Thermoelectric performance of weakly coupled granular materials

We study thermoelectric properties of inhomogeneous nanogranular materials for weak tunneling conductance between the grains, g_t < 1. We calculate the thermopower and figure of merit taking into account the shift of the chemical potential and the asymmetry of the density of states in the vicinity of the Fermi surface. We show that the weak coupling between the grains leads to a high thermopower and low thermal conductivity resulting in relatively high values of the figure of merit on the order of one. We estimate the temperature at which the figure of merit has its maximum value for two- and three-dimensional samples. Our results are applicable for many emerging materials, including artificially self-assembled nanoparticle arrays.Comment: 4 pages, 3 figure

Thermoelectric performance of granular semiconductors

We study thermoelectric properties of granular semiconductors with weak tunneling conductance between the grains, g_t < 1. We calculate the thermopower and figure of merit taking into account the shift of the chemical potential and the asymmetry of the density of states in the vicinity of the Fermi surface due to n- or p-type doping in the Efros-Shklovskii regime for temperatures less than the charging energy. We show that for weakly coupled semiconducting grains the figure of merit is optimized for grain sizes of order 5nm for typical materials and its values can be larger than one. We also study the case of compensated granular semiconductors and show that in this case the thermopower can be still finite, although two to three orders of magnitude smaller than in the uncompensated regime.Comment: 4 pages, 4 figure

Spectral asymptotics for solutions of 2×22\times 2 system of ordinary differential equations of the first order

The aim of the paper is to find representation for solutions of $2\times 2$ system of ordinary differential equations $$\mathbf{y^\prime} - B(x)\mathbf{y} = \lambda A(x)\mathbf{y}, \quad \ x \in [0, 1],$$ where $A(x) = diag\{a_1(x), a_2(x)\}$, $B(x) = (b_{ij}(x))$, $a_1(x) > 0, \ a_2(x) < 0$ and all the functions $a_{i}, b_{ij}$ belong to the Sobolev spaces $W^n_1[0,1]$ for given integer $n\geqslant 0$. We prove that there exists a fundamental matrix of solutions for the above system, which have representation $$Y(x, \lambda) = M(x)\left(I + \frac{R^1(x)}{\lambda} + \dots + \frac{R^n(x)}{\lambda^n} + o(1)\lambda^{-n}\right)E(x, \lambda),$$ where $o(1) \to 0$ uniformly for $x\in [0,1]$ as the spectral parameter $\lambda \to \infty$ in the half plane $\Re\,\lambda >-\kappa$ or $\Re\,\lambda <\kappa$, where $\kappa$ is any fixed real number. The main novelty is that we give explicit formulae for all matrices $M,E$ and $R^m$ in this representation.Comment: in Russian languag

Separation of ferromagnetic components by analyzing the hysteresis loops of remanent magnetization

© 2015, Pleiades Publishing, Ltd. The new method is suggested for separating ferromagnetic components in sediments through analyzing the coercivity spectra of the samples by the continuous wavelet transform with the Gaussian-based wavelet (MHAT). A total of 1056 samples of Lake Khuvsgul’s sediments (Mongolia) are studied. At least four groups of magnetic components are identified based on the analysis of their magnetization and remagnetization curves. Almost all samples are found to contain two components of bacterial origin which are represented by the assemblages of the interacting single-domain grains and differ by the grain compositions (magnetite and greigite). The applicability of the magnetic data for diagnosing magnetotactic bacteria in sediments and building paleoecological and paleoclimatic reconstructions is demonstrated

Operational experience of GNSS receivers with Chip Scale Atomic Clocks for baseline measurements

Currently, one of the topical issues of improving GLONASS system is modernization of its uniformity measurement equipment, including RF measurement equipment and electronic length measurement equipment. To this end, at the Spatial Reference Proving Ground of theSiberian State University of Geosystems and Technologies (SSUGT), the authors of this article carried out a successful experiment to measure a short GNSS baseline by receivers equipped with Chip Scale Atomic Clocks (CSACs) with instability of 10−11 showed that the mean deviation between the slant distance (D) measured using GNSS receivers connected to CSACs and their certified value varied in the range of 0.1–2.5 mm, with the average value of 0.9 mm. The mean deviation obtained using GNSS geodetic receivers not connected to CSAC and their certified value made up 9.4 mm. The obtained experimental results suggest that substitution of quartz frequency generators with temperature compensation used in geodetic GNSS receivers for Chip Scale Atomic Clocks in any metrological or verification kit increases accuracy and reliability of short baselines measurements results, which highly perspective in view of development of techniques for creating reference baselines with a reproduction error of unit length of about 1 mm per 1 km. The above-mentioned experiment opens up new horizons for the use of Chip Scale Atomic Clocks in such fields of science as metrological support of geodetic equipment, geodesy, etc

