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Search Results: 1 - 10 of 18995 matches for " Zhaofeng Song "
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Preparation and Characterization of Mullite-Silica Aerogel Composite Material  [PDF]
Zhaofeng Song, Haiquan Zhao
Open Journal of Organic Polymer Materials (OJOPM) , 2018, DOI: 10.4236/ojopm.2018.84004
Abstract: Silica aerogel due to the high specific surface area, nanometer level pores and low density of the micro structure, had excellent heat-insulating properties. But the characteristics of silica aerogel with low density and high voidage resulted in poor mechanical properties. In order to improve the strength of materials and meet the actual needs, in this paper the heat-insulating composite material was made from the silica aerogel and mullite fiber. This kind of composite material mainly contented of mullite fiber, formed macro block structure, that gas gel is coated and filled with mullite fiber. Furthermore, the composite material had good strength and kept excellent thermal stability at 600°C. In addition the density of composite decreased with the increasing of the gas gel content.
Preliminary Investigation on the Chemical Constituents and Antioxidant Activities of Two Phellinus Mushrooms Collected in Foshan  [PDF]
Feng Zhu, Weihong Lu, Weijie Feng, Zhaofeng Song, Chunyan Wang, Xin Chen
International Journal of Organic Chemistry (IJOC) , 2017, DOI: 10.4236/ijoc.2017.71003
Abstract: The Phellinus mushrooms have been known for its immunomodulatory, hypolipidemic, and anticancer activities. In the current work, the chemical constituents of two Phellinus mushrooms, Phellinus pini 141016# and Phellinus sp. 150802#, which were collected in Foshan city, Guangdong province, were investigated preliminarily by pre-test tube method and by comparison with the known natural compounds from Phellinus pini, and their antioxidant activities were evaluated by the biochemical assay of hydroxyl and 2,2-diphenyl-1-pricylhydrazyl (DPPH) radicals scavenging activity in vitro. The results show that both the two Phellinus mushrooms contain phenolics, alkaloids, lactones, steroids and terpenoids, and have potent antioxidant activities. The IC50 values of DPPH radicals and hydroxyl radicals for Phellinus pini 141016# were 74.37 μg/mL and 59.69 μg/mL, respectively, and the IC50 values of DPPH radicals and hydroxyl radicals for Phellinus sp. 150802# were 98.95 μg/mL and 165.47 μg/mL, respectively. They are comparable to the antioxidant activity of the standard antioxidant ascorbic acid.
Developing CALL to Meet the Needs of Language Teaching and Learning
Zhaofeng Jiang
English Language Teaching , 2008, DOI: 10.5539/elt.v1n2p108
Abstract: This paper illustrates the advantages and disadvantages of CALL. It points out that CALL is influenced by traditional language teaching and learning approaches to some extent .It concludes that what is important in our university system is that CALL design and implementation should match the users’ needs, since CALL is not always better than traditional language learning and teaching method.
Robust Inference for Time-Varying Coefficient Models with Longitudinal Data  [PDF]
Zhaofeng Wang, Jiancheng Jiang, Qunyi Qiu
Open Journal of Statistics (OJS) , 2015, DOI: 10.4236/ojs.2015.57070
Abstract:

Time-varying coefficient models are useful in longitudinal data analysis. Various efforts have been invested for the estimation of the coefficient functions, based on the least squares principle. Related work includes smoothing spline and kernel methods among others, but these methods suffer from the shortcoming of non-robustness. In this paper, we introduce a local M-estimation method for estimating the coefficient functions and develop a robustified generalized likelihood ratio (GLR) statistic to test if some of the coefficient functions are constants or of certain parametric forms. The robustified GLR test is robust against outliers and the error distribution. This provides a useful robust inference tool for the models with longitudinal data. The bandwidth selection issue is also addressed to facilitate the implementation in practice. Simulations show that the proposed testing method is more powerful in some situations than its counterpart based on the least squares principle. A real example is also given for illustration.

Response of 50 Years Regional Climatic Variation to Global Warming in the Desert Area in Northwestern China
ShuJuan Zhu,ZhaoFeng Chang
Environmental Research Journal , 2012, DOI: 10.3923/erj.2012.187.196
Abstract: The climate in desert is totally different from those in other landscapes. This stusy by analyzing the data collected in Minqin desert area during the period of 1961-2009, attempts to figure out how the temperature, precipitation and air humidity in the desert area of Northwestern China respond to global warming. The result revealed that: the increasing rate of the mean annual temperature in Minqin during 1961-2009 was greater than that of the global average and that of the 100 years average in China whereas lower than that in the arid area in Northeastern China in the recent 20 years. In Minqin, the temperatures in Winter and Spring rose significantly. The Winter and Spring temperatures and the annual maximum temperature showed big variations with great fluctuations. The annual air humidity increased dramatically while the precipitation displayed an insignificant increasing trend. There was a significant correlation between air humidity rising and precipitation increasing. However, there is no sound consistency between the periodic variations of air humidity and those of precipitation. The warmer Spring usually induced intensive sandstorms and the instability of air temperature often caused the yield reduction of crops/fruits in the study area.
