Maximum Energy Difference Research Articles

Wideband Waveform Design for Distributed Precision Jamming.

Precision electronic warfare is a hot direction for future jamming technology development, and distributed precision jamming (DIPJ) is one of its typical application scenarios. The task objective of DIPJ is to design jamming waveforms so that the jamming energy generated by a set of ultra-sparse array transmitters can be focused in the jamming region of interest while being suppressed in other specific protected regions, which can be viewed as a distributed multiple-input and multiple-output system waveform design problem under a three-dimensional scenario. This paper extends the jamming signal model in DIPJ from narrowband to wideband based on previous work to address a broader range of jamming tasks. After extending the model to wideband signals, a method based on the traditional maximum total energy difference optimization objective is first given for comparison. A wideband jamming waveform design method based on the majorization minimization algorithm with the desired power spectrum matching as the optimization target is designed for the problem that the maximum energy difference method cannot focus energy well in the jamming region. The simulation results show that the presented method can make the jamming energy well concentrated in the target region and evenly distributed over the whole bandwidth, while the energy in the whole bandwidth is suppressed in the protected region.

Self‐Assembled Junctions of 2D Single‐Layer Semiconductors: A Potential Way toward Advanced Photocatalysis

Self‐Assembled Junctions of <scp>2D</scp> Single‐Layer Semiconductors: A Potential Way toward Advanced Photocatalysis

On the measurement uncertainty of microdosimetric quantities using diamond and silicon microdosimeters in carbon-ion beams.

The purpose of this paper is to compare the response of two different types of solid-state microdosimeters, that is, silicon and diamond, and their uncertainties. A study of the conversion of silicon microdosimetric spectra to the diamond equivalent for microdosimeters with different geometry of the sensitive volumes is performed, including the use of different stopping power databases. Diamond and silicon microdosimeters were irradiated under the same conditions, aligned at the same depth in a carbon-ion beam at the MedAustron ion therapy center. In order to estimate the microdosimetric quantities, the readout electronic linearity was investigated with three different methods, that is, the first being a single linear regression, the second consisting of a double linear regression with a channel transition and last a multiple linear regression by splitting the data into odd and even groups. The uncertainty related to each of these methods was estimated as well. The edge calibration was performed using the intercept with the horizontal axis of the tangent through the inflection point of the Fermi function approximation multi-channel analyzer spectrum. It was assumed that this point corresponds to the maximum energy difference of particle traversing the sensitive volume (SV) for which the residual range difference in the continuous slowing down approximation is equal to the thickness of the SV of the microdosimeter. Four material conversion methods were explored, the edge method, the density method, the maximum-deposition energy method and the bin-by-bin transformation method. The uncertainties of the microdosimetric quantities resulting from the linearization, the edge calibration and the detectors thickness were also estimated. It was found that the double linear regression had the lowest uncertainty for both microdosimeters. The propagated standard (k = 1) uncertainties on the frequency-mean lineal energy and the dose-mean lineal energy values from the marker point, in the spectra, in the plateau were 0.1% and 0.2%, respectively, for the diamond microdosimeter, whilst for the silicon microdosimeter data converted to diamond, the uncertainty was estimated to be 0.1%. In the range corresponding to the 90% of the amplitude of the Bragg Peak at the distal part of the Bragg curve (R90 ) the uncertainty was found to be 0.1%. The uncertainty propagation from the stopping power tables was estimated to be between 5% and 7% depending on the method. The uncertainty on the and coming from the thickness of the detectors varied between 0.3% and 0.5%. This article demonstrate that the linearity of the readout electronics affects the microdosimetric spectra with a difference in values between the different linearization methods of up to 17.5%. The combined uncertainty was dominated by the uncertainty of stopping power on the edge.

