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PT-symmetry berry phases,topology and PT-symmetry breaking

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Communications in Theoretical Physics 2020年第4期72卷 45-51页

作者： Jinghui pi NingNing Sun Rong Lü Department of Physics Tsinghua UniversityBeijing 100084China Frontier Science Center for Quantum Information BeijingChina State Key Laboratory of Low-Dimensional Quantum Physics BeijingChina

We study the complex Berry phases in non-Hermitian systems with parity-and time-reversal(PT)*** investigate a kind of two-level system with PT *** find that the real part of the the complex Berry phases have two quantized values and they are equal to either 0 orΠ,which originates from the topology of the Hermitian *** also find that if we change the relative parameters of the Hamiltonian from the unbroken-PT-symmetry phase to the broken-PT-symmetry phase,the imaginary part of the complex Berry phases are divergent at the exceptional *** exhibit two concrete examples in this work,one is a two-level toys model,which has nontrivial Berry phases;the other is the generalized Su-Schrieffer-Heeger(SSH)model that has physical loss and gain in every *** results explicitly demonstrate the relation between complex Berry phases,topology and PT-symmetry breaking and enrich the field of the non-Hermitian physics.

关键词： PT symmetry Berry phases topology PT symmetry breaking

Lattice Strain Induced by Ion Implantation in AlGaAs/AlGaInAs Quantum Well Samples

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Chinese Physics Letters 2002年第4期19卷 599-601页

作者： Liu pi-Jun, Xia Yue-Yuan Department of Physics Shandong University

Si^+ ions of 350 keV have been implanted into AlGaAs/AlGaInAs quantum well samples in the dose range from 5×10^13cm^-2to 5×10^14cm^-2. The Raman spectra and high resolution x-ray diffraction (HRXRD) were measured from these implanted samples as well as the non-implanted sample. In the implanted layers the average strain which was evaluated by HRXRD increases with the implantation doses and varies from 0.0011 to 0.0029. The quantum well interface intermixing effect and compositional modification are also observed from HRXRD. At the higher doses, an abnormal annealing procedure takes place and it partly removes damage, but the strain remains almost unchanged in the epilayers.

关键词： Aluminum gallium arsenide

A field study of advanced municipal wastewater treatment technology for artificial groundwater recharge

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Journal of Environmental Sciences 2006年第6期18卷 1056-1060页

作者： pi Yun-zheng WANG Jian-long Laboratory of Environmental Technology Institute of Nuclear and New Energy Tsinghua University Beijing 100084 China

Field studies were conducted to investigate the advanced treatment of the municipal secondary effluent and a subsequent artificial groundwater recharge at Gaobeidian Wastewater Treatment Plant, Beijing. To improve the secondary effluent quality, the combined process of powdered activated carbon adsorption, flocculation and rapid sand filtration was applied, which could remove about 400 dissolved organic carbon （DOC） and 70% adsorbable organic halogens. The results of liquid size exclusion chromatography indicate that in the adsorption unit the removed organic fraction was mainly low molecular weight compounds. The fractions removed by the flocculation unit were polysaccharides and high molecular weight compounds. The retention of water in summer in the open recharge basins resulted in a growth of algae. Consequently, DOC increased in the polysaccharide and high molecular weight humic substances fraction. The majority of the DOC removal during soil passage took place in the unsaturated area. A limited reduction of DOC was observed in the aquifer zone.

关键词： artificial groundwater recharge soil aquifer treatment dissolved organic carbon

The Stability of Imitation Dynamics with Continuously Distributed Delays

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Journal of Systems Science & Complexity 2023年第5期36卷 2067-2081页

作者： FANG Caiya YANG Hui pi Jinxiu WU Wenjun School of Mathematics and Statistics Guizhou UniversityGuizhou 550025China Guizhou Provincial Key Laboratory for Games Decision Making and Control SystemsGuiyang 550025China

This paper investigates imitation dynamics with continuously distributed *** realistic technological,economic,and social environments,individuals are involved in strategic interactions simultaneously while the influences of their decision-making may not be observable *** shows that there exists a time delay *** distributions of delay are further considered to efficiently lucubrate the stability of interior equilibrium in the imitation dynamics with continuous distributions of delay in the two-strategy game ***,when the delay follows the uniform distributions and Gamma distributions,the authors present that interior equilibrium can be asymptotically ***,when the probability density of the delay is general density,the authors also determine a sufficient condition for stability derived from the expected *** but not least,the interested but uncomplicated Snowdrift game is utilized to demonstrate our theoretical results.

