A Survey of Recommendation Systems and Performance Enhancing Methods

With the development of web services like E-commerce, job hunting websites, movie websites, recommendation system plays a more and more importance role in helping users finding their potential interests among the overloading information. There are a great number of researches available in this field, which leads to various recommendation approaches to choose from when researchers try to implement their recommendation systems. This paper gives a systematic literature review of recommendation systems where the sources are extracted from Scopus. The research problem to address, similarity metrics used, proposed method and evaluation metrics used are the focus of summary of these papers. In spite of the methodology used in traditional recommendation systems, how additional performance enhancement methods like machine learning methods, matrix factorization techniques and big data tools are applied in several papers are also introduced. Through reading this paper, researchers are able to understand what are the existing types of recommendation systems, what is the general process of recommendation systems, how the performance enhancement methods can be used to improve the system's performance. Therefore, they can choose a recommendation system which interests them for either implementation or research purpose

Role of Astrocyte-Derived Extracellular Vesicles in Neuroinflammation Mediated by Drug Abuse

Neuronal damage and neuroinflammation is a hallmark feature of HIV-associated neurological disorders (HANDs). Opioids abuse accelerates the incidence and progression of HAND; however, the mechanisms underlying the potentiation of neuropathogenesis by these drugs remain elusive. Extracellular vesicles (EVs) are essential conduits in HIV and drug abuse-mediated synaptodendritic injury and neuroinflammation. Findings from our group have demonstrated that astrocyte-derived EV (ADEV)-miRNA-29b mediates HIV Tat and morphine-induced neuronal injury, thus underscoring the importance of such interactions in NeuroHIV. Besides, HIV Tat and morphine-mediated synaptodendritic injury via ADEVs, we are also interested in whether ADEVs contributes to neuroinflammation. Microglia are critical players in neuroinflammation. Morphine could regulate microglial function; However, the role of ADEVs in morphine-mediated dysregulation of microglia remains elusive. Additionally, drugs of abuse such as opioids can result in a breach of the blood-brain barrier (BBB), ultimately leading to enhanced monocyte transmigration and ensuing neuroinflammation. Recently studies provide compelling evidence that pericyte loss on the microvessels results in increased extravasation of peripheral immune cells. Mechanism(s) by which pericytes contribute to morphine-mediated neuroinflammation, however, remains less understood. The overarching goal of this thesis is to explore another undefined role of the morphine-mediated release of EV-miRNAs in regulating microglial and pericyte function(s), which, in turn, leading to neuroinflammation. We found that 1) morphine stimulated ADEVs can be taken up by microglial cells, leading, in turn, to impaired microglial phagocytosis via the TLR7-NF-kB -lincRNA-Cox2 axis and intranasal delivery of lincRNA-Cox2 siRNA restored microglial phagocytic activity of morphine-administered mice; 2) exposure of astrocytes in culture to morphine resulted in increased expression and secretion of miR-138 in the ADEVs which in turn, were taken up by the microglia, resulting in microglial activation, via binding to endosomal TLR7; 3) exposure of astrocytes to morphine resulted in induction and release the of miR-23a in the ADEVs, which, taken up by pericytes, leading to loss of pericyte thus lead to influx of monocyte (Figure 1). Our findings could have clinical ramifications in the future for developing EV-loaded RNA-based therapeutics that aimed at managing neuroinflammation-associated cognitive disorders in the context of chronic morphine abuse and HIV-opiate comorbidities

