Slip-ring induction generator with direct output voltage control

The main advantage of the variable speed power generation systems with slip-ring induction generator related to cage or synchronous generator is low power and low costs of the power electronics. As the speed range is limited the power converter can be designed on few percent of the generator power, that provide lower losses and costs and higher efficiency. The Direct Voltage Control method of slip ring induction generator is presented in this paper. This method bases on stator voltage vector feedback, that permits the generator can operate as a stand-alone set e.g. in island power systems. Moreover an autonomous operation mode provide the grid connected generator is useful even after the mains outage and can supply isolated part of a grid load. The Direct Voltage Control method uses a space vector theory. A stator voltage vector represented in the reference frame rotating with synchronous speed has fixed magnitude and position when the stator voltage amplitude, frequency and phase are fixed. To obtain the fixed values of the voltage vector amplitude and position, two voltage regulators are applied. One of them based on reference and actual stator voltage amplitude is responsible for rotor current amplitude. The second regulator based on reference and actual stator voltage angle referred to synchronous frame is responsible for rotor current frequency. Applied stator voltage control method do not use any information about the rotor speed or position, therefore it can be called sensorless. Moreover an instantaneous value of the generated stator voltage is controlled that provide not only fixed voltage frequency and amplitude but also controlled voltage phase. This is an important advantage in grid and generated voltage synchronization process

Properties of AC 8 wearing course mix produced in lowered temperatures with foamed bitumen in scope of Polish requirements

W artykule przedstawiono wyniki badań podstawowych parametrów fizycznych i mechanicznych betonu asfaltowego (AC 8S) wytwarzanego w obniżonych temperaturach w technologii asfaltu spienionego, zagęszczanego w temperaturze 95ºC, rozszerzone o ocenę wrażliwości temperaturowej mieszanki mineralno-asfaltowej. W celach porównawczych zaprezentowano wyniki badań mieszanki referencyjnej, tj. produkowanej w tradycyjnej technologii „na gorąco”, zagęszczanej w temperaturze 140ºC. W referencyjnej mieszance AC 8S stosowano asfalt 50/70, natomiast w mieszane wytwarzanej w obniżonych temperaturach użyto asfaltu 50/70 modyfikowanego woskiem syntetycznym Fischera-Tropscha (FT). Na podstawie uzyskanych wyników dokonano porównania obu mieszanek w zakresie zawartości wolnych przestrzeni w próbkach, wrażliwości na oddziaływanie wody z jednym cyklem zamrażania (ITSR) zgodnie z krajowymi procedurami badawczymi zamieszczonymi w Wymaganiach Technicznych WT-2 z 2010 r. i WT-2 z 2014 r., oraz modułów sztywności (Sm) oznaczonych w schemacie pośredniego rozciągania (IT-CY) pomierzonych w temperaturze -10ºC, 0ºC, 10ºC i 25ºC. Ponadto, w ramach analiz potwierdzono zależności między zawartością wolnych przestrzeni a wybranymi parametrami mechanicznymi rozpatrywanych mieszanek mineralno-asfaltowych. Stwierdzono, że beton asfaltowy wytwarzany w innowacyjnym procesie z zastosowaniem asfaltu spienionego modyfikowanego woskiem FT, zagęszczany w 95ºC uzyskał porównywalne właściwości do tradycyjnej mieszanki mineralno-asfaltowej zagęszczanej w temperaturze o 45ºC wyższej, spełniając przy tym krajowe wymagania.The article presents the results obtained from testing of asphalt concrete with foamed bitumen produced and compacted at lowered temperatures. The basic physical characteristics along with moisture resistance and stiffness moduli performance in different testing temperatures of a total of three mixes are shown. A reference hot-mix is compared with two low temperature mixes: one based on neat 50/70 bitumen and a second based on a Fischer-Tropsch wax modified binder. The results show that it is possible to produce a low temperature mix that is performing as well as the reference mixture

Modelling flows in the Kaczawa River for for the years 2030 and 2050 (summer half-year)

