bluuebunny/crossref_metadata_2025 huggingface dataset:
Are Mobility and COVID-19 Related? A Dynamic Analysis for Portuguese Districts
Authors: Casa Nova António , Ferreira Paulo , Almeida Dora , Dionísio Andreia , Quintino Derick
Published: June 2021

In this research work, we propose to assess the dynamic correlation between different mobility indices, measured on a daily basis, and the new cases of COVID-19 in the different Portuguese districts. The analysis is based on global correlation measures, which capture linear and non-linear relationships in time series, in a robust and dynamic way, in a period without significant changes of non-pharmacological measures. The results show that mobility in retail and recreation, grocery and pharmacy, and public transport shows a higher correlation with new COVID-19 cases than mobility in parks, workplaces or residences. It should also be noted that this relationship is lower in districts with lower population density, which leads to the need for differentiated confinement policies in order to minimize the impacts of a terrible economic and social crisis.
Passive Cooling Solutions to Improve Thermal Comfort in Polish Dwellings
Authors: Ferdyn-Grygierek Joanna , Grygierek Krzysztof , Gumińska Anna , Krawiec Piotr , Oćwieja Adrianna , Poloczek Robert , Szkarłat Julia , Zawartka Aleksandra , Zobczyńska Daria , Żukowska-Tejsen Daria
Published: June 2021

The household sector in Poland consumes more than 25% of final energy. At the same time, residents reported dissatisfaction with the thermal conditions during the summer months. This paper details the search for passive and energy-efficient solutions to improve thermal comfort in Polish dwellings. A five-story, multi-family building was selected for this research. Analyses were conducted in apartments located on the top two floors using EnergyPlus (for thermal calculations) and CONTAM (for air exchange calculations) simulation programs for current and future climatic conditions. The stochastic behavior of people when opening windows and automatically controlled systems supplying external air to the building was considered. Airing the apartments by opening windows increased the heating demand but reduced the number of thermal discomfort hours by over 90%. The degree of airing by opening windows depends on residents opening their windows; therefore, a mechanical supply of external air controlled by both internal and external temperatures was proposed and tested.
Comparison of Efficient Ways of Mud Cake Removal from Casing Surface with Traditional and New Agents
Authors: Kremieniewski Marcin , Wiśniowski Rafał , Stryczek Stanisław , Łopata Paweł
Published: June 2021

The tightness of the casing-rock formation interface is one of the most important elements of drilling and cementing jobs. In the absence of the required tightness, there is a risk of gas migration directly to the ground, groundwater or atmosphere. In order to eliminate this type of uncontrollable and unfavorable gas flows, the casing column is sealed with cement slurry in the annular space or beyond casing. Cement slurry displaces mud present in the annular space, although the mud cake cannot be completely removed, which is required for obtaining proper binding of cement slurry with the casing surface and the surface of the drilled formation. Therefore, it is important to prepare the well and remove the mud cake from the annular space with spacer fluid. An occasional lack of wellbore tightness requires continuous improvement of the cementing technology. Accordingly, analyses are conducted on mud cake removal with modified or new spacer fluids. Properly designed fluid should efficiently clean the surface of the casing and of the rock mass. One of the basic measurements is the analysis of the efficiency of mud cake removal from the surface of a rotational viscometer. The efficiency of traditional and newly designed fluids for mud cake removal from the casing surface with new and traditional agents has been compared further in this paper. The methodology of mud cake removal with the use of a rotational viscometer was also presented. Tests were performed for various concentrations of agents already used for spacer fluids and for a group of new agents. The efficiency of annular space cleaning was determined on the basis of a comparison with the results obtained for the reference sample, i.e., water which was used for mud cake removal from the rotor surface. The analysis of the results of experiments created bases for the comparison of the efficiency of the analyzed spacer fluids and finding the most suitable ones for mud cake removal from casing columns.
A Simple Theory and Performance Prediction for a Shrouded Wind Turbine with a Brimmed Diffuser
Authors: Watanabe Koichi , Ohya Yuji
Published: June 2021

We developed a new wind turbine system that consists of a diffuser shroud with a broad-ring brim at the exit periphery and a wind turbine inside it. The shrouded wind turbine with a brimmed diffuser, which we called a “wind lens turbine” (WLT), has demonstrated power augmentation by a factor of about 2–5 compared with a bare wind turbine for a given turbine diameter and wind speed. The increase in power output depends on the diffuser shape and length and the brim height. However, a simple theory presented in this paper argues that only two performance coefficients are needed to predict the performance of WLT. The coefficients are the back pressure coefficient of the brim and the pressure recovery coefficient of the diffuser. We theoretically showed that the back pressure coefficient was particularly important for the performance of WLT. Finally, the simple theory was evaluated with experimental results. The results showed good agreement with each other.
Characteristics of Mineralogy, Lithofacies of Fine-Grained Sediments and Their Relationship with Sedimentary Environment: Example from the Upper Permian Longtan Formation in the Sichuan Basin
Authors: Yang Hongzhi , Lin Liangbiao , Chen Liqing , Yu Yu , Li Du , Tian Jingchun , Zhou Wen , He Jianhua
Published: June 2021

