Performance Analysis of l_0 Norm Constraint Least Mean Square Algorithm

As one of the recently proposed algorithms for sparse system identification, $l_0$ norm constraint Least Mean Square ($l_0$-LMS) algorithm modifies the cost function of the traditional method with a penalty of tap-weight sparsity. The performance of $l_0$-LMS is quite attractive compared with its various precursors. However, there has been no detailed study of its performance. This paper presents all-around and throughout theoretical performance analysis of $l_0$-LMS for white Gaussian input data based on some reasonable assumptions. Expressions for steady-state mean square deviation (MSD) are derived and discussed with respect to algorithm parameters and system sparsity. The parameter selection rule is established for achieving the best performance. Approximated with Taylor series, the instantaneous behavior is also derived. In addition, the relationship between $l_0$-LMS and some previous arts and the sufficient conditions for $l_0$-LMS to accelerate convergence are set up. Finally, all of the theoretical results are compared with simulations and are shown to agree well in a large range of parameter setting.Comment: 31 pages, 8 figure

Single cell transcriptome profiling reveals cutaneous immune microenvironment remodeling by photodynamic therapy in photoaged skin

BackgroundThe immune microenvironment plays a critical role in maintaining skin homeostasis, which is closely related to the dysfunction in photoaged skin such as autoimmunity and tumorigenesis. Several recent studies have demonstrated the efficacy of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) in alleviating photoaging and skin cancer. However, the underlying immune mechanisms and the immune microenvironment change by ALA-PDT remain largely unknown.MethodsTo illustrate the effects of ALA-PDT on immune microenvironment in photoaged skin, single cell RNA sequencing (scRNA-seq) analysis of photoaged skin on the extensor side of the human forearm before and after ALA-PDT was performed. R-packages of Seurat, clusterProfiler, Monocle, CellChat were used for cell clustering, differentially expressed genes analysis, functional annotation, pseudotime analysis and cell-cell communication analysis. The gene sets related to specific functions were extracted from the MSigDB database, which were used to score the functions of immune cells in different states. We also compared our result with published scRNA-seq data of photoaged skin of the eyelids.ResultsThe increase score of cellular senescence, hypoxia and reactive oxygen species pathway in immune cells and the decrease of immune receptor activity function and proportion of naive T cells were found in skin photoaging. Moreover, the function of T cell ribosomal synthesis was also impaired or down regulated and function of G2M checkpoint was up regulated. However, ALA-PDT showed promising results in reversing these effects, as it improved the above functions of T cells. The ratio of M1/M2 and percentage of Langerhans cells also decreased with photoaging and increased after ALA-PDT. Additionally, ALA-PDT restored the antigen presentation and migration function of dendritic cells and enhanced cell-cell communication among immune cells. These effects were observed to last for 6 months.ConclusionALA-PDT has potential to rejuvenate immune cells, partially reversed immunosenescence and improved the immunosuppressive state, ultimately remodelling the immune microenvironment in photoaged skin. These results provide an important immunological basis for further exploring strategies to reverse skin photoaging, chronological aging and potentially systemic aging

Genomic data for 78 chickens from 14 populations

Background: Since the domestication of the red jungle fowls (Gallus gallus; dating back to~10 000 B.P.) in Asia, domestic chickens (Gallus gallus domesticus) have been subjected to the combined effects of natural selection and human-driven artificial selection; this has resulted in marked phenotypic diversity in a number of traits, including behavior, body composition, egg production, and skin color. Population genomic variations through diversifying selection have not been fully investigated. Findings: The whole genomes of 78 domestic chickens were sequenced to an average of 18-fold coverage for each bird. By combining this data with publicly available genomes of five wild red jungle fowls and eight Xishuangbanna game fowls, we conducted a comprehensive comparative genomics analysis of 91 chickens from 17 populations. After aligning ~21.30 gigabases (Gb) of high-quality data from each individual to the reference chicken genome, we identified ~6.44 million (M) single nucleotide polymorphisms (SNPs) for each population. These SNPs included 1.10 M novel SNPs in 17 populations that were absent in the current chicken dbSNP (Build 145) entries. Conclusions: The current data is important for population genetics and further studies in chickens and will serve as a valuable resource for investigating diversifying selection and candidate genes for selective breeding in chickens.Peer reviewedAnimal Scienc

