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Preventing Pressure Oscillations Does Not Fix Local Linear Stability Issues of Entropy-Based Split-Form High-Order Schemes

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communications on Applied Mathematics and computation 2022年第3期4卷 880-903页

作者： Hendrik Ranocha Gregor j.Gassner Applied Mathematics Münster University of Münster48149 MünsterGermany computer Electrical and Mathematical Science and Engineering(cEMSE)Division King Abdullah University of Science and Technology(KAUST)Thuwal 23955-6900Saudi Arabia Department of Mathematics and computer Science Center for Data and Simulation ScienceUniversity of CologneCologneGermany

Recently,it was discovered that the entropy-conserving/dissipative high-order split-form discontinuous Galerkin discretizations have robustness issues when trying to solve the sim-ple density wave propagation example for the compressible Euler *** issue is related to missing local linear stability,i.e.,the stability of the discretization towards per-turbations added to a stable base *** is strongly related to an anti-diffusion mech-anism,that is inherent in entropy-conserving two-point fluxes,which are a key ingredi-ent for the high-order discontinuous Galerkin *** this paper,we investigate if pressure equilibrium preservation is a remedy to these recently found local linear stability issues of entropy-conservative/dissipative high-order split-form discontinuous Galerkin methods for the compressible Euler *** equilibrium preservation describes the property of a discretization to keep pressure and velocity constant for pure density wave *** present the full theoretical derivation,analysis,and show corresponding numerical results to underline our *** addition,we characterize numerical fluxes for the Euler equations that are entropy-conservative,kinetic-energy-preserving,pressure-equilibrium-preserving,and have a density flux that does not depend on the *** source code to reproduce all numerical experiments presented in this article is available online(https://***/10.5281/zenodo.4054366).

关键词： Entropy conservation Kinetic energy preservation Pressure equilibrium preservation compressible Euler equations Local linear stability Summation-by-parts

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Assessing the influence of harvesting intensities on structural diversity of forests in south-west Germany

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Forest Ecosystems 2019年第3期6卷 249-260页

作者： Felix Storch Gerald Kadler jürgen Bauhus chair of Silviculture University of FreiburgD-79085 FreiburgGermany Department of Biometry Forest Research Institute of Baden-WürttembergD-79100 FreiburgGermany

Background: To increase ecosystem resilience and biodiversity, the maintenance and improvement of structural and compositional diversity of forests has become an important goal in forest management for many forest owners and jurisdictions. At the same time, future harvesting intensity (HI) may increase to meet the demand for woody biomass by an increasing bioeconomy sector. Yet, the influence of HI on forest structural diversity is largely unknown. Here, we address this issue by analyzing the relationship between HI and structural diversity based on large-scale national forest inventory (NFI) data, where the latter is quantified using a previously developed Forest Structure Index and HI is expressed as wood volume removal during the period 2002-2012 for the same inventory plots. Results: Our results show a surprisingly small impact of harvesting intensity on changes in structural diversity for most of the analysed types of forests. Only intense harvesting (> 80%-90% of initial growing stock) led to a significant reduction in structural diversity. At low to moderate HI most aspects of structural diversity were positively influenced. Only the quadratic mean DBH and the volume of large trees (≥ 40 cm DBH) were substantially negatively influenced at HI > 60% and 70% of initial growing stock, respectively. conclusions: In several forest types, HI could be increased without a reduction in overall structural diversity. Hence, structural diversity in these selectively managed forests appears to be a very resistant forest property in relation to HI. Other indicators at stand and landscape scale may be needed to adjust levels of HI that are suited to maintain forest biodiversity.

