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Presents information on a study on the growth of nanocluster carbon films using the cathodic arc process. Experiment of the study; Results and discussion of the experiment; Conclusion.

The nonnegative inverse eigenvalue problem (NIEP) is to characterize the spectra of entrywise nonnegative matrices. A finite multiset of complex numbers is called realizable if it is the spectrum of an entrywise nonnegative matrix. Monov conjectured that the k th -moments of the list of critical points of a realizable list are nonnegative. Johnson further conjectured that the list of critical points must be realizable. In this work, Johnson's conjecture, and consequently Monov's conjecture, is established for a variety of important cases including Ciarlet spectra, Suleĭmanova spectra, spectra realizable via companion matrices, and spectra realizable via similarity by a complex Hadamard matrix. Additionally we prove a result on differentiators and trace vectors, and use it to provide an alternative proof of a result due to Malamud and a generalization of a result due to Kushel and Tyaglov on circulant matrices. Implications for further research are discussed. [ABSTRACT FROM AUTHOR]

The article discusses the discovery of glowing purple light in the upper atmosphere by citizen scientists. Topics mentioned include the visible structure which was undocumented in the scientific literature, the distiction from the aurora common types, and the proposal to identify the arc as a Strong Thermal Emission Velocity Enhancement (STEVE).

We report the effect of ion beam mixing of Ni/Bi multilayers using 100 MeV Au ions as a function of irradiation fluences. X-ray diffraction study reveals the higher magnitude of NiBi 3 and NiBi phases compared to elemental Ni and Bi after ion irradiation. We observe an evolution of grainy structures to a molten-like surface with increasing ion fluences. These features were also reflected in the Rutherford Backscattering spectrometry spectra, in terms of the enhanced mixing with increasing ion fluences. The experimental findings were understood on the basis of inelastic thermal spike model calculations. [ABSTRACT FROM AUTHOR]

In this study, the BiVO 4 /BiOBr p-n heterojunction composite with special hierarchical structure was successfully prepared by a two-step hydrothermal synthesis method. The primary structure is BiVO 4 /BiOBr core-shell particle; the secondary structure is mesoporous spindle which is formed by BiVO 4 /BiOBr core-shell particles. In addition, BiVO 4 /BiOBr heterojunction is formed through simple in-situ ion conversion under the action of HBr. When the addition of HBr is 0.3 mL, BiVO 4 /BiOBr composite shows the optimal structure and photocatalytic performance. The synergistic effect between the heterojunction electric field and the special hierarchical structure can effectively inhibit the recombination and greatly increase the separation efficiency of the photogenerated electron-hole pairs. [ABSTRACT FROM AUTHOR]

Many applications, such as surveillance, inspection or search and rescue operations, can be performed with autonomous robots. Our aim is a control of modular autonomous systems in rescue robotics. One of the basic problems with autonomous robotics is the execution part where the control commands (translation and rotational velocities) are produced for mobile bases. Therefore we have focused on this area because there is only a small amount of available path following software for skidsteered mobile robots. Our goal was to develop a velocity controller that could be used for multiple skid-steered mobile bases. We considered differential drive mobile bases such as tracked skid-steering mobile bases. Our approach is based on an arc fitting algorithm, which takes into account the robot constraints and kinematical model. It produces a continuous trajectory where fitting to the given path is adapted based on given parameters. Moreover, we have included orientation angle compensation while the mobile robot is moving and ground inclination compensation. Our rescue robot is described, together with the simulation setup and algorithm implementation. We compared our algorithm to the Hector-based software and curvature velocity approach. The results for the proposed algorithm are shown for the simulation results and the experiment. [ABSTRACT FROM AUTHOR]

This paper presents an electrical arc model based on physical parameters of the arc including temperature, enthalpy, pressure, and also arc geometry. In this model, different mass flows and power losses are considered. The different powers including radiative and turbulent power as well as power gain and loss carried by axial and radial mass flows are calculated and simulated as a function of physical parameters. Moreover, the different arc diameter expressions and their influence on power losses are examined by arc experiments with high-speed imaging and arc dynamic behavior analysis. This model can provide the dynamic behavior of the arc easier in contrast to more complex physical models. The comparison with conventional arc models, such as Schwamaker, Habedank, Kema, and Schwarz, illustrates that the new arc model can better reproduce electrical measurements. [ABSTRACT FROM PUBLISHER]

