A Low Complexity Pilot Scheduling Algorithm for Massive MIMO

Pilot contamination is a fundamental bottleneck in massive multiple-input multiple-output (MIMO) cellular networks. In this letter, we aim to design a pilot scheduling method to reduce the effect of pilot contamination in multi-user multi-cell massive MIMO systems. Mathematically, the pilot scheduling problem can be formulated as a permutation-based optimization problem. However, finding the optimal solution requires an exhaustive search and is computationally prohibitive. Therefore, we propose a low-complexity near-optimal algorithm developed from the cross-entropy optimization framework to solve this problem. Simulation results reveal that our algorithm not only significantly outperforms the existing pilot-scheduling schemes but also achieves excellent performance with low complexity

Angle-of-Arrival Estimation with Practical Phone Antenna Configurations

With the advances of the Internet of Things and mobile connectivity, location-based services are becoming increasingly popular and continue to enhance our experience. Multiple antennas have been pivotal in providing reliable wireless communications and high-resolution localization. If the antennas of the array are isotropic, then the simplified array manifold determined by the array geometry can be used to estimate the angle-of-arrival (AOA). However, in the real world, mobile handsets tend to have very limited space, where the practical antennas are equipped on the same ground plane, and the array geometry hardly obeys the rule of half-wavelength spacing. Therefore, a practical antenna couples signals from other antennas, causing a mutual coupling effect. Complex array manifolds are produced on an antenna even if the received signal is propagated through a single path channel. In addition, the irregular radiation pattern of each antenna further impairs the AOA estimation capability. Given the above effects, the simplified array manifold determined by the array geometry can no longer provide precise localization. In this paper, we propose a generic array manifold model for both isotropic and practical antennas. We also present an efficient algorithm to enable AOA estimation on practical antennas on the basis of the proposed model and implement it on a 5G phone at a mid-band spectrum with a 100MHz channel bandwidth. Results reveal the promising performance of the proposed model, with the AOA estimation errors lower than 10∘ in over 90% of the scenarios

Hydrodynamic and Contact Contributions to Continuous Shear Thickening in Colloidal Suspensions.

Shear thickening is a widespread phenomenon in suspension flow that, despite sustained study, is still the subject of much debate. The longstanding view that shear thickening is due to hydrodynamic clusters has been challenged by recent theory and simulations suggesting that contact forces dominate, not only in discontinuous, but also in continuous shear thickening. Here, we settle this dispute using shear reversal experiments on micron-sized silica and latex particles to measure directly the hydrodynamic and contact force contributions to shear thickening. We find that contact forces dominate even continuous shear thickening. Computer simulations show that these forces most likely arise from frictional interactions

Contingent infrastructure and the dilution of ‘Chineseness’: Reframing roads and rail in Kampala and Addis Ababa

Amid growing interest in China’s role in financing and building infrastructure in Africa, there is still little research on how Chinese-financed infrastructures are negotiated and realised at the city and metropolitan scale. We compare the Light Rail Transit in Addis Ababa, Ethiopia with the expressway linking Kampala to Entebbe airport in Uganda, examining the processes of bargaining behind these transport infrastructures and their emergent effects on urban land use and city-dwellers’ mobility. We find that both projects were designed and implemented through opaque negotiations between African national elites and Chinese agencies, with little or no engagement from city authorities, leading to haphazard outcomes that are poorly integrated with broader planning. Yet we also suggest that despite being enabled and mediated by Chinese agencies, such projects do not embody a Chinese global vision. They instead reflect the entrepreneurial activities of Chinese contractors and the varying ways in which these connect with African national governments’ shifting priorities. Moreover, as they are subsumed into the urban context, these transposed infrastructures have been rapidly repurposed and their ‘Chineseness’ diluted, with one morphing into an infrastructure for the poor and the other into a site of private value extraction. We thus argue that, far from representing a domineering or neo-colonial influence, Chinese-financed infrastructures that land in institutionally complex African city-regions can be rapidly swallowed up into the political-economic landscape, producing contingent benefits and disbenefits that are far removed from the visions of any planners – Chinese or African, past or present

A particle swarm optimization based memetic algorithm for dynamic optimization problems

Copyright @ Springer Science + Business Media B.V. 2010.Recently, there has been an increasing concern from the evolutionary computation community on dynamic optimization problems since many real-world optimization problems are dynamic. This paper investigates a particle swarm optimization (PSO) based memetic algorithm that hybridizes PSO with a local search technique for dynamic optimization problems. Within the framework of the proposed algorithm, a local version of PSO with a ring-shape topology structure is used as the global search operator and a fuzzy cognition local search method is proposed as the local search technique. In addition, a self-organized random immigrants scheme is extended into our proposed algorithm in order to further enhance its exploration capacity for new peaks in the search space. Experimental study over the moving peaks benchmark problem shows that the proposed PSO-based memetic algorithm is robust and adaptable in dynamic environments.This work was supported by the National Nature Science Foundation of China (NSFC) under Grant No. 70431003 and Grant No. 70671020, the National Innovation Research Community Science Foundation of China under Grant No. 60521003, the National Support Plan of China under Grant No. 2006BAH02A09 and the Ministry of Education, science, and Technology in Korea through the Second-Phase of Brain Korea 21 Project in 2009, the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant EP/E060722/01 and the Hong Kong Polytechnic University Research Grants under Grant G-YH60

