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Search Results: 1 - 10 of 78403 matches for " Liwei Chen "
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The $L^p$ boundedness of the Bergman projection for a class of bounded Hartogs domains
Liwei Chen
Mathematics , 2013,
Abstract: We generalize the Hartogs triangle to a class of bounded Hartogs domains, and we prove that the corresponding Bergman projections are bounded on $L^p$ if and only if $p$ is in the range $(\frac{2n}{n+1},\frac{2n}{n-1})$.
Weighted Sobolev regularity of the Bergman projection on the Hartogs triangle
Liwei Chen
Mathematics , 2015,
Abstract: We prove a weighted Sobolev estimate of the Bergman projection on the Hartogs triangle, where the weight is some power of the distance to the singularity at the boundary. This method also applies to the $n$-dimensional generalization of the Hartogs triangle.
Weighted Bergman Projection on the Hartogs Triangle
Liwei Chen
Mathematics , 2014,
Abstract: We prove the $L^p$ regularity of the weighted Bergman projection on the Hartogs triangle, where the weights are powers of the distance to the singularity at the boundary. The restricted range of $p$ is proved to be sharp. By using a two-weight inequality on the upper half plane with Muckenhoupt weights, we can consider a slightly wider class of weights.
Research on Lorry Road User Charging Scheme
Chao Sui,Chen Liwei
Research Journal of Applied Sciences, Engineering and Technology , 2012,
Abstract: In the 2011-2015 Business Plan, a lorry road user charging scheme has been planned to implement by the Coalition Government by 2014. This study will describe the possible impacts of such a system on the road haulage sector and the ways in which logistics providers might utilize different operating practices and technology to improve their operational performance under such circumstances in the UK. And this essay will cover the possible uses for Intelligent Transport Systems and new working practices using specific case study examples. Finally, the impacts of LRUC and several feasible countermeasures will be discussed in the following text.
The Transformer Equipment Selection’s Update Decision Technical and Economic Analysis Model  [PDF]
Jincheng Shang, Zhongfu Tan, Chen Zhang, Liwei Ju
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B027
Abstract: Based on the current situation of the domestic transformer equipment selection, the paper analyses the SH15, S11 and S9 transformer from the angles of annual running power consumption, payback period, energy efficiency of the transformer, furthermore, determine the best optimal capacity, load factor and update Year of the SH15-type transformers. Example analysis results show that, from the point of view of the technical and economic the SH15-type transformer has better economic and environmental benefits, and large capacity SH15 transformer better comprehensive benefits.
Morphological Development of Sambong (Blumea balsamifera (L.) DC.) Leaf Studied by Frozen Section and Thin Section  [PDF]
Liwei Liu, Xiaolu Chen, Quan Yang, Yuxin Pang
Journal of Biosciences and Medicines (JBM) , 2016, DOI: 10.4236/jbm.2016.44002
Abstract:

The sambong (Blumea balsamifera (L.) DC.) leaf was investigated by applying frozen section and thin section technology, and observed through optical microscope. The results showed that the sambong leaf was firstly originated nearby the apical bud at the stem tip. The first leaf grows fast, that the mitosis happens frequently and the cytoplasm manufacture rapidly. The cells in the first few leaves have not yet differentiated into the spongy parenchyma and palisade parenchyma. In the mature leaf, the spongy parenchyma and palisade parenchyma were fully developed. The epidermal hairs were firstly developed on the abaxial side of the first leaf.

