Effect of annealing atmosphere on the structure and dielectric properties of unfilled tungsten bronze ceramics Ba4PrFe0.5Nb9.5O30

Unfilled tungsten bronze ceramics with the nominal formula Ba₄PrFe_0.5Nb_9.5O₃₀ were synthesized via the standard solid-state sintering route, and the effects of oxygen vacancies on the dielectric and electrical properties were investigated in addition to the structure. Room-temperature X-ray diffraction showed that the N₂-annealed sample had the largest cell volume. Low-temperature spectrum showed that N₂ annealing rendered the dielectric constant and dielectric loss more frequency dispersive, whereas O₂ annealing inhibited the frequency dispersion. The dc conductivity of all the samples originated from the electrons produced in the second ionization of oxygen vacancies and was most likely controlled by a mixed conduction mechanism of the electron and oxygen-vacancy ions. The N₂-annealed sample has the highest dc conductivity owing to its high concentration of oxygen vacancies. The broadening of the Raman lines and the decrease of Raman intensity for the N₂-annealed sample originated from a significant structural disorder. X-ray photoelectron spectra demonstrated that the increased oxygen vacancies caused by the change of valences of Fe and Pr ions contributed to the structural disorder.     

Synthesis of N-doped mesoporous carbons under different carbonization temperature and their application in supercapacitors

We have synthesized N-doped mesoporous carbon by the in-suit doping template method under the carbonized temperature of 900?°C. We found that the electrochemical performance of mesoporous carbon was enhanced by N-doping. So, we tried to increase the content of nitrogen to further optimize the electrochemical performance of the mesoporous carbon as electrode materials. During the process of synthesizing mesoporous carbon, the carbonized temperature played an important role in the formation of the carbon structure and its morphology, as well as in determining the content of nitrogen. We attained a considerable electrochemical performance enhancement by changing the carbonized temperature from 900 to 700?°C. We found the content of Nitrogen decreased with the increase of the carbonized temperature and the content of Nitrogen is 6.11% at 700?°C, 5.39% at 800?°C, 3.9% at 900?°C, respectively. The best electrochemical performance was observed in the product carbonized at 700?°C, which exhibited high specific capacitance (245.6 F/g at 0.5 A/g) and good cycle ability (more than 90% of the initial capacitance after 5000 cycles) in 6 M KOH electrolyte.     

User idea implementation in open innovation communities: Evidence from a new product development crowdsourcing community

In collaborative crowdsourcing communities for open innovation, users generate and submit ideas as idea co‐creators. Firms then select and implement valuable ideas for new product development. Despite the popularity and success of these open innovation communities, relatively little is known about the factors that determine the implementation of the user‐generated ideas. Based on research on individual creativity, we propose a conceptual model integrating users' previous experience, idea presentation characteristics and feedback valence to explain the likelihood of idea implementation. We validate our research model with a panel data analysis of 43 550 ideas submitted by 16 360 users in the MIUI new product development community hosted by Xiaomi, a large electronics manufacturing company in China. We find an inverted U‐shaped relationship between users' past successful experience and idea implementation. Furthermore, the length of ideas is positively associated with the likelihood of idea implementation. There is also an inverted U‐shaped relationship between supporting evidence and idea implementation. Finally, we demonstrate the negative effect of positive feedback and the positive effect of negative feedback on idea implementation. These findings offer rich insights to understand the phenomenon of open innovation better. Theoretical and practical implications are discussed.     

An airlight estimation method for image dehazing based on gray projection

Multimedia Tools and Applications - As the key parameter of dehazing algorithms, airlight value directly affect the calculation accuracy of sky region, and any deviation will lead to the chromatic...     

Popularity prediction of movies: from statistical modeling to machine learning techniques

Multimedia Tools and Applications - Film industries all over the world are producing several hundred movies rapidly and grabbing the attraction of people of all ages. Every movie producer is of...     

Processing capability and QoE driven optimized computation offloading scheme in vehicular fog based F-RAN

World Wide Web - The Fog Computing was proposed to extend the computing task to the network edge in lots of Internet of Things (IoT) scenario, such as Internet of Vehicle (IoV). However, the...     

A Pseudo-document-based Topical N-grams model for short texts

World Wide Web - In recent years, short text topic modeling has drawn considerable attentions from interdisciplinary researchers. Various customized topic models have been proposed to tackle the...     