Electronic structure of rare-earth semiconducting ErN thin films determined with synchrotron radiation photoemission spectroscopy and first-principles analysis

Erbium nitride (ErN) is an emerging rocksalt rare-earth semiconducting pnictide and has attracted significant interest in recent years for its potential applications in thermoelectric energy conversion, spintronic devices, and for the Gifford-McMahon cryocoolers. Due to the Er intra-$4f$ electronic transition, Er-doped III-nitride semiconductors such as GaN, InGaN, etc. exhibit strong emission in the retina-safe and fiber optical communication wavelength window of 1.54 \ensuremath{\mu}m that is researched extensively for developing solid-state lasers, amplifiers, and light-emitting devices. However, due to ErN's propensity for oxidation in ambient, high-quality ErN thin film growth has been challenging and an in-depth understanding of its electronic structure remains unanswered. In this work, the valence band electronic structure of ErN thin films is measured with normal as well as with resonant synchrotron-radiation photoemission spectroscopy. Photoemission measurements show a valence band maximum and Fermi energy difference of \ensuremath{\sim}2.3 eV in ErN. First-principles density functional theory (DFT) calculations are performed not only to explain the valence band electronic structure but also to determine transport properties such as effective mass and deformation potentials. Strong localized Er-$4f$ states are observed \ensuremath{\sim}6--8 eV below the valence band maxima and the valence band edge is found to exhibit N-$2p$ character. Resonant photoemission data corroborates the DFT calculations. To accurately capture the electronic structure in modeling, beyond generalized gradient approximation (GGA) methods such as (a) Heyd-Scuseria-Ernzerhof hybrid functional and (b) GGA+U Hubbard correction schemes are utilized. Determination of the electronic structure of ErN marks significant progress in developing ErN-based electronic, optoelectronic, and thermoelectric devices.

Multiple electron beam generation with different energies and comparable currents from a single cathode potential for high power traveling wave tubes (TWTs)

We present a technique for generating multiple electron beams with different energies and comparable currents from a single cathode stalk at a single potential using nested magnetically insulated coaxial diodes (MICDs). The application is for a multi-stream traveling wave tube. Particle-in-cell simulations are performed for an experimental parameter-based geometry where two thin-walled intense relativistic electron beams immersed in a strong uniform magnetic field propagate through a cylindrical vacuum channel. The analytically derived results are obtained by extending Fedosov’s solution for generating a hollow electron beam from an MICD on a cathode stalk in an infinite magnetic field. Two electron beams are generated and accelerated downstream assuming zero initial kinetic energy of the electrons from the cathodes. Results show both electron beam currents ranging from 66 to 2.8 kA with an energy difference ranging from 6% to 27% depending on voltages applied from 100 to 600 kV and the geometry of the two MICDs. An optimal geometry is a crucial factor in achieving the maximum energy difference between the electron beams for comparable currents. The analytical and numerical simulation results show good agreement. We are currently in the process of planning experiments using the electron beam accelerator (SINUS-6 at UNM) to validate the analytical and simulation results.

Effects of ultrasonic treatment on gel rheological properties and gel formation of high-methoxyl pectin

To explore modification effects of ultrasonic treatment on high-methoxyl pectin (HMP), HMP was used as raw material and processed by ultrasonic treatment under different powers (120, 240, 360 and 480 W). Rheological properties of HMP gel were tested. Moreover, the HMP gel formation process was analyzed through kinetic analysis. Results demonstrate that the viscosity of HMP was reduced significantly by ultrasonic treatment. However, the rheological properties of HMP gel were retained, and they still showed typical pseudoplastic and shear thinning properties. HMP gel of the low-power treatment group showed better viscoelasticity compared with those of the contrast group. The maximum G′ and G″ were achieved after HMP was treated by 120 W ultrasonic power when elasticity of HMP was enhanced significantly. Moreover, the structure of HMP was damaged by the cavitation effect and mechanical effect as ultrasonic power increased, thereby the strength of gel decreased significantly. Ultrasonic treatment could weaken the gel formation ability of HMP. During gel formation, the activation energy difference between the high-temperature and low-temperature stages reduced with increasing ultrasonic power. The 120 W treatment group achieved the maximum activation energy difference between the high-temperature and low-temperature stages, while the 480 W treatment group achieved the minimum activation energy difference.

