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131.
With the presented method of magnetic labeling die cast components are labeled and provided with production data as well as protection against plagiarism. The magnetic labels are cast close under the surface of the component during the casting operation. Serial numbers, data and graphical information was engraved on the surface of hard ferrite magnets by laser marking using a diode-pumped ytterbium fiber laser. The data and graphical information was encoded as data matrix codes. Inexpensive strontium ferrite magnets were used. Melting processes and thermally induced material changes on the magnet surface during the laser labeling of the magnets results in a local demagnetization. The measurable decrease of the magnetic field strength is a result of local heating above the Curie temperature and the geometrical change of the magnet surface. The patterns with changing magnetic flux density can be visualized directly by a magnetic viewer or measured by magnetic field sensors such as Hall effect sensors. This paper deals foremost with the laser labeling process and the induced changes on the surface of the magnets as well as visualization and measuring test. First results of casting trials are presented, to confirm the stability of the magnetic labeling procedure during the casting operation. 相似文献
132.
Ping Zhou Elmar Beeh Horst E. Friedrich 《Journal of Materials Engineering and Performance》2016,25(3):853-865
Magnesium alloys are promising materials for lightweight design in the automotive industry due to their high strength-to-mass ratio. This study aims to study the influence of tension-compression asymmetry on the radius of curvature and energy absorption capacity of AZ31B-O magnesium alloy sheets in bending. The mechanical properties were characterized using tension, compression, and three-point bending tests. The material exhibits significant tension-compression asymmetry in terms of strength and strain hardening rate due to extension twinning in compression. The compressive yield strength is much lower than the tensile yield strength, while the strain hardening rate is much higher in compression. Furthermore, the tension-compression asymmetry in terms of r value (Lankford value) was also observed. The r value in tension is much higher than that in compression. The bending results indicate that the AZ31B-O sheet can outperform steel and aluminum sheets in terms of specific energy absorption in bending mainly due to its low density. In addition, the AZ31B-O sheet was deformed with a larger radius of curvature than the steel and aluminum sheets, which brings a benefit to energy absorption capacity. Finally, finite element simulation for three-point bending was performed using LS-DYNA and the results confirmed that the larger radius of curvature of a magnesium specimen is mainly attributed to the high strain hardening rate in compression. 相似文献
133.
Stephen Kerber 《Fire Technology》2012,48(4):865-891
There has been a steady change in the residential fire environment over the past several decades. These changes include larger homes, different home geometries, increased synthetic fuel loads, and changing construction materials. Several experiments were conducted to compare the impact of changing fuel loads in residential houses. These experiments show living room fires have flashover times of less than 5 min when they used to be on the order of 30 min. Other experiments demonstrate the failure time of wall linings, windows and interior doors have decreased over time which also impact fire growth and firefighter tactics. Each of these changes alone may not be significant but the all-encompassing effect of these components on residential fire behavior has changed the incidents that the fire service is responding to. This analysis examines this change in fire dynamics and the impact on firefighter response times and operational timeframes. 相似文献
134.
This article explores efficient climate policies in terms of investment streams into fossil and renewable energy technologies. The investment decisions maximise social welfare while observing a probabilistic guardrail for global mean temperature rise under uncertain technology and climate parameters. Such a guardrail constitutes a chance constraint, and the resulting optimisation problem is an instance of chance constrained programming, not stochastic programming as often employed. Our analysis of a model of economic growth and endogenous technological change, MIND, suggests that stringent mitigation strategies cannot guarantee a very high probability of limiting warming to 2 °C since preindustrial time under current uncertainty about climate sensitivity and climate response time scale. Achieving the 2 °C temperature target with a probability P? of 75% requires drastic carbon dioxide emission cuts. This holds true even though we have assumed an aggressive mitigation policy on other greenhouse gases from, e.g., the agricultural sector. The emission cuts are deeper than estimated from a deterministic calculation with climate sensitivity fixed at the P? quantile of its marginal probability distribution (3.6 °C). We show that earlier and cumulatively larger investments into the renewable sector are triggered by including uncertainty in the technology and climate response time scale parameters. This comes at an additional GWP loss of 0.3%, resulting in a total loss of 0.8% GWP for observing the chance constraint. We obtained those results with a new numerical scheme to implement constrained welfare optimisation under uncertainty as a chance constrained programming problem in standard optimisation software such as GAMS. The scheme is able to incorporate multivariate non-factorial probability measures such as given by the joint distribution of climate sensitivity and response time. We demonstrate the scheme for the case of a four-dimensional parameter space capturing uncertainty about climate and technology. 相似文献
135.
