A typical assumption when performing analytical, numerical, and experimental studies in wave−structure interaction in multi-body problems such as for wave farms and very large floating structures is the homogeneity of the wave field. Important interactions between the floating elements are dependent on the direction, amplitude, and phase of the waves acting on each. Then, wave homogeneity is probably unrealistic in near-shore areas where these installations are to be deployed. In the present work, an existing interaction method, which allows the use of standard boundary element diffraction codes for solving the first order wave structure linear potential for each unique geometry in the problem, is shown to be able to account for inhomogeneous sea states across the domain of a multi-body problem requiring only minimal modification to its implementation. A procedure to use the method to include arbitrary incoming undisturbed wave conditions at each body is presented. A verification study... [more]

The economic sustainability of agricultural production is a crucial concern for most farmers, especially for pig producers who face dynamic changes in the market. Approaches for economic sustainability assessment found in the literature are mainly focused on the short-term economic viability of the farm and rarely take a long-term perspective. In this paper, we propose and test a new, innovative assessment and aggregation method, which brings about a broader view on more long-term aspects of economic sustainability. This wider view on economic sustainability, in addition to classical concepts such as technical efficiency, labor productivity, and farm profitability, incorporates the assessment of the levels of entrepreneurship, risk management, and the resilience of the invested resources. All indicators were scaled and aggregated using scaling and weighting procedures proposed by experts into subthemes and themes. The methodology was tested on a sample of 131 pig farms located in 6 EU... [more]

Industry 4.0 is generalizing the use of wireless connectivity in manufacturing and logistics. Specifically, in Smart Logistics, novel Industry 4.0 technologies are used to enable agile supply chains, with reduced management, energy and storage costs. Cellular networks allow connectivity throughout all the scenarios where logistics processes take place, each having their own challenges. This paper explores such scenarios and challenges, and proposes 5G technology as a global unified connectivity solution. Moreover, this paper proposes a system for exploiting the application-specific optimization capabilities of 5G networks to better cater for the needs of Smart Logistics. An application traffic modeling process is proposed, along with a proactive approach to network optimization that can improve the Quality of Service and reduce connectivity costs.

Recently, sustainable economic growth has taken the front line of the global development agenda. The common dependency on fossil fuel energy, greenhouse gas (GHG) emissions and the continuous rising demands for energy have posed challenges that put the world in a climate change trap. This work empirically analyzes the effect of innovation, oil price, oil price volatility and economic growth on GHG emissions over the period of 1991−2015. The study compares the emission level between European Union countries (EU) (26), oil-producing countries (22), China and the United States of America (USA) using the Driscoll−Kraay model. The main empirical finding points to a positive effect of innovation on GHG emission reduction initiatives in oil-importing economies. Particularly, EU countries significantly minimized emissions due to innovation, followed by China and the USA. Contrarily, the effect of innovation increases GHG emission in oil-exporting economies. The results also indicate broader si... [more]

This paper proposes an integrated magnetic structure for a CLLC resonant converter. With the proposed integrated magnetic structure, two resonant inductances and the transformer are integrated into one magnetic core, which improves the power density of the CLLC resonant converter. In the proposed integrated magnetic structure, two resonant inductances are decoupled with the transformer and can be adjusted by the number of turns in each inductance. Furthermore, two resonant inductances are coupled to reduce the number of turns in each inductance. As a result, the conduction loss can be reduced. The trade-off design of the integrated magnetic structure is carried out based on the Pareto optimization procedure. With the Pareto optimization procedure, both high efficiency and high-power density can be achieved. The proposed integrated magnetic structure is validated by theoretical analysis, simulations, and experiments.

The aim of this study was to investigate and analyze the impact of selected parameters during the tribocharging process of shredded poly(ethylene terephthalate) (PET) and high-density polyethylene (PE-HD) plastics on accumulated electric charge and electrostatic separation effectiveness. The accumulation of electric charge on surfaces of polymer particles as a result of their circular motion forced by the airflow cyclone container was investigated. The impact of the container material, time of tribocharging and the airflow intensity were experimentally examined. A container in which the particles of the considered polymers are electrified with opposite charges was selected. A high ability to accumulate surface charge on small particles of both polymers was demonstrated. The electrified mixed PET/PE-HD was subjected to a separation process. An electrostatic separator designed and constructed by the authors was used for to the separation. In turn, to assess the effectiveness of this sepa... [more]

