Exact solutions to differential-difference heat and mass transfer equations with a finite relaxation time

Certain exact solutions to the linear differential-difference heat and mass transfer equations with a finite relaxation time are specified. The exact solution to the one-dimensional Stokes problem with the periodic boundary condition when a first-order volume chemical reaction occurs is given. A wide class of exact solutions to the nonlinear differential-difference heat-conduction equation with the following source is described: $$\Theta _t = div[f(T)\nabla T] + g(\Theta ), = T(r,t + \tau ),$$ where T = T(r, t) is temperature and τ is the relaxation time. Certain more complex heat conduction models with a variable relaxation time that can depend on time and a temperature gradient are also considered.     

Crosslinking effect on polydimethylsiloxane elastic modulus measured by custom‐built compression instrument

A macroscopic compression test utilizing a simple custom‐built instrument was employed to measure polydimethylsiloxane (PDMS) elastic modulus. PDMS samples with varying crosslinking density were prepared with the elastomer base to the curing agent ratio ranging from 5 : 1 to 33 : 1. The PDMS network elastic modulus varied linearly with the amount of crosslinker, ranging from 0.57 MPa to 3.7 MPa for the samples tested. PDMS elastic modulus in MPa can be expressed as 20 MPa/PDMS base to curing agent ratio. This article describes a simple method for measuring elastic properties of soft polymeric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41050.     

Climate Change, “Grid Neutrality,” and Electricity Distributors

My late colleague and friend Alfred Kahn relayed how President Jimmy Carter hired him in 1977 to head the Civil Aeronautics Board to reform and ultimately deregulate the US airline industry. Accepting the job, he told a group of airline executives (to their fury), “I really don't know one plane from the other. To me they are all marginal costs with wings.” He used that term to signal his intention of reforming the industry in keeping with economic principles, uninfluenced by the romance of air travel.     

Electricity Deregulation Under Siege

It has not been a good few years for the advance of competition in electricity supply in a number of places in the world.     

Benzophenone vs. Copper/Benzophenone in Light‐Promoted Atom Transfer Radical Additions (ATRAs): Highly Effective Iodoperfluoroalkylation of Alkenes/Alkynes and Mechanistic Studies

Iodoperfluooralkylation of terminal alkenes and alkynes is effectively photo‐promoted by benzophenone 2 (BP) or the photoreducible copper(II) complex 1 . In particular, BP at 1 mol% in methanol upon 365 nm irradiation with a low‐pressure mercury lamp (type TLC=thin layer chromatography, 6 W) results in a fast reaction with excellent reaction yields. Complex 1 and BP 2 exhibited very similar reactivity, suggesting that the reactions involving 1 are likely to be governed by the benzophenone photoactivation processes, rather than copper(I)/(II) redox processes. Mechanistic investigations using transient absorption spectroscopy revealed that a deactivation pathway of the benzophenone triplet (³BP*) is via its reaction with the methanol solvent. We propose that the generated radicals, in particular ^.CH₂OH, play a key role in the initiation step forming R_f^. by reacting with R_fI, R_f^. then entering a radical chain cycle. ¹H NMR studies provided evidence that a substantial amount (∼7% NMR yield) of the hemiacetal CH₃OCH₂OH is formed, i.e., the possible by‐product of the reaction between ^.CH₂OH and R_fI. Finally, DFT calculations indicate that a triplet‐triplet energy transfer (TTET) process from ³BP* to perfluorooctyl iodide (C₈F₁₇I) is unlikely or should be rather slow under the reaction conditions, consistent with the transient absorption studies.

     

About the Nature of Quasi-Cleavage in Low-Carbon Steel Embrittled with Hydrogen

Metal Science and Heat Treatment - Scanning electron microscopy and confocal laser scanning microscopy are used to study a fracture surface of hydrogen-charged low-carbon steel, which has been...     

Experimental Search for Chemical Compositions of Superelastic Titanium Alloys with Enhanced Functional Properties

Metal Science and Heat Treatment - Ti – Zr-based alloys with a high zirconium content prepared by vacuum-arc remelting with nonconsumable tungsten electrode are studied. The optimum number of...     

Polymerization of propylene in liquid monomer using state-of-the-art high-performance titanium-magnesium catalysts

A comparative study of propylene polymerization in liquid monomer is performed under laboratory conditions using the IK-8-21 Ti-Mg catalyst designed at the Boreskov Institute of Catalysis and imported industrial catalysts (conditionally labeled TMC-1, -2, and -3). The activity and stereospecificity of the catalysts are estimated along with properties of the resulting polypropylene (granular composition and physicomechanical characteristics). It is shown that the IK-8-21 catalyst is not inferior to imported counterparts in terms of catalytic properties in the synthesis of polypropylene. The polypropylene powder formed on IK-8-21 is homogeneous and has good morphology. The physicomechanical characteristics of polypropylene synthesized on the domestic IK-8-21 catalyst are similar to those for polypropylene prepared with the imported TMK-1 catalyst.