Standardisierung der dünnschichtchromatographischen Trennungen von Flechtensäuren zur Chemotaxonomie von Flechten

Zusammenfassung Die dünnschichtchromatographische Trennung von Flechtenextrakten zur Unterstützung der Taxonomie wurde in Bezug auf die Trennleistung und auf die Reproduzierbarkeit optimiert. Dabei wurden besonders gute Trennleistungen erhalten mit dem Flie?mittelgemisch Benzol:Dioxa:Eisessig=90∶25∶4 bei Verwendung von Kieselgel, dessen Aktivit?t durch eine Umgebung mit relativer Feuchte von 70% festgelegt wurde, und mit Methylenchlorid als Eluiermittel bei Verwendung von mit Oxals?ure impr?gniertem Kieselgel und antiparallelem Aktivit?tsgradienten. Eine hohe Reproduzierbarkeit der Trennungen wurde erreicht durch Verwendung der Vario-KS-Kammer nach Geiss, die die Einstellung einer definierten Schichtaktivit?t bzw. eines definierten Aktivit?tsgradienten und eine reproduzierbare Vorbedampfung der Schicht mit Flie?mittel erm?glicht. Es konnte gezeigt werden, da? durch unterschiedliche chromatographische Trennungen der gleichen Extrakte und durch die Verwendung verschiedener Anf?rbereagenzien die Identifizierung und damit die Aussagekraft für taxonomische Probleme steigt.

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Standardisation of the thin-layer chromatographic separation of lichen acids for the chemotaxonomy of lichens

Summary The thin-layer chromatography of lichen extracts for taxonomic studies has been optimized in relation to separation and to reproducibility. Especially good separations were found with benzene:dioxane:acetic acid (90∶25∶4) developer and silica gel thin-layer plates, whose activity was fixed by an ambient moisture content of 70%, and with methylene chloride developer and silica gel plates impregnated with oxalic acid and antiparallel activity gradient. High reproducibility of separation was obtained using the Geiss Vario-KS tank, which allows the activity of the plates or the activity gradient to be adjusted and which also allows reproducible exposure of plates to the vapour of developing solvents. By different chromatographic separations of the same extracts and by using different colour reactions the accuracy of identification for taxonomic studies has been improved.

     

Sloshing waves in a heated viscoelastic fluid layer in an excited rectangular tank

In this paper, we have investigated the motion of a heated viscoelastic fluid layer in a rectangular tank that is subjected to a horizontal periodic oscillation. The mathematical model of the current problem is communicated with the linearized Navier–Stokes equation of the viscoelastic fluid and heat equation together with the boundary conditions that are solved by means of Laplace transform. Time domain solutions are consequently computed by using Durbin's numerical inverse Laplace transform scheme. Various numerical results are provided and thereby illustrated graphically to show the effects of the physical parameters on the free-surface elevation time histories and heat distribution. The numerical applications revealed that increasing the Reynolds number as well as the relaxation time parameter leads to a wider range of variation of the free-surface elevation, especially for the short time history.     

吸波材料与微波暗室问题的数学模型

为分析尖劈形材料的吸波性能,建立了半圆镜像模型将辐射波在尖劈空间的传播等效为射线对等分半圆的切割,确定了反射波线和吸波材料几何参数之间的解析关系.对于微波暗室问题,假设在余弦辐射体上随机选取一个方向的能量波束集中了其所有能量,分别建立了加权能量分布模型和Monte Carlo模型,仿真验证了两模型结论的一致性.     

The sloshing of stratified liquid in a two-dimensional rectangular tank

The sloshing of inviscid liquid of stratified density in a rectangular tank is analyzed.As the flow is no longer irrotional,the governing equation is found to be quite different from the Laplace equation used for the liquid of constant density.In particular it contains terms of mixed temporal and spatial derivatives.The problem is solved based on the variable separation method and Laplace transform for the constant Vaisala-Brunt frequency.It is found that the stratification of density may have small effects...     

Generation of linear and nonlinear waves in numerical wave tank using clustering technique-volume of fluid method

A two-dimensional (2D) numerical model is developed for the wave simulation and propagation in a wave flume.The fluid flow is assumed to be viscous and incompressible,and the Navier-Stokes and continui...     

Numerical study on electrostatic potential distribution of large cylindrical oil tanks

This study carried out a numerical simulation of electrostatic potential distribution in the cylindrical oil tank, focusing on spatial distribution of electrostatic potential and the variation tendency of the potential in the filling operation. Electrostatic potential distribution of stationary oil was illustrated, and the relationship between the electrostatic potential distribution and some parameters of the tank and oil was analyzed as well. Dynamic electrostatic distribution was studied when charged oil is filling into the tank, and ESD prevention measures’ effects on electrostatic potential distribution were simulated. Finally, calculation results of two other types of oil tanks were presented in brief.     

Wave-based analysis of dual acoustic black holes for anechoic termination of shock testing devices

Shock testing is an important issue for the survivability of an equipment under shock environment in aerospace and military industries. One of the problems faced in conventional shock testing devices is the need for redesigning of the geometry whenever the responses to different shock environments are tested. To circumvent the redesigning processes, a structure with two ‘acoustic black holes (ABHs)’ on both ends, referred to as the beam with dual ABHs, is proposed as a shock testing device. The beam with dual ABHs is capable of simulating diverse shock environments by controlling the applied force because it can be regarded as an infinite beam at high frequency range with the aid of the anechoic terminations by the ABHs. To systematically investigate the beam with dual ABHs, we develop a wave-based method that uses the reflection matrix of an ABH to perform free and forced vibration analyses. From the analyses on frequency response function and shock response spectrum of the beam with dual ABH, it is suggested that the beam with dual ABHs is feasible as a semi-permanent shock testing device.     

Capturing the experimental behaviour of a point-absorber WEC by simplified numerical models

The paper presents a wave basin experiment of a direct-driven point-absorber wave energy converter moving in six degrees of freedom. The goal of the work is to study the dynamics and energy absorption of the wave energy converter, and to verify under which conditions numerical models restricted to heave can capture the behaviour of a point-absorber moving in six degrees of freedom. Several regular and irregular long-crested waves and different damping values of the power take-off system have been tested. We collected data in terms of power output, device motion in six degrees of freedom and wave elevation at different points of the wave basin. A single-body numerical model in the frequency domain and a two-body model in the time domain are used in the study. Motion instabilities due to parametric resonance observed during the experiments are discussed and analysis of the buoy motion in terms of the Mathieu instability is also presented. Our results show that the simplified models can reproduce the body dynamics of the studied converter as long as the transverse non-linear instabilities are not excited, which typically is the case in irregular waves. The performance of the more complex time domain model is able to reproduce both the buoy and PTO dynamics, while the simpler frequency domain model can only reproduce the PTO dynamics for specific cases. Finally, we show that the two-body dynamics of the studied wave energy converter affects the power absorption significantly, and that common assumptions in the numerical models, such as stiff mooring line or that the float moves only in heave, may lead to incorrect predictions for certain sea states.     

小孔流速实验中的排水时间和流量系数的研究

本文以水作为理想流体,考虑到水头损失和孔口缩流效应,对小孔流速实验涉及的容器排水问题进行了系统的理论和实验研究.从理论上推导得出了圆柱形容器排水时间的解析解,分析了排水时间和自由液面速度、流量系数之间的规律,提出了排水时间的等效性.实验上,加工了底部开有不同小孔的大型圆柱形容器,测量了容器排水时间随液面高度的变化关系,借助实验结果计算了流量系数值,验证了容器排水时间的等效性关系,实验结果与理论计算符合较好.