Fast-ion measurements with neutron and gamma-ray spectroscopy in thermonuclear plasmas: recent results and future prospects

A high-performance thermonuclear plasma is a strong source of nuclear radiation, which includes neutron emission from the main fusion reactions and gamma-rays born from the interaction of supra-thermal ions and plasma impurities. Spectroscopic measurements of both types of radiation are an indirect probe of the distribution function of the fast ions leading to nuclear emission. In this paper we present a selection of recent results obtained with neutron and gamma-ray spectroscopy as a means to study the energy distribution of supra-thermal particles in high-performance thermonuclear plasmas. We focus in particular on the advancements made possible by the combination of dedicated instrumentation and detailed models based on the nuclear physics behind the emission. Future developments are finally addressed, especially regarding the availability of compact detectors with spectroscopy capabilities, which open up to a full tomographic reconstruction of the fast-ion velocity space

Montana Kaimin, September 27, 2001

Student newspaper of the University of Montana, Missoula

Understanding Student Cognition Through an Analysis of Their Preconceptions in Physics

Over the last three decades, many studies have been conducted to identify students’ preconceptions on various science topics. It is time now for a synthetic study of preconceptions to enhance our understanding of students’ everyday cognition and to benefit our effort in developing effective instructional inventions for conceptual change. Through a classroom-based study, we collected quantitative and qualitative data about students’ preconceptions in physics. Data analysis produced an in-depth understanding of the features of students’ preconceptions and cognition. For example, we found that students thought analogically as scientists did, but they used analogies differently. We also found that students’ preconceptions were highly correlated and that some preconceptions were more fundamental than others. Having the core preconception probably means having many others. The pedagogical and research implications of these findings are highlighted.Plusieurs études ont porté sur l’identification des idées préconçues qu’ont les élèves face à divers thèmes en sciences. Il faut maintenant passer à une synthèse de ces préconceptions pour améliorer notre connaissance du niveau de compréhension des élèves, d’une part, et pour appuyer nos efforts visant le développement de matériel pédagogique efficace qui mènera à des changements conceptuels, d’autre part. Une étude basée dans la salle de classe a permis aux auteurs de recueillir des données quantitatives et qualitatives sur les idées préconçues qu’ont les élèves au sujet de la physique. L’analyse des données a fourni des informations détaillées sur les caractéristiques des préconceptions et de la cognition des élèves. Par exemple, nous avons appris que les élèves raisonnent par analogie tout comme les scientifiques, mais que les deux groupes ne se servent pas des analogies de la même façon. De plus, nous avons noté une grande corrélation parmi les préconceptions des élèves et avons découvert que certaines préconceptions étaient plus fondamentales que d’autres. Il est probable que quand on tient la préconception de base, l’on en tient également plusieurs autres. Nous soulignons les répercussions de ces conclusions, tant pour la pédagogie que la recherche

Numerical investigation of a diffuse ventilation ceiling system for buildings with natural and hybrid ventilation

The need to meet requirements, both in terms of ventilation and thermal comfort in modern buildings, has led to the development of different concepts for ventilation, among which the so-called Diffuse Ceiling Ventilation (DCV). This system makes use of the space between the ceiling slabs and the suspended ceiling as a plenum for fresh air, while the suspended ceiling itself becomes an air diffuser element. If compared to traditional solutions, this allows a higher amount of ventilation air to be injected in the room at lower speed, and a more even distribution of the fresh air within the room. Furthermore, it allows an easy integration with sound-absorbing perforated ceiling panels, since their typical design makes them particularly fit to be used as air diffusers. This paper builds upon a previous work by the authors where CFD simulations were used to optimise the dimension and the distribution of the perforation pattern in the panels to achieve an even air speed distribution. In this work, the performance of the perforated ceiling is investigated in a more comprehensive way, evaluating the thermal comfort in the room when varying the outdoor temperature. This solution is in fact meant to work in combination with natural or hybrid ventilation strategies, where the fresh air flow is supplied from the façade. Numerical simulations were performed on a typical office room, considering both the winter and the summer season, for different inlet air temperatures. This solution demonstrated a positive impact on the indoor conditions and on the thermal comfort inside the room in most of the cases but the most extreme ones. The thermal stratification in the room demonstrated to remain within a satisfactory level

Global Transformer Architecture for Indoor Room Temperature Forecasting

A thorough regulation of building energy systems translates in relevant energy savings and in a better comfort for the occupants. Algorithms to predict the thermal state of a building on a certain time horizon with a good confidence are essential for the implementation of effective control systems. This work presents a global Transformer architecture for indoor temperature forecasting in multi-room buildings, aiming at optimizing energy consumption and reducing greenhouse gas emissions associated with HVAC systems. Recent advancements in deep learning have enabled the development of more sophisticated forecasting models compared to traditional feedback control systems. The proposed global Transformer architecture can be trained on the entire dataset encompassing all rooms, eliminating the need for multiple room-specific models, significantly improving predictive performance, and simplifying deployment and maintenance. Notably, this study is the first to apply a Transformer architecture for indoor temperature forecasting in multi-room buildings. The proposed approach provides a novel solution to enhance the accuracy and efficiency of temperature forecasting, serving as a valuable tool to optimize energy consumption and decrease greenhouse gas emissions in the building sector.publishedVersio

