defined vibration patterns for many applications in vibration engineering, testing and general product development. The potential of three completely different technologies is here benchmarked on a common test rig and advanced applications. SLDV, dynamic ESPI and hi-speed DIC are here first deployed in a complex and unique test on the estimation of FRFs with high spatial accuracy from a thin vibrating plate. The latter exhibits a broad band dynamics and high modal density in the common frequency domain where the techniques can find an operative intersection. A peculiar point-wise comparison is here addressed by means of discrete geometry transforms to put all the three technologies on trial at each physical point of the surface. Full field measurement technologies cannot estimate only displacement fields on a refined grid, but can exploit the spatial consistency of the results through neighbouring locations by means of numerical differentiation operators in the spatial domain to obtain rotational degrees of freedom and superficial dynamic strain distributions, with enhanced quality, compared to other technologies in literature. Approaching the task with the aid of superior quality receptance maps from the three different full field gears, this work calculates and compares rotational and dynamic strain FRFs. Dynamic stress FRFs can be modelled directly from the latter, by means of a constitutive model, avoiding the costly and time-consuming steps of building and tuning a numerical dynamic model of a flexible component or a structure in real life conditions. Once dynamic stress FRFs are obtained, spectral fatigue approaches can try to predict the life of a component in many excitation conditions. Different

  18. Preliminary measurements of gamma ray effects on characteristics of broad-band GaAs field-effect transistor preamplifiers

    International Nuclear Information System (INIS)

    Jackson, H.G.; Shimizu, T.T.; Leskovar, B.

    1985-01-01

    The effect of gamma radiation on electrical characteristics of cryogenically cooled broad-band low-noise microwave preamplifiers has been preliminarily evaluated. The change in the gain and noise figure of a 1-2 GHz preamplifier using GaAs microwave transistors was determined at gamma doses between 10 5 rad to 5 /times/ 10 8 rad. The gain and noise figure was measured at ambient temperatures of 300 K and 80 K. 8 refs., 2 figs

  19. Multi-cavity locally resonant structure with the low frequency and broad band-gaps

    Directory of Open Access Journals (Sweden)

    Jiulong Jiang

    2016-11-01

    Full Text Available A multi-cavity periodic structure with the characteristic of local resonance was proposed in the paper. The low frequency band-gap structure was comparatively analyzed by the finite element method (FEM and electric circuit analogy (ECA. Low frequency band-gap can be opened through the dual influence of the coupling’s resonance in the cavity and the interaction among the couplings between structures. Finally, the influence of the structural factors on the band-gap was analyzed. The results show that the structure, which is divided into three parts equally, has a broader effective band-gap below the frequency of 200 Hz. It is also proved that reducing the interval between unit structures can increase the intensity of the couplings among the structures. And in this way, the width of band-gap would be expanded significantly. Through the parameters adjustment, the structure enjoys a satisfied sound insulation effect below the frequency of 500Hz. In the area of low frequency noise reduction, the structure has a lot of potential applications.

  20. An Underwater Acoustic Vector Sensor with High Sensitivity and Broad Band

    Directory of Open Access Journals (Sweden)

    Hu Zhang

    2014-05-01

    Full Text Available Recently, acoustic vector sensor that use accelerators as sensing elements are widely used in underwater acoustic engineering, but the sensitivity of which at low frequency band is usually lower than -220 dB. In this paper, using a piezoelectric trilaminar optimized low frequency sensing element, we designed a high sensitivity internal placed ICP piezoelectric accelerometer as sensing element. Through structure optimization, we made a high sensitivity, broadband, small scale vector sensor. The working band is 10-2000 Hz, sound pressure sensitivity is -185 dB (at 100 Hz, outer diameter is 42 mm, length is 80 mm.

  1. How narrow-band and broad-band uvb irradiation influences the immunohistochemistry analyses of experimental animals’ skin – a comparative study. Part II

    Directory of Open Access Journals (Sweden)

    Katarzyna Borowska

    2017-09-01

    Full Text Available This is the second part of the artcle series impact narrow-band UVB radiation (NB-UVB and broad-band UVB radiation (BB-UVB on experimental animals’ skin (white Wistar female rats. The aim of this comparative study was immunohistochemistry analyses containing expression of p53 protein. Expression of p53 protein was performed on two experimental groups. One – exposed to NB-UVB; the other – exposed to BB-UVB radiation. The results indicate that p53 protein takes an active part in the process of apoptosis that is induced by both NB-UVB and BB-UVB. The results showed an increase in p53 expressing cells following BB-UVB than NB-UVB phototherapy.

  2. Comparison of UV action spectra for lethality and mutation in Salmonella typhimurium using a broad band source and monochromatic radiations

    International Nuclear Information System (INIS)

    Calkins, John; Selby, Christopher; Enoch, H.G.

    1987-01-01

    The UV-B region (280-320 nm) is thought to be primarily responsible for the mutagenic, lethal, and carcinogenic effects of solar radiation. We have conducted UV-B action spectroscopy for mutagenesis and survival of Ames' Salmonella typhimurium strain TA98 (uvrB, pKM101) using both monochromatic radiation from a dye laser and broader bandwidth radiation emitted from FS-20 sunlamps. A series of optical filters having different transmission cut-offs together with the sunlamp source provided bandwidths having successively less short wavelength components from which a ''broad band'' action spectrum was deduced. The two sets of action spectra differed both qualitatively and quantitatively: in comparison to the monochromatic action spectra, the ''broad band'' spectra showed up to a 200-fold reduced efficiency for both mutation induction and lethality by UV-B wavelengths. These results suggest a large protective effect of the background UV-A and/or visible radiations which were present during the broad spectrum irradiations and which are also present in solar radiation. Additional experiments show that to the extent tested this protective effect is not due to photo-reactivation or irradiance (dose rate) effects. (author)

  3. Analysis of Broad-band Frequency Selective Shielding Glass by FDTD method

    OpenAIRE

    笠嶋, 善憲; Kasashima, Yoshinori

    2010-01-01

    A frequency Selective shielding (FSS) glass is a print of many same size antennas on a sheet of glass, and it has high shielding properties for one specific frequency. In the past, the author analyzed theoretically the characteristics of the FSS, as a large scale array antenna. The FSS has narrow-band shielding characteristics. This time, the author analyzed accurately the characteristics of a FSS glass being a print of many same size dipole antennas on a sheet of glass by FDTD method. As the...

  4. A broad band X-ray imaging spectrophotometer for astrophysical studies

    Science.gov (United States)

    Lum, Kenneth S. K.; Lee, Dong Hwan; Ku, William H.-M.

    1988-01-01

    A broadband X-ray imaging spectrophotometer (BBXRIS) has been built for astrophysical studies. The BBXRIS is based on a large-imaging gas scintillation proportional counter (LIGSPC), a combination of a gas scintillation proportional counter and a multiwire proportional counter, which achieves 8 percent (FWHM) energy resolution and 1.5-mm (FWHM) spatial resolution at 5.9 keV. The LIGSPC can be integrated with a grazing incidence mirror and a coded aperture mask to provide imaging over a broad range of X-ray energies. The results of tests involving the LIGSPC and a coded aperture mask are presented, and possible applications of the BBXRIS are discussed.

  5. A tunable, linac based, intense, broad-band THz source forpump-probe experiments

    Energy Technology Data Exchange (ETDEWEB)

    Schmerge, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Adolphsen, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Corbett, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Dolgashev, V. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Durr, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fazio, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Fisher, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Frisch, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Gaffney, K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Guehr, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hastings, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hettel, B. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hoffmann, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hogan, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Holtkamp, N. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Huang, X. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Huang, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Kirchmann, P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); LaRue, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Limborg, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lindenberg, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Loos, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Maxwell, T. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Nilsson, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Raubenheimer, T. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Reis, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ross, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Shen, Z. -X. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stupakov, G. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Tantawi, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Tian, K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Wu, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Xiang, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Yakimenko, V. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-02-02

    We propose an intense THz source with tunable frequency and bandwidth that can directly interact with the degrees of freedom that determine the properties of materials and thus provides a new tool for controlling and directing these ultrafast processes as well as aiding synthesis of new materials with new functional properties. This THz source will broadly impact our understanding of dynamical processes in matter at the atomic-scale and in real time. Established optical pumping schemes using femtosecond visible frequency laser pulses for excitation are extended into the THz frequency regime thereby enabling resonant excitation of bonds in correlated solid state materials (phonon pumping), to drive low energy electronic excitations, to trigger surface chemistry reactions, and to all-optically bias a material with ultrashort electric fields or magnetic fields. A linac-based THz source can supply stand-alone experiments with peak intensities two orders of magnitude stronger than existing laser-based sources, but when coupled with atomic-scale sensitive femtosecond x-ray probes it opens a new frontier in ultrafast science with broad applications to correlated materials, interfacial and liquid phase chemistry, and materials in extreme conditions.

  6. Broad band energy distribution of UV-bright BL Lac objects

    International Nuclear Information System (INIS)

    Maraschi, L.; Tanzi, E.G.; Treves, A.

    1984-01-01

    IUE satellite data in the 1200-2000 and 1900-3200 A intervals of BL Lac objects are analyzed in terms of two discernible groups. A total of 25 BL Lac objects were observed, with differences between groups displayed in terms of the power slope of the energy of the UV emissions, i.e., slopes of 1 and 2. Comparisons of the spectra with those of quasars showed that quasars have a small spectral index in the 1000-6000 A band and no correlation exists between the spectral index and UV flux of the BL Lac objects. The comparisons underscore the lack of a thermal component for BL Lac objects. Steep spectral components in both BL Lac objects and highly polarized quasars emissions could both be due to synchrotron emission. Compton scattering of relativistic electrons off synchrotron photons could produce the X ray emissions. 44 references

  7. Broad band energy distribution of UV-bright BL Lac objects

    Energy Technology Data Exchange (ETDEWEB)

    Maraschi, L.; Tanzi, E.G.; Treves, A.

    1984-01-01

    IUE satellite data in the 1200-2000 and 1900-3200 A intervals of BL Lac objects are analyzed in terms of two discernible groups. A total of 25 BL Lac objects were observed, with differences between groups displayed in terms of the power slope of the energy of the UV emissions, i.e., slopes of 1 and 2. Comparisons of the spectra with those of quasars showed that quasars have a small spectral index in the 1000-6000 A band and no correlation exists between the spectral index and UV flux of the BL Lac objects. The comparisons underscore the lack of a thermal component for BL Lac objects. Steep spectral components in both BL Lac objects and highly polarized quasars emissions could both be due to synchrotron emission. Compton scattering of relativistic electrons off synchrotron photons could produce the X ray emissions. 44 references.

  8. YIG based broad band microwave absorber: A perspective on synthesis methods

    Science.gov (United States)

    Sharma, Vinay; Saha, J.; Patnaik, S.; Kuanr, Bijoy K.

    2017-10-01

    The fabrication of a thin layer of microwave absorber that operates over a wide band of frequencies is still a challenging task. With recent advances in nanostructure synthesis techniques, considerable progress has been achieved in realizations of thin nanocomposite layer designed for full absorption of incident electromagnetic (EM) radiation covering S to K band frequencies. The primary objective of this investigation is to achieve best possible EM absorption with a wide bandwidth and attenuation >10 dB for a thin absorbing layer (few hundred of microns). Magnetic yttrium iron garnet (Y3Fe5O12; in short YIG) nanoparticles (NPs) were prepared by sol-gel (SG) as well as solid-state (SS) reaction methods to elucidate the effects of nanoscale finite size on the magnetic behavior of the particles and hence their microwave absorption capabilities. It is found that YIG prepared by these two methods are different in many ways. Magnetic properties investigated using vibrating sample magnetometry (VSM) exhibit that the coercivity (Hc) of solid-state NPs is much larger (72 Oe) than the sol-gel NPs (31 Oe). Microwave absorption properties were studied by ferromagnetic resonance (FMR) technique in field sweep mode at different fixed frequencies. A thin layer (∼300 μm) of YIG film was deposited using electrophoretic deposition (EPD) technique over a coplanar waveguide (CPW) transmission line made on copper coated RT/duroid® 5880 substrates. Temperature dependent magnetic properties were also investigated using VSM and FMR techniques. Microwave absorption properties were investigated at high temperatures (up to 300 °C) both for sol-gel and solid-state synthesized NPs and are related to skin depth of YIG films. It is observed that microwave absorption almost vanishes when the temperature reached the Néel temperature of YIG.

  9. Nonlinear optics with broad-band lasers: Progress report, July 15, 1987-April 14, 1988

    International Nuclear Information System (INIS)

    Raymer, M.G.

    1988-01-01

    During this reporting period several important results were obtained on the fluctuation dynamics of both continuous-wave (cw) and pulsed dye lasers, as well as their effects in certain nonlinear optical processes: (1) A new method discovered for producing optical pulses with broad bandwidths (5 GHz) and smooth, slowly varying amplitude. The bandwidth is determined purely by phase fluctuations. (2) A theoretical treatment of pulsed dye lasers was developed to explain intensity autocorrelation measurements. (3) The effects of laser bandwidth on the resonance fluorescence spectrum of a two-level atom were calculated. (4) The source of mode intensity fluctuations in a multimode, cw dye laser were shown, both experimentally and theoretically, to be caused by deterministic chaos, rather than quantum noise as had been previously assumed in the literature

  10. Broad-band properties of the CfA Seyfert galaxies. III - Ultraviolet variability

    Science.gov (United States)

    Edelson, R. A.; Pike, G. F.; Krolik, J. H.

    1990-01-01

    A total of 657 archived IUE spectra are used to study the UV variability properties of six members of the CfA Seyfert I galaxy sample. All show strong evidence for continuum and line variations and a tendency for less luminous objects to be more strongly variable. Most objects show a clear correlation at zero lag between UV spectral index and luminosity, evidence that the variable component is an accretion disk around a black hole which is systematically smaller in less luminous sources. No correlation is seen between the continuum luminosity and equivalent width of the C IV, Mg II, and semiforbidden C III emission lines when the entire sample is examined, but a clear anticorrelation is present when only repeated observations of individual objects are considered. This is due to a combination of light-travel time effects in the broad-line region and the nonlinear responses of lines to continuum fluctuations.

  11. Broad-band spectral studies of optical lightnings and possible correlation with solar activity

    International Nuclear Information System (INIS)

    Bhat, C.L.; Sapru, M.L.; Kaul, R.K.; Razdan, H.

    1984-01-01

    Optical pulses from lightning discharges have been recorded in a ground-based experiment, meant primarily for the detection of cosmic X- and γ-ray bursts through the atmospheric fluorescence technique. It is shown that the spectral ratio Asub(v)/Asub(y), i.e. the ratio of pulse amplitudes in the violet to that in yellow wavelength bands (3400-4300 A and 4400-6000 A respectively) provides a good indication of the lightning channel temperature, the range of derived temperatures extending from 5.000 K to 60.000 K. Based on the distribution of observed Asub(v)/Asub(y) values on a daily basis, it has been possible to separate the observed lightning activity into two classes. One class of event is shown to be correlated with the peaking of the global atmospheric electric field and occurs preferentially on days when the ground-level cosmic ray intensity shows a significant decrease in association with an increase in geomagnetic activity. The results are discussed in terms of the contemporary views regarding solar control of atmospheric electricity and the various sun-weather correlations reported earlier. (author)

  12. Particle acceleration model for the broad-band baseline spectrum of the Crab nebula

    Science.gov (United States)

    Fraschetti, F.; Pohl, M.

    2017-11-01

    We develop a simple one-zone model of the steady-state Crab nebula spectrum encompassing both the radio/soft X-ray and the GeV/multi-TeV observations. By solving the transport equation for GeV-TeV electrons injected at the wind termination shock as a log-parabola momentum distribution and evolved via energy losses, we determine analytically the resulting differential energy spectrum of photons. We find an impressive agreement with the observed spectrum of synchrotron emission, and the synchrotron self-Compton component reproduces the previously unexplained broad 200-GeV peak that matches the Fermi/Large Area Telescope (LAT) data beyond 1 GeV with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) data. We determine the parameters of the single log-parabola electron injection distribution, in contrast with multiple broken power-law electron spectra proposed in the literature. The resulting photon differential spectrum provides a natural interpretation of the deviation from power law customarily fitted with empirical multiple broken power laws. Our model can be applied to the radio-to-multi-TeV spectrum of a variety of astrophysical outflows, including pulsar wind nebulae and supernova remnants, as well as to interplanetary shocks.

  13. High-performance broad-band spectroscopy for breast cancer risk assessment

    Science.gov (United States)

    Pawluczyk, Olga; Blackmore, Kristina; Dick, Samantha; Lilge, Lothar

    2005-09-01

    Medical diagnostics and screening are becoming increasingly demanding applications for spectroscopy. Although for many years the demand was satisfied with traditional spectrometers, analysis of complex biological samples has created a need for instruments capable of detecting small differences between samples. One such application is the measurement of absorbance of broad spectrum illumination by breast tissue, in order to quantify the breast tissue density. Studies have shown that breast cancer risk is closely associated with the measurement of radiographic breast density measurement. Using signal attenuation in transillumination spectroscopy in the 550-1100nm spectral range to measure breast density, has the potential to reduce the frequency of ionizing radiation, or making the test accessible to younger women; lower the cost and make the procedure more comfortable for the patient. In order to determine breast density, small spectral variances over a total attenuation of up to 8 OD have to be detected with the spectrophotometer. For this, a high performance system has been developed. The system uses Volume Phase Holographic (VPH) transmission grating, a 2D detector array for simultaneous registration of the whole spectrum with high signal to noise ratio, dedicated optical system specifically optimized for spectroscopic applications and many other improvements. The signal to noise ratio exceeding 50,000 for a single data acquisition eliminates the need for nitrogen cooled detectors and provides sufficient information to predict breast tissue density. Current studies employing transillumination breast spectroscopy (TIBS) relating to breast cancer risk assessment and monitoring are described.

  14. Harvesting Broad Frequency Band Blue Energy by a Triboelectric-Electromagnetic Hybrid Nanogenerator.

    Science.gov (United States)

    Wen, Zhen; Guo, Hengyu; Zi, Yunlong; Yeh, Min-Hsin; Wang, Xin; Deng, Jianan; Wang, Jie; Li, Shengming; Hu, Chenguo; Zhu, Liping; Wang, Zhong Lin

    2016-07-26

    Ocean wave associated energy is huge, but it has little use toward world energy. Although such blue energy is capable of meeting all of our energy needs, there is no effective way to harvest it due to its low frequency and irregular amplitude, which may restrict the application of traditional power generators. In this work, we report a hybrid nanogenerator that consists of a spiral-interdigitated-electrode triboelectric nanogenerator (S-TENG) and a wrap-around electromagnetic generator (W-EMG) for harvesting ocean energy. In this design, the S-TENG can be fully isolated from the external environment through packaging and indirectly driven by the noncontact attractive forces between pairs of magnets, and W-EMG can be easily hybridized. Notably, the hybrid nanogenerator could generate electricity under either rotation mode or fluctuation mode to collect energy in ocean tide, current, and wave energy due to the unique structural design. In addition, the characteristics and advantages of outputs indicate that the S-TENG is irreplaceable for harvesting low rotation speeds (10 Hz). The complementary output can be maximized and hybridized for harvesting energy in a broad frequency range. Finally, a single hybrid nanogenerator unit was demonstrated to harvest blue energy as a practical power source to drive several LEDs under different simulated water wave conditions. We also proposed a blue energy harvesting system floating on the ocean surface that could simultaneously harvest wind, solar, and wave energy. The proposed hybrid nanogenerator renders an effective and sustainable progress in practical applications of the hybrid nanogenerator toward harvesting water wave energy offered by nature.

  15. Random sized plasmonic nanoantennas on Silicon for low-cost broad-band near-infrared photodetection

    Science.gov (United States)

    Nazirzadeh, Mohammad Amin; Atar, Fatih Bilge; Turgut, Berk Berkan; Okyay, Ali Kemal

    2014-01-01

    In this work, we propose Silicon based broad-band near infrared Schottky barrier photodetectors. The devices operate beyond 1200 nm wavelength and exhibit photoresponsivity values as high as 3.5 mA/W with a low dark current density of about 50 pA/µm2. We make use of Au nanoislands on Silicon surface formed by rapid thermal annealing of a thin Au layer. Surface plasmons are excited on Au nanoislands and this field localization results in efficient absorption of sub-bandgap photons. Absorbed photons excite the electrons of the metal to higher energy levels (hot electron generation) and the collection of these hot electrons to the semiconductor results in photocurrent (internal photoemission). Simple and scalable fabrication makes these devices suitable for ultra-low-cost NIR detection applications. PMID:25407509

  16. A flexible experimental setup for femtosecond time-resolved broad-band ellipsometry and magneto-optics

    Energy Technology Data Exchange (ETDEWEB)

    Boschini, F.; Hedayat, H.; Piovera, C.; Dallera, C. [Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano (Italy); Gupta, A. [Department of Chemistry, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Carpene, E., E-mail: ettore.carpene@polimi.it [CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano (Italy)

    2015-01-15

    A versatile experimental setup for femtosecond time-resolved ellipsometry and magneto-optical Kerr effect measurements in the visible light range is described. The apparatus is based on the pump-probe technique and combines a broad-band probing beam with an intense near-infrared pump. According to Fresnel scattering matrix formalism, the analysis of the reflected beam at different polarization states of the incident probe light allows one to determine the diagonal and the off-diagonal elements of the dielectric tensor in the investigated sample. Moreover, the pump-probe method permits to study the dynamics of the dielectric response after a short and intense optical excitation. The performance of the experimental apparatus is tested on CrO{sub 2} single crystals as a benchmark.

  17. A flexible experimental setup for femtosecond time-resolved broad-band ellipsometry and magneto-optics

    International Nuclear Information System (INIS)

    Boschini, F.; Hedayat, H.; Piovera, C.; Dallera, C.; Gupta, A.; Carpene, E.

    2015-01-01

    A versatile experimental setup for femtosecond time-resolved ellipsometry and magneto-optical Kerr effect measurements in the visible light range is described. The apparatus is based on the pump-probe technique and combines a broad-band probing beam with an intense near-infrared pump. According to Fresnel scattering matrix formalism, the analysis of the reflected beam at different polarization states of the incident probe light allows one to determine the diagonal and the off-diagonal elements of the dielectric tensor in the investigated sample. Moreover, the pump-probe method permits to study the dynamics of the dielectric response after a short and intense optical excitation. The performance of the experimental apparatus is tested on CrO 2 single crystals as a benchmark

  18. Revealing the Faraday depth structure of radio galaxy NGC 612 with broad-band radio polarimetric observations

    Science.gov (United States)

    Kaczmarek, J. F.; Purcell, C. R.; Gaensler, B. M.; Sun, X.; O'Sullivan, S. P.; McClure-Griffiths, N. M.

    2018-05-01

    We present full-polarization, broad-band observations of the radio galaxy NGC 612 (PKS B0131-637) from 1.3 to 3.1 GHz using the Australia Telescope Compact Array. The relatively large angular scale of the radio galaxy makes it a good candidate with which to investigate the polarization mechanisms responsible for the observed Faraday depth structure. By fitting complex polarization models to the polarized spectrum of each pixel, we find that a single polarization component can adequately describe the observed signal for the majority of the radio galaxy. While we cannot definitively rule out internal Faraday rotation, we argue that the bulk of the Faraday rotation is taking place in a thin skin that girts the polarized emission. Using minimum energy estimates, we find an implied total magnetic field strength of 4.2 μG.

  19. INTERACTION BETWEEN THE BROAD-LINED TYPE Ic SUPERNOVA 2012ap AND CARRIERS OF DIFFUSE INTERSTELLAR BANDS

    International Nuclear Information System (INIS)

    Milisavljevic, Dan; Margutti, Raffaella; Crabtree, Kyle N.; Soderberg, Alicia M.; Sanders, Nathan E.; Drout, Maria R.; Kamble, Atish; Chakraborti, Sayan; Kirshner, Robert P.; Foster, Jonathan B.; Fesen, Robert A.; Parrent, Jerod T.; Pickering, Timothy E.; Cenko, S. Bradley; Silverman, Jeffrey M.; Marion, G. H. Howie; Vinko, Jozsef; Filippenko, Alexei V.; Mazzali, Paolo; Maeda, Keiichi

    2014-01-01

    Diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that are thought to be associated with carbon-rich polyatomic molecules in interstellar gas. However, because the central wavelengths of these bands do not correspond to electronic transitions of any known atomic or molecular species, their nature has remained uncertain since their discovery almost a century ago. Here we report on unusually strong DIBs in optical spectra of the broad-lined Type Ic supernova SN 2012ap that exhibit changes in equivalent width over short (≲ 30 days) timescales. The 4428 Å and 6283 Å DIB features get weaker with time, whereas the 5780 Å feature shows a marginal increase. These nonuniform changes suggest that the supernova is interacting with a nearby source of DIBs and that the DIB carriers possess high ionization potentials, such as small cations or charged fullerenes. We conclude that moderate-resolution spectra of supernovae with DIB absorptions obtained within weeks of outburst could reveal unique information about the mass-loss environment of their progenitor systems and provide new constraints on the properties of DIB carriers

  20. INTERACTION BETWEEN THE BROAD-LINED TYPE Ic SUPERNOVA 2012ap AND CARRIERS OF DIFFUSE INTERSTELLAR BANDS

    Energy Technology Data Exchange (ETDEWEB)

    Milisavljevic, Dan; Margutti, Raffaella; Crabtree, Kyle N.; Soderberg, Alicia M.; Sanders, Nathan E.; Drout, Maria R.; Kamble, Atish; Chakraborti, Sayan; Kirshner, Robert P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Foster, Jonathan B. [Yale Center for Astronomy and Astrophysics, Yale University, New Haven, CT 06520 (United States); Fesen, Robert A.; Parrent, Jerod T. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Lab, Hanover, NH 03755 (United States); Pickering, Timothy E. [Southern African Large Telescope, P.O. Box 9, Observatory 7935, Cape Town (South Africa); Cenko, S. Bradley [Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); Silverman, Jeffrey M.; Marion, G. H. Howie; Vinko, Jozsef [University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259 (United States); Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Mazzali, Paolo [Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF (United Kingdom); Maeda, Keiichi, E-mail: dmilisav@cfa.harvard.edu [Department of Astronomy, Kyoto University Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); and others

    2014-02-10

    Diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that are thought to be associated with carbon-rich polyatomic molecules in interstellar gas. However, because the central wavelengths of these bands do not correspond to electronic transitions of any known atomic or molecular species, their nature has remained uncertain since their discovery almost a century ago. Here we report on unusually strong DIBs in optical spectra of the broad-lined Type Ic supernova SN 2012ap that exhibit changes in equivalent width over short (≲ 30 days) timescales. The 4428 Å and 6283 Å DIB features get weaker with time, whereas the 5780 Å feature shows a marginal increase. These nonuniform changes suggest that the supernova is interacting with a nearby source of DIBs and that the DIB carriers possess high ionization potentials, such as small cations or charged fullerenes. We conclude that moderate-resolution spectra of supernovae with DIB absorptions obtained within weeks of outburst could reveal unique information about the mass-loss environment of their progenitor systems and provide new constraints on the properties of DIB carriers.

  1. Synthesis of BiVO4-GO-PVDF nanocomposite: An excellent, newly designed material for high photocatalytic activity towards organic dye degradation by tuning band gap energies

    Science.gov (United States)

    Biswas, Md Rokon Ud Dowla; Oh, Won-Chun

    2018-06-01

    BiVO4-GO-PVDF (PVDF = Polyvinylidene Difluoride) photocatalyst is successfully synthesized by ultrasonication method and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy techniques. Morphology of BiVO4-GO-PVDF looks like a human embryo embedded inside an amniotic sac. Photocatalytic performance of BiVO4-GO-PVDF for decolorization of methylene blue is investigated. BiVO4-GO-PVDF system reveals enhanced photocatalytic activity degradation of methylene blue (MB), Rhodamine B (RhB) & Safranin-O (SO) in water under visible light irradiation as compared to the pure BiVO4 catalyst, BiVO4 & PTFE decorated on the graphene sheet. The experimental result reveals that the covering of graphene sheets in this composite catalyst enhances photocatalytic performance under visible light. This enhanced activity is mainly attributed to effective quenching of the photogenerated electron-hole pairs confirmed by photoluminescence spectra. Trapping experiments of radicals and holes were conducted to detect reactive species generated in the photocatalytic system, experimental results revealed that direct hole oxidation reaction is obviously dominant during photocatalytic reactions on the BiVO4-GO-PVDF system.

  2. The Seismic Broad Band Western Mediterranean (wm) Network and the Obs Fomar Pool: Current state and Obs activities.

    Science.gov (United States)

    Pazos, Antonio; Davila, Jose Martin; Buforn, Elisa; Bezzeghoud, Mourad; Harnafi, Mimoun; Mattesini, Mauricio; Caldeira, Bento; Hanka, Winfried; El Moudnib, Lahcen; Strollo, Angelo; Roca, Antoni; Lopez de Mesa, Mireya; Dahm, Torsten; Cabieces, Roberto

    2016-04-01

    The Western Mediterranean (WM) seismic network started in 1996 as an initiative of the Royal Spanish Navy Observatory (ROA) and the Universidad Complutense de Madrid (UCM), with the collaboration of the GeoForschungsZentrum (GFZ) of Potsdam. A first broad band seismic station (SFUC) was installed close to Cádiz (South Spain). Since then, additional stations have been installed in the Ibero-Moghrebian region. In 2005, the "WM" code was assigned by the FDSN and new partners were jointed: Evora University (UEVO, Portugal), the Scientifique Institute of Rabat (ISRABAT, Morocco), and GFZ. Now days, the WM network is composed by 15 BB stations, all of them with Streckaisen STS-2 or STS-2.5 sensors, Quanterra or Earthdata digitizers and SeiscomP. Most them have co-installed a permanent geodetic GPS stations, and some them also have an accelerometer. There are 10 stations deployed in Spanish territory (5 in the Iberian peninsula, 1 in Balearic islands and 4 in North Africa Spanish places) with VSAT or Internet communications, 2 in Portugal (one of them without real time), and 3 in Morocco (2 VSAT and 1 ADSL). Additionally, 2 more stations (one in South Spain and one in Morocco) will be installed along this year. Additionally ROA has deployed a permanent real time VBB (CMG-3T: 360s) station at the Alboran Island. Due to the fact that part of the seismic activity is located at marine areas, and also because of the poor geographic azimuthal coverage at some zones provided by the land stations (specially in the SW of the San Vicente Cape area), ROA and UCM have acquired six broad band "LOBSTERN" OBS, manufactured by KUM (Kiel, Germany), conforming the OBS FOMAR pool. Three of them with CMG-40T sensor and the other with Trillium 120. These OBS were deployed along the Gibraltar strait since January to November 2014 to study the microseismicity in the Gibraltar strait area. In September 2015 FOMAR network has been deployed in SW of the San Vicente Cape for 8 months as a part of

  3. Efficient full-spectrum utilization, reception and conversion of solar energy by broad-band nanospiral antenna.

    Science.gov (United States)

    Zhao, Huaqiao; Gao, Huotao; Cao, Ting; Li, Boya

    2018-01-22

    In this work, the collection of solar energy by a broad-band nanospiral antenna is investigated in order to solve the low efficiency of the solar rectenna based on conventional nanoantennas. The antenna impedance, radiation, polarization and effective area are all considered in the efficiency calculation using the finite integral technique. The wavelength range investigated is 300-3000 nm, which corresponds to more than 98% of the solar radiation energy. It's found that the nanospiral has stronger field enhancement in the gap than a nanodipole counterpart. And a maximum harvesting efficiency about 80% is possible in principle for the nanospiral coupled to a rectifier resistance of 200 Ω, while about 10% for the nanodipole under the same conditions. Moreover, the nanospiral could be coupled to a rectifier diode of high resistance more easily than the nanodipole. These results indicate that the efficient full-spectrum utilization, reception and conversion of solar energy can be achieved by the nanospiral antenna, which is expected to promote the solar rectenna to be a promising technology in the clean, renewable energy application.

  4. Dynamics of a broad-band quantum cascade laser: from chaos to coherent dynamics and mode-locking

    Science.gov (United States)

    Columbo, L. L.; Barbieri, S.; Sirtori, C.; Brambilla, M.

    2018-02-01

    The dynamics of a multimode Quantum Cascade Laser, is studied in a model based on effective semiconductor Maxwell-Bloch equations, encompassing key features for the radiationmedium interaction such as an asymmetric, frequency dependent, gain and refractive index as well as the phase-amplitude coupling provided by the Henry factor. By considering the role of the free spectral range and Henry factor, we develop criteria suitable to identify the conditions which allow to destabilize, close to threshold, the traveling wave emitted by the laser and lead to chaotic or regular multimode dynamics. In the latter case our simulations show that the field oscillations are associated to self-confined structures which travel along the laser cavity, bridging mode-locking and solitary wave propagation. In addition, we show how a RF modulation of the bias current leads to active mode-locking yielding high-contrast, picosecond pulses. Our results compare well with recent experiments on broad-band THz-QCLs and may help understanding the conditions for the generation of ultrashort pulses and comb operation in Mid-IR and THz spectral regions

  5. Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at Z greater than 1

    Science.gov (United States)

    vanderWel, A.; Straughn, A. N.; Rix, H.-W.; Finkelstein, S. L.; Koekemoer, A. M.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; hide

    2012-01-01

    We identify an abundant population of extreme emission line galaxies (EELGs) at redshift z approx. 1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). 69 EELG candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared broad-band magnitudes. Supported by spectroscopic confirmation of strong [OIII] emission lines . with rest-frame equivalent widths approx. 1000A in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with approx.10(exp 8) Solar Mass in stellar mass, undergoing an enormous starburst phase with M*/M* of only approx. 15 Myr. These bursts may cause outflows that are strong enough to produce cored dark matter profiles in low-mass galaxies. The individual star formation rates and the co-moving number density (3.7x10(exp -4) Mpc(sup -3) can produce in approx.4 Gyr much of the stellar mass density that is presently contained in 10(exp 8) - 10(exp 9) Solar Mass dwarf galaxies. Therefore, our observations provide a strong indication that many or even most of the stars in present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z > 1.

  6. Boosting the Visible-Light Photoactivity of BiOCl/BiVO4/N-GQD Ternary Heterojunctions Based on Internal Z-Scheme Charge Transfer of N-GQDs: Simultaneous Band Gap Narrowing and Carrier Lifetime Prolonging.

    Science.gov (United States)

    Zhu, Mingyue; Liu, Qian; Chen, Wei; Yin, Yuanyuan; Ge, Lan; Li, Henan; Wang, Kun

    2017-11-08

    The efficient separation of photogenerated electron-hole pairs in photoactive materials is highly desired, allowing their transfer to specific sites for undergoing redox reaction in various applications. The construction of ternary heterojunctions is a practical strategy to enhance the migration of photogenerated electron that realizes the synergistic effect of multicomponents rather than the simple overlay of single component. Here, we demonstrate an available way to fabricate new BiOCl/BiVO 4 /nitrogen-doped graphene quantum dot (N-GQD) ternary heterojunctions that exhibit higher efficiency in charge separation than any binary heterojunction or pure material under visible-light irradiation. UV-vis diffuse reflectance spectroscopy demonstrated that the proposed BiOCl/BiVO 4 /N-GQD ternary heterojunctions possess the narrower band gap energy. More importantly, the ternary heterojunctions reveal the prolonged lifetime of photogenerated charges and enhanced the separation efficiency of photogenerated electron-hole pairs, which may be ascribed to sensitization based on an internal Z-scheme charge transfer at the interface of N-GQDs with oxygen functional groups. Furthermore, we examine the photoactive performance of proposed ternary heterojunctions in aqueous solution by using the photodegradation of bisphenol A as a model system and BiOCl/BiVO 4 /N-GQD ternary heterojunctions also display a dramatically enhanced photodegradation rate. The proposed charge separation and transfer process of BiOCl/BiVO 4 /N-GQD ternary heterojunctions for the enhanced photoactivity were deduced by electrochemical measurements, photoluminescence, and electron spin resonance. The results demonstrate that a Z-scheme charge process was formed between BiOCl/BiVO 4 binary heterojunctions and N-GQDs, leading to an efficient charge carrier separation and strong photocatalytic ability. Notably, this work may assist in a better understanding of the role of N-GQDs in kinds of heterojunctions

  7. The relation of the broad band with the E2g phonon and superconductivity in the Mg(B1-xCx)2 compound

    International Nuclear Information System (INIS)

    Parisiades, P.; Lampakis, D.; Palles, D.; Liarokapis, E.; Karpinski, J.

    2007-01-01

    We have carried out an extensive micro-Raman study on Mg(B 1-x C x ) 2 single crystals, for carbon concentrations up to x=0.15. The E 2g symmetry broad band for pure MgB 2 at ∼600cm -1 disappears even for small doping levels (x=0.027) and two well-defined peaks in the high-energy side of this band play a major role in the Raman spectra of the substituted compounds. We propose that a two-mode behavior of the compound might be present, induced by the coupling of the observed phonons with the electronic bands

  8. X-ray Emitting GHz-Peaked Spectrum Galaxies: Testing a Dynamical-Radiative Model with Broad-Band Spectra

    International Nuclear Information System (INIS)

    Ostorero, L.; Moderski, R.; Stawarz, L.; Diaferio, A.; Kowalska, I.; Cheung, C.C.; Kataoka, J.; Begelman, M.C.; Wagner, S.J.

    2010-01-01

    In a dynamical-radiative model we recently developed to describe the physics of compact, GHz-Peaked-Spectrum (GPS) sources, the relativistic jets propagate across the inner, kpc-sized region of the host galaxy, while the electron population of the expanding lobes evolves and emits synchrotron and inverse-Compton (IC) radiation. Interstellar-medium gas clouds engulfed by the expanding lobes, and photoionized by the active nucleus, are responsible for the radio spectral turnover through free-free absorption (FFA) of the synchrotron photons. The model provides a description of the evolution of the GPS spectral energy distribution (SED) with the source expansion, predicting significant and complex high-energy emission, from the X-ray to the γ-ray frequency domain. Here, we test this model with the broad-band SEDs of a sample of eleven X-ray emitting GPS galaxies with Compact-Symmetric-Object (CSO) morphology, and show that: (i) the shape of the radio continuum at frequencies lower than the spectral turnover is indeed well accounted for by the FFA mechanism; (ii) the observed X-ray spectra can be interpreted as non-thermal radiation produced via IC scattering of the local radiation fields off the lobe particles, providing a viable alternative to the thermal, accretion-disk dominated scenario. We also show that the relation between the hydrogen column densities derived from the X-ray (N H ) and radio (N HI ) data of the sources is suggestive of a positive correlation, which, if confirmed by future observations, would provide further support to our scenario of high-energy emitting lobes.

  9. The broad-band X-ray spectrum of IC 4329A from a joint NuSTAR/Suzaku observation

    Energy Technology Data Exchange (ETDEWEB)

    Brenneman, L. W.; Elvis, M. [Harvard-Smithsonian CfA, 60 Garden St., MS-67, Cambridge, MA 02138 (United States); Madejski, G. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Fuerst, F.; Harrison, F. A.; Grefenstette, B. W.; Madsen, K. K.; Rivers, E.; Walton, D. J. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Matt, G.; Marinucci, A. [Dipartimento di Matematica e Fisica, Università Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Ballantyne, D. R. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Boggs, S. E. [Space Science Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, F. E.; Craig, W. W. [DTU Space-National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Zhang, W. W. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2014-06-10

    We have obtained a deep, simultaneous observation of the bright, nearby Seyfert galaxy IC 4329A with Suzaku and NuSTAR. Through a detailed spectral analysis, we are able to robustly separate the continuum, absorption, and distant reflection components in the spectrum. The absorbing column is found to be modest (∼6×10{sup 21} cm{sup −2} ), and does not introduce any significant curvature in the Fe K band. We are able to place a strong constraint on the presence of a broadened Fe Kα line (E{sub rest}=6.46{sub −0.07}{sup +0.08} keV with σ=0.33{sub −0.07}{sup +0.08} keV and EW=34{sub −7}{sup +8} eV), though we are not able to constrain any of the parameters of a relativistic reflection model. These results highlight the range in broad Fe K line strengths observed in nearby, bright, active galactic nuclei (roughly an order of magnitude), and imply a corresponding range in the physical properties of the inner accretion disk in these sources. We have also updated our previously reported measurement of the high-energy cutoff of the hard X-ray emission using both observatories rather than just NuSTAR alone: E {sub cut} = 186 ± 14 keV. This high-energy cutoff acts as a proxy for the temperature of the coronal electron plasma, enabling us to further separate this parameter from the plasma's optical depth and to update our results for these parameters as well. We derive kT=50{sub −3}{sup +6} keV with τ=2.34{sub −0.11}{sup +0.16} using a spherical geometry, kT = 61 ± 1 keV with τ = 0.68 ± 0.02 for a slab geometry, with both having an equivalent goodness-of-fit.

  10. Broad self-trapped and slow light bands based on negative refraction and interference of magnetic coupled modes

    International Nuclear Information System (INIS)

    Fang, Yun-tuan; Ni, Zhi-yao; Zhu, Na; Zhou, Jun

    2016-01-01

    We propose a new mechanism to achieve light localization and slow light. Through the study on the coupling of two magnetic surface modes, we find a special convex band that takes on a negative refraction effect. The negative refraction results in an energy flow concellation effect from two degenerated modes on the convex band. The energy flow concellation effect leads to forming of the self-trapped and slow light bands. In the self-trapped band light is localized around the source without reflection wall in the waveguide direction, whereas in the slow light band, light becomes the standing-waves and moving standing-waves at the center and the two sides of the waveguide, respectively. (paper)

  11. Broad self-trapped and slow light bands based on negative refraction and interference of magnetic coupled modes.

    Science.gov (United States)

    Fang, Yun-Tuan; Ni, Zhi-Yao; Zhu, Na; Zhou, Jun

    2016-01-13

    We propose a new mechanism to achieve light localization and slow light. Through the study on the coupling of two magnetic surface modes, we find a special convex band that takes on a negative refraction effect. The negative refraction results in an energy flow concellation effect from two degenerated modes on the convex band. The energy flow concellation effect leads to forming of the self-trapped and slow light bands. In the self-trapped band light is localized around the source without reflection wall in the waveguide direction, whereas in the slow light band, light becomes the standing-waves and moving standing-waves at the center and the two sides of the waveguide, respectively.

  12. Pressure-induced amorphization of NaVO/sub 3 at room temperature and its re-crystallization

    International Nuclear Information System (INIS)

    Shen, Z.X.; Ong, C.W.; Tang, S.H.; Kuok, M.H.

    1994-01-01

    Pressure-induced amorphization is the subject of intense study for the past few years because of its importance in material science and in solid state physics. We reported a crystalline-amorphous phase transition at ca 60kbar in NaVO1/3, which is the lowest pressure for such transitions in ionic crystals. The transition is marked by the sudden appearance of very broad bands at the 800 and 350 cm/sup -1 regions. The amorphization includes the complete breaking up of the infinite chains of corner-linked tetrahedral VO/sub 4, most likely into VO/sup -/sub 3. On decompression, the amorphous phase transforms to another phase, probably also amorphous at ca 40 kbar. It reverts to the stable ambient condition α-phase upon heating. Here we report on the details of the transtitional region and the re-linking of the VO/sub 4 chains upon heating. (authors)

  13. Field measurements of the global UV-B radiation: a comparison between a broad-band radiometer and a Brewer spectrophotometer

    International Nuclear Information System (INIS)

    Anav, A.; Moriconi, M.L.; Di Menno, M.; Giannoccolo, S.

    1996-01-01

    The spectral responsivity shape plays an important role in the prospect of a wide use of broad-band meters in the UV-B monitoring. As most UV-B broad-band meters have a responsivity approximating an erythemal action spectrum, a measurement campaign was planned to verify if such an instrument could be successfully used to measure the unfiltered global irradiance. A Yankee radiometer mod. UV-B 1 and a Brewer spectrophotometer, considered as a reference meter, were compared for this purpose. A short theoretical treatment of the Yankee radiometer response and some results of the comparison are shown. Only clear-sky days data are selected so that the UV-B radiation reaching the ground could be modelled as the sum of the direct and isotropic diffuse components. The comparison results show a good agreement between the two instruments and confirm the capability of a broad-band UV-B radiometer of correctly measuring the global irradiance

  14. Passively mode-locked high power Nd:GdVO4 laser with direct in-band pumping at 912 nm

    Science.gov (United States)

    Nadimi, Mohammad; Waritanant, Tanant; Major, Arkady

    2018-01-01

    We report on the first semiconductor saturable absorber mirror mode-locked Nd:GdVO4 laser directly diode-pumped at 912 nm. The laser generated 10.14 W of averaged output power at 1063 nm with the pulse width of 16 ps at the repetition rate of 85.2 MHz. The optical-to-optical efficiency and slope efficiency in the mode-locked regime were calculated to be 49.6% and 67.4% with respect to the absorbed pump power, respectively. Due to the low quantum defect pumping the output power was limited only by the available pump power.

  15. VoIP Security

    OpenAIRE

    Fontanini, Piero

    2008-01-01

    VOIP or Voice Over Internet Protocol is a common term for phone service over IP based networks. There are much information about VoIP and some of how VoIP can be secured. There is however no standard for VoIP and no general solution for VoIP Security. The security in VoIP systems today are often non existing or in best case weak and often based on proprietary solutions. This master thesis investigates threats to VoIP system and describes existing alternatives for securing Vo...

  16. The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band

    NARCIS (Netherlands)

    De Visser, P.J.; Yates, S.J.C.; Guruswamy, T.; Goldie, D.J.; Withington, S.; Neto, A.; Llombart, N.; Baryshev, A.M.; Klapwijk, T.M.; Baselmans, J.J.A.

    2015-01-01

    We have measured the absorption of terahertz radiation in a BCS superconductor over a broad range of frequencies from 200 GHz to 1.1 THz, using a broadband antenna-lens system and a tantalum microwave resonator. From low frequencies, the response of the resonator rises rapidly to a maximum at the

  17. Relations between broad-band linear polarization and Ca II H and K emission in late-type dwarf stars

    Science.gov (United States)

    Huovelin, Juhani; Saar, Steven H.; Tuominen, Ilkka

    1988-01-01

    Broadband UBV linear polarization data acquired for a sample of late-type dwarfs are compared with contemporaneous measurements of Ca II H and K line core emission. A weighted average of the largest values of the polarization degree is shown to be the best parameter for chromospheric activity diagnosis. The average maximum polarization in the UV is found to increase from late-F to late-G stars. It is noted that polarization in the U band is considerably more sensitive to activity variations than that in the B or V bands. The results indicate that stellar magnetic fields and the resulting saturation in the Zeeman-sensitive absorption lines are the most probably source of linear polarization in late-type main-sequence stars.

  18. Two-dimensional simulation of broad-band ferrite electromagnetic wave absorbers by using the FDTD method

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Hyun Jin; Kim, Dong Il [Korea Maritime University, Busan (Korea, Republic of)

    2004-10-15

    The purpose of this simulation study is to design and fabricate an electromagnetic (EM) wave absorber in order to develop a wide-band absorber. We have proposed and modeled a bird-eye-type and cutting-cone-type EM wave absorber by using the equivalent material constants method (EMCM), and we simulated them by using a finite-difference time-domain (FDTD) method. A two or a three-dimensional simulation would be desirable to analyze the EM wave absorber characteristics and to develop new structures. The two-dimensional FDTD simulation requires less computer resources than a three-dimensional simulation to consider the structural effects of the EM wave absorbers. The numerical simulation by using the FDTD method shows propagating EM waves in various types of periodic structure EM wave absorbers. Simultaneously, a Fourier analysis is used to characterize the input pulse and the reflected EM waves for ferrite absorbers with various structures. The results have a wide-band reflection-reducing characteristic. The validity of the proposed model was confirmed by comparing the two-dimensional simulation with the experimental results. The simulations were carried out in the frequency band from 30 MHz to 10 GHz.

  19. Two-dimensional simulation of broad-band ferrite electromagnetic wave absorbers by using the FDTD method

    International Nuclear Information System (INIS)

    Yoon, Hyun Jin; Kim, Dong Il

    2004-01-01

    The purpose of this simulation study is to design and fabricate an electromagnetic (EM) wave absorber in order to develop a wide-band absorber. We have proposed and modeled a bird-eye-type and cutting-cone-type EM wave absorber by using the equivalent material constants method (EMCM), and we simulated them by using a finite-difference time-domain (FDTD) method. A two or a three-dimensional simulation would be desirable to analyze the EM wave absorber characteristics and to develop new structures. The two-dimensional FDTD simulation requires less computer resources than a three-dimensional simulation to consider the structural effects of the EM wave absorbers. The numerical simulation by using the FDTD method shows propagating EM waves in various types of periodic structure EM wave absorbers. Simultaneously, a Fourier analysis is used to characterize the input pulse and the reflected EM waves for ferrite absorbers with various structures. The results have a wide-band reflection-reducing characteristic. The validity of the proposed model was confirmed by comparing the two-dimensional simulation with the experimental results. The simulations were carried out in the frequency band from 30 MHz to 10 GHz.

  20. Comparing Broad-Band and Red Edge-Based Spectral Vegetation Indices to Estimate Nitrogen Concentration of Crops Using Casi Data

    Science.gov (United States)

    Wang, Yanjie; Liao, Qinhong; Yang, Guijun; Feng, Haikuan; Yang, Xiaodong; Yue, Jibo

    2016-06-01

    In recent decades, many spectral vegetation indices (SVIs) have been proposed to estimate the leaf nitrogen concentration (LNC) of crops. However, most of these indices were based on the field hyperspectral reflectance. To test whether they can be used in aerial remote platform effectively, in this work a comparison of the sensitivity between several broad-band and red edge-based SVIs to LNC is investigated over different crop types. By using data from experimental LNC values over 4 different crop types and image data acquired using the Compact Airborne Spectrographic Imager (CASI) sensor, the extensive dataset allowed us to evaluate broad-band and red edge-based SVIs. The result indicated that NDVI performed the best among the selected SVIs while red edge-based SVIs didn't show the potential for estimating the LNC based on the CASI data due to the spectral resolution. In order to search for the optimal SVIs, the band combination algorithm has been used in this work. The best linear correlation against the experimental LNC dataset was obtained by combining the 626.20nm and 569.00nm wavebands. These wavelengths correspond to the maximal chlorophyll absorption and reflection position region, respectively, and are known to be sensitive to the physiological status of the plant. Then this linear relationship was applied to the CASI image for generating an LNC map, which can guide farmers in the accurate application of their N fertilization strategies.

  1. Luminescence Properties of Self-Activated Mm(VO4)2 (M = Mg, Ca, Sr, and Ba) Phosphors Synthesized by Solid-State Reaction Method.

    Science.gov (United States)

    Min, Xin; Huang, Zhaohui; Fang, Minghao; Liu, Yan'gai; Tang, Chao; Wu, Xiaowen

    2016-04-01

    In this paper, M3(VO4)2 (M = Mg, Ca, Sr, and Ba) self-activated phosphors were prepared by a solid-state reaction method at 1,000 °C for 5 h. The phase formation and micrographs were analyzed by X-ray diffraction and scanning electron microscopy. The Ca3(VO4)2 phosphor does not show any emission peaks under excitation with ultraviolet (UV) light. However, the M3(VO4)2 (M = Mg, Sr, and Ba) samples are effectively excited by UV light chips ranging from 200 nm to 400 nm and exhibit broad emission bands due to the charge transfer from the oxygen 2p orbital to the vacant 3d orbital of the vanadium in the VO4. The color of these phosphors changes from yellow to light blue via blue-green with increasing ionic radius from Mg to Sr to Ba. The luminescence lifetimes and quantum yield decrease with the increasing unit cell volume and V-V distance, in the order of Mg3(VO4)2 to Sr3(VO4)2 to Ba3(VO4)2. The emission intensity decreases with the increase of temperatures, but presents no color shift. This confirms that these self-activated M3(VO4)2 phosphors can be suggested as candidates of the single-phase phosphors for light using UV light emitting diodes (LEDs).

  2. Super-Eddington accretion on to the neutron star NGC 7793 P13: Broad-band X-ray spectroscopy and ultraluminous X-ray sources

    Science.gov (United States)

    Walton, D. J.; Fürst, F.; Harrison, F. A.; Stern, D.; Bachetti, M.; Barret, D.; Brightman, M.; Fabian, A. C.; Middleton, M. J.; Ptak, A.; Tao, L.

    2018-02-01

    We present a detailed, broad-band X-ray spectral analysis of the ultraluminous X-ray source (ULX) pulsar NGC 7793 P13, a known super-Eddington source, utilizing data from the XMM-Newton, NuSTAR and Chandra observatories. The broad-band XMM-Newton+NuSTAR spectrum of P13 is qualitatively similar to the rest of the ULX sample with broad-band coverage, suggesting that additional ULXs in the known population may host neutron star accretors. Through time-averaged, phase-resolved and multi-epoch studies, we find that two non-pulsed thermal blackbody components with temperatures ∼0.5 and 1.5 keV are required to fit the data below 10 keV, in addition to a third continuum component which extends to higher energies and is associated with the pulsed emission from the accretion column. The characteristic radii of the thermal components appear to be comparable, and are too large to be associated with the neutron star itself, so the need for two components likely indicates the accretion flow outside the magnetosphere is complex. We suggest a scenario in which the thick inner disc expected for super-Eddington accretion begins to form, but is terminated by the neutron star's magnetic field soon after its onset, implying a limit of B ≲ 6 × 1012 G for the dipolar component of the central neutron star's magnetic field. Evidence of similar termination of the disc in other sources may offer a further means of identifying additional neutron star ULXs. Finally, we examine the spectrum exhibited by P13 during one of its unusual 'off' states. These data require both a hard power-law component, suggesting residual accretion on to the neutron star, and emission from a thermal plasma, which we argue is likely associated with the P13 system.

  3. Highly vibrationally excited O2 molecules in low-pressure inductively-coupled plasmas detected by high sensitivity ultra-broad-band optical absorption spectroscopy

    Science.gov (United States)

    Foucher, Mickaël; Marinov, Daniil; Carbone, Emile; Chabert, Pascal; Booth, Jean-Paul

    2015-08-01

    Inductively-coupled plasmas in pure O2 (at pressures of 5-80 mTorr and radiofrequency power up to 500 W) were studied by optical absorption spectroscopy over the spectral range 200-450 nm, showing the presence of highly vibrationally excited O2 molecules (up to vʺ = 18) by Schumann-Runge band absorption. Analysis of the relative band intensities indicates a vibrational temperature up to 10,000 K, but these hot molecules only represent a fraction of the total O2 density. By analysing the (11-0) band at higher spectral resolution the O2 rotational temperature was also determined, and was found to increase with both pressure and power, reaching 900 K at 80 mTorr 500 W. These measurements were achieved using a new high-sensitivity ultra-broad-band absorption spectroscopy setup, based on a laser-plasma light source, achromatic optics and an aberration-corrected spectrograph. This setup allows the measurement of weak broadband absorbances due to a baseline variability lower than 2   ×   10-5 across a spectral range of 250 nm.

  4. The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band

    Energy Technology Data Exchange (ETDEWEB)

    Visser, P. J. de, E-mail: p.j.devisser@tudelft.nl [Kavli Institute of NanoScience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands); Yates, S. J. C. [SRON Netherlands Institute for Space Research, Landleven 12, 9747AD Groningen (Netherlands); Guruswamy, T.; Goldie, D. J.; Withington, S. [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Neto, A.; Llombart, N. [Faculty of Electrical Engineering, Mathematics and Computer Science, Terahertz Sensing Group, Delft University of Technology, Mekelweg 4, 2628 CD Delft (Netherlands); Baryshev, A. M. [SRON Netherlands Institute for Space Research, Landleven 12, 9747AD Groningen (Netherlands); Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen (Netherlands); Klapwijk, T. M. [Kavli Institute of NanoScience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands); Physics Department, Moscow State Pedagogical University, Moscow 119991 (Russian Federation); Baselmans, J. J. A. [SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands); Faculty of Electrical Engineering, Mathematics and Computer Science, Terahertz Sensing Group, Delft University of Technology, Mekelweg 4, 2628 CD Delft (Netherlands)

    2015-06-22

    We have measured the absorption of terahertz radiation in a BCS superconductor over a broad range of frequencies from 200 GHz to 1.1 THz, using a broadband antenna-lens system and a tantalum microwave resonator. From low frequencies, the response of the resonator rises rapidly to a maximum at the gap edge of the superconductor. From there on, the response drops to half the maximum response at twice the pair-breaking energy. At higher frequencies, the response rises again due to trapping of pair-breaking phonons in the superconductor. In practice, this is a measurement of the frequency dependence of the quasiparticle creation efficiency due to pair-breaking in a superconductor. The efficiency, calculated from the different non-equilibrium quasiparticle distribution functions at each frequency, is in agreement with the measurements.

  5. The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band

    International Nuclear Information System (INIS)

    Visser, P. J. de; Yates, S. J. C.; Guruswamy, T.; Goldie, D. J.; Withington, S.; Neto, A.; Llombart, N.; Baryshev, A. M.; Klapwijk, T. M.; Baselmans, J. J. A.

    2015-01-01

    We have measured the absorption of terahertz radiation in a BCS superconductor over a broad range of frequencies from 200 GHz to 1.1 THz, using a broadband antenna-lens system and a tantalum microwave resonator. From low frequencies, the response of the resonator rises rapidly to a maximum at the gap edge of the superconductor. From there on, the response drops to half the maximum response at twice the pair-breaking energy. At higher frequencies, the response rises again due to trapping of pair-breaking phonons in the superconductor. In practice, this is a measurement of the frequency dependence of the quasiparticle creation efficiency due to pair-breaking in a superconductor. The efficiency, calculated from the different non-equilibrium quasiparticle distribution functions at each frequency, is in agreement with the measurements

  6. Broad band and enhanced photocatalytic behaviour of Ho3+-doped Bi2O3 micro-rods

    Science.gov (United States)

    Prasad, Neena; Karthikeyan, Balasubramanian

    2018-06-01

    Band-gap-tuned Bi2O3 micro-rods were synthesized using simple co-precipitation method by doping 5 wt% Ho3+ to mitigate the concentration of toxic dye from the polluted water using it as a photocatalyst. Structure and morphology of the prepared samples were identified using powder X-ray diffraction technique and scanning electron microscopy (SEM). Elemental composition and chemical state of the prepared samples were analyzed from the X-ray photoelectron spectroscopy (XPS). Considerable absorption in IR region was observed for Ho3+ doped Bi2O3 due to the electronic transitions of 5I8→5F4, 5I8→5F5, and 5I8→5I5, 5I6. The excellent ultra-violet (UV), white and infrared light (IR)-driven photocatalytic activity were suggested for pure and doped Bi2O3 samples. Ho3+-doped Bi2O3 micro-rods exhibits a better photocatalytic activity under white light irradiation. The consequence of the bandgap and the synergetic effect of Ho3+ and Bi2O3 on the photocatalytic degradation of MB were investigated.

  7. The effect of broad-band Alfven-cyclotron waves spectra on the preferential heating and differential acceleration of He{sup ++} ions in the solar wind

    Energy Technology Data Exchange (ETDEWEB)

    Maneva, Y. G. [Department of Physics, Catholic University of America, Washington DC, 20064 (United States) and Heliophysics Science Devision, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Ofman, L. [Department of Physics, Catholic University of America, Washington, DC 20064 (United States) and Heliophysics Science Devision, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Vinas, A. F. [Heliophysics Science Devision, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2013-06-13

    In anticipation of results from inner heliospheric missions such as the Solar Orbiter and the Solar Probe we present the results from 1.5D hybrid simulations to study the role of magnetic fluctuations for the heating and differential acceleration of He{sup ++} ions in the solar wind. We consider the effects of nonlinear Alfven-cyclotron waves at different frequency regimes. Monochromatic nonlinear Alfven-alpha-cyclotron waves are known to preferentially heat and accelerate He{sup ++} ions in collisionless low beta plasma. In this study we demonstrate that these effects are preserved when higherfrequency monochromatic and broad-band spectra of Alfven-proton-cyclotron waves are considered. Comparison between several nonlinear monochromatic waves shows that the ion temperatures, anisotropies and relative drift are quantitatively affected by the shift in frequency. Including a broad-band wave-spectrum results in a significant reduction of both the parallel and the perpendicular temperature components for the He{sup ++} ions, whereas the proton heating is barely influenced, with the parallel proton temperature only slightly enhanced. The differential streaming is strongly affected by the available wave power in the resonant daughter ion-acoustic waves. Therefore for the same initial wave energy, the relative drift is significantly reduced in the case of initial wave-spectra in comparison to the simulations with monochromatic waves.

  8. Exploring the origin of broad-band emissions of Mrk 501 with a two-zone model

    Science.gov (United States)

    Lei, Maichang; Yang, Chuyuan; Wang, Jiancheng; Yang, Xiaolin

    2018-04-01

    We propose a two-zone synchrotron self-Compton (SSC) model, including an inner gamma-ray emitting region with spherical shape and a conical radio emitting region located at the extended jet, to alleviate the long-standing "bulk Lorentz factor crisis" in blazars. In this model, the spectral energy distributions (SEDs) of blazars are produced by considering the gamma-ray emitting region inverse Compton scattering of both the synchrotron photons itself and the ambient photons from the radio emitting region. Applying the model to Mrk 501, we obtain that the radio emitting region has a comoving length of ˜0.15 pc and is located at sub-parsec scale from the central engine by modeling the radio data; the flux of the Compton scattering of the ambient photons is so low that it can be neglected safely. The characteristic hard gamma-ray spectrum can be explained by the superposition of two SSC processes, and the model can approximately explain the very high energy (VHE) data. The insights into the spectral shape and the inter-band correlations under the flaring state will provide us with a diagnostic for the bulk Lorentz factor of radio emitting region, where the low and upper limits of 8 and 15 are preferred, and for the two-zone SSC model itself. In addition, our two-zone SSC model shows that the gamma-ray emitting region creates flare on the timescale of merely a few hours, and the long time outbursts more likely originate from the extended radio emitting region.

  9. Supercapacitors based on two dimensional VO2 nanosheet electrodes in organic gel electrolyte

    KAUST Repository

    Baby, Rakhi Raghavan; Nagaraju, Doddahalli H.; Beaujuge, Pierre; Alshareef, Husam N.

    2016-01-01

    VO2 is a low band-gap semiconductor with relatively high conductivity among transition metal oxides, which makes it an interesting material for supercapacitor electrode applications. The performance of VO2 as supercapacitor electrode in organic

  10. BROAD BALMER WINGS IN BA HYPER/SUPERGIANTS DISTORTED BY DIFFUSE INTERSTELLAR BANDS: FIVE EXAMPLES IN THE 30 DORADUS REGION FROM THE VLT-FLAMES TARANTULA SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Walborn, Nolan R.; Sana, Hugues; Sabbi, Elena, E-mail: walborn@stsci.edu, E-mail: hsana@stsci.edu, E-mail: sabbi@stsci.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); and others

    2015-08-10

    Extremely broad emission wings at Hβ and Hα have been found in VLT-FLAMES Tarantula Survey data for five very luminous BA supergiants in or near 30 Doradus in the Large Magellanic Cloud. The profiles of both lines are extremely asymmetrical, which we have found to be caused by very broad diffuse interstellar bands (DIBs) in the longward wing of Hβ and the shortward wing of Hα. These DIBs are well known to interstellar but not to many stellar specialists, so that the asymmetries may be mistaken for intrinsic features. The broad emission wings are generally ascribed to electron scattering, although we note difficulties for that interpretation in some objects. Such profiles are known in some Galactic hyper/supergiants and are also seen in both active and quiescent Luminous Blue Variables (LBVs). No prior or current LBV activity is known in these 30 Dor stars, although a generic relationship to LBVs is not excluded; subject to further observational and theoretical investigation, it is possible that these very luminous supergiants are approaching the LBV stage for the first time. Their locations in the HRD and presumed evolutionary tracks are consistent with that possibility. The available evidence for spectroscopic variations of these objects is reviewed, while recent photometric monitoring does not reveal variability. A search for circumstellar nebulae has been conducted, with an indeterminate result for one of them.

