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În contextul situației pandemice provocate de Covid 19, etica şi valorile academice au avut de suferit în ceea ce privește informarea, promovarea și diseminarea normelor de conduită academică și profesională. Toate instituţiile publice au la bază fie codul de etică și deontologie, fie regulamente de conduită profesională pentru a contracara problemele unui comportament inadecvat. Prin urmare, au fost necesare noi metode de promovare adaptate comunicării online. Noile metode utilizate au facilitat transmiterea informaţiilor, care vizează drepturile şi obligaţiile studenţilor, normele de comportament și conduită ale personalului academic şi auxiliar, facilitând astfel respectarea standardelor de etică şi conduită acceptate și impuse de mediul universitar. Lucrarea de faţă abordează problematica metodelor utilizate în această perioadă, în care mediul on-line a constituit sfera de desfăşurare a tuturor acţiunilor întreprinse. E-mail-urile de informare și promovare, întâlnirile individuale sau în grup, dezbaterile pe diverse teme, şedinţele de consiliere şi-au găsit un teren propice de manifestare în mediul virtual. Aşadar, unei universităţi, care în societatea actuală are rolul de a reprezenta un pol de excelenţă cu funcţie de formator de opinie şi atitudine la toate nivelurile ei, îi revine dificila sarcină de a promova și veghea asupra valorilor morale şi etice

Optimization methods are finding more applications in all domains, as they play an essential role when dealing with real-life problems [...]

This paper proposes a study regarding the use of bioethanol as fuel for turbine engines used in aviation. For this purpose, three blends of 5, 10, and 15% concentrations of bioethanol mixed with Jet A fuel were tested on JET CAT P80 microturbo engine. During the engine testing, the following parameters were monitored: engine speed, generated force, temperature in front of the turbine, fuel volumetric flow rate, and vibration levels measured both on axial and radial direction. The tests were performed by maintaining the microturbo engine for about 1 min at three operating regimes: idle, cruise, and maximum speed. In addition, a comparative analysis between fuels for a test with the microturbo engine from the idle position to maximum position is presented. After the tests were conducted, a jet engine cycle analysis was performed at the max regime and the fuel specific consumption, the efficiency of the combustion chamber, and the thermal efficiency of the engine for each fuel blend were calculated. The tests were made without making any modifications to the engine components or automation system.

The article presents the first National Student Survey (NSS-RO) results. The questionnaire was opened to all Romanian students between November 2020 and January 2021 and involved 23,796 respondents from 76 higher education institutions. Initially designed to be a tool to improve the quality of higher education, given the epidemiological context created with the Covid-19 pandemic, it expanded with one section to measure students’ perception of its impact on higher education. This work intends to establish a correlation between student dropout intention during the Covid-19 pandemic and the direct support received from higher education institutions regarding material resources, such as tablets, laptops, or other similar tools. Secondly, it analyses the students’ perception of the transition into emergency remote education. We measured in this sense their opinion on how easily they accessed mainly online educational resources, the information received, and the teachers’ performance during classes. These results provide one of the first steps towards understanding the impact of the Covid-19 pandemic on the Romanian higher education system. The massive interference provoked a giant leap in digitalisation and significantly changed how universities apply Student-Centred Learning (SCL) practices. Also, this study contributes to the area of national student surveys.

This paper presents an experimental investigation on using high strength-to-weight composite materials to reduce the mass of a centrifugal compressor impeller by 600%. By reducing the blades number from 17 to 7 and by doubling their thickness, the compression ratio and efficiency were maintained close to the reference metallic impeller. Using autoclave technology, seven composite blades were manufactured individually and assembled to form the impeller. After manufacturing, small deviations were found at the blade’s tip. As these deviations were found to be symmetrical, impeller balancing was successfully performed removing a total of 45 g of mass, followed by an experimental test on a dedicated test bench. Experimental testing identified the resonant frequencies of the composite centrifugal impeller at 13.43 Hz 805 rot/min and at 77 Hz with a 0.1 mm/s amplitude at 4400 rot/min, highlighting feasibility and the advantage of a composite compressor impeller design with application in centrifugal compressors and rotating machine assemblies and sub-assemblies. As there are numerous numerical investigations performed on the strength analysis and on the lay-up orientations mechanical behaviour for polymer composite materials with respect to the design of centrifugal impellers, no experimental evaluations in relevant working conditions have been performed to date. As the paper contains relevant experimental data on the subject, the outcome of the paper may aid the oil and gas or aviation industries.

