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Yuping Yang

Publications and source records attributed to Yuping Yang.

At least 19 recordsLinked to original sources
arXiv2026

Measurement and Modeling of Structure-Induced Surface Scattering on Terahertz Channel

As terahertz (THz) frequencies emerge as promising candidates for next-generation wireless networks, accurate characterization of propagation mechanisms in indoor/outdoor environments becomes essential for system design and performance optimization. This article presents an experimental and theoretical investigation of structure-induced indoor surface scattering on THz channels, examining how material properties and structural configurations jointly govern channel power and angular distribution. Six representative indoor surfaces are characterized, revealing that intrinsic structural inhomogeneity -- particularly the quasi-periodic earlywood-latewood arrangement in pine wood -- induces measurable angular scattering whose dominant lobes and angular shifts are reproduced by a beam-propagation modeling (BPM) framework. Material-covered surface configurations are further investigated, demonstrating that thin dielectric covering layers can substantially modify reflection characteristics through thickness- and frequency- dependent thin-film interference effects. Wide-angle bistatic measurements conducted in a conference-room environment reveal that structured indoor elements, such as folded curtains, can enhance angular scattering and extend spatial coverage. These findings establish that structure-induced surface scattering mechanisms offer potential for constructing non-line-of-sight THz links in indoor environments.

physics.app-ph↗
arXiv2026

Transfer learning for functional linear regression via control variates

Transfer learning (TL) has emerged as a powerful tool for improving estimation and prediction performance by leveraging information from related datasets, with the offset TL (O-TL) being a prevailing implementation. In this paper, we adapt the control-variates (CVS) method for TL and develop CVS-based estimators for scalar-on-function regression, one of the most fundamental models in functional data analysis. These estimators rely exclusively on dataset-specific summary statistics, thereby avoiding the pooling of subject-level data and remaining applicable in privacy-restricted or decentralized settings. We establish, for the first time, a theoretical connection between O-TL and CVS-based TL, showing that these two seemingly distinct TL strategies adjust local estimators in fundamentally similar ways. We further derive convergence rates that explicitly account for the unavoidable but typically overlooked smoothing error arising from discretely observed functional predictors, and clarify how similarity among covariance functions across datasets governs the performance of TL. Numerical studies support the theoretical findings and demonstrate that the proposed methods achieve competitive estimation and prediction performance compared with existing alternatives.

stat.ME↗
arXiv2025

Combinatorial equivalence of separable elements in types $A$ and $B$

We study the combinatorial equivalence of separable elements in types $A$ and $B$. A bijection is constructed from the set of separable permutations in the symmetric group $S_{n+1}$ to the set of separable signed permutations in the hyperoctahedral group $B_n$. This bijection preserves descent statistics and induces a poset isomorphism under the left weak order. As a consequence, separable signed permutations are enumerated by the large Schr\"oder numbers, and their descent polynomials are shown to be $\gamma$-positive. Building on a recursive characterization of separable signed permutations via direct sum and skew sum operations, we derive explicit product formulas for the rank generating functions of the principal upper and lower ideals of separable signed permutations under the left weak order.

math.CO↗
arXiv2025

Eavesdropping Risk in Terahertz Channels by Covered Wavy Surfaces

Terahertz communications offer unprecedented data rates for next-generation wireless networks but suffer blockage susceptibility that restrict coverage and introduce physical-layer security vulnerabilities. Non-line-of-sight relay schemes using metallic wavy surfaces (MWS) address coverage limitations but require concealment beneath indoor materials for practical deployment. This work investigates THz channel characteristics and security vulnerabilities when MWS surfaces are covered with wallpaper, curtain, and wall plaster across 113-170 GHz. Results reveal that covering materials redistribute rather than eliminate eavesdropping threats, with persistent feasible interception scenarios remaining undetectable through conventional backscattering monitoring. These findings underscore the need for enhanced mechanisms designed for covered reflecting elements.

physics.app-ph↗
arXiv2025

On the classification of finite GK-dimensional pre-Nichols algebras and quasi-quantum groups

We prove that every pre-Nichols algebra of a nondiagonal object in the twisted Yetter-Drinfeld category ${_{\k G}^{\k G} {\mathcal{YD}^\Phi}}$ has infinite Gelfand-Kirillov dimension, where $G$ is a finite abelian group and $\Phi$ is a $3$-cocycle on $G$. This leads to a complete characterization of finite GK-dimensional Nichols algebras in this category. Specifically, for any finite-dimensional $V\in {_{\k G}^{\k G} {\mathcal{YD}^\Phi}}$, we show that the Nichols algebra $B(V)$ has finite Gelfand-Kirillov dimension if and only if it is of diagonal type and its associated root system is finite, that is, an arithmetic root system. Via bosonization, this result yields a classification of finite GK-dimensional coradically graded pointed coquasi-Hopf algebras over finite abelian groups that are generated by group-like and skew-primitive elements.