With the advent of direct current (DC) loads such as LED lighting, IT equipment, electric vehicles, and DC powers generated from renewable energy sources, low voltage DC (LVDC) distribution system is becoming a hot issue. One of the hurdles in the LVDC distribution system is arc flash at the contact points that occurs during the circuit is opening. Unlike alternating current, direct current has no zero points and sustains constantly. Therefore, there is a risk of electric fire due to continuous generating arcs when the load current is interrupted with an existing electrical contact type circuit breaker. Recently, the concept of a hybrid circuit breaker that takes advantage of traditional electrical contact type switch and the arcless semiconductor switch has been proposed, but how to cooperatively operate the two switches has become an issue. This paper analyzes the principle of a hybrid circuit breaker for blocking LVDC current and proposes a gate drive controller for it. Through 400V... [more]

Developing accurate models is necessary to optimize the operation of heating systems. A large number of field measurements from monitored heat pumps have made it possible to evaluate different heat pump models and improve their accuracy. This study used measured data from a heating system consisting of three heat pumps to compare five regression and two artificial neural network (ANN) models. The models’ performance was compared to determine which model was suitable during the design and operation stage by calibrating them using data provided by the manufacturer and the measured data. A method to refine the ANN model was also presented. The results indicate that simple regression models are more suitable when only manufacturers’ data are available, while ANN models are more suited to utilize a large amount of measured data. The method to refine the ANN model is effective at increasing the accuracy of the model. The refined models have a relative root mean square error (RMSE) of less th... [more]

In this paper, we demonstrate the high potentialities of pristine single-cation and mixed cation/anion perovskite solar cells (PSC) fabricated by sequential method deposition in p-i-n planar architecture (ITO/NiOX/Perovskite/PCBM/BCP/Ag) in ambient conditions. We applied the crystal engineering approach for perovskite deposition to control the quality and crystallinity of the light-harvesting film. The formation of a full converted and uniform perovskite absorber layer from poriferous pre-film on a planar hole transporting layer (HTL) is one of the crucial factors for the fabrication of high-performance PSCs. We show that the in-air sequential deposited MAPbI3-based PSCs on planar nickel oxide (NiOX) permitted to obtain a Power Conversion Efficiency (PCE) exceeding 14% while the (FA,MA,Cs)Pb(I,Br)3-based PSC achieved 15.6%. In this paper we also compared the influence of transporting layers on the cell performance by testing material depositions quantity and thickness (for hole transpo... [more]

Trans-critical CO2 vapor compression (VC) refrigeration cycles require a high compression ratio, which is associated with high expansion losses. To recover these expansion losses, a pressure exchange process between the low- and high-pressure sides of the VC cycle is proposed and examined in this study. The proposed pressure exchange system is an open type constant volume process where the high- and low-pressure flows mix inside the system. This prototype is inspired by the pressure exchangers used in reverse-osmosis (RO) desalination systems. In this system, a 2D model was generated and modeled using the computational fluid dynamics (CFD) technique. The numerical model ignored any losses due to leakage or hydraulic friction and the process is considered adiabatic. For the modeling, it was assumed that the inlet conditions for the two pressure exchanger flows are similar to the flow conditions at the evaporator and gas cooler outlets in a VC cycle. Two parameters are examined to test t... [more]

Methane hydrate has attracted attention as a next-generation resource, and many researchers have conducted various studies to estimate its productivity. Numerical simulation is the optimal method for estimating methane gas productivity. Meanwhile, using a reasonable input parameter is essential for obtaining accurate numerical modeling results. Permeability is a geotechnical property that exhibits the greatest impact on productivity. The permeability of hydrate-bearing sediment varies based on the sediment pore structure and hydrate saturation. In this study, an empirical permeability model was derived from experimental data using soil specimens from the Ulleung Basin, and the model was applied in numerical analysis to evaluate the sediment gas productivity and ground stability. The gas productivity and stability of hydrate-bearing sediments were compared by applying a widely used permeability model and the proposed model to a numerical model. Additionally, a parametric study was perfo... [more]

Energy efficiency of systems of water pumping is a complex problem since efficiency of two distinct interacting systems needs to be combined: water and power supply. This paper introduces a non-intrusive method of calculating the so-called “collective losses” of a cage induction motor. The term “collective losses”, which the authors define, allows for accurate estimation of motor efficiency. Control system of a pump determines operating point of a pumping station, and thus its efficiency. General estimated performance characteristics of a motor, components of a control system, are assumed to serve selection of a range of pumping speed variations. Rotational speed has a direct effect on motor load torque, pump power and head, and thus on motor performance. Hellwig’s statistical method was used to specify characteristics of estimated collective losses on the basis of experimental studies of 21 motors rated at up to 2.2 kW. The results of simulations and experiments are used to verify val... [more]

