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Qin Y.,Tianjin UniversityTianjin | Zhang X.,Tianjin UniversityTianjin | Wang Y.,Tianjin UniversityTianjin | Liu Y.,Tianjin UniversityTianjin
Sensors and Actuators, B: Chemical | Year: 2017

For gas sensor applications, a unique heterostructure array of W18O49/TiO2 core-shell nanowires with high alignment and uniform shell layer were fabricated by thermal oxidation of W film followed by sputter deposition and annealing of TiO2. The ordering of the rough aligned W18O49–core nanowires formed from thermal oxidation of metallic W film is found to be modulated considerably by the sputter deposition of shell layer. Thicker shell results in better alignment. The gas-sensing characteristics of the as-prepared W18O49/TiO2 nanowire sensor are evaluated at room temperature to 150 °C by measuring the dynamic response over NO2 concentration ranging from 0.5 to 5 ppm. The W18O49/TiO2 core-shell nanowires show temperature-dependent p-n response characteristic reversal. At room temperature, it behaves as an abnormal p-type semiconductor and exhibits good NO2-sensing performances including high sensitivity, good selectivity and excellent dynamic response-recovery characteristics. It is found that, with improved alignment, the heteronanowires array responses to sub-ppm level of NO2 with ultrafast response and recovery rate at room temperature. The measured response times are shorter than 5 s and the sensor can be recovered completely within 50s. The underlying gas-sensing mechanism correlated to the p-type response inversion at room temperature is analyzed in detail. © 2016 Elsevier B.V.

Shang Z.,Missouri University of Science and Technology | Li S.,Gas Technology Institute | Li L.,Tianjin UniversityTianjin | Liu G.,Tianjin UniversityTianjin | Liang X.,Missouri University of Science and Technology
Applied Catalysis B: Environmental | Year: 2017

A highly stable and extremely active nickel (Ni) nanoparticle catalyst, supported on porous γ-Al2O3 particles, was prepared by atomic layer deposition (ALD). The catalyst was employed to catalyze the reaction of dry reforming of methane (DRM). The catalyst initially gave a low conversion at 850 °C, but the conversion increased with an increase in reaction time, and stabilized at 93% (1730 L h−1 g Ni −1 at 850 °C). After regeneration, the catalyst showed a very high methane reforming rate (1840 L h−1 g Ni −1 at 850 °C). The activated catalyst showed exceptionally high catalytic activity and excellent stability of DRM reaction in over 300 h at temperatures that ranged from 700 °C to 850 °C. The excellent stability of the catalyst resulted from the formation of NiAl2O4 spinel. The high catalytic activity was due to the high dispersion of Ni nanoparticles deposited by ALD and the reduction of NiAl2O4 spinel to Ni during the DRM reaction at 850 °C. It was verified that NiAl2O4 can be reduced to Ni in a reductive gas mixture (i.e., carbon monoxide and hydrogen) during the reaction at 850 °C, but not by H2 alone. © 2016 Elsevier B.V.

Zhen X.,Tianjin University of Technology | Wang Y.,Tianjin UniversityTianjin
Renewable and Sustainable Energy Reviews | Year: 2015

Abstract Methanol is an alternative, renewable, environmentally and economically attractive fuel; it is considered to be one of the most favorable fuels for conventional fossil-based fuels. Methanol has been recently used as an alternative to conventional fuels for internal combustion (IC) engines in order to satisfy some environmental and economical concerns. Because of a number of relatively large research projects that have been ongoing recently, much progress has been made that is worth reporting. This paper systematically describes the methanol productions, including the productions from coal, natural gas, coke-oven gas, hydrogen, biomass etc. It introduces the potentials of methanol as a renewable resource taking into account the world supply and demand, economic benefits and the effects on human health and the environment. Thirteen methods of application such as methanol/gasoline, methanol/diesel blends which can be used on the IC engines are summarized. Finally, this paper puts forward some new suggestions on the weakness in the researches of methanol engine. © 2015 Elsevier Ltd.

