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The Double Chooz experiment presents improved measurements of the neutrino mixing angle θ 13 using the data collected in 467.90 live days from a detector positioned at an average distance of 1050 m from...
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The Double Chooz experiment presents improved measurements of the neutrino mixing angle θ 13 using the data collected in 467.90 live days from a detector positioned at an average distance of 1050 m from two reactor cores at the Chooz nuclear power plant. Several novel techniques have been developed to achieve significant reductions of the backgrounds and systematic uncertainties with respect to previous publications, whereas the efficiency of the \( {\overline{\nu}}_e \) signal has increased. The value of θ 13 is measured to be sin2 2θ 13 = 0.090 − 0.029 + 0.032 from a fit to the observed energy spectrum. Deviations from the reactor \( {\overline{\nu}}_e \) prediction observed above a prompt signal energy of 4 MeV and possible explanations are also reported. A consistent value of θ 13 is obtained from a fit to the observed rate as a function of the reactor power independently of the spectrum shape and background estimation, demonstrating the robustness of the θ 13 measurement despite the observed distortion. Keywords Oscillation Neutrino Detectors and Telescopes ArXiv ePrint: 1406.7763 An erratum to this article can be found at http://dx.doi.org/10.1007/JHEP02(2015)074
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The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques was conducted at the aerosol and cloud simulation chamber AIDA (Aerosol Interaction and Dynamics in the Atmosphere) at the Karlsruhe Institute of Tech...
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The AquaVIT-1 intercomparison of atmospheric water vapor measurement techniques was conducted at the aerosol and cloud simulation chamber AIDA (Aerosol Interaction and Dynamics in the Atmosphere) at the Karlsruhe Institute of Technology, Germany, in October 2007. The overall objective was to intercompare state-of-the-art and prototype atmospheric hygrometers with each other and with independent humidity standards under controlled conditions. This activity was conducted as a blind intercomparison with coordination by selected referees. The effort was motivated by persistent discrepancies found in atmospheric measurements involving multiple instruments operating on research aircraft and balloon platforms, particularly in the upper troposphere and lower stratosphere, where water vapor reaches its lowest atmospheric values (less than 10 ppm). With the AIDA chamber volume of 84 m~3, multiple instruments analyzed air with a common water vapor mixing ratio, by extracting air into instrument flow systems, by locating instruments inside the chamber, or by sampling the chamber volume optically. The intercomparison was successfully conducted over 10 days during which pressure, temperature, and mixing ratio were systematically varied (50 to 500 hPa, 185 to 243 K, and 0.3 to 152 ppm). In the absence of an accepted reference instrument, the absolute accuracy of the instruments was not established. To evaluate the intercomparison, the reference value was taken to be the ensemble mean of a core subset of the measurements. For these core instruments, the agreement between 10 and 150 ppm of water vapor is considered good with variation about the reference value of about ±10% (±1σ). In the region of most interest between 1 and 10 ppm, the core subset agreement is fair with variation about the reference value of ±20% (±1σ). The upper limit of precision was also derived for each instrument from the reported data. The implication for atmospheric measurements is that the substantially larger differences observed during in-flight intercomparisons stem from other factors associated with the moving platforms or the non-laboratory environment. The success of AquaVIT-1 provides a template for future intercomparison efforts with water vapor or other species that are focused on improving the analytical quality of atmospheric measurements on moving platforms.
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This article describes the setup and performance of the near and far detectors in the Double Chooz experiment. The electron antineutrinos of the Chooz nuclear power plant were measured in two identically designed detectors with di...
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This article describes the setup and performance of the near and far detectors in the Double Chooz experiment. The electron antineutrinos of the Chooz nuclear power plant were measured in two identically designed detectors with different average baselines of about 400 m and 1050 m from the two reactor cores. Over many years of data taking the neutrino signals were extracted from interactions in the detectors with the goal of measuring a fundamental parameter in the context of neutrino oscillation, the mixing angle $$\theta _{13}$$ θ 13 . The central part of the Double Chooz detectors was a main detector comprising four cylindrical volumes filled with organic liquids. From the inside towards the outside there were volumes containing gadolinium-loaded scintillator, gadolinium-free scintillator, a buffer oil and, optically separated, another liquid scintillator acting as veto system. Above this main detector an additional outer veto system using plastic scintillator strips was installed. The technologies developed in Double Chooz were inspiration for several other antineutrino detectors in the field. The detector design allowed implementation of efficient background rejection techniques including use of pulse shape information provided by the data acquisition system. The Double Chooz detectors featured remarkable stability, in particular for the detected photons, as well as high radiopurity of the detector components.
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In this paper an effective approach to estimate airfoil Turbulent Boundary-Layer Trailing-Edge (TBL-TE) far-field noise from measured surface pressure fluctuations (SPF) is evaluated. Measurements of both SPF and TE noise were per...
