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Now showing items 1 - 10 of 10

  • Mechanical properties of structures 3D printed with cementitious powders

    Peng Feng   Xinmiao Meng   Jian-Fei Chen   Lieping Ye  

    Graphical abstract Highlights • 3D specimens printed with cementitious materials are orthotropic. • Mechanical properties and failure depend on inter-layer and inter-strip bonds. • Stress–strain relationship and failure criterion proposed for 3D printed materials. • Behavior of 3D printed structures depends strongly on the printing direction. Abstract The three dimensional (3D) printing technology has undergone rapid development in the last few years and it is now possible to print engineering structures. This paper presents a study of the mechanical behavior of 3D printed structures using cementitious powder. Microscopic observation reveals that the 3D printed products have a layered orthotropic microstructure, in which each layer consists of parallel strips. Compression and flexural tests were conducted to determine the mechanical properties and failure characteristics of such materials. The test results confirmed that the 3D printed structures are laminated with apparent orthotropy. Based on the experimental results, a stress–strain relationship and a failure criterion based on the maximum stress criterion for orthotropic materials are proposed for the structures of 3D printed material. Finally, a finite element analysis was conducted for a 3D printed shell structure, which shows that the printing direction has a significant influence on the load bearing capacity of the structure.
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  • Large scale test of a novel back-pass non-perforated unglazed solar air collector

    Miguel A. Paya-Marin   James B.P. Lim   Jian-Fei Chen   R. Mark Lawson   Bhaskar Sen Gupta  

    Abstract This paper describes large scale tests conducted on a novel unglazed solar air collector system. The proposed system, referred to as a back-pass solar collector (BPSC), has on-site installation and aesthetic advantages over conventional unglazed transpired solar collectors (UTSC) as it is fully integrated within a standard insulated wall panel. This paper presents the results obtained from monitoring a BPSC wall panel over one year. Measurements of temperature, wind velocity and solar irradiance were taken at multiple air mass flow rates. It is shown that the length of the collector cavities has a direct impact on the efficiency of the system. It is also shown that beyond a height-to-flow ratio of 0.023 m/m³/hr/m 2 , no additional heat output is obtained by increasing the collector height for the experimental setup in this study, but these numbers would obviously be different if the experimental setup or test environment (e.g. location and climate) change. An equation for predicting the temperature rise of the BPSC is proposed. Graphical abstract Highlights • A back-pass solar collector (BPSC) wall panel monitored over one year. • Temperature, wind velocity and solar irradiance measured at multiple flow rates. • The length of the collector cavities directly affects the efficiency of the system. • Above a certain height-to-flow ratio no further heat output by longer collector. • A model for predicting the temperature rise of the BPSC is proposed.
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  • A comparative case study of cultivated land changes in Fujian and Taiwan

    Jian-fei Chen   Su-qiong Wei   Kang-tsung Chang   Bor-wen Tsai  

    In this study we chose Fujian and Taiwan for a comparative case study of cultivated land changes. Separated by a short strait, these two regions are similar in biophysical and cultural characteristics but differ in the level of economic development. Taiwan is ahead of Fujian by 15 to 20 years in economic development. We compared quantitative and qualitative changes of cultivated land in these two regions, and analyzed the proximate causes and the driving forces for cultivated land changes over time. The study showed a time lag, similar to that of economic development, in the dynamic (i.e., greater rates of change) period of cultivated land changes and the ranking of major driving forces. The results suggest that similar land-use changes can occur in different regions as the regions pass through comparable stages of economic development at different times.
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  • A comparative case study of cultivated land changes in Fujian and Taiwan

    Jian-fei Chen   Su-qiong Wei   Kang-tsung Chang    Bor-wen Tsai  

    In this study we chose Fujian and Taiwan for a comparative case study of cultivated land changes. Separated by a short strait, these two regions are similar in biophysical and cultural characteristics but differ in the level of economic development. Taiwan is ahead of Fujian by 15 to 20 years in economic development. We compared quantitative and qualitative changes of cultivated land in these two regions, and analyzed the proximate causes and the driving forces for cultivated land changes over time. The study showed a time lag, similar to that of economic development, in the dynamic (i.e., greater rates of change) period of cultivated land changes and the ranking of major driving forces. The results suggest that similar land-use changes can occur in different regions as the regions pass through comparable stages of economic development at different times.
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  • Anti-atherosclerotic effect of hesperidin in LDLr−/− mice and its possible mechanism

