Specific Energy Range Research Articles

High-energy photon polarimeter for astrophysics

A high-energy photon polarimeter for astrophysics studies in the energy range from 10 MeV to 800 MeV is considered. The proposed concept uses a stack of silicon micro-strip detectors where they play the roles of both a converter and a tracker. The purpose of this paper is to outline the parameters of such a polarimeter and to estimate the productivity of measurements. Our study supported by a Monte Carlo simulation shows that with a one-year observation period the polarimeter will provide 6% accuracy of the polarization degree for photon energies above 100 MeV, which would be a significant advance relative to the currently explored energy range of a few MeV. The proposed polarimeter design could easily be adjusted to the specific photon energy range to maximize efficiency if needed.

A study of the mean kinetic energy of recoil ions from ion-charge-resolved electron spectra produced in 3.5 keV electron-argon collisions

New experimental results for the dependence of mean kinetic energy (MKE) of argon recoil ions of charge state 1+ to 4+ on energy selected correlated Auger electrons produced in 3.5 keV electron impact with thermal argon atoms using TOF mass spectrometry and electron spectroscopy techniques are presented. Values of the MKE of recoil ions are deduced from the width of the TOF peaks. The measured average values of MKE of Ar+, Ar2+, Ar3+and Ar4+ recoil ions are found to be respectively 216 meV ± 5 meV, 247 meV ± 6 meV, 290 meV ± 7 meV, and 324 meV ± 8 meV in the electron energy range of 125–210 eV. The average charge state ratios (∑nσn/∑σn) of recoil ions have been determined to be 1.8, 2.4 and 2.0 in the electron energy range of 125–145 eV, 150–200 eV, and 200–210 eV respectively. For the investigated electron energy range 120–210 eV, the considered Auger transitions are found to dominate the direct ionization; for low electron energies (<100 eV), the direct multiple ionization dominates which has not been considered in this work. Survey of results obtained from the present measurements suggests that the MKE depends not only on the charge state of the recoil ions but also weakly on the specific energy range of ejected electrons in the considered collision reaction. Presently we are not aware of any theoretical calculations that can be compared with our results.

Differential and total cross sections and astrophysical [formula omitted]-factors for 2H(d,n)3He and 2H(d,p)3H reactions in a wide energy range

Differential cross sections of deuteron–deuteron fusion reactions are needed in astrophysics, precision cosmology, nuclear physics, and controlled nuclear fusion research. New parametrizations for center of mass differential cross sections, total cross sections and astrophysical S-factors in a wide range of specific energy from 0.5 keV/u to about 0.5 GeV/u have been obtained. Straightforward approximating formulae readily suitable for multithreaded algorithmization are given here for 2H(d,n)3He and2H(d,p)3H reactions. The energy range is about two orders of magnitude broader than that in the tables published earlier for neutron branch.

Impact erosion model for gravity-dominated planetesimals

Disruptive collisions have been regarded as an important process for planet formation, while non-disruptive, small-scale collisions (hereafter called erosive collisions) have been underestimated or neglected by many studies. However, recent studies have suggested that erosive collisions are also important to the growth of planets, because they are much more frequent than disruptive collisions. Although the thresholds of the specific impact energy for disruptive collisions (QRD*) have been investigated well, there is no reliable model for erosive collisions. In this study, we systematically carried out impact simulations of gravity-dominated planetesimals for a wide range of specific impact energy (QR) from disruptive collisions (QR∼QRD*) to erosive ones (QR<<QRD*) using the smoothed particle hydrodynamics method. We found that the ejected mass normalized by the total mass (Mej/Mtot) depends on the numerical resolution, the target radius (Rtar) and the impact velocity (vimp), as well as on QR, but that it can be nicely scaled by QRD* for the parameter ranges investigated (Rtar= 30–300km, vimp= 2–5km/s). This means that Mej/Mtot depends only on QR/QRD* in these parameter ranges. We confirmed that the collision outcomes for much less erosive collisions (QR < 0.01 QRD*) converge to the results of an impact onto a planar target for various impact angles (θ) and that Mej/Mtot ∝ QR/QRD* holds. For disruptive collisions (QR∼QRD*), the curvature of the target has a significant effect on Mej/Mtot. We also examined the angle-averaged value of Mej/Mtot and found that the numerically obtained relation between angle-averaged Mej/Mtot and QR/QRD* is very similar to the cases for θ = 45° impacts. We proposed a new erosion model based on our numerical simulations for future research on planet formation with collisional erosion.