The Longtan Formation of the Upper Permian in the Sichuan Basin has become a significant target for shale gas exploration in recent years. Multiple methods, including outcrop observations, thin sections, total organic matter content, X-ray diffraction and scanning electron microscopy were used to investigate the mineralogy, shale lithofacies assemblages and their relationships with the deposition environment. The mineral composition of the Longtan Formation has strong mineral heterogeneity. The TOC values of the Longtan Formation have a wide distribution range from 0.07% to 74.67% with an average value of 5.73%. Four types of shale lithofacies assemblages of the Longtan Formation could be distinguished, as clayey mudstone (CLS), carbonaceous shale (CAS), siliceous shale (SS) and mixed shale (MS) on the basis of mineral compositions. The TOC values of various types of shale lithofacies assemblages in the Longtan Formation varied widely. The shore swamp of the Longtan Formation is most influenced by the terrestrial input and mainly develops CLS and MS. The tidal flat is influenced by the terrestrial input and can also deposit carbonate minerals, developing CLS, CAS and MS. The shallow water melanged accumulation shelf develops CAS and MS, dominated by clay and carbonate minerals. The deep water miscible shelf develops CLS and SS, whose mineral composition is similar to that of the shore swamp, but the quartz minerals are mainly formed by chemical and biological reactions, which are related to the Permian global chert event. The depositional environment of the Longtan Formation controls the shale mineral assemblage of the Longtan Formation and also influences the TOC content.
Study on Companies from the Energy Sector from the Perspective of Performance through the Operating Cash Flow
Authors: Sabău-Popa Claudia Diana , Rus Luminița , Gherai Dana Simona , Mare Codruța , Țara Ioan Gheorghe
Published: June 2021

In this paper we analyzed the link between companies’ performance, in terms of cash and income, and the labor productivity or management rates, in case of the companies from the energy sector listed on the Bucharest Stock Exchange. We focused on the energy sector because of the impact that its expansion has on the evolution of economies around the world and because of its dynamics in the sense of gradually shifting to the use of energy from renewable sources. We have used panel regression models to analyze the operating cash flow and the profitability rates and the determination of a causal or dependency relationship with labor productivity or management rates. The results of this study show a significant negative correlation between operating cash flows and the average duration of stock rotation, and no correlation between productivity and the operating cash flow. Instead, the average duration of stock turnover does not at all influence the profitability rates, and productivity is always significant for the return on assets, ie forthe return on equitywith a positive coefficient, as expected. The gap between the average duration of payment of suppliers and the average duration of receivables does not significantly influence neither the cash flow nor the rates of return.
Effect of the Preheated Oxidizer Temperature on Soot Formation and Flame Structure in Turbulent Methane-Air Diffusion Flames at 1 and 3 atm: A CFD Investigation
Authors: Garnayak Subrat , Mohapatra Subhankar , Dash Sukanta K. , Lee Bok Jik , Reddy V. Mahendra
Published: June 2021

This article presents the results of computations on pilot-based turbulent methane/air co-flow diffusion flames under the influence of the preheated oxidizer temperature ranging from 293 to 723 K at two operating pressures of 1 and 3 atm. The focus is on investigating the soot formation and flame structure under the influence of both the preheated air and combustor pressure. The computations were conducted in a 2D axisymmetric computational domain by solving the Favre averaged governing equation using the finite volume-based CFD code Ansys Fluent 19.2. A steady laminar flamelet model in combination with GRI Mech 3.0 was considered for combustion modeling. A semi-empirical acetylene-based soot model proposed by Brookes and Moss was adopted to predict soot. A careful validation was initially carried out with the measurements by Brookes and Moss at 1 and 3 atm with the temperature of both fuel and air at 290 K before carrying out further simulation using preheated air. The results by the present computation demonstrated that the flame peak temperature increased with air temperature for both 1 and 3 atm, while it reduced with pressure elevation. The OH mole fraction, signifying reaction rate, increased with a rise in the oxidizer temperature at the two operating pressures of 1 and 3 atm. However, a reduced value of OH mole fraction was observed at 3 atm when compared with 1 atm. The soot volume fraction increased with air temperature as well as pressure. The reaction rate by soot surface growth, soot mass-nucleation, and soot-oxidation rate increased with an increase in both air temperature and pressure. Finally, the fuel consumption rate showed a decreasing trend with air temperature and an increasing trend with pressure elevation.
Insurance Instruments in Estimating the Cost Energy Assets with Renewable Energy Sources
Authors: Pukala Ryszard , Kirillova Nadezda , Dorozhkin Alexey
Published: June 2021

