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41.
Tiina Sikanen Thomas Zwinger Santeri Tuomikoski Sami Franssila Reijo Lehtiniemi Carl-Magnus Fager Tapio Kotiaho Antti Pursula 《Microfluidics and nanofluidics》2008,5(4):479-491
This work presents experimental [infrared (IR) thermography] and computational (finite element model) results of temperature
distributions of an electrokinetic separation chip. Thermal characteristics of both the electrolyte solution and the polymer
chip (SU-8) are taken into account in modeling temperature distributions during electrokinetic flow. Multiphysics and multiscale
simulation couples electrostatics, heat transfer, and fluid dynamics. The accompanying IR thermography is a non-contact method,
which can measure fractional temperature differences with sub-second time resolution. Any structures or temperature marker
molecules interfering with the experiment are not needed. Nominal spot size in the IR measurements is 30 μm with a field of
view of several millimeters enabling both local and chip-scale temperature monitoring simultaneously. As a result, we present
a computer model for electrokinetic chips, which enables simulation of fractional temperature changes during electrophoresis
under real operating conditions. The accuracy of the model is within ±1°C when the deviation in electrochemical processes
is taken into account. The simulation results also suggest that the temperature on the chip surface qualitatively reflects
the temperature inside the microchannel with an average offset of 1–2°C. 相似文献
42.
Esa Toukoniitty Johan Wärnå Dmitry Yu. Murzin Tapio Salmi 《Chemical engineering science》2010,65(3):1076-1087
Transient techniques are frequently used for catalytic gas-phase processes, but the application of transient techniques on catalytic three-phase systems is very scarce. Transient kinetic experiments provide valuable additional information about the behaviour of complex organic reaction systems, which was illustrated here with continuous enantioselective three-phase hydrogenation of ethyl benzoylformate over supported Pt catalyst particles in a fixed bed. The catalyst stability and the details of the adsorption–desorption behaviour of the reaction participants were revealed by transient experiments. Quantitative modelling of the data was based on kinetic experiments and characterisation of the reactor flow pattern by an inert tracer. Both liquid-phase species and adsorbed surface species were included in the modelling. The model predicted correctly the dynamic behaviour of the complex organic system under transient conditions. The approach is generally applicable to complex organic systems undergoing catalytic transformations. 相似文献
43.
A. Luukanen M. M. Leivo J. K. Suoknuuti A. J. Manninen J. P. Pekola 《Journal of Low Temperature Physics》2000,120(3-4):281-290
Evaporation of hot electrons from a normal-metal into a superconductor can be used for efficient Peltier type cooling in micrometer size tunnel junctions. We have cooled the electrons to one third,
1
and, as the main result of the present paper, a separate silicon nitride membrane to about one half of its starting temperature; all results have been obtained at temperatures well below 1K, where the lattice is weakly coupled to electrons thermally. The micromachined membrane can serve as a thermal bath for tiny samples, like bolometric radiation detectors in astronomy. 相似文献
44.
45.
The separation of γ- and α-linolenic acid containing triacylglycerols with an identical acyl carbon number and degree of unsaturation
was obtained on capillary supercritical fluid chromatography using a 25% cyanopropyl−75% methylpolysiloxane stationary phase.
The resolution of 1,3-dioleoyl-2-γ-linolenoyl-sn-glycerol and 1,3-dioleoyl-2α-linolenoyl-sn-glycerol was 1.35 on a 10 m×50 μm i.d. column, whereas the resolution was enhanced to 1.66 by combining two 10-meter columns
in series. The difference in the position of double bonds in one linolenic acid residue of triacylglycerols resulted in two
series of peaks in the separation of alpine currant (Ribes alpinum) and black currant (R. nigrum) seed oils. The use of the 10-meter column was found to be appropriate for the screening of the triacylglycerol profile in
both seed oils studied. 相似文献
46.
47.
In the present paper a cutting plane approach to solve mixed-integer non-linear programming (MINLP) problems, containing pseudo-convex functions, is given. It is shown how valid cutting planes for pseudo convex functions can be obtained and, furthermore, it is shown how a class of non-convex MINLP problems with a pseudo-convex objective function and pseudo-convex constraints, can be solved to global optimality with the considered cutting plane technique. Finally the numerical efficiency of the procedure, when solving some example problems, is illustrated. 相似文献
48.
Gerson Martin Päivi Mäki-Arvela Johan Wärnå Dmitry Yu. Murzin Tapio Salmi 《Topics in Catalysis》2014,57(17-20):1576-1581
The enantioselective hydrogenation of ethyl benzoylformate over (?)-cinchonidine (CD)-modified Pt/Al2O3 catalyst in semi-batch and continuous fixed bed reactors was studied as a function of the modifier concentration and reaction temperature. The kinetic results from the semibatch reactor showed a higher enantioselectivity and lower initial rate as the amount of modifier was increased. The results from the fixed bed reactor demonstrates that continuous enantioselective hydrogenation is possible and that continuous feeding of (?)-CD is needed to maintain a high steady-state enantioselectivity. 相似文献
49.
50.
A concentration-saturated helium mixture at the melting pressure consists of two liquid phases and one or two solid phases. The equilibrium system is univariant, whose properties depend uniquely on temperature. Four coexisting phases can exist on singular points, which are called quadruple points. As a univariant system, the melting pressure could be used as a thermometric standard. It would provide some advantages compared to the current reference, namely pure $^3$ He, especially at the lowest temperatures below 1 mK. We have extended the melting pressure measurements of the concentration-saturated helium mixture from 10 to 460 mK. The density of the dilute liquid phase was also recorded. The effect of the equilibrium crystal structure changing from hcp to bcc was clearly seen at $T=294$ mK at the melting pressure $P=2.638$ MPa. We observed the existence of metastable solid phases around this point. No evidence was found for the presence of another, disputed, quadruple point at around 400 mK. The experimental results agree well with our previous calculations at low temperatures, but deviate above 200 mK. 相似文献