bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow investigation around cylinders assembled in a confined straight channel geometry
Authors: Tanase Nicoleta-Octavia , Broboana Diana , Balan Corneliu 
Published: May 2021

Abstract
The paper is dedicated to experimental and numerical investigations of the dynamics of 3D-flow around a cylinder with 10 mm diameter. The cylinder is positioned in a confined geometry represented by a long straight channel with 50 mm width and 10 mm height. The study analyses the dependence on the Re-number of the path lines distributions in the vicinity of the immersed cylinder. The visualized flow patterns are fairly reproduced by the numerical solutions of the Navier-Stokes equations up to Re = 1000. The velocity and wall stresses are computed in the vicinity of the cylinder. One main goal of the present work is established by the correlation between the flow pattern, wake boundary and wall shear stress distributions down-stream the cylinder.
Determination of the separation points for the flow around blunt bodies: experimental and numerical studies
Authors: Tănase N O , Simionescu Ş M , Păduroiu M M , Bălan C 
Published: May 2021

Abstract
The paper is concerned with experimental studies and numerical modelling of the air flow around blunt bodies (cylinder, aerodynamic profile) inside a wind tunnel. The range of the investigated Reynolds numbers is 12000<Re<35000. The main goal of the work is to establish a CFD procedure to analyse the flow pattern in the vicinity of the bodies and to predict the position of the boundary layer detachment. The computations are performed with several turbulence models implemented in the ANSYS Fluent code. The direct visualizations and the numerical results are corroborated, with the aim to investigate the positions of the separation points and the flow spectrum developed downstream the bodies.
Evolution of renewable energy consumption in the European countries
Authors: Stoenoiu C E , Balan M C , Serban F M , Cristea C 
Published: May 2021

Abstract
This study performs an exploratory analysis of the evolution of consumption of RES for EU28 countries over the ten years studied. Through the analysis, the document presents: the consumption by sectors of production and by renewable energy sources, analyses the evolution of consumption from RES: between countries and regions. Regarding the consumption of RES, it is increasing, reaching in 2017 compared to 2008 to increase by 147.8%.
Numerical investigation of a reduced scale Lenz wind turbine model for aerodynamic tunnel applications
Authors: Bucur I O , Malael I , Preda D 
Published: May 2021

Abstract
Renewable energy sources represent efficient and reliable energy solutions for the modern world, as they are eco-friendly alternatives to fossil fuels or nuclear power plants. The technologies available nowadays allow researchers to perform in-depth computational fluid dynamics analysis for systems that can generate green energy. The wind energy industry developed considerably as classic wind turbine models (horizontal axis wind turbines and vertical axis wind turbines) are constantly optimized and new configurations are studied in order to asses better performances. This paper presents the numerical investigation campaign of a reduced scale Lenz wind turbine model. The Lenz model has three blades that are attached directly on a vertical shaft. For the numerical simulations of the model, the ANSYS Fluent software is employed. For the evaluation of its self-starting behaviour the six degree of freedom method was employed and the configuration was studied for different moments of inertia. Furthermore, the chosen range of inlet velocities allowed the investigation of the influence of high Reynolds numbers on the proposed Lenz model and the vorticity magnitude contours were computed for different azimuth angles. Future work includes the validation of the numerical results with experimental data obtained during a wind tunnel testing campaign.
Performance of autoclaved aerated concrete (AAC) exposed to standard fire
Authors: Stanescu Adrian Andrei , Lalu Octavian , Luca Oana , Gaman Florian 
Published: May 2021

Abstract
This paper presents the results of an experimental study carried out within the National Institute for Research, Development in Constructions, Urbanism and Sustainable Territorial Development URBAN INCERC, on a system of walls made of ACC blocks, according to the standard SR EN 771-4 [8], having a density of 480 kg/m3 and standardized compressive strength of 3.5 N/mm2, using mortar type binder class M2.5 with compressive strength of 2.5 N/mm2. It was exposed to the action of standardized fire for a period of 220 minutes, after 10 days from the execution of the masonry. The results showed that, following the tests on the burned samples, extracted from the wall subject to the test, the standardized unit compressive strength decreased by 54%.
Parameter tuning process for a closed-loop pneumatic actuator
Authors: Cococi V N , Safta C A , Călinoiu C 
Published: May 2021