关键词： Continuous distributed delay evolutionary games imitation dynamics stability

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Slip-model Performance for Underexpanded Micro-scale Rocket Nozzle Flows

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Journal of Thermal Science 2007年第3期16卷 223-230页

作者： joséA.Morí■igo joséHermidaQuesada Francisco Caballero Requena Dept.of Space Programmes Dept.of

In aerospace Micro-Electro Mechanical Systems （MEMS）, the characteristic length scale of the flow approaches the molecular mean free path, thus invalidating the continuum description and enforcing the use of particle methods, like the Direct Simulation Monte Carlo （DSMC）, to deal with the non-equilibrium regions. Within the slip-regime （0.01〈Kn〈-0.1） both approaches, continuum and particle-based, seem to behave well in terms of accuracy. The present study summarizes the implementation and results obtained with a 2nO-order slip boundary condition in a Navier-Stokes solver to address the rarefaction near the nozzle walls. Its assessment and application to a cold-gas micro-scale conical nozzle of 300μm throat diameter, discharging into the low-pressure freestream, constitutes the major aim of the work. The slip-model incorporates the velocity slip with thermal creep and temperature jump, thus permitting to deal with non-isothermal flows as well. Results show that the gas experiences an intense rarefaction in the lip vicinity, pointing to the limits of model validity. Furthermore, a strong Mach deceleration is observed, attributed to the rather thick subsonic boundary layer and supersonic bulk heating caused by the viscous dissipation, in contrast with the expansion to occur in large rocket nozzles during underexpanded operation.

关键词： Slip flow MEMS micronozzles

Multiple primary colorectal cancer: Individual or familial predisposition?

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World Journal of Gastrointestinal Oncology 2015年第12期7卷 434-444页

作者： josé A Pajares josé Perea Department of Gastreoenterology Gregorio Maranon University Hospital Department of Surgery 12 de Octubre University Hospital

Colorectal carcinoma(CRC) is one of the most frequent cancers. Along the surface of the large bowel, several foci of CRC may appear simultaneously or over the time. The development of at least two different tumours has been defined as multiple primary CRC(MPCRC):When more than one tumour is diagnosed at the same time, it is known as synchronous CRC(SCRC), while when a second neoplasm is diagnosed some time after the resection and/or diagnosis of the first lesion, it is called metachronous CRC(MCRC). Multiple issues can promote the development of MPCRC, ranging from different personal factors, such as environmental exposure, to familial predisposition due to hereditary factors. However, most studies do not distinguish this dichotomy. High- and low-pentrance genetic variants are involved in MPCRC. An increased risk for MPCRC has been described in Lynch syndrome, familial adenomatous polyposis, and serrated polyposis. Non-syndromic familial CRCs should also be considered as risk factors for MPCRC. Environmental factors can promote damage to colon mucosae that enable the concurrence of MPCRC. Epigenetics are thought to play a major role in the carcinogenesis of sporadic MPCRC. The methylation state of the DNA depends on multiple environmental factors(e.g., smoking and eating foods cooked at high temperatures), and this can contribute to increasing the MPCRC rate. Certain clinical features may also suggest individual predisposition for MPCRC. Different etiopathogenic factors are suspected to be involved in SCRC and MCRC, and different familial vs individual factors may be implicated. MCRC seems to follow a familial pattern, whereas individual factors are more important in SCRC. Further studies must be carried out to know the molecular basis of risks for MPCRC in order to modify, if necessary, its clinical management, especially from a preventive point of view.