The construction and commissioning of renewable energy sources is one of the priority areas of energy programs aimed at achieving sustainable development goals. The creation and operation of such sources is associated with significant risks, the management of which is based on real insurance instruments. This article focuses on the formation of a model for assessing the use of insurance in renewable energy projects and presents the business process, stages, risk drivers, and calculation of the economic efficiency of the use of insurance mechanisms in renewable energy projects.
Framework for the Introduction of Vehicle-to-Grid Technology into the Polish Electricity Market
Authors: Zagrajek Krzysztof , Paska Józef , Sosnowski Łukasz , Gobosz Konrad , Wróblewski Konrad
Published: June 2021

Vehicle-to-grid (V2G) technology is one of the advanced solutions that uses electric vehicles (EV) to balance electricity demand in the power system. It can be particularly useful in analyzing and then mitigating the risk of not delivering electricity to the end user. Therefore, it is necessary to analyze the possibility of operation of this technology in the legal framework. The article presents the analysis of the legal status in Poland, referring to the documents of the European Union and domestic legislation. Potential changes in Polish energy law that could facilitate the implementation of V2G technology are also proposed. In addition, the authors suggested the principles for the use of this technology, formulating a mechanism called the V2G Program. Within this Program, the V2G Service was defined and a business model of its implementation by a participant of the V2G Program (uEV) was presented. In addition, an uEV selection algorithm is provided so that the mathematical model of the V2G Service can be validated. Based on the performed simulations, it can be concluded that the implementation of the V2G Program requires significant changes in the Polish energy law, but it is feasible from the technical point of view.
Combining Baffles and Secondary Porous Layers for Performance Enhancement of Proton Exchange Membrane Fuel Cells
Authors: Mihanović Luka , Penga Željko , Xing Lei , Hacker Viktor
Published: June 2021

A numerical study is conducted to compare the current most popular flow field configurations, porous, biporous, porous with baffles, Toyota 3D fine-mesh, and traditional rectangular flow field. Operation at high current densities is considered to elucidate the effect of the flow field designs on the overall heat transfer and liquid water removal. A comprehensive 3D, multiphase, nonisothermal computational fluid dynamics model is developed based on up-to-date heat and mass transfer sub-models, incorporating the complete formulation of the Forchheimer inertial effect and the permeability ratio of the biporous layers. The porous and baffled flow field improves the cell performance by minimizing mass transport losses, enhancing the water removal from the diffusion layers. The baffled flow field is chosen for optimization owing to the simple design and low manufacturing cost. A total of 49 configurations were mutually compared in the design of experiments to show the quantitative effect of each parameter on the performance of the baffled flow field. The results elucidate the significant influence of small geometry modifications on the overall heat and mass transfer. The results of different cases have shown that water saturation can be decreased by up to 33.59% and maximal temperature by 7.91 °C when compared to the reference case which is already characterized by very high performance. The most influencing geometry parameters of the baffles on the cell performance are revealed. The best case of the 49 studied cases is further optimized by introducing a linear scaling factor. Additional geometry modifications demonstrate that the gain in performance can be increased, but at a cost of higher pressure drop and increased design complexity. The conclusions of this work aids in the development of compact and high-performance proton exchange membrane fuel cell stacks.
Combined Effect of Superabsorbent Polymers and Cellulose Fibers on Functional Performance of Plasters
Authors: Fořt Jan , Šál Jiří , Žák Jaroslav
Published: June 2021

Plaster has, from ancient times, been used as a decorative material. However, the advances in materials engineering such as thermal and moisture control provide new opportunities. Superabsorbent polymers (SAPs) have been found to possess passive moisture control that may find utilization in modern buildings. However, the main drawback is associated with a limited number of applicable SAPs due to mechanical strength loss. In this regard, concurrent utilization of cellulose fibers may provide additional benefits linked with the reinforcing of plaster structure and preservation of superior hygric properties. In this regard, this study investigates the combined effect of SAP and cellulose fibers on the material properties of cement-lime plaster in terms of its mechanic, thermal, and hygric properties. To access the capability of such modified plasters to control the interior moisture fluctuations, the moisture buffering value is determined. Obtained results show the effect of both applied admixtures on material performance, whilst the synergic effect was most obvious for humidity control accessed through the moisture buffer coefficient.
Potential of the Middle Cambrian Aquifer for Carbon Dioxide Storage in the Baltic States
Authors: Krūmiņš Jānis , Kļaviņš Māris , Dēliņa Aija , Damkevics Raivo , Segliņš Valdis
Published: June 2021

