Changes in the elastic characteristics of the railway subgrade have been determined using nonstop long-term (more than 50 days) train passage seismic observations. We examined the records of the broadband sensitive seismometer TC-120s in the low-frequency band (below 0.1 Hz) to obtain the subgrade response to various train passages and its relaxation after unloading. Analytical models of subgrade deformation by the train are proposed. When comparing models in the experiment, we showed that a lowpass filter (below 0.1 Hz) provides waveforms with parameters determined by the deformation properties of the soil. We carried out statistical processing of 1600 train seismic records and determined parameters characterizing the subgrade reaction to the vibration effects created by trains in the ultra-low-frequency range. Therefore, we can use these parameters to monitor after daily averaging and weekly smoothing. When observing the spring thawing of the soil, we considered the sensitivity of se... [more]

Single planar fuel cell elements consisting of metallic interconnectors that are bonded and sealed by a thin glass solder layer form the core of a solid oxide fuel cell. For reliable operation, the bonding layer has to adhere well and must be without voids or foreign material inclusions, which might cause gas leakage, electrical shorts or mechanical weakening and structural failure. Nondestructive testing (NDT) by the high-frequency ultrasound in immersion technique and by air-coupled ultrasound was optimized to find such defects. Another technique was flash light excited thermography for detection of voids. The NDT techniques used are complementary to each other, as they are based on different physical principles. Voids and small steel platelets of different sizes were prepared in the glass solder layer before the high-temperature bonding process and then monitored by the NDT techniques through the interconnector plates. Two selected NDT techniques were then validated in a probability... [more]

In order to meet the requirements of high-tech enterprises for high power quality, high-quality operation and maintenance (O&M) in smart distribution networks (SDN) is becoming increasingly important. As a significant element in enhancing the high-quality O&M of SDN, situation awareness (SA) began to excite the significant interest of scholars and managers, especially after the integration of intermittent renewable energy into SDN. Specific to high-quality O&M, the paper decomposes SA into three stages: detection, comprehension, and projection. In this paper, the state-of-the-art knowledge of SND SA is discussed, a review of critical technologies is presented, and a five-layer visualization framework of the SDN SA is constructed. SA detection aims to improve the SDN observability, SA comprehension is associated with the SDN operating status, and SA projection pertains to the analysis of the future SDN situation. The paper can provide researchers and utility engineers with insights into... [more]

Gas accidents threaten the safety of underground coal mining, which are always accompanied by abnormal gas concentration trend. The purpose of this paper is to improve the prediction accuracy of gas concentration so as to prevent gas accidents and improve the level of coal mine safety management. Combining the LSTM model with the LightGBM model, the LSTM-LightGBM model is proposed with variable weight combination method based on residual assignment, which considers not only the time subsequence feature of data, but also the nonlinear characteristics of data. During the data preprocessing, the optimal parameters of gas concentration prediction are determined through the analysis of the Pearson correlation coefficients of different sensor data. The experimental results demonstrate that the mean absolute errors of LSTM-LighGBM, LSTM and LightGBM are 1.94%, 2.19% and 2.77%, respectively. The accuracy of LSTM-LightGBM variable weight combination model is better than that of the two above mo... [more]

Nowadays, the energy sector is experiencing a profound transition. Among all renewable energy sources, wind energy is the most developed technology across the world. To ensure the profitability of wind turbines, it is essential to develop predictive maintenance strategies that will optimize energy production while preventing unexpected downtimes. With the huge amount of data collected every day, machine learning is seen as a key enabling approach for predictive maintenance of wind turbines. However, most of the effort is put into the optimization of the model architectures and its parameters, whereas data-related aspects are often neglected. The goal of this paper is to contribute to a better understanding of wind turbines through a data-centric machine learning methodology. In particular, we focus on the optimization of data preprocessing and feature selection steps of the machine learning pipeline. The proposed methodology is used to detect failures affecting five components on a win... [more]

Lower Cambrian shale and lower Silurian shale are both typical of oil-prone kerogen and siliceous composition, but different in thermal maturities. Porosity differences were determined in marine shales between the two shales. Measurements were utilized including organic geochemistry, XRD, scanning electron microscopy (SEM) and N2 gas adsorption. Pore volume (PV) of lower Silurian shale was approximately 1.5 times higher than that of lower Cambrian shale, and pore surface area (PSA) of lower Silurian shale was almost 2.5 times higher than that of lower Cambrian shale. Lower Cambrian shale and lower Silurian shale possess similar materials, but distinctive thermal degrees. Evolution mechanisms of different types of pores, especially organic matter (OM)-hosted pores, may trigger this different pore features. Pores of rigid framework are the residue of primary interparticle pores during the burial history. Pores associated with clay flakes can be preserved well adjacent to rigid grains or... [more]

