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Yingying Zhang

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math.CO Machine Learning math.RT eess.SP math.DG Applications Artificial Intelligence Computer Vision cond-mat.mtrl-sci Logic in Computer Science math.RA Networking and Internet Architecture physics.optics Software Engineering

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preprint2026arXiv

Robust Sequential Experimental Design for A/B Testing

Experimental design has emerged as a powerful approach for improving the sample efficiency of A/B testing, yet existing designs rely critically on correctly specified models. We study robust sequential experimental design under model misspecification and develop a unified framework that covers both contextual bandit and dynamic settings. Theoretically, we prove that our design bounds the worst-case mean squared error of the estimated treatment effect. Empirically, we demonstrate the effectiveness of the proposed approach using synthetic and real-world datasets from a leading technology company.

preprint2023arXiv

Applications of Gorenstein projective $τ$ -rigid modules

We first introduce the notion of $CM$ - $τ$ -tilting free algebras as the generalization of $CM$ -free algebras and show the homological properties of $CM$ - $τ$ -tilting free algebras. Then we give a bijection between Gorenstein projective $τ$ -rigid modules and certain modules by using an equivalence established by Kong and Zhang. Finally, we give a partial answer to Tachikawa's first conjecture by using Gorenstein projective $τ$ -rigid modules.

preprint2022arXiv

KRNet: Towards Efficient Knowledge Replay

The knowledge replay technique has been widely used in many tasks such as continual learning and continuous domain adaptation. The key lies in how to effectively encode the knowledge extracted from previous data and replay them during current training procedure. A simple yet effective model to achieve knowledge replay is autoencoder. However, the number of stored latent codes in autoencoder increases linearly with the scale of data and the trained encoder is redundant for the replaying stage. In this paper, we propose a novel and efficient knowledge recording network (KRNet) which directly maps an arbitrary sample identity number to the corresponding datum. Compared with autoencoder, our KRNet requires significantly ( $400\times$ ) less storage cost for the latent codes and can be trained without the encoder sub-network. Extensive experiments validate the efficiency of KRNet, and as a showcase, it is successfully applied in the task of continual learning.

preprint2022arXiv

NetRCA: An Effective Network Fault Cause Localization Algorithm

Localizing the root cause of network faults is crucial to network operation and maintenance. However, due to the complicated network architectures and wireless environments, as well as limited labeled data, accurately localizing the true root cause is challenging. In this paper, we propose a novel algorithm named NetRCA to deal with this problem. Firstly, we extract effective derived features from the original raw data by considering temporal, directional, attribution, and interaction characteristics. Secondly, we adopt multivariate time series similarity and label propagation to generate new training data from both labeled and unlabeled data to overcome the lack of labeled samples. Thirdly, we design an ensemble model which combines XGBoost, rule set learning, attribution model, and graph algorithm, to fully utilize all data information and enhance performance. Finally, experiments and analysis are conducted on the real-world dataset from ICASSP 2022 AIOps Challenge to demonstrate the superiority and effectiveness of our approach.

preprint2022arXiv

Reduction of wide subcategories and recollements

In this paper, we prove a reduction result on wide subcategories of abelian categories which is similar to Calabi-Yau reduction, silting reduction and $τ$ -tilting reduction. More precisely, if an abelian category $\mathcal{A}$ admits a recollement relative to abelian categories $\mathcal{A}'$ and $\mathcal{A}"$ , diagrammatically expressed by $$\xymatrix@!C=2pc{ \mathcal{A'} \ar@{>->}[rr]|{i_{*}} && \mathcal{A} \ar@<-4.0mm>@{->>}[ll]_{i^{*}} \ar@{->>}[rr]|{j^{*}} \ar@{->>}@<4.0mm>[ll]^{i^{!}}&& \mathcal{A''} \ar@{>->}@<-4.0mm>[ll]_{j_{!}} \ar@{>->}@<4.0mm>[ll]^{j_{*}} },$$ then the assignment $\cc\mapsto j^*(\cc)$ defines a bijection between wide subcategories in $\mathcal{A}$ containing $i_{*}(\mathcal{A}')$ and wide subcategories in $\mathcal{A}"$ . Moreover, a wide subcategory $\mathcal{C}$ of $\mathcal{A}$ containing $i_{*}(\mathcal{A}')$ admits a new recollement relative to $\mathcal{A}'$ and $j^{*}(\mathcal{C})$ which is induced from the original recollement.

preprint2022arXiv

Symmetry-protected higher-order exceptional points in staggered flatband rhombic lattices

