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radio frequency emission

Markus Dietrich, Gunter Hagen, Willibald Reitmeier, Katharina Burger, Markus Hien, Philippe Grass, David Kubinski, Jaco Visser, Ralf Moos
The upcoming more stringent automotive emission legislations and current developments have promoted new technologies for more precise and reliable catalyst control. For this purpose, radio-frequency-based (RF) catalyst state determination offers the only approach for directly measuring the NH₃ loading on selective catalytic reduction (SCR) catalysts and the state of other catalysts and filter systems. Recently, the ability of this technique to directly control the urea dosing on a current NH₃ storing zeolite catalyst has been demonstrated on an engine dynamometer for the first time and this paper continues that work...
July 12, 2017: Sensors
Liu Liu, Huiting Chang, Tao Xu, Yanan Song, Chi Zhang, Zhi Hong Hang, Xinhua Hu
The use of low-emissivity (low-e) materials in modern buildings is an extremely efficient way to save energy. However, such materials are coated by metallic films, which can strongly block radio-frequency signals and prevent indoor-outdoor wireless communication. Here, we demonstrate that, when specially-designed metallic metasurfaces are covered on them, the low-e materials can remain low emissivity for thermal radiation and allow very high transmission for a broad band of radio-frequency signals. It is found that the application of air-connected metasurfaces with subwavelength periods is critical to the observed high transmission...
July 7, 2017: Scientific Reports
Gururaj V Naik, Alex J Welch, Justin A Briggs, Michelle L Solomon, Jennifer A Dionne
Manipulating the frequency of electromagnetic waves forms the core of many modern technologies, ranging from imaging and spectroscopy to radio and optical communication. The process of converting photons from higher to lower energy is easily accomplished and technologically widespread. However, upconversion, which is the process of converting lower-energy photons into higher-energy photons, is still a growing field of study with nascent applications and burgeoning interest. Here, we experimentally demonstrate a new photon upconversion technique mediated by hot carriers in plasmonic nanostructures...
July 3, 2017: Nano Letters
Manuel Peter, Andre Hildebrandt, Christian Schlickriede, Kimia Gharib, Thomas Zentgraf, Jens Förstner, Stefan Linden
An important source of innovation in nanophotonics is the idea to scale down known radio wave technologies to the optical regime. One thoroughly investigated example of this approach are metallic nanoantennas which employ plasmonic resonances to couple localized emitters to selected far-field modes. While metals can be treated as perfect conductors in the microwave regime, their response becomes Drude-like at optical frequencies. Thus, plasmonic nanoantennas are inherently lossy. Moreover, their resonant nature requires precise control of the antenna geometry...
June 21, 2017: Nano Letters
Mohammad Suja, Sunayna Binte Bashar, Bishwajit Debnath, Longxing Su, Wenhao Shi, Roger Lake, Jianlin Liu
Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. In this paper, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm...
June 1, 2017: Scientific Reports
Sergey Usenko, Andreas Przystawik, Markus Alexander Jakob, Leslie Lamberto Lazzarino, Günter Brenner, Sven Toleikis, Christian Haunhorst, Detlef Kip, Tim Laarmann
Light-phase-sensitive techniques, such as coherent multidimensional spectroscopy, are well-established in a broad spectral range, already spanning from radio-frequencies in nuclear magnetic resonance spectroscopy to visible and ultraviolet wavelengths in nonlinear optics with table-top lasers. In these cases, the ability to tailor the phases of electromagnetic waves with high precision is essential. Here we achieve phase control of extreme-ultraviolet pulses from a free-electron laser (FEL) on the attosecond timescale in a Michelson-type all-reflective interferometric autocorrelator...
May 30, 2017: Nature Communications
Cleber Galvão Novaes, Ivana Lago da Silva Romão, Berlane Gomes Santos, Jéssica Palhares Ribeiro, Marcos Almeida Bezerra, Erik Galvão Paranhos da Silva
A method using digestion with diluted nitric acid and inductively coupled plasma optical emission spectrometry was applied to determine metal ions in the peel, pulp, and seed of Passiflora edulis f. flavicarpa and Passiflora cincinnata cultivated in the Bahia state, Brazil. Plasma parameters (radio frequency power and argon flow rates) were optimized. The quantification limits (µg g(-1)) were: Ca (43.0); Co (1.3); Cu (10.0); Fe (10.0); K (20.0); Mg (26.6); Mn (0.33); Na (56.6) and Zn (10.0). The accuracy of the method was evaluated by the analysis of certified reference materials (NIST 1567a Wheat Flour and NIST 1577b Bovine Liver)...
