Spin-orbit coupling and phase-coherence in InAs nanowires

We investigated the magnetotransport of InAs nanowires grown by selective area metal-organic vapor phase epitaxy. In the temperature range between 0.5 and 30 K reproducible fluctuations in the conductance upon variation of the magnetic field or the back-gate voltage are observed, which are attributed to electron interference effects in small disordered conductors. From the correlation field of the magnetoconductance fluctuations the phase-coherence length l_phi is determined. At the lowest temperatures l_phi is found to be at least 300 nm, while for temperatures exceeding 2 K a monotonous decrease of l_phi with temperature is observed. A direct observation of the weak antilocalization effect indicating the presence of spin-orbit coupling is masked by the strong magnetoconductance fluctuations. However, by averaging the magnetoconductance over a range of gate voltages a clear peak in the magnetoconductance due to the weak antilocalization effect was resolved. By comparison of the experimental data to simulations based on a recursive two-dimensional Green's function approach a spin-orbit scattering length of approximately 70 nm was extracted, indicating the presence of strong spin-orbit coupling.Comment: 8 pages, 7 figure

Architectures and Key Technical Challenges for 5G Systems Incorporating Satellites

Satellite Communication systems are a promising solution to extend and complement terrestrial networks in unserved or under-served areas. This aspect is reflected by recent commercial and standardisation endeavours. In particular, 3GPP recently initiated a Study Item for New Radio-based, i.e., 5G, Non-Terrestrial Networks aimed at deploying satellite systems either as a stand-alone solution or as an integration to terrestrial networks in mobile broadband and machine-type communication scenarios. However, typical satellite channel impairments, as large path losses, delays, and Doppler shifts, pose severe challenges to the realisation of a satellite-based NR network. In this paper, based on the architecture options currently being discussed in the standardisation fora, we discuss and assess the impact of the satellite channel characteristics on the physical and Medium Access Control layers, both in terms of transmitted waveforms and procedures for enhanced Mobile BroadBand (eMBB) and NarrowBand-Internet of Things (NB-IoT) applications. The proposed analysis shows that the main technical challenges are related to the PHY/MAC procedures, in particular Random Access (RA), Timing Advance (TA), and Hybrid Automatic Repeat reQuest (HARQ) and, depending on the considered service and architecture, different solutions are proposed.Comment: Submitted to Transactions on Vehicular Technologies, April 201

Material Flow Analysis of Plastic Waste in Qatar: Focusing on the Marine Environment

As the population continues to grow, the generation of waste and specifically plastic waste, has also increased significantly in the past decades both globally and regionally. However, little attention has been directed to this problem in the region. This study aims to delineate and map the status of the plastic waste problem in Qatar with a focus on the plastic inflow to the marine environment. A generic material flow diagram was built using a material flow analysis software named STAN, to depict the flow of the plastic waste. The study focuses on the plastic waste in the marine environment, depicting the different types, sizes and shapes of plastic particles, and the recovery and recycling efforts that have been made, in order to reduce plastic waste and minimize its risk on the environment

Regenerative approaches for V/UHTS feeder links: system analysis and on-board complexity reduction

The dramatically increasing demand for high data rates necessitates the proper dimensioning of the feeder links of very or ultra high throughput satellite (V/UHTS) systems. However, because most of the current solutions rely on transparent payloads, the deployment of a very large number of spatially separated ground stations is necessary to support the total system bandwidth by enabling a full reuse of the scarce available uplink bandwidth. This approach has a significant impact on the complexity and the costs of the ground segment infrastructure. Regenerative payloads could be considered to avoid this design bottleneck. By allowing demodulation and decoding on-board the satellite, the favourable link budget conditions of feeder links compared to the user links can be exploited. Using a spectral efficient transmission technique, the number of ground stations required to support a target sum throughput can be notably reduced. Meanwhile, regenerative solutions have until now barely been used in V/UHTS payloads due to their high on-board power consumption. As a consequence, candidate solutions are proposed in this work to overcome this limitation. A non-coherent modulation technique, known as Differential Amplitude Phase Shift Keying (DAPSK), is introduced to avoid on-board carrier synchronization. Moreover, polar codes are considered to minimize the power consumption of the channel decoder. A preliminary analysis of the expected on-board power consumption compared to that of a standard DVB-S2 approach is conducted using available results in the open literature. Link performance is also evaluated via numerical simulations