Higher-order exceptional points (EPs), which appear as multifold degeneracies in the spectra of non-Hermitian systems, are garnering extensive attention in various multidisciplinary fields. However, constructing higher-order EPs still remains as a challenge due to the strict requirement of the system symmetries. Here we demonstrate that higher-order EPs can be judiciously fabricated in PT -symmetric staggered rhombic lattices by introducing not only on-site gain/loss but also nonHermitian couplings. Zero-energy flatbands persist and symmetry-protected third-order EPs (EP3) arise in these systems owing to the non-Hermitian chiral/sublattice symmetry, but distinct phase transitions and propagation dynamics occur. Specifically, the EP3 arises at the Brillouin zone (BZ) boundary in the presence of on-site gain/loss. The single-site excitations display an exponential power increase in the PT -broken phase. Meanwhile, a nearly flatband sustains when a small lattice perturbation is applied. For the lattices with non-Hermitian couplings, however, the EP3 appears at the BZ center. Quite remarkably, our analysis unveils a dynamical delocalization-localization transition for the excitation of the dispersive bands and a quartic power increase beyond the EP3. Our scheme provides a new platform towards the investigation of the higher-order EPs, and can be further extended to the study of topological phase transitions or nonlinear processes associated with higher-order EPs.

preprint2021arXiv

RobustPeriod: Time-Frequency Mining for Robust Multiple Periodicity Detection

Periodicity detection is a crucial step in time series tasks, including monitoring and forecasting of metrics in many areas, such as IoT applications and self-driving database management system. In many of these applications, multiple periodic components exist and are often interlaced with each other. Such dynamic and complicated periodic patterns make the accurate periodicity detection difficult. In addition, other components in the time series, such as trend, outliers and noises, also pose additional challenges for accurate periodicity detection. In this paper, we propose a robust and general framework for multiple periodicity detection. Our algorithm applies maximal overlap discrete wavelet transform to transform the time series into multiple temporal-frequency scales such that different periodic components can be isolated. We rank them by wavelet variance, and then at each scale detect single periodicity by our proposed Huber-periodogram and Huber-ACF robustly. We rigorously prove the theoretical properties of Huber-periodogram and justify the use of Fisher's test on Huber-periodogram for periodicity detection. To further refine the detected periods, we compute unbiased autocorrelation function based on Wiener-Khinchin theorem from Huber-periodogram for improved robustness and efficiency. Experiments on synthetic and real-world datasets show that our algorithm outperforms other popular ones for both single and multiple periodicity detection.

preprint2020arXiv

Local State Space Analysis to Assist Partial Order Reduction

This paper presents an approach to more efficient partial order reduction for model checking concurrent systems. This approach utilizes a compositional reachability analysis to generate over-approximate local state transition models for all processes in a concurrent system where an independence relation and other useful information can be extracted. The extracted independence relation, compared to what can be obtained by statically analyzing the system descriptions, is more precise and refined, therefore leads to more efficient partial order reduction. This approach is demonstrated on a set of concurrent system examples. Significantly higher reduction in state space has been observed in several cases compared to what can be obtained using SPIN.

preprint2016arXiv

Erdős-Gallai-type results for total monochromatic connection of graphs

preprint2016arXiv

G-stable support $τ$ -tilting modules

Motivated by $τ$ -tilting theory developed by Adachi, Iyama and Reiten, for a finite-dimensional algebra $Λ$ with action by a finite group $G$ , we introduce the notion of $G$ -stable support $τ$ -tilting modules. Then we establish bijections among $G$ -stable support $τ$ -tilting modules over $Λ$ , $G$ -stable two-term silting complexes in the homotopy category of bounded complexes of finitely generated projective $Λ$ -modules, and $G$ -stable functorially finite torsion classes in the category of finitely generated left $Λ$ -modules. In the case when $Λ$ is the endomorphism of a $G$ -stable cluster-tilting object $T$ over a Hom-finite 2-Calabi-Yau triangulated category $\mathcal{C}$ with a $G$ -action, these are also in bijection with $G$ -stable cluster-tilting objects in $\mathcal{C}$ . Moreover, we investigate the relationship between stable support $τ$ -tilitng modules over $Λ$ and the skew group algebra $ΛG$ .