October 15, 2017: Food Chemistry
Lina Zheng, Pramod Kulkarni
A new, low-cost approach based on the application of atmospheric radio frequency glow discharge (rf-GD) optical emission spectroscopy (OES) has been developed for near real-time measurement of multielemental concentration in airborne particulate phase. This method involves deposition of aerosol particles on the tip of a cathode in a coaxial microelectrode system, followed by ablation, atomization, and excitation of the particulate matter using the rf-GD. The resulting atomic emissions are recorded using a spectrometer for elemental identification and quantification...
June 8, 2017: Analytical Chemistry
Marco A Allodi, Peter D Dahlberg, Richard J Mazuski, Hunter C Davis, John P Otto, Gregory S Engel
We propose here optical resonance imaging (ORI), a direct optical analog to magnetic resonance imaging (MRI). The proposed pulse sequence for ORI maps space to time and recovers an image from a heterodyne-detected third-order nonlinear photon echo measurement. As opposed to traditional photon echo measurements, the third pulse in the ORI pulse sequence has significant pulse-front tilt that acts as a temporal gradient. This gradient couples space to time by stimulating the emission of a photon echo signal from different lateral spatial locations of a sample at different times, providing a widefield ultrafast microscopy...
December 21, 2016: ACS Photonics
Fang-Hsing Wang, Kun-Neng Chen, Chao-Ming Hsu, Min-Chu Liu, Cheng-Fu Yang
In this study, Ga₂O₃-doped ZnO (GZO) thin films were deposited on glass and flexible polyimide (PI) substrates at room temperature (300 K), 373 K, and 473 K by the radio frequency (RF) magnetron sputtering method. After finding the deposition rate, all the GZO thin films with a nano-scale thickness of about 150 ± 10 nm were controlled by the deposition time. X-ray diffraction patterns indicated that the GZO thin films were not amorphous and all exhibited the (002) peak, and field emission scanning electron microscopy showed that only nano-scale particles were observed...
May 10, 2016: Nanomaterials
W J Wan, H Li, T Zhou, J C Cao
Homogeneous broadband and electrically pumped semiconductor radiation sources emitting in the terahertz regime are highly desirable for various applications, including spectroscopy, chemical sensing, and gas identification. In the frequency range between 1 and 5 THz, unipolar quantum cascade lasers employing electron inter-subband transitions in multiple-quantum-well structures are the most powerful semiconductor light sources. However, these devices are normally characterized by either a narrow emission spectrum due to the narrow gain bandwidth of the inter-subband optical transitions or an inhomogeneous broad terahertz spectrum from lasers with heterogeneous stacks of active regions...
March 8, 2017: Scientific Reports
Raimondas Buckus, Birute Strukčinskienė, Juozas Raistenskis, Rimantas Stukas, Aurelija Šidlauskienė, Rimantė Čerkauskienė, Dorina Nicolina Isopescu, Jan Stabryla, Igor Cretescu
During the last two decades, the number of macrocell mobile telephony base station antennas emitting radiofrequency (RF) electromagnetic radiation (EMR) in residential areas has increased significantly, and therefore much more attention is being paid to RF EMR and its effects on human health. Scientific field measurements of public exposure to RF EMR (specifically to radio frequency radiation) from macrocell mobile telephony base station antennas and RF electromagnetic field (EMF) intensity parameters in the environment are discussed in this article...
March 1, 2017: International Journal of Environmental Research and Public Health
S J Doyle, K G Xu
This paper presents the use of thermocouples and line broadening of argon 2p-1s emission lines for the measurement of gas temperature of an atmospheric argon microplasma jet. The measured temperatures are compared with rotational spectra fitting of OH (A-X) and N2 (C-B) emission. An rf microplasma jet with two electrical configurations and different temperature ranges was used. The calculated gas temperatures with thermocouples, argon lines, and OH ranged from 290 to 423 K and 393-510 K for the two configurations, depending on the rf power...
