Literatura científica selecionada sobre o tema "Multi-Instrumental observations"

Unique in the regime of wide-field astronomy is the multi-object spectroscopy system ‘FLAIR’ developed for the UK Schmidt Telescope (UKST). The current system can perform simultaneous observations of ∼ 90 objects across 40 sq. degrees of sky. FLAIR has given a whole new platform for performing astronomical observations with a Schmidt telescope in a non-photographic role. The system is simple to operate, highly stable, easy to interchange with standard photography and outclasses single-object spectroscopy systems on 2.0 m class telescopes for many types of observation. The system has continued to be developed to enhance its flexibility, robustness and versatility, culminating recently in the commissioning of new fibre feeds and formats. The facility to observe independent standard stars, and the capability of observing objects in two UKST fields in a single night has recently been demonstrated. FLAIR is a powerful, cost-effective addition to the instrumental repertoire of the Anglo-Australian Observatory in a way that was not even remotely envisaged when the UKST was built.

AbstractIn order to study the role played by the magnetic fields in the dynamics of the interstellar medium (ISM) a two-channel imaging polarimeter (IMPOL) has been constructed. The instrument is capable of multi-wavelength observations in the visible and very near infrared (IR) wavelengths, has a sensitive CCD detector and a built-in acquisition and guidance unit. When used with a 1.2m, f/13 telescope IMPOL gives a field of view of 6 × 6 arcmin with an angular resolution of 2" so that it is well-suited to observe both faint extended objects and moderately crowded stellar fields. The instrumental polarization is less than 0.05% and the accuracy of the measurements is primarily limited by photon noise in a typical observation. In this paper, we present a brief description of the instrument and observational techniques, as well as the results of a successful observation of a molecular cloud close to the open cluster IC 5146.

A novel methodology is formulated and investigated on test cases for the reconstruction of complete vertical aerosol extinction profiles in which a synergy of remote, in-situ, and airborne measurements is utilized. The GRASP Open aerosol retrieval algorithm is supplied with remote LIDAR and sunphotometer data to obtain aerosol extinction profiles within the LIDAR’s operation range for coarse and fine aerosol modes separately. These are supplemented with ground-based in-situ measurements of particle size distribution that are translated to coarse and fine aerosol extinction coefficients with the use of Mie theory. UAV-based observations with optical particle counters are included to add information on vertical aerosol variability in the near-surface region. The profiles are closed with an analytical interpolation that is fine-tuned to produce continuous and smooth extinction profiles throughout the whole troposphere that are in agreement with columnar aerosol optical depth measurements. We present the possibility of reconstructing a complete and calibrated aerosol extinction profile, based on the case studies at a Central European background station. We include data-denial experiments to show that the inclusion of UAV-based measurements improves such reconstructions by providing crucial information on aerosol profiles near the ground. The proposed methodology can prove to be a potent tool for studies of aerosol concentration and evolution, especially when the majority of the pollution resides near the surface. Such conditions are prevalent in many highly industrialized regions, including central and southern Poland.

Abstract. The scarcity of long instrumental records, uncertainty in reconstructions, and insufficient skill in model simulations hamper assessing how regional precipitation changed over past centuries. Here, we use standardized precipitation data to compare a regional climate simulation, reconstructions, and long observational records of seasonal (March to July) mean precipitation in England and Wales over the past 350 years. The Standardized Precipitation Index is a valuable tool for assessing agreement between the different sources of information, as it allows for a comparison of the temporal evolution of percentiles of the precipitation distributions. These evolutions are not consistent among reconstructions, a regional simulation, and instrumental observations for severe and extreme dry and wet conditions. The lack of consistency between the different data sets may be due to the dominance of internal climate variability over the impact of natural exogenous forcing conditions on multi-decadal timescales. The disagreement between sources of information reduces our confidence in inferences about the origins of hydroclimate variability for small regions. However, it is encouraging that there is still some agreement between a regional simulation and observations. Our results emphasize the complexity of hydroclimate changes during the recent centuries and stress the necessity of a thorough understanding of the processes affecting forced and unforced precipitation variability.