preprint2016arXiv

More on total monochromatic connection of graphs

A graph is said to be {\it total-colored} if all the edges and the vertices of the graph are colored. A total-coloring of a graph is a {\it total monochromatically-connecting coloring} ({\it TMC-coloring}, for short) if any two vertices of the graph are connected by a path whose edges and internal vertices on the path have the same color. For a connected graph $G$ , the {\it total monochromatic connection number}, denoted by $tmc(G)$ , is defined as the maximum number of colors used in a TMC-coloring of $G$ . Note that a TMC-coloring does not exist if $G$ is not connected, in which case we simply let $tmc(G)=0$ . In this paper, we first characterize all graphs of order $n$ and size $m$ with $tmc(G)=3,4,5,6,m+n-2,m+n-3$ and $m+n-4$ , respectively. Then we determine the threshold function for a random graph to have $tmc(G)\geq f(n)$ , where $f(n)$ is a function satisfying $1\leq f(n)<\frac{1}{2}n(n-1)+n$ . Finally, we show that for a given connected graph $G$ , and a positive integer $L$ with $L\leq m+n$ , it is NP-complete to decide whether $tmc(G)\geq L$ .

preprint2016arXiv

On mutation of τ-tilting modules

Mutation of τ-tilting modules is a basic operation to construct a new support τ-tilting module from a given one by replacing a direct summand. The aim of this paper is to give a positive answer to the question posed in [AIR, Question 2.31] about mutation of τ-tilting modules.

preprint2016arXiv

Regularity of Harmonic Maps from Polyhedra to CAT(1) Spaces

We determine regularity results for energy minimizing maps from an $n$ -dimensional Riemannian polyhedral complex $X$ into a CAT(1) space. Provided that the metric on $X$ is Lipschitz regular, we prove Hölder regularity with Hölder constant and exponent dependent on the total energy of the map and the metric on the domain. Moreover, at points away from the $(n-2)$ -skeleton, we improve the regularity to locally Lipschitz. Finally, for points $x \in X^{(k)}$ with $k \leq n-2$ , we demonstrate that the Hölder exponent depends on geometric and combinatorial data of the link of $x \in X$ .

preprint2016arXiv

Total monochromatic connection of graphs

A graph is said to be {\it total-colored} if all the edges and the vertices of the graph are colored. A path in a total-colored graph is a {\it total monochromatic path} if all the edges and internal vertices on the path have the same color. A total-coloring of a graph is a {\it total monochromatically-connecting coloring} ({\it TMC-coloring}, for short) if any two vertices of the graph are connected by a total monochromatic path of the graph. For a connected graph $G$ , the {\it total monochromatic connection number}, denoted by $tmc(G)$ , is defined as the maximum number of colors used in a TMC-coloring of $G$ . These concepts are inspired by the concepts of monochromatic connection number $mc(G)$ , monochromatic vertex connection number $mvc(G)$ and total rainbow connection number $trc(G)$ of a connected graph $G$ . Let $l(T)$ denote the number of leaves of a tree $T$ , and let $l(G)=\max\{ l(T) |$ $T$ is a spanning tree of $G$ $\}$ for a connected graph $G$ . In this paper, we show that there are many graphs $G$ such that $tmc(G)=m-n+2+l(G)$ , and moreover, we prove that for almost all graphs $G$ , $tmc(G)=m-n+2+l(G)$ holds. Furthermore, we compare $tmc(G)$ with $mvc(G)$ and $mc(G)$ , respectively, and obtain that there exist graphs $G$ such that $tmc(G)$ is not less than $mvc(G)$ and vice versa, and that $tmc(G)=mc(G)+l(G)$ holds for almost all graphs. Finally, we prove that $tmc(G)\leq mc(G)+mvc(G)$ , and the equality holds if and only if $G$ is a complete graph.

preprint2015arXiv

$3$ -Regular mixed graphs with optimum Hermitian energy

Let $G$ be a simple undirected graph, and $G^ϕ$ be a mixed graph of $G$ with the generalized orientation $ϕ$ and Hermitian-adjacency matrix $H(G^ϕ)$ . Then $G$ is called the underlying graph of $G^ϕ$ . The Hermitian energy of the mixed graph $G^ϕ$ , denoted by $\mathcal{E}_H(G^ϕ)$ , is defined as the sum of all the singular values of $H(G^ϕ)$ . A $k$ -regular mixed graph on $n$ vertices having Hermitian energy $n\sqrt{k}$ is called a $k$ -regular optimum Hermitian energy mixed graph. In this paper, we first focus on the problem proposed by Liu and Li [J. Liu, X. Li, Hermitian-adjacency matrices and Hermitian energies of mixed graphs, Linear Algebra Appl. 466(2015), 182--207] of determining all the $3$ -regular connected optimum Hermitian energy mixed graphs. We then prove that optimum Hermitian energy oriented graphs with underlying graph hypercube are unique (up to switching equivalence).