Effects of microwave and ultrasound irradiations on dark fermentative bio-hydrogen production from food and yard wastes

Lignocellulosic materials like food and yard wastes are difficult to hydrolyse and this results in decreased bio-hydrogen yields. As such, this study investigated the potential of microwave (MW) and ultrasound (UtS) irradiations for pre-treating food and yard wastes prior to dark fermentation. The specific energy was varied from 0 to 6946 kJ/kg total solids for each pre-treatment and the results obtained showed that both pre-treatments generally enhanced solids and organic matter solubilisation, with the effects more significant at high pre-treatment conditions. However, none of the pre-treatment conditions improved bio-hydrogen production. The main reasons identified for the low H2 yields were the possible formation of inhibitors due to pre-treatments while the higher concentrations of propionic acid and ethanol among the end-product metabolites could also have suppressed bio-hydrogen production. Consequently, neither MW nor UtS irradiation is feasible as pre-treatment of food and yard wastes for enhanced bio-hydrogen production under the range of specific energies studied.

A comprehensive analytical model for laser powder-fed additive manufacturing

This paper addresses a comprehensive analytical model for the laser powder-fed additive manufacturing (LPF-AM) process, also known as directed energy deposition AM. The model analytically couples the moving laser beam with Gaussian energy distribution, the powder stream and the semi-infinite substrate together, while considering the attenuated laser power intensity distribution, the heated powder spatial distribution and the melt pool 3D shape with its boundary variation. The particles concentration on transverse plane is modeled with Gaussian distribution based on optical measurement. The model can effectively be used for process development/optimization and controller design, while predicting adequate clad geometry as well as the catchment efficiency rapidly. Experimental validation through the deposition of Inconel 625 proves the model can accurately predict the clad geometry and catchment efficiency in the range of specific energy that is corresponding to high clad quality (maximum percentage difference is 6.2% for clad width, 7.8% for clad height and 6.8% for catchment efficiency).

Excited nuclear matter at Fermi energies: From transport properties to the equation of state

Properties of excited nuclear matter are one of the main subject of investigation in Nuclear Physics. Indeed, the response of nuclear matter under extreme conditions encountered in heavy-ion induced reactions (large compression, thermal and collective excitations, isopin diffusion) around the Fermi energy is strongly needed when studying the nuclear equation of state and the underlying in-medium properties concerning the nuclear interaction. In this contribution, we will present some experimental results concerning the transport properties of nuclear matter, focusing specifically on the determination of in-medium quantities such as mean free pathes and nucleon-nucleon cross sections around the Fermi energy. We will see that, in this specific energy range, energy and isospin dissipations exhibit very peculiar features, such as the crossover between 1-body to 2-body dissipation regimes corresponding to the transition between the nuclear response from Mean-Field to the nucleonic response through the appearance of nucleon-nucleon collisions.

Correlation of optical reflectivity with numerical calculations for a two-dimensional photonic crystal designed in Ge

A two dimensional photonic crystal (2DPhC) with triangular symmetry is investigated using optical reflectivity measurements and numerical calculations. The system has been obtained by direct laser writing, using a pulsed laser (λ = 775 nm), perforating an In-doped Ge wafer. A lattice of holes with well-defined symmetry has been designed. Analyzing the spectral signature of PBGs recorded experimentaly with finite difference time domain theoretical calculations one was able to prove the relation between the geometric parameters (hole format, lattice constant) of the system and its ability to trap and guide the radiation in specific energy range. It was shown that at low frequency and telecommunication ranges of transvelsal electric modes photonic band gap occur. This structure may have potential aplications in designing photonic devices with applications in energy storage and conversion as potential alternative to Si-based technology.

