Nontracking solar concentrators

We derive the theoretical upper limit for concentration of direct solar radiation at low latitudes with nontracking concentrators from the projected solid angle sampled by the apparent motion of the sun, for the case where the energy efficiency is referred to the energy incident on the entrance aperture. Based on the fact that the solar radiation is not uniformly distributed within this projected solid angle and that the apparent solar motion is known, we derive the optimal acceptance as a function of direction and time, which means rejecting the lower density radiation and switching off the device when losses would be higher than gains. Just as a device may gain concentration by rejecting radiation from certain directions, it can also gain by not operating at all, thus avoiding losses at certain times. Trough-type systems, which have translational symmetry, cannot be ideal nontracking concentrators, but for low losses they perform only slightly worse than general three-dimensional concentrators.     

Experimental and numerical analysis of seat belt bunching phenomenon

In current cars, loops are commonly used to redirect the webbing which reels out from the retractor to the passenger's shoulder. Some types of pillar loops, also called D-rings, lead to a non-systematic instability. The webbing, which should scroll without hindrance through the D-ring, laterally shifts, bunches and produces the overturning of the ring.     

Demosaicing algorithms for area- and line-scan cameras in print inspection

Most color image sensors use color filter arrays (CFA). With this sensor design the captured information at each sensor pixel position is restricted to a specific spectral portion (typically red, green and blue bands). To obtain the missing color responses at each pixel position, so-called CFA demosaicing algorithms are commonly used. We propose two new CFA demosaicing algorithms, which are well suited for industrial print inspection with respect to the requirements in accuracy and speed. As a main contribution, we introduce novel demosaicing algorithms for specific high-speed color digital time delay and integration (DTDI) CFA line-scan cameras. We compare the suggested CFA demosaicing algorithms to state-of-the art algorithms for area and line-scan camera operation modes. We show that the two new algorithms perform superior to conventional algorithms as indicated by reconstruction error.     

Comparison of analysis methods for package-induced stresses on moulded Hall sensors

Due to the piezoresistive and the piezo-Hall effect in semiconductor materials, Hall sensors show a strong temperature dependency and also a drift when subjected to temperature cycles Manic et al. (2000). Four factors mainly influence the mechanical stress in the sensitive layer. These are the geometry of the device, the differences of the coefficients of thermal expansion of the package materials, the temperature-dependent material properties and the time-dependent, viscous material properties. The objective of this investigation was to determine the mechanical stress in a moulded Hall sensor during the packaging process by finite-element simulation in comparison to experimental methods. It is shown that after each process-step the mechanical stress in the sensitive layer changes over time depending on the absolute value and the rate of the temperature change. Measurements of the inverse bending radius of glued and moulded chips show good agreement to the simulations.     

15-Methyl-1,2-hexadecanediol,a major constituent of hamster surface wax

Long chain 1,2-alkanediol diesters comprise about 15–20% of the acetone soluble skin surface wax of golden Syrian hamsters. The constituent 1,2-alkanediols, obtained through acidic methanolysis, were fractionated by preparative gas liquid chromatography of their isopropylidene derivatives. The major component (57%) was identified by nuclear magnetic resonance and mass spectrometry as 15-methyl-1,2-hexadecanediol.     

Teilkondensation und nichtadiabate Rektifikation binärer Gemische in Füllkörperrohren

Partial condensation and non-adiabatic rectification of binary mixtures in packed columns. Vertical tube assemblies are preferred for partial condensation of vapour mixtures. The mixture of vapours is fed through the tubes in countercurrent flow to the falling condensate, while coolant flows through the jacket. Only with very large ratios of length L to diameter d of the tubes, i.e. L/d 200, does the separatory effect of partial condensation, owing to rectification mass transfer between the phases, exceed the enrichment effect of partial condensation. Use of ring-shaped packings drastically reduces the characteristic diameter, so that the additional separatory effect occurs at relatively short tube lengths. In the present paper, experimental results concerning the separation efficiency of tubes packed with Raschig rings for non-adiabatic rectification and partial condensation of the “negative” binary mixture n-heptane/benzene are reported and evaluated with the aid of the extended two-film theory. It is found that the resistance to mass transfer averaged over the length of the tube lies entirely on the liquid side on non-adiabatic rectification. Correlation of the Sherwood number of the condensate taken over the length of the tube and the condensate loading clearly shows that the usual calculation of partial condensation with average total mass transfer coefficients does not give physically meaningful results in the case of liquid-side resistance to transport. Calculating procedures which account for the variation of the partial mass transfer coefficients along the tube should lead to improved evaluation or prediction of separation efficiency.