Dislocation networks in tungsten carbide studied by the weak-beam technique

Dislocation networks in tungsten carbide (WC) have been studied in the HVEM. The nodes of the network have been resolved by using the weak-beam technique in the high voltage electron microscope. They consist of parallel partial dislocations, which are concluded to have Burgers vectors of the type b = 1/6 <20<23>.     

Condebelt Drying of Paper and Paper board for Optiemizing Quality and Production for Many Cpades

ABSTRACT

The development history of the Condebelt paper and paperboard drying method is briefly described. The process conditions experienced by the web during Condebelt drying are essentially similar to those prevailing in the so–called press drying experiments. In fact, condebelt drying produces. qualitywise, results quite similar to those reported by press drying researchers from many laboratories. condebelt drying has been studied over a span of many years by means of several static units, as well as a pilot stage dynamic device. Based on these experiences, as well as several theoretical studies, designs have been developed for doing Condebelt drying as a production process. Condebelt drying is versatile, in that the process conditions can be altered to produce optimum quality for most paper and board grades. In this capability the Condebelt process is much superior to canventional cylinder drying. The very high drying rates characteristic of Condebelt dryers are discussed, along with the Consequences as far as machine room space saving is concerned. The good energy consumption prospects of the Condebelt process are briefly discussed.     

Electric and dielectric properties of metal chelates of an aromatic polyhydrazide

The influence of metal content of some metal chelates of an aromatic polyhydrazide on the DC and AC conductivity was studied in the temperature range of 293 to 573 K at a constant frequence of 1 kHz. The compounds studied were poly(m-phenylene-bis-1,3,4-oxadiazole) and Cu(II)-, Ni(II)- and Co(II)-chelates of the corresponding aromatic polyhydrazide. The conductivity is rather low and all compounds show a break point in the conductivity curve indicating a change in the conductivity mechanism. Cu(II)-ions seem to have the highest influence on the DC conductivity, while Ni(II)- and Co(II)-ions change the dielectric transition temperatures more than Cu(II).     

Recent Advances in Adaptive Sampling and Reconstruction for Monte Carlo Rendering

Monte Carlo integration is firmly established as the basis for most practical realistic image synthesis algorithms because of its flexibility and generality. However, the visual quality of rendered images often suffers from estimator variance, which appears as visually distracting noise. Adaptive sampling and reconstruction algorithms reduce variance by controlling the sampling density and aggregating samples in a reconstruction step, possibly over large image regions. In this paper we survey recent advances in this area. We distinguish between “a priori” methods that analyze the light transport equations and derive sampling rates and reconstruction filters from this analysis, and “a posteriori” methods that apply statistical techniques to sets of samples to drive the adaptive sampling and reconstruction process. They typically estimate the errors of several reconstruction filters, and select the best filter locally to minimize error. We discuss advantages and disadvantages of recent state‐of‐the‐art techniques, and provide visual and quantitative comparisons. Some of these techniques are proving useful in real‐world applications, and we aim to provide an overview for practitioners and researchers to assess these approaches. In addition, we discuss directions for potential further improvements.     

Sketching Clothoid Splines Using Shortest Paths

Clothoid splines are gaining popularity as a curve representation due to their intrinsically pleasing curvature, which varies piecewise linearly over arc length. However, constructing them from hand‐drawn strokes remains difficult. Building on recent results, we describe a novel algorithm for approximating a sketched stroke with a fair (i.e., visually pleasing) clothoid spline. Fairness depends on proper segmentation of the stroke into curve primitives — lines, arcs, and clothoids. Our main idea is to cast the segmentation as a shortest path problem on a carefully constructed weighted graph. The nodes in our graph correspond to a vastly overcomplete set of curve primitives that are fit to every subsegment of the sketch, and edges correspond to transitions of a specified degree of continuity between curve primitives. The shortest path in the graph corresponds to a desirable segmentation of the input curve. Once the segmentation is found, the primitives are fit to the curve using non‐linear constrained optimization. We demonstrate that the curves produced by our method have good curvature profiles, while staying close to the user sketch.     