Evaluation and scale-up of miniaturized rotor–stator impact mills

Two recently marketed, miniaturized rotor–stator impact mills of 70mm and 35mm rotor diameter were evaluated and compared to a conventional small scale model of 110mm rotor diameter, in order to reduce the minimum batch size while maintaining adequate predictability. The minimum batch size of the conventional scale model is about 1 to 4kg and far too big to establish rotor–stator impact milling technology at the early-stage of drug development due to limited availability of drug compound, and rather inefficient for the technical processing of costly drug compounds during the drug development cycle. Both miniaturized equipment models show comparable behavior on product particle size by process parameters feed rate and rotor speed in relation to the conventional scale model. The minimum, predictable batch size could be considerably reduced to 400g and 10g for the rotor–stator impact mills of 70mm and 35mm rotor diameter, respectively. Scale-up could be established between the two miniaturized models and the conventional scale model for process parameter feed rate by a common power factor concept available in literature, and for process parameter rotor speed by the cumulative specific stress energy of the rotating pins. Finally, both miniaturized rotor–stator impact mills enable significant improvements for the application in drug development, with reduced dynamic working range of cumulative specific stress energy, compared to rotor–stator impact mills at pilot and manufacturing scales.

Study of soil aggregate breakdown dynamics under low dispersive ultrasonic energies with sedimentation and X-ray attenuation.

It has been increasingly recognized that soil organic matter stabilization is strongly controlled by physical binding within soil aggregates. It is therefore essential to measure soil aggregate stability reliably over a wide range of disruptive energies and different aggregate sizes. To this end, we tested high-accuracy ultrasonic dispersion in combination with subsequent sedimentation and X-ray attenuation. Three arable topsoils (notillage) from Central Europe were subjected to ultrasound at four different specific energy levels: 0.5, 6.7, 100 and 500 J cm-3, and the resulting suspensions were analyzed for aggregate size distribution by wet sieving (2 000-63 μm) and sedimentation/X-ray attenuation (63-2 μm). The combination of wet sieving and sedimentation technique allowed for a continuous analysis, at high resolution, of soil aggregate breakdown dynamics after defined energy inputs. Our results show that aggregate size distribution strongly varied with sonication energy input and soil type. The strongest effects were observed in the range of low specific energies (< 10 J cm-3), which previous studies have largely neglected. This shows that low ultrasonic energies are required to capture the full range of aggregate stability and release of soil organic matter upon aggregate breakdown.

A t10-based method for evaluation of ore pre-weakening and energy reduction

Currently the effect of the pre-weakening of ore particles by high voltage pulses is evaluated by the percentage change of A∗b values between pulse-treated and untreated ore particles. The values of A∗b, widely used as an ore breakage competence indicator in the mineral industry, are determined from the parameters of the JKMRC breakage models. In this study a t10-based method was developed to predict the degree of size reduction, t10, of pulse-treated particles from that of untreated particles broken at the same size/energy level. This method incorporates one parameter, CAb, which is equivalent to the percentage change of A∗b values.The t10-based method was validated using nine sets of comparative JK Rotary Breakage Tester data on pulse-treated and untreated ore samples over a wide range of impact specific energies and particle sizes. The t10-based method can be used to calculate the energy reduction due to the pre-weakening effect in the downstream comminution process. It indicates that the energy reduction by pre-weakening increases with an increase in the target product fineness and the degree of pre-weakening, and with the decrease in feed particle size.

Large increase in the electron capture and excitation cross sections for Li+ colliding with atomic H under UV laser assistance

Neutralization and ash products due to electron capture processes in plasmas reduce the efficiency of energy generation in fusion Tokamak reactors. Therefore, lithium ions have been used to improve the efficiency of energy generation where good control of the electron capture process is required. Here, we show that an intense ( W cm−2), ultra-short (1 fs at full width half-maximum) Gaussian laser pulse in the UV region can enhance the electron capture process on in the low collision keV energy region. We find a factor of 10 enhancement in electron capture cross-section at impact energies lower than 10 keV amu−1 for an 80 nm wavelength laser and a factor of 2 for the excitation process in the hydrogen atom as compared to the laser-free case. In contrast, for a 200 nm wavelength laser the increase of the electron capture cross-sections takes place around 1 keV amu−1 by a factor of 3 and no enhancement for the excitation process. Our results show that the UV assisted production of Li can be controlled, particularly for short UV wave-length for a specific collision energy range. We anticipate that our findings will facilitate UV laser control of the Li production in Tokamak reactors and encourage further experimental work in this system.