preprint2015arXiv

Good upper bounds for the total rainbow connection of graphs

A total-colored graph is a graph $G$ such that both all edges and all vertices of $G$ are colored. A path in a total-colored graph $G$ is a total rainbow path if its edges and internal vertices have distinct colors. A total-colored graph $G$ is total-rainbow connected if any two vertices of $G$ are connected by a total rainbow path of $G$ . The total rainbow connection number of $G$ , denoted by $trc(G)$ , is defined as the smallest number of colors that are needed to make $G$ total-rainbow connected. These concepts were introduced by Liu et al. Notice that for a connected graph $G$ , $2diam(G)-1\leq trc(G)\leq 2n-3$ , where $diam(G)$ denotes the diameter of $G$ and $n$ is the order of $G$ . In this paper we show, for a connected graph $G$ of order $n$ with minimum degree $δ$ , that $trc(G)\leq6n/{(δ+1)}+28$ for $δ\geq\sqrt{n-2}-1$ and $n\geq 291$ , while $trc(G)\leq7n/{(δ+1)}+32$ for $16\leqδ\leq\sqrt{n-2}-2$ and $trc(G)\leq7n/{(δ+1)}+4C(δ)+12$ for $6\leqδ\leq15$ , where $C(δ)=e^{\frac{3\log(δ^3+2δ^2+3)-3(\log3-1)}{δ-3}}-2$ . This implies that when $δ$ is in linear with $n$ , then the total rainbow number $trc(G)$ is a constant. We also show that $trc(G)\leq 7n/4-3$ for $δ=3$ , $trc(G)\leq8n/5-13/5$ for $δ=4$ and $trc(G)\leq3n/2-3$ for $δ=5$ . Furthermore, an example shows that our bound can be seen tight up to additive factors when $δ\geq\sqrt{n-2}-1$ .

preprint2015arXiv

On (strong) proper vertex-connection of graphs

A path in a vertex-colored graph is a {\it vertex-proper path} if any two internal adjacent vertices differ in color. A vertex-colored graph is {\it proper vertex $k$ -connected} if any two vertices of the graph are connected by $k$ disjoint vertex-proper paths of the graph. For a $k$ -connected graph $G$ , the {\it proper vertex $k$ -connection number} of $G$ , denoted by $pvc_{k}(G)$ , is defined as the smallest number of colors required to make $G$ proper vertex $k$ -connected. A vertex-colored graph is {\it strong proper vertex-connected}, if for any two vertices $u,v$ of the graph, there exists a vertex-proper $u$ - $v$ geodesic. For a connected graph $G$ , the {\it strong proper vertex-connection number} of $G$ , denoted by $spvc(G)$ , is the smallest number of colors required to make $G$ strong proper vertex-connected. These concepts are inspired by the concepts of rainbow vertex $k$ -connection number $rvc_k(G)$ , strong rainbow vertex-connection number $srvc(G)$ , and proper $k$ -connection number $pc_k(G)$ of a $k$ -connected graph $G$ . Firstly, we determine the value of $pvc(G)$ for general graphs and $pvc_k(G)$ for some specific graphs. We also compare the values of $pvc_k(G)$ and $pc_k(G)$ . Then, sharp bounds of $spvc(G)$ are given for a connected graph $G$ of order $n$ , that is, $0\leq spvc(G)\leq n-2$ . Moreover, we characterize the graphs of order $n$ such that $spvc(G)=n-2,n-3$ , respectively. Finally, we study the relationship among the three vertex-coloring parameters, namely, $spvc(G), \ srvc(G)$ and the chromatic number $χ(G)$ of a connected graph $G$ .

preprint2015arXiv

The Vacancy Effect on Thermal Interface Resistance between Aluminum and Silicon by Molecular Dynamics

Thermal transport across interfaces is an important issue for microelectronics, photonics, and thermoelectric devices and has been studied both experimentally and theoretically in the past. In this paper, thermal interface resistance (1/G) between aluminum and silicon with nanoscale vacancies was calculated using non-equilibrium molecular dynamics (NEMD). Both phonon-phonon coupling and electron-phonon coupling are considered in calculations. The results showed that thermal interface resistance increased largely due to vacancies. The effect of both the size and the type of vacancies is studied and compared. And an obvious difference is found for structures with different type/size vacancies.