Control of chromium oxidation in the electric arc furnace (EAF) is a significant problem in stainless steel production due to variations of the chemical compositions in the EAF charge. One potential method to control chromium oxidation is to analyze the emission spectrum of the electric arc in order to find indicators of rising chromium content in slag. The purpose of this study was to determine if slag composition can be gained by utilizing electric arc emission spectra in the laboratory environment, despite electric arc voltage fluctuations and varying slag composition. The purpose of inducing voltage fluctuation was to simulate changes in the industrial EAF process. The slag samples were obtained from Outokumpu Stainless Oy Tornio Works, and three different arc currents were used. The correlation analysis showed that the emission spectra offer numerous peak ratios with high correlations to the X-ray fluorescence-measured slag CrOx/FeOxand MnO/SiO2ratios. These ratios are useful in determining if the reduction agents have been depleted in the EAF. The results suggest that analysis of laboratory-scale electric arc emission spectra is suitable for indicating the high CrOxor MnO content of the slag despite the arc fluctuations. Reliable analysis of other slag components was not successful. [ABSTRACT FROM AUTHOR]

Black slag from steel production is an industrial waste used as secondary material for some applications (forest tracks, cement, etc.). When it disposed to the open air, little is known about possible side effects that could appear with time. To foresee those side effects, various Raman equipments were used. This analytical strategy has been applied to six different black slag. Four of them were obtained from two steel producers (two original and two with treatment of 'inerting'), and the other two sampled in civil construction works, which supposedly should be treated. Results showed the original mineral phases of the samples (iron and other metal oxides, silicates, ferrites...) and the new phases (calcite, natron, nitratine, goethite, limonite, ilesite, etc.) resulting from the superficial reaction with the atmospheric acid compounds. This fact indicates a strong reactivity between slag and surrounding environment where they have been deposited. Only with one of the three setups, all the compounds could not be detected: (1) the handheld spectrometer detected the major ones and few of the minor ones, (2) the laboratory Raman microprobe ascertained nearly all of the compounds, but cannot be translated to the field and (3) Structural and Chemical Analyser (SCA), which combines micro-Raman spectroscopy and Scanning Electron Microscopy/ Energy Dispersive X-Ray Spectroscopy (SEM-EDS) on the same spot, recognized the trace compounds, which were the most harmful ones. These results demonstrate the greater applicability of this new strategy in comparison with traditional methods for the chemical characterization of black slag and its alteration products. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The principal component analysis (PCA) is applied for three purposes: spectral line identification, redundancy removal and spectral characteristic signals extraction. The spectral information is classified as the first and the second principal components, associated with Ar I lines and metal lines, respectively. With the mean value method, pulse interference resulted from the pulse current is eliminated from the spectral signals. The relationships among these extracted signals and the defects resulted from wire feed are discussed and the results show that the second principal component is closely related to these defects while the first principal component has relationship with the arc states. To test validity of the extracted signals, a back-propagation neural network is designed and appropriately trained with “Early Stopping” technique to detect these defects automatically. [Copyright &y& Elsevier]

This paper reviews progress in arc flash standards and requirements and the protective relaying techniques used to reduce arc flash energy, primarily through “high-speed detection and operation”. In some cases, the high-speed zone is permanent, and in others it is switched in during maintenance or repair. The need for high-speed “backup” arc flash protection will be discussed. Using a single high-speed zone of protection, thus establishing the level of “personal protective clothing,” begs the question “what if the single high-speed zone fails”? Several arc flash clearing time examples will demonstrate this concern. [ABSTRACT FROM AUTHOR]