  11. The proposals on cooperation to foreign centers of science on thermophysical properties of reactor materials in a broad band of pressure and temperatures realized at normal transient and emergency operation activity of nuclear power plants

    International Nuclear Information System (INIS)

    Fortov, V.E.

    1996-01-01

    The proposals on cooperation in the area of thermophysical properties of reactor materials in a broad band of pressure and temperature realized at normal transient and emergency operation activity of nuclear power plants are discussed. 1 fig

  12. Broad-band simulation of M7.2 earthquake on the North Tehran fault, considering non-linear soil effects

    Science.gov (United States)

    Majidinejad, A.; Zafarani, H.; Vahdani, S.

    2018-05-01

    The North Tehran fault (NTF) is known to be one of the most drastic sources of seismic hazard on the city of Tehran. In this study, we provide broad-band (0-10 Hz) ground motions for the city as a consequence of probable M7.2 earthquake on the NTF. Low-frequency motions (0-2 Hz) are provided from spectral element dynamic simulation of 17 scenario models. High-frequency (2-10 Hz) motions are calculated with a physics-based method based on S-to-S backscattering theory. Broad-band ground motions at the bedrock level show amplifications, both at low and high frequencies, due to the existence of deep Tehran basin in the vicinity of the NTF. By employing soil profiles obtained from regional studies, effect of shallow soil layers on broad-band ground motions is investigated by both linear and non-linear analyses. While linear soil response overestimate ground motion prediction equations, non-linear response predicts plausible results within one standard deviation of empirical relationships. Average Peak Ground Accelerations (PGAs) at the northern, central and southern parts of the city are estimated about 0.93, 0.59 and 0.4 g, respectively. Increased damping caused by non-linear soil behaviour, reduces the soil linear responses considerably, in particular at frequencies above 3 Hz. Non-linear deamplification reduces linear spectral accelerations up to 63 per cent at stations above soft thick sediments. By performing more general analyses, which exclude source-to-site effects on stations, a correction function is proposed for typical site classes of Tehran. Parameters for the function which reduces linear soil response in order to take into account non-linear soil deamplification are provided for various frequencies in the range of engineering interest. In addition to fully non-linear analyses, equivalent-linear calculations were also conducted which their comparison revealed appropriateness of the method for large peaks and low frequencies, but its shortage for small to

  13. Investigation of Relative Time Constant Influence of Inertial Part of Superheater on Quality of Steam Temperature Control Behind Boiler in Broad Band of Loading Variations

    Directory of Open Access Journals (Sweden)

    G. T. Kulakov

    2008-01-01

    Full Text Available The paper is devoted to computational investigation of influence relative time constant of an object which changes in broad band on quality of steam temperature control behind a boiler with due account of value of regulating action in the system with PI- and PID- regulator. The simulation has been based on a single-loop automatic control system (ACS. It has been revealed that the less value of the relative time constant of an object leads to more integral control error in system with PID- regulator while operating external ACS perturbation. Decrease of numerical value of relative time constant of an object while operating external perturbation causes decrease of relative time concerning appearance of maximum dynamic control error from common relative control time.

  14. Electronic reconstruction at the interface between the Mott insulator LaVO{sub 3} and the band insulator SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Stuebinger, Martin; Gabel, Judith; Gagel, Philipp; Sing, Michael; Claessen, Ralph [Universitaet Wuerzburg, Physikalisches Institut and Roentgen Center for Complex Material Systems (RCCM), 97074 Wuerzburg (Germany)

    2016-07-01

    Akin to the well known oxide heterostructure LaAlO{sub 3}/SrTiO{sub 3} (LAO/STO) the formation of a conducting interface is found between the strongly correlated, polar Mott insulator LaV{sup 3+}O{sub 3} (LVO) and the non-polar band insulator STO. Since LaV{sup 3+}O{sub 3} tends to overoxidize to the thermodynamically more favourable LaV{sup 5+}O{sub 4} phase when exposed to air, a suitable passivation is required. Therefore, we have employed pulsed laser deposition thin film growth of LVO films with a crystalline LAO capping layer. In situ photoemission measurements of samples before and after being exposed to air show that the V oxidation state can indeed be stabilized by the LAO capping layer. By transport measurements, we identify an insulator-to-metal transition at a combined LAO/LVO overlayer thickness of 4 to 5 unit cells. With LVO being a Mott insulator, passivation by the LAO capping opens the opportunity to study a band-filling controlled Mott insulator to metal transition induced by a purely electrostatic mechanism without interfering overoxidation of the LVO film.

  15. Fast broad-band photon detector based on quantum well devices and charge-integrating electronics for non-invasive FEL monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Antonelli, M., E-mail: matias.antonelli@elettra.eu; Cautero, G.; Sergo, R.; Castellaro, C.; Menk, R. H. [Elettra – Sincrotrone Trieste S.C.p.A., Trieste (Italy); Ganbold, T. [School in Nanotechnology, University of Trieste, Trieste (Italy); IOM CNR, Laboratorio TASC, Trieste (Italy); Biasiol, G. [IOM CNR, Laboratorio TASC, Trieste (Italy)

    2016-07-27

    The recent evolution of free-electron lasers has not been matched by the development of adequate beam-monitoring instrumentation. However, for both experimental and diagnostics purposes, it is crucial to keep such photon beams under control, avoiding at the same time the absorption of the beam and the possible destruction of the detector. These requirements can be fulfilled by utilizing fast and non-invasive photon detectors operated in situ, upstream from the experimental station. From this perspective, sensors based on Quantum Well (QW) devices can be the key to detecting ultra-short light pulses. In fact, owing to their high electron mobility, InGaAs/InAlAs QW devices operated at room temperature exhibit sub-nanosecond response times. Their direct, low-energy band gap renders them capable of detecting photons ranging from visible to X-ray. Furthermore, the 2D electron gas forming inside the QW is responsible for a charge amplification mechanism, which increases the charge collection efficiency of these devices. In order to acquire the signals produced by these QW sensors, a novel readout electronics has been developed. It is based on a high-speed charge integrator, which allows short, low-intensity current pulses to be read within a 50-ns window. The integrated signal is acquired through an ADC and the entire process can be performed at a 10-MHz repetition rate. This work provides a detailed description of the development of the QW detectors and the acquisition electronics, as well as reporting the main experimental results, which show how these tools are well suited for the realization of fast, broad-band beam monitors.

  16. A jet-dominated model for a broad-band spectral energy distribution of the nearby low-luminosity active galactic nucleus in M94

    Science.gov (United States)

    van Oers, Pieter; Markoff, Sera; Uttley, Phil; McHardy, Ian; van der Laan, Tessel; Donovan Meyer, Jennifer; Connors, Riley

    2017-06-01

    We have compiled a new multiwavelength spectral energy distribution (SED) for the closest obscured low-ionization emission-line region active galactic nucleus (AGN), NGC 4736, also known as M94. The SED comprises mainly high-resolution (mostly sub-arcsecond, or, at the distance to M94, ≲23 pc from the nucleus) observations from the literature, archival data, as well as previously unpublished sub-millimetre data from the Plateau de Bure Interferometer (PdBI) and the Combined Array for Research in Millimeter-wave Astronomy, in conjunction with new electronic MultiElement Radio Interferometric Network (e-MERLIN) L-band (1.5 GHz) observations. Thanks to the e-MERLIN resolution and sensitivity, we resolve for the first time a double structure composed of two radio sources separated by ˜1 arcsec, previously observed only at higher frequency. We explore this data set, which further includes non-simultaneous data from the Very Large Array, the Gemini telescope, the Hubble Space Telescope and the Chandra X-ray observatory, in terms of an outflow-dominated model. We compare our results with previous trends found for other AGN using the same model (NGC 4051, M81*, M87 and Sgr A*), as well as hard- and quiescent-state X-ray binaries. We find that the nuclear broad-band spectrum of M94 is consistent with a relativistic outflow of low inclination. The findings in this work add to the growing body of evidence that the physics of weakly accreting black holes scales with mass in a rather straightforward fashion.

  17. Broad-band conductivity and dielectric spectroscopy of composites of multiwalled carbon nanotubes and poly(ethylene terephthalate) around their low percolation threshold

    Science.gov (United States)

    Nuzhnyy, D.; Savinov, M.; Bovtun, V.; Kempa, M.; Petzelt, J.; Mayoral, B.; McNally, T.

    2013-02-01

    Composites of multiwalled carbon nanotubes with poly(ethylene terephthalate) (PET-MWCNT) with up to 3 vol% MWCNTs were prepared and characterized by broad-band AC conductivity and dielectric spectroscopy up to the infrared range using several techniques. A very low electrical percolation threshold of 0.07 vol% MWCNTs was revealed from the low-frequency conductivity plateau as well as from DC conductivity, whose values show the same critical power dependence on MWCNT concentration with the exponent t = 4.3. Above the plateau, the AC conductivity increases with frequency up to the THz range, where it becomes overlapped with the absorption of vibrational modes. The temperature dependence down to ˜5 K has shown semiconductor behaviour with a concentration-independent but weakly temperature-dependent small activation energy of ˜3 meV. The behaviour is compatible with the previously suggested fluctuation-induced tunnelling conductivity model through a thin (˜1 nm) polymer contact layer among the adjacent MWCNTs within percolated clusters. At higher frequencies, deviations from the simple universal conductivity behaviour are observed, indicating some distribution of energy barriers for an electron hopping mechanism.

  18. Comparison of broad band time series recorded parallel by FGI type interferometric water level and Lippmann type pendulum tilt meters at Conrad observatory, Austria

    Science.gov (United States)

    Ruotsalainen, Hannu; Papp, Gabor; Leonhardt, Roman; Ban, Dora; Szücs, Eszter; Benedek, Judith

    2016-04-01

    The Finnish Geodetic Institute (FGI) the progenitor of Finnish Geospatial Research Institute of NLS designed and built a 5.5m long prototype of interferometric water level tiltmeter (iWT) in early 2014. Geodetic and Geophysical Institute (GGI), Sopron, Hungary bought the instrument and started tilt measurement in August 2014 at the Conrad observatory (COBS), Austria to monitor geodynamical phenomena like microseisms, free oscillations of the Earth, earth tides, mass loading effects and crustal deformations in cooperation with Austrian Central Institute for Meteorology and Geodynamics (ZAMG) and the FGI. On the July 16 2015 a Lippmann-type 2D tilt sensor (LTS) was also installed by GGI on the 6 m long pier where iWT was set up previously. This situation opens a possibility to do broad band (from secular to seismic variations up to 15 Hz) geophysical signal analysis comparing the responses of long (several meters) and short (a few decimeters) base instruments implementing different physical principles (relative height change of a level surface and inclination change of the plumb line). The characteristics of the sensors are studied by the evaluation of the spectra of recorded signals dominated by microseisms. The iWT has internal interferometric calibration and it can be compared to Lippmanns tilt meter one. Both instruments show good long term ( > 1 day) stability when earth tides and ocean and air mass loading tilts are modelled.

  19. Sensitivity of broad-band ground-motion simulations to earthquake source and Earth structure variations: an application to the Messina Straits (Italy)

    KAUST Repository

    Imperatori, W.

    2012-03-01

    In this paper, we investigate ground-motion variability due to different faulting approximations and crustal-model parametrizations in the Messina Straits area (Southern Italy). Considering three 1-D velocity models proposed for this region and a total of 72 different source realizations, we compute broad-band (0-10 Hz) synthetics for Mw 7.0 events using a fault plane geometry recently proposed. We explore source complexity in terms of classic kinematic (constant rise-time and rupture speed) and pseudo-dynamic models (variable rise-time and rupture speed). Heterogeneous slip distributions are generated using a Von Karman autocorrelation function. Rise-time variability is related to slip, whereas rupture speed variations are connected to static stress drop. Boxcar, triangle and modified Yoffe are the adopted source time functions. We find that ground-motion variability associated to differences in crustal models is constant and becomes important at intermediate and long periods. On the other hand, source-induced ground-motion variability is negligible at long periods and strong at intermediate-short periods. Using our source-modelling approach and the three different 1-D structural models, we investigate shaking levels for the 1908 Mw 7.1 Messina earthquake adopting a recently proposed model for fault geometry and final slip. Our simulations suggest that peak levels in Messina and Reggio Calabria must have reached 0.6-0.7 g during this earthquake.

  20. Physically-Based Probabilistic Seismic Hazard Analysis Using Broad-Band Ground Motion Simulation: a Case Study for Prince Islands Fault, Marmara Sea

    Science.gov (United States)

    Mert, A.

    2016-12-01

    The main motivation of this study is the impending occurrence of a catastrophic earthquake along the Prince Island Fault (PIF) in Marmara Sea and the disaster risk around Marmara region, especially in İstanbul. This study provides the results of a physically-based Probabilistic Seismic Hazard Analysis (PSHA) methodology, using broad-band strong ground motion simulations, for sites within the Marmara region, Turkey, due to possible large earthquakes throughout the PIF segments in the Marmara Sea. The methodology is called physically-based because it depends on the physical processes of earthquake rupture and wave propagation to simulate earthquake ground motion time histories. We include the effects of all considerable magnitude earthquakes. To generate the high frequency (0.5-20 Hz) part of the broadband earthquake simulation, the real small magnitude earthquakes recorded by local seismic array are used as an Empirical Green's Functions (EGF). For the frequencies below 0.5 Hz the simulations are obtained using by Synthetic Green's Functions (SGF) which are synthetic seismograms calculated by an explicit 2D/3D elastic finite difference wave propagation routine. Using by a range of rupture scenarios for all considerable magnitude earthquakes throughout the PIF segments we provide a hazard calculation for frequencies 0.1-20 Hz. Physically based PSHA used here follows the same procedure of conventional PSHA except that conventional PSHA utilizes point sources or a series of point sources to represent earthquakes and this approach utilizes full rupture of earthquakes along faults. Further, conventional PSHA predicts ground-motion parameters using by empirical attenuation relationships, whereas this approach calculates synthetic seismograms for all magnitude earthquakes to obtain ground-motion parameters. PSHA results are produced for 2%, 10% and 50% hazards for all studied sites in Marmara Region.

  1. Synthesis and photoluminescence properties of Sm{sup 3+}substituted glaserite-type orthovanadates K{sub 3}Y[VO{sub 4}]{sub 2} with monoclinic structure

    Energy Technology Data Exchange (ETDEWEB)

    Duke John David, A., E-mail: dukejohndavid02@gmail.com [Voorhees College, Vellore, Tamil Nadu (India); Muhammad, G. Shakil [Islamiah College, Vaniyambadi, Tamil Nadu (India); Sivakumar, V. [National Institute of Technology (NIT), Rourkela (India)

    2016-09-15

    A novel phosphor of Glaserite type Orthovanadate K{sub 3}Y[VO{sub 4}]{sub 2} substituted with the trivalent rare-earth Sm{sup 3+} ions were synthesized by the conventional high temperature solid-state reaction method, their structural characterization and photoluminescent properties were investigated by X-ray diffraction and spectrofluorimetry. The phase-purity of glaserite structure in the synthesized compound was verified by XRD study. The morphology was measured by FESEM. Host lattice emits broad-band green color and it is originated from the [VO{sub 4}]{sup 3−}. Photoluminescence studies of Sm{sup 3+} activated samples show orange red emission. The charge transfer behaviours from [VO{sub 4}]{sup 3−} to Sm{sup 3+} ions (host to activator) in K{sub 3}Y{sub (1−x)}[VO{sub 4}]{sub 2}: {sub x}Sm{sup 3+} phosphors have been confirmed by photoluminescence and PL decay life time measurement. No concentration quenching was observed even for higher concentration of the dopant Sm{sup 3+} ions. The CIE chromaticity color coordinate values were calculated and it is very much closer to the NTSC standards. All the results clearly indicate that self-activated K{sub 3}Y{sub 1−x}[VO{sub 4}]{sub 2} with the rare earth {sub x}Sm{sup 3+} activated phosphors show great potential as a phosphor material for near-UV based white LEDs.

  2. Lattice relaxation and ferromagnetic character of (LaVO3)m/SrVO3 superlattices

    KAUST Repository

    Schuster, Cosima B.

    2013-08-01

    The experimental observation that vanadate superlattices (LaVO 3)m/SrVO3 show ferromagnetism up to room temperature (Lüders U. et al., Phys. Rev. B, 80 (2009) 241102(R)) is investigated by means of density functional theory, and the band structure for m = 5 and 6 is calculated. A buckling of the interface VO2 layers is found in both cases, but subtle differences in bond length lead to very different properties for even and odd values of m: in the even case, the two interface VO2 layers effectively decouple from the adjacent LaO layers due to a strong bond length enhancement. This results into a local inversion of the orbital occupancy and to the confinement of the charge carriers. In the odd case, the amplitude of the bond length variation is smaller, so that the charge carriers spill into the deeper-lying VO2 layers, and spin-polarised interfaces are obtained. © Copyright EPLA, 2013.

  3. Eu-emission quenching by electron screening in VO2 thin films

    International Nuclear Information System (INIS)

    Liu, H.; Lysenko, S.; Rua, A.; Vikhnin, V.; Vasquez, O.; Fernandez, F.E.

    2006-01-01

    As a kind of phase transition functional material, Vanadium dioxide (VO 2 ) thin films deposited on fused quartz substrate were fabricated using pulsed laser deposition (PLD) technique. Europium was introduced for structure study. By laser excitation at 526 nm, VO 2 thin film undergoes a reversible and ultrafast phase transition from semiconductor to metallic state, which results in a change of optical properties. In fluorescence measurement, Eu emission was found severely quenched in all as-grown thin films. After annealing the sample in air, a red Eu-emission appeared. The emission spectrum is characterized by a pronounced twin peak, centered at 617 nm ( 5 D - 7 F 2 ), surrounded by a set of broad, but relatively weaker bands (emission from 5 D to 7 F j manifold). The emission lifetime increased when the sample annealed at higher temperature for longer time. Each spectral component is actually a doublet which is the spectral overlap of emissions from Eu 3+ situated in two sites with different configurations. One is a linear h-Eu 3+ -h, where h stands for holes. Another is a right-angle configuration of h-Eu 3+ -h with Eu 3+ in the corner. In as-grown VO 2 film, Eu 3+ ions can either substitute V 4+ , leaving a negative charge around (Eu 3+ -O) - , or substitute V 5+ , leaving two negative charges around (Eu 3+ -O) -- . Due to trapped electrons in a large radius state, it covers Eu 3+ V 4+ -V 5+ complexes. It suggests that the screening by degenerate electronic gas may result in switching off the Eu-related optical response for a wide spectral region, causing emission quenching in VO 2 films

  4. Photoluminescence study of Dy3+ doped SrCeVO5 phosphor

    International Nuclear Information System (INIS)

    Suresh, K.; Dai, Ch. Vijay Anil; Murthy, K.V.R.

    2016-01-01

    Dy 3+ doped SrCeVO 5 phosphor was synthesized by the solid-state reaction method. Photoluminescence (PL) technique was performed to characterize the sample. The excitation spectra monitored under 520 nm and 610 nm wavelength was characterized by a broad band ranging from 220-400 nm. From the excitation spectra two main bands at 265 nm and 325 nm were observed. The PLE intensity of 520 nm monitored shows high intensity than 610 nm spectrum. The emission spectra of SrCeVO 5 phosphor under excitations at 265 nm and 325 nm exhibited main peak at 515 nm (cyan) which is a strong, intense well resolved peak with FWHM (full width at half maximum) of 130 nm is observed. This emission is mainly may be due to Ce ion but not Dy ion. The same emission under 640 and 670 nm excitations (up conversion) with good intensity was also observed. Commission international de l'eclairage (CIE) co-ordinates under these excitations revealed that this phosphor emit cyan colour and could be used for the generation of white light in display and lamp devices. (author)

  5. Phase coexistence in the metal-insulator transition of a VO2 thin film

    International Nuclear Information System (INIS)

    Chang, Y.J.; Koo, C.H.; Yang, J.S.; Kim, Y.S.; Kim, D.H.; Lee, J.S.; Noh, T.W.; Kim, Hyun-Tak; Chae, B.G.

    2005-01-01

    Vanadium dioxide (VO 2 ) shows a metal-insulator transition (MIT) near room temperature, accompanied by an abrupt resistivity change. Since the MIT of VO 2 is known to be a first order phase transition, it is valuable to check metallic and insulating phase segregation during the MIT process. We deposited (100)-oriented epitaxial VO 2 thin films on R-cut sapphire substrates. From the scanning tunneling spectroscopy (STS) spectra, we could distinguish metallic and insulating regions by probing the band gap. Optical spectroscopic analysis also supported the view that the MIT in VO 2 occurs through metal and insulator phase coexistence

  6. Selective synthesis and visible-light photocatalytic activities of BiVO4 with different crystalline phases

    International Nuclear Information System (INIS)

    Zhang Xi; Ai Zhihui; Jia Falong; Zhang Lizhi; Fan Xiaoxing; Zou Zhigang

    2007-01-01

    Tetragonal and monoclinic bismuth vanadate (BiVO 4 ) powders were selectively synthesized by aqueous processes. The characterizations of the as-prepared BiVO 4 powders were carried out by X-ray diffraction, nitrogen adsorption, scanning electron microscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic activities of different BiVO 4 samples were determined by degradation of methylene blue solution under visible-light irradiation (λ > 420 nm) and compared with that of TiO 2 (Degussa P25). The band gaps of the as-prepared BiVO 4 were determined from UV-vis diffuse reflectance spectra. It was found that monoclinic BiVO 4 with a band gap of 2.34 eV showed higher photocatalytic activity than that of tetragonal BiVO 4 with a band gap of 3.11 eV

  7. Infrared spectra of the ammonium ion in ammonium metavanadate NH 4VO 3

    Science.gov (United States)

    de Waal, D.; Heyns, A. M.; Range, K.-J.; Eglmeier, C.

    The ND stretching modes of isotopically dilute NH 3D + ions in NH 4VO 3 are in agreement with the predicted splitting into C s, C s and C1(2) components under C s site symmetry for the NH +4 ion. The three bands observed represent the three NH bonding distances in the crystal, and the position, shape and low temperature behaviour of each band confirms the existence of two types of hydrogen bonding in NH 4VO 3. The low temperature infrared modes of NH +4 and ND +4 in NH 4VO 3 and ND 4VO 3, respectively, can be assigned under space group Pbcm. Temperature dependence of these modes also reflects the presence of both normal and bifurcated hydrogen bonds in NH 4VO 3.

  8. Comparative optical study of thulium-doped YVO4 , GdVO4 , and LuVO4 single crystals

    Science.gov (United States)

    Lisiecki, R.; Solarz, P.; Dominiak-Dzik, G.; Ryba-Romanowski, W.; Sobczyk, M.; Černý, Pavel; Šulc, Jan; Jelínková, Helena; Urata, Yoshiharu; Higuchi, Mikio

    2006-07-01

    YVO4:Tm3+ crystals grown by the Czochralski technique and GdVO4:Tm3+ and LuVO4:Tm3+ crystals grown by the floating-zone technique were investigated using methods of optical spectroscopy. Polarized absorption and emission spectra were recorded at room temperature and at 6K . The crystal-field analysis was performed assuming the D2d site symmetry for Tm3+ ions. In this way the missing crystal-field components of the H63 ground multiplet were located. Room temperature absorption spectra were analyzed in the framework of the Judd-Ofelt theory. Evaluated radiative lifetimes of luminescent levels of Tm3+ follow a general trend diminishing in agreement with the sequence: YVO4:Tm3+→GdVO4:Tm3+→LuVO4:Tm3+ . Luminescence lifetimes measured for the systems under study are similar except for the F43 lifetime, which appears to be surprisingly short for LuVO4:Tm3+ . Anisotropy of optical spectra is particularly pronounced in LuVO4:Tm3+ . Peak absorption cross section for the band relevant for optical pumping at about 805nm is roughly three times higher for π polarization. Stimulated emission cross sections for the F43-H63 transition near 1800nm were evaluated using the reciprocity method. The diode-pumped continuous wave laser operation in GdVO4:Tm3+ with a slope efficiency of up to 40% is demonstrated. In LuVO4:Tm3+ the diode-pumped laser oscillation in a pulsed mode was observed.

  9. Gevaar VoIP voor telecomsector overdreven

    NARCIS (Netherlands)

    Deventer, M.O. van; Wegberg, M. van

    2004-01-01

    Het is een hype Voice-over-IP (VoIP) voor te stellen als een ontwrichtende technologie die de telecomindustrie ingrijpend zal veranderen. Maar hoe ontwrichtend is VoIP eigenlijk? Oskar van Deventer en Marc van Wegberg analyseren drie vormen van VoIP en laten zien dat alleen ‘VoIP-chat’ potentieel

  10. Accessing the VO with Python

    Science.gov (United States)

    Plante, R.; Fitzpatrick, M.; Graham, M.; Tody, D.; Young, W.

    2014-05-01

    We introduce two products for accessing the VO from Python: PyVO and VOClient. PyVO is built on the widely-used Astropy package and is well suited for integrating automated access to astronomical data into highly customizable scripts and applications for data analysis in Python. VOClient is built on a collection of C-libraries and is well suited for integrating with multi-language analysis packages. It also provides a framework for integrating legacy software into the Python environment. In this demo, we will run through several examples demonstrate basic data discovery and retrieval of data. This includes finding archives containing data of interest (VO registry), retrieving datasets (SIA, SSA), and exploring (Cone Search, SLAP). VOClient features some extended capabilities including the ability to communicate to other desktop applications from a script using the SAMP protocol.

  11. Broad band tunable dye laser development

    International Nuclear Information System (INIS)

    Lee, Jong Min; Kim, Jung Bog; Kim, Sung Ho; Go, Do Kyung; Lim, Chang Hwan; Rho, Si Pyo; Song, Kyu Seok; Lee, Byung Cheol; Rhi, Jong Hoon; Han, Jae Min; Cha, Hyung Ki; Cha, Byung Hun; Jeong, Do Yung; Han, Jae Min; Jung, Yeu Chang; Im, Ho; Yoo, Choon Sun; Jung, Byung Ik; Seok, Gum Sook

    1992-12-01

    The technical goal and objectives are the development of a tunable laser which can be tuned from UV to near IR and commercialization for uses in various fields. Two kinds of resonators are developed. User can select one resonator and change into the other without changing other parts. GIM type has a linewidth of 5GHz which is able to be used usually, and SLM type is very narrow linewidth of less than 1GHz. Each system can have one or two amplifiers depending on output power or cost. High stability and safety, cost-down, and modules into about 30 components have been tried. We hope that this laser can help developments in researches of university, industry, and institute. (Author)

  12. VO for Education: Archive Prototype

    Science.gov (United States)

    Ramella, M.; Iafrate, G.; De Marco, M.; Molinaro, M.; Knapic, C.; Smareglia, R.; Cepparo, F.

    2014-05-01

    The number of remote control telescopes dedicated to education is increasing in many countries, leading to correspondingly larger and larger amount of stored educational data that are usually available only to local observers. Here we present the project for a new infrastructure that will allow teachers using educational telescopes to archive their data and easily publish them within the Virtual Observatory (VO) avoiding the complexity of professional tools. Students and teachers anywhere will be able to access these data with obvious benefits for the realization of grander scale collaborative projects. Educational VO data will also be an important resource for teachers not having direct access to any educational telescopes. We will use the educational telescope at our observatory in Trieste as a prototype for the future VO educational data archive resource. The publishing infrastructure will include: user authentication, content and curation validation, data validation and ingestion, VO compliant resource generation. All of these parts will be performed by means of server side applications accessible through a web graphical user interface (web GUI). Apart from user registration, that will be validated by a natural person responsible for the archive (after having verified the reliability of the user and inspected one or more test files), all the subsequent steps will be automated. This means that at the very first data submission through the webGUI, a complete resource including archive and published VO service will be generated, ready to be registered to the VO. The efforts required to the registered user will consist only in describing herself/himself at registration step and submitting the data she/he selects for publishing after each observation sessions. The infrastructure will be file format independent and the underlying data model will use a minimal set of standard VO keywords, some of which will be specific for outreach and education, possibly including VO

  13. Integrating existing software toolkits into VO system

    Science.gov (United States)

    Cui, Chenzhou; Zhao, Yong-Heng; Wang, Xiaoqian; Sang, Jian; Luo, Ze

    2004-09-01

    Virtual Observatory (VO) is a collection of interoperating data archives and software tools. Taking advantages of the latest information technologies, it aims to provide a data-intensively online research environment for astronomers all around the world. A large number of high-qualified astronomical software packages and libraries are powerful and easy of use, and have been widely used by astronomers for many years. Integrating those toolkits into the VO system is a necessary and important task for the VO developers. VO architecture greatly depends on Grid and Web services, consequently the general VO integration route is "Java Ready - Grid Ready - VO Ready". In the paper, we discuss the importance of VO integration for existing toolkits and discuss the possible solutions. We introduce two efforts in the field from China-VO project, "gImageMagick" and "Galactic abundance gradients statistical research under grid environment". We also discuss what additional work should be done to convert Grid service to VO service.

  14. An open labeled, comparative clinical study on efficacy and tolerability of oral minipulse of steroid (OMP alone, OMP with PUVA and broad / narrow band UVB phototherapy in progressive vitiligo

    Directory of Open Access Journals (Sweden)

    Rath Namita

    2008-01-01

    Full Text Available Background: Several modalities of treatment have been tried in vitiligo with varied results; however, Indian data on comparative studies of two or more therapies are limited. Aims: We compared different phototherapy methods with an oral steroid as an adjunct to determine the method with the best tolerability and efficacy. Methods: Eighty-six patients with progressive vitiligo were randomly assigned to different study groups according to a continuous selection method over a period of one year. Group 1 was given OMP + PUVA, group 2 OMP + UVB (NB, group 3 OMP + UVB (BB and group 4 was given OMP alone. Each patient was followed up for six months and then released from treatment. Clinical evaluation was made at the end of three and six months. Results: In group 1 (OMP + PUVA, marked improvement was seen in 18.51% while moderate improvement was seen in 66.66% of the patients. Marked improvement was seen in 37.03% in group 2 (OMP + NB-UVB while 44.44% had moderate improvement. In group 3 (OMP + BB UVB, 8.33% showed marked improvement while moderate improvement was seen in 25% of the patients. Marked and moderate improvement was seen in 5 and 10% of group 4 (OMP patients, respectively. Conclusions: Our study compared four treatment modalities in vitiligo patients, out of which oral minipulse of steroids (OMP only had an adjunct value and was not very effective by itself. Narrow band UVB has a definite edge over broad band UVB and should be preferred when both options are available. NB-UVB and PUVA showed comparable efficacy.

  15. VoIP over WLAN

    OpenAIRE

    Nikkari, Joni

    2007-01-01

    Tässä opinnäytetyössä tutkitaan VoIP over WLAN -tekniikan mahdollisuuksia nykyaikaisessa käyttöympäristössä, sekä yritysmaailman että kotikäyttäjän näkökulmasta. Toimiakseen VoWLAN tarvitsee kaksi eri tekniikkaa: langattoman lähiverkon sekä WLAN-puhelimen, joka perustuu VoIP-tekniikkaan.; WLAN:ssa tietoliikenne kulkee normaalin kaapeloinnin sijasta radiotaajuuksia käyttämällä. Standardina toimii IEEE 802.11, joka määrittelee WLAN-verkkojen toiminnan. Standardia on kehitetty jatkuvasti, ja si...

  16. Synthesis, crystal structure and optical properties of BiMgVO 5

    Science.gov (United States)

    Benmokhtar, S.; El Jazouli, A.; Chaminade, J. P.; Gravereau, P.; Guillen, F.; de Waal, D.

    2004-11-01

    The new vanadate BiMgVO 5 has been prepared and its structure has been determined by single crystal X-ray diffraction: space group P21/n, a=7.542(6) Å, b=11.615(5) Å, c=5.305(3) Å, β=107.38(5)°, wR2=0.0447, R=0.0255. The structure consists of [Mg 2O 10] and [Bi 2O 10] dimers sharing their corners with [VO 4] tetrahedra. The ranges of bond lengths are 2.129-2.814 Å for Bi-O; 2.035-2.167 Å for Mg-O and 1.684-1.745 Å for V-O. V-O bond lengths determined from Raman band wavenumbers are between 1.679 and 1.747 Å. An emission band overlapping the entire visible region with a maximum around 650 nm is observed.

  17. Impact of leach on lead vanado-iodoapatite [Pb5(VO4)3I]: An infrared and Raman spectroscopic study

    International Nuclear Information System (INIS)

    Zhang Ming; Maddrell, E.R.; Abraitis, P.K.; Salje, E.K.H.

    2007-01-01

    Structural changes in lead vanado-iodoapatite [Pb 5 (VO 4 ) 3 I], leached in KOH/KCO 3 H buffer solution at 90 deg. C, were investigated using infrared (IR) and Raman spectroscopy. The untreated material shows characteristic phonon bands in three wavenumber regions (50-250, 300-500 and 750-870 cm -1 ). In comparison with a natural apatite, the replacement of phosphate by vanadium in the apatite structure leads to stretching and bending vibrations of the structural tetrahedra shift to lower frequencies. The leached samples all show extra bands between 3000 and 3600 cm -1 , characterised by two features: a broad tail and two sharp absorption bands near 3490 and 3538 cm -1 . The former is attributed to the H 2 O species absorbed by the gains or located between grain boundaries, whereas the latter two bands, which have the similar frequencies as those of hydroxyls in fluorapatite, are assigned as OH species which substitutes iodine in the leached materials. The leached samples also show an extra Raman band near 1058 cm -1 and IR bands near 1370 and 1420 cm -1 , which are the characteristic vibrations of CO 3 units. The uncorrelated relative intensities between CO 3 and OH bands and the absence of the characteristic C-OH vibrations (near 1017 and 1300 cm -1 ) of the HCO 3 ion in the Raman spectra indicate that hydrogen- and carbon-related species mainly exist in the form of CO 3 and OH rather than HCO 3 . CO 3 ions could be incorporated into the tetrahedral sites by substitution of VO 4 (B-type substitution) as a result of the leached-induced loss of vanadium

  18. Diode-end-pumped Tm:GdVO4 laser operating at 1818 and 1915 nm

    CSIR Research Space (South Africa)

    Esser, MJD

    2009-10-01

    Full Text Available wavelengths. We therefore embarked on ac- curately measuring absorption spectra of Tm:GdVO4 laser crystals at both 0.8 (pump band) and at 1.9 µm (emission band). The measurements were conducted with a Cary 5000 spectrometer with resolution set to 1 nm...

  19. VO2(B conversion to VO2(A and VO2(M and their oxidation resistance and optical switching properties

    Directory of Open Access Journals (Sweden)

    Zhang Yifu

    2016-03-01

    Full Text Available Vanadium dioxide VO2 has been paid in recent years increasing attention because of its various applications, however, its oxidation resistance properties in air atmosphere have rarely been reported. Herein, VO2(B nanobelts were transformed into VO2(A and VO2(M nanobelts by hydrothermal route and calcination treatment, respectively. Then, we comparatively studied the oxidation resistance properties of VO2(B, VO2(A and VO2(M nanobelts in air atmosphere by thermo-gravimetric analysis and differential thermal analysis (TGA/DTA. It was found that the nanobelts had good thermal stability and oxidation resistance below 341 °C, 408 °C and 465 °C in air, respectively, indicating that they were stable in air at room temperature. The fierce oxidation of the nanobelts occurred at 426, 507 and 645 °C, respectively. The results showed that the VO2(M nanobelts had the best thermal stability and oxidation resistance among the others. Furthermore, the phase transition temperatures and optical switching properties of VO2(A and VO2(M were studied by differential scanning calorimetry (DSC and variable temperature infrared spectra. It was found that the VO2(A and VO2(M nanobelts had outstanding thermochromic character and optical switching properties.

  20. Selective formation of VO2(A) or VO2(R) polymorph by controlling the hydrothermal pressure

    International Nuclear Information System (INIS)

    Ji Shidong; Zhang Feng; Jin Ping

    2011-01-01

    Missing VO 2 (A) usually occurs during the preparation of VO 2 polymorphs. This leads to an ambiguous understanding of the transformation between VO 2 polymorphs. The calculation of the ground state energies for different VO 2 polymorphs indicated that there is only a small energy gap between VO 2 (A) and VO 2 (R), which destined that the transformation from VO 2 (A) to VO 2 (R) should be pressure sensitive. This hypothesis was verified during the synthesizing of VO 2 polymorphs by reducing V 2 O 5 with oxalic acid through hydrothermal treatment process. Selective formation of pure phase VO 2 (A) or VO 2 (R) was achieved by controlling the hydrothermal pressure through varying the filling ratio at 270 deg. C. It was found that a filling ratio over 0.5 favors the formation of pure VO 2 (R) while a reduced filling ratio to 0.4 or lower results in the formation of VO 2 (A). Based on our experiments, VO 2 (B) nanobelts were always first formed and then it transformed to VO 2 (A) by assembling process at increased temperature or extended reaction time. Under further higher pressure, the VO 2 (A) transformed spontaneously to VO 2 (R) initialized from the volume shrinkage due to the formation of denser VO 2 (R). - Graphical abstract: Selective formation of VO 2 (A) or VO 2 (R) could be achieved by controlling the system pressure through varying the filling ratio during hydrothermal treatment. Highlights: → Selective formation of VO 2 polymorphs by controlling hydrothermal pressure. → Ground state energy characteristics were revealed for the first time. → Phase transformation mechanism was clearly elucidated.

  1. Runs 800, 813, 842 and physics runs from 18.1.77 to 21.5.77, Development of a new set-up for working line measurements including a Fast Fourier Transform Spectrum Analyser and using weak beam excitiation with broad-band noise

    CERN Document Server

    Borer, J

    1977-01-01

    Runs 800, 813, 842 and physics runs from 18.1.77 to 21.5.77, Development of a new set-up for working line measurements including a Fast Fourier Transform Spectrum Analyser and using weak beam excitiation with broad-band noise

  2. Efficient solar-driven water splitting by nanocone BiVO4-perovskite tandem cells

    Science.gov (United States)

    Qiu, Yongcai; Liu, Wei; Chen, Wei; Chen, Wei; Zhou, Guangmin; Hsu, Po-Chun; Zhang, Rufan; Liang, Zheng; Fan, Shoushan; Zhang, Yuegang; Cui, Yi

    2016-01-01

    Bismuth vanadate (BiVO4) has been widely regarded as a promising photoanode material for photoelectrochemical (PEC) water splitting because of its low cost, its high stability against photocorrosion, and its relatively narrow band gap of 2.4 eV. However, the achieved performance of the BiVO4 photoanode remains unsatisfactory to date because its short carrier diffusion length restricts the total thickness of the BiVO4 film required for sufficient light absorption. We addressed the issue by deposition of nanoporous Mo-doped BiVO4 (Mo:BiVO4) on an engineered cone-shaped nanostructure, in which the Mo:BiVO4 layer with a larger effective thickness maintains highly efficient charge separation and high light absorption capability, which can be further enhanced by multiple light scattering in the nanocone structure. As a result, the nanocone/Mo:BiVO4/Fe(Ni)OOH photoanode exhibits a high water-splitting photocurrent of 5.82 ± 0.36 mA cm−2 at 1.23 V versus the reversible hydrogen electrode under 1-sun illumination. We also demonstrate that the PEC cell in tandem with a single perovskite solar cell exhibits unassisted water splitting with a solar-to-hydrogen conversion efficiency of up to 6.2%. PMID:27386565

  3. Observation of reduced phase transition temperature in N-doped thermochromic film of monoclinic VO_2

    International Nuclear Information System (INIS)

    Wan, Meinan; Xiong, Mo; Li, Neng; Liu, Baoshun; Wang, Shuo; Ching, Wai-Yim; Zhao, Xiujian

    2017-01-01

    Highlights: • N-doped VO_2(M1) thin films have been synthesized by annealing in NH_3 atmosphere. • The phase purity, microstructure and optical property of VO_2 thin film can be regulated by NH_3 concentration. • First-principles calculations have been carried out to study the mechanism of N-doping on energy band structures of VO_2(M1). • The energy band gaps of VO_2(M1) are tuned by substitution N-doping or interstitial N-doping. - Abstract: Research on monoclinic (M1) phase of VO_2 has attracted a great of interest for smart coating applications due to its exceptional thermochromic property. Herein, we report the results using a novel approach to synthesize N-doped VO_2(M1) thin films with high purity by heat treatment in NH_3 atmosphere. The N dopant in the film can be regulated by varying NH_3 concentration during the annealing process. We find that the N atoms are located at the interstitial sites or substitute oxygen atoms, and the V-N bonds in the VO_2 thin films increase with NH_3 concentration. The metal to insulator transition (MIT) temperature (τ_c_,_h) of the VO_2 thin film is effectively reduced from 80.0 to 62.9 °C, while the solar modulation efficiency (ΔT_s_o_l) and the modulation efficiency at 2000 nm (ΔT_2_0_0_0_n_m) are 7.36% and 55.6% respectively. The band gap of N-doped VO_2 thin films related to MIT (E_g_1) is estimated to be as low as 0.18–0.25 eV whereas the band gap associated with the visible transparency (E_g_2) is about 1.50–1.58 eV. Based on the highly accurate first-principles calculations, the E_g_1 of VO_2 (M1) is reduced after substituted or interstitial N-doping, while the E_g_2 alters with the mode of N-doping, which is excellent agreement with experimental measurement.

  4. Preparation, characterization and enhanced visible-light photocatalytic activities of BiPO4/BiVO4 composites

    International Nuclear Information System (INIS)

    Wu, Siyuan; Zheng, Hong; Lian, Youwei; Wu, Yiying

    2013-01-01

    Graphical abstract: - Highlights: • BiPO 4 /BiVO 4 composites were successfully prepared by the hydrothermal method. • BiPO 4 /BiVO 4 composites exhibited broad absorption in the visible region. • Visible-light photocatalytic activities of BiPO 4 /BiVO 4 composites were enhanced. • P/V molar ratio and pH value of the reaction affect photocatalytic activity. • The mechanism of enhanced visible-light photocatalytic activities was discussed. - Abstract: BiPO 4 /BiVO 4 composites with different P/V molar ratios were prepared by the hydrothermal method and the effect of pH values of hydrothermal reaction on photocatalytic activity of BiPO 4 /BiVO 4 composite was investigated. The photocatalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectroscopy. The photocatalytic property of BiPO 4 /BiVO 4 was evaluated by photocatalytic degradation of Methylene blue under visible light irradiation. The results showed that the photocatalytic activity of the composites was much higher than that of pure BiPO 4 and BiVO 4 . The rate constant of Methylene blue degradation over BiPO 4 /BiVO 4 (P/V molar ratio of 5:1 and hydrothermal reaction pH value of 1.5) is 1.7 times that of pure BiVO 4 . The photocatalytic activity enhancement of BiPO 4 /BiVO 4 composite is closely related to the BiVO 4 functioning as a sensitizer to adsorb visible light and the heterojunction of BiPO 4 /BiVO 4 acting as an active center for hindering the rapid recombination of electron–hole pairs during the photocatalytic reaction

  5. Peripheral Quantitative Computed Tomography (pQCT), Broad Band Ultrasound Attenuation (BUA) and Speed of Sound (SOS) in a population of normal females aged from 8 to 20 years

    International Nuclear Information System (INIS)

    Bagni, B.; Corazzari, T.; Bagni, I.; Garuti, F.; Franceschetto, A.; Casolo, A.; Pansini, F.

    2002-01-01

    Aim: To evaluate, in a population of young healthy females aged from 8 to 20 years the bone mass peak (or density), the normal ranges versus age and menarche-age using two method: pQCT (peripheral Quantitative Computed Tomography) and ultrasound absorptiometry. Material and Methods: From 1998 to 2000 selective measurement of Bone Mineral Density (BMD) of trabecular bone at the ultradistal radius using pQCT, BUA (Broad Band Attenuation) and SOS ( Speed Of Sound) was carried out on 426 healthy females (aged from 8 to 20 years) in north Italy. BMD were measured using a single photon miniaturized tomographic scanner in the ultradistal radius, SOS and BUA were measured at the same time, using a water bath device obtaining parametric bidimensional images of BUA and SOS. The population studied refers to normal females free of bone metabolism alteration, in pre and post-pubertal status. Results: A normal range of BMD, BUA and SOS versus age and menarche age were established. A linear correlation was found between BUA and BMD measured with pQCT. SOS does not show any correlation with BMD. The pre-puberty and the post-puberty groups show statistically significant differences between SOS, BUA and BMD. We found the peak bone density (measured with pQCT) in the trabecular bone at the ultradistal radius at 15 years of age (mean menarche age of 10 years). The same position of the peak was found for BUA, for SOS the situation is not well defined. The analytical fitting of the data highlights a polynomial correlation of BMD vs. age, SOS vs. age, BUA vs. age. Conclusions: It appears that the sexual growth influences the position of peak bone density. The results obtained show a statistically significant correlation between BUA and BMD versus age, the menarche-age and the period of exposure of bone tissue to the oestrogen. After all, pQCT and ultrasound are useful techniques to evaluate bone density and structure also in a growing population. The results of this study shows the

  6. Transmission of reactive pulsed laser deposited VO{sub 2} films in the THz domain

    Energy Technology Data Exchange (ETDEWEB)

    Émond, Nicolas; Hendaoui, Ali; Ibrahim, Akram; Al-Naib, Ibraheem; Ozaki, Tsuneyuki; Chaker, Mohamed, E-mail: chaker@emt.inrs.ca

    2016-08-30

    Highlights: • Synthesis of vanadium dioxide (VO{sub 2}) thin films as a function of oxygen pressure (2–25 mTorr) using Reactive Pulsed Laser Deposition (RPLD). • Characterization of RPLD-grown VO{sub 2} thin films in the THz frequency range. • THz switches and/or sensors require VO{sub 2} films deposited at low oxygen pressure (i.e. low transition temperature, large amplitude contrast of THz transmission, narrow hysteresis width). • THz optical memory applications require VO{sub 2} films deposited at high oxygen pressure (broad hysteresis width). - Abstract: This work reports on the characteristics of the insulator-to-metal transition (IMT) of reactive pulsed laser deposited vanadium dioxide (VO{sub 2}) films in the terahertz (THz) frequency range, namely the transition temperature T{sub IMT}, the amplitude contrast of the THz transmission over the IMT ΔA, the transition sharpness ΔT and the hysteresis width ΔH. XRD analysis shows the sole formation of VO{sub 2} monoclinic structure with an enhancement of (011) preferential orientation when varying the O{sub 2} pressure (P{sub O2}) during the deposition process from 2 to 25 mTorr. THz transmission measurements as a function of temperature reveal that VO{sub 2} films obtained at low P{sub O2} exhibit low T{sub IMT}, large ΔA, and narrow ΔH. Increasing P{sub O2} results in VO{sub 2} films with higher T{sub IMT}, smaller ΔA, broader ΔH and asymmetric hysteresis loop. The good control of the VO{sub 2} IMT features in the THz domain could be further exploited for the development of advanced smart devices, such as ultrafast switches, modulators, memories and sensors.

  7. Mobile telephones: a comparison of radiated power between 3G VoIP calls and 3G VoCS calls.

    Science.gov (United States)

    Jovanovic, Dragan; Bragard, Guillaume; Picard, Dominique; Chauvin, Sébastien

    2015-01-01

    The purpose of this study is to assess the mean RF power radiated by mobile telephones during voice calls in 3G VoIP (Voice over Internet Protocol) using an application well known to mobile Internet users, and to compare it with the mean power radiated during voice calls in 3G VoCS (Voice over Circuit Switch) on a traditional network. Knowing that the specific absorption rate (SAR) is proportional to the mean radiated power, the user's exposure could be clearly identified at the same time. Three 3G (High Speed Packet Access) smartphones from three different manufacturers, all dual-band for GSM (900 MHz, 1800 MHz) and dual-band for UMTS (900 MHz, 1950 MHz), were used between 28 July and 04 August 2011 in Paris (France) to make 220 two-minute calls on a mobile telephone network with national coverage. The places where the calls were made were selected in such a way as to describe the whole range of usage situations of the mobile telephone. The measuring equipment, called "SYRPOM", recorded the radiation power levels and the frequency bands used during the calls with a sampling rate of 20,000 per second. In the framework of this study, the mean normalised power radiated by a telephone in 3G VoIP calls was evaluated at 0.75% maximum power of the smartphone, compared with 0.22% in 3G VoCS calls. The very low average power levels associated with use of 3G devices with VoIP or VoCS support the view that RF exposure resulting from their use is far from exceeding the basic restrictions of current exposure limits in terms of SAR.

  8. Performance of VoIP on HSDPA

    DEFF Research Database (Denmark)

    Wang, Bang; Pedersen, Klaus I.; Kolding, Troels E.

    2005-01-01

    This paper provides packet scheduler design and performance simulations for running VoIP services over high-speed downlink packet access (HSDPA) in WCDMA. The main challenge of supporting VoIP service on HSDPA is the tight delay requirement combined with the small VoIP packet size. A packet...... scheduler design incorporating VoIP packet aggregation and user multiplexing is proposed and the VoIP capacity is studied for a macro-cellular environment. Results are obtained for different delay budgets and packet scheduling settings, using either blind round robin or a slightly modified version...... of proportional fair scheduling. For proportional fair scheduling with code-multiplexing of 4-users, the downlink VoIP cell capacity on HSDPA is found to be in the range 72-104 users depending on whether the delay budget for the Node-B scheduling and user reception equals 80 ms or 150 ms, respectively....

  9. The influence of charge transfers effects in monazite-type LaVO{sub 4} and perovskite-type LaVO{sub 3} prepared by sol-gel acrylamide polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Herrera-Pérez, G., E-mail: guillermo.herrera@cimav.edu.mx [CONACYT Research Fellow. Centro de Investigación en Materiales Avanzados (CIMAV), Miguel de Cervantes 120, Chihuahua 31136, Chihuahua (Mexico); Jiménez-Mier, J. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, 04510 Mexico D. F (Mexico); Yang, W.-L. [The Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Reyes-Rojas, A.; Fuentes-Cobas, L.E. [Department of Physics of Materials Department. Centro de Investigación en Materiales Avanzados (CIMAV), Miguel de Cervantes 120, Chihuahua 31136, Chihuahua (Mexico)

    2016-08-15

    Highlights: • We elucidate the electronic structure through the vanadium L{sub 2,3} edge in LaVO{sub 4} by XAS. • The interpretation of XAS spectrum was performed by the multiplet calculation. • Our results suggest that LaVO{sub 4} can be considered in the charge transfer regime. - Abstract: Core-hole spectroscopy such as X-ray absorption spectroscopy (XAS) is useful to determine the electronic structure of strongly correlated and strongly hybridized compounds such as vanadates. Monazite-type LaVO{sub 4} and perovskite-type LaVO{sub 3} are good candidates to elucidate the electronic structure through the vanadium L{sub 2,3} edge. LaVO{sub 4} was prepared by sol-gel acrylamide polymerization and solid-state reaction. LaVO{sub 3} was obtained by reduction of LaVO{sub 4} using Zr as gatherer. Monoclinic crystal phase for LaVO{sub 4} and orthorhombic crystal phase for LaVO{sub 3} were confirmed by the Rietveld refinement of X-ray diffraction patterns. XAS comparison between Vanadium L{sub 2,3} edge confirms the presence of V{sup 5+} for the monazite and V{sup 3+} for the orthorhombic perovskite. Multiplet calculations including crystal field and charge transfer effects (CTM) were performed in order to elucidate the tetragonal (D{sub 4h} symmetry) parameters Dq, Ds and Dt, the charge transfer energy Δ, and d-d Coulomb repulsion energy U parameters. CTM confirms for LaVO{sub 3} the strong V 3d–O 2p hybridization with a significant contribution of covalent character due to the delocalization of 3d electrons. For LaVO{sub 4} this work suggest the reclassification of this band insulator as charge transfer insulator that shows a significant contribution of ionic character.

  10. The role of the isolated 6s states in BiVO{sub 4} on the electronic and atomic structures

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Jie; Wang, Lin-Wang [Joint Center for Artificial Photosynthesis and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2014-10-27

    BiVO{sub 4} is one of the most promising photoanodes for water-splitting applications. Similar to many d{sup 10} materials, where the full-shell d electrons are not directly involved in the bonding, the Bi 6s electrons form isolated low-energy bands in BiVO{sub 4}. By systematically altering the energy of the Bi 6s states, we find direct evidences that the isolated s states, through the s-p coupling, affect the BiVO{sub 4} properties, including valence band maximum position, charge density, and atomic structural distortion. We find that many good properties of BiVO{sub 4} for water splitting are related to the s-p coupling due to the existence of Bi 6s states. Based on this understanding, we propose that alloying Bi with Sb can enhance these properties, and hence improve the water-splitting efficiency.

  11. Vastly Enhanced BiVO4 Photocatalytic OER Performance by NiCoO2 as Cocatalyst

    KAUST Repository

    Palaniselvam, Thangavelu

    2017-08-07

    Here, a simple and efficient preparation of NiCoO nanoparticle modified nanoporous bismuth vanadate (BiVO) thin film and its application in photoelectrocatalytic (PEC) oxygen evolution reaction (OER) is demonstrated. The role of NiCoO in the composite electrode (BiVO/NiCoO) is twofold: OER cocatalyst and band structure modifier. It improves surface reaction kinetics for PEC OER and enhances charge separation efficiency simultaneously, which is believed to be a determining factor for the unprecedentedly high PEC OER performance of this BiVO/NiCoO nanocomposite. The photocurrent density of 3.6 mA cm at 1.23 V versus RHE in 0.1 m potassium phosphate buffered (pH = 7) electrolyte by BiVO/NiCoO is three times that of BiVO and significantly higher than most literature values. The BiVO/NiCoO nanocomposite shows/possess a high charge separation efficiency (η) of ≈72% as compared to only 23% for pure nanoporous BiVO at 1.23 V versus RHE, which demonstrates convincing role of NiCoO in the composite electrode. Both the excellent photocurrent density and great operational stability of this BiVO/NiCoO nanocomposite makes it a promising photocatalytic material for practical applications.

  12. Securing VoIP keeping your VoIP network safe

    CERN Document Server

    (Bud) Bates, Regis J Jr

    2015-01-01

    Securing VoIP: Keeping Your VoIP Network Safe will show you how to take the initiative to prevent hackers from recording and exploiting your company's secrets. Drawing upon years of practical experience and using numerous examples and case studies, technology guru Bud Bates discusses the business realities that necessitate VoIP system security and the threats to VoIP over both wire and wireless networks. He also provides essential guidance on how to conduct system security audits and how to integrate your existing IT security plan with your VoIP system and security plans, helping you prevent

  13. VO2 microcrystals as an advanced smart window material at semiconductor to metal transition

    Science.gov (United States)

    Basu, Raktima; Magudapathy, P.; Sardar, Manas; Pandian, Ramanathaswamy; Dhara, Sandip

    2017-11-01

    Textured VO2(0 1 1) microcrystals are grown in the monoclinic, M1 phase which undergoes a reversible first order semiconductor to metal transition (SMT) accompanied by a structural phase transition to rutile tetragonal, R phase. Around the phase transition, VO2 also experiences noticeable change in its optical and electrical properties. A change in color of the VO2 micro crystals from white to cyan around the transition temperature is observed, which is further understood by absorption of red light using temperature dependent ultraviolet-visible spectroscopic analysis and photoluminescence studies. The absorption of light in the red region is explained by the optical transition between Hubbard states, confirming the electronic correlation as the driving force for SMT in VO2. The thermochromism in VO2 has been studied for smart window applications so far in the IR region, which supports the opening of the band gap in semiconducting phase; whereas there is hardly any report in the management of visible light. The filtering of blue light along with reflection of infrared above the semiconductor to metal transition temperature make VO2 applicable as advanced smart windows for overall heat management of a closure.

  14. VO2 microcrystals as an advanced smart window material at semiconductor to metal transition

    International Nuclear Information System (INIS)

    Basu, Raktima; Pandian, Ramanathaswamy; Dhara, Sandip; Magudapathy, P; Sardar, Manas

    2017-01-01

    Textured VO 2 (0 1 1) microcrystals are grown in the monoclinic, M1 phase which undergoes a reversible first order semiconductor to metal transition (SMT) accompanied by a structural phase transition to rutile tetragonal, R phase. Around the phase transition, VO 2 also experiences noticeable change in its optical and electrical properties. A change in color of the VO 2 micro crystals from white to cyan around the transition temperature is observed, which is further understood by absorption of red light using temperature dependent ultraviolet–visible spectroscopic analysis and photoluminescence studies. The absorption of light in the red region is explained by the optical transition between Hubbard states, confirming the electronic correlation as the driving force for SMT in VO 2 . The thermochromism in VO 2 has been studied for smart window applications so far in the IR region, which supports the opening of the band gap in semiconducting phase; whereas there is hardly any report in the management of visible light. The filtering of blue light along with reflection of infrared above the semiconductor to metal transition temperature make VO 2 applicable as advanced smart windows for overall heat management of a closure. (paper)

  15. Lattice relaxation and ferromagnetic character of (LaVO3)m/SrVO3 superlattices

    KAUST Repository

    Schuster, Cosima B.; Lü ders, Ulrike; Fré sard, Raymond; Schwingenschlö gl, Udo

    2013-01-01

    The experimental observation that vanadate superlattices (LaVO 3)m/SrVO3 show ferromagnetism up to room temperature (Lüders U. et al., Phys. Rev. B, 80 (2009) 241102(R)) is investigated by means of density functional theory, and the band structure for m = 5 and 6 is calculated. A buckling of the interface VO2 layers is found in both cases, but subtle differences in bond length lead to very different properties for even and odd values of m: in the even case, the two interface VO2 layers effectively decouple from the adjacent LaO layers due to a strong bond length enhancement. This results into a local inversion of the orbital occupancy and to the confinement of the charge carriers. In the odd case, the amplitude of the bond length variation is smaller, so that the charge carriers spill into the deeper-lying VO2 layers, and spin-polarised interfaces are obtained. © Copyright EPLA, 2013.

  16. A comprehensive investigation of tetragonal Gd-doped BiVO{sub 4} with enhanced photocatalytic performance under sun-light

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Yangyang; Tan, Guoqiang, E-mail: tan3114@163.com; Dong, Guohua; Ren, Huijun; Xia, Ao

    2016-02-28

    Graphical abstract: - Highlights: • Tetragonal Gd-BiVO{sub 4} with enhanced photocatalytic activity was synthesized. • Gd doping can induce the phase transition from monoclinic to tetragonal BiVO{sub 4}. • GdVO{sub 4} seeds as crystal nucleus dominate the formation of tetragonal Gd-BiVO{sub 4}. • Tetragonal Gd-BiVO{sub 4} exhibits the excellent separation of electrons and holes. • The contribution of high photocatalytic activity under sun-light is from UV-light. - Abstract: Tetragonal Gd-doped BiVO{sub 4} having enhanced photocatalytic activity have been synthesized by a facile microwave hydrothermal method. The structural analysis indicates that Gd doping can induce the phase transition from monoclinic to tetragonal BiVO{sub 4}. The reaction results in precursor solutions imply that tetragonal GdVO{sub 4} seeds as crystal nucleus are the original and determined incentives to force the formation of tetragonal Gd-BiVO{sub 4}. The influences of the surface defect, band structure, and BET surface area on the improved photocatalytic activities of tetragonal Gd-doped BiVO{sub 4} are investigated systematically. The results demonstrate that the more surface oxygen deficiencies as active sites and the excellent mobility and separation of photogenerated electrons and holes are beneficial to the enhancement of the photocatalytic performance of tetragonal Gd-BiVO{sub 4}. The RhB photodegradation experiments indicate that the contribution of high photocatalytic activities under simulated sun-light is mainly from UV-light region due to the tetragonal structure feature. The best photocatalytic performance is obtained for tetragonal 10 at% Gd-BiVO{sub 4}, of which the RhB degradation rate can reach to 96% after 120 min simulated sun-light irradiation. The stable tetragonal Gd-BiVO{sub 4} with efficient mineralization will be a promising photocatalytic material applied in water purification.

  17. Metal-insulator phase transition in a VO2 thin film observed with terahertz spectroscopy

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Fischer, Bernd M.; Thoman, Andreas

    2006-01-01

    We investigate the dielectric properties of a thin VO2 film in the terahertz frequency range in the vicinity of the semiconductor-metal phase transition. Phase-sensitive broadband spectroscopy in the frequency region below the phonon bands of VO2 gives insight into the conductive properties...... of the film during the phase transition. We compare our experimental data with models proposed for the evolution of the phase transition. The experimental data show that the phase transition occurs via the gradual growth of metallic domains in the film, and that the dielectric properties of the film...

  18. Demokratski stil vođenja

    OpenAIRE

    Roko, Maruna

    2018-01-01

    Djelatnici u poduzeću s demokratskim stilom vođenja moraju biti zadovoljni plaćom i ostalim beneficijama, kao i uvjetima rada, te moraju biti motivirani zahvaljujući nemonotonosti posla i upravljačkim vještinama uprave. Velike prednosti demokratskog stila vođenja su veća fleksibilnost i zarada i izostanak neizvjesnosti i svakodnevnog stresa zbog rizika, dok se teški rad i upornost nagrađuju. Demokratski vođa mora konstantno ispitivati informacije na tržištu prodaje i nabave, proučavati zakons...

  19. Enhanced photocatalytic performance of BiVO_4 in aqueous AgNO_3 solution under visible light irradiation

    International Nuclear Information System (INIS)

    Huang, Chien-Kai; Wu, Tsunghsueh; Huang, Chang-Wei; Lai, Chi-Yung; Wu, Mei-Yao; Lin, Yang-Wei

    2017-01-01

    Graphical abstract: Ag"+ ions enhanced photocatalytic activity of BiVO_4 under visible light irradiation. - Highlights: • The presence of Ag"+ ions enhanced the photodegradation activity of BiVO_4. • Photoreduction of Ag deposited on the BiVO_4 surface was obtained. • Luminescence and electrochemical results elucidated the photocatalytic mechanism. • Holes and oxygen radicals were the main reactive species generated by BiVO_4/Ag"+. • Used BiVO_4/Ag"+ exhibited photocatalytic antibacterial activity toward E. coli. - Abstract: Monoclinic-phase bismuth vanadate (BiVO_4) with a 2.468 eV band gap exhibited enhanced synergic photodegradation activity toward methylene blue (MB) when combined with silver ions (Ag"+) in an aqueous solution under visible light irradiation. The mass ratio of AgNO_3 to BiVO_4 and the calcination temperature were discovered to considerably affect the degradation activity of BiVO_4/Ag"+. Superior photocatalytic performance was obtained when BiVO_4 was mixed with 0.01%(w/v) AgNO_3 solution, and complete degradation of MB was achieved after 25 min visible light irradiation, outperforming BiVO_4 or AgNO_3 solution alone. The enhanced photodegradation was investigated using systematic luminescence measurements, electrochemical impedance spectroscopy, and scavenger addition, after which a photocatalytic mechanism for MB degradation under visible light irradiation was identified that involved oxygen radicals and holes. This study also discovered the two dominating processes involved in enhancing the electron–hole separation efficiency and reducing their recombination rate, namely photoreduction of Ag"+ and the formation of a BiVO_4/Ag heterojunction. The synergic effect between BiVO_4 and Ag"+ was discovered to be unique. BiVO_4/Ag"+ was successfully used to degrade two other dyes and disinfect Escherichia Coli. A unique fluorescent technique using BiVO_4 and a R6G solution to detect Ag"+ ions in water was discovered.