The importance of CO2 removal from the atmosphere has long been an essential topic due to climate change. In this paper, the authors aim to demonstrate the suitability of the underground reservoirs for CO2 storage based on their geological characteristics. The research addressed the potential of geological formations for fossil CO2 storage in the Baltic States to support the goal of achieving carbon neutrality in the region. The geological, technical, and economic feasibility for CO2 storage has been assessed in terms of carbon sequestration in geological structures and the legal framework for safe geological storage of fossil CO2. Results indicate that prospective structural traps in the Baltic States, with reasonable capacity for CO2 storage, occur only in Southwestern Latvia (onshore) and in the Baltic Sea (offshore), whilst other regions in the Baltics either do not meet basic geological requirements, or have no economically feasible capacity for CO2 storage. Based on the examination of geological characteristics, the most fitting is the middle Cambrian reservoir in the Baltic sedimentary basin, and one of the most prospective structural traps is the geological structure of Dobele, with an estimated storage capacity of 150 Mt CO2. This study revealed that the storage capacity of the middle Cambrian reservoir (up to 1000 Mt CO2) within the borders of Southwestern Latvia is sufficient for carbon capture and safe storage for the whole Baltic region, and that geological structures in Latvia have the capacity to store all fossil CO2 emissions produced by stationary sources in the Baltic States for several decades.
Design of a Smart Nanogrid for Increasing Energy Efficiency of Buildings
Authors: Yerasimou Yerasimos , Kynigos Marios , Efthymiou Venizelos , Georghiou George E.
Published: June 2021

Distributed generation (DG) systems are growing in number, diversifying in driving technologies and providing substantial energy quantities in covering the energy needs of the interconnected system in an optimal way. This evolution of technologies is a response to the needs of the energy transition to a low carbon economy. A nanogrid is dependent on local resources through appropriate DG, confined within the boundaries of an energy domain not exceeding 100 kW of power. It can be a single building that is equipped with a local electricity generation to fulfil the building’s load consumption requirements, it is electrically interconnected with the external power system and it can optionally be equipped with a storage system. It is, however, mandatory that a nanogrid is equipped with a controller for optimisation of the production/consumption curves. This study presents design consideretions for nanogrids and the design of a nanogrid system consisting of a 40 kWp photovoltaic (PV) system and a 50 kWh battery energy storage system (BESS) managed via a central converter able to perform demand-side management (DSM). The implementation of the nanogrid aims at reducing the CO2 footprint of the confined domain and increase its self-sufficiency.
Vector Modulation-Based Model Predictive Current Control with Filter Resonance Suppression and Zero-Current Switching Sequence for Two-Stage Matrix Converter
Authors: Di Zhengfei , Xu Demin , Zhang Kehan
Published: June 2021

This paper proposes a novel model predictive current control scheme for two-stage matrix converter. The switching frequency is kept constant by fixing the switching instant. The control strategy achieves to control source reactive power in the input side and output currents in the output side. In addition, the advantage of the proposed strategy compared with conventional model predictive control is firstly proved using the principle of vector synthesis and the law of sines in the vector distribution area. Moreover, a zero-current switching sequence is proposed and implemented to insure zero-current switching operations and reduce the switching losses. Furthermore, in order to suppress the input filter resonance, which is easier to be inspired by the model predictive control, compared with traditional control strategies, an innovative active damping technique is proposed and implemented. Finally, both simulation and experiment are implemented to verify the performance of the proposed strategy. The results demonstrate that the control system features both good steady and transient performance.
Rooftop PV: Potential and Impacts in a Complex Territory
Authors: Bernasconi Diana , Guariso Giorgio
Published: June 2021

When developing a sustainability plan in a complex and heavily urbanized territory, one of the most relevant options available is installing rooftop photovoltaic (PV) panels. Thus, it is essential to determine the amount of available surface and the potential impact of such installations on the energy and emission budget of the area. Instead of processing remotely sensed imagery, which is a long process and does not allow considering the buildings’ ownership, this study develops an approach based on a cluster analysis of the urban/morphological characteristics of the municipalities. Once a clear group diversification is obtained, the roof surface of the center of gravity of each cluster is extrapolated to all similar settlements. This, together with the information of local solar irradiation, allowed us to compute each cluster’s potential solar energy production and its capability to respond to the local energy demand, a key parameter to decide about the possibility of a local smart electricity network. Finally, the emissions avoided thanks to solar PV development are computed in terms of carbon dioxide and other relevant pollutants. This approach is applied to the residential rooftop of Lombardy, a Northern Italy region with a wide variety of urban morphologies and landscapes. The potential production of rooftop PV exceeds the estimated electricity consumption of residential buildings and would allow sparing almost 4 M ton of CO2 equivalent or 5% of the overall regional emissions.
Complementing Syngas with Natural Gas in Spark Ignition Engines for Power Production: Effects on Emissions and Combustion
Authors: Caligiuri Carlo , Žvar Baškovič Urban , Renzi Massimiliano , Seljak Tine , Oprešnik Samuel Rodman , Baratieri Marco , Katrašnik Tomaž
Published: June 2021

