Summary This paper presents some applications of cyclic voltammetry at the interface of two immiscible electrolyte solutions by means of an experimental set-up described in a former publication. When using special sample preparation good results are obtained for the determination of iodide and quinine in pharmaceutical products as well as for the determination of quinine in tonic water and dodecylsulfate in a tooth-salt.Herrn Prof. Dr. Günther Tölg zum 60. Geburtstag gewidmet 相似文献
We show that, in dimensions equal or greater than three, classical strings do not join or split. This is part of a no-interaction theorem that is also proved. The quantum theory is considered. 相似文献
Summary The available laboratory data of turbulent boundary layer flow over two-dimensional obstacles have been examined in order
to identify the parameters (such as the aspect ratio or the surface roughness) driving the onset of separation. A comparison
with some linearized models suitable for atmospheric applications is also made. It results that i) the model response can
be highly sensitive to the detailed shape of the obstacle; ii) the ratio between obstacle length and boundary layer thickness
is relevant in determining the pressure perturbation near the surface; iii) the surface shear stress is poorly described in
most cases and in particular in the obstacle wake.
Riassunto I dati di laboratorio disponibili, relativi a strati limite turbolenti su ostacoli bidimensionali, sono stati esaminati al
fine di identificare i parametri guida della separazione (quali la pendenza o la rugosità della superficie). Inoltre è stato
fatto un confronto con i risultati di alcuni modelli linearizzati adatti per applicazioni atmosferiche. Ne risulta che i)
la risposta del modello è molto sensibile alla forma dettagliata dell’ostacolo; ii) il rapporto fra la lunghezza dell’ostacolo
e lo spessore dello strato limite turbolento incidente è importante nel determinare la perturbazione della pressione vicino
alla superficie; iii) lo ?shear stress? superficiale non è riprodotto con accuratezza nella maggioranza dei casi, in particolare
nella scia dell’ostacolo.
Резюме Анализируются имеющиеся лабораторные данные по турбулентному течению в пограничном слое над двумерными препятствиями, чтобы
идентифицировать параметры (такие как аспектное отношение или шероховатость поверхности), определяющие возникновение отрыва.
Проводится сравнение с некоторыми линеаризованными моделями, удобными для атмосферных приложений. Получены следующие результаты:
1) модельный отклик может быть очень чувствительным к детальной форме препятствия; 2) отношение между длиной препятствия и
толщиной поверхностного слоя является существенным при определении возмущения давления вблизи поверхности; 3) напряжение поверхностного
сдвига плохо описывается в большинстве случаев и, в частности, в спутной струе.
Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1?xRxF2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region. 相似文献
A method for calculating the parameters of formation of vacancies in crystals formed by spherically symmetrical atoms was developed. Both quantum effects at low temperatures and the possibility of the delocalization of atoms at high temperatures were studied. The parameters of formation of vacancies in carbon subgroup element crystals C-diam, Si, Ge, α-Sn, and Pb were calculated. The inclusion of the delocalization of atoms was shown to increase the enthalpy, entropy, and volume of vacancy formation. At low temperatures, the parameters of vacancy formation were found to depend strongly on the temperature, and the entropy of vacancy formation became negative. At high temperatures, close agreement with experimental data and theoretical estimates reported by other authors was obtained. The temperature dependence of vacancy parameters was studied for diamond heated isobarically from 100 to 4500 K. The applicability scope of the Arrhenius equation with a temperature-independent activation energy is discussed. The validity of the “compensation rule” (correlation between the entropy and enthalpy of vacancy formation) was demonstrated. It was also shown that the volume and entropy of vacancy formation were correlated over the whole temperature range studied.
It is well known that F. G. Tricomi (1923) is the originator of the theoryof boundary value problems for mixed type equations by establishing the Thicomi equation: y·uxx+uyy=0 which is hyperbolic for y < 0, elliptic for y=0. and parabolic for y= 0 and then applied it in the theory of transonic flows.Then A.V.Bitsadze together with M. A . Lavrent′ev (1950) established the Bitsadze Lavre nt′ev equation: sgn( y ) ·uxx+uyy=0 where sgn(y) = 1 for y > 0, = -1 for y<0, 0 for y=0 with the discontinuous coefficient sgn( y ) of uxx, while in the case of Tricomi equation the corre sponding coefficient y is continuous. In this paper we establish the mixed Bitsadze Lavrent′ev Tricomi equation. Lu=K(y)·uxx+sgn(x) ·uyy+r(x,y)·u=f(x,y), where the coefficient K=K(y) of uxx is increasing continuous and coefficient M=sgn(x) of uyy discontinuous, r=r(x,y) is once continuously differentiable, f=f(x,y) continuous. Finally we prove the uniqueness of quasi regular solutions and observe that these new results can bbe applied in fluid dynamics. 相似文献