A Multi-Level Decision Fusion Strategy for Condition Based Maintenance of Composite Structures.

In this work, a multi-level decision fusion strategy is proposed which weighs the Value of Information (VoI) against the intended functions of a Structural Health Monitoring (SHM) system. This paper presents a multi-level approach for three different maintenance strategies in which the performance of the SHM systems is evaluated against its intended functions. Level 1 diagnosis results in damage existence with minimum sensors covering a large area by finding the maximum energy difference for the guided waves propagating in pristine structure and the post-impact state; Level 2 diagnosis provides damage detection and approximate localization using an approach based on Electro-Mechanical Impedance (EMI) measures, while Level 3 characterizes damage (exact location and size) in addition to its detection by utilising a Weighted Energy Arrival Method (WEAM). The proposed multi-level strategy is verified and validated experimentally by detection of Barely Visible Impact Damage (BVID) on a curved composite fuselage panel.

Spectral properties of bisphenol F based on quantum chemical calculations

The quantum chemical calculation method is used in this paper to study the energy difference between the highest occupied molecular orbitals and lowest unoccupied molecular orbitals of three bisphenol F (BPF) isomers. The results show that the minimum energy difference occurs at 4,4'-dihydroxydiphenylmethane (4,4′-BPF); the middle energy difference occurs at 2,4'-dihydroxydiphenylmethane (2,4′-BPF); and the maximum energy difference occurs at 2,2'-dihydroxydiphenyl- methane (2,2′-BPF). Based on these results, the electron transition in 4,4′-BPF is easier than that in 2,4′-BPF, while the electron transition in 2,2′-BPF is the most difficult. This paper investigates the effect of the hydroxyl group, specifically concerning the spectroscopic properties of BPF isomers by observing the solvent effect, hydroxyl group amount and the element substitution of an oxygen atom in the hydroxyl group. The solvent effect results show that infrared spectroscopy intensity increases significantly for 4,4′-BPF in the polar solvent (methanol and water), but does not increase proportionally to the electric constant increase of the polar solvent. The multi hydroxyl substitution of BPF isomers results show that with an increase in the hydroxyl group amount, new characteristic peaks occur in FTIR spectra and Raman spectra, while the characteristic peaks in UV spectra are smoother in the range of 240–300 nm. The element substitution results show that the red shifts occur in a different element substituted 4,4′-BPF isomer in UV spectra, and the red shifts order is opposite of that involving substitution element electronegativity.

A new method for expiration code detection and recognition using gabor features based collaborative representation

Text in images and video contains important information for visual content understanding, indexing, and recognizing. Extraction of this information involves preprocessing, localization and extraction of the text from a given image. In this paper, we propose a novel expiration code detection and recognition algorithm by using Gabor features and collaborative representation based classification. The proposed system consists of four steps: expiration code location, character isolation, Gabor features extraction and characters recognition. For expiration code detection, the Gabor energy (GE) and the maximum energy difference (MED) are extracted. The performance of the recognition algorithm is tested over three Gabor features: GE, magnitude response (MR) and imaginary response (IR). The Gabor features are classified based on collaborative representation based classifier (GCRC). To encompass all frequencies and orientations, downsampling and principal component analysis (PCA) are applied in order to reduce the features space dimensionality. The effectiveness of the proposed localization algorithm is highlighted and compared with other existing methods. Extensive testing shows that the suggested detection scheme outperforms existing methods in terms of detection rate for large image database. Also, GCRC show very competitive results compared with Gabor feature sparse representation based classification (GSRC). Also, the proposed system outperforms the nearest neighbor (NN) classifier and the collaborative representation based classification (CRC).

Structure and stability of molecular and ionic complexes of AlCl3 with pyrazine and 4,4′-bipyridyl

Structural and thermodynamic characteristics of molecular and ionic complexes of aluminum trichloride with pyrazine (pyz) and 4,4′-bipyridyl (bipy) are calculated at the RI-BP86/def2-SVP level. It is found that for molecular 2AlCl3·3L and 4AlCl3·3L complexes an energy difference between isomers does not exceed 4 kJ/mol, and the rotation barrier of the AlCl3 moiety relative to the N-Al-N bond does not exceed 24 kJ/mol. A comparison of the stability of molecular and ionic complexes of aluminum in the gas phase shows that the maximum energy difference is ∼60 kJ/mol. For L = pyz the molecular complex is more stable whereas for L = bipy it is the ionic one.