Power generation units based on the bio-syngas system face two main challenges due to (i) the possible temporary shortage of primary sources and (ii) the engine power derating associated with the use of low-energy density fuels in combustion engines. In both cases, an external input fuel is provided. Hence, complementing syngas with traditional fuels, like natural gas, becomes a necessity. In this work, an experimental methodology is proposed, aiming at the quantification of the impact of the use of both natural gas and syngas in spark ignition (SI) engines on performance and emissions. The main research questions focus on investigating brake thermal efficiency (BTE), power derating, and pollutant emission (NOx, CO, THC, CO2) formation, offering quantitative findings that present the basis for engine optimization procedures. Experimental measurements were performed on a Toyota 4Y-E engine (a 4-cylinders, 4-stroke spark ignition engine) at partial load (10 kW) under different syngas energy shares (SES) and at four different spark ignition timings (10°, 25°, 35° and 45° BTDC). Results reveal that the impact of the different fuel mixtures on BTE is negligible if compared to the influence of spark advance variation on BTE. On the other hand, power derating has proven to be a limiting factor and becomes more prominent with increasing SES. An increasing SES also resulted in an increase of CO and CO2 emissions, while NOx and THC emissions decreased with increasing SES.
Some Key Issues in Hypersonic Propulsion
Authors: Bruno Claudio , Ingenito Antonella
Published: June 2021

This paper summarizes and discusses some critical aspects of flying hypersonically. The first is the L/D (lift over drag) ratio determining thrust and that in turn depends on the slenderness Küchemann’s τ parameter. This second parameter is found to depend on the relative importance of wave versus friction drag. Ultimately, all engineering drag is argued to depend on vorticity formed at the expense of the vehicle kinetic energy, thus requiring work by thrust. Different mixing strategies are discussed and shown to depend also on mechanisms forming vorticity when the regime is compressible. Supersonic combustion is briefly analyzed and found, at sufficiently high combustor Mach, to take place locally at constant volume, unlike conventional Brayton cycles.
Potential Impact of Renewable Energy on the Sustainable Development of Russian Arctic Territories
Authors: Brazovskaia Viktoriia , Gutman Svetlana , Zaytsev Andrey
Published: June 2021

In recent decades, there has been a positive trend in world politics in the field of promoting territories’ sustainable development. At the same time, one of the most relevant areas is to promote the transition to renewable energy sources (RES), which correspond to one of the UN’s goals—Sustainable Development Goal 7 (SDG 7) “Ensuring universal access to affordable, reliable, sustainable and modern energy sources for all”. This article is devoted to the study of the renewable energy sources’ impact on the sustainable development of the Russian Arctic zone. The authors chose the level of carbon dioxide (CO2) emissions as an indicator reflecting the impact of RES on sustainable development, since this factor is one of the main factors for assessing trends in the activities of countries aimed at achieving progress on most of the Sustainable Development Goals of territories. The hypothesis of the relationship between the use of renewable energy sources and the achievement of progress on the Sustainable Development Goals, one of the indicators of which is the level of CO2 emissions, was tested and confirmed. An econometric analysis of panel data for 15 countries that are actively implementing the concept of sustainable development, including decarbonizing policies, was carried out, where the resulting indicator for achieving progress on the SDG was the amount of CO2 emissions. The factors influencing the resulting variable were indicators selected based on a review of existing models, as well as indicators of the Sustainable Development Goals’ achievement. Using an econometric analysis of interdependence, the indicators of progress towards the Sustainable Development Goals that are more likely to have an impact on the level of CO2 emissions were identified. These are electricity consumption, the share of renewable energy sources in the energy balance, the average per capita income of the population, and carbon intensity. Based on the results obtained, it can be concluded that renewable energy sources are a factor contributing to the achievement of progress on the Sustainable Development Goals. The results obtained are also applicable to the Arctic region, since all countries that have territories in the Arctic zone adhere to the policy of decarbonization and try to reduce the use of fossil fuels.
Simulations of Airflow in the Roof Space of a Gothic Sanctuary Using CFD Models
Authors: Ponechal Radoslav , Krušinský Peter , Kysela Peter , Pisca Peter
Published: June 2021

For a deep understanding of the airflow in an environment of historic wooden trusses, it is necessary to analyze the object using simulation methods. To calculate the amount of air passing through the structural openings (components) using dynamic simulation, multi-zone network models based on the simplicity of modeling the individual zones are suitable. For a more detailed analysis of airflow and temperature distribution within one space, a computational fluid dynamics (CFD) simulation model was performed. The air volume through openings and surface temperatures was adopted from the multi-zone airflow network model. By using this simulation technique during a sunny summer day four characteristic states of air movement were simulated in the attic: more intense flow at noon and at midnight caused by a large temperature difference between air and surrounding surfaces and, subsequently, less intense flow when the air was mixed up effectively. The temperature distribution in the cross-sections did not only indicate an increase in temperature with increasing height (up to 50 °C at noon) but also a temperature increase near the southern roof. The surface temperature of the masonry walls was stable (19–33 °C), while the air temperature fluctuated. The image of the flow was completed by ventilation through the tower, which acted as a solar chimney. The airflow through the door to the tower was almost 0.5 m3 s−1 at summer midnight.
Amplitude-Preserved Wave Equation: An Example to Image the Gas Hydrate System
Authors: You Jiachun , Song Sha , Tinivella Umberta , Giustiniani Michela , Vargas-Cordero Iván
Published: June 2021