End-to-End QoS Measurement over a DVB-RCS Satellite Network

Satellites play an important role in the future network due to their wide area coverage and for providing connectivity in remote regions of the world. This paper presents the end-to-end quality of service (QoS) measurements taken employing a European Space Agency (ESA) testbed over DVB-RCS infrastructure, in collaboration with University of Surrey, UK. The applications chosen for these experiments are file transfer (FTP), web browsing (HTTP) and video streaming. File transfer and web browsing require reliable transport mechanism as a corrupted bit will hinder the intact data delivery. Therefore, these applications use transmission control protocol (TCP) as the transport protocol. TCP involves a three way handshake, which introduces extra delay during data transfer. Video streaming is a real time application. It is time-sensitive and requires lesser reliability compared to FTP and Web services. Hence, it employs user datagram protocol (UDP) at the transport layer, which do not offer any guarantee of reliable data delivery but timely. The parameters that have been used to evaluate quality of service (QoS) are packet delivery time, file download time, round trip delay, packet sizes and packet loss. The paper presented measurement results and comparative analysis of the QoS of the applications over the DVB-RCS testbed

Development of a new assessment tool for cervical myelopathy using hand-tracking sensor: Part 2: normative values

Purpose To set a baseline measurement of the number of hand flexion–extension cycles and analyse the degree of motion in young healthy individuals, measured by leap motion controller (LMC), besides describing gender and dominant hand differences. Methods Fifty healthy participants were asked to fully grip-and-release their dominant hand as rapidly as possible for a maximum of 3 min or until subjects fatigued, while wearing a non-metal wrist splint. Participants also performed a 15-s grip-and-release test. An assessor blindly counted the frequency of grip-and-release cycles and magnitude of motion from the LMC data. Results The mean number of the 15-s G–R cycles recorded by LMC was: 47.7 ± 6.5 (test 1, LMC); and 50.2 ± 6.5 (test 2, LMC). In the 3-min test, the total number of hand flexion–extension cycles and the degree of motion decreased as the person fatigued. However, the decline in frequency preceded that of motion’s magnitude. The mean frequency of cycles per 10-s interval decreased from 35.4 to 26.6 over the 3 min. Participants reached fatigue from 59.38 s; 43 participants were able to complete the 3-min test. Conclusions Normative values of the frequency of cycles and extent of motion for young healthy individuals, aged 18–35 years, are provided. Future work is needed to establish values in a wider age range and in a clinical setting

Complex and unexpected dynamics in simple genetic regulatory networks

Peer reviewedPublisher PD

Development of a new assessment tool for cervical myelopathy using hand-tracking sensor: Part 1: validity and reliability

Purpose To assess the reliability and validity of a hand motion sensor, Leap Motion Controller (LMC), in the 15-s hand grip-and-release test, as compared against human inspection of an external digital camera recording. Methods Fifty healthy participants were asked to fully grip-and-release their dominant hand as rapidly as possible for two trials with a 10-min rest in-between, while wearing a non-metal wrist splint. Each test lasted for 15 s, and a digital camera was used to film the anterolateral side of the hand on the first test. Three assessors counted the frequency of grip-and-release (G-R) cycles independently and in a blinded fashion. The average mean of the three was compared with that measured by LMC using the Bland–Altman method. Test–retest reliability was examined by comparing the two 15-s tests. Results The mean number of G-R cycles recorded was: 47.8 ± 6.4 (test 1, video observer); 47.7 ± 6.5 (test 1, LMC); and 50.2 ± 6.5 (test 2, LMC). Bland–Altman indicated good agreement, with a low bias (0.15 cycles) and narrow limits of agreement. The ICC showed high inter-rater agreement and the coefficient of repeatability for the number of cycles was ±5.393, with a mean bias of 3.63. Conclusions LMC appears to be valid and reliable in the 15-s grip-and-release test. This serves as a first step towards the development of an objective myelopathy assessment device and platform for the assessment of neuromotor hand function in general. Further assessment in a clinical setting and to gauge healthy benchmark values is warranted

Role of Caustic Addition in Bitumen-Clay Interactions

Coating of bitumen by clays, known as slime coating, is detrimental to bitumen recovery from oil sands using the warm slurry extn. process. Sodium hydroxide (caustic) is added to the extn. process to balance many competing processing challenges, which include undesirable slime coating. The current research aims at understanding the role of caustic addn. in controlling interactions of bitumen with various types of model clays. The interaction potential was studied by quartz crystal microbalance with dissipation monitoring (QCM-D). After confirming the slime coating potential of montmorillonite clays on bitumen in the presence of calcium ions, the interaction of kaolinite and illite with bitumen was studied. To represent more closely the industrial applications, tailings water from bitumen extn. tests at different caustic dosage was used. At caustic dosage up to 0.5 wt % oil sands ore, a negligible coating of kaolinite on the bitumen was detd. However, at a lower level of caustic addn., illite was shown to attach to the bitumen, with the interaction potential decreasing with increasing caustic dosage. Increasing concn. of humic acids as a result of increasing caustic dosage was identified to limit the interaction potential of illite with bitumen. This fundamental study clearly shows that the crit. role of caustics in modulating interactions of clays with bitumen depends upon the type of clays. Thus, clay type was identified as a key operational variable