Double necking in polymer tensile deformation

After initial necking of tensile polymer samples the deformation front moves along the gauge length at a stress which is smaller than the yield stress. The still undeformed parts of the sample are therefore subjected to conditions which favour deformation by a creep mechanism. If the extension rate is right, secondary necking becomes possible. Boundary conditions are discussed.     

X-ray characterization of three possible edible oleogelators: Experiment and theory

Three oleogelator molecules (Triacontane (TC), Stearic acid (SA), and Behenyl Lignocerate (BL)) were studied individually, in pairs, or all together to make an oleogel using triolein as the oil. WAXS, SAXS and USAXS were used to elucidate the solid structures from angstroms to a few micrometers. A two-dimensional mapping of atomic positions for each molecule was carried out to understand the crystalline multilayer structures formed. We assumed that the molecules were rigidly extended and that they underwent no significant (hindered) rotations so that the free energy is determined by the Lennard-Jones interactions of closely packed multilayers. TC molecules were predicted to form a tilt angle of ${\theta }_t\approx 33°$, yielding a SAXS line at $q\approx 0.194$ Å^─1, in acceptable agreement with the measured $q=0.181{\AA }^{-1}$. For SA crystals ${\theta }_t\approx 33°$ (predicted) yielding a SAXS line at $q=0.150{\AA }^{-1}$ compared to $q=0.159{\AA }^{-1}$ (observed). No mixed crystals were observed for any pair of molecules or when all three were used. USAXS data showed that SA forms large nanocrystals compared to TC and BL. All three combinations of molecular pairs showed basic scatterers smaller or similar to those of individual molecules. The theory presented here, together with the experimental results, showed why no mixed crystals are formed from two or all three molecules. Data from the USAXS region suggested that, when using all three molecules, a more compact fractal structure was obtained, compared with those if one or two of the molecules were used.     

Perceptions of group cohesion and mood in sport teams.

Perceptions of group cohesion and mood were investigated among netball, rowing, and rugby teams. Participants (N?=?415) completed the Group Environment Questionnaire and the Profile of Mood States—C. For task cohesion, high attraction to the group predicted low tension and anger and high group integration predicted low depression. For social cohesion, high attraction to the group predicted low tension, low depression, and high vigor, but group integration was not predictive of mood. Type of sport did not moderate cohesion–mood relationships, although significant between-sport differences in cohesion and mood scores were seen. Results are discussed in relation to the R. F. Baumeister and M. R. Leary (1995) proposition that the need to belong is a fundamental human motive. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low‐loss TCP/IP header compression for wireless networks

Wireless is becoming a popular way to connect mobile computers to the Internet and other networks. The bandwidth of wireless links will probably always be limited due to properties of the physical medium and regulatory limits on the use of frequencies for radio communication. Therefore, it is necessary for network protocols to utilize the available bandwidth efficiently. Headers of IP packets are growing and the bandwidth required for transmitting headers is increasing. With the coming of IPv6 the address size increases from 4 to 16 bytes and the basic IP header increases from 20 to 40 bytes. Moreover, most mobility schemes tunnel packets addressed to mobile hosts by adding an extra IP header or extra routing information, typically increasing the size of TCP/IPv4 headers to 60 bytes and TCP/IPv6 headers to 100 bytes. In this paper, we provide new header compression schemes for UDP/IP and TCP/IP protocols. We show how to reduce the size of UDP/IP headers by an order of magnitude, down to four to five bytes. Our method works over simplex links, lossy links, multi‐access links, and supports multicast communication. We also show how to generalize the most commonly used method for header compression for TCP/IPv4, developed by Jacobson, to IPv6 and multiple IP headers. The resulting scheme unfortunately reduces TCP throughput over lossy links due to unfavorable interaction with TCP's congestion control mechanisms. However, by adding two simple mechanisms the potential gain from header compression can be realized over lossy wireless networks as well as point‐to‐point modem links. This revised version was published online in June 2006 with corrections to the Cover Date.     

Analysis of the stability of embankment slopes by the method of limiting equilibrium

A method is suggested for calculating the slope stability of a soil mass, which differs from known methods based on equations for the equilibrium of individual elements of the mass in its assumptions about the height of application of interelement forces used by the author to derive a solution. There is a program for automated calculation.Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 8–10, September–October, 1993.     

Distributed multimedia applications on gigabit networks

MultiG, an open research program addressing issues that range from end-user requirements on distributed multimedia applications supporting collaborative work to medium-access protocols for multi-gigabit networks on optical fibers, is discussed. The projects in MultiG are described from the top down, beginning with computer-supported cooperative work. Distributed multimedia applications and application generators are then considered, followed by networking issues, including interprocess communication, transport services, network protocols, and high-speed protocol processing. Testbed activities and future plans are described     

Deformation characteristics of reinforced epoxy resin

Specimens, cut from a commercially produced epoxide resin reinforced by layers of glass cloth, were tested in tension at various strain-rates and temperatures, and at various orientations of the fibres to the tensile axis. Results are presented for elastic moduli, yield and fracture stresses, and elongations. These results give ample evidence of a decrease in the effectiveness of the reinforcement as deformation proceeds. Strain-ratechange tests show that the rate sensitivity of the composite rises rapidly as the strain increases beyond a critical value, which also indicates that the behaviour is increasingly governed by the properties of the matrix.