The existing multi-layer tree is of dynamic linked list type which has many limitations and is complicated due to the pointer-node structure. Static array representation gives more flexibility in programming of algorithms and operations like insertion, deletion, and search. It also reduces the storage space. This paper presents a new method for representing multi-layer forest data structure in array format. It also explains various tree operations, unique data compression algorithm and migration algorithm between traditional approach and the proposed data structure. Most of the fundamental algorithms like those from artificial intelligence that employ decision trees are based on trees/forest data structure. The current paper brings a completely new idea in the representation of these data structures without employing recursion and targeting memory optimizations with reduced code complexities. The applications of forest data structures are many and span over various interdisciplinary areas of Engineering, Medicine, Aviation, Locomotive, Marine, etc. The proposed novel approach not just introduces a new method to look at the tree data structure but also provides the flexibility to adapt to the existing methods as per the user needs. A few such applications in Simulink debugging and the Forest visualisation have been discussed in detail in this paper.

This paper presents an inside-cabin acoustic evaluation of the IAR PUMA 330 helicopter, manufactured by IAR S.A. Brasov. In this study, based on the acoustic assessment inside the helicopter, areas with high noise levels are identified. In this regard, several tests were carried out in accordance with the ISO 5129 standard. In the first stage of the assessment, a measurement campaign was performed to identify the acoustic leaks from the outside noise sources propagating inside the cabin (in the door area) and the acoustic attenuation of the helicopter structure. These tests were performed on the factory runway, with the helicopter in parked position (ground tests). During the ground tests, the helicopter engines were turned off. The tests consisted of placing two loudspeakers directed towards the helicopter door and generating pink noise. Inside the helicopter, the entire door frame opening was scanned with an intensity probe to identify acoustic leaks areas. The second assessment stage was to determine the areas of the cabin with the highest levels of noise. Within the measurement campaign, 16 microphones were placed inside the cabin, at the level of the passengers’ heads, arranged in seven zones. The tests were carried out with the helicopter engines started, staying at fixed point above the ground (hovering), and then a flight test, in which all the maneuvers necessary for the use of the helicopter were performed (in-flight tests). Based on the measurement results, it was possible to highlight the noise spectral components in each of the seven areas. The noise assessment revealed high noise levels inside the cabin, having as main noise sources the transmission gear and the door area, leading to the need for reducing the noise exposure for passengers and crew, thus the need to reduce noise levels inside the helicopter.

The COVID-19 pandemic, in addition to the sometimes-dramatic effects in the health sector, presented a wide range of challenges for the various sectors of the national economies. This article refers to the effects of the pandemic in the university field, especially for the period of 2021 until now. The period corresponds to the end of the pandemic overlapping with the post-pandemic return to normal. Although at the beginning of the pandemic the effects seemed terrible, being widespread and long-lasting, some effects were still useful and motivational for the “real world”. The effects in question are those of compulsory online teaching, so on a large scale, of all subjects from all disciplines. The authors modeled and implemented a database system that includes several types of tests to generate representative samples from the university population. In the content of the article, two such tests are exemplified for a single one-semester discipline: “Computer programming and programming languages II”. The experience of the authors revealed, by comparison, practical ways to teach the theory provided in the states of functions in the real world, using exclusively the online or the mixed environment. Finally, we provide a brief conclusion and ideas for future work.

The case study aims to validate, with real data, a hydropower simulation tool algorithm. The simulation tool has become a necessity for hydropower producers with high number of assets, in order to improve short-term scheduling, operational decisions and intraday power market actions. Through this case study, we discovered that some correction factors must be taken into account to compensate measuring devices errors. The results confirm that the algorithm can be used in real life hydropower operation.

