疏水缔合水溶性聚(丙烯酰胺/丙烯酸钠/N,N-双烯丙基十二胺)水溶液的粘度行为

采用前加碱二元胶束共聚-共水解法合成了三元疏水缔合水溶性聚合物聚(丙烯酰胺/丙烯酸钠/N,N-双烯丙基十二胺)[P(AM/NaAA/DiAC_(12))],研究了其水溶液的粘度行为。当x(DiAC_(12))=0．10%～0．40%时,在30℃、1 mol/L NaCl溶液中,其特性粘数[η]、Huggins常数K_H、粘均相对分子质量(?)分别为16．38～19．45 dL/g,0．214～0．394和8．36×10~6～10．36×10~6g/mol;K_H小于0．8,表明其分子内缔合作用较弱。P (AM/NaAA/DiAC_(12))在矿化度为19 334μg/g,盐水溶液中的表观粘度随疏水单体用量的增加而增加,随温度、剪切速率的增加而降低。在NaCl、CaCl_2的离子强度分别为1．26×10~(-3)～4．88×10~(-3)和1．07×10~(-4)～5．28×10~(-4)mol/kg的水溶液中,P(AM/NaAA/DiAC_(12))水溶液出现盐增粘现象,疏水单体用量越高,盐增粘效应越显著。     

N-苄基丙烯酰胺的合成

以丙烯腈和苯甲醇为原料，浓硫酸作催化剂，合成了N-苄基丙烯酰胺（N-BAA）。考察了反应温度、反应时间和催化剂用量等因素对产物收率的影响，得出了最佳反应条件：n（丙烯腈）：n（苯甲醇）：n（浓硫酸）=3：1：1．2，反应时间3h，反应温度60℃。在最佳条件下，N-BAA的收率可达92％。每100g粗产物用10％氢氧化钠溶液提纯，精制产物纯度可达99．80％，熔点为64～65℃。通过红外光谱对产物结构进行了表征。     

Evaluation of the Properties of Si3N4/Si3N4 Joint Brazed Using a Filler Alloy Containing Pd

Si3N4 ceramic was jointed to itself using a filler alloy of Cu76.5Pd8.5Ti15, and the mechanical properties of the jointwere measured and analyzed. By using a filler alloy of Cu76.5Pd8.5Ti15, the SisN4/SisN4 joints were obtained bybrazing at 1373～1473 K f     

线性调频信号检测方法的研究

在线性调频信号体制雷达的数字脉冲压缩系统中对数字脉压后的脉冲串进行DFT相参处理时，若采样时刻偏离脉压回波的峰值时刻，不同的采样频率使得DFT相参积累后的信噪比会有不同程度的损失。本文详细分析了采样频率分别为20MHz和10MHz时对信号相参积累的影响，并对幅值检测和M／N检测两种检测方法的检测性能进行了比较，仿真结果表明，M／N检测优于幅值检测。     

Wear and Creep Characteristics of a Carbon‐Derived Si3N4/SiC Micro/Nanocomposite

In the presented work some properties of a recently developed Si₃N₄/SiC micro/nanocomposite have been investigated. The material was tested using a pin on disc configuration. Under unlubricated sliding conditions using Si₃N₄ pin at 50 % humidity, the friction coefficient was in the range of 0,6 ‐ 0,7. The reduction of humidity resulted in a lower coefficient of friction, in vacuum the coefficient of friction had a value of about 0,6. The wear resistance in vacuum was significantly lower then that in air. The wear patterns on the Si₃N₄+SiC disc revealed that mechanical fracture was the wear controlling mechanism. Creep tests were realized in four point bending configuration in the temperature interval 1200‐1400 °C at stresses 50,100 and 150 MPa and the minimal creep deformation rate was established for each stress level. The activation energy, established from the minimal creep deformation had a value of about 360 kJ/mol and the stress exponent values were in the range of 0.8‐1.28. From the achieved stress exponents it can be assumed that under the studied load/temperature conditions the diffusion creep was the most probable creep controlling mechanism.     