Size diffusion for the growth of newly nucleated aerosol

Size diffusion is often regarded as a problem encountered with the numerical solution of the general dynamic equation for aerosols. We investigate here the real size diffusion arising in the solution of the more fundamental discrete rate equations, which treat condensation and evaporation on a molecular basis. The spreading of the aerosol distribution in molecular number content is obtained from previously derived moment equations, and is verified by numerical calculations. When the condensing material is volatile and its supersaturation is low, spreading values are very significant in the nanometer size range. The spreading of the aerosol distribution in radius tends to a constant value at large sizes, but this corresponds to a fall-off in the geometric standard deviation of the size distribution in the logarithm of the radius. Experimental examination of distributions at small sizes has the potential to give information on the volatility of the condensing material.     

Gas–Particle Distribution of PAHs in Wood Combustion Emission Determined with Annular Denuders,Filter, and Polyurethane Foam Adsorbent

Equipment consisting of annular denuders, a filter, and a polyurethane foam adsorbent was used for sampling 15 PAHs from the diluted emission from a heat-storing masonry heater. The denuder method was compared to the ISO 11338 method which was used for the sampling from hot and undiluted exhaust gas. The denuder method used with the exhaust dilution gave a realistic gas–particle distribution of PAHs in more atmospheric-like conditions compared to the sampling from undiluted exhaust gas where PAHs were almost totally in the gas phase. The results gained with the denuder method from the diluted exhaust are more relevant, e.g., from exposure and atmospheric processes point of view. The emissions from smoldering combustion conditions (SC) were compared with the emissions from normal combustion conditions (NC). The emission of each PAH was 7 to 14 times higher from SC than from NC, and the gas–particle distribution was shifted towards the particle phase due to increased condensation of PAHs. The PAHs could be divided into three groups based on their phase distributions. In the first group, PAHs existed mostly in the gas phase in both combustion cases; the vapor pressures of PAHs were lower than the saturation vapor pressures. In the second group, the gas phase was saturated and the concentration was almost the same in both combustion cases, whereas the particle phase concentration was higher in SC. In the third group, PAHs were mostly in the particle phase where the concentration was higher in SC.     

Dissolution of uraninite in acid solutions

The purpose of this work was to assess the oxidative dissolution of uranium from a uraninite-containing rock in acid sulfate solutions under test conditions relevant to uranium leach mines and acid mine waters. Uranium dissolution in acidified mineral salts solution was slow and the predominant carbonate mineral (rhodochrosite) in the rock sample continued to consume acid. Bacterial inoculation (Thiobacillus ferrooxidans) and additional Fe²⁺ or S⁰ were tested in efforts to enhance the dissolution. Addition of Fe enhanced the solubilization of uranium, whereas S-addition had little incremental effect on the dissolution with and without bacterial inoculation. © 1998 Society of Chemical Industry     

Triple crystallization behavior of fractionated ethylene/α-olefin copolymers of different catalyst type

Non-isothermal crystallization processes in fractions of Ziegler-Natta (ZN) and single site (SS) based ethylene/1-butene and ethylene/1-hexene copolymers have been studied by differential scanning calorimetry (DSC). Fractionation of used copolymers was done according to molar mass (MM) and composition (comonomer content). It was observed in DSC scans that for fractions with high MM (larger than 10 kg/mol) in addition to the main high-temperature crystallization peak (HTCP), a very-low temperature crystallization peak (VLTCP) is present at temperatures in between 60–75 °C. Such peak is absent for the first fractions having very-low MM. The partial crystallinity and peak temperatures, obtained from VLTCP, increase with MM and level off at MM around 60–100 kg/mol. It was found that the crystallinity as related to the area of the VLTCP is catalyst type dependent, and is higher for the SS catalyst compared to the ZN. Peak temperature of VLTCP linearly decreases with increasing comonomer content at fixed MM while the partial crystallinity practically does not change with comonomer content.