Sensorless speed detection of squirrel-cage induction machines using stator neutral point voltage harmonics

In this paper a sensorless speed detection method of induction squirrel-cage machines is presented. This method is based on frequency determination of the stator neutral point voltage primary slot harmonic, which is dependent on rotor speed. In order to prove method in steady state and dynamic conditions the simulation and experimental study was carried out. For theoretical investigation the mathematical model of squirrel cage induction machines, which takes into consideration actual geometry and windings layout, is used. Speed-related harmonics that arise from rotor slotting are analyzed using digital signal processing and DFT algorithm with Hanning window. The performance of the method is demonstrated over a wide range of load conditions.     

Trehalose improves flavour retention in dehydrated apricot puree

The influence of the addition of two sugars (trehalose and sucrose) on the retention of volatiles responsible for the characteristic aroma in dehydrated apricot puree was studied. Aroma compounds of fresh and both freeze‐dried and foam‐mat‐dried apricot puree were analysed by manual headspace solid‐phase microextraction coupled with gas chromatography (GC‐FID and GC‐MS). The best retention of aroma compounds in dehydrated apricot puree was obtained when trehalose was added, regardless of the dehydration process used (freeze drying or foam‐mat drying), although, generally, a much higher retention of flavour volatiles was obtained in freeze‐dried purees. Principal Component Analysis and Cluster Analysis were applied to all the apricot purees studied to obtain a simplified view of the relationship among the aroma compounds in dehydrated apricot purees. This study gives further insights into the mechanisms that occur when trehalose is applied as an additive and will enable the development of new processes to maximize this effect and to produce superior dried products.     

Differencing sea bass (Dicentrarchus labrax) fillets frozen in different conditions by impedance measurements

The potential of electrical impedance was investigated to differentiate thawed sea bass fillets (Dicentrarchus labrax) previously subjected to different freezing conditions. The HP 4284A Precise LCR meter was used to measure impedance magnitude (|Z|) and phase (?) at 27 frequencies from 0.1 to 1000 kHz. A needle‐type multi electrode array was tested as a probe for impedance measurements. The study showed that fast and non‐invasive control method based on measurement of ? on thawed fillets could assess the freezing conditions of white fish at higher frequencies of measurements (500–1000 kHz). The advantages of ? when compared with |Z| include its independence on temperature, on puncture depth of the probe and on duration of storage prior to freezing. Usage of a needle‐type multi electrode array reduced the effect of muscle tissue anisotropy; however, even at 1 MHz, the differences in electrical measurements varied around 10–11% depending on muscle fibre direction.     

A state of the art in structured light patterns for surface profilometry

Shape reconstruction using coded structured light is considered one of the most reliable techniques to recover object surfaces. Having a calibrated projector-camera pair, a light pattern is projected onto the scene and imaged by the camera. Correspondences between projected and recovered patterns are found and used to extract 3D surface information. This paper presents an up-to-date review and a new classification of the existing techniques. Some of these techniques have been implemented and compared, obtaining both qualitative and quantitative results. The advantages and drawbacks of the different patterns and their potentials are discussed.     

About regression-kriging: From equations to case studies

This paper discusses the characteristics of regression-kriging (RK), its strengths and limitations, and illustrates these with a simple example and three case studies. RK is a spatial interpolation technique that combines a regression of the dependent variable on auxiliary variables (such as land surface parameters, remote sensing imagery and thematic maps) with simple kriging of the regression residuals. It is mathematically equivalent to the interpolation method variously called “Universal Kriging” (UK) and “Kriging with External Drift” (KED), where auxiliary predictors are used directly to solve the kriging weights. The advantage of RK is the ability to extend the method to a broader range of regression techniques and to allow separate interpretation of the two interpolated components. Data processing and interpretation of results are illustrated with three case studies covering the national territory of Croatia. The case studies use land surface parameters derived from combined Shuttle Radar Topography Mission and contour-based digital elevation models and multitemporal-enhanced vegetation indices derived from the MODIS imagery as auxiliary predictors. These are used to improve mapping of two continuous variables (soil organic matter content and mean annual land surface temperature) and one binary variable (presence of yew). In the case of mapping temperature, a physical model is used to estimate values of temperature at unvisited locations and RK is then used to calibrate the model with ground observations. The discussion addresses pragmatic issues: implementation of RK in existing software packages, comparison of RK with alternative interpolation techniques, and practical limitations to using RK. The most serious constraint to wider use of RK is that the analyst must carry out various steps in different software environments, both statistical and GIS.     

Relationships between heterotrophic bacteria and cyanobacteria in the northern Adriatic in relation to the mucilage phenomenon

High variability of heterotrophic bacterial (HB; 0.1.10(9)-6.10(9) cells L(-1)), nanoflagellates (HNF; 0.02.10(6)-2.4.10(6) cells L(-1)) and cyanobacterial (CB; 10(6)-700.10(6) cells L(-1)) abundances were observed during approximately monthly measurements at six stations along the transect Po Delta-Rovinj from March 1999 to August 2002. Substantially higher values were observed during the stratification period (June-September) in the surface layer of the western stations that were under more direct influence of Po River discharges. Changes of the HB abundance were significantly correlated with temperature in the entire water column and chlorophyll a (Chla) concentration in the surface layer. The nutrients did not look to have directly influenced the HB growth, except orthophosphate in the eastern, more oligotrophic part of transect, where probably HB efficiently competed with phytoplankton for this nutrient. Temperature was also important for CB growth that, however, appeared to occur more intensively in waters with low nutrient concentrations. Probably, in these conditions CB can still develop, while larger autotrophs are strongly nutrient limited. In the upper water column of reduced salinity (35-37), the contributions of CB carbon biomass to the total picoplankton biomass (CB+HB) were mostly larger than 30% (up to 80%) in years with mucilage events (1991, 2000-2002) than in other years. For example, in 1999 only a few values were higher than 30% (up to 50%). In abundant presence of mucilaginous aggregates (e.g. in June 2000 and late June 2002) the chlorophyll a ascribed to CB accounted for much larger portions of total measured Chla. From these results it was concluded that cyanobacteria during mucilage events may play a substantially increased role both as primary producers and prey within the microbial loop of the northern Adriatic.     

The potential of immersive virtual reality for representations in design education

Virtual Reality - This paper examines the potential of immersive virtual reality technology for design education. A quasi-experimental study has been conducted with 40 students of different...