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Peng Gao

Publications and source records attributed to Peng Gao.

At least 451 records · Page 25Linked to original sources

A Complementary Tracking Model with Multiple Features

Discriminative Correlation Filters based tracking algorithms exploiting conventional handcrafted features have achieved impressive results both in terms of accuracy and robustness. Template handcrafted features have shown excellent performance, but they perform poorly when the appearance of target changes rapidly such as fast motions and fast deformations. In contrast, statistical handcrafted features are insensitive to fast states changes, but they yield inferior performance in the scenarios of illumination variations and background clutters. In this work, to achieve an efficient tracking performance, we propose a novel visual tracking algorithm, named MFCMT, based on a complementary ensemble model with multiple features, including Histogram of Oriented Gradients (HOGs), Color Names (CNs) and Color Histograms (CHs). Additionally, to improve tracking results and prevent targets drift, we introduce an effective fusion method by exploiting relative entropy to coalesce all basic response maps and get an optimal response. Furthermore, we suggest a simple but efficient update strategy to boost tracking performance. Comprehensive evaluations are conducted on two tracking benchmarks demonstrate and the experimental results demonstrate that our method is competitive with numerous state-of-the-art trackers. Our tracker achieves impressive performance with faster speed on these benchmarks.

cs.CV↗

Some extensions of Diananda's inequality

Let $M_{n,r}=(\sum_{i=1}^{n}q_ix_i^r)^{\frac {1}{r}}, r \neq 0$ and $M_{n,0}=\lim_{r \rightarrow 0}M_{n,r}$ be the weighted power means of $n$ non-negative numbers $x_i$ with $q_i > 0$ satisfying $\sum^n_{i=1}q_i=1$. For a real number $α$ and mutually distinct real numbers $r, s, t$, we define \begin{align*} Δ_{r,s,t,α}=\Big | \frac {M^α_{n,r}-M^α_{n,t}}{M^α_{n,r}-M^α_{n,s}}\Big |. \end{align*} A result of Diananda gives sharp bounds of $Δ_{1, 1/2, 0, 1}$ in terms of functions of $q$ only, where $q=\min q_i$. In this paper, we prove similar sharp bounds of $Δ_{r,s,t,α}$ for certain parameters $r, s, t, α$.

math.CA↗

A ferroelectric problem beyond the conventional scaling law

Ferroelectric (FE) size effects against the scaling law were reported recently in ultrathin group-IV monochalcogenides, and extrinsic effects (e.g. defects and lattice strains) were often resorted to. Via first-principles based finite-temperature ($T$) simulations, we reveal that these abnormalities are intrinsic to their unusual symmetry breaking from bulk to thin film. Changes of the electronic structures result in different order parameters characterizing the FE phase transition in bulk and in thin films, and invalidation of the scaling law. Beyond the scaling law $T_{\text{c}}$ limit, this mechanism can help predicting materials promising for room-$T$ ultrathin FE devices of broad interest.

cond-mat.mtrl-sci↗

SAQL: A Stream-based Query System for Real-Time Abnormal System Behavior Detection

Recently, advanced cyber attacks, which consist of a sequence of steps that involve many vulnerabilities and hosts, compromise the security of many well-protected businesses. This has led to the solutions that ubiquitously monitor system activities in each host (big data) as a series of events, and search for anomalies (abnormal behaviors) for triaging risky events. Since fighting against these attacks is a time-critical mission to prevent further damage, these solutions face challenges in incorporating expert knowledge to perform timely anomaly detection over the large-scale provenance data. To address these challenges, we propose a novel stream-based query system that takes as input, a real-time event feed aggregated from multiple hosts in an enterprise, and provides an anomaly query engine that queries the event feed to identify abnormal behaviors based on the specified anomalies. To facilitate the task of expressing anomalies based on expert knowledge, our system provides a domain-specific query language, SAQL, which allows analysts to express models for (1) rule-based anomalies, (2) time-series anomalies, (3) invariant-based anomalies, and (4) outlier-based anomalies. We deployed our system in NEC Labs America comprising 150 hosts and evaluated it using 1.1TB of real system monitoring data (containing 3.3 billion events). Our evaluations on a broad set of attack behaviors and micro-benchmarks show that our system has a low detection latency (<2s) and a high system throughput (110,000 events/s; supporting ~4000 hosts), and is more efficient in memory utilization than the existing stream-based complex event processing systems.

