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[IEEE 2019 IEEE International Electron Devices Meeting (IEDM) - San Francisco, CA, USA (2019.12.7-2019.12.11)] 2019 IEEE International Electron Devices Meeting (IEDM) - Integrated DFB Laser Diode and High-efficiency Mach-Zehnder Modulator using Membrane III-V Semiconductors on Si Photonics Platform
摘要： This paper presents a 3-D statistical channel impulse response (IR) model for urban line of sight (LOS) and non-LOS channels developed from 28- and 73-GHz ultrawide-band propagation measurements in New York City, useful in the design of 5G wireless systems that will operate in both the ultra-high frequency/microwave and millimeter-wave (mmWave) spectrum to increase channel capacities. A 3GPP-like stochastic IR channel model is developed from measured power delay profiles, angle of departure, and angle of arrival power spectra. The extracted statistics are used to implement a channel model and simulator capable of generating 3-D mmWave temporal and spatial channel parameters for arbitrary mmWave carrier frequency, signal bandwidth, and antenna beamwidth. The model presented here faithfully reproduces realistic IRs of measured urban channels, supporting air interface design of mmWave transceivers, filters, and multi-element antenna arrays.
关键词： 28 GHz,multipath,time cluster spatial lobe (TCSL),spatial lobe (SL),statistical simulator,5G,spatial channel model (SCM),73 GHz,Channel model,millimeter-wave (mmWave) propagation,3-D ray-tracing,time cluster (TC),impulse response (IR)
更新于2025-09-23 15:19:57
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Performance of Localized Coupled Cluster Methods in a Moderately Strong Correlation Regime: H??ckel-M??bius Interconversions in Expanded Porphyrins
摘要： Localized orbital coupled cluster theory has recently emerged as a nonempirical alternative to DFT for large systems. Intuitively, one might expect such methods to perform less well for highly delocalized systems. In the present work, we apply both canonical CCSD(T) and a variety of localized approximations thereto to a set of flexible expanded porphyrins — macrocycles that can switch between Hückel, figure-eight, and M?bius topologies under external stimuli. Both minima and isomerization transition states are considered. We find that M?bius(-like) structures have much stronger static correlation character than the remaining structures, and this causes significant errors in DLPNO-CCSD(T) and even DLPNO-CCSD(T1) approaches, unless TightPNO cutoffs are employed. If sub-kcal mol-1 accuracy with respect to canonical relative energies is required even for M?bius-type systems (or other systems plagued by strong static correlation), then Nagy and Kallay’s LNO-CCSD(T) method with “tight” settings is the suitable localized approach. We propose the present POLYPYR21 dataset as a benchmark for localized orbital methods, or more broadly, for the ability of lower-level methods to handle energetics with strongly varying degrees of static correlation.
关键词： topology interconversions,nondynamical correlation,expanded porphyrins,localized coupled cluster,canonical coupled cluster
更新于2025-09-23 15:19:57
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Lead Doped Ti-Oxo Clusters as Molecular Models of Perovskite-type PbTiO3 and Electron Transport Material in Solar Cells
摘要： In this work, we successfully prepared Pb-doped titanium-oxo clusters with core structures as isolated perovskite PbTiO3 species. In the obtained highly symmetric Pb8Ti7-oxo cluster, the central TiO6 octahedra are orthogonally extended to adjacent ones in corner-sharing way and the doped 8 Pb ions form a cubic arrangement, making it the first molecular model of perovskite PbTiO3. Moreover, they show high solution stability confirmed by MALDI-TOF-MS measurements. Based on solution processability, they can be easily spin-coated into homogeneous films, which were further applied as electron transport materials in perovskite solar cells to give the average PCE of ～15 % and improved device stability. The developed bottom-up cluster assembly method opens an efficient way for the construction of atomically precise models of perovskite metal oxides, and provides potential molecular tools to extend their applications.
关键词： perovskite,solar cells,cluster compounds,lead titanate,titanium-oxo cluster
更新于2025-09-23 15:19:57
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Electronic structure and stability of anionic AuGen (n?=?1–20) clusters and assemblies: a density functional modeling
摘要： In the present study electronic structure and stabilities of cationic gold-doped germanium clusters, AuGen (n = 1 to 20), and their assemblies have been investigated by density functional theory (DFT) modeling. Computational results show a good relationship between the thermodynamic parameters, average binding energy, embedding energy, fragmentation energy, etc., with the percentage hybridization between different Ge 4s, Ge 4p, and Au 5d atomic orbitals, which plays a dominating role in the stabilization of anionic AuGe7, AuGe10, Au(Ge7)2, Au(Ge9)2, and Au(Ge10)2 clusters. Other thermodynamic and chemical parameters are also found consistent with the observed thermodynamic stabilities of the nanoclusters. In smaller size range (n < 11), Au atom always absorbs on the surface or vertex of pure Ge cluster. From n = 11, endohedral doping starts. In the assembled clusters, Au atom play the role as a bridging atom in Au(Ge7)2, Au(Ge9)2, and Au(Ge10)2 clusters. Stability of the AuGe7, AuGe10, Au(Ge7)2, Au(Ge9)2, and Au(Ge10)2 are explained using magic number in shell-filled model and mixed (π-σ) aromatic rule. As per the symmetry and structure of AuGe12 cluster, it is comparable to a nido-cluster, and hence, its stability is explained using Wade-Mingos rule. Calculated VDE, ADE, HOMO-LUMO gap, and VIP have very close agreement with the experimental results. IR and Raman frequencies show that the vibration nature of the clusters could produce electromagnetic radiation in the far infrared region which is useful for medical applications.
