RHEOLOGICAL AND CALORIMETRIC PROPERTIES OF HEATED CORN STARCH-SOYBEAN PROTEIN ISOLATE DISPERSIONS

Differential scanning calorimetric (DSC) data on 10% (w/w) corn starch dispersion showed one endothermic peak and on soybean protein (SP) isolate dispersions two peaks attributed to 7S and 11S globulins. In corn starch-SP isolate mixtures, thermal transitions appear to occur independently of one another. Dynamic rheological data over 0.63–62.9 rad s^-1 revealed weak gel-like behavior of both 10% corn starch and SP isolate dispersions with magnitudes of storage modulus (G') being significantly higher than those of loss modulus (G") and both exhibiting slight frequency-dependence; G' of corn starch dispersion was higher than that of SP isolate and in mixed dispersions its magnitude decreased with increase in proportion of protein. The Maxwell model described creep-compliance data on dispersions high in corn starch, while the Burgers model described dispersions high in SP isolate. Plots of protein/starch ratio versus G' and instantaneous elastic modulus showed similar trends in phase separation and inversion.     

Frequency modulated atomic force microscopy on MgO(001) thin films: interpretation of atomic image resolution and distance dependence of tip-sample interaction

Atomically resolved images on a MgO(001) thin film deposited on Ag(001) obtained in ultrahigh vacuum by frequency modulated atomic force microscopy at low temperature are presented and analysed. Images obtained in the attractive regime show a different type of contrast formation from those acquired in the repulsive regime. For the interpretation of the image contrast we have investigated the tip-sample interaction. Force and energy were recovered from frequency shift versus distance curves. The derived force curves have been compared to the force laws of long-range, short-range and contact forces. In the attractive regime close to the minimum of the force-distance curve elastic deformations have been confirmed. The recovered energy curve has been scaled to the universal Rydberg model, yielding a decay length of l = 0.3?nm and ΔE = 4.2?aJ (26?eV) for the maximum adhesion energy. A universal binding-energy-distance relation is confirmed for the MgO(001) thin film.     

Three-dimensional mixed-mode fatigue crack growth in a functionally graded titanium alloy

The implementation of unitized structure in the aerospace industry has resulted in complex geometries and load paths. Hence, structural failure due to three-dimensional mixed-mode fatigue crack growth is a mounting concern. In addition, the development of functionally graded materials has further complicated structural integrity issues by intentionally introducing material variability to create desirable mechanical behavior. Ti-6Al-4V β-STOA (solution treated over-aged) titanium is a functionally graded metallic alloy that has been tailored for superior fatigue crack growth and fracture response compared with traditional titanium alloys. Specifically, the near-surface material of Ti β-STOA is resistant to fatigue crack incubation and the interior is more resistant to fatigue crack growth and fracture. Therefore, Ti β-STOA is well suited for applications where surface cracking is a known failure mode. Advances in experimental testing have shown that complex loading conditions and multi-faceted materials can be tested reliably. In this paper, the authors will experimentally generate three-dimensional mixed-mode surface crack data in functionally graded Ti-6Al-4V β-STOA and comment on the effect of the material tailoring.     

Experimental and computational investigation of three-dimensional mixed-mode fatigue

Experimental and computational methods were developed to model three-dimensional (3-D) mixed-mode crack growth under fatigue loading with the objective of evaluating proposed 3-D fracture criteria. The experiments utilized 7075-T73 aluminium forgings cut into modified ASTM E740 surface crack specimens with pre-cracks orientated at angles of 30, 45 and 60° in separate tests. The progress of the evolving fatigue crack was monitored in real time using an automated visualization system. In addition, the amplitude of the loading was increased at prescribed intervals to mark the location of the 3-D crack front for post-test inspection. In order to evaluate proposed crack growth equations, computer simulations of the experiments were conducted using a 3-D fracture model based on the surface integral method. An automatic mesher advanced the crack front by adding a ring of elements consistent with local application of fracture criteria governing rate and direction of growth. Comparisons of the computational and experimental results showed that the best correlation was obtained when K _II and K _III were incorporated in the growth rate equations.     

Toughening mechanisms in core-shell rubber modified polycarbonate

We have conducted a study of toughening mechanisms in rubber modified polycarbonate systems in order to evaluate the sequence of deformation events which improve fracture toughness. We conclude that cavitation of the rubber particles occurs first, followed by massive shear yielding of the matrix material. The size and shape of the deformation zone created in front of the crack is governed by the mechanical properties of the rubber particles and the stress state at the crack tip. The importance of using a variety of analytical techniques to characterize deformation mechanism is also illustrated.     

Design and fabrication of a superconducting magnet for an 18 GHz electron cyclotron resonance ion∕photon source NFRI-ECRIPS

A superconducting magnet was designed and fabricated for an 18 GHz ECR ion∕photon source, which will be installed at National Fusion Research Institute (NFRI) in South Korea. The magnetic system consists of a set of four superconducting coils for axial mirror field and 36 pieces of permanent magnets for hexapolar field. The superconducting coils with a cryocooler (1.5 W @ 4.2 K) allow one to reach peak mirror fields of 2.2 T in the injection and those of 1.5 T in the extraction regions on the source axis, and the resultant hexapolar field gives 1.35 T on the plasma chamber wall. The unbalanced magnetic force between the coils and surrounding yoke has been minimized to 16 ton by a coil arrangement and their electrical connection, and then was successfully suspended by 12 strong thermal insulating supports made of large numbers of carbon fibers. In order to block radiative thermal losses, multilayer thermal insulations are covered on the coil windings as well as 40-K aluminum thermal shield. Also new schemes of quench detection and safety system (coil divisions, quench detection coils, and heaters) were employed. For impregnation of the windings a special epoxy has been selected and treated to have a higher breaking strength and a higher thermal conductivity, which enables the superconductors to be uniformly and rapidly cooled down or heated during a quench.     

2010及2011年全球化学纤维发展趋势

2009年经济危机的爆发使全球除中国大陆和印度外的化学纤维产业生产受到一定程度的影响。尽管目前化学纤维的生产水平还没回到经济危机前,但化学纤维产业已经开始逐步复苏。在中国大陆,2010年上半年纤维的生产总量增加了13％左右;在美国,2010年前三季度的合成纤维生产量增长了12％（2009年则是减少20％）。