A Compact RFID Reader Antenna for UHF Near-Field and Far-Field Operations

A compact loop antenna is presented for mobile ultrahigh frequency (UHF) radio frequency identification (RFID) application. This antenna, printed on a 0.8 mm thick FR4 substrate with a small size of 31 mm × 31 mm, achieves good impedance bandwidth from 897 to 928 MHz, which covers USA RFID Band (902–928 MHz). The proposed loop configuration, with a split-ring resonator (SRR) coupled inside it, demonstrates strong and uniform magnetic field distribution in the near-field antenna region. Its linearly polarized radiation pattern provides available far-field gain. Finally, the reading capabilities of antenna are up to 56 mm for near-field and 1.05 m for far-field UHF RFID operations, respectively

On the Steady Standing Surface Wave Pattern of Flows in a Narrow Rectangular Straight Chute

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Experimental Study on Hydraulic Jumps with and Without Sediment

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Influence of adding phase change materials on the physical and mechanical properties of cement mortars

During the last years several studies of construction materials with incorporation of encapsulated phase change material (PCM) have been published. However, the utilization of non-encapsulated PCM is one of the main gaps. The main objective of this work was the study of physical and mechanical properties of cement mortars with incorporation of non-encapsulated PCM. It was possible to conclude that the utilization of non-encapsulated phase change materials can be seen as a good and more economical solution for the energy efficiency of the buildings, without prejudice of the properties.The authors acknowledge the Portuguese Foundation for Science and Technology (FCT) for the financial support of PhD scholarship SFRH/BD/95611/2013

Multidimensional Supernova Simulations with Approximative Neutrino Transport I. Neutron Star Kicks and the Anisotropy of Neutrino-Driven Explosions in Two Spatial Dimensions

By means of two-dimensional (2D) simulations we study hydrodynamic instabilities during the first seconds of neutrino-driven supernova explosions, using a PPM hydrodynamics code, supplemented with a gray, non-equilibrium approximation of radial neutrino transport. We consider three 15 solar mass progenitors with different structures and one rotating model, in which we replace the dense core of the newly formed neutron star (NS) by a contracting inner grid boundary, and trigger neutrino-driven explosions by systematically varying the neutrino fluxes emitted at this boundary. Confirming more idealized studies as well as supernova simulations with spectral transport, we find that random seed perturbations can grow by hydrodynamic instabilities to a globally asymmetric mass distribution, leading to a dominance of dipole (l=1) and quadrupole (l=2) modes in the explosion ejecta. Anisotropic gravitational and hydrodynamic forces are found to accelerate the NS on a timescale of 2-3 seconds. Since the explosion anisotropies develop chaotically, the magnitude of the corresponding kick varies stochastically in response to small differences in the fluid flow. Our more than 70 models separate into two groups, one with high and the other with low NS velocities and accelerations after 1s of post-bounce evolution, depending on whether the l=1 mode is dominant in the ejecta or not. This leads to a bimodality of the distribution when the NS velocities are extrapolated to their terminal values. The fast group has an average velocity of about 500 km/s and peak values in excess of 1000 km/s. Establishing a link to the measured distribution of pulsar velocities, however, requires a much larger set of calculations and ultimately 3D modeling. (abridged)Comment: 40 pages, 28 figures; significantly shortened and revised version according to referee's comments; accepted by Astronomy & Astrophysic

Comparison between light scattering and gravimetric samplers for PM10 mass concentration in poultry and pig houses