  20. Utilization of visible to NIR light energy by Yb"+"3, Er"+"3 and Tm"+"3 doped BiVO_4 for the photocatalytic degradation of methylene blue

    International Nuclear Information System (INIS)

    Regmi, Chhabilal; Kshetri, Yuwaraj K.; Ray, Schindra Kumar; Pandey, Ramesh Prasad; Lee, Soo Wohn

    2017-01-01

    Highlights: • Lanthanide doped BiVO_4 as highly efficient upconversion and photocatalytic material. • Well defined beads like morphology for better photocatalytic activity. • Effective utilization of NIR and visible light for efficient photocatalytic degradation of methylene blue. • Nontoxic to human cells, potential for application in biological fields. - Abstract: Lanthanide-doped BiVO_4 semiconductors with efficient photocatalytic activities over a broad range of the solar light spectrum have been synthesized by the microwave hydrothermal method using ethylenediaminetetraacetic acid (EDTA). The structural, morphological, and optical properties of the as-synthesized samples were evaluated by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray powder diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL). The chemical compositions were analyzed by X-ray photoelectron spectroscopy (XPS). The toxicity of the samples was measured using Mus musculus skin melanoma cells (B16-F10 (ATCC"® CRL-6475™)) and were found to be nontoxic for human cells. The photocatalytic efficiency of the prepared samples was evaluated by methylene blue (MB) degradation. The best photocatalytic activity was shown by BiVO_4 with 6:3:3 mol percentage of Yb"+"3:Er"+"3:Tm"+"3 in all solar light spectrum. The synthesized samples possess low band gap energy and a hollow structure suitable for the better photocatalytic activity. The observed NIR photoactivity supports that the upconversion mechanism is involved in the overall photocatalytic process. Therefore, this approach provides a better alternative upconversion material for integral solar light absorption.

  1. Extending Tactical Fleet Communications Through VoIP

    Science.gov (United States)

    2014-09-01

    corporate world , the military is leveraging VoIP communication solutions as well. Shore commands like Tactical Training Group Pacific use VoIP for...VoIP fuzzing (e.g., Asteroid , PROTOS, Sip-Proxy)  VoIP signaling manipulation (e.g., IAXAuthJack, IAXHangup, SIP-Kill)  VoIP media...as well, but instead of just matching the information to rules, it compares synchronization information between the protocols to determine if the

  2. Supercapacitors based on two dimensional VO2 nanosheet electrodes in organic gel electrolyte

    KAUST Repository

    Rakhi, R.B.

    2016-10-16

    VO2 is a low band-gap semiconductor with relatively high conductivity among transition metal oxides, which makes it an interesting material for supercapacitor electrode applications. The performance of VO2 as supercapacitor electrode in organic electrolytes has never been reported before. Herein, two-dimensional nanosheets of VO2 are prepared by the simultaneous solution reduction and exfoliation from bulk V2O5 powder by hydrothermal method. A specific capacitance of 405 Fg−1 is achieved for VO2 based supercapacitor in an organic electrolyte, in three electrode configuration. The symmetric capacitor based on VO2 nanosheet electrodes and the liquid organic electrolyte exhibits an energy density of 46 Wh kg−1 at a power density of 1.4 kW kg−1 at a constant current density of 1 Ag−1. Furthermore, flexible solid-state supercapacitors are fabricated using same electrode material and Alumina-silica based gel electrolyte. The solid-state device delivers a specific capacitance of 145 Fg−1 and a device capacitance of 36 Fg−1 at a discharge current density of 1 Ag−1. Series combination of three solid state capacitors is capable of lighting up a red LED for more than 1 minute.

  3. Observation of reduced phase transition temperature in N-doped thermochromic film of monoclinic VO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Meinan; Xiong, Mo [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Li, Neng, E-mail: lineng@whut.edu.cn [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Liu, Baoshun; Wang, Shuo [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Ching, Wai-Yim [Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, MO 64110 (United States); Zhao, Xiujian, E-mail: opluse@whut.edu.cn [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China)

    2017-07-15

    Highlights: • N-doped VO{sub 2}(M1) thin films have been synthesized by annealing in NH{sub 3} atmosphere. • The phase purity, microstructure and optical property of VO{sub 2} thin film can be regulated by NH{sub 3} concentration. • First-principles calculations have been carried out to study the mechanism of N-doping on energy band structures of VO{sub 2}(M1). • The energy band gaps of VO{sub 2}(M1) are tuned by substitution N-doping or interstitial N-doping. - Abstract: Research on monoclinic (M1) phase of VO{sub 2} has attracted a great of interest for smart coating applications due to its exceptional thermochromic property. Herein, we report the results using a novel approach to synthesize N-doped VO{sub 2}(M1) thin films with high purity by heat treatment in NH{sub 3} atmosphere. The N dopant in the film can be regulated by varying NH{sub 3} concentration during the annealing process. We find that the N atoms are located at the interstitial sites or substitute oxygen atoms, and the V-N bonds in the VO{sub 2} thin films increase with NH{sub 3} concentration. The metal to insulator transition (MIT) temperature (τ{sub c,h}) of the VO{sub 2} thin film is effectively reduced from 80.0 to 62.9 °C, while the solar modulation efficiency (ΔT{sub sol}) and the modulation efficiency at 2000 nm (ΔT{sub 2000nm}) are 7.36% and 55.6% respectively. The band gap of N-doped VO{sub 2} thin films related to MIT (E{sub g1}) is estimated to be as low as 0.18–0.25 eV whereas the band gap associated with the visible transparency (E{sub g2}) is about 1.50–1.58 eV. Based on the highly accurate first-principles calculations, the E{sub g1} of VO{sub 2} (M1) is reduced after substituted or interstitial N-doping, while the E{sub g2} alters with the mode of N-doping, which is excellent agreement with experimental measurement.

  4. Time limit and VO2 slow component at intensities corresponding to VO2max in swimmers.

    Science.gov (United States)

    Fernandes, R J; Cardoso, C S; Soares, S M; Ascensão, A; Colaço, P J; Vilas-Boas, J P

    2003-11-01

    The purpose of this study was to measure, in swimming pool conditions and with high level swimmers, the time to exhaustion at the minimum velocity that elicits maximal oxygen consumption (TLim at vVO(2)max), and the corresponding VO(2) slow component (O(2)SC). The vVO(2)max was determined through an intermittent incremental test (n = 15). Forty-eight hours later, TLim was assessed using an all-out swim at vVO(2)max until exhaustion. VO(2) was measured through direct oximetry and the swimming velocity was controlled using a visual light-pacer. Blood lactate concentrations and heart rate values were also measured. Mean VO(2)max for the incremental test was 5.09 +/- 0.53 l/min and the corresponding vVO(2)max was 1.46 +/- 0.06 m/s. Mean TLim value was 260.20 +/- 60.73 s and it was inversely correlated with the velocity of anaerobic threshold (r = -0.54, p energy cost of the respiratory muscles (r = 0.51), for p swimming pool, in high level swimmers performing at vVO(2)max, and that higher TLim seems to correspond to higher expected O(2)SC amplitude. These findings seem to bring new data with application in middle distance swimming.

  5. VoIP Accessibility: A Usability Study of Voice over Internet Protocol (VoIP) Systems and A Survey of VoIP Users with Vision Loss

    Science.gov (United States)

    Packer, Jaclyn; Reuschel, William

    2018-01-01

    Introduction: Accessibility of Voice over Internet Protocol (VoIP) systems was tested with a hands-on usability study and an online survey of VoIP users who are visually impaired. The survey examined the importance of common VoIP features, and both methods assessed difficulty in using those features. Methods: The usability test included four paid…

  6. Modeling the Broad-Band Emission from the Gamma-Ray Emitting Narrow-Line Seyfert-1 Galaxies 1H 0323+342 and B2 0954+25A

    International Nuclear Information System (INIS)

    Arrieta-Lobo, Maialen; Boisson, Catherine; Zech, Andreas

    2017-01-01

    Prior to the Fermi-LAT era, only two classes of Active Galactic Nuclei (AGN) were thought to harbor relativistic jets that radiate up to gamma-ray energies: blazars and radio galaxies. The detection of variable gamma-ray emission from Narrow Line Seyfert 1 (NLSy1) galaxies has put them on the spotlight as a new class of gamma-ray emitting AGN. In this respect, gamma-ray emitting NLSy1s seem to be situated between blazars (dominated by non-thermal emission) and Seyferts (accretion disc dominated). In this work, we model the Spectral Energy Distribution (SED) of two gamma-loud NLSy1s, 1H 0323+342 and B2 0954+25A, during quiescent and flaring episodes via a multi-component radiative model that features a relativistic jet and external photon fields from the torus, disc, corona and Broad Line Region (BLR). We find that the interpretation of the high-energy emission of jetted NLSy1s requires taking into account Inverse Compton emission from particles in the relativistic jet that interact with external photon fields. Minimal changes are applied to the model parameters to transition from average to flaring states. In this scenario, the observed variability is explained mainly by means of changes in the jet density and Doppler factor.

  7. Modeling the Broad-Band Emission from the Gamma-Ray Emitting Narrow-Line Seyfert-1 Galaxies 1H 0323+342 and B2 0954+25A

    Energy Technology Data Exchange (ETDEWEB)

    Arrieta-Lobo, Maialen; Boisson, Catherine; Zech, Andreas, E-mail: maialen.arrieta@obspm.fr [Laboratoire Univers et Theories, Observatoire de Paris, CNRS, Université Paris-Diderot, PSL Research University, Meudon (France)

    2017-12-08

    Prior to the Fermi-LAT era, only two classes of Active Galactic Nuclei (AGN) were thought to harbor relativistic jets that radiate up to gamma-ray energies: blazars and radio galaxies. The detection of variable gamma-ray emission from Narrow Line Seyfert 1 (NLSy1) galaxies has put them on the spotlight as a new class of gamma-ray emitting AGN. In this respect, gamma-ray emitting NLSy1s seem to be situated between blazars (dominated by non-thermal emission) and Seyferts (accretion disc dominated). In this work, we model the Spectral Energy Distribution (SED) of two gamma-loud NLSy1s, 1H 0323+342 and B2 0954+25A, during quiescent and flaring episodes via a multi-component radiative model that features a relativistic jet and external photon fields from the torus, disc, corona and Broad Line Region (BLR). We find that the interpretation of the high-energy emission of jetted NLSy1s requires taking into account Inverse Compton emission from particles in the relativistic jet that interact with external photon fields. Minimal changes are applied to the model parameters to transition from average to flaring states. In this scenario, the observed variability is explained mainly by means of changes in the jet density and Doppler factor.

  8. Monoclinic BiVO{sub 4} micro-/nanostructures: Microwave and ultrasonic wave combined synthesis and their visible-light photocatalytic activities

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yafang; Li, Guangfang; Yang, Xiaohui; Yang, Hao; Lu, Zhong [Key Laboratory for Green Chemical Process of Ministry of Education and Hubei Novel Reactor and Green Chemical Technology Key Laboratory, Wuhan Institute of Technology, Xiongchu Avenue, Wuhan 430073 (China); Chen, Rong, E-mail: rchenhku@hotmail.com [Key Laboratory for Green Chemical Process of Ministry of Education and Hubei Novel Reactor and Green Chemical Technology Key Laboratory, Wuhan Institute of Technology, Xiongchu Avenue, Wuhan 430073 (China); Engineering Research Center of Nano-Geomaterials of Ministry of Education, China University of Geosciences, Lumo Road, Wuhan 430074 (China)

    2013-02-25

    Graphical abstract: Monoclinic BiVO{sub 4} with different sizes and morphologies were synthesized by a facile microwave and ultrasonic wave combined technique for the first time and exhibited different optical properties and visible-light-driven photocatalytic efficiency. Highlights: Black-Right-Pointing-Pointer BiVO{sub 4} nanostructures were prepared by microwave and ultrasonic wave combined method. Black-Right-Pointing-Pointer BiVO{sub 4} nanostructures could be modulated by varying the solvent and pH value. Black-Right-Pointing-Pointer Different BiVO{sub 4} nanostructures exhibited different photocatalytic activities. Black-Right-Pointing-Pointer The photocatalytic performance was influenced by the band gap, phase and size. - Abstract: Monoclinic bismuth vanadate (m-BiVO{sub 4}) micro-/nanostructures with different sizes and morphologies were successfully prepared via a facile and rapid microwave and ultrasonic wave combined technique. The obtained BiVO{sub 4} products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and UV-vis diffuse reflection spectroscopy (DRS). It was found that the solvent and pH value had a significant influence on morphology, size and crystalline structure of the product. Nut-like, potato-like and broccoli-like monoclinic BiVO{sub 4} were fabricated in different solvents. The crystal phase could be modulated by varying the pH value of reaction system. The photocatalytic activities of the products were also evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation. The result revealed that the photocatalytic activities of BiVO{sub 4} nanostructures were closely related to the crystalline phase, band gap and particle size. Monoclinic BiVO{sub 4} nanoparticles with small crystal size and large band gap exhibited remarkable photocatalytic performance.

  9. Monoclinic BiVO4 micro-/nanostructures: Microwave and ultrasonic wave combined synthesis and their visible-light photocatalytic activities

    International Nuclear Information System (INIS)

    Zhang, Yafang; Li, Guangfang; Yang, Xiaohui; Yang, Hao; Lu, Zhong; Chen, Rong

    2013-01-01

    Graphical abstract: Monoclinic BiVO 4 with different sizes and morphologies were synthesized by a facile microwave and ultrasonic wave combined technique for the first time and exhibited different optical properties and visible-light-driven photocatalytic efficiency. Highlights: ► BiVO 4 nanostructures were prepared by microwave and ultrasonic wave combined method. ► BiVO 4 nanostructures could be modulated by varying the solvent and pH value. ► Different BiVO 4 nanostructures exhibited different photocatalytic activities. ► The photocatalytic performance was influenced by the band gap, phase and size. - Abstract: Monoclinic bismuth vanadate (m-BiVO 4 ) micro-/nanostructures with different sizes and morphologies were successfully prepared via a facile and rapid microwave and ultrasonic wave combined technique. The obtained BiVO 4 products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and UV–vis diffuse reflection spectroscopy (DRS). It was found that the solvent and pH value had a significant influence on morphology, size and crystalline structure of the product. Nut-like, potato-like and broccoli-like monoclinic BiVO 4 were fabricated in different solvents. The crystal phase could be modulated by varying the pH value of reaction system. The photocatalytic activities of the products were also evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation. The result revealed that the photocatalytic activities of BiVO 4 nanostructures were closely related to the crystalline phase, band gap and particle size. Monoclinic BiVO 4 nanoparticles with small crystal size and large band gap exhibited remarkable photocatalytic performance.

  10. The 2010 Broad Prize

    Science.gov (United States)

    Education Digest: Essential Readings Condensed for Quick Review, 2011

    2011-01-01

    A new data analysis, based on data collected as part of The Broad Prize process, provides insights into which large urban school districts in the United States are doing the best job of educating traditionally disadvantaged groups: African-American, Hispanics, and low-income students. Since 2002, The Eli and Edythe Broad Foundation has awarded The…

  11. The epitaxial growth and interfacial strain study of VO{sub 2}/MgF{sub 2} (001) films by synchrotron based grazing incidence X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Fan, L.L. [Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology, Yancheng 224051 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Chen, S. [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Liu, Q.H. [Science and Technology on Electro-optical Information Security Control Laboratory, Tianjin 300300 (China); Liao, G.M.; Chen, Y.L.; Ren, H. [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Zou, C.W., E-mail: czou@ustc.edu.cn [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China)

    2016-09-05

    High quality VO{sub 2} films with different thickness were epitaxially grown on MgF{sub 2} (001) substrates by oxide molecular beam epitaxy method. The evolution of interfacial strain was investigated by synchrotron based grazing incidence X-ray diffraction. By adjusting the incidence angles, the penetration depth of X-ray in VO{sub 2} film could be controlled and the thickness-depend lattice distortion in the epitaxial VO{sub 2} film was investigated. Due to the lattice mismatching, the pronounced tensile strain was observed in ultra-thin VO{sub 2} film. As the film thickness increasing, the interfacial strain relaxed gradually and became fully relaxed for thick VO{sub 2} films. Combined with the electric transport measurement, it was revealed that the phase transition temperature of ultra-thin VO{sub 2} film decreased greatly. The effect of interfacial strain induced phase transition modulation and the intrinsic mechanism was systematically discussed. - Highlights: • We prepared high quality VO{sub 2} epitaxial films on MgF{sub 2} (001) substrates by oxide molecular beam epitaxy method. • Synchrotron radiation grazing incidence X-ray diffraction was employed to detect evolution of strain along depth profile. • Based on a classic band structure model, the mechanism of strain controlled phase transition of VO{sub 2} was discussed.

  12. Light-induced ultrafast phase transitions in VO2 thin film

    International Nuclear Information System (INIS)

    Lysenko, S.; Rua, A.J.; Vikhnin, V.; Jimenez, J.; Fernandez, F.; Liu, H.

    2006-01-01

    Vanadium dioxide shows a passive and reversible change from a monoclinic insulator phase to a metallic tetragonal rutile structure when the sample temperature is close to and over 68 deg. C. As a kind of functional material, VO 2 thin films deposited on fused quartz substrates were successfully prepared by the pulsed laser deposition (PLD) technique. With laser illumination at 400 nm on the obtained films, the phase transition (PT) occurred. The observed light-induced PT was as fast as the laser pulse duration of 100 fs. Using a femtosecond laser system, the relaxation processes in VO 2 were studied by optical pump-probe spectroscopy. Upon a laser excitation an instantaneous response in the transient reflectivity and transmission was observed followed by a relatively longer relaxation process. The alteration is dependent on pump power. The change in reflectance reached a maximum value at a pump pulse energy between 7 and 14 mJ/cm 2 . The observed PT is associated with the optical interband transition in VO 2 thin film. It suggests that with a pump laser illuminating on the film, excitation from the d θ,ε - state of valence band to the unoccupied excited mixed d θ,ε -π* - state of the conduction band in the insulator phase occurs, followed by a resonant transition to an unoccupied excited mixed d θ,ε -π* - state of the metallic phase band

  13. Microstructure and thermochromic properties of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films

    Energy Technology Data Exchange (ETDEWEB)

    Khamseh, S.; Ghahari, M. [Institute for Color Science and Technology, Department of Nanomaterial and Nanocoatings, Tehran (Iran, Islamic Republic of); Araghi, H. [Islamic Azad University, Department of Materials Engineering, Science and Research Branch, Tehran (Iran, Islamic Republic of); Faghihi Sani, M.A. [Sharif University of Technology, Department of Materials Science and Engineering, Tehran (Iran, Islamic Republic of)

    2016-03-15

    W-doped VO{sub 2} films have been synthesized via oxygen annealing of V-W-V (vanadium-tungsten-vanadium) multilayered films. The effects of middle layer's thickness of V-W-V multilayered film on structure and properties of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films were investigated. The as-deposited V-W-V multilayered film showed amorphous-like structure when mixed structure of VO{sub 2} (M) and VO{sub 2} (B) was formed in VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films. Tungsten content of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films increased with increasing middle layer's thickness. With increasing middle layer's thickness, room temperature square resistance (R{sub sq}) of VO{sub X}-WO{sub X}-VO{sub X} ceramic thin films increased from 65 to 86 kΩ/sq. The VO{sub X}-WO{sub X}-VO{sub X} ceramic thin film with the thinnest middle layer showed significant SMT (semiconductor-metal transition) when SMT became negligible on increasing middle layer's thickness. (orig.)

  14. Electrochemical catalytic activity of tungsten trioxide- modified graphite felt toward VO2+/VO2+ redox reaction

    International Nuclear Information System (INIS)

    Shen, Yang; Xu, Hongfeng; Xu, Pengcheng; Wu, Xiaoxin; Dong, Yiming; Lu, Lu

    2014-01-01

    A novel graphite felt electrode modified with tungsten trioxide (WO 3 ) was developed to improve the electrochemical performance of graphite felt toward the VO 2 + /VO 2+ redox pair. WO 3 was prepared using a hydrothermal method, and the morphology of WO 3 structures was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical property of WO 3 -modified graphite felt toward VO 2 + /VO 2+ was carefully characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The hydrogen-vanadium redox flow battery (H-VRFB) test indicates that single cells using 1.1 mg cm −2 WO 3 -modified graphite felt exhibited excellent performance at 70 mA cm −2 , and the corresponding coulombic, voltage, and energy efficiencies were 99.1%, 88.66% and 87.86%, respectively

  15. Using VoIP to compete.

    Science.gov (United States)

    Werbach, Kevin

    2005-09-01

    Internet telephony, or VoIP, is rapidly replacing the conventional kind. This year, for the first time, U.S. companies bought more new Internet-phone connections than standard lines. The major driver behind this change is cost. But VoIP isn't just a new technology for making old-fashioned calls cheaper, says consultant Kevin Werbach. It is fundamentally changing how companies use voice communications. What makes VoIP so powerful is that it turns voice into digital data packets that can be stored, copied, combined with other data, and distributed to virtually any device that connects to the Internet. And it makes it simple to provide all the functionality of a corporate phone-call features, directories, security-to anyone anywhere there's broadband access. That fosters new kinds of businesses such as virtual call centers, where widely dispersed agents work at all hours from their homes. The most successful early adopters, says Werbach, will focus more on achieving business objectives than on saving money. They will also consider how to push VoIP capabilities out to the extended organization, making use of everyone as a resource. Deployment may be incremental, but companies should be thinking about where VoIP could take them. Executives should ask what they could do if, on demand, they could bring all their employees, customers, suppliers, and partners together in a virtual room, with shared access to every modern communications and computing channel. They should take a fresh look at their business processes to find points at which richer and more customizable communications could eliminate bottlenecks and enhance quality. The important dividing line won't be between those who deploy Vol P and those who don't, or even between early adopters and laggards. It will be between those who see Vol P as just a new way to do the same old things and those who use itto rethink their entire businesses.

  16. BiVO4 -TiO2 Composite Photocatalysts for Dye Degradation Formed Using the SILAR Method.

    Science.gov (United States)

    Odling, Gylen; Robertson, Neil

    2016-09-19

    Composite photocatalyst films have been fabricated by depositing BiVO4 upon TiO2 via a sequential ionic layer adsorption reaction (SILAR) method. The photocatalytic materials were investigated by XRD, TEM, UV/Vis diffuse reflectance, inductively coupled plasma optical emission spectrometry (ICP-OES), XPS, photoluminescence and Mott-Schottky analyses. SILAR processing was found to deposit monoclinic-scheelite BiVO4 nanoparticles onto the surface, giving successive improvements in the films' visible light harvesting. Electrochemical and valence band XPS studies revealed that the prepared heterojunctions have a type II band structure, with the BiVO4 conduction band and valence band lying cathodically shifted from those of TiO2 . The photocatalytic activity of the films was measured by the decolourisation of the dye rhodamine 6G using λ>400 nm visible light. It was found that five SILAR cycles was optimal, with a pseudo-first-order rate constant of 0.004 min(-1) . As a reference material, the same SILAR modification has been made to an inactive wide-band-gap ZrO2 film, where the mismatch of conduction and valence band energies disallows charge separation. The photocatalytic activity of the BiVO4 -ZrO2 system was found to be significantly reduced, highlighting the importance of charge separation across the interface. The mechanism of action of the photocatalysts has also been investigated, in particular the effect of self-sensitisation by the model organic dye and the ability of the dye to inject electrons into the photocatalyst's conduction band. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Visible light driven photocatalysis and antibacterial activity of AgVO3 and Ag/AgVO3 nanowires

    International Nuclear Information System (INIS)

    Singh, Anamika; Dutta, Dimple P.; Ballal, A.; Tyagi, A.K.; Fulekar, M.H.

    2014-01-01

    Graphical abstract: - Highlights: • Ag/AgVO 3 and pure AgVO 3 nanowires synthesized by sonochemical process. • Characterization done using XRD, SEM, TEM, EDX and BET analysis. • Visible light degradation of RhB by Ag/AgVO 3 within 45 min. • Antibacterial activity of Ag/AgVO 3 demonstrated. - Abstract: Ag/AgVO 3 nanowires and AgVO 3 nanorods were synthesized in aqueous media via a facile sonochemical route. The as-synthesized products were characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy together with an energy dispersion X-ray spectrum analysis, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The results revealed that inert atmosphere promotes the formation of Ag/AgVO 3 nanowires. The photocatalytic studies revealed that the Ag/AgVO 3 nanowires exhibited complete photocatalytic degradation of Rhodamine B within 45 min under visible light irradiation. The antibacterial activity of Ag/AgVO 3 nanowires was tested against Escherechia coli and Bacillus subtilis. The minimum growth inhibitory concentration value was found to be 50 and 10 folds lower than for the antibiotic ciprofloxacin for E. coli and B. subtilis, respectively. The antibacterial properties of the β-AgVO 3 nanorods prove that in case of the Ag dispersed Ag/AgVO 3 nanowires, the enhanced antibacterial action is also due to contribution from the AgVO 3 support

  18. Modular VO oriented Java EE service deployer

    Science.gov (United States)

    Molinaro, Marco; Cepparo, Francesco; De Marco, Marco; Knapic, Cristina; Apollo, Pietro; Smareglia, Riccardo

    2014-07-01

    The International Virtual Observatory Alliance (IVOA) has produced many standards and recommendations whose aim is to generate an architecture that starts from astrophysical resources, in a general sense, and ends up in deployed consumable services (that are themselves astrophysical resources). Focusing on the Data Access Layer (DAL) system architecture, that these standards define, in the last years a web based application has been developed and maintained at INAF-OATs IA2 (Italian National institute for Astrophysics - Astronomical Observatory of Trieste, Italian center of Astronomical Archives) to try to deploy and manage multiple VO (Virtual Observatory) services in a uniform way: VO-Dance. However a set of criticalities have arisen since when the VO-Dance idea has been produced, plus some major changes underwent and are undergoing at the IVOA DAL layer (and related standards): this urged IA2 to identify a new solution for its own service layer. Keeping on the basic ideas from VO-Dance (simple service configuration, service instantiation at call time and modularity) while switching to different software technologies (e.g. dismissing Java Reflection in favour of Enterprise Java Bean, EJB, based solution), the new solution has been sketched out and tested for feasibility. Here we present the results originating from this test study. The main constraints for this new project come from various fields. A better homogenized solution rising from IVOA DAL standards: for example the new DALI (Data Access Layer Interface) specification that acts as a common interface system for previous and oncoming access protocols. The need for a modular system where each component is based upon a single VO specification allowing services to rely on common capabilities instead of homogenizing them inside service components directly. The search for a scalable system that takes advantage from distributed systems. The constraints find answer in the adopted solutions hereafter sketched. The

  19. Enhanced photocatalytic performance of BiVO{sub 4} in aqueous AgNO{sub 3} solution under visible light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Chien-Kai [Department of Chemistry, National Changhua University of Education, Changhua City, Taiwan (China); Wu, Tsunghsueh [Department of Chemistry, University of Wisconsin-Platteville, Platteville (United States); Huang, Chang-Wei [Department of Chemistry, National Changhua University of Education, Changhua City, Taiwan (China); Lai, Chi-Yung [Department of Biology, National Changhua University of Education, Changhua, Taiwan (China); Wu, Mei-Yao, E-mail: meiyaowu0919@gmail.com [Research Centre for Traditional Chinese Medicine, Department of Medical Research, China Medical University Hospital, Taichung City, Taiwan (China); Lin, Yang-Wei, E-mail: linywjerry@cc.ncue.edu.tw [Department of Chemistry, National Changhua University of Education, Changhua City, Taiwan (China)

    2017-03-31

    Graphical abstract: Ag{sup +} ions enhanced photocatalytic activity of BiVO{sub 4} under visible light irradiation. - Highlights: • The presence of Ag{sup +} ions enhanced the photodegradation activity of BiVO{sub 4}. • Photoreduction of Ag deposited on the BiVO{sub 4} surface was obtained. • Luminescence and electrochemical results elucidated the photocatalytic mechanism. • Holes and oxygen radicals were the main reactive species generated by BiVO{sub 4}/Ag{sup +}. • Used BiVO{sub 4}/Ag{sup +} exhibited photocatalytic antibacterial activity toward E. coli. - Abstract: Monoclinic-phase bismuth vanadate (BiVO{sub 4}) with a 2.468 eV band gap exhibited enhanced synergic photodegradation activity toward methylene blue (MB) when combined with silver ions (Ag{sup +}) in an aqueous solution under visible light irradiation. The mass ratio of AgNO{sub 3} to BiVO{sub 4} and the calcination temperature were discovered to considerably affect the degradation activity of BiVO{sub 4}/Ag{sup +}. Superior photocatalytic performance was obtained when BiVO{sub 4} was mixed with 0.01%(w/v) AgNO{sub 3} solution, and complete degradation of MB was achieved after 25 min visible light irradiation, outperforming BiVO{sub 4} or AgNO{sub 3} solution alone. The enhanced photodegradation was investigated using systematic luminescence measurements, electrochemical impedance spectroscopy, and scavenger addition, after which a photocatalytic mechanism for MB degradation under visible light irradiation was identified that involved oxygen radicals and holes. This study also discovered the two dominating processes involved in enhancing the electron–hole separation efficiency and reducing their recombination rate, namely photoreduction of Ag{sup +} and the formation of a BiVO{sub 4}/Ag heterojunction. The synergic effect between BiVO{sub 4} and Ag{sup +} was discovered to be unique. BiVO{sub 4}/Ag{sup +} was successfully used to degrade two other dyes and disinfect Escherichia Coli. A

  20. Single crystal structures of the new vanadates CuMgVO{sub 4} and AgMgVO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Ben Yahia, Hamdi, E-mail: Hyahia@qf.org.qa [Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, PO Box 5825, Doha (Qatar); Shikano, Masahiro, E-mail: shikano.masahiro@aist.go.jp [Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Essehli, Rachid; Belharouak, Ilias [Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, PO Box 5825, Doha (Qatar)

    2016-08-01

    The new compounds CuMgVO{sub 4} and AgMgVO{sub 4} have been synthesized by a solid state reaction route. Their crystal structures were determined from single-crystal X-ray diffraction data. CuMgVO{sub 4} crystallizes with Na{sub 2}CrO{sub 4}-type structure with space group Cmcm, a = 5.6932 (10), b = 8.7055 (15), c = 6.2789 (10) Å, V = 311.20 (9) Å{sup 3}, and Z = 4, whereas AgMgVO{sub 4} crystallizes in the maricite-type structure with space group Pnma, a = 9.4286 (14), b = 6.7465 (10), c = 5.3360 (8) Å, V = 339.42 (9) Å{sup 3}, and Z = 4. Both structures of CuMgVO{sub 4}, and AgMgVO{sub 4} contain MgO{sub 4} chains made up of edge-sharing MgO{sub 6} octahedra. In CuMgVO{sub 4} the MgO{sub 4} chains are interconnected through CuVO{sub 4} double chains made up of VO{sub 4} and CuO{sub 4} tetrahedra sharing corners and edges, however in AgMgVO{sub 4} the chains are interlinked by the VO{sub 4} and AgO{sub 4} tetrahedra sharing only corners. - Highlights: • We have been able to grow CuMgVO{sub 4} and AgMgVO{sub 4} single crystals. • We solved their crystal structures using single crystal data. • We compared the crystal structures of CuMgVO{sub 4} and AgMgVO{sub 4}.

  1. New Methods for Processing and Quantifying VO2 Kinetics to Steady State: VO2 Onset Kinetics

    Directory of Open Access Journals (Sweden)

    Craig R. McNulty

    2017-09-01

    Full Text Available Current methods of oxygen uptake (VO2 kinetics data handling may be too simplistic for the complex physiology involved in the underlying physiological processes. Therefore, the aim of this study was to quantify the VO2 kinetics to steady state across the full range of sub-ventilatory threshold work rates, with a particular focus on the VO2 onset kinetics. Ten healthy, moderately trained males participated in five bouts of cycling. Each bout involved 10 min at a percentage of the subject's ventilation threshold (30, 45, 60, 75, 90% from unloaded cycling. The VO2 kinetics was quantified using the conventional mono-exponential time constant (tau, τ, as well as the new methods for VO2 onset kinetics. Compared to linear modeling, non-linear modeling caused a deterioration of goodness of fit (main effect, p < 0.001 across all exercise intensities. Remainder kinetics were also improved using a modified application of the mono-exponential model (main effect, p < 0.001. Interestingly, the slope from the linear regression of the onset kinetics data is similar across all subjects and absolute exercise intensities, and thereby independent of subject fitness and τ. This could indicate that there are no functional limitations between subjects during this onset phase, with limitations occurring for the latter transition to steady state. Finally, the continuing use of mono-exponential modeling could mask important underlying physiology of more instantaneous VO2 responses to steady state. Consequently, further research should be conducted on this new approach to VO2 onset kinetics.

  2. Luminescence and surface properties of Tb3+ doped Sr3(VO4)2 nanophosphors

    International Nuclear Information System (INIS)

    Bedyal, A.K.; Kumar, Vinay; Sharma, Vishal

    2013-01-01

    In this paper, we present a detailed investigation of the luminescence and surface properties of Tb 3+ doped Sr 3 (VO 4 ) 2 nanocrystalline phosphors, synthesized by the combustion method. X-ray diffraction (XRD) peaks in the patterns corresponding to the reflection of rhombohedral pure phase of Sr 3 (VO 4 ) 2 . The average particle sizes have been found in the range of 30-34 nm. Scanning electron microscopy (SEM) indicated that an agglomerated peanut like morphology was obtained. Photoluminescence (PL) spectroscopy has been utilized to investigate the spectral properties of the phosphor. Under 237 nm excitation, it shows several bands centered at 487, 544, 588 and 624 nm, which result from 5 D 4 → 7 F J (J = 6, 5, 4 and 3) transitions of Tb 3+ , and the green emission band ( 5 D 4 → 7 F 5 ) located at 544 nm is dominant. The chemical states and homogeneous dopants' distribution in the host were analyzed with X-ray photoelectron spectroscopy (XPS) and time of flight-secondary ion mass spectroscopy (TOF-SIMS), respectively. A ToF-SIMS imaging shows an uniform distribution of Tb 3+ in the Sr 3 (VO 4 ) 2 . (author)

  3. EPR and optical absorption studies of VO2+ doped L-alanine (C3H7NO2) single crystals

    International Nuclear Information System (INIS)

    Biyik, Recep

    2009-01-01

    VO 2+ doped L-alanine (C 3 H 7 NO 2 ) single crystals and powders are examined by electron paramagnetic resonance (EPR) and optical absorption spectroscopy. Three magnetically different sites are resolved from angular variations of L-alanine single crystal EPR spectra. In some specific orientations each VO 2+ line splits into three superhyperfine lines with intensities of 1:2:1 and maximum splitting value of 2.23 mT. The local symmetries of VO 2+ complex sites are nearly axial. The optical absorption spectra show three bands. Spin Hamiltonian parameters are measured and molecular orbital coefficients are calculated by correlating EPR and optical absorption data for the central vanadyl ion.

  4. The broad-band SEDs of four `hypervariable' AGN

    Science.gov (United States)

    Collinson, James S.; Ward, Martin J.; Lawrence, Andy; Bruce, Alastair; MacLeod, Chelsea L.; Elvis, Martin; Gezari, Suvi; Marshall, Philip J.; Done, Chris

    2018-03-01

    We present an optical-to-X-ray spectral analysis of four `hypervariable' AGN (HVAs) discovered by comparing Pan-STARRS data to that from the Sloan Digital Sky Survey over a 10 yr baseline (Lawrence et al.). There is some evidence that these objects are X-ray loud for their corresponding UV luminosities, but given that we measured them in a historic high state, it is not clear whether to take the high state or low state as typical of the properties of these HVAs. We estimate black hole masses based on Mg II and H α emission line profiles, and either the high- or low-state luminosities, finding mass ranges log (MBH/M⊙) = 8.2-8.8 and log (MBH/M⊙) = 7.9-8.3, respectively. We then fit energy-conserving models to the spectral energy distributions (SEDs), obtaining strong constraints on the bolometric luminosity and αOX. We compare the SED properties with a larger, X-ray selected AGN sample for both of these scenarios, and observe distinct groupings in spectral shape versus luminosity parameter space. In general, the SED properties are closer to normal if we assume that the low state is representative. This supports the idea that the large slow outbursts may be due to extrinsic effects (for example microlensing) as opposed to accretion rate changes, but a larger sample of HVAs is needed to be confident of this conclusion.

  5. Computer-aided design of broad band reflection type amplifiers

    DEFF Research Database (Denmark)

    Hammershaimb, Edgar; Jeppesen, Palle; Schjær-Jacobsen, Hans

    1974-01-01

    Microwave negative resistance reflection type amplifiers using stable transferred electron devices (TED's) are optimized by numerical optimization techniques programmed for an interactive graphic datascreen. The small signal impedance of packaged TED's is measured on an automatic network analyzer....... At the same time the impedance of unpackaged devices are obtained by on-line correction for the package parasitics. The microwave circuit chosen is a multiple slug coaxial cavity, that is modelled by sections of lossy transmission lines including step susceptances. The measured small signal impedance...... of the packaged TED's and the cavity model are used in a direct optimization procedure, in which the calculated minimum gain in the prescribed frequency range is progressively maximized by adjusting the lengths, characteristic impedances and positions of the slugs. The computed results are displayed...

  6. A prism based magnifying hyperlens with broad-band imaging

    DEFF Research Database (Denmark)

    Habib, Md. Samiul; Stefani, Alessio; Atakaramians, Shaghik

    2017-01-01

    Magnification in metamaterial hyperlenses has been demonstrated using curved geometries or tapered devices, at frequencies ranging from the microwave to the ultraviolet spectrum. One of the main issues of such hyperlenses is the difficulty in manufacturing. In this letter, we numerically and expe...

  7. Molecular Electronic Angular Motion Transducer Broad Band Self-Noise

    Science.gov (United States)

    Zaitsev, Dmitry; Agafonov, Vadim; Egorov, Egor; Antonov, Alexander; Shabalina, Anna

    2015-01-01

    Modern molecular electronic transfer (MET) angular motion sensors combine high technical characteristics with low cost. Self-noise is one of the key characteristics which determine applications for MET sensors. However, until the present there has not been a model describing the sensor noise in the complete operating frequency range. The present work reports the results of an experimental study of the self-noise level of such sensors in the frequency range of 0.01–200 Hz. Based on the experimental data, a theoretical model is developed. According to the model, self-noise is conditioned by thermal hydrodynamic fluctuations of the operating fluid flow in the frequency range of 0.01–2 Hz. At the frequency range of 2–100 Hz, the noise power spectral density has a specific inversely proportional dependence of the power spectral density on the frequency that could be attributed to convective processes. In the high frequency range of 100–200 Hz, the noise is conditioned by the voltage noise of the electronics module input stage operational amplifiers and is heavily reliant to the sensor electrical impedance. The presented results allow a deeper understanding of the molecular electronic sensor noise nature to suggest the ways to reduce it. PMID:26610502

  8. Bismuth zinc vanadate, BiZn2VO6: New crystal structure type and electronic structure

    International Nuclear Information System (INIS)

    Eliziario Nunes, Sayonara; Wang, Chun-Hai; So, Karwei; Evans, John S.O.; Evans, Ivana Radosavljević

    2015-01-01

    We report a combined experimental and computational study of the crystal structure and electronic properties of bismuth zinc vanadate, BiZn 2 VO 6 , known for its visible light photocatalytic activity. The crystal structure has been solved from laboratory powder X-ray diffraction data using the repeated minimisations from random starting values method. BiZn 2 VO 6 adopts a new structure type, based on the following building blocks: corner- and edge-sharing ZnO 4 tetrahedra, ZnO 6 octahedra and VO 4 tetrahedra, and Bi 2 O 12 dimers. It is the only known member of the BiM 2 AO 6 (M=Pb, Ca, Cd, Mn, Zn, Mg, Cu; A=V, P, As) family which does not appear to be structurally closely related to others. The electronic structure of BiZn 2 VO 6 , calculated by DFT methods, shows that it is an indirect gap semiconductor with a calculated band gap of 1.6 eV, which compares favourably to the experimentally measured value of 2.4 eV. - Graphical abstract: The crystal structure of BiZn 2 VO 6 , a new structure type in the BiM 2 AO 6 (M=Mg, Ca, Cd, Cu, Pb, Mn, Zn; A=V, P, As) family. - Highlights: • Structure solution from PXRD data by repeated minimisations from random starting values. • New structure type in the BiM 2 AO 6 (M=Pb, Ca, Cd, Mn, Zn, Mg, Cu; A=V, P, As) family. • Electronic structure calculation

  9. Utilization of visible to NIR light energy by Yb{sup +3}, Er{sup +3} and Tm{sup +3} doped BiVO{sub 4} for the photocatalytic degradation of methylene blue

    Energy Technology Data Exchange (ETDEWEB)

    Regmi, Chhabilal [Research Center for Eco-Multifunctional Nanomaterials, Sun Moon University, Chungnam 31460 (Korea, Republic of); Kshetri, Yuwaraj K. [Department of Advanced Materials Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Ray, Schindra Kumar [Research Center for Eco-Multifunctional Nanomaterials, Sun Moon University, Chungnam 31460 (Korea, Republic of); Pandey, Ramesh Prasad [Institute of Biomolecule Reconstruction, Department of BT-Convergent Pharmaceutical Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Lee, Soo Wohn, E-mail: swlee@sunmoon.ac.kr [Research Center for Eco-Multifunctional Nanomaterials, Sun Moon University, Chungnam 31460 (Korea, Republic of)

    2017-01-15

    Highlights: • Lanthanide doped BiVO{sub 4} as highly efficient upconversion and photocatalytic material. • Well defined beads like morphology for better photocatalytic activity. • Effective utilization of NIR and visible light for efficient photocatalytic degradation of methylene blue. • Nontoxic to human cells, potential for application in biological fields. - Abstract: Lanthanide-doped BiVO{sub 4} semiconductors with efficient photocatalytic activities over a broad range of the solar light spectrum have been synthesized by the microwave hydrothermal method using ethylenediaminetetraacetic acid (EDTA). The structural, morphological, and optical properties of the as-synthesized samples were evaluated by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray powder diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL). The chemical compositions were analyzed by X-ray photoelectron spectroscopy (XPS). The toxicity of the samples was measured using Mus musculus skin melanoma cells (B16-F10 (ATCC{sup ®} CRL-6475™)) and were found to be nontoxic for human cells. The photocatalytic efficiency of the prepared samples was evaluated by methylene blue (MB) degradation. The best photocatalytic activity was shown by BiVO{sub 4} with 6:3:3 mol percentage of Yb{sup +3}:Er{sup +3}:Tm{sup +3} in all solar light spectrum. The synthesized samples possess low band gap energy and a hollow structure suitable for the better photocatalytic activity. The observed NIR photoactivity supports that the upconversion mechanism is involved in the overall photocatalytic process. Therefore, this approach provides a better alternative upconversion material for integral solar light absorption.

  10. Investigation of the physical, optical, and photocatalytic properties of CeO2/Fe-doped InVO4 composite

    Science.gov (United States)

    Chaison, Jindaporn; Wetchakun, Khatcharin; Wetchakun, Natda

    2017-12-01

    The CeO2/Fe-doped InVO4 composites with various Fe concentrations (0.5, 1.0, 2.0, 5.0 and 6.0 mol%) was synthesized by homogeneous precipitation and hydrothermal methods. The as-synthesized samples were characterized by powder X-ray diffraction (XRD), Brunauer Emmett and Teller (BET)-specific surface area, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy (DRS). Fe-doping into InVO4 crystal induces the distortion of the crystalline structure, the transformation of InVO4 morphology, and the new energy subband level generation of Fe between the CB and VB edge of InVO4. The electron excitation from the VB to Fe orbitals results in the decreased band gap and the extended absorption of visible-light, and thus enhances its photocatalytic performance. Visible-light-driven photocatalytic degradation of Rhodamine B (RhB) dye in water was used to evaluate the photocatalytic performance of CeO2/Fe-doped InVO4 composites. The results revealed that there is an optimum Fe (5.0 mol %) doping level. The composite with the optimum doping level obtains high photocatalytic activity of CeO2/Fe-doped InVO4 composite compared to pure CeO2 and pure InVO4 host. The increase of photocatalytic activity of CeO2/Fe-doped InVO4 composite was ascribed to the surface area, crystal defect, and band gap energy. Moreover, the photocatalytic enhancement is also because iron ions act as a trapping site, which results in the higher separation efficiency of photogenerated electrons and holes pairs in the CeO2/InVO4 composite. The evaluation of radical scavengers confirmed that hydroxyl radical was the main active species during the photodegradation of RhB. These synergistic effects are responsible for the enhanced photocatalytic activity of CeO2/Fe-doped InVO4 composite. Furthermore, the possible enhanced photocatalytic mechanism

  11. Mg-doped VO2 nanoparticles: hydrothermal synthesis, enhanced visible transmittance and decreased metal-insulator transition temperature.

    Science.gov (United States)

    Zhou, Jiadong; Gao, Yanfeng; Liu, Xinling; Chen, Zhang; Dai, Lei; Cao, Chuanxiang; Luo, Hongjie; Kanahira, Minoru; Sun, Chao; Yan, Liuming

    2013-05-28

    This paper reports the successful preparation of Mg-doped VO2 nanoparticles via hydrothermal synthesis. The metal-insulator transition temperature (T(c)) decreased by approximately 2 K per at% Mg. The Tc decreased to 54 °C with 7.0 at% dopant. The composite foils made from Mg-doped VO2 particles displayed excellent visible transmittance (up to 54.2%) and solar modulation ability (up to 10.6%). In addition, the absorption edge blue-shifted from 490 nm to 440 nm at a Mg content of 3.8 at%, representing a widened optical band gap from 2.0 eV for pure VO2 to 2.4 eV at 3.8 at% doping. As a result, the colour of the Mg-doped films was modified to increase their brightness and lighten the yellow colour over that of the undoped-VO2 film. A first principle calculation was conducted to understand how dopants affect the optical, Mott phase transition and structural properties of VO2.

  12. Tunable photoluminescence and magnetic properties of Dy(3+) and Eu(3+) doped GdVO4 multifunctional phosphors.

    Science.gov (United States)

    Liu, Yanxia; Liu, Guixia; Dong, Xiangting; Wang, Jinxian; Yu, Wensheng

    2015-10-28

    A series of Dy(3+) or/and Eu(3+) doped GdVO4 phosphors were successfully prepared by a simple hydrothermal method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectrometry (EDS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). The results indicate that the as-prepared samples are pure tetragonal phase GdVO4, taking on nanoparticles with an average size of 45 nm. Under ultraviolet (UV) light excitation, the individual Dy(3+) or Eu(3+) ion activated GdVO4 phosphors exhibit excellent emission properties in their respective regions. The mechanism of energy transfer from the VO4(3-) group and the charge transfer band (CTB) to Dy(3+) and Eu(3+) ions is proposed. Color-tunable emissions in GdVO4:Dy(3+),Eu(3+) phosphors are realized through adopting different excitation wavelengths or adjusting the appropriate concentration of Dy(3+) and Eu(3+) when excited by a single excitation wavelength. In addition, the as-prepared samples show paramagnetic properties at room temperature. This kind of multifunctional color-tunable phosphor has great potential applications in the fields of photoelectronic devices and biomedical sciences.

  13. EPR and optical absorption studies of paramagnetic molecular ion (VO2+) in Lithium Sodium Acid Phthalate single crystal

    Science.gov (United States)

    Subbulakshmi, N.; Kumar, M. Saravana; Sheela, K. Juliet; Krishnan, S. Radha; Shanmugam, V. M.; Subramanian, P.

    2017-12-01

    Electron Paramagnetic Resonance (EPR) spectroscopic studies of VO2+ ions as paramagnetic impurity in Lithium Sodium Acid Phthalate (LiNaP) single crystal have been done at room temperature on X-Band microwave frequency. The lattice parameter values are obtained for the chosen system from Single crystal X-ray diffraction study. Among the number of hyperfine lines in the EPR spectra only two sets are reported from EPR data. The principal values of g and A tensors are evaluated for the two different VO2+ sites I and II. They possess the crystalline field around the VO2+ as orthorhombic. Site II VO2+ ion is identified as substitutional in place of Na1 location and the other site I is identified as interstitial location. For both sites in LiNaP, VO2+ are identified in octahedral coordination with tetragonal distortion as seen from the spin Hamiltonian parameter values. The ground state of vanadyl ion in the LiNaP single crystal is dxy. Using optical absorption data the octahedral and tetragonal parameters are calculated. By correlating EPR and optical data, the molecular orbital bonding parameters have been discussed for both sites.

  14. Facile synthesis and high activity of novel BiVO{sub 4}/FeVO{sub 4} heterojunction photocatalyst for degradation of metronidazole

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jinhai [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023 (China); School of Chemical Engineering, Guizhou University of Engineering Science, Bijie 551700 (China); Zhao, Wei; Guo, Yang; Wei, Zhongbo; Han, Mengshu [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023 (China); He, Huan [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023 (China); School of Public Health, University of Illinois at Chicago, Chicago, IL 60631 (United States); Yang, Shaogui [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023 (China); Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824 (United States); Sun, Cheng, E-mail: envidean@nju.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023 (China)

    2015-10-01

    Graphical abstract: - Highlights: • BiVO{sub 4}/FeVO{sub 4} was synthesized by a facile one-step hydrothermal method. • BiVO{sub 4}/FeVO{sub 4} displays superior photocatalytic activity. • The photocatalytic mechanism were discussed in detail. - Abstract: The novel BiVO{sub 4}/FeVO{sub 4} heterojunction photocatalyst was successfully synthesized by a facile hydrothermal method firstly. The physical and chemical properties of as-prepared samples were characterized based upon XRD, XPS, BET, SEM, EDS, TEM, UV–vis DRS and fluorescence spectrum techniques. The TEM images showed a clear interface between BiVO{sub 4} and FeVO{sub 4}, indicating that a heterojunction between BiVO{sub 4} and FeVO{sub 4} was formed during the hydrothermal reaction. In addition, the photodegradation activity of metronidazole (MNZ) was used as a measurement for photocatalytic performance of BiVO{sub 4}, FeVO{sub 4} and BiVO{sub 4}/FeVO{sub 4} heterojunction photocatalyst. It indicated that under visible light irradiation the photocatalytic activity of BiVO{sub 4}/FeVO{sub 4} heterojunction photocatalyst was very effective, and moreover, much higher than the single BiVO{sub 4} or single FeVO{sub 4}. The possible photocatalytic mechanism has been discussed on the basis of the theoretical calculation of the electronic structure, and the experimental results.

  15. A novel inorganic precipitation-peptization method for VO2 sol and VO2 nanoparticles preparation: Synthesis, characterization and mechanism.

    Science.gov (United States)

    Li, Yao; Jiang, Peng; Xiang, Wei; Ran, Fanyong; Cao, Wenbin

    2016-01-15

    In this paper, a simple, safe and cost-saving precipitation-peptization method was proposed to prepare VO2 sol by using inorganic VOSO4-NH3⋅H2O-H2O2 reactants system in air under room temperature. In this process, VOSO4 was firstly precipitated to form VO(OH)2, then monometallic species of VO(O2)(OH)(-) were formed through the coordination between VO(OH)2 and H2O2. The rearrangement of VO(O2)(OH)(-) in a nonplanar pattern and intermolecular condensation reactions result in multinuclear species. Finally, VO2 sol is prepared through the condensation reactions between the multinuclear species. After drying the obtained sol at 40°C, VO2 xerogel exhibiting monoclinic crystal structure with the space group of C2/m was prepared. The crystal structure of VO2 nanoparticles was transferred to monoclinic crystal structure with the space group of P21/c (VO2(M)) by annealing the xerogel at 550°C. Both XRD and TEM analysis indicated that the nanoparticles possess good crystallinity with crystallite size of 34.5nm as estimated by Scherrer's method. These results suggest that the VO2 sol has been prepared successfully through the proposed simple method. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Ab Initio Metadynamics Study of the VO2+/VO2+ Redox Reaction Mechanism at the Graphite Edge/Water Interface.

    Science.gov (United States)

    Jiang, Zhen; Klyukin, Konstantin; Alexandrov, Vitaly

    2018-06-08

    Redox flow batteries (RFBs) are promising electrochemical energy storage systems, for which development is impeded by a poor understanding of redox reactions occurring at electrode/electrolyte interfaces. Even for the conventional all-vanadium RFB chemistry employing V 2+ /V 3+ and VO 2 + /VO 2+ couples, there is still no consensus about the reaction mechanism, electrode active sites, and rate-determining step. Herein, we perform Car-Parrinello molecular dynamics-based metadynamics simulations to unravel the mechanism of the VO 2 + /VO 2+ redox reaction in water at the oxygen-functionalized graphite (112̅0) edge surface serving as a representative carbon-based electrode. Our results suggest that during the battery discharge aqueous VO 2 + /VO 2+ species adsorb at the surface C-O groups as inner-sphere complexes, exhibiting faster adsorption/desorption kinetics than V 2+ /V 3+ , at least at low vanadium concentrations considered in our study. We find that this is because (i) VO 2 + /VO 2+ conversion does not involve the slow transfer of an oxygen atom, (ii) protonation of VO 2 + is spontaneous and coupled to interfacial electron transfer in acidic conditions to enable VO 2+ formation, and (iii) V 3+ found to be strongly bound to oxygen groups of the graphite surface features unfavorable desorption kinetics. In contrast, the reverse process taking place upon charging is expected to be more sluggish for the VO 2 + /VO 2+ redox couple because of both unfavorable deprotonation of the VO 2+ water ligands and adsorption/desorption kinetics.

  17. Prenatal diagnosis of amniotic band syndrome

    Directory of Open Access Journals (Sweden)

    Laxmi Devi Padmanabhan

    2016-01-01

    Full Text Available Amniotic band can cause a broad spectrum of anomalies ranging from simple band constrictions to major craniofacial and visceral defects. It can cause significant neonatal morbidity. Accurate diagnosis will help in the management of the present pregnancy and in counseling with regard to future pregnancies. Here we report three cases of amniotic band syndrome detected in the prenatal period.

  18. For progress in natural science: Materials international investigations of structural phase transformation and THz properties across metal–insulator transition in VO2/Al2O3 epitaxial films

    Directory of Open Access Journals (Sweden)

    Mengmeng Yang

    2015-10-01

    Full Text Available Vanadium dioxide (VO2 epitaxial thin films on (0001-oriented Al2O3 substrates were prepared using radio frequency (RF magnetron sputtering techniques. To study the metal-insulator-transition (MIT mechanism and extend the applications of VO2 epitaxial films at terahertz (THz band, temperature-dependent X-ray diffraction (XRD and THz time domain spectroscopy of the VO2 epitaxial films were performed. Both the lattice constants and THz transmission exhibited a similar and sharp transition that was similar to that observed for the electrical resistance. Consequently, the MIT of the VO2/Al2O3 epitaxial films should be co-triggered by the structural phase transition and electronic transition. Moreover, the very large resistance change (on the order of ~103 and THz response (with a transmission modulation ratio of ~87% in the VO2/Al2O3 epitaxial heterostructures are promising for electrical switch and electro-optical device applications.

  19. Broad Bandwidth Meta-Material Antireflection Coatings for Measurement of the Cosmic Microwave Background

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop broad-band metamaterial antireflection (AR) coatings for the far-infrared and millimeter wave bands. The proposed coating technology could...

  20. Electrocatalytic activity of cobalt phosphide-modified graphite felt toward VO2+/VO2+ redox reaction

    Science.gov (United States)

    Ge, Zhijun; Wang, Ling; He, Zhangxing; Li, Yuehua; Jiang, Yingqiao; Meng, Wei; Dai, Lei

    2018-04-01

    A novel strategy for improving the electro-catalytic properties of graphite felt (GF) electrode in vanadium redox flow battery (VRFB) is designed by depositing cobalt phosphide (CoP) onto GF surface. The CoP powder is synthesized by direct carbonization of Co-based zeolitic imidazolate framework (ZIF-67) followed by phosphidation. Cyclic voltammetry results confirm that the CoP-modified graphite felt (GF-CoP) electrode has excellent reversibility and electro-catalytic activity to the VO2+/VO2+ cathodic reaction compared with the pristine GF electrode. The cell using GF-CoP electrode shows apparently higher discharge capacity over that based on GF electrode. The cell using GF-CoP electrode has the capacity of 67.2 mA h at 100 mA cm-2, 32.7 mA h larger than that using GF electrode. Compared with cell using GF electrode, the voltage efficiency of the cell based on GF-CoP electrode increases by 5.9% and energy efficiency by 5.4% at a current density of 100 mA cm-2. The cell using GF-CoP electrode can reach 94.31% capacity retention after 50 cycles at a current density of 30 mA cm-2. The results show that the CoP can effectively promote the VO2+/VO2+ redox reaction, implying that metal phosphides are a new kind of potential catalytic materials for VRFB.

  1. Broad spectrum bioactive sunscreens.

    Science.gov (United States)

    Velasco, Maria Valéria Robles; Sarruf, Fernanda Daud; Salgado-Santos, Idalina Maria Nunes; Haroutiounian-Filho, Carlos Alberto; Kaneko, Telma Mary; Baby, André Rolim

    2008-11-03

    The development of sunscreens containing reduced concentration of chemical UV filters, even though, possessing broad spectrum effectiveness with the use of natural raw materials that improve and infer UV absorption is of great interest. Due to the structural similarities between polyphenolic compounds and organic UV filters, they might exert photoprotection activity. The objective of the present research work was to develop bioactive sunscreen delivery systems containing rutin, Passiflora incarnata L. and Plantago lanceolata extracts associated or not with organic and inorganic UV filters. UV transmission of the sunscreen delivery system films was performed by using diffuse transmittance measurements coupling to an integrating sphere. In vitro photoprotection efficacy was evaluated according to the following parameters: estimated sun protection factor (SPF); Boot's Star Rating category; UVA/UVB ratio; and critical wavelength (lambda(c)). Sunscreen delivery systems obtained SPF values ranging from 0.972+/-0.004 to 28.064+/-2.429 and bioactive compounds interacted with the UV filters positive and negatively. This behavior may be attributed to: the composition of the delivery system; the presence of inorganic UV filter and quantitative composition of the organic UV filters; and the phytochemical composition of the P. incarnata L. and P. lanceolata extracts. Among all associations of bioactive compounds and UV filters, we found that the broad spectrum sunscreen was accomplished when 1.68% (w/w) P. incarnata L. dry extract was in the presence of 7.0% (w/w) ethylhexyl methoxycinnamate, 2.0% (w/w) benzophenone-3 and 2.0% (w/w) TiO(2). It was demonstrated that this association generated estimated SPF of 20.072+/-0.906 and it has improved the protective defense against UVA radiation accompanying augmentation of the UVA/UVB ratio from 0.49 to 0.52 and lambda(c) from 364 to 368.6nm.

  2. High-performance thermal sensitive W-doped VO{sub 2}(B) thin film and its identification by first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Dongyun; Xiong, Ping; Chen, Lanli [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Shi, Siqi, E-mail: sqshi@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Ishaq, Ahmad [National Center for Physics, Quaid-I-Azam University, Islamabad 44000 (Pakistan); Luo, Hongjie [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Gao, Yanfeng, E-mail: yfgao@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China)

    2017-03-01

    Graphical abstract: VO{sub 2}(B) thin films with high TCR and suitable resistance were first achieved by W doping. The mechanism for performance improvement was studied by first-principles calculations. The two-dimensional octahedral structure of VO{sub 2}(B) favors the strain control with W-doping for achieving a large TCR, which overcomes the contradiction between the high conductivity and large TCR generated by dopants in VO{sub 2}(M). - Highlights: • High performance W-doped VO{sub 2}(B) thin films were first achieved by co-sputtering. • Mechanism for performance improvement was studied by first-principles calculations. • The two-dimensional octahedral structure of VO{sub 2} (B) favors the strain control. • Achieved VO{sub 2} films possess high thermal sensitivity (TCR: −3.9%/K & R{sub 0}: 32.7 kΩ). - Abstract: VO{sub 2}(B) is currently a preferred phase structure for the application as bolometer material, which, however, suffers from low temperature-coefficient-of-resistance (TCR) values and large resistances. Here we present the combined experimental and first-principles calculations study on both doped and undoped VO{sub 2}(B) thin films enabling us to attain high TCR (−3.9%/k) and suitable square-resistance (32.7 kΩ) by controlled W doping employing the widely used magnetron sputtering technique. The TCR value is 50% larger than reported ones at the similar resistance. The underlying microscopic mechanism for the performance improvement was studied and results indicated that the introduction of extra electrons and the variation in the band structure resulting from the incorporation of W{sup 6+} ions in the VO{sub 2}(B) crystal lattice contribute to the enhancement of the electronic conductivity. Moreover, the special two-dimensional octahedral structure of monoclinic (C2/m) B-phase VO{sub 2} favors the strain control with W-doping for achieving a large TCR, which overcomes the analogous predicament between the high conductivity and large TCR

  3. Electronic transport in VO2—Experimentally calibrated Boltzmann transport modeling

    International Nuclear Information System (INIS)

    Kinaci, Alper; Rosenmann, Daniel; Chan, Maria K. Y.; Kado, Motohisa; Ling, Chen; Zhu, Gaohua; Banerjee, Debasish

    2015-01-01

    Materials that undergo metal-insulator transitions (MITs) are under intense study, because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO 2 has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of electronic transport in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach with Hubbard U correction (DFT + U) to model electronic transport properties in VO 2 in the semiconducting and metallic regimes, focusing on band transport using the Boltzmann transport equations. We synthesized high quality VO 2 films and measured the transport quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable transport properties

  4. Electronic transport in VO{sub 2}—Experimentally calibrated Boltzmann transport modeling

    Energy Technology Data Exchange (ETDEWEB)

    Kinaci, Alper; Rosenmann, Daniel; Chan, Maria K. Y., E-mail: debasish.banerjee@toyota.com, E-mail: mchan@anl.gov [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kado, Motohisa [Higashifuji Technical Center, Toyota Motor Corporation, Susono, Shizuoka 410-1193 (Japan); Ling, Chen; Zhu, Gaohua; Banerjee, Debasish, E-mail: debasish.banerjee@toyota.com, E-mail: mchan@anl.gov [Materials Research Department, Toyota Motor Engineering and Manufacturing North America, Inc., Ann Arbor, Michigan 48105 (United States)

    2015-12-28

    Materials that undergo metal-insulator transitions (MITs) are under intense study, because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO{sub 2} has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of electronic transport in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach with Hubbard U correction (DFT + U) to model electronic transport properties in VO{sub 2} in the semiconducting and metallic regimes, focusing on band transport using the Boltzmann transport equations. We synthesized high quality VO{sub 2} films and measured the transport quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable transport properties.

  5. Broad temperature adaptability of vanadium redox flow battery—Part 1: Electrolyte research

    International Nuclear Information System (INIS)

    Xiao, Shuibo; Yu, Lihong; Wu, Lantao; Liu, Le; Qiu, Xinping; Xi, Jingyu

    2016-01-01

    Highlights: • Impact of temperature (-35 °C-50 °C) on properties of VRFB electrolyte is studied. • V 2+ , V 3+ , V 3.5+ , V 4+ (VO 2+ ) and V 5+ (VO 2 + ) electrolytes are tested respectively. • V 2+ , V 3+ and V 3.5+ precipitates at low temperature can redissolve when temperature increases. • V 5+ precipitates at high temperature cannot redissolve when temperature decreases. • Conductivity and viscosity of the electrolytes are greatly affected by temperature. - Abstract: The broad temperature adaptability of vanadium redox flow battery (VRFB) is one of the key issues which affects the large-scale and safety application of VRFB. Typically, five types of vanadium electrolytes, namely V 2+ , V 3+ , V 3.5+ (V 3+ :VO 2+ = 1:1), V 4+ (VO 2+ ) and V 5+ (VO 2 + ), are the most common electrolytes' status existing in VRFB system. In this work, the physicochemical and electrochemical properties of these vanadium electrolytes are studied in detail at a broad temperature range (-35 °C–50 °C). The results show that all types of vanadium electrolytes are stable between -25 °C–30 °C. The temperature fluctuation will largely influence the conductivity and viscosity of the electrolytes. Besides, the electrochemical properties of the positive (VO 2+ ) and negative (V 3+ ) electrolytes are greatly affected by the temperature; and the charge transfer process fluctuates more greatly with the temperature variation than the charge diffusion process does. These results enable us to better and more comprehensively evaluate the performance of the electrolyte changing with the temperature, which will be beneficial for the rational choice of electrolyte for VRFB operation under various conditions.

