Improving subband spectral estimation using modified AR model

It has already been shown that spectral estimation can be improved when applied to subband outputs of an adapted filterbank rather than to the original fullband signal. In the present paper, this procedure is applied jointly to a novel predictive autoregressive (AR) model. The model exploits time-shifting and is therefore referred to as time-shift AR (TSAR) model. Estimators are proposed for the unknown TS-AR parameters and the spectrum of the observed signal. The TS-AR model yields improved spectrum estimation by taking advantage of the correlation between subseries that after decimation. Simulation results on signals with continuous and line spectra that demonstrate the performance of the proposed method are provided

Sonar and radar SAR processing for parking lot detection

In this paper, SAR processing algorithms for automotive applications are presented and illustrated on data from non-trivial test scenes. The chosen application is parking lot detection. Laboratory results obtained with a teaching sonar experiment emphasize the resolution improvement introduced with range-Doppler SAR processing. A similar improvement is then confirmed through full scale measurements performed with an automotive radar prototype operating at 77GHz in very close range conditions, typical of parking lot detection. The collected data allows a performance comparison between different SAR processing algorithms for realistic targets

Water resources analysis of the Rječina karst spring and river (Dinaric karst)

The paper deals with complex hydrological/hydrogeological behaviour in the Rječina karst spring and river basin located in the north-western part of the deep and developed Croatian Dinaric karst. The Rječina Spring is one of the major karst springs in Croatia, used for water supply of Rijeka City and its surrounding area. Beside the use of Rječina spring for water supply, the development of the Rijeka hydroelectric power plant (HEPP) also changed hydrological and hydrogeological regime of the whole catchment. In order to analyse the anthropogenic influences in the system, hydrological analysis of the Rječina river and spring discharge was done, as well as the analysis of the available data of groundwater measurements. The analysis showed that, due to the increase of water caption and decrease of precipitation, the average annual spring discharge decreased for approximately 25% in the 1980-2016 period. Detailed analysis of groundwater measurements indicated aquifer behaviour and the need for additional measurements and catchment delineation.Key words: hydrology, hydrogeology, karst, Rječina Spring, Rječina River, Dinaric karst.Analiza vodnih virov kraškega izvira in reke Rječina (Dinarski kras)Članek obravnava zapletene hidrološke/hidrogeološke razmere v zaledju kraškega izvira in reke Riečine v severozahodnem delu globokega in dobro razvitega hrvaškega Dinarskega krasa. Izvir Rječina je eden največjih kraških izvirov na Hrvaškem, zajet je za oskrbo s pitno vodo za mesto Reka in njeno okolico. Poleg rabe izvira Rječine za oskrbo z vodo je razlog za spremenjen hidrološki in hidrogeološki režim celotnega zaledja tudi gradnja hidroelektrarne Reka (HEPP). Za analizo antropogenih vplivov na sistem smo zato naredili hidrološko analizo pretokov reke in izvira Rječina pa tudi analizo razpoložljivih podatkov merjenja podzemne vode. Analiza je pokazala, da se je zaradi povečanja zajemanja vode in zmanjšanja količine padavin povprečen letni pretok izvira v obdobju 1980–2016 zmanjšal za približno 25 %. Podrobna analiza meritev podzemne vode je nakazala značilnosti delovanja vodonosnika ter pokazala potrebo po dodatnih meritvah in določitvi zaledja izvira.Ključne besede: hidrologija, hidrogeologija, kras, izvir Rječina, reka Rječina, Dinarski kras

Different Climate Changes at Two Locations on a Small Karst Island Korčula (Adriatic Sea, Croatia)

The article analyses the series of annual, monthly and daily air temperatures and annual and monthly rainfall at two meteorological stations in Vela Luka and Korčula on the island of Korčula (Croatia), for which there are long time series of observations. Today’s locations of meteorological stations are only 33.5 km apart. The average annual air temperature at the Vela Luka station is on average 1°C lower than that measured at the Korčula station. A significant upward trend in mean annual and mean monthly air temperatures was observed at both stations, with the increase being much milder at the Vela Luka station. Warming processes are significantly faster at the Korčula station than at the Vela Luka station. Significantly different values of air temperatures, and in particular the fact of different reactions of air temperatures to climate change at two stations, can be explained by their local position in relation to the open sea and orography of the surrounding terrain. While the Vela Luka station is exposed to the open sea and away from the mainland, at Korčula station the impact of the sea is less significant because the sea is located in a narrow channel between the island of Korčula and the Pelješac peninsula. The distance of the Korčula meteorological station from the Pelješac peninsula and the mainland is significantly smaller, which affects the faster trend of rising air temperatures at this station than at the Vela Luka station, where the influence of the sea mitigates the effect of global warming. Orography and proximity to land affect significantly higher rainfall occurrences at Korčula station. Average annual rainfall at this station is 231 mm or 27.5% higher than at Vela Luka station. Both stations show a trend of decreasing annual rainfall

Hazards caused by natural and anthropogenic changes of catchment area in karst

International audienceDetermination of the catchment area is the starting point in most hydrological analyses. It serves as a basis for many hydrological and water resources management calculations. The catchment boundaries and areas in karst regions are often fragmented and not accurately known. They can change over time due to natural and anthropogenic causes. Natural and man-made processes cause changes of catchment area on different time and space scales. Human intervention, especially construction of dams and reservoirs, as well as interbasin water transfer through long tunnels and pipelines can introduce instantaneous, definite and hazardous change. This paper presents seven examples of natural and anthropogenic factors which influenced changes of catchment area in the Dinaric karst: 1) Closing of the Obod Estavelle in the Fatniceko polje; 2) Operation of the Zakucac hydroelectric power plant on the Cetina River; 3) Problems caused by Salakovac Reservoir; 4) Catastrophic flooding in the Cetinje Polje; 5) Regulation and canalization of the Trebi?njica River; 6) Building of the underground hydroelectric power plant Ombla; 7) An earthquake in Southern Croatia and Western Herzegovina

Analysis of Long-Term (1878-2004) Mean Annual Discharges of the Karst Spring Fontaine de Vaucluse (France)

Statistical analyses have been carried out on a long-term (1878-2004) series of mean annual discharges of the famous karst spring Fontaine de Vaucluse (France) and the mean annual rainfall in its catchment. The Fontaine de Vaucluse is a typical ascending karst spring situated in the south-eastern region of France. The spring has an average discharge of 23.3 m3/s. The average annual rainfall is 1096 mm. Its catchment area covers 1130 km2. Using the rescaled adjusted partial sums (RAPS) method the existence of next five statistically significant different sub-series was established: 1) 1878-1910: 2) 1911-1941; 3) 1942-1959: 4) 1960-1964; 5) 1965-2004. The different spring discharge characteristics during this long period (1878-2004) can be caused by natural climatic variations, by anthropogenic influences, and possibly by climate changes. At this moment it should be stressed that objective and scientifically based reasons for different hydrological behaviour in five time sub-periods could not be found