preprint2015arXiv

Total proper connection of graphs

A graph is said to be {\it total-colored} if all the edges and the vertices of the graph is colored. A path in a total-colored graph is a {\it total proper path} if $(i)$ any two adjacent edges on the path differ in color, $(ii)$ any two internal adjacent vertices on the path differ in color, and $(iii)$ any internal vertex of the path differs in color from its incident edges on the path. A total-colored graph is called {\it total-proper connected} if any two vertices of the graph are connected by a total proper path of the graph. For a connected graph $G$ , the {\it total proper connection number} of $G$ , denoted by $tpc(G)$ , is defined as the smallest number of colors required to make $G$ total-proper connected. These concepts are inspired by the concepts of proper connection number $pc(G)$ , proper vertex connection number $pvc(G)$ and total rainbow connection number $trc(G)$ of a connected graph $G$ . In this paper, we first determine the value of the total proper connection number $tpc(G)$ for some special graphs $G$ . Secondly, we obtain that $tpc(G)\leq 4$ for any $2$ -connected graph $G$ and give examples to show that the upper bound $4$ is sharp. For general graphs, we also obtain an upper bound for $tpc(G)$ . Furthermore, we prove that $tpc(G)\leq \frac{3n}{δ+1}+1$ for a connected graph $G$ with order $n$ and minimum degree $δ$ . Finally, we compare $tpc(G)$ with $pvc(G)$ and $pc(G)$ , respectively, and obtain that $tpc(G)>pvc(G)$ for any nontrivial connected graph $G$ , and that $tpc(G)$ and $pc(G)$ can differ by $t$ for $0\leq t\leq 2$ .

preprint2013arXiv

Inequalities for eigenvalues of the weighted Hodge Laplacian

In this paper, we obtain "universal" inequalities for eigenvalues of the weighted Hodge Laplacian on a compact self-shrinker of Euclidean space. These inequalities generalize the Yang-type and Levitin-Parnovski inequalities for eigenvalues of the Laplacian and Laplacian. From the recursion formula of Cheng and Yang \cite{ChengYang07}, the Yang-type inequality for eigenvalues of the weighted Hodge Laplacian are optimal in the sense of the order of eigenvalues.

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Yingying Zhang

Research overview

Is this your work?

20 publications

Robust Sequential Experimental Design for A/B Testing

Applications of Gorenstein projective $τ$ -rigid modules

KRNet: Towards Efficient Knowledge Replay

NetRCA: An Effective Network Fault Cause Localization Algorithm

Reduction of wide subcategories and recollements

Symmetry-protected higher-order exceptional points in staggered flatband rhombic lattices

RobustPeriod: Time-Frequency Mining for Robust Multiple Periodicity Detection

Local State Space Analysis to Assist Partial Order Reduction

Erdős-Gallai-type results for total monochromatic connection of graphs

G-stable support $τ$ -tilting modules

More on total monochromatic connection of graphs

On mutation of τ-tilting modules

Regularity of Harmonic Maps from Polyhedra to CAT(1) Spaces

Total monochromatic connection of graphs

$3$ -Regular mixed graphs with optimum Hermitian energy

Good upper bounds for the total rainbow connection of graphs

On (strong) proper vertex-connection of graphs

The Vacancy Effect on Thermal Interface Resistance between Aluminum and Silicon by Molecular Dynamics

Total proper connection of graphs

Inequalities for eigenvalues of the weighted Hodge Laplacian

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Building this map preview

Yingying Zhang

Research overview

Is this your work?

20 publications

Robust Sequential Experimental Design for A/B Testing

Applications of Gorenstein projective τττ-rigid modules

KRNet: Towards Efficient Knowledge Replay

NetRCA: An Effective Network Fault Cause Localization Algorithm

Reduction of wide subcategories and recollements

Symmetry-protected higher-order exceptional points in staggered flatband rhombic lattices

RobustPeriod: Time-Frequency Mining for Robust Multiple Periodicity Detection

Local State Space Analysis to Assist Partial Order Reduction

Erdős-Gallai-type results for total monochromatic connection of graphs

G-stable support τττ-tilting modules

More on total monochromatic connection of graphs

On mutation of τ-tilting modules

Regularity of Harmonic Maps from Polyhedra to CAT(1) Spaces

Total monochromatic connection of graphs

333-Regular mixed graphs with optimum Hermitian energy

Good upper bounds for the total rainbow connection of graphs

On (strong) proper vertex-connection of graphs

The Vacancy Effect on Thermal Interface Resistance between Aluminum and Silicon by Molecular Dynamics

Total proper connection of graphs

Inequalities for eigenvalues of the weighted Hodge Laplacian

See the researcher in context

Building this map preview

Applications of Gorenstein projective $τ$ -rigid modules

G-stable support $τ$ -tilting modules

$3$ -Regular mixed graphs with optimum Hermitian energy