Abstract
Pneumatic drives are light weight, small-sizes, simple to install and to maintain. Pneumatic drives have a robust design and operation. They are clean and cheap, have no temperature limitation, and so, they are preferred in many branches of manufacturing and process industry. The well-known pneumatic actuators are widely used in closed-loop positioning systems because of their dynamic performance and mechanical flexibility in different electro-mechanical systems arrangements. The goal of the paper is to find the parameters of a closed-loop pneumatic actuator so that a good dynamic behaviour of the system is obtained. The parametric tuning process is developed by using numerical simulation technique. So, it was seen that using a proportional controller, the pneumatic actuator has an asymptotic stability for different values of the proportional gain K

p
. Starting with K

p
= 8 the system remains stable, but oscillations of low amplitude appears.
Review on Modern Photovoltaic Panels – Technologies and Performances
Authors: Budea S , Safta C A 
Published: May 2021

Abstract
In this article, the authors reviewed the modern technologies for manufacturing transparent, bifacial, flexible panels and other similar solutions. Passive or active cooling solutions, with air or water vapor, or energy storage solutions are analysed. If the passive air cooling of the photovoltaic panel can achieve a reduction of its temperature by only 10 °C, by active cooling, a cooling with over 30 °C can be obtained. These technologies are aimed to improve the energy efficiency of photovoltaic panels. The article presents examples of photovoltaic panels’ own applications, as well as hybrid PV, realizing the cooling of the PV panel and the recovery of the thermal energy in the form of hot air or hot water, with good efficiency.
Forecasting solar radiation using a deep long short-term memory artificial neural network
Authors: Carutasiu Mihail-Bogdan , Ionescu Alin , Ionescu Constantin , Necula Horia 
Published: May 2021

Abstract
Solar systems are widely used to mitigate the environmental impact of the energy sector and their importance has constantly increased due to the recent EU’s strategy to lower the CO2 emissions. Moreover, the newest Energy of Buildings Directive empathises the importance of producing energy from renewable sources to decrease the overall impact of buildings over the total end-use energy consumption. Generally, the systems’ performances are highly correlated with the incident solar radiation and outdoor air temperature. Thus, being able to accurately forecast these two parameters represents a vital step in dimensioning and maximizing the overall energy production. This Paper presents the results obtained by implementing a deep recurrent artificial neural network (ANN) trained with on year solar radiation data harvested from the UPB campus. The time series data was modelled using a special ANN architecture – the LSTM (Long Short-Term Memory) – due to its special designed internal ‘memory’ which increases its capabilities of predicting temporal sequence data. The model uses sequences of 24 hours and the resulted mean squared error (mse) for both training and validation data is under 30%.
Modelling the active sludge treatment process in recirculation basins using the simulink environment
Authors: Dordescu M , Nicolescu F 
Published: May 2021

Abstract
In the global context of environmental protection and the reduction of its pollution, wastewater treatment has a special role. Starting from this general framework and considering the need for an integrated approach to water as a natural resource, the aim is to introduce new treatment technologies in which human intervention tends to zero. That is why modelling, and simulation techniques highlight automation solutions and their implementation. In our paper we tried to model a biological purification process using Simulink techniques.
Hydraulic Modelling of the Water Supply System of Năsăud City, Bistriţa Năsăud County
Authors: Agafiţei Alina , Pavel Vasile Lucian , Rlan Toma Cristina Mihaela V. , Toma Daniel 
Published: May 2021