math.QA↗
arXiv2024

On the Classification of Finite Quasi-Quantum Groups over Abelian Groups

Using a variety of methods developed in the theory of finite-dimensional quasi-Hopf algebras, we classify all finite-dimensional coradically graded pointed coquasi-Hopf algebras over abelian groups. As a consequence, we partially confirm the generation conjecture of pointed finite tensor categories due to Etingof, Gelaki, Nikshych and Ostrik.

math.QA↗
arXiv2021

Nonlinear Lie-Type Derivations of finitary Incidence Algebras and Related Topics

This is a continuation of our earlier works \cite{KhrypchenkoWei, Yang20211, Yang20212} with respect to (non-)linear Lie-type derivations of finitary incidence algebras. Let $X$ be a pre-ordered set, $\mathcal{R}$ be a $2$-torsionfree and $(n-1)$-torsionfree commutative ring with identity, where $n\geq 2$ is an integer. Let $FI(X,\mathcal{R})$ be the finitary incidence algebra of $X$ over $\mathcal{R}$. In this paper, a complete clarification is obtained for the structure of nonlinear Lie-type derivations of $FI(X,\mathcal{R})$. We introduce a new class of derivations on $FI(X,\mathcal{R})$ named inner-like derivations, and prove that each nonlinear Lie $n$-derivation on $FI(X,\mathcal{R})$ is the sum of an inner-like derivation, a transitive induced derivation and a quasi-additive induced Lie $n$-derivation. Furthermore, if $X$ is finite, we show that a quasi-additive induced Lie $n$-derivation can be expressed as the sum of an additive induced Lie derivation and a central-valued map annihilating all $(n-1)$-th commutators. We also provide a sufficient and necessary condition such that every nonlinear Lie $n$-derivation of $FI(X,\mathcal{R})$ is of proper form. Some related topics for further research are proposed in the last section of this article.

math.RA↗
arXiv2021

Electronic controllable broadband and robust terahertz surface plasmon-polaritons switch based on hybrid ITO waveguide coupler

The surface plasmon-polaritons (SPPs) switch is the key element of the integrated devices in optical computation and terahertz (THz) communications. In this paper, we propose a novel design of THz SPPs switch based on quantum engineering. Due to the robustness of coherent quantum control technique, our switch is very robust against with perturbations of geometrical parameters and presents a good performance at on-state (and off-state) from 0.5 THz to 0.7 THz. The on-state and off-state of our device can be controlled by the external voltage. We believe this finding will be the great improvement for the integrated optical computing and THz communications.

physics.optics↗
arXiv2018

Recovering the Underlying Trajectory from Sparse and Irregular Longitudinal Data

In this article, we consider the problem of recovering the underlying trajectory when the longitudinal data are sparsely and irregularly observed and noise-contaminated. Such data are popularly analyzed with functional principal component analysis via the Principal Analysis by Conditional Estimation (PACE) method. The PACE method may sometimes be numerically unstable because it involves the inverse of the covariance matrix. We propose a sparse orthonormal approximation (SOAP) method as an alternative. It estimates the optimal empirical basis functions in the best approximation framework rather than eigen-decomposing the covariance function. The SOAP method avoids estimating the mean and covariance function, which is challenging when the assembled time points with observations for all subjects are not sufficiently dense. The SOAP method avoids the inverse of the covariance matrix, hence the computation is more stable. It does not require the functional principal component scores to follow the Gaussian distribution. We show that the SOAP estimate for the optimal empirical basis function is asymptotically consistent. The finite sample performance of the SOAP method is investigated in simulation studies in comparison with the PACE method. Our method is demonstrated by recovering the CD4 percentage curves from sparse and irregular data in the Multi-center AIDS Cohort Study.

stat.ME↗
arXiv2017

On nondiagonal finite quasi-qantum groups over finite abelian groups

In this paper, we initiate the study of nondiagonal finite quasi-quantum groups over finite abelian groups. We mainly study the Nichols algebras in the twisted Yetter-Drinfeld module category $_{\k G}^{\k G}\mathcal{YD}^Φ$ with $Φ$ a nonabelian $3$-cocycle on a finite abelian group $G.$ A complete clarification is obtained for the Nichols algebra $B(V)$ in case $V$ is a simple twisted Yetter-Drinfeld module of nondiagonal type. This is also applied to provide a complete classification of finite-dimensional coradically graded pointed coquasi-Hopf algebras over abelian groups of odd order and confirm partially the generation conjecture of pointed finite tensor categories due to Etingof, Gelaki, Nikshych and Ostrik.

