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Photonics ◽  
2022 ◽  
Vol 9 (1) ◽  
pp. 34
Author(s):  
Hassan Termos ◽  
Ali Nansour

This study focuses on a novel concept of transmitting of a quadrature phase shift keying (QPSK) modulation by an electro-optical frequency up-conversion using a cascaded Mach–Zehnder modulators (MZMs) link. Furthermore, we conduct and compare the results obtained by simulations using the Virtual Photonics Inc. (VPI) (Berlin, Germany) simulator and real-world experiments. The design and operating regime peculiarities of the MZM used as a sampling up-converter mixer in a radio over fiber (RoF) system are also analyzed. Besides, the simulation and experimental results of static and dynamic characteristics of the MZM have approximately the same behavior. The conversion gain of the cascaded MZMs link is simulated over many mixing frequencies and it can decrease from 17.5 dB at 8.3 GHz to −4.5 dB at 39.5 GHz. However, in real world settings, it may decrease from 15.5 dB at 8.3 GHz to −6 dB at 39.5 GHz. The maximum frequency range is attained at 78.5 GHz for up-conversion through simulations. Error vector magnitude (EVM) values have been done to evaluate the performance of our system. An EVM of 16% at a mixing frequency of 39.5 GHz with a bit rate of 12.5 Gbit/s was observed with the considering sampling technique, while it reached 19% in real-world settings with a sampling frequency of 39.5 GHz and a bit rate of 12.5 Gbit/s.


2021 ◽  
pp. 248-254
Author(s):  
Petru Cardei ◽  
Cristian Nuţescu ◽  
Mihai Matache ◽  
Oana Cristea

In this paper, a few assessments of the optimal parametric combinations in the operating regime of agricultural aggregates with ploughs of variable width are made. The starting point was from a classic expression of the tillage draft force required for traction. In order to find optimal points, some problems of constrained extreme have been formulated. Extremes provided by the optimal working width and speed have been found. Such optimal points have existed in the literature, for about half a century. Using these theoretical estimates of the optimal points sought, assessments of the possibilities for their experimental validation were made. Basic conditions for an experimental plan are formulated to highlight such optimal points.


2021 ◽  
Vol 12 (1) ◽  
pp. 191
Author(s):  
Miguel Suffo ◽  
Cristobal J. López-Marín

Current commercial software tools implement turbulence models on computational fluid dynamics (CFD) techniques and combine them with fluid-structural interaction (FSI) techniques. There are currently a great variety of turbulence methods that are worth investigating through a comparative study in order to delineate their behavior on scaffolds used in tissue engineering and bone regeneration. Additive manufacturing (AM) offers the opportunity to obtain three-dimensional printed scaffolds (3D scaffolds) that are designed respecting morphologies and that are typically used for the fused deposition model (FDM). These are typically made using biocompatible and biodegradable materials, such as polyetherimide (PEI), ULTEM 1010 biocompatible and polylactic acid (PLA). Starting from our own geometric model, simulations were carried out applying a series of turbulence models which have been proposed due to a variety of properties, such as permeability, speed regime, pressures, depressions and stiffness, that in turn are subject to boundary conditions based on a blood torrent. The obtained results revealed that the detached eddy simulation (DES) model shows better performance for the use of 3D scaffolds in its normal operating regime. Finally, although the results do not present relevant differences between the two materials used in the comparison, the prototypes simulated in PEI ULTEM 1010 do not allow their manufacture in FDM for the required pore size. The printed 3D scaffolds of PLA reveal an elastic behavior and a rigidity that are similar to other prototypes of ceramic composition. Prototypes made of PLA reveal unpredictable variability in pore and layer size which are very similar to cell growth itself and difficult to keep constant.


2021 ◽  
Vol 2064 (1) ◽  
pp. 012098
Author(s):  
A I Lipchak ◽  
S V Barakhvostov ◽  
N B Volkov ◽  
E A Chingina ◽  
I S Turmyshev

Abstract The paper presents the experimental results of triggering a high-voltage gas gap by YAG: Nd3+ laser radiation. The gas gap was used as the primary switch of a high-current pulsed e-beam RADAN-type accelerator. As a result, an operating regime when the instability and delay time appeared to be minimal was experimentally found. The developed gas gap and the found operating regimes sustain the switching instability no more than 0.3 ns. The physical mechanisms determining the switch-on delay and the obtained level of instability are discussed.


Water ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 2983
Author(s):  
Stephan Heimerl ◽  
Niklas Schwiersch

In times of the energy transition and the intensified expansion of renewable energy systems, this article presents an optimization approach for run-of-river power, i.e., dynamic water-level regulation. Its basic idea is to use river sections influenced by backwater more evenly via the operating regime of a hydropower plant. In contrast to conventional dam and weir water level management, the head of the reservoir is not shifted toward the weir while the discharge rate increases but is kept in position by temporarily raising the water level. This generates a greater head for higher discharge rates of an operating regime. As can be shown using an example, this has a direct effect on the performance and, in interaction with the discharge duration curve, on the annual work of the plant. The dynamic water-level regulation, thus, represents an environmentally compatible, energy-efficient optimization for run-of-river hydropower plants.