Electronic structures of [111]-oriented free-standing InAs and InP nanowires

We report on a theoretical study of the electronic structures of the [111]-oriented, free-standing, zincblende InAs and InP nanowires with hexagonal cross sections by means of an atomistic $sp^{3}s^{*}$, spin-orbit interaction included, nearest-neighbor, tight-binding method. The band structures and the band state wave functions of these nanowires are calculated and the symmetry properties of the bands and band states are analyzed based on the $C_{3v}$ double point group. It is shown that all bands of these nanowires are doubly degenerate at the $\Gamma$-point and some of these bands will split into non-degenerate bands when the wave vector $k$ moves away from the $\Gamma$-point as a manifestation of spin-splitting due to spin-orbit interaction. It is also shown that the lower conduction bands of these nanowires all show simple parabolic dispersion relations, while the top valence bands show complex dispersion relations and band crossings. The band state wave functions are presented by the spatial probability distributions and it is found that all the band states show $2\pi/3$-rotation symmetric probability distributions. The effects of quantum confinement on the band structures of the [111]-oriented InAs and InP nanowires are also examined and an empirical formula for the description of quantization energies of the lowest conduction band and the highest valence band is presented. The formula can simply be used to estimate the enhancement of the band gaps of the nanowires at different sizes as a result of quantum confinement.Comment: 9 pages, 8 figures. arXiv admin note: substantial text overlap with arXiv:1502.0756

On the existence of periodic solutions to second order Hamiltonian systems

In this paper, the existence of periodic solutions to the second order Hamiltonian systems is investigated. By introducing a new growth condition which generalizes the Ambrosetti–Rabinowitz condition, we prove a existence result of nontrivial T-periodic solution via the variational methods. Our result is new because it can deal with not only the superquadratic case, but also the anisotropic case which allows the potential to be superquadratic growth in only one direction and asymptotically quadratic growth in other directions

Two-dimensional thermoelastic contact problem of functionally graded materials involving frictional heating

AbstractThe two-dimensional thermoelastic sliding frictional contact of functionally graded material (FGM) coated half-plane under the plane strain deformation is investigated in this paper. A rigid punch is sliding over the surface of the FGM coating with a constant velocity. Frictional heating, with its value proportional to contact pressure, friction coefficient and sliding velocity, is generated at the interface between the punch and the FGM coating. The material properties of the coating vary exponentially along the thickness direction. In order to solve the heat conduction equation analytically, the homogeneous multi-layered model is adopted for treating the graded thermal diffusivity coefficient with other thermomechanical properties being kept as the given exponential forms. The transfer matrix method and Fourier integral transform technique are employed to convert the problem into a Cauchy singular integral equation which is then solved numerically to obtain the unknown contact pressure and the in-plane component of the surface stresses. The effects of the gradient index, Peclet number and friction coefficient on the thermoelastic contact characteristics are discussed in detail. Numerical results show that the distribution of the contact stress can be altered and therefore the thermoelastic contact damage can be modified by adjusting the gradient index, Peclet number and friction coefficient

Climatology of the Low-Level Jet at the Southern Great Plains Atmospheric Boundary Layer Experiments Site

A unique dataset obtained with combinations of minisodars and 915-MHz wind profilers at the Atmospheric Boundary Layer Experiments (ABLE) facility in Kansas was used to examine the detailed characteristics of the nocturnal low-level jet (LLJ). In contrast to instruments used in earlier studies, the ABLE instruments provide hourly, high-resolution vertical profiles of wind velocity from just above the surface to approximately 2 km above ground level (AGL). Furthermore, the 6-yr span of the dataset allowed the examination of interannual variability in jet properties with improved statistical reliability. It was found that LLJs occurred during 63% of the nighttime periods sampled. Although most of the observed jets were southerly, a substantial fraction (28%) was northerly. Wind maxima occurred most frequently at 200–400 m AGL, though some jets were found as low as 50 m, and the strongest jets tended to occur above 300 m. Comparison of LLJ heights at three locations within the ABLE domain and at one location outside the domain suggests that the jet is equipotential rather than terrain following. The occurrence of southerly LLJ varied annually in a way that suggests a connection between the tendency for jet formation and the large-scale circulation patterns associated with El Niño and La Niña, as well as with the Pacific decadal oscillation. Frequent and strong southerly jets that transport moisture downstream do not necessarily lead to more precipitation locally, however