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排序方式: 共有418条查询结果,搜索用时 15 毫秒
1.
Eui Dae Jung Amit Kumar Harit Do Hui Kim Chung Hyeon Jang Jong Hyun Park Shinuk Cho Myoung Hoon Song Han Young Woo 《Advanced materials (Deerfield Beach, Fla.)》2020,32(30):2002333
A series of anionic conjugated polyelectrolytes (CPEs) is synthesized based on poly(fluorene-co-phenylene) by varying the side-chain ionic density from two to six per repeat units (MPS2-TMA, MPS4-TMA, and MPS6-TMA). The effect of MPS2, 4, 6-TMA as interlayers on top of a hole-extraction layer of poly(bis(4-phenyl)-2,4,6-trimethylphenylamine (PTAA) is investigated in inverted perovskite solar cells (PeSCs). Owing to the improved wettability of perovskites on hydrophobic PTAA with the CPEs, the PeSCs with CPE interlayers demonstrate a significantly enhanced device performance, with negligible device-to-device dependence relative to the reference PeSC without CPEs. By increasing the ionic density in the MPS-TMA interlayers, the wetting, interfacial defect passivation, and crystal growth of the perovskites are significantly improved without increasing the series resistance of the PeSCs. In particular, the open-circuit voltage increases from 1.06 V for the PeSC with MPS2-TMA to 1.11 V for the PeSC with MPS6-TMA. The trap densities of the PeSCs with MPS2,4,6-TMA are further analyzed using frequency-dependent capacitance measurements. Finally, a large-area (1 cm2) PeSC is successfully fabricated with MPS6-TMA, showing a power conversion efficiency of 18.38% with negligible hysteresis and a stable power output under light soaking for 60 s. 相似文献
2.
3.
Zukerman M. Wong E.W.M. Rosberg Z. Gyu Myoung Lee Hai Le Vu 《Communications Letters, IEEE》2004,8(2):116-118
We provide teletraffic models for loss probability evaluation of optical burst switching (OBS). We show that the popular Engset formula is not exact for OBS modeling and demonstrate that in certain cases it is not appropriate. A new exact model is provided. The various models are compared using numerical results for various OBS alternatives with and without burst segmentation. 相似文献
4.
Improvement in hydrogen storage characteristics of magnesium by mechanical alloying with nickel 总被引:1,自引:0,他引:1
Myoung Youp Song 《Journal of Materials Science》1995,30(5):1343-1351
The hydriding and dehydriding kinetics of Mg are reviewed. It is reported that the hydriding and dehydriding reactions of Mg are nucleation-controlled under certain conditions and progress by a mechanism of nucleation and growth, and that the hydriding rates of Mg are controlled by the diffusion of hydrogen through a growing Mg hydride layer.The hydriding and dehydriding kinetics of Mg can be improved in consequence by a treatment such as mechanical alloying, which can facilitate the nucleation by creating defects and shorten diffusion distances by reducing the effective particle size of Mg.The hydriding and dehydriding characteristics of mechanically-treated Mg and mechanically-alloyed mixtures with the compositions Mg-x wt Ni (x=5, 10,25 and 55) are studied.The Mg2Ni phase develops in the mechanically-alloyed mixtures. The Mg-10wt% Ni and Mg-25 wt% Ni mixtures are activated easily, show much larger hydrogen storage capacities and much higher hydriding rates, and higher dehydriding rates, than other magnesium- based alloys or mixtures. 相似文献
5.
The change in the thickness and chemical states of the interfacial layer and the related electrical properties in Ta2O5 films with different annealing temperatures were investigated. The high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy analyses revealed that the 700 °C-annealed Ta2O5 film remained to be amorphous and had the thinnest interfacial layer which was caused by Ta-silicate decomposition to Ta2O5 and SiO2. In addition, the electrical properties were improved after annealing treatments. Our results suggest that an annealing treatment at 700 °C results in the highest capacitance and the lowest leakage current in Ta2O5 films due to the thinnest interfacial layer and non-crystallization. 相似文献
6.