2021 ◽  
Author(s):  
Ildar Radikovich Abdrakhmanov ◽  
Evgenii Alekseevich Kanin ◽  
Sergei Andreevich Boronin ◽  
Evgeny Vladimirovich Burnaev ◽  
Andrei Aleksandrovich Osiptsov

Abstract We propose a novel approach to data-driven modeling of a transient production of oil wells. We apply the transformer-based neural networks trained on the multivariate time series composed of various parameters of oil wells measured during their exploitation. By tuning the machine learning models for a single well (ignoring the effect of neighboring wells) on the open-source field datasets, we demonstrate that transformer outperforms recurrent neural networks with LSTM/GRU cells in the forecasting of the bottomhole pressure dynamics. We apply the transfer learning procedure to the transformer-based surrogate model, which includes the initial training on the dataset from a certain well and additional tuning of the model's weights on the dataset from a target well. Transfer learning approach helps to improve the prediction capability of the model. Next, we generalize the single-well model based on the transformer architecture for multiple wells to simulate complex transient oilfield-level patterns. In other words, we create the global model which deals with the dataset, comprised of the production history from multiple wells, and allows for capturing the well interference resulting in more accurate prediction of the bottomhole pressure or flow rate evolutions for each well under consideration. The developed instruments for a single-well and oilfield-scale modelling can be used to optimize the production process by selecting the operating regime and submersible equipment to increase the hydrocarbon recovery. In addition, the models can be helpful to perform well-testing avoiding costly shut-in operations.


Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6227
Author(s):  
Muhammed Saeed ◽  
Abdallah S. Berrouk ◽  
Munendra Pal Singh ◽  
Khaled Alawadhi ◽  
Muhammad Salman Siddiqui

The role of a pre-cooler is critical to the sCO2-BC as it not only acts as a sink but also controls the conditions at the main compressor’s inlet that are vital to the cycle’s overall performance. Despite their prime importance, studies on the pre-cooler’s design are hard to find in the literature. This is partly due to the unavailability of data around the complex thermohydraulic characteristics linked with their operation close to the critical point. Henceforth, the current work deals with designing and optimizing pre-cooler by utilizing machine learning (ML), an in-house recuperator and pre-cooler design, an analysis code (RPDAC), and a cycle design point code (CDPC). Initially, data computed using 3D Reynolds averaged Navier-Stokes (RANS) equation is used to train the machine learning (ML) model based on the deep neural network (DNN) to predict Nusselt number (Nu) and friction factor (f). The trained ML model is then used in the pre-cooler design and optimization code (RPDAC) to generate various designs of the pre-cooler. Later, RPDAC was linked with the cycle design point code (CDPC) to understand the impact of various designs of the pre-cooler on the cycle’s performance. Finally, a multi-objective genetic algorithm was used to optimize the pre-cooler geometry in the environment of the power cycle. Results suggest that the trained ML model can approximate 99% of the data with 90% certainty in the pre-cooler’s operating regime. Cycle simulation results suggest that the cycle’s performance calculation can be misleading without considering the pre-cooler’s pumping power. Moreover, the optimization study indicates that the compressor’s inlet temperature ranging from 307.5 to 308.5 and pre-cooler channel’s Reynolds number ranging from 28,000 to 30,000 would be a good compromise between the cycle’s efficiency and the pre-cooler’s size.


2021 ◽  
Vol 24 (68) ◽  
pp. 53-71
Author(s):  
D. Gonzalez-Calvo ◽  
R.M. Aguilar ◽  
C. Criado-Hernandez ◽  
L.A. Gonzalez-Mendoza

The planning of industrial maintenance associated with the production of electricity is vital, as it yields a current and future snapshot of an industrial component in order to optimize the human, technical and economic resources of the installation. This study focuses on the degradation due to fouling of a gas turbine in the Canary Islands, and analyzes fouling levels over time based on the operating regime and local meteorological variables. In particular, we study the relationship between degradation and the suspended dust that originates in the Sahara Desert. To this end, we use a computational procedure that relies on a set of artificial neural networks to build an ensemble, using a cross-validated committees approach, to yield the compressor efficiency. The use of trained models makes it possible to know in advance how the local fouling of an industrial rotating component will evolve, which is useful for maintenance planning and for calculating the relative importance of the variables that make up the system


Author(s):  
Marcin Połom ◽  
Paweł Wiśniewski

The present study attempts to examine the research gap in terms of comparing the environmental impact of trolleybuses and diesel buses in the conditions of a country with an unfavourable energy mix. The analysed example concerns the trolleybus transport system in Gdynia, in northern Poland, which also partially serves the neighbouring city of Sopot. In the last few years, two bus lines have been electrified with trolleybuses in the In-Motion-Charging technology, which enables operation on sections without an overhead network. Using the actual operational data, a comparative analysis of the emissivity of diesel buses and trolleybuses used on the same lines in an identical operating regime was conducted. Moreover, an attempt was made to estimate the damage costs of the emission of air pollutants for the above-mentioned means of transport. Research has shown that trolleybuses significantly help to reduce emissions of nitrogen oxides, non-methane volatile organic compounds and particulate matter, while increasing sulphur dioxide emissions on the served lines. They also generate lower specific emissions of carbon dioxide compared to diesel buses. However, taking into account the differences in the number of seats in these vehicles, the length of routes resulting from a need to provide access to the necessary infrastructure and the total amount of kilometres covered on a given route, they may cause higher emissions per year and per the product life cycle than diesel buses. This is related to the unfavourable structure of energy production in Poland, which is dominated by coal sources. The research results clearly show that the use of trolleybuses in public transport contributes to a reduction of the damage costs of the emission of pollutants that amount to approximately EUR (€) 30,000–60,000 per year for the analysed lines.


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