  6. Fabrication of Ni-doped BiVO_4 semiconductors with enhanced visible-light photocatalytic performances for wastewater treatment

    International Nuclear Information System (INIS)

    Regmi, Chhabilal; Kshetri, Yuwaraj K.; Kim, Tae-Ho; Pandey, Ramesh Prasad; Ray, Schindra Kumar; Lee, Soo Wohn

    2017-01-01

    Highlights: • Synthesis of a Ni-doped BiVO_4 semiconductor photocatalyst with reduced band gap energy. • Ni-doped BiVO_4 provided efficient photocatalytic activity for ibuprofen degradation and E. coli and green tide deactivation. • DFT calculation and thermodynamic modeling to understand the underlying mechanism. - Abstract: A visible-light-driven Ni-doped BiVO_4 photocatalyst was synthesized using a microwave hydrothermal method. The nominal Ni doping amount of 1 wt% provided excellent photoactivity for a variety of water pollutants, such as ibuprofen (pharmaceutical), Escherichia coli (bacteria), and green tides (phytoplankton). Each Ni-doped BiVO_4 sample exhibits better performance than pure BiVO_4. The degradation of ibuprofen reaches 80% within 90 min, the deactivation of Escherichia coli reaches around 92% within 5 h, and the inactivation of green tide (Chlamydomonas pulsatilla) reaches 70% upon 60 min of the visible light irradiation. The first principle calculation and thermodynamic modeling revealed that Ni doping in the vanadium site gives the most stable configuration of the synthesized samples with the formation of an in-gap energy state and oxygen vacancies. The in-gap energy state and the oxygen vacancies serve as an electron-trapping center that decreases the migration time of the photogenerated carrier and increases the separation efficiency of electron-hole pairs, which are responsible for the observed efficient photocatalytic, anti-bacterial and anti-algal activity of the samples. These properties thus suggest potential applications of Ni-doped BiVO_4 as a multifunctional material in the field of wastewater treatment.

  7. Luminous transmittance and phase transition temperature of VO 2 ...

    African Journals Online (AJOL)

    The phase transition temperature (τc) of the films was obtained from both the transmittance and sheet resistance against temperature curves. A change in sheet resistance of 2 to 3 orders of magnitude was observed for both undoped and Ce-doped VO2 films. Comparison between undoped and doped VO2 films revealed ...

  8. Lattice effects in HoVo(3) single crystal

    NARCIS (Netherlands)

    Sikora, M.; Marquina, C.; Ibarra, M. R.; Nugroho, A. A.; Palstra, T. T. M.

    We report the study of lattice effects in the Mott insulator HoVO3 performed by means of linear thermal expansion on a single crystal in the temperature range 10-290 K. The holmium orthovanadate HoVO3 reveals gradual orbital ordering (OO) below T-OO = 200K and orders antiferromagnetically at T-N =

  9. ) m /SrVO3 ( m = 5, 6) Superlattices

    KAUST Repository

    Dai, Qingqing; Lü ders, Ulrike; Fré sard, Raymond; Eckern, Ulrich; Schwingenschlö gl, Udo

    2018-01-01

    The (LaV3+O3)m/SrV4+O3 (m = 5, 6) superlattices are investigated by first principles calculations. While bulk LaVO3 is a C‐type antiferromagnetic semiconductor and bulk SrVO3 is a paramagnetic metal, semiconducting A‐type antiferromagnetic states

  10. Using VO Concept for Managing Dynamic Security Associations

    NARCIS (Netherlands)

    Demchenko, Y.; Gommans, L.; de Laat, C.T.A.M.

    2006-01-01

    This research paper presents results of the analysis how the Virtual Organisation (VO) concept can be used for managing dynamic security associations in collaborative applications and for complex resource provisioning. The paper provides an overview of the current practice in VO management at the

  11. Hydrothermal synthesis and electrochemical characterization of VO2 (B) with controlled crystal structures

    International Nuclear Information System (INIS)

    Jiang Wentao; Ni Juan; Yu Ke; Zhu Ziqiang

    2011-01-01

    Three different VO 2 (B) nanostructures, including urchin-like VO 2 (B), VO 2 (B) honeycombs and VO 2 (B) nanorods have been successfully fabricated through hydrothermal process by adjusting the concentrations of the oxalic acid. The microstructure and morphology of the VO 2 nanostructures were evaluated by using X-ray diffraction and scanning and transmission electron microscopies. Electrochemical properties measurements of urchin-like VO 2 (B) and VO 2 (B) honeycombs showed excellent cycling performance, especially the urchin-like VO 2 (B) exhibited higher discharge capacity and better capacity retention.

  12. Integrating the IA2 Astronomical Archive in the VO: The VO-Dance Engine

    Science.gov (United States)

    Molinaro, M.; Laurino, O.; Smareglia, R.

    2012-09-01

    Virtual Observatory (VO) protocols and standards are getting mature and the astronomical community asks for astrophysical data to be easily reachable. This means data centers have to intensify their efforts to provide the data they manage not only through proprietary portals and services but also through interoperable resources developed on the basis of the IVOA (International Virtual Observatory Alliance) recommendations. Here we present the work and ideas developed at the IA2 (Italian Astronomical Archive) data center hosted by the INAF-OATs (Italian Institute for Astrophysics - Trieste Astronomical Observatory) to reach this goal. The core point is the development of an application that from existing DB and archive structures can translate their content to VO compliant resources: VO-Dance (written in Java). This application, in turn, relies on a database (potentially DBMS independent) to store the translation layer information of each resource and auxiliary content (UCDs, field names, authorizations, policies, etc.). The last token is an administrative interface (currently developed using the Django python framework) to allow the data center administrators to set up and maintain resources. This deployment, platform independent, with database and administrative interface highly customizable, means the package, when stable and easily distributable, can be also used by single astronomers or groups to set up their own resources from their public datasets.

  13. Improving the electrocatalytic performance of carbon nanotubes for VO"2"+/VO_2"+ redox reaction by KOH activation

    International Nuclear Information System (INIS)

    Dai, Lei; Jiang, Yingqiao; Meng, Wei; Zhou, Huizhu; Wang, Ling; He, Zhangxing

    2017-01-01

    Highlights: • KOH-activated carbon nanotubes (CNTs) was investigated as superior catalyst for VO"2"+/VO_2"+ redox reaction for vanadium redox flow battery (VRFB) for the first time. • KOH activation for CNTs can result in the chemical etching of surface and improved wettability, accelerating the mass transfer of vanadium ions. • KOH activation can introduce many oxygen-containing groups as active sites on the surface of CNTs. • KOH-activated CNTs as positive catalyst could increase the comprehensive energy storage performance of VRFB. - Abstract: In this paper, carbon nanotubes (CNTs) was activated by KOH treatment at high temperature and investigated as catalyst for VO"2"+/VO_2"+ redox reaction for vanadium redox flow battery (VRFB). X-ray photoelectron spectroscopy results suggest that the oxygen-containing groups can be introduced on CNTs by KOH activation. The mass transfer of vanadium ions can be accelerated by chemical etching by KOH activation and improved wettability due to the introduction of hydrophilic groups. The electrochemical properties of VO"2"+/VO_2"+ redox reaction can be enhanced by introduced oxygen-containing groups as active sites. The sample treated at 900 °C with KOH/CNTs mass ratio of 3:1 (CNTs-3) exhibits the highest electrocatalytic activity for VO"2"+/VO_2"+ redox reaction. The cell using CNTs-3 as positive catalyst demonstrates the smallest electrochemical polarization, the highest capacity and efficiency among the samples. Using KOH-activated CNTs-3 can increase the average energy efficiency of the cell by 4.4%. This work suggests that KOH-activated CNTs is a low-cost, efficient and promising catalyst for VO"2"+/VO_2"+ redox reaction for VRFB system.

  14. Growth and laser characterization of a mixed laser crystal Nd: Lu 0.141Y 0.855VO 4

    Science.gov (United States)

    Zhao, Bin; Zhuang, Naifeng; Li, Tao; Guo, Feiyun; Zhuo, Zhuang; Ye, Jing; Chen, Jianzhong

    2011-11-01

    A new Nd: Lu 0.141Y 0.855VO 4 mixed laser crystal had been successfully grown by the Czochralski method. The reason of the crystal boule appearing additionally yellowish at the bottom was discussed. The X-ray powder diffraction analysis showed that the as-grown mixed crystal possesses the ZrSiO 4 structure. The effective segregation coefficients of Nd 3+ and Lu 3+ ions in the crystal were measured to be about 0.51 and 0.76, respectively. The room temperature fluorescence spectrum of the mixed crystal showed that the FWHM (full-width at half-maximum) of the 1064.9 nm fluorescence band was 5.1 nm, broader than that of Nd: YVO 4. A continuous-wave (CW) laser output was achieved with the Nd: Lu 0.141Y 0.855VO 4 crystal at 1.06 μm using laser diode pumping. The maximum CW output power of 1.7 W was obtained with the pump power of 7.6 W, higher than the 1.38 W achieved with the 0.5 at% Nd: LuVO 4 crystal under the same experimental conditions. All the results above show that the Nd: Lu 0.141Y 0.855VO 4 crystal is a promising laser material.

  15. Synthesis, characterization and formation mechanism of metastable phase VO2(A) nanorods

    International Nuclear Information System (INIS)

    Cheng, X.H.; Xu, H.F.; Wang, Z.Z.; Zhu, K.R.; Li, G.; Jin, Shaowei

    2013-01-01

    Graphical abstract: - Highlights: • Pure phases of VO 2 (B) and VO 2 (A) were prepared by a facile hydrothermal method. • Belt-like particles prepared at 180 °C was indexed as monoclinic VO 2 (B) phase. • Rod-like particles prepared at 230 °C was indexed as tetragonal VO 2 (A) phase. • VO 2 (A) nanorods resulted from VO 2 (B) nanobelts by assembly and crystal adjustment. - Abstract: Pure phase VO 2 (A) nanorods were synthesized via the reduction of V 2 O 5 by oxalic acid during the hydrothermal treatment. Two sets of samples were prepared by varying both system temperature and reaction time under a filling ratio of 0.40 for observing the formation and evolution of VO 2 (A) nanorods. Structures were characterized by X-ray diffraction, scanning and transmission electron microscopies, respectively. It was found that VO 2 (B) was firstly formed and then transformed into VO 2 (A) as the increasing system temperature or extending reaction time. An assembling and following crystal adjustment was proposed for explanation the formation process of VO 2 (A) from VO 2 (B). For VO 2 (A) nanorods, the phase transition temperature of 169.7 °C was higher than that of the VO 2 (A) bulk, it might be ascribed to the lower crystallinity or nonstoichiometry in VO 2 (A) nanorods. VO 2 nanostructures with controllable phases and properties should find their promising applications in a single VO 2 nanodevice

  16. On the Cryptographic Features of a VoIP Service

    Directory of Open Access Journals (Sweden)

    Dimitrios Alvanos

    2018-01-01

    Full Text Available Security issues of typical Voice over Internet Protocol (VoIP applications are studied in this paper; in particular, the open source Linphone application is being used as a case study. An experimental analysis indicates that protecting signalling data with the TLS protocol, which unfortunately is not always the default option, is needed to alleviate several security concerns. Moreover, towards improving security, it is shown that a VoIP application may operate over a virtual private network without significantly degrading the overall performance. The conclusions of this study provide useful insights to the usage of any VoIP application.

  17. BiVO4 nanoparticles: Preparation, characterization and photocatalytic activity

    Directory of Open Access Journals (Sweden)

    Venkataraman Sivakumar

    2015-12-01

    Full Text Available Bismuth vanadate (BiVO4 nanoparticles were synthesized by a simple thermal decomposition method. The synthesized bismuth vanadate nanoparticles were characterized by X-ray diffraction analysis, it is found that the synthesized sample belongs to monoclinic BiVO4. Fourier transform infrared spectroscopy confirms the formation of Bi-O bond in the sample. Ultraviolet–Visible (DRS-UV–Visible spectroscopy and photoluminescence spectroscopy reveal the optical property of the BiVO4 nanoparticles. The morphology was identified by both scanning electron microscopy and high-resolution transmission electron microscopy. Further, the photocatalytic activity of BiVO4 nanoparticles was investigated by photodegradation of methylene blue as a model organic pollutant.

  18. Raman scattering and x-ray diffractometry studies of epitaxial TiO2 and VO2 thin films and multilayers on α-Al2O3(11 bar 20)

    International Nuclear Information System (INIS)

    Foster, C.M.; Chiarello, R.P.; Chang, H.L.M.; You, H.; Zhang, T.J.; Frase, H.; Parker, J.C.; Lam, D.J.

    1993-01-01

    Epitaxial thin films of TiO 2 and VO 2 single layers and TiO 2 /VO 2 multilayers were grown on (11 bar 20) sapphire (α-Al 2 O 3 ) substrates using the metalorganic chemical vapor deposition technique and were characterized using Raman scattering and four x-ray diffractometry. X-ray diffraction results indicate that the films are high quality single crystal material with well defined growth plane and small in-plane and out-of-plane mosaic. Single-layer films are shown to obey the Raman selection rules of TiO 2 and VO 2 single crystals. The close adherence to the Raman selection rules indicates the high degree of orientation of the films, both parallel and perpendicular to the growth plane. Selection rule spectra of two and three layer TiO 2 /VO 2 multilayers are dominated by the VO 2 layers with only minimal signature of the TiO 2 layers. Due to the low band gap of semiconducting vanadium dioxide, we attribute the strong signature of the VO 2 layers to resonant enhancement of the VO 2 Raman component accompanied with absorption of the both the incident and scattered laser light from the TiO 2 layers

  19. Bismuth zinc vanadate, BiZn{sub 2}VO{sub 6}: New crystal structure type and electronic structure

    Energy Technology Data Exchange (ETDEWEB)

    Eliziario Nunes, Sayonara [Department of Chemistry, Durham University, South Road, Durham DH1 3LE (United Kingdom); Department of Materials Engineering, Federal University of São Carlos, 13565-905 São Carlos, SP (Brazil); Wang, Chun-Hai; So, Karwei; Evans, John S.O. [Department of Chemistry, Durham University, South Road, Durham DH1 3LE (United Kingdom); Evans, Ivana Radosavljević, E-mail: ivana.radosavljevic@durham.ac.uk [Department of Chemistry, Durham University, South Road, Durham DH1 3LE (United Kingdom)

    2015-02-15

    We report a combined experimental and computational study of the crystal structure and electronic properties of bismuth zinc vanadate, BiZn{sub 2}VO{sub 6}, known for its visible light photocatalytic activity. The crystal structure has been solved from laboratory powder X-ray diffraction data using the repeated minimisations from random starting values method. BiZn{sub 2}VO{sub 6} adopts a new structure type, based on the following building blocks: corner- and edge-sharing ZnO{sub 4} tetrahedra, ZnO{sub 6} octahedra and VO{sub 4} tetrahedra, and Bi{sub 2}O{sub 12} dimers. It is the only known member of the BiM{sub 2}AO{sub 6} (M=Pb, Ca, Cd, Mn, Zn, Mg, Cu; A=V, P, As) family which does not appear to be structurally closely related to others. The electronic structure of BiZn{sub 2}VO{sub 6}, calculated by DFT methods, shows that it is an indirect gap semiconductor with a calculated band gap of 1.6 eV, which compares favourably to the experimentally measured value of 2.4 eV. - Graphical abstract: The crystal structure of BiZn{sub 2}VO{sub 6}, a new structure type in the BiM{sub 2}AO{sub 6} (M=Mg, Ca, Cd, Cu, Pb, Mn, Zn; A=V, P, As) family. - Highlights: • Structure solution from PXRD data by repeated minimisations from random starting values. • New structure type in the BiM{sub 2}AO{sub 6} (M=Pb, Ca, Cd, Mn, Zn, Mg, Cu; A=V, P, As) family. • Electronic structure calculation.

  20. Synthesis and characterization of CoOx/BiVO4 photocatalysts for the degradation of propyl paraben.

    Science.gov (United States)

    Petala, Athanasia; Noe, Antigoni; Frontistis, Zacharias; Drivas, Charalampos; Kennou, Stella; Mantzavinos, Dionissios; Kondarides, Dimitris I

    2018-03-13

    Cobalt-promoted bismuth vanadate photocatalysts of variable cobalt content (0-1.0 wt.%) were synthesized and characterized with various techniques including BET, XRD, DRS, XPS and TEM. BiVO 4 exists in the monoclinic scheelite structure, while cobalt addition improves the absorbance in the visible region although it does not affect the band gap energy of BiVO 4 . Cobalt exists in the form of well-dispersed Co 3 O 4 nanocrystallites, which are in intimate contact with the much larger BiVO 4 nanoparticles. Photocatalytic activity was evaluated for the degradation of propyl paraben (PP) under simulated solar radiation. The activity of pristine BiVO 4 is significantly improved adding small amounts of cobalt and is maximized for the catalyst containing 0.5 wt.% Co. PP degradation in ultrapure pure water increases with increasing photocatalyst loading (100 mg/L to 1.5 g/L), and decreasing PP concentration (1600-200 μg/L). Experiments in bottled water, as well as in pure water spiked with bicarbonate and chloride ions showed little effect of non-target inorganics on degradation. Conversely, degradation is severely impeded in secondary treated wastewater. The enhancement of the photocatalytic activity of the synthesized catalysts is attributed to efficient electron-hole separation, achieved at the p-n junction formed between the p-type Co 3 O 4 and the n-type BiVO 4 semiconductors. Copyright © 2018 Elsevier B.V. All rights reserved.

  1. Mathematical Representation of VoIP Connection Delay

    Directory of Open Access Journals (Sweden)

    M. Halas

    2007-09-01

    Full Text Available The main topic of this article is to define mathematical formulation of VoIP connection delay model. It handles about all partial delay components, the mechanism of their generation, facilities and their mathematical formulation. Thereafter based on mathematical formulation of all partial delay components, the final mathematical model of whole VoIP call delay is created. In conclusion of this article the results of the designed mathematical model are compared with the experimentally gained results.

  2. Synthesis of carbon-doped nanosheets m-BiVO{sub 4} with three-dimensional (3D) hierarchical structure by one-step hydrothermal method and evaluation of their high visible-light photocatalytic property

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Deqiang; Zong, Wenjuan [Chongqing University, Key Laboratory of Three Gorges Reservoir Region’s Eco-Environment Ministry of Education and National Centre for International Research of Low-carbon and Green Buildings (China); Fan, Zihong [School of Environmental and Biological Engineering Chongqing Technology and Business University (China); Fang, Yue-Wen [East China Normal University, Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering (China); Xiong, Shimin; Du, Mao; Wu, Tianhui; Ji, Fangying, E-mail: jfy@cqu.edu.cn; Xu, Xuan, E-mail: xuxuan@cqu.edu.cn [Chongqing University, Key Laboratory of Three Gorges Reservoir Region’s Eco-Environment Ministry of Education and National Centre for International Research of Low-carbon and Green Buildings (China)

    2017-04-15

    To achieve an efficient visible-light absorption and degradation of bismuth vanadate (BiVO{sub 4}), in this paper, a carbon-doped (C-doped) nanosheets monoclinic BiVO{sub 4} (m-BiVO{sub 4}), with thicknesses within 19.86 ± 8.48 nm, was synthesized using polyvinylpyrrolidone K-30 (PVP) as a template and l-carbonic as the carbon source by one-step hydrothermal synthesis method. This C-doped BiVO{sub 4} in three-dimensional (3D) hierarchical structure enjoys high visible-light photocatalytic property. The samples were characterized using x-ray diffraction, scanning electron microscope, Raman spectra, energy dispersive spectrometer, transmission electron microscope, x-ray photoelectron spectroscopy, UV–Vis diffused reflectance spectroscopy, specific surface area, electron spin resonance, and transient photocurrent response, photoluminescence spectra, and incident-photon-to-current conversion efficiency, respectively. What is more, we studied the C-doping effect on the band-gap energy of BiVO{sub 4} based on First-principles. X-ray diffraction analysis showed that all photocatalysts were in the same single monoclinic scheelite structure. According to the other characterization results, the element C was successfully doped in BiVO{sub 4}, resulting in the 3D hierarchical structure of C-doped BiVO{sub 4} (P-L-BiVO{sub 4}). We speculated that it could be the directional coalescence mechanism by which the l-cysteine promoted the two-dimensional growth and C-doping process of BiVO{sub 4}, thus leading to the formation of nanosheets which were then promoted into 3D self-assembly by PVP and the shortening of the band gap. Among all samples, P-L-BiVO{sub 4} can make the highest removal ratio of rhodamine B under visible-light irradiation. The stability of P-L-BiVO{sub 4} was verified by recycle experiments. It showed that P-L-BiVO{sub 4} had strong visible-light absorption behavior and high electron–hole separation efficiency and stability, making a significant

  3. Microwave absorption in the singlet paramagnet HoVO4 in high pulsed magnetic fields up to 40 T

    International Nuclear Information System (INIS)

    Goiran, M.; Klingeler, R.; Kazei, Z.A.; Snegirev, V.V.

    2007-01-01

    Microwave absorption of the rare-earth (RE) oxide compound HoVO 4 (tetragonal-zircon structure) is investigated in pulsed magnetic fields up to 40 T in the low-temperature range. For a magnetic field along the tetragonal crystal axis a few resonance absorption lines are observed at the wavelengths 871, 406 and 305 μm corresponding to electron transitions from the ground and low-lying energy levels of the Ho 3+ ion. In addition, broad non-resonance absorption is observed at 871 and 406 μm in fields up to 15 T. The positions and intensities of the observed resonance lines are described quite well within the crystal field formalism with the known crystal field parameters. The effects of the small orthorhombic component of the crystal field, magnetic field misorientation out the symmetry axis and various pair interactions on the absorption spectra in HoVO 4 are analyzed and discussed

  4. Two-Dimensional SiO2/VO2 Photonic Crystals with Statically Visible and Dynamically Infrared Modulated for Smart Window Deployment.

    Science.gov (United States)

    Ke, Yujie; Balin, Igal; Wang, Ning; Lu, Qi; Tok, Alfred Iing Yoong; White, Timothy J; Magdassi, Shlomo; Abdulhalim, Ibrahim; Long, Yi

    2016-12-07

    Two-dimensional (2D) photonic structures, widely used for generating photonic band gaps (PBG) in a variety of materials, are for the first time integrated with the temperature-dependent phase change of vanadium dioxide (VO 2 ). VO 2 possesses thermochromic properties, whose potential remains unrealized due to an undesirable yellow-brown color. Here, a SiO 2 /VO 2 core/shell 2D photonic crystal is demonstrated to exhibit static visible light tunability and dynamic near-infrared (NIR) modulation. Three-dimensional (3D) finite difference time domain (FDTD) simulations predict that the transmittance can be tuned across the visible spectrum, while maintaining good solar regulation efficiency (ΔT sol = 11.0%) and high solar transmittance (T lum = 49.6%). Experiments show that the color changes of VO 2 films are accompanied by NIR modulation. This work presents a novel way to manipulate VO 2 photonic structures to modulate light transmission as a function of wavelength at different temperatures.

  5. Dominance of Plasmonic Resonant Energy Transfer over Direct Electron Transfer in Substantially Enhanced Water Oxidation Activity of BiVO4 by Shape-Controlled Au Nanoparticles.

    Science.gov (United States)

    Lee, Mi Gyoung; Moon, Cheon Woo; Park, Hoonkee; Sohn, Woonbae; Kang, Sung Bum; Lee, Sanghan; Choi, Kyoung Jin; Jang, Ho Won

    2017-10-01

    The performance of plasmonic Au nanostructure/metal oxide heterointerface shows great promise in enhancing photoactivity, due to its ability to confine light to the small volume inside the semiconductor and modify the interfacial electronic band structure. While the shape control of Au nanoparticles (NPs) is crucial for moderate bandgap semiconductors, because plasmonic resonance by interband excitations overlaps above the absorption edge of semiconductors, its critical role in water splitting is still not fully understood. Here, first, the plasmonic effects of shape-controlled Au NPs on bismuth vanadate (BiVO 4 ) are studied, and a largely enhanced photoactivity of BiVO 4 is reported by introducing the octahedral Au NPs. The octahedral Au NP/BiVO 4 achieves 2.4 mA cm -2 at the 1.23 V versus reversible hydrogen electrode, which is the threefold enhancement compared to BiVO 4 . It is the highest value among the previously reported plasmonic Au NPs/BiVO 4 . Improved photoactivity is attributed to the localized surface plasmon resonance; direct electron transfer (DET), plasmonic resonant energy transfer (PRET). The PRET can be stressed over DET when considering the moderate bandgap semiconductor. Enhanced water oxidation induced by the shape-controlled Au NPs is applicable to moderate semiconductors, and shows a systematic study to explore new efficient plasmonic solar water splitting cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. VO-Dance an IVOA tools to easy publish data into VO and it's extension on planetology request

    Science.gov (United States)

    Smareglia, R.; Capria, M. T.; Molinaro, M.

    2012-09-01

    Data publishing through the self standing portals can be joined to VO resource publishing, i.e. astronomical resources deployed through VO compliant services. Since the IVOA (International Virtual Observatory Alliance) provides many protocols and standards for the various data flavors (images, spectra, catalogues … ), and since the data center has as a goal to grow up in number of hosted archives and services providing, the idea arose to find a way to easily deploy and maintain VO resources. VO-Dance is a java web application developed at IA2 that addresses this idea creating, in a dynamical way, VO resources out of database tables or views. It is structured to be potentially DBMS and platform independent and consists of 3 main tokens, an internal DB to store resources description and model metadata information, a restful web application to deploy the resources to the VO community. It's extension to planetology request is under study to best effort INAF software development and archive efficiency.

  7. Electrostatic doping of a Mott insulator in an oxide heterostructure: the case of LaVO{sub 3}/SrTiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Andreas; Pfaff, Florian; Sing, Michael; Claessen, Ralph [Physikalisches Insititut and Roentgen Research Center for Complex Material Systems, Universitaet Wuerzburg, D-97074 Wuerzburg (Germany); Boschker, Hans; Kamp, Martin; Koster, Gertjan; Rijnders, Guus [Faculty of Science and Technology and MESA-plus Institute for Nanotechnology, University of Twente, 7500 AE Enschede (Netherlands)

    2012-07-01

    The discovery of a quasi-two-dimensional electron system at the interface between the two band insulators LaAlO{sub 3} and SrTiO{sub 3} has triggered intense investigations of oxide heterostructures with other material combinations. The hope is that by combining a polar overlayer with a non-polar substrate electronic reconstruction will lead to highly mobile interface charge carriers with special properties. The formation of a conducting interface layer in epitaxial LaVO{sub 3}/SrTiO{sub 3}, where LaVO{sub 3} is a Mott insulator, is studied by transport measurements and hard X-ray photoelectron spectroscopy. We identify an insulator-to-metal transition above a critical LaVO{sub 3} thickness with transport properties similar to those recently reported for LaAlO{sub 3}/SrTiO{sub 3} interfaces. Interestingly, our photoemission measurements give evidence that electronic charge is transferred exclusively to the LaVO{sub 3}-side of the interface caused by an electronic reconstruction within the film itself. This opens the opportunity to study a band-filling controlled Mott transition induced by a purely electrostatic mechanism.

  8. Very broad bandwidth klystron amplifiers

    Science.gov (United States)

    Faillon, G.; Egloff, G.; Farvet, C.

    Large surveillance radars use transmitters at peak power levels of around one MW and average levels of a few kW, and possibly several tens of kW, in S band, or even C band. In general, the amplification stage of these transmitters is a microwave power tube, frequently a klystron. Although designers often turn to klystrons because of their good peak and average power capabilities, they still see them as narrow band amplifiers, undoubtedly because of their resonant cavities which, at first sight, would seem highly selective. But, with the progress of recent years, it has now become quite feasible to use these tubes in installations requiring bandwidths in excess of 10 - 12 percent, and even 15 percent, at 1 MW peak for example, in S-band.

  9. Nanoscale Engineering in VO2 Nanowires via Direct Electron Writing Process.

    Science.gov (United States)

    Zhang, Zhenhua; Guo, Hua; Ding, Wenqiang; Zhang, Bin; Lu, Yue; Ke, Xiaoxing; Liu, Weiwei; Chen, Furong; Sui, Manling

    2017-02-08

    Controlling phase transition in functional materials at nanoscale is not only of broad scientific interest but also important for practical applications in the fields of renewable energy, information storage, transducer, sensor, and so forth. As a model functional material, vanadium dioxide (VO 2 ) has its metal-insulator transition (MIT) usually at a sharp temperature around 68 °C. Here, we report a focused electron beam can directly lower down the transition temperature of a nanoarea to room temperature without prepatterning the VO 2 . This novel process is called radiolysis-assisted MIT (R-MIT). The electron beam irradiation fabricates a unique gradual MIT zone to several times of the beam size in which the temperature-dependent phase transition is achieved in an extended temperature range. The gradual transformation zone offers to precisely control the ratio of metal/insulator phases. This direct electron writing technique can open up an opportunity to precisely engineer nanodomains of diversified electronic properties in functional material-based devices.

  10. Electronic structure and insulating gap in epitaxial VO2 polymorphs

    Directory of Open Access Journals (Sweden)

    Shinbuhm Lee

    2015-12-01

    Full Text Available Determining the origin of the insulating gap in the monoclinic V O2(M1 is a long-standing issue. The difficulty of this study arises from the simultaneous occurrence of structural and electronic transitions upon thermal cycling. Here, we compare the electronic structure of the M1 phase with that of single crystalline insulating V O2(A and V O2(B thin films to better understand the insulating phase of VO2. As these A and B phases do not undergo a structural transition upon thermal cycling, we comparatively study the origin of the gap opening in the insulating VO2 phases. By x-ray absorption and optical spectroscopy, we find that the shift of unoccupied t2g orbitals away from the Fermi level is a common feature, which plays an important role for the insulating behavior in VO2 polymorphs. The distinct splitting of the half-filled t2g orbital is observed only in the M1 phase, widening the bandgap up to ∼0.6 eV. Our approach of comparing all three insulating VO2 phases provides insight into a better understanding of the electronic structure and the origin of the insulating gap in VO2.

  11. Implementasi Server VoIP Berbasis SIP Pada LAN Nirkabel

    Directory of Open Access Journals (Sweden)

    Mohammad Shoffa Al Arofat

    2013-03-01

    Full Text Available Voice over Internet Protocol (VoIP merupakan teknologi yang memungkinkan percakapan suara jarak jauh melalui protokol internet. Dalam telekomunikasi, diperlukan teknologi pensinyalan yang berguna untuk membangun, mengawasi, dan melepas hubungan antara dua titik. Salah satu teknologi pensinyalan yang banyak digunakan untuk VoIP adalah Session Initiation Protocol, dengan implementasinya yang berupa perangkat lunak Open SIP Server. Selain pensinyalan, ada beberapa parameter yang perlu diperhatikan dalam implementasi VoIP, yaitu Mean Opinion Score (MOS, network impairment, dan bandwidth. Pengujian dilakukan terhadap enam codec, yaitu G.722, PCMA, PCMU, Speex, GSM, dan BV16. Berdasarkan hasil analisis dapat diambil kesimpulan bahwa codec yang menggunakan bandwidth paling rendah adalah Speex (27,12 kbps; Rata-rata delay yang dihasilkan oleh sipdroid lebih baik daripada jitsi.

  12. ) m /SrVO3 ( m = 5, 6) Superlattices

    KAUST Repository

    Dai, Qingqing

    2018-05-04

    The (LaV3+O3)m/SrV4+O3 (m = 5, 6) superlattices are investigated by first principles calculations. While bulk LaVO3 is a C‐type antiferromagnetic semiconductor and bulk SrVO3 is a paramagnetic metal, semiconducting A‐type antiferromagnetic states for both superlattices are found due to epitaxial strain. At the interfaces, however, the V spins couple antiferromagnetically for m = 5 and ferromagnetically for m = 6 (m‐dependence of the magnetization). Electronic reconstruction in form of charge ordering is predicted to occur with V3+ and V4+ states arranged in a checkerboard pattern on both sides of the SrO layer. As compared to bulk LaVO3, the presence of V4+ ions introduces in‐gap states that strongly reduce the bandgap and influence the orbital occupation and ordering.

  13. A potential amber-emitting KCaVO4:Sm3+ nanophosphor for near-UV LEDs

    Science.gov (United States)

    Biswas, Pankaj; Kumar, Vinay

    2018-05-01

    The Sm3+ doped KCaVO4 phosphor powders were synthesized via combustion route. The powder X-ray diffraction (pXRD) analysis established the crystalline structure and phase of the phosphor material. Williamson-Hall technique was employed to approximate the mean grain size and lattice micro-strain. The transmission electron microscope (TEM) studies were carried out to confirm the nano-sized grain formation. On 405 nm excitation, the phosphor gave amber emission which was assigned to 4G5/2 → 6HJ/2 (J = 7/2, 9/2) transitions of the Sm3+ ion. The concentration quenching mechanism was studied and the optimum dopant concentration in the phosphor was obtained as 2.0 mol%. The diffuse reflectance (DR) studies were carried out to obtain optical band gap (Eg) and Urbach energy (Ec) of the KCaVO4 phosphor which were estimated as 3.63 eV and 98.6 meV, respectively. The color coordinates (x = 0.61, y = 0.39) of the nanophosphor signified the amber shade in the color gamut. The high luminescent properties of KCaVO4:Sm3+ phosphor suggests that the material can be explored as a potential phosphor to be profitably excited by near-UV LEDs to bridge the amber gap in light emitting diodes (LEDs) for solid state lighting (SSL) applications.

  14. Two-dimensional orbital ordering in d{sup 1} Mott insulator Sr{sub 2}VO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Viennois, R; Giannini, E; Teyssier, J; Elia, J; Van der Marel, D [DPMC, Universite de Geneve, 24 quai Ernest Ansermet, CH-1211 Geneve (Switzerland); Deisenhofer, J, E-mail: Romain.Viennois@unige.c [Institute of Physics, University of Augsburg, Augsburg (Germany)

    2010-01-15

    The Mott insulator Sr{sub 2}VO{sub 4} is a unique d{sup 1} two-dimensional compound exhibiting an orbital ordering transition. In addition to the orbital ordering transition at about 100 K, we discovered a ferromagnetic transition below 10 K, thus confirming the predictions of recent band structure calculations. The magnetic properties proved to be strongly sensitive to the material purity, the actual oxygen stoichiometry and the crystallographic parameters. An additional transition is observed at 125 K, which is believed to be due to structural modifications.

  15. Study of some electronics properties of new superconductor Sr2VO3FeAs in ground state

    Directory of Open Access Journals (Sweden)

    M Majidiyan

    2010-09-01

    Full Text Available In this paper, some electronics properties of new superconductor Sr2VO3FeAs, such as density of states, band structure, density of electron cloud and bound lengths in the ground state have been calculated. According to N(Ef in ground state CV/T value has been estimated. The calculations were performed in the framework of density functional theory (DFT, using the full potential linearized augmented plane wave (FP-LAPW method with the general gradient approximation (GGA.

  16. Comparing GW+DMFT and LDA+DMFT for the testbed material SrVO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Taranto, Ciro; Toschi, Alessandro; Held, Karsten [Institute for Solid State Physics, Vienna University of Technology (Austria); Kaltak, Merzuk; Kresse, Georg [University of Vienna, Faculty of Physics and Center for Computational Materials Science (Austria); Parragh, Nicolaus; Sangiovanni, Giorgio [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany)

    2013-07-01

    We have implemented the GW+dynamical mean field theory (DMFT) approach in the Vienna ab initio simulation package. Employing the interaction values obtained from the locally unscreened random phase approximation (RPA), we compare GW+DMFT and LDA+DMFT against each other and against experiment for SrVO{sub 3}. We observed a partial compensation of stronger electronic correlations due to the reduced GW bandwidth and weaker correlations due to a larger screening of the RPA interaction, so that the obtained spectra are quite similar and well agree with experiment. Noteworthily, the GW+DMFT better reproduces the position of the lower Hubbard side band.

  17. Lattice effects in HoVo3 single crystal

    International Nuclear Information System (INIS)

    Sikora, M.; Marquina, C.; Ibarra, M.R.; Nugroho, A.A.; Palstra, T.T.M.

    2007-01-01

    We report the study of lattice effects in the Mott insulator HoVO 3 performed by means of linear thermal expansion on a single crystal in the temperature range 10-290 K. The holmium orthovanadate HoVO 3 reveals gradual orbital ordering (OO) below T OO =200 K and orders antiferromagnetically at T N =113 K. A first-order structural phase transition takes place at T S ∼38 K, which is probably accompanied by change of the OO type and hence the type of antiferromagnetic spin ordering

  18. Highly efficient visible-light-induced photocatalytic activity of Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterojunction photocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Chaiwichian, Saranyoo [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai50200 (Thailand); Inceesungvorn, Burapat [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Wetchakun, Khatcharin [Program of Physics, Faculty of Science, Ubon Ratchathani Rajabhat University, Ubon Ratchathani 34000 (Thailand); Phanichphant, Sukon [Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Kangwansupamonkon, Wiyong [National Nanotechnology Center, Thailand Science Park, Phahonyotin Road, Klong 1, Klong Luang, Phathumthani 12120 (Thailand); Wetchakun, Natda, E-mail: natda_we@yahoo.com [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai50200 (Thailand)

    2014-06-01

    Highlights: • Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterojunction photocatalysts were obtained using hydrothermal method. • Physicochemical properties played a significant role on photocatalytic efficiency. • Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterogeneous structures were greatly enhanced for degradation of MB. • A tentative mechanism of charge transfer process in MB degradation was proposed. - Abstract: The Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterojunction photocatalysts were synthesized by hydrothermal method. Physical properties of the heterojunction photocatalyst samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The XRD results indicated that BiVO{sub 4} retain monoclinic and tetragonal structures, while Bi{sub 2}WO{sub 6} presented as orthorhombic structure. The Brunauer, Emmett and Teller (BET) adsorption–desorption of nitrogen gas for specific surface area determination at the temperature of liquid nitrogen was performed on all samples. UV–vis diffuse reflectance spectra (UV–vis DRS) were used to identify the absorption range and band gap energy of the heterojunction photocatalysts. The photocatalytic performance of Bi{sub 2}WO{sub 6}/BiVO{sub 4} heterojunction photocatalysts was studied via the photodegradation of methylene blue (MB) under visible light irradiation. The results indicated that the heterojunction photocatalyst at 0.5:0.5 mole ratio of Bi{sub 2}WO{sub 6}:BiVO{sub 4} shows the highest photocatalytic activity.

  19. Fabrication of Ni-doped BiVO{sub 4} semiconductors with enhanced visible-light photocatalytic performances for wastewater treatment

    Energy Technology Data Exchange (ETDEWEB)

    Regmi, Chhabilal [Department of Environmental and Biochemical Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Kshetri, Yuwaraj K. [Department of Advanced Materials Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Kim, Tae-Ho [Division of Mechanics and ICT Convergence Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Pandey, Ramesh Prasad [Institute of Biomolecule Reconstruction, Department of BT-Convergent Pharmaceutical Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Ray, Schindra Kumar [Department of Environmental and Biochemical Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of); Lee, Soo Wohn, E-mail: swlee@sunmoon.ac.kr [Department of Environmental and Biochemical Engineering, Sun Moon University, Chungnam 31460 (Korea, Republic of)

    2017-08-15

    Highlights: • Synthesis of a Ni-doped BiVO{sub 4} semiconductor photocatalyst with reduced band gap energy. • Ni-doped BiVO{sub 4} provided efficient photocatalytic activity for ibuprofen degradation and E. coli and green tide deactivation. • DFT calculation and thermodynamic modeling to understand the underlying mechanism. - Abstract: A visible-light-driven Ni-doped BiVO{sub 4} photocatalyst was synthesized using a microwave hydrothermal method. The nominal Ni doping amount of 1 wt% provided excellent photoactivity for a variety of water pollutants, such as ibuprofen (pharmaceutical), Escherichia coli (bacteria), and green tides (phytoplankton). Each Ni-doped BiVO{sub 4} sample exhibits better performance than pure BiVO{sub 4}. The degradation of ibuprofen reaches 80% within 90 min, the deactivation of Escherichia coli reaches around 92% within 5 h, and the inactivation of green tide (Chlamydomonas pulsatilla) reaches 70% upon 60 min of the visible light irradiation. The first principle calculation and thermodynamic modeling revealed that Ni doping in the vanadium site gives the most stable configuration of the synthesized samples with the formation of an in-gap energy state and oxygen vacancies. The in-gap energy state and the oxygen vacancies serve as an electron-trapping center that decreases the migration time of the photogenerated carrier and increases the separation efficiency of electron-hole pairs, which are responsible for the observed efficient photocatalytic, anti-bacterial and anti-algal activity of the samples. These properties thus suggest potential applications of Ni-doped BiVO{sub 4} as a multifunctional material in the field of wastewater treatment.

  20. Highly Enhanced Photoelectrochemical Water Oxidation Efficiency Based on Triadic Quantum Dot/Layered Double Hydroxide/BiVO 4 Photoanodes

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yanqun; Wang, Ruirui; Yang, Ye; Yan, Dongpeng; Xiang, Xu

    2016-08-03

    The water oxidation half-reaction is considered to be a bottleneck for achieving highly efficient solar-driven water splitting due to its multiproton-coupled four-electron process and sluggish kinetics. Herein, a triadic photoanode consisting of dual-sized CdTe quantum dots (QDs), Co-based layered double hydroxide (LDH) nanosheets, and BiVO4 particles, that is, QD@LDH@BiVO4, was designed. Two sets of consecutive Type-II band alignments were constructed to improve photogenerated electron-hole separation in the triadic structure. The efficient charge separation resulted in a 2-fold enhancement of the photocurrent of the QD@LDH@BiVO4 photoanode. A significantly enhanced oxidation efficiency reaching above 90% in the low bias region (i.e., E < 0.8 V vs RHE) could be critical in determining the overall performance of a complete photoelectrochemical cell. The faradaic efficiency for water oxidation was almost 90%. The conduction band energy of QDs is -1.0 V more negative than that of LDH, favorable for the electron injection to LDH and enabling a more efficient hole separation. The enhanced photon-to-current conversion efficiency and improved water oxidation efficiency of the triadic structure may result from the non-negligible contribution of hot electrons or holes generated in QDs. Such a band-matching and multidimensional triadic architecture could be a promising strategy for achieving high-efficiency photoanodes by sufficiently utilizing and maximizing the functionalities of QDs.

  1. Potassium vanadium selenite, K(VO2)3(SeO3)2

    International Nuclear Information System (INIS)

    Harrison, W.T.A.; Dussack, L.L.; Jacobson, A.J.

    1995-01-01

    The hydrothermal synthesis and single-crystal structure of potassium vanadium(V) selenite, K(VO 2 ) 3 (SeO 3 ) 2 , are reported. K(VO 2 ) 3 (SeO 3 ) 2 is a layered phase based on a hexagonal tungsten-oxide-like array of corner-sharing VO 6 octahedra capped by Se atoms, and is isostructural with NH 4 (VO 2 ) 3 (SeO 3 ) 2 . (orig.)

  2. Covert Channels in SIP for VoIP Signalling

    Science.gov (United States)

    Mazurczyk, Wojciech; Szczypiorski, Krzysztof

    In this paper, we evaluate available steganographic techniques for SIP (Session Initiation Protocol) that can be used for creating covert channels during signaling phase of VoIP (Voice over IP) call. Apart from characterizing existing steganographic methods we provide new insights by introducing new techniques. We also estimate amount of data that can be transferred in signalling messages for typical IP telephony call.

  3. Gipsy 3D : Analysis, Visualization and Vo-Tools

    NARCIS (Netherlands)

    Ruiz, J. E.; Santander-Vela, J. D.; Espigares, V.; Verdes-Montenegro, L.; Hulst, J. M. van der

    2009-01-01

    The scientific goals of the AMIGA project are based on the analysis of a significant amount of spectroscopic 3D data. In order to perform this work we present an initiative to develop a new VO compliant package, including present core applications and tasks offered by the Groningen Image Processing

  4. Empirical assessment of VoIP overload detection tests

    NARCIS (Netherlands)

    Żuraniewski, P.; Mandjes, M.; Mellia, M.

    2010-01-01

    The control of communication networks critically relies on procedures capable of detecting unanticipated load changes. In this paper we explore such techniques, in a setting in which each connection consumes roughly the same amount of bandwidth (with VoIP as a leading example). We focus on

  5. VoIP under the EU regulatory framework : preventing foreclosure?

    NARCIS (Netherlands)

    Sadowski, B.M.; Straathof, B.

    2005-01-01

    In June 2004, the European Commission (EC) issued an "Information and Consultation Document" (European Commission 2004) that discussed how the Regulatory Framework of the European Union (EU) should be adapted to accommodate Voice over IP (VoIP) and invited relevant parties to comment on the

  6. Changepoint detection techniques for VoIP traffic

    NARCIS (Netherlands)

    Mandjes, M.; Zuraniewski, P.W.

    2013-01-01

    The control of communication networks critically relies on procedures capable of detecting unanticipated load changes. In this chapter we present an overview of such techniques, in a setting in which each connection consumes roughly the same amount of bandwidth (with VoIP as a leading example). For

  7. Biobjective VoIP Service Management in Cloud Infrastructure

    Directory of Open Access Journals (Sweden)

    Jorge M. Cortés-Mendoza

    2016-01-01

    Full Text Available Voice over Internet Protocol (VoIP allows communication of voice and/or data over the internet in less expensive and reliable manner than traditional ISDN systems. This solution typically allows flexible interconnection between organization and companies on any domains. Cloud VoIP solutions can offer even cheaper and scalable service when virtualized telephone infrastructure is used in the most efficient way. Scheduling and load balancing algorithms are fundamental parts of this approach. Unfortunately, VoIP scheduling techniques do not take into account uncertainty in dynamic and unpredictable cloud environments. In this paper, we formulate the problem of scheduling of VoIP services in distributed cloud environments and propose a new model for biobjective optimization. We consider the special case of the on-line nonclairvoyant dynamic bin-packing problem and discuss solutions for provider cost and quality of service optimization. We propose twenty call allocation strategies and evaluate their performance by comprehensive simulation analysis on real workload considering six months of the MIXvoip company service.

  8. Changepoint Detection Techniques for VoIP Traffic

    NARCIS (Netherlands)

    Mandjes, M.; Żuraniewski, P.; Biersack, E.; Callegari, C.; Matijasevic, M.

    2013-01-01

    The control of communication networks critically relies on procedures capable of detecting unanticipated load changes. In this chapter we present an overview of such techniques, in a setting in which each connection consumes roughly the same amount of bandwidth (with VoIP as a leading example). For

  9. Lithiation-driven structural transition of VO2F into disordered rock-salt LixVO2F

    Czech Academy of Sciences Publication Activity Database

    Chen, R.; Maawad, E.; Knapp, M.; Ren, S.; Beran, Přemysl; Witter, R.; Hempelmann, R.

    2016-01-01

    Roč. 6, č. 69 (2016), s. 65112-65118 ISSN 2046-2069 R&D Projects: GA MŠk(CZ) LM2011019 EU Projects: European Commission(XE) 283883 - NMI3-II Institutional support: RVO:61389005 Keywords : Li- Ion batteries * rechargeble lithium batteries * VO2F Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.108, year: 2016

  10. Electrospinning synthesis of InVO{sub 4}/BiVO{sub 4} heterostructured nanobelts and their enhanced photocatalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhendong; Lu, Qifang, E-mail: luqf0110@126.com; Guo, Enyan; Liu, Suwen [Qilu University of Technology, Shandong Provincial Key Laboratory of Processing and Testing Technology of Glass and Functional Ceramics, School of Material Science and Engineering (China)

    2016-08-15

    In the present work, one-dimensional InVO{sub 4}/BiVO{sub 4} heterostructured nanobelts with the width of about 800 nm have been successfully prepared by a simple electrospinning technique followed by the subsequent calcination process. The prepared products were characterized by thermogravimetry, fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, UV–Vis absorbance spectroscopy, high-performance liquid chromatography, and photoluminescence spectroscopy. The obtained InVO{sub 4}/BiVO{sub 4} heterostructured nanobelts presented an admirable morphology and excellent photocatalytic properties for the degradation of methylene blue solution under visible-light irradiation.Graphical AbstractThe electrospun precursor samples (a and b) displayed a well-defined one-dimensional (1D) belt structure. After calcined at 550 °C for 2 h (c and d), the samples can retain well the 1D morphology. And an obvious porous structure can be found from the TEM images of the calcined samples (e and f).

  11. Visible light driven photocatalysis and antibacterial activity of AgVO{sub 3} and Ag/AgVO{sub 3} nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Anamika [Department of Life Sciences, University of Mumbai, Santacruz (E), Mumbai 400 098 (India); Dutta, Dimple P., E-mail: dimpled@barc.gov.in [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Ballal, A. [Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Tyagi, A.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Fulekar, M.H. [School of Environment and Sustainable Development, Central University of Gujarat, Gandhinagar 382 030, Gujarat (India)

    2014-03-01

    Graphical abstract: - Highlights: • Ag/AgVO{sub 3} and pure AgVO{sub 3} nanowires synthesized by sonochemical process. • Characterization done using XRD, SEM, TEM, EDX and BET analysis. • Visible light degradation of RhB by Ag/AgVO{sub 3} within 45 min. • Antibacterial activity of Ag/AgVO{sub 3} demonstrated. - Abstract: Ag/AgVO{sub 3} nanowires and AgVO{sub 3} nanorods were synthesized in aqueous media via a facile sonochemical route. The as-synthesized products were characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy together with an energy dispersion X-ray spectrum analysis, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The results revealed that inert atmosphere promotes the formation of Ag/AgVO{sub 3} nanowires. The photocatalytic studies revealed that the Ag/AgVO{sub 3} nanowires exhibited complete photocatalytic degradation of Rhodamine B within 45 min under visible light irradiation. The antibacterial activity of Ag/AgVO{sub 3} nanowires was tested against Escherechia coli and Bacillus subtilis. The minimum growth inhibitory concentration value was found to be 50 and 10 folds lower than for the antibiotic ciprofloxacin for E. coli and B. subtilis, respectively. The antibacterial properties of the β-AgVO{sub 3} nanorods prove that in case of the Ag dispersed Ag/AgVO{sub 3} nanowires, the enhanced antibacterial action is also due to contribution from the AgVO{sub 3} support.

  12. Synthesis and electrical transport properties of the LaVO{sub 3}/SrTiO{sub 3} interface

    Energy Technology Data Exchange (ETDEWEB)

    Hentrich, Richard; Schultz, Ludwig; Huehne, Ruben [IFW Dresden (Germany); Haenisch, Jens [IFW Dresden (Germany); ITEP, Karlsruhe Institute of Technology (KIT) (Germany)

    2015-07-01

    We have investigated the two dimensional electron gas at the interface of band gap insulator SrTiO{sub 3} and mott insulator LaVO{sub 3} in comparison to the well-known, purely band insulating LaAlO{sub 3}/SrTiO{sub 3} system. Thin films of LaVO{sub 3} were grown epitaxially on TiO{sub 2} terminated SrTiO{sub 3} single crystal substrates using RHEED-monitored pulsed laser deposition. Optimal process parameters for layer-by-layer growth were found resulting in the growth of atomically smooth films of well-defined thickness. Electrical transport measurements revealed an insulator-metal transition at a film thickness of six unit cells, which is different to previously reported values. Conducting samples showed metallic behavior in a wide temperature range, with their conductivity showing little to no dependence on layer thickness. This led to the conclusion of the metallic behavior being a merely interface driven effect.

  13. Current Status of VO Compliant Data Service in Japanese Virtual Observatory

    Science.gov (United States)

    Shirasaki, Y.; Komiya, Y.; Ohishi, M.; Mizumoto, Y.; Ishihara, Y.; Tsutsumi, J.; Hiyama, T.; Nakamoto, H.; Sakamoto, M.

    2012-09-01

    In these years, standards to build a Virtual Observatory (VO) data service have been established with the efforts in the International Virtual Observatory Alliance (IVOA). We applied these newly established standards (SSAP, TAP) to our VO service toolkit which was developed to implement earlier VO standards SIAP and (deprecated) SkyNode. The toolkit can be easily installed and provides a GUI interface to construct and manage VO service. In this paper, we describes the architecture of our toolkit and how it is used to start hosting VO service.

  14. Congenital Constriction Band Syndrome

    OpenAIRE

    Rajesh Gupta, Fareed Malik, Rishabh Gupta, M.A.Basit, Dara Singh

    2008-01-01

    Congenital constriction bands are anomalous bands that encircle a digit or an extremity. Congenitalconstriction band syndrome is rare condition and is mostly associated with other musculoskeletaldisorders.We report such a rare experience.

  15. Improving the Accuracy of Predicting Maximal Oxygen Consumption (VO2pk)

    Science.gov (United States)

    Downs, Meghan E.; Lee, Stuart M. C.; Ploutz-Snyder, Lori; Feiveson, Alan

    2016-01-01

    Maximal oxygen (VO2pk) is the maximum amount of oxygen that the body can use during intense exercise and is used for benchmarking endurance exercise capacity. The most accurate method to determineVO2pk requires continuous measurements of ventilation and gas exchange during an exercise test to maximal effort, which necessitates expensive equipment, a trained staff, and time to set-up the equipment. For astronauts, accurate VO2pk measures are important to assess mission critical task performance capabilities and to prescribe exercise intensities to optimize performance. Currently, astronauts perform submaximal exercise tests during flight to predict VO2pk; however, while submaximal VO2pk prediction equations provide reliable estimates of mean VO2pk for populations, they can be unacceptably inaccurate for a given individual. The error in current predictions and logistical limitations of measuring VO2pk, particularly during spaceflight, highlights the need for improved estimation methods.

  16. n-VO{sub 2}/p-GaN based nitride–oxide heterostructure with various thickness of VO{sub 2} layer grown by MBE

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Minhuan [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Bian, Jiming, E-mail: jmbian@dlut.edu.cn [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Key Laboratory of Inorganic Coating Materials, Chinese Academy of Sciences, Shanghai 200050, China (China); Sun, Hongjun; Liu, Weifeng [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Zhang, Yuzhi [Key Laboratory of Inorganic Coating Materials, Chinese Academy of Sciences, Shanghai 200050, China (China); Luo, Yingmin [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams (Ministry of Education), School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

    2016-12-15

    Graphical abstract: The significant influences of VO{sub 2} layer thickness on the structural, electrical and contact properties of the n-VO{sub 2}/p-GaN based nitride-oxide heterostructure were investigated systemically. - Highlights: • High quality VO{sub 2} films with precisely controlled thickness were grown on p-GaN/sapphire substrates by oxide molecular beam epitaxy (O-MBE). • A distinct reversible SMT phase transition was observed for the n-VO{sub 2}/p-GaN based nitride-oxide heterostructure. • The clear rectifying transport characteristics originated from the n-VO{sub 2}/p-GaN interface were demonstrated before and after SMT of the VO{sub 2} over layer. • The XPS analyses confirmed the valence state of V in VO{sub 2} films was principally composed of V{sup 4+} with trace amount of V{sup 5+}. • The design and modulation of the n-VO{sub 2}/p-GaN based heterostructure devices will benefit significantly from these achievements. - Abstract: High quality VO{sub 2} films with precisely controlled thickness were grown on p-GaN/sapphire substrates by oxide molecular beam epitaxy (O-MBE). Results indicated that a distinct reversible semiconductor-to-metal (SMT) phase transition was observed for all the samples in the temperature dependent electrical resistance measurement, and the influence of VO{sub 2} layer thickness on the SMT properties of the as-grown n-VO{sub 2}/p-GaN based nitride-oxide heterostructure was investigated. Meanwhile, the clear rectifying transport characteristics originated from the n-VO{sub 2}/p-GaN interface were demonstrated before and after SMT of the VO{sub 2} over layer, which were attributed to the p-n junction behavior and Schottky contact character, respectively. Moreover, the X-ray photoelectron spectroscopy (XPS) analyses confirmed the valence state of vanadium (V) in VO{sub 2} films was principally composed of V{sup 4+} with trace amount of V{sup 5+}. The design and modulation of the n-VO{sub 2}/p-GaN based heterostructure

  17. UkrVO Joint Digitized Archive and Scientific Prospects

    Directory of Open Access Journals (Sweden)

    Vavilova I. B.

    2012-09-01

    Full Text Available The UkrVO (Ukrainian Virtual Observatory database consists of about 200 000 astronomical photographic plates and 500 000 CCD frames containing unique astronomical information for formulating important scientific tasks. This database is compiled from observations conducted in 1898-2011 at the observing sites of 8 Ukrainian observatories, with about 60 instruments. This paper deals with some principal scientific projects where the UkrVO databases are used, namely, the creation of the Joint Digitized Archive (JDA; compilation of new stellar catalogues; search for optical counterparts of gamma-ray bursts; spectroscopic study of solar flares and solar active formations; development of software for searches for new small bodies of the solar system.

  18. VO2 thermochromic smart window for energy savings and generation

    Science.gov (United States)

    Zhou, Jiadong; Gao, Yanfeng; Zhang, Zongtao; Luo, Hongjie; Cao, Chuanxiang; Chen, Zhang; Dai, Lei; Liu, Xinling

    2013-10-01

    The ability to achieve energy saving in architectures and optimal solar energy utilisation affects the sustainable development of the human race. Traditional smart windows and solar cells cannot be combined into one device for energy saving and electricity generation. A VO2 film can respond to the environmental temperature to intelligently regulate infrared transmittance while maintaining visible transparency, and can be applied as a thermochromic smart window. Herein, we report for the first time a novel VO2-based smart window that partially utilises light scattering to solar cells around the glass panel for electricity generation. This smart window combines energy-saving and generation in one device, and offers potential to intelligently regulate and utilise solar radiation in an efficient manner.

  19. Gate-tunable gigantic lattice deformation in VO2

    International Nuclear Information System (INIS)

    Okuyama, D.; Hatano, T.; Nakano, M.; Takeshita, S.; Ohsumi, H.; Tardif, S.; Shibuya, K.; Yumoto, H.; Koyama, T.; Ohashi, H.; Takata, M.; Kawasaki, M.; Tokura, Y.; Iwasa, Y.; Arima, T.

    2014-01-01

    We examined the impact of electric field on crystal lattice of vanadium dioxide (VO 2 ) in a field-effect transistor geometry by in-situ synchrotron x-ray diffraction measurements. Whereas the c-axis lattice parameter of VO 2 decreases through the thermally induced insulator-to-metal phase transition, the gate-induced metallization was found to result in a significant increase of the c-axis length by almost 1% from that of the thermally stabilized insulating state. We also found that this gate-induced gigantic lattice deformation occurs even at the thermally stabilized metallic state, enabling dynamic control of c-axis lattice parameter by more than 1% at room temperature

  20. Chapter 11: Web-based Tools - VO Region Inventory Service

    Science.gov (United States)

    Good, J. C.

    As the size and number of datasets available through the VO grows, it becomes increasingly critical to have services that aid in locating and characterizing data pertinent to a particular scientific problem. At the same time, this same increase makes that goal more and more difficult to achieve. With a small number of datasets, it is feasible to simply retrieve the data itself (as the NVO DataScope service does). At intermediate scales, "count" DBMS searches (searches of the actual datasets which return record counts rather than full data subsets) sent to each data provider will work. However, neither of these approaches scale as the number of datasets expands into the hundreds or thousands. Dealing with the same problem internally, IRSA developed a compact and extremely fast scheme for determining source counts for positional catalogs (and in some cases image metadata) over arbitrarily large regions for multiple catalogs in a fraction of a second. To show applicability to the VO in general, this service has been extended with indices for all 4000+ catalogs in CDS Vizier (essentially all published catalogs and source tables). In this chapter, we will briefly describe the architecture of this service, and then describe how this can be used in a distributed system to retrieve rapid inventories of all VO holdings in a way that places an insignificant load on any data supplier. Further, we show and this tool can be used in conjunction with VO Registries and catalog services to zero in on those datasets that are appropriate to the user's needs. The initial implementation of this service consolidates custom binary index file structures (external to any DBMS and therefore portable) at a single site to minimize search times and implements the search interface as a simple CGI program. However, the architecture is amenable to distribution. The next phase of development will focus on metadata harvesting from data archives through a standard program interface and distribution

  1. Implementation of Cloud Computing into VoIP

    Directory of Open Access Journals (Sweden)

    Floriana GEREA

    2012-08-01

    Full Text Available This article defines Cloud Computing and highlights key concepts, the benefits of using virtualization, its weaknesses and ways of combining it with classical VoIP technologies applied to large scale businesses. The analysis takes into consideration management strategies and resources for better customer orientation and risk management all for sustaining the Service Level Agreement (SLA. An important issue in cloud computing can be security and for this reason there are several security solution presented.

  2. Integration von VO-Management Technologien in UNICORE

    OpenAIRE

    Faroughi, A.

    2007-01-01

    Reliable authentication and authorisation are crucial for both service providers and their customers, where the former want to protect their resources from unauthorised access and fraudulent use while their customers want to be sure that unauthorised access to their data is prevented. In Grid environments Virtual Organisations (VO) have been adopted as a means to organise and control access to resources and data based on roles that are assigned to users. Moreover, attribute based authorisatio...

  3. The Volcanism Ontology (VO): a model of the volcanic system

    Science.gov (United States)

    Myer, J.; Babaie, H. A.

    2017-12-01

    We have modeled a part of the complex material and process entities and properties of the volcanic system in the Volcanism Ontology (VO) applying several top-level ontologies such as Basic Formal Ontology (BFO), SWEET, and Ontology of Physics for Biology (OPB) within a single framework. The continuant concepts in BFO describe features with instances that persist as wholes through time and have qualities (attributes) that may change (e.g., state, composition, and location). In VO, the continuants include lava, volcanic rock, and volcano. The occurrent concepts in BFO include processes, their temporal boundaries, and the spatio-temporal regions within which they occur. In VO, these include eruption (process), the onset of pyroclastic flow (temporal boundary), and the space and time span of the crystallization of lava in a lava tube (spatio-temporal region). These processes can be of physical (e.g., debris flow, crystallization, injection), atmospheric (e.g., vapor emission, ash particles blocking solar radiation), hydrological (e.g., diffusion of water vapor, hot spring), thermal (e.g., cooling of lava) and other types. The properties (predicates) relate continuants to other continuants, occurrents to continuants, and occurrents to occurrents. The ontology also models other concepts such as laboratory and field procedures by volcanologists, sampling by sensors, and the type of instruments applied in monitoring volcanic activity. When deployed on the web, VO will be used to explicitly and formally annotate data and information collected by volcanologists based on domain knowledge. This will enable the integration of global volcanic data and improve the interoperability of software that deal with such data.

