Spectral Gradient Sampling for Path Tracing

Spectral Monte‐Carlo methods are currently the most powerful techniques for simulating light transport with wavelength‐dependent phenomena (e.g., dispersion, colored particle scattering, or diffraction gratings). Compared to trichromatic rendering, sampling the spectral domain requires significantly more samples for noise‐free images. Inspired by gradient‐domain rendering, which estimates image gradients, we propose spectral gradient sampling to estimate the gradients of the spectral distribution inside a pixel. These gradients can be sampled with a significantly lower variance by carefully correlating the path samples of a pixel in the spectral domain, and we introduce a mapping function that shifts paths with wavelength‐dependent interactions. We compute the result of each pixel by integrating the estimated gradients over the spectral domain using a one‐dimensional screened Poisson reconstruction. Our method improves convergence and reduces chromatic noise from spectral sampling, as demonstrated by our implementation within a conventional path tracer.     

Probabilistic movement primitives under unknown system dynamics

Physical interaction requires robots to accurately follow kinematic trajectories while modulating the interaction forces to accomplish tasks and to be safe to the environment. However, current approaches rely on accurate physical models or iterative learning approaches. We present a versatile approach for physical interaction tasks, based on Movement Primitives (MPs) that can learn physical interaction tasks solely by demonstrations, without explicitly modeling the robot or the environment. We base our approach on the Probabilistic Movement Primitives (ProMPs), which utilizes the variance of the demonstrations to provide better generalization of the encoded skill, combine skills, and derive a controller that follows exactly the encoded trajectory distribution. However, the ProMP controller requires the system dynamics to be known. We present a reformulation of the ProMPs that allows accurate reproduction of the skill without modeling the system dynamics and, further, we extent our approach to incorporate external sensors, as for example, force/torque sensors. Our approach learns physical interaction tasks solely from demonstrations and online adapts the movement to force–torque sensor input. We derive a variable-stiffness controller in closed form that reproduces the trajectory distribution and the interaction forces present in the demonstrations. We evaluate our approach in simulated and real-robot tasks.     

Shear effect on dynamic behavior of microcantilever beam with manufacturing process defects

This paper is concerned with the investigation of the shear effect on the dynamic behavior of a thin microcantilever beam with manufacturing process defects. Unlike the Rayleigh beam model (RBM), the Timoshenko beam model (TBM) takes in consideration the shear effect on the resonance frequency. This effect become significant for thin microcantilever beams with larger slenderness ratios that are normally encountered in MEMS devices such as sensors. The TBM model is presented and analyzed by numerical simulation using Finite Element Method (FEM) to determine corrective factors for the correction of the effect of manufacturing process defects like the underetching at the clamped end of the microbeam and the nonrectangular cross section of the area. A semi-analytical approach is proposed for the extraction of the Young’s modulus from 3D FEM simulation with COMSOL Multiphysics software. This model was tested on measurements of a thin chromium microcantilever beam of dimensions (80 × 2 × 0.95 μm³). Final results indicate that the correction of the effect of manufacturing process defects is significant where the corrected value of Young’s modulus is very close to the experimental results and it is about 280.81 GPa.

     

Rheokinetics of curing of epoxy resins near the glass transition

The cure of four epoxy-amine systems was studied by viscometry, dynamic mechanical analysis, and DSC. The investigation was carried on at temperatures below and above the glass transition temperature (T_g) of completely cured products. Viscosity growth in the initial stage of cure is described by an exponential-type equation, and on approach to the gel-point by a power law, but the exponent did not coincide with the universal theoretical scaling-law value. A universal viscosity master curve can be constructed if one reduces viscosity and time by their characteristic values. Gel-times and activation energies of curing were found by different methods. It was established that the product of the initial rate of a reaction and the gel-time is constant at various conditions of cure. Time dependences of the degree of conversion (calculated from calorimetric and dynamic mechanical data) in the full range of conversions are described by first- and second-order kinetics, corrected by the factor reflecting self-accelerating character of the reaction. Kinetic constants found from both methods are the same. If a reaction leads to a transition to the glassy state over the course of curing, a self-acceleration equation is valid in the initial stage of the process only. The complete kinetic curve can be described by the DiBenedetto method relating shift of the T_g with the degree of conversion. The rate constant for vitrificating systems is presented as a sum of reciprocal values of chemical and diffusion constants. Time and temperature dependences of kinetic and diffusion constants were calculated.     

