Reversible skew laurent polynomial rings and deformations of poisson automorphisms

A skew Laurent polynomial ring S = R[x(+/- 1); alpha] is reversible if it has a reversing automorphism, that is, an automorphism theta of period 2 that transposes x and x(-1) and restricts to an automorphism gamma of R with gamma = gamma(-1). We study invariants for reversing automorphisms and apply our methods to determine the rings of invariants of reversing automorphisms of the two most familiar examples of simple skew Laurent polynomial rings, namely a localization of the enveloping algebra of the two-dimensional non-abelian solvable Lie algebra and the coordinate ring of the quantum torus, both of which are deformations of Poisson algebras over the base field F. Their reversing automorphisms are deformations of Poisson automorphisms of those Poisson algebras. In each case, the ring of invariants of the Poisson automorphism is the coordinate ring B of a surface in F-3 and the ring of invariants S-theta of the reversing automorphism is a deformation of B and is a factor of a deformation of F[x(1), x(2), x(3)] for a Poisson bracket determined by the appropriate surface

Concurrent, Tunable, Multi-band, Single Chain Radio Receivers for 5G RANs

A concurrent, tunable, tri-band, single chain radio receiver for 5G radio access networks is evaluated. The three concurrent bands are independently tunable over a frequency range from 600 MHz to 2.7 GHz. A hardware-in-the-loop test-bed provides a system level evaluation of the proposed receiver using direct RF digitization. The test-bed emulates a 5G heterogeneous network supporting three wideband, simultaneous connections. By measuring the receiver EVM, we demonstrate sufficient isolation between concurrent bands achieving 60 MHz of aggregated bandwidth as well as strong resilience to adjacent blockers

Tuneable Dual-band Antenna for Sub 1 GHz Cellular Mobile Radio Applications

In this paper, a compact tuneable dual-band slot antenna operating over the frequency range from 560 MHz to 1 GHz is presented and evaluated through a hardware-in-the-loop test-bed. The co-existence of high order modulation schemes is investigated in DTT and low LTE bands. EVM results show that the proposed antenna can support two operating frequency bands simultaneously where each band can be tuned independently for carrier aggregation with negligible crosstalk

Demonstration of RF Digitising Concurrent Dual-Band Receiver for Carrier Aggregation over TV White Spaces

In order to meet the high data rate, low latency and high energy efficiency requirements, the future radio units must utilise the frequency spectrum available at certain geographical location efficiently with a minimum amount of hardware. This requires frequency agility and concurrent multi-standard operation capabilities at the base and mobile terminals. To utilise the TV white spaces for mobile and wireless communication and enable their carrier aggregation with sub GHz LTE bands, this paper presents a single-chain, reconfigurable, RF digitising, dual-band receiver comprised of a tunable dual-band antenna, a reconfigurable digital down converter, a baseband processing unit and wideband LNA and ADC in the form of an oscilloscope. The presented dual-band receiver is tested through a hardware-in-the-loop test-bed which shows that up to 20 MHz aggregate bandwidths can be achieved. The receiver is able to provide equivalent error vector magnitude (EVM) performance across a wide range of frequencies avoiding any inter-band interference

Optical energy-constrained slot-amplitude modulation for dimmable VLC. Suboptimal detection and performance evaluation

Energy-constrained slot-amplitude modulation (ECSAM) enables light dimming, eliminates light flicker and constrains the peak optical power while providing robust communication links. However, the complexity of the maximum-likelihood (ML) based ECSAM receiver increases exponentially with required spectral efficiency. This paper provides a comprehensive performance evaluation of ECSAM for the indoor visible light communication (VLC) channel with multipath propagation under realistic illumination constraints and imperfect channel estimation. A sub-optimal receiver that employs a slot-by-slot detection algorithm followed by a slot-correction mechanism for reducing the receiver complexity is proposed. Additionally, the method for optimal selection of parameters when designing the signal waveform is presented. The analytical upper bound on the symbol error rate of ECSAM is derived using the union-bound technique. The results show that the error performance of the sub-optimal receiver are comparable to that of the optimal ML receiver. Compared with conventional power or bandwidth efficient VLC modulation techniques such as multiple pulse position modulation (MPPM) and pulse amplitude modulation (PAM), ECSAM provides complete flexibility in modifying the signal constellation for a desired dimming level to maximise the spectral efficiency and provide a robust bit error rate performance especially in the multipath propagation channel induced intersymbol interference