Abstract
The paper presents a study of hydraulic modelling of the drinking water and sewage distribution network in Nasaud City, Bistrija Nasaud County from Romania, which includes a calibrated simulation of the flow through networks, and allows the elaboration of a future strategy of developing the networks of water and sewage. The need to develop hydraulic models as accurately as possible results from the fact that, by creating and calibrating the hydraulic model of a system, a variety of system problems can be identified, solutions can be mitigated to them by addressing the problem of rehabilitation, expansion or design of new systems. The results can be tracked both at the scale of time, and in real time by simulating the functioning of the system at these time scales. We decided to approach the problems of sizing and verifying the network using software solutions packages, in this case the MIKE URBAN calculation program, which can import and export network data as ESRI ArcView shape files, allowing the network data to be directly imported and exported into and from ArcView. Thus, the network is completely resolved, the calculation of hydraulic sizing and verification of the network being performed in all nodes.
Total equivalent warming impact calculation for air conditioning technological application
Authors: Vinceriuc M , Tarlea G M 
Published: May 2021

Abstract
This paper shows an aggregated compact cooling liquids (refrigeration system) used in air conditioning technological process who works in present with R407C refrigerant. The paper has focused on theoretical study case. Regarding F-Gas Regulation the optimum alternative for this application is R134a refrigerant with Total Equivalent Warming Impact (TEWI) calculation.
Effect of DO, Alkalinity and pH on Nitrification Using Three Different Sunken Materials Types in Biological Aerated Filter BAFs
Authors: Faskol A S , Racoviţeanu G 
Published: May 2021

Abstract
The overall aim of this search investigated the effect of DO, alkalinity, and pH on nitrification in biological aerated filter system BAFs. The laboratory experiments by three identical pilot-scales downflow of BAFs using three different sunken materials types, 0.78±0.60 mm activated carbon-based material bed, 0.95±0.58 mm sand-based material bed, and 3.28±2.14 mm ceramic particle-based material bed, as attached growth zone in the treatment of municipal wastewater. As results of the experiments showed that activated carbon-based material bed when the mean concentration of dissolved oxygen was 6.76±2.25 mg/L and the mean alkalinity concentration was 77.25±2.60 mg CaCO3/L and the mean pH value was 7.21±0.20 the mean nitrification efficiency has reached of 90.11%. In the sand-based material bed when the mean concentration of dissolved oxygen was 7.33±1.82 mg/L and the mean alkalinity concentration was 77.56±2.77 mg CaCO3/L and the mean pH value was 7.22±0.20 the mean nitrification efficiency has reached of 87.74%. In the ceramic particle-based material bed when the mean concentration of dissolved oxygen was 6.37±1.84 mg/L and the mean alkalinity concentration was 77.31±2.71 mg CaCO3/L and the mean pH value was 7.22±0.20 the mean nitrification efficiency has reached of 85.17%.
Analysis of numerical and experimental results of a solar glazed air collector configuration in Romania climate
Authors: Sima C , Teodosiu C , Croitoru C , Bode F 
Published: May 2021

Abstract
This paper proposes an experimental and numerical study (based on CFD – Computational Fluid Dynamics technique) dealing with a glazed transpired solar collector (GTC), having the distance between the glass and absorber plate of 50 mm. The behaviour of the GTC has been studied for different air flow rates. Based on the results obtained, it can be concluded that this GTC configuration behaves best for air flow rates of about 300 m3/h. On the other hand, further studies are needed to improve the numerical model (especially regarding the introduction of boundary conditions based on measured data).
Seismic performance assessment based on displacement capacity of unreinforced masonry structures
Authors: Scupin A , Văcăreanu R , Pavel F 
Published: May 2021