关键词： Large-scale inventory Structural diversity index Harvesting intensity changes in structural diversity

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Decomposition dynamics of coarse woody debris of three important central European tree species

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Forest Ecosystems 2015年第4期2卷 339-352页

作者： Steffen Herrmann Tiemo Kahl jürgen Bauhus Institute of Forest Sciences Faculty of Environment and Natural ResourcesUniversity of Freiburg Swiss Federal Research Institute WSL

Background： coarse woody debris （cWD） is an important element of forest structure that needs to be considered when managing forests for biodiversity, carbon storage or bioenergy. To manage it effectively dynamics of cWD decomposition should be known. Methods： Using a chronosequence approach, we assessed the decomposition rates of downed cWD of Fagus sylvatica, Picea obies and Pinus sylvestfis, which was sampled from three different years of tree fall and three different initial diameter classes （〉10 - ≤20 cm, 〉20 - ≤40 cm, 〉40 cm）. Samples originating from wind throws in 1999 were collected along a temperature and precipitation gradient. Based on the decay class and associated wood densities, log volumes were converted into cWD mass and c content. Log fragmentation was assessed over one year for log segments of intermediate diameters （〉20 - 40 cm） after 8 and 18 years of decomposition. Results： Significantly higher decomposition constants （k） were found in logs of F. sylvotica （0.054 year^-1） than in P. abies （0.033 year^-1） and P. sylvestris （0.032 year^-1）. However, mass loss of P. sylvestris occurred mainly in sapwood and hence k for the whole wood may be overestimated. Decomposition rates generally decreased with increasing log diameter class except for smaller dimensions in P. obies. About 74 % of the variation in mass remaining could be explained by decomposition time （27 %）, tree species （11%）, diameter （17 %）, the interactive effects between tree species and diameter （4 %） as well as between decomposition time and tree species （3 %） and a random factor （site and tree; 9.5 %）, whereas temperature explained only 2 %. Wood fragmentation may play a more important role than previously thought. Here, between 14 % and 30 % of the decomposition rates （for the first 18 years） were attributable to this process. carbon （c） density （mgc· cm ^-3）, which was initially highest for F. sylvatico, followed by P. sylvestris and P. obies, decreased with increasing decay stage t

关键词： Dead wood carbon Decay rate Beech Spruce Pine

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Determination of Time-Dependent coefficients for a Weakly Degenerate Heat Equation

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computer Modeling in Engineering & Sciences 2020年第5期123卷 475-494页

作者： M.j.Huntul D.Lesnic Department of Mathematics Faculty of ScienceJazan UniversityJazanSaudi Arabia Department of Applied Mathematics University of LeedsLeedsLS29JTUK

In this paper,we consider solving numerically for the first time inverse problems of determining the time-dependent thermal diffusivity coefficient for a weakly degenerate heat equation,which vanishes at the initial moment of time,and/or the convection coefficient along with the temperature for a one-dimensional parabolic equation,from some additional information about the process(the so-called over-determination conditions).Although uniquely solvable these inverse problems are still ill-posed since small changes in the input data can result in enormous changes in the output *** finite difference method with the crank-Nicolson scheme combined with the nonlinear Tikhonov regularization are *** resulting minimization problem is computationally solved using the MATLAB toolbox routine *** both exact and noisy input data,accurate and stable numerical results are obtained.

关键词： Inverse problem weakly degenerate heat equation Tikhonov’s regularization

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The Global Boundary Stratotype Section and Point （GSSP） for the base of the cenomanian Stage, Mont Risou, Hautes-Alpes, France

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Episodes 2004年第1期27卷 21-32页

作者： W.j.Kennedy A.S.Gale j.A.Lees M.caron OxfordUniversityMuseumofNaturalHistory ParksRoadOxfordOXI3PWU.K. DepartmentofPalaeontology TheNaturalHistoryMuseumCromwellRoadLondonSW75BPU.K.andSchoolofEarthandEnvironmentalSciencesUniversityofGreenwichChathamMaritimeCampusChathamKentME44AWU.K. ResearchSchoolofGeologicalandGeophysicalSciences BirkbeckCollegeandUniversityCollegeLondonGowerStreetLondonWCIE6BTU.K. InstitutdeGeologie UniversitedeFribourgCH-1700FribourgSwitzerland.

