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Anomalous Dissipative Quantum Harmonic Oscillator

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Communications in Theoretical Physics 2008年第1期49卷 137-142页

作者： BAI zhan-wu Department of Mathematics and Physics North China Electric Power University Baoding 071003 China

We investigate the low-temperature statistical properties of a harmonic oscillator coupled to a heat bath, where the low-frequency spectrum vanishes. We obtain the exact result of the zero point energy. Due to the low frequency shortage of environmental oscillators＇ spectral density, the coordinate and momentum correlation functions decay as T^-4 arid T^-6 respectively at zero temperature, where T is the correlation time. The low-temperature behavior of the mean energy does not violate the third law of thermodynamics, but differs largely from the Ohmic spectrum case.

关键词： harmonic oscillator harmonic velocity noise zero point energy correlation function the thirdlaw of thermodynamics

Effects of magnesium and copper additions on tensile properties of Al-Si-Cr die casting alloy under as-cast and T5 conditions

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China Foundry 2023年第1期20卷 12-22页

作者： Hong-yi zhan Yi-wu Xu Pan Wang Jian-feng Wang Jin-ping Li le-peng zhang General Motors Global Research&Development China Science LaboratoryShanghai 201206China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China General Motors(China)Investment Co. Ltd.Shanghai 201206China China International Intellectech Corporation(CIIC) Beijing 100004China

Aluminum high pressure die casting(HPDC)technology has evolved in the past decades,enabling stronger and larger one-piece casting with significant part *** also offers a higher design freedom for more mass-efficient thin-walled body *** body structures that require excellent ductility and fracture toughness to be joined with steel sheet via self-piercing riveting(for instance,shock towers and hinge pillars,etc.),a costly T7 heat treatment comprising a solution heat treatment at elevated temperatures(450℃-500℃)followed by an over-ageing heat treatment is needed to optimize microstructure for meeting product *** enable cost-efficient mass production of HPDC body structures,it is important to eliminate the expensive T7 heat treatment without sacrificing mechanical *** die cast alloy chemistry is a potential solution to improve fracture toughness and ductility of the HPDC *** present study intends to tailor the Mg and Cu additions for a new Al-Si-Cr type die casting alloy(registered as A379 with The Aluminum Association,USA)to achieve the desired tensile properties without using T7 heat *** was found that Cu addition should be avoided,as it is not effective in enhancing strength while degrades tensile *** addition is very effective in improving strength and has minor impact on tensile *** investigated Al-Si-Cr alloy with a nominal composition of Al-8.5wt.%Si-0.3wt.%Cr-0.2wt.%Fe shows comparable tensile properties with the T7 treated AlSi10MnMg alloy which is currently used for manufacturing shock towers and hinge pillars.

关键词： Al-Si alloy intermetallics high pressure die casting tensile property T7 heat treatment

The relationships of solar flares with both sunspot and geomagnetic activity

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Research in Astronomy and Astrophysics 2012年第4期12卷 400-410页

作者： zhan-le Du Hua-Ning Wang Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China

The relationships between solar flare parameters （total importance, time duration, flare index, and flux） and sunspot activity （R z ） as well as those between geomagnetic activity （aa index） and the flare parameters can be well described by an integral response model with the response time scales of about 8 and 13 months, respectively. Compared with linear relationships, the correlation coefficients of the flare parameters with R z , of aa with the flare parameters, and of aa with R z based on this model have increased about 6%, 17%, and 47% on average, respectively. The time delays between the flare parameters with respect to R z , aa to the flare parameters, and aa to R z at their peaks in a solar cycle can be predicted in part by this model （82%, 47%, and 78%, respectively）. These results may be further improved when using a cosine filter with a wider window. It implies that solar flares are related to the accumulation of solar magnetic energy in the past through a time decay factor. The above results may help us to understand the mechanism of solar flares and to improve the prediction of the solar flares.

关键词： Sun: activity -- Sun: sunspots -- Sun: flares -- geomagnetic activity

The prediction method of similar cycles

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Research in Astronomy and Astrophysics 2011年第12期11卷 1482-1492页

作者： zhan-le Du Hua-Ning Wang Key Laboratory of Solar Activity National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

The concept of degree of similarity （η）, is proposed to quantitatively describe the similarity of a parameter （e.g. the maximum amplitude Rmax） of a solar cycle relative to a referenced one, and the prediction method of similar cycles is further developed. For two parameters, the solar minimum （Rmin） and rising rate （βa）, which can be directly measured a few months after the minimum, a synthesis degree of similarity （ηs） is defined as the weighted-average of the η values around Rmin and βa, with the weights given by the coefficients of determination of Rmax with Rmin and βa, respectively. The monthly values of the whole referenced cycle can be predicted by averaging the corresponding values in the most similar cycles with the weights given by the ηs values. As an application, Cycle 24 is predicted to peak around January 2013 i8 （month） with a size of about Rmax = 84 ± 17 and to end around September 2019.