  4. Reduction of V{sub 2}O{sub 5} thin films deposited by aqueous sol–gel method to VO{sub 2}(B) and investigation of its photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Monfort, Olivier [Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, 842 15 Bratislava (Slovakia); Roch, Tomas; Satrapinskyy, Leonid; Gregor, Maros; Plecenik, Tomas; Plecenik, Andrej [Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics, Comenius University, 842 48 Bratislava (Slovakia); Plesch, Gustav, E-mail: plesch@fns.uniba.sk [Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, 842 15 Bratislava (Slovakia)

    2014-12-15

    Graphical abstract: - Highlights: • Preparation of VO{sub 2}(B) films by aqueous sol–gel method and their characterization. • Influence of annealing conditions on the mechanism of V{sub 2}O{sub 5} film reduction. • The VO{sub 2}(B) films with energy gap of 2.8 eV show photocatalytic activity. • The films with higher roughness exhibit increased photoactivity. - Abstract: A way of preparation of VO{sub 2}(B) thin films by reduction of V{sub 2}O{sub 5} films synthesized from an aqueous sol–gel system has been developed and photocatalytic properties of the obtained films were studied. The reduction was performed by annealing of the V{sub 2}O{sub 5} film in vacuum as well as in H{sub 2}/Ar atmosphere, which was followed by temperature dependent XRD. It has been shown that the reduction is influenced by the layered-structure of the vanadium oxides. It is a two-step process, where the mixed-valence vanadium oxide V{sub 4}O{sub 9} is first formed before reaching the VO{sub 2}(B) phase. The film microstructure was characterized by SEM and AFM and the valence states of vanadium in VO{sub 2}(B) films were evaluated by XPS. The VO{sub 2}(B) polymorph shows an energy band-gap around 2.8 eV and it exhibits photocatalytic properties. It was measured by following the degradation of rhodamine B under UVA as well as metalhalogenide lamp irradiation, which has similar spectral distribution as natural sunlight. The VO{sub 2}(B) films show distinct photoactivities under both lamps, although they were found to be more active under the UVA irradiation. The film annealed under reducing hydrogen atmosphere, which exhibits higher granularity and surface roughness, shows higher photoactivity than the vacuum-annealed film.

  5. Theoretical studies of the optical and EPR spectra for VO^{2+} in Na_3C_6H_5O_7·2H_2O single crystal

    Directory of Open Access Journals (Sweden)

    Ch.-Y. Li

    2015-06-01

    Full Text Available On the basis of the perturbation formulas for a d^1 configuration ion in a tetragonal crystal field, the three optical absorption bands and electron paramagnetic resonance (EPR parameters (g factors g_i and hyperfine structure constants A_i for i = || and ⊥, respectively of VO^{2+} in Na_3C_6H_5O_7·2H_2O (TSCD single crystals were studied using the perturbation theory method. By simulating the calculated optical and EPR spectra to the observed values, local structure parameters and negative signs of the hyperfine structure constants A_i of the octahedral (VO_6^{8-} cluster in TSCD single crystal can be obtained.

  6. Broad-Application Test Reactor

    International Nuclear Information System (INIS)

    Motloch, C.G.

    1992-05-01

    This report is about a new, safe, and operationally efficient DOE reactor of nuclear research and testing proposed for the early to mid- 21st Century. Dubbed the Broad-Application Test Reactor (BATR), the proposed facility incorporates a multiple-application, multiple-mission design to support DOE programs such as naval reactors and space power and propulsion, as well as research in medical, science, isotope, and electronics arenas. DOE research reactors are aging, and implementing major replacement projects requires long lead times. Primary design drivers include safety, low risk, minimum operation cost, mission flexibility, waste minimization, and long life. Scientists and engineers at the Idaho National Engineering Laboratory are evaluating possible fuel forms, structural materials, reactor geometries, coolants, and moderators

  7. Topotactic insertion of lithium in the layered structure Li4VO(PO4)2: The tunnel structure Li5VO(PO4)2

    International Nuclear Information System (INIS)

    Satya Kishore, M.; Pralong, V.; Caignaert, V.; Malo, S.; Hebert, S.; Varadaraju, U.V.; Raveau, B.

    2008-01-01

    A new V(III) lithium phosphate Li 5 VO(PO 4 ) 2 has been synthesized by electrochemical insertion of lithium into Li 4 VO(PO 4 ) 2 . This phase, which crystallizes in the space group I4/mcm, exhibits a tunnel structure closely related to the layered structure of Li 4 VO(PO 4 ) 2 and to the tunnel structure of VO(H 2 PO 4 ) 2 . The topotactic reactions that take place during lithium exchange and intercalation, starting from VO(H 2 PO 4 ) 2 and going to the final phase Li 5 VO(PO 4 ) 2 are explained on the basis of the flexible coordinations of V 4+ and V 3+ species. The electrochemical and magnetic properties of this new phase are also presented and explained on the basis of the structure dimensionality. - Graphical abstract: Electrochemical synthesis of a new 3D V(III) lithium phosphate, Li 5 VO(PO 4 ) 2 . Starting from the 2D Li 4 VO(PO 4 ) 2 , the topotactic reaction that take place during lithium intercalation is explained on the basis of the flexible coordinations of V 4+ and V 3+ species

  8. Synthesis and modification of FeVO_4 as novel anode for lithium-ion batteries

    International Nuclear Information System (INIS)

    Liu, Xiaolin; Cao, Yuancheng; Zheng, Hao; Chen, Xiao; Feng, Chuanqi

    2017-01-01

    Graphical abstract: The FeVO_4/graphene are synthesized by combining hydrothermal and heat treatment method. It delivered an initial discharge capacity of 1302.3 mAh g"−"1 and remained capacity as 1046.5 mAh g"−"1 after 100 cycles and behaved better electrochemical properties than that of pure FeVO_4. - Highlights: • The FeVO_4 and FeVO_4/graphene are synthesized by combining hydrothermal and heat treatment method. • The FeVO_4/graphene nanocomposite exhibits outstanding electrochemical performance. • FeVO_4/graphene delivered an initial discharge capacity of 1302.3 mAh g"−"1 and remained capacity as 1046.5 mAh g"−"1 after 100 cycles. • The FeVO_4/graphene composite behaved better electrochemical properties than that of pure FeVO_4. - Abstract: FeVO_4 and FeVO_4/graphene nanorods were synthesized successfully by combining a facile hydrothermal and heat treatment method. The samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and transmission electron microscopy (TEM) techniques. The content of graphene in FeVO_4/graphene was determined by thermogravimetric analysis (TG). The electrochemical properties of the samples were also investigated by battery testing system. The results showed that the FeVO_4 formed were taken on morphology of nanorods with the length between 0.5 and 1 μm and the diameter in range of 50 to 100 nm. Besides, the size of FeVO_4/graphene was smaller than that of pure FeVO_4. The content of graphene in composite was about 25.0% by weight. The reversible discharge capacities of FeVO_4 and FeVO_4/graphene were 405.2 mAh g"−"1 and 1046.5 mAh g"−"1 separately after 100 cycles at the current density of 100 mAh g"−"1 in the voltage range of 0.01–3 V. The reasons for the FeVO_4/graphene composite to behave outstanding electrochemical properties were also discussed. The FeVO_4/graphene composite can be a novel and promising anode material for lithium ion battery application.

  9. An Efficient Back-off Mechanism for Simulation Study of VoWLAN Capacity Improvement using OPNET

    OpenAIRE

    Ahmed M. ABDEL NABI; Mohamed R. M. RIZK; Mohamed. S. IBRAHIM; Emad Eldin A. MAZIED

    2014-01-01

    Integration of delivering VoIP services over WLAN access networks (VoWLAN) increased the demand to support multiple of active simultaneous calls. Thus improving VoWLAN capacity has been addressed. The researchers are continuously contributing in improving VoWLAN capacity, (i.e. increasing the number of VoIP simultaneous calls), for various WLAN architectures. Although a lot of modifications have been developed for IEEE 802.11 standards toward improving its performance with real-time applicati...

  10. Crystallization Mechanism and Phase Transition Properties of W-doped VO2 Synthesized by Hydrothermal Method

    Directory of Open Access Journals (Sweden)

    LI Yao

    2017-11-01

    Full Text Available VO2 sol was firstly prepared using vanadyl sulfate as a vanadium source by precipitation-peptization method. Then tungsten(W doping vanadium dioxide(W-VO2 was prepared by hydrothermal crystallization of prepared sol with the presence of ammonium metatungstate. The morphologies, crystal structure of the as-prepared samples and phase transition properties were studied by X-ray diffraction(XRD, field emission scanning electron microscope(FESEMand differential scanning calorimetry(DSC analysis. The results indicate that rod-like W-VO2(B crystal with length of 1-2μm and radius of 100-200nm is firstly formed during hydrothermal treatment for 4-48h at 280℃, then the rod-like crystal dissolves gradually and sheet-like or snowflake-like crystal is formed with the phase transition from W-VO2(B to W-VO2(M and eventually, the W-VO2(M crystals can further grow up while the W-VO2(B gradually dissolves; the phase transition temperature of VO2 decreases with the increase in W doping content, and the phase transition temperature of W-VO2(M reduces to about 28℃ when the nominal dopant concentration is 6.0%(atom fraction.The "nucleation-growth-transformation-ripening" mechanism is proposed as the formation mechanism based on the hydrothermal crystallization and morphological evolution process of W-VO2(M.

  11. Time limit and time at VO2max' during a continuous and an intermittent run.

    Science.gov (United States)

    Demarie, S; Koralsztein, J P; Billat, V

    2000-06-01

    The purpose of this study was to verify, by track field tests, whether sub-elite runners (n=15) could (i) reach their VO2max while running at v50%delta, i.e. midway between the speed associated with lactate threshold (vLAT) and that associated with maximal aerobic power (vVO2max), and (ii) if an intermittent exercise provokes a maximal and/or supra maximal oxygen consumption longer than a continuous one. Within three days, subjects underwent a multistage incremental test during which their vVO2max and vLAT were determined; they then performed two additional testing sessions, where continuous and intermittent running exercises at v50%delta were performed up to exhaustion. Subject's gas exchange and heart rate were continuously recorded by means of a telemetric apparatus. Blood samples were taken from fingertip and analysed for blood lactate concentration. In the continuous and the intermittent tests peak VO2 exceeded VO2max values, as determined during the incremental test. However in the intermittent exercise, peak VO2, time to exhaustion and time at VO2max reached significantly higher values, while blood lactate accumulation showed significantly lower values than in the continuous one. The v50%delta is sufficient to stimulate VO2max in both intermittent and continuous running. The intermittent exercise results better than the continuous one in increasing maximal aerobic power, allowing longer time at VO2max and obtaining higher peak VO2 with lower lactate accumulation.

  12. Progressive recruitment of muscle fibers is not necessary for the slow component of VO2 kinetics.

    Science.gov (United States)

    Zoladz, Jerzy A; Gladden, L Bruce; Hogan, Michael C; Nieckarz, Zenon; Grassi, Bruno

    2008-08-01

    The "slow component" of O2 uptake (VO2) kinetics during constant-load heavy-intensity exercise is traditionally thought to derive from a progressive recruitment of muscle fibers. In this study, which represents a reanalysis of data taken from a previous study by our group (Grassi B, Hogan MC, Greenhaff PL, Hamann JJ, Kelley KM, Aschenbach WG, Constantin-Teodosiu D, Gladden LB. J Physiol 538: 195-207, 2002) we evaluated the presence of a slow component-like response in the isolated dog gastrocnemius in situ (n=6) during 4 min of contractions at approximately 60-70% of peak VO2. In this preparation all muscle fibers are maximally activated by electrical stimulation from the beginning of the contraction period, and no progressive recruitment of fibers is possible. Muscle VO2 was calculated as blood flow multiplied by arteriovenous O2 content difference. The muscle fatigued (force decreased by approximately 20-25%) during contractions. Kinetics of adjustment were evaluated for 1) VO2, uncorrected for force development; 2) VO2 normalized for peak force; 3) VO2 normalized for force-time integral. A slow component-like response, described in only one muscle out of six when uncorrected VO2 was considered, was observed in all muscles when VO2/peak force and VO2/force-time were considered. The amplitude of the slow component-like response, expressed as a fraction of the total response, was higher for VO2/peak force (0.18+/-0.06, means+/-SE) and for VO2/force-time (0.22+/-0.05) compared with uncorrected VO2 (0.04+/-0.04). A progressive recruitment of muscle fibers may not be necessary for the development of the slow component of VO2 kinetics, which may be caused by the metabolic factors that induce muscle fatigue and, as a consequence, reduce the efficiency of muscle contractions.

  13. Improving the electrocatalytic performance of carbon nanotubes for VO{sup 2+}/VO{sub 2}{sup +} redox reaction by KOH activation

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Lei; Jiang, Yingqiao; Meng, Wei; Zhou, Huizhu [School of Chemical Engineering, North China University of Science and Technology, Tangshan 063009 (China); Wang, Ling, E-mail: tswling@126.com [School of Chemical Engineering, North China University of Science and Technology, Tangshan 063009 (China); He, Zhangxing, E-mail: zxhe@ncst.edu.cn [School of Chemical Engineering, North China University of Science and Technology, Tangshan 063009 (China); State Key Laboratory Breeding Base of Nuclear Resources and Environment, East China Institute of Technology, Nanchang 330013 (China)

    2017-04-15

    Highlights: • KOH-activated carbon nanotubes (CNTs) was investigated as superior catalyst for VO{sup 2+}/VO{sub 2}{sup +} redox reaction for vanadium redox flow battery (VRFB) for the first time. • KOH activation for CNTs can result in the chemical etching of surface and improved wettability, accelerating the mass transfer of vanadium ions. • KOH activation can introduce many oxygen-containing groups as active sites on the surface of CNTs. • KOH-activated CNTs as positive catalyst could increase the comprehensive energy storage performance of VRFB. - Abstract: In this paper, carbon nanotubes (CNTs) was activated by KOH treatment at high temperature and investigated as catalyst for VO{sup 2+}/VO{sub 2}{sup +} redox reaction for vanadium redox flow battery (VRFB). X-ray photoelectron spectroscopy results suggest that the oxygen-containing groups can be introduced on CNTs by KOH activation. The mass transfer of vanadium ions can be accelerated by chemical etching by KOH activation and improved wettability due to the introduction of hydrophilic groups. The electrochemical properties of VO{sup 2+}/VO{sub 2}{sup +} redox reaction can be enhanced by introduced oxygen-containing groups as active sites. The sample treated at 900 °C with KOH/CNTs mass ratio of 3:1 (CNTs-3) exhibits the highest electrocatalytic activity for VO{sup 2+}/VO{sub 2}{sup +} redox reaction. The cell using CNTs-3 as positive catalyst demonstrates the smallest electrochemical polarization, the highest capacity and efficiency among the samples. Using KOH-activated CNTs-3 can increase the average energy efficiency of the cell by 4.4%. This work suggests that KOH-activated CNTs is a low-cost, efficient and promising catalyst for VO{sup 2+}/VO{sub 2}{sup +} redox reaction for VRFB system.

  14. Klasični (ekstenzivni) voćnjaci u Hrvatskoj

    OpenAIRE

    Čmelik, Zlatko

    2011-01-01

    Hrvatska ima vrlo povoljne pomoekološke uvjete za uzgoj voćaka. Tradicija uzgoja voćaka duga je više stoljeća, a voćke su se uzgajale na gotovo svim seoskim gospodarstvima, te dijelom i u urbanim sredinama. Intenzivan uzgoj voćaka počeo se značajnije širiti polovinom prošlog stoljeća. Intenzivan uzgoj je u određenoj mjeri potisnuo interes za klasičnim, ali se postojeći voćnjaci visokostablašica uglavnom nisu krčili već su u većoj mjeri bili zapušteni. U novije vrijeme klasični voćnjaci pon...

  15. In situ X-ray powder diffraction, synthesis, and magnetic properties of InVO 3

    Science.gov (United States)

    Lundgren, Rylan J.; Cranswick, Lachlan M. D.; Bieringer, Mario

    2006-12-01

    We report the first synthesis and high-temperature in situ X-ray diffraction study of InVO 3. Polycrystalline InVO 3 has been prepared via reduction of InVO 4 using a carbon monoxide/carbon dioxide buffer gas. InVO 3 crystallizes in the bixbyite structure in space group Ia-3 (206) with a=9.80636(31) Å with In 3+/V 3+ disorder on the (8 b) and (24 d) cation sites. In situ powder X-ray diffraction experiments and thermal gravimetric analysis in a CO/CO 2 buffer gas revealed the existence of the metastable phase InVO 3. Bulk samples with 98.5(2)% purity were prepared using low-temperature reduction methods. The preparative methods limited the crystallinity of this new phase to approximately 225(50) Å. Magnetic susceptibility and neutron diffraction experiments suggest a spin-glass ground state for InVO 3.

  16. Epitaxial growth and electronic structure of oxyhydride SrVO{sub 2}H thin films

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Tsukasa; Chikamatsu, Akira, E-mail: chikamatsu@chem.s.u-tokyo.ac.jp; Yamada, Keisuke; Onozuka, Tomoya [Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Shigematsu, Kei [Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa 213-0012 (Japan); Minohara, Makoto; Kumigashira, Hiroshi [Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Ikenaga, Eiji [Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, Mikazuki-cho, Hyogo 679-5198 (Japan); Hasegawa, Tetsuya [Department of Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kanagawa Academy of Science and Technology, Kawasaki, Kanagawa 213-0012 (Japan)

    2016-08-28

    Oxyhydride SrVO{sub 2}H epitaxial thin films were fabricated on SrTiO{sub 3} substrates via topotactic hydridation of oxide SrVO{sub 3} films using CaH{sub 2}. Structural and composition analyses suggested that the SrVO{sub 2}H film possessed one-dimensionally ordered V-H{sup −}-V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO{sub 2}H film was reversible to SrVO{sub 3} by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurements revealed the V{sup 3+} valence state in the SrVO{sub 2}H film, indicating that the hydrogen existed as hydride. Furthermore, the electronic density of states was highly suppressed at the Fermi energy, consistent with the prediction that tetragonal distortion induces metal to insulation transition.

  17. Epitaxial growth and electronic structure of oxyhydride SrVO2H thin films

    Science.gov (United States)

    Katayama, Tsukasa; Chikamatsu, Akira; Yamada, Keisuke; Shigematsu, Kei; Onozuka, Tomoya; Minohara, Makoto; Kumigashira, Hiroshi; Ikenaga, Eiji; Hasegawa, Tetsuya

    2016-08-01

    Oxyhydride SrVO2H epitaxial thin films were fabricated on SrTiO3 substrates via topotactic hydridation of oxide SrVO3 films using CaH2. Structural and composition analyses suggested that the SrVO2H film possessed one-dimensionally ordered V-H--V bonds along the out-of-plane direction. The synthesis temperature could be lowered by reducing the film thickness, and the SrVO2H film was reversible to SrVO3 by oxidation through annealing in air. Photoemission and X-ray absorption spectroscopy measurements revealed the V3+ valence state in the SrVO2H film, indicating that the hydrogen existed as hydride. Furthermore, the electronic density of states was highly suppressed at the Fermi energy, consistent with the prediction that tetragonal distortion induces metal to insulation transition.

  18. Research progress of VO2 thin film as laser protecting material

    Science.gov (United States)

    Liu, Zhiwei; Lu, Yuan; Hou, Dianxin

    2018-03-01

    With the development of laser technology, the battlefield threat of directional laser weapons is becoming more and more serious. The blinding and destruction caused by laser weapons on the photoelectric equipment is an important part of the current photo-electronic warfare. The research on the defense technology of directional laser weapons based on the phase transition characteristics of VO2 thin films is an important subject. The researches of VO2 thin films are summarized based on review these points: the preparation methods of VO2 thin films, phase transition mechanism, phase transition temperature regulating, interaction between VO2 thin films and laser, and the application prospect of vo2 thin film as laser protecting material. This paper has some guiding significance for further research on the VO2 thin films in the field of defense directional laser weapons.

  19. Multiple variables explain the variability in the decrement in VO2max during acute hypobaric hypoxia.

    Science.gov (United States)

    Robergs, R A; Quintana, R; Parker, D L; Frankel, C C

    1998-06-01

    We used multiple regression analyses to determine the relationships between the decrement in sea level (SL, 760 Torr) VO2max during hypobaric hypoxia (HH) and variables that could alter or be related to the decrement in VO2max. HH conditions consisted of 682 Torr, 632 Torr, and 566 Torr, and the measured independent variables were SL-VO2max, SL lactate threshold (SL-LT), the change in hemoglobin saturation at VO2max between 760 and 566 Torr (delta SaO2max), lean body mass (LBM), and gender. Male (N = 14) and female (N = 14) subjects of varied fitness, training status, and residential altitude (1,640-2,460 m) completed cycle ergometry tests of VO2max at each HH condition under randomized and single-blinded conditions. VO2max decreased significantly from 760 Torr after 682 Torr (approximately 915 m) (3.5 +/- 0.9 to 3.4 +/- 0.8 L.min-1, P = 0.0003). Across all HH conditions, the slope of the relative decrement in VO2max (%VO2max) during HH was -9.2%/100 mm Hg (-8.1%/1000 m) with an initial decrease from 100% estimated to occur below 705 Torr (610 m). Step-wise multiple regression revealed that SL-VO2max, SL-LT, delta SaO2max, LBM, and gender each significantly combined to account for 89.03% of the variance in the decrement in VO2max (760-566 Torr) (P decrement in VO2max during HH. The unique variance explanation afforded by SL-LT, LBM, and gender suggests that issues pertaining to oxygen diffusion within skeletal muscle may add to the explanation of between subjects variability in the decrement in VO2max during HH.

  20. The metropolitan VoD system based on ethernet/SCM PON

    Science.gov (United States)

    Ji, Wei; Yang, Hongliang; Feng, Dejun; Liu, Yang; Sun, Jande

    2008-11-01

    VoD is a very attractive service which used for entertainment, education and other purposes. In this paper, we present an evolution method that integrates the EPON and SCM-PON by WDM technology to provide high dedicated bandwidth for the metropolitan VoD services. Using DVB, IPTV protocol, unicasting and broadcasting method to maximize the system throughput and by numerical analysis, the hybrid PON system can implement the metropolitan VoD services.

  1. Enhancement in Photoelectrochemical Efficiency by Fabrication of BiVO4@MWCNT Nanocomposites

    Directory of Open Access Journals (Sweden)

    Yan Zhang

    2011-01-01

    Full Text Available An enormous enhancement in the photo-to-current conversion efficiency over the nanocomposite material composed by BiVO4 on the surface of MWCNTs, with respect to electrode of pure BiVO4, was observed. The heterojunction formed between MWCNTs and nano-BiVO4 is beneficial for the separation of photogenerated electrons and holes, resulting in more electrons that are able to transport efficiently to the surface and therefore enhance the photoefficiency.

  2. Band structure of semiconductors

    CERN Document Server

    Tsidilkovski, I M

    2013-01-01

    Band Structure of Semiconductors provides a review of the theoretical and experimental methods of investigating band structure and an analysis of the results of the developments in this field. The book presents the problems, methods, and applications in the study of band structure. Topics on the computational methods of band structure; band structures of important semiconducting materials; behavior of an electron in a perturbed periodic field; effective masses and g-factors for the most commonly encountered band structures; and the treatment of cyclotron resonance, Shubnikov-de Haas oscillatio

  3. Comparative study of optical and scintillation properties of YVO4, (Lu0.5Y0.5)VO4, and LuVO4 single crystals

    International Nuclear Information System (INIS)

    Fujimoto, Yutaka; Yanagida, Takayuki; Yokota, Yuui; Chani, Valery; Kochurikhin, Vladimir V.; Yoshikawa, Akira

    2011-01-01

    Optical and scintillation properties of YVO 4 , (Lu 0.5 Y 0.5 )VO 4 , and LuVO 4 single crystals grown by the Czochralski (CZ) method with RF heating system are compared. All vanadate crystals show high transmittance (∼80%) in the 400-900 nm wavelength range. In both photo- and radio-luminescence spectra, intense peak around 400-500 nm, which was ascribed to the transition from triplet state of VO 4 3- , was clearly observed. The main decay time component was about 38 μs (YVO 4 ), 18 μs ((Lu 0.5 Y 0.5 )VO 4 ), and 17 μs (LuVO 4 ) under 340 nm excitation. The scintillation light yields of YVO 4 , (Lu 0.5 Y 0.5 )VO 4 , and LuVO 4 crystals (obtained from the 137 Cs excited pulse height spectra) were evaluated to be about 11,200, 10,700, and 10,300 ph/MeV, respectively.

  4. VoSeq: a voucher and DNA sequence web application.

    Directory of Open Access Journals (Sweden)

    Carlos Peña

    Full Text Available There is an ever growing number of molecular phylogenetic studies published, due to, in part, the advent of new techniques that allow cheap and quick DNA sequencing. Hence, the demand for relational databases with which to manage and annotate the amassing DNA sequences, genes, voucher specimens and associated biological data is increasing. In addition, a user-friendly interface is necessary for easy integration and management of the data stored in the database back-end. Available databases allow management of a wide variety of biological data. However, most database systems are not specifically constructed with the aim of being an organizational tool for researchers working in phylogenetic inference. We here report a new software facilitating easy management of voucher and sequence data, consisting of a relational database as back-end for a graphic user interface accessed via a web browser. The application, VoSeq, includes tools for creating molecular datasets of DNA or amino acid sequences ready to be used in commonly used phylogenetic software such as RAxML, TNT, MrBayes and PAUP, as well as for creating tables ready for publishing. It also has inbuilt BLAST capabilities against all DNA sequences stored in VoSeq as well as sequences in NCBI GenBank. By using mash-ups and calls to web services, VoSeq allows easy integration with public services such as Yahoo! Maps, Flickr, Encyclopedia of Life (EOL and GBIF (by generating data-dumps that can be processed with GBIF's Integrated Publishing Toolkit.

  5. Ultrafast dynamics during the photoinduced phase transition in VO2

    Science.gov (United States)

    Wegkamp, Daniel; Stähler, Julia

    2015-12-01

    The phase transition of VO2 from a monoclinic insulator to a rutile metal, which occurs thermally at TC = 340 K, can also be driven by strong photoexcitation. The ultrafast dynamics during this photoinduced phase transition (PIPT) have attracted great scientific attention for decades, as this approach promises to answer the question of whether the insulator-to-metal (IMT) transition is caused by electronic or crystallographic processes through disentanglement of the different contributions in the time domain. We review our recent results achieved by femtosecond time-resolved photoelectron, optical, and coherent phonon spectroscopy and discuss them within the framework of a selection of latest, complementary studies of the ultrafast PIPT in VO2. We show that the population change of electrons and holes caused by photoexcitation launches a highly non-equilibrium plasma phase characterized by enhanced screening due to quasi-free carriers and followed by two branches of non-equilibrium dynamics: (i) an instantaneous (within the time resolution) collapse of the insulating gap that precedes charge carrier relaxation and significant ionic motion and (ii) an instantaneous lattice potential symmetry change that represents the onset of the crystallographic phase transition through ionic motion on longer timescales. We discuss the interconnection between these two non-thermal pathways with particular focus on the meaning of the critical fluence of the PIPT in different types of experiments. Based on this, we conclude that the PIPT threshold identified in optical experiments is most probably determined by the excitation density required to drive the lattice potential change rather than the IMT. These considerations suggest that the IMT can be driven by weaker excitation, predicting a transiently metallic, monoclinic state of VO2 that is not stabilized by the non-thermal structural transition and, thus, decays on ultrafast timescales.

  6. Resolving the chicken-and-egg problem in VO2: a new paradigm for the Mott transition

    Science.gov (United States)

    Najera, Oscar; Civelli, Marcello; Dobrosavljevi, Vladimir; Rozenberg, Marcelo

    We consider a minimal model to investigate the metal-insulator transition in VO2. We adopt a Hubbard model with two orbital per unit cell, which captures the competition between Mott and singlet-dimer localization. We solve the model within Dynamical Mean Field Theory, characterizing in detail the metal-insulator transition and finding new features in the electronic states. We compare our results with available experimental data obtaining good agreement in the relevant model parameter range. Crucially, we can account for puzzling optical conductivity data obtained within the hysteresis region, which we associate to a novel metallic state characterized by a split heavy quasiparticle band. Our results show that the thermal-driven insulator-to-metal transition in VO2 is entirely compatible with a Mott electronic mechanism, solving a long standing ''chicken-and-egg'' debate and calling for further research of ``Mottronics'' applications of this system. This work was partially supported by public Grants from the French National Research Agency (ANR), project LACUNES No ANR-13-BS04-0006-01, the NSF DMR-1005751 and DMR-1410132.

  7. Effect of the KOH chemical treatment on the optical and photocatalytic properties of BiVO4 thin films

    International Nuclear Information System (INIS)

    Mirabal-Rojas, R.; Depablos-Rivera, O.; Medina, J.C.; Thalluri, S.M.; Bizarro, M.; Perez-Alvarez, J.; Rodil, S.E.; Zeinert, A.

    2016-01-01

    In this work, we present the structural, optical and photocatalytic properties of BiVO 4 thin films produced by a dual-magnetron sputtering process using both Bi 2 O 3 (α-phase, 99.98 % purity) and V (99.9 % purity) targets under Ar/O 2 atmosphere with a ratio of 18:2. The films were deposited varying the power applied to the targets to obtain stoichiometric films, and the monoclinic structure was achieved by post-deposition annealing. The dual process was chosen to better control the Bi/V ratio since Bi and V have very different sputtering yields. In particular, the influence of a chemical treatment using potassium hydroxide (KOH) on the optical properties and different dye discolorations (acid blue 113 and methyl orange) is discussed. The optical properties were studied by reflectance and transmittance spectroscopy, where the spectra were fitted to obtain the refractive index dispersion and the optical band gap of the BiVO 4 as a function of the film structure, as determined by X-ray diffraction and Raman spectroscopy. (orig.)

  8. Effect of the KOH chemical treatment on the optical and photocatalytic properties of BiVO4 thin films

    Science.gov (United States)

    Mirabal-Rojas, R.; Depablos-Rivera, O.; Thalluri, S. M.; Medina, J. C.; Bizarro, M.; Perez-Alvarez, J.; Rodil, S. E.; Zeinert, A.

    2016-04-01

    In this work, we present the structural, optical and photocatalytic properties of BiVO4 thin films produced by a dual-magnetron sputtering process using both Bi2O3 (α-phase, 99.98 % purity) and V (99.9 % purity) targets under Ar/O2 atmosphere with a ratio of 18:2. The films were deposited varying the power applied to the targets to obtain stoichiometric films, and the monoclinic structure was achieved by post-deposition annealing. The dual process was chosen to better control the Bi/V ratio since Bi and V have very different sputtering yields. In particular, the influence of a chemical treatment using potassium hydroxide (KOH) on the optical properties and different dye discolorations (acid blue 113 and methyl orange) is discussed. The optical properties were studied by reflectance and transmittance spectroscopy, where the spectra were fitted to obtain the refractive index dispersion and the optical band gap of the BiVO4 as a function of the film structure, as determined by X-ray diffraction and Raman spectroscopy.

  9. Effect of the KOH chemical treatment on the optical and photocatalytic properties of BiVO{sub 4} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mirabal-Rojas, R.; Depablos-Rivera, O.; Medina, J.C. [Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones en Materiales, Mexico City (Mexico); Universidad Nacional Autonoma de Mexico, Posgrado en Ciencia e Ingenieria de Materiales, Mexico City (Mexico); Thalluri, S.M. [Politecnico di Torino, Department of Applied Science and Technology (DISAT), Torino (Italy); Bizarro, M.; Perez-Alvarez, J.; Rodil, S.E. [Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones en Materiales, Mexico City (Mexico); Zeinert, A. [Universite de Picardie Jules Verne, Laboratoire de Physique de la Matiere Condensee, Amiens (France)

    2016-04-15

    In this work, we present the structural, optical and photocatalytic properties of BiVO{sub 4} thin films produced by a dual-magnetron sputtering process using both Bi{sub 2}O{sub 3} (α-phase, 99.98 % purity) and V (99.9 % purity) targets under Ar/O{sub 2} atmosphere with a ratio of 18:2. The films were deposited varying the power applied to the targets to obtain stoichiometric films, and the monoclinic structure was achieved by post-deposition annealing. The dual process was chosen to better control the Bi/V ratio since Bi and V have very different sputtering yields. In particular, the influence of a chemical treatment using potassium hydroxide (KOH) on the optical properties and different dye discolorations (acid blue 113 and methyl orange) is discussed. The optical properties were studied by reflectance and transmittance spectroscopy, where the spectra were fitted to obtain the refractive index dispersion and the optical band gap of the BiVO{sub 4} as a function of the film structure, as determined by X-ray diffraction and Raman spectroscopy. (orig.)

  10. Temperature-agile and structure-tunable optical properties of VO2/Ag thin films

    International Nuclear Information System (INIS)

    Zhang, X.R.; Hu, X.; Wang, W.; Zhao, Y.; Reinhardt, K.; Knize, R.J.; Lu, Yalin

    2012-01-01

    By integrating together VO 2 's unique near-room-temperature (RT) semiconductor-metal (S-M) phase transition with a thin silver (Ag) layer's plasmonic properties, VO 2 /Ag multilayers could present a much enhanced optical transmission change when increasing the temperature from RT to over VO 2 's S-M phase-transition temperature. Changing VO 2 and Ag layer thicknesses can also significantly tune their transmission and absorption properties, which could lead to a few useful designs in optoelectronic and energy-saving industries. (orig.)

  11. VV and VO2 defects in silicon studied with hybrid density functional theory

    KAUST Repository

    Christopoulos, Stavros Richard G

    2014-12-07

    The formation of VO (A-center), VV and VO2 defects in irradiated Czochralski-grown silicon (Si) is of technological importance. Recent theoretical studies have examined the formation and charge states of the A-center in detail. Here we use density functional theory employing hybrid functionals to analyze the formation of VV and VO2 defects. The formation energy as a function of the Fermi energy is calculated for all possible charge states. For the VV and VO2 defects double negatively charged and neutral states dominate, respectively.

  12. Optimization of thermochromic VO2-based structures with tunable thermal emissivity

    International Nuclear Information System (INIS)

    Li Voti, R.; Larciprete, M.C.; Leahu, G.L.; Bertolotti, M.; Sibilia, C.

    2013-01-01

    In this paper we design and simulate VO 2 /metal multilayers to obtain a large tunability of the thermal emissivity of IR filters in the typical MWIR window of many infrared cameras. The multilayer structure is optimized to realise a low-emissivity filter at high temperatures useful for military purposes. The values of tunability found for VO 2 /metal multilayers are larger than the value for a single thick layer of VO 2 . Innovative SiO 2 /VO 2 synthetic opals are also investigated to enhance the optical tunability by combining the properties of a 3D periodic structure and the specific optical properties of vanadium dioxide.

  13. Maqueta VoIP con media gateway controllers

    OpenAIRE

    Goicoechea Bozal, Ignacio Javier

    2010-01-01

    El presente proyecto fin de carrera tiene como objeto estudiar y comprobar el funcionamiento de un protocolo VoIP basado en una arquitectura softswitch. La tecnología softswitch nace con el fin de facilitar la interconexión entre la red telefónica pública conmutada y redes basadas en paquetes. Por esta razón, las grandes compañías telefónicas son las principales usuarias de este tipo de arquitectura. Se han evaluado 3 posibles protocolos para controlar la maqueta que se desea diseñar: SGC...

  14. General Vo Nguyen Giap: Operational Genius or Lucky Amateur

    Science.gov (United States)

    1993-05-17

    34蓞 fta "" Coat" Si0-650sa 0102-LF-014-66 02 ABSTRACT OF. GENERAL VO NGUYEN GIAP: OPERATIONAL GENIUS OR LUCKY AMATEUR? Over the course of 30 years, from...and the revolution in operation’al. (nkinZ he procipitated. 37 ENDNOTES 1. Stanley Karnow, Vietnam: A History (New York: Penguin Books, 1984), p. 58...isl. Now York: Penguin Books, 1984. O’Ncill, Robert J. GeAl i(p: Politicigan d Stratmdst. New York: Fredcrick A. Praeger, 1969. Pimlotk John. Vktnam

  15. 78 FR 20119 - Broad Stakeholder Survey

    Science.gov (United States)

    2013-04-03

    ... DEPARTMENT OF HOMELAND SECURITY [Docket No. DHS-2012-0042] Broad Stakeholder Survey AGENCY... concerning the Broad Stakeholder Survey. DHS previously published this ICR in the Federal Register on August... across the Nation. The Broad Stakeholder Survey is designed to gather stakeholder feedback on the...

  16. Explaining the MoVO4- photoelectron spectrum: Rationalization of geometric and electronic structure.

    Science.gov (United States)

    Thompson, Lee M; Jarrold, Caroline C; Hratchian, Hrant P

    2017-03-14

    Attempts to reconcile simulated photoelectron spectra of MoVO 4 - clusters are complicated by the presence of very low energy barriers in the potential energy surfaces (PESs) of the lowest energy spin states and isomers. Transition state structures associated with the inversion of terminal oxygen ligands are found to lie below, or close to, the zero point energy of associated modes, which themselves are found to be of low frequency and thus likely to be significantly populated in the experimental characterization. Our simulations make use of Boltzmann averaging over low-energy coordinates and full mapping of the PES to obtain simulations in good agreement with experimental spectra. Furthermore, molecular orbital analysis of accessible final spin states reveals the existence of low energy two-electron transitions in which the final state is obtained from a finite excitation of an electron along with the main photodetachment event. Two-electron transitions are then used to justify the large difference in intensity between different bands present in the photoelectron spectrum. Owing to the general presence of terminal ligands in metal oxide clusters, this study identifies and proposes a solution to issues that are generally encountered when attempting to simulate transition metal cluster photoelectron spectroscopy.

  17. Plasmonic enhancement in BiVO4 photonic crystals for efficient water splitting.

    Science.gov (United States)

    Zhang, Liwu; Lin, Chia-Yu; Valev, Ventsislav K; Reisner, Erwin; Steiner, Ullrich; Baumberg, Jeremy J

    2014-10-15

    Photo-electrochemical water splitting is a very promising and environmentally friendly route for the conversion of solar energy into hydrogen. However, the solar-to-H2 conversion efficiency is still very low due to rapid bulk recombination of charge carriers. Here, a photonic nano-architecture is developed to improve charge carrier generation and separation by manipulating and confining light absorption in a visible-light-active photoanode constructed from BiVO4 photonic crystal and plasmonic nanostructures. Synergistic effects of photonic crystal stop bands and plasmonic absorption are observed to operate in this photonic nanostructure. Within the scaffold of an inverse opal photonic crystal, the surface plasmon resonance is significantly enhanced by the photonic Bragg resonance. Nanophotonic photoanodes show AM 1.5 photocurrent densities of 3.1 ± 0.1 mA cm(-2) at 1.23 V versus RHE, which is among the highest for oxide-based photoanodes and over 4 times higher than the unstructured planar photoanode. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Ab-initio calculations of structural, electronic, and optical properties of Zn3(VO4)2

    Science.gov (United States)

    Ahmed, Nisar; Mukhtar, S.; Gao, Wei; Zafar Ilyas, Syed

    2018-03-01

    The structural, electronic, and optical properties of Zn3(VO4)2 are investigated using full potential linearized augmented plane wave (FP-LAPW) method within the framework of density functional theory (DFT). Various approaches are adopted to treat the exchange and correlation potential energy such as generalized gradient approximation (GGA), GGA+U, and the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. The calculated band gap of 3.424 eV by TB-mBJ is found to be close to the experimental result (3.3 eV). The optical anisotropy is analyzed through optical constants, such as dielectric function and absorption coefficient along parallel and perpendicular crystal orientations. The absorption coefficient reveals high absorption (1.5× {10}6 {cm}}-1) of photons in the ultraviolet region.

  19. Elevated transition temperature in Ge doped VO2 thin films

    Science.gov (United States)

    Krammer, Anna; Magrez, Arnaud; Vitale, Wolfgang A.; Mocny, Piotr; Jeanneret, Patrick; Guibert, Edouard; Whitlow, Harry J.; Ionescu, Adrian M.; Schüler, Andreas

    2017-07-01

    Thermochromic GexV1-xO2+y thin films have been deposited on Si (100) substrates by means of reactive magnetron sputtering. The films were then characterized by Rutherford backscattering spectrometry (RBS), four-point probe electrical resistivity measurements, X-ray diffraction, and atomic force microscopy. From the temperature dependent resistivity measurements, the effect of Ge doping on the semiconductor-to-metal phase transition in vanadium oxide thin films was investigated. The transition temperature was shown to increase significantly upon Ge doping (˜95 °C), while the hysteresis width and resistivity contrast gradually decreased. The precise Ge concentration and the film thickness have been determined by RBS. The crystallinity of phase-pure VO2 monoclinic films was confirmed by XRD. These findings make the use of vanadium dioxide thin films in solar and electronic device applications—where higher critical temperatures than 68 °C of pristine VO2 are needed—a viable and promising solution.

  20. RGO/InVO4 hollowed-out nanofibers: Electrospinning synthesis and its application in photocatalysis

    International Nuclear Information System (INIS)

    Ma, Dong; Zhang, Yanxiang; Gao, Mengchun; Xin, Yanjun; Wu, Juan; Bao, Nan

    2015-01-01

    Graphical abstract: - Highlights: • RGO/InVO 4 hollow-out nanofibers were obtained by electrospinning method. • The properties of InVO 4 hollow-out nanofibers were deeply influenced by RGO. • RGO could reduce recombination of e − –h + pairs to improve photocatalytic activity. • Photo-induced h + and e − are the two main reactive species for RhB degradation. - Abstract: A composite of reduced graphene oxide (RGO) and InVO 4 nanofiber was successfully synthesized by an electrospinning technique. The as-collected fibers were calcined at 420 °C in air and then calcined at 550 °C in nitrogen gas to remove polyvinyl pyrrolidone (PVP), which could enable InVO 4 to crystallize and protect the RGO from oxidation. The InVO 4 in the composite illustrated a hollowed-out fibrous morphology and orthorhombic phase, and RGO nanosheets were nested in the InVO 4 nanofibers. The hybrid RGO could produce more hydroxyl groups and a higher oxygen vacancy density on the surface of RGO/InVO 4 composite. Compared with pure InVO 4 , the light absorption range of the as-prepared RGO/InVO 4 composite was expanded. In Rh B degradation, the RGO/InVO 4 hybrid nanofibers displayed a higher photocatalytic activity than pure InVO 4 nanofibers. The enhanced photocatalytic activity might be ascribed to the role of RGO as an electron transporter and acceptor in the composite, which could effectively inhibit the charge recombination and facilitate the charge transfer. The exported electron could attack an O 2 molecule to facilitate the generation of • O 2 − and • OH for the photodegradation process of Rh B.

  1. Extraction Of Electronic Evidence From VoIP: Identification & Analysis Of Digital Speech

    Directory of Open Access Journals (Sweden)

    David Irwin

    2012-09-01

    Full Text Available The Voice over Internet Protocol (VoIP is increasing in popularity as a cost effective and efficient means of making telephone calls via the Internet. However, VoIP may also be an attractive method of communication to criminals as their true identity may be hidden and voice and video communications are encrypted as they are deployed across the Internet. This produces in a new set of challenges for forensic analysts compared with traditional wire-tapping of the Public Switched Telephone Network (PSTN infrastructure, which is not applicable to VoIP. Therefore, other methods of recovering electronic evidence from VoIP are required.  This research investigates the analysis and recovery of digitised human, which persists in computer memory after a VoIP call.This paper proposes a proof of concept how remnants of digitised human speech from a VoIP call may be identified within a forensic memory capture based on how the human voice is detected via a microphone and encoded to a digital format using the sound card of your personal computer. This digital format is unencrypted whist processed in Random Access Memory (RAM before it is passed to the VoIP application for encryption and  transmission over the Internet. Similarly, an incoming encrypted VoIP call is decrypted by the VoIP application and passes through RAM unencrypted in order to be played via the speaker output.A series of controlled tests were undertaken whereby RAM captures were analysed for remnants of digital speech after a VoIP audio call with known conversation. The identification and analysis of digital speech from RAM attempts to construct an automatic process for the identification and subsequent reconstruction of the audio content of a VoIP call.

  2. Synthesis of LaVO4/TiO2 heterojunction nanotubes by sol-gel coupled with hydrothermal method for photocatalytic air purification.

    Science.gov (United States)

    Zou, Xuejun; Li, Xinyong; Zhao, Qidong; Liu, Shaomin

    2012-10-01

    With the aim of improving the effective utilization of visible light, the LaVO(4)/TiO(2) heterojunction nanotubes were fabricated by sol-gel coupled with hydrothermal method. The photocatalytic ability was demonstrated through catalytic removal of gaseous toluene species. The nanotube samples were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), surface photovoltage (SPV), Raman spectra and N(2) adsorption-desorption measurements. The characterization results showed that the samples with high specific surface areas were of typical nanotubular morphology, which would lead to the high separation and transfer efficiency of photo induced electron-hole pairs. The as-prepared nanotubes exhibited high photocatalytic activity in decomposing toluene species under visible light irradiation with fine photochemical stability. The enhanced photocatalytic performance of LaVO(4)/TiO(2) nanotubes might be attributed to the matching band potentials, the interconnected heterojunction of LaVO(4) versus TiO(2), and the large specific surface areas of nanotubes. Copyright © 2012 Elsevier Inc. All rights reserved.

  3. Synthesis, optical properties and photodegradation for methylene blue of Ni-vanadate K{sub 2}Ni(VO{sub 3}){sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Yuting; Pu, Yinfu; Huang, Yanlin, E-mail: huang@suda.edu.cn; Wang, Jing; Lu, Juan, E-mail: lujuan@suda.edu.cn, E-mail: juanlu@suda.edu.cn [Soochow University, College of Chemistry, Chemical Engineering and Materials Science (China)

    2015-11-15

    A Ni{sup 2+}-containing vanadate, K{sub 2}Ni(VO{sub 3}){sub 4} was developed as a new visible-light-driven photocatalyst. The nanoparticles were prepared by the modified Pechini method. The sample was characterized by the measurements such as X-ray powder diffraction, scanning electron microscope, and UV–Vis absorption spectrum. The photocatalytic activity of K{sub 2}Ni(VO{sub 3}){sub 4} nanoparticles was evaluated by the photodegradation of methylene blue under visible-light irradiation in air. K{sub 2}Ni(VO{sub 3}){sub 4} shows a photocatalytic activity due to the efficient absorption in the UV–Visible-light wavelength region with a narrowed band-gap energy of 2.08 eV and an indirectly allowed electronic transition. These results indicate that this vanadate garnet could be a potential photocatalyst driven by visible light. The effective photocatalytic activity was discussed on the basis of the special structural characteristic such as heavily distorted NiO{sub 6}, rich, activated optical centers with tunnel structure for high photocatalytic capacity, and discussed on the basis of the photoluminescence and the decay lifetime.

  4. Colloidal GdVO4:Eu3+@SiO2 nanocrystals for highly selective and sensitive detection of Cu2+ ions

    Science.gov (United States)

    Liang, Yanjie; Noh, Hyeon Mi; Park, Sung Heum; Choi, Byung Chun; Jeong, Jung Hyun

    2018-03-01

    Nowadays, in view of health and safety demands, the controlled design of selective and sensitive sensors for Cu2+ detection is of considerable importance. Therefore, we construct herein core-shell colloidal GdVO4:Eu3+@SiO2 nanocrystals (NCs) as optical sensor for the detection of Cu2+, which were synthesized by a facile hydrothermal reaction and encapsulated with a uniform layer of ultrathin silica through a sol-gel strategy. The NCs present strong red emission due to energy transfer from VO43- groups to Eu3+ when exciting with ultraviolet (UV) light. This intense red emission from Eu3+ could be selectively quenched in the presence of Cu2+ in comparison to other metal ions and the limit of detection is as low as 80 nM in aqueous solution. It is revealed that the spectral overlap between the emission band of NCs and the absorption of Cu2+ accounts for this intriguing luminescence behavior. The detection ability is highly reversible by the addition of ethylenediaminetetraacetic acid (EDTA) with the recovery of almost 100% of the original luminescence. The luminescence quenching and recovery processes can be performed repeatedly with good sensing ability. These remarkable performances allow the colloidal GdVO4:Eu3+@SiO2 NCs a promising fluorescence chemosensor for detecting Cu2+ ions in aqueous solution.

  5. Temperature-dependent Raman and ultraviolet photoelectron spectroscopy studies on phase transition behavior of VO{sub 2} films with M1 and M2 phases

    Energy Technology Data Exchange (ETDEWEB)

    Okimura, Kunio, E-mail: okifn@keyaki.cc.u-tokai.ac.jp; Hanis Azhan, Nurul [Graduate School of Engineering, Tokai University, Hiratsuka 259-1292 (Japan); Hajiri, Tetsuya [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Graduate School of Engineering, Nagoya University, Nagoya 464-8603 (Japan); Kimura, Shin-ichi [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871 (Japan); Zaghrioui, Mustapha; Sakai, Joe [GREMAN, UMR 7347 CNRS, Université François Rabelais de Tours, Parc de Grandmont, 37200 Tours (France)

    2014-04-21

    Structural and electronic phase transitions behavior of two polycrystalline VO{sub 2} films, one with pure M1 phase and the other with pure M2 phase at room temperature, were investigated by temperature-controlled Raman spectroscopy and ultraviolet photoelectron spectroscopy (UPS). We observed characteristic transient dynamics in which the Raman modes at 195 cm{sup −1} (V-V vibration) and 616 cm{sup −1} (V-O vibration) showed remarkable hardening along the temperature in M1 phase film, indicating the rearrangements of V-V pairs and VO{sub 6} octahedra. It was also shown that the M1 Raman mode frequency approached those of invariant M2 peaks before entering rutile phase. In UPS spectra with high energy resolution of 0.03 eV for the M2 phase film, narrower V{sub 3d} band was observed together with smaller gap compared to those of M1 phase film, supporting the nature of Mott insulator of M2 phase even in the polycrystalline film. Cooperative behavior of lattice rearrangements and electronic phase transition was suggested for M1 phase film.

  6. A low temperature study of antiferromagnetic YbVO{sub 4} by NMR thermally detected by nuclear orientation

    Energy Technology Data Exchange (ETDEWEB)

    Hutchison, W.D.; Prandolini, M.J.; Harker, S.J.; Chaplin, D.H. [Australian Defence Force Academy, School of Physics, University College, University of New South Wales (Australia); Bowden, G.J. [University of New South Wales, School of Physics (Australia); Bleaney, B. [Clarendon Laboratory (United Kingdom)

    1999-09-15

    NMR-TDNO results using an external {sup 60}CoCo (hcp) nuclear orientation thermometer for non-irradiated, single crystal, antiferromagnetic YbVO{sub 4} are compared with those obtained earlier with neutron activated samples using both internal and external {gamma}-ray thermometers. Detailed comparisons are made for the {sup 171}Yb (I=1/2, 14.31% abundant) stable nucleus. This strongly asymmetric, largely homogeneous, resonance lineshape was retained and is readily power broadened. Extremely broad, field-dependent homogeneous thermometric responses are observed in the expected frequency range for the quadrupolar stable nucleus {sup 173}Yb (I=5/2, 16.13% abundant) for both irradiated and non-irradiated samples.

  7. Equation of state and electronic properties of EuVO{sub 4}: A high-pressure experimental and computational study

    Energy Technology Data Exchange (ETDEWEB)

    Paszkowicz, Wojciech, E-mail: paszk@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw (Poland); López-Solano, Javier [Departamento de Física, MALTA Consolider Team, and Instituto de Materiales y Nanotecnología, Universidad de La Laguna, Tenerife 38205 (Spain); Izaña Atmospheric Research Center, Agencia Estatal de Meteorología (AEMET), Tenerife 38071 (Spain); Piszora, Paweł [Department of Materials Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań (Poland); Bojanowski, Bohdan [Institute of Physics, Szczecin University of Technology, Aleja Piastów 48, 70-310 Szczecin (Poland); Mujica, Andrés; Muñoz, Alfonso [Departamento de Física, MALTA Consolider Team, and Instituto de Materiales y Nanotecnología, Universidad de La Laguna, Tenerife 38205 (Spain); Cerenius, Yngve; Carlson, Stefan [MAX IV Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden); Dąbkowska, Hanna [Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)

    2015-11-05

    Structural, elastic and electronic properties of zircon-type and scheelite-type EuVO{sub 4} are investigated experimentally, by in-situ X-ray diffraction using synchrotron radiation, and theoretically within the framework of the density functional theory (DFT) and using the PBE prescription of the exchange-correlation energy. This study was motivated by the fact that the previous knowledge of the equation of state (EOS) was inconclusive due to a large scatter of the experimental and theoretical data, and by the lack of information on the dependence of the electronic structure with pressure. Under the applied experimental conditions, the zircon-type structure transforms to a scheelite-type one at 7.4(2) GPa, whereas the calculations yield a lower zircon–scheelite-coexistence pressure of 4.8 GPa. The experimental part of the study shows that the bulk modulus of the zircon-type phase is 119(3) GPa, perfectly supported by the DFT-calculated value, 119.1 GPa. The bulk modulus for the scheelite-type polymorph is higher, with an experimental value of 135(7) GPa and a theoretical one of 137.4 GPa. Compared to those reported in previous experimental and DFT or semiempirical works, the present values for the zircon-type phase are comparable or slightly lower, whereas those for the scheelite-type phase are markedly lower. Discrepancies between the present results and earlier reported ones are attributed to differences in details of the experimental method such as the pressure transmitting medium and the pressure calibration method. The calculated band structure confirms that zircon-type EuVO{sub 4} is a direct-gap semiconductor, with a bandgap energy at zero pressure of 2.88 eV. Under compression, the bandgap of the zircon phase increases with a coefficient of 10.3 meV/GPa up to the transition pressure, at which point the present calculations show a small drop of the bandgap energy. Above the transition pressure, the bandgap energy of the scheelite phase becomes almost

  8. Equation of state and electronic properties of EuVO4: A high-pressure experimental and computational study

    International Nuclear Information System (INIS)

    Paszkowicz, Wojciech; López-Solano, Javier; Piszora, Paweł; Bojanowski, Bohdan; Mujica, Andrés; Muñoz, Alfonso; Cerenius, Yngve; Carlson, Stefan; Dąbkowska, Hanna

    2015-01-01

    Structural, elastic and electronic properties of zircon-type and scheelite-type EuVO 4 are investigated experimentally, by in-situ X-ray diffraction using synchrotron radiation, and theoretically within the framework of the density functional theory (DFT) and using the PBE prescription of the exchange-correlation energy. This study was motivated by the fact that the previous knowledge of the equation of state (EOS) was inconclusive due to a large scatter of the experimental and theoretical data, and by the lack of information on the dependence of the electronic structure with pressure. Under the applied experimental conditions, the zircon-type structure transforms to a scheelite-type one at 7.4(2) GPa, whereas the calculations yield a lower zircon–scheelite-coexistence pressure of 4.8 GPa. The experimental part of the study shows that the bulk modulus of the zircon-type phase is 119(3) GPa, perfectly supported by the DFT-calculated value, 119.1 GPa. The bulk modulus for the scheelite-type polymorph is higher, with an experimental value of 135(7) GPa and a theoretical one of 137.4 GPa. Compared to those reported in previous experimental and DFT or semiempirical works, the present values for the zircon-type phase are comparable or slightly lower, whereas those for the scheelite-type phase are markedly lower. Discrepancies between the present results and earlier reported ones are attributed to differences in details of the experimental method such as the pressure transmitting medium and the pressure calibration method. The calculated band structure confirms that zircon-type EuVO 4 is a direct-gap semiconductor, with a bandgap energy at zero pressure of 2.88 eV. Under compression, the bandgap of the zircon phase increases with a coefficient of 10.3 meV/GPa up to the transition pressure, at which point the present calculations show a small drop of the bandgap energy. Above the transition pressure, the bandgap energy of the scheelite phase becomes almost constant, with

  9. Large modification in insulator-metal transition of VO{sub 2} films grown on Al{sub 2}O{sub 3} (001) by high energy ion irradiation in biased reactive sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Azhan, Nurul Hanis; Okimura, Kunio, E-mail: okifn@keyaki.cc.u-tokai.ac.jp [Graduate School of Science and Technology, Tokai University, Hiratsuka 259-1292 (Japan); Ohtsubo, Yoshiyuki; Kimura, Shin-ichi [Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871 (Japan); Zaghrioui, Mustapha; Sakai, Joe [GREMAN, UMR 7347 CNRS, Université François Rabelais de Tours, Parc de Grandmont, 37200 Tours (France)

    2016-02-07

    High energy ion irradiation in biased reactive sputtering enabled significant modification of insulator-metal transition (IMT) properties of VO{sub 2} films grown on Al{sub 2}O{sub 3} (001). Even at a high biasing voltage with mean ion energy of around 325 eV induced by the rf substrate biasing power of 40 W, VO{sub 2} film revealed low IMT temperature (T{sub IMT}) at 309 K (36 °C) together with nearly two orders magnitude of resistance change. Raman measurements from −193 °C evidenced that the monoclinic VO{sub 2} lattice begins to transform to rutile-tetragonal lattice near room temperature. Raman spectra showed the in-plane compressive stress in biased VO{sub 2} films, which results in shortening of V–V distance along a-axis of monoclinic structure, a{sub M}-axis (c{sub R}-axis) and thus lowering the T{sub IMT}. In respect to that matter, significant effects in shortening the in-plane axis were observed through transmission electron microscopy observations. V2p{sub 3/2} spectra from XPS measurements suggested that high energy ion irradiation also induced oxygen vacancies and resulted for an early transition onset and rather broader transition properties. Earlier band gap closing against the temperature in VO{sub 2} film with higher biasing power was also probed by ultraviolet photoelectron spectroscopy. Present results with significant modification of IMT behavior of films deposited at high-energy ion irradiation with T{sub IMT} near the room temperature could be a newly and effective approach to both exploring mechanisms of IMT and further applications of this material, due to the fixed deposition conditions and rather thicker VO{sub 2} films.

  10. Absorption band Q model for the earth

    International Nuclear Information System (INIS)

    Anderson, D.L.; Given, J.W.

    1982-01-01

    Body wave, surface wave, and normal mode data are used to place constraints on the frequency dependence of Q in the mantle. With a simple absorption band model it is possible to satisfy the shear sensitive data over a broad frequency range. The quality factor Q/sub s/(ω) is proportional to ω/sup α/ in the band and to ω and ω -1 at higher and lower frequencies, respectively, as appropriate for a relaxation mechanism with a spectrum of relaxation time. The parameters of the band are Q(min) = 80, α = 0.15, and width, 5 decades. The center of the band varies from 10 1 seconds in the upper mantle, to 1.6 x 10 3 seconds in the lower mantle. The shift of the band with depth is consistent with the expected effects of temperature, pressure and stress. High Q, regions of the mantle are attributed to a shift of the absorption band to longer periods. To satisfy the gravest fundamental spheroidal modes and the ScS data, the absorption band must shift back into the short-period seismic band at the base of the mantle. This may be due to a high temperature gradient or high shear stresses. A preliminary attempt is also made to specify bulk dissipation in the mantle and core. Specific features of the absorption band model are low Q in the body wave band at both the top and the base of the mantle, low Q for long-period body waves in the outer core, an inner core Q 2 that increases with period, and low Q/sub p//Q/sub s/ at short periods in the middle mantel. The short-period Q/sub s/ increases rapidly at 400 km and is relatively constant from this depth to 2400 km. The deformational Q of the earth at a period of 14 months is predicted to be 463

  11. VV and VO2 defects in silicon studied with hybrid density functional theory

    KAUST Repository

    Christopoulos, Stavros Richard G; Wang, Hao; Chroneos, Alexander I.; Londos, Charalampos A.; Sgourou, Efstratia N.; Schwingenschlö gl, Udo

    2014-01-01

    The formation of VO (A-center), VV and VO2 defects in irradiated Czochralski-grown silicon (Si) is of technological importance. Recent theoretical studies have examined the formation and charge states of the A-center in detail. Here we use density

  12. Influence of point defects on the performance of InVO4 photoanodes

    NARCIS (Netherlands)

    Van de Krol, R.; Ségalini, J.; Enache, C.S.

    2011-01-01

    The properties of thin film InVO4 photoanodes for water splitting have been studied. Compact films of InVO4 were prepared by spray pyrolysis and are found to be stable between pH 3 and 11. Although the indirect bandgap is 3.2 eV, a modest amount of visible light absorption is observed. The origin of

  13. VoIP interconnection ; between Internet, Cable, Mobile and Fixed Worlds

    NARCIS (Netherlands)

    Deventer, M.O. van; Keesmaat, I.

    2005-01-01

    Four worlds on their own that hardly interconnect; All use SIP, but differently - Internet world - Mobile world - Cable world - Fixed world - At most, only basic voice service will interoperate between those worlds In recent years, VoIP/multimedia services (VoIP: Voice over Internet Protocol) have

  14. VO2 nanostructures based chemiresistors for low power energy consumption hydrogen sensing

    CSIR Research Space (South Africa)

    Simo, A

    2014-05-01

    Full Text Available Mott-type VO(sub2) oxide nanobelts are demonstrated to be effective hydrogen gas sensors at room temperature. These nanobelts, synthesized by hydrothermal process and exhibiting the VO(sub2) (A) crystallographic phase, display room temperature H...

  15. Raman spectroscopic studies on CeVO4 at high pressures

    International Nuclear Information System (INIS)

    Rao, Rekha; Garg, Alka B.; Wani, B.N.

    2011-01-01

    Raman scattering investigations of CeVO 4 at high pressures is reported. Polycrystalline CeVO 4 was prepared by solid state reaction of CeO 2 and V 2 O 5 . High pressure Raman spectroscopic measurements were carried out as per experimental details given

  16. Epitaxial growth of higher transition-temperature VO2 films on AlN/Si

    Directory of Open Access Journals (Sweden)

    Tetiana Slusar

    2016-02-01

    Full Text Available We report the epitaxial growth and the mechanism of a higher temperature insulator-to-metal-transition (IMT of vanadium dioxide (VO2 thin films synthesized on aluminum nitride (AlN/Si (111 substrates by a pulsed-laser-deposition method; the IMT temperature is TIMT ≈ 350 K. X-ray diffractometer and high resolution transmission electron microscope data show that the epitaxial relationship of VO2 and AlN is VO2 (010 ‖ AlN (0001 with VO2 [101] ‖   AlN   [ 2 1 ̄ 1 ̄ 0 ] zone axes, which results in a substrate-induced tensile strain along the in-plane a and c axes of the insulating monoclinic VO2. This strain stabilizes the insulating phase of VO2 and raises TIMT for 10 K higher than TIMT single crystal ≈ 340 K in a bulk VO2 single crystal. Near TIMT, a resistance change of about four orders is observed in a thick film of ∼130 nm. The VO2/AlN/Si heterostructures are promising for the development of integrated IMT-Si technology, including thermal switchers, transistors, and other applications.

  17. Non-Exercise Estimation of VO[subscript 2]max Using the International Physical Activity Questionnaire

    Science.gov (United States)

    Schembre, Susan M.; Riebe, Deborah A.

    2011-01-01

    Non-exercise equations developed from self-reported physical activity can estimate maximal oxygen uptake (VO[subscript 2]max) as well as sub-maximal exercise testing. The International Physical Activity Questionnaire is the most widely used and validated self-report measure of physical activity. This study aimed to develop and test a VO[subscript…

  18. Body fat, abdominal fat and body fat distribution related to VO(2PEAK) in young children

    DEFF Research Database (Denmark)

    Dencker, Magnus; Wollmer, Per; Karlsson, Magnus K

    2011-01-01

    as a percentage of body mass (BF%) and body fat distribution as AFM/TBF. VO(2PEAK) was assessed by indirect calorimetry during maximal exercise test. Results. Significant relationships existed between body fat measurements and VO(2PEAK) in both boys and girls, with Pearson correlation coefficients for absolute...

