Chemoviscosity modeling for thermosetting resin systems, part 3

A new analytical model for simulating chemoviscosity resin has been formulated. The model is developed by modifying the well established Williams-Landel-Ferry (WLF) theory in polymer rheology for thermoplastic materials. By introducing a relationship between the glass transition temperature (T sub g (t)) and the degree of cure alpha(t) of the resin system under cure, the WLF theory can be modified to account for the factor of reaction time. Temperature-dependent functions of the modified WLF theory parameters C sub 1 (T) and C sub 2 (T) were determined from the isothermal cure data. Theoretical predictions of the model for the resin under dynamic heating cure cycles were shown to compare favorably with the experimental data. This work represents a progress toward establishing a chemoviscosity model which is capable of not only describing viscosity profiles accurately under various cure cycles, but also correlating viscosity data to the changes of physical properties associated with the structural transformations of the thermosetting resin systems during cure

Global Analysis of Data on the Spin-orbit-coupled A1Σ+ and b3Πu States of Cs2

We present experimentally derived potential curves and spin-orbit interaction functions for the strongly perturbed A1+ u and b3u states of the cesium dimer. The results are based on data from several sources. Laser-induced fluorescence Fourier transform spectroscopy (LIF FTS) was used some time ago in the Laboratoire Aim´e Cotton primarily to study the X1+ g state. More recent work at Tsinghua University provides information from moderate resolution spectroscopy on the lowest levels of the b3± 0u states as well as additional high resolution data. From Innsbruck University, we have precision data obtained with cold Cs2 molecules. Recent data from Temple University was obtained using the optical-optical double resonance polarization spectroscopy technique, and finally, a group at the University of Latvia has added additional LIF FTS data. In the Hamiltonian matrix, we have used analytic potentials (the Expanded Morse Oscillator form) with both finite-difference (FD) coupled-channels and discrete variable representation (DVR) calculations of the term values. Fitted diagonal and off-diagonal spin-orbit functions are obtained and compared with ab initio results from Temple and Moscow State universities

Radio/X-ray Offsets of Large Scale Jets Caused by Synchrotron Time Lags

In the internal shock scenario, we argue that electrons in most kpc (or even larger) scale jets can be accelerated to energies high enough to emit synchrotron X-rays, if shocks exist on these scales. These high energy electrons emit synchrotron radiation at high frequencies and cool as they propagate downstream along the jet, emitting at progressively lower frequencies and resulting in time lags and hence radio/X-ray (and optical/X-ray if the optical knot is detectable) offsets at bright knots, with the centroids of X-ray knots being closer to the core. Taking into account strong effects of jet expansion, the behaviour of radio/X-ray and optical/X-ray offsets at bright knots in M87, Cen A, 3C 66B, 3C 31, 3C 273, and PKS 1127-145 is consistent with that of synchrotron time lags due to radiative losses. This suggests that the large scale X-ray and optical jets in these sources are due to synchrotron emission.Comment: 4 pages, Accepted for publication in ApJ Letter

Chemoviscosity modeling for thermosetting resins

A chemoviscosity model, which describes viscosity rise profiles accurately under various cure cycles, and correlates viscosity data to the changes of physical properties associated with structural transformations of the thermosetting resin system during cure, was established. Work completed on chemoviscosity modeling for thermosetting resins is reported

Studies on chemoviscosity modeling for thermosetting resins

A new analytical model for simulating chemoviscosity of thermosetting resins has been formulated. The model is developed by modifying the well-established Williams-Landel-Ferry (WLF) theory in polymer rheology for thermoplastic materials. By introducing a relationship between the glass transition temperature Tg(t) and the degree of cure alpha(t) of the resin system under cure, the WLF theory can be modified to account for the factor of reaction time. Temperature dependent functions of the modified WLF theory constants C sub 1 (t) and C sub 2 (t) were determined from the isothermal cure data. Theoretical predictions of the model for the resin under dynamic heating cure cycles were shown to compare favorably with the experimental data. This work represents progress toward establishing a chemoviscosity model which is capable of not only describing viscosity profiles accurately under various cure cycles, but also correlating viscosity data to the changes of physical properties associated with the structural transformation of the thermosetting resin systems during cure

Macroporous materials: microfluidic fabrication, functionalization and applications

This article provides an up-to-date highly comprehensive overview (594 references) on the state of the art of the synthesis and design of macroporous materials using microfluidics and their applications in different fields

Active Thrusting and Folding Along the Northern Tien Shan and Late Cenozoic Rotation of the Tarim Relative to Dzungaria and Kazakhstan