cs.CR↗

On Copson's inequalities for $0<p<1$

Let $(λ_n)_{n \geq 1}$ be a non-negative sequence with $λ_1>0$ and let $Λ_n=\sum^n_{i=1}λ_i$. We study the following Copson inequality for $0 p$, \begin{align*} \sum^{\infty}_{n=1}\left (\frac 1{Λ_n} \sum^{\infty}_{k=n}λ_k x_k \right )^p \geq \left ( \frac {p}{L-p}\right )^p \sum^{\infty}_{n=1}x^p_n. \end{align*} We find conditions on $λ_n$ such that the above inequality is valid with the constant being best possible.

math.CA↗

Atomic Origin of Ti Deficient Dislocation in SrTiO3 Bicrystal and Their Electronic Structures

Dislocations in perovskite oxides have important impacts on their physical and chemical properties, which are determined by their unique atomic environments. In the present study, the structure of dislocations in a 10° low-angle grain boundary of SrTiO3 (STO) is characterized by spherical aberration corrected scanning transmission electron microscopy (Cs-STEM) and spectroscopy. In contrast to previous studies, the deficiency instead of enrichment of titanium (Ti) is observed at the dislocation cores mainly due to the Sr substitution and under occupancy of Ti. The presence of oxygen vacancies and partially reduced Ti are also detected at the Ti deficient dislocations cores. These findings indicate the atomic structure of dislocations can be very different even they have the same Burges vectors. Controllable elemental segregation in the dislocations and grain boundaries via bicrystal engineering should be very useful for design of devices with novel functions.

cond-mat.mtrl-sci↗

SybilFuse: Combining Local Attributes with Global Structure to Perform Robust Sybil Detection

Sybil attacks are becoming increasingly widespread and pose a significant threat to online social systems; a single adversary can inject multiple colluding identities in the system to compromise security and privacy. Recent works have leveraged social network-based trust relationships to defend against Sybil attacks. However, existing defenses are based on oversimplified assumptions about network structure, which do not necessarily hold in real-world social networks. Recognizing these limitations, we propose SybilFuse, a defense-in-depth framework for Sybil detection when the oversimplified assumptions are relaxed. SybilFuse adopts a collective classification approach by first training local classifiers to compute local trust scores for nodes and edges, and then propagating the local scores through the global network structure via weighted random walk and loopy belief propagation mechanisms. We evaluate our framework on both synthetic and real-world network topologies, including a large-scale, labeled Twitter network comprising 20M nodes and 265M edges, and demonstrate that SybilFuse outperforms state-of-the-art approaches significantly. In particular, SybilFuse achieves 98% of Sybil coverage among top-ranked nodes.

cs.CR↗

AIQL: Enabling Efficient Attack Investigation from System Monitoring Data

The need for countering Advanced Persistent Threat (APT) attacks has led to the solutions that ubiquitously monitor system activities in each host, and perform timely attack investigation over the monitoring data for analyzing attack provenance. However, existing query systems based on relational databases and graph databases lack language constructs to express key properties of major attack behaviors, and often execute queries inefficiently since their semantics-agnostic design cannot exploit the properties of system monitoring data to speed up query execution. To address this problem, we propose a novel query system built on top of existing monitoring tools and databases, which is designed with novel types of optimizations to support timely attack investigation. Our system provides (1) domain-specific data model and storage for scaling the storage, (2) a domain-specific query language, Attack Investigation Query Language (AIQL) that integrates critical primitives for attack investigation, and (3) an optimized query engine based on the characteristics of the data and the semantics of the queries to efficiently schedule the query execution. We deployed our system in NEC Labs America comprising 150 hosts and evaluated it using 857 GB of real system monitoring data (containing 2.5 billion events). Our evaluations on a real-world APT attack and a broad set of attack behaviors show that our system surpasses existing systems in both efficiency (124x over PostgreSQL, 157x over Neo4j, and 16x over Greenplum) and conciseness (SQL, Neo4j Cypher, and Splunk SPL contain at least 2.4x more constraints than AIQL).

cs.CR↗

A Novel Low-cost FPGA-based Real-time Object Tracking System

In current visual object tracking system, the CPU or GPU-based visual object tracking systems have high computational cost and consume a prohibitive amount of power. Therefore, in this paper, to reduce the computational burden of the Camshift algorithm, we propose a novel visual object tracking algorithm by exploiting the properties of the binary classifier and Kalman predictor. Moreover, we present a low-cost FPGA-based real-time object tracking hardware architecture. Extensive evaluations on OTB benchmark demonstrate that the proposed system has extremely compelling real-time, stability and robustness. The evaluation results show that the accuracy of our algorithm is about 48%, and the average speed is about 309 frames per second.