  19. MAXIMAL OXIGEN UPTAKE (VO2 MAX AS THE INDICATOR OF PHYSICAL WORKING CAPACITY IN SPORTSMEN

    Directory of Open Access Journals (Sweden)

    Zvezdana Rajkovaca

    2005-12-01

    Full Text Available The term “aerobic capacity” represents the sum of aerobic metabolic processes in human organism. It is the basis of the physical working capacity. Value of the maximal oxygen uptake (VO2max is the best indicator for the aerobic capacity evaluation.The purpose of this study was to check the possibility of using VO2max as the indicator of aerobic capacity in sportsmen and to check differences in VO2max values in regard to non-sportsmen.The goals were: 1.Analyses of the VO2max values in sportsmen of various sports 2. Comparison of values of sportsmen with the values of non-sportsmen.This study included 67 sportsmen (rowers, football players and judoists and 28 nonsportsmen. VO2max was measured by using a direct method.The results obtained show statistically higher VO2max values in rowers (4,52 L/min - 55,8 mL/kg/min in regard to football players (4,2 L/min – 53,6 mL/kg/min, judoists (3,58 L/min - 47,2 mL/ kg/min and non-sportsmen (3,28 L/min – 42,3 mL/kg/min. Successful rowing requires high anaerobic capacity and, therefore, high VO2max.These results show higher values of VO2max in sportsmen in regard to non-sportsmen, which is the result of training only.

  20. Electron currents associated with an auroral band

    International Nuclear Information System (INIS)

    Spiger, R.J.; Anderson, H.R.

    1975-01-01

    Measurements of electron pitch angle distributions and energy spectra over a broad auroral band were used to calculate net electric current carried by auroral electrons in the vicinity of the band. The particle energy spectrometers were carried by a Nike-Tomahawk rocket launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972. Data are presented which indicate the existence of upward field-aligned currents of electrons in the energy range 0.5-20 keV. The spatial relationship of these currents to visual structure of the auroral arc and the characteristics of the electrons carrying the currents are discussed

  1. Electron currents associated with an auroral band

    Science.gov (United States)

    Spiger, R. J.; Anderson, H. R.

    1975-01-01

    Measurements of electron pitch angle distributions and energy spectra over a broad auroral band were used to calculate net electric current carried by auroral electrons in the vicinity of the band. The particle energy spectrometers were carried by a Nike-Tomahawk rocket launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972. Data are presented which indicate the existence of upward field-aligned currents of electrons in the energy range 0.5-20 keV. The spatial relationship of these currents to visual structure of the auroral arc and the characteristics of the electrons carrying the currents are discussed.

  2. VO2 /TiN Plasmonic Thermochromic Smart Coatings for Room-Temperature Applications.

    Science.gov (United States)

    Hao, Qi; Li, Wan; Xu, Huiyan; Wang, Jiawei; Yin, Yin; Wang, Huaiyu; Ma, Libo; Ma, Fei; Jiang, Xuchuan; Schmidt, Oliver G; Chu, Paul K

    2018-03-01

    Vanadium dioxide/titanium nitride (VO 2 /TiN) smart coatings are prepared by hybridizing thermochromic VO 2 with plasmonic TiN nanoparticles. The VO 2 /TiN coatings can control infrared (IR) radiation dynamically in accordance with the ambient temperature and illumination intensity. It blocks IR light under strong illumination at 28 °C but is IR transparent under weak irradiation conditions or at a low temperature of 20 °C. The VO 2 /TiN coatings exhibit a good integral visible transmittance of up to 51% and excellent IR switching efficiency of 48% at 2000 nm. These unique advantages make VO 2 /TiN promising as smart energy-saving windows. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Self-limiting filters for band-selective interferer rejection or cognitive receiver protection

    Science.gov (United States)

    Nordquist, Christopher; Scott, Sean Michael; Custer, Joyce Olsen; Leonhardt, Darin; Jordan, Tyler Scott; Rodenbeck, Christopher T.; Clem, Paul G.; Hunker, Jeff; Wolfley, Steven L.

    2017-03-07

    The present invention related to self-limiting filters, arrays of such filters, and methods thereof. In particular embodiments, the filters include a metal transition film (e.g., a VO.sub.2 film) capable of undergoing a phase transition that modifies the film's resistivity. Arrays of such filters could allow for band-selective interferer rejection, while permitting transmission of non-interferer signals.

  4. Self-limiting filters for band-selective interferer rejection or cognitive receiver protection

    Energy Technology Data Exchange (ETDEWEB)

    Nordquist, Christopher; Scott, Sean Michael; Custer, Joyce Olsen; Leonhardt, Darin; Jordan, Tyler Scott; Rodenbeck, Christopher T.; Clem, Paul G.; Hunker, Jeff; Wolfley, Steven L.

    2017-03-07

    The present invention related to self-limiting filters, arrays of such filters, and methods thereof. In particular embodiments, the filters include a metal transition film (e.g., a VO.sub.2 film) capable of undergoing a phase transition that modifies the film's resistivity. Arrays of such filters could allow for band-selective interferer rejection, while permitting transmission of non-interferer signals.

  5. Photocatalytic perfermance of sandwich-like BiVO{sub 4} sheets by microwave assisted synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Suqin, E-mail: liusuqin888@126.com [Department of Chemical engineering and Food Science, Hubei University of arts and science, Xiangyang 441053 (China); Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Xiangyang 441053 (China); Tang, Huiling; Zhou, Huan [Department of Chemical engineering and Food Science, Hubei University of arts and science, Xiangyang 441053 (China); Dai, Gaopeng, E-mail: dgp2000@126.com [Department of Chemical engineering and Food Science, Hubei University of arts and science, Xiangyang 441053 (China); Wang, Wanqiang [Department of Chemical engineering and Food Science, Hubei University of arts and science, Xiangyang 441053 (China)

    2017-01-01

    Graphical abstract: Sandwich-like BiVO{sub 4} sheets were successfully synthesized via a facile microwave-assisted method. The as-prepared samples exhibit a high activity for the degradation of methyl orange under visible light irradiation. - Highlights: • Sandwich-like BiVO{sub 4} sheets were synthesized by a facile microwave-assisted method. • The presence of PEG-10000 plays a critical role in the formation of BiVO{sub 4} sheets. • Ostwald ripening is the primary driving force for the formation of sandwich-like BiVO{sub 4}. • The sandwich-like BiVO{sub 4} sheets exhibit a high visible-light photocatalytic activity. - Abstract: Sandwich-like BiVO{sub 4} sheets were successfully synthesized in an aqueous solution containing bismuth nitrate, ammonium metavanadate and polyethylene glycol with a molecular weight of 10,000 (PEG-10000) using a facile microwave-assisted method. The as-prepared samples were characterized by scanning electron microscopy, N{sub 2} adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectroscopy. The results show that the presence of PEG-10000 plays a critical role in the formation of BiVO{sub 4} sheets, and Ostwald ripening is the primary driving force for the formation of sandwich-like structures. The sandwich-like BiVO{sub 4} sheets exhibit a high activity for the degradation of methyl orange under visible light irradiation (λ ≥ 420 nm). The enhancement of photocatalytic activity of sandwich-like BiVO{sub 4} sheets can be attributed to its large surface area over the irregular BiVO{sub 4} particles.

  6. Photocatalytic perfermance of sandwich-like BiVO_4 sheets by microwave assisted synthesis

    International Nuclear Information System (INIS)

    Liu, Suqin; Tang, Huiling; Zhou, Huan; Dai, Gaopeng; Wang, Wanqiang

    2017-01-01

    Graphical abstract: Sandwich-like BiVO_4 sheets were successfully synthesized via a facile microwave-assisted method. The as-prepared samples exhibit a high activity for the degradation of methyl orange under visible light irradiation. - Highlights: • Sandwich-like BiVO_4 sheets were synthesized by a facile microwave-assisted method. • The presence of PEG-10000 plays a critical role in the formation of BiVO_4 sheets. • Ostwald ripening is the primary driving force for the formation of sandwich-like BiVO_4. • The sandwich-like BiVO_4 sheets exhibit a high visible-light photocatalytic activity. - Abstract: Sandwich-like BiVO_4 sheets were successfully synthesized in an aqueous solution containing bismuth nitrate, ammonium metavanadate and polyethylene glycol with a molecular weight of 10,000 (PEG-10000) using a facile microwave-assisted method. The as-prepared samples were characterized by scanning electron microscopy, N_2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectroscopy. The results show that the presence of PEG-10000 plays a critical role in the formation of BiVO_4 sheets, and Ostwald ripening is the primary driving force for the formation of sandwich-like structures. The sandwich-like BiVO_4 sheets exhibit a high activity for the degradation of methyl orange under visible light irradiation (λ ≥ 420 nm). The enhancement of photocatalytic activity of sandwich-like BiVO_4 sheets can be attributed to its large surface area over the irregular BiVO_4 particles.

  7. High quality diesel fuels by VO-LSGO hydrotreatment

    Energy Technology Data Exchange (ETDEWEB)

    Stanica-Ezeanu, Dorin; Juganaru, Traian [Petroleum and Gas Univ. of Ploiesti (Romania)

    2013-06-01

    The aim of the paper is to obtain a high quality Diesel fuel by hydro-deoxigenation of vegetable oils (VO) mixed with a low sulfur gasoil (LSGO). The process is possible by using a bi-functional catalyst Ni-Mo supported by an activated Al{sub 2}O{sub 3} containing 2% Ultrastable Y-zeolite. The experimental conditions were: T =340 - 380 C, Pressure = 50 bar, LHSV = 1,5 h{sup -1}, H{sub 2}/Feed ratio = 15 mole H{sub 2} /mole liquid feed. The liquid product was separated in two fractions: a light distillate (similar to gasoline) and a heavy distillate (boiling point > 200 C) with very good characteristics for Diesel engines. The reaction chemistry is very complex, but the de-oxygenation process is decisive for the chemical structure of hydrocarbons from final product. Finally, a schema for the reaction mechanism is proposed. (orig.)

  8. Efficient High Power Ho,Tm:GdVO4 Laser

    International Nuclear Information System (INIS)

    Wang Yue-Zhu; Zhu Guo-Li; Ju You-Lun; Yao Bao-Quan

    2011-01-01

    We report a 22.3 W cw diode-pumped cryogenic Ho(0.5at.%),Tm(at.5%):GdVO 4 laser at a wavelength of 2.05 μm. It is pumped by two fiber-coupled laser diodes with a fiber core diameter of 0.4 mm, both of which provide 42 W pump power near 802 nm. A cw output power of 22.3 W was obtained at the pump power of 51.0 W, corresponding to an optical-to-optical conversion efficiency of 43.7% when the ratio of the pump beam to oscillating laser beam in the crystal was ∼1.33:1. The M 2 factor was found to be 2.0 under an output power of 16.5 W. (fundamental areas of phenomenology(including applications))

  9. A structured approach to VO reconfigurations through Policies

    Directory of Open Access Journals (Sweden)

    Stephan Reiff-Marganiec

    2012-04-01

    Full Text Available One of the strength of Virtual Organisations is their ability to dynamically and rapidly adapt in response to changing environmental conditions. Dynamic adaptability has been studied in other system areas as well and system management through policies has crystallized itself as a very prominent solution in system and network administration. However, these areas are often concerned with very low-level technical aspects. Previous work on the APPEL policy language has been aimed at dynamically adapting system behaviour to satisfy end-user demands and – as part of STPOWLA – APPEL was used to adapt workflow instances at runtime. In this paper we explore how the ideas of APPEL and STPOWLA can be extended from workflows to the wider scope of Virtual Organisations. We will use a Travel Booking VO as example.

  10. Chapter 35: Describing Data and Data Collections in the VO

    Science.gov (United States)

    Kent, B. R.; Hanisch, R. J.; Williams, R. D.

    The list of numbers: 19.22, 17.23, 18.11, 16.98, and 15.11, is of little intrinsic interest without information about the context in which they appear. For instance, are these daily closing stock prices for your favorite investment, or are they hourly photometric measurements of an increasingly bright quasar? The information needed to define this context is called metadata. Metadata are data about data. Astronomers are familiar with metadata through the headers of FITS files and the names and units associated with columns in a table or database. In the VO, metadata describe the contents of tables, images, and spectra, as well as aggregate collections of data (archives, surveys) and computational services. Moreover, VO metadata are constructed according to rules that avoid ambiguity and make it clear whether, in the example above, the stock prices are in dollars or euros, or the photometry is Johnson V or Sloan g. Organization of data is important in any scientific discipline. Equally crucial are the descriptions of that data: the organization publishing the data, its creator or the person making it available, what instruments were used, units assigned to measurement, calibration status, and data quality assessment. The Virtual Observatory metadata scheme not only applies to datasets, but to resources as well, including data archive facilities, searchable web forms, and online analysis and display tools. Since the scientific output flowing from large datasets depends greatly on how well the data are described, it is important for users to understand the basics of the metadata scheme in order to locate the data that they want and use it correctly. Metadata are the key to data discovery and data and service interoperability in the Virtual Observatory.

  11. Graphene/VO2 hybrid material for high performance electrochemical capacitor

    International Nuclear Information System (INIS)

    Deng, Lingjuan; Zhang, Gaini; Kang, Liping; Lei, Zhibin; Liu, Chunling; Liu, Zong-Huai

    2013-01-01

    Graphical abstract: Graphene/VO 2 hybrid materials are prepared by one-step simultaneous hydrothermal reduction technology. The prepared graphene (1.0)/VO 2 hybrid material shows a specific capacitances of 225 F g −1 in 0.5 mol L −1 K 2 SO 4 solution. Furthermore, an asymmetric electrochemical capacitor with graphene (1.0)/VO 2 as a positive electrode and graphene as a negative electrode is assembled, and it can work in a cell voltage of 1.7 V and show excellent capacitive property. - Highlights: • Graphene/VO 2 hybrid material has been prepared by one-step hydrothermal reduction. • Graphene/VO 2 hybrid material exhibits high specific capacitance. • An asymmetric capacitor working at 1.7 V in aqueous solution is assembled based on graphene/VO 2 electrode. • The asymmetric capacitor exhibits high energy density. - Abstract: Vanadium oxides have attracted significant attention for electrochemical capacitor because of their extensive multifunctional properties. In the present work, graphene/VO 2 (RG/VO 2 ) hybrid materials with different RG amounts are prepared in a mixture of ammonium vanadate, formic acid and graphite oxide (GO) nanosheets by one-step simultaneous hydrothermal reduction technology. The hydrothermal treatment makes the reduction of GO into RG and the formation of VO 2 particles with starfruit morphology. The starfruit-like VO 2 particles are uniformly embedded in the hole constructed by RG nanosheets, which makes the electrode–electrolyte contact better. A high specific capacitance of 225 F g −1 has been achieved for RG(1.0)/VO 2 electrode with RG content of 26 wt% in 0.5 mol L −1 K 2 SO 4 electrolyte. An asymmetrical electrochemical capacitor is assembled by using RG(1.0)/VO 2 as positive electrode and RG as negative electrode, and it can be reversibly charged–discharged at a cell voltage of 1.7 V in 0.5 mol L −1 K 2 SO 4 electrolyte. The asymmetrical capacitor can deliver an energy density of 22.8 Wh kg −1 at a power density

  12. Wide Band to ''Double Band'' upgrade

    International Nuclear Information System (INIS)

    Kasper, P.; Currier, R.; Garbincius, P.; Butler, J.

    1988-06-01

    The Wide Band beam currently uses electrons obtained from secondary photon conversions to produce the photon beam incident on the experimental targets. By transporting the positrons produced in these conversions as well as the electrons it is possible to almost double the number of photons delivered to the experiments per primary beam proton. 11 figs

  13. Detection of broad ultraviolet Fe II lines in the spectrum of NGC 1068

    International Nuclear Information System (INIS)

    Snijders, M.A.J.; Netzer, Hagai; Boksenberg, A.

    1986-01-01

    Ultraviolet observations of the nucleus of NGC 1068, obtained by the IUE over a period of 5 yr, are combined to give a high signal-to-noise spectrum of this source. The ultraviolet stellar continuum, obtained by comparison with ground-based data, is subtracted to show the nuclear non-stellar component. The resulting spectrum shows clearly the presence of strong broad FeII emission bands similar to those observed in many broad-line objects. Broad profiles are also seen in other strong emission lines. These observations confirm the recent discovery of an optical Seyfert type 1 spectrum in NGC 1068. (author)

  14. Broad Prize: Do the Successes Spread?

    Science.gov (United States)

    Samuels, Christina A.

    2011-01-01

    When the Broad Prize for Urban Education was created in 2002, billionaire philanthropist Eli Broad said he hoped the awards, in addition to rewarding high-performing school districts, would foster healthy competition; boost the prestige of urban education, long viewed as dysfunctional; and showcase best practices. Over the 10 years the prize has…

  15. 77 FR 50144 - Broad Stakeholder Survey

    Science.gov (United States)

    2012-08-20

    ... DEPARTMENT OF HOMELAND SECURITY [Docket No. DHS-2012-0042] Broad Stakeholder Survey AGENCY... Information Collection Request: 1670-NEW. SUMMARY: The Department of Homeland Security (DHS), National... (Pub. L. 104-13, 44 U.S.C. Chapter 35). NPPD is soliciting comments concerning the Broad Stakeholder...

  16. 76 FR 34087 - Broad Stakeholder Survey

    Science.gov (United States)

    2011-06-10

    ... DEPARTMENT OF HOMELAND SECURITY [Docket No. DHS-2011-0027] Broad Stakeholder Survey AGENCY... Information Collection Request: 1670-NEW. SUMMARY: The Department of Homeland Security (DHS), National... (Pub. L. 104-13, 44 U.S.C. Chapter 35). NPPD is soliciting comments concerning the Broad Stakeholder...

  17. Energy star compliant voice over internet protocol (VoIP) telecommunications network including energy star compliant VoIP devices

    Science.gov (United States)

    Kouchri, Farrokh Mohammadzadeh

    2012-11-06

    A Voice over Internet Protocol (VoIP) communications system, a method of managing a communications network in such a system and a program product therefore. The system/network includes an ENERGY STAR (E-star) aware softswitch and E-star compliant communications devices at system endpoints. The E-star aware softswitch allows E-star compliant communications devices to enter and remain in power saving mode. The E-star aware softswitch spools messages and forwards only selected messages (e.g., calls) to the devices in power saving mode. When the E-star compliant communications devices exit power saving mode, the E-star aware softswitch forwards spooled messages.

  18. Improved photoelectrochemical performance of BiVO4/MoO3 heterostructure thin films

    Science.gov (United States)

    Kodan, Nisha; Mehta, B. R.

    2018-05-01

    Bismuth vanadate (BiVO4) and Molybdenum trioxide (MoO3) thin films have been prepared by RF sputtering technique. BiVO4 thin films were deposited on indium doped tin oxide (In: SnO2; ITO) substrates at room temperature and 80W applied rf power. The prepared BiVO4 thin films were further annealed at 450°C for 2 hours in air to obtain crystalline monoclinic phase and successively coated with MoO3 thin films deposited at 150W rf power and 400°C for 30 minutes. The effect of coupling BiVO4 and MoO3 on the structural, optical and photoelectrochemical (PEC) properties have been studied. Optical studies reveal that coupling of BiVO4 and MoO3 results in improvement of optical absorption in visible region of solar spectrum. PEC study shows approximate 3-fold and 38-fold increment in photocurrent values of BiVO4/MoO3 (0.38 mA/cm2) heterostructure thin film as compared to MoO3 (0.15 mA/cm2) and BiVO4 (10 µA/cm2) thin films at applied bias of 1 V vs Ag/AgCl in 0.5 M Na2SO4 (pH=7) electrolyte.

  19. The VO-Dance web application at the IA2 data center

    Science.gov (United States)

    Molinaro, Marco; Knapic, Cristina; Smareglia, Riccardo

    2012-09-01

    Italian center for Astronomical Archives (IA2, http://ia2.oats.inaf.it) is a national infrastructure project of the Italian National Institute for Astrophysics (Istituto Nazionale di AstroFisica, INAF) that provides services for the astronomical community. Besides data hosting for the Large Binocular Telescope (LBT) Corporation, the Galileo National Telescope (Telescopio Nazionale Galileo, TNG) Consortium and other telescopes and instruments, IA2 offers proprietary and public data access through user portals (both developed and mirrored) and deploys resources complying the Virtual Observatory (VO) standards. Archiving systems and web interfaces are developed to be extremely flexible about adding new instruments from other telescopes. VO resources publishing, along with data access portals, implements the International Virtual Observatory Alliance (IVOA) protocols providing astronomers with new ways of analyzing data. Given the large variety of data flavours and IVOA standards, the need for tools to easily accomplish data ingestion and data publishing arises. This paper describes the VO-Dance tool, that IA2 started developing to address VO resources publishing in a dynamical way from already existent database tables or views. The tool consists in a Java web application, potentially DBMS and platform independent, that stores internally the services' metadata and information, exposes restful endpoints to accept VO queries for these services and dynamically translates calls to these endpoints to SQL queries coherent with the published table or view. In response to the call VO-Dance translates back the database answer in a VO compliant way.

  20. Active terahertz metamaterials based on the phase transition of VO{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, H., E-mail: heungsoo.kim@nrl.navy.mil [Materials Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 (United States); Charipar, N. [Materials Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 (United States); Breckenfeld, E. [National Research Council Fellow at the Naval Research Laboratory, Washington, DC 20375 (United States); Rosenberg, A. [NOVA Research, Inc., Alexandria, VA 22308 (United States); Piqué, A. [Materials Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2015-12-01

    Vanadium dioxide (VO{sub 2}) thin films were prepared on single crystal sapphire substrates by pulsed laser deposition. VO{sub 2} films exhibited a significant resistivity drop (> 10{sup 4} Ω-cm) and large optical transmittance change (> 60%) in the near-infrared region across their semiconductor-to-metal transition. Hybrid metamaterial devices designed for the THz frequency regime were fabricated by combining double split-ring resonators (SRRs) with phase changing VO{sub 2} films. By changing the conductivity of VO{sub 2} via temperature, the behavior of the SRR gap was adjusted from capacitive to resistive in order to modulate the THz beam transmission at their resonance frequencies. A modulation efficiency greater than 50% was achieved at the magnetic resonance frequencies (0.3 THz and 0.7 THz) in these hybrid SRR–VO{sub 2} metamaterial devices. - Highlights: • Pulsed laser deposition of phase changing VO{sub 2} thin films • Hybrid metamaterial devices composed of split-ring resonators and phase changing VO{sub 2} • Tunable THz transmission with a modulation efficiency over 50%.

  1. The influence of VO2(B nanobelts on thermal decomposition of ammonium perchlorate

    Directory of Open Access Journals (Sweden)

    Zhang Yifu

    2015-09-01

    Full Text Available The influence of vanadium dioxide VO2(B on thermal decomposition of ammonium perchlorate (AP has not been reported before. In this contribution, the effect of VO2(B nanobelts on the thermal decomposition of AP was investigated by the Thermo- Gravimetric Analysis and Differential Thermal Analysis (TG/DTA. VO2(B nanobelts were hydrothermally prepared using peroxovanadium (V complexes, ethanol and water as starting materials. The thermal decomposition temperatures of AP in the presence of I wt.%, 3 wt.% and 6 wt.% of as-obtained VO2VO2(B nanobelts had a great influence on the thermal decomposition temperature of AP Furthermore, the influence of the corresponding V2Os, which was obtained by thermal treatment of VO2(B nanobelts, on the thermal decomposition of AP was also investigated. The resufs showed that VO2(B nanobelts had a greater influence on the thermal decomposition temperature of AP than that of V2Os.

  2. Compare the phase transition properties of VO2 films from infrared to terahertz range

    Science.gov (United States)

    Liang, Shan; Shi, Qiwu; Huang, Wanxia; Peng, Bo; Mao, Zhenya; Zhu, Hongfu

    2018-06-01

    VO2 with reversible semiconductor-metal phase transition properties is particularly available for the application in smart opto-electrical devices. However, there are rare reports on comparing its phase transition properties at different ranges. In this study, the VO2 films are designed with the similar crystalline structure and stoichiometry, but different morphologies by inorganic and organic sol-gel methods, and their phase transition characteristics are compared both at infrared and terahertz range. The results indicate that the VO2 film prepared by inorganic sol-gel method shows more compact nanostructure. It results in larger resistivity change, infrared and terahertz switching ratio in the VO2 film. Moreover, it presents that the phase transition intensity of VO2 film in terahertz range is more sensitive to its microstructure. This work is helpful for understanding the susceptibility of terahertz switching properties of VO2 to its microstructure. And it can provide insights for the applications of VO2 in terahertz smart devices.

  3. BiVO4 Photoanode with Exposed (040) Facets for Enhanced Photoelectrochemical Performance

    Science.gov (United States)

    Xia, Ligang; Li, Jinhua; Bai, Jing; Li, Linsen; Chen, Shuai; Zhou, Baoxue

    2018-03-01

    A BiVO4 photoanode with exposed (040) facets was prepared to enhance its photoelectrochemical performance. The exposure of the (040) crystal planes of the BiVO4 film was induced by adding NaCl to the precursor solution. The as-prepared BiVO4 photoanode exhibits higher solar-light absorption and charge-separation efficiency compared to those of an anode prepared without adding NaCl. To our knowledge, the photocurrent density (1.26 mA cm-2 at 1.23 V vs. RHE) of as-prepared BiVO4 photoanode is the highest according to the reports for bare BiVO4 films under simulated AM1.5G solar light, and the incident photon-to-current conversion efficiency is above 35% at 400 nm. The photoelectrochemical (PEC) water-splitting performance was also dramatically improved with a hydrogen evolution rate of 9.11 μmol cm-2 h-1, which is five times compared with the BiVO4 photoanode prepared without NaCl (1.82 μmol cm-2 h-1). Intensity-modulated photocurrent spectroscopy and transient photocurrent measurements show a higher charge-carrier-transfer rate for this photoanode. These results demonstrate a promising approach for the development of high-performance BiVO4 photoanodes which can be used for efficient PEC water splitting and degradation of organic pollutants. [Figure not available: see fulltext.

  4. Spectroscopic and optical properties of the VO2+ ion doped TeO2-TiO2-ZnO-Nb2O5 glass system

    Science.gov (United States)

    Swapna; Upender, G.; Sreenivasulu, V.; Prasad, M.

    2016-04-01

    Studies such as optical absorption, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Electron paramagnetic resonance (EPR) spectroscopy and Differential scanning calorimetry (DSC) were carried out on VO2+ ion doped TeO2-TiO2-ZnO-Nb2O5 glass system. Raman and FTIR spectra of the glasses revealed the presence of [TeO3], [TeO4] and [NbO6] structural units in the glass network. The Urbach energy (Δ E), cut-off wavelength (λ c ), optical band gap ( E opt ), optical basicity (Λ) and electron polarizability ( α) of the glasses were determined from optical absorption studies. The density ( ρ), molar volume ( V m ), oxygen molar volume ( V o ) and refractive index ( n) were also measured. Spin-Hamiltonian parameters were calculated from the EPR studies. When Nb2O5 was increased at the expense of ZnO, the density, optical band gap and Urbach energy of the glasses increased, and the electronic polarizability and optical basicity decreased. The EPR spectra clearly showed that vanadium was in the glass as VO2+ and occupied octahedral sites with tetrahedral compression. Spin-Hamiltonian parameters g‖ and g⊥ decreased as Nb2O5 content increased in the glass. The glass transition temperature ( T g ) also increased with increasing Nb2O5 content in the glass.

  5. Design of Dual-Band Two-Branch-Line Couplers with Arbitrary Coupling Coefficients in Bands

    Directory of Open Access Journals (Sweden)

    I. Prudyus

    2014-12-01

    Full Text Available A new approach to design dual-band two-branch couplers with arbitrary coupling coefficients at two operating frequency bands is proposed in this article. The method is based on the usage of equivalent subcircuits input reactances of the even-mode and odd-mode excitations. The exact design formulas for three options of the dual-band coupler with different location and number of stubs are received. These formulas permit to obtain the different variants for each structure in order to select the physically realizable solution and can be used in broad range of frequency ratio and power division ratio. For verification, three different dual-band couplers, which are operating at 2.4/3.9 GHz with different coupling coefficients (one with 3/6 dB, and 10/3 dB two others are designed, simulated, fabricated and tested. The measured results are in good agreement with the simulated ones.

  6. Amniotic constriction bands

    Science.gov (United States)

    ... Supplements Videos & Tools Español You Are Here: Home → Medical Encyclopedia → Amniotic band sequence URL of this page: //medlineplus.gov/ency/ ... birth. The baby should be delivered in a medical center that has specialists experienced in caring for babies ... or partial loss of function of a body part. Congenital bands affecting large parts of the body cause the ...

  7. Validation of a ramp running protocol for determination of the true VO2max in mice

    Directory of Open Access Journals (Sweden)

    Mohamed Ayachi

    2016-08-01

    Full Text Available In the field of comparative physiology, it remains to be established whether the concept of VO2max is valid in the mouse and, if so, how this value can be accurately determined. In humans, VO2max is generally considered to correspond to the plateau observed when VO2 no longer rises with an increase in workload. In contrast, the concept of VO2peak tends to be used in murine studies. The objectives of the present study were to determine whether (i a continuous ramp protocol yielded a higher VO2peak than a stepwise, incremental protocol, and (ii the VO2peak measured in the ramp protocol corresponded to VO2max. The three protocols (based on intensity-controlled treadmill running until exhaustion with eight female FVB/N mice were performed in random order: (a an incremental protocol that begins at 10 m.min-1 speed and increases by 3 m.min-1 every 3 min. (b a ramp protocol with slow acceleration (3 m.min-2, and (c a ramp protocol with fast acceleration (12 m.min-2. Each protocol was performed with two slopes (0° and 25°. Hence, each mouse performed six exercise tests. We found that the value of VO2peak was protocol-dependent (p 8 mmol.l-1 and a respiratory exchange ratio >1. The total duration of the 3 m.min-2 0° ramp protocol was shorter than that of the incremental protocol. Taken as a whole, our results suggest that VO2max in the mouse is best determined by applying a ramp exercise protocol with slow acceleration and no treadmill slope.

  8. Efek minuman kombinasi maltodekstrin dan vitamin C terhadap VO2maks atlet sepak bola

    Directory of Open Access Journals (Sweden)

    Desty Ervira Puspaningtyas

    2015-07-01

    Full Text Available Background: VO2max is one of win determiner in a game. Athletes receive training to improve technical skills, tactical skills, and physiology functions that can support the improvement of VO2max, so they can improve their achievement. Maltodextrin and vitamin C can be used as an ingredient for beverage products which can improve VO2max. Objective: To assess the effect of maltodextrin and vitamin C combination drink on VO2max in soccer athletes. Method: Type of this study was experimental design with the same subject design. The study was conducted from January 2014 until June 2014 at Culinary Laboratory Universitas Gadjah Mada (UGM and Stadium of Universitas Negeri Yogyakarta (UNY. Subjects of this study were 14 soccer players coming from Universitas Negeri Yogyakarta (UNY. Every subject had to fulfill the inclusion and exclusion criteria, and the subjects were chosen by purposive sampling. In the first treatment, subjects received the combination drink―a drink with a composition 15% of maltodextrin and 250 mg of vitamin C in 300 mL. After 6 days washout period, subjects received 300 mL plain water. Drinks were given 30 minutes before VO2max test. VO2max test method used in this study was yo-yo intermittent recovery test level 2 (IR-2. Results: VO2max when subjects consumed maltodextrin and vitamin C combination drink was significantly lower than VO2max when athletes consumed plain water (p=0,0000. Conclusion: Maltodextrin and vitamin C combination drink was less effective than plain water to enhance VO2max.

  9. Annealing Effect on the Photoelectrochemical Properties of BiVO_4 Thin Film Electrodes

    International Nuclear Information System (INIS)

    Siti Nur Farhana Mohd Nasir; Mohd Asri Mat Teridi; Mehdi Ebadi; Sagu, J.S.

    2015-01-01

    Monoclinic bismuth vanadate (BiVO_4) thin film electrodes were fabricated on fluorine-doped tin oxide via aerosol-assisted chemical vapour deposition (AACVD). Annealing and without annealing effect of thin films were analysed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet-visible spectrophotometry (UV-Vis) and current voltage measurement. All BiVO_4 thin films showed an anodic photocurrent. The sample of BiVO_4 annealed at 400 degree Celsius exhibited the highest photocurrent density of 0.44 mAcm"-"2 vs. Ag/ AgCl at 1.23 V. (author)

  10. TRANSPORTE DE VOZ (VoIP SOBRE REDES IPv4 e IPv6

    Directory of Open Access Journals (Sweden)

    Fausto Alexander Gamboa

    2012-05-01

    Full Text Available El presente artículo tiene como finalidad evaluar el comportamiento de la VoIP en redes IPv6 y compararlo con IPv4, de igual manera presentar las arquitecturas que la soportan. Con el fin de que los resultados sean los más cercanos a la realidad, el artículo no solo se soporta en simulaciones si no en implementaciones reales. Dentro de las conclusiones más sobresalientes se encontró que la VoIP6 presenta mejor rendimiento ante el Jitter y el retardo que VoIPv4.

  11. Thin-film VO2 submillimeter-wave modulators and polarizers

    International Nuclear Information System (INIS)

    Fan, J.C.C.; Fetterman, H.R.; Bachner, F.J.; Zavracky, P.M.; Parker, C.D.

    1977-01-01

    Submillimeter-wave modulators and switchable polarizers have been fabricated from VO 2 thin films deposited on sapphire substrates. By passing electric current pulses through elements made from these films, the films can be thermally cycled through the insulator-to-metal transition that occurs in VO 2 at about 65 degreeC. In the insulating state, the films are found to have negligible effect on the transmission at submillimeter wavelengths, while above the phase transition the transmission is strongly reduced by the free-electron effects characteristic of a metal. Other possible applications of such switchable VO 2 elements include variable bandpass filters and diffraction grating beam-steering devices

  12. Analisis Unjuk Kerja Aplikasi VoIP Call Android di Jaringan MANET [Performance Analysis of VoIP Call Application Android in MANET (Mobile Ad Hoc Network

    Directory of Open Access Journals (Sweden)

    Ryan Ari Setyawan

    2015-06-01

    Full Text Available Penelitian ini bertujuan menganalisis kinerja aplikasi  VoIP call android di jaringan MANET (mobile ad hoc network.  Hasil pengujian menunjukan bahwa aplikasi VoIP call android dapat digunakan di jaringan MANET. Delay yang dihasilkan paling besar di pengujian indoor dengan jarak 11-15 meter yakni sebesar 0,014624811 seconds. Packet loss yang dihasilkan pada range 1%-2% sedangkan standar packet loss yang ditetapkan oleh CISCO untuk layanan aplikasi VoIP adalah < 5%. Jitter yang dihasilkan yakni antara 0,01-0,06 seconds sedangkan standar yang ditetapkan oleh CISCO adalah ≤ 30 ms atau 0,03 seconds. Throughput yang dihasilkan pada proses pengujian yakni antar 161 kbps-481 kbps. *****This study aims to analyze the performance of VOIP call android application in the MANET (mobile ad hoc network. The results showed that VoIP applications could be implemented in MANET network. The highest  delay is produced in indoor testing  with distance of 11-15 meters,  which is equal to 0.014624811 seconds. Packet loss is generated in the range of 1% -2%, while packet loss standards set by Cisco for VoIP application services are <5%. The jitter is between 0.01 to 0.06 seconds, while the standard set by CISCO is ≤ 30 ms or 0.03 seconds. Throughput generated in the testing process is between 161 kbps-481 kbps.

  13. Ultrafast carrier dynamics in band edge and broad deep defect emission ZnSe nanowires

    Science.gov (United States)

    Othonos, Andreas; Lioudakis, Emmanouil; Philipose, U.; Ruda, Harry E.

    2007-12-01

    Ultrafast carrier dynamics of ZnSe nanowires grown under different growth conditions have been studied. Transient absorption measurements reveal the dependence of the competing effects of state filling and photoinduced absorption on the probed energy states. The relaxation of the photogenerated carriers occupying defect states in the stoichiometric and Se-rich samples are single exponentials with time constants of 3-4ps. State filling is the main contribution for probe energies below 1.85eV in the Zn-rich grown sample. This ultrafast carrier dynamics study provides an important insight into the role that intrinsic point defects play in the observed photoluminescence from ZnSe nanowires.

  14. Background Noise of the Aldeia da Serra Region (Portugal) from a temporary broad band network

    Science.gov (United States)

    Wachilala, Piedade; Borges, José; Caldeira, Bento; Bezzeghoud, Mourad

    2017-04-01

    In this study, we analyse seismic background noise to assess the effect of noise based on the detectability of a temporary network constituted by DOCTAR (Deep Ocean Test Array), who have been deployed in a period between 2011 and 2012 in Portugal mainland, and the Évora permanent seismic station. This network is constituted by 14 digital broadband stations (14 CMG-3ESP and one STS2 sensors) with a flat response between the 60 sec to 50 Hz, 24-bit and 120s to 60Hz respectively. The temporary network was operated in continuous recording mode (three-components) in a region located in the north of the region of Évora, within a radius of about 30 km around the village of Aldeia da Serra, region in which there is an important seismic activity in the context of Portugal mainland. We calculated power spectral densities of background noise for each station/component and compare them with high-noise model and low-noise model of Peterson (1993). We consider different for day and night local and for different periods of the year. Power spectral density estimates show moderate noise levels with all stations falling within the high and low bounds of Peterson (1993). Considering the results of the noise, we estimate the detection limit of each station and consequently the detectability of the network. From this information and taking in attention the events recorded during the period of DOCTAR operation we analyse the improvement promoted by this temporary network regarding the existent seismic networks to the local seismicity study. This work was partially supported by COMPETE 2020 program (POCI-01-0145-FEDER-007690 project). We acknowledge GFZ Potsdam for providing part of the data used in this study.

  15. Beam-based model of broad-band impedance of the Diamond Light Source

    Science.gov (United States)

    Smaluk, Victor; Martin, Ian; Fielder, Richard; Bartolini, Riccardo

    2015-06-01

    In an electron storage ring, the interaction between a single-bunch beam and a vacuum chamber impedance affects the beam parameters, which can be measured rather precisely. So we can develop beam-based numerical models of longitudinal and transverse impedances. At the Diamond Light Source (DLS) to get the model parameters, a set of measured data has been used including current-dependent shift of betatron tunes and synchronous phase, chromatic damping rates, and bunch lengthening. A matlab code for multiparticle tracking has been developed. The tracking results and analytical estimations are quite consistent with the measured data. Since Diamond has the shortest natural bunch length among all light sources in standard operation, the studies of collective effects with short bunches are relevant to many facilities including next generation of light sources.

  16. Beam-based model of broad-band impedance of the Diamond Light Source

    Directory of Open Access Journals (Sweden)

    Victor Smaluk

    2015-06-01

    Full Text Available In an electron storage ring, the interaction between a single-bunch beam and a vacuum chamber impedance affects the beam parameters, which can be measured rather precisely. So we can develop beam-based numerical models of longitudinal and transverse impedances. At the Diamond Light Source (DLS to get the model parameters, a set of measured data has been used including current-dependent shift of betatron tunes and synchronous phase, chromatic damping rates, and bunch lengthening. A matlab code for multiparticle tracking has been developed. The tracking results and analytical estimations are quite consistent with the measured data. Since Diamond has the shortest natural bunch length among all light sources in standard operation, the studies of collective effects with short bunches are relevant to many facilities including next generation of light sources.

  17. Teleseismic SKS splitting beneath East Antarctica using broad-band stations around Soya Coast

    Science.gov (United States)

    Usui, Y.; Kanao, M.

    2006-12-01

    We observed shear wave splitting of SKS waves from digital seismographs that are recorded at 5 stations around Soya Coast in the Lutzow-Holm Bay, East Antarctica. Their recording systems are composed of a three-component broadband seismometer (CMG-40T), a digital recording unit and a solar power battery supply. The events used were selected from 1999 to 2004 and phase arrival times were calculated using the IASPEI91 earth model (Kennet, 1995). In general, we chose the data from earthquakes with m>6.0 and a distance range 85° < Δ < 130° for the most prominent SKS waves We used the methods of Silver and Chan (1991) for the inversion of anisotropy parameters and estimated the splitting parameters φ (fast polarization direction) and δt (delay time between split waves) assuming a single layer of hexagonal symmetry with a horizontal symmetry axis. The weighted averages of all splitting parameters (φ, δt) for each station are AKR (30±4, 1.30±0.2), LNG (58±6, 1.27±0.2), SKL (67±10, 0.94±0.2), SKV (40±6, 1.28±0.3) and TOT (52±8, 1.26±0.3), where the weights are inversely proportional to the standard deviations for each solution. As compared to typical delay times of SKS waves which show 1.2s (Silver and Chan 1991; Vinnik et al., 1992), the result shows generally the same value. In previous study, Kubo and Hiramatsu (1998) estimate the splitting parameter for Syowa station (SYO), where is located near our using stations in East Antarctica, and the results are (49±3, 0.70±0.1). Although it is consistent with our results for fast polarization direction, δt for our results are large relatively to those of SYO. The difference may be due to either different incident angle or more complex anisotropic structure. We found that fast polarization direction is systematically parallel to coast line in the Lutzow-Holm Bay, East Antarctica, which is consistent with NE-SW paleo compressional stress. The absolute plate motion based on the HS2-NUVEL1 (Gripp and Gordon, 1990), that may reflect the present horizontal mantle flow, shows the direction of N120°E and velocity of 1cm/yr in this study region. Since it doesn't coincide with fast polarization direction (the difference is about 50°~90°), we conclude that the mechanism of observed anisotropy is lattice preferred orientation of olivine along the mantle flow which caused NE-SW paleo compressional stress. In future works, we will accomplish the analysis assumed more complex anisotropy systems, such as a two layer model of azimuthal anisotropy, because we could find there is the possibility of azimuthal variations of the splitting parameters in a few station.

  18. Optimized Variational 1D Boussinesq Modelling for broad-band waves over flat bottom

    NARCIS (Netherlands)

    Lakhturov, I.; Adytia, D.; van Groesen, Embrecht W.C.

    The Variational Boussinesq Model (VBM) for waves above a layer of ideal fluid conserves mass, momentum, energy, and has decreased dimensionality compared to the full problem. It is derived from the Hamiltonian formulation via an approximation of the kinetic energy, and can provide approximate

  19. Spectral and Broad Band Ultraviolet Measurements in Valencia (Spain): A Preliminary Comparison

    International Nuclear Information System (INIS)

    Tena, F.; Marin, M.J.; Martinez-Lozano, J.A.; Utrillas, M.P.; Gomez, J.L.

    2000-01-01

    The Solar Radiation Group of the University of Valencia, in collaboration with the National Institute of Meteorology (INM), recently began a database of erythemal UV irradiance measurements. Such measurements are obtained by a YES UVB-1 pyranometer (280-330 nm) that measures continuously, integrates the values and stores them in a database. The measured values are being compared with those obtained by the integration of the data registered by an Optronic OL 754 spectroradiometer (250-800 nm) considering clear days and different solar zenith angles. For the present study only the data corresponding to the summer (1999) are being considered because these are the days of the year with the higher erythemal values and also the season when people enjoy sunbathing. The results are used to deduce the ultraviolet index (UVI) related to the erythemal doses and the sunburn time. (author)

  20. Broad Band Observations of Gravitationally Lensed Blazar during a Gamma-Ray Outburst

    Directory of Open Access Journals (Sweden)

    Julian Sitarek

    2016-09-01

    Full Text Available QSO B0218+357 is a gravitationally lensed blazar located at a cosmological redshift of 0.944. In July 2014 a GeV flare was observed by Fermi-LAT, triggering follow-up observations with the MAGIC telescopes at energies above 100 GeV. The MAGIC observations at the expected time of arrival of the trailing component resulted in the first detection of QSO B0218+357 in Very-High-Energy (VHE, >100 GeV gamma rays. We report here the observed multiwavelength emission during the 2014 flare.

  1. Spectral and Broad Band Ultraviolet Measurements in Valencia (Spain): A Preliminary Comparison

    Energy Technology Data Exchange (ETDEWEB)

    Tena, F.; Marin, M.J.; Martinez-Lozano, J.A.; Utrillas, M.P.; Gomez, J.L

    2000-07-01

    The Solar Radiation Group of the University of Valencia, in collaboration with the National Institute of Meteorology (INM), recently began a database of erythemal UV irradiance measurements. Such measurements are obtained by a YES UVB-1 pyranometer (280-330 nm) that measures continuously, integrates the values and stores them in a database. The measured values are being compared with those obtained by the integration of the data registered by an Optronic OL 754 spectroradiometer (250-800 nm) considering clear days and different solar zenith angles. For the present study only the data corresponding to the summer (1999) are being considered because these are the days of the year with the higher erythemal values and also the season when people enjoy sunbathing. The results are used to deduce the ultraviolet index (UVI) related to the erythemal doses and the sunburn time. (author)

  2. Installation of a very broad band borehole seismic station in Ferrara (Emilia)

    OpenAIRE

    Pesaresi, Damiano; Dall'Olio, Lorella; Rovelli, Antonio; Romanelli, Marco; Barnaba, Carla; Abu Zeid, Nasser

    2012-01-01

    The Istituto Nazionale di Geofisica e Vulcanologia (INGV) is the Italian agency devoted to monitor in real time the seismicity on the Italian territory. The seismicity in Italy is of course variable in time and space, being also very much dependant on local noise conditions. Specifically, monitoring seismicity in an alluvial basin like the Po one is a challenge, due to consistent site effects induced by soft alluvial deposits and bad coupling with the deep bedrock (Steidl et al., 1996). This...

  3. Coaxial Sensors For Broad-Band Complex Permittivity Measurements of Petroleum Fluids

    Energy Technology Data Exchange (ETDEWEB)

    Folgeroe, K.

    1996-12-31

    This doctoral thesis verifies that dielectric spectroscopy and microwave permittivity measurements can be used to characterize petroleum liquids. It concentrates on developing sensors for three potential industrial applications: quality characterization of crude oil and petroleum fractions, monitoring of gas-hydrate formation in water-in-oil emulsions, and determination of water-content in thin liquid layers. The development of a permittivity measurement system for crude oil and petroleum fractions is described. As black oils have low dielectric constant and loss, the system must be very sensitive in order to measure the dielectric spectra and to distinguish oils of different permittivity. Such a system was achieved by combining impedance and scattering parameter measurements with appropriate permittivity calculation methods. The frequency range from 10 kHz to 6 GHz was found convenient for observing the main dispersion of the oils. All the oils had dielectric constants between 2.1 and 2.9 and dielectric loss below 0.01. The oils studied were samples of the feedstock for the cracker and coke processes at a petroleum refinery. This verifies that dielectric spectroscopy is a potential technique for on-line quality monitoring of the feedstock at petroleum refineries. Gas hydrates may cause major problems like clogging of pipelines. Dielectric spectroscopy is proposed as a means of monitoring the formation of gas hydrates in emulsions. It is found that open-ended coaxial probes fulfill the sensitivity requirements for such sensors. 312 refs., 87 figs., 20 tabs.

  4. Broad-band properties of the CfA Seyfert Galaxies. II - Infrared to millimeter properties

    Science.gov (United States)

    Edelson, R. A.; Malkan, M. A.; Rieke, G. H.

    1987-01-01

    IR and mm observations of the 48 Seyfert 1 and 2 galaxies (SG1s and SG2s) of the CfA sample (Huchra and Berg, 1987) are reported. Data obtained (1) in the NIR using the 1.55-m reflector at Stewart Observatory and the 3-m IRTF during 1984-1986, (2) in the FIR with IRAS, and (3) at 1.3 mm using the 12-m NRAO telescope at KPNO in June 1984 are presented in extensive tables and graphs and characterized in detail. None of the objects was detected at 1.3 mm, and the IR spectra of the SG2s are found to be significantly steeper (indicating thermal emission) than those of SG1s and QSOs (nonthermal emission). Turnover in the IR emission below 100 microns (in half of the objects detected at three or more IRAS wavelengths) is shown to be consistent with an accretion disk in dust-free SG1s and with unusually warm (35-65 K) dust in SG2s. It is inferred that a 60-100-micron cool excess is masking turnover in the other SGs, so that a general association of SG nuclei with strong star formation can be confirmed.

  5. Detecting Lamb waves with broad-band acousto-ultrasonic signals in composite structures

    Science.gov (United States)

    Kautz, Harold E.

    1992-01-01

    Lamb waves can be produced and detected in ceramic matrix composites (CMC) and metal matrix composites (MMC) plates using the acousto-ultrasonic configuration employing broadband transducers. Experimental dispersion curves of lowest symmetric and antisymmetric modes behave in a manner analogous to the graphite/polymer theoretical curves. In this study a basis has been established for analyzing Lamb wave velocities for characterizing composite plates. Lamb wave dispersion curves and group velocities were correlated with variations in axial stiffness and shear stiffness in MMC and CMC. For CMC, interfacial shear strength was also correlated with the first antisymmetric Lamb mode.

  6. Broad-band dielectric spectroscopy of tetragonal PLZT x/40/60

    Czech Academy of Sciences Publication Activity Database

    Buixaderas, Elena; Noujni, Dmitri; Veljko, Sergiy; Savinov, Maxim; Vaněk, Přemysl; Kamba, Stanislav; Petzelt, Jan; Kosec, M.

    2006-01-01

    Roč. 79, 6-7 (2006), s. 415-426 ISSN 0141-1594 R&D Projects: GA ČR(CZ) GA202/06/0403; GA ČR GA202/04/0993 Institutional research plan: CEZ:AV0Z10100520 Keywords : ferroelectrics * relaxors * dielectric behaviour * lattice dynamics dielectric spectroscopy * IR spectroscopy * THz spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.830, year: 2006

  7. New solar broad-band hard X-ray spectrometer: first results

    Czech Academy of Sciences Publication Activity Database

    Fárník, František; Garcia, H.; Karlický, Marian

    2001-01-01

    Roč. 201, č. 2 (2001), s. 357-372 ISSN 0038-0938 R&D Projects: GA ČR GA205/00/1726; GA AV ČR IAA3003003; GA AV ČR IBS1003006; GA AV ČR KSK2043105; GA AV ČR IAA303108 Institutional research plan: CEZ:AV0Z1003909 Keywords : X-ray * spectrometer * solar flare * radio emission Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.103, year: 2001

  8. Broad-band anti-reflection coupler for a : Si thin-film solar cell

    International Nuclear Information System (INIS)

    Lo, S.-S.; Chen, C.-C.; Garwe, Frank; Pertch, Thomas

    2007-01-01

    This work numerically demonstrates a new anti-reflection coupler (ARC) with high coupling efficiency in a Si substrate solar cell. The ARC in which the grating is integrated on a glass encapsulation and a three-layer impedance match layer is proposed. A coupling efficiency of 90% is obtained at wavelengths between 350 and 1200 nm in the TE and TM modes when the incident angle is less than 30 0 . In comparison with a 1μm absorber layer, the integrated absorption of an a-Si thin-film solar cell without a new ARC is doubled, at long wavelengths (750 nm ≤ λ ≤ 1200 nm), as calculated by FDTD method

  9. Broad-band Gausssian noise is most effective in improving motor performance and is most pleasant

    Directory of Open Access Journals (Sweden)

    Carlos eTrenado

    2014-02-01

    Full Text Available Modern attempts to improve human performance focus on stochastic resonance (SR. SR is a phenomenon in nonlinear systems characterized by a response increase of the system induced by a particular level of input noise. Recently, we reported that an optimum level of 0-15 Hz Gaussian noise applied to the human index finger improved static isometric force compensation. A possible explanation was a better sensorimotor integration caused by increase in sensitivity of peripheral receptors and/or of internal SR. The present study in 10 subjects compares SR effects in the performance of the same motor task and on pleasantness, by applying three Gaussian noises chosen on the sensitivity of the fingertip receptors (0-15 Hz mostly for Merkel receptors, 250-300 Hz for Pacini corpuscules and 0-300 Hz for all. We document that only the 0-300 Hz noise induced SR effect during the transitory phase of the task. In contrast, the motor performance was improved during the stationary phase for all three noise frequency bandwidths. This improvement was stronger for 0-300 Hz and 250-300 Hz than for 0-15 Hz noise. Further, we found higher degree of pleasantness for 0-300 Hz and 250-300 Hz noise bandwidths than for 0-15 Hz. Thus, we show that the most appropriate Gaussian noise that could be used in haptic gloves is the 0-300 Hz, as it improved motor performance during both stationary and transitory phases. In addition, this noise had the highest degree of pleasantness and thus reveals that the glabrous skin can also forward pleasant sensations. These new findings provide worthy information for neurorehabilitation.

  10. Realization of a broad band neutron spin filter with compressed, polarized 3He gas

    International Nuclear Information System (INIS)

    Surkau, R.; Otten, E.W.; Steiner, M.; Tasset, F.; Trautmann, N.

    1997-01-01

    The strongly spin dependent absorption of neutrons in nuclear spin polarized 3 -2pt vector He opens the possibility to polarize beams of thermal and epithermal neutrons. An effective 3 He neutron spin filter (NSF) requires high 3 He nuclear polarization as well as a filter thickness corresponding to a gas amount of the order of 1 bar l. We realized such a filter using direct optical pumping of metastable 3 He * atoms in a 3 He plasma at 1 mbar. Metastable exchange scattering transfers the angular momentum to the whole ensemble of 3 He atoms. At present 3 x 10 18 3 He-atoms/s are polarized up to 64%. Subsequent polarization preserving compression by a two stage compressor system enables to prepare NSF cells of about 300 cm 3 volume with 3 bar of polarized 3 He within 2 h. 3 He polarizations up to 53% were measured in a cell with a filter length of about 15 cm. By this cell a thermal neutron beam from the Mainz TRIGA reactor was polarized. A wavelength selective polarization analysis by means of Bragg scattering revealed a neutron polarization of 84% at a total transmission of 12% for a neutron wavelength of 1 A. (orig.)

  11. Statistical analysis concerning broad band measurements of radio frequency electromagnetic fields

    International Nuclear Information System (INIS)

    Lubritto, C.; D'Onofrio, A.; Palmieri, A.; Sabbarese, C.; Terrasi, F.; Petraglia, A.; Pinto, G.; Romano, G.

    2002-01-01

    Electromagnetic fields (EMF) actually represents one of the most common and the fastest growing environmental factors influencing human life. The care of the public community for the so called electromagnetic pollution is continually increasing because of the booming use of mobile phones over the past decade in business, commerce and social life. Moreover the incumbent third generation mobile systems will increase the use of all communication technologies, including fax, e-mail and Internet accesses. This extensive use has been accompanied by public debate about possible adverse effects on human health. In particular there are concerns related to the emission of radiofrequency radiation from the cellular phones and from base stations. Due to this very fast and wide development of cellular telephony more and more data are becoming available from monitoring, measuring and predicting electromagnetic fields as requested by the laws in order to get the authorization to install antenna and apparatus size of the database is such consistent that statistics have been carried out with a high degree of confidence: in particular in this paper statistical analysis has been focussed on data collected during about 1000 check measurements of electromagnetic field values performed by a private company in 167 different located in almost all Italian regions. One of the aim set consist in to find the most critical factors for the measurements, besides the field conformation: position in space, logistic conditions, technology employed, distance from the centre of the antenna, etc. The first step of the study deals with the building of a database fulfilled with information relevant to the measurements. In a second step, by means of appropriate statistical procedures, the electromagnetic field is evaluated and then the different measurement procedures are critically reviewed

  12. A compact planar multi-broad band monopole antenna for mobile devices

    Science.gov (United States)

    Zhong, Xiaoqing; Yao, Bin; Zheng, Qinhong; Yang, Jikong; Cao, Xiangqi

    2015-10-01

    A Multiple-frequency broadband planar monopole antenna is proposed in this Paper. The antenna is stimulated and numerically optimized by HFSS13.0 (High Frequency Structure Simulator). The size of it is 39mm×22mm×1.7mm. The antenna resonates at many frequencies. The parameter S112G(DCS1800 and PCS1900), 3G(UMTS), 4G(LTE2300 and LTE2500), ISM, WLAN. It is quiet appropriate for the present ultra-thin smart phones

  13. Chapter 18: Web-based Tools - NED VO Services

    Science.gov (United States)

    Mazzarella, J. M.; NED Team

    The NASA/IPAC Extragalactic Database (NED) is a thematic, web-based research facility in widespread use by scientists, educators, space missions, and observatory operations for observation planning, data analysis, discovery, and publication of research about objects beyond our Milky Way galaxy. NED is a portal into a systematic fusion of data from hundreds of sky surveys and tens of thousands of research publications. The contents and services span the entire electromagnetic spectrum from gamma rays through radio frequencies, and are continuously updated to reflect the current literature and releases of large-scale sky survey catalogs. NED has been on the Internet since 1990, growing in content, automation and services with the evolution of information technology. NED is the world's largest database of crossidentified extragalactic objects. As of December 2006, the system contains approximately 10 million objects and 15 million multi-wavelength cross-IDs. Over 4 thousand catalogs and published lists covering the entire electromagnetic spectrum have had their objects cross-identified or associated, with fundamental data parameters federated for convenient queries and retrieval. This chapter describes the interoperability of NED services with other components of the Virtual Observatory (VO). Section 1 is a brief overview of the primary NED web services. Section 2 provides a tutorial for using NED services currently available through the NVO Registry. The "name resolver" provides VO portals and related internet services with celestial coordinates for objects specified by catalog identifier (name); any alias can be queried because this service is based on the source cross-IDs established by NED. All major services have been updated to provide output in VOTable (XML) format that can be accessed directly from the NED web interface or using the NVO registry. These include access to images via SIAP, Cone- Search queries, and services providing fundamental, multi

  14. A Compact Printed Quadruple Band-Notched UWB Antenna

    Directory of Open Access Journals (Sweden)

    Xiaoyin Li

    2013-01-01

    Full Text Available A novel compact coplanar waveguide- (CPW- fed ultrawideband (UWB printed planar volcano-smoke antenna (PVSA with four band-notches for various wireless applications is proposed and demonstrated. The low-profile antenna consists of a C-shaped parasitic strip to generate a notched band at 8.01~8.55 GHz for the ITU band, two C-shaped slots, and an inverted U-shaped slot etched in the radiator patch to create three notched bands at 5.15~5.35 GHz, 5.75~5.85 GHz, and 7.25~7.75 GHz for filtering the WLAN and X-band satellite signals. Simulated and measured results both confirm that the proposed antenna has a broad bandwidth of 3.1~12 GHz with VSWR < 2 and good omnidirectional radiation patterns with four notched-bands.

  15. Chapter 29: Using an Existing Environment in the VO (IDL)

    Science.gov (United States)

    Miller, C. J.

    The local environment of a Brightest Cluster Galaxy (BCG) can provide insight into the (still not understood) formation process of the BCG itself. BCGs are the most massive galaxies in the Universe, and their formation and evolution are a popular and current research topic (Linden et al. 2006, Bernardi et al. 2006, Lauer et al. 2006). They have been studied for some time (Sandage 1972, Ostriker & Tremaine 1975, White 1976, Thuan & Romanishin 1981, Merritt 1985, Postman and Lauer 1995, among many others). Our goal in this chapter is to study how the local environment can affect the physical and measurable properties of BCGs. We will conduct an exploratory research exercise. In this chapter, we will show how the Virtual Observatory (VO) can be effectively utilized for doing modern scientific research on BCGs. We identify the scientific functionalities we need, the datasets we require, and the service locations in order to discover and access those data. This chapter utilizes IDL's VOlib, which is described in Chapter 24 of this book and is available at http://www.nvo.noao.edu. IDL provides the capability to perform the entire range of astronomical scientific analyses in one environment: from image reduction and analysis to complex catalog manipulations, statistics, and publication quality figures. At the 2005 and 2006 NVO Summer Schools, user statistics show that IDL was the most commonly used programming language by the students (nearly 3-to-1 over languages like IRAF, Perl, and Python). In this chapter we show how the integration of IDL to the VO through VOlib provides even greater capabilities and possibilities for conducting science in the era of the Virtual Observatory. The reader should familiarize themselves with the VOlib libraries before attempting the examples in this tutorial. We first build a research plan. We then discover the service URLs we will need to access the data. We then apply the necessary functions and tools to these data before we can do our

  16. Magnetic characterization of mixed phases in FeVO4sbnd Co3V2O8 system

    Science.gov (United States)

    Guskos, N.; Zolnierkiewicz, G.; Pilarska, M.; Typek, J.; Berczynski, P.; Blonska-Tabero, A.; Aidinis, K.

    2018-04-01

    Dynamic and static magnetic properties of four nFeVO4/(1-n)Co3V2O8 composites obtained in reactions between nFeVO4 and (1-n)Co3V2O8 (n = 0.82, 0.80, 0.78 and 0.76) have been investigated by dc magnetometry and electron paramagnetic resonance (EPR). All samples were diphase containing both the howardevansite-type and the lyonsite-type phases in different proportions. Dc magnetic susceptibility study showed the Curie-Weiss paramagnetic behavior with strong antiferromagnetic (AFM) interaction in the high-temperature range and the phase transition to the AFM state at low temperatures. The calculated effective magnetic moment could be justified by the presence of high spin Fe3+ and Co2+ ions. The appearance of hysteresis loop in isothermal magnetisation at low temperature indicates the existence of the ferromagnetic component in all four samples, but only 0.5% of all magnetic ions are involved in this phase. EPR spectra recorded in high-temperature range (T > 90 K) consisted of a single broad line centred at ∼3.2 kG. The fitting of observed spectra with two Gaussian lineshape functions allowed to study the temperature dependence of EPR parameters (resonance field, linewidth, integrated intensity). This analysis suggests that EPR signal arises from two spin subsystems: paramagnetic Fe3+ ions subjected to AFM interaction and AFM spin pairs/clusters of iron/cobalt visible only at high temperatures. At low temperatures two transitions to AFM states, due to the mixture of two structural phases, are registered in magnetic susceptibility measurements.

  17. Band parameters of phosphorene

    International Nuclear Information System (INIS)

    Lew Yan Voon, L C; Wang, J; Zhang, Y; Willatzen, M

    2015-01-01

    Phosphorene is a two-dimensional nanomaterial with a direct band-gap at the Brillouin zone center. In this paper, we present a recently derived effective-mass theory of the band structure in the presence of strain and electric field, based upon group theory. Band parameters for this theory are computed using a first-principles theory based upon the generalized-gradient approximation to the density-functional theory. These parameters and Hamiltonian will be useful for modeling physical properties of phosphorene. (paper)

  18. Infrared diffuse interstellar bands

    Science.gov (United States)

    Galazutdinov, G. A.; Lee, Jae-Joon; Han, Inwoo; Lee, Byeong-Cheol; Valyavin, G.; Krełowski, J.

    2017-05-01

    We present high-resolution (R ˜ 45 000) profiles of 14 diffuse interstellar bands in the ˜1.45 to ˜2.45 μm range based on spectra obtained with the Immersion Grating INfrared Spectrograph at the McDonald Observatory. The revised list of diffuse bands with accurately estimated rest wavelengths includes six new features. The diffuse band at 15 268.2 Å demonstrates a very symmetric profile shape and thus can serve as a reference for finding the 'interstellar correction' to the rest wavelength frame in the H range, which suffers from a lack of known atomic/molecular lines.

  19. Band parameters of phosphorene

    DEFF Research Database (Denmark)

    Lew Yan Voon, L. C.; Wang, J.; Zhang, Y.

    2015-01-01

    Phosphorene is a two-dimensional nanomaterial with a direct band-gap at the Brillouin zone center. In this paper, we present a recently derived effective-mass theory of the band structure in the presence of strain and electric field, based upon group theory. Band parameters for this theory...... are computed using a first-principles theory based upon the generalized-gradient approximation to the density-functional theory. These parameters and Hamiltonian will be useful for modeling physical properties of phosphorene....

