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Yong Chen

Publications and source records attributed to Yong Chen.

At least 307 records · Page 17Linked to original sources

Berry-Esséen bound for the Parameter Estimation of Fractional Ornstein-Uhlenbeck Processes with the Hurst Parameter $H\in (0,1/2)$

For an Ornstein-Uhlenbeck process driven by a fractional Brownian motion with Hurst parameter 0<H<1/2, one shows the Berry-Esséen bound of the least squares estimator of the drift parameter. Thus, a problem left in the previous paper (Chen, Kuang and Li in Stochastics and Dynamics, 2019+) is solved, where the Berry-Esséen bound of the least squares estimator is proved for 1/2<=H<=3/4. An approach based on Malliavin calculus given by Kim and Park \cite{kim 3} is used

math.PR↗

Modulation instability, rogue waves and spectral analysis for the sixth-order nonlinear Schrodinger equation

Modulation instability, rogue wave and spectral analysis are investigated for the nonlinear Schrodinger equation with the higher-order terms. The modulation instability distribution characteristics from the sixth-order to the eighth-order nonlinear Schrodinger equations are studied. Higher-order dispersion terms are closely related to the distribution of modulation stability regime, and n-order dispersion term corresponds to $n-2$ modulation stability curves in the modulation instability band. Based on the generalized Darboux transformation method, the higher-order rational solutions are constructed. Then the compact algebraic expression of the Nth-order rogue wave is given. Dynamic phenomena of first- to third-order rogue waves are illustrated, which exhibit meaningful structures. Two arbitrary parameters play important roles in the rogue wave solution. One can control deflection of crest of rogue wave and its width, while the other can cause the change of width and amplitude of rogue wave. When it comes to the third-order rogue wave, three typical nonlinear wave constructions, namely fundamental, circular and triangular are displayed and discussed. Through the spectral analysis on first-order rogue wave, when these parameters satisfy certain conditions, it occurs a transition between W-shaped soliton and rogue wave.

nlin.SI↗

Chaos in Born-Infeld-AdS black hole within extended phase space

Born-Infeld-AdS black holes in extended phase space may possess phase structures resembling that of van der Waals fluid in four-dimensional spacetime. We study dynamics of its state, which is in the unstable spinodal region initially on phase space, under time-periodic thermal perturbations. By applying the Melnikov method, it is found that there exists a critical amplitude $γ_c$ of the perturbations, which depends on the Born-Infeld parameter $b$ and the black hole charge $Q$, such that chaos occurs for $γ> γ_c$. We found that larger $b$ or $Q$ makes the onset of chaos easier. Space-periodic thermal perturbations on its equilibrium state are also studied and there is always chaos for whatever the perturbation amplitude is.

hep-th↗

Insight-HXMT observations of Swift J0243.6+6124 during its 2017-2018 outburst

The recently discovered neutron star transient Swift J0243.6+6124 has been monitored by {\it the Hard X-ray Modulation Telescope} ({\it Insight-\rm HXMT). Based on the obtained data, we investigate the broadband spectrum of the source throughout the outburst. We estimate the broadband flux of the source and search for possible cyclotron line in the broadband spectrum. No evidence of line-like features is, however, found up to $\rm 150~keV$. In the absence of any cyclotron line in its energy spectrum, we estimate the magnetic field of the source based on the observed spin evolution of the neutron star by applying two accretion torque models. In both cases, we get consistent results with $B\rm \sim 10^{13}~G$, $D\rm \sim 6~kpc$ and peak luminosity of $\rm >10^{39}~erg~s^{-1}$ which makes the source the first Galactic ultraluminous X-ray source hosting a neutron star.

astro-ph.HE↗

Exploring difference in public perceptions on HPV vaccine between gender groups from Twitter using deep learning

In this study, we proposed a convolutional neural network model for gender prediction using English Twitter text as input. Ensemble of proposed model achieved an accuracy at 0.8237 on gender prediction and compared favorably with the state-of-the-art performance in a recent author profiling task. We further leveraged the trained models to predict the gender labels from an HPV vaccine related corpus and identified gender difference in public perceptions regarding HPV vaccine. The findings are largely consistent with previous survey-based studies.

cs.CL↗

The $\rm{Y_{SZ,Planck} - Y_{SZ,XMM}}$ scaling relation and its difference between cool-core and non-cool-core clusters