cs.CV↗

A Novel Parallel Ray-Casting Algorithm

The Ray-Casting algorithm is an important method for fast real-time surface display from 3D medical images. Based on the Ray-Casting algorithm, a novel parallel Ray-Casting algorithm is proposed in this paper. A novel operation is introduced and defined as a star operation, and star operations can be computed in parallel in the proposed algorithm compared with the serial chain of star operations in the Ray-Casting algorithm. The computation complexity of the proposed algorithm is reduced from $O(n)$ to $O(\log^n_2)$.

cs.CV↗

High-efficiency perovskite-polymer bulk heterostructure light-emitting diodes

Perovskite-based optoelectronic devices have gained significant attention due to their remarkable performance and low processing cost, particularly for solar cells. However, for perovskite light-emitting diodes (LEDs), non-radiative charge carrier recombination has limited electroluminescence (EL) efficiency. Here we demonstrate perovskite-polymer bulk heterostructure LEDs exhibiting record-high external quantum efficiencies (EQEs) exceeding 20%, and an EL half-life of 46 hours under continuous operation. This performance is achieved with an emissive layer comprising quasi-2D and 3D perovskites and an insulating polymer. Transient optical spectroscopy reveals that photogenerated excitations at the quasi-2D perovskite component migrate to lower-energy sites within 1 ps. The dominant component of the photoluminescence (PL) is primarily bimolecular and is characteristic of the 3D regions. From PL quantum efficiency and transient kinetics of the emissive layer with/without charge-transport contacts, we find non-radiative recombination pathways to be effectively eliminated. Light outcoupling from planar LEDs, as used in OLED displays, generally limits EQE to 20-30%, and we model our reported EL efficiency of over 20% in the forward direction to indicate the internal quantum efficiency (IQE) to be close to 100%. Together with the low drive voltages needed to achieve useful photon fluxes (2-3 V for 0.1-1 mA/cm2), these results establish that perovskite-based LEDs have significant potential for light-emission applications.

physics.app-ph↗

Tunneling Topological Vacua via Extended Operators: (Spin-)TQFT Spectra and Boundary Deconfinement in Various Dimensions

Distinct quantum vacua of topologically ordered states can be tunneled into each other via extended operators. The possible applications include condensed matter and quantum cosmology. We present a straightforward approach to calculate the partition function on various manifolds and ground state degeneracy (GSD), mainly based on continuum/cochain Topological Quantum Field Theories (TQFT), in any dimension. This information can be related to the counting of extended operators of bosonic/fermionic TQFT. On the lattice scale, anyonic particles/strings live at the ends of line/surface operators. Certain systems in different dimensions are related to each other through dimensional reduction schemes, analogous to (de)categorification. Examples include spin TQFTs derived from gauging the interacting fermionic symmetry protected topological states (with fermion parity $\mathbb{Z}_2^f$) of symmetry group $\mathbb{Z}_4\times \mathbb{Z}_2$ and $(\mathbb{Z}_4)^2$ in 3+1D, also $\mathbb{Z}_2$ and $(\mathbb{Z}_2)^2$ in 2+1D. Gauging the last three cases begets non-Abelian spin TQFT/topological order. We consider situations where a TQFT lives on (1) a closed spacetime or (2) a spacetime with boundary, such that the bulk and boundary are fully-gapped and short or long-range entangled (SRE/LRE). Anyonic excitations can be deconfined on the boundary. We introduce new exotic topological interfaces on which neither particle nor string excitations alone condensed, but only fuzzy-composite objects of extended operators can end (e.g. a string-like composite object formed by a set of particles can end on a special 2+1D boundary of 3+1D bulk). We explore the relations between group extension constructions and partially breaking constructions (e.g. 0-form/higher-form/composite breaking) of topological boundaries, after gauging. We comment on the implications of entanglement entropy for some of such LRE systems.