Simple models of gravitational arcs are crucial for simulating large samples of these objects with full control of the input parameters. These models also provide approximate and automated estimates of the shape and structure of the arcs, which are necessary for detecting and characterizing these objects on massive wide-area imaging surveys. We here present and explore the ArcEllipse, a simple prescription for creating objects with a shape similar to gravitational arcs. We also present PaintArcs, which is a code that couples this geometrical form with a brightness distribution and adds the resulting object to images. Finally, we introduce ArcFitting, which is a tool that fits ArcEllipses to images of real gravitational arcs. We validate this fitting technique using simulated arcs and apply it to CFHTLS and HST images of tangential arcs around clusters of galaxies. Our simple ArcEllipse model for the arc, associated to a Sérsic profile for the source, recovers the total signal in real images typically within 10%-30%. The ArcEllipse+Sérsic models also automatically recover visual estimates of length-to-width ratios of real arcs. Residual maps between data and model images reveal the incidence of arc substructure. They may thus be used as a diagnostic for arcs formed by the merging of multiple images. The incidence of these substructures is the main factor that prevents ArcEllipse models from accurately describing real lensed systems. [ABSTRACT FROM AUTHOR]

A procedure has been developed for the direct atomic emission determination of medium concentrations of noble metals in mineral raw materials and products of their processing. The procedure is based on the application of a spectral complex, consisting of an arc source of spectrum excitation, a DFS-8 spectrograph, a receiver of spectrum emission with CCD structures, and a registration system including software. The detection limits are n × 10% for a number of noble metals and n × 10% for Ag with RSD of 7-14%. [ABSTRACT FROM AUTHOR]

Abstract: The hydrogen production from an easily transported liquid feedstock can be an efficient alternative for fuel cells application. The steam-oxidative reforming of bio-ethanol by a novel gliding arc discharge named Laval nozzle arc discharge (LNAD) was investigated in this paper at low temperature and atmospheric pressure. The conversion efficiency and product distributions, mainly of H2 and CO, were studied as functions of O/C ratio, S/C ratio, the ethanol flow rate and input power. The voltage–ampere (V–I) characteristic is also discussed here concerning the non-thermal plasma effect on the bio-ethanol reforming. A high conversion rate and fair H2 yield have been achieved, 90% and 40% respectively. When the ethanol flow rate (G ethanol) was 0.15 g s−1 and S/C = 2.0, the minimum specific energy requirement of H2 and CO were achieved at O/C = 1.4 with the specific energy input of 55.44 kJ per ethanol mole, 72.92 kJ mol−1 and 80.20 kJ mol−1 respectively. The optimal conditions for ethanol reforming seem to be S/C = 2.0 and O/C = 1.4–1.6, which are higher than those of the reaction''s stoichiometry. This paper shows interesting results in comparison with the ethanol reforming assisted by other discharges. Compared with others, it features good conversion rate, low energy consumption and significantly reduced nitrogen oxide emission. [Copyright &y& Elsevier]

Results are presented for metallographic analysis and mechanical tests for gas pipeline metal specimens, having operated for about fifteen years. Recommendations are given for further use on the basis of verification studies. [ABSTRACT FROM AUTHOR]

Abstract: An arc of a graph is an oriented edge and a 3-arc is a 4-tuple of vertices such that both and are paths of length two. The 3-arc graph of a graph is defined to have the arcs of as vertices such that two arcs are adjacent if and only if is a 3-arc of . In this paper, we study the independence, domination and chromatic numbers of 3-arc graphs and obtain sharp lower and upper bounds for them. We introduce a new notion of arc-coloring of a graph in studying vertex-colorings of 3-arc graphs. [ABSTRACT FROM AUTHOR]

Wavelength calibration for astronomical spectra usually involves the use of different arc lamps for different resolving powers to reduce the problem of line blending. We present a technique which eliminates the necessity of different lamps. A lamp producing a very rich spectrum, normally used only at high resolving powers, can be used at the lowest resolving power as well. This is accomplished by modelling the observed arc spectrum and solving for the wavelength calibration as part of the modelling procedure. Line blending is automatically incorporated as part of the model. The method has been implemented and successfully tested on spectra taken with the Robert Stobie spectrograph of the Southern African Large Telescope. [ABSTRACT FROM AUTHOR]

novel method is presented for the wavelength calibration of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). The proposed method combines the arc lines and night sky lines, and can achieve high performance. Firstly, the initial wavelength calibration is performed by employing arc lines. Afterwards, the centroids of sky lines are calculated by the initial calibration results and adjusted by the gravity method iteratively. Finally, the ultimate wavelength calibration is obtained by fitting the centroids of arc lines and sky lines with their corresponding wavelengths. Experiments are performed on the data observed by LAMOST, and the results of the proposed method are more accurate than that of the calibration only by arc lines or sky lines. The calibration sky lines are dense in the red channel (5,700-9,000 Å) of LAMOST, but only a few ones are in the blue channel (3,700-5,900 Å). The new method achieves excellent results in the red channel as the substantial sky lines are employed, and the calibration accuracy of the blue channel is also enhanced in some degree by the scare sky lines. [ABSTRACT FROM AUTHOR]