To mimic the adhesive effects of gecko toes, artificial surfaces have been manufactured recently using polydimethylsiloxanes (PDMS). However, the effects of repeated contacts on the adhesive properties remain largely unexplored. In this paper we report on the effect of repeated pull‐off force measurements on the adhesion behavior of PDMS (polymer kit Sylgard 184, Dow Corning) tested with a borosilicate glass probe. A decrease in pull‐off force with increase in number of test cycles is found until a plateau is reached. The initial value and the rate of change in pull‐off force strongly depend on the sample preparation procedure, including curing time and cross‐linking. It is proposed that the behavior is due to steady coverage of the probe with free oligomers. The results are crucial for developing reusable, durable, and residue‐free bioinspired adhesives. 相似文献
136.
It is known that in historical buildings as well as new buildings, facade claddings consisting of marble panels, are prone to damage patterns such as softening, crack formation, and bowing. The degree of damage is apparently dependent on the location of the building, the external climatic conditions, and the type of fastening of the facade panels. In this article, it is examined by means of nonstationary thermal simulation, to which extent the temperature fields, which develop in the facade panel, have an effect on the damage of the panel. It is shown that the diurnal and annual amplitude of the panel temperature induced by solar flux, external air temperature fluctuations, and long-wave input radiation and irradiation have a substantial influence on the damage process. On the example of the simulation of the thermal behavior of a facade panel for the building locations in Athens, Greece, Vienna, Austria, and Helsinki, Finland, it is shown that the observed increase of the susceptibility of marble facades to damages can be explained with the increase of the geographical latitude through the differences in the external climatic conditions. It is strongly recommended that architects and restorers install specific marble facade panels (like carrara marble) in close thermal contact with the wall behind, since this reduces the susceptibility of the facade to damage. 相似文献
137.
Piotr Didyk Elmar Eisemann Tobias Ritschel Karol Myszkowski Hans‐Peter Seidel 《Computer Graphics Forum》2010,29(2):713-722
High‐refresh‐rate displays (e. g., 120 Hz) have recently become available on the consumer market and quickly gain on popularity. One of their aims is to reduce the perceived blur created by moving objects that are tracked by the human eye. However, an improvement is only achieved if the video stream is produced at the same high refresh rate (i. e. 120 Hz). Some devices, such as LCD TVs, solve this problem by converting low‐refresh‐rate content (i. e. 50 Hz PAL) into a higher temporal resolution (i. e. 200 Hz) based on two‐dimensional optical flow. In our approach, we will show how rendered three‐dimensional images produced by recent graphics hardware can be up‐sampled more efficiently resulting in higher quality at the same time. Our algorithm relies on several perceptual findings and preserves the naturalness of the original sequence. A psychophysical study validates our approach and illustrates that temporally up‐sampled video streams are preferred over the standard low‐rate input by the majority of users. We show that our solution improves task performance on high‐refresh‐rate displays. 相似文献
138.
Stereoscopic 3D technology gives visual content creators a new dimension of design when creating images and movies. While useful for conveying emotion, laying emphasis on certain parts of the scene, or guiding the viewer's attention, editing stereo content is a challenging task. Not respecting comfort zones or adding incorrect depth cues, for example depth inversion, leads to a poor viewing experience. In this paper, we present a solution for editing stereoscopic content that allows an artist to impose disparity constraints and removes resulting depth conflicts using an optimization scheme. Using our approach, an artist only needs to focus on important high‐level indications that are automatically made consistent with the entire scene while avoiding contradictory depth cues and respecting viewer comfort. 相似文献
139.
140.
Mareike Frensemeier Dominik Schirra Martin Weinmann Olivier Weber Elmar Kroner 《Advanced Engineering Materials》2016,18(8):1388-1395
The two‐way shape‐memory effect (TWSME) in Nickel–titanium (NiTi) alloys is of interest for applications in aerospace, biomedicine, and microengineering due to its reversible shape recovery. In this study, the authors demonstrate two approaches to obtain switchable surface structures using the TWSME. Samples are structured using two surface geometries by either cold embossing, or pulse electrochemical machining (PECM). After planarization, a change from optically smooth to structured and vice versa is observed. The switch is induced through heating and cooling the sample above and below the phase transformation temperature. The protrusions reflect the pattern applied by the two processes. Both methods are promising for preparation of switchable metallic surfaces on larger areas. 相似文献