Theoretical analysis on waveform structures of pulse propagating in shallow water with an ideal thermocline

I.IntroductionDuetospatia1andtemporalvariabilityoftheocean-acousticenvironment,especially,theeffectsofboundaryaswel1asmediumonpropagationofacousticwavesinshal1owwater,theacousticpropagationisextrcmelycomp1icatcd.Multipathtransmissionisthebasiccharacteris-hcsofunderwatersoundchannels.Undctcrminedmultipathstructurescangreatlylimittheperformanceofunderwateracousticdetcction.However,ifthemultipathcharacteristicsofacousticpropagationinunderwatcrsoundchanne1sareknown,spaee-timeresolutionandpro-cess…     

Pointwise Stabilization for a Chain of Coupled Vibrating Strings

For the system representing a chain of coupled vibrating strings,we show that the associated semigroup satisfies the assumptionof spectrum-determined growth, and hence obtain conditions forenergy to decay strongly or exponentially. We examine in detailthe three-string case, and our results include those obtainedby others for the two-string case. Permanent address: Beijing Institute of Information and Control,Beijing, China.     

激发态卟啉衍生物研究(Ⅶ)——取代基对卟啉—硝基苯化合物发光特性的影响

本文报导共价链相连的X-P-Y“三合板”型化合物在二甲基甲酰胺(DMF)和苯溶液中的发光特性.结果发现:引入取代基X=Cl—,CH3O—和Y=苯、硝基苯对中心卟啉的吸收和荧光光谱均无明显影响,仅其峰值频率将因溶剂不同而有所偏移.此外,由Cl—取代的卟啉—苯的荧光强度总比CH3O—取代时高;若将Y取代基由苯改换为硝基苯时,将使CH3O—P—Y化合物的荧光增强,但在Cl—P—Y化合物中则出现相反的趋势.不论在何种化合物中,在Y取代基中的苯环上引入NO2—基后,均可使其消光系数减小,而且当硝基在邻位取代时,这一效应更为显著.所有这些变化规律均不因溶剂不同而异.如果我们认为X—P—Y化合物的发光强度变化和其中心的卟啉大环上的π电子云密度偏移有规律性的关联,那么上述的一些取代基效应是可以理解的.进而,我们认为:本文所报导的事实将有助于充实巧妙设计高效利用太阳能的分子体系的科学依据.     

电子探针定量分析的标准样品——几种多元氧化物单晶

在很高的温度和适宜的生长条件下,分别采用熔盐籽晶法和高温引上法生长了高质量的YAP、NAB、KTP、LN、BBO、SBN等多元氧化物单晶,它们具有优良的物理化学性能,严格的化学比,固定的组成与结构以及较好的化学均匀性和电子束轰击下的稳定性。广泛地用于激光和非线性光学领域。我们选用这些晶体为原材料研制电子探针定量分析的标准样品。经过测量和标定,这些单晶标样符合中华人民共和国国家标准GB 4930-85(电子探针显微分析标准样品通用技术条件)的规定。含有稀土元素的标样如NAB和YAP能发出绿色荧光,是电子显微术中理想的阴极发光材料。     

配位聚合物{[MnL][FeⅡFeⅢ(ox)3·1.5H2O]}∞的合成及其磁学性质

合成和表征了一种新的Schiff碱配合物MnL(ClO4)*3H2O(1)(其中L为n(水杨醛)∶n(二乙撑三胺)=1∶1缩合而成的Schiff碱).1与FeSO4*7H2O和K3[Fe(ox)3]*3H2O(ox=oxalate)进一步反应,生成了双金属层状配位聚合物{[MnL][FeⅡFeⅢ(ox)3]*1.5H2O}∞(2).IR和Mssbauer谱测定结果表明,2具有二维层状结构,其阴离子层由[FeⅡFeⅢ(ox)3]-单元构成.变温磁化率(5K～100K)测试结果表明,2中的自旋载体之间存在反铁磁交换作用.5K时的磁滞现象表明2在低温时可能存在铁磁有序,这可能是亚铁磁或自旋倾斜造成的.     

