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Jun He

Publications and source records attributed to Jun He.

At least 307 records · Page 17Linked to original sources
arXiv2015

Multi-objective Differential Evolution with Helper Functions for Constrained Optimization

Solving constrained optimization problems by multi-objective evolutionary algorithms has scored tremendous achievements in the last decade. Standard multi-objective schemes usually aim at minimizing the objective function and also the degree of constraint violation simultaneously. This paper proposes a new multi-objective method for solving constrained optimization problems. The new method keeps two standard objectives: the original objective function and the sum of degrees of constraint violation. But besides them, four more objectives are added. One is based on the feasible rule. The other three come from the penalty functions. This paper conducts an initial experimental study on thirteen benchmark functions. A simplified version of CMODE is applied to solving multi-objective optimization problems. Our initial experimental results confirm our expectation that adding more helper functions could be useful. The performance of SMODE with more helper functions (four or six) is better than that with only two helper functions.

cs.NE↗
arXiv2015

Nucleon Resonances Near 2 GeV

The nucleon resonances near 2 GeV are investigated through the $Σ$(1385) and $Λ(1520)$ photoproductions within a Regge-plus-resonance approach based on the new experimental data released by the CLAS Collaboration. The $Δ(2000)$ and the $N(2120)$ are found essential to reproduce the experimental data and should be assigned as second $[Δ5/2^+]$ and third $[N3/2^-]$ in the constituent quark model, respectively. A calculation of the binding energy and decay pattern supports that the $N(1875)$, which is listed in the PDG as the third $N3/2^-$ nucleon resonance instead of the $N(2120)$, is from the $Σ(1385)K$ interaction rather than a three quark state.

nucl-th↗
arXiv2015

Preserving Local Gauge Invariance with t-Channel Regge Exchange

Considering single-meson photo- and electroproduction off a baryon, it is shown how to restore local gauge invariance that was broken by replacing standard Feynman-type meson exchange in the t-channel by exchange of a Regge trajectory. This is achieved by constructing a contact current whose four-divergence cancels the gauge-invariance-violating contributions resulting from all states above the base state on the Regge trajectory. To illustrate the procedure, modifications necessary for the process $γ+p \to K^+ + Σ^{*0}$ are discussed in some detail. We also provide the general expression for the contact current for an arbitrary reaction.

hep-ph↗
arXiv2015

Personalized QoS Prediction of Cloud Services via Learning Neighborhood-based Model

The explosion of cloud services on the Internet brings new challenges in service discovery and selection. Particularly, the demand for efficient quality-of-service (QoS) evaluation is becoming urgently strong. To address this issue, this paper proposes neighborhood-based approach for QoS prediction of cloud services by taking advantages of collaborative intelligence. Different from heuristic collaborative filtering and matrix factorization, we define a formal neighborhood-based prediction framework which allows an efficient global optimization scheme, and then exploit different baseline estimate component to improve predictive performance. To validate the proposed methods, a large-scale QoS-specific dataset which consists of invocation records from 339 service users on 5,825 web services on a world-scale distributed network is used. Experimental results demonstrate that the learned neighborhood-based models can overcome existing difficulties of heuristic collaborative filtering methods and achieve superior performance than state-of-the-art prediction methods.