W pracy zaprezentowano wpływ potencjalnych zmian klimatu na odpływ w zlewni Kaczawy w perspektywie lat 2030 i 2050 dla półrocza letniego. Odpływ dla badanych okresów obliczono z wykorzystaniem modelu opad-odpływ NAM. Dane meteorologiczne wymagane przez model NAM zostały wygenerowane za pomocą modelu SWGEN, którego kalibrację przeprowadzono na podstawie dobowych danych z lat 1981-2000, obejmujących obserwacje maksymalnej, minimalnej, średniej temperatury powietrza, wartości opadu atmosferycznego i usłonecznienia. Wartości promieniowania całkowitego oszacowano za pomocą wzoru Blacka. Brakujące charakterystyki zbiorcze zostały interpolowane na podstawie istniejących danych. Symulacje przeprowadzono dla aktualnych warunków klimatycznych oraz trzech wybranych scenariuszy: GISS, CCCM oraz GFDL. Wartości parowania potencjalnego oszacowano, wykorzystując zmodyfikowany wzór Turca. Zmiany odpływu zobrazowano rozkładami prawdopodobieństwa i charakterystykami opisowymi. Symulacje umożliwiły określenie potencjalnych zmian średniego dobowego odpływu Kaczawy na wodowskazie Piątnica. Na podstawie przeprowadzonych symulacji stwierdzono wzrost prawdopodobieństwa wstąpienia przepływów ekstremalnych.The paper presents an effect of potential climate changes on water runoff from the Kaczawa River catchment in summer halves of the years 2030 and 2050. The runoffs for the studied periods were calculated using the rainfall-runoff model NAM. Meteorological data required by the NAM model were generated by the model SWGEN calibrated on daily data from the years 1981-2000. Data included observations of the maximum, minimum and average air temperature, precipitation and sunshine. The values of global radiation were estimated using the Black's formula. Missing characteristics were interpolated from the existing data. Simulations were performed for current climatic conditions and for the three selected scenarios: GISS, CCCM and GFDL. The values of potential evaporation were estimated using the modified Turc's formula. Changes in the outflow were illustrated by probability distribution functions and descriptive characteristics. Simulations enabled identification of potential changes in mean daily discharge at the gauge Piątnica. Based on simulations, an increase in the probability of extreme runoffs is expected

A modeling framework to assess the impact of climate change on river runoff

Global climate change is anticipated to have consequences on water resources and the environment both at global and local/regional levels. Efforts towards proper management of future water resources and resolving potential water-related conflicts require the formulation of appropriate techniques to downscale the output of global climate models (GCM) to local conditions for hydrologic prediction. The paper presents an integrated framework for modeling the impact of climate change on river runoff that combines methodology for downscaling climate change scenarios for a basin scale with a hydrological model to estimate the impact of climate change on a river runoff. The modeling framework uses long-term observations of meteorological and hydrological variables together with a climate change scenario to provide a projection of future flows for the specified time horizon. The framework is based on a spatial weather generator and a distributed rainfall-runoff model. Such a configuration enables a reflection of the uncertainty of future conditions by running multiple realizations of future conditions, and also take into account the spatial variability of hydrological properties in the catchment by maintaining the physical details at a given grid size. The performance of the framework was presented for the Kaczawa basin that is one of the main left bank tributaries of the Odra River – the second biggest river in Poland. The results show simulated changes of the future river flow regime caused by climatic changes for two time horizons: 2040 and 2080

Search for supersymmetry in events with large missing transverse momentum, jets, and at least one tau lepton in 20 fb−1 of √s= 8 TeV proton-proton collision data with the ATLAS detector

© 2014, The Author(s). A search for supersymmetry (SUSY) in events with large missing transverse momentum, jets, at least one hadronically decaying tau lepton and zero or one additional light leptons (electron/muon), has been performed using 20.3fb−1of proton-proton collision data at √ s= 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No excess above the Standard Model background expectation is observed in the various signal regions and 95% confidence level upper limits on the visible cross section for new phenomena are set. The results of the analysis are interpreted in several SUSY scenarios, significantly extending previous limits obtained in the same final states. In the framework of minimal gauge-mediated SUSY breaking models, values of the SUSY breaking scale Λ below 63 TeV are excluded, independently of tan β. Exclusion limits are also derived for an mSUGRA/CMSSM model, in both the R-parity-conserving and R-parity-violating case. A further interpretation is presented in a framework of natural gauge mediation, in which the gluino is assumed to be the only light coloured sparticle and gluino masses below 1090 GeV are excluded