Abnormal hopping conduction in semiconducting polycrystalline graphene

We report the observation of an abnormal carrier transport phenomenon in polycrystalline semiconducting graphene grown by solid carbon source molecular beam epitaxy. At the lowest temperatures in samples with small grain size, the conduction does not obey the two-dimensional Mott-type variable-range hopping (VRH) conduction often reported in semiconducting graphene. The hopping exponent $p$ is found to deviate from the 1/3 value expected for Mott VRH with several samples exhibiting a $p=2/5$ dependence. We also show that the maximum energy difference between hopping sites is larger than the activation energy for nearest-neighbor hopping, violating the assumptions of the Mott model. The 2/5 dependence more closely agrees with the quasi-one-dimensional VRH model proposed by Fogler, Teber, and Shklovskii (FTS). In the FTS model, conduction occurs by tunneling between neighboring metallic wires. We suggest that metallic edge states and conductive grain boundaries play the role of the metallic wires in the FTS model.

First-Principle Investigation of Lithium Intercalation Behavior of a (3, 3) Carbon Nanotube

Using first-principle calculations employing density functional theory (DFT) the stabilityof a (3, 3) carbon nanotube (CNT) intercalated with lithium atoms, with respect to their position aswell as Li/C ratio, is studied. On varying the distance of a lithium atom from the axis of the CNT in theradial direction, through the center of a graphitic hexagon, minimum of energy of the system occursat a distance of 3.8 °A from the axis. Keeping the distance of the lithium atom from the tube axis fixedat 3.8 °A, intercalation energy (E) was calculated while the number of lithium atoms is varied fromone (Li1C12, −0.511 eV) to six (Li6C12, −0.615 eV). It is found that the intercalation becomes morefavorable with the increase in number of lithium atoms intercalated and increase in the symmetryof the intercalated system. The maximum intercalation energy difference between successive lithiumatom additions lay within 0.1 eV.

Beam loading compensation for acceleration of multi-bunch electron beam train

The laser undulator compact X-ray source (LUCX) is a test bench used with the compact, high-brightness X-ray generator at KEK (High Energy Accelerator Research Organization). Our group is conducting experiments with LUCX to demonstrate the possibility of K-edge digital subtraction angiography, based on Compton scattering. One of the challenging problems is to generate high-brightness multi-bunch electron beams to compensate for the energy difference arising from the beam loading effect. In this paper we calculate the transient beam loading voltage and energy gain from the RF field in the gun and accelerating tube for a multi-bunch train. To do so we consider the process by which the RF field builds up in the gun and accelerating tube, and the special shape of the RF pulse. We generate and accelerate 100 bunches with a 50 nC electron bunch train, effectively compensating for the beam loading effect by adjusting the injection timing. Using a beam position monitor (BPM) and optical transition radiation (OTR) system, we measure the electron beam energy bunch by bunch. The average energy of a 100-bunch train is 40.5 MeV and the maximum energy difference from bunch to bunch is 0.26 MeV.

A New Chiral N,N‘,O-Donor Heteroscorpionate Ligand. Structures of Ni2+, Cu2+, Zn2+ Complexes and Study of Solution Equilibria by Means of 1H NMR/UV−Vis Titrations and EXSY NMR Spectroscopy

