一类超前型微分方程的振动准则

该文利用 [2 ]的方法讨论了一阶超前型微分方程 x′(t) =p(t) x(τ(t) ) ,t≥ 0 ,τ(t) >t的振动性 ,建立了几个新的振动准则 ,改进了 [1]中的相应结果     

线性时滞微分方程解的振动准则

建立线性时滞微分方程x (t) ∑ni=1 pi(t) x(t- τi(t) ) =0 ,　　t≥ to的所有解振动的新准则。当 pi(t) ,τi(t) (i=1 ,2 ,… ,n)均为常数时 ,条件是充分必要的。     

差分方程的振动性(英文)

作者研究差分方程Δnx (t) + p (t)Δn-1x(t) + H (t,x(g(t) ) ) =0 ,其中　 P∶ D→ R,H∶ D×R→ R,0≤ p (t)≤ 1,g∶ D→ D,limt→∞t∈ Dg(t) =∞ ,D={ t0 ,t0 + 1,t0 + 2 ,… } .得到保证这个方程的一切解都振动的若干充分条件     

二阶线性常微分方程的振动性与非振动性

讨论二阶线性常微分方程y＂+q(t)=0的振动性与非振动性,其中q∈C(［0,+∞),［0,+∞))。作者得出,如果存在t     

一类二阶非线性微分方程解的振动性

本文研究一类二阶非线性微分方程 X+q(t)φ(X,X)+p(t)g(X)h(X)=0的解的振动性。文[1]研究了方程 X+q(t)φ(X,X)+p(t)g (X)X~α=0的解的振动性,而文[2]研究了方程 X+p(t)g(X)h(X)=0的解的振动性。本文所得的结果包含了文[1]的全部结果及文[2]的部份结果。     

一阶非线性泛函方程解的振动性(英文)

考虑两类带有分布型超前或滞后量的方程 (Ⅰ)x'(t)=a(t)x(t)+φ, (Ⅱ)x'(t)=a(t)x(t)-φ.其中β(t)>a(t),t+a(t)→∞(t→∞),f(x)和φ(u)是满足某些条件的非线性函数。 本文给出了方程(Ⅰ)和(Ⅱ)的所有解振动的若干充分性判定定理。作为应用,我们又讨论了如下方程的振动性,并给出了相应的判定准则。 (Ⅲ)x'(t)=a(t)x(t)+φ[sum from i=1 to n a_i(t)f(x(t+τ_i(t)))], (Ⅳ)x'(t)=a(t)x(t)-φ[sum from i=1 to n a_i(t)f(x(t+τ_i(t)))] 本文的结果是张炳根的若干结果的推广。     

一个偶数阶时滞微分方程的振动准则

讨论了一类偶数阶时滞微分方程x~(n)(t)+p(t)f(x(g(t)))=0的振动性。通过转化到一个一阶时滞微分不等式,得到了该方程的一切解振动的一个新的充分性条件。作为n=2的情况,它包含了魏俊杰最近的结果。     

Duffing方程的遥远概周期解

本文通过指数二分性和上下解方法,在比较自然的条件下,证明了二阶非线性常微分方程u″+cu′+g(u)=p(t)的遥远概周期解的存在性,其中g∈C¹(R),而p是遥远概周期函数。     

小阻尼时变双项位势Duffing型方程的调和解

本文利用弯曲扭转拓扑映射的不动点定理,证明了如下结果：若a(t),b(t)是连续的T-周期函数,则小阻尼Duffing型方程x″+εx′+a(t)f(x)+b(t)g(x)=0至少存在四个调和解。     

带有极大值项的一阶中立型差分方程解的振动性和非振动性

本文讨论了带有极大值项的一阶中立型差分方程Δ (xn - pnxn-k) +qn maxs∈ [n-l,n] xs=0解的振动性 ,得到了该方程所有解振动的 1个新的充分性条件。特别当 pn =1 ,得到了该方程有非振动解的充分必要条件。     

A Review of Some Environmental Issues Affecting Marine Mining

This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested.     

Increased Particle Fluxes at the INDEX Site Attributable to Simulated Benthic Disturbance

Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement.     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

海上大直径钢管桩打桩过程中桩周土强度弱化研究

海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。     

Determination of In Situ Sediment Shear Strength from Advanced Piston Corer Pullout Forces

The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments.     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

《Acta Oceanologica Sinica》Vol. 33(2014) contents

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INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,