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Reusable solid wheels manufactured of the old steel BV1 (nearly equivalent to the solid or monobloc wheel steel R1 according to the new nomenclature) show in some cases rolling defects on the surface of the wheel disc. The fatigue behaviour of such defects is analysed by means of the linear-elastic fracture mechanics and Monte Carlo simulation and assessed to be able to derive the allowable defect size for the non-destructive testing. This paper was firstly presented at the Second International Symposium on Fatigue Design FD’95, held in Helsinki (Finland) on 5 – 8 September 1995. The complete research report is published under the title „Oberflächendefekte im Scheibenbereich” (Manufacturing surface defects in the disc area of solid wheels). The research work was sponsored by the Deutsche Forschungsgemeinschaft (DFG).
Old and new laboratory experiments on atmospheric optics with a focus on mirages, rainbows, and halos are presented. Some qualitative demonstrations serve primarily didactical purposes, e.g., by proving the existence of curved light rays in media with a gradient of the index of refraction, by directly visualizing the minimum-deviation curve for rainbow paths in water droplets, or by helping to elucidate the ray classes in hexagons that contribute to a specific halo. In addition, quantitative experiments allow a direct comparison of angular positions and intensities with analytical computations or Monte Carlo simulations of light scattering from small water droplets or ice hexagons. In particular, the latter can help us to understand complex halo phenomena.
© 1998 Optical Society of America
An inquiry among national experts on physics education research and teaching has been carried out using a questionnaire that deals with the organization of physics teacher training and the main tasks and research activities of professionals in physics education. The goal was to collect data on a European scale on physics teacher training at universities by professionals as well as on research activities by professionals in the field of physics education. Results are presented based on answers from 22 European countries.
Some laboratory demonstrations on atmospheric optics are presented. The focus is on dispersion effects in mirages, lateral mirages, and inferior mirages produced with small hot plates. We also show a demonstration of the upper-tangent-arc halo, produced with a hexagonal prism, rotating about two axes.
© 2003 Optical Society of America
Don't put metal objects in the microwave' is common safety advice. But why? Here we describe demonstration experiments involving placing household metallic objects in a microwave oven. These allow a better understanding of the interaction of microwaves with materials. Light bulbs and discharge lamps can also be used in instructive demonstrations.
Microwave ovens can be used to perform exciting demonstrations that illustrate a variety of physics topics. Experiments discussed here show superheating, visualize the inhomogeneous heating that takes place in a microwave and also show how to use a mobile phone to detect radiation leaking from the oven. Finally eggs can give some spectacular (though messy) explosions. In all cases please note the safety advice given.
This article forms the second of two papers on the subject of microwave cookers. In the first paper Michael Vollmer describes the physics behind the production of microwaves in the magnetron of the oven, the waveguide and the interaction between the microwaves and the food. This article looks at the physics of cooking, and how the appliance and the food industries have developed products which are now part of many of our students' lifestyles. We include many interesting demonstrations that illustrate this history and which could be used to teach many principles of physics.
This is the first of two articles about the physics of microwave ovens. This article deals with the generation of microwaves in the oven and includes the operation of the magnetrons, waveguides and standing waves in resonant cavities. It then considers the absorption of microwaves by foods, discussing the dielectric relaxation of water, penetration depths of electromagnetic waves in matter and, in considering the possible chemical changes during the microwave heating, multi-photon ionization or dissociation.
Thermography of Microsystems
(2004)
Diffraction revisited : position of diffraction spots upon rotation of a transmission grating
(2005)
The question of how the line spectrum of atoms is transformed into the continuous spectrum of thermal radiation of a gas by repeated absorption and emission of photons is addressed. We consider a simple model of a hydrogen-like gas in thermal equilibrium where only the Lyman-α transition is allowed and calculate the spectra for increasing thickness of the gas. The transition from line spectra for optically thin samples to the spectra of thermal radiation for optically thick samples is demonstrated. We estimate the emissivities for hot gases and study the line width of spectral lines due to self-absorption processes.
A procedure to experimentally simulate pollen coronas is discussed. Observed coronas are due to pine and birch pollen having different geometries. Using computer simulations, two-dimensional projections of a large number of pollenlike objects with adjustable shapes, with or without preferential orientation and statistical or regular spatial distribution, are generated. The photograph of the printout allows samples with typical sizes between 20 and 200 µm. Their diffraction patterns can closely resemble the ones observed in nature and predicted by theory.