The N,N',O-heteroscorpionate ligand 1-(4-methoxy-3,5-dimethyl-pyridin-2-yl)-2-methyl-1-pyrazol-1-yl-propan-2-ol (LOH) was prepared in two high-yield steps. Complexes [M(LOH)2][MCl4] (M2+ = Cu2+ and Zn2+) and [M(LOH)2]Cl2 (M2+ = Ni2+ and Cu2+) were prepared and characterized by X-ray crystallography. The speciation in solution (methanol:water 95:5) of the M2+/LOH systems was investigated by means of spectrophotometric (Ni2+ and Cu2+) and 1H NMR (Zn2+) titrations. The beta1 and beta2 global formation constants for the [M(LOH)]2+ and [M(LOH)2]2+ species were obtained and are in agreement with the Irving-Williams series: Ni2+< Cu2+> Zn2+. The Zn2+/LOH system was studied by means of quantitative 1H-1H EXSY spectroscopy (300 K, mixing time = 0.2-0.8 s), which allows the description of the equilibria occurring between five octahedral [Zn(LOH)2]2+ structural isomers and tetrahedral [Zn(LOH)Cl]Cl species. Exchange constants kijex and associated rate constants kij suggest that two types of interconversion occur: octahedral-octahedral (faster) and octahedral-tetrahedral (slower). DFT calculations (B3LYP/6-311+G(d)) were employed to evaluate the relative stability of the [Zn(LOH)2]2+ isomers, which are comparable for the five complexes with a maximum energy difference of 6.3 kJ/mol.

Substituent Effects on the Edge-to-Face Aromatic Interactions

The edge-to-face interactions for either axially or facially substituted benzenes are investigated by using ab initio calculations. The predicted maximum energy difference between substituted and unsubstituted systems is approximately 0.7 kcal/mol (approximately 1.2 kcal/mol if substituents are on both axially and facially substituted positions). In the case of axially substituted aromatic systems, the electron density at the para position is an important stabilizing factor, and thus the stabilization/destabilization by substitution is highly correlated to the electrostatic energy. This results in its subsequent correlation with the polarization and charge transfer. Thus, the stabilization/destabilization by substitution is represented by the sum of electrostatic energy and induction energy. On the other hand, the facially substituted aromatic system depends on not only the electron-donating ability responsible for the electrostatic energy but also the dispersion interaction and exchange repulsion. Although the dispersion energy is the most dominating interaction in both axial and facial substitutions, it is almost canceled by the exchange repulsion in the axial substitution, whereas in the facial substitution, together with the exchange repulsion it augments the electrostatic energy. The systems with electron-accepting substituents (NO2, CN, Br, Cl, F) favor the axial substituent conformation, while those with electron-donating substituents (NH2, CH3, OH) favor the facial substituent conformation. The interactions for the T-shape complex systems of an aromatic ring with other counterpart such as H2, H2O, HCl, and HF are also studied.

Role of NiAs phase in pressure-induced structural phase transitions in IIA-VI chalcogenides

The plane-wave-based pseudopotential method within density-functional theory has been used to study ambient- and high-pressure phases of a series of IIA-VI semiconductors. We analyze the stability of sodium chloride (NaCl), wurtzite, zinc blende, nickel arsenide (NiAs), and cesium chloride structures in these compounds. Static structural properties as well as energetics are reported. The intrinsic bulk stability of NaCl and its hexagonal analog, NiAs phases, has been addressed here. The static structural properties as well as the total energies as a function of volume for these two phases are found to be close to each other compared to other structures. We observe that with increasing ionicity of the compounds, the stability of the NaCl phase increases over the NiAs phase. From our calculations, a maximum total energy difference of \ensuremath{\sim}15 mRy per molecule at equilibrium volume of these phases is observed in the IIA-VI chalcogenides.

Adsorption of Pd onMoS2(1000):Ab initioelectronic-structure calculations

We present ab initio total energy calculations of the adsorption energy of one Pd monolayer on ${\mathrm{MoS}}_{2}(1000).$ We consider four different adsorption sites: the Pd atoms on top of Mo, on top of the hole site, on top of the surface S, and on the bridge position halfway between two adjacent S atoms. The largest adsorption energy obtained corresponds to the hexagonal site on top of Mo. The maximum energy difference between adsorption sites is 0.25 eV. Due to the lattice mismatch, a Pd monolayer should be expanded to grow pseudomorphically on this substrate. Comparing the energy difference between the adsorption sites to the energy involved in the expansion of a Pd monolayer, we conclude that Pd will tend not to grow pseudomorphically, in agreement with the experimental evidence. We have also evaluated the changes in the work function produced by the deposition of the Pd adlayer; we observe a systematic reduction with respect to the clean substrate.

