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排序方式: 共有972条查询结果,搜索用时 218 毫秒
1.
Yuelong Ma Le Zhang Tianyuan Zhou Bingheng Sun Chen Hou Shunshun Yang Jin Huang Rui Wang Farida A. Selim Zhongying Wang Ming Li Hao Chen Yun Wang 《Journal of the European Ceramic Society》2021,41(4):2834-2846
Ce:Y3Al5O12 transparent ceramics (TCs) with appropriate emission light proportion and high thermal stability are significant to construct white light emitting diode devices with excellent chromaticity parameters. In this work, strategies of controlling crystal-field splitting around Ce3+ ion and doping orange-red emitting ion, were adopted to fabricate Ce:(Y,Tb)3(Al,Mn)5O12 TCs via vacuum sintering technique. Notably, 85.4 % of the room-temperature luminescence intensity of the TC was retained at 150 °C, and the color rendering index was as high as 79.8. Furthermore, a 12 nm red shift and a 16.2 % increase of full width at half maximum were achieved owing to the synergistic effects of Tb3+ and Mn2+ ions. By combining TCs with a 460 nm blue chip, a warm white light with a low correlated color temperature of 4155 K was acquired. Meanwhile, the action mechanism of Tb3+ ion and the energy transfer between Ce3+ and Mn2+ ions were verified in prepared TCs. 相似文献
2.
《Journal of the European Ceramic Society》2020,40(3):881-886
In this paper we report on the preparation and laser performance of transparent 3at.% Yb:Sc2O3 ceramics by reactive sintering of commercially available powders under vacuum followed by hot isostatic pressing (HIP). Combinations of different vacuum sintering temperatures (1650 °C and 1750 °C) and different HIP treatments (1700 °C and 1800 °C at 200 MPa) were tested in order to understand how these steps influence the microstructure and thus the optical and lasing properties of the ceramic samples. All the samples showed a good optical quality. The microstructure analysis and the laser tests showed that the vacuum pre-sintering temperature is the key factor determining the quality of the samples and the laser performances. The best values of slope efficiency i.e. ηL = 50 % and output power i.e. Pout = 6.62 W were obtained for the sample pre-sintered under vacuum at 1650 °C and hot isostatically pressed at 1800 °C. 相似文献
3.
《International Journal of Hydrogen Energy》2020,45(53):28860-28869
Developing highly active, stable and sustainable electrocatalysts for overall water splitting is of great importance to generate renewable H2 for fuel cells. Herein, we report the synthesis of electrocatalytically active, nickel foam-supported, spherical core-shell Fe-poly(tetraphenylporphyrin)/Ni-poly(tetraphenylporphyrin) microparticles (FeTPP@NiTPP/NF). We also show that FeTPP@NiTPP/NF exhibits efficient bifunctional electrocatalytic properties toward both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Electrochemical tests in KOH solution (1 M) reveal that FeTPP@NiTPP/NF electrocatalyzes the OER with 100 mA cm−2 at an overpotential of 302 mV and the HER with 10 mA cm−2 at an overpotential of 170 mV. Notably also, its catalytic performance for OER is better than that of RuO2, the benchmark OER catalyst. Although its catalytic activity for HER is slightly lower than that of Pt/C (the benchmark HER electrocatalyst), it shows greater stability than the latter during the reaction. The material also exhibits electrocatalytic activity for overall water splitting reaction at a current density of 10 mA cm−2 with a cell voltage of 1.58 V, along with a good recovery property. Additionally, the work demonstrates a new synthetic strategy to an efficient, noble metal-free-coordinated covalent organic framework (COF)-based, bifunctional electrocatalyst for water splitting. 相似文献
4.
5.
Amirah Mohammad-Sidik Jian Sun Ryoung Shin Zhizhong Song Youzheng Ning Elsa Matthus Katie A. Wilkins Julia M. Davies 《International journal of molecular sciences》2021,22(2)
Extracellular ATP (eATP) has long been established in animals as an important signalling molecule but this is less understood in plants. The identification of Arabidopsis thaliana DORN1 (Does Not Respond to Nucleotides) as the first plant eATP receptor has shown that it is fundamental to the elevation of cytosolic free Ca2+ ([Ca2+]cyt) as a possible second messenger. eATP causes other downstream responses such as increase in reactive oxygen species (ROS) and nitric oxide, plus changes in gene expression. The plasma membrane Ca2+ influx channels involved in eATP-induced [Ca2+]cyt increase remain unknown at the genetic level. Arabidopsis thaliana Annexin 1 has been found to mediate ROS-activated Ca2+ influx in root epidermis, consistent with its operating as a transport pathway. In this study, the loss of function Annexin 1 mutant was found to have impaired [Ca2+]cyt elevation in roots in response to eATP or eADP. Additionally, this annexin was implicated in modulating eATP-induced intracellular ROS accumulation in roots as well as expression of eATP-responsive genes. 相似文献
6.