Influence of acceleration setting reaction by halogen light‐curing on GIC–dentin interface: Qualitative analysis by SEM

The aim of this study was to evaluate by scanning electron microscope (SEM) photomicrographs the influence of application of halogen light‐curing for fastening the set reaction of high‐viscosity glass ionomer cements (GIC) by assessing the material/dentin interface. Twelve human primary canines were assigned in four groups (n = 3) according to the GIC (Fuji IX, GC or Maxxion R, FGM) and application of halogen light‐curing (60 sec or control—no external energy). Blocks with approximately 6 mm of height were buildup on previously pre‐treated dentin surface in according to the experimental group. After storage at 37 °C, 100% humidity for 48 h, the specimens were then sectioned in slices with 1‐mm thick. The slices were qualitative analyzed using SEM to evaluate possible structural changes. Two examiners independently evaluated the images in order to observe the spherical hollow spaces of each tooth. The photomicrographs revealed the presence of spherical hollow spaces in all experimental groups. However, in both groups that received halogen light‐curing application, it was possible to observe that the presence of these hollow spaces decreased in size and quantity. It can be concluded that the halogen light‐curing application positively decreases in size and quantity in the presence of spherical hollow spaces in GIC.     

Strength properties and density of SO2 polluted spruce wood

2 pollution during approximately 1935 and 1992 respectively, was studied as to its mechanical properties (fracture toughness, acoustic emission (AE)) as well as its density and annual ring width changes. Earlywood and latewood width and density were measured with X-ray densitometry equipment. The mechanical tests were performed with specimens taken from the same trees using the wedge splitting technique. Using notched, rectangularly shaped specimens, the experiments allowed to determine the notch-tensile strength σ_NTS of each yearring in RL orientation separately by differentiating earlywood and latewood. The results show clear correlations between earlywood density and notch-tensile strength, good, inverse correlation to some extent between ring width and σ_NTS and also between AE emission activity and earlywood width for the less polluted trees. Data scattering with resulting less pronounced trends was found for all parameters measured for the more severely polluted trees. The results and correlations allow assuming that σ_NTS is influenced by the SO₂ pollution to some extent via treering growth (ring width) and density. The results point to a more pronounced influence of SO₂ pollution between approximately 1970 and 1985 than before that time, and a subsequent recovery of the tested wood properties in the trees that had survived this period.

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2 -belastet war, wurde auf seine mechanischen Eigenschaften und auf seine Dichte und Jahrringbreite hin untersucht. Früh- und Sp?tholzbreite und Dichte wurden mittels R?ntgendensitometrie, die mechanischen Eigenschaften mittels Keilspaltverfahren bestimmt. Durch die Verwendung von rechteckigen, gekerbten Proben lie? sich die Kerbzugfestigkeit σ_NTS jedes Jahrrings in RL-Orientierung bestimmen. Die Resultate zeigen einen klaren Zusammenhang zwischen Frühholzdichte und Kerbzugfestigkeit sowie einen gewissen inversen Zusammenhang zwischen Jahrringbreite und Kerbzugfestigkeit bzw. Schallemissionsaktivit?t und Frühholzbreite für die wenig gesch?digten B?ume. Bei den st?rker gesch?digten B?umen war die Streuung der Me?werte deutlich h?her und die Abh?ngigkeiten schw?cher ausgepr?gt. Die Resultate und Zusammenh?nge deuten darauf hin, da? die Kerbzugfestigkeit durch die SO₂ Belastung über den Jahrringwuchs (Jahrringbreite) und die Dichte beeinflu?t wird. Die Resultate zeigen einen st?rkeren Einflu? der SO₂ Belastung zwischen 1970 und 1985 und deuten auf eine Erholung in den Holzeigenschaften bei jenen B?umen, die diese Periode überlebt haben, hin.

