Efficient Caustic Rendering with Lightweight Photon Mapping

Robust and efficient rendering of complex lighting effects, such as caustics, remains a challenging task. While algorithms like vertex connection and merging can render such effects robustly, their significant overhead over a simple path tracer is not always justified and – as we show in this paper ‐ also not necessary. In current rendering solutions, caustics often require the user to enable a specialized algorithm, usually a photon mapper, and hand‐tune its parameters. But even with carefully chosen parameters, photon mapping may still trace many photons that the path tracer could sample well enough, or, even worse, that are not visible at all. Our goal is robust, yet lightweight, caustics rendering. To that end, we propose a technique to identify and focus computation on the photon paths that offer significant variance reduction over samples from a path tracer. We apply this technique in a rendering solution combining path tracing and photon mapping. The photon emission is automatically guided towards regions where the photons are useful, i.e., provide substantial variance reduction for the currently rendered image. Our method achieves better photon densities with fewer light paths (and thus photons) than emission guiding approaches based on visual importance. In addition, we automatically determine an appropriate number of photons for a given scene, and the algorithm gracefully degenerates to pure path tracing for scenes that do not benefit from photon mapping.     

Influence of diethylene glycol content on behavior of poly(ethylene terephthalate) fibers

Relationship between structural parameters of poly(ethylene terephthalate) (PET) fibers, their mechanical properties, and nonisothermal sorption of disperse dyes are investigated. Influence of diethylene glycol (DEG) addition and small changes in draw ratio are studied. Mechanical properties are characterized by stress–strain curves at constant deformation rate. The stress–strain relationships are described by means of derivative analysis. For treatment of nonisothermal experiments a simple kinetic model is suggested enabling to determine activation parameters of sorption. Further, the influence of a blank dye bath on the structure and properties of PET fibers is studied.     

The determination of β-ketoamide structures in poly(2-pyrrolidone)

Ketoamide and ketoimide units incorporated in poly(2-pyrrolidone) as a result of side reactions in the anionic polymerization may be quantitatively determined as 1,7-dibenzamido-heptane-4-one (IIa) after the total acid hydrolysis of the polymer and benzoylation of the hydrolyzate. Conditions were found for the quantitative analysis of these structures using liquid chromatography.     

Streptomycetes cultured on glass beads: Sample preparation for SEM

We demonstrate the preparation of samples of streptomycetes (Streptomyces coelicolor, S. aureofaciens) cultured on glass beads (balotina) for scanning electron microscopy. The main trick of the method consists in immobilization of glass beads with low-melting agarose. The samples are then fixed in OsO(4) vapors followed by dehydration in vapors of absolute ethanol. No air-to-liquid transition during the sample preparation occurs. Consequently, whole cell cycle of streptomycetes in the term of mycelial morphology can readily be studied by this method.     

Polychlorierte Biphenyle (PCB) im menschlichen Fettgewebe

Zusammenfassung Die vorliegende Arbeit beschreibt die Kontamination menschlichen Fettgewebes mit den sechs als Indikator-Kongeneren bekannten Polychlorbiphenylen, mit PCB Nr. 49 und den Mischinducern PCB Nr. 156, 170 und 189. Die niedrig chlorierten Biphenyle Nr. 28, 49 und 52 konnten nicht nachgewiesen werden, die Konzentration von PCB Nr. 101 betrug im Mittel 9 g/kg. Die Gehalte von PCB Nr. 138, 153 und 180 lagen geringfügig unter den von der DFG angegebenen Werten. Der Anteil der Mischinducer Nr. 138, 156, 170 und 189 machte nahezu 40% der Gesamtbelastung aus. Die Höhe der PCB-Kontamnation des Fettgewebes war altersabhängig, wobei für die Gruppe der 61-bis 70jährigen mit Ausnahme von PCB Nr. 101 ein sprunghafter Anstieg der Konzentrationen beobachtet wurde.