The development of electrical substations follows the trend of actual digital era. New developed measuring transducers increased considerably measurement range and their contribution to efficient operation of the substation is significant. Process interface becomes the key element in new substation automation system through direct interaction with primary equipment and real time maintenance possibility. Future engineers should be prepared to use emerging digital technology. Students need to know, understand and apply all these new challenges in power engineering and communication. The testing for present study was performed on the digital medium voltage bay from “Constantin Dinculescu” Electrical Substation Laboratory – University “Politehnica” of Bucharest, Romania. The aim of this study is to familiarize students with new digital technologies and to prove the easiest of the procedures for testing digital substations.

In the last decade, the Bologna Process has underlined many times the need for Student-Centred Learning (SCL), Innovation in Learning and Teaching, providing support to learners and removing obstacles that students face in order to fulfil their potential. As SCL is still at the core of the Bologna Process, the instruments which are meant to record the students’ perspective are very important. However, we consider that there is a deficit regarding the needed research that would lead to efficient ways of delivering positive outcomes for the entire academic community. In that sense, this paper will focus on how national student surveys have been developed in several countries, as there are some reasons to consider this instrument as one of the most efficient, especially in consolidating and developing learning and teaching. The paper will take into consideration three examples from the European Higher Education Area: the National Student Survey (United Kingdom), Studiebarometeret (Norway) and the National Sociological Research about Students’ Satisfaction (Romania) and will approach aspects such as the structures and stakeholders which are involved in developing and coordinating the process, the subjects tackled by these questionnaires, why and how they were selected. Our study provides an insight regarding the usefulness of a national student survey for the future development of European Higher Education Area. It also shows the potential relevance of these questionnaires for the Bologna Process. The paper will also present how these instruments have evolved across time and how they were received by the public opinion. We will draw a set of conclusions starting from examined good practices and the literature review. As a result of this paper, we consider that a national students’ survey represents one of the most useful tools for HE stakeholders in order to assess the quality of learning and teaching.

This paper presents research related influence of friction powders on enlarging the absorption band of acoustic liners used for reduction of tonal noise in fan duct of aero-engine. Kundt tube measurements done at COMOTI using fine powders (granules) made of various light-weight materials placed in the honeycomb cells of SDOF liners have shown a considerable broadening of the absorbed band of frequencies without a significant decreasing of absorption at the resonance frequency. Although the phenomenon is generally present for any type of powder, it was observed that for some powders the absorption is higher than for others. On the other hand, it was observed that the effect of the filling percentage of the cavity is important. Then, experiments done at the grazing flow facility of CNRS-Le Mans University have shown that the phenomenon is also present for high acoustic incident levels (up to 140dB) and M=0.13 while it still depends by the nature of powder material. The best results were obtained for the cork powder when the honeycomb is filled with powder at 66% of its height. For this material, the broadening of the transmission loss well was maximum. This phenomenon could be explained by the apparition of friction between powder granules which are taking place at very low scale consuming the noise power on a broader range of frequencies. It is supposed that the friction between the particles of powder have major influence because the best noise absorption was obtained for powders with a large distribution of particles’ dimensions while for particles with a small dimensional distribution (expanded polyester balls, for example) the transmission well broadening was smaller. The friction powders technology is simple and can be easily adapted to existing acoustic liner technologies with small manufacturing costs. This feature is conferred by the fact that powders can be easily poured in the honeycombs at the required height. The friction powder technology can be applied not only for the fan duct. In future, it could also be applied for reduction of jet noise reflected by pressure side of wing and for cabin noise reduction.

In this paper, the noise impact of a turbojet testing cell on the adjacent community is investigated. There are scenarios in which the noise from two different turbo engines is analysed. For the noise impact study, acoustic measurements were taken in the test cell to obtain the transmission loss of the three silencers of the test cell. To allow testing of high-power turbojets as Viper or R-11F-300 Tumansky, the test cell was restored and relocated to minimize the noise impact on the surrounding area. The study presents the affected buildings and the number of inhabitants exposed to noise that is assessed according to a German VBEB method based on noise level at facade of the buildings. The study presents the calculus methodologies of the acoustic propagation according ISO 9613-2 on the surrounding area and the noise limits according to the national legislation. To reduce the conflict areas, a technical solution for the intake silencer is proposed.

