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.
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.
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.
Zhang C.,Tianjin UniversityTianjin |
Tao Z.,Tianjin UniversityTianjin |
Wei X.,Tianjin UniversityTianjin |
Cao X.,Tianjin UniversityTianjin |
Cao X.,Institute of Information Security
Pattern Recognition Letters | Year: 2015
Abstract For most of the data analysis tasks (e.g. visual saliency detection), there are usually plenty of candidate methods to be selected. However, it is very difficult to choose a proper one for new instances, especially when the performances of these methods are with little difference overall. Though aggregation strategy aims to take advantage of the different methods, it often has the following weaknesses. Firstly, these methods often tend to combine the results from these candidate methods. Therefore, they suffer from high computation cost. Secondly, the performance may significantly degrade when there are obviously poor results. To address the two limitations above, we propose an instance-aware method selection approach which aims to select a single method instead of aggregating the results of all candidate ones. The proposed approach is based on the following observations: different methods often perform differently and the performance of a method often varies with respect to different instances. Hence, we devise the method selection manner to adaptively choose the best method for a specific instance. We transform the method selection problem into a multi-label annotation problem, which makes it general for many applications and flexible to employ metric learning technique. © 2015 Elsevier B.V.
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.