La couronne solaire est chauffée à plus de 1 MK. L'une des principales théories sur la formation de la couronne (Parker, 1988) suggère que l'énergie magnétique est dissipée dans la couronne par un grand nombre d'événements de chauffage impulsifs et peu énergétiques (1E24 ergs), appelés « nanoflares ». Le 30 mai 2020, lors de sa première séquence d'observation à haute résolution spatiale et temporelle, 1463 petits « événements » EUV de petite taille (400 - 4000 km) et de court temps de vie (10-200 s) ont été détectés dans le Soleil calme (QS) par l'imageur UV à haute résolution HRIEUV (174 Angström), à bord de Solar Orbiter. J'ai étudié si ces événements sont la signature du chauffage par nanoflares.Comme HRIEUV est sensible à une gamme de température continue, en particulier entre 1 MK et 0.3 MK, mon objectif était de vérifier si ces événements atteignent des températures coronales et, par conséquent, s'ils contribuent directement au chauffage coronal.Le 30 mai 2020, seules les données de SDO/AIA permettaient d'effectuer un diagnostic de température. C'est dans ce but que j'ai appliqué la méthode des « décalages temporels » aux canaux EUV de AIA. Ces décalages sont des signatures de chauffage ou de refroidissement pour des températures supérieures à 1 MK, au-delà de laquelle cinq des six canaux d'AIA ont leur pic de réponse. La comparaison des résultats entre les événements et le reste du QS a permis de conclure que les événements ont, pour la plupart, des décalages temporels inférieurs à la cadence d'AIA de 12 s. Des séquences d'observation ultérieures ont confirmé ces résultats avec une cadence d'AIA doublée. J'en ai déduit deux interprétations possibles : (1) les événements n'atteignent pas 1 MK, températures pour lesquelles les fonctions de réponse d'AIA se comportent de façon similaire ; (2) les temps de refroidissement sont trop courts pour que les décalages temporels soient résolus par AIA. Afin de mieux contraindre leur température, j'ai eu recours à la spectroscopie.J'ai donc analysé des observations coordonnées entre HRIEUV, AIA (imagerie), Solar Orbiter/SPICE et Hinode/EIS (spectroscopie) sur le QS, en 2022 et 2023. Tout d'abord, les événements sont détectés dans HRIEUV, puis identifiés dans AIA, ainsi que SPICE ou EIS. A partir des raies spectrales, j'ai construit des courbes de lumière et estimé la distribution de la densité en fonction de la température. J'ai conclu que l'émission de ces événements provient principalement de plasma froid (< 1 MK). Ainsi, la majorité d'entre eux ne contribuent pas directement au chauffage coronal.Afin de comprendre l'origine physique de ces événements, j'ai reproduit leurs signatures observationnelles avec le code d'évolution hydrodynamique 1D HYDRAD. Pour ce faire, j'ai calculé les courbes de lumière synthétiques de petites boucles soumises à un chauffage impulsif, en changeant les paramètres du modèle, tels que la longueur de la boucle ou l'amplitude du chauffage. J'ai cherché les paramètres qui reproduisent le mieux les observations, y compris le pic co-temporel des courbes de lumière. J'ai comparé les résultats pour deux types de boucles qui ont des propriétés très différentes : les boucles « chaudes » (T > 1E5 K) et les boucles « froides » (T < 1E5 K). Les résultats montrent que les boucles froides soumises à un chauffage impulsif sont de bons candidats pour expliquer l'origine des événements détectés par HRIEUV.En conclusion, ces événements ne sont probablement pas, pour la majeure partie d'entre eux, une signature du chauffage coronal, à moins que leur émission coronale ne soit inférieure aux limites instrumentales. Une des conséquences de ce travail est de réévaluer le rôle des petits événements EUV dans le chauffage coronal du QS, car ils pourraient jouer un rôle important dans le chauffage de la partie plus basse et plus froide de l'atmosphère solaire
The Solar corona temperature is maintained at more than 1 MK. One of the main theories of the coronal formation (Parker, 1988) suggests that the magnetic energy is dissipated into the corona through a high number of impulsive, low energetic (1E24 ergs) heating events, called “nanoflares.” On 30 May 2020, during its first high temporal and spatial resolutions observations, 1463 small (400 - 4000 km) and short-lived (10-200 s) EUV brightenings, referred to as “events”, were detected in the Quiet Sun (QS) by the high-resolution UV imager HRIEUV (174 Angström), on board Solar Orbiter. I tested the possibility that they might be signatures of nanoflare heating.As HRIEUV is sensitive to continuous temperature coverage, in particular between 1 MK and 0.3 MK, my goal was to verify if these events do reach coronal temperatures and, thus, if they contribute directly to the coronal heating.For the 30 May 2020 dataset, only SDO/AIA data were available to perform temperature diagnostics. To do so, I applied the “time lags” method to the coronal channels of AIA. This method provides signatures on plasma cooling or heating above 1 MK, as most AIA channels have their sensitivity peak at these temperatures. I compared the statistics between the events and the rest of the QS and concluded that the events are characterized by short time lags below the AIA cadence of 12 s. These results were confirmed by extending the study to later datasets using a higher AIA cadence of 6s. I proposed two possible interpretations: (1) the events peak below 1 MK, where the AIA response functions behave similarly; (2) the events' cooling time scale is too short to be resolved by the AIA cadence. Spectroscopic observations are thus necessary to better constrain the temperature of these events.To complete this work, I used co-temporal 2022 and 2023 QS data from HRIEUV, AIA (imagers), from Solar Orbiter/SPICE and HINODE/EIS (spectroscopy). I first detected events in HRIEUV and identified them in SPICE or EIS and in AIA. Then, I extracted the light curves from spectral lines emitted in a wide range of temperatures and applied spectroscopic diagnostics to derive the density as a function of temperature. I concluded that the emission of these events mainly originates from plasma below 1 MK. As such, most of them hardly contribute directly to the coronal heating.In order to understand the physical properties driving these events, I reproduced their observational signatures using the HYDRAD 1D hydrodynamics code. To do so, I computed the synthetic light curves from different models of short loops submitted to impulsive heating by changing parameters such as the loop length or the heating strength. I looked for the models that best reproduce the observations, including the light curves co-temporal peak. The work compares the results for two different types of loops that have very distinct properties: “hot” (T > 1E5 K) and “cool” (T < 1E5 K) loops. The results showed that cool loops submitted to impulsive heating are good candidates to explain the origin of most of the events detected by HRIEUV.To conclude, most of these events are probably not the signature of coronal heating phenomena, unless their coronal emission is below the instrumental limitations. One consequence of this work would be to reconsider their role in heating the QS corona, as they might instead provide a major contribution to the heating of the cooler lower solar atmosphere