The network expansion problem is a very important practical optimization problem when there is a need to increment the flow through an existing network of transportation, electricity, water, gas, etc. In this problem, the flow augmentation can be achieved either by increasing the capacities on the existing arcs, or by adding new arcs to the network. Both operations are coming with an expansion cost. In this paper, the problem of finding the minimum network expansion cost so that the modified network can transport a given amount of flow from the source node to the sink node is studied. A strongly polynomial algorithm is deduced to solve the problem.

Optimization of hydropower plants operation is a topic of great interest, especially when energy market rules are restrictive. The article focuses on finding the factors that influence the energy production and the variable cost of operation for one hydropower unit in order to improve the hydropower plants operational decisions and control strategy. In real operation, it is highly important to consider the efficiency at the settlement point, not only the turbine efficiency. A case study is conducted on 20 Kaplan hydropower units to find the start-up and shut-down cost and hourly operation variable cost. Based on the results, it can be concluded that maintenance costs can double the energy production variable cost if wrong operational decisions are applied.

This paper analyzes the performances and the emissions of the JETCAT P80 microengine, when jet A jet A + 10% biodiesel (BD), jet A + 20% biodiesel, and jet A + 30% biodiesel are utilized as fuel, and to each of these combinations is added 5% of Aeroshell Oil 500. The performances will be assessed based on the engine speed, for the generated thrust force, the temperature in front of the turbine, and on the fuel flow. The paper will investigate the performances and the emissions generated by the four fuel blends burning when the engine is idle, at the cruise and at the max regime. This will be realized by maintaining each of these regimes for approximately a minute and a half. During the tests, the vibrations were monitored both radially and axially for the observation of the engine function regimes. From the measurements, the concentrations of SO2, NOx, and CH4 will be analyzed, highlighting the emissions of SO2. There were performed measurements to determine the fuel blend's density in order to transform the values of the fuel flow from liter per hour into kilogram per second. Having these data registered from the engine, a jet engine cycle analysis at max regime will be performed based on the combustion efficiency, the thermal efficiency of the engine, and the specific fuel consumption.

Mufflers represent devices used to reduce sound and pulsations for internal combustion engines and other equipment like volumetric compressors. Depending on application they are designed to reduce low, medium or high frequency pulsations. The main design is represented by acoustic filters which use the acoustic analogy method. Dealing with low frequency pulsations this type of filters result in bulky constructions. The use of metamaterials results in a more compact design for these type of mufflers. This paper investigates by numerical simulations the transmission loss (TL) of such muffler based on acoustic black hole (ABH) metamaterial principle. In the first part of the paper the FEM results are compared with the acoustic measurements performed on an adapted impedance tube, in order to validate the model. In the second part the influences of the geometric parameters (length of the muffler, lamellae depth and thickness) will be investigated. The comparative analysis between the FEM and the measured results indicates good agreement. The geometric parameters analysis highlighted that the acoustic attenuation can be increased by using a long muffler.

Coflow-jet (CFJ) airfoil is a new type of zero-net mass flux active flow control of the airfoils. The concept was proposed by Zha et al from Miami University and presents several extraordinary aerodynamic characteristics like: super-lift coefficient, small or even negative drag coefficient and almost stall free behaviour. All these make the CFJ airfoils suitable for highly efficient airplanes including electric airplanes with distributed thrust. This paper presents an evaluation of the broadband aeroacoustic noise of a NACA 6415 CFJ airfoil and compares it with the basic NACA 6415. Numerical simulation for aerodynamic and aeroacoustic field using Navier –Stokes equations and aeroacoustic analogies are conducted with Ansys Fluent and Msc Actran solvers.

