一类具阻尼项的Hill方程振动性

给出了一类具阻尼项的Hill方程的振动性:x″+p(t)x′+q(t)x=0,t≥0其中p(t)和q(t)是连续的周期函数.     

二阶线性微分方程解的振动性(英文)

建立了一般形式的二阶微分方程x′′(t)+p(t)x′(t)+q(t)x(t)=0的一切解均为振动的若干新的充分条件.     

基于相干布居振荡的室温固体材料中可控光群速的发展

回顾了在室温条件下,固体材料中基于相干布居振荡而导致光群速改变的若干研究.介绍了光谱烧孔理论及此技术应用于固体介质中的最新进展.主要阐述了掺杂光纤中光速改变的物理机理和实验研究.最后,讨论了光群速可控的研究意义及应用展望.     

孔板型空化器羟自由基产量影响因素分析

 利用空化释放出的能量对过程进行强化是能量利用的新途径,羟自由基·OH产量直接反应了空化的强度和效果,为了提高·OH产量,寻求最优空化条件,对水力空化·OH产量的影响因素进行了实验研究。以多孔孔板作为空化的发生元件,采用亚甲基蓝作为·OH的捕捉剂,利用紫外-分光光度法间接测量·OH产量。分析了亚甲基蓝溶液浓度、入口压力、溶液温度、氧气混合速度和反应时间对·OH产量的影响规律。研究表明,亚甲基蓝溶液浓度在16~19μmol/L时对·OH的捕捉有较高的灵敏度和精确度;入口压力、溶液温度和氧气混合速度分别为0.2MPa、30℃和45L/h的条件时,OH产量最高;反应时间与·OH产量呈近似线性关系。     

How would global-mean temperature change in the 21st century?

The time series of HadCRUT3 global-mean surface air temperature (GSAT) anomaly, Pacific decadal oscillation (PDO) index, and the equatorial Pacific sea surface temperature (SST) were utilized, and their long-term trends and multiple time-scale periodic oscillations were explored in this study. A long-term trend with a warming rate about 0.44°C /century during 1850–2008, two cool floors occurred respectively around 1910 and during 1950–1970, and three warm flats happened in the 1870s, 1940s and since the year 1998 were found in the GSAT. In this duration, the variability of GSAT can be well reconstructed by the quasi-21-year, the quasi-65-year, and century-scale oscillations. The recent decadal warm flat is caused by their positive phase overlapping from these three oscillations. The maximum rising temperature reached 0.26°C was simulated in 2004 by the three oscillations. The quasi-21-year and the quasi-65-year oscillations were possibly caused by solar radiation and internal variability of the ocean-atmosphere system. Therefore, an outlook of GSAT for the 21st century was made based on the long-term trend and these three oscillations. It was expected that a cool floor and a warm flat of the GSAT would appear in the 2030s and 2060s, respectively. However, the highest warming range is predicted about 0.6°C, it is less than the threshold 2°C and IPCC projection.     

Relationship between the geometric features of carbon steel cavitation erosion debris and the cavitation erosion stages

The debris produced in vibration cavitation tests of three kinds of carbon steel were collected. Their geometric features were analyzed quantitatively and observed respectively by a profilometer and a scanning electronic microscope (SEM) with reference to the investigation of the cavitation damaged surface by SEM and X-ray diffraction (XRD). It was found that among the debris produced in all cavitation erosion stages, more than 45% were platelets because of the occurrence of dislocation and cleavage fracture, and only less than 25% were strands. The number of granule was small in the first cavitation erosion stage and increased rapidly to the number comparable with that of platelets in the next stage, and then reduced in the third stage. The sphericity values of the debris varied in accordance with the stages of cavitation damage, which were 0.3―0.4 in the incubation stage, 0.5―0.7 in the acceleration stage and not less than 0.5 in the maximum rate stage, although a slight decrease occurred in the third stage.     

脉冲时滞双曲型方程振动的充要条件

研究一类脉冲时滞双曲型方程的振动性,获得了该类方程在Dirichlet边界条件下所有解振动的一个充要条件。此外,还获得了该类方程所有有界解振动的一个充分条件。     

具有连续变量的脉冲偏差分方程解的振动性

考虑一类具有连续变量的脉冲偏差分方程A(x+τ,y)+A(x,y+τ)-A(x,y)+p(x,y)A(x-rτ,y-lτ)=0,x≥x0;y≥y0-τ,x≠xk,A(xk+τ,y)+A(xk,y+τ)-A(xk,y)=bkA(xk,y),y∈[y0-τ,∞),k∈N(1).其中p(x,y)≥0是[x0,∞)×[y0-τ,∞)上的非负连续函数,τ>0,bk是常数,r和l是正整数,0≤x0相似文献   

具有时滞的昼夜节律模型的周期振荡

对分子水平下一类具有时滞的昼夜节律模型,通过讨论其变分系统超越特征方程根的分布情况,得到了系统周期振荡的充分条件;应用全局Hopf分支理论,将分支周期解的存在性由局部延拓到全局,并通过数值例子验证了理论分析结果.     

黑洞双星高频准周期振荡3∶2∶1频率比的理想模型(英文)

在Blandford-Znajek(BZ)过程和非轴对称磁场的磁耦合(MC)过程共存模型的基础上解释了黑洞双星XTE J1550-564令人困惑的高频准周期振荡(HFQPO)的3∶2∶1频率比.结果表明:高频准周期振荡中的两个频率可以用MC过程导致的两个旋转热斑来拟合,另外一个高频准周期振荡频率与BZ过程产生的磁热斑有关.进一步地,讨论了与黑洞双星XTEJ1550-564高频准周期振荡、喷流以及态转变相关的天体物理环境.