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31.
Liu Keying Liu Anping Liu Ting 《Annals of Differential Equations》2006,22(1):33-39
This paper deals with the oscillatory properties of a class of nonlinear advanced difference equations. Sufficient criteria in the form of infinite sum for the equation to be oscillatory are obtained. In the linear cases, our results coincide with those in the literature. 相似文献
32.
Zhang Linli~ Liu Anping~ Chang Tao~ 《Annals of Differential Equations》2007,23(4):581-585
In this paper,by means of iterative analysis,the existence for periodic boun- dary value problem of first-order integro-differential differential equations are considered.Some new results are obtained. 相似文献
33.
In Europe, a limit value of 10 ng L(-1) was set by the European Commission for benzo[a]pyrene (B[a]P) in water intended for human consumption (Council Directive 98/83/EC) and, therefore, sensitive and reliable methods are needed to evaluate its presence. We report here on the development of a highly sensitive indirect competitive ELISA for the detection of B[a]P in potable water. Fourteen monoclonal antibodies were generated in mice using novel B[a]P derivatives. The immunoassay with the least interference and the best sensitivity was optimized and characterized. As co-solvent, ten percent methanol (v/v) was determined as the optimum concentration for B[a]P solubilization for use with the developed ELISA. With the purified antibody (clone 22F12) the average IC50 for B[a]P and corresponding detection limit at a signal:noise (S/N) ratio of 3 was 65 ng L(-1) and 24 ng L(-1), respectively. From the 16 EPA-designated PAHs, only chrysene, indeno[1,2,3-cd]pyrene, and benzo[b]fluoranthene showed a cross-reactivity (CR) higher than 20%. No CR was observed for two- and three-ringed aromatics as well as dibenz[ah]anthracene and benzo[ghi]perylene. The effect of pH value (range 6.5-9.5), ionic strength (specific electric conductivity 1 microS cm(-1)-2.5 mS cm(-1)), and inorganic ions (sodium, copper, iron, aluminium, manganese, chloride, sulfate, nitrate, and nitrite at maximum permissible levels according to the Council Directive) on both signal and sensitivity of the ELISA was studied. No significant influence of these parameters on the ELISA competition curve was found. We suggest that the optimized ELISA can be used to monitor potable water samples without previous extraction from the samples. The assay should facilitate the cleanup of B[a]P contaminated sites where B[a]P levels fall close to the limit value of the new drinking water directive. 相似文献
34.
Donor doping process and white light generation in CaMoO4 powders with multivalence Pr codoping 总被引:1,自引:0,他引:1
Both trivalent praseodymium (Pr3+) and quadrivalent praseodymium (Pr4+) were doped in molybdate powders. Visible emission from matrix was enhanced by multivalent Pr codoping. It was proposed that Pr3+ ions was donor and supplied quasi-free electron when Pr3+ took place the Pr4+ sites. The result showed that multivalence codoping would be an effective way to enhance emission of CaMoO4. White light can be generated from Ca0.98Pr0.02MoO4 powder via combination of broadband emissions originated from CaMoO4 matrix and radiative transition of Pr3+. It showed warm white light with Tc of 3450 K that implies promising application in white light emitting diodes (LEDs). 相似文献
35.
In this paper, a system of nonlinear impulsive partial differential equations with delay is investigated by the method of upper–lower solutions. The existence-uniqueness result of this system and the comparison principle of the corresponding equations are obtained. An application is given to some model problems in ecology. 相似文献
36.
Feng Zhang Zhisong Xiao Lu Yan Fang Zhu Anping Huang 《Applied Physics A: Materials Science & Processing》2010,101(4):777-780
Er3+ and Dy3+ codoped tellurite glasses have been synthesized. Five emission bands in the PL spectrum under 325 nm pumping were observed.