The paper is presenting the experimental analysis of the use of biodiesel from waste sunflower oil and a blend of sunflower oil with palm oil as fuel for aviation turbo-engines. A comparative analysis for fuel mixtures made of Jet A + 5% Aeroshell 500 Oil (Ke) with 10%, 30%, and 50% for each bio-fuel type has been performed and Ke has been used as reference. Firstly, the following physical and chemical properties were determined: density, viscosity, flash point, freezing point, calorific power. Then, elemental analysis and Fourier transform infrared spectroscopy (FTIR) analysis were conducted for Ke, biodiesel obtained from recycled sunflower oil (SF), biodiesel obtained from blending recycled sunflower oil, and recycled palm oil (SFP), and for each fuel blend. Secondly, experimental tests of the blends have been conducted on the Jet Cat P80® micro-turbo engine (Gunt Hamburg, Barsbüttel, Germany). The tests have been conducted at different engine working regimes as follows: idle, cruise, intermediate, and maximum. For each regime, a one-minute testing period was chosen, and the engine parameters have been monitored. The turbo engine instrumentation recorded the temperature after the compressor and before the turbine, the fuel consumption and air flow, pressure inside the combustion chamber, and generated thrust. The burning efficiency and the specific consumption have been calculated for all four above-mentioned regimes and for all fuel blends. Two accelerometers have been installed on the engine’s support to register radial and axial vibrations allowing the assessment of engine stability.

Commonly, millions of employees are exposed to occupational health issues, including noise exposure during working hours. Noise is most encountered in industry sector but can also be found in a wide range of other workplaces (airports, concert halls, offices, etc). In this article, we review the noise levels inside a machine shop, for a single working place, with the scope to assess the occupational safety, discuss research approach in identifying the noise issues, control and reduce it. Generally, noise exposure is an expensive issue, with many particularities to be solved and the exact cost is difficult to calculate. This study offers the perspective of what can be done for similar working places and how to perform this in order to protect the employees to be noise exposed above the legal noise limits and relevant conclusions are offered in this direction.

This paper presents an analysis of the possibility of using recycled pork fat-based biodiesel as fuel for aviation turbo-engines. The analysis consists of the assessment of four blends of Jet A kerosene with 10%, 30%, 50%, and 100% biodiesel and pure Jet A that was used as reference in the study. The first part of the paper presents the physical-chemical properties of the blends: density, viscosity, flash point, freezing point, and calorific power. Through Fourier transform infrared spectroscopy (FTIR) analysis, a benchmark was performed on the mixtures of Jet A with 10%, 20%, 30%, 50%, and 100% biodiesel compared with Jet A. The second part of the paper presents the test results of these blends used for fuelling a Jet Cat P80 turbo engine at the Turbo Engines Laboratory of the Aerospace Engineering Faculty of Polyethnic University of Bucharest. These functional tests were performed using different operating regimes as follows: idle, cruise, intermediate, and maximum. For each regime, a testing period of around 1 min was selected and the engine parameters were monitored during the test execution. The burning efficiency was calculated for the maximum regime for all mixtures. To evaluate the functioning stability of the turbo engine using biodiesel, two accelerometers were mounted on the engine support that recorded the radial and axial vibrations. Moreover, to assess the burning stability and to identify other acoustic spectral components when biodiesel is used, two microphones were placed near the jet region. A comparative analysis between blends was made by taking the Jet A fuel as reference.

The growth of the urban population and its activity in major cities has led to various public health challenges, including environmental pollution, which are reflected in a decrease in the well-being of societies. This paper presents a predictive tool used to mitigate the noise impact study of commercial centre noise on the surrounding houses, the study being conducted prior to its construction. Before the construction of the supermarket, the sound pressure levels from the fa&ccedil, ade of the surrounding building are measured to have a background noise level of the analysed area. The noise impact study is made using prediction software in which the houses and the shopping centre buildings are numerically modelled. The main noise sources of the commercial centre, defined in numerical predictions, are represented by the air conditioners, heat pumps situated on the roof and the noise generated by the activities from the supply ramp. The noise impact evaluation is performed at different heights and by determining the number of affected inhabitants. To reduce the number of exposed inhabitants to noise, four technical solutions are presented. The proposed noise solutions are based on technical and economic analyses and also on the urban landscape. The study presents the noise prediction for which the propagation calculus was made according to ISO 9613-2. The noise limits were evaluated according to the Romanian national legislation. The final part of this study presents the noise measurements performed after the construction of this shopping centre and the validation of the implemented noise reduction solution.

the document presents a proposal of a new approach on real hydropower dispatching issue, where the influence of regional energy market could not be neglected anymore.