There is a number of human rituals that are accompanied by sacrifices of food and drinks. Ritual practices of different people are a huge resource of these habits that are found all over the world. This research paper will focus on the role of instrumental music in guiding these sacrifices among selected communities inhabiting Southeast Asia’s mainland. Through a multi-perspective observation this research aims at showing order principles, musical requirements, and their variability, which will be analysed and discussed. Long term field work and participant observation over a specific period of time are the basic preconditions for this research. In addition, this research is also to question basic principles of conveying research outcomes and the use of well-established research tools in order to categorize and identify types of musical and ritual behaviour. The perspective of food offerings may shift the focus from musicality within rituals to the focus on social digestion in the context of sustaining communities.

Unmanned multi-rotor VTOL vehicles have recently gained importance in various applications such as videography, surveillance, search and rescue etc. suited to their small size and relatively cheap construction. Small scale UAVs struggle in providing satisfactory performance in terms of payload, range, and endurance because of higher viscosity-dominated losses, and due to yet to be understood rotor-rotor and rotor-airframe aerodynamic interactions. Viscosity dominated rotational flow field makes most potential flow methods, such as free wake model, invalid. A full N-S based approach for this problem is too expensive. Thus, a multi-rotor aerodynamic interaction study is necessary for understanding crucial phenomena, which will help in developing physics-based models which will be instrumental in multi-rotor UAV performance prediction and design optimization. In present work, a flow visualization and a high-speed stereo Particle Image Velocimetry (SPIV) study is done on two low Reynolds number multi-rotor arrangements with the aim of capturing vortex-vortex, blade-vortex and vortex-duct interactions. The first arrangement is a coaxial rotor in forward flight and another is an in-plane quad-rotor with and without duct. Instantaneous and average PIV data is being presented here with some observations and corresponding interpretations.