Three of them correspond to Er3+ and the other two correspond to Dy3+, respectively. The PL spectrum revealed that the intensity of Dy3+ characteristic emission was enhanced as Er3+ concentration increased while keeping Dy3+ concentration constant. Due to small mismatch between the energy level of Er3+:4F7/2 and Dy3+:4F9/2 resonant energy was possibly transferred between them. This process can give rise to an enhancement of the PL intensity of
484 and 574 nm from Dy3+. The PL spectra of these glasses cover the blue, green and red wavelength range and the intensities of those emission bands
could be controlled by adjusting the concentration of relevant rare-earth ions. These glasses with the controllable CIE coordinates
might be a potential candidate for the widely realistic application such as solid-state white lighting and multicolor display. 相似文献
37.
High quality Tm-doped YAlO3 (Tm:YAlO3) single crystals were obtained along crystallographic b-axis by the Czochralski technique. Optical absorption and fluorescence spectra for Tm3+ in YAlO3 crystals were investigated at room temperature. Based on Judd-Ofelt approach, the intensity parameters Ωt (t = 2, 4, 6) of Tm:YAlO3 were calculated to be Ω2 = 0.93 × 10−20 cm2, Ω4 = 2.23 × 10−20 cm2, and Ω6 = 1.12 × 10−20 cm2. The spectral parameters such as experimental and theoretical oscillator strengths, radiative transition probabilities, radiative lifetime and the fluorescence branching ratio were also obtained. All results indicate that Tm:YAlO3 is a potential candidate for compact, efficient mid-infrared lasers with laser diode pumping. 相似文献
38.
The frequency doubling of a 110-W linearly polarized diffraction-limited Yb-doped fiber oscillator power amplifier (FOPA) has generated 60-W near-diffraction-limited (M2 < or = 1.33) linearly polarized green output. The FOPA produces as much as 2.4 kW of peak power and less than 20-pm linewidth at a 10-MHz repetition rate and 5-ns pulse duration without the onset of nonlinear effects. With two lithium triborate crystals at noncritical phase matching, a maximum of 54.5% doubling efficiency has been demonstrated. The overall electrical efficiency to the green portion of the spectrum is 10%. 相似文献
39.
1IlltroductionInl99o,MiltinandB.lairl1]raisedadifferenceequationasapopulationmodelforthegrowthofthebobwhitequailpopulationofnorthernWisconsin.Inl994,Ladas,G.proposedthefollowingopenproblem[']:"(a)Investigatetheboundedness,persistence,permanence,oscillation,periodicity,andglobalattractivity;(b)ExtendEq.(*)byintroducingdelaysintothemodel,andinvestigatethedelayedequation.".Inl996,TangHeng-shengandOuChun-hua[3]considereditsglobalattrac-tivity,partlyansweredaboveopenproblem(a).Inl999,byintrodu… 相似文献
40.
路基冻害一直是困扰东北季冻区道路建设的一个重要问题。长春冬季天气寒冷,在温度梯度作用下路基土中水分产生迁移和聚集,引起路基冻胀。春季路基解冻,集聚的冰晶体融化,路基土处于饱和或过饱和状态,承载力极低,在交通车辆作用下发生路面鼓包、弹簧、断裂和翻浆冒泡等现象,给交通运输和经济建设带来极大的危害。孔隙是水分迁移的主要通道,是影响路基冻胀主要因素之一,其特征决定土体的冻胀敏感性。本文利用WD-5配置联机图象处理系统的电子显微镜,通过图像定量分析系统,对长春季冻区路基土的微观孔隙作了定量评价。经过分析得出:3个土样孔隙直径均是小于5μm的占主导地位,都具备冻胀条件;试样水平和垂直两个方向的孔隙分布较均匀,孔隙为辐射状或网状结构,多为扁圆和等轴形状;孔隙形态分维数分析认为,分维数高,大孔隙含量多,孔隙分布比较简单,在研究范围内,有利于水分迁移,冻胀性较强。 相似文献