cond-mat.str-el↗

SybilFrame: A Defense-in-Depth Framework for Structure-Based Sybil Detection

Sybil attacks are becoming increasingly widespread, and pose a significant threat to online social systems; a single adversary can inject multiple colluding identities in the system to compromise security and privacy. Recent works have leveraged the use of social network-based trust relationships to defend against Sybil attacks. However, existing defenses are based on oversimplified assumptions, which do not hold in real world social graphs. In this work, we propose SybilFrame, a defense-in-depth framework for mitigating the problem of Sybil attacks when the oversimplified assumptions are relaxed. Our framework is able to incorporate prior information about users and edges in the social graph. We validate our framework on synthetic and real world network topologies, including a large-scale Twitter dataset with 20M nodes and 265M edges, and demonstrate that our scheme performs an order of magnitude better than previous structure-based approaches.

cs.SI↗

Atomic-scale structure and chemistry of YIG/GGG Interface

Y3Fe5O12 (YIG) is a promising candidate for spin wave devices. In the thin film devices, the interface between YIG and substrate may play important roles in determining the device properties. Here, we use spherical aberration-corrected scanning electron microscopy and spectroscopy to study the atomic arrangement, chemistry and electronic structure of the YIG/Gd3Ga5O12 (GGG) interface. We find that the chemical bonding of the interface is FeO-GdGaO and the interface remains sharp in both atomic and electronic structures. These results provide necessary information for understanding the properties of interface and also for atomistic calculation.

cond-mat.mtrl-sci↗

Mean values of some Hecke characters

In this paper, we evaluate a smoothed character sum involving $\sum_{m}\sum_{n}\leg {m}{n}$, with quadratic, cubic or quartic Hecke characters $\leg {m}{n}$, and the two sums over $m$ and $n$ are of comparable lengths.

math.NT↗

Ferroic Domains of Alternating Polar and Nonpolar Orders Regulate Photocurrent in Single Crystalline CH3NH3PbI3 Films Self-grown on FTO/TiO2 Substrate

Photovoltaic conversion efficiency (PCE) of halide perovskite solar cells has risen spectacularly, yet the very crystalline structure of CH3NH3PbI3 remains ambiguous after extensive researches, and its polar nature remains hotly debated. Here we present compelling evidences that CH3NH3PbI3 crystals self-grown on FTO/TiO2 substrate consist of ferroic domains with alternating polar and nonpolar orders, in contrast to previous experimental and theoretical expectations, and polar domains possess reduced photocurrent. It is found that polar and nonpolar orders of CH3NH3PbI3 can be distinguished from their distinct lateral piezoresponse, energy dissipation, first and second harmonic electromechanical couplings, and temperature variation, even though their difference in crystalline lattice is very subtle, and they possess two-way memory effect through cubic-tetragonal phase transition. These findings resolve key questions regarding polar nature of CH3NH3PbI3 and its implication on photovoltaics, reconcile contradictory data widely reported, and point a direction toward engineering ferroic domains for enhanced PCE.

cond-mat.mtrl-sci↗

Promise of Commercialization: Carbon Materials for Low-Cost Perovskite Solar Cells

Perovskite solar cells (PVSCs) have attracted extensive studies due to their high power conversion efficiency (PCE) with low-cost in both raw material and processes. However, there remain obstacles that hinder the way to its commercialization. Among many drawbacks in PVSCs, we note the problems brought by the use of noble metal counter electrodes (CEs) such as gold (Au) and silver (Ag). The costly Au and Ag need high energy-consumption thermal evaporation process which can be made only with expensive evaporation equipment under vacuum. All the factors elevate the threshold of PVSCs' commercialization. Carbon material, on the other hand, is a readily available electrode candidate for the application as CE in the PVSCs. In this review, endeavors on PVSCs with low-cost carbon materials will be comprehensively discussed based on different device structures and carbon composition. We believe that the PVSCs with carbon-based CE hold the promise of commercialization of this new technology.

physics.app-ph↗

Vector rogue waves on a double-plane wave background

We study rogue wave excitation dynamics on a double-plane wave background through deriving rogue wave solution on the background. The results indicate that rogue wave still can be excited successfully from resonant perturbations with the two plane wave backgrounds. The obtained vector rogue wave can be decomposed to two rogue waves located on the two backgrounds separately. This enables us to investigate the superpositions of two of the three well-known fundamental rogue wave patterns, mainly including eye-shaped, anti-eye-shaped, and four-petaled one. The explicit conditions for different possible superpositions are clarified by a phase diagram for rogue wave pattern on each plane wave background. The detail analysis indicate that the rogue wave admits many different profiles, in contrast to the ones reported before. The studies can be extended directly to investigate other localized waves on double-plane wave background and even more plane waves involved cases.

nlin.PS↗