Results 1 - 10 of 19105
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[en] We calculate the polarized massive operator matrix element A(N) to 3-loop order in Quantum Chromodynamics analytically at general values of the Mellin variable N both in the single- and double-mass case in the Larin scheme. It is a transition function required in the variable flavor number scheme at O(α). We also present the results in momentum fraction space.
[en] Identifying the failures of the components of a nuclear power plant (NPP) is an important task in plant life management. The loss of a coolant accident (LOCA) of the primary heat transport (PHT) system of the Indian pressurised heavy water reactor (PHWR) is a failure which can be caused by aging of the system. LOCA is a double ended break of the inlet headers (IH) of the PHT. This work proposes a methodology for constructing optimal artificial neural networks (NN) to identify large breaks at high accuracy. This work considered the break sizes 0%, 20%, 60%, 100%, 120% and 200% of double ended break in IH where 0% is the normal condition of the IH and 200% the maximum break in IH. The 37 transient signals such as pressure and temperature of the IH which were originally generated by Santosh et al, were used to construct NNs in this work. For each break size, the signals were measured at 541 instants within a 60 seconds duration. And the transient data set of each break size consists of 541 instances (observations) and 37 features. The transient data set of all the break sizes is a 3246x38 matrix with the last column the break size targets.
[en] A new HCl-free chromatographic separation procedure has been developed for sequential separation of Zr and Mo from concrete matrices for selective measurement of 93Zr and 93Mo by ICP-MS/MS. The recoveries of greater than 90% for Zr and Mo from concretes could be achieved. The measurement condition was optimized for complete suppression of interferences from 93Nb and peak tailing from abundant isotopes of Zr and Mo in concrete matrices. The removal of interferences was verified by measurement of radio-contamination-free concretes used as a sample matrix blank. Method detection limits of 1.7 mBq g-1 and 0.2 Bq g-1 were achieved for, respectively, 93Zr and 93Mo in the concrete matrices. The interference removal factor for Nb (equivalent to the decontamination factor in radiochemical separation) was of the order of 105, and the abundance sensitivity was of the order of 10-8, indicating that the developed method is reliable for verifying the presence of ultralow concentrations of 93Zr and 93Mo. The present method is suitable for the rapid assessment of 93Zr and 93Mo for radioactivity inventory of concrete rubble. (author)
[en] In March 2011, in Minsk (Republic of Belarus), the Agreement was signed between the governments of two countries: the Government of the Russian Federation and the Government of the Republic of Belarus for cooperation in the NPP construction in the territory of the Republic of Belarus. The Agreement stipulates turnkey construction of the Belarusian NPP to be performed by the Russian party. The general contractor for construction is ‘Atomstroyexport’, (ASE), and the customer and operating organization is ‘Belarusian NPP’. Belarusian NPP will consist of two AES-2006 design VVER units with total capacity of up to 2400 (2x1200) MW.5 This design was selected because it was a Generation 3+ NPP with the following design features:5 — a new reactor design with additional safety systems: passive heat removal system; passive filtration system of leakage to the intershell space; double protective enclosure vessel; trap for molten corium in case of a beyond design basis accident; — maximum implementation of the defence-in-depth principle: setting up barriers to prevent ionizing radiation and radioactive substances discharge into the atmosphere, and the system of technical and organizational measures to protect the barriers, as well as preservation of their efficiency in the course of direct protection of the population; — AES-2006 design includes fuel matrix, fuel claddings, reactor coolant boundary; sealed enclosure of localization safety systems.