Axial injection in plasma gun through the cathode has clear benefit of longer particle residence time and optimum particle trajectory in the plume; however, accelerated wear of the cathode seem to be the major issue in this approach. This study investigates the arc instability phenomena in an axially injecting single cathode plasma torch design. Gun voltage measurements were used to evaluate the arc behavior. For comparison purpose, arc fluctuations with a standard solid cathode torch design under identical operating parameters have also been studied. A comparison of different internal hardware configurations is also done to understand and establish the important factors in the design of the axial injection and solid cathode systems. Further, this study presents the influence of plume elongation and accelerated gas velocities on the arc behavior in different configurations under low pressure environment. [ABSTRACT FROM AUTHOR]

Low-power laser/arc hybrid welding process of magnesium alloy shows that the weld capability of tungsten-inert-gas arc is improved under the action of laser pulses. The effect of laser pulse on arc plasma is analyzed by studying the plasma spectra, plasma shapes, and arc voltage in this paper. On the one hand, laser pulse attracts arc plasma to laser keyhole and improves the stability of arc plasma; on the other hand, laser pulse expands the arc plasma and concentrates the electric conducting route of arc plasma. All these increase the output power and energy density of arc plasma, so the welding penetration is improved. In addition, laser pulses are controlled to act on the negative wave of alternating-current arc (the target metal has negative polarity) in hybrid welding process to improve the stability of arc plasma and weld penetration. [ABSTRACT FROM AUTHOR]

An isomerically pure sample of Gd3N@C78 has been extracted from the carbon soot formed in the electric-arc generation of fullerenes using hollow graphite rods packed with Gd2O3 and graphite powder under an atmosphere of helium and dinitrogen. Purification has been achieved by chromatographic methods and the product has been characterized by mass spectrometry, UV/vis absorption spectroscopy, and cyclic voltammetry. Although a number of endohedral fullerenes have been found to utilize the D3h(5)-C78 cage, comparison of the spectroscopic and electrochemical properties of the previously characterized Sc3N@D3h(5)-C78 with those of Gd3N@C78 reveals significant differences that indicate that these two endohedrals do not possess the same cage structure. A single crystal X-ray diffraction study indicates that the fullerene cage does not follow the isolated pentagon rule (IPR) but has two equivalent sites where two pentagons abut. The endohedral has been identified as Gd3N@C2(22010)-C78. Two of the gadolinium atoms of the planar Gd3N unit are located within the pentalene folds formed by the adjacent pentagons. The third gadolinium atom resides at the center of a hexagonal face of the fullerene. [ABSTRACT FROM AUTHOR]

The technique of some nanosized substances synthesis in arc discharge plasma at atmospheric pressure is considered. The results of synthesis in the arc discharge with different feeding are presented: dc, power current of 50 Hz, ac of 44 kHz and their combinations. Also, the investigation results of influence of an acoustic field and a co-phased magnetic field on fullerene synthesis at atmospheric pressure are presented. [ABSTRACT FROM AUTHOR]

Magnesium alloy was welded with normal wire and activated flux coated wire. Weld bead penetration, arc voltage, arc profiles and welding arc electronic temperature were researched. Weld bead penetration, arc voltage and welding arc electronic temperature increased when activated flux coated wire was used. It is also found that the welding arc constricted in flux coated wire weld. It is believed that deep weld penetration associated with flux coated wire in this experiment is caused by arc constriction. [ABSTRACT FROM AUTHOR]

Abstract: In this paper it has been verified, by an exhaustive computer search, that in the smallest size of a complete arc is 12 and that complete 19-arcs and 20-arcs do not exist. Therefore, the spectrum of the sizes of the complete arcs in is completely determined. The classification of the smallest complete arcs is also given: the number of non-equivalent complete -arcs is 606 and for each of them the automorphism group has been found and some geometrical properties have been studied. The exhaustive search has been feasible because projective equivalence properties have been exploited to prune the search tree and to avoid generating too many isomorphic copies of the same arc. [Copyright &y& Elsevier]