Weichen Zhu Yuxuan He Minman Tong Xiaoyong Lai Shijia Liang Xu Wang Yanjuan Li Xiao Yan 《中国化学工程学报》2021,33(5):118-124
CH_4 storage associated with adsorbed natural gas(ANG) technology is an issue attracting great concern.Following the Advanced Research Project Agency-Energy(ARPA-E) targeted deliverable capacity of 315 cm~3·cm~(-3)(STP), hundreds of thousands of materials have been experimentally or theoretically evaluated,while the best results still show a 35% gap from the target. Moreover, recent theoretical research reveals that the target is beyond the possibility that real materials can be designed. To get rid of the awkward situation, we make attempts on investigating the CH_4 delivery performance under other operation conditions. Methods of raising the discharge temperature(to infinite high) or elevating the storage pressure(to 25 MPa) have been proved to show limited effectiveness. In this work, it is found that the ARPA-E target can be achieved by using a decreasing storage temperature strategy. By taking 280 Co RE(computation-ready, experimental) COFs(covalent organic frameworks) as ANG materials, when reduce the storage temperature to 190.6 K, the highest deliverable capacity can reach 392 cm~3·cm~(-3)(STP), and16.1% Co RE COFs can surpass the target. The target is also achievable when storage at 220 K. Structure performance relationships study shows strong correlation between deliverable capacity and void fraction. Hence, 120 hypothetical COFs are generated to ascertain the optimum void fraction. In addition,the performance of 2 D-COFs can be greatly enhanced by increasing the interlayer spacings, e.g. CH_4 deliverable capacity(storage at 190.6 K) of ATFG-COF can be improved from 239 to 411 cm~3·cm~(-3)(STP) when interlayer spacing is enlarged to 1.65 nm. 相似文献
7.
《Computers & Electrical Engineering》2014,40(8):276-291
This paper addresses mapping of streaming applications (such as MPEG) on multiprocessor platforms with time-division-multiplexed network-on-chip. In particular, we solve processor selection, path selection and router configuration problems. Given the complexity of these problems, state of the art approaches in this area largely rely on greedy heuristics, which do not guarantee optimality. Our approach is based on a constraint programming formulation that merges a number of steps, usually tackled in sequence in classic approaches. Thus, our method has the potential of finding optimal solutions with respect to resource usage under throughput constraints. The experimental evaluation presented in here shows that our approach is capable of exploring a range of solutions while giving the designer the opportunity to emphasize the importance of various design metrics. 相似文献
8.
《Computers & Electrical Engineering》2014,40(8):247-256
Video annotation is an important issue in video content management systems. Rapid growth of the digital video data has created a need for efficient and reasonable mechanisms that can ease the annotation process. In this paper, we propose a novel hierarchical clustering based system for video annotation. The proposed system generates a top-down hierarchy of the video streams using hierarchical k-means clustering. A tree-based structure is produced by dividing the video recursively into sub-groups, each of which consists of similar content. Based on the visual features, each node of the tree is partitioned into its children using k-means clustering. Each sub-group is then represented by its key frame, which is selected as the closest frame to the centroids of the corresponding cluster, and then can be displayed at the higher level of the hierarchy. The experiments show that very good hierarchical view of the video sequences can be created for annotation in terms of efficiency. 相似文献
9.
随着社会经济的发展和户籍管理制度改革的推进,农村劳动力不断外流,造成了"空心村"的大量存在,给农村基层民主建设带来了一系列问题.以苏北部分农村为考察个案,从经济、政治、思想观念三个角度系统分析了农村"空心村"形成的原因,阐述了"空心村"给农村发展带来的负面影响,探讨了农村"空心村"和谐发展的现实路径. 相似文献
10.
刘玲 《徐州工程学院学报》2011,(3)
农村包围城市、武装夺取政权的道路,是中国革命走向胜利的必由之路。这一理论成为新民主主义革命的理论基石,其理论联系实际的典范性意义已为人熟知。但是应当认识到,这一理论的内涵是多维的,对其重要性的认识不能只拘泥于某一方面。基此文章提出,这一理论是民主革命时期历时最长的实践,是毛泽东思想的重要组成部分,是一种寓涵着三大内容的革命范式,同时也是一种变被动为主动的防御和进攻策略,是重农理念的深入体现。 相似文献