arXiv subjects

Yong He

Publications and source records attributed to Yong He.

98 records · Page 6Linked to original sources

arXiv2016

Differentially Categorized Structural Connectome Hubs are Involved in Differential Microstructural Basis and Functional Implications and Contribute to Individual Identification

Human brain structural networks contain sets of centrally embedded hub regions that enable efficient information communication. However, it remains largely unknown about categories of structural brain hubs and their microstructural, functional and cognitive characteristics as well as contributions to individual identification. Here, we employed three multi-modal imaging data sets with structural MRI, diffusion MRI and resting-state functional MRI to construct individual structural brain networks, identify brain hubs based on eight commonly used graph-nodal metrics, and perform comprehensive validation analysis. We found three categories of structural hubs in the brain networks, namely, aggregated, distributed and connector hubs. Spatially, these distinct categories of hubs were primarily located in the default-mode system and additionally in the visual and limbic systems for aggregated hubs, in the frontoparietal system for distributed hubs, and in the sensorimotor and ventral attention systems for connector hubs. Importantly, these three categories of hubs exhibited various distinct characteristics, with the highest level of microstructural organization in the aggregated hubs, the largest wiring cost and topological vulnerability in the distributed hubs, and the highest functional associations and cognitive flexibility in the connector hubs, although they behaved better regarding these characteristics compared to non-hubs. Finally, all three categories of hub indices displayed high across-session spatial similarities and acted as a structural fingerprint with high predictive rates (100%, 100% and 84.2%) for individual identification. Collectively, our findings highlighted three categories of brain hubs with differential microstructural, functional and cognitive associations, which may shed light on the topological mechanisms of the human connectome.

q-bio.NC↗

arXiv2016

Model Interpolation with Trans-dimensional Random Field Language Models for Speech Recognition

The dominant language models (LMs) such as n-gram and neural network (NN) models represent sentence probabilities in terms of conditionals. In contrast, a new trans-dimensional random field (TRF) LM has been recently introduced to show superior performances, where the whole sentence is modeled as a random field. In this paper, we examine how the TRF models can be interpolated with the NN models, and obtain 12.1\% and 17.9\% relative error rate reductions over 6-gram LMs for English and Chinese speech recognition respectively through log-linear combination.

cs.CL↗

arXiv2010

UCMExporter: Supporting Scenario Transformations from Use Case Maps

The Use Case Maps (UCM) scenario notation is applicable to many requirements engineering activities. However, other scenario notations, such as Message Sequence Charts (MSC) and UML Sequence Diagrams (SD), have shown to be better suited for detailed design. In order to use the notation that is best appropriate for each phase in an efficient manner, a mechanism has to be devised to automatically transfer the knowledge acquired during the requirements analysis phase (using UCM) to the design phase (using MSC or SD). This paper introduces UCMEXPORTER, a new tool that implements such a mechanism and reduces the gap between high-level requirements and detailed design. UCMEXPORTER automatically transforms individual UCM scenarios to UML Sequence Diagrams, MSC scenarios, and even TTCN-3 test skeletons. We highlight the current capabilities of the tool as well as architectural solutions addressing the main challenges faced during such transformation, including the handling of concurrent scenario paths, the generation of customized messages, and tool interoperability.

cs.SE↗

arXiv2007

Single Molecule Photon Statistics from a Sequence of Laser Pulses

There are many ways of calculating photon statistics in quantum optics in general and single molecule spectroscopy in particular such as the generating function method, the quantum jump approach or time ordering methods. In this paper starting with the optical Bloch equation, within the paths interpretation of Zoller, Marte and Walls we obtain the photon statistics from a sequence of laser pulses expressed by means of quantum trajectories. We find general expressions for Pn(t) - the probability of emitting n photons up to time t, discuss several consequences and show that the interpretation of the quantum trajectories (i) emphasizes contribution to the photon statistics of the coherence paths accumulated in the delay interval between the pulses and (ii) allows simple classification of the terms negligible under certain physical constraints . Applying this method to the concrete example of two square laser pulses we find the probabilities of emitting 0,1 and 2 photons, examine several limiting cases and investigate the upper and lower bounds of P0(t), P1(t) and P2(t) for a sequence of two strong pulses in the limit of long measurement times. Implication to single molecule non-linear spectroscopy and theory of pairs of photons on demand are discussed briefly.

physics.optics↗

arXiv2005

Theory of Single Photon Control from a Two Level System Source

Generation of a single photon or a pair of photons from a single emitter is important for quantum information applications. Using the generating function formalism we investigate the theory of a few photons on demand for the square laser pulse and the rapid adiabatic following method. Exact theory and numerical solutions are used to design control fields for a two level emitter, which yield an optimal single or two photon source, under the constrains of finite laser field strength and finite interaction time. Comparison to experiments of Brunel et al, shows that the experiments were made close to optimal conditions.

quant-ph↗

arXiv2004

Super and Sub-Poissonian photon statistics for single molecule spectroscopy

We investigate the distribution of the number of photons emitted by a single molecule undergoing a spectral diffusion process and interacting with a continuous wave laser field. The spectral diffusion is modeled based on a stochastic approach, in the spirit of the Anderson-Kubo line shape theory. Using a generating function formalism we solve the generalized optical Bloch equations, and obtain an exact analytical formula for the line shape and Mandel's Q parameter. The line shape exhibits well known behaviors, including motional narrowing when the stochastic modulation is fast, and power broadening. The Mandel parameter, describing the line shape fluctuations, exhibits a transition from a Quantum sub-Poissonian behavior in the fast modulation limit, to a classical super-Poissonian behavior found in the slow modulation limit. Our result is applicable for weak and strong laser field, namely for arbitrary Rabi frequency. We show how to choose the Rabi frequency in such a way that the Quantum sub-Poissonian nature of the emission process becomes strongest. A lower bound on $Q$ is found, and simple limiting behaviors are investigated. A non-trivial behavior is obtained in the intermediate modulation limit, when the time scales for spectral diffusion and the life time of the excited state, become similar. A comparison is made between our results, and previous ones derived based on the semi-classical generalized Wiener--Khintchine theorem.

cond-mat.stat-mech↗

arXiv2003

Exact Solution for the Influence of Spectral Diffusion on Single-Molecule Photon-Statistics

We investigate the distribution of number of photons emitted by a single molecule undergoing a spectral diffusion process and interacting with a continuous wave field. Using a generating function formalism an exact analytical formula for Mandel's $Q$ parameter is obtained. The solution exhibits transitions between: (i) Quantum sub-Poissonian and Classical super-Poissonian behaviors, and (ii) fast to slow modulation limits. Our solution yields the conditions on the magnitude of the spectral diffusion time scales on which these transitions are observed. We show how to choose the Rabi frequency in such a way that the Quantum sub-Poissonian nature of the emission process becomes strongest, we find ${Ω^2 \over Γ} = {Γ_{\rm SD} + Γ\over 2}$ where $Γ_{\rm SD}$ ($Γ$) is the spectral diffusion (radiative) contribution to the width of the line shape.

cond-mat.stat-mech↗

arXiv1998

A method for obtaining Darboux transformations

In this paper we give a method to obtain Darboux transformations (DTs) of integrable equations. As an example we give a DT of the dispersive water wave equation. Using the Miura map, we also obtain the DT of the Jaulent-Miodek equation. \end{abstract}

math-ph↗