Natural gas hydrate is an important energy source. Therefore, it is extremely important to provide a clear imaging profile to determine its distribution for energy exploration. In view of the problems existing in conventional migration methods, e.g., the limited imaging angles, we proposed to utilize an amplitude-preserved one-way wave equation migration based on matrix decomposition to deal with primary and multiple waves. With respect to seismic data gathered at the Chilean continental margin, a conventional processing flow to obtain seismic records with a high signal-to-noise ratio is introduced. Then, the imaging results of the conventional and amplitude-preserved one-way wave equation migration methods based on primary waves are compared, to demonstrate the necessity of implementing amplitude-preserving migration. Moreover, a simple two-layer model is imaged by using primary and multiple waves, which proves the superiority of multiple waves in imaging compared with primary waves and lays the foundation for further application. For the real data, the imaging sections of primary and multiple waves are compared. We found that multiple waves are able to provide a wider imaging illumination while primary waves fail to illuminate, especially for the imaging of bottom simulating reflections (BSRs), because multiple waves have a longer travelling path and carry more information. By imaging the actual seismic data, we can make a conclusion that the imaging result generated by multiple waves can be viewed as a supplementary for the imaging result of primary waves, and it has some guiding values for further hydrate and in general shallow gas exploration.
Three-Phase PWM Inverter for Isolated Grid-Connected Renewable Energy Applications
Authors: Ali Ahmed Ismail M. , Takeshita Takaharu , Sayed Mahmoud A.
Published: June 2021

This paper proposes a three-phase isolated flyback inverter (IFBI) for single-stage grid-tied solar PV applications, considering a simple sinusoidal pulse-width modulation (SPWM) scheme. The proposed single-stage inverter employs a reduced passive elements count by considering three input-parallel output-differential (IPOD) flyback converter modules. Additionally, a single small size LC-input low-pass filter is utilized at the input paralleling point for ripple-free input current operation, which is essential in grid-connected renewable energy applications. In addition, a mathematical model of the IFBI is presented to confirm the existence of its low-order harmonic components. A simple PI controller-based control scheme, considering only two loops and five sensors, is used to control the proposed grid-tied IFBI. Continuous modulation scheme (CMS) combined with SPWM is used to diminish the low-frequency harmonic components. Moreover, a simple selective harmonic elimination (SHE) loop is used for second-order harmonic components (SOHC) elimination from grid-injected currents. The SHE has decreased the SOHC from 43% to 0.96%, which improves the grid current THD from 39% to 3.65%, to follow the IEEE harmonic standard limits. Additionally, the harmonic elimination technique decreases the circulating power between the inverter paralleled modules, which enhances the grid currents power factor. The proposed inverter is verified through a grid-connected 200 V, 1.6 kW, 60 Hz experimental prototype, and the switching frequency is 50 kHz. TMS-based DSP controller is used to control the grid-injected power to follow the reference power set-point.
Regional Climate Change Competitiveness—Modelling Approach
Authors: Karman Agnieszka , Miszczuk Andrzej , Bronisz Urszula
Published: June 2021

The article deals with the competitiveness of regions in the face of climate change. The aim was to present the concept of measuring the Regional Climate Change Competitiveness Index. We used a comparative and logical analysis of the concept of regional competitiveness and heuristic conceptual methods to construct the index and measurement scale. The structure of the index includes six broad sub-indexes: Basic, Natural, Efficiency, Innovation, Sectoral, Social, and 89 indicators. A practical application of the model was presented for the Mazowieckie province in Poland. This allowed the region’s performance in the context of climate change to be presented, and regional weaknesses in the process of adaptation to climate change to be identified. The conclusions of the research confirm the possibility of applying the Regional Climate Change Competitiveness Index in the economic analysis and strategic planning. The presented model constitutes one of the earliest tools for the evaluation of climate change competitiveness at a regional level.
An Energy Efficiency Estimation Procedure for Small Wind Turbines at Chosen Locations in Poland
Authors: Zalewska Justyna , Damaziak Krzysztof , Malachowski Jerzy
Published: June 2021

Contrary to the extensive amount of research on large wind turbines, substantial analyses of small wind turbines are still rare. In the present study, the wind energy potential of three locations in Poland is analyzed using real wind data from a five-year period and the parameters of the selected turbine model. Appropriate simulations are performed to assess the energy efficiency of the analyzed investments at a coastal, foothill, or lowland site. According to the results, the most favorable location for a small wind turbine is the coastal site (wind zone I). The payback time at this location is approximately 13 years, whereas the payback times at the other two analyzed are more than 3 times longer. The payback periods for the latter locations significantly exceed the estimated lifetime of the wind turbine, ruling out their economic viability. The cost of electricity generation varies greatly, from 0.16 EUR/kWh at the coastal location to 0.71 EUR/kWh at the lowland location. These results provide a reference for developing more efficient solutions, such as the use of a turbine with a shielded rotor, which can increase the power of the turbine by approximately 2.5 times.
Management of the Energy and Economic Potential of Nuclear Waste Use
Authors: Alshuraiaan Bader , Pushkin Sergey , Kurilova Anastasia , Mazur Magdalena
Published: June 2021