Five single oxide fluxes — MgO, CaO, TiO[sub2], MnO[sub2], and Cr[sub2]O[sub3] — were used to investigate the effect of active flux on the depth/width ratio in AZ3 lB magnesium alloy. The microstructure and mechanical property of the tungsten inert gas (TIG) welding seam were studied. The oxygen content in the weld seam and the arc images during the TIG welding process were analyzed. A series of emission spectroscopy of weld arc for TIG welding for magnesium with and without flux were developed. The results showed that for the five single oxide fluxes, all caii increase the weld penetration effectively and grain size in the weld seam of alternating current tungsten inert gas (ACTIG) welding of the Mg alloy. The oxygen content of the welds made without Ilux is not very different from those produced with oxide fluxes not considering trapped oxide. However, welds that have the best penetration have a relatively higher oxygen content among those produced with flux. It was found that the arc images with the oxide fluxes were only the enlarged form of the arc images without flux; the arc constriction was not observed. The detection of arc spectroscopy showed that the metal elements in the oxides exist as the neutral atom or the first cation in the weld arc. This finding would influence the arc properties. When TIG simulation was carried out on a plate with flux applied only on one side, the arc image video showed an asymmetric arc, which deviated toward the flux free side. The thermal stability, the dissociation energy, and the electrical conductivity of oxide should be considered when studying the mechanism for increased TIG flux weld penetration. [ABSTRACT FROM AUTHOR]

The article reviews literature on the advancements and trends in the area of atomic spectroscopy. According to the article, atomic spectrometry is one of the strongest methods for determination of elements and their compounds from a variety of samples. The article discusses optical methods atomic absorption, atomic emission spectrometry, chemometric methods, diode laser atomic absorption spectrometry, vapor generation techniques, arc and spark sources, inductively coupled plasmas, glow discharge atomic emission, and inductively coupled plasma mass spectrometry.

Rydberg spectral lines of an atom are sometimes superimposed on the continuous spectrum of a different configuration. Effects of interaction among different configurations in one of these cases are theoretically investigated, and a formula is obtained that describes the behavior of absorption spectrum intensity. This offers qualitative justification of some experimental results obtained by BEUTLER in studies of absorption arc spectra of noble gases and Ib spectra of some metal vapors. [ABSTRACT FROM AUTHOR]

Some droplets emitted by vacuum arc cathode spot and surrounded by dense plasma are referred to as droplet spots. The goal of this work is the study of spectral characteristics of the droplet spot light emission. The spectrum of droplets was compared with the spectrum of the cathode spot. The light emission of droplet spots after arc extinction was also studied. Non-monotonous (twinkling) glow of droplet spots was found to last for a long time (up to 1 ms) after arc extinction. [ABSTRACT FROM AUTHOR]

A model of steady-state solitary spots with a step-function dependence of the density of the energy flux from the plasma to the cathode surface on the surface temperature is suggested. While being simple and clear cut, this model, nevertheless, reflects essential features of the physics involved. It is found that a solution obtained by means of the method of matched asymptotic expansions is close to exact numerical results, in contrast to a solution obtained with the use of Steenbeck's principle of minimum power. [ABSTRACT FROM AUTHOR]

In a gas circuit breaker and a molded case circuit breaker, the hot gas between the two metals may transform into the arc plasma. We call this arc formation the “arcing phenomenon”. Since the hot gas somewhat has electrical conductivity, the arcing phenomenon presumably results from a physical mechanism different from that of dielectric breakdown through the cool gas. The present paper describes the transient aspects of the conductance of the hot air that is exposed to the DC voltage and the threshold conditions of the occurrence of the arcing phenomenon. The influence of the velocity of hot air on arcing phenomenon is also discussed. As far as the present experimental condition of 3 mm in gap is concerned, it might be concluded that the threshold voltages for the arcing occurrence in the hot air around 3000 K were 59, 51 and 48 V, for the air blow velocity of 65, 55 and 34 m/s, respectively. [Copyright &y& Elsevier]

