Transient-thermal and isothermal studies of thermo-sensitive polymer solution with ultrasound resonator technology

High resolution and high sensitivity ultrasound resonator technology offers unique possibilities for the investigation of polymer precipitation. Exemplarily, the aggregation of poly(N-isopropylacrylamide) units in block copolymers with poly(styrene sulfonate) is investigated. Long term changes, over hours and days, of both the ultrasound velocity and the attenuation were detected during isothermal studies at temperatures in the vicinity (below as well as above) of the critical solution temperature. Apparent activation free energies of the precipitation and re-dissolution of the poly(N-isopropylacrylamide) block have been determined for the first time. The apparent activation energies are in the order of up to a few thousands kJ/mol, which can be explained by a high cooperativity of the precipitation process.     

Analytical characterization of palatinit (author's transl)]

The reaction product of the catalytic hydrogenation of isomaltulose (palatinose) is a mixture of alpha-D-glucopyranosido-1,6-sorbitol and alpha-D-glucopyranosido-1,6-mannitol designated palatinit. Because of its high potential as a sugar substitute methods for the identification and characterization of hydrogenation products and for the determination of palatinit as an ingredient in food preparations and biological samples are required. Several working procedures are described in full detail including thin layer and gas chromatography as well as enzymatic and chemical determinations.     

Concurrent search of mobile users in cellular networks

In this paper, we propose to concurrently search for a number of mobile users in a wireless cellular network based on the probabilistic information about the locations of mobile users. The concurrent search approach guarantees that all k mobile users will be located within k time slots. It is shown that even in the worst case when mobile users appear equally in all the cells of the network, the concurrent search approach is able to reduce the average paging cost by 25%. More importantly, this is achieved without an increase in the worst case paging delay or in the worst case paging cost. Depending on the total number of mobile users to be located, total number of cells in the network, and the probabilistic information about the locations of mobile users, the reduction of the average paging cost due to the usage of the concurrent search approach ranges from 25% to 88%. The case in which perfect probabilistic information is unavailable is also studied.     

A novel wavelength-division multiplexer using grating-assisted two-mode interference

A novel design of wavelength-division multiplexer based on two-mode interference assisted by a highly dispersive grating structure is two-dimensionally simulated and analyzed using finite-difference time-domain method. We show that the designed grating waveguide provides a mode-dependent reflection spectrum which can be used to modify the beat lengths of the two selected wavelengths 1342 and 1560 nm, so that they can be divided in a very short distance about 48 /spl mu/m. Simulation results show that contrasts /spl sim/12 dB and insertion losses about 2 dB could be achieved.     

没有最好 只有更专业

在航空航天制造发展的过程中,材料的更新换代也呈现出高速的更迭变换,在未来航空航天制造中,一架飞机中复合材料、钛合金、镍合金和高温合金的含量将占主导地位,特别是复合材料的高速发展,有取代铝合金成为飞机制造应用中第一材料的趋势。虽然现在铝合金的比重还比较高,但是在军用直升机制造中已经采用了更多的复合材料,