Poland’s rural areas are characterised by a significant degree of development diversity, especially in the case of communes—the smallest territorial units. For development to take place, the entity responsible for its creation must incur the necessary investment expenditures. By implementing the public tasks assigned to them, communes are responsible for ensuring sustainable local development, which indirectly affects regional development and shapes the development of the entire country. Therefore, this article aims to assess the level and diversity of rural commune investment activities and their impact on the development of Poland’s rural areas. The empirical research conducted was aimed at verifying the following hypothesis: “The highest investment activity can be observed primarily in rural communes located in Eastern Poland”. The Regions of Eastern Poland are characterised by their peripheral location, both in the country and all of the EU. The research covered the 2007−2018 perio... [more]

Worst-case execution time (WCET) is an important metric in real-time systems that helps in energy usage modeling and predefined execution time requirement evaluation. While basic timing analysis relies on execution path identification and its length evaluation, multi-thread code with critical section usage brings additional complications and requires analysis of resource-waiting time estimation. In this paper, we solve a problem of worst-case execution time overestimation reduction in situations when multiple threads are executing loops with the same critical section usage in each iteration. The experiment showed the worst-case execution time does not take into account the proportion between computational and critical sections; therefore, we proposed a new worst-case execution time calculation model to reduce the overestimation. The proposed model results prove to reduce the overestimation on average by half in comparison to the theoretical model. Therefore, this leads to more accurate... [more]

The world’s demand for electrical energy is increasing rapidly while the use of fossil fuels is getting limited more and more by energy policies and the need for reducing the impact of climate change. New sources of energy are required to fulfill the world’s demand for electricity and they are currently found in renewable sources of energy, especially in solar and wind power. Choosing the optimal PV nominal power minimizes the unnecessary surplus of electrical energy that is exported to the grid and thus is not making any impact on the grid more than necessary. Oversizing the PV system according to the Croatian net-metering model results in switching the calculation of the costs to the prosumer model which results in a decrease of the project’s net present value (NPV) and an increase in the payback period (PP). This paper focuses on formulating and solving the optimization problem for determining the optimal nominal power of a grid-connected PV system with a case study for Croatia usin... [more]

This paper presents the results of numerical simulations for the developed and discussed conical two-phase atomizers with swirl flow, differing in the ratio of the height of the swirl chamber to its diameter. Experiments were carried out for SAN-1 with HS/DS = 1 and SAN-2 with HS/DS = 4 atomizers. The study was conducted over a range of Reynolds number for liquid ReL = (1400; 5650) and for gas ReG = (2970; 9900). Numerical calculations were performed with the use of computational fluid dynamics (CFD), which were verified on the basis of experimental data. Based on the analysis of experimental studies and simulations results the influence of operational parameters and changes of the atomizer geometry on the generated spray was demonstrated. As the gas flow rate increased and the swirl chamber height decreased, the spray angle increased. Higher velocity values of the liquid and greater turbulence occur in the center of the spray. The flow inside the atomizer determines the nature of the... [more]

The U.S. Deepwater Gulf of Mexico (DGOM) area that has some of the most prolific oil reservoirs is still awaiting the development of a viable enhanced oil recovery (EOR) process. Without it, DGOM will remain severely untapped. Exorbitant well costs, in excess of $200 million, preclude having extensive injection patterns, commonly used in EOR design frameworks. Aside from injection patterns, even operationally waterflooding has met with significant challenges because of injectivity issues in these over pressurized turbidities. The gas-assisted gravity drainage (GAGD) EOR process, that holds promise for deepwater environments because of lesser injectivity issues, among others, has been adapted in this work to overcome these limitations. A novel design in the form of a single well—gas assisted gravity drainage (SW-GAGD) process, has been demonstrated to emulate the benefits of a GAGD process in a cost-effective manner. Unlike conventional GAGD processes, which need multiple injectors and... [more]

Increasing the unplanned penetration of Distributed Generators (DGs) has spurred active and reactive power losses in the distribution system. This article suggests using a novel Strawberry Plant Propagation Algorithm (SPPA) for planning the placement of the DGs with the aim of reducing the network (active) power losses and improving the overall voltage profile. The proposed method (SPPA) has been tested on 33 and 69 node radial systems in MATLAB. A cost analysis was also performed and compared with other contemporary methods. The results for the considered variables show the significance of the proposed method in comparison to various other counterparts, including the Mine Blast Algorithm and Particle Swarm Optimization.