Zone model predictive control for pressure management of water distribution network

In the water distribution network (WDN), although the water demand of the node is changing constantly, the water quantity and water pressure of the node need to be met at each moment. To realize energy saving and consumption reduction, it is proposed to control the nodal water head of WDN in an appropriate narrow range. The frequent large fluctuation of the water demand, which may lead the water pressure exceed the expected range, increases the difficulty of the zone control. To realize optimized WND control, a novel zone predictive control is proposed, where two switching cases are considered. The switching condition is whether there are feasible solutions to keep the pressure within the expected region over the prediction horizon. When the condition is satisfied, the controller minimizes the variation of inputs with constraints of pressure range for ensuring the tank level staying within the expected zone and obtaining optimal economic cost. When the current pressure is out of the expected region or the condition is not satisfied due to the large variation of water demand, a reference trajectory of outputs is introduced, which is combined with the inputs as an optimization variable, and the constraints of expected zone are moved from the output to the introduced reference trajectory. Through minimizing the distance between reference trajectory and output, the controller will keep the tank level from deviating too far from the expected zone and will drive the tank level rapidly into the expected zone once the tank level exceeds the expected range. An application of the proposed zone MPC to WDN in Shinan District of Shanghai is given to illustrate its effectiveness.     

镜铁山矿倾斜矿体上盘边角矿回采方案研究

镜铁山矿Ⅰ#矿体向下延伸时倾角由急倾斜变为倾斜，若继续按照急倾斜矿体的回采方式布置采切工程，将会在矿体上盘或者下盘处残留三角形边角矿，进而导致矿石损失率增大。为有效解决因矿体倾角缓化出现的三角区域矿体难以回收的问题，首先提出了脉内布置分段沿脉巷和沿矿岩边界布置分段沿脉巷两类回采方案，其中脉内布置分段沿脉巷回采方案设计了15°、30°、45° 3种不同中深孔边孔角布置方案；然后分别从中深孔施孔精度要求、中深孔施工适应性、对矿体条件适应性、生产效率等4个方面定性分析了不同回采方案的优劣性；最后整合生产效率、施工适应性、通风效果、井巷工程量、工期和成本等12个指标组成优选评价体系，采用层次分析法（Analytic Hierarchy Process，AHP）构建了倾斜矿体上盘边角矿回采方案层次分析优选模型。计算得到3种脉内布置分段沿脉巷与沿矿岩边界布置回采方案的最终评价值分别为0.213、0.201、0.198和0.388，结果表明：沿矿岩边界布置分段沿脉巷为最优回采方案。实践表明：优选出的方案在实践中取得了理想效果，经济效益显著，可满足该矿倾斜矿体上盘边角矿回采需求。研究结果可为类似开采条件矿山的边角矿回采提供有益参考。     

In-situ preparation of cross-linked hybrid anion exchange membrane of quaternized poly (styrene-b-isobutylene-b-styrene) covalently bonded with graphene

Introducing graphene into polymer matrix is an effective way to enhance performances of anion exchange membrane (AEM). However, utilizing the advantages of graphene by physical approach is limited due to the weak interface interaction between graphene and polymer matrix. Herein, we report an effective strategy to covalently bond graphene with polymer matrix to improve the interface interaction and further to improve the properties of AEM. A series of cross-linked quaternized graphene-based hybrid AEM were fabricated by covalently bonding poly (vinylbenzyl chloride) grafted graphene (GN-g-PVBC) copolymer with chloromethyl functionalized poly (styrene-b-isobutylene-b-styrene) (SIBS) through the cross-linker (N,N,N′,N′-tetramethyl-1,6-hexanediamine) by in-situ synthetic approach. The interface interaction between graphene and QSIBS is greatly enhanced according to micromorphology characterization of the hybrid membrane. The cross-linked quaternized hybrid AEM containing 0.55 wt% of GN-g-PVBC exhibits obviously improved dynamical mechanical properties (storage modulus: 418 MPa), ion conductivity (1.81 × 10² S cm^?1), methanol barrier property (5.19 × 10^?7 cm² s^?1), selectivity (3.49 × 10⁴ S s cm^?3) at 60 °C and especially a comparably excellent chemical stability to that of Nafion 115 due to the enhanced interface interaction between graphene and the polymer matrix.