109,705 research outputs found
Decay of Correlation for Edge Colorings When q > 3Δ
Full text linkWe examine various perspectives on the decay of correlation for the uniform distribution over proper q-edge colorings of graphs with maximum degree Δ.
First, we establish the coupling independence property when q ≥ 3Δ for general graphs. Together with the recent work of Chen, Feng, Guo, Zhang and Zou (2024), this result implies a fully polynomial-time approximation scheme (FPTAS) for counting the number of proper q-edge colorings.
Next, we prove the strong spatial mixing property on trees, provided that q > (3+o(1))Δ. The strong spatial mixing property is derived from the spectral independence property of a version of the weighted edge coloring distribution, which is established using the matrix trickle-down method developed in Abdolazimi, Liu and Oveis Gharan (FOCS, 2021) and Wang, Zhang and Zhang (STOC, 2024).
Finally, we show that the weak spatial mixing property holds on trees with maximum degree Δ if and only if q ≥ 2Δ-1
q-Differential equations for q-classical polynomials and q-Jacobi-Stirling numbers
Full text linkWe introduce, characterise and provide a combinatorial interpretation for the so-called q-Jacobi–Stirling numbers.
This study is motivated by their key role in the (reciprocal) expansion of any power of a second order
q-differential operator having the q-classical polynomials as eigenfunctions in terms of other even order operators,
which we explicitly construct in this work. The results here obtained can be viewed as the q-version of
those given by Everitt et al. and by the first author, whilst the combinatorics of this new set of numbers is a
q-version of the Jacobi–Stirling numbers given by Gelineau and the second author
Q&A with Zhentao Zhang
No full textIn this interview with Zhentao Zhang, we discuss his research focusing on the molecular mechanisms underlying the aggregation of prion-like proteins in neurodegenerative diseases and spotlight his recent work in Cell Reports that shows that a yeast prion protein interacts with tau and facilitates its aggregation
Accruals, Cash-Flows and Tobin’s q : An Investment Perspective on Firm Accruals
Full text linkFollowing Zhang (Accounting Review, 2007) we cast firm accruals in terms of short-term investment. Since many studies consider accruals as a smoothed measure of cash flows, we first adopt Zhang specification and augment the standard Jones model with a cash-flow variable. Second, if accruals are indeed a form of short-term investment they should also be influenced by firm’s performance as measured by Tobin’s q. Consequently we propose a new version of the accrual model including a proxy for Tobin’s q. Given that accounting data and Tobin’s q are generally measured with errors, we also introduce a new estimation method based on a modified version of the Hausman artificial regression, featuring an optimal weighting matrix composed of higher moments instrumental variable estimators. Our results suggest that all the key parameters of the accrual models are indeed systematically biased with measurement errors. More importantly, our findings largely qualify Zhang’s conjecture on accruals, as both cash-flows and Tobin’s q are found strongly significant regressors of firm accruals. Relatedly we find that the Tobin’s q augmented model better isolate discretionary accruals so that the residuals of the equation are particularly well-suited to forecast stock returns.Discretionary accruals; Earnings management; Investment; Measurement errors; Higher moments; Instrumental variable estimators.
Dynamics Simulation of Remotely Operated Vehicle-Fiber Optic Micro Cable System
Full text linkLi Q, Xu H, Zhang Q, Wang X, Li ZG. Dynamics Simulation of Remotely Operated Vehicle-Fiber Optic Micro Cable System. Presented at the WCICA2008, Chongqing, China
Defect Chemistry Special Collection
No full textEngineering defects in materials to tune their properties for different applications has gained momentum in recent years. Chemistry - An Asian Journal and ChemNanoMat, together with Prof. Shuangyin Wang (Hunan University, China), Prof. Qiang Zhang (Tsinghua University, China), Prof. Wei Zhang (Shaanxi Normal University, China), and Prof. Yi Jia (Griffith University, Australia) are greatly honored to assemble a special collection of the latest works on Defect Chemistry, directed mainly towards electrocatalysis, photocatalysis, and electrochemical energy storage.No Full Tex
A note on the Zhang omnibus test for normality based on the Q statistic
No full textA discussion about the estimators proposed by Zhang (1999) for the true standard deviation C of a normal distribution is presented. Those estimators, called by Zhang q 1 and q 2 , are functions of the expected values of the order statistics from a standard normal distribution and they were the basis of the Q statistic used in the derivation of a new test for normality proposed by Zhang. Although the type I error and the power of the test was discussed by Zhang, no study was performed to test the reliability of q 1 and q 2 as estimators of C . In this paper, it is shown that q 1 is a very poor estimator for C especially when C is large. On the other hand, the estimator q 2 has a performance very similar to the well-known sample standard deviation S. When some correlation is introduced among the sample units it can be seen that the estimator q 1 is much more affected than the estimators q 2 and S.
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