检索结果-南通市图书馆

Journal of Forestry Research 2021年第5期32卷 1899-1909页

作者： Neşe Gülci Faculty of Forestry Kahramanmaras Sutcu Imam University46100 KahramanmarasTurkey

Different forest fires causing different degrees of effects occur in fire-sensitive forests due to various reasons such as climate *** as well as harmful aspects of forest fires are a multi-disciplinary research *** information systems(GIS)and remote sensing(RS)methods offer a number of benefits for researchers and operators in the field of forest fire *** present study analyses timber pricing based on forest contractor demands of post-salvage logging *** effect of timber obtained from compartment units on producers’pricing policy was *** forest fire area(2500 ha)located in Antalya in Turkey was selected as the main study *** parameters(aspect,slope and slope position),stand types(diameter class and crown closure),and burn severity were analyzed together using GIS and R software packages.A multi-linear regression model(R^(2)=0.752)demonstrated that factors that had the most impact on pricing were slope position,aspect,stand age,crown closure and burn *** model can be used to estimate salvage logging prices in Calabrian pine(Pinus brutia Ten.)stands with similar *** administrators and contractors may readily address the unit price of timber by estimating approximate costs in a given forest area for which they are going to *** will help reduce operational planning times of harvesting procedures in burned stands.

关键词： Timber extraction Forest fires Stumpage sale Cost estimation Sustainability Crown fire

Influence of the Choice of NN Potential Model on γd→τ~0d Observables near η-Threshold

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2016年第4期33卷 14-18页

作者： e.M.Darwish Physics Department Faculty of ScienceTaibah University Physics Department Faculty of ScienceSohag University

Influence of the choice of the NN potential model governing the deuteron wave function on the observables for coherent π0-photoproduction on the deuteron near η-threshoM is investigated by using a three-body model for the intermediate ηN N system with separable two-body interactions. Results for unpolarized differential cross section and polarization observables are predicted. It is revealed that the choice of the NN potential model has a visible effect on the differential cross section and most of the polarization observables, especially in the photon energy range of 600-800 MeV and extreme backward pion angles. We find that the deviation among results obtained by using different deuteron wave functions is quite large. The use of the CD-Bonn NN potential for deuteron wave function doubles the differential cross section in this kinematic region. Compared with the experimental data from CLAS collaboration for differential cross section, sizeable discrepancies are found.

关键词： of in Observables near Threshold NN that for on CLAS

exploring the mass gap:Black holes in green pea galaxies

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2024年第10期67卷 170-171页

作者： James e.Rhoads School of earth and Space exploration Arizona State UniversityTempeAZ 85287USA

We know about black holes primarily on two mass scales(e.g.,see Figure 22 of ref.[1]).Supermassive black holes inhabit the centers of galaxies,where they sometimes power active galactic nuclei(AGN).Their populations can be probed through AGN surveys,tidal disruption event surveys,and(in the closest galaxies)stellar and gas dynamics in the innermost regions where the black hole dominates the gravitational potential.

关键词： galaxies tidal galactic

effect of water on behaviour of Na_2B_4O_7·5H_2O and Na_2B_4O_7 in HCl-CH_3OH medium

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2010年第8期20卷 1541-1544页

作者： A.e.eRTAS .GIRGIN Mining engineering Department Hacettepe University

The reactivity of Na2B4O7·5HaO and Na2B4O7 in non-aqueous HCl-CH3OH solvent system was investigated. The effects of H2O, CH3OH/B mole ratio and reaction time on the reaction at room temperature were examined. experimental results show that when Na2B4O7·5H2O and Na2B4O7 are the reactants, the dissolved B203 contents are observed to be 98.2% and 99%, respectively, in 5min at the CH3OH/B mole ratio of 4. The decrease of water in the reaction medium was observed to increase the crystallization of NaCI in the order of Na2B4O7〉Na2B4O7·5H2O It was also observed that the boron solution obtained after the reaction could be hydrolyzed by the addition of H3BO3. The results show that HCl-CH3OH system is a more effective solvent compared to H2SO4-CH3OH both in the reactivity and the shortened reaction time.

关键词： non-metallic ores oxide ores hydrometallurgy leaching

ASYMPTOTIC LIMITS AND STABILIZATION FOR THe 1D NONLINeAR MINDLIN-TIMOSHeNKO SYSTeM

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2010年第3期23卷 414-430页

作者： F.D.ARARUNA P.BRAZ e SILVA e.ZUAZUA Departamento de Matemática Universidade Federal da Paraíba Departamento Ikerbasque Research Professor Basque Center for Applied Mathematics(BCAM)

This paper shows how the so called von Karman model can be obtained as a singular limit of a modified Mindlin-Timoshenko system when the modulus of elasticity in shear κ tends to infinity, provided a regularizing term through a fourth order dispersive operator is added. Introducing damping mechanisms, the authors also show that the energy of solutions for this modified Mindlin-Timoshenko system decays exponentially, uniformly with respect to the parameter k. As κ→∞, the authors obtain the damped von Karman model with associated energy exponentially decaying to zero as well.

关键词： Mindlin-Timoshenko system singular limit uniform stabilization vibrating beams von Karman system.

exact Solutions of Kolmogorov-Petrovskii-Piskunov equation Using the Modified Simple equation Method

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2014年第3期30卷 749-754页

作者： e.M.e.Zayed S.A.Hoda Ibrahim Mathematics Department Faculty of ScienceZagazig University

The modified simple equation method is employed to find the exact solutions of the nonlinear Kolmogorov-Petrovskii-Piskunov （KPP） equation. When certain parameters of the equations are chosen to be special values, the solitary wave solutions are derived from the exact solutions. It is shown that the modified simple equation method provides an effective and powerful mathematical tool for solving nonlinear evolution equations in mathematical physics.

