Search results for "sampling"
showing 10 items of 788 documents
Measurement of transport phenomena of volatile compounds: A review
2008
International audience; Measurement of the transport phenomena of volatile compounds is a central preoccupation in food flavour and is the subject of the present paper. After a theoretical reminder concerning transport phenomena, the methods used for the measurement of diffusion and mass transfer of volatile compounds are described with their principles, main advantages and drawbacks. These methods are illustrated by some results obtained for flavoured model food products.Several methods characterized by the type of diffusion coefficient measured, the method basis, the scale at which diffusion is measured and the means used to detect the diffusing molecule, are available to determine diffus…
Using the ARP-03 for high-resolution mapping of calcic horizons
2013
A b s t r a c t. The aim of this work is to present a fast and cheap method for high-resolution mapping of calcic horizons in vineyards based on geoelectrical proximal sensing. The study area, 45 ha located in southern Sicily (Italy), was characterized by an old, partially dismantled marine terrace and soils with a calcic horizon at different depths. The geoelectrical investigation consisted of a survey of the soil electrical resistivity recorded with the Automatic Resistivity Profiling-03 sensor. The electrical resistivity values at three pseudo-depths, 0-50, 0-100 and 0-170 cm, were spatialized by means of ordinary kriging. A principal component analysis of the three electrical resistivit…
Determination in situ of the size distribution of the atmospheric aerosol
1975
Abstract The aim of the present study was the investigation of the in situ number/size distribution of the atmospheric aerosol in the size range between 0·05 and 2 μm radius. The experimental system consisted of a 4-channel integrating nephelometer, a 2-channel optical particle counter and a condensation nucleus counter. With a new inversion method, which had been tested previously by model computations and by measurements with artificial aerosols, the in situ size distribution was computed from the data of the experimental system.
Passive sampling of PAHs in indoor air in Nepal
1999
PAHs were sampled in ten homes in the Makwanpur region, Nepal. SPMDs and moss bags (Sphagnum girgensohnii) were used as passive samplers. Soot particles on the SPMD surfaces were also analyzed for PAHs. The overall PAH concentrations in SPMDs were significantly higher than those in moss bags. Total PAH mean concentrations of ten houses were 535μg/g lipid for SPMDs and 7.2 μg/g moss (dw) for moss bags. Ratios of phenanthrene/anthracene in indoor SPMDs and particulate matter varied from 2.9 to 3.5 and ratios of fluoranthene/pyrene varied from 1.1 to 1.4. The values for moss bags were respectively 1.7–3.6 and 0.8–2.4. These ratios indicate that the PAHs are from combustion origin. The PAH conc…
Nano- and microplastic analysis: Focus on their occurrence in freshwater ecosystems and remediation technologies
2019
Plastic pollution is a global problem since 2016 when its production reached 322 million tonnes, excluding fibers. Daily discharges of microplastics (MPs, defined as <5 mm in size) are estimated in the range of 50,000 up to 15 million particles, whereas no information on nanoplastic (NP, <100 nm) release is available yet. Different processes further degraded these materials producing more MPs and NPs. This review attempts to fill the void of information on the state-of-art analysis of MPs and NPs (recently identified as emerging contaminants) and provides a critical overview on modern instrumentation, newly developed workflows, and promising techniques for their characterization (Raman and …
Optimum pulse shape for minimum spectral occupancy in FSK signals
1984
The characteristics of a frequency shift keying (FSK) signal giving rise to maximum power within a prescribed frequency band are determined. The baseband pulse shape extends over any integer number of bit periods. An integral equation for the optimum pulse shape is derived and some simple properties of the solution are investigated. The equation has been solved for some values of the product of the prescribed band times the pulse duration and the signal shape is shown. Our results for the particular case of pulses only one bit period long are presented for purpose of comparison with results known in the literature. Plots of out-of-band power for some values of the prescribed band and of pul…
Border surveys and Time Location Sampling (TLS): an application on incoming tourism in Sicily
2012
The increasing need of reliable and detailed information at a regional and subregional level poses some challenges related with the measurement of tourists flows, for tourism destination management, planning and promotion purposes,. The aim of this work is twofold; first, it intends to analyse and discuss the main features and limits of the official border surveys conducted in the majority of world’s countries, within the framework of Time Location Sampling (TLS) design; second, it suggests the implementation of TLS design at a subnational level, by presenting the sampling design of the survey on incoming tourists in Sicily, carried out between 2009-2010, aimed at estimating the unobserved …
Assessing the quality of the sampling of fuel peat using computer simulation
1995
A simulation scheme to assess and improve the performance of the sampling of fuel peat is considered. The scheme provides a practical possibility to inspect all possible sources of variation and error. Test results from a district heating plant are reported.
A critical review on the implementation of static data sampling techniques to detect network attacks
2021
International audience; Given that the Internet traffic speed and volume are growing at a rapid pace, monitoring the network in a real-time manner has introduced several issues in terms of computing and storage capabilities. Fast processing of traffic data and early warnings on the detected attacks are required while maintaining a single pass over the traffic measurements. To palliate these problems, one can reduce the amount of traffic to be processed by using a sampling technique and detect the attacks based on the sampled traffic. Different parameters have an impact on the efficiency of this process, mainly, the applied sampling policy and sampling ratio. In this paper, we investigate th…
Improving the Representativeness of a Simple Random Sample: An Optimization Model and Its Application to the Continuous Sample of Working Lives
2020
This paper proposes an optimization model for selecting a larger subsample that improves the representativeness of a simple random sample previously obtained from a population larger than the population of interest. The problem formulation involves convex mixed-integer nonlinear programming (convex MINLP) and is, therefore, NP-hard. However, the solution is found by maximizing the size of the subsample taken from a stratified random sample with proportional allocation and restricting it to a p-value large enough to achieve a good fit to the population of interest using Pearson&rsquo