The HC-move was defined as an unknotting operation of a ribbon 2-knot. Representing a ribbon 2-knot by a virtual arc, we see that the HC-move corresponds to one of the "forbidden moves", which unknot every virtual knot. Using this, we consider the α[sub 2]-invariant of a ribbon 2-knot and a relation between the Δ-move for a 1-knot and the HC-move for its spun 2-knot. [ABSTRACT FROM AUTHOR]

Presents a study which attempted to improve the measurement accuracy of arc length using the spectrum of arc light at a particular wavelength during gas tungsten arc welding with argon shield. Experimental system and procedure; Roles of different welding parameters in determining the overall spectral characteristics of the arc light; Spatial analysis; Precision sensing of arc length.

Discusses a study which presented a method to explore the dynamics of a low-voltage electric breaking arc from magnetic measurements. Mathematical model for the determination of arc dynamics; Examples of low-voltage electric breaking arc restrike; Characterization of the restrike; Conclusion.

Describes the method of simulating the behavior and the shape of an arc driven by magnetic force in a gas. Arc simulation model; Example of arc simulation; Conclusions.

Investigates the composition of background spectra radiated from an standard frequency (SF)6 post-arc channel after current zero. Measurement of radiation intensities of iron spectral lines and background spectra; Temperature dependence of radiation intensity of background spectra; Theoretical calculation of emission coefficients of background spectra; Conclusions.

Traces the origin of Kern's arc in meteorological optics as seen on the latitude of the circumzenithal arc on the opposite side of the zenith with the use of computer-stimulated halo patterns. Stimulation of the halo pattern with the Monte Carlo geometric ray-tracing technique; Discussion on the types of Kern's arc; Production by double-plate ice crystals.

It is often accompanied by an intense arc when solid-state graphene samples are irradiated by microwaves (MWs); however, arc spectra have not been studied. In this study, the arc spectra of reduced graphene oxide (RGO) powder, three-dimensional (3D) porous RGO, and RGO paper under MW irradiation were measured; these spectra exhibited diverse features. For the same reaction conditions and the same initial sample, the arc spectra should be the same if the reaction process and mechanisms are the same. Further analyses showed that the obtained RGO paper with an evident 2D band, a smaller D band, lower sheet resistance, and lower oxygen content was of higher quality than the RGO powder and 3D porous RGO obtained after MW irradiation. Based on these results, the diverse spectra may suggest different reaction processes and mechanisms. Overall, these findings provide novel insights into the preparation of graphene via MW reduction. Unlabelled Image • RGO powder, 3D porous RGO, and RGO paper show diverse spectra under MW irradiation. • The diverse spectra imply that different reaction processes and mechanisms are active for these materials. • The spectra of RGO powder and 3D porous RGO exhibit metal-like features. • RGO paper may exhibit the thermal effect and carbon atom rearrangement. • These findings provide novel insights for graphene preparation by MW reduction. [ABSTRACT FROM AUTHOR]

Electric arc instabilities in dc plasma torches lead to nonhomogeneous treatments of nanosized solid particles or liquids injected within thermal plasma jets. This paper shows that an additional acoustic resonator mounted on the cathode cavity allows reaching a significant damping of these instabilities, particularly the Helmholtz mode of arc oscillations. The acoustic resonator is coupled with the Helmholtz resonator of the plasma torch limiting the amplitude of arc voltage variations. It is also highlighted that this damping is dependent on friction effects in the acoustic resonator. [ABSTRACT FROM AUTHOR]

The effect of a transverse magnetic field on the anodic arc root movement inside a dc plasma torch has been investigated. The arc voltage fluctuation, which represents the degree of the arc instability, was reduced to 28.6% of the original value and the high frequency components in the voltage signal also decreased in their magnitudes. The inherent arc instability in a dc thermal plasma torch seems to be suppressed by a diamagnetic effect of the arc column. Furthermore, the measured voltage wave forms indicated that the arc root attachment mode would be controllable by a transverse magnetic field. [ABSTRACT FROM AUTHOR]