Following the unanimous recommendation of the International commission on Stratigraphy, the Global boundary Stratotype Section and Point (GSSP) for the base of the cenomanian Stage is defined at a level 36 metres below the top of the Marnes Bleues Formation, a level that corresponds to the the first appearance of the planktonic foraminiferan Rotalipora globotruncanoides Sigal, 1948, on the south side of Mont Risou, east of Rosans, Haute-Alpes, France, where it can be placed in the context of a series of secondary marker levels based on nannofossils, planktonic foraminifera, ammonites,and an ornate δ^13c curve.

关键词：地层学地层分界线层型地质构造

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Harmonic aspects of wind power integration

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journal of Modern Power Systems and clean Energy 2013年第1期1卷 14-21页

作者： Math H.j.BOLLEN Kai YANG Electric Power Engineering Lulea University of Technology93187 SkellefteaSweden

This paper discusses a number of ways in which wind power installations can impact the harmonic levels in the power *** turbines are an additional source of harmonic emission,especially when it concerns"non-characteristic harmonics."Parallel resonances can amplify the emission from individual turbines.A mathematical model is developed to quantify this *** resonances can result in high currents,driven by the background voltage distortion in the transmission grid,flowing into thewind *** of the transmission grid will increase lower order harmonics but reduce higher order harmonics.

关键词： Power quality Power system harmonics Wind power

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Inhibitory effects of interferons on pancreatic stellate cell activation

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World journal of Gastroenterology 2006年第6期12卷 896-901页

作者： jan-TidoBaumert GiselaSparmann j rgEmmrich StefanLiebe Robertjaster Department of Me-dicine Division of GastroenterologyMedical FacultyUniversity of RostockE-Heydemann-Str.618057 Rostock Germany

AIM： To analyze and to compare the effects of interferon （IFN）-α, IFN-β, and IFN-γ on pancreatic stellate cell （PSc） activation/n vitro and to elucidate the molecular basis of IFN action. METHODS： PScs were isolated from rat＇s pancreatic tissue, cultured and stimulated with recombinant rat IFNs. cell proliferation and collagen synthesis were assessed by measuring the incorporation of 5-bromo-2＇ -deoxyuridine （BrdU） into DNA and [^3H]-proline into acetic acid-soluble proteins, respectively. Apoptotic ceils were determined by FAcS analysis （sub-G1 peak method）. Exhibition of the myofibroblastic PSc phenotype was monitored by immunoblot analysis of （α-smooth muscle actin （α-SMA） expression. To assess the activation of signal transducer and activator of transcription （STAT）, Western blots using phospho- STAT-specific antibodies were performed. In studies on STAT1 function, expression of the protein was inhibited by siRNA. RESULTS： IFN-β and IFN-γ, but not IFN-α significantly diminished PSc proliferation and collagen synthesis. IFN-γ, was the only IFN that clearly inhibited α-SMA expression. Under the experimental conditions used, no enhanced rate of apoptotic cell death was observed in response to any IFN treatment. IFN-β and IFN-γ, induced a strong increase of STAT1 and STAT3 tyrosine phosphorylation, while the effect of IFN-α was much weaker. Inhibition of STAT1 expression with siRNA was associated with a significantly reduced growth-inhibitory effect of IFN-γ. cONcLUSION： IFN-β and particularly IFN-γ, display inhibitory effects on PSc activation in vitro and should be tested regarding their in vitro efficiency. Growth inhibition by IFN-γ action requires STAT1.

关键词： Interferons Pancreatic stellate cell Apoptosis

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Optimal distribution of active piezoelectric elements for noise attenuation in sandwich panels

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International journal of Smart and Nano Materials 2020年第4期11卷 400-416页

作者： j.F.A.Madeira A.L.Araujo IDMEc Instituto Superior TecnicoUniversidade de LisboaLisboaPortugal ADM ISELInstituto Politecnico de LisboaLisboaPortugal