© 2005 Optical Society of America
Light scattering from small particles changes if the particles are absorbing. Whereas the effect is small for coronas and Bishop's ring, glories show pronounced attenuation with increasing absorption. Results indicate suitable wavelength regions for studies of glory scattering from cloud tops. The behavior of core-shell particles could have applications for studying the atmosphere of Venus; in addition it provides more insight into the simple ray-path model of the glory.
© 2005 Optical Society of America
Coronas and glories
(2005)
Locomotion by blowing into the sail of your own sailboat: Muenchhausen story or real physics?
(2005)
Rolling contact fatigue generates cracks on the running surface of high strength railway rails which grow under a small angle into the rail head. These cracks can cause in its last stage the fracturing of the rail. The crack extension behaviour is – as the origin of these cracks too – influenced by the cold working of the rail steel. The crack growth in the first stage is fracture mechanically analyzed by means of two-dimensional modelling. The simulation results are assessed for the use of rail grinding. A criterion for the change of the crack growth direction could not be derived, but the following stages of the crack growth in the transverse direction and the final fracture and the conditions for secondary fractures are considered. Rolling contact fatigue generates cracks on the running surface of high strength railway rails which grow under a small angle into the rail head. These cracks can cause in its last stage the fracturing of the rail. The crack extension behaviour is – as the origin of these cracks too – influenced by the cold working of the rail steel. The crack growth in the first stage is fracture mechanically analyzed by means of two-dimensional modelling. The simulation results are assessed for the use of rail grinding. A criterion for the change of the crack growth direction could not be derived, but the following stages of the crack growth in the transverse direction and the final fracture and the conditions for secondary fractures are considered.
Measurements of illuminance during a solar eclipse are presented. The data are compared to theoretical predictions, based on a geometrical model for obscuration. The model assumes a straight and uniform motion of the sun and moon as well as a spherical shape of both, i.e. it neglects any effects of limb darkening. Furthermore, the sun's disk is assumed to have homogeneous luminosity, i.e. any luminosity variations due to sun spots are neglected. Input parameters are the duration of the eclipse, the duration of totality, the impact parameter, i.e. the distance between the two trajectories of sun and moon, and the sizes of sun and moon. The model applies to all types of eclipses, partial, annular and total.
A geometric model for the optical air mass of the atmosphere is developed. Using the model, simple formulae are derived for the optical thickness of light passing through (1) a molecular atmosphere, (2) an atmosphere with uniformly distributed tropospheric aerosols and (3) atmospheres with elevated aerosol layers. The formulae are used to model the spectra and perceived colours of the Sun and Moon.
The surface to volume ratio in thermal physics: from cheese cube physics to animal metabolism
(2008)
Despite the increasing number of accidents in process industry caused by human error, there are still too few efforts devoted to this area. This is mainly caused by people's tendency to overestimate human's capability in interacting with their working environment and moreover by the unavailability of reliable analysis methods.
Because of the current lack of adequate methods, human factors (HF) analysis is not widely performed in process industry. Some HF techniques developed in the process industry were examined regarding their practical applicability and were unfortunately proved to be unsuitable for an elaborate HF analysis. Therefore, a new approach was developed, which provides a systematic way in performing a qualitative HF analysis to achieve a safer operation and decrease the number of human failure events.
HF consideration during the design of a process plant is the key to minimize accidents caused by human error in process industry. Thus, an approach to incorporate HF into design phase is described in this article, which can help achieving a safer operation as early as possible with minimized costs. © 2009 American Institute of Chemical Engineers Process Saf Prog 2009
Twice in a blue moon
(2009)
Solar load and reflection effects and respective time constants in outdoor building inspections
(2009)
Among load cases concerning vehicle suspension strength and durability, the misuse case is very special because of large obstacles. In this paper, an extension of the flexible belt model RMOD-K 7 concerning misuse situations is discussed. In normal rolling conditions, contact occurs between tire and road surface. To handle misuse deformations, the contact between the inner surface of the tire and the rim has to be dealt with. Results of the validation process are shown, leading to normal forces up to 70 [kN]. The model can be used together with mbs full vehicle models. One example is the determination of the critical test velocity, which generates the maximum of suspension stresses and can be found using RMOD-K 7.