Effect of chiral helical force field on molecular helical enantiomers and possible origin of biomolecular homochirality

Biomolecular homochirality means that the amino acids in proteins, and sugars in nucleic acids, occur in one form: amino acids in L-form and sugars in D-form. So far, the reason why these molecules have such uniform chirality is not known. In this paper, it is suggested that a net natural chiral right-handed helical force field, produced by the Earth's orbital chirality (EOC), could affect the stability of molecular helical enantiomers and make the right-handed helical enantiomers more stable than their left-handed enantiomers, so terrestrial biological systems must select both right-handed helical nucleic acids based on D-sugars, and proteins based on L-amino acids. In given conditions, the maximum energy difference between biomolecular helical enantiomers ( ΔE max ⋎E left − E right ∥ ) caused by the EOC may be calculated theoretically to be in the order: B-DNA > A-RNA > A-DNA ⪢ α-protein > β-protein. Our experimental results strongly supported the hypothesis that the EOC could cause the spontaneous selection and amplification of right-handed helical enantiomers and could be the origin of homochirality on the Earth.

Vitamin C at 120 K: experimental and theoretical study of the charge density

Vitamin C is an extremely interesting molecule, not only for its important biological properties, but also for its crystal structure in which the formation of several hydrogen bonds plays an important role. We have collected X-ray diffraction data at −153°C up to sin θ/ λ=1.17 Å −1. The crystals do not undergo any phase transformation and the space group remains P2 1 with two independent molecules in the asymmetric unit. In the final difference Fourier map non-spherical electron density in the bonding regions was clearly indicated. A study by means of a multipole expansion of the electron density has been performed and the experimental electrostatic potential maps obtained. We have also computed the electron density by means of the crystal-orbital approach as coded in the program crystal95 [R. Dovesi et al., crystal95 User's Manual, University of Torino]. A complete ab initio conformational analysis of the isolated molecule has also been carried out at HF-SCF and density functional level, with reasonably large basis sets. The results of this analysis are: (i) vitamin C molecules are tightly bound in the crystal by a network of eight intermolecular H-bonds per molecule. The relative strength of these bonds is well accounted for by the experimental electrostatic potential. No relevant intramolecular interactions are present; (ii) crystal95 calculations give a value of 44 kcal mol −1 as the sublimation energy per mole of molecules, computed at correlated level with 6-21G(d,p) and Perdew 91 potential [J.P. Perdew and Y. Wang, Phys. Rev. B, 45 (1992) 13244; M. Causà and A. Zupan, Chem. Phys. Lett., 220 (1994) 145]; (iii) the crystal95 electron density maps are in good agreement with the experimental ones; (iv) the calculations on the isolated molecule reveal that the most stable conformers are different from the X-ray structure and are characterized by intramolecular H-bonds; the maximum energy difference among the 11 conformers taken into account is less than 6 kcal mol −1; (v) the NMR analysis in water reveals that the least populated side-chain conformation around bond C5–C6 is that found in our computed gas-phase conformers with the most folded-up side chain, which are indeed less prone to be solvated.

Excitation and relaxation processes of Eu 3+ crystal field transitions in Eu 2BaZnO 5

Eu 3+ luminescence for several excitation energies in off resonance conditions has been studied. Raman phonons and Raman crystal field transitions are also obtained. The reflectance between 1.25 and 3.7 eV shows the 5D and upper multiplets up to 27000 cm −1. There are two Eu sites with a maximum level energy difference of 19 cm −1 at RT. We present most of the CF levels for 7 F J ( J = 0–4) and 5 D J . The analysis of the relative intensities of the phonons and luminescence peaks as a function of the excitation energy and the temperature indicates that complex processes are happening in the excitation and that the lattice phonons have a determining role in Eu luminescence.