A Universal Receiver for Uplink NOMA Systems

Given its capability in efficient radio resource sharing, non-orthogonal multiple access (NOMA) has been identified as a promising technology in 5G to improve the system capacity, user connectivity, and scheduling latency. A dozen of uplink NOMA schemes have been proposed recently and this paper considers the design of a universal receiver suitable for all potential designs of NOMA schemes. Firstly, a general turbo-like iterative receiver structure is introduced, under which, a universal expectation propagation algorithm (EPA) detector with hybrid parallel interference cancellation (PIC) is proposed (EPA in short). Link-level simulations show that the proposed EPA receiver can achieve superior block error rate (BLER) performance with implementation friendly complexity and fast convergence, and is always better than the traditional codeword level MMSE-PIC receiver for various kinds of NOMA schemes.Comment: This paper has been accepted by IEEE/CIC International Conference on Communications in China (ICCC 2018). 5 pages, 4 figure

Turbo-like Iterative Multi-user Receiver Design for 5G Non-orthogonal Multiple Access

Non-orthogonal multiple access (NoMA) as an efficient way of radio resource sharing has been identified as a promising technology in 5G to help improving system capacity, user connectivity, and service latency in 5G communications. This paper provides a brief overview of the progress of NoMA transceiver study in 3GPP, with special focus on the design of turbo-like iterative multi-user (MU) receivers. There are various types of MU receivers depending on the combinations of MU detectors and interference cancellation (IC) schemes. Link-level simulations show that expectation propagation algorithm (EPA) with hybrid parallel interference cancellation (PIC) is a promising MU receiver, which can achieve fast convergence and similar performance as message passing algorithm (MPA) with much lower complexity.Comment: Accepted by IEEE 88th Vehicular Technology Conference (IEEE VTC-2018 Fall), 5 pages, 6 figure

WEATHERING COVID-19: Lessons from Wuhan and Milan for Urban Governance and Sustainability

The global spread of COVID-19 has exposed the world’s largest and densest urban centres to bearing the brunt of this pandemic. The invisible virus has forced thriving metropolises to empty their streets and shops to dead spaces absent of people and activity. It even triggers the doomsday question of, “Does COVID-19 mean the end of cities?” In this article, we compare how two great cities of the East and West – Wuhan and Milan – have responded to the deadly virus, with their internal and external strengths and constraints. We also take the reader deep into the two cities’ neighbourhoods for a realistic sense of how their local residents have dealt with COVID-19. We end by drawing critical lessons for urban governance and sustainability

The effects of different versions of a gateway STEM course on student attitudes and beliefs

Background Substantial research has been conducted focusing on student outcomes in mathematics courses in order to better understand the ways in which these outcomes depend on the underlying instructional methodologies found in the courses. From 2009 to 2014, the Mathematical Association of America (MAA) studied Calculus I instruction in United States (US) colleges and universities in the Characteristics of Successful Programs of College Calculus (CSPCC). One aspect of this study attempted to understand the impact of these courses on student experience. Results In this paper, we describe results from an examination of the effect of course structure on students’ attitudes and beliefs across different versions of Calculus I at a large research university in the USA. To do this, we implemented a follow-up study of the national MAA study of calculus programs in part to identify potential relationships between various course structures and changes in attitudes and beliefs during the course. We compare our results both internally across these course structures and to the national data set. Conclusions We find that the statistically significant changes measured in confidence and enjoyment exhibit differences across the different calculus implementations and that these changes are statistically independent of the underlying student academic backgrounds as shown by standardized test scores and high school GPA. This suggests that these observed changes in attitudes and beliefs relate to the experience in our varied course structures and not to the academic characteristics of students as they enter the course. In addition to our findings, we show how this national study can be used locally to study effects of courses on student affective traits

Optically levitated gyroscopes with a MHz rotating micro-rotor

The optically levitated particles have been driven to rotate at an ultra-high speed of GHz, and the gyroscopic application of these levitated particles to measure angular motion have long been explored. However, this gyroscope has not been proven either theoretically or experimentally. Here, a rotor gyroscope based on optically levitated high-speed rotating particles is proposed. In vacuum, an ellipsoidal vaterite particle with 3.58 $\mu$m average diameter is driven to rotate at MHz, and the optical axis orientation of the particle is measured by the particle rotational signal. The external inputted angular velocity makes the optical axis deviate from the initial position, which changes the frequency and amplitude of the rotational signal. The inputted angular velocity is hence detected by the rotational signal, and the angular rate bias instability of the prototype is measured to be $0.08^o/s$. It is the smallest rotor gyroscope in the world, and the bias instability can be further improved up to $10^{-9o}/h$ theoretically by cooling the motion and increasing the angular moment of the levitated particle. Our work opens a new application paradigm of the levitated optomechanical systems and possibly bring the rotor gyroscope to the quantum realm

Molecular origins of peptide entrapment in polyethylene oxide layers

A more quantitative understanding of peptide entrapment and elution from otherwise protein-repellent polyethylene oxide (PEO) brush layers will provide direction for development of new strategies for drug storage and delivery. Here we describe criteria for peptide integration and structural change within the PEO brush, and discuss the reversibility of peptide entrapment with changing solvent conditions. For this purpose, three cationic peptides were used: the arginine-rich amphiphilic peptide WLBU2, the chemically identical but scrambled peptide S-WLBU2, and the non-amphiphilic homopolymer poly-L-arginine (PLR). Circular dichroism (CD) was used to record the adsorption and conformational changes of (amphiphilic) WLBU2 and S-WLBU2, and (non-amphiphilic) polyarginine peptides, at uncoated (hydrophobic) and PEO-coated silica nanoparticles. UV spectroscopy and a quartz crystal microbalance with dissipation monitoring (QCM-D) were used to quantify changes in the extent of peptide elution. Peptide conformation was controlled between disordered and α-helical forms by varying the concentration of perchlorate ion. We show an initially more ordered (α-helical) structure promotes peptide adsorption into the PEO layer. Further, a partially helical peptide undergoes an increase in helicity after entry, likely due to concomitant loss of capacity for peptide-solvent hydrogen bonding. Peptide interaction with the PEO chains resulted in entrapment and conformational change that was irreversible to elution with changing solution conditions in the case of the amphiphilic peptide. In contrast, the adsorption and conformational change of the non-amphiphilic peptide was reversible. We also evaluated the effects of peptide surface density on the conformational changes caused by peptide-peptide interactions, and using CD, QCM-D, and UV spectroscopy, showed that these phenomena substantially affect the rate and extent of peptide elution from PEO brush layers. Specifically, for amphiphilic peptides at sufficiently high surface density, peptide-peptide interactions result in conformational changes which compromise their resistance to elution. In contrast, elution of a non-amphiphilic peptide is substantially independent of its surface density, presumably due to the absence of peptide-peptide interactions. The sequential and competitive adsorption behavior of WLBU2, S-WLBU2 and PLR at pendant PEO layers was studied by optical waveguide lightmode spectroscopy (OWLS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), CD and UV spectroscopy. Results strongly indicate that amphiphilic peptides are able to displace non-amphiphilic peptides that are adsorbed in PEO layers, while non-amphiphilic peptides cannot displace amphiphilic ones. In summary, peptides of high amphiphilicity are expected to dominate the competitive adsorption with less amphiphilic peptides in PEO layers