We construct a sample of 70 clusters using data from XMM-Newton and Planck to investigate the $Y_{\rm SZ,Planck}-Y_{\rm SZ, XMM}$ scaling relation and the cool-core influences on the relation. $Y_{\rm SZ,XMM}$ is calculated by accurate de-projected temperature and electron number density profiles derived from XMM-Newton. $Y_{\rm SZ,Planck}$ is the latest Planck data restricted to our precise X-ray size $θ_{\rm 500}$. To study the cool-core influences on$Y_{\rm SZ,Planck}-Y_{\rm SZ, XMM}$ scaling relation, we apply two criteria, limits of central cooling time and classic mass deposition rate, to distinguish cool-core clusters (CCCs) from non-cool-core clusters (NCCCs). We also use $Y_{\rm SZ,Planck}$ from other papers, which are derived from different methods, to confirm our results. The intercept and slope of the$Y_{\rm SZ,Planck}-Y_{\rm SZ, XMM}$ scaling relation are $A=-0.86 \pm 0.30$, $B=0.83 \pm 0.06$. The intrinsic scatter is $σ_{\rm ins}= 0.14 \pm 0.03$. The ratio of \mbox{$Y_{\rm SZ,Planck}/Y_{\rm SZ, XMM}$} is $1.03 \pm 0.05$, which is perfectly agreed with unity. Discrepancies of $Y_{\rm SZ,Planck}-Y_{\rm SZ, XMM}$ scaling relation between CCCs and NCCCs are found in observation. They are independent of cool-core classification criteria and $Y_{\rm SZ,Planck}$ calculation methods, although discrepancies are more significant under the classification criteria of classic mass deposition rate. The intrinsic scatter of CCCs (0.04) is quite small compared to that of NCCCs (0.27). The ratio of $Y_{\rm SZ,Planck}/Y_{\rm SZ, XMM}$ for CCCs is $0.89 \pm 0.05$, suggesting that CCCs' $Y_{\rm SZ,XMM}$ may overestimate SZ signal. By contrast, the ratio of $Y_{\rm SZ,Planck}/Y_{\rm SZ, XMM}$ for NCCCs is $1.14 \pm 0.12$, which indicates that NCCCs' $Y_{\rm SZ,XMM}$ may underestimate SZ signal.

astro-ph.CO↗

Optimizing the SSD Burst Buffer by Traffic Detection

Currently, Burst buffer has been proposed to manage the SSD buffering of bursty write requests. Although burst buffer can improve I/O performance in many cases, we find that it has some limitations such as requiring large SSD capacity and harmonious overlapping between computation phase and data flushing phase. In this paper, we propose a scheme, called SSDUP+1. SSDUP+ aims to improve the burst buffer by addressing the above limitations. First, in order to reduce the demand for the SSD capacity, we develop a novel method to detect and quantify the data randomness in the write traffic. Further, an adaptive algorithm is proposed to classify the random writes dynamically. By doing so, much less SSD capacity is required to achieve the similar performance as other burst buffer schemes. Next, in order to overcome the difficulty of perfectly overlapping the computation phase and the flushing phase, we propose a pipeline mechanism for the SSD buffer, in which data buffering and flushing are performed in pipeline. In addition, in order to improve the I/O throughput, we adopt a traffic-aware flushing strategy to reduce the I/O interference in HDD. Finally, in order to further improve the performance of buffering random writes in SSD, SSDUP+ transforms the random writes to sequential writes in SSD by storing the data with a log structure. Further, SSDUP+ uses the AVL tree structure to store the sequence information of the data. We have implemented a prototype of SSDUP+ based on OrangeFS and conducted extensive experiments. The experimental results show that our proposed SSDUP+ can save an average of 50% SSD space, while delivering almost the same performance as other common burst buffer schemes. In addition, SSDUP+ can save about 20% SSD space compared with the previous version of this work, SSDUP, while achieving 20%-30% higher I/O throughput than SSDUP.

cs.DC↗

A local search $4/3$-approximation algorithm for the minimum $3$-path partition problem