The objective of this study was to compare co-located real-time light scattering devices and equivalent gravimetric samplers in poultry and pig houses for PM10 mass concentration, and to develop animal-specific calibration factors for light scattering samplers. These results will contribute to evaluate the comparability of different sampling instruments for PM10, concentrations. Paired DustTrak light scattering device (DustTrak aerosol monitor, TSI, U.S.) and PM10 gravimetric cyclone sampler were used for measuring PM10 mass concentrations during 24 h periods (from noon to noon) inside animal houses. Sampling was conducted in 32 animal houses in the Netherlands, including broilers, broiler breeders, layers in floor and in aviary system, turkeys, piglets, growing-finishing pigs in traditional and low emission housing with dry and liquid feed, and sows in individual and group housing. A total of 119 pairs of 24 h measurements (55 for poultry and 64 for pigs) were recorded and analyzed using linear regression analysis. Deviations between samplers were calculated and discussed. In poultry, cyclone sampler and DustTrak data fitted well to a linear regression, with a regression coefficient equal to 0.41, an intercept of 0.16 mg m(-3) and a correlation coefficient of 0.91 (excluding turkeys). Results in turkeys showed a regression coefficient equal to 1.1 (P = 0.49), an intercept of 0.06 mg m(-3) (P < 0.0001) and a correlation coefficient of 0.98. In pigs, we found a regression coefficient equal to 0.61, an intercept of 0.05 mg m(-3) and a correlation coefficient of 0.84. Measured PM10 concentrations using DustTraks were clearly underestimated (approx. by a factor 2) in both poultry and pig housing systems compared with cyclone pre-separators. Absolute, relative, and random deviations increased with concentration. DustTrak light scattering devices should be self-calibrated to investigate PM10 mass concentrations accurately in animal houses. We recommend linear regression equations as animal-specific calibration factors for DustTraks instead of manufacturer calibration factors, especially in heavily dusty environments such as animal houses. (C) 2015 Elsevier Ltd. All rights reserved.The study was financed by the Dutch Ministry of Economic affairs, Agriculture and Innovation. Authors wish to thank the Campus de Excelencia Internacional of the Universitat Politecnica de Valencia (Spain) for funding Dr. Cambra-Lopez's postdoc contract.Cambra López, M.; Winkel, A.; Mosquera, J.; Ogink, NW.; Aarnink, AJA. (2015). Comparison between light scattering and gravimetric samplers for PM10 mass concentration in poultry and pig houses. Atmospheric Environment. 111:20-27. doi:10.1016/j.atmosenv.2015.03.051S202711

A Measurement of Small Scale Structure in the 2.2 < z < 4.2 Lyman-alpha Forest

The amplitude of fluctuations in the Ly-a forest on small spatial scales is sensitive to the temperature of the IGM and its spatial fluctuations. The temperature of the IGM and its spatial variations contain important information about hydrogen and helium reionization. We present a new measurement of the small-scale structure in the Ly-a forest from 40 high resolution, high signal-to-noise, VLT spectra at z=2.2-4.2. We convolve each Ly-a forest spectrum with a suitably chosen wavelet filter, which allows us to extract the amount of small-scale structure in the forest as a function of position across each spectrum. We compare these measurements with high resolution hydrodynamic simulations of the Ly-a forest which track more than 2 billion particles. This comparison suggests that the IGM temperature close to the cosmic mean density (T_0) peaks near z=3.4, at which point it is greater than 20,000 K at 2-sigma confidence. The temperature at lower redshift is consistent with the fall-off expected from adiabatic cooling ($T_0 \propto (1+z)^2$), after the peak temperature is reached near z=3.4. At z=4.2 our results favor a temperature of T_0 = 15-20,000 K. However, owing mostly to uncertainties in the mean transmitted flux at this redshift, a cooler IGM model with T_0 = 10,000 K is only disfavored at the 2-sigma level here, although such cool IGM models are strongly discrepant with the z ~ 3-3.4 measurement. We do not detect large spatial fluctuations in the IGM temperature at any redshift covered by our data set. The simplest interpretation of our measurements is that HeII reionization completes sometime near z ~ 3.4, although statistical uncertainties are still large [Abridged].Comment: Submitted to ApJ. Best printed in colo

