Tensile Fracture Toughness Measurements in Ceramics

A novel procedure is outlined whereby fracture toughness values for ceramics can be measured under uniaxial tension (mode I) in specimens containing a fatigue crack. Circumferentially notched rods of rapolycrystalline aluminum oxide were precracked in cyclic compression to introduce a fatigue crack at room temperature, following the technique proposed by Suresh and co-workers.^7,10,11 Subsequently, the precracked rods were fractured in pure tension. Highly reproducible values of fracture toughness were obtained using this method.     

Transverse mixing and heat transfer in horizontal rotary drum reactors

The transverse mixing of quartz sand (mean particle sizes 157, 323, 794 and 1038 μm) and sodium carbonate (soda) (mean particle size 137 μm) has been investigated in a laboratory rotary drum reactor of 300 mm length and 310 mm diam. Solid movement in the drum was observed by means of colored tracers and successive exposures as well as by means of hot tracers and recording the local temperature in the bulk of particles. Three different types of the particles and bulk behaviour could be observed for stickly particles. The time constant of the mixing was estimated as a function of the rotational speed of the drum. The “cooling-down” curves of the bulk of particles were measured in a laboratory oven of 250 mm diam. and 600 mm length. The temperature variation as a function of the time can be described by the Newtonian cooling law, from which the heat transfer coefficient at the wall α_w was estimated.The absolute value of α_w's and their dependence on the contact time and particle diameter cannot be calculated by the heat penetration model, which disregards the film resistance at the bulk/wall contact. By taking into account this resistance a good quality of fitting can be achieved.     

Real-time control of sewer systems using turbidity measurements

Real-time control (RTC) of urban drainage systems has been proven useful as a means to reduce pollution by combined sewer overflow discharges. So far, RTC has been investigated mainly with a sole focus on water quantity aspects. However, as measurement techniques for pollution of wastewater are advancing, pollution-based RTC might be of increasing interest. For example, turbidity data sets from an extensive measurement programme in two Paris catchments allow a detailed investigation of the benefits of using pollution-based data for RTC. This paper exemplifies this, comparing pollution-based RTC with flow-based RTC. Results suggest that pollution-based RTC indeed has some potential, particularly when measurements of water-quality characteristics are readily available.     

Spin dynamics and implications for superconductivity: some problems with thed-wave scenario

We review the spin dynamics of the normal state of the cuprates with special emphasis on neutron data in both the YBa₂Cu₃O_7– and La_2–x Sr _x CuO₄ systems. When realistic models of the Fermi surface shapes are incorporated, along with a moderate degree of spin fluctuations, we find good semiquantitative agreement with experiment for both cuprates. Building on the success of this Fermi-liquid-based scheme, we explore the implications ford-wave pairing from a number of vantage points. We conclude that our present experimental and theoretical understanding is inadequate to confirm or refute thed-wave scenario.     

Phase-retardation and full-polarization analysis of soft-x-ray synchrotron radiation close to the carbon K edge by use of a multilayer transmission filter

We have produced a multilayer transmission filter with 100 periods of Cr/C to achieve a significant phase retardation while maintaining good transmission for photon energies just below the carbon K edge. This device was installed into a polarimeter behind the SX700/3 monochromator at the Berlin synchrotron radiation laboratory, BESSY. The phase-retardation properties were observed as theoretically predicted. Agreement between experiment and calculation could be obtained by introduction of a rather small interface roughness in the simulation code (σ = 0.65 nm rms). An observed phase retardation of 5° was sufficient to permit, for the first time we believe, a complete and unambiguous polarization analysis of soft-x-ray synchrotron radiation (265-eV photon energy) with primary standards.     

Optical properties of broadband reflection holograms

The optical properties of highly chirped gratings of broadband reflection-type volume phase holograms are evaluated by a ray-tracing approach. The deformation of the fringes as well as the change of refractive index is attributed to swelling during processing. For high-efficiency holograms the problem can be reduced to geometric optics. The power density distribution in the focus of an on-axis mirror is calculated by a Monte Carlo integration. The results are discussed for replay conditions that are relevant for photovoltaic applications.     

Experimentelle Ermittlung von Bauteilbelastungen eines Power Tool Antriebsstrangs durch indirektes Messen in realitätsnahen Anwendungen als ein Baustein in der Teilsystemvalidierung

This article shows by experimental studies on angle grinders, how application-equivalent stresses on the components can be determined. For this purpose a distance measurement technique is applied with which the movement of the shaft is detected while the angle grinder is in operation. The research results support validation activities in product development and contribute to early validation. It helps to analyzing the dynamic and working life of the power tool and therefore construction targets are derived. The related applications are considered and power tools with measuring equipment in the lab are tested. The measurement results are presented and possible causes and effects on the life of the components are discussed. With the method of investigation it is possible to study the behavior of subsystems already in development phases in which the overall system is not physically present.