cs.DC↗
arXiv2015

$Z_c(3900)$ as a resonance from the $D\bar{D}^*$ interaction

In this paper it is proposed that the charged charmonium-like state $Z_c(3900)$ is a resonance above the threshold from the $D\bar{D}^*$ interaction. The $D\bar{D}^*$ interaction is described by the one-boson exchange model with light meson exchanges plus a short-range $J/ψ$ exchange. The scattering amplitude is calculated within a Bethe-Salpeter equation approach and the poles near the $D\bar{D}^*$ threshold are searched. In the isoscalar sector, two poles found under the $D\bar{D}^*$ threshold, i.e., bound states, have the quantum numbers $I^G(J^{PC})=0^-(1^{+-})$ and $0^+(1^{++})$. The latter can be related to the $X(3872)$. In the isovector sector, a bound state with $I^G(J^P)=1^+(1^+)$ is found with a large cutoff at about 3 GeV. If a cutoff at about 2 GeV is adopted with which a pole carrying the quantum number of the $X(3872)$ is produced at an energy of about 3871 MeV, the pole for the bound state with $1^+(1^+)$ runs across the threshold to a second Rienman sheet and becomes a resonance above the $D\bar{D}^*$ threshold, which can be identified with the $Z_c(3900)$. With such a cutoff, the $D\bar{D}^{*}$ invariant mass spectrum is also investigated and the experimental results found by BESIII can be reproduced.

hep-ph↗
arXiv2015

SOARAN: A Service-oriented Architecture for Radio Access Network Sharing in Evolving Mobile Networks

Mobile networks are undergoing fast evolution to software-defined networking (SDN) infrastructure in order to accommodate the ever-growing mobile traffic and overcome the network management nightmares caused by unremitting acceleration in technology innovations and evolution of the service market.Enabled by virtualized network functionalities, evolving carrier wireless networks tend to share radio access network (RAN) among multiple (virtual) network operators so as to increase network capacity and reduce expenses.However, existing RAN sharing models are operator-oriented, which expose extensive resource details, e.g. infrastructure and spectrum,to participating network operators for resource-sharing purposes. These old-fashioned models violate the design principles of SDN abstraction and are infeasible to manage the thriving traffic of on-demand customized services. This paper presents SOARAN, a service-oriented framework for RAN sharing in mobile networks evolving from LTE/LTE advanced to software-defined carrier wireless networks(SD-CWNs), which decouples network operators from radio resource by providing application-level differentiated services. SOARAN defines a serial of abstract applications with distinct Quality of Experience (QoE) requirements. The central controller periodically computes application-level resource allocation for each radio element with respect to runtime traffic demands and channel conditions, and disseminate these allocation decisions as service-oriented policies to respect element. The radio elements then independently determine flow-level resource allocation within each application to accomplish these policies. We formulate the application-level resource allocation as an optimization problem and develop a fast algorithm to solve it with a provably approximate guarantee.

cs.NI↗
arXiv2015

Theoretical investigation of the decay of the $N(2120)$ resonance to nucleon resonances near 1.7 GeV

Background: Until now the knowledge about nucleon resonances with a mass higher than 2 GeV has been scarce. Huge amounts of experimental data of the multipion photoproduction have been accumulated, and more can be expected in the future in facilities such as JLab 12 GeV. It makes it possible to investigate the decay of a nucleon resonance into another nucleon resonance. Purpose: The possibility to research the decay of the $N(2120)$ to nucleon resonances near 1.7 GeV in the three-pion photoproduction will be explored to provide useful information for future experimental study. Method: The pion and radiative decay amplitudes of nucleon resonances are studied within the constituent quark model, which is used to calculate the couplings constants, especially for the decay of a nucleon resonance near 2.1 GeV to another nucleon resonance near 1.7 GeV. The three-pion photoproduction off the neutron target, i.e.,$γn \toπ^{-}π^{-}Δ^{++}\to π^{-}π^{-}π^+ p$, is investigated based on the effective Lagrangian method with the coupling constant obtained form the decay amplitudes. Results: The resonance contribution with a state $N(^2P_M)\frac{3}{2}^{-}$ near 2.1 GeV decaying to a state $N(^4P_M)\frac{5}{2}^{-}$ near 1.7 GeV, i.\ e., $N(2120)\to N(1675)π$ is dominant in the process considered. The total cross section from the resonance contribution is at the order of 1 $μ$b and can be easily distinguished from the background. Conclusions: Our results suggest it is practicable to research the decay of the $N(2120)$ to the $N(1675)$ in experiment.