Engineering the Saccharomyces cerevisiae β-Oxidation Pathway to Increase Medium Chain Fatty Acid Production as Potential Biofuel
Liwei Chen, Jianhua Zhang, Wei Ning Chen
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0084853
Abstract: Fatty acid-derived biofuels and biochemicals can be produced in microbes using β-oxidation pathway engineering. In this study, the β-oxidation pathway of Saccharomyces cerevisiae was engineered to accumulate a higher ratio of medium chain fatty acids (MCFAs) when cells were grown on fatty acid-rich feedstock. For this purpose, the haploid deletion strain Δpox1 was obtained, in which the sole acyl-CoA oxidase encoded by POX1 was deleted. Next, the POX2 gene from Yarrowia lipolytica, which encodes an acyl-CoA oxidase with a preference for long chain acyl-CoAs, was expressed in the Δpox1 strain. The resulting Δpox1 [pox2+] strain exhibited a growth defect because the β-oxidation pathway was blocked in peroxisomes. To unblock the β-oxidation pathway, the gene CROT, which encodes carnitine O-octanoyltransferase, was expressed in the Δpox1 [pox2+] strain to transport the accumulated medium chain acyl-coAs out of the peroxisomes. The obtained Δpox1 [pox2+, crot+] strain grew at a normal rate. The effect of these genetic modifications on fatty acid accumulation and profile was investigated when the strains were grown on oleic acids-containing medium. It was determined that the engineered strains Δpox1 [pox2+] and Δpox1 [pox2+, crot+] had increased fatty acid accumulation and an increased ratio of MCFAs. Compared to the wild-type (WT) strain, the total fatty acid production of the strains Δpox1 [pox2+] and Δpox1 [pox2+, crot+] were increased 29.5% and 15.6%, respectively. The intracellular level of MCFAs in Δpox1 [pox2+] and Δpox1 [pox2+, crot+] increased 2.26- and 1.87-fold compared to the WT strain, respectively. In addition, MCFAs in the culture medium increased 3.29-fold and 3.34-fold compared to the WT strain. These results suggested that fatty acids with an increased MCFAs ratio accumulate in the engineered strains with a modified β-oxidation pathway. Our approach exhibits great potential for transforming low value fatty acid-rich feedstock into high value fatty acid-derived products.
Effect of Mach number on transonic flow past a circular cylinder
ChangYue Xu,LiWei Chen,XiYun Lu
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0325-x
Abstract: The effect of Mach number on transonic flow past a circular cylinder is investigated numerically for the free-stream Mach number M ∞ from 0.85 to 0.98 and the Reynolds number 2×105 based on the diameter of the cylinder. The work provides an insight into several salient features, including unsteady and quasi-steady flow state, formation of local supersonic zone, and evolution of turbulent shear layer. Results show that there exist two flow states dependent of a critical Mach number M cr around 0.9. One is an unsteady flow state characterized by moving shock waves interacting with the turbulent flow in the near region of the cylinder for M ∞M cr, suppressing vortex shedding from the cylinder. Some flow behaviors in the unsteady and quasi-steady flow states are revealed. From time evolution of flow structures, local supersonic zones are identified in the wake and generated by two typical processes, i.e. reverse flow behind the cylinder and shed vortices in the near wake. The convective Mach number M c of turbulent shear layers shed from the cylinder is identified nearly as M c<1 in the unsteady flow regime and M c>1 in the quasi-steady flow regime, resulting in different evolutions of the shear layers.
Effect of Mach number on transonic flow past a circular cylinder

ChangYue Xu,LiWei Chen,XiYun Lu,

科学通报(英文版) , 2009,
Abstract: The effect of Mach number on transonic flow past a circular cylinder is investigated numerically for the free-stream Mach number M ∞ from 0.85 to 0.98 and the Reynolds number 2×105 based on the diameter of the cylinder. The work provides an insight into several salient features, including unsteady and quasi-steady flow state, formation of local supersonic zone, and evolution of turbulent shear layer. Results show that there exist two flow states dependent of a critical Mach number M cr around 0.9. One is an unsteady flow state characterized by moving shock waves interacting with the turbulent flow in the near region of the cylinder for M ∞M cr, suppressing vortex shedding from the cylinder. Some flow behaviors in the unsteady and quasi-steady flow states are revealed. From time evolution of flow structures, local supersonic zones are identified in the wake and generated by two typical processes, i.e. reverse flow behind the cylinder and shed vortices in the near wake. The convective Mach number M c of turbulent shear layers shed from the cylinder is identified nearly as M c<1 in the unsteady flow regime and M c>1 in the quasi-steady flow regime, resulting in different evolutions of the shear layers. Supported by the National Natural Science Foundation of China (Grant Nos. 90405007, 90605005) and Science and Technology Innovative Foundation of Chinese Academy of Sciences (Grant No. CXJJ-237)
Wafer-scale graphene on 2 inch SiC with uniform structural and electrical characteristics
YuPing Jia,LiWei Guo,JingJing Lin,LianLian Chen,XiaoLong Chen
Chinese Science Bulletin , 2012, DOI: 10.1007/s11434-012-5161-8
Abstract: Wafer-scale graphene on SiC with uniform structural and electrical features is needed to realize graphene-based radio frequency devices and integrated circuits. Here, a continuous bi/trilayer of graphene with uniform structural and electrical features was grown on 2 inch 6H-SiC (0001) by etching before and after graphene growth. Optical and atomic force microscopy images indicate the surface morphology of graphene is uniform over the 2 inch wafer. Raman and transmittance spectra confirmed that its layer number was also uniform. Contactless resistance measurements indicated the average graphene sheet resistance was 720 Ω/□ with a non-uniformity of 7.2%. Large area contactless mobility measurements gave a carrier mobility of about 450 cm2/(V s) with an electron concentration of about 1.5×1013 cm 2. To our knowledge, such homogeneous morphology and resistance on wafer scale are among the best results reported for wafer-scale graphene on SiC.
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