White-light generation through Ce3+/Mn2+-codoped and Eu2+-doped Ba1.2Ca0.8SiO4 T-phase phosphors

Hexagonal Ba_1.20Ca_0.8?2x?ySiO₄:xCe³⁺,xLi⁺,yMn²⁺ phosphors exhibit two emission bands peaking near 400 and 600 nm from the allowed f–d transition of Ce³⁺ ions and the forbidden ⁴T₁–⁶A₁ transition of Mn²⁺ ions, respectively. The strong interaction between Ce³⁺/Mn²⁺ ions is investigated in terms of energy transfer, crystal field effect, and microstructure by varying their concentrations. They show a higher quenching temperature of 250 °C than that of a commercially used (Ba,Sr)₂SiO₄:Eu²⁺ phosphor (150 °C). Finally, mixtures of these phosphors with green-emissive Ba_1.20Ca_0.70SiO₄:0.10Eu²⁺ are tested and yielded correlated color temperatures from 3500 to 7000 K, and color rendering indices up to 95%.     

Coalition formation with local public goods and group-size effect

Many public goods that are provided by coalitions have a group-size effect. Namely, people prefer to consume a public good in a larger coalition. This paper studies local public goods games with anonymous and separable group-size effect. The core is nonempty when coalition feasible sets are monotonic and players’ preferences over public goods satisfy a condition called cardinal connectedness. Moreover, a core allocation consists of connected coalitions.     

Parametric study on a compound-drop spray flame

The introduction of compound-drop spray in a combustion system is a new concept. These droplets bear two gasification stages to cause an integral positive or negative effect on a premixed flame to raise or lower the local temperature of the gasification region. In this paper, we adopt a compound drop which contains a water core encased by a layer of shell fuel. A one-dimensional homogeneous lean or rich premixed flame with the dilute compound-drop spray was investigated by using large activation energy asymptotic analysis. The compound-drop spray burning mode was defined and divided into completely pre-vaporised burning (CPB), shell pre-vaporised burning (SPB) and shell partially pre-vaporised (SPP) burning modes by way of the gasification zones of the shell fuel and the core water relative to the flame position. The influences of the initial droplet radius, the shell-fuel mass fraction and the liquid loading of the compound-drop spray on the lean and rich flames were analysed. By means of the normalisation parameter of flame propagation mass flux (), enhancement, suppression or extinction of the compound-drop spray flame can be represented clearly. Furthermore, from the observation of extinction, the necessary conditions of extinction of a lean spray flame by the internal heat transfer are that the spray is a negative effect and causes a sufficient heat loss rate at flame sheet downstream side. For a rich spray flame, three extinction patterns were observed; they occur in SPP, SPB or at the critical SPB mode, but do not in CPB. The extinction maps of the compound-drop spray demarcate the patterns and also indicate the limitations and corresponding conditions of the flame extinction.     

Development and Infrared Applications of Chalcogenide Glass Optical Fibers

Chalcogenide glass fibers based on sulphide, selenide, telluride, and their rare earth doped compositions are being actively pursued both at the Naval Research Laboratory in Washington, D.C. (NRL) and worldwide. Great strides have been made in reducing optical losses using improved chem ical purification techniques, but further improvements are needed in both purification and fiberization technology to attain the theoretical optical losses. Despite this, current singlemode and multimode chalcogenide glass fibers are enabling numerous applications. Some of these applications include laser power delivery, chemical sensing, imaging, scanning near field microscopy spectroscopy, fiber infrared (IR) sources lasers, amplifiers, and optical switches. The authors assert that the research and development of chalcogenide glasses will grow in the foreseeable future, especially with respect to improvements the optical quality of the fibers and the performance of the fibers in existing future applications.     

Analytic solutions of a two-dimensional rectangular heat equation with a heat source

The method of separation of variables is applied in order to investigate the analytical solutions of a certain two-dimensional rectangular heat equation. In the analysis presented here, the partial differential equation is directly transformed into ordinary differential equations. The closed-form transient temperature distributions and heat transfer rates are generalized for a linear combination of the products of Fourier-Bessel series of the exponential type. Relevant connections with some other closely-related recent works are also indicated.     

Effects of top confinement and diluents on morphology in crystallization of poly(l‐lactic acid) interacting with poly(ethylene oxide)

Effects of top confinement and diluent poly(ethylene oxide) (PEO) on poly(l ‐lactic acid) (PLLA) crystal morphology have been investigated. When crystallized at 120 °C, uncovered neat PLLA sample exhibits higher growth rate ringless spherulites; while the covered sample exhibits lower growth rate ring‐banded spherulites. As PEO is introduced into PLLA, the morphology also undergoes significant changes. For the same T_c,PLLA = 120 °C, the PEO/PLLA blend with PEO composition greater than 25% exhibits ring‐banded patterns even in uncovered sample. However, in much greater PEO composition (>80 wt %), uncovered samples exhibit ring bands diverging into dendritic patterns, while top covered samples tend to maintain the spiral ring‐band patterns. Both PEO inclusion in PLLA and top cover on films impose growth kinetic alterations. Additionally, the top glass cover tends to prevent the lower surface tension PLLA to be accumulated on the surface, resulting in the formation of ring‐band pattern. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1160–1170     

High‐performance segmented polyurea by transesterification of diphenyl carbonates with aliphatic diamines

In an effort to develop a green process for the production of elastomeric polyurethane–urea (PUaE) through a nonisocyanate route, a highly practical method was found using diphenyl carbonate (DPC) instead of diisocyanate as the carbonylation agent. The transesterification of aliphatic diamines in a solvent such as tetramethylene sulfone (TMS) with DPC results in a new process obtaining new segmented PUaE with high molecular weights and excellent mechanical performance. The key to the present success lies in the timing and sequence of the diamine addition forming initial carbamate intermediates in situ and then in shifting the equilibrium toward polyurea product formation by phenol removal from the TMS solution so that high‐molecular‐weight polyurea could be formed favorably. The most optimized polyurea films made in this study has a η_inh of 0.64, with high‐performance characteristics showing tensile strength of greater than 30 MPa and elongation exceeding 400% with decomposition temperature (5%) of >280 °C. Well‐defined soft‐ and hard‐segment domains were observed for the products as determined by atomic force microscope. This new improved process to produce segmented polyurea thereby complies fully with the principles of green chemistry using readily available chemicals. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2781–2790