    Ye-Zi Sun   Jian-Fei Chen   Li-Min Shen   Ji Zhou   Cui-Fang Wang  

    Abstract Hesperidin, a citrus bioflavonoid, exerts numerous pharmacological activities. However, its protective effect against atherosclerosis in vivo remains poorly understood. In the present study, we aimed to observe the effects of hesperidin on high fat diet (HFD)-induced atherosclerosis using LDL receptor deficient (LDLr -/- ) mice. After 12 weeks of treatment, the animals were sacrificed. The blood samples were collected for further analysis. Mouse peritoneal macrophages were collected. Hepatic lipid content, quantification of atherosclerosis, assessment of oxidative stress and inflammation, gene expressions were performed on liver and aorta samples. The data showed that hesperidin ameliorated HFD-induced weight gain, improved insulin resistance and ameliorated hyperlipidemia. Hesperidin suppressed HFD-induced hepatic steatosis, atherosclerotic plaque area and macrophage foam cell formation. Further study showed that hesperidin down-regulated expressions of acetyl coenzyme A carboxylase alpha (ACCα) and fatty acid synthase (FAS) which are two key enzymes in fatty acid and triglyceride synthesis in liver; and upregulated expression of hepatic ATP-binding cassette transporters G8 (ABCG8), macrophage ATP-binding cassette transporters A1 (ABCA1) and G1 (ABCG1) which are transporters involved in the process of reverse cholesterol transport. Hesperidin also reduced oxidative stress by normalizing activities of antioxidant enzymes and inflammation in HFD-fed LDLr −/− mice. These findings suggest that hesperidin reduced atherosclerosis via its pleiotropic effects, including improvement of insulin resistance, amelioration of lipid profiles, inhibition of macrophage foam cell formation, anti-oxidative effect and anti-inflammatory action.
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  • Buckling of compound hyperbolic paraboloidal shells

    Jian-Fei Chen   Zheng-An Xu  

    Presents the first elastic buckling analysis of a compound hyperbolic paraboloidal (hypar) shell under a uniformly distributed load. The compound shell is composed of four hypar panels of rectangular ground plan. A special feature of this analysis is the use of the pulse junction to deal with the curvature discontinuities at the ridges. The stability-governing equations are derived from the general equations of Reissner for the linear elastic buckling of hyperbolic paraboloidal shells, taking into account the curvature discontinuities at the ridges. These equations are then solved in an approximate manner by assuming trigonometric variations of the buckling deformations. Numerical results are presented, which show that the buckling modes of the shell are either symmetrical or antisymmetrical about both axes of symmetry. For antisymmetric buckling the critical load of the compound shell is the same as that for a single hypar panel
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  • Molecular characterization and phylogenetic analysis of membrane protein genes of porcine epidemic diarrhea virus isolates in China

    Jian-Fei Chen   Dong-Bo Sun   Cheng-Bao Wang   Hong-Yan Shi   Xiao-Chen Cui   Sheng-Wang Liu   Hua-Ji Qiu   Li Feng  

    Six porcine epidemic diarrhea viruses (PEDVs) were isolated from the fecal samples of piglets infected with PEDV in 2006 in China. The membrane (M) protein genes of six PEDV isolates were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR), then cloned, sequenced, and compared with each other as well as those ten PEDV reference strains. The M protein genes of six Chinese PEDV isolates consisted of 692 nucleotides containing a single open reading frame (ORF) of 681 nucleotides, which encoded a 226aa-long peptide. The conserved intergenic motif (ATAAAC), as previously recognized in Br1/87, was found in the 5 nucleotides upstream of the initiator ATG of M protein genes of six Chinese PEDV isolates. The hexamer motif was also found in CV777, JMe2, LZC, and QH. The M protein of six isolates had three main transmembrane domains (aa20–38, aa43–65, aa75–97). The M protein of one isolate, CH/IMT/06, had one potential glycosylation site, but those of the other five isolates had two. The glycosylation sequence Asn-Phe-Thr was highly conserved in the M proteins of six PEDV isolates. The six PEDV isolates showed nucleotide sequence homology between 98.8 and 100%and deduced amino acid sequence homology between 98.2 and 100%with each other. The nucleotide and amino acid identity of M protein genes between the six PEDV isolates and ten reference PEDV strains varied from 97.2 to 99.4%and 96.9 to 100%, respectively. On the basis of the phylogenetic relationship of M protein genes, six Chinese PEDV isolates composed of a separate cluster including one Chinese strain JS-2004-02, however, not including the Chinese strain LJB/03. These results demonstrated that there was a new genotype of PEDV prevailing in China.
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  • Molecular characterization and phylogenetic analysis of membrane protein genes of porcine epidemic diarrhea virus isolates in China

