Hans Bernhard Reichow and the concept of Stadtlandschaft in German planning

The German architect and city planner Hans Bernhard Reichow (1899-1974) published his book Organische Stadtbaukunst: Von der Gro g stadt zur Stadtlandschaft (The organic art of building towns: from the metropolis to the city landscape) in 1948. This presented a uniquely comprehensive discussion of the concept of the Stadtlandschaft (city landscape) in urban planning, an issue which was at the focus of debate in relation to the post-war reconstruction of Germany. Reichow was radically opposed to the idea of the metropolis and proposed the establishment of a new-style Stadtlandschaft , composed of residential cells that were kept closely attuned to their natural landscapes. Discussions from a quarter of a century earlier seemed to reappear in that concept, such as the call for the metropolis to be abolished in the revolutionary years of 1918-1919 following the First World War - a call which, however, gave way to a more pragmatic approach during the Weimar Republic. It is astonishing that the idea of a tabula rasa was maintained by Reichow for so long. There is also another perturbing aspect: Reichow gave his idea the same name as the concept which Nazi town planners had adopted as their own. How was it possible for Reichow to incorporate a new version of the concept of Stadtlandschaft into planning the reconstruction of the new Germany? This article shows, based on the example of Reichow, how concepts of urban planning are carried through history, with new political interpretations being continually attached to them. It deals with the question of continuity at the level of the planners and examines specifically how this continuity and adaptability of the concept of Stadtlandschaft was possible. Reichow's concept is introduced in the first part of this article in order to trace the roots of Stadtlandschaft within history in the second part of the article; finally Reichow's work is put in a theoretical context.     

Emulsions in Metallurgical and Chemical Processes

A review of the metallurgical and chemical literature involving foams and emulsions is presented. Experimental techniques for the measurement of drop sizes in such systems are reviewed, and the basic mechanisms of drop breakup and coalescence are discussed, along with an analysis of the pertinent mass-transfer processes. A detailed discussion on a number of industrial processes using foams and emulsions is also presented.     

AZ31-0.84%Sb合金的机械性能与变形特征

The mechanical properties and deformation features of AZ31-0.84% Sb alloy have been studied by means of the measurement of the properties and morphology observation. Results show that UTS of AZ31-0. 84% Sb alloy at room temperature is 297 MPa, a higher value of UTS is still maintained up to 189 MPa as temperature elevated to 200℃. One of the main reasons for enhancing UTS of the alloy is attributed to the high volume fraction of the precipitates dispersed in the matrix, including Mg3Sb2 phase, which effectively hindered the movement of dislocations during the elevated temperature deformation. The deformation mechanisms of AZ31-0. 84% Sb alloy are the twins and dislocations activated on basal and non-basal planes, a c dislocations may be activated on the basal and nonbasalplanes in twins regions, and some of the thinner twins may shear through the dense dislocations within the thicker twins.     

Numerical analysis of vortex core phenomenon during draining from cylinder tank for various initial swirling speeds and various tank and drain port sizes

A dimple appears on a free surface while rotating a cylinder tank filled with liquid. The dimple starts to concentrically deeper to a drain port at the bottom center of the tank. Over time, the dimple penetrates the drain port, a free surface forms a long and slender string shape in the tank, and a so-called vortexing (air core) phenomenon occurs. The generation of a vortex core depends on the size of the tank and drain port, and on the properties of the liquid in the tank. In this study, the liquid level and the time at which the vortex core is initially generated are numerically investigated using different values of tank diameter, drain port diameter, and initial tank rotational speeds. Instead of a full three-dimensional analysis, a two-dimensional axisymmetric simulation is conducted. The momentum conservation equation in the circumferential direction is additionally solved in the two-dimensional mesh system. Several non-dimensional variables are created: the ratio of the air core generation distance and tank diameter, the diameter ratio of the tank and drain port, the rotational Reynolds number, the rotational Froude number, and the rotational Weber number. Finally, the nondimensional air core generation distance is correlated with the other non-dimensional parameters.     

SINGULARITY DETECTION FOR STRUCTURAL HEALTH MONITORING USING HOLDER EXPONENTS

The majority of structural health monitoring studies reported in the technical literature focus on identifying damage-sensitive features that can be extracted from dynamic response data. However, many of these studies assume the structure can be modelled as a linear system before and after damage and use parameters of these models as the damage-sensitive features. The study summarised in this paper proposes a damage-sensitive feature that takes advantage of the non-linearities associated with discontinuities introduced into the dynamic response data as a result of certain types of damage. Specifically, the Holder exponent, a measure of the degree to which a signal is differentiable, is the feature that is used to detect the presence of damage and determine when that damage occurred. A procedure for capturing the time-varying nature of the Holder exponent based on wavelet transforms is demonstrated through applications to non-stationary random signals with underlying discontinuities and then to a harmonically excited mechanical system that contains a loose part. Also, a classification procedure is developed to quantify when changes in the Holder exponent are significant. The results presented herein show the Holder exponent to be an effective feature for identifying damage that introduces discontinuities into the measured dynamic response data.     

IGNITION OF AMMONIUM PERCHLORATE

A simplified theory for the ignition of ammonium perchlorate is proposed, which is derived from a unified theory that also explains the low-pressure deflagration limit as well as the steady deflagration. The theory provides an approximate method of calculating the ignition delay and the minimum external he»t flux for a successful ignition, as functions of pressure and initial solid temperature. The ignition calculations show that there exists a pressure limit due to the weakness of the igniter strength, in addition to the low-pressure deflagration limit which is an inherent property of the solid independent of the igniter strength. The theory can be extended to other monopropellants for which exothermic reaction occurs only in the gas phase.     

Electrical conduction behaviour in the Ca0.5Zn0.5Fe2O4 system

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

NONISOTHERMAL ANALYSIS OF THE OXIDATION KINETICS OF OIL SHALE CARBONACEOUS RESIDUE

The intrinsic kinetics parameters for the oxidation of the carbonaceous residue in retorted oil shale have been determined from experimental data obtained under linearly increasing temperature. Various different mathematical procedures have been applied to the analysis of the data. The kinetics of this reaction can be described by an overall first-order expression in terms of the amount of unreacted carbonaceous residue with an activation energy of 91 kJ/mol. In comparison to the isothermal method, the nonisothermal technique is shown to be quite convenient and require fewer experimental runs for the determination of intrinsic kinetics.