关键词： Sun: activity -- Sun: general -- sunspots

Lattice relaxation,mirror symmetry and magnetic field effects on ultraflat bands in twisted trilayer graphene

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Science China(Physics,Mechanics & Astronomy) 2021年第6期64卷 114-120页

作者： Zewen wu Zhen zhan Shengjun Yuan Key Laboratory of Artificial Mic ro-and Nano-strucures of the Minisry of Education School of Physics and TechnologyWuhan UniversityWuhan 430072China

Twisted graphene multilayers exhibit strongly correlated insulating states and superconductivity due to the presence of ultraflat bands near the charge neutral *** this paper,the response of ultraflat bands to lattice relaxation and a magnetic field in twisted trilayer graphene(tTLG)with different stacking arrangements is investigated by using a full tight-binding *** show that lattice relaxations are indispensable for understanding the electronic properties of tTLG,in particular,of tTLG in the presence of mirror *** relaxations renormalize the quasiparticle spectrum near the Fermi energy and change the localization of higher energy flat ***,different from the twisted bilayer graphene,the Hofstadter butterfly spectrum can be realized at laboratory accessible strengths of magnetic *** work verifies tTLG as a more tunable platform than the twisted bilayer graphene in strongly correlated phenomena.

关键词： flat bands twisted trilayer graphene lattice relaxation mirror symmetry magnetic field tight-binding

Does a low solar cycle minimum hint at a weak upcoming cycle?

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Research in Astronomy and Astrophysics 2010年第10期10卷 950-955页

作者： zhan-le Du Hua-Ning Wang Key Laboratory of Solar Activity National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

The maximum amplitude （Rm） of a solar cycle, in the term of mean sunspot numbers, is well-known to be positively correlated with the preceding minimum （Rmin）. So far as the long term trend is concerned, a low level of Rmin tends to be followed by a weak Rm, and vice versa. We found that the evidence is insufficient to infer a very weak Cycle 24 from the very low Rmin in the preceding cycle. This is concluded by analyzing the correlation in the temporal variations of parameters for two successive cycles.

关键词： Sun activity -- Sun general -- sunspots

Role of the Bath Spectrum in the Specific Heat Anomalies of a Damped Oscillator

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Chinese Physics letters 2012年第6期29卷 54-57页

作者： BAI zhan-wu Department of Mathematics and Physics North China Electric Power UniversityBaoding 071003

The specific heat anomalies are analytically studied in the system in which a harmonic oscillator couples to a heat bath with harmonic *** physical explanation leads to a general spectral dependence of the specific heat *** condition of a dip appearance and the behaviors of the dip can be given according to the shape of the bath's power spectrum by employing the minimal heat bath model.

关键词： harmonic oscillator explanation

Altered 3D genome reorganization mediates precocious myeloid differentiation of aged hematopoietic stem cells in inflammation

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Science China Life Sciences 2025年

作者： Xinyu Cui Yu Dong Qiang zhan Yixin Huang Qianshu Zhu Zihao zhang Guang Yang Liping Wang Shijun Shen Jia Zhao Zhiyi Lin Jiatong Sun Zhongqu Su Yihan Xiao Chuyu zhang Yuwei Liang Lu Shen Lichen Ji Xuguang zhang Jiqing Yin Hong Wang Zhiyang Chen Zhenyu Ju Cizhong Jiang Rongrong le Shaorong Gao Clinical and Translational Research Center of Shanghai First Maternity & Infant Hospital Frontier Science Center for Stem Cells School of Life Sciences and Technology Tongji University Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education Orthopaedic Department of Tongji Hospital School of Life Sciences and Technology Tongji University Key Laboratory of Regenerative Medicine of Ministry of Education Institute of Aging and Regenerative Medicine Department of Developmental & Regenerative Medicine College of Life Science and Technology Jinan University Shandong Key Laboratory of Animal Bioengineering and Disease Prevention College of Animal Science and Technology Shandong Agricultural University Department of Joint Surgery Shanghai East Hospital Tongji University School of Medicine Shanghai Institute of Nutrition and Health Chinese Academy of Sciences

Inflammation is a driving force of hematopoietic stem cells(HSCs) aging, causing irreversible exhaustion of functional HSCs. However, the underlying mechanism of HSCs erosion by inflammatory insult remains poorly understood. Here, we find that transient LPS exposure primes aged HSCs to undergo accelerated differentiation at the expense of self-renewal, leading to depletion of HSCs. Meanwhile, the central regulator nuclear factor kappa B(NF-κB) mediating functional impairment by inflammation insult induces differential transcriptional response in aged HSCs compared with young HSCs, with precocious activation of myeloid lineage genes. Altered compartmentalization and chromatin loop formation are associated with aging-related differential transcriptional response in HSCs upon lipopolysaccharide(LPS)stimulation. Mechanistically, enhancer and promoter regions of myeloid lineage genes in aged HSCs are more accessible and display more rapid and prominent CTCF occupancy upon LPS stimulation. Our study provides comprehensive resources for the three-dimensional(3D)genome structure of HSCs and sheds light into the ordered genome organization and the associated transcriptome signature underlying HSCs aging.

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Functional regulation of monocyte-derived dendritic cells by microRNAs

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Protein & Cell 2012年第7期3卷 497-507页

作者： Yifan zhan Li wu The Walter and Eliza Hall Institute of Medical Research Parkville 3052Australia Department of Medical Biology University of MelbourneParkville 3010Australia Tsignhua University and Peking University Joint Center for Life Sciences and Tsinghua University School of Medicine Beijing 100084China

Dendritic cells(DCs)as a rare type of leukocytes play an important role in bridging the innate and adaptive immune system.A subset of DCs,monocyte-derived dendritic cells(moDCs),exists in very low numbers at steady state but become abundant in inflammatory *** inflammation-associated DCs are potent producers of pro-inflammatory cytokines and potent inducers of T helper *** behave as a“double-edge”sword so that they not only mediate protective immunity but also *** is still incompletely understood how their function is *** evidence indicates that microR-NAs(miRNAs),as a new class of gene regulators,potently regulate the function of *** we summarize recent progress in this area.

关键词： dendritic cells microRNA function