Effect of xanthan gum on processing and cooking quality of nontraditional pasta

SummaryThe physicochemical properties of three different commercial sources of xanthan gum (XG) were determined, and its subsequent effect on the processing and cooking quality of pasta containing nontraditional ingredients was characterised. Commercial durum flour was fortified with nontraditional ingredients (soya flour or oat flour, 10% w/w) and XG (2% w/w). Protein content, ash content, bulk density, water‐holding capacity and total glucose content significantly varied among XG samples from different vendors. Xanthan gum increased dough strength of durum flour and the extent of strengthening varied with vendor of XG. For example, time‐to‐peak ranged from 2.75 to 4.25 min; peak width from 2.5 to 3.75 BU; and end width from 2 to 3 BU depending on the vendor of XG. Processing properties differed depending on commercial source. Commercial XG that had the finest particle size required the lowest mechanical energy (range 253–270 J s−1) and had the greatest extrusion rate (range 3.38–3.65 g s−1), both of which resulted in the lowest specific mechanical energy (range 69–79 J g−1) required to extrude spaghetti samples.

Evolution of Hydrophobicity in Plasma Polymerised 1,7‐Octadiene Films

1,7‐Octadiene (OD) was plasma polymerised onto silicon wafers and glass slides under a broad range of input specific energies and deposition times to study the hydrophobicity of deposited films. Deposition of plasma polymerised 1,7‐octadiene (ppOD) film resulted in decrease of glass slide surface free energy (SFE) from ≈71 to 44 mJ · m−2. X‐ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectroscopy (ToF‐SIMS) results confirmed that this decrease is due to the concealing of polar SiOH groups by non‐polar CxHy functionalities. Atomic force microscopy (AFM) images along with ToF‐SIMS spectra suggested patchy‐like growth of ppOD films in the very early stages of polymerisation. It has been demonstrated that a precise control over the surface hydrophobicity is achieved by simply tuning the plasma polymerisation parameters.

High Velocity Impact Response of Composite Lattice Core Sandwich Structures

In this research, carbon fiber reinforced polymer (CFRP) composite sandwich structures with pyramidal lattice core subjected to high velocity impact ranging from 180 to 2,000 m/s have been investigated by experimental and numerical methods. Experiments using a two-stage light gas gun are conducted to investigate the impact process and to validate the finite element (FE) model. The energy absorption efficiency (EAE) in carbon fiber composite sandwich panels is compared with that of 304 stainless-steel and aluminum alloy lattice core sandwich structures. In a specific impact energy range, energy absorption efficiency in carbon fiber composite sandwich panels is higher than that of 304 stainless-steel sandwich panels and aluminum alloy sandwich panels owing to the big density of metal materials. Therefore, in addition to the multi-functional applications, carbon fiber composite sandwich panels have a potential advantage to substitute the metal sandwich panels as high velocity impact resistance structures under a specific impact energy range.

Supercapacitor Electrodes from Activated Carbon Monoliths and Carbon Nanotubes

Binderless monoliths of supercapacitor electrodes were prepared by the carbonization (N2) and activation (CO2) of green monoliths (GMs). GMs were made from mixtures of self-adhesive carbon grains (SACG) of fibers from oil palm empty fruit bunches and a combination of 5 & 6% KOH and 0, 5 & 6% carbon nanotubes (CNTs) by weight. The electrodes from GMs containing CNTs were found to have lower specific BET surface area (SBET). The electrochemical behavior of the supercapacitor fabricated using the prepared electrodes were investigated by electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD). In general an addition of CNTs into the GMs reduces the equivalent series resistance (ESR) value of the cells. A cell fabricated using electrodes from GM with 5% CNT and 5% KOH was found to have the largest reduction of ESR value than that from the others GMs containing CNT. The cell has steeper Warburg's slope than that from its respective non-CNT GM, which reflect the smaller resistance for electrolyte ions to move into pores of electrodes despite these electrodes having largest reduction in specific BET surface area. The cell also has the smallest reduction of specific capacitance (Csp) and maintains the specific power range despite a reduction in the specific energy range due to the CNT addition.

The quality factor of x-rays/gamma rays as one is realistic?