Uncertainties are the most significant challenges in the smart power system, necessitating the use of precise techniques to deal with them properly. Such problems could be effectively solved using a probabilistic optimization strategy. It is further divided into stochastic, robust, distributionally robust, and chance-constrained optimizations. The topics of probabilistic optimization in smart power systems are covered in this review paper. In order to account for uncertainty in optimization processes, stochastic optimization is essential. Robust optimization is the most advanced approach to optimize a system under uncertainty, in which a deterministic, set-based uncertainty model is used instead of a stochastic one. The computational complexity of stochastic programming and the conservativeness of robust optimization are both reduced by distributionally robust optimization.Chance constrained algorithms help in solving the constraints optimization problems, where finite probability get... [more]

CaCl2·6H2O is selected as the original substrate for research, and a new composite phase change material (CPCM) suitable for air-conditioning was developed through experiments. The new modified CaCl2·6H2O CPCM uses glycerol as a temperature regulator and barium hydroxide octahydrate as a nucleating agent. The experimental results show that when the mass ratio of CaCl2·6H2O to glycerol is 85:15, the melting temperature of the CPCM is 11.8 °C and the enthalpy of phase change is 112.86 J/g. The chemical composition of the CPCM was characterized by Fourier transform infrared spectroscopy, which confirmed that the material was successfully developed. When the amount of barium hydroxide octahydrate nucleating agent was 1.0 wt.%, the supercooling of the CPCM decreased to 1.22 °C. CPCM still show good stability after 50 thermal cycles and can be used in practical production.

In this study, the thermal stabilization of a water resource together with an energy production optimization in the power plant of the dam−reservoir coupled system is conducted. This coupled dam system is designed to consist of a primary (Włocławek) and secondary (Siarzewo) dam due to the erosion control aspect. The other beneficial aspect of this coupled dam design is to have an additional power plant, with the aim of achieving more efficient renewable energy production. One of the factors to be included in the conditions influencing the energy production is the ice formation in the reservoir and tailwater due to the hydrodynamic and meteorological conditions of the site location. Frazil formation and jam may reduce the power plant efficiency. The concept of thermal stabilization, based on the previous studies, refers to providing the ice cover in the reservoir section of a dam to isolate the water from thermal condition. In this research, the ice cover expansion is triggered by the d... [more]

Community energy is seen as a helping hand for local, decentralized energy transition. Besides the main goal of supporting the community-friendly and socially acceptable development of renewable energies, the hope is also that a pro-environmental influence on sustainability behavior will be triggered when joining a community energy project. An analysis of a survey among 16 community energy projects in Germany, with 565 completed questionnaires, shows that a certain part of the members pays more attention to their energy behavior and develop a more positive attitude towards a decentralized energy transition and citizen participation after joining the community energy project. Therefore, we can empirically support that climate protection projects, such as community energy, influence pro-environmental attitudes and behavior, but this does not apply equally to all population groups. Members with higher income and stronger interest in returns are less likely to change their behavior. Based... [more]

This research aims to enter the miniature refrigeration machine sector with the objective of designing a small scale unit while maintaining a competitive coefficient of performance (COP), comparing with a Peltier plates system. To this end, a research of the current technology was carried out in order to obtain indicative values on the scales that were being worked on and their application. After the previous research, a refrigeration cycle was designed in EES (engineering equation solver). From this design, different conclusions were obtained: (1) The correct sizing of the compressor revolutions together with its displacement is crucial for the equipment to be able to provide the desired cooling capacity. (2) In order to obtain the desired cooling capacity in the microscale refrigeration system, the heat exchangers must have fins. (3) Of the analysed refrigerants, R600a is the best choice, as it shows favourable characteristics (high COP and low compression ratio) when working in this... [more]

This work analyzes the heat transfer and fluid flow within a batch reactor for hydrothermal carbonization (HTC) of raw olive pomace (ROP). The autoclave is partially filled with a mixture of ROP and distilled water and hence it is considered as a dispersed medium. The reactor is heated through its lateral surface, whereas the bottom wall and the upper surface of the mixture are thermally insulated. Under the effect of heat and pressure, the fluid moves inside the reactor, while particles are subject to other forces. Additionally, the biomass (ROP) is decomposed into very fine particles to produce a solid product (hydrochar). COMSOL Multiphysics software is used for the analysis of heat transfer and fluid dynamics. Chemical kinetics of the reactions are modeled by a basic kinetics model. Numerical results are validated using experimental data carried out in similar operating conditions. They are in good agreement since the deviation between them does not exceed 6%. Isotherms, velocity f... [more]