Seong-Sik Myoung Yongshik Lee Jong-Gwan Yook 《Microwave Theory and Techniques》2007,55(7):1531-1538
This paper proposes a bandwidth-compensation method for miniaturized filters based on short-ended parallel coupled lines. Capacitive loading of such coupled lines is a relatively simple means of reducing the line lengths. In this study, a method is developed that predicts exactly the degree of reduction in the fractional bandwidth due to miniaturization. Using this method, the fractional bandwidth of the prototype coupled line filter can be adjusted, enabling miniaturized filters to maintain the targeted fractional bandwidth. The proposed bandwidth-compensation method applies for any type of filters with coupled lines realized with various transmission lines, with uniform or nonuniform line lengths. Experimental results are also presented that verify the validity of the method. 相似文献
7.
Hyeon Gyu Kim Yoo Hyun Park Yang Hyun Cho Myoung Ho Kim 《Journal of Intelligent Information Systems》2014,43(2):323-347
The join is an important operator in processing data streams. To produce outputs continuously over unbounded data streams, sliding windows are generally used to limit the scope of the join at a certain time. In the existing join algorithms, only a simple type of windows have been considered, which are updated whenever a new data item arrives on any input stream. On the other hand, a more common type of windows have not been addressed yet, whose intervals are updated periodically, i.e., slid by a predefined time interval. In this paper, we consider the time-slide windows in joining multiple data streams. The algorithm for the time-slide window join can vary according to (i) how frequently the join is evaluated and (ii) which structure is used for windowing. Regarding this, possible algorithms are discussed, and experimental results that compare their performances are provided in this paper. 相似文献
8.
Retrieving similar images based on its visual content is an important yet difficult problem. We propose in this paper a new method to improve the accuracy of content-based image retrieval systems. Typically, given a query image, existing retrieval methods return a ranked list based on the similarity scores between the query and individual images in the database. Our method goes further by relying on an analysis of the underlying connections among individual images in the database to improve this list. Initially, we consider each image in the database as a query and use an existing baseline method to search for its likely similar images. Then, the database is modeled as a graph where images are nodes and connections among possibly similar images are edges. Next, we introduce an algorithm to split this graph into stronger subgraphs, based on our notion of graph’s strength, so that images in each subgraph are expected to be truly similar to each other. We create for each subgraph a structure called integrated image which contains the visual features of all images in the subgraph. At query time, we compute the similarity scores not only between the query and individual database images but also between the query and the integrated images. The final similarity score of a database image is computed based on both its individual score and the score of the integrated image that it belongs to. This leads effectively to a re-ranking of the retrieved images. We evaluate our method on a common image retrieval benchmark and demonstrate a significant improvement over the traditional bag-of-words retrieval model. 相似文献
9.
A simple strategy was developed based on a new reactive function‐ and a salt‐containing new monomer, 4‐vinylbenzyl dimethyl 2‐(dimethylphosphino)ethyl phosphonium chloride (VDEPC), to obtain stable humidity‐sensitive membranes. The major ingredient of a humid membrane is crosslinked polyelectrolytes obtained from copolymers of VDEPC/2‐ethylhexyl acrylate (2‐EHA) = 1/0, 4/1, and 2/1. Isothermal humidity absorption experiments were performed for the estimation of humidity‐sensing materials. The crosslinked copolymers prepared from the reaction of VDEPC/2‐EHA = 4/1 with 1,4‐dichlorobutane showed an average impedance of 595, 39.1, and 3.9 KΩ at 30, 60, and 90% RH, respectively. Their hysteresis, temperature dependence, frequency dependence, and response time were measured. The reliability including water resistance and a long‐term stability were estimated for the application of the common humidity sensor. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1062–1070, 2003 相似文献
10.
We propose a control strategy that could steer the group of mobile agents in the plane to achieve a specified formation. The control law could be implemented in a fully decentralized manner so that each agent moves on their own local reference frame. Under the acyclic minimally persistent graph topology, each agent measures the relative displacements of neighboring agents and then adjusts the distances between them to achieve the desired formation. As well as achieving a fixed formation, we could resize the formation only by changing the leader edge, which connects the leader with the first‐follower in acyclic minimally persistent graph, without changing the structures of the control law. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献