关键词： ADE and VDE,Electronic structure,Cluster and cluster assembly,IR and Raman,DOS,Density functional theory
更新于2025-09-23 15:19:57
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Heterometallic Cluster Coordination Polymers Assembled from Cuprous-Halide Clusters and Organotina??Oxygen Pyridinecarboxylate Clusters
摘要： By using the bifunctional ligands bearing carboxylate and N-donor groups, the precursor of nBu2SnO undergoes a transformation to yield organotin–oxygen carboxylate clusters, namely, [(nBu2Sn)4(μ3-O)2(μ2-OH)2(INA)2] (INA = isonicotinate), [(nBu2Sn)5(μ3-O)3(μ2-OH)2(INA)2] and [(nBu2Sn)4(μ3-O)2(NA)4] (NA = nicotinate), resulting in different geometric building units with two or four extension points. Such organotin–oxygen carboxylate clusters assemble with various CunIn clusters such as Cu2I2 rhomboid dimer, Cu4I4 cubic tetramer, Cu6I6 prismatic hexamer to engender various heterometallic cluster coordination polymers.
关键词： organotin–oxygen pyridinecarboxylate clusters,heterometallic cluster coordination polymers,bifunctional ligands,structural dimensions,cuprous-halide clusters
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Using Physics Models to Analyze Aggregate Inline Measurement Data
摘要： A dilemma in cloud radio access networks (C-RANs) is how to keep a balance between the performance and the ef?ciency of centralized processing. To solve this problem, the joint design of training-based channel estimation and cluster formation are studied in this paper. To provide ef?cient cooperation strategies in C-RANs, individual C-RAN clusters are formed by the remote radio heads (RRHs), and a data-assisted channel estimation scheme is studied, which can reduce the redundant cost of training sequences. To ensure the performance of channel estimation and data transmissions, the cluster formation and the channel estimation are optimized jointly. In particular, an iterative training-based channel estimation scheme is designed by using convex optimization and the Broyden–Fletcher–Goldfarb–Shanno algorithm jointly. Moreover, a utility function of cluster formation can be established based on the estimates and the mean squared error of our proposed channel estimation algorithm, and the cluster formation of RRHs can be formulated as a coalitional formation game. Furthermore, a sub-optimal algorithm is also proposed to reduce the computational complexity. Finally, the simulation results are shown to evaluate the performance of our proposed algorithms.
关键词： optimization,Cloud-radio access networks,cluster formation,channel estimation,game theory
更新于2025-09-23 15:19:57
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Metallic Nanomaterials (Part A) || 5. Synthesis and characterization of size-controlled atomically precise gold clusters
摘要： In this article, synthetic strategies and characterization methodologies of atomically precise gold clusters have been summarized. The typical and effective synthetic strategies including a systematic “size-focusing” methodology has been developed for attaining atomically precise gold clusters with size control. Another universal synthetic methodology is ligand exchange-induced size/structure transformation (LEIST) based on from one stable size to another. These two methodologies have largely expanded the “universe” of atomically precise gold clusters. Elite of typical synthetic case studies of ligand protected gold clusters are presented. Important characterization techniques of these atomically precise gold clusters also are included. The identification and characterization of gold clusters have been achieved in terms of nuclearity (size), molecular formulation, and geometrical structures by the combination of these techniques. The determination of gold cluster structure based on single crystals is of paramount importance in understanding the relationship of structure–property. The criterion and selection of these typical gold clusters are all “strictly” atomically precise that all have been determined ubiquitously by single crystal diffraction. These related crystallographic data are retrieved from Cambridge Crystallographic Data Centre (CCDC) up to 30th November 2017. Meanwhile, the cutting edge and other important characterization methodologies including electron diffraction (ED), extended X-ray absorption fine structure (EXFAS), and synchrotron sources are briefly reviewed. The new techniques hold the promise of pushing the limits of crystallization of gold clusters. This article is not just an exhaustive and up to date review, generally summarized synthetic strategies, but also a practical guide regarding gold cluster synthesis. We called it a “Cookbook” of ligand protected gold clusters, including synthetic recipes and characterization details.