  20. High performance of solvothermally prepared VO2(B as anode for aqueous rechargeable lithium batteries

    Directory of Open Access Journals (Sweden)

    Milošević Sanja

    2015-01-01

    Full Text Available The VO2 (B was synthesized via a simple solvothermal route at 160oC in ethanol. The initial discharge capacity of VO2 (B anode, in saturated aqueous solution of LiNO3, was 177 mAh g-1 at a current rate of 50 mA g-1. After 50 cycles capacity fade was 4%, but from 20th-50th cycle no capacity drop was observed. The VO2 (B has shown very good cyclability at current rate of even 1000 mA g-1 with initial discharge capacity of 92 mAh g-1. The excellent electrochemical performance of VO2 (B was attributed to the stability of micro-nano structures to repeated intercalation /deintercalation process, very good electronic conductivity as well as the very low charge transfer resistance in the aqueous electrolyte. [Projekat Ministarstva nauke Republike Srbije, br. III45014

  1. Analysis of Voice Quality Problems of Voice Over Internet Protocol (VoIP)

    National Research Council Canada - National Science Library

    Tasyumruk, Lutfullah

    2003-01-01

    .... Additionally, the emergence of 3rd Generation (3G) cellular technology which offers high bandwidth will result in the convergence of the Internet and the cellular networks which will further stimulate the growth of VoIP...

  2. Selective scanning tunneling microscope light emission from rutile phase of VO2.

    Science.gov (United States)

    Sakai, Joe; Kuwahara, Masashi; Hotsuki, Masaki; Katano, Satoshi; Uehara, Yoichi

    2016-09-28

    We observed scanning tunneling microscope light emission (STM-LE) induced by a tunneling current at the gap between an Ag tip and a VO2 thin film, in parallel to scanning tunneling spectroscopy (STS) profiles. The 34 nm thick VO2 film grown on a rutile TiO2 (0 0 1) substrate consisted of both rutile (R)- and monoclinic (M)-structure phases of a few 10 nm-sized domains at room temperature. We found that STM-LE with a certain photon energy of 2.0 eV occurs selectively from R-phase domains of VO2, while no STM-LE was observed from M-phase. The mechanism of STM-LE from R-phase VO2 was determined to be an interband transition process rather than inverse photoemission or inelastic tunneling processes.

  3. Feasibility Study of VoIP Integration into the MYSEA Environment

    National Research Council Canada - National Science Library

    Tse, Lily

    2005-01-01

    .... VoIP is widely implemented with H.323 and Session Initiation Protocol (SIP) standards. However, both protocols are poorly designed for networks with common security solutions such as firewalls and Network Address Translation...

  4. Selective Oxidation of Alcohols Using Photoactive VO@g‑C3N4

    Data.gov (United States)

    U.S. Environmental Protection Agency — A photoactive VO@g-C3N4 catalyst has been developed for the selective oxidation of alcohols to the corresponding aldehydes and ketones. The visible light mediated...

  5. Control of room-temperature defect-mediated ferromagnetism in VO{sub 2} films

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Tsung-Han, E-mail: tyang3@ncsu.edu [NSF Center for Advanced Materials and Smart Structures, Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7907 (United States); Nori, Sudhakar; Mal, Siddhartha; Narayan, Jagdish [NSF Center for Advanced Materials and Smart Structures, Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7907 (United States)

    2011-09-15

    We report interesting ferromagnetic properties and their control in a vanadium-based oxide system driven by stoichiometric defects. Vanadium oxide (VO{sub 2}) thin films were grown on c-plane sapphire substrates by a pulsed laser deposition technique under different ambient conditions. The ferromagnetism of the epitaxial VO{sub 2} films can be switched on and off by altering the cooling ambient parameters. In addition, the saturated magnetic moments and coercivity of the VO{sub 2} films were found to be a function of the oxygen partial pressure during the growth process. The room-temperature ferromagnetic properties of VO{sub 2} films were correlated with the nature of the microstructure and the growth parameters. The origin of the induced magnetic properties are qualitatively understood to stem from intrinsic structural and stoichiometric defects.

  6. Photocatalytic C−H Activation of Hydrocarbons over VO@g‑C3N4

    Data.gov (United States)

    U.S. Environmental Protection Agency — A highly selective and sustainable method has been developed for the oxidation of methyl arenes and their analogues. The VO@g-C3N4 catalyst is very efficient in the...

  7. Reformatio in peius administratīvo pārkāpumu procesā

    OpenAIRE

    Berķis, Kaspars

    2009-01-01

    Maģistra darbā ir pētīta reformatio in peius aizlieguma principa piemērošanas problemātika administratīvo pārkāpumu procesā. Darba gaitā ir analizētas Latvijas Administratīvo pārkāpumu kodeksa, Administratīvā procesa likuma un kriminālprocesuālās tiesību normas, kas satur reformatio in peius aizlieguma principu. Darba ietvaros īpaša uzmanība pievērsta administratīvo tiesu prakses izpētei attiecībā uz reformatio in peius aizlieguma principa piemērošanu administratīvo pārkāpumu lietu izsk...

  8. Predictors of VO2Peak in children age 6- to 7-years-old

    DEFF Research Database (Denmark)

    Dencker, Magnus; Hermansen, Bianca; Bugge, Anna

    2011-01-01

    This study investigated the predictors of aerobic fitness (VO2PEAK) in young children on a population-base. Participants were 436 children (229 boys and 207 girls) aged 6.7 ± 0.4 yrs. VO2PEAK was measured during a maximal treadmill exercise test. Physical activity was assessed by accelerometers....... Total body fat and total fat free mass were estimated from skinfold measurements. Regression analyses indicated that significant predictors for VO2PEAK per kilogram body mass were total body fat, maximal heart rate, sex, and age. Physical activity explained an additional 4-7%. Further analyses showed...... the main contributing factors for absolute values of VO2PEAK were fat free mass, maximal heart rate, sex, and age. Physical activity explained an additional 3-6%....

  9. VO2 nanoparticles on edge orientated graphene foam for high rate lithium ion batteries and supercapacitors

    Science.gov (United States)

    Ren, Guofeng; Zhang, Ruibo; Fan, Zhaoyang

    2018-05-01

    With the fully exposed graphene edges, high conductivity and large surface area, edge oriented graphene foam (EOGF), prepared by deposition of perpendicular graphene network encircling the struts of Ni foam, is a superior scaffold to support active materials for electrochemical applications. With VO2 as an example, EOGF loaded VO2 nanoparticle (VO2/EOGF) electrode has high rate performance as cathode in lithium ion batteries (LIBs). In addition to the Li+ intercalation into the lattice, contribution of non-diffusion-limited pseudocapacitance to the capacity is prominent at high rates. VO2/EOGF based supercapacitor also exhibits fast response, with a characteristic frequency of 15 Hz when the phase angle reaches -45°, or a relaxation time constant of 66.7 ms. These results suggest the promising potential of EOGF as a scaffold in supporting active nanomaterials for electrochemical energy storage and other applications.

  10. Supercritical temperature synthesis of fluorine-doped VO2(M) nanoparticle with improved thermochromic property

    Science.gov (United States)

    Riapanitra, Anung; Asakura, Yusuke; Cao, Wenbin; Noda, Yasuto; Yin, Shu

    2018-06-01

    Fluorine-doped VO2(M) nanoparticles have been successfully synthesized using the hydrothermal method at a supercritical temperature of 490 °C. The pristine VO2(M) has the critical phase transformation temperature of 64 °C. The morphology and homogeneity of the monoclinic structure VO2(M) were adopted by the fluorine-doped system. The obtained particle size of the samples is smaller at the higher concentration of anion doping. The best reduction of critical temperature was achieved by fluorine doping of 0.13% up to 48 °C. The thin films of the fluorine-doped VO2(M) showed pronounced thermochromic property and therefore are suitable for smart window applications.

  11. Thermally tunable VO2-SiO2 nanocomposite thin-film capacitors

    Science.gov (United States)

    Sun, Yifei; Narayanachari, K. V. L. V.; Wan, Chenghao; Sun, Xing; Wang, Haiyan; Cooley, Kayla A.; Mohney, Suzanne E.; White, Doug; Duwel, Amy; Kats, Mikhail A.; Ramanathan, Shriram

    2018-03-01

    We present a study of co-sputtered VO2-SiO2 nanocomposite dielectric thin-film media possessing continuous temperature tunability of the dielectric constant. The smooth thermal tunability is a result of the insulator-metal transition in the VO2 inclusions dispersed within an insulating matrix. We present a detailed comparison of the dielectric characteristics of this nanocomposite with those of a VO2 control layer and of VO2/SiO2 laminate multilayers of comparable overall thickness. We demonstrated a nanocomposite capacitor that has a thermal capacitance tunability of ˜60% between 25 °C and 100 °C at 1 MHz, with low leakage current. Such thermally tunable capacitors could find potential use in applications such as sensing, thermal cloaks, and phase-change energy storage devices.

  12. VoIP for Telerehabilitation: A Pilot Usability Study for HIPAA Compliance

    Directory of Open Access Journals (Sweden)

    Valerie R. Watzlaf

    2012-06-01

    Full Text Available Consumer-based, free Voice and video over the Internet Protocol (VoIP software systems such as Skype and others are used by health care providers to deliver telerehabilitation and other health-related services to clients. Privacy and security applications as well as HIPAA compliance within these protocols have been questioned by practitioners, health information managers, and other healthcare entities. This pilot usability study examined whether four respondents who used the top three, free consumer-based, VoIP software systems perceived these VoIP technologies to be private, secure, and HIPAA compliant;  most did not.  While the pilot study limitations include the number of respondents and systems assessed, the protocol can be applied to future research and replicated for instructional purposes.  Recommendations are provided for VoIP companies, providers, and users. 

  13. EVALUATION AND DEVELOPMENT OF THE VO2 OF ATHLETES THAT ATTEND A SOCCER SCHOOL

    Directory of Open Access Journals (Sweden)

    Felipe Bittencourt Oliveira

    2012-11-01

    Full Text Available The goal of this study was to identify the effects from technical and physical activities on the VO2, of male athletes aged 14 to 15, participants of a soccer school, in the municipality of Rio Pardo - RS. The semi-experimental research involved 10 male adolescents. For the VO2 evaluation the 12 minute Cooper test was used. Interval-training work was applied, at which the athletes exercised 75% of their maximum speed, in 60-meter runs. After training for two months (at least two sessions a week the Cooper post-test was applied to check the improvement of the VO2. As results of this study, we can draw the conclusion that all adolescents involved in this training showed considerable improvement in their maximum VO2, especially the 15-year-old teens, who managed to obtain a much higher percentage level.

  14. Synthesis, Characterization and Antibacterial Activity of BiVO4 Microstructure

    Science.gov (United States)

    Ekthammathat, Nuengruethai; Phuruangrat, Anukorn; Thongtem, Somchai; Thongtem, Titipun

    2018-05-01

    Hyperbranched BiVO4 microstructure were successfully synthesized by a hydrothermal method. Upon characterization the products by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, selected area electron diffraction (SAED) and photoluminescence (PL) spectroscopy, pure monoclinic hyperbranched BiVO4 with dominant vibration peak at 810 cm-1 and strong photoemission peak at 360 nm was synthesized in the solution with pH 1. In the solution with pH 2, tetragonal BiVO4 phase was also detected. In this research, antibacterial activity against S. aureus and E. coli was investigated by counting the colony forming unit (CFU). At 37°C within 24 h, the monoclinic BiVO4 phase can play the role in inhibiting S. aureus growth (350 CFU/mL remaining bacteria) better than that against E. coli (a large number of remaining bacteria).

  15. Business Collaborations in Grids: The BREIN Architectural Principals and VO Model

    Science.gov (United States)

    Taylor, Steve; Surridge, Mike; Laria, Giuseppe; Ritrovato, Pierluigi; Schubert, Lutz

    We describe the business-oriented architectural principles of the EC FP7 project “BREIN” for service-based computing. The architecture is founded on principles of how real businesses interact to mutual benefit, and we show how these can be applied to SOA and Grid computing. We present building blocks that can be composed in many ways to produce different value systems and supply chains for the provision of computing services over the Internet. We also introduce the complementary BREIN VO concept, which is centric to, and managed by, a main contractor who bears the responsibility for the whole VO. The BREIN VO has an execution lifecycle for the creation and operation of the VO, and we have related this to an application-focused workflow involving steps that provide real end-user value. We show how this can be applied to an engineering simulation application and how the workflow can be adapted should the need arise.

  16. VoIP Quality Measurements in a Multilevel Secure (MLS) Environment

    National Research Council Canada - National Science Library

    Adams, Jr, Coy M

    2008-01-01

    Voice over Internet Protocol (VoIP) is growing in popularity in the civilian and military communities due to its low cost and the management advantages it offers over traditional Public Switched Telephone Networks (PSTN) phone systems...

  17. Classifier fusion for VoIP attacks classification

    Science.gov (United States)

    Safarik, Jakub; Rezac, Filip

    2017-05-01

    SIP is one of the most successful protocols in the field of IP telephony communication. It establishes and manages VoIP calls. As the number of SIP implementation rises, we can expect a higher number of attacks on the communication system in the near future. This work aims at malicious SIP traffic classification. A number of various machine learning algorithms have been developed for attack classification. The paper presents a comparison of current research and the use of classifier fusion method leading to a potential decrease in classification error rate. Use of classifier combination makes a more robust solution without difficulties that may affect single algorithms. Different voting schemes, combination rules, and classifiers are discussed to improve the overall performance. All classifiers have been trained on real malicious traffic. The concept of traffic monitoring depends on the network of honeypot nodes. These honeypots run in several networks spread in different locations. Separation of honeypots allows us to gain an independent and trustworthy attack information.

  18. CSF oligoclonal banding - slideshow

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/presentations/100145.htm CSF oligoclonal banding - series—Normal anatomy To use the ... 5 out of 5 Overview The cerebrospinal fluid (CSF) serves to supply nutrients to the central nervous ...

  19. Decay of superdeformed bands

    International Nuclear Information System (INIS)

    Carpenter, M.P.; Khoo, T.L.; Lauritsen, T.

    1995-01-01

    One of the major challenges in the study of superdeformation is to directly connect the large number of superdeformed bands now known to the yrast states. In this way, excitation energies, spins and parities can be assigned to the levels in the second well which is essential to establish the collective and single-particle components of these bands. This paper will review some of the progress which has been made to understand the decay of superdeformed bands using the new arrays including the measurement of the total decay spectrum and the establishment of direct one-step decays from the superdeformed band to the yrast line in 194 Hg. 42 refs., 5 figs

  20. Laparoscopic gastric banding

    Science.gov (United States)

    ... eat by making you feel full after eating small amounts of food. After surgery, your doctor can adjust the band ... You will feel full after eating just a small amount of food. The food in the small upper pouch will ...

  1. Broadband terahertz generation using the semiconductor-metal transition in VO2

    Directory of Open Access Journals (Sweden)

    Nicholas A. Charipar

    2016-01-01

    Full Text Available We report the design, fabrication, and characterization of broadband terahertz emitters based on the semiconductor-metal transition in thin film VO2 (vanadium dioxide. With the appropriate geometry, picosecond electrical pulses are generated by illuminating 120 nm thick VO2 with 280 fs pulses from a femtosecond laser. These ultrafast electrical pulses are used to drive a simple dipole antenna, generating broadband terahertz radiation.

  2. Size and composition-controlled fabrication of VO2 nanocrystals by terminated cluster growth

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre; Slack, Jonathan

    2013-05-14

    A physical vapor deposition-based route for the fabrication of VO2 nanoparticles is demonstrated, consisting of reactive sputtering and vapor condensation at elevated pressures. The oxidation of vanadium atoms is an efficient heterogeneous nucleation method, leading to high nanoparticle throughtput. Fine control of the nanoparticle size and composition is obtained. Post growth annealing leads to crystalline VO2 nanoparticles with optimum thermocromic and plasmonic properties.

  3. Human mitochondrial haplogroup H: the highest VO2max consumer--is it a paradox?

    Science.gov (United States)

    Martínez-Redondo, Diana; Marcuello, Ana; Casajús, José A; Ara, Ignacio; Dahmani, Yahya; Montoya, Julio; Ruiz-Pesini, Eduardo; López-Pérez, Manuel J; Díez-Sánchez, Carmen

    2010-03-01

    Mitochondrial background has been demonstrated to influence maximal oxygen uptake (VO(2max), in mLkg(-1)min(-1)), but this genetic influence can be compensated for by regular exercise. A positive correlation among electron transport chain (ETC) coupling, ATP and reactive oxygen species (ROS) production has been established, and mitochondrial variants have been reported to show differences in their ETC performance. In this study, we examined in detail the VO(2max) differences found among mitochondrial haplogroups. We recruited 81 healthy male Spanish Caucasian individuals and determined their mitochondrial haplogroup. Their VO(2max) was determined using incremental cycling exercise (ICE). VO(2max) was lower in J than in non-J haplogroup individuals (P=0.04). The H haplogroup was responsible for this difference (VO(2max); J vs. H; P=0.008) and this group also had significantly higher mitochondrial oxidative damage (mtOD) than the J haplogroup (P=0.04). In agreement with these results, VO(2max) and mtOD were positively correlated (P=0.01). Given that ROS production is the major contributor to mtOD and consumes four times more oxygen per electron than the ETC, our results strongly suggest that ROS production is responsible for the higher VO(2max) found in the H variant. These findings not only contribute to a better understanding of the mechanisms underneath VO(2max), but also help to explain some reported associations between mitochondrial haplogroups and mtOD with longevity, sperm motility, premature aging and susceptibility to different pathologies.

  4. Security and VO management capabilities in a large-scale Grid operating system

    OpenAIRE

    Aziz, Benjamin; Sporea, Ioana

    2014-01-01

    This paper presents a number of security and VO management capabilities in a large-scale distributed Grid operating system. The capabilities formed the basis of the design and implementation of a number of security and VO management services in the system. The main aim of the paper is to provide some idea of the various functionality cases that need to be considered when designing similar large-scale systems in the future.

  5. Influence of lattice distortion on phase transition properties of polycrystalline VO{sub 2} thin film

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Tiegui [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Wang, Langping, E-mail: aplpwang@hit.edu.cn [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Wang, Xiaofeng; Zhang, Yufen [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Yu, Yonghao, E-mail: yhyu@hit.edu.cn [Academy of Fundamental and Interdisciplinary Science, Harbin Institute of Technology, Harbin 150001 (China)

    2016-08-30

    Highlights: • Polycrystalline VO{sub 2} thin films were fabricated by high power impulse magnetron sputtering. • The reported lowest phase transition temperature for undoped polycrystalline VO{sub 2} thin film was reduced to 32 °C by this research. • XRD patterns at varied temperatures revealed that the main structual change was a gradual shift in interplanar spacing with temperature. - Abstract: In this work, high power impulse magnetron sputtering was used to control the lattice distortion in polycrystalline VO{sub 2} thin film. SEM images revealed that all the VO{sub 2} thin films had crystallite sizes of below 20 nm, and similar configurations. UV–vis-near IR transmittance spectra measured at different temperatures showed that most of the as-deposited films had a typical metal–insulator transition. Four-point probe resistivity results showed that the transition temperature of the films varied from 54.5 to 32 °C. The X-ray diffraction (XRD) patterns of the as-deposited films revealed that most were polycrystalline monoclinic VO{sub 2}. The XRD results also confirmed that the lattice distortions in the as-deposited films were different, and the transition temperature decreased with the difference between the interplanar spacing of the as-deposited thin film and standard rutile VO{sub 2}. Furthermore, a room temperature rutile VO{sub 2} thin film was successfully synthesized when this difference was small enough. Additionally, XRD patterns measured at varied temperatures revealed that the phase transition process of the polycrystalline VO{sub 2} thin film was a coordinative deformation between grains with different orientations. The main structural change during the phase transition was a gradual shift in interplanar spacing with temperature.

  6. Evaluation and Investigation of the Delay in VoIP Networks

    Directory of Open Access Journals (Sweden)

    V. Janata

    2011-06-01

    Full Text Available The paper is focused mainly on the delay problems, which considerably influence the final quality of connections in VoIP (Voice over IP networks. The paper provides a detailed exploration of the nature and mechanisms of the delay. The main purpose of the investigation was an attempt to formulate a mathematical model of delay in the VoIP network and its subsequent analysis by laboratory data.

  7. Enhanced photoelectrochemical response of plasmonic Au embedded BiVO4/Fe2O3 heterojunction.

    Science.gov (United States)

    Verma, Anuradha; Srivastav, Anupam; Khan, Saif A; Rani Satsangi, Vibha; Shrivastav, Rohit; Kumar Avasthi, Devesh; Dass, Sahab

    2017-06-14

    The effect of embedding Au nanoparticles (NPs) in a BiVO 4 /Fe 2 O 3 heterojunction for photoelectrochemical water splitting is studied here for the first time. The present nanostructured heterojunction offers three major advantages over pristine BiVO 4 and Fe 2 O 3 : (i) the formation of a heterojunction between BiVO 4 and Fe 2 O 3 enhances the charge carrier separation and transfer, (ii) the layer of Fe 2 O 3 provides protection to BiVO 4 from photocorrosion and, (iii) the Au NPs possessing surface plasmon resonance (SPR) enhance the photoelectrochemical response by transferring energy to metal oxides by hot electron transfer (HET) and plasmon resonant energy transfer (PRET). The present study reveals that the heterojunction ITO/BiVO 4 /Fe 2 O 3 (with 32% v/v Au solution in both layers) gives the best performance and mitigates the limitations of both pristine Fe 2 O 3 and BiVO 4 . A thirteen-fold increment in applied bias photon-to-current conversion efficiency (ABPE) was observed at 1.24 V vs. RHE under the condition of 1 Sun illumination. Monochromatic incident photon-to-current conversion efficiency (IPCE) measurements indicated that an Au embedded heterojunction is more effective in harvesting visible light in comparison to a heterojunction without Au NPs.

  8. The performance model of dynamic virtual organization (VO) formations within grid computing context

    International Nuclear Information System (INIS)

    Han Liangxiu

    2009-01-01

    Grid computing aims to enable 'resource sharing and coordinated problem solving in dynamic, multi-institutional virtual organizations (VOs)'. Within the grid computing context, successful dynamic VO formations mean a number of individuals and institutions associated with certain resources join together and form new VOs in order to effectively execute tasks within given time steps. To date, while the concept of VOs has been accepted, few research has been done on the impact of effective dynamic virtual organization formations. In this paper, we develop a performance model of dynamic VOs formation and analyze the effect of different complex organizational structures and their various statistic parameter properties on dynamic VO formations from three aspects: (1) the probability of a successful VO formation under different organizational structures and statistic parameters change, e.g. average degree; (2) the effect of task complexity on dynamic VO formations; (3) the impact of network scales on dynamic VO formations. The experimental results show that the proposed model can be used to understand the dynamic VO formation performance of the simulated organizations. The work provides a good path to understand how to effectively schedule and utilize resources based on the complex grid network and therefore improve the overall performance within grid environment.

  9. Broadband modulation of terahertz waves through electrically driven hybrid bowtie antenna-VO2 devices.

    Science.gov (United States)

    Han, Chunrui; Parrott, Edward P J; Humbert, Georges; Crunteanu, Aurelian; Pickwell-MacPherson, Emma

    2017-10-05

    Broadband modulation of terahertz (THz) light is experimentally realized through the electrically driven metal-insulator phase transition of vanadium dioxide (VO 2 ) in hybrid metal antenna-VO 2 devices. The devices consist of VO 2 active layers and bowtie antenna arrays, such that the electrically driven phase transition can be realized by applying an external voltage between adjacent metal wires extended to a large area array. The modulation depth of the terahertz light can be initially enhanced by the metal wires on top of VO 2 and then improved through the addition of specific bowties in between the wires. As a result, a terahertz wave with a large beam size (~10 mm) can be modulated within the measurable spectral range (0.3-2.5 THz) with a frequency independent modulation depth as high as 0.9, and the minimum amplitude transmission down to 0.06. Moreover, the electrical switch on/off phase transition depends very much on the size of the VO 2 area, indicating that smaller VO 2 regions lead to higher modulation speeds and lower phase transition voltages. With the capabilities in actively tuning the beam size, modulation depth, modulation bandwidth as well as the modulation speed of THz waves, our study paves the way in implementing multifunctional components for terahertz applications.

  10. Selective Synthesis of Mesoporous and Nanorod CeVO4 without Template

    International Nuclear Information System (INIS)

    Zhu Ling; Li Qin; Li Jiayan; Liu Xiangdong; Meng Jian; Cao Xueqiang

    2007-01-01

    A simple and efficient method has been established for the selective synthesis of mesoporous and nanorod CeVO 4 with different precursors by sonochemical method. CeVO 4 nanorod can be simply synthesized by ultrasound irradiation of Ce(NO 3 ) 3 and NH 4 VO 3 in aqueous solution without any surfactant or template. While mesoporous CeVO 4 with high specific surface area can be prepared with Ce(NO 3 ) 3 , V 2 O 5 and NaOH in the same way. Mesoporous CeVO 4 has a specific surface area of 122 m 2 g -1 and an average pore size of 5.2 nm; CeVO 4 nanorods have a diameter of about 5 nm, and a length of 100-150 nm. The ultrasound irradiation and ammonia in the reactive solution are two key factors in the formation of such rod-like products. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and differential thermal analyses (DTA), UV/vis absorption spectroscopy and Brunauer-Emmett-Teller (BET) were applied for characterization of the as-prepared products

  11. On-line Monitoring of VoIP Quality Using IPFIX

    Directory of Open Access Journals (Sweden)

    Petr Matousek

    2014-01-01

    Full Text Available The main goal of VoIP services is to provide a reliable and high-quality voice transmission over packet networks. In order to prove the quality of VoIP transmission, several approaches were designed. In our approach, we are concerned about on-line monitoring of RTP and RTCP traffic. Based on these data, we are able to compute main VoIP quality metrics including jitter, delay, packet loss, and finally R-factor and MOS values. This technique of VoIP quality measuring can be directly incorporated into IPFIX monitoring framework where an IPFIX probe analyses RTP/RTCP packets, computes VoIP quality metrics, and adds these metrics into extended IPFIX flow records. Then, these extended data are stored in a central IPFIX monitoring system called collector where can be used for monitoring purposes. This paper presents a functional implementation of IPFIX plugin for VoIP quality measurement and compares the results with results obtained by other tools.

  12. Familial aggregation of VO(2max) response to exercise training: results from the HERITAGE Family Study.

    Science.gov (United States)

    Bouchard, C; An, P; Rice, T; Skinner, J S; Wilmore, J H; Gagnon, J; Pérusse, L; Leon, A S; Rao, D C

    1999-09-01

    The aim of this study was to test the hypothesis that individual differences in the response of maximal O(2) uptake (VO(2max)) to a standardized training program are characterized by familial aggregation. A total of 481 sedentary adult Caucasians from 98 two-generation families was exercise trained for 20 wk and was tested for VO(2max) on a cycle ergometer twice before and twice after the training program. The mean increase in VO(2max) reached approximately 400 ml/min, but there was considerable heterogeneity in responsiveness, with some individuals experiencing little or no gain, whereas others gained >1.0 l/min. An ANOVA revealed that there was 2.5 times more variance between families than within families in the VO(2max) response variance. With the use of a model-fitting procedure, the most parsimonious models yielded a maximal heritability estimate of 47% for the VO(2max) response, which was adjusted for age and sex with a maternal transmission of 28% in one of the models. We conclude that the trainability of VO(2max) is highly familial and includes a significant genetic component.

  13. Synthesis and modification of FeVO{sub 4} as novel anode for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaolin [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University, Wuhan 430062 (China); Cao, Yuancheng [Key Laboratory of Optoelectronic Chemical Materials and Devices, Ministry of Education, School of chemical and Environment Engineering, Jianghan University, Wuhan 430062 (China); Zheng, Hao; Chen, Xiao [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University, Wuhan 430062 (China); Feng, Chuanqi, E-mail: cfeng@hubu.edu.cn [Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University, Wuhan 430062 (China)

    2017-02-01

    Graphical abstract: The FeVO{sub 4}/graphene are synthesized by combining hydrothermal and heat treatment method. It delivered an initial discharge capacity of 1302.3 mAh g{sup −1} and remained capacity as 1046.5 mAh g{sup −1} after 100 cycles and behaved better electrochemical properties than that of pure FeVO{sub 4}. - Highlights: • The FeVO{sub 4} and FeVO{sub 4}/graphene are synthesized by combining hydrothermal and heat treatment method. • The FeVO{sub 4}/graphene nanocomposite exhibits outstanding electrochemical performance. • FeVO{sub 4}/graphene delivered an initial discharge capacity of 1302.3 mAh g{sup −1} and remained capacity as 1046.5 mAh g{sup −1} after 100 cycles. • The FeVO{sub 4}/graphene composite behaved better electrochemical properties than that of pure FeVO{sub 4}. - Abstract: FeVO{sub 4} and FeVO{sub 4}/graphene nanorods were synthesized successfully by combining a facile hydrothermal and heat treatment method. The samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and transmission electron microscopy (TEM) techniques. The content of graphene in FeVO{sub 4}/graphene was determined by thermogravimetric analysis (TG). The electrochemical properties of the samples were also investigated by battery testing system. The results showed that the FeVO{sub 4} formed were taken on morphology of nanorods with the length between 0.5 and 1 μm and the diameter in range of 50 to 100 nm. Besides, the size of FeVO{sub 4}/graphene was smaller than that of pure FeVO{sub 4}. The content of graphene in composite was about 25.0% by weight. The reversible discharge capacities of FeVO{sub 4} and FeVO{sub 4}/graphene were 405.2 mAh g{sup −1} and 1046.5 mAh g{sup −1} separately after 100 cycles at the current density of 100 mAh g{sup −1} in the voltage range of 0.01–3 V. The reasons for the FeVO{sub 4}/graphene composite to behave outstanding electrochemical properties were also discussed. The FeVO

  14. Dosimetry of narrow band UVB treatments

    International Nuclear Information System (INIS)

    Goode, D.H.; Mannering, D.M.

    1996-01-01

    Full text: For many years psoriasis has been treated with broad band UVB lamps. These lamps have a bell shaped spectrum which peaks at 305 nm and extends from 280 nm to 350 nm. However research with monochromatic UV radiation has shown that wavelengths between 300 nm and 320 nm are the most efficacious for clearing psoriasis while wavelengths below 305 nm are most effective for producing the undesirable side effect of erythema (sunburn). In response to these findings Philips developed a narrow band UVB tube in which a large fraction of the output was confined to a narrow peak (bandwidth 2.5 nm) situated at 311 nm. Christchurch Hospital replaced broad band UVB with narrow band treatments in August 1995 and as this required UV exposures to be substantially increased new protocols had to be developed. Three aspects needed to be addressed. These were translating the dose from broad band to narrow band for current patients, determining the initial dose for new patients and developing a formula for increasing subsequent exposures to both types of patient. To translate doses the spectral irradiance (μW/cm 2 /nm) that would fall on the patient was measured in both the old broad band and the new narrow band treatment units and from this UV doses were calculated. All doses were expressed in mJ/cm 2 of unweighted UV over the range 250 nm to 400 nm. The erythemal effectiveness of the two units were compared by using the CIE 1987 curve to express doses in terms of the equivalent exposure of monochromatic 297 nm radiation. It was found that an exposure of 3.96 mJ/cm 2 from the broad band FS40 tubes and 12.79 mJ/cm 2 from the narrow band TL/01 tubes were both equivalent to 1.00 mJ/cm 2 of monochromatic 297 nm radiation so when transferring patients all broad band doses needed to be increased by a factor of 3.2. Before transferring any patients this factor was confirmed by conducting two minimal erythema dose (MED) tests on a normal subject, one in each unit. For new patients a

  15. Seasonal variation of VO 2 max and the VO2-work rate relationship in elite Alpine skiers.

    Science.gov (United States)

    Gross, Micah A; Breil, Fabio A; Lehmann, Andrea D; Hoppeler, Hans; Vogt, Michael

    2009-11-01

    Alpine ski performance relates closely to both anaerobic and aerobic capacities. During their competitive season, skiers greatly reduce endurance and weight training, and on-snow training becomes predominant. To typify this shift, we compared exhaustive ramp cycling and squat (SJ) and countermovement jumping (CMJ) performance in elite males before and after their competitive season. In postseason compared with preseason: 1) maximal oxygen uptake (VO 2 max) normalized to bodyweight was higher (55.2 +/- 5.2 vs 52.7 +/- 3.6 mL x kg(-1) x min(-1), P jump height was greater in SJ (47.4 +/- 4.4 vs 44.7 +/- 4.3 cm, P skiing seemingly provides an ample cardiovascular training stimulus for skiers to maintain their aerobic capacities during the racing season. We conclude that aerobic fitness and leg explosiveness can be maintained in-season but may be compromised by heavy or excessive preseason training. In addition, ramp test V O2/W slope analysis could be useful for monitoring both positive and negative responses to training.

  16. C=C bond cleavage on neutral VO3(V2O5)n clusters.

    Science.gov (United States)

    Dong, Feng; Heinbuch, Scott; Xie, Yan; Bernstein, Elliot R; Rocca, Jorge J; Wang, Zhe-Chen; Ding, Xun-Lei; He, Sheng-Gui

    2009-01-28

    The reactions of neutral vanadium oxide clusters with alkenes (ethylene, propylene, 1-butene, and 1,3-butadiene) are investigated by experiments and density function theory (DFT) calculations. Single photon ionization through extreme ultraviolet radiation (EUV, 46.9 nm, 26.5 eV) is used to detect neutral cluster distributions and reaction products. In the experiments, we observe products (V(2)O(5))(n)VO(2)CH(2), (V(2)O(5))(n)VO(2)C(2)H(4), (V(2)O(5))(n)VO(2)C(3)H(4), and (V(2)O(5))(n)VO(2)C(3)H(6), for neural V(m)O(n) clusters in reactions with C(2)H(4), C(3)H(6), C(4)H(6), and C(4)H(8), respectively. The observation of these products indicates that the C=C bonds of alkenes can be broken on neutral oxygen rich vanadium oxide clusters with the general structure VO(3)(V(2)O(5))(n=0,1,2...). DFT calculations demonstrate that the reaction VO(3) + C(3)H(6) --> VO(2)C(2)H(4) + H(2)CO is thermodynamically favorable and overall barrierless at room temperature. They also provide a mechanistic explanation for the general reaction in which the C=C double bond of alkenes is broken on VO(3)(V(2)O(5))(n=0,1,2...) clusters. A catalytic cycle for alkene oxidation on vanadium oxide is suggested based on our experimental and theoretical investigations. The reactions of V(m)O(n) with C(6)H(6) and C(2)F(4) are also investigated by experiments. The products VO(2)(V(2)O(5))(n)C(6)H(4) are observed for dehydration reactions between V(m)O(n) clusters and C(6)H(6). No product is detected for V(m)O(n) clusters reacting with C(2)F(4). The mechanisms of the reactions between VO(3) and C(2)F(4)/C(6)H(6) are also investigated by calculations at the B3LYP/TZVP level.

  17. VoIP attacks detection engine based on neural network

    Science.gov (United States)

    Safarik, Jakub; Slachta, Jiri

    2015-05-01

    The security is crucial for any system nowadays, especially communications. One of the most successful protocols in the field of communication over IP networks is Session Initiation Protocol. It is an open-source project used by different kinds of applications, both open-source and proprietary. High penetration and text-based principle made SIP number one target in IP telephony infrastructure, so security of SIP server is essential. To keep up with hackers and to detect potential malicious attacks, security administrator needs to monitor and evaluate SIP traffic in the network. But monitoring and following evaluation could easily overwhelm the security administrator in networks, typically in networks with a number of SIP servers, users and logically or geographically separated networks. The proposed solution lies in automatic attack detection systems. The article covers detection of VoIP attacks through a distributed network of nodes. Then the gathered data analyze aggregation server with artificial neural network. Artificial neural network means multilayer perceptron network trained with a set of collected attacks. Attack data could also be preprocessed and verified with a self-organizing map. The source data is detected by distributed network of detection nodes. Each node contains a honeypot application and traffic monitoring mechanism. Aggregation of data from each node creates an input for neural networks. The automatic classification on a centralized server with low false positive detection reduce the cost of attack detection resources. The detection system uses modular design for easy deployment in final infrastructure. The centralized server collects and process detected traffic. It also maintains all detection nodes.

  18. Synthesis, characterization and catalytic activity of two novel cis - dioxovanadium(V) complexes: [VO{sub 2}(L)] and [VO{sub 2}(HLox)

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Natalia M.L.; Chacon, Eluzir P.; Resende, Jackson A.L.C.; Carneiro, Jose Walkimar de M.; Lanznaster, Mauricio, E-mail: mlanz@vm.uff.b [Universidade Federal Fluminense (IQ/UFF), Niteroi, RJ (Brazil). Inst. de Quimica; Pinheiro, Carlos B. [Universidade Federal de Minas Gerais (DF/UFMG), Belo Horizonte (Brazil). Dept. de Fisica; Fernandez, Tatiana L.; Scarpellini, Marciela [Universidade Federal do Rio de Janeiro (IQ/UFRJ), RJ (Brazil). Inst. de Quimica

    2011-07-01

    Two novel complexes, [VO{sub 2}(L)] (1) and [VO{sub 2}(HLox)] (2), were synthesized and characterized by IV, UV-Vis and NMR spectroscopy, cyclic voltammetry, elemental analysis and X-ray diffraction. The synthesis of a new ligand, H{sub 2}Lox, is also described. Complexes 1 and 2 were obtained by the reaction of [VO(acac){sub 2}] with the ligands HL and H{sub 2}Lox, respectively. Alternatively, 2 was also obtained by the reaction of HL with [VO(acac)2] in the presence of hydroxylamine, and by the reaction of 1 with hydroxylamine. Crystallographic data show that complexes 1 and 2 have similar molecular structures, in which the cis-dioxovanadium(V) center is coordinated to L- or HLox{sup -}, respectively, in a distorted octahedral environment. The catalytic activity of these compounds towards cyclohexane oxidation was evaluated using H{sub 2}O{sub 2} and t-BuOOH as oxidants. Both complexes presented > 70% selectivity for cyclohexylhydroperoxide formation. B3LYP/6.31G(d) calculations were used to confirm the geometry and to help assign the electronic spectra. (author)

  19. Fine hierarchy of the V-O bonds by advanced solid state NMR: novel Pb4(VO2)(PO4)3 structure as a textbook case.

    Science.gov (United States)

    Tricot, Grégory; Mentré, Olivier; Cristol, Sylvain; Delevoye, Laurent

    2012-12-17

    We report here a complete structural characterization of a new lead Pb(4)(VO(2))(PO(4))(3) vanadophosphate compound by single crystal X-ray diffraction and (51)V and (31)P solid-state NMR spectroscopy. Although structural data are commonly used for the estimation of bond lengths and further delimitation of the true coordination number (e.g., octahedral: 6 versus 5 + 1 versus 4 + 2), we show here for the first time by solid-state NMR a more accurate appreciation of the V-O bonding scheme in this complex oxide which appears well adapted to the full series of vanado-phosphate materials. The direct characterization of V-O-P bridges through the J-mediated correlation (51)V{(31)P} heteronuclear multiple quantum coherence (J-HMQC) technique allows a contrasted hierarchy of the V-O electronic delocalization and indirectly supports the presence or not of the V-O bond. In the reported lead vanado-phosphate structure, the two vanadium polyhedra that have been assigned to octahedra from a bond length point of view have been finally reclassified as tetra- and penta-coordinated units on the basis of the solid-state NMR results. More generally, we believe that the improved characterization of interatomic bonds in various vanado-phosphate structures by solid-state NMR will contribute to a better understanding of the structure/property relationships in this important class of materials.

  20. Device Performance of the Mott InsulatorDevice Performance of the Mott Insulator LaVO3 as a Photovoltaic Material

    KAUST Repository

    Wang, Lingfei

    2015-06-22

    Searching for solar-absorbing materials containing earth-abundant elements with chemical stability is of critical importance for advancing photovoltaic technologies. Mott insulators have been theoretically proposed as potential photovoltaic materials. In this paper, we evaluate their performance in solar cells by exploring the photovoltaic properties of Mott insulator LaVO3 (LVO). LVO films show an indirect band gap of 1.08 eV as well as strong light absorption over a wide wavelength range in the solar spectrum. First-principles calculations on the band structure of LVO further reveal that the d−d transitions within the upper and lower Mott-Hubbard bands and p−d transitions between the O 2p and V 3d band contribute to the absorption in visible and ultraviolet ranges, respectively. Transport measurements indicate strong carrier trapping and the formation of polarons in LVO. To utilize the strong light absorption of LVO and to overcome its poor carrier transport, we incorporate it as a light absorber in solar cells in conjunction with carrier transporters and evaluate its device performance. Our complementary experimental and theoretical results on such prototypical solar cells made of Mott-Hubbard transition-metal oxides pave the road for developing light-absorbing materials and photovoltaic devices based on strongly correlated electrons.

  1. Associations between VO2max and vitality in older workers: a cross-sectional study

    Directory of Open Access Journals (Sweden)

    van der Beek Allard J

    2010-11-01

    Full Text Available Abstract Background To prevent early exit from work, it is important to study which factors contribute to healthy ageing. One concept that is assumed to be closely related to, and therefore may influence healthy ageing, is vitality. Vitality consists of both a mental and a physical component, and is characterised by a perceived high energy level, decreased feelings of fatigue, and feeling fit. Since VO2max gives an indication of one's aerobic fitness, which can be improved by increased levels of physical activity, and because feeling fit is one of the main characteristics of vitality, it is hypothesised that VO2max is related to vitality. Therefore, the aim of this study was to investigate the associations between VO2max and vitality. Methods In 427 older workers (aged 45 + years participating in the Vital@Work study, VO2max was estimated at baseline using the 2-km UKK walk test. Vitality was measured by both the UWES Vitality Scale and the RAND-36 Vitality Scale. Associations were analysed using linear regression analyses. Results The linear regression models, adjusted for age, showed a significant association between VO2max and vitality measured with the RAND-36 Vitality Scale (β = 0.446; 95% CI: 0.220-0.673. There was no significant association between VO2max and vitality measured with the UWES (β = -0.006; 95% CI:-0.017 - 0.006, after adjusting for age, gender and chronic disease status. Conclusions VO2max was associated with a general measure of vitality (measured with the RAND-36 Vitality Scale, but not with occupational health related vitality (measured with the UWES Vitality Scale. The idea that physical exercise can be used as an effective tool for improving vitality was supported in this study. Trial registration NTR1240

  2. Associations between VO2max and vitality in older workers: a cross-sectional study.

    Science.gov (United States)

    Strijk, Jorien E; Proper, Karin I; Klaver, Linda; van der Beek, Allard J; van Mechelen, Willem

    2010-11-09

    To prevent early exit from work, it is important to study which factors contribute to healthy ageing. One concept that is assumed to be closely related to, and therefore may influence healthy ageing, is vitality. Vitality consists of both a mental and a physical component, and is characterised by a perceived high energy level, decreased feelings of fatigue, and feeling fit. Since VO2max gives an indication of one's aerobic fitness, which can be improved by increased levels of physical activity, and because feeling fit is one of the main characteristics of vitality, it is hypothesised that VO2max is related to vitality. Therefore, the aim of this study was to investigate the associations between VO2max and vitality. In 427 older workers (aged 45 + years) participating in the Vital@Work study, VO2max was estimated at baseline using the 2-km UKK walk test. Vitality was measured by both the UWES Vitality Scale and the RAND-36 Vitality Scale. Associations were analysed using linear regression analyses. The linear regression models, adjusted for age, showed a significant association between VO2max and vitality measured with the RAND-36 Vitality Scale (β = 0.446; 95% CI: 0.220-0.673). There was no significant association between VO2max and vitality measured with the UWES (β = -0.006; 95% CI:-0.017 - 0.006), after adjusting for age, gender and chronic disease status. VO2max was associated with a general measure of vitality (measured with the RAND-36 Vitality Scale), but not with occupational health related vitality (measured with the UWES Vitality Scale). The idea that physical exercise can be used as an effective tool for improving vitality was supported in this study. NTR1240.

  3. Low-level laser therapy improves the VO2 kinetics in competitive cyclists.

    Science.gov (United States)

    Lanferdini, Fábio J; Krüger, Renata L; Baroni, Bruno M; Lazzari, Caetano; Figueiredo, Pedro; Reischak-Oliveira, Alvaro; Vaz, Marco A

    2018-04-01

    Some evidence supports that low-level laser therapy (LLLT) reduces neuromuscular fatigue, so incrementing sports performance. A previous randomized controlled trial of our group showed increased exercise tolerance in male competitive cyclists treated with three different LLLT doses (3, 6, and 9 J/diode; or 135, 270, and 405 J/thigh) before time-to-exhaustion cycling tests. Now, the present study was designed to evaluate the effects of these LLLT doses on the VO 2 kinetics of athletes during cycling tests. Twenty male competitive cyclists (29 years) participated in a crossover, randomized, double-blind, and placebo-controlled trial. On the first day, the participants performed an incremental cycling test to exhaustion to determine maximal oxygen uptake (VO 2MAX ) and maximal power output (PO MAX ), as well as a familiarization with the time-to-exhaustion test. In the following days (2 to 5), all participants performed time-to-exhaustion tests at PO MAX . Before the exhaustion test, different doses of LLLT (3, 6, and 9 J/diode; or 135, 270, and 405 J/thigh, respectively) or placebo were applied bilaterally to the quadriceps muscle. All exhaustion tests were monitored online by an open-circuit spirometry system in order to analyze the VO 2 amplitude, VO 2 delay time, time constant (tau), and O 2 deficit. Tau and O 2 deficit were decreased with LLLT applications compared to the placebo condition (p  0.05) were found between the experimental conditions for VO 2 amplitude and VO 2 delay time. In conclusion, LLLT decreases tau and O 2 deficit during time-to-exhaustion tests in competitive cyclists, and these changes in VO 2 kinetics response can be one of the possible mechanisms to explain the ergogenic effect induced by LLLT.

  4. Evidence for a Broad Autism Phenotype

    NARCIS (Netherlands)

    K. de Groot (Kristel); J.W. van Strien (Jan)

    2017-01-01

    textabstractThe broad autism phenotype implies the existence of a continuum ranging from individuals displaying almost no autistic traits to severely impaired diagnosed individuals. Recent studies have linked this variation in autistic traits to several domains of functioning. However, studies

  5. 33 CFR 117.921 - Broad River.

    Science.gov (United States)

    2010-07-01

    ... OPERATION REGULATIONS Specific Requirements South Carolina § 117.921 Broad River. (a) The draw of the S170 bridge, mile 14.0 near Beaufort, shall open on signal if at least 24 hours notice is given. (b) The draw...

  6. Education and Broad Concepts of Agency

    Science.gov (United States)

    Winch, Christopher

    2014-01-01

    Drawing on recent debates about the relationship between propositional and practical knowledge, this article is concerned with broad concepts of agency. Specifically, it is concerned with agency that involves the forming and putting into effect of intentions over relatively extended periods, particularly in work contexts (called, for want of a…

  7. Ultra wide band antennas

    CERN Document Server

    Begaud, Xavier

    2013-01-01

    Ultra Wide Band Technology (UWB) has reached a level of maturity that allows us to offer wireless links with either high or low data rates. These wireless links are frequently associated with a location capability for which ultimate accuracy varies with the inverse of the frequency bandwidth. Using time or frequency domain waveforms, they are currently the subject of international standards facilitating their commercial implementation. Drawing up a complete state of the art, Ultra Wide Band Antennas is aimed at students, engineers and researchers and presents a summary of internationally recog

  8. Luminescence of (Ca,Sr)3(VO4)2: Pr3+, Eu3+ phosphor for use in CuPc-based solar cells and white light-emitting diodes

    International Nuclear Information System (INIS)

    Lin, Han-Yu; Chang, Wei-Fu; Chu, Sheng-Yuan

    2013-01-01

    The purpose of this study is to enhance the red emission intensity and expand the blue excitation band of a (Ca,Sr) 2.82 (VO 4 ) 2 :0.12Eu 3+ phosphor for use in copper phthalocyanine (CuPc)-based solar cells and white light-emitting diodes. It was found that substitution of 3% Sr 2+ replacing Ca 2+ enhanced red emission intensity of Ca 2.82 (VO 4 ) 2 :0.12Eu 3+ by 14% under 465-nm by excitation. The Pr 3+ co-doping effect was realized when blue excitation intensity of (Ca 0.97 Sr 0.03 ) 2.82 (VO 4 ) 2 :0.12Eu 3+ , located in the weakest absorption of CuPc, was improved by 126% with the addition of 0.6 mol% Pr 3+ . The absorption spectrum of CuPc/optimized (Ca 0.9668 Sr 0.03 ) 2.82 (VO 4 ) 2 :0.006Pr 3+ , 0.12Eu 3+ mixtures provided evidence that the (Ca 0.9668 Sr 0.03 ) 2.82 (VO 4 ) 2 :0.006Pr 3+ , 0.12Eu 3+ phosphor could increase the efficiency of incident photons on CuPc-based solar cells. Moreover, the good temperature stability of emission intensity and chromaticity of (Ca 0.9668 Sr 0.03 ) 2.82 (VO 4 ) 2 :0.006Pr 3+ , 0.12Eu 3+ indicated a potential for this phosphor to be applied on the white light-emitting diodes. - Highlights: ► Substitution of 3% Sr 2+ replacing Ca 2+ enhanced red emission intensity of Ca 2.82 (VO 4 ) 2 :0.12Eu 3+ by 14% under 465 nm by excitation. ► Addition of 0.6 mol% Pr 3+ enhanced blue excitation intensity of (Ca 0.97 Sr 0.03 ) 2.82 (VO 4 ) 2 :0.12Eu 3+ , located in the weakest absorption of CuPc, by 126%. ► According to absorption measurements of CuPc/optimized (Ca 0.9668 Sr 0.03 ) 2.82 (VO 4 ) 2 :0.006Pr 3+ , 0.12Eu 3+ mixtures for the first time, the feasibility of our phosphor to assist CuPc in converting blue-wavelength photons was proved. ► High temperature stability of emission intensity and chromaticity of (Ca 0.9668 Sr 0.03 ) 2.82 (VO 4 ) 2 :0.006Pr 3+ , 0.12Eu 3+ indicated our phosphor is acceptable for WLED applications.

  9. VoVis: A Vocabulary-based Web Visualization Framework

    OpenAIRE

    Sharma, Swati

    2015-01-01

    The amount of data in today's digital world is growing day by day. Visualization is considered as the best form of communication because the human brain perceives it much faster than the text data that comprises with thousand of words. Because of the enormous and continuously increasing data, the demand to visualize it is also increasing. Information visualization is a wide research area that covers a broad range of data fields. There are various visualization frameworks, tools and technologi...

  10. Implementasi Protokol Keamanan TLS pada Aplikasi Layanan Komunikasi Suara Melalui Jaringan TCP/IP (VoIP)

    OpenAIRE

    Hariady, Ricky

    2011-01-01

    Saat ini layanan komunikasi suara melalui jaringan TCP/IP atau yang lebih dikenal dengan VoIP (Voice over IP) telah semakin banyak digunakan, namun teknologi VoIP yang ada saat ini masih rentan terhadap penyadapan ataupun pencurian data. Sementara protokol kriptografi TLS (Transport Layer Security) telah teruji dan banyak digunakan untuk mengamankan komunikasi melalui internet seperti pada layanan email dan web. Dengan mengimplementasikan protokol TLS pada sebuah aplikasi Vo...

  11. A cost-effective method to fabricate VO{sub 2} (M) nanoparticles and films with excellent thermochromic properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hua [CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xiao, Xiudi, E-mail: xiaoxd@ms.giec.ac.cn [CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640 (China); Lu, Xuanming [CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Chai, Guanqi; Sun, Yaoming; Zhan, Yongjun; Xu, Gang [CAS Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640 (China)

    2015-07-05

    Highlights: • Via solvent–thermal and pyrolysis method, VO{sub 2} (M) powder was synthesized in air. • Aiding by grinding, VO{sub 2} (M) nanoparticles with the size of 22 nm were obtained. • The VO{sub 2} films show great thermochromic properties with T{sub lum} = 62.1% and ΔT{sub sol} = 12.4%. • The haze is down to 1.9%, which is superior with films prepared by other methods. - Abstract: In this paper, high crystallinity and pure phase VO{sub 2} (M) powder is synthesized by a novel and facile method. Aiding by additional manual grinding and etching process, 22 nm high-quality VO{sub 2} (M) nanoparticles can be obtained. The structure and properties of the VO{sub 2} (M) particles were characterized by X-ray diffraction analysis, transmission electron microscopy, differential scanning calorimetry and UV–vis–NIR spectrophotometer. After mixing VO{sub 2} (M) nanoparticles with transparent polymer, thin films prepared by grinded VO{sub 2} nanoparticles show excellent thermochromic properties. The solar modulation ability is up to 12.4% with luminous transmittance of 62.7%. Moreover, The haze of films prepared by grinded VO{sub 2} (M) nanoparticles is down to 1.9%, which is far less than that of films prepared by original VO{sub 2} (Haze = 8.5%) and etched VO{sub 2} particles (Haze = 4.6%). Dramatical improvement of thermochromic property and definition indicate that it is a promising method to prepare large-scale VO{sub 2} nanoparticles and cost-effective smart window.

  12. Optical Characterization of Rare Earth-doped Wide Band Gap Semiconductors

    National Research Council Canada - National Science Library

    Hommerich, Uwe

    1999-01-01

    ...+) PL intensity under below gap excitation. Photoluminescence excitation (PLE) studies revealed that oxygen/carbon introduces a broad below gap PLE band, which provides an efficient pathway for E(3+) excitation...

  13. Enhanced visible-light-response photocatalytic degradation of methylene blue on Fe-loaded BiVO{sub 4} photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Chala, Sinaporn [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Wetchakun, Khatcharin [Program of Physics, Faculty of Science, Ubon Ratchathani Rajabhat University, Ubon Ratchathani 34000 (Thailand); Phanichphant, Sukon [Materials Science Research Centre, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Inceesungvorn, Burapat [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Wetchakun, Natda, E-mail: natda_we@yahoo.com [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand)

    2014-06-01

    Highlights: • Fe-loaded BiVO{sub 4} particles were prepared by hydrothermal method. • Physicochemical properties played a significant role in photocatalytic process. • All Fe-loaded BiVO{sub 4} samples showed higher photocatalytic activity than pure BiVO{sub 4}. • The Fe{sup 3+} ions may improve the separation of photogenerated electrons and holes. - Abstract: Pure BiVO{sub 4} and nominal 0.5–5.0 mol% Fe-loaded BiVO{sub 4} samples were synthesized by hydrothermal method. All samples were characterized in order to obtain the correlation between structure and photocatalytic properties by X-ray diffraction, Brunauer, Emmett and Teller, UV–vis diffuse reflectance spectrophotometry, photoluminescence spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and inductively coupled plasma-optical emission spectroscopy. The structure of all samples was single-phase monoclinic scheelite. The absorption spectrum of 5.0 mol% Fe-loaded BiVO{sub 4} shifted to the visible region, suggesting the potential application of this material as a superior visible-light driven photocatalyst in comparison with pure BiVO{sub 4}. Photocatalytic activities of all photocatalyst samples were examined by studying the degradation of methylene blue under visible light irradiation. The results clearly showed that Fe-loaded BiVO{sub 4} sample exhibited remarkably higher activity than pure BiVO{sub 4}.

  14. Enhanced visible-light-response photocatalytic degradation of methylene blue on Fe-loaded BiVO4 photocatalyst

    International Nuclear Information System (INIS)

    Chala, Sinaporn; Wetchakun, Khatcharin; Phanichphant, Sukon; Inceesungvorn, Burapat; Wetchakun, Natda

    2014-01-01

    Highlights: • Fe-loaded BiVO 4 particles were prepared by hydrothermal method. • Physicochemical properties played a significant role in photocatalytic process. • All Fe-loaded BiVO 4 samples showed higher photocatalytic activity than pure BiVO 4 . • The Fe 3+ ions may improve the separation of photogenerated electrons and holes. - Abstract: Pure BiVO 4 and nominal 0.5–5.0 mol% Fe-loaded BiVO 4 samples were synthesized by hydrothermal method. All samples were characterized in order to obtain the correlation between structure and photocatalytic properties by X-ray diffraction, Brunauer, Emmett and Teller, UV–vis diffuse reflectance spectrophotometry, photoluminescence spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and inductively coupled plasma-optical emission spectroscopy. The structure of all samples was single-phase monoclinic scheelite. The absorption spectrum of 5.0 mol% Fe-loaded BiVO 4 shifted to the visible region, suggesting the potential application of this material as a superior visible-light driven photocatalyst in comparison with pure BiVO 4 . Photocatalytic activities of all photocatalyst samples were examined by studying the degradation of methylene blue under visible light irradiation. The results clearly showed that Fe-loaded BiVO 4 sample exhibited remarkably higher activity than pure BiVO 4

  15. An Efficient Scheduling Scheme to Enhance the Capacity of VoIP Services in Evolved UTRA Uplink

    Directory of Open Access Journals (Sweden)

    Kim Yong-Seok

    2008-01-01

    Full Text Available An efficient scheduling scheme is proposed to increase the available capacity of VoIP services over evolved UTRA uplink. On top of the advantages of persistent scheduling, the proposed scheme adaptively share the resources of two VoIP users to get early-termination gain of dynamic scheduler. Through system-level simulations, the performance of the proposed algorithm is evaluated in terms of the capacity enhancement of VoIP services. Comparisons with the original persistent scheduling and the HSUPA scheduler reveal that the proposed scheme increases the capacity of VoIP services up to 20%.

  16. VO{sub x} effectively doping CVD-graphene for transparent conductive films

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Qinghua; Shi, Liangjing [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Zhang, Qinghong [State Key Laboratory of Modification of Chemical Fibers and Polymer Materials, College of Material Science and Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620 (China); Wang, Weiqi; Zheng, Huifeng [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Zhang, Yuzhi [The Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences,1295 Dingxi Road, Shanghai 200050 (China); Liu, Yangqiao, E-mail: yqliu@mail.sic.ac.cn [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Sun, Jing, E-mail: jingsun@mail.sic.ac.cn [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)

    2016-11-30

    Highlights: • Doping process operated easily. • Sheet resistance decreased efficiently after doping. • Sheet resistance of doped graphene is stable after exposed in the air. • Mechanism of doping process is studied. - Abstract: Chemical vapor deposition(CVD)-synthesized graphene is potentially an alternative for tin-doped indium oxide (ITO) transparent conductive films (TCFs), however its sheet resistance is still too high to meet many demands. Vanadium oxide has been widely applied as smart window materials, however, no study has been reported to use it as dopant to improve the conductivity of graphene TCFs. In this study, we firstly reported that VO{sub x} doping can effectively lower the sheet resistance of CVD-graphene films while keeping its good optical properties, whose transmittance is as high as 86–90%. The optimized VO{sub x}-doped graphene exhibits a sheet resistance as low as 176 Ω/□, which decreases by 56% compared to the undoped graphene films. The doping process is convenient, stable, economical and easy to operate. What is more, VO{sub x} can effectively increase the work function(WF) of the film, making it more appropriate for use in solar cells. The evolution of the VO{sub x} species annealed at different temperatures below 400 °C has been detailed studied for the first time, based on which the doping mechanism is proposed. The prepared VO{sub x} doped graphene is expected to be a promising candidate for transparent conductive film purposes.

  17. Preparation of BiVO4-Graphene Nanocomposites and Their Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Xuan Xu

    2014-01-01

    Full Text Available We prepared BiVO4-graphene nanocomposites by using a facile single-step method and characterized the material by x-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, ultraviolet-visible diffuse-reflection spectroscopy, and three-dimensional fluorescence spectroscopy. The results show that graphene oxide in the catalyst was thoroughly reduced. The BiVO4 is densely dispersed on the graphene sheets, which facilitates the transport of electrons photogenerated in BiVO4, thereby leading to an efficient separation of photogenerated carriers in the coupled graphene-nanocomposite system. For degradation of rhodamine B dye under visible-light irradiation, the photocatalytic activity of the synthesized nanocomposites was over ∼20% faster than for pure BiVO4 catalyst. To study the contribution of electrons and holes in the degradation reaction, silver nitrate and potassium sodium tartrate were added to the BiVO4-graphene photocatalytic reaction system as electron-trapping agent and hole-trapping agent, respectively. The results show that holes play the main role in the degradation of rhodamine B.

  18. The effect of Iron Supplying on VO2 MAX and Haematology Parameter on Menstrual Woman

    Science.gov (United States)

    Nailuvar Sinaga, Rika; Sari Harahap, Novita; Mediyana Sari, Rima

    2018-03-01

    One of the supporting factors to have good aerobic endurance requires high VO2 max levels supported by good quality and quantity level of Haematology parameter especially such as erythrocytes, hematocrit and hemoglobin. One of the components in hemoglobin is iron which functions as theoxygen transport to parts of all body required in the process of metabolism. The objective of this research was to find out the difference between VO2 Max and Haematology parameter between iron supplying and no iron supplyingonmenstrual woman. The type of this research is quasi experimental research with non-randomized control group Pretest-Postest Design. The subjectsarethe studentsat faculty of Sports Sciences, Medan State University with the criteria of female gender, monthly regular menstrual cycle, having the level of health and the level of training, willing to be a sample by filling out informed consent. The total number of research subjectsis twenty students, divided into two groups namely the treatment group and the control group. The hematology parameter was measuredby Haemotology analyzer and VO2 Max was measured by multi-stage run. The result showed that there was a significant effect of iron supplyingon the increase of erythrocyte level on menstrual women, hemotocrit, haemoglobin and an increase in VO2 Max. Iron supplying on menstrual woman has the effect on the increase of erythrocyte, hematocrit, hemoglobin level and VO2 Max

  19. Enhanced red emission of LaVO4:Eu3+ phosphors by Li-doping

    International Nuclear Information System (INIS)

    Park, Sung Wook; Yang, Hyun Kyoung; Chung, Jong Won; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun; Jang, Ki Wan; Lee, Ho Sueb; Yi, Soung Soo

    2010-01-01

    LaVO 4 phosphors were synthesized by using a solid state reaction, and were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL). The XRD patterns of the Li-doped LaVO 4 :Eu 3+ powder phosphors revealed a mixture of tetragonal and monoclinic phases. The tetragonal phase of the LaVO 4 :Eu 3+ phosphor showed a higher PL intensity than the monoclinic one, despite the presence of both monoclinic and tetragonal structures. The Li-doped LaVO 4 :Eu 3+ powder phosphors absorbed strongly at 396 nm and exhibited strong red emission at approximately 619.5 nm due to the 5 D 0 → 7 F 2 transition. The incorporation of Li + ions into the LaVO 4 :Eu 3+ powder can lead to a remarkable increase in photoluminescence. The enhanced luminescence is attributed to the incorporation of Li + ions that may act as a sensitizers for effective energy transfer. This phosphor has promising applications in near-UV light-emitting diodes(LEDs).

  20. Relationship between running kinematic changes and time limit at vVO2max

    Directory of Open Access Journals (Sweden)

    Leonardo De Lucca

    2012-06-01

    Exhaustive running at maximal oxygen uptake velocity (vVO2max can alter running kinematic parameters and increase energy cost along the time. The aims of the present study were to compare characteristics of ankle and knee kinematics during running at vVO2max and to verify the relationship between changes in kinematic variables and time limit (Tlim. Eleven male volunteers, recreational players of team sports, performed an incremental running test until volitional exhaustion to determine vVO2max and a constant velocity test at vVO2max. Subjects were filmed continuously from the left sagittal plane at 210 Hz for further kinematic analysis. The maximal plantar flexion during swing (p<0.01 was the only variable that increased significantly from beginning to end of the run. Increase in ankle angle at contact was the only variable related to Tlim (r=0.64; p=0.035 and explained 34% of the performance in the test. These findings suggest that the individuals under study maintained a stable running style at vVO2max and that increase in plantar flexion explained the performance in this test when it was applied in non-runners.