Cui X.-P.,CAS Institute of Chemistry | Cui X.-P.,Tianjin UniversityTianjin | Jiang K.-J.,CAS Institute of Chemistry | Huang J.-H.,CAS Institute of Chemistry | And 8 more authors.
Chemical Communications | Year: 2015

The perovskite CH3NH3PbI3 was prepared on a mesoscopic TiO2 film, starting from electrodepositing PbO, to iodination to PbI2, and then interdiffusion reaction with CH3NH3I. The as-prepared film was used as a light absorber for the perovskite solar cells, exhibiting a high PCE of 12.5% under standard AM 1.5 conditions. This journal is © The Royal Society of Chemistry.

Liu M.,Tianjin UniversityTianjin | Liu H.,Tianjin UniversityTianjin | Liu H.,Shanghai JiaoTong University | Zhang R.,Tianjin UniversityTianjin
Ocean Engineering | Year: 2015

Abstract Solid particle erosion in pipelines is a severe problem involved in hydrocarbon transportation and hence an important topic in flow assurance. A simplified CFD-based procedure is proposed to calculate the penetration rates in elbows for annular flow. This new method overcomes the disadvantages of current empirical or semi-empirical models. The procedure consists of three main sections: flow modeling, particle tracking, and penetration calculation. The k-ε model is employed to analyze the flow field in the core area of the pipe based on the assumption that the gas-liquid interface is regarded as an actual pipe wall. Then a Lagrangian method is adopted to track trajectories of the entrained droplets and sand particles in the core area, and the velocity decay of sand particles across the liquid film is calculated combined with the film thickness correlation. Based on the knowledge of the flow field and the particle motion, penetration rates are calculated by introducing the solid particle erosion equation. By comparing with experimental data available from the literature, the new method is proved to be reasonable in simplifying the simulation of annular flow field and shows good accuracy in erosion prediction. A better agreement between predicted erosion rates and experimental data can be made when applied to larger curvature radius elbows. © 2015 Elsevier Ltd.

Zhang P.,Tianjin UniversityTianjin | Zhao Y.,Tianjin UniversityTianjin | Wu H.,University of Jinan | Wang X.,Tianjin UniversityTianjin
Journal of Alloys and Compounds | Year: 2015

Abstract (Nd0.97Mn0.045)1.02Nb0.988O4 ceramics based on La3+ substitution were prepared via a conventional solid-state reaction method. The effects of La3+ substitution for Nd3+ on microwave dielectric properties of the (Nd0.97Mn0.045)1.02Nb0.988O4 ceramics were investigated. The X-ray patterns showed that the specimens presented single NdNbO4 phase with the monoclinic fergusonite structure in the range of x = 0.0-0.05, with a further increase of the amount of substitution ions, LaNb7O19 phase appeared in this system. For the main phase, the increase of dielectric constant could be attributed to the increase in the Nd-site bond ionicity. The Q × f value and τf value were correlated to lattice energy and bond energy, respectively. Moreover, at 1250 °C, the ((Nd0.97Mn0.045)1-xLax)1.02Nb0.988O4 ceramics with x = 0.05 possessed excellent microwave dielectric properties: εr = 21.93, Q × f = 66 700 GHz and τf = -1.08 ppm/°C. © 2015 Elsevier B.V.

Niu S.,Tsinghua University | Lv W.,Tsinghua University | Zhang C.,Tianjin UniversityTianjin | Shi Y.,Tsinghua University | And 5 more authors.
Journal of Power Sources | Year: 2015

Abstract A graphene/carbon nanotube (CNT)/sulfur (denoted GCS) hybrid with interconnected structure is prepared through a one-pot self-assembly approach initiated by l-ascorbic acid reduction under a mild condition. In such a solution-based assembly process, the formation of an interconnected graphene/CNT conductive network is accompanied by the uniform loading of sulfur, whose fraction is as high as of 70 wt%. The as-prepared GCS hybrid delivers an initial capacity of 1008 mAh g-1 at 0.3C and maintains 704 mAh g-1 after 100 cycles. Remarkably, at a high rate of 1.0C, the cathode shows an excellent cyclic performance with a capacity of 657 mAh g-1 after 450 ycles and the capacity decay is only 0.04% per cycle. Moreover, the superior rate performance of GCS hybrid is attributed to the conductive network formed by interconnected graphene sheets and CNT, which supply an unimpeded and continuous path for electron and Li ion transfer and accommodate the volume variation of sulfur during charge/discharge cycling. In addition, the residual functional groups on GCS can retain intimate contact of the conducting matrix with sulfur and effectively confine the diffusion of polysulfides. This study gives an eco-friendly and highly effective solution-based approach for carbon-sulfur electrode for lithium-sulfur battery. © 2015 Elsevier B.V.