Abstract
The National Geological Museum is a representative building for the typology of historic unreinforced masonry structures built in Romania at the beginning of the XX century. The seismic behaviour was studied with respect to the displacement capacity, by comparing the initial structural configuration of the building with the retrofitted one. Taking into account the irregularities of the structure and the localized reinforced concrete jacketing works done in the 80s’, global results were proven to be misleading. Thus, relative floor displacements were used to study the behaviour of individual walls involved in local failures. Limit state thresholds based on relative displacements were used in order to calibrate the initial model with the post-earthquake damage assessment and then they were compared to the results obtained for the retrofitted model to establish the effectiveness of the strengthening works.
General design considerations for applying thermal insulation layers underneath foundations of buildings placed within the main seismic regions of Romania
Authors: Popescu Andrei-Laurenţiu 
Published: May 2021

Abstract
Worldwide common efforts towards developing a sustainable, competitive, eco-friendly and efficient built environment have led to a new legal and technical spectrum of rules and requirements for high energy performance buildings. Provision of solutions for a continuous thermal envelope is sometimes essential in designing such buildings. Mitigating, as much as possible, the thermal bridging phenomenon is highly important and should be accounted from the very beginning in the design process. This issue can be addressed through various solutions when it comes to thermally insulating the superstructure but can be quite challenging and limited at infrastructure level, particularly for buildings set in areas exposed to earthquakes. This paper explores existing technical literature, local codes, norms and standards, with the twofold purpose of: (1) providing a view on the relevant available research and design prescriptions; and (2) outlining incipient general design considerations related to the feasibility of applying specific thermal insulation materials beneath buildings located within the main seismic regions of Romania.
Experimental study of the chemo-mechanical properties of the interfacial transition zone of concrete
Authors: Girboveanu A , Jebli M , Jamin F , Huon V , El Youssoufi M S , Georgescu D P 
Published: May 2021

Abstract
This article presents an experimental study of the chemical and mechanical properties of the cement paste / aggregate interphase. Interfacial Transition Zone (ITZ) represent the contact zone of the cement paste with the aggregate with a thickness of about 20 - 50 μm. This zone has different mechanical and chemical properties compared to the bulk paste. Cement paste / limestone aggregate composite samples were performed to allow the study of the chemical and mechanical properties of ITZ. The cement paste is made with Portland cement with a water/cement mass ratio of 0.4. Calcium concentration profiles in the ITZ show a high concentration of calcium due to the presence of portlandite and ettringite. The nano-indentation tests indicate weakness of ITZ compared to bulk cement paste.
Review of numerical studies on ventilation systems for subway networks in emergency situations
Authors: Kubinyecz Vladimir , Teodosiu Cătălin 
Published: May 2021

Abstract
Since the subway systems are constantly developing at a high rate to cope with the increasing number of commuters, their safety is a great challenge and extensive research was done to fulfil the safety regulations in this field. Numerical modelling represents a modern research method used more frequently in the academic environment over the last decades, being constantly validated through comparisons with results of other classical research methods. This paper presents a thorough analysis of the numerical studies on smoke evacuation in emergency situations from tunnels and subway stations, with a focus on the research concerning the use of platform screen doors (PSD) in emergency situations generated by fires. The numerical simulation software mostly used are Fire Dynamics Simulation and Ansys Fluent (based on Computational Fluid Dynamics modelling technique), their results being extensively compared with experiments and analytical formulae. Since most of the studies focus on determining the specific values of some fire related parameters (critical velocity of the ventilated air, backlayering distance of the smoke, maximum temperature in the smoke layer or maximum concentration of smoke pollutants), a lack of research regarding the efficient use of PSDs concomitant with the ventilation system in emergency mode has been identified.
A Fire Dynamics Simulator approximation of non-toxic smoke
Authors: Burlacu D , Georgescu A M 
Published: May 2021