nucl-th↗
arXiv2015

Average Convergence Rate of Evolutionary Algorithms

In evolutionary optimization, it is important to understand how fast evolutionary algorithms converge to the optimum per generation, or their convergence rate. This paper proposes a new measure of the convergence rate, called average convergence rate. It is a normalised geometric mean of the reduction ratio of the fitness difference per generation. The calculation of the average convergence rate is very simple and it is applicable for most evolutionary algorithms on both continuous and discrete optimization. A theoretical study of the average convergence rate is conducted for discrete optimization. Lower bounds on the average convergence rate are derived. The limit of the average convergence rate is analysed and then the asymptotic average convergence rate is proposed.

cs.NE↗
arXiv2015

Adaptive Stochastic Gradient Descent on the Grassmannian for Robust Low-Rank Subspace Recovery and Clustering

In this paper, we present GASG21 (Grassmannian Adaptive Stochastic Gradient for $L_{2,1}$ norm minimization), an adaptive stochastic gradient algorithm to robustly recover the low-rank subspace from a large matrix. In the presence of column outliers, we reformulate the batch mode matrix $L_{2,1}$ norm minimization with rank constraint problem as a stochastic optimization approach constrained on Grassmann manifold. For each observed data vector, the low-rank subspace $\mathcal{S}$ is updated by taking a gradient step along the geodesic of Grassmannian. In order to accelerate the convergence rate of the stochastic gradient method, we choose to adaptively tune the constant step-size by leveraging the consecutive gradients. Furthermore, we demonstrate that with proper initialization, the K-subspaces extension, K-GASG21, can robustly cluster a large number of corrupted data vectors into a union of subspaces. Numerical experiments on synthetic and real data demonstrate the efficiency and accuracy of the proposed algorithms even with heavy column outliers corruption.

stat.ML↗
arXiv2015

Analysis of Solution Quality of a Multiobjective Optimization-based Evolutionary Algorithm for Knapsack Problem

Multi-objective optimisation is regarded as one of the most promising ways for dealing with constrained optimisation problems in evolutionary optimisation. This paper presents a theoretical investigation of a multi-objective optimisation evolutionary algorithm for solving the 0-1 knapsack problem. Two initialisation methods are considered in the algorithm: local search initialisation and greedy search initialisation. Then the solution quality of the algorithm is analysed in terms of the approximation ratio.

cs.NE↗
arXiv2015

On the Easiest and Hardest Fitness Functions

The hardness of fitness functions is an important research topic in the field of evolutionary computation. In theory, the study can help understanding the ability of evolutionary algorithms. In practice, the study may provide a guideline to the design of benchmarks. The aim of this paper is to answer the following research questions: Given a fitness function class, which functions are the easiest with respect to an evolutionary algorithm? Which are the hardest? How are these functions constructed? The paper provides theoretical answers to these questions. The easiest and hardest fitness functions are constructed for an elitist (1+1) evolutionary algorithm to maximise a class of fitness functions with the same optima. It is demonstrated that the unimodal functions are the easiest and deceptive functions are the hardest in terms of the time-fitness landscape. The paper also reveals that the easiest fitness function to one algorithm may become the hardest to another algorithm, and vice versa.

cs.NE↗
arXiv2015

The internal structures of the nucleon resonances $N(1875)$ and $N(2120)$

A nucleon resonance with spin-parity $J^P=3/2^-$ and mass about 2.1 GeV is essential to reproduce the photoproduction cross sections for $Λ(1520)$ released by the LEPS and CLAS Collaborations. It can be explained as the third nucleon resonance state $[3/2^-]_3$ in the constituent quark model so that there is no position to settle the $N(1875)$ which is listed in the PDG as the third $N3/2^-$ nucleon resonance. An interpretation is proposed that the $N(1875)$ is from the interaction of a decuplet baryon $Σ(1385)$ and a octet meson $K$, which is favored by a calculation of binding energy and decay pattern in a Bethe-Salpeter approach.