Environmental meteorological parameters (temperature, humidity, air pressure, etc.) have an important impact on short gap streamer discharge. Based on the streamer theory and particle continuity equation of gas discharge, a short gap streamer discharge simulation model is established, and the influence of environmental parameters on the dynamic development process of streamer discharge is simulated and analyzed. The short gap air gap discharge characteristics were tested in a self-made gas discharge chamber. The results show that at low humidity (relative humidity 80%), with the increase of humidity, the electron density of the streamer channel decreases, the field strength of the streamer head decreases, the development speed of the streamer slows down, and the gap breakdown voltage increase. With a decrease of gas pressure, the electron density of the streamer channel decreases, the field strength of the streamer head decreases, the development speed of the streamer increases, and th... [more]

This paper presents a detailed analysis of dynamic properties and accuracy issues of the torque-producing stator current control loop for vector-controlled induction motor drives. In this paper, a necessary mathematical description of vector control of an induction motor is shown with respect to the x-axis and y-axis current control in the rotating reference frame. A derivation of a steady-state error for the torque-producing stator current control scheme with and without a decoupling algorithm is described. The presented derivation and dynamic behavior of both these schemes were extensively tested in the MATLAB-SIMULINK software, considering different values for the moment of inertia. This solution was implemented in a DSC-based induction motor drive using a voltage source inverter to obtain experimental results. Moreover, the advantages of using the presented decoupling block for compensation of the problem are discussed at the end of the paper.

Ultra-fast charging infrastructures are gaining increasing interest thanks to their ability to reduce the charging-time of plug-in electric vehicles to values comparable to those of the refueling of traditional vehicles in gas stations. This is a consequence of the increasing rated power of both on-board batteries and charging equipment. On the other hand, the increased values of charging power have led to an increased impact on the power distribution networks, particularly in terms of line currents and bus voltages. In presence of large penetration of ultra-fast charging devices, in fact, both currents and voltages are affected by larger variations whose values can exceed the admissible limits imposed by the technical constraints and by the levels of quality of service. In order to reduce the impact of this typology of vehicles’ charging on the electrical infrastructure, in this paper a methodology is presented which allows managing a microgrid in presence of ultra-fast charging stati... [more]

The International Maritime Organisation (IMO) calls for the maritime industry to restrict its CO2 emissions by −40% (IMO2030) and −70% (IMO2050). This paper answered the following research question: “Which technical, economic and emissions-related conditions predominantly determine the feasibility of a conceptual supply chain of liquid CO2 that is captured from the exhaust gases of LNG powered offshore vessels?” The captured CO2 is transported to land where it is utilized by a final customer. The study followed a systems engineering approach. Problem definition was followed by a requirements analysis (technology, emissions, economy and operations), design with scenarios and a case study with realistic vessel deployment, modeling and evaluation. All designs have technical uncertainties and financial risks, but the sale of captured CO2 could be a crucial advantage of the proposed concept over other concepts. The main conclusion is that emission and financial targets (payback time) can be... [more]

The concept of energy transition has been adopted by national governments, international and regional organizations. The COVID-19 pandemic triggered increasing attention to climate policy, energy transition, and economic resilience. This paper looks at energy transition in selected countries with the use of case studies—China, the European Union, India, Russia, Saudi Arabia, and the United States. The aim of the study is to analyze the main approaches to the energy transition in these countries and the barriers which may influence this process. The study applies foresight methods such as trend monitoring, case study, and STEPE methods for barrier analysis. The outcomes include identification of energy priorities in the national context, key directions for future transformation, and selected countries’ approaches to the energy transition after the COVID-19 pandemic. All considered countries are taking measures for the energy transition, but the motives, pace, and priorities differ. Thei... [more]

Multisource energy data, including from distributed energy resources and its multivariate nature, necessitate the integration of robust data predictive frameworks to minimise prediction error. This work presents a hybrid deep learning framework to accurately predict the energy consumption of different building types, both commercial and domestic, spanning different countries, including Canada and the UK. Specifically, we propose architectures comprising convolutional neural network (CNN), an autoencoder (AE) with bidirectional long short-term memory (LSTM), and bidirectional LSTM BLSTM). The CNN layer extracts important features from the dataset and the AE-BLSTM and LSTM layers are used for prediction. We use the individual household electric power consumption dataset from the University of California, Irvine to compare the skillfulness of the proposed framework to the state-of-the-art frameworks. Results show performance improvement in computation time of 56% and 75.2%, and mean squar... [more]

