Apparatus for steady-state kinetic measurements of the catalytic reduction of nitric oxide by ammonia on iron oxide

The reduction of nitric oxide with ammonia on an unsupported iron oxide catalyst has been studied in a continuous-flow recycle reactor using simulated flue gas. The responses of the employed reactor system to step and pulse inputs of tracer indicate that the system could be regarded as a continuous stirred tank reactor (CSTR). Preliminary tests were carried out to determine the effect of temperature and particle size on the measured reaction rates. Additional experiments were performed in order to study the influence of oxygen and water concentration on these rates. A gas chromatographic system has been developed to analyze the gas components NO, N₂O, NO₂, NH₃, H₂O, O₂, CO₂ and N₂. In addition, the concentrations of NO and NO₂ were measured with a nondisperse infrared (NDUV/NDIR) analyzer.     

A new method of excitation control based on fuzzy set theory

The synthesis of the structure of the power system stabiliser (PSS) and its parametrization are based entirely on methods of linear system theory. Thus the desired effect of the PSS is limited to a bounded area around one system operating point. The use of a controller based on fuzzy set theory introduces an event controlled excitation of the synchronous machine taking into account the power system operation. The desired response of the fuzzy controller is given by a set of rules which are obtained from the limits of the voltage regulator and the undesired performance of the conventional excitation control. A fuzzy controller has been developed for which simulation results are provided. These results support the concept of a fuzzy controller for the purpose of excitation control. They show that a well designed fuzzy controller is superior to a fast excitation control with an additional PSS     

Influence of water uptake on the mechanical properties of jute fiber-reinforced polypropylene

Jute fiber-reinforced polypropylene composites have been produced and characterized in order to investigate the influence of water on their mechanical properties. Being hydrophilic, jute fibers absorb a high amount of water causing swelling of fibers. On the other hand, the thermal shrinkage of polypropylene melt leaves some gaps between jute fibers and matrix material. We investigated whether these gaps could be filled by the swelling of wetted fibers. The fillup of these gaps would result in a higher shear strength between fibers and matrix during fracture. Our results suggest that swelling of jute fibers in a composite material can have positive effects on mechanical properties. © 1994 John Wiley & Sons, Inc.     

Polarisation transformer on Ti:LiNbO3 with reset-free optical operation for heterodyne/homodyne receivers

Experimental results for an integrated-optical state-of-polarisation (SOP) controller device on Ti:LiNbO3 for continuous broadband optical operation, with small temperature sensitivity and the possibility of integration with polarisation- insensitive directional couplers, are presented.     

Kinetic investigations in heterogeneous reaction systems by wavefront analysis

In this paper the previously introduced wavefront analysis is extended to heterogeneous reaction systems, which consist of several reaction steps. It is shown how three mainly informations obtained at the wavefront, namely the damping of the wavefront, the time-gradients at the wavefront and the propagation velocity of the wavefront, can be used for kinetic investigations of a reaction step under consideration.     

Spin Extrusion - A New Partial Forming Technology based on 7 NC-Axes Machining

Hollow shape component approaches, applied to shafts and similar workpieces, represent a major potential for ground-breaking innovations in lightweight engineering and safety designs. Among suitable forming technologies, spin extrusion is a pioneering and particularly flexible hollow-shaping technique. All outside form elements, straight or stepped cylinders, cones or spherical rotation elements emerge just from the kinematics of tools. The inside hollow shapes, as e.g. circular cross-sections, shaft to collar connections such as spherical triangles, polygons, splines or dovetail forms are manufactured with a shaping mandrel. Spin extrusion can be applied first and foremost at dimensions that are unattainable with other techniques. The application includes hollow shafts, thick-walled cups and semi-finished tubular products that are not to be found in off-the-shelf cross-sections. In these cases the possibility for using of massive bars is connected with very high price advantages. Furthermore material-saving machining is attracting special attention for high-grade materials.The paper characterizes substantial steps of process analysis and the appliance of a new, derived from the bound method, numerical simulation method for spin extrusion process. Holistic process analysis is the prime factor for process capability. The specific application of the developed special methods of simulation, the accumulation of process data and the integrating into the Computer numerical control of spin extrusion machine is a precondition guaranteeing high-quality assurance.     

Measurements of Attenuation of Third Sound: Evidence of Trapped Vorticity in Thick Films of Superfluid 4He

We present results of a study of third sound in thick ⁴He films in circular resonator geometry. Frequency and line shapes of third sound resonances are measured for temperatures between 0.3 and 2.1 K in saturated films approximately 30 nm thick. From these measurements we calculate the attenuation of the sound. We find that the attenuation at a given temperature is a function of history of the film, strongly affected by such events as large, sudden (more than milli-Kelvin per second) temperature spikes. We also observe variable frequency splitting of resonances, indicating trapped circulation. Our measurements, taken together with other reported attenuation experiments, are incompatible with dissipation mechanisms dependent on thermodynamic properties alone. Measurements indicate a linear dissipation mechanism, inconsistent with vortex drag and re-connection models. We conclude that high attenuation values, evidence of trapped circulation, and variation in attenuation values support the hypothesis that thick films of ⁴He contain high densities of remnant quantized vortices. The vortex populations suggested by trapped circulation are consistent with proposed linear dissipation mechanisms due to vortex-normal fluid interactions and vortex dimple drag.