关键词： modified simple equation method Kolmogorov-Petrovskii-Piskunov equation exact solutions solitary wave solutions

SOMe OSCILLATION CRITeRIA FOR SeCOND ORDeR NONLINeAR FUNCTIONAL ORDINARY DIFFeReNTIAL eQUATIONS

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Scientia 2007年第3期27卷 602-610页

作者： e.M.e.Zayed M.A.el-Moneam Mathematics Department Faculty of ScienceZagazig UniversityZagazigEgypt

The main objective of this article is to study the oscillatory behavior of the solutions of the following nonlinear functional differential equations（a（t）x＇（t））＇＋δ1p（t）x＇（t）＋δ2q（t）f（x（g（t））） = 0,for 0 ≤ to≤ t, where 51 = ：el and δ±1. The functions p,q,g ： [t0, ∞） → R, f ： R → are continuous, a（t）〉 0,p（t） ≥0,q（t）〉 0 for t ≥ to,lirn g（t） = ∞, and q is not identically zero on any subinterval of [to, ∞）. Moreover, the functions q（t）, g（t）, and a（t） are continuously differentiable.

关键词： Oscillatory and nonoscillatory solutions nonlinear functional differential equations

SOMe ReMARKS ON HYDROFOIL CAVITATION

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2012年第3期24卷 305-314页

作者： ARNDT Roger e. A. Saint Anthony Falls Laboratory University of Minnesota MinneapolisMN 55414 USA

This paper reviews numerical and experimental investigations of sheet/cloud cavitation carried out at the St. Anthony Falls Laboratory and at two collaborating facilities （Versuchsanstalt Ftir Wasserbau, Obernach, Germany and Osaka University, Japan） for more than a decade. Although significant advances have been made in the analysis of this flow several issues are still unresolved. The purpose of this paper is to examine the overall features of the problem, review the progress made to date and suggest avenues for new investigation.

关键词： cavitation hydrofoil numerical simulations

Improvement of sintering,nonlinear electrical,and dielectric properties of ZnO-based varistors doped with TiO2

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第6期25卷 575-580页

作者： Osama A Desouky K e Rady Bilbis Higher Institute of engineering (BHIe) Bilbis Sharqia Egypt engineering Basic Sciences Department Faculty of engineering Menoufia University Shebin EI-Kom Egypt

The effects of TiO2 on sintering and nonlinear electrical properties of（98.5-x）ZnO–0.5MnO2–0.5Co2O3-0.5Bi2O3–xTiO2（x = 0.3,0.5,0.7,0.9 mol%） ceramic varistors prepared by the ceramic technique are investigated in this *** optimum sintering temperature of the prepared samples is deduced by determining the firing shrinkage and water absorption *** optimum sintering temperature is found to be 1200℃,at which each of the samples shows a maximum firing shrinkage and minimum water *** minimum water absorption appears in a sample of x = 0.9 mol%.Higher sintering temperature and longer sintering time give rise to a reduction in bulk density due to the increased amount of porosity between the large grains of ZnO resulting from the rapid grain growth induced by the liquid phase *** crystal size of ZnO decreases with increasing TiO2 *** addition of TiO2 improves the nonlinear coefficient and attains its maximum value at x = 0.7 mol% of TiO2,further addition negatively affects it.A decrease in capacitance consequently in the dielectric constant is recorded with increasing the frequency in a range of 30 kHz–200 *** temperature and composition dependences of the dielectric constant and AC conductivity are also *** increase of temperature raises the dielectric constant because it increases ionic response to the field at any particular frequency.

关键词： ZnO varistors water absorption nonlinear electrical properties dielectric constant

Destructive Interactions between Pore Forming Agents and Matrix Phase during the Fabrication Process of Porous BiFeO_3 Ceramics

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2015年第8期31卷 798-805页

作者： e.Mostafavi A.Ataie School of Metallurgy and Materials engineering College of EngineeringUniversity of Tehran

Porous bismuth ferrite ceramics were synthesized by sacrificial pore former method. A mixture of BiFeO3 and 20 wt% of various pore formers including high density polyethylene, polyethylene glycol, polyvinyl alcohol, urea and graphite was intensively milled for 10 h in a planetary ball mill, uniaxially cold pressed and then subjected to the multi-stage heat treatment. The results revealed that urea and polyvinyl alcohol are appropriate candidates for maintaining the strength of the final porous structure. Density and porosity measurements showed that by employing 20 wt% of high density polyethylene and graphite, a porous sample with a maximum porosity of nearly 40% could be obtained. Mercury porosimetry results showed that using urea as a pore former gives porous bismuth ferrite with a mean pore diameter of 7μm, uniform pore distribution as well as interconnected pores. Moreover, reactions between BiFeO3 matrix phase and thermal decomposition products of pore formers can lead to degradation of the BiFeO3 phase in the final porous samples. Analysis of X-ray diffraction patterns illustrated that in the samples pro- cessed with graphite, high density polyethylene and polyvinyl alcohol as pore former, BiFeO3 matrix phase partially or completely decomposed to intermediate phases of Bi2Fe4O9 and Bi25FeO40. Using of urea did not damage the matrix phase and porous BiFeO3 within the original perovskite structure could be prepared. Furthermore, thermodynamic investigation was carried out for prediction of possible in- teractions between matrix phase and pore former at elevated temperatures.

关键词： Multiferroic Bismuth ferrite Porous ceramics Sacrificial pore former Porosity Phase composition