    Jian-Fei Chen   Dong-Bo Sun   Cheng-Bao Wang   Hong-Yan Shi   Xiao-Chen Cui   Sheng-Wang Liu   Hua-Ji Qiu and Li Feng  

    Six porcine epidemic diarrhea viruses (PEDVs) were isolated from the fecal samples of piglets infected with PEDV in 2006 in China. The membrane (M) protein genes of six PEDV isolates were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR), then cloned, sequenced, and compared with each other as well as those ten PEDV reference strains. The M protein genes of six Chinese PEDV isolates consisted of 692 nucleotides containing a single open reading frame (ORF) of 681 nucleotides, which encoded a 226aa-long peptide. The conserved intergenic motif (ATAAAC), as previously recognized in Br1/87, was found in the 5 nucleotides upstream of the initiator ATG of M protein genes of six Chinese PEDV isolates. The hexamer motif was also found in CV777, JMe2, LZC, and QH. The M protein of six isolates had three main transmembrane domains (aa20–38, aa43–65, aa75–97). The M protein of one isolate, CH/IMT/06, had one potential glycosylation site, but those of the other five isolates had two. The glycosylation sequence Asn-Phe-Thr was highly conserved in the M proteins of six PEDV isolates. The six PEDV isolates showed nucleotide sequence homology between 98.8 and 100%and deduced amino acid sequence homology between 98.2 and 100%with each other. The nucleotide and amino acid identity of M protein genes between the six PEDV isolates and ten reference PEDV strains varied from 97.2 to 99.4%and 96.9 to 100%, respectively. On the basis of the phylogenetic relationship of M protein genes, six Chinese PEDV isolates composed of a separate cluster including one Chinese strain JS-2004-02, however, not including the Chinese strain LJB/03. These results demonstrated that there was a new genotype of PEDV prevailing in China.
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  • An essential role for stromal interaction molecule 1 in neointima formation following arterial injury.

    Rui-wei Guo   Hong Wang   Pan Gao   Mao-Quan Li   Chun-yu Zeng   Yang Yu   Jian-fei Chen   Ming-bao Song   Yan-kun Shi   Lan Huang  

    AIMS There is evidence to suggest that stromal interaction molecule 1 (STIM1) functions as a Ca2+ sensor on the endoplasmic reticulum, leading to transduction of signals to the plasma membrane and opening of store-operated Ca2+ channels (SOC). SOC have been detected in vascular smooth muscle cells (VSMCs) and are thought to have an essential role in the regulation of contraction and cell proliferation. We hypothesized that knockdown of STIM1 inhibits VSMC proliferation and suppresses neointimal hyperplasia. METHODS AND RESULTS We examined the effect of the knockdown of STIM1 using a rat balloon injury model and cultured rat aortic VSMCs. Interestingly, knockdown of rat STIM1 by adenovirus delivery of small interfering RNA (siRNA) significantly suppressed neointimal hyperplasia in a rat carotid artery balloon injury model at 14 days after injury. The re-expression of human STIM1 to smooth muscle reversed the effect of STIM1 knockdown on neointimal formation. Rat aortic VSMCs were used for the in vitro assays. Knockdown of endogenous STIM1 significantly inhibited proliferation and migration of VSMCs. Moreover, STIM1 knockdown induced cell-cycle arrest in G0/G1 and resulted in a marked decrease in SOC. Replenishment with recombinant human STIM1 reversed the effect of siRNA knockdown. These results suggest STIM1 has a critical role in neointimal formation in a rat model of vascular injury. CONCLUSION STIM1 may represent a novel therapeutic target in the prevention of restenosis after vascular interventions.
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  • Epidemiology and vaccine of porcine epidemic diarrhea virus in China: a mini-review.

    Dongbo Sun   Xinyu Wang   Shan Wei   Jian-fei Chen   Li Feng  

    Porcine epidemic diarrhea (PED) is an intestinal infectious disease caused by porcine epidemic diarrhea virus (PEDV); manifestations of the disease are diarrhea, vomiting and dehydration. Starting from the end of 2010, a PED outbreak occurred in several pig-producing provinces in southern China. Subsequently, the disease spread throughout the country and caused enormous economic losses to the pork industry. Accumulating studies demonstrated that new PEDV variants that appeared in China were responsible for the PED outbreak. In the current mini-review, we summarize PEDV epidemiology and vaccination in China.
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