  1. Optical switching properties of VO2 films driven by using WDM-aligned lasers

    International Nuclear Information System (INIS)

    Tsai, K.Y.; Wu, F.-H.; Shieh, H.-P.D.; Chin, T.-S.

    2006-01-01

    Vanadium dioxide (VO 2 ) film had been demonstrated a high speed IR shutter driven by total optical modulation. However, it usually required a higher power heating laser of high power and precise optical systems to cover the probe beam on the sample with a heating beam of larger area. A new optical system, simply composed of wavelength division multiplexing (WDM), fiber lens or convex lens system, and a glass sheet with VO 2 thin film on it, was easily assembled to utilize VO 2 film as an IR shutter, implying the possibility to highly miniaturize the VO 2 -based optical shutter. A permanent low-transmittance (PLT) region forms on the film within the probe beam, resulting in a decrease in average power of the probe beam. Another ring-type switching area (switching ring) forms around the PLT region, resulting in the transmittance switching of the probe beam synchronously with the heating signal. VO 2 films can be switched with the highest rate of a continuous square heating signal of 3 mW at 120 kHz. A heating pulse of 0.7 ns and 13 mW can be used to stimulate an IR pulse with fiber lens

  2. Analisis Kualitas VoIP pada SCTP Menggunakan ECN dan AQM

    Directory of Open Access Journals (Sweden)

    La Surimi

    2015-07-01

    Abstract VoIP is the real time applications that are highly dependent on the quality of  delay and jitter, which it is difficult to be met by protocol that has reliable data transfer feature and  congestion control such as TCP. On the other hand the use of UDP that has no congestion control make chance of causing congestion in the network is very large. The use of SCTP as an alternative protocol was also not able to accommodate the weaknesses of TCP and UDP. Some research shows that repairs or modifications to the SCTP congestion control mechanism is needed. The Use of ECN and AQM in some studies show that these two mechanisms can reduce delay and jitter. This study tested the quality of VoIP over SCTP with ECN and AVQ, in NS2. Simulations carried out by independent replication technique, and the results showed that ECN and AVQ can increase the value of MOS VoIP calls significantly in non ideal network scenarios. This study also did comparison of SCTP MOS that uses ECN and AVQ with MOS values VoIP using TCP and UDP. The result showed that SCTP with ECN and AVQ outperform TCP but can not surpass UDP yet.   Keywords— VoIP, SCTP, ECN, AQM,AVQ.

  3. Effects of erythrocyte infusion on VO2max at high altitude

    DEFF Research Database (Denmark)

    Young, Jette Feveile; Sawka, M N; Muza, S R

    1996-01-01

    This study investigated whether autologous erythrocyte infusion would ameliorate the decrement in maximal O2 uptake (VO2max) experienced by lowlanders when they ascend to high altitude. VO2max was measured in 16 men (treadmill running) at sea level (SL) and on the 1st (HA1) and 9th (HA9) days...... of high-altitude (4,300 m) residence. After VO2max was measured at SL, subjects were divided into two matched groups (n = 8). Twenty-four hours before ascent to high altitude, the experimental group received a 700-ml infusion of autologous erythrocytes and saline (42% hematocrit), whereas the control...... group received only saline. The VO2max of erythrocyte-infused [54 +/- 1 (SE) ml.kg-1.min-1] and control subjects (52 +/- 2 ml.kg-1.min-1) did not differ at SL before infusion. The decrement in VO2max on HA1 did not differ between groups, averaging 26% overall, despite higher (P

  4. Band-notched spiral antenna

    Science.gov (United States)

    Jeon, Jae; Chang, John

    2018-03-13

    A band-notched spiral antenna having one or more spiral arms extending from a radially inner end to a radially outer end for transmitting or receiving electromagnetic radiation over a frequency range, and one or more resonance structures positioned adjacent one or more segments of the spiral arm associated with a notch frequency band or bands of the frequency range so as to resonate and suppress the transmission or reception of electromagnetic radiation over said notch frequency band or bands.

  5. Broad line regions in Seyfert-1 galaxies

    International Nuclear Information System (INIS)

    Groningen, E. van.

    1984-01-01

    To reproduce observed emission profiles of Seyfert galaxies, rotation in an accretion disk has been proposed. In this thesis, the profiles emitted by such an accretion disk are investigated. Detailed comparison with the observed profiles yields that a considerable fraction can be fitted with a power-law function, as predicted by the model. The author analyzes a series of high quality spectra of Seyfert galaxies, obtained with the 2.5m telescope at Las Campanas. He presents detailed analyses of two objects: Mkn335 and Akn120. In both cases, strong evidence is presented for the presence of two separate broad line zones. These zones are identified with an accretion disk and an outflowing wind. The disk contains gas with very high densities and emits predominantly the lower ionization lines. He reports on the discovery of very broad wings beneath the strong forbidden line 5007. (Auth.)

  6. Fourier evaluation of broad Moessbauer spectra

    International Nuclear Information System (INIS)

    Vincze, I.

    1981-01-01

    It is shown by the Fourier analysis of broad Moessbauer spectra that the even part of the distribution of the dominant hyperfine interaction (hyperfine field or quadrupole splitting) can be obtained directly without using least-square fitting procedures. Also the odd part of this distribution correlated with other hyperfine parameters (e.g. isomer shift) can be directly determined. Examples for amorphous magnetic and paramagnetic iron-based alloys are presented. (author)

  7. Fourier evaluation of broad Moessbauer spectra

    International Nuclear Information System (INIS)

    Vincze, I.

    1981-09-01

    It is shown by the Fourier analysis of broad Moessbauer spectra that the even part of the distribution of the dominant hyperfine interaction (hyperfine field or quadrupole splitting) can be obtained directly without using least-square fitting procedures. Also the odd part of this distribution correlated with other hyperfine parameters (e.g. isomer shift) can be directly determined. Examples covering the case of amorphous magnetic and paramagnetic iron-based alloys are presented. (author)

  8. Growth and laser characterization of mixed Nd:Lu xGd 1-xVO 4 laser crystals

    Science.gov (United States)

    Yu, Haohai; Yu, Yonggui; Zhang, Huaijin; Wang, Zhengping; Wang, Jiyang; Cheng, Xiufeng; Shao, Zongshu; Jiang, Minhua

    2006-08-01

    A new series Nd:Lu xGd 1-xVO 4 ( x=0.14, 0.32, 0.50, 0.61, 0.70 and 0.80) mixed laser crystals have been successfully grown by the Czochralski method. The X-ray powder diffraction (XRPD) analysis shows that the as-grown mixed crystals possess the ZrSiO 4 structure. The cell parameters are found to decrease with an increase of x. The optical absorption spectra of the mixed crystals have been measured at room temperature, and five strong-absorption bands centered at the wavelengths of 531, 594, 752, 807 and 880 nm have been revealed in all crystals. They are assigned to the different spin- and electric-dipole-allowed transition from the ground state to the 2K 13/2+ 4G 7/2+ 4G 9/2, 4G 5/2+ 2G 7/2, 4F 7/2+ 4S 3/2, 4F 5/2+ 2H 9/2 and 4F 3/2 energy levels, respectively. A continuous-wave (CW) laser output has been achieved with the mixed crystals at 1.06 μm under laser diode pumping. The maximum CW output power of 377.4 mW has been obtained with the pump power of 2 W, and the corresponding optical conversion efficiency is 18.8%.

  9. Thermally tunable broadband omnidirectional and polarization-independent super absorber using phase change material VO2

    Directory of Open Access Journals (Sweden)

    Zhejun Liu

    Full Text Available In this letter, we numerically demonstrate a thermally tunable super absorber by using phase change material VO2 as absorbing layer in metal-insulator-metal structure. An omnidirectional super absorption at λ=2.56μm can be realized by heating the patterned grating VO2 film due to magnetic resonance mechanism. Furthermore, a broadband super absorption higher than 0.8 in the entire 1.6μm–4μm region is achieved when VO2 film is patterned chessboard structure and transformed to metal phase beyond transition temperature. This broadband super absorption can be fulfilled in a wide range of incident angle (0°–70° and under all polarization conditions. Keywords: Phase change material, Metal-insulator-metal, Super absorption, Magnetic resonance

  10. Metal-insulator transition in nanocomposite VO{sub x} films formed by anodic electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Tsui, Lok-kun; Lu, Jiwei; Zangari, Giovanni, E-mail: gz3e@virginia.edu [Department of Materials Science and Engineering, University of Virginia, 395 McCormick Rd., Charlottesville, Virginia 22904 (United States); Hildebrand, Helga; Schmuki, Patrik [Department for Materials Science LKO, University of Erlangen-Nuremberg, Martensstr. 7, D-91058 Erlangen (Germany)

    2013-11-11

    The ability to grow VO{sub 2} films by electrochemical methods would open a low-cost, easily scalable production route to a number of electronic devices. We have synthesized VO{sub x} films by anodic electrodeposition of V{sub 2}O{sub 5}, followed by partial reduction by annealing in Ar. The resulting films are heterogeneous, consisting of various metallic/oxide phases and including regions with VO{sub 2} stoichiometry. A gradual metal insulator transition with a nearly two order of magnitude change in film resistance is observed between room temperature and 140 °C. In addition, the films exhibit a temperature coefficient of resistance of ∼ −2.4%/ °C from 20 to 140 °C.

  11. Developing VoIP Honeypots: a Preliminary Investigation into Malfeasant Activity

    Directory of Open Access Journals (Sweden)

    Craig Valli

    2010-06-01

    Full Text Available 30 years ago PABX systems were compromised by hackers wanting to make long distance calls at some other entities expense. This activity faded as telephony became cheaper and PABX systems had countermeasures installed to overcome attacks. Now the world has moved onto the provision of telephony via broadband enabled Voice over Internet Protocol (VoIP with this service now being provided as a replacement for conventional fixed wire telephony by major telecommunication providers worldwide. Due to increasing bandwidth it is possible for systems to support multiple voice connections simultaneously. The networked nature of the Internet allows for attackers of these VoIP systems to enumerate and potentially attack and compromise a wide range of vulnerable systems. This paper is an outline of preliminary research into malfeasant VoIP activity on the Internet.

  12. Influence of Security Mechanisms on the Quality of Service of VoIP

    Science.gov (United States)

    Backs, Peter; Pohlmann, Norbert

    While Voice over IP (VoIP) is advancing rapidly in the telecommunications market, the interest to protect the data transmitted by this new service is also rising. However, in contrast to other internet services such as email or HTTP, VoIP is real-time media, and therefore must meet a special requirement referred to as Quality-of-Service to provide a comfortable flow of speech. Speech quality is worsened when transmitted over the network due to delays in transmission or loss of packets. Often, voice quality is at a level that even prevents comprehensive dialog. Therefore, an administrator who is to setup a VoIP infrastructure might consider avoiding additional decreases in voice quality resulting from security mechanisms, and might leave internet telephony unprotected as a result. The inspiration for this paper is to illustrate that security mechanisms have negligible impact on speech quality and should in fact be encouraged.

  13. VO2 thin films synthesis for collaborators and various applications.

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Raegan Lynn [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Clem, Paul G. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2016-11-01

    Vanadium dioxide (VO2) is an attractive material for a variety of applications due to its metal-to-insulator transition (MIT) observed at modest temperatures. This transition takes VO2 from its low temperature insulating monoclinic phase to a high temperature (above 68°C) metallic rutile phase. This transition gives rise to a change in resistivity up to 5 orders of magnitude and a change in complex refractive index (especially at IR wavelengths), which is of interest for radar circuit protection and tunable control of infrared signature. Recently, collaborations have been initiated between CINT scientists and external university programs. The Enhanced Surveillance funds help fund this work which enabled synthesis of VO2 films for several collaborations with internal and external researchers.

  14. Quaternary system LiF-LiCl-LiVO3-Li2MoO4

    International Nuclear Information System (INIS)

    Anipchenko, B.V.; Garkushin, I.K.

    2000-01-01

    Interactions in the LiF-LiCl-LiVO 3 -Li 2 MoO 4 system are studied by differential thermal analysis. Rate of heating/cooling of the samples comprised 15 Grad/min, mass of sample composed 0.2 g. The system was investigated in the 300-650 Deg C range. X-ray diffraction method was used for determination of purity of the reagents. Composition and temperature of quaternary component eutectics are determined: 16.5 mol. % of LiF, 47.0 mol. % of LiCl, 28.8 mol. % of LiVO 3 , 7.6 mol. % of Li 2 MoO 4 ; 387 Deg C. Mean value of melting enthalpy of quaternary eutectics mixture in the LiF-LiCl-LiVO 3 -Li 2 MoO 4 system on the results of the tests was in the range of 222 kJ/kg [ru

  15. Tunable subwavelength hot spot of dipole nanostructure based on VO2 phase transition.

    Science.gov (United States)

    Park, Jun-Bum; Lee, Il-Min; Lee, Seung-Yeol; Kim, Kyuho; Choi, Dawoon; Song, Eui Young; Lee, Byoungho

    2013-07-01

    We propose a novel approach to generate and tune a hot spot in a dipole nanostructure of vanadium dioxide (VO2) laid on a gold (Au) substrate. By inducing a phase transition of the VO2, the spatial and spectral distributions of the hot spot generated in the feed gap of the dipole can be tuned. Our numerical simulation based on a finite-element method shows a strong intensity enhancement difference and tunability near the wavelength of 678 nm, where the hot spot shows 172-fold intensity enhancement when VO2 is in the semiconductor phase. The physical mechanisms of forming the hot spots at the two-different phases are discussed. Based on our analysis, the effects of geometric parameters in our dipole structure are investigated with an aim of enhancing the intensity and the tunability. We hope that the proposed nanostructure opens up a practical approach for the tunable near-field nano-photonic devices.

  16. Security Analysis System to Detect Threats on a SIP VoIP Infrasctructure Elements

    Directory of Open Access Journals (Sweden)

    Filip Rezac

    2011-01-01

    Full Text Available SIP PBX is definitely the alpha and omega of any IP telephony infrastructure and frequently also provides other services than those related to VoIP traffic. These exchanges are, however, very often the target of attacks by external actors. The article describes a system that was developed on VSB-TU Ostrava as a testing tool to verify if the target VoIP PBX is adequately secured and protected against any real threats. The system tests the SIP element for several usually occurring attacks and it compiles evaluation of its overall security on the basis of successfully or unsuccessfully penetrations. The article describes the applications and algorithms that are used by system and the conclusion consists recommendations and guidelines to ensure effective protection against VoIP PBX threats. The system is designed as an open-source web application, thus allowing independent access and is fully extensible to other test modules.

  17. Microwave assisted growth of nanorods vanadium dioxide VO2 (R): structural and electrical properties

    Science.gov (United States)

    Derkaoui, I.; Khenfouch, M.; Mothudi, B. M.; Moloi, S. J.; Zorkani, I.; Jorio, A.; Maaza, M.

    2018-03-01

    Nanostructured metal oxides have attracted a lot of attention recently owning to their unique structural advantages and demonstrated promising chemical and physical properties for various applications. In this study, we report the structural and electrical properties of vanadium dioxide VO2 (R) prepared via a single reaction microwave (SRC) synthesis. Our results are revealing that the components of VO2 (R) films have a rod-like shape with a uniform size distribution. The nanorods with very smooth and flat surfaces have a typical length of up to 2μm and a width of about several nanometers. The structural investigations reveal the high crystallinity of VO2 (R) ensuring good electrical contact and showing a high conductivity as a function of temperature. This synthesis method provides a new simple route to fabricate one-dimensional nanostructured metal oxides which is suitable for a large field of applications especially for smart windows.

  18. Heritability and Components of Resistance to Cercospora zeae-maydis Derived from Maize Inbred VO613Y.

    Science.gov (United States)

    Gordon, Stuart G; Lipps, Patrick E; Pratt, Richard C

    2006-06-01

    ABSTRACT Gray leaf spot (GLS), caused by the fungus Cercospora zeae-maydis, is one of the most important foliar diseases of maize. This study was undertaken to estimate heritability of C. zeae-maydis resistance and examine the relationship between previously identified resistance loci and certain components of resistance including incubation period, lesion number, and maximum lesion length. Partially inbred progenies arising from hybridization between maize inbred lines VO613Y (high level of partial resistance) and Pa405 (susceptible) were examined in Ohio and South Africa. Heritability estimates of resistance were calculated based on severity and incubation period values. The range of heritability estimates based on severity was broad, with values ranging from approximately 0.46 to 0.81 (mean = 0.59). Estimates of mean heritability for incubation period were lowest (0.18), indicating that this component would likely be unsuitable for selection of germ plasm intended for deployment in diverse regions. Length of GLS lesions was significantly affected by host genotype, with resistant genotypes having shorter lesions from one site in Ohio during two seasons. Genotype also had a significant effect on incubation period and lesion number; the lower values for these components also were associated with resistant genotypes. The combined action of these resistance components resulted in lower overall disease severity.

  19. RGO/InVO{sub 4} hollowed-out nanofibers: Electrospinning synthesis and its application in photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Dong [Key Lab of Marine Environment and Ecology, Ministry of Education, Ocean University of China, Qingdao 266100 (China); College of Resource and Environment, Qingdao Agricultural University, Qingdao 266109 (China); Zhang, Yanxiang [College of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Gao, Mengchun, E-mail: mengchungao@outlook.com [Key Lab of Marine Environment and Ecology, Ministry of Education, Ocean University of China, Qingdao 266100 (China); Xin, Yanjun; Wu, Juan [College of Resource and Environment, Qingdao Agricultural University, Qingdao 266109 (China); Bao, Nan [College of Environmental Science and Engineering, Shandong University, Jinan 250100 (China)

    2015-10-30

    Graphical abstract: - Highlights: • RGO/InVO{sub 4} hollow-out nanofibers were obtained by electrospinning method. • The properties of InVO{sub 4} hollow-out nanofibers were deeply influenced by RGO. • RGO could reduce recombination of e{sup −}–h{sup +} pairs to improve photocatalytic activity. • Photo-induced h{sup +} and e{sup −} are the two main reactive species for RhB degradation. - Abstract: A composite of reduced graphene oxide (RGO) and InVO{sub 4} nanofiber was successfully synthesized by an electrospinning technique. The as-collected fibers were calcined at 420 °C in air and then calcined at 550 °C in nitrogen gas to remove polyvinyl pyrrolidone (PVP), which could enable InVO{sub 4} to crystallize and protect the RGO from oxidation. The InVO{sub 4} in the composite illustrated a hollowed-out fibrous morphology and orthorhombic phase, and RGO nanosheets were nested in the InVO{sub 4} nanofibers. The hybrid RGO could produce more hydroxyl groups and a higher oxygen vacancy density on the surface of RGO/InVO{sub 4} composite. Compared with pure InVO{sub 4}, the light absorption range of the as-prepared RGO/InVO{sub 4} composite was expanded. In Rh B degradation, the RGO/InVO{sub 4} hybrid nanofibers displayed a higher photocatalytic activity than pure InVO{sub 4} nanofibers. The enhanced photocatalytic activity might be ascribed to the role of RGO as an electron transporter and acceptor in the composite, which could effectively inhibit the charge recombination and facilitate the charge transfer. The exported electron could attack an O{sub 2} molecule to facilitate the generation of • O{sub 2}{sup −} and • OH for the photodegradation process of Rh B.

  20. HEART RATE VARIABILITY AND BODY COMPOSITION AS VO2MAX DETERMINANTS

    Directory of Open Access Journals (Sweden)

    Henry Humberto León-Ariza

    Full Text Available ABSTRACT Introduction: The maximum oxygen consumption (VO2max is the gold standard in the cardiorespiratory endurance assessment. Objective: This study aimed to develop a mathematical model that contains variables to determine the VO2max of sedentary people. Methods: Twenty participants (10 men and 10 women with a mean age of 19.8±1.77 years were included. For each participant, body composition (percentage of fat and muscle, heart rate variability (HRV at rest (supine and standing, and VO2max were evaluated through an indirect test on a cycloergometer. A multivariate linear regression model was developed from the data obtained, and the model assumptions were verified. Results: Using the data obtained, including percentage of fat (F, percentage of muscle (M, percentage of power at very low frequency (VLF, α-value of the detrended fluctuation analysis (DFAα1, heart rate (HR in the resting standing position, and age of the participants, a model was established for men, which was expressed as VO2max = 4.216 + (Age*0.153 + (F*0.110 - (M*0.053 - (VLF*0.649 - (DFAα1*2.441 - (HR*0.014, with R2 = 0.965 and standard error = 0.146 L/min. For women, the model was expressed as VO2max = 1.947 - (Age*0.047 + (F*0.024 + (M*0.054 + (VLF*1.949 - (DFAα1*0.424 - (HR*0.019, with R2 = 0.987 and standard error = 0.077 L/min. Conclusion: The obtained model demonstrated the influence exerted by body composition, the autonomic nervous system, and age in the prediction of VO2max.

  1. Estimated Prestroke Peak VO2 Is Related to Circulating IGF-1 Levels During Acute Stroke.

    Science.gov (United States)

    Mattlage, Anna E; Rippee, Michael A; Abraham, Michael G; Sandt, Janice; Billinger, Sandra A

    2017-01-01

    Background Insulin-like growth factor-1 (IGF-1) is neuroprotective after stroke and is regulated by insulin-like binding protein-3 (IGFBP-3). In healthy individuals, exercise and improved aerobic fitness (peak oxygen uptake; peak VO 2 ) increases IGF-1 in circulation. Understanding the relationship between estimated prestroke aerobic fitness and IGF-1 and IGFBP-3 after stroke may provide insight into the benefits of exercise and aerobic fitness on stroke recovery. Objective The purpose of this study was to determine the relationship of IGF-1 and IGFBP-3 to estimated prestroke peak VO 2 in individuals with acute stroke. We hypothesized that (1) estimated prestroke peak VO 2 would be related to IGF-1 and IGFBP-3 and (2) individuals with higher than median IGF-1 levels will have higher estimated prestroke peak VO 2 compared to those with lower than median levels. Methods Fifteen individuals with acute stroke had blood sampled within 72 hours of hospital admission. Prestroke peak VO 2 was estimated using a nonexercise prediction equation. IGF-1 and IGFBP-3 levels were quantified using enzyme-linked immunoassay. Results Estimated prestroke peak VO 2 was significantly related to circulating IGF-1 levels (r = .60; P = .02) but not IGFBP-3. Individuals with higher than median IGF-1 (117.9 ng/mL) had significantly better estimated aerobic fitness (32.4 ± 6.9 mL kg -1 min -1 ) than those with lower than median IGF-1 (20.7 ± 7.8 mL kg -1 min -1 ; P = .03). Conclusions Improving aerobic fitness prior to stroke may be beneficial by increasing baseline IGF-1 levels. These results set the groundwork for future clinical trials to determine whether high IGF-1 and aerobic fitness are beneficial to stroke recovery by providing neuroprotection and improving function. © The Author(s) 2016.

  2. Visible-light-induced Ag/BiVO4 semiconductor with enhanced photocatalytic and antibacterial performance

    Science.gov (United States)

    Regmi, Chhabilal; Dhakal, Dipesh; Wohn Lee, Soo

    2018-02-01

    An Ag-loaded BiVO4 visible-light-driven photocatalyst was synthesized by the microwave hydrothermal method followed by photodeposition. The photocatalytic performance of the synthesized samples was evaluated on a mixed dye (methylene blue and rhodamine B), as well as bisphenol A in aqueous solution. Similarly, the disinfection activities of synthesized samples towards the Gram-negative Escherichia coli (E. coli) in a model cell were investigated under irradiation with visible light (λ ≥ 420 nm). The synthesized samples have monoclinic scheelite structure. Photocatalytic results showed that all Ag-loaded BiVO4 samples exhibited greater degradation and a higher mineralization rate than the pure BiVO4, probably due to the presence of surface plasmon absorption that arises due to the loading of Ag on the BiVO4 surface. The optimum Ag loading of 5 wt% has the highest photocatalytic performance and greatest stability with pseudo-first-order rate constants of 0.031 min-1 and 0.023 min-1 for the degradation of methylene blue and rhodamine B respectively in a mixture with an equal volume and concentration of each dye. The photocatalytic degradation of bisphenol A reaches 76.2% with 5 wt% Ag-doped BiVO4 within 180 min irradiation time. Similarly, the Ag-loaded BiVO4 could completely inactivate E. coli cells within 30 min under visible light irradiation. The disruption of the cell membrane as well as degradation of protein and DNA exhibited constituted evidence for antibacterial activity towards E. coli. Moreover, the bactericidal mechanisms involved in the photocatalytic disinfection process were systematically investigated.

  3. Estimated VO2max and its corresponding velocity predict performance of amateur runners

    Directory of Open Access Journals (Sweden)

    Bruno Ribeiro Ramalho Oliveira

    2012-03-01

    Full Text Available In recent years, there has been a substantial increase in the number of runners, with a proportional increase in their involvement in amateur street competition. Identification of the determinants of performance in this population appears necessary for optimization of time devoted to training. The objective of this study was to ascertain the association between estimated maximal oxygen uptake (VO2max, critical velocity (CV and VO2max velocity (VVO2max and athletic performance in the 3.6 km (uphill and 10 and 21.1 km (flatland events. Twelve amateur runners (nine male, mean age 36 ± 5 years underwent five tests: 1 and 5 km race on level ground, 3.6 km race with slope (≈8%, and indirect VO2max measurement. CV was determined from the linear relationship between distance and run time on the first two tests. The subjects then took part in two official 10 km and 21.1 km (half marathon races. VVO2max was calculated from the VO2max through a metabolic equation. VO2max showed the best association with running performance in the 10 and 21.1 km events. For the uphill race, VVO2max showed a better association. Overall, the variable with the highest average association was VO2max (0.91±0.07, followed by VVO2max (0.90±0.04 and VC (0.87±0.06. This study showed strong associations between physiological variables established by low-cost, user-friendly indirect methods and running performance in the 10 and 21.1 km (flatland and 3.6 km (uphill running events.

  4. Evaluation of VoIP QoS Performance in Wireless Mesh Networks

    Directory of Open Access Journals (Sweden)

    Mohammad Tariq Meeran

    2017-07-01

    Full Text Available The main focus of this research article is the evaluation of selected voice over Internet protocol (VoIP solutions in wireless mesh network (WMN scenarios. While WMNs have self-healing, self-forming, and dynamic topology features, they still pose challenges for the implementation of multimedia applications such as voice in various scenarios. Therefore, various solutions to make WMN more suitable for VoIP application have been proposed in the scientific literature. In this work, we have extensively explored a set of applicable scenarios by conducting experiments by means of a network simulator. The following scenarios were selected as the most representatives for performance evaluation: first responders, flooded village, remote village, and platoon deployment. Each selected scenario has been studied under six sub-scenarios corresponding to various combinations of the IEEE 802.11g, 802.11n, 802.11s, and 802.11e standards; the G.711 and G.729 codecs; and the ad hoc on demand distance vector (AODV and hybrid wireless mesh protocol (HWMP routing protocols. The results in terms of quality of service (measured with the mean opinion score rating scale, supported by the analysis of delay, jitter and packet loss, show that 802.11g integration with both VoIP codecs and AODV routing protocol results in better VoIP performance as compared to most other scenarios. In case of 802.11g integration with 802.11s, VoIP performance decreases as compared to the other sub-scenarios without 802.11s. The results also show that 802.11n integration with 802.11e decreases VoIP performance in larger deployments. We conclude the paper with some recommendations in terms of combinations of those standards and protocols with a view to achieve a higher quality of service for the given scenarios.

  5. Phononic Band Gaps in 2D Quadratic and 3D Cubic Cellular Structures.

    Science.gov (United States)

    Warmuth, Franziska; Körner, Carolin

    2015-12-02

    The static and dynamic mechanical behaviour of cellular materials can be designed by the architecture of the underlying unit cell. In this paper, the phononic band structure of 2D and 3D cellular structures is investigated. It is shown how the geometry of the unit cell influences the band structure and eventually leads to full band gaps. The mechanism leading to full band gaps is elucidated. Based on this knowledge, a 3D cellular structure with a broad full band gap is identified. Furthermore, the dependence of the width of the gap on the geometry parameters of the unit cell is presented.

  6. FTIR spectra of the solid solutions (Na0.88K0.12)VO3, (Na0.5K0.5)VO3, and Na(V0.66P0.34)O3

    Science.gov (United States)

    de Waal, D.; Heyns, A. M.

    1992-03-01

    It is known that three different solid solutions, (Na0.88K0.12)VO3, (Na0.5K0.5)VO3 and Na(V0.66P0.34)O3, form in the (Na,K)(V,P)O3 system. These compounds all have monoclinic crystal structures similar to the pure alkali metal metavanadates containing small cations, e.g. Li+ and Na+ (Space group C2/c). Metavanadates with large cations like K+, Rb+, C+s and NH+4 form orthorhombic crystals, space group Pbcm. All those are structurally related to the silicate pyroxenes. Na(V0.66P0.34)O3 and (Na0.88K0.12)VO3 have the same modified diopside structure as (alpha) - NaVO3 while (Na0.5K0.5)VO3 adopts the true diopside structure. The infrared spectra of the three solid solutions are reported here in comparison with those of (alpha) -NaVO3 and KVO3. The results are also correlated with those obtained in two independent high pressure Raman studies of NH4VO3 and RbVO3 as the introduction of a larger cation like K+ should increase the pressure in the structure.

  7. The hierarchically organized splitting of chromosome bands into sub-bands analyzed by multicolor banding (MCB).

    Science.gov (United States)

    Lehrer, H; Weise, A; Michel, S; Starke, H; Mrasek, K; Heller, A; Kuechler, A; Claussen, U; Liehr, T

    2004-01-01

    To clarify the nature of chromosome sub-bands in more detail, the multicolor banding (MCB) probe-set for chromosome 5 was hybridized to normal metaphase spreads of GTG band levels at approximately 850, approximately 550, approximately 400 and approximately 300. It could be observed that as the chromosomes became shorter, more of the initial 39 MCB pseudo-colors disappeared, ending with 18 MCB pseudo-colored bands at the approximately 300-band level. The hierarchically organized splitting of bands into sub-bands was analyzed by comparing the disappearance or appearance of pseudo-color bands of the four different band levels. The regions to split first are telomere-near, centromere-near and in 5q23-->q31, followed by 5p15, 5p14, and all GTG dark bands in 5q apart from 5q12 and 5q32 and finalized by sub-band building in 5p15.2, 5q21.2-->q21.3, 5q23.1 and 5q34. The direction of band splitting towards the centromere or the telomere could be assigned to each band separately. Pseudo-colors assigned to GTG-light bands were resistant to band splitting. These observations are in concordance with the recently proposed concept of chromosome region-specific protein swelling. Copyright 2003 S. Karger AG, Basel

  8. Growth and optical properties of Tm:GdVO4 single crystal

    International Nuclear Information System (INIS)

    Urata, Y.; Akagawa, K.; Wada, S.; Tashiro, H.; Fukuda, T.

    1999-01-01

    Thulium-doped gadolinium vanadate (Tm:GdVO 4 ) single crystal has been successfully grown by a modified Czochralski (CZ) technique. Effective distribution coefficient of Tm was determined to be 0.74. Absorption characterization was performed in the 800 nm region and the maximum absorption peak was found at 799 nm for π polarization. Fluorescence spectra for tuning at the maximum absorption were obtained around 1.8-2.0 μm region with 100 nm bandwidth. This suggests that a Tm:GdVO 4 crystal is expected as a new promising LD pumped solid-state laser in the 2 μm region. (orig.)

  9. Gate voltage controlled humidity sensing using MOSFET of VO2 particles

    CSIR Research Space (South Africa)

    Akande, Amos A

    2017-01-01

    Full Text Available (A), VO2 (AH) [4], [5] and M2 the intermediate phase between M1 and R phase. These phases have been generally useful in technologies such as thermal switch (thermochromic window), thermal/infrared sensors, A.A Akande holds PhD studentship...) is 272.1, A1 and A2 are respectively 0.118 and 12096 with a correlation coefficient, R2, of 0.925. These results suggest that the VO2 sensor is very resilient to humidity such that it does not saturate even when humidity approaches 100%. This sensor...

  10. 532 nm continuous wave mode-locked Nd:GdVO4 laser with SESAM

    International Nuclear Information System (INIS)

    Li, L; Liu, J; Liu, M; Liu, S; Chen, F; Wang, W; Wang, Y

    2009-01-01

    We obtain continuous wave mode-locked Nd:GdVO 4 -KTP laser with a SESAM. This is the first report of CW mode-locked Nd:GdVO 4 -KTP laser with a SESAM to our knowledge. 396 mw CW mode-locked pulse is achieved at the incident power of 7.653 W, with the repetition about 95 MHz. The pulse duration is assumed to be 5.5 ps, this is the shortest green pulse of 532 nm with SESAM

  11. PENGEMBANGAN PERSAMAAN VO2 MAX DAN EVALUASI HR MAX (STUDI AWAL PADA PEKERJA PRIA

    Directory of Open Access Journals (Sweden)

    Purnawan Adi Wicaksono

    2012-10-01

    Full Text Available Kapasitas fisik maksimum seseorang direpresentasikan dengan nilai konsumsi oksigen maksimum (VO2 Max dan denyut nadi maksimum (HR Max yang memberikan suatu informasi batasan kemampuan fisik maksimum seseorang dalam melakukan pekerjaan. Penelitian kali ini mempunyai tujuan untuk mencari nilai VO2 Max pekerja pria Indonesia untuk nantinya akan dikembangkan suatu persamaan prediksi VO2 Max yang didekati dengan hubungan linier antara denyut nadi (Heart Rate seperti yang dilakukan Astrand (2003, tinggi badan (Chatterjee et al, 2006, berat badan (Akalan et al, 2008, usia (Magrani et al, 2009 dan mengevaluasi persamaan HR Max manakah yang dapat diaplikasikan untuk mendekati nilai denyut nadi maksimum pekerja Indonesia. Responden dalam penelitian kali ini adalah 12  pekerja industri pria yang diambil dari beberapa industri di Depok dan sekitarnya. Kriteria responden yang berpartisipasi dalam penelitian kali ini adalah: berusia 20-40 tahun, bukan perokok baik aktif maupun pasif, sehat , tidak mengkonsumsi makanan, kafein, alkohol minimal 2 jam sebelum eksperimen (Balderrama et. al, 2007.Eksperimen yang dilakukan menggunakan metode maximal test dengan protokol treadmill. Adapun peralatan yang digunakan adalah seperangkat alat pengukur kondisi fisiologi Fitmate MED (COSMED srl-Italy terdiri dari Heart Rate Transmitter, Heart Rate Receiver, V mask (Hans Rudolph Inc,dan treadmill SportArt@60.  Eksperimen dilakukan menjadi dua bagian, yaitu istirahat dan tahap bekerja.Aktivitas istirahat terdiri dari tidur selama 20 menit, duduk selama 20 menit dan berdiri selama 10 menit. Eksperimen tahap kedua yaitu tahap kerja yang terdiri dari latihan selama 5 menit. Responden dipersilakan beristirahat selama 15 menit, setelah itu responden melaksanakan maximal test detik hingga responden merasa tidak sanggup lagi melanjutkan eksperimen. Hasil penelitian model prediksi VO2 max untuk pekerja industri pria mempunyai nilai 2,78 ± 0,5 liter/menit dan dengan regresi linier

  12. Impact of growth temperature on the crystal habits, forms and structures of VO2 nanocrystals

    International Nuclear Information System (INIS)

    Loeffler, Stefan; Auer, Erwin; Lugstein, Alois; Bertagnolli, Emmerich; Weil, Matthias

    2011-01-01

    We investigated the impact of the process temperature on the habits, forms and crystal structure of VO 2 nanocrystals grown by a vapor-transport method on (0001) quartz substrates. Four distinct growth regimes were discerned: orthorhombic nanowires, sheets, hemispheres, and nanowires with a monoclinic structure. The nanostructures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). I/V characterization of individual nanowires was enabled by Ti/Au contact formation via electron beam lithography and lift-off techniques. The expected metal-insulator transition (MIT) was found in monoclinic VO 2 nanowires. (orig.)

  13. VO-compliant libraries of high resolution spectra of cool stars

    Science.gov (United States)

    Montes, D.

    2008-10-01

    In this contribution we describe a Virtual Observatory (VO) compliant version of the libraries of high resolution spectra of cool stars described by Montes et al. (1997; 1998; and 1999). Since their publication the fully reduced spectra in FITS format have been available via ftp and in the World Wide Web. However, in the VO all the spectra will be accessible using a common web interface following the standards of the International Virtual Observatory Alliance (IVOA). These libraries include F, G, K and M field stars, from dwarfs to giants. The spectral coverage is from 3800 to 10000 Å, with spectral resolution ranging from 0.09 to 3.0 Å.

  14. Performance Study of Objective Speech Quality Measurement for Modern Wireless-VoIP Communications

    Directory of Open Access Journals (Sweden)

    Chan Wai-Yip

    2009-01-01

    Full Text Available Wireless-VoIP communications introduce perceptual degradations that are not present with traditional VoIP communications. This paper investigates the effects of such degradations on the performance of three state-of-the-art standard objective quality measurement algorithms—PESQ, P.563, and an "extended" E-model. The comparative study suggests that measurement performance is significantly affected by acoustic background noise type and level as well as speech codec and packet loss concealment strategy. On our data, PESQ attains superior overall performance and P.563 and E-model attain comparable performance figures.

  15. 76 FR 62309 - Implementing a Nationwide, Broadband, Interoperable Public Safety Network in the 700 MHz Band

    Science.gov (United States)

    2011-10-07

    ... the 700 MHz Band AGENCY: Federal Communications Commission. ACTION: Final rule. SUMMARY: In this... spectrum of the 700 MHz band. The Commission dismissed the request, but clarified that a reasonably broad... personnel including, but not limited to, activities of police, fire and medical emergency first responders...

  16. Hydrothermal Synthesis of VO2 Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows.

    Science.gov (United States)

    Li, Ming; Magdassi, Shlomo; Gao, Yanfeng; Long, Yi

    2017-09-01

    Vanadium dioxide (VO 2 ) is a widely studied inorganic phase change material, which has a reversible phase transition from semiconducting monoclinic to metallic rutile phase at a critical temperature of τ c ≈ 68 °C. The abrupt decrease of infrared transmittance in the metallic phase makes VO 2 a potential candidate for thermochromic energy efficient windows to cut down building energy consumption. However, there are three long-standing issues that hindered its application in energy efficient windows: high τ c , low luminous transmittance (T lum ), and undesirable solar modulation ability (ΔT sol ). Many approaches, including nano-thermochromism, porous films, biomimetic surface reconstruction, gridded structures, antireflective overcoatings, etc, have been proposed to tackle these issues. The first approach-nano-thermochromism-which is to integrate VO 2 nanoparticles in a transparent matrix, outperforms the rest; while the thermochromic performance is determined by particle size, stoichiometry, and crystallinity. A hydrothermal method is the most common method to fabricate high-quality VO 2 nanoparticles, and has its own advantages of large-scale synthesis and precise phase control of VO 2 . This Review focuses on hydrothermal synthesis, physical properties of VO 2 polymorphs, and their transformation to thermochromic VO 2 (M), and discusses the advantages, challenges, and prospects of VO 2 (M) in energy-efficient smart windows application. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Synthesis of vanadium oxides 5 wt.%VO2–MxOy by sol–gel process ...

    Indian Academy of Sciences (India)

    Experimental results indicated that the VO2–SiO2 catalysts .... crucible, which was supported by the beam of a balance in the oven. ... Epoxidation of cyclohexene on VO2–Mx Oy (M = Si, Al, Ti). 1189 ... tially amorphous nature of silica.

  18. Voice over Internet Protocol (VoIP) Technology as a Global Learning Tool: Information Systems Success and Control Belief Perspectives

    Science.gov (United States)

    Chen, Charlie C.; Vannoy, Sandra

    2013-01-01

    Voice over Internet Protocol- (VoIP) enabled online learning service providers struggling with high attrition rates and low customer loyalty issues despite VoIP's high degree of system fit for online global learning applications. Effective solutions to this prevalent problem rely on the understanding of system quality, information quality, and…

  19. Extraction of Electronic Evidence from VoIP: Forensic Analysis of A Virtual Hard Disk Vs RAM

    Directory of Open Access Journals (Sweden)

    david irwin

    2011-03-01

    Full Text Available The popularity of Voice over the Internet Protocol (VoIP is increasing as the cost savings and ease of use is realised by a wide range of home and corporate users. However, the technology is also attractive to criminals. This is because VoIP is a global telephony service, in which it is difficult to verify the user’s identification. The security of placing such calls may also be appealing to criminals, as many implementations use strong encryption to secure both the voice payload as well as to control messages making monitoring such VoIP calls difficult since conventional methods such as wire-tapping is not applicable to VoIP calls. Therefore, other methods of recovering electronic evidence and information from VoIP are required.  This research looks at what protocol evidence remains after a VoIP call has taken place examining both a virtual hard disk and the Random Access Memory (RAM. This paper proposes a set of identifiable credentials based on packet header information contained within the VoIP protocol stack. A series of controlled tests were undertaken whereby these credentials were forensically searched for on a virtual machine which was used to make the VoIP call. This experiment was then repeated by a search for the same protocol credentials within the RAM.

  20. The broad utility of Trizac diamond tile

    Science.gov (United States)

    Gagliardi, John I.; Romero, Vincent D.; Sventek, Bruce; Zu, Lijun

    2017-10-01

    Sample finishing data from a broad range of materials — glasses, sapphire, silicon carbide, silicon, zirconium oxide, lithium tantalate, and flooring materials — are shown effectively processed with Trizact™ Diamond Tile (TDT). This data should provide the reader with an understanding of what to expect when using TDT on hard to grind or brittle materials. Keys to maintaining effective TDT pad wear rates, and therefore cost effect and stable processes, are described as managing 1) the proper lubricant flow rate for glasses and silicon-type materials and 2) the conditioning particle concentration for harder-to-grind materials

  1. Surface defect assisted broad spectra emission from CdSe quantum dots for white LED application

    Science.gov (United States)

    Samuel, Boni; Mathew, S.; Anand, V. R.; Correya, Adrine Antony; Nampoori, V. P. N.; Mujeeb, A.

    2018-02-01

    This paper reports, broadband photoluminescence from CdSe quantum dots (QDs) under the excitation of 403 nm using fluorimeter and 403 nm CW laser excitation. The broad spectrum obtained from the colloidal quantum dots was ranges from 450 nm to 800 nm. The broadness of the spectra was attributed to the merging of band edge and defect driven emissions from the QDs. Six different sizes of particles were prepared via kinetic growth method by using CdO and elemental Se as sources of Cd and Se respectively. The particle sizes were measured from TEM images. The size dependent effect on broad emission was also studied and the defect state emission was found to be predominant in very small QDs. The defect driven emission was also observed to be redshifted, similar to the band edge emission, due to quantum confinement effect. The emission corresponding to different laser power was also studied and a linear relation was obtained. In order to study the colour characteristics of the emission, CIE chromaticity coordinate, CRI and CCT of the prepared samples were measured. It is observed that, these values were tunable by the addition of suitable intensity of blue light from the excitation source to yield white light of various colour temperatures. The broad photoluminescence spectrum of the QDs, were compared with that of a commercially available white LED. It was found that the prepared QDs are good alternatives for the phosphor in phosphor converted white LEDs, to provide good spectral tunability.

  2. Advances in X-Band and S-Band Linear Accelerators for Security, NDT, and Other Applications

    CERN Document Server

    Mishin, Andrey V

    2005-01-01

    At AS&E High Energy Systems Division, we designed several new advanced high energy electron beam and X-ray sources. Our primary focus has always been in building the world's most portable commercial X-band accelerators. Today, our X-band systems frequently exceed performance of the similar S-band machines, while they are more portable compared to the latter. The new designs of the X-band accelerators in the most practical energy range from 1 MeV to 6 MeV have been tested delivering outstanding results. Seventy 6 MeV X-band linacs systems have been produced. The most compact linac for security is used by AS&E in a self-shielded, Shaped Energy™ cargo screening system. We pioneered using the X-band linear accelerators for CT, producing high quality images of oil pipes and wood logs. An X-band linear accelerator head on a robotic arm has been used for electron beam radiation curing of an odd-shaped graphite composite part. We developed the broad-range 4 MeV to over 10 MeV energy-regulated X-band ...

  3. Synthesis and crystal structure of the new vanadate AgCaVO{sub 4}. Comparison with the arcanite structure

    Energy Technology Data Exchange (ETDEWEB)

    Nenert, Gwilherm [PANalytical B.V., Almelo (Netherlands)

    2017-07-01

    We report the synthesis and the crystal structure of the new vanadate AgCaVO{sub 4} from laboratory powder X-ray data. Contrary to the previously reported AgBVO{sub 4} (B=Mg, Cd), AgCaVO{sub 4} exhibits the arcanite structure (β-K{sub 2}SO{sub 4}). Although it exhibits the same structure than arcanite, significant differences are observed. These differences are explained by deriving the atomic displacement field. The change of connectivity within the structure between β-K{sub 2}SO{sub 4} and AgCaVO{sub 4} results from a rotation of the VO{sub 4} tetrahedra giving rise to a change from a face sharing to an edge sharing octahedral chains. Additionally, the thermal expansion of AgCaVO{sub 4} has been investigated up to 800 C.

  4. Anomalous optical switching and thermal hysteresis during semiconductor-metal phase transition of VO2 films on Si substrate

    International Nuclear Information System (INIS)

    Leahu, G.; Li Voti, R.; Sibilia, C.; Bertolotti, M.

    2013-01-01

    We present a detailed infrared study of the semiconductor-to-metal transition (SMT) in a vanadium dioxide (VO 2 ) film deposited on silicon wafer. The VO 2 phase transition is studied in the mid-infrared region by analyzing the transmittance and the reflectance measurements, and the calculated emissivity. The reflectance has been measured in two configurations: from the side of the VO 2 film and from that of Si wafer. The results show a strong asymmetry between the emissivity in the two configurations, and the fact that the emissivity dynamic range from the silicon side is twice as large than that from the VO 2 side. The temperature behaviour of the emissivity during the SMT put into evidence the phenomenon of the anomalous absorption in VO 2 , which has been explained by applying the Maxwell Garnett effective medium approximation theory

  5. Noise exposure in marching bands

    Science.gov (United States)

    Keefe, Joseph

    2005-09-01

    Previous studies involving orchestras have shown that music ensembles can produce hazardous noise levels. There are no similar data for marching bands and pep bands. In order to evaluate the noise levels produced by marching and pep bands, 1/3-octave-band sound-pressure levels were measured while these groups rehearsed and performed. Data were collected while marching with the bands to ensure a realistic environment. Comparing these data to OSHA and NIOSH criteria, marching and pep band exposures often exceed safe values. For typical exposures, OSHA doses range from 11% to 295%, while NIOSH doses range from 35% to 3055%. Exposures that would be considered hazardous in the workplace are common in marching and pep bands; students and band directors should take steps to recognize the risk posed by various instruments and various locations, and should implement hearing conservation efforts.

  6. Defect induced structural inhomogeneity, ultraviolet light emission and near-band-edge photoluminescence broadening in degenerate In2O3 nanowires

    Science.gov (United States)

    Mukherjee, Souvik; Sarkar, Ketaki; Wiederrecht, Gary P.; Schaller, Richard D.; Gosztola, David J.; Stroscio, Michael A.; Dutta, Mitra

    2018-04-01

    We demonstrate here defect induced changes on the morphology and surface properties of indium oxide (In2O3) nanowires and further study their effects on the near-band-edge (NBE) emission, thereby showing the significant influence of surface states on In2O3 nanostructure based device characteristics for potential optoelectronic applications. In2O3 nanowires with cubic crystal structure (c-In2O3) were synthesized via carbothermal reduction technique using a gold-catalyst-assisted vapor-liquid-solid method. Onset of strong optical absorption could be observed at energies greater than 3.5 eV consistent with highly n-type characteristics due to unintentional doping from oxygen vacancy ({V}{{O}}) defects as confirmed using Raman spectroscopy. A combination of high resolution transmission electron microscopy, x-ray photoelectron spectroscopy and valence band analysis on the nanowire morphology and stoichiometry reveals presence of high-density of {V}{{O}} defects on the surface of the nanowires. As a result, chemisorbed oxygen species can be observed leading to upward band bending at the surface which corresponds to a smaller valence band offset of 2.15 eV. Temperature dependent photoluminescence (PL) spectroscopy was used to study the nature of the defect states and the influence of the surface states on the electronic band structure and NBE emission has been discussed. Our data reveals significant broadening of the NBE PL peak consistent with impurity band broadening leading to band-tailing effect from heavy doping.

  7. Defect induced structural inhomogeneity, ultraviolet light emission and near-band-edge photoluminescence broadening in degenerate In 2 O 3 nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Souvik; Sarkar, Ketaki; Wiederrecht, Gary P.; Schaller, Richard D.; Gosztola, David J.; Stroscio, Michael A.; Dutta, Mitra

    2018-03-01

    We demonstrate here defect induced changes on the morphology and surface properties of indium oxide (In2O3) nanowires and further study their effects on the near-band-edge (NBE) emission, thereby showing the significant influence of surface states on In2O3 nanostructure based device characteristics for potential optoelectronic applications. In2O3 nanowires with cubic crystal structure (c-In2O3) were synthesized via carbothermal reduction technique using a gold-catalyst-assisted vapor–liquid–solid method. Onset of strong optical absorption could be observed at energies greater than 3.5 eV consistent with highly n-type characteristics due to unintentional doping from oxygen vacancy (VO) defects as confirmed using Raman spectroscopy. A combination of high resolution transmission electron microscopy, x-ray photoelectron spectroscopy and valence band analysis on the nanowire morphology and stoichiometry reveals presence of high-density of VO defects on the surface of the nanowires. As a result, chemisorbed oxygen species can be observed leading to upward band bending at the surface which corresponds to a smaller valence band offset of 2.15 eV. Temperature dependent photoluminescence (PL) spectroscopy was used to study the nature of the defect states and the influence of the surface states on the electronic band structure and NBE emission has been discussed. Our data reveals significant broadening of the NBE PL peak consistent with impurity band broadening leading to band-tailing effect from heavy doping.

  8. Increases in .VO2max with "live high-train low" altitude training: role of ventilatory acclimatization.

    Science.gov (United States)

    Wilhite, Daniel P; Mickleborough, Timothy D; Laymon, Abigail S; Chapman, Robert F

    2013-02-01

    The purpose of this study was to estimate the percentage of the increase in whole body maximal oxygen consumption (.VO(2max)) that is accounted for by increased respiratory muscle oxygen uptake after altitude training. Six elite male distance runners (.VO(2max) = 70.6 ± 4.5 ml kg(-1) min(-1)) and one elite female distance runner (.VO(2max)) = 64.7 ml kg(-1) min(-1)) completed a 28-day "live high-train low" training intervention (living elevation, 2,150 m). Before and after altitude training, subjects ran at three submaximal speeds, and during a separate session, performed a graded exercise test to exhaustion. A regression equation derived from published data was used to estimate respiratory muscle .VO(2) (.VO(2RM)) using our ventilation (.VE) values. .VO(2RM) was also estimated retrospectively from a larger group of distance runners (n = 22). .VO(2max) significantly (p altitude (196 ± 59 ml min(-1)), while (.VE) at .VO(2max) also significantly (p altitude (201 ± 36 ml min(-1)), along with a 10.8 ± 2.1 l min(-1) increase in (.VE), thus requiring an estimated 27 % of Δ .VO(2max) Our data suggest that a substantial portion of the improvement in .VO(2max) with chronic altitude training goes to fuel the respiratory muscles as opposed to the musculature which directly contributes to locomotion. Consequently, the time-course of decay in ventilatory acclimatization following return to sea-level may have an impact on competitive performance.

  9. Slow VO2 off-kinetics in skeletal muscle is associated with fast PCr off-kinetics--and inversely.

    Science.gov (United States)

    Korzeniewski, Bernard; Zoladz, Jerzy A

    2013-09-01

    The computer model of the bioenergetic system in skeletal muscle, developed previously, was used to study the effect of the characteristic decay time of the parallel activation of oxidative phosphorylation [τ(OFF)] during muscle recovery on the muscle oxygen consumption rate (Vo2) and phosphocreatine (PCr) work-to-rest transition (off)-kinetics and on the relationship between the Vo2 and PCr rest-to-work transition (on)- and off-kinetics in moderate and heavy exercise. An increase in τ(OFF) slows down the initial phase of the muscle Vo2 off-kinetics and accelerates the PCr off-kinetics. As a result, the relationship between the initial phase of the Vo2 off-kinetics (lasting approximately 3-60 s in computer simulations) and the PCr off-kinetics is inverse: the slower the former, the faster the latter. A faster initial phase of the Vo2 off-kinetics is associated with a slower late phase of the Vo2 off-kinetics, and as a result, the integral of Vo2 above baseline during recovery, representing the oxygen debt, is identical in all cases [values of τ(OFF)] for a given PCr decrease. Depending on τ(OFF), the muscle Vo2 on-kinetics was either equally fast or slower than the Vo2 off-kinetics in moderate exercise and always slower in heavy exercise. PCr on-kinetics was always faster than PCr off-kinetics. This study clearly demonstrates that τ(OFF) has a pronounced impact on the mutual relations between the muscle Vo2 and PCr on- and off-kinetics.

  10. Semiconductors bonds and bands

    CERN Document Server

    Ferry, David K

    2013-01-01

    As we settle into this second decade of the twenty-first century, it is evident that the advances in micro-electronics have truly revolutionized our day-to-day lifestyle. The technology is built upon semiconductors, materials in which the band gap has been engineered for special values suitable to the particular application. This book, written specifically for a one semester course for graduate students, provides a thorough understanding of the key solid state physics of semiconductors. It describes how quantum mechanics gives semiconductors unique properties that enabled the micro-electronics revolution, and sustain the ever-growing importance of this revolution.

  11. Tuning the work function of VO_2(1 0 0) surface by Ag adsorption and incorporation: Insights from first-principles calculations

    International Nuclear Information System (INIS)

    Chen, Lanli; Wang, Xiaofang; Shi, Siqi; Cui, Yuanyuan; Luo, Hongjie; Gao, Yanfeng

    2016-01-01

    Graphical abstract: - Highlights: • After adsorption, there is a charge transfer from Ag to VO_2(1 0 0) surface, which thus increases the electron concentration in VO_2 thin film. • Ag adsorption on VO_2(1 0 0) surface process is an exothermic chemical process, and the adsorption system is stable. • The work function can be tuned by Ag adsorption on and incorporation into the VO_2(1 0 0) surface, which in turn regulates the phase transition temperature of VO_2. - Abstract: VO_2 is an attractive material for application to thermochromic optoelectronic devices such as smart windows, and Ag/VO_2 double-layered structure can effectively decrease the phase transition temperature (T_c) of VO_2 thin film, which is very important for practical application of VO_2. Previous works has shown that the decrease in phase transition temperature (T_c) seems to be relevant with the work function of VO_2 in Ag/VO_2 double-layered thin film, although the underlying mechanism of tuning its T_c by Ag incorporation and adsorption on the VO_2(1 0 0) surface has been rarely investigated. Our first-principles calculations reveal that the adsorption of Ag atoms on the VO_2(1 0 0) surface rather than incorporation of Ag exhibits a lower work function, which is ascribed to an integrated effect of charge transfer from Ag to VO_2(1 0 0) surface and enhanced surface dipole moment. The results suggest that the decrease in work function of VO_2 with Ag adsorption favors the reduction in T_c. The current findings are helpful to understand the fundamental mechanism for yielding high-efficiency VO_2-based optoelectronic devices.

  12. Relation of oxygen uptake to work rate in prepubertal healthy children - reference for VO2/W-slope and effect on cardiorespiratory fitness assessment.

    Science.gov (United States)

    Tompuri, Tuomo; Lintu, Niina; Laitinen, Tomi; Lakka, Timo A

    2017-08-09

    Exercise testing by cycle ergometer allows to observe the interaction between oxygen uptake (VO 2 ) and workload (W), and VO 2 /W-slope can be used as a diagnostic tool. Respectively, peak oxygen uptake (VO 2 PEAK ) can be estimated by maximal workload. We aim to determine reference for VO 2 /W-slope among prepubertal children and define agreement between estimated and measured VO 2 PEAK . A total of 38 prepubertal children (20 girls) performed a maximal cycle ergometer test with respiratory gas analysis. VO 2 /W-slopes were computed using linear regression. Agreement analysis by Bland and Altman for estimated and measured VO 2 PEAK was carried out including limits of agreement (LA). Determinants for VO 2 /W-slopes and estimation bias were defined. VO2/W-slope was in both girls and boys ≥9·4 and did not change with exercise level, but the oxygen cost of exercise was higher among physically more active children. Estimated VO 2 PEAK had 6·4% coefficient of variation, and LA varied from 13% underestimation to 13% overestimation. Bias had a trend towards underestimation along lean mass proportional VO 2 PEAK . The primary determinant for estimation bias was VO2/W-slope (β = -0·65; PW-slope among healthy prepubertal children were similar to those published for adults and among adolescents. Estimated and measured VO 2 PEAK should not be considered to be interchangeable because of the variation in the relationship between VO 2 and W. On other hand, variation in the relationship between VO 2 and W enables that VO 2 /W-slope can be used as a diagnostic tool. © 2017 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

  13. Tuning the work function of VO{sub 2}(1 0 0) surface by Ag adsorption and incorporation: Insights from first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Lanli; Wang, Xiaofang [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Shi, Siqi, E-mail: sqshi@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Cui, Yuanyuan [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Luo, Hongjie [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Gao, Yanfeng, E-mail: yfgao@shu.edu.cn [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China)

    2016-03-30

    Graphical abstract: - Highlights: • After adsorption, there is a charge transfer from Ag to VO{sub 2}(1 0 0) surface, which thus increases the electron concentration in VO{sub 2} thin film. • Ag adsorption on VO{sub 2}(1 0 0) surface process is an exothermic chemical process, and the adsorption system is stable. • The work function can be tuned by Ag adsorption on and incorporation into the VO{sub 2}(1 0 0) surface, which in turn regulates the phase transition temperature of VO{sub 2}. - Abstract: VO{sub 2} is an attractive material for application to thermochromic optoelectronic devices such as smart windows, and Ag/VO{sub 2} double-layered structure can effectively decrease the phase transition temperature (T{sub c}) of VO{sub 2} thin film, which is very important for practical application of VO{sub 2}. Previous works has shown that the decrease in phase transition temperature (T{sub c}) seems to be relevant with the work function of VO{sub 2} in Ag/VO{sub 2} double-layered thin film, although the underlying mechanism of tuning its T{sub c} by Ag incorporation and adsorption on the VO{sub 2}(1 0 0) surface has been rarely investigated. Our first-principles calculations reveal that the adsorption of Ag atoms on the VO{sub 2}(1 0 0) surface rather than incorporation of Ag exhibits a lower work function, which is ascribed to an integrated effect of charge transfer from Ag to VO{sub 2}(1 0 0) surface and enhanced surface dipole moment. The results suggest that the decrease in work function of VO{sub 2} with Ag adsorption favors the reduction in T{sub c}. The current findings are helpful to understand the fundamental mechanism for yielding high-efficiency VO{sub 2}-based optoelectronic devices.

  14. A novel magneto-optical crystal Yb:TbVO4

    Science.gov (United States)

    Zhu, Xianchao; Tu, Heng; Hu, Zhanggui

    2018-04-01

    Highly transparent Yb:TbVO4 single crystal with dimensions of Ø27 × 41 mm3 alomost without scattering defects has been successfully grown by Czochralski technique. The spectra, thermal properties and laser-induced damage threshold were investigated in detailed. The Faraday rotation (FR) measurement was carried out by means of extinction method. The Verdet constant comes up to 80 rad m-1 T-1 at 1064 nm, significantly larger than TbVO4 (58 rad m-1 T-1) and TGG (40 rad m-1 T-1) reported. Meanwhile, the as-grown crystal presents lower absorption coefficient and higher magneto-optical figure of merit at measured wavelength in comparison with TGG. Moreover, the crystal exhibits a substantially improved extinction ratio (42 dB) in contrast with TbVO4 (29 dB), and exceeds the highest value of TGG (40 dB). These advantages make Yb:TbVO4 a highly promising magneto-optical material candidate for optical isolators in the visible-near infrared region.

  15. Femtosecond Near Edge X-ray Absorption Measurement of the VO2 Phase Transition

    International Nuclear Information System (INIS)

    Cavalleri, A.; Chong, H.H.W.; Fourmaux, S.; Glover, T.E.; Heimann, P.A; Kieffer, J.C.; Padmore, H.A.; Schoenlein, R.W.

    2004-01-01

    The authors measure the insulator-to-metal transition in VO 2 using femtosecond Near-Edge X-ray Absorption. Sliced pulses of synchrotron radiation are used to detect the photo-induced dynamics at the 516-eV Vanadium L 3 edge

  16. Increasing supported VoIP flows in WMNs through link-based aggregation

    CSIR Research Space (South Africa)

    Olwal, T

    2008-10-01

    Full Text Available As Voice over IP (VoIP) becomes a reality, service providers will be able to offer the service to remote and over populated areas that currently are not or are only partially reached by available Public Switched Telephone Network (PSTN...

  17. Task Specificity and the Influence of Memory on Visual Search: Comment on Vo and Wolfe (2012)

    Science.gov (United States)

    Hollingworth, Andrew

    2012-01-01

    Recent results from Vo and Wolfe (2012b) suggest that the application of memory to visual search may be task specific: Previous experience searching for an object facilitated later search for that object, but object information acquired during a different task did not appear to transfer to search. The latter inference depended on evidence that a…

  18. VoIP Speech Encryption System Using Stream Cipher with Chaotic ...

    African Journals Online (AJOL)

    pc

    2018-03-22

    Mar 22, 2018 ... The technologies of Internet doesn't give any security mechanism and there is ... VoIP system, both digital (e.g., PC, PDA) and analog (e.g., telephone) devices ... the protection to speech through traditional encryption schemes ...

  19. The Disruptor’s Dilemma: TiVo and the U.S. Television Ecosystem

    NARCIS (Netherlands)

    S.M. Ansari (Shahzad); R. Garud (Raghu); A. Kumaraswamy (Arun)

    2016-01-01

    textabstractFirms introducing disruptive innovations into multisided ecosystems may confront the disruptor’s dilemma – they must gain the support of the very incumbents they disrupt. We examine how these firms may address this dilemma through a longitudinal study of TiVo, a company that pioneered

  20. Multi-VO support in IHEP's distributed computing environment

    International Nuclear Information System (INIS)

    Yan, T; Suo, B; Zhao, X H; Zhang, X M; Ma, Z T; Yan, X F; Lin, T; Deng, Z Y; Li, W D; Belov, S; Pelevanyuk, I; Zhemchugov, A; Cai, H

    2015-01-01

    Inspired by the success of BESDIRAC, the distributed computing environment based on DIRAC for BESIII experiment, several other experiments operated by Institute of High Energy Physics (IHEP), such as Circular Electron Positron Collider (CEPC), Jiangmen Underground Neutrino Observatory (JUNO), Large High Altitude Air Shower Observatory (LHAASO) and Hard X-ray Modulation Telescope (HXMT) etc, are willing to use DIRAC to integrate the geographically distributed computing resources available by their collaborations. In order to minimize manpower and hardware cost, we extended the BESDIRAC platform to support multi-VO scenario, instead of setting up a self-contained distributed computing environment for each VO. This makes DIRAC as a service for the community of those experiments. To support multi-VO, the system architecture of BESDIRAC is adjusted for scalability. The VOMS and DIRAC servers are reconfigured to manage users and groups belong to several VOs. A lightweight storage resource manager StoRM is employed as the central SE to integrate local and grid data. A frontend system is designed for user's massive job splitting, submission and management, with plugins to support new VOs. A monitoring and accounting system is also considered to easy the system administration and VO related resources usage accounting. (paper)