Decaying Asymmetric Dark Matter Relaxes the AMS-Fermi Tension
Feng, Lei;Kang, Zhaofeng
High Energy Physics - Phenomenology , 2013,
Abstract: The first result of AMS-02 confirms the positron fraction excess observed by PAMELA, but in the dark matter (DM) interpretation, its softer spectrum brings a tension between AMS-02 and Fermi-LAT, which reported an excess of the electron plus positron flux. In this work we point out that the asymmetric cosmic ray from asymmetric dark matter (ADM) decay relaxes the tension, and find that at the two-body decay level a bosonic ADM around 2.4 TeV and decaying to\mu^-\tau^+ can significantly improve the fits. Based on the R-parity-violating supersymmetry with operators LLE^c, we propose a minimal model to realize that ADM scenario: Introducing a pair of singlets (X,\bar X) and coupling them to the visible sector via LH_uX, we then obtain a leptonic decaying ADM with TeV-scale mass.
Renormalization of Bilinear Quark Operators for Overlap Fermions
Thomas DeGrand,Zhaofeng Liu
Physics , 2005, DOI: 10.1103/PhysRevD.72.054508
Abstract: We present non-perturbative renormalization constants of fermionic bilinears on the lattice in the quenched approximation at beta=6.1 using an overlap fermion action with hypercubic(HYP)-blocked links. We consider the effects of the exact zero modes of the Dirac operator and find they are important in calculating the renormalization constants of the scalar and pseudoscalar density. The results are given in the RI' and MS bar schemes and compared to the perturbative calculations.
Decaying Dark Matter in the Supersymmetric Standard Model with Freeze-in and Seesaw mechanims
Zhaofeng Kang,Tianjun Li
Physics , 2010, DOI: 10.1007/JHEP02(2011)035
Abstract: Inspired by the decaying dark matter (DM) which can explain cosmic ray anomalies naturally, we consider the supersymmetric Standard Model with three right-handed neutrinos (RHNs) and R-parity, and introduce a TeV-scale DM sector with two fields \phi_{1,2} and a $Z_3$ discrete symmetry. The DM sector only interacts with the RHNs via a very heavy field exchange and then we can explain the cosmic ray anomalies. With the second right-handed neutrino N_2 dominant seesaw mechanism at the low scale around 10^4 GeV, we show that \phi_{1,2} can obtain the vacuum expectation values around the TeV scale, and then the lightest state from \phi_{1,2} is the decay DM with lifetime around \sim 10^{26}s. In particular, the DM very long lifetime is related to the tiny neutrino masses, and the dominant DM decay channels to \mu and \tau are related to the approximate \mu-\tau symmetry. Furthermore, the correct DM relic density can be obtained via the freeze-in mechanism, the small-scale problem for power spectrum can be solved due to the decays of the R-parity odd meta-stable states in the DM sector, and the baryon asymmetry can be generated via the soft leptogensis.
Baryon correlators containing different diquarks from lattice simulations
Zhaofeng Liu,Thomas DeGrand
Physics , 2006,
Abstract: Point to point vacuum correlators containing diquarks in the color anti-triplet representation are computed both in the quenched approximation and dynamical overlap simulations with two flavors. The scalar, pseudoscalar and axial vector diquarks are combined with light quarks to form color singlets. The scalar ("good") diquark channel shows a stronger attraction than the axial vector ("bad") channel in the quenched data set. The pseudoscalar diquark channel shows a finite volume zero mode artifact: the correlator becomes negative at large distance when the quark mass is small. By separating configurations without zero modes from those with zero modes, we found that the zero modes have an important contribution in both the attraction in the scalar channel and the repulsion in the pseudoscalar channel. In the axial vector diquark channel, we did not find apparent zero mode effects.
Naturally Large Radiative Lepton Flavor Violating Higgs Decay Mediated by Lepton-flavored Dark Matter
Seungwon Baek,Zhaofeng Kang
Physics , 2015,
Abstract: n the standard model (SM), lepton flavor violating (LFV) Higgs decay is absent at renormalizable level and thus it is a good probe to new physics. In this article we study a type of new physics that could lead to large LFV Higgs decay, i.e., a lepton-flavored dark matter (DM) model which is specified by the particle property of DM (a Majorana fermion) and DM-SM mediators (scalar leptons). Different from other similar setups, here we introduce both the left-handed and the right-handed scalar leptons. They allow large LFV Higgs decay and thus may explain the tentative Br$(h\ra\tau\mu)\sim1\%$ experimental results from LHC. In particular, we find that the stringent bound from $\tau\ra\mu\gamma$ can be naturally evaded. One reason, among others, is a large chirality violation in the mediator sector. Aspects of relic density and especially radiative direct detection of the leptonic DM are also investigated, stressing the difference from the previous lepton-flavored DM models.
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