nucl-th↗
arXiv2014

Study of the $B\bar{B}^*/D\bar{D}^*$ bound states in a Bethe-Salpeter approach

In this work the $B\bar{B}^*/D\bar{D}^*$ system is studied in the Bethe-Salpeter approach with quasipotential approximation. In our calculation both direct and cross diagrams are included in the one-boson-exchange potential. The numerical results indicate the existence of a isoscalar bound state $D\bar{D}^*$ with $J^{PC}=1^{++}$, which may be related to the $X(3872)$. In the isovector sector, no bound state is produced from the interactions of $D\bar{D}^*$ and $B\bar{B}^*$, which suggests the molecular state explanations for $Z_b(10610)$ and $Z_c(3900)$ are excluded.

hep-ph↗
arXiv2014

Performance Analysis on Evolutionary Algorithms for the Minimum Label Spanning Tree Problem

Some experimental investigations have shown that evolutionary algorithms (EAs) are efficient for the minimum label spanning tree (MLST) problem. However, we know little about that in theory. As one step towards this issue, we theoretically analyze the performances of the (1+1) EA, a simple version of EAs, and a multi-objective evolutionary algorithm called GSEMO on the MLST problem. We reveal that for the MLST$_{b}$ problem the (1+1) EA and GSEMO achieve a $\frac{b+1}{2}$-approximation ratio in expected polynomial times of $n$ the number of nodes and $k$ the number of labels. We also show that GSEMO achieves a $(2ln(n))$-approximation ratio for the MLST problem in expected polynomial time of $n$ and $k$. At the same time, we show that the (1+1) EA and GSEMO outperform local search algorithms on three instances of the MLST problem. We also construct an instance on which GSEMO outperforms the (1+1) EA.

cs.NE↗
arXiv2014

Discovery potential of hidden charm baryon resonances via photoproduction

In this work, we study the possibility to find $N^*_{c\bar{c}}$ and $Λ^*_{c\bar{c}}$ resonances with hidden charm with mass above 4 GeV in the photon-induced production. The cross sections for the photoproductions of hidden charmed baryons are predicted in the effective Lagrangian approach with the vector meson dominance mechanism. The $N^*(4412)$ can be produced directly by photon excitation with total cross section about 1 nb. The $N^*(4412)$ provides a obvious peak near threshold for $J/ψ$ photoproduction, which is promising to be checked by the future high precision experiment at JLab 12 GeV. The results will be helpful to the experimental search for the hidden-charmed baryon resonances in the coming experiment at JLab 12 GeV, such as SoLID, and the proposed electron-ion colliders at FAIR and HIAF.

nucl-th↗
arXiv2014

Theoretical study of the $Λ$(1520) photoproduction off proton target based on the new CLAS data

Based on the high precision experimental data released by the CLAS Collaboration recently, the interaction mechanism of the photoproduction of $Λ$(1520) off a proton target is investigated within a Regge-plus-resonance approach. With the decay amplitudes predicted in the constituent quark model, the roles played by nucleon resonances are studied. It is found that $N(2120)$ provides the most important contribution among the nucleon resonances predicted in the constituent quark model. The $t$ channel contribution with Regge trajectories and the $Λ$ intermediate $u$ channel are responsible to the behaviors of the differential cross section at forward and backward angles, respectively.

nucl-th↗
arXiv2014

The $Σ$(1385) photoproduciton from proton within a Regge-plus-resonance approach

The interaction mechanism of the $Σ$(1385) photoproduction from proton is investigated within a Regge-plus-resonance approach based on the experimental data released by CLAS Collaboration recently. The t-channel and u-channel contributions are responsible to the behaviors of the differential cross sections at forward and backward angles, respectively. The contributions from nucleon resonances including $N^*$ and $Δ^*$, which are determined by the predicted decay amplitudes in constituent quark model, are found small but essential to reproduce the differential cross section especially the contribution from $F_{35}$ state $Δ(2000)$.

nucl-th↗