Experiments on the motion of long alternating current arcs in atmospheric air show that the anode and cathode arc roots have different motion characteristics because of different formation mechanisms. During a half cycle of the arc current, the anode arc root moves towards the direction of magnetic force and occasionally has a jumping motion, while the cathode arc root moves sufficiently slow to consider it stationary and hardly has any jump. The arc column has a complex shape and moves under the drive of the magnetic force and is also quickened by the lower arc root. [ABSTRACT FROM AUTHOR]

The onset and rotation frequency of a helical instability in a metal halide lamp is studied for gravity conditions varying from microgravity to 1.8g during parabolic flights and at microgravity in the International Space Station. The results show that gravity-induced convection seriously alters the onset and behavior of the instability. Hypergravity and low lamp power increase the rotation frequency of the instability, which seems independent of the arc pressure. At microgravity conditions, only arc bending and no rotation has been observed. The arc bending increases with lamp power, allowing one to monitor the driving and damping forces of the instability. [ABSTRACT FROM AUTHOR]

In this paper, we present the investigation realized on an experimental setup that simulates an arc column subjected to the transient phase of a lightning current waveform in laboratory conditions. Optical emission spectroscopy is employed to assess space- and time-resolved properties of this high current pulsed arc. Different current peak levels are utilised in this work, ranging from 10 kA to 100 kA, with a peak time around 15 µs. Ionic lines of nitrogen and oxygen are used to determine the radial profiles of temperature and electron density of the arc channel over time from 2 µs to 36 µs. A combination of 192 N II and O II lines is considered in the calculation of the bound–bound contribution of the absorption coefficient of the plasma channel. Calculations of the optical thickness showed that self-absorption of these ionic lines in the arc column is important. To obtain temperature and electron density profiles in the arc, we solved the radiative transfer equation across the channel under an axisymmetric assumption and considering the channel formed by uniform concentric layers. For the 100 kA current peak level, the temperature reaches more than 38 000 K and the electron density reaches 5  ×  1018 cm−3. The pressure inside the channel is calculated using the air plasma composition at local thermodynamic equilibrium, and reaches 45 bar. The results are discussed and utilised to estimate the electrical conductivity of the arc channel. [ABSTRACT FROM AUTHOR]

The article reports on observation of aurora displays in several regions of the world. Topics include contribution of Bz magnetic components for aurora phenomena, initiation of aurora activity through solar streams and coronal holes, transformation in mechanism for initiation of coronal mass ejection, detection of low green glow in aurora activity at Caithness, Scotland on November 1-2, 2015 and recognition of rayed arc in auroras at Tarbat Ness, Moray on December 10-11, 2015.

Multileaf collimator (MLC) tracking is a promising and clinically emerging treatment modality for radiotherapy of mobile tumours. Still, new quality assurance (QA) methods are warranted to safely introduce MLC tracking in the clinic. The purpose of this study was to create and experimentally validate a simple model for fast motion-including dose error reconstruction applicable to intrafractional QA of MLC tracking treatments of moving targets.MLC tracking experiments were performed on a standard linear accelerator with prototype MLC tracking software guided by an electromagnetic transponder system. A three-axis motion stage reproduced eight representative tumour trajectories; four lung and four prostate. Low and high modulation 6 MV single-arc volumetric modulated arc therapy treatment plans were delivered for each trajectory with and without MLC tracking, as well as without motion for reference. Temporally resolved doses were measured during all treatments using a biplanar dosimeter. Offline, the dose delivered to each of 1069 diodes in the dosimeter was reconstructed with 500 ms temporal resolution by a motion-including pencil beam convolution algorithm developed in-house. The accuracy of the algorithm for reconstruction of dose and motion-induced dose errors throughout the tracking and non-tracking beam deliveries was quantified.Doses were reconstructed with a mean dose difference relative to the measurements of −0.5% (5.5% standard deviation) for cumulative dose. More importantly, the root-mean-square deviation between reconstructed and measured motion-induced 3%/3 mm γ failure rates (dose error) was 2.6%. The mean computation time for each calculation of dose and dose error was 295 ms.The motion-including dose reconstruction allows accurate temporal and spatial pinpointing of errors in absorbed dose and is adequately fast to be feasible for online use. An online implementation could allow treatment intervention in case of erroneous dose delivery in both tracking and non-tracking treatments. [ABSTRACT FROM AUTHOR]