Distribution of radioactive jackrabbit pellets in the vicinity of the B-C CRIBS, 200 East Area, U.S.A.E.C. Hanford Reservation

During 1972 and 1973 a study was conducted in the B-C Cribs, 200 East Area, to learn the extent to which jackrabbits (Lepus californicus) and their predators had dispersed buried radioactive wastes in their fecal pellets and scats. The specific objective was to gather sufficient data on the pattern of dispersal so that statistically valid sampling strategies could be developed in future programs, depending upon management planning objectives for the area. A secondary objective was to relate these data with parameters, such as topography, wind direction, vegetation types, animal behavior, that might help explain the pattern of dispersal. In 1972, 2625 circular sampling sites were surveyed along 30 transects radiating out 2.4 to 3.2 km from the B-C Cribs. Radioactive contaminated feces, urine, soil and vegetation were distributed in all directions from the cribs, but the area to the south and southwest was more densely and uniformly contaminated. Of the ultimate sampling units surveyed, 278 or 10.6% had activity in excess o f 10,000 counts per minute (cprn) measured with a Geiger-Mueller counter. Of these 278 circular areas, 179 or 64% were found within 0.5 km of the cribs, 23.4% were between 0.5 and 1.0 km, and the remaining 12.2% were further than 1 km from the central point. Although most droppings with a count rate greater than 20,000 cpm were found within 400 meters of the crib, pellets registering in excess of 100,000 cprn were found up to 1.6 km from the cribs. The pellets appeared to be distributed into the prevailing wind directions and contrary to the immediate contours: the only correlation seemed to be with increased vegetation density to the south and southwest, vegetation that is prime jackrabbit habitat. In May-June, 1973, 48 additional transects were run: 7 were parallel to lines established in the B-C Crib Area during 1972; 18 radiated from an abandoned gun battery site 3.2 km east of the cribs; and 23 were run from power lines 5 km south to southwest of the cribs back towards the source of contamination. No contaminated jackrabbit pellets were found at these distances, but one contaminated coyote scat was found near the gun battery site. During 1972 and 1973 field crews walked 106.7 km along 78 radii and recorded observations on 6671 ultimate sampling units of approximately 1.4 m{sup 2}

An Independently Tunable Tri-band Antenna Design for Concurrent Multi-band Single Chain Radio Receivers

In this paper, a novel tunable tri-band antenna is presented for concurrent, multi-band, single chain radio receivers. The antenna is manufactured on a 50×100 mm FR4 printed circuit board (PCB), and is able to provide three concurrent, independently tunable operating bands covering a frequency range from 600 MHz to 2.7 GHz. The antenna performance is investigated for both numerical and experimental methods when using, first, varactor diodes and, second, digitally tunable capacitors (DTCs) to tune frequencies, which shows the antenna gain can be improved by up to 2.6 dBi by using DTCs. A hardware-in-the-loop test-bed provides a system level evaluation of the proposed antenna in a direct RF digitized, concurrent, tri-band radio receiver. By measuring the receiver’s error vector magnitude, we demonstrate sufficient isolation between concurrent bands achieving 30 MHz of aggregated bandwidth as well as strong resilience to adjacent blockers next to each band. The data reported in this article are available from the ORDA digital repository (https://doi.org/10.15131/shef.data.5346295)

Mothers' voices: hearing and assessing the contributions of 'birth mothers' to the development of social work interventions and family support

This paper focuses on interviews with ‘birth mothers’ who experienced successive losses of their children to public care in one local area of London, England. Interviews were conducted during a project partnership between a London borough and university staff, aiming to provide a localised, pilot support initiative which responded to mothers’ viewpoints. To ‘hear’ mothers’ own voices more clearly, we analysed interview transcripts using a methodology which separates out elements of how the interviewee tells her story, how she speaks about herself and about her relationships, taking into account surrounding social complexities and researchers’ reactions to the story. To explain how professionals could subsequently draw upon these ‘mothers’ voices’ for a pilot support initiative, we identify some key messages for professionals from these interviews, including: women wanting clear and honest communication between themselves and workers, and between staff; women often feeling ‘let down’ by professional procedures and court processes that were moving too fast for them to keep up; women wanting to be treated with more respect. Women respected some professionals but not others and this seemed to relate partly to personalities. Some mothers experienced being ‘left alone’ or ‘abandoned’ to deal with the aftermath of children’s removal and/or adoption