THE VORTICITY STRUCTURE OF HOMOGENEOUS ISOTROPIC TURBULENCE IN IT5 FINAL PERIOD OF DECAY

流体力学工作者很早就认识到,湍流运动是由许许多多微小的涡旋廷动所组成.本论文的目的,在于从粘性不可压缩流体的线性性化以后的运动方程的漪旋运动解,来说明均匀各向同性湍流在后期衰变时期的运动现象.确定在这时期作为湍流元随机运动着的涡旋的物理条件是:首先,涡旋的涡量分布必须集中在涡旋的几何中心附近,其次,每一个涡旋的总角动量是一常数.我们运用辛和林家翘的方法来计算湍流中的二元速度关联函数,从而导致米里洪西科夫解.这个解的速度关联和湍能耗拍定律都和白却勒尔与爆生德的实验相符合.最后,我仍指出了湍流的湍性结构是和作为湍流元的涡旋的涡性结构有密切联系以及依据现有涡旋运动解来计算出高元速度关联和其他种类关联函数的可能性.     

Effect of Acid Treatment on Electrocatalytic Performance of PtNi Catalyst

In this paper, we describe the synthesis of the AC-PtNi/G catalysts with graphene as the carrier, via the alcohol reduction and the sulfuric acid treatment. The prepared catalysts were microscopically characterized by X-ray diffractometry(XRD), X-ray photoelectron spectroscopy(XPS), scanning electron microscopy(SEM), electron spectroscopy(EDAX), and transmission electron microscopy(TEM). We tested the electrochemical performance of the prepared catalysts using an electrochemical workstation and in situ infrared spectroscopy(FTIR). The results showed that the acid-treated AC-PtNi/G catalysts had a more uniform dispersion and with the increased of treatment time, the particle size of the catalyst became smaller. And the electrocatalytic performance of the AC-PtNi/G-48h catalyst treated with sulfuric acid for 48 h was significantly better than that of the untreated PtNi/G catalyst. Its electrochemically active surface area was 76.63 m²/g, and the peak current density value for catalytic oxidation of ethanol was 1218.83 A/g, which was 10 times that of ordinary commercial Pt/C catalyst. The steady-state current density value of 1100 s was 358.77 A/g, and it has excellent anti-CO toxicity performance. It was determined that a sulfuric acid treatment controlled catalyst particle size and increased the electrocatalytic activity of the catalytic oxidation of ethanol.     

A SIMPLIFIED DERIVATION OF CHERN-SIMONS COCHAIN AND A POSSIBLE ORIGIN OF θ-VACUUM TERM

In this paper, it is shown that the cohomlogy of generalized secondary classes, the Faddeev type cohomology and the generalized gauge transformation can be easily obtained by expanding the Chern form according to the degree of the forms in its submanifolds and using the closed property of the Chern form. It is also shown that a θ-vacuum term in the effective Lagrangian arises when gauge field in the group manifold is present.     

ANOf}ALIES OF ARBITRARY GAUGE GROUP AND ITS REDUCTION GROUP,EINSTEIN AND LORENTZ ANOMALIES

Based upon the properties of the characteristic classes and their Chern-Simons secondary characteristic classes. the "Abelian" anomalies in M²ⁿ⁺²,the Euler-Heisenberq effective actions in M²ⁿ⁺¹, as well as the non-Abelian anomalies in M²ⁿ for arbitrary gauge gzoup and its reduction subgroup have been investigated thoroughly and the application to the gravitational anomalies is made. It is shown that the "Ahelian" anomalies of such groups are equal to each other, their Eu1er-Xeisenberg actions are also closely related to each, other,and their non-Abelian anomalies are also equivalent if their common generating functional can be taken as a counter-term.For the gravitational anomalies we present the common genera- ting functional for both non-Abelian Einstein and Lorentz anomalies M⁴ⁿ⁺² and show the relationship between them.     

THE TOPOLOSICAL ORIGINS OF GAUGE ANOMALIES

In addition to the recent discovery that the Chern-Simons secondary classes are the topological origins generating special unitary gauge group anomalies, it is shown that some special orthogonal gauge group anomalies can also be generated, from the Pontrjagin and the Euler secondary classes. The common differential geometrical and topological background are explained as well.     