Advances on Penetrating Imaging of Building Layout Technique Using Low Frequency Radio Waves

Obtaining the internal layout of an unfamiliar building before entering the building has important practical significance and research value, as it can be applied for various services, such as anti-terrorism operations and disaster relief. Low-frequency electromagnetic waves can propagate through common building materials, and then the target information behind the wall is obtained safely and stably. Therefore, using low frequency radio waves to obtain the information behind the wall has become the research focus in the field of building layout reconstruction. To reveal the development context of this field and predict the possible future development trends, this paper summarizes the domestic and foreign public literature in this field since the onset of the 21st century. The results of the relevant literature indicate that the techniques of using low-frequency electromagnetic waves to reconstruct building layout currently include three types: through-the-wall radar imaging technology based on reflected wave measurement, radio-frequency tomography technology based on transmitted wave measurement, and wall position estimation technology based on multipath signals. These three technologies have achieved several practical research results. This article clarifies the development history of the main content covered by these technologies, which mainly includes the principle of through-the-wall radar imaging of stationary targets behind the wall, the observation mode of building internal structure based on through-the-wall radar, the reconstruction technology of building internal structure on the basis of through-the-wall radar imaging, the inversion technology of building internal structure on the basis of radio-frequency tomography, and the wall position estimation technology based on multipath signals. We also discuss the development trend of this field. In the past two decades, the development history of building layout penetrating imaging using low-frequency radio waves shows a change from the traditional airborne and vehicle-mounted building-layout-reconstruction platforms to new platforms such as microrobots and unmanned aerial vehicles. The corresponding reconstruction method has been developed from the traditional radar imaging technology to a variety of new methods, including image enhancement and sparse reconstruction. The results indicate that the building-layout-reconstruction technology is developing in the direction of systematization, diversification, and intelligence

Improvement of cooling performance of hybrid nanofluids in a heated pipe applying annular magnets

In this paper, convective heat transfer of Fe3O4–carbon nanotubes (CNTs) hybrid nanofluid was studied in a horizontal small circular tube under influence of annular magnets. The pipe has an inner diameter of 3 mm and a length of 1.2 m. Heat transfer characteristics of the Fe3O4–water nanofluid were examined for many parameters, such as nanoparticle volume fraction in the range of 0.4–1.2% and Reynolds number in the range of 476–996. In order to increase the thermal conductivity of the Fe3O4–water nanofluid, carbon nanotubes with 0.12–0.48% volume fraction were added into the nanofluid. It was observed that for the Fe3O4–CNTs–water nanofluid with 1.44% volume fraction and under a magnetic field, the maximal local Nusselt number at the Reynolds number 996 increased by 61.54% compared with without a magnetic field. Results also show that compared with the deionized water, the maximal enhancements of the average Nusselt number are 67.9 and 20.89% for the Fe3O4–CNTs–water nanofluid with and without magnetic field, respectively

Effect of various surfactants on stability and thermophysical properties of nanofluids

