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Now showing items 1 - 9 of 9

  • Dynamics analysis of space robot manipulator with joint clearance

    Yang Zhaoa   Zheng Feng Bai  

    A computational methodology for analysis of space robot manipulator systems, considering the effects of the clearances in the joint, is presented. The contact dynamics model in joint clearance is established using the nonlinear equivalent spring-damp model and the friction effect is considered using the Coulomb friction model. The space robot system dynamic equation of manipulator with clearance is established. Then the dynamics simulation is presented and the dynamics characteristics of robot manipulator with clearance are analyzed. This work provides a practical method to analyze the dynamics characteristics of space robot manipulator with joint clearance and improves the engineering application. The computational methodology can predict the effects of clearance on space robot manipulator preferably, which is the basis of space robot manipulator design, precision analysis and ground test.
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  • Synthesis and photo activity of flower-like anatase TiO2 with {001} facets exposed

    Yang Zhaoa   Qidong Zhaoa   Xinyong Lia   Yang Houa   Xuejun Zoua   Jingjing Wanga   Tengfei Jiangb   Tengfeng Xieb  

    Developing photocatalysts with specific morphology promises good opportunities to discover the geometry-dependent properties. Herein, flower-like anatase TiO2 assemblies with dominant {001} facets exposed were successfully synthesized via a simple, economical hydrothermal route with titanium sulfate and hydrofluoric acid. Their surface morphology and structure were investigated by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, and Brunauer鈥揈mmet鈥揟eller N2 gas adsorption鈥揹esorption isotherms. The optical property and the photo-induced charge carriers of the flower-like TiO2 were studied by UV鈥搗is diffuse reflectance spectroscopy and transient photovoltage technique. The flower-like TiO2 particles exhibited a good photocatalytic activity in degrading rhodamine B.
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  • Completed robust local binary pattern for texture classification

    Yang Zhaoa   bAuthor Vitae   Wei Jiac   Rong-Xiang HucAuthor Vitae   Hai Mina   bAuthor Vitae  

    Original Local Binary Pattern (LBP) descriptor has two obvious demerits, i.e., it is sensitive to noise, and sometimes it tends to characterize different structural patterns with the same binary code which will reduce its discriminability inevitably. In order to overcome these two demerits, this paper proposes a robust framework of LBP, named Completed Robust Local Binary Pattern (CRLBP), in which the value of each center pixel in a 3×3 local area is replaced by its average local gray level. Compared to the center gray value, average local gray level is more robust to noise and illumination variants. To make CRLBP more robust and stable, Weighted Local Gray Level (WLG) is introduced to take place of the traditional gray value of the center pixel. The experimental results obtained from four representative texture databases show that the proposed method is robust to noise and can achieve impressive classification accuracy.
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  • Tentative identification, quantitation, and principal component analysis of green pu-erh, green, and white teas using UPLC/DAD/MS

    Yang Zhaoa   Pei Chena   Longze Lina   J.M. Harnlya   Liangli (Lucy) Yuc   Zhangwan Lib  

    Tea (Camellia sinensis L.), an important drink and a natural medicine for thousands of years, contains many health beneficial compounds. Growing season, geographical region, and fermentation methods create many variations in tea compositions, which contribute to each tea’s uniqueness. In this study, a simple, rapid, and efficient ultra-performance liquid chromatography (UPLC) method combined with diode array detector (DAD) and mass spectroscopic (MS) detection and chemometrics analysis was used to analyse three different types of teas (green pu-erh, green tea, white tea). Using the developed method, 68 compounds were identified and 54 were quantified based on retention times, UV spectra, and MS spectra by referencing to available standards and data in the literatures. The results showed the chemical differences between the tested teas. Principal component analysis (PCA) was applied to classify and distinguish between tea samples.
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  • A microfluidic system enabling continuous characterization of specific membrane capacitance and cytoplasm conductivity of single cells in suspension

    Yang Zhaoa   Deyong Chena   Hao Lia   Yana Luoa   Bin Denga   Song-Bin Huangb   Tzu-Keng Chiub   Min-Hsien Wub   Rong Longc   Hao Hud   Junbo Wanga   Jian Chena  

    This paper presents a microfluidic system enabling continuous characterization of specific membrane capacitance (Cspecific membrane) and cytoplasm conductivity (σcytoplasm) of single cells in suspension. In this study, cells were aspirated continuously through a constriction channel while cell elongations and impedance profiles at two frequencies (1 kHz and 100 kHz) were measured simultaneously using microscopy imaging and a lock-in amplifier. 1 kHz impedance data were used to evaluate cellular sealing properties with constriction channel walls and 100 kHz impedance data were translated to quantify equivalent membrane capacitance and cytoplasm resistance of single cells, which were further translated to Cspecific membrane and σcytoplasm. Two model cell lines (kidney tumor cell line of 786-O (n=302) and vascular smooth muscle cell line of T2 (n=216)) were used to evaluate this technique, producing Cspecific membrane of 3.67±1.00 and 4.53±1.51 μF/cm2 and σcytoplasm of 0.47±0.09 and 0.55±0.14 S/m, respectively. Compared to previously reported techniques which can only collect Cspecific membrane and σcytoplasm from tens of cells, this new technique has a higher throughput, capable of collecting Cspecific membrane and σcytoplasm from hundreds of cells in 30 min immediately after cell passage.
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  • Chemical compositions, HPLC/MS fingerprinting profiles and radical scavenging properties of commercial Gynostemma pentaphyllum (Thunb.) Makino samples