February 2017: Review of Scientific Instruments
Andrew Mezentsev, Nikolai Østgaard, Thomas Gjesteland, Kjetil Albrechtsen, Nikolai Lehtinen, Martino Marisaldi, David Smith, Steven Cummer
A detailed analysis of Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) terrestrial gamma ray flashes (TGFs) is performed in association with World Wide Lightning Location Network (WWLLN) sources and very low frequency (VLF) sferics recorded at Duke University. RHESSI clock offset is evaluated and found to experience changes on the 5 August 2005 and 21 October 2013, based on the analysis of TGF-WWLLN matches. The clock offsets were found for all three periods of observations with standard deviations less than 100 μs...
July 16, 2016: Journal of Geophysical Research. Atmospheres: JGR
D L Campbell, I B Spielman
We theoretically explore a Rashba spin-orbit coupling scheme which operates entirely in the absolute ground state manifold of an alkali atom, thereby minimizing all inelastic processes. An energy gap between ground eigenstates of the proposed coupling can be continuously opened or closed by modifying laser polarizations. Our technique uses far-detuned 'Raman' laser coupling to create the Rashba potential, which has the benefit of low spontaneous emission rates. At these detunings, the Raman matrix elements that link m F magnetic sublevel quantum numbers separated by two are also suppressed...
March 2016: New Journal of Physics
M B Dreval, A M Shapoval, F I Ozherelyev, M M Makhov
An Hα camera has been designed and installed in the U-3M torsatron for spatially and temporally resolved measurements. This device provides fast measurements of the emission brightness profile in the noisy environment of the radio frequency (RF) heated plasma. Unusual topology of diagnostics and the data acquisition system are applied. All the system components, including digitizers, are assembled in a single unit. It allows the suppression of a low-frequency electromagnetic interference by eliminating the ground loops...
July 2016: Review of Scientific Instruments
T R Marsh, B T Gänsicke, S Hümmerich, F-J Hambsch, K Bernhard, C Lloyd, E Breedt, E R Stanway, D T Steeghs, S G Parsons, O Toloza, M R Schreiber, P G Jonker, J van Roestel, T Kupfer, A F Pala, V S Dhillon, L K Hardy, S P Littlefair, A Aungwerojwit, S Arjyotha, D Koester, J J Bochinski, C A Haswell, P Frank, P J Wheatley
White dwarfs are compact stars, similar in size to Earth but approximately 200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies...
September 15, 2016: Nature
Davide Barreca, Giorgio Carraro, Alberto Gasparotto, Chiara Maccato, Cinzia Sada, Elza Bontempi, Mariangela Brisotto, Olena Pliekhova, Urška Lavrenčič Štangar
Supported Fe2O3/WO3 nanocomposites were fabricated by an original vapor phase approach, involving the chemical vapor deposition (CVD) of Fe2O3 on Ti sheets and the subsequent radio frequency (RF)-sputtering of WO3. Particular attention was dedicated to the control of the W/Fe ratio, in order to tailor the composition of the resulting materials. The target systems were analyzed by the joint use of complementary techniques, that is, X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), and optical absorption spectroscopy...
October 2016: Environmental Science and Pollution Research International
Yong-Xin Liu, Edmund Schüngel, Ihor Korolov, Zoltán Donkó, You-Nian Wang, Julian Schulze
Self-organized spatial structures in the light emission from the ion-ion capacitive rf plasma of a strongly electronegative gas (CF_{4}) are observed experimentally for the first time. Their formation is analyzed and understood based on particle-based kinetic simulations. These "striations" are found to be generated by the resonance between the driving radio frequency and the eigenfrequency of the ion-ion plasma (derived from an analytical model) that establishes a modulation of the electric field, the ion densities, as well as the energy gain and loss processes of electrons in the plasma...
June 24, 2016: Physical Review Letters
V P Veiko, V N Lednev, S M Pershin, A A Samokhvalov, E B Yakovlev, I Yu Zhitenev, A N Kliushin
Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential "opening" radio pulses with a delay of 0.2-1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse...
June 2016: Review of Scientific Instruments
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