The effect of Fe3O4 nanoparticles and carbon nanotubes (CNTs) on the viscosity of a nanofluid is experimentally investigated from 278 to 313 K by changing the nanoparticle volume fraction. These nanoparticles were put into distilled water with various surfactants, i.e., Colace (docusate sodium), trisodium citrate dihydrate (TSC), polyvinyl pyrrolidone, cetyl trimethylammonium bromide, tetramethylammonium hydroxide (TMAH), acacia senegal (GA), sodium dodecyl benzene sulfonate, sodium dodecyl sulfate (SDS), and sodium laurylsulfonate (SLS). Based on the present measurements, new empirical formulas are proposed for Fe3O4–water, CNT–water and Fe3O4–CNT–water nanofluids to provide accurate predictions for the nanofluid viscosity. Based on the viscosity testing, stabilities and thermal conductivities of Fe3O4–TMAH, Fe3O4–Colace, Fe3O4–TSC, CNT–SDS, CNT–GA, Fe3O4–CNT–SLS, and Fe3O4–CNT–TSC nanofluids with a volume concentration of 0.5% are investigated in the present research. Results indicate that better stability, smaller viscosity, and higher thermal conductivity are obtained, when the surfactants TMAH, SDS, and SLS are added into the Fe3O4–water, CNT–water, and the Fe3O4–CNT–water nanofluid, respectively. The CNT–water and Fe3O4–CNT–water nanofluids exhibit a shear-thinning behavior, whereas a linear rheological behavior can be observed by water-based Colace–Fe3O4, TMAH–Fe3O4, and TSC–Fe3O4 nanofluids

Experimental investigation on convective heat transfer of ferrofluids inside a pipe under various magnet orientations

Some experimental tests were conducted to reveal the enhancement of the ferrofluid heat transfer under a permanent magnetic field. This research aims to investigate the effect of various external magnetic fields on convective heat transfer characteristics of the ferrofluid (magnetic nanofluid). Comparison of theoretical predictions and experimental data were conducted to validate the rationality of the test results, and a good agreement with less than 10% deviations was found. The deviations from experimental data decrease with an increase of the Reynolds number (Re) from 391 to 805. Results from the case with 5 cannulas indicate that a continuous increase in the magnetic flux density (by increasing the quantity of the magnets) can improve the heat transfer enhancement significantly. The ferrofluids with a magnetic cannula shows heat transfer enhancements of 26.5% and 54.5% at Re = 391 and 805, respectively

Investigation of mixed convection in an enclosure filled with nanofluids of Al2O3 –water and graphene-ethylene glycol

In this research work, heat transfer enhancement of mixed convection in an enclosure is investigated with a moving top wall. Numerical simulations based on an Al2 O3 –water nanofluid are conducted by using variable thermophysical properties. Flow fields and temperature distributions are analyzed by considering effects of two partially heated walls. Moreover, water–ethylene glycol mixed with graphene nanoplatelets (GnP-WEG) is also considered to analyze effects of the heating procedure, Reynolds number, Rayleigh number and volume fraction of the nanoparticles, as well as on the heat transfer enhancement. It is found that there is a velocity difference between the pure water and the Al2 O3 –water nanofluid due to the increase of the fluid viscosity by an injection of Al2 O3 nanoparticles into the water. Moreover, flow patterns are significantly affected by the Reynolds number and the Rayleigh number. The heat transfer in the enclosure is enhanced by the increase of the top wall moving velocity. Although heat transfer enhancement for most cases are obtained by increasing the volume fraction of graphene nanoplatelets, a mixture of 0.25% graphene nanoplatelets and the water–ethylene glycol (the base fluid) provides the largest enhancement of heat transfer at low Reynolds number (Re = 1)

Multiple Mobile Data Offloading Through Delay Tolerant Networks

To cope with the explosive traffic demands and limited capacity provided by the current cellular networks, Delay Tolerant Networking (DTN) is used to migrate traffic from the cellular networks to the free and high capacity device-todevice networks. The current DTN-based mobile data offloading models do not address the heterogeneity of mobile traffic and are based on simple network assumptions. In this paper, we establish a mathematical framework to study the problem of multiple mobile data offloading under realistic network assumptions, where 1) mobile data is heterogeneous in terms of size and lifetime, 2) mobile users have different data subscribing interests, and 3) the storage of offloading helpers is limited. We formulate the maximum mobile data offloading as a Submodular Function Maximization problem with multiple linear constraints of limited storage and propose greedy, approximated and optimal algorithms for different offloading scenarios. We show that our algorithms can effectively offload data to DTNs by extensive simulations which employ real traces of both humans and vehicles