We have studied geometries and rates of late Cenozoic thrust faulting and folding along the northern piedmont of the Tien Shan mountain belt, West of Urumqi, where the M= 8.3 Manas earthquake occurred on December 23, 1906. The northern range of the Tien Shan, rising above 5000 m, overthrusts a flexural foredeep, filled with up to 11,000 m of sediment, of the Dzungarian basement. Our fieldwork reveals that the active thrust reaches the surface 30 km north of the range front, within a 200-km-long zone of Neogene-Quaternary anticlines. Fault scarps are clearest across inset terraces within narrow valleys incised through the anticlines by large rivers flowing down from the range. In all the valleys, the scarps offset vertically the highest terrace surface by the same amount (10.2±0.7 m). Inferring an early Holocene age (10±2 kyr) for this terrace, which is continuous with the largest recent fans of the piedmont, yields a rate of vertical throw of 1.0±0.3mm/yr on the main active thrust at the surface. A quantitative morphological analysis of the degradation of terrace edges that are offset by the thrust corroborates such a rate and yields a mass diffusivity of 5.5±2.5 m^2/kyr. A rather fresh surface scarp, 0.8±0.15 m high, that is unlikely to result from shallow earthquakes with 6 < M < 7 in the last 230 years, is visible at the extremities of the main fold zone. We associate this scarp with the 1906 Manas earthquake and infer that a structure comprising a deep basement ramp under the range, gently dipping flats in the foreland, and shallow ramps responsible for the formation of the active, fault propagation anticlines could have been activated by that earthquake. If so, the return period of a 1906 type event would be 850 ±380 years. The small size of the scarp for an earthquake of this magnitude suggests that a large fraction of the slip at depth (≈2/3) is taken up by incremental folding near the surface. Comparable earthquakes might activate flat detachments and ramp anticlines at a distance from the front of other rising Quaternary ranges such as the San Gabriel mountains in California or the Mont Blanc-Aar massifs in the Alps. We estimate the finite Cenozoic shortening of the folded Dzungarian sediments to be of the order of 30 km and the Cenozoic shortening rate to have been 3 ± 1.5 mm/yr. Assuming comparable shortening along the Tarim piedmont and minor additional active thrusting within the mountain belt, we infer the rate of shortening across the Tien Shan to be at least 6 ± 3 mm/yr at the longitude of Manas (≈85.5°E). A total shortening of 125±30 km is estimated from crustal thickening, assuming local Airy isostatic equilibrium. Under the same assumption, serial N-S sections imply that Cenozoic shortening across the belt increases westwards to 203±50 km at the longitude of Kashgar (≈ 76 °E), as reflected by the westward increase of the width of the belt. This strain gradient implies a clockwise rotation of Tarim relative to Dzungaria and Kazakhstan of 7±2.5° around a pole located near the eastern extremity of the Tien Shan, west of Hami (≈96°E, 43.5°N), comparable to that revealed by paleomagnetism between Tarim and Dzungaria (8.6° ± 8.7°). A 6 mm/yr rate of shortening at the longitude of Manas would imply a rate of rotation of 0.45°/m.y. and would be consistent with a shortening rate of 12 mm/yr north of Kashgar. Taking such values to be representative of Late Cenozoic rates would place the onset of reactivation of the Tien Shan by the India-Asia collision in the early to middle Miocene (16 +22/−9 m.y.), in accord with the existence of particularly thick late Neogene and Quaternary deposits. Such reactivation would thus have started much later than the collision, roughly at the time of the great mid-Miocene changes in tectonic regimes, denudation and sedimentation rates observed in southeast Asia, the Himalayas and the Bay of Bengal, and of the correlative rapid change in seawater Sr isotopic ratio (20 to 15 Ma). Like these other changes, the rise of the Tien Shan might be a distant consequence of the end of Indochina's escape

Sequential nature of damage annealing and activation in implanted GaAs

Rapid thermal processing of implanted GaAs reveals a definitive sequence in the damage annealing and the electrical activation of ions. Removal of implantation-induced damage and restoration of GaAs crystallinity occurs first. Irrespective of implanted species, at this stage the GaAs is n-type and highly resistive with almost ideal values of electron mobility. Electrical activation is achieved next when, in a narrow anneal temperature window, the material becomes n- or p-type, or remains semi-insulating, commensurate to the chemical nature of the implanted ion. Such a two-step sequence in the electrical doping of GaAs by ion implantation may be unique of GaAs and other compound semiconductors