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In this paper an effective approach to estimate airfoil Turbulent Boundary-Layer Trailing-Edge (TBL-TE) far-field noise from measured surface pressure fluctuations (SPF) is evaluated. Measurements of both SPF and TE noise were performed on a NACA 0062 airfoil of 0.4 m chord at Reynolds numbers of 1.0-1.9 millions for various angles of attack. A non-homogeneously spaced array of five Kulite-sensors near the TE at x/c = 0.989 is employed to measure point spectra and spanwise two-point correlations of surface pressure fluctuations. Finally spanwise SPF length-scales are derived as function of frequency. Comparisons to measured TE noise and semi-empirical predictions of surface pressures and far-field noise show very good agreement. It is found, that the proposed method can cover a larger frequency range than standard acoustic measurement techniques. Therefore it can provide valuable assistance in extending spectra obtained conventionally, mainly to low frequencies. Furthermore, pressure and suction side contributions to far-field noise can be obtained separately.
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Understanding natural climate variability and its driving factors is crucial to assessing future climate change. Therefore, comparing proxy-based climate reconstructions with forcing factors as well as comparing these with paleo-c...
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Understanding natural climate variability and its driving factors is crucial to assessing future climate change. Therefore, comparing proxy-based climate reconstructions with forcing factors as well as comparing these with paleo-climate model simulations is key to gaining insights into the relative roles of internal versus forced variability. A review of the state of modelling of the climate of the last millennium prior to the CMIP5-PMIP3 (Coupled Model Intercom-parison Project Phase 5-Paleoclimate Modelling Intercom-parison Project Phase 3) coordinated effort is presented and compared to the available temperature reconstructions. Simulations and reconstructions broadly agree on reproducing the major temperature changes and suggest an overall linear response to external forcing on multidecadal or longer timescales. Internal variability is found to have an important influence at hemispheric and global scales. The spatial distribution of simulated temperature changes during the transition from the Medieval Climate Anomaly to the Little Ice Age disagrees with that found in the reconstructions. Thus, either internal variability is a possible major player in shaping temperature changes through the millennium or the model simulations have problems realistically representing the response pattern to external forcing. A last millennium transient climate response (LMTCR) is defined to provide a quantitative framework for analysing the consistency between simulated and reconstructed climate. Beyond an overall agreement between simulated and reconstructed LMTCR ranges, this analysis is able to single out specific discrepancies between some reconstructions and the ensemble of simulations. The disagreement is found in the cases where the reconstructions show reduced covariability with external forcings or when they present high rates of temperature change.
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In this paper an effective approach to estimate airfoil Turbulent Boundary-Layer Trailing-Edge (TBL-TE) far-field noise from measured surface pressure fluctuations (SPF) is evaluated. Measurements of both SPF and TE noise were per...
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In this paper an effective approach to estimate airfoil Turbulent Boundary-Layer Trailing-Edge (TBL-TE) far-field noise from measured surface pressure fluctuations (SPF) is evaluated. Measurements of both SPF and TE noise were performed on a NACA 0012 airfoil of 0.4 m chord at Reynolds numbers of 1.0-1.9 millions for various angles of attack. A non-homogeneously spaced array of five Kulite-sensors near the TE at x/c = 0.989 is employed to measure point spectra and spanwise two-point correlations of surface pressure fluctuations. Finally spanwise. SPF length-scales are derived as function of frequency. Comparisons to measured. TE noise and semi-empirical predictions of surface pressures and far-field noise show very good agreement. It is found, that the proposed method can cover a larger frequency range than standard acoustic measurement techniques. Therefore it can provide valuable assistance in extending spectra obtained conventionally, mainly to low frequencies. Furthermore, pressure and suction side contributions to far-field noise can be obtained separately.
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In this study, we assess how the anthropogeni- cally induced increase in greenhouse gas concentrations affects the climate of central and southern South America. We utilise two regional climate simulations for present day (PD) and...
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In this study, we assess how the anthropogeni- cally induced increase in greenhouse gas concentrations affects the climate of central and southern South America. We utilise two regional climate simulations for present day (PD) and pre-industrial (PI) times. These simulations are compared to historical reconstructions in order to investigate the driving processes responsible for climatic changes between the different periods. The regional climate model is validated against observations for both re-analysis data and GCM-driven regional simulations for the second half of the 20th century. Model biases are also taken into account for the interpretation of the model results. The added value of the regional simulation over global-scale modelling relates to a better representation of hydrological processes that are particularly evident in the proximity of the Andes Mountains. Climatic differences between the simulated PD minus PI period agree qualitatively well with proxy-based temperature reconstructions, albeit the regional model overestimates the amplitude of the temperature increase. For precipitation the most important changes between the PD and PI simulation relate to a dipole pattern along the Andes Mountains with increased precipitation over the southern parts and reduced precipitation over the central parts. Here only a few regions show robust similarity with studies based on empirical evidence. However, from a dynamical point-of-view, atmospheric circulation changes related to an increase in high-latitude zonal wind speed simulated by the regional climate model are consistent with numerical modelling studies ddressing changes in greenhouse gas concentrations. Our results indicate that besides the direct effect of greenhouse gas changes, large-scale changes in atmospheric circulation and sea surface temperatures also exert an influence on temperature and precipitation changes in southern South America. These combined changes in turn affect the relationship between climate and atmospheric circulation between PD and PI times and should be considered for the statistical reconstruction of climate indices calibrated within present- day climate data.