Robust Delay-Dependent Load Frequency Control of Wind Power System Based on a Novel Reconstructed Model

IEEE This article presents a novel reconstructed model for the delayed load frequency control (LFC) schemes considering wind power, which aims to improve the computational efficiency for PID controllers while retaining their dynamic performance. Via fully exploiting system states influenced by time delays directly, this novel reconstructed method is proposed with a controller isolated. Hence, when the PID controllers are unknown, the stability criterion based on this model can resolve controller gains with less time consumed. For given PID gains, this model can be employed to establish criteria for stability analysis, which can realize the tradeoff between the calculation accuracy and efficiency. The case study is first based on a two-area traditional LFC system to validate the merits of a novel reconstructed model, including accurately estimating the influence of time delay on system frequency stability with increased computational capability. Then, under traditional and deregulated environments, case studies are carried out on the two-area and three-area schemes, respectively. Through the novel reconstructed model, the efficiency of obtaining controller parameters is highly improved while their robustness against the random wind power, tie-line power changes, inertial reductions, and time delays remains almost unchanged

Intra-anal imiquimod cream against human papillomavirus infection in men who have sex with men living with hiv: A single-arm, open-label pilot study

Men who have sex with men (MSM) living with HIV have a high prevalence and incidence of anal high-risk human papillomavirus (hrHPV) and anal cancer. We conducted an open-label, single-arm pilot study to examine the tolerability of imiquimod cream among MSM aged ≥18 years, living with HIV, who tested positive for anal hrHPV at Melbourne Sexual Health Centre between April 2018 and June 2020. We instructed men to apply 6.25 mg imiquimod intra-anally and peri-anally 3 doses per week for 16 weeks (period 1) and then one dose per week for a further 48 weeks (period 2). Twenty-seven MSM enrolled in period 1 and 24 (86%) applied at least 50% of doses. All men reported adverse events (AEs), including 39.5% grade 1, 39.5% grade 2, and 21% grade 3 AEs on at least one occasion. Eighteen MSM (67%) temporarily stopped using imiquimod during period 1, most commonly due to local AEs (n = 11) such as irritation and itching. Eighteen MSM continued in period 2 and all applied at least 50% of doses with no treatment-limiting AEs reported. Imiquimod 3 doses per week caused local AEs in most men and was not well tolerated. In contrast, once-a-week application was well tolerated over 48-weeks with no treatment-limiting AEs

Coherent coupling between radio frequency, optical, and acoustic waves in piezo-optomechanical circuits

The interaction of optical and mechanical modes in nanoscale optomechanical systems has been widely studied for applications ranging from sensing to quantum information science. Here, we develop a platform for cavity optomechanical circuits in which localized and interacting 1550 nm photons and 2.4 GHz phonons are combined with photonic and phononic waveguides. Working in GaAs facilitates manipulation of the localized mechanical mode either with a radio frequency field through the piezo-electric effect, or optically through the strong photoelastic effect. We use this to demonstrate a novel acoustic wave interference effect, analogous to coherent population trapping in atomic systems, in which the coherent mechanical motion induced by the electrical drive can be completely cancelled out by the optically-driven motion. The ability to manipulate cavity optomechanical systems with equal facility through either photonic or phononic channels enables new device and system architectures for signal transduction between the optical, electrical, and mechanical domains

Interactions among mitochondrial proteins altered in glioblastoma

Mitochondrial dysfunction is putatively central to glioblastoma (GBM) pathophysiology but there has been no systematic analysis in GBM of the proteins which are integral to mitochondrial function. Alterations in proteins in mitochondrial enriched fractions from patients with GBM were defined with label-free liquid chromatography mass spectrometry. 256 mitochondrially-associated proteins were identified in mitochondrial enriched fractions and 117 of these mitochondrial proteins were markedly (fold-change ≥2) and significantly altered in GBM (p ≤ 0.05). Proteins associated with oxidative damage (including catalase, superoxide dismutase 2, peroxiredoxin 1 and peroxiredoxin 4) were increased in GBM. Protein–protein interaction analysis highlighted a reduction in multiple proteins coupled to energy metabolism (in particular respiratory chain proteins, including 23 complex-I proteins). Qualitative ultrastructural analysis in GBM with electron microscopy showed a notably higher prevalence of mitochondria with cristolysis in GBM. This study highlights the complex mitochondrial proteomic adjustments which occur in GBM pathophysiology

Hong-Ou-Mandel interference with a single atom

The Hong-Ou-Mandel (HOM) effect is widely regarded as the quintessential quantum interference phenomenon in optics. In this work we examine how nonlinearity can smear statistical photon bunching in the HOM interferometer. We model both the nonlinearity and a balanced beam splitter with a single two-level system and calculate a finite probability of anti-bunching arising in this geometry. We thus argue that the presence of such nonlinearity would reduce the visibility in the standard HOM setup, offering some explanation for the diminution of the HOM visibility observed in many experiments. We use the same model to show that the nonlinearity affects a resonant two-photon propagation through a two-level impurity in a waveguide due to a " weak photon blockade" caused by the impossibility of double-occupancy and argue that this effect might be stronger for multi-photon propagation