Hydraulic systems are widely used in the aeronautic, machinery, and energy industries. The functions that these systems perform require high reliability, which can be achieved by examining the causes of possible defects and failures and by taking appropriate preventative measures. One of the most popular methods used to achieve this goal is FMEA (Failure Modes and Effects Analysis), the foundations of which were developed and implemented in the early 1950s. It was systematized in the following years and practically implemented. It has also been standardized and implemented as one of the methods of the International Organization for Standardization (ISO) 9000 series standards on quality assurance and management. Apart from wide application, FMEA has a number of weaknesses, which undoubtedly include risk analysis based on the RPN (Risk Priority Number), which is evaluated as a product of severity, occurrence, and detection. In recent years, the risk analysis has been very often replaced... [more]

Energy efficiency programmes (EEPs) are schemes operated by utilities or other bodies in order to incentivize energy efficiency improvement, in particular by adoption of energy-efficient products and typically by means of an economic reward. Ample experience has been gained, especially in the U.S., where EEPs have been in use for decades, with the rationale of avoiding additional energy supply by improving energy efficiency. More recently, EEPs have been implemented in Europe and in Switzerland. This review paper presents insights from the U.S., the EU and especially from Switzerland, with a focus on levelised programme cost of saved energy (LPC) as a key performance indicator. These LPC values, which take the perspective of the programme operator, are typically low to very low compared to the cost of electricity supply, thereby representing an important argument in favour of their use. The country examples show that EEPs are being effectively and successfully put into practice, for ex... [more]

This paper presents simulation and bench test results for a special type of centrifugal pump that enables the transport of dispersive foaming liquids and simultaneous separation of the liquid phase. During the design phase, CFD (Computer Fluid Dynamics) simulations were performed using Ansys Fluent. The simulations covered changing the operating parameters of the pump (mass/volume flow rate), pressure analysis for the first impeller, and structural optimization of the pump components. In the second stage of the research, the pump and a measuring station were constructed to validate the results of the numerical simulations.

The current transformation of power systems is aiming towards distributed source integration and general decentralization. Renewable energy sources and support of local energy supply create conditions for widespread use of new technologies and smart grids. As the electrical grids become more electrically independent, the importance of frequency control will rise. Stability of the system in such cases is no longer only relying on rotating inertia of generators as in the centralized grid. This known scenario has already been analyzed by many with computational models for optimal safety precautions of the grid. This paper aims to update the common home appliance frequency characteristics through measurements and compare them to those currently used. These devices were divided into two groups: general categorization and light sources. Subsequently, the frequency sensitivity coefficients were evaluated and analyzed home appliances were sorted into three categories according to the size of t... [more]

The use of static frequency converters, which have a high switching frequency, generates voltage pulses with a high rate of change over time. In combination with cable and motor impedance, this generates repetitive overvoltage at the motor terminals, influencing the occurrence of partial discharges between conductors, causing degradation of the insulation of electric motors. Understanding the effects resulting from the frequency converter−electric motor interaction is essential for developing and implementing insulation systems with characteristics that support the most diverse applications, have an operating life under economically viable conditions, and promote energy efficiency. With this objective, a search was carried out in three recognized databases. Duplicate articles were eliminated, resulting in 1069 articles, which were systematically categorized and reviewed, resulting in 481 articles discussing the causes of degradation in the insulation of electric motors powered by frequ... [more]

In the transient process of the grid-connected converter (GCC), the existing research mainly focuses on the impact of the control loops. Little attention is paid to the transient stability issues driven by the imbalance between the input power and output power of GCC. This paper shows that the transient stability issues will still exist even if ignoring the dynamics of phase-locked loop (PLL) and current loop. In this paper, the models of the AC grid and the GCC are built under the assumption that the dynamics of the PLL and current loop are ignored. Then, by analyzing the transient process of GCC under non-severe remote voltage sag, the effects of the imbalance power on the transient stability of GCC are discussed. Moreover, for the GCC to operate stably after the transient process, there should be a maximum input power limit (MIPL) for GCC, and the imbalance power equation is applied in this paper to determine the transient stability of GCC. Furthermore, the effects of the current li... [more]

In an interior permanent magnet synchronous motor, an adhesive such as bond is generally injected into the magnet tolerance to prevent vibration of the permanent magnet within the insertion space. In this case, a disadvantage is that the magnet tolerance does not contribute to the performance. In this paper, ferrofluid is inserted to improve the torque density, utilizing the magnet tolerance. When inserting ferrofluid into the magnet tolerance, it is important to fix the magnet because conventional adhesives are not used, and it is important that the ferrofluid does not act as a leakage path within the insertion space. In this study, a new rotor configuration using a plastic barrier that satisfies these considerations was introduced. The analysis was conducted through finite element analysis (FEA), and this technique was verified by comparing the simulation results and the experimental results through a dynamo test. It was confirmed that the no-load back electromotive force in the fina... [more]