[en] We study the motion of a Brownian particle subjected to Lorentz force due to an external magnetic field. Each spatial degree of freedom of the particle is coupled to a different thermostat. We show that the magnetic field results in correlation between different velocity components in the stationary state. Integrating the velocity autocorrelation matrix, we obtain the diffusion matrix that enters the Fokker–Planck equation for the probability density. The eigenvectors of the diffusion matrix do not align with the temperature axes. As a consequence the Brownian particle performs spatially correlated diffusion. We further show that in the presence of an isotropic confining potential, an unusual, flux-free steady state emerges which is characterized by a non-Boltzmann density distribution, which can be rotated by reversing the magnetic field. The nontrivial steady state properties of our system result from the Lorentz force induced coupling of the spatial degrees of freedom which cease to exist in equilibrium corresponding to a single-temperature system. (paper)
[en] Thermal conductivity of NbO is studied experimentally and theoretically. Sputtered NbO samples, slightly overstoichiometric in oxygen, are x-ray amorphous with a combined NbO and NbO2 short-range order, which is consistent with the quantum mechanical data. Upon annealing, NbO2 crystallites form in the amorphous matrix due to an energetic preference of 44 meV atom−1 over NbO counterparts. The measured thermal conductivity at room temperature using time-domain thermoreflectance is 6.9 W m−1 K−1, followed by a continuous increase due to electronic contributions, and it yields a total increase of 40 W m−1 K−1 at 650 K partly due to crystallisation. Phonon–phonon scattering can be induced by introducing Ni0.75Ta0.25O layers in NbO. These multilayers exhibit a thermal conductivity of 5.4 W m−1 K−1 at room temperature and a monotonic drop upon increasing temperature. It is thus feasible to modulate the high-temperature thermal conductivity of amorphous NbO by an order of magnitude. Hence, amorphous NbO may be of interest for thermoelectric devices, sensors and thermal insulation applications. (paper)
[en] The exchange coupling effect in nanocomposite samples with ferromagnetic (FM) body-centred tetragonal (bct) Fe nanoparticles (NPs) (~20 nm) embedded in an MnN antiferromagnetic (AFM) matrix is investigated. Both the bct Fe NPs control sample and the MnN (×nm)/bct Fe NPs/MnN (20–35 nm)/Ta (5 nm) nanocomposite samples are synthesized by a gas-phase condensation method. Both the coercivity and the remanence ratio of the nanocomposite samples are significantly enhanced compared with the bct Fe NPs sample. The coercivity and the remanence ratio increase with MnN thickness up to 30 nm and then decrease. Additionally, the exchange coupling strength between the bct Fe NPs and AFM MnN matrix is enhanced by magnetic field training. The magnetic field training leads to a higher coercivity and remanence ratio after one cycle of field-cooled hysteresis loop measurement. The coercivity of the composite sample increases by 80%, while the remanence ratio increases by around 30% compared with the bct Fe NPs sample. This work may provide an alternative approach to the design and manufacturing of FM-AFM exchange-coupled permanent magnets. (paper)
[en] In this work, the performances of two ionic liquid matrices (ILMs) with the same ammonium counterpart for mass spectrometric analysis of the insoluble and soluble sucralfate were compared. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) was performed assisted by the butylammonium salts of α-cyano-hydroxycinnamic acid (CHCAB) and 2,5-dihydroxybenzoic acid (DHBB). CHCAB has a higher IE than DHBB, but better optical properties. CHCAB is more suitable for the analysis of sucralfate, although molecular ions of both compounds were detectable only with low intensities. Thus, optical properties of ILMs are crucial to enhance the sensitivity of MALDI MS detection of polysulfated oligosaccharides. © 2019, © 2019 Taylor & Francis Group, LLC.
[en] A novel lead-free 1–3-type composite based on a ferroelectric domain-engineered single crystal is put forward. In the porous polymer matrix of this composite, two different porous structures are observed, and the effect of these structures on the piezoelectric performance, electromechanical coupling and related anisotropy parameters of 1–3-type composites is first studied. New diagrams that link the volume fractions of the single-crystal component and the porous regions in the polymer medium are built to show validity of conditions for a large anisotropy of piezoelectric coefficients and electromechanical coupling factors , and . In the composites based on the complex alkali niobate alkali tantalate single crystal with small piezoelectric anisotropy (/|| = 2.1), the three anisotropy factors /|| ≥ 5, /|| ≥ 5 and /|| ≥ 5 hold simultaneously due to the presence of layers with heavily prolate and heavily oblate air pores in the porous polymer matrix. The two porosity levels influence the elastic anisotropy of the porous matrix, and this leads to an increase in the three anisotropy factors across wide volume-fraction ranges. Of independent interest is the high piezoelectric sensitivity of the composites for which the condition ≥1 V m N−1 holds at their piezoelectric coefficient ≈ (200–500) pC N−1 and electromechanical coupling factors ≈ ≈ 0.8–0.9. The studied parameters of the novel piezo-active 1–3-type composites are of value for various applications such as active elements of piezoelectric transducers, energy-harvesting devices and sensors. (paper)
[en] Due to a wide range of applications, plasmonic properties of metal nanoparticles have been widely explored, while the understanding of plasmonic behaviors of dielectric-metal composites is still limited. Herein, as a proof of concept, the relationship between compositions and plasmonic behaviors of Ag-SiO2 composites was investigated considering their extensive utilization as SERS substrates. Ag-SiO2 nanorods with regulated compositions were fabricated via glancing angle co-deposition. By increasing Ag relative deposition rate, structure of Ag-SiO2 nanorods evolves from Ag nanoparticles embedded into SiO2 matrix to quasi-one-dimensional Ag structure, inducing plasmon resonance changes over a wide range and corresponding SERS activity variations. Plasmonic resonance resulted from individual Ag nanoparticle, coupling effect of Ag nanoparticles, and quasi-one-dimensional Ag nanorods can be observed successively as Ag content increases in Ag-SiO2 nanorods. Meanwhile, SERS performance of Ag-SiO2 corresponds well with their plasmon behaviors and the maximum SERS signal was obtained from Ag-SiO2 composites with quasi-one-dimensional Ag structure. With the optimization of plasmon and SERS performance of Ag-SiO2 nanorods, we demonstrated the potential use of Ag-SiO2 nanorods in real applications as SERS chemical sensors for the detection of melamine. (paper)