A mathematical model is developed of the master circuit of an electric driver system including a power transformer and susceptible motion transmission of asynchronous and synchronous drives. Electric motors drive water pumps by means of motion transmission that comprises two elastic couplings of lumped mechanical parameters and a long shaft of distributed mechanical parameters. Differential equations for oscillatory processes for the long shaft and the elastic couplings are different. The shaft is described with partial derivative Euler−Poisson equations, which, combined with the boundary conditions, form mixed problems from the mathematical point of view. The elastic couplings, on the other hand, are described with the ordinary second type Lagrange equations. Based on the theory of electromagnetic field, the partial differential equations describe the skin effects across the rotor age bars. Vertical pumps are presented by means of a loading torque waveform as a function of the input s... [more]

By optimizing the positions of wind turbines in a wind farm, the power loss caused by wake effects can be reduced maximally. A new methodology of layout optimization is proposed utilizing a full-field wake model that integrates the near-field and far-field wake models after modifications, and a random search (RS) algorithm improved with a scale factor for acceleration in high-density layouts. The methodology is applied to a floating wind farm composed of modular platforms, which have a novel configuration and the ability to face toward the wind direction. The applicability and efficiency of the methodology and the improved RS algorithm are validated. The power production of optimized layouts shows a flat crest with an increased number of wind turbines. There is a layout with maximal output power in the wind farm. The real optimal layout should be determined in consideration of both output power and cost. Two sizes of platforms with different number of modules are compared in the applic... [more]

Monitoring the thermal comfort of building occupants is crucial for ensuring sustainable and efficient energy consumption in residential buildings. It enables not only remote real-time detection of situations, but also a timely reaction to reduce the damage made by harmful situations in targeted buildings. In this paper, we first design a new Internet of Things (IoT) architecture in order to provide remote availability of both indoor and outdoor conditions, with respect to the limited energy of IoT devices. We then build a multi-output prediction model of indoor parameters using a random forest learning algorithm, and based on a longitudinal real dataset of one year. Our prediction model considers outdoor conditions to predict the indoor ones. Hence, it helps to detect discomfort situations in real-time when comparing predicted variables to real ones. Furthermore, when detecting an indoor thermal discomfort, we provide a new genetic-based algorithm to find the most suitable values of i... [more]

The problem of rock mechanics and engineering is an old and new subject encountered by human beings in their struggle with nature for survival and development [...]

The increased focus on energy efficiency, both at the national and international levels, has fostered the diffusion and development of specific energy consumption benchmarks for most relevant economic sectors. In this context, energy-intensive facilities, such as hospitals and health structures, represent a unique case. Indeed, despite the high energy consumption of these structures, scientific literature lacks the presence of adequate energy performance benchmarks, especially in regard to the European context. Thus, this study aimed at defining energy benchmark indicators for the Italian private healthcare sector using data collected from the Italian mandatory energy audits according to Art.8 EU Directive 27/2012. The benchmark indicators’ definition was made using a methodology proposed by the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). This methodology provided the calculation of specific energy performance indicators (EnPIs) by... [more]

At present, the wheel loaders on the market have steering vibration problems, which can be summarized as follows: the front frame and the cab vibrate violently at the beginning and at the end of steering. This paper analyzed the steering vibration mechanism by collecting the pressure at different positions of the hydraulic steering system and AMESim simulation. A cushion valve was designed to solve the problem of steering vibration. Finally, the prototype test was carried out and it was concluded that the cushion valve reduced the steering pressure starting shock by 50%, the stop vibration was reduced by 75%, and the suction problem no longer occurred. Further, the analysis provides theoretical and experimental basis for research on the steering system of loaders, and also provides new ideas for the design and optimization of vehicle steering systems.

The demand for the high-performance and low-cost position control actuators in many applications promotes the development of three-phase hybrid stepper motors. The torque ripple, loss, and pullout torque of the motor are the key factors to be considered in the motor application. In order to solve the problems of the open-loop control mode, this paper proposes a new “sensorless closed-loop” control mode to significantly improve the performance of three-phase hybrid stepper motors. This control mode is developed by estimating the rotor position with the Extended Kalman filter observer, thereby realizing the closed-loop control of the motor with sensorless technology. This paper illustrates the effects of this control mode by analyzing motor noise, losses, and pullout-torque. The results show that the use of the “sensorless closed-loop” control mode presented can effectively improve the performance of the stepper motor while maintaining the advantages of the motor in terms of cost and siz... [more]