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911.
912.
Jin‐Tai Lin Yu‐Kai Hu Cheng‐Hung Hou Chen‐Cheng Liao Wei‐Tsung Chuang Ching‐Wen Chiu Ming‐Kang Tsai Jing‐Jong Shyue Pi‐Tai Chou 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(19)
Tin‐based perovskite, which exhibits narrower bandgap and comparable photophysical properties to its lead analogs, is one of the most forward‐looking lead‐free semiconductor materials. However, the poor oxidative stability of tin perovskite hinders the development toward practical application. In this work, the effect of pseudohalide anions on the stability and emission properties of single‐layer 2D tin perovskite nanoplates with chemical formula TEA2SnI4 (TEA = 2‐thiophene‐ethylammonium) is reported. The results reveal that ammonium thiocyanate (NH4SCN) is the most effective additive in enhancing the stability and photoluminescence quantum yield of 2D TEA2SnI4 (23 ± 3%). X‐Ray photoelectron spectroscopic investigations on the thiocyanate passivated TEA2SnI4 nanoplate show less than a 1% increase of Sn4+ signal upon 30 min exposure to air under ambient conditions (298 K, humidity ≈70%). Furthermore, no noticeable decrease in emission intensity of the nanoplate is observed after 20 h in air. The SCN‐ passivation during the growth stage of TEA2SnI4 is proposed to play a crucial role in preventing the oxidation of Sn2+ and hence boosts both stability and photoluminescence yield of tin perovskite nanoplates. 相似文献
913.
Wei Zhang Huangxu Li Zhian Zhang Ming Xu Yanqing Lai Shu‐Lei Chou 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(25)
Developing high‐voltage cathode materials is critical for sodium‐ion batteries to boost energy density. NASICON (Na super‐ionic conductor)‐structured NaxMnM(PO4)3 materials (M represents transition metal) have drawn increasing attention due to their features of robust crystal framework, low cost, as well as high voltage based on Mn4+/Mn3+ and Mn3+/Mn2+ redox couples. However, full activation of Mn4+/Mn3+ redox couple within NASICON framework is still a great challenge. Herein, a novel NASICON‐type Na4MnCr(PO4)3 material with highly reversible Mn4+/Mn3+ redox reaction is discovered. It proceeds a two‐step reaction with voltage platforms centered at 4.15 and 3.52 V versus Na+/Na, delivering a capacity of 108.4 mA h g?1. The Na4MnCr(PO4)3 cathode also exhibits long durability over 500 cycles and impressive rate capability up to 10 C. The galvanostatic intermittent titration technique (GITT) test shows fast Na diffusivity which is further verified by density functional theory calculations. The high electrochemical activity derives from the 3D robust framework structure, fast kinetics, and pseudocapacitive contribution. The sodium storage mechanism of the Na4MnCr(PO4)3 cathode is deeply studied by ex situ X‐ray diffraction (XRD) and ex situ X‐ray photoelectron spectroscopy (XPS), revealing that both solid‐solution and two‐phase reactions are involved in the Na+ ions extraction/insertion process. 相似文献
914.
Shuixin Xia Xun Zhang Haojie Zhao Jin Xie Lien‐Yang Chou Yi Yu Wei Liu 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(20)
The large‐scale implementation of lithium metal batteries (LMBs) has long been plagued by the uncontrollable Li deposition triggered safety issues. Herein, a lithiophilic three‐dimensional Li anode scaffold, which is prepared by molten Li infusion aided by confined growth of low‐cost Zn clusters, is rationally constructed for high‐performance LMBs. Owing to the synergy of the carbon host and the effective regulation from the Zn nanoclusters, the large volumetric change of Li metal is well mitigated and shows a smooth and dendrite‐free behavior. The Li anode scaffold can deliver much improved Coulombic efficiency, superior rate performance, and long cycle lifespan with much lower voltage polarization. Furthermore, the half cells of Li anode scaffold paired with LiFePO4/LiCoO2/sulfur can achieve a higher specific capacity and longer stable cycling life than those with conventional Li foil. The Li|LFP cells can achieve a stable cycling over 250 cycles at 1C with a higher capacity retention of ≈90.8%, and a higher initial discharge capacity of 924.6 mAh g?1 with a high capacity retention over 300 cycles can also be obtained in Li|S cells at 1C. This work demonstrates a cost‐effective and scalable strategy for stable Li metal anode toward next‐generation and high‐performance LMBs. 相似文献
915.