    Yang Zhaoa   Zhuohong Xiea   Yuge Niua   Haiming Shib   Pei Chenc   Liangli (Lucy) Yua  

    Jiaogulan, Gynostemma pentaphyllum (Thunb.) Makino, is one of the well-known botanical ingredients for functional foods and beverages. The present study developed a simple, rapid and effective HPLC procedure for simultaneous quantification of rutin and quercetin in jiaogulan. This study also investigated the chemical compositions including total phenolic contents (TPC), total flavonoid contents (TFC) and total saponin contents (TSC), and HPLC/UV/MS fingerprinting profiles of eleven commercial jiaogulan samples. In addition, the scavenging capacities against 2,2-diphenyl-1-picryhydrazyl (DPPH) and hydroxyl (HOSC) radicals were studied. The eleven jiaogulan samples had a TPC of 1.4-35.1 mg/g for MeOH and 6.3-52.3 mg/g for 50% acetone extracts; they had a TFC of 1.7-25.5 mg/g for MeOH and 3.8-50.3 mg/g for 50% acetone; and they had a TSC of 17.6-193.4 mg/g for MeOH and 24.9-681.2 mg/g for 50% acetone. The RDSC of these samples had a range of 5.7-148.7 μmol/g for MeOH and 33.6-416.8 μmol/g for 50% acetone extracts. The HOSC of these samples had a range of 122.1-1618.3 μmol/g for MeOH and 223.7-4113.0 μmol/g for 50% acetone extracts. In addition, quercetin-di-(rhamno)-hexoside, kaempferol 3-O-di-p-coumaroylhexoside, kaempferol 3-O-di-p-coumaroylhexoside, quercetin-rhamno-hexoside, rutin, kaempferol-rhamno-hexoside, kaempferol-3-O-rutinoside, quercetin and kaempferol were identified in the jiaogulan samples. Principle component analysis (PCA) classified the eleven jiaogulan samples into three groups. These results suggested the possible variation of commercial jiaogulan products in their chemical compositions and health properties, and a need of improved quality control and assurance mechanism.
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  • Synthesis of robust and high-performance aquaporin-based biomimetic membranes by interfacial polymerization-membrane preparation and RO performance characterization

    Yang Zhaoa   Changquan Qiua   Xuesong Lia   Ardcharaporn Vararattanavecha   Wenming Shena   Jaume Torresa   Claus Hélix-Nielsene   Rong Wanga   Xiao Hua   Anthony G. Fanea   Chuyang Y. Tanga  

    Aquaporins are water channel proteins with excellent water permeability and solute rejection, which makes them promising for preparing high-performance biomimetic membranes. Despite the growing interest in aquaporin-based biomimetic membranes (ABMs), it is challenging to produce robust and defect-free ABMs that can be easily scaled up. In the current study, a thin film composite (TFC) ABM was prepared by the interfacial polymerization method, where AquaporinZ-containing proteoliposomes were added to the m-phenylene-diamine aqueous solution. Control membranes, either without aquaporins or with inactive (mutant) aquaporins, were also similarly prepared. The separation performance of these membranes was evaluated by cross-flow reverse osmosis (RO) tests. Compared to the controls, the active ABM achieved significantly higher water permeability (? L/m2 h bar) with comparable NaCl rejection (?7%) at an applied pressure of 5 bar. Its permeability was ?0% higher compared to a commercial brackish water RO membrane (BW30) and an order of magnitude higher compared to a seawater RO membrane (SW30HR), which clearly demonstrates the great potential of the TFC ABM for desalination applications.
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  • Does obesity amplify the association between ambient air pollution and increased blood pressure and hypertension in adults? Findings from the 33 Communities Chinese Health Study

    Yang Zhaoa   Zhengmin (Min) Qianb   Jing Wangc   Michael G Vaughnd   Yu-Qin Liua   Wan-Hui Rene   Guang-Hui Donga  

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  • Microstructure and mechanical properties of polypropylene/poly (ethylene-co-octene copolymer)/clay ternary nanocomposites prepared by melt blending using supercritical carbon dioxide as a processing aid

    Feng-hua Su   Han-xiong Huanga   Yang Zhaoa  

    To improve the mechanical properties of polypropylene (PP), poly (ethylene-co-octene copolymer) (PEOc) and clay particles were incorporated by melt blending with the aid of supercritical carbon dioxide. Results from X-ray diffraction, electron microscopy, and rheology show that using sc-CO2 makes the clay layers mainly intercalated by polymer chains and well exfoliate in the nanocomposites relative to direct melt blending. This leads to a three-dimensional network structure formed in the nanocomposites as confirmed by rheology. Evidences from scanning electron microscope (SEM) indicate most of clay particles are mainly localized close to or inside the PEOc phase and others disperse separately in the PP phase. The incorporation of PEOc and clay significantly improve the impact strength of PP without the expense of lowering PP’s stiffness and strength. The use of sc-CO2 or PP-g-MA during melt-compounding can further improve the mechanical properties of the ternary nanocomposites. Compared to PP-g-MA, sc-CO2 is more favorable for dispersing clay in PP/PEOc blend and improving the mechanical properties of the nanocomposites.
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