Recently, issues related to the effects (benefit or harm) of processing nuclear waste and its further use as fuel have been increasingly often raised in the scientific discussion. In this regard, the research aims to investigate issues related to the assessment of the economic potential of nuclear waste use, as well as the cooperation between states in the context of the reduction of risks associated with nuclear waste storage and processing. The research methodology is based on an integrated approach, including statistical, factor analysis, and the proposed system of performance indicators for managing spent nuclear fuel use. The research was carried out on the basis of materials from Russia and the EU countries. In the course of the study, a model of cooperation between states has been developed (based on the example of technologies and methods of processing nuclear waste used in the EU and Russia) according to the nuclear waste (spent nuclear fuel) management algorithm. The model considers the risks and threats associated with ecology and safety. The developments and other results described in the study should be used in further research devoted to the use of nuclear waste as heat-producing elements.
Gate Road Support Deformation Forecasting Based on Multivariate Singular Spectrum Analysis and Fuzzy Time Series
Authors: Crnogorac Luka , Tokalić Rade , Gligorić Zoran , Milutinović Aleksandar , Lutovac Suzana , Ganić Aleksandar
Published: June 2021

Underground mining engineers and planners in our country are faced with extremely difficult working conditions and a continuous shortage of money. Production disruptions are frequent and can sometimes last more than a week. During this time, gate road support is additionally exposed to rock stress and the result is its progressive deformation and the loss of functionality of gate roads. In such an environment, it is necessary to develop a low-cost methodology to maintain a gate road support system. For this purpose, we have developed a model consisting of two main phases. The first phase is related to support deformation monitoring, while the second phase is related to data analysis. To record support deformations over a defined time horizon we use laser scanning technology together with multivariate singular spectrum analysis to conduct data processing and forecasting. Fuzzy time series is applied to classify the intensity of displacements into several independent groups (clusters).
COVID-19 and Dentistry
Authors: Devlin Hugh , Soltani Parisa
Published: June 2021

Dentistry is a healthcare profession requiring close contacts between the dental practitioner and the patient. In particular, many dental procedures generate aerosols and droplets which are proved to be the major transmission route for COVID-19.
Domestic Environmental Experience Design
Authors: Chowdhury Sajal , Noguchi Masa , Doloi Hemanta
Published: June 2021

The term ‘domestic environmental experience’ was defined as users’ experiences of cognitive perceptions and physical responses to their domestic built environments. Domestic environments can be enriched through the implementation of environmental experience design (EXD) by combining users’ environmental, spatial and contextual factors that may accommodate occupants’ needs and demands as well as their health and wellbeing. Here, an EXD theoretical concept has been developed based on the ‘User-Centred Design’ thematical framework.
Performance of Small-Scale Sawmilling Operations: A Case Study on Time Consumption, Productivity and Main Ergonomics for a Manually Driven Bandsaw
Authors: Borz Stelian Alexandru , Oghnoum Maryam , Marcu Marina Viorela , Lorincz Arpad , Proto Andrea Rosario
Published: June 2021

Sawmilling operations represent one of the most important phases of the wood supply chain, because they connect the conversion flow of raw materials into finite products. In order to maintain a high volume of processed wood, sawmills usually adopt different processing strategies in terms of equipment and methods, which can increase the value or volume of the lumber produced from logs. In this study, the performance of small-scale sawmilling operations was monitored, whilst also evaluating the exposure of workers to harmful factors. An assessment of time consumption, productivity, and main ergonomics was conducted during the use of a manually driven bandsaw. In addition, the exposure to noise was investigated to complement the knowledge in this regard. The results indicated a rather high time utilization in productive tasks, which may come at the expense of exposure to noise and to poor working postures. The modelling approach resulted in statistically significant time consumption models for different phases (blade adjustment, effective sawing, returning, unloading lumber, and loading and fixing lumber). The exposure to noise was close to 92 dB (A) (8 h) and, therefore, the level of emitted noise is likely to depend on the condition of the used blades, species sawn and on the dimensional characteristics of the logs. In terms of ergonomic risks, the poorest postures were those related to tasks such as moving the logs, loading the logs, fixing the logs, rotating and removing the logs, as well as unloading the lumber.
Temporal Dynamics of Root Reinforcement in European Spruce Forests
Authors: Flepp Gianluca , Robyr Roger , Scotti Roberto , Giadrossich Filippo , Conedera Marco , Vacchiano Giorgio , Fischer Christoph , Ammann Peter , May Dominik , Schwarz Massimiliano
Published: June 2021