Abstract The introduction of a novel torsional oscillation control technology, characterized by its high amplitude, extended attenuation length, and mode-coupled axial excitation, has been instrumental in enhancing drilling dynamics and augmenting the on-bottom drilling rate of penetration (ROP). To effectively integrate this technology, a strategic approach was employed, which involved the use of a multi-point elastic contact force software for tool placement modeling. This software is adept at pinpointing string elastic breakover points and discerning localized contact side forces within the drill string under specific drilling conditions. To realize the desired outcomes, the deployment of two torsional oscillation control tools was deemed necessary. A comprehensive evaluation was undertaken to gauge the efficacy of these tools. This involved juxtaposing the outcomes derived from the tools with the real-time operational results of downhole systems in the same field, spanning a 1000-foot interval. Key metrics, including downhole stick-slip and measurement while drilling (MWD) revolutions per minute (RPM), were meticulously assessed, considering their responsiveness to surface parameters and loads. The findings were promising. There was a marked improvement in the field ROP average, witnessing an increase of 8%. Furthermore, there was a notable decline in the peak-to-peak RPMs (stick-slip) relayed in real-time through the MWD tool. Another significant observation was the substantial reduction in the effective downhole reactive torque when juxtaposed with the offset data. The drilling dynamics data underscored an optimal downhole RPM coupled with an enhanced weight transfer. This was in alignment with the energy efficiencies projected by the model, which factored in the influence of the torsional oscillation technology and provided insights into optimal tool placement. An ancillary discovery was the improved downhole directional control. A more overarching insight was the diminished energy consumption during drilling relative to the offset. Moreover, this pioneering technology played a pivotal role in lowering the downhole MWD temperature. What sets this Torsional Oscillation Control technology apart is its innovative approach to mitigating the inherent elastic inertia moments within the drill string. These moments, which are typically stored and subsequently dissipated, are effectively addressed by this technology. A salient feature of this technology is its capability to curtail the energy loads, paving the way for heightened drilling efficiencies.

Abstract The application of high viscosity friction reducers (HVFRs) in unconventional plays has steadily increased over the past years, not only as alternatives to conventional friction reducers (FRs) but also as a direct replacement for the use of guar-based fluids. HVFRs demonstrate more efficient proppant transport, due to their unique rheological properties, concurrently with a high friction reduction effect allowing higher pumping rates. However, all these benefits come with few critical limitations related to frac water quality, compatibility with other additives, and static proppant suspension, which makes them very similar to conventional crosslinked gels regarding their Quality Assurance and Quality Control (QAQC) requirements at a well location during the field implementation. This paper illustrates the comprehensive laboratory efforts undertaken to evaluate different HVFR and crosslinked gel products, their successful field application supported by a robust and effective field QAQC process, and the critical importance of maintaining effective field-laboratory-field interaction/cycle to optimize the fluid design and maximize the results. Experimental studies on different products were conducted to measure the effect of frac water quality, HVFR loading, breaker loading, and compatibility with other additives used in the fluid recipe such as surfactants, scale inhibitors, and biocides. The ability of HVFR to suspend and transport proppant is not only a function of polymer loading but also highly influenced by fluid velocity as static and semi-dynamic proppant suspension tests demonstrate. Additionally, a full dynamic proppant transport test was also conducted using a multi-branched slot apparatus to simulate the flow inside a complex fracture network. Field execution followed a strict QAQC protocol including water analysis, field laboratory tests, water filtration, mixing procedure, product storage, and transport allowing direct onsite replication of the results that had been previously obtained in the laboratory. Constant communication between the field and the laboratory allowed a successful execution of several treatments in a challenging shale play in the Sichuan Region, China. These treatments achieved record proppant placements and, just as importantly, they demonstrated repeatability and consistency over time; which had not previously been attained. Laboratory testing proved critical in confirming that product segregation was occurring, even if there was no visual observation of this phenomenon, which had resulted in initial difficulties in fluid quality and reliability. The presence of constant QAQC engineering support on location was instrumental in rapidly identifying the potential root cause(s) and efficiently and correctly applying the necessary corrective actions. This paper will highlight the importance of laboratory testing, in order to design and optimize the fluid system. The paper will also demonstrate how critical the onsite QAQC is through actual examples of fluid optimization and field implementation. These two activities, although requiring a substantial resource commitment and effort, are both required to achieve successful execution.