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An experimental investigation into the properties of the vortex wake behind a wind turbine rotor has been carried out at model scale, using Particle Image Velocimetry (PIV). The two-blade model was operated at tip speed ratios in ...
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An experimental investigation into the properties of the vortex wake behind a wind turbine rotor has been carried out at model scale, using Particle Image Velocimetry (PIV). The two-blade model was operated at tip speed ratios in the range λ = 3-8, and chord Reynolds numbers Re = 6400 - 16 000. The blades were untwisted, with flat-plate aerofoil profile. Measurements of wake velocity and vorticity were obtained for a two-dimensional flow field representing an axial cross-section of the wake, extending 2.9 rotor diameters downstream of the rotor. The vorticity maps were compared with calculations made using the Rotor Vortex Lattice Method (ROVLM), an inviscid free-wake code recently developed at the University of Stuttgart. The PIV and ROVLM data show qualitative agreement in terms of the shape of the wake boundary, including downstream wake contraction, and quantitative agreement in terms of the tip vortex pitch. It appears that the fundamental behaviour of the helical vortex wake may be relatively insensitive to blade chord Reynolds number, so long as similarity of tip speed ratio is observed.
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This study aims to evaluate the direct effects of anthropogenic deforestation on simulated climate at two contrasting periods in the Holocene, ～ 6 and ～ 0.2 k BP in Europe. We apply We apply the Rossby Centre regional climate mo...
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This study aims to evaluate the direct effects of anthropogenic deforestation on simulated climate at two contrasting periods in the Holocene, ～ 6 and ～ 0.2 k BP in Europe. We apply We apply the Rossby Centre regional climate model RCA3, a regional climate model with 50 km spatial resolution, for both time periods, considering three alternative descriptions of the past vegetation: (ⅰ) potential natural vegetation (Ⅴ) simulated by the dynamic vegetation model LPJ-GUESS, (ⅱ) potential vegetation with anthropogenic land use (deforestation) from the HYDE3.1 (History Database of the Global Environment) scenario (Ⅴ+ H3.1), and (ⅲ) potential vegetation with anthropogenic land use from the KK10 scenario (Ⅴ + KK10). The climate model results show that the simulated effects of deforestation depend on both local/regional climate and vegetation characteristics. At ～ 6 k BP the extent of simulated deforestation in Europe is generally small, but there are areas where deforestation is large enough to produce significant differences in summer temperatures of 0.5-1 ℃. At ～0.2kBP, extensive deforestation, particularly according to the KK10 model, leads to significant temperature differences in large parts of Europe in both winter and summer. In winter, deforestation leads to lower temperatures because of the differences in albedo between forested and unforested areas, particularly in the snow-covered regions. In summer, deforestation leads to higher temperatures in central and eastern Europe because evapotranspiration from unforested areas is lower than from forests. Summer evaporation is already limited in the southernmost parts of Europe under potential vegetation conditions and, therefore, cannot become much lower. Accordingly, the albedo effect dominates in southern Europe also in summer, which implies that deforestation causes a decrease in temperatures. Differences in summer temperature due to deforestation range from -1 ℃ in south-western Europe to +1 ℃ in eastern Europe. The choice of anthropogenic land-cover scenario has a significant influence on the simulated climate, but uncertainties in palaeoclimate proxy data for the two time periods do not allow for a definitive discrimination among climate model results.
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This article presents a reliability analysis method and a series of case studies of different architectures for interlock systems of large and complex research infrastructures. Interlock systems play a crucial role in the protecti...
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This article presents a reliability analysis method and a series of case studies of different architectures for interlock systems of large and complex research infrastructures. Interlock systems play a crucial role in the protection of different types of machines, including present and future particle accelerators and fusion experiments. These infrastructures require multibillion Euros investments and accidents could cause irreparable damage. Protection systems are needed to prevent damage from an unintended release of large amounts of stored energy or power. Interlock systems define the signal exchange between the sensors that detect non-nominal conditions and the actuators that bring the machine into a safe state through a protection shutdown. The design of machine protection systems in general and interlock systems, in particular, is caught between the desired machine safety and machine availability, and the requirements vary between different infrastructures. For some infrastructures, interlock systems must be designed to strictly avoid unintentional shutdowns, as these can have a significant impact on the lifetime of vital equipment or their primary operational purpose. For others, unintentional shutdowns due to a failure in the interlock system are acceptable as long as their number is small compared to protection shutdowns caused by failures of other equipment, in order to maximize their scientific output. The case studies presented in the article compare different interlock architectures based on the probability of specific failure scenarios occurring.
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