Given a graph $G = (V, E)$, the $3$-path partition problem is to find a minimum collection of vertex-disjoint paths each of order at most $3$ to cover all the vertices of $V$. It is different from but closely related to the well-known $3$-set cover problem. The best known approximation algorithm for the $3$-path partition problem was proposed recently and has a ratio $13/9$. Here we present a local search algorithm and show, by an amortized analysis, that it is a $4/3$-approximation. This ratio matches up to the best approximation ratio for the $3$-set cover problem.

cs.DS↗

The enhanced X-ray Timing and Polarimetry mission - eXTP

In this paper we present the enhanced X-ray Timing and Polarimetry mission - eXTP. eXTP is a space science mission designed to study fundamental physics under extreme conditions of density, gravity and magnetism. The mission aims at determining the equation of state of matter at supra-nuclear density, measuring effects of QED, and understanding the dynamics of matter in strong-field gravity. In addition to investigating fundamental physics, eXTP will be a very powerful observatory for astrophysics that will provide observations of unprecedented quality on a variety of galactic and extragalactic objects. In particular, its wide field monitoring capabilities will be highly instrumental to detect the electro-magnetic counterparts of gravitational wave sources. The paper provides a detailed description of: (1) the technological and technical aspects, and the expected performance of the instruments of the scientific payload; (2) the elements and functions of the mission, from the spacecraft to the ground segment.

astro-ph.IM↗

Multi-dark soliton solutions for the multi-component coupled Maccari system

Based on the KP hierarchy reduction method, the general multi-dark soliton solutions in Gram type determinant forms for the multi-component coupled Maccari system are constructed. Especially, the three-component coupled Maccari system comprised of two-component short waves and single-component long waves are discussed in detail. Besides, the dynamics of one and two dark-dark solitons are analyzed. It is shown that the collisions of two dark-dark solitons are elastic by asymptotic analysis. Additionally, the two dark-dark solitons bound states are studied through two different cases (stationary and moving cases). The bound states can exist up to arbitrary order in the stationary case, however, only two-soliton bound state exists in the moving case. Besides, the oblique stationary bound state can be generated for all possible combinations of nonlinearity coefficients consisted of positive, negative and mixed cases. Nevertheless, the parallel stationary and the moving bound states are only possible when nonlinearity coefficients take opposite signs.

nlin.PS↗

Improved approximation algorithms for path vertex covers in regular graphs

Given a simple graph $G = (V, E)$ and a constant integer $k \ge 2$, the $k$-path vertex cover problem ({\sc P$k$VC}) asks for a minimum subset $F \subseteq V$ of vertices such that the induced subgraph $G[V - F]$ does not contain any path of order $k$. When $k = 2$, this turns out to be the classic vertex cover ({\sc VC}) problem, which admits a $\left(2 - {\rm Θ}\left(\frac 1{\log|V|}\right)\right)$-approximation. The general {\sc P$k$VC} admits a trivial $k$-approximation; when $k = 3$ and $k = 4$, the best known approximation results for {\sc P$3$VC} and {\sc P$4$VC} are a $2$-approximation and a $3$-approximation, respectively. On $d$-regular graphs, the approximation ratios can be reduced to $\min\left\{2 - \frac 5{d+3} + ε, 2 - \frac {(2 - o(1))\log\log d}{\log d}\right\}$ for {\sc VC} ({\it i.e.}, {\sc P$2$VC}), $2 - \frac 1d + \frac {4d - 2}{3d |V|}$ for {\sc P$3$VC}, $\frac {\lfloor d/2\rfloor (2d - 2)}{(\lfloor d/2\rfloor + 1) (d - 2)}$ for {\sc P$4$VC}, and $\frac {2d - k + 2}{d - k + 2}$ for {\sc P$k$VC} when $1 \le k-2 < d \le 2(k-2)$. By utilizing an existing algorithm for graph defective coloring, we first present a $\frac {\lfloor d/2\rfloor (2d - k + 2)}{(\lfloor d/2\rfloor + 1) (d - k + 2)}$-approximation for {\sc P$k$VC} on $d$-regular graphs when $1 \le k - 2 < d$. This beats all the best known approximation results for {\sc P$k$VC} on $d$-regular graphs for $k \ge 3$, except for {\sc P$4$VC} it ties with the best prior work and in particular they tie at $2$ on cubic graphs and $4$-regular graphs. We then propose a $1.875$-approximation and a $1.852$-approximation for {\sc P$4$VC} on cubic graphs and $4$-regular graphs, respectively. We also present a better approximation algorithm for {\sc P$4$VC} on $d$-regular bipartite graphs.