Chou J.C.-Y. Tai-Yi Huang Kuang-Li Huang Tsung-Yen Chen 《Parallel and Distributed Systems, IEEE Transactions on》2006,17(5):419-433
A number of structured peer-to-peer (P2P) lookup protocols have been proposed recently. A P2P lookup protocol routes a lookup request to its target node in a P2P distributed system. Existing protocols achieve balanced routing traffic among nodes by assuming that lookup requests are evenly targeted at every node. However, when lookup requests concentrate on a few nodes simultaneously, these nodes become hot spots. Due to uneven routing patterns in existing protocols, hot spots cause unbalanced routing traffic which leads to routing bottlenecks. In this paper, we present a novel structured P2P lookup protocol called SCALLOP that delivers balanced routing and avoids routing bottlenecks at occurrences of hot spots. Among existing protocols, SCALLOP is the first one to accomplish this goal at the fundamental nature of a routing protocol. SCALLOP achieves balanced routing by uniquely constructing a balanced lookup tree for each node. The balanced tree evenly distributes routing traffic among sibling nodes and, therefore, avoids or reduces routing bottlenecks. In addition, as a load-balanced protocol, SCALLOP delivers asymptotically optimal lookup performance at the tradeoff between routing path and routing table size. We conducted a set of simulations to demonstrate the effectiveness of SCALLOP. The results show that, compared-with a most-referenced and representative structured P2P lookup, protocol and a graph-based extension of this protocol, SCALLOP significantly reduces routing bottlenecks while all three protocols deliver comparable lookup performance. 相似文献
916.
Chih-Hsun Chou 《Fuzzy Systems, IEEE Transactions on》2006,14(3):372-385
In this paper, a genetic algorithm (GA) based optimal fuzzy controller design is proposed. The design procedure is accomplished by establishing an index function as the consequent part of the fuzzy control rule. The inputs of the controller, after scaling, are utilized by the index function for computing the output linguistic value. This linguistic value can then be used to map the suitable fuzzy control actions. This proposed novel fuzzy control rule has crisp input and fuzzified output characteristics. The index function plays a role in mapping the desired fuzzy sets for defuzzification resulting in a controlled hypersurface in the linguistic space formed by the input fuzzy variables. Two types of index functions, both linear and nonlinear, are introduced for controlling systems with different degrees of nonlinearity. The parameters of the index function are obtained by applying a simple GA with a suitable fitness function. Various controlled systems result in various parameter sets depending on their dynamics. Under the acquired optimal parameter set the optimal index function can be used to generate the desired control actions. Several simulation examples are given to verify the performance of the proposed GA-based fuzzy controller. 相似文献
917.
The assembly of molecular building blocks with metal ions generating microporous network solids has been the focus of intense activity. Because of their potential applications associated with channels and cavities, such materials have been examined for size- and shape-selective catalysis, separations, sensors, molecular recognition and nanoscale reactors. Within this context, assemblies of robust and chemically versatile porphyrin and metalloporphyrin building blocks remain rare. Supramolecular architectures of porphyrin solids based on weak van der Waals interactions, hydrogen bonding and metal-ligand coordination networks have been reported. Although there are frequent allusions to zeolite-like microporosity from crystallography and loss of initial guest solvent molecules, evidence of functional microporous behaviour is scarce. We have demonstrated repeatable sorption-desorption with high selectivity on the basis of size, shape and functional group of the sorbate by a microporous metalloporphyrin solid in analogy to zeolites. 相似文献
918.