The quantification of post-disturbance root reinforcement (RR) recovery dynamics is of paramount importance for the optimisation of forest ecosystem services and natural hazards risk management in mountain regions. In this work we analyse the long-term root reinforcement dynamic of spruce forests combining data of the Swiss National Forest Inventory with data on root distribution and root mechanical properties. The results show that root reinforcement recovery depends primarily on stand altitude and slope inclination. The maximum root reinforcement recovery rate is reached at circa 100 years. RR increases continuously with different rates for stand ages over 200 years. These results shows that RR in spruce stands varies considerably depending on the local conditions and that its recovery after disturbances requires decades. The new method applied in this study allowed for the first time to quantify the long term dynamics of RR in spruce stands supporting new quantitative approaches for the analysis of shallow landslides disposition in different disturbance regimes of forests.
Ball Convergence of a Parametric Efficient Family of Iterative Methods for Solving Nonlinear Equations
Authors: Regmi Samundra , Argyros Christopher , Argyros Ioannis , George Santhosh
Published: June 2021

The goal is to extend the applicability of Newton-Traub-like methods in cases not covered in earlier articles requiring the usage of derivatives up to order seven that do not appear in the methods. The price we pay by using conditions on the first derivative that actually appear in the method is that we show only linear convergence. To find the convergence order is not our intention, however, since this is already known in the case where the spaces coincide with the multidimensional Euclidean space. Note that the order is rediscovered by using ACOC or COC, which require only the first derivative. Moreover, in earlier studies using Taylor series, no computable error distances were available based on generalized Lipschitz conditions. Therefore, we do not know, for example, in advance, how many iterates are needed to achieve a predetermined error tolerance. Furthermore, no uniqueness of the solution results is available in the aforementioned studies, but we also provide such results. Our technique can be used to extend the applicability of other methods in an analogous way, since it is so general. Finally note that local results of this type are important, since they demonstrate the difficulty in choosing initial points. Our approach also extends the applicability of this family of methods from the multi-dimensional Euclidean to the more general Banach space case. Numerical examples complement the theoretical results.
Impact of Managed-Lane Pricing Strategies on Vehicle-Sourced NOx and HC Emissions
Authors: Du Jianbang , Qiao Fengxiang , Yu Lei , Lv Ying
Published: June 2021

Ground-level ozone is a secondary air pollutant that is formed by chemical reactions between precursors, including nitrogen oxides (NOx) and hydrocarbon (HC). Highway traffic, which can be controlled by traffic operational strategies, is one of the main sources of atmospheric NOx and HC. Managed-lane pricing is one of the popularly used freeway traffic management approaches, while its impacts on ground-level ozone-related vehicle emissions is, however, still unclear. This motivated the purpose of this research. A case study in Houston, USA indicates that, vehicles on managed lanes had fewer hard accelerations/decelerations and higher average speed, which resulted in higher per-vehicle emissions in grams/hour, while the total emissions of a vehicle were roughly comparable to what they would be on a general-purpose lane. Total daily NOx and HC emissions per managed lane were 31.9%–42.6% of those per general-purpose lane. The weight ratios between HC and NOx show that, the ground-level ozone formation of this area is hydrocarbon-limited.
Comparative Transcriptome Identifies Gene Expression Networks Regulating Developmental Pollen Abortion in Ogura Cytoplasmic Male Sterility in Chinese Cabbage (Brassica rapa ssp. pekinensis)
Authors: Hu Lijiao , Zhang Xiaowei , Yuan Yuxiang , Wang Zhiyong , Yang Shuangjuan , Li Ruina , Nath Ujjal Kumar , Zhao Yanyan , Tian Baoming , Shi Gongyao , Xie Zhengqing , Wei Fang , Wei Xiaochun
Published: June 2021

Ogura cytoplasmic male sterility (Ogura CMS), originally identified in wild radish (Raphanus sativus), has enabled complete pollen sterility in Brassica plants, but the underlying mechanism in Ogura CMS Chinese cabbage (Brassica rapa ssp. pekinensis) remains unclear. In this study cytological analysis showed that during microsporogenesis the meiosis occurred normally, and the uninucleated pollens subsequently formed, but the development of both binucleated and trinucleated pollens was obviously disrupted due to defects of pollen mitosis in the Ogura CMS line (Tyms) compared with the corresponding maintainer line (231–330). In transcriptome profiling a total of 8052 differentially expressed genes (DEGs) were identified, among which 3890 were up-regulated and 4162 were down-regulated at the pollen abortion stages in an Ogura CMS line. KOG cluster analysis demonstrated that a large number of DEGs were related to the cytoskeleton’s dynamics, which may account for the failure of pollen mitosis during development in the Ogura CMS line. The pivotal genes related to the phenylpropane synthesis pathway (PAL, 4CL and CAD) were significantly down-regulated, which probably affected the formation and disposition of anther lignin and sporopollenin, and eventually led to abnormality in the pollen exine structure. In addition, several key up-regulated genes (GPX7, G6PD and PGD1) related to the glutathione oxidation-reduction (REDOX) reaction indicated that the accumulation of peroxides in Ogura CMS lines during this period affected the pollen development. Taken together, this cytological and molecular evidence is expected to advance our understanding of pollen abortion induced by Ogura cytoplasmic action in Chinese cabbage.