cs.DS↗

A Self-Organizing Tensor Architecture for Multi-View Clustering

In many real-world applications, data are often unlabeled and comprised of different representations/views which often provide information complementary to each other. Although several multi-view clustering methods have been proposed, most of them routinely assume one weight for one view of features, and thus inter-view correlations are only considered at the view-level. These approaches, however, fail to explore the explicit correlations between features across multiple views. In this paper, we introduce a tensor-based approach to incorporate the higher-order interactions among multiple views as a tensor structure. Specifically, we propose a multi-linear multi-view clustering (MMC) method that can efficiently explore the full-order structural information among all views and reveal the underlying subspace structure embedded within the tensor. Extensive experiments on real-world datasets demonstrate that our proposed MMC algorithm clearly outperforms other related state-of-the-art methods.

cs.LG↗

Approximation algorithms for the three-machine proportionate mixed shop scheduling

A mixed shop is a manufacturing infrastructure designed to process a mixture of a set of flow-shop jobs and a set of open-shop jobs. Mixed shops are in general much more complex to schedule than flow-shops and open-shops, and have been studied since the 1980's. We consider the three machine proportionate mixed shop problem denoted as $M3 \mid prpt \mid C_{\max}$, in which each job has equal processing times on all three machines. Koulamas and Kyparisis [{\it European Journal of Operational Research}, 243:70--74,2015] showed that the problem is solvable in polynomial time in some very special cases; for the non-solvable case, they proposed a $5/3$-approximation algorithm. In this paper, we present an improved $4/3$-approximation algorithm and show that this ratio of $4/3$ is asymptotically tight; when the largest job is a flow-shop job, we present a fully polynomial-time approximation scheme (FPTAS). On the negative side, while the $F3 \mid prpt \mid C_{\max}$ problem is polynomial-time solvable, we show an interesting hardness result that adding one open-shop job to the job set makes the problem NP-hard if this open-shop job is larger than any flow-shop job. We are able to design an FPTAS for this special case too.

cs.DS↗

Quantitative analysis on the disparity of regional economic development in China and its evolution from 1952 to 2000

Domestic and foreign scholars have already done much research on regional disparity and its evolution in China, but there is a big difference in conclusions. What is the reason for this? We think it is mainly due to different analytic approaches, perspectives, spatial units, statistical indicators and different periods for studies. On the basis of previous analyses and findings, we have done some further quantitative computation and empirical study, and revealed the inter-provincial disparity and regional disparity of economic development and their evolution trends from 1952-2000. The results shows that (a) Regional disparity in economic development in China, including the inter-provincial disparity, inter-regional disparity and intra-regional disparity, has existed for years; (b) Gini coefficient and Theil coefficient have revealed a similar dynamic trend for comparative disparity in economic development between provinces in China. From 1952 to 1978, except for the "Great Leap Forward" period, comparative disparity basically assumes a upward trend and it assumed a slowly downward trend from 1979 to1990. Afterwards from 1991 to 2000 the disparity assumed a slowly upward trend again; (c) A comparison between Shanghai and Guizhou shows that absolute inter-provincial disparity has been quite big for years; and (d) The Hurst exponent (H=0.5) in the period of 1966-1978 indicates that the comparative inter-provincial disparity of economic development showed a random characteristic, and in the Hurst exponent (H>0.5) in period of 1979-2000 indicates that in this period the evolution of the comparative inter-provincial disparity of economic development in China has a long-enduring characteristic.

stat.AP↗

Testing small study effects in multivariate meta-analysis

Small study effects occur when smaller studies show different, often larger, treatment effects than large ones, which may threaten the validity of systematic reviews and meta-analyses. The most well-known reasons for small study effects include publication bias, outcome reporting bias and clinical heterogeneity. Methods to account for small study effects in univariate meta-analysis have been extensively studied. However, detecting small study effects in a multivariate meta-analysis setting remains an untouched research area. One of the complications is that different types of selection processes can be involved in the reporting of multivariate outcomes. For example, some studies may be completely unpublished while others may selectively report multiple outcomes. In this paper, we propose a score test as an overall test of small study effects in multivariate meta-analysis. Two detailed case studies are given to demonstrate the advantage of the proposed test over various naive applications of univariate tests in practice. Through simulation studies, the proposed test is found to retain nominal Type I error with considerable power in moderate sample size settings. Finally, we also evaluate the concordance between the proposed test with the naive application of univariate tests by evaluating 44 systematic reviews with multiple outcomes from the Cochrane Database.