Global Transformer Architecture for Indoor Room Temperature Forecasting

A thorough regulation of building energy systems translates in relevant energy savings and in a better comfort for the occupants. Algorithms to predict the thermal state of a building on a certain time horizon with a good confidence are essential for the implementation of effective control systems. This work presents a global Transformer architecture for indoor temperature forecasting in multi-room buildings, aiming at optimizing energy consumption and reducing greenhouse gas emissions associated with HVAC systems. Recent advancements in deep learning have enabled the development of more sophisticated forecasting models compared to traditional feedback control systems. The proposed global Transformer architecture can be trained on the entire dataset encompassing all rooms, eliminating the need for multiple room-specific models, significantly improving predictive performance, and simplifying deployment and maintenance. Notably, this study is the first to apply a Transformer architecture for indoor temperature forecasting in multi-room buildings. The proposed approach provides a novel solution to enhance the accuracy and efficiency of temperature forecasting, serving as a valuable tool to optimize energy consumption and decrease greenhouse gas emissions in the building sector

Modelling and validation of hygrothermal conditions in the air gap behind wood cladding and BIPV in the building envelope

Materials used in the building envelope are exposed to a wide range of varying and harsh conditions over extended periods. Knowledge about these precise conditions allows for improving the design of testing schemes and eventually extending the durability of building materials. In this study, a numerical model in WUFI-Pro Ver. 6.5 is calibrated with field measurements in the ventilated air gap of a Zero Emission Building located in Trondheim, Norway. Measurements were taken from 01.09.2020 until 31.08.2022 and involved recording the surface temperature of the wind barrier (19 locations) and the relative humidity of the air (11 locations) in the middle of the air gap behind wood cladding and building integrated photovoltaics. Several different air change rates in the air gap are investigated in the model. Using a constant air change rate of 100 h-1 showed the overall best performance (R2 = 0.940 for the wind barrier’s surface temperatures and R2 = 0.806 for the relative humidity of air in the middle of the air gap). The largest deviations between simulation results and measurements, however, can be attributed to the uncertainty of climate data input. The developed model can be used in future studies that significantly contribute to establishing better testing schemes and test conditions for building materials such as wind barriers and adhesive tapes, and eventually improve the long-term air tightness of buildings.publishedVersio

Thermo-fluid dynamic performance of a ventilated pitched roof: Numerical modelling and experimental validation

Wooden ventilated pitched roofs represent a widely spread construction solution in Nordic countries. They have several benefits, including the drainage of excessive moisture from the construction and the reduction of the surface temperature to prevent snow melting and thus icing at the eaves and gutters. Modelling ventilated components is complex and requires a thorough understanding of the phenomena occurring in the air cavity, where convection plays a central role in the heat transfer process. The approach and the assumptions adopted for the roof model are therefore crucial to investigate the thermo-fluid dynamics in the air cavity. A literature review showed the need for comprehensive numerical and experimental research focusing on ventilated roof constructions, especially for Nordic climates. This article presents the thermo-fluid dynamic modelling of a ventilated pitched roof, which belongs to a full-scale experimental building located in Trondheim (Norway), the ZEB Test Cell Laboratory. A model of the roof was created using the finite element method-based software COMSOL Multiphysics. Transient simulations were performed in different climate conditions and the results of temperature and air flow speed along the cross section of the roof were compared with measurement data for validation. The simulation results show a good agreement with measurement data for both air speed and temperature in the air cavity, particularly in the summer day. The deviations in the numerical results will be object of study in future research, where the modelling approach will be further explored by testing different inputs, including boundary conditions and turbulence models.publishedVersio

Multi‐Stage Validation of a Solar Irradiance Model Chain: An Application at High Latitudes

Evaluating how the sources of uncertainty in solar modelling (e.g., input parameters, developed model chain) can influence the results’ accuracy is one of the main challenges when applied at high latitudes. In this study, a multi-stage validation workflow is implemented around five main stages: data acquisition, data quality check, solar radiation modelling, photovoltaic energy modelling, and experimental validation. Different data sources such as satellite observations, numerical reanalysis, and on-site ground measurements are considered as inputs, while the outcomes from each step of the model chain (e.g., decomposition modelling, transposition modelling, photovoltaic energy modelling) are compared against observations recorded from the solar radiation network at the Norwegian University of Science and Technology (NTNU-Solarnet) in Trondheim (Norway). In the first and second validation stages, the decomposition and transposition models with measured input parameters show the best accuracy indicators, but they do not fulfill the validation criteria. Conversely, in the third validation stage, the photovoltaic energy models with on-site ground measurements as inputs are experimentally validated. In conclusion, at high latitudes, the most accurate results are obtained when monitored solar irradiation data are used instead of satellite observations and numerical reanalysis. Furthermore, the shortest model chain is preferred, with equal data sources.publishedVersio