math.QA↗
arXiv2017

Finite-dimensional quasi-Hopf algebras of Cartan type

In this paper, we present a general method for constructing finite-dimensional quasi-Hopf algebras from finite abelian groups and braided vector spaces of Cartan type. The study of such quasi-Hopf algebras leads to the classification of finite-dimensional radically graded basic quasi-Hopf algebras over abelian groups with dimensions not divisible by $2,3,5,7$ and associators given by abelian $3$-cocycles. As special cases , the small quasi-quantum groups are introduced and studied. Many new explicit examples of finite-dimensional genuine quasi-Hopf algebras are obtained.

math.QA↗
arXiv2016

Finite quasi-quantum groups of diagonal type

The goal of the present paper is to classify an interesting class of elementary quasi-Hopf algebras, or equivalently, finite-dimensional pointed Majid algebras. By a Tannaka-Krein type duality, this determines a big class of pointed finite tensor categories. Based on some interesting observations of normalized 3-cocycles on finite abelian groups, we elucidate an explicit connection between our objective pointed Majid algebras and finite-dimensional pointed Hopf algebras over finite abelian groups. With a help of this connection and the successful theory of diagonal Nichols algebras over abelian groups, we provide a conceptual classification of finite-dimensional graded pointed Majid algebras of diagonal type. Some efficient methods of construction are also given.

math.QA↗
arXiv2016

Generalized Clifford Algebras as Algebras in Suitable Symmetric Linear Gr-Categories

By viewing Clifford algebras as algebras in some suitable symmetric Gr-categories, Albuquerque and Majid were able to give a new derivation of some well known results about Clifford algebras and to generalize them. Along the same line, Bulacu observed that Clifford algebras are weak Hopf algebras in the aforementioned categories and obtained other interesting properties. The aim of this paper is to study generalized Clifford algebras in a similar manner and extend the results of Albuquerque, Majid and Bulacu to the generalized setting. In particular, by taking full advantage of the gauge transformations in symmetric linear Gr-categories, we derive the decomposition theorem and provide categorical weak Hopf structures for generalized Clifford algebras in a conceptual and simpler manner.

math.QA↗
arXiv2015

Mechanism and modulation of terahertz generation from a semimetal - graphite

Semi-metals might offer a stronger interaction and a better confinement for terahertz wave than semiconductors, while preserve tunability. Particularly, graphene-based materials are envisioned as terahertz modulators, filters and ultra-broadband sources. However, the understanding of terahertz generation from those materials is still not clear, thus limits us recognizing the potential and improving device performances. Graphite, the mother material of graphene and a typical bulk semi-metal, is a good system to study semi-metals and graphene-based materials. Here we experimentally modulate and maximize the terahertz signal from graphite surface, thus reveal the mechanism - surface field driving photon induced carriers into transient current to radiate terahertz wave. We also discuss the differences between graphite and semiconductors; particularly graphite shows no temperature dependency from room temperature to 80C. Above knowledge will help us understand terahertz generations, achieve maximum output and electric modulation, in semi-metal or graphene based devices.

physics.optics↗
arXiv2015

Quasi-Quantum Linear Spaces

We provide a classification of finite-dimensional graded pointed Majid algebras generated by finite abelian groups as group-like elements and a set of quasi-commutative skew-primitive elements. This amounts to a classification of finite quasi-quantum linear spaces in the sense of nonassociative geometry.

math.QA↗
arXiv2015

Finite quasi-quantum groups of rank two

This is a contribution to the structure theory of finite pointed quasi-quantum groups. We classify all finite-dimensional connected graded pointed Majid algebras of rank two which are not twist equivalent to ordinary pointed Hopf algebras.

math.QA↗
arXiv2015

Electrostatic Field Invisibility Cloak

Invisibility cloak is drawing much attention due to its special camouflage when exposed to physical field varing from wave (electromagnetic field, acoustic field, elastic wave, etc.) to scalar field (thermal field, static magnetic field, dc electric field and mass diffusion). Here, an electrostatic field invisibility cloak has been theoretically investigated, and experimentally demonstrated for the first time to perfectly hide a certain region from sight without disturbing the external electrostatic field. The desired cloaking effect has been achieved via both scattering cancelling technology and transformation optics (TO).This present work will pave a novel way for manipulating of electrostatic field where would enable a wide range of potential applications and sustainable products made available.

physics.optics↗