AbstractThe quality factor for x-rays, gamma rays and electrons assigned as one need to be revised. It is observed that as the energy decreases, mean lethal radiation dose (Do)decreases as well and become more potent. It is therefore proposed that radiation quality in biological systems should be assessed in the mitotic phase of the cell cycles. Furthermore, based on the mean lethal radiation dose within specific energy range, an appropriate quality factor of x-rays, gamma rays and electrons should be assigned.

Optical properties of two-dimensional quasicrystalline plasmonic arrays

Simulation models for the optical properties of 2D quasiperiodic plasmonic structures often fail due to their lack of periodicity. Therefore, it is necessary to find an appropriate model to describe the optical properties of such structures. In this paper we present a model which is able to describe the optical spectra of 2D metallic photonic quasicrystals on top of a waveguide. We take the 2D Fourier transform of the structure and consider all possible waveguide modes in the specific energy range. By utilizing the dispersion relations, the optical spectra can be calculated. The presented model is verified by measurements of a quasiperiodic lattice as well as a rectangular lattice as reference. We find distinct differences in the behavior of quasicrystalline vs rectangular lattices, in particular when investigating rotated and elongated plasmonic particles.

SATURATION LEVELS FOR WHITE-LIGHT FLARES OF FLARE STARS: VARIATION OF MINIMUM FLARE DURATION FOR SATURATION

Taking into account results obtained from models and from statistical analyses of obtained parameters, we discuss flare activity levels and flare characteristics of five UV Ceti stars. We present the parameters of unpublished flares detected over two years of observations of V1005 Ori. We compare parameters of the U-band flares detected over several seasons of observations of AD Leo, EV Lac, EQ Peg, V1054 Oph, and V1005 Ori. Flare frequencies calculated for all program stars and maximum energy levels of the flares are compared, and we consider which is the most correct parameter as an indicator of flare activity levels. Using the One Phase Exponential Association function, the distributions of flare equivalent duration versus flare total duration are modeled for each program star. We use the Independent Samples t-Test in the statistical analyses of the parameters obtained from the models. The results reveal some properties of flare processes occurring on the surfaces of UV Ceti type stars. (1) Flare energies cannot be higher than a specific value regardless of the length of the flare total duration. This must be a saturation level for white-light flares occurring in flare processes observed in the U band. Thus, for the first time it is shown that white-light flares have a saturation in a specific energy range. (2) The span values, which are the difference between the equivalent durations of flares with the shortest and longest total durations, are almost equal for each star. (3) The half-life values, minimum flare durations for saturation, increase toward the later spectral types.

Magnetic states of the ionosphere of Venus observed by Venus Express

Strong ultraviolet radiation from the Sun ionizes the upper atmosphere of Venus, creating a dense ionosphere on the dayside of the planet. In contrast to Earth, the ionosphere of Venus is not protected against the solar wind by a magnetic field. However, the interaction between charged ionospheric particles and the solar wind dynamic and magnetic pressure creates a pseudo-magnetosphere which deflects the solar wind flow around the planet ( Schunk and Nagy, 1980). The combination of changing solar radiation and solar wind intensities leads to a highly variable structure and plasma composition of the ionosphere. The instrumentation of the Venus Express spacecraft allows to measure the magnetic field (MAG experiment) as well as the electron energy spectrum and the ion composition (ASPERA-4 experiment) of the upper ionosphere and ionopause. In contrast to the earlier Pioneer Venus Orbiter (PVO) measurements which were conducted during solar maximum, the solar activity was very low in the period 2006–2009. A comparison with PVO allows for an investigation of ionospheric properties under different solar wind and EUV radiation conditions. Observations of MAG and ASPERA have been analyzed to determine the positions of the photoelectron boundary (PEB) and the “magnetopause” and their dependence on the solar zenith angle (SZA). The PEB was determined using the ELS observations of ionospheric photoelectrons, which can be identified by their specific energy range. It is of particular interest to explore the different magnetic states of the ionosphere, since these influence the local plasma conductivity, currents and probably the escape of electrons and ions. The penetration of magnetic fields into the ionosphere depends on the external conditions as well as on the ionospheric properties. By analyzing a large number of orbits, using a combination of two different methods, we define criteria to distinguish between the so-called magnetized and unmagnetized ionospheric states. Furthermore, we confirm that the average magnetic field inside the ionosphere shows a linear dependence on the magnetic field in the region directly above the PEB.