     

Increased Reactor Performance versus Reactor Safety Aspects in Acrylate Copolymerization

The aim of reducing cycle times of semibatch‐polymerization processes requires systematic investigations of the kinetics, careful adjustment of the desired polymer properties, proper thermal reactor design and reliable reactor safety assessment [1]. As a concrete example, a semibatch‐copolymerization was carefully examined with respect to four different aspects. Thermo‐kinetics of the reaction were investigated with isoperibolic reaction calorimetry and GC. In order to obtain reliable values for the overall heat transfer coefficient of the production scale reactor, cooling experiments were carried out with solvent and final copolymer solution as reactor content. For consistent reactor safety assessment additional investigations are necessary including case studies of breakdown incidences. These simulations were performed with a mathematical model based on the GC data and experimental vapor pressure curves. As a result of these calculations, a reduction of reaction time from 10 to 6 hours was possible. To convert into practice, it must be ensured that even in this shortened time a product of the same quality is produced.     

Occupant Tenability in Single Family Homes: Part II: Impact of Door Control,Vertical Ventilation and Water Application

This paper describes experimental investigations of fire service ventilation and suppression practices in full-scale residential structures, including a one-story, 112 m², 3 bedroom, 1 bathroom house with 8 total rooms and a two-story 297 m², 4 bedroom, 2.5 bathroom house with 12 total rooms. The two-story house featured a modern open floor plan, two-story great room and open foyer. Seventeen experiments were conducted varying fire location, ventilation locations, the size of ventilation openings and suppression techniques. The experimental series was designed to examine the impact of several different tactics on tenability: door control, vertical ventilation size, and exterior suppression. The results of these experiments examine potential occupant and firefighter tenability and provide knowledge the fire service can use to examine their vertical ventilation and exterior suppression standard operating procedures and training content. It was observed that door control performed better at controlling the thermal exposure to occupants than did fully opening the door. Additionally, the impact of increased vertical ventilation area was minimal, and only slightly reduced the thermal exposure to occupants in a few non-fire rooms. In the two-story structure, the non-fire rooms on the second floor consistently had larger thermal fractional effective rate (FER) values (approximately 2.5× the thermal risk to oocupants) than did the non-fire rooms on the first floor. Water application was also shown to reduce the thermal risk to occupants 60 s after water application 1/3rd the original values on second floor rooms of the two-storry structure and by at least 1/5th of the original values on the first floor rooms of both structures. Data also showed that the impact of front door ventilation on the toxic gases exposure was minimal, as the toxic gases FER actually increased after front door ventilation for several experiments. However, after vertical ventilation there was a 30% reduction in the toxic gases exposure rate in two of the one-story structure experiments.     

A selenium-based click AdoMet analogue for versatile substrate labeling with wild-type protein methyltransferases

Protein methylation is catalyzed by S-adenosyl-L-methionine-dependent protein methyltransferases (MTases), and this posttranslational modification serves diverse cellular functions. Some MTases seem to exhibit broad substrate specificities and comprehensive methods for target profiling are needed. Here we report the synthesis of a new AdoMet analogue for enzymatic transfer of a small propargyl group and labeling of modified proteins through copper-catalyzed azide-alkyne cycloaddition (CuAAC). Replacement of sulfur by selenium strongly enhanced the stability of the progargylic cofactor, leading, in combination with better activation by the selenonium center, to higher enzymatic reactivity. A broad spectrum of wild-type protein MTases acting on lysine, arginine, and glutamine residues accept this cofactor and modified substrates can be efficiently labeled by CuAAC click chemistry.