Construction of MnO2 Nanowire for a High-Performance Lithium Ion Supercapacitor

Developing lithium ion capacitors possessing both brilliant energy and power density is still significant for numerous re-searchers. In this paper, we synthesized MnO2 nanowires via a simple hydrothermal process. The nanostructure MnO2 can expose more electrochemical sites and thus optimize the kinetics of Li+. Moreover, we used MnO2 nanowires (MnO2 NWs) as anode and a N-doped porous carbon (NPC) as cathode to assemble lithium ion capacitors (MnO2 NWs//NPC LIC). Compared to the traditional supercapacitor with aqueous electrolyte, the MnO2 NWs//NPC LIC exhibits a wider voltage of 0-4.2 V, which is helpful to enhance its energy and power density. Furthermore, MnO2 NWs//NPC LIC can deliver an excellent capacity of 150 mAh g-1 with an excellent energy density of 82.7 Wh kg-1 and power density of 1.05 kW kg-1. Meanwhile, a good cyclic stability of LICs with a 20% retention after 1000 times charge and discharge process proves its practical potential, indicating a good promising for the application in storage devices

Relationship between Soil Chemical and Physical Properties and Vegetation in the Latest Decade of Alpine Grasslands of Southern Qinghai, China

The Tibetan Plateau is one of the most important ecosystems in the world (Yang et al. 2009), particularly because of the global importance of its climate (Tian et al. 2008; Wang et al. 2008). Grassland ecosystems on the plateau are sensitive to global change, because the plateau is located in marginal land areas where the growth and distribution of plants depend heavily on local climatic conditions (Zhang et al. 1996). The alpine grassland of Qinghai Province in China has been traditionally used for extensive grazing by sheep and yak (Bos grunniens), but is now degraded from overgrazing. This study investigated the relationship between soil chemical and physical properties and vegetation of alpine grasslands of southern Qinghai, China

Impacts of Yongding River Ecological Restoration on the Groundwater Environment: Scenario Prediction

Reclaimed water was discharged into the Yongding River channels as ecological water. Pollutants from such water may leak into the underlying aquifer and put the groundwater environment at risk. River leakage estimation under different possible river lining conditions and the established groundwater flow and reactive solute transport model were jointly applied to investigate the impact of the ecological restoration of the Yongding River on the local groundwater environment. Scenario-based investigations were conducted since the channel reconstruction in 2009. The results show that the seepage from the Yongding River without liners can greatly raise the groundwater level. Leakage through liners constructed with geomembranes can effectively control the seepage of water and the spread of solutes in the aquifer. From June 2009 to December 2010, the leakage amount has been only 1.65 × 10 m, and the unconfined aquifer shows a negative budget of 4.55 × 10 m. The spreading extent of flow and potential pollutants increases with the amount of leakage from the river. Water management strategies, such as the South-to-North Water Diversion Project and Yongding River restoration could help alleviate the water deficit of the Yongding River alluvium fan (YRAF) by reducing groundwater exploitation and increasing groundwater recharge. The necessity of the maintenance of riverbed liners and control of the water quality of Yongding River were highlighted by the scenario analysis. The methods applied in this study could be used for reference in the other polluted rivers, especially with liner installation

A New Model Predictive Control Method for Eliminating Hydraulic Oscillation and Dynamic Hydraulic Imbalance in a Complex Chilled Water System

To enhance the energy performance of a central air-conditioning system, an effective control method for the chilled water system is always essential. However, it is a real challenge to distribute exact cooling energy to multiple terminal units in different floors via a complex chilled water network. To mitigate hydraulic imbalance in a complex chilled water system, many throttle valves and variable-speed pumps are installed, which are usually regulated by PID-based controllers. Due to the severe hydraulic coupling among the valves and pumps, the hydraulic oscillation phenomena often occur while using those feedback-based controllers. Based on a data-calibrated water distribution model which can accurately predict the hydraulic behaviors of a chilled water system, a new Model Predictive Control (MPC) method is proposed in this study. The proposed method is validated by a real-life chilled water system in a 22-floor hotel. By the proposed method, the valves and pumps can be regulated safely without any hydraulic oscillations. Simultaneously, the hydraulic imbalance among different floors is also eliminated, which can save 23.3% electricity consumption of the pumps

Evaluation of rutting resistance of Asphalt Pavements by circular road tracking test

Paper presented at the 26th Annual Southern African Transport Conference 9 - 12 July 2007 "The challenges of implementing policy?", CSIR International Convention Centre, Pretoria, South Africa. ABSTRACT: Due to the frequent premature rutting failure in asphalt pavements in Jiangsu, a province in the east of China, a research programme using the circular road-tracking test was initiated. Different asphalt pavement structures were designed and tested to determine the critical factors in the occurrence of rutting, including different aggregate gradations, binder types and combinations of layers. Results show that the middle layer of the pavement plays an important role in rutting development, and an adequate aggregate gradation of the surface layer mix is essential to achieve the desirable rutting resistance. Moreover, asphalt with high viscosity helps to reduce rutting. The environmental influence on the occurrence of rutting is also discussed in the paper, and a pavement type with high rutting resistance, which is appropriate for Jiangsu’s climate, is recommended.This paper was transferred from the original CD ROM created for this conference. The material on the CD ROM was published using Adobe Acrobat technology. The original CD ROM was produced by Document Transformation Technologies Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: [email protected] URL: http://www.doctech.co.z