共查询到20条相似文献，搜索用时 46 毫秒
1.
一类非线性中立型时滞微分方程的振动性 总被引：3，自引：0，他引：3
研究了一类非线性中立型时滞微分方程(x(t)-P(t)g(x(t-τ)))′ Q(t)h(x(t-δ))=0解的振动性,其中P,Q∈C([t0,∞),R),g,h∈C(R,R),τ>0,δ≥0。通过建立这个方程与某个线性中立型微分方程的联系导出了1个较简单的振动准则。 相似文献
2.
姜福德 《中国海洋大学学报(自然科学版)》1987,(3)
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。 相似文献
3.
孔庆凯 《中国海洋大学学报(自然科学版)》1983,(1)
考虑如下的二阶方程 其中X(t,x,)是定义在域H:{0≤t< ∞,-∞0,n>0,f(t)为连续函数,f(t)≠0下讨论了方程(X)的不同类型解的渐近性态,给出了各种渐近解存在的充分必要条件。 相似文献
4.
武冬 《中国海洋大学学报(自然科学版)》1991,(2)
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。 相似文献
5.
孔庆凯 《中国海洋大学学报(自然科学版)》1990,(3)
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。 相似文献
6.
魏亚男 《中国海洋大学学报(自然科学版)》2023,(4):106-110
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。 相似文献
7.
孔庆凯 《山东海洋学院学报》1983,13(1):89-99
(一)引言 考虑如下的二阶方程 X=X（t,x,x）其中X（t,x,x）是定义在域H：{0≤t＜ ∞,-∞＜x∞＜ ∞,-∞＜x＜ ∞}上的连续函数，且满足解的存在唯一性条件和对初值的连续依赖性条件，x(t，x,x)是关于x的不减函数。 相似文献
8.
本文给出了几种规则形状二度体和三度体重力异常的希尔伯特变换式,提出了一种利用希尔伯特变换反演异常体的方法。这种方法充分利用了重力异常信息:利用重力异常Δg(x)曲线和它的希尔伯特变换H(x)曲线及Δg(x)-H(x)参量图上的某些特征点直接反演异常体形状参数及埋深。方法简单、实用。 相似文献
9.
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 相似文献
10.
以双功能褐藻胶裂解酶 (Pseudoalteromonas sp.strain No. 2 72 )分别降解均聚古罗糖醛酸(PG)和均聚甘露糖醛酸 (PM) ,经 Bio- Gel- P6和 POROS- HQ2 0分离得到 2种三糖纯品 ,经 ESI- MS,1 H- NMR,1 3 C- NMR,1 H- 1 H COSY,1 H- 1 3 C HMQC确定其结构为 Δ4,5-古罗糖醛酸 - α(1→ 4 ) - L-古罗糖醛酸 -α(1→ 4 ) - L -古罗糖醛酸 (简写为Δ GG)和Δ4,5-甘露糖醛酸 -β (1→ 4 ) - D-甘露糖醛酸 -β (1→ 4 ) - D-甘露糖醛酸 (ΔMM) ,为进一步从事构效关系研究提供结构信息。 相似文献
11.
Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance. 相似文献
12.
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。 相似文献
13.
Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification
An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. 相似文献
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Phylogenetic diversity and phenotypic characterization of cultivable bacterioplankton isolated from polar oceans 总被引：1，自引：0，他引：1
A set of 27 marine planktonic bacteria isolated from the polar regions was characterized by 16S rDNA sequencing and physiological and biochemical testing. More than half of these bacteria were positive for caseinase, gelatinase and 13-glucosidase, and could utilize glucose, maltose or malic acid as carbon source for cell growth. Twelve isolates expressed nitrate reduction activities. Except for one antarctic isolate BSwlO175 belonging to Actinobacteria phylum, these isolates were classified as γ-Proteobacteria, suggesting that γ-Proteobacteria dominated in cultivable marine bacterioplankton at both poles. Genus Pseudoalteromonas was the predominant group in the Chukchi Sea and the Bering Sea, and genus ShewaneUa dominated in cultivable bacterioplankton in the Prydz Bay. With sequence similarities above 97%, genus Psychrobacter was found at both poles. These 27 isolates were psychrotolerant, and significant 16S rDNA sequence similarities were found not only between arctic and antarctic marine bacteria （ 〉 99% ）, but also between polar marine bacteria and bacteria from other aquatic environments （ ≥ 98.8% ）, including temperate ocean, deep sea, pond and lake, suggesting that in the polar oceans less temperature-sensitive bacteria may be cosmopolitan and have a bipolar, even global, distribution at the species level. 相似文献
17.
Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas below the carbonate compensation depth, such as north of the West Indies where very fine clays exist, most of the samples are silty clays whose geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, contrary to some previously held ideas, most deep-sea clays are normally consolidated; the addition of carbonate has the effect of creating an open, stronger sediment skeleton. Interestingly, where information is available, the variation with depth of a sample's acoustic velocity follows the void ratio pressure relationship of the compression curve. This allows the construction of an in-situ sediment compression curve using the in-situ geophysical observations. 相似文献
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《海洋学报(英文版)》2014,(8):F0003-F0003
<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, 相似文献
20.
Nabil Sultan Pierre Cochonat Jean Fran ois Bourillet Florence Cayocca 《Marine Georesources & Geotechnology》2001,19(2):107-133
This article presents a methodology developed to evaluate the instability of submarine slopes that extend over a large area. Special attention was paid to (1) the complex geometry (bathymetry) and the expanse of the slope, (2) the heterogeneity of the sediment, and (3) the distribution of the pore pressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfies equilibrium conditions, was used for evaluating the stability of the marine slope. The submarine slope failure, which occurred on 16 October 1979 during the construction of the new Nice airport, was studied in order to test the developed model. Geotechnical parameters were taken from experimental tests carried out by IFREMER on 19 cores extracted at different depths (from 27 m to 1300 m) (Cochonat, Bourillet, and Savoye, 1993; Mulder et al., 1994). Many scenarios were proposed in order to explain the cause of the Nice slope failure (Habib, 1994). In this article, two of those scenarios were tested. Simulation results are presented and discussed. 相似文献