Electrical and growth characteristics of Au/Al0.15Ga0.85N:Si structures with various Si incorporations

We have investigated the growth characteristics of n-Al_0.15Ga_0.85N:Si/GaN and the electronic properties of Au/n-Al_0.15Ga_0.85N:Si diode structures grown by metal-organic chemical vapor deposition (MOCVD) with various Si incorporations. The Al_0.15Ga_0.85N:Si layers were grown on undoped GaN/sapphire (0001) epitaxial layers in a horizontal MOCVD reactor at the reduced pressure of 300 torr. The mirrorlike surface, free of defects, such as cracks or hillocks, can be seen in the undoped Al_0.15Ga_0.85N epilayer, which was grown without any intentional flow of SiH₄. However, many cracks are observed in the n-Al_0.15Ga_0.85N:Si, which was grown with Si incorporation above 1.0 nmol/min. While Au/n-Al_0.15Ga_0.85N:Si diodes having low incorporation of Si showed retively good rectifying behavior, the samples having high Si incorporation exhibited leaky current-voltage (I-V) behavior. Particularly, the Au/n-Al_0.15Ga_0.85N:Si structure grown with Si incorporation above 1.0 nmol/min cannot be used for electrical rectification. Both added tunneling components and thermionic emission influence the current transport at the Au/n-Al_0.15Ga_0.85N:Si barrier when Si incorporation becomes higher.     

Non-deterministic exponential time has two-prover interactive protocols

We determine the exact power of two-prover interactive proof systems introduced by Ben-Or, Goldwasser, Kilian, and Wigderson (1988). In this system, two all-powerful noncommunicating provers convince a randomizing polynomial time verifier in polynomial time that the inputx belongs to the languageL. We show that the class of languages having tow-prover interactive proof systems is nondeterministic exponential time.We also show that to prove membership in languages inEXP, the honest provers need the power ofEXP only.The first part of the proof of the main result extends recent techniques of polynomial extrapolation used in the single prover case by Lund, Fortnow, Karloff, Nisan, and Shamir.The second part is averification scheme for multilinearity of a function in several variables held by an oracle and can be viewed as an independent result onprogram verification. Its proof rests on combinatorial techniques employing a simple isoperimetric inequality for certain graphs:     

Influence of ethyl methacrylate content on the volume‐phase transition of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] microgels

A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry     

Active sites of Cu-ZSM-5 for the decomposition of acrylonitrile

The catalytic decomposition of acrylonitrile (AN) over Cu-ZSM-5 prepared with various Cu loadings was investigated. AN conversion, during which the nitrogen atoms in AN were mainly converted to N₂, increased as Cu loading increased. N₂ selectivities as high as 90–95% were attained. X-ray diffraction measurements (XRD) and temperature-programmed reduction by H₂ (H₂-TPR) showed the existence of bulk CuO in Cu-ZSM-5 with a Cu loading of 6.4 wt% and the existence of highly dispersed CuO in Cu-ZSM-5 with a Cu loading of 3.3 wt%. Electron spin resonance measurements revealed that Cu-ZSM-5 contains three forms of isolated Cu²⁺ ions (square-planar, square-pyramidal, and distorted square-pyramidal). The H₂-TPR results suggested that in Cu-ZSM-5 with a Cu loading of 2.9 wt% and below, Cu⁺ existed even after oxidizing pretreatment. The activity of AN decomposition over Cu/SiO₂ suggested that CuO could form N₂, but, independent of the CuO dispersion, nitrogen oxides (NO_x) were formed above 350 °C. Cu⁺ and the square-pyramidal and distorted square-pyramidal forms of Cu²⁺ showed low activity for AN decomposition. Temperature-programmed desorption of NH₃ suggested that N₂ formation from NH₃ proceeded on Cu²⁺, resulting in the formation of Cu⁺. The Cu⁺ ions were oxidized to Cu²⁺ at around 300 °C. Thus, high N₂ selectivity over Cu-ZSM-5 with a wide range of temperature was probably attained by the reaction over the square-planar Cu²⁺, which can be reversibly reduced and oxidized.     

Amtshaftung bei Bauführung im Hochwassergebiet; fehlerhafter Flächenwidmungsplan; Nachforschungspflichten der Gemeinde

Bestehen ausreichende Anhaltspunkte für die Hochwassergef?hrdung, ist die Gemeinde verpflichtet, sich durch Nachforschungen Gewissheit über das Vorliegen oder Nichtvorliegen eines Hochwasserabflussgebietes gem § 38 Abs 3 WRG zu verschaffen. Liegt ein solches vor, hat sie gem § 12 Abs 1 Z 2 krnt GplG dieses im Fl?chenwidmungsplan ersichtlich zu machen. Erteilt die Gemeinde eine Baubewilligung ohne diese von der Erteilung einer wasserrechtlichen Bewilligung abh?ngig zu machen, haftet sie für die Kosten der Bauführung, die bei gesetzes-konformer Vorgangsweise unterlassen worden w?re.