In this paper,a multiobjective optimization approach for obtaining the optimal distribution of surface-bonded piezoelectric sensors and actua-tors for noise attenuation in sandwich panels is *** noise attenuation is achieved by using negative velocity feedback control with co-located sensors and *** control gains are also optimized in order to obtain the most efficient noise attenuation in a given frequency *** in-house implementation of a viscoelastic soft core sandwich plate finite element,including surface-bonded piezoelectric sensors and actuators with active control capabilities,is used for obtaining the frequency response of the *** sound transmission capability of the panels is evaluated using the radiated sound power,along with the Rayleigh integral approach,which is suitable for lightly coupled structural/acoustic *** Direct MultiSearch(DMS)optimization algorithm is used to minimize the added weight due to the piezoelectric material,minimizing also the number of required controllers and maximizing the noise *** total length of the radiated sound power curve is shown to be an effective measure of noise attenuation in a given frequency ***-off Pareto fronts and the obtained optimal configurations are presented and discussed.

关键词： Sandwich structures piezoelectricity viscoelasticity active damping multiobjective optimization

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Helicobacter pylori serology in a birth cohort of New Zealanders from age 11 to 26

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World journal of Gastroenterology 2005年第21期11卷 3273-3276页

作者： j.Paul Fawcett Gill O.Barbezat Richie Poulton Barry j.Milne Harry H.X.Xia Nicholas j.Talley School of Pharmacy University of Otago DunedinNew Zealand Dunedin School of Medicine University of Otago DunedinNew Zealand Dunedin Multidisciplinary Health and Development Research Unit Dunedin School of Medicine University of Otago Dunedin New Zealand Department of Medicine The University of Hong Kong Queen Mary Hospital Hong Kong China Department of Medicine The University of Sydney Nepean HospitalNSW 2751Australia

AIM: To determine seroprevalence of Helicobacter pylori (Hpylori)in the Dunedin Multidisciplinary Health and Development Study (DMHDS) at age 26 in order to investigate seroconversion and seroreversion from age 11 to 26 and the association of seropositivity with risk factors for H pylori infection. METHODS: Participants in the DMHDS at age 26 and retrospectively at age 21 were tested for H pylori antibodies using two commercially available ELISA ***, socioeconomic status (SES), smoking,educational attainment and employment at age 26 were tested for association with H pylori seropositivity. RESULTS: At ages 21 and 26,seroprevalence of H pylori using one or other kit was 4.2% (n=795) and 6.3% (n=871) respectively, Seroreversion rate was lower than seroconversion rate (0.11% vs 0.53% per person-year) in contrast to the period from age 11 to 21 when seroreversion rate exceeded seroconversion rate (0.35% vs 0.11% per person-year). Serology in those tested at ages 11, 21, and 26 remained unchanged in 93.6% of the sample. Seroprevalence at age 26 was lower among those with a secondary school qualification (P=0.042) but was not associated with gender, SES, smoking or employment status. cONcLUSION: H pylori seroprevalence in a New Zealand birth cohort remains low between ages 11 and 26. H pylori infection remains stable from childhood to adulthood although seroreversion seems to be more common in the adolescent years than in young adults.

关键词： H pylori Seroprevalence cohort

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Polyelectrolyte multilayer electrostatic gating of graphene field-effect transistors

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Nano Research 2014年第11期7卷 1650-1658页

作者： Yung Yu Wang Peter j. Burke Department of chemical Engineering and Materials Science University of California Irvine Irvine California 92697 USA Department of Electrical Engineering and computer Science University of California Irvine Irvine California 92697 USA

We apply polyelectrolyte multilayer films by consecutive alternate adsorption of positively charged polyallylamine hydrochloride and negatively charged sodium polystyrene sulfonate to the surface of graphene field effect transistors. Oscillations in the Dirac voltage shift with alternating positive and negative layers clearly demonstrate the electrostatic gating effect in this simple model system. A simple electrostatic model accounts well for the sign and magnitude of the Dirac voltage shift. Using this system, we are able to create p-type or n-type graphene at will. This model serves as the basis for understanding the mechanism of charged polymer sensing using graphene devices, a potentially technologically important application of graphene in areas such as DNA sequencing, biomarker assays for cancer detection, and other protein sensing applications.

关键词： dirac point graphene transistor electrostatic gating polyallylaminehydrochloride (PAH) sodium polystyrenesulfonate (PSS)

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