In this paper, the neural network method was applied to predict the content of protein secondary structure elements that was based on 'pair-coupled amino acid composition', in which the sequence coupling effects are explicitly included through a series of conditional probability elements. The prediction was examined by a self-consistency test and an independent-dataset. Both indicated good results obtained when using the neural network method to predict the contents of alpha-helix, beta-sheet, parallel beta-sheet strand, antiparallel beta-sheet strand, beta-bridge, 3(10)-helix, pi-helix, H-bonded turn, bend, and random coil. 相似文献
919.
Devki N. Talwar Tzuen-Rong Yang Wu-Ching Chou 《Science and Technology of Advanced Materials》2016,17(1):777-791
A comprehensive lattice dynamical study is reported to emphasize the vibrational behavior of perfect/imperfect zinc-blende (zb) ZnSe, MnSe and Zn1?xMnxSe alloys. Low temperature far-infrared (FIR) reflectivity measurements performed on a series of molecular beam epitaxy grown Zn1?xMnxSe/GaAs (001) epilayers have a typical ‘intermediate-phonon-mode’ behavior. Besides perceiving ZnSe- and MnSe-like TO-phonon resonances, the study also revealed a weak Mn alloy-disorder mode below MnSe band. A classical effective-medium theory of multilayer optics is used to evaluate dielectric tensors of both epilayers and substrate for simulating reflectivity and transmission spectra of ultrathin epifilms and superlattices at near normal and/or oblique incidence. In the framework of a realistic rigid-ion model and exploiting an average t-matrix Greens function (ATM-GF) theory we appraised the vibrational properties of nitrogen and phosphorous doped Zn-Mn chalcogenides. Lattice relaxations around isolated NSe (PSe) defects in ZnSe and zb MnSe are evaluated by first principles bond-orbital model that helped construct perturbation models for simulating the localized vibrational modes (LVMs). Calculated shift of impurity modes for isotopic 14NSe (15NSe) defects in ZnSe offered a strong revelation of an inflexible defect–host interaction. By retaining force constant change parameter of 14NSe (15NSe) in heavily N-doped ZnSe, the ATM-GF theory predicted (a) three non-degenerate LVMs for the photoluminescence defect center VSe-Zn-14NSe (VSe-Zn-15NSe) of Cs symmetry, and (b) six impurity modes for the second nearest-neighbor NSe-Zn-NSe pair defect of C2v symmetry. From the range of simulated defect modes, we have ruled out the possibility of N-pairs and justified the presence of VSe-Zn-NSe complex centers – likely to be responsible for the observed large absorption bandwidth in highly N-doped ZnSe. High resolution measurements of FIR absorption and/or Raman scattering spectroscopy are needed to validate the accuracy of our theoretical conjectures. 相似文献
920.
Few Atomic Layered Lithium Cathode Materials to Achieve Ultrahigh Rate Capability in Lithium‐Ion Batteries 下载免费PDF全文
Zhixin Tai Chandrasekar M. Subramaniyam Shu‐Lei Chou Lingna Chen Hua‐Kun Liu Shi‐Xue Dou 《Advanced materials (Deerfield Beach, Fla.)》2017,29(34)
The most promising cathode materials, including LiCoO2 (layered), LiMn2O4 (spinel), and LiFePO4 (olivine), have been the focus of intense research to develop rechargeable lithium‐ion batteries (LIBs) for portable electronic devices. Sluggish lithium diffusion, however, and unsatisfactory long‐term cycling performance still limit the development of present LIBs for several applications, such as plug‐in/hybrid electric vehicles. Motivated by the success of graphene and novel 2D materials with unique physical and chemical properties, herein, a simple shear‐assisted mechanical exfoliation method to synthesize few‐layered nanosheets of LiCoO2, LiMn2O4, and LiFePO4 is used. Importantly, these as‐prepared nanosheets with preferred orientations and optimized stable structures exhibit excellent C‐rate capability and long‐term cycling performance with much reduced volume expansion during cycling. In particular, the zero‐strain insertion phenomenon could be achieved in 2–3 such layers of LiCoO2 electrode materials, which could open up a new way to the further development of next‐generation long‐life and high‐rate batteries. 相似文献