氧化铝柱上的Beckmann重排反应——一个新的异︽唑啉环合付产物

By using Beckmann rearrangement on alumina to prepare 7α-acetylamino-6, 14-endo-etheno-tetrabydrothebaine (2a) and its N-allyl analogue (2b) from the corrssponding ketoxime tosylates (1a and 1b), we obtained novel isoxazoline by-products (3a and 3b). Their structures were determined by IR, ^1H NMR, MS and elemental analyses. The mechanism of this side reaction was beiefly discussed.     

ON AN APPROXIMATE FORM OF THE COUPLED EQUATIONS OF THE ORDER PARAMETER WITH THE WEAK ELECTROMAGNETIC FIELD FOR THE IDEAL SUPERCONDUCTOR

A simplified derivation of the macroscopic electrodynamic equations of Umezawa, Hancini et al. for superconductors is given in the framework of the closed time path Green's functions (CTPGF)using generalized Ward-Takahashi identities. It is shown that the forms of the equations obtained are the same for both thermoe quilibrium and nonequilibrium stationary states provided the electromagnetic field is weak and its effect on the modulus of the order parameter can be neglected. The statistical behavior of the states is completely specified in the equations by parameters which can be calculated by the method of CTPGF.     

反相高效液相色谱法同时测定苍术中的两种聚乙炔类化合物

采用反相高效液相色谱法同时测定了苍术中的2种主要聚乙炔类成分(苍术素、苍术素醇)。采用Polaris-C18柱,以乙腈-水溶液为流动相进行梯度洗脱,流速1.0 mL/min,紫外检测波长340 nm。2种聚乙炔类化合物的检测限分别为0.069和0.016 μg,回收率为97.4%~104.6%。该方法操作简单,结果准确,重现性好,可用于苍术药材及饮片中2种主要聚乙炔类化合物的同时测定,具有很高的实用价值。     

珠江三角洲夏季臭氧区域污染及其控制因素分析

2006年夏季,在珠江三角洲(简称珠三角)开展了一次大型野外综合空气质量观测实验.实验包括了珠三角现有的环境监测网络和两个额外设置的超级观测站.本文基于环境监测网络的观测结果对区域臭氧污染状况和污染过程进行了分析,对各站点所记录的气团光化学属性进行了诊断.结果发现,两个超级站点分别对应着污染城市地区和下风向远郊区的光化学条件,它们较好地覆盖了区域尺度上主要的臭氧高值区.使用基于观测的模型对超级站上臭氧的光化学产生过程及臭氧控制区进行了分析.结果显示,第一,模式中的醛类化学和缺失的HONO化学对于臭氧光化学产生具有重要影响;第二,在城市地区,臭氧的光化学产生速率主要受人为源排放碳氢化合物控制;而在城市远郊区,臭氧的光化学产生速率主要受NO控制;第三,重要的人为源排放的碳氢化合物是烯烃和芳香烃.使用O′x和NOz的回归结果对臭氧产生效率进行了估算,发现城市和郊区的数值存在显著差异(分别为2.1和7.8),这从侧面支持了模型对于城市和郊区臭氧控制区属性的判断.     

h-BN掺杂Na2WO4-Mn/SiO2催化剂用于乙烷氧化脱氢制乙烯

采用混浆法制备了一系列六方氮化硼掺杂的Na2WO4/Mn/BxSiy催化剂,并应用于乙烷氧化脱氢制乙烯（ODHE）。考察了Na2WO4/Mn/BxSiy催化剂的ODHE反应性能,并详细探讨了反应温度、稀释气比例等条件对催化剂反应活性的影响。结果表明,h-BN的掺杂发现显著提高了Na2WO4/Mn/BxSiy催化剂C2H4选择性。Na2WO4/Mn/B5.0Si95催化剂在700℃时,表现出相对较高的活性并且CO2生成量极低（>70% 乙烯选择性,46.5%的乙烯收率,1.80%的CO2选择性）。通过X-射线粉末衍射（XRD）、扫描电镜（SEM）、H2程序升温还原（H2-TPR）、O2程序升温脱附（O2-TPD）和C2H6程序升温脱附（C2H6-TPD）等手段对催化剂进行了表征。研究发现,h-BN的加入对改变催化剂表面元素的化学状态,形成了更多具有低温活性的物相,对抑制深度氧化起到重要作用。同时,h-BN的掺杂也调变了催化剂的导热能力,避免床层热点的形成,提高了C2H4的选择性。