Adaptive determination of cut-off frequencies for filtering the in-cylinder pressure in diesel engines combustion analysis

[EN] In-cylinder pressure analysis is a key tool for engine research and diagnosis and it has been object of study from the beginning of the internal combustion engines. One of its most useful application is combustion analysis on the basis of the First Law of Thermodynamics. However, heat release law calculations use the in-cylinder pressure derivative signal. Hence, the noise is increased and pressure filtering becomes necessary to remove high frequency noise, thus allowing for accurate combustion analyses. In this work, a methodology to set the cut-off frequency of a low-pass filter is proposed. Statistical criteria are used to separate the signal from the noise through the calculation of the Discrete Fourier Transform of several consecutive in-cylinder pressures cycles. Thus, only physically meaningful information is preserved. The proposed methodology is compared with some adaptive and non-adaptive algorithms used to select the cut-off frequencies, and it shows a good ability to adapt to different engine operating conditions. © 2011 Elsevier Ltd. All rights reserved.The authors thank the Universidad Politécnica de Valencia (PAID-06-09) and Generalitat Valenciana (GV/2010/045) for its valuable support to this work.Payri González, F.; Olmeda González, PC.; Guardiola García, C.; Martín Díaz, J. (2011). Adaptive determination of cut-off frequencies for filtering the in-cylinder pressure in diesel engines combustion analysis. Applied Thermal Engineering. 31:2869-2876. https://doi.org/10.1016/j.applthermaleng.2011.05.012S286928763

Spin alignment of K∗(892)±K^*(892)^\pm mesons produced in neutron-carbon interactions

A new precise measurements of spin density matrix element $\rho_{00}$ of $K^*(892)^{\pm}$ mesons produced inclusively in neutron-carbon interactions at \~60 GeV have been carried out in the EXCHARM experiment at the Serpukhov accelerator. The values of $\rho_{00}$ obtained in the transversity frame are $0.424\pm0.011(stat)\pm0.018(sys)$ for $K^*(892)^+$ and $0.393\pm0.025(stat)\pm0.018(sys)$ for $K^*(892)^-$. Significant $P_T$ dependence of $\rho_{00}$ has been observed in $K^*(892)^+$ production.Comment: 8 pages, LaTeX, 3 eps figure

Problems with the use of pneumatic screw pumps to transport bulk cargo

An analysis is made of the performance of pneumatic screw pumps at the Bereznikovsky Soda Plant in order be able to transport light soda along a prescribed route and make use of a new nozzle section to make the pumps' operation more reliable. Specific recommendations are made to increase the throughput and reliability of pneumatic screw pumps. The expediency of replacing long lines of screw pumps by chamber pumps is also discussed. © 2013 Springer Science+Business Media New York

Interferometry of Direct Photons in Central 280Pb+208Pb Collisions at 158A GeV

Two-particle correlations of direct photons were measured in central 208Pb+208Pb collisions at 158 AGeV. The invariant interferometric radii were extracted for 100<K_T<300 MeV/c and compared to radii extracted from charged pion correlations. The yield of soft direct photons, K_T<300 MeV/c, was extracted from the correlation strength and compared to theoretical calculations.Comment: 5 pages, 4 figure

Observation of narrow baryon resonance decaying into pKs0pK^0_s in pA-interactions at 70GeV/c70 GeV/c with SVD-2 setup

SVD-2 experiment data have been analyzed to search for an exotic baryon state, the $\Theta^+$-baryon, in a $pK^0_s$ decay mode at $70 GeV/c$ on IHEP accelerator. The reaction $pA \to pK^0_s+X$ with a limited multiplicity was used in the analysis. The $pK^0_s$ invariant mass spectrum shows a resonant structure with $M=1526\pm3(stat.)\pm 3(syst.) MeV/c^2$ and $\Gamma < 24 MeV/c^2$. The statistical significance of this peak was estimated to be of $5.6 \sigma$. The mass and width of the resonance is compatible with the recently reported $\Theta^+$- baryon with positive strangeness which was predicted as an exotic pentaquark ($uudd\bar{s}$) baryon state. The total cross section for $\Theta^+$ production in pN-interactions for $X_F\ge 0$ was estimated to be $(30\div120) \mu b$ and no essential deviation from A-dependence for inelastic events $(\sim A^{0.7})$ was found.Comment: 8 pages, 7 figures, To be submitted to Yadernaya Fizika. v3-v5 - Some references added, minor typos correcte