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51.
Jaakko Yli-Ojanperä Jyrki M. Mäkelä Marko Marjamäki Antti Rostedt Jorma Keskinen 《Journal of aerosol science》2010,41(8):719-728
A concept of realizing a standard for aerosol particle number concentration was tested, based on generating singly charged aerosol particles in the size range from 10 up to 500 nm. To this end, a device named single-charged aerosol reference (SCAR) was designed, built, and tested. The device is based on electrical charging of nanoparticles and subsequent growth of the particles. With an accurate measurement of volume flow and electrical current from the singly charged particles, the number concentration can be accurately, and in the end, traceably determined. Laboratory tests have shown that the device can be used to generate a narrow (GSD<1.3) particle size distribution of singly charged particles. The device can be used for traceable calibration of instruments measuring the number concentration of the particles. 相似文献
52.
An Van Cleempoel Jorma Joutsensaari Esko Kauppinen Renaat Gijbels Magda Claeys 《Fullerenes, Nanotubes and Carbon Nanostructures》2013,21(4):599-627
Abstract Aerosol routes were used to produce fullerene particles in the nanometer size range. Particle formation mechanisms at processing temperatures of 400-700°C were studied by measuring particle number and mass size distributions in the gas phase by a differential mobility analyzer and a low-pressure impactor respectively. Subsequently, the foils of the impactor onto which fullerene particles were collected were examined by HPLC. 相似文献
53.
Antti Rostedt Anssi Arffman Kauko Janka Jaakko Yli-Ojanperä Jorma Keskinen 《Aerosol science and technology》2014,48(10):1022-1030
The Pegasor PPS-M sensor is an electrical aerosol sensor based on diffusion charging and current measurement without particle collection. In this study, the role and effect of each component in the instrument is discussed shortly and the results from a thorough calibration measurements are presented. A comprehensive response model for the operation of the PPS-M sensor was developed based on the calibration results and computational fluid dynamics (CFD) modeling results. The obtained response model, covering the effects of the particle charger, the mobility analyzer, and both diffusion and inertial losses, was tested in the laboratory measurements with polydisperse test aerosols, where a good correlation between the model and the measured results was found.
Copyright 2014 American Association for Aerosol Research 相似文献
54.
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This study analyses the role played by dynamic capability and intangible assets of international new ventures from developed
markets at the initial survival and growth stages of internationalization. 相似文献
55.
Three kinds of supporting material are needed for lectures: lecture notes, presentation material and guidance material for the lecturer. Current computer-aided presentation systems do not allow easy preparation and maintenance of these three interwoven materials. In this paper, we present the idea of three-level teaching material and describe a computer-based system (SHOW) that can be used to produce the different forms from a single source, and to show the presentation version in a lecturing situation. Novel features of the presentation part include abolition of the slide paradigm and discrimination of textual structures with colors during presentation. We also describe an empirical experiment on text discrimination techniques. It suggests that multiple color discrimination improves the learning of conceptually profound issues. 相似文献
56.
Taras Antal Emilia Harju Laura Pihlgren Mika Lastusaari Taina Tyystjärvi Jorma Hölsä Esa Tyystjärvi 《International Journal of Hydrogen Energy》2012
Radiation between 400 and 700 nm, used for oxygenic photosynthesis by cyanobacteria, algae and plants, represents only 44% of total solar energy while the range above 700 nm comprises 52%. An ability to use near infrared (NIR, 700–1200 nm) radiation would greatly improve the efficiency of photosynthesis, but NIR photons have too low energy to excite the photosystems of oxygenic photosynthesis. Here we show that a mechanism called photon up-conversion can turn NIR radiation into an energy source for photosynthesis. In the future, it may be possible to up-convert the NIR part of the solar energy flux to visible light for use in photo-induced biohydrogen production by oxygenic photosynthesis. 相似文献
57.
We study elastic traffic performance in time-slotted wireless random access networks, where the link access probabilities are adjusted at flow level each time a new flow (file transfer) arrives or a flow in progress terminates. By defining the capacity sets of such networks we carry out performance analysis in a dynamic setting, where the flows come and go and share the resources according to the balanced fairness principle. We derive flow throughput analytically for three special scenarios and devise an algorithm for general networks. At low loads, flow-optimized random access yields almost the same performance as optimal/deterministic scheduling. 相似文献
58.
Jorma Laaksonen Markus Koskela Sami Laakso Erkki Oja 《Pattern Analysis & Applications》2001,4(2-3):140-152
Self-Organising Maps (SOMs) can be used in implementing a powerful relevance feedback mechanism for Content-Based Image Retrieval
(CBIR). This paper introduces the PicSOM CBIR system, and describes the use of SOMs as a relevance feedback technique in it.
The technique is based on the SOM’s inherent property of topology-preserving mapping from a high-dimensional feature space
to a two-dimensional grid of artificial neurons. On this grid similar images are mapped in nearby locations. As image similarity
must, in unannotated databases, be based on low-level visual features, the similarity of images is dependent on the feature
extraction scheme used. Therefore, in PicSOM there exists a separate tree-structured SOM for each different feature type.
The incorporation of the relevance feedback and the combination of the outputs from the SOMs are performed as two successive
processing steps. The proposed relevance feedback technique is described, analysed qualitatively, and visualised in the paper.
Also, its performance is compared with a reference method. 相似文献
59.
Timo A. R?s?nen Jorma Koponen Hannu Lauri Matti Kummu 《Water Resources Management》2012,26(12):3495-3513
The Mekong River Basin in Southeast Asia is experiencing extensive hydropower development. Concerns have been raised about the consequences of the development for the ecosystems, livelihoods and food security in the region. The largest planned hydropower dam cascade in the basin, the Lancang-Jiang cascade, is currently under construction and already partly built into the Upper Mekong Basin, China. In this paper we assess the impact of the Lancang-Jiang cascade on downstream hydrology by using a combination of a hydrological model and a reservoir cascade optimization model. The hydrological changes were quantified in detail at the Chiang Saen gauging station in Thailand, the first gauge station downstream from the cascade, and in lesser detail at four other downstream locations in the Mekong mainstream. We found that on average the Lancang-Jiang cascade increased the December?CMay discharge by 34?C155?% and decreased the July?CSeptember discharge by 29?C36?% at Chiang Saen. Furthermore, the Lancang-Jiang cascade reduced (increased) the range of hydrological variability during the wet season (dry season) months. The dry season hydrological changes were significant also in all downstream gauging stations, even as far as Kratie in Cambodia. Thus the Mekong??s hydrological regime has been significantly altered by the Lancang-Jiang cascade, but what the consequences are for ecosystems and livelihoods, needs further study. 相似文献
60.
Reijo Kouhia Pekka Marjamki Jorma Kivilahti 《International journal for numerical methods in engineering》2005,62(13):1832-1856
Although there are many different algorithms for the integration of inelastic constitutive models, the fully implicit backward Euler method has become the most popular one. In this study further investigations on the accuracy of the backward Euler method have been carried out. Also the performance of the discontinuous Galerkin family and some implicit Runge–Kutta time integrators is evaluated. By using a simple scalar model problem accuracy of some integrators is studied when a single finite time step is applied. Conclusions drawn from this scalar model problem has been verified to apply also to a full six‐dimensional strain space formulation by numerical means. Special emphasis is placed on rate‐dependent inelastic creep models. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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