Pool boiling on modified surfaces using R-123

This article has been made available through the Brunel Open Access Publishing Fund.Saturated pool boiling of R-123 was investigated for five horizontal copper surfaces modified by different treatments, namely, an emery-polished surface, a fine sandblasted surface, a rough sandblasted surface, an electron beam-enhanced surface, and a sintered surface. Each 40-mm-diameter heating surface formed the upper face of an oxygen-free copper block, electrically heated by embedded cartridge heaters. The experiments were performed from the natural convection regime through nucleate boiling up to the critical heat flux, with both increasing and decreasing heat flux, at 1.01 bar, and additionally at 2 bar and 4 bar for the emery-polished surface. Significant enhancement of heat transfer with increasing surface modification was demonstrated, particularly for the electron beam-enhanced and sintered surfaces. The emery-polished and sandblasted surface results are compared with nucleate boiling correlations and other published data. © 2014 Syed W. Ahmad, John S. Lewis, Ryan J. McGlen, and Tassos G. Karayiannis Published with license by Taylor & Francis

On universality of the coupling of neutrinos to Z

We employ an effective Lagrangian approach and use LEP data to place severe bounds on universality violations of the couplings of $\nu_e$, $\nu_\mu$, and $\nu_\tau$ to the $Z$ boson. Our results justify the assumption of universality in these couplings that is usually made, as for example in the analysis of solar neutrinos detected at SNO.Comment: 8 pages, no figures. A few comments added. It matches version to be published in PR

Dual-band WLAN Antenna Array with Integrated Bandpass Filters for Harmonic Suppression

This paper presents the design and results of a dual-band antenna array integrated with bandpass filters. The array has a 1×2 configuration. The two bands of the array correspond to the two WLAN bands of 2.4 GHz and 5.8 GHz. Other than the two main bands, the standalone array exhibits spurious harmonics at various other frequencies. For the suppression of these harmonics, the array is integrated with two bandpass filters, centered at 2.4 GHz and 5.8 GHz. The filtering array was simulated and fabricated. Measured results show dual-bands at 2.4 GHz and 5.8 GHz at a return loss of more than 30 dB and also a successful full suppression of the spurious harmonic

Dual-band Filtenna Array for WLAN Applications

This paper presents the design and results of a dual-band antenna array integrated with bandpass filters for WLAN applications. The array is fed with a single 50 Ω port and consists of two radiating elements; thereby having a 1x2 array structure. The two bands of the antenna array correspond to the two WLAN bands of 2.4 GHz and 5.8 GHz. A standalone array has first been designed. Other than the two fundamental resonant frequencies, the standalone array exhibits spurious harmonics at various other frequencies. For the suppression of these harmonics, the array has been integrated with two bandpass filters, centered at 2.4 GHz and 5.8 GHz. The resulting filtenna array was simulated, fabricated and measured. Obtained simulation and measurement results agree well with each other and have been presented to validate the accuracy of the proposed structure. Measured return loss of the structure shows dual-bands at 2.4 GHz and 5.8 GHz of more than 30 dB each and also a successful suppression of the spurious harmonics of the antenna array has been achieved. Radiation patterns have also been simulated and measured and both results shown. The gain and efficiency have also been presented; with the values being 6.7 dBi and 70% for the 2.4 GHz band and 7.4 dBi and 81% for the 5.8 GHz band respectively

Reconfigurable WLAN Notch for UWB Filters

This paper presents the design and results of an ultra-wideband (3.1–10.6 GHz) filter with a reconfigurable WLAN notch at 5.8 GHz. Reconfigurability has been achieved by the implementation of Graphene based switching elements. The switches are in OFF state when Graphene is unbiased at a chemical potential of µc = 0.0eV and are in ON state when Graphene is biased at a chemical potential of µc = 1.0eV. The simulation and measurement results of the filter when the Graphene switches are OFF show an entire bandpass response from 3.1 GHz to 10.6 GHz and with low insertion loss. When the Graphene switches are ON, the simulation result shows that a sharp rejection of the WLAN band at 5.8 GHz is achieved, with a very low passband insertion loss. The obtained results of both states, i.e. switches OFF and switches ON, are as desired. An additional filter, implemented with PIN diodes as the switching elements, is also designed and measured. Upon comparison, the obtained results of PIN diodes in OFF and ON states match those of the Graphene switches in OFF and ON states

UWB Filtennas with Dual Bandnotch for WiMAX and WLAN Bands using Circular and Square Resonators

This paper presents the design and results of an UWB filtenna with dual bandnotch present at WiMAX 3.5 GHz and WLAN 5.8 GHz bands. The filtenna is formed by the implementation of a filtering section - consisting of a circular ring resonator and two square ring resonators - within an UWB antenna. The filtenna was simulated using electromagnetic software and the simulated results of return loss, radiation patters, gain and efficiency have been presented. The return loss of the filtenna show a passband from 2.93–12.32 GHz; with dual bandnotch present at 3.48 GHz and 6 GHz at a return loss of less than 3 dB. Also, the results indicate that the gain and efficiency of the filtenna is significantly reduced at the dual bandnotch frequencies. Obtained radiation results show stable bi-directional patterns in the E-plane and omnidirectional patterns in the H-plane