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排序方式: 共有2815条查询结果,搜索用时 15 毫秒
21.
22.
The estimation of the Direction-Of-Arrival (DOA) and the variance of the angular spread, using an array of sensors in the
case of a Ricean channel is considered, using the Maximum-Likelihood, Least-Squares and Weighted Least Squares criteria. The
Cramér-Rao bound is also obtained for the problem of interest. Simplification of the cost functions to reduce the dimension
of the problem has been carried out and the performance of the methods has been studied based on numerical experiments.
A major part of the work was carried out when K V S Hari was visiting the Department of Signals, Sensors and Systems during
Jul–Sep 1995, on leave from the Indian Institute of Science 相似文献
23.
A study compares two methods of reading text-based content on mobile phones: traditional scroll-based reading and Rapid Serial Visual Presentation, which displays words rapidly in a sequence. University students used a prototype called Feedo to test both methods, and their reading comprehension, efficiency, and preference ratings were measured. The results show that efficiency increases with fast RSVP, comprehension is equal, and preference rating is lower than with self-paced scroll. 相似文献
24.
25.
The dynamic performance of point-type smoke detectors is described by a simple model including two independent parameters, the static response threshold, and the characteristic length of the detector. An experimental system with constant rate of increase of smoke density under varying velocity conditions is used to determine the model parameters.Nomenclature
k
constant smoke density gradient (dB/m/s)
-
L
characteristic length of the detector (m)
-
m
i
smoke density inside the detector (dB/m)
-
m
o
smoke density outside the detector (dB/m)
-
m
or
measured smoke density at response (dB/m)
-
m
r
response threshold of the detector (dB/m)
-
t
time(s)
-
v
gas flow velocity at the detector (m/s)
-
time constant(s) 相似文献
26.
The kinetics of aluminium deposition from NaCl-AlCl3 melts (cAlCl3 < 10 mol%) contained in alumina crucibles was studied by linear sweep voltammetry and potential step amperometry at temperatures around 820°C. At low concentrations (cAlCl3 < 0.4 mol%) the reduction of AlCl3 on liquid aluminium has been found to be diffusion controlled. At higher concentrations a passivation of the aluminium electrode was observed during the deposition reaction. The passivation appears to be caused by precipitation of alumina from supersaturated melt in the diffusion layer at the aluminium cathode. 相似文献
27.
Dorota Johansson Björn Bergenståhl 《Journal of the American Oil Chemists' Society》1992,69(8):728-733
The influence of water on the interactions between fat and sugar crystals dispersed in triglyceride (vegetable) oils was qualitatively
estimated from sedimentation and rheological experiments. The experiments were performed both with and without food emulsifiers
(monoglycerides and lecithins) present in the oil. The effects of minor natural oil components (nontriglycerides) on the interactions
and on emulsifier adsorption to the crystals were examined by comparing a commercial refined oil and a chromatographically
purified oil. The results show that water generally increases the adhesion between fat and sugar crystals in oils and also
increases the surface activity of the oil-soluble food emulsifiers. Minor oil components give a small increase in the adhesion
between fat and sugar crystals in oils, but do not influence the adsorption of food emulsifiers in any systematic way. 相似文献
28.
Desislava Bögner Frederike Schmachtl Björn Mayr Christopher P. Franz Sabine Strieben Gregor Jaehne 《臭氧:科学与工程》2019,41(2):105-117
Recirculating Aquaculture Systems (RAS) reduce water consumption by efficient filtration to maintain appropriate levels of accumulating compounds and sludge. Sludge is mechanically separated by drum filters and disposed of to the detriment of overall system water budgets. Dissolved nitrogen compounds are reduced via nitrification–denitrification filters, requiring commercial external carbon sources. The reuse of sludge after ozone pre-treatment may represent the next step in RAS optimization. The present study analyzes the content of sludge from RAS and tests ozonation as a pre-treatment for recycling as carbon source. The dissociative effect of ozone and the physicochemical changes due to ozonation lead to a significant increase in soluble carbon availability. Predominantly long-chain fatty acid (FA) (saturated and unsaturated) with 16 and 18 carbon atoms independently of the treatment were found in the profiles. Saturated FA concentrations in solution increased after 20, 40, and 60 min ozonation. The solid content of the sludge was practically unaffected by ozonation in terms of FA profile: only saturated FA slightly increases after 40 min treatment. The implications of these findings for denitrifying bacteria are discussed.
Abbreviations: Recirculating Aquaculture Systems (RAS); Advanced Oxidation Processes (AOPs) 相似文献
29.
Peter?S.?Piispanen Bj?rn?Hedman Torbj?rn?NorinEmail author 《Journal of surfactants and detergents》2002,5(2):165-168
The syntheses of derivatives of dehydroabietic acid suitable for further manipulation into surfactants are presented. The
compounds are produced at very high yields and purity. They contain several different functional groups, e.g., carboxylic
acid, amine, ester, alcohol, and an aromatic group. The functional groups are useful as the linking unit to the hydrophilic
part in synthesizing surfactants. 相似文献
30.
A characterisation of three commonly used impellers was made in this study by measuring local mean velocities and the fluctuations of these velocities with the LDV technique. The data was used to estimate volumetric flow, velocity fluctuations and turbulent intensity in the impeller region of the tank. The impellers investigated were a high flow impeller, a pitched blade turbine and a Rushton turbine. The cylindrical vessel used was made of Perspex, had a dished bottom (DIN 28013), was equipped with four baffles and had an inner diameter of 0.45 m. It was found that the bulk velocities could be scaled with the tip-speed of the impeller (ND). The flow rate at constant impeller speed increased in the order high flow impeller — Rushton turbine — pitched blade turbine. The corresponding order for the turbulence fluctuation is: high flow impeller — pitched blade turbine — Rushton turbine. The velocity profile of the flow out from the high flow impeller was furthermore, not as smooth as could be expected. 相似文献