Li J.,HIGH-TECH | Liu S.,Tianjin UniversityTianjin | Wang J.,HIGH-TECH | Liu D.,Yunnan Academy of Agricultural Sciences | And 2 more authors.
Journal of Biotechnology | Year: 2016

In this work, we selected three fungi strains (Aspergillus niger, Aspergillus flavus and Aspergillus oryzae) as elicitors prepared from mycelium or fermentation broth to improve ginsenosides production in adventitious roots culture. The results showed that ginsenosides production (29.90 ± 4.67 mg g−1) was significantly enhanced upon elicitation with 200 mg L−1 A. niger elicitor prepared from mycelium, which was 3.52-fold of untreated group. HPLC-ESI–MSn analysis was performed, showing that ginsenoside Rb3 was present after treatment with the A. niger. Furthermore, we found that A. niger significantly enhanced accumulation of Nitric oxide (NO), salicylic acid (SA) and jasmonic acid (JA) involved in plant defense response, and significantly up-regulated the expression of the geranyl diphosphate synthase (GPS), farnesyl diphosphate synthase (FPS), squalene synthase (SS), squalene epoxidase (SE), dammarenediol synthase (DS), Two cytochrome P450 (CYP) genes (CYP716A47 and CYP716A53v2) and three UDP-glycosyltransferases (UGT) genes (UGTAE2, UGT94Q2 and UGTpg100). © 2016 Elsevier B.V.

Zhu N.,Tianjin UniversityTianjin | Wang J.,Tianjin UniversityTianjin | Liu L.,Tianjin UniversityTianjin
Energy Conversion and Management | Year: 2015

Abstract The COP (Coefficient of Performance) of the ground-source heat pump (GSHP) system decreased gradually year after year mainly caused by imbalance of thermal energy inputting, especially in heating-dominated climate zones. An experimental system of solar seasonal storage coupling with ground-source heat pump was designed and implemented. This system was installed in a group of new buildings of the new campus in Tianjin, China, which is located in cold climate zone and heat demand is dominated. To make evaluation to this system, a mathematical method was developed to calculate the COP of GSHP system and the coupled system. In this thermal storage experiment process, a system with 1500 m2 solar thermal collectors and 580 sets of 120 m deep ground thermal exchangers was involved in this research. Results show that the soil temperature has not descended but increased by 0.21°C, and the COP of system and heat pump unit increased 3.4% and 2.4% respectively compared to the operation data without solar seasonal storage process during last year. Although the effectiveness of solar seasonal storage coupled is not conspicuous as expected during the testing period, it indicates that the tendency of COP declination is prevented, and further illustrating that improving the COP of the system is a long-term work, the application of solar seasonal storage coupled with GSHP system should be encouraged for long-term operation. © 2015 Elsevier Ltd.

Wang Z.,Tianjin UniversityTianjin | Huachen Z.,Tianjin UniversityTianjin | Liu H.,Tianjin UniversityTianjin | Bu Y.,Imperial College London
Ocean Engineering | Year: 2015

Abstract Upheaval buckling is one of the most common problems threatening the safe operation of subsea pipelines, which is trigged by the increasing of temperature and inner pressure. In order to predict the critical buckling temperature and post buckling path of upheaval buckling, ABAQUS is used to build four kinds of numerical models, and they are static and dynamic models both in 2D and 3D. Two analysis procedures which combine the static and dynamic processes are applied to aforementioned models. The results show good agreement with existing test data. For snap upheaval buckling, pipelines have two different buckling modes. Such buckling modes are not found in experiments. In addition, only 3D dynamic model can catch such buckling modes. For bifurcation upheaval buckling, predicted buckling temperatures of those models are all acceptable with an error of 5%. © 2015 Elsevier Ltd.

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