---

Polychlorinated biphenyls in human adipose tissue

Summary This study describes the contamination of human adipose tissue with six selected polychlorinated biphenyls (PCB) known as indicator congeners, with PCB no. 49 and the mixed inducer PCB nos. 156, 170, and 189. The low chlorinated biphenyls nos. 28, 49, and 52 could not be found in the tissue samples, while the average concentration of PCB no. 101 was 9.0 g/kg. The content of PCB nos. 138, 153, and 180 was slightly below the values published by the Deutsche Forschungsgemeinschaft (DFG). The mixed inducer nos. 138, 156, 170, and 180 amounted to approximately 40% of all the PCBs measured. The PCB contamination was positively correlated with age: for the age group 61–70 years, with the exception of PCB no. 101, a distinct increase in the concentrations could be observed.

     

Adjustable band-pass filter with current active elements: two fully-differential and single-ended solutions

Four adjustable band-pass filtering solutions are presented and also compared in this paper. Two of them are suitable for single-ended signal processing and the other two are their fully-differential equivalents. Filters are built with two types of active elements. First is a simple current follower with multiple outputs and second is a current amplifier with adjustable current gain that is used to control the quality factor of each of filters. Dependency between gain and quality factor is direct in two cases or inverse in other cases and that is why the range of adjustability varies. Simulations with CMOS-transistor structures are included. Values of quality factor obtained for each of solutions are assessed.     

Analysis of magnetron sputtered boron oxide films

Boron oxide films were grown on silicon substrates by radio-frequency (rf) unbalanced magnetron sputtering of a boron target in argon-oxygen gas mixtures with different compositions. Microscopic analyses show that overall boron oxide films are amorphous. The film prepared at oxygen/argon flow rate ratio > 0.05 developed large crystallites of boric acid in localize areas of amorphous boron oxide matrices. These crystallites were unstable and at electron microscopic analysis they continuously transformed to a cubic HBO₂ phase and then completely vanished leaving an underlying amorphous boron oxide film behind. The analyses indicate the coexistence of B₆O, HBO₂ crystallites and amorphous boron oxide matrices. Fourier transform infrared (FTIR) spectra revealed spectral bands of BOH, BO, BOB and BH groups. Nanohardness and elastic modulus of a film prepared at low oxygen concentration approach 30 and 300 GPa, respectively. These parameters however vary with deposition conditions.     

Surface and porous recast layer analysis in µ-EDM of MWCNT-Al2O3 composites

Machining of ceramic materials has been a major challenge owing to high hardness and brittleness. The reinforcement of a conducting filler allows permissible machining in electrical discharge machining (EDM) process. The current effort analyses the impact of multi-walled carbon nanotubes (MWCNT) of concentrations of 2.5 and 5 vol. %, as conducting filler towards machinability of alumina composites in µ-EDM process. The influence of tool materials and its rotation are closely analyzed. A successful machining process is observed in both the two composites, with a higher material removal rate (MRR) in 5 vol. % MWCNTs. When the tool starts to rotate at 750 rpm, an increment of around 60–65% is observed in MRR for both the two composites. Similarly, the surface roughness (R_a) decreases by a factor of 20?25%. The brass tool is observed to yield better machining capabilities due to the frequent initiation of sparks. A highly porous machined surface is observed in both the two composites. This scenario depicts the spalling effect as more dominant than melting-evaporation effect. The extent of porous recast layer on the drilled edges is found to reduce with increasing the speed of tool rotation.     

Determination of the electromechanical coupling factor of gallium orthophosphate (GaPO4) and its influence on resonance-frequency temperature dependencies.

The quartz homeotype gallium orthophosphate (GaPO4) is a representative of piezoelectric single crystals of large electromechanical coupling factor. It is known that its coupling factor kappa26 associated with the resonators vibrating in the thickness-shear mode is approximately two times greater than that of quartz. This property increases the spacing between the series and parallel resonance frequencies of resonators, as well as the difference between the resonance frequency temperature dependencies of the fundamental and harmonic resonance frequencies of resonators vibrating in the thickness-shear mode. In this paper, the methods for determination of the coupling factor kappa26 are presented, and the computed values are compared with the measured ones. The influence of the coupling factor to the resonance-frequency temperature dependencies of the fundamental and third harmonics of selected rotated Y-cut GaPO4 resonators vibrating in the thickness-shear mode is presented. The purely elastic case for a laterally unbounded plate, which corresponds closely to the limiting case of high harmonic resonance frequency-temperature behavior was assumed for the calculations. The computed temperature coefficients for the Y-cut orientation and calculated turnover point temperatures TTP for different (YX1) orientations are presented.