关键词： Multiple primary colorectal cancer Synchronous colorectal cancer Metachronous colorectal cancer Chromosomal instability Microsatellite instability CpG island methylator phenotype

EXISTENCE RESULTS FOR THE KIRCHHOFF TYPE EQUATION WITH A GENERAL NONLINEAR TERM

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Acta Mathematica Scientia 2022年第5期42卷 2063-2077页

作者： Huirong pi Yong ZENG School of Mathematics and Information Guangci UniversityNanning 530004China

This paper is mainly concerned with existence and nonexistence results for solutions to the Kirchhoff type equation−(a+b∫_(R^(3))|∇u|^(2))Δu+V(x)u=f(u)in R^(3),with the general hypotheses on the nonlinearity f being as introduced by Berestycki and *** analysis introduces variational techniques to the analysis of the effect of the nonlinearity,especially for those cases when the concentration-compactness principle cannot be applied in terms of obtaining the compactness of the bounded Palais-Smale sequences and a minimizing problem related to the existence of a ground state on the Pohozaev manifold rather than the Nehari manifold associated with the equation.

关键词： Kirchhoff type equation general nonlinearity variational methods Pohozaev identity

Hillslope soil erosion and runoff model for natural rainfall events

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Acta Mechanica Sinica 2008年第3期24卷 277-283页

作者： Zhanyu Zhang Guohua Zhang Changqing Zuo Xiaoyu pi Agricultural Engineering College Hohai UniversityNanjing 210098 China Soil and Water Conservation Research Institute of JiangxiProvince Nanchang 330000 China The Water Service Bureau of Chaoyang of Beijing City Beijing 100026 China

By using the momentum theorem and waterbalance principle, basic equations of slope runoff were derived, soil erosion by raindrop splash and runoff were discussed and a model was established for decribing hillslope soil erosion processes. The numerical solution of the model was obtained by adopting the Preissmann format and considering the common solution-determining conditions, from which not only the runoff and soil erosion but also their processes can be described. The model was validated by ten groups of observation data of Soil Conservation Ecological Science and Technology Demonstration Park of Jiangxi Province. Comparisons show that the maximum relative error between simulation and experimental data is about 10.98% for total runoff and 15 % for total erosion, 5.2% for runoffprocess and 6.1% for erosion process, indicating that the model is conceptually realistic and reliable and offers a feasible approach for further studies on the soil erosion process.

关键词： Overland flow Raindrop splash Runoff Erosion process Numerical simulation

Effect of alkaline metal ions on the photoluminescence properties of Eu^(3+)-doped Ca_3Al_2O_6 phosphors

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Journal of Rare Earths 2016年第12期34卷 1193-1198页

作者： Kyeongsoon Park Joon Woo pi Deshmukh Abdul Hakeem Faculty of Nanotechnology and Advanced Materials Engineering Sejong University

Ca3–xAl2O6：x Eu^3＋（0.02≤x≤0.10） and Ca（2.92）Al2O6：0.04Eu^3＋,0.04M^＋（M^＋=Li^＋, Na^＋, and K^＋） phosphors were prepared by sol-gel method and their photoluminescence properties were investigated. The crystal structure of the annealed Ca3–xAl2O6：x Eu^3＋ and Ca（2.92）Al2O6：0.04Eu^3＋,0.04M^＋ phosphors was analyzed with X-ray diffraction（XRD）. The size and morphological characteristics of the annealed phosphors were investigated with a field emission scanning electron microscope（FE-SEM）. The photoluminescence properties were evaluated with a spectrofluorometer. The phosphors were effectively excited by the light of 396 nm and showed intense red emission at 616 nm, which originated from the 5D0→7F2 transition of Eu^3＋. Among the prepared phosphors, the Ca（2.96）Al2O6：0.04Eu^3＋ phosphor showed the strongest emission intensity and the highest color purity. The addition of alkaline metal ions（Li^＋, Na^＋, and K^＋） to Ca（2.96）Al2O6：0.04Eu^3＋ phosphor degraded the emission intensity and color purity.

关键词： phosphor photoluminescence emission sol-gel method Eu3+ rare earths