三磷酸胞苷在Duolite A-30树脂上的交换过程研究

根据CTP在离子交换树脂上的吸附容量和分离因数的大小,确定Duolite A-30树脂适合CTP与CDP,CMP之间的分离.对CTP在Duolite A-30树脂上的吸附动力学和热力学研究表明,在283.15K~303.15K之间,CTP的质量浓度在7.5g/L以上时,Duolite A-30树脂对CTP的吸附主要受颗粒扩散的控制,其有效扩散系数为D=3.47×10-7cm2/s,溶液的质量浓度≤1.0g/L时,CTP与Duolite A-30树脂之间的交换速率主要受液膜控制,其液膜扩散系数为Kf =4.112×10-4/s.同时测定了不同条件下三磷酸胞苷溶液在Duolite A-30树脂固定床离子交换柱中的穿透曲线,研究了进口浓度、进口流速、原料液温度、原料液的pH值及柱高对穿透曲线的影响.用二阶动力学推动力模型描述固定床动态过程,考察了轴向返混对穿透曲线的影响,并从穿透曲线回归得到总传质系数,模型计算值与实验数据符合良好.     

On the maximum modulus of complete trigonometric sums

LetQ _k (p) be a set consisting of all polynomials of degreek with integral coefficientsf(x)=a _k x ^k +...+a ₁ x, wherep×a _k . For givenk andp any polynomialf _k,p (x)εQ _k (p) satisfying ‖S(p, f _k,p )‖=sup ‖S(p, f)‖fεQ(p) is called a maximum modular polynomial inQ _k (p), where $$S(p,f) = \sum\limits_{x = 0}^{p - 1} {e^{2\pi if(x)/p} } $$ Moreover, we definec(k, p)=‖S(p, f _k.p (x))‖. The main results are the following theorems.

1. For k=p?1 and p≥3 we have $$c(k,p) = \sqrt {p^2 - 4(p - 1)\sin ^2 \frac{\pi }{p}} $$ Besides, we may take \(f_{k,p} (x) = \prod\limits_{r = 0}^{p - 2} {(x - r)} \)
2. For k=p?s, 2≤s≤(p+1)/2 and p≥5, we have $$c(k,p) \leqslant p - 4(s - 1)\sin ^2 \frac{\pi }{p}$$ .

In Theorems 3 and 4, an interesting connextion between the present question and the famous problem of Prouhet and Tarry is given, some conditions under which the sign of equality in Theorem 2 holds are given and a method used to construct a maximum modular polynomial inQ _k (p) is also given.     

Liposomes as signal amplification reagents for bioassays in microfluidic channels

Liposomes with encapsulated carboxyfluorescein were used in an affinity-based assay to provide signal amplification for small-volume fluorescence measurements. Microfluidic channels were fabricated by imprinting in a plastic substrate material, poly(ethylene terephthalate glycol) (PETG), using a silicon template imprinting tool. Streptavidin was linked to the surface through biotinylated-protein for effective immobilization with minimal nonspecific adsorption of the liposome reagent. Lipids derivatized with biotin were incorporated into the liposome membrane to make the liposomes reactive for affinity assays. Specific binding of the liposomes to microchannel walls, dependence of binding on incubation time, and nonspecific adsorption of the liposome reagent were evaluated. The results of a competitive assay employing liposomes in the microchannels are presented.     

Preparation of Y2Ba4Cu7O15-δ Superconductor without High Oxygen Pressure

The synthesis of bulk Y₂Ba₄Cu₇O_15-δ superconductor at atmospheric oxygen pressure via solid state sintering is reported. Temperature ranging from 860 to 890 °C as well as time interval over 2 to 15 days were used to investigate the formation of the Y₂Ba₄Cu₇O_15-δ phase. A time-temperature profile characterizing the conditions for the preparation of Y₂Ba₄Cu₇O_15-δ phase suggests the optimal condition to be sintering at 890 °C for over 10 days. Detailed results of X-ray diffraction, electrical resistivity, iodometric titration and magnetization measurements are described.