stat.ME↗

Client-side Straggler-Aware I/O Scheduler for Object-based Parallel File Systems

Object-based parallel file systems have emerged as promising storage solutions for high-performance computing (HPC) systems. Despite the fact that object storage provides a flexible interface, scheduling highly concurrent I/O requests that access a large number of objects still remains as a challenging problem, especially in the case when stragglers (storage servers that are significantly slower than others) exist in the system. An efficient I/O scheduler needs to avoid possible stragglers to achieve low latency and high throughput. In this paper, we introduce a log-assisted straggler-aware I/O scheduling to mitigate the impact of storage server stragglers. The contribution of this study is threefold. First, we introduce a client-side, log-assisted, straggler-aware I/O scheduler architecture to tackle the storage straggler issue in HPC systems. Second, we present three scheduling algorithms that can make efficient decision for scheduling I/Os while avoiding stragglers based on such an architecture. Third, we evaluate the proposed I/O scheduler using simulations, and the simulation results have confirmed the promise of the newly introduced straggler-aware I/O scheduler.

cs.DC↗

A Software-Defined Approach for QoS Control in High-Performance Computing Storage Systems

High-performance computing (HPC) storage systems become increasingly critical to scientific applications given the data-driven discovery paradigm shift. As a storage solution for large-scale HPC systems, dozens of applications share the same storage system, and will compete and can interfere with each other. Application interference can dramatically degrade the overall storage system performance. Therefore, developing a flexible and effective storage solution to assure a certain level of resources per application, i.e. the Quality-of-Service (QoS) support, is critical. One of the common solution to achieve QoS assurance for storage systems is using provisioning technique~\cite{3}. Provisioning refers to the ability of providing certain amount of resources for applications and expected workloads. However, provisioning has limitations such as requiring the detailed knowledge of the expected workloads. In addition, the storage workloads are transient hence expensive to be satisfied. Due to these limitations, providing QoS storage systems through provisioning is challenging. In this research, a software-defined approach~\cite{0} is proposed as a flexible solution to achieve QoS guarantee for storage systems. The driving force of using a software-defined approach instead of the traditional approaches, is that it has the ability to enable a more flexible, scalable, and efficient platform. For example, if any changes occurred in the system, it does not necessarily need to re-configure thousands of devices; instead, with re-configuring a logically centralized component, other devices will be automatically notified.

cs.DC↗

A Cross-Layer Solution in Scientific Workflow System for Tackling Data Movement Challenge

Scientific applications in HPC environment are more com-plex and more data-intensive nowadays. Scientists usually rely on workflow system to manage the complexity: simply define multiple processing steps into a single script and let the work-flow systems compile it and schedule all tasks accordingly. Numerous workflow systems have been proposed and widely used, like Galaxy, Pegasus, Taverna, Kepler, Swift, AWE, etc., to name a few examples. Traditionally, scientific workflow systems work with parallel file systems, like Lustre, PVFS, Ceph, or other forms of remote shared storage systems. As such, the data (including the intermediate data generated during workflow execution) need to be transferred back and forth between compute nodes and storage systems, which introduces a significant performance bottleneck on I/O operations. Along with the enlarging perfor-mance gap between CPU and storage devices, this bottleneck is expected to be worse. Recently, we have introduced a new concept of Compute-on-Data-Path to allow tasks and data binding to be more efficient to reduce the data movement cost. To workflow systems, the key is to exploit the data locality in HPC storage hierarchy: if the datasets are stored in compute nodes, near the workflow tasks, then the task can directly access them with better performance with less network usage. Several recent studies have been done regarding building such a shared storage system, utilizing compute node resources, to serve HPC workflows with locality, such as Hercules [1] and WOSS [2] etc. In this research, we further argue that providing a compute-node side storage system is not sufficient to fully exploit data locality. A cross-layer solution combining storage system, compiler, and runtime is necessary. We take Swift/T [3], a workflow system for data-intensive applications, as a prototype platform to demonstrate such a cross-layer solution

cs.DC↗