Abstract
Experimental research in fire safety engineering is often characterized by a low repeatability mainly caused by the destructive nature of the fire phenomena. One of the ways that these shortcomings might be avoided is by using numerical simulation for research in this particular branch of engineering. Accuracy in numerical simulation comes through validation of the results by comparison with experimental testing, and in this regard, this paper presents the use of the PyroSim fire simulation program, which is a user interface for the Fire Dynamics Simulator software package, for the purpose of simulating non-toxic smoke in a way that accurately describes its behavior and properties observed in experimental testing. A full-scale experiment has been conducted for the purpose of determining the optical properties of non-toxic smoke produced by a smoke machine and this paper presents the way that this smoke can be accurately represented in the simulation program, for the purpose of providing a basis for future simulations of experiments using smoke machine generated smoke. The methodology employed can be used in further research involving simulated smoke, such as CFD representations of firefighter training, people evacuation from smoke-filled enclosures and smoke exhaust in buildings.
Effects of thermal bridges on the heat demand of residential buildings
Authors: Sabie D D , Ghiaus A-G 
Published: May 2021

Abstract
This paper presents the influence of the thermal bridges effect on heating demand in residential buildings using numerical simulation. Quantitative evaluation on temperature field is performed by means of linear heat transfer coefficient. Specific details of existing thermal bridges within the building envelope have been identified and selected for analysis. The model simulation was performed using COMSOL Multiphysics software. Thermo-physical properties of the building envelope elements were selected from the software database and the boundary conditions have been setup. Meshing was done by dividing the virtual domain into an optimum number of finite elements. Model validation was done by comparative analysis between the values of the linear thermal transmittance obtained through numerical simulation and the reference values stipulated in C107-3-2005 technical regulation (catalogue of building thermal bridges). Specific solutions for correcting the thermal coupling between different building envelope elements were adopted in order to reduce the linear thermal transmittance up to 23% and the heat flow rate up to 71%. The evaluation of space heating demand shows the impact of correct treatment of thermal bridges on the reduction of energy consumption.
Neural networks and some practical applications in the field of artificial intelligence
Authors: Șuică Marian , Năstase Ilinca 
Published: May 2021

Abstract
Even since Antiquity, in ancient Greece 4th century BC, or in China, the 3rd century BC, but not only there, people have imagined and even created automatic mechanisms, mechanisms that somehow were trying to be shy replicas of real examples of intelligent life from nature, including replicas of Man’s creation, such as the first bronze man, but nonetheless, non-intelligent replicas. Subsequently, in the modern age, attempts have been made to simulate a human neural network, as well as the first steps towards artificially simulating the functioning of the human brain. We will present in this article concepts of neural networks and some practical applications in the field of artificial intelligence and their capabilities to simulate autonomous thinking through advanced programming and complex assimilation of large data sets, using the three major learning paradigms, namely: supervised learning, unsupervised learning, and reinforcement learning. All these new concepts, over the past 75 years, and the advances in information technology have led to the emergence and development of practical applications of artificial intelligence. In this way, the human dream of creation tends to live and fulfil itself, why not, even in the coming years.
Short-term evolution of dynamic characteristics of a RC building under seismic and ambient vibrations
Authors: Tiganescu Alexandru , Craifaleanu Iolanda Gabriela , Balan Stefan Florin 
Published: May 2021

AbstractThe post-earthquake evaluation of structural integrity is a critical point to be addressed in case of emergency situations triggered by the occurrence of seismic events. A valuable method that can provide important indices to experts performing this operation is the monitoring of structures with seismic sensors that record how the structure responds to earthquake ground motion. In the case of permanent monitoring systems, reliable information can be obtained by comparing the data recorded before, during and after the earthquake, and checking if any abnormal vibrations of the structure or dynamic parameter changes have occurred. The presented study analysed comparatively, for an 11-story reinforced concrete building, vibration data recorded before, during and after the October 28th, 2018 earthquake (MW= 5.5). Continuously recorded data was used to determine the hourly values of the fundamental frequency of the building. The short-term behaviour (72 hours) was assessed, highlighting the modal parameters variation during, before and after the earthquake. In addition, an analysis of the data recorded one and a half hours before the earthquake and one and a half hours after the earthquake provided useful information on the evolution of the building state and on how this “recovered” after the earthquake.