Density of xNa2S.(1 – x)B2S3 (x = 0 to 0.8) Glasses: Correlation with Short-Range Order

The densities of xNa₂S + (1 – x)B₂S₃ glasses have been measured for 0 ≤ x ≤ 0.80. The variation of the density with x is quite strong and is characterized by a sharp maximum at x ∼0.30. The density increases on the low-alkali side of the maximum from 1.7 g/mL for vitreous B₂S₃ up to 2.2 g/mL for the x = 0.3 glass and decreases on the highalkali side to 1.8 g/mL. The increase in the density at low alkali is associated with the increasing fraction of the heavy mass and relatively small volume tetrahedral boron group, Na⁺BS₄^–. The density decrease in the high-alkali range is associated with the decreasing fraction of these groups with the concomitant increase in the fraction of trigonal boron groups with increasing numbers of nonbridging (terminal) sulfurs. To model the density, a weighted fractional mass and volume model was used. The molar volumes of the individual short-range order (SRO) groups were determined from compositions where a particular SRO group was the single group in the glass, by fitting the density data, and by interpolating between groups of known volume. The composition dependence of the fractions of the individual SRO groups was developed by combining spectroscopic evidence with chemically reasonable hypotheses of the SRO of the glasses. In this way, the density was calculated from first principles with one adjustable parameter, that of the volume of the tetrahedral boron group. The calculated densities were found to agree well with the experimental values.     

Multiple-reflection effects in photoelastic stress analysis

The interpretation of fringes observed in photoelastic stress measurements made with coherent well-collimated optical radiation such as a laser beam and slab specimens with parallel surfaces is affected by multiple internal reflections of light within the sample, which are usually negligible when incoherent light is used. An analysis of the multiple-reflection effects in photoelastic measurements involving the plane polariscope configuration is presented. The results show that the isochromatic fringes are modified by the interference of multiply reflected waves. The multipass differential phase accumulations that display oscillatory magnitudes as functions of the model thickness and the optical wavelength result in a shifted and altered intensity profile across the isochromatic fringes. It is shown that for large values of reflectivity, as in the case of samples with reflective coating or partial mirrors, the bright fringes split into multiple peaks.     

Polygonal optical cavities

A general class of multifacet optical resonators that have uniform polygonal geometries is described. Expressions for the transmission of light through classical refractive escape from the cavities are presented. The conventional Fabry-Perot resonator is shown to be a special case of this general class of cavities. The effects of absorption and scattering of optical radiation on the transmission properties and cavity-quality factors are analyzed. These resonator structures have significant applications in a wide variety of optical devices.     

Modeling,analysis, and optimization of dimensional accuracy of FDM-fabricated parts using definitive screening design and deep learning feedforward artificial neural network

Additive manufacturing (AM) technologies such as fused deposition modeling (FDM) rely on the quality of manufactured products and the process capability.Current...     

Growth analysis of corn and soybean response to allelopathic effects of weed residues at various temperatures and photosynthetic photon flux densities

The effects of redroot pigweed (Amaranthus retroflexus L.) and yellow foxtail [Setariaglauca (L.) Beauv.] residues on corn (Zea mays L.) and soybeans [Glycine max (L.) Merr.] were evaluated at various temperatures and photosynthetic photon flux densities (PPFD) in a Biotron. Mathematical growth analysis techniques were used for the evaluation. Redroot pigweed markedly reduced leaf area duration (LAD), leaf weight ratio (LWR), and total dry matter production in both crops. Yellow foxtail residue inhibited total dry matter production in corn and soybeans 20 and 30 days after planting (DAP). It also reduced growth rate (GR) and LAD in corn and biomass increment ( W) in soybeans. Biomass increment was more closely correlated to LAD than net assimilation rate (NAR) in soybeans, whereas in corn NAR contributed more to W than LAD. The 30/20 ° C temperature with a PPFD of 380 E/m²/sec produced a larger W with a greater NAR and larger LAD in corn, resulting in maximum dry matter accumulation than 20/10 ° C and other levels of PPFD. Under similar conditions, soybeans showed little or no response to the changes. The results demonstrate the allelopathic effects of weed residues on growth and dry matter production, affecting LAD, LWR, and GR. The results also show that environmental temperature and PPFD may alter the allelopathic effects of weeds on crops. The possible interference with photosynthesis and the partitioning of biomass into leaf component relative to the total biomass produced by the plant may be the inhibitory effects of allelochemicals present in redroot pigweed and yellow foxtail residues.     

Performance Study of 90° Bend Substrate Integrated Waveguide Band-Pass Filter with Multi-transmission Zeroes for MIC Applications

Wireless Personal Communications - In wireless sensor networks, the privacy of an event is critical to its safety. The location privacy of the sensor node that reports the event is imperative to...     

Grain-boundary precipitation in Allvac 718Plus

Allvac 718Plus is a newly developed nickel-based superalloy designed to replace Inconel 718 in static and rotating applications in gas turbine engines. Fine γ′ precipitates act as its principal strengthening phase and a second plate-like phase is generally present at grain boundaries. This has been reported to be the δ phase (Ni₃Nb, D0_a, orthorhombic), and is used to pin grain boundaries and improve resistance to intergranular fracture. In Allvac 718Plus non-uniform precipitation of a δ-like phase was observed along the grain boundaries; however, no relation was found between grain-boundary misorientation and the occurrence of precipitation. The crystal structure and chemistry of this phase was found to be different from the orthorhombic Ni₃Nb δ phase reported previously in Inconel 718 and Allvac 718Plus. The true structure was found to be consistent with the hexagonal η-Ni₃Ti D0₂₄ structure, but its chemistry was close to Ni₆AlNb with partial ordering of Al and Nb over the prototype Ti sites. It was found that the serrated boundaries observed in the alloy were a result of discontinuous precipitation of η-Ni₆AlNb, which was a predominant precipitation mechanism throughout the microstructure.     

Isothermal titration calorimetry, transmission electron microscopy, and field emission scanning electron microscopy of a main-chain viologen polymer containing bromide as counterions

The interaction of a main-chain viologen polymer containing bromide as counterions with water and aqueous potassium bromide over a broad range of concentrations was studied with isothermal titration calorimetry. The dilution process of this polymer was endothermic as opposed to flexible poly(sodium acrylate) and poly(sodium styrenesulfonate). This result may be related to the different mechanism of hydration of pyridinium and bromide groups in the main chain. It also exhibited aggregation phenomenon in both water and aqueous potassium bromide solutions as detected by transmission electron microscopy like other flexible and rigid-rod polyelectrolytes. As the polymer concentrations in aqueous solutions increase, the aggregated polymer exhibited more defined ordered structures than random structures observed at low polymer concentrations. Field emission scanning electron microscopy also revealed the effect of variation of concentration of aqueous potassium bromide on the morphology of the polymer matrix. At increasing concentrations of aqueous potassium bromide, the polymer structures became more ordered than those in low concentrations.     

A non-parametric binarization method based on ensemble of clustering algorithms

Multimedia Tools and Applications - Binarization of document images still attracts the researchers especially when degraded document images are considered. This is evident from the recent Document...