关键词： alkyne,ligand exchange-induced size/structure transformation,phosphine,“size-focusing” methodology,size-controlled synthesis,thiolate,gold cluster
更新于2025-09-23 15:19:57
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[IEEE 2020 IEEE Conference of Russian Young Researchers in Electrical and Electronic Engineering (EIConRus) - St. Petersburg and Moscow, Russia (2020.1.27-2020.1.30)] 2020 IEEE Conference of Russian Young Researchers in Electrical and Electronic Engineering (EIConRus) - Study of External Flashes Influence and False Operation on Work Stability of Laser Speed Sensors
摘要： Relational fuzzy clustering (RFC) algorithms prove very useful in Web user session clustering because Web user sessions may contain fuzzy, conflicting and imprecise information. Though RFC algorithms are very sensitive to cluster initialization and works only if the numbers of clusters are specified in advance. However, at all times, the prior initialization of a number of clusters is not feasible due to the dynamically evolving nature of user sessions. Therefore, estimating the number of clusters and initializing suitable cluster prototype are a significant performance bottleneck in this method. In this paper, the discounted fuzzy relational clustering (DFRC) algorithm is proposed to address the major constraint of RFC. The DFRC algorithm identifies Web user session clusters from Web server access logs, without initializing the number of clusters and prototypes of initial clusters. The DFRC algorithm works in two stages. In the first stage, DFRC automatically identifies the number of potential clusters based on the successively discounted potential density function value of each relational data and their respective centres. In the second stage, DFRC assigns fuzzy membership values to each data point and forms fuzzy clusters from the relational matrix. The DFRC algorithm is applied on an augmented session dissimilarity matrix obtained from a publicly accessed NASA Web server log data. The experimental results are evaluated using different fuzzy validity measures. The extensive experiments are performed to test the effect of various parameters, including accept/reject ratio and neighbourhood radius on the performance of DFRC algorithm. The results were also compared with fuzzy relational clustering algorithm using cluster quality measures. It is observed that the quality of generated clusters using DFRC is superior as compared with that of RFC.
关键词： relational fuzzy clustering,fuzzy validity index,cluster quality,similarity measures,subtractive clustering,Augmented sessions
更新于2025-09-23 15:19:57
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Modeling radiative-shocks created by lasera??cluster interactions
摘要： Radiative-shocks induced by laser–cluster interactions are modeled using radiation-hydrodynamic simulations. A good agreement—in both shock velocity and density pro?les—is obtained between experiment and simulations, indicating that non-local thermodynamic equilibrium (NLTE) radiative effects are important in the experimental regime examined, particularly at early times ((cid:2)30 ns) due to the elevated temperatures ((cid:3)35 eV). The enhanced NLTE radiative emission causes the shock to be reduced in amplitude, increased in width, and reduced in propagation velocity, while the amplitude of the radiative precursor is increased. As the density and temperature conditions are relatively modest, this potentially has important implications for the scalings that are used in laboratory–astrophysics to transform between laboratory and astrophysical scales, which do not hold for non-LTE systems.
关键词： non-local thermodynamic equilibrium,laboratory–astrophysics,radiation-hydrodynamic simulations,radiative-shocks,laser–cluster interactions
更新于2025-09-23 15:19:57
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Spektroskopischer Nachweis einer attraktiven Kation-Kation- Wechselwirkung in OH-funktionalisierten ionischen Flüssigkeiten: ein H-Brücken-gebundenes kettenf?rmiges Trimer
摘要： Wir untersuchen die Bildung von wasserstoffverbrückten Dom?nen zwischen den kationischen Bestandteilen der ionischen Flüssigkeit (IL) 1-(3-Hydroxypropyl)-pyridinium-tetrafluoroborat [HPPy][BF4] mithilfe der kryogenen Ionen-Schwingungs-Pr?dissoziationsspektroskopie von kalten (≈ 35 K) ionischen Gasphasenclustern und quantenchemischen Berechnungen. Eine Analyse der OH-Streckschwingungen zeigt ein kettenf?rmiges OH···OH···OH···BF4?Strukturmotiv, an dem die drei Kationen in einem quin?ren kationischen Cluster (HPPy+)3(BF4?)2 beteiligt sind. Rechnungen belegen, dass die Anziehung dieser kooperativen H-Brücken die Coulomb-Absto?ung kompensiert und zu stabilen Komplexen führt, die erfolgreich mit den Komplexen konkurrieren, bei denen die OH-Gruppen überwiegend an Anionen gebunden sind. Unser experimenteller und theoretischer Ansatz liefert wichtige Einblicke in die kooperativen Effekte, die zur Bildung von wasserstoffverbrückten Dom?nen unter Einbeziehung der kationischen Bestandteile von ILs führen.
关键词： Cluster,Quantenchemie,Ionische Flüssigkeiten,Wasserstoffbrücken,Ionenspektroskopie
更新于2025-09-23 15:19:57