The cool side of Lyman Alpha Emitters

We extend a previous study of Lyman Alpha Emitters (LAEs) based on hydrodynamical cosmological simulations, by including two physical processes important for LAEs: (a) Lyman Alpha and continuum luminosities produced by cooling of collisionally excited HI in the galaxy, (b) dust formation and evolution; we follow these processes on a galaxy-by-galaxy basis. HI cooling on average contributes 16-18% of the Lyman Alpha radiation produced by stars, but this value can be much higher in low mass LAEs and further increased if the HI is clumpy. The continuum luminosity is instead almost completely dominated by stellar sources. The dust content of galaxies scales with their stellar mass, M_{dust} is proportional to M_*^0.7 and stellar metallicity, Z_*, such that M_{dust} is proportional to Z_*^1.7. As a result, the massive galaxies have Lyman Alpha escape fraction as low as f_alpha=0.1, with a LAE-averaged value decreasing with redshift such that it is (0.33,0.23) at z =(5.7,6.6). The UV continuum escape fraction shows the opposite trend with redshift, possibly resulting from clumpiness evolution. The model successfully reproduces the observed Lyman Alpha and UV luminosity functions at different redshifts and the Lyman Alpha equivalent width scatter to a large degree, although the observed distribution appears to be more more extended than the predicted one. We discuss possible reasons for such tension.Comment: 9 pages, accepted for publication in MNRA

The Signatures of Large-scale Temperature and Intensity Fluctuations in the Lyman-alpha Forest

It appears inevitable that reionization processes would have produced large-scale temperature fluctuations in the intergalactic medium. Using toy temperature models and detailed heating histories from cosmological simulations of HeII reionization, we study the consequences of inhomogeneous heating for the Ly-alpha forest. The impact of temperature fluctuations in physically well-motivated models can be surprisingly subtle. In fact, we show that temperature fluctuations at the level predicted by our reionization simulations do not give rise to detectable signatures in the types of statistics that have been employed previously. However, because of the aliasing of small-scale density power to larger scale modes in the line-of-sight Ly-alpha forest power spectrum, earlier analyses were not sensitive to 3D modes with >~ 30 comoving Mpc wavelengths -- scales where temperature fluctuations are likely to be relatively largest. The ongoing Baryon Oscillation Spectroscopic Survey (BOSS) aims to measure the 3D power spectrum of the Ly-alpha forest, P_F, from a large sample of quasars in order to avoid this aliasing. We find that physically motivated temperature models can alter P_F at an order unity level at k <~ 0.1 comoving Mpc^{-1}, a magnitude that should be easily detectable with BOSS. Fluctuations in the intensity of the ultraviolet background can also alter P_F significantly. These signatures will make it possible for BOSS to study the thermal impact of HeII reionization at 2 < z < 3 and to constrain models for the sources of the ionizing background. Future spectroscopic surveys could extend this measurement to even higher redshifts, potentially detecting the thermal imprint of hydrogen reionization.Comment: 14 pages, 17 figures, plus 4 pages of Appendix, matches published versio

HeII Reionization and its Effect on the IGM

Observations of the intergalactic medium (IGM) suggest that quasars reionize HeII in the IGM at z ~ 3. We have run a set of 190 and 430 comoving Mpc simulations of HeII being reionized by quasars to develop an understanding of the nature of HeII reionization and its potential impact on observables. We find that HeII reionization heats regions in the IGM by as much as 25,000 K above the temperature that is expected otherwise, with the volume-averaged temperature increasing by ~ 12,000 K and with large temperature fluctuations on ~ 50 Mpc scales. Much of the heating occurs far from QSOs by hard photons. We find a temperature-density equation of state of gamma -1 ~ 0.3 during HeII reionization, but with a wide dispersion in this relation having sigma ~ 10^4 K. HeII reionization by the observed population of quasars cannot produce an inverted relation (gamma - 1 < 0). Our simulations are consistent with the observed evolution in the mean transmission of the HeII Ly-alpha forest. We argue that the heat input due to HeII reionization is unable to cause the observed depression at z = 3.2 in the HI Ly-alpha forest opacity as has been suggested. We investigate how uncertainties in the properties of QSOs and of HeII Lyman-limit systems influence our predictions.Comment: 19 pages, 15 figures, plus 9 pages of Appendix. accepted by Ap